Method for Signals Detection in Single Crystal Diffraction Patterns through a Diffraction

Nondestructive Material Testing with Ultrasonics Introduction to theBasic PrinciplesNondestructive material testing with ultrasonics is more than 40 years old. From the very first examinations, using ultrasonic oscillations for detection of flaws in different materials, it has become a classical test method based on measurements with due regard to all the important influencing factors. Today it is expected that ultrasonic testing, supported by great advances in instrument technology, give reproducible test results within narrow tolerances. This assumes exact know- ledge of the influencing factors and the ability to apply these in testing technology.Not all influences have to be seriously regarded by the operator.。

In many cases some of the influences can be neglected without exceeding the permitted measurement tolerances. Due to this, the test sequence is simplified and the testing time reduced. Despite this, the future belongs to the qualified operator who carries out his task responsibly and who continuously endeavours to keep his knowledge at the latest state of the art.1.Why use ultrasonics for nondestructive material testing?At the beginning of the fifties the technician only knew radiography (x-ray or radioactive isotopes) as a method for detection of internal flaws in addition to the methods for nondestructive testing of material surfaces, e.g. the dye penetrant and magnetic particle method. After the Second World War the ultrasonic method, as described by Sokolov in 1935 and applied by Firestone in 1940, was further developed so that very soon instruments were available for ultrasonic testing of materials.he ultrasonic principle is based on the fact that solid materials are good conductors of sound waves. Where by the waves are not only reflected at the interfaces but also by internal flaws (material separations, inclusions etc.). The interaction effect of sound waves with the material is stronger the smaller the wave length, this means the higher the frequency of the wave.λ= C/fc = Sound velocity [km/s]f = Frequency [MHz]λ= Wave lenght [mm]This means that ultrasonic waves must be used in a frequency range between about0.5 MHz and 25 MHz and that the resulting wave length is in mm. With lower frequencies, the interaction effect of the waves with internal flaws would be so small that detection becomes questionable. Both test methods, radiography and ultrasonic testing, are the most frequently used methods oftesting different test pieces for internal flaws, partly covering the application range and partly extending it.This means that today many volume tests are possible with the more economical and non-risk ultrasonic test method, on the other hand special test problems are solved, the same as before, using radiography. In cases where the highest safety requirements are demanded (e.g. nuclear power plants, aerospace industry) both methods are used.2.Ultrasonic testing tasksIs there a primary classification of tasks assigned to the ultrasonic operator? If we limit ourselves to testing objects for possible material flaws then the classification is as follows:1. Detection of reflectors2. Location of reflectors3. Evaluation of reflectors4. Diagnosis of reflectors(reflector type, orientation, etc.)Instead of using the word "reflector", the ultrasonic operator very often uses the term "discontinuity". This is defined as being an "irregularity in the test object which is suspected as being a flaw". In reality, only after location, evaluation and diagnosis has been made, can it be determined whether or not there is a flaw which effects the purpose of the test object. The term "discontinuity" is therefore always used as long as it is not certain whether it concerns a flaw which means a non-permissible irregularity.3. Detection of discontinuitiesThe essential "tool" for the ultrasonic operator is the probe.The piezo electric element, excited by an extremely short electrical discharge, transmits an ultrasonic pulse. The same element on the other hand generates an electrical signal when it receives an ultrasonic signal thus causing it to oscillate. The probe is coupled to the surface of the test object with a liquid or coupling paste so that the sound waves from the probe are able to be transmitted into the test object.The operator then scans the test object, i.e. he moves the probe evenly to and fro across the surface. In doing this, he observes an instrument display for any signals caused by reflections from internal discontinuities.Every probe has a certain directivity, i.e. the ultrasonic waves only cover a certain section of the test object. The area effective for the ultrasonic test is called the"sound beam" which is characteristic for the applied probe and material in which sound waves propagate.A sound beam can be roughly divided into a convergent (focusing) area,the near- field, and a divergent (spreading) part, the far field.The length N of the near-field (near-field length) and the divergence angle is de- pendent on the diameter of the element, its frequency and the sound velocity of the material to be tested. The center beam is termed the acoustic axis. The shape of the sound beam plays an important part in the selection of a probe for solving a test problem. It is often sufficient to draw the acoustic axis in order to show what the solution to a test task looks like. A volumetric discontinuity (hollow space, foreign material) reflects the sound waves in different directions.The portion of sound wave which comes back to the probe after being reflected by the discontinuity is mainly dependent on the direction of the sound wave; i.e. it does not matter whether scanning is made with a straight-beam probe or an angle-beam probe or whether it is carried out from different surfaces on the test object.If the received portion of the reflected sound wave from the probe is sufficient then the detection of the existing volumetric discontinuity is not critical, this means that the operator is able to detect it by scanning from different directions. A plane (two-dimensional) discontinuity (e.g. material separation, crack) reflects the ultrasonic waves mostly in a certain direction.If the reflected portion of the sound wave is not received by the probe then it is unlikely that the discontinuity will be detected. The possibilities of detection only increase when the plane discontinuity is hit vertically by the sound beam. This applies to discontinuities which are isolated within the test object.With plane discontinuities which are open to the surface of the test object, e.g. a crack running vertically from the surface into the test object, a vertical scan of the crack does not always produce the required success. In this case wave overlapping occurs (interferences) due to sound wave reflection on the side wall of the test object which seems as if the sound wave bends away from the corresponding side wall.In such cases, the probability of crack detection is very good if the angle reflection effect is used. At the 90˚edge, between the crack and the surface of the test object, the sound waves are reflected back within themselves due to a double reflection.Use of the angle reflection effect is often even possible when a plane discontinuity, which is vertical to the surface, does not extend to the surface and under the condition that the sound wave reflections at the discontinuity and the surface are received by the probe.Often in thick-walled test objects, in which there are vertical discontinuities, this con- dition cannot be fulfilled so that the reflected sound waves from the discontinuity and the surface of the test object do not return to the probe. In this case, a second probe is used for receiving the reflected portions of sound thus enabling detection of the discontinuity.With this type of testing, the Tandem Technique, one probe is used as a transmitter, and the other probe is used as the receiver. Both probes are moved over the surface of the test object and are spaced apart at a fixed distance.Scanning is made for vertically positioned discontinuities at different depths of the test object, depending on the probe spacing.Although, with angle scanning in thin test objects, there is a possibility that plane discontinuities cannot be vertically hit, Fig.11 a, the detection sensitivity is much better, especially by suitable selection of the scanning angle and the test frequency so that the user favours the single probe test as opposed to the more complicated tandem method. This is normally the case when testing welds up to a thickness of about 30 mm.Of course the possibility of detecting discontinuities which are not vertically hit is reduced. However, this deficiency is often compensated by an additional test with another angle of incidence, Fig. 11 b, or by using a probe with a lower frequency. A typical procedure can be found in the corresponding specifications (test instructions) for weld testing.使用超声波对材料进行的非破坏性检测基本原理介绍使用超声波对材料进行非破坏性检测已经有40多年了。

专利名称：OPTIMUM DETECTION METHOD FOR DTMF SIGNALS发明人：BAUER, Wolfgang,KOZEK, Werner申请号：EP2006060875申请日：20060320公开号：WO06/120052P1公开日：20061116专利内容由知识产权出版社提供摘要：The invention relates to a method for optimum detection of DTMF signals in input signals, in which method a vectorial representation of the input signal is projected into a vectorial subspace adapted to the DTMF signal (3), and the energy of the projected signal representation is then determined (4, 5). The energy is used as decision criterion (6) in order to determine whether a DTMF signal is contained in the input signal (7a). The main aspect of the solution according to the invention consists in a decision criterion (6) which makes it possible to determine whether a DTMF signal is contained in the input signal (7a), the decision criterion (6) being based on the projection of a vectorial representation of the input signal into a vectorial space (3) and the determination of the energy of the projected signal representation (4, 5). This considerably reduces the computing power required to detect a DTMF signal.申请人：BAUER, Wolfgang,KOZEK, Werner地址：DE,AT,AT国籍：DE,AT,AT更多信息请下载全文后查看。

零中频接收机设计2013年09月24日13:09eechina分享关键词：零中频,接收机作者在：冷爱国，TI公司China Telecom system摘要相较传统的超外差接收机，零中频接收机具有体积小，功耗和成本低，以及易于集成化的特点，正受到越来越广泛关注，本文结合德州仪器（TI）的零中频接收方案（TRF3711），详细分析介绍了零中频接收机的技术挑战以及解决方案。

概述零中频接收机在几十年前被提出来，工程中经历多次的应用实践，但是多以失败告终，近年来，随着通信系统要求成本更低，功耗更低，面积更小，集成度更高，带宽更大，零中方案能够很好的解决如上问题而被再次提起。

本文将详细介绍零中频接收机的问题以及设计解决方案，结合TI的零中频方案TRF3711测试结果证明，零中频方案在宽带系统的基站中是可以实现的。

1、超外差接收机1.1超外差接收机问题为了更好理解零中频接收的优势，本节将简单总结超外差接收机的一些设计困难和缺点。

图一是简单超外差接收机的架构，RF信号经过LNA(低噪声放大器)进入混频器，和本振信号混频产生中频信号输出，镜像抑制滤波器滤出混频的镜像信号，中频滤波器滤除带外干扰信号，起到信道选择的作用，图中标示了频谱的搬移过程及每一部分的功能。

在超外差接收机种最重要的问题是怎样在镜像抑制滤波器和信号选择滤波器的设计上得到平衡，如图一所示，对滤波器而言，当其品质因子和插损确定，中频越高，其对镜像信号的抑制就越好，而对干扰信号的抑制就比较差，相反，如果中频越低，其对镜像信号的抑制就变差，而对干扰信号的抑制就非常理想，由于这个原因，超外差接收机对镜像滤波器和信道滤波器的选择传输函数有非常高的要求，通常会选用声表滤波器(SAW)，或者是采用高阶LC滤波器，这些都不利于系统的集成化，同时成本也非常高。

在超外差接收机中，由于镜像抑制滤波器是外置的，LNA必须驱动50R负载,这样还会导致面积和放大器噪声，增益，线性度，功耗的平衡性问题。

phrodo染料标记方法English:Phrodo dyes are a type of fluorescent dyes that are commonly used for labeling and tracking biological molecules in various experiments and applications. The labeling process involves conjugating the Phrodo dye to the target molecule by chemical reaction. This is typically achieved by coupling the dye to a functional group on the molecule of interest, such as an amine, thiol, or carboxylic acid group. One popular method for Phrodo dye labeling is using NHS-ester chemistry, which involves the reaction of the NHS-ester group on the dye with primary amines on the target molecule to form stable amide bonds. This method allows for efficient and specific labeling of the target molecule with the Phrodo dye, resulting in bright and highly fluorescent signals for imaging and detection. After labeling, the Phrodo-dyed molecules can be used for various applications, including fluorescence microscopy, flow cytometry, and cell-based assays, providing valuable insights into biological processes and interactions at the molecular level.中文翻译:Phrodo染料是一种荧光染料，常用于标记和跟踪生物分子在各种实验和应用中的应用。

血管内表皮生长因子检测原理英文回答：The detection principle of vascular endothelial growth factor (VEGF) involves measuring the levels of this important growth factor in the blood. VEGF is a proteinthat plays a crucial role in the formation of new blood vessels, a process known as angiogenesis.There are several methods for detecting VEGF in the blood, with the most common being enzyme-linked immunosorbent assay (ELISA). In ELISA, a specific antibody that binds to VEGF is coated onto a plate. Then, the blood sample is added, and if VEGF is present, it will bind to the antibody. A second antibody linked to an enzyme is then added, and a substrate for the enzyme is added, resultingin a color change that indicates the presence and amount of VEGF in the sample.Another method for detecting VEGF is through the use ofa protein microarray. This technique involves spotting tiny amounts of VEGF-specific antibodies onto a chip, which can then be exposed to the blood sample. If VEGF is present, it will bind to the antibodies on the chip, and this binding can be detected using fluorescent or chemiluminescent signals.In summary, the detection of VEGF in the blood involves using specific antibodies to capture and measure the levels of this important growth factor. These methods are crucial for understanding the role of VEGF in various diseases and for monitoring the response to VEGF-targeted therapies.中文回答：血管内皮生长因子（VEGF）的检测原理涉及测量血液中这一重要生长因子的水平。

通信系统英文版Title: Communication SystemsIntroduction:Communication systems play a crucial role in today's interconnected world. They facilitate the exchange of information and enable seamless connectivity across various devices and networks. This article will provide an in-depth overview of communication systems, covering five major points: types of communication systems, components of a communication system, transmission methods, signal processing techniques, and future developments. The article will conclude by highlighting the significance of communication systems in our daily lives.Body:1. Types of Communication Systems:1.1 Wired Communication Systems:- Description: Wired communication systems use physical cables to transmit data signals.- Examples: Ethernet, fiber optic cables, telephone lines.1.2 Wireless Communication Systems:- Description: Wireless communication systems transmit data signals through the air without the need for physical cables.- Examples: Wi-Fi, Bluetooth, cellular networks.2. Components of a Communication System:2.1 Transmitter:- Function: Converts information into a suitable signal for transmission.- Sub-components: Modulator, signal generator, amplifier.2.2 Transmission Medium:- Function: Provides a physical path for the signal to travel.- Types: Wired (copper cables, fiber optics) or wireless (air, space).2.3 Receiver:- Function: Receives and decodes the transmitted signal to extract the original information.- Sub-components: Demodulator, signal decoder, amplifier.3. Transmission Methods:3.1 Analog Transmission:- Description: Analog transmission conveys continuous signals, representing information in the form of varying voltage or current levels.- Advantages: Simple implementation, suitable for voice and audio signals.- Disadvantages: Prone to noise interference, limited bandwidth.3.2 Digital Transmission:- Description: Digital transmission represents information in discrete binary form (0s and 1s).- Advantages: Better noise immunity, higher data transmission rates, error detection and correction.- Disadvantages: Requires encoding and decoding processes.4. Signal Processing Techniques:4.1 Modulation:- Description: Modulation modifies the characteristics of a carrier signal to encode information.- Types: Amplitude modulation (AM), frequency modulation (FM), phase modulation (PM).4.2 Multiplexing:- Description: Multiplexing combines multiple signals into a single transmission medium.- Types: Time-division multiplexing (TDM), frequency-division multiplexing (FDM), code-division multiplexing (CDM).4.3 Error Detection and Correction:- Description: Error detection and correction techniques ensure the accuracy of transmitted data.- Methods: Parity checks, checksums, cyclic redundancy checks (CRC).5. Future Developments:- Advancements in communication systems include:5.1 5G Technology:- Description: 5G technology promises faster data rates, lower latency, and increased network capacity.- Applications: Enhanced mobile broadband, Internet of Things (IoT), autonomous vehicles.5.2 Internet of Things (IoT):- Description: IoT connects various devices and objects to the internet, enabling data exchange and automation.- Applications: Smart homes, industrial automation, healthcare monitoring.5.3 Quantum Communication:- Description: Quantum communication utilizes quantum phenomena for secure and efficient transmission of information.- Applications: Quantum cryptography, quantum key distribution.Conclusion:In conclusion, communication systems are vital for the seamless exchange of information in our interconnected world. This article provided an overview of communication systems, covering types, components, transmission methods, signal processing techniques, and future developments. Understanding these aspects helps us appreciate the significance of communication systems in our daily lives and anticipate the exciting advancements on the horizon.。

卫星定位周跳探测研究方法综述冯亚萍（咸阳师范学院实验室管理处，陕西咸阳712000）摘要：周跳探测是高精度卫星导航定位数据预处理的重要部分，对定位精度的提高以及后续数据处理及应用起到相当重要的作用。

基于此目的，文章根据分析周跳时利用信号频率的多少，对现有文献进行了单频、双频和三频三个主要周跳探测手段的分类，总结了各种周跳探测手段包含的方法及存在的优势和不足。

单频周跳探测所需数据少，探测简单易行，但对小周跳探测不敏感；双频、三频探测精度高，但需要更多频率的数据且探测存在不敏感周跳组合。

对这些问题目前一般通过单差或双差观测值、数学降噪、数据处理弱化电离层、组合系数最优化、多种探测法联合等手段加以克服。

该文的分析和总结将为以后的周跳探测技术发展提供一定参考。

关键词：卫星导航定位；周跳探测；数据预处理；单、双、三频信号；探测方法中图分类号：P228.4文献标识码：A文章编号：2096-9759（2023）07-0046-03A review of the research methods of satellite positioning cycle slip detectionFENG Yaping(Laboratory Mangement Department,Xianyang Normal University,Xianyang712000,Shaanxi,China) Absrtact:Cycle slip detection is an important part of high precision satellite navigation and positioning data pre-processing,w hich plays an important role in improving positioning accuracy and subsequent data processing and application.For this purpose, this paper classifies the single-frequency,double-frequency and triple-frequency detection methods according to the frequency of the signal used in cycle slip analysis,and summarizes the methods of cycle slip detection and their advantages and disadvantages. Single frequency cycle slip detection requires less data and is easy to detect,but is not sensitive to small cycle slip detection. Dual frequency and triple frequency detection have high accuracy,but more frequency data is needed and the detection has insensitive cycle slip combinations.Currently,these problems are generally overcome by means of single or double difference observations,mathematical noise reduction,data processing to weaken the ionosphere,optimization of combination coefficients, and the combination of multiple detection methods.The analysis and summary of this article will provide some reference for the development of cycle slip detection technology.Keywords:satellite navigation and positioning;cycle slip detection;Data pre-processing;single,dual and triple frequency sig-nals;detection method1引言全球卫星导航定位系统发展迅猛、应用广泛，从最开始的军事领域已经发展到了智能交通、通信、智慧出行、滑坡监测、防灾减灾等各个方面，成了日常生活中不可缺少的组成，随着其更深一步的作用于日常生活，人们对定位精度的要求也越来越高。

计算机期刊大全【前言】随着计算机技术的快速发展，越来越多的人开始关注计算机期刊，以获取最新的科研成果和技术进展。

本文旨在介绍全球范围内主要的计算机期刊，帮助读者了解各期刊的主题范围、影响因子、最新收录论文等信息，以提高论文发表效率和科研成果的质量。

【一、计算机科学顶级期刊】计算机领域的顶级期刊，对于任何一位计算机科学家来说，都是非常重要的。

这些期刊的文章水平高、质量优，其发表文章往往具有一定的权威性和影响力。

以下是全球最著名的计算机科学顶级期刊：1.《ACM Transactions on Computer Systems》（ACM TOCS）主题范围：该期刊关注计算机系统的设计、分析、实现和评估等方面，特别是操作系统、网络、分布式系统、数据库管理系统和存储系统等方面的最新研究成果。

影响因子：3.612发行周期：每年4期最新收录论文：Content-Based Data Placement for Efficient Query Processing on Heterogeneous Storage Systems, A Framework for Evaluating Kernel-Level Detectors, etc.2.《IEEE Transactions on Computers》（IEEE TC）主题范围：该期刊刊登计算机科学领域的创新性研究成果，重点关注计算机系统、组件和软件的设计、分析、实现和评估等方面的最新进展。

影响因子：4.804发行周期：每月1期最新收录论文：A Comprehensive View of Datacenter Network Architecture, Design, and Operations, An Efficient GPU Implementation of Imperfect Hash Tables, etc.3.《IEEE Transactions on Software Engineering》（IEEE TSE）主题范围：该期刊涉及软件工程领域的各个方面，包括软件开发、可靠性、维护、测试等方面的最新研究成果。

信号与噪声的计算RECEIVER SENSITIVITY / NOISERECEIVER SENSITIVITYSensitivity in a receiver is normally taken as the minimum input signal (Smin) required to produce a specified output signal having a specified signal-to-noise (S/N) ratio and is defined as the minimum signal-to-noise ratio times the mean noise power, see equation [1]. For a signal impinging on the antenna (system level) sensitivity is known as minimum operational sensitivity (MOS), see equation [2]. Since MOS includes antenna gain, it may be expressed in dBLi (dB referenced to a linear isotropic antenna). When specifying the sensitivity of receivers intended to intercept and process pulse signals, the minimum pulse width at which the specified sensitivity applies must also be stated. See the discussion ofpost-detection bandwidth (BV) later in this section for significance of minimum pulsewidth in the receiver design.We have a lower MOS if temperature, bandwidth, NF, or S/Nmin decreases, or if antenna gain increases. For radar, missile, and EW receivers, sensitivity is usually stated in dBm. For communications and commercial broadcasting receivers, sensitivity is usually stated in micro-volts or dBv.There is no standard definition of sensitivity level. The term minimum operational sensitivity (MOS) can be used in place of Smin at the system level where aircraft installation characteristics are included. The "black box" term minimum detectable signal (MDS) is often used for Smin but can cause confusion because a receiver may be able to detect a signal, but not properly process it. MDS can also be confused with minimum discernable signal, which is frequently used when a human operator is used to interpret the reception results. A human interpretation is also required with minimum visible signal (MVS) and tangential sensitivity (discussed later). Toavoid confusion, the terms Smin for "black box" minimum sensitivity and MOS for system minimum sensitivity are used in this section. All receivers are designed for a certain sensitivity level based on requirements. One would not design a receiver with more sensitivity than required because it limits the receiver bandwidth and will require the receiver to process signals it is not interested in. In general, while processing signals, the higher the power level at which the sensitivity is set, the fewer the number of false alarms which will be processed. Simultaneously, the probability of detection of a "good" (low-noise) signal will be decreased.Sensitivity can be defined in two opposite ways, so discussions can frequently be confusing. It can be the ratio of response to input or input to response. In using the first method (most common in receiver discussions and used herein), it will be a negative number (in dBm), with the more negative being "better" sensitivity, e.g. -60 dBm is "better" than -50 dBm sensitivity. If the second method is used, the result will be a positive number, with higher being "better." Therefore the terms low sensitivity or high sensitivity can be very confusing. The terms Smin and MOS avoid confusion.SIGNAL-TO-NOISE (S/N) RATIOThe Signal-to-Noise Ratio (S/N) (a.k.a. SNR) in a receiver is the signal power in the receiver divided by the mean noise power of the receiver. All receivers require the signal to exceed the noise by some amount. Usually if the signal power is less than or just equals the noise power it is not detectable. For a signal to be detected, the signal energy plus the noise energy must exceed some threshold value. Therefore, just because N is in the denominator doesn't mean it can be increased to lower the MOS. S/N is a required minimum ratio, if N is increased, then S must also be increased to maintain that threshold. The threshold value is chosen high enough above the mean noise level so that the probability of random noise peaks exceeding the threshold, and causing false alarms, is acceptably low.Figure 1 depicts the concept of required S/N. It can be seen that the signal at timeA exceeds the S/N ratio and indicates a false alarm or target. The signal at timeB is just at the threshold, and the signal at timeC is clearly below it. In the sample, if the temperature is taken as room temperature (To = 290 °K), the noise power input is -114 dBm for a one MHz bandwidth. Normally S/Nmin may be set higher than S/N shown in Figure 1 to meet false alarm specifications.The acceptable minimum Signal-to-Noise ratio (or think of it as Signal above Noise) for a receiver depends on the intended use of the receiver. For instance, a receiver that had to detect a single radar pulse would probably need a higher minimum S/N than a receiver that could integrate a large number of radar pulses (increasing the total signal energy) for detection with the same probability of false alarms. Receivers with human operators using a video display may function satisfactorily with low minimum S/N because a skilled operator can be very proficient at pickingsignals out of a noise background. As shown in Table 1, the setting of an acceptable minimum S/N is highly dependant on the required characteristics of the receiver and of the signal.A complete discussion of the subject would require a lengthy dissertation of the probability and statistics of signal detection, which is beyond the scope of this handbook, however a simplified introduction follows. Let's assume that we have a receiver that we want a certain probability of detecting a single pulse with a specified false alarm probability. We can use Figure 2 to determine the required signal-to-noise ratio.S/N EXAMPLEIf we are given that the desired probability of detecting a single pulse (Pd) is 98%, and we want the false alarm rate (Pn) to be no more than 10-3, then we can see that S/N must be 12 dB (see Figure 2).MAXIMUMDETECTIONRANGE (ONE-WAY)From the one-way radar equation section, the one way signal strength from a transmitter to a receiver is:For calculations involving receiver sensitivity the "S" can be replaced by Smin. Since Smin = (S/N)min kToB(NF), given by equation [1], the one-way radar equation can be solved for any of the other variables in terms of receiver parameters. In communication, radar, and electronic warfare applications, you might need to solve for the maximum range (Rmax) where a given radar warning receiver could detect a radiated signal with known parameters. We would then combine and rearrange the two equations mentioned to solve for the following one-way equation:We could use standard room temperature of 290 ° K as To, but NF would have to be determined as shown later.In this calculation for receiver Rmax determination, Pt , Gt , and are radar dependent, while Gr , S/Nmin, NF, and B are receiver dependent factors.Equation [3] relates the maximum detection range to bandwidth (B). The effects of the measurement bandwidth can significantly reduce the energy that can be measured from the peak power applied to the receiver input. Additional bandwidth details areprovided in the two-way radar equation section and the constant power (saturated ) jamming section, as well as in other parts of this sectionNOISE POWER, kToBThermal noise is spread more or less uniformly over the entire frequency spectrum. Therefore the amount of noise appearing in the output of an ideal receiver is proportional to the absolute temperature of the receiver input system (antenna etc) times the bandwidth of the receiver. The factor of proportionality is Boltzmann's Constant.Mean noise power of ideal receiver = kToB = PN (Watts)Mean noise power of a real receiver = (NF)kToB (Watts)The co nvention for the temperature of To is set by IEEE standard to be 290 °K, which is close to ordinary room temperature. So, assuming To = 290 °K, and for a bandwidth B = 1 Hz, kToB = 4x10-21 W = -204 dBW = -174 dBm.For any receiver bandwidth, multiply 4x10-21 W by the bandwidth in Hz, or if using dB;10 log kToB = -174 dBm + 10 Log (actual Bandwidth in Hz)or -114 dBm + 10 Log (actual Bandwidth in MHz)and so on, as shown by the values in Table 2.Typical values for maximum sensitivity of receivers would be:∙RWR -65 dBm∙Pulse Radar -94 dBm∙CW Missile Seeker -138 dBmIf antenna contributions are ignored (see note in Table 4) for a CW receiver with a 4 GHz bandwidth, the ideal mean noise power would be -174 dBm + 10 Log(4x10 9) = -174 dBm + 96 dB = -78 dBm. A skilled operator might only be able to distinguish a signal 3 dB above the noise floor (S/N=3 dB), or -75 dBm. A typical radar receiver would require a S/N of 3 to 10 dB to distinguish the signal from noise, and would require 10 to 20 dB to track. Auto tracking might require a S/N of approximately25 dB, thus, a receiver may only have sufficient sensitivity to be able to identify targets down to -53 dBm. Actual pulse receiver detection will be further reduced due to sin x/x frequency distribution and the effect of the measurement bandwidth as discussed in other sections. Integration will increase the S/N since the signal is coherent and the noise is not.Noise BandwidthEquivalent Noise Bandwidth (BN) - Set by minimum pulse width or maximum modulation bandwidth needed for the system requirements. A choice which is available to the designer is the relationship of pre- and post-detection bandwidth. Pre-detection bandwidth is denoted by BIF , while post-detection is denoted BV , where V stands for video. The most affordable approach is to set the post-detection filter equal to the reciprocal of the minimum pulse width, then choose the pre-detection passband to be as wide as the background interference environment will allow. Recent studies suggest that pre-detection bandwidths in excess of 100 MHz will allow significant loss of signals due to "pulse-on-pulse" conditions. Equations [4] and [5] provide BN relationships that don't follow the Table 3 rules of thumb.For a square law detector: (1)At high (S/N)out, the 1/(S/Nout) term goes to zero and we have:At low (S/N)out, the 1/(S/Nout) term dominates, and we have:For a linear detector: (1)H is a hypergeometric (statistical) function of (S/N)in∙H = 2 for (S/N)in << 1∙H = 1 for (S/N)in >> 1At high (S/N)out, the 1/(S/Nout) term goes to zero and we have:At low (S/N)out, the 1/(S/Nout) term dominates, and we have:Note (1): From Klipper, Sensitivity of crystal Video Receivers with RFPre-amplification, The Microwave Journal, August 1965.TRADITIONAL "RULE OF THUMB" FOR NARROW BANDWIDTHS(Radar Receiver Applications)Required IF Bandwidth For Matched Filter Applications:Matched filter performance gives maximum probability of detection for a given signal level, but:1.Requires perfect centering of signal spectrum with filter bandwidth,2.Time response of matched pulse does not stabilize at a final value, and3.Out-of-band splatter impulse duration equals minimum pulse width.As a result, EW performance with pulses of unknown frequency and pulse width is poor.Some authors define BV in terms of the minimum rise time of the detected pulse, i.e., BV = (0.35 to 0.5)/tr/ min, where tr = rise time.REVISED "RULE OF THUMB" FOR WIDE BANDWIDTHS (Wideband Portion of RWRs)The pre-detection bandwidth is chosen based upon interference and spurious generation concerns. The post-detection bandwidth is chosen to "match" the minimum pulse width. This allows1.Half bandwidth mistuning between signal and filter,2.Half of the minimum pulse width for final value stabilization, and3.The noise bandwidth to be "matched" to the minimum pulse width.As a result, there is:1.Improved EW performance with pulses of unknown frequency and pulse width,2.Measurement of in-band, but mistuned pulses, and3.Rejection of out-of-band pulse splatter.NOISE FIGURE / FACTOR (NF)Electrical noise is defined as electrical energy of random amplitude, phase, and frequency. It is present in the output of every radio receiver. At the frequencies used by most radars, the noise is generated primarily within the input stages of the receiver system itself (Johnson Noise). These stages are not inherently noisier than others, but noise generated at the input and amplified by the receiver's full gain greatly exceeds the noise generated further along the receiver chain. The noise performance of a receiver is described by a figure of merit called the noise figure (NF). The term noise factor is synonymous, with some authors using the term "factor" for numeric and "figure" when using dB notation. (The notation "Fn" is also sometimes used instead of "NF".) The noise figure is defined as:A range of NF values is shown in Table 4.An ideal receiver generates no noise internally. The only noise in its output is received from external sources. That noise has the same characteristics as the noise resulting from thermal agitation in a conductor. Thermal agitation noise is caused by the continuous random motion of free electrons which are present in every conductor. The amount of motion is proportional to the conductor's temperature above absolute zero. For passive lossy networks, the noise factor equals the loss value for the passive element:A typical series of cascaded amplifiers is shown in Figure 3.Loss (negative gain) can be used for the gain value of attenuators or transmission line loss, etc to calculate the noise out of the installation as shown in the following equation:If the bandwidths of the amplifiers are the same, equation [6] becomes:Pre-amplifier Location Affects Receiver Input NoiseAs shown in Figure 4, if a 2 to 12 GHz receiver installation doesn't have enough sensitivity, it is best to install an additional amplifier closer to the antenna (case 1) instead of closer to the receiver (case 2). In both cases, the line loss (L) and the amplifier gain (G) are the same, so the signal level at the receiver is the same. For case 1, S1 = Pin + G - L. In case 2, S2 = Pin - L + G, so S1 = S2. The noise generated by the passive transmission line when measured at the receiver is the same in both cases. However, the noise generated inside the amplifier, when measured at the receiver input, is different.For this example, case 2 has a noise level at the input to the receiver which is 19.7 dB higher than case 1 (calculations follow later).* Amplifier NF value from Table 4.Using equation [3] and the data in Tables 5a and 5b, the noise generated by the RF installation is shown in Tables 6a and 6b (the negligible noise contribution from the antenna is the same in both cases and is not included) (also see notes contained in Table 4):Nout 2 - Nout 1 = 19.7 dB. The input noise of -74 dBm was calculated using 10 log (kTB), where B = 10 GHz.Note that other tradeoffs must be considered: (1) greater line loss between the antenna and amplifier improves (decreases) VSWR as shown in the VSWR Section, and (2) the more input line loss, the higher the input signal can be before causing the pre-amplifier to become saturated (mixing of signals due to a saturated amplifier is addressed in the Receiver Tests Section ).Combining Receive Paths Can Reduce SensitivityIf a single aircraft receiver processes both forward and aft signals as shown in Figure 5, it is desirable to be able to use the receiver's full dynamic range for both directions. Therefore, one needs to balance the gain, so that a signal applied to the aft antenna will reach the receiver at the same level as if it was applied to the forward antenna.Common adjustable preamplifiers can be installed to account for the excessive transmission line loss. In this example, in the forward installation, the level of the signal at the receiver is the same as the level applied to the antenna. Since the aft transmission line has 5 dB less attenuation, that amount is added to the preamplifier attenuator to balance the gain. This works fine for strong signals, but not for weaker signals. Because there is less loss between the aft preamplifier and the receiver, the aft noise dominates and will limit forward sensitivity. If the bandwidth is 2-12 GHz, and if port A of the hybrid is terminated by a perfect 50 ohm load, the forward noise level would be -65.3 dBm. If port B is terminated,the aft noise level would be -60.4 dBm. With both ports connected, the composite noise level would be -59.2 dBm (convert to mw, add, then convert back to dBm). For this example, if the aft preamplifier attenuation value is changed to 12 dB, the gain is no longer balanced (7 dB extra loss aft), but the noise is balanced, i.e. forward = -65.6 dBm, aft = -65.3 dBm, and composite -62.4 dBm. If there were a requirement to see the forward signals at the most sensitive level, extra attenuation could be inserted in the aft preamplifier. This would allow the forward noise level to predominate and result in greater forward sensitivity where it is needed. Calculations are provided in Tables 7 and 8.Aft NF = 22.79 therefore 10 log NF = 13.58 dB. Input noise level = -74 dBm + 13.58 dB = -60.42 dBm -60.4 dBmFwd NF = 7.495 therefore 10 log NF = 8.75 dB. Input noise level = -74 dBm + 8.75 dB = -65.25 dBm -65.3 dBmThe composite noise level at the receiver = -59.187 dBm -59.2 dBm* Gain Balanced ** Noise Balanced *** S/N was set at 12 dBTANGENTIAL SENSITIVITYTangential sensitivity (TSS) is the point where the top of the noise level with no signal applied is level with the bottom of the noise level on a pulse as shownin Figure 6. It can be determined in the laboratory by varying the amplitude of the input pulse until the stated criterion is reached, or by various approximation formulas.The signal power is nominally 81 dB above the noise level at the TSS point. TSS depends on the RF bandwidth, the video bandwidth, the noise figure, and the detector characteristic.TSS is generally a characteristic associated with receivers (or RWRs), however the TSS does not necessarily provide a criterion for properly setting the detection threshold. If the threshold is set to TSS, then the false alarm rate is rather high. Radars do not operate at TSS. Most require a more positive S/N for track ( > 10 dB) to reduce false detection on noise spikes.SENSITIVITY CONCLUSIONWhen all factors effecting system sensitivity are considered, the designer has little flexibility in the choice of receiver parameters. Rather, the performance requirements dictate the limit of sensitivity which can be implemented by the EW receiver.1. Minimum Signal-to-Noise Ratio (S/N) - Set by the accuracy which you want to measure signal parameters and by the false alarm requirements.2. Total Receiver Noise Figure (NF) - Set by available technology and system constraints for RF front end performance.3. Equivalent Noise Bandwidth (BN)- Set by minimum pulse width or maximum modulation bandwidth needed to accomplish the system requirements. A choice which is available to the designer is the relationship of pre- (BIF) and post-detection (BV) bandwidth. The most affordable approach is to set the post-detection filter equal to the reciprocal of the minimum pulse width, then choose the pre-detection passband to be as wide as the background interference environment will allow. Recent studies suggest that pre-detection bandwidths in excess of 100 MHz will allow significant loss of signals due to "pulse-on-pulse" conditions.4. Antenna Gain (G) - Set by the needed instantaneous FOV needed to support the system time to intercept requirements.。

经验模式分解摘要近些年来，随着计算机技术的高速发展与信号处理技术的不断提高，人们对图像的分析结构的要求也越来越高。

目前图像处理已经发展出很多分支，包括图像分割、边缘检测、纹理分析、图像压缩等.经验模式分解（EMD）是希尔伯特—黄变换（Hilbert—HuangTransform)中的一部分，它是一种新的信号处理方法，并且在非线性、非平稳信号处理中取得了重大进步,表现出了强大的优势与独特的分析特点.该方法主要是将复杂的非平稳信号分解成若干不同尺度的单分量平稳信号与一个趋势残余项,所以具有自适应性、平稳化、局部性等优点。

鉴于EMD方法在各领域的成功应用以及进一步的发展,国内外很多学者开始将其扩展到了二维信号分析领域中，并且也取得的一定的进展.但是由于二维信号不同于一种信号，限于信号的复杂性和二维数据的一些处理方法的有限性，二维经验模式分解(BEMD）在信号分析和处理精度上还存在一些问题,这也是本文要研究和改善的重点.关键词：图像处理;信号分解;BEMDAbstractIn recent years，with the rapid development of computer technology and the continuous improvement of signal processing technology，the demand for the analysis structure of the image is becoming more and more high. At present, many branches have been developed in image processing, including image segmentation, edge detection，texture analysis, image compression and so on。

Empirical mode decomposition (EMD) is a part of Hilbert Huang transform （Hilbert—HuangTransform）. It is a new signal processing method, and has made significant progress in nonlinear and non—stationary signal processing, showing strong advantages and unique analysis points。

欧盟、美国和日本的药物警戒信号管理体系比较研究作者：施雯慧巴磊周健姚捷张学宁王冠融谭晓艳孙志明来源：《中国药房》2021年第04期摘要目的：比较欧盟、美国和日本的药物警戒信号管理体系，为建立和完善我国药物警戒信号管理体系提供参考。

方法：采用文献研究分析法，系统对比欧盟、美国和日本的相关监管机构在药物警戒信号定义、来源、检测方法和管理流程等方面的异同，并对我国药物警戒管理工作提出建议。

结果与结论：欧盟、美国和日本的监管机构对于信号的定义并不统一，欧盟药品管理局采用国际医学科学组织委员会第8工作组的定义，美国FDA采用自定定义，而日本监管机构未有明确定义;目前欧盟、美国和日本的药品上市后安全性监测仍主要依靠自发报告系统，且均已开展基于自发报告系统的信号检测，其中欧盟以比例报告比值比法为主，美国以多项伽马泊松分布缩减法为主，日本以报告比值比法为主;欧盟对于信号管理流程设有专门的指南，而美国和日本尚缺乏。

建议我国应加快健全药物警戒法律法规体系，制定系统的药物警戒实践指南，加强药品不良反应主动监测，并推进数据挖掘方法在信号检测中的应用，以加速我国药物警戒工作的规范化、国际化进程。

关键词欧盟;美国;日本;药物警戒;信號;主动监测;数据挖掘;启示ABSTRACT OBJECTIVE： To provide reference for constructing and improving the pharmacovigilance signal management system in China by comparing signal management system among the European Union （EU）， the United States （U. S.） and Japan. METHODS：Literature analysis method was used to systematically compare the similarities and differences on definitions， sources， detection methods and management process of pharmacovigilance signals among EU， U. S. and Japan. Some suggestions were put forward for pharmacovigilance management in China. RESULTS & CONCLUSIONS：Regulatory authorities of the EU， U. S. and Japan did not have a uniform definition on signals; EU drug administration adopted the definition of the eighth working group of Council for International Organizations of Medical Sciences， FDA adopted its own definition， while the Japanese regulatory agency had no clear definition. Currently， post-marketing surveillance still relied mainly on spontaneous reporting systems; EU， U. S. and Japan had carried out the signal detection based on the spontaneous reporting system; EU mainly adopted the proportional reporting ratio method， U. S. mainly adopts the multiple gamma Poisson Shrinker， and Japan mainly adopted the reporting ratio method. EU had special guidelines for signal management process， while the U. S. and Japan did not. It is recommended to accelerate the deve- lopment of the legal and regulatory framework on pharmacovigilance in China， draw up guidelines on pharmacovigilance practices， strengthen the active ADR surveillance and promote the application of data mining techniques in signal detection field， for accelerating the standardization and internationalization of China’s pharmacovigilance work.KEYWORDS European Union; The United States; Japan; Pharmacovigilance; Signal; Active surveillance; Data mining; Enlightenment新药的上市前试验通常用于验证药品的疗效，以及发现药品最常见的不良反应。

Level Limit Switch nivotester FTL 325 NSingle channel and three channel isolating amplifier with NAMUR input for connecting any NAMUR measuring sensorApplication•Level limit detection in liquid tanks and hazardous areas•For FM / CSA Division 1 (Zone 0 or Zone 20) measuring sensors •Liquid detection in pipes for dry running protection for pumps•Over-spill protection for tanks with combustible or noncombustible which are dangerous to the environment •Two-point control and level limit detection with one switching unitFeatures and benefits•Intrinsically safe signal circuits (FM IS) for problem-free use of measuring sensors in explosion hazardous areas•High functional safety through–line monitoring through to sensor –corrosion monitoring on tuning fork of the Liquiphant M and Liquiphant S (high temperature)measuring sensors•Compact housing for simple series installation on standard rails in control room cabinets•Simple wiring using plug-in terminal blocks•NAMUR interface to EN 50227(DIN 19234; NAMUR) orIEC 60947-5-6 or IEC 60947-5-6 to connect NAMUR sensors or electronic insertsTechnical InformationTI 353F/24/aeThe Power of Know HowNivotester FTL 325 NEndress+HauserFunction and system designMeasuring principle2Signal transmissionThe intrinsically safe signal input of the Nivotester FTL 325 N limit switch is galvani-cally isolated form the power supply and signal output.The Nivotester supplies a DC voltage to the Liquiphant M and Liquiphant S measur-ing sensors with electronic inserts FEL 56 and 58, or a sensor specified to EN 50227(DIN 19234; NAMUR) or IEC 60947-5-6 via a two-wire loop. At the same time, a control current is transferred along the same supply line.The control current ranges from < 1.2 mA to > 2.1 mA depending on the switching status.Signal evaluationThe Nivotester measures and evaluates the control current which is transferred along the power supply line of the sensors. The level alarm relay signals if the measuring sensor is covered or free. An LED on the front panel of the of the Nivotester indicates the switching status of the relay. Faults, such as a line interruption or short circuit, are also displayed.Fail-safe circuitBy correctly selecting the fail-safe circuit, you can ensure that the relay always operates in a de-energized state. The error current signal of the connected sensor (<1.2 mA or >2.1 mA) for each channel can be set with the DIL switches on theNivotester. This means that the isolating amplifier can be used for any application at the required operational safety level.Combined with a level limit switch, the de-energized state is defined as follows:•Maximum fail-safe: the relay de-energizes when the switching point is exceeded (measuring sensor covered), or a fault occurs, or the power supply fails•Minimum fail-safe: the relay de-energizes when the material drops below the switching point (measuring sensor uncovered), or a fault occurs, or the power supply fails Function monitoringTo increase operational safety, the Nivotester is equipped with a function monitoring system. A fault is indicated by an LED and causes the level alarm relay to de-energize in the affected channel. A fault is signalled when the Nivotester receives no more control signals. This occurs, for example, in the event of a short-circuit, an interruption in the signal line to the measuring sensor, vibration forks becomecorroded, or a defect in the Nivotester input circuit. The function of each channel can be monitored by pressing the test button (on the front cover of the Nivotester), which when pressed, interrupts the power supply to the sensor.Endress+Hauser Nivotester FTL 325 N3Function of the level limit switch and the current pulse, dependent on level and fail-safe circuit.Function of the level limit switch and the current pulse, dependent on level and fail-safe circuit.NAMUR ModuleThe FTL 325 N is equipped with a NAMUR interface to EN 50227 (DIN 19234;NAMUR) or IEC 60947-5-6. This means that the control signals generated by any measuring sensor (according to NAMUR recommendations) can be evaluated by the Nivotester.NOTE: NAMUR = Normen AusschcuS fur MeS und Regel-technik; Standardisation Association for Measurement and Control in chemical and pharmaceutical industries.The following Endress+Hauser level limit switches are specified to EN 50227(DIN 19234; NAMUR) or IEC 60947-5-6 and can be connected to the Nivotester:•Liquiphant M with FEL 56 or FEL 58 electronic insert•Liquiphant S (high-temperature) with FEL 56 or FEL 58 electronic insertAll sensors specified to EN 50227 and contact switches with the appropriate resis-tance circuit can be connected to the Nivotester. When contact switches are used without resistance circuit, alarm detection for short-circuit and signal line interruption can be switched off for the appropriate channel.Two-point control (∆s)Two-point control is possible in one tank using the multichannel Nivotester (e.g. for pump control). The switching hysteresis is specified by the installation location of the two measuring sensors.Nivotester FTL 325 NEndress+Hauser4Measuring systemA measuring device consists of one to three measuring sensors, a 1, 2 or 3 channel Nivotester and control or signal devices. A Liquiphant M or S with FEL 56 / 58electronic inserts can be used as a measuring sensor. Alternatively, any number of sensors specified to NAMUR or contact switches with appropriate resistance circuit can be used.Single channel Nivotester FTL 325 N-#1#1The measuring device of the single channel instrument consists of:•One measuring sensor •Single channel Nivotester •Control or signal devicesThree channel Nivotester FTL 325 N-#3#3There are five possible variants of measuring devices with the three channel unit.1.When all three single channels are used for measuring the level limit, themeasuring device consists of:•Three measuring sensors •Three channel Nivotester •Control or signal devicesContact switch with appropriate resistance circuit.Endress+Hauser Nivotester FTL 325 N52.When channels two and three are used for two-point control ∆s, the measuringdevice consists of:•Two measuring sensors •Three channel Nivotester •Control or signal devices3.When channels two and three are used for two-point control ∆s, and channel onefor overspill protection, the measuring device consists of:•Three measuring sensors •Three channel Nivotester •Control or signal devices4.When channel two is used for measuring the level limit with two level limit relaysand channel one is used for measuring other level limits, the measuring device consists of:•Two measuring sensors •Three channel Nivotester •Control or signal devicesNivotester FTL 325 NEndress+Hauser6Input parametersMeasured variable The limit signal can be triggered at minium or maximum height as required.The measuring range is dependent on the installation location of the sensors.•Input for FTL 325N: galvanically isolated from power supply and output.•Protection type: FM Intrinsically Safe, Class I, II, III; Division 1, Groups A-G.CSA Intrinsically Safe, Class I, II, III; Division 1, Groups A-G.•Connectable measuring sensors:- Liquiphant M FTL 50/51, FTL 50 H/51 H, FTL 51 C with electronic insert FEL 56 or FEL 58.- Liquiphant S (HT) FTL 70/71 with electronic insert FEL 56 or FEL 58.- Any number of sensors specified to EN 50227 (DIN 19234; NAMUR) or IEC 60947-5-6.- Contact switches with appropriate resistance circuit.•Measuring sensor power supply: from FTL 325 N Nivotester.•Connecting line: two-wire, shielding not required.•Line resistance: maximum 25 Ω per wire.•Signal transmission: current signal on power supply line.•Control current range: < 1.2 mA / > 2.1 mA.•Line interruption monitoring: < 200 µA and short-circuit > 6.1 mA (can be switched off).Further details for installing measuring sensors outside explosion hazardous zones can be found in the appropriate certificates.Output parameters•Relay output per channel: one potential-free relay contact for the level alarm.•De-energized current safety circuit: the function of the de-energized current safety circuit is dependent on the setting made on the electronic insert FEL 56 or 58sensors and on selection of the error current signal on the Nivotester.•Switch delay: approximately 0.5 seconds.•Switching power of the relay contacts:AC versionV ~ maximum 253 V I ~ maximum 2 AP ~ maximum 500 VA at cos ϕ >= 0.7 (power factor)DC versionV = maximum 40 V I = maximum 2 A P = maximum 80 W•Life: at least 105 switching operations at maximum contact load.•Function displays: LEDs for operation, level alarm and fault.Measuring range Input signalOutput signal5.When channel two is used for measuring the level limit with two level limit relays,the measuring device consists of:•One measuring sensor •Three channel Nivotester •Control or signal devicesNOTE: Since channel one is not used, the alarm must be switched to “OFF”.Endress+HauserNivotester FTL 325 N7Fault signal Galvanic isolationPower supplyElectrical connectionTerminal blocksThe removable terminal blocks are separated into intrinsically safe connections (at the top of the unit) and non-intrinsically safe connections (at the bottom of the unit).Terminal blocks are different colors to easily distinguish between the two types. Blue blocks are for the intrinsically safe section and grey for the non-intrinsically safe blocks. This ensures safety when wiring unit.Connecting the measuring sensor (the upper, blue terminal blocks)The two-wire connecting line between the Nivotester and the Liquiphant, Nivopuls or Soliphant measuring sensor can either be a commercially available installation cable or wires in a multi-wire cable for instrumentation purposes. Line resistance may be a maximum of 25 Ω per wire. If strong eletromagnetic interference is expected, e.g.from machines or radio devices, a shielded cable must be used. Only connect the shield to the ground connection, and not to the Nivotester.Using the measuring system in explosion hazardous areasPlease observe all local codes and regulations on explosion protectionconcerning the type and installation of intrinsically safe signal wiring. Please refer to the Safety Instruction XA 134F for maximum permissible values of capacitance and inductance.Connecting signal and control devices (the lower, grey terminal blocks)The relay function is dependent on the level and fail-safe circuit. If an instrument is connected at high inductance (e.g. contactor, solenoid valve, etc.), a spark suppres-sor must be installed to protect the relay contact.Connecting the supply voltage (the lower, grey terminal blocks)For voltage variations, refer to the Ordering Information section. A fuse is built into the power supply current circuit. This eliminates the need to connect a fine-wire fuse in series. The Nivotester is equipped with reverse polarity protection.AC version:•85 to 253 VAC, 50/60 Hz DC version:•20 to 60 VDC•DC supply, maximum 60 mA (one channel unit)•DC supply, maximum 115 mA (three channel unit)•Permissible residual ripple witin tolerance: V pp = maximum 2 V AC version:• 1.75 W maximum (one channel unit)• 2.25 W maximum (three channel unit)DC version:• 1.2 W maximum, at V min 20 V (one channel unit)• 2.25 W maximum, at V min 20 V (threee channel unit)Final switching status after switching on the power supply, approximately 10 to 20seconds, depending on the connected measuringPower supplyPower consumptionSetting time/lengthRelay de-energized, fault is indicated by red LEDsAll input and output channels and relay contacts are galvanically isolated from each other.Nivotester FTL 325 NEndress+Hauser8Operating conditions, installationInterference emission to EN 61326, Class B apparatusInterference emission to EN 61326, Appendix A (industry) and NAMUR Recommendation NE 21 (EMC)Electromagnetic compatibility (EMC)Endress+Hauser Nivotester FTL 325 N9Mechanical constructionDimensionsMounting distancesAll dimensions are in inches (mm)MaterialsHousing: Polycarbonate, light grey, RAL 7035Front cover: Polyamid P A6, blueRear connection (for top-hat DIN rail): Polyamid P A 6, black, RAL 9005Installation: on top-hat DIN rail, 35 x 7.5 mm or 35 x 15 mm to EN 50022Single channel: approximately 5.2 oz. (148 g)Three channel: approximately 8.8 oz. (250 g)WeightNivotester FTL 325 NEndress+Hauser10Connection terminalsSingle channel• 2 screw terminals, sensor power supply • 3 screw terminals, limit value relay• 2 screw terminals, SPST fault signal relay • 2 screw terminals, power supply Three channel• 3 x 2 screw terminals, sensor power supply, channel 1 to 3• 3 x 3 screw terminals, limit value relay LV-REL 1 to 3• 2 screw terminals, SPST fault signal relay • 2 screw terminals, power supply Connection cable cross section•maximum for single core, 0.004 in 2 (2.5 mm 2) or two core 0.002 in 2 (1.5 mm 2)Display and user interfaceOn-site setting with switches located behind hinged front panel (refer to graphic, page 11).•Green LED, standby•One red LED per channel for fault signaling•One yellow LED per channel for relay energizedOperating concept Display elementsEndress+Hauser Nivotester FTL 325 N11Operating elementsOne channel unit•Switch for fault current signal 2.1 mA / 1.2 mA •Switch for fault on/off setting Three channel unit•Switch for fault current signal 2.1 mA / 1.2 mA •Switch for fault on/off setting•Switch for “Single Channel” function (up to three channels)•Switch for “∆s”•Switch for one channel with “two parallel switched limit value relays”Certificates and approvalsCE markBy attaching the CE mark, Endress+Hauser confirms that the instrument fulfills all the requirements of the relevant EC directivesFM approved intrinsically safe, Class I, II, III; Division 1, Groups A-G CSA intrinsically safe, Class I, II, III; Division 1, Groups A-G•EN 50227 (DIN 19234; NAMUR) or IEC 60947-5-6, Interface (level limit) to NAMUR Recommendations•EN 60529, type of ingress protection for housing•EN 61010, safety specifications for electrical measurement, control and laboratory instruments•EN 61326, interference emission (Class B apparatus), interference immunity (Appendix A - Industry)Hazardous area approvals Other standards and guidelinesTI 353F/24/ae/08.03© 2003 Endress+Hauser, Inc.For application and selection assistance,in the U.S. call 888-ENDRESSFor total support of your installed base, 24 hours a day, in the U.S. call 800-642-8737Visit us on our web site, Supplementary documentationAccessoriesOrdering informationProtective housing, NEMA 4 rated (IP 66) equipped with integrated top-hat rail for mounting Nivotester unit(s), clear plastic cover which can be lead-sealed.7.09” W x 7.17” H x 6.50” D (180 x 182 x 165 mm).Part Number: 52010132Protective housingLiquiphant M FTL 50/51, FTL 50H/51H measuring sensor for level limit detection in liquids: TI 328F/24/aeLiquiphant M FTL 51C measuring sensor for level limit detection in liquids with corrosion-resistant coating: TI 347F/24/aeLiquiphant S FTL 70/71 measuring sensor for level limit detection in high temperatures up to 536°F (280°C): TI 354F/24/ae Protective housing: TI 355F/01/enOperating instructions, FTL 325 single channel: KA 170F/00/a6Operating instructions, FTL 325 three channel: KA 171F/00/a6FTL 325 N -1CertificatesO FM IS Cl. I,II, III; Div. 1, Grps. A-G S CSA IS CI. I, II, III; Div. 1, Grps. A-G 2Version1Top-hat rail installation, single channel 3Top-hat rail installation, three channel 3Voltage supplyA 85 to 253 VAC, 50/60 Hz E 20 to 30 VAC / 20 to 60 VDC 4Output1 1 level relay, SPDT; 1 alarm relay, SPST 3 3 level relays, SPDT; 1 alarm relay, SPSTNivotester FTL 325 N1 2 3 4。

8th International Conference on Manufacturing Science and Engineering (ICMSE 2018)Design Method of the Measuring System for the Mirror Surface Spacingof a compound lensPing Zhong1,a,Shaohui Pan1,b, Zhisong Li2,c and Xingyu Gao1,d1College of Science, Donghua University, Shanghai 201620, PR China2College of Information Science and Technology, Donghua University, Shanghai 201620, PR China a b*****************,c****************,d*****************Keywords:Optical fiber low coherence interference, lens mirror space, Signal-to-noise ratio, Band-pass filter, least square methodAbstract:Based on the principle of low coherent light interference of optical fiber, a new method for detecting the distance between the mirror surfaces of a compound lens is proposed. Firstly, a system based on the principle of low coherent light interference is designed. Secondly, the frequency calculation method of interference signal of measurement system is put forward, and the band-pass filter is designed for interference signal to improve the signal-to-noise ratios. Based on the characteristics of low coherence light interference signal, the least squares symmetric peak location algorithm is proposed, which realizes the precise locating of the peak of the interferometric signal. Besides, the experiment of measuring the distance between the compound lens is carried out and the measurement error is analyzed.IntroductionIn the manufacture of optical instruments, the center thickness machining precision and assembly precision of the lens have an important influence on the imaging quality of the optical system. Especially in high-performance precision optical systems such as aviation, aerospace and microscope systems, there are strict control requirements for the lens center thickness and the mirror spacing. So, how to get high precision measurement results is a challenging topic. At present, the method for measuring distance between the mirror surfaces of a compound lens is mainly divided into two types, the one is contact measurement and the other is non-contact measurement. The structure of contact measurement is relatively simple, but it has a large defect itself, such as easy to scratch the lens and destroy the lens. The frequent contact between the surfaces of the probe and lens can also make the worn lenses and affect the measurement accuracy. Non-contact measurement system is relatively complex, but it can perform nondestructive testing on the lens group. It is mainly to measure the relative position of the mirror surface by measuring the reflection signal of the lens surface. The methods mainly include image method [1], axial dispersion [2], differential confocal method [3], image calibration method [4, 5], etc. Low-coherence optical interferometry, as the main detection method of non-contact measurement for optical devices, is one of the hotspots today. In this paper, based on the principle of low-coherence light interference, a system for measuring the lens spacing of the compound lens is designed and the main factors affecting the detection accuracy are studied, and the effective method for signal filtering and waveform peak location is proposed.Measurement principle and system design of lens spacingLow-coherence light interferometry [6-12] is an interferometric technique using a broad-spectrum light source as a coherent light source. The coherence length is short and the interference peak can be generated only when the optical path of the measured light and the reference light is equal, so it has a good spatial positioning characteristic. By calculating the distance between the interference peaks at the apex of the front and rear mirror surfaces, the lens group spacing and the center thickness of the lens can be calculated. In this paper, the basic structure of Michelson interferometer is adopted, in which the light emitted the light source is passed through the optical fiber coupler to produce the measured light and the reference light respectively. On the one hand, the reflected signal come from the different surfaces of the sample has a different optical path. On the other hand, the referenceCopyright © 2018, the Authors. Published by Atlantis Press.This is an open access article under the CC BY-NC license (/licenses/by-nc/4.0/). 649optical path will change with the position of the reference mirror. Only the reflected signal from a specific location of the sample can be coherent with the reference light, where the location of the maximum intensity of coherent signal corresponds to the equal optical path position. The structure of the lens spacing measurement system is designed as shown in Fig.1.Fig.1. Lens group spacing detection system diagramThe light emitted from the wide-spectrum light source SLD (center wavelength 1310 nm, half-wave width 85 nm) is split by the fiber coupler and then enters the circulator 1 and the circulator 2, and forms measurement light and reference light, respectively. In order to facilitate the installation and debug the detection system, the visible light with the wavelength of 660nm and the measured light are mixed in the wavelength division multiplexer, and then, they are projected onto the front and back surfaces of the lens group by the collimator and reflected by the front and back surfaces of the lenses in the compound lens. Finally, the reflected light is shot into the ring through the collimator and the wavelength division multiplexer and recoupled into the optical fiber system from the port 3. In the same way, the reference light is reflected by a movable plane reflector. The returned reference light is ejected through port 3 of the ring and interferes with the measured light in the optical fiber coupler. The returned reference light is ejected through port 3 of the ring and interferes with the measured light in the optical fiber coupler. The path of the reference light can be changed by driving a plane reflector to move uniformly in a straight line. When the optical path of the measured light is equal to that of the reference light, that is, when the optical path difference is zero, the interference signal is strongest, at this time the maximum wave peak signal can be detected by the computer.Since the measuring beam contains many light rays reflected from the front and rear surfaces of multiple lenses, there will be multiple sets of maximum wave peaks in the process of moving plane reflector. According to the relative position of two zero light path difference, the measurement of lens spacing of compound lens can be completed. In the process of measurement, the information of the plane reflector is recorded in real time by a high resolution grating scale displacement sensor. In order to suppress the common-mode noise of the system and improve the signal-to-noise ratio of the system as much as possible, the system proposed in this paper uses a balanced detector for the photoelectric conversion of the interference signal. Then the data acquisition card is controlled by the computer, and the signal is processed by the computer. In order to further suppress the noise, a signal filter is designed.Signal filtering and waveform peak locationDesign of band-pass filterIn the detection system, the intensity of reflected light of the plane mirror is higher than the intensity of the tested lens. When the intensity ratio of the incident light passing through the reference light and detection light is 50:50, the interference signal is very weak. Fig.2(a) shows the waveform of the interference signals. In this case, the peaks of interference signals are difficult to extract. Through experiments, we can set the intensity ratio of the incident light passing through the reference light and detection light as 80: 20, and the output interference signals are very obvious as shown inFig.2(b).650Fig.2. The comparison of interference signal intensity.(a) the waveform of the interference signals while theintensity ratio is 50:50; (b) the waveform of the interference signals while the intensity ratio is 80:20It can be seen from Fig.2 (b) that, although the strong contrast interference signal can be obtained by setting the light intensity ratio between the reference light and detection light, the interference signal are often mixed with noise, which directly affects the location of peak signal. In this paper, a band-pass filter is designed to suppress the noise signal and improve the signal-to-noise ratio [13,14].The center wavelength of the designed filter can be calculated. Assuming that the moving speed of the plane mirror on a guide rail is mm/s during detection process and the center wavelength of the broadband light source is λ nm, then the center wavelength ( f ) of the filter can be calculated by the Eq.(1):=(2 ∕ )×10 . (1)For the system designed in this paper, v is 3.78mm/s , the wavelength rang of the broadband light source is 1290∼1330 nm, λ is 1310nm , thus the f =5.77×10 kHz and the frequency range of a band-pass filter is from 4.77kHz to 6.77kHz , and the center frequency can be selected as 5.77kHz .Method for locating the peak of interference signalIn this paper, the location of the peak of interference signal is the key to detection of lens spacing and can be determined by extracting the signal envelope. According` to the principle of low coherence interference, the wave peak of interference signal represents the interference generation between the reference light and detection light at zero optical paths. For measuring system, as long as the optical path difference between the two peaks of the interferometric signal from the lens group is obtained, the distance between the lenses of compound lens can be obtained. A simple method is to use the peak signal to determine the location of the zero optical path difference. However, because the adjacent extreme signals are so close to each other, the noise introduced in the detection process can easily cause location error which will lead to poor repeatability accuracy of the measurement system. The Gauss fitting algorithm has the advantage of locating peaks, but it requires that the interference signal has good symmetry. So it cannot meet the requirements of the system designed in this paper. In this paper, a symmetric peak location algorithm based on the least square method is proposed.First, the acquired interference signals are preprocess. Fig.3(a) shows the primary signals collected. The position of the mean value of the intensity is set to the abscissa axis. Fig.3(b) shows the sum of the absolute values for the same position signals. The envelope image of the signals is represented by a dotted line shown in Fig.3(b).According to the theory of partial coherence, when the value of function of the location points in envelope curve is greater than 1/e of the maximum value, these points are directly related to the coherence length of the light source. So the signals whose value is greater than 1/e of the maximum value point are selected as an effective processing signal, and then the location of peak signal can bedetermined by the a symmetric peak location algorithm based on least square. 651Fig.3. The method of locating signal peak.(a) The primary signals collected; (b) Envelope image of signal The method can be described as follows: i) Firstly, all points whose values are greater than 1/e of the maximum are selected, and then these points are plotted as a curve which called the original curve, it can be seen in Fig.4(a). After that, a symmetry axis which is parallel to the vertical axis and passes through the maximum value point of the original curve is drawn, then, the original curve revolves around the symmetry axis and forms another curve which is called revolved curve. ii) The revolved curve is moved left or right along the horizontal axis. Meanwhile, the mean square error between the original curve and the revolved curve is calculated. When the mean square error obtained is the smallest, the best translational position to the revolved curve is determined. iii) The revolved curve was moved according to the translation amount, as shown in Fig.4(b). Finally, the symmetrical position of the two curves is used as the zero-path difference position. The method utilizes the least squares method can equalize the errors brought by the interference signals and the measurement error and the system error can be effectively reduced.Fig.4. The method of locating wave crests.(a) Flip chart; (b) Flipping the curve after translationSpecular distance measurement experiment and error analysisAccording to the design principle of lens spacing detection system, a measurement system is set up as shown in Fig.5. Among them, the center wavelength of the detection system is 1310nm, and the half wavelength width of the SLD wide spectrum light source is 85nm, and its optical power is 10.8mW.Fig.5 Measurement test system for detecting the distance between the mirror surfaces of a compound lens (1) a wave division multiplexer, (2) Circulator 1, (3) 80/20 fiber couplers, (4) Circulator 2, (5) 50/50 opticalcouplers, (6) the single mode fiber , (7) balance detector652In order to test the measurement accuracy of the system designed in this article, an achromatic composite lens group is selected to perform experiment for detecting distance between the mirror surfaces. Among them, the compound lens includes 7 groups of lenses, and the structure of the combined lens is shown in Fig.6.Fig.6 The structure of the lens group to be measuredAccording to the experimental system and the detection algorithm, the measurement of the lens spacing of the compound lens is carried out. The interference signal improvement is very obvious, and the output interference signal waveform was shown in Fig.7(a), and Fig.7(b) is the waveform of the interference signal after filtered.Fig.7 Measurement of the waveforms of the interferometric signal in the lens group, (a) the waveforms of theinterfering signal before filtering,(b) the waveforms of the interfering signal after filteringIn order to evaluate the accuracy and stability of the test system, the lens group has been measured for many times. Table.1 lists the design values of the measured lenses, the average values of the ten measurements and the standard deviation calculated.Table.1 Measurement data of spacing thickness of lens groupSampleDesign thickness or spacing[mm] The mean value of measuring thickness or spacing [mm] Standard deviation[nm] Lens 15 .00 5.0327 59 Air gap 1-26.00 6.0155 101 Lens 25.00 4.9879 127 Air gap 2-35.00 5.0214 167 Lens 36.00 5.9897 201 Air gap 3-45.90 5.8591 221 Lens 46.00 6.0319 260 Air gap 4-58.00 7.9981 239 Lens 55.00 4.9794 327 Air gap 5-618.00 17.8951 389 Lens 65.00 5.0124 372 Air gap 6-77.00 6.9978 408 Lens 77.00 7.0214425 653According to the results of the measurement data, it can be seen that the relative intensity of the reflected light on the lens surface at the rear end of the lens group is weak and the standard deviation of measurement is relatively large due to the influence of the number of lenses contained a compound lens and the reflection loss of the lens surface. With the increase of the number of lens to be measured, the interference signal gradually get weakened and the precise of the positioning accuracy of the zero optical path difference position be reduced，which will lead to an increase in the measurement standard deviation in measuring the lens spacing of the compound lens.ConclusionIn this paper, based on the low coherent light interference method, a system for measuring the lens spacing of the compound lens is designed. A calculation method of interference signal frequency in measurement system is put forward, and a bandpass filter is designed, which can effectively improve the signal-to-noise ratio of the interferometric signal. The fitting method of the interference signal envelope is proposed. Based on the characteristics of the low-coherence interference signal, we used a least-squares correction information positioning method, which effectively improves the repeatability of the measurement. Finally, by testing the lens spacing of the combined lens, the effectiveness of the proposed design method is proved. The detection system not only is convenient, fast, and has no damage to optical devices, but also has high precision and strong stability. It has a good application prospect in optical processing and optical detection.AcknowledgementsThis work is supported by the National Natural Science Foundation of China (Grant No.51575099)References[1] A.V. Goncharov, L.L. Bailon and N.M. Devaney. Spie:Vol.7389(2009),p.738912.[2] M. Kunkel, J. Schulze. Glass Science and Technology: Vol.78(2005),p.245.[3] L.B. Shi, L.R. Qiu and Y. Wang. Chinese Journal of Scientific Instrument :Vol. 33(2012),p. 683.[4] H.W. Gao, H. Wang, Y.Y. Liu and Y. Yu. Journal of Electronic Measurement and Instrument:Vol.31(2017),p.820.[5] J.H. Zhang, Q Liu and R.H. Nie.Spie:Vol.36(2016),p.174.[6] P. Langehanenberg,A. Ruprecht. Spie:Vol.8844(2013),p.88444F.[7] J. Benitez, J. Mora.IEEE Photonics Technology Letters:Vol.29(2017),p.1735.[8] S. Merlo, P. Poma and E. Crisa. Sensors:Vol.17(2017).[9] O. Martinez-Matos, C. Rickenstorff and S. Zamora. Optics Express:Vol.25(2017),p.3222.[10] R. Abuter, M. Accardo and A .Amorim. Astronomy & Astrophysics:Vol.602(2017).[11] R.W Kunze, R. Schmitt. Tm-Technisches Messen:Vol.84(2017),p.575.[12] K.Li, M. Jiang, Z.Z. Zhao and Z.M.Wang. Optics Communications:Vol.389(2017),p.234.[13] J.M.Tang, H.W. Liu, Q.F. Zhang, B.P. Ren and Y.H. Liu. IEEE Transactions on AppliedSuperconductivity:Vol.28(2018).[14] H Lu, Z.Q. Yue and J.L. Zhao. Optics Communications:Vol.414(2018).654。

第 50 卷第 4 期2023 年 4 月Vol.50，No.4Apr. 2023湖南大学学报（自然科学版）Journal of Hunan University （Natural Sciences ）基于超声TOA 的环境感知王刚†，张文静 ，邱文浩（湖南大学 汽车车身先进设计制造国家重点实验室，湖南 长沙 410082）摘要：针对超声波传感器测量过程中方位角存在不确定性的问题，提出了一种基于超声反射波到达时间（Time of Arrival ，TOA ）的目标距离及方位角的测量方法，并据此发展了基于超声探测的环境感知方法.基于混合高斯拟合对回波信号进行处理，消除了信号串扰问题，提高了目标距离和方位信息的测量精度.基于传感器波束角的特性，实现了不同距离下目标的同时测量.通过引入“不确定度”，构建信度分配函数，采用DSmT （Dezert-Smarandache Theory ）方法进行数据融合，实现地图更新.搭建了实验装置与实验环境，并对相关方法进行了实验验证，实验结果表明，通过135次测量即可实现对环境基本轮廓的建图，建图误差在3 cm 以内.关键词：超声波传感器；到达时间；Dezert-Smarandache 理论；栅格地图中图分类号：TP24 文献标志码：AEnvironment Perception Based on Ultrasonic TOAWANG Gang †，ZHANG Wenjing ，QIU Wenhao（State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body ， Hunan University ， Changsha 410082， China ）Abstract ：In order to solve the uncertainty of azimuth in the ultrasonic sensor measurement process ， a targetdistance and azimuth measurement method based on time of arrival （TOA ） is proposed ， and an environment sensing method based on ultrasonic detection is developed. The echo signal is processed based on the mixed Gaussian fit⁃ting ， which eliminates the problem of signal crosstalk and improves the measurement accuracy of target distance and azimuth information. Based on the characteristics of the sensor beam angle ， the simultaneous measurement of targets at different distances is achieved. By introducing “uncertainty ”， a set of belief assignment functions is defined ， andthe DSmT （Dezert-Smarandache Theory ） method is used for data fusion to realize map updates. Finally ， the experi⁃mental device and environment are constructed for verification ， and the result shows that the basic contour of the en⁃vironment can be built through 135 measurements ， and the mapping error is less than 3 cm. Key words ：ultrasonic sensors ；time of arrival （TOA ）；Dezert-Smarandache theory ；grid map同时定位与地图构建（Simultaneous Localizationand Mapping ，SLAM ）是机器人进行环境感知以及定位导航的关键技术［1］.目前主流的SLAM 技术主要基于激光或者视觉，但是在一些极端恶劣环境下，例如∗收稿日期：2022-04-07基金项目：国家自然科学基金资助项目（11772123），National Natural Science Foundation of China （11772123）作者简介：王刚（1975―），男，湖南长沙人，湖南大学教授，博士生导师，博士† 通信联系人，E-mail ：*************.cn文章编号：1674-2974（2023）04-0021-10DOI ：10.16339/ki.hdxbzkb.2023151湖南大学学报（自然科学版）2023 年火灾导致的浓烟，受限于光波穿透能力，激光和视觉传感器的性能均会受到影响.与基于光的环境感知手段相比，超声波传感器具有成本低、抗环境干扰力强等优点，适用于上述恶劣环境，在环境感知领域已经有所运用［2-4］.在基于超声波传感器的SLAM建图过程中，由于传感器波束角往往较大，波束角范围内的回波信号都会被检测到，因此其测量结果在测量方位上存在较大的不确定性［5］.Tardós等［6］通过声呐扫描进行多次测量来获取反射物的位置信息时，由于波束角很宽，无法确定回波的具体方向，只能用声呐的中轴代替回波方向，这种方法存在明显的角度误差.为了解决超声波传感器测量方位存在不确定性的问题，Bank等［7］提出了切向回归技术，通过将超声波传感器检测到的锥形区域的重叠部分进行融合，并拟合边界直线段来获得环境地图，但这种方法只能检测较为简单的平面目标，对曲面特征的对象难以应用.金世俊等［2］在2009年通过贝叶斯法对每一次测量的扇形区域进行融合，实现栅格地图的更新.Lee等［8］提出一种基于模糊传感器融合从而建立栅格地图的方法.Li等［9］、Yuan等［10］通过引入不确定度，提出了利用DSmT理论进行数据融合来更新地图的方法.以上方法均未从根本上解决传感器的角度信息不确定性的问题，而是通过对多次测量得到的多个扇形区域进行融合，来间接减小超声波传感器测量方位的不确定性，因此上述方法均需要较多的测量次数，建图效率低，计算量较大.本文提出了一种基于超声反射波到达时间（Time of Arrival，TOA）的环境感知方法，通过比较超声回波到达不同传感器的时间，获得反射点的距离和方位，从而在根本上解决了测量方位的不确定性问题.同时，该方法还能对处于波束角内不同距离下的反射物体进行识别与区分，从而进一步减少了测量次数，提高了建图效率.在信号处理方面，利用混合高斯拟合和阈值检测法对回波信号进行处理，解决了信号串扰，提高了TOA测量结果的准确度.继而，基于DSmT（DeZert-Smarandache Theory）的数据融合方法，进行了栅格地图建模，进一步减小了测量误差引起的建图误差.最后通过搭建实验装置和实验环境验证了本文所提出的方法.实验结果表明，所提出的方法较好地复现了环境轮廓，且建图误差在3 cm以内.1 基于TOA的超声回波测量在超声波传感器测量过程中，其波束角范围内的回波信号都会被检测到，而原有的方法只能得到反射物体的距离信息，无法得到其回波方向，从而导致传感器测量方位的不确定性.因此，通常利用指定距离上的扇形区域来表示目标可能存在的位置，并通过融合多个扇形区域来获得反射物体的精确位置［2，8-11］，这种方法需要较多的测量次数.本文通过TOA来获得反射物体的方位角信息，以此来解决方位角的不确定性问题.TOA是一种以信号到达时间为基础，结合测距来获得位置信息的方法.图1（a）是本实验采用的超声测量装置，其中处于装置中间位置的传声器T用于发射超声波信号，左右两侧的传声器R1、R2用于接收超声回波信号.超声波传感器主要有静电式和压电式，静电式超声波传感器工艺复杂，需要较高的偏置电压，而压电式超声波传感器具有带宽较窄、在中心频率处的灵敏度高以及输出信号能量大的特性，因此本实验采用压电式超声波传感器.另外，超声波传感器的工作频率与测量的精确度正相关，而与信号传播距离负相关，因此超声波传感器需要选择合适的工作频率.通过实验测试发现，发射传声器的驱动电压与超声的测量范围正相关.即增大发射传声器的驱动电压，可以增大超声的测量范围.本文发射传声器工作在48 V驱动电压下，在2 m的距离范围内，工作频率为25 kHz的超声波传感器可以接收到清晰的回波信号，因此本文选用图1（b）所示工作频率为25 kHz的压电式超声波传感器.超声测距装置单次测量的步骤是：发射传声器T （a）超声波传感器装置图（b）超声接收器（左）及发射器（右）图 1 超声测量装置Fig. 1 Ultrasonic ranging device22第 4 期王刚等：基于超声TOA 的环境感知发出超声波脉冲信号，经反射物体的反射后，分别到达左右接收传声器R 1、R 2.通过对获取的信号进行信号处理，得到回波信号的到达时间，再与超声信号发射的起始时间求差，即可以得到超声回波信号的传播时间.当测量距离远大于传感器的间距时，反射物体的形状对反射点的测量距离和角度的影响很小［12］，因此在测量范围内对于连续光滑的反射物体，无论是什么形状，其轮廓在局部范围内都可以简化为一段直线，用这种方法得到的测量结果对于弧面也同样适用.为方便叙述，下文用反射区域来表示这一直线段.如图2所示，对于反射物体，回波信号相当于是发射传声器T 的平面镜像T'发出的，根据TOA 可以得到接收传声器R 1和R 2分别到虚拟发射传声器T'的距离L 1和L 2，d 为超声波传感器之间的距离.根据几何关系，可以得到发射传声器T 与反射区域的垂直距离L f 及反射区域的垂线与传声器连线之间的角度θ.L f =（1）θ=arccos(L 21-L 224dL f)（2）同时，由于传声器具有一定的波束角，为了保证信号的接收效果，信号回波方向与传声器中轴线的夹角ψ应该小于波束角，根据几何关系，可以得到：d ≥||L 1-L 22sin ψ（3）为了满足公式（3）以及保证传声器间距远小于测量距离，本文选取d =30 cm.可见，基于TOA 的测量方法可以直接得到反射区域回波的角度信息，而不需要融合多次测量数据来减小方位角的不确定性，因此该方法在保证精度的同时，大大提高了SLAM 建图效率.2 超声回波信号处理2.1 基于阈值检测和混合高斯拟合的信号处理根据文献［13］，接收传声器收到的回波信号可近似为：y (t )=x (t -t 0)cos [2πf 0(t -t 0)]+w (t )（4）其中，x (t -t 0)=a 0e -a 1()t -t 0(t -t 0)2u (t -t 0)（5）式中：u (t -t 0)是延时为t 0的阶跃函数，t 0对应脉冲的起始时间；a 0、a 1是信号的幅值和衰减系数；w (t )是均值为0的白噪声.以图3中细实线所示的某次测试得到的超声回波信号为例，通过选取合适的公式（5）中的参数a 0、a 1，可得到图3中短点线所示的理论回波信号的包络线.由于实际回波信号的包络线会随着反射物体位置的变化而改变，同时该理论回波信号包络线的后半部分会偏离实际回波信号，导致该包络线与实际回波信号的包络线重合度低.因此，根据公式（4）和（5）对应的理论回波信号，无法求得准确的脉冲起始时间.针对这个问题，本文通过对实际测量得到的回波信号进行分析，发现由3个高斯曲线叠加而成的混合高斯曲线能较好地拟合回波信号的包络线.该混合高斯拟合曲线的表达式如下：图 2 基于TOA 的超声测距几何示意图Fig. 2 Geometry of ultrasonic ranging based on TOA图 3 混合高斯拟合信号Fig. 3 The mixed Gaussian fitting signal23湖南大学学报（自然科学版）2023 年V g (t )=a 1exp ()-(t -b 1)2c 1+a 2exp ()-(t -b 2)2c 2+a 3exp ()-(t -b 3)2c 3（6）式中：a 1、a 2、a 3为各高斯函数的混合系数；b 1、b 2、b 3和c 1、c 2、c 3分别为各高斯函数的均值和方差.采用混合高斯拟合方法对图3所示的实测超声回波信号的包络曲线进行拟合，得到图3中粗实线所示的混合高斯拟合曲线.由图3可见，混合高斯拟合曲线与回波信号的包络线几乎完全重合，因此该高斯拟合曲线可以代替回波信号用于阈值检测，从而判断波达时间.通过多次测量发现，超声回波信号的包络线在第一次达到峰值的75%左右时，信号增长速度最快，即斜率最大，故此处的时间信息受噪声干扰的影响也最小.因此选取混合高斯拟合曲线第一次达到其峰值75%的时间作为波达时间.2.2 基于混合高斯拟合曲线的信号串扰抑制由于超声波传感器的波束角较大，因此当传感器之间的距离过近时，发射传声器产生与其中轴呈90°的旁瓣信号会直接传播到接收器.同时，根据压电式超声波传感器的工作原理，发射传声器在发出超声信号的同时，也会激发其壳体的机械振动，并通过传声器固定装置传播到接收传感器，进而引起其中敏感元件的响应.为了表述方便，本文用直达波信号来表示由这两种因素导致的传声器接收到的信号.当反射物体距离测量系统较近时，反射信号与直达波信号发生重叠，从而引起接收传声器的内部串扰现象［14-15］.图4可以很直观地解释内部串扰现象，图4中细实线代表实际测量得到的超声回波信号，虚线表示实际回波信号的包络线.其中回波信号的第一个峰对应于直达波信号，第二个峰对应于反射信号.由于目标较近，反射信号的传播时间较短，直达波信号的尾部，部分会与反射信号发生重叠，从而导致反射信号的峰值前移，引起波达时间的测量误差.通过多次测量发现，对于相同的传感器阵列，左右接收传声器测量得到的直达波信号基本保持不变.基于这个特性，本文先在无反射物体的情况下进行测量，得到直达波信号的混合高斯拟合曲线；而后，在每次正常测量后，将测量信号的包络线减去之前得到的直达波信号的混合高斯拟合曲线，就可以基本消除测量距离过近带来的信号重叠干扰.处理后信号的包络线V c (t )的表达式为：V c (t )=V (t )-V g (t )=V (t )-a 1exp ()-(t -b 1)2c 1- a 2exp ()-(t -b 2)2c 2-a 3exp ()-(t -b 3)2c 3（7）式中：V (t )为实际测量回波信号的包络线；V g (t )为混合高斯拟合的直达波信号包络线.图4中粗实线所示为采用上述方法处理后的超声回波信号，点画线为该信号的包络线，从图中可以发现，通过上述处理后，直达波信号被基本消除，从而消除了因直达波信号引起的回波信号到达时间的判断误差.测量距离过小，会导致反射物体的多重反射.此时，如果一次反射信号的传播时间过短，将导致该回波信号被直达波信号和多重反射信号完全淹没.如图5所示，当超声波传感器侧面靠近墙面时，垂直于墙面的旁瓣信号会经过墙面的反射再次回到接收传声器，从而引起信号串扰.图6中信号代表的是图5中R 1传声器收到的回波信号，由于R 1受到上述信号串扰的影响，信号存在严重的重叠干扰，这种情况下，利用混合高斯拟合方法无法获得准确的波形轮廓，由此导致较大的波达时间误差.为了解决这个问题，本文引入“不确定度”来降低这些误差对实验最终结果的影响，具体实现如下：通过多次实验测量，得到测量距离γ（单位：m ）与信号峰值V max （单位：V ）的近似关系如式（8）所示：图 4 重叠回波信号及处理后的结果Fig. 4 The overlapping echo signal and the processed signal24第 4 期王刚等：基于超声TOA 的环境感知V max =2.163γ2-2.948 γ+1.188（8）由于接收的超声波传感器R 1、R 2间距相对较小，灵敏度也基本一致，测量信号的能量也就是信号峰值应该相当.同时由于信号衰减，不同的测量距离也应该对应不同的信号峰值能量.因此，在对两接收传感器接收到的信号进行上述处理后，两信号的能量仍具有较大差异，或者处理后的峰值能量与计算得到的测量距离不满足式（8）所示的经验关系，则说明信号的串扰问题未完全消除，表明由该组信号得到的测量结果可能存在较大的误差，准确度和可靠度较低，不确定度较高.将测量距离γ代入式（8）即可得到理想的信号峰值能量V maxi ，该值与实际得到的峰值能量V maxp 相除得到比值ζd ，同时结合接收传声器R 1与R 2之间的峰值能量比ζv ，绘制ζd 、ζv 与实验测量距离相对误差的关系图.如图7所示，图中圆点是在不同距离和不同方向下实测的50组ζd 、ζv 与相对误差关系的数据，其灰度值越小表示测距相对误差越小.根据这些数据，制定对应的不确定度参数φ与ζd 、ζv 的关系如下：φ=ìíîïïïïïï0 ， (0.9<ζd ≤1)∪(0.5<ζv ≤1)-5ζd +4.5 ， (0.7≤ζd ≤0.9)∩(0≤ζv <0.2)-2.5ζv +1.5 ， (0≤ζd <0.7)∩(0.2≤ζv ≤0.5)(-5ζd +4.5)(-2.5ζv +1.5) ， (0.7≤ζd ≤0.9)∩(0.2≤ζv ≤0.5)1 ， (0≤ζd <0.7)∩(0≤ζv <0.2)（9）其中，ζv ≤1.图7中线条为根据式（9）绘制的相对误差随ζd 、ζv 变化的等高线图.从图7可以看出，式（9）基本上符合实验实际测量的ζd 、ζv 与相对误差的关系.在后续处理中，将φ引入计算，以此提高误差较大的测量结果的不确定度，从而降低其对最终实验测量结果的影响.2.3 不同距离下多个反射物体的探测由于超声波传感器具有一定的波束角，因此只要反射波处于波束角的范围内，接收传声器就能得到对应的回波信号.如图8所示，平面反射物体和曲面反射物体都位于传感器的波束角范围内，发射传声器T 发射的超声信号将在两个物体上分别发生反射，接收传声器将首先收到曲面的回波，之后收到平面的回波.通过比较两次回波的信号能量和传播时间并进行匹配，可以在单次测量后，同时得到曲面和平面的反射点.图9所示为在图8情况下接收传感器获取的超声回波信号.根据波达时间，可以确定先到达的为曲图 5 传声器侧面靠近墙面引起的串扰Fig. 5 Crosstalk caused by microphone side close to wall图 6 传声器侧面靠近墙面的回波信号Fig. 6 The echo signal caused by microphone side close to wall图 7 ζd 、ζv 与相对误差的关系图Fig. 7 The plot of ζd ， ζv and relative error25湖南大学学报（自然科学版）2023 年面反射信号，后到达的为平面反射信号.因此，如果在测量范围内存在多个反射物体，且反射物体间距足够的情况下，可通过单次测量，同时计算得到两个及以上的反射物体的距离和角度信息，从而提高探测效率.3 基于DSmT 的栅格信度分配函数建模及地图融合与更新3.1 DSmT 基本原理在采用超声波传感器绘制地图的过程中，获取到的测量信息具有不确定性、不精确性，甚至可能会高度冲突，特别是在栅格地图的绘制中，此现象尤为严重.针对这一问题，提出DSmT ［16］，即处理不确定、高度冲突和不精确证据源融合的完整理论，它可以将多个主体信息进行融合，并且允许根据信度函数正式组合任何类型的独立信息源.DSmT 具有多种比例冲突再分配规则［17］，其中比例冲突再分配规则6（Proportional Conflict Redistrbu⁃tion 6，PCR6）是按照合取规则的逻辑，将冲突质量重新分配到非空集的最精确的数学方法，同时还满足了空信度分配（Vacuous Belief Assignment ，VBA ）的中立性，并且对于合并两个以上的源有更好的直观结果［18］.PCR6规则如下：∀(X ≠∅)∈D Θ，m PCR6(X )=∑Y 1∩…∩Y M =X ∏j =1Mm j()Y j+∑i =1Mm i (X )2∑∩Y ∩X ≡∅()Y ，…，Y ∈()D æèçççççççöø÷÷÷÷÷÷÷÷÷÷÷÷÷∏j =1M -1m σ(j )()Y σ(j ))m i (X )+∑j =1M -1m σ(j )()Y σ(j )（10）其中，m i (X )+∑j =1M -1mσi (j )(Y σi (j ))≠0（11）式中：Θ为辨识框架，包含一组有限的穷举假设；D Θ为超幂集，即对一个事件所有可能判定结果的集合；M 为源的数目，即测量结果的个数；Y i ∈2Θ称为焦元；m i (Y i )为广义信度分配函数；整数σi 的取值范围为[1，i -1]∪[i +1，M ]，具体为：{σi (j )=j ， j <iσi (j )=j +1， j ≥i（12）3.2 栅格信度分配函数在进行测量和信号处理后，得到的反射物体的距离信息和角度信息依旧存在一定误差.图10为与图 10 反射物可能存在区域及信度函数参数示意图Fig. 10 Schematic diagram of the possible region of reflectorand the belief assignment function parameter图 8 同时测量不同距离下反射物体示意图Fig. 8 Diagram of simultaneously measuring reflectors with dif⁃ferent distances图 9 不同距离下反射物体的回波信号Fig. 9 The echo signal of reflected objects at different distances26第 4 期王刚等：基于超声TOA 的环境感知超声波传感器的单个测量结果对应的反射物可能存在的区域的模型，其中梯形区域表示物体可能存在的位置，三角区域表示物体不可能存在的位置，ω为超声波传感器的波束角，γ为反射点的测量距离，θ为反射点的测量角度，2ε为测量距离γ的误差范围.针对超声波传感器和栅格地图的特点，本文建立了辨识框架Θ={θ1，θ2}，θ1表示栅格被占用，θ2表示栅格没有被占用.根据DSmT 可以得到超幂集D Θ={∅，θ1，θ2，θ1∩θ2，θ1∪θ2}.地图中的每一个栅格存在M （M ≥2）次测量数据，并且把每一次测量数据都作为证据源.由此定义一组针对每个证据源的信度分配函数，m （θ1）定义栅格被占用的概率，主要由图10中的梯形区域决定，并且离测量点越远，占有概率越小.反之，m （θ2）定义栅格未被占用的概率，由图10中的三角区域决定，且与θ的角度差值越大，占有概率越小.m （θ1∩θ2）表示栅格既被占用又未被占用的概率，即冲突.m （θ1∪θ2）表示栅格未知的程度，也就是不确定度，此处指的是由测量结果得到栅格点数据的可靠程度，主要与波束角、测量距离相关.需要说明的是，由于冲突会在PCR6的计算过程中出现，因此无需建立信度分配函数m （θ1∩θ2） ［19］.由此，本文构建的信度分配函数m (⋅)：D Θ→[0，1]，如公式（13）所示：m ()θ1=ìíîïïïA /ε⋅()m ∼N ()μ1，Σ1，()0≤||α≤ω2∩()0≤d v ≤ε0 ，其他m ()θ2=ìíîïïïA ⋅()m ∼N ()μ2，Σ2，()0≤|α|≤ω2∩()0≤d <γ∩d v >ε0 ，其他m ()θ1∪θ2=1-m ()θ1-m ()θ2（13）式中：A 为根据测量距离γ与测量角度θ引入的信度函数；μ1、μ2表示正态分布的均值矩阵；Σ1、Σ2表示正态分布的协方差矩阵，上述5个参数的定义为：A =()1-φéëêêùûúú1-()γa 2()1-|α-θ|w μ1=éëêùûúd v d p Σ1=éëêêêêùûúúúú12π00ε μ2=éëêêùûúúd ||α-θ Σ2=éëêêêêùûúúúú1ωw 00w 2（14）式中：φ为不确定度参数；d 为栅格点到发射传声器的距离；d v 为栅格点Q 沿着传感器与测量点的连线TP 的方向到测量点P 的距离；d p 为栅格点Q 到连线TP 的垂直距离，具体如图10所示.图11为当测量点角度θ=15°、测量距离γ=0.5 m时，根据公式（13）得到的栅格不确定度m （θ1∪θ2）.从图11中可以看出，在波束角范围内的三角区域内，栅格数据的不确定度与栅格点和测量点角度之间的差值以及离测量点的距离正相关.在波束角以外，是装置无法测量到的区域，处于完全未知的状态，因此这里的不确定度等于最大值1，而最小值出现在发射超声波传感器的位置.由于栅格点存在数据不连续的问题，因此其不确定度最小值趋近于0.通过单次测量可以得到波束角范围内栅格点的占有概率，再图 11 θ=15°，γ=0.5 m 时，由公式（13）得到的不确定度 m （θ1∪θ2）Fig. 11 The uncertainty m （θ1∪θ2） obtained by formula （13）when θ=15°，γ=0.5 m27湖南大学学报（自然科学版）2023 年叠加不同方位的测量结果进行不断融合，可以逐渐减小栅格点的不确定度，最终获得全局的环境栅格地图.4 实验结果为了验证上述方法的有效性，搭建了如图12所示的实验环境，该实验环境是由木板围成的一个矩形区域，其右上方的斜板倾角为45°，右下角存在一开口，在环境中间放置一直径为166 mm 的塑料圆柱体，各点的坐标位置如图所示.超声波传感器的移动路径如图12中的虚线所示，虚线上的圆圈标记表示测量位置.装置从实验环境的右下方开口进入后，在测量路径前进方向上的±90°范围内，间隔45°进行5次测量.实验中有27个测量点，共进行了135次测量.相较于文献［11］所需的456次测量，本文提出的方法大大减少了测量次数，从而减少了计算量.实验装置如图13所示，其中单片机（STM32F103C8T6）用于产生超声波发射传感器所需要的25 kHz 震荡信号，再通过驱动电路（L298N ）驱动发射传声器发出超声信号，经反射物反射后，回波信号由接收传声器转化为电信号.该电信号经采集卡（NI USB-6356）采集后，传输给计算机进行信号分析与处理.实验中，传感器波束角ω为60°，接收传声器测量距离误差ε经多次测量确定为15 mm.图14所示为每次测量所得到的反射点位置，实线表示环境的实际轮廓，实心圆圈表示每次测量计算得到的反射点位置.从图14可以看出，由本文方法得到的测量点位置大多比较准确，基本位于环境实际轮廓的附近，但是也存在个别测量误差较大的点，误差主要出现在测量距离过近或者测量装置正对墙角的情况下，是由被测物体的多重反射造成的.但是在本文中测量装置随机游走时，这种情况出现的概率很小，其对建图结果的影响在后续的数据融合过程中逐渐被消除.通过构建每一个测量结果的栅格信度分配函数，并利用PCR6规则将多次测量得到的结果进行融合.环境栅格地图的融合过程及最终结果如图15所示，其中实线为环境的实际轮廓，虚线为测量轨迹，虚线上的圆圈标记表示测量位置，栅格的颜色深度表示栅格的占有概率，图15（a ）、15（b ）、15（c ）分别为测量装置完成轨迹的25%（34次测量）、50%（67次测量）和75%（101次测量）时得到的环境栅格地图，图15（d ）为测量装置完成全部轨迹（135次测量）后，最终融合得到的栅格地图.从图15中可以看出，随着测量次数的增加，环境的轮廓逐渐清晰，且误差较大的测量点对地图的影响逐渐减小，最终所得到的栅格占有信度高的区域基本与环境的实际轮廓重合.图15所示结果表明，所提出的方法也能获取到圆柱反射物体较清晰的轮廓信息.图 12 实验环境及测量路径（单位：mm ）Fig. 12 The experimental environment and measurementpath （unit ：mm）图 13 实验装置Fig. 13 The experimental device图 14 测量得到的反射点Fig. 14 The reflection points obtained by measurements28。

摘要摘要基于外辐射源的目标回波信号检测系统自身不主动发射信号，而是通过第三方非协同辐射源照射到目标，然后检测目标的反射回波对目标进行检测或跟踪。

与主动发射信号对目标进行回波信号检测的“有源回波信号检测”机制不同，基于外辐射源的目标回波信号检测系统的工作机制决定了其具有“无线电静默”的特点，所以具有反侦察、抗干扰、生存能力强的优势。

目前可以使用的民用机会照射源包括调频广播、地面数字电视信号、通信信号、卫星信号等。

针对单辐射源下目标回波检测的可靠性低，以及微弱回波信号检测困难的问题，本文以全球导航卫星(GPS)、数字视频广播卫星（DVB-S）、国际海事通信卫星(INMARSAT)作为外辐射源，提出了一种多个不同体制卫星辐射源下微弱回波信号的联合检测方法。

针对多个不同频的直达波信号同时混入参考通道，造成监测通道直达波和多径信号抑制效果较差的问题，该方法首先分离参考通道中的多个不同频率的直达波信号，并利用分离后的直达波信号依次用基于归一化最小方差的自适应滤波方法对监测通道中的直达波和多径干扰进行级联抑制，为后续微弱回波检测奠定了基础。

然后分别使分离之后的各个直达波信号与回波信号进行相关，得到多个时延-多普勒谱，将其最大值作为每个分布式多传感器的检测量，对检测统计量进行理论分析，并设计自适应检测门限，最后将检测结果进行决策融合，以达到对微弱回波自适应检测的目的。

仿真结果表明，该方法可以有效的检测微弱回波信号。

针对基于传统的时频二维相干检测方法对参考通道噪声敏感的问题，现有方法通过广义似然比或Rao检测方法达到了微弱回波检测的目的，然而这两种检测方法都是在单个辐射源场景下进行建模分析的，为了在多星联合场景下通过广义似然比方法和Rao检测方法对多个卫星下的微弱回波进行有效检测，本文首先对监测通道的接收信号建模，然后通过最大似然估计方法去估计信号的未知参数，通过这些未知参数的最大似然估计推导了基于两种检测算法的检测器，分析检测统计量并设计相应的检测门限进行检测。

傅里叶变换红外光谱和漫反射傅里叶变换红外光谱1.傅里叶变换红外光谱是一种分析物质结构的方法。

Fourier transform infrared spectroscopy is a method for analyzing the structure of substances.2.该技术基于物质分子对红外光的吸收和发射。

This technique is based on the absorption and emission of infrared light by molecular substances.3.通过分析红外光谱图，可以了解物质的功能团和结构。

By analyzing the infrared spectrum, we can understand the functional groups and structure of the substance.4.傅里叶变换是对信号进行频域分析的方法。

The Fourier transform is a method for frequency domain analysis of signals.5.通过傅里叶变换，可以将时域信号转化为频域信号。

Through Fourier transform, the time domain signal can be converted into frequency domain signal.6.在红外光谱分析中，傅里叶变换可以提取出样品的结构信息。

In infrared spectroscopy analysis, Fourier transform can extract structural information from the sample.7.这种分析方法对于化学品的鉴别和质量控制非常重要。

This analysis method is very important for theidentification and quality control of chemicals.8.傅里叶变换红外光谱还可以用于药物分析和环境监测。