Field II总结

alphafold2 参数摘要：1.概述alphafold2 参数2.alphafold2 参数的具体内容3.使用alphafold2 参数的注意事项4.alphafold2 参数的应用实例5.总结正文：alphafold2 是一款用于蛋白质结构预测的软件，它的参数设置对于预测结果的准确性和速度至关重要。

下面我们将详细介绍alphafold2 的参数，并提供一些使用和应用的建议。

一、alphafold2 参数的概述alphafold2 的参数设置包括以下几个方面：输入格式、模型类型、优化方式、温度、压力等。

其中，输入格式指定了输入数据的格式，包括pdb、gro、mol2 等格式;模型类型指定了预测的模型类型，包括二级结构模型、三级结构模型等;优化方式指定了预测的过程优化方式，包括采样、折叠识别等。

二、alphafold2 参数的具体内容下面我们将分别介绍几个重要的alphafold2 参数。

1.输入格式alphafold2 支持多种输入格式，包括pdb、gro、mol2 等格式。

其中，pdb 格式是最常用的格式，它包含了蛋白质的原子坐标信息、化学键信息等。

2.模型类型alphafold2 支持预测多种模型类型，包括二级结构模型、三级结构模型等。

其中，二级结构模型是指预测蛋白质的二级结构，包括alpha 螺旋、beta 折叠等;三级结构模型是指预测蛋白质的三级结构，包括原子之间的相对位置和距离等。

3.优化方式alphafold2 支持多种优化方式，包括采样、折叠识别等。

其中，采样是指通过随机抽样来提高预测的准确性;折叠识别是指通过识别已知的结构域来提高预测的准确性。

4.温度和压力alphafold2 还支持设置温度和压力等参数，这些参数可以影响预测的准确性和速度。

一般来说，温度越高、压力越大，预测的准确性越高，但同时计算的时间也会增加。

三、使用alphafold2 参数的注意事项在使用alphafold2 参数时，需要注意以下几点:1.输入格式应该正确，否则会导致预测结果不准确。

field的用法和短语例句【篇一】field的用法大全field的用法1：field的基本含义是“场地”,可指农业用地、矿物产地,也可指其他用作某种用途的场地,或场所如运动场、战场等,引申可表示“领域”“方面”“界”。

既可用作可数名词,也可用作不可数名词。

field的用法2：表示“在田野里”,介词用in; “在球场上”,介词用on; “在战场上”,介词用in或on皆可。

field的用法3：一般未经耕作的土地不叫field,在英国, field大多指青草牧场。

field的用法4：field用作动词表示“(板球或棒球)(准备)接或掷还(球),守(球)”“任守方”“(足球、板球、棒球等赛中)选派(某人)上场”“顺利处理”。

【篇二】field的常用短语用作名词 (n.)have a field dayhold the fieldtake the field【篇三】field的用法例句1. He was the fastest thing I ever saw on a baseballfield.他是我在棒球场上见过的跑得最快的家伙。

2. Pinch-hitter Francisco Cabrera lashed a single to left field.替补队员弗朗西斯科·卡布雷拉向左外场猛地击出一个一垒打。

3. He was on the training field for some light work yesterday.昨天他在训练场进行了一些强度较小的训练。

4. Expertly he zigzagged his way across the field, avoiding the deeper gullies.他熟练地左一拐右一拐地绕过深沟，穿过了原野。

5. We never defeated them on the field of battle.我们从未在战场上打败过他们。

针对field计算方法field计算方法，是一种计算特定领域内数据的方法论。

它是不同领域中研究者、工程师和决策者们为了解决特定问题而采用的一种手段。

在各个领域中，都可以看到不同的field计算方法的应用，如金融领域的风险计算、医学领域的疾病患病率计算，以及工程领域的结构强度计算等等。

field计算方法的核心思想是通过对领域内数据的分析和处理，得到相应的计算结果，从而为决策者们提供参考。

而这一过程通常需要借助于各种各样的数学、统计和计算机科学的方法。

下面，我们将重点探讨field计算方法的应用和特点。

首先，field计算方法在各个领域中具有广泛的应用。

在金融领域，field计算方法常常用于评估风险和收益。

通过对历史数据和市场信息进行分析，并应用复杂的数学模型，可以计算出投资组合的预期收益和风险程度。

这为投资者提供了重要的决策参考。

在医学领域，field计算方法被广泛应用于流行病学和临床研究。

通过对大量患者数据的收集和分析，可以计算出疾病的患病率、死亡率和治愈率等指标，为疾病预防和治疗提供依据。

在工程领域，field计算方法常常用于评估结构的强度和安全性。

通过对建筑物、桥梁和其他工程结构的设计和施工过程进行模拟和计算，可以预测实际结构的行为和响应，从而确保其在正常使用和极端情况下的安全性。

其次，field计算方法的特点在于其理论基础的复杂性和计算过程的精确性。

在应用field计算方法时，必须熟悉相应领域的理论模型，并依据实际条件选择合适的数学和统计方法。

同时，计算过程需要精确地进行，以确保计算结果的可靠性和准确性。

此外，field计算方法还要求研究者具备良好的数据分析和处理能力。

在应用field计算方法时，常常需要处理大量的实验数据和观测数据，并进行统计和推断。

因此，研究者们必须熟悉各种数据分析方法，并具备良好的编程和计算机技能。

然而，尽管field计算方法在各个领域中具有着广泛的应用和重要的意义，但也存在一些挑战和局限性。

field类详解-回复field类是Java中的一个引用类型，它用于表示类中的字段（或属性），即类中的变量。

在Java中，类是由字段和方法组成的，在类中定义了不同类型的字段，用于存储不同类型的数据。

field类提供了对字段的各种操作和访问方法，使得我们可以在类的内部和外部对字段进行操作和访问。

一、field类的定义和特点field类是Java反射机制中的一个关键类，它是ng.reflect包的一部分。

在使用反射机制时，我们可以通过field类来获取类的字段信息，并对字段进行操作。

field类具有以下特点：1. field类是Java中所有字段的基类，包括普通字段、静态字段、公共字段、私有字段等。

2. field类用于描述和操作字段的属性，提供了获取和设置字段值、获取和设置字段修饰符、获取和设置字段类型等方法。

3. field类是Java反射机制中的一个重要类，可以通过反射机制来实现对字段的动态操作，包括获取字段值、设置字段值、修改字段修饰符等。

4. field类的实例是通过Class类的getField()或getDeclaredField()方法获取的。

二、field类的常用方法1. 获取字段名称field类提供了getName()方法，用于获取字段的名称。

例如：Field field = MyClass.class.getDeclaredField("fieldName");String name = field.getName();2. 获取字段类型field类提供了getType()方法，用于获取字段的类型。

例如：Field field = MyClass.class.getDeclaredField("fieldName");Class<?> type = field.getType();3. 获取字段值field类提供了get()方法，用于获取字段的值。

文章标题：深度剖析matlabfield2的例子一、引言在本文中，我们将深入探讨matlabfield2的例子，从简单到复杂地解析其特点和应用。

通过对这个主题的全面评估，我们将能更深入地理解它的意义和价值。

二、matlabfield2的定义与基本概念matlabfield2是一个用于处理二维矢量场数据的Matlab工具包。

它提供了丰富的功能和方法，可用于分析和可视化二维矢量场的特征。

通过对数据进行采样、插值和转换，matlabfield2为用户提供了强大的工具来探索和理解二维矢量场的行为和模式。

三、matlabfield2的应用举例接下来，我们将通过几个具体的例子来展示matlabfield2的应用。

我们可以使用它来分析流体力学问题中的速度场数据。

通过对速度场进行采样和插值，我们可以获得关于流体流动的详细信息，从而更好地理解流体的运动规律和特性。

matlabfield2还可以应用于地理信息系统中的地图分析。

通过将地图上的矢量场数据转换为matlabfield2格式，我们可以进行地图数据的分析和可视化，从而更好地理解地理空间数据的分布和变化规律。

matlabfield2还可以用于分析气象数据中的风场信息。

通过对风场数据进行处理和转换，我们可以获得关于风向风速的详细信息，从而更好地理解气象变化和天气预测。

四、总结与展望通过对matlabfield2的例子进行深度剖析，我们不仅更好地理解了其基本概念和应用，还对二维矢量场数据的分析和处理有了更直观的认识。

在未来的工作中，我们可以进一步探索matlabfield2在其他领域的应用，并结合个人理解，不断拓展其在科学研究和工程实践中的价值。

五、个人观点与心得体会从个人角度来看，matlabfield2在二维矢量场数据处理方面有着很大的潜力和应用前景。

通过深入学习和使用matlabfield2，我不仅加深了对二维矢量场数据分析的理解，还提高了在科学研究和工程实践中处理相关问题的能力。

fieldmaxll使用手册
FieldMaxII是一个激光功率/能量测量仪器，它可以用于测量激光器的功率和能量。

在使用FieldMaxII之前，您需要确保已经阅读了使用手册，并且了解了其操作方法和注意事项。

首先，使用FieldMaxII之前，您需要确保设备已经正确连接并且通电。

接下来，您可以按照以下步骤操作FieldMaxII：
1. 打开仪器，按下电源按钮，等待仪器启动完成。

2. 选择测量模式，根据您的需要，选择功率测量模式或能量测量模式。

3. 设置参数，根据您的激光器参数，设置波长、功率范围等参数。

4. 进行测量，将激光束对准测量头，观察仪器显示屏上的测量数值。

5. 记录数据，根据需要，记录测量结果并进行分析。

在使用FieldMaxII时，需要注意以下事项：
确保测量头与激光束保持垂直，以确保准确测量。

注意避免将激光束直射到人眼或其他人体部位，以避免激光伤害。

在测量高能量激光时，需要使用适当的能量传感器，并注意安全防护。

如果您在使用FieldMaxII时遇到任何问题，可以参考使用手册中的故障排除部分，或者联系厂家或经销商寻求帮助。

总的来说，正确阅读并理解使用手册中的操作步骤和注意事项对于安全、准确地使用FieldMaxII是非常重要的。

希望以上信息能够帮助您更好地使用FieldMaxII测量仪器。

field类详解
Field 类是 Java 反射机制中的一个重要类，用于表示类中的字段（Field）。

通
过 Field 类，我们可以获取和修改一个类中的字段的值，以及动态创建和获取字段
的实例。

Field 类提供了一系列的方法，用于操作和管理字段。

其中一些常用的方法包括：
1. getName()：获取字段的名称。

2. getType()：获取字段的类型。

3. getModifiers()：获取字段的修饰符。

4. get()：获取字段的值。

5. set()：设置字段的值。

除了这些方法，Field 类还提供了一些其他的辅助方法，用于判断字段的一些
特性，比如是否是静态字段、是否是枚举常量等。

使用 Field 类需要注意的一些事项包括：
1. 对于私有字段，我们需要先通过 setAccessible(true) 方法来设置字段的可访问性，才能访问和修改其值。

2. 在获取和设置字段值时，我们需要传递一个对象实例。

对于静态字段，可以
传递 null，表示在静态上下文中进行操作。

实际应用中，Field 类经常与其他反射类一起使用，比如Class 类和Method 类。

通过 Class 类的 getDeclaredFields() 方法，我们可以获取一个类中所有的字段，进
而使用 Field 类的方法进行操作。

总结来说，Field 类是 Java 反射机制中用于表示字段的重要类，通过它我们可以动态获取和修改一个类中字段的值。

在实际应用中，Field 类结合其他反射类的使用，可以实现更加灵活和动态的编程。

Users’guide for the Field II programRelease3.24,May12,2014Jørgen Arendt JensenMay21,2014Jørgen Arendt JensenMay21,2014Department of Electrical Engineering,Build.349,Technical University of DenmarkDK-2800Lyngby,DenmarkE-mail:jaj@elektro.dtu.dkWeb:http://field-ii.dk/CONTENTS1Introduction3 2Program organization5 3Method of simulation73.1The spatial impulse response (7)3.2Simulation (7)3.3Focusing and apodization (8)3.4Attenuation (8)4Installation9 5Description of Matlab procedures115.1List of current procedures (11)5.2Procedures for Field initialization (13)5.3Procedures for transducer definition (17)5.4Procedures for element manipulation (45)5.5Procedures forfield calculation (50)6Examples596.1Phased array imaging (59)6.2Linear array imaging (61)6.3Flow data generation (64)Bibliography66iiiLIST OF FIGURES5.1Concave,round transducer with a radius of8mm divided into1by1mm mathematical elements (19)5.2Rectangles for a convex array with Rconvex equal to20mm (21)5.3Rectangles for an elevation focused,convex array with Rfocus equal to10mm and Rconvex equal to30mm (22)5.4Rectangles for an elevation focused,multi-row,convex array with Rfocus equal to7mm and Rconvexequal to30mm (24)5.5Rectangles for an elevation focused,linear array with Rfocus equal to15mm (26)5.6Rectangles for an elevation focused,multi-row linear array with Rfocus equal to10mm and5rows..27 5.7Display of the geometry and apodization of a linear array transducer (30)5.8Rectangles for a16elements linear array transducer (32)5.9Geomtery of multi-row linear array transducer.Currently x and y has been switched (33)5.10Rectangles for a16by5elements multi-row transducer (34)5.11Piston transducer with a radius of8mm divided into1by1mm mathematical elements (36)5.12Fully populated two-dimensional array with11by13elements (43)5.13Partially populated two-dimensional array with23elements (44)5.14Linear array transducer with afixed apodization of the mathematical elements (46)5.15Intensity profile for linear array transducer with an elevation focus lens (47)5.16Example of calculated response when using different physical element excitations (49)5.17Received voltage traces from the individual elements of a16elements linear array transducer,whentransmitting with three different elements (55)5.18Received voltage traces from the individual elements of a linear array transducer(top)and the sum ofall the individual responses(bottom) (57)12CHAPTERONEIntroduction This is the user guide for the version3.24of May12,2014of the Field II program.This version of the program runs under Matlab8.201and can simulate all kinds ultrasound transducers and the associated images.The focusing and apodization of the transducers can be controlled dynamically,and it is,thus,possible to simulate all kinds of ultrasound imaging systems.The versions can also be used for synthetic aperture imaging.The program is free for use,if you make a proper reference to the papers describing the program,when you publish results from its use.The reference are[1]and[2].Also the name of the program(Field II)should be mentioned in the publication.Some unfortunately forget this,and the program will only stay in the public domain,if people continue to properly acknowledge its use.This guide is intended as a presentation of the currently available routines.It includes a few examples and gives a small amount of background information.It is,however,not intended as an introduction to ultrasound scanning,and the reader should consult the extensive literature on this.The program executables can be downloaded from the Web-site for the program:http://field-ii.dk/It currently exist for a number of platforms like Windows,Linux,Mac OS-X.Versions for other operating systems are generally discontinued due to lack of demand.A parallel Pro version also rmation about this can be found on the web-site above.The web site also contains more extensive examples than are given in this guide,and up-to-date references and papers can also be found on the web-site.The manual is made as a clickable pdf document with hyperlinks.All links are indicated in blue,and when clicked on will lead to the indicated references,which can be a web-site,figure,equation,etc.The manual is organized as follows:Chapter2gives an overview of the organization of the program and how it is connected to Matlab.Chapter4details the installation from the programs on the web-site.A listing of all procedures callable in the program is given in Chapter5andfinally a few examples are given in6.More can be found on the web. Jørgen Arendt JensenMay21,2014Department of Electrical Engineering,Build.349,Technical University of DenmarkDK-2800Lyngby,DenmarkE-mail:jaj@elektro.dtu.dk1Older versions can be found on the web-site for Matlab4-734CHAPTERTWOProgram organization The program consists of a C program and a number of Matlab m-functions that calls this program.All calculationsare performed by the C program,and all data is kept by the C program.Three types of m-functions are found.The are used for initializing the program,defining and manipulating transducers, and for performing calculations.The initializing routines are preceeded byfield,the transducer commands by xdc, and the calculation routines by calc.Help on use of the routines can be obtained by typing help<routine name>. Each of the routines are described in the following section and then three examples of use are given.Thefirst shows how a phased array image is generated,the second simulates aflow system,and the last example is for a linear array system.The last example uses a computer generated phantom.The m-file for this phantom is also given in the example section.56CHAPTERTHREEMethod of simulation3.1The spatial impulse responseThe Field program system uses the concept of spatial impulse responses as developed by Tupholme and Stepanishen in a series of papers[9,10,11].The approach relies on linear systems theory tofind the ultrasoundfield for both the pulsed and continuous wave case.This is done through the spatial impulse response.This response gives the emitted ultrasoundfield at a specific point in space as function of time,when the transducer is excitated by a Dirac delta function.Thefield for any kind of excitation can then be found by just convolving the spatial impulse response with the excitation function.The impulse response will vary as a function of position relative to the transducer,hence the name spatial impulse response.The received response from a small oscillating sphere can be found by acoustic reciprocity.The spatial impulse response equals the received response for a spherical wave emitted by a point.The total received response in pulse-echo can,thus,be found by convolving the transducer excitation function with the spatial impulse response of the emitting aperture,with the spatial impulse response of the receiving aperture,and then taking into account the electro-mechanical transfer function of the transducer to yield the received voltage trace.An explanation and rigorous proof of this can be found in[14]and[15].Any excitation can be used,since linear systems theory is used.The result for the continuous wave case is found by Fourier transforming the spatial impulse response for the given frequency.The approach taken here can,thus,yield all the diffent commenly found ultrasoundfields for linear propagation.3.2SimulationA number of different authors have calculated the spatial impulse response for different transducer geometries.But in general it is difficult to calculate a solution,and especially if apodization of the transducer is taken into account.Here the transducer surface does not vibrate as a piston,e.g.the edges might vibarte less then the center.The simulation program circumvents this problem by dividing the transducer surface into squares and the sum the response of these squares to yield the response.Thereby any tranducer geometry and any apodization can be simulated.The approach is described in[1].The time for one simulation is also of major concern.As the squares making up the tranducer apertue are small,it is appropriate to use a far-field approximation,making simulation simple.Another issue in keeping the simulation time down is to use a low sampling frequency.Often spatial impulse responses are calculated using sampling frequencies in the GHz range due to the sharp discontinuities of the responses.These discontinuities are handled in the Field programs by accurately keeping track of the time position of the responses and uses the integrated spatial impulse response as an intermediate step in the calculations.Thereby no energy is lost in the response,which is far more important than having an exact shape of the spatial impulse response.Hereby the Field program ususally does better using100MHz sampling and approximate calculations,than using the exact analytic expression and GHz sampling.73.3Focusing and apodizationThe focusing and apodization is handled in the program through time lines as:Focusing:From timeFocus at0x 1,y 1,z 1t 1x 1,y 1,z 1t 2x 2,y 2,z 2......Apodization:From time Apodize with0a 1,1,a 1,2,···a 1,N e t 1a 1,1,a 1,2,···a 1,N e t 2a 2,1,a 2,2,···a 2,N e t 3a 3,1,a 3,2,···a 3,N e ......For each focal zone there is an associated focal point and the time from which this focus is used.The arrival time fromthe field point to the physical transducer element is used for deciding which focus is used.The focusing can also be set to be dynamic,so that the focus is changed as a function of time and thereby depth.The focusing is then set as a direction defined by two angles and a starting point on the aperture.All the time values for focusing are calculated relative to a point on the aperture.Initially this is set to (0,0,0).It can be set to other values through the procedure xdc center focus.This is used in linear array imaging,where the origin of the emitted and received beam is moved over the aperture.The focusing values are calculated by:t i =1c (x c −x f )2+(y c −y f )2+(z c −z f )2− (x i −x f )2+(y i −y f )2+(z i −z f )2 (3.1)where (x f ,y f ,z f )is the position of the focal point,(x c ,y c ,z c )is the reference center point on the aperture for the focus as set by xdc center focus,(x i ,y i ,z i )is the center for the physical element number i ,c is the speed of sound,and t i is the calculated delay time.The value is then quantized,if that is set for the aperture.The time line method is employed for the apodization,where the time decides which apodization vector is used.The vector holds one apodization value for each physical element.3.4AttenuationFrequency dependent attenuation can be included in the simulation by using the procedure set field.The attenuation is included through a frequency dependent term and a frequency independent term.The frequency dependent term is linearized through a center frequency att f0,so that the attenuation is zero dB at att f0.This is done to make the inclusion of the attenuation computationally efficient.The variation in distance over the aperture of the frequency dependent attenuation is usually not significant,and therefore only the frequency independent attenuation is varied over the aperture.The frequency dependent attenuation is then included on the response by using the mean distance to the aperture.The attenuation is assumed to be minimum phase.8Chapter 3.Method of simulationCHAPTERFOURInstallationThe excutable code for the program can be obtained free of charge from the web-site:http://field-ii.dk/Here the mex-file to run under Matlab and the m-files for calling the mex-files can be found.Versions are currently found for Linux(Intel processors,32and64bits),MAC OS and Windows32and64bits.The latest version is only found for64bits processors.Older versions are found for HP-UX(PA-RISC processors),SUN(OS4.1and Solaris), DEC ALPHA,Silicon Graphics,IBM AIX,but they are no longer supported.Matlab8.0or higher is required to run the program,but older versions from Matlab5and on are also found on the web-site.The individualfiles can be found at the web-site along with compressed Unix-style tar-files.A zipfile also exits for the windows version.The tar-file should be downloaded to the directory,that must hold thefiles.Thefile is then extracted by writing:gzip-d<name_of_tar_file>.tar.Ztar-xvf<name_of_tar_file>.tarto uncompress and extract thefile.The tar-file can then be deleted.The program can now be run from this directory or from an other directory by writing:addpath(’/home/user/field_II/m_files’);field_initwhere/home/user/field II/mfiles contains the Field II m-files.This ensure that the directory is included in the Matlab search path,and the user-written m-files can then be placed in a separate directory.910CHAPTERFIVE Description of Matlab procedures5.1List of current proceduresGeneral commandsFunction name Purpose Pagefield debug Initialize debugging13field end Terminate the Field II program system and release the storage13field guide Display the Field II users guide in Acrobat reader13field info Display information about the state of the Field II program system13field init Initialize the Field II program system14set sampling Set the sampling frequency the system uses15setfield Set various parameters for the program16Transducer commandsFunction name Purpose Pagexdc apodization Create an apodization time line for an aperture.17xdc baffle Set the baffle condition for the aperture.17xdc center focus Set the origin for the dynamic focusing line.18xdc concave Define a concave aperture.18xdc convert Convert rectangular description to triangular description.19xdc convex array Create a convex array transducer.20xdc convex focused array Create an elevation focused convex array transducer.2022 xdc convex focused multirow Create an elevation focused convex,multi-row trans-ducer.xdc dynamic focus Use dynamic focusing for an aperture23xdc excitation Set the excitation pulse of an aperture.24xdc focus Create a focus time line for an aperture.25xdc focused array Create an elevation focused linear array transducer.25xdc focused multirow Create an elevation focused linear,multi-row transducer.26xdc focus times Creating a focus time line for an aperture with all delay28values supplied by the user.xdc free Free storage occupied by an aperture.28xdc get Get information about an aperture.28xdc impulse Set the impulse response of an aperture.30xdc linear array Create a linear array transducer.31xdc linear multirow Create a linear multi-row array transducer.3111Function name Purpose Pagexdc lines Create an aperture bounded by a set of lines.34xdc piston Define a round,flat aperture.36xdc quantization Set quantization of the phase delays.37xdc rectangles Procedure for creating an aperture consisting of rectangles.38xdc show Show information about an aperture.3940 xdc times focus Creating a focus time line for an aperture with all delay values suppliedby the user.xdc triangles Make a multi-element aperture consisting of triangles.41xdc2d array Create a two-dimensional array transducer.41 Element manipulation commandsFunction name Purpose Pageele apodization Set the apodization for individual mathematical elements.45ele delay Set the delay for individual mathematical elements.46ele waveform Set the waveform for individual physical elements.47Field calculation commandsFunction name Purpose Pagecalc h Calculate the spatial impulse response.50calc hhp Calculate the pulse echofield.51calc hp Calculate the emittedfield.52calc scat Calculate the received signal from a collection of scatterers.53calc scat all Calculate the received signals from a collection of scatterers for all53transmit and receive elements in the aperture.55 calc scat multi Calculate the received signals from a collection of scatterers for all theelements in the aperture.12Chapter5.Description of Matlab procedures5.2Procedures for Field initializationField II user’s guidefield debug Purpose:Procedure for initialize debugging.This will print out various information about the programs innerworking.Initially no debugging is done.Calling:field debug(state)Input:State-1:debugging,0:no debugging.Output:none.Field II user’s guidefield endPurpose:Procedure for terminating the Field II program system and releasing the storage.Calling:field end;Input:none.Output:none.Field II user’s guidefield guidePurpose:Procedure for displaying the Field II users’guide(this guide)using the Adobe acrobat reader. Calling:field guideInput:none.Output:The Field II guide is displayed in a separate window using acrobat reader.Note that the Adobe pdf reader must be installed on the system,and it must be accessible under Matlab under the name acroread.The users guide should be in the search path of Matlab,preferrably in the same directory as the m-files for Field II with the name users guide.pdf.Field II user’s guidefield info Purpose:Procedure for showing information about the Field II program.The information is printed in the Matlabwindow.Calling:field info5.2.Procedures for Field initialization13Input:None.Output:Information is printed in the Matlab window.For boolean variables a value of1indicates true and0for false.Example:Print the information:field_infoCurrent Field II configuration:Version 2.88,December14,2001(Matlab version)Number of apertures in operation:3Apertures to be defined uses rectangles:0Apertures to be defined uses triangles:0Apertures to be defined uses bounding lines:1Program uses accuracte time calculation for rectangles:0Program uses fast integration for lines and triangles:1Speed of sound:1540.0000m/sSampling frequency:100.0000MHzWhether to use attenuation:0Frequency independent attenuation is:0.0000dB/mFrequency dependent attenuation around0.0000MHz is0.0000dB/[m Hz] Constant tau_m used in attenuation calculation:20.0000Number of bytes reserved:12024Maximum number of bytes that has been reserved:22924Number for next signal to be used:60656Internal state of the program:1Debug mode enabled:0Last calculation type done:0Whether calculation time should be shown:1Seconds between showing times5sA boolean value of1indicates true,0indicates falseField II user’s guidefield init Purpose:Procedure for initializing the Field II program system.Must be thefirst routine that is called before usingthe system.Calling:field init(suppress);Input:suppress An optional argument suppress with a value of zero can be given to suppress thedisplay of the initialfield screen.No ACII ouput will be given,if the argument is-1.Debug messages will be written ifenable byfield debug,and all error messages will also be printed.Output:none.14Chapter5.Description of Matlab proceduresInitial values:The following initial values are used by the program afterfield init has been called:Variable Content Valuec Speed of sound1540m/sfs Sampling frequency100·106Hzshow times Whether to print information about the time taken for thecalculation(yes=any positive numer).A number largethan2is taken as the time in seconds between the printingof estimates.debug Whether to show debuging information0(no)use att Whether to use attenuation0(no)att Frequency independent attenuation0.0dB/m.0.0dB/[m Hz]freq att Frequency dependent attenuation in around the center fre-quency att f0att f0Attenuation center frequency in Hz0.0Hzuse rectangles Whether to use rectangles for describing apertures1(yes)use triangles Whether to use triangles for describing apertures0(no)use lines Whether to use lines for describing apertures0(no)no ascii output Whether ASCII output is not printed0(no,output is printed)0(no)fast integration Whether to use fast integration for bound lines and trian-glesInitially the program is set to use rectangles for the modeling of transducers.All of the options can be changed by the procedure setfield.Example:Include the Field II m-files in Matlab’s search path and start the Field II simulation system:path(path,’/home/user/field_II/m_files’);field_initField II user’s guide set samplingPurpose:Set the sampling frequency the system uses.Remember that the pulses used in all apertures must be reset for the new sampling frequency to take effect.This procedure has been superseed by setfield,and it is for portability reasons better to use setfield.Calling:set sampling(fs);Input:fs-The new sampling frequency.Output:none.5.2.Procedures for Field initialization15Field II user’s guide setfieldPurpose:Set various parameters that determins the function of the program.Calling:setfield(option name,value);Input:use att Whether to use attenuation(<>0for attenuation)att Frequency independent attenuation in dB/m.freq att Frequency dependent attenuation in dB/[m Hz]around the center frequencyatt f0.att f0Attenuation center frequency in Hz.debug Whether to print debug information(1=yes)c Set the speed of sound in m/s.fs Set the sampling frequency.show time Show calculation times during calculation.(yes=any positive numer).Anumber large than2is taken as the time in seconds between the printing ofestimates.use rectangles Use rectangles for the apertures.(1=yes)use triangles Use triangles for describing apertures.(1=yes)use lines Use lines for describing apertures.(1=yes)fast integration Whether to use fast integration(1)of the responses for bound lines and tri-angles.Fast integration uses a simple trapezoidal time integration of the re-sponses,else a Romberg integration,as described in Numerical Receipes,areused.Output:none.Example:Set the attenuation to1.5dB/cm and0.5dB/[MHz cm]around3MHz and use this:set_field(’att’,1.5*100);set_field(’Freq_att’,0.5*100/1e6);set_field(’att_f0’,3e6);set_field(’use_att’,1);Note that the frequency independent and the frequency dependent terms should correspond,so that the frequency independent attenuation is the same as the frequency dependent term at the center frequency set.This is ensured if att=Freq att*att f0,else the attenuation can be too big or too low at large depths in tissue.16Chapter5.Description of Matlab procedures5.3Procedures for transducer definitionField II user’s guide xdc apodizationPurpose:Procedure for creating an apodization time line for an apertureCalling:xdc apodization(Th,times,values);Input:Th Pointer to the transducer aperture.times Time after which the associated apodization is valid.values Apodization values.Matrix with one row for each time value and a number of columnsequal to the number of physical elements in the aperture.At least one apodizationvalue in each row must be different from zero.Output:none.Field II user’s guide xdc bafflePurpose:Procedure for setting the baffle condition for the aperture.Calling:xdc baffle(Th,soft baffle);Input:Th Pointer to the transducer aperture.soft baffle Whether to use the soft-baffle condition:1-using soft baffle0-using rigid baffle(default for apertures)Output:none.Implementation:For a soft baffle,in which the pressure on the baffle surface is zero,the Rayleigh-Sommerfeld integral is used instead of the standard Rayleigh integral.This is:h s( r1,t)=S δ(t−| r1− r2|c)2π| r1− r2|cosϕdS(5.1)Here cosϕis the angle between the line through thefield point orthogonal to the aperture plane and the radius of the spherical wave.The anglesϕisfixed for a given radius of the projected spherical wave and thus for a given time.It isgiven bycosϕ=z pR=z pct(5.2)I can be shown thath s( r1,t)=z pcth( r1,t).(5.3)where h( r1,t)is the standard spatial impulse response.The spatial impulse response for the soft baffle case is,thus, be found from the normal spatial impulse response by multiplying with z p/(ct),which is the method employed by the Field II program.Example:5.3.Procedures for transducer definition17Create a16elements linear array,and divide the physical elements into2by3mathematical elements to increase the accuracy of the simulation.Then set the soft-baffle boundary condition.%Set initial parametersheight=5/1000;%Height of element[m]width=1/1000;%Width of element[m]kerf=width/4;%Distance between transducer elements[m]N_elements=16;%Number of elementsfocus=[0040]/1000;%Initial electronic focus%Define the transducerTh=xdc_linear_array(N_elements,width,height,kerf,2,3,focus);%Set the soft-baffle optionxdc_soft_baffle(Th,1);Field II user’s guide xdc center focus Purpose:Procedure for setting the center point for the focusing.This point is used as a reference for calculatingthe focusing delay times and as a starting point for dynamic focusing.Calling:xdc center focus(Th,point);Input:Th Pointer to the transducer aperture.point Focus center point.Output:none.Field II user’s guide xdc concavePurpose:Procedure for creating a concave transducerCalling:Th=xdc concave(radius,focal radius,ele size);Input:radius Radius of physical elements.focal radius Focal radius.ele size Size of mathematical elements.Output:Th A pointer to this transducer aperture.Example of transducer definition:Create a concave,round transducer with an8mm radius and a focal radius of20mm and divided it into1mm mathematical elements.%Set initial parameters18Chapter5.Description of Matlab proceduresFigure5.1:Concave,round transducer with a radius of8mm divided into1by1mm mathematical elements.R=8/1000;%Radius of transducerRfocal=20/1000;%Focal radius of transducerele_size=1/1000;%Size of mathematical elements%Define the transducerTh=xdc_concave(R,Rfocal,ele_size);The resulting transducer is shown in Fig.5.1.Field II user’s guide xdc convertPurpose:Procedure for converting an aperture from a rectangular description to a triangular description. Calling:xdc convert(Th);Input:Th Aperture to be converted.Output:None.Note:The number of mathematical elements gets to be twice as large since one rectangle is modeled by two triangles.5.3.Procedures for transducer definition19Field II user’s guide xdc convex arrayPurpose:Procedure for creating a convex array aperture.Calling:Th=xdc convex array(no elements,width,height,kerf,Rconvex,no sub x,no sub y,focus); Input:no elements Number of physical elements.width Width in x-direction of elements.height Width in y-direction of elements.kerf Distance in x-direction between elements.Rconvex Convex radius.no sub x Number of sub-divisions in x-direction of elements.no sub y Number of sub-divisions in y-direction of elements.focus[]Fixed focus for array(x,y,z).Vector with three elements.Output:Th A pointer to this transducer aperture.Example of transducer definition:Create a16element convex array with a convex radius of20mm:%Set initial parametersheight=5/1000;%Height of element[m]width=1/1000;%Width of element[m]kerf=width/4;%Distance between transducer elements[m]N_elements=16;%Number of elementsRconvex=20/1000;%Convex radius[m]focus=[0040]/1000;%Initial electronic focus%Define the transducerTh=xdc_convex_array(N_elements,width,height,kerf,Rconvex,1,5,focus);Note that the radii are quite small in order to show the aperture curvature.The resulting aperture is shown below.Field II user’s guide xdc convex focused arrayPurpose:Procedure for creating a mechanical elevation focused convex array aperture.Calling:Th=xdc convex focused array(no elements,width,height,kerf,Rconvex,Rfocus,no sub x, no sub y,focus);20Chapter5.Description of Matlab procedures。

【篇一】field的用法大全field的用法1：field的基本含义是“场地”,可指农业用地、矿物产地,也可指其他用作某种用途的场地,或场所如运动场、战场等,引申可表示“领域”“方面”“界”。

既可用作可数名词,也可用作不可数名词。

field的用法2：表示“在田野里”,介词用in; “在球场上”,介词用on; “在战场上”,介词用in或on皆可。

field的用法3：一般未经耕作的土地不叫field,在英国, field大多指青草牧场。

field的用法4：field用作动词表示“(板球或棒球)(准备)接或掷还(球),守(球)”“任守方”“(足球、板球、棒球等赛中)选派(某人)上场”“顺利处理”。

【篇二】field的常用短语用作名词 (n.)have a field dayhold the fieldtake the field【篇三】field的用法例句1. He was the fastest thing I ever saw on a baseball field.他是我在棒球场上见过的跑得最快的家伙。

2. Pinch-hitter Francisco Cabrera lashed a single to left field.替补队员弗朗西斯科·卡布雷拉向左外场猛地击出一个一垒打。

3. He was on the training field for some light work yesterday.昨天他在训练场进行了一些强度较小的训练。

4. Expertly he zigzagged his way across the field, avoiding the deeper gullies.他熟练地左一拐右一拐地绕过深沟，穿过了原野。

5. We never defeated them on the field of battle.我们从未在战场上打败过他们。

6. Two blocks beyond our school was a field where boys played football.离我们学校两个街区远的地方有个男孩们玩橄榄球的球场。