PHOTONICS, FIBER OPTIC SENSORS
AND THEIR APPLICATION IN SMART STRUCTURES
A.Selvarajan * and A.Asundi **
* Department of Electrical Communication Engineering, Indian Institute of Science, Bangalore - 560 012.
** Department of Mechanical Engineering, Hong Kong University, Hong Kong.
Abstract
Photonic sensors, signal processors and communication technologies have emerged as viable alternatives to electronics. Fiber optic sensors which can readily be integrated with smart materials and structures offer an immense potential in the realization of intelligent systems. This paper presents an overview of different types of fiber optic sensors and their application to smart structures.
1. INTRODUCTION
There has been a growing interest in the area of smart structures which are designed to react to their environment by use of integrated sensors and actuators in their body. Such structures not only can monitor the health of their body but also forewarn about the onset of abnormalities in their states and hence the impending failures. There are many advantages in such a system: less down time, less frequent maintenance, better utilization of material usage and improved safety, reliability and economy.
Several forecasts have predicted that there will be a tremendous growth in the sensors market. In contrast to the classical sensors based largely upon the measurement of electrical parameters such as variable resistance or capacitance, modern sensors make use of a variety of novel phenomena. More importantly, these sensors are directly suitable for digital control and also have a degree of smartness incorporated in them to combat problems of nonlinearity and long term drift.Several key technologies are likely to play a major role in the sensors of the future. Micro electro mechanical (MEM), microelectronic sensors based on piezoelectric materials, organic polymers and silicon have tremendous potential as smart sensors. F iber optics based sensors are also emerging as a viable and competitive technolog y.While many types of stand alone sensors are available, only some of them can be considered for integration with smart structures. Among these, fiber optic sensors are in the forefront in their choice for incorporation into materials and structures made of carbon and glass fiber reinforced polymer composites.
Materials technology has had a profound impact on the evolution of human civilization. This evolution has now culminated in the design of smart materials[1-8]. The class of engineered smart materials known as composites have made a major impact upon the design and application of structural components and engineering structures. If composites form the basis of the body design, there are a number of sensor and actuator materials which enable the body to become intelligent, continuously monitor and take corrective measures to keep it in good health.. The smart sensors [9-14] are to provide in association with other components like actuators and control systems the
required functional capability to smart structures so as to react to their internal and external environment and achieve adaptability very much like the living organisms. Smart structures and intelligent systems are topics of great interest at present [15-30]. Smart planes, smart space ships, smart bridges and highways, to mention a few, are examples of the fast developing area of smart structure systems in which an advanced combination of materials, sensors, actuators, control and processing need to be blended suitably for achieving the end result. From a technology view point smart structures can be understood to mean the integration of sensors, actuators and controls with a structural component so as to achieve adaptive functionality. The success of such a scheme will eventually depend on our ability to engineer biologically inspired materials systems with intelligence and life features. Electrorheological fluids, shape memory alloys, piezoelectric, magnetostrictive, and electrostrictive materials can all serve both as sensors and actuators. However their main
limitation is that it is difficult to embed them in composites. I t is clear that smart sensors are not stand alone devices but to be integrated within the body of materials and systems. Fiber optic sensors (FOS) are the new class of devices in the evolving smart sensor design.
With the advent of lasers and semiconductor optoelectronics, a great revolution in modern optics took place. Rapid developments in fiber optics gave an additional impetus to this. H olography and Fourier Optics are well known photonic techniques. The above developments have lead to the birth of a new discipline, popularly called Photonics. In photonics, photons play a role akin to electrons in electronic materials, devices and circuits. As a result, a large number of activities which were traditionally in the electronic domain are now shifting to the realm of photonics. To mention a few, progress in the use of photonics in sensing, signal processing, communication and computing has been rapid. The main advantages are in terms of speed and security. It is also well known that in addition to the high-tech and scientific activity, a whole range of mass items like compact discs, photo copiers and laser printers have been the result of photonic technologies. Gigabit transmission networks and information super highways are currently pushing the society to greater heights. Processing and computing using massively parallel architectures are on the verge of success. A wide range of fiber optic sensors are fast reaching the market place. Freedom from electromagnetic interference and unprecedented speed and bandwidth are prime reasons for all the success in photonics. Impressive though the developments in photonics till date is, it is yet to reach its full potential especially in terms of the market exploitation. Many great ideas have been propounded but fewer competitive and rugged products have found their way to the market place. Microlectronics still holds the sway when it comes to economy and ease of use. It appears that the near term prospe cts are better met with a hybrid approach, namely, part electronics and part photonics to realize compact, cost effective and intelligent systems. Eventually, photonics may take its due place as a superior market force.One of the exciting fields wherein photonics is expected to play a significant role is smart structures and intelligent systems of interest in engineering.This is where the real challenge lies even in the case of fiber optic sensors and photonic communication and control schemes. In smart structure applications, composite materials, fiber optic sensing and telemetry systems, piezoelectric actuators and microprocessor based control schemes seem to offer the best advantages as of now.
The different types of fiber optic sensors, components used in optical fiber sensing, sensor design and analysis, and distributed\ multiplexed sensor schemes are dealt with in the following sections. Application of FOS to smart structures and the role of integrated optics (IO) are also highlighted.
2. FIBER OPTIC SENSORS
The technology and applications of optical fibers have progressed very rapidly in recent years. Optical fiber, being a physical medium, is subjected to perturbation of one kind or the other at all times. It therefore experiences geometrical (size, shape) and optical (refractive index, mode conversion) changes to a larger or lesser extent depending upon the nature and the magnitude of the perturbation. In communication applications one tries to minimize such effects so that signal transmission and reception is reliable. On the other hand in fiber optic sensing, the response to external influence is deliberately enhanced so that the resulting change in optical radiation can be used as a measure of the external perturbation. In communication, the signal passing through a fiber is already modulated, while in sensing, the fiber acts as a modulator.I t also serves as a transducer and converts measurands like temperature, stress, strain, rotation or electric and magnetic currents into a corresponding change in the optical radiation. Since light is characterized by amplitude (intensity), phase, frequency and polarization, any one or more of these parameters may undergo a change. The usefulness of the fiber optic sensor therefore depends upon the magnitude of this change and our ability to measure and quantify the same reliably and accurately.
The advantages of fiber optic sensors are freedom from EMI, wide bandwidth, compactness, geometric versatility and economy. In general, FOS is characterized by high sensitivity when compared to other types of sensors. It is also passive in nature due to the dielectric construction. Specially prepared fibers can withstand high temperature and other harsh environments. In telemetry and remote sensing applications it is possible to use a segment of the fiber as a sensor gauge while a long length of the same or another fiber can convey the sensed information to a remote station. Deployment of distributed and array sensors covering extensive structures and geographical locations is also feasible. Many signal processing devices (splitter, combiner, multiplexer, filter, delay line etc.) can also be made of fiber elements thus enabling the realization of an all-fiber measuring system. Recently photonic circuits (Integrated Optics) is proposed as a single chip optical device or signal processing element which enable s miniaturization, batch production, economy and enhanced capabilities.
There are a variety of fiber optic sensors. These can be classified as follows.
A) Based on the modulation and demodulation process a sensor can be called as an intensity (amplitude), a phase, a
frequency, or a polarization sensor. Since detection of phase or frequency in optics calls for interferometric techniques, the
latter is also termed as an interferometric sensor. From a detection point of view the interferometeric technique implies
heterodyne detection/coherent detection. On the other hand intensity sensors are basically incoherent in nature. Intensity or
incoherent sensors are simple in construction, while coherent detection (interferometric) sensors are more complex in design
but offer better sensitivity and resolution.
B) Fiber optic sensors can also be classified on the basis of their application: physical sensors (e.g. measurement of
temperature, stress, etc.); chemical sensors (e.g. measurement of pH content, gas analysis, spectroscopic studies, etc.); bio-
medical sensors (inserted via catheters or endoscopes which measure blood flow, glucose content and so on). Both the
intensity types and the interferometric types of sensors can be considered in any of the above applications.
C) Extrinsic or intrinsic sensors is another classification scheme. In the former, sensing takes place in a region outside of the
fiber and the fiber essentially serves as a conduit for the to-and-fro transmission of light to the sensing region efficiently and
in a desired form. On the other hand, in an intrinsic sensor one or more of the physical properties of the fiber undergo a
change as mentioned in A) above.
3. BASIC COMPONENTS
A fiber optic sensor in general will consist of a source of light, a length of sensing (and transmission) fiber, a photodetector, demodulation, processing and display optics and the required electronics.
3.1 Optical fibers: These are thin, long cylindrical structures which support light propagation through total internal reflection. An optical fiber consists of an inner core and an outer cladding typically made of silica glass, although, other materials like plastics is some times used. Three types of fibers are in common use in FOS. The multimode (MM) fiber consists of a core region whose diameter (~50 μ m) is a large multiple of the optical wavelength. The index profile of the core is either uniform (step-index) or graded (eg.,parabolic). Plastic fibers have a step index profile and a core size of about 1mm. The microbend type or the evanescent type intensity sensors use MM fibers. MM fiber has the advantage that it can couple large amount of light and is easy to handle both arising from its large core size.
Single mode (SM) fiber is designed such that all the higher order waveguide modes are cut-off by a proper choice of the waveguide parameters as given below.
where, λ is the wavelength, a is the core radius, and n1and n2 are the core and cladding refractive
indices, respectively. When V < 2.405 single mode condition is ensured. SM fiber is an essential requirement for interferometric sensors. Due to the small core size (~4 μm) alignment becomes a critical factor.
The SM fiber mentioned above is not truly single mode in that two modes with degenerate polarization states can propagate in the fiber. This can lead to signal interference and noise in the measurement. The degeneracy can be removed and a single mode polarization preserving fiber can be obtained by the use of an elliptical core fiber of very small size or with built in stress. In either case light launched along the major axis of the fiber is preserved in its state of polarization. It is also possible to make a polarizing fiber in which only one state of polarization is propagated. Polarimetric sensors make use of polarization preserving fibers. Thus, multimode fiber, single mode fiber and polarization preserving fiber are the three classes of fibers which are used in the intensity type, the interferometric type and the polarimetric type of sensors, respectively.
3.2 Sources: In FOS semiconductor based light sources offer the best advantages in terms of size, cost, power consumption and reliability. Light emitting diodes (LEDs) and laser diodes (LDs) are the right type of sources for FOS although in laboratory experiments the He-Ne laser is frequently used. Features of LED include very low coherence length, broad spectral width, low sensitivity to back reflected light and high reliability. They are useful in intensity type of sensors only. LDs on the other hand exhibit high coherence, narrow linewidth and high optical output power, all of which are essential in interferometric sensors. Single mode diode lasers are made using distributed feedback or external cavity schemes. High performance Mach-Zehnder and Fabry-Perot type sensors need single mode lasers. LDs in general are susceptible to reflected (feedback) light and temperature changes. They are also less reliable and more expensive. Coupling of light from source to fiber is an important aspect and may call for special optical devices. Use of pigtailed source can alleviate this problem but such devices cost more. Fiber lasers and amplifiers are fast becoming commercial products and may play an important role in future FO sensors.
3.3 Detectors: Semiconductor photodiodes (PDs) and avalanche photodiodes (APDs) are the most suitable detectors in FOS. APD can sense low light levels due to the inherent gain because of avalanche multiplication, but need large supply voltage typically about 100 V. The various noise mechanisms associated with the detector and electronic circuitry limit the ultimate detection capability. Thermal and shot noise are two main noise sources and need to be minimized for good sensor performance. Detector response varies as a function of wavelength. Silicon PD is good for visible and near IR wavelengths. Generally there is no bandwidth limitation due to the detector as such, although the associated elecronic circuits can pose some limitation.
4. DESIGN AND ANALYSIS of fiber optic sensors
4.1 Intensity (amplitude) sensors
In this case, the signal to be measured (the measurand), intensity (amplitude) modulates the light carried by an optical fiber. For this class of sensors a normalized modulation index (m) can be defined as
where, ?I = change in optical power as a result of modulation by the measurand; I0 = optical power reaching
the detector when there is no modulation; and P = perturbation (measurand).
The sensor response expressed as a differential voltage per unit change in measurand is given by
where, q = detector responsivity (A/W); R = load resistance.
The limiting performance is reached when the signal voltage (power) is equal to the noise voltage (power). There are many noise sources within the detector as also in the processing circuits. For purposes of estimating the sensor performance, one usually considers the quantum of limit of detection i.e.; the fluctuations in the photon field being detected is the ultimate limit.
The minimum measurable quantity in the shot noise limit is given by
where e = electronic charge and B=detection bandwidth.
4.1.1 Microbend Sensor
The modulation due to a measurand can be brought about in the form of a microbend loss modulation, moving fiber, for example moving reflector or an absorbing layer modulation. Microbend sensor is an example of an intensity modulation sensor. A microbend sensor is shown in Fig.1.
Fig.1 Microbend sensor
It is designed using multimode fiber of a few meters in length which is placed between two rigid plates having an optimum corrugation profile such that the fiber experiences multiple bends. Due to the microbending induced losses, the lower order guided modes are converted to higher order modes and are eventually lost resulting in a reduction of the optical intensity coming out of the fiber. A displacement of the plates (due to say, pressure) causes a change in the amplitude of the bends and consequently an intensity modulation of light emerges from the fiber core. Microbend sensors have been used in some smart structure applications.
4.2. Interferometric (phase) sensors
Such a sensor is based on the detection of changes in the phase of light emerging out of a single mode fiber. The phase change in general is given by
where the three phase terms on the RHS are due to the length, the index and the guide geometry variations, respectively. The phase change is converted into an intensity change using interferometric schemes (Mach-Zehnder, Michelson, Fabry-Perot or Sagnac forms). In a simple system only the sensing and reference arms are made of fibers, while the rest are bulk optic components. However either all-fiber or integrated optic components can provide better stability and compactness compared to their bulk counterparts. Interferometric fiber optic sensors are by far the most commonly used sensors since they offer the best performance. They have found application as acoustic (e.g. hydrophones), rotation (eg., gyroscope), strain, temperature, chemical , biological and a host of other type of sensors.
The phase change of light propagating through a fiber of length 1 and propagation constant b = ko n, is given by
In the case of an acoustic wave impinging on the fiber the phase change, for a unit pressure change is
obtained as,
where n = refractive index, and a = radius of the fiber. The change
in b, due to radius variations is very small and can be neglected. The change in refractive index can be found from the optical indicatrix relation
where p ijhl is the photoelastic tensor and εhl is the strain. Optical fiber is made of isotropic glass
and has only two independent photoelastic constants p11 and p12.
Let
Combining all these we get
Explicit expressions for the induced phase shift (normalised to length)
due to some specific perturbations are given below.
(11)
(12)
(13)
where, ?P = change in hydrostatic pressure; p11, , p12 = photoelastic constants; n = Poisson's ratio; E = Young's modulus; a = linear
expansion coefficient; S = strain; λ = wavelength of light in free space; n = mean refractive index; a = core radius of the fiber; = rate of change of propagation constant with core radius; ?T = change in temperature.
The exact numerical value obtainable in each case depends on the type of fiber used. For typical pure silica fibers the phase sensitivities obtainable per meter are about 10 radians per bar pressure change, 105 radian per degree centigrade change and 11.5 radians per longitudinal strain.
Minimum Detectable Pressure, temperature and strain
In an optical interferometer the reference and modulated light are combined and detected using a photodetector. The current output from the detector is given by (taking small phase change and a fixed phase bias of π /2 for optimum detection),
The photon noise current associated with this detection is
Signal to noise ratio,
Minimum detectable pressure is found by setting SNR = 1. Hence Pmin is obtained as
where h = Plank's constant, n = optical frequency, ?f = detection bandwidth and q =
quantum efficiency.
The limiting sensitivities (ie., minimum detectable change in pressure etc.) then depends on the desired SNR. If we assume that a phase change of one microradian is the detection limit due to quantum noise limit then the detection thresholds (per unit length of fiber) for pressure, temperature and strain are, respectively, 10-7 bar, 10-8 degree C and 10-7 strain. These numbers indicate that the fiber optic interferometric (phase) sensors are very sensitive and therefore need careful packaging and handling if they are to be exploited in practical applications.
4.2.1 Mach- Zehnder interferometric sensor
A fiber optic Mach-Zehnder interferometric sensor consists of two 3-d
B couplers (beam divider\ combiner) and two lengths of fiber, one serving as a sensingarmand the other as reference arm as shown in Fig.2.
Fig.2 Mach-Zehnder interferometer
4.2.3 Sagnac interferometer (fiber optic gyroscope)
While mechanical gyros work on the principle of Newton's laws of motion, it is a different phenomenon in case of optical gyros. Here interferometry plays a major role in the guise of Sagnac effect. Essentially, the Sagnac principle is a phase modulation technique and can be explained as follows:
Two counter propagating beams, (one clockwise, CW, and another counterclockwise, CCW) arising from the same source, propagate inside an interferometer along the same closed path. At the output of the interferometer the CW and CCW beams interfere to produce a fringe pattern which shifts if a rotation rate is applied along an axis perpendicular to the plane of the path of the beam. Thus, the CW and CCW beams experience a relative phase difference which is proportional to the rotation rate. Consider a hypothetical interferometer, with a circular path of radius R as shown in fig. 3.
Fig 3. Sagnac Interferometer principle.
Light injected into the interferometer splits (by means of a beam splitter) into CW and CCW propagating beams. When the interferometer is stationary, the CW and CCW propagating beams recombine after a time period given by,
where R is the radius of the closed path and c is the velocity of light. But, if the interferometer is set into rotation with
an angular velocity, W rad/sec about an axis passing through the centre and normal to the plane of the interferometer, the beams re-encounter the beam splitter at different times, the CW propagating beam traverses a path length slightly greater (by ? s) than 2πR to complete one round trip. The CCW propagating beam traverses a path length slightly lesser than 2πR in one round trip. If the time taken for CW and CCW trips are designated as T+ and T-, then
The difference yields
With the consideration that, c2 ? (R W)2,
The round trip optical path difference is given by
and the phase difference is given by
or more generally
where A = area of the enclosed loop.
If the closed path consists of many turns of fiber, ?φ is given by,
where N = number of turns of fiber, each of radius R, and L = total length of the fiber. Sagnac effect can also be arrived at by using the frequency shift approach, particularly in case of resonating gyros. The CW and CCW ring laser modes have different frequencies due to difference in effective round trip optical path lengths caused by cavity rotation. Oscillations having wavelengths which fulfill the resonance condition
can be sustained in the cavity. As a general case, the Sagnac frequency shift is given by,
where A= the area enclosed and P = perimeter of the light path.
A minimum configuration fiber optic gyro which ensures perfect reciprocity is shown in fig.4
Fig 4. Minimum configuration fiber optic gyro.
If we take l = 0.85 m m, L = 200 m and D = 3 cm, we find that the Sagnac phase shift is p radians for a rotation rate of 1200o/s. To detect earth's rotation rate (15o/hour) we need therefore a detection capability of about 10 microradian phase shift. The constant phase shift introduced in a fiber of 200 m is of the order of 1010 rad. Thus the CW and CCW beams between which a small Sagnac phase shift due to rotation is to be sensed must traverse identical paths to an accuracy of about 1 in 1015 so that the reciprocity condition (i.e., no phase shift in the absence of rotation) is fulfilled. As in any interferometer, the detection limit of gyro is set by photon shot noise. If a 10 mW optical power is received at the detector, a noise equivalent phase shift of about 10-7 rad/ √ Hz can be sensed or an equivalent rotation rate of about 1o/hr/√ Hz can be detected.
4.3 Fiber Optic Polarimeter
The birefringence property arising from optical anisotropy is used in the study of photoelastic behaviour . The anisotropy may be due to naturally occuring crystalline properties or due to stress- induced birefringence . It is the latter that is used in a photoelastic fiber optic strain gauge. In a simple setup 2 lead fibers are used to illuminate and collect light passing through a photoelastic specimen. A pair of linear polarizers is used in the crossed form to obtain a conventional polariscope. In such a case the intensity at each point on the specimen is given by
where I0 is the total light intensity and θ is the angle that the principal stress directions make with respect to the axes of the polarisers . Due the stress birefringence the orthogonally polarized light waves travel with a phase difference α given by
where λ is wave length , n is the index of refraction ,d is the thickness in the
direction of light propagation ,C is stress-optic coefficient and fa= (λ \C) is known
as material fringe value. When the polarisers are oriented 450 w.r.t. principal stress
directions eqns 1 and 2 simplifies to
with α = (2π /fa ) σ d where the applied load is assumed to produce a uniaxial stress . By taking the derivative of the above equation we obtain
This has a maximum sensitivity when α =π/2 (quadrature condition ) . Under this condition (?Ι/Ι 0) / ?
∈=πΕ d/fa , where E is the elastic modulus and ∈ is the strain in the direction of applied load . The
photo-detector output which is expressed in terms of voltage sensitivity can be written as
It may be noted that in this case the fiber only serves as a light conduit and the set up described above is basically same as the conventional bulk optic polariscope .
5. DISTRIBUTED SENSORS
In some applications there may be a need for multisensor systems. Such a system can be realized in a number of ways. One way is to arrange a set of discrete (point) sensors in a network or array configuration, with individual sensor out puts multiplexed using a time division multiplexing (TDM) or frequency division multiplexing (FDM) or such other scheme. Alternatively, it is more interesting to exploit the inherent ability of the fiber sensors to create unique forms of distributed sensing. For example, optical time domain reflectometry (OTDR) and distributed Bragg grating sensors are two such schemes in common use (fig.5). In smart structure design and application these sensors play an important role.
There are number of methods for producing intra core gratings in a single mode fiber as used in distributed Bragg grating sensors. These include side writing techniques such as exposure to UV laser radiation from an Excimer laser . Such exposures could be in the form of two beam interference (holography ) or exposure to a face mask or point by point exposure . These methods are time consuming and suitable for single element strain sensors . In the case of distributed strain sensors on-line fabrication of arrays of FBG is desirable . A scheme utilizing a polarised Ti sapphire laser for this purpose has been reported.
Fig 5. Multiplexed sensor arrays using (a) OTDR and (b) WDM / Bragg grating principles.
6. ROLE OF INTEGRATED OPTICS
In optical fiber sensing, in some configurations such as interferometric sensors or gyroscope there is requirement of several (functional) optical components such as modulator, coupler, polarizer etc., for effective signal handling and analysis. Such components can be realized in bulk-optic, integrated-optic or all-fiber-optic form. Integrated optics (IO) combines thin-film and micro fabrication techniques to make optical wave guides and devices in planar form and offers the advantages of compactness, power efficiency and multi-function in single chip capabilities. For example, the couplers, polarizer and phase modulator required in the case of a fiber-optic gyroscope can easily be realized as a single chip on lithium niobate. Similarly various types of modulators useful in Mach-Zehnder type sensors can also be made
in IO form. When IO devices are made on semiconducting substrates like GaAs or InP, complete integration of both optical and electronic components is feasible.
7. APPLICATION TO SMART STRUCTURES
In general fiber optic sensors for smart structure applications require the following capabilities:
1. Monitor the manufacturing process of composite strucures.
2. Check out the performance of any part or point of the structure during assembly.
3. Form a sensor network and serve as a health monitoring and performance evaluation system during the operational period of the structure.
The choice of a suitable fiber and its coating as well as the embedding technique are the important starting points. Although normal silica fibers perform satisfactorily at temperatures upto 1000 0C, at still higher temperatures there results a loss of waveguiding property due to dopant diffusion. Therefore special fibers made of sapphire have been experimented at temperatures upto 2000 0 C. Next, for the case of fibers to be embedded into carbon-epoxy materials it is desirable to use a fiber coating of a similar organic composite material.. Climent et al [ ] have observed that the orientation of the optical fiber parallel to the strength members of the composite helps to avoid formation of voids and delaminations during curing . When 50\125 micron optical fibers were placed crosswise into IM7\8552 epoxy-carbon prepreg system it was found that a lenticular resin-rich region was formed around the fiber. The effect of this resin-rich zone is found to diminish with the orientation angle between the optical and the reinforcement fibers and is negligible for the case of parallel placement.
1. Process\cure monitoring of composites
Due to advantages such as high strength-to-weight ratios, good fatigue and corrosion resistance and flexibility to tailor mechanical properties, composite materials find application in many industries including aircraft, automobile, building and container industries. One important issue in their use is the need to demonstrate the reliability of composite structural members . To assure on this score it is necessary to evaluate the effects of impact damage, environmental effects and/or processing defects. Nondestructive evaluation of the above is both costly and time consuming. If sensors can be directly integrated into composite materials it will help monitor the internal state of the composite structural members and reduce the uncertainty and doubts as regards the status of the material. Such integrated sensors can generate quantitative data which will indicate the state of the cure of an epoxy matrix resin initially and later continuously monitor the in-service condition. Fourier Transform Infrared (FTIR), ultrasonic measurements and fluorescence spectroscopy are some of the known methods used in cure sensing. A fiber optic combined cure and in-service strain sensor was reported recently by May et al[ ]. The cure state is monitored on the basis of refractive index changes due to cross linking when the curing takes place while continuous strain monitoring during service is achieved using a Fabry-Perot Interferometric (FPI) technique. The combined sensor is embedded into the composite during fabrication. The sensor is as shown in fig.6.
Fig.6 Fabry-Perot Interferometric sensor for epoxy cure monitoring
It consists of a single mode input/output fiber and a single or multimode reflector fiber both of which are housed in a hollow-core capillary. A source and a detector are connected to the sensor gauge using 2x2 fiber coupler. There is a small air gap between the fibers and serves as a F-P cavity. As the sensor is strained the air gap changes in length and the sensor output varies . The F-P output can be calibrated to serve as a strain sensor. By suitably modifying the reflector fiber the same sensor can be used as a cure monitor. The reflector fiber is chosen such that the refractive index of the fiber is higher than that of the uncured epoxy, but less than that of the fully cured epoxy. While monitoring the cure state, a low coherence source such as LED is used. Due to this the F-P resonator is non-functional and the sensor behaves as a reflectometer. The input light is transmitted through the air gap and is reflected back at the cleaved end. The reflectance changes due to cross linking when the epoxy is fully cured. At this stage the low coherence source is replaced with a laser as also the processing electronics so that the sensor now responds to strain variations via the FP interference.
In another experiment Lou et al [ ] have demonstrated an Optical Time Domain reflectometer (OTDR) fiber sensor network embedded in a thermoset composite laminate. The system served as an integrated cure, strain and temperature sensor system. as shown in fig.7 two sections of 200\240 μ m polyimide-coated step index fibers were incorporated: i) in one section strain sensors were made by the introduction of reflective markers with an interaction length of 15cm as defined by adjacent markers and ii) the second section which served as the temperature sensors had 6 cm long liquid core fiber elements between markers. The cure sensor was a fiber element made of Hercules 3501-6 resin. The complete fiber network was embedded in a laminate composite made from AS4\3501-6 carbon fiber epoxy prepreg. Thin stainless steel tube sleeves were positioned at the ends of the laminate and the fibers were pulled through the same for protection. Proof-of-concept tests were carried out using slices of the panel fabricated as above and good correlation of results between fiber sensors and other surface attached thermocouples, strain gauges and extensometers were observed.
Fig 7.
Sensor
system for
process
and health
monitoring
of
composites.
2.Applicatio
in civil
engineering
Using a
microbend
sensor as
shown in
fig.8,
pressure,
load and
displacement measurements can be made on civil structures such buildings and bridges. Such a sensor is attractive because it is simple to use, low cost and very rugged. Initial calibration could be done with a compression testing machine.
Fig 8. A
Microbend sensor
for civil
engineering
application.
.
High
temperature
measurement :
A Michelson
optical fiber interferometer can be used to make high temperature measurements as discussed below[ ] . The Michelson interferometer is shown in fig
.9 .It comprises of a 2x2 coupler and a sensing and reference arm . The cleaved faces at the free ends of the above two fibers were coated with metal films for improved reflectivity .When coated with Cu or Ti films , the sensor can be used upto 12000C . The reference fiber
was wound around a PZT cylinder which can be modulated at a desired frequency to generate phase modulated carrier reference signal . Tests have shown that the sensor fringe visibility drastically changed when the sensor was exposed to high temperatures over a few hours .
This is attributed to the oxidation as well as the cracking of the films due to thermo mechanical mismatch .
Fig 9. Michelson Interferometer sensor
for high temperatures.
F-15 Airframe testing using Fabry
Perot interferometer :
An External Fabry Perot Interferometer (EFPI) as shown in fig. 6 has been used by Greene et.al [ ]for a full scale testing F-15 airframe . 6 EFPI strain sensors were attached to the flap hinge of the air frame For comparison purposes a foil strain gauge was also juxtaposed to the EFPI sensors . Hydraulic actuators were used to apply loads to the wing and flap of the air frame so as simulate the actual force conditions during flight . The strain output as measured by the collocated EFPI and foil strain gauge as shown in fig.10. There is a close agreement indicating that a fiber strain gauge is a viable alternative to the electrical based foil gauge .
Fig 10. Comparison strain measurements by FPI (open square) and foil gauge (open circle)
During their life cycle military aircrafts experience a wide range of load and flight environments. To ensure flight safety and air worthiness, it is necessary to track aircraft usage and damage growth in the structure. The damages can be of many kind- fatigue in metallic structures, delaminations and disbonds in composite structures and large scale structural damages. Two advanced programs , Smart Structures Concept Requirements definition (SSCORE) and Structural Health Monitoring System (SHMS) have been taken up by Northrop Corporation and Joint Airforce (Wright Labs\Naval Center) in USA to establish requirements , identify gaps and perform selective testing in the context of aircraft testing and maintenance. Fiber optic sensors have been identified along with other types of sensors as an important technology for further investigation [ ].
Application of Sagnac interferometer to earth movement detection:
A Sagnac Interferometer(SI) has the potential to measure strain of less than 100 microns over distances of order of few kms . This is very attractive because there are many telecommunication fiber cables laid throughout various regions of cities and countries . The principle of SI has already been explained . The induced fringe shift in a fiber optic gyro is given by
z l=f l n/ c
where f is the frequency difference between counter propagating beams . By differentiating we get n/c [f dl + l df ] = 0
where z f is assumed to be held constant . Such an operation is called closed loop operation . Thus we can write
df / f = - dl / l .
As an example if the frequency shifting AOM operates at 100 MHz and the processing electronic has a resolution capability of 1 Hz we can achieve a dl resolution of 100 microns if the fiber length is 10 Kms . A global monitoring system based on the network of available telecommunication fiber will greatly benefit in terms of public safety and the protection of vital infrastructure . Although FO rotational sensors are well developed , the application to detection of earth movement as discussed above need further experimentation .
1. A.S.Brown, Materials get smarter : Aerospace America v 28 n 3 Mar 1990 p 30-34
1. Y.Furuya, A.Sasaki, M.Taya, Enhanced mechanical properties of TiNi shape memory fiber/Al matrix composite : Materials
Transactions, JIM v 34 n 3 Mar 1993. p 224-227
1. P.A.Jardine,S.J Madsen,G.P. Mercado, Characterization of the deposition and materials parameters of thin- film TiNi for
microactuators and smart materials : Materials Characterization v 32 n 3 Apr 1994. p 169-178
1. J.Hodgkinson, John : What are smart materials anyway? : Materials World v 1 n 8 Aug 1993. p 449-450
1. R.S.Porter,: Smart polymers. A brief review : Plastics Engineering v 50 n 5 May 1994. p 67-68
1. M.Anjanappa,; Bi, J. : Theoretical and experimental study of magnetostrictive mini-actuators : Smart Materials and Structures v 3 n
2 Jun 1994. p 83-91
1. J.M.Giachino, , Smart Sensors,Sensors and Actuators v 10 n 3-4 Nov-Dec 1986 p 239-248
1. R.Rogowski,M. Holben,J. Heyman, P.Sullivan,: Method for monitoring strain in large structures: optical and radio frequency
devices. : Review of Progress in Quantitative Nondestructive Evaluation v 7A 1988 p 559-563
1. Haskard, R.Malcolm : Experiment in smart sensor design. : Sensors and Actuators, A: Physical v 24 n 2 Jul 1990 p 163-169
1. Najafi, Khalil : Smart sensors. :: Journal of Micromechanics and Microengineering v 1 n 2 Jun 1991 p 86- 102
1. Senturia, D.Stephen : Microsensors vs. ICs: A study in contrasts. :: IEEE Circuits and Devices Magazine v 6 n 6 Nov 1990 p 20-27 1. Manus, Henry : Validating data from smart sensors : Control Engineering v 41 n 9 Aug 1994. p 63-66
1. Bryzek, Janusz : Communications standard for low-cost sensors : Sensors (Peterborough, NH) v 11 n 9 Sept 1994.
1. A. Hickman, ; J. J Gerardi, .; Y.Feng, : Application of smart structures to aircraft health monitoring. : Journal of Intelligent
Material Systems and Structures v 2 n 3 Jul 1991 p 411-430
1. Stevens, Tim : Structures get smart. :: Materials Engineering (Cleveland) v 108 n 10 Oct 1991 p 18-20
1. Dry, M Carolyn .; Sottos, R.Nancy : Passive smart self-repair in polymer matrix composite materials :: Smart Structures and
Materials 1993: Albuquerque, NM, USA : Proceedings of SPIE - The International Society for Optical Engineering v 1916 1993.
Publ by Society of Photo-Optical Instrumentation Engineers, Bellingham, WA, USA. p 438-444
1. S.H Smith,.; A.A Boiarski,.; D.G.Rider, : Calibration approach for smart structures using embedded sensors : Experimental
Techniques v 16 n 2 Mar-Apr 1992. p 25-31
1. T. B.Salzano, ; C. A. Calder, ; D. W. DeHart, : Embedded-strain-sensor development for composite smart structures. :
Experimental Mechanics v 32 n 3 Sep 1992 p 225-229
1. Garcia, Ephrahim; Dosch, Jeff; Inman, J.Daniel : Application of smart structures to the vibration suppression problem. : Journal of
Intelligent Material Systems and Structures v 3 n 4 Oct 1992 p 659-667
1. Dry, Carolyn : Matrix cracking repair and filling using active and passive modes for smart timed release of chemicals from fibers
into cement matrices : Smart Materials and Structures v 3 n 2 Jun 1994. p 118-123
1. M.Garfinkle, : Smarter rotor-blade composite 'smart' spar :: Materials & Design v 15 n 1 1994. p 27-31
1. Anon : Smart systems. Not just a flash in the pan : Materials World v 2 n 1 Jan 1994. p 20-21
1. Greenhalgh, Skott; Pastore, Christopher; Garfinkle, Moishe : Aeroelastic airfoil smart spar : Composites Manufacturing v 4 n 4
Dec 1993. p 195-198
1. S.Hanagud, ; G.L.Nagesh Abu, : Smart structures in the control of airframe vibrations : Journal of the American Helicopter Society
v 39 n 2 Apr 1994. p 69-72
1. Jurgen, K.Ronald : Smart cars and highways go global. : IEEE Spectrum v 28 n 5 May 1991 p 26-36
1. Damle, Rajendra; Lashlee, Robert; Rao, Vittal; Kern, Frank : Identification and robust control of smart structures using artificial
neural networks : Smart Materials and Structures v 3 n 1 Mar 1994. p 35-46
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(Society of Automotive Engineers) Transactions v 100 n Sect 1 pt 2 1991, 912167 p 2647-2656
网络聊天英文缩写 121: one to one ADN: any day now ADR/addy: address AFAIK: as far as I know AFK: away from keyboard A/S/L: age, sex, location (or just "ASL") ASAP: as soon as possible B4: before B4N: bye for now BB: best boy BBFD: big bad forum discussion BBL: be back later BF: boyfriend or best friend BFF: best friends forever BFFL: Best Friends For Life BFN: bye for now BG: big grin / best girl BMA: best mate always BNR: but not really BRB: be right back BRT: be right there BTA: but then again BTW: by the way C: see? CID: crying in disgrace CNP: continued [in my] next post CP: chat post CU: see you CUL: see you later CY A: see you (later) CYO: see you online DBAU: doing business as usual DD, DH, DS, DW: dear daughter, dear husband, dear son, dear wife (often used on boards where you discuss personal things, but wish to keep private the names of your loved ones) DW: dont worry EIP: editing in progress FTW: for the win or f*** the world or For The World FUD: fear, uncertainty, and doubt
颜色英文缩写大全缩写方式一： 缩写英文中文 BK Black黑色 BN Brown棕色 BU Blue蓝色 CR Clear透明 DKGN Dark Green深绿色 GN Green绿色 GY Gray灰色 LT BU Light Blue浅蓝色 LT GN Light Green浅绿色 OG Orange橙色 PK Pink粉红色 PL Purple紫色 RD Red红色 TN Tan褐色 VI Violet粉紫色 WT White白色 YL Yellow黄色 缩写方式二：
序号英文简写英文中文1BGE beige米色 2BLU blue蓝色 3BLK black黑色 4LAV lavender淡紫色 5BGY Blue grey蓝灰色 6LBL lightblue浅蓝色 7VLT violet紫色 8SKY skyblue天蓝色 9WHI white白色 10 GRY grey灰色 11 NAT natural自然色 12 GRN green绿色 13 LPK lightpink浅粉色 14 AQU Aqua 水绿色 15 MAG magenta洋红色 16 TUR turquoise青绿色 17 PNK pink粉色 18 CRP crystal pink晶粉 19 SKN sky nature天蓝色 20 PLT purple tulip紫色 21 OLV olive橄榄绿
22HBL hotblue亮蓝 23FUS fuchsia紫红色 24 GLD golden金色 25PUR purple紫色 26 RED red 红色 27 SAL salmon 鲜肉色 28YLW yellow黄色 缩写方式三： 序号英文简写英文中文 1 WH White白色 2 BN Brown棕色 3 GN Green 绿色 4 YE Yellow黄色 5 GY Grey灰色 6 PK Pink粉红色 7 BU Blue蓝色 8 RD Red 红色 9 BK Black黑色 10VT Violet紫色 11GN/PK Green-pink绿 /粉红色12RD/BU Red-blue红/蓝色
Win7下安装linux双系统 经过大半天的摸索与实验终于在自己的电脑上成功的装上了Win7和Linux的双系统，现在我把详细的流程给大家分享了，希望有兴趣的可以去试试。 不要说什么百度一下一大片，百度上的流程都是相当相当的抽象，当然，这份流程也是通过百度上的一些方法然后加上自己的细化而来的。 首先要先做好准备工作，将Win7中的磁盘空间腾出38G左右，这里的腾出不是说磁盘中的剩余空间，而是要将部分磁盘进行压缩。具体方法如下： 右键单击计算机，选择管理，在管理窗口中有一项磁盘管理，如下图： 单击后在中间出现磁盘管理，如下图：
有绿框框着的是逻辑分区，此时就好对磁盘进行压缩，如果磁盘空间不够大的话就直接对最后一个逻辑分区进行手术。 先说说磁盘空间不够大的情况，可以先删除最后一个逻辑分区，方法是：右击最后一个逻辑分区，选择删除卷，然后选择是，此时你能看到在最后出现了可用空间，这时右击可用空间，选择格式化，此时不要将整个可用空间格式化，只用格式化8G空间就足够了，剩余的空间留着装Linux用。格式化时注意选择格式为FAT32。 如果磁盘空间足够大就只需将磁盘进行压缩，具体方法是，右击一个逻辑驱动器，选择压缩卷，只用腾出38G就足够了，然后将这38G按上面的方式格式化8G，其余不用管。
现在就可以在网上下载一份Linux系统镜像，下载地址 https://www.doczj.com/doc/718886581.html,/d/iso/1000001036.html（建议下载完整版） 下面就要将下载好的镜像复制到刚刚前面格式化好了的FAT32磁盘里，用Winrar解压软件，将镜像中的inages和ioslinu两个文件夹复制到FAT32磁盘的根目录中，当然，原来的镜像要保留不能修改。 然后将isolinux文件夹中的initrd.img和vmlinuz两个文件夹复制到FAT32磁盘的根目录下，同时将其也复制到C盘的根目录中。 刚才的工作结束后，你的FAT32磁盘中应该如下图所示： 接下来需要在网上下载EasyBCD 2.02，下载地 址:https://www.doczj.com/doc/718886581.html,/soft/58174.htm 安装EasyBCD程序，与安装一般软件一样，这里就不做详细说明了。 运行EasyBCD程序出现的第一个界面就是问你将EasyBCD的配置文件的保存路径，这里可以随便选择，我选择的是默认的C盘，下面的两个选框不用选，然后点右下角的确定。 下面是EasyBCD的界面：
DARPA ：国防高级研究计划局 ARPARNET(Internet) ：阿帕网 ICCC ：国际计算机通信会议 CCITT ：国际电报电话咨询委员会 SNA ：系统网络体系结构(IBM) DNA ：数字网络体系结构(DEC) CSMA/CD ：载波监听多路访问/冲突检测(Xerox) NGI ：下一代INTERNET Internet2 ：第二代INTERNET TCP/IP SNA SPX/IPX AppleT alk ：网络协议 NII ：国家信息基础设施(信息高速公路) GII ：全球信息基础设施 MIPS ：PC的处理能力 Petabit ：10^15BIT/S Cu芯片: ：铜 OC48 ：光缆通信 SDH ：同步数字复用 WDH ：波分复用 ADSL ：不对称数字用户服务线 HFE/HFC：结构和Cable-modem 机顶盒 PCS ：便携式智能终端 CODEC ：编码解码器 ASK(amplitude shift keying) ：幅移键控法 FSK(frequency shift keying) ：频移键控法 PSK(phase shift keying) ：相移键控法 NRZ (Non return to zero) ：不归零制 PCM(pulse code modulation) ：脉冲代码调制nonlinear encoding ：非线性编程 FDM ：频分多路复用 TDM ：时分多路复用 STDM ：统计时分多路复用 DS0 ：64kb/s DS1 ：24DS0 DS1C ：48DS0 DS2 ：96DS0 DS3 ：762DS0 DS4 ：4032DS0 CSU(channel service unit) ：信道服务部件SONET/SDH ：同步光纤网络接口 LRC ：纵向冗余校验 CRC ：循环冗余校验 ARQ ：自动重发请求 ACK ：确认 NAK ：不确认
Pxe 网络安装windows和linux 来自天地一沙鸥网络学习总结 上一个星期在数据中心装了几百台服务器，在研究通过网络安装windows系统，之前也在linux环境下搭建了pxe server环境下安装centos。这次在windows环境下利用tftp32工具和binlsrv在windows搭建环境，安装windows和linux系统。在vmware测试。在linux搭建环境还是比在windows环境下的要稳定很多。只是在日常工作中不是经常用linux，自己的工作电脑也是windows系统。所以还是在windows下使用的方便点，相对更加实际点。 Windows和linux都利用脚本自动安装。 介绍下工具的目录结构： W2k3.0 winxp.0 w2k.0 vmlinuz5.5 都是启动引导文件，2003和2000，xp都是在i386提取重命名的文件，vmlinuz是linux系统引导需要的文件。 Winxp.sif win2k3.sif 是windows无人值守安装脚本。 参考：https://www.doczj.com/doc/718886581.html,/895003/501329 这篇文章有纤细的介绍windows xp 2003 2000系统引导文件的制作。 引导菜单 Pxelinux.cfg目录下建立default文件，内容如下。注意kernel写的就是相应的引导文件。
DEFAULT vesamenu.c32 PROMPT 0 MENU TITLE PXE Boot Install All System BY backsan MENU BACKGROUND backsan.png TIMEOUT 600 LABEL hdd MENU LABEL 0‐‐‐‐Boot From HARDDISK kernel chain.c32 APPEND hd0 1 LABEL winxp MENU LABEL 1‐‐‐‐Boot Install Windows XP pro From Network kernel winxp.0 LABEL win2k MENU LABEL 2‐‐‐‐Boot Install Windows 2000 server From Network kernel w2k.0 LABEL win2k3 MENU LABEL 3‐‐‐‐Boot Install Windows 2003 server From Network kernel w2k3.0 LABEL centos5.5 MENU LABEL 4‐‐‐‐Boot Install centos5.5 From Network kernel vmlinuz5.5 append initrd=initrd5.5.img LABEL centos6.3 MENU LABEL 5‐‐‐‐Boot Install centos6.3 From Network kernel vmlinuz6.3 append initrd=initrd6.3.img。 脚本文件：2003server为例 [data] floppyless = "1" msdosinitiated = "1" ; Needed for second stage OriSrc = "\\192.168.80.34\tftp\win2k3\i386" OriTyp = "4"
英语网络聊天缩写用语 1 时间：2008-07-01 15:43 | 分类：学习笔记 - 2B or not 2B To Be Or Not To Be 4ever Forever （这俩常用到泛滥...） ------------- A ----------- A/S/L Age/Sex/Location （年龄，性别，,位置） AFAIC As Far As I'm Concerned （我所关心的...） AFAIK As Far As I Know （就我所知） AFK Away From Keyboard （离开键盘 --意思是离开电脑跟前，暂时不在）AIAMU And I'm A Monkey's Uncle （这个不明白，可能是自嘲吧） AISI As I See It （只见） AMBW All My Best Wishes （祝愿） AOTS All Of The Sudden （都是因为意外） ASAFP As Soon As "Friggin" Possible （骂人的F =DAMN 你他妈的快点）ASAP As Soon As Possible （快点，：不带脏的） ATST At The Same Time （同时） AWGTHTGTTA Are We Going To Have To Go Through This Again （我们要再来次吗）任务可用 AWGTHTGTTSA Are We Going To Have To Go Through This Sh** Again（带脏的意义同上） AYSOS Are You Stupid Or Something （脏话，你笨蛋还是怎么的） ------------- B ------------- B4 Before （之前） B4N Bye For Now （暂时分开---貌似是） BBFBBM Body By Fisher, Brains by Mattel （四肢发达头脑简单）
建筑行业通用英文缩写及含义
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常用的英语缩写（AＢＢRＥVIATIOＮS) 构件篇 英语缩写中文翻译COLUMN 柱子 POST 从梁上升起的柱子BAＳＥPLATE 底板 CAP PLATE 顶板 CＯVER PLＡTＥ盖板 ＥND PLATE 封板,短板 SEAL PＬAＴE 封板 SHEAR ＰLＡＴE 剪切板 COＮＮECTＩON PLATE 连接板 GIRＤER 主梁 ＢEAM 梁/次梁 ＳECONDARY BEAM 次梁 JOIＳT GIRDEＲ主桁架 ＪＯISＴ次桁架 ＢＲＡCE 支撑 ＬIＮTＥＬ过梁 ＭISC 杂件 ＥＭBED PALTE 预埋板件 AＮCＨＯR BOLT 地脚螺栓 FRAMＥ钢架 RAＩLＩNＧ扶手 STAIR 楼梯 RC WALL 混凝土墙 BRＡCＫET 马仔 ＰAＲT/TＹP ＰARＴ零件 ASSY 组合件CANOPY 雨棚 CATWAＬK 猫道 LＡDDER 爬梯 ＰURLIＮ檩条 ＦISH PＬATE 结合板 HＯＩSＴＢＥAM 起吊运输梁 BUＩLＴ－ＵP ＳECTIＯN 组合截面 ＢEARINGＰLATE 支撑板 ＣANTIＬEVＥRＢEAＭ悬臂梁/挑梁 ＣRANE GIＲDER 吊车梁 CROSS BEAＭ井字梁
GＩRT 抗风梁 RINＧBＥＡＭ圈梁 DIAＰHRＡGM 横隔板 ＳTIFFENER／ＳTIFF 加劲板/肋 GＵＳＳＥT ＰＬAＴＥ节点板 HＡNGEＲ吊杆／吊环GRIＰ夹具／卡子ＴIE BAR 拉结钢筋 ＴIＥBEＡＭ系梁 TＩＥTOD 系杆 TＩＥROＤ系杆FLANGE 翼缘/法兰WEＢＰLATＥ/WＥB 腹板 图纸/版本篇 DＥSＩGN ＤRＡWINＧ设计图SHOP DRAＷING 施工图/详图FABRＩＣAＴION DRAWＩNＧ加工图 ARCＨITＥCTＵRＥ建筑图 ＡS-BUＩＬT DＲAWING 竣工图 FＯR APPRＯＶAL 审批 ＦOR FＡB加工UPDATE 更新 ＦOR FIELＤUSED 现场使用 材料篇 SHS(SＱUARE HOLLOW SECＴION）方通/方管RHS（RＥＣTＡNＧLE HOＬLOW ＳEＣＴIOＮ) 矩形管 CＨS(CIRCULAR ＨOＬLOW SＥＣＴIOＮ）圆管/喉管GMS( ＧAＬＶMILＤSTEEＬ) 低碳钢 RSC（RＯLLＥＤSTEEL CＨANＮＥL) 槽钢 RSA（ＲOLLEＤSTEEＬAMＧLＥ) 角钢 ＨSB （HIＧN STRENＧTH BOLＴ）高强螺栓 TS(TUBE CHＡNNEL）方通/方管HSＳ（HOＬLOW SQUＡRE SECTION) 方通/方管 EＡ(ＥQUＡL ANGLＥ) 等边角钢 UA（UNEQUＡL ＡNGLE）不等边角钢ＵC（UNIVERSAL COLUＭNS）等边工字钢UB（UＮIVＥＲSAL BＥAM）不等边工字钢PＦＣ(ＰＡRALLEL FＬANGE CHＡNNEL）方脚槽钢CSK BOＬT 沉头螺栓 FLＡT BAＲ扁钢 CＨANNEL 槽钢
各种颜色的英文缩写R.(RED)红 O.(ORANGE)橙 Y.(YELLOW)黄 G.(GREEN)绿 B.(BLUE)蓝 P.(PURPLE)紫 YG.(YELLOW GREEN)黄绿 BG.(BLUE GREEN)蓝绿 PB.(PURPLE BLUE)蓝紫 RP.(RED PURPLE)红紫 pR.(PURPLISH RED)紫调红 yR.(YELLOWISH RED)黄调红 rO.(REDDISH ORANGE)红调橙 yO.(YELLOWISH ORANGE)黄调橙 rY.(REDDISH YELLOW)红调黄 gY.(GREENISH YELLOW)绿调黄 yG.(YELLOWISH GREEN)黄调绿 bG.(BLUEISH GREEN)蓝调绿 gB.(GREENISH BLUE)绿调蓝 pB.(PURPLISH BLUE)紫调蓝
色调(TONE)缩写词 l.(light)浅的 p.(pale)淡的 b.(bright)明亮的 d.(dull)浊的 s.(strong)强烈的 v.(vivid)鲜艳的 g.(grayish)灰调的 dk.(dark)暗的 dp.(deep)深的 lg.(light grayish)明灰调的dg.(dark grayish)暗灰调的beige米色 blue蓝色 black黑色 brown咖啡色 cream雪白 khaki卡其色 grey灰色 navy丈青色 offwhite灰白色
palegoldenrod苍麒麟色palegreen苍绿色paleturquoise苍绿色palevioletred苍紫罗蓝色pansy紫罗兰色papayawhip番木色peachpuff桃色 peru秘鲁色 pink粉红 plum杨李色powderblue粉蓝色purple紫色 red红色 rosybrown褐玫瑰红royalblue宝蓝色 rubine宝石红saddlebrown重褐色salmon鲜肉色 salmon pink橙红色sandy beige浅褐色sandybrown沙褐色
windows下虚拟linux 要在windows系统上虚拟linux系统，首先要在WINDOWS系统里边先装一个虚拟机，有好多版本，我用的是VMware Workstation汉化版，下载VMWare解压后根据提示正触安装VMWare到硬盘中 (1) 建立虚拟机 A.用鼠标左建双击桌面中的"VMware workstation"图标，运行虚拟机 B.建立一台虚拟机。点击“FILE(文件)”-“NEW(新建)”--“NewVirtual Machine( 新建虚拟机)”，弹出虚拟机创建菜单。 C.根据向导一步一步地创建虚拟机，首先选择安装方式是“TYPICAL(典型)”还是“CUS TOM(自定义)”安装。我这里选择典型。 D.因为这里是用于安装REDHAT，所以在Guest operating system(客户操作系统)“中选择”LINUX“，点击下一步。 E.在Virtual machine name(虚拟机名字)中输入你想建立的虚拟机的名字 F.在Location(位置)中选择虚拟机的安装位置。因为会在虚拟机中安装操作系统和应用软件，所以建议将虚拟机安装在一个有较大空间的磁盘分区中 G.如果你的电脑连接在网络中，那么选择一个合适的网络环境。我这里选择 Use bridged net-working(使用路由网络) H.点击finish,返回VMWARE主界面，LINUX虚拟机就建好了。上面的安装和设置，基本上不会出现什么异常的情况，下面就开始安装linux系统安装操作系统： A. 选中LINUX虚拟机，点击VMWARE工具栏中的Power ON按钮，启动LINUX 虚拟机 B.然后插入REDHAT光盘，虚拟系统根据你选择的安装方式开始安装。 3.从硬盘安装REDHAT 如果你认为从光驱中安装比较费时间，又不方便，那你可以将光盘文件转换成ISO文件拷贝在硬盘中，然后从硬盘安装。
网络常用英语缩写A字头： ASL = Age/Sex/Location AFAIC = As Far As I’m Concerned AFAIK = As Far As I Know AFK = Away From Keyboard AIAMU = And I’m A Monkey’s Uncle AISI = As I See It AKA = Also Known As AMBW = All My Best Wishes AOTS = All Of The Sudden ASAP = As Soon As Possible ATST = At The Same Time AYSOS = Are You Stupid Or Something B字头： B4 = Before B4N = Bye For Now BBIAB = Be Back In A Bit BBIAF = Be Back In A Few BBL = Be Back Later BBN = Bye Bye Now BCNU = Be Seein’You BF = Boyfriend BFN = Bye For Now BIF = Basis In Fact BITD = Back In The Day Biz = Business BM = Byte Me BMOTA = Byte Me On The Ass BNF = Big Name Fan BOHICA = Bend Over Here It Comes Again BR = Bathroom BRB = Be Right Back BRT = Be Right There BS = Big Smile BT = Byte This BTDT = Been There Done That BTW = By The Way BTWBO = Be There With Bells On BWDIK = But What Do I Know BWO = Black, White or Other C字头： Cam = Web Camera
windows下搭建Linux开发环境 以前一直都是安装的双系统来运行windows和linux,当想学习一下linux编程的时候就跑到linux下面去，做其他事情的时候就转到windows下面来。虽然在linux 下也学会了使用wine，也能够运行source insight看看程序，或者打开winamp听听歌，不过毕竟不是windows环境，还是有很多不方便的地方，winamp最小化了居然还原的时候桌面上没有图标；采用source insight打开linux源码，中文注释却全是乱码，好不容易转好了字体，打开来，字体大小不一，根本无法查看，最后只好放弃。 无意间，用vmware安装好了ubuntu的图形化界面，才发现一切原来如此简单。以前虽然也用过vmware，不过以前电脑配置实在是太差，在vmware下面安装linux 的图形化界面能安装成功，却无法使用，只好望洋兴叹。这次终于应用vmware把所有东西都搞定了，可以让我远离双系统了，也节省下了40G的硬盘空间。 1）vmware安装Ubuntu 很简单，感觉都没什么好说的，先安装vmware，windows安装程序，傻瓜式的安装，easy。然后到ubuntu网站去下载live cd或者dvd版本都行，个人建议下载live cd就可以了，安装以后基本的系统环境和常用软件都有了，当然IDE环境是没有的；不过我下载的dvd版本好像安装的时候也没有把IDE环境安装上去，还是我自己后来安装的，因此live cd和dvd在初始安装时，差别不大。 2）设置ubuntu环境 在vmware下面安装过的ubuntu图形界面，分辨率好像是800*600的，即使是全屏，也只能占这么大的屏幕，不是一般的郁闷；就像你面前有一顿美食，偏偏是锁在一个大铁笼子里的，而你的手能够到的却只有一两个菜，那个郁闷劲，确实让人难受。不过也没有关系，因为你没有安装vmware tools，所以你无法享受全屏带来的好处。安装过vmware tools以后，你就发现屏幕能根据具体大小进行自动调整了。不过我在安装vmware tools时，是出错了的，有一步编译出错了，不过最后还是安装成功了，只是在windows和linux之间共享的文件不能相互访问。不过，平时访问文件比较少，而且Ctrl+C/Ctrl+V，已经文件的复制、粘贴都能正常使用，因此对于我来说，这点缺憾我能接受，由于安装的ubuntu环境只是简单的办公环境，都是一些基本软件，惟一能派上用场的可能就是open office，而开发环境方面，只有最基本的一些软件。个人比较习惯于用IDE来开发程序，因为可以省去很多其他的麻烦，比如手动编写makefile文件，运行cvs命令进行cvs操作，或者是采用gdb 命令进行调试，这样可以更专注于程序编写。关于IDE开发还是采用最简单的vi开发，gcc编译，gdb调试，仁者见仁，智者见智，没有好坏，关键看个人喜好。 与我而言，我安装好ubuntu以后，需要安装一个最适合的IDE环境，以便于开发；在ubuntu下面安装软件，现在也是越来越方便了，有图形化的添加/删除界面，很是方便，惟一需要说明的是找一个合适的软件源，否则你会发现安装软件真是一件郁闷的事情，看着你的电脑以400Bps的速度从网络上面下载软件包时，估计你恨不得把网络给拆了，顺便把你的网络运营商给臭骂一通，其实这一切的根源在于你没有找到合适的软件源，我采用的是电信的ADSL线路，找的是lupa网络的源，也是电信的线路，速度不是一般的快，真的是很幸福，源地址为：deb https://www.doczj.com/doc/718886581.html,/ubuntu intrepid main universe；如果你是教育网的网络或
asl是Age, sex and location 的所写，年龄，性别和地址（国籍）lol是laugh out loud的缩写，意思是大声笑,笑的很开心的样子 ppl=people bbs=be back soon=很快回来 thx=thanks ur=your asap=as soon as possible g2g = got to go ttyl = talk to you later brb = be right back bbl = be back later bio brb=上个厕所就回 afk = away from keyboard (away) u = you plz = please y = why w8 = wait l8er = later cya = see ya (later) nvm = nevermind nm = not much gl = good luck gf = girlfriend bf = boyfriend luv=love RUOK=are you ok? sp=support cu=see u cul8er= see you later ft=faint ic=i see soho=small office home officer btw=by the way gn=gn8=gnight=good night=晚安 nn=nite=晚安 说明：一般第一个人常说gnight/gn8,然后第二个人用nite,后面的用nn什么的都可以了。不要问我为什么，约定俗成而已。
hiho=hola=yo=hi=hey=hellow=ello你好，大家好 wuz up=sup=what's up=(原意：怎么样你？/有什么事儿嘛？)也可作为问好用(当然是比较熟的两个人之间的问候)，回答时有事说事，没事用"nothing/nothin much/not much/nm等回答就可以。 OMG=oh my god=我的天；我靠！ OMFG=oh my fucking god=我的老天；我靠靠； wtf=what the fuck=怎么会事！？；我日！； OMGWTFBBQSOURCE !!!表震惊到了极致. n1=nice 1=nice one=漂亮 pwnz=ownz=牛比！(例句：pwnz demo!;lefuzee ownz all the others!) rullz=强！(例句：lefuzee rullz!;you guyz rull!!!) you rock!=你牛比！ lmao=laughing my ass off=笑的屁股尿流 rofl=roll on floor laughing=笑翻天了 roflmao=rofl+lmao=笑到爆了! 语气强度排序:hehe 缩写方式一： 缩写英 文中文 BK Black 黑色 BN Brown 棕色 BU Blue 蓝色 CR Clear 透明 DKGN Dark Green 深绿色 GN Green 绿色 GY Gray 灰色 LT BU Light Blue 浅蓝色 LT GN Light Green 浅绿色 OG Orange 橙色 PK Pink 粉红色 PL Purple 紫色 RD Red 红色 TN Tan 褐色 VI Violet 粉紫色 WT White 白色 YL Yellow 黄色 缩写方式二： 序号英文简写英文中文 1 BGE beige 米色 2 BLU blue 蓝色 3 BLK black 黑色 4 LAV lavender 淡紫色 5 BGY Blue grey 蓝灰色 6 LBL lightblue 浅蓝色 7 VLT violet 紫色 8 SKY skyblue 天蓝色 9 WHI white 白色 10 GRY grey 灰色 11 NAT natural 自然色 12 GRN green 绿色 13 LPK lightpink 浅粉色 14 AQU Aqua 水绿色 15 MAG magenta 洋红色 16 TUR turquoise 青绿色 17 PNK pink 粉色 18 CRP crystal pink 晶粉 19 SKN sky nature 天蓝色 20 PLT purple tulip 紫色 21 OLV olive 橄榄绿 22 HBL hotblue 亮蓝 23 FUS fuchsia 紫红色 24 GLD golden 金色 25 PUR purple 紫色 网络英语聊天中常用缩写短语（很好很强大！！！）来源：郭年顺的日志 问好 hiho = hola = yo = hi = hey = hellow 你好，大家好 wuz up = sup = S’up What's up?原意:怎么样你?有什么事儿嘛?也可作为问好用(熟人之间候) 再见 cya = cu =see ya see you 再见 laterz = later = cya later = see ya later see you later 再见 gn = gn8 = gnight good night 晚安 nn = nite 晚安 说明：一般第一个人常说gnight/gn8,然后第二个人用nite,后面的用nn什么的都可以了。不要问我为什么，约定俗成而已。 惊叹赞扬 OMG oh my god 我的天 OMFG oh my f ucking god = 我的老天；**靠 wtf what the f uck = 怎么会事！？；我日！ n1 = nice 1 nice one 漂亮 pwnz = ownz 牛比！(例句：pwnz demo!;lefuzee ownz all the others!) rullz 强！(例句：lefuzee rullz!;you guyz rull!!!) you rock! 你牛比！(口语中常用，irc中偶尔能看到。) lol laughing out loud / laugh out loud 很好笑.因为lol像笑脸，和我们常用的^-^一样 lmao laughing my ass off 笑的屁股尿流 rofl roll on floor laughing 笑翻天了 其他简写 FU fuck you *你；滚 STFU Shut the fuck up! ***给我闭嘴！ k=ok=okay=okie 好的，恩 gimme give me 给我 em them 他们的宾格 thx thanks 谢谢 ty thank you 原本用的不多，不过现在又开始兴起来了 happy bday = happy b-day happy birthday! 生日快乐 dunno dont know 不知道 kinda a little bit 有点(例句：The game is kinda hard for me.i kinda think i should get it d one as soon as possible.) cmon = c'mon come on 加油/别吹了/快点/起来（这个词意思太多了，不赘述了） hax = hack = cheat 作弊，说谎(很地道时尚的词，老外用的比较多) 颜色英文缩写大全 缩写方式一： 缩写英文中文 BK Black 黑色 BN Brown 棕色 BU Blue 蓝色 CR Clear 透明 DKGN Dark Green 深绿色 GN Green 绿色 GY Gray 灰色 LT BU Light Blue 浅蓝色 LT GN Light Green 浅绿色 OG Orange 橙色 PK Pink 粉红色 PL Purple 紫色 RD Red 红色 TN Tan 褐色 VI Violet 粉紫色 WT White 白色 YL Yellow 黄色 缩写方式二： 序号英文简写英文中文 1 BGE beige 米色 2 BLU blue 蓝色 3 BLK black 黑色 4 LAV lavender 淡紫色 5 BGY Blue grey 蓝灰色 6 LBL lightblue 浅蓝色 7 VLT violet 紫色 8 SKY skyblue 天蓝色 9 WHI white 白色 10 GRY grey 灰色 11 NAT natural 自然色 12 GRN green 绿色 13 LPK lightpink 浅粉色 14 AQU Aqua 水绿色 15 MAG magenta 洋红色 16 TUR turquoise 青绿色 17 PNK pink 粉色 18 CRP crystal pink 晶粉 19 SKN sky nature 天蓝色 20 PLT purple tulip 紫色 21 OLV olive 橄榄绿 22 HBL hotblue 亮蓝 23 FUS fuchsia 紫红色 24 GLD golden 金色 25 PUR purple 紫色 26 RED red 红色 27 SAL salmon 鲜肉色 28 YLW yellow 黄色 WIN7操作系统安装linux形成双系统详解： 需要软件EasyBCD2.0 和linux ISO系统镜像 安装前准备工作: 1 一个windows盘D E F任选其一都可以，将其格式化为FAT32格式，除C盘以外任意盘均可格式化FAT32，且此盘必须小于32GB，否则无法格式化FAT32。 2 磁盘最后末端要有未分配的空间，如果没有可利用WIN7 右键计算机—管理—磁盘管理—选择最后面的盘符右键单击选择删除卷（也就是删除相应盘符，建议删除最后一个盘符）。这样就有了未分配的磁盘空间，用来做linux。 3 硬盘模式调成AHCI 1将linux镜像复制到FAT32格式化的磁盘里 2用winrar解压软件，将镜像中的images 和ioslinu两个文件夹提取出来，与linux镜像一同放置在FAT32盘的根目录。原来镜像还要保留 3 isolinux文件夹中的initrd.img和vmlinuz两个文件复制到FAT32盘的根目录，同时也复制到C盘根目录下。 4 安装EasyBDC程序，一路默认安装即可。 5 运行EasyBDC程序出现第一个界面是问你将EasyBDC的配置文件放置在哪个盘里，随便选择即可，下面两个不用选中，我选择的是C盘，然后右下角确定。 6 进入easyBCD操作页面， 上图中当点击第4个的时候会出现一个记事本文本框，将以下代码输入进去。 title install linux root (hd0,1) kernel (hd0,1)/isolinux/vmlinuz initrd (hd0,1)/isolinux/initrd.img 将上述代码复制粘贴进出来的文本框内即可，其中红色部分是可以更改的仅仅代表一个名字，我将其修改为我的系统名字centOS了。如果你的系统没有100M的保留分区那么请将上述代码中的1改为0。 7 点击EasyBCD右上角的save 保存此时可以关闭EasyBCD了。 8 重新启动电脑不要选择WIN7 而选择NeoGrub Bootloder 9此时就可以按照图形界面开始安装，在选择安装文件位置的地方时选择你的FAT32的盘符，然后next即可 其余都是常识性的东西了！ Linux分区 第一个/Boot 100M 即可 第二个/ 5G 即可 第三个/swap 你实际内存的2倍。如果内存2G 那么相等即可。 上述分区仅供参考，因实际而酌情考虑。 FAT32在linux下的盘符： 在WIN7下查看右键计算机—管理—磁盘管理—通过这里查看你的FAT32盘是否是主分区 1我的FAT32是主分区： 如果你的盘里有系统保留分区100M 那从C盘开始hda1—D盘hda2—E盘hda3—F盘hda4 2 我的FAT32是逻辑分区： 那么观察你的FAT32是第几个逻辑分区，如果是第一个逻辑分区那么盘符就是hda5，同样以此类推，第二个逻辑分区是hda6，第三个hda7 质量管理体系中英文缩写与其解释 Engineering 工程 / Process 工序（制程） Man, Machine, Method, Material, 人，机器，方法，物料，环境- 可能导 4M&1E Environment 致或造成问题的根本原因 AI Automatic Insertion 自动插机 ASSY Assembly 制品装配 ATE Automatic Test Equipment 自动测试设备 BL Baseline 参照点 BM Benchmark 参照点 BOM Bill of Material 生产产品所用的物料清单 C&ED/C Cause and Effect Diagram 原因和效果图 AED CA Corrective Action 解决问题所采取的措施 电脑辅助设计.用于制图和设计3维物体 CAD Computer-aided Design 的软件 对文件的要求进行评审，批准，和更改 CCB Change Control Board 的小组 依照短期和长期改善的重要性来做持续 CI Continuous Improvement 改善 COB Chip on Board 邦定-线焊芯片到PCB板的装配方法. CT Cycle Time 完成任务所须的时间 DFM Design for Manufacturability 产品的设计对装配的适合性 设计失效模式与后果分析--在设计阶段 Design Failure Mode and Effect DFMEA 预测问题的发生的可能性并且对之采取 Analysis 措施 六西格玛(6-Sigma)设计 -- 设计阶段预 DFSS Design for Six Sigma 测问题的发生的可能性并且对之采取措施并提高设计对装配的适合性 DFT Design for Test 产品的设计对测试的适合性 实验设计-- 用于证明某种情况是真实DOE Design of Experiment 的 根据一百万件所生产的产品来计算不良DPPM Defective Part Per Million 品的标准 Design Verification / Design常用颜色英文缩写大全
网络英语聊天中常用缩写短语
颜色英文缩写大全
WIN7下硬盘安装linux双系统
质量管理体系中英文缩写与其解释
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