Cellular applications of a sensitive and selective fiber-optic nitric oxide biosensor based on a dye-labeled heme domain of soluble guanylate cyclase.

Nitric oxide-selective sensors have been prepared with the heme domain of soluble guanylate cyclase (sGC), the only known receptor for signal transduction involving nitric oxide. Expressed in and purified from E. coli, the heme domain contains a stoichiometric amount of heme that has electronic and resonance Raman spectra almost identical to those of heterodimeric (native) sGC purified from bovine lung. The small size of the heme domain, its inability to bind oxygen, and its high affinity for nitric oxide make it well-suited for sensor applications. The heme domain has been labeled with a fluorescent reporter dye and changes in this dye's intensity are observed based on the sGC heme domain's characteristic binding of nitric oxide. The current sensors are prepared with 100-microns optical fiber but could also be prepared using submicrometer fiber tips. These sensors have fast, linear, and reversible responses to nitric oxide and are unaffected by numerous common interferents, such as oxygen, nitrite and nitrate. The sensor limit of detection is 1 microM nitric oxide. Glutathione has been shown to decrease the sensitivity of the sensor; however, the sensor response remains linear and can be calibrated on the basis of the glutathione concentration present in the biological environment of interest. The sensors have been used to measure extracellular nitric oxide production by BALB/c mouse macrophages. Minimal nitric oxide was produced by untreated cells, while high levels of nitric oxide were released from activated cells, e.g., 111 +/- 2 microM in a given cell culture.     

NiFeCo--An alternative to permalloy for bubble domain detection?

The characteristics of bubble domain sensors fabricated from ternary NiFeCo films have been studied and compared with Permalloy film sensors. In 350 Å thick films, the ternary alloy exhibits a magnetoresistance ratio of 3.5 percent in contrast to 2.8 percent for Permalloy films prepared under similar conditions. Sensor sensitivity in functional bubble chips is correspondingly greater, while the sensor noise level is equal to-or lower than-that obtained with the Permalloy detector. Low coercivity and dispersion in NiFeCo films aid in producing an overall improvement in signal-to-noise ratio. The performance of NiFeCo sensors operating in 1-μm bubble ion-implanted contiguous-disk devices is described.     

An optical-fiber sensor for use in water systems utilizing digital signal processing techniques and artificial neural network pattern recognition

An optical-fiber sensor is reported which is capable of detecting ethanol in water. A single optical-fiber sensor was incorporated into a 1-km length of 62.5-/spl mu/m core diameter polymer-clad silica optical fiber. In order to maximize sensitivity, a U-bend configuration was used for the sensor where the cladding was removed and the core exposed directly to the fluid under test. The sensor was interrogated using optical time domain reflectrometry, as it is intended to extend this work to multiple sensors on a single fiber. In this investigation, the sensor was exposed to air, water, and alcohol. The signal processing technique has been designed to optimize the neural network adopted in the existing sensor system. In this investigation, a discrete Fourier transform, using a fast Fourier transform algorithm, is chosen and its application leads to an improvement in efficiency of the neural network i.e., minimizing the computing resources. Using the Stuttgart neural network simulator, a feed-forward three-layer neural network was constructed with the number of input nodes corresponding to the number of points required to represent the sensor frequency domain response.     

Analysis of parameter estimation heat conduction problems with phase change using the finite element method

A solution to a parameter estimation problem in heat conduction with phase change is presented. Specifically, the thermophysical properties of the material are estimated by using the temperature measurements of several sensors located inside the fixed domain. In the parameter estimation problem the error is minimized between given and modelled temperatures at sensor locations over the time interval where the experiment involved variation of the material parameters. The methods are illustrated with several examples. The effects on the solution of the locations of the sensors, the number of the sensors, the time step and the number of time steps are examined.     

Theoretical Analysis of Wireless Passive Impedance-Loaded SAW Sensors

This paper concentrates on the theoretical analysis of wireless passive surface acoustic wave (SAW) impedance-loaded sensors. A general method is proposed for simulating the impedance-loaded SAW sensors. It is based on the combined finite-element method and boundary element method (FEM/BEM). A FEM is used to account for the mass loading effect of electrodes and a Green's function is used to model the piezoelectric substrate. Comparison between the simulations and measurements on SAW devices shows a good agreement. The calculated amplitude variation of the impulse response in time domain shows a resonant characteristic with the change of the loaded impedance. It is found that the return loss reaches the maximum value when the resonant frequency of the loaded circuits matches the center frequency of the short-circuited SAW transponder. This phenomenon is successfully explained by using the proposed model. Some high-performance sensors with greater amplitude modulation and larger sensitive range could be designed using this method.      

A multichannel DSP-based instrument for displacement measurement using differential variable reluctance transducer

This paper presents a novel instrument for the analysis of signals coming from a matrix of differential variable reluctance transducers (DVRTs). The signal processing technique is based on a fast Fourier transform (FFT) evaluation. The main objectives are compactness and a short elaboration time. In particular, information from up to 11 different sensors can be simultaneously processed with an overall measuring time of about 300 /spl mu/s. Experimental results show a standard deviation in the /spl plusmn/0.3 /spl mu/m order.     

时域离散系统的可控度及其在传感器／作动器配置中的应用

本文研究了受控结构的时域离散化模型;提出了受控结构模态可控度的一种度量方法,并研究了它与采样周期的关系;首次提出了输出可控度的概念,并将它运用于作动器与传感器位置的最优选择,得出当作动器/传感器对位配置在某一最优位置时,输出可控度可取极值这一结论。文末的例子说明了该方法的应用。     

A High-Resolution MEMS Piezoelectric Strain Sensor for Structural Vibration Detection

This paper presents the modeling, fabrication, and testing of a high-performance dynamic strain sensor. Using microelectromechanical systems (MEMS) technology, ZnO piezoelectric microsensors are directly fabricated on silicon and steel substrates. The sensors are intended to be used as point sensors for vibration sensing without putting an extra burden on the host structures. A model that incorporates piezoelectric effects into an RC circuit, representing the sensor architecture, is developed to describe the voltage output characteristics of the piezoelectric microsensors. It is shown that the sensitivity of microplanar piezoelectric sensors that utilize the $e_{31}$ effect is linearly proportional to sensor thickness but unrelated to sensor area. Sensor characterization was performed on a cantilever beam cut from a fabricated silicon wafer. The experimental data indicate that the overall sensor and circuit system is capable of resolving better than 40.3 nanostrain time domain signal at frequencies above 2 kHz. The corresponding noise floor is lower than 200 femto-strain per root hertz and the sensitivity, defined as the sensor voltage output over strain input, is calculated to be 340 V/$varepsilon$ . Micro ZnO piezoelectric sensors fabricated on steel hard disk drive suspensions also show excellent results. The sensor not only has a better signal-to-noise ratio but also detects more vibration information than the combination of two laser-doppler-vibrometer measurements in different directions.      

Embedded micromachined fiber-optic Fabry-Perot pressure sensors in aerodynamics applications

Small size, high bandwidth pressure sensors are required for instrumentation of probes and test models in aerodynamic studies of complex unsteady flows. Optical-fiber pressure sensors promise potential advantages of small size and low cost in comparison with their electrical counterparts. We describe miniature Fabry-Perot cavity pressure sensors constructed by micromachining techniques in a turbine test application. The sensor bodies are 500 /spl mu/m squared, 300 /spl mu/m deep with a /spl sim/2 /spl mu/m-thick copper diaphragm electroplated on one face. The sensor cavity is formed between the diaphragm and the cleaved end of a single mode fiber sealed to the sensor by epoxy. Each sensor is addressed interferometrically in reflection by three wavelengths simultaneously, giving an unambiguous phase determination; a pressure sensitivity of 1.6 radbar/sup -1/ was measured, with a typical range of vacuum to 600 kPa. Five sensors were embedded in the trailing edge of a nozzle guide vane installed upstream of a rotor in a full-scale turbine stage transient test facility. Pressure signals in the trailing edge flow show marked structure at the 8 kHz blade passing frequency. To our knowledge, this is the first report of sensors located at the trailing edge of a normal-sized turbine blade.     

脉冲磁场传感器的时域标定

针对脉冲磁场测量的要求，对传感器的时域标定问题进行了研究，组建基于高压脉冲源，ＴＥＭ传输室，数字存贮示波器及计算机的时域标定系统，提出了基于输出误差模型的时域定数据处理方法，利用该模型可方便地获得的传感器的灵敏度，转折频率等参数，成功地利用所建立的误差修正模型对传感器造成的测量失真进行了恢复。     

Strain and temperature sensors using multimode optical fiber Bragg gratings and correlation signal processing

Multimode fiber optic Bragg grating sensors for strain and temperature measurements using correlation signal processing methods have been developed. Two multimode Bragg grating sensors were fabricated in 62/125 /spl mu/m graded-index silica multimode fiber; the first sensor was produced by the holographic method and the second sensor by the phase mask technique. The sensors have signal reflectivity of approximately 35% at peak wavelengths of 835 nm and 859 nm, respectively. Strain testing of both sensors has been done from 0 to 1000 /spl mu//spl epsiv/ and the temperature testing from -40 to 80/spl deg/C. Strain and temperature sensitivity values are 0.55 pm//spl mu//spl epsi/ and 6 pm//spl deg/C, respectively. The sensors are being applied in a power-by-light hydraulic valve monitoring system.     

Development and comparative analysis of fluxgate magnetic sensor structures in PCB technology

In this paper, we present a family of fluxgate magnetic sensors on printed circuit boards (PCBs), suitable for an electronic compass. This fabrication process is simple and inexpensive and uses commercially available thin ferromagnetic materials. We developed and analyzed the prototype sensors with software tools based on the finite-element method. We developed both singleand double-axis planar fluxgate magnetic sensors as well as front-end circuitry based on second-harmonic detection. Two amorphous magnetic materials, Vitrovac 6025X (25 /spl mu/m thick) and Vitrovac 6025Z (20 /spl mu/m thick), were used as the ferromagnetic core. We found that the same structures can be made with Metglas ferromagnetic core. The double-axis fluxgate magnetic sensor has a sensitivity of about 1.25 mV//spl mu/T with a linearity error of 1.5% full scale, which is suitable for detecting Earth's magnetic field (/spl plusmn/60 /spl mu/T full-scale) in an electronic compass.     

基于模糊贝叶斯网络的态势威胁评估模型

针对传感器测量数据的不确定性,提出基于模糊贝叶斯网络的态势威胁评估模型,该模型首先将不确定性数据分为模糊域和概率域两大类,然后在模糊域使用模糊综合评判得到威胁目标的动态威胁度,接着运用可能性概率转换理论将模糊表示的动态威胁度转化成概率域知识,最后在概率知识域使用贝叶斯网络推理算法得到目标的威胁等级.实例计算表明,该方法能够较好的反映威胁源的威胁等级,为武器系统选择跟踪打击目标提供决策依据,具有一定的实用性.     

Effects of electrode configuration on polymer carbon-black composite chemical vapor sensor performance

The performance of polymer carbon-black composite chemical vapor sensors as a function of underlying electrode size and geometry has been studied. The sensor performance parameters investigated were sensor response magnitude to a toluene analyte (100, 500, and 1000 ppm), fundamental sensor noise in the presence of air, and two concentrations of toluene (100 and 500 ppm), and signal-to-noise ratio (100 and 500 ppm). An array of sensors with 42 different circular electrode configurations were designed, fabricated, and tested where electrode gap was varied from 10 to 500 /spl mu/m and the diameter of the sensors was varied from 30 to 2000 /spl mu/m. Each array of electrodes was coated with an approximately 1 /spl mu/m-thick layer of conducting polymer carbon-black composite with an insulating poly(alkylacrylate) polymer. The response magnitude, fundamental noise, and signal-to-noise ratio of each sensor was measured and compared to electrode geometry, such as electrode gap, aspect ratio, and overall size. No significant dependence of sensor response magnitude and noise to electrode configuration has been observed to be larger than the variation from sensor to sensor. However, the signal-to-noise ratio tended to decrease for sensors with the smallest scales.     

基于钻头运动诱发套管头振动信号检测的井眼防碰监测方法

针对海上加密调整井的井眼防碰问题,设计了一种井筒防碰地面监测预警系统,并进行了现场应用。系统利用加速度传感器监测通过套管传输到套管头上的钻头振动信号,利用数据采集、信号滤波放大和专门编制的监测软件记录分析传感器采集的振动信号,通过对信号的时域、频域分析,确定信号特征与井间相对距离的关系,识别钻头对风险井套管的趋近或碰撞。应用结果表明,该系统能有效感知通过地层、套管传输到套管头的钻头振动信号,并能识别出钻头对风险邻井的趋近,验证了系统在设计理论和方法上的可行性,为加密调整井的井眼防碰、保证钻井安全提供了一种有效的手段。     

Flow-through vs flow-over: analysis of transport and binding in nanohole array plasmonic biosensors

We quantify the efficacy of flow-through nanohole sensing, as compared to the established flow-over format, through scaling analysis and numerical simulation. Nanohole arrays represent a growing niche within surface plasmon resonance-based sensing methods, and employing the nanoholes as nanochannels can enhance transport and analytical response. The additional benefit offered by flow-through operation is, however, a complex function of operating parameters and application-specific binding chemistry. Compared here are flow-over sensors and flow-through nanohole array sensors with equivalent sensing area, where the nanohole array sensing area is taken as the inner-walls of the nanoholes. The footprints of the sensors are similar (e.g., a square 20 μm wide flow-over sensor has an equivalent sensing area as a square 30 μm wide array of 300 nm diameter nanoholes with 450 nm periodicity in a 100 nm thick gold film). Considering transport alone, an analysis here shows that given equivalent sensing area and flow rate the flow-through nanohole format enables greatly increased flux of analytes to the sensing surface (e.g., 40-fold for the case of Q = 10 nL/min). Including both transport and binding kinetics, a computational model, validated by experimental data, provides guidelines for performance as a function of binding time constant, analyte diffusivity, and running parameters. For common binding kinetics and analytes, flow-through nanohole arrays offer ～10-fold improvement in response time, with a maximum of 20-fold improvement for small biomolecules with rapid kinetics.     

Determining oxygen diffusion coefficients in polymer films by lifetimes of luminescent complexes measured in the frequency domain

Polymer films doped with luminescent ruthenium complexes are proving to be important oxygen sensors. We describe a technique using lifetime measurements in the frequency domain for determining the diffusion coefficient of oxygen through various polymer supports. These fundamental measurements will allow for more rational design of improved sensors. Three types of polymers were doped with [Ru(4,7-diphenyl-1,10-phenanthroline)3]Cl2. We monitored the luminescence versus time after applying a step increase in the oxygen pressure at the surface of the film. We modeled the decrease in apparent lifetime as a function of time using the diffusion coefficient of oxygen in the polymer as the only adjustable parameter. The model accurately predicted the lifetime versus time curves, and diffusion coefficients agreed well with those obtained from intensity measurements. The advantages and disadvantages of the lifetime technique to those used earlier are discussed.     

Validation of time temperature superposition principle for high modulus asphalt concrete in the linear viscoelastic and fatigue domains

Validation of time–temperature superposition principle (TTSP) in the fatigue domain for a high modulus asphalt concrete (HMAC) is presented in this paper. All tests were performed in tension-compression under strain control mode. First, TTSP was validated in the linear viscoelastic domain. Then, fatigue tests were performed under three loading conditions, 9.2°C and 5 Hz, 11.0°C and 10 Hz and 12.9°C and 20 Hz, which are equivalent regarding TTSP. Two fatigue protocols were adopted: continuous fatigue test (FT) and fatigue test with rest period (FTRP). For FT, three samples were tested at 180μm/m for each loading condition whereas for FTRP, one sample was tested at 100 μm/m. The data were analysed by comparing the dynamic modulus evolution as a function of time or the fatigue life duration. The results showed that HMAC with fatigue damage remains thermorheologically simple (i.e., respects the TTSP) in the studied temperatures range.     

A Closed-Loop Digitally Controlled MEMS Gyroscope With Unconstrained Sigma-Delta Force-Feedback

In this paper, we describe the system architecture and prototype measurements of a MEMS gyroscope system with a resolution of 0.025 $^{circ}$/s/ $sqrt{{rm Hz}}$. The architecture makes extensive use of control loops, which are mostly in the digital domain. For the primary mode both the amplitude and the resonance frequency are tracked and controlled. The secondary mode readout is based on unconstrained $SigmaDelta$ force-feedback, which does not require a compensation filter in the loop and thus allows more beneficial quantization noise shaping than prior designs of the same order. Due to the force-feedback, the gyroscope has ample dynamic range to correct the quadrature error in the digital domain. The largely digital setup also gives a lot of flexibility in characterization and testing, where system identification techniques have been used to characterize the sensors. This way, a parasitic direct electrical coupling between actuation and readout of the mass-spring systems was estimated and corrected in the digital domain. Special care is also given to the capacitive readout circuit, which operates in continuous time.      

Digital and analog readout systems for fiber-optic strain sensors as applied to the monitoring of roller element bearing systems

A rotating machinery test rig was instrumented with fiber Fabry-Perot interferometer strain sensors for condition monitoring of rolling element bearings. Strain variations produced by ball passes were observed and analyzed in the time and frequency domain. Wavelength division multiplexing was utilized to simultaneously monitor the sensors with analog and digital readout systems--analog for high bandwidth and digital for high dynamic range and the monitoring of multiple sensors. The effects of imbalance on the shaft, changes in rotational speed, effects on the rotor system, and detection of bearing defects were investigated. Frequency peaks observed in the bearing sensor spectra closely matched predicted values. Imbalance and rotational speed tests showed good agreement with expected trends, and bearing defects were successfully detected.