Thin-film sensor for emergency shutdown of electrochemical generator

A thin-film sensor for detection of emergency situations in fuel cells of electrochemical generators is proposed. Experimental results of emergency modeling are presented. It is shown that the thin-film sensor can function as a high-speed warning device. A system is proposed for emergency shutdown by means of a thermal pulse from the thin-film sensor. Translated from Izmeritel'naya Tekhnika, No. 7, pp. 64–65, July, 2000.     

Self‐Powered Real‐Time Arterial Pulse Monitoring Using Ultrathin Epidermal Piezoelectric Sensors

Continuous monitoring of an arterial pulse using a pressure sensor attached on the epidermis is an important technology for detecting the early onset of cardiovascular disease and assessing personal health status. Conventional pulse sensors have the capability of detecting human biosignals, but have significant drawbacks of power consumption issues that limit sustainable operation of wearable medical devices. Here, a self‐powered piezoelectric pulse sensor is demonstrated to enable in vivo measurement of radial/carotid pulse signals in near‐surface arteries. The inorganic piezoelectric sensor on an ultrathin plastic achieves conformal contact with the complex texture of the rugged skin, which allows to respond to the tiny pulse changes arising on the surface of epidermis. Experimental studies provide characteristics of the sensor with a sensitivity (≈0.018 kPa^?1), response time (≈60 ms), and good mechanical stability. Wireless transmission of detected arterial pressure signals to a smart phone demonstrates the possibility of self‐powered and real‐time pulse monitoring system.     

Analysis of the d.c. and a.c. properties of K2O-doped porous Ba0.5Sr0.5TiO3 ceramic humidity sensor

A humidity sensor using K₂O-doped porous Ba_0.5Sr_0.5TiO₃ ceramic is investigated. This ceramic humidity sensor exhibits a porous structure. The porous ceramic easily absorbs water vapour throughout the pores. The log-conductance against relative humidity (r.h.) sensitivity of this sensor is greater than 4 orders of magnitude in the range of 15∼95% r.h. at 400 Hz and 25°C. The adsorption process of the sensor is very fast. Its adsorption response time in r.h. variation from 15 to 95% is within a few seconds. Charging-discharging and complex impedance analysis techniques are used to analysis the direct current (d.c.) and alternating current (a.c.) response of this device under 50∼95% r.h. The sample can be polarized like electrolytes on charging process due to electrode space charge and grain surface water molecular polarization effects. The degree of polarization is enhanced with increasing r.h. The conduction carriers of this sensor in a humid atmosphere are ions and electrons, and the dominant conduction carrier is the ion. Using complex impedance analysis techniques, an equivalent circuit model associated with “non-Debye” capacitance is built. This model separates the sample into three regions: crystal grain, grain surface and electrode surface. The grain surface resistance and electrode surface resistance decrease sharply with increasing r.h., but crystal grain resistance is not affected by water vapour.     

Fiber-optic thermometry and its application

The design of a distributed fiber-optic sensor of radiation heat flow (RHF) is presented. A measuring technique has been developed and results of measuring the “effective” transmission coefficient of an uncladded fiber under its lateral illumination have been obtained. An algorithm for measuring the RHF supplied in the process of testing specimens of materials on the radiant heating facility is proposed. Testing experiments have been performed and a good correlation between the readings of the distributed RHF sensor and the temperature in the specimens of materials measured by thermocouples has been observed. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 2, pp. 180–185, March–April, 2007.     

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Abstract

A high-bandwidth optical fibre current sensor has been developed at Salford to monitor the waveform of the driving current pulse feeding into a discharge-pumped excimer laser. The sensor is a conventional intrinsic Faraday effect device but overcomes the normal bandwidth-sensitivity limits because the very large electrical current pulse used to drive the excimer laser allows detectable polarization rotation over a 60 cm length of fibre. The performance of the intrinsic sensor is compared with that of a current-viewing resistor, and of a Be₁₂GeO₂₀ crystal sensor.     

脉冲大电流校准及溯源技术研究

为解决1~100kA的脉冲大电流校准问题,建立了脉冲大电流校准系统,开展了脉冲大电流校准及溯源技术研究。校准系统由脉冲大电流发生装置、脉冲分流器组、光纤电流传感器、罗氏线圈电流传感器、宽带数据采集系统及测量软件组成;通过该校准系统,可开展脉冲幅度为1~100kA,持续时间为20μs~100ms的脉冲大电流发生/测量系统的校准,开展罗氏线圈传感器、光纤电流传感器等测量器具的校准,校准不确定度优于1%。     

宽带脉冲大电流测量及大数据分析技术

多磁路调压变压器的脉冲电流具有频带宽、幅度大的特点,其测量与大数据分析易受到噪声等影响。本文研究了多磁路调压变压器宽带脉冲大电流测量与大数据分析技术,设计了基于法拉第磁光效应和光纤电流传感器的宽带脉冲大电流测量系统方案,采用卷积神经网络对测量得到的海量数据进行处理,消除测量过程中干扰对测量结果的影响。通过与罗氏线圈的测量结果比对,本文研究的方法测量结果的脉冲波形一致性好、脉冲峰值检测准确度较高,脉冲幅值误差符合测试要求。     

A CMOS Time-of-Flight Range Image Sensor With Gates-on-Field-Oxide Structure

This paper presents a new type of CMOS time-of-flight (TOF) range image sensor using single-layer gates on field oxide structure for photo conversion and charge transfer. This simple structure allows the realization of a dense TOF range imaging array with 1515 mum² pixels in a standard CMOS process. Only an additional process step to create an n-type buried layer which is necessary for high-speed charge transfer is added to the fabrication process. The sensor operates based on time-delay dependent modulation of photocharge induced by back reflected infrared light pulses from an active illumination light source. To reduce the influence of background light, a small duty cycle light pulse is used and charge draining structures are included in the pixel. The TOF sensor chip fabricated measures a range resolution of 2.35 cm at 30 frames per second and an improvement to 0.74 cm at three frames per second with a pulsewidth of 100 ns.     

A theoretical analysis of the systematic errors in determining the thermal characteristics of structural materials by a pulse method in a sample of finite dimensions

The problem of the three-dimensional nonstationary temperature field of a sample of material when a thermal pulse of short duration acts on its surface is solved numerically. The scales of the errors in determining the thermal characteristics of the material by a pulse method due to the assumption that heat transfer in the sample is a one-dimensional process, is estimated. The limits of the ranges of possible variation of the ratio of the area of the heated surface of the sample and the zone of thermal heating, which ensure minimum errors in determining the thermal characteristics, are established. Translated from Izmeritel’naya Tekhnika, No. 4, pp. 34–36, April, 2009.     

Electrostatic Self-Assembly of MXene on Ruthenium Dioxide-Modified Carbon Cloth for Electrochemical Detection of Kaempferol

A superior composite material consisting of MXene and ruthenium dioxide-modified carbon cloth is synthesized by pulsed laser deposition and electrostatic self-assembly, which is further utilized to construct a class of novel electrochemical (EC) sensors for kaempferol (KA) detection. The carbon-cloth-based electrodes modified by ruthenium dioxide and then MXene are characterized by X-ray diffraction, scanning electron microscope, and X-ray photoemission spectroscopy. The EC process on the modified electrodes is analyzed by cyclic voltammetry, EC impedance spectroscopy, and differential pulse voltammetry. It is found that positively charged RuO₂ not only possesses the remarkable electrical conductivity and electrocatalysis activity but also hampers the restacking of MXene, which accordingly enhances the exposure of the active surface area and greatly boosts the electrocatalysis activity of the entire composite. Consequently, this newly developed composite-based EC sensor exhibits a high sensitivity, selectivity, and remarkable stability to detect KA with two linear ranges of 0.06–1 and 1–15 µM. The inferred limit of detection is 0.039 µM via differential pulse voltammetry. More importantly, this novel EC sensor is found to be applicable for detecting KA in practical traditional Chinese medicines.     

Measurements of the Thermal Effusivity of a Drop-Size Liquid Using the Pulse Transient Hot-Strip Technique

The thermal effusivity of drop-size liquids was measured by the pulse transient hot-strip technique. A strip sensor, used as a thermometer and heat source, is deposited on a smooth surface of an electrically insulating background material – onto which an insulating liquid sample is applied, completely covering the strip probe. Experiments can be made controlling the thermal penetration depth to within some 10 μm of the liquid sample – here demonstrated by measuring a drop of water at about 1% uncertainty. Measurements were made on water and a series of silicone oils (kinematic viscosity from 5 to 50 cSt; 1 cSt = 10⁻⁶ m²· s⁻¹) in microgravity conditions using a 10 m drop tower (10⁻³ g, 1.4 s), to investigate if any potential natural convection in the liquid at normal gravity condition is present, influencing the results. However, no such influence was observed. Paper presented at the Fifteenth Symposium on Thermophysical Properties, June 22–27, 2003, Boulder, Colorado, U.S.A.     

Effect of velocity nonuniformity on the dynamic recrystallization of metals in shock waves

A series of mechanical tests on D16 aluminum alloy samples under uniaxial strain conditions in single and double impact loading regimes showed that dynamic recrystallization in localized shear bands takes place only in the latter case, with the second (additional loading) pulse delayed by 0.5–0.7 μs relative to the first shock-wave front. It is established that, in addition to well-known conditions (γ ≥ 3, $ \dot \gamma $ \dot \gamma ≥ 10⁴ s⁻¹, T ≥ 0.4T _m), a determining role in the dynamic recrystallization process is played by the nonuniformuty (variation) of mass velocity at the leading front of the compression pulse.     

Self‐Powered Pulse Sensor for Antidiastole of Cardiovascular Disease

Cardiovascular diseases are the leading cause of death globally; fortunately, 90% of cardiovascular diseases are preventable by long‐term monitoring of physiological signals. Stable, ultralow power consumption, and high‐sensitivity sensors are significant for miniaturized wearable physiological signal monitoring systems. Here, this study proposes a flexible self‐powered ultrasensitive pulse sensor (SUPS) based on triboelectric active sensor with excellent output performance (1.52 V), high peak signal‐noise ratio (45 dB), long‐term performance (10⁷ cycles), and low cost price. Attributed to the crucial features of acquiring easy‐processed pulse waveform, which is consistent with second derivative of signal from conventional pulse sensor, SUPS can be integrated with a bluetooth chip to provide accurate, wireless, and real‐time monitoring of pulse signals of cardiovascular system on a smart phone/PC. Antidiastole of coronary heart disease, atrial septal defect, and atrial fibrillation are made, and the arrhythmia (atrial fibrillation) is indicative diagnosed from health, by characteristic exponent analysis of pulse signals accessed from volunteer patients. This SUPS is expected to be applied in self‐powered, wearable intelligent mobile diagnosis of cardiovascular disease in the future.     

The growth and characterisation of Ni5Zn21 dendrites

We have investigated the growth of Ni–Zn alloys by a dc electrodeposition method and a pulse dc electrodeposition method with different pulse frequencies, under otherwise the same growth conditions. Dendritic growth is found in the Ni–Zn alloys produced by pulse dc electrodeposition, whereas such growth is absent in those fabricated by dc electrodeposition. The morphology of the as-grown Ni–Zn dendrites is highly influenced by the pulse frequency. The possible growth mechanism has been discussed. The corresponding magnetic properties are investigated at 5 K using a superconducting quantum interference device. We have observed a clear variation in the magnetisation behaviour as the pulse frequency is changed, which is likely to be attributable to the presence of precipitation of Ni nanoparticles.     

Sintering and humidity-sensitive behaviour of the ZnCr2O4–K22CrO4 ceramic system

Solid state reaction at elevated temperatures and the sintering behaviour of zinc chromite formed by zinc oxide and chromite oxide were investigated. Crystalline structure, surface and fractured morphologies and humidity-sensitivity characteristics of ZnCr2O4–K2CrO4–CuO were studied. The fired ceramic body, which proved to be mainly constructed from ZnCr2O4 spinel grains, was porous. The humidity characteristics of the sensor showed that the resistance decreased as a logarithmic function with an increase in humidity. The resistance values obtained were about 6×109 Ω and 3×104 Ω at 25 and 93% relative humidity (RH), respectively. Based on a.c. impedance measurements, an equivalent circuit associated with a network of resistors together with series capacitors has been suggested. It is assumed that such an equivalent circuit model of the sensor under the moist conditions represents the sensing mechanism as a diffusion process. This revised version was published online in November 2006 with corrections to the Cover Date.     

Thermophysical Analysis of Gioia Marble in Dry and Water-Saturated States by the Pulse Transient Method

Measurements of the thermophysical properties of Gioia marble in the temperature range from −20 to 60°C are presented. Thermophysical properties, namely, thermal diffusivity, thermal conductivity, and specific heat, were measured by the pulse transient technique. The data were compared for dry and water-saturated states. Despite the very low porosity of marble of about 0.6 vol%, an increase of the transport property parameters (thermal diffusivity and thermal conductivity) up to 20% after water saturation was found. To verify the differences in the transport parameters, the ultrasonic pulse velocity method was employed. A detailed analysis of thermophysical property data during the freeze/thaw process for dry and water-saturated marble was carried out in the temperature range from −8 to 1°C, where an anomaly in the water freezing process was observed. In order to study artificial aging of Gioia marble, up to 60 freeze/thaw cycles were performed. No significant changes in the thermophysical properties of Gioia marble were observed during the artificial aging process. Paper presented at the Seventeenth European Conference on Thermophysical Properties, September 5–8, 2005, Bratislava, Slovak Republic.     

Relaxation methods for the investigation of the influence of surfactants on the rate of corrosion

We develop a theory of the application of low-level relaxation methods (basic and pulse potentiostatic methods, basic and pulse galvanostatic methods, and the method of electrode impedance) to the investigation of the influence of surfactants on the rate of corrosion. To evaluate the possibilities of this theory. we consider an example of a corrosion model characterized by the adsorption of surfactants which affects the rates of both cathodic and anodic processes. The cathodic process includes the adsorption of hydrogen atoms and the anodic process includes the adsorption of subions of the metal. We deduce equations for the calculation of the electrode parameters of the model on the basis of the experimental data and show that the complexity of the proposed model is maximum for all relaxation methods, except the method of electrode impedance. Dneprodzerzhinsk State Technical University, Dneprodzerzhinsk. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 32, No. 4, pp. 75–80, July–August, 1996.     

Velocity-controlled shape-tracing system using eight opticalsensors

A novel two-dimensional shape-tracing system was developed that uses eight optical sensors and two stepping motors. Each optical sensor, which consists of an optical fiber and a Darlington phototransistor, senses the intensity of the reflected light from drawings to determine the motion pattern of stepping motors. A software velocity-control scheme was also considered, because the shape-tracing system was designed mainly for an automatic plasma arc cutting process. By programming the control software in assembler language, a maximum pulse frequency of 2000 pulse/s, which is equivalent to a 4.8-m/min linear velocity, could be attained in the developed system. The developed shape-tracing system can be applied not only for the plasma arc cutting process, but also for other shape-tracing processes, such as for cutting clothes     

2 cm spatial-resolution and 2 km range Brillouin optical fiber sensor using a transient differential pulse pair

We report a high-spatial-resolution and long-range distributed temperature sensor through optimizing differential pulse-width pair Brillouin optical time-domain analysis (DPP-BOTDA). In DPP-BOTDA, the differential signal suffers from a signal-to-noise ratio (SNR) reduction with respect to the original signals, and for a fixed pulse-width difference the SNR reduction increases with the pulse width. Through reducing the pulse width to a transient regime (near to or less than the phonon lifetime) to decrease the SNR reduction after the differential process, the optimized 8/8.2 ns pulse pair is applied to realize a 2 cm spatial resolution, where a pulse generator with a 150 ps fall-time is used to ensure the effective resolution of DPP-BOTDA. In the experiment, a 2 cm spatial-resolution hot-spot detection with a 2 °C temperature accuracy is demonstrated over a 2 km sensing fiber.     

Effect of heat pretreatment on electrical conductance changes by NO2 adsorption of lead phthalocyanine thin film

The sensing characteristics of an NO₂ gas sensor using lead phthalocyanine thin film are influenced by heat-pretreatment time and ambient gas. The response behaviour of conductance for the change in ambient gas was characterized using Elovich's equation. The first stage in the adsorption and desorption kinetics reflects surface phenomena and the second stage the film diffusion. Both components were improved by heat treatment in air. The rising time in the NO₂ adsorption process was within 2 min, and the recovery time within 5 min at 130 °C for the film annealed in air for 1 h. The heat pretreatment induced the formation of a continuous layer of fine particles, ∼ 0.1 μm in size, and larger single crystals isolated from each other, which formed on the continuous layer. The formation of the larger single crystals is not preferable in fabricating a sensor with fast rising and recovery times.