Modeling the thermal response of porcine cartilage to laserirradiation

During laser irradiation of biological tissue, a number of physical processes take place that determine temperature elevation and thermal damage rates. Some of those important to laser-tissue interaction are: 1) propagation of light in scattering media; 2) transformation of laser light into photochemical, acoustic, or thermal energy; 3) tissue-tissue and tissue-environment heat and mass transfer; 4) and the occurrence of low-energy phase transformations responsible for structural alterations. The aim of this study was to formulate a finite-element model (FEM) able to predict the temperature distribution in a slab of porcine nasal cartilage during laser irradiation. The FEM incorporates heat diffusion, light propagation in tissue, and water evaporation from the surfaces of the slab. Numerical results were compared to experimental temperature distributions where surface and internal temperatures were measured while heating cartilage using a pulsed Nd: YAG laser (λ = 1.32 μm). Rectangular specimens, 1-4-mm thick, were secured perpendicular to the laser beam and irradiated for 1-15 s using different laser-beam powers (1-10 W)     

Sympathetic nervous system activity in stress and biofeedback relaxation

This article describes several studies on the measurement of slow rhythms in the heart and in peripheral vasculature and their relationship to stress and relaxation. These studies are preliminary steps in an attempt to quantify stress and relaxation. Mental stress is a major, well-documented factor in the development of cardiovascular diseases; relaxation, however, is perceived as the opposite state, which, presumably, can negate these harmful effects. To compare the effects of stress-management or relaxation techniques, stress and relaxation must be first quantified. Three methods for quantifying sympathetic activity as an indicator of stress were analyzed. These are heart-rate variability (HRV), photoplethysmographic measurement of peripheral vasomotor activity, and a novel measurement of skin temperature variability. The study showed that due to "low pass filtering response" of the thermal-transfer function between the blood vessel and the skin's temperature, the temperature-variability measurement is minimally sensitive to mechanical factors or accidental noise. Therefore, the temperature variability could be useful for the continuous tracking of vascular activity and its sympathetic tone. Tracking changes in the pressure-wave envelope (PV) provides another alternative for studying sympathetic nervous system (SNS) effects on peripheral vasculature. A drastic reduction in PV and a loss of correlation between temperature variability on the left and right hand confirm the predominant role of SNS in mediating these signals. Functional responses of these signals to SNS-stimulating (mental stress) or blocking (biofeedback) maneuvers are perturbed in patients with CAD (coronary artery disease), suggesting that these tests could be used as simple diagnostic or screening tools.     

Steady-state response of non-linear circuits: A frequency-domain relaxation method

We propose here an efficient algorithm for finding the steady-state response of stiff non-linear circuits. It is based on a frequency-domain relaxation method and can be applied efficiently to obtain the steady-state waveforms of both periodic systems and multi-frequency-component systems. the solution at each iteration is obtained by solving an associated linear time-invariant circuit at every frequency component via modified nodal analysis. Our algorithm is very simple and can be applied efficiently to solve a large class of practical non-linear communication circuits which are notoriously stiff and hence rather time-consuming to solve with existing methods.     

涡流式电磁声发射检测声波响应特性

涡流式电磁声发射检测由于其局部非接触式加载方式,适用于恶劣环境下对金属构件损伤在线检测,同时也是对传统声发射技术的有利补充。针对不同电磁载荷条件下电磁声发射产生的声波响应问题进行深入研究。通过引入电致塑性理论和自由电子运动理论,分析涡流加载下裂纹尖端位错滑移速率变化及声发射能量释放机理,探究不同磁场方向加载下电子的定向移动对声发射响应影响,利用希尔伯特黄变换方法实现对声发射信号的特性分析。实验结果表明:电磁声发射过程中应力波特征与电磁加载条件密切相关。因此,电磁声发射过程为定向移动电子越过障碍势垒产生的特定声波响应。     

Alleviation of the acute stress response following mild orange essential oil administration

We investigated the effect of two different concentrations of orange aroma on peripheral and cardiac autonomic nervous system activity under a stressful condition in a highly reproducible manner. In the within‐subjects experiment, 19 subjects performed a 30‐min calculation task under three aroma conditions: 1% orange, 20% orange, and scentless air (control). Each aroma was delivered to the subject intermittently with the use of a proprietary olfactometer in a counter‐balanced order. Along with a visual analog scale (VAS), nose tip temperature and the cardiac activity on electrocardiograms were recorded throughout the experiment. Regardless of the aroma condition, significant decreases in nose tip temperature and the high‐frequency (HF) component of heart rate variability (HRV) and a significant increase in heart rate (HR) were observed during the task, denoting a typical acute stress response. However, the increase/decrease in HR and HF were significantly smaller with 1% orange than with 20% orange and the control condition, indicating an inhibition of sympathetic nervous system elevation and parasympathetic nervous system suppression. There were no significant differences between the two doses for the VAS scores. The findings suggest that mild orange essential oil inhalation inhibits the cardiac stress response while demonstrating no significant effect on subjective stress. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

固结灌浆期间盖重抬动对混凝土应力的影响研究

本文采用三维有限元方法,通过施加压力和位移两种方式模拟固结灌浆过程中的盖重上抬,并以黄登水电站11#坝段为工程实例,对混凝土在固结灌浆期间的开裂进行了研究。针对固结灌浆施工过程中混凝土表面裂缝问题,结合11#坝段浇筑过程、温控措施和观测数据,并考虑不同的灌浆压力、抬动位移及温度荷载的影响,计算拟定12种组合工况,对各种组合工况进行应力场分析。各工况仿真结果对比分析表明:有限的灌浆压力不会引起混凝土拉应力大幅度增长,而在较小的灌浆压力和温度应力双重作用下混凝土抗拉安全系数偏低;盖重有一定的抬动位移时会在混凝土表面引起较大的拉应力,叠加温度荷载后混凝土开裂风险加大。     

Detecting stress during real-world driving tasks using physiological sensors

This paper presents methods for collecting and analyzing physiological data during real-world driving tasks to determine a driver's relative stress level. Electrocardiogram, electromyogram, skin conductance, and respiration were recorded continuously while drivers followed a set route through open roads in the greater Boston area. Data from 24 drives of at least 50-min duration were collected for analysis. The data were analyzed in two ways. Analysis I used features from 5-min intervals of data during the rest, highway, and city driving conditions to distinguish three levels of driver stress with an accuracy of over 97% across multiple drivers and driving days. Analysis II compared continuous features, calculated at 1-s intervals throughout the entire drive, with a metric of observable stressors created by independent coders from videotapes. The results show that for most drivers studied, skin conductivity and heart rate metrics are most closely correlated with driver stress level. These findings indicate that physiological signals can provide a metric of driver stress in future cars capable of physiological monitoring. Such a metric could be used to help manage noncritical in-vehicle information systems and could also provide a continuous measure of how different road and traffic conditions affect drivers.     

压电换能器阻抗匹配研究

声波测井井下仪器在探测过程中需要将足够大的声波信号辐射到地层中,须用高压大功率脉冲信号激励发射换能器,同时在信号源与换能器之间,还应做到阻抗匹配。为有效提高信号源对换能器的激发效率,达到了阻抗匹配的目的,分析了信号源与换能器之间的理想匹配条件,介绍了如何在高压大功率信号源与换能器之间利用脉冲变压器和电阻、电感、电容组成阻抗匹配网络,给出了脉冲变压器和电感的制作和设计方法,并利用简要的实验方法对变压器和电感进行了参数测量,测量结果表明变压器和电感的计算和制作过程符合要求。最后用信号源对换能器进行了激发实验,实验结果说明通过该阻抗匹配网络取得了明显的效果。     

基于反应谱法的重力坝有限元等效动应力响应分析

提出了由有限元法得到的振型求船振型内力及振型等效应力,并根据反应谱法理论求解重力坝等效动应力响应的分析方法.本文对四个在建或拟建的重力坝,用悬臂梁反应谱法和有限元等效应力法分别进行了计算,比较了坝体几个典型部位等效动应力响应.结果表明,在坝体体型有突变的地方,有限元等效应力法相较悬臂梁法所得值有明显的增高,更敏锐的反映出了应力集中对坝体垂直动应力的影响.本文提出的方法简单易行,比悬臂梁反应谱法更能反映坝体体型的影响.     

联合循环机组汽机启动过程中的热应力控制

联合循环机组相对于火电机组而言,启停次数频繁。尽管采用不正确的方法也能顺利地启动、停机,但不兼顾机组自身热应力变化而随意操作,会对机组寿命造成很大的影响。论述了汽机启动过程中如何通过区分不同外部条件来设置机组转速、负荷,同时协调燃机排气温度控制,以达到减少汽机主要部件热应力,提高运行寿命的目的。     

电站锅炉声学测温中的声源选择及其声信号互相关特性分析

以选择声学测温中的声源和声信号为目的,针对电站锅炉的声学特性,分析了声学测温中的声信号的频率范围、声压级要求。比较了火花放电声源、电动声源和气动声源的优缺点,建议采用频率在1.5～10kHz,声压级大于120dB(0dB=20μPa)的气动声源。用Matlab编写程序并驱动扬声器发声,基于MKⅡ多通道声学测试分析系统,对几种典型声信号进行了常温下的互相关特性分析实验研究,指出了正弦信号不适合作为声学测温的声信号:扫频信号则要尽量减小扫频周期。提出了一种新的信号,伪随机二进制序列,在常温下的实验结果和理论上尖锐的互相关特性分析一致。利用压缩空气机作为气动声源,由频谱分析可知其具有类似白噪声的频率特性,互相关特性分析实验结果很好,进一步证明了气动声源的喷射声信号在测量精度上的优势。不仅为声学测温中的声源选择提供了指导,而且互相关特性分析对锅炉四管泄漏声源定位中的延时测量有一定的参考价值。     

Analysis of sEMG during voluntary movement-part II: voluntary response index sensitivity

In this paper, a method for analyzing surface electromyographic (sEMG) data recorded from the lower-limb muscles of incomplete spinal-cord injured (iSCI) subjects is evaluated. sEMG was recorded bilaterally from quadriceps, adductor, hamstring, tibialis anterior, and triceps surae muscles during voluntary ankle dorsiflexion performed in the supine position as part of a comprehensive motor control assessment protocol. Analysis of the sEMG centered on two features, the magnitude of activation and the degree of similarity [similarity index (SI)] of the sEMG distribution to that of healthy subjects performing the same maneuver (n = 10). The analysis calculations resulted in response vectors (RV) that were compared to healthy-subject-derived prototype response vectors resulting in a voluntary response index (VRI). Incomplete SCI subjects (n = 9) were used to test the sensitivity of this analysis method. They were given supported-weight treadmill ambulation training, which is expected to improve or at least not cause a deterioration of voluntary motor control. The VRI provided evidence that the quantitative sEMG analysis method used was able to differentiate between healthy subjects and those with iSCI, characterize individual differences among iSCI subjects, and track motor control changes occurring over time.     

Synchronization of a forced relaxation oscillator

The paper presents a method of synchronizing a relaxation oscillator to an external signal. the synchronization mechanism is linear and a detailed analysis is given. Very fast acquisition is shown to be possible. the oscillator synchronizes to the frequency of the forcing input or to a sub- or superharmonic. Possible applications include highspeed timing recovery systems where high acquisition speed is required.     

Analysis of temperature and stress fields in bars of induction motor cage during starting

Contents The analysis of thermal field and stresses field in the slot part of the bar of an induction motor in the course of starting have been presented in the paper. The changes of the bar parameters resulting from the temperature changes and the heat flow from the bar into the surroundings have been considered. The finite element method has been used in the calculations.

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Analyse des Temperatur- und Spannungsfeldes eines Stabs im Induktionsmotor während eines Anlaufs

Übersicht Der Beitrag enthält eine Analyse des Temperatur-und Spannungsfeldes im Nutteil des Induktionsmotorstabs während eines Anlaufs. Bei den Berechnungen hat man die Parameteränderungen des Stabs berücksichtigt, die aus den Temperaturänderungen und den Wärmeabfluß vom Stab zu der Umgebung folgen. Zur Berechnung wurde die Methode der finiten Elemente verwendet.

     

锅炉声波吹灰器应用探讨

从与传统锅炉吹灰器的对比入手,全面介绍了一种新型的锅炉吹灰器——声波吹灰器的原理、特点、应用方法、应用效果及应用中的注意事项     

Review of Fiber-optic Distributed Acoustic Sensing Technology

A distributed optical-fiber acoustic sensor is an acoustic sensor that uses the optical fiber itself as a photosensitive medium, and is based on Rayleigh backscattering in an optical fiber. The sensor is widely used in the safety monitoring of oil and gas pipelines, the classification of weak acoustic signals, defense, seismic prospecting, and other fields. In the field of seismic prospecting, distributed optical-fiber acoustic sensing (DAS) will gradually replace the use of the traditional geophone. The present paper mainly expounds the recent application of DAS, and summarizes recent research achievements of DAS in resource exploration, intrusion monitoring, pattern recognition, and other fields and various DAS system structures. It is found that the high-sensitivity and long-distance sensing capabilities of DAS play a role in the extensive monitoring applications of DAS in engineering. The future application and development of DAS technology are examined, with the hope of promoting the wider application of the DAS technology, which benefits engineering and society.