镀铝膜包装的食品金属检测技术

食品安全问题越来越受到广大群众关注,其中食品的金属检测是最常见的一类.目前食品包装和食品本身产品效应的干扰下的金属检测技术是食品金属检测的研究热点.文章分析了电磁检测原理和频率对检测灵敏度的影响,设计了双频金属检测系统,搭建了设备进行实验,验证了检测的可行性.最后使用检测样品对检测系统进行测试,实现了较高精度的镀铝膜包...     

传统水表检测装置的改造及检测方法的改进

文章针对传统水表检测装置及检测方法存在的一系列问题,对检测装置进行了改造,从而实现了检测过程的自动化控制,并对检测方法进行了改进,采用动态定量法来检测水表,通过试验数据和不确定度分析,验证了此方法能够提高水表检测的不确定度水平,显著减少检测用水量,提高检测效率.     

BGA焊点检测技术研究

本文讨论了BGA封装器件焊接的特点,并对BGA器件焊点检测方法进行了分析。重点对常用的BGA焊点检测技术——X射线检测进行研究,分析了X射线检测用于BGA焊点检测的原理,探讨了该方法的优点和待改进的地方。深入分析了自动X射线检测用于BGA焊点检测的数字图像处理技术,基于数字图像处理技术,详细阐述了从BGA检测图像预处理至BGA焊点缺陷检测的整个过程及其涉及的关键技术。     

金属材料缺陷的电磁超声/涡流复合检测技术研究

电磁超声检测和涡流检测因其非接触、检测速度快、对试件表面要求低等优点而被广泛应用于金属材料的缺陷检测中,但电磁超声检测存在近表面的检测盲区,涡流检测对内部深层缺陷灵敏度不高。基于电磁超声和涡流的复合检测方法,设计了能同时满足电磁超声检测和涡流检测的复合式探头,建立了电磁超声和涡流复合检测有限元模型,并对金属试件中不同类型的缺陷进行了检测实验。仿真和实验结果表明,该复合探头不仅能快速检测表面裂纹,而且可激发出具有明显指向性的纵波,一定程度上削弱了波形转换产生的干扰波,可实现对内部缺陷的准确定位、识别,为电磁超声和涡流复合式检测技术在板材的复杂缺陷检测中的应用提供了基础。     

无损检测在木材应用中的现状及发展趋势

无损检测技术在木材检测中的地位日益重要,本文主要从应力波检测、超声波检测、X射线检测和机械应力检测四个方面介绍了无损检测在木材中的应用,阐述了其基本原理和特点,概述了发展历史和研究现状,并展望了未来研究方向及工作重点。     

浅谈沥青混合料路面的平整度检测方法及影响因素

在社会发展飞速的今天，对于沥青路面检测的检测技术也在不断的发展。目前由原来的静态检测逐渐向动态检测发展，由之前的手工操作转变成自动化发展，由之前的有损检测转向了无损检测发展，单项检测转换成了集成检测。检测的速度也越来越快，效率越来越高，结果越来越精确，这就说明了沥青混合料路面的检测技术已经在不断的改进提高中。本文作者主要对沥青路面平整度的检测做了详细的阐述，并分析了影响沥青路面平整度的各方面因素，以供同行业参考。     

浅谈飞机电缆自动化检测系统的研制

随着航空技术尤其是航空电子电气技术的飞速发展,电缆检测由传统的手工检测转化为自动化检测,而自动化检测的载体自动化检测系统的研制也已提上日程。本文分析了国内外电缆检测技术现状,综述了我公司电缆自动化检测系统的研制过程及检测效率,并指出了电缆检测系统的发展方向。     

一种光电编码器检测装置的研制与应用

针对光电编码器检测中存在的问题研制出了相应的检测装置,并阐述了检测方法。该检测装置的特点在于:体积小,操作方便,检测快捷,检测结果数码管显示。检测装置能完成所有的检测项目,能够达到光电编码器快速、全面、精确检测的要求。     

漏磁检测技术在油罐底板检测中的应用

漏磁检测是近年来发展起来的一种无损检测技术,具有检测效率高、准确等优点。目前,该技术在油罐底板检测中得到了广泛的应用。本文在阐述漏磁检测技术原理的基础上,分析了影响漏磁检测的因素,并介绍了相关的罐底板漏磁检测设备,最后论述了漏磁检测技术的具体应用实例。     

基于磁致伸缩导波技术的锚杆新型检测方法设计

针对现有锚杆质量检测方法存在检测具有破坏性、检测过程复杂、检测精度不高等问题,提出一种基于磁致伸缩导波技术的锚杆无损检测新方法.在研究磁致伸缩导波检测原理以及锚杆中导波特性的基础上,研制了锚杆检测系统,并利用该系统在锚杆中激励出L(0,1)模态导波,完成了空气中以及混凝土结构中锚杆长度以及缺陷的检测实验,实现了对锚杆的非接触式无损检测.结果表明:该方法检测过程简单、检测精度高,能检测具有隐蔽性的锚杆等,可以实际应用在锚杆质量检测中.     

On the heat in the nozzle of the industrial pneumatic pulsator

An industrially applicable nozzle is the subject of this study. The nozzle is an auxiliary equipment of a pneumatic pulsator system for unclogging outlets of silos which store loose materials. The aim is to determine the amount of heat which is generated during one work cycle of the system. Investigation in this field has not been carried out so far, and the present-day designing process is significantly based on heuristic knowledge. The heat is calculated by using results of a numerical simulation. The Finite Volume Method has been used with a thermodynamically ideal gas model. The airflow is assumed to be transient, compressible and supersonic, and it is driven by a time-varying pressure difference. There is an estimation of discretization error of the numerical results carried out in order to confirm the reliability of the solution. The error estimation shows that the results lie in the vicinity of the exact solution of the governing equations. Instantaneous results of the simulation indicate a locally flow which intensifies flow parameters in a similar way as the converging-diverging nozzles do. The value of the total heat generated during gas conversion within the nozzle is negative; thus, the nozzle could be cooled during its functioning.     

蒸发盘管内制冷剂喷射蒸发的制冷系统研究

制冷剂高压能的利用对改善制冷系统运行有重要意义。基于场协同理论,提出了一种利用制冷剂在蒸发管内进行喷射的新型制冷系统,理论上分析了协同角随毛细管管径和喷射孔直径的变化规律,并进行了相关的可视化实验。理论分析结果表明:协同角随着喷射孔直径的增大而增大;随着毛细管管径的减小而减小,但是随之减小的速率降低。实验结果表明:和传统的毛细管节流制冷系统相比,开孔实验的制冷剂的充注量减少70%以上,COP提高了9%,系统达到稳定的时间减少了70%。     

Fractal study of the fluctuation characteristic in the calibration of the cryogenic thermocouples

The accuracy of the temperature measurement depends strongly on the accuracy of the temperature sensor. The commonly used cryogenic thermocouples are calibrated by using a specially designed calibration system. The calibration is performed in the temperature range of from liquid nitrogen temperature (about 77 K) to the room temperature (300 K). The calibration results show that the accuracy is around several tens of mK, which meets the requirement of the experiments. However, it is found that the temperature fluctuation of the thermocouple is quite larger even if the temperature is well controlled, which indicates that the non-linear aspect characteristic plays a certain role in the calibration. The temperature fluctuation of the calibration process is analyzed by using the non-linear analysis method.     

On the estimate of the rate constant in the homogeneous dissolution model

The aim is to determine how well the rate parameter of the homogeneous model of dissolution can be estimated in dependency on the chosen times to measure the empirical data. The approach is based on the theory of Fisher information. We show that if the probability distribution of the measurement errors is known, the data should be collected at a single time instant or its close proximity in order to obtain the best estimate. This is in sharp contrast with commonly used experimental protocols. Further, from the properties of the Fisher information we deduce how suitable is the model of measurement error and we show that asymmetric distribution of data close to the time origin is unavoidable.     

《电机不平衡磁拉力研究现状与展望》

对当前国内外电机不平衡磁拉力研究现状进行分析和综述,分析和总结不平衡磁拉力的机理、特征,并对不平衡磁拉力特别是非线性磁拉力的国内外发展概况进行介绍。归纳防止和减小不平衡磁拉力的有效措施,最后对电机不平衡磁拉力未来的研究方向进行展望。     

Evaluating the possible configurations of incorporating the loop heat pipe into the air-conditioning systems

The possible configurations of incorporating the loop heat pipe into the air-conditioning system to perform the reheat process are introduced and evaluated. The results show that the coefficient of performance of the system can be improved and the energy required by the compressor can be reduced when LHP is used instead of the heating element. For low room sensible heat factor, using loop heat pipe can improve the COP by approximately 2.1-fold over that when heating element is used. The results also show that the possible configurations of incorporating the loop heat pipe considered for small air-conditioning unit have the same COP, and among the possible configurations used in air-handling unit. The configuration where the loop heat pipe evaporator is placed in the supply air passage gives the highest COP followed by that where the loop heat pipe evaporator is placed in the return air passage then that where the loop heat pipe evaporator is placed in the passage of the outside air.     

脱靶量累加前馈补偿电视跟踪器的跟踪误差

电视跟踪系统通常采用速度、位置双闭环控制。前馈控制可以提高跟踪精度但无法实现;速度、加速度滞后补偿,跟踪精度提高有限。动态高型方法是在负反馈控制系统中增加若干积分环节以提高跟踪精度。随着目标速度的提高和光电跟踪设备自动化程度的提高,对电视跟踪器伺服系统的跟踪精度提出了越来越高的要求。本文创新性引出一种斜坡累加补偿方法,通过理论证明和仿真,指出它与动态高型技术高度相似,从而从新的角度解释了动态高型提高跟踪精度的机理,并为动态高型方法在工程上实现电视跟踪伺服系统的跟踪精度的提高提供了坚实的理论依据。     

On the numerical solution of the Dirichlet initial boundary-value problem for the heat equation in the case of a torus

The initial-boundary-value problem for the heat equation in the case of a toroidal surface with Dirichlet boundary conditions is considered. This problem is reduced to a sequence of elleptic boundary-value problems by a Laguerre transformation. The special integral representation leads to boundary-integral equations of the first kind and the toroidal surface gives one-dimensional integral equations with a logarithmic singularity. The numerical solution is realized by a trigonometric quadrature method in cases of open or closed smooth boundaries. The results of some numerical experiments are presented.     

Understanding the unit in the Rasch model

The purpose of this paper is to explain the role of the unit implicit in the dichotomous Rasch model in determining the multiplicative factor of separation between measurements in a specified frame of reference. The explanation is provided at two complementary levels: first, in terms of the algebra of the model in which the role of an implicit, multiplicative constant is made explicit; and second, at a more fundamental level, in terms of the classical definition of measurement in the physical sciences. The Rasch model is characterized by statistical sufficiency, which arises from the requirement of invariant comparisons within a specified frame of reference. A frame of reference is defined by a class of persons responding to a class of items in a well-defined response context. The paper shows that two or more frames of reference may have different implicit units without destroying sufficiency. Understanding the role of the unit permits explication of the relationship between the Rasch model and the two parameter logistic model. The paper also summarises an approach that can be used in practice to express measurements across different frames of reference in the same unit.     

Effects of the El Chichon volcanic cloud in the stratosphere on the intensity of light from the sky

This is the second of two papers dealing with the effects of volcanic debris from the eruption of El Chichon on light from the sunlit sky. The polarization of skylight was considered in the first of the two, whereas this one is devoted to skylight intensity. It is shown here that the magnitude of the skylight intensity is modified very significantly from its clear sky value by the volcanic cloud, as is its change with solar depression angle during twilight and its distribution over the sky during the day. Emphasis is on measurements at a wavelength of 0.07 microm. Generally the volcanic cloud produces a diminution of zenith intensity during twilight with a considerable enhancement of intensity over the sky throughout the main part of the day. The solar aureole is not as sharp as it is in normally clear conditions, but the volcanic cloud causes a very diffuse type of aureole which covers a large portion of the sky. The preferential scattering of the longer wavelengths of sunlight, which is made evident by brilliant red and yellow colors in the sunrise period, causes a pronounced change of longwave/shortwave color ratios during twilight from their values in clear atmospheric conditions. The combination of intensity data shown here with polarization data in the previous paper should give a relatively complete picture of the effects of volcanic debris on solar radiation in the atmosphere and be useful in the verification of radiative transfer models of atmospheric turbidity.