电子天平计量检定的影响因素及对策初探

电子天平的准确计量对高等学校、科研院所、医疗卫生等机构的应用需求非常大,其计量检定工作的顺利开展对上述机构具有重要的意义。对电子天平计量检定的影响因素及对策进行深入的探讨对提高检定质量有着直接的影响,本文首先对电子天平计量检定的意义进行了阐述,针对存放时间长、检定前未预热、未预压以及校准不正确等影响计量检定工作的因素进行了详细的分析,并对上述影响因素提出了解决的对策。除此之外,电子天平计量检定工作中环境因素、操作因素和方法因素对计量检定工作的影响也尤为显著。     

一种互不相溶的两种液体混合物相体积自动计量方法和装置

本文根据互不相溶的两种液体混合物的体积等于它们的相体积之和的原理,提出了一种两种液体混合物相体积自动计量方法和装置,通过电子天平称重与混合物的总体积和质量相关的量,解相关方程得到混合物中各相的体积,文中还给出了误差分析,该计量方法和装置已成功地应用于稠油蒸汽驱油物理模型实验。     

浅谈电子天平的原理、结构及使用维护方法

<正>天平是质量量值传递过程中必须使用的计量器具。天平计量性能的合格与否直接影响着量值传递的准确可靠。随着科学技术的发展,电子天平已逐步取代了机械天平而进入到各个领域。笔者在对电子天平进行计量检定时,发现许多使用电子天平的单位由于不了解电子天平的原理、结构及使用维护方法而造成了许多不必要的经济损失;另外,许多单位也经常向     

金银首饰店应配备合适的电子天平并正确使用

<正>0引言金银首饰店一般都有称量用的电子天平,这类天平属于贸易用计量衡器,是国家强制性检定计量器具的一种,必须定期进行检定。如果商家用来计量饰品克重的电子天平不准确,或未经检定,或所配备的电子天平无法满足金银珠宝的计量要求,会给消费者的利益带来损失。为了规范商场、金银首饰店的电子天平的配备和使用,本文分析了在使用中发现的一些问题并提出解决方法,以确保电子天平的准确度,维护广大消费者的利益。1存在的问题1.1电子天平使用环境不符合规程要求大多数金银首饰店的电子天平都放在玻璃柜上     

电子天平计量检定中的若干问题与建议

本文详细介绍了电子天平计量检定内容,列举了电子天平计量检定的几点影响因素,针对问题提出合理化建议,从而提高电子天平计量检定的精准性。     

电子天平的期间核查/运行检查

0前言 电子天平是一种计量器具，是检测实验室的主要检测设备之一，按照《中华人民共和国计量法》，出具公众数据的计量器具每年必须进行强制检定／校准。为了了解电子天平的状态，维护电子天平在两次校准期间校准状态的可信度，减少由于仪器稳定性变化造成的结果偏差，有必要对电子天平进行检查。对电子天平在两次周期检定／校准之间所进行的核查，叫做电子天平的期间核查。在计量认证中称“运行检查”。（CNACL201—2001实验室认可准则》（等同采用ISO／IEC17025：2005、《计量认证／审查认可评审准则》中均提出了对参考标准、测量设备进行期间核查／运行检查。期间核查／运行检查的目的是了解仪器的精度、准确度和灵敏度是否有变化，也对从上次检定到本次核查期间所做工作作一总结。未见有开展电子天平的期间核查／运行检查的文献报道。现报告如下。     

电子天平比对结果的分析与研究

根据浙江省质量技术监督局的安排,指定台州市计量技术研究院作为本次比对主导实验室,负责实施省内法定计量检定机构和社会第三方计量校准机构的计量比对工作。文章介绍了比对的技术方案、比对结果,指出电子天平校准工作中的不足,分析原因并提出建议和改进措施,有助于提高电子天平项目的检定校准技术能力,确保计量标准量值准确可靠。     

电子天平2000g称量点校准结果示值误差的不确定度评定

本文根据国家计量技术规范JJF1059-1999《测量不确定度评定与表示》、国家计量检定规程JJG1036-2008《电子天平》,并结合实际工作经验,应顾客要求,对其电子天平最大称量点2000g点校准结果进行的测量不确定度评定。     

如何使用电子天平检定砝码的折算质量

近年来,各级计量检定机构常采用电子天平作为砝码量值传递的衡量仪器,正确使用电子天平检定砝码的折算质量值,对确保质量量值传递系统的准确可靠极为重要。本文从实际工作经验出发,介绍了使用电子天平检定砝码折算质量值的检定内容、检定步骤及数据处理方法,对从事砝码量值传递工作的检定人员具有参考意义。     

电子天平的检定与计算

本文参考JJG1036-2008《电子天平检定规程》,根据平时工作经验对电子天平的检定和计算的内容作了归纳总结,期望与从事计量工作的同志共同探讨。     

数字可调移液器校准方法研究

针对目前尚无数字可调移液器的校准方法和测评标准,采用了国内外应用广泛的移液器容量测量方法一衡量法对数字可调移液器多种工作模式进行校准,参照国内标准的技术要求,发现现有的标准对数字可调移液器特别 是具有多种工作模式(普通模式、粘液模式、分液模式、混液模式等)的数字可调移液器并不完全适用.所以,制定一种适用干数字可调移液器的校准方法和测评标准,特别是对其不同工作模式进行针对性和有效性的校准和测评,是计量部门以及相关仪器生产厂家的迫切需要.     

基于半色调实地的纽介堡方程修正方法

目的从网点墨量与实地墨量不同的角度出发,构建基于半色调实地三刺激值的纽介堡方程修正模型,从而提高纽介堡方程的计算精度。方法以符合G7认证的印刷标准文件为研究对象,从网点墨量与实地墨量不同的角度出发,通过求解半色调实地三刺激值,构建基于半色调实地三刺激值的纽介堡方程修正模型,利用色差法对该修正模型进行精度验证。结果验证结果表明,修正模型色差精度最大可以提高2.2 NBS,平均色差精度可以提高1.0 NBS。结论基于半色调实地三刺激值的纽介堡方程修正模型能够有效提高方程精度,研究结果对于印刷分色具有重要意义。     

Online standard additions calibration of transient signals for inductively coupled plasma mass spectrometry

An online standard additions calibration method for transient signals in ICPMS is demonstrated in which a small volume of standard is injected as a spike into the sample/carrier stream, overlaying the analyte peak. This technique provides the advantages of conventional standard additions but requires only a single sample run. The method corrects for matrix effects and is suitable for transient signals in which the severity of the matrix effect changes over the analyte peak. The method uses a peak-fitting program to determine the area of the underlying peak and is shown to be effective for the determination of trace metal concentrations in both a high ionic strength matrix and in a biological matrix (urine). Eight analytes with concentrations in the range of 0.82-233.2 mug L-1 in urine were simultaneously determined using a standard spiking solution of 75 mug L-1 injected through a 100-muL loop. The measured concentrations for analytes free of spectral interferences agreed with the certified values, and the precision achieved was comparable to that achieved by the certifying agency. Using a conventional cross-flow nebulizer and Scott-type spray chamber, the accuracy obtained for online standard additions calibration was within 2%, and the precision was within 5%.     

基于P-Rob六自由度机械臂运动学建模与仿真

目的为实现后续机械臂控制算法研究,检验机械臂运动学模型构建的正确性,基于PersonalRobotics,对六自由度机械臂进行运动学模型构建和轨迹仿真。方法通过标准D-H法建立运动学模型,实现机械臂的正、逆运动学方程求解,根据机械臂的结构特性,对传统逆向运动学求解的解析法进行改进。结果使用仿真软件Matlab验证了运动学模型建立的准确性,改进的逆向运动学求解算法降低了传统求解算法的复杂度。使用仿真软件Matlab验证了运动学模型建立的准确性,并通过Matlab对改进的逆行运动学求解方法进行了验证,结果表明,改进的逆向运动学求解速度是传统逆向运动学求解速度的一半。结论根据六自由度机械臂的运动学研究,对实际机械臂的运动控制具有一定的参考价值。在实际的P-Rob机械臂上进行了仿真数据的测试,再次验证了运动学模型建立的准确性,仿真数据可应用于实际的机械臂控制中。实验现象表明针对此机械结构的机械臂,使用改进解析法求解逆解的方法计算简单、误差小、可行性强。     

Numerical treatment of diffusional phase transformation through fully implicit control volume method

Abstract

Solid state, diffusion controlled phase transformation kinetics with a moving boundary has been quantified using a fully implicit, fixed grid, finite difference method based on the control volume approach. In a departure from the usual modeling techniques for phase change problems, the region undergoing phase change has also been considered as a control volume. A new equation for the interface flux balance has been obtained that minimises the mass balance error that normally plagues the numerical solution of moving boundary problems. The model has been validated with the calculated phase thickness based on binary equilibrium diagram and available experimental data in the literature for the Cu–Zn system and a good match has been obtained. The results obtained by the present formulation are compared with those obtained from the other models. In addition to the improved accuracy of the prediction because of elimination of the mass balance error, the proposed method has the usual advantages of a fully implicit scheme.     

Particle size measurement of standard reference particle candidates with improved size measurement devices

In order to prepare standard reference particles, experimental and theoretical studies have been conducted on particle size measurement of two kinds of spherical glass beads. The sheath flow- type electrical sensing zone method and the revised sedimentation balance method were used for the measurement. The data were compared with those obtained by the microscopic method with a sample size greater than 10 000. The particle size distributions obtained by use of the sheath flow- type electrical sensing zone method and microscopic method are nearly equal for the two kinds of glass beads. However, deviations of less than 5% were observed between the improved sedimentation balance and microscopic methods. The experimental data of the microscopic method are within the 95% reliability region of the sheath flow-type electrical sensing zone method.     

A well‐conditioned and optimally convergent XFEM for 3D linear elastic fracture

A variation of the extended finite element method for three‐dimensional fracture mechanics is proposed. It utilizes a novel form of enrichment and point‐wise and integral matching of displacements of the standard and enriched elements in order to achieve higher accuracy, optimal convergence rates, and improved conditioning for two‐dimensional and three‐dimensional crack problems. A bespoke benchmark problem is introduced to determine the method's accuracy in the general three‐dimensional case where it is demonstrated that the proposed approach improves the accuracy and reduces the number of iterations required for the iterative solution of the resulting system of equations by 40% for moderately refined meshes and topological enrichment. Moreover, when a fixed enrichment volume is used, the number of iterations required grows at a rate which is reduced by a factor of 2 compared with standard extended finite element method, diminishing the number of iterations by almost one order of magnitude. Copyright © 2015 John Wiley & Sons, Ltd.     

A study on setting standard time using work achievement quotient

A method is proposed for setting standard time using a work achievement quotient approach. As an example, the vehicle safety inspection service for fork-lift trucks is considered. Conventionally, standard time has been set using a Predetermined Time System (PTS) method such as the Work Factor (WF) and Method-Time Measurement (MTM) methods or using a stopwatch method. The PTS method sometimes may be inappropriate because the analysis is too much trouble when the method is used for a work of a small manufacturing volume or of a long cycle time. Although simpler WF methods like the Ready Work Factor (RWF) method, etc., have been developed, users of these methods are expected to be trained and have completed hands-on analytical practice through a formal training course and to acquire the necessary skills in order to obtain accurate time measurements. When the stopwatch method is used to conduct the rating, subjective impressions can influence the results. To obtain accurate time measurements, a thorough training using films, etc., is necessary. In contrast, the method for setting standard time using the work achievement quotient approach can grasp individual variation of workers in time sequence and evaluate it dynamically. Thus, calculation is possible using a small statistical sample.     

空气净化产品净化效果的标准测试方法

分析了空气净化产品标准中产品净化效率测试方法所测得净化效率,与产品在实际应用中净化效率的区别。实验验证两者之间的显著差异,提出影响净化产品净化效率的多种因素以及将来空气净化产品可以完善的方向。     

Steady interface crack propagation between two viscoelastic standard solids

The problem of a crack propagating steadily in Mode III along the interface of two bonded viscoelastic materials modeled as standard linear solids is investigated. The mathematical method consists of the application of a Fourier transform and the solution of simultaneous Wiener-Hopf equations. The results show that the variation of the stress intensity factor with crack propagation velocity may exhibit different domains of behavior depending upon the relative magnitude of the short and long-time wave speeds of each constituent. The accuracy of the method is checked by a comparison of the general results with special limiting cases.