Effect of bushings in thermometric fixed-point cells

Bushings are tubular inserts that can be used with temperature fixed-point cells for the calibration of standard platinum resistance thermometers in accordance with the International Temperature Scale of 1990. They are made out of different materials such as glass and various metals with high thermal conductivities. Their function is to increase the thermal contact between the thermometer’s sensor and the phase boundary in the thermometer well of the cell. In the paper, the effect of bushings on the self-heating and on the immersion profiles of thermometers in fixed-point cells was researched. Three different thermometers were used: one fused silica sheathed and two Inconel sheathed. The self-heating was measured in the temperature range from the mercury triple-point to the zinc freezing-point with and without metal bushings: brass, aluminum and copper. The immersion profiles were measured in the zinc cell with and without an aluminum and a glass bushing. Besides experimental measurements, some qualitative results of numerical modeling are also presented. The bushings considerably lower the self-heating, in some cases even by more than 50%. But, on the other hand, bushings seem to increase the measured temperature, worsen the immersion profile and act as a radiation shield in the gap between the thermometer and the fixed-point cell at higher temperatures, where radiation is the dominant mode of heat transfer.     

地质钻机定点钻孔加载稳定性评价方法

针对定点钻孔的特点以及施工工况对系统性能的具体要求,运用模糊数学理论的分析方法建立具有隶属函数与实际性能分布的数学模型,并结合数理统计学和MATLAB软件对数据样本进行处理计算,得到该钻进设备在某时间节点处优良性能的模糊数值,最终通过实例计算验证模糊化分析方法具有较好的可操作性,且计算较为简便,为定点钻孔载荷稳定性的评价提供了较为可行的数学模型.     

A practical approach to the stereology of anisotropic structures

Inversion formulae for the rose of directions of fibre (surface) processes are evaluated by means of a parametric model of the rose of intersections. The problems of statistical tests of isotropy, degree of anisotropy and stereological formulae are solved. A short-cut sampling procedure for the three-dimensional case is proposed and applied in a metallographic situation.     

Production activity control: A practical approach to scheduling

There is a widely perceived gap within the domain of scheduling for manufacturing systems, namely, many of the methods employed by production supervisors are quite different from those developed by researchers. In a sense, this inconsistency highlights the important fact that much scheduling research has failed to win approval where it matters most, namely, within the manufacturing system.In this article, we argue for a practical approach to scheduling for manufacturing systems, one that we believe can narrow, and possibly bridge, the gap between theory and practice. This approach is based upon a well-defined and modular architecture for scheduling, termedproduction activity control. This architecture is the foundation of our proposed solution to scheduling, since it provides a coherent blueprint for the synthesis of information technology and scheduling strategies. The result of this synthesis is a design tool for production activity control, which allows for detailed and disciplined experimentation with a range of scheduling strategies in a controlled and simulated environment. Due to the unique modular property of the design tool, these strategies may then be implemented live in a flexible manufacturing facility, hence narrowing the gap between scheduling theory and manufacturing practice. Our overall approach is tested through an appropriate implementation in a modern electronics assembly plant.     

A case-based and practical approach for multivariate modeling of grinding process

Grinding process is claimed to be the only possible cost-effective means of shaping engineering part(s) or component(s) into finished products with required surface topology. However, because of the complicated relationship(s) between several phenomena and entities involved in a grinding process, determining functional relationship between relevant input(s), in-process variable(s), and output quality characteristic [or response] remains a critical and difficult task for researchers and practitioners. The complexity of the problem further increases as number of responses considered for modeling is more than one, and the situation is so-called multivariate or multiresponse surface modeling. Although various mechanistic and empirical modeling approaches have been proposed in literature, they are found to be of limited validity, with applied functional approximation and simplistic assumption(s). In addition, empirical models are sometimes based on off-line designed experimental data, which are expensive or uneconomical in many line layout type mass-manufacturing situations. This paper attempts to provide a case-based practical approach for practitioners, with detailed steps involved in multivariate modeling, based on conventional regression technique, and unconventional artificial neural network-based technique, using real-time production data. The two case examples selected to verify the approaches are from an automobile engine manufacturing unit located in eastern India.     

Estimation of the mean caliper: A new simple approach

Morphometric measurements are commonly carried out on structures the shape of which approximates that of a sphere. We calculated some stereological data of eosinophil granules by using digitized planimetry, performed on transmission electronmicrographs. By using a new approach for mean caliper (D) estimation and extrapolating an approximate granule axial ratio, we were able to calculate the granule density size. We deduced from a numerical analysis for various sphere sizes distributions from which an underestimation of not more than 4% may be contributed to D in most cases, assuming that the diameter coefficient of variation is less than 35%. The methodology we propose for mean ellipsoid caliper estimation seems to be useful in cases in which the disector method is not suitable.     

A unified approach to form error evaluation

Evaluation of form error is a critical aspect of many manufacturing processes. Machines such as the coordinate measuring machine (CMM) often employ the technique of the least squares form fitting algorithms. While based on sound mathematical principles, it is well known that the method of least squares often overestimates the tolerance zone, causing good parts to be rejected. Many methods have been proposed in efforts to improve upon results obtained via least squares, including those, which result in the minimum zone tolerance value. However, these methods are mathematically complex and often computationally slow for cases where a large number of data points are to be evaluated. Extensive amount of data is generated where measurement equipment such as laser scanners are used for inspection, as well as in reverse engineering applications.In this report, a unified linear approximation technique is introduced for use in evaluating the forms of straightness, flatness, circularity, and cylindricity. Non-linear equation for each form is linearized using Taylor expansion, then solved as a linear program using software written in C++ language. Examples are taken from the literature as well as from data collected on a coordinate measuring machine for comparison with least squares and minimum zone results. For all examples, the new formulations are found to equal or better than the least squares results and provide a good approximation to the minimum zone tolerance.     

A practical approach towards mathematical modeling of deposition rate during twin-wire submerged arc welding

The present paper deals with a shop floor applicable mathematical model for deposition rate during twin-wire submerged arc welding. The salient features of this model are (1) instead of melting rate, as modeled during past investigations, it quantifies the deposition rate, which is the actual outcome of the process and always remains smaller than the melting rate because of evaporation or spatters losses and (2) it estimates electrode extension in order to predict the deposition rate which makes the proposed model more practical than the models constituted with the help of experimental measurement of electrode extension. The model is more scientific than the simplified models where contact tube to work-piece distance has been considered as the electrode extension. A critical review of the relevant past investigation is given and a mathematical model is developed for deposition rate during the twin-wire welding with both the polarities, i.e., direct current electrode positive and direct current electrode negative. The model is calibrated using the results of 200 experimental runs and it is found to be very accurate with very high coefficient of regression and admissible standard error. The developed model is further validated with extra experimental runs. The practicality of the considered approach for prediction of deposition rate can further be used in future research for other consumable arc welding processes.     

A modeling approach for evaluating capacity flexibilities in uncertain markets

The flexibility of production capacities is a means for coping with the challenges in today’s market environment, especially when dealing with strong fluctuations in customers’ demands. The reliable planning and evaluation of these capacities and their inherent flexibilities are considered an important task for many companies. This paper presents a capacity/cost model that considers the impact of market uncertainties and the corresponding capacity flexibilities. It proposes a demand forecasting method, a modeling approach for capacity-related flexibilities and the analysis of the economical correlation between available and required capacities. Based on this, capacity planning can be optimized using this model. The different steps of applying this modeling approach are illustrated with the aid of an example.

一种面向大规模定制生产的制造费用估计方法研究

采用数据包络分析法(DEA)结合成本动因理论，根据生产过程中消耗的各种业务量估计制造费用。在估计产品制造费用中考虑了产品在投产后所在的产品生产集合，以及生产组织过程的因素对产品制造费用的影响。经过实际计算，得到了满意的结果。     

基于独立分量分析的潜艇振源贡献量定量计算方法

振动噪声控制对于潜艇具有重要意义。常用的振动噪声分析方法仅分析了噪声的来源,而未对振动噪声源对总振动噪声的贡献量进行定量计算。介绍盲源分离基本模型,以及基于独立分量分析理论和聚类评价方法提高盲分离性能的改进固定点算法,并基于该算法和先验信息理论提出一种定量计算振源贡献量的新方法。通过仿真试验分析基于两种不同分离准则算法的分离性能以及振源贡献量计算结果。将该方法应用于某型号潜艇缩比模型振源贡献量的定量计算中,对比分析表明该方法具有很高的计算精度。研究结论可为振动噪声的主动控制提供可靠的依据。     

基于体系结构的软件可靠性评估

对软件可靠性评估的重要工具之一——基于体系结构的可靠性模型进行了实验验证。为了准确地分析软件模块间的调用关系并估算模块的可靠度,首先,依据评估方式的不同将基于体系结构的软件可靠性模型划分为合成型与分级型两类;然后,对软件体系结构的确定与软件模块的划分进行了分析,并阐述了模块可靠度和模块间转移概率的估算方法与步骤;最后,对某地面目标模拟源主控系统软件进行了实例分析。结果表明,实验系统的确定可靠度值为0.938,而合成型、分级型模型估计值分别为0.972和0.969,由此验证了两种模型的可应用性,为工程应用中实施基于体系结构的软件可靠性评估提供了参考。     

基于Matlab的AR模型参数估计

基于Matlab用时间序列的最小二乘估计和FPE、AIC、BIC准则对AR(n)模型进行参数估计。用实例说明运用Matlab进行AR(n)参数估计,编程简单,分析直观     

Estimation of welded joint strength using genetic algorithm approach

The genetic algorithm approach is extended to the estimation of mechanical properties of the joining of brass materials. The mechanical properties of joint parts can be improved by selecting suitable parameters. The strength of the joint parts is affected by many factors, such as the gap between the parts, the torch angle, the quantity of the shielding gases, the pulse frequencies and the electrode tip angle during welding operations. Since all these factors affect the mechanical properties of the welded joint parts, the effects of these parameters need to be cautiously investigated. The present paper describes the use of the stochastic search process that is the basis of Genetic Algorithms (GA), in developing the strength value of the welded parts. Non-linear estimation models are developed using GAs. Developed models are validated with experimental data. The Genetic Algorithm Welding Strength Estimation Model (GAWSEM) is developed to estimate the mechanical properties of the welded joint for the brass materials. The effects of five welding design parameters on the strength value using the GAWSEM have been examined. The results indicated that the changes of the gap between the joint parts and the torch angle have an important effect on the welded joint strength value and the optimum quantity of the shielding gas and the pulse frequencies exist in the tensile strength of welded joints.     

A practical approach for simulation and manufacturing of a ball-end mill using a 5-axis CNC grinding machine

This paper presents a detailed manufacturing model that can be used for grinding a ball-end mill using 5-axis CNC (computer numerical controlled) grinding machine. The profile of the helical groove can be calculated exactly using the given wheel profile and relative movements between the workpiece and the grinding wheel. The proposed model is related to some analytical, differential geometry and kinematics to control the motions of the workpiece and grinding wheels in grinding processes. The manufacturing model presented in this paper provides a practical and efficient method for developing the simulation software for the design and the manufacture of a ball-end mill.     

空间直线度最小二乘评定结果的不确定度估计

评定模型的非线性和不可微给空间直线度最小二乘评定结果不确定度的估计带来困难,由空间直线度最小二乘评定模型出发,参照ISO国际测量不确定度表示指南,对影响不确定度估计的一些因素加以简化,推导了不确定估计公式。根据测量数据将推导公式估计结果与蒙特卡罗法运算的结果进行比较,结果表明采用本方法与蒙特卡罗方法获得的结果相符合,且本方法所用时间较少。     

Dynamic compensation of load cell response: A time-varying approach

This paper presents a new method for dynamic compensation of the load cell response using linear time-varying continuous-time filter. Load cells have an oscillatory response which always needs time to settle down. Therefore, it is justified to search a technique for an effective improvement of the sensor response. The paper describes a theoretical implementation of the proposed time-varying filter, and suggests the implementation technique with the aid of which this kind of filter can be implemented in practice. Simulation results verifying the effectiveness of the proposed filter are presented and compared to the traditional time-invariant configuration.     

A practical approach to the periodic continuation method for the simulation of high resolution TEM images of isolated crystal defects

The smallest spacing of the artificial structure necessary for a proper simulation of TEM images of isolated defects using the method of periodic continuation is studied for periodically repeated antiphase boundaries (APB) in a Au₄Mn crystal. The “net wavefield” of an APB at the exit face of the crystal is visualized by subtracting from the APB image the perfect crystal image (i.e. electron density) on both sides of the APB. It follows that, even for strongly scattering material, such as gold, the width of this “image” at the exit face does not exceed 1/100 of the foil thickness. In the electron microscope, however, the image widens further as a result of defocus, also with a proportionality factor of about 1/100. Hence it is suggested to use the smallest spacing for the dynamical diffraction calculations, which require most of the computing time, and to increase the repeat distance for the calculation of the electron microscope transfer.     

Generation of optimal control policy for flexible manufacturing cells: A Petri net approach

For flexible manufacturing cells (FMCs), the major control problem is to determine the optimal part routeing and machines dispatching policy. In this research, we present a methodology for generating optimal operating strategies for FMCs. The methodology is built on two techniques: stochastic timed Petri net (STPN) and Markov decision process (MDP). The operating strategy devised with the proposed methodology is deadlock-free and provides the best performance given a set of system parameters (machines, parts, machining times, etc.). Generation of programmable logic controller (PLC) codes is greatly facilitated as the generated strategy can be mapped directly to a ladder diagram representing the PLC code. The objective of real-time optimal control could then be achieved with this type of controller. An example is provided to illustrate the methodology.     

Estimation of the number of stellate cells in a liver with the smooth fractionator

To better evaluate the activation and proliferative response of hepatic stellate cells (HSC) in hepatic fibrosis, it is essential to have sound quantitative data in non‐pathological conditions. Our aim was to obtain the first precise and unbiased estimate of the total number of HSC in the adult rat, by combining the optical fractionator, in a smooth sampling design, with immunocytochemistry against glial fibrillary acidic protein. Moreover, we wanted to verify whether there was sufficiently relevant specimen inhomogeneity that could jeopardize the high expected estimate precision when using the smooth fractionator design for HSC. Finally, we wanted to address the question of what sampling scheme would be advisable a priori for future studies. Microscopical observations and quantitative data provided no evidence for inhomogeneity of tissue distribution of HSC. Under this scenario, we implemented a baseline sampling strategy estimating the number (N?) of HSC as 207E⁰⁶ (CV = 0.17). The coefficient of error [CE(N?)] was 0.04, as calculated by two formerly proposed approaches. The biological difference among animals contributed ? 95% to the observed variability, whereas methodological variance comprised the remaining 5%. We then carried out a half reduction of sampling effort, at the level of both sections and fields. In either occasion, the CE(N?) values were low (? 0.05) and the biological variance continued to be far more important than methodological variance. We concluded that our baseline sampling (counting 650–1000 cells/rat) would be appropriate to assess the lobular distribution and the N? of HSC. However, if the latter is the only parameter to be estimated, around half of our baseline sampling (counting 250–600 cells/rat) would still generate precise estimates [CE(N?) < 0.1], being in this case more efficient to reduce the number of sections than to reduce the sampled fields.