Designing mechanical systems for optimum diagnosability

An analysis and modeling method of the diagnostic characteristics for electro-mechanical systems is presented. Diagnosability analysis is especially relevant given the complexities and functional interdependencies of modern-day systems, since improvements in diagnosability can lead to a reduction of a system’s life-cycle costs. Failure and diagnostic analysis leads to system diagnosability modeling with the failure modes and effects analysis (FMEA) and component-indication relationship analysis. Methods are then developed for translating the diagnosability model into mathematical methods for computing metrics such as distinguishability and No Fault Found. These methods involve the use of matrices to represent the failure and replacement characteristics of the system. Diagnosability metrics are extracted by matrix multiplication. These metrics are useful when comparing the diagnosability of proposed designs or predicting the life-cycle costs of fault isolation.     

Designing piezoelectric films for micro electromechanical systems

Piezoelectric thin films are of increasing interest in low-voltage micro electromechanical systems for sensing, actuation, and energy harvesting. They also serve as model systems to study fundamental behavior in piezoelectrics. Next-generation technologies such as ultrasound pill cameras, flexible ultrasound arrays, and energy harvesting systems for unattended wireless sensors will all benefit from improvements in the piezoelectric properties of the films. This paper describes tailoring the composition, microstructure, orientation of thin films, and substrate choice to optimize the response. It is shown that increases in the grain size of lead-based perovskite films from 75 to 300 nm results in 40 and 20% increases in the permittivity and piezoelectric coefficients, respectively. This is accompanied by an increase in the nonlinearity in the response. Band excitation piezoresponse force microscopy was used to interrogate the nonlinearity locally. It was found that chemical solution-derived PbZr(0.52)Ti(0.48)O(3) thin films show clusters of larger nonlinear response embedded in a more weakly nonlinear matrix. The scale of the clusters significantly exceeds that of the grain size, suggesting that collective motion of many domain walls contributes to the observed Rayleigh behavior in these films. Finally, it is shown that it is possible to increase the energy-harvesting figure of merit through appropriate materials choice, strong imprint, and composite connectivity patterns.     

Designing performance measurement systems for just-in-time operations

Results of a study conducted to understand how performance is evaluated in just-in-time (JIT) operations are reported in this paper. The purpose of the study was to develop a series of propositions concerning the performance criteria, standards, measurement techniques, and reporting methods that are appropriate in JIT environments. Ten propositions are provided.     

Designing of epoxy resin systems for cryogenic use

The mechanical and thermal properties of several types of epoxy systems were designed based on the chemical structure, network structure and morphology aiming at cryogenic application. In this research di-epoxies or multifunctional epoxies were cured by several kinds of hardeners such as anhydride, amine or phenol and were blended with polycarbonate, carboxyl-terminated butadiene acrylonitrile copolymer or phenoxy. The mechanical properties and thermal properties of these cured epoxies were measured at room and liquid nitrogen temperature. It was found that the two-dimensional network structured linear polymer shows high performance even at cryogenic temperature. It was concluded that the controls of the structures are very important to optimize epoxy systems for cryogenic application.     

Designing transcranial magnetic stimulation systems

We explain the process of designing optimized transcranial magnetic stimulation systems and outline a method for identifying optimal system parameters such as the number of turns, the capacitor size, the working voltage, and the size of the stimulation coil. The method combines field analysis, linear and nonlinear circuit analysis, and neural strength-duration response parameters. The method uses boundary-element analysis to predict the electric field as a function of depth, frequency, current, and excitation coil size. It then uses the field analysis to determine the inductance as a function of size and, in general, current when a saturable core is used. Circuit analysis allows these electric field computations to be indexed against system parameters, and optimized for total system energy and stimulation coil size. System optimizations depend on desired stimulation depth. A distinguishing feature of the method is that it inherently treats excitation frequency as an unknown to be determined from optimization.     

Designing null detectors for analog-digital converters of scanning test systems

Conclusions A method for designing a pulsed null detector comprising an ac amplifier with forced discharging of its input and interstate capacitances was suggested.The restoration of zero by means of a pulsed feedback and the periodic zero-drift elimination reduces zero instability due to signals and stray effects down to values below the noise level of the ac input amplifier.Additional pulse correction reduces this noise level over a wider frequency range (from zero to 1/10 of the chopping frequency) than in other similar circuits.Thus, the suggested principle of forcibly discharging the capacitors serves to produce at a relatively low cost a highly-sensitive and high-speed null detector whose noise characteristics are superior to those of its constituent wide-band amplifier.Translated from Izmeritel'naya Tekhnika, No. 7, pp. 53–56, July, 1969.     

Designing and upgrading model of pre-denitrification systems

This paper reports a three-substrate steady-state integrated model, whose unknowns are expressed in explicit terms once concentrations of nitrogen compounds in the effluent flow are fixed. The model can be applied both to design and to upgrade wastewater treatment plants. The model is also able to evaluate the flexibility of existing wastewater treatment plants, which represents the capacity of the system to operate under different working conditions caused by increases in influent load or reductions in effluent quality standards. In this case the admissible variation of influent load or effluent concentration can be measured using suitable dimensionless flexibility indexes.List of symbols Q influent flow [L³ T^–1] - R₁ sludge recycle flow ratio - R₂ aerated mixed liquor recycle flow ratio - V_D denitrification reactor volume [L³] - V_N nitrification reactor volume [L³] - S biodegradable organic substrate concentration [M L^–3] - N-NH₄ ammonia nitrogen concentration [M L^–3] - N-NO₃ nitrate nitrogen concentration [M L^–3] - N_tot total nitrogen concentration [M L^–3] - O₂ oxygen concentration in the nitrification reactor [M L^–3] - X_H heterotrophic biomass concentration [M L^–3] - X_AUT autotrophic biomass concentration [M L^–3] - maximum removal rate of biodegradable organic substrate for an assigned value of temperature [T^–1] - maximum removal rate of nitrate for an assigned value of temperature [T^–1] - maximum removal rate of ammonia nitrogen for assigned values of pH and temperature [T^–1] - _S removal rate of biodegradable organic substrate [T^–1] - _D removal rate of nitrate [T^–1] - _N removal rate of ammonia nitrogen [T^–1] - K_S saturation coefficient for biodegradable organic substrate [M L^–3] - K_D saturation coefficient for nitrate [M L^–3] - K_SD saturation coefficient for organic substrate in the denitrification kinetic [M L^–3] - K_N saturation coefficient for ammonia nitrogen [M L^–3] - saturation coefficient for oxygen [M L^–3] - Y_H yield coefficient for heterotrophic microorganisms in the biodegradable organic substrate removal process - Y_D yield coefficient for heterotrophic microorganisms in the nitrate nitrogen removal process - Y_AUT yield coefficient for autotrophic microorganisms in the ammonia nitrogen removal process - (X_H)_r heterotrophic biomass concentration in the recycle sludge [M L^–3] - (X_AUT)_r autotrophic biomass concentration in the recycle sludge [M L^–3] - biodegradable organic mass consumption for unitary nitrate nitrogen mass reduction in the denitrification reactor - nitrogen consumption in the biodegradable organic oxidation process by mean of heterotrophic biomass     

Metrological tests of navigation equipment for users of space navigation systems in motion

A new method is proposed for experimental accuracy evaluation of equipment for users of space navigation systems installed on moving vehicles. Examples of GPS-receiver test are provided. Translated from Izmeritel'naya Tekhnika, No. 7, pp. 41–43, July, 2000.     

Designing integrated cellular manufacturing systems with tactical decisions

In this paper, we aim to design cellular manufacturing systems that optimize the performance of a manufacturing system subject to the optimization aspects of production planning. Consequently, the demand for each part – one of the production planning features – plays a vital role in determining the part families and the formation of machine cells in each period. In our study, holding and backorder costs follow a probabilistic structure, and they are described by a set of stochastic scenarios. In this model, five objective functions are employed: one of them minimizes the expected total holding and backorder costs in order to evaluate the risk in the model. The aim of this model is to select and optimize the assignment of parts and machines to different cells as well as the number of each produced part in each period. A new heuristic algorithm based on the optimization method is established to yield the best solution for this complicated mathematical formulation. Further, the performance of the proposed algorithm is verified using certain test problems in which the obtained results are compared with those obtained using the branch-and-bound algorithm and heuristic procedures.     

Designing cellular manufacturing systems with dynamic part populations

The effectiveness of a cellular manufacturing system is sensitive to fluctuations in the demand for products and the product mix. This paper presents a new formulation of the part family/machine cell formation problem that addresses the dynamic nature of the production environment by considering a multi-period forecast of product mix and demand during the formation of part families and machine cells. The goal of the multi-period formulation is to obtain a cellular design that continues to perform well with respect to the design objectives as the part population changes with time.     

浮筏隔振系统的一种新隔振效果建模方法

摘要：本文提出了一种浮筏隔振系统的新建模方法,这种新的方法基于阻抗理论,避开了以往阻抗矩阵在筏架处理中的困难,应用这种新建模方法简单可行,并且计算得到的隔振效果可与实验的加速度振级落差相对应,具有很强的工程实用性。本文将应用方法得到的结果与试验进行对比,取得了较好的结果。这种方法可为浮筏隔振系统的进一步研究与工程应用提供更有利的模型。为了与以往的阻抗建模方法加以区别,最后将这种方法命名为“传递系数法”。     

为设计而忙

许久了,我的博客没有更新,一直以忙为借口,无暇顾及。还好,自诩为设计而忙,这辈子无它可忙,忙些与设计相关的事,还觉得有意思。借《包装＆设计》“设计人生”栏目,谈谈近来忙些什么事？细想一下与其谈人生,不如谈谈我想做那些具体事。     

Designing multi-product lines: job routing in cellular manufacturing systems

An operation sequence-based method which integrates intra-cell layout cost with cell formation to minimize the total cost of the materials flow and machine investment is developed here for designing a cellular manufacturing system. The method comprises three distinct approaches: part-family formation, cell-formation, and layout configuration. In the first phase, an operation sequence-based similarity coefficient is applied in a p-median model to group the parts to form part families with similar operation sequences. In the second phase, machine assignment to part families is determined where a trade-off between potential inter-cell movement cost due to the. bottleneck machine and the potential benefit of assigning bottleneck machines to certain part-family is considered. In the third phase, intra-cell layout is determined for each cell so as to refine the initial layout of the cell further. Numerical examples are employed to demonstrate the mechanism of the procedure throughout all phases. A comparative study is also performed to support the present method     

A new rescheduling method for computer based scheduling systems

Providing a powerful interactive tool for the scheduler to quickly and easily react to the inevitable rescheduling changes is mandatory in today's complex and flexible manufacturing environment. The conventional approaches either employ the regeneration method, which results in unsatisfactory response times, or use. methods that require too much manual intervention for editing operations to be changed. A new rescheduling method is proposed in this paper which addresses these problems. The fundamental scheme of this rescheduling method is based on a scheduling graph as well as concepts of time effect and relationship effect. The scheduling graph is an alternative representation structure of a schedule Gantt chart. The time effect and relationship effect provide functions of (1) identifying those operations that require revision, (2) revising those identified affected operations (via a partial change of the scheduling graph structure) and (3) updating starting and ending times of those revised operations. The rescheduling method both reduces manual intervention of rescheduling to a minimum and permits net change (opposite to regeneration) rescheduling to be achievable. This rescheduling method can be embedded in current computer assistance scheduling systems so as to enhance their effectiveness.