Optimal cost design of flow lines with reconfigurable machines for batch production

Modular reconfigurable machines offer the possibility to efficiently produce a family of different parts. This paper formalises a cost optimisation problem for flow lines equipped with reconfigurable machines which carry turrets, machining modules and single spindles. The proposed models take into account constraints related to: (i) design of machining modules, turrets, and machines, (ii) part locations, and (iii) precedence relations among operations. The goal is to minimise equipment cost while reaching a given output and satisfying all the constraints. A mixed integer programming model is developed for the considered optimisation problem. The approach is validated through an industrial case study and extensive numerical experiments.     

V-band variable gain amplifier applying efficient design methodology with scalable transmission lines

In this study, a 60 GHz variable gain low noise amplifier with more than 20 dB gain is presented. An efficient design methodology employing scalable transmission lines is applied, which can avoid iterative EM simulations and predict the circuit behaviour very accurately. Different transmission line modelling approaches are compared to each other, and a simple yet flexible model is eventually chosen. The circuit has been fabricated and measured on-wafer. The power consumption of only 7.3 mW is, to the knowledge of the authors, the lowest value reported for a V-band amplifier.     

Defected ground and patch-loaded planar transmission lines

Two new structures, defected slotline and patch-loaded coplanar waveguide (CPW), are introduced and quasi-static geometrical models for them and for the defected ground structures in microstrip and in CPW configurations are developed, combining those structures with the patch-loaded slotline and the stepped impedance resonators (SIRs) in a microstrip; and thus, a unified approach for the realisation of series and parallel stubs in different planar transmission line configurations is presented. Complementarity between the different structures has been investigated. It has been found that an identical dumbbell-shaped defect and a SIR in a microstrip are complementary to each other. Consequently, a new technique is developed to compensate for the effect of a defect in the ground of a microstrip. All theoretical predictions have been confirmed with both EM simulations and measurements.     

基于动张力均方根反应谱的大跨越输电线路设计风荷载

作为一种典型的风致敏感结构,大跨越输电线路在强风作用下产生的随机振动张力,往往是线路结构设计中的控制荷载。本文基于导线的连续悬索动力方程和变形几何条件,建立了风振动态张力的广义自由度计算理论模型。依据随机振动理论,获得了动张力响应的功率谱。引入常用的工程设计参数为变量,推导了动张力的均方根反应谱表达式。将其整理和简化,给出了实用设计风荷载的计算公式。以某大跨越输电线路为背景,比较了公式与我国规范、国际电气协会规范取值。结果表明建议公式考虑因素全面,力学意义清晰,结果更为安全合理,可作为规范修订的参考。     

dc SQUID: Noise and optimization

A computer model is described for the dc SQUID in which the two Josephson junctions are nonhysteretic, resistively shunted tunnel junctions. In the absence of noise, current-voltage(I–V) characteristics are obtained as functions of the applied flux, _a , SQUID inductanceL, junction critical currentI ₀ , and shunt resistanceR. The effects of asymmetry inL, I ₀ , andR are discussed.I–V characteristics, flux-voltage transfer functions, and low-frequency spectral densities of the voltage noise are obtained at experimentally interesting values of the parameters in the presence of Johnson noise in the resistive shunts. The transfer functions and voltage spectral densities are used to calculate the flux and energy resolution of the SQUID operated as an open-loop, small-signal amplifier. The resolution of the SQUID with ac flux modulation is discussed. The flux resolution calculated for the SQUID of Clarke, Goubau, and Ketchen is1.6 × 10 ^–5 ₀ Hz^–1/2 , approximately one-half the experimental value. Optimization of the SQUID resolution is discussed: It is shown that the optimum operating condition is =2LI ₀ / ₀ 1. Finally, some speculations are made on the ultimate performance of the tunnel junction dc SQUID. When the dominant noise source is Johnson noise in the resistive shunts, the energy resolution per Hz is4k _B T(LC) ^1/2 , whereC is the junction capacitance, and the constraintR=( ₀ /2CI ₀ ) ^1/2 has been imposed. This result implies that the energy resolution is proportional to (junction area) ^1/2 . In the limiteI ₀ R k _B T, the dominant noise source is shot noise in the junctions; for =1, the energy resolution per Hz is then approximatelyh/2.Work supported by the U.S. ERDA.     

Ferranti and Merz: power transmission system design engineers

Ferranti and Merz were the architects of power transmission system design in Britain. Ferranti's design concept broke through the parochial model of electricity supply inherent in the Electricity Lighting Acts of 1882 and 1888. Although the concept of a remote high-power central station with high-voltage transmission and large-area distribution was not realised by Ferranti in 1889, it was realised by the power companies. Merz was foremost in using the Ferranti design concept in 1901 for the Newcastle, later the North East, Electric Supply Company (NESCo.). Later Merz introduced a new radical concept by the interconnection of a number of power stations. He did this first for NESCo. And in 1916 he proposed this as a model to be adopted for British electrification. Merz was unique in first solving the technical problems of power station interconnection and then realising that such a transmission system best suited an electricity supply for the industrial areas of Britain     

Left-handed transmission lines at millimetre and sub-millimetre wavelengths

Co-planar strip (CPS) transmission lines, aimed at operating up to sub-millimetre wavelengths, were periodically loaded by lumped capacitances and inductances in series and shunt configuration, respectively. Under this condition, propagation on the line is backward with group and phase velocities of opposite signs. The transmission lines were fabricated onto a quartz substrate by e-beam patterning and thin film deposition, silicon nitride and gold layers, on a deep sub-micron scale (~200 nm). A direct evidence of left-handedness between 160 and 380 GHz was achieved via the tracking of phase advance in a differential phase experiment using electro-optic sampling. The comparison between modelling results by electromagnetic full wave circuit analysis and experiment was performed in the time and frequency domains. It shows a good agreement in the dispersion characteristics and ultra-fast variations in the transmitted signals. At last, we took benefit of a lumped element fitting approach in order to discuss of the frequency capability of this non-resonant approach     

Minimum cost and weight design of fuselage frames: Part B: cost considerations,optimization, and results

An approach is presented to design fuselage frames for minimum weight, minimum cost, or a combination of the two. The approach combines structural requirements and manufacturing constraints into an optimization scheme that alters the geometry of the individual frame components until the objective function is minimized. In addition to the lowest weight and cost points, a near-optimal Pareto set of designs is found, out of which the design that minimizes both cost and weight is determined through a penalty function approach. Four different fabrication processes are considered: conventional sheet metal, high speed machined metal, hand laid-up composite, and resin transfer molded composite. For lightly loaded frames, an automated resin transfer molding process gives the lowest cost and weight designs. For highly loaded frames, high speed machining gives the lowest cost design but automated resin transfer molding gives the lowest weight design. The effects of fabrication process and some of the design and manufacturing constraints on cost and weight are examined.     

A comparative study of CrNx coatings Synthesized by dc and pulsed dc magnetron sputtering

Chromium nitride (CrN_x) coatings were prepared by reactively sputtering chromium metal target with various nitrogen flow rate percentages (f_N2) using a closed field unbalanced magnetron sputtering system operated in dc and middle frequency pulsed condition (100 kHz and 50% duty cycle). In this study, plasma examination proved that a large amount of ions with a wide range of ion energies (up to 65 eV and mainly from 10-30 eV region) was identified in the pulsed plasma compared to the low ion flux and energy (0-10 eV) in a dc discharged plasma. The results showed that the phase structure of CrN_x coatings was changed from nitrogen doped Cr(N) to pure β-Cr₂N, and to a mixture of β-Cr₂N and c-CrN and then to pure c-CrN phases with an increase in the f_N2 in both dc and pulsed conditions. However, the pulsed CrN_x coatings exhibit lower N concentrations than dc CrN_x coatings prepared under the same f_N2, which leads to the existing of β-Cr₂N phase within a wide range of f_N2 (30-50%). In comparison with the typical large columnar structure in the dc sputtered coatings, the pulsed CrN_x coatings exhibit dramatic microstructure improvements which benefited from the improved plasma density and ion bombardment from the pulsed plasma, where the super dense and nearly equi-axial structures were observed in a wide range of f_N2. The microstructure improvements contributed to the enhancements in the hardness and wear resistance of pulsed CrN_x coatings. In the pulsed CrN_x coatings, the hardness values were above 30 GPa when the f_N2 is in the range of 30-40%, which is related to the formation of the β-Cr₂N phase. With the formation of a mixture of β-Cr₂N and c-CrN phases in the coatings deposited with 40-50% f_N2, a low COF of 0.36 and wear rate of 1.66 × 10^− 6 mm³ N^− 1 m^− 1 can be achieved.     

Measurements and calculation for magnetically coated strip transmission lines

Measurement of the transmission parameters of magnetically coated strip conductors over a ground plane show that the series componentsRandLvary rapidly with frequency. If these components are resolved into an alternative configuration consisting of a parallel and series arrangement, this frequency variation is almost entirely absent. Calculation of the pulse transmission properties is then made much simpler. Comparison between calculated and measured waveforms is illustrated. The alternative circuit also suggests a line termination consisting of a resistance and capacitance which, both calculation and observation confirm, leads to good rise-time and pulse amplitude maintenance.     

CONWIP-based production lines with multiple bottlenecks: performance and design implications

This research focuses on CONWIP, a closed production control system where all containers traverse a circuit incorporating the entire production line. We develop estimates, for an important level of work in process inventory, for four important performance measures: the means and variances of time between departures and flowtime. We develop our estimates through the concept of a “conceptual bottleneck machine”. This concept enables us to develop an analogy between deterministic and stochastic systems. This concept also allows us to handle migrating bottlenecks, an issue generally neglected. The model is widely applicable, assuming only finite means and variances of the processing time distributions. We test our model computationally, both against existing models and on a wide range of randomly generated problems. Finally we detail insights, obtained from our analytical model, into how CONWIP production systems operate. These insights enable us to explain the sources of the values of our performance measures, thus aiding system design and modification.     

Supply chain design and cost analysis through simulation

This paper is grounded on a discrete-event simulation model, reproducing a fast moving consumer goods (FMCG) supply chain, and aims at quantitatively assessing the effects of different supply configurations on the resulting total supply chain costs and bullwhip effect. Specifically, 30 supply chain configurations are examined, stemming from the combination of several supply chain design parameters, namely number of echelons (from 3 to 5), re-order and inventory management policies (EOQ vs. EOI), demand information sharing (absence vs. presence of information sharing mechanisms), demand value (absence vs. presence of demand ‘peak’), responsiveness of supply chain players. For each configuration, the total logistics costs and the resulting demand variance amplification are computed. A subsequent statistical analysis is performed on 20 representative supply chain configurations, with the aim to identify significant single and combined effects of the above parameters on the results observed. From effects analysis, bullwhip effect and costs outcomes, 11 key results are derived, which provide useful insights and suggestions to optimise supply chain design.     

Bloch wave approach to the design of optimally matched non-effective medium composite right/left handed transmission lines

A simple method to design optimally matched composite right-/left-handed transmission lines (CRLH-TLs), based on the computation of the Bloch wave equivalent impedance of the corresponding unit cell circuit is presented. Although the matching of CRLH-TLs that can be considered as effective media is straightforward, it is shown that it is not the case for non-effective medium structures, which are also relevant realisations of this type of metamaterial in particular situations. Since the method does not rely on any assumptions on the parameters of the circuit, it is valid both for effective medium and non-effective medium CRLH-TLs. The reduction of the mismatch obtained with the proposed method also results in an improvement in the insertion loss and phase shift linearity in terms of S-parameters. Finally, we present some experimental validation of the benefits of the method by means of quartz-integrated CRLH-TLs realisations     

地下汽车库设备管线综合布置设计实例浅谈

受地下车库排风、人防、建造成本等因素的影响,各专业设备管线综合布置问题在地下车库设计中越来越突出。以某实际工程地下车库设计为例,对各专业管线综合布置设计的原则、布置方案和排布的方法和相应技术措施进行分析,结果表明当设计者遵循合理的布置原则和步骤进行管道综合设计时,不仅能提高计效率,满足指导施工安装的要求,还可以改善建筑使用效果并降低建造成本。     

Foamy-dielectric lens transmission lines for millimeter and submillimeter wavelength range

The principles of the construction of transmission lines based on lenses made of a material with a nearly unity refractive index (foamy-dielectric lens transmission line, FDLTL) are formulated. The transmission characteristics of two FDLTL variants for 3-mm wavelength band have been studied. It is shown that FDLTLs possess low damping and feature wave propagation in a single-mode regime.     

Applying a risk assessment approach for cost analysis and decision-making: a case study for a basic design engineering project

Abstract

Many uncertainties and cost variations occur in the work activities of a project, thereby causing many possibilities of under-estimating or over-estimating for a bid price. A comprehensive study for each process of risk management should be investigated to achieve project objectives. However, a limited number of studies have a comprehensive viewpoint to indicate the benefits of risk management and the effect on project performance for the engineering design stage of engineering–procurement–construction (EPC) projects, especially in the basic design stage. This research was conducted to identify and analyze the risks associated with a Basic Design Engineering (BDE) project for a high value-added petrochemical plant in Taiwan. First, a project risk management work flow was proposed as an effective tool to minimize the project risks and maximize the management capacity of practitioners. Second, the cost effect of project risks was described by conducting a case study for the design process of a high value-added petrochemical plant using a Monte Carlo simulation. A risk register was identified to support the data required for conducting simulation analysis. The results of this paper provide reference points for risk management planning of project execution and help project managers evaluate particular risks at the engineering design stage of EPC projects to avoid cost overruns.     

Wave-front propagation: design code for synchrotron radiation beam lines

Third-generation synchrotron radiation light sources provide partially coherent radiation. Certain topics in the optical design of beam lines and monochromators can be studied with electric-field distributions only rather than with intensity distributions of the light source. The radiation characteristics of a dipole or an undulator can be represented by a two-dimensional complex-electric-field distribution at a distance of several meters from the insertion device center. A method is described that transforms this field distribution through a complete beam line (consisting of mirrors and gratings) to the sample plane. Diffraction at apertures can be modeled and Stokes parameters can be evaluated. The derivation of the equations was performed with the algebraic code REDUCE. A comparison with the brightness formalism is provided.