Selection of a pull production control system in multi-stage production processes

In this paper, we conduct an analytical comparison of three pull production control systems: Kanban, CONWIP and Base-stock in multi-stage production processes. First, we compare the three control systems in a multi-stage serial production process. Then, we compare them in multi-stage assembly production processes, and present guidelines that allow us to select the best system. As a result, we show which structural parameters decide the superiority of one control scheme to the others, and how they are related. A key for superiority is a configuration of parameters, such as processing times and number of cards employed in the system. We show that there is no general superiority amongst the analysed concepts. Finally, we verify the effect of variability on the system performance, and generalise the analytical results of deterministic cases by conducting numerical experiments.     

钢铁材料及有色合金构件的多段半固态成形工艺研究

目的为了有效抑制半固态成形过程中的液相偏析,改善半固态成形构件微观组织和力学性能的均匀性。方法提出了包括多段流变成形和多段触变成形在内的多段半固态成形工艺。多段半固态成形工艺均由半固态坯/浆料制备、预成形、控温冷却和终成形4个阶段组成,分别在热模拟试验机和机械伺服压机上开展了SKD11工具钢和6061铝合金的半固态触变成形和半固态流变成形试验。结果在初成形阶段,具有较高液相分数的半固态坯/浆料以较高的应变速率初步充填型腔,限制了液相外流的时间和空间;在控温冷却阶段,半固态坯/浆料的液相分数因部分凝固而降低;在终成形阶段,具有较低液相分数的半固态坯/浆料以较低的应变速率完成型腔的充填,由于固相晶粒在此阶段发生塑性变形而提高了成形构件的力学性能。结论获得了组织均匀性较好的钢铁材料和有色合金构件,验证了多段半固态成形工艺的可行性。     

Design of the multi-stage quenching process for 7050 aluminum alloy

In order to attain good hardenability in the single-stage quenching process of Al–Zn–Mg–Cu alloys, rapid cooling rate is often desirable. But this would inevitably increase the residual stress. Therefore, the aim of this study is to achieve coupling control of the cooling rate and the residual stress by using the multi-stage quenching process. First, a series of single-stage quenching tests were conducted based on the end quenching equipment. Then in the double-stage quenching tests, a higher cooling rate was obtained comparing to the single-stage quenching. Based on this discovery, three kinds of multi-stage quenching processes were designed based on the experimental results of the single-stage quenching tests. The mechanism of the multi-stage quenching has been analyzed by comparing the cooling curves, the microstructure, the hardening depth, and the maximum residual stress. Furthermore the optimal multi-stage quenching process for 7050 aluminum alloy plate was obtained.     

Fatigue damage accumulation: Aspects of environmental interaction

The corrosion fatigue lifetime of materials can be predicted by simulating the multi-stage damage process with regard for the action of both corrosion and mechanical factors. This action can be represented in the form of damage accumulation maps, where the processes of pitting, pit-crack transition, and cracking are identified. For the construction of the models, we develop localized electrochemical methods used to determine the critical parameters of the processes, including the pit growth rate and the critical pit current density for the pit-crack transition. Published in Fizyko-Khimichna Mekhanika Materialiv, Vol. 42, No. 1, pp. 45–55, January–February, 2006.     

Near-net shaping — The key to new materials exploitation

Material wastage by normal machining can be extremely high. Near-Net shaping is a desirable alternative whereby final component shape is achieved through processes which manipulate material without significant loss or wastage. Whether for metals or modern new materials, real opportunitiesfor more effective use of material, elimination of waste, efficient use of energy and avoidance of multi-stage finishing operations are available. They can be exploited effectively for cost effective production using Near-Net Shaping techniques. The key options relevant to the high technology world of today are outlined and pointers provided for the future.     

Simultaneous Lot Sizing and Sequencing for Multistage Production Systems

Inventory and scheduling theory have, in general, been developed independently. This paper presents a model which integrates these two traditionally different aspects of production planning in a multi-stage environment by transforming a lot-sizing problem to an equivalent job-shop scheduling program. The proposed model may improve the effectiveness of existing decision making processes.     

How to simulate normal data sets with the desired correlation structure

The Cholesky decomposition is a widely used method to draw samples from multivariate normal distribution with non-singular covariance matrices. In this work we introduce a simple method by using singular value decomposition (SVD) to simulate multivariate normal data even if the covariance matrix is singular, which is often the case in chemometric problems. The covariance matrix can be specified by the user or can be generated by specifying a subset of the eigenvalues. The latter can be an advantage for simulating data sets with a particular latent structure. This can be useful for testing the performance of chemometric methods with data sets matching the theoretical conditions for their applicability; checking their robustness when the hypothesized properties fail; or generating data from multi-stage or multi-phase processes.     

Integrated production,distribution and scheduling in the aluminium industry: a continuous-time MILP model and decomposition method

This article deals with the multi-stage production–shipping and distribution–scheduling problem in the aluminium industry. Related processes take place in worldwide operating networks with multiple sites in each stage. The aim is to coordinate production activities and material flows worldwide months in advance and exactly to the day, so that temporary storage of intermediate products is reduced network wide or even set to zero. This paper includes a further development of the multi-stage production-shipping and distribution-scheduling problem including in-time supplies of all production sites (MSPSDS-IS). However, the in-time supplies at the sites often result in network-wide temporary storage before and/or after site production. In contrast, it should be possible that either stock-free material flows within the entire network or site-specific storage times are prescribed. The previous modelling is not able to meet these aforementioned requirements as it can be considered as special case of the generalised approach developed in the following. Therefore, a substantially extended continuous-time MILP model is presented. Furthermore, extensive computational experiments with a high-performance computer indicate that a modified version of the relax-and-fix heuristic, which was applicable to the MSPSDS-IS, also results in high-quality solutions and remarkable reductions in computation times.     

Incremental finite element analysis of geometrically altered structures

A conceptually simple, general method is described for the finite element simulation of multi-stage construction and excavation processes, including recognition of nonlinear material behaviour. Anomalous results reported in the literature for simulation of excavation of elastic media are examined, and shown to result from the inconsistent determination of nodal excavation forces from element boundary stresses.     

Kostenkontrolle bei mehrstufigen Produktionsprozessen

Zusammenfassung Die aus der Literatur bekannten Kostenkontrollansätze beschränken sich grundsätzlich auf einstufige Produktionsprozesse. In mehrstufigen Produktionsprozessen tritt das Problem der induzierten Kostenabweichungen auf. Bei Anwendung des Gesamtkosten- oder Endkostenansatzes zur Kostenerfassung einer Stelle werden bei mehrstufigen Prozessen Kostenabweichungen ausgewiesen, die von vorgelagerten oder nachgelagerten Stellen verursacht worden sind und damit induzierte Abweichungen darstellen. Zur stellenspezifischen Zuordnung dieser Kostenabweichungen wird daher ein neuer Kontrollansatz konzipiert, der unabhängig vom gewählten Gesamtkosten- oder Endkostenansatz eingesetzt werden kann. Dieser Kostenkontrollansatz ist analog zum Kontrollansatz einstufiger Produktionsprozesse aufgebaut und allgemein für jeden beliebigen Typ mehrstufiger Prozesse einsatzfähig.

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Summary Cost control approaches as known in literature are basically restricted to single-stage production processes. In multi-stage production processes the so calledinduced cost variances pose the problem, i.e. applying the two basic cost control approaches which show either the total or the terminal costs of a cost centre it frequently occurs that cost variances are shown in a cost centre, although they were caused and hence induced by preceeding or succeeding cost centres. A new cost control approach is developed which allows identification and assignment of induced cost variances to the responsible cost centres; this general cost control approach can be applied independent of the specific approach chosen, showing either the total costs or the terminal costs. It is built up by analogy to the cost control approach for a single-stage production process, but it also applies to any kind of multi-stage production process.

     

基于缩短供应链多阶响应周期的节点间信息处理研究

从处理供应链节点间信息的角度，提出了解决缩短供应链多阶响应周期，降低总周期成本的一种有效方法，并对执行供应链节点间信息处理的方法和步骤进行了研究；最后通过节点企业与其供应商之间的信息分析和处理的原模型及改进模型来说明运用这种方法能解决的问题和可能取得的效果。     

Desalination by distillation and by reverse osmosis — trends towards the future

As the requirement for fresh water increases worldwide, there is a need for more and more plants that are able to treat non-conventional water sources. Sea water has become an important source of fresh water in many arid regions. This feature provides an overview of recent process improvements in sea water desalination using reverse osmosis, multi-stage flash, multi-effect distillation and electrodialysis. Areas discussed include the use of alternative energy sources (wind energy, solar energy and nuclear energy) for reverse osmosis or distillation processes, and the impact of the different desalination process on the environment. Also covered are the implementation of hybrid processes in sea water desalination, and the pretreatment of desalination plants by pressure-driven membrane processes.     

环路声学共振多级行波热声发动机的机理研究

针对环路声学共振多级行波热声发动机的工作机理进行了研究,重点分析了环路声学共振4级行波热声发动机无负载工作情况,并比较了环路声学共振4级、8级、16级行波热声发动机的工作性能。计算结果表明,这一行波热声发动机具有较好的声场分布并通过增大回热器横截面积有效降低了回热器内的粘性流动损失。增加环路声学共振多级行波热声发动机的级数仍能获得较为理想的工作性能,并能够增加整机产生净声功率,降低谐振管消耗声功率的比例,相对传统带驻波谐振管的行波热声发动机更为紧凑。     

Optimal process targeting for multi-inputs,multi-stages and multi-characteristics production systems

In this paper, a process targeting model is developed for multi-stages, multi-inputs and multi-characteristics production systems. The model extends a previous single stage, multi-inputs and multi-characteristics production system to an n-stage flow line. Recursion and augmented matrix approaches were used to formulate the n-stage model. The optimal process targeting solution is based on minimising a Taguchi-type quadratic loss function across all production stages. A constrained version of the problem is considered in order to cover a wider class of real life industrial applications. The model is very useful especially for mixing-based processes, batch processes, and other multi-stage and multi-characteristic production processes. Finally, an illustrative example is provided.     

Economic acceptance sampling plans in complex multi-stage production systems

Specification of economic acceptance sampling schemes in complex multi-stage production systems is considered. The analysis is based on approximations of the distribution of lot fractions defective at all production stations of the system. A heuristic algorithm is developed that combines individual optimal solutions to subproblems corresponding to the production stations, to arrive at a near-optimal solution for the original problem. Numerical examples illustrate the application of the method to serial and non-serial manufacturing-assembly processes.     

基于微分求积法及V-变换的大规模动力系统快速数值计算方法

针对大规模动力系统动态响应的数值计算,传统的微分求积法通常在时间域上逐步离散、整体求解,存在“维数灾”问题。在多级高阶时域微分求积法的基础上,提出了基于V-变换的大规模动力系统动态响应的快速数值计算方法。利用微分求积法的加权系数矩阵满足V-变换这一重要特性,将离散后的雅可比矩阵方程进行解耦分块,推导形成了多级分块递推计算方法。数值算例表明,即使采用相当于Newmark方法2s倍的步长,微分求积法的计算精度仍比Newmark方法要高出2~3个数量级。进一步对3个不同规模的算例系统进行了测试,结果表明：相对于传统的数值计算方法,多级分块递推计算方法可以获得较大的加速比,能够显著提高大规模动力系统动态响应的计算效率。     

Channel coordination for multi-stage supply chains with revenue-sharing contracts under budget constraints

Real-life situations show that revenue-sharing (RS) contracts used in multi-stage supply chains have more complex structures than those that have been studied in recent research. In this paper, we study RS contracts in multi-stage supply chains where some members work with more than one upstream member. This general supply chain structure closely resembles those in actual practice under RS contracts. The literature on supply chain contracts has not adequately addressed contract design for supply chains with members who face budget constraints. We show that the RS contract could fail to coordinate supply chains when members are under particular budget constraints. In response, we propose a revenue-sharing with budget constraints (RSB) contract that adds no administrative cost. A properly designed RSB contract can be used to achieve supply chain coordination and to arbitrarily allocate profits in multi-stage supply chains. Our numerical results provide insights into ways supply chain coordination can be achieved under budget constraints through the RSB contract.     

Antireflection coatings on plastics deposited by plasma polymerization process

Antireflection coatings (ARCs) are deposited on the surfaces of optical elements like spectacle lenses to increase light transmission and improve their performance. In the ophthalmic industry, plastic lenses are rapidly displacing glass lenses due to several advantageous features. However, the deposition of ARCs on plastic lenses is a challenging task, because the plastic surface needs treatment for adhesion improvement and surface hardening before depositing the ARC. This surface treatment is usually done in a multi-stage process—exposure to energetic radiations, followed by deposition of a carbonyl hard coating by spin or dip coating processes, UV curing, etc. However, this treatment can also be done by plasma processes. Moreover, the plasma polymerization process allows deposition of optical films at room temperature, essential for plastics. The energetic ions in plasma processes provide similar effects as in ion assisted physical deposition processes to produce hard coatings, without requiring sophisticated ion sources. The plasma polymerization process is more economical than ion-assisted physical vapour deposition processes as regards equipment and source materials and is more cost-effective, enabling the surface treatment and deposition of the ARC in the same deposition system in a single run by varying the system parameters at each step. Since published results of the plasma polymerization processes developed abroad are rather sketchy and the techniques are mostly veiled in commercial secrecy, innovative and indigenous plasma-based techniques have been developed in this work for depositing the complete ARCs on plastic substrates.     

Anwendung des FWK-Konzepts für die Berechnung der Lebensdauer bei mehrstufiger Kriechbelastung

The application of the Consecutive-Wöhler-Curve-Concept in Computation of the life values for multi-stage creep It is known that at multi-stage creep load there cannot be calculated any reliable life values by means of linear damage accumulation hypotheses. A practicable non-linear statement was proposed by Pantelakis. Besides the one-stage creep life curve, results from two-stage tests are required for determining the damage exponent, With this exponent, which is a function of temperature and stress in the load stage applied first, the life values can be calculated only for two-stage sequences whose stress stages have to be identical to those of the two-stage tests. For the application of the consecutive Wöhler curve concept described in the following there is required the knowledge of the one-stage creep life curve and of the creep function for increasing and decreasing stress sequences derived from two-stage tests. Then, the life values can be calculated for the most different multi-stage loads. The stages should lie within the stress range used in the two-stage tests.     

Localised and delocalised optically induced conversion of composite glow peak 5 in LiF:Mg,Ti (TLD-100) to glow peak 4 as a function of postirradiation annealing temperature

The composite structure of glow peak 5 in LiF:Mg,Ti (TLD-100) has been investigated using optical bleaching by 310 nm (4 eV) light. The glow peak conversion efficiency of peak 5a (Tm = 187 degrees C) to peak 4 traps is very high at a value of 3+/-0.5 (1 SD) whereas the glow peak conversion efficiency of peak 5 (Tm = 205 degrees C) to peak 4 traps is 0.0026+/-0.0012 (1 SD). The high conversion efficiency of peak 5a to peak 4 arises from direct optical ionisation of the electron in the electron-hole pair. leaving behind a singly-trapped hole (peak 4), a direct mechanism, relatively free of competitive mechanisms. Optical ionisation of the 'singly-trapped' electron (peak 5), however, can lead to peak 4 only via multi-stage mechanisms involving charge carrier transport in the valence and conduction bands, a mechanism subject to competitive processes. The conduction/valence band competitive processes lead to the factor of one thousand decrease in the conversion efficiency of peak 5 compared to peak 5a.