Queueing network analysis on dynamic lot streaming

Lot streaming is a technique used to split a production lot into several smaller transfer batches. In this way, processing a product in a multistage serial production system by overlapping production between stages is available. As a result, production can be accelerated. In this paper, a modified N-policyM/G/1$N\text{-}\mathrm{policy}M/G/1$ queueing system with a non-reliable server is proposed. With the relevant parameters of this queueing system, the problem of lot streaming in dynamic situations can be solved. To obtain the optimal transfer batch size, a cost objective function including transport cost, repair cost, turning cost, and holding cost is formulated. Further, in order to illustrate the usefulness of the proposed methods, numerical examples are solved. On the basis of the results of these examples, some important conclusions are drawn.     

Lot sizing and furnace scheduling in small foundries

A lot sizing and scheduling problem prevalent in small market-driven foundries is studied. There are two related decision levels: (1) the furnace scheduling of metal alloy production, and (2) moulding machine planning which specifies the type and size of production lots. A mixed integer programming (MIP) formulation of the problem is proposed, but is impractical to solve in reasonable computing time for non-small instances. As a result, a faster relax-and-fix (RF) approach is developed that can also be used on a rolling horizon basis where only immediate-term schedules are implemented. As well as a MIP method to solve the basic RF approach, three variants of a local search method are also developed and tested using instances based on the literature. Finally, foundry-based tests with a real-order book resulted in a very substantial reduction of delivery delays and finished inventory, better use of capacity, and much faster schedule definition compared to the foundry's own practice.     

Performance analysis in a probabilistic re-entrant for an environmental stress testing operation

This paper presents an extended approximation model based on mean value analysis (MVA) technique for a probabilistic re-entrant line. The objective is to develop a solution method to determine the total cycle time and mean throughput of the environmental stress testing (EST) operation for a given number of lots loaded into the system. Further work was done to determine the maximum number of lots that can be loaded into the system and the target cycle time. This paper also looks at alternative ways to assign human resources within the operation in the event of large number of lots required. Using analytical and simulation methods, comparison results were made for a five-stage queuing system with re-entrant lines into the second stage under various probabilistic routing conditions. The method proposed can be used by operation managers to determine their lots’ cycle times, maximum number of lots and the operator assignments.     

室内效果图设计过程中的颜色配置问题

本文基于《3dMAX室内设计课程》所延伸出的室内色彩搭配艺术为目的,阐述了色彩在室内设计中起着改变或者创造某种格调的作用,会给人带来某种视觉上的差异和艺术上的享受。从而得出色彩是室内装饰设计不能忽视的重要因素,另外还阐述了色彩在实际运用上要注意的一些搭配问题。     

Preparation of Biopolyol from Empty Fruit Bunch Saccharification Residue Using Glycerol and PEG#300-Mediated Liquefaction for Application to Bio-Polyester and Bio-Polyurethane Production

Utilization of empty fruit bunch (EFB), a by-product of the palm oil production, needs to be developed because of the expanding palm oil production scale. EFB saccharification residue was obtained as a by-product of the enzymatic preparation of sugar from EFB. The liquefaction of EFB saccharification residue was performed using a mixture of polyethylene glycol (PEG) #300 and glycerol as a solvent and sulfuric acid as a catalyst. The liquefaction conditions such as liquefaction solvent ratio, liquefaction temperature, catalyst loading, and liquefaction time were optimized, and up to 90% of biomass conversion of the EFB saccharification residue was obtained. The biopolyol with approximately 890 mg KOH/g hydroxyl number was used for the synthesis of bio-polyurethane and bio-polyester, and the polymerized products were confirmed using Fourier Transform Infrared spectroscopy analysis. Basic thermal characteristics such as glass transition temperature and thermal decomposition temperature were determined to be 93.6 and 200°C using thermogravimetric analysis and differential scanning calorimetry, respectively.     

Architecture + Textiles = Architextiles

A hybrid term, ‘architextiles’ encompasses a wide range of projects and ways of thinking that unite architecture and textiles. By way of introduction to this issue, guest-editor Mark Garcia highlights the significant rise of interest in this confluence by theorists, architects, engineers, textile designers, materials scientists and artists. He also explains how, as a hybrid mode of design and practice, architextiles is better able to respond to society's fast-changing cultural and consumer demands, enabling the production of more dynamic, flexible, interactive, event and process-based spaces. Copyright © 2006 John Wiley & Sons, Ltd.     

A new approach to solve the multi-product multi-period inventory lot sizing with supplier selection problem

This research work deals with the multi-product multi-period inventory lot sizing with supplier selection problem. Formerly, this kind of problem was formulated and solved using an exhaustive enumeration algorithm and a heuristic algorithm. In this paper, a new algorithm based on a reduce and optimize approach and a new valid inequality is proposed to solve the multi-product multi-period inventory lot sizing with supplier selection problem. Numerical experiments ratify the success of the proposed heuristic algorithm. For the set of 150 benchmark instances, including 75 small-sized instances, 30 medium-sized instances, and 45 large-sized instances, the algorithm always obtained better solutions compared with those previously published. Furthermore, according to the computational results, the developed heuristic algorithm outperforms the CPLEX MIP solver in both solution quality and computational time.     

激光切割钢板Z轴全程随动路径研究

采用SLCM-1225数控激光切割机切割碳钢板,在保证切割质量的前提下,对切割路径进行了研究。通过分析激光切割碳钢板的特点,提出切割行程中的空程应包括处在数控状态下的Z轴行程,因此,XY平面内的最短行程可能不是切割效率最高的行程。为此,提出了一种Z轴全程随动的切割方法,并通过对同一切割图形的几种不同切割路径、切入点以及空程轨迹的分析比较,给出了可采用Z轴全程随动进行切割的空程路径所必须满足的条件,同时也为Z轴全程随动切割法的切割路径设计提供了一种可行的设计思路。试验结果表明,在切割质量不低于传统切割路径设计方案的基础上,Z轴全程随动切割法能使工作效率平均提高60%以上。在工业生产中,Z轴全程随动切割方法具备可操作性和推广价值。     

Town planning and radicalism in the progressive era: the legacy of F. L. Ackerman

Frederick L. Ackerman, the well-known American architect and town planner, was a pivotal figure in the progressive movement for housing and planning reform during the first half of the last century. Active at many levels of this movement, he worked with many of its major figures. This paper provides an overview of Ackerman's rich legacy of town planning and urban design, but deals most directly with Ackerman's radical political views. In particular, ittraces the formative influences on his views and analyses how these views influenced his career. It makes the case that Ackerman stood in sharp contrast to the leading lights of modern American planning who supported the capitalist system.     

A priori reformulations for joint rolling-horizon scheduling of materials processing and lot-sizing problem

In many production processes, a key material is prepared and then transformed into different final products. The lot sizing decisions concern not only the production of final products, but also that of material preparation in order to take account of their sequence-dependent setup costs and times. The amount of research in recent years indicates the relevance of this problem in various industrial settings. In this paper, facility location reformulation and strengthening constraints are newly applied to a previous lot-sizing model in order to improve solution quality and computing time. Three alternative metaheuristics are used to fix the setup variables, resulting in much improved performance over previous research, especially regarding the use of the metaheuristics for larger instances.