A Heuristic for a Class of Production Planning and Scheduling Problems

This paper describes a solution technique for a general class of problems referred to as aggregate planning and master scheduling problems. The technique is also applicable to multi-item single level capacitated lot sizing problems. The solution technique presented here is a heuristic that is practical for large problems e.g. 9 products and 36 periods. We have tested it for problems with varying number of time periods, number of products, setup costs, holding costs, overtime costs and capacity levels. For those problems that we could solve exactly using a branch and bound algorithm, the solutions produced by the heuristic were all within 1 % of optimality. For problems that we could not solve exactly, we are able to compute a lower bound on the optimal cost. Using the bound we are able to show that our heuristic solutions were within 2.93% of optimality on the average. Except for those problems having very high setup cost or problems with extreme seasonality, the algorithm produced solutions that were within 1 % of optimality on average.     

Road safety issues in remote Aboriginal communities in Western Australia

A series of interviews with the chairpersons of Aboriginal communities in a remote area of Western Australia were conducted to examine their attitudes to road safety problems. It was found that some road safety issues that were expected to be considered problems were not necessarily seen to be so by those interviewed. This finding suggests that the first stage of a road safety intervention program for Aboriginal people may need to include an awareness raising component. It also suggests that there is a need for more detailed research defining particular problems more accurately before effective and culturally appropriate countermeasures are developed.     

固态电解质中的聚合物复合体系研究进展

固态聚合物电解质因其质量轻、柔性好,且与电极材料接触良好、界面阻抗小,成为开发新一代高能量密度、高安全性乃至高柔韧性电化学器件的潜在材料,近年来获得了广泛关注。但因其离子电导率低、力学性能差等缺陷也成为限制其进一步商业化的关键问题。通过交联、共混、共聚等手段组成聚合物的复合体系有可能很好地解决这些问题,因此本文首先对聚合物中的离子导电机理进行了简要介绍,旨在从原理的角度阐释上述问题的解决策略;随后综述了近年来多种聚合物基复合电解质在电化学器件中的应用以及改性策略。最后对复合固态聚合物电解质目前面临的基础研究和实际应用问题进行了讨论,给出了解决这些问题的建议,以期为新型聚合物复合固态电解质的设计与制备提供新思路。     

Learning from design experience in an agent-based design system

A learning mechanism based on findings in cognitive science was added to an agent-based computational design system to determine if this mechanism would enable the system to learn from its experiences and transfer useful design knowledge to new problems. Learning and transfer were evaluated by examining how well knowledge learned while solving one problem could be applied to solve the same problem more effectively as well as how well this knowledge could be transferred to new design problems. An existing system, A-Design, was enhanced by giving it the ability to learn and store useful design knowledge so that this knowledge can be used in new design problems. Three electromechanical design problems were used to evaluate this new learning mechanism, and results indicate that this basic, cognitively based, learning mechanism is successful at transferring design knowledge to new problems with a few limitations. This knowledge transfer leads to a more effective design process.     

In press conditions and their effect on runnability and convertability in digital package printing

A major advantage of digital printing is that printing can be performed on demand, but like all printing techniques it suffers from specific runnability problems. This study reports on an investigation of problems during printing and how to improve the runnability, with the aim of pointing out the most critical factors. Test printing has been performed on three different paperboard types in digital print units, based on both dry and liquid toner electrophotographic technology. The results show that the three main problems during printing were feeding in sheet‐fed print units, cutting in web‐fed print units, and increasing curl after printing. Feeding problems in sheet‐fed print units were mainly explained by curl and varying format size of the paperboard, but also by exceeding thicknesses limits for the press. Curl after printing principally occurred due to high temperature loads caused by, for example, fusing and conditioning. Copyright © 2005 John Wiley & Sons, Ltd.     

Nationalisation of electricity supply 1947: reasons and problems

It is widely known that the electricity supply industry in Great Britain was nationalised (Electricity Act, 1947) by a Labour government in accordance with Clause 4 of the Party's then Constitution but there are other reasons why a large-scale reorganisation was needed. It is well-known, too, that the newly nationalised industry had problems in engineering, but there were also other problems. In this paper, the author discusses some of these other problems in which he was involved. Firstly, however, he gives a brief word about the industry's history     

Blood Access Outcomes Associated with Short Daily Hemodialysis

With the growing number of reports that daily hemodialysis (DHD) improves clinical outcomes and quality of life, there has been increased interest in the effects of more frequent venipunctures on blood accesses. Since 1996, we have converted 30 patients (27 in‐center, 3 home) from conventional 3/week dialysis to short, daily, 6/week dialysis (sDHD). Twenty‐five patients started for medical indications. End‐stage renal disease (ESRD) causes were diabetes mellitus (in 7), hypertension (6), glomerulonephritis (8), hereditary nephritis (2), and other (7). Mean (±SD) age was 57 ± 16 years. Patients had an average of 3.8 major comorbidities in addition to ESRD. Thirty patients were followed on sDHD for 388 patient‐months: 9 patients died after 4.2 ± 6.7 months, 3 were transplanted at 5.4 ± 2.2 months, and 3 were disenrolled at 9.3 ± 10.5 months. Fifteen patients remain on sDHD at 20.4 ± 14.1 months. Access problems for the 12 months prior to sDHD were compared to those that occurred while the patient was on sDHD. Problems were tracked by access type. There were 40 different accesses in 30 patients with a cumulative 28.07 access‐years pre‐DHD; 24 of these accesses were artificial bridge grafts (ABG) of either polytetrafluoroethylene or bovine material. There were 27 access problems pre‐DHD, or 0.962 problems per access‐year. On sDHD these same 30 patients had 41 accesses for 34.44 access‐years; 23 of these were ABGs. There were 31 access problems or 0.900 problems per access‐year. There were no significant differences in access problems comparing pre‐DHD with on‐sDHD, either in aggregate or when analyzed by access type. After 39 months of observation, there does not appear to be an increase in blood access problems when patients are converted from conventional dialysis to sDHD.     

A simple and efficient extension of a class of substructure based preconditioners to heterogeneous structural mechanics problems

Several domain decomposition methods with Lagrange multipliers have been recently designed for solving iteratively large‐scale systems of finite element equations. While these methods differ typically by implementational details, they share in most cases the same substructure based preconditioners that were originally developed for the FETI method. The success of these preconditioners is due to the fact that, for homogeneous structural mechanics problems, they ensure a computational performance that scales with the problem size. In this paper, we address the suboptimal behaviour of these preconditioners in the presence of material and/or discretization heterogeneities. We propose a simple and virtually no‐cost extension of these preconditioners that exhibits scalability even for highly heterogeneous systems of equations. We consider several intricate structural analysis problems, and demonstrate numerically the optimal performance delivered by the new preconditioners for problems with discontinuities. Copyright © 1999 John Wiley & Sons, Ltd.     

Project Management Problems

ABSTRACT

Twelve hundred different problems, as described by project practitioners, are sorted according to an adaptation of the classic management functions first described by Henri Fayol: planning, scheduling, organizing, staffing, directing, and controlling. Observations include that planning problems are most prevalent, that some problems vary with project structure, and that some problems vary with success level. The most surprising lesson is that many types of problems are equally or even more prevalent on successful projects.     

Segregation and Continued Mixing in an Automatic Capsule Filling Machine

During test production of an indomethacin 25 mg capsule preparation problems with single-dose variation and variation/reduction in dissolution rate were ascertained. The problems were identified as segregation and overmixing of the powder mixture, which contained magnesium stearate as lubricant. The problems were solved by removing the propeller mixer in the powder hopper and replacing the cylindric powder hopper with a coneshaped hopper, which resulted in mass flow.     

Cutting Plane and Branch and Bound for Solving a Class of Scheduling Problems

Two general purpose integer programming algorithms, one a fractional cutting-plane algorithm and the other a branch-and-bound algorithm, were investigated. The cutting-plane algorithm easily solves an important class of integer problems, a class of scheduling problems for the assigning of personnel to work shifts over a fixed period of time. Scheduling problems were constructed with 14 to 189 integer variables and with 14 to 21 constraints. The general branch-and-bound search was not effective on this class of scheduling problems, but it was effective on the classical test problems found in the literature of integer programming, many of which were not handled by the cutting-plane algorithm.     

On the use of the total scalar potential on the numerical solution of fields problems in electromagnetics

The paper summarizes the formulation of a set of computer algorithms for the solution of the three-dimensional non-linear Poisson field problem. Results are presented that were obtained by applying algorithms to the analysis of two-dimensional magnetostatic fields. Scalar and vector potentials were used, and it is shown that the convenient single valued scalar potential associated with the induced sources gives severe accuracy problems in permeable regions. The results become as good as those obtained using vector potential if the scalar potential associated with the total field is used for permeable regions. The combination of two scalar potentials has a significant advantage for three-dimensional problems.     

Pre‐college Electrical Engineering Instruction: The Impact of Abstract vs. Contextualized Representation and Practice on Learning

Background While engineering instructional materials and practice problems for pre‐college students are often presented in the context of real‐life situations, college‐level texts are typically written in abstract form. Purpose (Hypothesis ) The goal of this study was to jointly examine the impact of contextualizing engineering instruction and varying the number of practice opportunities on pre‐college students' learning and learning perceptions. Design/ Method Using a 3 × 2 factorial design, students were randomly assigned to learn about electrical circuit analysis with an instructional program that represented problems in abstract, contextualized, or both forms, either with two practice problems or four practice problems. The abstract problems were devoid of any real‐life context and represented with standard abstract electrical circuit diagrams. The contextualized problems were anchored around real‐life scenarios and represented with life‐like images. The combined contextualized‐abstract condition added abstract circuit diagrams to the contextualized representation. To measure learning, students were given a problem‐solving near‐transfer post‐test. Learning perceptions were measured using a program‐rating survey where students had to rate the instructional program's diagrams, helpfulness, and difficulty. Results Students in the combined contextualized‐abstract condition scored higher on the post‐test, produced better problem representations, and rated the program's diagrams and helpfulness higher than their counterparts. Students who were given two practice problems gave higher program diagram and helpfulness ratings than those given four practice problems. Conclusions These findings suggest that pre‐college engineering instruction should consider anchoring learning in real‐life contexts and providing students with abstract problem representations that can be transferred to a variety of problems.     

Cognitive problems,self-rated changes in driving skills,driving-related discomfort and self-regulation of driving in old drivers

Ageing in general is associated with functional decline that may have an adverse effect on driving. Nevertheless, older drivers have been found to show good judgement and to self-regulate their driving, which may enable them to continue driving safely despite functional decline. The process of the self-monitoring of driving ability and the awareness of functional decline, and its association with the self-regulation of driving is, however, not fully understood. The aim of the present study was to examine the perceived changes in driving skills, the discomfort experienced in driving, and the self-regulation of driving as measured by the avoidance of certain driving situations by older drivers with different levels of self-rated cognitive problems. Eight hundred and forty Danish drivers aged 75–95 completed a structured telephone interview. The results showed that the recognition of cognitive problems was associated with an experience of improvement in higher level driving skills but also of a decline in lower level driving skills. Moreover, cognitive problems recognised by drivers were associated with discomfort in, and avoidance of, driving situations. Finally, a linear relationship between discomfort in driving and avoidance was found and this tended to be stronger for drivers recognising cognitive problems. The results indicate that older drivers who recognise problems with cognitive functions display good self-assessment of changes in their driving skills. In addition, the results suggest that driving-related discomfort is an important factor affecting the self-regulation of driving. Finally, the findings indicate that driving-related discomfort functions as an indirect self-monitoring of driving ability and may contribute to the safe driving performance of Danish older drivers.     

水性涂料在车身中的应用现状及发展趋势

汽车车身采用水性涂料涂装具有环保优势,但生产成本高、能耗大、施工管理复杂.介绍了近年来汽车车身水性涂料涂装的应用状况及存在的问题,指出十多年来涂装材料工艺、设备的改进已逐步解决了以上问题.从汽车生命周期评估(LCA)来看,汽车车身水性涂料涂装的发展将能使节能、环保、产品性能和企业利益达到最佳的平衡.     

前轮毂压铸模具跑水的处理

以前轮毂压铸模具跑水导致的滑块卡死、斜导柱弯曲为例,通过对模具2次修改的过程表明,对于采用常规方式不能解决的模具问题,就要对模具的相关问题部位采用逐件分解、逐个确认的方法,去寻找问题产生的原因,针对原因采取适当的措施,才能从根本上解决模具的跑水。     

瓦楞纸箱在战储军品包装中的应用分析

目的在瓦楞纸箱技术应用现状的基础上,分析瓦楞纸箱在战储军品包装中存在的问题,提出规避和解决这些问题的建议和措施。方法通过实地调研,并在分析文献的基础上进行研究。结果结合实地调研部队仓库的实例,总结了3点目前瓦楞纸箱在军品包装中存在的问题。主要表现为军品用纸箱的选材单一、内部结构设计不合理、特殊防护功能薄弱等。结论结合目前瓦楞纸箱的应用现状,指出军用瓦楞纸箱技术相对落后,未及时跟随市场发展,需引入工艺先进的新型瓦楞纸箱。通过加强相关标准体系建设,推进军民融合发展,在军品包装中积极引进特殊功能纸箱,并采取从顶层设计加强军队仓库的标准化建设等措施,以提高战储军品的防护性能。     

Solution of adiabatic and nonadiabatic combustion problems using step-function reaction models

We consider the use of step-functions to model Arrhenius reaction terms for traveling wave solutions to combustion problems. We develop a methodology by which the Arrhenius reaction rate term is replaced by a suitably normalized step-function. The resulting model introduces interior interfaces and allows the conservation equations for energy and species to be solved explicitly within the subdomains bounded by the interfaces. The problem can then be reduced to a small number of nonlinear algebraic equations governing appropriate interface conditions. We apply this methodology to a variety of single-reaction problems and show that the resulting solutions agree with those obtained by the well-known front δ-function) approximations for large Zeldovich numbers. We then consider multiple reaction problems, specifically problems involving two independent reactions and problems involving sequential reactions. For these problems we compare the results with simpler front models as well as with Arrhenius kinetics. We show that the step-function models are generally superior to the front models where available and agree, both qualitatively and with reasonable quantitative accuracy, with solutions obtained via full Arrhenius kinetics.     

13. Measurement of the lattice constant of SiGe heteroepitaxial layers grown on a silicon substrate

The lattice constant of thin heteroepitaxial layers composed of single crystal SiGe solid solutions various compositions grown on silicon substracts were measured. The measurements were performed by X-ray diffraction method. The fact that the layers are thin and, therefore, there is also reflection from the silicon substrate (in addition to the reflection from the layer) is utilized for this measurement method. A review of the measurement method is given and the experimental results obtained by irradiating the samples with CuK_α are presented. Specific problems related to the measurement methods and to the layer lattice structure are also presented. There are: resolution problems between the reflections from the layer and the substrate for low Ge concentrations, deformation problems, the effects of the defects and non-uniform changes in the lattice constant at different crystallographic orientations.     

Sensibility of shells to buckling disturbances in connection with parameters of critical loading spectrum

This paper considers the critical loading density in the vicinity of the first eigenvalue for the stability problems of both a structurally orthotropic longitudinally-compressed cylindrical shell and a spherical panel. For structurally orthotropic shells it is shown that the critical loading spectrum in the above-mentioned problems can begin with the condensation point only when definite relations between structurally orthotropic parameters take place. In connection with the presence of eigenvalue condensation points in the stability problems it becomes expedient to obtain approximate solutions for nonhomogeneous problems where the right-hand part of the equation describes disturbances. The linear systems of such a type show a strong selectivity as regards to initial deflections and to small external disturbances. The experimental results were treated. The process of the additional shell deflection development was analyzed. It was established by experiment that the shells with more rigid longitudinal stiffeners are less sensitive to initial imperfections and disturbances that explains a good agreement of critical loadings of these imperfect shells with Euler loadings. The number of equivalent forms for the shells with longitudinally stiffened, transversely stiffened and non-stiffened shells has the following order, respectively: 0(1), 0(10), 0(100).