Maximizing customer satisfaction by optimal specification of engineering characteristics

The House of Quality has been widely discussed as a mechanism for converting customer attributes into engineering characteristics to ensure the design quality of new products and processes. In the past, this process has been subjective and heuristic. In this paper, we present a mathematical programming model for determining the optimal settings for engineering characteristics based on value functions constructed to capture customer preferences. The model can be used with either traditional subjective measures of customer preference or incorporate empirical models based on quantitative data. The robustness of the optimal solution to randomness in parameter estimates is investigated. An example is used to demonstrate the procedure.     

Optimization of machining process plan for planar surfaces

In manufacturing parts, multiple processes are frequently used in sequence to produce the designed feature. The sequence of processes can easily be identified from previous experience. But no work has been done to determine whether any of the processes in the sequence are really necessary. A mixed integer mathematical programming model has been set up to determine the optimal set of processes and the amount of material to be removed by each process to minimize either the total process time or the total production cost.     

Computational techniques in studies of physical processes underlying the synthesis of nanopowders

This paper examines a gas-phase process for the synthesis of nanopowders and presents a mathematical model for the physical processes involved in vapor effusion into vacuum and condensation for various substances. The model has been implemented as a computational algorithm.     

Analysis of the growth of concomitant nitride layers produced by a post-discharge assisted process

In the present work, the growth of concomitant nitride layers during a post-discharge process is studied. The analysis takes into account the similarities and differences between nitriding post-discharge processes and other nitriding processes, employing a mathematical simulation of nitrogen diffusion.The considered differences are related to the thermodynamic standard states, the nitrogen concentration on the surface and the sputtering of the surface (this one for plasma processes). Nitrogen diffusion and layer formation are described from the beginning of the process by means of a mathematical model.     

CONTINUOUS COOLING OF WET FOUNDRY SAND USING A FLUIDIZED BED

In order to establish the optimum cooling system for hot returned sand in metal casting processes, a mathematical model including simultaneous heat and mass transfer has been constructed. The present study is especially directed towards clarifying the dynamical behavior of sand cooling in a one-pass fluidized bed. A series of continuous cooling experiments has been made for various conditions. Characteristics of both transient and steady-state bed temperature are explained reasonably by the present model. Furthermore, a possible proposal has been given on the optimal operation, which raises heat exchange efficiency in fluidization cooling of hot molding sand.     

CONTINUOUS COOLING OF WET FOUNDRY SAND USING A FLUIDIZED BED

Abstract

In order to establish the optimum cooling system for hot returned sand in metal casting processes, a mathematical model including simultaneous heat and mass transfer has been constructed. The present study is especially directed towards clarifying the dynamical behavior of sand cooling in a one-pass fluidized bed. A series of continuous cooling experiments has been made for various conditions. Characteristics of both transient and steady-state bed temperature are explained reasonably by the present model. Furthermore, a possible proposal has been given on the optimal operation, which raises heat exchange efficiency in fluidization cooling of hot molding sand.     

Study on Numerical Simulation of Mold Filling and Solidification Processes under Pressure Conditions

The mold filling and solidification simulation for the high pressure die casting (HPDC) and low pressure die casting (LPDC) processes were studied.A mathematical model considering the turbulent flow and heat transfer phenomenon during the HPDC process has been established and paralled computation technique was used for the mold filling simulation of the process.The laminar flow characteristics of the LPDC process were studied and a simplified model for the mold filling process of wheel castings has been developed.For the solidification simulation under pressure conditions,the cyclic characteristics and the complicated boundary conditions were considered and techniques to improve the computational efficiency are discussed.A new criterion for predicting shrinkage porosity of Al alloy under low pressure condition has been developed in the solidification simulation process.     

物料与窑壁间歇接触对回转窑传热过程的强化效应

根据回转窑内物料颗粒的运动特点，推导了颗粒团在贴壁运动过程中的非稳态导热系数及界面处的接触传热系数，进而得出了物料与封盖窑壁间的换热系数；结合已有研究成果，建立了回转窑的传热数学模型。计算表明，未考虑物料与窑壁间歇接触对回转窑传热过程的强化效应时，物料温度偏低；温度越高，强化效应对物料温度的影响越大；考虑物料与窑壁间歇接触对回转窑传热过程的强化效应，有利于提高回转窑煅烧熟料的质量和热效率。     

Dynamical model of total and partial pressures in a vacuum system due to intermittent desorption

The dynamical characteristics of a vacuum system in respect of pressure are critical for studying the dynamical desorption processes such as those produced by mechanically stimulated desorption in vacuum. In the present work, a mathematical model of the instant pressure in a vacuum system has been developed assuming an intermittent square-wave desorbed gas flow. In this case, the duration of the pressure transient is proposed to be used as a generalized criterion of the rate of the desorbed gas flow and, consequently, of the instant pressure behaviour. The dependences of the transient duration on the pumping speed, system volume, molar mass of the desorbed gas as well as on the period and the on-off ratio of the desorption process have been revealed. The developed model made no assumptions on the physical nature of the gas source, i.e. desorption, leaking, etc., and can be used for different applications.     

Heat treatment of chlorinated waste in a rotating kiln: Problems with intermediate reaction products and solutions applied

At the CEA, the incineration of radioactive wastes is carried out thanks to the IRIS process involving a oxidizing pyrolysis step performed with a rotary kiln. If the running of the process is very satisfactory for processing waste of a given composition, it appears that the behavior of the kiln may diverge when the composition of the waste change. Through the example of wastes containing a large amount of PVC and thanks to a very simple modelling of the heating of the kiln, it has been demonstrated that the deposits are involved in overheating of the pyrolysis kiln. Fundamental investigation carried out about the thermal degradation of PVC and cellulose have shown that the formation of intermediate PVC decomposition compounds together with the residues coming from the decomposition of the cellulose could be responsible of the large amount of deposits. In order to avoid the malfunctions it has been proposed to revise the furnace operating parameters by specifying a waste feed sequence that ensure a relaxation period to the furnace. By this way, the running of the facility shows a very good stability with a very thin temperature oscillation that can easily be explained by a thermal modelling of the kiln.     

Predicting microstructural evolution and yield strength of microalloyed hot rolled steel plate

Abstract

A mathematical model has been developed to optimise process parameters for production of API grade steel plates by thermomechanical controlled processing at a plate mill in Bhilai Steel Plant, India. The model comprises the prediction of the microstructural evolution during hot rolling, the subsequent phase transformation, and, finally, the mechanical properties of microalloyed steels. Effects of chemistry and mill parameters on recrystallisation, grain growth, and precipitation kinetics were taken into consideration to describe the metallurgical processes. . The model has been validated through laboratory experiments as well as full-scale rolling at the plate mill.     

Time-dependent behavior of gas absorption in lubricant oil

Gas absorption behavior in liquid with time has been studied by applying a simple mathematical model. The model is based on a one-dimensional mass diffusion process due to the concentration difference in dissolving gas. In order to examine the model validity, selected experimental data in the literature have been analyzed with the present model. The model has faithfully reproduced the experimental transient behavior of dissolving gases, and physically meaningful model parameters, diffusion constant and solubility limit, have been obtained for dissolving gas (water and refrigerant) in various lubricant oils. The validity and the significance of the model are discussed.     

Modelling the Solidification Microstructure Formation of Cobalt Dendritic Alloys

In the present work a mathematical model has been developed to explain the microstructure characteristics obtained during the solidification process of dendritic cobalt alloys, under ordinary low cooling rate conditions. The model, taking into account physical aspects such as undercooling, cooling rate, solute diffusion, interfacial energy, and dendrite tip morphology, allowed results to explain the experimental microstructure changes observed when the processing conditions were varied. The mathematical model involved micro and macroscopic phenomena occurring during the solidification process of metallic alloys. The solutions of the governing equations were obtained applying a non-coupled scheme, which enables the possibility to simulate the solidification of complex geometry castings.     

A stochastic multimode model for time–cost tradeoffs under management flexibility

In this paper, we present a useful bicriteria model for analyzing the time–cost tradeoffs that can be achieved when undertaking a project consisting of a single task. Some related mathematical results are also presented. The model assumes that several different processes may be used to undertake the task, defining different operating modes, and also assuming that managers may change the process in use after the task is started, depending on the way the task is developing. The model is easy to use, and it can be applied to a large number of real-life situations when the objectives are to minimize cost and time. We present some ideas for an algorithm aimed at identifying sets of relevant strategies from which the decision-maker may choose a suitable strategy. We also present several mathematical properties that may be useful for such an algorithm.     

基于形状文法和模糊综合评价的磁州窑纹样提取与设计研究

目的 针对磁州窑纹样提取与改造过程中推演操作单一、原有艺术特征完整度降低的问题,提出一种基于形状文法的纹样推演策略。方法 建立具有典型艺术风貌的磁州窑纹样素材库,结合形状文法推演、改造原始纹样,得到新的衍生纹样,将其运用于文创产品设计,并通过模糊综合评价法对设计方案进行评价。结果 经形状文法推演、改造的纹样既保留了磁州窑原有艺术特征,又符合现代审美需求,磁州窑文创产品设计方案获得了较高的满意度。结论 基于形状文法的磁州窑纹样推演方法的可行性与有效性得到了验证,同时也为传统造物创新发展提供了新思路。     

罐式煅烧炉后期使用的管理和维护

包铝炭素分厂二车间所采用煅烧设备是八层五组二十室顺流式罐式煅烧炉,其中1#、2#煅烧炉处使用已达10年,超过设计使用寿命进入后期管理使用阶段。在此期间1#炉经历4次烘炉,2#炉经历2次烘炉,使得煅烧炉炉体变形严重,挥发份直接从罐内溢入火道,影响煅烧炉的正常使用。本文主要介绍炭素分厂二车间通过调整工艺参数,改进操作方式,改善煅烧炉使用情况,减缓煅烧炉老化趋势,从而确保煅烧炉的正常运行。     

A simulation study on the effects of particle size on the consolidation of polymer powder impregnated tapes

The powder prepreg technique offers a low-cost, high-speed method of manufacture of composites. Consolidation of the prepreg tows is a key step in the manufacture of a final `useful' part. The efficiency of the consolidation for any polymer powder prepreg tape produced from powder prepreg processes would conceivably depend on the material properties of the polymer, particle size, temperature, consolidation pressure and volume fraction of the tape. A mathematical process model that identifies and describes a set of parameters to predict the consolidation conditions of a given polymer powder prepreg tape has been developed. A simulation study that identifies the different parameters and compares the advantages and limitations of polymer physical properties and particle size has been performed. An integrated Flow Resistance (FR) index has been developed to mathematically describe the consolidation process. The results show that small powder particle sizes are beneficial to the process.     

Homogeneity of solution-grown single crystals: A theoretical analysis

Using mathematical modeling of crystal growth processes, we have analyzed the chemical homogeneity of single crystals grown from solution by conventional techniques. The results indicate that all of these techniques are, in principle, unsuitable for the growth of homogeneous single crystals. A mathematical model has been developed for a continuous isothermal growth process which insures constant solution growth conditions and chemical homogeneity of the growing crystal. The key conditions of a continuous isothermal growth process have been formulated which insure an intended uniform distribution of intentional and unintentional impurities in the bulk of the growing single crystal. Original Russian Text ? K.M. Rozin, O.G. Portnov, 2008, published in Neorganicheskie Materialy, 2008, Vol. 44, No. 2, pp. 238–241.     

Wet process rotary cement kilns: modeling and simulation

The knowledge of wet process kilns design and operation in the cement industry has not been improved substantially during the last decades since the pre-calcination process has been developed to become the technological standard. In spite of the tendency to replace wet process rotary kilns for cement production by modern dry process kilns with pre-calcination, there are still a substantial number of wet process kilns in operation. Their efficient operation requires an individually designed chain system to enhance the kiln performance. Currently the design of chain systems for wet process rotary cement kilns depends strongly on experience. Systematic theoretical and experimental investigations for the dimensioning of chain systems are not known. Based on a one-dimensional cell model, a simulation program for wet process rotary cement kilns with chain systems has been developed. With the aid of this simulation tool, the influence of chain systems on solid composition and temperature profiles, clinker throughput and fuel requirement is predicted and the design of chain systems can be optimized.     

Optimizing water tanks in water distribution systems by combining network reduction,mathematical optimization and hydraulic simulation

In the last two decades, water consumption in Germany has been decreasing, which causes the water tanks and pipes in water distribution systems to work inefficiently. This paper proposes a method that supports the planning process for tanks in water distribution systems. The method uses a combination of network reduction, mathematical optimization and hydraulic simulation. The mathematical optimization model is a non-convex Mixed Integer Quadratically Constrained Program (MIQCP) that is solved by a piecewise linearization. As this may lead to many binary variables and therefore high computing times, the size of the water distribution system model is reduced before building the optimization model. After applying several network reduction techniques and using a piecewise approximation of the original model, there may be some hydraulic differences between the original network model and the reduced network model. To make sure that the solution obtained in the optimization process is feasible in the original water distribution system model, the solution is verified by a hydraulic simulation. If the solution is not feasible, the reduced model has to be modified and solved again until the hydraulic simulation verifies a solution as feasible. In this paper, each of these processes is described and the results indicate the usefulness of each of them.