Design Optimization Software Research Articles

DESIGNING A MODIFIED ATMOSPHERE PACKAGING SYSTEM FOR FOODSERVICE PORTIONS ON NONRESPIRING FOODS: OPTIMAL GAS MIXTURE AND FOOD/HEADSPACE RATIO

There are more than 850,000 retail foodservice establishments, restaurants, schools, offices, vending machines, hospitals, sports arenas, quick-service outlets, in the United States, serving more than $1 billion worth of food daily. For foodservice a modified atmosphere packaging system could be a good alternative packaging. Modified atmosphere packaging can provide a longer shelf-life for nonrespiring food. The aim of this research was to show the potential application of a mathematical model in designing an optimal food/package system for Pacific Hake. The mathematical model was used to determine the optimal gas mixture and the ratio food/headspace in foodservice portions. According to the simulation study, optimal conditions for Pacific Hake in foodservice portions were a 40/20/40 gas mixture (CO2/O2/and N2) and a headspace/food ratio of 2:1. Optimal conditions consider maximum shelf-life and an adequate film collapse criterion. In addition, economical aspects were qualitatively considered. The utilization of a mathematical model significantly minimized the cost and time to find the optimal packaging design for foodservice portions.

Time- and Temperature-Dependent Thermo-Mechanical Modeling of a Packaging Molding Compound and its Effect on Packaging Process Stresses

For reliable virtual thermo-mechanical prototyping of electronic packages appropriate descriptions of the mechanical behavior of the constituent materials are essential. In many packages molding compounds are used for encapsulation and underfill to provide environmental protection and/or to improve the package thermal mechanical reliability. Therefore, among others, the availability of appropriate constitutive models for various epoxy-molding compounds is one of the requirements for computational prototyping. As there is a large variability of available molding compounds, it is essential to be able to experimentally establish the model parameters in an efficient manner. Because of the implied simplicity, linear visco-elastic models combined with the time-temperature superposition theory are mostly used in thermo-mechanical simulations. Among the various experimental possibilities to efficiently establish the model parameter functions, in the present paper the use of unidirectional creep testing is worked out for a chosen molding compound. Here isothermal one-day creep experiments at different temperatures (ranging below and above the glass transition temperature of the compound) are performed. The tensile creep compliance and the time-dependent Poisson’s ratio of the material at different temperatures are successfully used to construct visco-elastic master curves. As the Poisson’s ratio shows a significant change during a creep or relaxation test, its effect in partly constraint situations (as in packages) will be evident. Therefore it is not reliable to approximate this variable using a constant value. Further, the visco-elastic model of the material is implemented in a finite element program and verified by means of a shear stress relaxation experiment and a creep experiment both under nonisothermal conditions. Moreover, the effect of the creep behavior of the molding compound on the packaging process stress field and its evolution is investigated. Substantial cost saving was realized by package design optimization based on the reliable prediction of the packaging process stresses.

Molecular basis of the interphase dielectric properties of microelectronic and optoelectronic packaging materials

High frequency microelectronic and optoelectronic device packaging requires the use of substrate and encapsulation materials having a low dielectric constant, low dielectric loss and high volume resistivity. Most packaging materials are polymer-ceramic composites. A clear understanding of the broadband dielectric properties of composite materials is thus of great current importance for the effective development of high frequency packaging materials and optimized package design. Toward this goal, a general framework for understanding the dielectric properties of packaging materials was recently developed in which the dielectric constant of polymer-ceramic composite materials is characterized by the electrical properties of the polymer phase, the filler phase and an interphase region within the composite system. However, for this framework to be a viable tool for tailoring the dielectric properties of packaging materials, one must understand the dielectric properties of the polymer-filler interphase region, which represents a region of polymer surrounding and bonded to the surface of each filler particle having unique dielectric and physical characteristics. This work presents a model to explain and predict the dielectric properties of the composite interphase region based on dipole polarization theory.

Poped, a software for optimal experiment design in population kinetics

Population kinetic analysis is the methodology used to quantify inter-subject variability in kinetic studies. It entails the collection of (possibly sparse) data from dynamic experiments in a group of subjects and their quantitative interpretation by means of a mathematical model. This methodology is widely used in the pharmaceutical industry (where it is termed “pharmacokinetic population analysis”) and recently it is becoming increasingly used in other areas of biomedical research. Unlike traditional kinetic studies, where the number of subjects can be quite small, population kinetic studies require large numbers of subjects. It is, therefore, of great interest to design these studies in the most efficient manner possible, to maximize the information content provided by the data. In this paper we propose an algorithm and a computer program, poped, for the optimal design of a population kinetic experiment. In particular, the number of samples for each subject and the design of the individual sampling strategies, i.e. the number and location of the time points at which the output variable is sampled, will be considered. Among the various criteria proposed in the literature, D and ED optimality are the ones implemented in our software program, since they are the most widely used. A brief description of the techniques employed to perform design optimization is given, together with some details on their actual implementation. Some examples are then presented to show the program usage and the results provided.

Evaluation and optimization of package processing and design through solder joint profile prediction

Solder joints are generated using a variety of methods to provide both mechanical and electrical connection for applications such as flip-chip, wafer level packaging, fine pitch, ball-grid array, and chip scale packages. Solder joint shape prediction has been incorporated as a key tool to aid in process development, wafer level and package level design and development, assembly, and reliability enhancement. This work demonstrates the application of an analytical model and the Surface Evolver software in analyzing a variety of solder processing methods and package types. Bump and joint shape prediction was conducted for the design of wafer level bumping, flip-chip assembly, and wafer level packaging. The results from the prediction methodologies are validated with experimentally measured geometries at each level of design.

Augmenting a Waste Glass Mixture Experiment Study with Additional Glass Components and Experimental Runs

A glass composition variation study (CVS) for high-level waste (HLW) stored in Idaho is being statistically designed and performed in phases over several years. The purpose of the CVS is to investigate and model how HLW-glass properties depend on glass composition. The resulting glass property–composition models will be used to develop desirable glass formulations and for other purposes. Phases 1 and 2 of the CVS have been completed and are briefly described. This paper focuses on the CVS Phase 3 experimental design, which was chosen to augment the Phase 1 and 2 data with additional data points, as well as to account for additional glass components not studied in Phases 1 and/or 2. In total, 16 glass components were varied in the Phase 3 experimental design. The paper describes how these Phase 3 experimental design augmentation challenges were addressed using the previous data, preliminary property–composition models, and statistical mixture experiment and optimal experimental design methods and software. The resulting Phase 3 experimental design of 30 simulated HLW glasses is presented and discussed.

Special issue on commercial design optimization software: an introductory note

Twenty years later I have come to understand the true meaning of Jim Siddall's comment. Having worked with several colleagues in industry across the world and having followed their work quite closely I came to a couple of conclusions: The complexity of the optimal design problems that our industry colleagues address successfully far exceeds what many of us academics suspect or even dare undertake. Furthermore, the true heroes of the indisputable growth of design optimization use in industry (or the academy for that matter) are the software vendors---the companies and the people who have tried to put together software packages that are robust, friendly and accessible to users that may lack the sophistication or the time to use the immediate products of the academic endeavor. To be fair, these commercial software entities would not have been possible without the intellectual fruits of the academic research. The point however is not to minimize the latter's importance; rather, it is to recognize that we should applaud all such efforts, filter the hype of the marketplace, and support their collective use by students and colleagues in academia and industry alike. For example, thanks to the Excel Solver I have been able to do the unimaginable (to me anyway): have second-year college sophomores use design optimization intelligently in their project work. Thus, two years ago with encouragement from Vassili Toropov I undertook the project of establishing some sort of state of the art in commercial design optimization software by inviting the key players to make a bona fide journal article contribution into a special issue collection. The requirements put forth in the invitations were that (i) each article would not be a covert commercial marketing pitch, (ii) the capabilities and limitations of the software would be reasonably outlined, (iii) some specific examples of applications would be offered, and (iv) that the software in question would be available on the open market along with support and maintenance contracts (to exclude the extensive semi- commercial activities of many academics). Initially my intention was to concentrate only on non-structural software because of the extensive inclusion of optimizers in recent versions of FEM packages. Subsequently, I included structural optimization software as long as they were not a small part of a larger FEM package. The initial collection of papers reflects writings that took place about a year ago and I think that on the whole we met the requirements we set forth. The state of the art in algorithms and computational environments is evolving at a fast pace, yet I believe that the special issue herein will maintain its archival value as I am not aware of any other collection of its kind. The collection is reasonably complete, even though more contributions could have been included. (For example, I was unable to obtain a contribution from the developers of the Excel Solver but if they used the time to continue improving their product I could not complain.) I want to thank Vassili Toropov and George Rozvany for their support throughout this effort, as well as the many reviewers who kindly offered their advice and help in improving the manuscripts. One can say that all those individuals working in the field of design optimization are making a living out of it but this is painfully true for the authors of the articles in this special issue. And so I would like to express to them my gratitude and my respect. Panos Y. Papalambros (Guest Editor), Ann Arbor, September 2001

The OptdesX design optimization software

This paper describes the OptdesX design optimization software. The software provides a design environment for optimization of engineering problems. The software supports interactive variable and function selection, optimization with continuous and discrete algorithms, design space graphics, tolerance analysis, and control of noise in numerical derivatives, as well as numerous other features. The software is described and illustrated in terms of a small example problem. The software is available on Unix platforms only.

Variable Stiffness Spar Approach for Aircraft Maneuver Enhancement Using ASTROS

An innovative variable stiffness spar (VSS) approach is studied for improving aircraft roll performance. In this concept some of the existing wing spars are replaced by the adaptive-structure VSS to control the stiffness as a function of Mach number and altitude. The VSS stiffness scheduling is designed to maximize the roll rate while satisfying flutter, control surface hinge moment, and maximum deflection constraints. The VSS mechanism consists of segmented spar having articulated joints at the connections with wing ribs and an electrical actuator capable of rotating the spar. The wing stiffness provided by the spar varies sinusoidally as a function of the rotation angle. The objective of the present study is to explore when and how to best apply this concept and assess its payoffs in terms of performance gains. The F/A-18 pre-roll-modification aircraft was selected as the baseline aircraft for its low torsional wing stiffness and available flight data. The multidisciplinary design optimization software ASTROS * was used tier performing the analyses in the Mach number range of M = 0.8-1.2 at altitudes up to 35,000 ft (40,668 m). Results show that VSS can amplify the aeroelastic forces and significantly enhance roll performance of aireraft.

Optimal dimension of PQFP by using Taguchi method

This paper addresses the use of finite element techniques and Taguchi method to optimize package design for plastic quad flat packages (PQFP) with and without a heat slug assembled. Warpage in both types of PQFPs during the curing process of temperature changing from 175°C to room temperature was simulated by using three-dimensional finite element models. Taguchi method was applied to both models to isolate the major control factors that minimize package warpage. Results of this analysis suggest that PQFPs without heat slug should keep the thickness of both mold compound and die pad as smaller as possible. For PQFPs with heat slug assembled, it was found that larger Young’s modulus of heat slug material and smaller values of temperature coefficient of expansions of mold compound, die pad, and die attachment would yield the least warpage.

Optimal shape for laminar natural convective cavities containing air and heated from the side

An examination of the literature on thermofluid dynamics reveals that the shape optimization of natural convective cavities has not been examined so far, and of course, its features are not understood. In this paper, design optimization software is coupled with software on computational fluid dynamics with heat transfer to perform a shape optimization of the cross-section of a 2-D natural convective cavity containing air. An optimization process has been implemented in two parts; the first part minimizes the area (volume) of a pre-selected cavity, whereas the second part diminishes the maximum temperature of the hot vertical wall, a critical design constraint.

Reformulation of Edelbaum's Low-Thrust Transfer Problem Using Optimal Control Theory

The problem of optimal low-thrust transfer between inclined orbits is reformulated within the framework of optimal control theory. The original treatment considered the time-constrained inclination maximization with velocity as the independent variable allowing the use of the theory of maxima. Because the independent variable is double valued for some transfers, two expressions for the inclination change involving inverse-sine functions are needed to describe all possible transfers. The present analysis casts this problem as a minimum-time transfer between given noncoplanar circular orbits and obtains a single analytic expression for the orbital inclination involving a single inverse-tangent function, uniformly valid for all transfers. The D V penalty with respect to the exact transfer solution using the full six-state dynamic equations with optimized thrust proe le during the transfer is shown to be small. I. Introduction A NALYTIC solutions of the low-thrust transfer problem are very useful in preliminary mission analysis as well as spacecraft systems designandoptimization.The overalldesign of asolarelectric transfer vehicle or even an integrated spacecraft requires extensive parametric analyses for optimum sizing of the various power, propulsion, and thermal management systems to maximize delivered payload to the destination orbit. These parametric studies require hundredsofiterations, precluding theuseofthe numerically generated transfer solutions. The analytic solutions are also desirable for future onboard autonomous guidance applications, especially for smaller spacecraft such as in the mini- and microsatellite category where the application of low-thrust technology for orbit maintenance and control is most efe cient. In the early 1960s, Edelbaum 1;2 derived analytic expressions for the maximum change in inclination between two circular orbits of given size with continuous constant acceleration and e xed transfer time. Conversely, he derived an analytic expression for the total 1V needed to carry out the transfer between given inclined circular orbits.ThistheorywaslatergeneralizedbyWieselandAlfano, 3 who allowed for the variation of the out-of-plane or thrust yaw angle during each revolution, unlike Edelbaum, who used the simpler constant yawproe le.Thus, the (a,i)semimajor axisand inclination space was mapped by direct numerical integration of the simplie ed differential equations in a and i, such that the minimum time for a given transfer is read directly from the solution map. InRefs.4and5,theoptimalthrustpitchandyawproe lesrequired for a given transfer were determined in a semianalytic way by also considering discontinuous thrust due to eclipsing. However, these solutions are not analytic and, therefore, are dife cult to implement in systems design optimization software. In Ref. 6, rapid transfer calculations were demonstrated by analytic modeling of the various transfer parameters including shadowing and solar power degradation effects due to the Van Allen radiation belts. The thrust yaw angleisheldconstantthroughoutthetransfer,andtherequiredvalue is determined by iteration. This is not as optimal as the Edelbaum steering solution, which holds the yaw angle constant during each revolution but varies its value from revolution to revolution in an optimal manner. All of these analyses assume that the orbit remains or is forced to be circular after each cycle or revolution.

DESIGN AND SIMULATION OF THE ON-LINE TRIGGER AND RECONSTRUCTION FARM FOR THE HERA-B EXPERIMENT

The common third level trigger and forth level reconstruction farm for the future HERA-B experiment will have to perform full on-line event reconstruction and calibration for an expected input rate of 2000 events/s. More than a hundred powerful RISC processors connected in a network capable of distributing several hundreds of MB/s with low latency are likely to be necessary for this task. Proper simulation of the real time multi-processor systems is central for an optimal design (hardware and software protocol) of a scalable and flexible parallel data processing architecture. A discrete event, process oriented simulation developed in concurrent μC++ is used as a framework for modelling and evaluating different farm architectures. An object oriented graphic interface to the simulation allows the monitoring of various features and provides an easier way to optimize the system.

Principles for Hydrodynamical and Geometrical Design of Vibrated Bed Driers

ABSTRACT Processing in vibrated beds is characterized by the versatility and the easy controlability through parameters of vibration (amplitude, frequency and intensity). The main task of the control of processing is the synchronization of the residence time of particles in the processing area with the duration of drying. The drying time depends on the physical properties of the processed material, on the thermal parameters of the bed and on the operational parameters. The residence time depends on the mechanical properties of the particles, on the intensity of transport and on the eometrical parameters of the equipment. Since most of the parameters of the vibrational processing depend on the intensity of vibration, synchronization of the drying time with the residence time of particles, optimization of the process and optimal design of the vibrational equipment in general must be performed by the control of this operational parameter. Therefore a sophisticated algorithm and software for optimal control and design of vibrational processing equipment is needed. Such an algorithm based on the "Classification Scheme of Vibrated Systems" is described in this paper. The design algorithm has been tested using experimental data measured in a laboratory scale aerovibrofluidized bed dryer.

Experimental Measurement and Analysis of Microelectronics Application Polymer Materials Properties

AbstractA laser based surface scanning technique was utilized to measure the polyimide coated silicon wafer curvature resulting from thermal cycling and mismatch, Meanwhile, mechanical properties of polyimide thin film were characterized by DMA, TMA and tensile test. Based on the obtained material properties, A FEA model was developed to analyze the experimental results -reasonable correlation was obtained.Similar approaches were taken one step further in the MCM silicon substrate curvature measurement. In a MCM package with silicon substrate, epoxy adhesive, and ceramic package, substrate warpage was developed in a thermal cycle due to thermal mismatch between the substrate and the package and coupling effect linked by epoxy adhesive. Three different substrate curvature measurement techniques were applied to identify the substrate curvature and epoxy thin film properties were also well characterized. A 3D FEA model incorporating with the epoxy material properties was developed to analyze the substrate warpage and investigate an optimal package design.

Microsensor packaging and system partitioning

The possibility of using microfabrication technology for creating integrated sensors and actuators also brings with it new design problems. This paper addresses three of these design problems: system partitioning, package design and process optimization in the presence of the technological constraints that arise when one wishes to build both electronic components and sensor structures as part of the same device.

Role of data base management in design optimization systems

To study the role of data base and data base management system, an interactive design optimization software system called IDESIGN5 is developed to solve nonlinear programming problems. Four promising algorithms are included to overcome the lack of unanimous choice of an algorithm. Tuning parameters and procedures of algorithms are implemented through extensive numerical experimentation. The interactive process consists of menu displays, advice for decisions, and applicable messages. Input data can be created interactively and the designer can change problem parameters, algorithm, and design variable data at any point of execution. If a design variable does not effect the optimization process, it can be given a fixed value interactively. Discrete variable optimization can be performed by using design variable status capability of the system. Graphics facilities are provided for decision making. The system consists of several modules that communicate with each other through a data base managed by a data base management system. Several example problems are solved in batch and interactive environments to test the system.

Purposes and analysis of industrial package design

A simplified analysis is presented of the physsical phenomena and mechanical stresses involved in schock and vibration hazards which lead to concealed damages. The role of industrial packaging design in reducing the destructive mechanical stresses to harmless levels is discussed. Consideration is also given to the factors to which contribute to an optimal package design based on a compromise between the cost of occasional concealed damage and the cost of extra protection achieved by the liberal use of expensive packaging designs.