COMPUTATIONAL ASPECTS OF GEOMETRIC PROGRAMMING 3. SOME PRIMAL AND DUAL ALGORITHMS FOR POSYNOMIAL AND SIGNOMIAL GEOMETRIC PROGRAMS

In this paper we consider algorithmic and computational aspects of selected methods for posynomial and signomial programming problems. In particular, we consider the modified concave simplex method for dual posynomial programs and discuss some recent developments suggesting a new dual algorithm. We also consider linear programming based algorithms for primal posynomial programs. Finally, we discuss a recently developed branch and bound method for signomial programming.     

Calibration, Error Analysis, and Ongoing Measurement Process Monitoring for Mass Spectrometry

We consider problems of quantifying and monitoring accuracy and precision of measurement in mass spectrometry, particularly in contexts where there is unavoidable day-to-day/period-to-period changes in instrument sensitivity. First, we consider the issue of estimating instrument sensitivity based on data from a typical calibration study. Simple method-of-moments methods, likelihood-based methods, and Bayes methods based on the one-way random effects model are illustrated. Then, we consider subsequently assessing the precision of an estimate of a mole fraction of a gas of interest in an unknown. Finally, we turn to the problem of ongoing measurement process monitoring and illustrate appropriate setup of Shewhart control charts in this application.     

Satisfying partial demand in facilities location

In this paper we consider the location of new facilities which serve only a certain proportion of the demand. The total weighted distances of the served demand is minimized. We consider the problem in the plane for the location of one facility and on a network for the location of >m-facilities. Some computational experience with these models are reported.     

Entrepreneurs’ views of the gerontech market

As the population of older adults in the world grows older adults hold potential as customers for new technologies and innovations. Despite the great potential that the Gerontechnology market has, many entrepreneurs are wary of focusing their efforts towards this segment.This study examines entrepreneurs' perception of older adults as a target population for their endeavor. Using a research tool that was distributed among 100 entrepreneurs in Israel, the study examines how knowledge about aging and the aging market, ageism and personal experience influence entrepreneur's willingness to consider older adults as a target audience for their endeavor. Although the participants held ageist perceptions towards older adults, these perceptions did not influence their willingness to consider older adults as a target audience for their endeavor. Knowledge about aging and about the aging market were the strongest predictors of entrepreneurs' willingness to consider older adults as a target audience for their endeavor.     

生物序列的语义分析与第二密码规则的探索(续)

本文继续讨论蛋白质一级结构序列的语义结构,利用组合分析与图论方法讨论Swiss-Prot数据库的组合结构,给出Swiss-Prot数据库中蛋白质一级结构序列的关键词与核心词的定义、搜索算法与特性参数。并由此给出蛋白质一级结构序列的核心词词典．并由此讨论数据库的复杂性问题、同源蛋白质的分类、预测与比对等问题。     

The Buyer-Vendor Coordination Problem: Modeling Inbound and Outbound Cargo Capacity and Costs

In this paper, we generalize the deterministic demand buyer-vendor coordination problem to simultaneously consider cargo capacity constraints and general inbound/outbound transportation costs. To this end, we first consider a replenishment cost structure that includes a fixed cost as well as a stepwise inbound freight cost for the vendor. We then extend our results to consider the case where both the vendor and the buyer are subject to this freight cost structure. Hence, in the second model, both the inbound and the outbound transportation costs/constraints of the buyer-vendor pair are modeled explicitly. For each case, we provide heuristic algorithms with promising error bounds. The error bounds for these heuristic methods are 6 and 25%, respectively. Using the costs of these heuristics as upper bounds, we also develop finite time exact solution procedures.     

Standard stochastic pulse signals: Applications, reproduction, certification

We consider notions of application, modelling, and certification for stochastic pulse signals with normalized statistical characteristics as a means for monitoring metrological parameters of information measurement systems. We describe a signal model, present examples of its application, and consider a generalized functional scheme for a generator and principles for algorithmic certification of the model. Translated from Izmeritel'naya Tekhnika, No. 6, pp. 24–33, June, 1997.     

Introducing secure modes of operation for optical encryption

We analyze optical encryption systems using the techniques of conventional cryptography. All conventional block encryption algorithms are vulnerable to attack, and often they employ secure modes of operation as one way to increase security. We introduce the concept of conventional secure modes to optical encryption and analyze the results in the context of known conventional and optical attacks. We consider only the optical system "double random phase encoding," which forms the basis for a large number of optical encryption, watermarking, and multiplexing systems. We consider all attacks proposed to date in one particular scenario. We analyze only the mathematical algorithms themselves and do not consider the additional security that arises from employing these algorithms in physical optical systems.     

3种不同的高速列车头车造型仿生设计

目的探讨3种不同的高速列车头型的仿生设计方式对产品功能和性能的影响。方法根据产品和仿生对象进行耦合的内容不同进行分类,分析了3种内容侧重不同的高速列车头型仿生设计方案,并介绍了基本的设计过程。结论车头造型仿生设计的实用功能耦合要考虑生物形态的气动特性,生物形式美感耦合则注重生物的比例、曲面过渡和色彩搭配等,象征语意耦合则关心生物的象征意义。按照这3种仿生设计类型的不同特点进行设计,可以提高设计质量,加快设计速度。     

The development of a robust design methodology for time‐oriented dynamic quality characteristics with a target profile

Innovative engineering techniques are often sought within the manufacturing environment to improve product quality and promote more cost‐effective strategies. Robust design methods are frequently used to serve this purpose, with the objective of minimizing the variability inherent within a particular process or system. A review of the literature suggests that most robust design research involves the study of static quality characteristics, given a pre‐defined specification interval or region and target value. In addition to proposing a methodology for working with dynamic quality characteristics where the specifications and target value may change over time, this paper offers two other distinct contributions. First, those researchers who have examined dynamic systems traditionally consider the effects of a signal factor on a response variable on the identification of optimal factor settings. In contrast, this paper will consider the effects of a quality characteristic changing over time, thus removing the need to confine the problem to signal–response systems. Furthermore, most researchers consider the optimization of the process mean according to the costs of non‐conforming to an established specification interval or region. This paper, however, utilizes a methodology involving the simultaneous optimization of the process mean and variance while expanding the problem to consider a loss in quality attributed to deviation from a target value over time. Copyright © 2010 John Wiley & Sons, Ltd.     

Goal-oriented adaptivity based on a model hierarchy of mean-field and full-field homogenization methods in linear elasticity

Homogenization methods are drawing increasing attention for simulation of heterogeneous materials like composites. For balancing the accuracy and the numerical efficiency of such strategies, we deal with both model and discretization errors of the finite element method (FEM) on a macroscale. Within a framework of goal-oriented adaptivity, we consider linear elastic heterogeneous materials, for which first-order homogenization schemes apply. A novel model hierarchy is proposed based on mean-field and full-field homogenization methods. For the former, we consider several well-established schemes like Mori-Tanaka or self-consistent as basic models, and for the latter, as superior models, unit cell problems are solved via the FEM under an a priori chosen boundary condition. For a further stage of the model hierarchy, we consider hierarchical unit cells within the frame of the FEM toward an adaptive selection of the unit cell size. By means of several numerical examples, we illustrate the effectiveness of the proposed adaptive approach.     

Parallel-machine rescheduling with machine disruptions

In this study we consider a rescheduling problem on identical parallel machines. The rescheduling is undertaken because of a period of unavailability on one of the machines. We consider the total flow time as an efficiency measure and stability is gauged in terms of the number of jobs processed on different machines in the original and new schedules. We show that all efficient schedules with respect to efficiency and stability measures can be generated in polynomial time.     

Nucleation in Quantum Liquids

In order to understand how nucleation proceeds in quantum liquids such as ⁴He and ³He, and the peculiarities of such quantum systems, I present a review of nucleation in condensed matter. By describing successive experiments, I first illustrate the interest and use of the elementary "standard theory" of nucleation. Then I consider its limitations and the existence of "spinodal" and instability limits, possibly in the frame of "density functional" methods. When finally discussing nucleation at low temperature, I consider a further improvement of the standard theory, namely the possibility of nucleation by quantum tunneling. The main emphasis is on crystallization and cavitation in liquid helium, but I also consider water, liquid hydrogen, wetting, the nucleation of steps on crystal surfaces, vortices etc.     

基于截面组合法和截面弹簧刚度考虑跨内塑性铰的钢框架高等分析

采用截面组合法推导工字形或H形截面的屈服方程, 并在端部和跨内分别假想有一个零长度的弹簧考虑截面的刚度, 提出了有分布荷载作用的杆件仅使用一个单元就能准确模拟跨内塑性铰的钢框架高等分析方法。通过对引入的非节点自由度进行凝聚, 使得所提出的单元与常规单元具有相同的节点自由度。该方法还利用稳定函数考虑单元的剪切变形和几何非线性、初始屈服方程中考虑残余应力、折减弹性模量法考虑初始缺陷。算例结果表明, 采用所提出的方法可得到高效率和高精度的结果。     

Second Sound in a Strongly Anisotropic System of Quasiparticles in He(II)

In this paper we consider the problem of second sound propagation in a quasiparticle system which has a high level of anisotropy. The main aim of the research is to derive an exact expression for the second sound velocity in such a system, which is valid for any value of the velocity of the quasiparticle system relative to the superfluid. We can then consider the propagation of thermal perturbations in anisotropic systems of both phonons and rotons in He(II). We compare the results with previous     

The Layout of Divisible Activities on the Line

We consider the layout of divisible activities on the line. Each activity is divisible in the sense that it may be a collection of disjoint intervals, with the sum of the lengths of the intervals being known. We construct objective functions involving measures of costs proportional to distances between activities, establish that to find optimal layouts it is enough to consider only symmetric layouts, and present algorithms for choosing best symmetric layouts.     

The value of updated information on future price behaviour

This paper studies the value of information on future price behaviour. We consider a one-period inventory modelling framework with random period length and two order opportunities. The selling price is determined dynamically and the demand is price-sensitive. The second ordering-pricing decision reflects the updated information on future price behaviour on supply chain flexibility. We consider three models with different levels of flexibility: the static model, the quantity flexible model and the combined quantity and timing (fully) flexible model. We compare between the values of three different features in the supply chain: updated information on price behaviour, dynamic pricing and supply flexibility. And we demonstrate the effect of holding cost and demand uncertainty on these three values. We also consider a specific condition with fixed selling prices. We give explicit analysis on the optimal order decisions, and analytically show the impact of information and quantity flexibility on the optimal order decisions.     

Biomechanics of the cardiovascular system: the aorta as an illustratory example.

Biomechanics relates the function of a physiological system to its structure. The objective of biomechanics is to deduce the function of a system from its geometry, material properties and boundary conditions based on the balance laws of mechanics (e.g. conservation of mass, momentum and energy). In the present review, we shall outline the general approach of biomechanics. As this is an enormously broad field, we shall consider a detailed biomechanical analysis of the aorta as an illustration. Specifically, we will consider the geometry and material properties of the aorta in conjunction with appropriate boundary conditions to formulate and solve several well-posed boundary value problems. Among other issues, we shall consider the effect of longitudinal pre-stretch and surrounding tissue on the mechanical status of the vessel wall. The solutions of the boundary value problems predict the presence of mechanical homeostasis in the vessel wall. The implications of mechanical homeostasis on growth, remodelling and postnatal development of the aorta are considered.     

压弯钢构件火灾下的极限稳定性分析

为考虑温度对材料性质的影响以及不同的温度载荷效应,基于有限积分法建立了压弯钢构件火灾下的非线性分析格式;在此基础上,利用杆件分析法考虑了钢构件火灾下的几何效应,就初始缺陷等因素对构件极限的影响进行了分析,探讨了反映火灾下钢构件响应机制的温度与变形等相关变量之间的关系。本文方法与试验进行了比较,计算结果验证了方法的有效性。     

A case for trading risk in complex conceptual design trade studies

Complex conceptual system design trade studies traditionally consider risk after a conceptual design has been created. Further, one person is often tasked with collecting risk information and managing it from each subsystem. This paper proposes a method to explicitly consider and trade risk on the same level as other important system-level variables during the creation of conceptual designs in trade studies. The proposed risk trading method advocates putting each subsystem engineer in control of risk for each subsystem. A risk vector is proposed that organizes many different risk metrics for communication between subsystems. A method of coupling risk models to dynamic subsystem models is presented. Several risk visualization techniques are discussed. A trade study example is presented based upon a simplified spacecraft model. Results from introducing the risk trading methodology into a simulated Collaborative Design Center are presented. The risk trading method offers an approach to more thoroughly consider risk during the creation of conceptual designs in trade studies.