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Systematic transient analysis in water supply systems is intended to determine the reliability of water supply and the integrity of hydraulic devices when hydraulic transients (i.e., water hammers) occur. In the analysis, parameters such as wavespeed, pipe diameter, friction, and others, usually considered as known inputs in traditional water hammer models, are actually subject to uncertainties due to natural or human behaviors. The paper considers these uncertainties and investigates their effects on the reliability of water transportation systems and water supply networks under transient conditions with or without protection devices. In addition, the optimization of transient protection devices is also evaluated based on the probabilistic analysis. The results show that the probabilistic analysis method could inspect the influence of the different input uncertainties on the system responses under transient conditions and provide detailed information on the design for water supply systems and protection devices. A one-dimensional water hammer model of pipe fluid systems and Monte Carlo simulation method are used in this investigation. DOI: 10.1061/(ASCE)WR.1943-5452.0000074 CE Database subject headings: Probability; Design; Optimization; Water supply; Water distribution systems; System reliability. Author keywords: Probabilistic analysis; Transient design; Optimization; Water supply system; System reliability.

The implicit goal of water network design is to provide acceptable service during normal and peak demands and to limit damages to property and people during fires. Despite this, fire damages are seldom explicitly included in network design. This paper presents a single-objective particle swarm optimization program that incorporates a new measure of expected conditional fire damages to size local water distribution mains for fire flow protection in residential service areas. The optimization approach generates trade-off information to help utilities determine the cost effectiveness of adding new pipe capacity to reduce the risk of fire damages in water networks. The optimization program was applied to an 8-pipe network and a 34-pipe network to generate trade-off curves for pipe cost and tire damages. A sensitivity analysis indicated that the level of uncertainty in fire flow had a little impact on pipe sizing and cost in the eight-pipe network. Optimization results in the 34-pipe network supported the industry practice of using a minimum 150- mm distribution main sizing to provide fire flow protection. DOI: 10.1061/(ASCE)WR.1943-5452.0000075 CE Database subject headings: Water distribution systems; Design; Optimization; Fires. Author keywords: Water distribution systems; Optimization; Fires; Damage.

As voice coil motor (VCM) type actuators were miniaturized and high performance was required, the necessity of an integrated design method was felt keenly instead of a general sequential design method. And, it was checked that the integrated design method based on accurate FE analyses were needed in ODD mainly using VCM type actuators as mobile devices were diversified. In this paper, the integrated design method based on the coupled-field-analysis is suggested. First, the coupled-field-analysis that can precisely analyze dynamic characteristics of multi-axis VCM type actuators was systemized through the verification model to obtain the base of the integrated design method. The design procedure that were proper for multi-axis VCM type actuators was analyzed considering design variables, objective functions, and constraints. To check superiorities of the integrated design method, this method was applied to the real development of three VCM type actuators. Finally, it was checked that the integrated design method based on the coupled-field-analysis was superior to the sequential design method through application examples. Index Terms--Actuators, design, electromagnetic analysis, finite element methods, optimization methods.

In this paper, we propose an efficacious memory array design method for low temperature poly-silicon technique. According to the four steps of our suggested method, we can draw a regular layout form of memory array. The regular property allows both ready calculation of the layout area and easy design of the memory controller. Since our proposed method does not leave any gaps in our layout, it is a powerful way to save area in the LTPS technique. It is also suitable for an electronic design automation (EDA) tool to implement a memory compiler with systematic and required size memory IP. Since the true single phase clock (TSPC) master-slave latch (MSL) is a fast and simple structure to implement a clocked storage element, we use TSPC-MSL as our memory cells to increase working frequency by a wide margin. Furthermore, according to our oblique memory array design method, we propose a verification formula to double-check whether our design is optimal or not at any time. Index Terms--LTPS, memory array design, memory layout, TSPC.

This paper suggests a design methodology for slider air bearings over a discrete track recording (DTR) disk using a simplified static analysis including the flying-height (FH) loss equation instead of a computationally expensive, time consuming transient dynamic analysis. Because a slider over a DTR disk has different flying characteristics than a slider over a continuous track recording (CTR) disk, the design of the slider requires modification. However, it is challenging to dynamically simulate slider air bearings over a DTR disk. Furthermore, it is nearly impossible to design the slider using an expensive dynamic analysis as a solver. Therefore, we define the flying characteristics of the DTR slider as a function of that of the CTR slider by using the FH loss equation based on averaged flow effect. A design optimization problem is formulated to meet the design requirements of the DTR slider, which include target FH, FH flatness, altitude FH drop, pitch and roll angle ranges, and altitude pitch drop. The design problem is changed to an inverse problem using a conventional static analysis for a CTR disk instead of an expensive dynamic analysis for a DTR disk. Simulation results showed that the optimally designed DTR slider can meet the target FH while satisfying all design requirements over the entire recording band. Index Terms--Design optimization, discrete track recording (DTR), patterned groove, slider air bearing.

In genetic algorithm (GA) based topology optimization problems, characteristics of an initial population are important for the rapid and stable convergence. This paper introduces an algorithm generating randomly an initial population with superior hereditary characteristics. To avoid the generation of small structural spots, the blurring technique is proposed. The connectivity of seed elements considerging the magnetic flux flow in the design domain is focused. Differently from the classical GA by linear strings, this study deals with two-dimensonal chromosomes and the geographic crossover method to increase the diversity of offspring. The proposed design algorithm is applied to the yoke optimization of magnetic actuators. Index Terms--Finite-element analysis, genetic algorithm, structural connectivity, topology optimization.

It is necessary to develop a perpendicular magnetic recording head for the high magnetic field density of the recording region with small magnetic field leakage. This work suggests a topology design of the perpendicular magnetic recording head based on the density method. In order to determine the shape of a magnetic head with the return yoke, the topology optimization method is combined with the finite element method. Obtained results are also compared with results of the previous studies. Index Terms--Perpendicular magnetic recording system, recording head shape design, sensitivity analysis, topology optimization.

A multivariable and multiobjective organic light emitting diode (OLED) design and optimization procedure is presented that produces a microcavity OLED with optimal optical and electrical characteristics. We propose here a design procedure that splits the design process into two design stages where each stage can be optimized independently. In the first stage we design the OLED with optimal electrical and optical performance, where the mirrors are specified by their optimal spectral reflectivity, transmissivity, absorptance, and the phase shift on reflection. In the second stage we synthesize the top and the bottom multilayer mirrors with a minimal number of layers that satisfy the required optimal spectral dependencies determined in the first part of the design process. As a case study we presentan optimized design for a top-emitting OLED with a simple bilayered cavity consisting of N, N'-di(naphthalene-l-yl)-N, N'-diphenylbenzidine (NPB) as the hole transport layer and tris(8-hydroxyquinoline)aluminium ([Alq.sub.3]) as the electron transport layer. Conventional devices with an ITO--LiF/Al electrode pair and a Ag--Ag electrode pair are used as reference devices to benchmark the performance of our design. Electrical simulations using the drift-diffusion model and optical simulations employing the integrated dipole antenna approach are implemented to test the performance of the devices. The optimized device shows improved optical and electrical performance when compared with the reference devices. OCIS codes: 310.4165, 250.0250.

We propose an optical design for miniature 2.5x zoom fold optics with liquid elements. First, we reduce the volumetric size of the system. Second, this newly developed design significantly reduces the number of moving groups for this 2.5x miniature zoom optics (with only two moving groups compared with the four or five groups of the traditional zoom lens system), thanks to the assistance of liquid lens elements in particular. With regard to the extended optimization of this zoom optics, relative illuminance (RI) and the modulation transfer function (MTF) are considered because the more rays passing through the edge of the image, the lower will be the MTF, at high spatial frequencies in particular. Extended optimization employs the integration of the Taguchi method and the robust multiple criterion optimization (RMCO) approach. In this approach, a Pareto optimal robust design solution is set with the aid of a certain design of the experimental set, which uses analysis of variance results to quantify the relative dominance and significance of the design factors. It is concluded that the Taguchi method and RMCO approach is successful in optimizing the RI and MTF values of the fold 2.5x zoom lens system and yields better and more balanced performance, which is very difficult for the traditional least damping square method to achieve. OCIS codes: 110.0110, 120.3620, 220.1000, 220.0220.

We propose and optimize a hybrid erbium-doped fiber amplifier/fiber Raman amplifier (EDFA/FRA). A large number of parameters of a wide-band hybrid amplifier consisting of an erbium-doped fiber amplifier (EDFA) and a fiber Raman amplifier (FRA) have been optimized using an effective and fast global optimization method called particle swarm optimization. Two types of hybrid EDFA/FRA with six- and 10-pumped FRAs have been optimized. A large number of variables affect the hybrid EDFA/FRA performance, thus we need a global optimization method to be able to deal with these variables. Particle swarm optimization helps us to find optimum parameters of a hybrid EDFA/FRA and reduce the gain spectrum variations to 2.91 and 2.03 dB for the six and 10 pumped FRAs, respectively. The optimum design supports the amplification of 60 signal channels in the wavelength range of 1529.2-1627.1 nm for a wavelength-division multiplexing system. OCIS codes: 060.2310, 060.2320.

The design process is difficult to accelerate due to its iterative nature, which increases project cost and delays completion time of a design project. Many previous studies tried to find the optimal structure and sequence of a design process minimizing iteration. In a multiproject environment, however, waiting time caused by resource shortage is a more critical reason for a lengthy project than iteration time. In this paper, we propose a novel sequencing method that reduces waiting time in a multiproject environment by dynamically changing the sequence of design tasks, according to availability of resources. It is called a dynamic sequencing method, as opposed to the traditional static sequencing method by which every design project follows a predefined optimal sequence. In order to evaluate the effect of this method, we developed a design-process model for simulating iteration and waiting in a multiproject environment. The simulation results show that dynamic sequencing is significantly better than traditional static sequencing with respect to average duration of projects. It is noted that more significant improvements can be obtained for the bottlenecked and unbalanced processes, both of which conditions would otherwise have negative effects on process performance. [DOI: 10.1115/1.3066599] Keywords: design process, multiproject environment, dynamic sequencing, DSM, stochastic processing network

This paper presents a computational method to design a compliant finger for robotic manipulations. As traditional mechanical fingers require bulky electromagnetic motors and numerous relative moving parts to achieve dexterous motion, we propose a class of fingers; the manipulation of which relies on finger deflections. These compliant fingers are actuated by shape memory alloy (SMA) wires that exhibit high work-density, frictionless, and quiet operations. The combination of compliant members with embedded SMA wires makes the finger more compact and lightweight. Various SMA wire layouts are investigated to reduce their response time while maintaining sufficient output force. The mathematical models of finger deflection caused by SMA contraction are then derived along with experimental validations. As finger shapes are essential to the range of deflected motion and output force, we find its optimal initial shapes through the use of a shape parametrization technique. We further illustrate our method by designing a humanoid finger that is capable of three-dimensional manipulation. Since compliant fingers can be fabricated monolithically, we expect the proposed design method to be utilized for applications of various scales. [DOI: 10.1115/1.3042152] Keywords: compliant mechanisms, shape memory alloy, shape optimization, robotic finger

A spot-shadowing technique to mitigate damage growth in a high-energy laser is studied. Its goal is to minimize the energy loss and undesirable hot spots in intermediate planes of the laser. A nonlinear optimization algorithm solves for the complex fields required to mitigate damage growth in the National Ignition Facility amplifier chain. The method is generally applicable to any large fusion laser. OCIS codes: 140.3280, 220.1230.

Previous research has shown that weakening of inelastic structures can limit the maximum response accelerations they experience during ground motions, but may lead to an increase in the displacements (or interstory drifts). Added damping by using fluid viscous devices, on the other hand, reduces the interstory drifts and has no significant effect on total accelerations, when structures behave inelastically. The weakening and damping technique, thus, limits the total acceleration due to the weakening, and reduces the interstory drifts by adding damping, and hence addresses the two main causes for both structural and nonstructural damage in buildings. Optimal weakening and damping, which is the subject of this paper, involves the determination of the optimal locations and amount of weakening of the structural components as well as the optimal locations and magnitudes of added dampers. Weakening of the structure might create stability issues in the building that can be automatically considered, if active control theory is used for design. Based on a nonlinear active control procedure, control forces are calculated and implemented using equivalent passive dampers and weakening elements in order to achieve the closest effects. The methodology is applied to a case study of an eight-story nonlinear building tested using a set of ground motions corresponding to different hazard levels. Results show that the optimal design leads to a reduction of both peak interstory drifts and peak total accelerations. DOI: 10.1061/(ASCE)0733-9445(2008)134:10(1638) CE Database subject headings: Optimization; Seismic effects; Damping; Inelasticity; Ground motion.

Real-time reservoir operation models carried out under short operating horizons have no information about the seasonal changes in streamflow. The overall operation may improve provided that long-term information can be incorporated into the short-term process. This paper proposes a procedure that attempts to do such incorporation by means of stochastic and deterministic optimization. Long-term (monthly) and short-term (daily) reservoir inflow forecasts are assumed to be uncertain and reliable, respectively. The idea is to first solve a monthly operation model by an explicit stochastic programming approach and then use its information to guide the daily operation, which is solved by deterministic optimization. The monthly information will decide whether hedging should start being implemented during the daily operation in order to mitigate a potential future shortage. This stochastic-deterministic procedure is applied to a case study in Japan and the results show that it provides operating rules relatively similar to the ones obtained when perfect forecasts are used for the monthly inflows. CE Database subject headings: Reservoirs; Optimization models; Stochastic models; Water supply; Japan; Case reports.

Powerful simulation/optimization (S/O) models exist for designing groundwater well systems and pumping strategies. However, it can be challenging to use S/O modeling effectively for large, complex, and computationally intensive problems within project time and cost constraints. Here, we present a generic two-stage optimization procedure for making S/O modeling more practical. Application is illustrated for developing optimal transient 30-year pump-and-treat designs for Blaine Naval Ammunition Depot (NAD), Nebraska, and using an innovative hybrid advanced genetic algorithm with tabu search features (AGT). AGT includes standard genetic algorithm and tabu search features plus healing, elitism, threshold acceptance, and a new subset/subspace decomposition optimization. The screening stage simplifies the optimization problem, and selects desirable remediation wells from among many candidates. During this stage, computational effort is lessened by reducing the number of state variables needing evaluation, and the solution space dimensionality (including temporal dimensions). Subset/subspace decomposition optimization of steady flow rates is used to identify desirable sets of candidate wells. The transient optimization stage develops mathematically optimal time-varying pumping rates for well subsets identified by the screening stage. It also includes reoptimization using the original objective function plus goal programming to increase strategy robustness. Initializing the AGT with feasible solutions reduces computational effort. Within a short period the procedure developed optimal pump and treat system designs for NAD. The procedure yields better objective function values than trial and error. Because optimization causes tight constraints, the computed strategy is sensitive to changes in model parameters. Increasing strategy robustness via AGT and goal programming degrades the value of the initial objective function. CE Database subject headings: Groundwater management; Optimization; Groundwater pollution; Remedial action; Plumes; Wells; Pumps.

Process parameter optimization has been widely investigated in single-tool machining operations. However; for multitool machining operation optimization, the research reported in literature is scarce. In this paper, a novel heuristic algorithm based on particle swarm optimization (PSO) is proposed to optimize, in terms of minimum machining time, the process parameters for two-tool parallel turning operations with n features. Both single-pass and multipass operations are considered. The simulation results show that the performance of the proposed algorithm, in terms of mini machining time and required computational time, is superior to an exhaustive search algorithm. [DOI: 10.1115/1.2823077]

Solar thermal electricity (STE) generation offers an excellent opportunity to supply electricity with a non-C[O.sub.2] emitting technology. However, present costs hamper widespread deployment and therefore research and development efforts are concentrated on accelerated cost reductions and efficiency improvements. Many focus on the latter, but in this paper we rather focus on attaining very low levelised electricity costs (LEC) by designing a system with very low material cost, while maintaining appreciable conversion efficiency and achieving low maintenance cost. All investigated designs were dimensioned at a 50 MW scale production. Calculated LECs show that a new proposed hybrid of ocean thermal energy conversion with an offshore solar pond (OTEC-OSP) may have the lowest LEC of 0.04 [euro]/kWh. Addition of a floating offshore solar pond (OSP) to an OTEC system increases the temperature difference in the Rankine cycle, which leads to an improved efficiency of 12%, while typical OTEC efficiencies are 3%. This higher efficiency leads to much lower investments needed for power blocks, while the OSP is fabricated using very low-cost plastic foils. The new OTEC-OSP design can be located in many sunny coastal areas in the world. Keywords: Ocean thermal energy conversion; Solar pond: Solar thermal electricity; Cost optimization

Simple formulas are often used to estimate the sensitivity of coded mask x-ray or gamma-ray telescopes, but these are strictly applicable only if a number of basic assumptions are met. Complications arise, for example, if a grid structure is used to support the mask elements, if the detector spatial resolution is not good enough to completely resolve all the detail in the shadow of the mask, or if any of a number of other simplifying conditions are not fulfilled. We derive more general expressions for the Poisson-noise-limited sensitivity of astronomical telescopes using the coded mask technique, noting explicitly in what circumstances they are applicable. The emphasis is on using nomenclature and techniques that result in simple and revealing results. Where no convenient expression is available a procedure is given that allows the calculation of the sensitivity. We consider certain aspects of the optimization of the design of a coded mask telescope and show that when the detector spatial resolution and the mask to detector separation are fixed, the best source location accuracy is obtained when the mask elements are equal in size to the detector pixels. OCIS codes: 340.7430, 100.1830, 110.4280.

The design of multilayer mirrors with more than two materials is one of the key technologies for investigating lithography. We study a new procedure for optimizing multilayer mirrors of different combinations of materials at a wavelength of 13.4nm. By adding Be and C layers in different orders to a Si/Mo stack, we have observed enhancement of the reflectivity and a reduction in the number of layers. The Luus-Jaakola optimization procedure has been implemented for the global optimization of the multi-layer mirrors. With this algorithm it is not necessary to specify initially the number of layers present in a given design. OCIS codes: 310.0310, 340.0340.

System power reliability under varying weather conditions and the corresponding system cost are the two main concerns for designing hybrid solar-wind power generation systems. This paper recommends an optimal sizing method to optimize the configurations of a hybrid solar wind system employing battery banks. Based on a genetic algorithm (GA), which has the ability to attain the global optimum with relative computational simplicity, one optimal sizing method was developed to calculate the optimum system configuration that can achieve the customers required loss of power supply probability (LPSP) with a minimum annualized cost of system (ACS). The decision variables included in the optimization process are the PV module number, wind turbine number, battery number, PV module slope angle and wind turbine installation height. The proposed method has been applied to the analysis of a hybrid system which supplies power for a telecommunication relay station, and good optimization performance has been found. Furthermore, the relationships between system power reliability and system configurations were also given. Keywords: Hybrid solar--wind system; Optimization; LPSP; Annualized cost of system; Genetic algorithm

This paper deals with the design optimization problem of a structural-acoustic system in the presence of uncertainties. The uncertain vibroacoustic numerical model is constructed by using a recent nonparametric probabilistic model which takes into account model uncertainties and data uncertainties. The formulation of the design optimization problem includes the effect of uncertainties and consists in minimizing a cost function with respect to an admissible set of design parameters. The numerical application consists in designing an uncertain master structure in order to minimize the acoustic pressure in a coupled internal cavity, which is assumed to be deterministic and excited by an acoustic source. The results of the design optimization problem, solved with and without the uncertain numerical model show significant differences. [DOI: 10.1115/1.2827988] Keywords: robust design, model uncertainties, structural acoustics

The dynamic response of a radio-frequency (RF) microelectromechanical system to a time-varying electrostatic force is optimized to enhance robustness to variations in material properties and geometry. The device functions as an electrical switch, where an applied voltage is used to close a circuit. The objective is to minimize the severity of the mechanical impact that occurs each time the switch closes because severe impacts have been found to significantly decrease the life of these switches. Previous works have demonstrated that a classical vibro-impact model, a single-degree-of-freedom oscillator subject to mechanical impact with a single rigid barrier, captures the relevant physics adequately. Certain model parameters are described as random variables to represent the significant unit-to-unit variability observed during fabrication and testing of a collection of nominally identical switches; these models for unit-to-unit variability are calibrated to available experimental data. Our objective is to design the shape and duration of the voltage waveform so that impact kinetic energy at switch closure is minimized for the collection of nominally identical switches, subject to design constraints. A voltage waveform designed using a deterministic model for the RF switch is found to perform poorly on the ensemble. An alternative waveform is generated using the proposed optimization procedure with a probabilistic model and is found to decrease the maximum impact velocity by a factor of 2 relative to the waveform designed deterministically. The methodology is also applied to evaluate a design change that reduces the impact velocity further and to predict the effect of fabrication process improvements. [DOI: 10.1115/1.2827981] Keywords: MEMS dynamics, input shaping, nonlinear dynamics, vibro-impact system, reduced-order modeling

In some industrial applications, influence coefficient balancing methods fail to find the optimum vibration reduction due to the limitations of the least-squares optimization methods. Previous min-max balancing methods have not included practical constraints often encountered in industrial balancing. In this paper, the influence coefficient balancing equations, with suitable constraints on the level of the residual vibrations and the magnitude of correction weights, are cast in linear matrix inequality (LMI) forms and solved with the numerical algorithms developed in convex optimization theory. The effectiveness and flexibility of the proposed method have been illustrated by solving two numerical balancing examples with complicated requirements. It is believed that the new methods developed in this work will help in reducing the time and cost of the original equipment manufacturer or field balancing procedures by finding an optimum solution of difficult balancing problems. The resulting method is called the optimum min-max LMI balancing method. [DOI: 10.1115/1.2730535] Keywords: rotors, mechanical balancing, influence coefficient method, optimization

The efficient and effective search for the optimum design solution of a water distribution network using genetic algorithms (GAs) is governed by several factors such as representation scheme, population size, hydraulic simulation model, fitness function, penalty method, GA operators, number of generations, and more importantly the size of the search space. This paper proposes a modified GA that uses basic operators along with their derivatives randomly. Further, a methodology based on critical path method is suggested to reduce the search space. A software tool, GA-WAT, based on the proposed methodology is developed and first tested and verified for its efficiency and effectiveness on two previously published single source networks. Later, it is applied to the optimal design of a larger, two-source hypothetical network. The results obtained indicate that the modified GA with reduction in search space proposed herein is more effective, especially for large practical networks. CE Database subject headings: Water distribution systems; Optimization; Design; Algorithms; Pipe networks; Water supply.

In this article, we show that the manufacturing target for a product characteristic affected by degradation is not the value that maximizes the quality of the product. By sacrificing some quality at the manufacturing stage it is possible to increase the product's lifetime and thus reduce the quality loss over a long period. We propose a procedure for finding the optimal manufacturing target that maximizes both quality and reliability of the product. Keywords: Manufacturing target, product design, quality, reliability, 1. Introduction Many characteristics of a product are subject to degradation. During the product usage, those characteristics degrade, resulting in the deterioration of the product's performance. How should we set [...]

Abstract: Air-breathing divers should attempt to maximize foraging efficiency under the constraint of limited oxygen availability. For diving water birds, high buoyancy (owing to the air in the plumage) and [...]

The drive for energy independence has created a window of opportunity for innovations in oil recovery. New artificial lift methods like progressing cavity pumping have been successfully applied to downhole pumping applications. The multilobe pumps are also making inroads into the industry to be used under different operating conditions. Although the design has been mainly based on empirical standards and trial and error modifications, a more phenomenally optimum design of the pump is required to achieve a high efficiency standard. The optimal relationship between the pitch and the diameter of the housing is obtained to achieve a maximum flow rate for multilobe pumps. [DOI: 10.1115/1.2358142]

The hybrid cellular automaton (HCA) algorithm is a methodology developed to simulate the process of structural adaptation in bones. This methodology incorporates a distributed control loop within a structure in which ideally localized sensor cells activate local processes of the formation and resorption of material. With a proper control strategy, this process drives the overall structure to an optimal configuration. The controllers developed in this investigation include two-position, proportional, integral and derivative strategies. The HCA algorithm combines elements of the cellular automaton (CA) paradigm with finite element analysis (FEA). This methodology has proved to be computationally efficient to solve topology optimization problems. The resulting optimal structures are free of numerical instabilities such as the checkerboarding effect. This investigation presents the main features of the HCA algorithm and the influence of different parameters applied during the iterative optimization process. [DOI: 10.1115/1.2336251]

In this paper, a class of nonlinear minimum mean-squared error multiuser detectors is derived based on a multivariate Gaussian approximation of the multiple-access interference for large systems. This approach leads to expressions identical to those describing the probabilistic data association (PDA) detector, thus providing an alternative analytical justification for this structure. A simplification to the PDA detector based on approximating the covariance matrix of the multivariate Gaussian distribution is suggested, resulting in a soft interference-cancellation scheme. Corresponding multiuser soft-input, soft-output detectors delivering extrinsic log-likelihood ratios are derived for application in iterative multiuser decoders. Finally, a large-system performance analysis is conducted for the simplified PDA, showing that the bit-error rate (BER) performance of this detector can be accurately predicted and related to the replica method analysis for the optimal detector. Methods from stalistical neurodynamics are shown to provide a closely related alternative large-system prediction. Numerical results demonstrate that for large systems, the BER is accurately predicted by the analysis and found to be close to optimal performance. Index Terms--Code-division multiple access (CDMA), Gaussian approximation (GA), large-system analysis, multiuser detection, optimum detection.

Abstract: Software rejuvenation is a preventive and proactive maintenance policy that is particularly useful for counteracting the phenomenon of software aging. In this study we consider an operational software system [...]

Research into the development of an optimization model to aid the formulation of IS strategy. The research outlines an industrial case study which validates the use of a Linear Goal Programming mathmatical approach to analyze IS investment projects.

This paper presents a gradient-based parameter optimization method to find the optimal compensator that minimizes the standard deviation ([[sigma].sub.PES]) of the position error signal (PES) in a hard disk drive servo system. By using the plant response data and the PES gradient information based on the nominal plant model, optimal digital controllers that minimized the 3[[sigma].sub.PES] of a plant with uncertainty were selected within a pre-found robust stable region. As a result, an optimal track-following controller that minimized the standard deviation of the measured PES ([[sigma].sub.PESm]) was able to be obtained without the prior knowledge of the disturbance and noise model. Furthermore, we proved that if the measurement noise is white, an optimal controller that minimizes the 3[[sigma].sub.PESm] also minimizes the 3[[sigma].PES]. Both simulation and implementation results suggest that such a gradient-based search process is faster than nongradient optimization methods such as Random Neighborhood Search and genetic algorithms. Index Terms--Gradient method, hard disk drive (HDD) servo, optimization, track mis-registration (TMR).

This paper is concerned with designing an optimum composite flexible wing structure to enhance flutter speed by imposing modal frequency distribution constraints and comparing it with an optimum design obtained with the flutter velocity constraint. The composite wing is subjected to three flight conditions to satisfy stress constraints in addition to modal frequency distribution or flutter constraints. The multidisciplinary optimization system ASTROS was used for this study. This study indicates that flutter velocity of a wing structure can be enhanced with less increase in the weight of the structure by using frequency distribution constraints than flutter velocity constraint. In the case of a design with modal frequency constraints, the distribution of the [+ or -] 45[degrees] and 90[degrees] fiber layers provided required stiffness distribution in order to produce an acceptable solution with less increase in weight than the design obtained with flutter velocity constraint. It is speculated that the required stiffness change in order to achieve necessary modal frequency separation can be achieved to prevent flutter by providing a system of 'smart' actuating elements distributed within the internal substructure of a wing. DOI: 10.1061/(ASCE)0893-1321 (2003)16:1(19) CE Database keywords: Flutter; Frequency distribution; Composite structures.

Many engineering optimization problems require the calculation of eigenvalue sensitivities. Several straightforward methods have been developed for calculating partial derivatives of distinct complex eigenvalues. Recent work has expanded these methods to include systems with repeated real eigenvalues. A new method is presented that embeds eigenvalue derivative computation into an established numerical eigenvalue algorithm, namely, QR decomposition. The technique is shown to have computational advantages for high-order systems.

This work demonstrates the successful synthesis of path generating compliant mechanisms by the process of topology and shape design optimization. As geometric topology variation of continuum structures is difficult to treat and analysis of the displacement path or trajectory of such structures is computationally intensive, a highly effective and efficient optimal design procedure is needed. This paper describes the use of a recently developed morphological geometric representation scheme coupled with an evolutionary algorithm to synthesize the mechanism. The scheme uses arrangements of skeleton and 'flesh' to define structural geometry, which facilitates transmission of topological/shape characteristics across generations in the evolutionary process and will not render any geometrically invalid designs. The evolutionary algorithm solves the problem as a discrete optimization problem, with a proficient constraint handling capability. [DOI: 10.1115/1.1480818]

Design problems for machine products are generally hierarchically expressed. With conventional product optimization methods, however, it is difficult to concurrently optimize all design variables of portions within such hierarchical structures. This paper proposes a design optimization method using genetic algorithms containing hierarchical genotype representations, so that the hierarchical structures of machine system designs are exactly expressed through genotype coding, and optimization can be concurrently conducted for all of the hierarchical structures. Crossover and mutation operations for manipulating the hierarchical genotype representations are also developed. The proposed method is applied to a machine-tool structural design and a 2 DOF robot arm design to demonstrate its effectiveness. [DOI: 10.1115/1.1486013]

A study of aircraft structures is presented with reference to the use of aeroservoelastic analysis. The performance of design optimization is examined and verified experimentally.

Research is presented describing how high-temperature superconducting power transformers are designed to optimize performance. The most effective design in terms of low load and non-load losses must take into account the transformer volume and the voltage of the impedance.

Though many methods of system identification are currently available for parameter estimation of structural systems, the challenge lies in the numerical difficulty in convergence when the number of unknowns is large. In this study, the genetic algorithms (GA) approach is adopted, which has several advantages over classical system identification techniques. Nevertheless, if applied directly, this approach requires tremendous computational time when dealing with structural systems large in both unknowns and degrees of freedom. A method is proposed herein to alleviate this problem by conducting a GA search in modal domains of a much smaller dimension than the physical domain. The objective function is defined based on the estimated modal response in time domain and the corresponding modal response transformed from the measured response. With some modification, this method also works well even with incomplete response measurement. Numerical examples of structural systems of up to 50 degrees of freedom are presented. Effects of measurement noise are considered.

A simplified optimization procedure is described for a novel fiber reinforced plastic bridge system. The bridge system is modeled using a transformed anisotropic plate that is discretized using the Ritz method. This provides a structural model that is incorporated into a stiffness-based optimization algorithm using the optimality criteria method. The resulting procedure provides a useful design tool that can be used to produce a minimum weight design without resorting to finite-element analysis, which is only used to check the strength of the final design. A two-lane highway bridge serves as a demonstration problem.

Linear buckling of column structures is an important design constraint in many structures, particularly where weight is a primary concern. Active strengthening is the application of feedback control to increase the critical buckling load of the structure. An important feature of this control problem is that the structure is inherently unstable when the axial load surpasses the critical buckling load. This research presents a design method for creating optimal buckling control systems using state or static output feedback. The primary feature of this method is the ability to select the designed closed loop, actively strengthened, critical buckling load. The stability of the resulting controllers is determined using Lyapunov methods. Simulation and experimental demonstration of this algorithm is performed using a column employing piezoelectric actuators, and MEMS-based strain sensors. The optimal buckling controllers developed are able to increase the critical buckling load by a factor of 2.9. The closed loop system is able to support lower axial loads indefinitely (>30 min).

A simulated annealing-based heuristic has been developed to obtain the least-cost design of a looped water distribution network. A Newton search method was used to solve the hydraulic network equations. Simulated annealing is a stochastic optimization method that can work well for large-scale optimization problems that are cast in discrete or combinatorial form, as with the problem proposed. The results obtained with this approach for networks currently appearing in the literature as case studies in this field (whose solution by other optimization methods was known) have proved the ability of the heuristic to handle this kind of problem.

An optimal input design technique was tested in flight using a computerized system. The theory of the optimal input design technique is described and The F-18 High Alpha Research Vehicle (HARV) test aircraft is discussed. The optimal input was found to decrease estimated parameter standard errors by about 20%, improving to around 72% for a longitudinal case. Properly designed, a 3-2-1-1 input can provide good performance relative to the optimal square wave.

Two different applications of the reasonable design approach to the multidisciplinary optimization of a high-speed civil transport model are described. These include the creation of a response surface approximation for structural bending material weight, and the creation of response surface approximations for components of aerodynamic drag. The advantages of using reasonable surface models created via the reasonable design space approach are discussed.

The design optimization of a blade-stiffened composite panel is described. A A one-dimensional resin infusion model has been developed to calculate the infiltration time of the resin into a fabric form of the panel. The effects of design variables and manufacturing process variables on structural performance were determined. A simplified buckling analysis model was also developed to calculate the critical buckling loads, and minimized the panel mass subject to buckling constraints.

The applications of disciplinary modeling and optimization methods and frameworks for space transportation systems conceptual design and analysis are presented. The physics-based and empirical models in space transportation design analyses are described. Two general schemes for the integration of these models into computational frameworks for automated vehicle synthesis and optimization, and the optimization approaches used are described.

A multimodel and multiobjective formulation of the servostructural optimization problem in aircraft preliminary design is presented. The scheme involved the simultaneous treatment of structural and control variables along with constraints and objective factors related to various aeroservoelastic and structural performances. The computational part of optimization process has been shortened by adopting reduced-order models.