Alternative Design Concepts Research Articles

Practical Seakeeping Performance Measures for High Speed Displacement Vessels

The seakeeping performance of high-speed displacement vessels is generally assessed, in a probabilistic manner, by using criteria-based measures of merit. Given a set of seakeeping criteria, these measures, such as the Percentage Time of Operation (PTO) and the Seakeeping Performance Index (SPI), could provide an assessment of the operability of the vessel in a specified sea area. The criteria-based measures are based upon the probability of exceeding specified ship motions in a sea environment particular to the vessel's mission. Given the operational area of the vessel, the percentage of time the vessel operates in a particular sea state can be determined by comparing the predicted motions to the motion limiting criteria. However, because the seakeeping criteria are used in a pass/fail manner, the criteria-based procedures give no credit for reducing motions that do not exceed criteria. This may result in misleading conclusions when the relative seakeeping performance of alternative design concepts is compared. It is shown that criteria-free measures, based upon a normalized summation of critical ship responses for a range of ship speeds and wave headings in a specified sea area, may produce more reliable results when the seakeeping performance of alternative designs are compared. This approach also has the clear advantage of not requiring a set of seakeeping criteria, which is subjective in nature. To demonstrate the effect of typical measures of merit on seakeeping performance assessment, six typical high-speed displacement vessel forms are considered in a comparative analysis. Both the criteria-free and criteria-based measures of merit are employed to compare the seakeeping performance of selected vessels. The results indicate that the choice of seakeeping performance measure of merit depends on the nature of seakeeping analysis and criteria-free measures offer a simple, practical, and realistic assessment in comparative seakeeeping studies.

Probabilistic Structural Optimization Under Reliability, Manufacturability, and Cost Constraints

A methodology is presented for probabilistic design optimization of aircraft structures subject to a set of multidisciplinary constraints including reliability, manufacturability, and manufacturing cost. Using the advanced firstorder second-moment method, reliability of each structural component is evaluated by considering its primary static failure mode. Metrics-based analytical models are used in manufacturability analysis, and semi-empirical models are used for manufacturing cost estimation. The described design methodology is developed into a software tool and applied to probabilistic sizing optimization of a moderately loaded built-up wing spar. Using two alternative web design concepts, one limited by buckling and the other by diagonal semitension field action, the spar model is optimized for weight considering uncertainties in the material properties, structural sizing, and loading parameters. The optimization problem is solved using the method of sequential quadratic programming for different values of target reliability, with or without any limit on manufacturing cost. The optimization results are used to highlight the interactions between reliability, weight, and cost, whereas the probabilistic sensitivities are used to examine the influence of each random variable on structural reliability.

Self-contained automated construction deposition system

This article presents a novel autonomous system concept for automated construction of houses and other buildings via deposition of concrete and similar materials. The overall system consists of a novel cable-suspended mobility subsystem (a self-contained extension of the RoboCrane), a deposition nozzle subsystem, a metrology subsystem, and a material supply subsystem. This article focuses mainly on the kinematics and statics analysis for control of the self-contained cable-suspended mobility subsystem. We also present alternate design concepts for the mobility system. The purpose of the Cartesian metrology system is to provide an outer-loop controller to provide the required Cartesian pose motions despite uncertainties and unmodeled effects such as cable stretch, wear, and flexibility, plus wind loads.

Materials and design development for bipolar/end plates in fuel cells

Abstract Bipolar/end plate is one of the most important and costliest components of the fuel cell stack and accounts to more than 80% of the total weight of the stack. In the present work, we focus on the development of alternative materials and design concepts for these plates. A prototype one-cell polymer electrolyte membrane (PEM) fuel cell stack made out of SS-316 bipolar/end plate was fabricated and assembled. The use of porous material in the gas flow-field of bipolar/end plates was proposed, and the performance of these was compared to the conventional channel type of design. Three different porous materials were investigated, viz. Ni–Cr metal foam (50 PPI), SS-316 metal foam (20 PPI), and the carbon cloth. It was seen that the performance of fuel cell with Ni–Cr metal foam was highest, and decreased in the order SS-316 metal foam, conventional multi-parallel flow-field channel design and carbon cloth. This trend was explained based on the effective permeability of the gas flow-field in the bipolar/end plates. The use of metal foams with low permeability values resulted in an increased pressure drop across the flow-field which enhanced the cell performance.

Predicting the thermomechanical distortion of extreme ultraviolet lithography reticles for preproduction and production exposure tools

The thermomechanical distortion of extreme ultraviolet lithography (EUVL) reticles during exposure may lead to significant image placement (IP) errors. As throughput requirements for high-volume manufacturing (HVM) increase, the necessary illumination power levels rise, resulting in further distortion of the reticle. The thermal response of the EUVL reticle is predicted using finite element models for a typical HVM exposure tool. The effect of increasing the EUV source power on reticle heating is investigated by comparing the thermal distortion expected in exposure tools using different throughput values corresponding to the α tool, β tool, and the HVM exposure tool (γ tool). The effect of imperfect contact between the EUVL reticle and the chuck surface on the IP errors due to thermal distortion is studied for different effective contact area ratios. Also, an alternative design concept is proposed, aimed at providing a solution to the microparticle trapping problem (between the reticle and the chuck).

Quality function deployment for designing a basic statistics course

The quality of academic programs is drastically affected by the design of the courses within the program. The design and delivery of courses are the most essential elements for building quality in academic programs. The purpose of this paper is to customize the techniques of quality function deployment (QFD) for designing courses and demonstrate its use in the design of a basic statistics course in the Department of Systems Engineering, King Fahd University of Petroleum and Minerals. In this study, organizations from industry are used as external customers. Faculty members and students are utilized as internal customers to identify the course technical requirements. Then QFD process planning matrices are used for developing several alternative course design concepts. Then based on a simple decision criterion the design concept that closely meets customer requirements is identified. The result of the analysis is a balanced basic statistics course.

Design Concept and Engineering Techniques of Taiwan Strait Crossing

The Taiwan Strait Crossing will have invaluable influence on many aspects including communication, economics, prosperity, and social developments of both sides and on the national unity of China. It includes bridge and undersea tunnel with total length of about 150 to 250 km depending on the selection of closing lines. The descriptions of issues regarding the design concept, construction techniques, availability of materials, and skilled laborers, equipment availability, and transportation networks are focused in this article. An alternative design concept with composition of bridge and submerged casing crossing is also offered for further discussion.

Application of type synthesis theory to the redesign of a complex surgical instrument.

Surgical instruments consist of basic mechanical components such as gears, links, pivots, sliders, etc., which are common in mechanical design. This paper describes the application of a method in the analysis and design of complex surgical instruments such as those employed in laparoscopic surgery. This is believed to be the first application of type synthesis theory to a complex medical instrument. Type synthesis is a methodology that can be applied during the conceptual phase of mechanical design. A handle assembly from a patented laparoscopic surgical stapler is used to illustrate the application of the design method developed. Type synthesis is applied on specific subsystems of the mechanism within the handle assembly where alternative design concepts are generated. Chosen concepts are then combined to form a new conceptual design for the handle assembly. The new handle assembly is improved because it has fewer number of parts, is a simpler design and is easier to assemble. Surgical instrument designers may use the methodology presented here to analyze the mechanical subsystems within complex instruments and to create new options that may offer improvements to the original design.

Machine Design: A CAD Approach

Machine Design: A CAD Approach

Diffractive optical elements with modulated zone sizes

Abstract The standard design for phase-only diffractive optical elements comprises a transformation of the continuous phase function into a surface relief by means of wrapping the phase into regular intervals of M2π. This results in a structure with diffractive zones aligned in a horizontal plane. We present an alternative design concept with modulated zone sizes leading to non-periodic boundary positions and non-aligned surface structures. The diffractive properties are compared to those of conventional diffractive optical elements. It can be shown that they are fully equivalent for the design wavelength, but exhibit a different spectral behaviour for deviating wavelengths. These properties are exploited for the improvement of the optical performance of blazed gratings and diffractive lenses under conditions of deviating wavelengths. Special emphasis is put on the optimization of the ratio between diffractive efficiencies of the design order and other orders for blazed gratings and focusing diffractive lenses, as well as the suppression of interference effects within Gaussian beams collimated with diffractive lenses.

Diffractive optical elements with modulated zone sizes

The standard design for phase-only diffractive optical elements comprises a transformation of the continuous phase function into a surface relief by means of wrapping the phase into regular intervals of M2π. This results in a structure with diffractive zones aligned in a horizontal plane. We present an alternative design concept with modulated zone sizes leading to non-periodic boundary positions and non-aligned surface structures. The diffractive properties are compared to those of conventional diffractive optical elements. It can be shown that they are fully equivalent for the design wavelength, but exhibit a different spectral behaviour for deviating wavelengths. These properties are exploited for the improvement of the optical performance of blazed gratings and diffractive lenses under conditions of deviating wavelengths. Special emphasis is put on the optimization of the ratio between diffractive efficiencies of the design order and other orders for blazed gratings and focusing diffractive lenses, as well as the suppression of interference effects within Gaussian beams collimated with diffractive lenses.

Future USN Aircraft Carrier Analysis of Alternatives

ABSTRACT In March 1996, the Department of Defense established a new program, then known as CVX, to develop a new class of aircraft carrier that would eventually replace the Nimitz class. The first step in the concept develop was exploring a wide range of alternative design concepts in a formal study known as an Analysis of Alternatives (AOA), which assessed their cost and operational effectiveness. About 70 total ship studies were developed to explore the range of design features, including airwing size and type, propulsion type, ship mobility performance, and a variety of survivability features. The AOA also assessed the performance of and total ownership cost of a large number of potential subsystem technologies. This paper summarizes the total ship studies developed for the AOA, describes the ship system performance and total ownership cost of these alternatives, and discusses the rationale for determining some of the primary system requirements. Thus, the paper will provide insight into the Navy's intentions for system requirements and features to be incorporated into the U.S. Navy's future aircraft carriers.

Implementation of bending-torsion coupling in the design of a wind-turbine rotor-blade

An investigation is performed on the implementation of bending-torsion coupling of a composite wind turbine rotor blade to provide passive pitch-control. Limited passive torsion deformation is realised with a structural coupling between flapwise bending and elastic twist of a constant speed rotor-blade. The blade and skin laminate configuration are analysed with a FEM program, in which a complete blade with spar webs is modelled. This conventional blade configuration has some disadvantages. Therefore alternative design concepts are reviewed, where the coupling plies are restricted to a load-bearing spar, while a softer skin provides for the aerodynamic shape. From additional analysis, it is found that, while for the two alternative design concepts the stress concentrations at the leading edge joint are bypassed, the bending-torsion coupling response is lower. An experiment was performed to validate the calculation methods. The experimental results show good correlation with theoretical predictions. It is recommended to investigate further the fatigue life properties of a glass/carbon hybrid FRP with off-axis fibre orientations.

3 Simultaneously Considering Life‐Cycle Cost And Effectiveness For System Design Evaluation

AbstractSystems seek to satisfy identified needs and/or defined objectives. Effectiveness is the degree to which these needs or objectives are met. But need satisfaction incurs an aggregate cost to the user over the life cycle of the system. Therefore, both cost and effectiveness should be considered simultaneously during system design and development.In this paper, emphasis is placed on life‐cycle cost analysis within the context of system effectiveness, both driven by Design Dependent Parameters. Our aim is to provide insight into the essential concepts and the process for considering both cost and effectiveness simultaneously, with a unique Design Evaluation Display as the centrepiece. development.There are many technical and managerial decisions and actions taken throughout the system life cycle. Most actions, particularly those in the early life‐cycle phases, have significant implications and greatly affect life‐cycle cost and system effectiveness. Accordingly, Cost‐Effectiveness Analysis should be employed in the evaluation of alternative system design concepts and configurations, alternative production schemes, alternative logistic support policies, alternative disposal plans, etc. This analysis process is iterative in nature and can be applied to any phase of the system life cycle.The basic concepts inherent in Cost‐Effectiveness Analysis are being applied to a broad range of problems in both the defence and the civilian sectors of public activities. More recently, CEA is finding a place in the design and development of systems for commercial and business applications worldwide. In all applications, the simultaneous consideration of life‐cycle cost and effectiveness is an essential element in system design evaluation.

C. Rubbia’s hybrid plant concept: a preliminary technical and economic analysis

The long term development of nuclear energy depends, inter alia, on the ability to use the abundant fertile materials (238U and/or thorium) and on an accepted management of the long-lived radioactive wastes. In order to meet both these objectives, C. Rubbia has presented a new version of an old concept: the hybrid reactor where a subcritical reactor is fed with neutrons produced by spallation. In his concept, the reactor is a molten lead cooled fast reactor, which can use either the uranium or the thorium cycle, and burn the minor actinides and some fission products. The present work is a preliminary and partial technical and economic analysis of the reactor part of C. Rubbia’s proposal as they were set forth in a French Parliamentary audition in November 1996. The technical conclusions are that many of the design options proposed are not optimum and the uncertainties important, which is not particularly surprising at this stage of the concept. The economic ‘guesstimate’ yields a cost per kWh anywhere between one and two times that of a modern light water reactor, which is in contradiction with C. Rubbia’s claims (half the cost!), but in a range which warrants more conceptual work before drawing any conclusions. Alternative design concepts are suggested.

Design-to-Cost Applied Within an Integrated System Model

In an environment of declining financial budgets for space projects, new approaches - such as Design-To-Cost - are being implemented to improve today's satellite design processes. Using an example of a current mission (the power subsystem of the Solar Probe spacecraft) under study at NASA's Jet Propulsion Laboratory, the main part of the paper discusses an Integrated System Model (structured into a performance model, a cost model, and an effectiveness model) that is part of a model-based design process used to perform cost-effectiveness trades. A simulation tool is used during the first step to size the components of the power subsystem, and then simulate its performance during operation. The determined dimensions are transferred into an EXCELTM-spreadsheet and linked to the components' costs. With a cost accounting tool that combines cost estimating relationships with the Work Breakdown Structure of the power subsystem, the life-cycle cost of each alternative design concept is computed. To determine the cost-risk of the different design alternatives for each component, cost probability distributions are introduced. By performing Monte-Carlo simulations, cost sensitivities are revealed. In the next step of the trade study process, the effectiveness of the alternatives is analyzed. Having determined cost and effectiveness, estimates can be made for where the different alternatives lie in the design space. The last part of the paper identifies the main drivers for the spacecraft's performance and cost. Finally it is shown how the mission design benefited from the Integrated System Model and from the application of Design-To-Cost.

DECISION MAKING IN PRELIMINARY PRODUCT DESIGN: COMBINING ECONOMIC AND QUALITY CONSIDERATIONS

ABSTRACT A common task performed during preliminary design is the selection, based on customer preference, between two alternative design concepts. This selection process is used as a means to improve the design, but is complicated by several factors: (1) most designs seek to satisfy multiple quality attributes, (2) the attributes may be subjective in nature and not immediately quantified, (3) the attribute objectives may be in conflict, and (4) there is typically uncertainty in the level of performance achieved by each design concept. The methodology described in this paper links design variables-tangible features of the design concept which can be manipulated by the design-er-to multi-attribute value, a number indicating customer preference. The design comparison is made by mapping the competing designs into customer value space, and applying a measure of overall customer preference which considers both cost and a quality attribute. The uncertainty of this mapping process is addressed, and an estimate of the most preferred design is provided.

Tools for integrated modeling, design, and nonlinear control

Increasingly, design engineers are identifying new opportunities for innovation by incorporating active microprocessor control into mechanical systems of all types; e.g., spacecraft and aircraft, ground vehicles, robots, and machine tools. These mechanical systems are often complex, multibody dynamical systems with rigid and elastic substructures. Their behavior is often inherently nonlinear over their operational range. Effective design of such systems and their controls relies on computer analysis for composing and screening alternative design concepts before constructing expensive prototypes. As a consequence, there has been a considerable amount of work on computational tools to support the development of models for systems with embedded control elements. To achieve optimal performance, it is critical to integrate the design of the system structures and the embedded control architecture and laws.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The ring-network circulator for integrated circuits: theory and experiments

The theoretical model of a ring network junction circulator introduced in 1965 is reexamined and further elaborated, in view of its prospects for compatibility with accomplished and anticipated advances in microcircuit technology. Following a brief review of the theory, solutions are presented to illustrate the potential for novel, efficient designs with options including miniature, self-magnetized, reversible, broadband, superconducting, or other advantageous characteristics. New experimental models are showing good conformance to theoretical predictions for this promising alternative circulator design concept.

Design of a Cooperative Problem-Solving System for En-Route Flight Planning: An Empirical Evaluation

Both optimization techniques and expert systems technologies are popular approaches for developing tools to assist in complex problem-solving tasks. Because of the underlying complexity of many such tasks, however, the models of the world implicitly or explicitly embedded in such tools are often incomplete and the problem-solving methods fallible. The result can be "brittleness" in situations that were not anticipated by the system designers. To deal with this weakness, it has been suggested that "cooperative" rather than "automated" problem-solving systems be designed. Such cooperative systems are proposed to explicitly enhance the collaboration of the person (or a group of people) and the computer system. This study evaluates the impact of alternative design concepts on the performance of 30 airline pilots interacting with such a cooperative system designed to support en-route flight planning. The results clearly demonstrate that different system design concepts can strongly influence the cognitive processes and resultant performances of users. Based on think-aloud protocols, cognitive models are proposed to account for how features of the computer system interacted with specific types of scenarios to influence exploration and decision making by the pilots. The results are then used to develop recommendations for guiding the design of cooperative systems.