A decomposition procedure for large-scale optimum plastic design problems

A decomposition procedure is proposed in this paper for solving a class of large-scale optimum design problems for perfectly-plastic structures under several alternative loading conditions. The conventional finite element method is used to cast the problem into a finite dimensional constrained nonlinear programming problem. Structures of practically meaningful size and complexity tend to give rise to a large number of variables and constraints in the corresponding mathematical model. The difficulty is that the state-of-the-art mathematical programming theory does not provide reliable and efficient ways of solving large-scale constrained nonlinear programming problems. The natural idea to deal with the large-scale structural problem is somehow to decompose the problem into a collection of small-size problems each of which represents an analysis of the behaviour of each finite element under a single loading condition. This paper proposes one such way of decomposition based on duality theory and a recently developed iterative algorithm called the proximal point algorithm.     

A large-scale distributed decision-making procedure for a single-machine scheduling problem

This paper presents a distributed scheduling procedure for a large-scale single-machine problem with precedence constraints, and identifies phenomena using large-scale distributed decision-making for a decomposable and distributed situation. The approach proposed exhibits efficient computational performance over a large-sized work load (23,000 jobs and 2,209,536 precedence constraints) in a distributed computing environment. We highlight three findings: (1) the communication burden originating from the large-scale problem can lead to performance loss while distributed agents collaborate to solve the problem, but after a threshold the computational gain by distribution offsets the loss; (2) when the problem size is sufficiently large, the real computation gain outperforms the expected gain by the number of agents (super-linear effect); and (3) when the number of precedence constraints of each agent differs, the slowest agent processing the largest number of precedence constraints restrains the computational performance (load imbalance). We believe that our research is the first distributed decision-making model that meets the requirements of distributed information, distributed decision authority, and distributed computation in a large-scale single-machine scheduling situation with precedence constraints.     

塑料模具设计过程中常见问题探讨

随着社会的不断发展,塑料模具在航天、造船、机械加工等多种行业的应用变得越来越广泛,塑料模具的产生也大大丰富了模具的制造材料种类,促进了加工制造业的发展,但是塑料模具在应用时因其较高的标准和其应用场所的不同,对于塑料模具的影响也是不同的,为更好地促进模具行业的发展,诞生了一种较为新颖的塑料模具制作工艺,就是浇铸模具。     

On the consistency of risk acceptance criteria with normative theories for decision-making

In evaluation of safety in projects it is common to use risk acceptance criteria to support decision-making. In this paper, we discuss to what extent the risk acceptance criteria is in accordance with the normative theoretical framework of the expected utility theory and the rank-dependent utility theory. We show that the use of risk acceptance criteria may violate the independence axiom of the expected utility theory and the comonotonic independence axiom of the rank-dependent utility theory. Hence the use of risk acceptance criteria is not in general consistent with these theories. The level of inconsistency is highest for the expected utility theory.     

Protective actions in the late phase--intervention criteria and decision-making

Major countermeasures in the late phase of a nuclear or radiological accident where long-lived radionuclides have been dispersed in the environment are relocation/resettlement, foodstuff restrictions, agricultural countermeasures and clean-up of contaminated areas. There has essentially been a broad acceptance internationally of the principles for their introduction, but it has not been possible to reach an agreement for the purpose of defining a net benefit based upon the exact weighting to be attached to each of the attributes influencing the decision on intervention, e.g. socio-psychological attributes. Optimisation of protection, i.e. maximising the net benefit, is not a question of developing radiation protection philosophy to fully include socio-psychological factors but rather to include these factors--in parallel with the radiological protection factors--in cooperation between radiation protection experts and e.g. experts in social and psychological sciences under the responsibility of the decision-maker, who will take the final decision on the introduction of long-term countermeasures.     

Failure criteria for use in the design environment

This paper is concerned with the comparison of composite failure data with the design criteria used for the design of GRP process equipment. This industry sector makes extensive use of composite materials and employs a pragmatic approach to design. Full details were discussed in Part A of this exercise. Examination of the test data yields a number of issues associated with what must be included within a predictive capability, such as the correct interpretation of stress strain behaviour, the use of appropriate material constants, and a thorough understanding of the test methods used to measure material and component responses. Not all of these points are relevant to the design of structures for long-term service as design strains are limited to low values and not all combinations of load apply. Given the relative simplicity of the design methods used it is considered that the correlation between calculation and measurement is satisfactory. Some improvements are possible and these are the subject of consideration in the on-going revision of standards documentation.     

Quantitative criteria for the design of dither-based quantizingsystems

This paper addresses the problem of designing quantizing systems employing dither. These are composed of a dither generator, a quantizer, a subtracting block and a low-pass digital filter. Quantitative criteria for choosing the parameters that influence the resolution and accuracy of the quantizing system are given, and the system performance is determined under worst, best, and average conditions for discrete binary, uniform, and Gaussian dither signals. The results presented also can be applied when the signal plus input-referred noise are quantized     

Vacuum-system design for the large-scale cryogenic gravitational wave telescope

The large-scale cryogenic gravitational wave telescope (LCGT) requires ultra-high vacuum tubes which the laser beams pass through. Two 3-km vacuum tubes are kept in ∼10⁻⁷ Pa of vacuum pressure so as to reduce scattering-effects due to residual gas molecules. The stainless-steel material with electro-chemical buffing is the most available for use as long tubes of 1 m in diameter. To reduce noises due to scattered light from the surface of tubes, a lot of baffles are inserted into the tubes.     

Gradient-based criteria for sequential experiment design

Computer experiments are often used as inexpensive alternatives to real-world experiments. Statistical metamodels of the computer model's input-output behavior can be constructed to serve as approximations of the response surface of the real-world system. The suitability of a metamodel depends in part on its intended use. While decision makers may want to understand the entire response surface, they may be particularly keen on finding interesting regions of the design space, such as where the gradient is steep. We present an adaptive, value-enhanced batch sequential algorithm that samples more heavily in such areas while still providing an understanding of the entire surface. The design points within each batch can be run in parallel to leverage modern multi-core computing assets. We illustrate our approach for deterministic computer models, but it has potential for stochastic simulation models as well.     

Fatigue life of welded joints according to energy criteria in the critical plane

We have determined theoretical notch coefficients with use of the fictitious radius in tube-tube and flange-tube welds. The parameter of normal and shear strain energy density in critical planes is applied for estimation of fatigue life under cyclic conditions of pure bending, pure torsion and combined proportional bending with torsion. The critical planes were determined with use of two methods based on the maximum parameters of, respectively, normal and shear strain energy density. __________ Translated from Problemy Prochnosti, No. 4, pp. 118–124, July–August, 2006.     

Use of safety factors for the design of steel structures according to the Eurocodes

This paper informs about the safety concept of the Eurocodes as defined in EN 1990/1/ and how it is implemented in the EN 1993/3/ for the design of steel structures.     

Optimum design criteria for elastic structures subject to random dynamic loads

A new stochastic optimization method, which makes use of a constraint on structural reliability, is proposed for structures subject to dynamic random loads. A minimum weight problem is posed, in which a constraint condition imposes that the failure probability must be smaller than a given admissible level. The failure is determined by the first crossing outside the safe domain of a suitable structural response vector. The method is used to find the optimal shape of an elastic vertical column supporting a fixed mass positioned on the top, subject to a Gaussian filtered stationary stochastic horizontal acceleration process. The column, with variable annular cross-section, is described by a deterministic elastic multi-degree-of-freedom system. It is assumed that failure is reached when its lateral displacement exceeds an acceptable threshold value. Under this constraint, the structural weight is minimized and the optimal shape is determined for different structural conditions.     

Optimization of the procedure of plasma spraying of erosion-resistant coatings according to strength criteria

It is shown that mechanical characteristics of the coatings depend on their technological conditions of their deposition. We propose a procedure of optimization of the technological process and control over this process according to the criteria of strength and specific consumption of materials by analyzing an example of plasma spraying of erosion-resistant coatings. The erosion resistance exhibits the most stable correlation with the cohesive strength of the coatings. The regression equations are used to determine the maximum levels of cohesive strength of the coatings and erosion resistance for the optimal combinations of technological parameters of. Translated from Problemy Prochnosti, No. 6, pp. 136–151, November–December, 2008.     

Quarter-wave design criteria for omnidirectional structural colors

Structural colors are caused by light interference from periodic multi-layer dielectric stacks and exhibit rich, highly-chromatic colors. However, avoiding a color shift due to angular variation remains a challenge. The design criteria for angle-independent structural colors have been studied by treating a quarter-wave stack of alternating dielectric material layers as a one-dimensional photonic crystal. A refractive index zone has been identified that exhibits narrowband omnidirectionality for structural colors in the visible wavelength range. It was found that a quarter-wave stack of high refractive index (RI) paired-layers (n _H = 2.85 and n _L = 2.5), which have low RI contrast (n _H /n _L = 1.14), is key in fabricating omnidirectional structural color materials. The theoretical predictions discussed here are verified experimentally using a titania/halfnia (TiO₂/HfO₂) multilayer stack.     

Novel method to construct large-scale design space in lubrication process utilizing Bayesian estimation based on a small-scale design-of-experiment and small sets of large-scale manufacturing data

A large-scale design space was constructed using a Bayesian estimation method with a small-scale design of experiments (DoE) and small sets of large-scale manufacturing data without enforcing a large-scale DoE. The small-scale DoE was conducted using various Froude numbers (X₁) and blending times (X₂) in the lubricant blending process for theophylline tablets. The response surfaces, design space, and their reliability of the compression rate of the powder mixture (Y₁), tablet hardness (Y₂), and dissolution rate (Y₃) on a small scale were calculated using multivariate spline interpolation, a bootstrap resampling technique, and self-organizing map clustering. The constant Froude number was applied as a scale-up rule. Three experiments under an optimal condition and two experiments under other conditions were performed on a large scale. The response surfaces on the small scale were corrected to those on a large scale by Bayesian estimation using the large-scale results. Large-scale experiments under three additional sets of conditions showed that the corrected design space was more reliable than that on the small scale, even if there was some discrepancy in the pharmaceutical quality between the manufacturing scales. This approach is useful for setting up a design space in pharmaceutical development when a DoE cannot be performed at a commercial large manufacturing scale.     

Minimizing L max for large-scale,job-shop scheduling problems

The academic literature in 2000 presented a procedure for solving the job-shop-scheduling problem of minimizing L _max. The iterative-adaptive simulation-based procedure is shown here to perform well on large-scale problems. However, there is potential for improvement in closing the gap between best-known solutions and the lower bound. In the present paper, a simulated annealing post-processing procedure is presented and evaluated on large-scale problems. A new neighbourhood structure for local searches in the job-shop scheduling problem is developed. The procedure is also evaluated using benchmark problems and new upper bounds are established.