一种实用的自组织模糊控制器设计方法

介绍一种基于模糊智能比例因子自调整的自组织模糊控制器设计方法 ,给出这种模糊控制器与常规模糊控制器在性能指标上的比较结果 .     

Kagome蜂窝夹层平板的多功能优化设计

采用“等效介质模型”, 分析了复合材料夹层蜂窝平板的整体换热系数。在此基础上, 针对轻质蜂窝(相对密度小于0. 3) , 选取蜂窝面内等效剪切刚度表征夹层结构的承载能力, 综合考虑散热能力和结构承载能力, 比较了Kagome 蜂窝与传统的正三角形、正方形和正六边形蜂窝的性能。结果显示Kagome 蜂窝不但散热性能很好, 而且通过对蜂窝相对密度和尺寸的优化, 在结构质量相同的情况下, Kagome 蜂窝的综合性能比传统蜂窝具有明显优势。      

Carbon-nanotube-based voltage-mode multiple-valued logic design

Multivalued logic has always attracted the attention of digital system and logic designers. However, the high-performance and low-power CMOS process, which has been developed over the last two decades, has traditionally assisted successful circuit implementation of binary logic. Consequently, in spite of its large potential multivalued logic design is seldom a circuit designer's choice. This paper presents a novel method of multiple-valued logic design using carbon-nanotube field-effect transistors (CNFETs). The geometry-dependent threshold voltage of CNFETs has been effectively used to design a ternary logic family. We have developed a SPICE-compatible model of ballistic CNFETs that can account for varying geometries and operating conditions. SPICE simulations have been performed on the proposed logic gates, and the transfer characteristics as well as transient behavior have been extensively studied. Finally, a comparison in terms of power and performance of the ternary logic family vis-a/spl grave/-vis traditional complementary field-effect transistor binary logic family has been presented.     

Self-checking logic design for FPGA implementation

Field programmable gate arrays (FPGAs) are being increasingly used in many systems including intelligent instrumentation. A synthesis algorithm for generating self-checking combinational logic for implementation on look-up table based FPGAs is presented. The algorithm maps Boolean functions into FPGAs such that self-checking features are automatically incorporated into designs, allowing on-line detection of faults in the combinational function block within any configurable logic block of an FPGA and on the interconnect lines that connect these blocks. This is accomplished by utilizing two types of cells, a functional cell and a checker cell, that generate complementary outputs during normal operation, and outputs of the same value in the presence of a fault. If a fault occurs in any intermediate functional cell, it is automatically propagated to the primary outputs. A checker cell is then used to verify the correctness of the final outputs, thus allowing self-checking.     

Arbitrary branched and intersecting cracks with the extended finite element method

Extensions of a new technique for the finite element modelling of cracks with multiple branches, multiple holes and cracks emanating from holes are presented. This extended finite element method (X‐FEM) allows the representation of crack discontinuities and voids independently of the mesh. A standard displacement‐based approximation is enriched by incorporating discontinuous fields through a partition of unity method. A methodology that constructs the enriched approximation based on the interaction of the discontinuous geometric features with the mesh is developed. Computation of the stress intensity factors (SIF) in different examples involving branched and intersecting cracks as well as cracks emanating from holes are presented to demonstrate the accuracy and the robustness of the proposed technique. Copyright © 2000 John Wiley & Sons, Ltd.     

On the use of the hybrid causal logic method in offshore risk analysis

In the Norwegian offshore oil and gas industry risk analyses have been used to provide decision support for more than 20 years. The focus has traditionally been on the planning phase, but during the last years a need for better risk analysis methods for the operational phase has been identified. Such methods should take human and organizational factors into consideration in a more explicit way than the traditional risk analysis methods do. Recently, a framework, called hybrid causal logic (HCL), has been developed based on traditional risk analysis tools combined with Bayesian belief networks (BBNs), using the aviation industry as a case. This paper reviews this framework and discusses its applicability for the offshore industry, and the relationship to existing research projects, such as the barrier and operational risk analysis project (BORA). The paper also addresses specific features of the framework and suggests a new approach for the probability assignment process. This approach simplifies the assignment process considerably without loosing the flexibility that is needed to properly reflect the phenomena being studied.     

An abductive propositional logic for design reasoning

Abstract

Design can be seen as a reasoning process based on non‐classic logic, in which non‐monotonicity and abduction are two essential features. This paper introduces Abductive Propositional Logic (APL), which is a simple but powerful formal system to deal with these two features. To show its capabilities, APL is used to analyze the reasoning of a conceptual design of a scooter. The results reveal that APL is not only a profound basis for developing computer supported design systems, but also a useful tool for analyzing design processes.     

A Josephson logic design employing current-switched junctions

A logic scheme using Josephson tunnel junctions in a current-steering mode is described. Switching from voltageV = 0toV neq 0is accomplished by adding a fraction of the control-line currents to the bias current. In one form the addition is accomplished by shunting the junction to be switched with a loop containing a second junction serving a diode-like function and causing one or more control lines to possess inductive coupling to the loop. A five-element circuit demonstrating AND, OR and INVERSION operations carried out by this approach has been fabricated and works as expected.     

Supply current spectrum estimation of digital cores at early design

A new, approximate method is presented to calculate a digital core supply current spectrum. The method is based on characterisation of supply current pulses in terms of the rise and fall times and pulse width. The upper limits (an envelope) for the supply current spectrum are derived using logic signal transition densities at digital core internal nodes. Contrary to the known methods, the proposed one uses limited data and generates much needed supply current information strongly desired by a system designer at a very early system planning. By using the probabilistic and statistical techniques the method is only weakly dependent on input sequence pattern and gives reliable final results.     

二维树状分叉碳纤维的浮动催化法制备

采用两段加热卧式浮动催化法合成了二维树状分叉碳纤维。讨论了制备条件如:催化剂(二茂铁)、催化促进剂(噻吩)以及它们在碳源溶液中的含量、苯／氢的比例、氢气的流量等对生长二维树状分叉碳纤维的影响。二维树状分叉碳纤堆的分叉纤堆相互平行排列,直径与母体纤维接近,部分分叉碳纤维与其它碳纤维交叉相连。提出了二维树状分叉碳纤维的生长机理和交叉结构可能的生长模式;二维树状分叉碳纤维的生长符合气相生长碳纤堆的生长机理,是纳米碳纤维在反应管高温区继续生长的结果。可以预测,控制一定的条件,可以用两段加热卧式浮动催化法合成二维碳纤维网状结构,在复合材料等领域有潜在的应用价值。     

Optimal design of sandwich panels made of wood veneer hollow cores

In response to the growing interest in replenishable, lightweight, stiff and strong materials, a novel sandwich panel with a hollow core has been manufactured using commercially produced 3-ply veneer. In this paper, the out-of-plane shear behaviour of the novel hollow core is analysed and the expressions for the failure loads are developed. A strength-based optimisation problem is formulated for predicting the optimum values of the panel dimensions that would produce minimum panel weight when subjected to bending. It has been found that the minimum weight, as predicted by the full four-parameter optimisation, is slightly lower than that obtained by using the closed form expressions derived on the basis of simplified three-parameter optimisation. Relationships between the active failure modes are explored. Design maps are shown for a wide range of loading that can be used to calculate the minimum panel weight and the corresponding values of the geometric parameters. The approach developed is general and is equally applicable for sandwich panels with similar hollow cores made of other materials.     

自航式鱼雷发射装置发射管长度优化研究

基于某型鱼雷自航发射的内弹道数学模型，选择自航管的总长度作为优化目标。讨论了约束函数的取值，确定了优化问题的数学表达，采用惩罚函数法进行寻优计算，针对约束函数具有不可微和非线性的特点。采用模式搜索算法进行了无约束优化的求解，给出了优化结果并进行了比较。     

Definition of a multimaterials design method

Although methods of product design and materials selection have been developed, the recent rise of multimaterials (composites, hybrids, etc.) has shown a lack of tools for engineering in this domain. The present contribution aims at the development of a multimaterials design method based on the adaptation of existing methods and on the conclusions of a case study. In comparison with materials selection, the originality of multimaterials design relates to searching materials coupling mechanisms to satisfy a set of requirements. More, it appears that manufacturing process and validation tests are very important points that must be integrated early in the design process.     

On the static equilibria of branched elastic rods

Structures featuring rod-like bodies connected in a branched ensemble are ubiquitous. They appear in antennae, replicating DNA strands, and, most visibly, in the plant kingdom. In spite of this, modeling these branched structures using rod theories have received little attention in the literature. With the help of a general rod theory, which was originally developed by Green and Naghdi, balance laws for these structures are discussed. The governing equations established are then shown to be equivalent to variational principles for tree-like structures. These principles are adopted from works by Ivanov and Tuzhilin and may lead to the development of nonlinear stability criteria for these structures. It is also shown how the conditions at a branching point in these structures can be understood using recent interpretations of Eshelby’s work on material (configurational) forces in adhesion problems. The static configurations are illuminated for several structures using Euler’s theory of the elastica. Instances of multiple possible configurations and novel extensions to the classical problem of the tallest column are also discussed.     

Microstructural design in work hardenable perforation stretch formed micro-truss cores

Periodic cellular materials (PCMs) are lightweight composites of space and metal that can be fabricated using simple sheet forming methods. This study uses both finite element and experimental methods to examine the effects of perforation geometry on the range of accessible micro-truss architectures and the resulting inelastic buckling resistance during uniaxial compression of AA3003 micro-truss cores. By modifying the conventional perforation geometry, it was possible to change the plastic strain distribution between the hinge and strut region, opening up new possibilities for microstructural design in PCMs.     

An accurate AC demagnetizing method using a linear inductance for high permeability cores

A new simple and accurate ac demagnetizing method for high permeability cores is presented. In this method, a linear inductance is connected in parallel with the winding of the core to stabilize the level ofBHminor loops at zero flux level during the whole process of ac demagnetization. The ac demagnetization error is suppressed to less than 0.5% even in 50% Ni-Fe cores. The optimal ac demagnetizing time is longer than 0.5 sec., and the optimal ac demagnetizing waveform of current source is sinusoidal. Experimentally, high demagnetizing accuracy was obtained over a frequency range of 10 Hz-2 kHz. Two cores with the same dimensions and materials are simultaneously ac demagnetized by means of a linear inductance connected in parallel with the primary windings of two cores connected series-aiding, whose secondary windings are connected parallel-opposing and short circuited; thus, the remanent flux level after ac demagnetization is nondestructively detected by destructive readout in other core. This ac demagnetizing method is useful for measuring some magnetic properties such as initial permeability and BH curves and for resetting the small-signal transformer cores and second-harmonic analog memory elements.     

Analysis and design of ferrite cores for eddy-current-killedoscillator inductive proximity sensors

Finite element modeling of ferrite cores used in the design of eddy-current-killed oscillator inductive proximity sensors was performed. Based on contemplation of the practical operation of the sensors, ferrite core geometries were compared with a reference core by the eddy-current power loss in a metal target at a fixed distance from the face of each transducer. Several of these cores were experimentally evaluated for sensing distance to verify the results of the simulation. It was observed that, for fixed coil, fixed target distance, and given target, the low-frequency sensing distance of a particular transducer is approximately proportional to the fourth root of eddy-current power loss in the target     

On expanding Boolean algebra into a new dual-biform logic algebra

Some interesting problems, such as those occurring with non-coherent structure functions, require an expansion of existing Bolean algebra that can manipulate special coherent structure functions and their duals. In this paper, we formalize an algebra called A-Algebra (A New Dual Biform Logic Algebra).Some aspects of this algebra lead to the puzzling question, ‘When is the conjunction of a coherent structure function and its complemented-dual function a tautology (ƒ(x)ƒ^Δ·′(x))?′. In addition, we suggest that new algorithmic efficiencies may exist through the use of this algebra.