Approximate Design Method Research Articles

Inaccurate search based sequential approximate constrained optimization method for Solid Rocket Motor design

Surrogate based constrained optimization methods are widely utilized in practical solid rocket motor (SRM) design problems. To improve the design performance, this paper proposes an inaccurate search based sequential approximate constrained optimization (ISSACO) method consisting of an efficient recursive evolution Latin hypercube design (RELHD) method and a three-stage constrained sampling method. The RELHD method divides large-sample experiment design problem into several small-sample design problems to ensure the computational efficiency and the design uniformity at the same time. The three-stage constrained sampling method employs the elite archives mechanism to balance the feasibility and the optimality in optimization. Results of the numerical cases indicate that the proposed ISSACO algorithm is competitive with other state-of-art constrained optimization method in efficiency and effectiveness. The finocyl grain design and the impulse mass ratio optimization are also conducted to make further verifications, and the ISSACO method can efficiently obtain feasible optimum and proves to be a potential method for computationally intensive solid rocket motor design problems.

Exploration of low-carbon approximate probability design method for concrete structures

Exploration of low-carbon approximate probability design method for concrete structures

Development and Numerical validation of an Aerospike nozzle Contour Design

Aerospike nozzle simplified design and analysis, as well as test results, are presented. New techniques in nozzle design have been used to improve the performance of current rocket engines. The use of an aerospike nozzle is one such technique. It outperforms the existing proven bell nozzle in terms of overall performance. This study analyses the development and flow analysis of an aerospike nozzle at sea level, validating their results by taking into account currently used bell nozzles. The flow over the aerospike pump is investigated in higher depth using computational fluid dynamics under an autonomous fire testing condition. This test showed that the approximate design method used to determine an aerospike nozzle shape can lead to extremely effective nozzles. A model of the current 7.45 kN bell nozzle was selected as a specimen to develop an aerospike Nozzle. Gambit and Fluent software were used to model and examine the flow characteristics of building the aerospike nozzle. The developed aerospike nozzle shows a nearly 2% increase in performance over the existing nozzle.

An approximate design method of grinding worm with variable meshing angle and grinding experiments of face gear

A kind of approximate definition method of grinding worm surface with variable meshing angle is proposed for grinding face gears. The influence of the parameter of the virtual shaper and the alignment errors of the grinding worm on the tooth surface deviation of face gear is investigated. A set of nonlinear contact equations is established for dressing grinding worm with standard double cone dressing wheel based on a kind of 5-axis CNC machine tools. The compensation method used to correct deviations of face gear tooth surface by dressing the corresponding points on the grinding wheel is derived, based on the corresponding relation between surface points of face gear and the meshing angles. Two grinding experiments are performed for both orthogonal and non-orthogonal face gears. The experiments indicated that the tooth surface precision of face gear ground by this method can reach level 6 by Chinese standard GB11365-89 comparing with the same size of bevel gear, and the pitch precision can reach level 4 which is higher.

Neural Network-Based Model-Free Learning Approach for Approximate Optimal Control of Nonlinear Systems

This paper studies the infinite time horizon optimal control problem for continuous-time nonlinear systems. A completely model-free approximate optimal control design method is proposed, which only makes use of the real-time measured data from trajectories instead of a dynamical model of the system. This approach is based on the actor-critic structure, where the weights of the critic neural network and the actor neural network are updated sequentially by the method of weighted residuals. It should be noted that an external input is introduced to replace the input-to-state dynamics to improve the control policy. Moreover, strict proof of convergence to the optimal solution along with the stability of the closed-loop system is given. Finally, a numerical example is given to show the efficiency of the method.

Design of the glass pulse-tube cryocooler

With the purpose of generating the curiosity of the public, a pulse-tube cryocooler with regenerator, pulse-tube, inertance tube and reservoir made of glass has been designed constructed and operated. The dimensions of the glass regenerator have been determined using REGEN3.3 [1] from given parameters of the conductive porous medium inside of the regenerator and a 150K target cooling temperature at the cold head. The geometry of the glass pulse-tube and glass inertance tube has been fixed using an approximate design method [2], and the entire system parameters checked using SAGE [3]. The thickness of each glass component is based on a charge pressure of around 7 bar and a pressure ratio of about 1.35. The dimensions of the after-cooler are calculated using ISOHX [4] assuming a gas temperature of 300 K at the inlet of the regenerator.

Approximate computing of two-variable numeric functions using multiplier-less gradients

Approximate computing of non-trivial numeric functions is a well-known design technique and, therefore, used in several different application areas. Its main idea is the relaxation of conventional correctness constraints to achieve high performance results in terms of throughput and/or energy consumption. In this paper we propose an automated approximate design method for the fast hardware generation of two-dimensional numeric functions. By using multiplier-less gradients in combination with an advanced non-uniform segmentation scheme, high hardware performance is achieved. To qualify our approach, exhaustive evaluation is carried out, considering six different two-variable numeric functions. In a first step, a global complexity estimation is performed with varying design constraints on the algorithmic level. Out of this, most suitable candidates are selected for logic and physical CMOS synthesis. The results are compared to actual references highlighting our work as a powerful approach for the hardware-based calculation of two-variable numeric functions, especially in terms of throughput and energy consumption.

Effect of interactions between piled raft components and soil on behavior of piled raft foundation

The use of piled raft foundations has been considered as an economical alternative to conventional deep foundations because a portion of the applied load is thought to be transferred to the raft. In analyzing the behavior of a piled raft as a settlement reducer, an accurate estimate of settlement of the system should be made, based on the adequate understanding of nonlinear behavior of piles in layered soils as well as the interaction between the raft, soils, and piles. This study developed a computer program incorporating an approximate hybrid analysis method for the practical design of piled raft foundations. In the presented method of analysis, the interactions between pile-soil, raft-soil, pile-soil-pile and raft-soil-pile are considered, and the effect of nonlinear behavior of piles and the interactions between piled raft components and soil are investigated by comparing with 3-dimensional FEM program analysis results.

Approximate design method for reactive liquid extractors based on thermodynamic equilibrium correlations

Approximate methods are suitable for rapid analysis of alternatives during the conceptual phase of a process design. Few approximate methods for liquid–liquid extraction have been published and few theoretical studies have been carried out in this field on reactive liquid extractors. The purpose of this study was to provide a simple, reliable and rapid approximate method for the design of separation columns for liquid mixtures that have reacted and are in a simultaneous equilibrium of reaction and phases. The developed design method involves two stages: (a) analysis of the liquid–liquid equilibrium correlations with no reaction and their extension to reactive systems and (b) coupling of the correlations with the stage by stage design method. Hand, Othmer–Tobias and Bachman–Brown correlations were used for the tie lines fit; whereas Hlavatý, log γ and β function were used for the solubility curves.The correlations, in terms of transformed variables, were applied to six reactive systems that presented adequate fits for the design of the reactive liquid extractors. The following cases were used to compare the results obtained with the approximate design method with those reported in the literature: (i) The hydrolysis of methyl octanoate, (ii) A theoretical system with five components and parallel reactions, and (iii) The esterification of acetic acid with n-propanol; a very good agreement was found.

Sızma Testleri İçin Bir Model Ağ Üzerinde Siber Saldırı Senaryolarının Değerlendirilmesi

The scope of this work is to investigate the effects of baffle cut and baffle spacing on the heat transfer coefficient and pressure drop in a shell and tube heat exchanger. For this aim, analyses are made for a standard dimensioned heat exchanger with variable baffle cut and spacing. It is observed that both heat transfer coefficient and pressure drops values decrease with the increase of baffle cut and baffle spacing. This paper demonstrates successful application of Genetic Algorithm for the optimal design of shell-and-tube heat exchangers. Approximate design methods for shell-and-tube have been investigated and a generalized procedure has been developed to run the GA algorithm and to find the global minimum heat exchanger area

Study on Design Method of the Double Arc Gear Hobs

This article find that one of the effecting the double circular arc gear s running performance is the double circular arc gear tooth profile precision, through analysis to the running-in properties of double arc gear. The problems about tooth profile precision of gear hobs caused by the current profiling theory and approximate design method of gear hobs are analyzed. In the design of circular arc gear hob, use the space engagement theory, can eliminating the tooth error. Acquiring the equation of hobs basic of worm tooth surface by analytical and calculation that the establishment of basic gear rack and worm of hob meshing. The hob not only eliminate the tooth profile error in manufacturing, but also improve the running performance of double circular arc gear, and provides the theory evidence for engineering practice.

Performance of stainless steel winery tanks during the 02/27/2010 Maule Earthquake

The Maule Earthquake (February 27, 2010, Chile), one of the largest recorded in history, affected a large area of the country, where several important industries were located. The wine industry was particularly vulnerable, because most of the Chilean wine was produced in the affected area. With the support of the industry and the government, a large reconnaissance effort was undertaken. The inspection found several issues with the tanks and other elements used in the wine making process that resulted in large losses, including lack of structural seismic design and detailing, lack of redundancy, and inadequate anchorage design and execution. A summary of the major findings of this inspection are presented, followed by a comparison of the results of a linear and nonlinear finite element models of one case of the tank typology most damaged by the earthquake, namely a leg-supported tank, with the observed performance. The finite element models were able to predict the location of stress and strains concentrations and the type of damage that led to the failure of the structures represented by the models. Additionally, the capacity obtained from the models compared favorably with the capacity obtained using an approximate design method proposed by other researchers. These results could be used to develop seismic design and construction guidelines to lower the vulnerability of the wine industry in future earthquakes.

Üniversite Sanayi İşbirliği ve Fen Bilimleri Enstitüleri

The scope of this work is to investigate the effects of baffle cut and baffle spacing on the heat transfer coefficient and pressure drop in a shell and tube heat exchanger. For this aim, analyses are made for a standard dimensioned heat exchanger with variable baffle cut and spacing. It is observed that both heat transfer coefficient and pressure drops values decrease with the increase of baffle cut and baffle spacing. This paper demonstrates successful application of Genetic Algorithm for the optimal design of shell-and-tube heat exchangers. Approximate design methods for shell-and-tube have been investigated and a generalized procedure has been developed to run the GA algorithm and to find the global minimum heat exchanger area

Compact MNG zeroth order resonator antenna

In this paper a compact one unit cell mu negative (MNG) zeroth-order resonator (ZOR) antenna is designed and analyzed. A ZOR antenna based on the MNG transmission line (TL) has been previously introduced. The feeding structure of the previously presented MNG antenna is a microstrip line in parallel with the antenna. This feeding mechanism enlarges the overall size of the antenna and also increases the cross polarization level of the radiated fields. In this paper we propose a MNG TL based ZOR antenna with a coaxial feed and with a specific matching mechanism which results in compactness of the antenna and reducing its cross polarization level. An approximate design method for the proposed antenna is presented using its equivalent circuit and according to its operation mechanism. A prototype antenna has been fabricated and tested. The measured return loss and radiation patterns are given and the overall performance of the antenna is compared with some of the previously reported compact metamaterial antennas.

Approximate Optimal Control Design for Nonlinear One-Dimensional Parabolic PDE Systems Using Empirical Eigenfunctions and Neural Network

This paper addresses the approximate optimal control problem for a class of parabolic partial differential equation (PDE) systems with nonlinear spatial differential operators. An approximate optimal control design method is proposed on the basis of the empirical eigenfunctions (EEFs) and neural network (NN). First, based on the data collected from the PDE system, the Karhunen-Loève decomposition is used to compute the EEFs. With those EEFs, the PDE system is formulated as a high-order ordinary differential equation (ODE) system. To further reduce its dimension, the singular perturbation (SP) technique is employed to derive a reduced-order model (ROM), which can accurately describe the dominant dynamics of the PDE system. Second, the Hamilton-Jacobi-Bellman (HJB) method is applied to synthesize an optimal controller based on the ROM, where the closed-loop asymptotic stability of the high-order ODE system can be guaranteed by the SP theory. By dividing the optimal control law into two parts, the linear part is obtained by solving an algebraic Riccati equation, and a new type of HJB-like equation is derived for designing the nonlinear part. Third, a control update strategy based on successive approximation is proposed to solve the HJB-like equation, and its convergence is proved. Furthermore, an NN approach is used to approximate the cost function. Finally, we apply the developed approximate optimal control method to a diffusion-reaction process with a nonlinear spatial operator, and the simulation results illustrate its effectiveness.

THEORETICAL ESTABLISHMENT AND EVALUATION OF A NOVEL OPTIMAL PYRAMIDAL HORN DESIGN CRITERION

This paper proposes a novel design criterion for optimal pyramidal horns. According to the criterion, the optimal aperture phase error parameters of a pyramidal horn are determined from the minimization of the horn's lateral surface area. We present two families of curves that illustrate the optimal aperture phase error parameters for frequency and directivity values in the area of practical interest. We also discuss two simple approximate design methods for the calculation of the optimal horn parameters. Comparisons with well-known design methods demonstrate the e-cacy of our approach. The designed horns have also smaller aperture area and require less installation space than other optimal proposals in the published literature. Moreover, the proposed criterion produces, under certain conditions, the lightest horn for a given directivity; as a result its fabrication requires less material compared to other structures. The present approach is a useful design tool when the size and weight of a pyramidal horn are of concern.

날개-평판 접합부에서의 날개 앞전 판 최적화를 통한 유동특성 향상

말굽와류로 대표되는 3차원 유동현상은 필연적으로 주유동에 대한 2차 유동의 형태로 발생되며, 유동손실을 유발하게 된다. 본 논문에서는 2차유동 손실을 일으키는 주요 요인중의 하나인 말굽와류의 강도를 감쇄시키기 위해 일반적인 날개 앞전에 설치한 판에 대해, 판의 설치 높이, 길이, 폭 및 두께 등의 형상변수를 설계변수로 정하여 이를 최적화하였다. 근사최적설계 기법을 이용 최적화를 수행하였으며, <TEX>$FLUENT^{TM}$</TEX>와 <TEX>$iSIGHT^{TM}$</TEX>를 이용하였다. 최적화 수행결과, 기준 모델의 경우보다 전압력 계수가 약 7.5% 감소하였다. 3-Dimensional flow which is represented by horseshoe vortex is generated as a type of secondary flow about the main flow. As well, it causes the flow loss. The present study deals with the leading edge fence shape on a wing-body junction to decrease a horseshoe vortex, one of the main factors to generate the secondary flow losses. The shape of leading-edge fence was optimized with the design variables of the installed height, length, width, and thickness of the fence as the design variables. Approximate optimization design method is used as the optimization. The study was investigated using <TEX>$FLUENT^{TM}$</TEX> and <TEX>$iSIGHT^{TM}$</TEX>. Total pressure coefficient of the optimized design case was decreased about 7.5 % compare to the baseline case.

Application of Orthotropic Thin Plate Theory to Filled Steel Grid Decks for Bridges

Although AASHTO LRFD specifications provide moment capacity equations as an approximate design method and recommend an orthotropic plate model as the refined method for the analysis of filled grid decks, no guidelines are provided for the determination of the flexural rigidities associated with the plate analysis. This technical note briefly reviews orthotropic thin plate theory, discusses the determination of the flexural rigidities using Huber’s assumption, and applies the theory to concrete-filled steel grid decks. The accuracy of the orthotropic plate analysis is assessed by comparing it to results of an earlier finite-element analysis.

An Approximate Design Method of Discrete-time 2DOF controller and its Parameter Tuning.

In this paper, we propose an approximate design method for feedforward element of discrete-time 2DOF controller parameterized by stable rational function. The proposed method is based on the approximate matching of the response sequence in time domain. The relation of the parameter of feedforward element and output sequence is expressed in the form of simple linear equation, through which we can design low order feedforward element. The proposed method also has a feature that the iterative controller parameter tuning algorithm can be derived by applying the iterative solution commonly utilized in numerical calculation. The results of the numerical simulation show the effectiveness of the proposed method.

A design method for rectangular hollow sections in bending

Local deformation of individual cross-sectional members is of great interest in the bending of aluminium alloy extrusions for automotive applications. The primary concern is the impact of such distortions on the manufacturability of components as well as the dimensional tolerances of the final build. This paper presents analytical models for the determination of local post-buckling and suck-in deformations in bending. The models are based on the deformation theory of plasticity combined with an energy method using appropriate shape functions. The analytical predictions are verified with experimental results. Based on the present findings, an approximate design method for evaluation of the bendability of sections in industrial forming operations is proposed. The results show that the slenderness ratio ( b/ t) and the width of the flange are the main parameters related to the bending radius at the onset of plastic buckling and the magnitude of local deformations, respectively. Material parameters have proven to be relatively more important to buckling radius than to deformation of individual cross-sectional members. Although there is some discrepancy between the experimental and theoretical results at tight nominal bend radii, the overall correlation is surprisingly good. It is, therefore, concluded that the present approach provides an efficient method for the evaluation of the bendability of rectangular hollow sections.