Study of the Transformation of Gallium Arsenide Surface Layers under the Action of Light by Means of Surface Acoustic Waves

Journal of Communications Technology and Electronics - Changes in the state of the surface layer of semi-insulating (111) GaAs in air under the action of white light are studied using surface...     

单面开孔空间结构风压分布及风致内压研究

本文利用计算流体动力学通用软件FLUENT对具有复杂体型的大跨空间屋盖结构进行数值分析,研究了结构在体型逐渐变化的过程中风压分布的变化规律;针对单面开孔结构的风致内压问题,以及内压对结构的影响做了深入的研究,得到一些有价值的结论.     

Decomposition of singular large sparse matrix by adding dummy links and dummy degrees

Abstract

This paper proposes a simple scheme to decompose an n×n nonpositive definite matrix, A, associated with simultaneous equations, A X = B, into a triple‐factors (lower triangular, diagonal, and upper triangular matrices), i.e., Å = L D U, without interchanging rows or columns of A, but with A expanded with new rows and new columns to an m×m matrix Å. Whenever a near‐zero diagonal element, say ā_ii , is encountered and used as a pivoting element, an appropriate positive real number, say p, is added to this diagonal element, and a new term —px_k is also added to the i‐th equation, where x_k is a new variable called “dummy variable'’. If we also add a new equation —px_i + px_k = 0 to enforce the new added variable x_k equal to x_i then the modified i‐th equation has the same effect as the original equation. Therefore, the original solution X can be found directly from the expanded solution of the modified expanded equation. The method is very useful in solving the following problems: (1) nonlinear problems near the limit state, (2) postbuckling analysis, (3) system equations with constraint conditions, and (4) getting eigenvectors from eigenvalues.     

Variant-based cost estimation based on Information Management

Based on the product information structure related to the Manufacturing Engineering Reference Model, a method for variant-based cost estimation is proposed. The structure defines a product in terms of elements and their relations. The elements and their properties constitute product characteristics that can be used to compare products. For proper use in different engineering processes, the product characteristics are related to the four cost drivers - geometry, material, processes and production planning. The main advantage of the proposed method is a more flexible way of defining and valuing product characteristics without the use of rigid product classes and codes.     

Solving optimization problems by searching along a curve

Abstract

This paper proposes a curve for the one‐dimensional search method in optimization problems. The search is along a curve instead of a line. This curve is determined by a parameter [u] from the following three points: (1) the initial point X_o, (2) the Cauchy point X_c, (3) the Newton point X_N, and has the following four characteristics: (1) tangents to the steepest descent direction at X_o, (2) passes through X_N, (3) decreases monotonically from X_o to X_N for a quadratic function, (4) no complex computation on the parameter u. Therefore, the proposed method has the following advantages: (1) it is globally convergent, (2) it is locally q‐quadratically (or q‐superlinearly for quasi‐Newton point) convergent, (3) the search procedure is as simple as the line search method.     

Viscosity estimation of triacylglycerols and of some vegetable oils, based on their triacylglycerol composition

The experimentally determined kinematic viscosities of simple triacylglycerols [trilaurin, trimyristin (MMM), tripalmitin (PPP), tristearin (SSS), triolein (OOO), and trilinolein (LiLiLi) were correlated to a modified Andrade-type equation. The constants for the modified equation were derived for each simple triacylglycerol. The method was also used to estimate the viscosity of mixed triacylglycerols [1,2-dimyristoyl-3-palmitoyl (MMP), 1,2-dioleoyl-3-palmitoyl (OOP), 1,2-dimyristoyl-3-oleoyl (MMO), and 1,2-dipalmitoyl-3-oleoyl (PPO)], binary triacylglycerol mixtures (PPO/OOP, PPP/SSS, and OOO/SSS of different portions), and three types of vegetable oils [refined, bleached, and deodorized palm oil; cocoa butter; and canola oil] by applying modified Kay’s rule utilizing the simple triacylglycerol constants derived earlier. In all cases, the estimated values for liquid viscosity were compared with experimental values determined in this work and with previous work from the literature. When applied to vegetable oils, the method requires knowledge of their triacylglycerol composition. Despite its simplicity, the method gives a reasonable estimate. The method may be used to predict the viscosity of different blends of vegetable oils, and the accuracy is expected to increase when more experimental data on simple triacylglycerols become available.     

Decision-directed compensation of modulation-index drift for highbit rate equalized GMSK radio LANs

For an equalized Gaussian minimum shift keying system, the modulation-index drift from 0.5 associated with a simple direct FM implementation may result in a severe degradation on the equalizer performance. A decision-directed compensation for the drift is proposed. Computer simulations show that a large part of the performance loss due to modulation-index drift can be recovered with the proposed method