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51-1785 HB3651 2012-42665 CIP Drixler, Fabian. Mabiki: infanticide and population growth in eastern Japan, 1660-1950. California, 2013. 417p bibl index afp ISBN 9780520272439, $75.00; ISBN 9780520953611 e-book, contact publisher for [...]

A tapered helix monopole as a part of a rectenna for the detection of terahertz radiation is proposed. The antenna consists of a truncated conical helix extruded from a planar spiral and in a nanometric metallic whisker connected to one of its edges. The whisker faces a semiconductor substrate constituting the antenna ground plane. The structure is designed to be combined with a rectifying junction, realized just below the whisker base, which produces the direct conversion of terahertz electromagnetic field into dc current. The figure of merit of the structure is the electric field enhancement factor at the metallic whisker/semiconductor interface. Numerical full-wave simulations show that, for the tapered helix monopole, the field enhancement factor value can be higher than 26 000, which is approximately one order of magnitude greater than previously reported values in the literature. Detailed description of the fabrication process and investigation of antenna performances for different values of geometrical parameters are presented.

Nickel nanowires have been formed by the stationary electrochemical deposition of nickel into mesoporous silicon from the modified Watts bath. The polycrystalline nature of the Ni deposit has been established as well as expansion of its lattice parameter in comparison with bulk nickel. Control of the potential of porous silicon during electrochemical deposition allows to determine the moment of complete filling of pore space with Ni. The maximum achieved filling factor was 67% of the pores. The pore dimensions have been found to define the length and the diameter of the Ni nanowires that have equaled to 10 um and 100-120 nm, respectively.

Different copper nanostructures have been deposited onto porous silicon (PS) by using HF-based solutions of CuSO4 and immersion technique. The variation of the porous template parameters and deposition regimes has been found to allow obtaining of copper nanoparticles, copper rough films and porous copper layers. The dimensions, roughness, structural parameters and phase composition of the obtained copper nanostructures have been established.

In this study we present an efficient global optimization method, DIviding RECTangle (DIRECT) algorithm, for parametric analysis of dynamic systems. In a bounded constrained problem the DIRECT algorithm explores multiple potentially optimal subspaces in one search. The algorithm also eliminates the need for derivative calculations which are required in some efficient gradient-based methods. In this study the first optimization example is to find the dynamic parameters of a tennis racket. The second example is a biomechanical parametric study of a heel-toe running model governed by six factors. The effectiveness of the DIRECT algorithm is compared with a genetic algorithm in an analysis of heel-toe running. The result shows that the DIRECT algorithm obtains an improved result in 83% less execution time. It is demonstrated that the straightforward DIRECT algorithm provides a general procedure for solving global optimization problems efficiently and confidently.

Abstract This study investigated the performance of parallel optimization by means of a genetic algorithm (GA) for lubrication analysis. An air-bearing design was used as the illustrated example and the parallel computation was conducted in a single system image (SSI) cluster, a system of loosely network-connected desktop computers. The main advantages of using GAs as optimization tools are for multi-objective optimization, and high probability of achieving global optimum in a complex problem. To prevent a premature convergence in the early stage of evolution for multi-objective optimization, the Pareto optimality was used as an effective criterion in offspring selections. Since the execution of the genetic algorithm (GA) in search of optimum is population-based, the computations can be performed in parallel. In the cases of uneven computational loads a simple dynamic load-balancing scheme is proposed for optimizing the parallel efficiency. It is demonstrated that the huge amount of computing demand of the GA for complex multi-objective optimization problems can be effectively dealt with by parallel computing in an SSI cluster.

A feasible solution must be obtained in a reasonable time with high probability of global optimum for a complex tribological design problem. To meet this decisive requirement in a multi-objective optimization problem, the popular and powerful genetic algorithms (GAs) are adopted in an illustrated air bearing design. In this study, the goal of multi-objective optimization is achieved by incorporating the criterion of Pareto optimality in the selection of mating groups in the GAs. In the illustrated example the diversity of group members in the evolution process is much better maintained by using Pareto ranking method than that with the roulette wheel selection scheme. The final selection of the optimal point of the points satisfied the Pareto optimality is based on the minimum–maximum objective deviation criterion. It is shown that the application of the GA with the Pareto ranking is especially useful in dealing with multi-objective optimizations. A hybrid selection scheme combining the Pareto ranking and roulette wheel selections is also presented to deal with a problem with a combined single objective. With the early generations running the Pareto ranking criterion, the resultant divergence preserved in the population benefits the overall GA's performance. The presented procedure is readily adoptable for parallel computing, which deserves further study in tribological designs to improve the computational efficiency.

The study deals with the development of a hybrid search algorithm for efficient optimization of porous air bearings. Both the compressible Reynolds equation and Darcy's law are linearized and solved iteratively by a successive-over-relaxation method for modeling parallel-surface porous bearings. Three factors affecting the computational efficiency of the numerical model are highlighted and discussed. The hybrid optimization is performed by adopting genetic algorithm (GA) for initial search and accelerated by simplex method (SM) for refined solution. A simple and useful variable transformation is presented and used to convert the unconstrained SM to a constrained method. In this study, the hybrid search algorithm for a multi-variable design exhibits better efficiency compared with the search efficiency by using the SM. The proposed hybrid method also eliminates the need of several trials with random initial guesses to ensure high probability of global optimization. This study presents a new approach for optimizing the performance of porous air bearings and other tribological components.

This study presents an air-bearing design procedure by using Taguchi's Design of Experiments (TDE) to simulate the analysis of systems without adequate models. Instead of taking data from experiments, the performance of air bearings is obtained by an empirical verified numerical model. This arrangement eliminates the errors inevitably introduced in tests. When comparing with full factorial analysis, the number of tests is significantly reduced by using TDE in the demonstrated study. The optimum set of the variables predicted by TDE is numerically verified in the cases investigated. The analysis of orthogonal arrays consisting of three levels shows better performance prediction than the two levels analysis. The straightforward and easy to use procedure can be applied conjunction with numerical optimization technique to give an excellent start-point to minimize search time in a multi-variable design as illustrated in this report.

This study deals with the procedure to estimate the stiffness and damping of air-lubricated bearings under dynamic conditions. Unconstrained minimization methods were used in the nonlinear least squares (NLS) analysis to obtain the dynamic parameters of simulated noisy data with small signal-to-noise ratios (SNR). In the analysis the contaminating noise, either uniform or normally distributed noise, was scaled to give a known SNR and added to a simulated noise-free data. Even with poor initial-guess in the NLS as demonstrated in this study, both simplex and Powell's methods reach minimal variance with far fewer searching steps than those of the lattice and Hooke's methods. In the example of experimental study, the effect of an arbitrary data truncation point on the parameter estimation can be minimized in the fitting process by adding additional parameter-phase angle. The result shows good agreement between experimentally determined stiffness and theoretical prediction. This study provides a general procedure for dynamic analysis of air-lubricated bearings from noisy experimental measurements.

This study presents an engineering approach for optimizing performance of fluid-film lubricated bearings. Unconstrained nonlinear programming methods, lattice search and simplex method, were used as the optimization schemes to improve the merit of studied bearings with two or more design variables. The analysis of elliptical bearings shows high eccentricity ratio and two large pressure zones for high-speed stability can be obtained by maximizing film pressures in the upper and lower lobes. In this study, lattice method exhibits slightly more efficient search compared with that of simplex method in several two-variable optimum designs. The automatic mesh generation technique used in the pocket-shaped bearing analysis makes the numerical optimization as a flexible design tool. The effect of side flow restrictions on the load-carrying capacity of an optimized pocket-shaped slider bearing is clearly verified. The analysis of the aerostatic bearing explains an example of multi-objective minimization. A similar procedure can be easily adopted to analyze bearings with other profiles, or to maximize user-defined performance using more complicated models.

This study deals with the development of a computational procedure for solving the isothermal compressible Reynolds equation as the governing equation of air-bearing analysis. Newton's method is used to linearize Reynolds equation and an iterative successive relaxation process is adopted to solve for the air film pressure. The optimal value of relaxation factor for the cases studied is suggested in this report for numerical stability and computational efficiency. The model is verified numerically by examining the conservation of mass flow of the lubricant. The dimensional analysis of the governing equation permits the model to be readily applied to any given film geometry.The computer model developed can evaluate the air film pressure distribution, load capacity, frictional force, and mass flow of an air bearing. The proposed computational scheme efficiently analyzes the performance of air-lubricated journal bearings at large eccentricity ratios. A similar procedure can be employed to investigate the performance of highspeed noncircular air bearing or gas-lubrication film under slip-flow conditions. This study gives an analytical basis for the design of orifice-compensated externally pressurized air-lubricated bearing.

Nickel nanowires have been formed by stationary electrochemical deposition of nickel into mesoporous silicon templates from the modified Watts bath. Monitoring of the porous silicon potential during the electrochemical deposition has given the determination of the emergence of Ni on the outer surface of porous layer. Maximum filling factor of porous silicon with Ni has been achieved to 67%. The pore dimensions have been found to define the length and diameter of the Ni nanowires that have equaled to 10 μm and 100–120 nm, respectively. The polycrystalline nature of the nickel nanowires, as well as the expansion of nickel lattice constant in comparison with bulk material has been established by analyzing the X-ray diffraction spectra. The synthesized samples have possessed ferromagnetic properties, which have been confirmed by temperature measurements of the magnetization. Smaller values of the specific magnetization of the Ni/PS samples and the atomic magnetic moment of Ni atoms at the low temperature with respect to those of bulk material have been suggested to be mostly caused by formation of nickel silicide at the beginning of the Ni electrochemical deposition.