An improved hybrid Cartesian/immersed boundary method for fluid–solid flows

An improved hybrid Cartesian/immersed boundary method is proposed based on ghost point treatment. A second‐order Taylor series expansion is used to evaluate the values at the ghost points, and an inverse distance weighting method to interpolate the values due to its properties of preserving local extrema and smooth reconstruction. The present method effectively eliminates numerical instabilities caused by matrix inversion and flexibly adopts the interpolation in the vicinity of the boundary. Some typical fluid–solid flows, including viscous flow past a circular cylinder, a sphere, two cylinders in a side‐by‐side arrangement, and an array of 18 staggered cylinders, are examined. These benchmark simulations reasonably indicate the reliability and capability of the present method. Copyright © 2007 John Wiley & Sons, Ltd.     

Demonstration of high extinction ratio modal interference in a two-mode fiber and its applications for all-fiber comb filter and high-temperature sensor

We show that high extinction ratio (>20 dB) modal interference in a two-mode dispersion compensating fiber can be utilized to build a compact, easy-to-fabricate tunable all-fiber optical comb filter. Wavelength tunability over the full free spectral range of the comb filter is demonstrated with an electrical power of 115mW using an on-fiber thin film micro-heater deposited directly on the fiber. In another configuration, the comb filter is used as a temperature sensor with dynamic range of >300 °C and sensitivity of <0.1 °C. The temperature sensor is capable of measuring a temperature as high as 500 °C.     

The Preparation of Heptacyclo[6.6.0.0.2,60.3,130.4,11 0.5,90.10,14]Tetradecane Derivatives and the Analysis of Their NMR Spectra

The title compound is functionalized by a series of reactions to yield derivatives in the forms of hydroxides, ketones, ketals, lactones, etc. Their structures are analyzed by NMR spectroscopy.     

A post aza Baylis-Hillman/Heck coupling approach towards the synthesis of constrained scaffolds

An intramolecular Heck coupling of the product of an aza Baylis-Hillman reaction to afford conformationally constrained scaffolds is reported.     

The MT-MSXα(R) method: Applications to Li2, F2, and N2 molecules

The multiple scattering Xα(R) method with the scaling parameter α expressed as a function of the internuclear distance is applied to the Li₂, N₂, and F₂ molecules. Compared with the results obtained by the Xα method, the calculated Xα(R) equilibrium distances are smaller, the total energies are lower, and the dissociation energies are larger.     

A new parallel sorting algorithm based upon min-mid-max operations

In this paper we propose a new parallel sorting algorithm which is based upon an operation which sorts three elements. This algorithm is similar to the parallel odd-even merge sorting algorithm proposed by Batcher, except in the latter, the basic operation sorts only two elements. The correctness of our algorithm is also proved.This research work was partially supported by a grant from the National Science Council, Republic of China under the contract NSC73-0201-E007-01.     

Nonlinear analysis of a multi-cavity gyro-twystron

To preserve high gain, high efficiency and high power merits of gyroklystron, a gyro-twystron is designed using an electron beam with α(v_⊥/v_z) greater than unity. With a multi-cavity section of high gain, the length of the waveguide output section can be made shorter than the threshold length of the absolute instability without losing total system gain. Numerical simulations are carried out to analyze a ka-band gyro- twystron consisting of three TE₁₁₁ mode cavities and an output section of a TE₁₁ mode waveguide. Stability study is performed to ensure the tube without self-excited oscillations. With α=1.5, the 3-dB linear and saturated gain bandwidth in excess of 2 % can be obtained by stagger tuning for an 80 kV, 3 A electron beam with 5 % axial velocity spread. The maximum saturated gain is more than 55 dB at 33 % efficiency. By tapering the magnetic field of the last 2 cm of the interaction region, the efficiency can be increased to 43 % without degrading the bandwidth, which corresponds to an output power of 103 kW.     

Instrumental neutron activation analysis in study of the toxicity of trialkyltin-methacrylic copolymer as an antifouling agent

The analysis of tin in biological materials is rarely reported. In this study, instrumental neutron activation analysis was used to determine the tin together with some other trace elements in various organs of rats treated with trialkyltin-methacrylic copolymer. No appreciable accumulation of tin and variation of distribution of trace elements (Cr, Fe, Zn and Co) in various organs are found. The pathological changes in the liver sections cannot be observed either. This therefore indicates that the toxicity of trialkyltin-methacrylic copolymer is low, if any.     

A Hybrid Metaheuristic for the Quadratic Assignment Problem

The quadratic assignment problem (QAP) is known to be NP-hard. We propose a hybrid metaheuristic called ANGEL to solve QAP. ANGEL combines the ant colony optimization (ACO), the genetic algorithm (GA) and a local search method (LS). There are two major phases in ANGEL, namely ACO phase and GA phase. Instead of starting from a population that consists of randomly generated chromosomes, GA has an initial population constructed by ACO in order to provide a good start. Pheromone acts as a feedback mechanism from GA phase to ACO phase. When GA phase reaches the termination criterion, control is transferred back to ACO phase. Then ACO utilizes pheromone updated by GA phase to explore solution space and produces a promising population for the next run of GA phase. The local search method is applied to improve the solutions obtained by ACO and GA. We also propose a new concept called the eugenic strategy intended to guide the genetic algorithm to evolve toward a better direction. We report the results of a comprehensive testing of ANGEL in solving QAP. Over a hundred instances of QAP benchmarks were tested and the results show that ANGEL is able to obtain the optimal solution with a high success rate of 90%. This work was supported in part by the National Science Council, R.O.C., under Contract NSC 91-2213-E-005-017.