基于改进叶素动量理论的水平轴风电机组气动性能计算

综合考虑到风剪切、塔影效应、三维旋转效应的影响,本文对传统的叶素动量理论（bladeelementmomentum,BEM）进行改进,建立风电机组气动性能计算模型,基于该模型编制计算程序,以商用1．5MW风电机组为计算实例,计算出其在不同的风速、转速和桨距角配置下的轴向和切向气动荷载分布,以及推力、功率和风能利用系数,与传统BEM模型及风电设计分析软件FOCUS5计算值对比,验证了该模型的正确性和优越性。     

Large amplitude flexural vibration of rectangular plates

By using an approximate formulation due to Berger it is shown that the vibration of rectangular plates with large amplitudes may be treated in a simple and unified manner. Numerical results are given for various boundary conditions.     

Postbuckling Formulation for Symmetric Laminated Panels with Various Edge Support Conditions

A study into the structural postbuckling response of symmetric laminated composite plates subjected to in-plane compressive load is presented in this contribution. Various cases of support conditions are investigated: loaded ends are either simply supported or clamped, while the unloaded edges are a combination of simple support, clamp, and free. The method of analysis used is the combination of the semienergy approach using the semianalytical finite-strip methodology and the well-known von Karman large-deflection equations. Extensive validation of the analytical solution with published theoretical solutions and experimental data are presented. The final form of the expression is quite versatile and can be readily used for design purposes.     

Phase Transformations of α-Alumina Made from Waste Aluminum via a Precipitation Technique

We report on a recycling project in which α-Al₂O₃ was produced from aluminum cans because no such work has been reported in literature. Heated aluminum cans were mixed with 8.0 M of H₂SO₄ solution to form an Al₂(SO₄)₃ solution. The Al₂(SO₄)₃ salt was contained in a white semi-liquid solution with excess H₂SO₄; some unreacted aluminum pieces were also present. The solution was filtered and mixed with ethanol in a ratio of 2:3, to form a white solid of Al₂(SO₄)₃·18H₂O. The Al₂(SO₄)₃·18H₂O was calcined in an electrical furnace for 3 h at temperatures of 400–1400 °C. The heating and cooling rates were 10 °C/min. XRD was used to investigate the phase changes at different temperatures and XRF was used to determine the elemental composition in the alumina produced. A series of different alumina compositions, made by repeated dehydration and desulfonation of the Al₂(SO₄)₃·18H₂O, is reported. All transitional alumina phases produced at low temperatures were converted to α-Al₂O₃ at high temperatures. The X-ray diffraction results indicated that the α-Al₂O₃ phase was realized when the calcination temperature was at 1200 °C or higher.     

Interactive Mixture as a Rapid Drug Delivery System

The effectiveness of an interactive mixture as a rapid drug delivery system is compared with that of a solid dispersion. The influences of drug load, particle size, and crystallinity of these test systems are investigated. The interactive mixtures and solid dispersions were prepared from polyethylene glycol (PEG) 3350 and hydrophobic nifedipine drug by means of physical mixing and melting methods, respectively. The formed products were subjected to drug particle size and crystallinity analyses, and dissolution tests. In comparison with the interactive mixtures, the solid dispersions with low drug load were more effective as a rapid drug delivery system, as the size of a given batch of drug particles was markedly reduced by the molten PEG 3350. The rate and extent of drug dissolution were mainly promoted by decreasing effective drug particle size. However, these were lower in the solid dispersions than in the interactive mixtures when a high load of fine drug particles was used as the starting material. This was attributed to drug coarsening during the preparation of the solid dispersion. Unlike solid dispersions, the interactive mixtures could accommodate a high load of fine drug particles without compromising its capacity to enhance the rate and extent of drug dissolution. The interactive mixture is appropriate for use to deliver a fine hydrophobic drug in a formulation requiring a high drug load.     

Inverse halftoning and kernel estimation for error diffusion

Two different approaches in the inverse halftoning of error-diffused images are considered. The first approach uses linear filtering and statistical smoothing that reconstructs a gray-scale image from a given error-diffused image. The second approach can be viewed as a projection operation, where one assumes the error diffusion kernel is known, and finds a gray-scale image that will be halftoned into the same binary image. Two projection algorithms, viz., minimum mean square error (MMSE) projection and maximum a posteriori probability (MAP) projection, that differ on the way an inverse quantization step is performed, are developed. Among the filtering and the two projection algorithms, MAP projection provides the best performance for inverse halftoning. Using techniques from adaptive signal processing, we suggest a method for estimating the error diffusion kernel from the given halftone. This means that the projection algorithms can be applied in the inverse halftoning of any error-diffused image without requiring any a priori information on the error diffusion kernel. It is shown that the kernel estimation algorithm combined with MAP projection provide the same performance in inverse halftoning compared to the case where the error diffusion kernel is known.     

Structural and optical properties of nc-Si:H thin films deposited by layer-by-layer technique

Hydrogenated nanocrystalline silicon (nc-Si:H) thin films deposited on c-Si and quartz substrates by layer-by-layer (LBL) technique using radio-frequency plasma enhanced chemical vapour deposition system. The effects of rf power on the interlayer elemental profiling, structural and optical properties of the films were investigated by Auger electron spectroscopy, Fourier transform infrared spectroscopy, Raman scattering spectroscopy, X-ray diffraction and optical transmission and reflection spectroscopy. The results revealed that the LBL deposition leads to a formation of different ranges of crystallite sizes of nc-Si corresponds 3–6 and 8–26 nm respectively. LBL deposition also demonstrated a capability to increase the crystalline volume fraction of nc-Si up to 65.3 % with the crystallite size in between 5 and 6 nm, at the rf power in between 80 and 100 W. However, the crystalline volume fraction decreased for the rf power above 100 W due to the growth of nc-Si was suppressed by the formation of SiO₂. In addition, the onset of crystallization of the films deposited on c-Si and quartz substrates are different with increase in the rf power. The effects of rf power on the growth of nc-Si, and the hydrogen content, structural disorder, crystallite size of nc-Si and oxygen diffusion into the LBL layer with the change of optical energy gap under the variation of rf power are also discussed.     

Automation of the use of fluorescent microspheres for the determination of blood flow

Fluorescent-labeled microspheres (FM) are a new tool for the determination of organ blood flow. However, the FM-method is labor intensive, because of the necessity to recover the microspheres from the tissue samples. The aim of this study was to automate the FM-method. A Zymate-Robotic System (Zymark, Idstein, Germany) was modified to handle a novel filtration device. The robot is surrounded by 12 different stations which are necessary to process the samples. It performs the sequential steps which are needed to recover the microspheres from the samples. The dyes are finally released from the FM with a solvent and their fluorescent intensity is measured online using a spectrophotometer (Perkin Elmer, Uberlingen, Germany). The robotic system is able to recover the FM through digestion and filtration of the tissue samples using the new filter, to dissolve the FM and to release the dyes so that their fluorescent intensities can be measured for the calculation of organ blood flow.