Application of solution structure theorems to Cattaneo–Vernotte heat conduction equation with non-homogeneous boundary conditions

In this study, a non-Fourier heat conduction problem formulated using the Cattaneo–Vernotte (C–V) model with non-homogeneous boundary conditions is solved with the superposition principle in conjunction with solution structure theorems. It is well known that the aforementioned analytical method is not suitable for such a class of thermal problems. However, by performing a functional transformation, the original non-homogeneous partial differential equation governing the physical problem can be cast into a new form such that it consists of a homogeneous part and an additional auxiliary function. As a result, the modified homogeneous governing equation can then be solved with solution structure theorems for temperatures inside a finite planar medium. The methodology provides a convenient, accurate, and efficient solution to the C–V heat conduction equation with non-homogeneous boundary conditions.     

The effect of annealing ambient on carrier recombination in boron implanted silicon

The selection of either an oxidising or inert ambient during high temperature annealing is shown to affect dopant activation and electron–hole recombination in boron implanted silicon samples. Samples implanted with B at fluence between 3 × 10¹⁴ cm^–2 to 3 × 10¹⁵ cm^–2 are shown to have lower dopant activation after oxidation at 1000 °C compared to an equivalent anneal in an inert ambient. In addition, emitter recombination is shown to be up to 15 times higher after oxidation compared with an inert anneal for samples with equivalent passivation from deposited Al₂O₃ films. The observed increase in recombination for oxidised samples is attributed to the enhanced formation of boron‐interstitial defect clusters and dislocation loops under oxidising conditions. It is also shown that an inert anneal for 10 minutes at 1000 °C prior to oxidation has no significant impact on sheet resistance or recombination compared with a standard oxidation process.

     

利用紫外Mie散射激光雷达探测澳门地区沙尘暴事件

研制了一台工作波长为355nm的紫外高能Mie散射激光雷达,并利用该激光雷达在2010年一次沙尘暴事件期间对澳门上空的大气进行了探测,得到了澳门地区不同时刻的气溶胶消光系数垂直廓线。利用Fernald方法反演得到的气溶胶近地面消光系数随时间的变化与当地气象数据具有较好的一致性,气溶胶消光系数与当地可吸入颗粒物浓度的相关性达到了0.93。气溶胶垂直廓线显示,在沙尘暴来临期间存在明显的沙尘气溶胶凝集层。通过气溶胶轨迹倒推,分析了沙尘气溶胶的来源及路径。观测结果表明,该激光雷达可以在特殊天气条件下对澳门地区气溶胶进行有效探测,这将有助于深化对澳门上空气溶胶特性的研究。     

Rules extraction in short memory time series using genetic algorithms

Data mining is performed using genetic algorithm on artificially generated time series data with short memory. The extraction of rules from a training set and the subsequent testing of these rules provide a basis for the predictions on the test set. The artificial time series are generated using the inverse whitening transformation, and the correlation function has an exponential form with given time constant indicative of short memory. A vector quantization technique is employed to classify the daily rate of return of this artificial time series into four categories. A simple genetic algorithm based on a fixed format of rules is introduced to do the forecasting. Comparing to the benchmark tests with random walk and random guess, genetic algorithms yield substantially better prediction rates, between 50% to 60%. This is an improvement compared with the 47% for random walk prediction and 25% for random guessing method. Received 29 August 2000     

Measurement of στ product of solid state laser materials by an alternative method: Application to Nd3+ doped YVO4 crystal for 4 F 3/2→4 I 11/2 transition

In this paper an alternative approach for measurement of στ product for ⁴ F _3/2→⁴ I _11/2 transition of Nd³⁺ doped YVO₄ crystal is reported. In this method a microchip laser is formed by keeping a small piece of the sample in plane-plane resonator and a diode laser (808 nm) is used for pumping. The pump power induced thermal lensing effect is used to make the cavity stable. The cavity mode area is estimated by measuring the thermal lens focal length at the threshold and the average pump area is measured by Gaussian fit to the intensity profiles of the pump beam. The value of στ product of Nd:YVO₄ crystal obtained by this method is within 10% of the reported values. The advantage of this method is that it is a simple method for direct measurement of στ product of laser crystals.     

Thermal Degradation Behavior and Kinetic Analysis of Biodegradable Polymers Using Various Comparative Models, 1

Thermal degradation behavior of a biodegradable polymer (PBS) has been investigated by conventional and MTGA methods. The kinetic parameters of degradation were calculated by a general analytical solution and by the Coats‐Redfern, Ozawa, Horowitz‐Metzger, and MTGA methods. The results reveal that the reaction mechanism at lower temperature is probably the F1 model through the reaction of random chain cleavage via cis‐elimination. However, the reaction mechanism at higher temperature is likely to be D1 model because of the dominant diffusion control effect.

     

Natural anti-HIV agents. Part 3: Litseaverticillols A-H, novel sesquiterpenes from Litsea verticillata

Bioassay directed-fractionation led to the identification of litseaverticillols A-H (1-8) from the leaves and twigs of Litsea verticillata Hance. These new sesquiterpenes possess a unique skeleton that was recently designated as ‘litseane’. The structures of these compounds were determined by spectroscopic means including 1D and 2D NMR data. Structural configurations were determined by ROESY experiments. Mosher ester reactions and optical rotation measurements established the sesquiterpenes 1-8 as racemates. Isolates 1-8 inhibited HIV-1 replication in HOG.R5 cells with IC₅₀ values ranging from 2 to 15 μg/ml (8-58 μM) while affecting the growth of HOG.R5 at concentrations 2-3-fold higher. Based on this data, structure-activity relationships can be discerned, suggesting compounds of this class are good candidates for analog production.     

Determination of six polyynes in Oplopanax horridus and Oplopanax elatus using polyethylene glycol modified reversed migration microemulsion electrokinetic chromatography

A PEG‐modified reversed migration MEEKC method was developed for simultaneous determination of six polyynes, including oplopandiol, falcarindiol, oplopandiol acetate, (11S, 16S, 9Z)‐9,17‐octadecadiene‐12,14‐diyne‐1,11,16‐triol,1‐acetate, oplopantriol B, and oplopantriol A, in Oplopanax horridus and Oplopanax elatus. The running buffer containing 0.8% v/v ethyl acetate, 3.8% w/v SDS, 6.6% v/v n‐butanol in 20 mM phosphate buffer (pH 2.5), followed by mixing with propan‐2‐ol at 30% v/v and PEG‐1000 at 15% w/v, was applied in the analysis. The proposed method was successfully applied to determine the six polyynes in five samples of Oplopanax horridus and one of O. elatus. The result showed that the types and amounts of polyynes present were obviously different when comparing the two herbs. Besides, the developed PEG‐modified reversed MEEKC method might be suitable for the analysis of hydrophobic analytes in herbal medicines.     

On the stability of elastico-viscous flow between roating cylinders

Summary Thomas andWalters (9, 2, 3) have recently shown that for a certain elastico-viscous liquid, the presence of elasticity has a destabilizing effect on the flow. The problem is reconsidered in the present paper for another idealized elastico-viscous liquid which is as simple as that considered byThomas andWalters. It is shown that in this case, the presence of elasticity has a stabilizing influence. It is concluded that a stability experiment would be a useful addition to the experiments usually set up to characterise elastico-viscous liquids.