Analysis and measurement of candle flame shapes

A combined analytical and experimental study was performed to determine the length and width of a candle flame. Measurements were made of laminar steady flames from photographs of straight-wick candles composed of n-tetracosane and normal paraffin waxes. The wicks studied ranged in diameter from about 1 to 9 mm, and in height from about 2 to 10 mm, with aspect ratios (diameter to length) of 0.1 to 2. The flame length from the pool surface and the flame width at the top of the wick were found. It was also noted and recorded that the flame attachment point along the vertical wick varied. The attachment point was found to depend on the aspect ratio of the wick. A model based on stagnant layer burning for a finite cylinder was used, along with the Roper laminar burner model for flame height. With slight adjustment to a constant, the width of the flame was well predicted, and the prediction for the flame height was about 60% too high and offset. In addition, the model gave insight to produce an accurate simple correlation for flame height in terms of wick aspect ratio and Rayleigh number.     

唇形油封结构参数对摩擦面温度的影响

为研究轴速、前后唇角、接触宽度、抱轴力等参数对油封摩擦面上温度最大值的影响,文章利用FLU-ENT建立了唇形油封的二维轴对称模型,并进行计算.结果表明:随着轴速的增加,摩擦面上的温度最大值逐渐增加；前唇角的变化对摩擦面上的温度最大值影响较小,在轴速较低时几乎没有影响；后唇角的变化对摩擦面上的温度最大值几乎没有影响；随着...     

Effect of binder melt flow on the leading edge flames of solid propellant sandwiches

This study reports the effect of binder melt flow on the burning behaviour, specifically the burning rate controlling sites referred to as the leading edge flames (LEFs), of different types of sandwich propellants, namely, pure, micro-aluminized and nano-aluminized binder. The distance between the LEFs anchored over the lamina interface edges of sandwiches is measured from the combustion images captured under high spatio-temporal resolution. Similarly, the extent of binder melt flow is also measured from the quenched surfaces of sandwiches. The burning rate experiments are performed as well on sandwiches with different middle lamina contents and thicknesses at pressures of 2, 4 and 7 MPa. Two different curing agents are considered to examine the melt flow behaviour of the binder. The curing agent significantly influences the inter-LEF distance mainly in the case of pure binder sandwiches, however, its effect is negligible in aluminized binder sandwiches because of the presence of Al particles that impedes the flow to appreciable extent. Substantial protrusion of the middle lamina relative to the lamina interfaces is observed in micro-aluminized binder sandwiches due to significant accumulation of Al particles on the burning surface. In the case of nano-aluminized binder sandwiches, such protrusion is relatively marginal since nano-Al particles burn quickly, which enables the gas phase flame to locate close to the burning surface, although the extent of Al accumulation is considerably more than in the former case. This causes the nano-aluminized binder sandwiches as a whole to burn significantly faster than the other two cases in the pressure range (<7 MPa) where the LEFs predominantly control the sandwich burning rates.     

Resummed corrections to the ρ parameter in the complex mass scheme

We present all order results for the heavy top corrections to the ρ parameter in the complex mass scheme. We derive translation formulas between the complex mass and the on-shell scheme and show that they are ultimately equivalent. We show that a naive treatment with a fixed width for the top quark cannot give even approximately correct results.     

Exercising flexible load contracts: Two simple strategies

A flexible load contract is a type of swing option where the holder has the right to receive a given quantity of electricity within a specified period, at a fixed maximum effect (delivery rate). The contract is flexible, in the sense that delivery (the take hours) is called one day in advance. We investigate two simple strategies for exercising flexible load contracts, where both use price information from the forward market. For 10 contracts traded in the period 1997–2001, we calculate the performance of the two strategies and compare with the reported performance of one complex dynamic programming approach as well as the actual results obtained by three anonymous market participants. The comparison indicates that our simple computer‐efficient strategies perform better on average and produce more stable results. Copyright © 2007 John Wiley & Sons, Ltd.     

Innovation in the cluster validating techniques

To detect database records containing approximate and exact duplicates because of data entry error or differences in the detailed schemas of records from multiple databases or for some other reasons is an important line of research. Yet no comprehensive comparative study has been performed to evaluate the effectiveness of Silhouette width, Calinski & Harbasz index (pseudo F-statistics) and Baker & Hubert index (γ index) algorithms for exact and approximate duplicates. In this paper, a comparative study and effectiveness of these three cluster validation techniques which involve measuring the stability of a partition in a data set in the presence of noise, in particular, approximate and exact duplicates are presented. Silhouette width, Calinski & Harbasz index and Baker & Hubert index are calculated before and after inserting the exact and approximate duplicates (deliberately) in the data set. Comprehensive experiments on glass, wine, iris and ruspini database confirms that the Baker & Hubert index is not stable in the presence of approximate duplicates. Moreover, Silhouette width, Calinski and Harbasz index and Baker & Hubert indice do not exceed the original data indice in the presence of approximate duplicates.     

Adsorptive separation in the enhancement of butene dehydrogenation

Fixed-bed columns containing solid catalysts and adsorbents were employed for simultaneous reaction and separation. The models developed for butene dehydrogenation reaction were validated with experimental data. The model was then employed for variable bed configurations with and without the effect of pressure and vacuum swing reaction (PSR and VSR). The models for the mass and momentum transfer in the catalyst bed and adsorber were solved using orthogonal collocation within the method of lines. The reactor/separator performances were tested for beds with varying numbers of layers of catalysts and adsorbents arranged sequentially. The reaction columns behaved as reactor/separators in series. As the number of layers increased, a homogeneous distribution of the catalyst and adsorbent was approached in the limit. These configurations with variable catalyst/adsorbent distributions were investigated in terms of product purity, selectivity, conversion, recovery and yield. Improved reactor performance was observed with pressure and vacuum swing separation systems and in particular with close to well-mixed reactor/separator configurations.     

有限环Zk上码字的广度性质及两种递归算法

本文定义了环Zk上码字的一种数学特征,即码字的广度,研究了码字广度的一些性质,给出了计算环Zk上码字广度的两种递归算法.     

Light meson spectrum and their leptonic decay widths in the frame work of constituent quark models

The phenomenological non-relativistic quark model has been employed to obtain the ground state masses of light vector mesons and their radially excited states and their decay widths.The full hamiltonian used in the investigation has kinetic energy,the confinement potential and the one-gluon-exchange potential.A good agreement is obtained with the experimental masses and their leptonic decay widths.     

大型轴类锻件新型凸面砧拔长研究

拔长是大型轴类锻件成型的重要工序.本文针对其锻造中拔长过程,研究了一种新的型砧,以期改善拔长时工件应力应变状态,提高锻件内在质量.并应用有限元分析软件deform-3D进行数值模拟,分别研究了型砧角度α、砧宽比对锻件内部应力、应变的影响,列出了对比试验结果.从而确定了基本的型砧参数.