STEAM DRYING OF WOOD CHIPS IN PNEUMATIC CONVEYING DRYERS

ABSTRACT

A model for a pneumatic conveying dryer is presented. Although the main emphasis is put on superheated steam drying of wood chips, it can be used for other porous materials as well

The model includes a comprehensive two-dimensional model for the drying of single wood chips which accounts for the main physical mechanisms occurring in wood during drying. The external drying conditions in a pneumatic conveying dryer were calculated by applying the mass, heat and momentum equations for each incremental step in dryer length. A plug flow assumption was made for the dryer model and the single particle and dryer models were solved in an iterative manner. The non-spherical nature of wood chips were accounted for by measuring the drag and heat transfer coefficients

Model calculations illustrate the complex interactions between steam, particles and walls which occur in a flash dryer. The drying rate varies in a very complex manner through the dryer. The internal resistance to mass transfer becomes very important in The drying of less permeable wood species such as spruce. Two effects were observed as the particle size was increased: firstly the heat transfer rate decreased, and secondly the residence time increased. To some extent, these effects compensate for each other, however, the net result is that larger chips have a higher final moisture content.     

Digital communication signals identification using an efficient recognizer

Automatic recognition of the communication signals plays an important role for various applications. Most of the existing techniques require high levels of signal to noise ratio (SNR). In this paper, we propose a high efficient technique for classification of the digital modulations that requires a low level of SNRs. This technique includes two main modules: feature extraction module and the classifier module. In the feature extraction module we use the auto-regressive modeling together other useful features. These features are a combination set of the entropy and energy of the signal, variance of the coefficients wavelet packet transform, fourth order of moment and zero-crossing rate. In the classifier module we have used the two structures of the neural networks: multi-layer perceptron (MLP) neural network and radial basis neural networks. Simulation results show the proposed technique has very high recognition accuracy for identification of the considered digital modulations even at very low SNRs.     

An irregular frequency reuse scheme for cellular OFDMA systems

While conventional frequency reuse techniques need to allocate mutually exclusive frequency resources to adjacent cells, this paper proposes a technique for OFDMA systems to use pseudo‐random subchannel allocation patterns based on the preamble number. Although sophisticated cell planning is not required for the proposed technique, irregular frequency patterns can allow efficient interference avoidance and high data throughput. Copyright © 2010 John Wiley & Sons, Ltd.     

考虑非规则荷载下土体残余应变的时域积分方法

非规则荷载下土体残余应变发展模型是一个目前仍在探索的问题，现有的土层时域积分方法难以考虑土体的残余应变效应。阐述了一种在规则和非规则荷载下土体残余应变的表示方法，将其与双曲线型动态骨架曲线相结合，推导出一种能较好考虑非规则荷载下残余应变效应且方便程序实现的土体应力-应变关系。将此土体应力-应变关系应用于土层地震反应时域积分方法中，获得了一种考虑土体残余应变效应的时域积分方法，基于MATLAB平台编制了RS-DYMATLAB计算程序。利用实验数据对方法进行了验证，结果表明，本方法是一种合理可行的、能较好地考虑土体的残余应变效应的土层地震反应分析方法。     

The science of sex appeal: An evolutionary perspective.

Growing evidence shows that features we find attractive in members of the opposite sex signal important underlying dimensions of health and reproductive viability. It has been discovered that men with attractive faces have higher quality sperm, women with attractive bodies are more fertile, men and women with attractive voices lose their virginity sooner, men who spend more money than they earn have more sex partners, and lap dancers make more tips when they are in the fertile phase of their menstrual cycle. This paper highlights recent evidence showing that the way we perceive other people has been shaped by our evolutionary history. An evolutionary approach provides a powerful tool for understanding the consistency and diversity of mating preferences and behaviors across individuals and cultures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

恒包络信号识别与快速突发捕获

为了迅速判断恒包络信号的起始点,详细推导了信号平坦度的计算公式,将信号平坦度概念引入到信号捕获和端点检测领域,在快衰落信道下通过计算噪声和信号平坦度不同,快速区分噪声和恒包络信号;并利用搜索窗快速定位信号起始点位置。经过试验表明在信噪比不低于5dB条件下,该参数能够迅速捕获恒包络信号,并能准确得判定信号的起始点位置,该方法适用在实时性要求比较高的领域。     

直立锁边大型不规则多曲金属屋面施工技术

直立锁边屋面系统采用浮动结构设计，即无穿孔、无穿刺的隐蔽式安装设计。青岛体育中心游泳跳水馆屋盖形状复杂且为不规则多曲面，采用扇形铝镁锰合金直立锁边暗扣式设计，既体现了建筑形象特征，又满足了屋面保温、防潮、隔声及雨水疏导等多种要求。     

Robust detection of a weak signal with redescending M‐estimators: A comparative study

On finite samples redescending M‐estimators outperform linear bounded Huber's M‐estimators. To provide stable detection of a weak signal of arbitrary shape, robust Neyman–Pearson detection rules based on redescending M‐estimators of location are introduced and studied. It is shown that, on the whole, robust detectors based on redescending M‐estimators outperform conventional Huber's linear bounded detectors rules under light‐ and heavy‐tailed noise distributions both on large and small samples. Copyright © 2009 John Wiley & Sons, Ltd.     

An Almost Sure Result on Sampling of Bandlimited Random Signals

The Shannon-Nyquist sampling theorem for deterministic signals is a fundamental result in the field of telecommunication and signal processing, and many re- sults on this topic have been obtained. However, very few results on random signals have been published, after Kol- mogorov mentioned the importance of Shannon-formula for stochastic signals in 1956. In this paper, following the almost sure result for bandlimited stochastic processes pro- posed by Seip in 1990, we give an almost sure result of the classical sampling theorem for bandlimited random signals with local average sampling.     

高精度异型铜合金带材生产

本文简要回顾了我国异型铜带的开发情况。着重介绍洛阳铜加工厂引进的法国格里赛公司高精度异型铜带生产线的工艺特点以及几年实践的认识。