中学生物教学中"植物细胞有丝分裂实验" 改进的探索

植物细胞有丝分裂是中学生物实验课的一个重要内容，本文是对实验的选材，方法改进的一种探索，通过实验得出豌豆是本实验比较可靠的实验材料。     

新型化学电源--燃料电池

燃料电池是一种等温并直接将储存在燃料和氧化剂中的化学能高效、环境友好地转化为电能的新型发电装置．燃料电池不受热机效率的限制，能量转换效率高，无污染、无噪音，具有满足环境保护的要求．预计燃料电池系统将在洁净煤燃料电池电站、电动汽车、移动电源、不间断电源、潜艇及空间电源等方面有着广泛的应用前景和巨大的潜在市场．本文介绍了燃料电池的的优点、主要种类、工作原理、国内外发展概况以及燃料电池的前景展望。     

几种基于细胞特异感受的生物学技术

综合了细胞芯片，细胞传感器和膜片钳这几种基于细胞特异感受的生物学技术原型及应用状况。     

原电池教学设计

基础教育课程改革倡导师生在教学中进行科学探究，让学生自行建构知识网络。根据这种理念，就原电池一节的教学设计了一种科学探究的教学模式。     

Mathematical Analysis of Energy Efficiency in IEEE 802.11 DCF

The standardized IEEE ,802. II distributed coordination function （ DCF） provides a contention-based distributed channel access mechanism for mobile stations to share the wireless medium. However, when stations are mobile or portable units, power consumption becomes a primary issue since terminals are usually battery driven. This paper proposes an analytical model that calculates the energy efficiency of both the basic and the RTS/CTS access mechanisms of the IEEE 802. II protocol. The model is validated with simulation results using NS-2 simulation package. The effects of the network size, the average packet length, the initial contention window and maximum backoff stages on the energy efficiency of both access mechanisms are also investigated. Results show that the basic scheme has low energy efficiency at large packet length and large network size, and depends strongly on the number of stations and the backoff procedure parameters. Conversely, the RTS/CTS mechanism provides higher energy efficiency when the network size is large, and is more robust to variations in the backoff procedure parameters.     

三角债清理的图论模型分析

三角债是我国当前经济领域中存在的一个突出问题。文章建立了三角债的图论模型,并证明了任一债务网络皆可转换为最小债务网络,从而简化了三角债清理工作。     

加强信息网络环境下的图书馆建设

信息网络的迅速发展，对图书馆提出了严峻挑战的同时也带来机遇。图书馆要面对时代变化，不断进行自身建设，才能适应社会发展需要。     

EBF网络特征映射和恢复及其在鲁棒话者识别中的应用

The performance of speaker verification systems is often compromised under real-world environments. For example, variations in handset characteristics could cause severe performance degradation. This paper presents a novel method to overcome this problem by using a non-linear handset mapper. Under this method, a mapper is constructed by training an elliptical basis function network using distorted speech features as inputs and the corresponding clean features as the desired outputs. During feature recuperation, clean features are recovered by feeding the distorted features to the feature mapper. The recovered features are then presented to a speaker model as if they were derived from clean speech. Experimental evaluations based on 258 speakers of the TIMIT and NTIMIT corpuses suggest that the feature mappers improve the verification performance remarkably.     

Modeling water and carbon fluxes above summer maize field in North China Plain with back-propagation neural networks

INTRODUCTION Dynamics of carbon and water vapor fluxesexchange between the atmosphere and the ecosystembiosphere, depend on complex and non-liner interplayamong physiological, ecological, biochemical andedaphic factors and meteorological conditions (Jarvis,1995; Leuning et al., 1995). There are many studiesquantifying the fluxes across different time and spacescales as well as assessing the environment con-straints on them by some kinds of biophysical orempirical models whose resul…     

移动自组网AODV多路径路由研究

AODV协议是唯一通过IETF批准成为RFC文档的移动自组网按需控制路由协议．分析AODV路由协议工作过程及优缺点，并介绍了几种典型的基于AODV的多路径路由改进协议，最后对这些多路径协议进行优缺点分析及性能比较。