A Subcarriers Allocation Scheme for Cognitive Radio Systems Based on Multi-Carrier Modulation

Cognitive radio (CR) is a dynamic spectrum access technology as a solution to spectrum under-utilization problem in some licensed bands. Operating over an exceedingly wide spectrum, CR systems usually adopt multi-carrier modulation (MCM) to implement flexible channelization. Consequently, efficient channel allocation scheme becomes extremely important to an MCM based CR (MCM-CR) system. In this paper, a maximum likelihood detection model is developed to detect the presence and locations of licensed users (LUs) signals in the frequency domain. Performance of the detection model, including the optimal detection region, detection probability and false alarm probability, is analyzed. A one-order two-state Markovian chain model is proposed to predict channel status information. In particular, a novel subcarrier allocation scheme for MCM-CR systems is proposed, taking into account the confidence of channel estimation, quality of services (QoS) of rental users (RUs) and throughput. To validate the analytical results, simulations have been conducted to show effectiveness of the proposed scheme.     

抽油机井防污染洗井技术研究与应用

针对抽油机井化学清蜡成本较高、效果不明显，而热洗方式虽然操作容易且成本较低，但洗井时易产生倒灌，使油层受到污染的问题，研究了一种防污染洗井管柱。文中重点介绍了洗井管柱的结构及组成、热洗封隔器的结构及原理、技术指标、试验效果。为解决低渗透油田热洗污染油层的问题，提供了一条有效的途径。     

Cit-CSP及其应用

介绍了Cit-CSP--Cit/E-commerce信息安全保障平台子系统，并阐述了它所提供的消息摘要、块加密、加密(公钥)、签名和MAC等功能和服务。     

Sol-Gel Synthesis of Palladium-Doped Silica Nanocomposite Fiber Using Triton X-100 Micelle Template and the Application for Hydrogen Gas Sensing

Palladium-doped silica nanocomposites were synthesized via a sol-gel technique combined with a template of Triton X-100 micelle. The freshly prepared sol sample of Pd-doped silica nanocomposites was investigated by TEM. Determined from the TEM image, the sizes of the Pd nanoparticles are narrowly distributed, which are around 30 nm in diameter. The prepared sol solution of the sample was injected into a Tygon Microbore Autoanalysis tubing. After 14 days gelatinization, a transparent porous optical fiber was obtained. The response of the fiber to hydrogen gas was tested by using a fiber-optic spectrometric method. The palladium-doped silica nanocomposite fiber is sensitive upon exposure to hydrogen gas and the response is reversible. This palladium-doped silica nanocomposite fiber can be applied as a new kind of hydrogen gas sensor     

安钢集团信息化实施策略探讨

近年来，为了更好地应对新的市场挑战，钢铁企业都在积极推进信息化建设，以实现管理提升、效益提升的目标。本文结合安钢集团的实际情况，对信息化实施策略进行初步的探讨，希望能对企业信息化建设有所借鉴。     

酚醛树脂复合板在热连轧机中的应用

重点分析了现有F7机架出口导卫装置的情况。原导卫材料是由铸钢制造 ,由于摩擦和高温常常引起热连轧带钢表面划伤 ,根据现场实际情况用酚醛树脂复合板替代铸钢导卫装置。实践表明 ,这种改造即可行又可靠 ,并取得了好的效果     

Design of Millimeter Wave TFMS Bandpass Filter

In this paper, a Ka-band thin film microstrip line(TFMS) filter with multi-layer structure on silicon substrate is introduced. The simulated results show that it is possible to design compact millimeter-wave filter on silicon substrate with process compatible to current VLSI technology.     

数字频率合成技术在地球站中的应用

数字分频式微波频率合成器,具有结构简单,造价低,良好的低相嗓特性等优点,因而被通信卫星地球站所广泛采用。论述了数字分频式频率合成技术在工星通信地球站中的应用,提出了采用高度集成锁相环器件:PE3336设计一种低相噪特性的微波数字频率源的工程实例,并将之用于某通信卫星转发器地球站设备中。     

基于约束优化的联想记忆模型学习算法

本文提出了一种对称互连神经元网络的学习策略,利用全局约束优化方法确定连接权。优化过程采用了梯度下降技术。这种学习算法可以保证训练样本成为系统的稳定吸引子,并且具有优化意义上的最大吸引域。本文讨论了网络的存储容量,训练样本的渐近稳定性和吸引域大小。计算机实验结果说明了学习算法的优越性。