基于自适应邻域嵌入的无监督特征选择算法

无监督特征选择算法可以对高维无标记数据进行有效的降维,从而减少数据处理的时间和空间复杂度,避免算法模型出现过拟合现象.然而,现有的无监督特征选择方法大都运用k近邻法捕捉数据样本的局部几何结构,忽略了数据分布不均的问题.为了解决这个问题,提出了一种基于自适应邻域嵌入的无监督特征选择(adaptive neighborhood embedding based unsupervised feature selection, ANEFS)算法,该算法根据数据集自身的分布特点确定每个样本的近邻数,进而构造样本相似矩阵,同时引入从高维空间映射到低维空间的中间矩阵,利用拉普拉斯乘子法优化目标函数进行求解.6个UCI数据集的实验结果表明：所提出的算法能够选出具有更高聚类精度和互信息的特征子集.     

流量阶跃变化时供暖房间内温度场的数值模拟

两位通断式调节是一种计量供热系统控制模式,与欧洲供热系统控制模式不同的是,其温控阀只有启、闭两种状态.用数值模拟方法研究了该调控模式对室内热环境的影响规律.     

Growth of GaN Thin Films Using Plasma Enhanced Atomic Layer Deposition: Effect of Ammonia-Containing Plasma Power on Residual Oxygen Capture

In recent years, the application of (In, Al, Ga)N materials in photovoltaic devices has attracted much attention. Like InGaN, it is a direct band gap material with high absorption at the band edge, suitable for high efficiency photovoltaic devices. Nonetheless, it is important to deposit high-quality GaN material as a foundation. Plasma-enhanced atomic layer deposition (PEALD) combines the advantages of the ALD process with the use of plasma and is often used to deposit thin films with different needs. However, residual oxygen during growth has always been an unavoidable issue affecting the quality of the resulting film, especially in growing gallium nitride (GaN) films. In this study, the NH₃-containing plasma was used to capture the oxygen absorbed on the growing surface to improve the quality of GaN films. By diagnosing the plasma, NH₂, NH, and H radicals controlled by the plasma power has a strong influence not only on the oxygen content in growing GaN films but also on the growth rate, crystallinity, and surface roughness. The NH and NH₂ radicals contribute to the growth of GaN films while the H radicals selectively dissociate Ga-OH bonds on the film surface and etch the grown films. At high plasma power, the GaN film with the lowest Ga-O bond ratio has a saturated growth rate, a better crystallinity, a rougher surface, and a lower bandgap. In addition, the deposition mechanism of GaN thin films prepared with a trimethylgallium metal source and NH₃/Ar plasma PEALD involving oxygen participation or not is also discussed in the study.     

天然气制合成油的发展前景

天然气制合成油(Gas to Liquid)是最近几年广泛关注的热点,主要介绍了GTL生产工艺及其发展促进因素,并预测了其在中国的发展前景.     

高应力区大体积混凝土基础破坏机理分析与治理技术研究

分析了高应力区大体积混凝土破坏的原因和机理,提出了综合采用卸压沟、基础底部锚网梁等防治高应力区大体积混凝土基础破坏的方法,有效的解决了高应力区内大体积设备基础易破坏的难题。     

聚合物/小分子有机光伏电池活性层形貌调控研究进展

近年来,基于新的有机半导体材料的合成、器件结构的优化以及对太阳电池活性层形貌的有效调控,有机光伏电池(OPV)得到了迅速的发展。目前基于聚合物/小分子共混体系的单结OPV的光电转换效率已经超过18%。首先,概述了聚合物/小分子OPV的研究进展;接着,介绍了OPV的工作原理和相分离机理,并分析了OPV的光电性能、活性层形貌特征参数以及相分离过程这三者之间的关系;其次,探讨了不同物理调控手段对活性层形貌的影响,主要介绍了调节溶液的聚集、成膜过程中优化活性层形貌以及薄膜后处理等优化活性层的方法,重点介绍了聚合物/小分子OPV的活性层形貌调控的方法;最后,对OPV未来的发展方向进行了展望。     

MIDP2.0中AMS对MIDlet生命周期控制的设计与实现

本文首先对MIDP2．0和AMS进行了简要介绍。然后对MIDlet的生命周期展开了详细的讨论。最后通过对几个协同完成控制功能的类的分析,描述了AMS对MIDlet生命周期控制的设计和实现。     

粉末PET固相缩聚的研究

系统地研究了粉末聚酯(PET)固相缩聚,得到了有效的干燥结晶条件:140℃干燥120 min,180℃再结晶45 min,切片含水率低于30μg／g;研究了反应温度,粉末粒径和N2流量对PET固相缩聚的影响,分析粉末固相缩聚存在N2流量阈值的机理。结果表明:反应温度越高,颗粒越小,固相缩聚反应速度越快;粉末 PET预聚体在一定温度下固相缩聚,存在N2流量阈值。在此流量下,达到该温度下的该粒径粉末的最大界面扩散速率和固相缩聚的最大反应速度。相同反应温度下,粉末粒径越小,阈值N2流量越大。     

嵌入式移动代理的设计与实现

随着移动通信的快速发展,以及手持移动设备的增多,人们已经进入到一个移动计算的时代。移动管理是移动通信中的核心问题。针对IETF的移动IP协议的不足,论文提出了基于嵌入式WindowsCE.net操作系统实现通信设备的移动管理方案。首先简述移动IP协议,并指出其不足之处;然后介绍了嵌入式移动代理的整体框架;最后详细说明了移动代理的实现。该方案主要特点如下:可以最大限度地减小移动管理对移动管理基础设施的依赖;嵌入式移动代理可以为操作系统提供透明的移动服务。     

Corrosion behaviour of Al1.3CrFeNi chemically complex alloy

In this study, corrosion behaviour of double-phase Al_1.3CrFeNi chemically complex alloy was investigated, including hot corrosion and electrochemical corrosion. Hot corrosion behaviour of Al_1.3CrFeNi alloy was explored in molten 75 wt-% Na₂SO₄?+?25 wt-% NaCl salt. The result revealed that the corrosion kinetic curve of Al_1.3CrFeNi alloy followed the exponential rate rule through mass loss measurement. In addition, it prevented that the formed corrosion layer had obvious stratification including external granular Al₂O₃ and inner porous Cr₂O₃ when corrosion time was up to 100?h. Besides, it should be noted that the Al_1.3CrFeNi alloy was sensitive to the molten salt containing chlorine, which makes the alloy surface leave voids and bring about acceleration of corrosion. Meanwhile, electrochemical corrosion resistance of Al_1.3CrFeNi alloy in NaCl solution with different concentrations (0.6, 1.0 and 2.0?mol?L^?1) was investigated at room temperature. The results revealed that Al_1.3CrFeNi alloy showed superior corrosion resistance in NaCl solution due to the existence of Al and Cr which aid the formation of protective oxide layer.