国际油价预测之新思想——分时间段类型研究

站在全新的角度——在不同类型的时段分别研究油价预测模型的优劣.通过小波变换对油价序列进行奇异性分析,将油价序列所处的时间段分为两类：含奇异点时段,不含奇异点时段.并在不同类型的时段分类比较多元回归模型、延迟因变量回归模型、神经网络模型的拟合预测效果,最终得出无论何时进行油价预测,在上述模型中效果最为理想的是神经网络模型.     

商品零售价格指数的非参数自回归预测模型

为了更好地捕获我国商品零售价格指数的非线性特征,本文基于局部线性估计理论,建立了我国商品零售价格指数的非参数自回归预测模型,并应用此模型对我国2004—2007年的价格指数进行了预测分析.结果表明,相对于传统的ARMA模型,非参数自回归模型能够更好地解决我国社会商品零售价格指数预测这一非线性问题,而且预测精度较高.     

Production and characterization of biosurfactant from Bacillus subtilis CCTCC AB93108

The production and properties of the biosurfactant synthesized by Bacillus subtilis CCTCC AB93108 were studied. The maximum concentration of the surfactant is 1.64 g/L when the bacteria grow in a medium supplemented with glucose as carbon sources. The isolated biosurfactant is a complex of protein and polysaccharide without lipids. It reduces the surface tension of distilled water to 45.9 mN/m, and its critical micelle concentration (CMC) is 2.96 g/L. It can stabilize emulsions of several aromatic and aliphatic hydrocarbons, such as benzene, xylene, n-pentane, n-nonane, gasoline and diesel oil. It presents high emulsification activity and stability in a wide range of temperature (4-100℃) and a long period of duration.     

Prediction-based energy-efficient target tracking protocol in wireless sensor networks

A prediction based energy-efficient target tracking protocol in wireless sensor networks (PET) was proposed for tracking a mobile target in terms of sensing and communication energy consumption. In order to maximize the lifetime of a wireless sensor network (WSN), the volume of messages and the time for neighbor discovery operations were minimized. The target was followed in a special region known as a face obtained by planarization technique in face-aware routing. An election process was conducted to choose a minimal number of appropriate sensors that are the nearest to the target and a wakeup strategy was proposed to wakeup the appropriate sensors in advance to track the target. In addition, a tracking algorithm to track a target step by step was introduced. Performance analysis and simulation results show that the proposed protocol efficiently tracks a target in WSNs and outperforms some existing protocols of target tracking with energy saving under certain ideal situations.     

Electrodeposition of Ni-Co-Fe2O3 composite coatings

Ni-Co-Fe₂O₃ composite coatings were electrodeposited using cetyltrimethylammonium bromide (CTAB)-modified Watt’s nickel bath with Fe₂O₃ particles dispersed in it. The effects of the plating parameters on the chemical composition, structural and morphological characteristics of the electrodeposited Ni-Co-Fe₂O₃ composite coatings were investigated by energy dispersive X-ray (EDS) spectroscopy, X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The results reveal that Fe₂O₃ particles can be codeposited in the Ni-Co matrix. The codeposition of Fe₂O₃ particles with Ni-Co is favoured at high Fe₂O₃ particle concentration and medium stirring, and the deposition of Co is favoured at high concentration of CTAB. Moreover, the study of the textural perfection of the deposits reveals that the presence of particles leads to the worsening of the quality of the observed 〈220〉 preferred orientation. Composites with high concentration of embedded particles exhibit a preferred crystal orientation of 〈111〉. The more the embedded Fe₂O₃ particles in the metallic matrix, the smaller the sizes of the crystallite for the composite deposits.     

我国企业应收账款风险的成因分析及其防范措施

文章分析了应收账款风险产生的原因,指出产生应收账款风险的原因有＂销售部门与财务部门有效沟通及协调不足、企业内部激励机制单一,企业法律保护意识薄弱、催收方法不合理、减少存货、盲目追求片面的竞争,缺乏风险防范意识、信用管理制度的缺失、财务会计制度的某些条款不尽合理、企业的经营目的不明确＂。针对以上应收账款形成风险的原因,本文提出了＂加强销售与财务的共同管理,结‘对’管理、建立完善的信用管理体系、建立赊销审批制度、采取合理的催款程序及方法、掌握客户债务的动态变化、规避不合理的财务制度、从企业管理的角度看应收账款＂等防范措施。     

浅谈气象预测在公路预防性养护中的作用

本文针对气候变化,对公路养护带来的不利影响,需联合气象预测加强预防性     

基于H.264/AVC的自适应快速多参考帧选择算法

在不同尺寸块编码模式下,时域和空域运动相关性对最优参考帧选取的影响是不同的.本文通过分析视频序列的统计特性和视频帧内的空间相关性,提出了一种基于运动相关性的自适应多参考帧快速选择算法.该算法根据视频序列自身特征,自适应地去除不必要的参考帧,降低编码复杂度.实验结果显示,在保证编码质量的前提下,本算法平均可以节省编码时间40%以上.     

基于模糊优选神经网络与GIS结合的流域面雨量预测方法

提出了一种模糊优选神经网络模型与地理信息系统(GIS)相结合的流域面雨量预测方法.利用GIS软件对流域点雨量进行了空间分析,作为模糊优选神经网络的期望输出对网络进行训练,从而在流域面雨量与各站点观测雨量之间建立映射关系.新的点雨量观测数据输入训练好的网络,即可快捷得到本次降雨流域面雨量.     

基于叠加原理的气体浓度场数值计算方法

以线性偏微分方程叠加原理为基础,介绍了一种数值计算具有复杂边界条件和源项的气体浓度场的新方法.忽略浓度场对速度场的影响,则已知速度场的组分输运方程为线性对流扩散方程,可以应用线性叠加原理.首先将具有复杂边界条件和源项的浓度场问题分解为若干具有简单边界条件和源项的浓度场问题,然后对每个简单浓度场问题做一次数值模拟,获得其数值解,最后通过叠加这些简单浓度场的数值解,就可以求出复杂浓度场问题的解.该方法的应用可以达到减少数值试验数量、节约计算时间的目的.