Machine-Learning based methods in short-term load forecasting

Short-term load forecasting is of great significance to the secure and efficient operation of power systems. However, loads can be affected by a variety of external impact factors and thus involve high levels of uncertainties. So it is a challenging task to achieve an accurate load forecast. This paper discusses three commonly-used machine-learning methods used for load forecasting, i.e., the support vector machine method, the random forest regression method, and the long short-term memory neural network method. The features and applications of these methods are analyzed and compared. By integrating the advantages of these methods, a fusion forecasting approach and a data preprocessing technique are proposed for improving the forecasting accuracy. A comparative study based on real load data is performed to verify that the proposed approach is capable of achieving a relatively higher forecasting accuracy.     

三维空间孔道的精确校核

二维空间孔道的传统校核方法是把三维问题化成二维问题,再简化或近似处理,这样的方法在高精度场合往往不能满足设计要求;还有的是对孔表面网格化、布尔运算等,算法复杂,难于实现。本文从计算几何理论上探讨了三维空间孔的精确校核方法,简单、易行、可靠。     

燃烧合成三元碳化合物Ti2AlC1-x

采用Ti，Al和C元素粉末为反应物原料，通过燃烧合成法首次成功地制备出了单相三元碳化合物Ti2AlC1-x。实验结果表明：若以“理想”晶体结构化学式Ti2AlC化学计量比为起始反应原料配比，燃烧产物主晶相为Ti2AlC2；以缺碳的非化学计量比(Ti2AlC1-x)为反应原料配比，即Ti：Al：C=3：1．5：1=2：1：0．7(摩尔比)，得到单相的燃烧产物Ti2AlC1-x。从热力学原理的角度探讨了不同原料摩尔配比对燃烧产物相组成的影响机理。     

钨酸铵溶液浓度对超微钨粉形貌的影响

以钨酸铵溶液为原料，采用超声喷雾干燥法制备了超微钨粉。研究了该方法中钨酸铵浓度对超微钨粉形貌的影响。结果表明，当溶液中钨酸铵的浓度为10%时，得到了球形度很好的非完全结晶的前驱体。当钨酸铵浓度达25％时，得到了层片状的晶态前驱体。钨酸铵溶液浓度对干燥时晶体生长速度具有重要的影响。分别采用这2种前驱体在630℃，保温30min和氢气流莆4L／min条仲下能够完全还原，得到超微α—W粉。所制得的钨粉形貌完全遗传了其前驱体的形貌，分别得到球状和层状钨粉。球状钨粉由纳米颗粒聚集而成。片层状钨粉的厚度在1mm以下。     

用扩冲法修复凹形护环的新工艺

详细介绍了用扩冲法对液压胀形出现凹形的护环进行修复的方法。实践证明,扩冲法修复护环简单、经济、实用。     

The Trend Toward Latin American Economic Integration

Revolutionary developments in the patterns of world trade have taken place during the past five years, and Latin America is no exception. This article discusses the effects of the Latin American Free Trade Association, the Central American Common Market, and the Inter-American Development Bank on the economic integration of Latin America.     

Effect of pulse parameters on microstructure of joint in laser beam welding for SiC_p/6063 composite

1　INTRODUCTIONSiC particlesreinforcedcomposites ,thankstotheirlowcostsandhighlevelofstructuralproperties ,areshowingtheirpotentialincivilandmilitaryappli cation .SiC particlesreinforcedaluminummatrixcomposites wideapplicationinaerospaceandautomo tiveareattributedtotheirperformanceofhighspecif icstrength ,highspecificstiffness ,highelasticmodu lusandexcellentwearresistance .Thecoefficientofthermalexpansionandthermalconductivitycanberegulatedbychangingthecontentandsizeofrein forcingparticl…     

笔式界面软件资源管理模型及其实现*

针对目前文档管理模式和WIMP界面交互范式对笔式交互的不足,提出了笔式界面软件文档资源管理的统一模型,能够有效地管理笔式界面软件所产生的文档数据,并且根据此模型实现了笔式界面的文档资源管理系统,采用了PIBG交互范式和实物界面.评估结果表明,根据此模型设计的系统,能够提高用户工作效率,降低用户的认知负担.