基于静态和移动传感器的WSN的k-覆盖研究

针对无线传感器网络的k-覆盖问题进行了研究。首先定义一个表征网络覆盖效率的过度提供因子,并在此基础上对静态传感器网络和全移动传感器网络的k-覆盖问题进行分析,得到这两种情形下的过度提供因子以及全移动传感器网络中移动传感器的最大移动距离;进而提出一种由静态传感器和少量移动传感器构成的混合网络结构,并得到了这种网络结构下不依赖于网络大小的k-覆盖以及调度移动传感器移动的分布式移动调度算法,从而实现有效覆盖。仿真结果表明,提出的混合网络结构不仅能够实现精确的k-覆盖,而且相比于其他k-覆盖算法,有更高的覆盖率。     

Up-flow roughing filtration: Rehabilitation of a water treatment plant in Tarata,Bolivia

This paper presents the methodology used for the rehabilitation of the pretreatment stage in a water treatment plant for a village located in Bolivia which has 3500 inhabitants. The treatment plant was initially composed by horizontal-flow roughing filters and slow sand filters, but due to the high contents of colloidal turbidity of the providing source, it did not work properly. A plan of rehabilitation was made which comprised laboratory tests, pilot tests and proposal of modifications based on the results of previous stages. The laboratory tests were made in order to find the optimum conditions to coagulate the raw water. It was found that horizontal-flow roughing filters must be turned into up-flow roughing filters, so a pilot plant was built and was operated for three months in order to find suitable design parameters. The results obtained obtained during the operation of the pilot plant and the proposal of modifications are presented. The results of operation of the final plant, which are also reported, demonstrated the advantages of the up-flow roughing filtration as a pretreatment stage when it is neccesary to add chemical products in small treatment plants.     

升钟湖夏季水和沉积物中磷形态分布特征

为探究升钟湖水和沉积物中磷污染情况,于2019年8月(夏季),采集了升钟湖湖区15个样点的水样和沉积物样品,测定了升钟湖表层水、间隙水及沉积物的磷形态,并分析各种形态磷之间的相关性。结果表明:①升钟湖表层水总磷含量介于0.033～0.085 mg/L,各形态的磷含量由高到低依次为DTP(61.93%)、DOP(40.00%)、PP(38.07%)和DIP(21.93%);②间隙水的总磷含量介于3.49～7.57 mg/L,是水体磷的“源”,正磷酸盐仅占总磷的1.9%;③沉积物总磷含量介于299.04～1 138.69 mg/kg,Psenner法连续分级提取出表层沉积物共有5种形态的磷,各形态磷含量由高到低依次为残渣磷(Res-P:44.78%)、金属氧化物结合态磷+有机碎屑腐殖酸磷(NaOH-P:22.92%)、钙结合态磷(HCl-P:14.82%)、可还原态磷(BD-P:13.39%)和弱吸附态磷(NH₄Cl-P:4.09%),各形态磷含量均表现一定的空间分布差异,其中,总磷含量整体为西北部高于东南部;④相关性分析结果显示,沉积物中磷的释放主要通过BD-P、N...     

On positive definiteness of strain energy in nonlocal elasticity

The positive definiteness of strain energy in nonlocal elasticity is studied. It is shown that the strain energy of nonlocal elasticity with a continuous positive valued and monotone decreasing interaction kernel is not necessarily positive definite.     

新工科背景下单片机实验教学改革研究

针对当前单片机实验教学中存在的各种问题,为适应新工科建设背景下新兴产业工科人才的培养,提出了教学改革措施。根据学科融合交叉培养机制,建立工程师教学团队;修订实验讲义内容,改进实验教学方式,制定了适应不同层次学生的考核评价标准。实践表明,新的教学方式和评价体制更能激发学生的兴趣,提高了学生实践创新能力,使学生具备了单片机应用系统开发能力,并在学科竞赛中取得良好成绩。     

短毫米波单交错梯形慢波结构高频特性的研究

能与现代MEMS技术兼容的单交错梯形慢波结构可应用于短毫米波小型化高功率耦合腔行波管。采用三维电磁场程序对该结构在短毫米波段的高频特性进行了数值计算。分析了几何尺寸对色散特性、耦合阻抗的影响,找到了对它们影响最明显的敏感尺寸。     

新型可溶性聚N-(2-氯乙基)-2-氨基苯甲酰胺的合成与性能

报道了一种新型可溶性聚N-(2-氯乙基)-2-氨基苯甲酰胺的化学合成,并用红外光谱、紫外-可见光谱、循环伏安法、X-射线衍射和溶解率测定对其结构与性能进行了研究。结果表明:这种聚苯胺衍生物没有共轭的醌式骨架,不具有电活性,可能是不导电的,呈现出非晶态结构,在乙醇、氯仿、DMF等普通有机溶剂中具有较好的溶解性。     

Reduced formation of undesirable by-products from photocatalytic degradation of trichloroethylene

Photocatalytic degradation of trichloroethylene (TCE) was investigated using a tubular photoreactor packed with TiO₂ powders prepared by sol–gel techniques. Powders of the following metals: Cr, Fe, Ni, Cu and Pt, or Ca(OH)₂ were uniformly mixed with the TiO₂ powders and then their effect on the formation of COCl₂, CHCl₃, and CHCl₂COCl as by-products was examined. Concentrations of COCl₂ and CHCl₃ were determined in a product gas stream by GC/MS while CHCl₂COCl accumulated on the catalyst surface. When the catalysts were immersed in water after TCE photodegradation, the formation of Cl^- and CHCl₂COO⁻ ions was confirmed by ion-chromatography. Of the chemicals tested, only Cu and Ca(OH)₂ inhibited the formation of the chlorinated by-products. With increasing Cu and Ca(OH)₂ content, TCE conversion decreased while the stoichiometric ratio ([CO₂]_formed/[TCE]_degraded) increased. Concentrations of COCl₂, CHCl₃, and CHCl₂COCl decreased with increasing Cu and Ca(OH)₂ content. Especially, the formation of COCl₂ was remarkably suppressed with Ca(OH)₂.     

高温强酸型酸化缓蚀剂的研究

随着石油勘探的迅猛发展,为防止管道腐蚀,添加缓蚀剂是最为经济适用的方法,尤其是添加抗高温、高酸型缓蚀剂。因此,文章综述了近年来国内外高温、强酸缓蚀剂的研究现状,并分析了未来发展的方向。