基于在线购买历史聚合的B2C电子商务差异化折扣模型

众多B2C网站已建立起会员等级制度,并据此向买家提供价格折扣。但会员等级制模型仅考虑买家交易金额,无法全面反映买家在线购买历史(online purchase history),故不能准确提供差异化折扣。针对上述问题,提出了一种面向B2C电子商务的差异化折扣模型,该模型包含能体现买家在线购买历史的交易、退单、推荐购买、晒单等四个指标,将买家在线购买历史聚合为一个综合值,进而通过min-max标准化方法进行线性转换,将转换后的聚合值与会员等级基准折扣结合得到最终的差异化折扣,从而使得B2C网站可向同级别会员实施更精准的一对一营销和价格歧视策略。以京东商城为背景的仿真实验结果证明了本文新模型的有效性。     

Redistribution Mechanism of Chloromethylsilanes Catalyzed by HZSM-5 with Big and Small Apertures

The disproportionation to produce(CH_3)_2SiCl_2 can convert CH_3SiCl_3 and(CH_3)_3 SiCl wastes into treasure. In this paper, B3 LYP/6-311++G(3 df, 2 pd) basis set was used to calculate the mechanism of disproportionation, reaction catalyzed by 7 T cluster HZSM-5 with small aperture and 24 T cluster HZSM-5 with large aperture. The results showed that the activation energies for the rate-determining step of the reaction catalyzed by 7 T and 24 T HZSM-5 were 362.06 and 220.05 k J/mol, respectively. In combination with the structural analysis, activation energy analysis and LOL analysis were carried out for 7 T and 24 T HZSM-5. The obtained results show that the 24 T HZSM-5 with large aperture is good for disproportionation reaction compared to 7 T HZSM-5 with small aperture.     

富锂正极材料结构设计和表面调控的研究进展

富锂正极材料因具有较高的理论能量密度,被视为极具发展潜能的新一代正极材料,但该材料在循环过程中容量和电压衰减显著,导致其实际商业应用受阻.本文综合评述了通过结构设计和表面调控提高富锂正极材料储锂性能的研究进展,介绍了富锂正极材料的充放电工作机制,及导致其比容量和电压衰减的原因,讨论了近年来通过新型结构设计(如构筑蛋黄-蛋壳中空结构、中空多壳层结构等)和表面调控(如尺寸控制、暴露晶面控制、表面尖晶石化、表面包覆、表面掺杂等）策略,抑制富锂正极材料表面氧析出和晶型转变并稳定材料结构,从而抑制电压和比容量衰减,有效提高电池的循环寿命和库伦效率的相关研究成果,最后,提出了通过结构设计和表面调控提高富锂正极材料电化学性能面临的挑战,并对未来发展方向进行了展望.     

Y0.78Yb0.2Er0.02F3多孔纳米粒子的合成与上转换发光

以Y2O3,Yb2O3,Er2O3,NH4F等试剂为原料,采用水热法在180 ℃下保温10 h获得了NH4Y1.56Yb0.4Er0.04F7球形纳米粒子. 所获得的纳米粒子在氮气保护下400 ℃灼烧2 h,制备出Y0.78Yb0.2Er0.02F3纳米粒子. 利用Scherrer公式计算出NH4Y2F7:Yb3 ,Er3 和YF3:Yb3 ,Er3 的粒径分别为65.8和68.3 nm. TEM照片展示粒子近球形,其大小与Scherrer公式计算结果一致. TEM还揭示每个粒子上面应带有许多小孔. 氮气吸附脱附实验进一步证实了粒子上存在小孔. 在980 nm的红外激光激发下,NH4Y1.56Yb0.4Er0.04F7不发光,而Y0.78Yb0.2Er0.02F3发出明亮的绿光,表明所获得的Y0.78Yb0.2Er0.02F3具有强的上转换发光.     

ATPF—a dedicated proton therapy facility

A proton therapy facility based on a linac injector and a slow-cycling synchrotron is proposed. To obtain good treatments for different cancer types, both the spot scanning method and the double-scattering method are adopted in the facility, whereas the nozzles include both gantry and fixed beam types. The proton accelerator chain includes a synchrotron of 250 MeV in maximum energy, an injector of 7 MeV consisting of an RFQ and a DTL linac, with a repetition rate of 0.5 Hz. The slow extraction using the third-order resonance and together with the RFKO method is considered to be a good method to obtain a stable and more-or-less homogenous beam spill. To benefit the spot scanning 200 between 60 MeV and 230 MeV. A new method method, the extraction energy can be as many as about - the emittance balancing technique of using a solenoid or a quadrupole rotator is proposed to solve the problem of unequal emittance in the two transverse planes with a beam slowly extracted from a synchrotron. The facility has been designed to keep the potential to be upgraded to include the carbon therapy in the future.     

L-(8-羟基-5-甲基喹啉)半胱氨酸修饰电极的制备及其对汞离子选择性检测

利用Shifft碱反应将L-半胱氨酸和5-甲酰基-8-羟基喹啉一步合成L-(8-羟基-5-甲基喹啉)半胱氨酸,通过金-硫键将L-(8-羟基-5-甲基喹啉)半胱氨酸自组装到金电极表面制备L-(8-羟基-5-甲基喹啉)修饰金电极。L-(8-羟基-5-甲基喹啉)半胱氨酸分子中的羟基氧和氮可与Hg2+形成稳定的五元环配合物,因此该修饰电极能选择性吸附Hg2+,结合方波伏安法用于Hg2+电化学检测。在0.01mol/L HCl中,富集时间为160s,Hg2+浓度在1.0×10-9~1.0×10-8 mol/L、1.0×10-8~1.0×10-7 mol/L浓度范围内与方波伏安峰电流分段呈现良好的线性关系,检出限为0.92×10-9 mol/L。     

荧光法快速分析胶囊中的头孢拉定含量

研究了头孢拉定水溶液的荧光光谱，建立了头孢拉定的快速荧光测定法。荧光强度与头孢拉定含量在１．４ ｍ ｇ／Ｌ～１．４ ｇ／Ｌ的质量浓度范围内呈线性关系。检出限为０．１８ ｍ ｇ／Ｌ。对质量浓度为１．４ ｍ ｇ／Ｌ的头孢拉定标准溶液进行１１ 次平行测定的相对标准偏差为１．３％ 。方法操作简便、快速，用于胶囊中头孢拉定含量的测定。     

Linux的进程地址空间研究

本文研究了Linux进程的虚拟地址空间管理，包括页表结构、内存分配策略、线性地址区间结构，线性地址到物理地址的映射等。     

亚甲蓝聚合体的吸收光谱及聚合状态的研究

本文用环己烷作萃取剂，从亚甲蓝的阴离子表面活性剂水溶液中将亚甲蓝二聚体萃取至有机相，测定其紫外－可见吸收光谱，最大吸收波长为604nm，摩尔吸光系数为8.74×10^4L·mol^-1·cm^-1；通过差示光谱推算构成二聚体的单分子倾角（α）为49.7°。计算出水溶液中亚甲蓝二聚体的聚合常数为2.487×10^4。