空间行波管电子枪中阴极热形变及冷启动特性研究

本文利用ANSYS软件对空间行波管的电子枪进行了稳态热分析,得到了电子枪阴极温度随灯丝功率的变化结果,计算结果与试验结果一致,验证了ANSYS热分析的正确性。在此基础上分析了阴极的热形变对电子枪性能参数的影响,同时模拟了电子枪中阴极的冷启动情况,得出阴极在-35℃条件下,在210s内阴极温度可以达到正常工作温度980℃。     

基于异质图表达学习的跨境电商推荐模型

跨境电商产品推荐已经成为电子商务领域新兴的研究议题之一。由于电商产品信息复杂多样、“用户-产品”关联矩阵极为稀疏并且冷启动问题突出,因此传统的协同过滤推荐模型很难奏效。而改进的深度协同过滤模型,只考虑了用户对产品的“显式”和“隐式”的反馈信息,忽视了由用户与项目组成的图结构信息,推荐性能很难满足平台和用户的要求。为了解决这些难题,该文提出基于异质图表达学习的图神经网络模型(HGNR)用于个性化的跨境电商产品推荐,该模型具有2个显著的优势：(1) 构造“用户-产品-主题”3部图作为模型的输入,通过图卷积神经网络(GCN)在异质图上进行高质量信息传播和聚合;(2)能够获取高质量的用户和产品表征向量,实现了用户和产品复杂交互关系的建模。在真实的跨境电商订单数据集上的实验结果表明,HGNR模型不仅在推荐性能上表现出色,还能有效提升冷启动用户的推荐准确率,与9种推荐基准算法相比,HGNR在评价指标HitRate@10, Item-coverage@10, MRR@10上至少提升了3.33%, 0.91%, 0.54%。     

An atomtronics transistor for quantum gates

We present a mechanism for quantum gates where the qubits are encoded in the population distribution of two-component ultracold atoms trapped in a species-selective triple-well potential. The gate operation is a specific application of a different design for an atomtronics transistor where inter-species interaction is used to control transport, and can be realized with either individual atoms or aggregates like Bose–Einstein condensates (BEC). We demonstrate the operational principle with a static external potential, and show feasible implementation with a smooth dynamical potential.     

S波段宽带大功率连续波耦合腔行波管3维模拟设计

 使用3维PIC粒子模拟软件定量分析了耦合腔行波管的大信号注波互作用行为。使用完整的仿真模型完成了S波段连续波管型的设计,达到如下设计指标：工作频率2.0~2.3 GHz,输出功率4.3 kW,频带内增益波动±0.7 dB。提出了使用大介电常数微扰介质棒减小耦合阻抗计算误差的方法,研究了行波管的冷腔特性,给出了色散、耦合阻抗等参数。     

低温试验冷库传热系数的测量研究

简述了对于低温冷库传热系数测量所采用的一般方法,采用稳态法对一低温试验冷库进行了测量实验,然后通过非稳态积分法对试验数据进行验证。针对冷风机电机功率较大的特点,本实验采用变频器将电机功率调小,从而成功得出该低温试验冷库的传热系数。并与理论计算的数据进行对比,找出存在差别的原因。     

Significant influence of particle surface oxidation on deposition efficiency, interface microstructure and adhesive strength of cold-sprayed copper coatings

The critical velocity for particle deposition in cold spraying is a key parameter, which depends not only on the material type, but also the particle temperature and oxidation condition. The dependency of deposition efficiency of cold spray Cu particles on the particle temperature and surface oxidation was examined. The effect of particle surface oxide scales on the interfacial microstructure and adhesive strength of the cold-sprayed Cu coatings was investigated. The results show that the deposition efficiency significantly increases with increasing the gas temperature but decreases with augmenting the oxygen content of the starting powder. The oxide inclusions at the interfaces between the deposited particles inhibit the effective bonding of fresh metals and remarkably lower the bond strength of the deposited Cu coatings on steel.     

高分子链的去拥挤转变及低温流动

简述了拥挤理论的基本原理,运用拥挤理论来说明高分子链间弱相互作用对高分子链所处的状态的影响,特别是对高分子玻璃化转变的影响.在实验中,采用固体核磁共振方法探测高分子的链间邻近度,并比较了不同链间邻近度的高分子样品在玻璃化转变温度以下的压力诱导流行行为,发现即使测试温度比高分子玻璃化转变温度低132℃,高分子链在压力下依...     

Determination of mercury in saliva with a flow-injection system

A simple, fast and reliable method, with a low detection limit, has been developed for the determination of total mercury in saliva samples. The method uses a brominating reagent, followed by on-line addition of KMnO₄ at room temperature to convert organically bound mercury to inorganic mercury ions, and determines mercury by flow-injection cold-vapour atomic absorption spectrometry. Using the method described, complete recoveries of five mercury compounds from saliva were attained. Results obtained on real samples using the new method were comparable to that obtained using the established method with batch system. The detection limit of this method, based on three standard deviations of the blank, is 0.05 μg l⁻¹ Hg in a saliva sample of 500 μl. A sample throughput of 80 measurements per hour is possible with the method. The calibration curves are linear up to 20 μg l⁻¹ and the dynamic range extends to 40 μg l⁻¹ Hg. At a concentration of 1μg l⁻¹ mercury in saliva, the relative standard deviation is about 2% for 11 replicates; a total volume of 0.5 ml saliva is required for three replicates.     

冷原子荧光法间接测定水中氰化物

本文详细研究了氰化物蒸馏条件及其稳定性问题，建立了一个冷原子荧光法间接测定水中氰化物的方法，并用于海水及氰化液中痕量ＣＮ－的测定，结果令人满意。ＣＮ－检出限为０．０２μｇ／ｍＬ，回收率９５％～９８％，变异系数７．３％～８．９％。     

Evaluation and application of argon and helium microstrip plasma for the determination of mercury by the cold vapor technique and optical emission spectrometry

The suitability of a 2.45-GHz atmospheric pressure, low-power microwave microstrip plasma (MSP) operated with Ar and He for the determination of Hg by continuous-flow cold vapor (CV) generation, using SnCl₂/HCl as the reducing agent, and optical emission spectrometry (OES) using a small CCD spectrometer was studied. The areas of stability for a discharge in the Ar and in the He MSP enclosed in a cylindrical channel in a quartz wafer were investigated. The excitation temperatures as measured for discharge gas atoms (Ar I, He I), and the electron number densities at 35–40 W and 15–400 mL min⁻¹ were found to be at the order of 3,200–5,500 K and 0.8 × 10¹⁴–1.6 × 10¹⁴ cm⁻³, respectively. The relative intensity of the Hg I 253.6-nm line and the signal-to-background ratio as a function of the forward power (35–40 W) as well as of the flow rate of the working gas (15–400 mL min⁻¹) were evaluated and discussed. For the selected measurement conditions, the Ar MSP was established to have the lower detection limit for Hg (0.6 ng mL⁻¹) compared with the He MSP. The linearity range is up to 300 ng mL⁻¹ and the precision is on the order of 1–3%. With the optimized CV Ar MSP-OES method a determination of Hg in spiked domestic and natural waters at concentration levels of 20–100 μg L⁻¹ and an accuracy of 1–4% could be performed. In an NIST domestic sludge standard reference material, Hg (3.64 μg g⁻¹) could be determined with a relative standard deviation of 4% and an agreement better than 4%.