Exposure assessment of process by-product nanoparticles released during the preventive maintenance of semiconductor fabrication facilities

This study characterized the process by-product particles (mostly nanoparticles) released during the preventive maintenance of semiconductor fabrication facilities, such as chemical mechanical planarization (CMP), plasma-enhanced chemical vapor deposition (PECVD), and ion implantation. Manual sampling and real-time measurements with direct reading instruments were conducted to assess the exposure levels of nanoparticles and their physical and chemical properties. Significant amount of nanoparticles were observed in the breathing zone of the workers during the maintenance of the PECVD and ion implanters with the peak number concentrations as high as 6,470,000 and 65,444 #/cm³, respectively, indicating that the deposited residual chemicals in the reaction chambers were released as airborne nanoparticles by the maintenance activities. In contrast, nanoparticles released during the maintenance of the local scrubber, CMP, and replacing CMP slurry drums were insignificant. Causes of the particle release were discussed and suggestions were made to mitigate the nanoparticle release and reduce the exposure levels.     

Transition from strong-field sequential to nonsequential double ionization at near-infrared wavelengths and low intensities

Within a quantum-mechanical model, we investigate strong-field double ionization of a model helium atom by near-infrared, linearly polarized laser pulses at intensities far below the recollision threshold. The quantum simulations show a clear mechanism change from sequential to nonsequential double ionization (NSDI) as the laser intensity increases. For NSDI, the two-electron correlated momentum distribution exhibits a strong final-state Coulomb repulsion effect for high-energy photoelectrons, but absent for low-energy photoelectrons. This repulsion effect is ascribed to field double ionization from doubly-excited states populated by recollision of the first ionized electron when it returns to the parent ion. Such recollision-induced excited states are absent at ultraviolet wavelengths due to the very low returning kinetic energies, resulting to the absence of final-state repulsion effect in NSDI.     

Global Existence and Decay Rates of the Solutions Near Maxwellian for Non-linear Fokker–Planck Equations

In this paper, we study the global existence and decay rates of the solutions near Maxwellian for non-linear Fokker–Planck equations in the whole space. The global existence is proved by combining uniform-in-time energy estimates with local solution constructed by Picard type iteration sequence. The decay rates of the nonlinear model is obtained by using the precise spectral analysis of the linearized Fokker–Planck operator as well as the energy method. The nonlinearity in the model brings new difficulty to the energy estimates, which is resolved by additional tailored weighted-in-v energy estimates suitable for Fokker–Planck operators.     

Fidelity-Based Ant Colony Algorithm with Q-learning of Quantum System

International Journal of Theoretical Physics - Quantum ant colony algorithm (ACA) has potential applications in quantum information processing, such as solutions of traveling salesman problem,...     

Al掺杂对Mg_2Si介电性质影响的第一性原理研究

采用基于密度泛函理论的第一性原理平面波超软赝势方法,计算了本征Mg_2Si和Al掺杂Mg_2Si的形成能、电子结构和介电函数.结果表明,Al掺杂Mg_2Si后,Al以替位杂质(Al替Mg位,即AlMg)或填隙杂质(Al位于晶胞间隙位,即Ali)的形式进入Mg_2Si晶格.费米能级进入导带,体系呈n型导电.掺杂后体系的介电函数的实部和虚部在低频时比未掺杂时均增大,主要是由于晶格中的施主杂质Al离子束缚着附近的过剩电子,在外加交变电场的作用下,束缚在Al离子周围的电子要克服一定的势垒不断地往复运动造成松弛极化和损耗.另外,掺杂体系相对于未掺杂体系,介电函数的虚部在0.5 eV附近出现了一个额外的介电峰,该峰主要是由电子从价带跃迁到Al杂质能级引起的.计算结果为Mg_2Si基光电子器件的设计和应用提供了理论依据.     

航天器热试验查询统计系统的设计与实现

针对航天器真空热试验数据量大、数据利用率不高的特点,提出了一种基于数据库的试验数据查询统计方法方法,以改善现有的以文件系统为主的数据存储模式;通过对试验数据格式的分析和现有工作流程的优化,将试验数据查询系统分为系统管理、试验管理、策略管理和统计分析等四个大的功能模块,利用过滤算法自动生成试验工况点信息,并通过试验工况点自动生成单次试验的统计报告,进而实现对所有试验数据的综合查询统计功能;目前系统已应用于航天器热试验任务中,经过测试,系统功能和性能指标满足试验需求,解决了实际问题。     

激波与椭圆形重气柱相互作用的PLIF实验

在水平激波管中,采用平面激光诱发荧光(planar laser-induced fluorescence, PLIF)方法对椭圆形重气柱界面的Richtmyer-Meshkov不稳定性进行实验。气柱由SF₆混入一定比例的丙酮蒸气构成,环境气体为空气。通过改变椭圆形气柱的长短轴比值,得到了激波马赫数为1.25时,3种初始界面的演化形态。通过相对体积分数标定,得到了界面失稳演化过程中的相对体积分数分布,观察到了激波作用后界面气体聚集、转移、消散等现象。实验结果发现,对于流向轴长与展向轴长之比较大的气柱界面,初始界面产生的涡量更大且分布更广,其界面不稳定性发展得越迅速和剧烈。失稳发展迅速的界面甚至出现涡对碰撞并产生尾部射流结构的现象。初始界面直接决定了失稳发展初期形成的涡对强度和间距,并对后期演化有重要影响。     

低分子量含氟聚合物的制备、官能化及特性

低分子量含氟聚合物是重要的新型功能材料,在国防工业中占有特殊地位。同时,作为高科技战略物资,近年来逐渐成为研究热点。本文对低分子量含氟聚合物的制备方法、官能化及特性进行了综述,重点介绍了低分子量含氟聚合物的制备和官能化方法的研究进展,并总结和详细介绍了低分子量含氟聚合物的特性,最后对该领域的前景和发展方向进行了展望。     

Zinc Recovery from Wulagen Sulfide Flotation Plant Tail by Applying Ether Amine Organic Collectors

Separating oxidized zinc minerals from flotation tailings is always a challenge. In this study, a flotation tailing from Wulagen zinc mine in China (Zn grade < 1%) was processed using froth flotation with combinations of amines (OPA 10, OPA 1214, OPA 13, DDA) and Na₂S to study the effects of these amines on the zinc recovery as well as their interactions with other reagents, aiming to screen out a proper reagent scheme to improve zinc separation from extremely low-grade zinc flotation tailings. The results show that different amines led to different flotation performance, and the collectors were ranked as OPA 1214, OPA 13, OPA 10 and DDA in a decreasing order based on flotation collectivity and selectivity. An increase in the concentration of each collector increased the zinc recovery but reduced the concentrate zinc grade. Interactions were also observed between different amines and Na₂S and Na₂SiO₃, and OPA 1214 outdid the others in saving the usage of both the Na₂S and Na₂SiO₃. The measured adsorption of collector onto smithsonite was found to correlate well with flotation test results. It was concluded that hydrocarbon chains can be held accountable for the difference in the flotation performance with different amines. The longer the hydrocarbon chain, the stronger the hydrophobic association ability of amine, which is conducive to the selective amine adsorption onto sulfurized smithsonite particles and hence the smithsonite flotation.     

PMT overshoot study for the JUNO prototype detector

The quality of PMT signals is crucial for large-size and high-precision neutrino experiments, but most of these experiments are affected by the overshoot of PMT signals from the positive HV-single cable scheme. Overshoot affects the trigger, dead time and charge measurement from a detector. For the JUNO prototype detector, we have performed a detailed study and calculation on PMT signal overshoot to control the ratio of overshoot to signal amplitude to ~1%, with no effect on other PMT parameters.