Improvement of quantitative analysis of molybdenum element using PLS-based approaches for laser-induced breakdown spectroscopy in various pressure environments

An experimental setup has been designed and realized in order to optimize the characteristics of laser-induced breakdown spectroscopy system working in various pressure environments. An approach combined the normalization methods with the partial least squares(PLS) method are developed for quantitative analysis of molybdenum(Mo) element in the multi-component alloy,which is the first wall material in the Experimental Advanced Superconducting Tokamak. In this study, the different spectral normalization methods(total spectral area normalization,background normalization, and reference line normalization) are investigated for reducing the uncertainty and improving the accuracy of spectral measurement. The results indicates that the approach of PLS based on inter-element interference is significantly better than the conventional PLS methods as well as the univariate linear methods in the various pressure for molybdenum element analysis.     

High-Sensitivity In-Situ Diagnosis of NO_2 Production and Removal in DBD Using Cavity Ring-Down Spectroscopy

A highly-sensitive in-situ diagnosis approach for nitrogen dioxide （NO2） has been developed in dielectric barrier discharge （DBD） based on pulsed cavity ring-down spectroscopy （CRDS）. Absorption bands of NO2 in a spectral region from 508 nm to 509 nm were used, and a detection limit of 17.5 ppb was achieved. At this level of sensitivity, the quantitative and real-time monitoring of the production and removal of NO2 are accomplished for the first time in the discharge region. By measuring the removal amount and rate at different NO2 initial number densities from 1.54 ×10^13 cm^-3 to 2.79 × 10^14 cm^-3, we determined the relationship between them and NO2 initial number densities. The removal amount linearly increases with the initial number density, while the removal rate increases logarithmically. At a lower initial number density, the removal rate is limited. By considering the chemical kinetic mechanism in plasma, a qualitative explanation for the above phenomena is proposed： the additional NO2 produced by discharge limits the removal rate, since the NO2 concentration is dominated by the competition between the forward reactions （production） and the reverse reactions （removal）.     

Ab initio Calculations of Electron-Impact Excitation Cross Sections for N_2 Molecule

One of the great difficulties in understanding nitrogen plasma elementary processes is the lack of an available database of the cross-sections of electron-impact excitations and radiations. Ab initio calculations of vibrational excitation cross sections for electron collisions with nitrogen molecules in low-lying states using similarity function approach, such as a-a＇, a-w, B-B＇ and B-W transition systems, are reported here for the first time. In the meantime, the average excitation energies of neighboring levels of these systems have been calculated. In order to obtain the cross sections, accurate spectroscopic constants and transition dipole moments have been investigated. Potential energy curves and other electronic transition dipole moments for the low-lying states of N2 have been re-evaluated using complete active space self-consistent field （CASSCF） approach with aug-cc-pVqZ basis set. The calculated cross-sections could provide a database for studying the elementary processes and the properties in N2 plasma.     

Influence of a Static Magnetic Field on Laser Induced Tungsten Plasma in Air

In this work,laser induced tungsten plasma has been investigated in the absence and presence of 0.6 T static transverse magnetic field at atmospheric pressure in air.The spectroscopic characterization of laser induced tungsten plasma was experimentally studied using space-resolved emission spectroscopy.The atomic emission lines of tungsten showed a significant enhancement in the presence of a magnetic field,while the ionic emission lines of tungsten presented little change.Temporal variation of the optical emission lines of tungsten indicated that the atomic emission time in the presence of a magnetic field was longer than that in the absence of a magnetic field,while no significant changes occurred for the ionic emission time.The spatial resolution of optical emission lines of tungsten demonstrated that the spatial distribution of atoms and ions were separated.The influence of a magnetic field on the spatial distribution of atoms was remarkable,whereas the spatial distribution of ions was little influenced by the magnetic field.The different behaviors between ions and atoms with and without magnetic field in air were related to the various atomic processes especially the electrons and ions recombination process during the plasma expansion and cooling process.     

Berry位相因子对NO／N_2体系中NOX~2∏_（3／2）R（1．5）v＝

Ｂｅｒｒｙ位相因子对ＮＯ／Ｎ_２体系中ＮＯＸ~２∏_（３／２）Ｒ（１．５）ｖ＝０→１跃迁ＬＭＲ光谱线型的影响丁洪斌，周伟明，林钧岫（大连理工大学应用物理研究所，大连１１６０２４）量子力学中的绝热定理是众所周知的，其实质是量子系统在缓慢变化的环境中将保持?..     

LIBS在气溶胶诊断方面的应用

LIBS是一种原子发射光谱技术,其基本原理是利用强脉冲激光把待测样品表面烧蚀、激发为等离子体,然后用光谱仪和CCD记录等离子体发射的光谱,对光谱分析即可得到待测物质中元素的种类和浓度信息。LIBS技术由于具有快速、无需对样品预处理、可同时测量多种元素以及适应固体、液体和气体等多种样品形态的优点,被称为未来化学分析之星,它在实现气溶胶原位检测上具有极大的应用潜力。     

Simulations and Measurement of Electron Energy and Effective Electron Temperature of Nanosecond Pulsed Argon Plasma

The behavior of argon plasma driven by nanosecond pulsed plasma in a low-pressure plasma reactor is investigated using a global model, and the results are compared with the experimental measurements. The time evolution of plasma density and the electron energy probability function are calculated by solving the energy balance and Boltzmann equations. During and shortly after the discharge pulse, the electron energy probability function can be represented by a bi-Maxwellian distribution, indicating two energy groups of electrons. According to the effective electron temperature calculation, we find that there are more high-energy electrons that play an important role in the excitation and ionization processes than low-energy electrons. The effective electron temperature is also measured via optical emission spectroscopy to evaluate the simulation model. In the comparison, the simulation results are found to be in agreement with the measurements. Furthermore, variations of the effective electron temperature are presented versus other discharge parameters, such as pulse width time, pulse rise time and gas pressure.     

岩石深基坑裂隙水综合防排施工方法

为了保证深基坑施工的顺利进行,通过利用明沟排水、盲沟排水、集水井(坑)排水以及基坑周边地表水的防护等多种方法,对岩石深基坑施工进行排水.通过几种方法的综合应用,本工程取得了良好的效果:既节约了成本,又保证了工程在基础阶段的施工进度和安全.由此可见,只有灵活应用好各种排水方法,积极主动地解决排水问题,才能保证深基坑施工的顺利进行.     

殚精竭虑建精品工程以质量创优促企业发展

1 工程项目管理质量风险因素分析 工程项目管理是一个全方位、全过程的规划组织控制与协调,质量管理是项目管理的核心。质量风险包含损失和不确定两个重要因素,正是由于我们难以确定工程质量本身何     

自密实混凝土在型钢混凝土组合梁施工中的应用

为解决高密度配筋型钢混凝土梁的混凝土施工质量问题,通过对自密实混凝土配合比的设计及其工作性能研究、对梁主筋的优化设计和施工质量控制措施的优化,使得型钢混凝土组合梁的施工质量达到了设计及规范要求.总结出了自密实混凝土的工作性能,形成了可借鉴的质量控制措施.