气体间漏率等效关系的直接模拟蒙特卡洛分析

研究气体间漏率的等效关系, 对提高检漏数据判读的准确性具有重要意义。本文基于对金属压扁型漏孔的研究, 通过建立分析模型, 运用直接模拟蒙特卡罗法数值模拟方法得出了气态工质的漏率曲线及不同工质间漏率的等效关系, 验证了气态工质泄漏模型的正确性, 可实现已知示漏气体漏率情况下实际工质漏率的虚拟预示。研究结果表明, 不同气态工质在同一条件下漏率存在着较大差异, 但都随两端压差增大而增大, 呈近二次多项式变化趋势, 仿真结果与理论分析相符。气态工质间漏率等效性在He漏率≤10^-6Pa·m³/s和He漏率≥10^-3Pa·m³/s时趋于恒值;而当He漏率在[10-6, 10-3]Pa·m3/s时, 漏率等效性存在着先上升后下降的多项式变化形式, 且最大值出现在这一区域之间。研究结果为实际工质与示漏工质间漏率等效数值研究提供了基本方法和参考数据。     

KMC模拟活性剂作用下的薄膜外延生长

运用动力学蒙特卡罗方法模拟了两种原子组成的薄膜外延生长时的形貌,给出了一种原子作为活性剂时的同质外延生长情况,从动力学角度模拟了表面活性剂向上漂浮的行为,模拟结果发现,在原子间结合能满足Eaa〉EBB〉EAB时,在基底上先沉积少量活性剂原子薄膜更趋于向层状模式生长;温度越高,活性剂原子越容易与沉积原子发生交换,薄膜表面更加光滑平整。同时,也发现活性剂原子的漂浮行为对温度有一个敏感的临界温度,大于这个温度时,活性剂原子呈现漂浮行为。     

Magnetocaloric Properties of the Perovskite GdCuO3: Monte Carlo Simulation

Journal of Superconductivity and Novel Magnetism - This work aims to examine the magnetocaloric properties of the Perovskite GdCuO3, such as the total magnetization, the susceptibility, and the...     

高温高压下LiF热力学性质的第一性原理计算

利用第一性原理方法并结合准谐徳拜模型计算了B1相结构LiF在高温高压下的热力学性质,其零温零压下的平衡体积和体弹模量的计算结果与实验值相符。通过准谐徳拜模型获得了该结构的相对体积、体弹模量、热容、熵、徳拜温度与温度和压强的关系。     

Finite Element Analysis of Hydrogen Transport in Steel Pressure Vessel at High Temperature

Hydrogen embrittlement is commonly considered as an important failure mechanism for some typical steel pressure vessels and pipes made of such as Cr–Mo and 4130X steels at high-pressure hydrogen environment. In previous work, we investigated the hydrogen transport mechanisms of Crmo steel pressure vessels at room temperature. Furthermore, high temperature environment may affect the hydrogen transport mechanisms and hydrogen-induced crack behaviors in these structures to a large extent. In this paper, we study the hydrogen transport mechanisms in 2.25Cr–1Mo steel pressure vessel at high temperature under the support of National Key Fundamental Research and Development Project of China (2015.1-2019.12). The main work is to explore the effects of temperature, hydrogen concentration, and structural sizes on the transient hydrogen diffusion and distribution behaviors in Crmo steel pressure vessels using finite element analysis. Numerical results show that elevated high temperature accelerates the hydrogen embrittlement sensitivity, especially at structural discontinuities.     

FTIR Study of Electronic Transitions in Solid Oxygen at High Pressure and Low Temperature

We report near-IR measurements of the electronic ^3– _g¹ _g(0,1) transitions of solid oxygen at high pressure and low temperature. Most of the P-T diagram was investigated up to the phase by means of isothermal and isobaric scans. The electronic spectra are a powerful tool to investigate the unique properties of solid oxygen, which is a localized-spin system. Magnetism of the high pressure phase plays a major role in determining the frequency of these bands, which are strongly temperature and density dependent. The analysis of this dependence allows us to model the spin correlation function and the intermolecular exchange integral.     

Temperature Effects on the Absorption Spectra of Li in Solid H2 Under High Pressure: A Path Integral Monte Carlo Study

The temperature dependence (5–45 K) of the absorption spectra of a Li atom doped in solid hydrogen at P=1.2 GPa is investigated using the path integral Monte Carlo (PIMC) method with a constant pressure ensemble. Higher temperature in our research range does not cause rearrangement of the trapping site structures. The significantly broadening and spreading of the three component absorptions with increasing temperature are observed. For the trapping site structures belonging to lower symmetry point groups, the singlet to doublet splitting decreases as temperature gets larger. An insight on the temperature-induced behaviors of the Li absorption spectrum in the doped system has been made by using the simulated results.     

超高压与低温协同作用处理土豆实验研究

以土豆为实验原料,考察了超高压低温冷冻与解冻过程以及常规冷冻与解冻方式对土豆品质的影响.研究结果表明,经过高压低温处理过的土豆比常规方式处理后的品质明显得到提高,质地和微观组织得到了明显地改善,汁液损失减少;高压快速冷冻(PSF200MPa and-20℃)过程在保持土豆原有的外观、风味、质构和营养上与其他高压方式相比具有明显优势;当处理压力高于100MPa时,该过程对微生物的灭活具有显著的作用,同时相转变具有促进灭活效果的作用.     

Investigation of High Voltage Discharges in Low Pressure Gases Through Large Ceramic Superconducting Electrodes

A device has been built and tested, in which a ceramic superconducting cathode and a copper anode cause electrical discharges in low pressure gases, at temperatures between 50 and 70 K. The electrodes are connected to a capacitors array charged up to 2000 kV; peak currents are of the order of 10⁴ A. The cathode has the diameter of 10 cm and is fabricated by OCMTG technology. In discharges at voltage above 500 kV two new phenomena were observed, probably related to each other. First, the discharge does not look like a spark, but is a flat, glowing discharge, which originates from the whole surface of the superconducting electrode. Furthermore, a radiation pulse is emitted at the discharge, which propagates orthogonally to the cathode, towards the anode and beyond it, in a collimated beam, apparently without any attenuation. The radiation pulse carries an energy of 10^–3 J at least. The features and the nature of this radiation have been investigated by several means, still it was not possible to identify it; we can only exclude that it is electromagnetic radiation or any other radiation with energy-momentum relationship E=cp.     

蒙特卡洛法在检测机构服务窗口等待问题的分析

对检测技术机构的客户服务窗口等待问题,用蒙特卡洛法进行窗口排队仿真分析,分别模拟了在开设一个窗口和两个窗口的情况下客户的排队等待状态.在Excel上通过2000次模拟的统计仿真分析.通过窗口利用率和客户等待时向等参量的对比得出分析结果.该方法成本低,仿真情况贴近现实,实用性强,分析结果可以为管理层的决策提供参考建议.     

Spatial Imaging of Charge Transport in Germanium at Low Temperature

The purpose of this experiment is to observe the oblique propagation of electrons through germanium by exciting a point source of charge carriers with a focused laser pulse on one face of a germanium crystal. After the electrons are drifted through the crystal by a uniform electric field, the pattern of charge density arriving on the opposite face is mapped and used to reconstruct the trajectories of the electrons. These measurements will verify in detail the Monte Carlo analysis utilized in the Cryogenic Dark Matter Search to model the transport of charge carriers in high-purity germanium detectors, including both oblique electron propagation and inter-valley scattering.     

Infrared Studies of Ar(H2)2 at Low Temperature and High Pressure

An extensive infrared absorption study of the compound Ar(H ₂)₂ in the range of pressure from 5 to 30 GPa, and between 30 K and room temperature is presented. This study has permitted the identification and assignment of high–frequency and low frequency vibron–phonon combination bands, as well as of the roto–vibrational bands. Spectra changes lowering temperature, with the appearance of the Q ₁(0) vibrational peak, are interpreted as arising from conversion of ortho–hydrogen into para–hydrogen in the solid.     

Program FAKE: Monte Carlo Event Generators as Tools of Theory in Early High Energy Physics

The term Monte Carlo method indicates any computer-aided procedure for numerical estimation that combines mathematical calculations with randomly generated numerical input values. Today it is an important tool in high energy physics while physicists and philosophers also often consider it a sort of virtual experiment. The Monte Carlo method was developed in the 1940s, in the context of U.S. American nuclear weapons research, an event often regarded as the origin of both computer simulation and “artificial reality” (Galison 1997). The present paper interrogates this strong claim by focusing on the emergence of Monte Carlo event generators in particle physics in the early 1960s. This historical case study shows how, as Monte Carlo computation became part of the toolbox of particle physicists around 1960, it was neither usually referred to as a “computer simulation” nor was it regarded as a surrogate for experimentation. In revising the history of this method, this paper asks, in what context did particle physicists of the 1960s decide to create FAKE, the first high-energy-physics Monte Carlo event simulator? What was their goal? And what epistemic role did FAKE play? In answering these questions, it is argued that Monte Carlo computations were not introduced into particle physics to simulate experiments, but rather they played the role of theoretical tools. The Monte Carlo method was able to do this thanks to its random component, a property which provided a means of modeling a specific phenomenon, so-called “(particle) resonances”. Indeed, in doing so, event generators even came to mutually assimilate and reshape the notions of particle and resonance, taking up an epistemic function which had previously been confined to physical-mathematical formulae: that of a medium which could express aspects of particle theory.

     

聚晶金刚石的高温高压制备及其性能研究进展

聚晶金刚石(PCD)刀具在加工非铁基材料时,尤其是一些超硬、耐磨材料时,其寿命和加工精度远高于传统刀具。聚晶金刚石的性能与原材料和烧结条件密切相关。概述了不同因素对以陶瓷为粘结剂的聚晶金刚石和无粘结剂的纳米聚晶金刚石的硬度、断裂韧性的影响并比较了不同种类PCD的热稳定性能。分析得到以过渡金属硼化物和碳化硅为粘结剂所制备的PCD的热稳定性能较好,优于以钴为粘结剂制备的PCD;在Hall-Petch定律作用下,以纳米尺寸陶瓷为粘结剂的PCD硬度更高,韧性更强;无粘接剂的纳米聚晶金刚石的力学、热学性能最为优异。最后,结合实际应用对聚晶金刚石的制备提出了参考性的建议。     

Solid-Fluid Phase Coexistence of Hard Heteronuclear Dumbbells via Cell Theory and Monte Carlo Simulation

We study the solid-fluid equilibria of hard heteronuclear dumbbells using cell theory and isobaric ensemble Monte Carlo simulations. Calculations for six cases of L* (bond length) and σ* (sphere diameter ratio) near the homonuclear limit are discussed with two base-centered monoclinic orientationally-ordered crystal structures which have been considered. The two crystal structures exhibit nearly identical properties at freezing within the accuracy of the calculations for the cases we present. The reduced pressure at coexistence increases with decreasing σ*.     

A Monte Carlo Study of Disorder in the High Pressure Mixed Crystal N2-Ar

In order to obtain a better notion of the experimental results in our laboratory, Monte Carlo calculations have been performed of the N ₂-Ar crystal on the N ₂-rich side, in the p-T region where the and phases exist in pure N ₂. Considering the enthalpy, the system prefers the Ar atoms to be located on the sphere positions. The * phase is present for mixtures down to but is most likely metastable. The *-* transition shifts to lower temperatures with decreasing . The 2 ^nd order transition within the phase continues to exist to even smaller . In contrast to the * -* transition, the transition temperature for the 2 ^nd order transition does not shift to lower temperatures. For a mixture of it is within 5 K from the pure 2 ^nd order transition at a pressure of 7.0 GPa.     

高速高压低温温度传感器的试验研究

简要介绍了高速高压低温条件下温度传感器的试验研究方法。试验研究的着重点是尽量利用现有的设备、试验条件和有关的氢氧发动机研制过程中的试验，对传感器进行一些针对性试验，以取得可靠的试验数据。通过对试验数据的分析和研究，验证考核传感器的性能。主要给出了强度试验、动态特性试验和恢复系数试验的模拟试验方案和方法及搭载试验方法，给出了某传感器进行上述试验的试验结果，结果表明，这种试验研究方法是可行且可靠的。     

Measurements of Hydrogen Thermal Conductivity at High Pressure and High Temperature

The thermal conductivity for normal hydrogen gas was measured in the range of temperatures from 323 K to 773 K at pressures up to 99 MPa using the transient short hot-wire method. The single-wire platinum probes had wire lengths of 10 mm to 15 mm with a nominal diameter of 10 μm. The volume-averaged transient temperature rise of the wire was calculated using a two-dimensional numerical solution to the unsteady heat conduction equation. A non-linear least-squares fitting procedure was employed to obtain the values of the thermal conductivity required for agreement between the measured temperature rise and the calculation. The experimental uncertainty in the thermal-conductivity measurements was estimated to be 2.2 % (k = 2). An existing thermal-conductivity equation of state was modified to include the expanded range of conditions covered in the present study. The new correlation is applicable from 78 K to 773 K with pressures to 100 MPa and is in agreement with the majority of the present thermal-conductivity measurements within ±2 %.