Numerical studies for plasmas of a linear plasma device HIT-PSI with geometry modified SOLPS-ITER

The HIT-PSI is a linear plasma device built for physically simulating the high heat flux environment of future reactor divertors to test/develop advanced target plate materials.In this study,the geometry-modified SOLPS-ITER program is employed to examine the effects of the magnetic field strength and neutral pressure in the device on the heat flux experienced by the target plate of the HIT-PSI device.The findings of the numerical simulation indicate a positive correlation between the magnetic field strength and the heat flux density.Conversely,there is a negative correlation observed between the heat flux density and the neutral pressure.When the magnetic field strength at the axis exceeds 1 tesla and the neutral pressure falls below 10 Pa,the HIT-PSI has the capability to attain a heat flux of 10 MW·m-2 at the target plate.The simulation results offer a valuable point of reference for subsequent experiments at HIT-PSI.

Conceptual design of the tail research experiment at the Space Plasma Environment Research Facility(SPERF-TREX)

The Space Plasma Environment Research Facility(SPERF)for ground simulation of the space plasma environment is a key component of the Space Environment Simulation Research Infrastructure(SESRI),a major national science and technology infrastructure for fundamental research.It is designed to investigate outstanding issues in the space plasma environment,such as energetic particle acceleration,transport,and interaction with electromagnetic waves,as well as magnetic reconnection processes,in magnetospheric plasmas.The Tail-Research EXperiment(TREX)is part of the SPERF for laboratory studies of space physics relevant to magnetic reconnection,dipolarization and hydromagnetic wave excitation in the magnetotail.SPERFTREX is designed to carry out three types of experiments:the tail plasmoid for magnetic reconnection,dipolarization front formation,and magnetohydrodynamic waves excited by highspeed plasma jets.In this paper,the scientific goals and three scenarios of SPERF-TREX for typical processes in space plasmas are presented,and experimental plans for SPERF-TREX are also reviewed,together with the plasma sources applied to generate the plasma with the desired parameters and various magnetic configurations.

Laboratory observation of electron energy distribution near three-dimensional magnetic nulls

The acceleration of electrons near three-dimensional(3D)magnetic nulls is crucial to the energy conversion mechanism in the 3D magnetic reconnection process.To explore electron acceleration in a 3D magnetic null topology,we constructed a pair of 3D magnetic nulls in the PKU Plasma Test(PPT)device and observed acceleration of electrons near magnetic nulls.This study measured the plasma floating potential and ion density profiles around the 3D magnetic null.The potential wells near nulls may be related to the energy variations of electrons,so we measured the electron distribution functions(EDFs)at different spatial positions.The axial variation of EDF shows that the electrons deviate from the Maxwell distribution near magnetic nulls.With scanning probes that can directionally measure and theoretically analyze based on curve fitting,the variations of EDFs are linked to the changes of plasma potential under 3D magnetic null topology.The kinetic energy of electrons accelerated by the electric field is 6 eV(v_(e)~7v_(Alfvén-e))and the scale of the region where accelerating electrons exist is in the order of serval electron skin depths.

Three-dimensional magnetic reconnection in complex multiple X-point configurations in an ancient solar-lunar terrestrial system

Magnetic reconnection processes in three-dimensional(3D)complex field configurations have been investigated in different magneto-plasma systems in space,laboratory,and astrophysical systems.Two-dimensional(2D)features of magnetic reconnection have been well developed and applied successfully to systems with symmetrical property,such as toroidal fusion plasmas and laboratory experiments with an axial symmetry.But in asymmetric systems,the 3D features are inevitably different from those in the 2D case.Magnetic reconnection structures in multiple celestial body systems,particularly star-planet-Moon systems,bring fresh insights to the understanding of the 3D geometry of reconnection.Thus,we take magnetic reconnection in an ancient solar-lunar terrestrial magneto-plasma system as an example by using its crucial parameters approximately estimated already and also some specific applications in pathways for energy and matter transports among Earth,ancient Moon,and the interplanetary magnetic field(IMF).Then,magnetic reconnection of the ancient lunar-terrestrial magnetospheres with the IMF is investigated numerically in this work.In a 3D simulation for the Earth-Moon-IMF system,topological features of complex magnetic reconnection configurations and dynamical characteristics of magnetic reconnection processes are studied.It is found that a coupled lunar-terrestrial magnetosphere is formed,and under various IMF orientations,multiple X-points emerge at distinct locations,showing three typical magnetic reconnection structures in such a geometry,i.e.,the X-line,the triple current sheets,and the A-B null pairs.The results can conduce to further understanding of reconnection physics in 3D for plasmas in complex magnetic configurations,and also a possible mechanism for energy and matters transport in evolutions of similar astrophysical systems.

Inward particle transport driven by biased endplate in a cylindrical magnetized plasma

The inward particle transport is associated with the formation of peaked density profiles,which contributes to improve the fusion rate and the realization of steady-state discharge.The active control of inward particle transport is considered as one of the most critical issues of magnetic confinement fusion.Recently,it is realized preliminarily by adding a biased endplate in the Peking University Plasma Test(PPT)device.The results reveal that the inward particle flux increases with the bias voltage of the endplate.It is also found that the profile of radial electric field(Er)shear is flattened by the increased bias voltage.Radial velocity fluctuations affect the inward particle more than density fluctuations,and the frequency of the dominant mode driving inward particle flux increases with the biased voltage applied to the endplate.The experimental results in the PPT device provide a method to actively control the inward particle flux using a biased endplate and enrich the understanding of the relationship between E_(r)×B shear and turbulence transport.

航空发动机OEI应急工况模拟试验方法研究

本文针对旋翼航空器单台发动机不工作(One Engine Inoperative,OEI)工况进行了模拟试验方法研究,重点研究了两种热加载试验技术,即感应线圈加热试验方法和热模拟电阻加热试验方法。首先,进行了感应加热和热模拟电阻加热的热-力加载性能测试,明确了两种试验方法的技术特点。其次,通过对某种典型镍基高温合金在两种加热方式下进行OEI模拟试验研究,分析了在两种加热方式下OEI对材料性能的影响,评估和比较了感应加热和热模拟电阻加热的OEI工况试验模拟效果。结果表明,由于热模拟电阻加热方法有控温精度高的优点,并且可在试样表面形成较大的均温区,因此能够更好地模拟OEI工况。相比之下,感应加热方法易在试样表面引入较大的热梯度,从而影响测温的一致性,并可能造成较大的热应力,导致OEI工况模拟的效果欠佳。因此推荐采用热模拟机试验方法作为OEI工况模拟的首选方法。

生物质与煤掺烧燃烧特性的实验研究

利用热重分析仪,在不同条件下,对单一生物质、煤及其混合物的燃烧特性进行分析,研究了木屑、稻壳、稻草及耒阳白沙煤的着火温度、燃烧最大速率温度和燃烬温度等燃烧特性参数。实验结果表明,生物质的着火温度比白沙煤低,生物质在燃烧过程中有两个明显的失重阶段,而煤只有一个明显的失重阶段。通过掺烧可以使生物质与煤的混合物着火温度降低,着火时间缩短,延长了整个燃烧的温度区间,使煤能更好地燃尽,使燃料的燃烧特性得到了优化。随着生物质掺混比例的提高,掺混样品着火点温度降低得更加明显;且生物质颗粒尺寸由R90变为R200时,同样的掺混比例下,尺寸R200的掺混样品着火温度更低。

统计诊断理论用于航空发动机滑油系统故障诊断

某新型发动机滑油系统故障的统计判别诊断法,用人工智能方法及所建立的数值统计诊断理论模型,来判别发动机滑油系统的工作状态。最后结合具体故障案例,实现滑油系统故障的统计诊断,实践结果验证该方法诊断发动机滑油系统故障的正确性。

基于分组检查概率法的飞机液压系统故障原因分析

针对某新型飞机液压系统故障诊断中,液压系统附件数量众多,查找故障附件所需时间较长,严重影响飞机出动率。本文提出分组检查概率法分析飞机液压系统故障原因,将分组检查概率理论引入到飞机液压系统故障诊断领域,旨在缩短查找故障附件所需时间。实践结果表明,此方法能有效缩短飞机液压系统的排故时间,确保部队战训任务顺利完成,提高飞机出动率。

基于逻辑诊断理论的航空发动机起动系统故障诊断的应用

针对某型飞机发动机故障诊断中,故障现象与故障原因之间关系极为复杂、不确定,提出了该型发动机故障的逻辑诊断方法,建立了逻辑诊断的数值理论模型。根据以往方法建立逻辑诊断矩阵不足,提出了采用人工智能之方法,利用专家知识动态建立逻辑诊断矩阵过程模型。本文结合具体故障案例,在计算机上实现了该型发动机故障的逻辑诊断,验证了该方法诊断发动机系统故障的正确性。

基于贝叶斯诊断理论的航空发动机燃气涡轮机故障原因分析

将贝叶斯数值理论应用到航空发动机燃气涡轮机的故障诊断过程中,通过建立燃气涡轮机贝叶斯数值诊断理论模型,计算出系统所表现出的故障征兆对故障成因的概率,利用状态识别极限法则,来判定涡轮机系统所处的工作状态。经过长期实践验证,此方法具有良好的故障诊断、识别效果,有效提高了该型燃气涡轮机故障诊断过程中不确定性信息处理的能力及推理的质量。

基于模糊诊断理论的航空发动机自动停车故障原因的分析

针对某型航空发动机空中自动停车故障诊断中故障症状与故障原因之间关系极为复杂、不确定等问题,提出了该型发动机故障的模糊诊断方法,建立了发动机自动停车故障模糊诊断的数值理论模型,利用专家知识动态建立了模糊诊断矩阵过程模型,并结合具体自动停车故障案例,实现了该型发动机自动停车故障的模糊诊断。

强流脉冲电子束表面改性的物理模型及数值模拟

推导出了强流脉冲电子束处理过程的应力场方程,利用数值模拟,得到了温度场和应力场的分布曲线,分别给出了熔化深度、升降温的速率及温度梯度的大小,准静态应力和热应力波的幅值、应力波的传播及反射过程,利用数值模拟结果对实验中观察到的实验现象熔化深度、材料表层及次表层数微米范围内组织结构的变化及数百微米的硬度提高等给出了解释。

强流脉冲电子束轰击产生表面熔坑的数值模拟研究

在纯Al强流脉冲电子束表面改性实验的基础上 ,通过数值计算方法对其温度场和熔化过程进行了模拟 ,给出了脉冲半高宽度为 0 5μs、能量为 3J cm2 电子束轰击铝靶后 :熔化深度约为 2 5μm ,与TEM的观察结果一致 ,熔化从 0 4μs开始到 1 6μs结束 ,最先完全熔化的位置约为 1 4μm ,亚表层首先熔化并且迅速膨胀 (沉积的能量在最大射程的 1 3处达到最大值 ) ,体积膨胀力大约为 2 75MPa ,引起了熔体从亚表层通过表层向外喷发 ,熔体的喷发速度约为 1 330m s,随后表面从内向外经历速率为 1 0 9K s的冷却过程 ,因而使得表面形成类似于火山坑状的”熔坑”。

抗原肽与MHC分子相互作用的QSAR模型研究

分别采用氨基酸序列及氨基酸结构描述符方法定量研究了短肽-MHC(majorhistocompatibilitycomplex)分子结合亲合力的定量构效关系(QSAR)模型,用这两个模型对短肽与HLA-A*0201分子结合的805个预测样本进行了预测,预测准确度分别达到66.8%和65.5%.采用了去除“劣点”方法检验模型的鲁棒性,结果证明两个模型都具有良好的鲁棒性.通过改变两个模型的参数,对氨基酸残基个数为8或10的CTL(cytotoxicyTlymphocyte)表位进行预测.

纯镁在强流脉冲电子束轰击下的表面熔化和汽化行为

采用熔化和汽化两种模式对纯镁表面进行了脉冲电子束轰击处理,并在实验和理论基础上用数值方法模拟了温度场、熔化过程及汽化过程的演化。结果表明,在熔化模式下,次表层先熔化和准静态压应力共同作用导致次表层液滴喷发,形成典型的火山口形貌,并产生强的瞬间冲击热应力;在汽化模式下,沸腾在表层一定范围内同时进行,使得表面起伏不平,并产生大量小液滴,在电子束流中,这些小液滴被充上负电,并在电场力的作用下重新返回表面,从而解释了汽化后的特殊表面形貌。汽化量的计算值与实测值也符合较好。

疲劳热像法研究综述

能量方法是疲劳研究的重要方法,新兴的红外热像技术则是实现这一方法的重要手段.红外热像法作为一种无损、实时及非接触的测试技术,已被广泛地应用于疲劳研究中.近年来,提出了一些用于快速确定材料及构件疲劳极限的热像法,并得到了很好地开发与推广.文中介绍了疲劳热像法的兴起、发展与深入研究,讨论了该领域出现的主要问题及当前的研究热点,并展望了疲劳热像法的研究前景.

脉冲电子束辐照中增强扩散效应的数值计算

针对强流脉冲电子束 (HCPEB)表面改性的特点 ,采用适当的数学模型和数值模拟的方法 ,对9Cr1 8钢经Ti离子注入后又使用强流脉冲电子束表面辐照处理中产生的增强扩散效应进行了研究 ,计算结果与实验结果较为吻合。分析表明 ,扩散激活能的下降是导致增强扩散的主要原因 ,这与HCPEB改性过程产生的非平衡辐照缺陷浓度密切相关。

强流脉冲电子束纯铝表面改性过程的热力学模拟

针对强流脉冲电子束表面改性的特点,建立了相应的数学物理模型,以纯铝材表面改性实验为基础,计算了由强流脉冲电子束辐照材料表面所产生快速升降温与熔凝过程,对其中的熔化、蒸发、热应力波等现象分别进行了数值模拟。计算结果表明,熔化深度约在1-10μm,与实验结果接近;蒸发作用影响较小,汽化层厚度仅为纳米量级;热应力波的幅值约在0.1 MPa量级,且与脉冲的能量密度大致成正比,但是对材料结构和性能有重要影响。

静电近似下抛物形电导率模型电弧的螺旋不稳定性

在静电近似下 ,给出了圆柱等离子体中电弧放电螺旋不稳定性的一个简化线性分析 ,得到了显式解析解 .由这个解能给出稳定性判据及不稳定性增长率等定量结果 .在外加均匀磁场情况下 。