Experimental investigation of high-mach-number 3D hydrodynamic jets at the national ignition facility

The first hydrodynamic experiments were performed on the National Ignition Facility. A supersonic jet was formed via the interaction of a laser driven shock ( approximately 40 Mbar) with 2D and 3D density perturbations. The temporal evolution of the jet's spatial scales and ejected mass were measured with point-projection x-ray radiography. Measurements of the large-scale features and mass are in good agreement with 2D and 3D numerical simulations. These experiments provide quantitative data on the evolution of 3D supersonic jets and provide insight into their 3D behavior.     

Experimental investigation of dipolar interaction in suspensions of magnetic nanoparticles

The structure and the magnetisation behaviour of two different systems of magnetic nanoparticles (MNP), namely Resovist^® with a wide core size distribution (diameter, σ=0.3) and SHP-20 with a rather narrow distribution (σ=0.1), were investigated by magnetorelaxometry (MRX) and magnetisation measurements in a wide concentration range. MRX on fluid and solid suspensions yielded the distribution of hydrodynamic diameters and effective magnetic anisotropy energies (E_A), where towards higher iron concentrations the spatial particle correlation, i.e. aggregation, and also the width of the E_A distribution were increased significantly. It was further found that these effects quantitatively depend on the suspension medium, where an increased salt concentration enhanced the aggregate size distribution and E_A dispersion. At mentioned higher MNP concentrations, the quasistatic magnetisation, normalised with respect to the iron content, decreased by up to 40%. In the case of SHP-20, where single core MNPs dominate, the maximum of this drop down of the magnetisation occurred at a field strength that corresponds to the strength of mean squared dipolar interaction.     

带二次流的多喷管超声速引射器性能实验研究

 为研究多喷管超声速引射器在有二次流情况下的性能,采用模拟器产生给定总温和总压的模拟二次流,在多喷管超声速引射器实验台上进行了一系列实验。重点考察了多喷管引射器的性能以及一次流总压和喷管安装构型对其性能的影响。实验结果表明：多喷管超声速引射器可保证二次流在设计工况下正常工作;二次流的加入大大减小了一次流的总压损失;较低的一次流总压具有更好的压力匹配性能,但引射增压能力也有所降低;合理的喷管安装构型可同时提高引射增压能力和压力匹配能力。提出了将二次流作为“助推器”,以帮助多喷管引射器在较低工况下实现启动的方案,在不增加系统复杂度的前提下提高了引射器的压力匹配能力。     

带二次流的多喷管超声速引射器性能实验研究

为研究多喷管超声速引射器在有二次流情况下的性能,采用模拟器产生给定总温和总压的模拟二次流,在多喷管超声速引射器实验台上进行了一系列实验。重点考察了多喷管引射器的性能以及一次流总压和喷管安装构型对其性能的影响。实验结果表明：多喷管超声速引射器可保证二次流在设计工况下正常工作;二次流的加入大大减小了一次流的总压损失;较低的一次流总压具有更好的压力匹配性能,但引射增压能力也有所降低;合理的喷管安装构型可同时提高引射增压能力和压力匹配能力。提出了将二次流作为“助推器”,以帮助多喷管引射器在较低工况下实现启动的方案,在不增加系统复杂度的前提下提高了引射器的压力匹配能力。     

气体火花开关重复频率特性的实验研究

气体火花开关在重复频率脉冲功率技术中具有广泛的应用,影响气体火花开关绝缘恢复与重复频率工作性能的因素众多。实验研究了气体火花开关的能量沉积和气压对开关重复频率指标的影响,给出了气体火花开关绝缘恢复时间与气压及开关导通功率的关系式,初步分析了气体开关击穿通道在自然散热（不吹气）条件下,重复频率稳定工作的最高功率与重复频率指标、气压的关系。     

气体火花开关重复频率特性的实验研究

气体火花开关在重复频率脉冲功率技术中具有广泛的应用,影响气体火花开关绝缘恢复与重复频率工作性能的因素众多。实验研究了气体火花开关的能量沉积和气压对开关重复频率指标的影响,给出了气体火花开关绝缘恢复时间与气压及开关导通功率的关系式,初步分析了气体开关击穿通道在自然散热(不吹气)条件下,重复频率稳定工作的最高功率与重复频率指标、气压的关系。     

相反拓扑指数的Laguerre-Gaussian模的产生和模间相互作用的实验研究

实验研究了带有相反拓扑指数的Laguerre-Gaussian(LG)模间的相互作用，发现含有相反拓扑指数的两个LG模在传播过程中其光场发生变化，观察到随着传播距离的增加，两个LG模的中心位相奇点会逐渐连成为一个弧形暗线形状.实验上验证了带有相反拓扑指数的光学涡流中的螺旋位错在传播过程中会演变为边位错这一理论结果.     

Observation of stable,high-mach-number electrostatic shocks in a collisionless plasma

Observation of stable, large amplitude ion acoustic shocks with a high Mach number M> 1.6 in a collisionless plasma is described. Discussions about the nature and behavior of the waves are also given.     

介质阻挡放电等离子体与激波相互作用实验研究

 主要针对介质阻挡放电等离子体改变激波系结构展开了实验研究。验证了介质阻挡放电等离子体气动激励能够对边界层施加影响,顺气流放电时能减小激波强度,逆气流放电时能增大激波强度。逆气流放电时,3组电极放电与4组电极放电比较,3组电极放电时压比更高。由于在该实验中放电区域比边界层小得多,介质阻挡放电产生的体积力远小于高速来流条件下的气动力,因此对激波的作用效果十分微弱。     

介质阻挡放电等离子体与激波相互作用实验研究

主要针对介质阻挡放电等离子体改变激波系结构展开了实验研究。验证了介质阻挡放电等离子体气动激励能够对边界层施加影响,顺气流放电时能减小激波强度,逆气流放电时能增大激波强度。逆气流放电时,3组电极放电与4组电极放电比较,3组电极放电时压比更高。由于在该实验中放电区域比边界层小得多,介质阻挡放电产生的体积力远小于高速来流条件下的气动力,因此对激波的作用效果十分微弱。     

激光烧蚀等离子体射流与固体靶相互作用实验研究

利用激光烧蚀等离子体射流可以获得数km/s 甚至上千km/s 的射流速度,远超目前绝大多数设备所能提供的模拟速度,并且覆盖了极大的温度与密度范围,作为加载手段具有广阔的应用前景。通过实验方法,探索和发展激光烧蚀等离子体射流这一新型实验模拟手段,利用高功率激光烧蚀产生高温高压等离子体射流,实现超高速气体动力学实验室模拟的新途径。以此作为加载条件,研究超高速物体与气体相互作用的气体动力学特性。通过建立激光烧蚀等离子体射流与固体靶相互作用实验方法,可进一步研究等离子体射流的产生、发展以及高速物体气体动力学,为下一步开展天体物理、小行星形貌、超高速陨石与行星大气相互作用机制等相关研究奠定基础。     

Experimental investigation on reversal of secondary Bjerknes force between two bubbles in ultrasonic standing wave

The direction of the secondary Bjerknes force between a free bubble and an attached bubble was experimentally investigated. The behavior of the two bubbles in an ultrasonic standing wave of 27 kHz was observed using an imaging system with a high-speed video camera. It was demonstrated experimentally that the direction of the force reversed at a specific separation distance between the two bubbles, which was defined as the threshold distance. The threshold distance changed with the radius of the attached bubble. In addition, a theoretical calculation was performed using a previously derived model that coupled the vibrations of two free bubbles [Ida, Phys. Lett. A 297, 210-217 (2002)]. The experiment data for the threshold distance qualitatively agreed with the theoretical predictions, except when the separation distance was very small. Then, it was discovered that the free bubble became trapped near the attached bubble when the separation distance between the two bubbles was very small. This indicated that a stable equilibrium point for the separation distance exists that cannot be predicted by the theoretical model.     

Experimental investigation of the characteristic features of bremsstrahlung from high-energy electrons in thin amorphous targets

Radiation from 0–900 MeV electrons in thin amorphous films is investigated experimentally in the photon energy range 20–700 keV. The Landau-Pomeranchuk-Migdal suppression of the soft part of the bremsstrahlung spectrum and the Ter-Mikaélyan density effect are detected. Coherent bremsstrahlung on macroscopic inhomogeneities in the target material is observed. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 5, 369–373 (10 March 1997)     

蛋白质相互作用网络特征的理论再现

无标度性、小世界性、功能模块结构及度负关联性是大量生物网络共同的特征. 为了理解生物网络无标度性、小世界性和度负关联性的形成机制, 研究者已经提出了各种各样基于复制和变异的网络增长模型. 在本文中,我们从生物学的角度通过引入偏爱小复制原则及变异和非均匀的异源二聚作用构建了一个简单的蛋白质相互作用网络演化模型.数值模拟结果表明,该演化模型几乎可以再现现在实测结果所公认的蛋白质相互作用网络的性质：无标度性、小世界性、度负关联性和功能模块结构. 我们的演化模型对理解蛋白质相互作用网络演化过程中的可能机制提供了一定的帮助. 关键词： 蛋白质相互作用网络 偏爱小 非均匀的异源二聚作用 功能模块结构     

Experimental investigation of the three-dimensional interaction of a strong shock with a spherical density inhomogeneity

Laser-driven experiments are described which probe the interaction of a very strong shock with a spherical density inhomogeneity. The interaction is viewed from two orthogonal directions enabling visualization of both the initial distortion of the sphere into a double vortex ring structure as well as the onset of an azimuthal instability that ultimately results in the three-dimensional breakup of the ring. The experimental results are compared with 3D numerical simulations and are shown to be in remarkable agreement with the incompressible theory of Widnall et al. [J. Fluid Mech. 66, 35 (1974)].     

电极感应熔化气雾化制粉技术中非限制式喷嘴雾化过程模拟

电极感应熔化气雾化(electrode induction melting gas atomization, EIGA)是一种制备超洁净无夹杂物的先进制粉技术,本文以粉末高温合金的氩气雾化过程为研究示例,对现有用于实际生产的国内某厂家提供的EIGA用非限制式喷嘴进行建模,采用商用计算流体力学软件FLUENT,分布采用欧拉-欧拉VOF(volume of fluid)多相流方法与欧拉-拉格朗日DPM (discrete phase model)离散相方法,对非限制式环缝喷嘴主雾化与二次雾化过程进行了数值模拟.通过对主雾化过程中多相流大涡模拟速度流场,主雾化过程中不同阶段高温熔体云图模拟以及二次雾化过程中TAB (Taylor analogy breakup)模型速度流场及TAB模型粒度分布的模拟研究,实现了对EIGA制粉技术中非限制式喷嘴雾化过程的全过程模拟,并预测了雾化后的粉末粒度分布.在此基础上,采用本文模拟使用的非限制式环缝喷嘴,设定与模拟条件一致(进气压力4 MPa,液流直径约4 mm)的实验条件,制备的粉末大部分颗粒的直径大小在100μm左右,该实验结果与模拟得到的粉末直径D50=100μm大小一致,进一步验证了模拟数据的合理性.该方法也适用于非限制式喷嘴里,其他金属或合金的雾化过的模拟研究.     

Experimental investigation of the generation of large-amplitude internal solitary wave and its interaction with a submerged slender body

A principle of generating the nonlinear large-amplitude internal wave in a stratified fluid tank with large cross-section is proposed according to the‘jalousie’control mode.A new wave-maker based on the principle was manufactured and the experiments on the generation and evolution of internal solitary wave were conducted.Both the validity of the new device and applicability range of the KdV-type internal soliton theory were tested.Furthermore,a measurement technique of hydrodynamic load of internal waves was developed.By means of accurately measuring slight variations of internal wave forces exerted on a slender body in the tank,their interaction characteristics were determined.It is shown that through establishing the similarity between the model scale in the stratified fluid tank and the full scale in the numerical simulation the obtained measurement results of internal wave forces are confirmed to be correct.     

Correlation of primary and secondary relaxations in a supercooled liquid

The widespread assumption that primary and secondary relaxations in glass-forming materials are independent processes is scrutinized using spin-lattice relaxation weighted stimulated-echo spectroscopy. This nuclear magnetic resonance (NMR) technique is simultaneously sensitive to the dynamics on well-separated time scales. For the deeply supercooled liquid sorbitol, which exhibits a strong secondary relaxation, the primary relaxation (that is observable using NMR) can be modified by suppressing the contributions of those subensembles which are characterized by relatively slow secondary relaxations. This is clear evidence for a correlation between primary and secondary relaxation times. In the disordered crystal orthocarborane high-frequency processes are absent and consequently no such modifications could be achieved.