Variational calculation of the electronic density at surfaces

The applicability of variational principles for single-particle expectation values to the inhomogeneous electron gas at surfaces is demonstrated. Jellium metal surface densities, correct to second order, are determined by application of the formalism to the operator $\text{W=}\text{∑}\text{i}\text{δ(x}{}_{\mathrm{i}}\text{?x)}$. The surface dipole barrier thus obtained is shown to lead to essentially exact results over a substantial range of the variational parameter employed. The procedure for inclusion of the discrete ionic lattice is also indicated.     

Generation of isothermal density perturbations in the inflationary universe

It is shown that not only adiabatic perturbations of the density but also isothermal density perturbations are generated in the inflationary universe. The magnitude of isothermal perturbations can be sufficiently large for the subsequent galaxy formation. The spectrum of isothermal perturbations can differ considerably from a flat one.     

X-ray reflection and the electron density profile at liquid metal surfaces

The angular dependence of the reflection coefficient of X-rays from a planar liquid metal surface is shown to be sensitive to the thickness of the electron density profile in the surface region.     

Inverse-scattering theory and the density perturbations from inflation

We show how to use inverse-scattering theory as the basis for the inflationary reconstruction program, the goal of which is to gain information about the physics which drives inflation. Inverse-scattering theory provides an effective and well-motivated procedure, having a sound mathematical basis and being of sufficient generality that it can be considered the foundation for a nonparametric reconstruction program. We show how simple properties of the power spectrum translate directly into statements about the evolution of the background geometry during inflation.     

Evolution of density perturbations in a realistic universe

Prompted by the recent more precise determination of the basic cosmological parameters and growing evidence that the matter-energy content of the universe is now dominated by dark energy and dark matter we present the general solution of the equation that describes the evolution of density perturbations in the linear approximation. It turns out that as in the standard CDM model the density perturbations grow very slowly during the radiation dominated epoch and their amplitude increases by a factor of about 4000 in the matter and later dark energy dominated epoch of expansion of the universe.     

改善ITER 弹丸注入芯部加料的研究

研究了五种不同组合的固态氢同位素靶丸H₂、HD、D₂、DT 和T₂ 在聚变等离子体中的消融率。结果表明, 燃料靶丸的同位素效应, 可导致更深的靶丸消融物质沉积。在同样的本底等离子体条件和弹丸初始参数下, 注入氚丸比氢丸的穿透深度增加约40%。适度减轻一些ITER 的加料困难。进一步的研究表明从中平面高场侧注入靶丸对芯部加料有显著改善。考虑托卡马克非均匀磁场的影响, 被电离的消融云内的垂直漂移电流产生极化, 引起带电消融物沿大半径方向朝外漂移。数值模拟计算表明, 只要用初始速度为每秒几百米的低速弹丸, 便能使靶丸的消融物质沉积到ITER 等离子体中心。     

Investigations of H-mode plasmas triggered directly by pellet injection in the DIII-D tokamak

The transition from low-confinement (L-mode) to high-confinement (H-mode) plasmas has been directly produced by injecting frozen deuterium pellets in the DIII-D tokamak. H-mode transitions were produced at edge electron and ion temperatures below the L-mode values. This implies that a critical edge temperature is not necessary for H-mode transitions. The experimentally determined edge plasma parameters were well below those predicted by several theories of the H-mode transition to trigger the H-mode, indicating a need for revision of these theories.     

Height and density correlations at liquid surfaces; application to X-ray scattering

We calculate height-height correlation functions, near-surface density-density correlation functions and the corresponding frequency integrated spectra for a heat conducting viscous fluid. We calculate scattering cross-sections for the static and dynamic X-ray scattering experiments recently developed to investigate the nanometer-scale structure and fluctuations of liquid interfaces. We show that the density-density correlations make an important contribution to the scattering, even using evanescent waves, and that they are strongly affected by the surface. We also discuss the implications for X-ray photon correlation spectroscopy and X-ray inelastic scattering. Received 12 October 2001 Published online 6 June 2002     

Boundary effects in local inflation and spectrum of density perturbations

We observe that when a local patch in a radiation filled Robertson–Walker universe inflates by some reason, outside perturbations can enter into the inflating region. Generally, the physical wavelengths of these perturbations become larger than the Hubble radius as they cross into the inflating space and their amplitudes freeze out immediately. It turns out that the corresponding power spectrum is not scale invariant. Although these perturbations cannot reach out to a distance inner observer shielded by a de Sitter horizon, they still indicate a curious boundary effect in local inflationary scenarios.     

Some calibrated surfaces in manifolds with density

Hyperplanes, hyperspheres and hypercylinders in Rⁿ${\mathbb{R}}^n$ with suitable densities are proved to be weighted area-minimizing by a calibration argument.     

HL-2A充气弹丸注入初步实验结果

介绍了充气夹心弹丸的基本结构、制作工艺和充气弹丸注入器的基本构成以及在HL-2A等离子体中注入的初步实验结果。实验中采用以聚苯乙烯为主的空心微球为载体,直径～0.76mm,壳体厚度～20μm,充满～1.5MPa的氘气的充气弹丸。实验结果表明,充气弹丸注入速度～200m·s^-1,注入深度～12cm,加料效率～60%。     

X波段五腔渡越管振荡器的理论与实验研究

提出了一种新结构的X波段五腔渡越管振荡器，进行了理论和实验研究。根据场分布进行了一维非线性分析，结果表明该结构可以产生高功率微波，并判断了工作模式，为TM01模的3π/5模。采用粒子模拟验证了一维非线性分析的结论，并优化设计出五腔渡越管振荡器,优化结果为:输出功率约1 GW， 工作频率9.3 GHz，束波转换效率约22%。实验中，通过参数调节，得到频率约9.25 GHz，峰值功率约780 MW，脉宽（半高宽）21 ns的输出微波，束波转换效率约为16%。实验结果与模拟结果基本符合。