Local solutions of the Landau equation with rough,slowly decaying initial data

We consider the Cauchy problem for the spatially inhomogeneous Landau equation with soft potentials in the case of large (i.e. non-perturbative) initial data. We construct a solution for any bounded, measurable initial data with uniform polynomial decay in the velocity variable, and that satisfies a technical lower bound assumption (but can have vacuum regions). For uniqueness in this weak class, we have to make the additional assumption that the initial data is Hölder continuous. Our hypotheses are much weaker, in terms of regularity and decay, than previous large-data well-posedness results in the literature. We also derive a continuation criterion for our solutions that is, for the case of very soft potentials, an improvement over the previous state of the art.     

新型全色发光材料NaCaPO_4:Dy~(3+)制备及发光性能

釆用高温固相法制备了NaCaPO4∶Dy3+系列样品,并在紫外(UV)及真空紫外(VUV)区域研究了系列样品的发光性能.紫外激发光谱显示在350nm处有最强的激发峰,可以有效地吸收紫外光并将其转化为可见光.真空紫外激发光谱表明,NaCaPO4∶Dy3+能有效地吸收无汞荧光灯的激发源并将其转化为可见光.系列样品发光均呈现为白色,这种材料有潜力作为全色显示材料应用于发光二极管(LED)和无汞荧光灯中.     

N_2O分子C~1Ⅱ态的吸收光谱及解离动力学

通过四波混频差频的方法产生高分辨的真空紫外激光,用以测量143.6至146.9 nm范围内的射流冷却N_2O分子吸收光谱,对应于C~1Ⅱ←Ⅹ~1∑~+的吸收跃迁.谱图显示出三个分立的振动谱峰叠加在宽吸收背景上,谱峰间隔分别是521和482 cm~(-1).前人的高精度量子化学计算表明C~1Ⅱ态在N-O键长方向表现为无势垒的排斥态.而在N-N键伸缩及N_2O弯曲振动方向则表现为束缚态,因此观测到的振动谱峰被归属为激发态的Feshbach共振.通过反Fourier变换可以得到Feshbach共振对应的非稳定周期轨道的特征周期为61 fs,相应的振动频率为546 cm~(-1).鉴于这一频率与弯曲振动频率非常接近,非稳定周期轨道被认为是由C~1Ⅱ态的弯曲振动与解离运动相互作用而形成的,N-N伸缩振动没有参与形成非稳定周期轨道.由此,N_2O分子C~1Ⅱ态光激发-解离过程得以清晰地阐述.     

HL—1M装置的真空进展

总结了１９９４ 至１９９８ 年度ＨＬ－１Ｍ 装置的真空进展，包括真空壁条件、真空运行参数、放电进展、影响壁条件的主要因素及其控制指标等     

Vacuum Ultraviolet Irradiation of Polymers

The interest in incoherent sources for wavelength-selective photochemistry has increased lately, but little is still known about the behavior of polymers when exposed to far UV and vacuum UV (VUV) radiation. The same dearth of information exists regarding UV (VUV) radiation emitted by low-pressure plasmas during polymer treatment. In order to study VUV-UV effects on several polymers (polyethylene - PE, polystyrene - PS, hexatriacontane - HTC, and poly(methyl methacrylate) - PMMA), we have used the well-characterized emissions from hydrogen (broad-band emission) and hydrogen/argon mixture (near-monochromatic radiation) plasmas as light sources. During irradiation, samples were kept under vacuum or in a flow of pure oxygen at low pressure; in both cases the radiation fluxes at the sample position have been precisely determined by careful spectroscopic calibration experiments. We have employed a quartz crystal microbalance (QCM) to measure in-situ any possible mass change of the various polymers. Following irradiation, samples were analysed by ellipsometry (for thickness and refractive index), X-ray photoelectron spectroscopy (XPS, to evaluate the near-surface composition and content of various functional groups), and atomic force microscopy (AFM, for surface topography and roughness measurements).     

XH3Y（X=C,Si,Ge;Y=Cl,Br,I,D）型气相分子合成技术

ＸＨ３Ｙ（Ｘ＝Ｃ，Ｓｉ，Ｇｅ；Ｙ＝Ｃｌ，Ｂｒ，Ｉ，Ｄ）型气相分子合成技术周泽义邓珂（中国科技大学选键化学开放实验室合肥２３００２６）谢立（安徽省计量测试研究所合肥２３００２２）关键词气相分子真空合成正交表中图分类号Ｏ６２１．２５５１ＩＶＸ的Ｃ、Ｓｉ、...     

多层长渡越时间轴向绝缘堆的闪络概率分析

 对基于J.C.Martin经验公式的多层长渡越时间轴向绝缘堆的闪络概率分析方法进行了分析与总结。在对比各种类似分析方法优劣的基础上，提出了一种较为成熟的针对多层长渡越时间轴向绝缘堆的闪络概率分析方法，为类似绝缘堆结构的设计提供了理论依据。同时，对其中的不确定因素和存在的问题也进行了较为详细的分析和讨论，为闪络概率分析方法的进一步完善奠定了基础。     

真空紫外辐射对碳/环氧复合材料性能的影响

 介绍了真空紫外线的模拟和射流式真空紫外辐射模拟设备的工作原理、技术参数及特点,并利用该设备及其它分析手段对环氧树脂浇铸体(EP648)和碳/环氧复合材料(C/E648)在真空紫外线辐照作用下的出气、质量损失率、层间剪切强度和表面状态的变化进行了研究。试验结果表明：真空紫外线辐照导致材料产生明显的出气效应,质量损失率呈现先递增后趋于平缓的趋势;17 280esh辐照剂量下,EP648的质量损失是C/E648的3.4倍,C/E648的层间剪切强度与辐照前相比下降了13.3%;环氧树脂破损较重,而碳纤维表面状态基本完好,并对内部的环氧树脂起到一定的保护作用。     

Is Universe a big pattern? Comment on Newell and Venkataramani's essay

This note is motivated by the contribution of Alan Newell to this thematic issue of C. R. Mécanique honoring Pierre Coullet. The point of this comment is to show that some ideas in Newell and Venkataramani's essay are already there in the present theory of the ultimate structure of our Universe, although formulated in a completely different way. In particular, the relationship between the structure of the Universe at small scale and the nagging question of the missing mass is present in both theories, whereas a precise link between the observations and either theory is yet to be found.     

真空熔融气相色谱法测定固体中痕量氩气的研究

建立了用气相色谱法测定固体内部痕量惰性气体的新方法.有效地解决了处于低真空状态待测气样的给样问题,优化了样品气体的纯化条件.用多种基准物质绘制了不同柱长的校正曲线,证明了新方法的可靠性.