INFLUENCE OF C+-IMPLANTATION DOSE ON BLUE EMISSION AND MICROSTRUCTURES OF Si-BASED POROUS β-SIC

Crystal Si were implanted with different doses of C⁺ from 10¹¹ to 10¹⁷ cm^-2 at an energy of 50 keV. β-SiC precipitates were formed by thermal annealing at 1050 ℃ for 1 h and porous structures were prepared by electrochemical anodization. Under the excitation of ultraviolet, the samples, with C⁺ dose ≥10¹⁵ cm^-2 have intense blue emission which is stronger than the photoluminescence (PL) intensity of reference porous silicon (PS), and increases as C⁺ dose increases; the samples with C⁺ dose ≤10¹⁴ cm^-2 show similar PL spectra to those of PS. The blue peak intensity in PL spectra is correlated with the TO phonon absorption strength of β-SiC in infrared absorption spectra. The transmission electron microscopy study shows that the blue peak is also correlated with the microstructures. Because porous β-SiC is nanometer in size, it is suggested that the quantum confinement effect be responsible for the blue light emission.     

INFLUENCE OF LOW FREQUENCY NOISE AND ITS CONTROL

In this paper,we will illustrate the importance to study the influence of low frequency noise.We havesuccessfully controlled the noise from a blower inlet in factory in Beijing .After analusing the noise reductionmeasures,we have proposed a theory to use the effective stiffness S_e=S_0(ω/ω_0)/instead of the usual one,thetheory accords well with the experiment.Finally,we have recommended some criteria for judging lowfrequency noise interference on the basis of our surveys.     

INFLUENCE OF Pb ON THE STRUCTURAL PROPERTIES OF 2212 SINGLE CRYSTALS IN Bi-Sr-Ca-Cu-O SYSTEM

The effect of Pb on the structural properties is studied in PbxBi2Sr2CaCu2Oy single crystals by electron diffraction and EDX elemental analysis. Results show: a/b increases with increasing Pb content, and the structural modulation changes following 4,7b-mixed (4. 7b, 8. 556)-disappeared. There is a phase transition happened at Pb content about 10% (Elemental percentage calculation only contains four elements of Bi, Sr, Ca, Pb. The content is in atom percentage. ) A new phase which has 2a and 1. 5b superstructure is observed in high Pb concentration region.     

REFLECTION OF SOUND PULSE BY PLANE INTERFACE BETWEEN AIR AND POROUS MEDIUM

This paper presents a theoretical analysis of the reflection of a sound pulse by the plane interfacebetween air and ideal porous medium.A general expression of impulse response for a pulsed pointsource is derived.The detailed analysis is presented for three special cases:1)source and receiverlocated on a line perpendicular to the interface,semi-infinite media;2)a layer of porous medium;3)semi-infinite media,grazing incidence.In the second case,the problem is solved by consideringthe multi-reflections in the layer of porous medium.Experimental results are compared with the-oretical calculations for a kind of porous material.     

EFFECT OF OXYGEN CONTENT ON STABILITY AND RESISTIVITY OF NdCaCuO SYSTEM

对样品Ｎｄ２－ｘＣａｘＣｕＯ４＋δ进行了Ｘ－射线衍射、热重分析、原位电导和氧含量的测定和分析，发现样品的电导对氧含量的变化非常敏感，随着氧含量的减少，电阻率大大下降，并且电阻率在低温表现的半导体行为减弱．Ｃａ掺杂不明显的改变体系的载流子浓度，但使样品Ｎｄ２－ｘＣａｘＣｕＯ４＋δ更容易失氧．真空中退火的样品在空气中不稳定且易潮解．     

CLUSTER AND PRINCIPAL COMPONENT ANALYSIS OF THE SOLVENT EFFECTS ON THE C˭O STRETCHING FREQUENCY OF ACETOPHENONE

The solvatochromic shift of the C?O stretching frequency of acetophenone is studied by cluster (CA) and principal component analysis (PCA) confirming our previous results about the determining contributions to the polarity, polarizability, and electrophilicity of the medium on this effect. It is shown that the used combination of Varimax mode of PCA and multiple regression (apportioning modeling) makes it possible to obtain absolute principal component scores (APCS), which include the solvent parameters describing definite solute–solvent interactions. The adequateness of the suggested chemometric model is checked by “reverse” CA of 25 solvents as objects with respect to the APCS calculated.     

FTIR AND DSC STUDIES OF MECHANICALLY DEFORMED β-PVDF FILMS

Films of semicrystalline poly(vinylidene fluoride) (PVDF) in the β-phase were studied by Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). The main goal of this study was to improve the understanding of the structural changes that occur in β-PVDF during a mechanical deformation process. FTIR spectroscopy was used to examine the structural variations as a function of strain. DSC data allowed measurement of the melting temperatures and enthalpies of the material before and after deformation, providing information about the changes in the crystalline fraction. After the molecular vibrations were assigned to the corresponding vibrational modes, we investigated the energy and intensity variations of these vibrations at different deformations. A reorientation of the chains from perpendicular to parallel to the stress direction was observed to occur in the plastic region. During the deformation, a decrease in the degree of crystallinity of the material was observed, but the thickness of the lamellae did not change significantly.     

AMPLITUDE AND PHASE CHARACTERISTICS OF ELEMENTS CLOSELY ARRANGED ON THE CYLINDRICAL ARRAY

The theoretical calculations of the surface pressure amplitude and phase distribution are givenfor an infinitely long cylinder on which the piston elements are closely arranged.The analysis includesthe effects of sound scattering by the cylinder.A generalexpression is derived,which gives the directivityof an element and phase distributions on a circumference of the cylinder for various frequencies.The theoretical results by and large coincide with the measurements.Using the theoretical formulae inthis paper we can provide correct compensations of delay time or amplitude and phase weightingdesired for beam forming in the array design.     

EFFECTS OF HEAT TREATMENT ON STRUCTURE AND PROPERTIES OF ULTRAFINE K—Co—Mo CATTALYSTS

Co-Mo ultrafine particles were prepared by sol-gel method with citric acid as a complexant.The obtained dried gel was calcined in air and argon atmospheres,respectively.After promoting by K2CO3 and sulifiding,the two catalysts were single CoMoO4 crystallites with average size of 60nm.For the sample treated in argon,the main species in the sample were CoMoO3,besides,some Co-MoO4 existed,and the average size was about 20nm.These results indicated that the decomposition of citric acid reduced the CoMoO4 species and decreased the particle size remarkalby.BET measurements showed that,trating the dried gel in argon,the obtained Co-Mo particle and corresxponding sulifded sample possessed a larger surface area.For the sulfided catalysts,MoS2 and EXAFS results indicated that the sulfided sample whose precursor treated in argon possessed smaller average size.The catalytic activity measurement showed that the decrease of the particle sizes resulted in better properties for mixed alcohol synthesis.     

多孔硅蓝光发射与发光机制

在制备出光致发光能量为２．７ｅＶ的发射蓝光多孔硅的基础上对它进行了较系统的研究：测量了它的光致发光时间分辨光谱，用傅里叶交换红外光谱分析了其表面吸附原子的局域振动模，研究了γ射线辐照对其发光的影响，并与发红、黄光的多孔硅作了对比，通过空气中长期存放、激光和紫外线照射的方法，研究了光致发光峰能量为２．７ｅＶ的多孔硅发光稳定性．我们及其它文献中报道的多孔硅蓝光发射的实验结果与量子限制模型矛盾，但能用量子限制／发光中心模型解释．我们认为多孔硅的２．７ｅＶ发光是多孔硅中包裹纳米硅的ＳｉＯ_x层中某种特征发光中心引起的． 关键词：     

激光辅助阳极化制备多孔硅的蓝光发射与红外研究

发现由n型单晶硅光照辅助阳极化制备的多孔硅在经过较长时间室温空气中放置氧化后，部分样品出现了蓝色光致荧光.荧光及红外透射、反射测量表明，在较强的氩离子488nm激光照射下制备的样品，经放置氧化后形成氧化层的组织较好，即氧化层中的应力较小、非晶程度相对较低、Si-O-Si的网络结构比较完整.而这样的氧化层是有利于多孔硅光致荧光中的蓝光发射的. 关键词：     

蓝光发射和红光发射多孔硅的XPS分析

绿色发光多孔硅在空气中经两种不同的氧化处理分别得到红色发光和蓝色发光.X射线光电子能谱分析显示红色发光多孔硅中含有一定比例的Si、SiOx(x=1～2)以及少量的氟化物;蓝色发光多孔硅的主要成份是SiO2及少量的氟化物.红处透射谱显示蓝光发射多孔硅几乎只存在Si-O-Si峰,而红光发射多孔硅除主要有Si-O-Si峰外,还有明显的SiHx峰.分析表明多孔硅中的蓝光发射来源于SiO2中的缺陷中心.     

INFLUENCE OF HIGH PRESSURE ON EMISSION SPECTRA AND CRYSTAL FIELD STRENGTH FOR Eu3+ IN GdOBr

The emission spectra of the Eu³⁺ion in GdOBr∶Eu³⁺ were measured in the range of pressure from 0 GPa to 12.4 GPa. The energy level schemes establis hed from the spectra show that the splittings of the ⁷F₁,⁷F₃ and ⁵D₁ multiplets decrease obviously with increasing pressure. The crystal-field parameters B^k_q and the crystal-field strength parameter S versusB^k_q were determined at different pressures. With pressurization S reduces and theJ-mixings of the state functions for the Eu³⁺ ion decrease, which is in agreement with the decrease of the multiplet splittings. This shows that for Eu³⁺ in REOX∶Eu³⁺ the diminution of the crystal-field strength with pressure, the authenticity of which is under suspicion for several years, is certain.     

非平衡态下高温超导体的光场致发射

外加电场的作用下高温超导体材料体内电子平衡态的化学势偏移导致出现非平衡状态，这种非平衡状态将影响高温超导体光场致发射的性质。本对高温超导体的光场致发射受非平衡态的影响进行了研究。     

水含量对溶胶-凝胶SiO2增透膜结构和性能的影响

利用正硅酸乙脂(TEOS)的碱催化,溶胶-凝胶法制备多孔SiO₂增透膜.较详细地研究了工艺参量H₂O/TEOS摩尔比对薄膜结构和性能的影响.结果表明,随H₂O/TEOS摩尔比的增大,薄膜厚度、折射率和致密度减小;而薄膜透射率增大.     

燃煤过程中多环芳烃污染物生成排放的影响因子研究

区分出影响燃煤过程中多环芳烃有机污染物生成排放的外因条件和内在因素。外因条件包括：锅炉燃烧温度及排烟温度;内在因素包括：炉前煤显微煤岩组成、挥发份及发热量。研究结果为煤燃烧有机污染控制提供了重要的基础信息和理论依据。     

EFFECTIVE POTENTIAL OF λφ41+3 AT ZERO AND FINITE TEMPERATURES

The effective potential of $\lambda$$\varphi$⁴₁₊₃ model with both signs of parameter m² is evaluated at T=0 by means of a simple but effective method for regularization and renormalization. Then at T≠0, the effective potential is evaluated in imaginary time Green function approach, using the Plana formula. A critical temperature for restoration of symmetry breaking in the standard model of particle physics is estimated to be T_c≌510 GeV.     

煤中氯对多环芳烃生成的影响研究

本文在管式炉上研究了煤中氯对多环芳烃生成的影响,测定了煤中氯含量不同时多环芳烃生成量的变化,并分析了在不同气氛下不同含氯量的煤燃烧时多环芳烃与二(?)英生成的相互关系.实验结果表明,在空气中燃烧及氮气气氛热解条件下,随着氯含量的增加,多环芳烃呈减少趋势;氯代反应是导致多环芳烃生成量减少的一个主要原因.     

激光对双原子分子自发辐射的影响

在偶极近似下，研究了激光场中双原子分子的修饰态（ｄｒｅｓｓｅｄ ｓｔａｔｅ），讨论了修饰态之间的自发辐射；与没有激光时相应过程比较，结果表明激光影响下荧光呈多重结构。