气粒混合物非灰辐射特性合并宽窄谱带K分布模型

气粒混合物辐射问题具有全场性、非灰性、耦合性等特点,准确预估高温燃气/粒子非灰辐射特性是非常重要的。本文将合并宽窄谱带K分布模础(CWNBCK)与离散坐标法(DOM)结合,开展了非灰气粒混合物辐射换热问题的模拟工作,分别验证了一维和三维情况下应用该模型的准确性,给出不同工况下的热流源项、壁面热流或辐射热流等。结果表明:该模型能够给出与SNB模型精度基本相同的结果,考虑其计算效率的提高,可以在工程实际中应用该模型计算非灰气粒混合物辐射换热。     

分布式冷热电三联供系统的单耗分析模型研究

基于"单耗分析"理论,建立了针对燃料为天然气的分布式冷、热、电三联产系统的常见运行模式下的多热源、多冷源的燃料单耗模型和成本单耗模型.利用该模型进行了案例计算,结果清楚地表明了系统各个环节燃料附加单耗的分布.通过对计算结果的分析,得出了一些有益的结论.     

基于无信息变量消除法与岭极限学习机的新型变量选择方法：以CO气体浓度反演为例

变量选择是光谱分析领域一个重要的组成部分。为了克服传统区间选择法的缺点与不足,基于无信息变量消除法和岭极限学习机提出一种新型的变量选择与评价方法。首先,利用无信息变量消除法剔除整个光谱区间中无信息的波长点;其次,为了解决传统建模方法(偏最小二乘法、BP神经网络等)存在的共线性问题,采用岭极限学习机方法建立回归模型;最后,最佳的特征光谱波长点组合利用特征选择路径图和稀疏度-误差折中曲线进行确定。CO气体的浓度反演实验结果表明：(1)利用无信息变量消除法可以有效筛选出最能表征CO气体透过光谱的特征波长点;(2)岭极限学习机方法具有快速建模、避免共线性和高精度等优点(CO气体浓度反演模型的决定系数可达0.995);(3)特征选择路径图和稀疏度-误差折中曲线可以直观地帮助用户寻找出最佳的特征波长点组合。     

Recent study of nanomaterials prepared by inert gas condensation using ultra high vacuum chamber

The ultra high vacuum chamber was developed in the Department of Nuclear Physics, University of Madras with the funding from DST, India. This UHV chamber is used to prepare nanocrystalline materials by inert gas condensation technique (IGCT). Nanocrystalline materials such as PbF₂, Mn²⁺-doped PbF₂, Sn-doped In₂O₃ (ITO), ZnO, Al₂O₃, Ag₂O, CdO, CuO, ZnSe:ZnO etc., were prepared by this technique and characterized. Results of some of these materials will be presented in this paper. In solid-state²⁰⁷Pb NMR on PbF₂ a separate signal due to the presence of grain boundary has been observed. The structural phase transition pressure during the phase transformation from the cubic phase to orthorhombic phase under high pressure shows an increase with the decrease in grain size. Presence of electronic centres in nanocrystalline PbF₂ is observed from Raman studies and the same has been confirmed by photoluminescence studies. Al₂O₃ was prepared and⁵⁶Fe ions were implanted. After implantation segregation of⁵⁶Fe ions was examined by SEM. The oxidation properties of ITO were studied by HRTEM. As against the expectation of oxide coating on individual nanograins of In-Sn alloy, ITO nanograins grew into faceted nanograins on heat treatment in air and O₂ atmosphere. The growth of ITO under O₂ atmosphere showed pentagon symmetry. The PMN was initially prepared by solid-state reaction. Further, this PMN relaxor material will be used to convert into nanocrystalline PMN by IGCT with sputtering and will be studied     

聚酰胺酸合成工艺研究

 采用超声波在线测量溶液粘度的方法，研究了合成聚酰胺酸过程中实验条件的影响，并对实验结果进行分析，由此确定了合成高分子量聚酰胺酸的最佳实验条件。研究表明：在加料次序为先加二胺后加二酐（二酐与二胺的摩尔比为1.01～1.02：1）、试剂中含水量尽可能少，反应温度0～5℃、反应时间以溶液粘度到达最大值为止的条件下，所合成的聚酰胺酸溶液粘度最大，可满足惯性约束聚变（ICF）充气腔靶端口膜的需要。     

浅谈焦炉煤气鼓风机高压变频调速控制系统的设计

本文对焦炉煤气加压控制系统进行了分析，在焦炉煤气加压机控制系统中运用变频调速技术对其进行改造，从而实现煤气加压机运转的自动调节，有效地稳定了焦炉煤气母管压力，保证了安全运行，并且达到节约能源的效果。解决了两台鼓风机并列运行，靠调节回流阀无法实现压力恒定这个始终困扰焦炉生产的难题。     

Breakdown voltage analysis of Al0.25Ga0.75N/GaN high electron mobility transistors with partial silicon doping in the AlGaN layer

In this paper,two-dimensional electron gas（2DEG） regions in AlGaN/GaN high electron mobility transistors（HEMTs） are realized by doping partial silicon into the AlGaN layer for the first time.A new electric field peak is introduced along the interface between the AlGaN and GaN buffer by the electric field modulation effect due to partial silicon positive charge.The high electric field near the gate for the complete silicon doping structure is effectively decreased,which makes the surface electric field uniform.The high electric field peak near the drain results from the potential difference between the surface and the depletion regions.Simulated breakdown curves that are the same as the test results are obtained for the first time by introducing an acceptor-like trap into the N-type GaN buffer.The proposed structure with partial silicon doping is better than the structure with complete silicon doping and conventional structures with the electric field plate near the drain.The breakdown voltage is improved from 296 V for the conventional structure to 400 V for the proposed one resulting from the uniform surface electric field.     

气源分子束外延生长的InPBi薄膜材料中的深能级中心

利用深能级瞬态谱(DLTS)研究了气源分子束外延(GSMBE)生长的InP1-xBix材料中深能级中心的性质。在未有意掺杂的InP中测量到一个多数载流子深能级中心E1,E1的能级位置为Ec-0.38 e V,俘获截面为1.87×10~(-15)cm~2。在未有意掺杂的InP0.9751Bi0.0249中测量到一个少数载流子深能级中心H1,H1的能级位置为Ev+0.31 eV,俘获截面为2.87×10~(-17)cm~2。深中心E1应该起源于本征反位缺陷PIn,深中心H1可能来源于形成的Bi原子对或者更复杂的与Bi相关的团簇。明确这些缺陷的起源对于InPBi材料在器件应用方面具有重要的意义。     

A model of melting of rare gases within bubbles of crystalline metal matrix

Abstract

On the basis of experimental results obtained in the present and some other works a model of melting of rare gas solids within bubbles formed in a crystalline metal matrix as a result of ion implantation is proposed. Rare gas solid is supposed to melt on heating at the expense of the bubble volume expansion by emission of a dislocation loop. On this basis the melting temperature can be estimated as one which is enough to provide for a pressure inside a bubble sufficient for the initiation of the dislocation loop punching. Values of melting temperatures obtained in this way are in good agreement with available experimental data.     

Etude de la restauration de l'aluminium irradié aux electrons (Etape III)

The nature of the electron bombarded aluminium electrical recovery process has been studied by combining quenches with irradiations. Measured Frenkel pair formation rates per incident electrons as well as annealing kinetics emphasize the role of impurity interstitial trapping.