非平衡定态相图新概念及其应用——激活低压金刚石气相生长热力学

在激活的低压条件下，金刚石气相稳定生长的同时石墨会被腐蚀．这是近二三十年来国际上的一个热力学难题，甚至被认为是“热力学的悖论”．用非平衡热力学耦合理论可以给予很好的解释，并推导出非平衡定态相图的全新概念．在新型相图中金刚石在低压下是稳定相，而石墨被激活成为亚稳相．理论计算与文献报道的大量实验数据定量化地相符     

人造金刚石低压气相生长的相图计算

用非平衡热力学耦合模型计算了由CH₄/H₂，CO/H₂和乙炔火焰等气相体系生长金刚石的相图．与经典平衡热力学理论计算结果不同的是这些相图都有一个金刚石生长区存在．相图中的金刚石生长区是实现金刚石气相生长的热力学基础，它的存在体现了超平衡氢原子等激活粒子对石墨的激活和对金刚石的稳定作用．计算的相图与报道的实验结果基本相符，因而对金刚石气相生长的理论和实验研究具有重要的指导意义 关键词：     

现代热力学的完整分类系统--非平衡非耗散热力学新领域

在同一体系中同时有多个不可逆过程时，不可逆过程之间会有相互影响，原来的非自发过程有可能在其他自发过程的影响下得以进行，这种现象就称为热力学耦合或反应耦合，长期以来，经典热力学把热力学第二定律的等式作为平衡体系的充分必要条件，其中隐含了一个前提性的假定，即经典热力学的对象只限于非耦合的体系，摈弃这一隐含的前提性假定以后，热力学自身就发展成为一个现代热力学的完整学术体系，适用于任何宏观体系（包括极其复杂的生命体系），现代热力学的完整学术体系中包含了一个崭新的非平衡非耗散热力学新领域，由于该领域属于热力学第二定律的等式部分，因此可以定量计算，并得到一系列理论计算的非平衡相图，与文献上报道的激尖低压金刚石合成等的大量实验数据相符。     

非平衡定态相图新概念及其应用

在激活的低压条件下，金刚石气相稳定生长的同时石墨会被腐蚀、这是近二三十年来国际上的一个热力学难题，甚至被认为是“热力学的悖论”，用非平衡热力学耦合理论可以给予很好的解释，并推导出非平衡定态相图的全新概念，在新型相图中金刚石在低压下是稳定相，而石墨被激活成为亚稳相，理论计算与文献报道的大量实验数据定量化地相符。     

评《非平衡定态相图——人造金刚石的低压气相生长热力学》一书 (王季陶著,科学出版社出版)

《非平衡定态相图———人造金刚石的低压气相生长热力学》一书于2000年3月由科学出版社出版,这是复旦大学王季陶教授得到国家自然科学基金委员会优秀研究成果专著出版基金资助的出版物.书名中有两个关键词引人注目.其一是广为人知的“金刚石”,自古以来它以其璀璨夺目而一直是人们心目中的宝石之王;到近代人们又认识到它是具有最高硬度和弹性模量的超硬材料,但它的其他优异性能和潜在的高技术应用还远超出一般人所知的范围.另一个名词是“非平衡定态相图”,虽然大多数科技工作者都知道“相图”是怎么回事,但“非平衡定态相图”却是本书作者…     

强迫耗散系统的有序结构和系统的发展(Ⅱ)，广义能量极小值原理和系统的发展

利用大气非线性动力学证明了广义能量极小值原理，进一步从理论上证明它是同大气非平衡 态热力学最小熵产生原理在物理上是一致的.前者表明，强迫耗散动力系统的终态广义能量 达极小值；而最小熵产生原理表明，远离热力学平衡态的开放系其终态时系统内部的不可逆 过程最弱.而且，系统广义能量达极小值和系统熵产生达极小值的终态一般是一个稳定的定 态，它对应着系统的某种有序结构.也就是说它是一个“低耗高效”的有序定态.大气系统作 为自然界一个典型的物理复杂系统，其最小熵产生原理和广义能量极小值原理隐示了自然界 复杂系统的一个一 关键词： 强迫耗散系统 能量极值原理 有序结构 动力系统     

评<非平衡定态相图--人造金刚石的低压气相生长热力学>一书

<非平衡定态相图--人造金刚石的低压气相生长热力学>一书于2000年3月由科学出版社出版,这是复旦大学王季陶教授得到国家自然科学基金委员会优秀研究成果专著出版基金资助的出版物.书名中有两个关键词引人注目.其一是广为人知的"金刚石",自古以来它以其璀璨夺目而一直是人们心目中的宝石之王;到近代人们又认识到它是具有最高硬度和弹性模量的超硬材料,但它的其他优异性能和潜在的高技术应用还远超出一般人所知的范围.     

介观电化学反应的随机热力学（英文）

本文讨论了离子和电极之间发生的介观电子转移反应的随机热力学.基于反应速率常数与电极电势的关系,发现反应体系的热耗散β_q等于反应系统的动力学不可逆性减去体系的内部熵变项.尽管体系的热耗散对于电极电势存在线性依赖,由体系熵变△s以及热耗散β_q的加和定义的体系总熵变△s_t=△s+β_q仍满足传统的涨落定理     

统计物理方法在离散变量模型中的应用及推广

提出离散变量模型,并基于此模型由最大熵原理出发,展现了统计物理方法在热力学系统中的具体应用.该方法可以推广应用至由大量"个体"所构成的"总体"非物理系统中,如金融系统,社会生产系统等.文中还指出由最大熵原理得到的概率分布函数同时适用于平衡态和非平衡定态的热力学系统.     

模板对异构体选择性生长的动力学控制作用与化学气相沉积金刚石的生长机理

阐述了模板的动力学控制作用对大尺度有序结构特别是亚稳相的生长，对自由能相差很小的异构体的选择生长所具有的重要作用.汲取现有金刚石生长理论的合理思想，以模板概念为基础给出了对化学气相沉积(CVD)过程的动力学热力学综合描述：1)碳原子在碳氢化合物中的化学势高于固相碳，气相碳氢化合物的碳原子有可能落到化学势较低的固态碳的各种异构体.2)气相碳通过表面反应实现向固相碳的转化.3)表面的模板作用是控制气相碳原子转换方式的主要动力学因素，不同的表面(石墨各种取向的表面及金刚石不同取向的表面)选择了落入其上的碳原子的结构方式及能量状态.4)因此,衬底的不同区域可发生几种不同的独立的表面反应过程,这些反应对应于不同表面的生长.5）而这些表面反应的方向性及速度受表面临域热力学因素的影响，反应的方向性决定了某种晶面是生长或刻蚀，在特定的温度、压强及各种气体分压下可以实现金刚石的生长和石墨的刻蚀.6)衬底局域晶格结构及键价结构和衬底表面气相的温度、压强及各种气体分压等热力学条件共同决定了成核的临界条件.7）与外界有能量和物质交换的等离子体系统，以及气相中发生的一系列化学反应，仅起到了维持某种固相表面生长所需要的非平衡热力学条件和化学条件的作用.金刚石和石墨表面具有的模板动力学控制作用，在特定热力学条件下主导自身外延层的生长方式；异质衬底的某些局域微观结构可以作为新相生长成核的局域模板；不同材料、不同的处理方法、及不同的化学环境下的衬底具有不同的局域微观结构，从而决定了多晶薄膜的取向优势. 关键词： 模板 异构体 选择性生长 金刚石薄膜     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.