与大学生谈学物理

 物理学的发展已经历了三次大的突破,并导致了三次技术革命和工业革命,大大推动了人类社会的发展。十七、十八世纪,牛顿力学的建立和热力学的发展,推动了人类社会的发展.     

光学玻璃的发展及其应用

随着光子学技术的发展，利用玻璃和光的相互作用改变光的极化态、频率、相干性和单色性，以及产生光子和探测光子的新型光功能玻璃成为光学玻璃发展的主要方向。本文针对光学玻璃及其在光学和信息技术等相关应用领域的重要性和发展作了介绍，重点阐述了非线性光学玻璃、梯度折射率光学玻璃、激光玻璃以及其他光功能玻璃的主要特性和发展状况，并对我国的光学玻璃工业发展作了回顾。     

对自由电子激光（FEL）发展的评论

分析了自由电子激光的技术特性，评估了国内外的发展现状、趋势和应用前景，对发展自由电子激光的意义，它的地位、作用和难点进行了评论，对我国自由电子激光今后的发展提出了一些建议。     

现代机构精度分配理论的发展方向和关键

本文分析、探讨了机构精度分配理论和方法的组成和发展概况及其发展方向,在此基础上指出了发展现代机构精度分配理论问题的关键及其前景。     

大气痕量气体遥感探测仪发展现状和趋势

阐述了大气痕量气体探测技术的发展历程;详细介绍了几种国外先进的大气痕量气体遥感探测仪器的设计理念、工作原理和功能、工作模式、谱段设置和主要技术指标。讨论了我国遥感用星载大气痕量气体探测仪器的发展现状,给出了两种典型探测仪器的工作模式、谱段设置和主要性能指标。指出了未来星载大气痕量气体探测仪器的发展方向是提高遥感仪器的光谱分辨率、空间分辨率、灵敏度和定标精度以及发展主动遥感技术等,意在为我国今后这一领域的发展提供借鉴。     

光子学的发展和光子产业

论述了光子学、光子技术的产生、发展和突破;阐明了光子学的定义、内涵、范畴和前沿;提出了关于第1类和第Ⅱ类光子产业的设想;予测了光子产业发展.     

空间太阳能电站发展及研究

随着国际能源危机的日益紧迫,空间太阳能电站（SPS）概念受到了世界各国的广泛关注,发展SPS,优化能源结构也成为我国解决能源需要的可靠途径。本文对SPS的起源、概念和发展历程进行了阐述,针对当前SPS典型系统模型,分析和总结了SPS的关键技术。结合我国当前的技术水平和未来科技发展的进步,对我国发展SPS提出了设想,采用先进的轻型薄膜聚光设计概念初步提出了一种新型SPS构型,并介绍了该构型的组成、功能及光路设计。该结构大大减小了系统质量,降低了运载的发射成本和发射难度,可为未来我国SPS的发展提供有益补充和借鉴。     

国防光学计量技术的发展与展望北大核心CSCD

随着光学理论的发展和科技的进步,光学技术得到了迅速发展,对光学计量技术提出了新的要求和挑战。针对光学计量在国防军事中的重要性,分析了我国装备保障的发展对国防光学计量的新要求,介绍了国防科技工业光学一级计量站在光学成像和光辐射基础物理量计量、武器光电装备综合参数计量保障、光学前沿技术计量以及军用光电测试仪器研发方面的发展现状,提出了国防光学计量面临的主要问题及未来的发展方向。     

干涉成像光谱仪技术的新发展

综述了成像光谱仪的发展过程以及空间调制干涉成像光谱仪技术的新原理、新技术、新发展。对干涉成像光谱技术的原理进行了论述 ,分析了Sagnac型和偏振型干涉成像光谱仪的分光机理和成像原理。提出了未来光谱仪技术的发展方向。     

纤维光学的新进展

本文回顾了纤维光学的发展,并对近十多年来的发展作了评述。指出,低消耗光学纤维和梯度折射率透镜的出现和发展,光学纤维传感器的广泛应用,塑料光纤和红外光纤的迅速发展使纤维光学发展到一个新阶段,促进了通信技术、应用光学技术、检验技术发生重大变革。本文还对纤维光学今后的发展进行了讨论。     

Sound scattering from partially water-filled elastic spherical shell with an internal elastic plate

According to the equation of motion in the elastic medium and integral equation of target scattering, the sound scattering from the partially water-filled elastic spherical shells with and without an inner plate is studied using the finite element and boundary element method, and the scattering normalized form functions of the shell filled with different volume of water are computed and the mechanism of resonance scattering is analyzed. The results show that the resonance of the shell with partially water-filled and without the plate is mainly related to the volume of water, and the resonance is produced by inner water and the spherical shell. The resonance characteristics of partially water-filled elastic shell with the plate are similar to that of empty structured elastic spherical shell, and the sound field in inner water is weaker which indicates the main resonance characteristics are decided by spherical shell and the plate. In addition, the scattering characteristics of spherical shell with plate and one side full water-filled are greatly different from the partially water-filled ones.     

Power ultrasound in the meat industry (freezing,cooking and fermentation): Mechanisms,advances and challenges

High intensity ultrasound (HIUS) has a wide range of applications in different sectors of food processing. It is a promising and emerging technology demonstrating the potential to promote food processes without or at least damage to the quality of products. Among the processes of the meat industry, freezing, thawing, cooking and fermentation are very sensitive and important, because they have significant effects on product quality and are also very energy and time consuming. This review paper provides an interpretation of high intensity ultrasound (HIUS) applications, a summary of recent outstanding published research and an overview of the freezing/thawing, cooking/frying and fermentation processes in meat and its products assisted by HIUS. The effects, benefits and drawbacks as well as the challenges ahead in the commercialization of this technology in the meat industry are studied. The research results confirmed that the use of HIUS in the meat freezing/thawing, cooking/frying and fermentation in combination with the corresponding processing methods demonstrates a great potential to promote the process, improve the general quality of the final product and reduce the time and energy required. However, many issues remain that require further research to address these challenges. These challenges and subsequent research that is useful for developing and increasing the efficiency of this technology have been reviewed. After the literature review, it is concluded that HIUS may be a useful technology for meat processing because of its significant effects on the quality factors and related process variables that leads to the preservation of the initial nutritional and sensory properties of meat and its products. Of course, research must be continued to eliminate the disadvantages or minimize the undesirable effects of this technology on the final product and to remove barriers to commercialization and optimization of this method.     

Experimental study on SC RF cavities by using China large grain niobium for ILC

Large grain niobium has the potential of simplifying the production sequence and consequently reducing the cost of the superconducting RF cavities for ILC.To investigate the feasibility of fabrication and the possibility to achieve high gradient by large grain cavities,two 1.3 GHz cavities were made of China large grain niobium and a series of vertical tests were carried out following several different surfaces treatment procedures.Two cavities have both reached the high gradient of more than 43 MV/m repeatedly and the maximum accelerating field of 47.9 MV/m has been achieved by China large grain niobium.This paper introduces the features of the fabrication and surface treatments on the large grain cavities and presents the preliminary results of the research.     

Ultrasonic evaluation of the physical and mechanical properties of granites

Masonry is the oldest building material that survived until today, being used all over the world and being present in the most impressive historical structures as an evidence of spirit of enterprise of ancient cultures. Conservation, rehabilitation and strengthening of the built heritage and protection of human lives are clear demands of modern societies. In this process, the use of nondestructive methods has become much common in the diagnosis of structural integrity of masonry elements.With respect to the evaluation of the stone condition, the ultrasonic pulse velocity is a simple and economical tool. Thus, the central issue of the present paper concerns the evaluation of the suitability of the ultrasonic pulse velocity method for describing the mechanical and physical properties of granites (range size between 0.1-4.0 mm and 0.3-16.5 mm) and for the assessment of its weathering state. The mechanical properties encompass the compressive and tensile strength and modulus of elasticity, and the physical properties include the density and porosity. For this purpose, measurements of the longitudinal ultrasonic pulse velocity with distinct natural frequency of the transducers were carried out on specimens with different size and shape. A discussion of the factors that induce variations on the ultrasonic velocity is also provided.Additionally, statistical correlations between ultrasonic pulse velocity and mechanical and physical properties of granites are presented and discussed. The major output of the work is the confirmation that ultrasonic pulse velocity can be effectively used as a simple and economical nondestructive method for a preliminary prediction of mechanical and physical properties, as well as a tool for the assessment of the weathering changes of granites that occur during the serviceable life. This is of much interest due to the usual difficulties in removing specimens for mechanical characterization.     

高光谱成像技术在果蔬品质与安全无损检测中的原理及应用

水果和蔬菜的品质与安全是消费者最为关心的问题。传统的化学检测方法是一种费时费力的破坏性检测技术。随着成像和光谱技术的快速发展,高光谱成像技术已经广泛应用于农产品品质与安全的快速无损检测中。高光谱成像技术融合了传统的成像和光谱技术的优点,可以同时获取被检测物体的空间信息和光谱信息,因此该技术既可以像检测物体的外部品质,又可以像光谱技术一样检测物体的内部品质和品质安全。目前,已经有大量的基于高光谱成像技术检测水果和蔬菜品质与安全的研究性论文发表,为了深入了解高光谱成像技术的检测原理并跟踪国内外最新的研究进展,综述了高光谱成像技术在水果和蔬菜外部品质、内部品质和品质安全检测中的原理、发展和应用。另外,还简要介绍和讨论了高光谱成像系统的构成、常用的数据分析方法、发展趋势及面临的挑战。     

Hydrogen for novel materials and devices

We start by recalling some of the properties of hydrogen and present a summary of the phenomena caused by the reversible hydrogen sorption by metals and various forms of condensed carbon, at the surface and into the bulk, using molecular hydrogen gas, hydrogen plasma and electrochemically sorbed hydrogen. We then describe the use of hydrogen to modify the surface and bulk properties of various materials with a focus on applications and devices: electronic and optic phase transitions of thin films and related energy devices, surface polishing and cleaning, decrepitation and amorphization of intermetallics, growth of carbon nanostructures and electron emission from diamond-like and graphitic carbon, longrange perturbation of the electron distribution of graphitic structures by hydrogen defects, and the consequences for potential nanoelectronics. Received: 8 November 2000 / Accepted: 20 November 2000 / Published online: 9 February 2001     

橄榄油的聚集荧光猝灭及吸收光谱特性的研究

素有“液体黄金”之称的橄榄油已成为健康食用油的代名词,不仅身价陡增,而且在非产地市场也已成为一种畅销油。在橄榄油检测技术中光谱法与其他技术相比具有快速、无损、无样品处理等优势而备受关注,而不同的光谱检测方法在检测的物质成分上各有侧重,例如红外光谱法侧重于脂肪酸含量的检测、拉曼光谱法侧重于分子的检测、荧光光谱法侧重于光敏物质的检测以及吸收光谱法侧重于光敏物质和不饱和脂肪酸的检测等。荧光及吸收光谱对光敏物质反应极其灵敏,而橄榄油富含叶绿素等光敏物质,因此荧光及吸收光谱成为一种鉴别橄榄油的有效技术手段。叶绿素是一种含有环卟啉结构的有机分子,该类分子结构具有吸光特性,且不同的叶绿素吸收光谱各异,其中绿色植物的叶绿素a含量最多。为深入研究叶绿素的吸收光谱及荧光特性在橄榄油鉴别中的应用,将特级初榨橄榄油中掺入不同比例的玉米油,已达到间接调控橄榄油中叶绿素含量的目的,测量不同掺伪比例橄榄油的荧光及吸收光谱并研究与叶绿素浓度的相关性,以此来研究叶绿素浓度与掺伪量对橄榄油吸收光谱及荧光特性的影响。取10份同批次的特级初榨橄榄油,将其中9份按照等比例稀释,并对10份样品按照掺伪量依次排序;依次采集这10份样品的荧光及吸收光谱,比较叶绿素浓度与掺伪量的相关性及对这两种光谱技术在橄榄油鉴别中的影响。随着叶绿素浓度的上升,荧光强度由弱变强,并在某一时刻后会出现荧光强度急剧减弱的现象,即聚集荧光猝灭。这种现象主要是由于叶绿素的环卟啉分子结构引起的分子间π-π作用,使未被激发的低能分子与高能分子堆叠在一起,能量的辐射跃迁（荧光）也转变为分子间的能量转移（热能交换）。对于吸收光谱,随着叶绿素浓度的上升,吸收光谱的强度也逐渐增强。橄榄油中叶绿素吸收的能量主要去向包括镁电子辐射跃迁产生荧光以及分子间热能交换两部分,而橄榄油的吸收光谱并未出现类似于聚集荧光猝灭的现象,且吸收光谱强度与掺伪浓度间存在近似线性相关的关系。结果表明：当聚集荧光猝灭出现时,叶绿素吸收的能量仍然与浓度呈线性相关,此时高、低能分子堆叠引起的热能交换效率提高。     

不同微波条件对蛋清蛋白糖基化产物不均匀性的影响

实验研究微波对蛋清蛋白粉与葡萄糖干样混合体系的影响,构建微波条件下蛋清蛋白-葡萄糖圆柱体反应模型。通过改变微波的功率,时间和位置,采用红外热像仪、荧光、紫外,高效液相色谱等方法研究微波场中蛋清蛋白糖基化产物不均匀性。将蛋清蛋白粉末与葡萄糖等质量混合,手工震荡和研钵充分研磨后在平皿表面铺一薄层粉末,放置于微波炉中心反应。将反应后的样品按左、中、右分成三个规则区域均匀采样。热像图表明微波功率越高,样品表面温度越高。凝胶电泳图表明240 W微波加热30 min样品边缘已经发生了反应,而且样品中间部分几乎还未反应;自由氨基含量测定表明高功率长时间微波作用才会观测到明显糖基化反应而低功率短时间条件下反应不明显,且边缘部分的样品反应总是比中间部分的样品剧烈;通过荧光光谱可知,蛋清蛋白和葡萄糖发生了反应,而样品边缘部分荧光强度降低得比样品中间部分多说明样品边缘反应更加剧烈;紫外光谱测定表明越剧烈的微波条件样品紫外吸收越多,边缘部分紫外吸收最高。液相结果也证实了这一点,糖基化样品边缘部分5-羟甲基糠醛(HMF)含量明显高于样品中间部分,且随时间和功率逐渐增加。     

火成岩中长石含量与其特征光谱间响应关系研究

长石是地表岩石最重要的造岩矿物,在地壳中的比例高达60%,几乎是所有火成岩的主要矿物成分。随着高光谱技术的发展,国内外众多学者研究主要造岩矿物含量与其特征光谱的响应关系,对遥感岩矿识别以及矿化蚀变信息提取提供了多种可能性。该研究以USGS光谱库里18个火成岩样本为基础数据,研究长石的特征光谱及其与含量之间的定量关系。通过原始光谱反射率及其变换(包括小波三层分解高频分量、小波二层分解、去包络线后光谱、去包络线后小波三层分解高频分量及去包络线后小波二层分解),研究其与长石的含量之间的相关关系,结果表明：(1)分析六种光谱反射率的变换,去包络线后小波三层分解高频分量的光谱反射率与长石含量的相关关系最好,且相关系数正负不断变化,根据相关系数极值获得长石的特征谱带为431,570,972,1 456,1 856,2 292.9和2 481 nm;(2)原始光谱反射率与长石含量的相关性曲线趋势较为平缓,而经小波分解得到的高频分量后,趋势明显,经去包络线及小波分解得到高频分量后,相关性曲线的变化趋势愈加明显,由此可见,自变量的微小变化就会引起因变量变化,当岩石中长石的含量极小时,小波分解处理能够提高模型的精度。将长石含量与特征光谱的关系量化,运用多元逐步线性回归分析以及最小二乘法建模,建立6个线性回归模型和6个最小二乘法回归模型,结果表明：(1)去包络线后的光谱比原始光谱建立的回归模型精度更高,经过小波二层分解后的低频分量建模的回归模型精度优于未进行小波分解的光谱,其中去包络线后小波二层分解低频分量建立的回归模型效果最佳。(2)多元线性回归建立的模型精度优于最小二乘法,同时筛选对因变量影响较大的自变量,972,1 456,1 856,2 292.9以及2 481 nm。因此选择去包络线后的光谱进行多元线性回归法进行分析长石含量与光谱反射率之间关系,考虑到不同的特征吸收波段对长石含量的影响因子不同,可以利用长石的特征光谱定量反演某一区域内的长石的含量,对识别矿物具有重要意义。     

某机载惯导设备原位测试仪设计

针对某机载惯导设备在外场的测试需求,设计了以PC-104为显示、控制和数据处理核心,并扩展程控数字表、多通道矩阵板,构建了原位测试仪的硬件电路。根据系统的功能要求和硬件电路特性,利用LabWindows/CVI虚拟仪器平台编制了人机接口界面和测试程序,控制硬件电路对某惯导设备的静态电阻和在线电压进行测试,并接收、分析、处理惯导原位工作时输出的实时串行数据,完成对惯导设备的静态测试和动态性能监测,实现对某机载惯导设备原位测试过程的自动化和测试结果管理的智能化,提高了测试效率和测试精度。该仪器通过改变或控制测试仪器的类别,可实现对多路信号多种性能指标的测试。应用结果表明,该测试仪具有性能稳定、操作简便、应用领域广、通用性强等特点。