ADS注入器Ⅱ热冲击损伤研究(英文)

由于束流脉冲无法控制而引起直线加速器的热冲击损伤是造成加速器无法完成聚束及偏转的主要因素,而对热冲击进行定量的热应力评估可以有效地避免RFQ、超导腔以及其他加速元件等加速器设备的损伤,这在研制强流直线加速器的过程中至关重要。本研究引用一种新颖的计算方法定量分析整个注入器的热冲击损伤并明确了三种不同材料高纯铌、无氧铜和不锈钢对应的加速器件的热冲击的特征。基于有限元方法对瞬态热应力进行分析,得出三种不同材料对应的加速器件在入射角度为90度时的温度分析结果。对于所研制的注入能量低于10 MeV的强流直线加速器来讲,得到可允许的入射时间为20μs。     

跨越三个世纪的公案——谁先发明了电话?

简单介绍了电话的发明者安东尼奥·缪西(Antonio Meucci)发明电话的经历.经验和教训都说明:科学研究与发明创造都是只有第一,没有第二的竞赛;但是对发明创造而言,创新性和实用性的结合才更有价值,而及时、有效的知识产权保护不仅是对自身价值的确立,也是一种社会责任的体现.一个个案的公正是重要的,更重要的是一个制度的公正,只有社会形成保护首创、尊重第一的氛围与制度,才能鼓励后来者不断创新,保证我们生活于其中的社会的进步.重新确立缪西的电话发明的优先权,体现的正是人类尊重创新的精神和情感及价值标准.     

中能重离子碰撞中参与者区域的粘滞系数与熵密度之比(英文)

在同位旋依赖的量子分子动力学(IQMD)和Boltzmann-Uehling-Uhlenbeck(BUU)的框架下研究了重离子碰撞过程中核物质的剪切粘滞系数与熵密度的比值。用不同的方法提取了剪切粘滞系数(η)、熵密度(s)和其他相关的物理量。随着碰撞能量的增加,粘滞系数和熵密度的比值在BUU模型中逐渐趋于一个饱和值而在IQMD模型中出现了一个极小值,认为这个局域的最小值或饱和值对应于中能重离子碰撞中发生的核物质液气相变现象。     

圆周运动公式的圆周图示记忆法

匀速圆周运动是曲线运动章节的教学重点．现行高中及中专教材均以两节的篇幅来讨论这种运动．一节是建立匀速圆周运动的概念,引入描述匀速圆周运动快慢的4个量,即周期(T)、频率(v)、角速度(ω)、线速度(v),并讨论这4个量的关系．另一节则从受力的角度讨论圆周运动的向心力及向心加速度．共涉及6个量．由于这6个量之间彼此存在一定的关系,这就使圆周运动具有较多的公式．如果学生能熟练掌握这些公式以及它们之间相互关系的规律,解题就能     

ADS注入器Ⅱ超导磁铁电源控制器的设计

针对加速器驱动次临界系统(ADS)注入器Ⅱ对超导磁铁电源系统的要求,设计了一款主要由光纤模块、数模转换器(DAC)和模数转换器(ADC)相关电路组成的高稳定度的超导磁铁电源控制器。提出了一种基于数字电位器(DCP)与现场可编程门阵列(FPGA)所组成的DAC,该DAC可以实现高稳定度的超导磁铁电源的控制,电源电流值通过该DAC给定,其电压给定输出稳定度优于2×10-5,完全满足超导磁铁电源系统5×10-5量级的稳定度要求。最后给出了系统的实际测试数据,验证了设计的合理性和使用的可靠性。     

物理所光学研究的历史和现状

光学是物理所最早设置的学科方向之一,伴随物理所的发展历史,取得过许多重要的成就.文章在回顾与光学相关的这段历史的基础上,概述了物理所人在光学领域所取得的主要学术成就及人才培养和队伍建设情况,最后简要介绍了目前开展的研究工作,浅析了进一步发展所面临的不足和对策.     

主动中子多重性法估算铀材料质量的不确定性（英文）

近年来,国际社会对核材料保护、控制和衡算日益加强。对不明材料损失量(MUF)的关注逐渐提升。铀材料质量不确定性测量在估算铀材料生产量中扮演重要角色。由于铀材料自发裂变相对较弱,主动中子多重性法被应用于估算铀材料质量。通过拟合对不同系列铀金属壳的数值模拟结果,获得了描述铀材料质量与主动中子多重性特征之间的算法和参数。得到的关系表明,可以通过分析不同重数中子多重性探测结果获得铀部件的质量。对不同探测条件下的模拟结果的定量分析,确定了探测系统设置对铀质量估算的影响,以及认知不确定性和随机不确定在估算过程中传播对质量估算的影响。对不确定度的分析获得了本文模拟采用的探测系统的最佳源强和探测时间窗设置,在此设置下,质量估算的不确定性最小。     

Hobson文科物理教材选载导读——怎样才能提高一个国家的人民的科学素质

美国阿肯色大学的退休物理学教授阿特.霍布森(Art Hobson)从上世纪70年代开始开设一门以提高学生的科学素养为目的的文科物理课程,并编写了教科书《Physics Concepts and Connections》.他的课程很受欢迎,这本书也极有特色,现在已出了第4版,在130多所美国大学中使用.由于这本书和他提倡在物理教学中联系社会问题,2006年美国物理教师协会(AAPT)授予他密立根奖(AAPT的最高奖之一).新版的中译本不久将由高等教育出版社出版.(由北京大学秦克诚、刘培森、周国荣先生翻译)这本书的主要特点是:1)强调科学的认知过程,一切知识来自实践并最终由实验检验,特别是"我们怎么知道"一栏尤见特色,反对一切迷信和伪科学;2)不用数学的概念式教学,除E=mc2外书中没有数学公式;3)教给学生最新的物理学,如对量子力学的非局域性、粒子物理学中的大统一、弦假说、超对称、希格斯场等最新概念的介绍;4)讲授物理学的社会联系,对与物理学有关的社会问题的讨论遍布全书,在介绍了有关的物理学原理之后紧接着讨论.这本书的许多内容是别的物理教材中找不到的.为了让读者先睹为快,让更多的老师们更快地了解国外文科物理教学情况,本刊从下期起将选载本书的一些有特色的章节.本期先刊登霍布森教授的《怎样才能提高一个国家的人民的科学素质》一文,作为以后选载的导读.     

自制简易圆周运动速度方向演示仪

曲线运动中物体速度的方向是时刻改变的,怎样确定做曲线运动的物体在任意时刻速度的方向呢?人教版高一物理课本"曲线运动"一章中,是让学生通过观察砂轮磨刀具时飞溅的火花,旋转雨伞时雨滴飞出等实例,从而得出:"曲线运动中质点在某一点(或某一时刻)的速度方向是曲线在该点的切线方向."但课堂教学时,不便操作,难于演示,学生得不到"眼见为实"的效果,没有身临其境的感觉.     

开缝式风力机静态失速特性的研究

本文通过数值模拟的方法,研究了三种开缝方案对风力机静态失速特性的影响,模拟结果表明,开缝式风力机静态失速特性较为平坦,风力机开缝对静态失速进行控制的方法是可行的,由下风面到上风面开缝的方案在多冲角工况下有较好的静态失速特性.开缝结构的吸气口具有堵塞效应,排气口的排气会明显干涉来流的流动,因此开缝方向和开缝口处的形状对开缝效果的影响显著.     

在NaCl和HTAB共存条件下甲基纤维素溶液凝胶化行为

利用流变仪研究了甲基纤维素(MC)溶液在NaCl、十六烷基三甲基溴化铵(HTAB)以及两者共存下MC溶液的凝胶化行为,发现其凝胶化温度随着NaCl浓度的增加而下降,随着HTAB浓度的增加而上升;但是MC/NaCl的凝胶化温度保持不变,与HTAB浓度 无关,而MC/HTAB溶液的凝胶化温度则随着NaCl浓度的增加而下降．以上的实验结果表明,在NaCl存在下,HTAB将被诱导形成胶束,因此MC/NaCl的凝胶化温度保持不变;反之,当NaCl不存在时,HTAB将优先吸附到MC上而不会在溶液中形成胶束,尽管其浓度     

夏秋两季洱海、太湖表层混合层的深度变化特征及其机理分析

湖泊表层混合层深度的变化不仅影响湖泊水生生态系统的演变, 而且影响流域的局地气候、降水量的时空格局等. 基于2008年夏秋两季洱海(高原湖泊)和太湖(平原湖泊)的气象与水温廓线观测资料, 分析探讨了两湖表层混合层深度的变化特征及其机制. 结果表明: 夏季洱海能维持持续的分层现象, 秋季有明显的日分层现象, 而在相应的两季中, 太湖仅可能存在日分层现象; 洱海表层混合层深度较同期太湖更浅; 太湖两季的表层混合层深度变化较洱海频繁, 即太湖水体混合与分层的交替过程对气象条件的响应较洱海更为迅速. 太湖这类浅水湖泊, 水深是抑制其存在稳定、持续分层的关键因素, 在合适的辐射条件下, 可形成日分层现象; 而洱海这类深度的湖泊, 净热量通量是影响其是否存在持续、稳定分层的主要因子. 该研究为进一步探讨湖泊与大气两种湍流运动的耦合机制及水生生态环境演替规律等提供了有力的参考.     

Effect of the deletion of the C region on the structure and hydration of insulin-like growth factor 1: a molecular dynamics investigation

The structure and hydration of insulin-like growth factor 1 and an inactive mutant lacking the C region have been investigated in aqueous solution by molecular dynamics simulation. The overall structures of the two polypeptide resemble those determined by NMR spectroscopy. The deletion of the C region in the wild polypeptide introduces structural stability in the mutant, leading to a better definition of the secondary structure elements. A detailed hydration analysis was performed using the radial distribution functions and energy distributions. The backbone of the mutant is in general more solvent accessible than the wild polypeptide backbone. The structural rearrangements induced in the mutant led to changes in the solvent exposition of Tyr24 and Tyr60, which are residues important for ligand—receptor complex formation. Tyr24 exhibited a similar degree of solvent exposition in both IGF-I and in the mutant; however, its hydroxyl group in the wild polypeptide is better solvated than in the mutant. Tyr60 was found to be solvent exposed in the wild protein, while in the mutant the involvement of its hydroxyl group in intramolecular hydrogen bonds led to it being buried away from the solvent.     

Spectral Properties of Single BODIPY Dyes in Polystyrene Microspheres and in Solutions

The absorption, fluorescence, fluorescence quantum yield, and photostability of five BODIPY dyes are characterized and compared as single dyes in two environments, in 40-nm polystyrene spheres and in solution. The absorption and fluorescence spectra of the dyes in spheres are similar in profile but shifted to lower energies compared to those in solution. All the dyes are highly fluorescent, with three having fluorescence quantum yields of 1.0. For three of the five dyes, the yields were the same in spheres as in solution (1.00, 1.00, and 0.73). The high concentration of these dyes in spheres does not quench their fluorescence. For two other dyes the yields dropped, from 1.00 to 0.55 in one case and 0.83 to 0.50 in another, comparing the dyes in solution versus in spheres. The photodegradation of the dyes decreases in spheres compared to in solution in all but one case. For one dye, it decreases as much as 800-fold. Dyes overlooked because of low fluorescence or stability in solution could become useful fluorescent materials in the microsphere environment.     

序列脉冲激光在不同大气模型下的热晕效应研究

考虑到大气中吸收系数随高度变化,通过内插法得到不同大气模型一定高度下大气的吸收系数,建立序列脉冲激光在地对空垂直传输的热晕模型。通过数值计算方法分析风场渡越时间内脉冲数为2时的序列脉冲在中纬度地区夏季和冬季、热带地区、近北极地区夏季和冬季5种大气模型下的热晕效应。结果表明:当光束孔径为0.25 m,初始功率为200 kW,波形为高斯状的激光束在近北极冬季传输10 km后沿横轴方向光强峰值偏移0.056 9 m,而热带光强峰值强度偏移最远为0.224 m,为近北极冬季时的4倍;脉冲激光在热带传输10 km后的靶面功率仅为15.06 kW,近北极冬季靶面功率为热带的10.5倍。热带地区的热晕效应最明显,中纬度地区次之,近北极地区最弱。激光在夏季传输要比冬季传输的热晕效应严重,而且近北极地区夏季要比中纬度地区冬季的热晕效应更严重。     

Exciton-Boson Formalism in the Theory of Laser-Excited Semiconductors and Its Application in Coherent Four-Wave-Mixing Spectroscopy

By the use of a bosonization transformation and group-theoretical arguments, the Hamiltonian of an electron–hole–photon system in a laser-excited direct two-band semiconductor is transcribed into that of an exciton–photon system with the particle spins rigorously taken into consideration. It is shown that the third-order optical nonlinearities in the spectral region below the band edge have their microscopic origin in two-exciton correlations, which are expressed in terms of the effective exciton–exciton and anharmonic exciton–photon interactions. The dependence of the interparticle interactions on the spin states of quasiparticles is behind the polarization dependence of the semiconductor nonlinear optical response. On the example of the system of heavy hole excitons in quantum wells, grown from compounds with the zinc blende type of symmetry, it is demonstrated that the effective exciton–exciton interaction in two-exciton states with nonzero total spin is repulsive, while in zero-spin states it is attractive, which may result in the biexciton formation. The derived Heisenberg equations of motion for the exciton and biexciton operators form the basis for a theoretical study of the coherent four-wave-mixing in GaAs and ZnSe quantum wells. It is readily apparent from the equations that in different polarization configurations the coherent four-wave-mixing is generated by different ingredients of two-exciton Coulomb correlations: in the co-circular configuration, it is the interexciton repulsion, in the cross-linear configuration, the formation of the biexciton and its coupling to excitons, and in the collinear configuration, both of them jointly. The obtained expressions for the time-resolved and frequency-resolved four-wave-mixing signals adequately describe the main characteristics and various details of wave mixing phenomena, including a biexciton signature in the appropriate polarization configurations. Results of the work clarify the microscopic mechanism of the polarization dependence in coherent four-wave-mixing spectroscopy in semiconductor quantum wells.     

Immunodetection of type I acidic keratins associated to periderm granules during the transition of cornification from embryonic to definitive chick epidermis

The change in the modality of cornification from embryonic to definitive epidermis in the chick has been studied using immunocytochemistry and electron microscopy to show that the initial soft cornification based on an acidic type I alpha-keratin transits to a definitive hard cornification based on beta-proteins in the claw, scales and feathers. The first two periderm layers contain acidic keratins associated with periderm granules and participate in a mild form of cornification before shedding of the periderm. The transition from embryonic to adult cornification is best seen in the transitional layers of the claw where numerous periderm granules merge with packets or bundles of corneous beta-proteins. This process is hardly seen in scale and feathers where periderm granules remain most in the periderm or in the feather sheath. Periderm granules disappear in corneocytes generated underneath the periderm in scales or in the transitional layer in claws and are replaced by beta-proteins associated to other types of acidic alpha-keratins. This process produces a mechanically resistant corneous material underneath the softer periderm, adapted to terrestrial demand for mechanical protection in scales and in the dorsal part of the claw, the unguis. In the ventral part of the claw, the sub-unguis, scarce or no beta-proteins are accumulated resulting in a softer corneous layer. The study indicates that specific alpha-keratins form the cytoskeletal framework of definitive corneocytes in claws, scales and feathers, and that specialized corneous beta-proteins are deposited over this framework to produce epidermal layers with higher mechanical resistance.     

Thermodynamically equilibrium roton states of nanoparticles in molten and vapour phases

We show a possibility for a thermodynamically equilibrium nanocrystalline structure consisting of nanosized solid inclusions to appear in a melt just beyond the melting curve. Thermodynamic stability of the nanocrystalline structure in the melt results from the free energy lowering due to rotational motion of nanoparticles. The main contribution to the reduction of the free energy of the system is due to an increase in the rotational entropy and change in formation energy of nanocrystals, i.e. the nanocrystalline structure in the melt, like vacancies in a crystal, is an equilibrium defect structure of the melt. It is demonstrated that similar nanocrystalline structures can also appear in the vapour phase in the form of liquid nanodrops and in liquid solutions, e.g. in He II.     

ICP-AES测定云南楚雄糖尿病患者发样微量元素的研究

探讨微量元素与糖尿病间的关联性及临床意义。采用ICP-AES等离子体发射光谱仪测定了楚雄地区糖尿病患者人发中11种元素,采用2,3-二氨基萘荧光法测定发样中的硒元素。选取糖尿病患者120例,对照组35例。糖尿病组发样中常量元素Ca、Mg低于对照组,P高于对照组;除Cd、Cr、Fe外,微量元素Zn、Se、Ni、Mn、Cu等5种元素低于对照组,并有显著差异(P0.01)。糖尿病组间性别比较数据显示男性除发Ni、Mn、P外,其余元素含量均低于女性,其中发锌远低于女性。3个不同年龄段糖尿病人群的微量元素含量变化显示Fe、P2种元素随年龄增加含量增高;Mg、Cd2种元素随年龄增加含量减少;其余各元素变化情况为Fe、P元素在老年组中较高,Cu、Cd、Mg较低;Mn、Cr、Cu元素含量在中年组中较高,而Zn、Se略低;Zn、Se在青年组较高,而Mn、Cr低。城市人群发中Zn、Cd、Cu、Mg、Ca含量比农村人群高;Se元素含量二者间差别也不大,其余元素含量均低于农村人群。楚雄地区糖尿病患者发中Zn、Se、Mg、Mn4种元素水平低,楚雄地区糖尿病患者致病原因可能与地区属低Se水平和患者体内硒水平低有关。     

Application of a continued-fraction-based theory to magneto-optical intraband transition in GaAs and CdS

The quantum theory of intraband magneto-optical transition in semiconductors introduced previously in terms of continued-fraction-based power-series-expansion technique is reviewed in connection with examination of temperature- and dimensional-dependence of the width in GaAs and CdS in which piezoelectric scattering is dominant. With the same values of the piezoelectric coupling constant K and the expansion parameter the width in two-dimensions increases with temperature as in three-dimensions. Furthermore, the width becomes smaller uniformly as the dimension is reduced in the direction of static magnetic field in the quantum limit, which is physical. Therefore, the continued-fraction-based theory gives quite good interpretation of the acoustic phonon scattering in the quantum limit.