由58Fe 和209Bi 熔合后的相关衰变过程得到的109号元素的证据

本文报导了合成109号元素的实验。用能量为4.95,5.05和5.15MeV/u 的~(58)Fe 束轰击~(209)Bi 靶,研究了全熔合产物衰变模式的特性。总辐照剂量为7×10~(17)粒子。所用的实验方法是:用静电场速度过滤器在飞行过程中分离向前方向成峰的反应产物,经过飞行时间装置后注入到位置灵敏固态探测器中,测量其动能,估算出质量、入射的时间和位置。以所有的出射粒子的能量和时间来记录很有限的反应产物发生级联α粒子和(或)自发裂变的继发衰变。在5.15 MeV/u 时的一个特别的衰变过程是:在5ms 和22ms 先分别发射两个α粒子,最后,在13s 后发生自发裂变。第一个α粒子的动能为11.10±0.04MeV。对各种可能的解释进行了详细的分析,例如纯属偶然的信号相关,转移反应产物的衰变和从能量上看允许的余核蒸发等。最后表明质量数为266的109号元素的同位素、即全熔合后的单中子蒸发道、从统计的观点看是最好的指定。本文同时也讨论了合成新元素的前景。     

趣谈球类运动的物理

文章集中在球类运动中球的飞行和滚动所涉及到的物理.选择了几个人们可能感兴趣的问题,如表面粗糙度和尺寸对球飞行的影响,弧线球和飘球的成因,投篮的角度和速度,斯诺克球台的库高和保龄球球道上油的作用,做了定件或半定量的讲述.文章作者认为,物理研究有助于运动水平的提高,在物理教学中也有助于激发学生的学习兴趣.     

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。     

毛细现象公式的导出

液体表面分子间的吸引力、液体表面的分子有一种使其面积缩成最小的力,或称一种抵抗表面积扩张的力,此力称“表面张力”．液体表面是指液体与空气或其他液体相接触的自由面．若不指明,即可认为相对于空气而言．表面张力的大小与接触面的物质有密切关系．此外,表面张力还与温度有关,温度越高,表面张力越小．表面张力的方向总是与液面相切,与分界线相垂直．若在液面作一长为L的直线,将液面分成两部分,这两部分之间的相互牵引力为F,即表面张力F=σL．其中σ为液体表面张力系数．单位为N/m．由于表面张力的作用,液滴表面有收缩到最小的趋势,而使液滴成近似球形的状态．     

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。     

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.