内爆芯部温度空间分布计算

利用空间分划的平衡辐射输运方程,结合Multi1D辐射流体程序计算了辐射驱动内爆芯部的X光发射空间分布,计算结果表明:高能X光的发射区域随X光子能量的增大而减小,低能X光的发射区域随X光子能量的减小而减小。考虑芯部中间区域和芯部边缘区域物质的不透明度,利用遗传算法计算了芯部的温度空间分布,并与模拟结果作了比较,二者的不确定度小于4%。     

On the consistency of the postulates of special relativity

The special theory of relativity is based on two postulates: (I) All inertial frames are equivalent for the performance of physical experiments; and (II) the velocity of light is a universal constant. It is shown that if postulate I is true, then postulate II is not true, and if postulate II is true, then postulate I is not true. Further, it is shown that the only possible velocity consistent with postulate I follows the rule that the velocity of light with respect to the observer is equal to the velocity of light with respect to the source plus the velocity of the source with respect to the observer.     

聚对苯二甲酸乙二酯的拉曼光谱特性

为了研究聚对苯二甲酸乙二酯(PET)分子拉曼振动模式的特性,采用拉曼光谱法对PET纤维的拉曼光谱特性进行研究,并对PET纤维分别进行酸、碱、盐处理,获得酸、碱、盐处理前后纤维的拉曼光谱,分析与比较了处理前后拉曼光谱的特性;同时,采用原子力显微镜对其形貌结构进行观察。结果表明,在200～1 750 cm-1范围,NaOH处理的PET纤维的拉曼光谱强度高于未经处理的PET纤维,当拉曼频移大于1 750 cm-1时,经碱处理的PET拉曼峰强度低于未经处理的PET拉曼峰强度,且荧光背景减弱,H₂SO₄处理的PET纤维强度显著低于未经处理的PET纤维,CuSO₄处理的PET纤维强度较未经处理的PET纤维的强度明显增高。原子力显微镜测结果表明,碱和PET纤维分子的相互作用使化学键断裂,分子结构发生改变,经NaOH处理后的PET纤维表面较未经处理的PET纤维表面更为粗糙,H₂SO₄处理的PET表面相对未经处理的PET纤维表面粗糙度降低,经CuSO₄处理的PET纤维表面比未经处理的PET纤维粗糙度增加。PET纤维的拉曼光谱与原子力显微镜结果相一致,表明拉曼光谱与原子力显微镜的结合有望成为高聚物物性的表征技术。     

Temperature dependence of thermodynamic properties of a polarizable potential model of water

The temperature dependence of several thermodynamic properties of water is determined at atmospheric pressure by a set of computer simulations with a polarizable potential model. It is found that the maximum of the density occurs at the correct temperature, but the decrease in density with increasing temperature is more rapid than expected for real water. Consequently, the temperature dependence of other quantities, especially that of the thermal expansion coefficient, is reproduced with some inaccuracies. The model, however, turns out to be a definitive improvement over similar non-polarizable ones, for which the density maximum is either missing or found to be shifted considerably with temperature.     

压电式光纤相位调制器相移系数测试

介绍了压电式光纤相位调制器的相移系数理论公式,提出了基于杨氏双缝干涉原理的相移系数测量方法。对测量方法的可行性进行分析,通过实验对测量方法进行了验证。实际研制了一个基于压电陶瓷环的光纤相位调制器件,实验测得的相移系数与理论分析结果基本一致。利用研制的压电式光纤相位调制器实现了两路准直光束之间的相位锁定,在远场实现了相干合成,干涉条纹可见度从3%提升至43%。     

Determination of interferometer phase distributions by use of wavelets

A new technique for directly extracting phase gradients from two-dimensional (2-D) interferometer fringe data is presented. One finds the gradients by tracking the maximum modulus of the continuous wavelet transform of the fringe data and the phase distribution that is obtained, with a small error, by integration. Problems associated with phase unwrapping are thereby avoided. The technique is compared with standard methods, and excellent agreement is found. In common with Fourier-transform methods, the technique is capable of extracting the full 2-D phase distribution from a single image.     

The effect of flow on the piston problem of acoustics

A compressible fluid, bounded on one side by an infinite plane, flows with constant subsonic speed U parallel to the plane, and acoustic disturbances are caused by a small amplitude vibration of a circular piston set in the plane. The effect of the mean flow on this classical radiation problem is investigated and the distant field is expressed in elementary form. For the compact piston, whose radius is small compared with a wavelength, it is confirmed (in agreement with earlier work) that the distant field is not simply that of a point source with strength equal to the displaced volume flux since the piston has an additional blockage effect on the mean flow. The total excess energy flow is calculated for the compact piston with any subsonic mean flow (and also for the non-compact piston with low Mach number mean flow) and is compared with that for the complementary problem of a moving piston in a quiescent fluid. Since this is the previous problem referred to a reference frame that moves with the mean flow, the pressure and velocity fluctuations are as before, but the energy balance is different since the drag force on the piston does work in the latter case.     

Effect of planar defects on the stability of the Bragg glass phase of type-II superconductors

It is shown that the Bragg glass phase can become unstable with respect to planar crystal defects as twin or grain boundaries. A single defect plane that is oriented parallel to the magnetic field as well as to one of the main axis of the Abrikosov flux line lattice is always relevant, whereas we argue that a plane with higher Miller index is irrelevant, even at large defect potentials. A finite density of parallel defects with random separations can be relevant even for larger Miller indices. Defects that are aligned with the applied field restore locally the flux density oscillations which decay algebraically with distance from the defect. The current-voltage relation is changed to lnV(J) approximately -J(-1). The theory exhibits striking similarities to the physics of Luttinger liquids with impurities.     

大参数周期信号随机共振解析

通过调节双稳系统参数实现大参数频率范围内周期信号的随机共振, 在工程上具有重要意义. 推导了双稳系统参数的归一化变换, 利用归一化变换原理对大参数周期信号的随机共振进行了数值仿真, 阐明该原理适用于任意频率周期信号. 对大参数随机共振用电路模拟进行了实验验证, 揭示了通过调节双稳系统参数可以实现大参数频率范围内的随机共振. 分析了二次采样实现大参数周期信号随机共振的机理, 通过数值仿真与参数归一化变换方法进行了比较. 仿真结果表明, 在输入信号幅度变化的情况下, 二次采样方法易出现发散现象, 而归一化变换具有更好的稳定性与适应性.     

The structure of the b-completion of space-time

Structured space, as a natural generalization of the manifold concept, is defined to be a topological space with a sheaf of real function algebras which are suitably localized and closed with respect to composition with smooth Euclidean functions. Vector fields, differential forms, linear connection and curvature are introduced on structured spaces. It is shown that structured spaces correctly model space-times with singularities. Schmidt's b-boundary of space-time is constructed in the category of structured spaces, and well known difficulties with the b-boundaries of the closed Friedman and Schwarzschild space-times are disentangled. It is argued that the b-boundary of space-time, when considered in the category of structured spaces, can serve as a good definition of classical singularities.     

Theory of frequency modulation spectroscopy of coherent dark resonances

The interaction of a three-level atom in the A configuration with a frequency-modulated (FM) field is analyzed theoretically for the first time. The two-frequency model for solving the problem of frequency modulation spectroscopy of coherent dark resonances is described and analyzed for a three-level A system. The effectiveness of the two-frequency model is demonstrated by comparing the results obtained using this model with the results of solving the exact problem of interaction of a A system with an FM field, which can be solved by the density matrix method. It is shown that the simple two-frequency model corresponds to the exact solution and is in qualitative agreement with experimental data.     

Accuracy of Determining Reverberation Parameters during Recovery of a Signal with Reverberation Distortions in the Case of Discrete Delays

We discuss the accuracy of determining reverberation parameters, which is required to recover a signal with reverberation distortions. It is shown that if the signal with distortions is digitized under conditions of the sampling theorem, then it is insufficient to determine the delay time of the retarded signal with an accuracy of the sampling interval. We present an iterative algorithm for determining the reverberation parameters with sufficient accuracy.     

活性炭超级电容器电极材料放电过程非线性特征研究

论述了活性炭超级电容器材料充放电性能的测试方法步骤和测试结果,在此基础上,通过模拟,确定放电电流随时间的变化规律.建立物理模型,用固体物理理论,从微观角度研究材料的电阻随温度的变化,进而得到活性炭超级电容器材料放电电流强度随温度和放电时间变化规律的解析式,探讨材料原子的非简谐振动对电极材料放电性能的影响.结果表明:(1)电极材料放电电流随时间的变化并不遵从将它作为线性元件处理时的按时间的负指数规律变化,而是非线性减小,减小的情况与温度有关;(2)活性炭超级电容器材料的电阻随温度升高而增大.增大情况与原子振动情况有关:将原子振动作简谐近似处理时,材料的电阻的倒数几乎与温度成反比,考虑到原子非振动后,其电阻随温度升高而增大的情况加剧,温度愈高,非简谐振动项的影响愈大;(3)本文提出的物理模型和采用的理论,能对活性炭超级电容器电极材料放电性能进行有效的研究.     

Effect of oxygen on regulation of properties of moderately boron-doped diamond films

Regulation of oxygen on properties of moderately boron-doped diamond films is fully investigated. Results show that, with adding a small amount of oxygen (oxygen-to-carbon ratio < 5.0%), the crystal quality of diamond is improved, and a suppression effect of residual nitrogen is observed. With increasing ratio of O/C from 2.5% to 20.0%, the hole concentration is firstly increased then reduced. This change of hole concentration is also explained. Moreover, the results of Hall effect measurement with temperatures from 300 K to 825 K show that, with adding a small amount of oxygen, boron and oxygen complex structures (especially B₃O and B₄O) are formed and exhibit as shallow donor in diamond, which results in increase of donor concentration. With further increase of ratio of O/C, the inhibitory behaviors of oxygen on boron leads to decrease of acceptor concentration (the optical emission spectroscopy has shown that it is decreased with ratio of O/C more than 10.0%). This work demonstrates that oxygen-doping induced increasement of the crystalline and surface quality could be restored by the co-doping with oxygen. The technique could achieve boron-doped diamond films with both high quality and acceptable hole concentration, which is applicable to electronic level of usage.     

Calculation of Electronic Structure of Zinc-Blende CdS

The linear-muffin-tin orbital method is used to study the electronic-energy-band structure of zinc-blende CdS. Incorporating the 4d states of Cd into the valence band gives substantially the main-valenceband width, and yields valenceband features in agreement with the experiment. The calculated equilibrium lattice constant is in accord with the measured result. The fundamental band gap is found to be direct at T point and the value is about 1.21 eV. The band structure calculation shows that the present results are in good agreement with experiments and other calculations.     

数值模拟二维间隙表面等离子波导传输特性

利用表面等离子激元的新颖特性,设计了二维间隙表面等离子波导.以这种结构为基础通过变形和组合形成90°直角弯曲波导、T型光功率分配器和光开光,采用时域有限差分法研究了它们的传输特性.结果表明:不同于介质光波导的弯曲损耗来自于辐射泄漏,90°直角弯曲间隙表面等离子波导的能量损耗主要来自于金属中的欧姆热损耗.在间隙达到40 nm以上后,当直行段的长度适当时,弯曲段的透射率较相同长度的直波导的透射率要大.T型光功率分配器在两输出波导的间隙宽度比达到0.6及以上时,不同于传统介质波导的分光原则,能量主要沿等效折射率较小的输出臂流出.当两输入光的相位反相时,T型光开关处于输出截止的状态,当两输入光的相位同相时,T型光开关处于输出导通的状态.所有波导间隙均小于衍射极限,实现了超衍射极限传播,可用于未来了超大规模集成光路中.     

多间隙气体开关电感

介绍了一种用于快脉冲直线变压器的低电感多间隙气体开关。专门构造了多种形式的单通道放电实验,测量了在不同形态单通道放电时的开关电感,研究发现:单通道放电时开关电感除了受到角向电流的影响,还与电弧通道引起的放电回路面积变化有关,开关电感理论计算值与单通道放电时的实测结果最接近;开关在自放电和触发时,均形成了多通道放电,电感明显降低,触发时开关电感最小约为49 nH,电极角向电流的影响可以忽略。     

磁场和耦合强度对极化子有效质量和平均声子数的影响

应用线性组合算符和幺正变换方法,研究磁场和耦合强度对极化子有效质量和平均声子数的影响.数值计算表明:极化子的有效质量随耦合强度的增加而增加,这是由于耦合强度增加时,电子与晶格振动之间的相互作用增加所致;而磁场强度增加时,有效质量是先增加,达到一个极大值后,再逐渐减少,出现共振现象.平均声子数随耦合强度的增加而增加,当磁场强度大于共振时的磁场强度时,随磁场强度的增加而减少,反之,结论相反.     

匹配型保偏光纤自动对轴技术

The auto alignment technique is studied for the PM fiber (PMF) of matching refractive index(MRI). The polarization observation by lens effect tracing technique(POL) is introduced. Based on the POL,an auto alignment system is designed and its performance is then tested. Different light intensity distribution characteristic is found on the different observation surfaces in a series of experients. The widest range of adjustment is achieved when the observation surface corresponds to a light intensity distribution with five characteristic points. This means it is easier to focus.The five point method is presented after analysis of the curves of the five characteristic points with respect to the azimuth angle of the optical fiber.By comparison with the POL,this method is easier to be realized and has higher measurement accuracy,so it is suitable for auto alignment system.     

Reconstruction of scattering properties of rough air-dielectric boundary

The article is devoted to elaboration of the method of reconstruction of rough surface scattering properties. The object with rough surface is made of transparent dielectric material. Typically these properties are described with bi-directional scattering distribution function (BSDF). Direct measurement of such function is either impossible or very expensive. The suggested solution provides physically reasonable method for the rough surface BSDF reconstruction. The method is based on Monte-Carlo ray tracing simulation for BSDF calculation. Optimization technique is further applied to correctly reconstruct the BSDF. The results of the BSDF reconstruction together with measurement results are presented in the article as well.