Quantum imaging of nonlocal spatial correlations induced by orbital angular momentum

Through scanned coincidence counting, we probe the quantum image produced by parametric down-conversion with a pump-beam carrying orbital angular momentum. Nonlocal spatial correlations are manifested through splitting of the coincidence spot into two.     

A kinetic study of an advanced reburning process

The possibility of a positive synergism among flue gas recirculation, staged combustion and selective non-catalytic reduction technologies to achieve N-containing emission reductions has been investigated by simulating a 320 MW industrial-scale furnace boiler. A detailed chemical kinetic scheme coupled with a simplified fluid dynamic of the system has allowed us to compare the effectiveness of ammonia and isocyanic acid in removing N-containing pollutant emitted (NPE) with hot exhausts. By keeping the same flue gas composition for both cases, the effect of temperature and the impact of different amounts of NH3 and HNCO injected in the final combustion stage has been analysed. Ammonia was the most effective reducing agent for the particular conditions examined. Due to its high reactivity, the maximum effectiveness of the NH3-promoted process occurs at 940 K and an NH3 molar ratio of about 1.25. NH2 dominates the process mainly following two paths: N2 can be produced from direct interaction between NH2 and NO or via intermediate formation of NNH. On the other hand, HNCO is less effective than ammonia, owing to the influence of the particular radical environment within the boiler. HNCO oxidation is influenced by the amine radical pool which partly contributes to N2 formation but is, at the same time, an important source of NOx in the conditions analysed.     

Nuclear correlations and the r process

We show that long-range correlations for nuclear masses have a significant effect on the synthesis of heavy elements by the r?process. As calculated by Delaroche et?al. [Phys. Rev. C 81, 014303 (2010)], these correlations suppress magic number effects associated with minor shells. This impacts the calculated abundances before the third r-process peak (at mass number A≈195), where the abundances are low and form a trough. This trough and the position of the third abundance peak are strongly affected by the masses of nuclei in the transition region between deformed and spherical. Based on different astrophysical environments, our results demonstrate that a microscopic theory of nuclear masses including correlations naturally smoothens the separation energies, thus reducing the trough and improving the agreement with observed solar system abundances.     

Experimental falsification of Leggett's nonlocal variable model

Bell's theorem guarantees that no model based on local variables can reproduce quantum correlations. Also, some models based on nonlocal variables, if subject to apparently "reasonable" constraints, may fail to reproduce quantum physics. In this Letter, we introduce a family of inequalities, which use a finite number of measurement settings, and which therefore allow testing Leggett's nonlocal model versus quantum physics. Our experimental data falsify Leggett's model and are in agreement with quantum predictions.     

Experimental observation of bias-dependent nonlocal Andreev reflection

We investigate transport through hybrid structures consisting of two normal metal leads connected via tunnel barriers to one common superconducting electrode. We find clear evidence for the occurrence of nonlocal Andreev reflection and elastic cotunneling through a superconductor when the separation of the tunnel barrier is comparable to the superconducting coherence length. The probability of the two processes is energy dependent, with elastic cotunneling dominating at low energy and nonlocal Andreev reflection at higher energies. The energy scale of the crossover is found to be the Thouless energy of the superconductor, which indicates the phase coherence of the processes. Our results are relevant for the realization of recently proposed entangler devices.     

光照强度对太阳能电池特性影响的实验研究

阐述了太阳能电池特性的相关理论,用实验方法研究了太阳能电池开路电压、短路电流、最大输出功率、最佳负载电阻及填充因子与光照强度的关系,结果表明,太阳能电池的开路电压、短路电流、最大输出功率随光照强度的增强而增大,最佳负载电阻和填充因子随光照强度的增强而减小,其中随着光照强度减弱而最佳负载电阻增大并未发现有相关的理论分析或仿真结果的报道,其他结果与太阳能电池特性相关理论一致.     

Experimental test of nonlocal realistic theories without the rotational symmetry assumption

We analyze the class of nonlocal realistic theories that was originally considered by Leggett [Found. Phys. 33, 1469 (2003)10.1023/A:1026096313729] and tested by us in a recent experiment [Nature (London) 446, 871 (2007)10.1038/nature05677]. We derive an incompatibility theorem that works for finite numbers of polarizer settings and that does not require the previously assumed rotational symmetry of the two-particle correlation functions. The experimentally measured case involves seven different measurement settings. Using polarization-entangled photon pairs, we exclude this broader class of nonlocal realistic models by experimentally violating a new Leggett-type inequality by 80 standard deviations.     

先进光源磁铁支撑基座稳定性的实验研究

基座作为磁铁支架的基础,其制作工艺以及与地面连接固定方式的不同将影响磁铁与支架的稳定性。基于先进光源对磁铁支撑系统稳定性的极高要求,开展了基座安装浇筑实验,选取工程上常用的几种混凝土施工工艺,制作统一外形尺寸的实验件,通过锤击法逐一测试其固有频率,评估其稳定性,得到二次灌浆可有效提高稳定性、环氧基灌浆料获得的稳定性优于水泥基灌浆料等结论。基于固有频率测试结果,以HEPS支撑系统为例分析了不同的基座安装方式对系统模态的影响。     

空间太阳阵二次放电的模拟实验研究

二次放电是造成空间高压大功率太阳阵功率损失的主要原因.通过地面模拟实验研究，确定 了二次放电阈值电压并监测了二次放电脉冲电流，对高压太阳阵二次放电特性及其击穿机理 进行了讨论.结果表明，高压太阳阵工作电压和电池串间电流的提高增加了高压太阳阵发生 二次放电事件的可能性；通过采用特殊的结构设计和在太阳阵电池串之间涂覆RTV胶，可以 有效抑制二次放电事件的发生. 关键词： 高压太阳阵 空间静电放电 二次放电     

Experimental study on the activation process of GaAs spin—polarized electron source

GaAs spin-polarized electron source is a new kind of electron source, where the GaAs semiconductor crystal is used as a photocathode under the irradiation of helicity light. In this paper the activation process of the GaAs spin-polarized electron source is unvestigated experimentally in detail, during which the negative electron affinity of the photo cathode should be achieved more carefully by absorbing the caesium and oxygen on the surface of the GaAs crystal under ultrahigh vacuum conditions. Besides the different activation processes, the important physical parameters are studied to achieve the optimum activation results. At the same time the stability and lifetime of the polarized electron beam are explored for future experiments. Some important experimental data have been acquired.     

Experimental reconstruction of nonlocal response of thermal nonlinear optical media

We study experimentally and theoretically the nonlocal response of a medium with thermal nonlinearity and show that despite its inherently infinite range it can be accurately characterized by a well-defined nonlocal response function. We retrieve the shape of this function and analyze its transformation with the change of boundaries.     

Experimental observation of three-color optical quantum correlations

Quantum correlations among bright pump, signal, and idler beams produced by an optical parametric oscillator, all with different frequencies, are experimentally demonstrated. We show that the degree of entanglement between signal and idler fields is improved by using information on pump fluctuations. To our knowledge this is the first observation of three-color optical quantum correlations.     

简易实验测量太阳常数

使用普通物理实验室器材测量了太阳常数.利用牛顿冷却定律以及比尔-朗伯定律进行分析处理,实验结果与通用数据误差在5%以内.本实验经过改进,还可以配合相关天体物理实验,研究太阳辐射及其剧烈活动.     

低温水平加注管路系统预冷过程实验研究

低温管路系统的预冷过程主要依靠人员的经验进行控制,对预冷过程的判定缺乏有效的量化指标。主要通过对低温加注管路系统预冷实验,对低温管路内的温度变化情况和管内的低温介质流态进行测量和分析,为准确判断低温加注管路完成预冷提供理论依据。     

Experimental study on negative laser bending process of steel foils

In this paper, laser bending experiments were carried out on the stainless foil for producing negative bending angles. BM-dominated laser parameters, such as larger ratio of beam diameter to specimen thickness and lower scanning speed, help to produce negative bending angles. However, the bending direction in BM-dominated process will be uncertain due to the influence of the specimen's initial stress state and surface conditions. For this reason, experiments on stainless foil loaded with controlled pre-stresses were carried out for producing certain negative bending angles. The effect of the pre-stress and laser parameters are investigated experimentally. The experimental results show that negative bending angles could be produced conveniently when the pre-stresses were induced by elastic pre-bending which direction away from the laser beam, and the angles increase remarkably with the pre-stresses increasing. A set of reasonable laser parameters (laser power, scanning speed and beam diameter) for good quality negative bending angles forming were gotten by analyzing the effect of each parameter respectively in the experiments.     

竖直星型翅片管结霜的实验研究

星型翅片管结霜是影响空浴式汽化器性能的一个重要因素。在不同的环境温湿度条件下,通过改变汽化介质的压力和流量,研究竖直星型翅片管的霜层生长规律,以及结霜对翅片管的传热性能的影响。研究发现,霜层的生长与环境温度,空气湿度,介质流量、压力等因素都有关系,其中空气湿度的影响尤为明显。结霜过程是个非稳态过程,霜层的生长会降低翅片管的传热性能,从而降低翅片管的出口气体温度。通过对竖直星型翅片管结霜性能的研究,对优化环境参数、发挥气化器最大性能,确定除霜方法都具有重要意义。     

Experimental study on the coalescence process of SiO2 supported colloidal Au nanoparticles

We report on an experimental study of the coalescence-driven grow process of colloidal Au nanoparticles on SiO₂ surface. Nanoparticles with 30, 50, 80, 100 nm nominal diameters on a SiO₂ substrate were deposited, from solutions, by the drop-casting method. Then, annealing processes, in the 573–1173 K temperature range and 900–3600 s time range, were performed. Using scanning electron microscopy analyses, the temporal evolution of the nanoparticles sizes has been studied. In particular, for all classes of nanoparticles, the experimental-obtained diameters distributions evidenced double-peak shapes (i. e. bimodal distributions): a first peak centered (and unchanged changing the annealing temperature and/or time) at the nominal diameter of the as-deposited nanoparticles, 〈D₀〉, and a second peak shifting at higher mean diameters, 〈D_C〉, increasing the annealing temperature and/or time. This observation suggested us a coalescence-driven growth process of a nanoparticles sub-population. As a consequence, the temporal evolution of 〈D_C〉 (for each class of nanoparticles and each annealing temperature), within the well-established particles coalescence theoretical framework, has been analyzed. In particular, by the analyses of the experimental data using relations as prescribed by the theoretical model, a characteristic size-dependent activation energy for the Au nanoparticles coalescence process has been evaluated.     

Experimental study on the aging process of the LR 115 cellulose nitrate radon detector

An experimental determination of the aging process of cellulose nitrate detector material was based on the examination of special properties of the LR 115 solid state nuclear track detectors (SSNTDs) of various ages up to 18 years. The examined relevant parameters are the bulk etching rate v_b and the track etching rate v_t. These parameters are responsible for the appearance, the size and the registration efficiency of tracks of -particles from radon gas in the detector. To find a correlation between these material parameters and the detector sensitivity an experimental calibration of indoor room and outdoor soil detector devices based on LR 115 took place at the Umweltforschungszentrum Leipzig-Halle (Germany). To avoid routine calibration work in external radon exposure facilities a correction of the age dependent calibration factors with the material parameters measured in one's own laboratory was targeted. In this study a general age dependence, however, was not found. The following statements for practical applications can be made. (i) the bulk etching rate v_b for detectors of the same batch has a depth dependence and this dependence is constant over 2 years (LR 115 September 1994). (ii) detectors of different batches older than 5 years and stored at room temperature show an odd v_b behaviour when v_b is used for describing track shapes. (iii) the calibration factor of detectors of different batches that were stored at about +4°C is constant over 5 years (LR 115 September 1994 and February 1999, Table 2).

The conclusion is that LR 115 detectors not older than 5 years and stored in a refrigerator at about +4°C should be preferred for radon measurements. Furthermore these detectors should be recalibrated every year and the microscope work of this calibrations should be performed by the same person who performs the measurements.

In addition, a phenomenon related to fundamental track formation mechanisms was found, that the time straggling of the time t_through when vertical tracks penetrate the 12 μm thick detector layer is independent of the age of the detectors and the energy of the -particle at the detector surface.