采用多量子阱器件的无线光通信差拍接收方案研究

研究一种采用光折变多量子阱器件的无线光通信自差拍接收方案。与寻常相干接收方案相比,省去了中频跟踪电子系统;与量子阱器件零拍方案相比,采用中频窄带滤波器,提高了接收端机的输出信噪比。理论上研究了自差拍相干接收方案,从其物理机制出发,结合信噪比分析,探讨了影响相干接收方案的主要因素。建立了该方案的实验系统,并开展了有意义的实验研究。理论分析及实验结果表明,该方案对激光大气传输所引起的诸多不利影响皆有一定的抑制作用,因而有可能应用于卫星地面激光通信和地面无线光通信系统。     

一维光晶格中超流Fermi气体基态性质的研究

研究了一维光晶格中超流Fermi气体基态解的性质.在平均场理论框架下,利用超流Fermi体系中原子间相互作用能与晶格势能相互平衡的条件,得到了一维光晶格中超流Fermi气体在整个BEC-BCS跨越区的一组基态解,给出了基态的原子数密度空间分布、总原子数和能量.进一步对系统从BEC端转变到BCS端时的基态解性质进行了深入分析和对比.结果表明,一维光晶格中超流Fermi气体基态分布具有一些特殊的性质,由于Fermi压力,相比而言超流Fermi气体在BCS端的基态原子数密度空间分布较为扩展,平均能量明显偏高.     

AOTF高光谱成像0级干扰抑制方法研究

随着光谱成像技术的发展,以高空间分辨率和高光谱分辨率获得的图像极大地提高了地物目标的识别能力,为准确获取地物被测目标的二维空间影像信息和一维光谱信息,设计完成一种基于声光可调滤波器(AOTF)的高光谱成像系统,但由于系统中偏振片消光比有限,导致视场外的0级光与被测目标的+1级衍射光发生重叠,而AOTF无驱动时成像可近似为0级干扰的图像,为此提出一种AOTF加驱动图像减无驱动图像的0级干扰抑制方法。并采用该系统样机进行外场光谱成像实验,对结果进行0级干扰抑制方法修正,修正后的结果表明该方法不仅大幅度消除了0级光的干扰,而且还提高了整个成像光谱的测量精度。     

ZrO2纳米粉体的形貌可控合成及其吸附性能研究

利用水热法,以Zr(SO4)2·4H2O为原料,添加Na2SO4后合成出花状和棒状形貌可控的纳米ZrO2纳米粉体.随着SO42-浓度升高,t-ZrO2含量逐渐减少,颗粒微观形貌由三维花状变为二维棒状.利用XRD和SEM研究了Na2SO4对ZrO2粉体相结构、微观形貌和粒径的影响规律.确定了SO42-对结构和形貌调控的关键性作用,并提出了可能的成型机理.花状ZrO2对罗丹明B有良好的吸附性能,吸附容量达到20 mg/g,而棒状ZrO2的吸附性能一般,仅为4 mg/g.     

Equivalent distributed capacitance model of oxide traps on frequency dispersion of C-V curve for MOS capacitors

An equivalent distributed capacitance model is established by considering only the gate oxide-trap capacitance to explain the frequency dispersion in the C-V curve of MOS capacitors measured for a frequency range from 1 kHz to1 MHz.The proposed model is based on the Fermi-Dirac statistics and the charging/discharging effects of the oxide traps induced by a small ac signal.The validity of the proposed model is confirmed by the good agreement between the simulated results and experimental data.Simulations indicate thatthe capacitance dispersion of an MOS capacitor under accumulation and near flatband is mainly caused by traps adjacent to the oxide/semiconductor interface,with negligible effects from the traps far from the interface,and the relevant distance from the interface at which the traps can still contribute to the gate capacitance is also discussed.In addition,by excluding the negligible effect of oxide-trap conductance,the model avoids the use of imaginary numbers and complex calculations,and thus is simple and intuitive.     

基于离散单元法的颗粒阻尼耗能减振特性研究

采用离散单元法并从能量耗散的角度研究颗粒阻尼对系统减振特性的影响。建立了颗粒介质细观下的法向、切向和滚动方向的粘弹性接触模型和能量耗散模型,通过冲击激励和简谐激励下系统振动响应的多参数能量耗散分析来研究颗粒阻尼的耗能机理和减振特性。数值试验表明,颗粒介质可以在一个较宽的振动幅值范围内有效的发挥其阻尼效应,其耗能具有阶梯状周期性的特点。填充率是影响颗粒阻尼耗能减振效果的主要工程可控参数并对系统共振频率产生重大影响,当填充率接近极值时,系统出现无阻尼共振及共振频率超出无颗粒系统固有频率的现象。系统在最优填充率下共振时,颗粒与箱体保持恒定相位差的超振幅稳态运动。较小粒径的颗粒可以提高能量耗散率并使振动系统更快趋向静平衡状态,而恢复系数和摩擦系数则对法向和切向耗能的比值有较大影响。     

弧形光源镜头式光幕灵敏度分布研究

针对室内大靶面光幕测试需求,对一种镜头式光幕探测灵敏度进行了分析,探测光幕由弧形光源配接天幕靶组成。介绍了镜头式光幕测试系统的构成,分析了扇面光幕的工作机理,给出了相应的灵敏度计算公式,根据镜头成像和扇面光幕形成原理,研究了光源放置距离R以及镜头物距l对镜头式光幕探测灵敏度的影响,并通过实验进行了验证。研究结果表明:文中所提的镜头式光幕能够正常工作,研究结果对进一步工程化设计提供了参考。     

Detecting high-dimensional multipartite entanglement via some classes of measurements

Mutually unbiased bases, mutually unbiased measurements and general symmetric informationally complete measurements are three related concepts in quantum information theory. We investigate multipartite systems using these notions and present some criteria detecting entanglement of arbitrary high dimensional multi-qudit systems and multipartite systems of subsystems with different dimensions. It is proved that these criteria can detect the k-nonseparability(k is even) of multipartite qudit systems and arbitrary high dimensional multipartite systems of m subsystems with different dimensions.We show that they are more efficient and wider of application range than the previous ones. They provide experimental implementation in detecting entanglement without full quantum state tomography.     

溶胶-凝胶软模板法合成锂钛离子筛

以乙酸锂和钛酸丁酯为锂源和钛源,十六烷基三甲基溴化铵(CTAB)为软模板,采用溶胶-凝胶法,通过焙烧得到添加CTAB的锂钛化合物(Li₄Ti₅O₁₂),经过盐酸酸洗,制备出锂钛离子筛(H₄Ti₅O₁₂, HTO)。经过热重分析(TG-DTG)、X射线(XRD)、扫描电镜(SEM)、接触角及性能测试,考察了锂钛离子筛的晶相、形貌及时间对吸附容量的影响。对比CTAB的加入量,0.1 g的CTAB的离子筛前驱体杂质更少,晶相比较纯。HTO准二级动力学相关系数R²(0.997 24)大于准一级动力学相关系数R²(0.984 35),该吸附过程符合化学吸附。HTO在Li⁺溶液中24 h的吸附容量达到24.44 mg/g,经过8次吸附脱附后,吸附容量仍保持在23.68 mg/g,仅降低3.1%。因此,HTO有良好的循环吸附性能和稳定性,具有很广阔的市场前景。     

Enhanced mobility of MoS2 field-effect transistors by combining defect passivation with dielectric-screening effect

A facile method of combining the defect engineering with the dielectric-screening effect is proposed to improve the electrical performance of MoS₂ transistors. It is found that the carrier mobility of the transistor after the sulfur treatment on the MoS₂ channel is greatly enhanced due to the reduction of the sulfur vacancies during vulcanization of MoS₂.Furthermore, as compared to those transistors with HfO2 and SiO2 as the gate dielectric, the Al2O3-gate dielectric MoS₂ FET shows a better electrical performance after the sulfur treatment, with a lowered subthreshold swing of 179.4 m V/dec,an increased on/off ratio of 2.11 × 10⁶, and an enhanced carrier mobility of 64.74 cm²/V·s(about twice increase relative to the non-treated MoS₂ transistor with SiO2 as the gate dielectric). These are mainly attributed to the fact that a suitable k-value gate dielectric can produce a dominant dielectric-screening effect overwhelming the phonon scattering, increasing the carrier mobility, while a larger k-value gate dielectric will enhance the phonon scattering to counteract the dielectricscreening effect, reducing the carrier mobility.