The influence of the nanostructure geometry on the thermoelectric properties

We discuss the influence of nanostructure geometry on the thermoelectric properties in quantum ring consists of one QD in each arm, each QD connects with side QD. The calculations are based on the time-dependent Hamiltonian model, the steady state is considered to obtain an analytical expression for the transmission probability as a function of system energies. We employed the transmission probability to calculate the thermoelectric properties. We investigate thermoelectric properties through three configurations of this nanostructure. Figure of merit enhanced in configuration (II) when side QD connected to upper arm of quantum ring. The magnetic flux threads quantum ring. The effect of magnetic flux on the thermoelectric properties is examined.     

Fano effect in a double T-shaped interferometer

We study the coherent transport in a one-dimensional lead with two side-coupled quantum dots using the Keldysh’s Green function formalism.The effect of the interdot Coulomb interaction is taken into account by computing the firstand second order contributions to the self-energy.We show that the Fano interference due to the resonance of one dotis strongly affected by the fixed parameters that characterize the second dot. If the second dot is tuned close to resonance an additionalpeak develops between the peak and dip of the Fano line shape of the current. In contrast, when the second dotis off-resonance and its occupation number is close to unity the interdot Coulomb interaction merely shifts the Fano line and no other maxima appear.The system we consider is more general than the single-dot interferometer studied experimentally by Kobayashi et al. [Phys. Rev. B 70, 035319 (2004)] and may be used for controlling quantum interference and studying decoherence effects in mesoscopic transport.     

A novel encoder/decoder design scheme utilizing differential detection in OCDMA systems

In this paper, we report the use of differential detection in optical code-division multiple access (OCDMA) systems which use encoders and decoders based on unbalanced codes and utilize bipolar modulation/differential detection to demonstrate a significant improvement in system performance. Differential detection has been reported earlier also requiring a large number of one-chips in the code for (balanced codes) or with unbalanced codes with very long temporal dimensions requiring a large number of delay elements (either the delay lines in the ladder-type structures or the gratings in the multiple fiber gratings) making the encoder/decoder structures. We use single pulse per row codes to design our system and carry out the simulations for showing the results. The improved BER performance is achieved that can be traded for increasing the number of codes. Using optical simulation tool, the OCDMA system has been simulated for four users. The results of this system utilizing differential detection and another system that uses the same coding scheme but employing direct detection, for the same number of interfering users, are shown for comparison. The BER and the power penalty plots are shown for the two systems. Also, it is shown that performance degradation occurs due to the linear and non-linear effects of the fiber medium. The BER worsens more rapidly with link length for direct detection case, whereas for differential detection with an initial improvement of 8 dB, the increase in BER is insignificantly small for a link length of 500 km.     

Interference phase of mass neutrino in Reissner-NordstrSm-de Sitter space-time

The chemical potential of electrons in a strong magnetic field is investigated. It is shown that the magnetic field has only a slight effect on electron chemical potential when B < 1011 T, but electron chemical potential will decrease greatly when B > 1011 T. The effects of a strong magnetic field on electron capture rates for 60Fe are discussed, and the result shows that the electron capture sharply decreases because of the strong magnetic field.     

Interferences in Photodetachment of a Negative Molecular Ion Model

By employing a two-center model, the total and differential cross sections in the photodetachment of ＂a negative molecular ion＂ are studied theoreticedly and obtained for the case of light polarization paredlel to the molecular axis. We find that in contrast to the smooth behavior of the total cross section for perpendicular polarized light, the cross section for parallel polarized light shows an interesting oscillatory structure. The oscillations in the toted cross section may provide a method to determine the distance between the two centers. We explain the oscillation in the toted cross section as an interference effect using closed-orbit theory. We also cedculated the detached-electron flux distributions on a screen placed at a large distance from the negative molecular ion. The distributions display multiple-ring-like interference patterns. Such interference patterns are similar to those in the photodetachment microscopy experiments.     

Laser self-mixing interference fibre sensor

Fibre sensors exhibit a number of advantages over other sensors such as high sensitivity, electric insulation, corrosion resistance, interference rejection and so on. And laser self-mixing interference can accurately detect the phase difference of feedback light. In this paper, a novel laser self-mixing interference fibre sensor that combines the advantages of fibre sensors with those of laser self-mixing interference is presented. Experimental configurations are set up to study the relationship between laser power output and phase of laser feedback light when the fibre trembles or when the fibre is stretched or pressed. The theoretical analysis of pressure sensors based on laser self-mixing interference is indicated to accord with the experimental results.     

多噪声背景下光码分多址多用户干扰的抑制

针对光码分多址(OCDMA)的多用户干扰问题, 研究采用APD光电检测器的系统中存在多种噪声情况下, 基于最大值判决的光码分多址并行干扰抑制方法的多用户干扰抑制效果。阐述了其工作原理, 即在发送端对比特“0”和比特“1”分别使用一个地址码和它的移位变形进行映射, 以避免发送比特“0”时无光脉冲通过, 实现并行干扰抑制; 接收端判决电路采用最大值判决, 以避免门限判决所引起的误判, 进一步减小多用户干扰。系统采用光正交码作为地址码, 分析推导了系统的误码率表达式。根据所得的误码率表达式, 进行了数值仿真并与其他多用户干扰抑制方法进行比较。仿真结果表明, 本方法对多用户干扰的抑制作用与系统用户数和码重有关; 与引入双硬限幅器方法、多比特传输方法的多用户干扰抑制作用相比, 抑制效果要优于多比特传输的方法; 当接收功率较低时, 该方法优于引入双硬限幅器的方法, 因此可以有效的抑制多用户干扰。     

基体干扰对ICP-AES分析土壤样品中主、次量元素的影响研究

为了研究分析方法中的干扰因素对于分析结果的影响程度,针对地球化学中常用的分析手段ICP-AES法,选择土壤标准物质采用与被测样品相同消解方法,作为工作校准曲线来抵消基体影响因素。比较了在土壤基体和无土壤基体条件下测得的土壤样品中各主、次量元素结果的相对偏差,分析了其中联系和规律。发现无土壤基体干扰的结果RE值均在0左右浮动,正负偏移比例基本一致,若排除谱线干扰因素的话,基体匹配方法能有效消除土壤中基体干扰影响。而土壤基体干扰对Al,Ca,Fe,Mg,P,Ti和Ba元素分析结果有较大负偏差影响,最大偏离差Mg 279.5 nm谱线达-14.49%,影响程度排序为Ti,Mg＞P,Fe＞Ca,Ba＞Al,对其他元素Na,Cr,Cu,V,Li,Mn,Ni和Sr则无明显影响。与原本设想的结果相反,基体干扰对我们视作基体的高含量元素测试结果影响十分大,反而对次量元素影响表现并不显著。在综合基体干扰中,Ca和Mg两元素自身组分含量影响权重明显,表现为自身组分含量与分析结果相对偏差值有明显线性相关性。其他元素自身组分与基体影响结果无线性趋势,自身含量的影响权重很小。谱线的选择,干扰因素的排除对结果的确定十分重要。干扰影响的因素和规律一直是ICP光谱学者致力研究探索的课题。这些研究结果对ICP-AES分析土壤样品时谱线的选择及结果准确度的判定有很好的指导意义。     

光纤锥在线型马赫-曾德干涉仪的折射率传感特性

提出了一种基于光纤锥的在线型光纤马赫-曾德干涉仪式折射率传感器.传感器是在一根单模光纤上使用光纤熔接机拉制出两个光纤锥,光纤锥的直径为43.7μm,长度为480μm.干涉仪中光纤锥充当光纤耦合器,激发出光纤高阶模,并将高阶模耦合进单模光纤使之与纤芯基模形成模间干涉.被环境溶液的折射率、温度的变化改变模式间相位差,将导致干涉仪的传输光谱发生漂移,从而实现传感测量.实验结果表明:当环境溶液的折射率变化范围为1.335~1.403RIU时,传感器的折射率灵敏度为-128.233nm/RIU;当水溶液的温度变化范围为30~75℃时,传感器的温度灵敏度为0.111nm/℃.该传感器具有制作方法简单、灵敏度高、成本低等特点,可应用于生物传感测量.     

硅-有机物材料混合电光调制器的优化设计

设计了一种基于绝缘上层硅的硅-有机物材料混合马赫-曾德干涉型高速电光调制器.利用光束传播法对顶层硅为220nm的绝缘上层硅基片上的3dB分束器/合束器的结构参数进行模拟,优化后附加损耗仅为0.106dB.为提高模式转换效率,在条形波导和slot波导之间设计了模式转换器,光耦合效率高达98.8%,实现了光模式高效转化.利用时域有限差分法模拟了slot波导平板区掺杂浓度对波导内光学损耗的影响,在几乎不产生光学损耗的情况下,得到平板区轻掺杂浓度为71017/cm3,调制器设计总损耗为0.493dB.利用薄膜模式匹配法对slot波导结构进行仿真分析,考虑slot区等效电容及平板区等效电阻对带宽的影响,优化后得到slot波导结构的限制因子为0.199.采用slot波导与强非线性有机材料LXM1结合的绝缘上层硅平台实现了强普克尔效应,得到电光调制器半波电压长度积为1.544V·mm,电学响应3dB带宽为137GHz.