Anisotropic transport properties of quantum dot arrays fabricated by the edge-defined nanowires

The anisotropic transport properties of quantum dot arrays fabricated by the nanoimprinted multilayer quantum wires have been investigated. The vertical transport characteristics are estimated by the carrier capture time from the electron reservoir to the low dimensional structures, which turned out to be longer than the spontaneous emission lifetime. The lateral transport characteristics are modeled after the quantum conductance between quantum dot arrays which are readily available from the miniband structures. The resulting lateral transport revealed that lateral quantum conductance can be minimized when the Fermi level is kept at the center of the miniband gap when the gap is larger than 4 kT.     

Observation of Coherent Charge-State Mixing in Asymmetric Bloch Transistors

The reduced switching current of an excited energy band in a Bloch transistor can be used to detect microwave-induced interband transitions. Spectroscopic measurements of the band gap are performed by mapping the frequency dependence of the excitation threshold where the microwave photon energy and band gap are equal. This excitation threshold also provides a probe of charge-state mixing on the island of the transistor. Any asymmetry in the junctions of the transistor makes the coherent mixing of charge states appear as a finite gap splitting at the electrostatic degeneracy point between states differing by one excess Cooper pair on the island. The measured gap splitting in an asymmetric transistor clearly demonstrates the effect.     

3D Metal printed heat sinks with longitudinally varying lattice structure sizes using direct metal laser sintering

This research relates to the design, modelling and fabrication of 3D metal printed heat sinks. The heat sinks presented in the research are the commonly used longitudinal fin solid heat sink (LFSHS) and three LFSHS lattice structure designs, differing only in their lattice sizes, fabricated using the Direct Metal Laser Sintering (DMLS) technique in Maraging Steel (MS1), on an EOSINT M280 system. In order to increase the heat sink surface area, the heat sinks are manufactured with mesh lattices along the length of the fins, while keeping the overall heat sink volume constant. The research is focused on pushing the limitations of the DMLS technique for the development of repeating unit, lattice structures heat sinks, and to examine the effect of incrementally varying the lattice sizes with regards to the resultant surface area of the heat sink and the thermal performance of the system. The results obtained under natural convection show that the thermal performance of the LFSHS outperformed all lattice structure heat sinks. This is due to the fact that, the pressure drop across the lattice heat sinks were so high, due to lattice meshes that it negated the positive effect of the greater surface area.     

基于逻辑合取的语言真值概念格合并算法

针对人工智能领域中有关不确定性自然语言的研究，将格值逻辑引入概念格，提出了自然语言转换为语言真值的方法，并基于语言真值格蕴涵代数建立了语言真值概念格.通过对各语言真值形式背景及形式概念间关系的分析，演示了由多个语言真值概念格的合并而构造完整概念格的具体过程，进而给出了语言真值概念格基于逻辑合取的合并定理与算法.实验表明，与Bordat算法相比，当属性个数增多时，适当的合并算法能够使其时间复杂度呈指数型降低.     

Evaluation of external quantum efficiency of a 12.35% tandem solar cell comprising dye-sensitized and CIGS solar cells

A tandem solar cell is constructed by series connection of a semi-transparent dye-sensitized solar cell (DSSC) as a top cell and a Cu(In, Ga)Se₂ (CIGS) solar cell as a bottom cell, where the isolated DSSC and CIGS cells show the conversion efficiency of 8.27% and 11.71%, respectively. The DSSC/CIGS tandem cell exhibits the improved conversion efficiency of 12.35% with photocurrent density of 14.1 mA/cm², open-circuit voltage of 1.435 V and fill factor of 0.61. External quantum efficiency (EQE) of the tandem cell is investigated under DC and AC modes. EQE of the isolated DSSC and CIGS cell can be measured by either DC mode or AC mode, whereas EQE for the tandem cell is detected only under AC mode with bias light. Bias light intensity is found to play the crucial role in determining the precise EQE of the tandem cell. At the given chopping frequency as low as 10 Hz, the measured EQE at bias light corresponding to 1 sun intensity is consistent with the simulated EQE data.     

A new procedure to generate resonance integral table with an explicit resonance interference for transport lattice codes

Resonance interference could not be considered explicitly in the conventional resonance treatment employing subgroup and direct resonance integral methods when using coarse energy group structure. This problem comes from the lack of information for the resonance shapes of resonant nuclides in the resonance interference formulas. As energy group boundaries get coarser, inaccuracy in estimating self-shielded cross sections with resonance interference gets bigger. A new method has been proposed to conserve the self-shielded cross sections for each group through an explicit consideration of resonance interference effect, which results in a good accuracy in predicting the multiplication factor. This method can be applicable to various mixing combinations of constituent resonant nuclides with resonance interference and can cover wide dilution range. The MERIT code has been used to generate resonance integral tables and to estimate resonance interference effects. And the 2-D transport lattice code KARMA has been used to perform sample calculations to see the effectiveness of the newly developed method. Sample calculations have been performed for single pins with various temperatures, ²³⁵U enrichments and dilution levels with the 47 and 190 energy group structures. The computational results show that this method is able to estimate self-shielded cross sections in each coarse energy group accurately for various temperatures and various geometry and composition configurations.     

高Q腔中激发相干态的制备

提出了一种基于高Q光腔中的原子与一行波光场相互作用来制备光场激发相干态和二阶激发相干态的新方法。与已提出的方法比较，该方法具备一些优点：不应用微扰理论且除了最后测量外仅用一步就可完成制备，但该方法成功几率只有50%。     

环境为热浴的开放量子系统模型的研究

基于具有non-Markovian特性的关于量子系统约化密度矩阵的精确系统动力学方程，分别根据方程所具有的非封闭、不等时、积分微分方程的特性，通过Born逼近和Markov逼近得到关于量子系统约化密度矩阵的封闭、等时和微分的Markovian主方程；逐一分析了Markovian主方程的Lindblad形式、具有方便检验正定性的GKS表达形式、针对单量子位系统的Bloch球表达形式和无需明确的环境信息也能对开放系统进行描述的Kraus表达形式；分析并比较了能去除系统动力学方程non-Markovian特性的4种Markov逼近方法以及其他四种特定情形下常见的Markovian主方程；对于不适用于Markov逼近的情形，分析了能满足开放量子系统动力学对于系统状态要求的post-Markovian主方程；当热浴与量子系统发生能量交换，且热浴与量子系统组成的封闭系统能量守恒时，给出了热浴状态不恒定时开放量子系统的动力学方程，并通过Markov逼近得到Markovian主方程。     

Influence of residual solvent on physical and chemical properties of amorphous glassy polymer films

One of the most important areas of current research is the study of the influence of the prehistory of samples of amorphous glassy polymers on their physical and chemical properties. The study of structural changes by high temperature IR spectroscopy compared with of quantum chemical calculations allows for an understanding of the mechanism and nature of such processes. The changes in the structure of the polymer chain depending on the type of solvent used in the formation of the films are demonstrated using the examples of several different classes of polymers. In turn, the impact of such changes in the structure on the physical and chemical properties of the polymer films is demonstrated. © 2013 Society of Chemical Industry