Spin states in InAs/AlSb/GaSb semiconductor quantum wells

We investigate theoretically the spin states in InAs/AlSb/GaSb broken-gap quantum wells by solving the Kane model and the Poisson equation self-consistently. The spin states in InAs/AlSb/GaSb quantum wells are quite different from those obtained by the single-band Rashba model due to the electron-hole hybridization. The Rashba spin splitting of the lowest conduction subband shows an oscillating behavior. The D'yakonov-Perel' spin-relaxation time shows several peaks with increasing the Fermi wave vector. By inserting an AlSb barrier between the InAs and GaSb layers, the hybridization can be greatly reduced. Consequently, the spin orientation, the spin splitting, and the D'yakonov-Perel' spin-relaxation time can be tuned significantly by changing the thickness of the AlSb barrier.

Dyakonov-Perel spin relaxation in InSb/AlxIn(1-x)Sb quantum wells

We investigate theoretically the Dyakonov-Perel spin relaxation time by solving the eight-band Kane model and Poisson equation self-consistently. Our results show distinct behavior with the single-band model due to the anomalous spin-orbit interactions in narrow band-gap semiconductors, and agree well with the experiment values reported in recent experiment [K. L. Litvinenko et al., New J. Phys. 8, 49 (2006)]. We find a strong resonant enhancement of the spin relaxation time appears for spin align along [1 (1) over bar0] at a certain electron density at 4 K. This resonant peak is smeared out with increasing the temperature.

Calculation of the band structure of semiconductor quantum wells using scattering matrices

The transfer-matrix method widely used in the calculation of the band structure of semiconductor quantum wells is found to have limitations due to its intrinsic numerical instability. It is pointed out that the numerical instability arises from free-propagating transfer matrices. A new scattering-matrix method is developed for the multiple-band Kane model within the envelope-function approximation. Compared with the transfer-matrix method, the proposed algorithm is found to be more efficient and stable. A four-band Kane model is used to check the validity of the method and the results are found to be in good agreement with earlier calculations.

六轮摇臂式月球车环境交互动力学建模研究

目前，移动机器人被广泛应用于危险的非结构环境中，在诸如行星探测、灾难搜救、军事侦察、矿山开采等作业中， 机器人将起着越来越重要的作用。机器人在非结构环境中的运动能力和环境适应能力决定了机器人的作业性能。具备稳定性、机动性、越障能力、通过能力与可靠性的移动机器人将具有更好的环境适应能力，进而更好地完成作业任务。 本文针对中国科学院知识创新工程方向性项目“月球车月面探测作业支撑技术研究” 的实际需求， 在对国内外的同类研究深入分析综合的基础上， 对月球车移动系统与环境交互动力学的几个关键问题进行了研究与探讨。(1)研究月球车的运动稳定性和机动性问题。基于车体固定坐标系和地面固定坐标系， 分别建立了四轮转向的六轮摇臂转向架式月球车的转向动力学模型， 证明在两种坐标系下的模型转向动力学方程的一致性；分析了月球车运动的稳态特性和瞬态特性，采用机动性因子来定量地描述月球车运动的稳定性和机动性及其相互关系， 并用机动性因子来设计月球车的稳定性和机动性。(2)研究如何保持理想运动姿态的问题。建立了保持月球车运动姿态的理想模型， 模拟人驾驶汽车的过程建立月球车跟踪规划路径行驶的视觉预瞄模型，设计了保持月球车理想姿态行驶的模型参考自适应控制方案。(3)研究月球车的运动在环境扰动的干扰下会偏离规划路径的问题。利用Laplace 变换考察月球车运动动力学系统对几种典型的环境干扰力形式 的响应，研究环境干扰力对月球车运动的影响。(4)根据车辆地面力学的理论，设计月球车车轮的结构参数，使其充分利 用土壤推力，考虑纵列式月球车多轮通过土壤参数的修正，在NASA 建议的五种土壤上对月球车的支承通过性指标进行了计算； 研究刚性驱动轮在松软路面上行驶车轮滑转率和车轮结构参数对车轮挂钩牵引力、驱动力矩、车轮驱动效率等车轮驱动动力学特性的影响。(5)针对月球车在松软路面上不能正常行驶的主要原因是车轮过度下陷这个问题， 结合月球车行驶动力学模型， 设计以车轮滑转率为状态变量的滑模驱动控制器。仿真结果表明， 采用该控制器可以避免车轮的过度 滑转下陷，保证月球车能够在软质路面上正常行驶。(6)评价六轮摇臂转向架式月球车的越障能力，给出了车轮牵引系数与垂直越障高度的定量函数关系式； 针对月球车越障能力的评价以及越障时各车轮驱动力矩的协调分配的问题， 建立一种基于运动轨迹角的月球车越障能力判断准则， 引入了越障指数，用于定量地评价月球车的越障能力。(7)利用闭链坐标变换和瞬时重合坐标法，结合Kane 方程，同时考虑三维不平地形、松软路面和车轮的滑移，建立了六轮摇臂转向架式月球车的三维姿态动力学模型。

基于ROV援潜救生自主作业方法研究

利用ROV代替潜水员进行潜艇供排气管对接作业是援潜救生的发展趋势，其中供排气管对接技术是为失事艇员提供生命保障的关键技术。由于水下作业环境比较复杂以及水下作业难度大等特点，人工遥控ROV进行援潜对接供排空气管作业过程中，还停留在只是能够打开潜艇供排气系统花甲板盖的工作上，还没有实现对类似接通供排空气管精确作业的工作。受到海流、风浪、失事潜艇周围较大涡流、供排气管的拖曳阻力、水下可视条件以及高精度定位等因素的限制，作业任务越复杂，要求ROV系统上机械手精确定位精度越高，操纵的难度也越大，由人工操作很难实现。在现有ROV人工操作的基础上，使ROV系统具有自主作业功能，更能发挥其在对接空气管作业中的能力，提高作业效率，缩短救援时间，因此本文在现有ROV基础上扩展预编程自主控制驾驶功能模块即ROV-A系统，借助预编程技术ROV-A系统在对接空气管作业中的一些特殊任务时能够实现自主作业功能。 本文结合中国科学院沈阳自动化研究所水下机器人中心未来援潜救生关键技术研究内容，针对为失事潜艇接通空气管作业中的一些关键技术，开展基于具有自主作业能力的ROV-A系统自主作业方法研究，深入研究了具有自主作业能力ROV-A系统的运动规划与协调控制技术以及水下作业力控制技术，以实现高精度的机械手末端位置控制与期望力跟踪；针对潜艇供排气系统的已知结构研究了水下目标定位技术，为对接空气管的特定需求发展具有自主作业能力的水下作业技术提供理论依据。重点研究针对系统特点的运动规划与多性能指标实现归一化问题；研究基于系统动力学模型误差的系统位姿控制问题；研究基于阻抗力控制水下作业目标定位问题；在系统运动规划与控制研究的基础上，研究能实现机械手末端精确轨迹跟踪的控制策略问题以及力控制问题。本论文研究内容如下： （1）根据ROV-A系统特点，从描述系统的空间位置和姿态着手，研究了ROV-A系统的空间运动学与基于Kane方法的动力学，得出载体基座自由运动模式的系统空间运动数学模型，为论文后续研究工作奠定了基础。 （2）针对对接空气管作业中的一些高精度和复杂的作业，研究了系统作业时的运动规划问题。针对系统运动学冗余、作业规划约束性能指标多，例如机械手可操作性，关节限制，载体的姿态，避障等等，结合梯度投影法和最小范数伪逆矩阵法以及任务优先逆运动学方法，引入模糊控制技术，将模糊控制的定性知识表达与任务优先逆运动学算法相结合，以水下作业末端位置控制及轨迹跟踪为前提，对系统运动分配、关节限位、避免奇异有无海流下的系统性能优化等运动规划进行了研究，仿真证明运动规划算法的有效性。 （3）研究了基于动力学模型的系统基本控制问题。针对系统动力学模型的复杂性和不精确性，在基于载体输出反馈控制的基础上，设计了基于输出反馈自适应控制算法，通过自适应学习的方式直接逼近系统动力学方程状态量之间的非线性关系，在外界不停扰动下逐渐提高系统的控制精度；基于Lyapunov稳定性理论，证明了存在外界干扰和自适应逼近误差条件下ROV-A系统控制器的闭环稳定性；通过仿真实验验证控制系统的有效性，为系统的控制提供了一种新思路。同时在基于位置运动控制的基础上引入了力控制，通过对常规PID外环力控制器基础上的改进，在系统离线规划的前提下实现力与位置控制的解耦，通过仿真验证期望力的稳定跟踪。 （4）研究了基于ROV-A系统阻抗力控制的水下矩形围壁环境约束的位置定位方法。通过在对具有先验知识的矩形围壁环境约束的学习理解基础上，应用外部阻抗力控制环包容内部位置运动控制环的控制策略。利用力传感器的反馈信息变化确定系统末端执行器与约束环境的接触特征点，根据环境的先验知识推理出环境定位信息。通过计算机仿真实验验证了水下具有先验知识环境的定位方法和ROV-A系统的控制策略的有效性。仿真结果证明定位方法和控制策略是可行的。 （5）结合系统控制，分析了系统在为失事潜艇对接空气管作业中的恒定和时变两种期望力输入作业模式，提出了基于在线运动规划下外部力控制环包容内部位置环控制方法，利用ROV-A系统完成了为失事潜艇自主对接空气管中两个典型作业。介绍了整个控制方法的组成和执行过程，分析了综合控制策略，最后通过仿真实验分析了综合力控制方法的性能，包括恒力和时变期望力输入进行了深入研究。

Learning with Deictic Representation

Most reinforcement learning methods operate on propositional representations of the world state. Such representations are often intractably large and generalize poorly. Using a deictic representation is believed to be a viable alternative: they promise generalization while allowing the use of existing reinforcement-learning methods. Yet, there are few experiments on learning with deictic representations reported in the literature. In this paper we explore the effectiveness of two forms of deictic representation and a naive propositional representation in a simple blocks-world domain. We find, empirically, that the deictic representations actually worsen performance. We conclude with a discussion of possible causes of these results and strategies for more effective learning in domains with objects.

Aproveitamento do resíduo gerado na produção de mini beterrabas para a produção de farinha.

2011

Health-Related Quality of Life for individuals with hepatitis C: A narrative review.

BACKGROUND The assessment of Health-Related Quality of Life (HRQoL) in hepatitis C (HCV) infected individuals continues to gain importance. However, rarely do reviews of this literature consider quantitative and qualitative accounts of HRQoL collectively, which only allows partial insight into the topic. This narrative review aims to address this gap in the literature. METHODS Literature searches were conducted using seven databases with two separate search strategies, and results assessed for eligibility using specific inclusion/exclusion criteria; a data extraction sheet was used to identify the dominant themes for each research paradigm which were then distilled to key findings to construct the narrative. RESULTS Quantitative investigation reveals a low HRQoL in individuals with HCV due to a complex multifactorial cause. During treatment for HCV, a further transient reduction is observed, followed by improvement if a sustained virological response is achieved. Qualitative data provide a recognisable voice to the everyday challenges experienced by individuals with HCV including insights into diagnosis and stigmatisation, contextualising how a reduced HRQoL is experienced day-to-day. Methodological limitations of these findings are then discussed. Much of the quantitative data has little relevance to current substance users as they are excluded from most trials, and appraisal of the qualitative literature reveals a marked difference in the lived experience of HCV infected current substance users and that of other HCV groups. CONCLUSION Concurrent analysis of quantitative and qualitative paradigms provides a deeper understanding of the true burden of HCV illness on HRQoL. Greater utilisation of qualitative research within international clinical guidelines is likely to be of benefit in identifying relevant HRQoL outcomes for substance users.

LOCALIZED ENHANCEMENTS OF Fe+10 DENSITY IN THE CORONA AS OBSERVED IN Fe xi 789.2 nm DURING THE 2006 MARCH 29 TOTAL SOLAR ECLIPSE

Habbal, Shadia Rifai; Morgan, Huw; Johnson, Judd; Arndt, Martina Belz; Daw, Adrian; Jaeggli, Sarah; Kuhn, Jeff; Mickey, Don, LOCALIZED ENHANCEMENTS OF Fe+10 DENSITY IN THE CORONA AS OBSERVED IN Fe xi 789.2 nm DURING THE 2006 MARCH 29 TOTAL SOLAR ECLIPSE, The Astrophysical Journal, Volume 663, Issue 1, pp. 598-609

'What Foes more dang'rous than too strong Allies?': Anglo-Welsh relations in eighteenth-century London

Prescott, Sarah, ''What Foes more dang'rous than too strong Allies?': Anglo-Welsh relations in eighteenth-century London', The Huntington Library Quarterly (2006) 69 (4) pp.535-554 RAE2008

The Cambrian Muse: Welsh Identity and Hanoverian Loyalty in the Poems of Jane Brereton (1685-1740)

Prescott, S. (2005). The Cambrian Muse: Welsh Identity and Hanoverian Loyalty in the Poems of Jane Brereton (1685-1740). Eighteenth -Century Studies. 38(4), pp.587-603. RAE2008

Women, Authorship and Literary Culture, 1690 - 1740

Prescott, S. (2003). Women, Authorship and Literary Culture, 1690 - 1740. Basingstoke: Palgrave Macmillan. RAE2008

Elizabetha Triumphans

Archer, J. and Knight, S. (2007). Elizabetha Triumphans. In J. Archer; E. Goldring; and S. Knight (Eds.), The Progresses, Pageants, and Entertainments of Queen Elizabeth I (pp.1-23). Oxford: Oxford University Press. RAE2008