CALORIMETRIC STUDY OF THERMOCHROMIC COMPLEXES. 2. HEAT CAPACITY AND PHASE TRANSITION OF BIS(N,N‐DIETHYLETHYLENEDIAMINE)COPPER(II) PERCHLORATE

Abstract

The thermochromic phase transition of bis(N,N-diethylethylenediamine) copper(II) perchlorate has been studied by adiabatic calorimetry in the 12–359 K temperature range. A large heat capacity anomaly was observed at 317.64 K with a long heat-capacity tail extending down to ～200 K. The enthalpy and entropy of the phase transition were found to be δ_trs H = 17.43 kJ mol^?1 and δ_trs S = 55.21 J K^?1 mol^?1, respectively. Together with a calorimetric study of a homologous thermochromic complex, bis(N,N-diethylethylenediamine)copper(II) tetrafluoroborate (J. Phys. Chem. Solids, 55, 99 (1994)), the nature of the present thermochromic phase transition is well described by a puckering motion of the copper-ligand chelate rings and a change in the ligand-field strength estimated on the basis of the angular overlap model. The correlation between structures, electronic spectra and thermal properties is discussed.     

Novel multisection design of anisotropic diffusion phantoms

Diffusion-weighted magnetic resonance imaging provides access to fiber pathways and structural integrity in fibrous tissues such as white matter in the brain. In order to enable better access to the sensitivity of the diffusion indices to the underlying microstructure, it is important to develop artificial model systems that exhibit a well-known structure, on the one hand, but benefit from a reduced complexity on the other hand. In this work, we developed a novel multisection diffusion phantom made of polyethylene fibers tightly wound on an acrylic support. The phantom exhibits three regions with different geometrical configuration of fibers: a region with fibers crossing at right angles, a region with parallel fibers and homogeneous density, and, finally, a region with parallel fibers but with a gradient of fiber density along the axis of symmetry. This gives rise to a gradual change of the degree of anisotropy within the same phantom. In this way, the need to construct several phantoms with different fiber densities is avoided, and one can access different fractional anisotropies in the same experiment under the same physical conditions. The properties of the developed phantom are demonstrated by means of diffusion tensor imaging and diffusion kurtosis imaging. The measurements were performed using a diffusion-weighted spin-echo and a diffusion-weighted stimulated-echo pulse sequence programmed in-house. The influence of the fiber density packing on the diffusion parameters was analyzed. We also demonstrate how the novel phantom can be used for the validation of high angular resolution diffusion imaging data analysis.     

Modeling and passivity analysis of nonholonomic Hamiltonian systems with rheonomous affine constraints

This paper is devoted to modeling and theoretical analysis of Hamiltonian systems subject to nonholonomic rheonomous affine constraints. We first define rheonomous affine constraints and explain geometric representation of them. Next, a complete nonholonomicity condition for the rheonomous affine constraints is developed in terms of the rheonomous bracket. Then, the nonholonomic Hamiltonian system with rheonomous affine constraints (NHSRAC) is derived via a transformation and model reduction for the expanded Hamiltonian system defined on the expanded phase space. After that, we investigate passivity of the NHSRAC with the control input term and the output equation. Finally, in order to confirm the application potentiality of our new results, we show an example, a radius-variable ball on rotating table with a time-varying angular velocity.     

基于叠栅条纹的光刻对准理论分析及标定方法

在线光栅用于纳米光刻对准理论的基础上,为实现光栅方向的标定和掩模硅片对准,提出一种利用相位斜率消除角位移的新方法,并给出线光栅标记及其对准原理。在对准前,掩模对准标记和硅片对准标记存在角位移,重点讨论了此种情况下叠栅条纹的特性以及与光栅物理参数的关系,并给出了相应的计算公式。基于傅里叶频域分析法,对叠栅条纹频率成分与条纹的关系做了简要分析。利用提取叠栅条纹行列方向的一维相位,通过数据拟合,得出了相位斜率与角位移的内在关系,实现了条纹方向的标定。模拟实验结果表明,该方法简单可靠,可分辨的最小角位移低于0.02°。     

基于多路复用体全息光栅的角度放大器设计

为设计基于多路复用体全息光栅的角度放大器, 建立了多路复用角度放大器(MAM)模型, 从效率均衡性和角度分布均匀性两个方面归纳了其设计规则; 研究了光刻过程中的误差对MAM性能的影响; 分析了实际发散光束对MAM性能的影响. 研究表明:控制光栅空间频率和光栅倾斜角可以实现需要的MAM角度分布, 控制光栅厚度和折射率调制深度可以实现MAM最佳衍射效率; MAM最大复用路数不超过10路; 增大光栅倾角或者记录光与工作光波长之比有利于抑制参考光角度误差带来的MAM出射角分布误差, 减小光栅厚度有利于抑制厚度误差与折射率调制深度误差对衍射效率的影响; 当远场发散角大于光栅角半宽时, 最佳衍射效率下降到50%以下且角度选择曲线失去局部最小值; 增大空间频率或者光栅厚度可以减小所需的折射率调制深度, 增多MAM可复用路数, 但是不利于效率均衡性设计和抑制发散光束的影响.     

圆锥运动下磁场辅助角速度测量方法与实验

利用磁场传感器可辅助载体进行角速度测量.在用于飞行载体时,由于载体通常伴随有圆锥运动,并且载体自身会对内部磁场产生干扰,使磁场传感器输出产生畸变,从而导致利用磁场辅助测量的载体角速度的误差较大.针对这个问题,提出了一种基于实时误差补偿的在圆锥运动及磁场干扰影响条件下利用磁场辅助进行角速度测量的方法.该方法利用载体过去1周旋转的数据,实时对圆锥运动与磁场干扰进行补偿,然后根据补偿结果计算当前载体的角速度.当载体角速度越大时,精度越高.通过飞行实验对该方法进行了验证,实验结果表明,在角速度大于300 (°)/s时,角速度误差小于1(°)/s.     

基于激光干涉条纹的联合基座相对变形测量方法

在联合基座上安装CCD光电变形测量系统发射和接收单元,通过测量所得图像中条纹倾角的变化,来检测基座扭转角的变化,通过测得条纹中心位置在焦平面X和Y方向的变化来检测横向和纵向变形。针对条纹图像,通过对每个条纹放大以及条纹单行图像像素的灰度值细分,可以得出条纹每一行的中心点,所有行的中心点连线构成条纹的中轴骨架线,从而形成一种新的条纹细分检测方法;然后将细分后的条纹分组排列,根据所有条纹斜率相同,分组后组内和组间间距近似为常值的前提条件进行最小二乘拟合和运算便可求取倾角。误差分析计算和试验结果表明,系统对扭转角的检测精度可以达到25″,对横向和纵向变形的检测精度可达5″,成为试验船的实用方法。     

Trajectory optimization and applications using high performance solar sails

The high performance solar sail can enable fast missions to the outer solar system and produce exotic non-Keplerian orbits. As there is no fuel consumption, mission trajectories for solar sail spacecraft are typically optimized with respect to flight time. Several investigations focused on interstellar probe missions have been made, including optimal methods and new objective functions. Two modes of interstellar mission trajectories, namely “direct flyby” and “angular momentum reversal trajectory”, are compared and discussed. As a foundation, a 3D non-dimensional dynamic model for an ideal plane solar sail is introduced as well as an optimal control framework. A newly found periodic double angular momentum reversal trajectory is presented, and some properties and potential applications of this kind of inverse orbits are illustrated. The method how to achieve the minimum periodic inverse orbit is also briefly elucidated.     

ON UNIQUENESS OF MEROMORPHIC FUNCTIONS WITH SHARED-SETS IN AN ANGULAR DOMAIN

In this article, we deal with the uniqueness problems on meromorphic functions sharing two finite sets in an angular domain instead of the whole plane C. In particular, we investigate the uniqueness for meromorphic functions of infinite order in an angular domain and obtain some results. Moreover, examples show that the conditions in theorems are necessary.     

零刚度弹性梁旋转式陀螺研究

设计并制作了在零扭转刚度条件下的一种用于旋转体偏航角速率测量的陀螺。分析该陀螺工作原理,建立该陀螺的数学模型,设计和制作了零扭转刚度陀螺的敏感结构。利用交流电桥提取电容变化信号,进而实现对旋转体偏航角速度的测量。在旋转体自旋角速度不同的情况下,对陀螺输出信号进行测量,分别得到载体的旋转速率φ=10×2πrad/s时,比例系数K=20.96 mV/[(°)·s-1];φ=12×2πrad/s时,K=21.12 mV/[(°)·s-1],φ=14×2πrad/s时,K=21.10 mV/[(°)·s-1]。理论研究和性能测试表明,在陀螺振动元件的弹性梁扭转刚度为0时,陀螺输出信号的大小只与偏航角速度Ω有关,与载体旋转角速率φ无关。