多片导模法蓝宝石晶体的缺陷研究

使用导模法(EFG)生长了多片a面蓝宝石晶体。显微拉曼光谱结合电感耦合等离子体发射光谱(ICP-AES)测试得出晶体的气泡中可能存在含S化合物。晶体表面明显的生长条纹主要与温度、生长速度的波动以及模具的加工精度有关。化学腐蚀分析表明晶体位错密度在4.2×10⁴ cm^-2,未存在小角度晶界缺陷,双晶摇摆曲线半峰宽(FWHM)为70.63″。由于采用石墨保温材料,晶体中存在F心与F⁺色心。晶体在400~3 000 nm波段透过率高于80%,空气中退火后可减弱色心吸收。本文研究结果可为蓝宝石晶体缺陷形成理论研究提供参考,也可为导模法蓝宝石工业生产技术改进提供借鉴。     

Methylcobalamin‐Loaded PLCL Conduits Facilitate the Peripheral Nerve Regeneration

The feasible fabrication of nerve guidance conduits (NGCs) with good biological performance is important for translation in clinics. In this study, poly(d ,l ‐lactide‐co‐caprolactone) (PLCL) films loaded with various amounts (wt; 5%, 15%, 25%) of methylcobalamin (MeCbl) are prepared, and are further rolled and sutured to obtain MeCbl‐loaded NGCs. The MeCbl can be released in a sustainable manner up to 21 days. The proliferation and elongation of Schwann cells, and the proliferation of Neuro2a cells are enhanced on these MeCbl‐loaded films. The MeCbl‐loaded NGCs are implanted into rats to induce the regeneration of 10 mm amputated sciatic nerve defects, showing the ability to facilitate the recovery of motor and sensory function, and to promote myelination in peripheral nerve regeneration. In particular, the 15% MeCbl‐loaded PLCL conduit exhibits the most satisfactory recovery of sciatic nerves in rats with the largest diameter and thickest myelinated fibers.     

ENHANCED BLOCK-SPARSE SIGNAL RECOVERY PERFORMANCE VIA TRUNCATED e2/e1-2 MINIMIZATION

In this paper, we investigate truncated $ℓ_2/ℓ_{1−2}$ minimization and its associated alternating direction method of multipliers (ADMM) algorithm for recovering the block sparse signals. Based on the block restricted isometry property (Block-RIP), a theoretical analysis is presented to guarantee the validity of proposed method. Our theoretical results not only show a less error upper bound, but also promote the former recovery condition of truncated ℓ₁₋₂ method for sparse signal recovery. Besides, the algorithm has been compared with some state-of-the-art algorithms and numerical experiments have shown excellent performances on recovering the block sparse signals.     

二次锥规划的光滑牛顿法

在光滑Fischer-Burmeister函数的基础上,本文给出了二次锥规划的一种新的光滑牛顿法.该方法所采用的系统不是等价于中心路径条件,而是等价于最优性条件本身.算法对初始点没有任何限制,且具有Q-二阶收敛速度.     

粘性对离心泵性能的换算方法的探索

在同一试验台架上，采用三种不同粘度的油以及水作为输送介质，实测了相同比转速，相同叶轮外径和出口宽度，但不同叶型的叶轮的外特性，同时，采用美国AHI、前苏联ГОСТ以及德国KSB的换算方法得到了以清水实验外特性为基准的粘性换算曲线，对比了各换算曲线与实测性能之间、叶型与粘性外特性之间的关系。结果表明：叶型对外特性影响明显，且各换算结果都和试验值具有较大的偏差，尤其是前苏联的方法偏离试验值更大。     

Stability of Random Networks under Evolution of Attack and Repair

With a simple model, we study the stability of random networks under the evolution of attack and repair. We introduce a new quantity, i.e. invulnerability I（s）, to describe the stability of the system. It is found that the network can evolve to a stationary state. The stationary value Ic has a power-law dependence on the initial average degree （κ）, with the slope about -1.5. In the stationary state, the degree distribution is a normal distribution, rather than a typical Poisson distribution for general random graphs. The clustering coefficient in the stationary state is much larger than that in the initial state. The stability of the network depends only on the initial average degree （κ）, which increases rapidly with the decrease of （κ）.     

A New Method to Measure the Divergence of X-Ray Beams from Capillaries

A new method to measure the divergence of x-ray beams propagated out from several capillaries is introduced, This new method is based on Bragg＇s law and is proven efficiently by the experimental measurement with collimators and straight polycapillaries.     

含二羟基二苯酮的系列热致液晶共聚酯的合成和表征──Ⅲ．含4，4＇－二羟基二苯砜结构的共聚酯

含二羟基二苯酮的系列热致液晶共聚酯的合成和表征──Ⅲ．含４，４＇－二羟基二苯砜结构的共聚酯董德文，池振国，倪玉山，丁孟贤（中国科学院长春应用化学研究所长春１３００２２）陈玉（东北师范大学分析测试中心长春１３００２４）关键词４，４＇－二羟基二苯酮，热致...     

A GROUP OF EXACT (3+1) DIMENSIONAL CYLINDRICALLY SYMMETRIC WAVE SOLUTIONS TO THE EINSTEIN GRAVITATIONAL FIELD EQUATION

Starting with the diagonal spacetime metric tensor, the Einstein gravitational field equation is solved, and a set of exact (3+1) dimensional cylindrically symmetric wave solutions with two arbitrary functions are found. In these solutions all nonvanishing components of spacetime metric tensor are varying with the same propagating factor (ct-z) while the waves are travelling along z axis. The physical picture and the condition of positive energy density of the wave solutions are discussed.     

掺铒SiOx的光致发光特性

利用分子束外延设备生长了掺铒SiO_x,观察到铒掺入的同时O的掺入效率也得到提高.铒可以促进氧的掺入的原因是铒与氧在硅衬底表面反应，以络合物形式掺入硅中，从而提高了硅中氧的浓度.测量了铒在SiO_x中的光致发光特性，结果表明掺铒的SiO_x的发光强度从18K到300K仅下降了约1/2，这说明Er掺在SiO_x中是一种降低发光强度的温度淬灭效应的途径，最后讨论了温度淬灭的机制. 关键词：