超小水线面单体船波浪载荷确定方法探讨

通过分析波浪和船体的相对位置,利用微段载荷求和的方法计算静波浪载荷,提出超小水线面单体船的波浪载荷计算方法,实例计算表明在静水平衡状态的基础上,可以有效地计算其静波浪载荷,为超小水线面单体船的研究提供参考。

超长细比设计钢板肋杆件跨单体结构悬浮全隐框玻璃幕墙系统施工技术

本文针对北京泰康健康管理研究中心的悬浮幕墙施工过程抗结构变形和温度变形等结构特点和施工难度,详细阐述设计攻关、超长超薄钢板起吊安装方法、超钢结构长细比设计杆件吊装后调直及结构变形控制等关键技术及难点,并通过对施工全过程有限元仿真分析证明,该技术高效、合理,实操性强。

超分子聚合物制备新方法:超分子单体的共价聚合

超分子聚合物是超分子化学与高分子化学交叉的前沿研究领域,近年来受到了国内外研究学者的广泛关注.可控制备超分子聚合物对于研究超分子聚合物的结构与性能关系、设计合成特定功能的超分子聚合物具有重要的意义.本文将总结通过超分子单体的共价聚合反应以制备超分子聚合物的方法.不同于传统的制备超分子聚合物的方法,超分子单体的共价聚合方法将不易调控的非共价聚合转化为可控的共价聚合,为实现超分子聚合物的可控制备提供了新思路.

UItrastructural Observation on Rat Spermatozoa Treatedwith Tripchlorolide(T_4) from Tripterygium wilfordii

Adult male rats were treated orally with monomer T_4(Tripchlorolide) isolated from Tripterygium wilfordii, at the dose of 50μg/kg/day,6 days/week for6 weeks.Ultrathin section and freeze etching replica of seminiferous tubules and epididymal spermatozoa were examined with elec-tron microscope. The results showed that the spemiogenesis was inhibited T_4 in seminiferous tu-bules. However,the damage and disruption of the spermatozoa were more serious in the epididymis.Damage of the structure and function ot microtubule and microfilament may be the chief reason for sperm damage. Sperm membrane was also very sensitive to the treatiment of monomer T_4.

三洋VPC-G250,移动拍摄能手

日本三洋公司新近推出的VPC—G250新款数码相机是一款颇有特色的产品。VPC—G250可拍摄带声音的移动场面,这时一种“动画摄影”功能。VPC—G250采用新开发的超单体式LSI(大规模集成电路),凭借高速硬件进行图像处理。如果使用标准画质模式(320x240点),可进行最长达5秒钟(10张/秒)的移动场面拍摄。这些图像可以在照相机内进行图像再生,而且还能在照相机内直接做成AVI文件,无需进行文件变换,便可在电脑上播放。VPC—G250配有声音记录功能,能够在Internet主页上剪贴带声音的移动场面,或使用AV输出端子。

Effects of directional solidification parameters and crystal selector on microstructure of single crystal of Ni-base superalloys

The single crystal of nickel-base super alloy is widely used for making turbine blades.The microstructure of the alloy,especially the deviation of preferred orientation of single crystal,possesses the most important effects on the mechanical properties of the blades.In this study,the single crystal ingot and blade of DZ417G alloy are prepared by means of the spiral crystal selector as well as the directional solidification method,and the effect of the parameters(i.e.,the shape of samples,the withdrawal rate)and the structure of the spiral crystal selector on the formation of single crystal and the crystal orientation are investigated.This method can prepare not only the single crystal ingot with simple shape but also the single crystal blades with the complex shape,the simple with rod-shape can form the single crystal easily with a relatively fast withdrawal rate,but the blade with complex shape requires much slower withdrawal rate to form single crystal.The length of the crystal selector almost has no effect on the crystal orientation.However,the angle of selector plays an obvious role on the orientation;the selector with a smaller angle can effectively reduce the deviation of preferred orientation;the appropriate angle of selector to obtain optimal orientation is found to be around30°and the deviation of preferred orientation is about30°for this selector.

Direct Vibrational Energy Transfer in Monomeric Water Probed with Ultrafast Two Dimensional Infrared Spectroscopy

Vibrational relaxation dynamics of monomeric water molecule dissolved in d-chloroform solution were revisited using the two dimensional Infrared （2D IR） spectroscopy. The vibrational lifetime of OH bending in monomeric water shows a bi-exponential decay. The fast compo- nent （T1=（1.2±0.1） ps） is caused by the rapid population equilibration between the vibrational modes of the monomeric water molecule. The slow component （T2=（26.4±0.2） ps） is mainly caused by the vibrational population decay of OH bending mode. The reorientation of the OH bending in monomeric water is determined with a time constant of t=（1.2±0.1） ps which is much faster than the rotational dynamics of water molecules in the bulk solution. Furthermore, we are able to reveal the direct vibrational energy transfer from OH stretching to OH bending in monomeric water dissolved in d-chloroform for the first time. The vibrational coupling and relative orientation of transition dipole moment between OH bending and stretching that effect their intra-molecular vibrational energy transfer rates are discussed in detail.

NiFe alloy particles doping effect of Gd-Ba-Cu-O bulks processed by a new cold-seeding technology

The process of cold seeding melt growth of GdBa2Cu3Oy （Gd123） bulk superconductors using NdBa2Cu3Oy （Nd123） thin films was reported. In addition, a novel cold seeding concept of combining MgO crystal and buffer pellet was also introduced. The misorientation caused by the lattice mismatch between MgO and Gd123 melt was overcome by choosing suitable heat treatment program and Gd2BaCuO5 （Gd211） content of the buffer pellet. The doping effect of soft ferromagnetic NiFe alloy particles was also reported. The bulk sample with 0.4% （mole fraction） doping amount shows the best performance on the flux trapping. The critical current density is largely enhanced under the external field of 1-2 T, which is promising for large-scale applications. This effect is originated from the substitution of Fe and Ni ions for the Cu sites contributing to magnetic flux pinning.

Fluid flow characteristics of single inclined circular jet impingement for ultra-fast cooling

The fluid flow characteristics of the single bunch inclined jet impingement were investigated with different jet flow velocities,nozzle diameters,jet angles and jet-to-target distances for ultra-fast cooling technology.The results show that the peak pressure varying significantly from nearly 0.5 to above 13.4 kPa locates at the stagnation point with different jet diameters,and the radius of impact pressure affected zone is small promoted from 46 to 81 mm in transverse direction,and 50 to 91 mm in longitude direction when the jet flow velocity changes from 5 to 20 m/s.However,the fluid flow velocity is relatively smaller near the stagnation point,and increases gradually along the radius outwards,then declines.There is an obvious anisotropic characteristic that the flow velocity component along the jet direction is about twice of the contrary one where the jet anlge is 60°,jet diameter is 5 mm,jet length is 8 mm and jet height is 50 mm.

Fractal Interpretation of Ultrasonic Crystallization of Solutions

Experiments were performed on the crystallization of a CuSO4 solution upon the action of the temperature gradient with the forming of mono crystals three wedges crystal system （prisms）. We found that the fractal dimension of crystals equals 2.45, which is consistent with the literature data. Crystal growth is represented as the N-rd translation of each side of the crystal lattice with its own speed and with relation to the formation of similar structures--fractals. A mathematical model of ultrasonic crystallization of a CuSO4 solution was proposed. The model is based on the combined use of differential transport equations of momentum, mass, energy and sound waves and a method of similarity and dimensional analysis. The calculated formulas for the concentration of Ccr, the equivalent diameter of the formed crystals dcr and the intensity of internal energy source Ф, associated with the interaction of crystals with the hydro mechanical, heat and sound fields were obtained. Fractal interpretation of ultrasonic crystallization of the CuSO4 solution was made. It was found that on the growth of crystal size d^r directly affects translation N, i.e., an increase in the number of sets of crystals of infinitely small size e, correspond to the size of the crystal lattice. In turn, translation of crystals depends on the geometry of the crystallizer and the physical parameters of external force fields, acting on the CuSO4 solution. A connection of results of the mathematical modeling with the results of fractal analysis of the ultrasonic crystallization of solutions was established.

可回收的交联超分子聚脲材料

热固性塑料的共价交联网络结构赋予了材料优异的力学性能和尺寸稳定性,但也使其难以再加工及循环利用.废弃的热固性塑料造成了严重的资源浪费和环境污染.最近,清华大学徐江飞、张希及合作者通过超分子单体的共聚合,将低含量的多重氢键基元引入交联聚合物的主链中,制备了可回收的交联超分子聚脲材料.这一材料既保有了交联聚合物的优良力学性能,又充分利用了超分子聚合物动态可逆的特点,使其具有了可回收和可再生的性质.该项研究的分子设计思路简洁精美,可用于制备不同的交联聚合物,有望成为具有一定普遍意义的循环再利用材料设计的新策略.

POSS-embedded supramolecular hyperbranched polymers constructed from a 1→7 branching monomer with controllable morphology transitions

The research on the supramolecular hyperbranched polymers(SHPs) that combines the advantages of supramolecular polymer and hyperbranched architecture has attracted considerable interests in many applications. Here we demonstrate a simple approach to prepare POSS-embedded supramolecular hyperbranched polymers(POSS-SHPs) with varied morphology and size by controlling monomer concentration and mixed solvents. The SHPs formations can further transfer into the core-shell structured micelles by addition of competitive guests based on the double supramolecular driving forces.

Growth of Sr_2CuO_(3+δ) superconductor single crystals at high pressure

We have successfully synthesized Sr 2 CuO3+δ single crystals under high pressure and high temperature for the first time. The structure analysis show that this material crystallizes into tetragonal structure isostructural La 2 CuO4 with single CuO 2 plane. The magnetic susceptibility as well as resistance measurements indicates that the bulk superconductivity with the critical transition temperature 37 K is achieved in the crystal.

Robust superconductivity and transport properties in (Li_(1-x)Fe_x)OHFeSe single crystals

The recently discovered(Li_(1-x) Fe_x)OHFe Se superconductor with T c about 40 K provides a good platform for investigating the magnetization and electrical transport properties of Fe Se-based superconductors. By using a hydrothermal ion-exchange method,we have successfully grown crystals of(Li_(1-x) Fe_x)OHFe Se. X-ray diffraction on the sample shows the single crystalline Pb O-type structure with the c-axis preferential orientation. Magnetic susceptibility and resistive measurements show an onset superconducting transition at around T c=38.3 K. Using the magnetization hysteresis loops and Bean critical state model, a large critical current J s is observed in low temperature region. The critical current density is suppressed exponentially with increasing magnetic field.Temperature dependencies of resistivity under various currents and fields are measured, revealing a robust superconducting current density and bulk superconductivity.

Introduction to holographic superconductor models

In the last years it has been shown that some properties of strongly coupled superconductors can be potentially described by classical general relativity living in one higher dimension,which is known as holographic superconductors.This paper gives a quick and introductory overview of some holographic superconductor models with s-wave,p-wave and d-wave orders in the literature from point of view of bottom-up,and summarizes some basic properties of these holographic models in various regimes.The competition and coexistence of these superconductivity orders are also studied in these superconductor models.

FeTe1-xSex monolayer films： towards the realization of high-temperature connate topological superconductivity

We performed angle-resolved photoemission spectroscopy studies on a series of FeTe_(1-x)Se_x monolayer films grown on Sr TiO_3.The superconductivity of the films is robust and rather insensitive to the variations of the band position and effective mass caused by the substitution of Se by Te.However,the band gap between the electron-and hole-like bands at the Brillouin zone center decreases towards band inversion and parity exchange,which drive the system to a nontrivial topological state predicted by theoretical calculations.Our results provide a clear experimental indication that the FeTe_(1-x)Se_x monolayer materials are high-temperature connate topological superconductors in which band topology and superconductivity are integrated intrinsically.

A note on the entropy of mean curvature flow

The entropy of a hypersurface is given by the supremum over all F-functionals with varying centers and scales, and is invariant under rigid motions and dilations. As a consequence of Huisken's monotonicity formula, entropy is non-increasing under mean curvature flow. We show here that a compact mean convex hypersurface with some low entropy is diffeomorphic to a round sphere. We also prove that a smooth selfshrinker with low entropy is a hyperplane.