基于移动光晶格布洛赫振荡的原子干涉重力仪

针对目前传统的原子干涉重力仪—马赫-曾德尔型原子重力仪存在体积较大,影响设备便携性的问题,北京大学实现了国内首个基于移动光晶格的布洛赫振荡原理的小型化原子干涉重力仪。本实验系统的采样率达到0.9 Hz,能够满足长期实时测量的需求,且实验系统中原子的竖直位移约为3 cm,灵敏度达到4.6×10^(2)μGal·Hz^(-1/2),在2800 s积分时间内,分辨率可以达到6.5(0.7)μGal。实验成果为原子干涉重力仪的小型化与实用化指明了未来的发展方向。

基于频繁标引格的移动内容推荐方法研究

针对目前移动内容服务系统缺乏自动构建情境服务规则机制的问题，在情境化用户偏好本体模型的基础上，提出量化频繁标引格结构以建立用户内容偏好与情境之间的语义关联，为规则冲突问题和上下文数据可用性问题提供了解决方案。频繁标引格相对于频繁格进一步减少了产生规则所需的结点数目，更便于不同规则的提取和相关参数的计算。设计了频繁标引格分层构建的算法和推荐规则提取的优先级机制，通过实验验证了算法的有效性，并与相关方法进行了比较分析。

抓斗移动式格栅除污机在抽水泵站的应用研究

水资源污染已成为我们目前面临的新问题和新挑战,废水再利用成为解决水资源短缺的一项重要工程。我国为了满足人类生产生活用水的需求,大力兴建水坝、调水工程,来解决水资源的时空分布。同时,利用现代化的高科技,对污水进行处理,达到废水二次利用的目的。

Solving Electromagnetism Differential Equations Based on Random Walk

An approach of solving the finite difference equations with Monte Carlo method was presented. The accuracy of algorithm is guaranteed by the Central Limit Theorem. The computation of the value on each single node is independent of each other, which makes it easy to realize the algorithm in parallel processing and greatly improves the efficiency while dealing with local area computation. As long as different kinds of boundary conditions are statistics modeled,wide applications can the be made where the finite difference method is of competence.

Kinematics and dynamics analysis of a three-degree-of-freedom parallel manipulator

Kinematics and dynamics analyses were performed for a spatial 3-revolute joint-revolute joint-clylindric pair(3-RRC) parallel manipulator.This 3-RRC parallel manipulator is composed of a moving platform,a base platform,and three revolute joint-revolute joint-column pair chains which connect the moving platform and the base platform.Firstly,kinematics analysis for 3-RRC parallel manipulator was conducted.Next,on the basis of Lagrange formula,a simply-structured dynamic model of 3-RRC parallel manipulator was derived.Finally,through a calculation example,the variation of motorial parameters of this 3-RRC parallel manipulator,equivalent moment of inertia,driving force/torque and energy consumption was discussed.The research findings have important significance for research and engineering projects such as analyzing dynamic features,mechanism optimization design and control of 3-RRC parallel manipulator.

Characteristics of unsteady flow in porous media while considering threshold pressure gradient with Green＇s function

The flow behavior in porous media with threshold pressure gradient(TPG) is more complex than Darcy flow and the equations of motion, and outer boundary and inner boundary with TPG are also different from Darcy flow for unsteady flow of a producing well in a reservoir. An analytic method to solve this kind of problem is in a need of reestablishment. The classical method of Green's function and Newman product principle in a new way are used to solve the unsteady state flow problems of various shapes of well and reservoir while considering the TPG. Four Green's functions of point, line, band and circle while considering the TPG are achieved. Then, two well models of vertical well and horizontal well are built and simultaneously the function to calculate the moving boundary of each well model is provided. The results show that when considering TPG the pressure field is much different, which has a sudden pressure change, with a moving boundary in it. And the moving boundary of each well model increases with time but slows down rapidly, especially when the TGP is large.

Comparison of Improved Meshless Interpolation Schemes for SPH Method and Accuracy Analysis

In the smoothed particle hydrodynamics (SPH) method, a meshless interpolation scheme is needed for the unknown function in order to discretize the governing equation.A particle approximation method has so far been used for this purpose.Traditional particle interpolation (TPI) is simple and easy to do, but its low accuracy has become an obstacle to its wider application.This can be seen in the cases of particle disorder arrangements and derivative calculations.There are many different methods to improve accuracy, with the moving least square (MLS) method one of the most important meshless interpolation methods.Unfortunately, it requires complex matrix computing and so is quite time-consuming.The authors developed a simpler scheme, called higher-order particle interpolation (HPI).This scheme can get more accurate derivatives than the MLS method, and its function value and derivatives can be obtained simultaneously.Although this scheme was developed for the SPH method, it has been found useful for other meshless methods.

Research on Translation Gateway for IPv4/IPv6

In this paper, a model of translation gateway is proposed. The communications between IPv4 network and IPv6 network are realized by using the Microsoft intermediate driver technology in environment of Windows 2000.

论ナカヲ句节的格式化现象及其格标识ヲ的功能弱化问题

本文围绕句节的语法功能及其理论背景的格标识功能弱化问题进行了探讨,对有关该课题的代表性观点特别是杉本武的论说进行了重点介绍和剖析,并在此基础上,运用大量翔实语料,进行了质疑、分析、推论、验证。作为结论指出:杉本武的"状况格"说不具日语格关系中所显现出来的普遍意义和规律,句节和""等稳定形式一样,业已格式化。

Numerical Study on Influence of Key Parameters of Aerodynamic Characteristics of Shaftless Ducted Rotor

Shaftless ducted rotor(SDR)is a new type of ducted rotor system designed with ducted-rotor-motor integration,which is quite different from traditional ducted rotor(DR)in aerodynamic characteristics.The sliding mesh based on unstructured grid is used to simulate the aerodynamic characteristics of SDR and DR.Then,the effects of five key parameters,namely,the rotor disk height,the number of blades,the spread angle of the duct,the central hole radius and the ducted lip radius on the aerodynamic characteristics of the SDR are investigated.It is found that the same-sized SDR produces a larger total lift than the DR in hovering,but the lift proportion of its duct is reduced.In the forward flight,a large low-speed region is generated behind the SDR duct,and the reflux vortex in blade root above the advancing blade has the trend for inward diffusion.The rotor disk height has similar effects on SDR and DR.Increasing the number of blades can effectively increase the total lift of SDR,which also increases the lift proportion of duct.Increasing the spread angle of the duct will lead to the rotor lift coefficient decrease,reducing the central hole radius can increase the total lift,but the component lift coefficient decreases.Appropriately increasing the ducted lip radius can increase the total lift,which begins to decrease after reaching a certain value.

Style and Body Language in the Moving Image

Audio visual style has a complex multi-functionality and the important part of this deals with the way that the character body is visualized and how body language is implemented in the moving image. With a number of examples of contemporary film and television, the article will line up of key issues of body language in the moving image. This article describes two important aspects of body language in visual media--how visual style mediates the body expressions of fictional character and real persons in news on television and how aspects of the visual style always represent bodily presence in the moving image.

Numerical Evaluation of Longitudinal Motions of Wigley Hulls Advancing in Waves by Using Bessho Form Translating-Pulsating Source Green's Function

In the framework of 3D potential flow theory, Bessho form translating-pulsating source Green's function in frequency domain is chosen as the integral kernel in this study and hybrid source-and-dipole distribution model of the boundary element method is applied to directly solve the velocity potential for advancing ship in regular waves. Numerical characteristics of the Green function show that the contribution of local-flow components to velocity potential is concentrated at the nearby source point area and the wave component dominates the magnitude of velocity potential in the far field. Two kinds of mathematical models, with or without local-flow components taken into account, are adopted to numerically calculate the longitudinal motions of Wigley hulls, which demonstrates the applicability of translating-pulsating source Green's function method for various ship forms. In addition, the mesh analysis of discrete surface is carried out from the perspective of ship-form characteristics. The study shows that the longitudinal motion results by the simplified model are somewhat greater than the experimental data in the resonant zone, and the model can be used as an effective tool to predict ship seakeeping properties. However, translating-pulsating source Green function method is only appropriate for the qualitative analysis of motion response in waves if the ship geometrical shape fails to satisfy the slender-body assumption.

Research on Enterprise Mobile Office Platform based on Cloud Computing

This paper systematically analyzes the structure and function of mobile office system in cloud platform, puts forward the method how to blend the advantages of cloud computing to organically integrate mobile office scene. Firstly, this paper introduces the key technology of mobile OA platform based on cloud computing; secondly, this paper proposes the ideas of cloud computing middleware combination with original system, and on this basis, forming a mobile office architecture model based on cloud computing, gives the mobile office platform architecture scheme, combined with the actual development problems in some model specifications and solutions to build mobile office system based on cloud computing..

Developing Spline Based Overset Grid Assembling Approach and Application to Unsteady Flow Around a Moving Body

Overset or Chimera grid approach is one of methods to cope with complex geometries. A spline based overset grid assembling system has been developed. The system is based on structured grid approach and covers comprehensive features for overset assembling, i.e., grid generation, grid modification, and computing Domain Connectivity Information （DCI） for overset interpolation. Ferguson spline curve is used to compute curves through grid points and cell centers for trimming grids and computing DCI robustly and accurately. Flow simulation around Kriso Container Ship （KCS） with jointed grids shows good continuity of flow field between the grids. The overset grid assembling is enhanced to unsteady problem as dynamic overset approach coupled with a solver which also has been developed in National Maritime Research Institute, Japan. Computed results for pitchup spheroid are compared with measured data and show good agreement in unsteady force acting on the spheroid. It is confirmed that the system has capability to simulate flow field around jointed grids and unsteady flow with dynamic overset assembling approach practically.

TWO IMPROVED ALGORITHMS AND IMPLEMENTATION FOR A SINGULARLY PERTURBED PROBLEM ON MOVING MESHES

This paper applies a difference scheme to a singularly perturbed problem. The authors provide two algorithms on moving mesh methods by using Richardson extrapolation which can improve the accuracy of numerical solution. In traditional algorithms of moving meshes, the initial mesh is a uniform mesh. The authors change it to Bakhvalov-Shishkin mesh, and prove that it improves efficiency by numerical experiments. Finally, the results of the two algorithms are analyzed.

A fast integration method for translating-pulsating source Green＇s function in Bessho form

The singularities and oscillatory performance of translating-pulsating source Green＇s function in Bessho form were analyzed. Relative numerical integration methods such as Gaussian quadrature rule, variable substitution method （VSM）, and steepest descent integration method （SDIM） were used to evaluate this type of Green＇s function. For SDIM, the complex domain was restricted only on the 0-plane. Meanwhile, the integral along the real axis was computed by use of the VSM to avoid the complication of a numerical search of the steepest descent line. Furthermore, the steepest descent line was represented by the B-spline function. Based on this representation, a new self-compatible integration method corresponding to parametric t was established. The numerical method was validated through comparison with other existing results, and was shown to be efficient and reliable in the calculation of the velocity potentials for the 3D seakeeping and hydrodynamic performance of floating struc- tures moving in waves.

Climate change and contrasting plasticity in timing of a two-step migration episode of an Arctic-nesting avian herbivore

Greenland white-fronted geese Anser albifrons flavirostris wintering in Britain and Ireland migrate over the sea for 700-1200 km to stage 3-5 weeks in Iceland in spring, continuing a similar distance over the sea and Greenland Ice Cap to West Greenland breeding grounds. During 1969 to 2012, the geese advanced the mean departure date from Ireland by 15 days, during which time also they attained threshold fat stores earlier as well as departing in fatter condition. Over that period, Iceland spring-staging geese shifted from consuming underground plant storage organs to grazing managed hayfields, which provide fresh grass growth despite sub-zero temperatures, when traditional natural foods are inaccessible in frozen substrates. In 2012 and 2013, geese arrived three weeks earlier to Iceland, in fatter condition and accumulated fat significantly slower than in 1997-1999 and 2007. Although geese accumulated sufficient fat stores earlier in Iceland in 2007, 2012 and 2013, they departed around the same date as in 1997-1999, prolonging spring staging by three weeks. Plasticity in winter departure dates is likely due to improved winter feeding conditions （enabling earlier departure in better condition） and a novel predictable food resource in Iceland. Greenland white-fronted geese attained threshold fat stores in Iceland earlier, but remained rather than departing earlier to Greenland. Despite arriving earlier in Iceland, arrival dates on the breeding areas have not changed since the 1880s, presumably because of relatively constant cool springs and heavy snowfall in West Greenland during recent years [Current Zoology 60 （2）： 233-242, 2014].

Fabrication of Tailored Bragg Gratings by the Phase Mask Dithering/Moving Technique

The most relevant aspects related to the phase mask dithering/moving method for the fabrication of complex Bragg grating designs are reviewed. Details for experimental implementation of this technique is presented, including theoretical analysis of the calibration functions for the correct dither/displacement. Results from tailored Bragg grating structures fabricated by this method are shown. Apodized Bragg gratings with modeled spatial profiles were implemented, resulting in side mode suppression levels of more than 20 dB in gratings showing transmission filtering level higher than 30 dB. Chirped gratings with the spectral bandwidth up to 4 nm, π-shift and sampled Bragg gratings with equalized peaks equally spaced by 0.8 nm （100 GHz） were also fabricated.