Rapid Price Hike and Tumble of Cocoon Risks in Chinese Silk Industry

Back to 1994, a transient price hike of cocoon silk eventually led to a predicament for Chinese silk industry in the following years. A decade later, is that slump going to happen again?

Projected area and drag coefficient of high velocity irregular fragments that rotate or tumble

3 degrees of freedom(DOF)exterior ballistic computer models are used in fragment studies to calculate individual trajectories of each fragment based on drag coefficient and the projected(presented)area in the direction of velocity of center of mass.The expectation of a randomly distributed projected area is commonly used for fragments that tumble(random rotation)during flight.We forecast a model where the expected drag coefficient is dependent of shape and Mach number.Rotation or tumbling only affects the expected projected area.Models of projected areas during tumbling and rotation are presented.An examination of the data by Mc Cleskey(1988)indicates that the volume of the fragment to the power of2/3 is a better parameter to characterize the drag coefficient of the fragments than the maximum projected area.Hydrocode simulations are used to verify results and to study projected area and drag coefficient of fragments.

Lessons From a Stock Tumble

China's bullish stock market survived a startling "correction," when the benchmark Shanghai Composite Index witnessed a 15-percent drop from May 30 to June 5 this year. Zhao Xiao, professor at the University of Science and Technology Beijing, calls for a major play of market itself, in spite of irrational exuberance.

China Textile and Apparel Exports Tumbled 11.12% in Jan.-Jul.

Between January and July2009,China’s textile and clothing exports declined by 11.12% compared with a year ago to $91.464 billion and cotton products exports plummeted 0.97 compared to

宋元南戏与洛阳考论

宋元南戏既反映了古代洛阳的人文实况,又为洛阳增添了文学趣味。在《琵琶记》剧本中,洛阳承担着重要的空间背景任务,是作品安排场次的要点。《破窑记》虽经艺术处理,但作者依然把蒙正觅瓜的地点放在洛阳。宋元戏文佚曲不仅反映出唐宋时期汴、洛之间频繁的社会交往,体现了市民阶层新兴力量的道德追求,而且彰显了洛阳的园林景观之美,其盛况超过李格非《洛阳名园记》中的介绍。

两种视力表检查89位学龄前儿童视力的对比研究

目的比较学龄前儿童Lea Symbols与Tumbling E两种视力表的检测率、单眼视力值,建立3～4周岁儿童正常的视力值。方法招募温州市区29～53月龄的89名学龄前儿童,入选标准是身体一般情况良好,智力发育正常,除屈光不正外无其他眼病。以随机顺序用两种视力表检查儿童单眼视力,用间插的logMAR记分方法记录结果。招募23名成人志愿者,分别用两种视力表检查单眼视力,获得两者之间的换算关系。结果成人44眼Lea Symbols的平均视力比Tumbling E高0.02 logMAR。89名儿童Lea Symbols视力表的检测率为88%,而Tumbling E视力表的检测率为65%,统计学分析两者差异有显著性(P<0.01)。60位儿童中115眼能同时配合查Lea Symbols与Tumbling E,Lea Symbols的平均视力为0.17±0.09,TumblingE的平均视力为0.25±0.09,两者作配对t检验差异具有显著性(P<0.01)。两种视力表视力相关性高(r=0.73,P<0.01),两种视力表视力差值不随视力水平的改变而变化(P=0.60)。正常屈光状态下儿童Lea Symbols平均视力0.16±0.07(120眼),Tumbling E的平均视力0.23±0.07(91眼)。结论Lea Symbols视力表和Tumbling E视力表是测量视力可靠且有效的方法,检查4周岁以下儿童的视力时首选LeaSymbol视力表。与Tumbling E视力表相比,Lea Symbol视力表过高估计视力,原因可能在于两种视力表的不同设计以及儿童的认知水平差异。

Comparative Analysis of a Rare Autumn Rainstorm and a Spring Rainstorm in Xiamen Area

According to Ouyang potential temperature V-3θ charts, a rare autumn rainstorm in Xiamen on November 18, 2011 was compared with a spring rainstorm on March 29, 2005 firstly, and then the main characteristics of the autumn rainstorm were analyzed based on wind profiler data of Doppler weather radar. The results showed that ultra-low temperature on the top of the troposphere was more obvious in autumn than that in spring; clockwise tumble effect was distinct and warm and wet layer reached 300 hPa in both spring and autumn. Clockwise tumble effect appeared in various forms in autumn and spring. That is, the wind blew from the east at low altitudes and the west at high altitudes before the autumn rainstorm oc- curred; when the maximum wind speed appeared at 500 hPa, heavy rainfall occurred. During the spring rainstorm process, wind direction was con- sistent at each level and wind speed increased with the rise of altitude during early days. Afterwards, the wind blew from the east at low altitudes and the west at high altitudes. During the autumn rainstorm process, the heavy rainfall at the first stage was closely related to thickness of the 20 m/s wind speed layer at 3 -5 km. If the thickness declined sharply when the 20 m/s wind speed layer expended downwards, heavy rainfall would occur soon afterwards. Moreover, the precipitation intensity weakened immediately as the 20 m/s wind speed layer began to be stable. The heavy rainfall at the second stage was closely related to thickness of the 24 m/s wind speed layer, and the appearance, development and weakening of the 24 m/s wind speed layer foreboded the occurrence of heavy rainfall. Moreover, the thickness of the 24 m/s wind speed layer decreased to the minimum, and then heavy rainfall would appear soon afterwards. Hereafter, the thickness increased and then decreased again.

The Influence of Inflow Condition on the Generation of Tumbling Flow Using Detached Eddy Simulation

One of the objectives of car manufacturers is to improve engine performance, reduce consumption reduce emissions. To achieve this objective, it is important to understand the phenomena involved in the combustion chambers of engines. These phenomena are numerous and complex in nature such: the aerodynamics, fuel-air mixture, turbulence, combustion and the cycle to cycle instabilities that cause more problems. One of the factors responsible for the phenomenon of cycle to cycle variations is the instability of the characteristics of the vortex flow Tumble. This instability may be due to changes in initial conditions. This study is achieved in order to contribute in a better understanding of engine flow by using a Detached Eddy Simulation Shear-Stress Transport (DES SST) model, which is a hybrid RANS/LES model. These simulations have been performed with the commercial CFD (computational fluid dynamic) code (FLUENT) coupled with our own development based on UDF facilities given by FLUENT. To explore the suitability of the 3D DES STT to simulate the internal flow, the calculation is performed for a model tumbling flow at constant volume. This flow has been measured in an experimental set up and measurements are used to initiate and to validate simulations. For this case study, we consider simplified engine geometry. To generate tumbling motion, we use non-reacting DES with a single cycle (SC) strategy. Also, with this strategy we study the effect of initial conditions on the instabilities that accompany a vortex type tumble.

Dual-quaternion-based modeling and control for motion tracking of a tumbling target

This paper investigates the problem of controlling a chasing spacecraft(chaser)to track and rendezvous with an uncontrolled target.Based on the actual situation,the torque-free motion of an axisymmetric prolate rigid body is employed to represent the short-term attitude motion of the tumbling target.By taking advantage of the dual quaternion’s compact and efficient description of the general rigid motion,the coupled and integrated model of the 6-degree-of-freedom(6-DOF)relative motion between the chaser and the tumbling target is derived in the chaser’s body fixed frame after taking full consideration of coordinate transformation.Based on the logarithm of dual quaternion,a sliding mode control(SMC)law based on the exponential reaching law and the continuous relay function is brought forward to address the problem of synchronization control of the 6-DOF relative motion.Simulation results illustrate the effectiveness of the proposed method.

Nonlinear suboptimal tracking control of spacecraft approaching a tumbling target

We investigate the close-range relative motion and control of a spacecraft approaching a tumbling target. Unlike the traditional rigid-body dynamics with translation and rotation about the center of mass（CM）, the kinematic coupling between translation and rotation is taken into consideration to directly describe the motion of the spacecraft＇s sensors or devices which are not coincident with the CM. Thus, a kinematically coupled 6 degrees-of-freedom（DOF） relative motion model for the instrument（feature point） is set up. To make the chaser spacecraft＇s feature point track the target＇s, an optimal tracking problem is defined and a control law with a feedback-feedforward structure is designed. With quasi-linearization of the nonlinear dynamical system, the feedforward term is computed from a specified constraint about the dynamical system and the reference model, and the feedback action is derived starting from the state-dependent Ricca equation（SDRE）. The proposed controller is compared with an existing suboptimal tracking controller, and numerical simulations are presented to illustrate the effectiveness and superiority of the proposed method.

New conception in continuum theory of constitutive equation for anisotropic crystalline polymer liquids

A new continuum theory of the constitutive equation of co-rotational derivative type is developed for anisotropic viscoelastic fluid—liquid crystalline (LC) polymers. A new concept of simple anisotropic fluid is introduced. On the basis of principles of anisotropic simple fluid, stress behaviour is described by velocity gradient tensor and spin tensor instead of the velocity gradient tensor in the classic Leslie—Ericksen continuum theory. Analyzing rheological nature of the fluid and using tensor analysis a general form of the constitutive equ- ation of co-rotational type is established for the fluid. A special term of high order in the equation is introduced by author to describe the sp- ecial change of the normal stress differences which is considered as a result of director tumbling by Larson et al. Analyzing the experimental results by Larson et al., a principle of Non- oscillatory normal stress is introduced which leads to simplification of the problem with relaxation times. The special behaviour of non- symmetry of the shear stress is predicted by using the present model for LC polymer liquids. Two shear stresses in shear flow of LC polymer liquids may lead to vortex and rotation flow, i.e. director tumbling in the flow. The first and second normal stress differences are calculated by the model special behaviour of which is in agree- ment with experiments. In the research, the com- putational symbolic manipulation such as computer software Maple is used. For the anisotropic viscoelastic fluid the constitutive equation theory is of important fundamental significance.

Manifestation of Color Confinement in the YY Model for Atomic Nuclei

In this paper, a manifestation of the well-known color confinement from the QCD (quantum chromodynamics) in the newly developed YY model for the atomic nucleus is presented. There is a wonderful correspondence between the structural requirements from the YY model and some elementary properties of the color dynamics from QCD. The open questions in the YY model, namely the holding forces for triple nodes and for pairing space links, are exactly covered by the three-color compensation or by the paired color anti-color balance. We will see what colors and anti-colors do mean in the YY model, how up quarks and down quarks get assigned a color or anti-color. We will discover some relationships between gluon-based interactions as described in the standard model and pairing space links in the YY model.

山本裕典

山本裕典的红发，不仅让他在电视剧《Tumbling》星魅力无限．夺人眼球．也给他带来了夏日的旺盛人气。娱乐秀、学园祭．甚至还有舞台剧．到处都是山本裕典忙碌的身影，丰富的活动也让喜欢他的fans应接不暇。

Lea Symbols与Tumbling E视力表在学龄前儿童视力检查中的应用

目的比较LeaSymbols视力表与TumblingE视力表在学龄前儿童中视力的检测率、视力值和双眼间视力差异。方法对温州市某幼儿园一小班24名36～50(平均43.2±3.71)个月的儿童以随机顺序先后用LeaSymbols与TumblingE视力表检查单眼视力,视力值用logMAR记录方法来表示,用logMAR单位记录双眼视力差异。结果Leasymbols视力表的检测率为96%,Tum-blingE视力表的检测率为71%,其中33只眼能配合查Leasymbols与TumblingE,TumblingE的视力为0.26±0.10,Leasymbols的视力为0.19±0.10,两者呈线形相关(相关系数r=0.76),两者作配对t检验有显著性差异(t=6.068,p<0.0001),16名儿童用LeaSymbols测得的双眼视力差别为-0.004±0.065,用TumblingE测得的双眼视力差别为-0.019±0.067,两者呈线形相关(相关系数r=0.65),统计学分析两者无显著性差异(p=0.296)。结论Leasymbols视力表检查学龄前儿童视力特别是3～4周岁的儿童检测率高,LeaSymbols与TumblingE视力表一样能够很好地反映双眼间视力的差别,但与TumblingE视力表相比,LeaSymbols视力表存在过高估计视力的可能。视力的测定是个心理物理学过程,对于学龄前儿童,我们不能简单地根据视力小于0.8判断其弱视,而是要从儿童的认知水平来考虑。

Area-oriented coordinated trajectory planning of dual-arm space robot for capturing a tumbling target

The growing amount of space debris poses a threat to operational spacecraft and the long-term sustainability of activities in outer space. According to the orbital mechanics, an uncontrolled space object will be tumbling, bringing great challenge to capture and remove it. In this paper, a dual-arm coordinated ‘‘Area-Oriented Capture'(AOC) method is proposed to capture a non-cooperative tumbling target. Firstly, the motion equation of the tumbling target is established, based on which, the dynamic properties are analyzed. Then, the ‘‘Area-Oriented Capture'concept is presented to deal with the problem of large pose(position and attitude) deviation and tumbling motion. An area rather than fixed points/devices is taken as the object to be tracked and captured. As long as the manipulators’ end-effectors move to a specified range of the objective areas(not fixed points on the target, but areas), the target satellite will be hugged by the two arms.At last, the proposed method and the traditional method(i.e. fixed-point oriented capture method)are compared and analyzed through simulation. The results show that the proposed method has larger pose tolerance and takes shorter time for capturing a tumbling target.

Detumbling strategy based on friction control of dual-arm space robot for capturing tumbling target

The rotational motion of a tumbling target brings great challenges to space robot on successfully capturing the tumbling target.Therefore,it is necessary to reduce the target's rotation to a rate at which capture can be accomplished by the space robot.In this paper,a detumbling strategy based on friction control of dual-arm space robot for capturing tumbling target is proposed.This strategy can reduce the target's rotational velocity while maintaining base attitude stability through the establishment of the rotation attenuation controller and base attitude adjustment controller.The rotation attenuation controller adopts the multi-space hybrid impedance control method to control the friction precisely.The base attitude adjustment controller applies the dual-arm extended Jacobian matrix to stabilize the base attitude.The main contributions of this paper are as follows:(1)The compliant control method is adopted to achieve a precise friction control,which can reduce the target angular velocity steadily;(2)The dual-arm extended Jacobian matrix is applied to stabilize the base attitude without affecting the target capture task;(3)The detumbling strategy of dualarm space robot is designed considering base attitude stabilization,realizing coordinated planning of the base attitude and the arms.The strategy is verified by a dual-arm space robot with two 7-DOF(degrees of freedom)arms.Simulation results show that,target with a rotation velocity of 20(°)/s can be effectively controlled to stop within 30 s,and the final deflection of the base attitude is less than 0.15°without affecting the target capture task,verifying the correctness and effectiveness of the strategy.Except to the tumbling target capture task,the control strategy can also be applied to other typical on-orbit operation tasks such as space debris removal and spacecraft maintenance.

Composite anti-disturbance position and attitude control for spacecrafts with parametric uncertainty and flexible vibration

The rendezvous and proximity operations with respect to a tumbling non-cooperative target pose high requirement for the position and attitude control accuracy of servicing spacecraft.However,multiple disturbances including parametric uncertainties,flexible vibration,and unknown nonlinear dynamics degrade the control performance significantly.In order to enhance the system anti-disturbance ability,this paper proposes a composite anti-disturbance control law for the spacecraft position and attitude tracking.Firstly,the relative position and attitude dynamic models with multiple disturbances are established,where the refined descriptions of multiple disturbances are accomplished based on their characteristics.Then,by combining a dual Disturbance ObserverBased Control(DOBC)and a sliding mode control,a composite controller with hierarchical architecture is proposed,where the dual DOBC in the feedforward channel is used to reject the flexible vibration,environment disturbance,and complicated nonlinear dynamics,while the parametric uncertainties are attenuated by the sliding mode control in the feedback channel.Stability analysis is carried out for the closed-loop system by unifying the sliding mode dynamics and observer dynamics.Finally,the effectiveness of the proposed controller is verified via numerical simulation and hardware-in-the-loop test.

Numerical Simulations of Hydrodynamics of Nematic Liquid Crystals:Effects of Kinematic Transports

In this paper,we investigate the effects of kinematic transports on the nematic liquid crystal system numerically and theoretically.The model we used is a"1+2"elastic continuum model simplified from the Ericksen-Leslie system.The numerical experiments are carried out by using a Legendre-Galerkin spectral method which can preserve the energy law in the discrete form.Based on this highly accurate numerical approach we find some interesting and important relationships between the kinematic transports and the characteristics of the flow.We make some analysis to explain these results.Several significant scaling properties are also verified by our simulations.

Numerical Investigation of Tumbling Phenomena Based on a Macroscopic Model for Hydrodynamic Nematic Liquid Crystals

This paper is concerned with the numerical investigation of a macroscopic model for complex fluids in“1+2”dimension case.We consider the planar pressure driven flow where the direction of the molecules is constrained in the shear plane.The modified Crank-Nicolson finite difference scheme satisfying a discrete energy law will be developed.By using this scheme,it is observed numerically that the direction of the molecules will tumble from the boundary layer and later on the inner layer with a much longer time period.This is consistent with the theoretical prediction.Moreover,we find some complex phenomena,where the tumbling rises from boundary layer and is then embedded into the interior area more clearly when the viscosity coefficientµof the macro flow has a larger value.The norm of the molecular director d will endure greater change as well.This implies that the viscosity of flow plays the role of an accelerator in the whole complex fluids.Comparing these results with the theoretical analysis,we can find that the gradient of the velocity has direct impact on the tumbling phenomena.These results show that the proposed scheme is capable of exploring some physical phenomena embedded in the macro-micro model.

Tumbling dynamics of individual absorbed polymer chains in shear flow

The tumbling dynamics of individual absorbed polymer chains in shear flow is studied by employing multi-particle collision dynamics simulation techniques combined with molecular dynamics simulations.We find that the dependence of tumbling frequencies on shear rate is independent of both adsorption strength and surface corrugate.