美国信息能力在线测评SAILS和TRAILS简介

美国肯特州立大学设计的信息素养能力标准评估项目SAILS和信息素养能力实时测评量表TRAILS,可用于评估大、中学生的信息知识和能力水平。作为标准化测试项目,它们具有较高的信度和效度,实施管理简便,能提供内部和外部评价比较。

THE RESEARCH OF INCREASING LIFT ANDREDUCING DRAG FOR WING-TIP SAILS

ased on Quasi-Vortex-Lattiee method, a program is presented to com-pute the aerodynamic forces for nonplanar wing with wing-tip sails. By using thisprogram, the aerodynamic force is calculated and the sails are designed for an aircraftwith rectangular wing of 8.6 aspect ratio. The calculation results show that thosewing-tip sails, whose total area is 3. 1 percent of the aircraft’s basic wing area, will haveremarkable effect on reducing induced drag, and the lift-dependent drag factor can bereduced by about 18.5 to 21 .5 percent. Wind tunnel tests are conducted in NH-2 windtunnel of Nanjing Aeronautical and Astronautical University, and the results demon-strate the correctness of the above calculation results. The influences of sail parameterson performance and handling qualities of aircraft are also analyzed.

Time-optimal rendezvous transfer trajectory for restricted cone-angle range solar sails

The advantage of solar sails in deep space exploration is that no fuel consumption is required. The heliocentric distance is one factor influencing the solar radiation pressure force exerted on solar sails. In addition, the solar radiation pressure force is also related to the solar sail orientation with respect to the sunlight direction. For an ideal flat solar sail, the cone angle between the sail normal and the sunlight direction determines the magnitude and direction of solar radiation pressure force. In general, the cone angle can change from 0° to 90°. However, in practical applications, a large cone angle may reduce the efficiency of solar radiation pressure force and there is a strict requirement on the attitude control. Usually, the cone angle range is restricted less more than an acute angle （for example, not more than 40°） in engineering practice. In this paper, the time-optimal transfer trajectory is designed over a restricted range of the cone angle, and an indirect method is used to solve the two point boundary value problem associated to the optimal control problem. Relevant numerical examples are provided to compare with the case of an unrestricted case, and the effects of different maximum restricted cone angles are discussed. The results indicate that （1） for the condition of a restricted cone-angle range the transfer time is longer than that for the unrestricted case and （2） the optimal transfer time increases as the maximum restricted cone angle decreases.

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.

A Study on a Vessel with Multiple Flat and Hard Sails to Keep Service Speed in High Winds

Ships which have large structures above water surface,such as pure car carriers(PCCs) and container vessels,have large speed reduction by wind pressure.In the present study,the running speed of a large PCC with two or more sails for using wind power is simulated.The simulated results demonstrate that the ship can keep a constant service speed even in winds of 20m/s except head and bow winds.This sail system can shorten annual average navigation time by about 4 hours per voyage.

Displaced orbits generated by solar sails for the hyperbolic and degenerated cases

Displaced non-Keplerian orbits above planetary bodies can be achieved by orientating the solar sail normal to the sun line. The dynamical systems techniques are employed to analyze the nonlinear dynamics of a displaced orbit and different topologies of equilibria are yielded from the basic configurations of Hill＇s region, which have a saddlenode bifurcation point at the degenerated case. The solar sail near hyperbolic or degenerated equilibrium is quite unstable. Therefore, a controller preserving Hamiltonian structure is presented to stabilize the solar sail near hyperbolic or degenerated equilibrium, and to generate the stable Lissajous orbits that stay stable inside the stabilizing region of the controller. The main contribution of this paper is that the controller preserving Hamiltonian structure not only changes the instability of the equilibrium, but also makes the modified elliptic equilibrium become unique for the controlled system. The allocation law of the controller on the sail＇s attitude and lightness number is obtained, which verifies that the controller is realizable.

Quasi-periodic orbits of small solar sails with time-varying attitude around Earth–Moon libration points

This paper proposes new quasi-periodic orbits around Earth–Moon collinear libration points using solar sails.By including the time-varying sail orientation in the linearized equations of motion for the circular restricted three-body problem(CR3BP),four types of quasi-periodic orbits(two types around L1 and two types around L2)were formulated.Among them,one type of orbit around L2 realizes a considerably small geometry variation while ensuring visibility from the Earth if(and only if)the sail acceleration due to solar radiation pressure is approximately of a certain magnitude,which is much smaller than that assumed in several previous studies.This means that only small solar sails can remain in the vicinity of L2 for a long time without propellant consumption.The orbits designed in the linearized CR3BP can be translated into nonlinear CR3BP and high-fidelity ephemeris models without losing geometrical characteristics.In this study,new quasi-periodic orbits are formulated,and their characteristics are discussed.Furthermore,their extendibility to higher-fidelity dynamic models was verified using numerical examples.

Optimal interplanetary trajectories for Sun-facing ideal diffractive sails

A diffractive sail is a solar sail whose exposed surface is covered by an advanced diffractive metamaterial film with engineered optical properties. This study examines the optimal performance of a diffractive solar sail with a Sun-facing attitude in a typical orbit-to-orbit heliocentric transfer. A Sun-facing attitude, which can be passively maintained through the suitable design of the sail shape, is obtained when the sail nominal plane is perpendicular to the Sun–spacecraft line. Unlike an ideal reflective sail, a Sun-facing diffractive sail generates a large transverse thrust component that can be effectively exploited to change the orbital angular momentum. Using a recent thrust model, this study determines the optimal control law of a Sun-facing ideal diffractive sail and simulates the minimum transfer times for a set of interplanetary mission scenarios. It also quantifies the performance difference between Sun-facing diffractive sail and reflective sail. A case study presents the results of a potential mission to the asteroid 16 Psyche.

美国信息素质标准化评价工具SAILS的设计开发及对我国信息素质教育的借鉴作用

我国大学生信息素质能力标准和评价体系的研究日益受到关注,而针对评价指标设计和开发可操作性强的测试工具尚未引起足够的重视。美国在此领域起步较早,目前信息素质标准化评价工具SAILS开发较完善且已普遍推广。本文重点介绍该评价工具的设计理念、开发过程和测试原理,展示其科学严谨的开发流程及优势特色,同时探讨其对我国设计开发类似的信息素质标准化测评系统的启示,并以英语文学专业学生的信息素质评价及其对于提高学生研究能力的指标为例来说明其在我国应用于具体学科专业的可行性和设想。

COSCO Sails on

China Ocean Shipping Group Co. gears up to navigate the global financial storm Global shippers are experiencing some aches and pains as the

Dynamic analysis of spinning solar sails at deployment process

The spinning deployment process of solar sails is analyzed in this study. A simplified model is established by considering the out-of-plane and in-plane motions of solar sails. The influences of structure parameters, initial conditions, and feedback control parameters are also analyzed.A method to build the geometric model of a solar sail is presented by analyzing the folding process of solar sails. The finite element model of solar sails is then established, which contains continuous cables and sail membranes. The dynamics of the second-stage deployment of solar sails are simulated by using ABAQUS software. The influences of the rotational speed and out-of-plane movement of the hub are analyzed by different tip masses, initial velocities, and control parameters.Compared with the results from theoretical models, simulation results show good agreements.

Angular velocity determination of spinning solar sails using only a sun sensor

The direction of the sun is the easiest and most reliable observation vector for a solar sail running in deep space exploration. This paper presents a new method using only raw measurements of the sun direction vector to estimate angular velocity for a spinning solar sail. In cases with a constant spin angular velocity, the estimation equation is formed based on the kinematic model for the apparent motion of the sun direction vector; the least-squares solution is then easily calculated. A performance criterion is defined and used to analyze estimation accuracy. In cases with a variable spin angular velocity, the estimation equation is developed based on the kinematic model for the apparent motion of the sun direction vector and the attitude dynamics equation. Simulation results show that the proposed method can quickly yield high-precision angular velocity estimates that are insensitive to certain measurement noises and modeling errors.

Feasibility analysis of the angular momentum reversal trajectory via hodograph method for high performance solar sails

In this paper a new phase space of hodograph method is adopted to investigate and better understand the two-dimensional angular momentum reversal(H-reversal) trajectories for high performance solar sails within a fixed cone angle.As the hodograph method and the H-reversal trajectory are not very common,both of them are briefly introduced.The relationship between them are constructed and addressed with a sample trajectory.How the phase space varies according to the sail quality and the fixed sail cone angle is also studied.Through variation of the phase space,the minimum sail lightness number can be obtained by solving a set of algebraic equations instead of a parameter optimization problem.For a given sail lightness number,there are three types of the two-dimensional possible heliocentric motion,including the spiral inward trajectories towards the Sun,the H-reversal trajectories and the directly outward escape trajectories.The boundaries that separate these different groups are easily determined by using the phase space.Finally,the method and procedures to achieve the feasible region of the H-reversal trajectory with required perihelion distance are presented in detail.

Shape memory composite structures for self-deployable solar sails

Shape memory composites(SMCs)combine mechanical performances of composite materials with functional behavior of shape memory polymers.They can be used to produce the external frame of self-deployable solar sails with very low weight in comparison with traditional composite booms.Furthermore,heat activation is necessary for deploying instead of complex mechanical devices.In this study,the mechanical behavior of a solar sail with SMC frame is simulated by means of finite element modeling.Design considerations are made on sail deployment configuration,size/weight ratio of solar sails,and SMC properties.An experimental activity has been also performed to provide suitable candidates for the composite laminates of the SMC structure.Mechanical and instrumented recovery tests have been carried out on 2-plies carbon-fiber laminates with a shape memory interlayer.

Spiral trajectories induced by radial thrust with applications to generalized sails

In this study,new analytical solutions to the equations of motion of a propelled spacecraft are investigated using a shape-based approach.There is an assumption that the spacecraft travels a two-dimensional spiral trajectory in which the orbital radius is proportional to an assigned power of the spacecraft angular coordinate.The exact solution to the equations of motion is obtained as a function of time in the case of a purely radial thrust,and the propulsive acceleration magnitude necessary for the spacecraft to track the prescribed spiral trajectory is found in a closed form.The analytical results are then specialized to the case of a generalized sail,that is,a propulsion system capable of providing an outward radial propulsive acceleration,the magnitude of which depends on a given power of the Sun-spacecraft distance.In particular,the conditions for an outward radial thrust and the required sail performance are quantified and thoroughly discussed.It is worth noting that these propulsion systems provide a purely radial thrust when their orientation is Sun-facing.This is an important advantage from an engineering point of view because,depending on the particular propulsion system,a Sun-facing attitude can be stable or obtainable in a passive way.A case study is finally presented,where the generalized sail is assumed to start the spiral trajectory from the Earth’s heliocentric orbit.The main outcome is that the required sail performance is in principle achievable on the basis of many results available in the literature.

Self-excited oscillation of spinning solar sails utilizing solar radiation pressure

The present paper proposes a control method to excite spinning solar sail membranes for three-dimensional use.Using optical property switching,the input is given as the change in magnitude of the solar radiation pressure.The resonance point of this system varies with the vibration state due to its nonlinearity and the change in equilibrium state.To deal with this,a state feedback control law that automatically tracks the resonance point is developed in the present study.The proposed method enables decentralized control of the actuators on the sail,each of which determines the control input independently using only the information of vibration state.The proposed method is validated using numerical simulations.The results show that the nonlinear system behaves differently from the linear system,and the vibration grows using the decentralized control regardless of resonance point variation.

Dynamic Analysis and Parametric Optimization of Telescopic Tubular Mast Applied on Solar Sail

Large-scale solar sails can provide power to spacecraft for deep space exploration.A new type of telescopic tubular mast(TTM)driven by a bistable carbon fiber-reinforced polymer tube was designed in this study to solve the problem of contact between the sail membrane and the spacecraft under light pressure.Compared with the traditional TTM,it has a small size,light weight,high extension ratio,and simple structure.The anti-blossoming and self-unlocking structure of the proposed TTM was described.We aimed to simplify the TTM with a complex structure into a beam model with equal linear mass density,and the simulation results showed good consistency.The dynamic equation was derived based on the equivalent model,and the effects of different factors on the vibration characteristics of the TTM were analyzed.The performance parameters were optimized based on a multiobjective genetic algorithm,and prototype production and load experiments were conducted.The results show that the advantages of the new TTM can complete the deployment of large-scale solar sails,which is valuable for future deep space exploration.

“SAIL·立学”课堂校本化实践路径探索

“SAIL·立学”是江苏南通“立学课堂”的校本化实践。一方面其丰富了“立学课堂”的实践经验,为课堂教学提供了鲜活的一手资料,另一方面“立学课堂”的高站位又为“SAIL·立学”课堂的实践指明了正确方向“。情境体验“”夯基固本“”学科融合“”知行合一”是其教学策略“。课标引航,以学定教“”问题导航,限时讲授“”活动探航,小组合作“”评价续航,踊跃展示”是其教学流程。让学习在课堂上真实发生、让核心素养培育真正落地;向海图强、以海育人、培塑有大海气质的时代新人;促进教师专业发展、促进学校品质提升,这是“SAIL·立学”课堂的价值旨归。

SARS患者、疫区公众PTSD的对照研究

目的:调查SARS患者、疫区公众创伤后应激障碍(PTSD)症状的发生情况及主要影响因素。方法:采用自编的应激源-认知问卷、经修订的事件影响量表(IES-R)、领悟社会支持量表(PSSS)、简易应对方式问卷(SCSQ)、自尊量表(SES)、艾森克个性问卷(EPQ)对114例SARS患者,93例疫区公众进行测试。结果:①SARS患者PTSD可疑者检出率为55.1%,疫区公众为31.18%,组间比较差异显著(字2=14.840,P=0.000);②相关分析结果:SARS患者、疫区公众PTSD可疑者发生率不同的主要原因是应激源强度与特征的不同;消极应对方式是SARS患者、公众发生PTSD症状的危险因素,自尊是SARS患者发生PTSD症状的保护因素。结论:①SARS事件应激暴露强度不同相关人群中均产生了PTSD症状,SARS患者PTSD可疑者检出率较高。②组间差异的主要原因是应激源强度的不同,不同人群产生PTSD的影响因素不完全相同。

急性期SARS患者的血液系统损害

[目的]探讨急性期SARS患者血液系统的损害。[方法]用全自动血细胞分析仪检测44例SARS患者外周血WBC计数及分类、红细胞、血红蛋白和血小板,用流式细胞仪检测SARS患者外周血T淋巴细胞亚群;并与正常对照组比较。[结果]与对照组比较,SARS组患者WBC总数显著下降,淋巴细胞百分数和绝对数显著下降,中性粒细胞绝对数显著下降,百分数显著增加;血小板显著降低;红细胞和血红蛋白与对照组比较无显著性差异;CD3+、CD4+和CD8+细胞绝对数显著下降,CD3+、CD4+、CD8+细胞百分数和CD4+／CD8+比值与对照组比较无显著性差异。[结论]SARS冠状病毒感染损伤患者的淋巴细胞、中性粒细胞和血小板,使患者细胞免疫功能下降,而红细胞无明显受损。