Preliminary investigation of seismic damage to two steel space structures during the 2013 Lushan earthquake

Severe damage to steel space structures is rarely reported when compared to other structural systems damaged during past major earthquakes around the world. Two gymnasiums of steel space structures in downtown Lushan County that were damaged during the 2013 M7.0 Lushan earthquake in China were investigated and the observations are summarized in this paper. Typical damage to these two steel space structures ranges from moderate to severe. Moderate damage includes global buckling and dislocation of bolted connections of truss members, and inelastic elongation of anchor bolts and sliding of pedestal plates of supports. Severe damage includes member fracture caused by local buckling, and fracture failure of anchor bolts and welds. The distribution of structural damage to these two structures is described in detail and future research opportunities are suggested.

Recent Advances in Space-Deployable Structures in China

Deployable space structure technology is an approach used in building spacecraft,especially when realizing deployment and folding functions.Once in orbit,the structures are released from the fairing,deployed,and positioned.With the development of communication,remote-sensing,and navigation satellites,space-deployable structures have become cutting-edge research topics in space science and technology.This paper summarizes the current research status and development trend of spacedeployable structures in China,including large space mesh antennas,space solar arrays,and deployable structures and mechanisms for deep-space exploration.Critical technologies of space-deployable structures are addressed from the perspectives of deployable mechanisms,cable-membrane form-finding,dynamic analysis,reliable environmental adaptability analysis,and validation.Finally,future technology developments and trends are elucidated in the fields of mesh antennas,solar arrays,deployable mechanisms,and on-orbit adjustment,assembly,and construction.

The rough representation and measurement of quotient structure in algebraic quotient space model

Granular computing is a very hot research field in recent years. In our previous work an algebraic quotient space model was proposed,where the quotient structure could not be deduced if the granulation was based on an equivalence relation. In this paper,definitions were given and formulas of the lower quotient congruence and upper quotient congruence were calculated to roughly represent the quotient structure. Then the accuracy and roughness were defined to measure the quotient structure in quantification. Finally,a numerical example was given to demonstrate that the rough representation and measuring methods are efficient and applicable. The work has greatly enriched the algebraic quotient space model and granular computing theory.

Stability Analysis of Space Compcoite Structore and Its Ultimate Bearing Capacity

In this paper, using incremental equilibrium equation, the authors have studiedthe effeet of ultimate bearing capacity of every component on structuralstability, and discussed the stability analysis method for space compositestructures. With the help of the test results for the concrete filled ateel tubeskeleton of the long-spen RC arch bridse, it is proved that the proposed methodis accurate and reliable.

DECENTRALIZED ROBUST CONTROL FOR UNCERTAIN FLEXIBLE SPACE STATION

A decentralized variable-structure robust control technique for uncertain large-scale systems is proposed and using the proposed technique. a decentralized robust control system for uncertain flexible space station is designed. The designed robust control system can guarantee the stability and safe operation of space station in a wide range of system parameters variations and highly intensive external disturbances. In addition. because decentralized adaptation laws for the upper bounds of system uncertainties are introduced, the control technique is particularly applicable to the uncertain flexible space station with complex structure whose bounds of system uncertainties can not be determined or vary with time.

Torsional effect of space structure in frequent earthquakes

Taking a concrete frame supporting space structure as the research object,we systematically studied its lateral-torsion coupling effect of reverse problems in consistent earthquake excitation.Firstly,based on its reverse forms and features,we put forward a mechanical analysis model(flexibility layer model) and a calculation method using the response spectrum method and the weighted average method,and verified their validity and feasibility using case analysis.The result shows that the translation displacement change trend of the space structure is basically the same whether reverse exists in the supporting structure or not,but the supporting structure torsion has an effect on the displacement with a relative increase of 10%.

Wrinkling analysis of square space membrane structure under corner tension forces

An analytical approach based on the bifurcation theory is presented,in which the wrinkles are treated as the local buckling phenomena of the elastic thin plate with little bending stiffness.The average wrinkling wavelength was determined by incorporating the stress field and the out-of-plane force equilibrium condition of the wrinkled membrane.The wrinkling amplitude was then obtained by associating the characteristics of wrinkling texture with the obtained wrinkling wavelength.Results reveal that the wrinkled pattern exhibits a noticeable difference when the tension load is changed gradually,and two wrinkling styles are identified.The first style occurs for symmetric and moderately asymmetric loading,and it is characterized by small,radial corner wrinkles;the second style occurs for strongly asymmetric loading and is characterized by a deep,large diagonal wrinkle.The analytical predictions on the wrinkling characteristics and the developed rules are validated against wrinkling experimental observations.

A Group Oriented Cryptosystem for the Vector Space Access Structure

A group oriented cryptosystem for the vector space access structure was proposed. This cryptosystem adopts self-certified public keys. It allows the participants of an authorized subset to cooperatively access an encrypted message. All data delivered in the cryptosystem are public. Therefore it does not need a partial decrypting results combiner and any secure communication channel. The security of the group oriented cryptosystem is based on the intractability of the discrete log problem and difficulty of factoring large integers. The suspected attacks can not break it.

Space Structuring of the Northern Foot of the Qinling Mountains(Xi'an Section) based on Landscape City

Northern foot of the Qinling Mountains(Xi'an Section) is a transitional section between the Qinling Mountains and Xi'an City, so it has great ecological signifi cance. On the basis of sorting out landscape city, space structuring of the northern foot of the Qinling Mountains was studied within the theoretical framework of landscape city, it was disclosed that northern foot of the Qinling Mountains was a signifi cant ecological screen for the landscape city spatial pattern of Xi'an, and an important carrier for its "mountain, water and city" cultures. Then, fi ve infl uence factors for the space structuring of the study area were given, and basic contents of the space structuring analyzed from fi ve perspectives of spatial structure, spatial form, ecological environment, integration of regional spaces, historical and cultural context, so as to explore ecological conservation and moderate utilization of the northern foot of the Qinling Mountains from the perspective of space structuring.

Sustainable Design in Space Structures

The sustainable design approach presented in this paper supports an increased commitment to environmental stewardship and conservation, and results in an optimal balance of cost, environmental, societal, and human benefits while meeting the mission and function of the intended space structure. The aim of this paper is to develop the guidelines that could be applied in the design of a space structure in order to achieve the optimal overall lifetime performance of the space structure. Space structures are more than inanimate hunks of metal, glass and fabric. Every space structure that we design as structural engineers is like a child - a child that is conceived with a passionate vision of its form, structure and purpose; nurtured through the schematic design phase and the development of construction documents; and cared for during the labor pains of plan check corrections, requests for information, shop drawing review, and construction observation. Like children, our space structures mature, perform necessary functions during their lives, and eventually, grow old and die. The design of a sustainable space structure is a much more challenging and cross-disciplinary process than in the past and therefore it is necessary that the space structure is viewed as an integrated system and that all members of the design team work in a fully integrated fashion.

AN ANALYTICAL METHOD FOR SOLVING INTERNAL FORCES AND DEFORMATIONS OF BAR-SYSTEM STRUCTURE IN SPACE

In this paper, based on the idea of finite element method, the initial parametric method in bending, problem of a beam is extended to analyse the bar-system structure by employing Dirac function and llcavisidc step function.Then a new method for analysing the internal forces and deformations of bar-system structure in space is suggested by improving the mixed method in statically indeterminate structure.The inferred process and obtained answer will be more succinct and accurate when the problem of internal forces and deformations of bar-system structure is analysed by using the new method provided in this paper.

Information Space and Information Process: Genesis and Evolution

In this article,the phenomenon of“information space”and its methods of study,its types,elementary structure and qualitative characteristics are discussed,the author’s definition of the concept of“information”is given,the structure of the information process,and the phases,which are the basis for the evolution of the information space and the universe of human activity,are considered.

Approximations by Ideal Minimal Structure with Chemical Application

The theory of rough set represents a non-statistical methodology for analyzing ambiguity and imprecise information.It can be characterized by two crisp sets,named the upper and lower approximations that are used to determine the boundary region and accurate measure of any subset.This article endeavors to achieve the best approximation and the highest accuracy degree by using the minimal structure approximation space MSAS via ideal J.The novel approach(indicated by JMSAS)modifies the approximation space to diminish the bound-ary region and enhance the measure of accuracy.The suggested method is more accurate than Pawlak’s and EL-Sharkasy techniques.Via illustrated examples,several remarkable results using these notions are obtained and some of their properties are established.Several sorts of near open(resp.closed)sets based on JMSAS are studied.Furthermore,the connections between these assorted kinds of near-open sets in JMSAS are deduced.The advantages and disadvan-tages of the proposed approach compared to previous ones are examined.An algorithm using MATLAB and a framework for decision-making problems are verified.Finally,the chemical application for the classification of amino acids(AAs)is treated to highlight the significance of applying the suggested approximation.

Vibration suppression for rotating space slender flexible structures based on novel deformation description and NNSMC controller with hyperbolic tangent function

Rotating Space Slender Flexible Structures(RSSFS)are extensively utilized in space operations because of their light weight,mobility,and low energy consumption.To realize the accurate space operation of the RSSFS,it is necessary to establish a precise mechanical model and develop a control algorithm with high precision.However,with the application of traditional control strategies,the RSSFS often suffers from the chattering phenomenon,which will aggravate structure vibration.In this paper,novel deformation description is put forward to balance modeling accuracy and computational efficiency of the RSSFS,which is better appropriate for real-time control.Besides,the Neural Network Sliding Mode Control(NNSMC)strategy modified by the hyperbolic tangent(tanh)function is put forward to compensate for modeling errors and reduce the chattering phenomenon,thereby improving the trajectory tracking accuracy of the RSSFS.Firstly,a mathematical model for the RSSFS is developed according to the novel deformation description and the vibration theory of flexible structure.Comparison of the deformation accuracy between different models proves that the novel modeling method proposed has high modeling accuracy.Next,the universal approximation property of the Radial Basis Function(RBF)neural network is put forward to determine and compensate for modeling errors,which consist of higher-order modes and the uncertainties of external disturbances.In addition,the tanh function is proposed as the reaching law in the conventional NNSMC strategy to suppress driving torque oscillation.The control law of modified NNSMC strategy and the adaptive law of weight coefficients are developed according to the Lyapunov theorem to guarantee the RSSFS stability.Finally,the simulation and physical experimental tests of the RSSFS with different control strategies are conducted.Experimental results show that the control law according to the novel deformation description and the modified NNSMC strategy can obtain accurate tracking of the rotation and reduce the vibration of the RSSFS simultaneously.

Computational dynamics of soft machines

Soft machine refers to a kind of mechanical system made of soft materials to complete sophisticated missions, such as handling a fragile object and crawling along a narrow tunnel corner, under low cost control and actuation. Hence, soft machines have raised great challenges to computational dynamics. In this review article, recent studies of the authors on the dynamic modeling, numerical simulation, and experimental validation of soft machines are summarized in the framework of multibody system dynamics. The dynamic modeling approaches are presented first for the geometric nonlinearities of coupled overall motions and large deformations of a soft component, the physical nonlinearities of a soft component made of hyperelastic or elastoplastic materials, and the frictional contacts/impacts of soft components, respectively. Then the computation approach is outlined for the dynamic simulation of soft machines governed by a set of differential-algebraic equations of very high dimensions, with an emphasis on the efficient computations of the nonlinear elastic force vector of finite elements. The validations of the proposed approaches are given via three case studies, including the locomotion of a soft quadrupedal robot, the spinning deployment of a solar sail of a spacecraft, and the deployment of a mesh reflector of a satellite antenna, as well as the corresponding experimental studies. Finally, some remarks are made for future studies.

Static analysis of synchronism deployable antenna

A 3D synchronism deployable antenna was designed, analyzed, and manufactured by our research group. This an-tenna consists of tetrahedral elements from central element. Because there are springs at the ends of some of the rods, spider joints are applied. For analysis purpose, the structure is simplified and modelled by using 2D beam elements that have no bending stiffness. Displacement vectors are defined to include two translational displacements and one torsional displacement. The stiff-ness matrix derived by this method is relatively simple and well defined. The analysis results generated by using software de-veloped by our research group agreed very well with available test data.

ANALYSIS OF MATERIAL MECHANICAL PROPERTIES FOR SINGLE-WALLED CARBON NANOTUBES

Abstract The carbon-carbon bond between two nearest-neighboring atoms is mod- eled as a beam and the single-walled carbon nanotubes are treated as the space frame structures in order to analyze the mechanical properties of carbon nanotubes. Based on the theory of Tersof- Brenner force feld, the energy relationships between the carbon-carbon bond and the beam model are obtained, and the stifness parameters of the beam are determined. By applying the present model, the Young’s moduli of the single-walled carbon nanotubes with diferent tube diameters are determined. And the present results are compared with available data.

A CLIMATOLOGY OF EXTRATROPICAL TRANSITION OF TROPICAL CYCLONES IN THE WESTERN NORTH PACIFIC

Based on best-track data and JRA-25 reanalysis,a climatology of western North Pacific extratropical transition (ET) of tropical cyclone (TC) is presented in this paper. It was found that 35% (318 out of 912) of all TCs underwent ET during 1979-2008. The warm-season (June through September) ETs account for 64% of all ET events with the most occurrence in September. The area 120°E-150°E and 20°N-40°N is the most favorable region for ET onsets in western North Pacific. The TCs experiencing ET at latitudes 30°N-40°N have the greatest intensity in contrast to those at other latitude bands. The distribution of ET onset locations shows obviously meridional migration in different seasons. A cyclone phase space (CPS) method was used to analyze the TC evolution during ET. Except for some cases of abnormal ET at relatively high latitudes,typical phase evolution paths-along which TC firstly showed thermal asymmetry and an upper-level cold core and then lost its low-level warm core-can be used to describe the main features of ET processes in western North Pacific. Some seasonal variations of ET evolution paths in CPS were also found at low latitudes south of 15°N,which suggests different ET onset mechanisms there. Further composite analysis concluded that warm-season ETs have generally two types of evolutions,but only one type in cold season (October through next May). The first type of warm-season ETs has less baroclinicity due to long distance between the TC and upper-level mid-latitude system. However,significant interactions between a mid-latitude upper-level trough and TC,which either approaches or is absorbed into the trough,and TC's relations with downstream and upstream upper-level jets,are the fingerprints for both a second type of warm-season ETs and almost all the cold-season ETs. For each type of ETs,detailed structural characteristics as well as precipitation distribution are illustrated by latitude.

A study on wrinkling characteristics and dynamic mechanical behavior of membrane

An eigenvalue method considering the membrane vibration of wrinkling out-of-plane deformation is introduced, and the stress distributing rule in membrane wrinkled area is analyzed. A dynamic analytical model of rectangular shear wrinkled membrane and its numerical analysis approach are also developed. Results indicate that the stress in wrinkled area is not uniform, i.e. it is larger in wrinkling wave peaks along wrinkles and two ends of wrinkle in vertical direction. Vibration modes of wrinkled membrane are strongly correlated with the wrinkling configurations. The rigidity is larger due to the heavier stress in the part of wrinkling wave peaks. Therefore, wave peaks are always located at the node lines of vibration mode. The vibration frequency obviously increases with the vibration of wave peaks.

Deformation of wrinkled membrane inflatable structures under concentrated loads

The axisymmetric deformation of a paraboloidal membrane inflatable structure subjected to a concentrated load at its apex and a uniform internal pressure was analyzed. The wrinkle angle was obtained according to the membrane theory when wrinkles appeared and determined the wrinkle region. The wrinkled deformation was obtained based on the relaxed energy function. The effects of inflation pressure and concentrated loads on the wrinkle angle were analyzed and the deformation was obtained at the apex of structure. According to the numerical analysis, the shape of deformed meridians with wrinkles was obtained.