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28 February 2011, Volume 16 Issue 1    Next Issue
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A new algorithm for non-newtonian flow and its application in mould filling process Han X.-H.; Kong X.; Zhou X.-H.; Li X.-K. 2011, 16 (1):  1-10.  doi: 10.1007/s12204-011-1087-6 Abstract ( 13 )   PDF (1332KB) ( 29 )   The simulation of injection molding process requires a stable algorithm to model the molten polymer with non-isothermal non-Newtonian property. In this paper, a staggered and iterative scheme is particularly designed to solve the velocity-pressure-temperature variables. In consideration of the polymer characteristic of high viscosity and low thermal conductivity, the non-Newtonian momentum-mass conservation equations are solved by the Crank-Nicolson method based split (CNBS) scheme, and the energy conservation equation with convective character is discretized by the characteristic Galerkin (CG) method. In addition, an arbitrary Lagrangian Eulerian (ALE) free surface tracking and mesh generation method is introduced to catch the front of the fluid flow. The efficiency of the proposed scheme is demonstrated by numerical experiments including a lid-driven cavity flow problem and an injection molding problem. © 2011 Shanghai Jiaotong University and Springer-Verlag Berlin Heidelberg. Related Articles | Metrics

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Nonlinear feedforward and feedback control design for autonomous underwater glider Yang H.; Ma J. 2011, 16 (1):  11-16.  doi: 10.1007/s12204-011-1088-5 Abstract ( 12 )   PDF (409KB) ( 26 )   Underwater gliders are highly efficient, buoyancy-driven, and winged autonomous underwater vehicles. Their dynamics are multivariable nonlinear systems with unstable internal dynamics and thus their motion control is a significant challenge. To improve the inherent efficiency and enhance the behavior of the underwater glider over a wide operating regime, a nonlinear feedforward and feedback controller was developed. The nonlinear feedforward control design is based on a new stable inversion technique which determines a causal and bounded solution for the unstable internal dynamics. The feedback control law was designed by a quadratic optimal control method. Simulation results show that the derived control system is able to deal with nonminimum phase system and successfully achieves the tracking of planned output trajectories from initial to final conditions. Furthermore, the control effort is very low, which means the glider with limited power storage has longer range and higher endurance. © 2011 Shanghai Jiaotong University and Springer-Verlag Berlin Heidelberg. Related Articles | Metrics

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Dynamic investigation on floating raft with elastic limiters Wen J.-M.; Feng Q.; Zhang J.-H. 2011, 16 (1):  17-23.  doi: 10.1007/s12204-011-1089-4 Abstract ( 11 )   PDF (404KB) ( 27 )   In this paper, we consider a floating raft isolation system with elastic limiters. The limiters might be "contact" or "no contact", thus forming a unilateral system generating possible contacts. In order to avoid the large displacement of the floating raft under shock, limiters might be adopted but good limiters design requires the values of the gaps. Based on the contact dynamics, the multi-degree-freedom dynamic model of floating raft isolation system with elastic limiters is established. The artificial neural network has been developed to dingtinguish the contact state of elastic limiters at each step. The example analysis shows that the algorithm of neural network for contact can shorten the time of caclaution. From the example analysis, we get some interesting results that may be useful to the ship engineering. © 2011 Shanghai Jiaotong University and Springer-Verlag Berlin Heidelberg. Related Articles | Metrics

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Wrinkle analysis of the space inflatable paraboloid antenna Xiao W.-W.; Chen W.-J.; Fu G.-Y. 2011, 16 (1):  24-33.  doi: 10.1007/s12204-011-1090-y Abstract ( 15 )   PDF (2251KB) ( 27 )   The presence of wrinkles in the membrane is the main factor to induce the reflector surface inaccuracy of the space inflatable antenna. Based on the commercial finite element package ABAQUS, a numerical procedure for membrane wrinkle analysis was set up and used to analyze a space inflatable antenna which was under inner pressure to evaluate its wrinkle characteristics. First, the inner pressure effect on the reflector's wrinkle pattern was studied thoroughly. As inner pressure increases, both the number and the amplitude of the wrinkles decrease, but the total deformation of the whole reflector surface increases much. Second, the influence of the interactions between antenna's parts was investigated comprehensively. Any kind of unwanted interaction deteriorates reflector's wrinkle characteristics. The works are valuable to the development and research of the space inflatable antenna. © 2011 Shanghai Jiaotong University and Springer-Verlag Berlin Heidelberg. Related Articles | Metrics

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Investigation on transient dynamic behaviors of low-tension undersea cables Huo C.-F.; Yao B.-H.; Fu B.; Lian L. 2011, 16 (1):  34-39.  doi: 10.1007/s12204-011-1091-x Abstract ( 21 )   PDF (494KB) ( 27 )   This paper presents a numerical analysis of the dynamic transient behaviors of undersea cables. In this numerical study, the governing equations based on Euler-Bernoulli beam theory are adopted, and they can satisfy many applications no matter what the magnitude of the cable tension is. The nonlinear coupled equations are solved by a popular central finite difference method, and the numerical results of transient behaviors are presented when several kinds of surrounding conditions, such as different towing speeds of surface vessel, different currents and waves with various frequencies and amplitudes, are exerted. Then a detailed comparison of the results, including the upper end tension and cable shape in time-domain, is made under the above external excitations, and finally the possible reasons for these are further explained. © 2011 Shanghai Jiaotong University and Springer-Verlag Berlin Heidelberg. Related Articles | Metrics

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Research on the performance of passive heave compensator for tethered remotely operated vehicle system Wu K.-T.; Yao B.-H.; Fu B.; Ren P.; Lian L. 2011, 16 (1):  40-44.  doi: 10.1007/s12204-011-1092-9 Abstract ( 13 )   PDF (334KB) ( 27 )   A passive heave compensator is designed to enhance the operation safety of a 4.5 km remotely operated vehicle (ROV). This paper proposes a novel idea of designing a compensator with relatively low natural period to optimize gas volume and while adding a special device to remove the problem of ineffectiveness and resonance in long seas. Numerical simulations are done based on serious dynamic model of the whole system, including the compensator, the umbilical tether and the vehicle, solved by the fourth-order Runge-Kutta scheme. The compensator provides great attenuation of motion and tension in most sea states. As the working depth increases, the system natural period decreases, resulting in the occurrence of risk of resonance. By regulating the system damping, the compensator can be effective in these situations. © 2011 Shanghai Jiaotong University and Springer-Verlag Berlin Heidelberg. Related Articles | Metrics

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Numerical study for turbulent flow of drag and flow noise with wavy wall Meng K.-Y.; Zhang H.-X.; Shi Y.-L.; Pan Y.-C. 2011, 16 (1):  45-54.  doi: 10.1007/s12204-011-1093-8 Abstract ( 12 )   PDF (1161KB) ( 27 )   In this paper, a numerical simulation of flow-induced noise by the low Mach number turbulent flow with a sinusoidal wavy wall was presented based on the unsteady incompressible Navier-Stokes equations and Lighthill's acoustic analogy. Large eddy simulation (LES) was used to investigate the space-time flow field and the Smagorinsky sub-grid scale (SGS) model was introduced for turbulence model. Using Lighthill's acoustics analogy, the flow field simulated by LES was taken as near-field sound sources and radiated sound from turbulent flow was computed by the Curle's integral formulation under the low Mach number approximation. Both spanwise wavy wall and streamwise wavy wall with various wall wave amplitudes were discussed to investigate their effects on reducing the drag and flow noise. The relationship between flow noise and drag on the wavy wall is also studied. © 2011 Shanghai Jiaotong University and Springer-Verlag Berlin Heidelberg. Related Articles | Metrics

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Multi-element ultrasound phased array applicator for the ablation of deep-seated tissue Ji X.; Shen G.-F.; Bai J.-F.; Li D.-H.; Yu Y.; Qiao S.; Chen Y.-Z. 2011, 16 (1):  55-60.  doi: 10.1007/s12204-011-1094-7 Abstract ( 17 )   PDF (1505KB) ( 27 )   High-intensity focused ultrasound (HIFU) has attracted increasing interests as a promising noninvasive modality for the treatment of deep tumors in the thoracic and abdominal cavity. A 90-element HIFU spherical phased array applicator operated at 1MHz has been developed for deep tissue ablation. The spherical array with a 5 cm wide central hole has a 21 cm diameter and an 18 cm radius of curvature. Annular element distribution with unequal element spacing is used to reduce the number of elements. The array is constructed with piezoelectric lead zirconate titanate (PZT-8) circular elements that are 1.4 cm in diameter and have a wall with thickness of 0.2 cm. The array offers an effective ablating depth of at least 8 cm in the tissue for both simulations and ex vivo experiments. The simulations demonstrate that the developed array can steer the focus with good quality of intensity distributions up to 6mm off center over ranges from 17 to 21 cm when the water depth is set at 11 cm. We also present the beam focusing capability in deep tissue through a series of ex vivo experiments by measuring discoloration areas after sonications. These results indicate that the developed array is ideal for the ablation of deep-seated tissue. © 2011 Shanghai Jiaotong University and Springer-Verlag Berlin Heidelberg. Related Articles | Metrics

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Upper limb musculo-skeletal model for biomechanical investigation of elbow flexion movement Zhang L.-L.; Zhou J.; Zhang X.-A.; Wang C.-T. 2011, 16 (1):  61-64.  doi: 10.1007/s12204-011-1095-6 Abstract ( 20 )   PDF (399KB) ( 29 )   A biomechanical musculo-skeletal model of upper limb is presented in this paper, which can provide accurate representations of muscles and joints, and capture important interactions between joints. The upper limb model is made up of seven segments: ribs, sternum, clavicle, scapular, humerus, radius and ulna, considered as a single rigid body respectively and includes 22 muscles. The individual muscle forces can be calculated by using an electromyography (EMG) assisted method, which is verified by comparing the simulation results with other researches of an elbow flexion motion. These comparisons show that the muscle forces and the estimated joint moment match well with previous literatures. © 2011 Shanghai Jiaotong University and Springer-Verlag Berlin Heidelberg. Related Articles | Metrics

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Determination of interfacial heat flux of stainless steel solidification on copper substrate during the first 0.2 s Zhang W.; Yu Y.; Fang Y.; Li J.-G. 2011, 16 (1):  65-70.  doi: 10.1007/s12204-011-1096-5 Abstract ( 10 )   PDF (683KB) ( 29 )   Interfacial heat transfer is a key issue in many solidification processes. In the paper, a novel experimental apparatus has been designed and on this basis, the instantaneous interfacial heat transfer between molten steel or solidified shell and copper substrate during the first 0.2 s has been studied. The investigated parameters include melt superheat, substrate temperature and surface roughness. The results show that the peak value of the interfacial heat flux in the first stage of liquid/solid contact increases with melt superheat and changes slightly with substrate temperature and surface roughness. The interfacial heat flux in the stage of solid/solid contact has a similar trend of slow decrease in most conditions. © 2011 Shanghai Jiaotong University and Springer-Verlag Berlin Heidelberg. Related Articles | Metrics

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Kinematics analysis and experiment of a cockroach-like robot Gao Y.; Chen W.-H.; Lu Z. 2011, 16 (1):  71-77.  doi: 10.1007/s12204-011-1097-4 Abstract ( 25 )   PDF (1172KB) ( 29 )   This article describes the structure of the cockroach-like robot. Both kinematics and locomotion control are inspired by biological observations in cockroaches. Based on cockroach-like robot kinematics analysis, screw theory, and the production-of-exponential (POE) formula, this paper focuses on the inverse kinematics which uses Paden-Kahan sub-problems to obtain directly the displacement of joint angles. The forward kinematics derives the relationship between joint angles according to the natural restrictions. Then, by using the POE formula, it can deduce the body pose and realize online trajectory control and planning. Through simulation and experimentation, it is proved that the straight-line walking and turning gait algorithms have static stability and the inverse kinematics analysis of cockroach-like robot is correct. © 2011 Shanghai Jiaotong University and Springer-Verlag Berlin Heidelberg. Related Articles | Metrics

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A new model for soil consolidation based on microstructure Zhang J.-R.; Tao G.-L. 2011, 16 (1):  78-82.  doi: 10.1007/s12204-011-1098-3 Abstract ( 14 )   PDF (607KB) ( 29 )   This paper introduces a new means to predict consolidation deformation of soil from its microstructure. Based on a kind of pore-size distribution density function, a fractal model for soil consolidation is established. Through this model, the relation between macroscopic deformation and microcosmic pore property of soil is founded. In order to justify this proposed model for soil consolidation, consolidation experiments of soft clay are performed. Afterward, the microstructure of soft clay unconsolidated and consolidated under every pressure is studied by a scanning electron microscope (SEM). The results show that the proposed model for soil consolidation is valid in predicting consolidation deformation. © 2011 Shanghai Jiaotong University and Springer-Verlag Berlin Heidelberg. Related Articles | Metrics

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Industry foundation classes based integration of architectural design and structural analysis Qin L.; Deng X.-Y.; Liu X.-L. 2011, 16 (1):  83-90.  doi: 10.1007/s12204-011-1099-2 Abstract ( 20 )   PDF (1228KB) ( 29 )   The numerous construction projects in China provide the best environment for the development of information technology applied in building design. Various commercial CAD/CAE software applications are purchased by design firms for multi-disciplinary design tasks. However, researches on integration and interoperability are seldom considered. This study pursues a breakthrough point of integration in the architectural and structural domains and expects further development in other aspects. A central building information modeling (BIM) framework based on the industry foundation classes (IFC) is proposed to handle the data exchange between IFC-compatible architectural models and structural models. A central XML(extensible markup language)-based unified finite element model (FEM) is proposed for model conversion among various commercial structural CAE software applications. In addition to bidirectional data interfaces among IFC-based BIM, XML-based FEM and various commercial FEMs, some other components such as visualization, calculation and model editing/check are also equipped into the prototype system. © 2011 Shanghai Jiaotong University and Springer-Verlag Berlin Heidelberg. Related Articles | Metrics

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Numerical study on bank effects for a ship sailing in shallow channel Yao J.-X.; Zou Z.-J.; Wang H.-M. 2011, 16 (1):  91-96.  doi: 10.1007/s12204-011-1100-0 Abstract ( 17 )   PDF (1242KB) ( 29 )   A numerical study on bank effects in shallow channels is carried out by using a first-order Rankine source panel method. A container ship sailing along a vertical bank and a sloping bank at different forward speeds, different water depths and different distances between the bank and the ship hull is taken as example. The sway force and yaw moment acting on the hull are calculated and the influences of the speed, water depth and distance between the bank and ship hull on the hydrodynamic force and moment are analyzed. This study can provide insight into the bank effects, as well as to give guidance on ship manoeuvring and control in restricted waterways, which is helpful to the navigation safety. © 2011 Shanghai Jiaotong University and Springer-Verlag Berlin Heidelberg. Related Articles | Metrics

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Mechanical behavior of tubular T-joint after fire Jin M.; Zhao J.-C.; Chang J.; Liu M.-L. 2011, 16 (1):  97-104.  doi: 10.1007/s12204-011-1101-z Abstract ( 18 )   PDF (1106KB) ( 28 )   This paper presents experimental results of the post-fire behavior of tubular T-joints. The research aims at the failure modes and the residual strengths of the T-joints after fire. Three tests of full-scale tubular T-joints are conducted. The first one is carried out to study the mechanical behavior of T-joints under ambient temperature. The other two tests are performed to study the influence of pre-load, heating and cooling phase on residual load-bearing capacity of the tubular T-joints. The test results show that the sustained axial load on the brace has remarkable influence on the residual deflection of the T-joints which is cooled down to room temperature. The results of the experiments also indicate that the axial load level and heating and cooling history have more significant effects on the compressive stiffness of the T-joints than the residual strength. In the numerical study, the result of finite element model agrees well with the test result. The work in this paper provides a basis for further parametric analysis and theoretical study on the structural evaluation after fire. © 2011 Shanghai Jiaotong University and Springer-Verlag Berlin Heidelberg. Related Articles | Metrics

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Timing sequence changes of landscape plants in Shanghai Area, China Yang X.-J.; Tang D.-Q.; Shao Q.-Y.; Zhang J.-Y. 2011, 16 (1):  105-111.  doi: 10.1007/s12204-011-1102-y Abstract ( 18 )   PDF (588KB) ( 29 )   Based on published reports and direct observation, the common resources of landscape plant species in the Shanghai area were identified and studied in terms of the landscape characteristics of timing sequence changes over a one year time period. The results showed that there were 199 common landscape plant species in Shanghai, distributed in 67 families and 129 genera. These plants were categorized by three ornamental characteristics: flowers, foliage and fruits. The species were thus further analyzed according to the time periods which these characteristics were present. The results showed that flower ornamental distributed throughout the year, particularly from April to June, and plant species with colorful foliage could be seen every month, and particularly in November and December. On the other hand, few plant species with fruit ornamentals were observed in Shanghai area. The diversity of landscape timing sequence changes of the 199 plant species under examination was then analyzed by using the Shannon-Weiner and Simpson index formulas. The results showed that the higher diversity was observed in January, February and from August to October, while the lowest diversity was recorded from March to July and during November and December. The diversity of landscape characteristics of these plants was ranked according to foliage, flowers and fruit. Using this method, one park and one plant community were selected to evaluate the advantages and disadvantages of their time-changing plant landscape, with the goal of assessing the validity of the chosen ranking method. These results in the present study would be helpful to evaluate the plant landscape in a specified space and further enrich the diversity of plant and landscape by a target-oriented way. © 2011 Shanghai Jiaotong University and Springer-Verlag Berlin Heidelberg. Related Articles | Metrics

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Model test for dynamic construction mechanical effect of large-span loess tunnel He B.-G.; Zhu Y.-Q.; Ye C.-L.; Zhang Z.-Q. 2011, 16 (1):  112-117.  doi: 10.1007/s12204-011-1103-x Abstract ( 17 )   PDF (665KB) ( 29 )   It has been a focus of debate for a large time on construction methods for large-span loess tunnel. Reasonable construction method has much effect on stability of tunnel and construction schedule. Deformation and failure of surrounding rock are quite complex. Associating with the large-span loess tunnel of Zhengzhou-Xi'an high-speed passenger rail line in China, large scale model test with geometric proportion 1:20 is applied to study on dynamic mechanical behavior of various construction methods. They include full-face excavation with support and no support, and benching method with support. It is found that pre-deformation and stress accumulation take place ahead of working face. The effects of three construction methods are further studied, particularly in terms of tunnel displacement and stress changes. It is revealed that benching method transfers load to an unexcavated area, limits horizontal deformation, reduces stress concentration effectively, lengthens the distance between location of peak for stress concentration and working face, and consequently increases stability. The model test results not only supply theoretical foundation for determination of reasonable construction method, but also can act as reference for similar tunnel and underground engineering construction. © 2011 Shanghai Jiaotong University and Springer-Verlag Berlin Heidelberg. Related Articles | Metrics

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Optimal thrust allocation logic design of dynamic positioning with pseudo-inverse method Yang S.-Z.; Wang L.; Sun P. 2011, 16 (1):  118-123.  doi: 10.1007/s12204-011-1104-9 Abstract ( 9 )   PDF (839KB) ( 30 )   This article presents a method named pseudo-inverse to solve the optimal thrust allocation of dynamic positioning (DP) system, proposes to optimally determine the azimuth angle of thrusters instead of man-control or semi-auto control, and combines with the pseudo-inverse methods to get the optimal solutions for dynamic positioning control system. It is able to greatly reduce the risk of manual mode. Three different kinds of modes are proposed and detailedly illuminated, and can be used to solve much more complex nonlinear constraint problems, such as typical forbidden vector boundary. Several illustrative examples are provided to demonstrate the effectiveness and correctness of the proposed thrust allocation modes. © 2011 Shanghai Jiaotong University and Springer-Verlag Berlin Heidelberg. Related Articles | Metrics

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Influence of excitation frequency on slosh-induced impact pressures of liquefied natural gas tanks Cai Z.-H.; Wang D.-Y.; Li Z. 2011, 16 (1):  124-128.  doi: 10.1007/s12204-011-1105-8 Abstract ( 20 )   PDF (702KB) ( 30 )   Liquid sloshing phenomena in No. 2 tank of 140 km3 liquefied natural gas (LNG) carriers have been studied numerically and experimentally. The scale of the model tank was selected as 1/55.9. Roll and pitch motions were tested. For measuring impact pressures, seventeen pressure sensors were installed on the tank model. A large number of excitation frequencies and filling heights were investigated. The experimental results showed that when the frequency of tank motion is close to the natural frequency of fluid inside the tank, large impact pressures may be caused. Resonance frequencies and maximum impact pressures of different filling height were presented. Among all the experimental situations, the maximum impact pressure always occurs at the place near 70% height of tank where should be especially concerned. A computational fluid dynamics (CFD) model was developed to simulate the sloshing in the tank. The model was based on the Reynolds-averaged Navier-Stokes (RANS) equations, with a standard κ-ε turbulence model. The volume of fluid (VOF) method was used to predict free surface elevations. Dynamic mesh technique was used to update the volume mesh. Computations for pressure time histories and peak pressures were compared to experimental results. Good agreement was observed. © 2011 Shanghai Jiaotong University and Springer-Verlag Berlin Heidelberg. Related Articles | Metrics