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71.
Youn Doh Ha Min-Geun Kim Hyun-Seok Kim Seonho Cho 《Structural and Multidisciplinary Optimization》2011,44(3):319-336
Fluid–structure interaction problems are solved by applying a smoothed particle hydrodynamics method to a weakly compressible
Navier–Stokes equation as well as an equilibrium equation for geometrically nonlinear structures in updated Lagrangian formulation.
The geometrically exact interface, consisting of B-spline basis functions and the corresponding control points, includes the
high order geometric information such as tangent, normal, and curvature. The exactness of interface is kept by updating the
control points according to the kinematics obtained from response analysis. Under the scheme of explicit time integration
and updated Lagrangian formulation, the required shape design velocity should be updated at every single step. The update
scheme of design velocity is developed using the sensitivity of physical velocity. The developed sensitivity analysis method
is further utilized in gradient-based shape optimization problems and turns out to be very efficient since the interaction
pairs of particles determined in the response analysis can be directly utilized. 相似文献
72.
There are nodes and edges in a topological map. Node data has been used as a main source of information for the localization of mobile robots. In contrast, edge data is regarded as a minor source of information, and it has been used in an intuitive and heuristic way. However, edge data also can be used as a good source of information and provide a way to use edge data efficiently. For that purpose, we define a data format which describes the shape of an edge. This format is called local generalized Voronoi graph's angle (LGA). However, the LGA is constituted of too many samples; therefore, real time localization cannot be performed. To reduce the number of samples, we propose a compression method which utilizes wavelet transformation. This method abstracts the LGA by key factors using far fewer samples than the LGA. Experiments show that the LGA accurately describes the shape of the edges and that the key factors preserve most information of the LGA while reducing the number of samples. 相似文献
73.
This article concerns the nonlinear tracking control of trailer systems that consist of a steering tractor and a passive trailer, linked together with rigid joint and having nonholonomic velocity constraints. We propose a globally asymptotically stable (GAS) tracking control law using the Lyapunov direct method. The GAS tracking control law is completed by considering the posture term of the trailer systems. We selected two types of trailer systems for examples: the two‐wheeled trailer system and the car‐like trailer system. The simulation results represent the effectiveness of our proposed method. In addition, there is a plan to test the path following ability of the trailer system. ©1999 John Wiley & Sons, Inc. 相似文献
74.
The fluorosilicone block copolymers of poly(perfluoroalkylethyl acrylate)‐b‐poly(3‐[tris(trimethylsilyloxy)silyl] propyl methacrylates) (PFA‐b‐PSiMAs) having perfluoroalkyl and silicone‐containing side chains were obtained by three‐step synthetic approaches. In the first step, hydroxyl‐terminated poly(perfluoroalkylethyl acrylate) macromonomer (PFAM) was prepared by the free‐radical polymerization of perfluoroalkylethyl acrylate and 2‐mercaptoethanol. In the second step, PFAM initiator (PFAMI) was prepared from the condensation reaction of the hydroxyl‐terminated PFAM and 4,4′‐azobis‐4‐cyanopentanoic acid chloride (ACPC). ACPC was obtained from the reaction of 4,4′‐azobis‐4‐cyanopentanoic acid and phosphorus pentachloride. In the third step, PFA‐b‐PSiMAs (BPFSs) were synthesized from the reaction of PFAMI macroinimer and SiMA. Fourier transform infrared spectroscopy and 1H‐NMR analyses verified that the syntheses of ACPC, hydroxyl‐terminated PFAM, PFAMI, and BPFS were completed successfully. The intrinsic surface energies of BPFSs and their surface modification effects on poly(vinyl chloride) film were investigated by analyzing the surface free energies and atomic compositions of the outermost layer of the surfaces. BPFSs exhibit extremely low surface free energies of about 9.7–13.0 dynes/cm. It was confirmed that BPFS, having extremely low surface free energy, is preferentially enriched at the outermost layer of the surface of BPFS/poly(vinyl chloride) blend. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1917–1926, 1999 相似文献
75.
In-Jin Shon Byung-Ryang Kim Jung-Mann Doh Jin-Kook Yoon Kee-Do Woo 《Journal of Alloys and Compounds》2010,489(1):L4-L8
Extremely dense WC with a relative density of up to 99% was obtained within 3 min under a pressure of 80 MPa using the high frequency induction heating sintering method (HFIHS) method. The average grain size of the WC was about 87 nm. The advantage of this process is not only rapid densification to obtain a near theoretical density but also the prohibition of grain growth in nanostructured materials. The hardness and fracture toughness of the dense WC produced by the HFIHS were investigated. 相似文献
76.
Manufacturing enterprises continuously have to cope with changing markets that are unpredictable and diverse, with increased global competition and with ever-changing customer demands. These requirements have led to the emergence of the virtual enterprise (VE). The creation of these enterprises, called as VEs, is becoming a growing trend as enterprises concentrate on their core competencies and economic benefit. An enterprise participating as a member of the VE should take initiative in involvement according to the internal production condition, which is changing dynamically with independent management sovereignty. However, most of researches have not considered these issues, that is the constituting enterprises have been regarded as one of the enterprises having their work stations distributed geographically. This paper proposes a multi-agent-based task assignment system for VEs, which attempts to address the selection of individually managed partners and the process of assigning tasks to them. A case example of assigning the tasks to partners is presented to illustrate and prove the proposed system's applicability. 相似文献
77.
Chil-Hoon Doh Dong-Hun Kim Hyo-Suck Kim Hye-Min Shin Young-Dong Jeong Seong-In Moon Bong-Soo Jin Seung Wook Eom Hyun-Soo Kim Ki-Won Kim Dae-Hee Oh Angathevar Veluchamy 《Journal of power sources》2008
Thermal and electrochemical processes in a 1000 mAh lithium-ion pouch cell with a graphite anode and a LixCoO2 cathode during a safety test are examined. In overcharge tests, the forced current shifts the cell voltage to above 4.2 V. This causes a cell charged at the 1 C rate to lose cycleability and a cell charged at the 3 C rate to undergo explosion. In nail penetration and impact tests, a high discharge current passing through the cells gives rise to thermal runaway. These overcharge and high discharge currents promote joule heat within the cells and leads to decomposition and release of oxygen from the de-lithiated LixCoO2 and combustion of carbonaceous materials. X-ray diffraction analysis reveals the presence of Co3O4 in the cathode material of a 4.5 V cell heated to 400 °C. The major cathode product formed after the combustion process cells abused by forced current is Co3O4 and by discharge current the products are LiCoO2 and Co3O4. The formation of a trace quantity of CoO through the reduction of Co3O4 by virtue of the reducing power of the organic solvent is also discussed. 相似文献
78.
79.
Won Tae Kang Byeong Rog Shin Doeg Hee Doh 《Journal of Mechanical Science and Technology》2014,28(1):175-182
An experimental investigation on the effective shape of a floor splitter to reduce sub-surface vortices and cavitation which arise in the vicinity of the pump bells in pump sump is performed. A test model sump was designed based on the Froude number similitude for the recommended structure layout by HI-9.8 standard for pump intake design. To obtain an effective shape of the splitter as an anti-vortex device (AVD), three types of quadrilateral submerged bar with different shape and dimension in sectional area are considered. From the experimental results with and without the splitter attached on the floor under the bell mouth, it was confirmed that the installation of the AVD is very effective to reduce abnormal vortices including sub-surface vortices, pre-swirls and other undesirable hydraulic phenomena. Because of the splitter, sub-surface vortices under the bell mouth did not appear anymore and the swirl was dramatically weakened. The evaluation of AVD was made by the measurement of swirl angles indicating the strength of the vortices and pre-swirls. Splitters with square sections showed partly large swirl angles beyond the acceptable criteria of HI standard though a large square was more effective than a small one. Meanwhile, the splitter with trapezoidal section was showed swirl angle values of less than 5 degrees in all cases of pump operation. Among the three types of AVD, the trapezoidal splitter is the most effective one to suppress the vortices. It is very useful to reduce the occurrence of submerged vortices and to obtain stable inflow condition for designing a high performance pump sump. 相似文献
80.
M. Muthtamilselvan D. Prakash Deog-Hee Doh 《Journal of Mechanical Science and Technology》2014,28(9):3709-3718
This work is made to study the effect of local thermal non-equilibrium (LTNE) on transient MHD laminar boundary layer flow of viscous, incompressible nanofluid over a vertical stretching plate embedded in a sparsely packed porous medium. The flow in the porous medium is governed by simple Darcy model. The model used for the nanofluid incorporates the effects of Brownian motion and thermophoresis. Three temperature model is used to represent the local thermal non-equilibrium among the particle, fluid, and solid-matrix phases. By applying similarity analysis, the governing partial differential equations are transformed into a set of time dependent nonlinear coupled ordinary differential equations and they are solved by Runge-Kutta Fehlberg Method along with shooting technique. Numerical results of the boundary layer flow characteristics for the fluid, particle and solid phases are obtained for various combinations of the physical parameters. It is found that the thermal non-equilibrium effects are strongest when the fluid/particle, fluid/solid Nield numbers and thermal capacity ratios are small. Moreover, the amount of heat transfer is maximum in nanoparticles than that of fluid and solid phases because of enhancement of thermal conductivity in nanofluids. 相似文献