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261.
In this paper, we present the results of our numerical seakeeping analyses of a 6750-TEU containership, which were subjected to the benchmark test of the 2 nd ITTC–ISSC Joint Workshop held in 2014. We performed the seakeeping analyses using three different methods based on a 3D Rankine panel method, including 1) a rigid-body solver, 2) a flexible-body solver using a beam model, and 3) a flexible-body solver using the eigenvectors of a 3D Finite Element Model(FEM). The flexible-body solvers adopt a fully coupled approach between the fluid and structure. We consider the nonlinear Froude–Krylov and restoring forces using a weakly nonlinear approach. In addition, we calculate the slamming loads on the bow flare and stern using a 2D generalized Wagner model. We compare the numerical and experimental results in terms of the linear response, the time series of the nonlinear response, and the longitudinal distribution of the sagging and hogging moments. The flexible-body solvers show good agreement with the experimental model with respect to both the linear and nonlinear results, including the high-frequency oscillations due to springing and whipping vibrations. The rigid-body solver gives similar results except for the springing and whipping. 相似文献
262.
An optimization technique was used to generate a wing-in-ground-effect (WIG) configuration which can achieve the maximum lift
and satisfy the height stability criteria within the design constraints. For the analysis of the aerodynamic coefficients,
the vortex lattice method (VLM) was applied with the inviscid and potential flow approximations. The sequential quadratic
programming (SQP) method, which is a nonlinear optimization method, was employed as an optimization tool. The lift and moment
coefficients, including the stability analysis computed by VLM, were compared with the experimental results of a medium-sized
WIG, and a good correlation was found between them. In addition, the optimization tool was validated by finding the optimal
position of the side wing attached on the WIG craft. Then, various optimum examples are shown, with generation of the wing
section, the determination of the planform configuration, the aspect ratio, and the position of the tail wing within the design
constraints. It was shown that the present optimization tool can be used effectively for the optimal design of a WIG craft. 相似文献
263.
Young Ho Kim Kyung-Il Chang Jong Jin Park Seon Ki Park Sang-Hyun Lee Young-Gyu Kim Kyung Tae Jung Kuh Kim 《Journal of Marine Systems》2009,78(2):249
Reanalyzed products from a MOM3-based East Sea Regional Ocean Model with a 3-dimentional variational data assimilation module (DA-ESROM), have been compared with the observed hydrographic and current datasets in the Ulleung Basin (UB) of the East/Japan Sea (EJS). Satellite-borne sea surface temperature and sea surface height data, and in-situ temperature profiles have been assimilated into the DA-ESROM. The performance of the DA-ESROM appears to be efficient enough to be used in an operational ocean forecast system.Comparing with the results from Mitchell et al. [Mitchell, D. A., Watts, D. R., Wimbush, M., Teague, W.J., Tracey, K. L., Book, J. W., Chang, K.-I., Suk, M.-S., Yoon, J.-H., 2005a. Upper circulation patterns in the Ulleung Basin. Deep-Sea Res. II, 52, 1617-1638.], the DA-ESROM fairly well simulates the high variability of the Ulleung Warm Eddy and Dok Cold Eddy as well as the branching of the Tsushima Warm Current in the UB. The overall root-mean-square error between 100 m temperature field reproduced by the DA-ESROM and the observed 100-dbar temperature field is 2.1 °C, and the spatially averaged grid-to-grid correlation between the two temperature fields is high with a mean value of 0.79 for the inter-comparison period.The DA-ESROM reproduces the development of strong southward North Korean Cold Current (NKCC) in summer consistent with the observational results, which is thought to be an improvement of the previous numerical models in the EJS. The reanalyzed products show that the NKCC is about 35 km wide, and flows southward along the Korean coast from spring to summer with maximum monthly mean volume transport of about 0.8 Sv in August–September. 相似文献
264.
The seasonal variation of the surface circulation in the Japan/East Sea (JES) and the Tsushima/Korea Straits (TKS) is reviewed and discussed, focusing on mesoscale and submesoscale variabilities.The monsoon modified by coastal geographical features near Vladivostok generates a dipole of vortex off Vladivostok which induces dramatic changes in the surface circulation in the northwest JES, splitting the Subpolar Gyre into two smaller gyres by generating the Vladivostok Dome. Between these two smaller gyres, the Northwest Thermal Front is formed and current reversal is induced along the North Korean coast. The winter monsoon also induces a current reversal along the Sakhalin coast. The volume transport of the surface Subpolar Gyre has two maxima in January and August. The maximum in August is induced by the summer intensification of the Liman-North Korean Cold Current and the shallow and narrow surface coastal jet generated by the sea ice and snow melting. The maximum in January is induced by the northwest monsoon and associated cooling.Salient features in the TKS are the submesoscale variabilities. In the western channel, submesoscale eddies with length scale of about 80 km and time scale of 5–6 days develop in the cold period. On the lee side of the Tsushima Islands, Karman-like vortex pairs are generated in the warm period. Anticyclonic vortices generated at the northern tip of the Tsushima Islands have a time scale of 5 to 8 days, length scale of 35 to 60 km, and propagate toward the JES with a phase speed of 8 cm/s. Cyclonic vortices south of the anticyclonic counter part of the vortex pairs are rather stationary with intermittent occasional propagation toward the east. The development of stratification seems to be necessary for the development of Karman-like vortex pairs.Summarizing the results above, a schematic surface circulation with seasonal change is proposed. 相似文献
265.
Yoo-Chul Kim Youn-Mo Lee Myeong-jo Son Tae-wan Kim Jung-Chun Suh 《Journal of Marine Science and Technology》2009,14(3):275-284
We generate cutter paths free of interference and gouging for manufacturing model propellers using a five-axis numerical control
(NC) machine. Our approach is faster than using a general-purpose computer-aided design (CAD)/computer-aided manufacturing
(CAM) system. A roughing cut is made using only three axes for efficiency, and the finishing cut is made using all five axes
to avoid collisions. Elements of the cutter path that might produce gouging are eliminated and the pose of the cutter is adjusted
to eliminate interference. A number of models, including surface-piercing propellers, have been manufactured. 相似文献
266.
In this paper, a powerful tool for analyzing motor vehicle data based on the vector quantization (VQ) technique is demonstrated. The technique uses an approximation of a probability density function for a stochastic vector without assuming an “a priori” distribution. A self‐organizing map (SOM) is used to transform accident data from an N‐dimensional space into a two‐dimensional plane. The SOM retains all the original data yet provides an effective visual tool for describing patterns such as the frequency at which a particular category of events occurs. This enables new relationships to be identified. Accident data from three cities in Italy (Turin, Milan, and Legnano) are used to illustrate the usefulness of the technique. Crashes are aggregated and clustered crashes by type, severity, and along other dimensions. The paper includes discussion as to how this method can be utilized to further improve safety analysis. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
267.
Namkug Ku Ju-hwan Cha Kyu-Yeul Lee Jongwon Kim Tae-wan Kim Sol Ha Donghun Lee 《Journal of Marine Science and Technology》2010,15(4):374-385
This paper describes the development of a self-driving mobile welding robot. The robot is used to weld U-shaped welding areas
in enclosed double-hull structures. In order to place itself inside the double-hull structure, the robot is capable of passing
through an access hole 600 mm wide and 800 mm high. This research addresses the mechanical and control systems of the robot.
The mechanical system of the robot consists of an eight-axis mobile platform, and a six-axis welding unit. The control system
consists of a main controller, a welding machine controller (arc sensor board), and seam tracking sensors, i.e., a touch sensor,
a laser sensor, and an arc sensor. To reduce the number of cables that would be dragged by the welding robot, the main controller
is designed as an embedded type that is mounted on the back of the mobile platform. 相似文献
268.
Recent improvements in the quality of life have led to a consumer need for emotional quality. This need is regarded as extremely
important, particularly for products that require a close interaction between products and users and thus that directly lead
to product purchase. As a result, research on how to design user-friendly products has become an important task for corporations.
Discomfort evaluation in product use has been extensively researched for this purpose. Most of the research concludes that
the joint angles of the human body are the main cause of discomfort and propose a discomfort evaluation method based on joint
angles. In general, when a person uses great force, they feel discomfort, and the level of discomfort varies depending on
the size of the force. Accordingly, it can be inferred that the force acting on the muscle is one of the important causes
of discomfort, and research on the correlation between discomfort and muscle forces is needed. In this study, the authors
developed a method to evaluate discomfort during ingress into a vehicle to design a side panel for comfortable ingress into
a vehicle. The correlation between the muscle forces and discomfort was investigated, and a discomfort evaluation method based
on muscle forces was developed. To calculate the muscle forces during the ingress motion, an experimental mock-up of a vehicle
was made, and a motion capture experiment during the ingress motion was conducted with various side panel design parameters.
The biomechanical simulation tool was used to perform motion simulation based on the motion data obtained. The mathematical
correlation between the calculated muscle forces and discomfort was obtained by means of fuzzy logic, and the discomfort evaluation
method developed in this study was used to propose a method for designing a comfortable side panel for a vehicle. 相似文献
269.
H. Yang B. Kim Y. Park W. Lim S. Cha 《International Journal of Automotive Technology》2009,10(3):381-390
In recent studies, various types of multi-mode electric variable transmissions for hybrid electric vehicles have been proposed.
A multi-mode electric variable transmission consists of two or more different types of a planetary gear hybrid powertrain
system (PGHP), which can change power flow type using clutches to improve transmission efficiency. Input split systems are
generally used for the single-mode powertrain because of their overall superiority, but other power split systems such as
output split and compound split systems can be used in the dual-mode powertrain. In this study, we analyze the power transmission
characteristics of output split systems, and evaluate their fuel economies in the FTP72 cycle, acceleration performance, and
constant vehicle speeds. These results enable the selection of appropriate systems for a dual-mode powertrain. 相似文献
270.
S. Kim J. M. Nouri Y. Yan C. Arcoumanis 《International Journal of Automotive Technology》2009,10(3):277-284
The spray characteristics of a 6-hole injector were examined in a single cylinder optical direct injection spark ignition
engine. The effects of injection timing, in-cylinder charge motion, fuel injection pressure, and coolant temperature were
investigated using the 2-dimensional Mie scattering technique. It was confirmed that the in-cylinder charge motion played
a major role in the fuel spray distribution during the induction stroke while injection timing had to be carefully considered
at high injection pressures during the compression stroke to prevent spray impingement on the piston. 相似文献