• Journal of the Society of Naval Architects of Korea
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• v.47 no.4
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• pp.496-507
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• 2010

It is well known that when a high-speed planing craft travels in following seas it experiences long-periodic motions due to low encounter frequency, and it often loses its course keeping stability. Therefore, it is necessary to study the sea-keeping performance and stability of it in the following seas. In this paper, the vertical motions of a planing craft were measured in following regular waves, and the test results were compared with the theoretical results. In the case of the same encounter frequency, non-dimensionalized motion amplitudes become larger as Froude number is higher, and non-dimensionalized motion amplitudes in head waves are larger than those in following waves. The mean values of the motions in following waves are similar to the running attitudes of a craft in calm water at the same Froude number.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.2
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• pp.139-148
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• 2016

The passive control methods such as horizontal and vertical fences on the lower surface of the bluff body were applied to suppress the vortex shedding and enhance the aerodynamic stability of flow. For investigating the effects of the passive control methods, wind tunnel experiments on the unsteady flow field around a bluff body near a moving ground were performed. The boundary layer and velocity profiles were measured by the Hot Wire Anemometer (HWA) system and the vortex shedding patterns and flow structures in a wake region were visualized via the Particle Image Velocimetry (PIV) system. Also, it is a measuring on moving ground condition that the experimental values of the critical gap distances, Strouhal numbers and aerodynamic force FFT analyses. Through the experiments, we found that the momentum supply due to moving ground caused the vortex shedding at the lower critical gap distance rather than that of fixed ground. The horizontal and vertical fences increase the critical gap distance and it can suppress the vortex shedding. Consequently, the stability characteristics of the bluff body near a moving ground could be effectively enhanced by the simple passive control such as the vertical fences.

• Journal of Environmental Science International
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• v.1 no.1
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• pp.35-43
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• 1992

Handling the emergency problems such as Chemobyl accident require real time prediction of pollutants dispersion. One-point real time sounding at pollutant source and simple model including turbulent-radiation process are very important to predict dispersion at real time. The stability categories obtained by one-dimensional numerical model (including PBL dynamics and radiative process) are good agreement with observational data (Golder, 1972). Therefore, the meteorological parameters (thermal, moisture and momentum fluxes; sensible and latent heat; Monin-Obukhov length and bulk Richardson number; vertical diffusion coefficient and TKE; mixing height) calculated by this model will be useful to understand the structure of stable boundary layer and to handling the emergency problems such as dangerous gasses accident. Especially, this simple model has strong merit for practical dispersion models which require turbulence process but does not takes long time to real predictions. According to the results of this model, the urban area has stronger vertical dispersion and weaker horizontal dispersion than rural area during daytime in summer season. The maximum stability class of urban area and rural area are "A" and "B" at 14 LST, respectively. After 20 LST, both urban and rural area have weak vertical dispersion, but they have strong horizontal dispersion. Generally, the urban area have larger radius of horizontal dispersion than rural area. Considering the resolution and time consuming problems of three dimensional grid model, one-dimensional model with one-point real sounding have strong merit for practical dispersion model.al dispersion model.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.8
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• pp.905-912
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• 2011

In order to protect equipment such as controllers, it is important to improve the driving stability of $6{\times}6$ skidsteering vehicles driven on rough roads. The estimation and improvement of the driving stability should be based on the vertical acceleration, roll acceleration, and pitch acceleration. These variables will be used to achieve multivariable control and increase the vehicle driving stability. In this study, to improve vehicle stability by reducing the vertical acceleration, roll angular acceleration, and pitch angular acceleration, the skyhook control method is employed to control MR(Magnetorheological) dampers equipped with the vehicle. The proposed control system is tested in multibody dynamic simulation.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.4
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• pp.296-303
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• 2012

The captive model test of submerged body using CPMC(Computerized Planar Motion Carriage) was carried out at the Ocean Basin of KORDI/MOERI. The target model is a submarine with general hullform. The forces and moments acting on the submerged body were measured by 6-axis waterproof gage. The oblique motion test and turning test were carried out in horizontal and vertical planes of the model. Maneuvering coefficients and derivatives were obtained from the test results. The stability indices in horizontal and vertical planes were obtained by using maneuvering derivatives. In this paper the introduction of test equipment and test results are presented.

• The Journal of the Korean dental association
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• v.50 no.1
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• pp.13-21
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• 2012

In an edentulous situation, the dentist must make several determinations when constructing artificial teeth. These include vertical and horizontal relationships of mandible with respect to the maxilla, occlusal form and position, vertical dimension, occlusal relationships during both centric closure and eccentric excursive movements. Artificial teeth are attached to a movable base resting on movable and displaceable living tissue subject to damage. They act as a unit; therefore, they must be arranged to function as a unit. Bilateral balanced occlusion is that stability of the denture is attained when bilateral contacts ex ist throughout all dynamic and static states of the denture during function. Lateral excursion in a balanced scheme implies simultaneous working side and nonworking side contact, while occlusal contacts are maintained on both anterior and posterior teeth as the mandible moves anteriorly into protrusion.

• Geomechanics and Engineering
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• v.8 no.4
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• pp.523-540
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• 2015

Based on limit equilibrium principles, this study presents a theoretical derivation of a new analytical formulation for estimating magnitude and lateral earth pressure distribution on a retaining wall subjected to seismic loads. The proposed solution accounts for failure wedge inclination, unit weight and friction angle of backfill soil, wall roughness, and horizontal and vertical seismic ground accelerations. The current analysis predicts a nonlinear lateral earth pressure variation along the wall with and without seismic loads. A parametric study is conducted to examine the influence of various parameters on lateral earth pressure distribution. Findings reveal that lateral earth pressure increases with the increase of horizontal ground acceleration while it decreases with the increase of vertical ground acceleration. Compared to classical theory, the position of resultant lateral earth force is located at a higher distance from wall base which in turn has a direct impact on wall stability and economy. A numerical example is presented to illustrate the computations of lateral earth pressure distribution based on the suggested analytical method.

• Bulletin of the Society of Naval Architects of Korea
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• v.26 no.4
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• pp.35-43
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• 1989

An expert system is a software program that solves problems traditionally solved only by a human expert. An expert system captures and manipulates the knowledge and strategies that a human expert applies to solve a problem. In ship design work, experience and knowledge are very important. If expert system for ship design could be developed, efficiency of design work would be increased very much through use of it. This paper is concerned with a general characteristics of expert system and development of the prototype expert system for ship design-a system which can be utilized to improve the vertical plane stability of SWATH Ship.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.527-532
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• 2010

In this study, vertical and horizontal accelerometers were installed at the both side of car body and tachometer was installed on the bogie, for the purpose of stability analysis of Korail Airport Express Train during driving. By applying the developed algorithm, the peak-to-peaks of horizontal and vertical acceleration which were matched with location by tachometer were found and compared with the threshold values. The threshold values per velocities which were presented in the "Metro Train Performance Criteria" were applied here. The validity of the developed algorithm was shown by comparing the site investigation and the measured values at frost heave locations.

• Proceedings of the KSR Conference
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• 2001.05a
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• pp.295-302
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• 2001

The lateral stability of curved continuous welded rail (CWR) is studied fur buckling prevention. This study includes the influences of vehicle induced loads on the thermal buckling behavior of straight and curved CWR tracks. quasi-static loads model is assumed to determine the uplift region, which occurs due to the vertical track deformation induced by wheel loads of vehicle. Parametric numerical analyses are performed to calculate the upper and lower critical buckling temperatures of CWR tracks. The parameters include track lateral resistance, track curvature, longitudinal stiffness, tie-ballast friction coefficient, axle load, truck center spacing, and the ratio of lateral to vertical vehicle load. This study provides a guideline for the improvement or stability for dynamic buckling in on tracks.