• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.5
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• pp.15-22
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• 2014

The automobile cruise control system tries to maintain a constant velocity in the face of disturbance mainly caused by mass changes or changes in the slope of a road. The controller should compensate for such disturbances and model uncertainties. In this paper, we study on the disturbance observer based controller for cruise control system. In the presence of disturbances and model uncertainties, we carry out computer simulations in order to compare the performance of the conventional PI controller and DOB controller. From the simulation results, we found that the performance of DOB controller is superior to that of the conventional PI controller.

• Korean Journal of Applied Biomechanics
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• v.13 no.2
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• pp.75-87
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• 2003

The purpose of this study was to identify the mechanical factors that are crucial to the successful double salto backward piked dismount on the parallel bars. The subjects were 5 national gymnasts(G1: sucessed landing, G2: failed landing), two video cameras were used to record the dismount of the subjects. It summarizes that (a) It is important to make small slope angle(X axis, Y axis) at release, whereas it makes large shoulder angle and trunk rotation angle. (b) It is important to prepare landing in advance, reducing vertical velocity and making large hip angle at BTO(body take off). (c) It is also important to make small knee angle and hip angle, and reduce the angle of trunk rotation.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.196-196
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• 2016

Landslide dam failure presents as a severe natural disaster due to its adverse impact to people and property. If the landslide dams failed, the discharge of a huge volume of both water and sediment could result in a catastrophic flood in the downstream area. In most of previous studies, breaching process used to be considered as a constructed dam, rather than as a landslide dam. Their erosion rate was assumed to relate to discharge by a sediment transport equation. However, during surface erosion of landslide dam, the sediment transportation regime is greatly dependent on the slope surface and the sediment concentration in the flow. This study aims to accurately simulate the outflow hydrograph caused by landslide dam by overtopping through a 2D surface flow erosion/deposition model. The lateral erosion velocity in this model was presented as a function of the shear stress on the side wall. The simulated results were then compared and it was coherent with the results obtained from the experiments.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.15 no.2
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• pp.182-187
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• 1986

Experimental measurements of the heat transfer and heat flux to a jet impinging on a heated surface were obtained in the nucleate boiling regimes. Tes-variables were jet at velocity and aspect ratio ($b/\ell$) of the heated surface. A slope of nucleate boiling curve increased with increasing the aspect ratio of the heated surface, namely approaching a rectangular square, and it is shown that surface tension has an important role for the onset of nucleate boiling heat transfer. A generalized correlation of the jet nucleate boiling heat transfer. A generalized correlation of the jet nucleate boiling heat transfer was found using a pi theorem.

• Journal of Korea Water Resources Association
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• v.42 no.9
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• pp.715-724
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• 2009

In case of inclined crest groyne, flow constriction with water is different. Therefore, it is proper to apply to narrow channel or there is a risk of overflow with water level rising caused by installation of groynes. This study were conducted experiments on inclined crest groyne. Main factors of inclined crest groyne are angles of crests slope and changes of water level. Velocity profile around groyne was measured by LSPIV (Large Scale Particle Image Velocimetry). Flow fields around groyne were analyzed focused on main channel and recirculation area. From the results, Thalweg change has little an effect on rate length and height of recirculation rises on increasing rate length. Length of recirculation area was about 12$\sim$16 times of rate length of groyne. Maximum velocity in main channel area was measured about 1.45$\sim$2.1 times of approach velocity and has little an effect on crest angle of groyne. Back water velocity recirculation area was decreased on approach velocity. This result presents to make stable flow to bank protection.

• Journal of the Korean Geophysical Society
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• v.5 no.4
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• pp.329-336
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• 2002

Electrical resistivity dipole-dipole, seismic refraction, and seismic reflection methods were performed to delineate the boundaries the Yongdong basin(Cretaceous) in terms of physical properties and to ultimately identify the margin architectures of the faults or unconformities. Higer resistivities (approximately >2000 ohm-m) most likely originate from the basement of the basin, contrasting with the lower resistivities from infilled sedimentary rocks. Faults at the eastern margin and unconformities at the western boundary are characterized as high-slope($70^{\circ}$) and gentle-slope($30^{\circ}$) gradients in the resistivity sections, respectively Such features for the boundaries are also suggested by the lower values of seismic velocity and resistivity for the western margin.

• The Journal of Korean Physical Therapy
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• v.20 no.3
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• pp.9-18
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• 2008

Purpose: We determined the effect of global synkinesis(GS) on gait ability, muscle contraction, and central neuron action potentials in post-stroke hemiplegic subjects. Methods: Thirty hemiplegia patients were evaluated for walking ability, muscle contraction, central neuron action potential, and comparing differences between the H-GS(high-global synkinesis) group and L-GS(low-global synkinesis) group. To obtain the GS level, surface electromyography(EMG) data were digitized and processed to root mean square(RMS). Walking ability was tested with a modified motor assessment scale(MMAS), a 10 m walking test, timed up and go(TUG) test, and a Fugl-Meyer assessment(FMA). Muscle contraction ability was measured as maximal isometric contraction(MIC) peak, MIC slope, and MIC ramp up using mechanomyography(MMG). Central neuron action potential was measured as the H/Mmax ratio or V/Mmax ratio using EMG. The data were analyzed with t-tests to determine the statistical significance. Results: MMAS(p<0.01), 10 m walking velocity(p<0.01), TUG(p<0.01), FMA-HKA(Hip, Knee, Ankle)(p<0.05), FMA-coordination(p<0.05), MIC peak (p<0.05), MIC slope(p<0.01), and MIC ramp up(p<0.05) were significantly different between H-GS and L-GS, as was the V/Mmax ratio(p<0.05), but H/Mmax was not. Conclusion: Lower GS levels indicated better walking ability and motor function. Therefore, intervention programs should consider GS levels in gait training of chronic hemiplegia.

• Journal of the Korean Geographical Society
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• v.32 no.4
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• pp.421-434
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• 1997

Flume experiments are conducted to describe channel adjustments at stream confluences and to examine some factors to which changes in channel characteristics are subject. There are different factors controlling channel size and shape; shereas the fomer is primarily controlled by water discharge alone, the latter including channel slope is influenced by sediment load as well as water discharge. The morphometric adjustments of confluent tributaries can be consequently classified into three types based upon changes in sediment concentration which are associated with the relative increasing rates of water discharge and sediment load at these sites. Flow is accelerated at stream confluences due to the convergence of confluent flows, causing an sharp increase in velocity. It restrains an increase in channel capacity, and furthers a decrease in channel slope, of a receiving stream. As a result, effects of slight increases in sediment concentration hardly appear on changes in channel characterisitics at stream confluences.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.15 no.3
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• pp.159-166
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• 2003

In this study, we develop a finite element model to directly solve the Laplace equation while keeping the same computational efficiency as the models based on the extended mild-slope equation which has been widely used for calculation of wave transformation in shallow water. For this, the computational domain is discretized into finite elements with a single layer in the vertical direction. The velocity potential in the element is then expressed in terms of the potentials at the nodes located at water surface, and the Galerkin method is used to construct the numerical model. A common shape function is adopted in horizontal direction, and the cosine hyperbolic function in vertical direction, which describes the vertical behavior of progressive waves. The model was developed for vertical two-dimensional problems. In order to verify the developed model, it is applied to vertical two-dimensional problems of wave reflection and transmission. It is shown that the present finite element model is comparable to the models based on extended mild-slope equations in both computational efficiency and accuracy.

• Korean Journal of Agricultural Science
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• v.37 no.3
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• pp.435-449
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• 2010

Soils in the sloping uplands in Korea are subject to intensive land use with high input of agrochemicals and are vulnerable to soil erosion. Development of the environmentally sound land management strategy is essential for a sustainable production system in the sloping upland. This report addresses the status of upland agriculture and the best management practices for the uplands toward the sustainable agriculture. More than 60% of Korean lands are forest and only 21% are cultivating paddy and upland. Uplands are about 7% of the total lands and about 62% of the uplands are in the slopes higher than 7%. Due to the site-specificity of the upland, many managerial and environmental problems are occurring, such as severe erosion, shallow surface soils with rocky fragments, and loadings of non-point source (NPS) contaminants into the watershed. Based on the field trials, most of the sloping uplands were classified as Suitability Class III-V and the major limiting factor was slope and rock fragments. Due to this, soils were over-applied with N fertilizer, even though N rate was the recommendation. This resulted in decreases in yield, degradation of soil quality and increases in N loading to the leachate. Various case studies drew management practices toward sustainable production systems. The suggested BMP on the managerial, vegetative, and structural options were to practice buffer strips along the edges of fields and streams, winter cover crop, contour and mulching farming, detention weir, diversion drains, grassed waterway, and slope arrangement. With these options, conservation effects such as reductions in raindrop impact, flow velocity, runoff and sediment loss, and rill and gully erosion were observed. The proper management practice is a key element of the conservation of the soil and water in the sloping upland.