• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.1
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• pp.193-201
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• 1995

The role of thermal contact resistance between a casting and a metal mold as well as natural convection in the melt during solidification of a pure metal is numerically studied. Numerical simulation is performed for a rectangular cavity using the coordinate transformation by boundary-fitted coordinate and pure aluminum is used as the phase- change material. The influences of thermal contact resistance on the interface shape and position, solidified volume fraction, temperature field and local heat transfer are investigated.

• Journal of Mechanical Science and Technology
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• v.14 no.6
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• pp.622-632
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• 2000

In a high precision vertical machining center, the estimation of cutting forces is important for many reasons such as prediction of chatter vibration, surface roughness and so on. The cutting forces are difficult to predict because they are very complex and time variant. In order to predict the cutting forces of end-milling processes for various cutting conditions, their mathematical model is important and the model is based on chip load, cutting geometry, and the relationship between cutting forces and chip loads. Specific cutting force coefficients of the model have been obtained as interpolation function types by averaging forces of cutting tests. In this paper the coefficients are obtained by neural network and the results of the conventional method and those of the proposed method are compared. The results show that the neural network method gives more correct values than the function type and that in the learning stage as the omitted number of experimental data increase the average errors increase as well.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.977-981
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• 2002

The ordinary differential equations governing free vibrations of elastic horizontally curved beams are derived, in which the effect of shear deformation as well as the effects of vertical, rotatory and torsional inertias are included. Frequencies and mode shapes are computed numerically for parabolic curved beams with the hinged-hinged, hinged-clamped and clamped-clamped ends. Comparisons of natural frequencies between this study and ADINA are made to validate the theories and numerical methods developed herein. The lowest three natural frequency parameters are reported, with and without the effect of shear deformation, as functions of the three non-dimensional system parameters: the horizontal rise to span length ratio, the slenderness ratio and the stiffness parameter.

• Journal of the korean society of oceanography
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• v.36 no.4
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• pp.93-100
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• 2001

The concentrations of 20 congeners of PCBs were determined in surficial and dated sediments from Jinhae, Busan, Ulsan and Yeongil Bay of Korea to assess current distributions as well as historical trends. The concentration ranges of total CBs in sediments were nd-138.60 ng/g dry wt. The concentrations of total CBs were significantly different among bays in the southeastern coastal areas (Kruskal-Wallis Test, p=0.036), Showing the Order Of Busan>Ulsan>Yeongil>Jinhae Bay. Predominant PCB homologues were penta-, hexa- and hepta-CBs. The down-core distributions of PCBs showed that the highest concentrations occurred in the late 1960s, coinciding with the onset of industrialization of Korea. The compositions of PCB congeners in sediment among bays were uniform, suggesting that major sources were not changed over time.

• 한국해양학회지
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• v.23 no.1
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• pp.13-23
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• 1988

A simple model is presented which may explain the distributions of cold surface water near Ulsan. The model considers the problem as an advection-diffusion process with cold source confined within narrow coastal areas. The natural warming due to vertical process (interaction either with the atmosphere above or with the subsurface water below) also plays an important role. A simple numerical computation reproduces the observations quite well. The localization of cold surface water occurs at the point where the local warm current separates from the coast.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.206-210
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• 1998

A study on dynamic characteristics of rotating disks in magneto optical disk drives is presented. Natural frequencies of rotating disks are investigated experimentally and numerically. The frequency response and critical speeds of the ASMO disk are discussed. The characteristics of airflow around the disk and their effects on disk vibrations are also investigated. It is found that the numerical calculation of the natural frequencies of rotating disks agrees well with the experimental results. The airflow around the disk in the cartridge affects the characteristics of the disk vibrations to reduce the modal frequencies of the disk. The experiment shows that negative vertical offsets of the disk in the cartridge possibly increase the vibration amplitudes. As being influenced by the geometry of the cartridge, the rotation of the disk causes an asymmetric airflow in the presence of window.

• Journal of Chest Surgery
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• v.11 no.2
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• pp.175-180
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• 1978

A rare form of tetralogy of Fallot, in which large ventricular septal defect was located at subpulmonary position rather than beneath a well developed crista supraventricularis was operated in this Department. This case satisfied the criteria for the diagnosis of tetralogy of Fallot, having large ventricular septal defect beneath the aortic valve with overriding of aorta, pulmonary stenosis and right ventricular hypeFtrophy. The operation was done through a median sternotomy using cardiopulmonary bypass. A vertical right ventriculotomy was extended to the pulmonary valve ring. Pulmonary and aortic valve were adjacent to each other, in contrast to the situation of classic tetralogy of Fallot. Pulmonary valvulotomy was done and ventricular septal defect was closed. with Teflon, and right ventricular outflow tract was reconstructed with woven Dacron covered by pericardial patch after minimal resection of septal band. The post-operatiove courses was uneventful except wound infection. The patient was discharged 15 days after open heart surgery.

• Structural Engineering and Mechanics
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• v.56 no.1
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• pp.1-25
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• 2015

The main goal of this study was to develop a convenient strengthening technique for retrofitting of reinforced concrete members. For this purpose a new retrofitting material so-called prefabricated-HSPRCC (high performance steel plate reinforced cementitious composite) panel was developed by using high performance concrete and perforated steel plate. Prefabricated-HSPRCC composes advantages of steel and high performance concrete. The prefabricated-HSPRCC panels were either only bonded on the specimens using epoxy mortar or anchored to the specimen by steel bolts as well as bonding. Effect of different variations such as prefabricated-HSPRCC panel thicknesses, steel plate thicknesses, puncture orientation of perforated steel plate, existence of anchorage etc. were studied through a simple experimental work. The behaviour of the specimens under vertical point load was also studied by using simple mechanics. The retrofitted specimens were found to exhibit much better performance both in terms of strength and deformation capability. The anchorage application was found to positively affect this improved performance. Furthermore, as a result of the tests the best parameters of prefabricated-HSPRCC plate for improving strength and deformation capacities were determined.

• Geomechanics and Engineering
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• v.8 no.6
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• pp.801-810
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• 2015

The ultimate pullout capacity under inclined dynamic loading is an important measure of the destruction degree of vertical screw piles (anchors) under dynamic actions. Based on the static and dynamic tests on two kinds of model screw piles, the ultimate bearing capacity was researched considering different distance-width ratio of blade (D/W) and preloading ratio. The results compared well with other experimental data available in the literature. This research reveals that D/W might determine the failure model of the piles (anchors), for example D/W = 3.14 or 5; a critical dynamic-static loading ratio (DSLR) existed in the experiments. The critical DSLR was reached under the conditions of 40%~60% preloading (D/W = 3.14) or 20%~40% preloading (D/W = 5), respectively.

• Geomechanics and Engineering
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• v.8 no.6
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• pp.845-857
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• 2015

The 3D numerical analysis is carried out to investigate the settlement behavior of flexible mat foundations subjected to vertical loads. Special attention is given to the improved analytical method (YS-MAT) that reflects the mat flexibility and soil spring coupling effect. The soil model captures the stiffness of the soil springs as well as the shear interaction between the soil springs. The proposed method has been validated by comparing the results with other numerical approaches and field measurements on mat foundation. Through comparative studies, the proposed analytical method was in relatively good agreement with them and capable of predicting the behavior of the mat foundations.