• Journal of the Korean Geotechnical Society
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• v.31 no.11
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• pp.49-60
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• 2015

Open-water sediment disposal has many applications in costal construction. Dumping of sediment in open water can be divided into descending stage under water and sedimentation stage on the seabed, and retained rate is evaluated from analyzed results of these two successive stages. Descending particle cloud have two distinct thermal and swam phase, and trajectory equations for each phase are derived to describe settling velocity and radius of particle cloud. For sedimentation stage, a numerical simulator is used to calculate growth factors for particle fiction angle and current velocity. Retained rate is defined as a mass rate of remained sediment inside the circle which has a center at dumping point on the sea level and user-defined effective radius. Retained rate map for Singapore coast is presented with water depth of 20 m, current velocity of 0.0~1.5 m/s, and effective radius of 5 m. It will decrease sediment mass loss during disposal operation and minimize surrounding environmental pollution.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.308-322
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• 1991

A set of experiments of Counter-Current Flow Limit(CCFL or Flooding) was performed to improve the drawbacks of Wallis' Correlation which neglects the effects of channel size, channel length, injection method and the boundary conditions at the inlet of liquid and gas phase. In these experiments using water and air, the followings were found ; (i) The effects of channel size and length were quite significant. In large tubes(D>20mm), the flooding front occurred at the bottom of the channel and when the gas flow increased the front moved upward ; however, in small tubes(D<20mm), there were no upward movement of flooding front and the flooding just occurred at the liquid inlet. (ii) The effect of water inlet device was not as significant as that of channel length though the inlet boundary conditions could affect the flow development and flooding afterward. (iii) Once the flooding front reached the inlet of water injection device, an newly reduced flow condition was set up and resulted in another flooding corresponding to the new condition.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.27-30
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• 2005

Hanwha Corporation succeeded in domestic development of thruster heat shield for KOMPSAT-2 propulsion subsystem partly. Thruster heat shield, one of the main components of DTM, is designed to prevent the critical radiative heat exchange between thruster and satellite during firing. To overcome the manufacturing difficulties, an electro-forming process is preferred to classical welding process. In this case, an inner diameter of a new shield will be decreased a little due to the change of manufacturing process. The interference problem between thruster nozzle and heat shield was investigated through structural analysis by KARI. Hanwha manufactured heat shield based on the analysis results. In this paper, full development process is described for design, analysis, manufacturing of heat shield.

• 한국HCI학회:학술대회논문집
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• 2008.02a
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• pp.210-214
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• 2008

It is actually impossible to model and store all objects which exist in real home environment into robot's database in advance. To resolve this problem, this paper proposes new object modeling method that can be available for robot self-modeling, which is capable of estimating whole model's shape from partial surface data using Generic Model. And this whole produce is conducted to cylindrical objects like cup, bottles and cans which can be easily found at indoor environment. The detailed process is firstly we obtain cylinder's initial principle axis using points coordinates and normal vectors from object's surface after we separate cylindrical object from 3D image. This 3D image is obtained from 3D sensor. And second, we compensate errors in the principle axis repeatedly. Then finally, we do modeling whole cylindrical object using cross sectional principal axis and its radius To show the feasibility of the algorithm, We implemented it and evaluated its accuracy.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.3
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• pp.259-268
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• 2015

An optimization method for the tube hydroforming process is developed using the equivalent static loads method for non linear static response structural optimization (ESLSO). The aims of the tube hydroforming optimization are to determine the axial forces (axial feedings) and the internal pressures, and to obtain the desired shape without failures after hydroforming analysis. Therefore, the magnitude of the forces should be design variables in the optimization process. Also, some tube hydroforming optimization needs to consider the result of the thickness in nonlinear dynamic analysis as responses. However, the external forces are considered as constants and the thickness is not a response in the linear response optimization process of the original ESLSO. Thus, a new ESLSO process is proposed to overcome the difficulties and some examples are solved to validate the proposed method.

• Fire Science and Engineering
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• v.32 no.2
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• pp.17-23
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• 2018

In this study, the relations of the wall thermal conductivity and surface temperature in a compartment fire are investigated using Buckingham Pi theorem. The dimensionless parameters of the previous study are analyzed in order to correlate the dimensionless groups of the heat release rate, the thermal conductivity, the volume of compartment and the convective heat transfer coefficient. In addition the reduced scale of compartment, which has 1/6 size of ISO 9705 Room Corner Tester, is manufactured and the oxygen concentration and the maximum temperature in the space are measured for the gasoline pool fire ($10cm{\times}10cm$, $15cm{\times}15cm$ and $20cm{\times}20cm$). Finally, the criterion of the wall temperature increase are suggested in accordance with the thermal conductivity and the convective heat transfer coefficient. In addition, the dimensionless empirical equation using Buckingham Pi theorem considering the heat release rate are presented suggested. The results of this study will be useful especially for the fire phenomenon investigation of the wall thermal conductivity coefficient and shape in the compartment space.

• Fire Science and Engineering
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• v.12 no.1
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• pp.3-8
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• 1998

This study has been conducted experimentally on the effects of natural convection heat transfer characteristics for inclined flat plate with vertical fin in air. The effects of various fin length, flat plate inclined angle and Grashof number are mainly investigated The experimented results are as follows: The mean heat transfer coefficient increase according to the decrease of H/S in the various fin lengh. The mean heat transfer coefficient at H/S-0.5, 1.0, 1.5 for Gr=2.11$\times$103. $\theta$=00 increase by 107%, 43%, 15% than H/S=2.0. The mean heat transfer coefficient decrease with the increase of $\theta$ the inclined angles. The mean heat transfer coefficient at Gr=2.97$\times$103 is constant, at $\theta$= 00 for H/S=0.5 decrease by 33% than $\theta$=90$^{\circ}$. The mean heat transfer coefficient increase as Grashof as Grashof number increase. The mean heat transfer coefficient at Gr=2.31$\times$103, Gr=2.61$\times$103, Gr=2.97$\times$103 for H/S=1.0, $\theta$=0$^{\circ}$increase by 9%, 16%, 28% than Gr=2.11$\times$103.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.11
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• pp.217-223
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• 2019

The application of 3D printing technology is expanding due to the production of the complex-shape parts and the one-step manufacturing process. Moreover, various technical solutions in 3D printing are emerging through continuous research and development. Representative technologies include SLS technology, in which a desired area is sintered and laminated by irradiating a powder-type material with a laser. In addition, high-performance engineering plastic parts are being manufactured in increasing numbers. In this study, tensile specimens were fabricated from polyamide 12, a widely available polymer, and the glass bead-reinforced polyamide 12. The specimen-build orientation was divided into 0°, 45°, and 90° on the fabrication platform, and the tensile test temperature was -25℃, 25℃, and 60℃. The test results showed that the tensile modulus of both materials decreases as the build orientation becomes closer to 90°. In addition, the tensile strength of glass bead-reinforced PA12 showed more dependence on the build orientation than PA12. In addition, the tensile modulus and tensile strength decreased with increasing test temperature.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.7
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• pp.1583-1590
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• 2011

As the existing radiation scanning systems use 2-dimensional radiation scanned images, the low accuracy has been pointed out as a problem of it. This research analyzes the applicability of the stereo image processing technique to X-ray scanned images. Two 2-dimensional radiation images which have different disparity values are acquired from a newly designed stereo image acquisition system which has one additional line sensor to the conventional system. Using a matching algorithm the 3D reconstruction process which find the correspondence between the images is progressed. As the radiation image is just a density information of the scanned object, the direct application of the general stereo image processing techniques to it is inefficient. To overcome this limitation of a stereo image processing in radiation area, we reconstruct 3-D shapes of the edges of the objects. Also, we proposed a new volume based 3D reconstruction algorithm. Experimental results show the proposed new volume based reconstruction technique can provide more efficient visualization for cargo inspection. The proposed technique can be used for such objects which CT or MRI cannot inspect due to restricted scan environment.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.10
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• pp.817-829
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• 2014

One of the main issues in tissue engineering has been the development of a three-dimensional (3D) structure, which is a temporary template that provides the structural support and microenvironment necessary for cell growth and differentiation into the target tissue. In tissue engineering, various biomaterials and their processing techniques have been applied for the fabrication of 3D structures. In particular, 3D printing technology enables the fabrication of a complex inner/outer architecture using a computer-aided design and manufacturing (CAD/CAM) system, and it has been widely applied to the fabrication of 3D structures for tissue engineering. Novel cell/organ printing techniques based on 3D printing have also been developed for the fabrication of a biomimetic structure with various cells and biomaterials. This paper presents a comprehensive review of the functional scaffold and cell-printed structures based on 3D printing technology and the application of this technology to various kinds of tissues regeneration.