• Journal of Korea Foundry Society
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• v.42 no.1
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• pp.3-11
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• 2022

In this study, the parameters on the shrinkage defect of HR3C alloy was secured through computer simulation research, and the ingot mold with greater than 85% of sound area was designed and manufactured. Moreover, the optimized coagulation was proposed at design stage through computer simulation and test was performed upon ingot manufactured. After the test, the defect pattern was analyzed through cutting and non-destructive inspection to verify the parameter and ingot mold design. Based on the verification results, shrinkage defect parameters such as Niyama, Feed Efficiency, and Hot Tear Intensity of HR3C Alloys were obtained. In addition, through the secured parameters, a plan for designing ingot mold with a Non-defect area of 85% or more was secured.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.5
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• pp.1074-1083
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• 1993

NC simulation has been used to replace the test cutting of NC machining. Although it can reduce the NC part programming effort, it still has a problem. If any error is found during the simulation, then the part has to be reprogrammed and it is time consumming. This paper presents a method for verifying and editing the NC code after the post-processing without going back to the part programming stage. A data structure and an algorithm to verify and edit the NC code interactively with the aid of graphics is introduced. Z-map method is used for the shaded image display and cross-sectional view display of the macined parts. The method was implemented in a IBM/PC-386 with MS-Windows software, and the multi-window function of the of the MS-Windows is used for the simultaneous editing and verification.

• Journal of Korea Foundry Society
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• v.29 no.1
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• pp.33-37
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• 2009

Cartesian grid system has mainly been used in the casting simulation even though it does not nicely represent sloped and curved surfaces. These distorted boundaries cause several problems. A special treatment is necessary to clear these problems. In this paper, we propose a new method that can consider the cutting cells which are cut by casting and mold based on the partial cell treatment (PCT). This method provides a better representation of geometry surface and will be used in the computation of velocities that are defined on the cell boundaries in the Cartesian grid system. Various test examples for several casting process were computed and validated. The analysis results of more accurate fluid flow pattern and less momentum loss owing to the stepped boundaries in the Cartesian grid system were confirmed. By using the cut cell method, performance of computation gets better because of reducing the whole number of meshes.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.3
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• pp.214-221
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• 2005

For decades, airships have being developed in Europe (especially German) and America. Airships are planning to be used for advertisements and airliners as well. In Korea, KARI (Korea Aerospace Research Institute) is developing stratospheric communication airship and the similar research is carried out in Japan. Among them, Zeppelin of German has the cutting-edge airship technology with Zeppelin NT. In this paper, the flight performance and stability were evaluated by comparing mathematical theory and the real test. The stability was examined through dynamic modeling and assured by designing controllers at each flight mode. Elevator angle, rudder angle, magnitude of thrust and tilting angle of thrust vector were used as control inputs. Moreover, after measuring the airship velocity, flight direction, magnitude and direction of the wind, attitude angles and trajectories of the airship at each flight mode, the results were compared with the simulation. To get the reasonable data, low-pass filter and band-stop filter were designed to get rid of the sensor noise and engine vibration. The test was accomplished at cruise mode, turning mode, and deceleration. To conclude, with comparing the simulation data and flight test data, it could be known that the dynamic model used in this paper was reasonable.

• Journal of Korean Society of Water and Wastewater
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• v.14 no.1
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• pp.108-116
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• 2000

Chlorine is widely used as a disinfectant in drinking-water systems throughout the world. Chlorine residual was used as an indicator for prediction of water quality in water distribution systems. The variation of chlorine residual in drinking water distribution systems of Suwon city was simulated using EPANET. EPANET is a computerized simulation model which predicts the dynamic hydraulic and water quality behavior within a water distribution system operating over an extended time period. Sampling and analysis were performed to calibrated the computer model in 1999 (Aug. Summer). Water quality variables used in simulations are temperature, roughness coefficient, pipe diameter, pipe length, water demand, velocity and so on. Extended water residence time affected water quality due to the extended reaction time in some areas. All area showed the higher concentration of chlorine residual than 0.2mg/l(standard). So it can be concluded that any area in Suwon city is not in biological regrowth problem. Rechlorination turned out to be an useful method for uniform concentration of free chlorine residual in distribution system. The cost of disinfectant could be saved remarkably by cutting down the initial chlorine concentration to the level which guarantees minimum concentration (0.2mg/l) throughout the distribution system.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.518-522
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• 2011

Cartesian grid system has mainly been used in the casting simulation even though it does not nicely represent sloped and curved surfaces. These distorted boundaries cause several problems. A special treatment is necessary to clear these problems. A cut cell method on Cartesian grids has been developed to simulate three-dimensional mold filling Cut cells at a cast-mold interface are generated on Cartesian grids. Governing equations were computed using volume and areas of cast at cut cells. In this paper, we propose a new method that can consider the cutting cells which are cut by casting and mold based on the patial cell treatment (PCT). This method provides a better representation of geometry surface and will be used in the computation of velocities that are defined on the cell boundaries in the Cartesian gird system. Various test examples for several casting process were computed and validated. The analysis results of more accurate fluid flow pattern and less momentum loss owing to the stepped boundaries in the Cartesian grid system were confirmed. We can know the momentum energy at the cut cell is conserved by using the cut cell method. By using the cut cell method. performance of computation gets better because of reducing the whole number of meshes.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.37
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• pp.44.1-44.6
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• 2015

Background: The present study introduces the design and fabrication of a simple surgical guide with which to perform genioplasty. Methods: A three-dimensional reconstruction of the patient's cranio-maxilla region was built, with a dentofacial skeletal model, then derived from CT DICOM data. A surgical simulation was performed on the maxilla and mandible, using three-dimensional cephalometry. We then simulated a full genioplasty, in silico, using the three-dimensional (3D) model of the mandible, according to the final surgical treatment plan. The simulation allowed us to design a surgical guide for genioplasty, which was then computer-rendered and 3D-printed. The manufactured surgical device was ultimately used in an actual genioplasty to guide the osteotomy and to move the cut bone segment to the intended location. Results: We successfully performed the osteotomy, as planned during a genioplasty, using the computer-aided design and computer-aided manufacturing (CAD/CAM) surgical guide that we initially designed and tested using simulated surgery. Conclusions: The surgical guide that we developed proved to be a simple and practical tool with which to assist the surgeon in accurately cutting and removing bone segments, during a genioplasty surgery, as preoperatively planned during 3D surgical simulations.

• Laser Solutions
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• v.13 no.2
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• pp.10-16
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• 2010

Laser-assisted machining is dependent on absorbed energy density into workpiece. Generally, the absorptivity of laser beam is dependent on wave length of laser, materials, surface roughness, etc. Various shapes and energy densities for beam irradiation can be used to laser-assisted machining. In this thesis, efficient method of heat source modeling was developed and designed by using one fundamental experimental trials. And then, laser-assisted machining of rod-shaped cast iron was simulated by using commercial FEM code MARC. Simulations and experiments with various conditions were carried out to determine suitable condition of pre-heating for laser-assisted turning process. Temperature distribution of cutting zone could be predicted by simulation.

• Journal of the Korea Society for Simulation
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• v.15 no.4
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• pp.137-142
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• 2006

D/In modern production industries, computer aided systems have been improving the efficiency and convenience of the various stages of work. However. as the complexity of computerized production systems increases, various techniques are still necessary. The problem we addressed occurs in computer systems that automatically make manufacturing process plans in the metal grating manufacturing industry. In the grating layout design, the key to saving the manufacturing cost is to find a design with the minimal number of cutting operations. The proposed genetic algorithm explores the feasible alternatives within the space until an optimal solution is obtained.

• Geomechanics and Engineering
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• v.11 no.1
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• pp.117-139
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• 2016

Previous studies for soil movements induced by tunneling have primarily focused on the free soil displacements. However, the stiffness of existing structures is expected to alter tunneling-induced ground movements, the sheltering influences for underground structures should be included. Furthermore, minimal attention has been given to the settings for the shield machine's operation parameters during the process of tunnels crossing above and below existing tunnels. Based on the Shanghai railway project, the soil movements induced by an earth pressure balance (EPB) shield considering the sheltering effects of existing tunnels are presented by the simplified theoretical method, the three-dimensional finite element (3D FE) simulation method, and the in-situ monitoring method. The deformation prediction of existing tunnels during complex traversing process is also presented. In addition, the deformation controlling safety measurements are carried out simultaneously to obtain the settings for the shield propulsion parameters, including earth pressure for cutting open, synchronized grouting, propulsion speed, and cutter head torque. It appears that the sheltering effects of underground structures have a great influence on ground movements caused by tunneling. The error obtained by the previous simplified methods based on the free soil displacements cannot be dismissed when encountering many existing structures.