• Journal of Korea Foundry Society
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• v.17 no.5
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• pp.465-471
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• 1997

An integrated computer program consisting of a pre-processor, main solver, and post-processor was developed for the design of large steel castings. The pre-processor, based on the AutoCAD, enables the user to produce approval drawings, casting design drawings and mesh diagrams in sequence using a personal computer. In the main solver, two numerical models were employed; one models the fluid flow during mold filling, and the other models the heat transfer and solidification. The post-processor can be used to present simulation results such as flow pattern, mold filling sequences, solidification times, temperature gradients and location of shrinkage defects by color graphics. In order to validate the applicability of the present integrated program, a series of experiments on simple-shaped steel castings were carried out. After the validation of the present model, it was applied to the casting design of the large steel anchor of an SC42 alloy. Various solidification parameters such as a temperature distribution and a solidification time in the casting and the mold were compared with those obtained experimentally. Simulated results predicting shrinkage defects were in good agreement with those obtained experimentally. It was found that the present method can be successfully applied to the quantitative casting design for complex-shaped large steel castings.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.4
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• pp.77-87
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• 1994

This paper deals with an automated forming sequence design system by which designers can determine desirable operation sequences even if they have little experience in the design of cold forging process. The forming sequence design in the cold forging is very important and requires many kinds of technical and empirical knowledge. They system isproposed, which generates forming sequence plans for the multistage cold forging of axisymmtrical solid products. Since the process of metal forming can be considered as a transformation of geometry, treatment of the geometry of the product is a key in planning process. To recognize the geometry of the product section, section entity representation and primitive geometries were used. Section entity representation can be used for the calculation of maximum diameter, maximum height, and volume. Forming sequence for the part can be determined by means of primitive geometries such as cylinder, cone, convex, and concave. By utilizing this geometrical characteristics (diameter, height, and radius), the product geometry is expressed by a list of the priitive geometries. Accordingly the forming sequence design is formulated as the search problem which starts with a billet geometry and finishes with a given product one. Using the developed system, the sequence drawing with all dimensions, which includes the proper sequence of operations for the part, is generated under the environment of AutoCAD. Based on the results of forming sequence, process variables(strain, punch pressure, die inner pressure, and forming load) are determined.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.227-227
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• 2018

티롤리안 위어(Tyrolean Weir)는 유송잡물 및 유사의 영향이 비교적 높은 산악지역에 설치되는 취수구조물로 대부분 저류면적이 제한된 자류식(Run-Off River) 수력발전 및 소규모 농업용수 취수시설에 적합한 구조물이다. 티롤리안 위어는 일반적인 취수시설과 비교하여 구조물의 규모를 최소화할 수 있어 친환경적 취수구조물로 분류할 수 있다. 아직까지 국내에서는 설치사례가 없고 연구성과 또한 부족하여 적용성에 한계가 있는 것이 사실이다. 본 연구에서는 3차원 유동해석 프로그램인 FLOW-3D를 이용하여 티롤리안 위어의 월류흐름특성을 분석하고 스크린 경사와 월류수위 변화에 따른 유량계수를 산정하였다. 티롤리안 위어 스크린경사에 따른 수치모형실험을 위해 3차원 AUTO CAD 프로그램을 이용하여 위어폭 11.0m, 길이 10m 및 수로경사 2:3의 솔리드 모형을 구성하였으며, 티롤리안 위어 스크린 경사를 $0^{\circ}$, $5^{\circ}$, $10^{\circ}$, $15^{\circ}$, $20^{\circ}$, $25^{\circ}$, $30^{\circ}$로 변화시키며 월류수심 변화에 따른 수치모형실험을 수행하였다. 금회 수치해석 분석결과 다음과 같은 결론을 얻을 수 있었다. 1) 티롤리안 위어 스크린 경사가 증가할수록 유량계수가 증가하였다. 2) 월류수심 1.4m일때 월류량의 표준편차는 0.767이며 월류수심 4.4m일때 표준편차는 9.580으로 월류수심이 증가할수록 스크린 경사에 따른 표준편차는 증가하는 것으로 확인되었다. 3) 티롤리안 위어 스크린 경사가 클수록 월류수심은 감소하고 접근수로부 유속이 증가하였으며 스크린 경사가 작을수록 월류수심은 증가하고 유속이 감소하는 경향을 확인하였다. 4) 티롤리안 위어 스크린 경사가 작고 월류수심이 클수록 광정위어와 유사한 흐름특성을 보였다.

• Safety and Health at Work
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• v.13 no.1
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• pp.40-50
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• 2022

Background: Underground mines have several hazards that could lead to serious consequences if they come into effect. Acquiring, evaluating, and using the real-time data from the atmospheric monitoring system and miner's positional information is crucial in deciding the best course of action. Methods: A graphical user interface-based software is developed that uses an AutoCAD-based mine map, real-time atmospheric monitoring system, and miners' positional information to guide on the shortest route to mine exit and other locations within the mine, including the refuge chamber. Several algorithms are implemented to enhance the visualization of the program and guide the miners through the shortest routes. The information relayed by the sensors and communicated by other personnel are collected, evaluated, and used by the program in proposing the best course of action. Results: The program was evaluated using two case studies involving rescue relating to elevated carbon monoxide levels and increased temperature simulating fire scenarios. The program proposed the shortest path from the miner's current location to the exit of the mine, nearest refuge chamber, and the phone location. The real-time sensor information relayed by all the sensors was collected in a comma-separated value file. Conclusion: This program presents an important tool that aggregates information relayed by sensors to propose the best rescue strategy. The visualization capability of the program allows the operator to observe all the information on a screen and monitor the rescue in real time. This program permits the incorporation of additional sensors and algorithms to further customize the tool.

• Journal of KIBIM
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• v.12 no.4
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• pp.19-31
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• 2022

With the development of 3D-based CAD (Computer Aided Design), attempts at freeform building design have expanded to small and medium-sized buildings in Korea. However, a standardized system for continuous utilization of shape data and BIM conversion process implemented with 3D-based NURBS is still immature. Without accurate review and management throughout the Freeform building project, interference between members occurs and the cost of the project increases. This is very detrimental to the project. To solve this problem, we proposed a continuous utilization process of 3D shape information based on BIM parameters. Our process includes algorithms such as Auto Split, Panel Optimization, Excel extraction based on shape information, BIM modeling through Adaptive Component, and BIM model utilization method using ID Code. The optimal cutting reference point was calculated and the optimal material specification was derived using the Panel Optimization algorithm. With the Adaptive Component design methodology, a BIM model conforming to the standard cross-section details and specifications was uniformly established. The automatic BIM conversion algorithm of shape data through Excel extraction created a BIM model without omission of data based on the optimized panel cutting reference point and cutting line. Finally, we analyzed how to use the BIM model built for automatic conversion. As a result of the analysis, in addition to the BIM utilization plan in the general construction stage such as visualization, interference review, quantity calculation, and construction simulation, an individual management plan for the unit panel was derived through ID data input. This study suggested an improvement process by linking the existing research on atypical panel optimization and the study of parameter-based BIM information management method. And it showed that it can solve the problems of existing Freeform building project.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.11
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• pp.67-73
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• 2021

Tanks are key weapons of ground combat that are equipped with powerful weapons and have strong protective bodies. One tank component, the engine clutch flange, is located in the part of the tank where the engine and transmission are installed, and it is a key part of the power transfer and shutoff. The engine clutch flange transmits high power to secure the mobility of the tank; thus, it must have high strength and hardness. In addition, high durability and safety must be ensured because tank operations must exclude concerns about damage. In this study, an engine clutch female flange for tanks made of SNCM439 was developed. The 2D design used AutoCAD programs, and the 3D shape design used CATIA programs. The structural analysis was conducted using ANSYS. The mesh grid has a tetrahedron shape and is created by adding a mid-side node. After the mechanical properties and constraints of SNCM439 were entered, the changes in the safety factor, total deformation, and Von-Mises stress were identified according to the increase in torque. Prototype processing was performed to verify the engine clutch female flange for the tank. To determine the productivity of the product, the cutting processing time was measured when processing the prototypes. Based on the results of measuring the cutting processing time, it is concluded that research is needed to improve productivity because MCT slot cutting processing is time consuming.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.306-306
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• 2020

횡월류위어(side weir)는 하천의 수위가 한계수위 이상으로 상승할 경우 본류로부터 저류지나 분수로(distributary channel)로 흐름을 전환하기 위하여 사용하는 수공구조물로 강변저류지나 off-line저류지의 유입부에 흐름방향과 평행하게 설치되어 유량관리 및 전환, 홍수통제, 에너지 소산, 수위조절, 일정 유량의 취수 및 분배, 초과 홍수량의 전환 등의 목적으로 이용되는 구조물이다. 횡월류 위어의 월류 흐름은 일반위어와 같이 위어마루부 직각방향으로 흐르지 않고 본류 흐름특성에 따라 비스듬하게 유입된다. 이러한 흐름특성으로 횡월류위어 월류량은 본류의 하폭, 흐름특성, 위어길이 및 설치위치 등에 따라 각기 다르게 산정된다. 현재 국내에서 진행된 횡월류위어 흐름특성에 관련된 연구는 대부분 직선수로에 집중되어 있으며 사행하천의 흐름특성에 따른 연구는 부족한 실정이다. 금회 연구에서는 3차원 상용프로그램인 FLOW-3D를 이용하여 사행하천구간 유입부 설치위치 특성에 따른 횡월류 위어 유입흐름 특성을 분석하였다. 사행하천 구간 횡월류위어 설치위치에 따른 3차원 흐름해석을 위해 AUTO CAD 프로그램을 이용하여 수로길이 30m, 수로폭 2m의 구형 사행수로를 구성하였고, 횡월류위어 유입부 위치를 20°~120°로 변화시키며 수치모형실험을 수행하였다. 해석결과 수로흐름은 유입부 설치각이 작을수록 상·하류 수위차가 작아지며 유속이 감소하며 설치위치각이 클수록 수로내 평균유속은 증가하는 것으로 확인되었다. 유입부 설치각이 작을수록 방류량이 증가하여 수로내 흐름분리현상 증가하였고 이로인한 지체현상이 발생하는 것으로 확인되었다. 본 연구로 사행하천구간에 횡월류위어가 설치된 경우, 월류량과 수리학적 흐름특성을 해석할 때 3차원 수치모형실험이 유용한 해석도구로 이용될 수 있음이 확인되었다. 이후 수치모형실험이 수공구조물 설계 및 해석 시 참고자료로 이용 가능할 것으로 사료된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.250-250
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• 2021

횡월류위어(side weir)는 하천의 수위가 한계수위 이상으로 상승할 경우 본류로부터 저류지나 분수로(distributary channel)로 흐름을 전환하기 위하여 사용하는 수공구조물로 강변저류지나 off-line저류지의 유입부에 흐름방향과 평행하게 설치되어 유량관리 및 전환, 홍수통제, 에너지 소산, 수위조절, 일정 유량의 취수 및 분배, 초과 홍수량의 전환 등의 목적으로 이용되는 구조물이다. 횡월류 위어의 월류 흐름은 일반위어와 같이 위어마루부 직각방향으로 흐르지 않고 본류 흐름특성에 따라 비스듬하게 유입된다. 이러한 흐름특성으로 횡월류위어 월류량은 본류의 하폭, 흐름특성, 위어길이 및 설치위치 등에 따라 각기 다르게 산정된다. 현재 국내에서 진행된 횡월류위어 흐름특성에 관련된 연구는 대부분 직선수로에 집중되어 있으며 사행하천의 흐름특성에 따른 연구는 부족한 실정이다. 금회 연구에서는 3차원 상용프로그램인 FLOW-3D를 이용하여 사행하천구간 유입부 설치위치 특성에 따른 횡월류 위어 유입흐름 특성을 분석하였다. 사행하천 구간 횡월류위어 설치위치에 따른 3차원 흐름해석을 위해 AUTO CAD 프로그램을 이용하여 수로길이 30m, 수로폭 2m의 구형 사행수로를 구성하였고, 횡월류위어 유입부 위치를 20°~120°로 변화시키며 수치모형실험을 수행하였다. 해석결과 수로흐름은 유입부 설치각이 작을수록 상·하류 수위차가 작아지며 유속이 감소하며 설치위치각이 클수록 수로내 평균유속은 증가하는 것으로 확인되었다. 유입부 설치각이 작을수록 방류량이 증가하여 수로내 흐름분리현상 증가하였고 이로인한 지체현상이 발생하는 것으로 확인되었다. 본 연구로 사행하천구간에 횡월류위어가 설치된 경우, 월류량과 수리학적 흐름특성을 해석할 때 3차원 수치모형실험이 유용한 해석도구로 이용될 수 있음이 확인되었다. 이후 수치모형실험이 수공구조물 설계 및 해석 시 참고자료로 이용가능할 것으로 사료된다.

• Restorative Dentistry and Endodontics
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• v.30 no.2
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• pp.79-85
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• 2005

The purpose of this study was to evaluate the obturation efficiency of a non-standardized gutta-percha cone in curved root canals prepared with 0.06 taper nickel-titanium instruments. Sixty simulated curved root canals in clear resin blocks were prepared with crown-down technique using 0.06 taper rotary $ProTaper^{TM}$and ProFile (Dentsply-Maillefer) until apical canal was size 30. Root canals were randomly divided into 4 groups of 15 blocks and obturated with cold-laterally compacted gutta-percha technique by using either a non-standardized size medium gutta-percha cone or an ISO-standardized size 30 one as a master cone. Gutta-percha area ratio were calculated at apical levels of 1, 3 and 5 mm using AutoCAD 2000 after cross-sectioning, and the data were analyzed with one-way and two-way ANOVAs and Duncan's multiple range test. Non-standardized size medium cone groups showed significantly higher gutta-percha area ratio than standardized cone groups at all apical levels (p < 0.01). Non-standardized cone groups used significantly less accessory cones than standardized cone groups (p < 0.01).

• The Korean Journal of Nuclear Medicine
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• v.36 no.5
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• pp.288-297
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• 2002

Purpose: Soft tissue attenuation and scattering are major methodological limitations of myocardial perfusion SPECT. To overcome these limitations, algorithms for attenuation, scatter correction and resolution recovery (ASCRR) is being developed, while quantitative myocardial SPECT has also become available. In this study, we investigated the efficacy of an ASCRR-corrected quantitative myocardial SPECT method for the diagnosis of coronary artery disease (CAD). Materials and Methods: Seventy-five patients (M:F=51:24, $61.0{\pm}8.9$ years old) suspected of CAD who underwent coronary angiography (CAG) within $7{\pm}12$ days of SPECT(Group-I) and 20 subjects (M:F=10:10, age $40.6{\pm}9.4$) with a low likelihood of coronary artery disease (Group-II) were enrolled. Tl-201 rest/ dipyridamole-stress Tc-99m-MIBI gated myocardial SPECT was performed. ASCRR correction was peformed using a Gd-153 line source and automatic software (Vantage-Pro; ADAC Labs, USA). Using a 20-segment model, segmental perfusion was automatically quantified on both the ASCRR-corrected and uncorrected images using an automatic quantifying software (AutoQUANT; ADAC Labs.). Using these quantified values, CAD was diagnosed in each of the 3 coronary arterial territories. The diagnostic performance of ASCRR-corrected SPECT was compared with that of non-corrected SPECT. Results: Among the 75 patients of Group-I, 9 patients had normal CAG while the remaining 66 patients had 155 arterial lesions; 61 left anterior descending (LAD), 48 left circumflex (LCX) and 46 right coronary (RCA) arterial lesions. For the LAD and LCX lesions, there was no significant difference in diagnostic performance. In Group-II patients, the overall normalcy rate improved but this improvement was not statistically significant (p=0.07). However, for RCA lesions, specificity improved significantly but sensitivity worsened significantly with ASCRR correction (both p<0.05). Overall accuracy was the same. Conclusion: The ASCRR correction did not improve diagnostic performance significantly although the diagnostic specificity for RCA lesions improved on quantitative myocardial SPECT. The clinical application of the ASC-RR correction requires more discretion regarding cost and efficacy.