• Journal of Navigation and Port Research
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• v.47 no.1
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• pp.10-17
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• 2023

A series of studies on the development of autonomous surface ships have been promoted in domestic and foreign countries. One of the main technologies for the development of autonomous ships is path-following control, which is closely related to securing the safety of ships at sea. In this regard, the path-following performance of an autonomous ship should be first evaluated at the design stage. The main aim of this study was to develop a visual and quantitative evaluation method for the path-following control performance of an autonomous ship at the design stage. This evaluation technique was developed using a computational fluid dynamics (CFD)-based path-following control model together with a line-of-sight (LOS) guidance algorithm. CFD software was utilized to visualize waves around the ship, performing path-following control for visual evaluation. In addition, a quantitative evaluation was carried out using the difference between the desired and estimated yaw angles, as well as the distance difference between the planned and estimated trajectories. The results demonstrated that the ship experienced large deviations from the planned path near the waypoints while changing its course. It was also found that the fluid phenomena around the ship could be easily identified by visualizing the flow generated by the ship. It is expected that the evaluation method proposed in this study will contribute to the visual and quantitative evaluation of the path-following performance of autonomous ships at the design stage.

• Tunnel and Underground Space
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• v.14 no.1
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• pp.54-68
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• 2004

In this study, scaled model tests were performed on blasting demolition of reinforced concrete structures and the experimental results were analyzed in comparison with the results of numerical analysis. The tests were designed to induce a progressive collapse, and physical properties of the scaled model were determined using scale factors obtained ken dimension analysis. The scaled model structure was made of a mixture of plaster, sand and water at the ratio determined to yield the best scaled-down strength. Lead wire was used as a substitute for reinforcing bars. The scaled length was at the ratio of 1/10. Selecting the material and scaled factors was aimed at obtaining appropriately scaled-down strength. PFC2D (Particle Flow Code 2-Dimension) employing DEM (Distinct Element Method) was used for the numerical analysis. Blasting demolition of scaled 3-D plain concrete laymen structure was filmed and compared to results of numerical simulation. Despite the limits of 2-D simulation the resulting demolition behaviors were similar to each other. Based on the above experimental results in combination with bending test results of RC beam, numerical analysis was carried out to determine the blasting sequence and delay times. Scaled model test of RC structure resulted in remarkably similar collapse with the numerical results up to 900㎳ (mili-second).

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.5
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• pp.653-660
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• 2007

Since the temperature of asphalt for deck plate of steel bridge during paying procedure is relatively high as $240^{\circ}C\;to\;260^{\circ}C$, the temperature of deck plate of bridge rises mere than $100^{\circ}C$ and excessive displacement and stress could occur. In order to avoid undesirable failure of base plate and determine the optimal pavement pattern, a thorough thermal analysis is needed. General structural model which is made of beam and plate element should be modified for transient heat transfer analysis; asphalt pavement material and convection effect on surface of structure need to be added. A new technique with the Equivalent Heat Source (EHS) for numerical thermal analysis for steel bridge under thermal load of Guss asphalt pavement is proposed. Since plate/beam elements which were generally used for structural analysis for bridge cannot explain convection effect easily on plate/beam surface, EHS which is determined based on calculated temperature with convection effect is used. To verify the EHS proposed in this study, numerical analyses with plate elements are performed and the results are compared with estimated temperatures. EHS might be used for other thermal analyses of steel bridge such as welding residual stress analysis and bridge fire analysis.

• Journal of the Korea Organic Resources Recycling Association
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• v.18 no.3
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• pp.77-86
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• 2010

In this study, the model of the indirect wind suction waste sorting machine for characteristics of the screening of waste was studied using computational fluid dynamics and the drag coefficient for the model and the suction wind speed were obtained. The wind separator are developing by installing a cyclone air outlet to the suction blower impeller waste is selective in a way that does not pass the features and characteristics of the inlet pipe of the pressure loss and separation efficiency can have a significant impact on. Using Wind separator for selection of waste in the waste prior research on the aerodynamic properties are essential. For plastic cases, it is reasonable to take the drag coefficient between 0.8 and 1.0, and for cans, compression depending on whether the cans, the drag coefficient is in the range from 0.2 to 0.7. The separation efficiency of waste as change suction speed was the highest efficiency when the suction speed was 25~26 m/s. Shape of the inlet, depending on how the transfer pipe of the duct pressure loss occurs because the inlet velocity changes through the appropriate design standards to allow for continued research is needed.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.2
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• pp.71-78
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• 2014

There is a big risk of bullet impact because military rotorcraft is run in the battle environment. Due to the bullet impact, the rapid increase of the internal pressure can cause the internal explosion or fire of fuel cell. It can be a deadly damage on the survivability of crews. Then, fuel cell of military rotorcraft should be designed taking into account the extreme situation. As the design factor of fuel cell, the internal fluid pressure, structural stress and bullet kinetic energy can be considered. The verification test by real object is the best way to obtain these design data. But, it is a big burden due to huge cost and long-term preparation efforts and the failure of verification test can result in serious delay of a entire development plan. Thus, at the early design stage, the various numerical simulations test is needed to reduce the risk of trial-and-error together with prediction of the design data. In the present study, the bullet impact numerical simulation based on SPH(smoothed particle hydrodynamic) is conducted with the commercial package, LS-DYNA. Then, the resulting equivalent stress, internal pressure and bullet's kinetic energy are evaluated in detail to examine the possibility to obtain the configuration design data of the fuel cell.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.3
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• pp.163-169
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• 2022

According to the Credit Information Act, in order to protect customer information by relationship of credit information subjects, it is destroyed and stored separately in two stages according to the period after the financial transaction effect is over. However, there is a limitation in that the destruction of personal credit information of customers whose financial transaction effect has expired cannot be collectively destroyed when the transaction has been terminated, depending on the nature of the financial product and transaction. To this end, the IT person in charge is developing a computerized program according to the target and order of destruction by investigating the business relationship by transaction type in advance. In this process, if the identification of the upper relation between tables is unclear, a compliance issue arises in which personal credit information cannot be destroyed or even information that should not be destroyed because it depends on the subjective judgment of the IT person in charge. Therefore, in this paper, we propose a model and algorithm for identifying the referenced table based on SQL executed in the computer program, analyzing the upper relation between tables with the primary key information of the table, and visualizing and objectively selecting the range to be destroyed. presented and implemented.

• Journal of the Korean Geotechnical Society
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• v.15 no.1
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• pp.5-13
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• 1999

Maximum stress in pile is developed when it is driven. If the stress is greater than allowable stress of the pile, the pile will be damaged and result in stability problem. Therefore, the stress should be estimated correctly beforehand and overstress should be prevented during pile driving. There are many methods to estimate compressive stresses in concrete piles when they are driven. Nowadays, computer analysis on wave equation offers a satisfactory results. But. under certain circumstances, application of this method is difficult. Then, estimation of the stress utilizing simple formulae might be practical. In this study, relatively reasonable formulae were selected and the stresses which were measured in situ and calculated from the formulae were compared and analysed. The results show that the calculated values from Uto and Huyuki's formula were reasonably accurate and more accurate values were acquired if the values are modified by multiplying the reduction factors according to ground and construction conditions.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.3
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• pp.261-269
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• 2015

In this study, numerical analysis of curved channel steam-methanol reformer was conducted using the computational fluid dynamics (CFD) commercial code STAR-CCM. A pre-numerical analysis of reference model with a cylindrical channel reactor was performed to validate the combustion model of the CFD commercial code. The result of advance validation was in agreement with reference model over 95%. After completing the validation, a curved channel reactor was designed to determine the effects of shape and length of flow path on methanol conversion efficiency and generation of hydrogen. Numerical analysis of the curved-channel reformer was conducted under various flow rate ($10/15/20{\mu}l/min$). As a result, the characteristics of flow and mass transfer were confirmed in the cylindrical channel and curved channel reactor, and useful information about methanol conversion efficiency and hydrogen generation was obtained for various flow rate.

• KIEAE Journal
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• v.16 no.1
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• pp.89-94
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• 2016

This study is part of three-dimensional(3D) heat transfer analysis program developmental process. The program is being developed without it's own built in 3D-modeller. So 3D-model must be created from another 3D-modeller such as generic CAD programs and imported to the developed program. After that, according to the 3D-geometric data form imported model, 3D-mesh created for numerical calculation. But the 3D-model created from another 3D-modeller is likely to have errors in it's geometric data such as mismatch of position between vertexes or surfaces. these errors make it difficult to create 3D-mesh for calculation. These errors are must be detected and cured in the pre-process before creating 3D-mesh. So, in this study four kinds of filters and functions are developed and tested. Firstly, 'vertex error filter' is developed for detecting and curing for position data errors between vertexes. Secondly, 'normal vector error filter' is developed for errors of surface's normal vector in 3D-model. Thirdly, 'intersection filter' is developed for extracting and creating intersection surface between adjacent objects. fourthly, 'polygon-line filter' is developed for indicating outlines of object in 3D-model. the developed filters and functions were tested on several shapes of 3D-models. and confirmed applicability. these developed filters and functions will be applied to the developed program and tested and modified continuously for less errors and more accuracy.

• Korean Journal of Occupational Health Nursing
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• v.2
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• pp.52-59
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• 1992

본 연구는 예방적 건강행위에 대한 필요성 인식 정도와 실천정도를 파악하고 이를 요인분석하여 산업장의 예방적 건강행위를 이끌기 위한 프로그램의 기틀을 세우기 위해 시도되었다. 연구도구는 참고문헌과 선행연구 등을 참조하여 본 연구자가 만든 설문지를 사전 조사후 수정, 보완하여 사용하였다. 연구대상은 경기도 소재의 2개 기계제조업체에 근무하는 근로자들이였으며 1989년 5월 5일부터 10일까지 자료를 수집하였다. 수집된 자료 중 탈락 및 기재가 불충분한 질문지를 제외한 284명의 응답자를 분석에 사용하였다. 자료분석은 SPSS를 이용하여 전산처리하였으며, 연구결과는 다음과 같다. 1) 예방적 건강행위의 필요성 인식정도의 평균은 122.1점으로 매우 높은 점수분포를 나타냈으며, 실천정도의 평균은 87.6점으로 필요성 인식정도 보다는 낮은 실천정도를 나타냈었다. 2) 예방적 건강행위에 대한 필요성 인식정도와 실천 정도간의 상관관계를 분석한 결과 29개 예방적 건강행위 중 20개의 항목에서 통계적으로 유의한 상관관계를 보였다. 이것을 예방적 건강행위에 대한 필요성 인식정도가 높을수록 실천정도가 높은 것을 의미하는 것으로 인식정도가 행위에 영향을 미침을 반영하고 있다. 3) 요인분석결과 29개의 예방적 건강행위 항목들은 7가지의 요인으로 범주화되었으며 각 범주들은 요인부하량이 높은 것들을 참고로 하여 보건의료자원활동을 통한 예방적 건강행위, 개인위생에 대한 예방적 건강행위, 작업과 관련된 건강행위, 식습관을 통한 예방적 건강행위, 휴식을 통한 예방적 건강행위, 기호습관(금연, 금주)을 통한 예방적 건강행위, 활동을 통한 예방적 건강행위등으로 명명할 수 있었다. 결론적으로 생산직에 종사하고 있는 근로자들은 예방적 건강행위에 대한 필요성을 깊이 인식하고 있으나, 실천정도는 그에 미치지 못하고 있었다. 그러나 예방적 건강행위의 필요성 인식정도와 실천정도간의 상관관계에서 29개 항목중 20개 항목에서 유의한 상관관계를 보여 인식정도가 높을 수록 실천정도가 높은 것으로 나타났다. 이는 근로자의 건강에 대한 인식 및 태도가 가장 직접적으로 영향을 미칠 수 있는 산업간호사의 역할 중 보건교육에 대한 업무가 보다 중요한 비중으로 수행되어져야 함을 시사하는 결과라고 볼수 있다.