• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.9
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• pp.1-10
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• 2021

Recently, the repair and recycling of damaged mechanical parts via metal additive manufacturing processes have been industrial points of interest. This is because the repair and recycling of damaged mechanical parts can reduce energy and resource consumption. The directed energy deposition(DED) process has various advantages such as the possibility of selective deposition, large building space, and a small heat-affected zone. Hence, it is a suitable process for repairing damaged mechanical parts. The shaft is a core component of various mechanical systems. Although there is a high demand for the repair of the shaft, it is difficult to repair with traditional welding processes because of the thermal deformation problem. The objective of this study is to propose a repair procedure for a damaged shaft using the DED process and discuss its applications. Three types of cases, including a small shaft with a damaged surface, a medium-size shaft with a worn bearing joint, and a large shaft with serious damage, were repaired using the proposed procedure. The microstructure and hardness were examined to discuss the characteristics of the repaired component. The efficiency of the repair of the damaged shaft is also discussed.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.6
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• pp.1100-1109
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• 2022

Herein, a case study was conducted on the bilge pumping performance of a 24,000TEU class container ship with an overall length of 400m. Although the bilge system of the 24,000TEU class container ship was designed in accordance with the rule requirements of the Classification Society, the bilge system did not satisfy the 2 m/s requirements of SOLAS Reg.II-1/35-1 under the rated flow rate and maximum flow rate conditions of the bilge pump installed in the ship. In particular, assumptions were made that No.1 ~ No.4 cargo holds were flooded and filled entirely by sea water and the evaluation of bilge pumping performance had been performed for No.1 ~ No.4 cargo holds. According to the evaulation results of the, the mean water velocity at the main bilge pipe for No.2, No.3, and No.4 cargo holds did not meet the 2 m/s criterion. To resolve this problem, in this study, the branch bilge pipe in each cargo hold was changed from 150A to 200A and the mean water velocity at the main bilge pipe for No.2, No.3, and No.4 was calculated as 2.479m/s, 2.476m/s, and 2.459m/s, respectively.

• Journal of the Korean Society of Earth Science Education
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• v.16 no.2
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• pp.291-301
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• 2023

In this study, the STEAM elements and convergence types which appeared in the creative and convergent activities in authorized elementary school science textbooks for 5^th and 6^th graders were analyzed. For this study, creative and convergence activities presented in 9 different science textbooks for 5^th and 6^th graders were selected and the STEAM elements and convergence types were analyzed by each publisher, grade-semester, and science field. The results of this study are as follows. First, there was a large variation by publisher in the total frequency of STEAM elements and the frequency of each element in creative and convergence activities. Second, the ratio of convergence type consisting of two elements was very high, and the higher the number of fused elements, the lower the ratio appeared in overall. Third, the art (A) element had the highest frequency in all grade-semesters, and the technology (T), engineering (E), mathematics (M) elements differed in the distribution of frequency by grade-semesters. Fourth, the engineering (E) element in the 'integration' field, and the art (A) element in the fields of 'movement and energy', 'material', 'earth and universe', and 'life' had the highest frequency.

• The Korean Journal of Nuclear Medicine Technology
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• v.19 no.2
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• pp.93-101
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• 2015

Purpose In SPECT image, scatter count is the cause of quantitative count error and image quality degradation. Thus, a wide range of scatter correction(SC) methods have been studied and this study is to evaluate the accuracy of CT based SC(CTSC) used in SPECT/CT as the comparison with existing energy window based SC(EWSC). Materials and Methods SPECT/CT images were obtained after filling air in order to acquire a reference image without the influence of scatter count inside the Triple line insert phantom setting hot rod(74.0 MBq) in the middle and each SPECT/CT image was obtained each separately after filling water instead of air in order to derive the influence of scatter count under the same conditions. In both conditions, Astonish(iterative : 4 subset : 16) reconstruction method and CT attenuation correction were commonly applied and three types of SC methods such as non-scatter correction(NSC), EWSC, CTSC were used in images filled with image. For EWSC, 9 sub-energy windows were set additionally in addition to main(=peak) energy window(140 keV, 20%) and then, images were acquired at the same time and five types of EWSC including DPW(dual photo-peak window)10%, DEW(dual energy window)20%, TEW(triple energy window)10%, TEW5.0%, TEW2.5% were used. Under the condition without fluctuations in primary count, total count was measured by drawing volume of interest (VOI) in the images of the two conditions and then, the ratio of scatter count of total counts was calculated as percent scatter fraction(%SF) and the count error with image filled with water was evaluated with percent normalized mean-square error(%NMSE) based on the image filled with air. Results Based on the image filled with air, %SF of images filled with water to which each SC method was applied is NSC 37.44, DPW 27.41, DEW 21.84, TEW10% 19.60, TEW5% 17.02, TEW2.5% 14.68, CTSC 5.57 and the most scattering counts were removed in CTSC and %NMSE is NSC 35.80, DPW 14.28, DEW 7.81, TEW10% 5.94, TEW5% 4.21, TEW2.5% 2.96, CTSC 0.35 and the error in CTSC was found to be the lowest. Conclusion In SPECT/CT images, the application of each scatter correction method used in the experiment could improve the quantitative count error caused by the influence of scatter count. In particular, CTSC showed the lowest %NMSE(=0.35) compared to existing EWSC methods, enabling relatively accurate scatter correction.

• Journal of the Korean Data and Information Science Society
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• v.27 no.2
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• pp.275-284
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• 2016

Accurate electricity demand forecasts is essential in reducing energy spend and preventing imbalance of the power supply. In forcasting electricity demand, we considered double seasonal Holt-Winters model and TBATS model with sliding window. We selected a specific time zone as the reference line of daily electric demand because it is least likely to be influenced by external factors. The forecasting performance have been evaluated in terms of RMSE and MAPE criteria. We used the observations ranging January 4, 2009 to December 31 for testing data. For validation data, the records has been used between January 1, 2012 and December 29, 2012.

• KIEAE Journal
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• v.17 no.4
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• pp.75-81
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• 2017

Purpose: Most contemporary office buildings supply external views, a sense of openness and a sense of time to their occupants by adopting the curtain walls, which are equipped with an outer cover having large window area. As a result, the amount of radiation increases, adversely affecting cooling load during the summer in office buildings. Although solar radiation decreases heating load and reduces energy costs during the winter period, due to the characteristics of offices where occupants work largely during daytime, the cooling load is important compared to the heating. Therefore, diverse measures to resolve those trade-offs and annual energy cost have been investigated. Method: In this study, the annual thermal load was comparatively analyzed according to the slat angle of the venetian blind along with lighting control technique. Result: After selecting effective conditions, in order to resolve such issues, this study established automated control strategies of slat angle depending on the window-to-wall ratio and zone orientation, so that the findings of this study can be effectively generalized to other circumstances.

• Progress in Medical Physics
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• v.27 no.1
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• pp.31-36
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• 2016

The paper discusses radiation dose of dual energy CT on which copper modulation layer, is mounted in order to improve diagnostic performance of the dual energy CT. The radiation dose is estimated using MCNPX and its results are compared with that of the conventional dual energy CT system. CT X-ray spectra of 80 and 120 kVp, which are usually used for thorax, abdominal, head, and neck CT scans, were generated by the SPEC78 code and were used for the source specification 'SDEF' card for MCNPX dose modeling. The copper modulation layer was located 20 cm away from a source covering half of the X-ray window. The radiation dose was measured as changing its thickness from 0.5 to 2.0 mm at intervals of 0.5 mm. Since the MCNPX tally provides only normalized values to a single particle, the dose conversion coefficients of F6 tally for the modulation layer-based dual energy CBCT should be calculated for matching the modeling results into the actual dose. The dose conversion coefficient is $7.2*10^4cGy/output$ that is obtained from dose calibration curve between F6 tally and experimental results in which GAFCHORMIC EBT3 films were exposed by an already known source. Consequently, the dose of the modulation layer-based dual energy cone beam CT is 33~40% less than that of the single energy CT system. On the basis of the results, it is considered that scattered dose produced by the copper modulation layer is very small. It shows that the modulation layer-based dual energy CBCT system can effectively reduce radiation dose, which is the major disadvantage of established dual energy CT.

• The Magazine for Energy Service Companies
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• s.54
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• pp.64-69
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• 2008

야간의 잉여전력으로 열을 저장해두었다 주간에 이용하는 축열공조에는 50여년에 걸친 긴 역사가 있었다. 이 방식이 가지는 효용에 일찍부터 눈뜬 선각자들의 노력에도 불구하고 당초 보급은 늦어져 그다지 진전이 없었다고 한다. 이러한 정세가 일변한 것은 전력공급에 병목현상이 생겨 부하 평준화가 안정공급에 있어 필요불가결의 과제가 되었기 때문이다. 특히 공조는 피크성이 강한 수요이므로 공조용 전력을 야간으로 옮기는 작업의 이점이 큰 것은 당연하다. 비 수요시간대의 요금이 큰 폭으로 떨어짐으로써 수요자측에서 보아도 야간의 전력을 어떻게 활용할까하는 것은 매력적인 연구테마였다. 이리하여 축열공조가 관심을 불러 보급이 기도에 놓인 지 2O년 가까이 되었다. 처음에는 물을 사용한 축열이 대부분이었으나, 축열조 용량의 제약으로 얼음을 만들어 저장하는 빙축열방식이 도입되어 현재의 표준적인 축열방식이되었다. 그러나 빙축열에도 비용상의 문제가 있어 전면적인 보급에 이르기까지는 아직 연구의 여지가 더 남아있는 듯하다. 한편, 교토의정서의 발효 등에 의해 지구환경에 대한 관심이 높아지게 되었다. 이 같은 배경 속에 건물및 건축설비의 에너지절약 기술의 중요성이 대두되고, 특히 창 주변의 공조방식, 조광제어, 축열 공조시스템 등, 건물부하의 직접적인 저감과 전력부하 평준화에 의한 환경부하저감 및 운영비용의 저감을 목적으로 한 건물일체형 설비시스템을 적극적으로 도입하기에 이르렀다. 환경을 배려한 건축구조.설비시스템의 채택 사례가 증가하며 건축물 종합환경성능 평가시스템과 성능검증 등 건물설비의 평가.검증 수법도 연구되어 건물에 적합한 운용면에서의 사고가 중요함이 인식되었다. 이와 같이 건축구조와 설비시스템의 양면에서 에너지절약성 및 환경성, 쾌적성, 편리성의 추구가 적극적으로 도입되는 가운데, 슬래브축열시스템은 건축구조와 공조설비가 균형있게 융합됨으로써 초기비용의 삭감과 부하 평준화에 의한 경제성 향상, 복사에의한 실내환경의 향상 등의 효과를 기대할 수있는 시스템으로 추목받고 있다.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.422-425
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• 2009

A sea water source cascade heat pump was designed and tested in this study. The system was designed to perform a single stage operation in summer, as well as a cascade operation in winter to ensure the high temperature lift. A steady-state simulation model was developed to analyze and optimize its performance. The simulation results show that the R717 exhibits best performance among combinations considered in this study. A R410A also exhibits the highest performance among HFCs with the smallest compressor displacement. A 15-RT R410A-R134a pilot system was installed in the 5-story commercial building at Samcheok City by the East Sea. A scroll type R410A compressor, a reciprocating type R134a compressor, plate type condenser/evaporator/ cascade heat exchanger and two electronic expansion valves were used to build a pilot. A titanium plate type heat exchanger is also used for the heat exchanging with a sea water. The heat source/sink water is supplied from the well below the seashore in the depth of 5 m. In the initial test of the system, supply water temperature was rising up to $67^{\circ}C$ using a sea water heat source of $9^{\circ}C$, while an ambient temperature was $4.5^{\circ}C$.

• 한국태양에너지학회:학술대회논문집
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• 2009.04a
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• pp.250-255
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• 2009

This study was analyzed the long term performance of the demonstration system for solar energy desalination in Jeju. we used a solar thermal system as heat source of the single-stage fresh water generator with plate-type heat exchangers and a photovoltaic power system as electric source for hydraulic pumps. The demonstration system was designed and installed at Jeju-island in 2006. The system was comprised of the desalination unit with daily fresh water capacity designed as $2m^3$ a $120m^2$ evacuated tubular solar collector to supply the heat, a $6m^3$ heat storage tank, and a 5kW photovoltaic power generation to supply the electricity of hydraulic pumps for the heat medium fluids. Through the operation during about 3 years, In a clear day more than $400W/m^2$, the daily fresh water showed to produce more than about 500liter, and from January, 2007 to March, 2009 for 3 years, solar irradiance daily averaged was measured $370W/m^2$, the daily fresh water yield showed that can be produced about 330liter.