• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.258-263
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• 2000

River water is higher in temperature than the surrounding environment during the winter. It is highly suitable a heat source for heat pump system. Despite its suitability, however, it is not widely used, due to its fouling and corrosive nature in heat exchanger tubes of evaporator. It is designed prior-treatment system which come into direct contact with the river water, such as auto-seamer, ozone generator for bactericidal test and auto-cleaning system. And it is analyzed treatment effects for its operation. It is designed two-stage compression heat pump system using R-134a with heating load 35.16kW, ad analyzed its performance. As a result it is obtained 3.08 COP when mid-point pressure is 1,200kPa, and bypass ratio of flowing refreigerant to high-stage compressor is 25.1%

• Journal of Astronomy and Space Sciences
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• 제28권2호
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• pp.123-132
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• 2011

It is generally believed that the occurrence of a magnetic storm depends upon the solar wind conditions, particularly the southward interplanetary magnetic field (IMF) component. To understand the relationship between solar wind parameters and magnetic storms, variations in magnetic field polarity and solar wind parameters during magnetic storms are examined. A total of 156 storms during the period of 1997~2003 are used. According to the interplanetary driver, magnetic storms are divided into three types, which are coronal mass ejection (CME)-driven storms, co-rotating interaction region (CIR)-driven storms, and complicated type storms. Complicated types were not included in this study. For this purpose, the manner in which the direction change of IMF $B_y$ and $B_z$ components (in geocentric solar magnetospheric coordinate system coordinate) during the main phase is related with the development of the storm is examined. The time-integrated solar wind parameters are compared with the time-integrated disturbance storm time (Dst) index during the main phase of each magnetic storm. The time lag with the storm size is also investigated. Some results are worth noting: CME-driven storms, under steady conditions of $B_z$ < 0, represent more than half of the storms in number. That is, it is found that the average number of storms for negative sign of IMF $B_z$ (T1~T4) is high, at 56.4%, 53.0%, and 63.7% in each storm category, respectively. However, for the CIR-driven storms, the percentage of moderate storms is only 29.2%, while the number of intense storms is more than half (60.0%) under the $B_z$ < 0 condition. It is found that the correlation is highest between the time-integrated IMF $B_z$ and the time-integrated Dst index for the CME-driven storms. On the other hand, for the CIR-driven storms, a high correlation is found, with the correlation coefficient being 0.93, between time-integrated Dst index and time-integrated solar wind speed, while a low correlation, 0.51, is found between timeintegrated $B_z$ and time-integrated Dst index. The relationship between storm size and time lag in terms of hours from $B_z$ minimum to Dst minimum values is investigated. For the CME-driven storms, time lag of 26% of moderate storms is one hour, whereas time lag of 33% of moderate storms is two hours for the CIR-driven storms. The average values of solar wind parameters for the CME and CIR-driven storms are also examined. The average values of ${\mid}Dst_{min}{\mid}$ and ${\mid}B_{zmin}{\mid}$ for the CME-driven storms are higher than those of CIR-driven storms, while the average value of temperature is lower.

• 한국제4기학회지
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• 제33권1_2호
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• pp.25-35
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• 2021

In this study, we identified characteristics of heatwaves on the Korean Peninsula and related atmospheric circulation patterns using data on the daily maximum temperature (TMX) and reanalysis data for the past 42 years (1979-2020) and analyzed their connection to the Arctic oscillation (AO). The heatwave on the Korean Peninsula showed to be stronger and more frequent in the 2000s. The recent strong and frequent heatwaves on the Korean Peninsula are mainly affected by abnormal high-pressure over the Korean Peninsula on the middle/upper-level atmosphere and the strengthening of the North Pacific high pressure. Interestingly, composite difference of sea level pressure showed very similar results to the positive AO pattern. The correlation coefficients between the summertime AO and the TMX and HWD of the Korean Peninsula were 0.407 and 0.437, respectively, which showed a statistical significance in 1%, and showed a clear relationship with the abnormal high-pressure over the Korean Peninsula and the strengthening of the North Pacific high pressure. In addition, in the positive AO phase, the TMX and HWD of the Korean peninsula were approximately 30.1 ℃ and 14.6 days, which were about 1.2 ℃ and 8.8 days higher than in the negative AO phase, respectively. As a result of the 15-year moving average correlation analysis, the relationship between the heatwave and AO on the Korean Peninsula has increased significantly since 2003, and the linear relationship between them has become more apparent. Moreover, after the 2000s, when the relationship developed, AO had more strongly induced the atmospheric circulation pattern to be more favorable to the occurrence of heatwaves in the Korean Peninsula. This study implies that understanding the AO, which is the large-scale variability in the Northern Hemisphere, and the Arctic-mid latitude teleconnection, can improve the performance of global climate models and help predict the seasonality of the summer heatwave on the Korean Peninsula.

• Fisheries and Aquatic Sciences
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• 제3권1호
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• pp.14-22
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• 2000

The relationship between the distribution of demersal fishes and that of the water masses was examined by using the catches data and hydrographic data in the Yellow Sea and the East China Sea on May 13-19, 1996 and May 10-17, 1997. During the study period, the dominant fish species were Cleisthenes pinetorum herzinsteini, Lophiomus setigerus and Pseudosciaena polyactis. These three low temperature water species accounted for $21-24\%$ of the total catches. The percentage of the low temperature water species was high in the Yellow Sea and the coastal area on the continental shelf of the East China Sea but was low in the vincinity of Kyushu during the study period. In the East China Sea, the isotherm of $15^{\circ}C$ at 50m, mid layer depth, was located more southeast in 1996 than in 1997. The bottom water temperature was about it lower in 1996 than in 1997. The direction of the detided current on the continental shelf of the East China Sea was southward in 1996 and northward in 1997. Yellow Sea Bottom Cold Water (YSBCW) strongly expanded to south in 1996 when the northward current was weak. But, Tsushima Warm Current (TSWC) strongly intruded into the continental shelf of the East China Sea in 1997. As YSBCW expanded strongly to south in 1996, the percentage of the low temperature water species relative to the total catches was high. But, TSWC strongly intruded and the percentage of low temperature water fishes was low in 1997.

• Journal of the Korean Wood Science and Technology
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• 제38권6호
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• pp.541-546
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• 2010

본 연구의 목적은 3시간 오존산화 처리식용유와 pMDI를 혼합하여 고온과 중온에서의 접착제를 제조하였고, 이를 상태 인장전단 접착강도 시험을 통하여 식용유의 목재 접착제 응용 가능성을 확인하였다. 고온조건에서 3시간 오존산화 식용유의 상태 접착강도 시험 결과, 오존산화 식용유 : pMDI 비율이 1 : 0.5일 때 4.74 kgf/$cm^2$, 1 : 0.75일 때 7.14 kgf/$cm^2$, 1 : 1일 때 9.29 kgf/$cm^2$, 1 : 2일 때 16.53 kgf/$cm^2$, 1 : 3일 때 17.42 kgf/$cm^2$, 1 : 4일 때 16.75 kgf/$cm^2$를 나타냈다. 따라서 3시간 오존산화 식용유 : pMDI 비율이 1 : 2∼1 : 3일 때 가장 높은 접착력을 보임을 알 수 있어, 두 물질의 적정 당량비가 이 비율에서 형성됨을 알 수 있었다. 중온조건에서 3시간 처리한 식용유의 상태 접착강도 시험 결과, 식용유 : pMDI 비율이 1 : 0.5일 때 3.16 kgf/$cm^2$, 1 : 0.75일 때 6.13 kgf/$cm^2$, 1 : 1일 때 8.18 kgf/$cm^2$ 1 : 2일 때 11.82 kgf/$cm^2$이 나타났다. 즉, 고온, 중온에서의 오존산화 처리한 식용유:pMDI 혼합비율이 1 : 2~1 : 3 부근에서 높은 접착력을 보였고, 목재접착제로서 고온에서 접착 할 경우 합판에서의 이용 가능성이 높을 것으로 판단된다.

• 한국정밀공학회지
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• 제34권3호
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• pp.199-203
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• 2017

Hot embossing techniques are used to engrave patterns on plastic substrates. Roll based hot embossing uses a heated roll for a continuous process. A heated roll with relief patterns is impressed on a preheated plastic substrate. Then, the substrate is cooled down quickly to prevent thermal shrinkage. The roll speed is normally very slow to ensure substrate temperature increase up to the glass transition temperature. In this paper, we propose a noncontact preheating technique using focused infrared light. The infrared light is focused as a line beam on a plastic substrate using an elliptical mirror just before entering the hot embossing roll. The mid range infrared light efficiently raises the substrate temperature. For preliminary tests, substrate deformation and temperature changes were monitored according to substrate speed. The experiments show that the proposed technique is a good possibility for high speed hot embossing.

• 대기
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• 제21권4호
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• pp.361-371
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• 2011

In this study, characteristics and trends of tropical night (TN) are investigated by using the KMA 14 observation data for the recent 50 years (1958-2007) over South Korea. The TN is defined as a day with a daily minimum temperature exceeds the absolute threshold temperature ($25^{\circ}C$), and the relative deviation from normal temperature, 95th percentile of all observed daily minimum temperature. Although the spatial distribution of TN occurrence depends on the choice of the definitions, the frequency of TN shows strong spatial and interannual variations with the minimum at high land area (Chupungnyeong and wet years) and maximum at southern coastal area and large city area (Jeju, Busan, Seoul, Daegu). Most of TN occurs in August (56%) and July (41%), and the duration date of TN is proportional to the frequency of TN without regard to the definition method. In general, increasing trends are found in the TN time series without regard to the analysis method, but the trends are clearly depending on the analysis period and geographic locations. Decreasing trends are prominent during the most of analysis period, especially until the mid of 1990, whereas strong increasing trends are found during recent 30 years (1988-2007), especially at Jeju, Ulsan, Daegu and Pohang. Also the severity of TN is significantly increased in recent years.

• 한국환경생태학회지
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• 제20권3호
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• pp.299-310
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• 2006

만경강 하구역 염습지에 우점 분포하는 5종 염생식물의 개체군 형성 전략에 대하여 유묘 출현율, 생물량, 뿌리 줄기길이생장, 교차이식 생존율, 토양환경 요인 등을 2005년 2월에서 10월까지 조사하였다. 유묘 출현 시기는 칠면초가 가장 빨랐으며 그다음으로 가는갯능쟁이, 퉁퉁마디, 갯개미취, 나문재 순으로 나타났다. 염생식물의 수분상태와 염도에 따른 발아율은 칠면초가 침수구 상태의 고온과 저염도에서, 퉁퉁마디가 고염도에서, 가는갯능쟁이와 갯개미취가 건조구와 침수구에서, 나문재가 건조상태의 고염도에서도 발아가 잘 되었다. 5종 염생식물의 교차이식 생존율은 저위염습지에 칠면초, 중위염습지에 퉁퉁마디, 가는갯능쟁이, 갯개미취, 고위염습지에 나문재가 높았다. 토양환경요인은 비슷하였으나 토성은 점토, 모래, 미사 순으로 높게 나타났다. 따라서 본 연구결과 5종 염생식물의 개체군 형성 전략은 칠면초는 저위염습지에, 퉁퉁마디, 가는갯능쟁이 그리고 갯개미취는 중위염습지에, 나문재는 고위염습지에 분포하여 이루어진다고 여겨진다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.538-541
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• 2006

PSC(Prestressed Concrete) box girder bridges have been widely applied in Korea. A number of these bridges have been built by the segmental construction method in the longitudinal direction and(or) vertically along the cross-sectional depth with MSS(Moving Scaffolding System). An actual 2-span continuous PSC box girder bridge of Kyeongbu high speed railway was selected and instrumented with 96 vibrating wire embedded type strain gauges and 2 thermocouples. The long-term behavior of the bridge was monitored through two major points located at mid-span of the first span and at the internal support. Data collection started just after the casting of the first segment (U section). Concrete strain and temperature data were gathered regularly by a data logger (CR10) during 600 days under and after construction. According to this measurement, the parabolic longitudinal strain distribution in the top slab at mid-span is shown. And also, the same distribution at the interior support is shown. The compressive strains at the cantilever region are larger than at the web position and the internal part in the top slab. Strain difference largely happened during the early construction period.

• 센서학회지
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• 제28권4호
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• pp.256-261
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• 2019

In this study, mid-infrared transparent zinc sulfide (ZnS) ceramics were fabricated through hydrothermal synthesis with different molar ratios of S/Zn (S/Zn = 0.8, 1.0, 1.2, 1.4, and 1.6). The ZnS ceramics were sintered at a relatively low temperature of $850^{\circ}C$ to prevent the occurrence of the hexagonal phase featuring optical anisotropy. The phase composition, microstructure, and optical properties of the ZnS ceramics were subsequently investigated by employing X-ray diffraction, scanning electron microscopy, and Fouriertransform infrared spectroscopy. The results obtained indicate that the ZnS nanoparticles feature the cubic phase, without the hexagonal phase. Moreover, with increasing S, the crystallinity and particle size of the ZnS nanoparticles increased. The crystallinity and density of the ZnS ceramics improved when the molar ratio of S was higher than the molar ratio of Zn, thereby enhancing the transmittance. Furthermore, the ZnS ceramic with an S/Zn value of 1.2 was found to exhibit the highest transmittance of approximately 69% owing to the reduced occurrence of the hexagonal phase and a high density of 99.8%.