• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.132-135
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• 2004

High-performance concrete (HPC) may be expected to differ from usual concrete with respect to shrinkage behavior, and it shows high autogenous shrinkage due to the use of very low water-binder ratio (w/b) and various admixtures. Therefore, in order to minimize the shrinkage stress and to ensure the service life of concrete structure, volumetric change of HPC should be understood. In this study, small prisms made of HPC with w/b of 0.32 and blast-furnace slag content of $0\%,\;30\%,\;and\;50\%$ were prepared to measure the volumetric changes such as autogenous shrinkage, drying shrinkage, and swelling under three different curing conditions. It was observed that the concrete cured. sealed condition showed only autogenous shrinkage while the concrete let to dry condition at temperature of $20^{\circ}C$ and relative humidity of $60\%$ during the test period showed both autogenous and drying shrinkage. Moreover, the concrete exposed to dry condition after 2-day water curing swelled and then started to shrink with age. The total shrinkage (autogenous+drying) of this concrete was smaller than that of the concrete cured dry condition, especially at early-age. Therefore, the early-age moisture curing is very effective to control or minimize the volumetric change and its induced stress of HPC.

• 한국재료학회지
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• 제9권4호
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• pp.409-413
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• 1999

Recently, the polymeric insulators have been accepted in several countries for the outdoor high voltage applications. In comparison with the conventional porcelain, polymeric insulators offer various advantages such as light weight, superior vandal resistance and better contamination performance. The outdoor polymeric insulating materials such as silicone rubber, ethylene propylene diene monomer(EPDM), ethylene vinyl acetate(EVA) and epoxy are aged such as silicone rubber, ethylene propylene diene monomer(EPDM), ethylene vinyl acetate(EVA) and epoxy are aged under the various natural environment with the long-term performance in outdoor. In this paper, the effects of UV-under the various natural environment with the long-term performance in outdoor. In this paper, the effects of UV-ray on the surface of silicone rubber were investigated by using the weather-Ometer. The accelerated aging stresses were simulated by UV radiation, high temperature and humidity as well as water spray. These aging characteristics were examined through contact angle measurements, tracking resistance test, FT-IR and SEM/EDS analysis. The experimental results showed that tracking resistance decreases with increase in the UV-ray irradiation period. But the surface of silicone rubber kept hydrophobicity. It is found that the inorganic filler such as)$ Al(OH_3$ improves tracking resistance and the $Tio_2$is very effective in preventing degradation of silicone rubber surface from UV-ray.

• Tribology and Lubricants
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• 제15권4호
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• pp.335-342
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• 1999

Corrosion of the disk has been an ongoing concern for the manufacturers of hard disk drives. With the advent of magnetoresistive (MR) head, very low levels of corrosion and contamination become more critical since the raised defects and corrosion products on the disk surface-anything that heats the MR sensor due to the contact-can distort the output signal of the head. This phenomenon is called as thermal asperity. In this paper, the effect of corrosion as a form of Co migration on the occurrence of thermal asperity in MR drives was investigated. The corrosion test at high temperature (60$^{\circ}C$) and high relative humidity (80%) was emphasized in this study and the testing results at ambient condition were compared. The corrosion on the disks was characterized as the amount of Co ion migration using an ion chromatography (IC) and a time-of-flight secondary ion mass spectroscopy (TOF-SIMS). It is proved that corrosion on the disk surface after storage testing is closely correlated to the amount of Co ions migration from the magnetic layer to disk surfaces and higher Co migration causes more thermal asperities in the drive. In order to reduce Co migration, several methods such as burnishing process and structure of the carbon overcoat were investigated. It is found that the hydrogenated carbon overcoat shows the least Co migration among different types of overcoat layer. However, the most effective way to reduce Co migration is the application of Cr layer between the overcoat and the magnetic alloy layer.

• Journal of Welding and Joining
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• 제35권3호
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• pp.15-20
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• 2017

In this paper, two types of assemblies using CNT-filled SACAs (with 0.03 wt% CNTs and without CNT) were prepared to investigate the influence of carbon nanotubes (CNTs) on the reliability properties of solderable anisotropic conductive adhesives (SACAs) with a low-melting-point alloy (LMPA). Two types of reliability test including thermal shock (TS: -55 to $125^{\circ}C$, 1000 cycles) and high-temperature and high-humidity (HTHH: $85^{\circ}C$, 85% RH, 1000 h) tests were conducted. The SACA assemblies with and without CNTs showed stable electrical reliability properties due to the formation of wide and stable metallurgical interconnection between corresponding metallizations by the molten LMPA fillers. Although the mechanical pull strength of CNT-filled SACA assemblies was decreased after thermal aging (because of the excessive layer growth and planarization of the IMCs), the CNT-filled SACA with 0.03wt% CNTs showed enhanced mechanical reliability properties compared with the SACA assemblies no CNTs. This enhancement in mechanical performance was due to the reinforcement effect of the CNTs. These results demonstrate that CNTs within the CNT-filled SACAs can improve the reliability properties of CNT-filled SACAs joints due to their superior physical properties.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.317-320
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• 2005

In recent years, according to the development of construction technique, the constructions of longer span bridges, taller buildings, deeper offshore structures, and other megastructures are calling for construction materials with increasingly improve properties. So, the demand for high-strength concrete(HSC) have been increased and many new structures have been built using HSC with the compressive strength about 100MPa. However, it is well-known that as the strength of concrete increases, concrete becomes more brittle. Recent studies, however, shown that the brittleness of HSC can be improved by adding some fibers to the concrete. Especially steel fiber reinforced concrete(SFRC) can be used in this case. Many research works have shown that SFRC results in better crack and deflection control, higher shear strength, improved fatigue performance, increased impact strength, reformed flexural strength, advanced fracture toughness and enhanced postcracking resistance. So, this is a study on the long-term response of SFRC applied to HPC about 40MPa. Therefore, in this study, the test results of twenty-six high-strength concrete specimens and steel fiber-reinforced concrete specimens, with steel fiber content of 1 $\%$ by volume were presented. And the results are analyzed by using of the factors of time, mix properties, humidity/temperature, and loading conditions.

• 한국전자통신학회논문지
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• 제16권3호
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• pp.429-436
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• 2021

기상청에서 운용 중인 윈드프로파일러는 저층을 집중 관측하는 저층 모드와 고층을 집중 관측하는 고층 모드로 나누어 관측한다. 북강릉과 창원에 설치된 LAP-3000 윈드프로파일러는 저층 모드와 고층 모드의 샘플링 주파수를 동일하게 설정한 것이 특징으로, 동일한 고도에서 두 모드로 관측한 바람을 비교해볼 수 있다. 두 지점의 2020년 1년 동안 풍속을 분석한 결과, 두 모드의 상관성이 라디오존데와의 상관성보다 최대 0.2 낮았다. 두 모드의 풍속에 대한 T-test 수행 결과는 온위, 비습이 급변하는 구간 자주 나타나는 10월에 특히 유의미한 차이를 보였다. 대기경계층의 발달 차이는 관측 모드에 따라 풍속의 정확도에 영향을 미친다.

• 한국잠사곤충학회지
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• 제15권1호
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• pp.37-48
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• 1973

The purpose of this studies is to improve the cohesion of raw silk through various analyses on cocoon drying, cooking, reeling, re-reeling, and on the properties of water. Also we investigated the correlation between silk testing items which we have reached to the following results. 1. Drying of cocoon When cocoons were slowly dried with 100$^{\circ}C$, the results of cohesion became much better. On the other hand, the results were considerably decreased in case the temperature with 115$^{\circ}C$. 2. Cooking of cocoon In case of the cooking of cocoon, we found that the result of cohesion was best with incomplete cooking, that of the control was next, while in over cooking, the results were very low. Also the results of cohesion were much better when using the method of over cooking with sericin arrestive agent than that of incomplete cooking with sericin agglutinating agent. 3. Reeling of cocoon A) When the temperature of reeling bath was 25-45$^{\circ}C$, the results of cohesion test were much better, but at the temperature below 25$^{\circ}C$ or above 45$^{\circ}C$, the results became worse. B) With out the process of croissieur, the results of cohesion were too bad, but in case of croissieur more than 1cm, cohesion became better rapidly. Further more, we understood that the results of cohesion were improving slightly with longer length of croissieur. C) When the velocity of reeling was increased, the results of cohesion also improved. The best results were shown when reeling velocity was 180-220 r.p.m. But when the velocity was increased more than 220 r.p.m., the results of cohesion got worse more or less. D) When the temperature of the drying pipe in reeling machine was raised, the results of cohesion also showed a tendency to improve. 4. Re-reeling A) We could net reach a conclusion as to have correlation between the number of dipping repeat in vacuum tank and the results of cohesion before re-reeling process. B) When we used Seracol 500 as an agglutination protective agent with l/1000 to l/2000 of water, the results of cohesion test were better. C) When we used Pearl-lite as an agglutination protective agent with 1/1000 to 1/2000 of water, the results of cohesion were considerably better. D) We gained tile best results when used Cohesion Improving Chemical, A-80, with 500-1500 times diluted. 1) Results of cohesion was improved when humidity was low or temperature was high in the rereeling machine. 5. Filature water A) The water pH near the isoelectric point of protein showed the best cohesion, but the farther water pH, the worser results were obtained. B) With the increasing of M-alkalinity in filature water, the results of cohesion were worse. Above all, we understood the tendency of the results of cohesion get worse when the M-alkalinity is increased above 200 ppm. C) By increasing the total hardness of the filature water, it improved the results of cohesion. Especially, when the total hardness was above 300ppm, the results were extremely high. 6. Effects combination of each results A) The result of effects combination in filature processes with the obtained best conditions was distinctively improved. But the results could not reach in mathematicaly double effect. When reelied under worse conditions, the results of cohesion test were too bad. There was "effect limit" for the promotion. B) Generally the results of cohesion were bad when the filature conditions(the temperature, pressure and the properties of water, etc) are processed as sericin loss to be high. On the other hand, the results were very good when lower sericin loss was controlled in filature conditions. C) When filature conditions such as reeling velocity and croissieur length provide pysical cohesion ability and when raw silk dry fast during reeling and re-reeling, we found the result of cohesion was better. 7. Correlation of silk testing items. A) A negative correlation exists between the results of cohesion test and cleanness defect. Another word, the result of cohesion test was found to be worse as cleanness defect increased. B) In cleanness, cohesion has negative correlation against the number of slugs, but we could not find any correlation against long loops, loose ends. C) Cohesion has negative correlation against average neatness and low neatness defect. The better the results of neatness respectively, the better the results of cohesion found. D) There is no correlation between tenacity and the results of cohesion test, but there was high positive correlation between the results of elongation and those of cohesion test. The more elongation, the better the results of cohesion was found.

• 한국버섯학회지
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• 제14권4호
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• pp.249-252
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• 2016

하이테크 산업은 이른바 스마트 농업의 융합에 장벽을 극복하기 위해 농업의 경관을 바꾸고있다. 정밀 농업의 핵심인 온도, 습도, 위치 정보 및 실시간 요약 정보 모든 중요한 ICT 제어 기술은 버섯 재배 온도, 습도, 조명, 이산화탄소 등의 제어가 가능한 컨테이너형 버섯재배시스템을 설계제작하였으며, 버섯 재배에 활용가능성을 노루궁뎅이버섯을 대상으로 시험을 수행하였다. 노루궁뎅이버섯의 초발이소요일수는 청색 LED광에서 6~7일, 광량 $40{\sim}47Pmol/m^2s$ 적색 LED광에서 4~6일로 유사하였고 생체중은 적색 LED광에서 95g으로 타처리구에 비해 우수하였다. 앞으로 컨테이너형 버섯재배시스템의 국내활용도 향상시켜 국내 판매와 캐나다 등 극한지역을 포함한 외국 수출이 계획되어 있다.

• 대한토목학회논문집
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• 제29권4A호
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• pp.291-297
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• 2009

실험을 통해 고장력 볼트의 릴렉세이션를 측정하였다. 종류와 표면 처리가 다른 볼트를 사용하여 체결길이가 서로 다른 블록형태와 겹침이음형태의 시험체를 조립하였다. 항온항습실에서 시간 경과에 따라 볼트에 도입된 축력을 변형률 게이지를 통하여 측정하였다. 볼트축력의 감소율은 모든 시험체에서 10% 미만으로 나타났다. 결합 형태, 볼트종류, 체결길이 그리고 볼트의 표면 처리가 서로 다른 여러 경우에 대해 실험결과를 이 연구에서 제안한 릴렉세이션 추정 모델을 이용하여 비교, 검토하였다. 제안한 모델은 여러 경우에 대한 실험 결과와 모두 합리적으로 잘 합치하고 있다. F13T와 F10T 볼트사이에 차이점을 발견할 수 없으나 다크로 볼트의 최종 체결력 감소율은 일반 볼트보다 30% 정도 높으며, 또한 전체적으로 볼트 체결길이가 짧아짐에 따라, 전단면의 수가 증가함에 따라 높아지는 경향을 보여주고 있다.

• 한국건설순환자원학회논문집
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• 제6권4호
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• pp.283-288
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• 2018

균열 자기치유 소재는 균열발생 시점부터 노출환경 조건에 따라 활성화되기 때문에 치유성능과 균열면의 노출환경 조건과의 관계 규명이 매우 중요하다. 이에 본 연구에서는 자기치유형 보수 모르타르의 치유성능에 노출환경 조건이 미치는 영향을 투수시험을 통하여 조사하였다. 균열시험체의 초기 균열폭에 대한 온도 및 습도의 영향을 조사한 결과, 양생온도의 영향은 미미하였으나, 건습변화에 의해서는 균열닫힘 현상이 발생하고 있음을 확인하였다. 그리고 자기치유형 보수 모르타르 시험체의 균열부위에서 생성된 치유물질은 calcite 광물로 확인되었다. 밀도가 높은 calcite 광물은 중력의 영향을 받아 침강하기 때문에, 균열면의 방향에 따라 치유성능에 다소 차이를 나타냈으며, 또한 대기노출 조건보다 습윤노출 조건에서 치유성능이 크게 향상되었다.