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        검색결과 30

        4.
        2018.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Recently, measuring instruments for SHM of structures has been developed. In general, the wireless transmission of sensor signals, compared to its wired counterpart, is preferable due to the absence of triboelectric noise and elimination of the requirement of a cumbersome cable. However, in extreme environments, the sensor may be less sensitive to temperature changes and to the distance between the sensor and data logger. This may compromise on the performance of the sensor and instrumentation. Therefore, in this paper, free vibration experiments were conducted using wireless MEMS sensors at an actual site. Measurement was assessed in time and frequency domain by changing the temperature variation at(- 8℃, - 12℃ and - 16℃) and the communication distance (20m, 40m, 60m, 80m).
        4,000원
        5.
        2018.05 구독 인증기관·개인회원 무료
        Airport concrete pavement slabs show contraction and expansion behavior due to environmental factors such as temperature and humidity. Among the various environmental factors, temperature is the most influential factor in the concrete slab. However, it is inadequate to consider air temperature or surface temperature as influential factors especially for airport concrete slabs with very large thicknesses. Therefore, this study intends to utilize the equivalent linear temperature difference calculated from the data of the thermometer embedded in 5 depths(50mm, 150mm, 250mm, 350mm, 450mm) on the airport concrete slab. Equivalent linear temperature difference is the temperature difference between the uppermost and lowermost part of the concrete slab, which shows the same behavior due to actual temperature. Since the upper part of the concrete slab is more affected by air temperature than the lower part, the daily temperature range is large. Therefore, the equivalent linear temperature difference increases during the day and decreases at night, and concrete slabs show curl-down during the day and curl-up at night. This daily variation of curling behavior causes a difference in HWD experimental results. The HWD(Heavy Weight Deflectometer) test is mainly performed to investigate the condition of the pavement. And the calculated values are deflection, ISM(Impact Stiffness Modulus), LTE(Load Transfer Efficiency). The equivalent linear temperature difference represents the behavior of the concrete slab by the environmental load, and the calculated values by the HWD test represent the behavior. Therefore, the purpose of this study is to investigate the behavior of concrete slab by combined load including environmental load and traffic load through correlation analysis between these values. This study was supported by Incheon International Airport Corporation(BEX00625) and Korea Airports Corporation.
        6.
        2015.04 구독 인증기관·개인회원 무료
        The apple leaf miner, Phyllonorycter ringoniella(Lepidoptera:Gracillariidae),is an important pest of apple trees in Japan, Korea and China. It is very important to know the development time of overwinter pupae for predicting the adult spring emergence in apple orchard. In total 556 damaged leaves caused by P. ringoniella were collected three times in two locations, Pohang and Mungyeong, and then were reared in five incubators with 10, 15, 20, 25, and 30℃, RH 60±5%, and a photoperiod of 16:8 (L:D) h, respectively. There were larvae, pupae of P. ringoniella and its parasitoids inside these damaged leaves. Larval population was 44% inside the curled leaves, but found all dead. Pupal population was 41%, but 41% were found dead. Parasitism was 14.5% ranged from 4.5 to 17.9%. This means that the winter survival was only 23.9%. Surviving pupal developmental rate was linearly related to the temperature treated. Lower threshold was estimated to 3.58℃ with degree-day accumulation to adult emergence of 153.8 DD. From this information, adult emergence was predicted during early April. However this estimation was only based on the partial data from which current experiments are on-going. Further sophisticated research outcome will produce better understanding of the overwintering moth development and its modeling.
        7.
        2013.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Numerical analysis has been carried out to investigate thermal characteristics for hydraulic system. Overall performance of hydraulic system is largely influenced by oil flow field with heat transfer. Especially thermal characteristics for operating conditions with high oil temperature caused by heavy load and continuous operation are dominant. Oil temperature variation with time in the system is predicted for various flow conditions. Local fluid flow fields at the pipelines, valves, and oil pump in the hydraulic system are considered with thermodynamic and transport properties such as density and viscosity. These results in the study can be applied to the optimal design of hydraulic system.
        4,000원
        8.
        2013.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Local Nusselt number and temperature field distribution within the compound duct with gap have been measured. Measurement of air and wall temperature span a range of gap width from 2mm to 6mm. Also, the Reynolds number is variated from 20,000 to 40,0000. In order to observe the correlations between gap width and turbulent heat transfer, the present measurement has tried to verify the enhancement effect of heat transfer when a gap exists within the compound channel. From this measurement, we could see that the pulsating flow has generated a strong turbulent flow mixing within the compound channel. And the turbulent flow mixing in the pulsating flow plays an effective role of enhancing the Nusselt number by making the fluid temperature uniformly within the compound channel.
        4,000원
        10.
        2011.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        포장의 동결깊이는 30년간의 기온자료를 분석하여 만든 동결지수를 근거로 하여 동상방지층의 두께를 결정한다. 본 연구에서의 현장계측 지역은 동결지수에 따라 동결지수 550~650℃·일, 450~550℃·일, 350~450℃·일로 구분하여 지역을 선정하였고, 각 지역별로 절토부, 절성경계부, 저성토부(2m 이하 성토부) 구간으로 단면을 구분하였다. 각 단면에 동상방지층 유 무를 구분하여 포장층별로 계측기(온도, 함수비)를 설치하고 데이터를 수집하였다. 현장 모니터링 시스템을 통하여 수집된 데이터 분석을 통하여 포장된 도로의 동결깊이를 결정하는데 이용할 수 있다. 연구 결과, 동상방지층이 없을 경우 동결지수 550~650℃·일 지역에서는 대기온도에 따라 겨울철 노상층의 온도가 0℃ 이하로 나타났고, 동결지수 450~550℃·일 지역에서는 지역별로 상이했으며, 동결지수 350~450℃·일 지역에서는 동상방지층이 없어도 노상층의 온도가 0℃ 이하로 나타나지 않았다. 또한, 포장 단면별로 동결깊이를 비교한 결과 대기온도에 따라 동결깊이는 절토부가 가장 높았으며, 절성경계부, 저성토부 순으로 단면별 차이가 나타났다.
        4,300원
        11.
        2011.02 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Specific heat of a crystal is the sum of electronic specific heat, which is the specific heat of conduction electrons, and lattice specific heat, which is the specific heat of the lattice. Since properties such as crystal structure and Debye temperature do not change even in the superconducting state, the lattice specific heat may remain unchanged between the normal and the superconducting state. The difference of specific heat between the normal and superconducting state may be caused only by the electronic specific heat difference between the normal and superconducting states. Critical temperature, at which transition occurs, becomes lower than Tc0 under the influence of a magnetic field. It is well known that specific heat also changes abruptly at this critical temperature, but magnetic field dependence of jump of specific heat has not yet been developed theoretically. In this paper, specific heat jump of superconducting crystals at low temperature is derived as an explicit function of applied magnetic field H by using the thermodynamic relations of A. C. Rose-Innes and E. H. Rhoderick. The derived specific heat jump is compared with experimental data for superconducting crystals of MgCNi3, LiTi2O4 and Nd0.5Ca0.5MnO3. Our specific heat jump function well explains the jump up or down phenomena of superconducting crystals.
        4,000원
        12.
        2010.10 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Magnetars are neutron stars possessing a magnetic field of about 1014-1015 G at the surface. Thermodynamic properties of neutron star matter, approximated by pure neutron matter, are considered at finite temperature in strong magnetic fields up to 1018 G which could be relevant for the inner regions of magnetars. In the model with the Skyrme effective interaction, it is shown that a thermodynamically stable branch of solutions for the spin polarization parameter corresponds to the case when the majority of neutron spins are oriented opposite to the direction of the magnetic field (i.e. negative spin polarization). Moreover, starting from some threshold density, the self-consistent equations have also two other branches of solutions, corresponding to positive spin polarization. The influence of finite temperatures on spin polarization remains moderate in the Skyrme model up to temperatures relevant for protoneutron stars. In particular, the scenario with the metastable state characterized by positive spin polarization, considered at zero temperature in Phys. Rev. C 80, 065801 (2009), is preserved at finite temperatures as well. It is shown that, above certain density, the entropy for various branches of spin polarization in neutron matter with the Skyrme interaction in a strong magnetic field shows the unusual behavior, being larger than that of the nonpolarized state. By providing the corresponding low-temperature analysis, we prove that this unexpected behavior should be related to the dependence of the entropy of a spin polarized state on the effective masses of neutrons with spin up and spin down, and to a certain constraint on them which is violated in the respective density range.
        4,000원
        13.
        2010.05 구독 인증기관·개인회원 무료
        The legume pod borer, Maruca vitrata (Fabricius) (Lepidoptera: Crambidae) causes serious damage to some legume crops of genus Vigna and Sesbania in Korea. In the current study, laboratory studies on the temperature-dependent development of the insect were performed at 8 constant temperatures ranging from 13℃ to 34℃ at 3℃ intervals. Lower developmental threshold (LDT) for eggs, larvae, and pupae were calculated as 10.0, 12.5 and 13.3℃, respectively, using the linear-regression equations of the developmental rates. Degree-days required to complete a stage were estimated as 48, 187, and 94, for egg, larval, and pupal stages, respectively. The larvae couldn't survive at 13 and 16℃, and the larval survival rate was the highest at 28℃. The egg hatching rate was the lowest at 13℃. In the adult stage, the pre-oviposition period was the shortest at 22℃, and the total egg number was the most with ca. 500 at 25℃. Degree-days for the stages of 1st-4th larval instars, egg, and adult emergence-50% oviposition were calculated during the reproductive development season of red bean using single sine method and Suwon weather station data based on LDTs, respectively. Finally, the adult occurrence time was estimated after the degree-days were cumulated reversely from the distribution data of larval stages observed in a red bean field
        14.
        2009.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The egg size and weight of the gray field slug, Deroceras reticulatum Müller, was 1.91×2.19 ㎜ and 3.3 ㎎ at 24℃, respectively. Its weight increased from newly laid eggs to adults for 17 weeks at four temperature regimes and was heaviest at 20℃, followed by 24, 16 and 28℃. Likewise, hatching rate of the egg batches was highest with 95% at 20℃, followed by 24, 16 and 28℃ with significant differences. The number of eggs in the batches was increased with 20 at 20℃ while it was only 10 at 28℃. The average accumulated egg-laying days was longest with 15 days at 20℃ while shortest with 9 days at 24℃. The range of egg-laying period was shortest with 84-134 days at 16℃ and longest at 20℃. Thus, the total number of eggs laid by adult D. reticulatum was highest with 217 at 20℃ and lowest with 105 at 16℃. The egg period was 12-19 days while the juvenile period and adult longevity were 51-68 days and 85-134 days, respectively. The life span of D. reticulatum from egg to adult was longest with 216 days at 20℃, followed by 193 days at 24℃, 170 days at 16℃ and 151 days at 28℃. Accordingly, the most favorable temperature for the oviposition, development and longevity of D. reticulatum is 20℃.
        4,000원
        15.
        2009.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        AQUA/AMSR-E 인공위성 자료를 활용하여 3차원 최적내삽 해수면온도 합성장을 생산하였고 시간평균장과 비교하여 문제점과 한계점을 기술하였다. 3-D SST 합성장은 북태평양 중앙부에서 전체적으로 0.05˚C 이하의 작은 오차를 보였으나, 위성 결측이 있는 연안에서는 0.4˚C 이상의 비교적 큰 오차를 유발하였다. 강한 강수나 구름으로 인한 결측이 있는 부분에서는 0.1-0.15˚C에 달하는 오차를 보였다. 시간평균장과 비교한 결과, 구름 부근의 화소에서는 해수면온도를 낮게 계산하는 경향이 있었으며, 해수면온도의 공간적 구배를 감소시키는 평활화가 전체적으로 나타났다. 적도 부근 저위도에서 OI SST는 실제 해수면온도에는 없는 불연속성을 만드는 경향이 있었고, 이는 OI 과정에서 사용한 윈도우의 크기와 해양 현상의 수평 규모가 위도에 따라 변화하는데서 기인하였다. 현상의 공간 규모의 척도인 로스비 내부변형 반경은 북태평양에서 O(1) 정도로 위도에 따른 공간적 변화가 큰 것으로 나타났다. 본 연구는 SST합성장 생산과정에 위도와 해수의 수직적 밀도 구조와 밀접한 관련이 있는 해양 현상의 수평적 규모의 시공간적 변동 특성을 고려해야 함을 제시한다.
        4,200원
        18.
        1996.04 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        완화형 강유전체의 가장 대표적인 PMN계에서 첨가제의 종류와 함량, 측정온도, 인가 전계의형태 등의 변화에 따른 전계인가 변화특성을 광법위하게 조사하였다. Columbite precursor법에의해 분말을 준비하고 고상소결방법에 의하여 모든 시편을 제조하였다. 순수한 PMN에 첨가제로서 PbTiO3와 Pb(Zr, Ti)O3를 첨가한 경우에 완전한 perovskite 구조의 고용체가 형성되었음을 알 수 있었다. Tεmax이상에서는 변위의 이력이 크게 발생하는 강유전체의 거동을 보여주었다. 양방향으로 전계를 인가하여 변위를 이용하면 발생 strain은 실온 근방에서 온도에 대하여 안정적이지만 단방향 전계에 따른 변위는 온도에 따라 크기가 변한다는 것을 알 수 있었고 유전상수가 큰 경우가 전왜의 크기 또한 큰 것을 알 수 있었다. 0.9MN-0.1PT와 0.8PMN-0.2PZT의 경우 최대가 되는 온도는 유전율이 최대가 되는 온도보다 더 낮은 온도에서 나타났다.
        4,000원
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