In this study, we examined dimensional changes in processing carbon fiber composites using a cost-competitive domestic high-speed router. Lacking temperature compensation features found in typical machines, it faces increased defect rates due to temperature fluctuations during processing. To mitigate this, we defined specific processing temperature conditions, established hole positions as distance references for various temperatures, and measured dimensional changes. This enabled us to calculate necessary dimensional corrections, minimizing thermal deformation.

In this study, numerical analysis was performed for the purpose of analyzing the flow characteristics and performance according to the change in the inflow hydrogen temperature and differential pressure of the receptacle of the hydrogen charging system. The pressure distribution and turbulent kinetic energy in the filter area were analyzed by changing the outlet pressure condition under the inlet hydrogen temperature condition, and the flow velocity change at the outlet was compared and analyzed. As a result of the analysis, as the differential pressure decreased, the flow rate at the outlet of the receptacle decreased by up to about 70% at the 2.86 MPa condition compared to the 1.86 MPa condition, and the mass flow rate decreased by about 56.5% at the maximum. It was found that the standard CV performance was not satisfied when the differential pressure at the inlet and outlet was 1.12 MPa or less under the 363K temperature condition.

PURPOSES : In this study, we aimed to evaluate the transition temperature (Tt) of asphalt binders using molecular dynamics simulations, which can provide a more accurate assessment of the mechanical properties of a material at the molecular level and can be applied to material development and design. METHODS : Unlike conventional macro- or meso-level simulations, we utilized MD simulations to evaluate the Tg of asphalt binders based on material composition and aging degree as input variables. In this analysis, 11 temperatures ranging from 434 K to 233 K at 20 K intervals were utilized, and the bulk volume and density were calculated through MD simulations. RESULTS : The MD simulation successfully predicted the Tg of the asphalt binder, and the molecular-level properties and interactions determined in this study can be applied not only to material development but also to the determination of constitutive equations or contact models used in continuum mechanics or discrete element methods. The calculated Tg was slightly different depending on the aging of the asphalt binder; however, it was found to accurately reflect the transitional characteristics. CONCLUSIONS : This study demonstrated the potential of MD simulations as valuable tools for material development and design in the construction industry. The results indicate that the use of MD simulations can lead to more accurate and efficient material development and design by providing a more detailed understanding of material properties and interactions at the molecular level.

In order to respond to environmental pollution, developed countries, including Korea, have begun to conduct research to utilize hydrogen energy. For mass transfer of hydrogen energy, storage as liquid hydrogen is advantageous, and in this case, the volume can be reduced to 1/800. As such, the transportation technology of liquefied hydrogen for ships is expected to be needed in the near future, but there is no commercialized method yet. This study is a study on the technology to test the performance of the components constituting the membrane type storage container in a cryogenic environment as a preparation for the above. It is a study to find a way to respond by analyzing in advance the problems that may occur during the shear test of adhesives. Through this study, the limitations of ISO4587 were analyzed, and in order to cope with this, the specimen was supplemented so that fracture occurred in the adhesive, not the adhesive gripper, by using stainless steel, a low-temperature steel, to reinforce the thickness. Based on this, shear evaluation was performed under conditions lowered to minus 243℃, and it was confirmed that the breaking strength was higher at cryogenic temperatures.

이 논문에서는 내구성이 우수한 것으로 알려져 있는 펄트루젼 FRP의 습도 노출 및 동결 융해 영향을 검토하고, 이에 따른 국부좌굴강도 영향을 검토하기 위한 해석적 연구를 수행하였다. FRP는 일반적으로 내구성이 우수하다고 알려져 있기 때문 에, 해양 구조물 등 습윤환경에서 적용하기 위한 다양한 연구가 진행되고 있으며, 특히 구조용 부재로 제작되는 펄트루젼 FRP 부재는 하절기와 동절기의 온도변화에 노출되기 때문에 이에 대한 검토가 필요하다. 펄트루젼 FRP의 습도 노출 및 동결 융해 영향은 기존 연구의 실험 결과를 참고하였으며, 국부좌굴강도는 정밀해법을 통해 영향을 검토하였다. 검토 결과 펄트루젼 FRP 는 습도노출 및 동결융해의 영향으로 인해 최대 약 20%의 인장강도 및 탄성계수 변화를 나타내었으나, 국부좌굴강도는 약 3% 로 그 영향이 상대적으로 작은 것으로 나타났다. 따라서, 온도이력 및 습윤환경에서도 펄트루젼 FRP는 국부좌굴강도의 큰 변화 를 나타내지 않고 높은 내구성을 나타낼 수 있을 것으로 판단된다.

To elucidate how cultivation temperature affected various traits including pileus color, yield and morphology of Pleurotusspp. Main results were as follows. Pileus lightness of all cultivars of Pleurotustested became higher as cultivation temperature increased, while those of Santari, Hwang-geumsantari and Sunjung at 21oC were lower than at 18oC. Redness and yellowness of pileus decreased as cultivation temperature increased; those of chromatic pileus cultivars showed noticeable difference. Yellowness of cultivar with chromatic pileus was higher than that of cultivar with achromatic pileus. Yield was increased as cultivation temperature increased, Wonhyeung 1ho; low temperature favored cultivar showed high yield when it was cultivated at low temperature andno fruiting body at 21oC. Valid number of stipes were generally higher at 18oC, and its correlation coefficient with yield was low. Length and stipe thickness changed consistently (larger and thicker) upon cultivation temperature; the coefficient of determination(R2) 0.514 for lengthof Heuktari and 0.963for stipe thickness of Santari were high. Correlation coefficient of one trait was highly related with multiple traits. In the future, we will conduct research on the changes of expressed genes involved in the pigments for pileus color by RNA expression analysis.

This study aimed to evaluate the germination characteristics, -glucan and antioxidant contents, and antioxidant activity of naked oat according to germination temperature (20, 25, and 30oC) and time (24, 48, and 72 h). Sprout length was highest at 25oC, and the rotten degree was increased as the germination temperature and time increased. The -glucan content of naked oat increased after 24 h of germination at all temperatures and then decreased by 72 h of germination. Total polyphenol content, flavonoid content, and antioxidant activity increased as the germination temperature and time increased.

Research is being actively conducted on the continuous thin plate casting method, which is used to manufacture magnesium alloy plate for plastic processing. This study applied a heat transfer solidification analysis method to the melt drag process. The heat transfer coefficient between the molten magnesium alloy metal and the roll in the thin plate manufacturing process using the melt drag method has not been clearly established until now, and the results were used to determine the temperature change. The estimated heat transfer coefficient for a roll speed of 30 m/min was 1.33 × 105 W/m2·K, which was very large compared to the heat transfer coefficient used in the solidification analysis of general aluminum castings. The heat transfer coefficient between the molten metal and the roll estimated in the range of the roll speed of 5 to 90 m/min was 1.42 × 105 to 8.95 × 104 W/m2·K. The cooling rate was calculated using a method based on the results of deriving the temperature change of the molten metal and the roll, using the estimated heat transfer coefficient. The DAS was estimated from the relationship between the cooling rate and DAS, and compared with the experimental value. When the magnesium alloy is manufactured by the melt drag method, the cooling rate of the thin plate is in the range of about 1.4 × 103 to 1.0 × 104 K/s.

A strain of Alexandrium species was established by isolating cells from Jangmok Bay, Korea. Its morphology and molecular phylogeny based on LSU rRNA gene sequences were examined. In addition, growth responses of this Alexandrium species to changes in temperature, salinity, and nutrient concentrations were investigated. This Alexandrium species from Jangmok Bay had a ventral pore on the 1′, which was morphologically consistent with previously described Alexandrium tamarense and A. catenella. Phylogenetic analyses revealed that this isolate was assigned to A. pacificum (Group IV) within A. tamarense species complex. In growth experiments, relatively high growth rates and cell densities of A. pacificum (Group IV) were observed at 15°C and 20°C. This species also grew under a wide range of salinity. This indicates that this Korean isolate of A. pacificum (Group IV) is a stenothermic and euryhaline species. In growth responses to changes in nutrient levels, enhanced growth rates and cell densities of A. pacificum (Group IV) were observed with additions of nitrate and phosphate. In particular, rapid uptakes of phosphate by A. pacificum (Group IV) were observed in experimental treatments, indicating that the increase in phosphate concentration could stimulate the growth of A. pacificum (Group IV).

In this study, the adsorption/desorption performance of toluene was evaluated using zeolite adsorbent to replace activated carbon with one-off and ignition characteristics. For the proper operation of the VOCs adsorption/desorption and condensate recovery steps, the operating range by various adsorption/desorption temperatures was selected. The adsorbent is a bead-type zeolite, which was put into an adsorption tower of 10 LPM scale. As a result, it was demonstrated that 0.079 mg/g was adsorbed at a low temperature (20°C) during adsorption. In the case of desorption, it was found that VOCs adsorbed on the adsorbent were completely recovered after the desorption operation at 220°C for about 160 minutes. However, in the heating rate step for desorption, it was not possible to maintain an appropriate heating rate by filling the tower with zeolite. This was complemented by applying a copper plate with high thermal conductivity, and it was shown that the time was shortened by about 10 minutes or more. When VOCs are emitted at high concentrations during the desorption process, they can be reused as energy resources through low-temperature maintenance, and a condensation method was attempted. The efficiency of condensing chiller (cooler) with temperature control and liquid nitrogen condensing was compared. It was found that the chiller condensing efficiency increased as the temperature decreased. In the case of liquid nitrogen condensation, the liquid nitrogen temperature was maintained at -196°C, showing a stable efficiency of 90%.

The purpose of this study was to examine the microbiological and physicochemical changes on packaged tofu stored at temperatures of 5, 13, 23, and 30oC, and measure the consumable period from the expiry date to ultimately evaluate the microbiological safety on the extension of the consumable period. From the investigation, the pH value of tofu at each storage temperature (5, 13, and 23oC) showed a slight decrease over the storage period, although there was no significant change. The hardness of packaged tofu decreased more rapidly as temperature and storage time increased and the tofu started to show signs of decomposition at the same time. Analysis on the microbial change of tofu at different storage temperature revealed that the number of general bacteria also increased as the temperature increased. It was further found that packaged tofu takes 25 days at 5oC, 7 days at 13oC, and 1 day at 23oC from the expiry date until the general bacteria count is at least at the early decomposition level which is 10oC log CFU/g. However, no coliform bacteria was detected from tofu after storing at 5, 13 and 23oC. When packaged tofu was stored at 5oC, the L value changed significantly after 26 days, whereas the a and b values showed no significant change during the storage period (P>0.05). When storing tofu at 13oC and 23oC the L value decreased after 8 and 3 days, respectively. However, both a and b values increased (P<0.05).

PURPOSES : This aim of this study is to develop a model for predicting road surface temperature using an LSTM network to predict road surface temperature associated with road icing. METHODS : A long short-term memory (LSTM) neural network suitable for time-series data with time correlation is used in the analysis. Moreover, an optimal neural network architecture is designed via hyperparameter search and verification using learning and validation data. Finally, the generalization performance is evaluated based on the RMSE using unseen data as test data. RESULTS : The results show that the predicted data are similar to the actual road surface temperature patterns , and that the network appears to be generalized. CONCLUSIONS : The LSTM model improves the accuracy and generalization of road surface temperature prediction, as compared with other machine learning models.

본 논문에서는 구조물의 좌굴 온도와 좌굴 형상을 제어하는 새로운 크기 최적화 방법에 대해서 소개한다. 구조적 안정성 관점에서 구조물의 좌굴 온도와 좌굴 형상을 예측하는 것은 중요한 주제 중 하나이다. 이를 공학적인 직관을 통해 예측하고 최적화된 구조 설계 를 하는 것은 너무나 어려운 과제이다. 이러한 한계점을 해결하기 위해 본 연구에서는 유한요소 시뮬레이션과 치수 최적 설계 방식의 조합을 제안한다. 구조물의 좌굴 온도와 좌굴 형상이 구조물의 두께에 영향을 받는다는 생각에서 착안해 설계 변수를 구조물의 노드 의 두께 값으로 설정했다. 좌굴 온도 값과 좌굴 형상을 목적 함수로 정해진 부피 값을 제약 조건으로 두었다. 치수 최적 설계를 통해 원 하는 좌굴 온도와 좌굴 형상을 유도하기 위한 최적의 두께 분포를 결정할 수 있다. 제안된 치수 최적 설계의 타당성은 본 논문의 다양 한 직사각형 복합 구조물 예제들을 사용해서 검증하였다.

The precipitation effect of Al-6%Si-0.4%Mg-0.9%Cu-(Ti) alloy (in wt.%) after various heat treatments was studied using a laser flash device (LFA) and differential scanning calorimetry (DSC). Solid solution treatment was performed at 535 oC for 6 h, followed by water cooling, and samples were artificially aged in air at 180 oC and 220 oC for 5 h. The titanium-free alloy Al-6%Si-0.4%Mg-0.9%Cu showed higher thermal diffusivity than did the Al-6%Si-0.4%Mg-0.9%Cu-0.2%Ti alloy over the entire temperature range. In the temperature ranges below 200 oC and above 300 oC, the value of thermal diffusivity decreased with increasing temperature. As the sample temperature increased between 200 oC and 400 oC, phase precipitation occurred. From the results of DSC analysis, the temperature dependence of the change in thermal diffusivity in the temperature range between 200 oC and 400 oC was strongly influenced by the precipitation of θ'-Al2Cu, β'-Mg2Si, and Si phases. The most important factor in the temperature dependence of thermal diffusivity was Si precipitation.