The thermal integrity of spent nuclear fuels has to be maintained during their long-term dry storage. The detailed temperature distributions of spent fuel assemblies are essential for evaluating the integrity of their dry storage systems. In this study, a subchannel analysis model was developed for a canister of a single fuel assembly using the COBRA-SFS code. The thermal parameters affecting the peak cladding temperature (PCT) of the spent fuel assembly were identified, and sensitivity analyses were performed based on these parameters. The subchannel analysis results indicated the presence of a recirculation flow, based on natural convection, between the fuel assembly and downcomer region. The sensitivity analysis of the thermal parameters indicated that the PCT was affected by the emissivity of the fuel cladding and basket, convective heat transfer coefficient, and thermal conductivity of the fluid. However, the effects of the wall friction factor of the canister, form loss coefficient of the grid spacers, and thermal conductivities of the solid materials, on the PCT were predominantly ignored.

Neoporphyra kitoi Ma. Abe, N. Kikuchi, Tamaki, Tom. Sato, Murase, Fujiyoshi & Mas. Kobayashi has been known as an endemic species in Japan. Its high temperature tolerance suggests that it could be advantageous for cultivation. In this study, we collected it from the Ulleungdo island, Korea and transferred it into Pyropia for a new combination, identified as Pyropia kitoi (Ma. Abe, N. Kikuchi, Tamaki, Tom. Sato, Murase, Fujiyoshi & Mas. Kobayashi) D.J. Kim, T.O. Cho & B.Y. Won comb. nov. based on morphological and molecular analyses. Pyropia kitoi is also reported as a new record species in the list of Korean macroalgal flora. Although we didn’t observe the emergence of new blades from the rhizoidal cells, which is a key character for this species, our molecular analysis of rbcL revealed that our samples from Korea were congruent with “Neoporphyra kitoi” from Japan and were nested within the clade of Pyropia. The gene sequence divergence between the Korean and Japanese samples was 0-0.2%.

본 연구는 금속 인공물을 감소시키기 위한 VAT(view angle tilting)와 SEMAC(slice encoding for metal correction) 기법 적용에 따른 온도 변화 범위를 관찰하고자 하였다. 제작된 인체 모방 팬텀을 활용하였고, 검사방법으로는 임상에서 실제로 사용하고 있는 고속스핀에코(fast spin echo, FSE) 기법의 영상 파라미터들을 그대로 이용하였다. VAT 와 SEMAC 기법은 FSE와 같은 파라미터로 설정한 다음 VAT 파라미터는 100%와 SEMAC 파라미터는 25로 설정하였다. 온도 측정 방법으로는 수소원자 공명주파수전이법(proton resonance frequency shift, PRFS)기법을 활용하였으며, 광 섬유 온도계(fiber-optic sensor, FOS)로 절대 온도를 측정한 후 비교 분석하였다. 온도 변화는 SEMAC 기법에서 기존 FSE 기법 (0.28℃±0.10℃)에 비해 1.63℃±0.12℃로 약 6배 상승하였고(SEMAC-FOS = 1.59℃), VAT 기법은 약 2배 증가(VAT-FOS = 0.51℃)가 확인되었다. 특히, SEMAC 기법은 VAT 기법(VAT-FOS = 0.51℃, VAT-PRFS = 0.54℃ ±0.02℃)과 비교하여 약 3배가 증가하여 가장 높은 온도 상승이 관찰되었다. 이는 SEMAC 기법 적용 시 자기공명영상 전자파 인체 영양에 대한 안전기준을 충족하기 위해 영상 파라미터 최적화 작업의 필요성을 시사한다.

Cnidium officinale M. is an important crop that is widely used as a raw material for health functional foods. However, it is experiencing cultivation difficulties due to climate change and abnormally high temperatures. In response to this problem, the characteristics and main causes of the high-temperature damage occurring in C. officinale M. cultivation fields were analyzed. A survey of five farmhouse fields in Jecheon and Bonghwa, major C. officinale M. cultivation areas in Korea in 2018, indicated that about 5% to 37% of the cultivation fields in Jecheon and 5% to 15% of the fields in Bonghwa died from wilting. The high-temperature damage of the C. officinale M. fields is divided into two categories: upper leaves drying due to solar radiation and temperature, and lower leaves dying serially to the radiant heat of the vinyl mulch. Damage caused by radiant heat was typically greater. This is due to the greenhouse effect that occurs in the small space between the black vinyl mulching and the soil. The heat radiated to the surface of the ridge creating an environmental condition that greatly exceeded the atmospheric temperature especially on hot days. As a result, short plants with underground parts, such as C. officinale M., can suffer more high-temperature damage than other plants, so it is considered that it is necessary to develop related technologies such as mulching materials that can reduce pavement temperature in the future.

Western coastal area of Chungnam, including Cheonsu Bay and Garorim Bay, has suffered from hot and cold extremes. In this study, the extreme sea surface temperature on the western coast of Chungnam was analyzed using the quantile regression method, which extracts the linear regression values in all quantiles. The regional MOHID (MOdelo HIDrodinâmico) model, with a high resolution on a 1/60o grid, was constructed to reproduce the extreme sea surface temperature. For future prediction, the SSP5-8.5 scenario data of the CMIP6 model were used to simulate sea surface temperature variability. Results showed that the extreme sea surface temperature of Cheonsu Bay in August 2017 was successfully simulated, and this extreme sea surface temperature had a significant negative correlation with the Pacific decadal variability index. As a result of future climate prediction, it was found that an average of 2.9oC increased during the simulation period of 86 years in the Chungnam west coast and there was a seasonal difference (3.2oC in summer, 2.4oC in winter). These seasonal differences indicate an increase in the annual temperature range, suggesting that extreme events may occur more frequently in the future.

Cars using diesel have always had problems with reducing exhaust fumes, and have been studied steadily in this regard. There were studies on the remanufacturing effect of DOC catalyst deactivated by diesel vehicle smoke reduction device, analysis of vehicle fire accident cases caused by damage to diesel vehicle smoke reduction device, and related studies on the remanufacturing effect of diesel vehicle smoke reduction device DPF. This study also developed a burner system in a smoke reduction device suitable for exhaust engines to completely burn smoke generated by institutions using diesel engines in low-temperature exhaust gases. The main systems to be developed are high-performance heaters, burner structures that can maintain ignition in exhaust flows, and exhaust flow control units that reduce exhaust gas backflow effects caused by diesel engines.

Radiant tubes heat exchangers are critical components that facilitate the heat transfer process to steel in an annealing furnace, and it addresses several engineering problems, such as thermal stress and mechanical failure due to long-term thermal cycling, which can significantly affect the longevity of the tubes and maintenance requirements. In this study, we used commercial software (ANSYS) to simulate the thermal stress and deformation of radiant tubes subjected to extreme thermal conditions and pressure loads. We evaluated both thermally induced deformation and creep deformation, which is a time-dependent deformation under constant stress over the long term. The results showed that uneven temperature conditions and pressure loads lead to significant deformation and potential failures. To mitigate these engineering challenges, we also tested several designs that include supporting brackets. This study provides valuable insights for designing radiant tube heat exchangers in annealing furnaces to extend their lifespan and ensure system safety.

Cars using diesel have always had problems with reducing exhaust fumes, and have been studied steadily in this regard. There were studies on the remanufacturing effect of DOC catalyst deactivated by diesel vehicle smoke reduction device, analysis of vehicle fire accident cases caused by damage to diesel vehicle smoke reduction device, and related studies on the remanufacturing effect of diesel vehicle smoke reduction device DPF. This study is also to develop a burner structure in a smoke reduction device suitable for an exhaust engine to completely burn smoke generated by an engine using a diesel engine in a low-temperature exhaust gas. The main systems to be developed are high-performance heaters, burner structures that can maintain ignition in exhaust flows, and exhaust flow control units that reduce exhaust gas backflow effects caused by diesel engines.

This study investigates the melting point and brazing properties of the aluminum (Al)-copper (Cu)-silicon (Si)-tin (Sn) alloy fabricated for low-temperature brazing based on the alloy design. Specifically, the Al-20Cu-10Si-Sn alloy is examined and confirmed to possess a melting point of approximately 520oC. Analysis of the melting point of the alloy based on composition reveals that the melting temperature tends to decrease with increasing Cu and Si content, along with a corresponding decrease as the Sn content rises. This study verifies that the Al-20Cu-10Si-5Sn alloy exhibits high liquidity and favorable mechanical properties for brazing through the joint gap filling test and Vickers hardness measurements. Additionally, a powder fabricated using the Al-20Cu-10Si-5Sn alloy demonstrates a melting point of around 515oC following melting point analysis. Consequently, it is deemed highly suitable for use as a low-temperature Al brazing material.

PURPOSES : The numeric-based Highway Pavement Management System (HPMS), along with an advanced three-dimensional pavement condition monitoring profiler vehicle (3DPM), in South Korea has presented remarkable advancements in pavement management since the early 2000. Based on these results, visual distress on pavement surfaces can be easily detected and analyzed. Additionally, the entire expressway pavement surface conditions in South Korea can be easily monitored using the current graphical user interface-based advanced information graphic (AIG) approach. Therefore, a critically negative pavement section can be detected and managed more easily and efficiently. However, the actual mechanical performance of the selected pavement layer still needs to be investigated in a more thorough manner not only to provide more accurate pavement performance results but also to verify the feasibility of the current 3DPM and AIG approaches. In this study, the low-temperature performance of the selected asphalt pavement layer section was evaluated to further verify and strengthen the feasibility of the current 3DPM and AIG approaches developed by the Korea Expressway Corporation. METHODS : Based on 3DPM and AIG approach, the positive and negative-riding-quality road sections were selected, respectively. The asphalt material cores were extracted from each section then bending beam rheometer mixture creep test was performed to measure their low-temperature properties. Based on the experimental results, thermal stress results were computed and visually compared. RESULTS : As expected, the asphalt material from the negative driving performance section presented a poorer low-temperature cracking resistance than that from the positive driving performance section. CONCLUSIONS : Current 3DPM equipment can successfully evaluate expressway surface conditions and the corresponding material performance quality. However, more extensive experimental studies are recommended to verify and strengthen the findings of this study

PURPOSES : Due to the frequent occurrence of accidents on icy roads during nighttime, it would be advantageous to notify road managers and drivers about the most perilous areas. This would allow road managers to treat the icy roads with de-icing chemicals and enable drivers to be better prepared for potential hazards. Essential information about pavement temperature is required to identify icy spots on the road. METHODS : With the goal of estimating nighttime pavement temperature on the National Highways in Korea using atmospheric data, the current study investigated a widely recognized forecasting method known as deep neural network (DNN). To achieve this objective, the input data for the models were gathered from the weather agency's website. The dataset comprised of relative humidity, air temperature, dew point temperature, as well as the differences in air temperature and humidity between two consecutive days. RESULTS : In order to assess the effectiveness of the built DNN model, a comparison was made using baseline pavement temperature data gathered through an infrared-based pavement temperature sensor installed in a highway patrol car. The results indicated that the DNN model achieved a mean absolute error (MAE) of 0.42 and a root mean square error (RMSE) of 0.62. In comparison, a conventional regression model yielded an MAE of 2.07 and an RMSE of 2.64. Thus, the DNN model demonstrated superior performance in comparison to the conventional regression model. CONCLUSIONS : Considering the increasing focus on preventive maintenance, these newly developed prediction models can be implemented proactively as a preventive measure against icing. This proactive approach has the potential to significantly improve traffic safety on winter roads.

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.

본 연구에서는 육계사에 차열 페인트와 히트펌프의 적용에 따른 내부 온도 변화를 분석 하였다. 이를 위하여 환기율, 환기 방법, 시간별 환기 변화에 따른 실험 조건을 설정하였으며 육 계사 외부 및 내부 기온을 측정하였다. 그 결과, 차열 페인트를 도포한 육계사에서는 최대 1－2°C 실내 기온 상승을 억제하 는 효과가 나타났으며 히트펌프를 가동한 육계사에서는 외기 온도의 영향을 제일 적게 받는 환기율 0%일 때 내부 기온 감소 가 제일 크게 나타났다. 계사 내부의 온도가 외기 온도보다 높 을 경우에는 환기율을 높게 설정하여 환기팬을 이용한 냉방이 더욱 효과적이나 계사 내부 온도가 외기 온도와 유사하거나 낮을 경우에는 히트펌프를 이용하는 것이 가장 효과적일 것으 로 판단된다. 히트펌프 가동 시 외기 온도의 영향이 적은 환기 율을 0%로 설정하였을 때 내부 기온이 가장 큰 폭으로 감소하 였으나 실제 육계사에서는 분진, 이물질, 암모니아 등을 고려 하여 최소환기율 정도로 환기율을 설정한 후 히트펌프를 가동 하는 것이 가장 효율적일 것으로 판단된다. 본 연구는 실험 기 간이 짧아 데이터가 많지 않으며 실제 육계가 사육되고 있는 환경에서 실험을 진행한 것이 아니라는 한계가 있다. 향후 후 속 연구로 실제 닭이 사육되고 있는 환경에서의 히트펌프 효 과 분석과 히트펌프의 전력사용량, 냉방부하, 환기팬 가동시 간 등 다양한 환경인자를 포함한 연구가 진행되어야 할 것으 로 판단된다.

For the commercialization of hydrogen energy, a technology enabling safe storage and the transport of large amounts of hydrogen is needed. Porous materials are attracting attention as hydrogen storage material; however, their gravimetric hydrogen storage capacity (GHSC) at room temperature (RT) is insufficient for actual use. In an effort to overcome this limitation, we present a N-doped microporous carbon that contains large proportion of micropores with diameters below 1 nm and small amounts of N elements imparted by the nitrogen plasma treatment. The N-doped microporous carbon exhibits the highest total GHSC (1.59 wt%) at RT, and we compare the hydrogen storage capacities of our sample with those of metal alloys, showing their advantages and disadvantages as hydrogen storage materials.

백은무(Kalanchoe pumila)는 돌나물과(Crassulaceae)에 속 한 다육식물의 일종이다. 이 종은 학술적으로는 알려진 바가 거의 없는 미지의 식물이나 군생하여 자라며 분홍색 꽃을 개화 하기 때문에 관상가치가 높다. 이에 따라 본 연구에서는 온도 처리에 따른 백은무의 생육과 개화특성에 대해서 조사하였다. 온도는 주간/야간의 온도를 20/15, 24/19, 28/23, 32/27℃ 의 네 가지 단계로 설계하였다. 결과에서 백은무는 20/15℃ 처리구에서 초폭, 줄기의 지름, 피복면적, 엽수, 엽장, 엽폭, 지상부와 지하부의 생체중과 건물중, 꽃대의 길이, 꽃수, 화 장, 화폭이 가장 높은 것으로 나타났다. 따라서 백은무는 상대 적으로 저온의 환경에서 더 많은 탄소동화작용을 수행하는 것 으로 보인다. 한편, 24/19℃ 처리구에서는 초장과 정규식생지 수를 나타내는 normalized difference vegetation index (NDVI)가 가장 높은 것으로 나타났으며, 28/23℃ 처리구에서 는 근장과 안토시아닌 반사 지수 2를 나타내는 anthocyanin reflectance index 2(ARI2)가 가장 높은 것으로 나타났다. 32/27℃ 처리구에서는 대부분의 매개변수가 가장 낮은 것으 로 나타났으며, 생육이 거의 정지된 것으로 판단된다. 특히 과 거 연구에서 스트레스 지수로 활용된 매개변수인 CIELAB L* 과 b*는 32/27℃ 처리구에서 가장 높게 나타났다. 상관관계 분석에서는 L*은 지상부와 지하부의 생체중 및 건물중과 음의 상관관계를 가지는 것으로 나타나 잎의 명도(lightness)가 높 을수록 식물의 생육에 부정적인 것으로 평가되었다. 추가적으 로 b*도 이와 유사한 결과를 나타내었다. 결과적으로 백은무 의 식물체 크기를 유의미하게 증대시키고 개화 품질을 촉진시 켜 관상가치를 극대화하기 위해서는 20/15℃ 수준에서 재배 할 것을 권고한다.

In this study, numerical modeling on the gas flow and off-gases in the low temperature carbonization furnace for carbon fiber was analyzed. The furnace was designed for testing carbonization process of carbon fibers made from various precursors. Nitrogen gas was used as a working gas and it was treated as an incompressible ideal gas. Three-dimensional computational fluid dynamics for steady state turbulent flow was used to analyze flow pattern and temperature field in the furnace. The off-gas mass fraction and cumulative emission gas of species were incorporated into the CFD analyses by using the user defined function(UDF). As a results, during the carbonization process, the emission of CO2 was the dominant among the off-gases, and tow moving made the flow in the furnace be uniform.

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.

The influence of MgO addition on the densification and microstructure of alumina (Al2O3) was studied. Compacted alumina specimens were manufactured using ball-milling and one-directional pressing followed by sintering at temperatures below 1700oC. Relative density, shrinkage, hardness, and microstructure were investigated using analytical tools such as FE-SEM, EDS, and XRD. When the MgO was added up to 5.0 wt% and sintered at 1500oC and 1600oC, the relative density exhibited an average value of 97% or more at both temperatures. The maximum density of 99.2% was with the addition of 0.5 wt% MgO at 1500oC. Meanwhile, the specimens showed significantly lower density values when sintered at 1400oC than at 1500oC and 1600oC owing to the relatively low sintering temperature. The hardness and shrinkage data also showed a similar trend in the change in density, implying that the addition of approximately 0.5 wt% MgO can promote the densification of Al2O3. Studying the microstructure confirmed the uniformity of the sintered alumina. These results can be used as basic compositional data for the development of MgOcontaining alumina as high-dielectric insulators.

In this study, we evaluated the effects of acid leaching on the properties of Cr powder synthesized using self-propagating high-temperature synthesis (SHS). Cr powder was synthesized from a mixture of Cr2O3 and magnesium (Mg) powders using the SHS Process, and the byproducts after the reaction were removed using acid leaching. The properties of the recovered Cr powder were analyzed via X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), particle size analysis (PSA), and oxygen content analysis. The results show that perfect selective leaching of Cr is challenging because of various factors such as incomplete reaction, reaction kinetics, the presence of impurities, and incompatibility between the acid and metal mixture. Therefore, this study provides essential information on the properties under acidic conditions during the production of high-quality Cr powder using a self-propagating high-temperature synthesis method.