Research has been conducted on acoustic metamaterials that control the transmission characteristics of reflected and refracted waves using phase delay by resonators. Using one-dimensional theory, the phase delay equations for the 1/4 wavelength and Helmholtz resonator are presented. These one-dimensional analysis results are compared with the results predicted by three-dimensional FEM. The advantages and disadvantages of 1/4 wavelength and Helmholtz resonator were confirmed in implementing phase delay. An acoustic metamaterial with a refraction angle of 30° was manufactured using multiple tubes and then the sound pressure distribution was measured. A relatively large sound pressure was measured at the target position of 30°, which was compared with the 3D FEM analysis results. Simulations confirmed that a phase delay range closer to 2π was more effective in refraction, but varying the number of resonators was found to have minimal impact on which additional research is needed for generalization.

PURPOSES : This study aims to determine the type (e.g., melting point, freezing point, latent heat fusion) and optimal content of phase change material (PCM) based on the numerical and experimental analyses evaluating the effects of heat transfer in PCM-modified asphalt pavement systems. METHODS : The effect of PCM on the thermophysical properties of PCM-modified asphalt concrete can be taken as an effective volumetric heat capacity. The volumetric fraction of PCM was calculated using an iterative method. The numerical model was established and computed using the MATLAB 2020 software. The optimum PCM design tool was developed to select the type and contents of the PCM. The PCM was chosen based on the following criteria: black-ice-formation delay time, minimize temperature increase, and increase temperature area. To validate the numerical model, asphalt mixtures were modified with varying PCM contents, and the temperature response of the PCMmodified asphalt samples was examined via temperature test. RESULTS : The numerical results showed that incorporating PCM into the asphalt mixture can slow the cooling rate of the pavement system. The predicted results from the optimum PCM design tool were highly consistent with the measured values from the laboratory temperature test. CONCLUSIONS : The temperature of PCM-modified asphalt pavement can be predicted via numerical method. The effect of PCM on the thermophysical properties can be considered as effective volumetric heat capacity; while the volume fraction of PCM can be calculated via an iterative method. The accuracy of the numerical model was confirmed by a high agreement between the measured and predicted values.

Todarodes pacificus is an important marine resource commercialized in South Korea, Japan, and China. The objective of this work is to investigate the effectiveness of different mathematical models (diffusive model, Newton's model, Henderson-pabis's model, Page's model, and Weibull's model) in precisely explaining the moisture gain/loss and salt gain of the squid slices immersed in saline solutions. Brine concentrations of immersion used were 2.5, 5, 10, and 15% (w/w) for various durations (0-360 min). The effective diffusion coefficients of salt ranged from 0.549×10−9 to 0.841×10−9 m2/s, while the moisture values ranged from -0.077×10−9 to 0.374×10−9 m2/s. The experimental results of moisture and salt transfer fitted well into the Henderson-Pabis and Page models, respectively. The results presented in this study support the potential to predict the mass transfer of squid using mathematical modeling.

An enthalpy exchange element (EEE) is frequently made of papers, and a concern exists on growth of fungus or bacteria. This concern may be eliminated if polymer membrane is used instead of paper. Furthermore, most existing enthalpy exchangers have cross-flow configuration, which yields lower performance than counter-flow one. In this study, a counter-flow enthalpy exchange element was made using PVDF and cellulose composite. Heat and moisture transfer tests were conducted changing the frontal air flow rate from 150 m 3 /h to 350 m 3 /h at both the heating and the cooling condition. Results showed that the temperature efficiencies were approximately the same independent of the weather condition. Humidity efficiencies at the heating condition, however, were higher than those at the cooling condition. Furthermore, the heat transfer coefficients approached the theoretical value as the flow rate increased. In addition, the vapor transmission rates at the heating condition were higher than those at the cooling condition, probably due to the higher humidity efficiency at the heating condition. Future research will be focused on moisture diffusion characteristics of the composite membrane, which requires further measurements of water holdup, equilibrium adsorption curve, etc.

The impregnation of solid foods into the surrounding hypotonic or hypertonic solution was explored as a method to infuse NaCl in pork loin cube without altering its matrix. Mass transfer kinetics using a diffusive model as the mathematical model for moisture gain/loss and salt gain and the resulting textural properties were studied for the surrounding solutions of NaCl 2.5, 5.0, 10.0 and 15% (w/w). It was possible to access the effects of brine concentration on the direction of the resulting water flow, quantify water and salt transfer, and confirm tenderization effect by salt infusion. For brine concentrations up to 10% it was verified that meat samples gained water, while for processes with 15% concentration, pork loin cubes lost water. The effective diffusion coefficients of salt ranged from 2.43×10-9 to 3.53×10-9 m2/s, while for the values of water ranged from 1.22×10-9 to 1.88×10-9 m2/s. The diffusive model was able to represent well salt gain rates using a single parameter, i.e. an effective diffusion coefficient of salt through the meat. However, it was not possible to find a characteristic effective diffusion coefficient for water transfer. Within the range of experimental conditions studied, salt-impregnated samples by 5% (w/w) brine were shown with minimum hardness, chewiness and shear force.

Acidic and basic mixtures of odorous compounds are commonly emitted from various sources, and, in an absorption process, pH conditions in the liquid phase significantly affect the performance. In this study, the effect of pH on mass transfer in a bubble column reactor was evaluated using hydrogen sulfide and ammonia as a model mixture. Their mass transfer coefficients were then calculated. Furthermore, the total mass transfer coefficients as a function of pH were evaluated, and the experimental data were fitted into an empirical equation using dimensionless numbers. The mass transfer rates of hydrogen sulfide, the non-ionic form, increased dramatically with increasing pHs, while those of ammonia were almost unchanged because of its high solubility. As a result, a favorable pH condition for less soluble compounds must be selected to achieve high absorption capacity. The total mass transfer rates, which took into account pH effects as well as all the non-ionic and ionic constituents together, were found to be from 2.2 to 2.4 × 10−3 min−1 for hydrogen sulfide and ammonia, respectively, and they were almost constant at different pHs. The empirical equations, which were derived to obtain the best fit for the total mass transfer rates, implied that a method to increase diffusivity of each compound should be applied to improve overall mass transfer. In addition, when using the empirical equation, a mass transfer coefficient at a given set of pH and operating conditions can be calculated and used to design a water scrubbing process.

바이오파울링은 정삼투 공정(FO)에서 비가역성 오염을 야기한다. 바이오파울링 성장과정에서 미생물은 신호전달물질(AHL)의 분비를 통해 의사소통하며, 이를 쿼럼 센싱(QS)이라 한다. 본 연구에서는 Rhodococcus sp. BH4의 용해액에 있는 AHL 분해효소(quorum quencher; QQ)를 이용하여 FO에서의 바이오파울링을 저감하고자 한다. QQ 물질 유무에 따라 P.aeruginosa 종의 막 표면의 바이오필름 성장 및 부착량을 비교한 회분식 실험에서 10mg/L의 QQ 물질이 AHL을 70% 이상 분해함을 확인했다. FO 장치를 이용한 실험실 규모의 연속 실험에서는 10mg/L의 QQ 물질 존재 시 체외 고분자물질(EPS)이 대조군에 비해 80% 이상 감소했다. 위 연구를 통해 QQ가 FO에서 바이오파울링을 저감하는 새로운 방법이 될 수 있음을 확인하였다.

Numerical models of composite floor systems with various thickness of phase change material and sizes of circular spacers were developed based on finite element analysis. In order to perform a heat transfer analysis, thermal properties of steels were determined and those of phase change material were estimated from experiment results. In addition, the thermal insulation performance of composite floor systems with respect to different thickness of phase change material and sizes of circular spacers was predicted. To verify the validity of analysis, analysis results were compared with vertical furnace fire test results of equivalent conditions. As a result, available thicknesses of phase change material and sizes of circular spacers were proposed to satisfy the thermal insulation criteria of Korean Standards.

최근 2차원 나노 물질을 응용하여 수처리 막의 성능을 향상시킬 수 있는가에 대한 연구가 활발하다. 그 노력의 한 가운데에 원자 두께를 가지고 있으면서 손쉽게 구할 수 있고 층으로 쌓을 수도 있는 2차원 물질인 그래핀이 자리하고 있다. 이 총설에서 우리는 그래핀으로부터 만들 수 있는 두 가지 막 구조에 관한 기초 물질 전달 현상을 최근 연구 성과를 중심으 로 다룬다. 그 물질 자체로 이미 물질 전달 차단성을 갖는 그래핀에 정확히 제어된 크기의 구멍을 뚫을 수 있다면 아마도 원 자 크기 수준으로 얇은 두께 때문에 그래핀 막은 같은 기공 크기의 어느 막보다도 빠른 궁극적 투과도를 나타낼 것이며, 이 로부터 선택도를 담보할 수 있다면 다양한 막 분리 공정에 적용할 수 있을 것이다. 그 한 예로, 나노미터 이하의 기공을 가정 한 초박막 침투성 그래핀 막에 대한 분자동역학 연구와 몇몇 초기 실험 결과들이 해수담수화 막으로서의 가능성을 보인 점은 주목할 만하다. 그래핀 물질로부터 다른 구성을 가진 막을 설계할 수 있는데, 이 막은 적당히 산화된 그래핀 마이크로 판들을 무작위로 적층함으로써 구현할 수 있다. 그래핀 판 적층 간격을 나노미터 이하로 쉽게 제어할 수 있기 때문에 이 구조 역시 수처리 및 해수담수화 막으로서의 가능성을 시사한다. 기존 막기술에 존재하지 않던 구조와 물질 전달 성질을 가짐으로써 두 종류의 그래핀 막은 앞으로 수처리 기술을 비롯한 다양한 막 기술의 응용분야에서 효과적으로 기여할 가능성이 충분하다.

PURPOSES : A finite difference model considering snow melting process on porous asphalt pavement was derived on the basis of heat transfer and mass transfer theories. The derived model can be applied to predict the region where black-ice develops, as well as to predict temperature profile of pavement systems where a de-icing system is installed. In addition, the model can be used to determined the minimum energy required to melt the ice formed on the pavement. METHODS : The snow on the porous asphalt pavement, whose porosity must be considered in thermal analysis, is divided into several layers such as dry snow layer, saturated snow layer, water+pavement surface, pavement surface, and sublayer. The mass balance and heat balance equations are derived to describe conductive, convective, radiative, and latent transfer of heat and mass in each layer. The finite differential method is used to implement the derived equations, boundary conditions, and the testing method to determine the thermal properties are suggested for each layer. RESULTS: The finite differential equations that describe the icing and deicing on pavements are derived, and we have presented them in our work. The framework to develop a temperature-forecasting model is successfully created. CONCLUSIONS : We conclude by successfully creating framework for the finite difference model based on the heat and mass transfer theories. To complete implementation, laboratory tests required to be performed.

알로에의 최소공정개발 연구의 일환으로 DIS(dewatering & impregnation soaking) 공정에 미치는 온도의 효과를 조사하였다. 삼투탈수는 분자량 4000의 PEG을 삼투제로 하여 이의 40%(w/v) 용액에 두께 0.5 cm의 알로에 잎 슬라이스를 넣고 간헐적으로 교반하면서 2시간 동안 수행하였다. 서로 다른 침지온도(25-55oC)가 DIS의 성능(수분소실 및 고형분 획득)에 미치는 영향을 현미경관찰에 의한 세포조직 구조의 경시변화를 모니터링하면서 조사, 비교되었고, 동역학적으로 분석하였다. 고온(55oC) 처리에서는 저온(25 and 35oC)에서보다 더 높은 수분소실을 보였으나 세포조직의 파괴를 동반하였다. 또, 품질지표값으로서의 glucomannan 함량은 세포조직구조를 잘 유지하였던 침지온도 35oC에서 얻어졌다. 얻어진 시료의 실온건조제품을 재수화시켜 조사하고 동역학적으로 해석한 결과, 재수화 동역학은 Peleg 및 Weibull 모델로 잘 설명할 수 있었다. DIS 제품은 DIS 처리하지 않은 제품에 비해 세포구조 및 재수화성질의 향상을 주어 적정온도하에서 DIS 처리함으로써 최소공정의 알로에 제품을 얻을 수 있음을 확인하였다.

This study was performed to investigate the effects of aluminum sulfate administration on the brain tissues of old rats, when given at different concentrations. The experiment attempted to further ascertain whether aluminum exposure cause Alzheimer's disease. Seventy-five aged Sprague-Dawley rats were divided into five groups; a control group, 2 ppm aluminum sulfate group, 20 ppm aluminum sulfate group, 40 ppm aluminum sulfate group, and 200 ppm aluminum sulfate group, and were kept on the respective diets for 12 weeks. In order to understand the influence of aluminum on the brain, serum aluminum concentrations, phospholipid composition, and catecholamine concentrations were compared between the aluminum-treated groups and the normal group. According to the results, serum aluminum was higher in the aluminum sulfate-treated groups than in the normal group. Within the cortex, catecholamine concentrationes were significantly increased but cerebellum and brainstem tissue were significantly decreased, in the aluminum sulfate-treated groups compared to the normal group. For phospholipid composition, phosphatidyl inositol was significantly increased wherase phosphatidyl choline, phosphatidyl ethanolamine, and phosphatidyl serine were significantly decreased in the aluminum sulfate-treated groups versus the normal group. Based on the data, increased aluminum consumption in experimental animals causes increased serum aluminum levels and catecholamine variation. These phenomena are very similar to conditions of Alzherimer's disease. Therfore, the results of this experiment further suggest that aluminum cause Alzherimer's disease, coinciding with reports that aluminum is a cause of neurofibrilly tangles in the brain.

본 연구에서는 방사성폐기물의 화학처리공정에 자주 사용되는 유동관식 장치 중 튜브형 반응기, 다단식 용매추출 장치, 흡착탑 등 물질전달이 수반되는 장치에 있어 각종 매개변수들이 반응수율이나 물질전달수율에 미치는 영향과 민감도를 살펴보았다. 먼저 각 장치에 대한 거동을 묘사하기 위하여 수학적 모델링을 수행하였고 전산모사를 통하여 해당 장치의 거동을 예측하였다. 그리고 그 결과로부터 해당 공정의 고유한 매개변수들이 반응수율 또는 물질전달수율에 미치는 영향과 민감도를 분석하였다. 튜브형 반응기에서는 확산계수, 반응속도상수 등이 반응수율에 미치는 영향을, 다단식 용매추출 장치에서는 연속상과 분산상의 분배계수, 연속상 흐름의 역혼합 등이 추출수율 및 장치 내 농도 분포에 미치는 영향을 고찰하였다. 또 흡착탑에 있어서는 흡착평형상수 및 유체-흡착재간 물질전달계수 등이 흡착 속도에 미치는 영향을 조사하였다.

Isotopes of alkali and alkaline earth metals (AM and AEM) are the main contributors to the heat load and the radiotoxicity of spent fuel (SF) . These components are separated from the SF and dissolved in a molten LiCl in an electrolytic reduction process. A mass transfer model is developed to describe the diffusion behavior of Cs, Sr, and Ba in the SF into the molten salt. The model is an analytical solution of Fick's second law of diffusion for a cylinder which is the shape of a cathode in the electrolytic reduction process. And the model is also applied to depict the concentration profile of the oxygen ion which is produced by the electrolysis of LiO. The regressed diffusion coefficients of the model correlating the experimentally measured data are evaluated to be greater in the order of Ba, Cs, and Sr for the metal ions and the diffusion of the oxygen ion is slower than the metal ions which implies that different mechanisms govern the diffusion of the metal ions and the oxygen ions in a molten LiCl.