• Nutrition Research and Practice
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• 제13권6호
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• pp.529-534
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• 2019

BACKGROUND/OBJECTIVES: The leaves of Moringa oleifera (MO) and Moringa stenopetala (MS) commonly grown in Ethiopia possess potential nutritional and medicinal value. The aim of this study was to evaluate the nutritional and functional characteristics of the dried leaf powder from two Moringa species to develop sustainable nutritional supplements for Ethiopians from locally grown plant sources. MATERIALS/METHODS: Freshly harvested and air-dried MO and MS leaves were authenticated and the nutritional contents, such as protein, ash, lipids, and selected vitamins and minerals, were analyzed using standard analytical procedures. Amino acid compositions were also determined by an amino acid analyzer. Nine-week-old mice were randomly divided into four groups to investigate the anti-obesity effects of Moringa. The first group was fed a basal diet, the second group a high-fat diet, and the others were fed a high-fat diet containing 0.1% Moringa leaf powder from each species. After seven weeks, serum indices related to lipid profiles from each mouse were analyzed. RESULTS: The present study revealed high protein (28-29%) and ash (7-11%) contents. Glutamic acid, aspartic acid, proline, and leucine were the most abundantly found amino acids in both species. The predominant minerals in the leaf powder were calcium (826-1,530 mg/100 g), potassium (794-904 mg/100 g), and magnesium (286-431 mg/100 g). Pyridoxine (475.06 mg/100 g) and vitamin E (34.2 mg/100 g) were found only in MS. Niacin was found only in MO at 32.21 mg/100 g, whereas ascorbic acid was found in both species (3.89 and 6.19 mg/100 g dry weight for MO and MS, respectively). The results of the animal study showed that mice on a high-fat diet containing 0.1% MO leaf powder alleviated the elevation of cholesterol, triglycerides, and low-density lipoprotein cholesterol induced by the high fat diet. MO was more effective than MS in preventing hypercholesterolemia and fat deposition. CONCLUSION: The findings in this work confirmed that Moringa leaves of both MO and MS possessed high nutritional value but MO was better at preventing the harmful effects of the high-fat diet than MS.

• 한국수소및신에너지학회논문집
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• 제32권1호
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• pp.41-52
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• 2021

NiO and Co3O4-doped porous La(CoNi)O3 perovskite oxides were prepared from excess Ni addition by a hydrothermal method using porous silica template, and characterized as bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) for Zn-air rechargeable batteries in alkaline solution. Excess Ni induced to form NiO and Co3O4 in La(CoNi)O3 particles. The NiO and Co3O4-doped porous La(CoNi)O3 showed high specific surface area, up to nine times of conventionally synthesized perovskite oxide, and abundant pore volume with similar structure. Extra added Ni was partially substituted for Co as B site of ABO3 perovskite structure and formed to NiO and Co3O4 which was highly dispersed in particles. Excess Ni in La(CoNi)O3 catalysts increased OER performance (259 mA/㎠ at 2.4 V) in alkaline solution, although the activities (211 mA/㎠ at 0.5 V) for ORR were not changed with the content of excess Ni. La(CoNi)O3 with excess Ni showed very stable cyclability and low capacity fading rate (0.38 & 0.07 ㎶/hour for ORR & OER) until 300 hours (~70 cycles) but more excess content of Ni in La(CoNi)O3 gave negative effect to cyclability.

• 전기전자학회논문지
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• 제24권4호
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• pp.1004-1010
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• 2020

본 논문은 단상 영구자석 동기전동기의 초기 회전자 자극 검출 기법을 제안한다. 대상 전동기는 저속 및 정지 상태에서 역기전력을 기반으로 위치 정보를 얻을 수 없다. 따라서 초기 개루프 기동이 필요하며 이 과정에서 저 전류 및 소프트 기동을 위한 초기 회전자 위치 정보가 필요하다. 제안하는 초기 회전자 자극 검출 알고리즘의 경우 비대칭 공극의 영향 및 영구자석 자속의 영향을 고려하였으며, 고주파 전압 신호 주입을 기반으로 정확한 검출을 위한 오프셋 전압을 이용하였다. 이때 고주파 전압 신호로부터 유도된 고주파 전류의 경우 가상의 dq축을 이용하여 유도된 전류의 최댓값 취득을 통해 회전자 영구자석 자극을 판별한다. 본 논문에서는 센서리스 운전의 저전류 및 소프트 기동을 위해 제안된 초기 회전자 자극 검출 알고리즘을 홀센서 신호를 근거로 효용성 및 타당성을 다수의 실험을 통해 검증하였다.

• 대기
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• 제32권4호
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• pp.307-322
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• 2022

A drone has recently got attention as an instrument for weather observation in lower atmosphere because it can produce the high spatiotemporal resolution weather data even though the weather phenomenon is inaccessible. Sea fog is a weather phenomenon occurred in lower atmosphere, and has observational limitations because it occurs on the sea. Therefore, goal of this study is to analyze the vertical structures about inflow, development and dispersion of sea fog using the high-resolution weather data with the meteorological sensor-equipped drone. This study observed sea fogs in the west coast of the Korean peninsula from March to October 2021 and investigated one sea fog inflowed into the coast on June 8th 2021. θ_e - q_v diagrams (θ_e: equivalent potential temperature, q_v: water vapor ratio) and vertical wind structures were analyzed. At inflow of sea fog, moist adiabatically stable layer was formed in 0-300 m and prevailing wind was switched from south-southwesterly to west-southwesterly under 120 m. Both changes are favorable for sea fog on the location. θ_e and q_v plummeted in a layer 0-183 m. The inflowed sea fog developed from 183 m to 327 m by mixing with ambient atmosphere on top of sea fog. Also, strong mechanical turbulence near ground drove a vertical mixing under stable layer. At dispersion of sea fog, as θ_e on ground gradually increased, air condition was changed to neutral. Evaporation occurred on both bottom and top in sea fog. These results induced dissipation of sea fog.

• 대한금속재료학회지
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• 제47권10호
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• pp.621-628
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• 2009

Thermomechanical processes were carried out to evaluate their effects on the mechanical and the microstructural property of a ferritic-martensitic steel. Modified 9Cr-1Mo steels were hot-rolled at a temperature of either $780^{\circ}C$ or $850^{\circ}C$ after normalizing at $1050^{\circ}C$ and then were air-cooled. Continuous annealing at $850^{\circ}C$ for 2 hours immediately after the hot rolling was also performed and they were compared to the specimens without thermomechanical process. The result showed that there were little differences between the hot rolled specimens in terms of the precipitation density and size. However, V content inside the MX precipitates increased in the case of the specimen rolled at $850^{\circ}C$. The application of the continuous annealing induced coarsening of the Nb-rich MX precipitation as well as an increase in the amount of V-rich MX precipitation, which is expected to enhance high temperature mechanical properties of the ferritic-martensitic steel.

• 대한금속재료학회지
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• 제47권1호
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• pp.13-20
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• 2009

This work presents functionally graded coatings (FGC) of hydroxyapatite (HA) and metallic powders on Ti-6Al-4V implants using plasma spray coating method. HA has been the most frequently used coating material due to its excellent compatibility with human bones. However, because of the abrupt changes in thermomechanical properties between HA and the metallic implant across an interface, and residual stress induced on cooling from coating temperture to room temperature, debonding at the interface occurs in use sometimes. In this work, FGC of HA and Ti or Ti-alloy powders is made to mitigate the abrupt property changes at the interface and the effect of FGC on residual stress release is investigated by evaluating the mechanical bond strength between the implant and the HA coating layers. Thermal annealing is done after coating in order to crystallize the HA coating layer which tends to have amorphous structure during thermal spray coating. The effects of types and compositional ratio of metallic powders in FGC and annealing conditions on the bond strength are also evaluated by strength tests and the microstructure analysis of coating layers and interfaces. Finally, biocompatibility of the coating layers are tested under ISO 10993-5.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.554-565
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• 2021

Air bubble entrainment is a phenomenon that can significantly reduce the efficiency of liquid motion in piping systems. In the present study, the bubble formation mechanism in a globe valve with 90% water fraction flow is explained by visualization study and pressure oscillation analysis. The shadowgraph imaging technique is applied to illustrate the unsteady flow inside the transparent valve. This helps to study the effect of bubbles induced by the globe valve on pressure distribution and valve flow coefficient. International Society of Automation (ISA) recommends locations for measuring pressure drop of the valve to determine its flow coefficient. This paper presents the comparison of the pressures at different locations along with the upstream and the downstream of the valve with the values at recommended positions by the ISA standard. The results show that in partially filled pipe flow, the discrepancies in pressure between different measurement locations in the valve downstream are significant at valve openings less than 30%. The aerated flow induces the oscillation in pressure and flow rate, which leads to the fluctuation in the flow coefficient of the valve. The flow coefficients have a linear relationship with the Reynolds number. For the same increase of Reynolds number, the flow coefficients grow faster with larger valve openings and level off at the opening of 50%.

• 센서학회지
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• 제30권4호
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• pp.191-195
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• 2021

Pure ZnFe₂O₄ and Fe₂O₃-ZnFe₂O₄ hetero-composite spheres were prepared by ultrasonic spray pyrolysis of a solution containing Zn- and Fe-nitrates. Additionally, the sensing characteristics of these spheres in the presence of 5 ppm ethanol, benzene, p-xylene, toluene, and CO (within the temperature range of 275-350 ℃) were investigated. The Fe₂O₃-ZnFe₂O₄ hetero-composite sensor with a cation ratio of [Zn]:[Fe]=1:3 exhibited a high response (resistance ratio = 140.2) and selectivity (response to p-xylene/response to ethanol = 3.4) to 5 ppm p-xylene at 300 ℃, whereas the pure ZnFe₂O₄ sensor showed a comparatively lower gas response and selectivity. The reasons for the superior response and selectivity to p-xylene in Fe₂O₃-ZnFe₂O₄ hetero-composite sensor were discussed in relation to the electronic sensitization due to charge transfer at Fe₂O₃-ZnFe₂O₄ interface and Fe₂O₃-induced catalytic promotion of gas sensing reaction. The sensor can be used to monitor harmful volatile organic compounds and indoor air pollutants.

• 한국환경과학회지
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• 제30권7호
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• pp.585-595
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• 2021

We used seawater temperature data, measured in the Garolim Bay, to analyze temperature variation on an hourly and daily basis. Lagrange's interpolation using before and after data was applied to restore nonconsecutive missing temperature data. The estimated error of the data restoration was 0.11℃. Spectral analyses of seawater temperature showed significant periodicities of approximately 12.4 h (semidiurnal tide) and 15.0 d (long-period tide), which is close to those of M₂ and M_f partial tides. Variation in seawater temperature was correlated more with tidal height than with air temperature around the Garolim Bay. In June and December, when the seawater temperature difference between the inside and outside of the Garolim Bay was very large, the periodicities of 12.4 h and 15.0 d were highly prominent. These results indicate that the exchange of seawater between the inside and outside of the Garolim Bay induced variations in seawater temperature owing to tide. Understanding temperature variation because of tide helps to prevent abnormal mortality of cultured fish and to predict seawater temperature in the Garolim Bay.

• 터널과지하공간
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• 제32권6호
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• pp.558-567
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• 2022

고준위방사성폐기물의 지중저장 안정성 평가의 일환으로 가열 중인 화강암의 온도변화와 열응력 발생 양상을 파악하기 위하여 가열실험을 실시하였다. 폐기물의 붕괴열 발생조건을 가정하고 정육면체 형태의 화강암 시편에 적용하여 온도와 변위의 분포를 측정하였다. 시편의 온도는 가열봉에서 발생하는 전도로 인하여 즉각적으로 상승하지만 동시에 외기에 노출되거나 하중재하장치에 접촉되어 있는 표면을 통하여 상당한 양의 열에너지가 소산되었다. 해당 실험에 대한 분석과 이해를 위해 실험조건을 삼차원 유한요소 수치해석으로 재구현하였다. 실험에서 관찰된 열-역학 연계 현상과 주변조건의 변화를 해석에 적용하고 이를 실내실험 결과와 비교하여 검증하였다. 이를 통해 가열실험에 영향을 주는 인자들을 분석하고 향후 관련 연구에서 고려되어야 할 부분을 요약하였다.