• Journal of Mechanical Science and Technology
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• 제20권5호
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• pp.717-727
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• 2006

The present study experimentally investigated the effect of flow direction and other flow parameters on two-phase flow distribution of refrigerants at a T-junction, and also suggested a prediction model for refrigerant in a T-junction by modifying previous model for air-water flow. R-22, R-134a, and R-410A were used as test refrigerants. As geometric parameters, the direction of the inlet or branch tube and the tube diameter ratio of branch to inlet tube were chosen. The measured data were compared with the values predicted by the models developed for air-water or steam-water mixture in the literature. We propose a modified model for application to the reduced T-junction and vertical tube orientation. Among the geometric parameters, the branch tube direction showed the biggest sensitivity to the mass flow rate ratio for the gas phase, while the inlet quality showed the biggest sensitivity to the mass flow rate ratio among the inlet flow parameters.

• 대한수학회보
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• 제61권3호
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• pp.717-734
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• 2024

Let R be a commutative ring with identity and m, n be positive integers. In this paper, we introduce the class of weakly (m, n)-prime ideals generalizing (m, n)-prime and weakly (m, n)-closed ideals. A proper ideal I of R is called weakly (m, n)-prime if for a, b ∈ R, 0 ≠ a^mb ∈ I implies either aⁿ ∈ I or b ∈ I. We justify several properties and characterizations of weakly (m, n)-prime ideals with many supporting examples. Furthermore, we investigate weakly (m, n)-prime ideals under various contexts of constructions such as direct products, localizations and homomorphic images. Finally, we discuss the behaviour of this class of ideals in idealization and amalgamated rings.

• 한국재료학회지
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• 제15권11호
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• pp.717-721
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• 2005

Silica powders were synthesized using emulsion solution containing water, nonionic surfactant of Triton N-57, and cyclohexane. Silica powders were prepared at low cost using inexpensive starting material of sodium silicate and ammonium sulfate. Morphology, size and size distribution were observed and determined using SEM. The powder was identified as silica by FT-IR and XRD analysis. Particle size and size distributions were affected by concentration of reactants, reaction time, and concentration of surfactant. Particle size were increased with increasing concentration of reactants and particles became dense with increasing reaction time. As R value increased, tile particle size was increased, reached a certain value and then decreased again. The silica powders synthesized under optimum condition were spherical in shape, $0.8{\mu}m$ in average particle size, narrow in particles size distribution, and well dispersed.

• Structural Engineering and Mechanics
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• 제25권6호
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• pp.717-732
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• 2007

A formula to approximate the fundamental period of a fixed-free mass-spring system with varying mass and varying stiffness is formulated. The formula is derived mainly by taking the dominant parts from the general form of the characteristic polynomial, and adjusting the initial approximation by a coefficient derived from the exact solution of a uniform case. The formula is tested for a large number of randomly generated structures, and the results show that the approximated fundamental periods are within the error range of 4% with 90% of confidence. Also, the error is shown to be normally distributed with zero mean, and the width of the distribution (as measured by the standard deviation) tends to decrease as the total number of discretized elements in the system increases. Other possible extensions of the formula are discussed, including an extension to a continuous cantilever structure with distributed mass and stiffness. The suggested formula provides an efficient way to estimate the fundamental period of building structures and other systems that can be modeled as mass-spring systems.

• 한국식품위생안전성학회지
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• 제21권4호
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• pp.204-212
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• 2006

근적외선 분광광도기을 이용하여 참기름의 Acid value, iodine value, palmitic acid, stearic acid, oleic acid, linoleic acid 및 linolenic acid를 비파괴적으로 신속하게 정량할 수 있는 가능성을 조사하였다. 시료의 스펙트럼측정은 투과방식을 이용하여 $400\sim2500nm$ 범위에서 측정하였다. MPLS를 이용하여 도출된 Acid value, Iodine value, palmitic acid, stearic acid, oleic acid, linoleic acid 및 linolenic acid의 검량선 상관도는 각각 0.9907, 0.9077, 0.9527, 0.9210, 0.9829, 0.9736, 0.9709이었고 검증했을때의 상관도는 각각 0.989, 0.944, 0.924, 0.717, 0.989, 0.967, 0.990이었으며 SEP는 0.058, 0.562, 0.194, 0.168, 0.221, 0.297, 0.072로 나타나 기존의 분석법을 대신하거나 예비시험법으로 활용할 수 있는 유용한 방법임이 입증되었다 본 연구에서 개발한 방법은 매우 간단하게 참기름의 품질평가 및 진위여부를 판단할 수 있어 다수의 시료를 검사해야 하는 기관과 실시간으로 품질관리를 필요로 하는 생산현장에서 예비시험법으로 활용함으로써 인력절감 및 실험환경 개선등의 효과를 얻을 수 있을 것으로 기대된다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.422-425
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• 2009

A sea water source cascade heat pump was designed and tested in this study. The system was designed to perform a single stage operation in summer, as well as a cascade operation in winter to ensure the high temperature lift. A steady-state simulation model was developed to analyze and optimize its performance. The simulation results show that the R717 exhibits best performance among combinations considered in this study. A R410A also exhibits the highest performance among HFCs with the smallest compressor displacement. A 15-RT R410A-R134a pilot system was installed in the 5-story commercial building at Samcheok City by the East Sea. A scroll type R410A compressor, a reciprocating type R134a compressor, plate type condenser/evaporator/ cascade heat exchanger and two electronic expansion valves were used to build a pilot. A titanium plate type heat exchanger is also used for the heat exchanging with a sea water. The heat source/sink water is supplied from the well below the seashore in the depth of 5 m. In the initial test of the system, supply water temperature was rising up to $67^{\circ}C$ using a sea water heat source of $9^{\circ}C$, while an ambient temperature was $4.5^{\circ}C$.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2009년도 춘계학술대회 논문집
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• pp.280-285
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• 2009

1998년 8월부터 2005년 6월까지 한반도 주변 해역에서 현장관측한 해수의 고유 광특성(IOPs)과 외형적 광특성(AOPs) 자료들을 이용하여 원격반사도$(R_{rs}(\lambda))$와 성분별 흡광계수의 총 합 $(\alpha(\lambda)=\alpha_w(\lambda)+\alpha_{ph}(\lambda)+\alpha_{ss}(\lambda)+\alpha_{dom}(\lambda))$의 상관관계를 분석하고, $R_{rs}(\lambda)$ 밴드비를 이용하여 흡광계수 산출 알고리즘을 개발하였다. 파장에 따른 $R_{rs}(\lambda)$와 총합 $\alpha(\lambda)$의 상관관계는 반비례적인 관계를 보였고, 파장 443 nm일 때 상관도$(R^2)$는 0.717이다. $\alpha_{ph}(\lambda)$ 산출알고리즘은 엽록소의 흡광과 관련된 파장 490 nm와 부유물의 산란과 관련된 파장 555 nm의 $R_{rs}(\lambda)$ 밴드비의 함수 형태로 구성하였고, 파장 443 nm일 때 RMS 값은 0.223이다. $\alpha_{ss}(\lambda)$과 $\alpha_{dom}(\lambda)$ 산출 알고리즘은 용존유기물의 흡광과 관련된 파장 412 nm와 부유물의 산란과 관련된 파장 555 nm의 $R_{rs}(\lambda)$ 밴드비의 함수 형태로 구성하였고, 파장 412 nm일 때 RMS 값은 각각 0.324와 0.230이다. $\alpha_{ph}(\lambda),\;\alpha_{ss}(\lambda),\;\alpha_{dom}(\lambda)$ 산출 알고리즘들은 대체적으로 현장값보다 높게 추정하였고 스펙트럼들은 잘 재현해냈다. 추후 이에 대한 개선과 알고리즘의 검보정이 요구된다.

• 한국식품영양과학회지
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• 제31권4호
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• pp.717-721
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• 2002

ESR spectroscopy를 이용하여 한약재의 방사선 조사여부를 확인하였다. 국내산 한약재 4종으로 칡, 당귀, 아가리쿠스, 황기를 0, 1, 5 및 10 kGy의 Co-60 감마선을 조사한 후, 이를 시료로 Bruker-EPR spectrometer를 이용하여 조사로 생성된 라디칼을 측정하였다. 실험결과 조사직후 감마선 조사된 한약재 4종은 ESR 특성 신호를 나타내어 비조사시료와 확실하게 구별할 수 있었다. 적용선량의 범위에서(1~10 kGy) 조사선량이 증가함에 따라 ESR 신호 크기는 직선적으로 증가하였으며, 선량의 증가에 따른 신호 크기의 증가를 나타낸 $R^2$값은 0.9428~0.9942의 높은 값을 나타내었다. 또, 이들 신호는 상온에서 2주까지는 감소하였으나 저장기간 후에도 관찰할 수 있었으므로 ESR spectroscopy를 이용한 한약재의 방사선 조사여부 판별은 6주간의 저장 후에도 측정 가능한 방법임을 알 수 있었다.

• 설비공학논문집
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• 제27권2호
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• pp.81-86
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• 2015

Performance of freezing and refrigeration systems in supermarket, which utilized $CO_2$ as a refrigerant, was investigated by using the Pack Calculation II. The configuration of simulated systems was basic parallel refrigeration system, cascade system, and two-stage system. The $CO_2$ cascade system showed higher COP than basic parallel R404A system by 13% for MT and 62% for LT, respectively. Among the $CO_2$ cascade systems, R717(MT)-$CO_2$(LT) showed the highest performance. Open-type intercooler method showed higher performance than liquid injection for the two-stage $CO_2$ systems.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.707-717
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• 2021

To the date, shipbuilding companies have applied shop primer coating which protects the steel surface from global oxidization in environment. Proper shop primer requires either anti-corrosion ability during construction or anti-porosity ability during welding, and those properties contradict to each other. This report tried to derive an optimizing parameter on these conflicting properties to select a proper shop primer. First, sufficient amounts of the natural salt spray tests were carried out to achieve a series of data for the anti-corrosion ability. Second, lots of T-joint fillet welding test were performed to evaluate the trapped porosity formed in the weld pool. According to the experimental data, we could achieve either the rust-formation rate or the porosity-formation rate, then, each rate was generalized as formulae. Then, we tried to combine these conflicting properties to decide an optimum shop primer.