• 설비공학논문집
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• 제5권2호
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• pp.141-155
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• 1993

Thermodynamic properties of R-32 are calculated and its refrigeration performance is evaluated for the purpose the feasibility study of replacing R-22 with R-32. (1) Refrigeration effect of R-32 is superior to that of R-22 because heat of evaporation of R 32 is about 50% higher than that of R-22. However, COP of R-32 system is 10-30% lower than that of R-22 system. It is mainly attributed to the vapor pressore of R-32 being about 62% higher than R-22. (2) Since the pressure ratio and the specific heat ratio of R-32 system is higher than those of R -22, compressor discharging temperature rises as high as to $130-150^{\circ}C$. It may cause mechanical failure of compressor due to the breakdown of lubricant. Compressor should be improved to lower the temperature if R-32 is to replace R-22. (3) Averaged two-phase heat transfer coefficient of R-32 is about 10-20% higher than that of R-22. It may assume better heat exchanger effectiveness but not guarantee the better COP of R-32 system than R-22. (4) The high vapor pressure is the first reason to drop R-32 out of the line of R-22 alternative refrigerant. So, refrigerant mixtures based on R-32 are recommended to adjust the vapor pressure first and keep superior volumetric capacity of R-32.

• 산업기술연구
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• 제34권
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• pp.21-26
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• 2014

The effect of refrigerant R-134a and R-430a on the performance of refrigeration equipment for R-134a is investigated. Refrigeration effect, compression work and coefficient of performance of refrigeration equpment for both R-134a and R-430a are obtained by experimentation. These performances comparison between R-134a and R-430a is made in case of the maximum load. Refrigeration effect for R-134a and that for R-430a is almost equal while compression work for R-134a is less than that for R-430a. Consequently it shows that coefficient of performance for R-134a is relatively 11% higher than that for R-430a.

• 대한수학회보
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• 제55권5호
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• pp.1397-1404
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• 2018

For a connected graph G, an r-maximum edge-coloring is an edge-coloring f defined on E(G) such that at every vertex v with $d_G(v){\geq}r$ exactly r incident edges to v receive the maximum color. The r-maximum index $x^{\prime}_r(G)$ is the least number of required colors to have an r-maximum edge coloring of G. In this paper, we show how the r-maximum index is affected by adding an edge or a vertex. As a main result, we show that for each $r{\geq}3$ the r-maximum index function over the graphs admitting an r-maximum edge-coloring is unbounded and the range is the set of natural numbers. In other words, for each $r{\geq}3$ and $k{\geq}1$ there is a family of graphs G(r, k) with $x^{\prime}_r(G(r,k))=k$. Also, we construct a family of graphs not admitting an r-maximum edge-coloring with arbitrary maximum degrees: for any fixed $r{\geq}3$, there is an infinite family of graphs ${\mathcal{F}}_r=\{G_k:k{\geq}r+1\}$, where for each $k{\geq}r+1$ there is no r-maximum edge-coloring of $G_k$ and ${\Delta}(G_k)=k$.

• The Korean Journal of Ecology
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• 제27권3호
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• pp.165-171
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• 2004

상수리나무 뿌리의 분해율과 분해과정에 따른 영양염류의 변화를 조사하였다. 33개월경과 후 뿌리의 분해율은 직경 0.2㎝ 미만(R₁), 0.5∼1㎝(R₂), 1∼2㎝(R₃), 2∼4㎝(R₄)가 각각 49.6%, 47.5% 66.4%, 66.1%, 분해상수 k는 각각 0.249/yr, 0.234/yr, 0.397/yr, 0.393/yr로 직경이 큰 것의 분해율이 높았다. 상수리나무 뿌리는 유사한 직경의 상수리나무 가지에 비해 분해가 빠른 것으로 나타났다. 분해 과정에 따른 뿌리의 질소 함량은 모든 직경급에서 증가하는 경향을 보였다. 33개월경과 후 뿌리의 질소 잔존률은 R₁, R₂, R₃ 그리고 R₄ 각각 66.5%, 86.7%, 84.4%, 44.4%이었다. 분해중인 뿌리의 인 함량은 분해 초기에 감소하다 후반부에는 증가하는 경향을 보였으며, 33개월 후 인의 잔존률은 R₁, R₂, R₃ 그리고 R₄ 각각 64.7%, 62.4%, 93.1% 30.7%이었다. 분해중인 뿌리의 칼륨 함량은 분해가 진행됨에 따라 초기 값보다 현저하게 감소하였으며, 33개월경과 후 칼륨의 잔존률은 R₁, R₂, R₃그리고 R₄에서 각각 11.6%, 10.6%, 5.9%, 7.7%이었다. 분해과정 중 칼슘 함량의 변화는 직경급에 따라 달랐으며, 33개월경과 후 칼슘의 잔존률은 R₁, R₂, R₃ 그리고 R₄에서 각각 66.2%, 51.0%, 39.1%, 48.3%이었다. 뿌리의 마그네슘 함량은 직경이 작을수록 초기 함량이 높았으며, 분해가 진행됨에 따라 R₄에서는 초기 값에 비해 함량이 증가하였으나 Rl₁ R₂, R₃에서는 초기 값보다 감소하였다. 33개월경과 후 마그네슘 잔존률은 R₁, R₂, R₃ 그리고 R₄에서 각각 15.3%, 29.9%, 24.6%, 69.4%로 칼슘과는 달리 직경이 큰 뿌리에서 잔존률이 높았다.on of hub-and-spoke system, integration of logistics bases, introduction of (automatic) parking building, diversification of transportation mode, and etc. At the same time, we constructed three practically executable scenarios based on those ideas. The first is "Center Hub" scenario, the second is "Metropolitan Hub" scenario. The third and last scenario is "Regional Consolidation of Warehouses (distribution centers)".f worldly desire' and 'cordiality' that one could be deserved his diligency becoming a part of the harmonious idealistic living place. Fourthly, on the character of story teller. Originally he is a incomer of "Gang-Ho" from real world. so that reason, he is showing dualism not to deny the loyalty oath to his king, while he intends to satisfy with the life in "Gang- Ho" separating himself from real world. As a gentry, at that time, the loyalty oath is inevitable one and that is found from

• 대한기계학회논문집
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• 제15권6호
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• pp.2189-2205
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• 1991

본 연구에서는 혼합냉매의 열역학적 물성치를 정확하게 예측하기 위하여 척력 과 인력항으로 된 간단한 형태의 상태방정식을 택하고 이를 이용하여 순수성분에 대한 열역학적 물성치 자료와 혼합냉매에 대한 기액평형상태 자료를 이용하여 혼합물에 대 한 열역학적 물성치를 보다 더욱 정확하게 예측 할 수 있는 방법에 관해 연구하고자 한다.혼합냉매에 대한 상태방정식과 이상기체 상태의 비열자료를 기초로 열역학적 관계식을 이용하여, 압력-엔탈피, 온도-엔트로피 관계를 공식화하며, 혼합냉매에 대한 열펌프 및 냉동사이클 해석에 필요한 자료를 제시한다.

• 동아시아식생활학회지
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• 제3권2호
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• pp.107-119
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• 1993

The objeative of this study was to investigate the possibility of estimation of internal quality by observing visible state of strawberry. Several tests such as color("L", "A", H,V,C), degree of blackred ness, opening state of calyx, vitamin C content, brix degree, acidity, freshness, overall quality, chlorophyll content, and anthocyanin content were performend during circulation at 20$^{\circ}C$. Acidity(R=-0.96), chloroph-yll content(r=-0.99), vitamin C content(r=-0.98), freshness(r=-0.96), and overall quality(-0.99), degree of blackredness(r=0.98) and opening state of calyx(=0.98), color saturation(r=0.99), degree of blackredness(r=0.98) and opening state of calyx(=0.98) increased during circulation at 20$^{\circ}C$. in correlation between visible indicators andd internal qualities, "L" valu and brix degree was r=-0.74, "a" and brix degree was r=0.93 Hue and anthocyanin content was r=0.74, value and chlorophyll content, brix degree were r=-0.91, r=-0.77, chroma and brix degree was r=0.96. The correlations between color saturation and vitamin C content(r=-0.96), chlorophyll content(r=-0.98), freshness(r=-0.98), overall quality(r=-0.94), loss of total polyphenol(0.94) and acidity(r=-0.94) showed high correlation. The correlatiions between degree of blackrednes and vitamin C content(r=-0.99), chlorophyll content(r=-0.94), anthocyanin content(=-0.74), freshness(r=-0.97) overall quality (r=-0.95), loss of total polyphenol(r=0.93) and acidity(r=-0.91) chlorophyll content(r=-0.99), freshness(r=-0.98), overall quality(r=-0.92), loss of total polyphenol(r=0.99) and acidity(r=0.83) showed high correlation.

• 대한기계학회논문집
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• 제14권5호
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• pp.1337-1348
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• 1990

본 연구에서는 Peng-Robinson 상태 방정식을 기본으로 하여 먼저 단일 성분의 냉매에 대한 열역학적 물성치를 구한 뒤 그 정확도를 검증하고, 동일한 형태의 상태식 과 적절한 혼합 법칙을 통해 혼합냉매의 기액 평형 상태와 냉동 및 열펌프 사이클 해 석에 필요한 엔탈피와 엔트로피 등의 열역학적 물성치를 추산하고자 한다.단일 성 분의 냉매로서는 R13B1, R22, R12, R152a, R114를 택하였고, 혼합냉매로서는 앞의 단 일성분 냉매를 혼합한 것 중에서 그 기초적인 실험 자료가 아미 알려진 R13B1/R114, R22/R114, R12/R114 R152a/R114, R13B1/R152a 및 R13B1/R12를 택하였다. 이는 추후 상이한 냉매를 단일식으로 나타낼 수 있는 대응상태의 원리를 사용한 열물성 계산의 기반이 될 수 있을 것이다.

• 대한간호학회지
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• 제28권1호
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• pp.184-192
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• 1998

This study was done to examine the correlations between weight, BMI and risk factors of coronary heart disease in men and women in their forties and fifties. The subjects were 412 adults. who had regular health examinations between January and December of 1996 at S-Hospital in Seoul. The data were analyzed using ANOVA, Scheffe test, and Pearson correlation coefficient. The results are as follows : 1. The men between 50 and 59 years of age had higher levels for BMI, weight, systolic blood pressure, diastolic blood pressure, total cholesterol. LDL-cholesterol, triglyceride, fasting blood sugar, plasminogen activator-1, and hemoglobin A,C than the group of women in their forties. Yet. HDL-cholesterol was lower than in the former group. 2. In the group of men in their forties, weight was significantly correlated to diastolic blood pressure(r=.22), LDL-cholesterol(r=.20), plasminogen activator-inhibitor-1(r=.35) HDL-cholesterol(r=-.19). Their BMI was significantly correlted to systolic blood pressure(r=.27), diastolic blood pressure (r=.33), total cholesterol(r=.23), LDL-cholesterol (r=.26), plasminogen activator-1(r=.36) and HDL-cholesterol(r=-.25). 3. As for the group of women in their forties weight was significantly correlated to systolic blood pressure(r=.20), diastolic blood pressure(r=.22), triglyceride(r=.32) , plasminogen activator inhibitor-1 (r=.30) and HDL-cholesterol(r= -.37). Their BMI was significantly correlated to diastolic blood pressure (r=.25) triglyceride(r=.47), plasminogen activator-1 (r=.35), fibrinogen(r=.27) and HDL-cholesterol(r=-.47). 4. In the group of men in their fifties. weight was significantly correlated to total cholesterol (r=32), LDL-cholesterol(r=.29). plasminogen activator inhibitor-1(r=.26). Their BMI was significantly correlated to systolic blood pressure(r=.24), diastolic blood pressure (r=.22), total cholesterol (r=.34), LDL-cholesterol (r=.32), and plasminogen activator-1(r=.25). 5. In the group of women in their fifties, weight was significantly correlated to diastolic blood pressure(r=.33), total cholesterol(r=.21), LDL-cholesterol(r=.20), plasminogen activator inhibitor-1 (r=.43) and HDL-cholesterol(r=-.21). Their BMI was significantly correlated to systolic blood pressure(r=.25), diastolic blood pressure(r=.40), total cholesterol(r=.24), LDL-cholesterol(r=.24), triglyceride(r=22), and HDL-cholesterol (r=-.30). The above findings indicate that the BMI was more predictive than weight as a risk factor for coronary artery disease for men and women in their forties and fifties.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.247-249
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• 2008

Low Temperature a-Si:H TFT on stainless steel substrate has been developed for the flexible electrophoretic display. Stability of low temperature a-Si:H TFT is more important point than its initial device characteristics. Thus, we have studied device characteristics of low temperature a-Si:H TFT in terms of stability for driving electrophoretic display.

• Korean Journal of Mathematics
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• 제21권4호
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• pp.463-471
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• 2013

Let R be a ring with identity 1, $I(R){\neq}\{0\}$ be the set of all nonunit idempotents in R, and M(R) be the set of all primitive idempotents and 0 of R. We say that I(R) is additive if for all e, $f{\in}I(R)$ ($e{\neq}f$), $e+f{\in}I(R)$. In this paper, the following are shown: (1) I(R) is a finite additive set if and only if $M(R){\backslash}\{0\}$ is a complete set of primitive central idempotents, char(R) = 2 and every nonzero idempotent of R can be expressed as a sum of orthogonal primitive idempotents of R; (2) for a regular ring R such that I(R) is a finite additive set, if the multiplicative group of all units of R is abelian (resp. cyclic), then R is a commutative ring (resp. R is a finite direct product of finite field).