• Korean Journal of Mathematics
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• v.32 no.3
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• pp.533-544
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• 2024

Given a groupoid (X, *) and a real-valued function d : X → R, a new (derived) function Φ(X, *)(d) is defined as [Φ(X, *)(d)](x, y) := d(x * y) + d(y * x) and thus Φ(X, *) : R^X → R^X2 as well, where R is the set of real numbers. The mapping Φ(X, *) is an R-linear transformation also. Properties of groupoids (X, *), functions d : X → R, and linear transformations Φ(X, *) interact in interesting ways as explored in this paper. Because of the great number of such possible interactions the results obtained are of necessity limited. Nevertheless, interesting results are obtained. E.g., if (X, *, 0) is a groupoid such that x * y = 0 = y * x if and only if x = y, which includes the class of all d/BCK-algebras, then (X, *) is *-metrizable, i.e., Φ(X, *)(d) : X² → X is a metric on X for some d : X → R.

• Honam Mathematical Journal
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• v.32 no.4
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• pp.747-761
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• 2010

It is known that there are no real hypersurfaces with parallel structure Jacobi operator $R_{\xi}$ (cf.[16], [17]). In this paper we investigate real hypersurfaces in a nonflat complex space form using some conditions of the structure Jacobi operator $R_{\xi}$ which are weaker than ${\nabla}R_{\xi}$ = 0. Under further condition $S\phi={\phi}S$ for the Ricci tensor S we characterize Hopf hypersurfaces in a complex space form.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.5
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• pp.633-641
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• 1999

Experiments were carried out to investigate the condensation heat transfer characteristics for R22 and its alternatives, R407C (R32/125/134a, 23/25/52wt%) and R410A (R32/125, 50/50wt%). A concentric tube heat exchanger was made to conduct condensation heat transfer tests. Mass flux and saturation temperature of refrigerants at the test section inlet were varied to get the corresponding heat transfer coefficients. Serial and parallel input of secondary fluid (water) were applied to the test subsections. Compared with existing correlations of condensation heat transfer, experimental heat transfer coefficients obtained in this study were generally higher than the predicted values, and mean absolute deviations from several correlations were shown. Wall subcooling was introduced to get a new correlation for condensation heat transfer coefficients by modifying Shah's equation. The RMS deviation of the measured heat transfer coefficients from the new correlation in this study for R22 is 9.9% and that for R407C and R410A are 10.2% and 14.6%, respectively.

• International Journal of Air-Conditioning and Refrigeration
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• v.6
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• pp.93-103
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• 1998

The nucleate boiling heat transfer experiments are performed using a ternary refrigerant R407C which is a candidate of alternatives of HCFC 22. The boiling phenomena of R-32, R-125 and R-134a which are the constituent refrigerants of R407C are also investigated. The nucleate boiling heat transfer coefficients of R407C are less than those of HCFC 22 which have the similar physical and transport properties. In our experimental pressure range, which is similar to the operational pressure of air conditioning system, the deterioration of boiling heat transfer coefficients of mixture refrigerant R407C does not appear for moderate wall superheat region. Since nucleate boiling heat transfer coefficients cannot be obtained from ideal mixing law of mixture, Thome's method was used to predict. To account for the heat flux effect and system pressure in Thome's method, the correcting factor, a(P.L1T), was introduced and obtained from experiments for ternary refrigerant R407C.

• Journal of Korean Academy of Nursing
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• v.28 no.1
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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.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.112-112
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• 2009

레이저 용접은 아크 용접에 비해 상대적으로 빠른 용접과 깊은 용입이 가능하며, 낮은 열입력을 가지는 장점이 있다. 하지만 알루미늄 합금 용접 시 균열 감수성의 증가 및 용접강도가 저하되는 단점을 가지고 있다. 이러한 단점을 극복하는 방법으로 모재의 화학조성을 제어하는 방법과 부가적인 용접와이어를 공급하는 방법이 제안되었으나 레이저 용접에 적용하기 쉽지 않다. 아크 용접과 전자빔 용접에서는 열원에 오실레이션을 적용하여 결정립 구조를 제어하여 용접강도를 증가하는 방법이 제안되었다. 따라서 본 연구에서는 알루미늄 합금 5J32-T4의 용접균열 저감 및 용접강도 향상을 위해 레이저 위빙을 적용하였다. 1mm 두께의 알루미늄 5J32-T4를 사용하였으며, 4kW급 디스크 레이저와 레이저용 스케너를 이용하여 레이저 위빙을 구현하였다. 고온균열을 평가하기 위해 자기구속형 균열 평가방법을 사용하였으며, 용접강도를 평가하기 위해 겹치기 용접을 수행한 시편을 이용하였다. 고온균열 실험결과 레이저 위빙 적용 시 직선 용접에 비해 균열 감수성이 감소한 것을 확인하였다. 전단인장강도 측정결과 레이저 위빙의 적용에 따라 직선 용접에 비해 높은 전단인장강도의 확보가 가능하였다.

• Korean Journal of Mathematics
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• v.32 no.3
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• pp.545-560
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• 2024

In the present study, we have constructed a new Banach series space |𝛶^r|^u_p by using concept of absolute Jordan totient summability |𝛶^r, u_n|_p which is derived by the infinite regular matrix of the Jordan's totient function. Also, we prove that the series space |𝛶^r|^u_p is linearly isomorphic to the space of all p-absolutely summable sequences ℓ_p for p ≥ 1. Moreover, we compute the α-, β- and γ- duals of this space and construct Schauder basis for the series space |𝛶^r|^u_p. Finally, we characterize the classes of infinite matrices (|𝛶^r|^u_p, X) and (X, |𝛶^r|^u_p), where X is any given classical sequence spaces ℓ_∞, c, c₀ and ℓ₁.

• Journal of the Korean Chemical Society
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• v.43 no.4
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• pp.384-385
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• 1999

Two anhydrous crystal structures of fully dehydrated, $Ca^{2+}$- and $Tl^+$-exchanged zeolite X, TEX>$Ca_{18}Tl_{56}Si_{100}Al_{92}O_{384}($Ca_{18}Tl_{56}$-X;\alpha=24.883(4)\AA)$ and TEX>$Ca_{32}Tl_{28}Si_{100}Al_{92}O_{384}($Ca_{32}Tl_{28}$-X;\alpha=24.973(4)\AA)$ per unit cell, have been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd3 at $21(1)^{\circ}C.$ $Ca_{18}Tl_{56}-X$ was prepared by ion exchange in a flowing stream of 0.045 M aqueous $Ca(NO_3)_2$ and 0.005 M $TlNO_3$. $Ca_{32}Tl_{28}-X$ was prepared similarly using a mixed solution of 0.0495 M $Ca(NO_3)_2$ and 0.0005M $TlNO_3$. Each crystal was then dehydrated at 360 $^{\circ}C$ and $2{\times}10^{-6}$ Torr for 2 days. Their structures were refined to the final error indices, $R_1=0.039\;and\;R_2=0.036$ with 382 reflections for $Ca_{18}Tl_{56}-X$ , and $R_1=0.046\;and\;R_2=0.045$ with 472 reflections for $Ca_{32}Tl_{28}$-X for which $/>3\sigma(I).$ In the structures of dehydrated $Ca_{18}Tl_{56^-}X\;and\;Ca_{32}Tl_{28}$-X, $Ca^{2+}\;and\;Tl^+$ ions are located at six crystallographic sites. Sixteen $Ca^{2+}$ ions fill the octahedral sites I at the centers of double six rings ($Ca_{18}Tl_{56}$-X:Ca-O=2.42(1) and O-Ca-O=93.06(4)$^{\circ}$; $Ca_{32}Tl_{28}$-X Ca-O=2.40(1) $\AA$ and O-Ca-O=93.08(3)$^{\circ}$). In the structure of $Ca_{18}Tl_{56}$-X, another two $Ca^{2+}$ ions occupy site II (Ca-O=2.35(2) $\AA$ and O-Ca-O=111.69(2)$^{\circ}$) and twenty six $Tl^+$ ions occupy site II opposite single six-rings in the supercage; each is 1.493 $\AA$ from the plane of three oxygens $(Tl-O=2.70(8)\AA$ and O-Tl-O=92.33(4)$^{\circ}$). About four $Tl^+$ ions are found at site II',1.695 $\AA$ into sodalite cavity from their three oxygen plane (Tl-O=2.81 (1) and O-Tl-O=87.48(3)). The remaining twenty six $Tl^+$ ions are distributed over site III'(Tl-O=2.82 (1) $\AA$ and Tl-O=2.88(3)$^{\circ}$). In the structure of $Ca_{32}Tl_{28}$-X, sixteen $Ca^{2+}$ ions and fifteen $Tl^+$ ions occupy site III' (Ca-O=2.26(1) $\AA$ and O-Ca-O=119.14(4)$^{\circ}$; Tl-O=2.70(1) $\AA$ and O-Tl-O=92.38$^{\circ}$) and one $Tl^+$ ion occupies site II'. The remaining twelve $Tl^+$ ions are distributed over site III'. It appears that $Ca^{2+}$ ions prefer sites I and II in that order and $Tl^+$ ions occupy the remaining sites.

• Journal of Korean Society of Forest Science
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• v.112 no.1
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• pp.23-31
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• 2023

Predicting forest productivity is essential to evaluate sustainable forest management or to enhance forest ecosystem services. Ordinary least squares (OLS) and partial least squares (PLS) regression models were used to develop predictive models for forest productivity (site index) from the site characteristics and soil profile, along with soil physical and chemical properties, of 112 Quercus mongolica stands. The adjusted coefficients of determination (adjusted R²) in the regression models were higher for the site characteristics and soil profile of B horizon (R²=0.32) and of A horizon (R²=0.29) than for the soil physical and chemical properties of B horizon (R²=0.21) and A horizon (R²=0.09). The PLS models (R²=0.20-0.32) were better predictors of site index than the OLS models (R²=0.09-0.31). These results suggest that the regression models for Q. mongolica can be applied to predict the forest productivity, but new variables may need to be developed to enhance the explanatory power of regression models.

• Microbiology and Biotechnology Letters
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• v.19 no.2
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• pp.122-127
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• 1991

A bacterial strain NO. 32 which produced thermostable ${\alpha}$-amylase was isolated from soil and identified to genus of Bacillus. To enhance ${\alpha}$-amylase productivity, a successive mutation of Bacillus sp. No. 32 was attempted with treatment of N-methyl-N'-nitro-N-nitrosoguanidine (NTG). The resulting mutant, Bacillus sp. No. 32H417, which is risistant to refampicin and deficient in spore formation, produced about 90-fold high level of ${\alpha}$-amylase when compared with parental strain. The properties of the enzyme for thermostability were investigated. The optimal temperature and pH for enzyme reaction were 95$^{\circ}C$ and pH6.5, respectively, in the presence of 0.3mM $Ca^{2+}$ as an effective stabilizer.