• Communications of the Korean Mathematical Society
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• v.34 no.4
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• pp.1099-1104
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• 2019

In [1], Ali and Dar proved the ${\ast}$-version of classical theorem due to Posner [15, Theorem] with involution of the second kind. The main objective of this paper is to improve the above mentioned result without the condition of the second kind involution. Moreover, a related result has been discussed.

• Journal of the Korean association of regional geographers
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• v.20 no.1
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• pp.30-48
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• 2014

Relying on the interaction indices - dominance index, relative strength index and entropy index, this paper analyzes the structural features of urban network in the Seoul metropolitan area with the flows of commuting, business, and freight. Analytical results show that the Seoul metropolitan urban system is vertical, size-dependent, one-way, and the highest city-dominant network rather than horizontal, size-neutral, two-way, complementary one. The network of freight flow is a little bit more symmetrical than the networks of commuting and business. However, the interaction with Seoul is still determinant in all aspects of hierarchical structure, relative strength, and symmetry of flow.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.05a
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• pp.428-430
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• 2018

Accidents of commuting vehicles for kindergarteners and nursery school students continue to occur despite various safety policies from the government. In order to minimize such accidents, it is necessary to use both the vehicle-mounted safety commutation management software which can be easily operated by the driver, and the mobile app to manage the safe schooling of the children that can inform such information to parents timely. In this paper, we describe the design and implementation of the safety management software architecture.

• Journal of applied mathematics & informatics
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• v.5 no.3
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• pp.819-826
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• 1998

The purpose of this paper is to prove the following results; (1) Let R be a prime ring of char $(R)\neq 2$ and I a nonzero left ideal of R. The existence of a nonzero symmetric bi-derivation D : $R\timesR\;\longrightarrow\;$ such that d is sew-commuting on I where d is the trace of D forces R to be commutative (2) Let m and n be integers with $m\;\neq\;0.\;or\;n\neq\;0$. Let R be a noncommutative prime ring of char$ (R))\neq \; 2-1\; p_1 \;n_1$ where p is a prime number which is a divisor of m, and I a nonzero two-sided ideal of R. Let $D_1$ ; $R\;\times\;R\;\longrightarrow\;and\;$ $D_2\;:\;R\;\times\;R\;longrightarrow\;R$ be symmetric bi-derivations. Suppose further that there exists a symmetric bi-additive mapping B ; $R\;\times\;R\;\longrightarrow\;and\;$ such that $md_1(\chi)\chi ＋ n\chi d_2(\chi)=f(\chi$) holds for all $\chi$$\in$I, where $d_1 \;and\; d_2$ are the traces of $D_1 \;and\; D_2$ respectively and f is the trace of B. Then we have $D_1=0 \;and\; D_2=0$.

• Journal of the Korean Mathematical Society
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• v.45 no.2
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• pp.425-433
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• 2008

Let R be a ring with identity $1_R$ and let U(R) denote the group of all units of R. A ring R is called locally finite if every finite subset in it generates a finite semi group multiplicatively. In this paper, some results are obtained as follows: (1) for any semilocal (hence semiperfect) ring R, U(R) is a finite (resp. locally finite) group if and only if R is a finite (resp. locally finite) ring; U(R) is a locally finite group if and only if U$(M_n(R))$ is a locally finite group where $M_n(R)$ is the full matrix ring of $n{\times}n$ matrices over R for any positive integer n; in addition, if $2=1_R+1_R$ is a unit in R, then U(R) is an abelian group if and only if R is a commutative ring; (2) for any semiperfect ring R, if E(R), the set of all idempotents in R, is commuting, then $R/J\cong\oplus_{i=1}^mD_i$ where each $D_i$ is a division ring for some positive integer m and |E(R)|=$2^m$; in addition, if 2=$1_R+1_R$ is a unit in R, then every idempotent is central.

• Kyungpook Mathematical Journal
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• v.55 no.1
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• pp.1-12
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• 2015

Let R be a ring and $D:R^n{\longrightarrow}R$ be n-additive mapping. A map $d:R{\longrightarrow}R$ is said to be the trace of D if $d(x)=D(x,x,{\ldots}x)$ for all $x{\in}R$. Suppose that ${\alpha},{\beta}$ are endomorphisms of R. For any $a,b{\in}R$, let < a, b > $_{({\alpha},{\beta})}=a{\alpha}(b)+{\beta}(b)a$. In the present paper under certain suitable torsion restrictions it is shown that D = 0 if R satisfies either < d(x), $x^m$ > $_{({\alpha},{\beta})}=0$, for all $x{\in}R$ or ${\ll}$ d(x), x > $_{({\alpha},{\beta})}$, $x^m$ > $_{({\alpha},{\beta})}=0$, for all $x{\in}R$. Further, if < d(x), x > ${\in}Z(R)$, the center of R, for all $x{\in}R$ or < d(x)x - xd(x), x >= 0, for all $x{\in}R$, then it is proved that d is commuting on R. Some more related results are also obtained for additive mapping on R.

• Journal of Korean Society of Rural Planning
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• v.23 no.3
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• pp.121-131
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• 2017

Although the educational facility are an important considerations on a social equity standpoint, educational environment in rural areas has been continuously deteriorated by numerous social problems such as decreasing birth rate and increasing of local school closing. The purpose of this study is to evaluate the accessibility of educational environment in rural areas on village level. First, we evaluate physical accessibility based on legally defined commuting distance. Second, the implication of village population of potential accessibility is analyzed. Lastly, the facility centrality index of each village is estimated for assessing the relations of educational accessibility. The main results of this study are as follows; (1) The accessibility of most villages in Pyeongchang-gun is vulnerable that 81.10% for elementary school, 73.17% for middle school, and 82.32% for high school, respectively; (2) The average commuting distance per student considering estimated number of students for each educational facilities indicated 2.75km for elementary school, 4.37km for middle school, and 5.79km for high school; (3) the facility centrality index is highly correlated to educational facilities but not to village population.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1886-1894
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• 2009

The widening national capital area of Korea has caused a traffic jam problem with increasing commuting hours. In addition, as the economic crisis goes on, the people moving to the outside of a city has increased. So we expect that the expansion of this metropolitan area will do grow and it will cause a more severe traffic jam in the near future. Therefore, We will study about 'Rapid Railroad Operation in Metropolitan Area' to solve this problem and improve rail's competitive power as a reasonable transportation method. The Rapid Railroad can sharply reduce commuting hours. Also, it is more eco-friendly transportation than the others. Through many cases revealed in both domestics and overseas, we will solve the problem of a traffic jam getting senous m metropolitan area. After studying successful cases of overseas, rapid railroad, such as France and Japan, we will study domestic cases of Yongsan$\sim$Dong-inchoen, Guro$\sim$Cheonan and Gaehwa$\sim$Sin-nonhyeon, and comparison will do made among these case. In conclusion, The introduction of Rapid Railroad show the effective plan for strengthen the competitiveness and solve the traffic problem.

• Journal of Technologic Dentistry
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• v.11 no.1
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• pp.47-63
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• 1989

The study was made to clarify the degree of fatigue of dental technicians in service at the general &local hospital or the dental laboratories in the large cith of korea. The objectives of this study were 235 dental technicians who replied the questionaire which was sent by postal service out of 600 dental technicians selected by random sampling among the workers of the each dental laboratory. The instruments used in this study was the same one as developed by Industry Fatigue committee of Japan Industry Hygiene Association. This instrument was included total 30 items which is consisted of 10 perceived symptoms of fatigue in physical, mental and neuro-sensory dimension respectably. Reliability was tasted with the data of objectives, in which value of Cronbach's $\alpha$ was 9457. The following results were obtained. 1. It was revealed that the influencing demographic variables on the perceived symptoms of fatigue of dental technicians were sex, age, marital status, educational background, job carrier, working part, working hour and commuting hour. The shorted the age or job carrier, thge higher dearee of the perceived symptoms of fatigue. The longer working hours of commuting hours, the higher degree of the perceived symptoms of fatigue. The degree of the perceived symptoms of fatigue in females, unmarried person, the one with higher educational background, workers except orthodontic appliances and poorcelain contouring were higher than the other group. 2. The higher degree of the rest & leisure condition, the lower degree of the physical, mental and neuro-sensory perceived symptoms. 3. The higher degree of environmental condition of the working, the lower degree of the physical, mental and neurosensory perceived symptoms.

• Journal of Korean Society of Rural Planning
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• v.18 no.3
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• pp.165-174
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• 2012

Development of transportation and communication technology has affected our daily life and has caused to separate residential places from working places. Particularly in rural areas, the life zones are incorporated into larger towns or urban areas due to their lack of cultural, social and economic infrastructures. Thus, the analysis of the depended region and the life zone is important for the planning of regional revitalization programs and related project. The purpose of this study is to propose a regional dependency model (RDM) using the origin-destination(O-D) matrix of commuters and compare it with the Nystuen & Dacey model for regional correlation. The regional characteristics are analysed and our RDM were tested using the commuting data on Seoul metropolitan area(Seoul, Gyeong-gi, Incheon) and Chungchung area. The regional correlation model can only explain the determination of regional interaction without considering the direction of regional correlation but our model can show the direction of regional dependencies.