• East Asian mathematical journal
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• 제33권5호
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• pp.571-585
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• 2017

Let M be a connected n-dimensional submanifold of a Euclidean space $E^{n+k}$ equipped with the induced metric and ${\Delta}$ its Laplacian. If the position vector x of M is decomposed as a sum of three vectors $x=x_1+x_2+x_0$ where two vectors $x_1$ and $x_2$ are non-constant eigen vectors of the Laplacian, i.e., ${\Delta}x_i={\lambda}_ix_i$, i = 1, 2 (${\lambda}_i{\in}R$) and $x_0$ is a constant vector, then, M is called a 2-type submanifold. In this paper we showed that a 2-type surface M in $E^3$ satisfies ${\langle}{\Delta}x,x-x_0{\rangle}=c$ for a constant c, where ${\langle},{\rangle}$ is the usual inner product in $E^3$, then M is an open part of a circular cylinder. Also we showed that if a quadric hypersurface M in a Euclidean space satisfies ${\langle}{\Delta}x,x{\rangle}=c$ for a constant c, then it is one of a minimal quadric hypersurface, a genaralized cone, a hypersphere, and a spherical cylinder.

• 대한수학회보
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• 제20권1호
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• pp.45-49
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• 1983

If R is ring and M is a right (or left) R-module, then M is called a faithful R-module if, for some a in R, x.a=0 for all x.mem.M then a=0. In [4], R.E. Johnson defines that M is a prime module if every non-zero submodule of M is faithful. Let us define that M is of prime type provided that M is faithful if and only if every non-zero submodule is faithful. We call a right (left) ideal I of R is of prime type if R/I is of prime type as a R-module. This is equivalent to the condition that if xRy.subeq.I then either x.mem.I ro y.mem.I (see [5:3:1]). It is easy to see that in case R is a commutative ring then a right or left ideal of a prime type is just a prime ideal. We have defined in [5], that a chain of right ideals of prime type in a ring R is a finite strictly increasing sequence I$_{0}$.contnd.I$_{1}$.contnd....contnd.I$_{n}$; the length of the chain is n. By the right dimension of a ring R, which is denoted by dim, R, we mean the supremum of the length of all chains of right ideals of prime type in R. It is an integer .geq.0 or .inf.. The left dimension of R, which is denoted by dim$_{l}$ R is similarly defined. It was shown in [5], that dim$_{r}$R=0 if and only if dim$_{l}$ R=0 if and only if R modulo the prime radical is a strongly regular ring. By "a strongly regular ring", we mean that for every a in R there is x in R such that axa=a=a$^{2}$x. It was also shown that R is a simple ring if and only if every right ideal is of prime type if and only if every left ideal is of prime type. In case, R is a (right or left) primitive ring then dim$_{r}$R=n if and only if dim$_{l}$ R=n if and only if R.iden.D$_{n+1}$ , n+1 by n+1 matrix ring on a division ring D. in this paper, we establish the following results: (1) If R is prime ring and dim$_{r}$R=n then either R is a righe Ore domain such that every non-zero right ideal of a prime type contains a non-zero minimal prime ideal or the classical ring of ritght quotients is isomorphic to m*m matrix ring over a division ring where m.leq.n+1. (b) If R is prime ring and dim$_{r}$R=n then dim$_{l}$ R=n if dim$_{l}$ R=n if dim$_{l}$ R<.inf. (c) Let R be a principal right and left ideal domain. If dim$_{r}$R=1 then R is an unique factorization domain.TEX>R=1 then R is an unique factorization domain.

• Journal of Positioning, Navigation, and Timing
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• 제1권1호
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• pp.29-34
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• 2012

A software GNSS signal generator for the GPS L1/L2/L5 and Galileo E1/E5 signals is proposed in this paper. And this signal generator is designed and implemented with several components by considering the reuse and expansion of components for similar GNSS signals. The characteristics of the reusability of the components are confirmed with the carrier generation and the band-pass filter components. And the functionality of the GNSS multi-band IF signal generator is validated by using the commercial software GPS L1 receiver, and the performance of signal acquisition, tracking and accuracy of horizontal position error are analyzed for this validation. As a result, the GPS L1 signal generator operates successfully and it could be expected that other signal generators also operate well because most of components are the same as those of the GPS L1 signal generator.

• 대한수학회보
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• 제56권5호
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• pp.1219-1233
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• 2019

Let $E{\rightarrow}M$ be an arbitrary vector bundle of rank k over a Riemannian manifold M equipped with a fiber metric and a compatible connection $D^E$. R. Albuquerque constructed a general class of (two-weights) spherically symmetric metrics on E. In this paper, we give a characterization of locally symmetric spherically symmetric metrics on E in the case when $D^E$ is flat. We study also the Einstein property on E proving, among other results, that if $k{\geq}2$ and the base manifold is Einstein with positive constant scalar curvature, then there is a 1-parameter family of Einstein spherically symmetric metrics on E, which are not Ricci-flat.

• 대한수학회지
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• 제38권5호
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• pp.915-935
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• 2001

Let V be any valuation domain and let E be a subset of the quotient field K of V. We study the ring of integer-valued polynomials on E, that is, Int(E, V)={f$\in$K[X]｜f(E)⊆V}. We show that, if E is precompact, then Int(E, V) has many properties similar to those of the classical ring Int(Z).In particular, Int(E, V) is dense in the ring of continuous functions C(E, V); each finitely generated ideal of Int(E, V) may be generated by two elements; and finally, Int(E, V) is a Prufer domain.

• 충청수학회지
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• 제22권1호
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• pp.1-5
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• 2009

Let {$X_n,\;n{\geq}1}$ be a sequence of independent identically distributed(i.i.d.) sequence of positive random variables with common absolutely continuous distribution function(cdf) F(x) and probability density function(pdf) f(x) and $E(X^2)<{\infty}$. The random variables $\frac{X_i{\cdot}X_j}{(\Sigma^n_{k=1}X_k)^{2}}$ and $\Sigma^n_{k=1}X_k$ are independent for $1{\leq}i if and only if {$X_n,\;n{\geq}1}$ have gamma distribution.

• 대한수학회보
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• 제57권5호
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• pp.1319-1334
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• 2020

In this paper, we study the basic theory of the category of graded w-Noetherian modules over a graded ring R. Some elementary concepts, such as w-envelope of graded modules, graded w-Noetherian rings and so on, are introduced. It is shown that: (1) A graded domain R is graded w-Noetherian if and only if R^g_𝔪 is a graded Noetherian ring for any gr-maximal w-ideal m of R, and there are only finite numbers of gr-maximal w-ideals including a for any nonzero homogeneous element a. (2) Let R be a strongly graded ring. Then R is a graded w-Noetherian ring if and only if R_e is a w-Noetherian ring. (3) Let R be a graded w-Noetherian domain and let a ∈ R be a homogeneous element. Suppose 𝖕 is a minimal graded prime ideal of (a). Then the graded height of the graded prime ideal 𝖕 is at most 1.

• 한국통신학회논문지
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• 제30권4A호
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• pp.350-357
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• 2005

근거리무선통신 (Dedicated Short Range Communication, DSRC)은 지능형교통시스템 서비스 제공을 위한 통신 수단으로, 수 미터에서 수백 미터인 근거리 영역의 노변장치(Road Side Equipment, RSE)와 차량탑재장치(On-Board Equipment, OBE)와의 양방향 고속통신을 수행하는 통신시스템이다. 본 논문에서는 SiGe HBT 공정을 이용하여 근거리무선통신 송신기용 5.8 GHz 상향믹서를 설계 및 제작하였다. 설계된 상향믹서는 믹서코어 회로와 더불어 IF/LO/RF 입출력 정합 회로, IF/LO 입력 발룬 회로와 RF 출력 발룬 회로가 단일칩으로 구현되었다. 제작된 상향믹서는 $2.7 mm\times1.6mm$의 크기를 가지며, 3.5 dB의 전력변환이득과 -12.5 dBm의 OIP3, 42 dB의 LO to E isolation, 38 dB의 LO to RF isolation, 3.0 V의 공급전압 하에서 29 mA의 전류소모로 측정되었다.

• 한국운동역학회지
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• 제25권1호
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• pp.57-64
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• 2015

Purpose : The purpose of this study was to analyze setter toss motion kinematically according to toss types. Method : Dependent variables were elapsed time, vertical displacement of the body center, the projected speed of the ball, and differences of the joint angle to the target for four setters positioning. Result : There was no significant difference in the time but the ball contact time was shorter when the toss distance of P3 was longer. There was significant difference in the vertical displacement of COM (p<.05). The vertical displacement of COM showed that the vertical movement gradually decreased when the quick distance was longer. The vertical displacement of COM was difference (p<.05), also there was difference of the ball speed (p<.001) at the Release point(E4). There was significant difference in the knee joint angle at a certain moment among the Release(E4) and Landing point(E5)(p<.05). The hip joint was significant difference among the Apex(E2), Ball Touch(E3), Release(E4), and the Landing point(E5) on the surface(E2, E3, E4 p<.05; E5 p<.005). The shoulder angle was significant difference among the Ball Touch(E3), Release(E4) and the Landing point(E5) on the surface(E3, E4 p<.05; E5 p<.001). The elbow was significant difference in the Apex(E2) (p<.05). The wrist was significant difference in the Release(E4) (p<.05). Conclusion : If we find the clue to expect the direction of the setter's ball, we have to fine the clues in the Apex(E2) that hip join and elbow, Ball Touch(E3) that hip joint and shoulder joint, Release(E4) that wrist, elbow, hip joint, and knee joint.

• 한국컴퓨터정보학회논문지
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• 제12권3호
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• pp.213-223
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• 2007

본 논문은 인터넷 쇼핑몰 이용자의 성별에 따른 구매 전 지각된 위험과 구매의도에 관한 연구이다. 이를 위해서 인터넷 쇼핑몰 사이트에서의 지각된 위험이 구매의도에 영향을 미치는지 알아보고, 도출 되어진 구매 전 지각된 위험이 성별에 따라 차이가 있는지와 함께 성별에 따른 구매 전 지각된 위험과 구매의도의 관계에 영향력이 있는지를 검증하는 것이 본 연구의 목적이다. 분석 결과, 구매 전 지각된 위험은 경제적 위험, 제품성능위험, 사회적 위험, 기술/시간손실 위험 Privacy 위험의 5가지 요인으로 구성되었다. 먼저 구매 전 지각된 위험이 구매의도에 영향을 미치는지 분석 하였고, 구매 전 지각된 위험이 성별에 따라 차이가 있는지를 분석하였다. 마지막으로 성별에 따른 구매 전 지각된 위험과 구매 의도의 관계가 달라지는지를 분석하였다. 결국 인터넷 쇼핑몰 사이트의 구매 전 지각된 위험은 구매의도에 영향을 미치고 있고, 성별에 따라서도 구매 전 지각된 위험에 차이가 있다는 결과를 보여주고 있다. 이는 인터넷 쇼핑몰을 이용하여 구매하는 구매자들은 위험이라는 인식을 갖고 이용하고 있음을 의미하고 있다.