• 대한수학회보
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• 제53권2호
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• pp.441-460
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• 2016

We introduce the notions of h-v-semi-slant submersions and almost h-v-semi-slant submersions from almost quaternionic Hermitian manifolds onto Riemannian manifolds. We obtain characterizations, investigate the integrability of distributions, the geometry of foliations, and a decomposition theorem. We find a condition for such submersions to be totally geodesic. We also obtain an inequality of a h-v-semi-slant submersion in terms of squared mean curvature, scalar curvature, and h-v-semi-slant angle. Finally, we give examples of such maps.

• 대한수학회보
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• 제58권3호
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• pp.637-657
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• 2021

In this paper, we decompose (under unitary similarity) the Kronecker sum A ⊞ A (= A ⊗ I + I ⊗ A) into a direct sum of irreducible matrices, when A is a 3×3 matrix. As a consequence we identify 𝒦(A⊞A) as the direct sum of several full matrix algebras as predicted by Artin-Wedderburn theorem, where 𝒦(T) is the unital algebra generated by Tand T^*.

• 대한수학회논문집
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• 제36권1호
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• pp.173-187
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• 2021

In this paper, we deal with the notion of a v-semi-slant submersion from an almost Hermitian manifold onto a Riemannian manifold. We investigate the integrability of distributions, the geometry of foliations, and a decomposition theorem. Given such a map with totally umbilical fibers, we have a condition for the fibers of the map to be minimal. We also obtain an inequality of a proper v-semi-slant submersion in terms of squared mean curvature, scalar curvature, and a v-semi-slant angle. Moreover, we give some examples of such maps and some open problems.

• 대한원격탐사학회지
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• 제25권6호
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• pp.531-546
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• 2009

The main objective of this study is to analyse the polarimetric characteristics of the various terrain targets by ground-based polarimetric SAR system and to confirm the compatible and effective polarimetric analysis method to reveal the polarization properties of different terrain targets by the GB-SAR. The fully polarimetric GB-SAR data with HH, HV, VH, and VV components were focused using the Deramp-FFT (DF) algorithm. The focused GB-SAR images were processed by the H/A/$\alpha$ polarimetric decomposition and the combined H/$\alpha$ or H/A/$\alpha$ and Wishart classification method. The segmented image and distribution graphs in H/$\alpha$ plane using Cloude and Pottier's method showed a reliable result that this quad-polarization GB-SAR data could be useful to classified corresponding scattering mechanism. The H/$\alpha$-Wishart and H/A/$\alpha$-Wishart classification results showed that a natural media and an artificial target were discriminated by the combined classification, in particular, after applying multi-looking and the Lee refined speckle filter.

• 정보보호학회논문지
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• 제13권2호
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• pp.127-132
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• 2003

Cryptosystems have received very much attention in recent years as importance of information security is increased. Most of Cryptosystems are defined over finite or Galois fields GF($2^m$) . In particular, the finite field GF($2^m$) is mainly used in public-key cryptosystems. These cryptosystems are constructed over finite field arithmetics, such as addition, subtraction, multiplication, and multiplicative inversion defined over GF($2^m$) . Hence, to implement these cryptosystems efficiently, it is important to carry out these operations defined over GF($2^m$) fast. Among these operations, since multiplicative inversion is much more time-consuming than other operations, it has become the object of lots of investigation. Recently, many methods for computing multiplicative inverses at hi호 speed has been proposed. These methods are based on format's theorem, and reduce the number of required multiplication using normal bases over GF($2^m$) . The method proposed by Itoh and Tsujii[2] among these methods reduced the required number of times of multiplication to O( log m) Also, some methods which improved the Itoh and Tsujii's method were proposed, but these methods have some problems such as complicated decomposition processes. In practical applications, m is frequently selected as a power of 2. In this parer, we propose a fast method for computing multiplicative inverses in GF($2^m$) , where m = ($2^n$) . Our method requires fewer ultiplications than the Itoh and Tsujii's method, and the decomposition process is simpler than other proposed methods.

• 한국인터넷방송통신학회논문지
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• 제17권6호
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• pp.69-78
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• 2017

5G 스마트폰의 샤논과 신호처리의 푸리에가 표본화정리(최고 주파수의 2배분1 즉, $\frac{1}{2f_n}=T$)에서 만난다. 본 논문에서는 초기 샤논 정리가 Point-to-Point에서 샤논 용량을 구했지만 5G는 Multi point MIMO로 기술이 발전했음을 Relay 채널에서 보인다. 푸리에 변환은 고정매개변수로 신호처리를 했는데, 멀티미디어 시대에 2N-1 다변수인 푸리에-Jacket 변환을 제안해서 성능을 분석했다. 이 연구에서 저자는 시간 계산 측면에서 프리 코딩 / 디코딩 복잡성을 줄이기위한 Jacket 기반의 빠른 방법을 제안함으로써 신호 처리의 복잡성 문제를 해결한다. 재킷 변환은 신호 처리 및 코딩 이론에서 응용 프로그램을 찾는 것으로 나타냈다. 재킷 변환은 속성 $AA^{\dot{+}}=nl_n$이 있는 필드 F에 대해 $n{\times}n$ 행렬 $A=(a_{jk})$로 정의되며, 여기서 $A^{\dot{+}}$는 A의 원소 역행렬의 전치 행렬, 즉 $A^{\dot{+}}=(a^{-1}_{kj})$이며, 이는 변환을 일반화하고 중심 가중 변환, 특히 재킷 변환 특성을 이용하여, 저자는 전송 기반의 중계 기반 DF 협동 무선 네트워크에서 분산 다중 입력 다중 출력 채널의 프리 코딩 및 디코딩에 적용하여 새로운 고유치 분해 (EVD : eigenvalue decomposition) 방법을 제안한다. 단일 심볼 디코딩 가능한 시공간 블록 코드를 사용한다. 본 논문은은 제안 된 Jacket 기반 EVD 방법이 기존의 EVD 방법에 비해 계산 시간이 현저히 단축되었다. 계산 시간 단축과 관련된 성능은 수학적 분석 및 수치결과를 통해 정량적으로 평가했다.

• Korea-Australia Rheology Journal
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• 제18권2호
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• pp.91-98
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• 2006

We compare FT (Fourier Transform) and SD (Stress Decomposition), the interpretation methods for LAOS (Large Amplitude Oscillatory Shear). Although the two methods are equivalent in mathematics. they are significantly different in numerical procedures. Precision of FT greatly depends on sampling rate and length of data because FT of experimental data is the discrete version of Fourier integral theorem. FT inevitably involves unnecessary frequencies which must not appear in LAOS. On the other hand, SD is free from the problems from which FT suffers, because SD involves only odd harmonics of primary frequency. SD is based on two axioms on shear stress: [1] shear stress is a sufficiently smooth function of strain and its time derivatives; [2] shear stress satisfies macroscopic time-reversal symmetry. In this paper, we compared numerical aspects of the two interpretation methods for LAOS.

• 대한수학회보
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• 제26권2호
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• pp.109-114
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• 1989

This paper deals with the classifying spaces of finite groups. To any finite group G we associate a space BG with the property that .pi.$_{1}$(BG)=G, .pi.$_{i}$ (BG)=0 for i>1. BG is called the classifying space of G. Consider the problem of finding a stable splitting BG= $X_{1}$$^{V}$ $X_{1}$$^{V}$..$^{V}$ $X_{n}$ localized at pp. Ideally the $X_{i}$ 's are indecomposable, thus displaying the homotopy type of BG in the simplest terms. Such a decomposition naturally splits $H^{*}$(BG). The main purpose of this paper is to give the classification theorem in stable homotopy theory for groups with periodic cohomology i.e. cyclic Sylow p-subgroups for p an odd prime and to calculate some universal stable element. In this paper, all cohomology groups are with Z/p-coefficients and p is an odd prime.prime.

• 대한수학회보
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• 제45권1호
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• pp.59-66
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• 2008

Keskin and Harmanci defined the family B(M,X) = ${A{\leq}M|{\exists}Y{\leq}X,{\exists}f{\in}Hom_R(M,X/Y),\;Ker\;f/A{\ll}M/A}$. And Orhan and Keskin generalized projective modules via the class B(M, X). In this note we introduce X-local summands and X-hollow modules via the class B(M, X). Let R be a right perfect ring and let M be an X-lifting module. We prove that if every co-closed submodule of any projective module P contains Rad(P), then M has an indecomposable decomposition. This result is a generalization of Kuratomi and Chang's result [9, Theorem 3.4]. Let X be an R-module. We also prove that for an X-hollow module H such that every non-zero direct summand K of H with $K{\in}B$(H, X), if $H{\oplus}H$ has the internal exchange property, then H has a local endomorphism ring.

• Kyungpook Mathematical Journal
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• 제58권1호
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• pp.91-103
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• 2018

In this paper, we generalize the concept of deferred density to that of deferred f-density, where f is an unbounded modulus and introduce a new non-matrix convergence method, namely deferred f-statistical convergence or $S^f_{p,q}$-convergence. Apart from studying the $K{\ddot{o}}the$-Toeplitz duals of $S^f_{p,q}$, the space of deferred f-statistically convergent sequences, a decomposition theorem is also established. We also introduce a notion of strongly deferred $Ces{\grave{a}}ro$ summable sequences defined by modulus f and investigate the relationship between deferred f-statistical convergence and strongly deferred $Ces{\grave{a}}ro$ summable sequences defined by f.