• 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.

• 대한수학회보
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• 제46권6호
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• pp.1069-1077
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• 2009

In 1984, Oshiro [11] has studied the decomposition of continuous lifting modules. He obtained the following: every continuous lifting module has an indecomposable decomposition. In this paper, we study extending lifting modules. We show that every extending lifting module has an indecomposable decomposition. This result is an expansion of Oshiro's result mentioned above. And we consider some application of this result.

• Kyungpook Mathematical Journal
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• 제46권1호
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• pp.11-18
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• 2006

Let R be a ring with identity and let $M=M_1{\bigoplus}M_2$ be an amply supplemented R-module. Then it is proved that $M_i$ has ($D_1$) and is $M_j-^*ojective$ for $i{\neq}j$, i = 1, 2, if and only if for any coclosed submodule X of M, there exist $M\acute{_1}{\leq}M_1$ and $M\acute{_2}{\leq}M_2$ such that $M=X{\bigoplus}M\acute{_1}{\bigoplus}M\acute{_2}$.

• 마이크로전자및패키징학회지
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• 제23권3호
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• pp.15-20
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• 2016

In an effort to overcome the weakness of aerogel, polymer aerogels have been prepared by copolymerizing the different types of monomers through sol-gel process. Polymerizing the successive phase of a high internal phase emulsion, which has interconnected porous structure, porous polymer aerogel can be manufactured. In this paper, we use the styrene/divinylbenzene chain as a basic monomer structure, and additionally use 2-ethylhexyl methacrylate (2-EHMA) or 2-ethylhexyl acrylate (2-EHA) as monomers for distinguishing the visible mechanical properties of synthesized polymer aerogel. We can observe the different tendency of polymer aerogels by kinds of monomer or ratio. Flexibility and microstructure can be changed by the types of monomer. EHA polymer aerogel shows high flexibility and thin microstructure, and EHMA polymer aerogel shows high hardness and thick microstructure. EHA/EHMA polymer aerogel shows the intermediate nature between them. By utilizing the mechanical properties of three types of polymer aerogels to adequate situation or environment, polymer aerogels could be used as drug agent, ion exchange resin, oil filter and insulator, and so on.

• 정보보호학회논문지
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• 제26권6호
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• pp.1471-1481
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• 2016

최근 IoT에 대한 관심이 급증함에 따라 다양한 IoT 서비스들이 출시되고 있다. 그 중 스마트홈은 사용자의 주거공간에 IoT를 접목함으로써 우리의 생활과 매우 밀접하게 연관되어 있다. 그렇기 때문에, 정당하지 않은 사용자가 스마트홈 내부의 디바이스에 접근한다면, 일상생활과 매우 밀접한 만큼 사용자에게 더 큰 피해를 입힐 수 있다. 예를 들어 스마트홈 내부의 도어락에 인증되지 않은 공격자가 접근하여 명령을 수행할 수 있게 된다면, 주거 침입의 형태로 큰 재산 피해를 입을 수도 있다. 이를 방지하기 위해 본 논문에서는 패스워드 기반의 인증 및 키 교환(PAKE)을 이용하여 사용자와 디바이스가 홈 게이트웨이를 통해 인증과 키 교환을 할 수 있는 3자간 PAKE(3PAKE) 기법을 제안한다.

• 한국콘텐츠학회논문지
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• 제4권4호
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• pp.189-196
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• 2004

최근 ATM스위치를 위한 대부분의 연구는 병렬 하드웨어 자체에 규칙성과 자체 라우팅 특성을 가지는 다단계 상호연결 네트워크에 근거하여왔다. 그러나 네트워크는 동시에 또는 병렬로 전송되지만 서로 충돌을 피찰 수 없다는 측면에서는 블러킹 네트워크라고 할 수 있는데, 주로 밴얀 네트워크가 그 구조에 사용되어왔다. 밴얀 형태의 스위치에 있어서 처리율을 증가시키고, 블러킹을 제거하기 위해서 즉 내부링크의 속도를 증가시키고, 모든 스위치 노드에 버퍼를 두고, 병렬로 다중 연결링크를 두고, 그 네트워크 전에 부하를 균등하게 하는 통 여러 가지 방법들이 사용되어 왔다. 따라서 본 논문에서는 모든 블러킹이 제거되고 하드웨어 복잡도를 향상시키기 위하여 재순환 선플?스체인지 네트워크의 사용을 제안하였다. 이 구성은 하드웨어 복잡도 면에서 한층 단순하여진 구조인 재순환 셔플?스체인지 네트워크와, 동일한 목적지로 전달되는 패킷들에 있어서 우선순위가 결정된 후 순위가 높은 패킷은 다음 네트워크로 보내고, 순위가 낮은 패킷들을 재순환하는 트리구조의 순위 네트워크로 구성된다. 전송된 패킷은 밴얀 네트워크에서 분할 및 합성 알고리즘을 통하여 자체 라우팅 방식으로 최종 목적지에 전송되도록 구성된다. 처리율과 대기 시간 및 버퍼 크기에 따른 패킷의 손실율은 통일한 부하에 따라 각 포트에 도달한 패킷들의 확률을 이항분포로서 적용된다. 이때, $50\%$의 부하 정도면 버퍼 사이즈 $B_{size}=15$이상 즉, 16이면 허용 가능한 손실윤을 나타낸다. 그러므로 본 논문은 하드웨어의 복잡도 측면에서 기존의 바이토닉 정렬기를 재순환 셔플잌스체인지 네트워크로 구성하여 단순화 시켰다.

• 시큐리티연구
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• 제1호
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• pp.351-370
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• 1997

This study concerns possible measures to prevent separatists' terrorist acts against overseas Korean businessmen. Of late, many Korean enterprises are helping a number of foreign countries develop their economy, by building factories and manning regional offices in those countries. But recent development of terrorism especially against Korean businessmen is alarming. This report discusses the need for Korean enterprises heading overseas to prepare themselves with awareness of terrorism and possible protective measures against it, besides their routine pursuance of profits; and for the government and prospective enterprises to refrain from investing in those countries having active separatist movements. If an investment has become inevitable, a careful survey of the region in conflict should be conducted and self-protective measures should be put in place through security information exchange, emergency coordination and training of personnel, etc. This study will first review the past terrorist incidents involving employees of overseas Korean enterprises, and then will focuss on seeking effective measures on the basis of the reported incidents. In carrying out the study, related literature from both home and abroad have been used along with the preliminary materials reported and known on the Internet from recent incidents. 1. The separatist movements of minority groups Lately, minority separatist groups are increasingly resorting to terrorism to draw international attention with the political aim of gaining extended self rule or independence. 2. The state of terrorism against overseas Korean enterprises and Koreans Korean enterprises are now operating businesses, and having their own personnel stationed, in 85 countries including those in South East Asia and Middle East regions. In Sri Lanka, where a Korean enterprise recently became a target of terrorist bombing, there are 75 business firms from Korea and some 700 Korean employees are stationed as of August 1996. A total of 19 different terrorist incidents have taken place against Koreans abroad since 1990. 3. Terrorism preventive measures Terrorism preventive measures are discussed in two ways: measures by the government and by the enterprises. ${\blacktriangleleft}$ Measures by the government - Possible measures at governmental level can include collection and dissemination of terrorist activity information. Emphasis should be given to the information on North Korean activities in particular. ${\blacktriangleleft}$ Measures by individual enterprises - Organizational security plan must be established by individual enterprises and there should also be an increase of security budget. A reason for reluctant effort toward positive security plan is the perception that the security budget is not immediately linked to an increment of profit gain. Ensuring safety for overseas personnel is a fundamental obligation of an enterprise. Consultation and information exchange on security plan, and an emergency support system at a threat to security must be sought after and implemented. 4. Conclusion Today's terrorism varies widely depending on reasons and causes, and its means has become increasingly informationalized and scientific as well while its method is becoming more clandestine and violent. Terrorist organizations are increasingly aiming at enterprises for acquisition of budgets needed for their activities. Korean enterprises have extended their business realm to foreign countries since 1970, exposing themselves to terrorism. Enterprises and their employees, therefore, should establish their own security measures on the one hand while the government must provide general measures, on the other, for the protection of the life and property of Korean residents abroad from terrorist attacks. In this regard, set-up of a counter terrorist organization that coordinates the efforts of government authorities in various levels in planning and executing counter terrorist measures is desired. Since 1965, when the hostile North Korea began to step up its terrorist activities against South Koreans, there have been 7 different occasions of assassination attempt on South Korean presidents and some 500 cases of various kidnappings and attempted kidnappings. North Korea, nervous over the continued economic growth and social stabilization of South Korea, is now concentrating its efforts in the destruction and deterioration of the national power of South Korea for its earlier realization of reunification by force. The possibility of North Korean terrorism can be divided into external terrorist acts and internal terrorist acts depending on the nationality of the terrorists it uses. The external terrorist acts include those committed directly by North Korean agents in South Korea and abroad and those committed by dissident Koreans, hired Korean residents, or international professionals or independent international terrorists bought or instigated by North Korea. To protect the life and property of Korean enterprises and their employees abroad from the threat of terrorism, the government's administrative support and the organizational efforts of enterprises should necessarily be directed toward the planning of proper security measures and training of employees. Also, proper actions should be taken against possible terrorist acts toward Korean business employees abroad as long as there are ongoing hostilities from minority groups against their governments.