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객체 지향 데이타 모델에서 중첩 장기 트랜잭션 환경에 관한 연구
金淇龍,高進光 弘益大學校 科學技術硏究所 1993 科學技術硏究論文集 Vol.3 No.-
The traditional transaction concept is very useful because it hides the effects of failures and concurrent processing from the programmer. It has been very effective in areas such as airline reservations, car rentals and electronic funds transfer. Transactions for these applications are generally simple, and are characterized by short duration in the sense that they will generally finish within minutes(most probably within seconds). Recently however, there has been widespread use of databases in advanced (non-traditional) applications. It has been found that the traditional transaction concept has limited applicability in many of these in advanced applications. For example, in CAD/CAM, office automation, publication environments and software development environments, transactions are usually very complex, needs to acess many data items and reside in the system for a long duration. Transactions of this kind are usually called long-lived transactions In this paper, we first review three model of advanced transaction, that is long duration transaction, nested transaction, cooperative transaction. And, we review a model of CAD transactions which allows a group of cooperating designers to arrive at a complex design without being forced to wait over a long duration, and which also allows a group of designers to collaborate on a design with another group by assigning subtasks.
SMS와 PDA를 이용한 원격지 시스템 접속 구현 및 성능비교
김진광(Jin-Gwang Kim),최동출(Dong-Chul Choi),고진광(Jin-Gwang Koh),배상현(Sang-Hyun Bae) 한국정보과학회 영남지부 2004 한국정보과학회 영남지부 학술발표논문집 Vol.12 No.1
시스템 관리자가 장애 사실을 알게 되는 경우는 콘솔의 장애 알림을 확인하는 경우와 사용자에 의한 장애 발생 보고에 의해서 확인할 수 있다. 실질적으로 관리자는 장애 및 경고 발생 시 곧바로 알게 되는 경우는 빈도가 낮다. 대부분의 경우는 관리자가 시스템과 원거리에 있거나 개인 용무로 시스템 장애를 인지하지 못할 경우이다. 시스템에 장애 발생시 SMS을 통하여 장애 내용을 인지한 후 관리 대상 시스템과 원거리에 위치했다면 해당 시스템의 고장진단 및 장애 처리를 위하여 PDA를 통해 해당 서버에 접속하고 일반적인 서버 관리와 SMS에 의한 장애 인지 후 PDA를 이용한 무선 접속을 통해 장애 처리 하는 경우에 대하여 비교 분석한다. 본 논문에서 구현된 시스템은 시간과 장소에 구애 받지 않고 여러 대의 시스템을 효율적으로 운용하는데 도움을 줄 수 있다.
분산 데이터베이스 환경에서 데이터 상호 관련성을 고려한 죠인 연산의 비용 최소화
고진광,윤홍상,이현창 순천대학교 기초과학연구소 1997 基礎科學硏究誌 Vol.8 No.-
Query Processing for information retrieval in distributed database environment plans and executes the priority of join operation of respond to user's request. But it cannot ignore overhead for processing the priority of join operation In this paper, we measure the cost of join operation, changing the size of relation, and decide a suitable relation size for join operation to reduce overhead for processing the priority. Also, this work generates new relations involved data with relationship to reduce join frequency between original relations existed in different sites. A lot of new relations may be generated and it is hard to select a relation among them needed to user's request. Therefore we demonstrate a method to select a relation with a appropriate size obtained through simulation. Relation selected is able to reduce the cost of join operation and process a rapid response for user request. As a result, a selected relation may be a appropriate relation to any query.
분산 데이타베이스에서 질의 최적화를 위한 단편화 릴레이션간의 세미-죠인
고진광,고병오,이준 順天大學校 1991 論文集 Vol.10 No.1
Semi-join is a widely used join operation during query processing in distributed databases. Numerous algorithms were introduced previously that decide the order of a semi-join operation in the referenced relations of a given query. Thses algorithms bear important research topic that determine how we can minimize the transmission cost of a semi-join operation for two given relation. This paper proposes a strategy that process the semi-join operation between fragmented relations in distributed database query processing. In the proposed alsorithm introduced in this paper the following enhancements are made. In the case of horizontally fragmented relations, an earlier known method suggested by Yu & Chang is expanded as follows. The weight for each distributed site is redefined and it generalizes Yu & Chang's algorithm to be applied universally. In the case of vertically fragmented relations, without restructuring each fragment, the join attribute is sent to one suitable site, which is selected, and the reduced key attribute of the fragment of that site is then sent to the other site that contains the vertical fragment. Comparison of transmission cost of the proposed method and the previous known methods selected for performance comparison demonstrates that the method proposed in this paper is more efficient than the previous known algorithms. We believe that the proposed algorithm can contribute in optimization of queries, particularly the efficient processing of the semi-join operation, in distributed query processing.
고진광,고병오,박대식 순천대학교 기초과학연구소 1992 基礎科學硏究誌 Vol.3 No.-
DBMS offers information to users which is stored in database. Therefore, DBMS does not provide users with needed informations unless it is stored in database. This paper studies adding inferential facility to informix existing relational DBMS, designs and implements IFES(Inferential Front-end System) to provide wider and more accurate information. TBKEY(Table Key) table and RNT(Relation Name Table) are also stored in IDB to support inferential facility. TBKEY table contains name of certain database and key attribute of the relation and RNT contains name of database and name of head and body tables related with the relation. And it is possible for informix to manage these tables. This paper puts emphasis on storing tables of IDB in informix not in the form of file but in the form of relation like existing database.
Jumping on water: Surface tension–dominated jumping of water striders and robotic insects
Koh, Je-Sung,Yang, Eunjin,Jung, Gwang-Pil,Jung, Sun-Pill,Son, Jae Hak,Lee, Sang-Im,Jablonski, Piotr G.,Wood, Robert J.,Kim, Ho-Young,Cho, Kyu-Jin American Association for the Advancement of Scienc 2015 Science Vol.349 No.6247
<P>Jumping on water is a unique locomotion mode found in semi-aquatic arthropods, such as water striders. To reproduce this feat in a surface tension-dominant jumping robot, we elucidated the hydrodynamics involved and applied them to develop a bio-inspired impulsive mechanism that maximizes momentum transfer to water. We found that water striders rotate the curved tips of their legs inward at a relatively low descending velocity with a force just below that required to break the water surface (144 millinewtons/meter). We built a 68-milligram at-scale jumping robotic insect and verified that it jumps on water with maximum momentum transfer. The results suggest an understanding of the hydrodynamic phenomena used by semi-aquatic arthropods during water jumping and prescribe a method for reproducing these capabilities in artificial systems.</P>
Underactuated Adaptive Gripper Using Flexural Buckling
Gwang-Pil Jung,Je-Sung Koh,Kyu-Jin Cho IEEE 2013 IEEE TRANSACTIONS ON ROBOTICS Vol.29 No.6
<P>In gripping devices, adapting to highly unstructured environments such as irregularly shaped objects and surfaces continues to be challenging. To achieve safe and reliable gripping, many researchers have employed various underactuated mechanisms such as differential and compliant mechanisms. All these mechanisms have demonstrated successful gripping performances. They, however, have hardly considered scalability issues of underactuated mechanisms originating from additional force transmissions and onerous mechanism assembly. In this paper, we propose a structurally simple and scalable underactuated mechanism. The mechanism is demonstrated on a gripping device called the “Buckling gripper.” The Buckling gripper achieves adaptive gripping on rugged, uneven, and undulating surfaces typically found in the natural world. The key design principle of the Buckling gripper is inspired by a caterpillar's proleg that highly deforms depending on the shape of the contact surface. This key principle is applied to the gripper via flexural buckling. Normally, buckling is avoided in mechanical designs, but the buckling behavior of a flexure with an adequately selected length provides wide gripping range with a narrow range of force variation, which provides a sufficient number of contacts with even contact forces. As a result, the Buckling gripper achieves adaptive gripping on various surfaces, similar to a caterpillar.</P>