A Survey on IEEE 802.11 MAC Analytical Modeling for MAC Performance Evaluation

Heo, Ung,Yu, Changfang,You, Kang-Soo,Choi, Jae-Ho The Korea Institute of Convergence Signal Processi 2011 융합신호처리학회 논문지 (JISPS) Vol.12 No.2

The paper surveys various analytical models for IEEE 802.11 medium access control protocols and critically discusses recent issues developing in wireless mobile ad hoc networks and their MACs. The surveyed MAC protocols include the standard IEEE 802.11 MAC suites such as IEEE 802.11 DCF, IEEE 802.11 PCF, IEEE 802.11e EDCA, and IEEE 802.11 ad hoc mode; and also the newer, de facto MAC protocols. We study the analytic models of the standard MAC suites followed by the newer analytic models that have been published in recent years. Also, the paper tries to include most of current literatures discussing analytic modeling of MAC in conjunction to some critical issues such as contention among ad hoc nodes, hidden terminal problems, and real-time service support.

전자상거래에 관한 연구

姜興中 건국대학교 사회정책연구소 1998 사회과학연구 Vol.9 No.-

일정한 보강섬유 굴곡이 있는 두꺼운 복합재료에서의 초음파 전파에 관한 연구

전흥재,장필성 한국비파괴검사학회 2001 한국비파괴검사학회지 Vol.21 No.3

복합재료는 우수란 재료특성을 가지고 있어 기존의 금속 재료를 대신하여 많은 분야에서 사용되고 있다. 최근 들어서 큰 하중을 받는 구조재로 사용이 확대되면서 많은 수의 복합재료 단일층을 두껍게 적층한 두꺼운 복합재료의 사용이 늘어나고 있다. 복합재료를 두껍게 적층하는 경우 성형과정 중에 보강섬유 굴곡이 발생하기 쉬운데 두꺼운 복합재료 내에 발생한 보강섬유의 굴곡은 강성 및 강도를 감소시켜 구조물의 안정성을 저하시킨다. 따라서 두꺼운 복합재료로 만들어진 구조물에 내재된 보강섬유 굴곡의 유무나 정도를 알아내는 것은 안정성 확보를 위해 매우 중요하다. 본 연구에서는 초음파를 이용한 비파괴 평가를 위해 굴곡진 보강섬유를 가진 복합재료 내에서 초음파 전파 특성에 대한 연구를 수행하였다. 여러 가지 일정한 굴곡비의 보강섬유 굴곡을 가지는 두꺼운 복합재료에 대해서, 평면파(plan wave) 이론과 파선 추적(ray tracing) 이론을 이용한 수치 해석 방법으로 초음파 전파에서 보강섬유의 굴곡의 영향을 예측하고, 보강섬유의 굴곡비를 가지는 복합재료 시편을 제작하여, 초음파 투과법(through-transmission) 시험을 수행하였다. 이를 통해 일정한 보강섬유의 굴곡을 가지는 복합재료 내의 초음파 전파 특성과, 보강섬유의 굴곡 정도에 따른 초음파 전파 특성의 변화를 이론적으로 얻어진 결과와 비교하여 두꺼운 복합재료 내에 존재하는 보강섬유의 굴곡이 초음파 전파에 미치는 영향을 알 수 있었다. There has been a growing interest in thick composite materials especially for primary structures. Fiber waviness is one of the manufacturing defects frequently encountered in thick composite structures and affects the mechanical properties such as stiffness and strength significantly. Therefore, nondestructive evaluation technique that can detect fiber waviness of thick composite is very important for the integrity of structures. In this study, efforts were made to understand ultrasonic wave propagation in thick composites with uniform fiber waviness by adopting the ray and plane wave theories. Both theoretical and experimental investigations were conducted to understand the wave propagation in thick composites with uniform fiber waviness. The experiments were conducted through-transmission method to verify the predicted results. The experimental results showed good agreement with the theoretical predictions.

중심위 교합채득 방법에 따른 하악과두의 상대적 위치와 재현도 비교에 관한 연구

문흥엽,황현식 대한치과교정학회 1994 대한치과교정학회지 Vol.24 No.4

In the past, the jaw and occlusal relationship in centric occlusion were merely considered in case of orthodontic diagnosis and treatment planning. As the fact that functional disturbance of the temporomandibular joint may be caused by occlusal interference was recognized, the importance of functional occlusion and centric relation is emphasized today. Known the importance of centric relation, there are various opinions about definition of centric relation and its taking methods. The purpose of this study was to investigate the relative centric condyle position and to compare the reproducibility of the recordings utilizing different centric relation records obtained by different taking methods. The15 adults with normal occlusion were participated in this study. Every four centric relation records were taken in each of three methods - leaf gauge, Dawson and myomonitor method. Then the relative centric condyle position, the distance between the condylar position in centric occlusion and the position in centric relation and the reproducibility were studied using SAM 2 articulator and mandibular position indicator. The results were as follows ; 1. The trend of condyle position was different depending on centric relation taking methods. 2. The position of condyle in centric relation by leaf gauge and Dawson methods was superior to that by myomonitor method, and the position by myomonitor method, was relatively antero-inferior. 3. The distance between the condylar positions in centric occlusion and the position in centric relation was longest in myomonitor method. 4. The reproducibility had little differences in transverse direction among three methods, while leaf gauge method showed the highest reproducibility and myomonitor method did the lowest reproducibility in antero-posterior and supero-inferior direction.

우리나라의 海外資原 開發輸入現況과 當面課題 : 鑛物資原을 中心으로 Based on the mineral resource

姜興中 건국대학교 1984 論文集 Vol.19 No.1

International resource crises never happened only recently, it has already took place from 1960's since that we have experienced the enlargement of the East-West trade and miltilateral trade, which is products that was occured according to the South-North trade. In 1973, when the U.S. had controlled her staple agriculture pro products and forty-one items of export, the resource crises of the whole world had begun. To make us more miserable, as the Middle East had started the war and the Arabs had regareded petroleum as their arms, international economic rules had been upset. Futhermore, each country that have her own resources have cnanged how to protect her resources from that time to now, for each country is over-protecting her resources under name of the resource nationalism. These days our which almost depend on foreigns the raw materials for export is deeply recognizing this problems. Therefore we lave to study this problems considering the reinforcement of foreign competitive power for export goods, and then thoroughly inquire and analyses the import system of developed foreign resource in advanced countries, we lave to consolidate suitable system to us. This thesis which is written according to the view of the above, is prescribed ideas of resource, and limit of development import, is analysised the actual results and present condition of foreign resource, is shown the new direction to the import of development foreign resource system in our country now.

우리나라 국민기초생활보장제도 활성화에 관한 이론적 고찰

박민서,임흥수 목포대학교 복지사회연구소 2000 福祉社會硏究 Vol.3 No.-

대구·경북 지방자치단체의 중소기업지원 현황과 개선방안

전경태,임흥식 啓明大學校 産業經營硏究所 2003 經營經濟 Vol.36 No.2

The purpose of this study is to investigate some problems and seek out positive solutions for SMEs industry in Daegu City and Gyeongsangbuk-Do. There are a variety of problems affecting the SMEs industry; small scale business management, weak product competitiveness, weak financial chronic structure, low manufacturing techniques and equipment underdevelopment, lack of countermeasures for the information age, lack of special marketing strategy and labour, production system problem, etc. To solve these hardships affecting SMEs industry in Daegu City and Gyeongsangbuk-Do, firms and regional government should focus on the development of the high value-added products, business rationalization, purchasing extensions for products, improvement of the financial support and marketing systems, initiate a flexible production system, support technological development, develop a government support system for the transition of information, prepare for new world trade system, assist in quality control, standard distribution system and adapt an efficient industrial structure and internet trade center. It is necessary to build small but well-built firms.

동북아지역자치단체간 경제협력방안에 대한 연구 : Focusing on "NEAR(North East Asia Regional Government Association)"

전경태,임홍식 계명대학교 국제학연구소 2004 국제학논총 Vol.9 No.-

Multilateralism, which has been discussed in the switchover of GATT to WTO, is turning rapidly toward regionalism and FTA (Free Trade Agreement). Close cooperation in the field of economy, society, and culture functions as the foundation of economic growth. Development from an industrial society to an intellectual society, IT (Information Technology) revolution, and internationalism driven by WTO has universalized globalization. Under the circumstances, it is expected that international commerce expands into non-commercial products like service and labor. Regional economic cooperation including NAFTA, EU, and MERCOSUR has been fashionable in the recent international economy. World economic order is thus reorganized focusing an united regional economic cooperation. Also, formations of the world market and regional economic cooperation are accelerated by global market and regionalism, which are main but contrary axes of WTO. In Northeast Asian region, Chinese economy is being rapidly developed, Russia is trying to establish its position for own purposes, and Japanese economy is turning around. Also, we are seeking new paradigm to develop our economy. Under the circumstances, united economic cooperation in Northeast Asia is becoming increasingly important. However, pertinent nations do not take a positive attitude toward the cooperation, because their own purposes are different each other. In Northeast Asian region, many nations are interested in economic cooperation due to doubt for WTO talks and APEC role, emerging regional economic cooperation like EU and NAFTA, and Asian financial crisis. The nations are propelling FTA for economic, political, and diplomatic benefits. Regional economic cooperation becomes an indispensable subject in the economic circumstance for the 21st century. Nevertheless, united economic cooperation in Northeast Asia falls behind in the race with Europe and North America. A new approach to regional economic cooperation is necessary. Northeast Asia retains high potentiality from the cooperation due to geographical adjacency, historical homogeneousness, gigantic market, and related economic factors. The cooperation in Northeast Asian region, which is being discussed, is expected to bring the world's biggest economic bloc regarding population and trade scale. Also, the cooperation may maximize member nations' benefits and bring capability to compete effectively with other economic blocs like EU and NAFTA. New approach and strategy are required to make the Northeast Asian community. The essence is to integrate upward not downward to overcome barriers among member nations such as economic differentials and different political systems. Systematic approach with expanding trade and investment is necessary to achieve the integration.

전처리 환경조건 변화에 의한 국내산 크라프트지의 물리적 특성 평가

김형진,최원정,최형기 한국공업화학회 2003 응용화학 Vol.7 No.2

This study was carried out in order to evaluate the physical properties of domestic kraft paper according to the changes of pre-conditioning environmental conditions. For the testing of physical and mechanical strength of paper, the specimens must be preconditioned under the specific environmental factors, such as temperature and RH. Recently, Korean Industrial Standard is revising for the coincidence with International Standard Organization. In this study, the physical and mechanical properties of kraft paper were considered by the two kinds of standard, KS M7011 and ISO 187, and evaluated by the linear regression equation.

기능적 자기공명 영상법의 이해

서정진,정광우,강형근 全南大醫大 2003 전남의대학술지 Vol.39 No.4