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나카가미 페이딩 채널하에서 MIMO-OFDM 시스템의 성능분석
강경식,김원섭,박춘호,Kang, Kyung-Sik,Kim, Won-Sub,Park, Chun-Ho 한국정보통신학회 2011 한국정보통신학회논문지 Vol.15 No.8
본 논문에서는 주변 환경에 따라 다양한 채널 상태를 나타낼 수 있는 분산형 나카가미 페이딩 채널하에서 선형의 시공간 블록코드 (Space-Time Block Code) 직교 설계로부터 평균 비트 에러율(Bit Error Rate)성능을 평가하여 MIMO(Multiple Input Multiple Output) 채널의 안테나 열 구성과 동작환경의 영향을 분석하였고 향상된 BER을 위한 MT 안테나의 설계조건과 페이딩 지수 m을 제안 한다. 시스템 성능의 분석을 위해 M-PSK(M-ary Phase Shift Keying)변조 방식과, M-QAM(M-ary Quadra -ture Amplitude Modulation)변조 방식을 사용 하였고, 분석 식은 각각 적분된 나카가미 페이딩 변수와 적분되지 않은 나카가미 페이딩 변수로부터 시스템의 성능을 비교 분석하였다. 채널 배열의 구성은 행렬의 수식적 계산에 의해 얻게 되며, AOA 확산이 감소하는 것에 따라 STBC(Space - Time Block Codes) BER성능이 감소하며, 이와 같은 손실은 안테나 간격의 증가나, 배열구성의 변경을 통해 보상 될 수 있다. In this paper, I analyzed array organization of MIMO channel antenna and effect of operation environment by evaluating average BER from linear Space-Time Block Code orthogonal design and suggests designing condition of MT antenna for improved BER and the fading index m. To analyze system performance, I used M-PSK and M-QAM modulation, and to use analysis equations I used integrated by Nakagami fading variable, non-integrated Nakagami fading variable. We can get the organization of channel array by using mathematical calculation on matrix. STBE BER performance will decrease as AOA spreading decrease and such loss can be compensated from extending antenna spacing, and changing array organization.
인지기능에 비만 역설은 존재하는가?: 고령화연구패널자료(2006-2016)를 이용하여
강경식 ( Kyung Sik Kang ),이용재 ( Yongjae Lee ),박소희 ( Sohee Park ),김희진 ( Heejin Kimm ),정우진 ( Woojin Chung ) 한국보건행정학회 2020 보건행정학회지 Vol.30 No.4
Background: There have been many studies on the associations between body mass index (BMI) and cognitive function. However, no study has ever compared the associations across the methods of categorizing BMI. In this study, we aimed to fill the gap in the previous studies and examine whether the obesity paradox is valid in the risk of cognitive function. Methods: Of the 10,254 people aged 45 and older from the Korean Longitudinal Study of Ageing from 2006 to 2016, 8,970 people were finalized as the study population. The dependent variable was whether a person has a normal cognitive function or not, and the independent variables of interest were BMI categorized by the World Health Organization Western Pacific Regional Office (WHO-WPRO) method, the WHO method, and a 10-group method. Covariates included sociodemographic factors, health behavior factors, and health status factors. A generalized linear mixed model analysis with a logit link was used. Results: In the adjusted model with all covariates, first, in the case of BMI categories of the WHO-WPRO method, underweight (odds ratio [OR], 1.16; 95% confidence interval [CI], 1.15-1.17), overweight (OR, 1.36; 95% CI, 1.35-1.36), and obese (OR, 1.34; 95% CI, 1.33-1.34) groups were more likely to have a normal cognitive function than a normal-weight group. Next, in the case of BMI categories of the WHO method, compared to a normal-weight group, underweight (OR, 1.15; 95% CI, 1.14-1.16) and overweight (OR, 1.06; 95% CI, 1.06-1.07) groups were more likely to have a normal cognitive function; however, obese (OR, 0.62; 95% CI, 0.61-0.63) group was less likely to have it. Lastly, in the case of the 10-group method, as BMI increased, the likelihood to have a normal cognitive function changed like a wave, reaching a global top at group-7 (26.5 kg/m<sup>2</sup>≤ BMI <28.0 kg/m<sup>2</sup>). Conclusion: The associations between BMI and cognitive function differed according to how BMI was categorized among people aged 45 and older in Korea, which suggests that cognitive function may be positively associated with BMI in some categories of BMI but negatively in its other categories. Health policies to reduce cognitive impairment need to consider this association between BMI and cognitive function.
화재안전기준(NFSC)에 따른 기계분야 소방설비 설계, 시공, 감리 유지관리 업무 표준화 방안에 대한 제안
김성일,강경식,Kim, Sung-Il,Kang, Kyung-Sik 대한안전경영과학회 2017 대한안전경영과학회지 Vol.19 No.3
The study seeks to cooperate with the investigation of a fire investigation based on public-private partnership. Fire protection systems provide a wide variety of viewpoints from the perspectives of design, construction, management, maintenance, maintenance and maintenance systems at a particular point in time, construction, management, and maintenance systems. What is controversial is that there are illegal activities such as illegal activities of the Patent Office, misconduct of construction work and unreasonable construction of construction works.As a theoretical framework, the present study identified the four key elements of a successful disaster response system : responsiveness, control, professionalism, and bias.
임종철,강경식,Lim, Jong-chul,Kang, Kyung-sik 대한안전경영과학회 2017 대한안전경영과학회지 Vol.19 No.1
Currently, Korea is actually increasing and increasing demand for leisure such as parts for A/S of automobile parts of the car, as well as trends in borrowing and finished parts are also required a steady increase in automobile traffic daetsu. There is one car and want to be driving a car A/S parts supplier smoothly for many years and that it is often the case if it is not supplied in a timely fashion, it is a reality that many eonseong hear from customers. These symptoms can be confirmed that the logistics systems of a system of selling auto parts supplier but above all a problem for several reasons, which will be considered as areas for improvement should be done urgently. Enterprises internally cooperation automotive supplier, but the need to get out to re-examine urgently complemented by the logistics system of systems to allow better respond to complex environmental changes of our customers grow, and now also the proliferation of small ship-run screen and Darvin, there is increasing distribution and logistics services, including logistics costs as a lack of work force that the company is itgetda can be called by the reality that the chances of getting a lot of jeyakreul own growth. Given this situation, the procurement of logistics enterprises. In-house logistics. Classified as sales logistics examined the long-term improvement of logistics distribution networks based on this part to derive into the problems of logistics and parts distribution system of Korean auto parts dealer.
물류센터의 오더픽킹 최적설계를 위한 DPS와 DAS의 생산성 비교
유강철(Kang Chul You),강경식(Kyung Sik Kang),임석철(Suk Chul Rim) 한국SCM학회 2012 한국SCM학회지 Vol.12 No.2
Among the activities in the distribution centers, order picking is regarded as the most time-consuming and costly activity. Digital Picking System(DPS) and Digital Assorting System(DAS) have been widely used as new IT-based order picking system. Despite some similarities, since the two methods require different hardware, layout, and software, it is important to choose the more desirable system earlier in design stage of the distribution centers. However, to the best of our knowledge, there is no research result that supports such an important decision. In this study, we will present a model to compare the productivity between DPS and DAS. We consider the number of customers, number of items, and order volume as the independent variables; and measure the productivity as the average time to complete the picking of the same set of orders using simulation.
SCM을 위한 정보시스템의 확산이 채찍효과에 미치는 영향에 관한 연구
임희택,강경식,Lim, Hee-Taek,Kang, Kyung-sik 대한안전경영과학회 2017 대한안전경영과학회지 Vol.19 No.1
The size of the market for SCM information systems have globally and steadily increased. And there are businesses that obtained innovative business performance by introducing SCM information systems. However, many businesses have still undergone trial and error in the process to introduce and operate SCM. As external factors including suppliers, customers, etc. and internal factors of businesses have been analyzed to be failure factors of executing SCM information systems, the businesses that try to introduce SCM information systems need to understand possible failure factors and establish the solutions. Therefore, this study tries to verify the diffusion of SCM information systems and effects on bullwhip effects. The study is expected to suggest empirical data that people will refer to the establishment of next counterstrategies according to the lapse of the period that systems are introduced based on theoretical bases related to the diffusion of SCM information systems.