• 한국통신학회논문지
• /
• 제39C권7호
• /
• pp.546-551
• /
• 2014

본 논문에서는 릴레이 기반의 선박 통신 네트워크에서 데이터 전송률을 높이기 위한 기회주의적 서브채널 할당기법을 제안한다. 릴레이 시스템을 기반으로 하는 기존 연구에서, 릴레이는 매 프레임마다 기지국으로부터 수신 받은 데이터를 선박에게 즉시 전달 해준다. 이때, 이중 홉 네트워크(기지국과 릴레이, 릴레이와 선박 간 링크)에서 전송 가능한 최대 수율은 두 링크의 채널 상태에 의해 결정된다. 만약, 채널 상태에 따른 두 링크가 가지는 채널 용량의 차이가 크다면 자원이 낭비되는 상황이 발생하게 된다. 이러한 문제점은 시스템의 성능을 저하시키며, 제한된 무선 자원을 효율적으로 활용하지 못하는 문제점이 발생하게 된다. 따라서 본 논문에서는 두 링크 사이에서 발생하는 자원의 낭비를 최소화 시킴과 동시에 자원을 효율적으로 할당 할 수 있는 기법을 제안한다. 또한 제안하는 기법의 계산 복잡도를 줄이기 위해서 차선의 기법을 제안한다. 시뮬레이션 결과를 통해서, 제안하는 기법은 기존 연구 대비 계산의 복잡도는 증가하지만 시스템의 데이터 전송률 성능이 최대 14.0% 향상됨을 확인 할 수 있다.

• Asian Pacific Journal of Cancer Prevention
• /
• 제15권1호
• /
• pp.229-237
• /
• 2014

Background: Dentists are typically the first professionals who are approached to treat ailments within the oral cavity. Therefore they should be well-equipped in detecting suspicious lesions during routine clinical practice. This study determined the levels of knowledge on early signs and risk factors associated with oral cancer and identified which factors influenced dentist participation in prevention and early detection of oral cancer. Materials and Methods: A survey on dentists' knowledge and their practices in prevention and early detection of oral cancer was conducted using a 26-item self-administered questionnaire. Results and Conclusions: A response rate of 41.7% was achieved. The level of knowledge on early signs and risk habits associated with oral cancer was high and the majority reported to have conducted opportunistic screening and advised patients on risk habit cessation. Factors that influenced the dentist in practising prevention and early detection of oral cancer were continuous education on oral cancer, age, nature of practice and recent graduation. Notably, dentists were receptive to further training in the area of oral cancer detection and cessation of risk habits. Taken together, the study demonstrated that the dental clinic is a good avenue to conduct programs on opportunistic screening, and continuous education in these areas is necessary to adequately equip dentists in running these programs. Further, this study also highlighted knowledge deficits and practice shortcomings which will help in planning and developing programs that further encourage better participation of dentists in prevention and early detection of oral cancer.

• 한국정보통신학회논문지
• /
• 제19권5호
• /
• pp.1077-1083
• /
• 2015

본 논문에서는 다중 셀 상향링크 네트워크에서 합 용량을 크게 개선할 수 있는 에너지 효율적 기회적 간섭 정렬 기술을 소개한다. 각 사용자는 요구되는 신호 질을 만족하면서 타 셀 기지국에게 발생하는 간섭량을 최소화하는 측면에서 최적의 송신 벡터 설계 및 전력 제어를 수행한다. 주요 결과로써, 줄어든 간섭 레벨로 인하여 제안하는 기회적 간섭 정렬 기술은 전력 제어가 없는 기존 기회적 간섭 정렬보다 대부분의 신호 대 잡음 비 영역에서 더욱 높은 합 용량을 취득할 수 있음을 보인다. 뿐만 아니라, 제안하는 기회적 간섭 정렬 기술과 함께 수신 단에서 zero-forcing 검파 및 minimum mean square error (MMSE) 검파기를 사용할 경우 둘 사이 성능 비교를 수행하고, MMSE 검파 기반 기회적 간섭 정렬 기술이 우수한 성능을 취득할 수 있음을 보인다.

• 한국통신학회논문지
• /
• 제31권8A호
• /
• pp.798-803
• /
• 2006

다중사용자 다중입출력 시스템에서 채널 적응 기술을 사용하면 시스템의 통신용량을 증가시킬 수 있다. 하지만 이를 위해서는 많은 양의 사용자 채널품질 정보가 송신 단에 되돌림 되어야 한다. 다중사용자 다중입출력 시스템으로 기존에 제안된 per user unitary and rate control(PU2RC)는 사전코딩(preceding) 정보와 그때의 채널품질정보가 요구되며, 스케줄링의 효율이 떨어지는 단점이 있었다. 이러한 단점을 극복하기 위하여 본 논문에서는 되돌림 정보량 줄이는 새로운 방법을 제안한다. 제안된 기법은 미리 알려진 사전코딩행렬을 사용하고 사용자의 채널상황에 따라 선택적 되돌림(opportunistic feedback) 방법을 사용한다. 모의실험을 통하여 제안된 기법이 기존의 PU2RC 대비 훨씬 적은양의 되돌림 정보량으로 비슷한 통신용량 성능을 보장함을 보인다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제12권10호
• /
• pp.4662-4677
• /
• 2018

The dynamic opportunistic device-to-device (DO-D2D) network will frequently emerge in the fifth generation (5G) wireless communication due to high-density and fast-moving mobile devices. In order to improve the Quality of Experience (QoE) of users with different computing capacity devices in the DO-D2D network, in this paper, we focus on the study of how to reduce the packets retransmission delay and satisfy heterogeneous devices. To select as many devices as possible to transmit simultaneously without interference, the concurrent transmitters-selecting algorithm is firstly put forward. It jointly considers the number of packets successfully received by each device and the device's connectivity. Then, to satisfy different devices' demands while primarily ensuring the base-layer packets successfully received by all the devices, the layer-cooperation instantly decodable network coding is presented, which is used to select transmission packets combination for each transmitter. Simulation results illustrate that there is an appreciable retransmission delay gain especially in the poor channel quality network compared to the traditional base-station (BS) retransmission algorithm. In addition, our proposed algorithms perform well to satisfy the different demands of users with heterogeneous devices.

• 한국인터넷방송통신학회논문지
• /
• 제16권1호
• /
• pp.61-67
• /
• 2016

기회전송 증가 릴레이 시스템은 무선채널의 페이딩을 효과적으로 극복하고 무선 자원을 효율적으로 사용할 수 있는 장점을 갖는다. 그러나 지금까지 기회전송 증가 릴레이 시스템 연구에서는 릴레이의 위치가 공간적으로 고정되어 있는 것을 가정하였다. 일반적으로 모바일 환경에서는 사용자 터미널이 릴레이로 사용되는데, 사용자 터미널은 계속해서 움직이기 때문에 고정된 릴레이를 가정하는 것은 현실적이지 않다. 따라서 본 논문은 공간적으로 랜덤하게 분포된 사용자 터미널의 위치를 포아송 포인트 프로세스 (Poisson point process)로 모델링하고, 기회전송 증가 릴레이 시스템의 성능을 유도하였다. 유도 결과 릴레이가 랜덤하게 분포된 경우에도 릴레이가 고정된 경우와 마찬가지로 시스템의 성능이 향상되었으며, 릴레이의 밀도와 송수신 각도가 시스템의 성능에 영향을 주는 것을 알 수 있었다. 또한 최대비 결합과 선택결합 수신방법에 따른 시스템의 성능을 비교하였다.

• Asian Pacific Journal of Cancer Prevention
• /
• 제14권9호
• /
• pp.5101-5105
• /
• 2013

The incidence and mortality of cervical cancer remains high in India even after sixty years of introduction of the Pap smear (cervical cytology) which is an effective means of identifying preinvasive lesions of carcinoma cervix. The morbidity and mortality due to cervical cancer has come down drastically in countries with well established screening programmes at national level. This study aims at screening women for cervical cancer opportunistically during their visit to hospital and to study various types of neoplastic and non-neoplastic lesions of the cervix by cervical smear study (Pap smear study). In the present study, a total of 350 cervical smears were studied. The age of patients ranged from 19 years to 80 years with mean age being 37.5 years. Out of 350 cases, the diagnosis of neoplasia was given in 43 cases and 258 cases were diagnosed as inflammatory smears. Forty-cases were normal and 9 cases were inadequate to evaluate. Forty-three patients who were found to have neoplastic lesions on cytology were referred for further investigations like colposcopy and biopsy to confirm the diagnosis and avail proper treatment. Limitation of the present study was small sample size as all female patients aged between 20 and 60 years visiting hospital were not included in the screening, other screening tests like VIA (visual inspection with acetic acid test) and HPV DNA (human papilloma virus) tests were not done. Until the time centrally organised screening programmes for cervical cancer are established in India, arrangements should be made for hospital based opportunistic screening for all women attending hospital. The cost effectiveness of different screening tests for cervical cancer should be evaluated.

• 한국의류학회지
• /
• 제33권2호
• /
• pp.244-255
• /
• 2009

The purpose of this study was 1) to inquire into characteristics of apparel manufacturers and distributors in China, 2) to classify private Guanxi and organizational relationship type, 3) to find differences in private Guanxi to enterprise type and the class of participations' position, and 4) to also find effects of private Guanxi on organizational relationship. Apparel manufacturers and distributors in China participated in the study. Random sampling method was used to collect the data. Data from 173 questionnaires were used for the statistical analysis. Descriptive analysis, factor analysis, Cronbach's alpha coefficient, t-test, and regression analysis were conducted. Two factors of private Guanxi were classified(i.e., affective Guanxi, instrumental Guanxi). Three factors of organizational relationship type were identified(i.e., opportunistic relationship, cooperative relationship, vertical relationship). The results indicated that distributors regarded affective Guanxi as important more than manufactures and employees regarded affective Guanxi and instrumental Guanxi as important more than presidents. Distributors regarded cooperative relationship as important more than manufactures. Employees regarded organizational relationship as important more than presidents. Affective Guanxi positively affected on cooperative relationship and vertical relationship but negatively affected on opportunistic relationship. Instrumental Guanxi positively affected on opportunistic relationship and vertical relationship. The result of this study may give valuable information to retail merchandisers and strategists who participated in fashion business in China.

• Tuberculosis and Respiratory Diseases
• /
• 제45권2호
• /
• pp.465-469
• /
• 1998

저자들은 악성 임파종의 항암요법후 갑자기 진행되는 폐침윤(ground glass & consolidation) 소견을 보인 Pneumocystis carinii(PCP)와 Cytomegalovirus(CMV)의 복합 폐염 환자를 치료하였으나 계속 진행되는 호흡 부전으로 사망하였다.

• Journal of Communications and Networks
• /
• 제15권1호
• /
• pp.77-86
• /
• 2013

Cognitive radio (CR) has emerged as one of effective methods to enhance the utilization of existing radio spectrum. Main principle of CR is that secondary users (SUs) are allowed to use the spectrum unused by primary users (PUs) without interfering PU's transmissions. In this paper, PUs operate on a slot-by-slot basis and SUs try to exploit the slots unused by PUs. We propose OSA protocols in the single channel and we propose an opportunistic spectrum access (OSA) protocols in the multi-channel cognitive radio networks with one control channel and several licensed channels where a slot is divided into contention phase and transmission phase. A slot is divided into reporting phase, contention phase and transmission phase. The reporting phase plays a role of finding idle channels unused by PUs and the contention phase plays a role of selecting a SU who will send packets in the data transmission phase. One SU is selected by carrier sense multiple access / collision avoidance (CSMA/CA) with request to send / clear to send (RTS/CTS) mechanism on control channel and the SU is allowed to occupy all remaining part of all idle channels during the current slot. For mathematical analysis, first we deal with the single-channel case and we model the proposed OSA media access control (MAC) protocol by three-dimensional discrete time Markov chain (DTMC) whose one-step transition probability matrix has a special structure so as to apply the censored Markov chain method to obtain the steady state distribution.We obtain the throughput and the distribution of access delay. Next we deal with the multi-channel case and obtain the throughput and the distribution of access delay by using results of single-channel case. In numerical results, our mathematical analysis is verified by simulations and we give numerical results on throughput and access delay of the proposed MAC protocol. Finally, we find the maximum allowable number of SUs satisfying the requirements on throughput and access delay.