• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권11호
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• pp.4623-4643
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• 2015

This paper considers physical-layer security protocols in multicast cognitive radio (CR) networks. In particular, we propose dual-hop cooperative decode-and-forward (DF) and randomize-and-forward (RF) schemes using partial relay selection method to enhance secrecy performance for secondary networks. In the DF protocol, the secondary relay would use same codebook with the secondary source to forward the source's signals to the secondary destination. Hence, the secondary eavesdropper can employ either maximal-ratio combining (MRC) or selection combining (SC) to combine signals received from the source and the selected relay. In RF protocol, different codebooks are used by the source and the relay to forward the source message secretly. For each scheme, we derive exact and asymptotic closed-form expressions of secrecy outage probability (SOP), non-zero secrecy capacity probability (NzSCP) in both independent and identically distributed (i.i.d.) and independent but non-identically distributed (i.n.i.d.) networks. Moreover, we also give a unified formula in an integral form for average secrecy capacity (ASC). Finally, our derivations are then validated by Monte-Carlo simulations.

• Journal of Communications and Networks
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• 제13권6호
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• pp.655-663
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• 2011

Diffuse optical wireless (DOW) systems have the advantage that they do not require point-to-point siting so one transmitter can communicate with several receivers. In this paper, we investigate multiple access scheduling methods for downlink orthogonal frequency division multiplexing (OFDM) in diffuse optical wireless networks. Unlike the radio frequency (RF) channel, the DOW channel has low-pass filter characteristics and so requires different scheduling methods than those developed for the RF channel. Multi-user diversity orthogonal frequency division multiple access (OFDMA) systems nominate a cluster of subcarriers with the largest signal-to-noise-ratio for transmission. However, in a DOW channel, most users would choose the lowest frequency clusters of subcarriers. To remedy this problem, we make two proposals. The first is to use a variable cluster size across the subcarriers; the lower frequency clusters will have fewer subcarriers while the higher frequency clusters will have more subcarriers. This will equalize the capacity of the clusters. The second proposal is to randomize a user's cluster selection from a group of clusters satisfying a minimum threshold. Through simulation it is shown that combining these strategies can increase the throughput while ensuring a fair distribution of the available spectrum.

• 한국전자파학회논문지
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• 제10권6호
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• pp.855-865
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• 1999

본 논푼에서는 주파수 선택적 레일리 페이딩 채널에서 16 QAM-TCM의 BER 성능을 개선하는 방법을 제시한다. 주파수 선택적 페이딩 환경에서는 ISI 등, 페이딩에 의한 성능열화가 극히 심하므로 이에 대한 보상 방안으로 가우시안 보상기법을 이용한 다중 파일롯 심별에 의한 보상 방법을 제안하였다. 또한 대역폭 확장 없이 우수한 부호화 이득을 얻을 수 있는 트렐리스 부호화 방법을 적용하였으며 연집 에러를 방지하고자 비트 리버설 블럭 인터리벙 기법을 개선하여 적용하였다. 컴퓨터 시율레이션 결과 주파수 선택적 레일리 페이 딩 환경에서 기존의 PSAM 방법을 적용한 것보다 우수한 성능 개선 효과를 확인 할 수 있었다

• 전자공학회논문지S
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• 제35S권5호
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• pp.1-10
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• 1998

Satellite communication is getting more important in the coming 21st century because of its wide areas sevice capability, ease of access, and fast channel establishment. As such, satellite communication networks will be the basis of the global communication system in cooperation with the ground ATM networks. In this paper, we consider an efficient transmission methodology of ATM cells over the satellite communication channel. We first analyze possible bottlenecks and performance deterioration factors in the case, and then propose an enhanced cell trasmission mechanism. In order to use satellite channel for ATM cell transmission, the application of complicated channel coding is inevitable. However, the forwared error control such as convolutional encoding brings forth burst errors, which calls for the application of some kind of interleaving mechanism to randomize the burst errors at the receiver. Another aspect which should b econsidered in satellite communication system is the inherent transmission delay, which can be very considered in satellite communication system is te inherent transmission delay, which can be very critical to the delay-sensitive ATM traffic. Therefore, we propose that the processing delay at the block interleaving stage should be controlled propose a variable-size block interleaving mechanism which utilizes the predicted transmission delay for each traffic in the queues of the transmitter. According to the computer simulation, the proposed mechanism could improve the overall performance by drastically reducing the ATM cell drop rate owing to the excessive transmission delay.

• 대한치과기공학회지
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• 제34권1호
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• pp.25-36
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• 2012

Purpose: The purpose of this study is to investigate the status of oral health behaviors and oral health status, and to analysis the association between health behavior and chronic disease and oral health status of male workers. Methods: The survey used structured self administered questionnaires from September to October in 2009 in Daegu and Gyeongsangbuk-do province, randomize thirty workplace which work more than 50 workers and carry out a survey targeting 30 to 50 age male laborers who work selected workplace. Total of 1,532 replies were analysed. Results: Age, education, monthly income, job was significantly associated with number of toothbrushing, scaling experience, number of missing teeth. Smoking, amount of smoking, frequency of drinking, number of tooth brushing, unmet need and subjective oral health condition, HBP and DM was significantly associated with the number of missing teeth. In logistic regression, age(above 40), monthly income and DM were significant factors on loss of teeth. Conclusion: In conclusion, it is important to provide education on the teeth-brushing and DM management to workers engaged in a small or medium sized workplace with many tooth loss and low educational status, and to recommend a regular scaling as well as to establish policy for creating conditions upon an oral health check-up and a tooth scaling and allow the maintenance of an oral health.

• The Journal of Korean Physical Therapy
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• 제17권4호
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• pp.519-535
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• 2005

The main purpose of this study is to evaluate the effects of manual therapies which are Posterior Anterior Central Vertebral Pressure (PACVP) and Posterior Anterior Unilateral Vertebral Pressure(PAUVP} in patients having a chronic pain in the neck. This study focused on sixty patients having a chronic pain in the neck from 19 years old and 65years old. There are 33 females and 27 males each. This study randomize two groups from all subjects that have been mentioned above. Group 1 received a cervical spine manual therapy, Group 2 received a conservative physical therapy. Each therapy was held for 3 times a week, totally, 6 times for two weeks. The tape was used to measure cervical range of motion(ROM) in six areas-flexion, extension, left lateral flexion, right lateral flexion, left rotation, right rotation. 100mm Visual Analogue Scale(100mm VAS) was used to measure the subjective pain level. All measurements of each patient were measured at pre-treatment and 2 weeks post-treatment. The results of this study would be summarized as follow: 1. The manual treatment group has much more recovery than that of conservative physical therapy group in terms of the degree of the ROM improvement showing a significant difference between two groups(p<0.05) 2. The manual treatment group has more recovery than that of the conservative physical therapy group in the improvement of pain(p<0.05).

• 응용통계연구
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• 제23권3호
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• pp.533-543
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• 2010

직접면접으로 민감한 질문을 할때 발생하는 무응답이나 거짓응답의 문제를 개선하고자 Warner (1965)가 최초로 제안한 확률화응답모형에 관한 연구는 이후 많은 연구자들에 의해 개선, 발전되어 오고 있다. 본 연구에서 표본은 층화임의복원추출법에 의해 추출되었으며, 표본배분은 최적배분법에 의해 배분되었다. 한편, Kim과 Elam (2005)의 2단계 층화확률화응답모형을 확장한 3단계 층화확률화응답모형을 사용하였다. Kim과 Elam (2005)의 2단계 층화확률화응답모형과 상대효율을 비교한 결과 본 논문에서 제시한 3단계 층화확률화모형의 효율성이 상대적으로 높다는 결과가 도출되었다. 그러나 2단계확률화응답모형을 3단계로 확장함으로써 상대적으로 효율성은 증대되지만 반대로 조사과정의 어려움이 예상된다.

• Asian Pacific Journal of Cancer Prevention
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• 제17권8호
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• pp.4031-4035
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• 2016

Background: In the adjuvant treatment of breast cancer, anthracycline and taxane based regimens can be used concomitantly or sequentially. The best order in the sequential regimens has yet to be well established. This study evaluated the feasibility of 4 cycles of adjuvant taxotere ($100mg/m^2$) every 3 weeks followed by 4 cycles of doxorubicin ($60mg/m^2$) and cyclophosphamide ($600mg/m^2$) every 3 weeks. The primary outcome was the safety profile. Secondary outcomes were disease free survival (DFS) and overall survival (OS). Materials and Methods: This non-randomize prospective phase II stud was performed at Jordan University of Science and Technology and its affiliated King Abdulla Teaching Hospital between July 2009 and August 2010. Data collection was closed on May $31^{th}$, 2015 giving a median follow up period of 62 months. The study was approved by the institutional review board and a written informed consent was obtained for each patient. Results: Fifty patients were enrolled. The median age was 53.1 years (range 34-76). One patient (2%) had stage I disease, 17 (34%) stage II, and 32 (64.0%) stage III. Forty-six patients were evaluable for efficacy analysis. The completion rate was 95.7%. No dose modifications were needed. The incidences of grade 3-4 neutropenia and febrile neutropenia were 14 % and 10%. No grade 3-4 non-hematological adverse events were encountered. At a median follow up time of 62 months the OS and the DFS rates were 76.1% and 56.5%. Those for stages I and II combined were 100% and 75%. Conclusions: Taxotere first followed by doxorubicin-cyclophosphamide appears a feasible regimen as evidenced by an acceptable completion rate, a satisfactory safety profile, and an OS and DFS rates comparable to other studies.

• 한국컴퓨터정보학회논문지
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• 제17권10호
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• pp.79-88
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• 2012

본 연구에서는 센서와 게이트웨이간의 응용레벨 전송 세션을 세분화하고 각 세션을 주기적으로 갱신하는 기법을 적용하여 모델화하였다. 또한 이 모델에서의 인증을 위한 전송오버헤드를 최소화하기 위해 생체정보의 측정주기에 따른 동적인 유효 세션기법을 적용하였고 비인가 게이트웨이가 유효세션 시간을 예측하지 못하도록 유효세션 시간을 랜덤화 하였다. 이 모델은 비인가 센서기기의 무결성 침해와 기밀성 침해를 차단하는 효과가 있다. 본 모델의 평가를 위해 TinyOS 2.1 환경에서 구현하여 실험하였다. 따라서 전송할 생체정보가 서로 다른 측정주기를 갖는 것을 통해 효율성을 제공하도록 하였다. 결과적으로 제안한 기법을 3가지 실험을 통해 유효성을 확인하였다.

• Asian-Australasian Journal of Animal Sciences
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• 제30권10호
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• pp.1500-1506
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• 2017

Objective: High $NH_3$ emissions from poultry houses are reported to have negative impacts on health, welfare and safety of birds and humans, and on the environment. Objective of the present study was to determine the effects of two litter amendments on the $NH_3$ levels in broiler closed houses under hot-humid conditions. Methods: Giving a completely randomize design, nine closed houses, each housed 32,500 birds on paddy husk litter, were randomly allocated into two treatment (Mizuho; a bacterial culture mix and Rydall OE; an enzymatic biocatalyst) and control groups. $NH_3$ levels were determined thrice a day (0600, 1200, and 1800 h), at three heights from the litter surface (30, 90, and 150 cm), at 20 predetermined locations of a house, from day 1 to 41. Results: Rydall significantly reduced the $NH_3$ level compared to control and Mizuho. $NH_3$ levels at 30 cm were significantly higher than that of 90 and 150 cm. The $NH_3$ levels at 30 cm height were higher than 25 ppm level from day 9, 11, and 13 in Mizuho, control, and Rydall groups, respectively to day 41. $NH_3$ levels at 150 cm height were higher than maximum threshold limit of 50 ppm for human exposure from day 12, 14, and 15 in Mizuho, control, and Rydall groups, respectively to day 33. Being significantly different among each other, the $NH_3$ level was highest and lowest at 0600 and 1800 h. Litter amendments had no significant effects on growth performance. Rydall significantly increased the litter N content on day 24. Conclusion: It was concluded that the $NH_3$ levels of closed house broiler production facilities under tropical condition are so high that both birds and workers are exposed to above recommended levels during many days of the growing period. Compared to microbial culture, the enzymatic biocatalyst was found to be more effective in reducing $NH_3$ level.