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박동찬,김석찬,Park, Dong-Chan,Kim, Suk-Chan 한국통신학회 2005 韓國通信學會論文誌 Vol.30 No.7C
이 논문에서는 BICM-OFDM(Bit Interleaved Coded modulation-Orthogonal Frequency Division Multiplexing) 시스템을 위한 비트 할당 기법에 대하여 연구한다. 부채널의 상태에 따라 부반송파의 전송 매개 변수를 조절하면 OFDM 시스템의 성능을 크게 개선시킬 수 있다. 여기서는 BICM-OFDM 시스템을 위한 적응 전송 기법으로 데이터 전송률을 일정하게 유지하면서 비트 오류율이 최소가 되도록 부반송파에 비트를 할당한다. 또한, 할당하는 비트 수가 정수인 제한 조건 하에서 최적의 해를 얻기 위해 이산 라그랑지 승수 방법을 사용한다. 모의실험을 통해 제안한 비트 할당 기법의 계산량이 크지 않으며, BICM-OFDM 시스템에 제안한 기법을 사용하면 약 $2\~3$ dB의 신호대 잡음비의 이득을 얻을 수 있음을 보인다. We consider an adaptive bit-loading technique for bit interleaved coded modulation-orthogonal frequency division multiplexing(BICM-OFDM) systems. By adjusting transmission parameter of each subcarrier adaptively depending on the subchannel state, the performance of OFDM system can be improved dramatically. In this paper, the number of bits for each subcarrier is allocated to minimize bit error rate keeping the constant throughput for the adaptive transmission technique of BICM-OFDM system which can be applied to real time transmission. Also, We use the discrete Lagrange multiplier method to get the optimum solution under the integer bit allocation constraint. Simulation results show that computational amount of the proposed bit allocation technique is not high and BICM-OfDM system using the proposed technique can get the SNR gain by 2$\~$3 dB over nonadaptive one.
박동찬,김석찬,Park Dong chan,Kim Suk chan 한국통신학회 2005 韓國通信學會論文誌 Vol.30 No.4c
적응 전송 기법은 변조방식, 부호율, 전력 등의 전송 매개변수를 채널의 상태에 적응시켜 무선 통신시스템의 성능을 향상시키는 기법이다. OFDM (Orthogonal frequency division multiplexing) 시스템에서는 이러한 적응기법을 부반송파별로 적용시킬 수 있다. 이 논문에서는 각 부채널의 상태에 따라 부반송파에 최적의 부호율을 적응시키는 적응부호율 OFDM 시스템을 고려한다. 성능 분석을 통해 적응부호율 OFDM 시스템이 비트오류율 $10^{-6}$에서 고정부호율 OFDM 시스템에 비해 $3\sim6$ dB의 신호 대 잡음비 이득 또는 $30\sim50\%$의 데이터 전송률 증가를 얻을 수 있음을 보인다. Adaptive transmission techniques can improve the performance of wireless communication system by adaptively changing the transmission parameter such as modulation, code-rate, and power according to the channel state. For orthogonal frequency division multiplexing (OFDM) system, the adaptive transmission techniques can be applied to each subcarrier unit. In this paper, we consider the adaptive code-rate OFDM system in which optimal code-rate is applied to each subcarrier according to the subchannel state. Performance analysis show that $3\sim6$dB gain of SNR or up to $30\sim50\%$ increase of data rate are achieved in the condition of bit error rate $10^{-6}$.
유기인계 농약 중독환자에서 기계환기 필요성에 대한 예측인자 분석
박동찬 ( Dong Chan Park ),박정배 ( Jung Bae Park ),김윤정 ( Yun Jeong Kim ),신수정 ( Soo Jeong Shin ),문유호 ( You Ho Mun ),박신률 ( Sin Ryul Park ),류현욱 ( Hyun Wook Ryoo ),서강석 ( Kang Suk Seo ),정제명 ( Jae Myung Chung ) 대한임상독성학회 2010 대한임상독성학회지 Vol.8 No.2
Purpose: The purpose of this study is to investigate the factors that predict using mechanical ventilation for patients with organophosphate intoxication. Methods: We retrospectively reviewed the medical records of 111 patients with acute organophosphate intoxication and who were treated in our emergency center from January 2000 to December 2008. We compared the toxicologic characteristics, the laboratory findings and the APACHE II scores between the Mechanical Ventilation group (MV group) and the non-Mechanical Ventilation group (the non MV group). Results: Sixty three patients were in the MV group and 48 patients were in the non MV group. In the MV group, the patients had an older age (p<0.001), a larger amount of ingestion (p<0.001), a lower initial serum cholinesterase level (p=0.003), a higher APACHE II score (p<0.001) and they ingested a more toxic agent (p=0.001). There were no significant differences in gender, the type of visit and the arrival time between the MV group and the non MV group. Conclusion: We suggest that the patient’s age, the amount of organophosphate ingestion, the toxicity of the agent, the initial serum cholinesterase level and the APACHE II score are important factors to determine if mechanical ventilation will be applied for patients with organophosphate intoxication.
주거환경만족도 평가의 신뢰성 향상을 위한 기초연구 - 주거실태조사의 설문구성 방식을 중심으로 -
박동찬(Park, Dong Chan),최정민(Choi, Jung Min) 한국주거환경학회 2019 주거환경(한국주거환경학회논문집) Vol.17 No.2
This paper aims to investigate the reliability verification of residential satisfaction evaluation in terms of the SP(Same-Pattern) responses suspected as outliers under the 2006-2017 KHS. Based on the research hypothesis developed from the distributional characteristics in the Same-Pattern (SP) responses obtained across 2006-2017 KHS, each of three distinctive questionnaires types (type B, R, and D) are prepared and distributed to 750 respondents (2,250 respondents in total) through online. The key findings are as follows: First, the “Reduced type R”, in which the number of questionnaire items is reduced in an attempt to lower the likelihood of unreliable answers resulting from the fatigue effect, adversely affected the result and presented even greater tendency towards SP responses. It is concluded that such simple measures of reducing the number of questionnaires do not effectively address the problem of SP occurrence that is suspected of being outliers. Second, the “Divided type D”, in which the questionnaire items were divided into multiple sub-groups in an attempt to increase the awareness of respondents and prod them into action, presented the lowest occurrence of SP responses. Moreover, this type is likely to have the lowest possibility of co-existing outliers, the result confirmed by the verification process using statistical and machine-learning analysis. Third, it became clear that reducing the number of questionnaires while simultaneously inserting heterogeneous intermediary questionnaires is the most effective method to conduct the table-formulated satisfaction evaluation utilizing a Likert scale. However, since an excessive partition may cause unnecessary psychological pressure on respondents and increase the likelihood of SP outliers, it is highly recommended to utilize the carefully designed framework for the best result.