• Membrane and Water Treatment
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• 제2권3호
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• pp.175-185
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• 2011

Ultrafiltration is an emerging technology for drinking water treatment because it produces better water quality as compared with conventional treatment systems. More recently, the combination of UF technology with other processes in order to improve its performance has been observed. These associations aim to maximize the contaminants removal and reduce membrane fouling. The operational performance of contaminants removal and water production of two UF pilot plants was compared. The first plant (Guarapiranga) was fed with raw water and the second plant (ABV) with pre-treated water by the coagulation, flocculation and sedimentation processes at Alto da Boa Vista WTP (Sao Paulo, Brazil). Both units operated continuously for approximately 2,500 hours, from September/2009 to January/2010. The results showed that the ABV UF pilot plant was able to operate at higher specific fluxes (6.2 $L.d^{-1}.m^{-2}.kPa^{-1}$ @ $25^{\circ}C$) than Guarapiranga (3.1 $L.d^{-1}.m^{-2}.kPa^{-1}$ @ $25^{\circ}C$). However, the number of chemical cleanings conducted in both pilot units during the considered operation period was the same (4 chemical cleanings for each plant), which shows that the pre-treatment reduced the membrane fouling. The water quality at ABV for all the variables analyzed was better, but the feed water quality was also better due to pretreatment. The rejection values for the different contaminants were higher at Guarapiranga mainly because of a pollution load reduction after pre-treatment at ABV. Even with the better performance of the ABV UF pilot plant, it is necessary to take into consideration the complexity of the complete treatment system, and also the costs involved in the construction and operation of a full-scale treatment unit.

• IEIE Transactions on Smart Processing and Computing
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• 제3권3호
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• pp.135-141
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• 2014

The inherent feature of the highly efficient spectrum usage has made Orthogonal Frequency Division Multiplexing (OFDM) preferable for Communication Standards. This study evaluated the performance of a Least Square (LS) estimator for a comb-type pilot insertion scheme over a fast fading Rayleigh channel. A High Peak-to-Average Power Ratio (PAPR) is one of the major downsides of the OFDM. The effects of an increase in the number of subcarriers on PAPR and the performance of the LS Estimator were studied. Increasing the number of subcarriers while keeping the pilots overhead constant resulted in improved performance of the LS estimator but the PAPR increased with increasing number of subcarriers. Therefore some trade-off between the number of subcarriers and the performance of the OFDM system is needed. The Mean Square Error (MSE) expression was also derived for the LS estimator in the case of a comb-type pilot arrangement. The MSE expression clearly explains the effects of the number of subcarriers on the performance of the LS estimator.

• ETRI Journal
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• 제28권5호
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• pp.688-691
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• 2006

This letter addresses the superimposed pilot aided multiuser channel estimation for the uplinks of multi-input multi-output orthogonal frequency-division multiplexing systems. To mitigate the embedded-data effects on the performance of channel estimation, a novel combining algorithm is proposed. Optimal pilot symbols are developed with respect to the least square channel estimate's mean square error. The averaged sum-capacity lower bound is derived and simulated. Simulation results show that on a low signal-to-noise ratio regime, our proposed scheme achieves better performance and higher capacity than the conventional pilot aided approach.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2005년도 춘계종합학술대회
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• pp.1109-1112
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• 2005

멀티캐리어 DS-CDMA시스템은 동일 시점에서 파일롯 채널을 제외한 모든 부채널에 동일 한 데이터가 전송된다. 이때 채널 추정을 위한 파일럿 채널의 수가 증가하게 되면 보다 정확한 채널 추정이 가능하나 데이터 채널의 감소로 인해 주파수 다이버시티의 효과가 크게 줄어들게 되어 전체적인 시스템성능을 저하시키게 된다. 따라서 파일롯 채널과 데이터 채널의 수에 대한tradeoff 가 존재하며 채널환경에 따른 요구되는 최적의 파일럿채널의 수가 결정되어야 한다. 본 논문에서는 파일롯 채널을 이용한 채널추정을 갖는 멀티캐리어 DS-CDMA시스템의 성능을 분석하고 채널환경에 따른 최적의 파일롯 채널구조를 제시한다. 전체 전송대역폭을 일정하게 유지했을 때 특정 채널환경에서 전체 부 반송파의 개수 및 파일롯 채널의 개수에 대한 최적값이 존재한다. 본 논문에서는 이와 같은 채널환경에 따른 파일롯 및 데이터 채널의 최적값을 수학적인 분석을 통해 제시한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권1호
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• pp.237-253
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• 2019

For massive multiple-input multiple-output (MIMO) circumstances with time division duplex (TDD) protocol, pilot contamination becomes one of main system performance bottlenecks. This paper proposes an uplink pilot sequence assignment to alleviate this problem for spatially correlated massive MIMO circumstances. Firstly, a single-cell TDD massive MIMO model with multiple terminals in the cell is established. Then a spatial correlation between two channel response vectors is established by the large-scale fading variables and the angle of arrival (AOA) span with an infinite number of base station (BS) antennas. With this spatially correlated channel model, the expression for the achievable system capacity is derived. To optimize the achievable system capacity, a problem regarding uplink pilot assignment is proposed. In view of the exponential complexity of the exhaustive search approach, a pilot assignment algorithm corresponding to the distinct channel AOA intervals is proposed to approach the optimization solution. In addition, simulation results prove that the main pilot assignment algorithm in this paper can obtain a noticeable performance gain with limited BS antennas.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 ICEIC The International Conference on Electronics Informations and Communications
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• pp.27-30
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• 2004

OFDMA is considered as one of the major candidates for broadband wireless access. The OFDMA signal is usually coherently demodulated, requiring the channel estimation which can be estimated using a known pilot signal. In multi-cell environment, the performance of channel estimation is mainly limited by intercell interference. It is desirable to use a pilot signal that can estimate the channel information robust to the intercell interference in the OFDMA uplink system. In this paper, we consider two types of pilot signal applicable to multi-cell OFDMA uplink systems: One is time-multiplexed pilot signal and the other is code­multiplexed pilot signal. Simulation results show that the code-multiplexed pilot is suitable for low mobility environment and time-multiplexed pilot is suitable for high mobility environment.

• 임상간호연구
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• 제28권3호
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• pp.242-250
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• 2022

Purpose: This study was conducted to evaluate the performance following the application of the pilot program for the education nurse system of the Ministry of Health and Welfare in a medical institution. Methods: This study was employed a non-homogeneous comparative group design by comparing new nurses who entered the medical institution after the pilot project from December 2019 to April 2020 with new nurses who entered before the pilot project during the same period. Satisfaction, academic achievement, job adaptation, personal turnover within one year, and patient safety incident rate were investigated as performance indicators. Results: After the pilot project, the overall satisfaction among new nurses, preceptors, and fellow nurses increased, but there were no significant changes in academic achievement and job adaptation in new nurses. The personal turnover rate decreased from 15.6% to 9.1%, and the patient safety incident rate also decreased from 26.3% to 15.7%. Also, the preceptor overtime also decreased from 3.67 to 0.66 hours. Conclusion: The performance of the pilot project for the education nurse system was related to improvements in satisfaction, turnover rate of new nurses, patient safety incident rate, and preceptor overtime. Above all long-term monitoring of each performance indicator is necessary through the continuation of the education nurse system of the Ministry of Health and Welfare.

• 한국항공운항학회지
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• 제31권2호
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• pp.66-71
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• 2023

In the case of the Navy, if some of the co-pilots are included in the long-term promotion process due to the limited number of co-pilots, operational flight and administrative tasks will be added to the co-pilots not included in the rest of the Pilot in commander process. Therefore, to solve this problem, the co-pilot who has passed the PQS step-by-step process minimizes the personnel gap in the flight operation unit through a system that evaluates whether it is possible to perform its duties as a co-pilot through actual flight after entering the school. The advantage of the PQS course is that you can control flight plans on your own and minimize gaps in flight and ground work while carrying out the curriculum, but you can't focus on education or improve your skills due to irregular training flight cycles. Therefore, in this study, after collecting opinions on effective flight cycles through a survey of pilots of P-3C, the Navy's fixed-wing aircraft representative, we will analyze the association of aircraft volume performance by flight cycle to derive the optimal flight cycle of the P-3C pilot course.

• 디지털융복합연구
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• 제10권8호
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• pp.15-20
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• 2012

스마트그리드의 성공적 구축을 위해 스마트그리드 시범사업이 추진 및 확대되고 있다. 이 시범사업을 보다 바람직한 방향으로 발전시키기 위해서는 타당하고 객관적인 성과 평가가 이루어져야 한다. 본 연구에서는 국내 현실에 맞는 스마트그리드 시범사업 성과 평가기준을 제시하고, 시범사업 형태에 따라 지속적으로 평가기준을 발전시켜 나갈 수 있는 기반을 마련하고자 한다. 이에 주요 연구문헌 검토와 전문가회의를 통해 스마트그리드 시범사업 성과 평가기준의 초안을 마련하였다. 이렇게 마련된 평가기준 초안은 전문가 델파이 조사를 통해 국내 현실에서의 타당성을 검증하였다. 총 2차례의 델파이조사를 거쳤으며, 조사 결과 6개 평가항목에 18개 평가기준을 도출하였다.

• 한국정보통신학회논문지
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• 제10권10호
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• pp.1863-1868
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• 2006

본 논문에서는 선택형 중첩 파일럿 채 예측기 법을 적용하여 페이딩 채널환경에서의 OFDM기반 DSRC 시스템의 성능을 개선시킬 수 있는 통신 시스템 모델을 제안한다. OFDM기반의 DSRC에 대한 표준화 작업이 진행중인 IEEE802.11p의 물리 계층을 따르는 OFDM시스템에 대해서 AWGN 및 페이딩이 존재하는 채널을 고려하여 시스템 성능을 구해내고, 제안하는 선택형 파일럿 중첩 채널 예측기 법을 적용하는 OFDM기반 DSRC 시스템의 성능과 비교한다. 시뮬레이션을 통해 제안하는 시스템이 채널 예측 에러를 감소시켜 기존 방식에 비해 우수한 성능을 나타냄 보인다.