• Journal of the KSME
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• v.22 no.6
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• pp.471-476
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• 1982

1.열펌프 시스템의 성능은 최적설계를 하므로서 이론적, Rankine C.O.P에 접근시킬 수 있다. 2.. 산업체 중저온 폐열회수이용에는 열펌프가 매우 유망하며 냉온수를 동시에 이용하는 경우는 더욱 유리하다. 3. 우리나라 산업계에서 보통 투자회수기간을 3년으로 본다면 전력시설용량을 500kw 이상의 산업용 소동력, 대동력의 경우 열펌프의 성적계수는 약 3.5 정도가 하한으로 볼 수 있다. 4. 공기 또는 물 열원의 가정용 열펌프는 전력비가 비싸므로 아직은 실용성이 없다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.8 no.3
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• pp.39-48
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• 1998

GAC(GloabvalAvalanche Characteristics)은 부울함수가 전파특성 관점에서 얼마나 우수한지를 전체적인 관점에서 나타내는 특성으로 Zhang-Zheng(1995)에 의해서 제안되었다. GAC을 측정하는 기준으로는 와 가 있으며, 두 기준값이 작을수록 부울함수는 보다 우수한 전파특성을 갖는다. Zhang-Zheng은 GAC이 우수한 균형인 부울함수를 설계하는 두 가지 방법을 제시하였으며, 균형인 부울함수f의 대수적 차수가 3 이상일 때 의 하한이 $2^이라고 추측하였다. 본 논문에서는Zhang-Zheng의 방법보다 우수한 새로운 설계방법을 제시하며, 이를 이용하여 그들의 추측에 대한 반례를 제시한다.한다.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.3
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• pp.195-201
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• 2000

This paper discusses methods for the stable bottom detection and the optimum bottom offset which enable to separate the fish echoes from the bottom echoes with echo integration of demersal fish. In preprocessing of the echo signal, the bottom detection has to be done stably against the fluctuation of echo level and the bottom offset has to be set to a minimum height such that near bottom fish echoes are included Two methods of bottom detection, namely echo level threshold method and maximum echo slope method were compared and analyzed. The echo level method works well if the ideal threshold level was given but it sometimes misses the bottom because of the fluctuation of the echo. Another method to detect the bottom which uses maximum echo slope indicates the simple and stable bottom detection. In addition, the bottom offset has to be set near to the bottom but not to include the bottom echo. Optimum bottom offset should be set a few samples before the detected bottom echo which relates the beginning of pulse shape and acoustic beam pattern to the bottom feature.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.26 no.1
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• pp.49-62
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• 1993

Structure of intertidal algal communities of the islands on the South Sea of Korea was studied in summer of 1987 and 1988. The area includes Manjedo, Ch'ujado, Kwantaldo, Munsom, Yosodo, Komumdo, Soridi, Yokchido, Pijindo and Hongdo. Three biologically distinct zones, were commonly recognized in the intertidal bulk of the all examined islands. In the high intertidal zone, only a few species showing thin, tubular and sheet like forms were observed, and the most abundant species was Gloiopeltis spp.. Corallina pilulifera, Hizikia fusiformis and Chondria crassicaulis were most abundant species of the mid intertidal zone, which was formed near the mean sea level. The structure of the low intertidal zone was much more complex than the high and mid, the most abundant species were Laurencia spp. and Sargassum sagamianum. All of the coarsely branched and articulated calcareous species were distributed below mean sea level.

• Journal of Navigation and Port Research
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• v.41 no.3
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• pp.87-92
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• 2017

To enhance the reliability and/or resilience of the PNT service included in the e-Navigation strategy of the IMO, the evaluation of the AIS-TWR method for the asynchronous R-mode for maritime service, which is available even in the absence of the GNSS, is described. For the AIS-TWR, which is capable of ranging through message exchange even without high precision synchronization, the operation scenario and the error factors according to the AIS system specifications are proposed and analyzed. Cramer-Rao Lower Bound is presented for the performance evaluation of the AIS-TWR algorithm. A simulation by AIS-TWR method of two AIS systems in a 3 km static environment shows estimation error of about 41m compared to the real value..

• The Journal of the Acoustical Society of Korea
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• v.22 no.2
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• pp.88-95
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• 2003

The auditory experiments based on subjective responses were undertaken for the standard heavy and light weight impact noise and rubber ball impact noise, jumping noise to investigate relations between floor Impact noise levels and subjective responses and to establish the upper/lower limits of floor impact noises. As a result, it was shown that relations between floor Impact noise levels and subjective responses was linear and the lower limit of heavy-weight impact noise was L/sub i, Fmax, AW/=46㏈ and the lower limit of light-weight impact noise was L'/sub n,AW/=56㏈. Finally the 3 subjective classes of floor impact noises were established.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.1
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• pp.31-37
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• 2002

전자파 잔향실(Reverberating Shielded Enclosure)의 개념은 전자파 차폐실(Shielded Enclosure)에서 얻어진 측정결과를 개선하기 위하여 1968년도에 제안되었다. 이후 Reverberating 또는 Mode-Stirred Chamber는 EM Immunity 측정뿐만 아니라 EMI측정에서도 많이 적용되어 왔지만, 국제 표준 방식으로 적용되어 오지 못하다가 최근 EMI 복사 전력 측정 및 EM Immunity 측정시설로 유용하게 사용될 수 있다는 점이 부각되어 국제 표준 방식으로 적용하자는 분위기가 무르익어 이에 대한 활발한 논의가 계속되어 오고 있다. 이러한 전자파 잔향실을 이용하여 EMI 및 EMS 시험을 실시할 수 있는 방법을 규격화시키자는 제안이 '96년 프랑스 Mandelieu 국제 전자파 장해 특별위원회(CISPR:International Special Committee on Radio Interference)회의에서 검토된 후 '97년 일본 Yokosuka CISPR 회의에서 정식의제로 채택되었다. 이 안건에 대하여 대부분의 국가들이 제안 취지에 찬성하여 NWIP(New Work Item Proposal) 문서가 각국에서 회람되었다. 초기 전자파 잔향실은 전자파 장해 및 복사 내성 측정을 위한 대용시험 시설로서 1968년 미국 Mendes에 의해 전자파 차폐실 구조에 Stirrer를 이용하여 필드의 균일도를 확보할 수 있다는 전자파 잔향실 개념이 처음으로 제안되었다. 이후 이 분야의 연구는 미국 표준 기술 연구소(NIST: National Institute of Standard and Technology)등에서 연구가 활발히 진행되고 있으며, 국제 표준화 기구인 CISPR에서 전자파 장해 및 내성 시험을 위한 대용시험 시설로서 활용하기 위하여 규격 작업이 진행중에 있다. 또한 최근 전자파 장해 방지를 위한 규제 주파수가 1∼18㎓ 까지 확장됨에 따라 이 주파수 대역에서 시험장으로 활용할 수 있는 전자파 잔향실이 새롭게 부각되고 있다. 전자파 잔향실은 기본적으로 공진 모드를 활용하기 때문에 일정한 크기의 잔향실 내부에서 전자파 균일성을 확보할 수 있는 모드 수에 의해 하한 주파수가 결정되며 충분한 모드 분포상태에서 Stirrer를 사용하여 필드 경계를 이동시킴으로서 확률적으로 균일한 필드분포를 확보하게 된다. 주파수가 증가함에 따라 모드수는 증가하기 때문에 하한 주파수 이상의 대역에 대한 시험시설로 활용할 수 있으며, 특히 ㎓ 대역에서 사용하기에 적합한 대용시험시설이라고 볼 수 있다.

• Journal of the Korean Data and Information Science Society
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• v.26 no.2
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• pp.367-376
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• 2015

Today, big data has become a hot keyword in that big data may be defined as collection of data sets so huge and complex that it becomes difficult to process by traditional methods. Clustering method is to identify the information in a big database by assigning a set of objects into the clusters so that the objects in the same cluster are more similar to each other clusters. The similarity measures being used in the cluster analysis may be classified into various types depending on the nature of the data. In this paper, we computed upper and lower limits for probability interestingness measure based similarity measures without marginal probability such as Yule I and II, Michael, Digby, Baulieu, and Dispersion measure. And we compared these measures by real data and simulated experiment. By Warrens (2008), Coefficients with the same quantities in the numerator and denominator, that are bounded, and are close to each other in the ordering, are likely to be more similar. Thus, results on bounds provide means of classifying various measures. Also, knowing which coefficients are similar provides insight into the stability of a given algorithm.

• Plant Journal
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• v.14 no.2
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• pp.39-44
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• 2018

In this study, I analyzed the effects on stabilizing the draft system, boiler efficiency when changing excess air ratio under 870 MW load limit operation condition in a large capacity coal fired power plant and decided optimum excess air ratio. It is positively necessary to choose adequate excess air ratio for stabilizing draft system because air pre-heater pressure drop and induced draft fan first stall margin are changing when adjusting excess air ratio. This study therefore, measured air pre-heater pressure drop, induced draft fan first stall margin, boiler efficiency, loss and has chosen adequate excess air ratio adjusting excess air ratio from 1.153 to 1.127. So it is recommended that the operation point needs to be changed to 1.127 that is not only to decrease air pre-heater pressure drop and to stabilize draft system and to secure stall margin but also to maintain boiler efficiency to equivalent level.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.4
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• pp.7-12
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• 2019

Ambient backscatter communication is limited to channel estimation technique through a pilot signal, which is a channel estimation method in current RF communication, due to transmission power efficiency. In a limited transmission power environment, the research of traditional ambient backscatter communication has been studied assuming that it is an ideal channel without signal distortions due to channel conditions. In this paper, we propose an expectation-maximization(EM) algorithm, one of the blind channel estimation techniques, as a channel estimation method in ambient backscatter communication system which is the state of channel following normal distribution. In the proposed system model, the simulations confirm that channel estimate through EM algorithm is approaching the lower bound of the mean square error compared with the Bayesian Cramer-Rao Boundary(BCRB) to check performance. It shows that the channel parameter can be estimated in the ambient backscatter communication system.