• Journal of Positioning, Navigation, and Timing
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• 제12권3호
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• pp.229-236
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• 2023

As the importance and dependency of the positioning, navigation, and timing (PNT) information provided by the radio navigation satellite service (RNSS) increases, the vulnerability of RNSS to jamming can lead to significant risks. The signal design under the consideration of anti-jamming performance helps to provide service which is robust to jamming environment. Therefore, it is necessary to evaluate the jamming robustness performance during the design of new signals. In this paper, we introduce figures-of-merit (FoMs) that can be used for an anti-jamming performance analysis of designed signals of interest. We then calculate the FoMs, such as the quality factor (Q factor), tolerable jamming-to-signal ratio (tolerable J/S), and range to jammer (d) for legacy RNSS signals and analyze the results. Finally, based on the results of the analysis, we derive waveform design conditions to obtain good anti-jamming performance. As a result, this paper shows that the waveforms with wide bandwidth leading to good spectral efficiency provide strong anti-jamming performance.

• 한국의학물리학회지:의학물리
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• 제6권2호
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• pp.13-19
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• 1995

준소조사면을 대상으로 한 측정자료로부터 콜리메이터에의한 산란영향과 웨지(wedge) 사용에 따른 부가적 효과를 알아보았다. 6MV 의료용 선형가속기에서 발생된 방사선속의 중심축에서 공기중과 폴리스틸렌 팬톰, 물에대해 점리함 및 반도체검출기를 이용한 측정으로 헤드산란(위ㆍ아래 콜리메이터)의 방사선 기원과 그 크기를 결정하였다. 편평화 필터에서 형성된 산란이 대부분 윗 콜라메이터 조절에 의한 영향이 가장 크게 미침을 알수 있었다. 준소조사면에서 웨지인자(wedge factor)의 깊이에대한 영향은 웨지 각이 클수록 많은 경향을 보였고 조사변에대한 영향은 0.28%였다. 임상적으로 10 $\times$10$\textrm{cm}^2$ 이하의 준소조사면과 wedge가 부가적으로 사용되는 10cm 깊이 이하의 조사면 변화에대한 관심으로 헤드산란 및 워지에의한 영향을 확인함으로서보다 적합한 선량계산을 도모하고자 하였다.

• Geomechanics and Engineering
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• 제20권1호
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• pp.1-7
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• 2020

In structures excavated in rock mass, load progressively increases to a level and remains constant during the construction. Rocks display different elastic properties such as E_i and ʋ under different loading conditions and this requires to use the true values of elastic properties for the design of safe structures in rock. Also, rocks will undergo horizontal and vertical deformations depending on the amount of load applied. However, under constant loads, values of E_i and ʋ will vary in time and induce variations in the behavior of the rock mass. In some empirical equations in which deformation modulus of the rock mass is taken into consideration, elastic parameters of intact rock become functions in the equation. Hence, the use of time dependent elastic properties determined under constant loading will yield more reliable results than when only constant elastic properties are used. As well known, rock material will play an important role in the deformation mechanism since the discontinuities will be closed due to the load. In this study, E_i and ʋ values of intact rocks were investigated under different constant loads for certain rocks with high deformation capabilities. The results indicated significant time dependent variations in elastic properties under constant loading conditions. E_i value obtained from deformability test was found to be higher than the E_i value obtained from the constant loading test. This implies that when static values of elastic properties are used, the material is defined as more elastic than the rock material itself. In fact, E_i and ʋ values embedded in empirical equations are not static. Hence, this workattempts to emerge a new understanding in designing of safer structures in rock mass by numerical methods. The use of time-dependent values of E_i and ʋ under different constant loads will yield more accurate results in numerical modeling analysis.

• 한국수산과학회지
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• 제27권6호
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• pp.727-732
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• 1994

식물플랑크톤의 엽록소 a 당 in vivo fluorescence 세기 (R)가 netplankton과 nanoplankton 사이에 차이가 있는지 남해에서 조사하였다. In vivo fluorescence (IVF)와 엽록소 a는 서로 다른 두 크기의 플랑크톤에서 자각 좋은 상관관계를 보였으나 비율 R은 netplankton과 nanoplankton 사이에 유의적으로 차이가 있었으며 nanoplankton의 R 값이 netplankton 보다 약 7배 높았다. 그러므로 IVF로 식물플랑크톤의 크기별 생물량을 측정할 때 R에 대한 식물플랑크톤 크기의 영향을 고려하여야한다.

• 한국전기전자재료학회논문지
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• 제27권4호
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• pp.244-249
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• 2014

In this research, it have developed a sensor that could diagnose inner deterioration of covered wires. With this sensor it observed results from simulation, and the attribute required for realization. For simulation it have used FLUX, it have considered all of geometric and electromagnetic information from coil and base metal that influences eddy current sensor's property in order to predict the final result. It assumed there is no mutual inductance in the coil with N number of turns, because equivalent current flows in coil that is continuously connected in eddy current sensor. It assumed circular coil loop draws a circle, always have self inductance, and they are connected in series and overlapped according number of turns (N) in coil, and bobbin configuration. Actual sensor was produced with consideration of inductance and number of turns (N). In conclusion, it were able to test the dependency through results from simulation, actual measurement, and modeling of simulation. It is considered that attributes of respective base metal and structure can be predicted by simulating in advance.

• Journal of Advanced Marine Engineering and Technology
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• 제29권8호
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• pp.883-890
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• 2005

The industrial growth and the raised living quality have led to the massive energy consumption. As a result. the polluted environment and the limited amount of energy resources emerged as serious problems to be resolved in 21st century. Especially, in the case of Korea whose imported energy dependency rate is 98.2$\%$ in 2003 and constantly increasing every rear. more than 24$\%$ of overall energy consumption is for housing and commercial use. In order to cope with the shortage of natural energy resources, it is inevitable to develop alternative sustainable energy resources including seawater heat. so that they can replace existing resources. The heat transfer air velocity 3.5 m/s is proper to consideration with the body the pipe size 200A is more suitable than look due to the air velocity quantify and the ratio of pipe surface area. And the error between experimental data with simulation is below 5.34$\%$ so the suggested equation for calculating heat transfer capacity can be used. Therefore out of many methods utilizing seawater heat. this work Presents the efficiency of using sea water heat as a resource for air-conditioners which can be converted from the outside air through the air-to-heat conversion tube . Consequently. this method provides pretty reasonable energy efficiency.

• 한국소음진동공학회논문집
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• 제27권1호
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• pp.20-27
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• 2017

This study investigated the problems in current practice of drive-train resonance analysis procedure and suggested solutions. The first problem is the resonance occurrence at the un-identified resonance point by the current practice, as for a solution the force spectrum analysis for each critical force transmitting component was suggested. The second one is the inaccurate estimation of potential resonance point in eigenfrequency analysis because of the non-consideration about the eigenfrequency dependency on rotor-speed, the fine linearization at each rotor speed point all over operational range was proposed to account for the affection. Lastly the insufficient time for resonance activation under run-up simulation condition was recognized as a problem in resonance load increasing analysis, as an alternative, steady state condition was suggested to estimate the maximum load increasing level.

• 시큐리티연구
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• 제8호
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• pp.379-407
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• 2004

The cyber-crime is one of the results occurring from the increased dependency toward information-telecommunication devices. Currently, the Korean National Police Agency and many other related law enforcement agencies have made efforts to respond against the cyber-crimes. However, the number of cyber-crime is increasing steadily. The worse problem is that the arresting rate for the cyber-crime has been decreased than before. The reasons of decreasing arresting rate come from many different kinds of cyber-crime methods with the developed computer and network technology, Also, the easy concealment of the cyber-crime by the violater and the difficulty of specification against the data objected to search and seizure make the crackdown difficult. The other difficulties come from the lack of professionally trained investigators, the lack of high-technological investigation devices, and the failure of the technology development for the search and seizure of evidences because of the budget deficit. That is to say, these phenomenon show the comprehensive problem of the cyber-police system. Accordingly, to respond against newly changed cyber-crime activities and to investigate effectively, the cyber-police has to take consideration into the professional reorganization of the cyber-police, the development of the investigation technology, and the adjustment of current cyber-crime laws. Most importantly, the cyber-police needs the high-technological investigation devices, the development of the investigation methods, and the training for the professional human resources with the enough budget support.J

• 한국관광식음료학회지:관광식음료경영연구
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• 제8권
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• pp.179-195
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• 1997

Today's hotel cannot be defined merely as a place of providing food and lodgin. It must be a high level cultural ground serving as a place of rest for the people and as a place of art, culture and communication for the local community. Although each hotel has its own distinctiveness it must share a unified services and product sales strategies with one another in order to raise each other's sales values. The service is evaluated on the basis of the customer's own living standard and social class. There ought to be variety of personal and material services taking the sophistication and complexity of the customer's needs into onsideration. More effective marketing strategy is called for upon knowing such sales strategy and service marketing of the hotel management. Hotel's food marketing must take into consideration the product's simulaneous and vanishing qualities, its dependency upon ordering and its relationship to human services industries. Methods of increasing profit and customer satisfaction management need to be made. Especially the changes in the customer's tourist mind set and eat-out behavior play as important variabls, and the management needs to be reflexive enough to respond quickly to those changes.