• 한국항만경제학회지
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• 제33권4호
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• pp.37-58
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• 2017

설문조사 및 응답자의 지각을 바탕으로 하는 항만선택연구의 암묵적인 가정은 항만선택속성들의 선호크기가 선택행위에 비례적이라는 것이다. 그러나 항만선택 속성들도 직선만이 아닌 비선형적 특성을 갖을 수 있다. 본 연구는 항만선택연구에 성격이 유사한 카노모형을 원용하여 항만선택속성의 비선형적 특성을 확인 하였다. 연구결과 선사의 항만선택속성들중 복합운송연계성과 항만규모 등이 당연특성으로 평가되는 등 여러 속성들이 비선형적 특성으로 평가되었다. 따라서 항만공사와 운영사 등의 항만 서비스제공자들은 선사들의 비선형적 항만선택특성을 반영한 항만운영전략을 구축해야 할 것이다. 본 연구가 항만선택 특성을 탐색적으로 분석하였기 때문에 추후 국내외 항만 및 이해당사자들을 대상으로 한 추가적인 검증연구가 필요하다. 또한 분석 및 전략수립에 활용한 카노모형 및 중요도 선택분석방법도 명확한 특성의 파악과 전략지침의 제시가 가능하도록 개선할 필요가 있다.

• 농업과학연구
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• 제47권4호
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• pp.717-726
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• 2020

The physical characteristics of the major varieties of perilla were analyzed to use as basic data for the design of a high-quality, high-efficiency perilla cleaner and stone separator. Because the size, thousand-grain weight, angle of repose, angle of friction, bulk density and terminal velocity of perilla have significant differences according to the perilla variety, the different of characteristics by variety should be considered for performance improvement of a perilla cleaner and stone separator. Therefore the cleaner and stone separator using a sieve could be improved by the application of a detachable sieve or by using equipment such as a 2 - 3 stage sieve and regulating the slope. Moreover, because differences in the terminal velocity occur due to the differences in the size and thousand-grain weight according to the perilla variety, a blower with an adjustable fan speed was considered for the design of the improved cleaner. Additionally, it was shown that the length of perilla has the greatest correlation based on a comparison of the coefficients of the other characteristics. Accordingly, the length of perilla could be used as a major factor for the fine adjustment and parts replacement of the device. These results can be used as basic data for a high-quality, high-efficiency perilla cleaner and stone separator. In the future, the development of the machine and follow-up studies based on the basic data are needed to determine the optimized operating conditions and mechanism of action.

• 한국해양공학회지
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• 제31권3호
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• pp.219-226
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• 2017

In this study, the impact characteristics of subsea pipelines that were installed in various soil types and burial depths were evaluated by a numerical method. An impact scenario replicated a dropped ship anchor that fell vertically and impacted an installed subsea pipeline. In order to calculate the impact force through terminal velocity, FLUENT, a computational fluid dynamic program and MDM (Moving Deforming Mesh) technique were applied. Next, a dynamic finite element program, ANSYS Explicit Dynamics, was used for impact analysis between the anchor and pipeline (or, subsea if they were buried). Three soil types were considered: loose sand, dense sand and soft clay by applying the Mohr-coulomb model to the seabed. The buried depth was assumed to be 0 m, 1 m and 2 m. In conclusion, a subsea pipeline was the most stable when buried in dense sand at a depth of 2 m to prevent impact damage.

• 한국대기환경학회지
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• 제17권1호
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• pp.39-50
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• 2001

The spatial distribution characteristics of airborbe mercury(Hg) were investigated used its concentration data from six measurement sites selected to represent:(1) three terminal sites with heavy traffic loads in urban area, (2) one urban residential site and (3) two mountainous sites in Korea. The measurement data obtained during September 1997 through May 1998 indicated that the mean concentration of Hg from different study sites were comparably high with the mean values spanning from 5-9ng./㎥. The concentration from all those sites were systmatically high compared to those of most background sites around world or to other Korean sites investigaed previously. When results of correlation analysis between Hg and relevant parameters were compared among different study sites. temperature was most frequently found out to be in strong correlation with Hg concentrations. Results of factor analysis also indicated that Hg concentrations could be affected simultaneously by th factors affecting such parameters as ozone, temperature, ozone, carbon monoxide, and PM. The findings of enhanced Hg levels from Ji-Ri Mountain relative to terminal site suggest that is distributions may be rather homogeneous not enough to clearly distinguish areal differences and the associated source signatures between urban and rural area. The existence of systmatically high concentrations from all investigated sites also indicate that the impact of its source processes should be quite ubiquitous, while highly variable in relatively long term scale.

• 한국안전학회지
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• 제20권2호
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• pp.67-72
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• 2005

This paper proposes the influences of harmonic current on electrical characteristics of an induction motor. Recently, a power system gets more worse as nonlinear load makes harmonics to affect energy lose of system and shorten lift of machines. In this paper, the electrical effect and THD(Total Harmonic Distortion) of harmonic current to an induction motor which is of great use in the industrial fields are measured and analyzed. A power conversion equipment(inverter) is installed to produce harmonics and variable reactors are installed to reduce the harmonics having an effect on the input terminal. Then the effects of the reactors are measured and analyzed. Also average voltage, current, power and 110 by harmonics are analyzed. The results show that Inn is increased by increasing load of the induction motor and installing reactors. And the harmonics affecting the input terminal are decreased by increasing reactor 3[mH] to 6[mH], however, average power of the induction motor is decreased. Therefore, it is very important that reactors should be carefully installed considering the merits and demerits resulting from the installation of reactors.

• 전기학회논문지P
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• 제58권4호
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• pp.476-482
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• 2009

This paper describes the development of capacitive sensor for the diagnosis of liquid dielectrics, which is widely used as the electrical insulating oil of transformer, circuit breaker, cable and etc. To survey the dielectric properties of the virgin and aged electrical insulating oils, we utilized the highly precise measuring system, using the principle of cross capacitance. The measured properties were used to determine the design factors of the sensor. Then the factors were optimized with the help of computational analysis. To evaluate diagnosis by the sensor, we performed accelerated thermal aging test about electrical insulating oils. The condition of aged specimens were investigated by measurements of relative permittivity i.e. capacitance change by capacitive sensor. And to evaluate the hysteresis characteristics with the change of temperature, we constructed a testing system, which was composed with vacuum drying oven, oil chamber and measuring instruments, such as LCR meter, MUX and so forth. Through the results of this investigation, we confirmed the superior characteristics of the newly developed sensor.

• 한국군사과학기술학회지
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• 제17권5호
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• pp.620-628
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• 2014

This paper describes the analysis results of channel characteristics in the operating area of satellite OTM (On-The-Move) terminal. The communication channel between the Koreasat-5 and OTM terminal on a test car was measured and recorded in downtown of Daejeon, using the received beacon signal of around 20 GHz. And the measurement data were statistically analyzed and then compared with highway and national road environments. The statistical evaluation of satellite channel was conducted by using probability density function and Markov model and then presented average connection duration(ACD), average fade duration(AFD), and level crossing rate(LCR) of downtown environment.

• 한국콘텐츠학회논문지
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• 제19권12호
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• pp.416-424
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• 2019

정보기술(IT)망 및 운영기술(OT)망 영역 모두에서 컴퓨터에 접근을 위해서 사용하는 인증기술은 ID/PW, 공인인증서, OTP 등이다. 이러한 인증기술들은 비즈니스 중심의 IT망의 특성을 반영한 것으로 볼 수 있다. 이들 인증기술이 동일하게 운영기술이 중심인 SCADA제어망에서도 사용되고 있는 실정이다. 하지만, 이러한 인증기술들은 엄격한 제어가 요구되는 OT제어망 환경의 특성이 반영된 것으로 볼 수 없다. 본 논문에서는 운영자의 모바일 단말과 제어망의 물리적 단말주소 및 운용자 위치정보 특성을 활용하여 제어정보 처리가 중심인 OT SCADA제어망에 적합한 강화된 새로운 사용자 인증방안을 제안하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.216-217
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• 2007

In this study, we analyzed the electrical loss characteristics between ribbon and output terminal of constituent material according to electrical resistance during interconnection process of PV module. From this result, the electrical output power reduction rate caused by interaction between ribbon and cell's interconnection was 2.88%. There was 1W electrical output power reduction through the 16 solar cells. So it is expected that the wider size of PV module gives the higher loss in electricity production. Also, the average output power of PV module passed lamination process was increased by 0.081W per one solar cell and the increase rate was 3.7%.PV module's electrical loss before and after lamination process according to constituent material's terminal was 0.49W and 0.50W, respectively.

• 생물환경조절학회지
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• 제16권3호
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• pp.264-268
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• 2007

국내 육성 품종인 3년생 '홍로'와 도입 품종인 4년생 '갤럭시갈라' 사과를 대상으로 정아 고사 시 장과지 및 액아의 활용 가치를 알아보고자 결과지 길이 및 꽃눈 위치 따른 개화 및 과실 특성을 조사하였다. '홍로'와 '갤럭시갈라' 모두 개화시, 만개기 및 낙화기는 20 cm 이상 결과지에서 5 cm 미만과 $10{\sim}15cm$ 결과지보다 다소 늦었다. 화총당 꽃수도 때 정도 적었다. 과중, 종자수, 당산비 등 대부분의 과실 특성은 5 cm 미만과 $10{\sim}15cm$ 20 cm 이상 결과지보다 높았지만, 당도와 산 함량은 반대의 경향이었다. 20 cm 이상 결과지의 정아와 액아 간 대부분의 과실 특성은 액아에서 좋은 경향을 나타내었지만, '홍로' 사과의 종자수, '갤럭시갈라'의 Hunter a값을 제외하고는 유의한 차이를 나타내지 않았다. 그리고 두 품종 모두 과중과 종자 간 높은 상관성을 나타내었다. 따라서 정아 고사 시 장과지로 대체 활용할 수 있고 '갤럭시갈라'의 경우 액화아의 이용도 가능하였다.