• JOURNAL OF ELECTRICAL WORLD
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• s.294
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• pp.80-85
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• 2001

최근 인버터의 에너지절약 및 이용 합리화는 공조용뿐만 아니라 전에는 별로 생각하지 않았던 반송(搬送)기계, 기타 일반산업기계에도 니즈가 높아가고 있다. 그 결과 여러 가지 에너지절약 방법에 의한 대처방안이 추진되고 있다. 1999년 4월에 시행된 개정 (일본)省에너지법에서도 (1)팬, 펌프, 블로어, 컴프레서 등의 유체기계에 대해서는 회전수 제어 등으로 송출량과 압력을 적절히 조정하여 전동기의 부하를 저감시킬 것 (2) 전동력응용설비를 부하변동이 큰 상태에서 사용할 때는 부하에 따른 운전제어를 할 수 있도록 회전수제어장치 등을 설치하도록 검토할 것 과 같이 공조용도 이외의 일반용도에 대해서도 인버터 설치를 장려하고 있다. 그래서 본고에서는 인버터운전에 의한 에너지절약을, 공조용도에 한정하지 않고 부하특성에 따른 것과 운전상태에 따른 것에 대하여 각각의 에너지절약 실현방법을 소개한다. 2장에서는 인버터운전으로 에너지절약을 할 수 있는 기본적인 생각을 기술한다. 3장에서는 부하특성에 따른 에너지절약 방법으로 2승저감토크 부하, 정토크 부하, 정출력 부하로 분류하여 상용운전에서의 에너지로스 요인을 분석, 인버터운전이 에너지절약이 되는 이유를 기술한다. 4장에서는 각 운전상태에 따른 에너지절약방법으로 시동$\cdot$가속, 일정속도 운전, 감속$\cdot$정지 모드로 분류하여 각각의 상태에서의 에너지로스의 요인을 분석, 인버터운전이 에너지절약이 되는 이유를 기술한다. 5장에서는 공조용도 이외의 분야에서 새로운 에너지절약이 가능하게 된 구체적인 사례 도입에 있어서의 주안점과 효과에 대해 소개한다.

• Korean Journal of Materials Research
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• v.3 no.4
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• pp.422-423
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• 1993

In this short note, we report the result of measurement for the ferro- to paramagnetic phase transition temperature, that is Curie point of bulk gadolinium. This note is written to give the solid validity for the previous measurement of Curie point shift of gadolinium film (1. Rhee, E. Lee and S. Lee, Kor. J. of Mat. Research,3, 3, 1993). The Curie point of bulk gadolinium is determined by measuring the resistance of sample as function of temperatures. At Curie point, we can observe the resistivity anomaly which arises due to the heat capacity difference between below and above Curie point. Finally, the curie point of bulk gadolinium is found to be 19.2${\pm}$0.$3^{\circ}C$.

• Aerospace Engineering and Technology
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• v.10 no.2
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• pp.65-73
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• 2011

After launch, in order to inject the geostationary satellite into its operational orbit, the perigee altitude are forced to be raised to geostationary altitude by firing onboard LAE(Liquid Apogee Engine) at apogee of the transfer orbit. In this process, the LAE burn is divided into three or four separated burns in order to control the orbit very precisely by giving feedback the determined orbit informations and to inject the satellite in predefined longitude. This paper proposes an algorithm to determine LAE firing time slots and ${\Delta}V$ vectors under assumption of impulsive LAE burning, and additionally, a method to compensate errors induced by continuous burning. And computer simulations have been performed to validate proposed algorithms.

• Nuclear Engineering and Technology
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• v.13 no.3
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• pp.153-161
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• 1981

The dynamic behavior of the Ko-ri Unit 1 nuclear reactor following some credible and postulated accidents has been analyzed to a certain extent by means of neutronics and temperature equations formulated in terms of point reactor model. In general, the result of numerical calculation is harnessed to be incorporated in more elaborate models so as to predict transient behavior in a reliable mode as a part of accident analysis. It is shown in the case of power response upon an uncontrolled withdrawal of rod cluster control assembly at hot full power that the point reactor kinetics model proves to be good enough to reproduce the generic features described in the final safety analysis report of the Ko-ri Unit 1.

• Communications for Statistical Applications and Methods
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• v.17 no.3
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• pp.367-376
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• 2010

Recently various methods were suggested and reviewed for estimating diffusion processes. Out of suggested estimation method, we mainly concerns on the estimation method using saddlepoint approximation method, and we suggest a term saddlepoint approximation(ASP) method which is the simplest saddlepoint approximation method. We will show that ASP method provides fast estimator as much as Euler approximation method(EAM) in computing, and the estimator also has good statistical properties comparable to the maximum likelihood estimator(MLE). By simulation study we compare the properties of ASP estimator with MLE and EAM, for Ornstein-Uhlenbeck diffusion processes.

• KDI Journal of Economic Policy
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• v.26 no.2
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• pp.281-314
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• 2004

This paper theoretically formulated and empirically explored the relationship between exchange rate pass-through (ERPT) for (average) market price and an individual country's price, using steel products data in the US market, with special reference to two major steel exporting countries, Korea and Japan. It was found that the direction of market ERPT can be different from that of individual ERPT that each exporter experiences, due to strategic interactions among producers and different parameters. Vector error correction (VEC) models and impulse response analysis were used with the statistical inference based on the bootstrap-after- bootstrap of Kilian (1998) for short-run, and the fully modified estimation of Phillips and Hansen (1990) was used for long-run. Empirical results indicate that market ERPT in the US market due to changes in Korea-US exchange rates is different from those due to changes in Japan-US exchange rates. The framework developed in this study indicates that this phenomenon is attributed to either (i) the two countries have individual ERPTs of different magnitudes and directions for the products in the US market, or (ii) the pricing strategies of the other exporters' (to the US steel market) respond differently depending on whether the price of the product from Korea changes or that from Japan does. As each exporter's ERPT can be significantly different, and market response to each country's ERPT can be also different, this study concludes that it is crucial for an exporter to understand how competitors in the market respond to changes in its price, as well as to understand how its price changes when the relevant exchange rate fluctuates.

• Journal of the Korean Vacuum Society
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• v.15 no.2
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• pp.209-215
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• 2006

We investigated the optical property and the electronic subband structure of InAs quantum dots in an InAsGa/GaAs well structure utilizing photoluminescence (PL), PL excitation (PLE) and near infrared transmission spectroscopy. From transmission and PLE spectra, we found three bound states in the InAs quantum dot and two bound states in InGaAs/GaAs quantum well, and correlated to the results of intersubband transitions observed in photocurrent spectrum.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.83-83
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• 2017

수자원공학에서 일강수량 모의기법은 다양한 목적으로 활용되고 있지만, 일반적으로 홍수와 가뭄의 영향을 고려할 수 있는 수공구조물의 위험도 및 신뢰성 평가 및 수자원 계획을 수립하기 위한 입력 자료생성을 목적으로 활용된다. 유역 단위의 분석시 단일 지점에 대한 강수 모의 기법을 적용할 경우 각각의 지점에서 관측된 강수 자료의 시계열 및 통계치 특성이 효과적으로 재현되지만 공간적으로 발생하는 즉, 지점 간의 종속관계를 재현하지 못하는 문제가 발생한다. 이러한 이유로 공간적인 전이 특성이 있는 가뭄 분석 및 유역내 유출량의 공간적 변동 특성 분석에 단일지점별 모의 결과를 이용할 경우 관측 자료와 상반된 공간적 변동성으로 인하여 잘못된 가뭄 및 유출 분석 결과가 도출되는 문제점이 있다. 따라서, 실제적으로 발생하는 강수 특성을 반영한 유역 단위의 홍수 및 가뭄 등의 수문 분석을 위해서는 지점간의 종속성을 반영할 수 있는 다지점 강수 모의 모형의 적용이 필수적이다. 본 연구에서는 다지점 모의에 있어서, Wilks 모형의 지점별 시변동 특성과 공간상관성 재현 능력, HMM 모형이 갖는 강수 사상별로 분포된 양적 분포 패턴 재현 능력을 복합적으로 나타낼 수 있는 새로운 다지점 일강수량 모의 모형인 기계학습 기반 범주화 기법을 이용한 다지점 일강수량 모의 모형(ML-MRS)을 개발하였다. 또한, 지점별 강수량에 적용되는 확률분포모형은 Gamma 분포로 구성된 혼합모형을 적용하여 단일 확률 분포 모형의 자료 적합 문제를 개선하였다. 모의를 통한 일강수량 시계열 자료는 일 강수자료의 통계량을 효과적으로 모의하였으며, 다지점 모형의 모의 결과를 적용한 가뭄 모의 결과 관측 자료에서 나타나는 공간적 패턴이 재현되었다. 본 모형은 시 공간적 사상을 효과적으로 재현함으로서 지역의 변동특성을 반영한 가뭄, 홍수, 기상 현상 분석 등 활용도가 매우 높을 것으로 판단된다.

• Economic and Environmental Geology
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• v.44 no.5
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• pp.399-412
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• 2011

A DEM (digital elevation model) is produced using a digital topographic map and is now a commonly used tool in geologic surveys. This study aimed to clarify the relationship between knickpoints and faults in the Namdae stream by analyzing a DEM of the area. The Namdae drainage basin was divided into three subbasins (S1, S2 and S3) and their knickpoints developed for the middle to mid-upper regions were extracted from the DEM. The relative steepness Ks and concavity depending on the incision rate was higher in S1 than in S2 and S3 regions. We assumed that the incision rate caused by active erosion resulted from several faults crossing the basins rather than differences in rock types. There are 77 knickpoints in the Namdae drainage area, including the low-ranking branch, and 24 of thses are on the main river system (S1, S2, S3). Of these 77 knickpoints, 27 (38%) are matched by faults, and from the three basins, 13 (54%) correspond with faults, indicating that the knickpoints are connected closely with the faults. For example the average Ks (relative steepness), was 38.8, but in the overlapping area of the Samdang and Doocheon faults the Ks value was 42.99~43.39. We suggest that the faults resulted in geomorphic deformation such as the high-Ksn knickpoints. There was little evdence of relationship between the knickpoints and rock boundaries, with 54% of the knickpoints distributed on the S1, S2, and S3 subbasins. We concluded that the drainage basin knickpoints are the result of fault movement and are a type of geomorphologic deformation that could be useful for surveying Quaternary faults or fault extension.

• Journal of the Korean Association of Geographic Information Studies
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• v.1 no.1
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• pp.8-17
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• 1998

This paper presents a method of construction and re-use of a GCP database for precision geometric correction of high resolution satellite images. Accurate geometric correction can be achieved by using accurate GCPs. The GCP information which is extracted from maps or other sources is saved in a database in conjunction with the corresponding image chips. The usage of the GCPs from the database gives reusability and efficiency in marking new GCPs. An image matching algorithm was developed to determine the corresponding positions between an image chip and a new image. The proposed technique can save time in the regular operation of satellite image preprocessing by propagating the pre-determined GCPs to the new image correction.