• The Transactions of the Korea Information Processing Society
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• 제7권1호
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• pp.252-265
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• 2000

In this thesis, the analysis of data processing method and the amount of computation in the whole geometry processing is conducted step by step. Floating-point ALU design is based on the characteristics of geometry processing operation. The performance of the devised ALU fitting with the geometry processing operation is analyzed by simulation after the description of the proposed ALU and geometry processor. The ALU designed in the paper can perform three types of floating-point operation simultaneously-addition/subtraction, multiplication, division. As a result, the 23.5% of improvement is achieved by that floating-point ALU for the whole geometry processing and in the floating-point division and square root operation, there is another 23% of performance gain with adding area-performance efficient SRT divisor.

• Journal of the Korean School Mathematics Society
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• 제17권2호
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• pp.291-319
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• 2014

The purpose of this study is to investigate students' thinking and understanding through working on Worked-out Examples on numbers and operations, specifically, radical and real numbers and operations in the middle grades. For this purpose, we developed a set of Worked-out Examples; middle school students independently worked on them. Then two students were interviewed. These data were analyzed by using the framework of mathematical proficiency. The data analysis suggested that the students seemed to go through the processes involving a combination of understanding and computation, computation and reasoning, and understanding, computation and reasoning. Also, it appeared that most of the students have difficult solving problems involving with radical and real numbers in related to strategic competence.

• The Bulletin of The Korean Astronomical Society
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• 제37권2호
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• pp.129.1-129.1
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• 2012

서포트 벡터 머신(Support Vector Machine, SVM)과 인공신경망 모형(Neural Network, NN)을 사용하여 태양 양성자 현상(Solar proton event, SPE)의 플럭스 세기를 예측해 보았다. 이번 연구에서는 1976년부터 2011년까지 10MeV이상의 에너지를 가진 입자가 10개 cm-1 sec-1 ster -1 이상 입사할 경우를 태양 양성자 현상으로 정의한 NOAA의 태양 고에너지 입자 리스트와 GOE위성의 X-ray 플레어 데이터를 사용하였다. 여기에서 C, M, X 등급의 플레어와 관련있는 178개 이벤트를 모델의 훈련을 위한 데이터(training data) 89개와 예측을 위한 데이터(prediction data) 89개로 구분하였다. 플러스 세기의 예측을 위하여, 우리는 로그 플레어 세기, 플레어 발생위치, Rise time(플레어 시작시간부터 최대값까지의 시간)을 모델 입력인자로 사용하였다. 그 결과 예측된 로그 플럭스 세기와 관측된 로그 플럭스 세기 사이의 상관계수는 SVM과 NN에서 각각 0.32와 0.39의 값을 얻었다. 또한 두 값 사이의 평균 제곱근 오차(Root mean square error)는 SVM에서 1.17, NN에서는 0.82로 나왔다. 예측된 플럭스 세기와 관측된 플럭스 세기의 차이를 계산해 본 결과, 오차 범위가 1이하인 경우가 SVM에서는 약 68%이고 NN에서는 약 80%의 분포를 보였다. 이러한 결과로부터 우리는 NN모델이 SVM모델보다 플럭스 세기를 잘 예측하는 것을 알 수 있었다.

• Korean Journal of Optics and Photonics
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• 제11권5호
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• pp.347-352
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• 2000

We have stabIhzed the laser frequency of a commercial dIode laser using a ULE (Ultra-low expansion material) reference cavIty and the cunent modulation charactenstics of the dIode itself The liuewIdth of the frce running laser was about a 1 MHz (rms) for a sampling time of 1 s and the drift rate was 300 kHz/s. Vvhen the laser is locked to oue sIde of the transmission signal from the ULE reference cavity, the lincwidth was reduced to 46 kHz (nus) for a sampling time longer than 10 ms. The root Allan variance was less than 2 kHz for a sampling time langeI than10 ms. 10 ms.

• Korean Journal of Optics and Photonics
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• 제6권3호
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• pp.222-227
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• 1995

A single mode, 100-mW diode laser was injection-locked by the master laser which was spectrally narrowed with Littman-type grating feedback. In the incomplete-injection-locking, we observed that two frequencies were simultaneously generated from the slave laser. The power ratio and frequency shift of two frequency components were proportional to the square of injected laser intensity. When the ratio of the injection intensity to the slave laser intensity was about $10^{-3}$, the injection-locking bandwidth was to be about 1.4 GHz. The bandwidth proportionally increased to the square root of the injection intensity, which was in good agreement with the theoretical predictions. The Iinewidth of the locked-laser was about 2.5 MHz, which was five times as narrow as that of free-running operation. ation.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제17권8호
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• pp.1891-1898
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• 2013

To efficiently execute 3D graphic APIs, such as OpenGL and Direct3D, special purpose arithmetic unit(SFU) which supports floating-point sine, cosine, reciprocal, inverse square root, base-two exponential, and logarithmic operations is designed. The SFU uses second order minimax approximation method and lookup table method to satisfy both error less than 2 ulp(unit in the last place) and high speed operation. The designed circuit has about 2.3-ns delay time under 65nm CMOS standard cell library and consists of about 23,300 gates. Due to its maximum performance of 400 MFLOPS and high accuracy, it can be efficiently applicable to mobile 3D graphics application.

• The Korean Journal of Applied Statistics
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• 제28권1호
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• pp.75-82
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• 2015

We discuss confidence intervals for sensitive binomial attributes obtained by a direct question method and indirect question method. The Randomized Response Technique(RRT) by Warner (1965) is an indirect question method that uses a randomization device to reduce the response burden of respondents. We used the mean coverage probability (MCP), root mean squared error (RMSE), and mean expected width (MEW) to compare the confidence intervals by the two methods. The numerical comparisons indicated found that the MEW of RRT is too large and the RRT is so conservative that the MCP exceeds a nominal level(${\alpha}$); therefore, it is necessary to complement these problem in order to increase the utility of the indirect question method.

• The Korean Journal of Applied Statistics
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• 제30권1호
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• pp.69-82
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• 2017

R-indicator (representativeness indicator) is used to check the representativeness of samples when non-responses occur. The representativeness is related with the accuracy of parameter estimator and the accuracy is related with bias of the estimator. Hence, unbiased estimator generates high accuracy. Therefore, high value of R-indicator guarantees the accuracy of parameter estimation with a small bias. R-indicator is calculated through propensity scores obtained by logit or probit modeling. In this paper we investigate the degree of relation between R-indicator and different non-response rates in strata using simulation studies. We also analyze a modified Korea Economic Census data for real data analysis.

• Korean Journal of Optics and Photonics
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• 제9권2호
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• pp.86-91
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• 1998

Multimode planar waveguides have been fabricated by an electric-field assisted ion exchange in soda-lime glass substrates. Measurements of the mode indices have been made and the index profiles modeled on modified Fermi function are explained by a comparative analysis with the concentration profiles obtained using an electron probe X-ray micro analyzer. The analytical measurements showed that no more than 95% of sodium ions were replaced by the cesium ions. We established formulas for guide depth, mobility, and refractive index change, given the applied electric field, the diffusion temperature, and the time. We have verified the linear relations in the formulas not only between guide and root of diffusion time but also between guide depth and the applied electric filed experimentally.

• Proceedings of the Korea Water Resources Association Conference
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• 한국수자원학회 2012년도 학술발표회
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• pp.945-945
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• 2012

본 연구에서는 낙동강 수계의 안동댐 유역을 대상지역으로 선정하여 미래 기후변화 시나리오에 따른 댐 유역의 수환경 영향을 예측해 보고자 하였다. 특히 미래기후에 대한 수환경 평가는 기후자료를 입력 값으로 요구하는 강우-유출모형을 이용하거나 유량 이외에 유사, 영양물질과 같은 수질인자를 동시에 모의할 수 있는 유역모형을 이용하여 평가하는 것이 일반적이다. 이를 위해 선행연구로 IPCC(Intergovernmental Panel on Climate Change)에서 제공하는 AR4 시나리오의 RCM 자료를 ANN(Artificial Neural Network)기법을 이용하여 안동댐 유역의 총 4개 기상관측소에 대한 과거 20년(1991~2010) 실측자료를 바탕으로 미래 강수 및 습도 그리고 온도에 대해 상세화 하여 미래 기후 시나리오를 생산하였다. 또한 안동댐 유역 단위의 수질을 예측하기 위해 토양과 토지이용 및 토지관리 상태에 따른 수문-수질 모의가 가능한 유역모형인 SWAT(Soil and Water Assessment Tool)을 이용하였다. 과거의 기상자료와 수질자료를 이용하여 유역모델의 검 보정을 실시하였으며 모형의 보정 및 검증결과에 따른 적합성과 상관성을 판단하기 위해 결정계수($R^2$)와 평균제곱근오차(Root Mean Square Error, RMSE)를 사용하였으며, 모형의 효율성 검증으로는 Nash and Sutcliffe(1970)가 제안한 모형효율성계수(NSE)를 사용하였다. 최종적으로 기후 시나리오에 대해서 전망된 지역상세기후를 유역모형의 입력자료로 이용하여 안동댐 유역의 미래수문 및 수질을 예측하고자 하였다.