• 제목/요약/키워드: 임의시간

검색결과 1,198건 처리시간 0.027초

Conjugate Gradient Least-Squares Algorithm for Three-Dimensional Magnetotelluric Inversion (3차원 MT 역산에서 CG 법의 효율적 적용)

  • Kim, Hee-Joon;Han, Nu-Ree;Choi, Ji-Hyang;Nam, Myung-Jin;Song, Yoon-Ho;Suh, Jung-Hee
    • Geophysics and Geophysical Exploration
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    • 제10권2호
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    • pp.147-153
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    • 2007
  • The conjugate gradient (CG) method is one of the most efficient algorithms for solving a linear system of equations. In addition to being used as a linear equation solver, it can be applied to a least-squares problem. When the CG method is applied to large-scale three-dimensional inversion of magnetotelluric data, two approaches have been pursued; one is the linear CG inversion in which each step of the Gauss-Newton iteration is incompletely solved using a truncated CG technique, and the other is referred to as the nonlinear CG inversion in which CG is directly applied to the minimization of objective functional for a nonlinear inverse problem. In each procedure we only need to compute the effect of the sensitivity matrix or its transpose multiplying an arbitrary vector, significantly reducing the computational requirements needed to do large-scale inversion.

Processing of ρ-intersect Operation on RDF Data Using Suffix Array (RDF 데이터에서 접미사 배열을 이용한 ρ-intersect 연산의 처리)

  • Kim, Sung-Wan;Kim, Youn-Hee
    • Journal of the Korea Society of Computer and Information
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    • 제16권7호
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    • pp.95-103
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    • 2011
  • The actual utilization of Semantic Web technology which aims to provide more intelligent and automated service for information retrieval over the Web becomes gradually reality. RDF is widely used as the one of standard formats to present and manage the voluminous data on the Web. Efficient query processing on RDF data, therefore, is one of the ongoing research topics. Retrieving resources having a specific association from a given resource is the typical query processing type and several researches for this have done. However the most of previous researches have not fully considered discovering the complex relationship among resources such as returning the association between resources as the query processing result. This paper introduces the indexing and query processing for ρ-intersect operation which is one of the semantic association retrieval types. It includes an indexing scheme using suffix array and optimal processing approaches for handling ρ-intersect operation. The experimental evaluations shows that the average execution times for the proposed approach is 3~7 times faster than the previous approach.

Context-free Marker Controlled Watershed Transform for Efficient Multi-object Detection and Segmentation (다중 물체의 효과적 검출과 분할을 위한 문맥자유 마커제어 분수계 변환)

  • Seo, Gyeong-Seok;Jo, Sang-Hyeon;Choe, Heung-Mun;Park, Chang-Jun
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • 제38권3호
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    • pp.237-246
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    • 2001
  • A high speed context-free marker-controlled and minima imposition-free watershed transform is proposed for efficient multi-object detection and segmentation from a complex background. The context-free markers are extracted from a complex backgrounded multi-object image using a noise tolerant attention operator. These make marker-controlled watershed possible for the over-segmentation reduction without region merging. The proposed method presents a marker-constrained labeling that can speed up the segmentation of a marker-controlled watershed transform by eliminating the necessity of the minima imposition. Simulation results show that the proposed method can efficiently detects and segments multiple objects from a complex background while reducing over- segmentation and the computation time.

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Compressed Sensing and the Applications of Wireless Communications (압축 감지 기술과 무선통신 응용)

  • Hwang, Dae-Sung;Kim, Dae-Sung;Choi, Jin-Ho;Ha, Jeong-Seok
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • 제46권5호
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    • pp.32-39
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    • 2009
  • Compressed Sensing is a method to sample analog signals at a rate under the Nyquist rate. With this scheme, it is possible to represent signals with a relatively smaller number of measurements than that of the conventional sampling method, and the original signals are reconstructed with high probability from the acquired measurements using the linear programming. Compressed sensing allows measurement time and/or the amount of ADC (analog-to-digital converter) resources for the signal acquisitions to be reduced. In this paper, we presents the backgrounds of the compressed sensing, a way to acquire measurements from an analog signal with a random basis, and the signal recovery method. Also we introduce applications of compressed sensing in wireless communications.

The application of the combinatorial schemes for the layout design of Sensor Networks (센서 네트워크 구축에서의 Combinatorial 기법 적용)

  • Kim, Joon-Mo
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • 제45권7호
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    • pp.9-16
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    • 2008
  • For the efficient routing on a Sensor Network, one may consider a deployment problem to interconnect the sensor nodes optimally. There is an analogous theoretic problem: the Steiner Tree problem of finding the tree that interconnects given points on a plane optimally. One may use the approximation algorithm for the problem to find out the deployment that interconnects the sensor nodes almost optimally. However, the Steiner Tree problem is to interconnect mathematical set of points on a Euclidean plane, and so involves particular cases that do not occur on Sensor Networks. Thus the approach of using the algorithm does not make a proper way of analysis. Differently from the randomly given locations of mathematical points on a Euclidean plane, the locations of sensors on Sensor Networks are assumed to be physically dispersed over some moderate distance with each other. By designing an approximation algorithm for the Sensor Networks in terms of that physical property, one may produce the execution time and the approximation ratio to the optimality that are appropriate for the problem of interconnecting Sensor Networks.

A Study on the Wind-Induced Response Characteristics of Freeform Shaped Tall Building using FSI Analysis (FSI 해석에 의한 비정형 초고층 빌딩의 풍응답 특성에 관한 연구)

  • Park, Sung Chul;Kim, Hyo Jin;Han, Sang Eul
    • Journal of the Computational Structural Engineering Institute of Korea
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    • 제27권4호
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    • pp.223-230
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    • 2014
  • In this paper, the wind-induced response characteristics of freeform shaped tall building is studied by using FSI analysis. The analytical models are twist shaped ones at representing type of atypical tall building, and this study focused on the relationship between twist angle and wind acceleration. Firstly, 1-way FSI analysis is performed, so maximum lateral displacement of the analytical model for 100 years return period wind speed is calculated, then the elastic modulus of a structure that satisfies the constraints condition is evaluated. And 2-way FSI analysis is carried out. so acceleration of the analytical model for the evaluated modulus of elasticity and arbitrary density is predicted through time history analysis. The basic model is a set of a square shape, height is 400m, slenderness ratio is 8, and twist model is rotated at square model from 0 to 90 degrees at intervals of 15 degrees and from 90 to 360 degrees at intervals of 90 degrees. According to the result of predicting wind acceleration by the shape of each model, the wind vibration effect of square shape model is confirmed to be sensitive more than a twist shape ones.

A Study on Construction of Acoustical Phoneme Models Using Hidden Markov Network (Hidden Markov Network를 이용한 음향학적 음소모델 작성에 관한 검토)

  • Oh Se-Jin;Lim Young-Choon;Hwang Cheol-Jun;Kim Bum-Koog;Chung Hyun-Yeol
    • Proceedings of the Acoustical Society of Korea Conference
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    • 한국음향학회 2000년도 학술발표대회 논문집 제19권 2호
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    • pp.29-32
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    • 2000
  • 본 논문에서는 음성인식 시스템의 음향모델 개선을 위한 기초적 연구로서, 문맥적인 요소를 필요로 하는 SSS(Successive State Splitting)와 필요로 하지 않는 SSS-free 알고리즘을 이용한 HMnet(Hidden Markov Network) 음향모델 작성방법에 대해 검토하고 작성한 음향모델을 한국어에 적용하여 그 유효성을 확인하였다. HMnet을 이용한 음소모델의 작성방법은 전체 학습 데이터에 대해서 각각 2개의 상태를 가지는 초기 모델을 작성한 후, 이를 시간과 문맥방향으로의 최대 분포를 가지는 상태를 재분할한 후 임의의 상태수가 될 때까지 상태분할을 계속적으로 수행케 하여 각 음소모델을 작성하게 된다. 작성한 HMnet 음향모델의 유효성을 확인하기 위해 ETRI 445 단어의 3인에 대한 화자종속 음소인식 실험을 수행하였다. 인식실험 결과, SSS 알고리즘을 이용한 화자종속실험의 경우 상태수 520에서 평균 62.8%의 인식률을, SSS-free 알고리즘의 경우 상태수 420에서 평균 64.2%의 인식률을 얻었다. 이 결과는 HMM을 이용한 경우(약43.4%)보다 20%이상의 인식률 향상을 보여 이 알고리즘의 유효성을 확인할 수 있었다. SSS와 SSS-free를 비교한 경우, SSS-free가 SSS보다 낮은 상태수에서 평균 $1.4\% 향상된 인식률을 보였다.

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Effect of Combined Rainfall Observation with Radar and Rain Gauge (강우 레이더와 지상 우량계의 통합관측효과)

  • Yoo, Chul-Sang;Kim, Kyoung-Jun
    • Journal of Korea Water Resources Association
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    • 제40권11호
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    • pp.841-849
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    • 2007
  • This study evaluated the effect of combined rainfall observation of using rain gauge and rain radar. The effect of combined observations is to be evaluated by considering the decrease of measurement error due to combined use of design orthogonal observation methods. As an example, this study evaluated the rain gauge network of the Keum river basin, and showed how the density of rain gauges could be decreased by combining the radar observation. This study applied the researches on sampling error by North and Nakamoto(1989), Yoo et al. (1996) and Yoo (1997), also the simple NFD model for representing the rainfall field. The model parameters were decided using the rainfall characteristics (correlation time and length) estimated using the data collected in the Keum River Basin by 28 rain gauges and the operation rule of radar was assumed arbitrarily. This study considered the rain gauge density criteria provided by WMO(1994) and the rain gauge density installed in the Keum river basin to decrease the rain gauge density under the condition of introducing the radar.

Optimization of Microwave-Assisted Extraction under Atmospheric Pressure Condition for Soluble Ginseng Components (상압조건의 마이크로웨이브 추출공정에서 가용성 인삼성분의 추출조건 최적화)

  • Kwon, Joong-Ho;Kim, Kyung-Eun;Lee, Gee-Dong
    • Korean Journal of Food Science and Technology
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    • 제32권1호
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    • pp.117-124
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    • 2000
  • Considering the thermal unstableness of ginseng components, microwave-assisted extraction(MAE) was performed under the atmospheric pressure condition. The monitoring of extraction characteristics and the optimization of extraction conditions were made by response surface methodology. The extraction efficiency of soluble ginseng components was high at lower ethanol concentration and at higher microwave power, while crude saponin content was easily extracted at higher ethanol concentration. Estimated conditions for the maximized extraction of soluble components including crude saponin, total phenolics and electron donating ability were 5460 in ethanol concentration, 4190 W in microwave power, and within 4 min in extraction time. Predicted values at the optimum condition(60% ethanol, 80 W microwave power and 4 min extraction time) were in good agreement with observed values.

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Improved Progressive Photon Mapping Using Photon Probing (포톤 탐사법을 이용한 개선된 점진적 포톤 매핑)

  • Lee, Sang-Gil;Shin, Byeong-Seok
    • Journal of the Korea Computer Graphics Society
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    • 제16권3호
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    • pp.41-48
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    • 2010
  • Photon mapping is a traditional global illumination method using many photons emitted from the light source for photo-realistic rendering. However, this method needs a lot of resources to perform tracing of millions of photons. Progressive photon mapping solves this problem. Typical progressive photon mapping performs ray tracing at first to find the hit points on diffuse surface of objects. Next, light source repeatedly emits a small number of photons in photon tracing pass, and power of photons in each sphere that has a fixed radius with the hit points in the center is accumulated. This method requires less resources than previous photon mapping, but it spends much time for gathering enough photons since each of photons progresses through a random direction and rendering high quality image. To improve the method, we propose photon probing that calculates variance of photons in the sphere and controls radius of sphere. In addition, we apply cone filter in radiance estimation step for reducing aliasing at the edges in result image.