• 컴퓨터교육학회논문지
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• 제19권1호
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• pp.101-109
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• 2016

컴퓨팅 사고 교육에서 알고리즘의 설계는 학습자의 논리적 사고력과 절차적 사고력이 요구되는 중요한 학습 과정이다. 하지만 알고리즘 학습에 관한 연구와 학습자가 실제 학습에서 겪는 오류에 관한 연구가 부족한 실정이다. 이에 본 연구는 알고리즘 설계 학습에서 순서도를 활용한 프로그래밍 제어 구조 설계에서 발견된 학습자의 오류를 분석하여, 오류 유형을 제시하였다. 대학생을 대상으로 한 강의에서 세 가지 제어 구조에 관한 평가 문항을 제시한 결과, 순차 구조에서는 오류 유형이 발견되지 않았다. 하지만 조건 구조에서는 2개의 조건문이 중첩된 경우 조건 설정에서 오류가 발생하였다. 반복 구조에서는 반복의 횟수를 조절하는 조건, 반복되는 명령문의 위치, 중첩된 반복문에서 조건과 명령문의 위치 오류가 발견되었다. 본 연구에서 나타난 오류 유형은 초 중등학교와 대학에서 실시하고 있는 컴퓨팅 사고 교육의 알고리즘 설계 학습에 참고할 수 있는 사례가 될 것이다.

• 한국정보전자통신기술학회논문지
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• 제5권3호
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• pp.169-173
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• 2012

무선통신 시스템에서 신호의 다중경로 전달 과정에 의해 발생하는 지연 확산 현상 때문에 인접 심벌 간 간섭 (ISI, Inter-Symbol Interference)에 영향을 받는다. 본 논문에서는 다중 경로를 갖는 채널에서 채널 부호화 기법과 등화기가 결합하여 동작하는 터보 등화기를 갖는 시스템의 성능을 검증하였다. 그 결과 본 논문에서 사용한 터보 등화기를 이용하여 반복 복호를 하였을 때는, 1회 반복 시 BER 10-4을 기준으로 반복이 없는 등화기를 사용하였을 때 보다 1.5 dB 성능이 향상되었다. 또한 터보 등화기의 반복이 2, 3 회로 늘어남에 따라 약 3.5 dB 성능이 향상되었고, 3회 이상 반복하였을 때는 더 이상 성능이 향상되지 않음을 알 수 있었다.

• 대기
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• 제29권3호
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• pp.241-255
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• 2019

Bias correction (BC) and quality control (QC) are essential steps for the proper use of satellite observations in data assimilation (DA) system. BC should be calculated over quality controlled observation. And also QC should be performed for bias corrected observation. In the Korea Institute of Atmospheric Prediction Systems (KIAPS) Package for Observation Processing (KPOP), we adopted an adaptive BC method that calculates the BC coefficients with background at the analysis time rather than using static BC coefficients. In this study, we have developed an iterative QC-BC method for Advanced Microwave Sounding Unit-A (AMSU-A) to reduce the negative feedback from the interaction between BC and QC. The new iterative QC-BC is evaluated in the KIAPS 3-dimensional variational (3DVAR) DA cycle for January 2016. The iterative QC-BC method for AMSU-A shows globally significant benefits for error reduction of the temperature. The positive impacts for the temperature were predominant at latitudes of $30^{\circ}{\sim}90^{\circ}$ of both hemispheres. Moreover, the background warm bias across the troposphere is decreased. Even though AMSU-A is mainly designed for atmospheric temperature sounding, the improvement of AMSU-A pre-processing module has a positive impact on the wind component over latitudes of $30^{\circ}S$ near upper-troposphere, respectively. Consequently, the 3-day-forecast-accuracy is improved about 1% for temperature and zonal wind in the troposphere.

• 한국공간구조학회논문집
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• 제17권4호
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• pp.149-157
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• 2017

An innovative analysis method is proposed in this paper for the determination of ultimate resistance of prestressed concrete beams. The proposed method can be applied to simply supported or continuous beams in a unified manner whether structure and external loads are symmetric or not. Through the iterative nonlinear strain compatibility solutions, this method can also be applied to the non-prismatic section/un-symmetrical composite structures under moving load. The conventional studies have used the failure criteria when the strain of concrete reaches 0.003. However compared with bonded case, the value of strain in the reinforcement is much smaller than bonded case, thus, unbonded prestressed cases show compressive failure mode. It is shown that the proposed method gives acceptable results within 5% error compared with the prior experimental results. It can be shown that the proposed method can reach the solution much faster than typical three-dimensional finite element analysis for the same problem. This method is applicable to the existing unbonded prestressed members where deterioration has occurred leading to the reduced ultimate resistance or safety. In all, the proposed procedure can be applied to the design and analysis of newly constructed structures, as well as the risk assessment of rehabilitated structures.

• 한국정밀공학회지
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• 제16권6호
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• pp.148-159
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• 1999

A numerical method is presented for the dynamic analysis of spur gears rotating with very high angular speeds. For an efficient computation each gear is assumed to consist of a rotating rigid disk and an elastic tooth having mass, and finite element formulations are used for the equations of motion of the tooth. The geometric constraint is imposed between the rigid disk and the elastic tooth to fix them, and contact condition is imposed between the meshing teeth of the gears. At each iteration of each time step the Lagrange multiplier and contact force are revised by using the constraint error vector, and then the whole equations of motion are time integrated with the given Lagrange multiplier and contact force. For the accurate solution the velocity and acceleration constraints as well as the displacement constraint are satisfied by the monotone reductions of the constraint error vectors. Computing procedures associated with the iterative schemes are explained and numerical simulations are conducted with the spur gears.

• 전자공학회논문지C
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• 제36C권5호
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• pp.13-26
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• 1999

본 논문은 다양한 회로 연결선 모형 중에서 연결선 변수 및 동작 환경에 다라 최적 모형을 쉽게 선택할 수 있는 기준을 제시하고자 한다. 이를 위하여 먼저 연결선의 총 저항, 인덕턴스, 커패시턴스 값 및 신호의 동작주파수를 기반으로 정량적 모형화 오차 분석에 근거하여 인덕턴스의 영향을 고려하여 모형화해야 하는 RLC-class 모형 영역과 그럴 필요가 없는 RC-class모형 영역으로 분할하는 방법을 제시한다. 칩 내부 연결선의 대부분을 차지하는 RC-class 회로 모형은 모형 차수 축소 기법을 통하여 효율적으로 해석될 수 있다. RLC-class 회로 모형은 주어진 허용 모형화 오차 및 전기 변수에 따라 ILC(Iterative Ladder Circuit) 거시 모형, MC(Method of Characteristics)거시 모형 및 상태 기반 컨벌루션(comvolution) 방법 중에서 최적인 모형을 선정하게 된다. 본 논문은 SPICE류의 범용 회로 시뮬레이션 앨고리즘을 가정할 때, 세부 모형들의 시뮬레이션 비용을 감안하고서 최적 모형을 찾는 영역 구성도를 제시한다. 본 논문에서 제시하는 거시모형화 방법은 회로의 수동성을 유지하며, 따라서 무조건적 안정도를 보장할 수 있다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 추계학술대회논문집
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• pp.79-82
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• 2004

In this study, a new refinement technique for 3-dimensional hexahedral element mesh is proposed, which is aimed at the control of mesh density. With the proposed scheme the mesh is refined adaptively to the elemental error which is estimated by 'a posteriori' error estimator based on the energy norm. A desired accuracy of an analysis i.e. a limit of error defines the new desired mesh density map on the current mesh. To obtain the desired mesh density, the refinement procedure is repeated iteratively until no more elements to be refined exist. In the algorithm, at first the regions of mesh to be refined are defined and, then, the zero-thickness element layers are inserted into the interfaces between the regions. All the meshes in the regions, in which the zero-thickness layers are inserted, are to be regularized in order to improve the shape of the slender elements on the interfaces. This algorithm is tested on a simple shape of 2-d quadrilateral element mesh and 3-d hexahedral element mesh. A numerical example of elastic deformation of a plate with a hole shows the effectiveness of the proposed refinement scheme.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 추계종합학술대회 논문집
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• pp.759-762
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• 1999

In this paper, we introduce the concept of a HAPS(High Altitude Platform Station) system which is expected to be a next generation communication system and suggest several error correcting codes to provide high quality services. Since a HAPS system encounters serious signal attenuation due to rain and scattering in the air, concatenated codes which have a high coding gain is considered to be a proper error correcting method. In this paper, we provide performance analyses result of two candidate coding schemes for a HAPS. The first one is a conventional concatenated coding scheme, and the second one is a iterative decoding method known as Turbo Codes.

• Journal of the Korean Data and Information Science Society
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• 제25권5호
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• pp.1151-1160
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• 2014

In DNA microarray studies, the number of genes far exceeds the number of samples and the gene expression measures are highly correlated. Partial least squares regression (PLSR) is one of the popular methods for dimensional reduction and known to be useful for the classifications of microarray data by several studies. In this study, we suggest a modified version of the partial least squares regression to analyze gene expression data with survival information. The method is designed as a new gene selection method using PLSR with an iterative procedure of imputing censored survival time. Mean square error of prediction criterion is used to determine the dimension of the model. To visualize the data, plot for variables superimposed with samples are used. The method is applied to two microarray data sets, both containing survival time. The results show that the proposed method works well for interpreting gene expression microarray data.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권1호
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• pp.253-271
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• 2017

In this paper, considering that perfect channel state information (CSI) is hard to achieve in practice, the downlink capacity of distributed antenna systems (DAS) with imperfect CSI and multiple receive antennas is investigated over composite Rayleigh fading channel. According to the performance analysis, using the numerical calculation, the probability density function (PDF) of the effective output SNR is derived. With this PDF, accurate closed-form expressions of ergodic capacity and outage probability of DAS with imperfect CSI are, respectively, obtained, and they include the ones under perfect CSI as special cases. Besides, the outage capacity of DAS in the presence of imperfect CSI is also derived, and a Newton's method based practical iterative algorithm is proposed to find the accurate outage capacity. By utilizing the Gaussian distribution approximation, another approximate closed-form expression of outage capacity is also derived, and it may simplify the calculation of accurate outage capacity. These theoretical expressions can provide good performance evaluation for downlink DAS for both perfect and imperfect CSI. Simulation results verify the effectiveness of the theoretical analysis, and the system capacity can be improved by increasing the receive antennas, and decreasing the estimation error or path loss. Moreover, the system can tolerate the estimation error variance up to about 0.01 with a slight degradation in the capacity.