• 한국산학기술학회논문지
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• 제18권5호
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• pp.738-744
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• 2017

최근 신재생에너지의 확대 보급과 더불어 전기저장장치(ESS, Energy Storage System)가 활발하게 도입되고 있다. 하지만 현재 전기저장장치에 대한 도입효과와 경제성 및 계통에 미치는 영향에 대한 구체적인 평가방법이 없어 효과적인 도입운용이 어려운 실정이다. 특히 주파수조정용 ESS에 대한 국제적인 기술표준 및 제도가 마련되지 않아, 이의 설치에 따른 전기품질, 계통영향, 기여도 등은 물론 편익 산정에 대한 종합적인 연구가 필요한 실정이다. 따라서 본 논문에서는 주파수조정용 ESS의 성능검증 방안을 마련하기 위하여, 기존발전기의 주파수조정 성능평가 방법인 미국 PJM의 AGC(Automatic Generation Control, 발전기 자동발전제어) 성능 평가방식을 분석하여, 주파수조정용 ESS의 성능평가 알고리즘을 제안하였고, 고가발전기의 정산금과 화력발전기의 정산금을 이용하여 500MW급의 주파수조정용 ESS의 도입에 따른 편익을 산정할 수 있는 경제성 평가 알고리즘을 제시하였다. 제안한 알고리즘의 유용성을 확인하기 위하여, 실 계통 데이터를 바탕으로 시뮬레이션을 수행한 결과, 전기저장장치가 기존의 발전기에 비하여 아주 우수한 성능을 가지고 있음을 확인하였고, 500MW 도입시 연간 약 3,457~4,296억의 편익이 발생함을 확인하였다.

• 한국군사과학기술학회지
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• 제14권4호
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• pp.539-547
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• 2011

In this paper, a method of generating path planning map is developed using digitalized geographic information such as FDB(Feature DataBase). FDB is widely used by the Army and needs to be applied to all weapon systems of newly developed. For the autonomous navigation of a robot, it is necessary to generate a path planning map by which a global path can be optimized. First, data included in FDB is analyzed in order to identify meaningful layers and attributes of which information can be used to generate the path planning map. Then for each of meaningful layers identified, a set of values of attributes in the layer is converted into the traverse cost using a matching table in which any combination of attribute values are matched into the corresponding traverse cost. For a certain region that is gridded, i.e., represented by a grid map, the traverse cost is extracted in a automatic manner for each gird of the region to generate the path planning map. Since multiple layers may be included in a single grid, an algorithm is developed to fusion several traverse costs. The proposed method is tested using a experimental program. Test results show that it can be a viable tool for generating the path planning map in real-time. The method can be used to generate other kinds of path planning maps using the digitalized geographic information as well.

• 한국항공우주학회지
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• 제35권8호
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• pp.685-692
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• 2007

본 연구에서는 헬리콥터 하중 해석을 위한 통합해석코드에서 사용되는 에어포일의 공력 성능 테이블 작성 자동화를 위한 GUI 프로그램을 개발하였다. 개발 후 상용화를 위해 PC환경에서 사용이 보편화 되어 있는 윈도우 운영체제 기반으로 프로그램을 개발하였다. 또한, 별도의 과정을 거치지 않고도 계산 과정 및 생성된 격자 표시등의 결과를 확인할 수 있는 후처리 기능을 포함하여 사용자의 편의를 도모하였다. 기 검증된 기존의 전산유체역학 코드를 기본으로 하여 다양한 받음각과 마하수 영역에서 공력해석이 자동적으로 수행되도록 하였으며, 계산 격자는 에어포일 표면 좌표가 입력되면 자동으로 생성되도록 하였다. FORTRAN 으로 작성된 전산유체역학 코드를 별도의 변환 과정 없이 C++ 기반의 GUI 프로그램과 연동시키기 위하여 Mixed-Language 기법을 사용하였다.

• 전자공학회논문지A
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• 제32A권11호
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• pp.52-62
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• 1995

We developed a two-dimensional numerical simulator which can analyze the electrical as well as optical characteristics and evaluate the detection performances of self-signal processing infrared detectors. It solves the poisson equation and the electron, hole current continuity equations including the optical generation and recombination models. To speed up convergency rate. the Newton algorithm is used. Automatic triangular grid generator make it easy to simulate the devices with the various read-out geometries. This simulator can show the variation of spatial resolution which is caused by the transit velocity and transit time dispersion in bifurcate and horn geometries respectively. Also, we calculated the responsivity, noise, and detectivity in respect of the applied electric field and background field-of-view. The results obtained from simulation correspond to those of experiments, and it is verified that horn read-out geometry has the superior spatial resolution and detection performance to bifurcate geometry.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.538-543
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• 2007

A procedure is proposed to generate optimal grid with minimal user intervention while keeping a prescribed level of accuracy, using an adaptive X-FEM and applied to shape optimization. In spite of various advantages of X-FEM, however, there are several obstacles for practical applications. Because of using a uniform background mesh and additional degree of freedoms for enrichment, an X-FEM is usually computationally more expensive than traditional finite element method. Furthermore, there are often accuracy problems. For an automatic procedure of optimal mesh generation, an h-adaptive scheme and a posteriori error estimation obtained by a post-processing process are utilized. The procedure is shown by 2-D shape optimization examples.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.510-513
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• 2008

The traditional computational fluid or structure dynamics analysis approaches have contributed to solve many delicate engineering problems. But for the most of recent engineering problems which are influenced by fluid-structure interaction effect strongly, traditional individual approaches have limited analysis abilities for the exact simulation. Owing to above-mentioned reason, nowadays fluid-structure interaction analysis has become a matter of concern and interest. FSI analysis require several unprecedented techniques for the combining individual analysis tool into integrated analysis tool. The Arbitrary Lagrangian-Eulerian(ALE, in short) method is the new description of continum motion,which combines the advantages of the classical kinematical descriptions, i.e. Lagrangian and Eulerian description, while minimizing their respective drawbacks. In this paper, the ALE description is adapted to simulate fluid-structure interaction problems. An automatic re-mesh algorithm and a fluid-structure coupling process are included to analyze the interaction and moving motion during the 2-D axisymmetric solid rocket interior FSI phenomena simulation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권10호
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• pp.2768-2787
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• 2023

As an important research direction of the application of computer science in the medical field, the automatic generation technology of radiology report has attracted wide attention in the academic community. Because the proportion of normal regions in radiology images is much larger than that of abnormal regions, words describing diseases are often masked by other words, resulting in significant feature loss during the calculation process, which affects the quality of generated reports. In addition, the huge difference between visual features and semantic features causes traditional multi-modal fusion method to fail to generate long narrative structures consisting of multiple sentences, which are required for medical reports. To address these challenges, we propose a multi-feature optimization Transformer (MFOT) for generating radiology reports. In detail, a multi-dimensional mapping attention (MDMA) module is designed to encode the visual grid features from different dimensions to reduce the loss of primary features in the encoding process; a feature pre-fusion (FP) module is constructed to enhance the interaction ability between multi-modal features, so as to generate a reasonably structured radiology report; a detail enhanced attention (DEA) module is proposed to enhance the extraction and utilization of key features and reduce the loss of key features. In conclusion, we evaluate the performance of our proposed model against prevailing mainstream models by utilizing widely-recognized radiology report datasets, namely IU X-Ray and MIMIC-CXR. The experimental outcomes demonstrate that our model achieves SOTA performance on both datasets, compared with the base model, the average improvement of six key indicators is 19.9% and 18.0% respectively. These findings substantiate the efficacy of our model in the domain of automated radiology report generation.

• International Journal of Computer Science & Network Security
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• 제22권5호
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• pp.294-302
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• 2022

Detection of fake news is a complex and a challenging task. Generation of fake news is very hard to stop, only steps to control its circulation may help in minimizing its impacts. Humans tend to believe in misleading false information. Researcher started with social media sites to categorize in terms of real or fake news. False information misleads any individual or an organization that may cause of big failure and any financial loss. Automatic system for detection of false information circulating on social media is an emerging area of research. It is gaining attention of both industry and academia since US presidential elections 2016. Fake news has negative and severe effects on individuals and organizations elongating its hostile effects on the society. Prediction of fake news in timely manner is important. This research focuses on detection of fake news spreaders. In this context, overall, 6 models are developed during this research, trained and tested with dataset of PAN 2020. Four approaches N-gram based; user statistics-based models are trained with different values of hyper parameters. Extensive grid search with cross validation is applied in each machine learning model. In N-gram based models, out of numerous machine learning models this research focused on better results yielding algorithms, assessed by deep reading of state-of-the-art related work in the field. For better accuracy, author aimed at developing models using Random Forest, Logistic Regression, SVM, and XGBoost. All four machine learning algorithms were trained with cross validated grid search hyper parameters. Advantages of this research over previous work is user statistics-based model and then ensemble learning model. Which were designed in a way to help classifying Twitter users as fake news spreader or not with highest reliability. User statistical model used 17 features, on the basis of which it categorized a Twitter user as malicious. New dataset based on predictions of machine learning models was constructed. And then Three techniques of simple mean, logistic regression and random forest in combination with ensemble model is applied. Logistic regression combined in ensemble model gave best training and testing results, achieving an accuracy of 72%.

• 대한기계학회논문집B
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• 제22권9호
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• pp.1325-1334
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• 1998

The objectives of the present study are to develop a systematic method rather than a conventional trial-and-error method for an optimal shape design using a mathematical theory, and to apply it to engineering problems. In the present study, an optimal condition for a minimum pressure loss in a two-dimensional curved duct flow is derived and then an optimal shape of the curved duct is designed from the optimal condition. In the design procedure, one needs to solve the adjoint Navier-Stokes equations which are derived from the Navier-Stokes equations and the cost function. Therefore, a computer code of solving both the Navier-Stokes and adjoint Navier-Stokes equations together with an automatic grid generation is developed. In a curved duct flow, flow separation occurs due to an adverse pressure gradient, resulting in an additional pressure loss. Optimal shapes of a curved duct are obtained at three different Reynolds numbers of 100, 300 and 800, respectively. In the optimally shaped curved ducts, the separation region does not exist or is significantly reduced, and thus the pressure loss along the curved duct is significantly reduced.

• 전력전자학회논문지
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• 제11권4호
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• pp.349-360
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• 2006

이중여자 유도형 풍력발전 시스템은 다른 풍력발전 시스템에 비하여 에너지 변환 효율이 우수하고 전력변환 장치의 용량이 작아도 되는 특성이 있다. 이러한 특징을 살리기 위해서는 풍력발전 시스템에 입력되는 에너지의 변화를 고려하여 발전기의 제어기를 설계해야 한다. 본 논문에서는 상위 제어기와 하위 제어기로 구분하여 이중여자 유도 발전기의 제어기를 설계하였다. 상위 제어가는 풍력발전 시스템에 입력되는 에너지가 변화함에 따라서 발전기의 운전모드를 결정하고 제어 기준값을 계산한다. 발전기의 운전모드는 최저 속도 제어와 가변 토크 제어, 그리고 토크 제한 모드로 구성된다. 하위 제어기는 상위 제어기의 지령에 따라서 발전 시스템의 전류를 제어한다. 또한 본 논문에서는 3kW급 권선형 유도기를 사용한 이중여자 유도형 풍력발전기의 시뮬레이터를 제작하였다. 설계한 제어기는 시뮬레이터에 적용하여 실험적으로 검증하였다.