• International Journal of Computer Science & Network Security
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• v.23 no.5
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• pp.1-6
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• 2023

Text mining (TM) is most widely used to process the various unstructured text documents and process the data present in the various domains. The other name for text mining is text classification. This domain is most popular in many domains such as movie reviews, product reviews on various E-commerce websites, sentiment analysis, topic modeling and cyber bullying on social media messages. Cyber-bullying is the type of abusing someone with the insulting language. Personal abusing, sexual harassment, other types of abusing come under cyber-bullying. Several existing systems are developed to detect the bullying words based on their situation in the social networking sites (SNS). SNS becomes platform for bully someone. In this paper, An Enhanced text mining approach is developed by using Ensemble Algorithm (ETMA) to solve several problems in traditional algorithms and improve the accuracy, processing time and quality of the result. ETMA is the algorithm used to analyze the bullying text within the social networking sites (SNS) such as facebook, twitter etc. The ETMA is applied on synthetic dataset collected from various data a source which consists of 5k messages belongs to bullying and non-bullying. The performance is analyzed by showing Precision, Recall, F1-Score and Accuracy.

• Composites Research
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• v.20 no.3
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• pp.31-36
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• 2007

A quantitative prediction method for initial crack length in a carbon/epoxy (CF/EP) composite beam using active piezoelectric transducers was established in this study. Wavelet Transform (WT)-based signal processing and identification technique in time-frequency domain was developed to facilitate the determination of damage presence and severity. Dynamic response of a CF/EP composites beam containing a continuously expanding crack, coupled with a pair of active piezoelectric disks, was examined under a narrow band excitation, and then applied with the proposed signal processing technique.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.197-197
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• 2021

최근 기후변화와 하천 제방의 노후화로 인해 수재해 위험이 지속적으로 증가하고 있다. 그러나 기존의 재래적인 하천 제방의 점검은 많은 인력과 예산 소모로 비효율적이며 제방 전구간 점검의 한계, 객관성의 한계 등 많은 한계점들이 존재하여 효과적인 홍수 대응을 위해 새로운 모니터링과 예/경보 시스템의 구축이 반드시 필요한 상황이다. 따라서 본 연구는 인공위성을 이용한 하천 제방 변위 산출과 수문학적 요인과의 관계 분석을 통해 하천 제방 건강상태 모니터링 시스템 방안을 제안하고자 한다. Sentinel-1 SAR 영상과 유럽 우주국(ESA)의 위성 영상 전처리 도구인 SNAP을 이용하여 2020년 여름 붕괴된 남원시의 금곡교 제방의 봄(4~5월), 여름(7~8월)의 변위를 산출하였고, 제방의 위험도 산정을 위해 토양수분관계를 분석하였다. 선행 연구(김상우,2019)에서는 농촌진흥청에서 제공하는 TDR(Time Domain Reflectrometry) 관측값과 Sentinel-1 SAR의 후방 산란계수의 토양수분관계가 일치하는 경향을 제시하여, 본 연구에서는 이를 이용하여 제방 후 방산란계수를 산출하고 변위와 토양수분도의 상관관계를 분석하여 변위 추세와 토양수분도의 추세가 일치하는 경향을 확인하였다. 본 연구 결과를 통해 향후에는 위성을 이용하여 산출한 제방의 변위와 토양수분도의 불확실성을 보완하고 기온, 수위, 토양도, 지하수위와 같은 수문기상학적 데이터의 분석을 통해 초정밀, 자동화 하천 제방 건강상태 모니터링 시스템이 구현 가능할 것으로 기대한다.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.122-122
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• 2020

Urban flood simulation plays a vital role in national flood early warning, prevention and mitigation. In recent studies on 2-dimensional flood modeling, the integrated run-off inundation model is gaining grounds due to its ability to perform in greater computational efficiency. The adaptive quadtree shallow water numerical technique used in this model implements the adaptive mesh refinement (AMR) in this simulation, a procedure in which the grid resolution is refined automatically following the flood flow. The method discounts the necessity to create a whole domain mesh over a complex catchment area, which is one of the most time-consuming steps in flood simulation. This research applies the dynamic grid refinement method in simulating the recent extreme flood events in Metro Manila, Philippines. The rainfall events utilized were during Typhoon Ketsana 2009, and Southwest monsoon surges in 2012 and 2013. In order to much more visualize the urban flooding that incorporates the flow within buildings and high-elevation areas, Digital Surface Model (DSM) resolution of 5m was used in representing the ground elevation. Results were calibrated through the flood point validation data and compared to the present flood hazard maps used for policy making by the national government agency. The accuracy and efficiency of the method provides a strong front in making it commendable to use for early warning and flood inundation analysis for future similar flood events.

• Steel and Composite Structures
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• v.48 no.2
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• pp.131-143
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• 2023

The CFRP bar was used to achieve more ductile and durable headed-stud shear connectors in composite components. Three series of push-out tests were firstly conducted, including specimens reinforced with pure steel fibers, steel and CFRP bars. The distributed stress was measured by the commercial PPP-BOTDA (Pre-Pump-Pulse Brillouin optical time domain analysis) optical fiber sensor with high spatial resolution. A series of numerical analyses using non-linear FE models were also made to study the shear force transfer mechanism and crack response based on the test results. Test results show that the CFRP bar increases the shear strength and stiffness of the large diameter headed-stud shear connection, and it has equivalent reinforcing effects on the stud shear capacity as the commonly used steel bar. The embedded CFRP bar can also largely improve the shear force transfer mechanism and decrease the tensile stress in the transverse direction. The parametric study shows that low content steel fibers could delay the crack initiation of slab around the large diameter stud, and the CFRP bar with normal elastic modulus and the standard reinforcement ratio has good resistance to splitting crack growth in headed stud shear connectors.

• Current Optics and Photonics
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• v.7 no.5
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• pp.485-495
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• 2023

The pixel size in high-resolution complementary metal-oxide-semiconductor (CMOS) image sensors continues to shrink due to chip size limitations. However, the pixel pitch's miniaturization causes deterioration of optical performance. As one solution, a quad color filter (CF) array with pixel binning has been developed to enhance sensitivity. For high sensitivity, the microlens structure also needs to be optimized as the CF arrays change. In this paper, the covered microlens, which consist of four microlenses covered by one large microlens, are proposed for the quad CF array in the backside illumination pixel structure. To evaluate the optical performance, the suggested microlens structure was simulated from 0.5 ㎛ to 1.0 ㎛ pixels at the center and edge of the sensors. Moreover, all pixel structures were compared with and without in-pixel deep trench isolation (DTI), which works to distribute incident light uniformly into each photodiode. The suggested structure was evaluated with an optical simulation using the finite-difference time-domain method for numerical analysis of the optical characteristics. Compared to the conventional microlens, the suggested microlens show 29.1% and 33.9% maximum enhancement of sensitivity at the center and edge of the sensor, respectively. Therefore, the covered microlens demonstrated the highly sensitive image sensor with a quad CF array.

• International journal of advanced smart convergence
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• v.13 no.2
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• pp.148-153
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• 2024

This article embarks on an exploration of how the burgeoning landscape of AI technology is reshaping and augmenting creative expression within the realm of 3D animation. As AI continues to evolve and mature, its integration into the process of 3D animation creation has become an increasingly focal point of investigation and analysis. The article undertakes a comprehensive examination of the myriad applications of AI within the domain of 3D animation, shedding light on its multifaceted contributions to various aspects of the creative process. Furthermore, it delves into the transformative impact that AI technology has on enhancing creative expression within 3D animation, particularly through increased productivity, personalized content creation, and the expansion of creative boundaries. By automating repetitive and time-consuming tasks inherent in traditional production methods, AI liberates artists and animators to unleash their creative ingenuity and push the boundaries of their craft. Through empirical research and case studies, the article elucidates how AI serves as a catalyst for innovation, fostering a conducive environment for the exploration of novel techniques and artistic styles.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.3
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• pp.25-34
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• 1993

The long-term behavior, such as in excavation problems of weak medium, can be dealt with by the elasto-viscoplasticity models. In this paper, a combined formulation of elasto-viscoplasticity using boundary elements and finite elements without using internal cells is presented. The domain integral introduced due to the viscoplastic stresses is transformed into a boundary integral applying direct integration in cylindrical coordinates. The results of the developed boundary element analysis are compared with those from the explicit solution and from the finite element analysis. It is observed that the boundary element analysis without internal cells results in some error because of its deficiency in handling the nonlinearity in local stress concentration. Therefore, a coupled analysis of boundary elements and finite elements, in which finite elements are used in the area of stress concentration, is developed. The coupled method is applied to a time dependent inelastic problem with semi-infinite boundaries. It results in reasonable solution compared with other methods where relatively higher degree of freedoms are employed. Thus, it is concluded that the combined analysis may be used for such problems in the effective manner.

• Journal of Korea Water Resources Association
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• v.52 no.5
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• pp.361-372
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• 2019

The purpose of this study is to develop a two-dimensional land surface flood analysis model based on uniform square grid using the governing equations except for the convective acceleration term in the momentum equation. Finite volume method and implicit method were applied to spatial and temporal discretization. In order to reduce the execution time of the model, parallel computation techniques using CPU were applied. To verify the developed model, the model was compared with the analytical solution and the behavior of the model was evaluated through numerical experiments in the virtual domain. In addition, inundation analyzes were performed at different spatial resolutions for the domestic Janghowon area and the Sebou river area in Morocco, and the results were compared with the analysis results using the CAESER-LISFLOOD (CLF) model. In model verification, simulation results were well matched with the analytical solution, and the flow analyses in the virtual domain were also evaluated to be reasonable. The results of inundation simulations in the Janghowon and the Sebou river area by this study and CLF model were similar with each other and for Janghowon area, the simulation result was also similar to the flooding area of flood hazard map. The different parts in the simulation results of this study and the CLF model were compared and evaluated for each case. The results of this study suggest that the model proposed in this study can simulate the flooding well in the floodplain. However, in case of flood analysis using the model presented in this study, the characteristics and limitations of the model by domain composition method, governing equation and numerical method should be fully considered.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.32-33
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• 2003

Mechanism of a periodic oscillation of shock-induced combustion over a two- dimensional wedges and axi-symmetric cones were investigated through a series of numerical simulations at off-attaching condition of oblique detonation waves(ODW). A same computational domain over 40 degree half-angle was considered for two-dimensional and axi-symmetric shock-induced combustion phenomena. For two-dimensional shock-induced combustion, a 2H2+02+17N2 mixture was considered at Mach number was 5.85with initial temperature 292 K and initial pressureof 12 KPa. The Rankine-Hugoniot relation has solution of attached waves at this condition. For axi-symmetric shock-induced combustion, a H2+2O2+2Ar mixture was considered at Mach number was 5.0 with initial temperature 288 K and initial pressure of 200 mmHg. The flow conditions were based on the conditions of similar experiments and numerical studies.[1, 3]Numerical simulation was carried out with a compressible fluid dynamics code with a detailed hydrogen-oxygen combustion mechanism.[4, 5] A series of calculations were carried out by changing the fluid dynamic time scale. The length wedge is varied as a simplest way of changing the fluid dynamic time scale. Result reveals that there is a chemical kinetic limit of the detached overdriven detonation wave, in addition to the theoretical limit predicted by Rankine-Hugoniot theory with equilibrium chemistry. At the off-attaching condition of ODW the shock and reaction waves still attach at a wedge as a periodically oscillating oblique shock-induced combustion, if the Rankine-Hugoniot limit of detachment isbut the chemical kinetic limit is not.Mechanism of the periodic oscillation is considered as interactions between shock and reaction waves coupled with chemical kinetic effects. There were various regimes of the periodicmotion depending on the fluid dynamic time scales. The difference between the two-dimensional and axi-symmetric simulations were distinct because the flow path is parallel and uniform behind the oblique shock waves, but is not behind the conical shock waves. The shock-induced combustion behind the conical shockwaves showed much more violent and irregular characteristics.From the investigation of characteristic chemical time, condition of the periodic instability is identified as follows; at the detaching condition of Rankine-Hugoniot theory, (1) flow residence time is smaller than the chemical characteristic time, behind the detached shock wave with heat addition, (2) flow residence time should be greater than the chemical characteristic time, behind an oblique shock wave without heat addition.