• 정보보호학회논문지
• /
• 제11권2호
• /
• pp.27-35
• /
• 2001

최근 무선 이동 통신의 발전을 기반으로 향후 이동 통신 시스템은 많은 사용자들에게 현재보다 더 나은 고품질의 멀티미디어 서비스를 제공할 것으로 기대된다. 따라서 이와 관련된 많은 기술적 응용 분야들이 고려되고 있으며, 특히 보안 관련 분야의 도입을 통해 기밀성 및 안전성을 획득하려 하고 있다 본 논문에서는 이와 관련하여 무선 이동 통 신상에서 상대적으로 계산 능력이 뛰어난 Agent의 도움을 통해 사용자의 전자 서명 및 암호화를 수행할 수 있는 수신 자 지정 대리 서명 방식을 제안한다 제안 방식은 대리 서명을 수행할 경우 발생할 수 있는 사용자 및 대리 서명 Agent의 부정 서명 생성 및 부인 행위를 방지하도록 구성되어 있다. 동시에 정당한 수신자가 서명을 확인하도록 함으로서 이동 통신상에서 기밀성을 획득하는 안전한 방식이라 하겠다.

• 한국인터넷방송통신학회논문지
• /
• 제21권4호
• /
• pp.1-8
• /
• 2021

전세계 수많은 사용자들이 특정 실시간 가상 환경을 공유하는 MMOG(Massive Multi-player On-line Game)를 지원하고자 본 논문에서 P2P(Peer-to-Peer)와 클라우드 컴퓨팅의 기술적 장점을 결합하는 기법을 제시한다. 본 논문에서 제시된 클라우드 컴퓨팅 기반의 P2P 시스템은 사용자 수가 급증할 경우에도 사용자 자원을 기반 구조에 추가함으로써 준수한 수준의 확장성을 제공할 수 있다. 또한 이 시스템은 사용자들의 처리 능력을 활용함으로써 클라우드에 있는 서버의 부하 즉 상당한 컴퓨팅 능력과 통신량을 절감할 수 있다. 본 논문에서 MMOG의 확장성을 위한 클라우드 컴퓨팅 기반의 P2P 시스템의 개념과 기본적 구조가 기술된다. 대규모 사용자 집단에 대한 경제적 비용과 서비스 품질의 규모를 고려하는 이 구조가 실현되기 위해서는 효율적이고 효과적인 자원의 공급과 부하의 배분이 반드시 필요하다. 시뮬레이션 결과 제시된 P2P 시스템은 동시에 실행되는 사용자들의 수가 증가할 때 클라우드와 사용자 제공 자원의 양을 제어함으로써 사용자들의 충분한 대역폭을 활용하는 반면 서버의 대역폭을 감소시킬 수 있는 것으로 나타났다.

• 한국포장학회지
• /
• 제27권3호
• /
• pp.175-180
• /
• 2021

Although it has recently been regulated for use as an eco-friendly policy in Korea, the use of EPS (Expanded Polystyrene) cooling boxes, which are used as cold chain delivery insulation boxes for fresh agricultural and livestock products, is also increasing rapidly as e-commerce logistics such as delivery have increased rapidly due to COVID-19. Studies were conducted to optimize the EPS cooling container through internal air heat flow of CFD (Computational Fluid Dynamics) analysis and FEM (Finite Element Method) random vibration analysis using domestic PSD (Power Spectral Density) profile of the EPS cooling box to which the refrigerant is applied in this study. In the analysis of the internal air heat flow by the refrigerant in the EPS cooling box, the application of vertical protrusions inside was excellent in volume heat flow and internal air temperature distribution. In addition, as a result of random vibration analysis, the internal vertical protrusion gives the rigid effect of the cooling box, so that displacement and stress generation due to vibration during transport are smaller than that of a general cooling container without protrusion. By utilizing the resonance point (frequency) of the EPS cooling box derived by the Model analysis of ANSYS Software, it can be applied to the insulation and cushion packaging design of the EPS product line, which is widely used as insulation and cushion materials.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제13권1호
• /
• pp.236-245
• /
• 2021

In this study, direct numerical and large eddy simulations of transitional flows around studs were conducted to investigate the effectiveness of turbulence stimulators at very low speeds for the minimum propulsion power condition of four knots. For simplicity, the studs were assumed to be installed on a flat plate, while the wake was observed up to 0.23 m downstream behind the second stud. For applicability to a model ship, we also studied the flow characteristics behind the first and second studs installed on a curved plate, which was designed to describe the geometry of a bulbous bow. A laminar-to-turbulent transition was observed in the wake at Re_D ≥ 921 (U_∞≥0.290 m/s), and the wall shear stress at Re_D = 1162 (U_∞ = 0.366 m/s) in the second wake was similar to that of the fully developed turbulent boundary layer after a laminar-to-turbulent transition in the first wake. At Re_D = 581 (U_∞ = 0.183 m/s), no turbulence was stimulated in the wake behind the first and second studs on the flat plate, while a cluster of vortical structures was observed in the first wake over the curved plate. However, a cluster of vortical structures was revealed to be generated by the reattachment process of the separated shear layer, which was disturbed by the first stud rather than directly initiated by the first stud. It was quite different from a typical process of transition, which was observed at relatively high Re_D that the spanwise scope of the turbulent vortical structures expanded gradually as it went downstream.

• 대한조선학회논문집
• /
• 제59권3호
• /
• pp.183-191
• /
• 2022

A design method for a propeller type rim-driven axial-flow turbine for a micro-hydropower system is presented. The turbine consists of pre-stator, impeller and post-stator, where the pre-stator plays a role as a guide vane to provide circumferential velocity to the on-coming flow, and the impeller as a rotational power generator by absorbing angular momentum of the flow. BEM(Blade Element Method), which is based on the turbine Euler equation, is employed to design the pre-stator and impeller blades. NACA 66 thickness form and a=0.8 mean camber line, which is widely accepted as a marine propeller blade section, is used for the pre-stator and turbine blade section. A CFD method, derived from the discretization of the RANS equations, is applied for the analysis of the designed turbine system. The design conditions of the turbine is confirmed by the CFD calculation. Turbine characteristic curve is calculated by the CFD method, in order to provide the performance characteristics at off-design operation conditions. The proposed procedures for the design of a propeller type rim-driven axial-flow turbine are established and confirmed by the CFD analysis.

• 창의정보문화연구
• /
• 제6권1호
• /
• pp.31-40
• /
• 2020

본 연구의 목적은 블록코딩 소프트웨어(SW) 교육과 초등학생의 회복탄력성의 상관관계를 통계적으로 분석한 후 그 결과를 통해 SW 교육의 의의를 찾는 데 있다. 본 연구에서는 인천광역시 소재 A초등학교의 4학년 학생 61명을 대상으로 회복탄력성 사전 검사를 실시하였다. 학습자의 수준에 맞추어 code.org라는 비영리단체의 블록코딩 SW 교육 프로그램을 활용하여 15차시의 수업을 진행하였고 사후 검사를 실시하여 회복탄력성의 개선도를 분석하였다. 연구 결과, 블록코딩 SW 교육을 받은 학생들이 회복탄력성의 대영역인 자기조절력, 긍정성, 대인관계능력 중 자기조절력과 긍정성 등 2개의 영역에서 유의미한 향상을 나타냈으며, 회복탄력성 종합 점수가 통계적으로 유의미하게 증가하였음을 확인하였다. 이를 통해 SW 교육이 학생들의 컴퓨팅 사고력을 기르는 것뿐만 아니라 그들이 삶을 긍정적이고 유연하게 살아나갈 수 있는 힘인 회복탄력성을 기르는 데에도 영향을 줄 수 있다는 가능성을 엿볼 수 있었다.

• 융합신호처리학회논문지
• /
• 제22권4호
• /
• pp.164-170
• /
• 2021

해상 풍력발전기의 운동 성능 분석 및 개선을 위한 연구가 수행되었다. 본 연구에 사용된 형상은 과거 연구를 참고하여 가져온 것이며 이를 바탕으로 수선면적의 크기를 80% 60% 40% 20%로 각각 설계하여 이에 따른 운동성능을 확인해 보았다. 해상상태는 Sea State 4, 5, 6에서 계산을 수행하였다. 계산과정에서는 상업용 전산 유체역학(ANSYS)과 AQUA를 사용하여 계산을 수행하였다. 전반적인 운동성능의 경우 이론과 동일하게 수선면적의 크기가 줄어들수록 HEAVE, ROll, PITCH와 같은 운동이 줄어드는 것을 확인할 수 있었다. 하지만 수선면적의 크기가 급격히 줄어든 형상의 경우 복원성 계산을 진행하였을 때 복원성능에서 만족하지 못하는 경우가 발생할 수도 있다는 것을 확인할 수 있었다. 또한 해상상태에 따른 적정의 수선면이 있을 수도 있다는 것을 확인할 수 있었다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제15권11호
• /
• pp.4065-4083
• /
• 2021

Super-resolution can improve the clarity of low-resolution (LR) images, which can increase the accuracy of high-level compute vision tasks. Portable devices have low computing power and storage performance. Large-scale neural network super-resolution methods are not suitable for portable devices. In order to save the computational cost and the number of parameters, Lightweight image processing method can improve the processing speed of portable devices. Therefore, we propose the Enhanced Information Multiple Distillation Network (EIMDN) to adapt lower delay and cost. The EIMDN takes feedback mechanism as the framework and obtains low level features through high level features. Further, we replace the feature extraction convolution operation in Information Multiple Distillation Block (IMDB), with Ghost module, and propose the Enhanced Information Multiple Distillation Block (EIMDB) to reduce the amount of calculation and the number of parameters. Finally, coordinate attention (CA) is used at the end of IMDB and EIMDB to enhance the important information extraction from Spaces and channels. Experimental results show that our proposed can achieve convergence faster with fewer parameters and computation, compared with other lightweight super-resolution methods. Under the condition of higher peak signal-to-noise ratio (PSNR) and higher structural similarity (SSIM), the performance of network reconstruction image texture and target contour is significantly improved.

• Journal of Information Science Theory and Practice
• /
• 제10권spc호
• /
• pp.135-142
• /
• 2022

Recently, with the development of data processing technology and the increase of computational power, methods to solving social problems using Artificial Intelligence (AI) are in the spotlight, and AI technologies are replacing and supplementing existing traditional methods in various fields. Meanwhile in Korea, heavy rain is one of the representative factors of natural disasters that cause enormous economic damage and casualties every year. Accurate prediction of heavy rainfall over the Korean peninsula is very difficult due to its geographical features, located between the Eurasian continent and the Pacific Ocean at mid-latitude, and the influence of the summer monsoon. In order to deal with such problems, the Korea Meteorological Administration operates various state-of-the-art observation equipment and a newly developed global atmospheric model system. Nevertheless, for precipitation nowcasting, the use of a separate system based on the extrapolation method is required due to the intrinsic characteristics associated with the operation of numerical weather prediction models. The predictability of existing precipitation nowcasting is reliable in the early stage of forecasting but decreases sharply as forecast lead time increases. At this point, AI technologies to deal with spatio-temporal features of data are expected to greatly contribute to overcoming the limitations of existing precipitation nowcasting systems. Thus, in this project the dataset required to develop, train, and verify deep learning-based precipitation nowcasting models has been constructed in a regularized form. The dataset not only provides various variables obtained from multiple sources, but also coincides with each other in spatio-temporal specifications.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제16권2호
• /
• pp.692-712
• /
• 2022

Buoys used for Aid to Navigation systems are widely used to guide the sea paths and are powered by batteries, requiring continuous battery replacement. However, since human labor is required to replace the batteries, humans can be exposed to dangerous situation, including even collision with shipping vessels. In addition, Maritime sensors are installed on the route signs, so that these are often damaged by collisions with small and medium-sized ships, resulting in significant financial loss. In order to prevent these accidents, maritime object detection technology is essential to alert ships approaching buoys. Existing studies apply a number of filters to eliminate noise and to detect objects within the sea image. For this process, most studies directly access the pixels and process the images. However, this approach typically takes a long time to process because of its complexity and the requirements of significant amounts of computational power. In an emergent situation, it is important to alarm the vessel's rapid approach to buoys in real time to avoid collisions between vessels and route signs, therefore minimizing computation and speeding up processes are critical operations. Therefore, we propose Fast Connected Component Labeling (FCCL) which can reduce computation to minimize the processing time of filter applications, while maintaining the detection performance of existing methods. The results show that the detection performance of the FCCL is close to 30 FPS - approximately 2-5 times faster, when compared to the existing methods - while the average throughput is the same as existing methods.