• Korean Chemical Engineering Research
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• v.53 no.2
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• pp.164-173
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• 2015

This study aims to design energy supply systems from various energy sources for transportation sectors and comparatively analyze the life cycle cost of different scenario-based systems. For components of the proposed energy supply system, we consider a typical oil refinery, byproduct hydrogen system, renewable energy source (RES)-based electric generation system and existing electricity grid. We also include three types of vehicles in transportation sector such as internal combustion engine vehicle (ICEV), electric vehicle (EV), fuel cell vehicle (FCV). We then develop various energy supply scenarios which consist of such components and evaluate the economic performance of different systems from the viewpoint of life cycle cost. Finally we illustrate the applicability of the proposed framework by conducting the design problem of energy supply systems of Jeju, Korea. As the results of life cycle cost analysis, EV fueled by electricity from grid is the most economically feasible. In addition, we identify key parameters to contribute the total life cycle cost such as fuel cost, vehicle cost, infra cost and maintenance cost using sensitivity analysis.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.4
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• pp.409-415
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• 2011

Purpose: To design applied anamorphic lens that focal length ratio is 3:1 optical system to improve detecting distance. Methods: We defined a boundary condition as $50^{\circ}{\sim}60^{\circ}$ for viewing angle, horizontal direction 36mm, vertical direction 12 mm for focal length, f-number 4, $15{\mu}m{\times}15{\mu}m$ for pixel size and limit resolution 25% in 33l p/mm. Si, ZnS and ZnSe as a materials were used and 4.8 ${\mu}m$, 4.2 ${\mu}m$, 3.7 ${\mu}m$ as a wavelength were set. optical performance with detection distance, narcissus and athermalization in designed camera were analyzed. Results: F-number 4, y direction 12 mm and x direction 36 mm for focal length of the thermal optical system were satisfied. Total length of the system was 76 mm so that an overall volume of the system was reduced. Astigmatism and spherical aberration was within ${\pm}$0.10 which was less than 2 pixel size. Distortion was within 10% so there was no matter to use as a thermal optical camera. MTF performance for the system was over 25% from 33l p/mm to full field so it was satisfied with the boundary condition. Designed optical system was able to detect up to 2.9 km and reduce a diffused image by decreasing a narcissus value from all surfaces except the 4th surface. From sensitivity analysis, MTF resolution was increased on changing temperature with the 5th lens which was assumed as compensation. Conclusions: Designed optical system which used anamorphic lens was satisfied with boundary condition. an increasing resolution with temperature, longer detecting distance and decreasing of narcissus were verified.

• Journal of the Korean GEO-environmental Society
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• v.11 no.10
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• pp.41-48
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• 2010

In this study, grain size distribution of dredged soil and suspended solid distribution of supernatant in containment area were measured and compared with design prediction for suitability evaluation on prediction of suspended solid concentration of supernatant in conventional design of containment area. In addition to that, relationship were also analyzed between current velocity and suspended solid concentration of supernatant. Evaluation results show a relatively good agreement between field measurement and design prediction. On contrast, field measurement and design prediction show a quite different value each other in the early stage of dredging or at a point that current velocity increases. It is believed that this is due to that conventional design method of containment area does not account for ponding depth and current velocity which change sensitively with dredging period. Since current velocity and distribution of suspended solid concentration measured simultaneously show a similar trend, it is observed that there exists a close relationship between current velocity and distribution of suspended solid concentration. Therefore, a new design method for containment area, which can consider sedimentation of suspended solid that changes with interface height of dredged soil, ponding depth, current speed of supernatant, is necessary in order to predict the situation change of containment area more precisely.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.6
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• pp.586-595
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• 2010

An analytical study based on physical understandings and aero-thermodynamic theories was conducted to observe the performance characteristics and to derive the essential design parameters of dual ramjet(dual-combustion/dual-mode) propulsion for wide Mach number. The performances and operating limitations of the engines with two types combustors, such as constant pressure- and constant area- combustor, over various flight Mach numbers was investigated. Finally, the transition Mach number from ramjet to scramjet was carried out to optimize performance load balancing of ramjet and scramjet.

• Journal of Internet Computing and Services
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• v.13 no.3
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• pp.127-137
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• 2012

With the spread of the new technologies like a smart phone, a smart pad, N-Screen service for financial transaction quickly became commonplace through the Internet. Although it has been developed related technologies and policies since the N-Screen has been provided in Korea, infrastructure for financial services is still lacking. It also has many potential problems including phishing or malware attacks, privacy information exposure & breaches, etc. This work suggests the financial security framework in the side of information protection through threat vulnerability analysis. Further, we examine the possibility of effective application methods based on political technical design.

• Journal of the Korea Convergence Society
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• v.6 no.6
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• pp.81-86
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• 2015

The threats to privacy and security have received increasing attention as ubiquitous healthcare applications over the Internet become more prevalent, mobile and universal. In particular, we address the communication security issues of access sharing of health information resources in the ubiquitous healthcare environment. The proposed scheme resolves the sender and data authentication problem in information systems and group communications. We propose a novel key management scheme for generating and distributing cryptographic keys to constituent users to provide form of data encryption method for certain types of data concerning resource constraints for secure communications in the ubiquitous healthcare domains.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.1
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• pp.83-93
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• 1997

This paper deals with measurements and evaluation of the time-changing electric and magnetic fields at a high-voltage laboratory. The electromagnetic disturbances originate mainly from ground faults and on/off operations of electric power equipments. The electronic circuits and control devices are very sensitive to electromagnetic interferences. It is necessory to evaluate the levels of interferences for a given electromagnetic environment. The electric field was observed by the electric field sensor having the bandwidth of the range from 40 Hz to 200 MHz, and the time-changing magnetic field was measured by the loop sensor of which the output is directly proportional to the incident signal. Also, the frequency components of the time-changing electric and magnetic fields induced by an oscillatory transient current and a chopped impulse voltage were analyzed by terms of the fast Fourier transformation, and those give the information about the levels of the electromagnetic interferences and the design of the electromagnetic shielding enclosures.

• The Transactions of the Korea Information Processing Society
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• v.7 no.11S
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• pp.3675-3683
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• 2000

The Handoff is the core technical factor that is required when mobile host moves from one area to another, while transmitting and receiving data. The existing works try to minimize the loss of pockets by forwarding packets to the Cell which a mobile host will move to. However, though the loss quantity is little, the accumulated loss can del(rade the performance of the TCP, and can be a serious problem if data is sensitive to the loss of packets. In this paper, we can reduce a memory requesting in FA by restricting the mobile host to move within at most 2 movable cells and design the improved handoff protocol for Mil to receive packets seamlessly in spite of handoff. We can evaluate that the suggested method is superior to the previous method, as a result of comparing with it.

• Annual Conference of KIPS
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• 2015.10a
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• pp.613-616
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• 2015

최근 스마트폰 기기의 보급 및 소셜 서비스 산업의 고도화로 인해, 빅데이터가 등장하였다. 한편 빅데이터에서 효율적으로 정보를 분석하는 대표적인 플랫폼으로 하둡이 존재한다. 하둡은 클러스터 환경에 기반한 우수한 확장성, 장애 복구 기능 및 사용자가 기능을 정의할 수 있는 맵리듀스 프레임워크 등을 지원한다. 아울러 하둡은 개인정보나 위치 데이터 등의 민감한 정보를 보호하기 위해 Kerberos를 통한 사용자 인증 기법을 제공하고, HDFS 압축 코덱을 활용한 AES 코덱 기반 데이터 암호화를 지원하고 있다. 그러나 하둡 기반 소프트웨어를 사용하고 있는 국내 기관 및 기업은 국내 ARIA 데이터 암호화를 적용하지 못하고 있다. 이를 해결하기 위해 본 논문에서는 하둡을 기반으로 ARIA 암호화를 지원하는 HDFS 데이터 암호화 기법을 제안한다.

• Journal of Internet Computing and Services
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• v.20 no.1
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• pp.11-16
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• 2019

Wireless sensor network is important for precision farming to monitor the growth environment of crops in open field, but radio signals are susceptible to different types of interference such as weather and physical objects. This paper designs and implements an environmental monitoring and weather forecast acquisition systems for smart field irrigation based on LoRa(Long Range) and then applies it to a test bed. And we evaluate the network reliability in terms of packet transmission success rate by comparing its condition on two criteria; the existence of obstacle or rain. The results show that much rain falls can affect on packet loss in LoRa field networks with obstacles.