• Journal of Environmental Impact Assessment
• /
• v.21 no.3
• /
• pp.469-481
• /
• 2012

CCS(Carbon Dioxide Capture and Storage) is considered as the most effective counterplan in the mitigation of climate change. Even though the risk of leakage of $CO_2$ stored in the geologic formation is very low, the public is expected to disagree with the initiation of a CCS project without proper management plans ensuring the safety. In this study, recognition of laypeople were surveyed about CCS, climate change, characteristics of carbon dioxide, storage concepts, ground pressure, the impact of carbon dioxide, and carbon dioxide for leakage. Thereafter the factors that could affect to recognition of CCS were analyzed by regression analysis. A survey was carried out to find out the public understanding and awareness about climate change and CCS. It is the purpose of this study to propose appropriate risk management strategies based on the findings from the survey.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.29 no.12 s.243
• /
• pp.1645-1652
• /
• 2005

Pick-and-place systems using suction cups have been being widely used and continuously developed in production automation. There are, however, some drawbacks in constructing such systems. One of them is that it generates high level noise due to air compressors. And the system must have complex constitutions of mechanical component such as air compressors, air tubes, air valves, etc. Moreover, it needs continuous air supply to maintain vacuum in suction cups. If there is a failure in any suction cup, the total suction system may fail owing to air leakage. To overcome these drawbacks, we propose PMS (Permanent Magnet Suction) mechanism which has permanent magnets for vacuuming suction cups with no air compressor. The basic concept of PMS mechanism is to rotate permanent magnets with fixed angle. Simple rotation of permanent magnets changes the direction of the magnetic force applied at the suction cups. Since each suction cup has no direct connection with any of the others, the air leakage at one suction cup is not critical. The proposed suction mechanism was designed and fabricated. With some experiments, the feasibility and performance of the PMS mechanism was shown. The strong points of the PMS mechanism are in its simple structure, generating low noise, high energy efficiency, and no need of continuous energy supply.

• Journal of the Korean Society for Precision Engineering
• /
• v.33 no.2
• /
• pp.139-147
• /
• 2016

Performances of urethane packing in the hydraulic breaker were analyzed using a finite element method. Because of high temperature and high pressure in the hydraulic breaker, it is better to use urethane rather than rubber as a packing material. We obtained the physical properties of urethane at elevated temperature by the tensile test. We analyzed buffer seal and U-packing maintaining the pressure and preventing oil leakage. Deformation, stress distribution, contact length, contact pressure of packing at each pressure step were obtained using finite element analysis. As the temperature increases, stress and contact force tend to decrease at low pressure. As the gap between piston and cylinder increases, contact length and contact forces decrease. Consequently, it is possible to design the packing section using these analyses, and construct a system to predict the possibility of oil leakage in the hydraulic breaker.

• Tribology and Lubricants
• /
• v.22 no.3
• /
• pp.119-126
• /
• 2006

In this paper, the contact behavior characteristics of a primary sealing components such as a seal ring and a seal seat has been presented for a small hydro-power turbine. Using the non-linear FEM analysis, the maximum temperature, the axial displacement, radial differences between a seal ring and a seal seat, and maximum contact normal stress have been analyzed for three optimized sealing profiles in which are designed based on the FEM analysis and Taguchi's experimental method. The three primary sealing profiles between a seal ring and a seal seat are strongly related to a leakage of a water for a hydro-power turbine and wear of a primary sealing component. The computed results show that the contact rubbing area between a seal ring and a seal seat is very important for reducing a friction heating and wear in a sealing gap, and increasing a contact normal stress in primary sealing components. Based on the FEM computation, models II and III in which have a small rubbing surface of seal rings show low dilatation of primary sealing components, and high normal contact stress between a seal ring and a seal seat. Thus, the FEM computed results recommend a short contacting width of a primary sealing component for reducing a leakage and thermal distortions, and expanding a seal life. This means that a conventional primary sealing component may be switched to a reduced sealing face of seal rings.

• Journal of Chest Surgery
• /
• v.15 no.2
• /
• pp.188-193
• /
• 1982

Between 1967 and 1980, a total of 99 patients with a benign stricture of esophagus, resulting from a chemical burn, underwent a reconstructive procedure in which various segments of colon were used to bridge the gap between the cervical esophagus and the stomach. There were 42 males and 57 females and most were in their twenties and thirties. The most frequent site of the stricture was upper 1/3 of the thoracic esophagus [48.5%] and the next most common site was the low cervical esophagus [23.2%]. In 89 cases, the right colon with or without the terminal ileum was used as the conduit in an isoperistaltic manner and in 10, the left colon was used in an antiperistaltic position, because the right colon was not suitable as the conduit. There was a higher incidence of regurgitation [90% vs 0%], leakage at cervical anastomosis [80% vs 27%] and stenosis at anastomotic site [70% vs 15%] in an antiperistaltic left colon anastomosis, as compared to isoperistaltic right colon anastomosis. This was felt to be due to the orad peristaltic motion of the transplanted colon which acted as a functional obstruction distal to the esophagocolic suture line, resulting in breakdown of the anastomosis, leakage and eventual stenosis at the site of anastomosis. In conclusion, colon is useful and effective conduit as an esophageal substitute. Either the right or the left colon can be used for this purpose, provided that it is placed in an isoperistaltic position to minimize some of the complications listed above.

• Journal of Electrical Engineering and Technology
• /
• v.8 no.5
• /
• pp.1157-1162
• /
• 2013

We proposed AlGaN/GaN high-electron-mobility transistors (HEMTs) using thermal oxidation for NiOx passivation. Auger electron spectroscopy, secondary ion mass spectroscopy, and pulsed I-V were used to study oxidation features. The oxidation process diffused Ni and O into the AlGaN barrier and formed NiOx on the surface. The breakdown voltage of the proposed device was 1520 V while that of the conventional device was 300 V. The gate leakage current of the proposed device was 3.5 ${\mu}A/mm$ and that of the conventional device was 1116.7 ${\mu}A/mm$. The conventional device exhibited similar current in the gate-and-drain-pulsed I-V and its drain-pulsed counterpart. The gate-and-drain-pulsed current of the proposed device was about 56 % of the drain-pulsed current. This indicated that the oxidation process may form deep states having a low emission current, which then suppresses the leakage current. Our results suggest that the proposed process is suitable for achieving high breakdown voltages in the GaN-based devices.

• Journal of the Korean Society of Safety
• /
• v.22 no.2 s.80
• /
• pp.41-46
• /
• 2007

This paper considers the electrical shock risk of the human body due to underwater leakage current in such places of public baths. Many submerged electric facilities in a public bath may create a severe electric shock hazard for the human body, since wet body in an accidentally energized bathtub can result in low electrical resistance through the human body for leakage or fault currents. Therefore a major consideration, in the context of electrical safety underwater, is the shock risk to the bather as a result of electric current flowing through the water in bathtub. To assess the electric shock risk and to analyze the potential distribution in a bathtub, 2 different situation cases are set up, then experimental and simulation methods are adopted. The validity of 2 cases of simulation and experiment data in a bathtub for electric distribution underwater are compared and analyzed. Also electric shock risk assessment underwater in a real public bathtub by simulation program package, Flux 3D, was conducted herein, and the results are presented and discussed.

• Journal of the Korea Society of Computer and Information
• /
• v.19 no.4
• /
• pp.25-33
• /
• 2014

This paper proposes a power-efficient scheduling scheme that stochastically minimizes the power consumption of real-time tasks while meeting their deadlines on multicore processors. In the proposed scheme, uncertain computation amounts of given tasks are translated into probabilistic computation amounts based on their past completion amounts, and the mean power consumption of the translated probabilistic computation amounts is minimized with a finite set of discrete clock frequencies. Also, when system load is low, the proposed scheme activates a part of all available cores with unused cores powered off, considering the leakage power consumption of cores. Evaluation shows that the scheme saves up to 69% power consumption of the previous method.

• International Journal of Internet, Broadcasting and Communication
• /
• v.10 no.4
• /
• pp.6-11
• /
• 2018

As embedded memory technology evolves, the traditional Static Random Access Memory (SRAM) technology has reached the end of development. For deepening the manufacturing process technology, the next generation memory technology is highly required because of the exponentially increasing leakage current of SRAM. Non-volatile memories such as STT-MRAM (Spin Torque Transfer Magnetic Random Access Memory), PCM (Phase Change Memory) are good candidates for replacing SRAM technology in embedded memory systems. They have many advanced characteristics in the perspective of power consumption, leakage power, size (density) and latency. Nonetheless, nonvolatile memories have two major problems that hinder their use it the next-generation memory. First, the lifetime of the nonvolatile memory cell is limited by the number of write operations. Next, the write operation consumes more latency and power than the same size of the read operation.These disadvantages can be solved using the compiler. The disadvantage of non-volatile memory is in write operations. Therefore, when the compiler decides the layout of the data, it is solved by optimizing the write operation to allocate a lot of data to the SRAM. This study provides insights into how these compiler and architectural designs can be developed.

• Proceedings of the KIEE Conference
• /
• 2001.07c
• /
• pp.1697-1699
• /
• 2001

In this paper, the circuit of AC Choppers for $CO_2$ laser power supply are proposed and investigated. IGBT-controlled ac voltage regulators, operating at high frequency chopping mode. Chopping-to-supply duty ratio plays an important role in terms of laser output. Laser input energy is varied by controlling the leakage transformer used with the proposed system. This improved circuit employs a 3 electrode - type and Ring Blower. This improved circuit system has many advantages compared with the conventional SMPS such as simple design requirement, easy implementation, high reliability, low switching loss, and consequently high efficiency. As a result, the maximun output was 16W at duty-ratio of 92%, total gas mixture of $CO_2$ : $N_2$ : He = 1 : 9 : 15, total pressure of 15torr.