• Journal of the Korea Institute of Information Security & Cryptology
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• v.14 no.2
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• pp.75-83
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• 2004

We present a realization of an LFSM that utilizes an LFSR. This is based on a well-known fact from linear algebra. This structure is used to show that a previous attempt at using a cellular automata in place of an LFSR in constructing a stream cipher did not necessarily increase its security. We also give a general method for checking whether or not a nonlinear filter generator based on an LFSM allows reduction to one that is based on an LFSR and which is vulnerable to Anderson information leakage.

• Journal of Korean Neurosurgical Society
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• v.42 no.2
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• pp.112-117
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• 2007

Objective : Kyphoplasty and vertebroplasty are two minimally invasive procedures for osteoporotic vertebral compression fractures. The purpose of this retrospective study was to compare the radiological findings and clinical outcomes between two procedures. Methods : Osteoporotic vertebral fractures were treated in 76 vertebrae, using kyphoplasty (n=35 vertebrae) and using vertebroplasty (n=41 vertebrae). Fractured vertebral bodies were diagnosed by correlating the clinical symptoms with radiologic study. The responses of pain symptoms were measured by a self-reported Visual Analog Scale (VAS) score. Plain X-rays were checked preoperatively and postoperatively at admission and 6 months. The vertebral body height and kyphotic angle were measured to assess the reduction of the sagittal alignment. Results : The mean pain scores were decreased significantly for both procedures postoperatively, but there were no significant differences between two groups. Kyphoplasty led to a significant reduction of the vertebral body height and improvement of kyphotic angle. There were no neurological deficits after kyphoplasty, but one patient experienced paraparesis after vertebroplasty. During the 6 months follow-up both procedures provided stabilization of the sagittal alignment. Conclusion : Kyphoplasty and vertebroplasty are considered effective minimally invasive techniques for the stabilization of osteoporotic vertebral body fractures, leading to a statistically significant reduction in pain. Kyphoplasty significantly restore sagittal alignment. Also, complications and the incidence of bone cement leakage are significantly lesser than vertebroplasty. Therefore, kyphoplasty seems to be reasonable procedure for osteoporotic vertebral body compression fractures when medical treatment fail.

• Journal of IKEEE
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• v.19 no.1
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• pp.94-100
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• 2015

In this paper, 50V power U-MOSFET which replace the body(PN) diode with Schottky is proposed. As already known, Schottky diode has the advantage of reduced reverse recovery loss than PN diode. Thus, the power MOSFET with integrated Schottky integrated can minimize the reverse recovery loss. The proposed Schottky body diode U-MOSFET(SU-MOS) shows reduction of reverse recovery loss with the same transfer, output characteristic and breakdown voltage. As a result, 21.09% reduction in peak reverse current, 7.68% reduction in reverse recovery time and 35% improvement in figure of merit(FOM) are observed when the Schottky width is $0.2{\mu}m$ and the Schottky barrier height is 0.8eV compared to conventional U-MOSFET(CU-MOS). The device characteristics are analyzed through the Synopsys Sentaurus TCAD tool.

• Geomechanics and Engineering
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• v.17 no.5
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• pp.485-496
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• 2019

Sealing of leakage in waterfront or water-retaining structures is one of the major issues in geotechnical engineering practices. With demands for biological methods as sustainable ground improvement techniques, bioclogging, defined as the reduction in hydraulic conductivity of soils caused by microbial activities, has been considered as an alternative to the chemical grout techniques for its economic advantages and eco-friendliness of microbial by-products. This study investigated the feasibility of bioaugmentation and biostimulation methods to induce fermentation-based bioclogging effect in coarse sands. In the bioaugmentation experiments, effects of various parameters and conditions, including grain size, pH, and biogenic gas generation, on hydraulic conductivity reduction were examined through a series of column experiments while Leuconostoc mesenteroides, which produce an insoluble biopolymer called dextran, was used as the model bacteria. The column test results demonstrate that the accumulation of bacterial biopolymer can readily reduce the hydraulic conductivity by three-to-four orders of magnitudes or by 99.9-99.99% in well-controlled environments. In the biostimulation experiments, two inoculums of indigenous soil bacteria sampled from waterfront embankments were prepared and their bioclogging efficiency was examined. With one inoculum containing species capable of fermentation and biopolymer production, the hydraulic conductivity reduction by two orders of magnitude was achieved, however, no clogging was found with the other inoculum. This implies that presence of indigenous species capable of biopolymer production and their population, if any, play a key role in causing bioclogging, because of competition with other indigenous bacteria. The presented results provide fundamental insights into the bacterial biopolymer formation mechanism, its effect on soil permeability, and potential of engineering bacterial clogging in subsurface.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1157-1161
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• 2011

Parametric study has been conducted to calculate the capacity of vacuum pump system that will be used to maintain the pressure of the tube system under atmosphere level. Recently many railroad researchers pay attention to the tube train system as one of the super high speed transportation system. To achieve the ultra super high speed, the inside of tube system should be maintained the low pressure level. In the low pressure environment, it is well known that air resistance of train is drastically decreased. Vacuum pump system will be used to make the low pressure level of tube system, exhaust the leakage air and supplement additional vacuum pumping. Qualitative and quantitative study has been conducted to review the effects of major parameters concerned with the capacity of vacuum pump system. As a results of these studies, we get the lump capacity of vacuum pump for various parameters. These results can be used to analyse the effects of the reduction of air resistance.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.2_spc
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• pp.237-245
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• 2020

Metal seals are the main components that establish the containment boundary in bolted casks, which store spent nuclear fuel. These seals are degraded by heat and radiation. In addition, creep occurs when the seals are exposed to intense heat for an extended period. This creep results in the stress relaxation of the seals, which consequently impairs the seal integrity. The stress relaxation can reduce the sealing performance of the metal seal, which can further cause leakage in the storage cask. Moreover, the reduction of bolt tension leads to sealing performance degradation. In this study, the results of high-temperature-accelerated tests were obtained to evaluate the containment integrity of metal seals and the decrease in bolt tension. During the tests, the leakage rate, bolt strain, and ambient temperature of the metal seals were measured and analyzed. The metal seals were found to maintain containment integrity for 50 years of storage. The validity of the acceleration test was also investigated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.4
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• pp.437-442
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• 2013

In recent times, surface texturing methods have been widely applied to reduce friction and improve the reliability of machine components such as parallel thrust bearings, mechanical face seals, and piston rings. In this study, a numerical analysis is carried out to investigate the effect of uniformly spaced hemispherical dimples on the lubrication characteristics of a slider bearing using a commercial computational fluid dynamics (CFD) code, FLUENT. The pressure distributions, load capacity, leakage flowrate, and friction force are strongly affected by the dimple diameter and the number of dimples. In particular, the load capacity and friction force decrease linearly with the dimple density whereas the leakage increases. These results can be used for designing the optimum dimple characteristics in order to improve the lubrication performance of slider bearings, for which further studies are required.

• Fire Science and Engineering
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• v.29 no.3
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• pp.21-30
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• 2015

In this study, we try to suggest measures to reduce leakage at a joint between CPVC piping for a sprinkler system and a pipe expansion through reviews of domestic and foreign standards and related tests. The quality of the waterproof rubber packing material between a valve socket and pipe expansion nut was examined. In the leak test, the valve socket material over the expansion part of the metal pipe nut was found to use a metal part or a schlorinated polyvinyl chloride pipe nut part. In addition, the KS B 0221 standard for parallel pipe threads with threaded and thread inspection criteria and inspection standards in order to ensure an acceptable quality of valve socket, there is a need to amend the regulations to comply with the KS B 5223 (screw thread limit gauges parallel pipe threads). We do not have detailed standards for expansion piping nuts for waterproof rubber ring material, so we need to amend the relevant criteria for EPDM material to be used with excellent waterproofing, for which both NBR and EPDM are currently used.

• Environmental and Resource Economics Review
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• v.21 no.4
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• pp.851-891
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• 2012

The objective of this study can be presented as follows: First, given the consumption-based carbon accounting method which has now been claimed, this study reviews the emissions within Korea and the resulting position change in international society. Second, when each nation makes efforts to reduce carbon emissions under the Copenhagen Accord, this study, using the Computable General Equilibrium (CGE) model, reviews the resulting carbon leakage and analyzes the effect from the various border adjustment measures. However, reflecting uncertainties in the negotiation processes, this study attempts to apply scenarios with regards to the reduction-mandatory nation group. In addition, this study tries to observe the impact on Korea through testing the various border adjustment measures, including the free allocation and embodied carbon tariffs.

• Journal of Korean Society of Water and Wastewater
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• v.34 no.5
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• pp.335-344
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• 2020

Due to global climate change, mega-droughts have occurred frequently. Since long-term droughts make it difficult to secure the water resources, water supply needs to be restricted in a reasonable manner. In the event of limited water supply, the waterworks need to develop a restricted water supply strategy. This study showed that analyzing daily water supply could be used to respond to the first stage of a drought. According to an analysis of Korea's major water authorities, there was about 7~21% of room for daily minimum water supply in case of a drought. Restricting the water supply by lowering pressure is a good strategy for local water authorities with high water leakage rate since leakage is inversely dependent with pressure. For this method, it is necessary to quantify water deficiency and pressure at each node using a simulation. Since DDA-based software is not possible to predict changes in demand at nodes with pressure reduction, WaterGEMS, a PDA software, was used to quantitatively predict water shortages and pressures at each node. Locations where water is deficient need to install booster pumps or to be dispatched with water tank truck and bottled water. Without these support, lowering pressure could not be an option for water works. This paper suggests a method for waterworks to plan a drought by lowering pressure to restrict water supply using daily water supply analysis and PDA based simulation.