• Progress in Superconductivity and Cryogenics
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• v.22 no.3
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• pp.13-19
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• 2020

This study presents the experiment and simulation results on the magnetic field response and electrical stability behaviors of no-insulation (NI) and metal insulation with stainless steel tape (MI-SS) which wound in form of racetrack type coils. First of all, the structural design of the racetrack type bobbin was shown along with its parameters. Then, the current-voltage tests were carried out to measure the critical current of both test coils. Also, the sudden discharging and charging tests were performed in the steady state to estimate the decay field time and magnetic field response, respectively. Finally, the overcurrent tests were conducted in the transient state to investigate the electrical stability of these test coils. Based on the experimental results, the contact surface resistances were calculated and applied to the field coils (FCs) of 10-MW-class second generation high temperature superconducting generator (2G HTSG) used in wind offshore environment. The charging delay time and electrical stability for NI and MI-SS HTS FCs of 10-MW-class 2G HTSG are analyzed by the equivalent circuit model and the key parameters which were obtained from the electromagnetic finite element analysis results.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.17 no.2
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• pp.73-83
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• 2014

This study was conducted to evaluate defects in Zelkova serrata trees using an ultrasonic tomograph (PICUS) and suggest a management plan to maintain it as a natural and cultural resource. In previous study, health information of 16 protected trees were obtained by surveying the following categories; tree appearance, crown, bark, root exposure, water and nutrition, deterioration, pest, vitality, ground status, and pollutant. The average score of health was 16.5 in 16 trees, which means that general monitor is needed for management. In this study, the evaluation result of tree's inside defects using an ultrasonic tomograph showed that 43.8% of decay rate has been found in 16 trees. In fact, some trees look to be good even though they actually have a defects causing broken by natural disaster such as strong wind. Therefore, it is urgent to put some support to the trees and come up with a protective plan. The results of this study would be useful as basic data in developing a guideline for the efficient conservation and management of big and old trees.

• Ocean Systems Engineering
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• v.4 no.3
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• pp.215-241
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• 2014

Steel catenary riser (SCR) is a popular/economical solution for the oil/gas production in deep and ultra-deep water. The behavioral characteristics of SCR have a high correlation with the motion of floating production facility at its survival and operational environments. When large motions of surface floaters occur, such as FPSO in 100-yr storm case, they can cause unacceptable negative tension on SCR near TDZ (touch down zone) and the corresponding elastic deflection can be large due to local dynamic buckling. The generation, propagation, and decay of the elastic wave are also affected by SCR and seabed soil interaction effects. The temporary local dynamic buckling vanishes with the recovery of tension on SCR with the upheaval motion of surface floater. Unlike larger-scale, an-order-of-magnitude longer period global buckling driven by heat and pressure variations in subsea pipelines, the sub-critical local dynamic buckling of SCR is motion-driven and short cycled, which, however, can lead to permanent structural damage when the resulting stress is greatly amplified beyond the elastic limit. The phenomenon is extensively investigated in this paper by using the vessel-mooring-riser coupled dynamic analysis program. It is found that the moment of large downward heave motion at the farthest-horizontal-offset position is the most dangerous for the local dynamic buckling.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.spc
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• pp.1-19
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• 2020

Based on the current high-level radioactive waste management basic plan and the analysis results of spent nuclear fuel characteristics, such as dimensions and decay heat, an improved geological disposal concept for spent nuclear fuel from domestic nuclear power plants was proposed in this study. To this end, disposal container concepts for spent nuclear fuel from two types of reactors, pressurized water reactor (PWR) and Canada deuterium uranium (CANDU), considering the dimensions and interim storage method, were derived. In addition, considering the cooling time of the spent nuclear fuel at the time of disposal, according to the current basic plan-based scenarios, the amount of decay heat capacity for a disposal container was determined. Furthermore, improved disposal concepts for each disposal container were proposed, and analyses were conducted to determine whether the design requirements for the temperature limit were satisfied. Then, the disposal efficiencies of these disposal concepts were compared with those of the existing disposal concepts. The results indicated that the disposal area was reduced by approximately 20%, and the disposal density was increased by more than 20%.

• Korean Journal of Veterinary Service
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• v.40 no.4
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• pp.259-264
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• 2017

In this study, the changes of low molecular weight compounds during natural decay process for 4 weeks were analyzed. Natural corruptions were observed in the slate warehouse with summer humidity and temperature throughout the rainy season by using commercially available compound feeds. Koiganal was detected from 14 days of natural decay and corruption with chicken, pig, and Korean cattle feed. Ethyl palmitate, Ethyl pentadecanoate and, Methyl elaidatel were detected from chicken, pig, and Korean cattle feed. So, Koiganal can be useful for monitoring the degree of pollution of corruption of livestock feeds in advance.

• International Journal of Advanced Culture Technology
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• v.6 no.3
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• pp.151-162
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• 2018

In deriving the economic order quantity (EOQ) formula, it is tacitly assumed that the buyer has to pay product price while receiving the product from the supplier. However, as a marketing policy, some suppliers permit a delay in payments to the buyers to increase demand for the product they made. Credit transactions would have a positive effect on both suppliers and buyers. For a supplier who offers trade credit, it is an effective means of price differentiation to increase the demand for the product. Availability of opportunity to delay the payment in buyer effectively reduces the cost of holding stocks and therefore, the buyer has a lot of price options to choose his sales price for a customer. Since the buyer's order is affected by the customer's demand, the problems of determining the sales price and EOQ are interdependent and must be solved simultaneously. From this perspective, this paper evaluates the problem of determining the optimal sales price and EOQ for the buyer at the same time when the supplier allows a delay in payments for the product whose demand is represented as a function that decreases linearly with the sales price. For the analysis, it is also assumed that inventory is exhausted not only by customer's but also by decay.

• Journal of Environmental Health Sciences
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• v.28 no.2
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• pp.183-192
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• 2002

Indoor air quality is affected by source strength of pollutants, ventilation rate, decay rate, outdoor level and so on. Although technologies exist to measure these factors directly, direct measurements of all factors are impractical in most field studies. The purpose of this study was to develop an alternative methods to estimate these factors by multiple measurements. Daily indoor and outdoor NO$_2$concentrations for 21 days in 20 houses in summer and winter, Seoul. Using a mass balance model and linear regression analysis, penetration factor (ventilation divided by sum of air exchange rate and deposition constant) and source strength factor(emission rate divided by sum of air exchange rate and deposition constant) were calculated. Subsequently, the ventilation and source strength were estimated. During sampling period, geometric mean of natural ventilation was estimated to be 1.10$\pm$1.53 ACH, assuming a residential NO$_2$decay rate of 0.8 hr$^{-1}$ in summer. In winter, natural ventilation was 0.75$\pm$1.31 ACH. And mean source strengths in summer and winter were 14.8ppb/hr and 22.4ppb/hr, respectively. Although the method showed similar finding previous studies, the study did not measure ACH or the source strength of the house directly. As validation of natural ventilations, infiltrations were measured with $CO_2$tracer gas in 18 houses. Relationship between ventilation and infiltration was statistically correlated (Pearson r=0.63, p=0.02).

• Journal of the Korean Wood Science and Technology
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• v.23 no.2
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• pp.77-82
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• 1995

With the aim to utilize pine wood(Pinus densiflora Sieb. et Zucc.) as an interior building materials, such as flooring material, monoethylene glycol(MEG) resin solution was impregnated into greenwood. Specimens of three different qualities, that is, normal wood, resinous wood and compression wood, were prepared. Distribution of resin element(phosphorus) in MEG resin solution-impregnated woods and preservative effectiveness against brown rot fungi(Tyromyces palustris and Serpula lacrymans) of these woods were investigated. The results were as follows: 1. The concentration of phosphorus into cell walls of resinous wood and compression wood was lower compared to that of normal wood. This shows that the quality of wood has an influence on the penetration of MEG resin solution into the wood. It was shown from a leaching test that MEG resin could be leached out easily from the cell walls. 2. The resinous wood and compression wood, even without MEG resin solution impregnation had high decay resistance. For normal wood, significant improvement of preservative effectiveness was observed after impregnation of MEG resin solution. It was shown that MEG resin was leached out from the woods after leaching test, resulting in the reduction of preservative effectiveness. From this result, suitability of MEG resin solution-impregnated woods as an interior materials was recognized.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2003.11a
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• pp.590-595
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• 2003

An Exponential experiment system which is composed of a neutron detector, a signal analysis system and a neutron source, Cf-252 has been installed in order to experimentally determine the neutron effective multiplication factor for a PWR spent fuel assembly. The axial background neutron flux is measured in a preliminary performance test. From the results, the spacer grid position is determined to be consistent with the design specifications within a 2.3% relative error. The induced fission neutron for four of the assemblies is also measured by scanning the neutron source, Cf-252 or the neutron detector. The exponential decay constants have been evaluated by the application of the Poisson regression to the net induced fission neutron counts. The measured keffs determined on the basis of the exponential decay constants of Cl5 appeared to be 0.541, 0.540, 0.597 and 0.556, respectively, which are comparable with 0.55195$\pm$0.00232 of the MCNP calculation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.5
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• pp.2067-2080
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• 2016

Cooperative spectrum sensing (CSS) for vacant licensed bands is one of the key techniques in cognitive radio networks. Currently, sequential probability ratio test scheme (SPRT) is considered as a powerful soft decision approach to improve the sensing result for CSS. However, SPRT assumes all secondary users (SU) are honest, and thus offering opportunities for malicious SUs to launch the spectrum sensing data falsification attack (SSDF attack). To combat such misbehaved behaviors, recent efforts have been made to trust mechanism. In this paper, we argue that powering SPRT with traditional trust mechanism is not enough. Dynamic SSDF attackers can maintain high trust in an alternant process of submitting honest or false sensing data, resulting in difficultly detecting them. Noting that the trust value of dymamic SSDF attackers behave highly volatile, a novel trusted SPRT scheme (VSPRT) based on volatility decay analysis is proposed in this paper to mitigate the harmful effect of dynamic SSDF attackers in the process of the soft-decision data fusion, and thus improving the accuracy of the final sensing result. Simulation results show that the VSPRT scheme outperforms the conventional SPRT schemes.