• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.32-33
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• 2003

Mechanism of a periodic oscillation of shock-induced combustion over a two- dimensional wedges and axi-symmetric cones were investigated through a series of numerical simulations at off-attaching condition of oblique detonation waves(ODW). A same computational domain over 40 degree half-angle was considered for two-dimensional and axi-symmetric shock-induced combustion phenomena. For two-dimensional shock-induced combustion, a 2H2+02+17N2 mixture was considered at Mach number was 5.85with initial temperature 292 K and initial pressureof 12 KPa. The Rankine-Hugoniot relation has solution of attached waves at this condition. For axi-symmetric shock-induced combustion, a H2+2O2+2Ar mixture was considered at Mach number was 5.0 with initial temperature 288 K and initial pressure of 200 mmHg. The flow conditions were based on the conditions of similar experiments and numerical studies.[1, 3]Numerical simulation was carried out with a compressible fluid dynamics code with a detailed hydrogen-oxygen combustion mechanism.[4, 5] A series of calculations were carried out by changing the fluid dynamic time scale. The length wedge is varied as a simplest way of changing the fluid dynamic time scale. Result reveals that there is a chemical kinetic limit of the detached overdriven detonation wave, in addition to the theoretical limit predicted by Rankine-Hugoniot theory with equilibrium chemistry. At the off-attaching condition of ODW the shock and reaction waves still attach at a wedge as a periodically oscillating oblique shock-induced combustion, if the Rankine-Hugoniot limit of detachment isbut the chemical kinetic limit is not.Mechanism of the periodic oscillation is considered as interactions between shock and reaction waves coupled with chemical kinetic effects. There were various regimes of the periodicmotion depending on the fluid dynamic time scales. The difference between the two-dimensional and axi-symmetric simulations were distinct because the flow path is parallel and uniform behind the oblique shock waves, but is not behind the conical shock waves. The shock-induced combustion behind the conical shockwaves showed much more violent and irregular characteristics.From the investigation of characteristic chemical time, condition of the periodic instability is identified as follows; at the detaching condition of Rankine-Hugoniot theory, (1) flow residence time is smaller than the chemical characteristic time, behind the detached shock wave with heat addition, (2) flow residence time should be greater than the chemical characteristic time, behind an oblique shock wave without heat addition.

• Journal of Radiation Protection and Research
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• v.34 no.2
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• pp.87-94
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• 2009

Tritium is the one of the dominant contributors to the internal radiation exposure of workers at pressurized heavy water reactors (PHWRs). This nuclide is likely to release to work places as tritiated water vapor (HTO) from a nuclear reactor and gets relatively easily into the body of workers by inhalation. Inhaled tritium usually reaches the equilibrium of concentration after approximately 2 hours inside the body and then is excreted from the body with a half-life of 10 days. Because tritium inside the body transports with body fluids, a whole body receives radiation exposure. Internal radiation exposure at PHWRs accounts for approximately 20-40% of total radiation exposure; most internal radiation exposure is attributed to tritium. Thus, tritium is an important nuclide to be necessarily monitored for the radiation management safety. In this paper, metabolism for tritium is established using its excretion rate results in urine samples of workers at PHWRs and an effective half-life, a key parameter to estimate the radiation exposure, was derived from these results. As a result, it was found that the effective half-life for workers at Korean nuclear power plants is shorter than that of International Commission on Radiological Protection guides, a half-life of 10 days.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.8
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• pp.1113-1120
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• 2011

Enzymatic interesterification was conducted with the palm mid fraction (PMF) and stearic ethyl ester for 1, 5, and 9 hr at 46$^{\circ}C$. The reaction was catalyzed by Lipozyme TLIM (2, 3, and 4% by weight of total substrates) in a shaking water bath at 180 rpm. As the reaction continued, oleic acid (C18:1) content at the sn-2 position decreased, whereas saturated fatty acid (C16:0 and C18:0) content increased. In the high performance chromatography analysis, 1,3-dipalmitoyl-2-oleoyl glycerol content decreased, whereas 1(3)-palmitoyl-2-oleoyl-3(1)-stearoyl glycerol (POS) content increased up to the reaction equilibrium. The rate of acyl migration increased with increasing molar ratio and enzyme load as well as reaction time. The optimal reaction conditions for maximizing POS content (53.5 area%) and minimizing acyl migration (23.1 area%) were obtained with a PMF : stearic ethyl ester=1:2 (molar ratio), Lipozyme TLIM 3 wt%, and a reaction time of 5 hr.

• Journal of the Korean Geotechnical Society
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• v.21 no.8
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• pp.107-116
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• 2005

Generally, when the stability of the geosynthetic reinforced soil slopes is analyzed, the required tensile forces of each reinforcement layers are calculated from total reinforcement forces which are necessary to retain the equilibrium state of slip mass in which the slip surfaces are assumed to be a linear or bilinear. It is assumed that the reinforcement forces are increased or constant with depth. However, according to the instrumented field data and laboratory model test results, the maximum tensile strain of reinforcement in a reinforced soil slope is developed in a certain elevation, not a bottom of the slope. In the concept of reinforced soil, postulated failure surfaces are the traces of the position in which the reinforcement tensile forces are maximum in the layer, and the reinforcement tensile forces are related to the stress state on the postulated failure surface. Therefore, in this study, based on the distribution of normal stress on the slip surface, a new method for the evaluation of required tensile forces is suggested and a number of the instrumented field data are analyzed by newly suggested method. As a result, it is shown that the newly suggested method produces relatively accurate reinforcement tension forces.

• Geomechanics and Engineering
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• v.21 no.1
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• pp.23-33
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• 2020

An advancing cutting roof for gob-side entry retaining with no-pillar mining under specific geological conditions is more conducive to the safe and efficient production in a coalmine. This method is being promoted for use in a large number of coalmines because it has many advantages compared to the retaining method with an artificial filling wall as the gateway side filling body. In order to observe the inner structure of the gateway cutting roof and understand its stability mechanism, an equivalent material simulation experiment for a coalmine with complex geological conditions was carried out in this study. The results show that a "self-stabilization bearing structure" equilibrium model was found after the cutting roof caving when the cut line deviation angle was unequal to zero and the cut height was greater than the mining height, and the caving roof rock was hard without damage. The model showed that its stability was mainly controlled by two key blocks. Furthermore, in order to determine the optimal parameters of the cut height and the cut line deviation angle for the cutting roof of the retaining gateway, an in-depth analysis with theoretical mechanics and mine rock mechanics of the model was performed, and the relationship between the roof balance control force and the cut height and cut line deviation angle was solved. It was found that the selection of the values of the cut height and the cut line deviation angle had to conform to a certain principle that it should not only utilize the support force provided by the coal wall and the contact surface of the two key blocks but also prevent the failure of the coal wall and the contact surface.

• Journal of Korea Port Economic Association
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• v.27 no.2
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• pp.355-372
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• 2011

Various incentive policies for transshipment cargo have been enforced without any evaluation of the effectiveness. Therefore, the purpose of this study is to evaluate the effect of volume incentive on container transshipment cargo. To be different from previous studies, this study tries to quantitatively assess the incentive effects by using econometric techniques. The result derived from the ARIMA type models indicates that the total amount of the increased transshipment cargo during the last 7 years is about one million TEU. In the meanwhile, the multivariate long run equilibrium model implies that the increased transshipment cargo is less than 0.5 million TEU for the 7 years. Furthermore, the structural break tests indicate that the volume incentive does not change the model structures. It means that the effect of volume incentive is not statistically significant. Consequently, the test results conclude the effect of volume incentive on transshipment cargo is not significant although the volume of transshipment cargo is increased to some extent by volume incentive. Considering the magnitude of BPA's expenditure, we doubt the effectiveness of volume incentive. This study, therefore, encourages the port authority to research a more efficient way to induce transshipment cargo rather than focusing on only volume incentives.

• Journal of Korea Port Economic Association
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• v.35 no.3
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• pp.1-18
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• 2019

The competition between port authorities (PAs) and terminal operating companies (TOCs) in providing port logistics services has gained importance. The PAs enter into leasing contracts with TOCs in various ways. This study aims to model a contract method that maximizes the joint profit between a PA and a TOC. Particularly, this study aims to model the equilibrium by comparing four types of contract schemes in the non-coordination, cooperation, Cournot, and collusion models. The results of the analysis show that the two-part tariff scheme generates a higher joint profit than the fixed and fee contracts. It is understood that risk- and profit-sharing between the PAs and TOCs helps the latter to maximize the throughput and the joint profit. These results are expected to provide an important theoretical basis for decision-making about port rent and freight between the PAs and TOCs.

• International Commerce and Information Review
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• v.14 no.4
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• pp.517-541
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• 2012

Since the Korea-Chile FTA in 2003, eight FTAs are now in force including Korea-EU and Korea-US FTA. The government anticipate that FTAs increase the GDP of Korea. Government-related research institutes officially reports the positive economic impact in Korea. However, the report does not show that how much Busan economy is affected by the FTAs. For this reason, we study the economic effects of FTAs in Busan. We compare the trade statistics before and after the time each FTA is in force. The resulting figures show that the exports and trades of Busan with the FTA nations increased significantly after the enforcement. For example, the exports to Chile increased by 273% when we compare the three-year average trade. We also construct an econometrics model to estimate the price elasticity. The estimated elasticity of exports for manufactured goods is 1.38 while that of imports is 0.83. Among the manufacturing industry, machinery has the highest price elasticity, 1.8. The average tariff for manufactured goods is 3.9% for FTA nations, while that is 5.8% for Busan. This higher price fall in Busan is offset by the lower price elasticity to make Busan's export increase be greater than Busan's import increase. Busan's export increases by 4.8% while import increases by 3.7%. So, it is expected to be added to the annual trade surplus of approximately $107million.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.22 no.4
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• pp.287-293
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• 2011

Objectives : The region of chromosome 5p14 is known to be associated with autism spectrum disorder (ASD). The cadherin9 (CDH9) and cadherin10 (CDH10) genes are located in the region of chromosome 5p14 and reported to be associated with ASD in the Caucasian population. We performed an association study to identify if single nucleotide polymorphisms (SNPs) located on the CDH9 and CDH10 genes are associated in the Korean population. Methods : Genomic DNA was extracted from the blood of 214 patients with ASD and 258 controls. SNPs selected from two genes were genotyped using an Illumina Golden-Gate Genotyping assay with VeraCode technology. Statistical analysis was performed using SAS and Plink software. Results : All controls and ASD patients were in Hardy-Weinberg equilibrium. In the results of logistic regression analyses for the genotype model and the chi-square test for the allele model, we found that SNPs on the CDH9 and CDH10 genes were not associated with ASD. Conclusion : Our data suggests that the CDH9 and CDH10 genes are not associated with ASD in the Korean population.

• Korean Journal of Agricultural and Forest Meteorology
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• v.16 no.3
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• pp.157-168
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• 2014

From a complex systems perspective, ecohydrological systems in forests may be characterized with (1) large networks of components which give rise to complex collective behaviors, (2) sophisticated information processing, and (3) adaptation through self-organization and learning processes. In order to demonstrate such characteristics, we applied the recently proposed 'process networks' approach to a temperate deciduous forest in Gwangneung National Arboretum in Korea. The process network analysis clearly delineated the forest ecohydrological systems as the hierarchical networks of information flows and feedback loops with various time scales among different variables. Several subsystems were identified such as synoptic subsystem (SS), atmospheric boundary layer subsystem (ABLS), biophysical subsystem (BPS), and biophysicochemical subsystem (BPCS). These subsystems were assembled/disassembled through the couplings/decouplings of feedback loops to form/deform newly aggregated subsystems (e.g., regional subsystem) - an evidence for self-organizing processes of a complex system. Our results imply that, despite natural and human disturbances, ecosystems grow and develop through self-organization while maintaining dynamic equilibrium, thereby continuously adapting to environmental changes. Ecosystem integrity is preserved when the system's self-organizing processes are preserved, something that happens naturally if we maintain the context for self-organization. From this perspective, the process networks approach makes sense.