• Ocean and Polar Research
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• v.24 no.4
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• pp.491-500
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• 2002

Magnetic anomalies in the Dokdo and it's surroundings were investigated with respect to structure and origin of the Dokdo and surrounding seamounts. After normal and diurnal correction of measured magnetic data, crossover correction was applied to reduce errors between sets of magnetic anomalies. The errors from crossover operation result in decrease of about 51%, from 62.2 nT to 30.1 nT in standard deviation. Reduction-to-the-pole, second vertical derivative and analytic signal processing were applied to explore magnetic anomaly signatures in detail. Magnetic anomalies are most complicated in the 1st-Dok seamount, show SWW-NEE linear pattern in the 2nd-Dok seamount and lower to the 3rd-Dok seamount. Different magnetic anomaly patterns in three seamounts imply that three volcanic seamounts were formed at different times and are composed of rocks that were produced in different conditions. It seems that the 3rd-Dok seamount was first to form and followed by the 1st-Dok seamount. The complicated magnetic and second vertical derivative anomaly patterns in the 1st-Dok seamount may be due to subsidiary cones around crater or the presence of intruded magma bodies below sea surface and the Dokdo is probably a marginal subsidiary part of crater.

• Korean Chemical Engineering Research
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• v.53 no.6
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• pp.690-694
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• 2015

Recently, direct formic acid fuel cells (DFAFC) among direct liquid fuel cells is studied actively. Economical hydrocarbon membranes alternative to fluorinated membranes for DFAFC's membrane are receiving attention. In this study, characteristics of sulfonated poly(ether ether ketone, sPEEK) and sulfonated poly(arylene ether sulfone, PAES) membranes were compared with Nafion membrane at DFAFC operation condition. Formic acid crossover current density of hydrocarbon membranes were lower than that of Nafion 211 fluorinated membrane. I-V performance of sPEEK MEA(Membrane and Electrode Assembly) was similar to that of Nafion 211 MEA due to similar membrane resistance each other. sPEEK MEA with low formic acid crossover showed higher stability compared with Nafion 211 MEA.

• Korean Chemical Engineering Research
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• v.52 no.4
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• pp.425-429
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• 2014

Until a recent day, degradation of PEMFC MEA(membrane and electrode assembly) has been studied, separated with membrane degradation and electrode degradation, respectively. But membrane and electrode were degraded coincidentally at real PEMFC operation condition. During simultaneous degradation, there was interaction between membrane degradation and electrode degradation. Hydrogen permeability was used often to measure degradation of electrolyte membrane in PEMFC. In case of hydrogen permeability measured by LSV(Linear Sweep Voltammetry) method, the degradation of electrode decrease the value of hydrogen crossover current due to LSV methode's dependence on electrode active area. In this study hydrogen permeability was measured by gas chromatograph(GC) when membrane and electrode degraded at the same time. It was showed that degradation of electrode did not affect the hydrogen permeability measured by GC because of GC methode's independence on electrode active area.

• Journal of the Korean Institute of Intelligent Systems
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• v.15 no.6
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• pp.661-667
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• 2005

In this paper, we propose a new hybrid genetic algorithm for sequential ordering problem (SOP). In the proposed genetic algorithm, the Voronoi quantized crossover (VQX) is used as a crossover operator and the path-preserving 3-Opt is used as a local search heuristic. VQX is a crossotver operator that uses the epistasis information of given problem instance. Since it is a crossover proposed originally for the traveling salesman problem (TSP), its application to SOP requires considerable modification. In this study, we appropriately modify VQX for SOP, and develop three algorithms, required in the modified VQX, named Feasible solution Generation Algorithm, Precedence Cycle Decomposition Algorithm, and Genic Distance Assignment Method. The results of the tests on SOP instances obtained from TSPLIB and ZIB-MP-Testdata show that the proposed genetic algorithm outperforms other genetic algorithms in stability and solution quality.

• Journal of Korea Multimedia Society
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• v.6 no.6
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• pp.1034-1045
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• 2003

In this paper, we study a multicast transport technique for multimedia services of mobile hosts in wireless network environments. To reduce packet loss during hand-off, we propose a Pre-join scheme in overlapped area and a Buffering scheme in crossover routers. To support seamless service in real time multimedia application, these scheme use an optimal path routing which was provided in remote subscription scheme and a prediction scheme of host movements which was considered overlapped area. To evaluate the peformance of our scheme, we compare Bi-direction tunneling of mobile If, Remote subscription, and MoM by using NS-2. As a result, our scheme shows better performance in network overhead, packet loss and bandwidth's use than other schemes.

• Journal of the Korean Vacuum Society
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• v.19 no.3
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• pp.169-176
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• 2010

Cryopumps can provide economical profits with a relatively high pumping speed per size. However, it is somewhat doubtful that pumping performance of cryopums, which is very sensitive to the temperature of the adsorption panel, can be maintained or recovered fast for large continuous or impulsive gas loads. The official evaluation items indicating cryopump performance for gas loads are the maximum throughput and the crossover value. There are two other, unofficial but widely used, items, the Ar recovery time and gulp characteristics. Although these evaluation items look absolutely different with each other, there are close relations and even duplications in their test schemes. Therefore, it is necessary to study how to improve practically each test procedure, and combine or unify some procedures.

• The Korean Journal of Pharmacology
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• v.31 no.2
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• pp.261-269
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• 1995

Background; To explore the efficacy of aspartate as NAD regenerating agent for ethanol and acetaldehyde oxidation, we performed crossover challenge in two groups of volunteers by coadministration of various doses of aspartate, asparagine and ethanol. Methods; 18 healthy male volunteers were randomly divided into two groups. 6 volunteers of the first group were administered 5 gm monosodium aspartate(MSA), 5 gm asparagine or placebo with 100 ml of $40^{\circ}$ whiskey by the 3 way-crossover design, while 12 volunteers of the other group were administered placebo, 1, 2 or 5 bottles of $Aspar^(circledR)$ containing 1 gm of MSA per bottle with 100 ml of $40^{\circ}$ whiskey by the 4 way-crossover design. Ethanol(and acetaldehyde) concentrations in venous blood drawn at 0, 0.25, 0.5, 1, 2, 4, 8th hour after ethanol ingestion were analysed by gas chromatogaphy. Subjective symptoms, liver function tests and psychomotor function tests were also performed during the study periods. Result; Plasma concentration and AUC of acetaldehyde in asparagine and MSA trials on ethanol ingestion were significantly lower than those of placebo trial in the 1st group. Plasma ethanol concentration of 5 bottle $Aspar^(circledR)$ trial was significantly lower than that of placebo trial in the 2nd group. Improvement of subjective symptoms or psychomotor performance by the treatment was not statistically significant. Conclusion; Aspartate and asparagine may be prospective candidates for acceleration of ethanol metabolism and prevention of ethanol toxicity.

• Journal of Chest Surgery
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• v.54 no.1
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• pp.53-58
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• 2021

Background: We aimed to investigate the characteristics of primary spontaneous pneumothorax (PSP) in adolescents and to analyze the relationship between the occurrence of PSP and air pollutants. Methods: Data pertaining to age, sex, body mass index, smoking status, initial pneumothorax volume, presence of bullae, treatment methods, and city of residence were retrospectively obtained from January 2010 to December 2014. We investigated the association between short-term exposure to air pollutants (SO2, NO2, O3, CO, and PM10) and the occurrence of PSP using a case-crossover design with conditional logistic regression. Results: We collected information from 598 patients who were admitted for PSP, with a mean follow-up duration of 62.9 months. The majority (91.1%) of the patients were male. In the case-crossover design, conditional logistic regression showed that no air pollutant was associated with the occurrence of pneumothorax. The results were consistent across all city subgroups (Anyang, Gunpo, Uiwang, and Gwacheon). Conclusion: In our study, the incidence rate of pneumothorax was 153.8 per 100,000 person-years in male adolescents and 16.7 per 100,000 person-years in female adolescents. The case-crossover design showed that PSP in adolescents is unlikely to be related to air pollution.

• Nutrition Research and Practice
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• v.7 no.5
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• pp.373-379
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• 2013

The consumption of fruits and vegetables that have high polyphenol content has been previously associated with a reduced risk for cardiovascular disease. We investigated the effects of onion peel extract on plasma total antioxidant capacity, lipid peroxidation, and leukocyte DNA damage. This study was a randomized, double-blind, placebo-controlled, crossover trial. Healthy female subjects received either onion peel extract or placebo (dextrin) for two weeks, underwent a 1-week washout period, and then received the other treatment for an additional two weeks. After two weeks of onion peel extract supplementation, the total cholesterol level, low-density lipoprotein cholesterol level, and atherogenic index significantly decreased (P < 0.05). No changes were observed in activities of erythrocyte antioxidant enzymes or levels of lipid peroxidation markers following onion peel extract supplementation. Additionally, no significant difference was found in plasma antioxidant vitamin (retinol, tocopherols, carotenoids, and coenzyme Q10) levels or ex vivo $H_2O_2$-provoked oxidative DNA damage after onion peel extract supplementation. The present interventional study provides evidence of the health benefits of onion peel extract and demonstrates its effects in modulating lipid profiles in healthy young Korean women.

• Steel and Composite Structures
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• v.25 no.4
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• pp.427-442
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• 2017

This paper presents unprecedented damped oscillation behaviours of a precast steel-concrete composite slab panel for track support. The steel-concrete composite slab track is an innovative slab track, a form of ballastless track which is becoming increasingly attractive to asset owners as they seek to reduce lifecycle costs and deal with increasing rail traffic speeds. The slender nature of the slab panel due to its reduced depth of construction makes it susceptible to vibration problems. The aim of the study is driven by the need to address the limited research available to date on the dynamic behaviour of steel-concrete composite slab panels for track support. Free vibration analysis of the track slab has been carried out using ABAQUS. Both undamped and damped eigenfrequencies and eigenmodes have been extracted using the Lancsoz method. The fundamental natural frequencies of the slab panel have been identified together with corresponding mode shapes. To investigate the sensitivity of the natural frequencies and mode shapes, parametric studies have been established, considering concrete strength and mass and steel's modulus of elasticity. This study is the world first to observe crossover phenomena that result in the inversion of the natural orders without interaction. It also reveals that replacement of the steel with aluminium or carbon fibre sheeting can only marginally reduce the natural frequencies of the slab panel.