• Journal of Korean Medicine for Obesity Research
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• v.9 no.1
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• pp.1-14
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• 2009

Complex microbial communities play an important role in the human health and co-evolved with human in the form of symbiosis. Many literatures provide new evidences that the increased prevalence of obesity cannot be attributed solely to changes in the human genome, nutritional habits, or reduction of physical activity in our daily lives. The intestinal flora was recently proposed as an environmental factor responsible for the control of body weight and energy metabolism. A number of studies suggest that the modulation of gut microbiota affects host metabolism and has an impact on energy storage and demonstrated a role for the gut microbiota in weight gain, fat increase, and insulin resistance. Variations in microbiota composition are found in obese humans and mice and the microbiota from an obese mouse confers an obese phenotype when transferred to an axenic mouse. As well, the gut microbial flora plays a role in converting nutrients into calories. Specific strategies for modifying gut microbiota may be a useful means to treat or prevent obesity. Dietary modulations of gut microbiota with a view to increasing bifidobacteria have demonstrated to reduce endotoxemia and improve metabolic diseases such as obesity. The fermentation of medicinal herbs is intended to exert a favorable influence on digestability, bioavailability and pharmacological activity of herbal extract. Therefore we also expect that the fermented herbal extracts may open up a new area to treat obesity through modulating gut microbiota.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.3
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• pp.139-144
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• 2003

Nickel fine powders were prepared from nickel chloride aqueous solution containing ethanol as an organic solvent, and their oxidation behaviors were investigated. The reduction reaction by hydrazine from nickel chloride aqueous solution containing ethanol depend on reaction temperature. The reduction reaction time by hydrazine decreased with the increase of reaction temperature. By controlling reaction temperature, the products could be obtained spherical particles in the range of 0.1 $\mu\textrm{m}$~1.0 $\mu\textrm{m}$. Also, As reaction temperature increased from $40^{\circ}C$ to $80^{\circ}C$, the particle size slightly increased and had a broad size distribution owing to the presence of the coarse particles. The mean particle size and specific surface area of nickel powders prepared at $60^{\circ}C$ were 0.3 $\mu\textrm{m}$ and 31.8 $\m^2$/g, respectively. Weight loss of the powders at $300^{\circ}C$ was due to composition of $_Ni(OH)2$. In case of heat treatment at $200^{\circ}C$ in air, oxidation resistance of nickel powders was remarkable than that of as-synthesized.

• Transactions of the Korean hydrogen and new energy society
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• v.20 no.2
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• pp.116-124
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• 2009

We investigated the influences of cobalt coating deposited by DC electroplating on the ferritic stainless steel, STS 430, as a protective layer on a metallic interconnect for SOFC applications. Cobalt coated STS 430 revealed a uniform and denser-packing oxide surface and a reduced growth rate of $Cr_2O_3$ scales after oxidation at $800^{\circ}C$in air. Cobalt coating layer was oxidized to $CoCo_2O_4$ and Co containing mixed oxide spinels such as $Co_2CrO_4$, $CoCr_2O_4$, and $CoCrFeO_4$. The area specific resistance value of Co coated sample was $0.020\;{\Omega}cm^2$ lower than that of uncoated at $800^{\circ}C$ in air during 500 h. After 1000 h oxidation, cobalt oxide coating layer suppressed chromium outward diffusion.

• Korean Journal of Applied Biomechanics
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• v.27 no.4
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• pp.239-245
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• 2017

Objective: The bobsleigh shoes used in the start section are one of the most important equipment for improving the competition. Despite the importance of the start section, there are no shoes that are specific for bobsleigh athletes in Korea and Korean athletes have to wear sprint spike shoes and practice the start instead of wearing bobsleigh shoes. The objective of the present study was to provide data for improving the performance of Korean bobsleigh athletes by investigating the differences in their split time, plantar pressure, and forefoot bending angle based on skill levels at the start of a run under the same conditions as training conditions. Method: Six Korean bobsleigh athletes were divided into two groups, superior (n=3) and non-superior (n=3). A digital speedometer measured the split time at the start; the Pedar-X system (Novel, Germany) measured plantar pressure. Plantar pressures and split times were measured as the athletes pushed a bobsleigh and sprinted at full speed from the start line to the 10-m mark on the bobsleigh track. An ultra-high-speed camera was used to measure the forefoot bending angle during the start phase. Results: Significant between-group differences were found in split times (p<.000; superior = 2.38 s, non-superior = 2.52 s). The superior group had a larger rearfoot (p<.05) contact area, maximum rearfoot force (p<.01), and a larger change in angles 3 and 4 (p<.05). Conclusion: At the start of a bobsleigh run, proper use of the rearfoot for achieving effective driving force and increasing frictional resistance through a wider frictional force can shorten start time.

• Applied Chemistry for Engineering
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• v.25 no.2
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• pp.193-197
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• 2014

The electrode for gas sensor was prepared by using pitch-based activated carbon fibers and polyvinyl alcohol (PVA) to investigate the toxic gas sensing characteristics. The physicochemical properties of activated carbon fibers electrode for gas sensor were analyzed with SEM and BET. Toxic gases sensing property of the electrode was also identified by different toxic gases such as $NH_3$, NO and $CO_2$. The specific surface area of activated carbon fibers electrode for gas sensor was decreased by 33% owing to PVA used as a binder compared with the activated carbon fibers. However, its pore size distribution of the ACF electrode was not greatly influenced by PVA. The activated carbon fibers electrode for gas sensor responded to toxic gases by electron hopping unlike semiconductor based gas sensors. In this study, activated carbon fibers electrode was decreased to 7.5% in resistance for the NH3 gas of the 100 ppm concentration and its $NH_3$ gas sensing property was confirmed the most excellent compared with other toxic gases.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.76-76
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• 2011

Polymer-fullerene based bulk heterojunction (BHJ) solar cells can be fabricated in large area using low-cost roll-to-roll manufacturing methods. However, because of the low mobility of the BHJ materials, there is competition between the sweep-out of the photogenerated carriers by the built-in potential and recombination within the thin BHJ film [12-15]. Useful film thicknesses are limited by recombination. Thus, there is a need to increase the absorption by the BHJ film without increasing film thickness. Metal nanoparticles exhibit localized surface plasmon resonances (LSPR) which couple strongly to the incident light. In addition, relatively large metallic nanoparticles can reflect and scatter the light and thereby increase the optical path length within the BHJ film. Thus, the addition of metal nanoparticles into BHJ films offers the possibility of enhanced absorption and correspondingly enhanced photo-generation of mobile carriers. In this work, we have demonstrated several positive effects of shape controlled Au and Ag nanoparticles in organic P3HT/PC70BM, PCDTBT/PC70BM, Si-PCPDTBT/PC70BM BHJ-based PV devices. The use of an optimized concentration of Au and Ag nanomaterials in the BHJ film increases Jsc, FF, and the IPCE. These improvements result from a combination of enhanced light absorption caused by the light scattering of the nanomaterials in an active layer. Some of the metals induce the plasmon light concentration at specific wavelength. Moreover, improved charge transport results in low series resistance.

• Journal of the Korean Ceramic Society
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• v.51 no.4
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• pp.265-270
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• 2014

Among the Ruddlesden-Popper series, $La_4Ni_3O_{10}$ has received widespread attention as a promising cathode material by reason of its favorable properties for realizing high performance of intermediate temperature solid oxide fuel cells (IT-SOFCs). The $La_4Ni_3O_{10}$ cathode is prepared using the facile sol-gel method by employing tri-blockcopolymer (F127) to obtain a single phase in a short sintering time. There are no reactions between the $La_4Ni_3O_{10}$ cathode and the $Ce_{0.9}Gd_{0.1}O_{2-\delta}$ (GDC) electrolyte upon sintering at $1000^{\circ}C$, indicating that the $La_4Ni_3O_{10}$ cathode has good chemical compatibility with the GDC electrolyte. The maximum electrical conductivity of $La_4Ni_3O_{10}$ reaches approximately 240 S $cm^{-1}$ at $100^{\circ}C$ and gradually decreases with increasing temperaturein air atmosphere. The area specific resistance value of $La_4Ni_3O_{10}$ composite with 40 wt% GDC is $0.435{\Omega}cm^2$ at $700^{\circ}C$. These data allow us to propose that the $La_4Ni_3O_{10}$-GDC composite cathode is a good candidate for IT-SOFC applications.

• Clinical and Experimental Pediatrics
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• v.57 no.4
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• pp.186-192
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• 2014

Purpose: The prevalence of macrolide-resistant Mycoplasma pneumoniae (MRMP) has increased worldwide. The aim of this study was to estimate the proportion of MRMP in a tertiary hospital in Korea, and to find potential laboratory markers that could be used to predict the efficacy of macrolides in children with MRMP pneumonia. Methods: A total of 95 patients with M. pneumoniae pneumonia were enrolled in this study. Detection of MRMP was based on the results of specific point mutations in domain V of the 23S rRNA gene. The medical records of these patients were reviewed retrospectively and the clinical course and laboratory data were compared. Results: The proportion of patients with MRMP was 51.6% and all MRMP isolates had the A2063G point mutation. The MRMP group had longer hospital stay and febrile period after initiation of macrolides. The levels of serum C-reactive protein (CRP) and interleukin-18 in nasopharyngeal aspirate were significantly higher in patients who did not respond to macrolide treatment. CRP was the only significant factor in predicting the efficacy of macrolides in patients with MRMP pneumonia. The area under the curve for CRP was 0.69 in receiver operating characteristic curve analysis, indicating reasonable discriminative power, and the optimal cutoff value was 40.7 mg/L. Conclusion: The proportion of patients with MRMP was high, suggesting that the prevalence of MRMP is rising rapidly in Korea. Serum CRP could be a useful marker for predicting the efficacy of macrolides and helping clinicians make better clinical decisions in children with MRMP pneumonia.

• Journal of Sensor Science and Technology
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• v.29 no.6
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• pp.420-426
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• 2020

A metal oxide semiconductor gas sensor is operated by measuring the changes in resistance that occur on the surface of nanostructures for gas detection. ZnO, which is an n-type metal oxide semiconductor, is widely used as a gas sensor material owing to its high sensitivity. Various ZnO nanostructures in gas sensors have been studied with the aim of improving surface reactions. In the present study, the sol-gel and vapor phase growth techniques were used to fabricate nanostructures to improve the sensitivity, response, and recovery rate for gas sensing. The sol-gel method was used to synthesize SnO₂ nanoparticles, which were used as the seed layer. The nanoparticles size was controlled by regulating the process parameters of the solution, such as the pH of the solution, the type and amount of solvent. As a result, the SnO₂ seed layer suppressed the aggregation of the nanostructures, thereby interrupting gas diffusion. The ZnO nanostructures with a sol-gel processed SnO₂ seed layer had larger specific surface area and high sensitivity. The gas response and recovery rate were 1-7 min faster than the gas sensor without the sol-gel process. The gas response increased 4-24 times compared to that of the gas sensor without the sol-gel method.

• Journal of Welding and Joining
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• v.27 no.6
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• pp.74-79
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• 2009

Titanium and titanium alloy can be reproduced immediately even if oxide films($TiO_2$) break apart in sea water. Therefore, since titanium demonstrates large specific strength and outstanding resistance to stress corrosion cracking, crevice corrosion, pitting and microbiologically influenced corrosion in sea water environment, it has been widely applied to heat exchanger for ships. In particular, with excellent elongation, pure titanium may be deemed as optimal material for production of heat exchanger plate which is used with wrinkles formed for efficient heat exchange. Conventional plate type heat exchanger prevented leakage of liquid through insertion of gasket between plates and mechanical tightening by bolts and nuts, but in high temperature and high pressure environment, gasket deterioration and leakage occur, so heat exchanger for LPG re-liquefaction device etc do not use gasket but weld heat exchanger plate for use. On the other hand, since welded plate cannot be separated, it is important to obtain high quality reliable welds. In addition, for better workability and production performance, lasers that can obtain weldment with large aspect ratio and demonstrate fast welding speed even in atmospheric condition not in vacuum condition are used in producing products. So far, 1st report and 2nd report compared and analyzed embrittlement degrees by bead colors of weldment through quantitative analysis of oxygen and nitrogen and measurement of hardness as fundamental experiment for the evaluation of titanium laser welding, and evaluated the welding performance and mechanical properties of butt welding. This study welded specimens in various conditions by using laser and GTA welding machine to apply edge welding to heat exchanger, and evaluated the mechanical strength through tensile stress test. As a result of tensile test, laser weldment demonstrated tensile strength 4 times higher than GTA welds, and porosity could be controlled by increasing and decreasing slope of laser power at overlap area.