• Journal of the Korean Society of Clothing and Textiles
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• v.35 no.11
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• pp.1297-1308
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• 2011

This research investigates the application of ZnO (zinc oxide) nanoparticles and $TiO_2$ (titanium dioxide) nanoparticles to polypropylene nonwoven fabrics via an electrospinning technique for the development of textile materials that can decompose harmful gases. To fabricate uniform ZnO nanocomposite fibers, two types of ZnO nanoparticles were applied. Colloidal $TiO_2$ nanoparticles were chosen to fabricate $TiO_2$ nano- composite fibers. ZnO/poly(vinyl alcohol) (PVA) and $TiO_2$/PVA nanocomposite fibers were electrospun under a variety of conditions that include various feed rates, electric voltages, and capillary diameters. The morphology of electrospun nanocomposite fibers was examined with a field-emission scanning electron micro- scope and a transmission electron microscope. Decomposition efficiency of gaseous materials (formaldehyde, ammonia, toluene, benzene, nitrogen dioxide, sulfur dioxide) by nanocomposite fiber webs with 3wt% nano-particles (ZnO or $TiO_2$) and 7$g/m^2$ web area density was assessed. This study shows that ZnO nanoparticles in colloid were more suitable for fabricating nanocomposite fibers in which nanoparticles are evenly dispersed than in powder. A heat treatment was applied to water-soluble PVA nanofiber webs in order to stabilize the electrospun nanocomposite fibrous structure against dissolution in water. ZnO/PVA and $TiO_2$/PVA nanofiber webs exhibited a range of degradation efficiency for different types of gases. For nitrogen dioxide, the degradation efficiency was 92.2% for ZnO nanocomposite fiber web and 87% for $TiO_2$ nanocomposite fiber web after 20 hours of UV light irradiation. The results indicate that ZnO/PVA and $TiO_2$/PVA nano- composite fiber webs have possible uses in functional textiles that can decompose harmful gases.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.9
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• pp.5743-5747
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• 2015

In this study, Fe-based bulk amorphous alloy powder manufactured using gas atomization fabrication was used for laser welding. the fracture behavior of welding layer were analyzed. Tensile test results show that the destruction occurred immediately after the elastic deformation, After plastic deformation of the substrate, the destruction occurred. The actual maximum tensile strength of the welding layer and the substrate are 959.9MPa and 220.4MPa. welding layer were each $485.5{\pm}21$ and $197.4{\pm}14$ to the substrate and the actual microhardness, The welding layer has very high hardness. The welding layer showed a very weak fine acicular structure. The base material was shown in the micro structure appear a coarse grain. SEM observations of the fracture after the tensile test. Fracture morphology of the base metal and the welding layer showed ductile fracture and brittle fracture, respectively.

• Resources Recycling
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• v.9 no.3
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• pp.46-53
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• 2000

Recently, the efficient disposal of the waste rubber is necessary due to increasing amount of the waste rubbers. In this paper, method of recycling waste rubbers as components of medium for hydroponic rose culture was suggested. We investigated growth of rose, and macro- and micro-elements, pH and EC of the media amended with waste rubber, In the beginning of culture, stress symptoms such as thin brittle stem and incipient wilting were observed, but they disappeared in a few weeks. Concentration of $Zn^{2+}$ in media at flowering increased in proportion to contents of waste tire in the media. pH of media at flowering were in the range of 5.70 to 6.35. Rose growth in all media, except in wasterock wool mixed with EPDM powder at 9:3 ratio, was normal and equivalent to the control in terms of stem length, number of stems harvested and fresh weight.

• Smart Structures and Systems
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• v.6 no.5_6
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• pp.641-659
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• 2010

Structural Health Monitoring (SHM) gradually becomes a technique for ensuring the health and safety of civil infrastructures and is also an important approach for the research of the damage accumulation and disaster evolving characteristics of civil infrastructures. It is attracting prodigious research interests and the active development interests of scientists and engineers because a great number of civil infrastructures are planned and built every year in mainland China. In a SHM system the sheer number of accompanying wires, fiber optic cables, and other physical transmission medium is usually prohibitive, particularly for such structures as offshore platforms and long-span structures. Fortunately, with recent advances in technologies in sensing, wireless communication, and micro electro mechanical systems (MEMS), wireless sensor technique has been developing rapidly and is being used gradually in the SHM of civil engineering structures. In this paper, some recent advances in the research, development, and implementation of wireless sensors for the SHM of civil infrastructures in mainland China, especially in Dalian University of Technology (DUT) and Harbin Institute of Technology (HIT), are introduced. Firstly, a kind of wireless digital acceleration sensors for structural global monitoring is designed and validated in an offshore structure model. Secondly, wireless inclination sensor systems based on Frequency-hopping techniques are developed and applied successfully to swing monitoring of large-scale hook structures. Thirdly, wireless acquisition systems integrating with different sensing materials, such as Polyvinylidene Fluoride(PVDF), strain gauge, piezoresistive stress/strain sensors fabricated by using the nickel powder-filled cement-based composite, are proposed for structural local monitoring, and validating the characteristics of the above materials. Finally, solutions to the key problem of finite energy for wireless sensors networks are discussed, with future works also being introduced, for example, the wireless sensor networks powered by corrosion signal for corrosion monitoring and rapid diagnosis for large structures.

• Nuclear Engineering and Technology
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• v.40 no.1
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• pp.21-36
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• 2008

High bum-up fuel technology has been developed through a national R&D program, which covers key technology areas such as claddings, $UO_2$ pellets, spacer grids, performance code, and fuel assembly tests. New cladding alloys were developed through alloy designs, tube fabrication, out-of-pile test and in-reactor test. The new Zr-Nb tubes are found to be much better in their corrosion resistance and creep strength than the Zircaloy-4 tube, owing to an optimized composition and heat treatment of the new Zr-Nb alloys. A new fabrication technology for large grain $UO_2$ pellets was developed using various uranium oxide seeds and a micro-doping of Al. The uranium oxide seeds, which were added to $UO_2$ powder, were prepared by oxidizing and heat-treating scrap $UO_2$ pellets. A $UO_2$ pellet containing tungsten channels was fabricated for a thermal conductivity enhancement. For the fuel performance analysis, new high burnup models were developed and implemented in a code. This code was verified by an international database and our own database. The developed spacer grid has two features of contoured contact spring and hybrid mixing vanes. Mechanical and hydraulic tests showed that the spacer grid is superior in its rodsupporting, wear resistance and CHF performance. Finally, fuel assembly test technology was also developed. Facilities for mechanical and thermal hydraulic tests were constructed and are now in operation. Several achievements are to be utilized soon by the Korea Nuclear Fuel and thereby contribute to the economy and safety of PWR fuel in Korea

• Tribology and Lubricants
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• v.34 no.6
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• pp.217-225
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• 2018

In this study, we spray a Ni-Cr composite powder onto AISI 4340 steel using the high velocity oxygen fuel method. We subsequently subject the Ni-Cr coating (as-sprayed) to ultrasonic nanocrystal surface modification (UNSM) process to improve the tribological performance. This study aims at increasing the wear resistance and durability of the Ni-Cr coating by altering the surface integrity and microstructure via the UNSM process. The UNSM process reduces the surface roughness of the as-sprayed coating by about 64%, which is explained by observing the elimination of high peaks and valleys and filling up micro-pores. Furthermore, a change in the microstructure of the coating due to continuous high-frequency strikes to the surface by a tip can lead to an increase in hardness from about 48 to 60 HRC. Furthermore, we investigate the characterization of the friction and wear behavior of Ni-Cr coating by a ball-on-disc tribometer in the dry conditions. We determine that after the UNSM process, there is a significant reduction in the friction coefficient of the as-sprayed coating from approximately 1.1 to 0.75. This is owing to the increased hardness and smoothed surface roughness. In addition, we investigate the surface morphology and wear track of the coatings before and after the UNSM process using a scanning electron microscope, energy dispersive spectrometer, and three-dimensional laser scanning microscope. We observe that the wear track of the Ni-Cr coating after the UNSM process is lower than that of the as-sprayed one. Thus, we confirm that the UNSM process has a significant influence on the improvement of the tribological performance of the Ni-Cr composite coating.

• Journal of the Korean institute of surface engineering
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• v.54 no.6
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• pp.340-347
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• 2021

Among various metal oxide semiconductors, ZnO has an excellent electrical, optical properties with a wide bandgap of 3.3 eV. It can be applied as a photocatalytic material due to its high absorption rate along with physical and chemical stability to UV light. In addition, it is important to control the morphology of ZnO because the size and shape of the ZnO make difference in physical properties. In this paper, we demonstrate synthesis of size-controlled ZnO tetrapods using an atmospheric pressure plasma system. A micro-sized Zn spherical powder was continuously introduced in the plume of the atmospheric plasma jet ignited with mixture of oxygen and nitrogen. The effect of plasma power and collection sites on ZnO nanostructure was investigated. After the plasma discharge for 10 min, the produced materials deposited inside the 60-cm-long quartz tube were obtained with respect to the distance from the plume. According to the SEM analysis, all the synthesized nanoparticles were found to be ZnO tetrapods ranging from 100 to 600-nm-diameter depending on both applied power and collection site. The photocatalytic efficiency was evaluated by color change of methylene blue solution using UV-Vis spectroscopy. The photocatalytic activity increased with the increase of (101) and (100) plane in ZnO tetrapods, which is caused by enhanced chemical effects of plasma process.

• Korean Journal of Metals and Materials
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• v.46 no.5
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• pp.321-327
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• 2008

Cu based amorphous ($Cu_{54}Zr_{22}Ti_{18}Ni_6$) coating was produced by cold spraying as a new fabrication process. The microstructure and macroscopic properties of amorphous coating layer was investigated and compared with those of cold sprayed pure Cu coating. Amorphous powders were prepared by gas atomization and Al 6061 was used as the substrate plate. X-ray diffraction results showed that Cu based amorphous powder could be successfully deposited by cold spraying without any crystallization. The Cu based amorphous coating layer ($300{\sim}400{\mu}m$ thickness) contained 4.87% porosity. The hardness of Cu based amorphous coating represented $412.8H_v$, which was correspond to 68% of the hardness of injection casted bulk amorphous material. The wear resistance of Cu based amorphous coating was found to be three times higher than that of pure Cu coating. The 3-point bending test results showed that the adhesion strength of Cu based amorphous coating layer was higher than that pure Cu coating. It was also observed that hard Cu base amorphous particle could easily deform soft substrate by particle collisions and thus generated strong adhesion between coating and substrate. However, the amorphous coating layer unexpectedly represented lower corrosion resistance than pure Cu coating, which might be resulted from the higher content of porosity in the cold sprayed amorphous coating.

• Composites Research
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• v.20 no.4
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• pp.9-17
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• 2007

Powder metallurgy has been employed for the development of SiC particle reinforced aluminum metal matrix composites by means of hot isotropic pressing and vacuum hot pressing. A material model based on micro-mechanical approach then has been presented for the processes. Densification occurs by the inelastic flow of matrix materials during the consolidation, and consequently it depends on many process conditions such as applied pressure, temperature and volume fraction of reinforcement. The model is implemented into finite element software so that the process simulation can be performed enabling the predicted relative density to be compared with experimental data. In order to determine the performance of finished products, further tensile test has been conducted using the developed specimens. The effect of internal void of the materials on mechanical properties therefore can be investigated.

• Korean Journal of Exercise Nutrition
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• v.13 no.2
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• pp.101-107
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• 2009

The objectives of this study were to investigate 1) the nutritional knowledge, 2) the use of nutritional supplements, and 3) nutrient intakes of male elite bodybuilders (n=20). Participants carried out a comprehensive survey, anthropometric assessment, and 1 day food record. Daily nutrient intakes of the subjects were analyzed using Computer Aided Nutritional Analysis Program (Can-pro 3.0). The mean age of the subjects was 23.4 years. The mean duration of exercise was 5.3 years. The average scores of nutritional knowledge were 71.0%. The subjects were gathered nutrition information from nutrition book (65%), mass communication (50%), friends (50%) and coach (30%) in order. Ninety percentage of the subjects reported that they were taking nutritional supplements. Major reasons for taking nutritional supplements were to improve performance and to build-up muscle. The most frequently taken nutritional supplements were protein powder (85%), multivitamin/mineral (75%), BCAA (60%) and glutamine (55%) in order. The average daily energy intakes of the subjects were 4,248.7 kcal. The mean intake of protein was 370.3 g/day (3.93 g/kg BW). The ratio of total energy intake from carbohydrate, protein and lipid was 51 : 34 : 15. The intakes of most vitamin and minerals through food and nutrition supplements were much higher than those of each nutrient of the RDAs. Especially, vitamin B complex and vitamin C intakes were ranged from 500 to 3,000% of KNHNES. More research needs to be conducted to determine the optimal amounts of carbohydrates, protein, lipid and micro-nutrients for the bodybuilders.