• Korean Journal of Materials Research
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• v.22 no.2
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• pp.66-70
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• 2012

Ti-Ni alloys are widely used in numerous biomedical applications (e.g., orthodontics, cardiovascular science, orthopaedics) due to their distinctive thermomechanical and mechanical properties, such as the shape memory effect, superelasticity and low elastic modulus. In order to increase the biocompatibility of Ti-Ni alloys, many surface modification techniques, such as the sol-gel technique, plasma immersion ion implantation (PIII), laser surface melting, plasma spraying, and chemical vapor deposition, have been employed. In this study, a Ti-49.5Ni (at%) alloy was electrochemically etched in 1M $H_2SO_4$+ X (1.5, 2.0, 2.5) wt% HF electrolytes to modify the surface morphology. The morphology, element distribution, crystal structure, roughness and energy of the surface were investigated by scanning electron microscopy (SEM), energy-dispersive Xray spectrometry (EDS), X-ray diffractometry (XRD), atomic force microscopy (AFM) and contact angle analysis. Micro-sized pores were formed on the Ti-49.5Ni (at%) alloy surface by electrochemical etching with 1M $H_2SO_4$+ X (1.5, 2.0, 2.5) wt% HF. The volume fractions of the pores were increased by increasing the concentration of the HF electrolytes. Depending on the HF concentration, different pore sizes, heights, surface roughness levels, and surface energy levels were obtained. To investigate the osteoblast adhesion of the electrochemically etched Ti-49.5Ni (at%) alloy, a MTT test was performed. The degree of osteoblast adhesion was increased at a high concentration of HF-treated surface structures.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.9 no.1
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• pp.1-11
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• 2011

Tetraethoxysilane(TEOS) as a silica precursor and hydrochloric acid as an acid catalyst have been used in a surfactant-template synthesis of micrometer-sized mesoporous silica microspheres based on the macroemulsion technique. Increase in the concentration of tetraethoxysilane of the reaction mixture has a serious destructive effect on the particle shape and pore structure. As the acid concentration increases, relatively small microspheres are formed without destroying their spherical morphology of the particles as well as the pore structures. However, due to the attractive interaction between particles in an acidic condition, strong silica agglomerates are formed, and therefore are subject to a post-ultrasonic treatment to separate into an individual single particle.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.167-170
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• 1997

For the optimal net shape forging of semi-solid materials (SSM), it is important to predict the deformation for variation of strain rate. It should be necessruy to conduct a formation of stress-strain curve in semi-solid alloys for analysis of the thixoforming process. Particularly, important problem to application of computer aided engineering in SSM processing is to prevent a segregation of liquid component during compression process. The liquid segregation is studied as multistage change of the strain rate and test piece size to prevent the liquid segregation during the compression process. The compression test for semi-solid aluminium alloy with a controlled solid fraction is performed by dynamic material test system with a furnace. Moreover morphology of structure and fraction of pore are investigated through compression test.

• Macromolecular Research
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• v.14 no.1
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• pp.59-65
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• 2006

We report a new approach to fabricate electrospun polymer nonwoven mats with porous surface morphology by varying the collector temperature during electrospinning. Polymers such as poly(L-lactide) (PLLA), polystyrene (PS), and poly(vinyl acetate) (PVAc) were dissolved in volatile solvents, namely methylene chloride (Me) and tetrahydrofuran (THF), and subjected to electrospinning. The temperature of the collector in the electrospinning device was varied by a heating system. The resulting nonwoven mats were characterized by using scanning electron microscopy (SEM), field emission SEM (FESEM), and atomic force microscopy (AFM). We observed that the surface morphology, porous structure, and the properties such as pore size, depth, shape, and distribution of the nonwoven mats were greatly influenced by the collector temperature.

• Bulletin of the Korean Chemical Society
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• v.27 no.1
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• pp.53-58
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• 2006

A powder of destructive adsorbent was prepared by impregnating Mn and Cu on the surface of amorphous aluminosilicate. It catalytically dimerized tert-butyl mercaptan into di-tert-butyl disulfide on its surface. Turnover of the dimerization was strongly dependent on the surface morphology of the adsorbent, which could be altered by modification of aluminosilicate support. During the process of impregnation, which involved heat treatment at 500 ${^{\circ}C}$, the shape of the pore was preserved, though large fraction of micropores were eliminated. The reactive sites on the surface were poisoned as dimerization products strongly adhered on them. Therefore, high surface area was not always desirable. When the surface was heavily populated with “inkbottled” pores with a narrow entrance in uniform size, heavy poisoning of the reactive sites turned the destructive adsorbents almost useless.

• Korean Journal of Materials Research
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• v.25 no.10
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• pp.509-515
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• 2015

MAO ceramic coatings were prepared on AZ61 magnesium alloy for various processing times ranging from 5 to 60 min, in an electrolyte solution based on silicate-fluoride. The mechanical, electrochemical and, microstructural properties and the phase compositions of the coating layers were investigated. In this work, unlike previous studies, coatings with high amounts of the $Mag_2SiO_4$ phase were formed which contained small amounts of MgO and $MgF_2$ at a processing condition of 30 min. A microstructural analysis revealed that the porosity of the coatings was reduced considerably with an increase in the processing time, together with a change in the pore geometry from an irregular to a spherical shape. Potentiodynamic polarization and mechanical testing results showed that the coatings acquired after a processing time of 30 min were superior to all of the others.

• The Korean Journal of Ecology
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• v.26 no.5
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• pp.237-246
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• 2003

A mountain village is defined as that which is autogenously formed over at least 100 years and supported by agricultural yields and forest products and forest area portion of which is over 70% in Guidelines for the Comprehensive Development Planning of Mountain Village. Recently, concerns about management planning of the Green and Eco-Village causes researches related to the Mountain Village's economics, tourism attractiveness, experience programming and investigation of the ecosystem and environment based on the village area. This kind of eco-village project should be supported by ecological evaluation of its spatial structure. But there is rare research of the village spatial structure studied from the ecological viewpoint originally. The purpose of this study is to interpret the spatial structure of Korean mountain village on the landscape ecological paradigm. The paradigm components are patches, corridors, networks, and matrix which explain the land and spatial structure at landscape scale. For this purpose, we selected two case study areas- Sansu and Ajick villages in Gimje city, Jeonlabukdo. We interpreted and evaluated the spatial structure by three steps: (1) to clarify the existing land mosaic pattern by land use mapping (2) to estimate the pore size as development area in matrix (3) to investigate the funnel effect of patch shape. These landscape ecological steps and frameworks could be applied for the proper methodology as fundamentals of eco-village planning and design.

• Journal of Welding and Joining
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• v.33 no.4
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• pp.7-16
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• 2015

New lasers such as high power, high brightness and short wavelength laser are using diverse industry. Also new technologies are developing actively to solve various issues such as spattering, process monitoring, deep penetration and key-hole stability. ICALEO is the international congress where recent technology for laser material processing and laser system are present. At 2014, it was held at San Diego in USA and more than 260 papers were presented from 28 country. The effect of the laser beam shape such as Gaussian like and top-hat was investigated on acoustic emission signal and pore formation in welding. Inline penetration depth was measured with ICI(Inline Coherent Imaging) technique and the data was verified with real time X-ray image on laser welding. The laser welding performance at low pressure environment was evaluated for the thick plate alloy steel. UV laser was used to weld various metals such as Cu, Aluminum, steel and stainless steel. The effect of the wavelength of the laser on the formation of the wave at the wall of the key-hole front and the absorptivity was investigated.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.6
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• pp.713-719
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• 2005

SPME (Soild phase microextraction) has been used in the analysis of many volatile organic compounds, such as geosmin and 2-methylisoborneol (2-MIB), trihalomethanes (THMs) in drinking water. SPME fiber is characterized by high adsorption capacity (DVB/CAR/PDMS, DVB/PDMS etc.). Although the highly active adsorption capacities of the SPME fiber are often to the chemical functional group, surface properties play a significant role in determining the surface adsorption capacities. The objectives of this study were to evaluate effect of residual chlorine on analysis of geosmin and 2-MIB. Image taken by SEM before preloaded with chlorine, the surface and porous media was almost perfect spherical shape and no clogging of pores. However, after preloaded with chlorine the surface was aggregated and pore was blocked. The recovery rate of geosmin and 2-MIB coexisting with chlorine was reduced by 35 to 62%. The recovery rate with preloaded with chlorine was reduced by 25 to 43%. The lower concentration of geosmin and 2-MIB and the higher concentration of chlorine existed in water, the lower the recovery rate was.

• Journal of Surface Science and Engineering
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• v.49 no.2
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• pp.125-129
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• 2016

Anodizing is a technology to generate thicker and high-quality films than natural oxide films by treating metals via electrochemical methods. Electrochemical manufacturing method of nano structure is an efficient technology in terms of cost reduction, high productivity and complicated shapes, which receives the spotlight in diverse areas. Especially, artificial films generated by anodizing technology possess excellent mechanical characteristics including hardness and wear resistance. It is also easy to modify thickness and adjust shape of those artificial films so that they are mainly used in sensors, filters, optical films and electrolytic condensers. In this study, experiment was performed to observe the effect of current density on porous film formation in two-step anodizing for Al alloy. Anodizing process was performed with 10 vol.% sulfuric acid electrolyte while the temperature was maintained at $10^{\circ}C$ using a double beaker. and $10{\sim}30mA/cm^2$ was applied for 40 minutes using a galvanostatic method. As a result, both pore diameters and distances between pores tended to increase as the local temperature and electrolysis activity increased due to the increase in applied current density.