• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.3
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• pp.300-306
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• 2009

Welding technology is applicable in many kinds of fields, with the help of its advantages such as easy operational procedure and structural simplification. However, in the process of welding, hazardous materials and fumes cause huge fire broke-outs, explosions, and health-conscious problems. Also, as heavy metals in fumes have a harmful effect on the environment, recently, this has emerged as a urgent social issue. This study has been aimed at the recommendation of the most environment-friendly, among materials currently used in plumbing welding, and it has been done at the result of the analysis of amount, ingredient, and size in collected fumes created in the experiment of welding five rods to galvanized steel pipes and steel pipe ones. At the test result, due to the effect of Zn-coating, galvanized steel pipes, when welded to rods, created more fumes than steel pipe ones. In the mean time, when it comes to welding rods, among five, WR-03 produced fumes the least. Therefore, a combination of the test results clearly indicates that the case of welding WR-03 to cast-iron pipes turned out to be the most environment-friendly.

• Advances in nano research
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• v.14 no.2
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• pp.195-200
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• 2023

Safety in sports is important because if an athlete has an accident, he may not be able to lead an everyday life for the rest of his life. The safety of sports facilities is very effective in creating people's sports activities, with the benefits of staying away from physical injury, enjoying sports, and mental peace. Everyone has the right to participate in sports and recreation and to ensure that they want a safe environment. This study prepares a very good Nickel-Cobalt -Silicon carbide (Ni/Co-SiC) nanocomposite with convenient geometry on the leg press machine rod, employing the pulse electrodeposition technique to reduce the rod's wear and increase the durability of sports equipment and control sports damages. The results showed that the Ni/Co-SiC nanocomposite formed at 2 A/dm2 shows extraordinary microhardness. The wear speed for the Ni/Co-SiC nanocomposite created at 4 A/dm2 was 15 mg/min, showing superior wear resistance. Therefore, the Ni/Co-SiC nanocomposite can reduce sports equipment's wear and decrease sports injuries. Ni-Co/SiC nanocomposite layers with various scopes of silicon carbide nanoparticles via electrodeposition in a Ni-Co plating bath, including SiC nanoparticles to be co-deposited. The form and dimensions of Silicon carbide nanoparticles are watched and selected using Scanning Electron Microscopy (SEM).

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2001.11a
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• pp.55-56
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• 2001

지난 수년간 유럽을 중심으로 Carbonate의 PSD (Particle Size Distribution)가 도공지 의 백색도, 불투명도, Coverage등에 미치는 영향에 대하여 많은 연구가 진행되어 왔다. 현재 국내의 Coating Pigment System 역시 Carbonate 위주로 구성되어 있으나, 입자 분포에 따른 실증적 연구가 선진국에 비하여 부족한 상태이다. 본 연구는 최근 유럽에서 사용 중인 Narrow PSD Carbonate가 도공지 품질에 미치는 영향을 검토한 것으로서, 특히 Multiple Coating에서의 도공층 구조변화와 그에 따른 백지물성 및 인쇄적성의 변화를 연구한 것이다. 실험의 Case는 Broad PSD CaC03와 Narrow PSD CaC03를 비 교하였 다 .. Color F Formulation은 Pre Color에서 #1 Clay 30 p따t와 각각 CaC03 70 p따t를 사용하였다. 그리고 바인더와 첨가제는 동일하게 사용하였다 .. Top color Formulation 또한 동일하 게 사용하였다. 코팅방식은 speed 450rrνmin, pre rod coating, top blade coating 방식 으로 CLC (Cy lindrical Laboratory Coater)를 사용하여 코팅하였다. 백지품질은 백색도, 평활도 ,광택도, 거칠음도, Bum Out Test와 Coverage( SEM 사 진 Z -direction) 등을 측정하였다. 인쇄품질은 인쇄 광택도, 인쇄 Picking strength와 2 도 인쇄 농도를 측정하였다. 백색도는 Narrow PSD CaC03를 사용한 것이 Broad PSD CaC03를 사용한 것 대비 약1% 우수하였다. 이것은 Narrow PSD CaC03를 사용한 것이 filter cake이 많이 open 되 어 있어 dewatering이 빠르고, Wet void volume이 증가되 어 부동화점 의 농도가 낮 아져 원지 층으로 침 투되 는 pigment가 작고 표층에 잔류하는 pigment와 void volume의 증가로 인해 기공층이 증가한 것으로 판단된다. 그리고, 백지광택도, 거칠음도 등 또한 Narrow PSD CaC03를 사용한 것이 우수하였 다. 이는 Pre color에서 coverage의 개선으로 top color층의 도공량 uniformity가 개선 된 이유라고 생각한다. 그러나 인쇄품질은 백지와 비교하여 차이가 없었다. 이것은 top 칼라 Formulation이 동일하고, 인쇄시 잉크흡수 거동은 top color 층에 주로 영향을 받기 때문이라고 판단 된다. 향후에는 인쇄품질의 향상을 위하여 Case 2의 CaC03 100% 사용가능성 및 Pre Color 는 Case 2로 고정하고, Top칼라를 변경하는 방법을 또한 생각할 필요가 있다고 판단된다.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.910-920
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• 2008

In Korea, more than 70% of the territory consists of mountains. Therefore, the construction of roads and railways has generally involved with a steep rock slope in which the event of rockfalls are often occurred due to the weathered rock conditions and rainfalls etc. This is dangerous when the rock falls into the road and railway on which vehicles and trains are running. In order to prevent such rockfalls, the rockfall protection fence consisting of post, wire rope, and PVC coating steel net has most used at the bottom of rock slopes. In a general practice, an absorbing rockfall energy, 50kJ is specified by the Ministry of Construction and Transportation. However, questions still remain about whether the rockfall protection fence works effectively or not. In this study, a typical wire rope used in the standard rockfall protection fence was replaced by the high carbon steel wire rod and to validate its capacity of rockfall energy absorbing the field rockfall tests were conducted. The testing results show that a new rockfall protection fence using the high carbon steel wire rods can absorb the rockfall energy more than 50kJ and 20% of construction cost was saved in comparison with the previous rockfall protection fence.

• Laser Solutions
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• v.4 no.3
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• pp.30-39
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• 2001

This work was tamed out to apply a laser welding technique in joining between a Zn coated low carbon steel plate(SECC) and a free cutting carbon steel shaft(SUM24L) with or without W coating. Experiments were carried out and analysed by applying the FD(factorial design)method to obtain the optimum Laser welding condition. Optical microscopy, SEM, TEM and XRD analyses were performed in order to observe the microstructures in the fusion zone and the HAZ. Mechanical properties of the welded specimens were examined by microhardness test, tensile test and twist test. There was no flawed Zn in the fusion zone by EDS analysis. This means that during the welding process, Zn gas could be eliminated by appropriate shielding gas flow rate and butt welding gap. Ni coating itself did not influence on the tensile strength and hardness. However, twist bending strength and the weld depth of the Ni-coated free cutting carbon steel were lower as compared with those of the uncoated free cutting carbon steel. It was attributed to a lower absorbance of laser beam to the shin Ni surface. According to the results of the factorial design tests, the twist bending strength of welded specimens was primarily affected by pulse width, laser power, frequency and speed.

• Journal of Surface Science and Engineering
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• v.33 no.5
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• pp.373-380
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• 2000

The flow melting behavior of the electrolytic tinplate during reflow treatment was investigated in terms of morphology and structure of coating layers which were electrodeposited with variation of electrolyte temperature. It was commonly found that the nucleation density of the electrodeposits showed little difference with the electrolyte temperature, and the growth of electrodeposited tin occurred along <100> direction of (002) plane. At low electrolyte temperature, the (002) plane of tin nucleated paralleling to the substrate and grew perpendicularly to the substrate, which rendered porous rod-like deposits. With increasing the temperature, the (002) plane nucleated declining $15^{\circ}$ to the substrate and also grew to the normal <100> direction, which enabled lateral growth of the tin crystals and rendered compact deposits. During reflow treatment, the matte deposit transformed to the reflowed state via transition regions consisted of contraction, island formation, and wetting . The matte deposits formed at low temperature exhibited wide transition regions because of poor thermal transfer between crystals due to their porous nature. While that formed at high temperature transformed very rapidly to the reflowed state by enhanced thermal transfer between the compact crystals.

• Archives of Pharmacal Research
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• v.28 no.5
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• pp.619-625
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• 2005

Beads loaded with the water-soluble drug, phenylpropanolamine HCl (PPA), were prepared using an extruder and double arm counter-rotating roller modified from a traditional pill machine. The mean diameter of the cylindrical rod-like extrudate from the ram extruder was 3 mm; that of the uncoated bead after cutting and spheronization by the modified double arm counter-rotating roller was 3.26~3.28 mm. Although the surface of the beads was moderately rough and irregular, some exhibited hump-shaped protrusions, the sphericity was acceptable (roundness 1.15) and adequate for the subsequent coating process. An increase in mean diameter of the coated beads and improvements in friability and sphericity were observed in proportion to the amount of coating material applied (ethylcellulose or Eudragit？？ RS 100). It was also found that the release rate of PPA from the coated beads could be controlled by the amount and type of coating materials applied or with the incorporation of Eudragit ？？ RS 100 into the core matrix. Further modifications to the double arm counter-rotating roller, including adjustment of the rotation speed and distance between the rollers, would yield smaller uncoated beads with improved roundness and surface roughness. In conclusion , the present method could be potentially applied to prepare controlled release drug delivery beads or pellet dosage forms.

• Journal of the Korean Ceramic Society
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• v.43 no.8 s.291
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• pp.463-468
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• 2006

Hydrothermal deposition of hydroxyapatite coatings on two types of $ZrO_2$ substrates (3 mol% $Y_2O_3$-doped and 13 mol% $CeO_2$-doped tetragonal $ZrO_2s$) was studied using aqueous solutions of $Ca(NO_3)_2\;4H_2O$ and $(NH_4)_2HPO_4$ containing EDTA (ethylene diamine tetra acetic acid) disodium salt as a chelating agent for $Ca^{2+}$ ions. For the precipitation of the coatings, the $EDTA-Ca^{2+}$ chelates were decomposed by oxidation with $H_2O_2$ at $90^{\circ}C$. The deposition behavior, morphology, and orientation of the coatings were investigated while varying the solution pH using scanning electron microscopy and X-ray diffractometry. For the two sub-strates, sparse deposition of the coating was obtained at pH 5.5, whereas a uniform deposition was obtained at pH 7.1, 9.8, and 11.4 with a denser microstructure for the higher pH. The coating consisted of thin needle-like or plate-like crystals ($1-2{\mu}m$ length or diameter) at pH 7.1, but fine rod-like crystals ($1-2{\mu}m$ length, $0.1{\mu}m$ diameter) at pH 9.8 and 11.4. The coatings were $1-3{\mu}m$ thick and showed a preferred orientation of the hydroxyapatite crystals with their c axis (i.e., the elongated direction) perpendicular to the substrate surface especially for pH 9.8 and 11.4.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.46 no.4
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• pp.28-36
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• 2014

We studied the green synthesis and antibacterial activity of paper coated with chitosan-silver (Ag) green nanocomposites for packaging applications. Green synthesis of Ag nanoparticles (AgNPs) was achieved by a chemical reaction involving a mixture of chitosan-silver nitrate ($AgNO_3$) in an autoclave at 15 psi, $121^{\circ}C$, for 30 min. AgNPs and their formation in chitosan was confirmed by UV-Vis spectroscopy, transmission electron microscopy (TEM) and dynamic light scattering (DLS). As-prepared chitosan-AgNPs composite materials were coated on manila paper using Meyer rod. Surface morphology and Ag contents in coating layer were characterized by field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDS). The mechanical properties such as tensile strength and elongation were significantly affected by coating with chitosan-AgNPs. The antibacterial test of coated paper was performed qualitatively and quantitatively against Escherichia coli (E. coli). It was shown to be effective in suppressing the growth of E. coli with increasing Ag contents on the surface of coated paper and more than 95 R (%) of antimicrobial rate was obtained at chitosan-AgNPs coated papers.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.217-220
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• 2009

This paper presents fabrication method of nano-structured PMMA substrates as well as evaluations of their optical transmittance. For anti-reflective surface, surface coating method had been conventionally used. However, it requires high cost, complicated process and post-processing times. In this study, we suggested the fabrication method of anti-reflective surface by the hot embossing process. Using the nano patterned master fabricated by anodic aluminum oxidation process. Anodic aluminum oxide(AAO) is widely used as templates or a molds for various applications such as carbon nano tube (CNT), nano rod and nano dots. Anodic aluminum oxidation process provides highly ordered regular nano-structures on the large area, while conventional pattering methods such as E-beam and FIB can fabricate arbitrary nano-structures on small area. We fabricated a porous alumina hole array with various inter-pore distance and pore diameter. In order to replicate nano-structures using alumina nano hole array patterns, we have carried out hot-embossing process with PMMA substrates. Finally the nano-structured PMMA substrates were fabricated and their optical transmittances were measured in order to evaluate the charateristivs of anti-reflection. Anti-reflective structure can be applied to various displays and automobile components.