• Journal of the Korea Safety Management & Science
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• v.24 no.2
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• pp.61-66
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• 2022

Recently, the Severe Disaster Punishment Act (January 27, 2022) was implemented, and the importance of industrial safety and health is being re-recognized. In addition, the reality is that the management burden is increasing, such as investing huge costs in reducing safety accidents centered on large companies. In this situation, we would like to help improve the working environment consistent with safety and health by deriving diagnosis and improvement measures for the current situation through a survey of production workers working in mid-sized and small-sized enterprises.

• Journal of ILASS-Korea
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• v.17 no.4
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• pp.185-191
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• 2012

Particulate matters (PM) that is generated by most diesel engine is regulated by the mass concentration measured by the conventional method it had been. Recently, Europe PMP (Particle Measurement Program) decided to start the regulation of vehicle's nano-sized particle number (PN) from the year of 2011 because of nano-particle's higher degree of harm to the human body. So firstly, the standard level of PN emission is introduced in the Euro 5/6 emissions regulation with a limit of $6{\times}10^{11}$ per km for light duty vehicle. Also KPMP(Korea Particle Measurement Program) was organized to copy quickly international technical trend. In this paper, it was investigated the nano-sized PN measurement characteristics for different particle generators between spray type and soot type. And the difference ratio between particle generators, the characteristic of PN concentration, counting efficiency and linearity was analyzed. Then, we make conclusions as followed. When particle diameter is increased, counting efficiency of two generators is decreased. Also Secondary calibration method is more higher 3% than Primary calibration method. Finally, SOF which is included in soot particles is not totally removed so it have great influence on test result of counting efficiency and linearity.

• Composites Research
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• v.32 no.3
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• pp.141-147
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• 2019

In this study, micro-sized and nano-sized pure aluminum (Al) powders were compressed by unidirectional pressure at room temperature. Although neither type of Al bulk was heated, they had a high relative density and improved mechanical properties. The microstructural analysis showed a difference in the process of densification according to particle size, and the mechanical properties were measured by the Vickers hardness test and the nano indentation test. The Vickers hardness of micro Al and nano Al fabricated in this study was five to eight times that of ordinary Al. The grain refinement effect was considered to be one of the strengthening factors, and the Hall-Petch equation was introduced to analyze the improved hardness caused by grain size reduction. In addition, the effect of particle size and dispersion of aluminum oxide in the bulk were additionally considered. Based on these results, the present study facilitates the examination of the effect of particle size on the mechanical properties of compacted bulk fabricated by the powder metallurgy method and suggests the possible way to improve the mechanical properties of nano-crystalline powders.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.4
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• pp.123-130
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• 2020

Nano seed incorporated in micro-sized 4BS (Tetrabasic lead Sulfate) seed was applied to the positive electrode active material and compared with Nano 4BS seed (NS). The dispersion of NS decreased due to the aggregation phenomenon, while the nano seed incorporated in micro-sized 4BS seed (INS) could confirm excellent dispersion. As the content of INS increased, the particle size of the active material became small and constant, which was confirmed through SEM and particle size analysis. The specific surface area for the reaction was increased and the high-rate discharge and lifetime characteristics were improved. In order to confirm the variation in particle size distribution in the plate manufacturing process, internal resistance and voltage were measured for 200 AGM lead-acid batteries, and it was confirmed that batteries quality variation decreased.

• Safety and Health at Work
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• v.2 no.3
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• pp.282-289
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• 2011

Objectives: We sought to establish a novel method to generate nano-sized carbon black particles (nano-CBPs) with an average size smaller than 100 nm for examining the inhalation exposure risks of experimental rats. We also tested the effect of nano-CBPs on the pulmonary and circulatory systems. Methods: We used chemical vapor deposition (CVD) without the addition of any additives to generate nano-CBPs with a particle size (electrical mobility diameter) of less than 100nm to examine the effects of inhalation exposure. Nano-CBPs were applied to a nose-only inhalation chamber system for studying the inhalation toxicity in rats. The effect on the lungs and circulatory system was determined according to the degree of inflammation as quantified by bronchoalveolar lavage fluid (BALF). The functional alteration of the hemostatic and vasomotor activities was measured by plasma coagulation, platelet activity, contraction and relaxation of blood vessels. Results: Nano-CBPs were generated in the range of 83.3-87.9 nm. Rats were exposed for 4 hour/day, 5 days/week for 4 weeks to $4.2{\times}10^6$, $6.2{\times}10^5$, and $1.3{\times}10^5$ particles/$cm^3$. Exposure of nano-CBPs by inhalation resulted in minimal pulmonary inflammation and did not appear to damage the lung tissue. In addition, there was no significant effect on blood functions, such as plasma coagulation and platelet aggregation, or on vasomotor function. Conclusion: We successfully generated nano-CBPs in the range of 83.3-87.9 nm at a maximum concentration of $4.2{\times}10^6$ particles/$cm^3$ in a nose-only inhalation chamber system. This reliable method can be useful to investigate the biological and toxicological effects of inhalation exposure to nano-CBPs on experimental rats.

• Proceedings of the Optical Society of Korea Conference
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• 2009.02a
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• pp.133-134
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• 2009

Cold temperature development (CTD) of electron beam (EB) patterned resists and subsequent dry etching were investigated for fabrication of nano-patterned Niobium (Nb). Bulky Nb fims on GaAs substrates were deposited with EB evaporation. Line patterns on Nb cathode were fabricated by EB patterning and reactive ion etching (RIE). Size deviations of nano-sized line patterns from CAD designed patterns are dependent on the EB total exposure, but it can be improved by CTD of EB-exposed resist. Line patterns of 10 to 300 nm widths of EB-exposed resist patterns were drawn under various exposure conditions of $0.2{\mu}s$/dot (total 240,000 dot) with a constant current (50 pA). Compared with room temperature development (RTD), the CTD improves pattern resolution due to the suppression of backscattering effect. RIE with $CF_4$ was performed for formation of several nano-sized line patterns on Nb. Each EB-resist patterned samples with RTDs and CTDs were etched with two different $CF_4$ gas pressures of 5 Pa. Nb etching rate increases while GaAs (or ZEP) etching rate decreases as the chamber pressure increases. This different dependent of the etching rate on the $CF_4$ pressure between Nb and GaAs (or ZEP) has a significant meaning because selective etching of nano-sized Nb line patterns is possible without etching of the underlying active layer.

• Journal of the Korean Magnetics Society
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• v.15 no.3
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• pp.172-176
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• 2005

Four nano-sized Fe-nano particle samples synthesized by Chemical Vapor Condensation (CVC) were analyzed using $M\ddot{o}ssbauer$ spectroscopy, XRD, BET and TEM. The samples were consisted as functions of carrier gas and decomposition temperature. The synthesized nanoparticles consisted of two- or three-layers with the circular shape. The average particle size was increased with increasing the decomposition temperature. At $500^{\circ}C$ for the decomposition temperature, $Fe_3C$ was formed more under the environment of CO carrier gas than that of $CH_4$. However, at $1,100^{\circ}C$, almost of Fe-nano particles were transformed into $Fe_3C$ with using both carrier gas.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1086-1091
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• 2004

The boundary layer is a very important characteristic of a liquid-vapor interface since it governs the heat and mass transfer phenomena across an interface. However, the thickness of a boundary layer is generally micro- or nano-sized, which requires highly accurate measurement devices and, consequently, costs the related experiments very high and time-consuming. Due to these size dependent limitations, the experiments related with a nano-scaled size have suffered from the errors and the reliability of the obtained data. This study is performed to grasp the characteristics of a liquid-vapor interface, by using a molecular dynamics method. The simulation results were compared with other studies if possible. Although other studies reported that there existed a temperature discontinuity over an interface when the system was reduced to micro- or nano-sized, we confirmed that there was no such a temperature discontinuity.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.12
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• pp.2624-2630
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• 2002

Organic/inorganic hybrid materials have rapidly become a fascinating research field. In this study, $polyimide/TiO_2$ composites were synthesized from nano-sized anatase $TiO_2$ and two types of polyimide, that is, BPDA-PPD and PMDA-ODA. Nano-sized $TiO_2$ particles were prepared from $TiOEt_4$ solution by the sol-gel method. The synthesized PI/$TiO_2$ composites were characterized by using XRD, TGA, FT-IR, TEM, and Atomic Force Microscope(AFM). $TiO_2$ particles were dispersed well in polyimides and the mechanical and thermal stability of polyimide was improved with $TiO_2$ nano particles.

• Journal of the Korean Applied Science and Technology
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• v.20 no.4
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• pp.346-352
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• 2003

BaTiO$_3$, powders were prepared by sol-gel process from different aging time and reaction temperature. Particle shape, size and crystal structure of prepared $BaTiO_3$ powders were analyzed by SEM, XRD and FT-IR. Effect of aging time alternation didn't particularly show up. Spherical nano-sized $BaTiO_3$ powders were obtained from condition more than reaction temperature $55^{\circ}C$, and obtained sintered $BaTiO_3$ powders of tetragonal phase from heat-treatment at $1,100^{\circ}C$.