• Journal of Environmental Health Sciences
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• v.29 no.1
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• pp.1-7
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• 2003

This study was carried out to investigate the airborne microbial pollution in hospital environment. Using a mechanical air sampler, microbiological samples were taken from intensive care unit, general ward room, patients wailing room and outdoor of 20 hospitals in Seoul, Korea. The concentration of airborne bacteria and fungi ranged 97-410 cfu/㎥ and 37-77 cfu/㎥, respectively and patients waiting room had highest bacterial count. 10 genera of molds were identified and the most frequently recovered molds were Aspergillus, followed by Penicillium, Alternaria and Cladosporium. Among Staphylococcus species, S. haemolyticus and S. epidermidis were predominant and 47% of Staphylococcus species were isolated from intensive rare unit.

• Design & Manufacturing
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• v.13 no.4
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• pp.10-16
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• 2019

Semiconductor chip is bonded to the substrate by melting solder bumps. In general, the chip bonding is applied by a Reflow process or a Thermo-Compression(TC) bonding process. In this paper, we introduce a Laser Assisted Thermo-Compression bonding (LATCB) process to improve the anxiety of the existing process(Reflow, TC bonding). In the LATCB process, the chip is bonded to the substrate by irradiating a laser with a uniform energy density in the same area as the chip to melt only the solder bumps and press the chip with a Transparent Compression Module (TCM). The TCM consists of a fused silica header for penetrating the laser and pressurizing the chip, and a piezoelectric actuator (P.A.) coupled to both ends of the header for micro displacement control of the header. In addition, TCM is a structure that can pressurize the chip and deliver it to the chip and solder bumps without losing the energy of the laser. Fused silica, which is brittle, is vulnerable to deformation, so the header may be damaged when an external force is applied for pressurization or a displacement differenced is caused by piezoelectric actuators at both ends. On the other hand, in order to avoid interference between the header and the adjacent chip when pressing the chip using the TCM, the header has a notch at the bottom, and breakage due to stress concentration of the notch is expected. In this study, the thickness and notch length that the header does not break when the external force (500 N) is applied to both ends of the header are optimized using structural analysis and Coulomb-Mohr failure theory. In addition, the maximum displacement difference of the P.A.s at both ends where no break occurred in the header was derived. As a result, the thickness of the header is 11 mm, and the maximum displacement difference between both ends is 8 um.

• Food Science of Animal Resources
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• v.28 no.5
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• pp.675-680
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• 2008

The physical quality and microbial safety of Korean beef jerky was evaluated at various steps during its preparation. Microbial counts in raw beef demonstrated mesophillic bacteria at 4.20 Log CFU/g, psychrotrophic bacteria at 3.85 Log CFU/g, anaerobic bacteria at 4.90 Log CFU/g, and yeast and molds at 1.92 Log CFU/g. Spore-forming bacteria and coliforms were not detected in raw beef samples. Spices and spiced meats showed similar trends in microbial counts, demonstrating minimal microbial contamination during these stages of preparation. The final beef jerky product exhibited counts of mesophillic bacteria at 1.15-1.66 Log CFU/g, psychrotrophic bacteria at 1.15-1.66 Log CFU/g, and anaerobic bacteria at 0.81-1.72 Log CFU/g. Spore-forming bacteria, yeast and molds, and coliforms were not detected in beef jerky. Significant differences from added ingredients occurred for instron textural profile analysis traits for hardness. In general, Korean beef jerky with humectant and tenderizer had lower hardness than control (without humectant and tenderizer). Also, the sample added with 0.01% protease from Streptomyces griseus had lower hardness than all samples. All samples had 0.7l to 0.72 water activities, and the color and pH were not shown in significant changes of all samples.

• Journal of the Korea Institute of Building Construction
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• v.14 no.1
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• pp.1-10
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• 2014

The SC structure can have relatively liberal sectional surfaces, and allows modularization for pre-forming in factories and structural stability. It can be used for the shear walls in the core of general buildings or the structural members for parking buildings. In the future, it could be applied to moving large bus terminals, and widely used for general industrial structures as it can expedite the process compared to other methods. This study examined the applicability of SC structures to the retaining walls of a parking building and reviewed its economic value by comparing its construction term, quality control benefits, and cost compared to RC structures. It was found that SC structures are about 1.6-1.7 times more expensive than RC structures in terms of the cost of fabrication and installation. However, the construction term can be reduced by 27% to save indirect costs for constructors, as well as the cost of removing molds and material loss required when installing RC structures.

• Journal of the Korean Society of Safety
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• v.18 no.1
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• pp.76-80
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• 2003

There will be a big problem in disposing of waste tie coming from the cars. Because many of these have been thrown away to the field and environmentally polluted. New, We need to find out how to dispose or recycle these waste material. It is thought that recycling this material especially mixing with concrete will be a good idea. This study is focused how each material do its behavior due to the size of waste type particle and its amount into concrete material. 0.4mm-10mm range of particle has been applied to the material : Also, 1.0%, 1.5%, 2.0% range of tyre particle proportion has been applied to make cylinder molds. The concrete mold with waste-tyre particle has vibration-absorbing ability. It is found that 0.4 -0.6mm particle mixing concrete has been more solid organized. And this waste tyre material could be applied to the general concrete, it is found.

• Transactions of Materials Processing
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• v.14 no.3 s.75
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• pp.200-206
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• 2005

In general, a lot of small electrode is needed for making precision injection molds, such as cell phone mold and precision connector mold, because of the limitations of NC milling process. Those small electrodes usually have very simple shapes and the actual cutting time is so short, but many NC programs and set-up process, a very complicated and time consuming Job, are needed for each electrode. This paper deals the method for increasing the productivity of machining electrodes. In this work, the process standardization of machining electrode was done and special jig fer machining small electrodes was developed. Automatic tool path optimization software was also developed to minimize tool changing time. In addition, in-line cutting tool measuring system was adopted. The productivity of machining for small electrode has been increased up to $100\%$.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.217-222
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• 2000

A large Pc structure building is system that consisted of bearing wall and slab joint. It has general structure stability from unity thar each members tied at joint. The strength of mortar that packing in joint among panels is important to internal force in entire building system. Do, if we could get early strength estimation with microwave. It would bring good construction planning, reduce construction time, and judge building stability and so on. The purpose of this study is to develop early estimation method for making better quality control and constructing good PC panel structure. The results of this study were as follows :1) With sealed molds, reduced moisture volatilization to more than 60% and enlarged 30% accelerated compressive strength than before one. 2) To get more accelerated strength, we should control maximum temperature difference to $30^{\circ}C$ downward 3)Interrelation with 7-day and 28-day strength were 0.831,0.902, and it is above than before one

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.237-238
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• 2006

Micro drilling is a very important machining method to produce precise parts or small molds. General macro-program for drilling is a non-efficient method because of many movements to safety height. In this research new macro-program was suggested to raise machining-efficiency. New micro-drilling method caused the much reduction of machining time and the same tool life.

• Journal of the Korea Organic Resources Recycling Association
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• v.26 no.1
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• pp.39-45
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• 2018

Research on FA(Fly ash) is actively carried out, while the research on BA(Bottom ash) is not so, and research on BA recycling field is urgently required. Therefore, in this study, we investigated the lightweight and thermal insulation characteristics of BA mortar by comparing BA mortar made with porous dry BA(air-cooled) and general mortar. To investigate the lightweight of BA, density test, unit volume mass test and SEM(Scanning Electron Microscope) test were performed. BA mortar and general mortar molds were prepared for the thermal insulation test at room temperature and humidity environment determined by KS A 0006 and they were dried at the temperature of $105{\pm}2^{\circ}C$ until the weight became constant. As a result of the lightweight test, the lightweight of BA mortar is about 30% lighter than the general mortar. Therefore, BA is expected to contribute to reduce the building load when used as building material. As a result of thermal insulation test, the thermal conductivity of BA mortar is about 30% better than that of general mortar.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.409-412
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• 2006

In process of reinforced concrete(RC) box structure, the heat of hydration may cause serious thermal cracking problems. In order to eliminate hydration heat of mass concrete, this paper reports results of hydration heat control in mass concrete using the OCHP(Oscillating Capillary tube Heat Pipe). Recently OCHP is drawn special attention from these points of low cost as well as short construction schedule for the manufacturing of heat exchanger, flexibility, simplification and high performance. There were three RC box molds$(1.2{\times}1.2{\times}1.2m)$ which shows a difference as compared with each other. One was not equipped with OCHP. While others were equipped with OCHP and these were cooled with air natural convection and spraying water respectively. The OCHP was composed of copper pipe with 12 turns(O.D : 4mm, I.D : 2.8mm). The working fluid was R-22 and its charging ratio was 30(Vol. %). In order to analyze the distribution of temperature and index figure of thermal crack in sequential placement of mass concrete, we used HYCON of computer program. As a result of the experiment, the peak temperature decreased about $15.6\sim23.4^{\circ}C$ than the general specimen and the probability of thermal crack generated in mass concrete decreased up to 0%.