• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1577-1582
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• 2000

In this study, the experimental modal analysis is performed to investigate the dynamic characteristics of slider-air bearings in hard disk drives. Bump response of the slider is acquired by measuring the relative velocity for two points using the laser interferometer, in which the disk is scratched lightly by a sharp knife to make a bump. From the measurements, the modal parameters of the head slider, modal frequencies and damping ratios of roll and pitch, are estimated by data processing and parameter estimation.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.1
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• pp.104-109
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• 2016

The noncontact vibration exciter system using the electro-magnet for a thin plate is studied in this paper. Based on the Euler-Bernoulli beam theory, the equation of motion of thin plate is derived. The main purpose of this experiment is to match the input-frequency and response frequency of thin plate. The test equipment is configured to vibrate on both sides of the thin plate using the electro-magnet. Two frequencies(input frequency and response frequency) in our experiments show very good agreement. This study results will contribute to basic investigate of an alternative air-knife system for the steel industry.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.291-292
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• 2006

Currently A demand of high precision workpiece is increasing in industry. At present, roundness measuring machine using Air bearing, coordinate measuring machine that are used from measurement station. but these machines will not be able to apply to In-line process. because of like these machine's price are very expensive and measurement time is long. also, the complexity of conventional roundness measurement method based on fourier transform, it makes difficult to development analysis program. This work present new architecture of a Out-diameter measuring system fur analysis of roundness of product. In this system, the influence of table motion errors is minimize by using two LVDT sensor and knife edge contact tip. We are produce a test machine and make an experimenter on Out-diameter of test bearing. The measurement result compared with roundness measuring machine.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.115-121
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• 2017

The efficiency of railway track cleaning vehicle for eliminating fine particulate matter (PM10 and PM2.5) in a subway tunnel depends strongly on the structure of the air blowing and suction system installed under the train. To increase the efficiency of underbody suction system, this paper proposes a novel method to use the Coanda effect for the air blower and dust suction module. In particular, through Computational Fluid Dynamics (CFD) analysis, the flow control device induced by the Coanda effect enables an increase in the overall flow velocity and to stabilize the flow distribution of the suction module at a control angle of $90^{\circ}$. In addition, the flow velocity drop at the edge of the air knife-type blower can be improved by placing small inserts at the edge of the blower. Those 4 modular designs of the dust suction system can help remove the dust accumulated on the track and tunnel by optimizing the blowing and suction flows.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.150.2-150.2
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• 2017

This research was conducted to investigate in detail the effect of $PO_4{^{3-}}$, $CO_3{^{2-}}$ and $F^-$ anions on the electrochemical properties of the thin air-formed oxide film-covered AZ31 Mg alloy. In this work, native air-formed oxide films on AZ31 Mg alloy samples were prepared by knife-abrading method and the changes in the electrochemical properties of the air-formed oxide film were investigated in electrolytes containing 0.01 M, 0.05 M and 0.1 M of $PO_4{^{3-}}$, $CO_3{^{2-}}$ and $F^-$ anions. It was observed that the trend of open circuit potential (OCP) transients changed only in the solution containing $PO_4{^{3-}}$ ions. The Nyquist plots obtained from electrochemical impedance spectroscopy (EIS) showed that the resistance of the new surface films formed in fluoride ion containing bath increased with the increase in concentration of fluoride ions but the resistance of surface films formed in carbonate ion containing bath decreased with the increase in concentration of carbonate ions. The potentiodynamic polarization curves illustrated that under anodic polarization, there was growth of porous passive layer only in fluoride ion containing solution while the surface layer formed in phosphate and carbonate ion containing solutions lost its passivity at high anodic potential of $2.5V_{Ag/AgCl}$.

• Journal of the Korean Wood Science and Technology
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• v.46 no.4
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• pp.309-314
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• 2018

Size reduction is an important pre-processing operation for utilizing biomass as a sustainable resource in industrial-scale energy production and as a raw material for other industries. This work investigates the size reduction characteristics of air-dried Miscanthus sacchariflorus Goedae-Uksae 1 (Amur silver grass) via image processing and identifies the morphological characteristics of comminuted and screened M. sacchariflorus. At chopping lengths of 18, 40, 80, and 160 mm, 81%, 77%, 78%, and 76% of the particles, respectively, passed through a 4-mm sieve. Even a knife mill with a very small screen aperture (>1 mm) admitted over 10% of the particles. The average circularity and aspect ratio of the particles were <0.30 and >10, respectively. These results confirm that in all preparation modes, most M. sacchariflorus particles were needle-like in shape, irrespective of the type of preparation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.7
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• pp.763-770
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• 2004

The problem of edge overcoating developed near the edge of the steel strip is studied quantitatively in the gas wiping process of continuous hot-dip galvanizing. It has been assumed that the edge overcoating occurs due to the reduced impact pressure of wiping gas on the strip edge and it is one of detrimental problems to the quality of coating products. In order to analyse the edge overcoating problem numerically, three-dimensional unsteady flows due to the gas wiping are calculated by using a commercial code, STAR-CD. Standard $\kappa$-$\varepsilon$ model is used as a turbulence model. The 1D code for calculation of coating thickness is constructed by using continuity and Navier-Stokes equations. The calculation results have shown good agreement with measurements of edge overcoating thickness, taken from galvanizing line trials. Therefore it is conformed that the major cause of edge overcoating is the reduced impact pressure of wiping gas on the strip surface.

• Journal of Food Hygiene and Safety
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• v.19 no.2
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• pp.74-83
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• 2004

Raw-fish food contains a lot of moisture and is a high-protein food. It is a first-stage processed food taking a lot of manual work. Therefore, it is classified as a PHF food, very liable to cause a bacterial food-poisoning. But its manufacturers are usually small-sized and a systematic sanitation management is difficult to expect. But the manufacturer participating in this study produces chilled fresh raw-fish food. Fish are sliced into two fillets, which are packaged under vacuum, kept and distributed in refrigerators, and sold within a day. It is a newly-developed kind of raw-fish food, and a more improved kind of raw-fish food making possible a systematic sanitation management. The HACCP (Hazard Analysis and Critical Control Point) is a systematic and continuous process-control method which is very efficient for controling food sanitation and reducing the expenses. A new HACCP model has been developed to be applied to a large-sized chilled fresh raw-fish food manufacturer. To ascertain its efficiency, the baterial examination was done to its workplace and products. The significance test was done on its data by "SPSS 12.0 for Window" and "Mann-Whitney U Test". The numbers of bacteria on its final products were significantly different in flatfish and porgy. The number of bacteria tended to decrease in each time-differential sampling (P＜.00l). The final food products showed no food-poisoning bacteria in all the time-differential tests and in all the samplings, which proves that the CCP of the HACCP system is under control. After the SSOP program was applied, no pathogenic bacteria were found in the work-place, and the kinds and numbers of bacteria decreased. The numbers of general bacteria and colon bacilli also showed a significant difference from those before the SSOP program in the filleting board (P＜.05), in the skinning board (P＜.0l), in the neck-removing knife (P＜.05), and in the filleting knife (P＜.01). The working equipments, periodically disinfected, also showed a significant difference in sanitary conditions (in the dehydrator, P＜.05). The number of bacteria found on the food-touching surface was within the standard (below 500/l00 cm$^2$) After the SSOP program was applied, the general bacteria and colon bacilli were not found. The quality of water used in the food processing was also within the standard. The numbers of bacteria falling from the air in the work-place were negligible in all the samplings (＜30CFU/l000ι). The staphylococci and fungi were not found.

• Macromolecular Research
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• v.8 no.6
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• pp.276-284
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• 2000

A wettability chemogradient on poly(L-lactide-co-glycolide) (PLGA) films was prepared by treating the films in air with corona from a knife-type electrode whose power increases gradually along the sample length. The PLGA surfaces oxidized gradually with the increasing corona power, and the wettability chemogradient was created on the surfaces as evidenced by the measurement of water contact angles and electron spectroscopy for chemical analysis. The wettability chemogradient PLGA surfaces were used to investigate the interaction of four different types of cells such as hepatoma (Hep G2), osteoblast (MG 63), bovine aortic endothelial (CPAE), and fibroblast (NIH/3T3) cells in terms of the surface hydrophilicity/hydrophobicity of PLGA. The cells adhered and grown on the chemogradient surface along the sample length were counted and observed by scanning electron microscopy. It was observed that the cells were adhered, spread, and grown more onto the positions with moderate hydrophilicity of the wettability chemogradient PLGA surface than the more hydrophobic or hydrophillic positions, regardless of the cell types used. The maximum adhesion and growth of the cells appeared at around water contact angles of 53～55°. This result seems closely related with the serum protein adsorption on the surface; the serum proteins were also adsorbed more onto the positions with moderate hydrophilicity of the wettability chemogradient surface. It seems that the wettability plays important roles for cell adhesion, spreading and growth on the PLGA surface. The surface modification technique used in this study may be applicable tothe area of tissue engineering for the improvement of tissue compatibility of films- or scaffold-type substrates.

• Proceedings of the Korea Crystallographic Association Conference
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• 2002.11a
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• pp.5-6
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• 2002

The new spectrometer for X-ray Induced Electron Emission Spectroscopy (XIEES) .has been recently developed in KRISS in collaboration with PTI (Russia). The spectrometer allows to perform research using the XAFS, SXAFS, XANES techniques (D.C.Koningsberger and R.Prins, 1988) as well as the number of techniques from XIEES field(L.A.Bakaleinikov et all, 1992). The experiments may be carried out with registration of transmitted through the sample x-rays (to investigate bulk samples) or/and total electron yield (TEY) from the sample surface that gives the high (down to several atomic mono-layers in soft x-ray region) near surface sensitivity. The combination of these methods together give the possibility to obtain a quantitative information on elemental composition, chemical state, atomic structure for powder samples and solids, including non-crystalline materials (the long range order is not required). The optical design of spectrometer is made according to Johannesson true focusing schematics and presented on the Fig.1. Five stepping motors are used to maintain the focusing condition during the photon energy scan (crystal angle, crystal position along rail, sample goniometer rail angle, sample goniometer position along rail and sample goniometer angle relatively of rail). All movements can be done independently and simultaneously that speeds up the setting of photon energy and allows the using of crystals with different Rowland radil. At present six curved crystals with different d-values and one flat synthetic multilayer are installed on revolver-type monochromator. This arrangement allows the wide range of x-rays from 100 eV up to 25 keV to be obtained. Another 4 stepping motors set exit slit width, sample angle, channeltron position and x-ray detector position. The differential pumping allows to unite vacuum chambers of spectrometer and x-ray generator avoiding the absorption of soft x-rays on Be foil of a window and in atmosphere. Another feature of vacuum system is separation of walls of vacuum chamber (which are deformed by the atmospheric pressure) from optical elements of spectrometer. This warrantees that the optical elements are precisely positioned. The detecting system of the spectrometer consists of two proportional counters, one scintillating detector and one channeltron detector. First proportional counter can be used as I/sub 0/-detector in transmission mode or by measuring the fluorescence from exit slit edge. The last installation can be used to measure the reference data (that is necessary in XANES measurements), in this case the reference sample is installed on slit knife edge. The second proportional counter measures the intensity of x-rays transmitted through the sample. The scintillating detector is used in the same way but on the air for the hard x-rays and for alignment purposes. Total electron yield from the sample is measured by channeltron. The spectrometer is fully controlled by special software that gives the high flexibility and reliability in carrying out of the experiments. Fig.2 and fig.3 present the typical XAFS spectra measured with spectrometer.