• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1442-1445
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• 2003

In precision machinery industry, it's required with small size and low noise design to using in constant liquid delivery equipment. To accomplish it's purpose, we designed the check valve with rubber sheet of circle shapes as a possible assembly in pump body. The test equipment for piezoelectric pump was able to test pressure-flow property and output property of piezoelectric pump by variation(magnitude of voltage and frequency) of input power.

• 설비공학논문집
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• 제15권4호
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• pp.274-286
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• 2003

Numerical simulations are performed to investigate the turbulent convective heat transfer of the supercritical carbon dioxide flows in vertical and horizontal square ducts. The gas cooling process at the supercritical state experiences a sudden change in thermodynamic and transport properties. This results in the extraordinary variations of the heat transfer coefficients in the supercritical state, which are much different from those of single or two phase flows. Algebraic second moment closure which can include the effects of large thermophysical property variations of carbon dioxide and of buoyancy is employed to model the Reynolds stresses and turbulent heat fluxes in the governing equations. The previous correlations for the turbulent heat transfer coefficient for the supercritical carbon dioxide flows couldn't reflect the buoyancy effect. The present results are used to establish a new heat transfer coefficient correlation including the effects of large thermophysical property variation and buoyancy on in-duct cooling process of supercritical carbon dioxide.

• Journal of Biosystems Engineering
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• 제25권1호
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• pp.11-18
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• 2000

In precision chemical application increment of biological efficacy with less chemical is the virtue. spraying rate and droplet size is closely related to biological efficacy. this study was performed to develope a spray-control-system that could control spraying rate and droplet size independently. Twin-fluid nozzles were selected and tested to certify if the nozzles were suitable for the objective of this study. Characteritics of the nozzles i.e., spraying rte and droplet size change u8nder the changes of spraying pressure and air pressure were statistically modeled. The model had I to 1 matching property between dependent variables and independent variables. Using the property and the model, inverse relationship could be determined between variables. A feedback spray control system was developed and tested with predetermined error of 5 % in pressure. The system showed 4 % error in spraying rate and 9 % error in droplets size. Performance of the system could be upgraded by fine tuning but, in practical sense keeping air pressure in the field sprayer was the bottle neck of commercialization of the spray system.

• 한국진공학회지
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• 제7권s1호
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• pp.118-122
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• 1998

$Al_2O_x$(0$Al_2O_3$ gradient coatings were formed by evaporating pure aluminium(99.9%) in $O_2$ environment with an IBAD facility, 12keV $Ar^+$ was used to irradiate the coatings simultaneously during the deposition. Sample's composition and depth profile were analysed by RBS and AES measurement, and their microhardness and porosity property were also measured in the experiment. Results show that, the oxygen concentration in the deposited coatings has a nearly linear relationship with the inputting gas flow before $O_2$ partial pressure in the target chamber reaches $1.2\times10^{-3}$ mbar under which stoichiometric $Al_2O_3$ could be formed; and sample's microhardness and porosity property is affected significantly by the oxygen concentration in the coatings.

• 한국세라믹학회지
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• 제43권10호
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• pp.653-659
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• 2006

The glass-SiC composites have been manufactured via viscous flow of glass for investigating their sinterability and various properties. The relative density of 99.6% could be achieved when 5 wt% SiC was mixed with glass powder, glass-rearranged at 460$^{\circ}C$ for 3 h and then sintered at 665$^{\circ}C$ for 1 h. The sintered density was decreased as adding more than 5 wt% SiC to glass powder. The resistance properties against hyper velocity copper jet formed by explosion of K215 warhead were compared with other ceramics such as $Al_2O_3$ and pyrex, resulting in lower values than that of $Al_2O_3$.

• 전자공학회논문지A
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• 제30A권12호
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• pp.69-76
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• 1993

The statistical methodology using RSM (response surface method) was used too ptimize the deposition conditions of selective CVD tungsten process for improving the deposition rate and the adhesion property. Temperature, flow rate of SiH$_4$ and WF$_6$ and H$_2$ and Ar carrier gases were chosen for the deposition variables and process characteristics due to carrier gas were intensively investigated. It was observed that temperature was the main factor influencingthe deposition rate in the case of H$_2$ carrier gas while the reactant ratio, $SiH_{4}/WF_{6}$, had the principal effect on the deposition rate in the case of Ar carrier gas. The increased deposition rate and the good adhesion to Si were obtained under Ar carrier gas compared to H$_2$ carrier gas. The optimum conditions for deposition rate and antipeeling property were found to be the temperature range of 300~32$0^{\circ}C$ and the reactant ratio, $SiH_{4}/WF_{6}$, of 0.5~0.6.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1998년도 제13차 학술회의논문집
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• pp.468-473
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• 1998

A mathematical model was developed for a continuous re-actor in which free radical polymerization of methyl methacrylate (MMA) occurred. Elementary reactions considered in this study were initiation, propagation, termination, and chain transfers to monomer and solvent. The reactor model took into account the density change of the reactor contents and the gel effect. A control system was designed for a continuous reactor using extended Kalman filter (EKF) based non-linear model predictive controller (NLMPC) to control the conversion and the weight average molecular weight of the polymer product. Control input variables were the jacket inlet temperature and the feed flow rate. For the purpose of validation of the control strategy, on-line digital control experiments were conducted with densitometer and viscometer for the measurement of the polymer properties. Despite the com-plex and nonlinear features of the polymerization reaction system, the EKF based NLMPC performed quite satisfactorily for the property control of the continuous polymerization reactor.

• Molecules and Cells
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• 제41권5호
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• pp.373-380
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• 2018

Synapses and neural circuits form with exquisite specificity during brain development to allow the precise and appropriate flow of neural information. Although this property of synapses and neural circuits has been extensively investigated for more than a century, molecular mechanisms underlying this property are only recently being unveiled. Recent studies highlight several classes of cell-surface proteins as organizing hubs in building structural and functional architectures of specific synapses and neural circuits. In the present minireview, we discuss recent findings on various synapse organizers that confer the distinct properties of specific synapse types and neural circuit architectures in mammalian brains, with a particular focus on the hippocampus and cerebellum.

• 한국초전도ㆍ저온공학회논문지
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• 제20권2호
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• pp.11-15
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• 2018

In this study, a cancer treatment by accumulating and aggregating ferromagnetic particles in newborn blood vessels was examined. It is necessary for this treatment to control dispersion-aggregation property of ferromagnetic particles. Ferromagnetic particles required in this method disperse at low magnetic field, aggregate at high magnetic field and maintain the aggregation even after removal of the magnetic field. In order to control the dispersion-aggregation property, the surface of magnetite particles was modified with higher fatty acids having different lengths. As a result, we succeeded to prepare propionic acid-modified magnetite particles that form irreversible aggregation by magnetic field. The model experiments simulating newborn blood vessels showed that these particles can block the flow by the magnetic field, and the blockage was maintained after removal of the magnetic field.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2011년도 춘계 학술논문 발표대회 1부
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• pp.65-67
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• 2011

This research analyzed the mechanical properties of high strength concrete produced by limestone aggregate, and summarized the result as follows: Due to the property of unhardened concrete, slump flow value increased more or less according to the increase in LG replacement, but didn't show a big difference while clear tendency of air content couldn't be found. Due to the property of hardened concrete, there appeared an increase in the rate of compressive strength the more LG replacement increased, and the modulus of elasticity also showed a tendency similar to the increase rate of compressive strength.