• Journal of Biosystems Engineering
• /
• v.42 no.1
• /
• pp.1-11
• /
• 2017

Purpose: Methods: Three-dimensional CFD modeling was conducted to analyze the flow structure and discharge flow rate corresponding to the variation in the geometry of the flow channel in a microtube. Additionally, experiments were carried out, and the discharge flow rate was measured at various inlet pressures and inclination angles of the microtube. Results: The quantitative data of velocity distribution and discharge flow rate were obtained. As the width and length of the microtip increased, the discharge flow rate decreased significantly because of the increase in the loss of pressure along the microtube. As the depth of the microtip increased, the flow rate also increased because of the reduction in the flow resistance. However, in this analysis, the variation in the angle of the microtip did not influence the flow rate. From the experimental results, it was observed that the flow rate increased linearly with the increase in the inlet pressure, and the effects of the inclination angle were not clearly observed in those test cases. The values of the flow rate obtained from the experiments were significantly lower than that obtained from the CFD analysis. This is because of the distortion of the shape of the flow path inside the microtube during the fabrication process. The distortion of the flow path might decrease the flow cross-sectional area, and it would increase the flow resistance inside the microtube. The variation in the flow rate corresponding to the variation in the inlet pressure showed similar trends. Conclusions: Therefore, the results of the numerical analysis obtained from this study can be efficiently utilized for optimizing the shape of the microtip inside a microtube.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.10 no.6
• /
• pp.823-829
• /
• 1986

The Large-scale structure of the circular jet in the transition region, which influences the subsequent flow in the turbulent region, was studied experimentally. Measuring equipments are composed of the two channel hot-wire anemometer, the computer controlled two-directional traverse mechanism, the data acquisition system, and FFT-analyzer. The circular jet has 50mm diameter. The mean velocity distribution, the velocity fluctuation, the auto 'cross correlations and the power spectra were acquired at moderate Reynolds number of 10$^{4}$. And the VITA method was used to measure the convection velocity of Large-scale eddy. The phase of u'is in advance of that of v'in all regions. .over bar. $R_{u}$(.tau.=0) is approximately zero in the potential core region, but a small regular deviation is observed. At a position in the mixing layer region the convection velocity is different along the part of the eddy, and in this experiment the convection velocity of the inner region is larger than the outer region. The averge convection velocity of the eddy along y/D=0 was approximately constant in the transition region.D=0 was approximately constant in the transition region.

• Journal of Sensor Science and Technology
• /
• v.23 no.2
• /
• pp.114-121
• /
• 2014

We report a polysilicon active area membrane field effect transistor (PSAFET) pressure sensor for low stress deflection of membrane. The PSAFET was produced in conventional FET semiconductor fabrication and backside wet etching. The PSAFET located at the front side measured pressure change using 300 nm thin-nitride membrane when a membrane was slightly strained by the small deflection of membrane shape from backside with any physical force. The PSAFET showed high sensitivity around threshold voltage, because threshold voltage variation was composed of fractional function form in sensitivity equation of current variation. When gate voltage was biased close to threshold voltage, a fractional function form had infinite value at $V_{tn}$, which increased the current variation of sensitivity. Threshold voltage effect was dominant right after the PSAFET was turned on. Narrow transistor channel established by small current flow was choked because electron could barely cross drain-source electrodes. When gate voltage was far from threshold voltage, threshold voltage effect converged to zero in fractional form of threshold voltage variations and drain current change was mostly determined by mobility changes. As the PSAFET fabrication was compatible with a polysilicon FET in CMOS fabrication, it could be adapted in low pressure sensor and bio molecular sensor.

• Journal of Radiation Protection and Research
• /
• v.39 no.4
• /
• pp.176-181
• /
• 2014

The object of this paper is to evaluate the fission product inventories and radiological doses in a non-LOCA event, based on the U.S. NRC's regulatory methodologies recommended by the TID-14844 and the RG 1.195. For choosing a non-LOCA event, one fuel assembly was assumed to be melted by a channel blockage accident. The Hanul nuclear power reactor unit 6 and the CE $16{\times}16$ fuel assembly were selected as the computational models. The burnup cross section library for depletion calculations was produced using the TRITON module in the SCALE6.1 computer code system. Based on the recently licensed values for fuel enrichment and burnup, the source term calculation was performed using the ORIGEN-ARP module. The fission product inventories released into the environment were obtained with the assumptions of the TID-14844 and the RG 1.195. With two kinds of source terms, the radiological doses of public in normal environment reflecting realistic circumstances were evaluated by applying the average condition of meteorology, inhalation rate, and shielding factor. The statistical analysis was first carried out using consecutive three year-meteorological data measured at the Hanul site. The annual-averaged atmospheric dispersion factors were evaluated at the shortest representative distance of 1,000 m, where the residents are actually able to live from the reactor core, according to the methodology recommended by the RG 1.111. The Korean characteristic-inhalation rate and shielding factor of a building were considered for a series of dose calculations.

• 유체기계공업학회:학술대회논문집
• /
• 2004.12a
• /
• pp.289-296
• /
• 2004

The present study has been performed to investigate the influences of rectangular fins on heat transfer in an impingement/effusion cooling system with crossflow. To simulate the impingement/effusion cooling system with initial crossflow, two perforated plates are placed in parallel and staggered arrangements with a gap distance of 2 times of the hole diameter. The crossflow passes between the plates, and various rectangular fins are installed on the plates. Reynolds number based on the hole diameter is fixed to 10,000 and the flow rate of crossflow is changed from 0.5 to 1.5 times of that of the impinging jet. A naphthalene sublimation method is used to obtain the heat/mass transfer coefficients on the effusion plate. Also to analyze the flow characteristics, a numerical calculation is performed. When rectangular fins are installed, the flow and heat transfer pattern is changed greatly from case without fins. In the injection hole region, the jet impinges on effusion plate without deflection and wall jet spreads symmetrically. In the effusion region, the crossflow accelerates due to the decrease of cross-sectional area in the channel. Local heat/mass transfer coefficients are enhanced significantly compared to case without fins. As the blowing ratio increases, the effect of fins against the crossflow becomes more significant and then the higher average heat/mass transfer coefficients are obtained than the case without fins.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.29 no.10 s.241
• /
• pp.1289-1297
• /
• 2005

The flow in a microchannel is usually characterized as a low Reynolds number (Re) so that good mixing is quite difficult to be achieved. In this regard, we developed a novel chaotic micromixer, named Serpentine Laminating Micromixer (SLM) in the present study, Part 1. In the SLM, the higher level of chaotic mixing can be achieved by combining two general chaotic mixing mechanisms: splitting/recombination and chaotic advection. The splitting and recombination (in other term, lamination) mechanism is obtained by the successive arrangement of 'F'-shape mixing units in two layers. The chaotic advection is induced by the overall three-dimensional serpentine path of the microchannel. Chaotic mixing performance of the SLM was fully characterized numerically. To compare the mixing performance, a T-type micromixer which has the same width, height and length of the SLM was also designed. The three-dimensional numerical mixing simulations show the superiority of the SLM over the T-type micromixer. From the cross-sectional simulation results of mixing patterns, the chaotic advection effect from the serpentine channel path design acts favorably to realize the ideal lamination of fluid flow as Re increases. Chaotic mixing mechanism, proposed in this study, could be easily integrated in Micro-Total-Analysis-System, Lab-on-a-Chip and so on.

• The Korean Journal of Physiology and Pharmacology
• /
• v.21 no.6
• /
• pp.687-694
• /
• 2017

Plumbagin, a hydroxy 1,4-naphthoquinone compound from plant metabolites, exhibits anticancer, antibacterial, and antifungal activities via modulating various signaling molecules. However, its effects on vascular functions are rarely studied except in pulmonary and coronary arteries where NADPH oxidase (NOX) inhibition was suggested as a mechanism. Here we investigate the effects of plumbagin on the contractility of skeletal artery (deep femoral artery, DFA), mesenteric artery (MA) and renal artery (RA) in rats. Although plumbagin alone had no effect on the isometric tone of DFA, $1{\mu}M$ phenylephrine (PhE)-induced partial contraction was largely augmented by plumbagin (${\Delta}T_{Plum}$, 125% of 80 mM KCl-induced contraction at $1{\mu}M$). With relatively higher concentrations (>$5{\mu}M$), plumbagin induced a transient contraction followed by tonic relaxation of DFA. Similar biphasic augmentation of the PhE-induced contraction was observed in MA and RA. VAS2870 and GKT137831, specific NOX4 inhibitors, neither mimicked nor inhibited ${\Delta}T_{Plum}$ in DFA. Also, pretreatment with tiron or catalase did not affect ${\Delta}T_{Plum}$ of DFA. Under the inhibition of PhE-contraction with L-type $Ca^{2+}$ channel blocker (nifedipine, $1{\mu}M$), plumbagin still induced tonic contraction, suggesting $Ca^{2+}$-sensitization mechanism of smooth muscle. Although ${\Delta}T_{Plum}$ was consistently observed under pretreatment with Rho A-kinase inhibitor (Y27632, $1{\mu}M$), a PKC inhibitor (GF 109203X, $10{\mu}M$) largely suppressed ${\Delta}T_{Plum}$. Taken together, it is suggested that plumbagin facilitates the PKC activation in the presence of vasoactive agonists in skeletal arteries. The biphasic contractile effects on the systemic arteries should be considered in the pharmacological studies of plumbagin and 1,4-naphthoquinones.

• Journal of the Korean Chemical Society
• /
• v.25 no.2
• /
• pp.97-102
• /
• 1981

The conversion of methanol to hydrocarbons has been studied over synthetic ZSM-5 zeolite catalyst having high silica to alumina ratio. The conversion products were olefins, paraffins, cycloparaffins, and aromatics, and the catalyst showed especially high selectivity toward the formation of aromatics. The catalyst showed the shape-selectivity and the size of molecules in the product was limited approximately to the size of 1,3,5-trimethylbenzene. Hydrogen form(HZSM-5) was more active, indicating reactions following the dehydration of methanol seemed to be mainly catalyzed by acid sites. Comparison of the reaction characteristics and acid site distribution of the ZSM-5 catalyst with those of mordenite and faujasite type catalysts suggests that cross-linked pore channel structure and the strong acidity of the ZSM-5 catalyst are primarily responsible for the selective formation of aromatics over this catalyst.

• The KIPS Transactions:PartD
• /
• v.15D no.4
• /
• pp.495-504
• /
• 2008

Aspect Oriented Programming(AOP) is a relatively new programming paradigm and has properties that other programming paradigms don't have. This new programming paradigm provides new modularization of software systems by cross-cutting concerns. In this paper, we propose a regression test method for program evolution by AOP. By using JoinPoint, we can catch a pointcut-name which makes it possible to test the incorrect pointcut strength fault and the incorrect aspect precedence fault. Through extending proof rules to aspect, we can recognize failures to establish expected postconditions faults. We can also trace variables using set() and get() pointcut and test failures to preserve state invariant fault. Using control flow graph, we can test incorrect changes in control dependencies faults. In order to show the correctness of our proposed method, channel management system is implemented and tested by using proposed methods.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.1672-1677
• /
• 2004

Leading edge extension(LEX) in a highly swept shape applied to a delta wing features the modem air-fighters. The LEX vortices generated upon the upper surface of the wing at high angle of attack enhance the lift force of the delta wing by way of increased negative suction pressure over the surfaces. The present 3-D stereo PIV includes the Identification of 2-D cross-correlation equation, stereo matching of 2-D velocity vectors of two cameras, accurate calculation of 3-D velocity vectors by homogeneous coordinate system, removal of error vectors by a statistical method followed by a continuity equation criterion and so on. A delta wing model with or without LEX was immersed in a circulating water channel. Two high-resolution, high-speed digital cameras($1280pixel{\times}1024pixel$) were used to allow the time-resolved animation work. The present dynamic stereo PIV represents the complicated vortex behavior, especially, in terms of time-dependent characteristics of the vortices at given measuring sections. Quantities such as three velocity vector components, vorticity and other flow information can be easily visualized via the 3D time-resolved post-processing to make the easy understanding of the LEX effect or vortex emerging and collapse which are important phenomena occurring in the field of delta wing aerodynamics.