• The Korean Journal of Physiology
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• v.21 no.2
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• pp.225-239
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• 1987

The effects of adenosine on the mechanical contractions and electrical activities were investigated in guinea-pig stomach. Spontaneous contractions of the antral region were recorded with force transducer, and the phasic contractions of fundic region were induced by electrical field stimulation. Electrical responses of smocth muscle cells were recored using glass capillary microelectrodes filled with 3M-KCl. Field stimulation was applied transmurally by using a pair of platinum wire (0.5 mm in diameter) placed on both sides of tissue. All experiments were performed in tris-buffered Tyrode solution which was aerated with 100% $O_2$ and kept at $35^{\circ}C$. The results obtained were as follows. 1) Adenosine suppressed the spontaneous contractions of antrum in a dose-dependent manner. 2) The inhibitory effect on antral spontaneous contractions was not influenced by the administration of guanethidine $(5{\times}10^{-6}\;M)$ and atropine $10^{-6}\;M$, or in the presence of dipyridamole $10^{-7}\;M$. 3) The phasic contractions of fundus induced by electrical field stimulation, which disappeared rapidly by the addition of tetrodotoxin $(3{\times}10^{-7}\;M)$, were potentiated by adenosine in the presence of guanethidine. 4) Adenosine decreased the amplitude and the maximum rate of rise of slow waves, and the increased amplitude and rate of rise evoked in the high calcium solution or in the presence of TEA were decreased by adenosine. 5) The non-adrenergic, non-cholinergic inhibitory junction potential (IJP) was inhibited by adenosine in the antral region, while the excitatory junction potential (EJP) in the fundic region was potentiated. From the above results, the following conclusions could be made. 1) Adenosine suppresses the spontaneous contractions of antrum strip by the decrease in amplitude and rate of rise of slow waves. 2) The release of neurotransmitter(s) from non-adrenergic, non-cholinergic nerve terminals is inhibited by adenosine.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.11
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• pp.2150-2158
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• 1992

This study was carried out to investigate the flow structure and mixing process of a cross mixing flow formed by two round jets with respect to the ratio of mass flow rate. This flow configuration is of great practical relevance in a variety of combustion systems, and the flow behaviour of a cross jet defends critically on the ratio of mass flow rate and the cross angle. The mass flow rate ratios of two different jets were controlled as 1.0, 0.8, 0.6, and 0.4, and the crossing angle of two round jets was fixed at 45 degree. The velocities issuing from jet nozzle with an exit diameter of 20mm were adjusted to 40m/s, 32m/s, 24m/s, and 16m/s, and the measurements have been conducted in the streamwise range of $1.1X_0$to $2.5X_0$ by an on-line measurement system consisted of a constant temperature type two channel hot-wire anemometry connected to a computer analyzing system. The original air flow was generated by a subsonic wind tunnel with reliable stabilities and uniform flows in the test section. For the analysis of the cross mixing flow structure in the downstream region after the cross point, the mean velocity profiles, the resultant velocity contours, and the three-dimensional profiles depending upon the mass flow rate ratio have been concentrately studied.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.7
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• pp.829-835
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• 2010

This paper presents a disposable power generator for microfluidic devices; the power generator has a tubular PEMFC and a $H_2$ generator. The tubular PEMFC has a tubular MEA (diameter: 1.52 mm) that is supported by a spiral wire electrode. The $H_2$ generator supplied $H_2$ to the tubular PEMFC; $H_2$ was generated via the reaction of Al foil (27 mg) and 5 M NaOH (0.12 ml). The open circuit voltage and power density of a unit cell of the tubular PEMFC were 0.81 V and $16.4\;mW/cm^2$ (0.35 V), respectively. The $H_2$ generator generated 11.6 ml $H_2$ for 15min. The power generator was continuously operated for 15 min at 0.64 mW (0.71 V) and for 10 min at 1.06 mW (0.46 V). We experimentally verified that it is feasible to use the proposed power generator as a power source for microfluidic devices; in the experiment, an LED (2.5 mW; 1.8 V) was lit for 10 min by using three serially connected TPEMFCs and one $H_2$ generator.

• Journal of IKEEE
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• v.11 no.4
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• pp.145-151
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• 2007

In this work, small-size, high-performance solenoid-type RF chip inductors utilizing a low-loss ${Al_2}{O_3}$ core material were investigated. The size of the chip inductors fabricated in this work were $0.86{\times}0.46{\times}0.45m^3$, $1.5{\times}1.0{\times}0.7m^3$, $2.1{\times}1.5{\times}1.0m^3$, and $2.4{\times}2.0{\times}1.4m^3$ and copper (Cu) wire with $27{\sim}40{\mu}m$ diameter was used as the coils. High frequency characteristics of the inductance, quality factor, and impedance of developed inductors were measured using an RF Impedance/Material Analyzer (HP4291B with HP16193A test fixture). It was observed that the developed inductors with the number of turns of 7 have the inductance of 13 to 100nH and exhibit the self-resonant frequency (SRF) of 6.4 to 1.1GHz. The SRF of inductors decreases with increasing the inductance and the inductors have the quality factor of 50 to 80 in the frequency range of 300MHz to 1.3GHz. In this study, small-size solenoid-type RF chip inductors with high inductance and high quality factor were fabricated successfully.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.454-454
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• 2014

Silicon microwire array is one of the promising platforms as a means for developing highly efficient solar cells thanks to the enhanced light trapping efficiency. Among the various fabrication methods of microstructures, deep reactive ion etching (DRIE) process has been extensively used in fabrication of high aspect ratio microwire arrays. In this presentation, we show precisely controlled Si microwire arrays by tuning the DRIE process conditions. A periodic microdisk arrays were patterned on 4-inch Si wafer (p-type, $1{\sim}10{\Omega}cm$) using photolithography. After developing the pattern, 150-nm-thick Al was deposited and lifted-off to leave Al microdisk arrays on the starting Si wafer. Periodic Al microdisk arrays (diameter of $2{\mu}m$ and periodic distance of $2{\mu}m$) were used as an etch mask. A DRIE process (Tegal 200) is used for anisotropic deep silicon etching at room temperature. During the process, $SF_6$ and $C_4F_8$ gases were used for the etching and surface passivation, respectively. The length and shape of microwire arrays were controlled by etching time and $SF_6/C_4F_8$ ratio. By adjusting $SF_6/C_4F_8$ gas ratio, the shape of Si microwire can be controlled, resulting in the formation of tapered or vertical microwires. After DRIE process, the residual polymer and etching damage on the surface of the microwires were removed using piranha solution ($H_2SO_4:H_2O_2=4:1$) followed by thermal oxidation ($900^{\circ}C$, 40 min). The oxide layer formed through the thermal oxidation was etched by diluted hydrofluoric acid (1 wt% HF). The surface morphology of a Si microwire arrays was characterized by field-emission scanning electron microscopy (FE-SEM, Hitachi S-4800). Optical reflection measurements were performed over 300~1100 nm wavelengths using a UV-Vis/NIR spectrophotometer (Cary 5000, Agilent) in which a 60 mm integrating sphere (Labsphere) is equipped to account for total light (diffuse and specular) reflected from the samples. The total reflection by the microwire arrays sample was reduced from 20 % to 10 % of the incident light over the visible region when the length of the microwire was increased from $10{\mu}m$ to $30{\mu}m$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.9
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• pp.384-390
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• 2018

Air and soil are being contaminated by the environmental pollution as a result of climate change and urbanization, resulting in water pollution reaching serious levels. In this studies, we investigated the use of antimicrobial copper for the removal of biological pollutants from water system. Specifically, we tested its effects against E. coli, B. subtilis, S. aureus, K. pneumoniae and P. aeruginosa. Made a sphere shape having a diameter of 2cm using a strip-shaped copper wire of 0.5g, 1g and 2g. And then, to confirm the antimicrobial activities, each copper ball was equipped in the broth which inoculated each pathogens. The results showed that bacterial growth of the five test bacteria was inhibited by more than 99% after reaction with a 0.5 g copper ball for at least 20 minutes. Based on the these results, if perform the further experiment such cytotoxicity, it is expected that will be enough to be used as a filter for water quality purification. The developed technique is expected to be widely applied in various industries.

• Journal of Radiation Protection and Research
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• v.36 no.4
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• pp.200-208
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• 2011

The neutron fluence measurement and evaluation technology is very important for material irradiation test. The most essential technology in this study is the neutron irradiation evaluation method using a fluence monitor. The fluence monitors were fabricated with metal wires of the purity ${\geq}$ 99.9%, whose dimensions were 0.1mm diameter, about 3 mm length, and around 150-200 ${\mu}g$ mass range. Three wire samples (Fe, Ni, Ti) were prepared for one irradiation aluminum capsule. Five capsules were irradiated in the OR5 hole of the HANARO reactor at 30 MW power for about 25 days. After irradiation tests, radiation activities were measured with the high purity germanium (HPGe) detector. The reaction rates were calculated by using the measured radiation activity data, and then neutron fluence were obtained from the reaction rates and the weighted neutron cross section with calculated neutron spectrum at the fluence monitor position.

• Journal of the Korean Magnetics Society
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• v.25 no.4
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• pp.123-128
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• 2015

The iron is an element having a high yield strength, mechanical hardness, good electrical conductivity, and also it has been used in various fields because of ease machining. In bridges have been used tendon made of a steel wire for large loads and light weight. Tension measurement of tendon employed in PreStressed Concrete (PSC) bridge is very important for the bridge safety check. NDT (Non-Destructive Testing) is essential for the safety check, however, magnetic NDT is difficult to apply due to the non-linear magnetization curve and hysteresis loop in the magnetic properties. In this work, for basic study of magnetic NDT application, we have constructed a B-H loop measuring system for 7-strand tendon of which diameter is 15.5 mm, and which can apply tensile stress up to 2.0 GPa. We have measured hysteresis loops of two kinds of tendons under different tensile stress. Amplitude permeability and maximum magnetic induction near knee show the most sensitive and high linearity depends on tensile stress. Relative amplitude permeability was decreased from 500 to 200 and maximum magnetic flux density changed 0.6 T.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.3 s.49
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• pp.47-55
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• 2006

Seismic performance and retrofit of reinforced concrete (RC) two-column piers widely used at roadway bridges in Korea was experimentally evaluated. Ten two-column piers that were 400 mm in diameter and 2,000 mm in height were constructed. These piers were subjected to hi-directional cyclic loadings under a constant axial load of $0.1f_{ck}A_g$. Test parameters were the confinement steel ratio, loading pattern, lap splice of longitudinal reinforcing bars, and retrofitting method. Specimens with lap-spliced longitudinal bars were retrofitted with steel jacket, pre-stressing steel wire, and steel band. Test result showed that while the specimens subjected to bi-directional lateral cyclic loadings which consisted of two main amplitudes in the transverse axis and two sub amplitudes in longitudinal axis, referred to as a T-series cyclic loadings, exhibited plastic hinges both at the top and bottom parts of the column, the specimens subjected to bi-directional lateral cyclic loadings in an opposite way, referred to as a L-series cyclic loadings, exhibited a plastic hinge only at the bottom of the column. The displacement ductility of the specimen under the T-series loadings was bigger than that of the specimen under the L-series loadings. Specimen retrofitted with pre-stressing steel wires exhibited poor ductility due to the upward shift of the plastic hinge region because of over-reinforcement, but specimens retrofitted with steel jacket and steel band showed the required displacement ductility. Steel band can be an effective retrofitting scheme to improve the seimsic performance of RC bridge piers, considering its practical construction.

• Korean Journal of Agricultural and Forest Meteorology
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• v.2 no.4
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• pp.204-208
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• 2000

Little information is available for the temporal variation in air temperature profile within rice canopies under development, while much works have been done for a fully developed canopy. Fine wire thermocouples of 0.003 mm diameter (chromel-constantan) were installed at 10 vertical heights by a 10 cm step in a paddy rice field to monitor the air temperatures over and within the developing rice canopy from one month after transplanting (June 29) to just before heading (August 24). According to a preliminary analysis of the data, we found neither the daytime temperature maximum nor the night time minimum at the active radiation surface (the canopy height with maximum leafages) during this period, which is a typical profile of a fully developed canopy. Air temperature within the canopy never exceeded that above the canopy at 1.5 m height during the daytime. Temporal march of the within-canopy profile seemed to be controlled mainly by the ambient temperature above the canopy and the water temperature beneath the canopy, and to some extent by the solar altitude, resulting in alternating isothermal and inversion structures.