• Fire Science and Engineering
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• v.26 no.6
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• pp.24-30
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• 2012

This study is on the method of the detection for flame and series arc which can be happened at poor contact point added a vibration in part of contact point of low voltage line. In general, the causes of electric fire are over current, short circuit, poor contact, ect. The over-current or short circuit among those causes is detected by measuring a instant current value, but poor contact is difficult to detect by measuring a excessive value of the voltage and current and a distortion of waveforms. And therefore, in this paper, it is studied on the optimal technique of the arc judgement using fuzzy logic and MDET (Multi Dimension Estimation Technique). And it carries out the simulation for arc detection and the experiment for controller and load test. In result, the controller and detection algoristhm, is classified with normal wave and abnormal arc wave without relation with each loads and so the controller can detect a series arc successfully.

• Journal of Welding and Joining
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• v.16 no.4
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• pp.39-46
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• 1998

$CO_2$ gas shielded arc welding has been characterized with its harsh arc compared to Ar-based shielding gases and with its high level of spattere specially in welding current range of 250~300 amperes. In this range of welding current, the metal transfer mode showed to be changed from short circuit to globular with the increase of welding voltage resulting in so-called the transitional mode in which both modes of transfer appeared together. To characterize the transitional mode, the short circuit events were divided into two groups, i.e. normal short circuit (N.S.C) which has short circuit time $(t_s)$ over 2msec and instantaneous short circuit (I.S.C) of $t_s$$\leq$2msec. The experimental results showed that the number of N.S.C decreased almost linearly with the increase of welding voltage and appeared to be not related with spatter generation rate. However I.S.C became to be pronounced in the transitional condition and its number reached the maximum value at around 29.0 volts. Considering the relation with the spatter generation rate, it was found that the number of I.S.C had a very strong correlation with the spatter generation rate of the transitional condition. It was further demonstrated that spatter generation rate decreased quite linearly with the decrease of I.S.C frequency. It implies that I.S.C is the most important waveform factor controlling the spatter generation of the transitional mode, i.e. in the middle range of welding current. Based on these results, It was discussed that in the transitional mode the basic concept of waveform control for suppressing spatter generation would be different from the one applied for typical short circuit transfer mode of low welding current.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2170-2172
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• 1999

A low energy large aperture(LELA) pulsed electron beam generator of a cold cathode type has been developed for environmental applications, for example, waste water cleaning, flue gas cleaning, and pasteurization etc. The operational principle is based on the emission of secondary electrons from cold cathode when ions in the plasma hit the cathode, which are accelerated toward exit window by the gradient of an electric potential. We have fabricated the LELA electron beam generator with the peak energy of 200keV and beam diameter of 200mm and obtained the large aperture electron beam in air. The electron beam current density has been investigated as a function of glow discharge current, accelerating voltage and radial distribution in front of the exit window foil. The plasma density and electron temperature have been measured in order to confirm the relation with the electron beam current density. We are going to upgrade the LELA electron beam generator in the electron energy, electron beam current and stability of operation for various applications.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.1
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• pp.1-8
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• 2005

We fabricate PLT(5) thin film on Pt/TiO/sub x/SiO₂/Si substrate by using sol-gel method and investigate leakage current, switching and retention properties. The leakage current density of PLT(5) thin film is 3.56×10/sup -7/A/㎠ at 4V. In the examination of switching properties, pulse voltage and load resistance were 2V～5V and 50Ω～3.3kΩ, respectively. Switching time has a tendency to decrease from 0.52㎲ to 0.14㎲ with the increase of pulse voltage, and also the time increases from 0.14㎲ to 13.7㎲ with the increase of load resistance. The activation energy obtained from the relation of applied pulse voltage and switching time is about 135kV/cm. The error of switched charge density between hysteresis loop and experiment of polarization switching is about 10%. Also, polarization in retention decreases as much as about 8% after l0/sup 5/s.

• Journal of the Korean Institute of Telematics and Electronics
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• v.22 no.3
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• pp.54-59
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• 1985

From the foregoing papers, it has been clarified that the push-pull current-fed DC-DC converter is excellent in stability as compared with the other conventional DC-DC con-verters. The relation between the stability of the converter and the capacitance of smoothing condenser is analyzed, considering the ESR of smoothing condenser and the 1 st order phase lag of the feedback circuit. From the results, it is known that when the capacitance of smoothing condenser is reduced, the stability of the converter is also excellent as compared with the conventional buck type converter, whereas there are limitations for practical use, since the ripple of output voltage increases by increasing of output current.

• Journal of Welding and Joining
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• v.27 no.5
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• pp.42-48
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• 2009

Pipe welding is used in various ranges such as civil engineering and ship building engineering. Until now, many technicians work for pipe welding manually under harmful, dangerous and difficult conditions. So it is necessary to install automation process. For automation pipe welding, relation between welding parameters & bead shape should be considered. Using this relation, bead shape could be expected from welding parameters. FCAW was used in this study. Instead of pipe workpiece, fillet joint plate is used, which were inclined 0,45,90,135,180 degree. By analyzing between welding parameters (current, welding speed, voltage) and bead shape parameters with non-linear multiple regression, bead shape parameters could be expected. Piecewise Cubic Hermite Interpolation was used to expect smooth curved bead shape with bead shape parameters. From these processes, bead shape could be expected from welding parameters.

• The Korean Journal of Physiology
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• v.27 no.2
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• pp.175-183
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• 1993

There are many report suggesting that influx and intracellular calcium concentration $([Ca^{2+}]_i)$ are related to cell signalling in various cells. However, it has not been reported that calcium channel activation is affected by the substances involved in signal transduction pathways in the mouse eggs. In this study, the effects of isoprenaline (ISP) and cyclic AMP on calcium influx through calcium channels were investigated to show their relationship with the signal transduction process in unfertilized mouse eggs. Using whole cell voltage clamp techniques, calcium currents, elicited by the depolarizing pulses of 300 ms duration (from -50 mV to 50 mV in 10 mV increments) from a holding potential of -80 mV, were recorded. The current-voltage (I-V) relation of calcium currents was shown to be bell-shaped; the current began to activate at -50 mV and reached its maximum $(-1.33{\pm}0.16\;nA:\;mean{\pm}S.E.,\;n=7)$ at -10 mV, then decayed at around 50 mV. Calcium currents were fully activated within $7\;ms{\sim}20\;ms$ and completely inactivated 200 ms after onset of the step pulse. ISP within the concentration ranges of $10^{-8}\;M{\sim}10^{-4}\;M$ dose-dependently increased the amplitude calcium current. The permeable cyclic AMP analogue,8-bromocyclic AMP, also increased its maximal amplitude by 46ft at $10^{-5}\;M$, while protein kinase inhibitor (PKI), which is known to inhibit 0.02 phosphorylating units of cyclic AMP-dependent protein kinase (PKA) per microgram decreased calcium currents. Currents recorded in the presence of PKI were resistant to increase by the application of $10^{-5}\;M$. Also, PKI inhibited the calcium current increase elicited by ISP treatment. These results suggest that $\beta-adrenergic$ regulation of the calcium channel is mediated by the cAMP-dependent protein kinase. This signal transduction pathway might play a role in regulating $[Ca^{2+}]_i$, level due to the increase of calcium influx in mouse eggs.

• The Korean Journal of Physiology and Pharmacology
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• v.9 no.2
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• pp.69-75
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• 2005

TRPM7, a cation channel protein permeable to various metal ions such as $Mg^{2+}$, is ubiquitously expressed in variety of cells including lymphocytes. The activity of TRPM7 is tightly regulated by intracellular $Mg^{2+}$, thus named $Mg^{2+}$-inhibited cation (MIC) current, and its expression is known to be critical for the viability and proliferation of B lymphocytes. In this study, the level of MIC current was compared between immature (WEHI-231) and mature (Bal-17) B lymphocytes. In both cell types, an intracellular dialysis with $Mg^{2+}$-free solution (140 mM CsCl) induced an outwardly-rectifying MIC current. The peak amplitude of MIC current and the permeability to divalent cation ($Mn^{2+}$) were several fold higher in Bal-17 than WEHI-231. Also, the level of mRNAs for TRPM7, a molecular correspondence of the MIC channel, was significantly higher in Bal-17 cells. The amplitude of MIC was further increased, and the relation between current and voltage became linear under divalent cation-free conditions, demonstrating typical properties of the TRPM7. The stimulation of B cell receptors (BCR) by ligation with antibodies did not change the amplitude of MIC current. Also, increase of extracellular $[Mg^{2+}]_c$ to enhance the $Mg^{2+}$ influx did not affect the BCR ligation-induced death of WEHI-231 cells. Although the level of TRPM7 was not directly related with the cell death of immature B cells, the remarkable difference of TRPM7 might indicate a fundamental change in the permeability to divalent cations during the development of B cells.

• The Korean Journal of Physiology and Pharmacology
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• v.4 no.5
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• pp.403-408
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• 2000

The outward currents elicited in hamster eggs by depolarizing pulses were studied. The currents appeared to comprise at least two components, a transient outward component $(I_{to})$ and a steady-state outward component $(I_{\infty}).\;I_{to}$ was transiently followed by the cessation of inward $Ca^{2+}$ current $(I_{Ca}),$ and its current-voltage (I-V) relation was a mirror image of that of $(I_{Ca}).$ Either blockade of $(I_{Ca})$ by $Co^{2+}$ or replacement of $Ca^{2+}$ with $Sr^{2+}$ abolished $I_{to}$ without change in $I_{\infty}.$ Intracellular EGTA (10 mM) inhibited $I_{to}$ but not $I_{\infty}.$ suggesting strongly that generation of $I_{to}$ requires intracellular $Ca^{2+}.$ Apamin (1 nM) abolished selectively $I_{to},$ indicatingthat $I_{to}$ is $Ca^{2+}-dependent\;K^+$ current. On the other hand, $I_{\infty}$ was $Ca^{2+}-independent.$ Both $I_{to}$ and $I_{\infty}$ were completely inhibited by internal $Cs^+$ and external TEA. The estimated reversal potential of $I_{to}$ was close to the theoretical $E_K.$ Taken together, both outward currents were carried by $K^+$ channels. From these results, $I_{to}$ is likely to be a current responsible for the hyperpolarizing responses seen in hamster eggs at fertilization.

• Journal of Welding and Joining
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• v.14 no.5
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• pp.87-94
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• 1996

It has been well known in GMA welding process that wire feeding speed (WFS) or deposition rate increases linealy with the increase of wire extension. In this investigation, however, such an well-known relationship was .reconsidered in terms of contact-tube to work distance (CTWD) instead of wire extension. To verify the proposed relationship between WFS and CTWD, bead-on-plate welding was performed with various CTWDs in the range of 15∼35mm under the condition of near-constant voltage and current As expected, the test results showed an excellent linear relation between WFS and CTWD. Furthermore, the value of the slope turned out to be quite similar to those of previous investigators obtained either theoretically or experimentally through the Precise measurement of electrode extension. Present result also demonstred that the increase of CTWD could be very practical measure for increaring deposition rate without any increase of heat input Depending on the tip recess the practical maximum of CTWD was appeared to be limited somewhere in 25∼30mm mainly due to the entrappment of porocity.