• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.2
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• pp.135-145
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• 2020

Wave observation is widely used to direct observation method for observing the water surface elevation using wave buoy or pressure gauge and remote-sensing wave observation method. The wave buoy and pressure gauge can produce high-quality wave data but have disadvantages of the high risk of damage and loss of the instrument, and high maintenance cost in the offshore area. On the other hand, remote observation method such as radar is easy to maintain by installing the equipment on the land, but the accuracy is somewhat lower than the direct observation method. This study investigates the data quality of MIROS Wave and Current Radar (MWR) installed at Dokdo and improve the data quality of remote wave observation data using the wave buoy (CWB) observation data operated by the Korea Meteorological Administration. We applied and developed the three types of wave data quality control; 1) the combined use (Optimal Filter) of the filter designed by MIROS (Reduce Noise Frequency, Phillips Check, Energy Level Check), 2) Spike Test Algorithm (Spike Test) developed by OOI (Ocean Observatories Initiative) and 3) a new filter (H-Ts QC) using the significant wave height-period relationship. As a result, the wave observation data of MWR using three quality control have some reliability about the significant wave height. On the other hand, there are still some errors in the significant wave period, so improvements are required. Also, since the wave observation data of MWR is different somewhat from the CWB data in high waves of over 3 m, further research such as collection and analysis of long-term remote wave observation data and filter development is necessary.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.3
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• pp.230-237
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• 2012

This paper proposes an active-clamp ac-dc converter with direct power conversion that has a simple structure and achieves high efficiency. The proposed converter is derived by integrating the step-down ac chopper and the output-voltage doubler. The proposed converter provides direct ac-dc conversion and dc output voltage without using any full-bridge diode rectifier. The step-down ac chopper using an active-clamp mechanism serves to clamp the voltage spike across the main switches and provides zero-voltage turn-on switching. The resonant-current path formed by the leakage inductance of the transformer and the resonant capacitor of the output-voltage doubler achieves the zero-current turn-off switching of the output diodes. The operation principle of the converter is analyzed and verified. A 500W prototype is implemented to show the performance of the proposed converter. The prototype provides maximum efficiency of 95.1% at the full load.

• Journal of Power Electronics
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• v.18 no.3
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• pp.662-671
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• 2018

This paper presents a new structure for a step up dc-dc converter, which has several advantageous features. Firstly, the input dc source and the clamped capacitor are connected in series to transfer energy to the load through dual voltage multiplier cells. Therefore, the proposed converter can produce a very high voltage and a high conversion efficiency. Secondly, a double voltage clamped circuit is introduced to the primary side of the coupled inductor. The energy of the leakage inductance of the coupled inductor is recycled and the inrush current problem of the clamped circuits can be shared equally by two synchronous clamped capacitors. Therefore, the voltage spike of the switch tube is solved and the current stress of the diode is reduced. Thirdly, dual voltage multiplier cells can absorb the leakage inductance energy of the secondary side of the coupled inductor to obtain a higher efficiency. Fourthly, the active switch turns on at almost zero current and the reverse-recovery problem of the diodes is alleviated due to the leakage inductance, which further improves the conversion efficiency. The operating principles and a steady-state analysis of the continuous, discontinuous and boundary conduction modes are discussed in detail. Finally, the validity of this topology is confirmed by experimental results.

• The Korean Journal of Physiology
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• v.27 no.2
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• pp.115-122
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• 1993

There is evidence that noradrenaline enhances spontaneous contractions dose-dependently in guinea-pig antral circular muscle. To investigate the mechanism of this excitatory action, slow waves and membrane currents were recorded using conventional microelectrode techniques in muscle strips and the whole cell patch clamp technique in isolated gastric myocytes. On recording slow waves, noradrenaline $(10^{-5}\;M)$ induced the hyperpolarization of the membrane potential, although the shape of the slow waves became tall and steep. Also, spike potentiaIs occurred at the peaks of slow waves. These changes were completely reversed by administration of phentolamine $(10^{-5}\;M),\;an\;{\alpha}-adrenoceptor$ blocker. Noradrenaline-induced hyperpolarization was blocked by apamin $(10^{-7}\;M)$, a blocker of a class of $Ca^{2+}\;-dependent\;K^+$ channels. To investigate the mechanisms for these effects, we performed whole cell patch clamp experiments. Norndrenaline increased voltage-dependent $Ca^{2+}$ currents in the whole range of test potentials. Noradrenaline also increased $Ca^{2+}\;-dependent\;K^+$\;currents, and this effects was abolished by apamin. These results suggest that the increase in amplitude and the generation of spike potentials on slow waves was caused by the activation of voltage-dependent $Ca^{2+}$ channel via adrenoceptors, and hyperpolarization of the membrane potential was mediated by activation of apamin-sensitive $Ca^{2+}\;-dependent\;K^+\;channels$.

• JSTS:Journal of Semiconductor Technology and Science
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• v.17 no.2
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• pp.174-179
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• 2017

We designed the CMOS analog integrate and fire (I&F) neuron circuit for driving memristor based on resistive-switching random access memory (RRAM). And we fabricated the RRAM device that have $HfO_2$ switching layer using atomic layer deposition (ALD). The RRAM device has gradual set and reset characteristics. By spice modeling of the synaptic device, we performed circuit simulation of synaptic device and CMOS neuron circuit. The neuron circuit consists of a current mirror for spatial integration, a capacitor for temporal integration, two inverters for pulse generation, a refractory part, and finally a feedback part for learning of the RRAM. We emulated the spike-timing-dependent-plasticity (STDP) characteristic that is performed automatically by pre-synaptic pulse and feedback signal of the neuron circuit. By STDP characteristics, the synaptic weight, conductance of the RRAM, is changed without additional control circuit.

• Atmosphere
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• v.26 no.4
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• pp.541-551
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• 2016

A real-time quality control algorithm for $PM_{10}$ concentration measured by Continuous Ambient Particulate Monitor (FH62C14, Thermo Fisher Scientific Inc.) has been developed. The quality control algorithm for $PM_{10}$ data consists of five main procedures. The first step is valid value check. The values should be within the acceptable range limit. Upper ($5,000{\mu}g\;m^{-3}$) and lower ($0{\mu}g\;m^{-3}$) values of instrument detectable limit have to be eliminated as being unrealistic. The second step is valid error check. Whenever unusual condition occurs, the instrument will save error code. Value having an error code is eliminated. The third step is persistence check. This step checks on a minimum required variability of data during a certain period. If the $PM_{10}$ data do not vary over the past 60 minutes by more than the specific limit ($0{\mu}g\;m^{-3}$) then the current 5-minute value fails the check. The fourth step is time continuity check, which is checked to eliminate gross outlier. The last step is spike check. The spikes in the time series are checked. The outlier detection is based on the double-difference time series, using the median. Flags indicating normal and abnormal are added to the raw data after quality control procedure. The quality control algorithm is applied to $PM_{10}$ data for Asian dust and non-Asian dust case at Seoul site and dataset for the period 2013~2014 at 26 sites in Korea.

• The Korean Journal of Physiology
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• v.29 no.2
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• pp.233-241
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• 1995

The nonapeptide bradykinin has been shown to exhibit an array of biological activities including relaxation/contraction of various smooth muscles. In order to investigate the effects of bradykinin on the contractility and the electrical activity of antral circular muscle of guinea-pig stomach, the isometric contraction and membrane potential were recorded. Also, using standard patch clamp technique, the $Ca^{2+}-activated$ K currents were recorded to observe the change in cytosolic $Ca^{2+}$ concentration. $0.4 {\mu}M$ bradykinin induced a triphasic contractile response (transient contraction-transient relaxation-sustained contraction) and this response was unaffected by pretreatment with neural blockers (tetrodotoxin, atropine and guanethidine) or with apamin. Bradykinin induced hyperpolarization of resting membrane potential and enhanced the amplitude of slow waves and spike potentials. The enhancement of spike potentials was blocked by neural blockers. Both the bradykinin-induced contractions and changes in membrane potential were reversed by the selective $B_2$-receptor antagonist $(N{\alpha}-adamantaneacetyl-_{D}-Arg-[Hyp, Thy,_{D}-Phe]-bradykinin)$. In whole-cell patch clamp experiment, we held the membrane potential at -20 mV and spontaneous and transient changes of Ca-activated K currents were recorded. Bradykinin induced a large transient outward current, consistent with a calcium-releasing action of bradykinin front the intracellular calcium pool, because such change was blocked by pretreatment with caffeine. Bradykinin-induced contraction was also blocked by pretreatment with caffeine. From these results, it is suggested that bradykinin induces a calciumrelease and contraction through the $B_{2}$ receptor of guinea-pig gastric smooth muscle. Enhancement of slow wave activity is an indirect action of bradykinin through enteric nerve cells embedded in muscle strip.

• Journal of the korean academy of Pediatric Dentistry
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• v.25 no.4
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• pp.671-682
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• 1998

Electrophysiological phenomena of pyramidal cells in the CA1 area of the dorsal hippocampus were recorded from and filled with neurobiotin in anesthetized rats. The electropharmacological properties of membrane as well as the cellular-synaptic generation of rhythmic slow activity (theta) were examined. The intracellular response characteristics of these pyramidal cells were distinctly different from responses of interneurons. Pyramidal cells had a high resting membrane potential, a low input resistance, and a large amplitude action potential. A afterhyperpolarization was followed a single action potential. Most of pyramidal cells did not display a spontaneous firing. Pyramidal cells displayed weak inward rectification and anodal break excitation. The slope of the frequency-current relation was 53.4 Hz/nA for the first interspike interval and 15.9 Hz/nA for the last intervals, suggesting the presence of spike frequency adaptation. Neurobiotin-filled neurons showed pyramidal morphology. Cells were generally bipolar dendritc processes ramifying in stratum lacunosum-moleculare, radiatum, and oriens. Commissural stimulation discharged pyramidal cells, followed by excitatory and inhibitory postsynaptic potentials (EPSPs and IPSPs). The frequency of theta-related membrane potential oscillation was voltage-independent in pyramidal neurons. At strong depolarization levels (less than 30 mV) pyramidal cells emitted sodium spike oscillation, phase-locked to theta. The observations provide direct evidence that theta-related rhythmic hyperpolarization of principal cells is brought by the rhythmically discharging interneurons. Furthermore, the findings in which interneurons were also paced by rhythmic inhibitory postsynaptic potentials during theta suggest that they were periodically hyperpolarized by their GABAergic septal afferents.

• Current Research on Agriculture and Life Sciences
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• v.21
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• pp.17-21
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• 2003

This study aimed to identify leaf sheath function through the investigation of effect of removal times and removed number of leaf sheath on growth and flowering in gladiolus. The leaf sheath influenced on the growth and flowering regardless of light condition at early growth stages. When total leaf sheath were removed in early growth stages, flower stalk length and spike length remarkably decreased. Whereas days of flowering were little different by leaf sheath removal. Also when removed numbers of leaf sheath were 1, 2 and 3, the growth and flowering were little different compared to control. But when removed numbers of leaf sheath were 4, flower stalk length decreased above 25cm compared to others treatment, spike length and number of flower decreased and stem diameter became thick abnormally.

• The Korean Journal of Physiology
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• v.20 no.2
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• pp.165-174
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• 1986

The voltage clamp studies were undertaken to elucidate the properties of the slow inward current, $i_{si}$, in the small preparations of the rabbit sinoatrial node. The slow inward current, $i_{si}$, which is known to be responsible for the late one-third of pacemaker potential and whole range of upstroke phase of action potential was analysed with the effects of isoprenaline, cobalt, ouabain and higenamine. The results obtained are as follows; 1) Voltage of SA node preparation was held at zero current level, usually-40mV and the slow inward current, $i_{si}$, was activated by depolarizing clamp pulses. Peak values of $i_{si}$, in steady state were at $-10{\pm}0mV$ in most preparations. 2) Isoprenaline, ${\beta}-agonist$ increased $i_{si}$ and no shift was noticed in voltage-dependency. 3) Cobalt ion in the concentration of 1 mM abolished is, in entire range of membrane potential and the difference of two current levels before and after $Co^{2+}$ treatment could be considered as pure $i_{si}$ magnitude. 4) In the therapeutic concentration of ouabain $(5{\times}10^{-8}M)$ slightly increased is, and reduced the time to reach the peak value. 5) Higenamine $(10^{-6}M)$ changed the configurations of action potential (i. e. rapid upstroke phase and notch in the spike) and increase spontaneous rate. It also increased is, and the effect of higenamine was blocked ${\beta}-blocker$, propranolol $(10^{-6}M)$.