• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.12
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• pp.68-74
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• 2010

A sub-${\mu}$W CMOS Wien-Bridge oscillator for ultra low power (ULP) radio applications is presented. The Wien-Bridge oscillator is based on an non-inverting opamp amplifier with a closed-loop gain $1+R_2/R_1$ as a means of providing necessary loop gain. An additional RC network provides appropriate phase shift for satisfying the Barkhausen oscillation condition at the given frequency of 1/($2{\pi}RC$). In this design, we propose a novel loop gain control method based on a variable capacitor network instead of a rather conventional variable resistor network. Implemented in $0.18{\mu}m$ CMOS, the oscillator consumes only 560 nA at the oscillation frequency of 22 kHz.

• Korean Journal of Optics and Photonics
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• v.6 no.1
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• pp.33-38
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• 1995

We have measured the excited state absorption in $Ce:YAlO_{3}$, crystals for the first time and assigned it for a 5d$\rightarrow$conduction band transition. Two broad absorption bands were observed at 555 nm and 465 nm fowllowing the 308 nm XeCl laser excitation and their cross sections and oscillator strengths were calculated. We have also measured the fluorescence lifetimes in between 300 K and 700 K to study the nonradiative relaxation from the lowest 5d state of $Ce^{3+}$ ions and explained ESA and the transition process from the state in terms of a configurational coordinate.dinate.

• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.997-1008
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• 2012

This work provides an alternative derivation of third order response functions in four wave mixing spectroscopy of multichromophoric macromolecular systems considering only single exciton states. For the case of harmonic oscillator bath linearly and diagonally coupled to exciton states, closed form expressions showing all the explicit time dependences are derived. These expressions can provide more solid physical basis for understanding 2-dimensional electronic spectroscopy signals. For more general cases of system-bath coupling, the quantum master equation (QME) approach is employed for the derivation of multistep time evolution equations for Green function-like operators. Solution of these equations is feasible at the level of 2nd order non-Markovian QME, and the new approach can account for inter-exciton coupling, dephasing, relaxation, and non-Markovian effects in a consistent manner.

• 전기의세계
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• v.23 no.5
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• pp.47-53
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• 1974

The electrical cardiac pacemaker model described in this paper simulates the most important functional properies of cardiac pacemaker cells. It is a minimum-parameter model which has a simple relaxation oscillator circuit as its main element. The electrical cardiac pacemaker model is analyzed in detail in order to show that its characteristic is similar to that of cardiac pacemaker cells. The main feature of the model is the possibility of controlling the time course phase 4 depolarization, the threshold level and the maximum level of repolarization, the rate of cardiac pacemaker. Emphasis is placed on phenomena of acceleration and frequency entrainment. This particular pacemaker model is very useful for the study of interactions between cardiac pacemakers and the description of the mechanism of arrhythmias.

• Applied Microscopy
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• v.47 no.3
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• pp.131-147
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• 2017

In this work further optical and electrical investigations of pure and Zr doped $Mn_3O_4$ (from 0 up to 20 at.%) thin films as a function of frequency. First, the refractive index, the extinction coefficient and the dielectric constants in terms of Zr content are reached from transmittance and reflectance data. The dispersion of the refractive index is discussed by means of Cauchy model and Wemple and DiDomenico single oscillator models. By exploiting these results, it was possible to estimate the plasma pulse ${\omega}_p$, the relaxation time ${\tau}$ and the dielectric constant ${\varepsilon}_{\infty}$. Second, we have performed original ac and dc conductivity studies inspired from Jonscher model and Arrhenius law. These studies helped establishing significant correlation between temperature, activation energy and Zr content. From the spectroscopy impedance analysis, we investigated the frequency relaxation phenomenon and hopping mechanisms of such thin films. Moreover, a special emphasis has been putted on the effect of the oxidation in air of hausmannite thin films to form $Mn_2O_3$ ones at $350^{\circ}C$. This intrigue phenomenon which occurred at such temperature is discussed along with this electrical study. Finally, all results have been discussed in terms of the thermal activation energies which were determined with two methods for both undoped and Zr doped $Mn_3O_4$ thin films in two temperature ranges.

• Journal of the Korean Institute of Telematics and Electronics
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• v.8 no.2
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• pp.24-33
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• 1971

A noble method of delta modulation by means of pair transistor circuit having negative resistance charcteristic is presented. An RC parallel circuit is inserted between two eiuitter tarminals of the pair transistor circuit, and their emitters are driven by a square pulsed current source. Basically this is a relaxation oscillator circuit. But when the value of capacitors and resistanc R, and the pulse height of driving source are properly chosen, the RC parallel circuit apparently functions as integrating circuit of driviving pulses. Compared with the integrated voltage of capacitor C, a signal input voltatage supplied in series with RC parallel circuit between two emitters makes on or off either of the pair transistors. as the result, one bit pulse is sent out from the coupling resistance terminal of conducted transistor. The circuit diagram used for this experiment is presented, it i% composed with simple mod ulster circuit, differential amplifier and pulse shaping amplifier, The characteristics of the components of this ciruit are discussed, and especially quantumized noise in this delta modulation system is discussed in order to improve the signal to noise ratio which has a close relation with circut constants, quantumized voltage, pulse height and width of driving current source.

• Progress in Medical Physics
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• v.18 no.2
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• pp.73-80
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• 2007

Fruitful findings have been produced from five out of sixty cells which were obtained from each 63 individual Aplisia caught at the Jeju coast. Spiking patterns of three out of five cells, such as relaxation oscillator, bursting within a short time of the inter-burst interval, chaotic bursting, period doubling sequences, bursting with long trains of action potentials separated by short silent periods, regular repeated beating or elliptic bursting, and silent states had been changed in order as the temperature was lowered to $10^{\circ}C\;from\;32^{\circ}C$. In the intervals of every about 40 minutes repeated ups and downs of temperature produced similar firing patterns at the allowable temperature ranges. The other two cells showed difference from these. The amplitudes of the action potentials of the two cells will not be highly decreased in 24 hours. Average spike frequencies, the inter-burst interval, peak to peak spike amplitude of action potentials, minimum potential values are compared and analyzed by using the computer programme. The spike frequencies according to temperature show the distribution of bell type, with maximal spike frequencies at intermediate temperatures and minimal ones at either end. The most common pattern consist of high spike frequency during failing and low one during rising temperatures.