• ETRI Journal
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• v.43 no.5
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• pp.923-931
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• 2021

We studied the influence of GaAs top-layer thickness on the small-signal modulation response and 56 Gb/s four-level pulse-amplitude modulation eye quality of 850 nm vertical-cavity surface-emitting lasers (VCSELs). We considered the proportionality of the gain-saturation coefficient to the photon lifetime. The simulation results that employed the transfer-matrix method and laser rate equations led to the conclusion that the proportionality should be considered for proper explanation of the experimental results. From the obtained optical eyes, we could determine an optimum thickness of the GaAs top layer that rendered the best eye quality of VCSEL. We also compared two results: one result with a fixed gain-saturation coefficient and the other that considered the proportionality. The former result with the constant gain-saturation coefficient demonstrated a better eye quality and a wider optimum range of the GaAs top-layer thickness because the resultant higher damping reduced the relaxation oscillation.

• Current Optics and Photonics
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• v.4 no.6
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• pp.466-471
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• 2020

We analyze the transverse nuclear magnetizations of 129Xe and 131Xe in a vapor cell containing natural Xe, 87Rb, and buffer gases. Th e Xe atoms are polarized th rough spin-exch ange optical pumping (SEOP) with Rb atoms under low-magnetic-field conditions. From the free-induction-decay (FID) signal, we measure the nuclear magnetization of the Xe atoms in the Xe-Rb vapor cell. Furthermore, we measure the dependence of the gyromagnetic ratio on the magnetization of 129Xe and 131Xe by examining the amplitude of the FID signal of each isotope, and we evaluate the relationship between the magnetic field gradient and transverse relaxation rate for both of the 129Xe and 131Xe isotopes.

• The Korean Journal of Pharmacology
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• v.16 no.1 s.26
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• pp.25-34
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• 1980

The in vitro guinea pig ureter responded to 5 sec trains of electrical stimuli with two contractions; the first an 'on response' (ON) occurred with $0.1{\sim}0.3$ sec after the onset o the stimulus train, the second an 'off response'(OFF) occurred $0.2{\sim}1.0$ sec after the termination of the stimulus train. Relaxation occurred between the two responses during a time when the stimulus was still being delivered. Longer duration and/or higher frequencies of stimuli within the train were required to elicit the OFF than the ON. Decreasing temperature from $37^{\circ}$ to $22^{\circ}$ decreased ON amplitude and increased OFF amplitude. $Ca^{++}$-free solution, 2 mM EDTA, 1 mM $Mn^{++}$ or $1{\mu}M$ verapamil rapidly abolished ON. OFF persisted when ON had disappeared by repeated stimulation at 0.12 train per sec. Conversely, caffeine, $50{\mu}M$ and theophylline, $10{\mu}M$ abolished OFF with only slight reduction of ON, and sodium nitroprusside decreased preferentially ON amplitude rather than OFF. Relaxation between ON and OFF was incomplete in low $Na^+$ solution. ON and OFF were not affected by the neural blockers tetrodotoxin, atropine or phentolamine, also pyrilamine and methysergide, and relaxation between ON and OFF was $Na^+$ dependent. Furthermore, ON depends on free $Ca^{++}$ and OFF is more dependent on bound or stored $Ca^{++}$.

• Geophysics and Geophysical Exploration
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• v.25 no.3
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• pp.99-108
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• 2022

Among induced polarization (IP) methods, spectral IP (SIP) uses alternating current as a transmission source to measure amplitudes and phase of complex electrical resistivity at each source frequency, which disperse with respect to source frequencies. The frequency dependence, which can be explained by a relaxation model such as Cole-Cole model or equivalent models, is analyzed to estimate SIP parameters from dispersion curves of complex resistivity employing multi-objective optimization (MOO). The estimation uses a generic algorithm to optimize two objective functions minimizing data misfits of amplitude and phase based on Cole-Cole model, which is most widely used to explain IP relaxation effects. The MOO-based estimation properly recovered Cole-Cole model parameters for synthetic examples but hardly fitted for the real laboratory measures ones, which have relatively smaller values of phases (less than about 10 mrad). Discrepancies between scales for data misfits of amplitude and phase, used as parameters of MOO method, and it is in necessity to employ other methods such as machine learning, which can deal with the discrepancies, to estimate SIP parameters from dispersion curves of complex resistivity.

• Journal of the Korean Society for Marine Environment & Energy
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• v.20 no.2
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• pp.63-75
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• 2017

In offshore environment, an accurate estimation of a wave-structure interaction has been an important issue for safe and cost effective design of fixed and floating offshore structures exposed to a harsh environment. In this study, a wave-structure interaction around a circular column was investigated with regular waves. To simulate 3D two-phase flow, open source computational fluid dynamics libraries, called OpenFOAM, were used. Wave generation and absorption in the wave tank were activated by the relaxation method, which implemented in a source term. To validate the numerical methods, generated Stokes 2nd-order wave profiles were compared with the analytic solution with deep water condition. From the validation test, grid longitudinal and vertical sizes for wave length and amplitude were selected. The simulated wave run-up and wave loads on the circular column were studied and compared with existing experimental data.

• 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.

• Korean Journal of Optics and Photonics
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• v.5 no.3
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• pp.394-403
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• 1994

Chaos characteristics of laser diodes with external optical feedback is investigated. For a FabryPerot resonator laser, optical feedback by external mirror is assumed. The simulation is performed in such a way that a current of $1.3J_{th}$ is injected into the $1.3{\mu}m$wavelength "InGaAsP" buried hetero structure laser. With the increment of K, the system shows the evolution of four steps as follows: i) When the optical feedback coefficient K is very small, the relaxation oscillation is damped and the system reaches the steady state showing the stable operation characteristics. ii) As K increases a little bit, the relaxation oscillation is not damped any more and the system begins to maintain the periodic oscillation. iii) When K is increased further, the oscillation shows the larger amplitude and the long periodic length. iv) When K is increased very large, the system gets unstable and enters into the coherejlce collapse state. state.

• The Korean Journal of Physiology and Pharmacology
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• v.19 no.3
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• pp.257-262
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• 2015

It is well known that cigarette smoke can cause erectile dysfunction by affecting the penile vascular system. However, the exact effects of nicotine on the corpus cavernosum remains poorly understood. Nicotine has been reported to cause relaxation of the corpus cavernosum; it has also been reported to cause both contraction and relaxation. Therefore, high concentrations of nicotine were studied in strips from the rabbit corpus cavernosum to better understand its effects. The proximal penile corpus cavernosal strips from male rabbits weighing approximately 4 kg were used in organ bath studies. Nicotine in high concentrations ($10^{-5}{\sim}10^{-4}M$) produced dose-dependent contractions of the corpus cavernosal strips. The incubation with $10^{-5}M$ hexamethonium (nicotinic receptor antagonist) significantly inhibited the magnitude of the nicotine associated contractions. The nicotine-induced contractions were not only significantly inhibited by pretreatment with $10^{-5}M$ indomethacin (nonspecific cyclooxygenase inhibitor) and with $10^{-6}M$ NS-398 (selective cyclooxygenase inhibitor), but also with $10^{-6}M$ Y-27632 (Rho kinase inhibitor). Ozagrel (thromboxane $A_2$ synthase inhibitor) and SQ-29548 (highly selective TP receptor antagonist) pretreatments significantly reduced the nicotine-induced contractile amplitude of the strips. High concentrations of nicotine caused contraction of isolated rabbit corpus cavernosal strips. This contraction appeared to be mediated by activation of nicotinic receptors. Rho-kinase and cyclooxygenase pathways, especially cyclooxygenase-2 and thromboxane $A_2$, might play a pivotal role in the mechanism associated with nicotine-induced contraction of the rabbit corpus cavernosum.

• Korean Journal of Animal Reproduction
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• v.19 no.4
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• pp.245-250
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• 1996

This study was undertaken to illustrate the uterotonic effect of Leonurus sibiricus. It was dissolved in sterile water and several different dosages were administered both in vitro and in vivo study. Rat uterine tissue for in vitro bioassay was obtained from estrous rat. From the low to high dosages of Leonurus sibiricus were tried and each uterine contraction was recorded and integrated. Anesthetized estrous rat for in vivo study was cannulated into the jugular vein for infusion of the compound. Another cannula with a balloon tipped and water filled was inserted into the uterus to measure uterine activity. While the uterine tissue did not respond to low dosage of compound, high dosage of compound stimulated the tissue to contract less than 1 minute with low amplitude. In vivo rat uterus showed a certain, consistent pattern of contractions which was initial relaxation and followed by prolonged and increased amplitude of contractions. It also caused a short breathing stop which might be due to acute acidosis.

• Annals of Clinical Neurophysiology
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• v.1 no.2
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• pp.106-111
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• 1999

Backgroud : The generators of N37 and P37 of posterior tibial nerve somatosensory evoked potential(PTSEP) have not been exactly known. Recently, some reports suggested that P37 and N37 might have different generator. We conducted a study to know the generators of P37 and N37 of PTSEP using gating mechanism. Methods : We evaluated subcortical and cortical somatosensoy evoked potentials(SEPs) in response to posterior tibial nerve stimulation in 3 experimental conditions of foot movement and compared them with PTSEPs in full relaxation of foot. The experimental conditions were: (a) active flexion-extention of stimulated foot, (b) isometric contraction of the stimulated foot, (c) passive flexion-extention of the stimulate foot. We analyzed the latencies and amplitudes of following potentials; P30, N37, P37, and N50. Results : The amplitude of P30 potential did not change during at any paradigms. The amplitudes of P37 and N50 were significantly attenuated in all condition. However, the amplitude of N37 showed no significant change during at any paradigms. Conclusions : These results suggest that the generators of P37 and N37 of PTSEP be different in cortex.