• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.10 no.4
• /
• pp.93-99
• /
• 2011

This paper proposes a novel network jitter estimation algorithm for robust VoIP communication system. The proposed method computes the current network environment mode using the differences of arrival time and generation time from sequential received packets. According to the current network environment mode, the jitter variance weights is adjusted to minimize the error for estimating the network jitter. The jitter average and variance are calculated by the autoregressive estimated algorithm, and then the network jitter is estimated by applying the jitter variance weights.

• Journal of Korean Physical Therapy Science
• /
• v.13 no.2
• /
• pp.67-83
• /
• 2006

The present study examined that in Vivo/Vitro test is investigated in normotensive sham-operated rats (NSR) and aldosterone-analogue deoxycorticosterone acetate (DOCA)-salt hypertensive rats (ADHR) and that the antihypertensive effect was induced by silver spike point (SSP) electrical stimulation at meridian points(CV-3, -4, Ki-12, SP-6, LR-3, BL-25, -28, -32, -52), specifically, such as aldosterone in 24 hour urine analysis from healthy volunteer. The gross examination and morphometric-histological changes, such as hypertrophy, production of necrotic tissues, and the changes of cell arrangement on the kidney, and adrenal gland were markedly observed in aldosterone-analogue DOCA-salt hypertensive rats compared with those from normotensive sham-operated rats. The systolic blood pressure, weight of kidney and adrenal gland were significantly increased in ADHR than that in NSR. The required time of PSS-induced resting tone was significantly increased in ADHR than that in NSR. However, the voltage-dependent K+ (Kv) currents were significantly decreased in ADHR than that in NSR. The urine analysis showed that the concentration of aldosterone was significantly decreased in resting state from the elderly people compared with those from the adolescent healthy volunteer. The current of 1 Hz continue type of SSP electrical stimulation significantly decreased in the concentration of aldosterone of 24 hour urine from the elderly people. These results suggest that the development of aldosterone analogue-induced hypertension is associated with changed the weight of kidney and adrenal gland, blood pressure, resting tone and Kv currents, which directly affects blood pressure. Therefore, the hypertension is a risk factor on cerebrovascular disease. Moreover, these results suggest that the diminished responsiveness to SSP electrical stimulation, especially current of 1Hz continue type, in elderly people may be, in part, related by the increased of antihypertensive effects.

• The Journal of the Convergence on Culture Technology
• /
• v.5 no.4
• /
• pp.379-385
• /
• 2019

The purpose of this study is to investigate the damage status of wood sleepers on concrete track of urban transit at different locations and to analyze the causes of damages. In addition, the turnout maintenance history during the service period of about 24 years was analyzed in conjunction with the train passing tonnage and that was to compare the current repair history. The most frequent damage components were rail, tie plate, spike and wooden sleeper. And, the damage caused by the defect of the rail fastening system such as spike and tie plate according to the deformation of the wooden sleeper was analyzed as the main type of damage. As a result, the damage of track components of turnout system was on the increase because they are directly affected by the train passing tonnage. The supplementary points of the check sheet for current turnout maintenance were derived and the improvement proposal was suggested based on the research results.

• Journal of Electrical Engineering and Technology
• /
• v.9 no.6
• /
• pp.2224-2236
• /
• 2014

The performance of an isolated high voltage full bridge converter is improved using a voltage doubler. In a conventional high voltage full bridge converter, the diode of the transformer secondary voltage undergoes a voltage spike due to the leakage inductance of the transformer and the resonance occurring with the parasitic capacitance of the diode. In addition, in the phase shift control, conduction loss largely increases from the freewheeling mode because of the circulating current. The efficiency of the converter is thus reduced. However, in the proposed converter, the high voltage dual converter consists of a voltage doubler because the circulating current of the converter is reduced to increase efficiency. On the other hand, in the proposed converter, an input current is distributed when using parallel input / serial output and the output voltage can be doubled. However, the voltages in the 2 serial DC links might be unbalanced due to line impedance, passive and active components impedance, and sensor error. Considering these problems, DC injection is performed due to the complementary operations of half bridge inverters as well as the disadvantage of the unbalance in the DC link. Therefore, the serial output of the converter needs to control the balance of the algorithm. In this paper, the performance of the conventional converter is improved and a balance control algorithm is proposed for the proposed converter. Also, the system of the 1.5[kW] PCS is verified through an experiment examining the operation and stability.

• Journal of Power Electronics
• /
• v.13 no.2
• /
• pp.206-213
• /
• 2013

In this paper, an improved passive snubber is investigated in a single-phase single-stage full-bridge boost power factor correction (PFC) converter, by which the voltage spike across primary side of the power transformer can be suppressed and the absorbed energy can be transferred to the output side. When compared with the basic passive snubber, the two single-inductors are replaced by a coupled-inductor in the improved snubber. As a result, synchronous resonances in the snubber can be achieved, which can avoid the unbalance of the voltage and current in the snubber. The operational principle of the improved passive snubber is analyzed in detail based on a single-phase PFC converter, and the design considerations of both the snubber and the coupled-inductor are given. Finally, a laboratory-made prototype is built, and the experimental results verify the feasibility of the proposed method and the validity of the theoretical analysis and design method.

• Biomedical Science Letters
• /
• v.15 no.2
• /
• pp.127-133
• /
• 2009

This study was designed to investigate the effects of high concentration of (-)-epigallocatechin-3-gallate(EGCG) on the neuronal activity of rat substantia nigra dopaminergic neurons. Sprague-Dawley rats aged 14 to 16 days were decapitated under ether anesthesia. After treatment with pronase and thermolysin, the dissociated dopaminergic neurons were transferred into a chamber on an inverted microscope. Spontaneous action potentials and potassium currents were recorded by standard patch-clamp techniques under current and voltage-clamp modes respectively. 18 dopaminergic neurons(80%) revealed inhibitory responses to 40 and 100 ${\mu}M$ of EGCG and 4 neurons(20%) did not respond to EGCG. The spike frequency and resting membrane potential of these cells were decreased by EGCG. The amplitude of afterhyperpolarization was increased by EGCG. Whole potassium currents of dopaminergic neurons were increased by EGCG(n=10). These experimental results suggest that high concentration EGCG decreases the neuronal activity of the dopaminergic neurons by altering the resting membrane potential and afterhyperpolarization.

• Biomedical Science Letters
• /
• v.16 no.1
• /
• pp.46-52
• /
• 2010

This study was designed to investigate the effects of sphingosine-1-phosphate on the neuronal activity of rat medial vestibular nuclear neurons. Sprague-Dawley rats aged 14 to 16 days were decapitated under ether anesthesia. After treatment with pronase and thermolysin, the dissociated medial vestibular nuclear neurons were transferred into a chamber on an inverted microscope. Spontaneous action potentials and potassium currents were recorded by standard patch-clamp techniques under current and voltage-clamp modes respectively. 15 medial vestibular nuclear neurons revealed excitatory responses to 1 and $5\;{\mu}M$ of sphingosine-1-phosphate. The spike frequency and resting membrane potential of these cells were increased by sphingosine-1-phosphate. The amplitude of afterhyperpolarization was decreased by sphingosine-1-phosphate. Whole potassium currents of medial vestibular nuclear neurons were decreased by sphingosine-1-phosphate (n=12). Sphingosine-1-phosphate did not affect the charybdotoxin-treated potassium currents. These experimental results suggest that sphingosine-1-phosphate increases the neuronal activity of the medial vestibular nuclear neurons by altering the resting membrane potential and afterhyperpolarization.

• Journal of Power Electronics
• /
• v.16 no.4
• /
• pp.1256-1267
• /
• 2016

Distributed stray inductance exerts a significant influence on the turn-off voltages of power switching devices. Therefore, the design of low stray inductance bus bars has become an important part of the design of high-power converters. In this study, we first analyze the operational principle and switching transient of a T-type converter. Then, we obtain the commutation circuit, categorize the stray inductance of the circuit, and study the influence of the different types of stray inductance on the turn-off voltages of switching devices. According to the current distribution of the commutation circuit, as well as the conditions for realizing laminated bus bars, we laminate the bus bar of the converter by integrating the practical structure of a capacitor bank and a power module. As a result, the stray inductance of the bus bar is reduced, and the stray inductance in the commutation circuit of the converter is reduced to more than half. Finally, a 10 kVA experimental prototype of a T-type converter is built to verify the effectiveness of the designed laminated bus bar in restraining the turn-off voltage spike of the switching devices in the converter.

• Journal of Power Electronics
• /
• v.18 no.4
• /
• pp.965-974
• /
• 2018

A new zero-voltage-switching (ZVS) push-pull pulse-width modulation (PWM) converter is proposed in this paper. The wide ZVS condition for all of the switches is obtained by utilizing the energy stored in the output inductor and magnetizing inductance. As a result, the switching losses can be dramatically reduced. A simple auxiliary circuit including two small diodes and one capacitor is added at the secondary side of a high frequency (HF) transformer to reset the primary current during the circulating stage and to clamp the voltage spike across the rectifier diodes, which enables the use of low-voltage and low-cost diodes to reduce the conducting and reverse recovery losses. In addition, there are no active devices or resistors in the auxiliary circuit, which can be realized easily. A detailed steady operation analysis, characteristics, design considerations, experimental results and a loss breakdown are presented for the proposed converter. A 500 W prototype has been constructed to verify the effectiveness of the proposed concept.

• Journal of Power Electronics
• /
• v.18 no.1
• /
• pp.11-22
• /
• 2018

This paper presents a single switch, high step-up, non-isolated dc-dc converter suitable for renewable energy applications. The proposed converter is composed of a coupled inductor, a passive clamp circuit, a switched capacitor and voltage lift circuits. The passive clamp recovers the leakage inductance energy of the coupled inductor and limits the voltage spike on the switch. The configuration of the passive clamp and switched capacitor circuit increases the voltage gain. A wide continuous conduction mode (CCM) operation range, a low turn ratio for the coupled inductor, low voltage stress on the switch, switch turn on under almost zero current switching (ZCS), low voltage stress on the diodes, leakage inductance energy recovery, high efficiency and a high voltage gain without a large duty cycle are the benefits of this converter. The steady state operation of the converter in the continuous conduction mode (CCM) and discontinuous conduction mode (DCM) is discussed and analyzed. A 200W prototype converter with a 28V input and a 380V output voltage is implemented and tested to verify the theoretical analysis.