• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.21 no.1
• /
• pp.12-18
• /
• 1985

In general the impulse sound sources of underwater generated by electric arc discharge had used static energy of the charged capacitors. The author proposed an underwater arc discharge sound source using secondary voltage of high voltage transformer without capacitors. The arc discharge device was composed of a high voltage transformer and a switching system. The impulse current in the primary turn of the high voltage transformer is controlled by the switching system and inductive current of the secondary turn in the high voltage transformer is used in making impulsive arc discharge. A series of experiment have been carried out to observe the acoustic characteristics of the impulse sound source generated by the arc discharge. The results obtained were as follows: 1. Secondary current at the time of arc discharge keeps after ohm's law in the beginning and the maximum current flows out as soon as arc discharge breaks out. 2. A time difference between a start of applied current and a generation of arc discharge sound is the 3msec and it is generated arc sound when breaking down electric insulation at maximum voltage. 3. The sharper the end of electrodes and the higher the secondary voltage, the higher the sound pressure level. 4. Arc discharge sound was generated even at the distance of 100cm between electrodes and was stably reproductive at the gap of 1cm to 100cm. 5. Electric arc discharge sound wave is a shock wave of pulse-width of 0.15msec and spectral distribution of it is plenty of low frequency components less than 10 KHz.

• The Korean Journal of Nuclear Medicine
• /
• v.12 no.2
• /
• pp.23-31
• /
• 1978

Hyperthyroidism may be defined as those clinical conditions which result from an increase in the circulating levels of one or both thyroid hormones. Hyperthyroidism in broad sense could be classified with toxic diffuse goiter, toxic adenomatous goiter, and toxic multinodular goiter on the basis of the circulating thyroid hormone levels. For this study, the subject included 94 cases with hyperthyroidism were presented in 77 with toxic diffuse goiter, 8 with toxic adenomatous goiter, and 9 with toxic multinodular goiter on the levels of $^{125}IT_3$ resin uptake rate and serum thyroxine ($T_4$). The observed results were as follows: 1) In the cases of hyperthyroidism including toxic diffuse goiter, toxic adenomatous goiter, and toxic multinodular goiter, 20.21% of the patients were male and 79.79% female. The majority of the patients were in 2nd to 4th decades of their lives. 2) There were objective signs clearly manifested in hyperthyroidism including toxic diffuse goiter and toxic adenomatous goiter which were rare in the multinodular goiter. The clinical signs in toxic diffuse and toxic adenomatous goiter included wide pulse pressure, tachycardia, systolic murmur, exophthalmos, tremor and warm skin etc. (Table 3.) 3) The most freauent complaints of the patients with hyperthyroidism were palpitation, weight loss, increased appetite, perspiration, heat intolerance, nervousness, exertional dyspnea, and menstrual disturbance etc. (Table 4.) There was no clear difference in the incidence of symptoms between toxic diffuse goiter and toxic adenomatous goiter, but there was clear difference between toxic multinodular goiter. 4) Considering of results of $^{125}IT_3$ resin uptake rate and serum $T_4$ level in toxic diffuse goiter, toxic adenomatous goiter and toxic multinodular goiter, $^{125}I\;T_3$ resin uptake rate was $49.15{\pm}9.94%$ (mean) and serum $T_4\;21.29{\pm}7.04ug/dl$ (mean) in toxic diffuse goiter. In toxic multinodular goiter, $^{125}I\;T_3$ resin uptake rate was $32.47{\pm}6.74%$ (mean) and serum $T_4$ level $11.03{\pm}5.0ug/dl$, and then there was clear difference in the results of $^{125}I\;T_3$ resin uptake rate and serum $T_4$ between toxic diffuse goiter and toxic multinodular goiter. The levels of $^{125}I\;T_3$ resin uptake rate and serum $T_4$ in toxic adenomatous goiter were $40.32{\pm}13.08%$ (mean), $15.47{\pm}8.25ug/dl$ (mean) respectively, so there was no clear difference between toxic diffuse goiter and toxic adenomatous goiter. 5) There was no significant differnece in length and width performed with thyroid scanning in toxic diffuse goiter, toxic adenomatous goiter, and toxic multinodular goiter.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2018.06a
• /
• pp.62-62
• /
• 2018

Pt is still considered as one of the most active electrocatalysts for ORR in alkaline fuel cells. However, the high cost and scarcity of Pt hamper the widespread commercialization of fuel cells. As a strong candidate for the replacement of Pt catalyst, silver (Ag) has been extensively studied due to its high activity, abundance, and low cost. Ag is more stable than Pt in the pH range of 8~14 as the equilibrium potential of Ag/Ag+ being ${\approx}200mV$ higher than that of Pt/PtO. However, Ag is the overall catalytic activity of Ag for oxygen reduction reaction(ORR) is still not comparable to Pt catalyst since the surface Ag atoms are approximately 10 times less active than Pt atoms. Therefore, further enhancement in the ORR activity of Ag catalysts is necessary to be competitive with current cutting-edge Pt-based catalysts. We demonstrate the architectural design of Ag catalysts, synthesized using plasma discharge in liquid phase, for enhanced ORR kinetics in alkaline media. An attractive feature of this work is that the plasma status controlled via electric-field could form the Ag nanowires or dendrites without any chemical agents. The plasma reactor was made of a Teflon vessel with an inner diameter of 80 mm and a height of 80 mm, where a pair of tungsten(W) electrodes with a diameter of 2 mm was placed horizontally. The stock solutions were made by dissolving the 5-mM AgNO3 in DI water. For the synthesis of Agnanowires, the electricfield of 3.6kVcm-1 in a 200-ml AgNO3 aqueous solution was applied across the electrodes using a bipolar pulsed power supply(Kurita, Seisakusyo Co. Ltd). The repetition rate and pulse width were fixed at 30kHz and 2.0 us, respectively. The plasma discharge was carried out for a fixed reaction time of 60 min. In case of Ag nanodendrites, the electric field of 32kVcm-1 in a 200-ml AgNO3 aqueous solution was applied and other conditions were identical to the plasma discharge in water in terms of electrode configuration, repetition rate and discharge time. Using SEM and STEM, morphology of Ag nanowires and dendrites were investigated. With 3.6 kV/cm, Ag nanowire was obtained, while Ag dendrite was constructed with 32 kV/cm. The average diameter and legth of Ag nanowireses were 50 nm and 3.5 um, and thoes values of Ag dendrites were 40 nm and 3.0 um. As a results of XPS analysis, the surface defects in the Ag nanowires facilitated O2 incorporation into the surface region via the interaction between the oxygen and the electron cloud of the adjacent Ag atoms. The catalytic activity of Ag for oxygen reduction reaction(ORR) showed that the catalytic ORR activity of Ag nanowires are much better than Ag nanodendrites, and electron transfer number of Ag nanowires is similar to that of Pt (${\approx}4$).

• Nuclear Engineering and Technology
• /
• v.40 no.6
• /
• pp.451-458
• /
• 2008

After more than 10 years construction, KSTAR (Korea Superconducting Tokamak Advanced Research) had finally completed its assembly in June 2007, and then achieved the goal of first-plasma in July 2008 through the four month's commissioning. KSTAR was constructed with fully superconducting magnets with material of $Nb_3Sn$ and NbTi, and their operation temperatures are maintained below 4.5K by the help of Helium Refrigerator System. During the first-plasma operation, plasmas of maximum current of 133kA and maximum pulse width of 865ms were obtained. The KSTAR Integrated Control System (KICS) has successfully fulfilled its missions of surveillance, device operation, machine protection interlock, and data acquisition and management. These and more were all KSTAR commissioning requirements. For reliable and safe operation of KSTAR, 17 local control systems were developed. Those systems must be integrated into the logically single control system, and operate regardless of their platforms and location installed. In order to meet these requirements, KICS was developed as a network-based distributed system and adopted a new framework, named as EPICS (Experimental Physics and Industrial Control System). Also, KICS has some features in KSTAR operation. It performs not only 24 hour continuous plant operation, but the shot-based real-time feedback control by exchanging the initiatives of operation between a central controller and a plasma control system in accordance with the operation sequence. For the diagnosis and analysis of plasma, 11 types of diagnostic system were implemented in KSTAR, and the acquired data from them were archived using MDSpius (Model Driven System), which is widely used in data management of fusion control systems. This paper will cover the design and implementation of the KSTAR integrated control system and the data management and visualization systems. Commissioning results will be introduced in brief.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.50 no.11
• /
• pp.70-77
• /
• 2013

We suggest a low area and high efficiency switched-mode power supply (SMPS) with a pulse width modulation (PWM) generator based on a pseudo relaxation-oscillating technique. In the proposed circuit, the PWM duty ratio is determined by the voltage slope control of an internal capacitor according to amount of charging current in a PWM generator. Compared to conventional SMPSs, the proposed control method consists of a simple structure without the filter circuits needed for an analog-controlled SMPS or the digital compensator used by a digitally-controlled SMPS. The proposed circuit is able to operate at switching frequency of 1MHz~10MHz, as this frequency can be controlled from the selection of one of the internal capacitors in a PWM generator. The maximum current of the core circuit is 2.7 mA, and the total current of the entire circuit including output buffer driver is 15 mA at 10 MHz switching frequency. The proposed SMPS has a simulated maximum ripple voltage of 7mV. In this paper, to verify the operation of the proposed circuit, we performed simulation using Dongbu Hitek BCD $0.35{\mu}m$ technology and measured the proposed circuit.

• Physical Therapy Korea
• /
• v.18 no.1
• /
• pp.83-92
• /
• 2011

Osteoarthritis is a degenerative joint disease and is led to physical disability. Yet the development of effective disease-modifying treatments has lagged. In this study, I examined the effect of physical therapeutic intervention through microcurrent stimulation and attempt to find which degree of intensity, either 25 ${\mu}A$ or 500 ${\mu}A$ with a regular 5 pps pulse, is more effective in the osteoarthritis. Osteoarthritis was induced with a mixture of 2% carrageenan and 2% kaolin in 26 male Sprague-Dawley rats. The mixture (0.1 $m{\ell}$) was injected into the intra-articular capsule of knee joint once a week for three weeks. Five animals did not show degenerative changes by radiological findings and excluded in the following experiment. Osteoarthritic animals were randomly divided into 3 groups ($n_1$, $n_2$, $n_3$=7/each): untreated, treated with 25 ${\mu}A$, treated with 500 ${\mu}A$. All experimental groups received microcurrent stimulation for four weeks (15 min/day, 5 days/week). The ethological inspection of foot print analysis on the walking corridor was accomplished every week. Histological preparations and immunohistochemical staining with insulin-like growth factor-1 were also done in the articular cartilages. All of these parameters were compared with those of osteoarthritic control group (n=7). The ethological inspection of foot print analysis revealed that changes of walking track (paw width) and stride length was significantly increased in both experimental groups. The better results were observed in experimental group treated with 25 ${\mu}A$ intensity without significance than group treated with 500 ${\mu}A$. Histological preparations disclosed that routine hyaline cartilage of articular surface were altered to fibrous cartilage in untreated group and experimental group treated with 500 ${\mu}A$ intensity. But a little changes were seen in experimental group treated with 25 ${\mu}A$ intensity. Immunolocalization of insulin-like growth factor-1 was simultaneously decreased according to the duration of osteoarthritis, and did not show significant difference among the groups. In this study discovered that the microcurrent stimulation, especially 25 ${\mu}A$ intensity, had a positive effect by the ethological inspection, histological and immunohistochemical stainings. These results suggest that microcurrent stimulation with low-intensity might be effective in the promotion of healing process for the osteoarthritis.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.24 no.9
• /
• pp.883-891
• /
• 2013

In wireless smart phone charging scenario, the transmitter pad is larger than the size of the receiver pad. Thus, it is important to supply a constant power to the receiver regardless of its location. In this paper, we propose a new method to regulate the receiver's power by adjusting a drain bias of class E power amplifier. The proposed LF-band wireless power transfer system is as follows: a buck converter power supply which is controlled by a pulse width modulation(PWM) IC TL494, a class E amplifier using a low cost IRF510 power MOSFET, a transmitter coil whose dimension is $16cm{\times}18cm$, a receiver coil whose dimension is $6cm{\times}8cm$, and a full bridge rectifier using Schottky diodes. A measured performance show a maximum output power of 4 W and system efficiency of 67 % if we fix the bias voltage. If we adjust the bias voltage, the received power can be maintained at a constant power of 2 W regardless of receiver pad location.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.18 no.9
• /
• pp.2280-2288
• /
• 2014

The conventional dimming control methods of LED (Light-emitting dioades) include Analog, PWM (Pulse Width Modulation), and FM (Frequency Modulation) Control. Analog dimming is controlled by adjusting forward current of Power LED. Although Analog dimming is possible to control linearly the brightness levels on a whole range (0%~100%), it comes into existence a variation of wavelength by changing the Power LED's forward current. PWM dimming has achieved by varying in duty of full current flowing to the Power LED. Generally, PWM dimming doesn't make variation of wavelength but have difficulty with adjusting the linear brightness level between 0% and 10%. FM dimming method is on the same wavelength as PWM dimming, however, it has problem of flickering at low level of dimming. This paper propose a efficient dimming control method of Power LED in order to overcome the disadvantages of the above mentioned methods. We apply to Analog method in low level of dimming control and use PWM method in dimming range from 10% to 100%. For the experiment, we design and implement a circuit and test the proposed method. Consequently, we can control the linear brightness of Power LED across the whole range and get the constant wave at different dimming level. The experimental results show the benefits of the proposed method.

• Journal of Korean Society of Environmental Engineers
• /
• v.29 no.5
• /
• pp.556-563
• /
• 2007

We carried out a laboratory scale experiment about the characteristics of chemically active species produced in hybrid gas-liquid discharges. The electrode configuration which had high voltage electrode in the gas phase and ground electrode in the liquid was utilized while high voltage electrode has been typically positioned in the liquid in other studies. Our electrode was configured in such a way as to increase the energy efficiency of chemical reactions by creating a higher electrical field strength and a narrower pulse width than the typical electrode configuration. The highest ozone concentration was obtained at 45 kV which was the medium value in operating voltages. The decrease of solution conductivity increased the resistance of liquid phase and the electric field strength through the gas phase, so ozone gene-ration rate was enhanced. The increase of voltage promoted the production rate of hydrogen peroxide by increasing the electric field strength. In a lower voltage, the increase of solution conductivity increased the degradation rate of $H_2O_2$, so the $H_2O_2$ generation rate decreased. On the other hand, the effects of UV radiation, shock waves etc. increased the $H_2O_2$ generation rate as the solution conductivity increased. A higher rate of $H_2O_2$ generation can be achieved by mixing argon to oxygen which generates a stronger and more stable discharges.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.24 no.4
• /
• pp.354-361
• /
• 2004

This Paper describes a crack scattering model for SH wave based on the boundary integral equation(BIE) method, where the fundamental unknown is crack opening displacement(COD). When a time harmonic plane wave was incident on a 2-D isolated crack (slit) of width 2a, the COD distributions were numerically calculated as a function of ka. The calculated COD agreed well with results obtained with other methods. The far-field scattering amplitude, which completely characterizes the flaw response, was calculated in two ways. The Kirchhoff approximation and the BIE-COD exact formulation were compared in terms of incidence angle and frequency ka in a pulse-echo mode. Maximum response was obtained for both methods at the specular reflection direction. Away from the specular direction, the Kirchhoff approximation becomes less accurate. The time domain crack response was also calculated using a band-limited spectrum of center frequency 10 MHz. At oblique incidence to the crack both methods show the existence of an antisymmetric flash points occurring from the crack edge. The Kirchhoff approximation provides an exact time interval between flash points, although it unrealistically gives the same amplitude.