• Korean Journal of Metals and Materials
• /
• v.50 no.11
• /
• pp.861-866
• /
• 2012

A dense nanostructured TiN-AlN composite was prepared from high-energy ball milled TiN-AlN mixture powders by pulsed current activated sintering (PCAS). A highly dense TiN-AlN bulk composite was obtained within 2 minutes at $1500^{\circ}C$ with the simultaneous application of 80 MPa pressure and pulsed current. The fine crystalline structure of the TiN-AlN mixture, which was obtained by high-energy milling, was effectively maintained during PCAS and resulted in the enhancement of the mechanical properties. The micro hardness and fracture toughness of TiN-AlN composite were $1780kg/mm^2$ and $5MPa.m^{1/2}$, respectively. The mechanical properties were higher than monolithic AlN or TiN.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.34D no.4
• /
• pp.17-26
• /
• 1997

A enw channel current model of GaAs MeSFET suitagle for applications to microwave CAD has been developed. The current model includes the bias-dependent frequency dispersion effects and its parameters are extracted from the pulsed I-V measurements at several quiescent bias points. The model is verified by applying to the nonlinear circuit designs of power amplifier and MMIC mixer.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.62 no.4
• /
• pp.510-516
• /
• 2013

This paper suggests a 3-phase series-resonant type high voltage capacitor charger for an EML pulsed power system. The operating principle on the charger is explained by an equivalent circuit. Additionally, we analyze the charging characteristic in one discontinuous conduction mode and three continuous conduction modes. The analysis shows that the resonant current per phase is two thirds of the 3-phase charger's average charging current and one third of the single-phase charger's average charging current with the same capacity. We suggest a design method of the 3-phase capacitor charger in each operational mode and present an example of 3.5 kW capacitor charger at ${\omega}_s=0.33{\omega}_r$. The 3.5 kW 3-phase capacitor charger prototype is assembled with a TI28335 controller and a 40 kJ, 7 kV capacitor. The design rules based on the analysis are verified by experiment.

• KIEE International Transactions on Electrophysics and Applications
• /
• v.4C no.3
• /
• pp.96-100
• /
• 2004

The Nd： YAG laser is commonly used throughout many fields such as accurate material processing, IC marking, semiconductor annealing, medical operation devices, etc., due to the fact that it has good thermal and mechanical properties and is easy to maintain. In materials processing, it is essential to vary the laser power density for specific materials. The laser power density can be mainly controlled by the current pulse width and pulse repetition rate. It is important to control the laser energy in those fields using a pulsed laser. In this paper we propose the constant-frequency current resonant half-bridge converter and monitoring of capacitor charging voltage. This laser power supply is designed and fabricated to have less switching loss, compact size, isolation with primary and secondary transformers, and detection of capacitor charging voltage. Also, the output stabilization characteristics of this Nd： YAG laser system are investigated. The test results are described as a function of laser output energy and flashlamp arc discharging constant. At the energy storage capacitor charges constant voltage, the laser output power is 2.3％ error range in 600[V].

• Korean Journal of Materials Research
• /
• v.16 no.10
• /
• pp.639-646
• /
• 2006

Over the last two decades, microbiologically influenced corrosion (MIC) of metallic materials has received considerable attention due to its serious effects on industrial field. In this context, it is important to devise control methods which inhibit biofilm formation on various metallic compounds and are compatible with environment. It was change of various conditions (duty cycle, current density, $AgNO_3$ concentration and pH) for injection of Ag particles in anodized Aluminum alloy pore using pulsed current. Optimal condition was obtained by means of FE-SEM, ICP analysis etc. The antibacterial metal's specimen were manufactured under optimal condition and this specimen were tested the antibacterial characterization and anticorrosion characterization. In result of test, we can confirmed that the antibacterial characterization and anticorrosion characterization of the specimens of injected Ag particles in anodized Aluminum alloy pore using pulsed current were better than the anodized Aluminum alloy specimens.

• Journal of IKEEE
• /
• v.26 no.4
• /
• pp.537-544
• /
• 2022

This paper analyzes the occurrence and cause of bond wires fusing used in the manufacture of pulsed high power amplifiers. Recently GaN HEMT has been spotlight in the fields of electronic warfare, radar, base station and satellite communication. In order to produce the maximum output power, which is the main performance of the high-power amplifier, optimal impedance matching is required. And the material, diameter and number of bond wires must be determined in consideration of not only the rated current but also the heat generated by the transient current. In particular, it was confirmed that compound semiconductor with a wide energy band gap such as GaN trigger fusing of the bond wire due to an increase in thermal resistance when the design efficiency is low or the heat dissipation is insufficient. This data has been simulated for exothermic conditions, and it is expected to be used as a reference for applications using GaN devices as verified through IR microscope.

• Journal of Korean Ophthalmic Optics Society
• /
• v.12 no.1
• /
• pp.69-74
• /
• 2007

The axial speed of plasma current sheath was measured with Rogowski coils and compared with the theory of snowplow model. Current sheath speed is measured with $10^6cm/s$. The speed of light gas, $H_2$ and He were similar to the theory of model, but the heavy gas, Ar was not similar to the theory. The disagreement of the heavy gas was guessed as a results of the instability of the current sheath.

• Physical Therapy Korea
• /
• v.13 no.3
• /
• pp.33-40
• /
• 2006

The purpose of this study was to assess the effects of High-Voltage Pulsed Current (HVPC) and ultrasound on adjuvant-induced arthritis in rats. Adjuvant arthritis was induced in female Sprauge-Dawley rats by the subcutaneous injection of a single dose of $.1m{\ell}$ of Complete Freund's Adjuvant (CFA) (1 mg of Mycobacterium Butyricum suspended in $.1m{\ell}$ paraffin oil) into the right hind paw. A randomized, parallel-groups design of 24 subjects was used. All rats were randomly assigned to control (n=8), ultrasound (n=8), and HVPC (n=8) were compared with those of injured rats. The rats in the pulsed ultrasound group were treated at 1 MHz frequency with $.5W/cm^2$ intensity in 1:4 mode for 5 minutes per day. The rats in the HVPC group were treated at 120 pulses per second and $50{\mu}s$ phase duration, 20 mA intensity for 30 min per day. Treatment was done in the left and right hind limb for 2 weeks. We evaluated clinical, radiographic, hematologic and histopathologic findings before and after treatment and obtained the following results. 1. Edema of the right hind paw was more significantly reduced in the ultrasound and HVPC groups than the control group on days 9, 12, and 14 (p<.05). Edema of the left hind paw was more significantly reduced in ultrasound and HVPC groups than the control group on days 12, 14 (p<.05). 2. WBC counts of the ultrasound and HVPC groups as compared with the control group were becoming remarkably decreased after the treatment. 3. In radiologic findings, arthritis formation was seen according to the score of arthritis, which was the highest in the control group, upon the observation of radiographs of the left and right hind paws. However, no statistically significant difference was present in the score within three groups. 4. In the histopathologic findings, ultrasound and HVPC groups had effectively suppressed erosions of articular cartilage and inflammatory cell infiltrations. Therefore, the results of the study show that rats that were treated with the ultrasound and HVPC effectively suppressed adjuvant arthritis. However, no statistically significant difference was present between the ultrasound group and the HVPC group.

• Asian-Australasian Journal of Animal Sciences
• /
• v.24 no.9
• /
• pp.1314-1317
• /
• 2011

To evaluate the effects of pulsed electric field (PEF) application on scalder and chiller water on Campylobacter contamination, four different treatments under three different water conditions including hard scalder water ($55^{\circ}C$), soft scalder water ($45^{\circ}C$) and chiller water, were applied as follows: i) a control treatment with no salt and no electric treatment, ii) a PEF only treatment, iii) a PEF treatment with 0.5% salt water, and iv) a PEF treatment with 1% salt water treatment. The use of PEF in hard scalding water showed an effect of reducing Campylobacter when compared to the control during the 200 s timeframe. With the addition of salt, the intervention caused at least 5.81 log CFU/ml reduction of Campylobacter counts after 200 s of PEF exposure. Similar effects were observed under soft scalding conditions. Campylobacter reductions were evident under chilling conditions with up to 2.00 log for PEF only, 5.77 log for PEF+0.5% salt and 2.69 log for PEF+1% salt treatment in water. Therefore, the current PEF setting for the scalder and chiller water can be successfully used to reduce pathogenic loads of Campylobacter on broiler chicken carcasses, and further research may be necessary to apply it in the poultry processing industry.

• Proceedings of the KIEE Conference
• /
• 2001.07c
• /
• pp.1703-1705
• /
• 2001

The pulsed Nd:YAG laser is used widely for materials processing and medical instrument etc. It is important to control the laser energy in those fields using a pulsed Nd:YAG laser. In this paper, constant-frequency current resonant half-bridge inverter and Cockcroft-Walton circuit are used to charge the energy storage capacitor variably. This laser power supply is designed and fabricated which has no high-voltage transformer, less switching losses, compact size and capability in varying the laser output power. Also, the output characteristics of this Nd:YAG laser system are investigated. The tested results are described.