• JSTS:Journal of Semiconductor Technology and Science
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• v.6 no.3
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• pp.154-161
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• 2006

This paper describes the new types of ngative differential resistance (NDR) IC applications which use a monolithic quantum-effect device technology based on the RTD/HBT heterostructure design. As a digital IC, a low-power/high-speed MOBILE (MOnostable-BIstable transition Logic Element)-based D-flip flop IC operating in a non-return-to-zero (NRZ) mode is proposed and developed. The fabricated NRZ MOBILE D-flip flop shows high speed operation up to 34 Gb/s which is the highest speed to our knowledge as a MOBILE NRZ D-flip flop, implemented by the RTD/HBT technology. As an analog IC, a 14.75 GHz RTD/HBT differential-mode voltage-controlled oscillator (VCO) with extremely low power consumption and good phase noise characteristics is designed and fabricated. The VCO shows the low dc power consumption of 0.62 mW and good F.O.M of -185 dBc/Hz. Moreover, a high-speed CML-type multi-functional logic, which operates different logic function such as inverter, NAND, NOR, AND and OR in a circuit, is proposed and designed. The operation of the proposed CML-type multi-functional logic gate is simulated up to 30 Gb/s. These results indicate the potential of the RTD based ICs for high speed digital/analog applications.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.12
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• pp.16-22
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• 2020

The characteristics of the LCL filter for grid-connected inverters have been discussed in academia and industry. An online simulation tool was applied to compare and analyze the difference between the LCL filter and L filter. LCL filters were modeled and simulated using a range of professional simulation simulators, and the LCL filters were found to have good filtering effects for high-frequency harmonics. First, this paper summarizes the transfer functions of the LCL filter and provides the Bode plot diagram. The accuracy and validity of the filter attenuation characteristics were confirmed by a fast Fourier transform based on off-line simulation tools, such as PSIM and MATLAB, depending on the given parameters of the LCL filter. Finally, the Typhoon HIL402 real-time simulation was performed for hardware in the loop simulation to verify the actual filtering characteristics of the LCL filter.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.6
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• pp.739-745
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• 2017

Many studies have been conducted to reduce environmental pollution by ships and reduce fuel consumption. As part of this effort, research on power conversion systems through DC distribution systems that link renewable energy with conventional power grids has been pursued as well. The diode rectifiers currently used include many lower harmonics in the input current of the load and distort supply voltage to lower the power quality of the whole system. This distortion of voltage waveforms causes the malfunctions of generators, load devices and inverter pole switching elements, resulting in a large number of switching losses. In this paper, a controller is presented to improve DC output waveforms, the input Power Factor and the THD of an AFE type PWM rectifier used for PLL. DC output voltage waveforms have been improved, and the input Power Factor can now be matched to the unit power factor. In addition, the THD of the input power supply has been proven by simulation to comply with the requirements of IEEE Std514-2014.

• Proceedings of the KIPE Conference
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• 2009.11a
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• pp.105-110
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• 2009

The On Line Electric Vehicles(OLEV) that can pick up inductive power from underground coils on driving with high efficiency have been developed this year, and is now proposed in this paper. The IPS(Inductive Power Supply) system consists of power supply inverters, power supply rails, pick up modules, and a regulator. There are 3 generations of IPS have been developed so far, and the $4^{th}$ generation IPS is being developed. The $1^{st}$ generation has been demonstrated this Feb. 27, which is equipped with mechanically auto tracking pick-up module with 1cm air gap, and showed 80% power efficiency. The $2^{nd}$ generation IPS applied to an 120kW (average)/240kW(peak) motor powered electric bus has 17cm air gap with 72% power efficiency. For the $2^{nd}$ generation IPS, the Power supply inverter has 440V, 3phase input and 200A @ 20kHz output. The test power supply rail of 240m long is segmented by 60m each, where newly developed core structure and power cable are constructed under the road covered with asphalt of 5cm thickness. The pick-up modules which consist of core, winding wire, and rectifiers are fixed to the bottom of the bus which can carry more than 40 passengers and can pick up max. 60kW. To remove parasitic component and to transfer maximum power between them resonant circuit topology is applied to the primary and secondary sides. The EMF level is below 62.5mG at 1.75m from the center of the road to meet the regulation. Several effective ways of reducing EMF levels have been developed. In addition, effective ways to solve problems related high frequency power cables buried in ground and it's proof from soil have been studied also. This development shows that the IPS system is capable of supplying enough power to the pick-up of OLEV and can reduce battery size, weight and cost, which means the IPS with OLEV is one of the best candidate for EV.

• Journal of the Korean Society for Railway
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• v.16 no.1
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• pp.7-13
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• 2013

A scaled version of a roller rig is developed to demonstrate the dynamic characteristics of a railway vehicle for academic purposes. This rig is designed based on Jaschinski's similarity law. It is scaled to 1/10 of actual size and allows 9-DOF motion to examine the up and down vibration of a train set. The test rig consists of three sub-hardware components: (i) a driving roller mechanism with a three-phase AC motor and an inverter, (ii) a bogie structure with first and second suspensions, and (iii) the vehicle body. The motor of the rig is capable of 3,600rpm, allowing the test to simulate a vehicle up to a maximum speed of 400Km/hr. Because bearings and joints are properly connected to the sub-structures, various motion analyses, such as a lateral, pitching, and yawing motion, are allowed. The slip motion between the rail and the wheel set is also monitored by several sensors mounted in the rig. After the construction of the hardware, an experiment is conducted to obtain the natural frequencies of the dynamic behavior of the specimen. First, the test rig is run and data are collected from six sets of accelerometers. Then, a numerical analysis of the model based on the ADAMS program is derived. Finally, the measurement data of the first three fundamental frequencies are compared to the analytical result and the validation of the test rig is conducted. The results show that the developed roller rig provides good accuracy in simulating the dynamic behavior of the vehicle motion. Although the roller rig designed in this paper is intended for academia, it can easily be implemented as part of a dynamic experiment of a bogie and a vehicle body for a high-speed train as part of the research efforts in this area.

• Progress in Medical Physics
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• v.16 no.1
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• pp.10-15
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• 2005

IAEA's guidance levels have been provided for western people to the end. Guidance levels lower than the IAEA'S will be necessary in view of Korean people's proportions. Therefore, we need to develope the standard doses for Korean people. And we conducted a nationwide survey of patient dose from x-ray examinations in Korea. In this study, the 278 institutions were selected from Members Book of Korean Hospital Association. The valid response rate was approximately 57.9%. Doses were calculated from the questionnaires by NDD method. We obtained the results were as follows; 1) General radiographic equipments were distributed for 42.0%, fluoroscopic equipments 29.4%, dental equipments 13.2%, CT units 8.1 % and mamographic units 7.2%. 2) According to classification by rectification, three-phase equipments were 29.9%, inverter-type generators 29.5%, single-phase equipments 25.5%, constant voltage units 9.0% and unknown units 6.0%. 3) According to classification by receptor system, film-screen types were 46.8%, CR types 26.8%, DR types 17.7% and unknown types 8.9%. 4) The number of examinations were chest 49.2%, spine 16.8% and abdomen 12.7%. 5) Patient doses were head AP 3.44 mGy, abdomen AP 4.25 mGy and chest PA 0.39 mGy.