• International Journal of Oral Biology
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• v.35 no.4
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• pp.137-144
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• 2010

To evaluate the biohazard properties of an extremely low frequency electromagnetic field (ELF-EMF), we explored the physical properties of the ELF-EMF that generates the electric current induction in the secondary coil from the chamber of a primary solenoid coil. We subsequently explored the biological effects of a strong alternating electromagnetic field (EMF), ranging from 730-960 Gauss, on the mouse testis. Mice were exposed to an alternating EMF field induced by a rectangular electric current at 1, 7, 20, 40, and 80 Hertz, for 1, 3, 5, and 7 hours. The mouse testes were examined for proliferative activity and apoptosis using the in situ terminal deoxynucleotidyl transferase (TdT) method and by immunostaining of proliferating cell nuclear antigen (PCNA), respectively. We found that the electric currentm induction increased in the 6-8 Hertz range, and that exposure to an ELF-EMF induced the apoptosis of mouse spermatocytes. In situ TdT staining was found to be most prominent in 7 Hertz group, and gradually reduced in the 20, 40, and 80 Hertz groups. These data suggest that a strong EMF can induce reproductive cell death within a short time, and the harmful effects of the EMF are maximal at low frequency alternating EMFs.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.323-326
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• 1997

In this study, we investigated the circardian rhythm of complexity of cardiac dynamics in humans. Dynamic 24-hour electrocardiographic recordings were obtained from 30 healthy ambulant subjects aged 41 to 50 years. or each recordings, normalized low frequency (0.04-0.1 hertz) and high frequency (>0.15 hertz) component are calculated. our different indexes obtained from separate algorithms of nonlinear dynamics - approximate entropy, correlation dimension, Lyapunov exponent and fractal dimension - were calculated. During early morning, low frequency component rose rapidly with concomitant withdrawl of high frequency component. All the our indexes of nonlinear dynamics showed remarkably same circardian rhythm: an early morning dip preceded by a steep decline during late night, a gradual recovery during evening and a peak around midnight. These data indicate that the simultansous losses of all of the our different mechanisms of nonlinear control of heart rate during early morning, concomitent with the surge of symapathetic activity and reduction of vagal activity, may contribute to the increased incidence of cardiovascular events during morning hours.

• Progress in Superconductivity
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• v.7 no.2
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• pp.109-113
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• 2006

The Arithmetic Logic Unit (ALU) is a core element of a computer processor that performs arithmetic and logic operations on the operands in computer instruction words. We have developed and tested an RSFQ multi-bit ALU constructed with half adder unit cells. To reduce the complexity of the ALU, We used half adder unit cells. The unit cells were constructed of one half adder and three de switches. The timing problem in the complex circuits has been a very important issue. We have calculated the delay time of all components in the circuit by using Josephson circuit simulation tools of XIC, $WRspice^{TM}$, and Julia. To make the circuit work faster, we used a forward clocking scheme. This required a careful design of timing between clock and data pulses in ALU. The designed ALU had limited operation functions of OR, AND, XOR, and ADD. It had a pipeline structure. The fabricated 1-bit, 2-bit, and 4-bit ALU circuits were tested at a few kilo-hertz clock frequency as well as a few tens giga-hertz clock frequency, respectively. For high-speed tests, we used an eye-diagram technique. Our 4-bit ALU operated correctly at up to 5 GHz clock frequency.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.2
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• pp.125-134
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• 1992

This paper presents a cycloconverter with an LC resonant circuit for an induction motor drive. The cycloconverter can keep input displacement factor at 1.0 by independently controlling real and reactive power under any load conditions. Furthermore it can keep power factor at about 1.0 since input and output current waveforms are nearly sinusoidal. Since it uses high frequency resonant circuit for commutation source, it can produce an output voltage of hundreds of hertz. Since it is also possible to make a system of high capacity using the cycloconverter, it is appropriate to drive motors with high speed and high capacity as well as general purpose motors, In this paper, we describe the operating principles of the cycloconverter and power control algorithms, and analyze its waveforms and present its characteristics. Expermental results are shown for the volts/hertz control of the induction motor and the validity of the proposed model is verified.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.04a
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• pp.131-138
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• 1998

In this study, a numerical procedure to solve a contact problem has been developed. The procedure takes the advantage of signal processing technique in frequency domain to achieve the shorter computer processing time. The Boussinesq's equation was adopted as the response function. This procedure is applicable to the non-periodic surface profile as well as the periodic one. The validity of this procedure has been established by comparing the numerical results with the exact solutions. The effectiveness of this procedure is lied on the shorter computing time than any other contact analysis algorithm.

• 제어로봇시스템학회:학술대회논문집
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• 1999.10a
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• pp.274-277
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• 1999

This paper is concerned with estimating the mass of a loose part in the steam generator of a nuclear power plant. Although there is the basic principle known as “Hertz Theory”for estimating mass and energy of a spherical part impacted on an infinite flat plate, the theory is not directly applicable because real plants do not comply with the underlying ideal assumptions. (Say, the steam generator is of a cylindrical and hemisphere shape.) In this work, a practical method is developed based on the basic theory and considering amplitude and energy attenuation effects. Actually, the impact waves propagating along the plate to the sensor locations become significantly different in shape and frequency spectrum from the original waveform due to the plate and surrounding conditions, distance attenuation and damping loss. To show the validity of the present mass estimation algorithm, it has been applied to the mock-up impact test data and also to real plant data. The results show better performance comparing to the conventional Hertz schemes.

• Journal of the Semiconductor & Display Technology
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• v.9 no.1
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• pp.1-4
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• 2010

We investigated a linear carbon nanotube motor serving as the key building block for nano-scale motion control by using molecular dynamics simulations. This linear nano-motor, is based on the electrostatically telescoping multi-walled carbon-nanotube with ultralow intershell sliding friction, is controlled by the gate potential with the capacitance feedback sensing. The resonant harmonic peaks are induced by the interference between the driving frequencies and its self-frequency. The temperature is very important factor to operate this nanomotor.

• Progress in Superconductivity
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• v.8 no.2
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• pp.181-185
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• 2007

For more than two decades Nb trilayer ($Nb/Al_2O_3/Nb$) process has been serving as the most stable fabrication process of the Josephson junction integrated circuits. Fast development of semiconductor fabrication technology has been possible with the recent advancement of the fabrication equipments. In this work, we took an advantage of advanced fabrication equipments in developing a superconducting Arithmetic Logic Unit (ALU) by using Nb trilayers. The ALU is a core element of a computer processor that performs arithmetic and logic operations on the operands in computer instruction words. We used DC magnetron sputtering technique for metal depositions and RF sputtering technique for $SiO_2$ depositions. Various dry etching techniques were used to define the Josephson junction areas and film pattering processes. Our Nb films were stress free and showed the $T{_c}'s$ of about 9 K. To enhance the step coverage of Nb films we used reverse bias powered DC magnetron sputtering technique. The fabricated 1-bit, 2-bit, and 4-bit ALU circuits were tested at a few kilo-hertz clock frequency as well as a few tens giga-hertz clock frequency, respectively. Our 1-bit ALU operated correctly at up to 40 GHz clock frequency, and the 4-bit ALU operated at up to 5 GHz clock frequency.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.1
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• pp.27-33
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• 2011

In this paper, for a software-based Global Positioning System receiver (SGR), the principle capturing Global Positioning System (GPS) signal is researched extensively in order to analyze the processing of the GPS raw data signal at the lowest level, and the process of capturing the GPS signal was simulated by Matlab. The simulation results show the accuracy and the feasibility of this method, which is comparable to study under a true environment. We know that the improvement of the receiving facilities is of very vital significance to the performance of this system, and the fine frequency can be found through comparing phases within a few tens of Hertz.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.389-393
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• 2003

This paper presents circuit modeling and characterization of silicon-based on-chip integrated inductors in Giga Hertz range for wireless communication products. We compare several different designs of on-chip inductors for self-resonant frequency and quality factor. The measurement data could be used as a design guide for manufacturing practical spiral inductors for wireless applications. We provide the equivalent inductor circuit parameters from the actual measurement data.