• The Journal of Korean Academy of Sensory Integration
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• v.13 no.2
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• pp.75-84
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• 2015

Objective : The aim of this study was to provide mechanism information of a link between arousal and sensory modulation to increase understanding of neurophysiological study. Subject : Optimal arousal state of a child is an important issue in sensory integration therapy. Limbic system and reticular formation are related to sensory modulation by sensory input. Sensory inputs processes from reticular formation to cortex via ascending reticular activation system for moderate arousal. A lot of neurotransmitters such as cholinergic neurons and monoamin neurons help this processes. Mechanism of arousal was measured by functions of central nervous system (CNS) and autonomic nervous system (ANS) using objective tools such as an electroencephalogram (EEG) and electrodermal responses. Functions of CNS and ANS showed differences between normal children and children with disabilities. Optimal sensory input using sensory integration therapy for children with disabilities helps to act reticular formation, limbic system, and cortex and to maintain appropriate arousal. Conclusion : Such quantitative studies by using neurophysiological methods provide evidence for sensory integration therapy.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.5A
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• pp.473-483
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• 2004

In this paper, we numerically investigated the optimum pump light power best compensating for pulse distortion due to both chromatic dispersion and self phase modulation (SPM) as a function of channel input power in 8 channel ${\times}$ 40 Gbps wavelength division multiplexing (WDM systems. Also we investigated the allowable maximum channel input power dependence on modulation format and fiber dispersion coefficient in the various pump light power of OPC. The considered WDM transmission system is based on path-averaged intensity approximation (PAIA) mid-span spectral inversion (MSSI) compensation method, which has highly-nonlinear dispersion shifted fiber (HNL-SDF) as nonlinear medium of optical phase conjugator (OPC) in the mid-way of total transmission line. We confirmed that optimal pump light power of HNL-DSF OPC depend on modulation format, initial channel input power, total transmission length and fiber dispersion. But optimal pump light power of HNL-DSF OPC must be selected to make power conversion ratio to almost unity. And we confirmed that, if we allow a 1 dB eye opening penalty (EOP), the tolerable maximum channel input power is increased by using RZ than NRZ as modulation format when pump light power of HNL-DSF OPC is not optimal value but another values.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.605-610
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• 1991

In inverter system for driving induction motor, the output harmonics are hamrful in induction motor drive because it leads to ripple torque and induction interference. For electrical drives using PWM(Pulsewidth Modulation) inverters and ac motors, the methods for efficiency optimal control have been developed. In this paper, two different PWM methods for inverter and voltage control technique are described. In order to reduce or minimize losses, various forms of PWM strategy such as, PM (Positive Modulation) and NM (Negative Modulation) are discussed. The results show the feasibility of obtaining practically sinusoidal output waveforms which are highly desirable in most inverter application.

• Journal of Korea Multimedia Society
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• v.8 no.12
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• pp.1623-1630
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• 2005

Adaptive modulation and coding (AMC), which has a number of variation levels in accordance with the fading channel variation, is a promising technique for communication systems. In this paper, we present an AMC method using the cluster in OFDM system for bandwidth efficiency and performance improvement. The AMC schemes applied into each cluster or some clusters are determined by the minimum or the average SNR value among all the sub carriers within the corresponding cluster. It is important to find the optimal information on cluster because AMC performance can be varied according to the number and position of cluster. It is shown by computer simulation that the AMC method outperforms the fixed modulation in terms of bandwidth efficiency and its performance can be determined by the position and number of clusters.

• Journal of Korea Multimedia Society
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• v.9 no.12
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• pp.1628-1635
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• 2006

A new frequency-modulated m-sequence correlation technique was described. It has. been seen that the frequency modulation scheme leads to higher signal-to-noise ratio than direct sequencing and less hardware effort than PSK modulation scheme. The operating frequency of the correlation system was deduced. The optimal frequency for the frequency-modulated m-sequence correlation system should be 1.35 times of the center frequency of the transducer. The application of this correlation technique to electromagnetic ultrasonic system was computer-simulated.

• Journal of Power Electronics
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• v.16 no.2
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• pp.473-479
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• 2016

In this paper, the PSC PWM method is chosen as the optimal modulation method for a 20MW VSC HVDC, with consideration of the harmonic distortion of the output voltage, the switching frequency, and the control implementation difficulty. In addition, a new PSC PWM method is proposed in order to achieve an easy application and to solve the redundant control problems encountered in the previous PSC PWM method. To verify the proposed PSC PWM method, PSCAD/EMTDC simulations for an 11-level MMC RTDS HILS test and an 11-level MMC prototype converter test were performed. As can be seen from the results of these tests, the proposed PSC PWM method shows good results in an 11-level MMC with redundant sub-modules.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.527-533
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• 1998

An optimized PWM switching strategy for an induction motor voltage control is developed and demonstrated. Space vector modulation in voltage source inverter offers improved DC-bus utilization and reduced commutation losses, and has been therefor recognizedas the perfered PWM method, especially in the case of digital implementation. Three-phase invertor voltage control by space vector modulation consists of switching between the two active and one zero voltage vector by using the proposed optimal PWM algorithm. The prefered switching sequence is defined as a function of the modulation index and period of a carrier wave. The sequence is selected by suing the inverter switching losses and the current ripple as the criteria. For low and medium power application, the experimental results indicate that good dynamic response and reduced harmonic distortion can be achieved by increasing switching frequency.

• Journal of Communications and Networks
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• v.9 no.2
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• pp.136-140
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• 2007

In this paper, an adaptive minimum transmit power modulation scheme under constant data rate and fixed bit error rate (BER) for the multiple-input multiple-output (MIMO) system is proposed. It adjusts the modulation order and allocates the transmit power to each spatial sub-channel when meeting the user's requirements at the cost of minimum transmission power. Compared to the other algorithm, it can obtain good performance with lower computational complexity and can be applied to the wireless communication system. Computer simulation results present the efficiency of the proposed scheme. And its performance under different channel condition has been compared with the other algorithm.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.739-741
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• 1993

This paper deals with the Improvement of inverter output waveform with space vector modulation using the DSP-chip. The proposed scheme can be considered as a alternative of the conventional, subharmonic method. This scheme features a maximum output voltage that is 15% greater. The number of switchings is also 30% less than the one obtained by subharmonic modulation method(SHM) A performance function(PF) which is the time integral function of the inverter output voltage is introduced in this paper. An optimal PWM pattern is obtained by minimizing the distortion factor of performance function. The experiment was carried out with an TMS320C25.

• Journal of Web Engineering
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• v.20 no.6
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• pp.1813-1828
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• 2021

In a computing environment, higher resolutions generally require more memory bandwidth, which inevitably leads to the consumption more power. This may become critical for the overall performance of mobile devices and graphic processor units with increased amounts of memory access and memory bandwidth. This paper proposes a lossless compression algorithm with a multiple differential pulse-code modulation variable sign code Golomb-Rice to reduce the memory bandwidth requirement. The efficiency of the proposed multiple differential pulse-code modulation is enhanced by selecting the optimal differential pulse code modulation mode. The experimental results show compression ratio of 1.99 for high-efficiency video coding image sequences and that the proposed lossless compression hardware can reduce the bus bandwidth requirement.