• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.24 no.6B
• /
• pp.1015-1023
• /
• 1999

We propose nonlinear processing schemes for robust acquisition of direct-sequence spread spectrum (DS/SS) signals in wideband pulse jamming. To mitigate the interference effect due to impulse-like wideband jamming signals, the received signal is preprocessed by using the median filter, a simple order statistic filter Since only parts of the PN sequence are used for rapid acquisition, it is indispensable for analytic design of an acquisition scheme to have an appropriate model of the partial PN signal. The partial correlation of the median filtered PN signal is approximated by a two-piecewise linear model using an approximate upper bound. The acquisition performance of the proposed schemes is compared to that of other schemes. Finally, the analytic design is verified by computer simulation.

• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.46 no.5
• /
• pp.1-7
• /
• 2009

In recent years, compressed sensing (CS) algorithm has been studied in various research areas including medical imaging. To use the CS algorithm, the signal that is to be reconstructed needs to have the property of sparsity But, most medical images generally don't have this property. One method to overcome this problem is by using sparsifying transform. However, MR imaging, compared to other medical imaging modality, has the unique property that by using appropriate image acquisition pulse sequences, the image contrast can be modified. In this paper, we propose the possibility of applying the CS algorithm with non-sparsifying transform to the pulse sequence modified MR images and improve the reconstruction performance of the CS algorithm by using an appropriate sparsifying transform. We verified the proposed contents by computer simulation using Shepp-Logan phantom and in vivo data.

• Proceedings of the KSMRM Conference
• /
• 1997.10a
• /
• pp.39-39
• /
• 1997

• Journal of The Korean Radiological Technologist Association
• /
• v.29 no.1
• /
• pp.274-274
• /
• 2003

• Journal of The Korean Radiological Technologist Association
• /
• v.29 no.1
• /
• pp.276-276
• /
• 2003

• Bulletin of the Korean Chemical Society
• /
• v.22 no.5
• /
• pp.439-440
• /
• 2001

• Journal of the Korean Society of Radiology
• /
• v.14 no.7
• /
• pp.957-964
• /
• 2020

T2 FLAIR sequence of MRI in Acute Ischemic Stroke patients is meaningful to those who have the diagnosis of cerebral hemorrhage and neurological deficiency, including the detection of cerebral infarction around Cerebrospinal fluid. However, because of the long acquisition time and mutative motion artifacts caused by movement, It is difficult to take the MRI image acquisition for non-cooperative patients who need to apply a rapid image acquisition. In this study, we applied the EPI-FLAIR sequence, which is one of the fastest pulse sequences in use, which is a combination of EPI sequence and T2 FLAIR sequence, to patients with acute ischemic cerebral infarction. Based on the qualitative and quantitative evaluation results of the EPI-FLAIR and T2 FLAIR image, we will evaluate the diagnostic usefulness of the EPI-FLAIR sequence.

• Proceedings of the KIEE Conference
• /
• 2001.07c
• /
• pp.1631-1633
• /
• 2001

In manufacturing processes, various and suitable pulse shapes are required for the purpose of material processing and the pulseshape is regarded as a dominant factor due to the specific property of processing materials. Therefore, in this study, a variable pulse width, high duty cycle Pulse Forming Network(PFN) is constructed by time sequently. The power supply for this experiment consists of three switching circuits. The PFN elements operate at low voltage and drive the primary of HV leakage transformer. The secondary of the transformer has a full-wave rectifier, which passes the pulse energy to the load in a continuous sequence of properly phased and nested increments. We investigated laser pulse width as various delay time among three switching circuit. As a result, we tan obtain various laser pulse width from about 4ms to 10ms. The maximum laser pulse width obtained at this experiment was about 10ms at delay time of 4ms among each switching circuit.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.19 no.5
• /
• pp.399-406
• /
• 2014

This study investigates the structure and operation of the ITER VS converter and proposes a sequence control method for six series-connected VS converters to reduce reactive power. The operation and the proposed sequence control method are verified through RTDS simulation. The ITER VS converter must supply voltage/current to the superconducting magnets for plasma current vertical stabilization, and the four-quadrant operation must proceed without a zero-current discontinuous section. The operation mode of the VS converter is separated into a 12- and 6-pulse circulating current and transition modes according to the size of the load current. The output voltage of the unit VS converter is limited because of the rated voltage; however, the superconducting coil must increase the operating output voltage. Thus, the VS converter must be connected in a 6-series to provide the required operating output voltage. The output voltage of the VS converters is controlled continuously; however, reactive power is limited within a minimized value of the grid. In this study, the unit converter is compared with converters connected in a 6-series to determine a suitable sequence control method. The output voltage is the same in all cases, but the maximum reactive power is reduced from 100% to 73%. This sequence control method is verified through RTDS simulation.

• Journal of Power Electronics
• /
• v.19 no.2
• /
• pp.560-568
• /
• 2019

This paper studies the inherent relationship between currents and zero-sequence components. Then a precise algorithm is proposed to calculate the injected zero-sequence component to control the DC-Link neutral-point voltage balance, which can result in a more efficient and flexible neutral point voltage balance with a desirable performance. In addition, it is shown that carried-based PWM with the calculated zero-sequence component scheme can be equivalent to space-vector pulse-width modulation (SVPWM). Based on the proposed method, the optimal zero-sequence component of the feasible modulation indices is analyzed. In addition, the unbalanced load limitation of the DC-Link neutral-point voltage balance control is also revealed. Simulation and experimental results are shown to verify the validity and practicality of the proposed algorithm.