• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.4
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• pp.89-95
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• 2008

In the maritime communication, Orthogonal Frequency Division Multiplexing (OFDM) communication terminal should be operated with low power consumption, because the communication should be accomplished in the circumstance of disaster. Therefore, Low power FFT processor is required to be designed with current mode signal processing technique than digital signal processing. Current- to-Voltage Converter (IVC) is a device that converts the output current signal of FFT processor into the voltage signal. In order to lessen the power consumption of OFDM terminal, IVC should be designed with low power design technique and IVC should have wide linear region for avoiding distortion of signal voltage. To design of one-chip of the FFT LSI and IVC, IVC should have a small chip size. In this paper, we proposed the new IVC with wide linear region. We confirmed that the proposed IVC operates linearly within 0.85V to 1.4V as a function of current-mode FFT output range of -100~100[uA]. Designed IVC will contribute to realization of low-power maritime data communication using OFDM system.

• The Journal of the Acoustical Society of Korea
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• v.20 no.8
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• pp.31-37
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• 2001

Following the recent trends of reducing the size of multimedia devices, we tried for the development of a compact-sized speaker to produce low-frequency sounds efficiently. For this work, equivalent-circuit analysis was used to get fundamental resonant frequency and then the structure of speaker components has been changed appropriately. As a result, an 80mm small-sized speaker was developed. The performance test showed that the resonant frequency of our system is 79 Hz while that of numerical analysis was 81Hz. At a distance of 1m from our speaker, the frequency ranges 80 Hz to 15kHz and the average sound pressure was found to be 84±2 dB. The second (at 400 Hz) and the third (at 100 Hz) high-frequency distortions of our system were 0.5% and 1.8% respectively, which is to be compared with the distortions of 0.9% and 6% in conventional speakers.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.3
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• pp.1195-1211
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• 2016

The emerging video coding standard High Efficiency Video Coding (HEVC) has shown almost 40% bit-rate reduction over the state-of-the-art Advanced Video Coding (AVC) standard but at about 40% computational complexity overhead. The main reason for HEVC computational complexity is the inter prediction that accounts for 60%-70% of the whole encoding time. In this paper, we propose several fast coding unit (CU) encoding schemes based on the Merge mode and motion estimation information to reduce the computational complexity caused by the HEVC inter prediction. Firstly, an early Merge mode decision method based on motion estimation (EMD) is proposed for each CU size. Then, a Merge mode based early termination method (MET) is developed to determine the CU size at an early stage. To provide a better balance between computational complexity and coding efficiency, several fast CU encoding schemes are surveyed according to the rate-distortion-complexity characteristics of EMD and MET methods as a function of CU sizes. These fast CU encoding schemes can be seamlessly incorporated in the existing control structures of the HEVC encoder without limiting its potential parallelization and hardware acceleration. Experimental results demonstrate that the proposed schemes achieve 19%-46% computational complexity reduction over the HEVC test model reference software, HM 16.4, at a cost of 0.2%-2.4% bit-rate increases under the random access coding configuration. The respective values under the low-delay B coding configuration are 17%-43% and 0.1%-1.2%.

• Korean Journal of Head & Neck Oncology
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• v.7 no.1
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• pp.24-34
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• 1991

Lymphangioma is a benign, growth of lymphatic tissue that is present at birth or develops in early childhood, which may cause serious alterations in growth and developmemt. The problems with facial lymphangioma is usually releated directly to their size and to the area of the face which is involved. The lesions themselves may range from small, localized blemishes to huge facial masses involving both soft tissue and underlying bone and causing great distortion and asymmetry. The facial bones are seldom involved, but the natutal evolution of an individual lesion often cannot be accurately predicted when the child is first seen. Any changes in the underlying facial bone could be due either to a direct growth of the lesion into the bone, or secondary to pressure of the lesion growing outside the bone itself. A case of cystic lymphangioma extending from the neck to the tongue is reported. A six-year-old female was admitted because of swelling of the tongue. At that time, the tongue reportedly reached the extraoral size of 7x5x2.5cm and a soft, diffuse swelling of left anterior neck was revealed. The removal of cystic mass including left neck dissection and partial glossectomy were undertaken. The another case of lymphangioma is located on mandibular cheek. A twenty nine-year-old male was admitted because of palpable mass of the left mandibular area and fissure of palate. The radical excision of mass with mandibulectomy of body were undertuken. Thus we reported such a rare case and reviewed the lymphangioma.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.11C
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• pp.925-931
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• 2008

In video coding standard H.264/AVC, variable block size mode algorithm improves compression efficiency but has need of a large amount of computation for various block modes and mode decision. Meanwhile, decided inter block modes depend on the complexity of a block image, and then the more complex a macroblock is, the smaller its block size is. This paper proposes fast inter block mode decision algorithm. It limits valid block modes to the block modes with a great chance for decision using the image complexity and carries out motion estimation rate-distortion optimization with only the valid block modes. In addition to that, it applies fast motion estimation PDE to the valid block modes with only the $16{\times}16$ block mode. The reference software JM 9.5 was executed to estimate the proposed algorithm's performance. The simulation results showed that the proposed algorithm could save about 24.12% of the averaged motion estimation time while keeping the image quality and the bit rate to be -0.02dB and -0.12% on the average, respectively.

• Transactions of Materials Processing
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• v.13 no.8
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• pp.663-670
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• 2004

The bending phenomenon has been known to be occurred by the difference of velocity at the die exit. The difference of velocity at the die exit section can be obtained by the different velocity of billets through the multi-hole container. The difference of velocity at the die exit can be controlled by the two variables, the one of them is the different velocity of extrusion punch through the multi-hole container, the other is the difference of hole diameter of muliti-hole container. In this paper the difference of hole diameter is applied. So it can bend during extruding products because of the different amount of two billets when billets would be bonded in the porthole dies cavity. And the bending curvature can be controlled by the size of holes. The experiments with aluminum material for the curved tube product had been done for circular or rectangular curved tube section. The results of the experiments show that the curved tube product can be formed by the extru-bending process without the defects such as distortion of section and thickness change of wall of tube and folding and wrinkling. The curvature of product can be controlled by shape of cross section and the difference of billet diameters. And it is known that the bonding and extruding and bending process can be done simultaneously in the die cavity by the experiments that rectangular hollow curved tubes could be extruded by porthole dies with four different size billets made of aluminum material. And it shows that bending phenomenon can happen during extruding with for different billets from the analysis by DEFORM-3D.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.7 s.361
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• pp.29-34
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• 2007

This paper presents a novel photonic bandgap (PBG) structure for size reduction and linearity improvement in power amplifier. The proposed structure is a two-dimensional (2-D) periodic lattice patterned on a dielectric slab that does not require nonplanar fabrication process. Throughout the experi-mental results, this structure has more broad stopband and high suppression performance than conventional three cell PBG and distorted uniplanar compact-PBG (DUC-PBG). This new PBG structure can be applied with power amplifier for linearity improvement. The 3rd intermodulation distortion (IMD3) of the power amplifier using new PBG structure is -36.16 dBc for (code division multiple access) CDMA applications. Compared with power amplifier without the proposed PBG structure, improved IMD3 is -13.49 dBc.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.12A
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• pp.1009-1018
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• 2003

A new fading channel estimation technique is proposed for an OFDM based modem In the ITS system. The algorithm is based on the transfer function extraction of the channel using the pilot signals and compensated the channel preceding the equalization. The newly derived algorithm is division-free arithmetic operations allows the faster circuit operation and the smaller circuit size. Proposed techniques compensate firstly the distortion which is generated at fading channels and secondly eliminate inter-symbol interference. All algorithms are suitability estimated and improved for a system implementation using digital circuits. As the results, the circuit size is reduced by 20% of the conventional design and achieved about 10% performance improvement at low SNR under 10dB in case of ITS system adapted 16-QAM mode.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.5
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• pp.2357-2380
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• 2019

In this paper, we investigate the impact of hardware impairments (HWIs) on the performance of a downlink massive MIMO system. We consider a single-cell system with maximum ratio transmission (MRT) as precoding scheme, and with all the HWIs characteristics such as phase noise, distortion noise, and amplified thermal noise. Based on the system model, we derive closed-form expressions for a typical user data rate under two scenarios: when a common local oscillator (CLO) is used at the base station and when separated oscillators (SLOs) are used. We also derive closed-form expressions for the downlink transmit power required for some desired per-user data rate under each scenario. Compared to the conventional system with ideal transceiver hardware, our results show that impairments of hardware make a finite upper limit on the user's downlink channel capacity; and as the number of base station antennas grows large, it is only the hardware impairments at the users that mainly limit the capacity. Our results also show that SLOs configuration provides higher data rate than CLO at the price of higher power consumption. An approach to minimize the effect of the hardware impairments on the system performance is also proposed in the paper. In our approach, we show that by reducing the cell size, the effect of accumulated phase noise during channel estimation time is minimized and hence the user capacity is increased, and the downlink transmit power is decreased.

• Journal of Biomedical Engineering Research
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• v.37 no.1
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• pp.1-6
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• 2016

The biomedical information (heart rate, HRV, $SpO_2$ etc) from the Photoplethysmography (PPG) signal section can be estimated without the motion artifacts if the PPG signal section in the motion artifacts is detected accurately. But the PPG signal is easily exposed to the motion artifacts by the decrease of the medical instrument size and applying as portable or wearable. Besides, it is difficult to completely eliminate the motion artifacts from the PPG signal without distortion and ensure reliability as well. In this paper, the method was suggested to determine the motion artifacts or not on the PPG signal of the section divided into intervals of constant length. By comparing the spectrum of each section, it can be determined whether the motion artifacts are or not after obtaining the spectrum of each section by the Goertzel algorithm. Moreover, an amount of computation while maintaining a high detection rate can be reduced by using the Goertzel algorithm.