• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.1B
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• pp.60-70
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• 2011

IPTV was introduced as the new growth engine of the broadcasting and telecommunications industry and has experienced a high growth rate as its subscribers exceeded 2 million in early 2010. However there have been some doubts on if the IPTV market will keep current growth drift. One of such suspicions is that IPTV market has not been developed by the competitiveness of IPTV industry itself. In addition, the recent slowdown of subscribers' growth and IPTV players' operating at a loss has been suggested as obstacles to the IPTV market growth. This sort of phenomenon has been brought about by ambiguous proposition of IPTV's own value as well as IPTV service positioning gap. To resolve these problems this study empirically investigates what customers want to get from IPTV service by analyzing switching value of IPTV subscribers. This study also identifies which values must be strategically considered to develop next generation IPTV services, in particular mobile IPTV services. Following the investigation, this study analyzes the possible positioning gap of mobile IPTV. Through this analysis, this study suggests which sort of service values need to be reconciled.

• Journal of Biomedical Engineering Research
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• v.20 no.2
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• pp.205-212
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• 1999

When we want to observe and record a patient's EEG in an operating room, the operation of electrosurgical unit(ESU) causes undesirable artifacts with high frequency and high voltage. These artifacts make the amplifiers of the conventional EEG system saturated and prevent the system from measuring the EEG signal. This paper describes a high-performance bipolar EEG amplifier for a CSA (compressed spectral array ) system with reduced ESU artifacts. The designed EEG amplifier uses a balanced filter to reduce the ESU artifacts, and isolates the power supply and the signal source of the preamplifier from the ground to cut off the current from the ESU to the amplifier ground. To cancel the common mode noise in high frequency, a high CMRR(common mode rejection ratio) diffferential amplifier is used. Since the developed bipolar EEG amplifier shows high gain, low noise, high CMRR, high input impedance, and low thermal drift, it is possible to observe and record more clean EEG signals in spite of ESU operation. Therefore the amplifier may be applicable to a high-fidelity CSA system.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.3
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• pp.215-220
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• 1999

$SO_2$and CO gas removal characteristics of a wire-to-cylinder type nonthermal discharge plasma reactor in various applied voltage (-dc, ac, fast rising pulse and high frequency pulse) and a crossed dc magnetic field have been investigated. The experiment has been emphasized on the oxidizing characteristics of $SO_2$ and CO gas by $O_3$ and the applying of a crossed magnetic field, which would induce the cyclotronic and drift motions of electrons making the residual time longer in the removal airgap space. And it also would enhance the energy of electrons and the electrophysicochemical actions to remove the pollutant gases effectively. It is found thatthe corona onset voltage and the breakdown voltage were decreased with increasing the crossed magnetic field and decrease initial fed $SO_2$and CO concentration. As a result, a higher ozone generation and $SO_2$ and CO gas removal rate of 20[%] can be obtained with -dc, ac and fast rising pulse corona discharges in the crossed dc current-induced magnetic field. But high frequency pulse didn't show effect in applying of a crossed magnetic field.

• Journal of Power Electronics
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• v.13 no.3
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• pp.369-380
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• 2013

Direct torque control based on space vector modulation (SVM-DTC) protects the DTC transient merits. Furthermore, it creates better quality steady-state performance in a wide speed range. The modified method of DTC using SVM improves the electrical magnitudes of asynchronous machines, such as minimizing the stator current distortions, the stator flux with electromagnetic torque without ripple, the fast response of the rotor speed, and the constant switching frequency. In this paper, the proposed method is based on two new control strategies for direct torque control with space vector modulation. First, fuzzy logic control is used instead of the PI torque and a PI flux controller to minimizing the torque error and to achieve a constant switching frequency. The voltages in the direct and quadratic reference frame ($V_d$, $V_q$) are achieved by fuzzy logic control. In this scheme, the switching capability of the inverter is fully utilized, which improves the system performance. Second, the close loop of stator flux estimation based on the voltage model and a low pass filter is used to counteract the drawbacks in the open loop of the stator flux such as the problems saturation and dc drift. The response of this new control strategy is compared with DTC-SVM. The experimental and simulation results demonstrate that the proposed control topology outperforms the conventional DTC-SVM in terms of system robustness and eliminating the bad outcome of dc-offset.

• Korean Journal of Materials Research
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• v.17 no.10
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• pp.509-515
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• 2007

In order to fabricate adhesiveless 2-layer flexible copper clad laminate (FCCL) used for COF (chip on film) with high peel strength, polyimide (PI; Kapton-EN, $38\;{\mu}m$) surface was modified by reactive $O_2^+$ and $N_2O^+$ ion beam irradiation. 300 mm-long linear electron-Hall drift ion source was used for ion irradiation with ion current density (J) higher than $0.5\;mA/cm^2$ and energy lower than 200 eV. By vacuum web coating process, PI surface was modified by linear ion source and then 10-20 nm thick Ni-Cr and 200 nm thick Cu film were in-situ sputtered as a tie layer and seed layer, respectively. Above this sputtered layer, another $8-9{\mu}m$ thick Cu layer was grown by electroplating and subsequently acid and base resistance and thermal stability were tested for examining the change of peel strength. Peel strength for the FCCLs treated by both $O_2^+$ and $N_2O^+$ ion irradiation showed similar magnitudes and increased as the thickness of tie layer increased. FCCL with Cu (200 nm)/Ni-Cr (20 nm)/PI structure irradiated with $N_2O^+$ at $1{\times}10^{16}/cm^2$ ion fluence was proved to have a strong peel strength of 0.73 kgf/cm for as-received and 0.34 kgf/cm after thermal test.

• Current Optics and Photonics
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• v.2 no.2
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• pp.195-202
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• 2018

A Scanning Rayleigh Doppler lidar for wind profiling based on a non-polarized beam splitter cube optically contacted FPI is developed for wind measurement from high troposphere to low stratosphere in 5-35 km. Non-polarized beam splitter cube optically contacted to the FPI are used for a stable optical receiver. Zero Doppler shift correction is used to correct for laser or FPI frequency jitter and drift and the timing sequence is designed. Stability of the receiver for Doppler shift discrimination is validated by measuring the transmissions of FPI in different days and analyzed the response functions. The maximal relative wind deviation due to the stability of the optical receiver is about 4.1% and the standard deviation of wind velocity is 1.6% due to the stability. Wind measurement comparison experiments were carried out in Jiuquan ($39.741^{\circ}N$, $98.495^{\circ}E$), Gansu province of China in 2015, showing good agreement with radiosonde result data. Continuous wind field observation was performed from October 16th to November 12th and semi-continuous wind field of 19 nights are presented.

• Steel and Composite Structures
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• v.39 no.1
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• pp.65-80
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• 2021

Irregularities of a building in plan and elevation, which results in the change in stiffness on different floors highly affect the seismic performance and resistance of a structure. This study motivated to investigate the seismic responses of high-rise steel-frame buildings of twelve stories with various stiffness irregularities. The building has five spans of 3200 mm distance in both X- and Z-directions in the plan. The design package SAP2000 was adopted for the design of beams and columns and resulted in the profile IPE500 for the beams of all floors and box sections for columns. The column cross-section dimensions vary concerning the number of the story; one to three: 0.50×0.50×0.05m, four to seven: 0.45×0.45×0.05 m, and eight to twelve: 0.40×0.40×0.05 m. Real recorded ground accelerations obtained from the Vrancea earthquake in Romania together with dead and live loads corresponding to each story were considered for the applied load. The model was validated by comparing the results of the current method and literature considering a three-bay steel moment-resisting frame of eight-story height subject to seismic load. To investigate the seismic performance of the buildings, the time-history analysis was performed using ABAQUS. Deformed shapes corresponding to negative and positive peaks were provided followed by the story drifts and fragility curves which were used to examine the probability of collapse of the building. From the results, it was concluded that regular buildings provided a seismic performance much better than irregular buildings. Furthermore, it was observed that building with torsional irregularity was more vulnerable to seismic failure.

• Journal of the Earthquake Engineering Society of Korea
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• v.27 no.5
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• pp.203-211
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• 2023

For fast-built and safe precast concrete (PC) construction, the dry mechanical splicing method is a critical technique that enables a self-sustaining system (SSS) during construction with no temporary support and minimizes onsite jobs. However, due to limited experimental evidence, traditional wet splicing methods are still dominantly adopted in the domestic precast industry. For PC beam-column connections, the current design code requires achieving emulative connection performances and corresponding structural integrity to be comparable with typical reinforced concrete (RC) systems with monolithic connections. To this end, this study conducted the standard material tests on mechanical splices to check their satisfactory performance as the Type 2 mechanical splice specified in the ACI 318 code. Two PC beam-column connection specimens with dry mechanical splices and an RC control specimen as the special moment frame were subsequently fabricated and tested under lateral reversed cyclic loadings. Test results showed that the seismic performances of all the PC specimens were fully comparable to the RC specimen in terms of strength, stiffness, energy dissipation, drift capacity, and failure mode, and their hysteresis responses showed a mitigated pinching effect compared to the control RC specimen. The seismic performances of the PC and RC specimens were evaluated quantitatively based on the ACI 374 report, and it appeared that all the test specimens fully satisfied the seismic performance criteria as a code-compliant special moment frame system.

• Journal of the Korean earth science society
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• v.43 no.6
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• pp.661-679
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• 2022

Plate tectonics, with the continental drift theory and later strongly supported by the sea-floor spreading theory with evidence of paleo-geomagnetic fields, ocean floor sediments, successfully explained the slow but continuous movements of rigid lithospheres in geological time. Initially, plate motions were described as relative movements between adjacent plates, mainly based on paleo-geomagnetic reversal data. The advent of space geodetic techniques in the 1980s enabled direct measurements of plate velocities and assessment of deformations within certain regions. In this review, early relative plate motion models are briefly summarized, the no-net-rotation frame theory and corresponding models are explained, and the characteristics of the most recent models that incorporate intraplate deformation are described. Additionally, the plate motion section of the International Terrestrial Reference Frame is introduced, and a few recent case studies of local plate motion are briefly described; for example, in South America, Europe, Antarctica, and Turkey. Finally, studies of plate motion in northeastern Asia focusing on the Korean Peninsula are introduced.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.18 no.2
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• pp.55-61
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• 1982

Simultaneous investigations for drift bottle and dye diffusion experiment were carried out in Suyeong bay. Seawater in Suyeong bay flowed differently in the vicinity of Suyeong river estuary and Nam-cheon Dong respectively. The speed of current did not exceed one knot in this bay. The dye patch moved to Kwangan beach in the dye diffusion experiment. The relationship between apparent diffusivity and diffusion time was appeared as Ka=0.0025t super(1.9). The variance was calculated to be 2.9 power of the diffusion time. And the exponent diffusivity versus the scale of diffusion time was appeared to be 1.3.