• Journal of Power Electronics
• /
• v.3 no.2
• /
• pp.99-114
• /
• 2003

This paper presents a feasible development on a highly accurate quick response adjustable speed drive implementation fur general purpose induction motor which operates on the basis of sensorless slip frequency type vector controlled sine-wave PWM inverter with an automatic tuning machine parameter estimation schemes. In the first place, the sensorless vector control theory on the three-phase voltage source-fed inverter induction motor drive system is developed in slip frequency based vector control principle. In particular, the essential procedure and considerations to measure and estimate the exact stator and rotor circuit parameters of general purpose induction motor are discussed under its operating conditions. The speed regulation characteristics of induction motor operated by the three-phase voltage-fed type current controlled PWM inverter using IGBT's is illustrated and evaluated fur machine parameter variations under the actual conditions of low frequency and high frequency operations for the load torque. In the second place, the variable speed induction motor drive system, employing sensorless vector control scheme which is based on three -phase high frequency carrier PWM inverter with automatic toning estimation schemes of the temperature -dependent and -independent machine circuit parameters, is practically implemented using DSP-based controller. Finally, the dynamic speed response performances for largely changed load torque disturbances as well as steady state speed vs. torque characteristics of this induction motor control implementation are illustrated and discussed from an experimental point of view.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.7B
• /
• pp.632-641
• /
• 2006

Recently FCC has considered about the unlicensed device operation in licensed bands. However, this operation can give the harmful interference to the existent licensed system while unlicensed devices operate. Therefore, there should be strict requirements to protect licensed system. So in this paper we propose dynamic frequency selection method in the MAC layer, which is based on the cognitive radio technology. The proposed dynamic frequency selection method creates channel lists after sensing the licensed channels. And it helps the CR base station immediately to moves the current channels that are used by the unlicensed system to other available bands dynamically when a licensed system's signal is detected. This method can reduce interference that is caused by unlicensed devices. In addition, it can maximize channel utilization with enabling coexistence of unlicensed system and licensed system.

• Proceedings of the KSRS Conference
• /
• 2006.03a
• /
• pp.91-94
• /
• 2006

China Coastal Waters (CCW) usually appears in the seas surrounding Jeju Island annually(June to October) and is very pronounced in August. Generally, low-salinity water appears to the western seas of Jeiu Island from June through October and gradually propagates to the eastern seas, where CCW meets the Tsushima Current. Empirical orthogonal function (EOF) analysis of SLAs and SSTs indicated that the valiance in SLAs and SSTs was 95.05%(the first mode to third mode) and 98.09%(the first mode), respectively The PSD of the western waters for the first mode of EOF analysis of SLAs was stronger than that of the eastern waters because of the influence of CCW. The PSD for the EOF analysis of SSTs was similar in all areas (the Yangtze Estuary and the seas to the west and east of Jeju Island), with a period of approximately 260 days.

• Proceedings of the KSRS Conference
• /
• v.1
• /
• pp.426-429
• /
• 2006

Flood caused by Typhoon and severe rain during summer is the most destructive natural disasters in Korea. Almost every year flood has resulted in a big lost of national infrastructure and loss of civilian lives. It usually takes time and great efforts to estimate the flood-related damages. Government also has pursued proper standard and tool for using state-of-art technologies. High resolution satellite imagery is one of the most promising sources of ground truth information since it provides detailed and current ground information such as building, road, and bare ground. Once high resolution imagery is utilized, it can greatly reduce the amount of field work and cost for flood related damage assessment. The classification of high resolution image is pre-required step to be utilized for the damage assessment. The classified image combined with additional data such as DEM and DSM can help to estimate the flooded areas per each classified land use. This paper applied object-oriented classification scheme to interpret an image not based in a single pixel but in meaningful image objects and their mutual relations. When comparing it with other classification algorithms, object-oriented classification was very effective and accurate. In this paper, IKONOS image is used, but similar level of high resolution Korean KOMPSAT series can be investigated once they are available.

• Proceedings of the KSRS Conference
• /
• v.2
• /
• pp.831-835
• /
• 2006

NOAA/AVHRR data were used to analyze sea surface temperatures (SSTs) and thermal fronts (TFs) in the Korean seas. Temporal and spatial analyses were based on data from 1993 to 2000. Harmonic analysis revealed mean SST distributions of $10{\sim}25^{\circ}C$. Annual amplitudes and phases were $4{\sim}11^{\circ}C$ and $210{\sim}240^{\circ}$, respectively. Inverse distributions of annual amplitudes and phases were found for the study seas, with the exception of the East China Sea, which is affected by the Kuroshio Current. Areas with high amplitudes (large variations in SSTs) showed 'low phases' (early maximum SST); areas with low amplitudes (small variations in SSTs) had 'high phases' (late maximum SST). Empirical orthogonal function (EOF) analyses of SSTs revealed a first-mode variance of 97.6%. Annually, greater SST variations occurred closer to the continent. Temporal components of the second mode showed higher values in 1993, 1994, and 1995. These phenomena seemed to the effect of El $Ni{\tilde{n}}o$. The Sobel edge detection method (SEDM) delineated four fronts: the Subpolar Front (SPF) separating the northern and southern parts of the East Sea; the Kuroshio Front (KF) in the East China Sea, the South Sea Coastal Front (SSCF) in the South Sea, and a tidal front (TDF) in the West Sea. Thermal fronts generally occurred over steep bathymetric slopes. Annual amplitudes and phases were bounded within these frontal areas. EOF analysis of SST gradient values revealed the temporal and spatial variations in the TFs. The SPF and SSCF were most intense in March and October; the KF was most significant in March and May.

• Journal of Welding and Joining
• /
• v.16 no.5
• /
• pp.119-133
• /
• 1998

To implement full automation in pipe welding, it si most important to develop special sensors and their related systems which act like human operator when detecting irregular groove conditions. In this study, an automatic pipe Gas Metal Arc Welding (GMAW) system was proposed to full control pipe welding procedure with intelligent sensor systems. A five-axes manipulator was proposed for welding torch to automatically access to exact welding position when pipe size and welding angle were given. Pool status and torch position were measured by using a weld-pool image monitoring and processing technique in root-pass welding for weld seam tracking and weld pool control. To overcome the intensive arc light, pool image was captured at the instance of short circuit of welding power loop. Captured image was processed to determine weld pool shape. For weld seam tracking, the relative distance of a torch position from the pool center was calculated in the extracted pool shape to move torch just onto the groove center. To control penetration of root pas, gap was calculated in the extracted pool image, and then weld conditions were controlled for obtaining appropriate penetration. welding speed was determined with a fuzzy logic, and welding current and voltage were determined from a data base to correspond to the gap. For automatic fill-pass welding, the function of human operator of real time weld seam control can be substituted by a sensor system. In this study, an arc sensor system was proposed based on a fuzzy control logic. Using the proposed automatic system, root-pass welding of pipe which had gap variation was assured to be appropriately controlled in welding conditions and in torch position by showing sound welding result and good seam tracking capability. Fill-pass welding by the proposed system also showed very successful result by tracking along the offset welding line without any control of human operator.

• Current Optics and Photonics
• /
• v.4 no.1
• /
• pp.1-8
• /
• 2020

We research a system of compressed-sensing computational ghost imaging (CSCGI) based on the intensity fluctuation brought by turbulence. In this system, we used the gamma-gamma intensity-fluctuation model, which is commonly used in transmission systems, to simulate the CSCGI system. By setting proper values of the parameters such as transmission distance, refractive-index structure parameter, and sampling rates, the peak signal-to-noise ratio (PSNR) performance and bit-error rate (BER) performance are obtained to evaluate the imaging quality, which provides a theoretical model to further research the ghost-imaging algorithm.

• Current Optics and Photonics
• /
• v.4 no.2
• /
• pp.95-102
• /
• 2020

The impact of graphene and poly(methyl methacrylate) (PMMA) substrates on the response of a fiber Bragg grating (FBG) due to mechanical deflection was investigated. For this purpose, four FBGs with grating lengths of 5, 15, 25, and 35.9 mm were utilized. Higher sensitivity was found for FBGs of larger grating length and for those bonded to graphene substrate. It was concluded that FBGs of smaller grating length (5 and 15 mm) were more sensitive in compression mode, while those of larger grating length (25 and 35.9 mm) were seen to be highly sensitive in tension mode.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.47 no.12
• /
• pp.31-38
• /
• 2010

This paper presents the design of a graphic memory for QVGA-scale LCD Driver IC (LDI). The graphic memory is designed based on the pseudo-SHAM for the purpose of small area, and the memory cell structure is designed using a bit line partitioning method to improve sensing characteristics and drivabilties in the line-read operation. Also, a collision protection circuit using C-gate is designed to control collisions between read/write operations and self-refresh/line-read operations effectively. The graphic memory circuit has been designed in transistor level using $0.18{\mu}m$ CMOS technology library and the operations of the graphic memory have been verified using Hspice. The results show that the bit-bitb line voltage difference, ${\Delta}V$ increases by 40%, the charge sharing time between bit and bitb voltages $T_{CHGSH}$ decreases by 30%, and the current during line-read decreases by 40%.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.17 no.6
• /
• pp.33-39
• /
• 2017

Today, residential facilities is planned and built based on modular architecture. In the modular housing, sizes and locations of spaces like rooms, kinchin, and bathrooms can be changed from-time-to-time. Therefore, current home automation systems based on predesigned and fixed system with wired sensors can not be suitable for the modular housing. As a result, a new concept-based homw automation system is required which is able to adopt varying home environment. Since the change of spaces will change the number of and types of necessary sensors, the home automation system enables to detect automatically and naturally the added or removed different types of wireless sensors and provides home automation services. In this paper, a home automation system is studied and implemented which can adopt varying space environment by detecting automatically added or removed sensors and provide new user interfaces for displaying sensing information.