• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.11
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• pp.1-10
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• 2007

In this paper, we proposed channel estimation scheme for LR-UWB system which has low data rate for WPAN in IEEE 802.15.4a. At the transmitter, we proposed dynamic power level allocation depends on channel condition in specific period when we modulate signal. We use two orthogonal code to estimate channel at once. It can estimate channel more accurately by using two code which shows good correlation characteristic then it can estimate more accurately by spreading gain. Using estimated channel condition, we synchronize symbol timing of transmitted signal. Then determined power allocation scheme and channel information is transmitted to transmiter side. Finally, using these information, transmiter side change the power level of repeated pulse to adopt to channel condition. Simulation is performed under S-V channel for LR-WPAN in IEEE 802.15.4a and we compare the performance with a different type of receiver type. We use coherent and non-coherent method at the receiver. Simulation result shows us at the NLOS channal performance evaluation is greater than that of LOS channel and the result is independent of receiver type. In the NLOS channel, as the signal delay spreading is big, performance evaluation is also increased.

• Journal of the Microelectronics and Packaging Society
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• v.10 no.1
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• pp.31-38
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• 2003

In the current electronic technology atmosphere, MEMS (Microelectromechanical System) technology is regarded as one of promising device manufacturing technologies to realize market-demanding device properties. In the packaging of MEMS devices, the packaged structure must maintain hermeticity to protect the devices from a hostile atmosphere during their operations. For such MEMS device vacuum packaging, we introduce the LTCC (Low temperature Cofired Ceramic) packaging technology, in which embedded passive components such as resistors, capacitors and inductors can be realized inside the package. The technology has also the advantages of the shortened length of inner and surface traces, reduced signal delay time due to the multilayer structure and cost reduction by more simplified packaging processes owing to the realization of embedded passives which in turn enhances the electrical performance and increases the reliability of the packages. In this paper, the leakage rate of the LTCC package having several interfaces was measured and the possibility of LTCC technology application to MEMS devices vacuum packaging was investigated and it was verified that improved hermetic sealing can be achieved for various model structures having different types of interfaces (leak rate: stacked via; $4.1{\pm}1.11{\times}10^{-12}$/ Torrl/sec, LTCC/AgPd/solder/Cu-tube; $3.4{\pm}0.33{\times}10^{-12}$/ Torrl/sec). In real application of the LTCC technology, the technology can be successfully applied to the vacuum packaging of the Infrared Sensor Array and the images of light-up lamp through the sensor way in LTCC package structure was presented.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.5
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• pp.370-376
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• 2016

Corrosion on the surface of a structure can generate cracks or cause walls to thin. This can lead to fracturing, which can eventually lead to fatalities and property loss. In an effort to prevent this, laser imaging technology has been used over the last ten years to detect thin-plate structure, or relatively thin piping. The most common laser imaging was used to develop a new technology for inspecting and imaging a desired area in order to scan various structures for thin-plate structure and thin piping. However, this method builds images by measuring waves reflected from defects, and subsequently has a considerable time delay of a few milliseconds at each scanning point. In addition, the complexity of the system is high, due to additional required components, such as laser-focusing parts. This paper proposes a laser imaging method with an increased scanning speed, based on excitation and the measurement of standing waves in structures. The wavenumber of standing waves changes at sections with a geometrical discontinuity, such as thickness. Therefore, it is possible to detect defects in a structure by generating standing waves with a single frequency and scanning the waves at each point by with the laser scanning system. The proposed technique is demonstrated on a wall-thinned plate with a linear thickness variation.

• Journal of Internet Computing and Services
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• v.17 no.4
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• pp.11-17
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• 2016

In this paper, we proposed a multi-viewer system with multiple HD cameras based AVB(Audio Video Bridge) ethernet cable using IP networking, and FPGA(Xilinx Zynq 702) for bus safety systems. This AVB (IEEE802.1BA) system can be designed for the low latency based on FPGA, and transmit real-time with HD video and audio signals in a vehicle network. The proposed multi-viewer platform can multiplex H.264 video signals from 4 wide-angle HD cameras with existed ethernet 1Gbps. and 2-wire 100Mbps cables. The design of Zynq 702 based low latency to H.264 AVC CODEC was proposed for the minimization of time-delay in the HD video transmission of car area network, too. And the performance of PSNR(Peak Signal-to-noise-ratio) was analyzed with the reference model JM for encoding and decoding results in H.264 AVC CODEC. These PSNR values can be confirmed according the theoretical and HW result from the signal of H.264 AVC CODEC based on Zynq 702 the multi-viewer with multiple cameras. As a result, proposed AVB multi-viewer platform with multiple cameras can be used for the surveillance of audio and video around a bus for the safety due to the low latency of H.264 AVC CODEC design.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.3
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• pp.104-111
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• 2018

The sensorless control of high efficiency air compressors using a permanent magnet type synchronous motor as an oil-free air compressor is quite common. However, due to the nature of the air compressor, it is difficult to install a position sensor. In order to control the permanent magnet type synchronous motor at variable speed, the inclusion of a position sensor to grasp the position of the rotor is essential. Therefore, in order to achieve sensorless control, it is essential to use a permanent magnet type synchronous motor in the compressor. The position estimation method based on the back electromotive force, which is widely used as the sensorless control method, has a limitation in that position errors occur due either to the phase delay caused by the use of a stationary coordinate system or to the estimated back electromotive force in the transient state caused by the use of a synchronous coordinate system. Therefore, in this paper, we propose a method of estimating the position and velocity using a rotation angle tracking observer and reducing the speed ripple through a disturbance observer. An experimental apparatus was constructed using Freescale's MPU and the feasibility of the proposed algorithm was examined. It was confirmed that even if a position error occurs at a certain point in time, the position correction value converges to the actual vector position when the position error value is found.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.4
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• pp.34-40
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• 2004

In this paper, we have studied the OCT(Optical Coherence Tomography) system which has been advantages of high resolution, 2-D cross-sectional images, low cost and small size configuration. The characteristics of light source determine the resolution and coherence length. The light source has a commercial SLD with a central wavelength of 1,285 ill11, 35.3 nm(FWHM). The optical delay line is necessary to make equal with the optical path length to scattered light or reflected light from a sample. In order to make equal the optical path length, the stage that is attached to a reference mirror is controled by a step motor. And the interferometer is configured with the Michelson interferometer by using a single mode fiber, and the scanner can be focused on the sample by using a reference ann Also, the 2-dimension cross-sectional images were measured with scanning the transverse direction of the sample by using a step motor. After detecting the internal signal of lateral direction, a scanner is moved to obtain the cross-sectional image of 2-dimension by using step motor. A photodiode, which has high detection sensitivity and excellent noise characteristics has been used. The detected small signal has a noise and interference. After filtering and amplifying the signal, the output signal is demodulated the waveform And then, a cross-sectional image is seen through converting this signal into a digitalized signal by using an AID converter. The resolution of the sample is about 30${\mu}{\textrm}{m}$, which corresponds to the theoretical resolution. Also, the cross-sectional images of onion cells were measured in real time scheme.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.6
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• pp.887-895
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• 2019

Recently, the number of underground road development projects has been increasing to solve traffic problems in the national capital region and metropolitan areas with intensified overcrowding, and there has been a tendency to plan underground roads by applying a double-deck tunnel technology that has advantages in constructability and economical efficiency. The double-deck tunnel has a structure where one excavation section is divided into two parts and used as up and down lines, and is mainly used as a road for small vehicles only due to its low floor height. In addition, due to the small cross-sectional area, it has characteristics different from those of general road tunnels in terms of ventilation and disaster prevention. In this regard, this study proposed an operational plan that applies an oversized exhaust system, which is one of semi-transverse ventilation systems, to small cross-sectional tunnels like double-deck tunnel with low floor height, and a comparative analysis between smoke exhaust characteristics according to the fire occurrence locations and oversized exhaust systems was conducted using the Fire Dynamics Simulator (FDS). The results showed that unlike uniform exhaust, intensive smoke exhaust using the oversized exhaust port maximized the delay effect of smoke diffusion and limited the smoke within 50 m above and below the fire point.

• Journal of KIISE:Computer Systems and Theory
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• v.37 no.5
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• pp.292-303
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• 2010

On-chip cache memories play an important role in both performance and energy consumption points of view in resource-constrained embedded systems by filtering many off-chip memory accesses. We propose a 2-level data cache architecture with a low energy-delay product tailored for the embedded systems. The L1 data cache is small and direct-mapped, and employs a write-through policy. In contrast, the L2 data cache is set-associative and adopts a write-back policy. Consequently, the L1 data cache is accessed in one cycle and is able to provide high cache bandwidth while the L2 data cache is effective in reducing global miss rate. To reduce the penalty of high miss rate caused by the small L1 cache and power consumption of address generation, we propose an ECP(Early Cache hit Predictor) scheme. The ECP predicts if the L1 cache has the requested data using both fast address generation and L1 cache hit prediction. To reduce high energy cost of accessing the L2 data cache due to heavy write-through traffic from the write buffer laid between the two cache levels, we propose a one-way write scheme. From our simulation-based experiments using a cycle-accurate simulator and embedded benchmarks, the proposed 2-level data cache architecture shows average 3.6% and 50% improvements in overall system performance and the data cache energy consumption.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.1C
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• pp.55-64
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• 2006

In this paper, a new web-based remote 3D imaging communication system employing an adaptive matching algorithm is suggested. In the proposed method, feature values are extracted from the stereo image pair through estimation of the disparity and similarities between each pixel of the stereo image. And then, the matching window size for disparity estimation is adaptively selected depending on the magnitude of this feature value. Finally, the detected disparity map and the left image is transmitted into the client region through the network channel. And then, in the client region, right image is reconstructed and intermediate views be synthesized by a linear combination of the left and right images using interpolation in real-time. From some experiments on web based-transmission in real-time and synthesis of the intermediate views by using two kinds of stereo images of 'Joo' & 'Hoon' captured by real camera, it is analyzed that PSNRs of the intermediate views reconstructed by using the proposed transmission scheme are highly measured by 30dB for 'Joo', 27dB for 'Hoon' and the delay time required to obtain the intermediate image of 4 view is also kept to be very fast value of 67.2ms on average, respectively.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.3
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• pp.63-74
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• 1999

A sliding mode fuzzy control (SMFC) algorithm is presented for vibration of large structures. Rule-base of the fuzzy inference engine is constructed based on the sliding mode control, which is one of the nonlinear control algorithms. Fuzziness of the controller makes the control system robust against the uncertainties in the system parameters and the input excitation. Non-linearity of the control rule makes the controller more effective than linear controllers. Design procedure based on the present fuzzy control is more convenient than those of the conventional algorithms based on complex mathematical analysis, such as linear quadratic regulator and sliding mode control(SMC). Robustness of presented controller is illustrated by examining the loop transfer function. For verification of the present algorithm, a numerical study is carried out on the benchmark problem initiated by the ASCE Committee on Structural Control. To achieve a high level of realism, various aspects are considered such as actuator-structure interaction, modeling error, sensor noise, actuator time delay, precision of the A/D and D/A converters, magnitude of control force, and order of control model. Performance of the SMFC is examined in comparison with those of other control algorithms such as $H_{mixed 2/{\infty}}$ optimal polynomial control, neural networks control, and SMC, which were reported by other researchers. The results indicate that the present SMFC is an efficient and attractive control method, since the vibration responses of the structure can be reduced very effectively and the design procedure is simple and convenient.