• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.2
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• pp.702-721
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• 2012

In the DVB-T2 system with a multiple-input single-output (MISO) transmission mode, Alamouti coded orthogonal frequency division multiplexing (OFDM) signals are transmitted simultaneously from two spatially separated transmitters in a single frequency network (SFN). In such systems, each transmit-receive link may have a distinct carrier frequency offset (CFO) due to the Doppler shift and/or frequency mismatch between the local oscillators. Thus, the received signal experiences dual CFOs. This not only causes dual phase errors in desired data but also introduces inter-carrier interference (ICI), which cannot be removed completely by simply performing a CFO compensation. To overcome this problem, this paper proposes an iterative detection with dual phase errors compensation technique. In addition, we propose a successive-iterative ICI cancellation technique. This technique successively eliminates ICI in the initial iteration by exploiting pre-detected data pairs. Then, in subsequent iterations, it performs a fine interference cancellation using a priori information, iteratively fed back from the channel decoder. In contrast to previous works, the proposed techniques do not require estimates of dual CFOs. Their performances are evaluated via a full DVB-T2 simulator. Simulation results show that the DVB-T2 receiver equipped with the proposed dual phase errors compensation and the successive-iterative ICI cancellation techniques achieves almost the same performance as ideal dual CFOs-free systems, even for large dual CFOs.

• Structural Engineering and Mechanics
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• v.30 no.2
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• pp.135-146
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• 2008

This study utilizes the fine-tuning and small-digit characteristics of the successive zooming genetic algorithm (SZGA) to propose a method of structural damage detection in a continuum structure, where the differences in the natural frequencies of a structure obtained by experiment and FEM are compared and minimized using an assumed location and extent of structural damage. The final methodology applied to the structural damage detection is a kind of pseudo-discrete-variable-algorithm that counts the soundness variables as one (perfectly sound) if they are above a certain standard, such as 0.99. This methodology is based on the fact that most well-designed structures exhibit failures at some critical point due to manufacturing error, while the remaining region is free of damage. Thus, damage of 1% (depending on the given standard) or less can be neglected, and the search concentrated on finding more serious failures. It is shown that the proposed method can find out the exact structural damage of the monitored structure and reduce the time and amount of computation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.665-666
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• 2006

In precision laser microfabrication, focusing is essential to acquire good machining precision and uniform machining quality. If it does not perform, laser machining cannot be realized. So, confocal scanning method with high depth resolution is used for focus detection technique. This paper is concerned with a procedure for design, analysis and performance test of an autofocus fine actuating stage, which is composed of flexure-hinge type lever mechanism and piezoelectric actuator. Through series of analytical design, the stage is simplified as a rigid bodies(lever and main body) and springs(flexure hinges). The simplified model was applied to determine the dimension of flexure hinges and lever. After structural analysis confirmed design requirement, an actual stage was made and verified through an experiment on the static and dynamic characteristics(maximum stroke and 1st natural frequency). The fabricated stage was satisfied with the design requirement.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.43.1-43.1
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• 2013

We report the preliminary results of our GMVA(Global mm VLBI Array) observation at the frequency of 86 GHz. Observation were made in the dual polarization mode (LCP and RCP), to produce the polarimetric maps with the maximum angular resolution which the array is capable of. We aim to link the source-integrated AGN polarization properties with the polarized spatial source structure, by mapping the polarized "fine structure" of the target AGN. We selected 2 targets, 0954+658 and 0716+714, which (1) have been observed multiple times by the PdBI polarimetric monitoring program; (2) have sufficient integrated fluxes ($S_{90GHz}$ > 1 Jy) ; (3) are close enough to resolve the source structure < 1 pc with given angular resolution ; and (4) are located at high northern declination for good UV coverages. As preliminary results, we present LL and RR polarized images of each target with the maximum angular resolution of ${\sim}60{\mu}as$. Extended structures, probably the jet outflows, are discovered in both sources.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.581-584
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• 2003

The phase differences and noise signals are in general serious on output of a instrumentation amplifier for signal conditioning of a sensor driven at high frequency due to a time-varying input signal. In this study, we get the better amplification and S/N ratio using the rectified signal for the input of instrumentation amplifier. This driving circuits were designed and constructed by OrCAD and laboratory PCB process. All of the elements used on the circuit including highly speedy OP-Amp. was SMD type and the MI sensor was fabricated by meander-patterned amorphous ribbon. The output sensitivity of this circuit was $105.3mV/V{\cdot}Oe$. That's why this driving circuit is good at detection of fine magnetic field.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.1B
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• pp.79-89
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• 2002

A synchronization method is presented for IEEE 802.11a wireless OFDM system. First the coarse symbol synchronization is achieved by measuring the moving power average of the received envelope signal. The detection probabilities and optimum thresholds for the symbol synchronization are derived. By measuring the correlation between the short training signal and received envelope signal, fine symbol synchronization can be acquired. And the frequency synchronization is achieved using long training signal. A symbol synchronization error causes a phase rotation of the constellation. After the compensation for fading channel, the rotation due to the symbol timing error can be corrected. With this method, synchronization can be well achieved over frequency selective channels.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.11
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• pp.4395-4412
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• 2020

The multisource image fusion has become an active topic in the last few years owing to its higher segmentation rate. To enhance the accuracy of multimodal pig-body feature segmentation, a multisource image fusion method was employed. Nevertheless, the conventional multisource image fusion methods can not extract superior contrast and abundant details of fused image. To superior segment shape feature and detect temperature feature, a new multisource image fusion method was presented and entitled as NSST-GF-IPCNN. Firstly, the multisource images were resolved into a range of multiscale and multidirectional subbands by Nonsubsampled Shearlet Transform (NSST). Then, to superior describe fine-scale texture and edge information, even-symmetrical Gabor filter and Improved Pulse Coupled Neural Network (IPCNN) were used to fuse low and high-frequency subbands, respectively. Next, the fused coefficients were reconstructed into a fusion image using inverse NSST. Finally, the shape feature was extracted using automatic threshold algorithm and optimized using morphological operation. Nevertheless, the highest temperature of pig-body was gained in view of segmentation results. Experiments revealed that the presented fusion algorithm was able to realize 2.102-4.066% higher average accuracy rate than the traditional algorithms and also enhanced efficiency.

• ETRI Journal
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• v.43 no.1
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• pp.120-132
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• 2021

A frequency diverse array (FDA) multiple-input multiple-output (MIMO) radar employs a small frequency increment across transmit elements to produce an angle-range-dependent beampattern for target angle and range detection. The joint angle and range estimation problem is a trilinear model. The traditional trilinear alternating least square (TALS) algorithm involves high computational load due to excessive iterations. We propose a fast-convergence trilinear decomposition (FC-TD) algorithm to jointly estimate FDA-MIMO radar target angle and range. We first use a propagator method to obtain coarse angle and range estimates in the data domain. Next, the coarse estimates are used as initialized parameters instead of the traditional TALS algorithm random initialization to reduce iterations and accelerate convergence. Finally, fine angle and range estimates are derived and automatically paired. Compared to the traditional TALS algorithm, the proposed FC-TD algorithm has lower computational complexity with no estimation performance degradation. Moreover, Cramer-Rao bounds are presented and simulation results are provided to validate the proposed FC-TD algorithm effectiveness.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.6
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• pp.529-536
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• 2015

A defect could be generated in bolts for a use of oil filters for the manufacturing process and then may affect to the safety and quality in bolts. Also, fine defects may be imbedded in oil filter system. So it is very important that such defects be investigated and screened during the multiple manufacturing processes. Therefore, in order effectively to evaluate the fine defects, the FEM simulations were performed to make characterization in the crack detection of the bolts and the parameters such as number of turns of the coil, the coil size, applied frequency were calculated based on the simulation results. Simulations were carried out for the defect signal of eddy current probe. Exciter and receiver were utilized. In this paper, the FEM simulations were performed in both bobbin-type and pancake-type probe, both probes were optimized under Eddy current FEM simulations and the results of calculation were discussed.

• Journal of Information Science Theory and Practice
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• v.1 no.2
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• pp.36-57
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• 2013

Blogs are readily available sources of opinions and sentiments which allows bloggers to exert a certain level of influence over the blog readers. Previous studies had attempted to analyze blog features to detect influence within the blogosphere, but had not studied in details influence at the blogger-level. Other studies studied bloggers' personalities with regards to their propensity to blog, but did not relate the personalities of bloggers to influence. Bloggers may differ in their way or manner of exerting influence. For example, bloggers could be active participants or just passive shares, or whether they express ideas in a rational or subjective manner, or they are received positively or negatively by the readers. In this paper, we further analyze the engagement style (frequency, scope, originality, and consistency of the blog postings), persuasion style (appeals to reasons or emotions), and persona (degree of compliance) of individual bloggers. Methods used include similarity analysis to detect the sharing-creating aspect of engagement style, subjectivity analysis to measure persuasion style, and sentiment analysis to identify persona style. While previous studies analyzed influence at blog site level, our model is shown to provide a fine-grained influence analysis that could further differentiate the bloggers' influence style in a blog site.