• Smart Structures and Systems
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• v.12 no.3_4
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• pp.327-344
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• 2013

Beam string structure (BSS) is introduced as a new type of hybrid prestressed string structures. The composition and mechanics features of BSS are discussed. The main principles of wavelet packet transform (WPT), principal component analysis (PCA) and support vector machine (SVM) have been reviewed. WPT is applied to the structural response signals, and feature vectors are obtained by feature extraction and PCA. The feature vectors are used for training and classification as the inputs of the support vector machine. The method is used to a single one-way arched beam string structure for damage detection. The cable prestress loss and web members damage experiment for a beam string structure is carried through. Different prestressing forces are applied on the cable to simulate cable prestress loss, the prestressing forces are calculated by the frequencies which are solved by Fourier transform or wavelet transform under impulse excitation. Test results verify this method is accurate and convenient. The damage cases of web members on the beam are tested to validate the efficiency of the method presented in this study. Wavelet packet decomposition is applied to the structural response signals under ambient vibration, feature vectors are obtained by feature extraction method. The feature vectors are used for training and classification as the inputs of the support vector machine. The structural damage position and degree can be identified and classified, and the test result is highly accurate especially combined with principle component analysis.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.4
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• pp.71-79
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• 2015

This paper proposes a new touch screen sensing method that improves the drawback of conventional single-line sensing methods for mutual capacitance touch screen panels (TSPs). It introduces a dual sensing and voltage shifting method, which reduces the ambient noise effectively and enhances the touch signal strength. The dual sensing scheme reduces the detection time by doubling the integration speed using both edges of excitation pulse signals. The voltage shifting method enhances the signal-to-noise ratio (SNR) by increasing the voltage range of integrations, and maximizing the ADC's input dynamic range. Simulation and experimental results using a commercial 23" large touch screen show an SNR performance of 43dB and a scan rate 2 times faster than conventional schemes - key properties suited for a large touch screen panels. We implemented the proposed method into a TSP controller chip using Magnachip's CMOS 0.18um process.

• Current Optics and Photonics
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• v.6 no.6
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• pp.521-549
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• 2022

Fiber lasers have made remarkable progress over the past three decades, and they now serve far-reaching applications and have even become indispensable in many technology sectors. As there is an insatiable appetite for improved performance, whether relating to enhanced spatio-temporal stability, spectral and noise characteristics, or ever-higher power and brightness, thermal management in these systems becomes increasingly critical. Active convective cooling, such as through flowing water, while highly effective, has its own set of drawbacks and limitations. To overcome them, other synergistic approaches are being adopted that mitigate the sources of heating at their roots, including the quantum defect, concentration quenching, and impurity absorption. Here, these optical methods for thermal management are briefly reviewed and discussed. Their main philosophy is to carefully select both the lasing and pumping wavelengths to moderate, and sometimes reverse, the amount of heat that is generated inside the laser gain medium. First, the sources of heating in fiber lasers are discussed and placed in the context of modern fiber fabrication methods. Next, common methods to measure the temperature of active fibers during laser operation are outlined. Approaches to reduce the quantum defect, including tandem-pumped and short-wavelength lasers, are then reviewed. Finally, newer approaches that annihilate phonons and actually cool the fiber laser below ambient, including radiation-balanced and excitation-balanced fiber lasers, are examined. These solutions, and others yet undetermined, especially the latter, may prove to be a driving force behind a next generation of ultra-high-power and/or ultra-stable laser systems.

• Korean Journal of Ecology and Environment
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• v.54 no.4
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• pp.346-362
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• 2021

A sediment control dam is an artificial structure built to prolong sedimentation in the main dam by reducing the inflow of suspended solids. These dams can affect changes in dissolved organic matter (DOM) in the water body by changing the river flow regime. The main DOM component for Yeongju Dam sediment control of the Naeseongcheon River was analyzed through 3D excitation-emission matrix (EEM) and parallel factor (PARAFAC) analyses. As a result, four humic-like components (C1~C3, C5), and three proteins, tryptophan-like components (C2, C6~C7) were detected. Among DOM components, humic-like components (autochthonous: C1, allochthonous: C2~C3) were found to be dominant during the sampling period. The total amount of DOM components and the composition ratio of each component did not show a difference for each depth according to the amount of available light (100%, 12%, and 1%). Throughout the study period, the allochthonous organic matter was continuously decomposing and converting into autochthonous organic matter; the DOM indices (fluorescence index, humification index, and freshness index) indicated the dominance of autochthonous organic matter in the river. Considering the relative abundance of cyanobacteria and that the number of bacteria cells and rotifers increased as autochthonous organic matter increased, it was suggested that the algal bloom and consequent activation of the microbial food web was affected by the composition of DOM in the water body. Research on DOM characteristics is important not only for water quality management but also for understanding the cycling of matter through microbial food web activity.

• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.3
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• pp.23-33
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• 2012

Dynamic response measurements from natural excitation were carried out for three 18-story office buildings to determine their inherent properties. The beam-column frame system was adopted as a typical structural form, but a core wall was added to resist the lateral force more effectively, resulting in a mixed configuration. To extract modal parameters such as natural frequencies, mode shapes and damping ratios from a series of vibration records at each floor, the most advanced operational system identification methods based on frequency- and time-domain like FDD, pLSCF and SSI were applied. Extracted frequencies and mode shapes from the different identification methods showed a greater consistency for three buildings, however the three lower frequencies extracted were 1.2 to 1.7 times as stiff as those obtained using the initial FE models. Comparing the extracted fundamental periods with those estimated from the code equations and FE analysis, the FE analysis results showed the most flexible behavior, and the most simple equation that considers the building height as the only parameter correlated fairly well with test results. It is recognized that such a discrepancy arises from the fact that the present tests exclude the stiffness decreasing factors like concrete cracking, while the FE models ignore the stiffness increasing factors, such as the contribution of non-structural elements and the actual material properties used.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.250-250
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• 2012

Recently, multiferroic materials have attracted much attention due to their fascinating fundamental physical properties and potential technological applications in magnetic/ferroelectric data storage systems, quantum electromagnets, spintronics, and sensor devices. Among single-phase multiferroic materials, $BiFeO_3$, in particular, has received considerable attention because of its very interesting magnetoelectric properties for application to spintronics. Enhanced ferromagnetism was found by Fe-site ion substitution with magnetic ions. In this study, $BiFe_{1-x}Ni_xO_3$ (x=0 and 0.05) bulk ceramic compounds were prepared by solid-state reaction and rapid sintering. High-purity $Bi_2O_3$, $Fe_3O_4$ and NiO powders were mixed with the stoichiometric proportions, and calcined at $450^{\circ}C$ for 24 h to produce $BiFe_{1-x}Ni_xO_3$. Then, the samples were directly put into the oven, which was heated up to $800^{\circ}C$ and sintered in air for 20 min. The crystalline structure of samples was investigated at room temperature by using a Rigaku Miniflex powder diffractometer. The Raman measurements were carried out with a Raman spectrometer with 514.5-nm-excitation Ar+-laser source under air ambient condition on a focused area of $1-{\mu}m$ diameter. The field-dependent magnetization and the temperature-dependent magnetization measurements were performed with a vibrating-sample magnetometer. The x-ray diffraction study demonstrates the compressive stress due to Ni substitution at the Fe site. $BiFe_{0.95}Ni_{0.05}O_3$ exhibits the rhombohedral perovskite structure R3c, similar to $BiFeO_3$. The lattice constant of $BiFe_{0.95}Ni_{0.05}O_3$ is smaller than of $BiFeO_3$ because of the smaller ionic radius of Ni3+ than that of Fe3+. The field-dependent magnetization of $BiFe_{0.95}Ni_{0.05}O_3$ exhibits a clear hysteresis loop at 300 K. The magnetic properties of $BiFe_{0.95}Ni_{0.05}O_3$ were improved at room temperature because of the existence of structurally compressive stress.

• Korean Security Journal
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• no.33
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• pp.103-135
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• 2012

The object is that this research searches the relationship of the office given condition actual condition of the country important facility private security guard and job satisfaction degree. In order to grasp and analyze the real state of the country important facility private security guards directly, the questionnaire, that is the general measurement tool, was utilized and the guard whom it works in the airport, the port region and general work place, that is the national important facility of Busan and Ulsan area, was aimed at. The enough survey object was illustrated to the facility and person in charge in the security company and the item was previewed and the total 400 sheets was distributed and 331 sheets (82.8%) except the doubleness subject intention and incongruent questionnaire was utilized for the analysis. The statistic processing of collected data utilized the SPSS version 15.0 the statistical package program through data coding and cleaning process and performed the frequency analysis, reliability analysis, t-test, one way analysis of variance, Pearson analysis, and regression analysis. The relationship of the office given condition actual condition of the guard about the national important facility and job satisfaction degree was classified into the interpersonal relationship, task characteristic, office environment, and complement factor and the difference of the job satisfaction degree according to the general characteristic was verified. If the conclusion obtained through the method of study described in the above looked at, for as to general tendency, the low wages and poor field environment was continued. In the general characteristic, the man was higher than the excitation about the job satisfaction level. As there was lots of the age and the scholarship was low, the age was high. And as there was lots of the career and income, the police of a petition or search and guide staff was high and the job satisfaction degree in which relatively the employee and the other job group is high so that the case of being the former student incidence can be the poorest was shown rather than the facility security agent. As the interrelation analysis result job satisfaction was high, the change of occupation pseudo was low and the organizational commitment degrees was increased. The regression analysis result job satisfaction degree was exposed to reach the meaningful effect on the change of occupation pseudo and organizational commitment. It had an effect on the change of occupation pseudo as the task characteristic and office ambient level was low. It had an effect on the organizational commitment as the extend of satisfaction about the task characteristic and interpersonal relationship, complement, and office ambient level were high. If the research result of this time is integrated, the support of the political system including the interpersonal relationship thesis between top and bottom of the organized I and substantial complement actualization is urgently needed between the office given condition improvement effort in the country important facility defense manpower field and police of a petition and special guard.