• Smart Structures and Systems
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• v.3 no.3
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• pp.341-356
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• 2007

A good understanding of normal modal variability of civil structures due to varying environmental conditions such as temperature and wind is important for reliable performance of vibration-based damage detection methods. This paper addresses the quantification of wind-induced modal variability of a cable-stayed bridge making use of one-year monitoring data. In order to discriminate the wind-induced modal variability from the temperature-induced modal variability, the one-year monitoring data are divided into two sets: the first set includes the data obtained under weak wind conditions (hourly-average wind speed less than 2 m/s) during all four seasons, and the second set includes the data obtained under both weak and strong (typhoon) wind conditions during the summer only. The measured modal frequencies and temperatures of the bridge obtained from the first set of data are used to formulate temperature-frequency correlation models by means of artificial neural network technique. Before the second set of data is utilized to quantify the wind-induced modal variability, the effect of temperature on the measured modal frequencies is first eliminated by normalizing these modal frequencies to a reference temperature with the use of the temperature-frequency correlation models. Then the wind-induced modal variability is quantitatively evaluated by correlating the normalized modal frequencies for each mode with the wind speed measurement data. It is revealed that in contrast to the dependence of modal frequencies on temperature, there is no explicit correlation between the modal frequencies and wind intensity. For most of the measured modes, the modal frequencies exhibit a slightly increasing trend with the increase of wind speed in statistical sense. The relative variation of the modal frequencies arising from wind effect (with the maximum hourly-average wind speed up to 17.6 m/s) is estimated to range from 1.61% to 7.87% for the measured 8 modes of the bridge, being notably less than the modal variability caused by temperature effect.

• Wind and Structures
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• v.20 no.2
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• pp.349-361
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• 2015

Higher-mode vertical vortex-induced vibrations (VIV) have been observed on several steel box-girder suspension bridges where different vertical modes are selectively excited in turn with wind velocity in accordance with the Strouhal law. Understanding the relationship of VIV amplitudes for different modes of vibration is very important for wind-resistant design of long-span box-girder suspension bridges. In this study, the basic rectangular cross-section with side ratio of B/D=6 is used to investigate the effect of different modes on VIV amplitudes by section model tests. The section model is flexibly mounted in wind tunnel with a variety of spring constants for simulating different modes of vibration and the non-dimensional vertical amplitudes are determined as a function of reduced velocity U/fD. Two 'lock-in' ranges are observed at the same onset reduced velocities of approximately 4.8 and 9.4 for all cases. The second 'lock-in' range, which is induced by the conventional vortex shedding, consistently gives larger responses than the first one and the Sc-normalized maximum non-dimensional responses are almost the same for different spring constants. The first 'lock-in' range where the vibration frequency is approximately two times the vortex shedding frequency is probably a result of super-harmonic resonance or the "frequency demultiplication". The main conclusion drawn from the section model study, central to the higher-mode VIV of suspension bridges, is that the VIV amplitude for different modes is the same provided that the Sc number for these modes is identical.

• Nuclear Engineering and Technology
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• v.52 no.2
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• pp.397-416
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• 2020

Investigations of the commercial aircraft impact effect on nuclear island infrastructures have been drawing extensive attention, and this paper aims to perform the safety assessment of Generation III nuclear power plant (NPP) buildings subjected to typical commercial aircrafts crash. At present Part II, based on the verified finite element (FE) models of aircrafts Airbus A320 and A380, as well as the NPP containment and auxiliary buildings in Part I of this paper, the whole collision process is reproduced numerically by adopting the coupled missile-target interaction approach with the finite element code LS-DYNA. The impact induced damage of NPP plant under four impact locations of containment (cylinder, air intake, conical roof and PCS water tank) and two impact locations of auxiliary buildings (exterior wall and roof of spent fuel pool room) are evaluated. Furthermore, by considering the inner structures in the containment and raft foundation of NPP, the structural vibration analyses are conducted under two impact locations (middle height of cylinder, main control room in the auxiliary buildings). It indicates that, within the discussed scenarios, NPP structures can withstand the impact of both two aircrafts, while the functionality of internal equipment on higher floors will be affected to some extent under impact induced vibrations, and A380 aircraft will cause more serious structural damage and vibrations than A320 aircraft. The present work can provide helpful references to assess the safety of the structures and inner equipment of NPP plant under commercial aircraft impact.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1244-1245
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• 2008

Recently, piezoelectric transformer is applied to wide fields. Multi layer piezoelectric transformer has the advantage of high step up ratio, electromechanical coupling coefficient(Kp) and mechanical quality factor(Qm), but is indicated of peeling-phenomenon of electrode, rising sintering temperature made price of costly electrode. So in this study, it discuss on method for fabrication of rosen type piezoelectric transformers. For the fabrication as rosen type piezoelectric transformers, synthesized the powder using 0.01Pb$(ni_{1/3}Nb_{2/3})O_3$ - 0.08Pb$(Mn_{1/3}Nb_{2/3})O_3$ - 0.91Pb$(Zr_{0506}Ti_{0496})O_3$ (abbreviated as PNN-PMN-PZT) ceramics. The density, microstructure, dielectric and piezoelectric properties as a function of sintering temperature were investigated. The results indicated that the optimized properties of ceramics were obtained at sintering temperature of 1200$^{\circ}C$, showed the value of $d_{33}$=273pC/N, $K_p$=0.60 $Q_m$=1585, ${\varepsilon}_r$=1454, density=7.917$g/cm^3$ and $tan{\delta}$=0.0064.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.3
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• pp.991-996
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• 2015

Side population (SP) cells have stem cell-like properties with a capacity for self-renewal and are resistant to chemotherapy and radiotherapy. Therefore the presence of SP cells in human breast cancer probably has prognostic value. Objective: To investigate the characteristics of SP cells and identify the relationship between the SP cells levels and clinico-pathological parameters of the breast tumor and disease-free survival (DFS) in breast cancer patients. Materials and Methods: A total of 122 eligible breast cancer patients were consecutively recruited from January 1, 2006 to December 31, 2007 at Yunnan Tumor Hospital. All eligible subjects received conventional treatment and were followed up for seven years. Predictors of recurrence and/or metastasis and DFS were analyzed using Cox regression analysis. Human breast cancer cells were also obtained from fresh human breast cancer tissue and cultured by the nucleic acid dye Hoechst33342 with Verapami. Flow cytometry (FCM) was employed to isolate the cells of SP and non-SP types. Results: In this study, SP cells were identified using flow cytometric analysis with Hoechst 33342 dye efflux. Adjusted for age, tumor size, lymph nodal status, histological grade, the Cox model showed a higher risk of recurrence and/or metastasis positively associated with the SP cell level (1.75, 1.02-2.98), as well as with axillary lymph node metastasis (2.99, 1.76-5.09), pathology invasiveness type (1.7, 1.14-2.55), and tumor volume doubling time (TVDT) (1.54, 1.01-2.36). Conclusions: The SP cell level is independently associated with tumor progression and clinical outcome after controlling for other pathological factors. The axillary lymph node status, TVDT and the status of non-invasive or invasive tumor independently predict the prognosis of breast cancer.

• Transactions of the Korean hydrogen and new energy society
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• v.13 no.3
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• pp.169-180
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• 2002

Rayleigh scattering and laser induced predissociative fluorescence are used to obtain two-dimensional images of temperature and species concentration in a laminar non-premixed flame of a diluted hydrogen jet. Rayleigh scattering cross-sections are experimentally obtained at 248nm. Planar images of OH and $O_2$ with tunable KrF excimer laser which has a) $0.5cm^{-1}$ linewidth, b) 0.5nm tuning range, c) 150mJ pulse energy, and d) 20ns pulse width are obtained to determine spatial distributions of OH and $O_2$. The technique is based on planar laser induced predissociative fluorescence (PLIPF) in which collisional quenching is almost avoided because of the fast predissociation. Dispersed LIPF spectra of OH and $O_2$ are also measured in a flame in order to confirm the excitation of single vibronic state of OH and $O_2$. OH and $O_2$ are excited on the $P_2$(8) and $Q_1$(11) line of the $A^2{\Sigma}^{+}({\nu}^{'}=3)-X^{2}{\Pi}({\nu}^{''}=o)$ band and R(17) line of the Schumann-Runge band $B^{3}{\Sigma}_{u}{^-}(\nu^{'}=0)-X^{3}{\Sigma}_{g}{^-}({\nu}^{''}=6)$, respectively. Fluorescence spectra of OH and Hot $O_2$ are captured and two-dimensional images of the hydrogen flame field are successfully visualized.

• Geomechanics and Engineering
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• v.14 no.4
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• pp.367-376
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• 2018

Samples composed of coal and rock show different mechanical properties of the pure coal or rock mass. For the same coal seam with different surrounding rocks, the frequency and intensity of rock burst can be significantly different in. First, a method of measuring the strain variation of coal in the coal-rock combined sample was proposed. Second, laboratory tests have been conducted to investigate the influences of rock lithologies, combined forms and coal-rock height ratios on the deformation and failure characteristics of the coal section using this method. Third, a new bursting liability index named combined coal-rock impact energy speed index (CRIES) was proposed. This index considers not only the time effect of energy, but also the influence of surrounding rocks. At last, a new approach considering the influences of roof and/or floor was proposed to evaluate the impact capability of coal seam. Results show that the strength and elastic modulus of coal section increase significantly with the coal-rock height ratio decreasing. In addition, the values of bursting liability indexes of the same coal seam vary greatly when using the new approach. This study not only provides a new approach to measuring the strain of the coal section in coal-rock combined sample, but also improves the evaluation system for evaluating the impact capability of coal.

• Korean Journal of Plant Resources
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• v.20 no.3
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• pp.234-241
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• 2007

The present study was undertaken to classify and describe the riparian vegetation of the 6 river${\cdot}$stream of Korea Peninsula. As a result the vegetation was divided into nineteen communities. The vegetation units obtained in the present study were as follow: A: Salix koreensis community, B: Salix gracilistyla community, C: Robinia pseudo-acacia community, D: Amorpha fluticosa community, E: Brousonnetia papyrifera community, F: Phyllostachys bambusoides community, G: Rubus corchorifolius community, H: Phramities japonica community, I: Phramites communis community, J: Miscanthus sacchariflorus community, K: Miscanthus sinesis var. purpurascens community, L: Artemisia princeps var. orientalis community, M: Humulus japonicus community, N: Zoysia japonica community, O: Inperata cylindrica var. koenigii community, P: Agropyron tsukushiense var. transiens community, Q: Juncos effusus var. decipiens community, R: Rumex crispus community, S: Persicaria hydropiper community. The vegetation characteristics of riversides was recovered in the surveyed results according to river${\cdot}$stream basin, in other words, 10 communities in the upper river${\cdot}$stream riparian, 15 communities in the middle river${\cdot}$stream riparian, 10 communities in the down river${\cdot}$stream riparian. The Phragmites japonica community in the upper and Phragmites communis community in the down was analyzed by common community of the 6 river${\cdot}$stream riparian, respectively, but none in the middle. The standing profile of vegetation across 6 river${\cdot}$stream was seen stepwise Phragmites japonica community, Salix gracilistyla community, Miscanthus sinensis var. purpurascens community, shrub community by natural waterway in the upper, Salix gracilistyla community, Phragmites communis community, Rumex crispus community, Miscanthus sacchariflorus community, Humulus japonicus community in the middle, Phragmites communis community in the down. The differences of distributional featurs of vegetation emerged from the riparian of the 6 river${\cdot}$stream, but don't from the 6 river${\cdot}$stream.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.8
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• pp.627-631
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• 2011

[ $[Li_{0.04}(Na_{0.54}K_{0.46})_{0.96}](Nb_{1-0.04-X}TaxSb_{0.04})O_3$ ]lead-free piezoelectric ceramics have been prepared by normal sintering at $1,100^{\circ}C$ for 5 h. X-ray diffraction analysis indicated that specimens demonstrate orthorhombic symmetry when $Ta\leq5$ mol%. While transforming into tetragonal symmetry when $x\geq20$ mol%. These suggest that the orthorhombic and tetragonal phases co-exist in the ceramics with 5 mol% $cm^3$. As the result of SEM images, the grain growth was decreased with the increase of Ta substitution. The ceramics become 'softening', leading to improvements in $k_p$, $\varepsilon_r$ and $d_{33}$, but a decrease in $Q_m$. Excellent properties of $k_p$= 0.46, $d_{33}$= 293 pC/N, ${\varepsilon}_r$= 1,583 and Tc= $340^{\circ}C$ were obtained when Ta= 15 mol%.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.8
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• pp.501-507
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• 2017

A unimorph piezoelectric cantilever generator with an interdigitated electrode (IDE) was developed for vibration energy harvester applications driven in the longitudinal mode. Hard lead zirconate titanate (PZT) ceramic with a high $Q_m$ of 1,280 was used as the piezoelectric active material. Ten PZT sheets produced by tape casting were laminated and co-fired with an Ag/Pd IDE at $1,050^{\circ}C$ for 2 h. The approximately $280{\mu}m$-thick co-fired PZT laminate with the IDE was attached to a stainless steel substrate with an adhesive epoxy for the fabrication of an IDE unimorph cantilever. Its energy harvesting characteristics were evaluated: an output power of $1.1{\mu}W$ at 120 Hz across the resistive load of $700k{\Omega}$ was obtained, corresponding to a normalized power factor of $4.1{\mu}W/(G^2{\cdot}cm^3)$.