bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Curcumin against In Vitro Adhesion of Implant Device-Associated Bacteria on Nanosized Titanium Dioxide
Authors: Oh Seung Han , Na In Young , Choi Kyoung Hee
Published: July 2013

Although titanium dioxide (TiO2) is an implantable biomaterial with its antibacterial activity, infection on TiO2 surfaces remains a problem for medical settings. According to our previous studies, curcumin, the main component of turmeric (Curcuma longa), partially hindered the attachment of Streptococcus mutans to human tooth surfaces. Therefore, it was examined whether several implant device-associated bacteria were able to adhere to nanosized TiO2 surfaces. In addition, the effect of curcumin on the bacterial adhesion was investigated. Bacterial strains were cultured on pure Ti and TiO2 surfaces with various nanotube sizes in the absence or presence of curcumin and observed by scanning electron microscopy. Consequently, most bacteria adhered to Ti and TiO2 surfaces. However, curcumin increased the adhesion of bacteria including S. mutans. The results suggest that bacterial adhesion to implant titanium surfaces can be augmented via curcumin ingestion.
Preparation of Ce0.8Sm0.2O1.9 Thin Films by Electrophoretic Deposition and their Fuel Cell Performance
Authors: Ichiboshi Hiroki , Myoujin Kenichi , Kodera Takayuki , Ogihara Takashi
Published: July 2013

Ce0.8Sm0.2O1.9 (Samaria-doped ceria: SDC) precursors were synthesized by carbon-assisted spray pyrolysis. SDC thin films were prepared by electrophoretic deposition using the SDC precursor particles. The as-prepared SDC thin films were sintered at 1600 °C for 10 h. Uniform films with a thickness of approximately 20 μm were obtained. A fuel cell using the prepared thin films showed a maximum power density of 60.6 mW/cm2 and an open circuit voltage (OCV) of 0.63 V at 700 °C.
Fabrication of BiFeO3-Bi(Zn1/2Ti1/2)O3 Solid Solution Thin Films Using Perovskite-Type Oxide Interface Layer
Authors: Hayashi Mari , Yasui Shintaro , Funakubo Hiroshi , Uchida Hiroshi
Published: July 2013

Bi-based perovskite-type oxide materials such as BiFeO3 (BFO) and Bi (Zn1/2Ti1/2)O3 and the related compounds receive much attention and have been developed actively as important candidates for Pb-free ferroelectric materials instead of toxic Pb-based perovskite oxide materials. Recently, many researches have been reported for thin films of Bi-based materials by various film-deposition techniques for actual application of semiconductive devices, microactuators, etc. In this study, we tried preferential crystal growth of BFZT films on semiconductive silicon substrates using uniaxial-(100)-oriented LaNiO3 (LNO) buffer layer. BFO films were fabricated via chemical solution deposition (CSD) technique on platinized silicon wafer [(111)Pt/TiO2/(100)S and (100)LNO-coated platinized silicon [(100)LNO/(111)Pt/TiO2/(100)S substrates. XRD analysis indicated that the films fabricated on (111)Pt/TiO2/(100)Si substrate consisted of randomly-oriented BFZT crystal with lower crystallinity. On the other hand, the films on (100)LNO/(111)Pt/TiO2/(100)Si consisted of uniaxial-one-oriented BFZT crystal with higher crystallinity. The crystallization temperature these films were 500°C, respectively. These results suggest that the BFZT crystal was grown successfully on uniaxial oriented (100)LNO plane which also had perovskite-type crystal structure. Consequently, one-oriented BFZT films were prepared on Si substrate successfully using (100)LNO buffer layer.
Oxygen Tracer Diffusion in BaTiO3 Ceramics - Effect of Zr Impurity from Planetary Ball Milling
Authors: Watanabe Ken , Sakaguchi I. , Hishita S. , Haneda H. , Ohashi N.
Published: July 2013

We investigated the effect of Zr impurities on the oxygen diffusion pathway in BaTiO3 ceramics by using an ion-imaging technique. Zr impurities were introduced into BaTiO3 ceramics by a planetary ball milling process. The oxygen tracer diffused quickly from the surface up to the grain boundary and then appeared as discontinuous steps at the grain boundary. The results indicate that the grain boundary acted as a blocking layer against oxygen diffusion. The blocking for oxygen diffusion at the grain boundary is thought to originate during the formation and distribution of complex defects between the charged oxygen vacancies and the Ba vacancies near the grain boundary.
Drug Adsorption Property of Surfaces of Polarized Calcium Phosphate Powders
Authors: Horiuchi Naohiro , Nakamura Miho , Nagai Akiko , Yamashita Kimihiro
Published: July 2013

Calcium phosphate powders (hydroxyapatite, α-tricalcium phosphate, β-tricalcium phosphate, and tetracalcium phosphate) were electrically polarized by an applied dc voltage. Thermally stimulated depolarization current measurements confirmed that each calcium phosphate powder exhibited surface charges after polarization treatment. The surface adsorption of simvastatin on each powder was investigated. We observed a difference in adsorption between polarized and non-polarized powders. This difference in adsorption is due to the electrostatic force between the polarized surface and the open-ring form of simvastatin, which has a larger electrical polarity than its closed-ring form.
Preparation of Ceramics/Polymer Film Capacitor Using Barium Titanate Nanoparticles with High Dielectric Property and their Dielectric Property
Authors: Kita Tatsuya , Kondo Shuhei , Tsukamoto Shuhei , Takei Takahiro , Kumada Nobuhiro , Nakashima Kouichi , Fujii Ichiro , Suzuki Tohru , Uchikoshi Tetsuro , Sakka Yoshio , Wada Satoshi
Published: July 2013

Barium titanate (BaTiO3, BT) nanoparticle accumulations were prepared by an electrophoresis deposition (EPD) method, and their dielectric properties were measured. The BTKK accumulation exhibited high dielectric constant of 100. To prepare the BT ceramic/polymer film capacitors, the polymer was injected into the accumulations in vacuum. Finally, dielectric properties were measured, and it was clarified that the dielectric constant of the ceramic/polymer film capacitors became smaller than those of the accumulation because of surfactant used as particle dispersion.
Piezoelectric Properties and Dielectric Property of Li Added KNN Ceramics
Authors: Mitani Akihiro , Oba Yoshinari
Published: July 2013

Recently, high performance lead-free piezoelectric materials are strongly demanded for environmental issues. (K0.5Na0.5)NbO3 (KNN) has been attracting interest as lead-free piezoelectric ceramics because of its high Curie temperature and excellent piezoelectric properties. In this study, we investigated effects of Li addition on piezoelectric properties of (Li,Na,K)(Nb+Ta)O3+CuO,BaTiO3 . We found that optimum Li ratio of A site and B site on the perovskite structure increases relative density and .
Characteristics of TVOC, Aldehydes and Ketones Emitted from Fiber Hot-Pressing in Manufacturing of MDF made from Poplar and Pine
Authors: Wang Y.L. , Lu Zhi Gang , Zhang P.P. , Zhou Han Dong
Published: July 2013

This study, by means of GC-MS and HPLC, investigated the characteristics of volatile organic compounds (VOCs) released from fiber hot-pressing in a medium density fiberboard (MDF) production line with a production capacity of 80,000 m3/a. The quantity of total volatile organic compounds (TVOC), aldehydes and ketones were calculated. The results showed that the concentration of TVOC reached 1.8940 mg/m3. The main components include terpenes, acrolein and acetone, benzenes series and saturated hydrocarbons. The concentration of the mixture of aldehydes and ketones was 5.1136 mg/m3.
Singularity Analysis of 6-PUS Vertical Parallel Mechanism
Authors: Wang Chao Qun , Wu Hong Tao
Published: July 2013

Different from the general 6-SPS Stewart platform, 6-PUS parallel mechanism is a kind of fully parallel mechanism whose actuators are all fixed at the frame. The advantages of this mechanism are light movable mass, small inertia and good dynamic characteristics. This paper is focused on the singularity analysis of the 6-PUS parallel mechanism. Based on the Jacobian matrix which is derived from the kinematical equation, the analytic singularity locus equations are obtained and the three types singularities of the parallel mechanism are analyzed. Moreover, the position-singularity of the mechanism is discussed through some specific examples.
Crack Location in Beams Using Wavelet Analysis
Authors: Solís Mario , Algaba Mario , Galvín Pedro
Published: July 2013

This paper applies a methodology for damage detection in beams proposed by the authors. The methodology is based on a continuous wavelet analysis of the difference of mode shapes between a damaged state and a reference state. The wavelet transform is used to detect changes in the mode shapes induced by damage. The wavelet coefficients for each mode are added up and normalized to unity in order to obtain a clear and precise damage assessment. A curve fitting approach reduces the effect of experimental noise in the mode shapes. When only a small number of measuring points are available, a cubic spline interpolation technique provides additional “virtual” measuring points. The interpolation technique may also be used when measuring points are not equally spaced. It also serves as a softening technique of the mode shapes when applied, and no curve fitting approach is used in that case. An antisymmetric extension at both ends of the mode shapes is used to avoid the edge effect in the wavelet transform. The paper presents the results obtained for steel beams with an induced crack. Several sizes and locations of the crack have been considered. The paper addresses several issues affecting the accuracy of the proposed methodology, such as the number of measuring points and the effect of the extension, curve fitting and interpolation techniques.
Smart Structural Health Monitoring Validated on a Simple Plate under Compressive Loading
Authors: Viechtbauer Christoph , Schröder Kai Uwe , Schagerl Martin
Published: July 2013

The subject of this research is the implementation of a Smart Structural Health Monitoring based on structural analysis and its validation on the plate under compressive loading. In the given context the structural analysis provides the most probable failure mode of the structure, e.g. buckling and the stress and deformation state at failure. With this information an algorithm analyses the onset of failure and infers from these analysis results the measurement values, which have to be monitored to identify the damage. By means of this, an appropriate sensor and the optimal sensor placement are chosen. As this pre-process supports the damage identification it is referred to as Smart Structural Health Monitoring (SSHM). The potential of SSHM to optimize the damage identification process is compared to a simple Structural Health Monitoring is demonstrated with a plate under compressive loading. In an experimental setup the plate is loaded up to buckling. After buckling the loading still increases up to failure of the plate caused by the deformations in the post buckling region. With a minimum of sensors and in combination with the analysis results of the SSHM the damage of the plate is detected, located and quantified.
Numerical Procedures for Damage Mechanisms Analysis in CFRP Composites
Authors: Caputo Francesco , Gennaro Di Felice , Lamanna Giuseppe , Lefons Antonio , Riccio Aniello
Published: July 2013

Damage after impact often involves aeronautic structures. The aircraft can be involved in impacts during the assembly stage and operative life. Typical impacts can be related to falling tools, hailstones, debris on the take-off strip thrown against the aircraft by the rolling tyres, maintenance operations. There are two categories of damage impact: Low and High Velocity Impact (LVI, HVI). Damages coming from low velocity impacts are difficult to identify because they are often within the composite structure and the use of non-destructive testing, e.g. ultrasonic test, is not convenient. In order to prevent catastrophic events the designers must increase the safety margin and thereby the weight of the aircraft. The present study shows two different numerical procedures based on finite elements method to investigate on some damage mechanisms of a carbon fibre reinforced plastic (CFRP) structures (e.g. interface debonding, fibre or matrix cracking) and the residual strength of such structures under live loads.
Experimental Testing of a Cross-Entropy Algorithm to Detect Damage
Authors: González Arturo , Covián Enrique , Casero Miguel , Cooper John
Published: July 2013

Cross-entropy optimization has recently been applied to the damage detection in structures subject to static loading. The optimization procedure minimizes the error between the measured deflection data and theoretical deflection data obtained from artificially generated finite element models based on assumed statistical distributions of stiffness for each discretized element. Following a number of iterations, the finite element model with stiffness properties producing deflections closer to reality is established as the mathematical model closest to the true structure. However, while previous testing of the algorithm has been relatively successful, it has been limited to theoretical simulations. Therefore, this paper conducts lab experiments on a beam loaded statically to test the accuracy of the algorithm. Deflections are measured for beam scenarios under different loading levels. The accuracy of the results is discussed and recommendations are made to improve the performance of the algorithm when implemented in practice.
The Dynamic Behaviour of a Buried Water Pipe and its Effect on Leak Location Using Acoustic Methods
Authors: de Almeida Fabricio , Joseph Phillip , Brennan Michael , Whitfield Stewart , Dray Simon
Published: July 2013

Leakage in buried pipes is one of the main concerns for water companies due to the scarcity of potable water sources. Older metallic pipelines have been replaced by plastic pipes in such systems, which makes it more difficult to locate leaks using acoustics and vibration. This is mainly because of the high attenuation of leak signals caused by the damping in the pipe-wall. To investigate acoustic methods in leak location in controlled conditions, a bespoke test rig was constructed in the UK. In this paper, data from this test-rig is used to discuss some issues that arise when using two contemporary correlators. Of particular interest, is the way in which a resonance in the system can have a profound effect on the estimate of the position of the leak depending on the way in which the leak noise signals are processed.
Assessment of Historic Structures Based on GPR, Ultrasound, and Impact-Echo Data Fusion
Authors: Safont Gonzalo , Salazar Addisson , Vergara Luis , Vidal Antonio , Gonzalez Alberto
Published: July 2013

This paper presents a method for assessment of historic structures based on the fusion of data from ground-penetrating radar (GPR), ultrasound, and impact-echo testing. The method consists of the following steps: measuring, feature extraction, fusion, representation, and evaluation. The employed techniques for an application in scale models of historical walls are described. Thus, experimental deployment; signal feature processing; fusion operators (including order statistics digital filters); 2D non-destructive testing images, and figures of merits of the fused results are explained in detail. The deformation of different imperfections in the material structure related to the application of weight load increments applied on the wall is analyzed by using different kinds of fusion configurations.
Modelling of Piezo-Bond Structure System for Structural Health Monitoring Using EMI Technique
Authors: Bhalla Suresh K. , Moharana Sumedha
Published: July 2013

During the last two decades, active research has gone into the theoretical and the practical aspects of the electro-mechanical impedance (EMI) technique for structural health monitoring (SHM).This paper reviews the theoretical developments in modelling the force transfer mechanism between the piezoelectric-ceramic (PZT) patch and the host structure pertinent to the EMI technique. The review covers the modelling efforts spanning about last one and a half decades. The models reviewed include the shear lag based model, simplified shear lag model, the refined shear lag model and the continuum shear lag model. The first three listed models ignored the inertia term. The last model, that is the continuum based model, takes care of all the piezo, structural and adhesive effects rigorously and simultaneously. Typical comparisons between the outcomes resulting from the models are discussed.
Damage Detection of Shear Connectors Based on Power Spectral Density Transmissibility
Authors: Li Jun , Hao Hong
Published: July 2013

Damage of shear connectors in slab-on-girder structures will result in shear slippage between slab and girder, which significantly reduces the load-carrying capacity of the bridge. This paper proposes a dynamic damage detection approach to identify the damage of shear connectors in slab-on-girder bridges with power spectral density transmissibility (PSDT). PSDT formulates the relationship between the auto-spectral density functions of two responses. Measured impact force and acceleration responses from hammer tests are analyzed to obtain the frequency response functions at the slab and girder sensor locations by experimental modal analysis. When measurement data from the undamaged structure are available, PSDT from the slab response to the girder response is derived with the obtained frequency response functions. PSDT matrices in the undamaged and damaged states are directly compared to identify the damage of shear connectors. When the measurement data from the undamaged structure are not available, PSDT matrices from measured response at a reference sensor response to those of the slab and girder in the damaged state can also be used to detect the damage of shear connectors. Experimental studies with a concrete slab supported by two steel girders are conducted to investigate the accuracy and efficiency of the proposed approach. Identification results demonstrated that damage of shear connectors can be identified accurately and efficiently with and without measurement data from the undamaged structure.
Identifying Dynamic Characteristics of a Short-Span Viaduct from Vehicle-Induced Vibrations Considering Different Pavement and Parapet Conditions
Authors: Chang K.C. , Kim C.W.
Published: July 2013

In analyzing the vehicle-inducedvibrations of short- to medium-span bridge, this study adopts the conventionalmultivariate autoregressive (MAR) model along with a stabilization diagram (SD) that is introduced to resolve the difficulty indeciding the optimal model order and to reduce the variation of identifiedcharacteristics. Such a combined identification technique is applied to identify dynamic characteristics of a simple steel highway viaduct in Osaka, Japan, with three pavement andparapet conditions. Two issues are investigated through the field experiment: firstly, the accuracy and precision of the present technique is verified, especially in the frequencyidentification; and secondly, the vehicle-bridge interactions (VBI) issues areinvestigated. The bridge frequencies vary due to differentpavement and parapet conditions, but no obvious variation in the mode shapes is observed. Observations also demonstrate that the correlations betweenvehicle and bridge responses are not strong enough to guarantee the successfulidentification of bridge parameters from the raw vehicle responses. Somefurther data processing techniques should be applied to realize the indirect identification of bridge’s dynamic characteristics utilizingvehicle vibrations.n analyzing the vehicle-induced vibrations of short-to medium-span bridge, this study adopts the conventional multivariate autoregressive (MAR) model along with a stabilization diagram (SD) that is introduced to resolve the difficulty in deciding the optimal model order and to reduce the variation of identified characteristics. Such a combined identification technique is applied to identify dynamic characteristics of a simple steel highway viaduct in Osaka, Japan, with three pavement and parapet conditions. Two issues are investigated through the field experiment: firstly, the accuracy and precision of the present technique is verified, especially in the frequency identification; and secondly, the vehicle-bridge interactions (VBI) issues are investigated. The bridge frequencies vary due to different pavement and parapet conditions, but no obvious variation in the mode shapes is observed. Observations also demonstrate that the correlations between vehicle and bridge responses are not strong enough to guarantee the successful identification of bridge parameters from the raw vehicle responses. Some further data processing techniques should be applied to realize the indirect identification of bridges dynamic characteristics utilizing vehicle vibrations.
Impact of Road Profile when Detecting a Localised Damage from Bridge Acceleration Response to a Moving Vehicle
Authors: Hester David , González Arturo
Published: July 2013

Previous work by the authors have shown that the acceleration response of a damaged beam subject to a constant moving load can be assumed to be made up of three components: ‘dynamic’, ‘static’ and ‘damage’. Therefore, appropriate filtering of the acceleration signal can be used to highlight the ‘damage’ component and quantify its severity. This paper builds on these findings to examine if the same approach can be used to identify damage in the more realistic case of a bridge loaded by a sprung vehicle travelling on a road profile. The consideration of a road profile has the effect of exciting the vehicle modes of vibration which will corrupt the spectrum of bridge accelerations with road/vehicle frequencies. Some of these vehicle frequencies may be lower than the first frequency of the bridge and close to the frequency of the ‘damage’ component. In the latter, the vehicle frequencies are difficult to remove without also filtering part of the ‘damage’ component out. As a result, the approach is shown to perform best for low vehicle speeds.
A Full-Field Stress Based Damage Assessment Approach for In Situ Inspection of Composite Structures
Authors: Dulieu-Barton Janice M. , Fruehmann R.K. , Quinn Simon
Published: July 2013

This paper describes the development of a stress / strain based in-situ damage inspection strategy focused around, but not exclusively, using thermoelastic stress analysis (TSA). The underlying philosophy is that defects and damage in a component or structure only constitute a cause for concern if these influence the stress field, i.e. the defect or damage acts as a stress raiser that reduces the service load limit. To assess this, it is necessary for the inspection method to map the distribution of stresses in the component, rather than the location and extent of an irregularity in the material. Imaging based techniques, such as TSA, digital image correlation (DIC) or digital speckle pattern interferometry (DSPI) provide non-contact maps of the surface stresses, deformations and/or strains. The full field data enables the engineer to evaluate if stress concentrations are present within the structure and, if data from a previous inspection is available, to assess if the distribution of stresses within the structure has changed from a previous 'undamaged' state. One of the key issues addressed in the current work has been the transition from a standard test setup, as typically used in laboratory work, to a more flexible (portable) setup relevant to industry requirements, e.g. site inspections. An approach that enables similar resolution (by comparison to current laboratory standard setups) stress and strain data to be captured using natural frequency excitation of a structure has been demonstrated on various full scale components.
Pedestrian Timber Bridges: Experimental Investigation and Modelling
Authors: Casciati Sara , Faravelli Lucia , Bortoluzzi Daniele
Published: July 2013

For a specific pedestrian timber link case study, the authors had the chance to collect measurements of the structural response for a period of a few days but with the chance to repeat the monitoring in different seasonal weather conditions. This paper provides a synthesis of the data collected up to now. A parallel numerical model was implemented accounting for different potential constitutive law of the timber components and different hypotheses on the supports behavior.
Control Performance Evaluation to Avoid Pounding of Bridges
Authors: Heo Gwang Hee , Kim Chung Gil , Jeon Seung Gon , Kim Eun Ji
Published: July 2013

Earthquake inflicts damage on bridges in various ways. In this research an experimental study was carried out to decrease the damage caused by the pounding of bridges as earthquake load was added. For the experiment, we designed a model of successive bridge composed of a reinforced concrete bridge top and I section steel. At each bridge pier was placed a rubber bearing which was frequently used for seismic isolation. As for damper, we ourselves designed and produced a MR damper of 30 KN. Five experimental conditions were given ranging from without damper, with damper but no electricity input, with damper and electricity input, each with two different algorithms. For the experiment, we inflicted a 50% reduced wave of Kobe earthquake horizontally on the model, and compared the displacements and power data under each condition. The result proved that the MR damper of our own design was effective to prevent the successive bridge model from colliding by exerting a sizable amount of influence on its displacement and power data.
Evaluating the Structural Capacity of Concrete Elements through In Situ Instrumentation
Authors: Byrne David , Goggins Jamie
Published: July 2013

The difficulty in predicting the long term load capacity of concrete elements is well documented. Time dependent effects such as creep and shrinkage coupled with varying loading events, particularly during construction, can all have an adverse effect on the long term performance of a concrete structure. This paper proposes a method that utilises in-situ instrumentation to predict the load carrying capacity of concrete members. During the construction of the Engineering building at the National University of Ireland, Galway over 260 sensors were embedded in a number of key concrete elements. The sensors are being continually monitored with the use of automatic datalogging equipment and the data is being used to monitor changes in geometric and material properties along with the subsequent time dependent deterioration of the elements. The paper will illustrate how the in-situ data from the demonstrator building can be used to estimate the real time behaviour of the concrete elements and how these elements might respond to future changes in use and potential retrofitting. A cost analysis will show how such a monitoring system can be used to reduce the uncertainty levels involved when retrofitting concrete buildings.
Stochastic Modeling of Time Series with Application to Local Damage Detection in Rotating Machinery
Authors: Obuchowski Jakub , Wylomanska Agnieszka , Zimroz Radoslaw
Published: July 2013

Raw vibration signals measured on the machine housing in industrial conditions are complex and can be modeled as an additive mixture of several processes (with different statistical properties) related to normal operation of machine, damage related to one (or more) of its part, some noise, etc. In the case of local damage in rotating machines, contribution of informative process related to damage is hidden in the raw signal so its detection is difficult. In this paper we propose to use the statistical modeling of vibration time series to identify these components. Building the model of raw signal may be ineffective. It is proposed to decompose signal into set of narrowband sub-signals using time-frequency representation. Next, it is proposed to model each sub-signal in the given frequency range and classify all signals using their statistical properties. We have used several parameters (called selectors because they will be used for selection of sub-signals from time-frequency map for further processing) for analysis of sub-signals. They have base in statistics theory and can be useful for example in testing of normality of data set (vibration time series from machine in good condition is close to Gaussian, damaged not). Results of such modeling will be used in the sub-signals classification procedure but also in defects detection. We illustrate effectiveness of novel technique using real data from heavy machinery system.
Damage Identification in a Laboratory Offshore Wind Turbine Demonstrator
Authors: Gómez González Ana , Zugasti Ekhi , Anduaga Javier
Published: July 2013

This paper presents a method to detect and identify damage in a laboratory offshore wind turbine support structure. The structure consists of three different parts: the jacket, the tower and the nacelle. The jacket is a lattice structure joined with several bolts. The tower consists of three different sections joined by bolts. The nacelle is composed of a single piece. The different parts are also joined with bolts. The damage in the structure is simulated by loosening some of the bolts in the jacket. Two damage detection algorithms, namely AutoRegressive methods and NullSpace methods, have been tested in a primitive variation of this structure without the jacket, obtaining good results. In this paper we present the application of the last damage detection method to the new structure with the jacket and an extension to identification of the damage.
Failure Analysis of Wind Turbines by Probability Density Evolution Method
Authors: Sichani M.T. , Nielsen S.R.K. , Liu W.F. , Chen J.B. , Li J. , Peng Y.B.
Published: July 2013

The aim of this study is to present an efficient and accurate method for estimation of the failure probability of wind turbine structures which work under turbulent wind load. The classical method for this is to fit one of the extreme value probability distribution functions to extracted maxima of the response of wind turbine. However this approach may contain high amount of uncertainty due to arbitrariness of the data and the distributions chosen. Therefore less uncertain methods are meaningful in this direction. The most natural approach in this respect is the Monte Carlo (MC) simulation. This however has no practical interest due to its excessive computational load. This problem can alternatively be tackled if the evolution of the probability density function (PDF) of the response process can be realized. The evolutionary PDF can then be integrated on the boundaries of the problem, i.e. the exceedance threshold of the response, which results in the accurate values of the failure probability. For this reason we propose to use the probability density evolution method (PDEM). PDEM can alternatively be used to obtain distribution of the extreme values of the response process by simulation. This approach requires less computational effort than integrating the evolution of the PDF; but may have less accuracy. In this paper we present the results of failure probability estimation by the PDEM. The results will then be compared to the extrapolated values from the extreme value distribution fits to the samples response values.
Modal Analysis for Crack Detection in Small Wind Turbine Blades
Authors: Ulriksen Martin Dalgaard , Skov Jonas Falk , Dickow Kristoffer Ahrens , Kirkegaard Poul Henning , Damkilde Lars
Published: July 2013

The aim of the present paper is to evaluate structural health monitoring (SHM) techniques based on modal analysis for crack detection in small wind turbine blades. A finite element (FE) model calibrated to measured modal parameters will be introduced to cracks with different sizes along one edge of the blade. Changes in modal parameters from the FE model are compared with data obtained from experimental tests. These comparisons will be used to validate the FE model and subsequently discuss the usability of SHM techniques based on modal parameters for condition monitoring of wind turbine blades.
Monitoring Changes in the Soil and Foundation Characteristics of an Offshore Wind Turbine Using Automated Operational Modal Analysis
Authors: de Sitter Gert , Weitjens Wout , El-Kafafy Mahmoud , Devriendt Christof
Published: July 2013

This paper will show the first results of a long term monitoring campaign on an offshore wind turbine in the Belgian North Sea. It will focus on the vibration levels and resonant frequencies of the fundamental modes of the support structure. These parameters will be crucial to minimize O&M costs and to extend the lifetime of offshore wind turbine structures. For monopile foundations for example, scouring and reduction in foundation integrity over time are especially problematic because they reduce the fundamental structural resonance of the support structure, aligning that resonance frequency more closely to the lower frequencies. Since both the broadband wave energy and the rotating frequency of the turbine are contained in this low frequency band, the lower natural frequency can create resonant behavior increasing fatigue damage. Continuous monitoring of the effect of scour on the dynamics of the wind turbine will help to optimize the maintenance activities on the scour protection system. To allow a proper continuous monitoring during operation, reliable state-of-the-art operational modal analysis techniques should be used and these are presented in this paper. The methods are also automated, so that no human-interaction is required and the system can track the natural frequencies and damping ratios in a reliable manner.
Analyzing the Strain Sensing Response of Photoactive Thin Films Using Absorption Spectroscopy
Authors: Ryu Dong Hyeon , Loh Kenneth J.
Published: July 2013

Structural health monitoring systems are required for detecting damage in structures so as to facilitate their timely maintenance and repair and to prevent catastrophic structural failure. To date, a variety of different sensor platforms (e.g., piezoelectric materials, fiber optics, and wireless sensors) have been proposed for SHM. However, they still suffer from high energy demand, large form factors, and durability issues, particularly when applied for monitoring space structures and reusable spacecraft. In a previous study, a bio-inspired and photocurrent-based strain sensor has been developed. This poly(3-hexylthiophene) (P3HT)-based nanocomposite sensor has been shown to generate photocurrent whose magnitude varies in tandem with applied strain. However, the photocurrent generation performance of the sensor is quite low. In addition, the strain sensing mechanism is not fully understood. In this study, the performance of the photoactive thin films were enhanced, and its strain sensing characteristics were analyzed using ultraviolet-visible (UV-Vis) absorption spectroscopy. First, multilayered photoactive and P3HT-based thin films were assembled via spin coating. The photocurrent generation performance of the films was evaluated using two methodologies, namely its photocurrent time history and current-voltage (IV) response. Uniform coating of the photoactive layer and high purity aluminum electrodes were crucial for improving their photocurrent generation. Second, light absorption properties of the P3HT-based photoactive layer were investigated at different strain levels using a UV-Vis spectrophotometer. Light absorption was shown to vary linearly with applied tensile strains.
Characterization of CFRP Using Laser Vibrometry
Authors: Malinowski Pawel , Wandowski Tomasz , Ostachowicz Wieslaw
Published: July 2013

The investigation was focused on Carbon Fibre Reinforced Polymers (CFRP). In the first part of research the aim was the characterization of CFRP surfaces. These surfaces were influenced by release agent, hydraulic fluid, moisture and overheating. In the second part of research adhesive bond quality was investigated. Three different cases of possible weak bonds were focused on. Weak bond caused by release agent contamination, moisture contamination and poor curing of adhesive. The characterization was conducted using laser vibrometry used as NDT tools. An active element in the form of piezoelectric transducer was used to excite the samples made out of CFRP material. Laser vibroemter was used to register the surface response. Combining the piezoelectric excitation with laser sensing a tool was obtained to measure precisely the propagating elastic waves. The excited waves were measured in defined points by the vibrometer obtaining the wavefield. In order to characterize the surface and bonding quality an indicator was proposed based on propagating wave parameters. The guided elastic wave velocity depends material properties (Young modulus, density, Poisson ratio) and thickness of the sample. It was assumed that comparison of the velocities can provide an information about the bond condition. All the investigated scenarios showed deviation from the reference case.
Compressive Sensing for Structural Damage Detection of Reinforced Concrete Structures
Authors: Jayawardhana Madhuka , Zhu Xin Qun , Liyanapathirana Ranjith , Gunawardana Upul
Published: July 2013

High energy consumption, excessive data storage and transfer requirements are prevailing issues associated with structural health monitoring (SHM) systems, especially with those employing wireless sensors. Data compression is one of the techniques being explored to mitigate the effects of these issues. Compressive sensing (CS) introduces a means of reproducing a signal with a much less number of samples than the Nyquist's rate, reducing the energy consumption, data storage and transfer cost. This paper explores the applicability of CS for SHM, in particular for damage detection and localization. CS is implemented in a simulated environment to compress SHM data. The reconstructed signal is verified for accuracy using structural response data obtained from a series of tests carried out on a reinforced concrete (RC) slab. Results show that the reconstruction was close, but not exact as a consequence of the noise associated with the responses. However, further analysis using the reconstructed signal provided successful damage detection and localization results, showing that although the reconstruction using CS is not exact, it is sufficient to provide the crucial information of the existence and location of damage.
Vision-Based Sensing in Dynamic Tests
Authors: Casciati Fabio , Casciati Sara , Wu Li Jun
Published: July 2013

The availability of a suitable data acquisition sensor network is a key implementation issue to link models with real world structures. Non-contact displacement sensors should be preferred since they do not change the system properties. A two-dimensional vision-based displacement measurement sensor is the focus of this contribution. In particular, the perspective distortion introduced by the angle between the optic axis of the camera and the normal to the plane in which the structural system deforms is considered. A two-dimensional affine transformation is utilized to eliminate the distortion from the recorded to the distortion-free image. The results of a laboratory experiment show the potential of the proposed approach.
Investigating the Flexural Behaviour of Foams at High Strain Rate Using Optical Measurement Techniques
Authors: Crump Duncan A. , Dulieu-Barton Janice M.
Published: July 2013

Polymer closed cell foam beam specimens manufactured from H100 Divinycell (Diab) are tested in four point bend at three loading speeds using a specially designed rig and an Instron VHS test machine. Synchronised high speed images are captured using white light and infra-red thermography (IRT) to obtain the mid-point full-field deflection and strains using digital image correlation (DIC) along with the temperature evolutions. There is a marked increase in the maximum load to failure with loading rate and the optical techniques provide an opportunity to analyse the strain and temperature evolution within the specimens.
Design and Validation of Embedded Piezoelectric Transducers for Damage Detection Applications in Concrete Structures
Authors: Karaiskos Grigoris , Flawinne Sébastien , Sener Jean Yves , Deraemaeker Arnaud
Published: July 2013

Current maintenance of concrete civil infrastructure such as buildings, bridges, dams and highways, is based on scheduled inspection consisting in visual and/or local inspection techniques (i.e. acoustic/ultrasonic methods, radiography, eddy-current methods). A major trend in the field is the development of automated on-line monitoring systems. The current study is focused on the use of ultrasonic wave propagation techniques based on embedded piezoelectric transducers for the on-line monitoring of the damage state in concrete. The technique is based on the use of an ultrasonic emitter-receiver pair and the construction of a damage indicator focused on the early wave arrival. The proposed simple monitoring system is implemented during several pull-out tests on concrete blocks. The results demonstrate the excellent performance of the system which is able to detect the initiation and follow the evolution of the cracking until complete failure.
Application of the Hilbert-Huang Transform for Identification of Changes in Boundary Conditions of a Bridge Using Vibration Data due to Traffic
Authors: González Arturo , Aied Hussein
Published: July 2013

The translational restraints associated to pin and rocker bearings are typically idealized in the form of fixed and free conditions. However, elastomeric bearings need to be represented with springs to reasonably predict the time- and frequency-domain response of bridges under traffic-induced vibrations. Therefore, changes in the response of these bearings are common as a result of aging, deterioration, variation in loading levels and/or environmental changes. The latter makes difficult to discern if changes in the frequency content of the structural response to ambient vibration are due to changes in temperature, changes in normal operational loads or the occurrence of damage. In this paper, the bridge is idealized by a beam model supported on a hysteretic translational sprung support. The purpose is twofold: (a) to gather a better understanding of the variations of the bridge response with bearing performance; and (b) to be able to quickly identify an anomaly in the bearing. Empirical Mode Decomposition and the Hilbert-Huang Transform are employed to capture changes in the bearing stiffness from the bridge response.
Imaging and Characterizing Structural Defects through the Estimation of Local Dispersion Curves
Authors: Flynn Eric B. , Jarmer Gregory S. , Chong See Yenn , Lee Jung Ryul
Published: July 2013

We describe a method to effectively image and characterize structural features and defects using local estimates of wavenumber for propagating guided Lamb waves at a fine grid of spatial sampling points. The guided waves are rapidly excited at each grid point using a scanning Q-switched laser system and sensed by a single fixed ultrasonic transducer. Through reciprocity, this produces a full-wave-field time history of a virtual wave being excited from the transducer.We first demonstrate the unique capability of the measurement system by showing frequency-wavenumber intensity diagrams that resolve up to 5th order guided Lamb wave modes. Well then show how, using frequency-wavenumber processing, localized wavelength estimates can be obtained by isolating each guided Lamb wave mode, extracting a specific frequency bin, and identifying the center-wavelength of a sliding wavenumber band-pass filter that maximizes the energy at each grid point. This procedure is repeated across all frequency bins in order generate estimates of the local dispersion curves at each spatial sample point on the structure. The approach was capable of producing detailed images of hidden wall-thinning in an aluminum plate and local impact delamination in a complicated composite component.
Engine Assembly Quality Defect Inspection Based on EMD-Envelope Spectra
Authors: Ye Wei Jun , Shao Yi Min
Published: July 2013

As the complicate structure and unstable working condition, the vibration signal of engines always be non-stationary and drown in strong noise, especially for the case of slight quality defection. Such case directly results in difficulties for inspection and diagnosis of engine incipient defection. A new inspecting method based on empirical mode decomposition (EMD) and envelope spectrum is proposed in this paper. In the new method, the intrinsic mode functions (IMF) of de-noised angular vibration signals are firstly obtained; then the envelope spectrums of IMFs are obtained through envelope analysis, lastly the discrepancy of the envelope spectrums between normal and abnormal case is extracted to be the feature indicator for the engine quality inspection. This method is validated experimentally. The results show that the proposed method has an excellent performance in the quality inspecting in the presence of abnormal clearance between crankshaft and connecting rod of the engine.
Novel Approaches for Processing of Multi-Channels NDT Signals for Damage Detection in Conveyor Belts with Steel Cords
Authors: Blazej Ryszard , Jurdziak Leszek , Zimroz Radoslaw
Published: July 2013

Belt conveyors are one of the most popular methods of material transport in many branches of industry, especially in mining. The average length of mining belt conveyor is about 1000 m. Taking into account that total length of transportation ways in averaged mine can approach several dozen of kilometers and network of several conveyors may cover large area, maintenance of such specific transportation system is very difficult. In this work we propose an automatic multi-channel system for data acquisition and processing for damage detection in belts. Belts with steel cords are considered here, they consist of top and bottom rubber covers and steel cords in between them. Due to many reasons (mainly sharpness of transported materials) covers may be damaged and it may initiate degradation process or straight damages in steel cords. Properties of steel cords are therefore crucial for overall strength of belts, if they are damaged, it may cause catastrophic failure of the whole conveyor. So, monitoring of belts conditions is a crucial issue. We proposed a monitoring system that measure and process data from array of magnetic sensors. The system allows to acquire up to 24 channels of NDT signals and uses automatic algorithms to process them in order to get information about begin of the belt loop, location of joints of particular belt segments and the final location and size of damages related to corrosion or cuts of steel cords inside belts. These techniques will be presented in the paper. Our approach has been validated in a lignite mine for several conveyor belts.
Additives for Solid Polymer Electrolytes: The Layered Nanoparticles
Authors: Si Satyabrata
Published: July 2013

The massive exploitation of modern technology results in increasing demand of energy of the entire world, which has urged extensive research and development in the areas of energy production from non-conventional resources, their storage and distribution. Electrolyte is one of the components in various electrochemical devices, like solar cells, fuel cells, rechargeable battery etc. Besides the conventional liquid electrolytes, polymer based electrolytes gain particular attention because of their solid nature, flexibility and ease of availability. For the last few decades, use of inorganic nanoparticles as additives is one of the most promising ways to improve the electrochemical performance of polymer electrolytes. The resulting nanocomposite polymer electrolytes can display enhanced conductivity, mechanical stability and improved interfacial stability towards electrode materials. This review highlights the recent research efforts given to the nanocomposites systems containing various layered transition metal hydroxides for making solid polymer electrolytes. Also various approaches adopted to understand the ion conduction mechanism of solid polymer electrolytes has also been discussed.