2-D Statistical Damage Detection of Concrete Structures Combining Smart Piezoelectric Materials and Scanning Laser Doppler Vibrometry

In the present study a new structural health monitoring (SHM) technique isproposed as well as a new damage index based on 2-D error statistics. The proposedtechnique combines the electromechanical impedance technique (EMI) which is based onthe use of piezoelectric Lead Zirconate Titanate (PZT) patches and Scanning LaserDoppler Vibrometry (SLDV) for damage detection purposes of concrete structures andearly age monitoring. Typically the EMI technique utilizes the direct and inversepiezoelectric effect of a PZT patch attached to a host structure via an impedance analyzerthat is used for both the actuation and sensing the response of the PZT-Host structuresystem. In the proposed technique the attached PZTs are actuated via a function generatorand the PZT-Host structure response is obtained by a Scanning Laser DopplerVibrometer. Spectrums of oscillation velocity of the surface of the attached PZTs verticalto the laser beam versus frequency are obtained and are evaluated for SHM purposes.This damage detection approach also includes the use of a damage index denoted asECAR (Ellipse to Circle Area Ratio) based on 2-D error statistics and is compared to theRoot Mean Square Deviation (RMSD) damage index commonly used in SHMapplications. Experimental results include ascending uniaxial compressive load ofconcrete cubic specimens, ascending three point bending of reinforced concrete beamspecimens and early age monitoring of concrete. Results illustrate the efficiency of theproposed technique in damage detection as well as early age monitoring as, in the firstcase, both severity and location of damage can be determined by examining the values ofdamage indices for each damaged state and in the early age monitoring case damageindices follow the strength gain curve.

Potential of acoustic emissions from three point bending tests as rock failure precursors

Development of failure in brittle materials is associated with microcracks,which release energy in the form of elastic waves called acoustic emissions. This paper presents results from acoustic emission measurements obtained during three point bending tests on Nestos marble under laboratory conditions.Acoustic emission activity was monitored using piezoelectric acoustic emission sensors,and the potential for accurate prediction of rock damage based on acoustic emission data was investigated. Damage localization was determined based on acoustic emissions generated from the critically stressed region as scattered events at stresses below and close to the strength of the material.

Improving the seismic performance of base-isolated liquid storage tanks with supplemental linear viscous dampers

Large tanks are extensively used for storing water,petrochemicals and fuels.Since they are often cited in earthquake-prone areas,the safe and continuous operation of these important structures must be ensured even when severe earthquakes occur,since their failure could have devastating financial and socio-environmental consequences.Base-isolation has been widely adopted for the efficient seismic protection of such critical facilities.However,base-isolated tanks can be located relatively close to active faults that generate strong excitations with special characteristics.Consequently,viscous dampers can be incorporated into the isolation system to reduce excessive displacement demands and to avoid overconservative isolator design.Nonetheless,only a few studies have focused on the investigation of seismic response of base-isolated liquid storage tanks in conjunction with supplemental viscous dampers.Therefore,the impact of the addition of supplemental linear viscous dampers on the seismic performance of tanks isolated by single friction pendulum devices is investigated herein.Four levels of supplemental damping are assessed and compared with respect to isolators′displacement capacity and accelerations that are transferred to the tanks.

Selection of optimal land uses for the reclamation of surface mines by using evolutionary algorithms

A methodology for the selection of the optimal land uses of the reclamation of mined areas is proposed. It takes into consideration several multi-nature criteria and constraints, including spatial constrains related to the permissible land uses in certain parts of the mined area. The methodology combines desirability functions and evolution searching algorithms for selection of the optimal reclamation scheme. Its application for the reclamation planning of the Amynteon lignite surface mine in Greece indicated that it handles effectively spatial and non-spatial constraints and incorporates easily the decision-makers preferences regarding the reclamation strategy in the optimization procedure.

Security Measures Against CBRN Threats:Case Study Olympic Games

In this paper we present how an serious security relevant event can be taken care of duing Olympic Games.Remote healthcare treatment will be given to injured persons during nuclear radiological biological attacks or in the case of physical disasters. The "Emergency-112" wireless telemedicine platform provides the hardware and software inrastructures in order to cope with the most extreme scenarios.A fully autonomous mobile system interconnects a group of injured persons with the expert medical institution.The unlimited capabilities of the system allows the Emergency-112 platform to be sed for rescue and surveillance operations regardless the terrain or the weather conditions.A dynamic hybrid system monitors the available spectrum and actively switches between different telecommunication access gateways.

Mineralogical Investigation and Washability Treatment of the Nickeliferous Lateritic Deposit of Nome (Albania)

The Nome nickel laterite deposit is located in the North East of Albania. The ore deposit, developed between ultramafic rocks and limestones during Early Cretaceous to Eocene, represents part of the Albanian Mirdita ophiolite zone. The lateritization of the deposit was observed mainly in three separate areas, the Has-Kukes-Lure in the North, Pogradec-Librazhd in the center and Devoll in the South. The main mineralogical components of the ore are goethite, hematite and quartz, while the secondary ones are chlorite (clinochlore, Ni-chlorite), kaolinite and lizardite. Nickel is mainly found in chlorite. The ore is characterized by the presence of spheroid particles, such as oval, pisoid, peloid and composite spheroid. According to the microscopical examination the ore is characterized in general as allotriomorphic, inequigranular and the texture is oolitic-pisolitic. For the mineral processing gravimetric and magnetic separation are used in the size fractions &#458 + 4 mm, &#454 + 1 mm, &#451 + 0.250 mm and &#450.250 + 0.063 mm. The chemical and mineralogical analyses, as well as the microscopic examination have shown that mineral processing by magnetic separation gives the most satisfactory results for the size fractions &#451 + 0.250 mm and &#450.250 + 0.063 mm.

A new hybrid decision support tool for evaluating the sustainability of mining projects

The integration of sustainable development challenges and opportunities into the decision making process during the design and/or implementation of multi-disciplinary mining projects is generally not supported by decision support systems(DSS). A new hybrid decision support tool, which features an integrated assessment of sustainable development issues as they apply to mining projects, is hereby proposed. The proposed DSS framework, named ‘‘Acropolis DSS", can be used to assist involved stakeholders in critical decisions, especially when addressing issues such as stakeholder participation, transparency,and trade-offs. The proposed DSS is based on a multi-criteria decision analysis combined with the multi-attribute utility theory.

在同心和偏心圆环中有屈服应力的黏塑性流体流动的模型和数值模拟(英文)

Numerical solution of yield viscoplastic fluid flow is hindered by the singularity inherent to the Herschel-Bulkley model.A finite difference method over the boundary-fitted orthogonal coordinate system is util-ized to investigate numerically the fully developed steady flow of non-Newtonian yield viscoplastic fluid through concentric and eccentric annuli.The fluid rheology is described with the Herschel-Bulkley model.The numerical simulation based on a continuous viscoplastic approach to the Herschel-Bulkley model is found in poor accordance with the experimental data on volumetric flow rate of a bentonite suspension.A strict mathematical model for Herschel-Bulkley fluid flow is established and the corresponding numerical procedures are proposed.However,only the case of flow of a Herschel-Bulkley fluid in a concentric annulus is resolved based on the presumed flow structure by using the common optimization technique.Possible flow structures in an eccentric annulus are pre-sumed,and further challenges in numerical simulation of the Herschel-Bulkley fluid flow are suggested.

Secure Packet Video Transmission over Wireless Multimedia Sensor Networks

This paper proposes a packet scheduling scheme thatoptimizing the coded video transmission overmultipath wireless multimedia sensor networks interms of received video distortion and power efficiencyenhances the security aspects of the underlyingsystem.When the aggregate transmission rateavailable at the network cannot support the requiredtransmission rate,the scheduling algorithm can selectivelydrop combinations of video packets prior totransmission to adapt the rate of the sender to thelimitations of the wireless channel capacity.Twoscheduling algorithms are proposed.The Baselinescheme utilizes a novel distortion prediction modeland decides upon which packet can be dropped priorto transmission based on the packet’s impact on thevideo distortion.In addition to the bandwidthlimitations,the Power aware packet scheduling is an extension of the Baseline capable of estimating thepower that will be consumed by each node during thetransmission;hence it can control the power consumptionby selectively drop packets of low importanceto the decoded video.Simulation results indicatethe efficiency of the proposed scheduling schemein terms of received video distortion(PSNR)andpower consumption.

Simulation of Propagation Loss Models and Antenna Designs for Naval Troposcatter and Tropospheric Duct Communications

Tropospheric Scattering(Troposcatter) and Tropospheric Ducting are two different mechanisms due to in-homogenoueties in the lower part of the Earths atmosphere.Their common influence in propagation of microwaves is studied here in order to achieve a feasible naval communication system.Although not new,Troposcatter together with Tropospheric Ducting communications are regaining popularity in current military and civil applications such as isolated islands and oil extraction facilities in the open sea.The innovation proposed here is the application of such systems in naval communications where at least one of the stations is mobile.Several propagation together with fading models are simulated using appropriate programs and scientific simulation packets in order to predict maximum range of such communication systems in each dominant mode of operation.Then appropriate antenna design proposals are given to overcome the high propagation loss and minimize possible interferences.

Large and Moderate Deviations for Projective Systems and Projective Limits

One of the active fields in applied probability, the last two decades, is that of large deviations theory i.e. the one dealing with the (asymptotic) computation of probabilities of rare events which are exponentially small as a function of some parameter e.g. the amplitude of the noise perturbing a dynamical system. Basic ideas of the theory can be tracked back to Laplace, the first rigorous results are due to Cramer although a clear definition was introduced by Varadhan in 1966. Large deviations estimates have been proved to be the crucial tool in studying problems in Statistics, Physics (Thermodynamics and Statistical Mechanics), Finance (Monte-Carlo methods, option pricing, long term portfolio investment) and in Applied probability (queuing theory). The aim of this work is to describe one of the (recent) methods of proving large deviations results, namely that of projective systems. We compare the method with the one of projective limits and show the advantages of the first. These advantages are due to the fact that: 1) the arguments are direct and the proofs of the basic results of the theory are much easier and simpler;2) we are able to extend most of these results using suitable projective systems. We apply the method in the case of a) sequences of i.i.d. r.v.’s and b) sequences of exchangeable r.v.’s. All the results are being proved in a simple “unified” way.

On the QoS Assessment of Video Sessions in Heterogeneous 3G-WLAN Networks with Seamless and Secure Mobility Support

Real-time video data transmission is currently emerging as a popular application among mobile users but it is very sensitive to QoS degradation due to packet losses in wireless networks.In order to achieve service continuity and integrity upon handoffs among heterogeneous networks,provisioning of seamless and secure mobility is required.However,in order to reduce the delay and packet losses during vertical handovers we need to employ supportive protocols like context transfer.In this paper we evaluate the QoS of video transmission over a heterogeneous 3G-WLAN network.The aggregate video data traffic is represented by a dynamic two-dimensional Markov chain model,which has been evaluated against real video data measurement.Upon the vertical handover, appropriate AAA handshaking and enhanced mobility management using context transfer have been considered.Perceived QoS evaluation of video streams was performed based on peak signal-noise ratio(PSNR) measurements,while we analyticallyestimated the number of packet losses during handovers.The results show that both packet loss within the converged network and loss occurrence affecting the perceived video quality is reduced. Moreover,the proposed context transfer scheme minimizes handover delay and the number of lost packet up to 3 times compared to standard AAA handshaking.

Ultrahigh Acceleration of Plasma Blocks by Nonlinear Forces for Side-On Laser Ignition of Solid Density Fusion Fuel

A fundamental difference of very high intensity laser interaction with plasmas from solid targets appears with lasing at picosecond （ps） pulse durations in contrast to pulses of nanosec-onds （ns）. This can be seen from the more than 10,000 times higher acceleration with ps pulse du-rations than with thermal pressure determined interaction. A ps pulse duration produces instantly acting high-efficiency nonlinear （ponderomotive） electrodynamic force dominated acceleration in contrast to heating with longer pulses. The ps pulses accelerate high-density plasma blocks. This can be used by a new scheme of side-on driven laser fusion with generating a flame ignition in uncompressed fusion fuel of solid density resulting in a reaction velocity of more than 2000 km/s for DT.

Motivation Factors in the Military: Ethical Leadership and Virtue Ethics

This paper focuses on employee motivation factors in military organizations.In the context of the special mission of the military profession,military leadership is approached in an effort to demonstrate the importance and necessity of its ethical dimension in relation to employee motivation.On the motivation factors related to employee personality traits,the paper seeks to demonstrate—through Aristotle’s philosophical reasoning(virtue ethics)—that military virtues have to define each member of the Armed Forces in order to fulfill his/her mission.The methodology part of this paper uses the method of interview with permanent officers of the Hellenic Armed Forces in order to prove the strong relationship between ethical leadership,virtue ethics,and employee motivation in the military.

A Novel Process for the Study of Breakage Energy versus Particle Size

The energy size relationship is examined, either as the specific energy required breaking a particulate material from an initial size d1 to a final size d2, where d is usually the d80 size, or as the specific energy required to break a single particle. The present work uses the results obtained using a controlled frequency centrifugal crusher to crush particles of a predetermined size class under different rotation frequencies related to the kinetic energy of the particles at the moment of crushing. The paper calculates the relationship between the rotation frequency and the kinetic energy of the particles before crushing and examines the size distribution of the products. The study results allow presenting the relationship between the kinetic energy of the particles and the mass of particles produced below the initial size class. The work also produces the optimum mathematical model that describes this relationship among three proposed ones. According to this model one can calculate the energy required breaking half of the initial mass below the initial size class and the corresponding specific energy is appointed to the average size of the class. The parameters of the mathematical model can be used to compare the grindability of the different materials. The process can be used as an alternative to the drop weight technique used so far for the study of the breakage energy of minerals and rocks.

Editor's Note

It is with great pleasure that I am serving as a Guest Editor for special issues of the CHINA COMMUNICATIONS JOURNAL on Communications and Information Security in Feb.and June,2007. The goal of these issues is to present the direction that the field has been taking in the last 3-5 years,introduce new

结合催化气化过程的高效直接碳固体氧化物燃料电池(英文)

This study explores strategies to develop highly efficient direct carbon fuel cells(DCFCs) by com-bining a solid-oxide fuel cell(SOFC) with a catalyst-aided carbon-gasification process. This system employs Cu/CeO 2 composites as both anodic electrodes and carbon additives in a cell of the type: carbon|Cu-CeO 2/YSZ/Ag|air. The study investigates the impact on in situ carbon-gasification and DCFC performance characteristics of catalyst addition and variation in the carrier gas used(inert He versus reactive CO2). The results indicate that cell performance is significantly improved by infusing the catalyst into the carbon feedstock and by employing CO2 as the carrier gas. At 800 ℃, the maxi-mum power output is enhanced by approximately 40% and 230% for carbon/CO2 and car-bon/catalyst/CO2 systems, respectively, compared with that of the carbon/He configuration. The increase observed when employing the catalyst and CO2 as the carrier gas can be primarily at-tributed to the pronounced effect of the catalyst on carbon-gasification through the re-verse-Boudouard reaction, and the subsequent in situ electro-oxidation of CO at the anode three-phase boundary.

Strategy for Effective Evacuation of Pedestrians Using GIS and GPS Measurements

During a residential settlement evacuation, a large number of individuals do not have access to any private means of transport in order to be evacuated;these people are assembled at Evacuation Assembly Points (E.A.P.s), so as to be picked up, gathered and evacuated by the competent authorities. The present study aims to evaluate whether some pedestrian assembly points are adequate for these people’s fastest assembly, taking into account the demographic characteristics of the studied population and the incline of the studied area’s ground. In order for said fastest assembly and evacuation to be achieved Geographical Information Systems (G.I.S.) and GPS measurements have been employed. The suggested method has led to the creation of the households’ classification maps based upon their inhabitants’ response time in order to improve the pre-existent Intervention Teams’ contingency plans. First, in order to identify the demographic characteristics of the studied population, we have employed the field survey method;second, we have determined the fastest and ergo optimal evacuation routes using the Dijkstra algorithm. What is more, the results hereof prove that it is feasible that the time it takes to gather the pedestrians be optimized by way of choosing the best evacuation point, whilst a method of large crowds’ evacuation in groups has been developed. The latter could constitute a useful tool for Civil Protection Agents and responders.

Detection of Angioectasias and Haemorrhages Incorporated into a Multi-Class Classification Tool for the GI Tract Anomalies by Using Binary CNNs

The proposed deep learning algorithm will be integrated as a binary classifier under the umbrella of a multi-class classification tool to facilitate the automated detection of non-healthy deformities, anatomical landmarks, pathological findings, other anomalies and normal cases, by examining medical endoscopic images of GI tract. Each binary classifier is trained to detect one specific non-healthy condition. The algorithm analyzed in the present work expands the ability of detection of this tool by classifying GI tract image snapshots into two classes, depicting haemorrhage and non-haemorrhage state. The proposed algorithm is the result of the collaboration between interdisciplinary specialists on AI and Data Analysis, Computer Vision, Gastroenterologists of four University Gastroenterology Departments of Greek Medical Schools. The data used are 195 videos (177 from non-healthy cases and 18 from healthy cases) videos captured from the PillCam(R) Medronics device, originated from 195 patients, all diagnosed with different forms of angioectasia, haemorrhages and other diseases from different sites of the gastrointestinal (GI), mainly including difficult cases of diagnosis. Our AI algorithm is based on convolutional neural network (CNN) trained on annotated images at image level, using a semantic tag indicating whether the image contains angioectasia and haemorrhage traces or not. At least 22 CNN architectures were created and evaluated some of which pre-trained applying transfer learning on ImageNet data. All the CNN variations were introduced, trained to a prevalence dataset of 50%, and evaluated of unseen data. On test data, the best results were obtained from our CNN architectures which do not utilize backbone of transfer learning. Across a balanced dataset from no-healthy images and healthy images from 39 videos from different patients, identified correct diagnosis with sensitivity 90%, specificity 92%, precision 91.8%, FPR 8%, FNR 10%. Besides, we compared the performance of our best CNN algorithm versus our same goal algorithm based on HSV colorimetric lesions features extracted of pixel-level annotations, both algorithms trained and tested on the same data. It is evaluated that the CNN trained on image level annotated images, is 9% less sensitive, achieves 2.6% less precision, 1.2% less FPR, and 7% less FNR, than that based on HSV filters, extracted from on pixel-level annotated training data.

Using AC Conductivity Measurements to Study the Influence of Mechanical Stress on the Strength of Geomaterials

The Dielectric Spectroscopy technique is a tool that can be used to provide information regarding the physical and chemical properties of materials. In this work Dielectric Spectroscopy (DS) measurements were conducted on marble specimens that were previously subjected to uniaxial compressive stress up to fracture in order to investigate the influence of the mechanical stress on the dielectric properties of the specimens. Specifically, the ac conductivity (σac) was measured when an ac electric field in the frequency range 1 kHz - 1 MHz was applied upon dry and saturated specimens which were subjected successively to higher levels of mechanical stress. The experimental results indicate that there are systematic variations in the values of the ac conductivity after each stress application at a higher stress level. Such variations become more intense at higher stress values and can be used to indicate the upcoming fracture since significant increase of conductivity is recorded when microcracks formations appear and propagate in the sample bulk.