Showing papers by "University of Patras published in 1999"
TL;DR: A considerable number of laminate theories, analytical approaches, numerical solutions and computational models have been reported for the analysis of laminates and structures with piezoelectric actuators or sensors as mentioned in this paper.
Abstract: A considerable number of laminate theories, analytical approaches, numerical solutions and computational models have been reported for the analysis of laminates and structures with piezoelectric actuators or sensors. This article provides a review of published work in this area of mechanics. The reported laminate theories and structural mechanics are classified based on fundamental assumptions, the approximation of the through-the-thickness variation of the electromechanical state variables, the method of representation of piezoelectric layers, and their capability to model curvilinear geometries and thermal effects. The performance, advantages and limitations of the various categories of laminate theories are subsequently assessed by correlating results obtained by representative average models. The capability of each theory to model global structural response, local through-the-thickness variations of electromechanical variables, stresses, and piezoelectric laminates of high thickness is also quantified. This review article includes 103 references.
324 citations
TL;DR: The literature does not consistently support the importance of anticoagulation monitoring techniques during CPB, and a small number of well-controlled studies suggest that bleeding and transfusion outcomes can be improved by refining heparin monitoring techniques.
Abstract: The literature does not consistently support the importance of anticoagulation monitoring techniques during CPB. This is best reflected by studies that have evaluated the impact of the ACT method on blood loss and transfusion outcomes. Inconsistent findings from studies that evaluated the impact of ACT monitoring may be related to either suboptimal study design (i.e., retrospective, unblinded, nonrandomized) or possibly the diagnostic inprecision of the ACT method used in these studies. There are a small number of well-controlled studies, some of which suggest that bleeding and transfusion outcomes can be improved by refining heparin monitoring techniques, either by sustaining better anticoagulation during CPB or by optimizing protamine doses (i.e., when empiric protocols result in excessive protamine doses). More well-controlled studies are needed to better define the importance of anticoagulation management during CPB.
274 citations
TL;DR: In this article, the effect of operational parameters, i.e., dye concentration, photocatalyst content, pH of the solution and incident light energy on the degradation rate of aqueous solutions of acid orange 7 (AO7) was examined.
249 citations
TL;DR: A unified view of algorithms for adaptive transversal FIR filtering and system identification has been presented, and the LMS algorithm and its offspring have been presented and interpreted as stochastic approximations of iterative deterministic steepest descent optimization schemes.
Abstract: A unified view of algorithms for adaptive transversal FIR filtering and system identification has been presented. Wiener filtering and stochastic approximation are the origins from which all the algorithms have been derived, via a suitable choice of iterative optimization schemes and appropriate design parameters. Following this philosophy, the LMS algorithm and its offspring have been presented and interpreted as stochastic approximations of iterative deterministic steepest descent optimization schemes. On the other hand, the RLS and the quasi-RLS algorithms, like the quasi-Newton, the FNTN, and the affine projection algorithm, have been derived as stochastic approximations of iterative deterministic Newton and quasi-Newton methods. Fast implementations of these methods have been discussed. Block-adaptive, and block-exact adaptive filtering have also been considered. The performance of the adaptive algorithms has been demonstrated by computer simulations.
232 citations
TL;DR: The interaction between thrombin and vascular endothelial growth factor (VEGF), the specific endothelial cell mitogen and key angiogenic factor, is investigated, revealing a time- and dose-dependent up-regulation of mRNA for VEGF receptors (KDR and flt-1).
229 citations
TL;DR: In this article, the recently introduced end-bridging (EB) Monte Carlo move is revisited, and a thorough analysis of its geometric formulation and numerical implementation is given, along with detailed results from applying the move along with concerted rotation, in atomistic simulations of polyethylene (PE) melt systems with mean molecular lengths ranging from C78 up to C500, flat molecular weight distributions, and polydispersity indices I ranging from 1.02 to 1.12.
Abstract: The recently introduced end-bridging (EB) Monte Carlo move is revisited, and a thorough analysis of its geometric formulation and numerical implementation is given. Detailed results are presented from applying the move, along with concerted rotation, in atomistic simulations of polyethylene (PE) melt systems with mean molecular lengths ranging from C78 up to C500, flat molecular weight distributions, and polydispersity indices I ranging from 1.02 to 1.12. To avoid finite system-size effects, most simulations are executed in a superbox containing up to 5000 mers and special neighbor list strategies are implemented. For all chain lengths considered, excellent equilibration is observed of the thermodynamic and conformational properties of the melt at all length scales, from the level of the bond length to the level of the chain end-to-end vector. In sharp contrast, if no end bridging is allowed among the Monte Carlo moves, no equilibration is achieved, even for the C78 system. The polydispersity index I is f...
226 citations
TL;DR: In this article, an algorithm for the construction of global reduced mechanisms, based on concepts from the Computational Singular Perturbation method, was presented for a laminar premixed CH4/Air flame and a complex detailed chemical kinetics mechanism.
198 citations
TL;DR: In this paper, it was shown that poly(vinyl chloride-co-vinyl acetate-comaleic acid) is a substrate favoring the deposition of vaterite crystals from stable supersaturated solutions at pH 8.50 and 25 °C.
Abstract: Poly(vinyl chloride-co-vinyl acetate-co-maleic acid) (vinyl chloride 83%, vinyl acetate 13%, carboxylated 1%) was found to be a substrate favoring the deposition of vaterite crystals from stable supersaturated solutions at pH 8.50 and 25 °C. Induction times preceding calcium carbonate precipitation were inversely proportional to the solution supersaturation, and a surface energy of 23 mJm-2 was calculated according to classical nucleation theory. The relatively low value may be attributed to the heterogeneous character of vaterite nucleation. The linear dependence of the rates of vaterite formation on the solution supersaturation, in which the crystallization took place, in combination with the independence of the measured rates on the fluid dynamics, suggested that vaterite overgrowth was controlled by surface diffusion. This finding was in agreement with the results obtained for the crystallization of vaterite on cholesterol. Our results suggest that the kinetics of overgrowth may be very important for ...
184 citations
TL;DR: This article focuses on gradient-based backpropagation algorithms that use either a common adaptive learning rate for all weights or an individual adaptivelearning rate for each weight and apply the Goldstein/Armijo line search.
Abstract: This article focuses on gradient-based backpropagation algorithms that use either a common adaptive learning rate for all weights or an individual adaptive learning rate for each weight and apply the Goldstein/Armijo line search. The learning-rate adaptation is based on descent techniques and estimates of the local Lipschitz constant that are obtained without additional error function and gradient evaluations. The proposed algorithms improve the backpropagation training in terms of both convergence rate and convergence characteristics, such as stable learning and robustness to oscillations. Simulations are conducted to compare and evaluate the convergence behavior of these gradient-based training algorithms with several popular training methods.
182 citations
173 citations
TL;DR: In this article, the marine debris concentration on the seafloor of Patras and Echinadhes Gulfs is 240 and 89 items/km2, respectively, and the most abundant debris is plastic followed by metal.
TL;DR: In this paper, the three-dimensional problem of isolation of vibration by a row of piles is studied numerically on the basis of a model replacing the rows of piles by an effective trench in order to reduce the modelling complexity.
01 Jan 1999
TL;DR: A review of the state of the art in anaerobic digestion modelling can be found in this paper, where the authors identify the key areas that require further research endeavors and identify the challenges that need to be addressed.
Abstract: Anaerobic digesters often exhibit significant stability problems, that may be avoided only through appropriate control strategies. Such strategies require, in general, the development of appropriate mathematical models, which adequately portray the key processes that take place. This paper reviews the current state of the art in anaerobic digestion modelling, and identifies the key areas that require further research endeavors.
TL;DR: In this article, steadystate tracing techniques were applied to study mechanistic aspects of the carbon and oxygen reaction pathways to form CO over Ni/La2O3 and Ni/Al 2O3 catalysts, and it was found that under steadystate reaction conditions, the quantity of reversibly adsorbed CH4 and the active carbon-containing intermediate species in the carbon pathway to forming CO originating from CH4 is higher than the respective quantities derived from the CO2 molecule.
TL;DR: In the elite female rhythmic gymnasts, psychological and somatic efforts have profound effects on growth and sexual development, and adult height is not expected to be affected.
Abstract: Optimal growth depends upon both environmental and genetic factors. Among environmental factors that could alter growth and sexual maturation are stress and intensive physical training. The influence of these factors has been documented in a variety of sports, but there is limited information on rhythmic gymnasts, who have entirely different training and performance requirements. The study was conducted during the 13th European Championships in Patras, Greece, and included 255 female rhythmic gymnasts, aged 11‐23 yr. The study included measurement of height and weight, assessment of breast and pubic hair development, estimation of body fat and skeletal maturation, and registration of menarcheal age and parental height. Gymnasts were taller than average height for age, with mean height above and mean weight below the 50th percentile. Actual height SD score was positively correlated to weight SD score (P , 0.001), number of competitions (P 5 0.01), and body mass index (BMI; P , 0.001). Predicted adult height SD score was positively correlated to weight SD score (P , 0.001) and negatively to body fat (P 5 0.004). There was a delay in skeletal maturation of 1.3 yr (P , 0.001). Pubertal development was following bone age rather than chronological age. The mean age of menarche was significantly delayed from that of their mothers and sisters (P 5 0.008 and P 5 0.05, respectively), was positively correlated to the intensity of training and to the difference between chronological age and bone age (P , 0.001 and P 5 0.002, respectively), and was negatively correlated to body fat (P , 0.001). In the elite female rhythmic gymnasts, psychological and somatic efforts have profound effects on growth and sexual development. Despite these aberrations, adult height is not expected to be affected. (J Clin Endocrinol Metab 84: 4525‐ 4530, 1999)
TL;DR: Results indicate that the proposed method can successfully be used for the estimation of the useful energy extracted from the system and the temperature rise in the stored water of solar domestic water heating (SDHW) systems with the minimum of input data.
TL;DR: Although the children with difficulties in literacy development had achieved a satisfactory performance in phonological processing, their performance was nevertheless significantly lower than that of the normal achievers; phonemic awareness and speech rate tasks were among the best predictors of learning to read and spell Greek words.
Abstract: This study examined the patterns of reading and spelling performance of first-grade Greek children who either were facing difficulties in literacy acquisition or were normal achievers. In addition, we studied the relationship between obtained literacy development levels and the children's phonological awareness and ability to retain phonological information in short-term memory. The participants were tested in the reading of single letters, letter clusters, words, and nonwords, as well as in word and nonword spelling. Furthermore, their phonological processing knowledge was assessed via a battery of phonological awareness tasks and short-term memory phonetic-representation tasks. The main findings of the study were as follows: (a) Accurate decoding of Greek was achieved by almost every young child (attributed mainly to the nature of the Greek writing system); (b) the time the children needed to process a written item was the crucial index of their difficulty in literacy acquisition; (c) spelling was perfo...
TL;DR: In the Mediterranean Sea, high heat flows in the resulting volcanic arcs and back-arc extensional areas have set-up hydrothermal convection systems as discussed by the authors, with the subduction of the oceanic part of the African plate below Europe.
TL;DR: In this article, the association of two rare earth ions (i.e., Eu3+ and Tb3+) with poly(ethylene glycol) in the absence and in the presence of 2,2'-bipyridine, which acted as an antenna of near-UV radiation was studied.
Abstract: Steady-state luminescence spectroscopy and luminescence decay analysis have been employed to study the association of two rare earth ions (i.e., Eu3+ and Tb3+) with poly(ethylene glycol) in the absence and in the presence of 2,2‘-bipyridine, which acted as an antenna of near-UV radiation. Three different systems have been studied at various polymer concentrations, i.e., aqueous solutions, transparent composite organic/inorganic sol−gel matrixes made by hydrolysis of tetramethoxysilane, and polymer matrixes. The photophysical behavior of the luminescent species has been studied in conjunction with the poly(ethylene glycol) content. In both aqueous solutions and silica matrixes, luminescence intensity and decay time were found to increase by increasing polymer concentration. Addition of 2,2‘-bipyridine resulted in complex formation between the ligand and the lanthanide ions. This complex was stabilized by association with the polymer chains. Excitation at the ligand absorption wavelength (337 nm) resulted i...
TL;DR: In this article, an Upflow Anaerobic Sludge Blanket (UASB) was used for treating dairy wastewater. But the results showed that the advantages of using a UASB versus a conventional digester become questionable for the high COD (>42 g/l), non-diluted dairy wastewater case.
TL;DR: It becomes apparent how efficient FCMs are in expressing qualitative information and knowledge about the process structure in the modelling of control systems.
TL;DR: This work aims to demonstrate the importance of knowing the carrier and removal status of canine coronavirus, as a source of infection for other animals, not necessarily belonging to the same breeds.
Abstract: We wish to thank Drs. C. Bissas, N. Georgopoulos, P. Ghikas, C. Kremmydas, P. Leonardos, S. Papapetropoulos, and, last but not least, A. Protonotariou, for their great help in sample collection. This work was supported by European Framework Program EPET II grant 236/234/603 to G.M.M.
TL;DR: In this article, an artificial neural network (ANN) was used to predict the performance of a thermosiphon solar domestic water heating system, which is measured in terms of the useful energy extracted and the stored water temperature rise.
TL;DR: In this article, a study of 40 primary school students' (ages between 11 and 12 years) conceptions concerning the greenhouse effect was conducted, which led to the formation of seven distinct models of thinking regarding this environmental phenomenon.
Abstract: Individual, semistructured interviews were used for the study of 40 primary school students' (ages between 11 and 12 years) conceptions concerning the greenhouse effect. Analysis of the data led to the formation of seven distinct models of thinking regarding this environmental phenomenon. The inferred models are differentiated according to the following criteria: (a) the position and distribution of the greenhouse gases; (b) the existence of connections between the greenhouse effect and the ozone layer, or its depletion; and (c) the types of radiation considered to be involved in the greenhouse effect. However, children's models involve a common core of beliefs, according to which the greenhouse effect is due to solar radiation that heats up the earth and the atmosphere, while getting trapped by certain atmospheric gases, and severely changes the climate, melts the polar ice, and raises the sea level. Furthermore, the alternative conceptions involved in students' models are systematically examined to establish their teaching implications. The main teaching implications discussed here concern: (a) the concept of uniform diffusion of atmospheric gases; (b) the conceptual distinction between ultraviolet and other forms of solar radiation; (c) the conceptual distinction between sunlight and terrestrial radiation; and (d) the conceptual distinction between the roles of the ozone layer and greenhouse gases in the atmosphere. These teaching implications might consititute a valuable research tool for the determination of appropriate educational goals and conditions. © 1999 John Wiley & Sons, Inc. Sci Ed83:559–576, 1999.
TL;DR: The solution to the problem of inadequate pain relief lies not so much in the development of new drugs and new techniques, but in the effective strategy of delivering these to patients through the introduction of acute pain management services on surgical wards.
Abstract: Despite a growing trend in acute pain management, many deficiencies still account for the high incidence of moderate to severe postoperative pain to date. Patients nowadays continue to receive inadequ
TL;DR: Zyme is regulated by steroid hormones in the breast carcinoma cell line BT-474, and estrogens and progestins, and to a lesser extent androgens, up-regulate the zyme gene in a dose-dependent manner.
TL;DR: In this article, a dynamic finite element code implementing the equivalentlinear soil behavior (FLUSHPLUS) was used for the analyses and it was found that the step-like topography amplified greatly the intensity of motion without affecting its frequency content.
TL;DR: In this paper, numerical and experimental results from an investigation on the laser forming process of metallic plates are discussed, a three-dimensional finite-element algorithm has been developed, which includes a non-linear transient coupled thermal-structural analysis; the temperature dependency of the thermal and mechanical properties of the material being accounted for.
TL;DR: In this article, a multiaxial fatigue failure criterion for composite materials is presented along with an assessment of the capability it offers for design under multi-axial constant or variable amplitude stresses.
Abstract: A multiaxial fatigue failure criterion for composite materials is presented in this paper along with an assessment of the capability it offers for design under multiaxial constant or variable amplitude stresses. The applicability of this criterion, based on the well known quadratic failure tensor polynomial criterion for static loading, is validated through comparisons with uniaxial and multiaxial fatigue experimental data. Static and fatigue tests were carried out during this study on glass/polyester specimens cut off-axis from a multidirectional laminate at different angles. The agreement between experimental values and theoretical predictions is good. The proposed criterion is also compared to existing fatigue criteria and an overall assessment of their performance is given. Some theoretical design considerations for the case of irregular stress spectra, introducing the concept of multiaxial Miner coefficient, are finally presented.
TL;DR: In this paper, the pore-scale flow mechanisms and the relative permeabilities during steady-state two-phase flow in a glass model pore network were studied experimentally for the case of strong wettability (θe < 10°).
Abstract: The pore-scale flow mechanisms and the relative permeabilities during steady-state two-phase flow in a glass model pore network were studied experimentally for the case of strong wettability (θe < 10°). The capillary number, the fluid flow rate ratio, and the viscosity ratio were changed systematically, while all other parameters were kept constant. The flow mechanisms at the microscopic and macroscopic scales were examined visually and videorecorded. As in the case of intermediate wettability, we observed that over a broad range of values of the system parameters the pore-scale flow mechanisms include many strongly nonlinear phenomena, specifically, breakup, coalescence, stranding, mobilization, etc. Such microscopically irreversible phenomena cause macroscopic nonlinearity and irreversibility, which make an Onsager-type theory inappropriate for this class of flows. The main effects of strong wettability are that it changes the domains of the system parameter values where the various flow regimes are obs...