Robust seismic design optimization of steel structures

Stochastic performance measures can be taken into account, in structural optimization, using two distinct formulations: robust design optimization (RDO) and reliability-based design optimization (RBDO). According to a RDO formulation, it is desired to obtain solutions insensitive to the uncontrollable parameter variation. In the present study, the solution of a structural robust design problem formulated as a two-objective optimization problem is addressed, where cross-sectional dimensions, material properties and earthquake loading are considered as random variables. Additionally, a two-objective deterministic-based optimization (DBO) problem is also considered. In particular, the DBO and RDO formulations are employed for assessing the Greek national seismic design code for steel structural buildings with respect to the behavioral factor considered. The limit-state-dependent cost is used as a measure of assessment. The stochastic finite element problem is solved using the Monte Carlo Simulation method, while a modified NSGA-II algorithm is employed for solving the two-objective optimization problem.     

Gradient vector flow fast geometric active contours

In this paper, we propose an edge-driven bidirectional geometric flow for boundary extraction. To this end, we combine the geodesic active contour flow and the gradient vector flow external force for snakes. The resulting motion equation is considered within a level set formulation, can deal with topological changes and important shape deformations. An efficient numerical schema is used for the flow implementation that exhibits robust behavior and has fast convergence rate. Promising results on real and synthetic images demonstrate the potentials of the flow.     

Differences in susceptibility to Mannheimia haemolytica-associated mastitis between two breeds of dairy sheep

We used a Mannheimia haemolytica isolate to study differences in susceptibility to experimental mastitis between two breeds of dairy sheep. The isolate was deposited into the teat duct of Karagouniko (K, n=8) or Frisarta (F, n=8) ewes. The animals were monitored by means of clinical, bacteriological, cytological and pathological methods. K ewes did not develop any systemic or mammary clinical signs, whilst F ewes became ill and developed acute clinical mastitis 12 h later (P<0.001). Bacteria were isolated from 34/48 samples from K ewes and from 46/46 samples from F ewes. Positive California mastitis test (CMT) results were 17/24 samples from K ewes and 23/23 samples from F ewes; leucocytes were seen in Giemsa-stained films. Total pathology score summed over all group K ewes was 41 (maximum possible: 128); Man. haemolytica was isolated from 12/24 tissue samples. Total pathology score summed over all group F ewes was 93; Man. haemolytica was isolated from 24/24 tissue samples. Hyperplastic lymphoid nodules consisting of lymphocytes and plasma cells with germinal activity were characteristically present at the border between teat duct-teat cistern of group K ewes; no such structures were observed in teats of group F ewes. The results identified differences in susceptibility/resistance to a mastitis pathogen among animals of the two breeds. Defence mechanisms of the teat appeared to be inadequate against the invading organisms; as lymphoid nodules have been considered important defensive mechanisms of the ovine teat, their observed lack in Frisarta ewes might have predisposed them to development of mastitis.     

Electrochemical study of arsenate and water reduction on iron media used for arsenic removal from potable water

Zerovalent iron filings have been proposed as a filter medium for removing As(III) and As(V) compounds from potable water. The removal mechanism involves complex formation of arsenite and arsenate with the iron surface and with iron oxides produced from iron corrosion. There is conflicting evidence in the literature on whether As(V) can be reduced to As(III) by iron filter media. This research uses electrochemical methods to investigate the redox reactions that occur on the surface of zerovalent iron in arsenic solutions. The effect of arsenic on the corrosion rate of zerovalent iron was investigated by analysis of Tafel diagrams for iron wire electrodes in anaerobic solutions with As(V) concentrations between 100 and 20,000 microg/L. As(V) reduction in the absence of surface oxides was investigated by analysis of chronoamperometry profiles for iron wire electrodes in solutions with As(V) concentrations ranging from 10000 to 106 microg/L. The effect of pH on As(V) reduction was investigated by analyses of chronopotentiometry profiles for iron wire electrodes at pH values of 2, 6.5, and 11. For freely corroding iron, the presence of As(III) and As(V) decreased the iron corrosion rate by a factor of 5 as compared to that in a 3 mM CaSO4 blank electrolyte solution. The decrease in corrosion rate was independent of the arsenic concentration and was due to the blocking of cathodic sites for water reduction by arsenic compounds chemisorbed to the iron surface. The chronoamperometry and chronopotentiometry experiments showed that elevated pH and increased As(III) to As(V) ratios near the iron surface decreased the thermodynamic favorability for As(V) reduction. Therefore, reduction of As(V) occurred only at potentials that were significantly below the apparent equilibrium potentials based on bulk solution pH values and As(III) to As(V) ratios. The potentials required to reduce more than 1% of the As(V) to As(III) were below those that are obtainable in freely corroding iron media. This indicates that there will be minimal or no reduction of As(V) in iron media filters under conditions relevant to potable water treatment.     

The Effect of Microcosm Biofilm Decontamination on Surface Topography,Chemistry, and Biocompatibility Dynamics of Implant Titanium Surfaces

Since the inception of dental implants, a steadily increasing prevalence of peri-implantitis has been documented. Irrespective of the treatment protocol applied for the management of peri-implantitis, this biofilm-associated pathology, continues to be a clinical challenge yielding unpredictable and variable levels of resolution, and in some cases resulting in implant loss. This paper investigated the effect of microcosm biofilm in vitro decontamination on surface topography, wettability, chemistry, and biocompatibility, following decontamination protocols applied to previously infected implant titanium (Ti) surfaces, both micro-rough -Sandblasted, Large-grit, Acid-etched (SLA)-and smooth surfaces -Machined (M). Microcosm biofilms were grown on SLA and M Ti discs. These were treated with TiBrushes (TiB), combination of TiB and photodynamic therapy (PDT), combination of TiB and 0.2%CHX/1%NaClO, plus or minus Ultraviolet-C (UV-C) radiation. Surface topography was evaluated by Scanning Electron Microscopy (SEM) and Laser Surface Profilometry. Surface function was analysed through wettability analysis. Surface chemistry evaluation of the discs was performed under SEM/Energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). Biocompatibility was tested with the cytocompatibility assay using human osteoblast-like osteosarcoma cell line (MG-63) cells. Elemental analysis of the discs disclosed chemical surface alterations resulting from the different treatment modalities. Titanium, carbon, oxygen, sodium, aluminium, silver, were identified by EDX as the main components of all the discs. Based on the data drawn from this study, we have shown that following the decontamination of Ti surfaces the biomaterial surface chemistry and topography was altered. The type of treatment and Ti surface had a significant effect on cytocompatibility (p = 0.0001). Although, no treatment modality hindered the titanium surface biocompatibility, parameters such as the use of chemical agents and micro-rough surfaces had a higher cytotoxic effect in MG-63 cells. The use of smooth surfaces, and photofunctionalisation of the TiO₂ layer had a beneficial effect on cytocompatibility following decontamination.     

Computation of Drought Index SPI with Alternative Distribution Functions

The Standardized Precipitation Index (SPI) is widely used as drought meteorological index, to identify the duration and/or severity of a drought. The SPI is usually computed by fitting the gamma probability distribution to the observed precipitation data. In this work, the possibility to calculate SPI by fitting to the precipitation data the normal and the log-normal probability distributions was studied. For this purpose, 19 time series of monthly precipitation of 76?years were used, and the assumption that the gamma probability distribution would provide better representation of the precipitation data than log-normal and normal distributions, at various time scales (1, 3, 6, 12 and 24?months) was tested. It is concluded that for SPI of 12 or 24?months, the log-normal or the normal probability distribution can be used for simplicity, instead of gamma, producing almost the same results.     

Performance of growing–fattening lambs fed diets containing different proportions of cotton seed meal

A lamb feedlot study was conducted to evaluate the nutritional value of cotton seed meal (CSM) as compared with that of sunflower meal as protein supplements for growing lambs. Forty-five Karagouniko male lambs immediately after weaning, having an average liveweight of approximately 14.7 kg, were assigned randomly to one of three growing lamb rations. CSM substituted for sunflower meal in a growing–finishing feedlot diet at levels of 0, 10 and 20% to provide 0, 50 and 100% of supplemental protein requirement, respectively. Diets were fed ad libitum and water was offered freely. All diets were approximately isonitrogenous and isocaloric. After being fed for 61 days and having reached a liveweight of approximately 27.6 kg, five lambs from each treatment were slaughtered and carcass data were collected. No significant differences (P > 0.05) in feed intake or the weight increase of lambs were found among groups given the 0, 10 and 20% treatments, indicating that lambs utilized CSM as effectively as sunflower meal when fed on an equal crude protein and crude fibre basis. The dressing percentage of the cold carcass, but not the warm carcass, and intestinal content weight were significantly influenced (P < 0.05) by the diet. Cooler shrink and intestinal fat, and perirenal fat and the combined weight of intestinal and perirenal fat were significantly (P < 0.05) correlated. Feeding margin was highest for the control diet, intermediate for the 10% CSM diet and lowest for the 20% CSM diet. It was concluded that CSM is accepted readily by growing sheep and can be incorporated into diets as a source of supplemental protein for growing–fattening lambs. No evidence of gossypol toxicity was noted. © 1999 Society of Chemical Industry     

Enabling technologies for the ‘always best connected’ concept

‘Always Best Connected’ (ABC) is considered one of the main requirements for next generation networks. The ABC concept allows a person to have access to applications using the devices and network technologies that best suits his or her needs or profile at any time. Clearly, this requires the combination of a set of existing and new technologies, at all levels of the protocol stack, into one integrated system. In this paper, a considerable set of the technologies, that are expected to play a key role towards the ABC vision, are presented. Starting from a reference architecture, the paper describes the required enhancements at certain levels of a traditional protocol stack, as well as technologies for mobility and end‐to‐end Quality of Service (QoS) support. The paper concludes with a case study that reveals the advantages of the ABC concept. This article replaces a previously published version (Wireless Communications and Mobile Computing; 5 (2): 175‐191. [DOI: 10.1002/wcm.207]). Retraction notice DOI: 10.1002/wcm.426 . Copyright © 2006 John Wiley & Sons, Ltd.