Probabilistic safety assessment of self-centering steel braced frame

The main drawback of conventional braced frames is implicitly accepting structural damage under the design earthquake load, which leads to considerable economic losses. Controlled rocking self-centering system as a modern low-damage system is capable of minimizing the drawbacks of conventional braced frames. This paper quantifies main limit states and investigates the seismic performance of self-centering braced frame using a Probabilistic Safety Assessment procedure. Margin of safety, confidence level, and mean annual frequency of the self-centering archetypes for their main limit states, including PT yield, fuse fracture, and global collapse, are established and are compared with their acceptance criteria. Considering incorporating aleatory and epistemic uncertainties, the efficiency of the system is examined. Results of the investigation indicate that the design of low- and mid-rise self-centering archetypes could provide the adequate margin of safety against exceeding the undesirable limit-states.     

Microstructures and Grain Refinement of Additive-Manufactured Ti-xW Alloys

Metallurgical and Materials Transactions A - It is necessary to better understand the composition–processing–microstructure relationships that exist for materials produced by additive...     

Role of splenectomy in human liver transplantation under modern-day immunosuppression

Between January 1987 and October 1991, 1466 patients underwent consecutive Orthotopic Liver Transplantation (OLTx) at the University of Pittsburgh. Forty of these patient's had concomitant splenectomy with OLTx. These patients were compared to 147 randomly selected OLTx patients without splenectomy within the same time period. One-year patient and graft survival (PS and GS) were lower in splenectomized (Splx) patients compared to nonsplenectomized (non-Splx) patients (59% vs 86% PS, 55% vs 80% GS, respectively). One-month and one-year patient mortality in the Splx group was higher than in the non-splx patients (20% vs 3.4%, P < 0.001 for one month; 40% vs 14.3%, P = 0.003 for one year, respectively). One-month and one-year sepsis-related mortality was also high in Splx patients (17.5% vs 2.7%, P = 0.0022, for one month, and 30% vs 11.5%, P = 0.0043, for one year, respectively). We conclude that concomitant splenectomy with OLTx has a significantly higher patient mortality mainly due to its septic complications and, at present, unless there is a specific indication for a splenectomy, the routine addition of this procedure to liver allograft surgery would not be recommended.     

Synthesis,characterization, and swelling kinetic study of porous superabsorbent hydrogel nanocomposite based on sulfonated carboxymethylcellulose and silica nanoparticles

New superabsorbent nanocomposite was synthesized by free-radical graft polymerization of sulfonated-carboxymethyl cellulose (SCMC) with acrylic acid (AA) in the presence of polyvinylpyrrolidone (PVP) and silica nanoparticles. Carboxymethyl cellulose (CMC) was first sulfonated using chlorosulfonic acid, and then AA monomers were grafted onto SCMC. FTIR results confirmed that sulfonation of CMC as well as grafting of AA monomers onto SCMC has been performed successfully. Moreover, the presence of silica nanoparticles into superabsorbent nanocomposite was evaluated with EDX analysis. The element mappings show a homogenous distribution of silica nanoparticles throughout the hydrogel nanocomposite. SEM images exhibited porous morphology for hydrogel nanocomposite, which was due to the incorporation of PVP in its network. The experimental findings from TGA analysis indicated that incorporation of PVP and silica nanoparticles into the hydrogel network improved thermal stability of superabsorbent nanocomposite. Swelling kinetic studies revealed that superabsorbent nanocomposite hydrogel had higher equilibrium swelling capacity and swelling rate compared with the neat hydrogel sample. Besides that, superabsorbent nanocomposite depicted excellent salt and pH-sensitive behavior in different saline and pH solutions. As a consequence, this hydrogel nanocomposite acts as useful water reservoir, which might be most profitable in agricultural applications.     

An EM based probabilistic two-dimensional CCA with application to face recognition

Recently, two-dimensional canonical correlation analysis (2DCCA) has been successfully applied for image feature extraction. The method instead of concatenating the columns of the images to the one-dimensional vectors, directly works with two-dimensional image matrices. Although 2DCCA works well in different recognition tasks, it lacks a probabilistic interpretation. In this paper, we present a probabilistic framework for 2DCCA called probabilistic 2DCCA (P2DCCA) and an iterative EM based algorithm for optimizing the parameters. Experimental results on synthetic and real data demonstrate superior performance in loading factor estimation for P2DCCA compared to 2DCCA. For real data, three subsets of AR face database and also the UMIST face database confirm the robustness of the proposed algorithm in face recognition tasks with different illumination conditions, facial expressions, poses and occlusions.     

On the influence of alloy composition on the oxidation performance and oxygen-induced phase transformations in Ti–(0–8) wt%Al alloys

Adopting a high-throughput combinatorial approach, a compositionally graded Ti–xAl (0 ≤ x ≤ 8 wt%) specimen was prepared to conduct a rapid systematic investigation of the influence of composition and exposure time on the oxidation performance of the titanium-rich section of the binary Ti–Al system. The compositionally graded specimen was solution heat treated and subjected to oxidation tests at 650 °C for different exposure times. The morphology, structure, and composition of the oxide scale as well as the microstructural changes in the base material were studied across the entire composition range, using a suite of characterization techniques. The observations revealed the presence of Al₂O₃ in the topmost layer of the oxide scale in addition to TiO₂, indicating its early formation during oxidation. An increase in Al concentration improves the scaling rate of Ti; however, this is observed only for extended exposure times (i.e., 50 and 100 h), and a parabolic oxidation law is obeyed in the composition-time domain. The formation of the α₂ phase (Ti₃Al) also takes place for relatively higher Al contents (i.e., 8 wt%).     

Computational fluid dynamics modeling of mass transfer for aroma compounds recovery from aqueous solutions by hydrophobic pervaporation

In this work, a mass transfer study on aroma compound recovery by pervaporation process was performed using a model based on solution–diffusion theory. CFD method was employed to solve the governing mass transfer equations by considering the flux coupling. Concentration profiles of penetrants inside the membrane as well as permeation flux and aroma permeate concentration through the membrane were determined. The modeling results were validated by the experimental data obtained for pervaporative recovery of isopentyl acetate and n-hexanol from their binary aqueous solutions with composite PDMS membrane. The influence of key operating parameters such as feed aroma concentration and temperature on the flux and permeate concentration was also investigated theoretically and experimentally. The results showed that the aroma permeate concentration as well as the total and partial fluxes increased with an increase in the feed aroma content and feed temperature. The predicted results were in good agreement with experimental data.     

Environmental impacts of desalination on the ecology of Lake Urmia

Lake Urmia, the second largest hypersaline lake by area in the world, has fluctuated in salinity over time, but in recent years, it has reached a maximum of 340 g/L. The lake is the main habitat for the endemic Iranian brine shrimp, Artemia urmiana, and is a protected aquatic environment. Efforts have been made by the Iranian government to enhance the diversity of its wildlife. One approach has been to look for a method to reduce the salt content of the lake. We investigate the feasibility of this by first considering the water chemistry of Lake Urmia and then the various technologies used to extract salt from marine and brackish waters. Average concentrations of Na, Mg, K, Ca, Cl, SO₄, and HCO₃ were 125 g/L, 11.3 g/L, 2.63 g/L, 0.55 g/L, 216 g/L, 22.4 g/L, and 1.38 g/L, respectively, and cations and anions were balanced, However, Lake Urmia waters have a ‘very high’ salinity hazard and a high sodium adsorption ratio (SAR). Moreover, the saturation index (SI) for each of the major cations was greater than zero, indicating that the water in Lake Urmia is supersaturated, and precipitation is likely. The extraction of available salts from the lake for the use in petrochemical industries is economically feasible. However, technologies based on removing salts by distillation or reverse osmosis and then using this fresh water to dilute lake salinity are problematic. A better strategy would be better to allow more fresh water to reach the lake rather than creating fresh water through reverse osmosis and distillations processes. While concerns have been raised about the salinity tolerance of A.urmiana, it has successfully tolerated various salinity ranges from 166 to 340 g/L, and so the species is not threatened, unless the lake desiccates. Because the lake is saturated with salts, it seems unlikely that salinity could increase much higher.     

Clarification of pomegranate juice by microfiltration with PVDF membranes

Microfiltration was used to clarify pomegranate juice using two polyvinylidene fluoride membranes with pore sizes of 0.22 and 0.45 μm. Changes were studied in the chemical properties of the juice after passing through each membrane. Characteristics such as turbidity changed for both membranes (more than 95%). The permeate flux decreased over time as a result of membrane fouling. The degree of decline in the membrane with pore size of 0.22 μm was greater than another one. In both membranes, fouling resistance increased over time from 5 × 10⁹ m²/kg to 4.43 × 10¹⁰ m²/kg for 0.22 μm and to 1.29 × 10¹⁰ m²/kg for 0.45 μm after 45 min. This increase had a sharp slope in the first stages of the testing. Fouling index changes over time showed similar behavior. Scanning electron microscopy images showed that the cake layer had the greatest impact on membrane fouling after processing by preventing turbid components from entering pores.     

Pyrolytic carbon coating for cytocompatibility of titanium oxide nanoparticles: a promising candidate for medical applications

Nanoparticles for biomedical use must be cytocompatible with the biological environment that they are exposed to. Current research has focused on the surface functionalization of nanoparticles by using proteins, polymers, thiols and other organic compounds. Here we show that inorganic nanoparticles such as titanium oxide can be coated by pyrolytic carbon (PyC) and that the coating has cytocompatible properties. Pyrolization and condensation of methane formed a thin layer of pyrolytic carbon on the titanium oxide core. The formation of the PyC shell retards coalescence and sintering of the ceramic phase. Our MTT assay shows that the PyC-coated particles are cytocompatible at employed doses.