Enhancing the seismic performance of mid‐rise wood‐frame buildings with rigid spine columns

Wood‐frame buildings (WFBs) are the most commonly used structural systems for residential applications in North America. Past researches have shown that WFBs are susceptible to soft‐story mechanisms. In this study, a simple, efficient, and economical retrofit strategy, which utilizes continuous pinned‐supported rigid spine columns (RSCs) over the height of the building, is proposed. The retrofit aims to provide uniform deformation through the height of the building to prevent soft‐story mechanisms. This retrofit strategy was applied to a six‐story WFB located in Vancouver, British Columbia, Canada. A three‐dimensional nonlinear finite element model of the prototype building was developed using OpenSees. A comprehensive parametric study was conducted to identify the most economical RSC design. Seismic performance of the prototype building, with and without the most economical RSC design, was assessed through extensive nonlinear time history analyses. Results showed that the proposed retrofit strategy can effectively improve the seismic behavior of WFBs to prevent soft‐story mechanisms.     

Investigation of well test behavior in gas condensate reservoir using single-phase pseudo-pressure function

Gas condensate reservoirs present complicated thermodynamic behavior when pressure falls below the dew point pressure, due to fluid dropout and change in the fluid composition. Condensate blockage in the near wellbore region reduces the well deliverability. Mixture composition change in the reservoir makes the interpretation of well tests in gas condensate reservoirs a serious challenge. In this study, at first the capillary number effect and Non-Darcy Flow on compositional simulation of gas condensate reservoirs were investigated and then well test analysis was carried out. The main objective of this work was to examine gas condensate well test analysis using single-phase gas pseudo-pressure and radial composite model assuming capillary number effect and Non-Darcy Flow. For this purpose some fluid samples were selected and results compared. Results indicate that estimation of reservoir properties below the dew point is in good agreement with actual input, particularly for lean fluid samples.     

Kinetic Model for Invertase‐Induced Sucrose Hydrolysis: Initial Time Lag

The kinetics of sucrose hydrolysis by invertase was studied in order to find a comprehensive model for the reaction pathway and mechanism. First, three common models of Michaelis‐Menten (MM), substrate inhibition (S²), and substrate clusters' inhibition (S³(I)) were investigated. The third model was found to better predict the initial sucrose concentration. Then, the S³(I) model was modified to cover the remaining pathway (S³(II)). Finally, a new comprehensive model (S³(III)) was evaluated, which in addition to what is considered in the two previously mentioned models (S³(I) and S³(II)) also involved the initial time lag. The model predictions showed an excellent agreement with the experimental data. The mean absolute error for the MM model is significantly reduced for the S³(III) model.     

Effect of nano-sized calcium carbonate on cure kinetics and properties of polyester/epoxy blend powder coatings

Today's strict environmental laws pose significant challenges for coating's formulators to look for eco-friendly products. Powder coatings, particularly polyester/epoxy blends have demonstrated their ability as alternatives to traditional solvent-borne coatings. Recently, the use of nanoparticles such as nano-CaCO₃ (nCaCO₃) has been suggested as a beneficial strategy towards powder coating application with improved properties. Here, we study the effect of nCaCO₃ on morphology, cure behavior, adhesion and hardness of polyester/epoxy systems. The nanoparticles shape, size and dispersion state were investigated through X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) methods. Furthermore, isothermal cure characterization of the neat and filled systems was performed using a torque rheometer. The most important finding based on the rheological studies was the catalytic effect of nCaCO₃ on cure reaction of polyester/epoxy, leading to the shorter curing time. Moreover, the kinetic analyses of rheograms revealed a marked decrease in the activation energy of the cure process upon raising nCaCO₃ content. Interestingly, pull-off adhesion and hardness tests showed that the hardness and adhesion strength were dramatically increased by the addition of nCaCO₃ into the polyester/epoxy system compared to pure blend resin. Therefore, considering the strong competition in powder coating market, the use of nCaCO₃ as a commercial and inexpensive nanofiller is necessary not only to reduce the dwell time which has benefits in terms of the energy consumption and economics, but also to improve the performance of final polyester/epoxy coating.     

Imprinted polymer-based extraction for speciation analysis of inorganic tin in food and water samples

In this study, an ion imprinted polymer (IIP), tin (IV)–4-(2-pyridylazo) resorcinol (PAR) complex (Sn(IV)–PAR–IIP) has been synthesized for speciation and selective solid-phase extraction (SPE) of tin species from food and water samples. For this purpose, copolymerization of Sn(IV)–4-(2-pyridylazo) resorcinol (PAR) complex was performed using methacrylic acid (MAA), ethylene glycol dimethacrylate (EGDMA), and 2,2′-Azobisisobutyronitrile (AIBN) as functional monomer, cross-linking agent, and initiator, respectively. The polymer particles were characterized by FT-IR, and thermogravimetric (TG) analyses. The effects of different variables such as solution pH, mass of the polymer, extraction and elution time, and type and volume of the eluent for elution of tin were evaluated by Box–Behnken design and response surface methodology. The significance of independent variables and their interactions were tested by the analysis of variance (ANOVA) with 95% confidence limits. The optimal conditions at extraction step were 8, 70 mg, and 25 min for solution pH, amount of polymer, and extraction time, respectively. Also, the optimal values for the elution step were 6.5 mL of HCl (4 M) as the eluent volume and type and elution time of 120 min. The detection limit of the proposed method was found to be 1.3 μg L^?1 and a linear dynamic range (LDR) in the range of 5–200 μg L^?1 was obtained. The influence of various cationic interferences on recovery percentage of Sn(IV) was studied. The method was applied to recovery and determination of tin species in different real samples.     

Fabrication and characterization of robust hydrophobic lotus leaf-like surface on Si3N4 porous membrane via polymer-derived SiNCO inorganic nanoparticle modification

Robust hydrophobic surface was produced by modifying the surface of porous Si₃N₄ membrane, via aminolysis and pyrolysis process, with organosilane-derived inorganic SiNCO nanoparticles, which are tightly adhered to the Si₃N₄ grains. The resultant material had a high water contact angle of 142°, attributed to -Si-CH₃ surface terminal groups and a lotus leaf-like hierarchical structure of the nanoparticles, which had a frame structure with Si-N and Si-O covalent bonds in their bulk. The hydrophobic behavior remained practically unchanged after exposure of the produced membranes to aqueous solutions of humic acid, HCl and NaOH, to benzene, as well as to stirring abrasive slurry with SiC particles, and after exposure at high temperatures, up to 500?°C, to air. The inorganic membrane can be considered for use in a broad range of applications which require robust hydrophobic surfaces.     

Enhanced oil recovery from carbonate reservoirs by spontaneous imbibition of low salinity water

An experimental study was performed to investigate the impact of low salinity water on wettability alteration in carbonate core samples from southern Iranian reservoirs by spontaneous imbibition. In this paper, the effect of temperature, salinity, permeability and connate water were investigated by comparing the produced hydrocarbon curves. Contact angle measurements were taken to confirm the alteration of surface wettability of porous media. Oil recovery was enhanced by increasing the dilution ratio of sea water, and there existed an optimum dilution ratio at which the highest oil recovery was achieved. In addition, temperature had a very significant impact on oil recovery from carbonate rocks. Furthermore, oil recovery from a spontaneous imbibition process was directly proportional to the permeability of the core samples. The presence of connate water saturation inside the porous media facilitated oil production significantly. Also, the oil recovery from porous media was highly dependent on ion repulsion/attraction activity of the rock surface which directly impacts on the wettability conditions. Finally, the highest ion attraction percentage was measured for sodium while there was no significant change in pH for all experiments.