Seismic design of special moment‐resisting steel frame with prevention of soft‐storey mechanism failure

Most structures with masonry infills that are continuous along their height, which are interrupted in the lowest storey, are damaged by earthquakes. These structures are anticipated to collapse due to the undesirable soft‐storey mechanism formed by lateral stiffness of masonry infills in other storeys. The seismic design criteria of UBC97 code for special moment‐resisting steel frame (SMRSF) are reviewed. In this paper, a new criterion for seismic design of such structures is presented. The proposed criteria are used to design three SMRSFs: 5, 8 and 15 storeys. Nonlinear time‐history dynamic analyses are applied for the designed SMRSFs based on the proposed criteria. Displacements and storey drifts, which are obtained by the proposed method, are compared with nonlinear time‐history dynamic analysis results, finally. Copyright © 2011 John Wiley & Sons, Ltd.     

Effect of soft‐storey mechanism caused by infill elimination on displacement demand in nonlinear static procedure using coefficient method

In recent earthquakes, many buildings have been damaged due to the soft‐storey mechanism failure. The seismic design codes for buildings do not contain enough criteria to predict the real displacement of such buildings. This paper focuses on evaluating the nonlinear displacement of buildings that fail in soft‐storey mechanism form. Results show that the nonlinear static procedure with coefficient method, which is described in Chapter 3 of ASCE/SEI 41‐06, does not have sufficient accuracy for estimation of structure displacement demand in such buildings. In this paper, the coefficient methodology is used for evaluating the target displacement for 5‐storey, 8‐storey and 15‐storey special moment resisting steel frames. For this purpose, dynamic nonlinear time‐history analysis has been applied for the mentioned structures having a soft‐storey mechanism failure form. The numerical results of storey displacement and interstorey drift were compared with those values obtained from the coefficient method described in Chapter 3 of ASCE/SEI 41‐06. Copyright © 2012 John Wiley & Sons, Ltd.     

Hydrodynamics of pulsed spouted beds: Effects of pulsation waveform,amplitude, and frequency

The effect of flow pulsations is studied via a discrete element model on hydrodynamics of spouted bed, which is being used in many important industries like drying processes. Decreased horizontal air percolation and preserving upward momentum, increased particle circulation, increased particle traverse distance, and better homogeneity are resulted from flow pulsations in spouted beds. Among the waveforms studied, square and triangular waveforms differ most and least from steady spouting, respectively. The predictions indicate that the pulsed spouted bed has the potential to enhance both gas and particle motion, hence being useful in drying and other operations.     

Synthesis and dissolution behavior of nanosized silicon and magnesium co-doped fluorapatite obtained by high energy ball milling

Nanosized hydroxyapatite (HA) powders exhibit a greater surface area than coarser crystals and are expected to show an improved bioactivity. In addition, properties of HA can be tailored over a wide range by incorporating different ions into HA lattice. The aim of this study was to prepare and characterize silicon and magnesium co-doped fluorapatite (Si–Mg–FA) with a chemical composition of Ca_9.5Mg_0.5 (PO₄)_5.5(SiO₄)_0.5F₂ by the high-energy ball milling method. Characterization techniques such as X-ray diffraction analysis (XRD), Fourier transformed infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM) were utilized to investigate the structural properties of the obtained powders. Dissolution behavior was evaluated in simulated body fluid (SBF) and physiological normal saline solution at 37 °C for up to 28 days. The results of XRD and FTIR showed that nanocrystalline single-phase Si–Mg–FA powders were synthesized after 12 h of milling. In addition, incorporation of magnesium and silicon into fluorapatite lattice decreased the crystallite size from 53 nm to 40 nm and increased the lattice strain from 0.220% to 0.296%. Dissolution studies revealed that Si–Mg–FA in comparison to fluorapatite (FA), releases more Ca, P and Mg ions into SBF during immersion. 175 ppm Ca, 33.5 ppm P and 48 ppm Mg were detected in the SBF containing Si–Mg–FA after 7days of immersion, while for FA, it was 75 ppm Ca, 21.5 ppm P and 29 ppm Mg. Release of these ions could improve the bioactivity of the obtained nanopowder. It could be concluded that the prepared nanopowders have structural properties such as crystallite size (~40 nm), crystallinity degree (~40%) and chemical composition similar to biological apatite. Therefore, prepared Si–Mg–FA nanopowders are expected to be appropriate candidates for bone substitution materials and also as a phase in polymer or ceramic-based composites for bone regeneration in tissue engineering applications.     

An efficient and scalable plagiarism checking system using Bloom filters

With the easy access to the huge volume of articles available on the Internet, plagiarism is getting worse and worse. Most recent approaches proposed to address this problem usually focus on achieving better accuracy of similarity detection process. However, there are some real applications where plagiarized contents should be detected without revealing any information. Moreover, in such web-based applications, running time, memory consumption, communication and computational complexity should be also taken into account. In this paper, we propose a similar document detection system based on matrix Bloom filter, a new extension of standard Bloom filter. The experimental results on a real dataset show that the system can achieve 98% of accuracy. We also compare our approach with a method recently proposed for the same purpose. The results of the comparison show that the Bloom filter-based approach achieves much better performance than other in terms of the aforementioned factors.     

Interlaminar stress analysis in general thick composite cylinder subjected to nonuniform distributed radial pressure

Interlaminar stresses in thick a composite cylinder with general layer stacking subjected to uniform and nonuniform distributed radial pressure are studied. The layerwise theory of Reddy is employed for formulation of the problem. An analytical method is presented for solving the governing equations. To increase accuracy, interlaminar stresses are obtained by integrating the equilibrium equation of elasticity. After a convergence study, the accuracy of the layerwise laminate theory is investigated using the predictions of finite element method. Predictions of Hooke's law and integration method for interlaminar stresses are compared. Uniform and nonuniform internal and external loads are considered and a parametric study is done for various cylinders.     

An experimental and theoretical study on the prediction of forming limit diagrams using new BBC yield criteria and M–K analysis

In the present paper, a comprehensive study on the prediction of forming limit diagrams (FLDs) for an AA3003-O aluminium alloy is developed theoretically and experimentally. For obtaining the experimental FLDs, an out-of-plane formability test was performed based on the technique proposed by Ozturk and Lee [F. Ozturk, D. Lee, J. Mater. Process. Technol. 170 (2005) 247–253]. The classical Marciniak–Kuczynski (M–K) model and some new yield criteria are utilized to simulate the necking phenomenon and calculate the limit strains theoretically. The employed yield functions are: the BBC2000, BBC2002, and BBC2003 yield criteria proposed by Banabic et al. [D. Banabic, S.D. Comsa, T. Balan, in: Proceedings of the Cold Metal Forming 2000 Conference, Cluj-Napoca, 2000, p. 217; D. Banabic, T. Kuwabara, T. Balan, D.S. Comsa, D. Julean, Int. J. Mech. Sci. 45 (2003) 797–811; D. Banabic, H. Aretz, D.S. Comsa, L. Paraianu, Int. J. Plast. 21 (2005) 493–512]. To calibrate and determine each particular coefficients of performed yield functions an appropriate error-function is defined and minimized by a Newton algorithm. To compare the calculated yield stresses and r-values with experimental data a relative root mean square deviation method presented by Leacock [Alan G. Leacock, J. Mech. Phys. Solids 54 (2006) 425–444] is used. Work-hardening effects on the FLD are analyzed by using Swift and Voce hardening laws. The effect of yield surface on the prediction of numerical FLDs and the number of experimental anisotropy parameters on the accuracy of yield functions are also studied.     

Experimental study of onset of subcooled annular flow boiling

An experimental study on the onset of nucleate boiling (ONB) is performed for water annular flow to provide a systematic database for low pressure and velocity conditions. A parametric study has been conducted to investigate the effect of pressure, inlet subcooling, heat and mass flux on flow boiling. The test section includes a Pyrex tube with 21 mm inner diameter and a stainless steel (SS-304) rod with outer diameter of 6 mm. Pressure, heat and mass flux are in the range of 1.73 < P < 3.82 bar, 40 < q < 450 kW/m² and 70 < G < 620 kg/m² s, respectively. The results illustrate that inception heat flux is extremely dependent on pressure, inlet subcooling temperature and mass flux; for example in pressure, velocity and inlet subcooling as 3.27 bar, 230 kg/m² s and 41.3 °C; consequently q_w,ONB is 177.3 kW/m². In other case with higher inlet temperature of 71.5 °C and with P, 3.13 bar and G, 232 kg/m² s the inception heat flux reached to 101.6 kW/m². The data of ONB heat flux are over estimated from the existing correlation, and maximum deviation of wall superheat (ΔT_w,ONB) from correlations is 30%. Experimental data of inception heat flux are within 22% of that predicted from the correlation.     

Mixing parameters for an airlift bioreactor considering constant cross sectional area of riser to downcomer: Effect of sparging gas location

The effect of mode of sparging gas on the mixing parameters of an internal loop airlift bioreactor was investigated. Two bioreactors of identical volume of 14×10³ cm³ and the optimum riser to downcomer cross sectional area ratio of 0.6 were studied. In one bioreactor a gas sparger was located in the draft tube and in the annulus in another. Liquid mixing characteristics, i.e., mixing time and circulation time, were employed to describe the performance of the bioreactors. The tracer injection method was used to determine the mixing parameters. A mathematical modeling based on the tanks-in-series model was employed to characterize the hydrodynamics behavior of the bioreactors. Matlab 7.1 software was used to solve the model equations in the Laplace domain and determine the model parameter, the number of stages. A comparison between the simulation results and experimental data showed that the applied model can accurately describe the behavior of the bioreactors. The results showed that when the gas sparger was located in the draft tube, the liquid mixing time, circulation time, and the number of stage were less than while the gas sparger was located in annulus. This is due to more wall effects, more energy losses and pressure drop in the case of gas injection in the annulus.     

Indirect Synthesis of Bis(2‐PhInd)ZrCl2 Metallocene Catalyst,Kinetic Study and Modeling of Ethylene Polymerization

Bis(2‐phenylindenyl)zirconium dichloride (bis(2‐PhInd)ZrCl₂) catalyst was synthesized via the preparation of bis(2‐phenylindenyl)zirconium dimethyl (bis(2‐PhInd)ZrMe₂) followed by chlorination to obtain the catalyst. Performance of the catalyst for ethylene polymerization and its kinetic behavior were investigated. Activity of the catalyst increased as the [Al]:[Zr] molar ratio increased to 2333:1, followed by reduction at higher ratios. The maximum activity of the catalyst was obtained at a polymerization temperature of 60 °C. The rate‐time profile of the reaction was of a decay type under all conditions. A general kinetic scheme was modified by considering a reversible reaction of latent site formation, and used to predict dynamic polymerization rate and viscosity average molecular weight of the resulting polymer. Kinetic constants were estimated by the Nelder‐Mead numerical optimization algorithm. It was shown that any deviation from the general kinetic behavior can be captured by the addition of the reversible reaction of latent site formation. Simulation results were in satisfactory agreement with experimental data.