Effect of Extraordinary Large Floods on at-site Flood Frequency

The peak flow of extraordinary large floods that occur during a period of systematic record is a controversial problem for flood frequency analysis (FFA) using traditional methods. The present study suggests that such floods be treated as historic flood data even though their historical period is unknown. In this paper, the extraordinary large flood peak was first identified using statistical outlier tests and normal probability plots. FFA was then applied with and without the extraordinary large floods. In this step, two goodness-of-fit tests including mean absolute relative deviation and mean squared relative deviation were used to identify the best-fit probability distributions. Next, the generalized extreme value (GEV), three-parameter lognormal (LN3), log-Pearson type III (LP3), and Wakeby (WAK) probability distributions were used to incorporate and adjust the extraordinary large floods with other systematic data. Finally, procedures with and without historical adjustment were compared for the extraordinary large floods in terms of goodness-of-fit and flood return-period quantiles. The results of this comparison indicate that historical adjustment from an operational perspective was more viable than without adjustment procedure. Furthermore, the results without adjustment were unreasonable (subject to over- and under-estimation) and produced physically unrealistic estimates that were not compatible with the study area. The proposed approach substantially improved the probability estimation of rare floods for efficient design of hydraulic structures, risk analysis, and floodplain management.     

Flow resistance in a compound gravel-bed bend

In this paper, the effect of a gravel-bed in a compound bend (similar to sinusoidal top view) of a natural river (Zayandehrud River flowing through Isfahan, Iran) has been investigated for flow resistance analysis, measuring the velocity with a micro current meter. The data were analysed and the following observations were made. In a compound bend, the law of the wall can be valid for up to 66% of the flow depth from the bed. The parabolic law is the most effective method for the determination of shear velocity. Based on the existing criteria for verifying the equilibrium boundary layer, the flow cannot be in equilibrium. The shear stress distribution and the sediment transport parameters have considerable influence on resistance to flow. Froude number and the flow depth relative to the representative gravel size have little effect on the flow resistance estimation.     

Investigation of decision making process: a hypermedia approach

Research in decision making has concentrated mainly on the decision outcome (choice) rather than on the process of the decision making. This pattern is primarily due to the lack of an acceptable unobtrusive tool for investigation of the decision process. Further, the lack of a consistent decision aid in empirical works has hindered the comparison of results. The purpose of this paper is to present a flexible and adaptable computer-based system for empirical examination of information processing. The main thrust of the proposed system is to provide guidelines to the restrictive/channeling approach to system design. This system can be easily modified to suit different experimental research requirements. It should support more realistic decision tasks, which often are criticized in decision experiments. Furthermore, availability of this system should encourage more research work on the process of decision making. The nature of this support system is linked to the literature, and specifications and components of the system are provided.     

Multiscale analysis of viscoelastic laminated composite plates using generalized differential quadrature

In this paper, a laminated composite plate is analyzed using a multiscale method. At first, material properties of a lamina are obtained using an analytical micromechanical approach called simplified unit cell method (SUCM), and then in structural level, the generalized differential quadrature method (GDQM) is used to analyze a laminated composite plate. By means of the Boltzmann superposition principle, the viscoelastic behavior of the matrix is obtained. The Prony series is considered to define the compliance of matrix. To verify the results, graphiteT300/epoxy5208 composite material is analyzed and the results are compared with existing experimental data. The multiscale algorithm includes obtaining overall properties of the composite by SUCM; then, these properties are used to define the bending stiffness. Governing equations of motion of laminated composite plate are solved via GDQM and Newton–Raphson method. Variations of stresses and displacements versus time and volume fraction of the fibers are shown for laminated composite plates with different boundary conditions.     

Acoustic damping flexible polyurethane foams: Effect of isocyanate index and water content on the soundproofing

High-efficiency sound absorbing flexible polyurethane foams (FPUFs) are manufactured using nonpolar polyester resin, methylene diphenyl diisocyanate, and other reagents by one-shot bulk polymerization. In this study, the impact of the isocyanate index (90, 100, and 110) and water content (2.5 and 5%) on the microphase separation and soundproofing behavior of FPUFs are examined using atomic force microscopy, Fourier transform infrared spectroscopy, optical microscope, and an impedance tube device. The results reveal that the increase of the isocyanate index and water content leads to the increase of the cell size, cell size distribution, open-cell content, cell wall roughness, and microphase separation. Also, maximum sound absorption coefficient (α) reaches to 0.98 and the average of α in the frequency range of 1500–4000 Hz increases from 0.7 to 0.87 by increasing the water content from 2.5 to 5% and isocyanate index from 90 to 110; therefore, acoustic damping performance enhances up to 26.24% due to the synergic effects of microphase separation on the viscose media formation, open-cell content, cell wall roughness, cell size, and cell size distribution. In conclusion, FPUFs with an optimal amount of microphase separation and drainage flow can be a promising candidate for sound insulating materials. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47363.     

Waterborne acrylic–polyaniline nanocomposite as antistatic coating: preparation and characterization

An antistatic and electrically conductive acrylic–polyaniline nanocomposite coating was successfully synthesized by interfacial polymerization of aniline in the presence of acrylic latex. The acrylic latex was prepared through emulsion polymerization, and aniline was polymerized by in situ interfacial polymerization at the interface of acrylic latex/chloroform phase. Fourier transform infrared spectroscopy (FTIR), UV–Vis spectroscopy and CHNS elemental analysis revealed the existence of 6.24 wt% emeraldine salt of polyaniline (PAni) in the dried film of the nanocomposite. Scanning electron microscopy (SEM) confirmed the presence of colloidal polymer particles in the aqueous phase which was confirmed to have some advantages, including prevention of aggregation of particles, dispersibility improvement and enhancement of the PAni nanofibers aspect ratio in the acrylic polymer matrix. According to SEM results, PAni fibers with the length ranging from 12 to 67 µm and diameters between 0.078 and 1 µm, highly dispersed in the acrylic polymer matrix, were successfully synthesized. Thermal, electrical and mechanical properties of the acrylic copolymer were significantly affected by PAni incorporation. The onset degradation temperature in thermogravimetric analysis revealed that the thermal stability of the nanocomposite was improved compared to that of the pure acrylic copolymer. The nanocomposite film showed electrical conductivity of about 0.025 S/cm at room temperature, along with satisfactory mechanical properties, attractive as an antistatic material in coating applications.     

Nafion/histidine functionalized carbon nanotube: High-performance fuel cell membranes

Here we show preparation and characterization of a new type of composite membrane based on Nafion^®/histidine modified carbon nanotube by imidazole groups (Im-CNT), for direct methanol fuel cell (DMFC) applications. Due to the presence of this imidazole-based amino acid on the surface of CNT, new electrostatic interactions can be formed in the interface of Nafion^® and Im-CNT. Physical characteristics of these nanocomposite membranes are investigated by water uptake, methanol permeability, ion exchange capacity, proton conductivity, as well as fuel cell performance results.     

Inelastic initial local buckling of skew thin thickness-tapered plates with and without intermediate supports using the isoparametric spline finite strip method

In this paper, skew isotropic plates subjected to in-plane loadings are analyzed using a stability analysis based on the isoparametric spline finite strip method, which includes inelasticity. Using this method, the initial inelastic local buckling of skew plates with or without intermediate line supports is studied based on Ramberg–Osgood representation of the stress–strain curve using the deformation theory of plasticity. Stiffness and stability matrices are formulated by energy expressions using the small deflection theory. The effect of tapered section on the local buckling of skew plates is taken into account. Finally, the inelastic local buckling loads of these plates are obtained and the results are compared with known solutions in the literature.     

高温局部荷载作用下短粗腹板的失效机制

提出计算高温和局部荷载作用下短粗热轧钢板的极限强度的分析模型。该局部荷载可能出现在火灾中钢框架结构梁柱连接的受压区,由集中荷载所产生。建模中假定翼缘上的理想塑性铰会导致腹板屈服,计算没有考虑板的局部屈曲。根据温度区域和连接受压区的长度提出两种可能的失效机制,这与周边温度升高时构件的失效屈服不同。基于本文提出的分析模型,对一个典型连接件进行参数研究,归纳不同的热梯度和局部荷载作用长度下腹板极限强度的变化。分析结果表明:在对钢结构进行防火设计时,必须考虑到连接件在高温下的反应,才能提高建模的准确性。     

Feasibility of Treatment of Refinery Wastewater by a Pilot Scale MF/UF and UF/RO System for Reuse at Boilers and Cooling Towers

A pilot-scale hybrid membrane system, consisting of a ceramic microfilter (MF), two differentpolyvinyl chloride (PVC) and polyacrylonitrile (PAN) ultrafilters (UF), and a polyamide reverse osmosis (RO) filter, has been utilized to decrease harmful and damaging components in wastewater produced from Tehran Refinery with aim to be reused at boilers and cooling towers. Taguchi method was employed to find optimum operating conditions including transmembrane pressure, cross flow velocity (CFV), temperature, and backwash time. Further, analysis of variance (ANOVA) was performed to determine the significance of controlling factors on total organic carbon rejection and normalized permeate flux. MF (ceramic)/UF (PVC) system reduced, %: oil 99.7; chemical oxygen demand (COD) 82; biochemical oxygen demand (BOD) 79.3; conductivity 60.5; total dissolved solids (TDS) 52.6; turbidity 99.7 and total hardness 73.2. MF(ceramic)/UF (PAN) system reduced: oil, COD, BOD, conductivity, TDS, turbidity, and total hardness by 99.8; 84.2; 80.8; 62.72; 55; 99.9 and 78.4%, respectively. UF (PAN)/RO system decreased, %: oil 99.5; COD 99; BOD 99; conductivity 98; TDS 98; turbidity 98.7 and total hardness 99.94. Obtained treated wastewater by this system can be reused as feed water of boilers.