Role of soil inherent anisotropy in peak friction and maximum dilation angles of four sand-geosynthetic interfaces

Using a modified direct shear apparatus, an extensive experimental investigation is conducted into the influence of the inherent anisotropy of sand on the mobilization of the peak and critical state friction angles as well as the maximum dilation angle of the interfaces between an inherently anisotropic crushed sand and two woven geotextiles, one nonwoven geotextile, and one geomembrane. Experimental findings confirm that both peak and maximum dilation angles of sand-geosynthetic interfaces are affected from soil inherent anisotropy depending on the bedding plane inclination with respect to the shear plane. However, a unique critical state (residual) friction angle is attained for each interface type irrespective of the bedding plane inclination angle. Compiling results of a total of 141 tests, it is shown that a unique rule describes stress-dilation relationship of four different dense crushed sand-geosynthetic interfaces. The experimental data indicate that the ?_p vs. θ and ψ_max vs. θ curves are symmetrical with respect to θ?=?90° for the sand-woven geotextile and sand-geomembrane interfaces. Finally, it is shown that a constitutive equation by Pietruszczak and Mroz (2001) can predict the variation of ?_p with θ for the sand-woven geotextile and sand-geomembrane interfaces.     

A Novel Strategy for Synthesis of Polystyrene/Fe3O4 Nanocomposite: RAFT Polymerization,Functionalization, and Coordination Techniques

A facile strategy for the synthesis of polystyrene/Fe₃O₄ nanocomposite is suggested. For this purpose, styrene and 4-chloromethyl styrene monomers was copolymerized through reversible addition of fragmentation chain transfer technique [P(St-co-CMSt)] and then the chlorine groups of CMSt units were converted to diethyl malonate groups through a nucleophilic substitution reaction. Afterward, esteric groups of diethyl malonate were hydrolyzed to afford carboxylic acid-functionalized polystyrene. This polymer with carboxylic acid groups can adsorbed onto the surface of Fe₃O₄ nanoparticles through the interaction with hydroxyl groups onto the surface of the nanoparticles. We envision that the synthesized PSt/Fe₃O₄ nanocomposite may be find applications in electromagnetic interference shielding and environment sciences.     

Selection of the best ARMAX model for forecasting energy demand: case study of the residential and commercial sectors in Iran

The main purpose of the present study is to develop a simple yet proper top-down model for forecasting the energy demand of the residential and commercial sectors in Iran. This model can be used as a tool of scenario analysis to predict the emerging energy demand in future. The proposed model would be systematically developed and selected based on various quantified exogenous variables. For this purpose, a certain model out of a collection of 41,472 parallel models with different inputs and dynamics is chosen as the most appropriate model. According to the logical conjunctive relationships between the variables, the structure of all competing models is established to log-linear. Different possible combinations of various measures for the exogenous variables generate parallel models. Then, an automated fuzzy decision-making (FDM) process determines the best model. Finally, defining several scenarios, the energy demand of the residential and commercial sectors in Iran for the period of 2013 to 2021 is forecasted. The results showed that despite of de-subsidization, which is included by a dummy variable, the energy demand will grow by an average rate of about 3 % annually.     

Removal of Cd(II) from aqueous solution by using polyaniline/polystyrene nanocomposite

One of the suitable methods for removing heavy metals from water and waste water is the use of a surface adsorption process. In this study, polyaniline/polystyrene (PAn/PS) nanocomposite was prepared in aqueous solution by the polymerization of styrene and aniline using potassium iodate and ammonium peroxydisulfate as oxidants in the presence of surfactive dopant sodium dodecylbenzenesulfonate and poly(vinyl pyrrolidone) as surfactant. The capability of separating Cd(II) ions was studied, and the results were compared with those obtained with other adsorbents. The results indicated that removal percentage was increased by increasing the concentration of adsorbent, contact time, and the pH of the solution. J. VINYL ADDIT. TECHNOL.,, 2012. © 2012 Society of Plastics Engineers     

Identification of Acid Mine Drainage Potential Using Sentinel 2a Imagery and Field Data

Mine Water and the Environment - Secondary iron minerals associated with acid mine drainage (AMD) such as copiapite, jarosite, schwertmannite, goethite, ferrihydrite, and hematite can be generated...     

Influence of particle shape on the shear strength and dilation of sand-woven geotextile interfaces

The influence of particle shape on the mechanical behavior of sand-woven geotextile interfaces over a wide domain of soil density and normal stress is studied. A uniformly graded angular fine sand, and a blend of well rounded glass beads with identical particle size distributions, were selected as granular material. Experiments revealed the impact of particle shape on peak and residual friction angles as well as the maximum dilation angle of interfaces between both granular media and woven geotextile. It was observed that the residual friction angles of interfaces between angular sand/glass-beads and woven geotextile are very similar to the residual friction angles of angular sand and glass-beads in soil–soil direct shear test. It is understood that the peak friction angle and maximum dilation angle of angular sand-woven geotextile were slightly lower than corresponding values for angular sand in soil–soil direct shear test. While the peak friction angle and maximum dilation angle of angular sand-woven geotextile interface decrease with the increase in normal stress, experiments showed that these factors are insensitive to normal stress for glass beads-woven geotextile interfaces, at least for the range studied herein. All interfaces with woven geotextile as the contact surface exhibit an abrupt loss of shear strength in the post-peak regime of behavior. Finally, a unified stress-dilation law for the angular sand-woven geotextile, glass beads-woven geotextile, and angular sand-roughened steel interfaces is obtained.     

An in vitro focus on doxorubicin hydrochloride delivery of novel pH‐responsive poly(2‐succinyloxyethylmethacrylate) and poly[(N‐4‐vinylbenzyl),N,N‐diethylamine] diblock copolymers

Novel pH‐responsive poly(2‐succinyloxyethylmethacrylate)‐b‐poly[(N‐4‐vinylbenzyl),N,N‐diethylamine] [poly(SEMA‐b‐VEA)] diblock copolymers were synthesized via reversible addition fragmentation transfer (RAFT) polymerization to investigate their self‐assembly micellar behavior. The self‐assembly behaviors of synthesized diblock copolymers with distinct molecular weights (labeled (1) to) were confirmed by ¹H NMR spectroscopy, TEM and dynamic light scattering measurements. Doxorubicin hydrochloride (DOX) loading capacity was evaluated, and the in vitro cytotoxicity effect of DOX‐loaded diblock copolymer was also studied by assessing the survival rate of the breast cancer cell line MCF‐7 with 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay. The results exhibited remarkable controlled release in the MTT assay. The DOX encapsulation efficiency was calculated to be 96.4%. The size and zeta potential of DOX‐loaded poly(SEMA‐b‐VEA) diblock copolymers were 204 nm and +5.7 mV at a pH of 7.4. DOX release values after 440 h at pH 7.4, 5.4 and 4 were 22.15%, 31.43% and 47.06%, respectively. The released values of DOX‐loaded poly(SEMA‐b‐VEA) and at pH 7.4 were 22.15%, 20.5% and 17.5%, respectively. Cell survival ratios were 18.9%, 23.16% and 16.92% after 72 h. Poly(SEMA‐b‐VEA) copolymers can be considered in nanomedicine applications due to their excellent pH‐responsive micellar behavior. © 2017 Society of Chemical Industry     

Novel ‘schizophrenic’ diblock copolymer synthesized via RAFT polymerization: poly(2-succinyloxyethyl methacrylate)-b-poly[(N-4-vinylbenzyl),N,N-diethylamine]

This article describes the synthesis and characterization of a novel ‘schizophrenic’ diblock copolymer [poly(2-succinyloxyethyl methacrylate)-b-poly[(N-4-vinylbenzyl),N,N-diethylamine)]; PSEMA-b-PVEA] via reversible addition of fragmentation chain transfer (RAFT) polymerization technique. The chemical structures of all samples as representatives were characterized by means of Fourier transform infrared (FTIR), and ¹H nuclear magnetic resonance (NMR) spectroscopies. The molecular weights of PHEMA and PVEA segments were calculated to be 9770 and 12,630 gmol^?1, respectively, from ¹H NMR spectroscopy. The self-assembly behavior of the synthesized PSEMA-b-PVEA diblock copolymer was investigated by means of ¹H NMR spectroscopy, dynamic light scattering (DLS) measurements, and transmission electron microscopy (TEM) observation. The average sizes of the PSEMA-b-PVEA micelles at pHs 3.0, 6.0, and 10.0 were obtained to be 294, 237, and 201 nm, respectively, from DLS analysis. The zeta potential measurements at various pHs demonstrated that the synthesized PSEMA-b-PVEA diblock copolymer has zwitterionic properties, and the range of isoelectric point’s (IEP’s) was determined as 5.8–7.3. It is expected that the synthesized PSEMA-b-PVEA diblock copolymer considered as a prospective candidate in nanomedicine applications such as drug delivery, mainly due to its excellent ‘schizophrenic’ micellization behavior.