Optimization using simulation and response surface methodology with an application on subway train scheduling

This paper presents a technique based on discrete‐event simulation and response surface methodology to model and then optimize the schedule of subway train travels. The aim of this study is to find appropriate headways—time intervals between the travels of two consecutive trains—at different hours in order to optimize average passenger travel time and rate of carriage fullness. For physical reasons and the observance of safety standards, an increase in the train speed in order to decrease average passenger travel time may not exceed some specified limits. One of the ways to decrease this average is to appropriately adjust headways of trains in the schedule. For this purpose, a metamodel of multinomial type is fitted to the data obtained from simulation tests to describe the relation between input variables (headways) and output variables (average passenger travel time in system and carriage fullness rate), and then optimal combinations of input variables are obtained using a weighed metric method and sequential quadratic programming.     

CO2 biofixation by Synechococcus elongatus from the power plant flue gas under various light–dark cycles

Clean Technologies and Environmental Policy - Carbon dioxide emission, which acts as one of the major agents of greenhouse gases (GHG), has significant effects on global warming. Nowadays, there is...     

In situ atom transfer radical polymerization of styrene to in-plane functionalize graphene nanolayers: grafting through hydroxyl groups

We report synthesis of a novel diamine 1,2-bis(4-(Hydrazonomethyl)phenoxy)ethane (bis- HPE) and a derived novel polyimide. The diamine was reacted with PMDA and ODA to synthesize copolyimide. Unmodified and modified silica particles were dispersed in the polyimide to prepare polyimide-silica hybrids: (a) unmodified (PSH-UM), and (b) modified (PSH-M). The PSH-UM were prepared by generating silica particles in situ in PI. In PSH-M, structural group identical to PI, 2,6- bis(3-(triethoxysilyl)propyl)pyrrolo[3,4-f]isoindole-1,3,5,7(2H,6H)-tetraone was introduced into silica nano-particles. The structural similarity enhanced compatibility between organic–inorganic components by like-like chemical interactions as both contain flexible alkyl groups. PSH-M have shown improved surface smoothness, hydrophobicity and thermal stability. Such properties are mandatory for stable coatings. The structure of silica and PI was affirmed by FTIR, EDX, and solid-state 29Si NMR spectroscopy. Morphological and thermal properties of the prepared PI-SiO₂ nano-composites were investigated by field emission scanning electron microscopy, atomic force microscopy, contact angle measurement and thermogravimetric analysis.     

Application of Taguchi approach in describing the mechanical properties and thermal decomposition behavior of poly(vinyl chloride)/clay nanocomposites: Highlighting the Role of organic modifier

Mechanical and thermal properties of poly(vinyl chloride) (PVC)/nanoclay (NC) composites prepared via melt‐blending in a single‐screw extruder were investigated. The effects of NC type, NC content, and K‐value of PVC were evaluated by using L9 orthogonal array of the Taguchi approach. The most influential variables and significance of interactive effects were examined for the highest values of Young's modulus and hardness. Scanning electron micrographs and X‐ray diffraction patterns revealed the formation of exfoliated/intercalated structures. Although the K‐value has a minor individual effect on mechanical characteristics, the interaction of the K‐value with NC type and NC content is significant. The composites were also characterized and tested by using analysis by thermal gravimetry, differential thermogravimetry, and differential scanning calorimetry methods. The results of the thermal studies indicated that decomposition of the organic modifier of NCs has a catalytic effect on the dehydrochlorination of PVC. This finding justifies the rather low mechanical properties of PVC/organoclay nanocomposites. Fourier‐transform infrared spectra of the samples were indicative of accelerated degradation reactions, which provided support for above observations. J. VINYL ADDIT. TECHNOL., 22:182–190, 2016. © 2014 Society of Plastics Engineers     

One-Step Synthesis of Zirconia and Magnetite Nanocomposite Immobilized Chitosan for Micro-Solid-Phase Extraction of Organophosphorous Pesticides from Juice and Water Samples Prior to Gas Chromatography/Mass Spectroscopy

In this research, a magnetic sorbent was prepared by immobilizing zirconia and magnetite (Fe₃O₄) nanoparticles in chitosan, which is characterized and used as an effective nanosorbent in magnetic dispersive micro-solid-phase extraction (MDMSPE) of organophosphorous pesticides (OPPs) from juice and water samples prior to gas chromatography-mass detection (GC-MS). The properties and morphology of synthesized sorbent were characterized by scanning electron microscopy (SEM), Fourier transform-infrared spectroscopy (FT-IR), vibrating sample magnetometry (VSM), and differential scanning calorimetric (DSC) analysis. The main experimental parameters including pH level, extraction time, sorbent mass, salt concentration, and desorption conditions were investigated and optimized to maximize extraction efficiency. Under optimized conditions, the calibration curves were obtained in the concentration range of 0.1–500 ng mL^?1 with correlation coefficients between 0.9993 and 0.9999. The limits of detection (signal-to-noise ratio (S/N) = 3) and limits of quantification (S/N = 10) of the method ranged from 0.031 to 0.034 ng mL^?1 and 0.105–0.112 ng mL^?1, respectively. The intra-day and inter-day RSDs were 2.2–5.7 and 2.5–7.5%, respectively. The method was successfully applied to the analysis of OPPs in fruit juices (apple, peach, and cherry) and water (mineral, tap, and river) real samples, with recoveries in the range of 86.0–106.0% for the spiked juice and water samples. The results showed that with combination of high selectivity of zirconia and magnetic property of magnetite as well as immobilizing ability of chitosan, the fabricated sorbent exhibited exceptional extraction ability toward the OPPs.