Rapid and green functionalization of multi-walled carbon nanotubes by glucose: structural investigation and the preparation of dopamine-based poly(amide-imide) composites

Functionalization of multi-walled carbon nanotubes (MWCNTs) by glucose was performed through esterification reaction. The reaction was carried out in water, in the presence of N,N′-carbonyldiimidazole as a catalyst. Glucose-functionalized MWCNTs (MWCNTs-Gl) were characterized by a set of methods including Fourier-transform infrared spectroscopy, X-ray diffraction, field emission scanning, and transmission electron microscopy. Thermogravimetric analysis (TGA) results also demonstrated the presence of organic portions of the functionalized MWCNTs. MWCNT-Gl/poly(amide-imide) (PAI) composite films with different MWCNTs-Gl content (5, 10, and 15 wt%) were prepared by ultrasonication-assisted solution blending method. Microscopic observations showed that the dispersion of the MWCNTs-Gl was improved by the organic groups on the MWCNT surface and functional groups on the PAI. TGA results showed that the hybrid films exhibited a good thermal stability. According to mechanical tensile tests, the tensile strength and the Young’s modulus of the MWCNT-Gl/PAI composites were increased with increasing MWCNTs-Gl content.     

Augmented ε-constraint method in multiobjective staff scheduling problem: a case study

Staff scheduling is one of the most relevant issues among production planning managers. The problem is to set up an appropriate schedule for various employees to maximize the performance measurement. There are different conflicting criteria with any scheduling problem such as cost minimization, efficiency maximization, etc. The proposed model of this paper develops a new multiobjective decision-making scheduling problem, and the resulted problem is solved using two different techniques of goal programming and augmented epsilon constraint. The implementation of the new proposed model is demonstrated with a real-world case study, and they are analyzed. The preliminary results indicate that the epsilon-constraint method somewhat performs better than goal programming technique.     

Numerical simulation of 2-D laminar flow subjected to the Lorentz force effect in a channel with backward-facing step

This paper presents the numerical solutions of a two-dimensional laminar flow over a backward-facing step in the presence of the Lorentz body force. The Navier-Stokes equations in a vorticity-stream function formulation are numerically solved using a uniform grid mesh of 2001 × 51 points. A second-order central difference approximation is used for spatial derivatives. The solutions progress in time with a fourth-order Runge-Kutta method. The unsteady backward-facing step flow solution is computed for Reynolds numbers 100 to 800. The size and genesis of the recirculating regions are dramatically affected by applying the Lorentz force. The results demonstrate that using an appropriate configuration for applying the Lorentz force can make it an essential tool for controlling the flow in channels with a backward-facing step.     

Solving a new mathematical model for a hybrid flow shop scheduling problem with a processor assignment by a genetic algorithm

This paper presents a new mathematical model for a hybrid flow shop scheduling problem with a processor assignment that minimizes makespan (i.e., C _max) and cost of assigning a number of processors to stages. In this problem, it is assumed that there are a number of parallel identical processors which are assigned to all of the stages with an unlimited intermediate storage between any two successive stages. To solve such a hard problem, first a new heuristic algorithm is proposed to compute the makespan that is embedded in the proposed genetic algorithm in order to find the best sequence of jobs, and then processors are assigned to the stages simultaneously. A number of test problems have been solved and related results are illustrated and analyzed.     

Interaction between chronic arsenic exposure via drinking water and plasma lactate dehydrogenase activity

Arsenic is a potent environmental pollutant that has caused one of the largest public health poisonings in the history of human civilization, affecting tens of millions of people worldwide especially in Bangladesh. Lactate dehydrogenase (LDH) in blood plays an important role in predicting cell or organ damage and as an important clue to the diagnosis of a variety of cancers. However, effect of chronic arsenic exposure on the LDH level in blood has not yet been documented. Since the chronic arsenic exposure is associated with organ damages and multi-site cancers, this research aimed at assaying the plasma level of LDH activity in the population who were exposed to arsenic chronically in Bangladesh. A total of 185 individuals living in arsenic-exposed areas and 121 individuals living in non-exposed area in Bangladesh were recruited as study subjects. Arsenic content in drinking water, hair and nails were estimated by Inductively Coupled Plasma Mass Spectroscopy (ICP-MS) and LDH activity was assayed by a spectrophotometer. Significant increase in LDH activity was observed with increasing concentrations of arsenic in water, hair and nails. Further, the study subjects were split into four groups based on the three ways of each exposure metrics (water, hair and nail arsenic concentrations) where the study subjects in the non-exposed area were used as a reference (lowest exposure) group. LDH activity was found to be increased in the higher exposure groups of water and hair arsenic concentrations. LDH activity was also increased at low to medium exposure groups of nail arsenic concentrations.Thus, the elevated plasma LDH activity might be helpful for the early prognosis of organ or tissue damage in the individuals who were exposed to arsenic chronically.     

钢拱架在升温状态下的非线性弹塑性分析

提出了一种新型的非离散化方法,用于分析钢拱架在升温状态下的性能。钢拱架中单轴对称的横截面上具有弹性和塑性区域,经受着任意方向的热效应,如沿拱的长度方向和沿横截面的深度方向。公式中考虑了高温时可能产生的几何及材料非线性,以及潜在的悬链线效应的影响。采用ABAQUS对几何模型进行了非线性分析,通过与分析结果的对比验证了该模型的有效性与准确性。所提出的方法也给出了一些重要参数,如温度加载时钢拱架横截面底部纤维的温度分布,横截面顶部纤维与底部纤维的温差。所提出的模型也使有限元程序能更加准确地进行计算,并为钢拱架的抗火设计提供了一个计算的平台。     

Exposure to fine particulate matter in ten night clubs in Athens Greece: Studying the effect of ventilation, cigarette smoking and resuspension

The aim of the present work is to study the occupants' exposure to fine particulate concentrations in ten nightclubs (NCs) in Athens, Greece. Measurements of PM₁ and PM_2.5 were made in the outdoor and indoor environment of each NC. The average indoor PM₁ and PM_2.5 concentrations were found to be 181.77 μg m^− 3 and 454.08 μg m^− 3 respectively, while the corresponding outdoor values were 11.04 μg m^− 3 and 32.19 μg m^− 3. Ventilation and resuspension rates were estimated through consecutive numerical experiments with an indoor air quality model and were found to be remarkably lower than the minimum values recommended by national standards. The relative effects of the ventilation and smoking on the occupants' exposures were examined using multiple regression techniques. It was found that given the low ventilation rates, the effect of smoking as well as the occupancy is of the highest importance. Numerical evaluations showed that if the ventilation rates were at the minimum values set by national standards, then the indoor exposures would be reduced at the 70% of the present exposure values.     

Pullout behavior of polymeric strip in compacted dry granular soil under cyclic tensile load conditions

Assessment of the reinforcement behavior of soil under cyclic and monotonic loads is of great importance in the safe design of mechanically stabilized earth walls. In this article, the method of conducting a multistage pullout (MSP) test on the polymeric strip (PS) is presented. The post-cyclic behavior of the reinforcement can be evaluated using a large-scale pullout apparatus adopting MSP test and one-stage pullout (OSP) test procedures. This research investigates the effects of various factors including load amplitude, load frequency, number of load cycles and vertical effective stress on the peak apparent coefficient of friction mobilized at the soil-PS interface and the pullout resistance of the PS buried in dry sandy soil. The results illustrate that changing the cyclic tensile load frequency from 0.1 Hz to 0.5 Hz does not affect the pullout resistance. Moreover, the influence of increasing the number of load cycles from 30 to 250 on the peak pullout resistance is negligible. Finally, the effect of increasing the cyclic tensile load amplitude from 20% to 40% on the monotonic pullout resistance can be ignored. The peak apparent coefficient of friction mobilized at the soil-PS interface under monotonic and cyclic load conditions decreases with the increase in vertical effective stress.     

Optimal placing and sizing of parking lots including different levels of charging stations in electric distribution networks

Background: Low emission, high efficiency, and convenience of using plug-in electric vehicles (PEVs) are considered as significant benefits of PEVs. However, installation of parking lots (PLs) in order to supply PEVs causes some financial and technical challenges for electric distribution networks. The changes in system reliability, power loss, voltage drop, and costs associated with the installation of PLs are considered as some of the aforementioned challenges. Therefore, optimal placing and sizing of PEV PLs including different levels of charging stations ((CS); slow, medium, and fast) are presented in this paper. Since PLs have the potential to exchange electricity by electric network, they can be taken into account as distributed generations (DGs) and their installation can be considered from the perspective of installation of DGs. An objective function including system reliability, power loss, voltage drop, and PL cost/revenue is proposed for the optimal planning. Results: Genetic algorithm is employed to solve the optimisation problem. Simulation is carried out on a 33-bus radial distribution network. For the planning purposes of PLs, three different levels of CSs (slow, medium, and fast) in PLs are considered. The effect of increasing the penetration of PEVs in PLs is also examined on planning the PLs. The effect of different dispatch times on the selection of different CS levels (slow, medium, and fast) is investigated as well. Furthermore, the effect of applying tariffs and incentives for the customers is analysed for the selection of CS levels. Finally, the effect and importance of combinations of the CSs with different levels are investigated.     

Crack detection of the cantilever beam using new triple hybrid algorithms based on Particle Swarm Optimization

The presence of cracks in a concrete structure reduces its performance and increases in the size of cracks result in the failure of the structure. Therefore, the accurate determination of crack characteristics, such as location and depth, is one of the key engineering issues for assessment of the reliability of structures. This paper deals with the inverse analysis of the crack detection problems using triple hybrid algorithms based on Particle Swarm Optimization (PSO); these hybrids are Particle Swarm Optimization-Genetic Algorithm-Firefly Algorithm (PSO-GA-FA), Particle Swarm Optimization-Grey Wolf Optimization-Firefly Algorithm (PSO-GWO-FA), and Particle Swarm Optimization-Genetic Algorithm-Grey Wolf Optimization (PSO-GA-GWO). A strong correlation exists between the changes in the natural frequency of a concrete beam and the crack parameters. Thus, the location and depth of a crack in a beam can be predicted by measuring its natural frequency. Hence, the measured natural frequency can be used as the input parameter of the algorithm. In this paper, this is applied to identify crack location and depth in a cantilever beam using the new hybrid algorithms. The results show that among the proposed triple hybrid algorithms, the PSO-GA-FA and PSO-GWO-FA algorithms are much more effective than PSO-GA-GWO algorithm for the crack detection.