Water quality assessment of the River Kabul at Peshawar, Pakistan: Industrial and urban wastewater impacts

Untreated wastewater discharges may have significant short term and long term effects on the quality of a river system. Present study was undertaken to assess the present status of the water quality of the River Kabul near Peshawar in Pakistan. Seven sites were sampled upstream and downstream in the River Kabul in 2009. Samples were also taken from waste water channel (Budni Drain) that carries waste-water of Peshawar Industrial Estate as well as the domestic sewers to assess the pollution contribution of these sources to the River Kabul. Physico-chemical and microbiological parameters of the samples were analyzed during the study, as well as possible sources of contamination were investigated. The study showed that the pollution level in river is rising from upstream (at city entrance) to downstream (at city exit) due to discharge of domestic waste water effluents, agricultural activities, and solid waste dumping directly into the river.     

Simulation of concrete flow in V-funnel test and the proper range of viscosity and yield stress for SCC

The present paper highlights the flow simulation of self consolidating concrete (SCC) in V-funnel test that is used to determine the concrete filling ability and its resistance against segregation. Simulations were performed using a two-dimensional smoothed particle hydrodynamic (SPH) method to determine the discharge time where SCC was considered as a homogeneous Bingham fluid. The numerical predictions are lower than experimental data because of the assumptions of two-dimensional and homogeneous flow. Having the SPH method employed, SCCs with different viscosities and yield stresses were simulated to compare the discharge time with the suggested criteria in EFNARC (2002) and (2005) guidelines. Based on simulations results, the appropriate range of viscosities and yield stresses as well as a relation between rheological properties and discharge time for SCC taking into account EFNARC (2002) and (2005) guidelines are suggested. Using the suggested relations, one can assess the proper SCC filling ability without conducting the V-funnel test.     

Interior search algorithm (ISA): A novel approach for global optimization

This paper presents the interior search algorithm (ISA) as a novel method for solving optimization tasks. The proposed ISA is inspired by interior design and decoration. The algorithm is different from other metaheuristic algorithms and provides new insight for global optimization. The proposed method is verified using some benchmark mathematical and engineering problems commonly used in the area of optimization. ISA results are further compared with well-known optimization algorithms. The results show that the ISA is efficiently capable of solving optimization problems. The proposed algorithm can outperform the other well-known algorithms. Further, the proposed algorithm is very simple and it only has one parameter to tune.     

Investigation on the effects of ultrasonic vibration on material removal rate and surface roughness in wire electrical discharge turning

An investigation has been made to combine ultrasonic vibration and wire electrical discharge turning. Design of a submerged, precise, flexible, and corrosion-resistant rotary spindle is introduced. The spindle was mounted on a five-axis wire electrical discharge machine to rotate the workpiece in order to generate free-form cylindrical geometries. An auxiliary device that produces ultrasonic vibration was installed between the two wire guides. The ultrasonic system consists of an ultrasonic generator, a transducer, and a wire holder. When the wire is being driven, the transducer together with the wire holder vibrates under the resonance condition. Material removal rate (MRR) indicates efficiency and cost-effectiveness of the process. Experimental results show that wire vibration induced by ultrasonic action has a significant effect on material removal rate. This study has been conducted to evaluate the influence of four design factors: power, pulse off time, spindle rotational speed, and ultrasonic vibration over material removal rate. This has been done by means of design of experiments technique. Analysis of variance was used to determine significant effective factors and also to obtain an equation based on data regression. Experimental results indicate that ultrasonic vibration and power are the most significant influencing parameters on MRR. Rotational speed and pulse off time are the next in ranking. In order to study surface roughness, R _a is measured in different machining parameters.     

Experimental study and numerical modeling of arc and weld pool in stationary GTA welding of pure aluminum

In this study, a 2D mathematical model was developed for both arc and weld pool in stationary GTA welding. In arc model, current continuity equation has been solved in both arc and cathode regions without any assumption of fixed current density on the cathode surface which was essential in most previous works. The results of arc model were presented for both copper and aluminum anodes to investigate the effect of anode material on arc properties. It was seen that aluminum anode has lower maximum anode current density and heat flux but the distributions are wider than copper anode. Furthermore, shear stress on anode surface is higher in the case of aluminum anode. Also, calculated results of this study were compared with other available theoretical and experimental results. It has been shown that the agreement between calculated and experimental results was fairly good. The necessary information to simulate the weld pool, including the anode current density and heat flux to the workpiece were taken from the arc model. In this model, due to high thermal conductivity of pure aluminum, fluid flow into the weld pool was ignored. Effects of arc variables, i.e., arc length, applied current and welding time on the shape and size of the weld pool were investigated as well. In order to check the validity of the weld pool model, a comparison between calculated results and the results of our experimental tests was conducted. Generally, these comparisons reveal an acceptable agreement between calculated results and experimental data.     

Development of a mathematical model to study the feasibility of creating a clad AZ31 magnesium sheet via twin roll casting

A previously developed and validated thermal-fluid mathematical model of the twin roll casting (TRC) process for magnesium alloy AZ31 was used to quantitatively study the feasibility of producing a clad magnesium strip via the TRC process. The clad material was varied to identify the effect of material composition on the feasibility of producing a clad strip. The clad alloys chosen included pure Zn, pure Al, AA3003, and AA5182 aluminum alloys. In the analysis, the effect of casting speed and clad sheet thickness (100 and 500 μm) on the thermal history in the magnesium strip and clad layer was analyzed. Assessment of the process feasibility was determined based on the exit temperature of the clad strip at the centerline, temperature of the clad sheet prior to the roll bite entry, and fraction solid of both the core (magnesium sheet) and clad along the core/clad interface. The results indicated that using pure Zn as a clad material is not feasible due to premelting of the clad strip prior to introduction into the TRC apparatus. All three aluminum alloys studied proved to be feasible in terms of a clad material, and it was found that the effect of clad thickness and clad material chemical composition on the thermal history (temperature distribution) of the clad strip was negligible. It was also predicted using the thermodynamics package FactSage? that the intermetallic phase at the core/clad interface will be primarily γ-Mg (Mg₁₇Al₁₂). For AA5182 clad material, formation of β-Mg (Al₃Mg₂) is also possible.     

Investigating the acoustical properties of carbon fiber‐, glass fiber‐, and hemp fiber‐reinforced polyester composites

Wood is one of the main materials used for making musical instruments due to its outstanding acoustical properties. Despite such unique properties, its inferior mechanical properties, moisture sensitivity, and time‐ and cost‐consuming procedure for making instruments in comparison with other materials (e.g., composites) are always considered as its disadvantages in making musical instruments. In this study, the acoustic parameters of three different polyester composites separately reinforced by carbon fiber, glass fiber, and hemp fiber are investigated and are also compared with those obtained for three different types of wood specimens called poplar, walnut, and beech wood, which have been extensively used in making Iranian traditional musical instruments. The acoustical properties such as acoustic coefficient, sound quality factor, and acoustic conversion factor were examined using some non‐destructive tests based on longitudinal and flexural free vibration and also forced vibration methods. Furthermore, the water absorption of these polymeric composites was compared with that of the wood samples. The results reveal that the glass fiber‐reinforced composites could be used as a suitable alternative for some types of wood in musical applications while the carbon fiber‐reinforced composites are high performance materials to be substituted with wood in making musical instruments showing exceptional acoustical properties. POLYM. COMPOS., 35:2103–2111, 2014. © 2014 Society of Plastics Engineers     

Increased shelf life of Oncorhynchus mykiss (Rainbow trout) through Cu-Clay nanocomposites

Food Science and Biotechnology - Microbial growth is widely responsible for shortened shelf life of cold water-living fish products. So, it seems that current chemical-based food packaging has no...     

Nonlinear transient heat conduction analysis of hollow thick temperature-dependent 2D-FGM cylinders with finite length using numerical method

Nonlinear transient heat conduction analysis is developed for hollow thick temperature-dependent 2D-FGM cylinders subjected to transient non-uniform axisymmetric thermal loads. It is demonstrated here that the temperature-dependency in addition to the material properties variation in the 2D- FGM would lead to highly nonlinear governing equations. To do this, the graded finite element method is employed to model the structures and a quadratic Lagrange shape function has been used to improve the accuracy of the temperature distribution for the two-dimensional heat conduction analysis. Furthermore, time variation of the temperatures and the effects of material distribution variability in two radial and axial directions and the temperature-dependency of the material properties on the temperature are discussed in detail. It is assumed that the material, geometry and volume fraction distribution are axisymmetric but not uniform along the axial direction. According to the results, the variation of the material properties in two dimensions has significant effect on temperature distribution; therefore, it gives more designing flexibility benefits to the designers to implement this kind of material for the thermal barriers purposes.     

A novel non-enzymatic hydrogen peroxide sensor based on single walled carbon nanotubes–manganese complex modified glassy carbon electrode

A simple procedure was developed to prepare a glassy carbon (GC) electrode modified with single wall carbon nanotubes (SWCNTs) and phenazine derivative of Mn-complex. With immersing the GC/CNTs modified electrode into Mn-complex solution for a short period of time 20–100 s, a stable thin layer of the complex was immobilized onto electrode surface. Modified electrode showed a well defined redox couples at wide pH range (1–12). The surface coverages and heterogeneous electron transfer rate constants (k_s) of immobilized Mn-complex were approximately 1.58 × 10⁻¹⁰ mole cm⁻² and 48.84 s⁻¹. The modified electrode showed excellent electrocatalytic activity toward H₂O₂ reduction. Detection limit, sensitivity, linear concentration range and k_cat for H₂O₂ were, 0.2 μM and 692 nA μM⁻¹ cm⁻², 1 μM to 1.5 mM and 7.96(±0.2) × 10³ M⁻¹ s⁻¹, respectively. Compared to other modified electrodes, this electrode has many advantageous such as remarkable catalytic activity, good reproducibility, simple preparation procedure and long term stability.