Cell-laden microengineered pullulan methacrylate hydrogels promote cell proliferation and 3D cluster formation

The ability to encapsulate cells in three-dimensional (3D) environments is potentially of benefit for tissue engineering and regenerative medicine. In this paper, we introduce pullulan methacrylate (PulMA) as a promising hydrogel platform for creating cell-laden microscale tissues. The hydration and mechanical properties of PulMA were demonstrated to be tunable through modulation of the degree of methacrylation and gel concentration. Cells encapsulated in PulMA exhibited excellent viability. Interestingly, while cells did not elongate in PulMA hydrogels, cells proliferated and organized into clusters, the size of which could be controlled by the hydrogel composition. By mixing with gelatin methacrylate (GelMA), the biological properties of PulMA could be enhanced as demonstrated by cells readily attaching to, proliferating, and elongating within the PulMA/GelMA composite hydrogels. These data suggest that PulMA hydrogels could be useful for creating complex, cell-responsive microtissues, especially for applications that require controlled cell clustering and proliferation.     

Prospects of nuclear power plants for sustainable energy development in Islamic Republic of Iran

This paper presents the feasible contributive share of electricity generation from each energy resources. This includes the economical feasibilities and all demographic projections involved in forecasting methodology, which explicitly reflect on overall national power demand projection in the Energy prospects of Islamic Republic of Iran till 2033. The Energy demand and reliability are presented with a view to elaborate on significant role and required capacity of Nuclear Power Plants (NPP) towards fulfillment of an energy mix policy in the country.     

Effect of Nanostructured Microporous Surfaces on Pool Boiling Augmentation

ABSTRACT

Nanostructured microporous surfaces were electrodeposited at various electrolyte temperatures on copper substrate to investigate the saturated pool boiling enhancement of distilled water at atmospheric pressure. Surface structure topography and wickability were analyzed to investigate their relation to critical heat flux. Scanning electron microscope showed that the micro-clusters have nanostructures from cubic at 5°C to dendritic at 60°C electrolyte temperature. Rate-of-rise experiments demonstrated that dendritic copper structure has the best capillary performance. The experimental results of pool boiling heat transfer indicate that the critical heat flux increased with surface wickability. Electrodeposited porous surface in hot electrolyte showed the highest critical heat flux and heat transfer coefficient of the 124 W/cm² and 17 W/cm²K, respectively, which is 50% and 270% higher than that of plain surface. However, the two-step electrodeposition and annealing were used in fabrication of surfaces, but the mechanical strength of layer needs more improvement by changing the electrochemical process parameters.     

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.