Simultaneous Modeling of Young's Modulus, Yield Stress, and Rupture Strain of Gelatin/Cellulose Acetate Microfibrous/Nanofibrous Scaffolds Using RSM.

Electrospinning is a promising method to fabricate bioengineered scaffolds, thanks to utilizing various types of biopolymers, flexible structures, and also the diversity of output properties. Mechanical properties are one of the major components of scaffold design to fabricate an efficacious artificial substitute for the natural extracellular matrix. Additionally, fiber orientations, as one of the scaffold structural parameters, could play a crucial role in the application of fabricated fibrous scaffolds. In this study, gelatin was used as a highly biocompatible polymer in blend with cellulose acetate (CA), a polysaccharide, to enhance the achievable range of mechanical characteristics to fabricated fibrous electrospun scaffolds. By altering input variables, such as polymers concentration, weight ratio, and mandrel rotation speed, scaffolds with various mechanical and morphological properties could be achieved. As expected, the electrospun scaffold with a higher mandrel rotation speed shows higher fiber alignment. A wide range of mechanical properties were gained through different values of polymer ratio and total concentration. A general improvement in mechanical strength was observed by increasing the concentration and CA content in the solution, but contradictory effects, such as high viscosity in more concentrated solutions, influenced the mechanical characteristics as well. A response surface method was applied on experimental results in order to describe a continuous variation of Young's modulus, yield stress, and strain at rupture. A full quadratic version of equations with the 95% confidence level was applied for the response modeling. This model would be an aid for engineers to adjust mandrel rotation speed, solution concentration, and gelatin/CA ratio to achieve desired mechanical and structural properties

A Thoroughgoing Design of a Rapid-cycle Microfluidic Droplet-based PCR Device to Amplify Rare DNA Strands

DNA is a molecule and assortment of fruitful information of organisms and a wide range of viruses. Polymerase chain reaction (PCR) is a process used to amplify DNA strands in order to generate millions of them and extract the applicable information. Although conventional methods for PCR are flourishing to a certain extent, they have such major drawbacks as contamination, high material consumption, and low-speed function. By the combination of PCR devices with the microfluidic approach and integrating them with droplet generation technology, the mentioned problems can be eliminated. In this study, a novel two-step rapid-cycle droplet-based PCR (dPCR) device, considering the design of microchannel and heat transfer system, has been presented. First, numerous studies have been conducted to select the proper droplet generator for the integration of the droplet generation with the PCR device. Then, with the careful attention to the requirements of a PCR device, the geometry of different zones of the PCR device has been, meticulously, designed. In the next and last step, the heat transfer system for the designed zones of the PCR device has been planned. Afterward, results are examined carefully which indicate that in a cycle of PCR, they are not any major discrepancies between the designed dPCR and the ideal one—the one that is intended to be created

Design of Matched and Mismatched Filters Based on Peak Sidelobe Level Minimization

‎This paper focuses on the design of matched filters with low peak sidelobe level as well as mismatched‎ ‎filters with low loss in processing gain and peak sidelobe level‎, ‎for phase codes‎. ‎We propose an algorithm ‎which employs the least-p-th norm minimax based on the genetic algorithm‎, ‎and a method based on the‎ ‎semidefinite programming to deal respectively with the resulting matched and mismatched optimization problems‎. A framework is also presented to design mismatched filters that are robust to Doppler shifts. ‎Simulation results show that using the proposed methods for finding matched filters leads to better peak sidelobe‎ ‎level and integrated sidelobe level for binary and polyphase codes compared to previous works‎. ‎In addition‎, ‎the mismatched filters designed by the proposed methods have very low peak sidelobe level in‎ ‎the binary and polyphase cases‎

A New Recursive Formulation for the Mixed Redundancy Strategy in Reliability Optimization Problems

One of the common approaches for improving the reliability of a specific system is to use parallel redundant components in subsystems. This approach, which is known as the redundancy allocation problem (RAP), includes the simultaneous selection of the component type and its level for each subsystem in order to maximize the system reliability.Traditionally, there are two redundancy strategies, namely active and standby, for the redundant components. Recently, a new powerful strategy called mixed strategy has been developed. It has been proved that the mixed strategy has a better performance when compared to both previous strategies. The main issue in utilizing the mixed strategy is its complicated formulation and sophisticated calculations, leading to a time-consuming procedure for solving the problems. Hence, in this paper, a new formulation based on the recursive approach is introduced to ease the calculation of the mixed strategy. In the new formulation, the complex double integral calculations are removed and the calculation times is reduced. The proposed recursive formulation provides a general statement for the mixed strategy formula which is not changed by altering the number of components in each subsystem. This flexibility and stability in the formula can be very important, especially for large scale cases. In order to evaluate the new approach and to compare its performances with the previous formulation, a benchmark problem with 14 subsystems is considered and the results of the two formulation are compared with each other

Nano-particles transport in a concentric annulus: a lattice Boltzmann approach

A combination of the lattice Boltzmann method and lagrangian Runge-Kutta procedure is used to study dispersion and removal of nano-particles in a concentric annulus. The effect of aspect ratio, Rayleigh number and particles diameter are examined on particles removal and their dispersion characteristics. Simulations are performed for the Rayleigh number ranges from 103 to 105 and aspect ratio of 2, 3 and 4. Higher aspect ratios have led to weaker recirculation strength. The finest particles move on stochastic path due to the effect of Brownian motion. The Brownian motion has a greater effect on the removal of nano-particles with respect to thermophoresis

A thoroughgoing design of a rapid-cycle microfluidic droplet-based PCR device to amplify rare DNA strands

DNA is a molecule and assortment of fruitful information of organisms and a wide range of viruses. Polymerase chain reaction (PCR) is a process used to amplify DNA strands in order to generate millions of them and extract the applicable information. Although conventional methods for PCR are flourishing to a certain extent, they have such major drawbacks as contamination, high material consumption, and low-speed function. By the combination of PCR devices with the microfluidic approach and integrating them with droplet generation technology, the mentioned problems can be eliminated. In this study, a novel two-step rapid-cycle dropletbased PCR (dPCR) device, considering the design of microchannel and heat transfer system, has been presented. First, numerous studies have been conducted to select the proper droplet generator for the integration of the droplet generation with the PCR device. Then, with the careful attention to the requirements of a PCR device, the geometry of different zones of the PCR device has been, meticulously, designed. In the next and last step, the heat transfer system for the designed zones of the PCR device has been planned. Afterward, results are examined carefully which indicate that in a cycle of PCR, they are not any major discrepancies between the designed dPCR and the ideal one-the one that is intended to be created

Election control through social influence with voters’ uncertainty

The problem of election control through social influence consists in finding a set of nodes in a social network of voters to be the starters of a political campaign aimed at supporting a particular target candidate. The voters reached by the campaign change their views on the candidates. The goal is to model the spread of the campaign in such a way as to maximize the chances of winning for the target candidate. Herein, differently from previous work, we consider that each voter is associated with a probability distribution over the candidates modeling the likelihood of the voter to vote for each candidate. In a first model we propose, we prove that, under the Gap-ETH, the problem cannot be approximated to within a factor better than 1 / no(1), where n is the number of voters. In a second model, which is a slight relaxation of the first one, the problem instead admits a constant-factor approximation algorithm. Finally, we present simulations on both synthetic and real networks, comparing the results of our algorithm with those obtained by a standard greedy algorithm for Influence Maximization

Multi-criteria optimization of curved and baffle-embedded micromixers for bio-applications

Micromixers are key components of microfluidic devices in many bio-applications namely, cell analysis, nanoparticle synthesis, and polymerase chain reaction (PCR). The shared challenges in designing a micromixer are low mixing efficiency or/and high-pressure drop. Improving one of these performance parameters is usually concurrent with deteriorating in the other. In biological contexts, further constraints like compatibility or viability in shear stress and pressure add to the complications of mixer designing. Exploiting the layout optimization method to design passive micromixers decreases dependence on the experience of designers. In this paper, a curved micromixer was studied with obstacles to create normal advection and curved microchannels to generate Dean vortices. Five geometric parameters including radius of microchannel, angle of baffles, height of baffles, thickness of baffles, and aspect ratio of the channel were considered as design parameters. The mixing efficiency and the pressure drop in the mixing channel were designated as the design objectives and evaluated for biologically-pertinent Reynolds numbers of 3, 27, and 81, through the integration of 3D Navier–Stokes and convection–diffusion equations in a CFD platform. Design nodes were systematically appointed by Taguchi design of experiments method and a polynomial response surface model was fitted on these points to develop continuous approximation functions for mixing index and pressure drop based on design parameters. Finally, a multi-objective genetic algorithm was performed to find the Pareto-optimal population and draw it in a multi-criteria diagram. The accuracy of this Pareto front prediction was verified by CFD simulation to be a maximum 3% error for mixing index and 7% error for pressure drop. The diagram helps designers glean the data needed for a trade-off between each criterion by a quick reflection on this diagram and design a mixer that best fits their requirements