Process analysis of two-layered tube hydroforming with analytical and experimental verification

Two-layered tubular joints are suitable for special applications. Designing and manufacturing of two layered components require enough knowledge about the tube material behavior during the hydroforming process. In this paper, hydroforming of two-layered tubes is investigated analytically, and the results are verified experimentally. The aim of this study is to derive an analytical model which can be used in the process design. Fundamental equations are written for both of the outer and inner tubes, and the total forming pressure is obtained from these equations. Hydroforming experiments are carried out on two different combinations of materials for inner and outer tubes; case 1: copper/aluminum and case 2: carbon steel/stainless steel. It is observed that experimental results are in good agreement with the theoretical model obtained for estimation of forming pressure able to avoid wrinkling.     

A novel efficient algorithm for mobile robot localization

Being autonomous is one of the most important goals in mobile robots. One of the fundamental works to achieve this goal is giving the ability to a robot for finding its own correct position and orientation. Different methods have been introduced to solve this problem. In this paper, a novel method based on the harmony search (HS) algorithm for robot localization through scan matching is proposed. Simulation results show that the proposed method in comparison with a genetic algorithm-based approach has better accuracy and higher performance. Furthermore a new hybrid algorithm based on harmony search and differential evolution (DE) algorithms is proposed and evaluated on different benchmark functions. Finally the hybrid algorithm has been applied for mobile robot localization and it outperformed the HS-based approach.     

Copolymer-Templated Nickel Oxide for High-Efficiency Mesoscopic Perovskite Solar Cells in Inverted Architecture

Despite the outstanding role of mesoscopic structures on the efficiency and stability of perovskite solar cells (PSCs) in the regular (n–i–p) architecture, mesoscopic PSCs in inverted (p–i–n) architecture have rarely been reported. Herein, an efficient and stable mesoscopic NiO_x (mp-NiO_x) scaffold formed via a simple and low-cost triblock copolymer template-assisted strategy is employed, and this mp-NiO_x film is utilized as a hole transport layer (HTL) in PSCs, for the first time. Promisingly, this approach allows the fabrication of homogenous, crack-free, and robust 150 nm thick mp-NiO_x HTLs through a facile chemical approach. Such a high-quality templated mp-NiO_x structure promotes the growth of the perovskite film yielding better surface coverage and enlarged grains. These desired structural and morphological features effectively translate into improved charge extraction, accelerated charge transportation, and suppressed trap-assisted recombination. Ultimately, a considerable efficiency of 20.2% is achieved with negligible hysteresis which is among the highest efficiencies for mp-NiO_x based inverted PSCs so far. Moreover, mesoscopic devices indicate higher long-term stability under ambient conditions compared to planar devices. Overall, these results may set new benchmarks in terms of performance for mesoscopic inverted PSCs employing templated mp-NiO_x films as highly efficient, stable, and easy fabricated HTLs.     

Living,Self‐Replicating Ferrofluids for Fluidic Transport

Magnetic actuation offers a means to wirelessly control flow in ferrofluids for applications including microfluidic pumping and targeted drug delivery. Despite the promise of these concepts, practical use of synthetic ferrofluids as actuators of flow frequently requires high concentrations and is hindered by low ferrohydrodynamic coupling efficiency and inhomogeneous flow fields. Inspired by the magnetic properties and hydrodynamic forms displayed by magnetotactic bacteria (MTB), this work studies the use of these microbes as a living, self‐replicating ferrofluid for improved fluidic transport via magnetically coerced rotation. Using multicore iron oxide nanoparticles as a performance benchmark, MTB under rotating magnetic fields are shown to produce more homogeneous and efficient flow. Coupling is enhanced whether the comparison is made in terms of volume of magnetic material or total volume fraction. To clarify the mechanistic role of interactions with boundaries in transport, a computational model is developed and validated experimentally. Applying this model, two distinct and feasible magnetic control strategies are predicted: a rotating gradient field that generates directional flow despite boundaries that promote flow in opposing directions and a magnetostatic gating field that enables spatially selective actuation. The advantageous properties identified for MTB open a design space for these strategies to be realized.