Tunable, reconfigurable, and programmable acoustic metasurfaces: A review

The advent of acoustic metasurfaces (AMs), which are the two-dimensional equivalents of metamaterials, has opened up new possibilities in wave manipulation using acoustically thin structures. Through the interaction between the acoustic waves and the subwavelength scattering, AMs exhibit versatile capabilities to control acoustic wave propagation such as by steering, focusing, and absorption. In recent years, this vibrant field has expanded to include tunable, reconfigurable, and programmable control to further expand the capacity of AMs. This paper reviews recent developments in AMs and summarizes the fundamental approaches for achieving tunable control, namely, by mechanical tuning, active control, and the use of field-responsive materials. An overview of basic concepts in each category is first presented, followed by a discussion of their applications and details about their performance. The review concludes with the outlook for future directions in this exciting field

A Compact Deep Architecture for Real-time Saliency Prediction

Saliency computation models aim to imitate the attention mechanism in the human visual system. The application of deep neural networks for saliency prediction has led to a drastic improvement over the last few years. However, deep models have a high number of parameters which makes them less suitable for real-time applications. Here we propose a compact yet fast model for real-time saliency prediction. Our proposed model consists of a modified U-net architecture, a novel fully connected layer, and central difference convolutional layers. The modified U-Net architecture promotes compactness and efficiency. The novel fully-connected layer facilitates the implicit capturing of the location-dependent information. Using the central difference convolutional layers at different scales enables capturing more robust and biologically motivated features. We compare our model with state of the art saliency models using traditional saliency scores as well as our newly devised scheme. Experimental results over four challenging saliency benchmark datasets demonstrate the effectiveness of our approach in striking a balance between accuracy and speed. Our model can be run in real-time which makes it appealing for edge devices and video processing

A Numerical Study of Gas and Particle Flows in the Aerosol Deposition Process

Aerosol deposition is an emerging coating process for solid state deposition of ceramic particles at room temperature. The industrial applications for aerosol deposition method are MEMS, fuel cells, optical devices and RF components. During deposition, various parameters play influential roles such as nozzle geometry, powder size and material, pressure inside the deposition chamber and carrier gas pressure. Two different drag expressions for the particle phase modeling are proposed and compared in order to capture the physics governing the fluid-particle flow in partial vacuum conditions. Then, the main focus is dedicated to the effect of three-dimensional analysis, gas flow rate and substrate location on the gas flow and particle condition upon impact on the substrate. Numerical study is performed using a two-way coupled Eulerian-Lagrangian model for a slit sonic nozzle with various gas flow rates and standoff distances. Locations of the predicted shocks for the free jet case are validated against the theoretical and experimental studies in the literature. By placing a substrate in the computational domain at various standoff distances, the characteristics of gas flow, bow shock and importantly particle trajectories and conditions upon impact have been examined rigorously. Accordingly, the optimized model to predict particles velocity are proposed and the effect of different parameters on particles velocity during the spray and upon impact are discussed

Monte Carlo investigation of prostate cancer ion therapy by using SOBP technique in the GEANT4 toolkit and MCNPX code

Regarding the useful results concerned with an external radio-therapy in treatment of tumors, we consider in this paper a standard model of the human prostate phantom based on MIRD phantom for the Monte Carlo simulation in GEANT4 toolkit and also on MCNPX code for a prostate cancer treatment. We calculate the lateral as well as the dose profiles in the tumor region for both proton and alpha beams in a similar range, and finally having implemented the SOBP technique, we compare the results of the two beams in the corresponding codes used in this analysis

Detection of atrial fibrillation in ECG hand-held devices using a random forest classifier

Atrial Fibrillation (AF) is characterized by chaotic electrical impulses in the atria, which leads to irregular heartbeats and can develop blood clots and stroke. Therefore, early detection of AF is crucial for increasing the success rate of the treatment. This study is focused on detection of AF rhythm using hand-held ECG monitoring devices, in addition to three other classes: normal or sinus rhythm, other rhythms, and too noisy to analyze. The pipeline of the proposed method consists of three major components: preprocessing and feature extraction, feature selection, and classification. In total, 491 hand-crafted features are extracted. Then, 150 features are selected in a feature ranking procedure. The selected features are from time, frequency, time-frequency domains, and phase space reconstruction of the ECG signals. In the final stage, a random forest classifier is used to classify the selected features into one of the four aforementioned ECG classes. Using the scoring mechanism provided by PhysioNet/Computing in Cardiology (CinC) Challenge 2017, the overall score (mean±std) of 81.9±2.6% is achieved over the training dataset in 10-fold cross-validation. The proposed algorithm tied for the first place in the PhysioNet/CinC Challenge 2017 with an overall score of 82.6% (rounded to 83%) on the unseen test dataset.Scopu

Simulation of the Behavior of Corrosion Damaged Reinforced Concrete Beams with/without CFRP Retrofit

Harsh environmental conditions along with aggressive chemical agents are known as one of the main reasons behind damages observed in reinforced concrete members. Corrosion of reinforcement worldwide is one of the leading causes of damages occurred in reinforced concrete over the lifespan. There are many critical energy and transportation infrastructures located on coastal regions exposed to high humidity and chloride content where they are highly prone to reinforcement corrosion. This calls for retrofit methods, which safeguard not only the strength but also the durability of corrosion deteriorated reinforced concrete structures. Carbon fiber polymers considering their mechanical and chemical properties are recognized as one of the main retrofit techniques. In this study, the influence of different levels of corrosion on the structural behavior of reinforced concrete beams is studied. ABAQUS software package is employed to simulate the nonlinear behavior of reinforced concrete beams with tensile reinforcements and stir-ups corrosion degrees of 20% and 40%. The structural behavior of original damaged specimen as well as the same specimen strengthen with carbon fiber reinforced polymer (CFRP) is studied. The purpose of the retrofit is compensate for the loss of shear and flexural capacity of the member due to corrosion. Different variants for the arrangement of CFRP strips are studied and compared. The result of the current research further uncaps the efficiency of fiber polymers to secure strength and durability of corrosion damaged reinforced concrete members

Evaluation of Challenging Areas of Accrual Accounting Implementation in the Public Sector

The purpose of this research is evaluation of the challenging areas of implementation of accrual accounting in the General Department of the Ministry of Economy and Finance of Mazandaran Province. The methodology of this study is mixed, so that in the qualitative part, through systematic screening, the challenging areas of accrual accounting implementation in the public sector are identified. Then, during two stages of Delphi analysis, an attempt is made to check the reliability of the identified dimensions. Finally, in the quantitative part, through interpretive ranking analysis, it seeks to evaluate the areas identified in the context of the General Department of the Ministry of Economy and Finance of Mazandaran province. The results of the study in the qualitative part indicated the existence of 9 challenging areas for the implementation of accrual accounting in the public sector, and during the process of fuzzy Delphi analysis, 8 criteria were confirmed as the reasons for the gap in the implementation of accrual accounting. Then, in the quantitative part, it was determined that the challenge of applying accounting standards of the public sector is an effective factor in creating a gap in the implementation of accrual accounting in the General Department of the Ministry of Economy and Finance of Mazandaran province