A circularly polarized printed elliptical wide-slot antenna with high bandwidth-dimension-ratio for wireless applications

Wireless Networks - This paper outlines a simple design of a compact wideband microstrip-line fed antenna having two rotated elliptical wide-slots (EWSs). Here, both the elliptical wide-slots are...     

Efficient data management and control over WSNs using SDN‐enabled aerial networks

The recent developments in collaborative search, acquisition, and tracking have hoisted the geographical barrier. The network between unmanned aerial vehicles (UAVs) and wireless sensor networks (WSNs) is one such collaboration, which comprises battery‐powered static sensor nodes that act as sources and sinks and UAVs that act as relays. This collaborative network presents with opportunities and advantages, but at the same time, configuration of such networks is an arduous task. The WSN nodes are characterized by constant depleting power. Their network itself requires constant management and reconfiguration. These requisites can be slaked through the formation of an efficient data dissemination algorithm, which acclimates according to the network state. Considering this, a data dissemination approach is presented in this paper, which constructs a virtual topology predicated on the charge of WSN nodes utilizing software‐defined networks (SDNs) through UAVs. The topology is constantly monitored and reconfigured when required. The aerial nodes are equipped with multiple‐input multiple‐output (MIMO) antennas in order to facilitate simultaneous communication with the ground nodes, the base station, and the SDN controller. An efficient sleep timer and backoff counter strategies are also utilized by the proposed approach. The SDN controller facilitates the topology formation and maintenance of a sleep timer and a backoff counter. The proposed model is compared with clustered hierarchical layouts and hexagonal cell layouts through the network simulations. The results suggest significant improvements in the proposed model for various metrics, such as lifetime, delay, latency, delivery ratio, and throughput in comparison with the existing solutions.     

Design and investigations on a compact,UWB, monopole antenna with reconfigurable band notches for 5.2/5.8 GHz WLAN and 5.5 GHz Wi‐MAX bands

This article represents a microstrip line–fed novel circular monopole antenna with ultra‐wideband (UWB) characteristics. The compact antenna provides reconfigurable notches at WLAN (5.2/5.8 GHz) and Wi‐MAX (5.5 GHz) frequency bands. The band rejection is achieved by etching an open‐ended L‐shaped slot in the ground plane, which effectively mitigates the interference between WLAN, Wi‐MAX, and UWB systems with an effective patch area of 36.26%. The proposed antenna operates from 3.05 to 12.11 GHz with VSWR 2 except at stopband (3.89‐5.93 GHz) to filter the WLAN and Wi‐MAX signals. The simulated return loss, gain, and radiation pattern of the proposed antenna has been experimentally verified with the fabricated one which holds a good agreement.     

A Skin‐Inspired Substrate with Spaghetti‐Like Multi‐Nanofiber Network of Stiff and Elastic Components for Stretchable Electronics

Mimicking the skin's non‐linear self‐limiting mechanical characteristics is of great interest. Skin is soft at low strain but becomes stiff at high strain and thereby can protect human tissues and organs from high mechanical loads. Herein, the design of a skin‐inspired substrate is reported based on a spaghetti‐like multi‐nanofiber network (SMNN) of elastic polyurethane (PU) nanofibers (NFs) sandwiched between stiff poly(vinyldenefluoride‐co‐trifluoroethylene) (P(VDF‐TrFE)) NFs layers embedded in polydimethylsiloxane elastomer. The elastic moduli of the stretchable skin‐inspired substrate can be tuned in a range that matches well with the mechanical properties of skins by adjusting the loading ratios of the two NFs. Confocal imaging under stretching indicates that PU NFs help maintain the stretchability while adding stiff P(VDF‐TrFE) NFs to control the self‐limiting characteristics. Interestingly, the Au layer on the substrate indicates a negligible change in the resistance under cyclic (up to 7000 cycles at 35% strain) and dynamic stretching (up to 35% strain), which indicates the effective absorption of stress by the SMNN. A stretchable chemoresistive gas sensor on the skin‐inspired substrate also demonstrates a reasonable stability in NO₂ sensing response under strain up to 30%. The skin‐inspired substrate with SMNN provides a step toward ultrathin stretchable electronics.     

Shape optimization of a corner-recessed square tall building to reduce mean wind pressure using a multi-objective genetic algorithm

The current study aims to determine how the corner recession affects tall buildings with square plans. A series of numerical simulations have been conducted to find the parametric models' wind pressure. Visualization tools, such as contour plots and streamlines, present the wind flow near the buildings. Numerical simulations are conducted using RANS k-ℇ turbulence models considering a length scale of 1:300. Subsequently, a shape optimization study has been carried out to propose a suitable percentage of corner recession, which should minimize the wind pressure on different faces of the building. As design factors, the amount of corner recession (S) and the wind incidence angle (Ø) are taken, along with the mean pressure coefficients (C_p) on the various building faces. Due to the eight axes symmetry of the building configuration, the random sampling technique is used for the Design of Experiment while accounting for the 0°–45° wind angle of attack. The Response Surface Approximation (RSA) is used to construct surrogate models of the objective functions. The RSA models are validated with wind tunnel test results presented in previously published articles. The optimization study is carried out using the multi-objective genetic algorithm technique.     

Seismic response of precast reinforced concrete wall subjected to cyclic in-plane and constant out-of-plane loading

This paper provides insight into the seismic behavior of a full-scale precast reinforced concrete wall under in-plane cyclic loading combined with out-of-plane loading replicated by sand backfill to simulate the actual condition of basement walls. The tested wall exhibited flexural cracks, owing to the high aspect ratio and considerable out-of-plane movement due to lateral pressure from the backfill. The wall performed satisfactorily by exhibiting competent seismic parameters and deformation characteristics governed by its ductile response in the nonlinear phase during the test with smaller residual drift. Numerical analysis was conducted to validate experimental findings, which complied with each other. The numerical model was used to conduct parametric studies to study the effect of backfill density and aspect ratio on seismic response of the proposed precast wall system. The in-plane capacity of walls reduced, while deformation characteristics were unaffected by the increase in backfill density. An increase in aspect ratio leads to a reduction in in-plane capacity and an increase in drift. Curves between the ratio of in-plane yield capacity and design shear load of walls are proposed for the backfill density, which may be adopted to determine the in-plane yield capacity of the basement walls based on their design shear.     

Occurrence and removal of antibiotics, hormones and several other pharmaceuticals in wastewater treatment plants of the largest industrial city of Korea

Occurrence and removal efficiencies of 20 pharmaceuticals and personal care products (PPCPs) including antibiotics, hormones, and several other miscellaneous pharmaceuticals (analgesics, antiepileptics, antilipidemics, antihypertensives, antiseptics, and stimulants) were investigated in five wastewater treatment plants (WWTPs) of Ulsan, the largest industrial city of Korea. The compounds were extracted from wastewater samples by solid-phase extraction (SPE) and analyzed by High-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS). The results showed that acetaminophen, atenolol and lincomycin were the main individual pollutants usually found in concentrations over 10 μg/L in the sewage influent. In the WWTPs, the concentrations of analgesic acetaminophen, stimulant caffeine, hormones estriol and estradiol decreased by over 99%. On the contrary, the antibiotic sulfamethazine, the antihypertensive metoprolol, and the antiepileptic carbamazepine exhibited removal efficiencies below 30%. Particularly, removal of antibiotics was observed to vary between − 11.2 and 69%. In the primary treatment (physico-chemical processes), the removal of pharmaceuticals was insignificant (up to 28%) and removal of majority of the pharmaceuticals occurred during the secondary treatment (biological processes). The compounds lincomycin, carbamazepine, atenolol, metoprolol, and triclosan showed better removal in WWTPs employing modified activated sludge process with co-existence of anoxic-oxic condition. Further investigation into the design and operational aspects of the biological processes is warranted for the efficient removal of PPCPs, particularly antibiotics, to secure healthy water resource in the receiving downstream, thereby ensuring a sustainable water cycle management.     

Numerical studies on evaluation of smoke control system of underground metro rail transport system in India having jet injection system: A case study

The rail based urban transport system is being developed for national capital of India, New Delhi. The smoke control using ventilation in case of fire inside the tunnel, similar to Delhi Metro corridor has been investigated using computational fluid dynamics technique. A section of tunnel having dimensions 400 m long, 5.5 m wide and 6 m high is considered for simulation. The analysis has been carried out by assuming a variable fire source with a peak heat release rate (HRR) of 16 MW, located at the center of the tunnel. Ventilation ducts are located in the ceiling near the tunnel portals and are inclined at 10 degrees to the plane of the ceiling through which fans discharge air. The influence of the fire HRR curve slope on the smoke flow dynamics in a realistic tunnel model fitted with jet injection type longitudinal ventilation system has been investigated. In case of fire two cases are studied: (1) fans activated immediately after detection, (2) fans activated at delayed times to take into account the response time for the fans to achieve its maximum speed. The velocity of supply and exhaust fans necessary to remove smoke in 30 s from the upstream direction is determined. The velocities of fan required to produce desired critical velocity in the longitudinal direction for different HRR of fire is predicted.     

Attenuation of methylene blue dye during riverbank filtration through sandy aquifers

Although several studies have focused on the removal of organics and pathogens during riverbank filtration (RBF), no study has been carried out on the attenuation of dyes during RBF. In the present work, removal of methylene blue (MB) through aquifer materials collected from five RBF sites in India has been investigated. Brunauer Emmet Teller (BET) surface areas of the aquifer materials were 1.2–6.5 m²/g. Adsorption followed the pseudo‐second‐order kinetics and Langmuir isotherm, suggesting monolayer adsorption. Column results showed saturation capacity of 0.467–1.234 mg MB/g for different aquifer materials. Retardation factors for MB were found to be very high ranging from 430 to 987, due to its high hydrophobicity (octanol/water partition coefficient = 5.85). Results showed that BET surface area or the roughness played a very important role in the retardation of MB. Results suggest that the breakthrough of MB in a RBF well in sandy aquifers will take several years.     

Effect of methanol gasoline blended fuels on the performance and emissions of SI engine

This article presents experimental results of the effect of methanol gasoline blends as alternate fuels for the spark ignition (SI) engine. As the cost of the gasoline is periodically increasing the quest for the alternative fuels are evolved with which the emissions are reduced along with improved engine performance. A set of experiments have been conducted to investigate the effect of gasoline methanol blends in methanol percentages of M5, M10 and M15 on the engine performance and emissions. A significant reduction in emissions is observed with methanol blends compared to the standard gasoline with improved engine performance and emission characteristics. The fuels blends ranging from M10 to M15 have been found suitable for reduced emissions and improved engine performance.