Search results for: rectangular microstrip patch antenna (RMPA)

Authors: M. V. Belubekyan, S. R. Martirosyan

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On the example of an elastic rectangular plate streamlined by a supersonic gas flow, we have investigated the phenomenon of divergence and of panel flatter of the overrunning of the gas flow at a free edge under assumption of the presence of concentrated inertial masses and moments at the free edge. We applied a new approach of finding of solution of these problems, which was developed based on the algorithm for an analytical solution finding. This algorithm is easy to use for theoretical studies for the wides circle of nonconservative problems of linear elastic stability. We have established the relation between the characteristics of natural vibrations of the plate and velocity of the streamlining gas flow, which enables one to draw some conclusions on the stability of disturbed motion of the plate depending on the parameters of the system plate-flow. Its solution shows that either the divergence or the localized divergence and the flutter instability are possible. The regions of the stability and instability in space of parameters of the problem are identified. We have investigated the dynamic behavior of the disturbed motion of the panel near the boundaries of region of the stability. The safe and dangerous boundaries of region of the stability are found. The transition through safe boundary of the region of the stability leads to the divergence or localized divergence arising in the vicinity of free edge of the rectangular plate. The transition through dangerous boundary of the region of the stability leads to the panel flutter. The deformations arising at the flutter are more dangerous to the skin of the modern aircrafts and rockets resulting to the loss of the strength and appearance of the fatigue cracks.

Keywords: stability, elastic plate, divergence, localized divergence, supersonic panels flutter

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Authors: Carolina Morales, Ricardo Castro-Huerta, Enrique A. Mundaca

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The edaphic fauna is the main factor involved in the transformation of nutrients and soil decomposition processes. Edaphic organisms are highly sensitive to soil disturbances, which normally causes changes in the composition and abundance of such organisms. Fire is known to be a disturbing factor since it affects the physical, chemical and biological properties of the soil and the whole ecosystem. During the summer (December-March) of 2017, Chile suffered the major fire events recorded in its modern history, which affected a vast area and a number of ecosystem types. The objective of this study was first to use remote sensing satellite images and GIS (Geographic Information Systems) to assess and identify levels of fire severity in disturbed areas and to compare the responses of the soil mesofauna diversity among such areas. We identified four areas (treatments) with an ascending level of severity, namely: mild, medium, high severity, and free of fire. A non-affected patch of forest was established as a control. Three samples from each treatment were collected in the form of a soil cube (10x10x10 cm). Edaphic mesofauna was obtained from each sample through the Berlese-Tullgren funnel method. Collected specimens were quantified and identified, using the RTU (Recognisable Taxonomic Unit) criterion. Diversity was analysed using inferential statistics to compare Simpson and Shannon-Wiener indexes across treatments. As predicted, the unburned forest patch (control) exhibited higher diversity values than the treatments. Significantly higher diversity values were recorded in those treatments subjected to lower fire severity. We conclude that remote sensing zoning is an adequate tool to identify different levels of fire severity and that an edaphic mesofauna is a group of organisms that qualify as good bioindicators for monitoring soil recovery after fire events.

Keywords: bioindicator, Chile, fire severity level, soil

Procedia PDF Downloads 149

Authors: Ashneel Ajay Singh, Anish Maharaj, Havish Naidu, Michelle Kumar

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Mangrove patches are the foundation species located in the estuarine land areas. These patches provide a nursery, food source and protection for numerous aquatic, intertidal and well as land-based organisms. Mangroves also help in coastal protection, maintain water clarity and are one of the biggest sinks for blue carbon sequestration. In the Pacific Island countries, numerous coastal communities have a heavy socioeconomic dependence on coastal resources and mangroves play a key ecological and economical role in structuring the availability of these resources. Fiji has a large mangrove patch located in the Votua area of the Ba province. Globally, mangrove population continues to decline with the changes in climatic conditions and anthropogenic activities. Baseline information through wetland maps and time series change are essential references for development of effective mangrove management plans. These maps reveal the status of the resource and the effects arising from anthropogenic activities and climate change. In this study, we used remote sensing and GIS tools for mapping and temporal change detection over a period of >20 years in Votua, Fiji using Landsat imagery. Landsat program started in 1972 initially as Earth Resources Technology Satellite. Since then it has acquired millions of images of Earth. This archive allows mapping of temporal changes in mangrove forests. Mangrove plants consisted of the species Rhizophora stylosa, Rhizophora samoensis, Bruguiera gymnorrhiza, Lumnitzera littorea, Heritiera littoralis, Excoecaria agallocha and Xylocarpus granatum. Change detection analysis revealed significant reduction in the mangrove patch over the years. This information serves as a baseline for the development and implementation of effective management plans for one of Fiji’s biggest mangrove patches.

Keywords: climate change, GIS, Landsat, mangrove, temporal change

Procedia PDF Downloads 169

Authors: Iman A. Saad, Loay E. George

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Iris pattern is an important biological feature of human body; it becomes very hot topic in both research and practical applications. In this paper, an algorithm is proposed for iris recognition and a simple, efficient and fast method is introduced to extract a set of discriminatory features using first order gradient operator applied on grayscale images. The gradient based features are robust, up to certain extents, against the variations may occur in contrast or brightness of iris image samples; the variations are mostly occur due lightening differences and camera changes. At first, the iris region is located, after that it is remapped to a rectangular area of size 360x60 pixels. Also, a new method is proposed for detecting eyelash and eyelid points; it depends on making image statistical analysis, to mark the eyelash and eyelid as a noise points. In order to cover the features localization (variation), the rectangular iris image is partitioned into N overlapped sub-images (blocks); then from each block a set of different average directional gradient densities values is calculated to be used as texture features vector. The applied gradient operators are taken along the horizontal, vertical and diagonal directions. The low order norms of gradient components were used to establish the feature vector. Euclidean distance based classifier was used as a matching metric for determining the degree of similarity between the features vector extracted from the tested iris image and template features vectors stored in the database. Experimental tests were performed using 2639 iris images from CASIA V4-Interival database, the attained recognition accuracy has reached up to 99.92%.

Keywords: iris recognition, contrast stretching, gradient features, texture features, Euclidean metric

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Authors: Yahya Asanoglu, Celaletdin Ergun

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Ceramic-matrix composites (CMC) have significant prominence in various engineering applications because of their heat resistance associated with an ability to withstand the brittle type of catastrophic failure. In this study, specific raw materials have been chosen for the purpose of having suitable CMC material for high-temperature dielectric applications. CMC material will be manufactured through the polymer infiltration and pyrolysis (PIP) method. During the manufacturing process, vacuum infiltration and autoclave will be applied so as to decrease porosity and obtain higher mechanical properties, although this advantage leads to a decrease in the electrical performance of the material. Time and temperature adjustment in pyrolysis parameters provide a significant difference in the properties of the resulting material. The mechanical and thermal properties will be investigated in addition to the measurement of dielectric constant and tangent loss values within the spectrum of Ku-band (12 to 18 GHz). Also, XRD, TGA/PTA analyses will be employed to prove the transition of precursor to ceramic phases and to detect critical transition temperatures. Additionally, SEM analysis on the fracture surfaces will be performed to see failure mechanism whether there is fiber pull-out, crack deflection and others which lead to ductility and toughness in the material. In this research, the cost-effectiveness and applicability of the PIP method will be proven in the manufacture of CMC materials while optimization of pyrolysis time, temperature and cycle for specific materials is detected by experiment. Also, several resins will be shown to be a potential raw material for CMC radome and antenna applications. This research will be distinguished from previous related papers due to the fact that in this research, the combination of different precursors and fabrics will be experimented with to specify the unique cons and pros of each combination. In this way, this is an experimental sum of previous works with unique PIP parameters and a guide to the manufacture of CMC radome and antenna.

Keywords: CMC, PIP, precursor, quartz

Procedia PDF Downloads 151

Authors: Muhammad Safi, Abdul Manan

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In recent years, research in aircraft avionics systems (i.e., radars and antennas) has grown revolutionary. Aircraft technology is experiencing an increasing inclination from all mechanical to all electrical aircraft, with the introduction of inhabitant air vehicles and drone taxis over the last few years. This develops an overriding need to summarize the history, latest trends, and future development in aircraft avionics research for a better understanding and development of new technologies in the domain of avionics systems. This paper focuses on the future trends in antennas and phased arrays for avionics systems. Along with the general overview of the future avionics trend, this work describes the review of around 50 high-quality research papers on aircraft communication systems. Electric-powered aircraft have been a hot topic in the modern aircraft world. Electric aircraft have supremacy over their conventional counterparts. Due to increased drone taxi and urban air mobility, fast and reliable communication is very important, so concepts of Broadband Integrated Digital Avionics Information Exchange Networks (B-IDAIENs) and Modular Avionics are being researched for better communication of future aircraft. A Ku-band phased array antenna based on a modular design can be used in a modular avionics system. Furthermore, integrated avionics is also emerging research in future avionics. The main focus of work in future avionics will be using integrated modular avionics and infra-red phased array antennas, which are discussed in detail in this paper. Other work such as reconfigurable antennas and optical communication, are also discussed in this paper. The future of modern aircraft avionics would be based on integrated modulated avionics and small artificial intelligence-based antennas. Optical and infrared communication will also replace microwave frequencies.

Keywords: AI, avionics systems, communication, electric aircrafts, infra-red, integrated avionics, modular avionics, phased array, reconfigurable antenna, UAVs

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Authors: N. Ourabia, M. Boubaker Ourabia

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An approach for modeling and numerical simulation of passive planar structures using the edge line concept is developed. With this method, we develop an efficient modeling technique for microstrip discontinuities. The technique obtains closed form expressions for the equivalent circuits which are used to model these discontinuities. Then, it would be easy to handle and to characterize complicated structures like T and Y junctions, truncated junctions, arbitrarily shaped junctions, cascading junctions and more generally planar multiport junctions. Another advantage of this method is that the edge line concept for arbitrary shape junctions operates with real parameters circuits. The validity of the method was further confirmed by comparing our results for various discontinuities (bend, filters) with those from HFSS as well as from other published sources.

Keywords: optimization, CAD analysis, microwave circuits, S-parameters

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Authors: Fu Jia

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The effects of soil-structure interaction (SSI) are often studied using axial-symmetric three-dimensional (3D) models to avoid the high computational cost of the more realistic, fully 3D models, which require 2-3 orders of magnitude more computer time and storage. This paper analyzes the error and presents correction factors for system frequency, system damping, and peak amplitude of structural response computed by axisymmetric models, embedded in uniform or layered half-space. The results are compared with those for fully 3D rectangular foundations of different aspect ratios. Correction factors are presented for a range of the model parameters, such as fixed-base frequency, structure mass, height and length-to-width ratio, foundation embedment, soil-layer stiffness and thickness. It is shown that the errors are larger for stiffer, taller and heavier structures, deeper foundations and deeper soil layer. For example, for a stiff structure like Millikan Library (NS response; length-to-width ratio 1), the error is 6.5% in system frequency, 49% in system damping and 180% in peak amplitude. Analysis of a case study shows that the NEHRP-2015 provisions for reduction of base shear force due to SSI effects may be unsafe for some structures and need revision. The presented correction factor diagrams can be used in practical design and other applications.

Keywords: 3D soil-structure interaction, correction factors for axisymmetric models, length-to-width ratio, NEHRP-2015 provisions for reduction of base shear force, rectangular embedded foundations, SSI system frequency, SSI system damping

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Authors: Pakawhat Khumkhreung, Yottana Khunatorn

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The flow pattern inside rectangular intake air duct of 300 MW lignite coal-fired power plant is investigated in order to analyze and reduce overall inlet system pressure drop. The system consists of the 45-degree inlet elbow, the flow instrument, the 90-degree mitered elbow and fans, respectively. The energy loss in each section can be determined by Bernoulli’s equation and ASHRAE standard table. Hence, computational fluid dynamics (CFD) is used in this study based on Navier-Stroke equation and the standard k-epsilon turbulence modeling. Input boundary condition is 175 kg/s mass flow rate inside the 11-m² cross sectional duct. According to the inlet air flow rate, the Reynolds number of airstream is 2.7x10⁶ (based on the hydraulic duct diameter), thus the flow behavior is turbulence. The numerical results are validated with the real operation data. It is found that the numerical result agrees well with the operating data, and dominant loss occurs at the flow rate measurement device. Normally, the air flow rate is measured by the airfoil and it gets high pressure drop inside the duct. To overcome this problem, the airfoil is planned to be replaced with the other type measuring instrument, such as the average pitot tube which generates low pressure drop of airstream. The numerical result in case of average pitot tube shows that the pressure drop inside the inlet airstream duct is decreased significantly. It should be noted that the energy consumption of inlet air system is reduced too.

Keywords: airfoil, average pitot tube, combustion air, CFD, pressure drop, rectangular duct

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Authors: Mireille Vonlanthen, Pasquale Porcu, Ernesto Rivera

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Dendritic macromolecules are presenting unique physical and chemical properties. One of them is the faculty of transferring energy from a donor moiety introduced at the periphery to an acceptor moiety at the core, mimicking the antenna effect of the process of photosynthesis. The mechanism of energy transfer is based on the Förster resonance energy exchange and requires some overlap between the emission spectrum of the donor and the absorption spectrum of the acceptor. Since it requires a coupling of transition dipole but no overlap of the physical wavefunctions, the energy transfer by Förster mechanism can occur over quite long distances from 1 to a maximum of 10 nm. However, the efficiency of the transfer depends strongly on distance. The Förster radius is the distance at which 50% of the donor’s emission is deactivated by FRET. In this work, we synthesized and characterized a novel series of dendrimers bearing pyrene moieties at the periphery and a Ru (II) complex at the core. The optical and photophysical properties of these compounds were studied by absorption and fluorescence spectroscopy. Pyrene is a well-studied chromophore that has the particularity to present monomer as well as excimer fluorescence emission. The coordination compounds of Ru (II) are red emitters with low quantum yield and long excited lifetime. We observed an efficient singulet to singulet energy transfer in such constructs. Moreover, it is known that the energy of the MLCT emitting state of Ru (II) can be tuned to become almost isoenegetic with respect to the triplet state of pyrene, leading to an extended phosphorescence lifetime. Using dendrimers bearing pyrene moieties as ligands for Ru (II), we could combine the antenna effect of dendrimers as well as its protection effect to the quenching by dioxygen with lifetime increase due to triplet-triplet equilibrium.

Keywords: dendritic molecules, energy transfer, pyrene, ru-trisbipyridine complex

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Authors: Hansraj Bookun, Angela Tan, Rachel Xuan, Linheng Zhao, Kejia Wang, Animesh Singla, David Kim, Christopher Loupos

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Introduction: Incisional wound complications in vascular surgery patients represent a significant clinical and econometric burden of morbidity and mortality. The objective of this study was to trial the feasibility of applying the Prevena negative pressure incision management system as a routine dressing in patients who had undergone arterial surgery. Conventionally, Prevena has been applied to groin incisions, but this study features applications on multiple wound sites such as the thigh or major amputation stumps. Method: This was a cross-sectional observational, single-centre case series of 12 patients who had undergone major vascular surgery. Their wounds were managed with the Prevena system being applied either intra-operatively or on the first post-operative day. Demographic and operative details were collated as well as the length of stay and complication rates. Results: There were 9 males (75%) with mean age of 66 years and the comorbid burden was as follows: ischaemic heart disease (92%), diabetes (42%), hypertension (100%), stage 4 or greater kidney impairment (17%) and current or ex-smoking (83%). The main indications were acute ischaemia (33%), claudication (25%), and gangrene (17%). There were single instances of an occluded popliteal artery aneurysm, diabetic foot infection, and rest pain. The majority of patients (50%) had hybrid operations with iliofemoral endarterectomies, patch arterioplasties, and further peripheral endovascular treatment. There were 4 complex arterial bypass operations and 2 major amputations. The mean length of stay was 17 ± 10 days, with a range of 4 to 35 days. A single complication, in the form of a lymphocoele, was encountered in the context of an iliofemoral endarterectomy and patch arterioplasty. This was managed conservatively. There were no deaths. Discussion: The Prevena wound management system shows that in conjunction with safe vascular surgery, absolute wound complication rates remain low and that it remains a valuable adjunct in the treatment of vasculopaths.

Keywords: wound care, negative pressure, vascular surgery, closed incision

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Authors: Yung-Gi Chen, Pei-Leun Kang, Yu-Hsin Lin, Shwu-Jen Chang

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Myocardial tissue has limited self-repair ability due to its loss of differentiation characteristic for most mature cardiomyocytes. Therefore, the effective use of stem cell technology in regenerative medicine is an important development to alleviate the current difficulties in cardiac disease treatment. The main purpose of this project was to develop a 3-D hydrogel electrical stimulating system for promoting the differentiation of stem cells into myocardial cells, and the patch will be used to repair damaged myocardial tissue. This project was focused on the preparation of the electrical stimulation system with carbon/CaCl₂ electrodes covered with carbon nanotube-hydrogel. In this study, we utilized screen imprinting techniques and used Poly(lactic-co-glycolic acid)(PLGA) membranes as printing substrates to fabricate a carbon/CaCl₂ interdigitated electrode that covered with alginate/carbon nanotube hydrogels. The single-walled carbon nanotube was added in the hydrogel to enhance the mechanical strength and conductivity of hydrogel. In this study, we used PLGA (85:15) as electrode preparing substrate. The CaCl₂/ EtOH solution (80% w/v) was mixed into carbon paste to prepare various concentration calcium-containing carbon paste (2.5%, 5%, 7.5%, 10% v/v). Different concentrations of alginate (1%, 1.5%, 2% v/v) and SWCNT(Diameter < 2nm, length between 5-15μm) (1, 1.5, 3 mg/ml) are gently immobilized on the electrode by cross-linking with calcium chloride. The three-dimensional hydrogel electrode was tested for its redox efficiency by cyclic voltammetry to determine the optimal parameters for the hydrogel electrode preparation. From the result of the final electrodes, it indicated that the electrode was not easy to maintain the pattern of the interdigitated electrode when the concentration of calcium of chloride was more than 10%. According to the gel rate test and cyclic voltammetry experiment results showed the SWCNT could increase the electron conduction of hydrogel electrodes significantly. So far the 3D electrode system has been completed, 2% alginate mixed with 3mg SWCNT is the optimal condition to construct the most complete structure for the hydrogel preparation.

Keywords: myocardial tissue engineering, screen printing technology, poly (lactic-co-glycolic acid), alginate, single walled carbon nanotube

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Authors: Amir Sattari, Mac Panah, Naeim Rashidfarokhi

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To enhance the mixing of fluid in a rectangular enclosure with a circular inlet and outlet, an energy-efficient approach is further investigated through computational fluid dynamics (CFD). Particle image velocimetry (PIV) measurements help confirm that the pulsation of the inflow velocity improves the mixing performance inside the enclosure considerably without increasing energy consumption. In this study, multiple CFD simulations with different turbulent models were performed. The results obtained were compared with experimental PIV results. This study investigates small-scale representations of flow patterns in a ventilated rectangular room. The objective is to validate the concept of an energy-efficient ventilation strategy with improved thermal comfort and reduction of stagnant air inside the room. Experimental and simulated results confirm that through pulsation of the inflow velocity, strong secondary vortices are generated downstream of the entrance wall-jet. The pulsatile inflow profile promotes a periodic generation of vortices with stronger eddies despite a relatively low inlet velocity, which leads to a larger boundary layer with increased kinetic energy in the occupied zone. A real-scale study was not conducted; however, it can be concluded that a constant velocity inflow profile can be replaced with a lower pulsated flow rate profile while preserving the mixing efficiency. Among the turbulent CFD models demonstrated in this study, SST-kω is most advantageous, exhibiting a similar global airflow pattern as in the experiments. The detailed near-wall velocity profile is utilized to identify the wall-jet instabilities that consist of mixing and boundary layers. The SAS method was later applied to predict the turbulent parameters in the center of the domain. In both cases, the predictions are in good agreement with the measured results.

Keywords: CFD, PIV, pulsatile inflow, ventilation, wall-jet

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Authors: Sonia Besbes, Mahmoud El Hajem, Habib Ben Aissia, Jean Yves Champagne, Jacques Jay

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In this work, we present a computational study for the characterization of the flow in a rectangular bubble column. To simulate the dynamic characteristics of the flow, a three-dimensional transient numerical simulations based on a coupled discrete phase model (DPM) and Volume of Fluid (VOF) model are performed. Modeling of bubble column reactor is often carried out under the assumption of a flat liquid surface with a degassing boundary condition. However, the dynamic behavior of the top surface surmounting the liquid phase will to some extent influence the meandering oscillations of the bubble plume. Therefore it is important to capture the surface behavior, and the assumption of a flat surface may not be applicable. So, the modeling approach needs to account for a dynamic liquid surface induced by the rising bubble plume. The volume of fluid (VOF) model was applied for the liquid and top gas which both interacts with bubbles implemented with a discrete phase model. This model treats the bubbles as Lagrangian particles and the liquid and the top gas as Eulerian phases with a sharp interface. Two-way coupling between Eulerian phases and Lagrangian bubbles are accounted for in a single set continuous phase momentum equation for the mixture of the two Eulerian phases. The effect of gas flow rate on the dynamic and time-averaged flow properties was studied. The time averaged liquid velocity field predicted from simulations and from our previous PIV measurements shows that the liquid is entrained up flow in the wake of the bubbles and down flow near the walls. The simulated and measured vertical velocity profiles exhibit a reasonable agreement looking at the minimum velocity values near the walls and the maximum values at the column center.

Keywords: bubble column, computational fluid dynamics (CFD), coupled DPM and VOF model, hydrodynamics

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Authors: Keunhong Chae, Seokho Yoon

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Recently, the global navigation satellite system (GNSS) such as Galileo and GPS is employing more satellites to provide a higher degree of accuracy for the location service, thus calling for a more efficient signaling scheme among the satellites used in the overall GNSS network. In that the network throughput is improved, the spatial diversity can be one of the efficient signaling schemes; however, it requires multiple antenna that could cause a significant increase in the complexity of the GNSS. Thus, a diversity scheme called the cooperative signaling was proposed, where the virtual multiple-input multiple-output (MIMO) signaling is realized with using only a single antenna in the transmit satellite of interest and with modeling the neighboring satellites as relay nodes. The main drawback of the cooperative signaling is that the relay nodes receive the transmitted signal at different time instants, i.e., they operate in an asynchronous way, and thus, the overall performance of the GNSS network could degrade severely. To tackle the problem, several modified cooperative signaling schemes were proposed; however, all of them are difficult to implement due to a signal decoding at the relay nodes. Although the implementation at the relay nodes could be simpler to some degree by employing the time-reversal and conjugation operations instead of the signal decoding, it would be more efficient if we could implement the operations of the relay nodes at the source node having more resources than the relay nodes. So, in this paper, we propose a novel cooperative signaling scheme, where the data signals are combined in a unique way at the source node, thus obviating the need of the complex operations such as signal decoding, time-reversal and conjugation at the relay nodes. The numerical results confirm that the proposed scheme provides the same performance in the cooperative diversity and the bit error rate (BER) as the conventional scheme, while reducing the complexity at the relay nodes significantly. Acknowledgment: This work was supported by the National GNSS Research Center program of Defense Acquisition Program Administration and Agency for Defense Development.

Keywords: global navigation satellite network, cooperative signaling, data combining, nodes

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Authors: Arpit Rai

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In this work, we propose PatchMix, a semi-supervised method for pre-training visual representations. PatchMix mixes patches of two images and then solves an auxiliary task of predicting the label of each patch in the mixed image. Our experiments on the CIFAR-10, 100 and the SVHN dataset show that the representations learned by this method encodes useful information for transfer to new tasks and outperform the baseline Residual Network encoders by on CIFAR 10 by 12% on ResNet 101 and 2% on ResNet-56, by 4% on CIFAR-100 on ResNet101 and by 6% on SVHN dataset on the ResNet-101 baseline model.

Keywords: self-supervised learning, representation learning, computer vision, generalization

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Authors: Rahim Jafari, Tuba Okutucu-Özyurt

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The hydrodynamics and heat transfer characteristics of a vaporized elongated bubble in a rectangular microchannel have been simulated based on Cahn-Hilliard phase-field method. In the simulations, the initially nucleated bubble starts growing as it comes in contact with superheated water. The growing shape of the bubble compared with the available experimental data in the literature.

Keywords: microchannel, boiling, Cahn-Hilliard method, simulation

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Authors: Ahmed A. Al-Mudhafar, Ali A. Abduljabar, Hayder Jawad Albattat

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This work suggests a new microwave resonator sensor (MRS) device for measuring the oil’s breakdown voltage of high voltage transformers. A precise high-sensitivity sensor is designed and manufactured based on a microstrip split ring resonator (SRR). To improve the sensor sensitivity, a RF amplifier of 30 dB gain is linked through a transmission line of 50Ω.The sensor operates at a microwave band (L) with a quality factor of 1.35x105 when it is loaded with an empty tube. In this work, the sensor has been tested with three samples of high voltage transformer oil of different ages (new, middle, and damaged) where the quality factor differs with each sample. A mathematical model was built to calculate the breakdown voltage of the transformer oils and the accuracy of the results was higher than 90%.

Keywords: active resonator sensor, oil breakdown voltage, transformers oils, quality factor

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Authors: Jaya Bishnu Pradhan

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Weaving mat is one of the common activities performed in different community generally in the rural part of Nepal. Mat weavers’ practice mathematical ideas and concepts implicitly in order to perform their job. This study is intended to uncover the mathematical ideas embedded in mat weaving that can help teachers and students for the teaching and learning of school geometry. The ethnographic methodology was used to uncover and describe the beliefs, values, understanding, perceptions, and attitudes of the mat weavers towards mathematical ideas and concepts in the process of mat weaving. A total of 4 mat weavers, two mathematics teachers and 12 students from grade level 6-8, who are used to participate in weaving, were selected for the study. The whole process of the mat weaving was observed in a natural setting. The classroom observation and in-depth interview were taken with the participants with the help of interview guidelines and observation checklist. The data obtained from the field were categorized according to the themes regarding mathematical ideas embedded in the weaving activities, and its possibilities in teaching learning of school geometry. In this study, the mathematical activities in different sectors of their lives, their ways of understanding the natural phenomena, and their ethnomathematical knowledge were analyzed with the notions of pluralism. From the field data, it was found that the mat weaver exhibited sophisticated geometrical ideas in the process of construction of frame of mat. They used x-test method for confirming if the mat is rectangular. Mat also provides a good opportunity to understand the space geometry. A rectangular form of mat may be rolled up when it is not in use and can be converted to a cylindrical form, which usually can be used as larder so as to reserve food grains. From the observation of the situations, this cultural experience enables students to calculate volume, curved surface area and total surface area of the cylinder. The possibilities of incorporation of these cultural activities and its pedagogical use were observed in mathematics classroom. It is argued that it is possible to use mat weaving activities in the teaching and learning of school geometry.

Keywords: ethnography, ethnomathematics, geometry, mat weaving, school pedagogy

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Authors: John Yahng, Hansraj Riteesh Bookun

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Objective: This was a retrospective cross-sectional study evaluating the safety of discharge on the first postoperative day following carotid surgery - principally carotid endarterectomy. Methods: Between January 2010 to October 2017, 252 patients with mean age of 72 years, underwent carotid surgery by seven surgeons. Their medical records were consulted and their operative as well as complication timelines were databased. Descriptive statistics were used to analyse pooled responses and our indicator variables. The statistical package used was STATA 13. Results: There were 183 males (73%) and the comorbid burden was as follows: ischaemic heart disease (54%), diabetes (38%), hypertension (92%), stage 4 kidney impairment (5%) and current or ex-smoking (77%). The main indications were transient ischaemic attacks (42%), stroke (31%), asymptomatic carotid disease (16%) and amaurosis fugax (8%). 247 carotid endarterectomies (109 with patch arterioplasty, 88 with eversion and transection technique, 50 with endarterectomy only) were performed. 2 carotid bypasses, 1 embolectomy, 1 thrombectomy with patch arterioplasty and 1 excision of a carotid body tumour were also performed. 92% of the cases were performed under general anaesthesia. A shunt was used in 29% of cases. The mean length of stay was 5.1 ± 3.7days with the range of 2 to 22 days. No patient was discharged on day 1. The mean time from admission to surgery was 1.4 ± 2.8 days, ranging from 0 to 19 days. The mean time from surgery to discharge was 2.7 ± 2.0 days with the of range 0 to 14 days. 36 complications were encountered over this period, with 12 failed repairs (5 major strokes, 2 minor strokes, 3 transient ischaemic attacks, 1 cerebral bleed, 1 occluded graft), 11 bleeding episodes requiring a return to the operating theatre, 5 adverse cardiac events, 3 cranial nerve injuries, 2 respiratory complications, 2 wound complications and 1 acute kidney injury. There were no deaths. 17 complications occurred on postoperative day 0, 11 on postoperative day 1, 6 on postoperative day 2 and 2 on postoperative day 3. 78% of all complications happened before the second postoperative day. Out of the complications which occurred on the second or third postoperative day, 4 (1.6%) were bleeding episodes, 1 (0.4%) failed repair , 1 respiratory complication (0.4%) and 1 wound complication (0.4%). Conclusion: Although it has been common practice to discharge patients on the second postoperative day following carotid endarterectomy, we find here that discharge on the first operative day is safe. The overall complication rate is low and most complications are captured before the second postoperative day. We suggest that patients having an uneventful first 24 hours post surgery be discharged on the first day. This should reduce hospital length of stay and the health economic burden.

Keywords: carotid, complication, discharge, surgery

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Authors: Yang Xiong, Hua Cheng

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In this paper, for the basic problem of wireless sensor network topology control and deployment, the Roesser model in rectangular grid sensor networks is presented. In addition, a general constructive realization procedure will be proposed. The procedure enables a distributed implementation of linear systems on a sensor network. A non-trivial example is illustrated.

Keywords: grid sensor networks, Roesser model, state-space realization, multidimensional systems

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Authors: Hafawa Messaoudi, Taoufik Aguili

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Due to the rapid growth in the use of wireless communication systems, there has been a recent increase in public concern regarding the exposure of humans to Radio Frequency (RF) electromagnetic radiation. This is particularly evident in the case of mobile telephone handsets. Previously, the insertion of a ferrite sheet between the antenna and the human head, the use of conductive materials (such as aluminum), the use of metamaterials (SRR), frequency selective surface (FSS), and electromagnetic band gap (EBG) structures to design high performance devices were proposed as methods of reducing the SAR value. This paper aims to provide an investigation of the effectiveness of various available Specific Absorption Rate (SAR) reduction solutions.

Keywords: EBG, HIS, metamaterials, SAR reduction

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Authors: Sharat Chandra, Zilong Wang, Ru-Rong Ji, Andrey Bortsov

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Chronic pain (CP) therapeutic approaches have limited efficacy. As a result, doctors are prescribing opioids for chronic pain, leading to opioid overuse, abuse, and addiction epidemic. Therefore, the development of effective and safe CP drugs remains an unmet medical need. Voltage-gated sodium (Nav) channels act as cardiovascular and neurological disorder’s molecular targets. Nav channels selective inhibitors are hard to design because there are nine closely-related isoforms (Nav1.1-1.9) that share the protein sequence segments. We are targeting the Nav1.7 found in the peripheral nervous system and engaged in the perception of pain. The objective of this project was to screen a 1.5 million compound library for identification of inhibitors for Nav1.7 with analgesic effect. In this study, we designed a protocol for identification of isoform-selective inhibitors of Nav1.7, by utilizing the prior information on isoform-selective antagonists. First, a similarity search was performed; then the identified hits were docked into a binding site on the fourth voltage-sensor domain (VSD4) of Nav1.7. We used the FTrees tool for similarity searching and library generation; the generated library was docked in the VSD4 domain binding site using FlexX and compounds were shortlisted using a FlexX score and SeeSAR hyde scoring. Finally, the top 25 compounds were tested with molecular dynamics simulation (MDS). We reduced our list to 9 compounds based on the MDS root mean square deviation plot and obtained them from a vendor for in vitro and in vivo validation. Whole-cell patch-clamp recordings in HEK-293 cells and dorsal root ganglion neurons were conducted. We used patch pipettes to record transient Na⁺ currents. One of the compounds reduced the peak sodium currents in Nav1.7-HEK-293 stable cell line in a dose-dependent manner, with IC50 values at 0.74 µM. In summary, our computer-aided analgesic discovery approach allowed us to develop pre-clinical analgesic candidate with significant reduction of time and cost.

Keywords: chronic pain, voltage-gated sodium channel, isoform-selective antagonist, similarity search, virtual screening, analgesics development

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Authors: Abdullah A. Al Orainy

Abstract:

Small cell backhaul solutions need to be cost-effective, scalable, and easy to install. This paper presents an overview of small cell backhaul technologies. Wireless solutions including TV white space, satellite, sub-6 GHz radio wave, microwave and mmWave with their backhaul characteristics are discussed. Recent research on issues like beamforming, backhaul architecture, precoding and large antenna arrays, and energy efficiency for dense small cell backhaul with mmWave communications is reviewed. Recent trials of 5G technologies are summarized.

Keywords: backhaul, small cells, wireless, 5G

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Authors: Siamak Dawazdah Emami, Amin Khodaei, Harith Bin Ahmad, Hairul A. Adbul-Rashid

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The Fano resonance effect on plasmonic nanoparticle materials results in such materials possessing a number of unique optical properties, and the potential applicability for sensing, nonlinear devices and slow-light devices. A Fano resonance is a consequence of coherent interference between superradiant and subradiant hybridized plasmon modes. Incident light on subradiant modes will initiate excitation that results in superradiant modes, and these superradient modes possess zero or finite dipole moments alongside a comparable negligible coupling with light. This research work details the derivation of an electrodynamics coupling model for the interaction of dipolar transitions and radiation via plasmonic nanoclusters such as quadrimers, pentamers and heptamers. The directivity calculation is analyzed in order to qualify the redirection of emission. The geometry of a configured array of nanostructures strongly influenced the transmission and reflection properties, which subsequently resulted in the directivity of each antenna being related to the nanosphere size and gap distances between the nanospheres in each model’s structure. A well-separated configuration of nanospheres resulted in the structure behaving similarly to monomers, with spectra peaks of a broad superradiant mode being centered within the vicinity of 560 nm wavelength. Reducing the distance between ring nanospheres in pentamers and heptamers to 20~60 nm caused the coupling factor and charge distributions to increase and invoke a subradiant mode centered within the vicinity of 690 nm. Increasing the outside ring’s nanosphere distance from the centered nanospheres caused the coupling factor to decrease, with the coupling factor being inversely proportional to cubic of the distance between nanospheres. This phenomenon led to a dramatic decrease of the superradiant mode at a 200 nm distance between the central nanosphere and outer rings. Effects from a superradiant mode vanished beyond a 240 nm distance between central and outer ring nanospheres.

Keywords: fano resonance, optical antenna, plasmonic, nano-clusters

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Authors: Sankara Ganesh Dhoopam, Phaneendra Aduri

Abstract:

Lattice towers are light weight structures which are primarily governed by the effects of wind loading. Ensuring a precise assessment of wind loads on the tower structure, antennas, and associated equipment is vital for the safety and efficiency of tower design. Earlier, the Indian standards are not available for design of telecom towers. Instead, the industry conventionally relied on the general building wind loading standard for calculating loads on tower components and the transmission line tower design standard for designing the angular members of the towers. Subsequently, the Bureau of Indian Standards (BIS) revised these standards and angular member design standard. While the transmission line towers are designed using the above standard, a full-scale model test will be done to prove the design. Telecom angular towers are also designed using the same with overload factor/factor of safety without full scale tower model testing. General construction in steel design code is available with limit state design approach and is applicable to the design of general structures involving angles and tubes but not used for angle member design of towers. Recently, in response to the evolving industry needs, the Bureau of Indian Standards (BIS) introduced a new standard titled “Isolated Towers, Masts, and Poles using structural steel -Code of practice” for the design of telecom towers. This study focuses on a 40m four legged angular tower to compare loading calculations and member designs between old and new standards. Additionally, a comparative analysis aligning with the new code provisions with international loading and design standards with a specific focus on American standards has been carried out. This paper elaborates code-based provisions used for load and member design calculations, including the influence of "ka" area averaging factor introduced in new wind load case.

Keywords: telecom, angular tower, PLS tower, GSM antenna, microwave antenna, IS 875(Part-3):2015, IS 802(Part-1/sec-2):2016, IS 800:2007, IS 17740:2022, ANSI/TIA-222G, ANSI/TIA-222H.

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Authors: Siva Teja Golla, B. Venkatesham

Abstract:

The recent technologies in hybrid and high-end cars have subsided the noise from major sources like engines and transmission systems. This resulted in the unmasking of the previously subdued noises. These noises are becoming noticeable to the passengers, causing annoyance to them and affecting the perceived quality of the vehicle. Sloshing in the fuel tank is one such source of noise. Sloshing occurs due to the excitations undergone by the fuel tank due to the vehicle's movement. Sloshing noise occurs due to the interaction of the fluid with the surrounding tank walls or with the fluid itself. The noise resulting from the interaction of the fluid with the structure is ‘Hit noise’, and the noise due to fluid-fluid interaction is ‘Splash noise’. The type of interactions the fluid undergoes inside the tank, and the type of noise generated depends on a variety of factors like the fill level of the tank, type of fluid, presence of objects like baffles inside the tank, type and strength of the excitation, etc. There have been studies done to understand the effect of each of these parameters on the generation of different types of sloshing noises. But little work is done in the psychoacoustic aspect of these sounds. The psychoacoustic study of the sloshing noises gives an understanding of the level of annoyance it can cause to the passengers and helps in taking necessary measures to address it. In view of this, the current paper focuses on the calculation of the psychoacoustic parameters like loudness, sharpness, roughness and fluctuation strength for the sloshing noise. As the noise generation mechanisms for the hit and splash noises are different, these parameters are calculated separately for them. For this, the fluid flow regimes that predominantly cause the hit-and-splash noises are to be separately emulated inside the tank. This is done through a reciprocating test rig, which imposes reciprocating excitation to a rectangular tank filled with the fluid. By varying the frequency of excitation, the fluid flow regimes with the predominant generation of hit-and-splash noises can be separately created inside the tank. These tests are done in a quiet room and the noise generated is captured using microphones and is used for the calculation of psychoacoustic parameters of the sloshing noise. This study also includes the effect of fill level and the presence of baffles inside the tank on these parameters.

Keywords: sloshing, hit noise, splash noise, sound quality

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Authors: A. Terfous, Y. Liu, A. Ghenaim, P. A. Garambois

Abstract:

With increasing urbanization worldwide, it is crucial to sustainably manage sediment flows in urban networks and especially in stormwater detention basins. One key aspect is to propose optimized designs for detention tanks in order to best reduce flood peak flows and in the meantime settle particles. It is, therefore, necessary to understand complex flows patterns and sediment deposition conditions in stormwater detention basins. The aim of this paper is to study flow structure and particle deposition pattern for a given tank geometry in view to control and maximize sediment deposition. Both numerical simulation and experimental works were done to investigate the flow and sediment distribution in a storm tank with a cavity. As it can be indicated, the settle distribution of the particle in a rectangular tank is mainly determined by the flow patterns and the bed shear stress. The flow patterns in a rectangular tank differ with different geometry, entrance flow rate and the water depth. With the changing of flow patterns, the bed shear stress will change respectively, which also play an influence on the particle settling. The accumulation of the particle in the bed changes the conditions at the bottom, which is ignored in the investigations, however it worth much more attention, the influence of the accumulation of the particle on the sedimentation should be important. The approach presented here is based on the resolution of the Reynolds averaged Navier-Stokes equations to account for turbulent effects and also a passive particle transport model. An analysis of particle deposition conditions is presented in this paper in terms of flow velocities and turbulence patterns. Then sediment deposition zones are presented thanks to the modeling with particle tracking method. It is shown that two recirculation zones seem to significantly influence sediment deposition. Due to the possible overestimation of particle trap efficiency with standard wall functions and stick conditions, further investigations seem required for basal boundary conditions based on turbulent kinetic energy and shear stress. These observations are confirmed by experimental investigations processed in the laboratory.

Keywords: storm sewers, sediment deposition, numerical simulation, experimental investigation

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Authors: Muhammad Umar Kiani, Waseem Sakawat

Abstract:

This study presents the development of FEM code using Quadrilateral 4-Node (Q4) and Triangular 3-Node (T3) elements. Code is formulated using MATLAB language. Instead of using both elements in the same code, two separate codes are written. Quadrilateral element is difficult to handle directly, that is why natural coordinates (eta, ksi) are used. Due to this, Q4 code includes numerical integration (Gauss quadrature). In this case, complete numerical integration is performed using 2 points. On the other hand, T3 element can be modeled directly, by using direct stiffness approach. Axially loaded element, cantilever (special constraints) and Patch test cases were analyzed using both codes and the results were verified by using Ansys.

Keywords: FEM code, MATLAB, numerical integration, ANSYS

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Authors: Karan Modi, Rajesh Kumar, Jyoti Katiyar, Shreya Thusoo

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This paper presents Finite Element Method (FEM) for analyzing the internal responses generated in thin rectangular plates with various edge conditions and rigidity conditions. Comparison has been made between the FEM (ANSYS software) results for displacement, stresses and moments generated with and without the consideration of hole in plate and different aspect ratios. In the end comparison for responses in plain and composite square plates has been studied.

Keywords: ANSYS, finite element method, plates, static analysis

Procedia PDF Downloads 440