Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
40,338
result(s) for
"Hussein"
Sort by:
Passive frequency comb generation at radiofrequency for ranging applications
Optical frequency combs, featuring evenly spaced spectral lines, have been extensively studied and applied to metrology, signal processing, and sensing. Recently, frequency comb generation has been also extended to MHz frequencies by harnessing nonlinearities in microelectromechanical membranes. However, the generation of frequency combs at radio frequencies (RF) has been less explored, together with their potential application in wireless technologies. In this work, we demonstrate an RF system able to wirelessly and passively generate frequency combs. This circuit, which we name quasi-harmonic tag (qHT), offers a battery-free solution for far-field ranging of unmanned vehicles (UVs) in GPS-denied settings, and it enables a strong immunity to multipath interference, providing better accuracy than other RF approaches to far-field ranging. Here, we discuss the principle of operation, design, implementation, and performance of qHTs used to remotely measure the azimuthal distance of a UV flying in an uncontrolled electromagnetic environment. We show that qHTs can wirelessly generate frequency combs with μWatt-levels of incident power by leveraging the nonlinear interaction between an RF parametric oscillator and a high quality factor piezoelectric microacoustic resonator. Our technique for frequency comb generation opens new avenues for a wide range of RF applications beyond ranging, including timing, computing and sensing.
In contrast to the commonly studied optical frequency combs, here, the authors demonstrate a radio frequency system able to wirelessly and passively generate frequency combs as a battery-free solution for far-field ranging of unmanned vehicles in GPS-denied settings.
Journal Article
A chip-less and battery-less subharmonic tag for wireless sensing with parametrically enhanced sensitivity and dynamic range
Massive deployments of wireless sensor nodes (WSNs) that continuously detect physical, biological or chemical parameters are needed to truly benefit from the unprecedented possibilities opened by the Internet-of-Things (IoT). Just recently, new sensors with higher sensitivities have been demonstrated by leveraging advanced on-chip designs and microfabrication processes. Yet, WSNs using such sensors require energy to transmit the sensed information. Consequently, they either contain batteries that need to be periodically replaced or energy harvesting circuits whose low efficiencies prevent a frequent and continuous sensing and impact the maximum range of communication. Here, we report a new chip-less and battery-less tag-based WSN that fundamentally breaks any previous paradigm. This WSN, formed by off-the-shelf lumped components on a printed substrate, can sense and transmit information without any need of supplied or harvested DC power, while enabling full-duplex transceiver designs for interrogating nodes rendering them immune to their own self-interference. Also, even though the reported WSN does not require any advanced and expensive manufacturing, its unique parametric dynamical behavior enables extraordinary sensitivities and dynamic ranges that can even surpass those achieved by on-chip sensors. The operation and performance of the first implementation of this new WSN are reported. This device operates in the Ultra-High-Frequency range and is capable to passively and continuously detect temperature changes remotely from an interrogating node.
Journal Article
Association between environmental stress factors, salivary cortisol level and dental caries in Egyptian preschool children: a case-control study
Dental caries remains the most common chronic disease in childhood. This study aimed to identify environmental stressors in children and estimate the association between salivary cortisol level as a stress biomarker and childhood caries. We conducted a case-control study involving 80 Egyptian children. The cases were 40 children with early childhood caries (ECC). The controls included 40 caries-free children. Data were collected from the parents or caregivers of the children using a questionnaire. The clinical examination included caries experience and an oral hygiene index. Saliva samples were collected and tested for unbounded cortisol levels. The results from the current study showed that the mean age for participants was 5.09 ± 0.66 years. Twenty-one of the children with ECC were girls. In multivariate regression, there is a significant association between ECC and elevated salivary cortisol levels (> 0.57 µg/dl) with an adjusted odds ratio (AOR) of 9.649 (
p
= 0.003), father smoking (AOR = 5.791,
p
= 0.030), sleeping with a bottle or food in the mouth (AOR = 8.481,
p
= 0.027), and poor oral hygiene evaluated through the Silness-Löe Plaque Index (AOR = 6.681,
p
= 0.001). As a conclusion, the study indicates that salivary cortisol is an independent stress biomarker in relation to early childhood caries. Salivary cortisol as a stress biomarker can help clinicians provide an additional assessment tool for identifying caries risk in children.
Journal Article
Spectral shifted Chebyshev collocation technique with residual power series algorithm for time fractional problems
In this paper, two problems involving nonlinear time fractional hyperbolic partial differential equations (PDEs) and time fractional pseudo hyperbolic PDEs with nonlocal conditions are presented. Collocation technique for shifted Chebyshev of the second kind with residual power series algorithm (CTSCSK-RPSA) is the main method for solving these problems. Moreover, error analysis theory is provided in detail. Numerical solutions provided using CTSCSK-RPSA are compared with existing techniques in literature. CTSCSK-RPSA is accurate, simple and convenient method for obtaining solutions of linear and nonlinear physical and engineering problems.
Journal Article
Design, and dynamic evaluation of a novel photovoltaic pumping system emulation with DS1104 hardware setup: Towards innovative in green energy systems
Diesel engines (DEs) commonly power pumps used in agricultural and grassland irrigation. However, relying on unpredictable and costly fuel sources for DEs pose’s challenges related to availability, reliability, maintenance, and lifespan. Addressing these environmental concerns, this study introduces an emulation approach for photovoltaic (PV) water pumping (WP) systems. Emulation offers a promising alternative due to financial constraints, spatial limitations, and climate dependency in full-scale systems. The proposed setup includes three key elements: a PV system emulator employing back converter control to replicate PV panel characteristics, a boost converter with an MPPT algorithm for efficient power tracking across diverse conditions, and a motor pump (MP) emulator integrating an induction motor connected to a DC generator to simulate water pump behaviors. Precise induction motor control is achieved through a controlled inverter. This work innovatively combines PV and WP emulation while optimizing system dynamics, aiming to develop a comprehensive emulator and evaluate an enhanced control algorithm. An optimized scalar control strategy regulates the water MP, demonstrated through MATLAB/Simulink simulations that highlight superior performance and responsiveness to solar irradiation variations compared to conventional MPPT techniques. Experimental validation using the dSPACE control desk DS1104 confirms the emulator’s ability to faithfully reproduce genuine solar panel characteristics.
Journal Article