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Experimental demonstration of tunable refractometer based on orbital angular momentum of longitudinally structured light

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Light(Science & Applications) 2018年第1期7卷 669-680页

作者： ahmed h.Dorrah Michel Zamboni-Rached mo mojahedi Edward S.Rogers Sr.Department of Electrical and Computer Engineering University of TorontoTorontoON M5S 3G4Canada School of Electrical and Computer Engineering University of CampinasCampinas–SP 13083-852Brazil

The index of refraction plays a decisive role in the design and classification of optical materials and devices;therefore,its proper and accurate determination is *** most refractive index(RI)sensing schemes,however,there is a trade-off between providing high-resolution measurements and covering a wide range of *** propose and experimentally demonstrate a novel mechanism for sensing the index of refraction of a medium by utilizing the orbital angular momentum(OAM)of structured *** a superposition of co-propagating monochromatic higher-order Bessel beams with equally spaced longitudinal wavenumbers,in a comb-like setting,we generate non-diffracting rotating light structures in which the orientation of the beam’s intensity profile is sensitive to the RI of the medium(here,a fluid).In principle,the sensitivity of this scheme can exceed~2700°/RI unit(RIU)with a resolution of~105 ***,we show how the unbounded degrees of freedom associated with OAM can be deployed to offer a wide dynamic range by generating structured light that evolves into different patterns based on the change in *** rotating light structures are generated by a programmable spatial light *** provides dynamic control over the sensitivity,which can be tuned to perform coarse or fine measurements of the RI in real ***,in turn,allows high sensitivity and resolution to be achieved simultaneously over a very wide dynamic range,which is a typical tradeoff in all RI sensing *** thus envision that this method will open new directions in refractometry and remote sensing.

关键词： tunable light momentum

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Influence of temperature on the properties of one-dimensional piezoelectric phononic crystals

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Chinese Physics B 2018年第9期27卷 342-345页

作者： ahmed Nagaty ahmed Mehaney Arafa h Aly Physics Department Faculty of Sciences Beni-Suef University

The current study investigates the influence of temperature on a one-dimensional piezoelectric phononic crystal using tunable resonant frequencies. Analytical and numerical examples are introduced to emphasize the influence of temperature on the piezoelectric phononic crystals. It was observed that the transmission spectrum of a one-dimensional phononic crystal containing a piezoelectric material（0.7 PMN-0.3 PT） can be changed drastically by an increase in *** resonant peak can be shifted toward high or low frequencies by an increase or decrease in temperature, ***, we deduced that temperature can exhibit a large tuning in the phononic band gaps and in the local resonant frequencies depending on the presence of a piezoelectric material. Such result can enhance the harvesting energy from piezoelectric materials, especially those that are confined in a phononic crystal.

关键词： phononic crystals resonant modes piezoelectric material thermal properties and temperature

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Low band gap frequencies and multiplexing properties in 1D and 2D mass spring structures

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Chinese Physics B 2016年第11期25卷 333-339页

作者： Arafa h Aly ahmed Mehaney Physics Department Faculty of Sciences Beni-Suef University

This study reports on the propagation of elastic waves in 1D and 2D mass spring *** analytical and computation model is presented for the 1D and 2D mass spring systems with different *** enhancement in the band gap values was obtained by modeling the structures to obtain low frequency band gaps at small ***,the evolution of the band gap as a function of mass value is *** attention is devoted to the local resonance property in frequency ranges within the gaps in the band structure for the corresponding infinite periodic lattice in the 1D and 2D mass spring system.A linear defect formed of a row of specific masses produces an elastic waveguide that transmits at the narrow pass band *** frequency of the waveguides can be selected by adjusting the mass and stiffness coefficients of the materials constituting the ***,we pay more attention to analyze the wave multiplexer and DE-multiplexer in the 2D mass spring *** show that two of these tunable waveguides with alternating materials can be employed to filter and separate specific frequencies from a broad band input *** presented simulation data is validated through comparison with the published research,and can be extended in the development of resonators and MEMS verification.

关键词： multiplexing waveguide tunable separate dimensions devoted verification stiffness validated infinite

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Nonalcoholic fatty liver disease and COVID-19:An epidemic that begets pandemic

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World Journal of Clinical Cases 2021年第17期9卷 4133-4142页

作者： Musaab ahmed mo.amed h ahmed College of Medicine Ajman UniversityAjman 346United Arab Emirates Department of Medicine and hIV Metabolic Clinic Milton Keynes University Hospital NHS Foundation TrustMilton Keynes MK56LDUnited Kingdom

Coronavirus disease 2019(COVID-19)caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)has become a global pandemic,affecting all the individuals across the ***-19 has gained significant attention due to its high prevalence among individuals with diabetes,nonalcoholic fatty liver disease(NAFLD),and metabolic *** is the hepatic manifestation of metabolic syndrome and can be associated with a high risk of developing type 2 *** association of COVID-19 and NAFLD has also gained more attention because NAFLD is highly associated with the epidemic of *** is a potential risk factor for SARS-CoV-2 infection and severe COVID-19,independent of metabolic ***,it is not yet clear whether the epidemics of obesity and NAFLD have perpetuated the current pandemic of *** research is urgently needed to assess the following:(1)Whether NAFLD is a high risk factor for SARS-CoV-2 infection;(2)Whether NAFLD is associated with the severe form of COVID-19;and(3)Whether the presence of NAFLD can explain the racial variation in the morbidity and mortality associated with *** review summarizes the interactions between COVID-19 and NAFLD,mechanism of liver injury by COVID-19,and effect of lockdown due to COVID-19 on patients with NAFLD.

关键词： Fatty liver COVID-19 Diabetes Obesity Pandemic

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Exploring tree diversity and stand structure of savanna woodlands in southeastern Sudan

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Journal of Arid Land 2020年第4期12卷 609-617页

作者： ahmed M M hASOBA ahmed A h SIDDIG Yousif E YAGOUB Faculty of Forest Sciences and Technology University of GeziraMadani 22212Sudan Faculty of Forestry University of KhartoumKhartoum North 13314Sudan Department of Environmental Conservation University of Massachusetts AmherstAmherst 01003USA

Savanna woodlands in Sudan host great biodiversity, provide a plethora of ecosystem goods and services to local communities, and sustain numerous ecological functions. Although the importance of the Acacia trees in these areas is well known, up-to-date information about these woodlands' diversity is limited and changes in their woody vegetation composition, density, diversity and relative frequency are not monitored over time. This study explored tree diversity and stand stage structure in Nuara Reserved Forest, a typical savanna woodland ecosystem in southeastern Sudan. A total of 638 circular sample plots(1000 m^2 for each) were established using a systematic sampling grid method. The distance between plots was 200 m. In each plot, all living trees with diameter at breast height(DBh) ≥5.00 cm were identified and counted, and their DBh values were recorded. From these data, tree composition, diversity, density and stage structure were assessed. There were 12,259 individual trees representing four species(Acacia seyal, Balanites aegyptiaca, Acacia Senegal and Acacia mellifera) that belong to two families. The dominant species was Acacia seyal. Average tree density was 191 trees/hm^2 and the Shannon-Weiner index for trees diversity was 0.204. Overall, young trees comprised 86.30% of the forest. The state of tree richness and density in the study area was low compared to other similar environments in the region and around the world. We recommended adoption of a proper management system that includes monitoring of woody vegetation diversity in this forest, and management actions to enhance tree diversity and sustain ecosystem services to local communities. In addition to care for the dominant Acacia seyal stands, more attention and conservation should be devoted to reestablishing Acacia senegal and Acacia mellifera trees because of their high ecological and economic values for local communities.

关键词： species diversity stand structure savanna woodland ecosystem forest monitoring forest management ecosystem services Nuara Reserved Forest

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Obstructive sleep apnea syndrome and fatty liver: Association or causal link?

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World Journal of Gastroenterology 2010年第34期16卷 4243-4252页

作者： mo.amed h ahmed Christopher D Byrne Chemical Pathology Department Southampton University Hospital NHS Trust Southampton SO16 6YD United Kingdom Endocrinology and Metabolism DOHaD Division University of Southampton and Southampton University Hospitals Trust Southampton SO16 6YD United Kingdom

Obstructive sleep apnea (OSA) is a complex disorder that consists of upper airway obstruction, chronic intermittent hypoxia and sleep fragmentation. OSA is well known to be associated with hypoxia, insulin resistance and glucose intolerance, and these factors can occur in the presence or absence of obesity and metabolic syndrome. Although it is well established that insulin resistance, glucose intolerance and obesity occur frequently with non-alcoholic fatty liver disease (NAFLD), it is now becoming apparent that hypoxia might also be important in the development of NAFLD, and it is recognized that there is increased risk of NAFLD with OSA. This review discusses the association between OSA, NAFLD and cardiovascular disease, and describes the potential role of hypoxia in the development of NAFLD with OSA.

关键词： Sleep apnea syndrome hyperlipidemia Non-alcoholic fatty liver disease Insulin resistance

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Analyzing the effect of earthquakes on OpenStreetMap contribution patterns and tweeting activities

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Geo-Spatial Information Science 2018年第3期21卷 195-212页

作者： ahmed Ahmouda hartwig h.hochmair Sreten Cvetojevic Geomatics Program Fort Lauderdale Research and Education CenterUniversity of FloridaFloridaFort LauderdaleUSA

Natural disasters,such as wildfires,earthquakes,landslides,or floods,lead to an increase in topical information shared on social media and in increased mapping activities in volunteered geographic information(VGI)*** earthquakes in Nepal and Central Italy as case studies,this research analyzes the effects of natural disasters on short-term(weeks)and longer-term(half year)changes in OpenStreetMap(OSM)mapping behavior and tweet activities in the affected *** increase of activities in OSM during the events can be partially attributed to those focused OSM mapping campaigns,for example,through the humanitarian OSM Team(hOT).Using source tags in OSM change-sets,it was found that only a small portion of external mappers actually travels to the affected regions,whereas the majority of external mappers relies on desktop mapping ***,the study analyzes the spatio-temporal sequence of posted tweets together with keyword filters to identify a subset of users who most likely traveled to the affected regions for support and rescue *** also explores where,geographically,earthquake information spreads within social networks.

关键词： Volunteered geographic information(VGI) OpenStreetMap(OSM) Twitter natural disaster human dynamics

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Oilfield produced water treatment in internal-loop airlift reactor using electrocoagulation/flotation technique

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Chinese Journal of Chemical Engineering 2018年第4期26卷 879-885页

作者： Saad h.Ammar ahmed S.Akbar Department of Chemical engineering AL-Nahrain University

Oilfield produced water is large quantities of salty water trapped in underground formations and subsisted under high temperatures and pressures that are brought to the surface along with oil during production. Produced water(PW) contains a lot of pollutants such as hydrocarbons and metals, this water must be treated before disposal. Therefore, different techniques are being used to treat produced water. Electrocoagulation is an efficient treatment technique involving the dissolution of anodes and formation of electro-coagulants, while the simultaneous generation of h_2 bubbles at the cathode leads to the pollutant removal by flotation. Electrocoagulation(EC)method is one of the most promising and widely used processes to treat oilfield produced water. In the present work, a conventional internal-loop(draught tube) airlift reactor was utilized as electrocoagulation/flotation cell for PW treatment by inserting two aluminum electrodes in the riser section of the airlift reactor. The EC airlift reactor was operated in a batch mode for the liquid phase. Different experimental parameters were studied on the oil and turbidity removal efficiencies such as current density, initial ph, electrocoagulation time, and air *** experimental results showed that mixing of the oil droplets in the PW was accomplished using only the liquid recirculation resulted by h_2 microbubbles generated by EC process which enhanced the oil removal. The experimental results further showed that the EC time required achieving ≥ 90% oil removal efficiency decreases from 46 to 15 min when operating current density increases from 6.8 to 45.5 mA·cm^(-2). This reactor type was found to be highly efficient and less energy consuming compared to conventional existing electrochemical cells which used mechanical agitation.

关键词： Produced water Wastewater treatment Electrocoagulation/flotation Internal loop Airlift reactor

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Carbon nanotube-based nanoelectromechanical resonatoras mass biosensor

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Chinese Physics B 2020年第7期29卷 583-587页

作者： ahmed MElseddawy Adel hPhillips ahmed S Bayoumi Faculty of Graduate Studies University of WindsorWindsorOntarioCanada Faculty of Engineering Ain-Shams UniversityCairoEgypt Faculty of Engineering Kafr-Elsheikh UnversityKafr-ElsheikhEgypt

The use of single walled carbon nanotube-based nanoelectromechanical system(NEMS)resonator to sense the biomolecules'mass is investigated under the influence of an external ac-field.A single walled carbon nanotube(SWCNT)cantilever has been proposed and studied if the mass is attached at the tip or various intermediate *** shift of the resonant frequency and the quality factor have been investigated and show high sensitivity to the attached mass of biomolecule and its *** proposed SWCNT-based NEMS resonator is a good candidate for sensing and tracing biomolecules'mass as concentration of acetone in human exhale,resulting in a painless,correct,and simple diabetics'diagnosis.

关键词： single walled carbon nanotube nanoelectromechanical system resonator ac-field biomolecule

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Improving the Transmission Security of Vein Images Using a Bezier Curve and Long Short-Term Memory

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Computers, Materials & Continua 2024年第6期79卷 4825-4844页

作者： ahmed h.Alhadethi Ikram Smaoui ahmed Fakhfakh Saad M.Darwish Computer Science and School of Electronics and Telecommunications University of SfaxSfax3029Tunisia LETI Laboratory University of SfaxSfax3029Tunisia Digital Research Center of Sfax Technopark of SfaxSfax3029Tunisia Department of Information Technology Institute of Graduate Studies and ResearchAlexandria UniversityAlexandriaEgypt

The act of transmitting photos via the Internet has become a routine and significant *** the security measures to safeguard these images from counterfeiting and modifications is a critical domain that can still be further *** study presents a system that employs a range of approaches and algorithms to ensure the security of transmitted venous *** main goal of this work is to create a very effective system for compressing individual biometrics in order to improve the overall accuracy and security of digital photographs by means of image *** paper introduces a content-based image authentication mechanism that is suitable for usage across an untrusted network and resistant to data loss during *** employing scale attributes and a key-dependent parametric Long Short-Term Memory(LSTM),it is feasible to improve the resilience of digital signatures against image deterioration and strengthen their security against malicious ***,the successful implementation of transmitting biometric data in a compressed format over a wireless network has been *** applications involving the transmission and sharing of images across a *** suggested technique utilizes the scalability of a structural digital signature to attain a satisfactory equilibrium between security and picture *** effective adaptive compression strategy was created to lengthen the overall lifetime of the network by sharing the processing of *** scheme ensures a large reduction in computational and energy requirements while minimizing image quality *** approach employs multi-scale characteristics to improve the resistance of signatures against image *** proposed system attained a Gaussian noise value of 98%and a rotation accuracy surpassing 99%.

关键词： Image transmission image compression text hiding Bezier curve histogram of Oriented Gradients(hOG) LSTM image enhancement Gaussian noise rotation

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