| 1. |
- Sheykhifard, Z., et al.
(författare)
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Magnetic graphene/Ni-nano-crystal hybrid for small field magnetoresistive effect synthesized via electrochemical exfoliation/deposition technique
- 2018
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Ingår i: Journal of Materials Science-Materials in Electronics. - : Springer Science and Business Media LLC. - 0957-4522 .- 1573-482X. ; 29:5, s. 4171-4178
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional heterostructures of graphene (Gr) and metal/semiconducting elements convey new direction in electronic devices. They can be useful for spintronics because of small spin orbit interaction of Gr as a non-magnetic metal host with promising electrochemical stability. In this paper, we demonstrate one-step fabrication of magnetic Ni-particles entrapped within Gr-flakes based on simultaneous electrochemical exfoliation/deposition procedure by two-electrode system using platinum as the cathode electrode and a graphite foil as the anode electrode. The final product is an air stable hybrid element including Gr flakes hosting magnetic Ni-nano-crystals showing superparamagnetic-like response and room temperature giant magnetoresistance (GMR) effect at small magnetic field range. The GMR effect is originated from spin scattering through ferromagnetic/non-magnetic nature of Ni/Gr heterostructure and interpreted based on a phenomenological spin transport model. Our work benefits from XRD, XPS, Raman, TEM, FTIR and VSM measurements We addressed that how our results can be used for rapid manufacturing of magnetic Gr for low field magneto resistive elements and potential printed spintronic devices.
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| 2. |
- Khankeh, HR, et al.
(författare)
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The Barriers, Challenges, and Strategies of COVID-19 (SARS-CoV-2) Vaccine Acceptance: A Concurrent Mixed-Method Study in Tehran City, Iran
- 2021
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Ingår i: Vaccines. - : MDPI AG. - 2076-393X. ; 9:11
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Tidskriftsartikel (refereegranskat)abstract
- Acceptance and willingness to receive the vaccine are among the main factors in the success or failure of a health system in implementing the vaccination program. The present study was conducted in Tehran, the political and economic capital of Iran, to determine the acceptance of the COVID-19 vaccine and identify its associated factors, and explain the most important barriers and acceptance strategies for vaccination. This research was a concurrent quantitative and qualitative mixed-method study. In the quantitative part, 1200 individuals aged more than 18 years were selected from the households in 22 districts of Tehran City, with a multistage stratified cluster sampling method. Two questionnaires were used to evaluate the acceptance of the COVID-19 vaccine and vaccine acceptance determinants. The qualitative content analysis method addressed the influencing factors, as well as challenges and strategies related to the acceptance of the COVID-19 vaccine in four groups of Tehran inhabitants: the elderly, people with underlying diseases, healthcare workers, and the general population. The related data were simultaneously collected by applying in-depth semi-structural interviews and a data analysis process. Furthermore, we used the Graneheim and Lundman method for data analysis. We analyzed the data of 1200 people with a mean (SD) age of 46.4 (11.1) years, and approximately 58% of them were men. The vaccine acceptance was 83.6% (95% CI: 81.3–85.9). Among those who welcomed vaccination, 58% preferred the imported vaccines, 25% the Iranian ones, and 17% both. There was a significant association between the variables of age (adjusted odds ratio [AOR] = 1.72, 95% CI: 1.01–2.93), being single (AOR = 0.54, 95% CI: 0.41–0.91), moderate pharmacotherapy adherence (AOR = 0.58, 95% CI: 0.4–0.85), and the willingness to receive COVID-19 vaccine. Qualitative study after interviewing 45 people from four study groups showed an insufficient social trust in healthcare system officials, pharmaceutical and vaccine production companies; distrust in the effectiveness of the vaccines, concerns about the vaccine adverse effects, being tracked by microchips after vaccination, traditional anti-vaccination movements, the feeling the inessentiality of vaccination, and uncertainty about the fair distribution of the vaccine. These concerns were the main challenges addressed by the study groups. A good proportion of Tehran residents reported their willingness to receive the COVID-19 vaccine. Additionally, they expressed their critical concerns, such as insufficient trust in the healthcare system, vaccine safeties, and adverse effects that were the significant barriers to vaccine acceptance. It seems that conflicts raised by the shortage of vaccines and their import due to the sanctions have led to intense desire and demand in the general population, and especially the elderly, for vaccination. Besides, vaccination phobia in some individuals requires further investigations.
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| 3. |
- Khankeh, H, et al.
(författare)
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Comparison of vaccine hesitancy during the low and high points of COVID-19 in a population under international sanctions: A longitudinal mixed-methods study in Iran
- 2023
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Ingår i: Frontiers in public health. - : Frontiers Media SA. - 2296-2565. ; 10, s. 958899-
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Tidskriftsartikel (refereegranskat)abstract
- Along with the challenges of COVID-19 vaccine supply in low-income countries, vaccine hesitancy was another problem for the health system. The aim of this study was to deeply understand the challenges of vaccine acceptance, the vaccination process, and to compare the affecting vaccine acceptance in the high and low points of the epidemic in Iran.MethodsIn the qualitative part of this mixed-methods study, content analysis was used to investigate experiences and perceptions about COVID-19 vaccination in four groups. In the quantitative study, in March 2021 (low point), and on August 1, 2021 (high point), two population-based cross-sectional studies were performed in Tehran and its rural, with sample sizes of 1,200 and 1,872 people aged over 18 years, respectively. Multinomial (polytomous) logistic regression was used to determine the factors affecting hesitation and unwillingness to receive the vaccine.ResultsDisbelief in vaccine safety, vaccine distrust, ignorance and confusion, and inadequate facilities were the common reasons extracted in the two qualitative studies. At the low and high points of the epidemic, vaccine acceptance was 83.6% (95% CI: 81.3–85.9) and 65.8% (95% CI: 65.8–71.0), respectively. Residence in rural areas, (Odds Ratio: 0.44, p = 0.001), being a student (Odds Ratio: 0.41, p = 0.011), housewives (Odds Ratio: 0.63, p = 0.033), illiteracy (Odds Ratio: 4.44, p = 0.001), and having an underlying disease (Odds Ratio: 4.44, p = 0.001) were factors affecting on vaccine acceptance.DiscussionCounter-intuitively, acceptance did not increase at the peak of epidemic. The presence of obstacles, such as increased distrust in the effectiveness of vaccines due to the occurrence of multiple peaks in different vaccinated countries, as well as the influence of the media, anti-vaccine campaigns, and lack of proper communication about risks caused more hesitation. More investigation to understand how people accept or reject vaccine and its long term consequences is recommended.
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| 4. |
- Ranjbar, M., et al.
(författare)
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CoFeB-Based Spin Hall Nano-Oscillators
- 2014
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Ingår i: IEEE Magnetics Letters. - 1949-307X .- 1949-3088. ; 5, s. 3000504-
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate magnetization auto-oscillations driven by pure spin currents in spin Hall nano-oscillators based on CoFeB/Pt bilayers. Despite the very low anisotropic magnetoresistance of CoFeB, a substantial microwave signal power can be detected, even at room temperature, indicating that a sizable spin wave amplitude is generated. Spin torque ferromagnetic resonance measurements reveal that the generated auto-oscillation frequency lies below the ferromagnetic resonance frequency of CoFeB and is therefore well described by a self-localized spin wave bullet mode.
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| 5. |
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| 6. |
- Sbiaa, R., et al.
(författare)
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Ferromagnetic resonance measurements of (Co/Ni/Co/Pt) multilayers with perpendicular magnetic anisotropy
- 2016
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Ingår i: Journal of Physics D. - : Institute of Physics Publishing (IOPP). - 0022-3727 .- 1361-6463. ; 49:42
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Tidskriftsartikel (refereegranskat)abstract
- Multilayers of [Co/Ni(t)/Co/Pt]×8 with varying Ni thickness were investigated for possible use as a free layer in magnetic tunnel junctions and spintronics devices. The thickness t of the Ni sub-layer was varied from 0.3 nm to 0.9 nm and the resulting magnetic properties were compared with (Co/Ni) and (Co/Pt) multilayers. As determined from magnetic force microscopy, magnetometry and ferromagnetic resonance measurements, all multilayers exhibited perpendicular magnetic anisotropy. Compared with (Co/Pt) multilayers, the sample with t of 0.9 nm showed almost the same anisotropy field of μ 0 H k = 1.15 T but the damping constant was 40% lower. These characteristics make these multilayers attractive for spin torque based magnetoresistive devices with perpendicular anisotropy.
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| 7. |
- Spicer, T. M., et al.
(författare)
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Spatial mapping of torques within a spin Hall nano-oscillator
- 2018
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Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 98:21
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Tidskriftsartikel (refereegranskat)abstract
- Time-resolved scanning Kerr microscopy (TRSKM) was used to study precessional magnetization dynamics induced by a radio frequency (RF) current within a Al2O3/Py(5 nm)/Pt(6 nm)/Au(150 nm) spin Hall nano-oscillator structure. The Au layer was formed into two needle-shaped electrical contacts that concentrated the current in the center of a Py/Pt mesa of 4 mu m diameter. Due to the spin Hall effect, current within the Pt layer drives a spin current into the Py layer, exerting a spin transfer torque (STT). By injecting RF current and exploiting the phase sensitivity of TRSKM and the symmetry of the device structure, the STT and Oersted field torques have been separated and spatially mapped. The STT and torque due to the in-plane Oersted field are observed to exhibit minima at the device center that is ascribed to spreading of RF current that is not observed for DC current. Torques associated with the RF current may destabilize the position of the self-localized bullet mode excited by the DC current and inhibit injection locking. The present study demonstrates the need to characterize both DC and RF current distributions carefully.
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| 8. |
- Arpanaei, F., et al.
(författare)
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Hyperaccelerated Power Optimization in Multi-Band Elastic Optical Networks
- 2024
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Ingår i: 2024 Optical Fiber Communications Conference and Exhibition, OFC 2024 - Proceedings.
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Konferensbidrag (refereegranskat)abstract
- We show that solving interrelated inverse differential equations can address pre-tilt power optimization, resulting in a few-second-computed optimal power for each span and boosting average channel generalized signal-to-the-noise ratio (GSNR) by up to 0.5 dB.
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| 9. |
- Ghanbarpour, A., et al.
(författare)
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Evaluation of heat sink performance using PCM and vapor chamber/heat pipe
- 2021
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Ingår i: Renewable energy. - : Elsevier Ltd. - 0960-1481 .- 1879-0682. ; 163, s. 698-719
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a numerical study on heat sink thermal performance using phase change materials (PCM) and a vapor chamber for heat source cooling. Heat sink performance in both natural and forced convection heat transfer modes is investigated. The influence of various geometrical parameters such as number, height and thickness of fins for three different modes of conventional heat sink, PCM-based heat sink and heat sink integrated with vapor chamber is studied. Numerical results showed that the number of fins and fin height were more effective than the fin thickness in reducing heat source temperature. Furthermore, in natural convection, the addition of PCM and vapor chamber to the heat sink reduces the heat source temperature by a maximum of 33.1% and 9.5%, respectively, compared to a conventional heat sink. But in forced convection, the use of vapor chamber reduces the heat source temperature by 7.9% while the addition of PCM to the heat sink affects its performance adversely. In fact when fresh air is blown to the heat sink, it provides a higher temperature potential at all the surfaces.
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| 10. |
- Haidar, Mohammad, et al.
(författare)
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Thickness- and temperature-dependent magnetodynamic properties of yttrium iron garnet thin films
- 2015
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 117:17
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Tidskriftsartikel (refereegranskat)abstract
- The magnetodynamical properties of nanometer-thick yttrium iron garnet films are studied using ferromagnetic resonance as a function of temperature. The films were grown on gadolinium gallium garnet substrates by pulsed laser deposition. First, we found that the damping coefficient increases as the temperature increases for different film thicknesses. Second, we found two different dependencies of the damping on film thickness: at room temperature, the damping coefficient increases as the film thickness decreases, while at T = 8 K, we find the damping to depend only weakly on the thickness. We attribute this behavior to an enhancement of the relaxation of the magnetization by impurities or defects at the surfaces.
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