Cloud computing is a fast-growing industry that offers various online services, including software, computing resources, and databases. Its payment model is usage-based, whereas consistency is based ...on resource-sharing. Cloud storage is popular among individuals and businesses because it reduces cost, increases productivity, boosts performance, and improves security. However, cloud computing comes with security risks as data are stored with third-party providers, and Internet access limits visibility and control. Effective data security and data protection are key issues compared with traditional on-premise computing. There are several methods for ensuring data security in the cloud, of which cryptography is the most important. Cryptography offers a range of security features including authentication, confidentiality, integrity, and availability. However, a thorough examination of the different cryptography methods in a single study is lacking. This study comprehensively examined different cryptography methods, including deoxyribose nucleic acid (DNA), elliptic curve, homomorphic, hybrid, lightweight, and novel methods. The analysis addresses their methodology, algorithms, results, applications, and limitations and provides valuable suggestions for data security in the cloud. This paper proposes the use of elliptic curve cryptography (ECC) to ensure safe communication and lightweight cryptography for Internet of Things (IoT) devices with limited resources. This emphasizes the benefit of combining asymmetric security with symmetric efficiency in hybrid cryptography.
Radio bursts from the solar corona can provide clues to forecast space-weather hazards. After recent technology advancements, regular monitoring of radio bursts has increased and large observational ...datasets are produced. Hence, manual identification and classification of them is a challenging task. In this article, we describe an algorithm to automatically identify radio bursts from dynamic solar radio spectrograms using a novel statistical method. We use e-CALLISTO (
Compound Astronomical Low Cost Low Frequency Instrument for Spectroscopy and Transportable Observatory
) radio spectrometer data obtained at Gauribidanur Observatory near Bangalore in India during 2013 – 2014. We have studied the classifier performance using the receiver operating characteristics. Further, we analyze type III bursts observed in the year 2014 and find that
75
%
of the observed bursts were below 200 MHz. Our analysis shows that the positions of flare sites, which are associated with the type III bursts with upper frequency cutoff
≳
200
MHz originate close to the solar disk center.
We report low-frequency observations of quasi-periodic, circularly polarized, harmonic type III radio bursts whose associated sunspot active regions were located close to the solar limb. The measured ...periodicity of the bursts at 80 MHz was approx =5.2 s, and their average degree of circular polarization (dcp) was approx =0.12. We calculated the associated magnetic field B (1) using the empirical relationship between the dcp and B for the harmonic type III emission, and (2) from the observed quasi-periodicity of the bursts. Both the methods result in B approx = 4.2 G at the location of the 80 MHz plasma level (radial distance r approx = 1.3 R sub(middot in circle)) in the active region corona.
We report ground based, low frequency heliograph (80 MHz), spectral (85-35 MHz), and polarimeter (80 and 40 MHz) observations of drifting, non-thermal radio continuum associated with the "halo" ...coronal mass ejection that occurred in the solar atmosphere on 2013 March 15. The magnetic field strengths (B) near the radio source were estimated to be B approximately 2.2 approximately 0.4 G at 80 MHz and B approximately 1.4 + or - 0.2 G at 40 MHz. The corresponding radial distances (r) are r approximately 1.9 Rmiddot in circle (80 MHz) and r approximately 2.2 Rmiddot in circle (40 MHz).
Abstract This paper investigates the mechanical properties and corrosion behavior of Metal Matrix Composites prepared using Al7075 alloy as a matrix, Silicon Carbide and Titanium Carbide as ...reinforcement particles. Two step stir casting process was used to fabricate the composites by varying volume fractions of Silicon Carbide and Titanium Carbide (0 to 15 vol. %). Microstructural analysis, mechanical and corrosion behavior were used to evaluate the performance of the composites. Uniform distribution of reinforcement particle was observed through optical photomicrographs. Vickers micro hardness tests were performed and the hardness values were increased with an increase in reinforcement from 0 to 15 vol. %. The tensile strength of the 10 vol. % of aluminum hybrid matrix composite was better than that of the base alloy. In 3.5% NaCl solution, it was observed that the 15 vol. % of the aluminum hybrid matrix composite have higher corrosion resistance in comparison the base alloy.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Hard disk drives (HDDs) are used as secondary storage in digital electronic devices owing to low cost and large data storage capacity. Due to the exponentially increasing amount of data, there is a ...need to increase areal storage densities beyond ~1 Tb/in
. This requires the thickness of carbon overcoats (COCs) to be <2 nm. However, friction, wear, corrosion, and thermal stability are critical concerns below 2 nm, limiting current technology, and restricting COC integration with heat assisted magnetic recording technology (HAMR). Here we show that graphene-based overcoats can overcome all these limitations, and achieve two-fold reduction in friction and provide better corrosion and wear resistance than state-of-the-art COCs, while withstanding HAMR conditions. Thus, we expect that graphene overcoats may enable the development of 4-10 Tb/in
areal density HDDs when employing suitable recording technologies, such as HAMR and HAMR+bit patterned media.
Dissipation Scale Lengths of Solar Wind Turbulence Raja, K. Sasikumar; Subramanian, Prasad; Ingale, Madhusudan ...
Astrophysical journal/The Astrophysical journal,
02/2019, Letnik:
872, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Knowing the lengthscales at which turbulent fluctuations dissipate is key to understanding the nature of weakly compressible magnetohydrodynamic turbulence. We use radio wavelength interferometric ...imaging observations that measure the extent to which distant cosmic sources observed against the inner solar wind are scatter-broadened. We interpret these observations to determine that the dissipation scales of solar wind density turbulence at heliocentric distances of 2.5-20.27 R range from 13500 to 520 m. Our estimates from 10 to 20 R suggest that the dissipation scale corresponds to the proton gyroradius. They are relevant to in situ observations to be made by the Parker Solar Probe and are expected to enhance our understanding of solar wind acceleration.
Abstract
Eruptive activity in the solar corona can often lead to the propagation of shock waves. In the radio domain the primary signature of such shocks are type II radio bursts, observed in dynamic ...spectra as bands of emission slowly drifting toward lower frequencies over time. These radio bursts can sometimes have an inhomogeneous and fragmented fine structure, but the cause of this fine structure is currently unclear. Here we observe a type II radio burst on 2019 March 20th using the New Extension in Nançay Upgrading LOFAR, a radio interferometer observing between 10–85 MHz. We show that the distribution of size scales of density perturbations associated with the type II fine structure follows a power law with a spectral index in the range of
α
= −1.7 to −2.0, which closely matches the value of −5/3 expected of fully developed turbulence. We determine this turbulence to be upstream of the shock, in background coronal plasma at a heliocentric distance of ∼2
R
⊙
. The observed inertial size scales of the turbulent density inhomogeneities range from ∼62 Mm to ∼209 km. This shows that type II fine structure and fragmentation can be due to shock propagation through an inhomogeneous and turbulent coronal plasma, and we discuss the implications of this on electron acceleration in the coronal shock.
We obtain scatter-broadened images of the Crab Nebula at 80 MHz as it transits through the inner solar wind in 2017 and 2016 June. These images are anisotropic, with the major axis oriented ...perpendicular to the radially outward coronal magnetic field. Using these data, we deduce that the density modulation index ( ) caused by turbulent density fluctuations in the solar wind ranges from to between 9 and 20 R . We also find that the heating rate of solar wind protons at these distances ranges from to . On two occasions, the line of sight intercepted a coronal streamer. We find that the presence of the streamer approximately doubles the thickness of the scattering screen.
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