Synergistic microwave and structural studies of C-type Ho2Si2O7

Ho₂Si₂O₇ material exists in four polymorphs, a triclinic low temperature phase (type-B), a monoclinic modification (type-C), high temperature monoclinic (type-D), and high temperature orthorhombic modification (type-E). The structural properties are measured by XRD and the morphology is noted through scanning electron microscopy (SEM). The dc electrical resistivity (ρ) as a function of temperature and dielectric properties of C-type Ho₂Si₂O₇ in the microwave region is measured. The activation energy is calculated from ln ρ versus 1/k_BT plot. The activation energy is 0.119 ± 0.001 eV. Both the real (?′) and imaginary parts of permittivity (?″) decrease slightly as the frequency increases up to 1.5 GHz, after that ?′ increases while ?″ decreases as the frequency increases. At around 2.45 GHz, resonance is observed.     

Structural and microwave absorption properties of Ni(1−x)Co(x)Fe2O4 (0.0 ≤ x ≤ 0.5) nanoferrites synthesized via co-precipitation route

Ni-Co nanoferrites show excellent magneto-dielectric properties and these materials can be used to miniaturize the size of the high frequency devices which is the order of the day. Nanocrystalline Ni-Co ferrites having general formula Ni_1−xCo_xFe₂O₄ (x = 0.0, 0.1, 0.2, 0.3, 0.4, and 0.5) were prepared by co-precipitation method. The structural morphology of the prepared samples was carried out using scanning electron microscopy. The results showed the spherical shaped nanoparticles varying in the range of 16-40 nm. The complex relative permittivity (?_r) and complex relative permeability (μ_r) were measured using vector network analyzer for all the samples in the frequency range of 1 MHz to 3 GHz. The variation of complex relative permittivity (?_r) as a function of frequency is explained in accordance with Maxwell-Wagner model and Koop's phenomenological theory. The effect of frequency and cobalt concentration on permeability are reported. The reflectivity (R) of nanoferrites is also calculated. The value of minimum reflection loss (RL) is about −18 dB at 2.45 GHz with a thickness of 2.1 ± 0.1 mm. The results indicate that Ni_1−xCo_xFe₂O₄ nanoparticles have excellent microwave absorbing properties and have a great potential for military use.     

Time-based DDoS attack detection through hybrid LSTM-CNN model architectures: An investigation of many-to-one and many-to-many approaches

Internet data thefts, intrusions and DDoS attacks are some of the big concerns for the network security today. Detection of these anomalies, is gaining tremendous impetus with the development of machine learning and artificial intelligence. Even now researchers are shifting the base from machine learning to the deep neural architectures with auto-feature selection capabilities. We in this paper propose multiple deep neural network architectures which can select, co-learn and teach the gradients of the neural network by itself with no human intervention. This is what we call as meta-learning. The models are configured in both many to one and many to many design architectures. We combine long short-term memory (LSTM), bi-directional long short-term memory (BiLSTM), convolutional neural network (CNN) layers along with attention mechanism to achieve the higher accuracy values among all the available deep learning model architectures. LSTMs overcomes the vanishing and exploding gradient problem of RNN and attention mechanism mimics the human cognitive attention that screens the network flow to obtain the key features for network traffic classification. In addition, we also add multiple convolutional layers to get the key features for network traffic classification. We get the time series analysis of the traffic done for the possibility of a DDoS attack without using any feature selection techniques and without balancing the dataset. The performance analysis is done based on confusion matrix scores, that is, accuracy, false alarm rate (FAR), sensitivity, specificity, false-positive rate (FPR), F1 score, area under curve (AUC) analysis and loss functions on well-known public benchmark KDD Cup'99 data set. The results of our experiments reveal that our models outperform existing techniques, showing their superiority in performance.     

Biaxial stress relaxation of high impact polystyrene (HIPS) above the glass transition temperature

A procedure was developed and experiments were performed to measure the biaxial stress relaxation of High Impact Polystyrene (HIPS) sheets above the glass transition temperature. Tests were performed at various temperatures and strain magnitudes. The data were normalized to unity at time zero to isolate the time dependence of the stress from the strain dependence. The results show that the time dependent biaxial stress relaxation properties were independent of the magnitude of the stress or strain for small strains. The stress relaxation curves were fitted to a Prony series and i1 was found that time‐temperature superposition could be applied to interpolate the normalized relaxation. Uniaxial stress relaxation tests were also performed and the results were compared to that of the biaxial testing program.     

Fabrication and Characterization of Matrix-Type Transdermal Patches Loaded with Ramipril and Repaglinide Through Cellulose-based Hydrophilic and Hydrophobic Polymers: In Vitro and Ex Vivo Permeation Studies

Transdermal patches loaded with ramipril and repaglinide were prepared with the ambition to develop matrix-type transdermal drug delivery system for enhanced permeability and hence improved bioavailability. Different formulations were designed by intermittent concentrations of hydroxypropyl methylcellulose K4M as hydrophilic polymer and ethyl cellulose as hydrophobic polymer. Solvent casting method was used for the fabrication of transdermal patches. Oleic acid and propylene glycol were used to enhance permeability along with polyethylene glycol 400 as plasticizer. Newly designed patches were then evaluated for various physicochemical and mechanical properties. Compatibility studies were performed by Fourier transformed infrared spectroscopy which did not reveal any interaction between drug and polymers. Crystalline nature of drugs was confirmed when they were subjected to X-ray diffraction study and surface morphological studies using scanning electron microscopy. Transdermal patches were of good mechanical strength with folding endurance of more than 300-fold and 100% flatness. Percent drug contents of ramipril and repaglinide ranged from 90 to 105%, i.e., analogous to official limits. In vitro and ex vivo permeation studies were executed using franz diffusion cell. The cumulative amount of drug permeated through skin was 55.22–112.72% for repaglinide and 73.14–91.46% for ramipril. The release behavior of the permeated drug was analyzed by the application of model-dependent approaches. The results showed that Korsmeyer–Peppas model was found to be dominating in most of the formulations and drugs followed diffusion mechanism. It could be concluded that hydroxypropyl methylcellulose K4M and ethyl cellulose has great potential for ramipril and repaglinide as a vector for transdermal drug delivery effectively because of the formation of smooth surfaces of patches, high folding endurance, and entrapment efficiency with the ability to release the drugs in sustained manner.     

CPU–RAM-based energy-efficient resource allocation in clouds

The Journal of Supercomputing - Cloud computing provides online services and solutions for dynamic and on-demand resource provisioning. These resources consume high energy leading to higher...     

Microwave Absorption Properties of Radar Absorbing Nanosized Cobalt Ferrites for High Frequency Applications

Radar absorbing materials of nickel-cobalt ferrites (NCF) of general formula Ni_(1?x)Co_(x)Fe₂O₄ (0.0≤x≤0.5, in step of 0.1) were synthesized by the coprecipitation route. X-ray diffraction studies confirmed that all the samples exhibit the single-phase cubic spinel structure. The average particle size of as obtained samples has been found in the range of 38–41 nm. The structural morphology of the prepared samples was carried out using SEM. SEM images indicated that the final product consists of nanorods with a diameter of about 80 nm and length up to about 150 nm, and their chemical compositions were measured using the energy dispersive spectroscopy (EDS) technique. The infrared spectra are measured in the frequency range 700–350 cm^?1. Furthermore, the influence of Co on the magnetic and microwave absorbance characteristics by using VSM and network analyzer of Ni_(1?x)Co_(x)Fe₂O₄ (0.0≤x≤0.5 nanoparticles has been investigated respectively in detail. Our experimental results show that the low loss Ni substituted Co ferrites is an excellent magnetic material for VHF (very high frequency: 30–300 MHz) miniature antenna applications.