Optical Investigation of Sm<Superscript>3+</Superscript> Doped in Phosphate Glass

Samarium doped zinc-magnesium-phosphate glasses having composition (60 – x)P₂O₅–10MgO–30ZnO–xSm₂O₃ where x = 0.1, 0.3, 0.6, 1.0 mol % were prepared by melt quenching technique. Archimedes method was used to measure their densitieswhich are lying in the range 2.65–2.91 g/cm³. On the basis of the increasing trend in the density while increasing the content of Sm₂O₃ it can be concluded that the bridging oxygen is converted to non-bridging oxygen The UV-Vis absorption spectroscopy was carried on in the wavelength range 310–900 nm where the absorption spectra consist of six absorption peaks corresponding to the transitions from the ground state ⁶H_5/2 to various excited energy levels. The optical band gaps are calculated to be 3.93–4.41 eV, 3.31–3.73 eV and 0.27–0.29 eV for direct band gap, indirect band gap and Urbach energy, respectively. The physical parameters like oxygen packing density, refractive index, molar refractivity, metallization, and electronic polarizability are also studied. The Differential Scanning Calorimetry (DSC) technique is used to evaluate the thermal stability.     

Stable and reproducible synthesis of gold nanorods for biomedical applications: a comprehensive study

Gold nanorods (GNRs) are ideal choice in biomedical research due to their amenability of synthesis, tunable plasmonic properties, less toxicity and ease of detection but their diverse biological applications necessitate stable structure. Despite two decades'' efforts made towards reproducible anisotropic structures synthesis, still the kinetic control during GNRs growth has not been achieved. This study is an attempt to apprehend thermodynamic and kinetic parameters for synthesising mono‐disperse, reproducible and highly stable GNRs with desired aspect ratios. Effects of various growth parameters and assay steps on the facile and reproducible synthesis of GNRs are analysed. GNRs'' environmental and biological colloidal stability is studied through UV–Vis spectroscopy based particle instability parameter (PIP < 0.1). The authors hereby report GNRs with tunable longitudinal surface plasmon resonance (682–906 nm) having different aspect ratios (2.5–4.6) that are stable at 28–60°C; however, prolonged high temperature ( > 60°C) and alkaline pH can trigger colloidal instability. GNRs remain stable at higher salt concentration, physiological and slightly acidic pH. GNRs can be stored in 0.001 M cetyltrimethylammonium bromide for 3 months without compromising their stability. PEGylated GNRs are quite stable in cellular media solution (PIP < 0.1). With current optimised growth conditions, no aggregation at physiological pH and stability at high temperatures make GNRs an ideal candidate in biomedical applications.Inspec keywords: gold, nanorods, nanofabrication, nanomedicine, toxicology, thermodynamics, ultraviolet spectra, visible spectra, surface plasmon resonance, pH, cellular biophysicsOther keywords: nanorod synthesis, biomedical applications, tunable plasmonic properties, toxicity, reproducible anisotropic structures synthesis, thermodynamic parameters, kinetic parameters, GNR, biological colloidal stability, UV‐Vis spectroscopy, particle instability parameter, tunable longitudinal surface plasmon resonance, aspect ratios, alkaline pH, physiological pH, slightly acidic pH, cetyltrimethylammonium bromide, cellular media solution, optimised growth conditions, aggregation, wavelength 682 nm to 906 nm, time 3 month, Au     

Reversible data hiding in compressed and encrypted images by using Kd-tree

In this paper, a joint scheme and a separable scheme for reversible data hiding (RDH) in compressed and encrypted images by reserving room through Kd-tree were proposed. Firstly, the plain cover image was losslessly compressed and encrypted with lifting based integer wavelet transform (IWT) and set partition in hierarchical tree (SPIHT) encoding. Then, several shift operations were performed on the generated SPIHT bit-stream. The shifted bit-stream was restructured into small chunks and packed in the form of a large square matrix. The binary square matrix was exposed to Kd-tree with random permutations and reserving uniform areas of ones and zeros for secret data hiding. After that, a joint or a separable RDH scheme can be performed in these reserved spaces. In the joint RDH scheme, the secret data were embedded in the reserved spaces before encrypting with multiple chaotic maps. Thus, secret data extraction and cover image recovery were achieved together. In the separable RDH scheme, the secret data were embedded in the reserved spaces after encrypting with multiple chaotic maps. Since message extraction and cover image recovery are performed separately, anyone who has the embedding key can extract the secret message from the marked encrypted copy, while cannot recover the cover image. A complete encoding and decoding procedure of RDH for compressed and encrypted images was elaborated. The imperceptibility analysis showed that the proposed methods bring no distortion to the cover image because there was no change to the original cover image. The experimental results showed that the proposed schemes can perform better for secret data extraction and can restore the original image with 100% reversibility with much more embedding capacity and security. The proposed schemes significantly outperform the state-of-the-art RDH methods in the literature on compressed and encrypted images.

     

A secure mutual authenticated key agreement of user with multiple servers for critical systems

Recent technological advances in almost all critical systems’ domains have led to an explosive growth of multimedia big data. Those advances encompass the ever increasing innovative digital and remote mobile devices being operated on the users’ end. Due to the openness of critical system, the service providers in such networks are facing security challenges to authenticate those mobile devices on the field, and delivering services. In this scenario, the Multi-server authentication (MSA) framework seems to be a promising solution that enables its subscribers to avail services from different servers without getting registered to each server individually. In last few years many MSA protocols depending on RC-Offline authentication during mutual authentication, have been presented. However, to date, there is no efficient MSA scheme to our knowledge that is free of all three weaknesses, simultaneously. That is, 1) free from storage of server-based parameters (public keys or other values) in smart card by registration authority, 2) free from the assumption of publishing of server-based public keys publicly and 3) free from a single secret sharing with all servers so that it could avoid server masquerading (insider) attack. Considering these limitations, we present a multi-server authentication protocol that withstands above drawbacks using lightweight cryptographic operations. The rationale of the proposed work was to present an efficient RC-Offline MSA scheme. Our scheme is also backed by formal security analysis based on GNY logic and automated security verification using ProVerif tool.

     

Hesitant Fuzzy-Sets Based Decision-Making Model for Security Risk Assessment

Security is an important component in the process of developing healthcare web applications. We need to ensure security maintenance; therefore the analysis of healthcare web application's security risk is of utmost importance. Properties must be considered to minimise the security risk. Additionally, security risk management activities are revised, prepared, implemented, tracked, and regularly set up efficiently to design the security of healthcare web applications. Managing the security risk of a healthcare web application must be considered as the key component. Security is, in specific, seen as an add-on during the development process of healthcare web applications, but not as the key problem. Researchers must ensure that security is taken into account right from the earlier developmental stages of the healthcare web application. In this row, the authors of this study have used the hesitant fuzzy-based AHP-TOPSIS technique to estimate the risks of various healthcare web applications for improving security-durability. This approach would help to design and incorporate security features in healthcare web applications that would be able to battle threats on their own, and not depend solely on the external security of healthcare web applications. Furthermore, in terms of healthcare web application's security-durability, the security risk variable is measured, and vice versa. Hence, the findings of our study will also be useful in improving the durability of several web applications in healthcare.     

Data Reliability and Sensors Lifetime in Bridge Health Monitoring using LoRaWAN-Zigbee

The Wireless Sensor Network (WSN) is regarded as the fastest expanding technological trend in recent years due its application in a variety of sectors. In the monitoring region, several sensor nodes with various sensing capabilities are installed to gather appropriate data and communicate it to the gateway. The proposed system of the heterogeneous WSN employing LoRaWAN-Zigbee based hybrid communication is explored in this research study. To communicate in a network, two Long–Range Wide Area Network (LoRaWAN) sensor clusters and two Zigbee sensor clusters are employed, together with two Zigbee and LoRaWAN converters. The suggested Golden eagle shepherd optimization (GESO) method then forms Zigbee as well as LoRaWAN networking clusters. Furthermore, depending on energy usage and data packet size, the fitness of each sensor node is assessed using the Dynamic Intelligent Reasoning Based Neural (DIRN) approach. MATLAB software is used to implement and execute this study. When the Zigbee network’s transmission distance is 650 m and the LoRaWAN network’s transmission range is 3.5 km, the system can function with a packet loss rate of less than 0.04 percent. This study shows significant gains in the performance of the system when compared to traditional approaches based on digital findings obtained on software solutions.     

Effect of process parameters on droplet spreading behaviour over porous surface

Droplet spreading behaviour over a porous surface is a complex phenomenon, and is a basic component of many industrial processes, for example the spray coating process. The coating process has wide applications and this includes coating of urea fertilizer to produce slow release urea. The quality of coating film in such applications is affected by many factors, one of them being droplet spreading on the substrate. Droplet spreading behaviour is affected by process parameters such as viscosity, density, surface tension, impact velocity, porosity, etc. Droplet spreading on a porous surface involves penetration into the porous surface and spreading on the surface. Previously, the effect of individual process parameters has been studied. The current work aims at finding the interactive effect of process parameters on droplet spreading behaviour by using response surface methodology. The combined effect of liquid viscosity, impact velocity, and surface porosity has been studied on contact angle, spreading factor, and residual drop volume. The results show that minimum contact angle can be achieved with maximum impact velocity, minimum porosity, and minimal liquid viscosity. Similar behaviour was observed with droplet residual volume. Maximum spreading factor was attained at minimum viscosity and porosity while impact velocity was at maximum level.     

Influence of Nd-Co Substitution on Structural,Electrical, and Dielectric Properties of X-Type Hexagonal Nanoferrites

A series of single phase X-type hexagonal ferrites with concentration Sr_2?x Nd _x Ni₂Fe_28?y Co _y O₄₆ (x = 0.02, 0.04, 0.06, 0.08, 0.10 and y = 0.1, 0.2, 0.3, 0.4, 0.5) has been prepared by sol-gel method sintered at 1250 °C for 6 h. The x-ray diffraction analysis reveals the single phase of X-type hexagonal ferrites. The particle size was calculated by using SEM and TEM. The ferrite substituted with Nd³⁺ and Co²⁺ has average particle size in the range of 40-50 nm. The room temperature electrical resistivity experiences the significant enhancement from a value of 1.1 × 10⁷ to 2.03 × 10⁸ Ωcm with the increase in Nd³⁺ and Co²⁺ concentration. The dielectric constant exhibits high value at low frequencies and decreases with the increase of frequency. The tangent dielectric loss shows the abnormal behavior which can be explained on the basis of hopping between the Fe²⁺ and Fe³⁺ ions on octahedral sites. The maximum value of tangent loss at low frequencies reflects the application of these materials in medium frequency devices (MF).     

Improved ‘reduced volume’ method of analysis

The ‘reduced volume’ method for determining the cement content of hardened mortar or concrete samples has certain drawbacks. Here the authors describes improvements to the apparatus which had enabled more consistently accurate readings up to 0.01 cm of the volume of inert matter remaining after the usual RV test procedures. Dr Ahmad works at the Irrigation Research Institute in Lahore and Professor Iqbal is director of the Institute of Chemistry, Punjab University.     

System identification in a networked environment using second order statistical properties

System identification for networked control is considered. Due to the time-delays in the network, it can be difficult to work with a discrete-time model and a continuous-time model is therefore chosen. A covariance function based method that relies on the second order statistical properties of the output signal, where it is assumed that the input signal samples are from a discrete-time white noise sequence, is proposed for estimating the parameters. The method is easy to use since the actual time instants when new input signal levels are applied at the actuator do not have to be known. An analysis of the networked system and the effects of the time-delays is made, and the results of the analysis motivate and support the chosen approach. Numerical studies indicate that the method is robust to randomly distributed time-delays, packet drop-outs, and additive measurement noise.