Phosphorus implantation into 4H-silicon carbide

Sheet resistances in nitrogen- and phosphorus-implanted 4H-SiC are measured to assess the time and temperature dependencies of this variable. In 4H-SiC implanted with 3 × 10¹⁵ cm^?2 nitrogen ions to a depth of 2800 Å, the minimum sheet resistance observed is 534 Ω/□. The minimum sheet resistance in 4H-SiC implanted with 4 × 10¹⁵ cm^?2 phosphorus ions to a depth of 4000 Å is 51 Ω/□, a record low value for any implanted element into any polytype of SiC. Time-independent sheet resistances are observed following anneals at 1700°C for nitrogen and phosphorus samples. Lower temperature anneals produce sheet resistances which decrease monotonically with increasing time of anneal. Overall, sheet resistances from phosphorus-implanted 4H-SiC are an order of magnitude below those measured from nitrogen implanted samples. The response of phosphorus to low-temperature annealing is significant, and sheet resistances below 500 Ω/□ are achieved at 1200°C. Activation of phosphorus is attempted in an oxidizing atmosphere with and without prior argon annealing. A three-hour gate oxidation in wet O₂ at 1150°C, followed by a 30 min argon anneal, produced a sheet resistance of 1081 Ω/□. Oxidation after argon annealing caused sheet resistances to increase by about 20% compared to samples subjected solely to argon annealing. It is also found that oxide growth rates are much higher over phosphorus implanted than over unimplanted 4H-SiC. Reasons for the disparity in sheet resistances between nitrogen and phosphorus implants, and for the difference in oxide growth rates are suggested.     

The influence of grain size on the erosion rate of metals

The objective of this work was to understand the influence of grain size on solid impingement erosion behavior characterized by deformation at high strain rates and large strains. Experiments were carried out at a velocity of 40 m/s, impact angle of 90 deg with 300 to 450 μm steel shot as erodent on iron, copper, and titanium with varying grain sizes. The results indicate that the erosion rate is independent of grain size in iron and copper while it is apparently grain size dependent in titanium. The results are rationalized in terms of the negligible contribution of the Hall-Petch component to the flow stress at large strains in the case of copper and iron. The decreasing erosion rate in titanium with increasing grain size was due to the increased interstitial content picked up during thermal treatment and consequent increase in strain hardening and strain rate hardening and not due to increased grain sizeper se. Adiabatic shear bands were observed in coarse-grained iron under actual erosion conditions.     

Optimal repair stage for K-out-of-N systems

Optimization studies on reliability systems is currently a fascinating area of research. In recent investigations, optimization techniques have been extended to cover even more complex reliability systems with larger applicational scope. In this paper, we study a complex system in terms of a K-out-of-N system (for example, occuring in mass transmission and computer networks) with provision for a repair facility. We develop an optimization procedure to help identify the Optimal Repair Stage for the system under certain conditions. The applicational use of the theoretical results is illustrated through numerical work, specifically the negative exponential law governing stochastic repair times.     

Optimization of microstructure development during hot working using control theory

A new approach for controlling microstructure development during hot working processes is proposed. This approach is based on optimal control theory and involves state-space type models for describing the material behavior and the mechanics of the process. The effect of process control parameters such as strain, strain rate, and temperature on important microstructural features can be systematically formulated and then solved as an optimal control problem. This method has been applied to the optimization of grain size and process parameters such as die geometry and ram velocity during the extrusion of plain carbon steel. Experimental results of this investigation show good agreement with those predicted in the design stage.     

Simulating quantum transport in nanoscale MOSFETs: ballistic hole transport, subband engineering and boundary conditions

We present a modeling scheme for simulating ballistic hole transport in thin-body fully depleted silicon-on-insulator pMOSFETs. The scheme includes all of the quantum effects associated with hole confinement and also accounts for valence band nonparabolicity approximately. This simulator is used to examine the effects of hole quantization on device performance by simulating a thin (1.5-nm) and thick (5-nm) body double-gated pMOSFET in the ballistic limit. Two-dimensional electrostatic effects such as drain-induced barrier lowering (DIBL) and off-equilibrium transport are emphasized as part of this study. The effect of channel orientation on the device performance is examined by simulating pMOSFETs with channels directed along <100> and <110>. Simulated device characteristics for identical nMOSFETs and pMOSFETs are compared in order to explore the effects of subband engineering on CMOS technology. Novel floating boundary conditions used in simulating ballistic transport are highlighted and discussed.     

State-dependent current source stretches timer pulse widths

A new principle of a state-dependent current source has been presented which can usefully be employed with conventional timer circuits to obtain large time delays. Two schemes employing this principle, one using a Schmitt trigger and the other using a modified monostabic, have been described.     

An Optimized Novel Trust-Based Security Mechanism Using Elephant Herd Optimization

Routing strategies and security issues are the greatest challenges in Wireless Sensor Network (WSN). Cluster-based routing Low Energy adaptive Clustering Hierarchy (LEACH) decreases power consumption and increases network lifetime considerably. Securing WSN is a challenging issue faced by researchers. Trust systems are very helpful in detecting interfering nodes in WSN. Researchers have successfully applied Nature-inspired Metaheuristics Optimization Algorithms as a decision-making factor to derive an improved and effective solution for a real-time optimization problem. The metaheuristic Elephant Herding Optimizations (EHO) algorithm is formulated based on elephant herding in their clans. EHO considers two herding behaviors to solve and enhance optimization problem. Based on Elephant Herd Optimization, a trust-based security method is built in this work. The proposed routing selects routes to destination based on the trust values, thus, finding optimal secure routes for transmitting data. Experimental results have demonstrated the effectiveness of the proposed EHO based routing. The Average Packet Loss Rate of the proposed Trust Elephant Herd Optimization performs better by 35.42%, by 1.45%, and by 31.94% than LEACH, Elephant Herd Optimization, and Trust LEACH, respectively at Number of Nodes 3000. As the proposed routing is efficient in selecting secure routes, the average packet loss rate is significantly reduced, improving the network’s performance. It is also observed that the lifetime of the network is enhanced with the proposed Trust Elephant Herd Optimization.     

Blockchain: Secured Solution for Signature Transfer in Distributed Intrusion Detection System

Exchange of data in networks necessitates provision of security and confidentiality. Most networks compromised by intruders are those where the exchange of data is at high risk. The main objective of this paper is to present a solution for secure exchange of attack signatures between the nodes of a distributed network. Malicious activities are monitored and detected by the Intrusion Detection System (IDS) that operates with nodes connected to a distributed network. The IDS operates in two phases, where the first phase consists of detection of anomaly attacks using an ensemble of classifiers such as Random forest, Convolutional neural network, and XGBoost along with genetic algorithm to improve the performance of IDS. The novel attacks detected in this phase are converted into signatures and exchanged further through the network using the blockchain framework in the second phase. This phase uses the cryptosystem as part of the blockchain to store data and secure it at a higher level. The blockchain is implemented using the Hyperledger Fabric v1.0 and v2.0, to create a prototype for secure signature transfer. It exchanges signatures in a much more secured manner using the blockchain architecture when implemented with version 2.0 of Hyperledger Fabric. The performance of the proposed blockchain system is evaluated on UNSW NB15 dataset. Blockchain performance has been evaluated in terms of execution time, average latency, throughput and transaction processing time. Experimental evidence of the proposed IDS system demonstrates improved performance with accuracy, detection rate and false alarm rate (FAR) as key parameters used. Accuracy and detection rate increase by 2% and 3% respectively whereas FAR reduces by 1.7%.     

Spent cumin seeds generated from ayurvedic industry as a source of bioactive compounds for nutraceutical/functional food applications

Spent cumin (SC) generated from the ayurvedic medicine industry was screened for essential oil, oleoresin and dietary fiber content; and compared with fresh cumin (FC). Significant amount of essential oil and oleoresin was retained in SC as compared to FC. The composition of essential oil from SC and FC were significantly different as evident from GC and GC/MS analysis. Percentage retention of the major flavor compound in cumin, cuminaldehyde, in SC was 80.05% with respect to that of FC. Essential oil from SC exhibited promising antimicrobial activities. Essential oil from SC inhibited C. tropicalis fungi (zone of inhibition 44 ± 2.25 mm), which was better than the standard drug clotrimazole. The oleoresin, soluble and insoluble dietary fiber contents of SC were 6.43, 5.36, and 66.1%, respectively. Soluble dietary fiber from SC exhibited potential water holding and swelling capacities and has better prebiotic properties, suggesting application as a functional food ingredient.

Practical applications

Value addition of agro‐industrial waste pertain great interest for research, as it is a probable source of bioactive phytochemicals. Spent cumin generated from the ayurvedic medicine industry was screened for bioactive components; and compared with fresh cumin. The study indicates that the cumin seed residue from industries could be utilized for further value addition for the recovery of essential oil, oleoresin, and antioxidant dietary fiber. The present work is of great significant to food/pharmaceutical industries in terms of better utilization of natural resources for sustainable development and to address the issue of environmental pollution by better management of industrial waste.