Independent control of the frequency and condition of oscillation: a caution

Over the years researchers have developed and reported a huge number of sinusoidal oscillator circuits and classified them, according to the tunability of their frequencies of oscillation, as enjoying independent control of the frequency and condition of oscillation. This classification is based on obtaining the frequency and the condition of oscillation using the Barkhausen criterion. This article serves as a caution as it appears that this classification is incorrect. Experimental and SPICE simulation results that support this caution are included.     

Convolution-based global simulation technique for millimeter-wave photodetector and photomixer circuits

A fast convolution-based time-domain approach to global photonic-circuit simulation is presented that incorporates a physical device model in the complete detector or mixer circuit. The device used in the demonstration of this technique is a GaAs metal-semiconductor-metal (MSM) photodetector that offers a high response speed for the detection and generation of millimeter waves. Global simulation greatly increases the accuracy in evaluating the complete circuit performance because it accounts for the effects of the millimeter-wave embedding circuit. Device and circuit performance are assessed by calculating optical responsivity and bandwidth. Device-only simulations using GaAs MSMs are compared with global simulations that illustrate the strong interdependence between device and external circuit.     

Modeling of concrete cracking—A hybrid technique of using displacement discontinuity element method and direct boundary element method

This paper presents a new approach by making use of a hybrid method of using the displacement discontinuity element method and direct boundary element method to model concrete cracking by incorporating fictitious crack model. Fracture mechanics approach is followed using the Hillerborg's fictitious crack model. A boundary element based substructure method and a hybrid technique of using displacement discontinuity element method and direct boundary element method are compared in this paper. In order to represent the process zone ahead of the crack, closing forces are assumed to act in such a way that they obey a linear normal stress-crack opening displacement law. Plain concrete beams with and without initial crack under three-point loading were analyzed by both the methods. The numerical results obtained were shown to agree well with the results from existing finite element method. The model is capable of reproducing the whole range of load–deflection response including strain-softening and snap-back behavior as illustrated in the numerical examples.     

Effect of Al concentration on photoluminescence properties of sol-gel derived hydrogen annealed ZnO

The effect of the Al/Zn atomic ratio on the photoluminescence properties of hydrogen annealed undoped and Al rich ZnO (AZO) films was studied. The Al/Zn atomic ratios in the AZO films were varied from 0 to 40%. All the AZO films exhibited three peaks in the UV, green and red regions, whereas the undoped ZnO films had two peaks in the UV and green regions. The PL intensity in the UV and red regions increased with an increase in Al concentrations. The highest PL intensity in the UV region was observed in the 20% Al/Zn atomic ratio due to improvement in crystal quality which was also confirmed by XRD measurements. The PL emission in the red region was due to complex luminescent centers like (V_zn-Al_zn)^?. A blue shift was seen in the red region with the introduction of Al. The 20% AZO films obtained the strongest signal at ?420 cm^?1, whereas no FTIR signal was observed at 420 cm^?1 in undoped ZnO. The bond signature at ?420 cm^?1 might be responsible for the highest PL intensity in NBE and red regions.     

A Blockchain-Based Architecture for Securing Industrial IoTs Data in Electric Smart Grid

There are numerous internet-connected devices attached to the industrial process through recent communication technologies, which enable machine-to-machine communication and the sharing of sensitive data through a new technology called the industrial internet of things (IIoTs). Most of the suggested security mechanisms are vulnerable to several cybersecurity threats due to their reliance on cloud-based services, external trusted authorities, and centralized architectures; they have high computation and communication costs, low performance, and are exposed to a single authority of failure and bottleneck. Blockchain technology (BC) is widely adopted in the industrial sector for its valuable features in terms of decentralization, security, and scalability. In our work, we propose a decentralized, scalable, lightweight, trusted and secure private network based on blockchain technology/smart contracts for the overhead circuit breaker of the electrical power grid of the Al-Kufa/Iraq power plant as an industrial application. The proposed scheme offers a double layer of data encryption, device authentication, scalability, high performance, low power consumption, and improves the industry’s operations; provides efficient access control to the sensitive data generated by circuit breaker sensors and helps reduce power wastage. We also address data aggregation operations, which are considered challenging in electric power smart grids. We utilize a multi-chain proof of rapid authentication (McPoRA) as a consensus mechanism, which helps to enhance the computational performance and effectively improve the latency. The advanced reduced instruction set computer (RISC) machines ARM Cortex-M33 microcontroller adopted in our work, is characterized by ultra-low power consumption and high performance, as well as efficiency in terms of real-time cryptographic algorithms such as the elliptic curve digital signature algorithm (ECDSA). This improves the computational execution, increases the implementation speed of the asymmetric cryptographic algorithm and provides data integrity and device authenticity at the perceptual layer. Our experimental results show that the proposed scheme achieves excellent performance, data security, real-time data processing, low power consumption (70.880 mW), and very low memory utilization (2.03% read-only memory (RAM) and 0.9% flash memory) and execution time (0.7424 s) for the cryptographic algorithm. This enables autonomous network reconfiguration on-demand and real-time data processing.     

Synthesis and characterization of manganese containing mesoporous bioactive glass nanoparticles for biomedical applications

Mesoporous bioactive glass (BG) nanoparticles based in the system: SiO₂–P₂O₅–CaO–MnO were synthesized via a modified Stöber process at various concentrations of Mn (0–7 mol %). The synthesized manganese-doped BG nanoparticles were characterized in terms of morphology, composition, in vitro bioactivity and antibacterial activity. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) analysis confirmed that the particles had spherical morphology (mean particle size: 110?nm) with disordered mesoporous structure. Energy dispersive X-ray spectroscopy (EDX) confirmed the presence of Mn, Ca, Si and P in the synthesized Mn-doped BG particles. Moreover, X-ray diffraction (XRD) analysis showed that Mn has been incorporated in the amorphous silica network (bioactive glass). Moreover, it was found that manganese-doped BG particles form apatite crystals upon immersion in simulated body fluid (SBF). Inductively coupled plasma atomic emission spectroscopy (ICP-OES) measurements confirmed that Mn is released in a sustained manner, which provided antibacterial effect against Bacillus subtilis, Pseudomonas aeruginosa and Staphylococcus aureus. The results indicate that the incorporation of Mn in the bioactive glass network is an effective strategy to develop novel multifunctional BG nanoparticles for bone tissue engineering.     

WSe2 Homojunction Devices: Electrostatically Configurable as Diodes,MOSFETs, and Tunnel FETs for Reconfigurable Computing

In this paper, electrostatically configurable 2D tungsten diselenide (WSe₂) electronic devices are demonstrated. Utilizing a novel triple‐gate design, a WSe₂ device is able to operate as a tunneling field‐effect transistor (TFET), a metal–oxide–semiconductor field‐effect transistor (MOSFET) as well as a diode, by electrostatically tuning the channel doping to the desired profile. The implementation of scaled gate dielectric and gate electrode spacing enables higher band‐to‐band tunneling transmission with the best observed subthreshold swing (SS) among all reported homojunction TFETs on 2D materials. Self‐consistent full‐band atomistic quantum transport simulations quantitatively agree with electrical measurements of both the MOSFET and TFET and suggest that scaling gate oxide below 3 nm is necessary to achieve sub‐60 mV dec^?1 SS, while further improvement can be obtained by optimizing the spacers. Diode operation is also demonstrated with the best ideality factor of 1.5, owing to the enhanced electrostatic control compared to previous reports. This research sheds light on the potential of utilizing electrostatic doping scheme for low‐power electronics and opens a path toward novel designs of field programmable mixed analog/digital circuitry for reconfigurable computing.     

Cost-Effective Low Vt Ni-FUSI CMOS on SiON by Means of Al Implant (pMOS) and Yb+P Coimplant (nMOS)

Low V_t Ni fully silicided (FUSI) devices are demonstrated making use of Al implantation for pMOS and Yb or Yb+P implantation for nMOS combined with Ni-silicide phase engineering. When Yb(+P) and Al implantation are followed by a high temperature anneal, significant segregation of Yb or Al toward the Ni-FUSI/SiON interface is observed and large Vt shifts of 450 mV (330 mV) and 200 mV are obtained for nMOS NiSi FUSI/SiON devices and pMOS Ni-rich FUSI/SiON devices, respectively, as compared to the undoped reference devices. The Vt shifts are preserved down to the shortest gate lengths. For both Al and Yb, the V_t shifts are explained by the dopants reacting with and modifying the dielectric. Thus, the low V_t dual implantation approach proposed achieves a low-cost "dual dielectric" implementation without the need of dual deposition of dielectrics or capping layers. In the case of Yb implantation followed by a high temperature anneal, a significant reduction in the inversion dielectric thickness is observed, indicating that the reaction between Yb and SiON results in the formation of a high-k dielectric. The Yb diffusion and reaction at the interface can be engineered using a P coimplant.     

Boundary element analysis of reinforced concrete structural elements

A simple and practical technique for the discrete representation of reinforcement in two-dimensional boundary element analysis of reinforced concrete structural elements is presented. The bond developed over the surface of contact between the reinforcing steel and concrete is represented using fictitious one-dimensional spring elements. Potentials of the model developed are demonstrated using a number of numerical examples. The results are seen to be in good agreement with the results obtained using standard finite element software.     

Molecular Dynamics Modeling of Latent Heat Enhancement in Nanofluids

A discrete computational approach based on molecular dynamics (MD) simulations is proposed for evaluating the latent heat of vaporization of nanofluids. The computational algorithm, which considers the interaction of the solid and the fluid molecules, is used for obtaining the enhancement of the latent heat of a base fluid due to the suspension of nanoparticles. The method is validated by comparing the computed latent heat values of water with standard values at different saturation temperatures. Simulation of a water–platinum nanofluid system is performed, treating the volume fraction and size of nanoparticles as parameters. The trends in the variation are found to match well with experimental results on nanofluids. Discussions are also presented on the limitations of the proposed model, and on methods to overcome them.