Advanced CAD tool for noise modeling of RF/microwave field effect transistors with large gate widths

In the millimeter-wave frequency range, electromagnetic (EM) effects can significantly influence a device behavior. As the core of modern communication systems, active devices such as field effect transistors (FETs) require up-to-date models to accurately integrate such effects, especially in terms of noise performance since most of communication systems operate in noisy environments. Furthermore, to keep low-noise amplification over a wide frequency band, the transistor noise resistance R_n must be substantially reduced to make the system insensitive to impedance matching. Since this can be realized through large gate-width devices, a novel large gate-width FET noise model is proposed which efficiently integrates EM wave propagation effects, one of the most important EM effects in mm-wave frequencies.     

Using an active resistive damper in hybrid active power filter to avoid resonance over-voltage

This paper presents a hybrid active power filter (HAPF) comprising an active resistive damper (ARD). The ARD consists of three resistances connected to the grid through three bi-directional electronic switches (IGBTs). The ARD can rapidly damp over voltages or over currents under resonance conditions, when the active part (inverter) of the HAPF is disconnected from the grid due to electrical or non-electrical failures. To drive the bi-directional electronic switches of the ARD, a control method is presented in this paper. The control method is based on comparison of resonance over voltage magnitude with a reference voltage (voltage protection level) to control the bi-directional electronic switches. Also the magnitude–frequency characteristics and the control method of the HAPF based on source current detection strategy are analyzed in detail in this paper. Performance of the HAPF with and without the ARD is analyzed in this paper and the results are compared with each other. Finally, the simulation results are provided to validate the proposed topology.     

Influence of prior cold working on the tribological behavior of Cu–0.65 wt.%Cr alloy

The influence of prior cold working on the friction and wear behavior of Cu–0.65 wt.%Cr alloy under dry sliding against a steel disk was investigated on a pin-on-disk wear tester. The worn surfaces and debrises of Cu–Cr alloy were analyzed by scanning electron microscope (SEM) and energy dispersive X-ray (EDX) spectrum. The results indicated that prior cold working and aging had an effect on the hardness and wear resistance of Cu–Cr alloy; in other words hardness and wear rate increased with the amount of cold working. At constant aging temperature, the wear rate of Cu–Cr alloys increase with cold working and reached maximum at 50% cold working. At constant amount of cold working aged specimens at 500 °C shows higher wear resistance than 450 °C. Crack initiation and propagation in the tribolayer and at the interface of subsurface and tribolayer was the dominant mechanism during the sliding process.     

An Iontronic Multiplexer Based on Spatiotemporal Dynamics of Multiterminal Organic Electrochemical Transistors

The seamless integration of electronics with biology requires new bio-inspired approaches that, analogously to nature, rely on the presence of electrolytes for signal multiplexing. On the contrary, conventional multiplexing schemes mostly rely on electronic carriers and require peripheral circuitry for their implementation, which imposes severe limitations toward their adoption in bio-applications. Here, a bio-inspired iontronic multiplexer based on spatiotemporal dynamics of organic electrochemical transistors (OECTs), with an electrolyte as the shared medium of communication, is shown. The iontronic system discriminates locally random-access events with no need of peripheral circuitry or address assignment, thus deceasing significantly the integration complexity. The form factors of OECTs that allow for intimate biointerfacing as well as the electrochemical nature of the communication medium, open new avenues for unconventional multiplexing in the emerging fields of bioelectronics, wearables, and neuromorphic computing or sensing.     

An optimization framework for multicasting in MCMR wireless mesh network with partially overlapping channels

This paper focuses on the problem of maximizing throughput in multicast routing in Multi-Channel, Multi-Radio (MCMR) wireless mesh network. We propose an optimization framework based on binary integer programming that minimizes interference in multicast communication. Our Multicasting with multiple Gateways and Partially Overlapped Channels (MG-POC) framework utilizes a rational node selection to construct multicast tree that increases network performance. MG-POC is efficient as it (1) constructs the paths between source and receivers with minimal number of data forwarding nodes; (2) employs multiple gateways to substantially reduce interference and usage of resources; (3) benefits from wireless broadcast advantage and partially overlapped channels in channel assignment; (4) solves channel assignment and tree construction problems simultaneously. A weakly decoupled approach is also presented which finds a nearly optimal solution for large network problems in a reasonably short amount of time. Our schemes are proved to offer a connected and loop-free tree; and their performance are well compared to that of several existing methods on different simulation scenarios. The results of our simulations also demonstrate that incorporating multi-gateway and partially overlapping channels has a significant impact on minimizing network interference which, in turn, dramatically enhances network throughput.     

The microstructural characterization of semi-solid slurries

Due to recent interest in semi-solid metal (SSM) processing, there is a need for fundamental knowledge on the formation and solidification of primary particles. The primary particle size, distribution, morphology, and percentage are the main concerns because particle quantity and size affect not only the mechanical properties of as-cast SSM parts but also the flow characteristics of SSM slurries during die filling. Microstructural characterization is a basic tool for measuring the critical parameters that influence the resulting properties. This article describes the tools and techniques available for structural analysis of SSM slurries. It also attempts to elucidate the ambiguities and interpretations of special structural features.     

Image compression using JPEG with reduced blocking effects via adaptive down-sampling and self-learning image sparse representation

Multimedia Tools and Applications - Blocking is an annoying effect in image compression using JPEG especially at low bit-rates. In this paper, a two-phase method is proposed for reducing JPEG...