off-State Degradation in Drain-Extended NMOS Transistors: Interface Damage and Correlation to Dielectric Breakdown

Off-state degradation in drain-extended NMOS transistors is studied. Carefully designed experiments and well-calibrated simulations show that hot carriers, which are generated by impact ionization of surface band-to-band tunneling current, are responsible for interface damage during off-state stress. Classical on-state hot carrier degradation has historically been associated with broken equivSi-H bonds at the interface. In contrast, the off-state degradation in drain-extended devices is shown to be due to broken equivSi-O- bonds. The resultant degradation is universal, which enables a long-term extrapolation of device degradation at operating bias conditions based on short-term stress data. Time evolution of degradation due to broken equivSi-O- bonds and the resultant universal behavior is explained by a bond-dispersion model. Finally, we show that, under off-state stress conditions, the interface damage that is measured by charge-pumping technique is correlated with dielectric breakdown time, as both of them are driven by broken equivSi-O- bonds.     

Using Sorted Switching Median Filter to remove high-density impulse noises

We propose a novel Sorted Switching Median Filter (i.e. SSMF) for effectively denoising extremely corrupted images while preserving the image details. The center pixel is considered as “uncorrupted” or “corrupted” noise in the detecting stage. The corrupted pixels that possess more noise-free surroundings will have higher processing priority in the SSMF sorting and filtering stages to rescue the heavily noisy neighbors. Five noise models are considered to assess the performance of the proposed SSMF algorithm. Several extensive simulation results conducted on both grayscale and color images with a wide range (from 10% to 90%) of noise corruption clearly show that the proposed SSMF substantially outperforms all other existing median-based filters.     

Facile Fabrication of PbS Nanocrystal:C60 Fullerite Broadband Photodetectors with High Detectivity

Hybrid PbS nanocrystal/C₆₀ fullerite photodetectors are fabricated using a simple one‐step drop casting procedure onto pre‐patterned interdigitated electrodes. The devices exhibit a broad spectral response from the near UV through to the near infrared yielding a detectivity, D*, of above 10¹⁰ Jones from 400 nm to ≈1050 nm. The ability to further extend the spectral response to wavelengths ≈1350 nm in the near infrared via tuning of the PbS nanocrystal diameter is also demonstrated. The dynamic responses of the devices are presented, exhibiting a fast photocurrent rise time (<40 ns) followed by a long bi‐exponential decay with characteristic lifetimes of τ₁ = 5.3 μs ± 0.1 μs and τ₂ = 37.8 μs ± 0.7 μs. These devices, which have a detectivity approaching that of commercial detectors, a broader spectral response, and a fast rise time, offer an attractive low‐cost solution for large‐area broadband photodetectors.     

Machine learning in vehicular networking: An overview

As vehicle complexity and road congestion increase, combined with the emergence of electric vehicles, the need for intelligent transportation systems to improve on-road safety and transportation efficiency using vehicular networks has become essential. The evolution of high mobility wireless networks will provide improved support for connected vehicles through highly dynamic heterogeneous networks. Particularly, 5G deployment introduces new features and technologies that enable operators to capitalize on emerging infrastructure capabilities. Machine Learning (ML), a powerful methodology for adaptive and predictive system development, has emerged in both vehicular and conventional wireless networks. Adopting data-centric methods enables ML to address highly dynamic vehicular network issues faced by conventional solutions, such as traditional control loop design and optimization techniques. This article provides a short survey of ML applications in vehicular networks from the networking aspect. Research topics covered in this article include network control containing handover management and routing decision making, resource management, and energy efficiency in vehicular networks. The findings of this paper suggest more attention should be paid to network forming/deforming decision making. ML applications in vehicular networks should focus on researching multi-agent cooperated oriented methods and overall complexity reduction while utilizing enabling technologies, such as mobile edge computing for real-world deployment. Research datasets, simulation environment standardization, and method interpretability also require more research attention.     

Efficient identity-based security schemes for ad hoc network routing protocols

Wireless ad hoc networks consist of nodes with no central administration and rely on the participating nodes to share network responsibilities. Such networks are more vulnerable to security attacks than conventional wireless networks. We propose two efficient security schemes for these networks that use pairwise symmetric keys computed non-interactively by the nodes which reduces communication overhead. We allow nodes to generate their broadcast keys for different groups and propose a collision-free method for computing such keys. We use identity-based keys that do not require certificates which simplifies key management. Our key escrow free scheme also uses identity-based keys but eliminates inherent key escrow in identity-based keys. Our system requires a minimum number of keys to be generated by the third party as compared to conventional pairwise schemes. We also propose an authenticated broadcast scheme based on symmetric keys and a corresponding signature scheme.     

A reliable energy-efficient pressure-based routing protocol for underwater wireless sensor network

Recently, Underwater Wireless Sensor Networks (UWSNs) has witnessed significant attention from both academia and industries in research and development, due to the growing number of applications for wide range of purposes including commercial, scientific, environmental and military. Some of the major applications include pollution monitoring, tactical surveillance, tsunami warnings and offshore exploration. Efficient communication among sensors in UWSNs is a challenging task due to the harsh environments and peculiar characteristics of UWSNs. Therefore, design of routing protocol for efficient communication among sensors and sink is one of the fundamental research themes in UWSNs. In this context, this paper proposes a location-free Reliable and Energy efficient Pressure-Based Routing (RE-PBR) protocol for UWSNs. RE-PBR considers three parameters including link quality, depth and residual energy for balancing energy consumption and reliable data delivery. Specifically, link quality is estimated using triangle metric method. A light weight information acquisition algorithm is developed for efficient knowledge discovery of the network. Multi-metric data forwarding algorithm is designed based on route cost calculation which utilizes residual energy and link quality. Simulations are carried out in NS-2 with Aqua-Sim package to evaluate the performance of RE-PBR. The performance of the proposed protocol is compared with the stat-of-the-art techniques: DBR and EEDBR. The comprehensive performance evaluation attests the benefit of RE-PBR as compared to the state-of-the-art techniques in terms of network lifetime, energy consumption, end-to-end delay and packet delivery ratio.     

Wide and multi-band reconfigurable Vivaldi antenna with slot-line feed

This paper presents a Vivaldi antenna. The antenna incorporates a slot-line feed, and is designed to operate in a wideband mode, along with four narrowband modes. The wideband mode extends from 1 to 3 GHz. A series of PIN diode switches is employed to reconfigure between the five different operating modes. Wideband-to-multiband reconfigurations are achieved by adjusting the antenna loading internally, and also by the incorporation of band-stop filters. To obtain the wideband mode, wideband matches load is used. On the other hand, to obtain the narrowband modes, two rectangular slits with narrowband matches load are used. The proposed Vivaldi antenna provides wideband operation. It is also supports operation within the LTE, GSM (L-band), GPS, and WiMAX bands.     

A churn prediction model for prepaid customers in telecom using fuzzy classifiers

The incredible growth of telecom data and fierce competition among telecommunication operators for customer retention demand continues improvements, both strategically and analytically, in the current customer relationship management (CRM) systems. One of the key objectives of a typical CRM system is to classify and predict a group of potential churners form a large set of customers to devise profitable and targeted retention campaigns for keeping a long-term relationship with valued customers. For achieving the aforementioned objective, several churn prediction models have been proposed in the past for the accurate identification of the customers who are prone to churn. However, these previously proposed models suffer from a number of limitations which place strong barriers towards the direct applicability of such models for accurate prediction. Firstly, the feature selection methods adopted in majority of the past work neglected the information rich variables present in call details record for model development. Secondly, selection of important features was done through statistical methods only. Although statistical methods have been applied successfully in diverse domains, however, these methods alone without the augmentation of domain knowledge have the tendency to yield erroneous results. Thirdly, the previous models have been validated mainly with benchmark datasets which do not provide a true representation of real world telecom data consisting of noise and large number of missing values. Fourthly, the evaluation measures used in the past neglected the True Positive (TP) rate, which actually highlights the ability of a model to correctly classify the percentage of churners as compared to non-churners. Finally, the classifiers used in the previous models completely neglected the use of fuzzy classification methods which perform reasonably well for data sets with noise. In this paper, a fuzzy based churn prediction model has been proposed and validated using a real data from a telecom company in South Asia. A number of predominant classifiers namely, Neural Network, Linear regression, C4.5, SVM, AdaBoost, Gradient Boosting and Random Forest have been compared with fuzzy classifiers to highlight the superiority of fuzzy classifiers in predicting the accurate set of churners.     

EMI Shielding Characteristics of Electrically Conductive Polymer Blends of PS/PANI in Microwave and IR Region

Conductive polymeric blends (CPBs) of polystyrene and polyaniline (PS/PANI) were prepared by solution casting method in various compositions. Film thickness of CPBs was achieved?～?250 micron. PS/PANI blend films were analyzed for electromagnetic interference (EMI) shielding characteristics in microwave and near-infrared (NIR) regions. PS/PANI blends showed remarkable features. Most mobile telecommunications use GHz frequency range and shielding effectiveness was observed in 9 GHz to 18 GHz. In 9 GHz to 18 GHz frequency range, 45 dB shielding effectiveness was measured. CPBs were also analyzed in the NIR region and showed transmittance of <1%. Microwaves and NIR radiation are the most abundant in the environment and cause damage to human health. Both types of radiation causes serious damage to electronic devices as well.

     

Gaining Insight into the Effect of Organic Interface Layer on Suppressing Ion Migration Induced Interfacial Degradation in Perovskite Solar Cells

Ion migration induced interfacial degradation is a detrimental factor for the stability of perovskite solar cells (PSCs) and hence requires special attention to address this issue for the development of efficient PSCs with improved stability. Here, an “S‐shaped, hook‐like” organic small molecule, naphthalene diimide derivative (NDI‐BN), is employed as a cathode interface layer (CIL) to tailor the [6,6]‐phenylC61‐butyric acid methylester (PCBM)/Ag interface in inverted PSCs. By realizing enhanced electron extraction capability via the incorporation of NDI‐BN, a peak power conversion efficiency of 21.32% is achieved. Capacitance–voltage measurements and X‐ray photoelectron spectroscopy analysis confirmed an obvious role of this new organic CIL in successfully blocking ionic diffusion pathways toward the Ag cathode, thereby preventing interfacial degradation and improving device stability. The molecular packing motif of NDI‐BN further unveils its densely packed structure with π–π stacking force which has the ability to effectually hinder ion migration. Furthermore, theoretical calculations reveal that intercalation of decomposed perovskite species into the NDI clusters is considerably more difficult compared with the PCBM counterparts. This substantial contrast between NDI‐BN and PCBM molecules in terms of their structures and packing fashion determines the different tendencies of ion migration and unveils the superior potential of NDI‐BN in curtailing interfacial degradation.