Orthogonally polarized RF optical single sideband generation with integrated ring resonators

We review recent work on narrowband orthogonally polarized optical RF single sideband generators as well as dualchannel equalization,both based on high-Q integrated ring resonators.The devices operate in the optical telecommunications C-band and enable RF operation over a range of either fixed or thermally tuneable frequencies.They operate via TE/TM mode birefringence in the resonator.We achieve a very large dynamic tuning range of over 55 dB for both the optical carrier-to-sideband ratio and the dual-channel RF equalization for both the fixed and tunable devices.     

A network selection method for handover in vehicle-to-infrastructure communications in multi-tier networks

Network selection is very important for a successful handover in a multi-tier heterogeneous networks. However, the primary challenges currently faced by research community is the lack of availability of network information at the mobile node side for efficiently select the most appropriate target network. It is practically difficult for an UE to get network information from base stations/access point of the neighbouring networks before connecting to them. In response to this, this paper proposes a network selection method that applies the knowledge of mobility data and the network load information to carry out an efficient handover for vehicle-to-infrastructure communication over multi-tier heterogeneous networks. We first derive key parameters, such as relative direction index, proximity index, residence time index, and network load index to select the best candidate network. A moving vehicle would be able to select the most appropriate target network by selecting one or more of the above parameters. We then test our algorithms by developing a dual mode vehicle On-Board Unit equipped with both Long Term Evolution-Advanced (LTE-A) and Wi-Fi network interface cards in OPNET simulator. The performance of the proposed handover method is evaluated by extensive OPNET-based simulation experiments. In the simulation model, we consider a multi-tier heterogeneous network comprising of a macro and multiple small cells of LTE-A and IEEE 802.11n technologies. Results show that our proposed handover method offers about 50% higher throughput and up to 43% higher packet delivery ratio than the conventional received signal strengths based network selection method.

     

Designing Energy Efficient Strategies Using Markov Decision Process for Crowd-Sensing Applications

Mobile Networks and Applications - In mobile crowd-sensing, smartphone users take part in sensing and then share the data to the server (cloud) and get an incentive. These data can be utilized for...     

Additive Functionalization and Embroidery for Manufacturing Wearable and Washable Textile Supercapacitors

Electronic textiles require rechargeable power sources that are highly integrated with textiles and garments, thereby providing outstanding durability and washability. In contrast, present power sources fabricated using conventional ex situ strategies are difficult to integrate with clothing and can degrade during garment washing. Here, a new manufacturing strategy named additive functionalization and embroidery manufacturing (AFEM) is reported, which enables textile‐based supercapacitors (TSCs) to be directly fabricated on woven, knitted, and nonwoven fabrics. The additive principle of AFEM allows developing TSCs with different types of electrode materials, device architectures, pattern designs, and array connections. High‐machine‐speed, programmable‐design industrial embroidering equipment is used to fabricate TSCs with high areal energy storage and power capabilities, which are retained during many cycles of severe mechanical deformation and industrial laundering with waterproof encapsulation.     

ECC-CoAP: Elliptic Curve Cryptography Based Constraint Application Protocol for Internet of Things

Constraint Application Protocol (CoAP), an application layer based protocol, is a compressed version of HTTP protocol that is used for communication between lightweight resource constraint devices in Internet of Things (IoT) network. The CoAP protocol is generally associated with connectionless User Datagram Protocol (UDP) and works based on Representational State Transfer architecture. The CoAP is associated with Datagram Transport Layer Security (DTLS) protocol for establishing a secure session using the existing algorithms like Lightweight Establishment of Secure Session for communication between various IoT devices and remote server. However, several limitations regarding the key management, session establishment and multi-cast message communication within the DTLS layer are present in CoAP. Hence, development of an efficient protocol for secure session establishment of CoAP is required for IoT communication. Thus, to overcome the existing limitations related to key management and multicast security in CoAP, we have proposed an efficient and secure communication scheme to establish secure session key between IoT devices and remote server using lightweight elliptic curve cryptography (ECC). The proposed ECC-based CoAP is referred to as ECC-CoAP that provides a CoAP implementation for authentication in IoT network. A number of well-known cryptographic attacks are analyzed for validating the security strength of the ECC-CoAP and found that all these attacks are well defended. The performance analysis of the ECC-CoAP shows that our scheme is lightweight and secure.

     

Real-time event-driven sensor data analytics at the edge-Internet of Things for smart personal healthcare

The Journal of Supercomputing - Real-time service has become a key for efficient serving of the Internet of Things (IoT)-based smart e-Healthcare. Several orientations have tried to pave this side...     

Cyberloafing in the workplace: mitigation tactics and their impact on individuals’ behavior

With the Internet permeating every aspect of daily life, organizations of all types are increasingly concerned about the degree to which their employees are cyberloafing by shirking their work responsibilities to surf the Internet, check e-mail, or send text messages. Although technological interventions against cyberloafing have been shown to be effective, they might be perceived by employees as an invasion to their privacy, and are expected to have repercussions on employee behavior and loyalty. The main objectives of this study are to (1) examine how the introduction of such technological interventions might affect employees’ emotions and fairness perceptions, and (2) understand the effect of the interventions on behavioral outcomes, i.e., employees’ intentions to cyberloaf and their loyalty to the company. We developed a justice-based framework that we empirically test using a field experiment composed of field surveys complemented with hypothetical scenarios describing new organizational initiatives to curb employees’ cyberloafing. Our findings suggest that technological interventions, although associated with perceptions of unfairness, are effective at controlling cyberloafing, albeit at the expense of employee loyalty. On the other hand, contrary to prior findings, we find that fairness perceptions of technological interventions, although reinforcing employee loyalty, are ineffective at curbing cyberloafing. These findings are especially enlightening in that they contradict a common belief that perceived fairness encourages employees, as a sign of their appreciation for this fairness, to curb their misuse of IT. The findings also help managers fine-tune their cyberloafing policies to achieve a long-lasting remedy to their employees’ cyberloafing while maintaining a necessary level of employee loyalty.     

Phase Transitions in Spin-1/2 Falicov–Kimball Model on a Two-dimensional Triangular Lattice

Phase transitions from low-temperature (ordered) phases to high-temperature (disordered/homogeneous) phases for different fillings are studied on a triangular lattice using the spin-dependent Falicov–Kimball model. Numerical diagonalization and Monte Carlo simulation methods are used to study thermodynamic properties of the system. It has been observed that low-temperature ordered phases persist up to a finite temperature and after reaching a critical temperature (\(T_c\)), homogeneous phases are observed for all parameter space. We have also calculated the temperature dependence of specific heat and observed a sharp jump at \(T_c\) indicating the phase transition, and this \(T_c\) increases with increase in on-site Coulomb correlation U and electron fillings.     

Strong,Conductive, Foldable Graphene Sheets by Sequential Ionic and π Bridging

The goal of this work is to develop an inexpensive low‐temperature process that provides polymer‐free, high‐strength, high‐toughness, electrically conducting sheets of reduced graphene oxide (rGO). To develop this process, we have evaluated the mechanical and electrical properties resulting from the application of an ionic bonding agent (Cr³⁺), a π–π bonding agent comprising pyrene end groups, and their combinations for enhancing the performance of rGO sheets. When only one bonding agent was used, the π–π bonding agent is much more effective than the ionic bonding agent for improving both the mechanical and electrical properties of rGO sheets. However, the successive application of ionic bonding and π–π bonding agents maximizes tensile strength, toughness, long‐term electrical stability in various corrosive solutions, and resistance to mechanical abuse and ultrasonic dissolution. Using a combination of ionic bonding and π–π bonding agents, high tensile strength (821 MPa), high toughness (20 MJ m^?3), and electrical conductivity (416 S cm^?1) were obtained, as well as remarkable retention of mechanical and electrical properties during ultrasonication and mechanical cycling by both sheet stretch and sheet folding, suggesting high potential for applications in aerospace and flexible electronics.     

Hyperporous Sponge Interconnected by Hierarchical Carbon Nanotubes as a High‐Performance Potassium‐Ion Battery Anode

Recently, commercial graphite and other carbon‐based materials have shown promising properties as the anode for potassium‐ion batteries. A fundamental problem related to those carbon electrodes, significant volume expansion, and structural instability/collapsing caused by cyclic K‐ion intercalation, remains unsolved and severely limits further development and applications of K‐ion batteries. Here, a multiwalled hierarchical carbon nanotube (HCNT) is reported to address the issue, and a reversible specific capacity of 232 mAh g^?1, excellent rate capability, and cycling stability for 500 cycles are achieved. The key structure of the HCNTs consists of an inner CNT with dense‐stacked graphitic walls and a loose‐stacked outer CNT with more disordered walls, and individual HCNTs are further interconnected into a hyperporous bulk sponge with huge macropore volume, high conductivity, and tunable modulus. It is discovered that the inner dense‐CNT serves as a robust skeleton, and collectively, the outer loose‐CNT is beneficial for K‐ion accommodation; meanwhile the hyperporous sponge facilitates reaction kinetics and offers stable surface capacitive behavior. The hierarchical carbon nanotube structure has great potential in developing high‐performance and stable‐structure electrodes for next generation K and other metal‐ion batteries.