Electroluminescence from porous silicon in the cathodic reduction of persulfate ions: Degree of reversibility of the tuning effect

The temporal evolution of the spectra of cathodic electroluminescence from porous silicon in an electrolyte containing persulfate ions S₂O ₈ ^2? was studied in the galvanostatic mode. It was shown that irreversible changes in luminescence properties of porous silicon occur under cathodic polarization. These changes are manifested in a decrease in the signal intensity and a long-wavelength shift of the electroluminescence (EL) spectrum when the substrate potential remains virtually unchanged (pseudo-tuning). The irreversibility of the change in luminescence parameters is related to a concurrent electrochemical oxidation of the surface of porous silicon, which hinders the bipolar injection of carriers into luminescence-active crystallites. The results obtained suggest that the degradation phenomena observed under cathodic polarization are due to those same processes which are responsible for EL excitation, which casts doubt on the interpretation of the tuning effect, known in the literature, as a consequence of a purely electronic process in porous silicon.     

Implementation of OpenFlow based cognitive radio network architecture: SDN&R

Wireless Networks - The static conventional network architecture is ill-suited to the growing management complexity and highly dynamic wireless network topologies. Software Defined Radio systems...     

Versatile instrument for MOSFET characterization

An instrument is presented for measuring major MOSFET parameters. It implements the method of charge pumping as well as providing static I–V characteristics. The former capability enables one to investigate the quality of semiconductor-insulator interfaces and to determine mean surface-state density. Employing a USB-compatible microcontroller, the instrument has a reasonable size (100 × 80 × 50 mm³), mass (300 g), and power consumption (at most 2.5 W). The instrument is controlled via a USB bus by a personal computer running specially designed software under Microsoft® Windows 2000/XP®. It can measure currents from 1 pA to 10 mA with the gate or drain voltage varied across the range ±10 V, the MOSFET under test being connected as a two-port. Mean surface-state densities down to 10⁹ cm^?2 eV^?1 can be determined.     

A Strong Authentication Scheme with User Privacy for Wireless Sensor Networks

Wireless sensor networks (WSNs) are used for many real‐time applications. User authentication is an important security service for WSNs to ensure only legitimate users can access the sensor data within the network. In 2012, Yoo and others proposed a security‐performance‐balanced user authentication scheme for WSNs, which is an enhancement of existing schemes. In this paper, we show that Yoo and others' scheme has security flaws, and it is not efficient for real WSNs. In addition, this paper proposes a new strong authentication scheme with user privacy for WSNs. The proposed scheme not only achieves end‐party mutual authentication (that is, between the user and the sensor node) but also establishes a dynamic session key. The proposed scheme preserves the security features of Yoo and others' scheme and other existing schemes and provides more practical security services. Additionally, the efficiency of the proposed scheme is more appropriate for real‐world WSNs applications.     

A lightweight portable intrusion detection communication system for auditing applications

The goal of this paper is to develop, deploy, test, and evaluatea a lightweight portable intrusion detection system (LPIDS) over wireless networks by adopting two different string matching algorithms: Aho‐Corasick algorithm and Knuth‐Morris‐Pratt algorithm (KMP). Thus, this research contributes in three ways. First, an efficient and lightweight IDS (LPIDS) is proposed. Second, the LPIDS was developed, implemented, tested, and evaluated using Aho‐Corasick and KMP on two different hardware platforms: Wi‐Fi Pineapple and Raspberry Pi. Third, a comparative analysis of proposed LPIDS is done in terms of network metrics such as throughput, power consumption, and response time with regard to their counterparts. Additionally, the proposed LPIDS is suggested for consultants while performing security audits. The experimental results reveal that Aho‐Corasick performs better than KMP throughout the majority of the process, but KMP is typically faster in the beginning with fewer rules. Similarly, Raspberry Pi shows remarkably higher performance than Wi‐Fi Pineapple in all of the measurements. Moreover, we compared the throughput between LPIDS and Snort, it is observed and analyzed that former has significantly higher throughput than later when most of the rules do not include content parameters. This paper concludes that due to computational complexity and slow hardware processing capabilities of Wi‐Fi Pineapple, it could not become suitable IDS in the presence of different pattern matching strategies. Finally, we propose modification of Snort to increase the throughput of the system.     

CHIP: Collaborative Host Identity Protocol with Efficient Key Establishment for Constrained Devices in Internet of Things

Wireless Personal Communications - The Internet of Things (IoT) is the next evolutionary paradigm of networking technologies that interconnects almost all the smart objects and intelligent sensors...     

Analysis of frequency dependences of conductance of MIS structures with the fluctuation-and tunneling-based theoretical models taken into account

A method for analyzing the frequency dependences of normalized conductance of MIS structures taking into account the effects of the surface-potential fluctuations and penetration of electrically active states deeper into the insulator is suggested. The parameters for estimating the broadening of the dependences are chosen. Analytic expressions for these parameters are derived. A method for separating the effects of the tunneling-and fluctuation-based mechanisms of broadening on the form of the conductance’s frequency dependence is suggested.     

Excitonic Chemiluminescence in Si and CdSe Nanocrystals Induced by their Interaction with Ozone

The results of a systematic study of spectral and kinetic patterns of ozone‐adsorption‐induced luminescence (AL) in nanostructured Si and, for the first time, in colloidal CdSe/ZnS quantum dots (QDs) are reported and compared with photoluminescence (PL) of the same structures. The common excitonic nature of light emission under ozone chemisorption and photoexcitation is confirmed by excellent coincidence of AL and PL emission bands. This coincidence is maintained during correlated quenching of AL and PL emission caused by nonradiative defects generated under ozone adsorption. A possible mechanism for energy conversion is proposed in the framework of an exothermic oxidation reaction of core materials caused by ozone. The significant role of the quantum confinement effect differentiates the observed phenomenon from well‐known chemiluminescence in molecular systems. This research establishes a physicochemical basis for the development of a gas sensor with high selectivity to ozone. Also, our findings may be useful for testing core–shell colloidal QDs with ozone.     

Realization of Mobile Femtocells: Operational and Protocol Requirements

Femtocells are commissioned in wide range of commercial systems, such as CDMA, GSM, LTE, Wi-Fi, and WiMAX, and offer economically viable solutions to improve network scalability and indoor coverage. The ability to offer multitude of context-aware and value added services, and per-user customization have caught world-wide research interest on femtocells. In this article, we have investigated the feasibility to use femtocells as short-range mobile base stations, and discussed the demanding architectural requirements and challenges. The protocol stack on legacy femtocells must be modified to realize mobility. Mobility introduces new challenges in security and user privacy. Firstly, we analyze several candidate mobility protocols that are deployable on Mobile Femtocells (MFs). Among them, Host Identity Protocol (HIP) was chosen due to enhanced support in flexible mobility, security and end-user privacy. Secondly, we propose the indispensable modifications that enable device mobility, and the suitable transport architecture options based on direct IP links and relay chains. Finally, with the simulation results, the proposal is verified, and the architectural options are evaluated. That, in turn, proves the proposed mobility protocol has low latency in location locking with respect to another competing protocol and low resource utilization as it is depicted from mean round trip time.     

Excitation of luminescence in porous silicon with adsorbed ozone molecules

A new effect of the excitation of luminescence in porous silicon during adsorption of ozone from the gaseous phase was investigated. The signals of ozone-induced luminescence and photoluminescence decay with time of ozone exposure in a strictly correlated way; simultaneously, an oxide-phase growth is observed in porous silicon. A linear relationship was found between the luminescence intensity and the amount of oxide phase formed in the presence of ozone. Correlated shifts in the spectra of ozone-induced luminescence and photoluminescence are observed if the porosity of silicon varies. A mechanism for this effect is proposed. According to this mechanism, in the case of the dissociative adsorption of ozone, the exothermic reaction of oxidation of backbonds of a silicon atom takes place on the surface of nanocrystallites. Energy released is spent for the excitation of electron spectrum of silicon crystallites. The radiative relaxation in the case of ozone excitation proceeds similarly to that of the photon excitation of luminescence in porous silicon.