2D materials based heterostructure for quantum tunneling: a lithography free technique.

Two-dimensional electron gas (2DEG) systems have played a vital role in the development of superior electronic devices including tunnel junctions consisting of two such 2DEG systems. With the advent of the new 2D electronic material systems, it has opened a new route for 2D–2D tunneling in such extended systems. In this study, we have utilized a plasma enhanced chemical vapor deposition (PECVD) technique to directly deposit graphene (nanowalls) and h-BN on Si/SiO2 substrates to construct two-dimensional material based, vertically stacked electron tunneling devices free of expensive and cumbersome microfabrication steps. In the first study, we fabricated direct quantum tunneling devices by depositing atomically thin tunnel barriers of h-BN as the tunneling barrier with equally doped (p-doped under ambient conditions) graphene nanowalls as the active electrode layers (top and bottom) on Si/SiO2 substrates. Current-voltage (I-V) measurements for varying h-BN thicknesses of these single barrier tunneling devices showed linear I-V characteristics at low bias but an exponential dependence at higher bias. Our measurements of the electron tunnel current through the barrier demonstrated that the h-BN films act as a good tunnel barrier. The barrier thickness dependent tunneling current was in good agreement with the tunnelling currents computed using the Bardeen transfer Hamiltonian approach with equally doped top and bottom graphene electrodes. Presence of negative differential resistance (NDR) is characteristic of the current–voltage relationship of a resonant tunneling device, enabling many unique applications. NDR arises at a voltage bias corresponding to aligned band structures of the 2D systems, causing a sharp peak in the tunnelling current. The existence of devices with NDR has been reported since the late 1950\u27s in devices that contained degenerately doped p-n junctions with thin oxide barriers (tunnel diodes) and double barrier heterojunction devices where quantum tunneling effects are utilized. The NDR in the I-V characteristics of these devices has been used in many applications involving microwave/millimeter wave oscillators, high speed logic devices and switches. We investigated NDR phenomenon in our graphene/h-BN systems in two different routes. In the first case, graphene/h-BN/graphene single barrier device, the bottom and top graphene layers were unequally doped. One of the graphene layers was n-type doped using ammonia or hydrazine. Nitrogen doping using ammonia was accomplished during the growth by incorporating ammonia in the PECVD system. Hydrazine doping was accomplished by exposing the graphene to hydrazine vapor in vacuum. The unequal doping of graphene causes alignment of the band structures of graphene systems giving rise to NDR. The tunnelling devices consisting of unequally doped graphene with a single barrier shows resonant quantum tunneling with the presence of a pronounced peak in the current corresponding to NDC whose peak current value and the voltage value depend on the doping levels. The results are explained according to the modified Bardeen tunneling model. Next, resonant tunneling behavior was demonstrated in Graphene/h-BN/Graphene/h-BN/Graphene double barrier (DB) devices by directly depositing graphene and h-BN successive layers on Si/SiO2 substrates using PECVD. DB Tunneling junctions with various barrier widths were investigated (by varying the thickness of the second graphene layer). The I-V parameters of tunneling current at room temperature demonstrated resonant tunneling with negative differential conductance. A quantum mechanical double barrier tunneling model was used to explain the phenomenon, by solving the Schrödinger\u27s equation in either side of the system. A systematic behavior of the current peak values and the corresponding voltage values in I-V curves were seen to be in good agreement with the transmission coefficient calculated using a quantum mechanical model. Josephson tunneling is a different kind of tunneling phenomenon in superconductors, in which superconducting cooper pairs tunnel across a thin insulating barrier. A supercurrent can flow between two superconductors that are separated by a narrow insulating barrier. The current is influenced by the phase difference between the two superconductors. We fabricated Josephson junctions with atomically thin tunnel barriers by combining h-BN with magnesium diboride (MgB2) active electrode layers on a Si/SiO2 substrate using a PECVD (for h-BN) and a Hybrid Physical-Chemical Vapor Deposition (HPCVD) (for Mg ). The I-V characteristics were measured above and below the transition temperature Tc (37 K). A measurable supercurrent was detected below Tc

The Effect of Distance Learning Delivery Methods on Student Performance and Perception

The aim of this study was to investigate student perception and performance resulting from different distance learning delivery methods. A quantitative research method was applied to determine students’ views on synchronous and asynchronous delivery methods. This study was applied at the University of Hail, Deanship of Preparatory Year. The participants were 49 freshman female students. The results showed that there was a significant difference between student performance in both delivery methods—the synchronous delivery method and the synchronous with asynchronous delivery method. In addition, there was also a significant difference in student perception in the two groups. Based on this, it is possible to do more research in order to understand the role of the Learning Management System (LMS) and identify how instructors integrate the technology in higher education and online learning. Continuous professional development is needed so that the instructors can be updated about new technology

Detection of mine roof failure using inexpensive LiDAR technology

Slope, Roof, and mine wall stability problems are some of the main reasons for deaths at U.S. surface or underground mining. The safety instruments were not enough to prevent that failure or even predict it before it occurs. However, the cost of such a tool that can be helpful in detecting roof failures is very high and not reachable in most instances. The present study investigates the feasibility of using the M16 Leddar Evaluation Kit to detect the roof failure in mines. The M16 Leddar Evaluation kit cost is between 300$-800$, so it is the reachable price if it provides the required safety in mines. In fact, the underground mines have many openings, so the needs for instruments that can be distributed in all tunnels and safe all workers are urgent. The Leica Scan Station P40-3D Laser Scanner costs $123915.00, so in mine industry, it is not worthy to establish the mining with such high cost like that. Buying one unit of the Leica ScanStation P40-3D Laser Scanner to provide the safety and minimize the expenses in the mining industry is not a practical idea which is providing safety to some of the workers in one tunnel spot and neglect the others. Steel movement plate has been built and attached to a linear actuator that can move with a resolution around 0.00375 mm per step and stroke 50 mm in order to simulate the roof failures in mines. It is not possible to try the M16 in real mine due to the time limits and absence of not unstable mines locally, besides the intention that the author has to start with an office environment. The M16 Leddar Evaluation kit is aimed directly to movement plate and collecting the deformation derived by the actuator. The results collected has many of anomalies and irregular data that can be eliminated by doing some of the statistical identification of outliers. The results show that the M16 Leddar evaluation kit is capable of detecting the movement plate profile with a precision between 0.1 mm and 3 mm per integration period --Abstract, page iii

An Enhanced Source Location Privacy based on Data Dissemination in Wireless Sensor Networks (DeLP)

open access articleWireless Sensor Network is a network of large number of nodes with limited power and computational capabilities. It has the potential of event monitoring in unattended locations where there is a chance of unauthorized access. The work that is presented here identifies and addresses the problem of eavesdropping in the exposed environment of the sensor network, which makes it easy for the adversary to trace the packets to find the originator source node, hence compromising the contextual privacy. Our scheme provides an enhanced three-level security system for source location privacy. The base station is at the center of square grid of four quadrants and it is surrounded by a ring of flooding nodes, which act as a first step in confusing the adversary. The fake node is deployed in the opposite quadrant of actual source and start reporting base station. The selection of phantom node using our algorithm in another quadrant provides the third level of confusion. The results show that Dissemination in Wireless Sensor Networks (DeLP) has reduced the energy utilization by 50% percent, increased the safety period by 26%, while providing a six times more packet delivery ratio along with a further 15% decrease in the packet delivery delay as compared to the tree-based scheme. It also provides 334% more safety period than the phantom routing, while it lags behind in other parameters due to the simplicity of phantom scheme. This work illustrates the privacy protection of the source node and the designed procedure may be useful in designing more robust algorithms for location privac

Resource Efficient Authentication and Session Key Establishment Procedure for Low-Resource IoT Devices

open access journalThe Internet of Things (IoT) can includes many resource-constrained devices, with most usually needing to securely communicate with their network managers, which are more resource-rich devices in the IoT network. We propose a resource-efficient security scheme that includes authentication of devices with their network managers, authentication between devices on different networks, and an attack-resilient key establishment procedure. Using automated validation with internet security protocols and applications tool-set, we analyse several attack scenarios to determine the security soundness of the proposed solution, and then we evaluate its performance analytically and experimentally. The performance analysis shows that the proposed solution occupies little memory and consumes low energy during the authentication and key generation processes respectively. Moreover, it protects the network from well-known attacks (man-in-the-middle attacks, replay attacks, impersonation attacks, key compromission attacks and denial of service attacks)

Efficient Use of Linguistic and Situational Contexts for Enhanced Understanding of the Content of English Screen Subtitles

Research in the production of powerful screen subtitles receives more attention from those who are interested in movies business for the benefit of viewers worldwide. Arguably viewers hardly benefit from screen subtitles due to the inconsistency between scenes and the pragmatic meaning of subtitles. Specifically, the study aims to examine the extent to which understanding pragmatic meaning of screen subtitles largely depends on understanding linguistic and situational contexts elements. The force of context is assumed to have powerful effect interpretation of the source text. Both descriptive and experimental methods were adopted. These included a test and paper-and-pencil-questionnaires where participants provided their impressions about the effect of context in eliminating pragmatic meaning of screen subtitles. Participants were experienced viewers of subtitled films. Results showed that linguistic forms and contextual cues together form a powerful element in understanding the pragmatic meaning of screen subtitles. Results also revealed that communicative translation fits the screen translation giving more attention to the effect of context. The association of context and communicative translation makes subtitles globally more economical and intelligible. Context forms a central pragmatic element for film language to be intelligible. Keywords—Interpretation, context-dependent-interpretation, International context, scenes, linguistic context DOI: 10.7176/JLLL/92-03 Publication date:October 31st 2022