Graphene as a transparent conducting and surface field layer in planar Si solar cells

This work presents an experimental and finite difference time domain (FDTD) simulation-based study on the application of graphene as a transparent conducting layer on a planar and untextured crystalline p-n silicon solar cell. A high-quality monolayer graphene with 97% transparency and 350 Ω/□ sheet resistance grown by atmospheric pressure chemical vapor deposition method was transferred onto planar Si cells. An increase in efficiency from 5.38% to 7.85% was observed upon deposition of graphene onto Si cells, which further increases to 8.94% upon SiO₂ deposition onto the graphene/Si structure. A large increase in photon conversion efficiency as a result of graphene deposition shows that the electronic interaction and the presence of an electric field at the graphene/Si interface together play an important role in this improvement and additionally lead to a reduction in series resistance due to the conducting nature of graphene.     

Performance of new relay selection scheme for buffer-assisted multihop decode-and-forward networks

In this paper, a new relay selection scheme is proposed to reduce the end-to-end packet delivery delay for buffer-assisted multihop decode-and-forward cooperative networks. The proposed method selects a relay node having more packets in the associated buffer and relay's proximity to the destination node. Mathematical expressions for the outage probability and average packet delay in Rician fading are obtained by modeling the system as a Markov chain. The proposed relay selection scheme has less packet delay as compared to the max-link relay selection scheme with marginally higher outage probability. Thus, the proposed relay selection scheme is a good alternative to low latency wireless applications.     

Social centrality using network hierarchy and community structure

Several centrality measures have been formulated to quantify the notion of ‘importance’ of actors in social networks. Current measures scrutinize either local or global connectivity of the nodes and have been found to be inadequate for social networks. Ignoring hierarchy and community structure, which are inherent in all human social networks, is the primary cause of this inadequacy. Positional hierarchy and embeddedness of an actor in the community are intuitively crucial determinants of his importance. The theory of social capital asserts that an actor’s importance is derived from his position in network hierarchy as well as from the potential to mobilize resources through intra-community (bonding) and inter-community (bridging) ties. Inspired by this idea, we propose a novel centrality measure social centrality (SC) for actors in social networks. Our measure accounts for—(1) an individual’s propensity to socialize, and (2) his connections within and outside the community. These two factors are suitably aggregated to produce social centrality score. Comparative analysis of SC measure with classical and recent centrality measures using large public networks shows that it consistently produces more realistic ranking of nodes. The inference is based on the available ground truth for each tested networks. Extensive analysis of rankings delivered by SC measure and mapping with known facts in well-studied networks justifies its effectiveness in diverse social networks. Scalability evaluation of SC measure justifies its efficacy for real-world large networks.     

Multifunctional Optoelectronics via Harnessing Defects in Layered Black Phosphorus

Layered black phosphorus (BP), a promising 2D material, tends to oxidize under ambient conditions. While such defective BP is typically considered undesirable, defect engineering has in fact been exploited in contemporary materials to create new behaviors and functionalities. In this spirit, new opportunities arising from intrinsic defect states in BP, particularly through harnessing unique photoresponse characteristics, and demonstrating three distinct optoelectronic applications are demonstrated. First, the ability to distinguish between UV‐A and UV‐B radiations using a single material that has tremendous implications for skin health management is shown. Second, the same device is utilized to show an optically stimulated mimicry of synaptic behavior opening new possibilities in neuromorphic computing. Third, it is shown that serially connected devices can be used to perform digital logic operations using light. The underpinning photoresponse is further translated on flexible substrates, highlighting the viability of the technology for mechanically conformable and wearable systems. This demonstration paves the way toward utilizing the unexplored potential offered by defect engineering of 2D materials for applications spanning across a broad range of disciplines.     

Sulphur-phosphous components in gear oils: part 1, oxidation stability studies by P-NMR spectroscopic techniques

In the present investigations, the mechanism of oxidation stability of sulphur and phosphorus-based additives such as S-alkyl O,O-dialkyl phosphorodithioate, alkyl amine salt of dialkyl dithiophosphoric acid, dialkyl hydrogen phosphite and zinc dialkyl dithiophosphate used in lubricants has been studied by liquid and solid state ³¹P/^lH-NMR spectroscopic techniques. These techniques have enabled to monitor the complex changes that occur during oxidation at different intervals during long duration oxidation tests and provide qualitative and quantitative information of products formed during degradation of S–P based additives. The nature of both soluble and insoluble products of decomposition has been /determined. The studies have revealed few important aspects regarding thermal stability of these additives. The ashless S-alkyl O,O-dialkyl phosphorodithioate have better thermal oxidative stability and retain their identity for longer period compared to other similar ashless additives and zinc dialkyl dithiophosphates. The loss of additives during oxidation is 12% in case of S-alkyl O,O-dialkyl phosphorodithioate compared to other mentioned additives (40–100%) during 64 h of heating at 165 °C in the presence of air and catalyst. The decomposed products are also solublised in case of S-alkyl O,O - dialkyl phosphorodithioate and dialkyl hydrogen phosphite, and small amount of solids are formed compared to other additives. During oxidation the main components are being converted into more complex insoluble polyphosphates. The nature of soluble and insoluble products of decomposition as a result of thermal degradation are similar irrespective of the types of additive used. The mechanism of degradation and subsequent composition and structure of products formed has been discussed in detail. These studies will facilitate correlation of the structure and performance of these additives in lubricants.     

Fluid Dynamics Effects on Microstructure Prediction in Single-Laser Tracks for Additive Manufacturing of IN625

Metallurgical and Materials Transactions B - Single-track laser fusion were simulated using a heat-transfer-solidification-only (HTS) model and its extension with fluid dynamics (HTS_FD) model...     

A Fractal Dimension Based Framework for Night Vision Fusion

In this paper, a novel fusion framework is proposed for night-vision applications such as pedestrian recognition, vehicle navigation and surveillance. The underlying concept is to combine low-light visible and infrared imagery into a single output to enhance visual perception. The proposed framework is computationally simple since it is only realized in the spatial domain. The core idea is to obtain an initial fused image by averaging all the source images. The initial fused image is then enhanced by selecting the most salient features guided from the root mean square error (RMSE) and fractal dimension of the visual and infrared images to obtain the final fused image. Extensive experiments on different scene imaginary demonstrate that it is consistently superior to the conventional image fusion methods in terms of visual and quantitative evaluations.      

Experimental investigation into the effect of adhesion properties of PEEK modified by atmospheric pressure plasma and low pressure plasma

High performance polymer, Polyether Ether Ketone (PEEK) (service temperature ?250°C to +300°C, tensile strength: 120 MPa) is gaining significant interest in aerospace and automotive industries. In this investigation, attention is given to understand adhesion properties of PEEK, when surface of the PEEK is modified by two different plasma processes (i) atmospheric pressure plasma and (ii) low pressure plasma under DC Glow Discharge. The PEEK sheets are fabricated by ultra high temperature resistant epoxy adhesive (DURALCO 4703, service temperature ?260°C to +350°C). The surface of the PEEK is modified through atmospheric pressure plasma with 30 and 60 s of exposure and low pressure plasma with 30, 60, 120, 240, and 480 s of exposure. It is observed that polar component of surface energy leading to total surface energy of the polymer increases significantly when exposed to atmospheric pressure plasma. In the case of low pressure plasma, polar component of surface energy leading to total surface energy of the polymer increases with time of exposure up to 120 s and thereafter, it deteriorates with increasing time of exposure. The fractured surface of the adhesively bonded PEEK is examined under SEM. It is observed that unmodified PEEK fails essentially from the adhesive to PEEK interface resulting in low adhesive bond strength. In the case of surface modified PEEK under atmospheric pressure plasma, the failure is entirely from the PEEK and essentially tensile failure at the end of the overlap resulting in significant increase in adhesive bond strength. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010