Quantum transport of Dirac electrons in graphene in the presence of a spatially modulated magnetic field

We have investigated the electrical transport properties of Dirac electrons in a monolayer graphene sheet in the presence of a perpendicular magnetic field that is modulated weakly and periodically along one direction.We find that the Landau levels broaden into bands and their width oscillates as a function of the band index and the magnetic field.We determine the $\sigma_{yy}$ component of the magnetoconductivity tensor for this system which is shown to exhibit Weiss oscillations.We also determine analytically the asymptotic expressions for $\sigma_{yy}$.We compare these results with recently obtained results for electrically modulated graphene as well as those for magnetically modulated conventional two-dimensional electron gas (2DEG) system.We find that in the magnetically modulated graphene system cosidered in this work,Weiss oscillations in $\sigma_{yy}$ have a reduced amplitude compared to the 2DEG but are less damped by temperature while they have a higher amplitude than in the electrically modulated graphene system. We also find that these oscillations are out of phase by $\pi$ with those of the electrically modulated system while they are in phase with those in the 2DEG system.Comment: Accepted in PRB: 10 pages, 3 figure

Distributed Optimization in Energy Harvesting Sensor Networks with Dynamic In-network Data Processing

Energy Harvesting Wireless Sensor Networks (EH- WSNs) have been attracting increasing interest in recent years. Most current EH-WSN approaches focus on sensing and net- working algorithm design, and therefore only consider the energy consumed by sensors and wireless transceivers for sensing and data transmissions respectively. In this paper, we incorporate CPU-intensive edge operations that constitute in-network data processing (e.g. data aggregation/fusion/compression) with sens- ing and networking; to jointly optimize their performance, while ensuring sustainable network operation (i.e. no sensor node runs out of energy). Based on realistic energy and network models, we formulate a stochastic optimization problem, and propose a lightweight on-line algorithm, namely Recycling Wasted Energy (RWE), to solve it. Through rigorous theoretical analysis, we prove that RWE achieves asymptotical optimality, bounded data queue size, and sustainable network operation. We implement RWE on a popular IoT operating system, Contiki OS, and eval- uate its performance using both real-world experiments based on the FIT IoT-LAB testbed, and extensive trace-driven simulations using Cooja. The evaluation results verify our theoretical analysis, and demonstrate that RWE can recycle more than 90% wasted energy caused by battery overflow, and achieve around 300% network utility gain in practical EH-WSNs

Theory of Weiss oscillations in the magnetoplasmon spectrum of Dirac electrons in graphene

We present the collective excitations spectrum (magnetoplasmon spectrum) of Dirac electrons in a weakly modulated single graphene layer in the presence of a uniform magnetic field. We consider electric modulation in one-dimension and the magnetic field applied perpendicular to graphene.We derive analytical results for the intra-Landau band plasmon spectrum within the self-consistent-field approach. We find Weiss oscillations in the magnetoplasmon spectrum which is the primary focus of this work. Results are presented for the intra-Landau band magnetoplasmon spectrum as a function of inverse magnetic field. These results are also compared with those of conventional 2DEG. We have found that the Weiss oscillations in the magnetoplasmon spectrum are larger in amplitude compared to those in conventional 2DEG for the same modulation strength, period of modulation and electron density.Comment: 9 pages, 1 figure Phys. Rev. B (accepted for publication

An efficient disjunctive query enabled ranked searchable encryption scheme

Cloud computing motivates data owners to economically outsource large amounts of data to the cloud. To preserve the privacy and confidentiality of the documents, the documents need to be encrypted prior to being outsourced to the cloud. In this paper, we propose a lightweight construction that facilitates ranked disjunctive keyword (multi-keyword) searchable encryption based on probabilistic trapdoors. The security analysis yieldsthat the probabilistic trapdoors help resist distinguishability attacks. Through the computational complexity analysis we realize that our scheme outperforms similar existing schemes. We explore the use of searchable encryption in the telecom domain by implementing and deploying our proof of concept prototypeonto the British Telecommunication's Public Cloud offering and testing it over a real corpus of audio transcriptions. The extensive experimentation thereafter validates our claim that our scheme is lightweight

Wasteland reclamation strategy for household timber security of tribes in Jharkhand, India

The study sought to examine the timber dependency on forests and evolve wasteland reclamation strategy to eliminate the forest dependency in Bundu block of Ranchi District in Jharkhand, India. Multi-stage random sampling technique was applied to select 164 tribal households from 9 sample villages. Data were collected using structured interviews and non-participant observations which were analyzed using descriptive statistics viz., frequency, percentage, mean and range. Results revealed that forests contributed maximum timber (136.36 m3 annum-1) followed by traditional agroforestry (69.09 m3 annum-1), community forestry (41.33 m3 annum-1) and homestead forestry (35.71 m3 annum-1). Timber extracted is mostly consumed in housing (124.66 m3 annum-1) followed by agricultural implements (82.71 m3 annum-1), furniture (35.25 m3 annum-1), carts/ carriages (17.60 m3 annum-1), fencing (10.23 m3 annum-1), cattle shed/ store house (9.10 m3 annum-1) and others (2.94 m3 annum-1). Forests were exposed to timber pressure of 136.36 m3 annum-1 (48.27%) posing ample deforestation and degradation. The strategy consisted of timber and bamboo plantations is designed which would secure 1065.60 m3 annum-1 of timber, 0.455 lakh annum-1 of bamboo culms, 568.26 tons annum-1 of bamboo leaf and agricultural products. The strategy would yield income of Rs. 34210.78 household-1 annum-1 and employment of 67.15 person-days household-1 annum-1. Financial viability of proposed interventions has been worked out by meticulous economic calculations of Net Present Value, Benefit Cost Ratio and Internal Rate of Return. The execution of strategy would eliminate the current unsustainable timber extraction, safeguard the future timber predicament and ensure environmental security

Fuzzy keywords enabled ranked searchable encryption scheme for a public Cloud environment

Searchable Encryption allows a user or organization to outsource their encrypted documents to a Cloud-based storage service, while maintaining the ability to perform keyword searches over the encrypted text. However, most of the existing search schemes do not take the almost certain presence of typographical errors in the documents under consideration, when trying to obtain meaningful and accurate results. This paper presents a novel ranked searchable encryption scheme that addresses this issue by supporting fuzzy keywords. The proposed construction is based on probabilistic trapdoors that help resist distinguishability attacks. This paper for the first time proposes Searchable Encryption as a Service (SEaaS). The proposed construction is deployed on the British Telecommunication’s public Cloud architecture and evaluated over a real-life speech corpus. Our security analysis yields that the construction satisfies strong security guarantees and is also quiet lightweight, by analyzing its performance over the speech corpus

Effect of varying shade levels on vegetative performance and chlorophyll contents of groundnut (Arachis hypogea L.) shoots

Groundnut, also commonly known as peanut (Arachis hypogaea), is a tropical legume mainly grown to produce oil and for human and animal consumption. Light has been the most important factor influencing plant growth, with changes in irradiance having impacts on plant growth, morphology, and anatomy. This research was aimed to evaluate the effect of varying levels on vegetative performance and chlorophyll contents of groundnut shoots. This experiment was conducted in the Botanical Garden of the Department of Biology, Kaduna State University, Kaduna State Nigeria. Healthy seeds of Arachis hypogaea were procured from Institute for Agricultural Research (IAR), Samaru, Zaria. The seeds of A. hypogea were sown in polythene bags containing garden soil. This experiment was laid under Randomized Complete Block Design (RCBD), each treatments were replicated three (3) times. Growth parameters were measured using ruler and digital weighing balance. It was observed that, seeds germinated after 9 days. From the results obtained, shade affected all growth parameters studied. A. hypogea grown under shade showed reduction in number of leaves, root length, leaves fresh weight and dry weight, stem fresh and dry weights, root fresh and dry weight respectively. Results of chlorophyll composition showed the lowest content of chlorophyll in groundnut shoots grown under shade. It is recommended that, planting of groundnut under shade should be avoided because it ffects growth and chlorophyll compositions in A. hypogea shoots