Efficient query execution on broadcasted index tree structures

The continuous broadcast of data together with an index structure is an effective way of disseminating data in a wireless mobile environment. The index allows a mobile client to tune in only when relevant data is available on the channel and leads to reduced power consumption for the clients. This paper investigates the execution of queries on broadcasted index trees when query execution corresponds to a partial traversal of the tree. Queries exhibiting this behavior include range queries and nearest neighbor queries. We present two broadcast schedules for index trees and two query algorithms executed by mobile clients. Our solutions simultaneously minimize tuning time and latency and adapt to the client’s available memory. Experimental results using real and synthetic data compare results for a broadcast with node repetition to one without node repetition and they show how a priority-based data management can help reduce tuning time and latency.     

Oscillatory natural convection of water-glycerin mixture in a tall rectangular cavity: Transition to the chaos

This paper presents results of a numerical investigation involving bifurcation sequence leading to chaos in natural convection inside a vertically tall rectangular cavity having an aspect ratio equal to 15 and a Prandtl number equal to 125, corresponding to water-glycerin mixture. The flow is characterized by a vertical stratification of the temperature field for Grashof numbers greater than or equal to 200 that is outside the conduction regime and it is stationary monocellular up to a critical value Gr_c = 2800 where a periodic oscillatory regime appears. As Grashof number is increased, a transition from a steady periodic bicellular flow to an oscillatory multicellular flow, with 2 main central cells and 2 secondary cells, occurs. The regime remains periodic until Gr = 3100 where there is a first appearance of the chaotic regime which extends over a narrow interval of the Grashof number delimited by Gr = 3200.     

Sedimentology, mineralogical evaluation and industrial applications of the Pleistocene Al-Yamaniyyah clay deposits, near 'Agaba, Southern Jordan

Three clay horizons of different physical properties and different thicknesses were recognized in the study area. These horizons are intercalating with silt, sand and segregated salt crystals. The sediments were deposited during the Pleistocene in a nearshore environment and separated from sea by old reef terraces. Two alluvial terraces were found. The Al-Yamaniyyah clayey deposits contain considerable amounts of clay minerals, namely for the greater part smectite, vermiculite and kaolinite. Illite/mica, chlorite and goethite were present as minor constituents. The studied clay materials have indicated to be suitable for potteries and heavy ceramic products.     

THERMAL CRACKING (VISBREAKING) STUDIES ON QUYARAH RESIDUES

Visbreaking experiments on Quyarah long residue have been conducted in a continuous laboratory-scale visbreaking unit at different temperatures from 435^°C to 490^°C at one pressure (7 bar) and constant residence time (90 sec.). Data on yield of different products have been reported. Further, thermal cracking experiments on visbroken vacuum gas oil under relatively high severity were also given in the same unit in order to reduce the residual yield of Quyarah crude.     

Future groundwater conditions under long-term water stresses in an arid urban area

The urban area of Greater Dhahran has an extremely arid climate where the average annual rainfail is less than 71 mm. The Umm Er Radhuma (UER) aquifer in that area is the main source of domestic and landscape irrigation demands. Groudwater use has increased drastically during the last 15 years due to extensive developments in the area. Numerical simulation techiques and hydrogeochemical investigations were carried out to assess the effects of increasing pumping rates on the piezometric surface in the UER aquifer and to predict the future levels and quality of water under different pumping scenarios. A groundwater flow model was developed and calibrated for the area. The increase in the water extraction rate between 1967 and 1990 has resulted in a decline in the piezometric surface by about 4 m in the Dhahran area. The results of simulation investigations indicated that if the present trend of the groundwater withdrawal rate continues, the water level is expected to drop by an additional 2 and by the end of the year 2000, by an additional 6 m by the end of 2010. If the present increasing rate in groundwater withdrawal is reduced by 50%, the additional drawdown will also be reduced to about 1 and 2.5 m by the end of years 2000 and 2010, respectively. The average total dissolved solids (TDS) has increased from 2750 to 3545 mg/l between 1967 and 1990 and will continue to rise to 3922 and 4361 by the end of years 2000 and 2010, respectively. These original findings are important because they postulates the negative impacts of increasing groundwater pumping from an aquifer in an arid urban area on future groundwater levels and quality. Therefore, effective groundwater management and conservation schemes should be adopted to maintain the long-term productivity and quality of aquifers in the area.     

Full-Duplex Relaying Schemes for Cooperative NOMA Networks with SWIPT

Wireless Personal Communications - Existing security approaches for safeguarding data exchange among the sensor nodes are investigated in presence of apriori information of an adversary in...     

0D/2D Heterostructures Vertical Single Electron Transistor

Mixed-dimensional heterostructures formed by the stacking of 2D materials with nanostructures of distinct dimensionality constitute a new class of nanomaterials that offers multifunctionality that goes beyond those of single dimensional systems. An unexplored architecture of single electron transistor (SET) is developed that employs heterostructures made of nanoclusters (0D) grown on a 2D molybdenum disulfide (MoS₂) channel. Combining the large Coulomb energy of the nanoclusters with the electronic capabilities of the 2D layer, the concept of 0D–2D vertical SET is unveiled. The MoS₂ underneath serves both as a charge tunable channel interconnecting the electrode, and as bottom electrode for each v-SET cell. In addition, its atomic thickness makes it thinner than the Debye screening length, providing electric field transparency functionality that allows for an efficient electric back gate control of the nanoclusters charge state. The Coulomb diamond pattern characteristics of SET are reported, with specific doping dependent nonlinear features arising from the 0D/2D geometry that are elucidated by theoretical modeling. These results hold promise for multifunctional single electron device taking advantage of the versatility of the 2D materials library, with as example envisioned spintronics applications while coupling quantum dots to magnetic 2D material, or to ferroelectric layers for neuromorphic devices.     

Prediction-based secured handover authentication for mobile cloud computing

Mobile cloud computing (MCC) is a new technology that brings cloud computing and mobile networks together. It enhances the quality of service delivered to mobile clients, network operators, and cloud providers. Security in MCC technology, particularly authentication during the handover process, is a big challenge. Current vertical handover authentication protocols encounter different problems such as undesirable delays in real-time applications, the man in the middle attack, and replay attack. In this paper, a new authentication protocol for heterogeneous IEEE 802.11/LTE-A mobile cloud networks are proposed. The proposed protocol is mainly based on the view of the 3GPP access network discovery and selection function, which uses the capacities given by the IEEE 802.11 and the 3GPP long term evolution-advanced (LTE-A) standards interconnection. A prediction scheme, with no additional load over the network, or the user is utilized to handle cloud computing issues arising during authentication in the handover process. The proposed handover authentication protocol outperformed existing protocols in terms of key confidentiality, powerful security, and efficiency which was used to reduce bandwidth consumption.

     

An Efficient Compressive Sensing Routing Scheme for Internet of Things Based Wireless Sensor Networks

Wireless Personal Communications - Internet of Things (IoT) integrates diverse types of sensors, mobiles and other technologies to physical world and IoT technology is used in a wide range of...