Densely deployment of sensors is generally employed in wireless sensor networks (WSNs) to ensure energy-efficient covering of a target area. Many sensors scheduling techniques have been recently proposed for designing such energy-efficient WSNs. Sensors scheduling has been modeled, in the literature, as a generalization of minimum set covering problem (MSCP) problem. MSCP is a well-known NP-hard optimization problem used to model a large range of problems arising from scheduling, manufacturing, service planning, information retrieval, etc. In this paper, the MSCP is modeled to design an energy-efficient wireless sensor networks (WSNs) that can reliably cover a target area. Unlike other attempts in the literature, which consider only a simple disk sensing model, this paper addresses the problem of scheduling the minimum number of sensors (i.e., finding the minimum set cover) while considering a more realistic sensing model to handle uncertainty into the sensors' target-coverage reliability. The paper investigates the development of a genetic algorithm (GA) whose main ingredient is to maintain scheduling of a minimum number of sensors and thus to support energy-efficient WSNs. With the aid of the remaining unassigned sensors, the reliability of the generated set cover provided by the GA, can further be enhanced by a post-heuristic step. Performance evaluations on solution quality in terms of both sensor cost and coverage reliability are measured through extensive simulations, showing the impact of number of targets, sensor density and sensing radius.
Gas sensors based on titanium dioxide (TiO2) and zinc oxide (ZnO) nanocomposites are considered energy-saving devices that are utilized to find dangerous or harmful gases in an environment. The performance of nitrogen dioxide (NO2) gas sensors have been improved by spin-coating a TiO2 and TiO2:ZnO nanocomposite with varying concentrations (90TiO2:10ZnO, 70TiO2:30ZnO, and 50TiO2:50ZnO). To correlate structural properties with gas-sensing behavior, structural and morphological characterization has been done using FESEM, XRD, and EDX. Without any ZnO-specific crystalline phase, TiO2
... Show More
In this work, porous silicon gas sensor hs been fabricated on n-type crystalline silicon (c-Si) wafers of (100) orientation denoted by n-PS using electrochemical etching (ECE) process at etching time 10 min and etching current density 40 mA/cm2. Deposition of the catalyst (Cu) is done by immersing porous silicon (PS) layer in solution consists of 3ml from (Cu) chloride with 4ml (HF) and 12ml (ethanol) and 1 ml (H2O2). The structural, morphological and gas sensing behavior of porous silicon has been studied. The formation of nanostructured silicon is confirmed by using X-ray diffraction (XRD) measurement as well as it shows the formation of an oxide silicon layer due to chemical reaction. Atomic force microscope for PS illustrates that the p
... Show MoreThe paper discusses the structural and optical properties of In2O3 and In2O3-SnO2 gas sensor thin films were deposited on glass and silicon substrates and grown by irradiation of assistant microwave on seeded layer nucleated using spin coating technique. The X-ray diffraction revealed a polycrystalline nature of the cubic structure. Atomic Force Microscopy (AFM) used for morphology analysis that shown the grain size of the prepared thin film is less than 100 nm, surface roughness and root mean square for In2O3 where increased after loading SnO2, this addition is a challenge in gas sensing application. Sensitivity of In2O3 thin film against NO2 toxic gas is 35% at 300oC. Sensing properties were improved after adding Tin Oxide (SnO2) to be mo
... Show MoreThe study effect irradiation on optical properties of film (PVA: CuCL2) prepared by casting method, with thickness of (30±1) μm. And used Cs137 to obtained Gamma ray with energy (662)keV and time irradiation(5,6 and 7) weeks and affectivity (4.3) ci. The spectra absorbance and transmittance register in range (300-1100) nm .
Results show that the optical band gap for (PVA: CuCl2) decreasing after irradiation with gamma ray from (3.2,3.1,3 and 2.7)eV, urbach energy values increase with the increasing time radiation. And the absorption constants (α,k,n,) and the optical conductivity are changing after irradiated with gamma ray .
The world is confronted with the twin crisis of fossil fuel depletion and environmental degradation caused by fossil fuel usage. Biodiesel produced from renewable feedstocks such as Jatropha seed oil or animal fats by transesterification offers a solution. Although biodiesel has been produced from various vegetable oils such as Jatropha seed oil, the reaction kinetics studies are very few in literature, hence the need for this study. Jatropha curcas seed oil was extracted and analyzed to determine its free fatty acid and fatty acid composition. The oil was transesterified with methanol at a molar ratio of methanol to oil 8:1, using 1% sodium hydroxide catalyst, at different temperature
... Show More
(2)
In this study, the contribution of the bond C–I has been derived and incorporated in empirical formula to calculate zero-point energies (ZPE) of Iodo compounds. The calculated ZPE for 38 molecules containing this bond correlate well with experimental values. The comparison of these results with semiempirical (AM1) ZPE appears very satisfactory
The local asphalt concrete fracture properties represented by the fracture energy, J-integral, and stress intensity factor are calculated from the results of the three point bending beam test made for pre notches beams specimens with deformation rate of 1.27 mm/min. The results revealed that the stress intensity factor has increased by more than 40% when decreasing the testing temperature 10˚C and increasing the notch depth from 5 to 30mm. The change of asphalt type and content have a limited effect of less than 6%.
Kinetic experiments were performed to induce of the green methyl dye adsorption from aqueous solution on the bauxite clay. This study includes determination of the adsorption capacity of bauxite clay to methyl green dye adsorption and study the effect of some parameters ( temperature , time ) on the kinetic of the adsorption process of the dye were studied. Quantity of dye adsorbed was increased when the temperature increases from 298 to 318K which indicates that methyl green adsorption processes are endothermic nature . In order to describe the kinetic data and the rate adsorption constants of the pseudo-first-order and second-order kinetics were used . The kinetics data were applied well
... Show More
Sloped solar chimney system is a solar chimney power plant with a sloped collector. Practically, the sloped collector can function as a chimney, then the chimney height can be reduced and the construction cost would be reduced.The continuity, Naver-stockes, energy and radiation transfer equations have been solved and carried out by Fluent software. The governing equations are solved for incompressible, 3-D, steady, turbulent standard model with Boussiuesq approximation to develop for the sloped solar chimney system in this study and evaluate the performance of solar chimney power plant in Baghdad city of Iraq numerically by Fluent (14) software with orking conditions such as solar radiation intensity (30
... Show MoreBackground: Energy drinks are non alcoholic beverages which contain stimulant drugs chiefly caffeine and marketed as mental and physical stimulators. Consumption of energy drinks is popular practice among college students as they are exposed to academic stress. Caffeine which is the main constituent of energy drinks could become an addictive substance or cause intoxication. Objectives: This study aims to assess the prevalence of energy drinks consumption among medical students of alkindy college of Medicine.Type of the study: A cross sectional study.Methods: It was performed at alkindy medical college on March 2016. A total number of 600 students were contacted to participate in this study. A self administered questionnaire was used to c
... Show More