The magnetization reversal processes of Sm2Gd10.5Fe8Co64Zr2.5Cu13 alloy in the as-quenched state

The magnetization reversal processes of the as-quenched Sm₂Gd_10.5Fe₈Co₆₄Zr_2.5Cu₁₃ ribbons obtained by melt-spinning method have been investigated. From the analysis of the initial magnetization curve it was deduced that the main mechanism of magnetization reversal process is the pinning of domain walls at the grain's boundaries. From the dependence of the reversible magnetization components as a function of magnetic field it was found that reversible rotation of magnetic moment vector results in high initial values of this component. The presence of several maxima on the differential susceptibility curves derived from the irreversible magnetization component in both direction of magnetization implies existence of several pinning sites for domain walls. The interaction between the alloy grains have been examined by using the so-called δm(μ₀H_i) plot. The values of δm(μ₀H) for investigated alloy remains positive for an applied field up to 1.15 T and negative for higher fields. Such behavior of δm(μ₀H_i) dependence certifies that the dominant interaction between grains is the short range exchange interactions but low values of δm(μ₀H) implies that these interactions are week.     

Dependence of pressure on elastic,electronic and optical properties of CeO2 and ThO2: A first principles study

The phase transformation of CeO₂ and ThO₂ from fluorite to cotunnite-type structure under pressure is predicted within the density functional theory implemented with the GGA-PW91 method, the pressure induced structural phase transition occurs at 28.9 GPa for CeO₂ and 29.8 GPa for ThO₂. These values are in excellent agreement with the experimentally measured data. The elastic, electronic and optical properties at normal as well as for high-pressure phase have been calculated, particular attention is devoted to the cotunnite phase. Further, the dependence of the elastic constants, the bulk modulus B, the energy band gaps and the dielectric function on the applied pressure are presented.     

User-generated contents and reasoning-based personalization: Ingredients for a novel model of mobile TV

During the last years, we have witnessed the boom of the digital market due to the proliferation of emergent audiovisual services and the increasing number of broadband networks. In this scenario, users insistently demand innovative services for exchanging and sharing their own audiovisual contents. In order to meet these needs, in this paper we propose a system that broadcasts user-generated audiovisual contents for handheld devices in a mobile network based on the DVB-H broadcasting standard. Besides, our system offers diverse added-value services to these new active users, such as: (i) multi modal access (via Web or by client applications running locally in handheld devices) to digital contents, (ii) exploitation of return channels to transmit interactive contents that enhance the user’s experience, and (iii) annotation, sharing and personalized distribution of audiovisual contents. To achieve these goals, our system adopts well-known technologies for broadcasting and semantic annotation of audiovisual contents, as well as emergent technology from the so-called Web 2.0. A prototype of our system has been experimentally evaluated with a group of students from the University of Vigo, who were enthusiastic about the personalization capabilities offered by our TV system for a mobile setting.     

Bi-level surface modification of hard disk media by carbon using filtered cathodic vacuum arc: Reduced overcoat thickness without reduced corrosion performance

The corrosion performance of commercial hard disk media which was subjected to bi-level surface modification has been reported. The surface treatment was carried out by bombarding the surface of the magnetic media with C⁺ ions at 350 eV followed by 90 eV using filtered cathodic vacuum arc (FCVA). The energy and embedment depth of the impinging C⁺ ions were adjusted by applying an optimized bias to the substrate and simulated by a Stopping and Range of Ions in Matter (SRIM) code which predicted the formation of a graded atomically mixed layer at the carbon-media interface. Cross-section transmission electron microscopy (TEM) revealed the formation of a 1.8 nm dense nano-layered carbon overcoat structure on the surface of the media. Despite an ~ 33% reduction in the thickness, the bi-level surface modified disk showed corrosion performance similar to that of a commercially manufactured disk with a thicker carbon overcoat of 2.7 nm. This improvement in the corrosion/oxidation resistance per unit thickness can be attributed to the formation of a dense and highly sp³ bonded carbon layer, as revealed by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. This study demonstrates the effectiveness of the bi-level surface modification technique in forming an ultra-thin yet protective overcoat for future hard disks with high areal densities.     

Liquid-level sensor based on tapered chirped fiber grating

An optic-fiber liquid-level sensor based on tapered chirped grating was proposed and demonstrated experimentally.With a properly designed column buoy hung to chain wheel,the liquid-level variation was converted to axial strain,which made the reflection spectrum of the tapered chirped grating narrowed or broadened correspondingly.And a high-sensitive liquid-level sensor was obtained by monitoring the bandwidth variation of the tapered chirped grating.Compared with traditional absolute wavelength or power detection,this special monitoring technique based on bandwidth modulation makes the liquid-level sensor insensitive to spatially uniform temperature variations and power fluctuations from down-lead or light source.     

Ultra-high-temperature tensile properties and fracture behavior of ZrB2-based ceramics in air above 1500 °C

Nearly fully dense ZrB₂–SiC–graphite composites were fabricated from commercially available powder at 1900 °C by hot pressing. The tensile strength of ZrB₂-based ceramics was measured in air up to 1750 °C, which is the first reported tensile strength measurement in air above 1500 °C. A mechanical testing apparatus capable of testing material in ultra-high temperature under air atmosphere was built, evaluated, and used. Tensile strength was measured as a function of temperature up to 1750 °C in air. The respective average values of the tensile strength measured at 1550 °C, 1650 °C, and 1750 °C are 58.4, 44.8, and 21.8 MPa, which are 49.4%, 37.9%, and 18.4% of their room-temperature strength (118.2 MPa), respectively. Moreover, the tensile fracture behaviors and mechanism of ZrB₂-based ceramics at different testing temperatures were discussed based on microstructure characterization.     

Degradation of hexahydro‐1,3,5‐trinitro‐1,3, 5‐triazine (RDX) by anaerobic mesophilic granular sludge from a UASB reactor

BACKGROUND: This study investigated the performance of anaerobic mesophilic granular sludge for the degradation of hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX). Batch tests were conducted to investigate the effects of different supplements on the RDX degradation ability of anaerobic granular sludge, as well as the contributions of both physicochemical and biological processes involved in RDX removal from aqueous solution. RESULTS: Anaerobic granular sludge exhibited good performance in treating RDX as the sole substrate. Biodegradation was the main mechanism responsible for RDX removal. Ammonium had no significant promoting effect on the degradation process. The presence of glucose was found to enhance the degradation of RDX by anaerobic granular sludge, while the addition of sulfate and nitrate had adverse effects on the reductive transformation of RDX. CONCLUSIONS: Anaerobic granular sludge is capable of removing RDX from aqueous solution with high efficiency. This study showed good prospects for high‐rate anaerobic processes in the treatment of munition wastewater. The results can be used for the design and optimization of high rate anaerobic systems for the elimination of RDX. Copyright © 2010 Society of Chemical Industry     

Estimated daily intake of pesticide residues exposure by vegetables grown in greenhouses in Al-Qassim region,Saudi Arabia

Residues of 23 pesticides (13 insecticides, 3 fungicides, 3 herbicides, 2 acaricides, 1 rodenticide and 1 nematicide) in 160 different vegetable samples cultivated under greenhouse conditions and collected from 4 major supermarkets located in Al-Qassim region, Saudi Arabia were monitored. A multiresidue method was carried out by gas chromatography with mass spectrometry (GC–MS). Residues were found in 89 samples. Fifty four samples were found above the maximum residue levels (MRLs). The most frequently found pesticides were carbaryl followed by biphenyl and then carbofuran. MRL values exceeded most often in cabbage (11 samples) followed by squash, green pepper and carrot (7 samples each) followed by cucumber and lettuce (6 samples each), egg-plant (5 samples) and then tomato (4 samples). Also, cabbage showed the highest contamination rates (16 samples), followed by carrot, cucumber and green pepper (12 samples each), squash (11 samples), lettuce and tomato (9 samples each) and egg-plant (8 samples). The highest concentrations were determined in lettuce followed by squash, cabbage and carrot. Al-Qassim region population’s average daily intake (EDI) has been estimated between 2 × 10^?5 and 0.597 μg/kg body weight/day and the hazard index (EDI/acceptable daily intake (ADI)) less than the unity for the tested compounds. The data illustrated that the intakes are much lower than the ADIs and the exposure level to whole pesticides was below the level to produce health risk. The data indicated also the need for regular monitoring programs for pesticide residues in vegetables cultivated under greenhouse conditions, at the national level, to protect consumers’ health.     

Performance analyses of VHTR plants with direct and indirect closed Brayton cycles and different working fluids

This paper investigated the performance of Very High Temperature Reactor (VHTR) power plants with helium working fluid and direct and indirect Closed Brayton Cycles (CBCs), and with binary mixture working fluids of He–Xe and He–N₂ (molecular weight of 15 g/mole) and indirect CBCs. Also investigated are the effects of using low- and high-pressure compressors with intercooling, versus a single compressor, using bleed cooling the reactor pressure vessel in direct CBC helium plants, and varying the reactor exit temperature from 700 °C to 950 °C on the plant thermal efficiency, cycle pressure ratio and the size of and number of stages in the turbine and compressor. Analyses are performed for a shaft rotation speed of 3000 rpm, reactor thermal power of 600 MW and a temperature pinch of 50 °C in the intermediate heat exchanger (IHX) for the indirect CBCs.     

Experimental and analytical system identification of Eynel arch type steel highway bridge

This paper describes a full scale arch type steel highway bridges, its finite element modelling and Operational Modal Analysis. Eynel Highway Bridge which has arch type structural system with a total length of 336 m and located in the Ayvacık county of Samsun, Turkey is selected as a case study. The bridge connects the villages which are separated with Suat Uğurlu Dam Lake. The three dimensional finite element model is constructed using project drawings and an analytical modal analysis is then performed to generate natural frequencies and mode shapes in the three-orthogonal directions. The ambient vibration tests on the bridge deck under natural excitation such as traffic, human walking and wind loads are conducted using Operational Modal Analysis. Sensitive seismic accelerometers are used to collect signals obtained from the experimental tests. To obtain experimental dynamic characteristics, two output-only system identification methods are employed namely, Enhanced Frequency Domain Decomposition method in the frequency domain and Stochastic Subspace Identification method in time domain. The correlation between the finite element model and experimental results is studied. Good agreement is found between dynamic characteristics in the all measurement test setups performed on the bridge deck. It is demonstrated that the ambient vibration measurements using Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification methods are enough to identify the most significant modes of steel highway bridges. It is seen that there are some differences between analytical and experimental natural frequencies and experimental natural frequencies are generally bigger than the others.