Head tracked retroreflecting 3D display

In this paper, we describe a single‐user glasses‐free (autostereoscopic) 3D display where images from a pair of picoprojectors are projected on to a retroreflecting screen. Real images of the projector lenses formed at the viewer's eyes produce exit pupils that follow the eye positions by the projectors moving laterally under the control of a head tracker. This provides the viewer with a comfortable degree of head movement. The retroreflecting screen, display hardware, infrared head tracker, and means of stabilizing the image position on the screen are explained. The performance of the display in terms of crosstalk, resolution, image distortion, and other parameters is described. Finally, applications of this display type are suggested.     

Performance evaluation of a mesh-evolving quality-of-service-aware multicast routing protocol for mobile ad hoc networks

The tremendous amount of multimedia applications running across the wireless communication medium makes quality of service (QoS) a fundamental requirement for mobile ad hoc networks. However, it is not easy to incorporate QoS into these networks. Moreover, the growing number of group-oriented applications also necessitates the efficient utilisation of network resources. The multicast model is a promising technique which can achieve this efficiency by facilitating the inherent broadcast capability of the wireless medium. The mesh-evolving ad hoc QoS multicast (MAQM) routing protocol is developed to address the resource efficiency and QoS problems with one, integrated solution. MAQM achieves multicast efficiency by tracking the availability of resources for each node within its neighbourhood. The QoS status is monitored continuously and announced periodically to the extent of QoS provision. Using these features, MAQM nodes can make their decisions on joining a new multicast session based on the sustainability of their perceived QoS. MAQM also evolves the initial multicast tree into a mesh during the course of an ongoing session to achieve a more robust network topology. Thus, MAQM integrates the concept of QoS-awareness into multicast routing in mobile ad hoc networks. Since ad hoc networks require the protocol control overhead to be as small as possible, we analyse the multicast session establishment process of MAQM to see its impact on the protocol performance in terms of system control overhead. We also evaluate the performance of MAQM through computer simulations using various qualitative and quantitative criteria. The simulation results validate our mathematical analysis of the control overhead and show that MAQM significantly improves multicast efficiency through its QoS-aware admission and routing decisions with an acceptably small overhead. Thus, MAQM shows that QoS is not only essential for, but also applicable to mobile ad hoc networks.     

Detection of aflatoxin M1 levels by ELISA in white-brined Urfa cheese consumed in Turkey

Aflatoxin M1 (AFM1) is the hydroxylated metabolite of aflatoxin B1 found in a variety of foods. In this study, 127 samples of white-brined Urfa cheese produced mainly in the southeast of Turkey from raw ovine and bovine milks were surveyed for the presence of AFM1 using a competitive Enzyme Linked Immunosorbent Assay (ELISA) technique. The results showed that at detectable levels (≥50 ng/kg), 36 cheese samples (28.3%) were contaminated with AFM1 ranging from 70.61 to 770.97 ng/kg. Of the 36 cheese samples, 13 (10.2%) were found to have levels that exceeded the legal limits of 250 ng/kg established by the Turkish Food Codex. Consequently, the AFM1 contamination levels determined in this study in white-brined Urfa Cheese, which is commonly consumed in the southeast part of Turkey, were not considered to be a serious public health hazard. It was considered to be a potential risk for customers, particularly for infant health.     

Decolorization and COD reduction of UASB pretreated poultry manure wastewater by electrocoagulation process: a post-treatment study

The performance of electrocoagulation (EC) technique for decolorization and chemical oxygen demand (COD) reduction of anaerobically pretreated poultry manure wastewater was investigated in a laboratory batch study. Two identical 15.7-L up-flow anaerobic sludge blanket (UASB) reactors were first run under various organic and hydraulic loading conditions for 216 days. Effects of operating parameters such as type of sacrificial electrode material, time of electrolysis, current density, initial pH, and electrolyte concentration were further studied to optimize conditions for the post-treatment of UASB pretreated poultry manure wastewater. Preliminary tests conducted with two types of sacrificial electrodes (Al and Fe) resulted that Al electrodes were found to be more effective for both COD and color removals than Fe electrodes. The subsequent EC tests performed with Al electrodes showed that optimal operating conditions were determined to be an initial pH of 5.0, a current density of 15mA/cm(2), and an electrolysis time of 20min. The results indicated that under the optimal conditions, about 90% of COD and 92% of residual color could be effectively removed from the UASB effluent with the further contribution of the EC technology used as a post-treatment unit. In this study, the possible acute toxicity of the EC effluent was also evaluated by a static bioassay test procedure using guppy fish (Lebistes reticulatus). Findings of this study clearly indicated that incorporation of a toxicological test into conventional physicochemical analyses provided a better evaluation of final discharge characteristics.     

Recovery of ammonium nitrogen from the effluent of UASB treating poultry manure wastewater by MAP precipitation as a slow release fertilizer

Magnesium ammonium phosphate hexahydrate (MgNH₄PO₄·6H₂O, MAP) precipitation was studied on up-flow anaerobic sludge blanket (UASB) pretreated poultry manure wastewater in a lab-scale batch study. To recover high strength of ammonium nitrogen (NH₄⁺–N = 1318 mg/L) from UASB effluent, three combinations of chemicals including MgCl₂·6H₂O + KH₂PO₄, MgSO₄·7H₂O + NaHPO₄·7H₂O, and MgO + 85% H₃PO₄ were first applied at the stoichiometric ratio (Mg²⁺:NH₄⁺–N:PO₄³⁻–P = 1:1:1) and at different pH levels ranging from 4.45 to 11. Preliminary test results indicated that maximum NH₄⁺–N removal, as well as maximum chemical oxygen demand (COD) and color reductions, were obtained as 85.4%, 53.3% and 49.8% at pH 9.0 with the addition of MgCl₂·6H₂O + KH₂PO₄, respectively. The paired experimental data obtained from batch studies were statistically evaluated by a non-parametric Mann–Whitney test and a two-sample t-test. Based on the previous results, another batch experiments were then performed at pH 9.0 using MgCl₂·6H₂O + KH₂PO₄ for different molar ratios applied as overdose (1.2:1:1, 1.5:1:1, 1:1:1.2, 1:1:1.5) and underdose (0.5:1:1, 0.8:1:1, 1:1:0.5, 1:1:0.8). In the final step, the fertility of the MAP precipitate as struvite was also tested on the growth of three test plants including purslane (Portulaca oleracea), garden cress (Lepidum sativum) and grass (Lolium perenne). Findings of this experimental study clearly confirmed the recovering of NH₄⁺–N from UASB pretreated poultry manure wastewater by MAP precipitation, and also the application of recovered MAP sludge as a valuable slow release fertilizer for agricultural use.     

Recovery of an arbitrary edge on an existing surface mesh using local mesh modifications

This study describes an algorithm for recovering an edge which is arbitrarily inserted onto a pre‐triangulated surface mesh. The recovery process does not rely on the parametric space of the surface mesh provided by the geometric modeller. The topological and geometrical validity of the surface mesh is preserved through the entire recovery process. The ability of inserting and recovering an arbitrary edge onto a surface mesh can be an invaluable tool for a number of meshing applications such as boundary layer mesh generation, solution adaptation, preserving the surface conformity, and possibly as a primary tool for mesh generation. The edge recovery algorithm utilizes local surface mesh modification operations of edge swapping, collapsing and splitting. The mesh modification operations are decided by the results of pure geometrical checks such as point and line projections onto faces and face‐line intersections. The accuracy of these checks on the recovery process are investigated and the substantiated precautions are devised and discussed in this study. Copyright © 2001 John Wiley & Sons, Ltd.     

150MW水轮发电机定子端部绝缘泄漏处理

介绍棉花滩水电厂3号水轮发电机（150 MW）定子端部绝缘盒缺陷的处理情况,分析缺陷产生原因,总结出一套缺陷处理的工序及工艺,为大型水轮发电机定子端部绝缘缺陷处理积累了实践经验。     

Effect of Ti sublayer on the ORR catalytic efficiency of dc magnetron sputtered thin Pt films

A series of thin Pt films were deposited by dc magnetron sputtering directly on a commercial hydrophobic carbon paper substrate having a thin microporous Vulcan-XC72 layer or upon a thin Ti sublayer sputtered on the top of the microporous carbon film. The electrocatalytic properties of the sputtered Pt films toward the oxygen reduction reaction were investigated in 0.5 M H₂SO₄ solution and in a hydrogen PEM fuel cell. The catalyst with ultralow Pt loading of 22 μg cm⁻² deposited on a 33 Å thick Ti sublayer is robust, mechanically stable, possesses highly developed surface area and improved catalytic efficiency. Its performance as a MEA cathode in a single hydrogen PEM fuel cell (577 mA cm⁻² at 0.4 V cell voltages and a maximum power of 0.954 W) proved to be much superior compared to that of MEA with the same cathode Pt loading but without Ti sublayer (173 mA cm⁻² at 0.4 V, 0.231 W, respectively).     

The dynamic stability of a rotating pre-twisted asymmetric cross-section Timoshenko beam subjected to lateral parametric excitation

A finite element model is presented to study the dynamic stability of a pre-twisted Timoshenko beam having asymmetric aerofoil cross-section subjected to lateral parametric excitation. Solutions referred to as combination resonance are investigated. The effects of shear deformation and rotary inertia are included in the analysis. The effects of coupling due to centre of flexure distance from the centroid and the shear coefficient on the stability are considered. The change in these effects due to pre-twist angle is investigated. It is concluded from the results that the pre-twist angle has an influence on the effects of coupling and the shear coefficient.     

On properties at interfaces of friction welded near-nanostructured Al 5083 alloys

Equal-channel angular pressing is a material processing method that allows very high strains to be imposed, which leads to extreme work hardening and micro-structural refinement, with minimal change of external sample dimensions. It offers possibilities of good mechanical properties, such as high strength and ductility, while allowing flexibility of choice of alloy composition for better corrosion behavior, lower materials costs, and so on. This study characterizes for the first time the microstructure and properties of aluminum friction welded after severe plastic deformation via the equal-channel angular pressing method. In this study, 5,083 aluminum alloys, which were exposed to severe plastic deformation using square cross-sectional equal-channel angular pressing die, were joined with friction welding method. It was found that tensile and fatigue strengths of severe plastic deformed and welded specimens were higher than those of the purchased specimens. Hardness values were also consistent with the strength results. However, the refining of grain size as shown from microstructures results in a significant increase in hardness and mechanical properties.