Emission Optics of the Steigerwald Type Electron Gun

The emission optics of a Steigerwald type electron gun is re-examined. The virtual and real points of divergence, divergence angles and beam-widths of the electron beams at different telefocusing strength are measured in detail for first time . Two different Wehnelt cylinders are used to establish a contrasting viewpoint. The original `focusing' curves measured by Braucks are reconstructed and will be explained only through a `new' interpretation which is different from the conventional views. While the image of the emitting surface in front of the filament is indeed telefocused beyond the anode, the envelope of the beam does not `focus' as expected. A new model for the emission mechanism is established based on our results.Comment: 14 pages, 10 figure

Parallel computations and control of adaptive structures

The equations of motion for structures with adaptive elements for vibration control are presented for parallel computations to be used as a software package for real-time control of flexible space structures. A brief introduction of the state-of-the-art parallel computational capability is also presented. Time marching strategies are developed for an effective use of massive parallel mapping, partitioning, and the necessary arithmetic operations. An example is offered for the simulation of control-structure interaction on a parallel computer and the impact of the approach presented for applications in other disciplines than aerospace industry is assessed

Superconductivity and Magnetism in REFeAsO1-xFx (RE=Rare Earth Elements)

Fluoride-doped iron-based oxypnictides containing rare-earth gadolinium (GdFeAsO0.8F0.2) and co-doping with yttrium (Gd0.8Y0.2FeAsO0.8F0.2) have been prepared via conventional solid state reaction at ambient pressure. The non-yttrium substituted oxypnictide show superconducting transition as high as 43.9 K from temperature dependent resistance measurements with the Meissner effect observed at a lower temperature of 40.8 K from temperature dependent magnetization measurements. By replacing a small amount of gadolinium with yttrium Tc was observed to be lowered by 10 K which might be caused by a change in the electronic or magnetic structures since the crystal structure was not altered.Comment: 4 pages, 4 figures, Journal of Physics: Conference Series (Proceedings in the LT25 Low Temperature Physics Conference) Submitte

Structural properties of graphene oxide coatings from different sheets sizes

The structural properties of different sizes of graphene oxide (GO) sheets were observed. It is worth to mention that smaller size GO sheets (ultrasonicated 10h) exhibits higher absorption intensity, and the absorption peak was shifted towards lower wavelength (~223 nm) due to the fragmentation of the GO sheets. It has caused an extension of a π-conjugated system, thereby enhance the absorption intensity and energy. After electrophoretic deposition (EPD), the coatings exhibit a reduction in the oxygen content with oxygen-related band (ORB) values of the larger GO sheets is higher than that of small size GO sheets. The surface morphology of both the coatings are homogenous and the layers adhered well to the underlying copper. However, larger GO sheets exhibit rougher and coarser morphology than that of small size GO sheets. It is reflected in the thickness measurement where the large size GO sheets exhibit thicker film (3.16 ± 0.01 µm) while small size GO sheets possess thinner film (1.95 ± 0.02 µm)

Renewable Energy from Living Plants to Power IoT Sensor for Remote Sensing

Renewable energy which can be used to replace traditional energy sources from fossil fuel is in dire demand to protect the earth from the further negative effect of climate change resulting from mining or drilling of fossil fuel and its related pollution. There are various renewable energy sources available, however, there is none currently that does not compete for arable land in nature or land for food production to enable the installation of the renewable energy facility. Thus, in this research, it is proposed a novel type of electrical energy which can be harvested from living plants and coexist well with nature without competing for any arable lands and at the same time generate energy for human needs. Plants generate energy from photosynthesis, respiration, and intercellular activities, and this energy, although is minute, still can be harvested as a new potential energy source to power any ultra-low power sensor for remote sensing purposes. Thus, it is presented in this paper, a characterization of the specific setup condition to harvest optimum minimum 3V from living plants and a power management circuit that can further boost the energy to an optimum level to power a wireless IoT sensor for remote sensing purposes. It turns the living plant into a plant-based cell. As there is wide vegetation in forests, jungles, plantations, and agricultural lands on earth, the combination of this energy from the plants could be a promising source of new renewable energy to mankind as this vegetation can exist for both food and energy production while it does not compete for arable land for the installation of energy sources such as what happens in fossil fuel, solar or wind energy to create greener earth

Composting paper and grass clippings with anaerobically treated palm oil mill effluent

Purpose The purpose of this study is to investigate the composting performance of anaerobically treated palm oil mill effluent (AnPOME) mixed with paper and grass clippings. Methods Composting was conducted using a laboratory scale system for 40 days. Several parameters were determined: temperature, mass reduction, pH, electrical conductivity, colour, zeta potential, phytotoxicity and final compost nutrients. Results The moisture content and compost mass were reduced by 24 and 18 %, respectively. Both final compost pH value and electrical conductivity were found to increase in value. Colour (measured as PtCo) was not suitable as a maturity indicator. The negative zeta potential values decreased from −12.25 to −21.80 mV. The phytotoxicity of the compost mixture was found to decrease in value during the process and the final nutrient value of the compost indicates its suitability as a soil conditioner. Conclusions From this study, we conclude that the addition of paper and grass clippings can be a potential substrate to be composted with anaerobically treated palm oil mill effluent (AnPOME). The final compost produced is suitable for soil conditioner

Corrosion Protection Coatings from Size-Specified Graphene Oxide

Corrosion performance of graphene oxide (GO) coatings from different sheets sizes in 3.5 wt% NaCl solution was investigated. The GO dispersion was subjected to 5 and 10 hours of ultrasonication before electrophoretically deposited (EPD) onto the copper substrate. It was found that the EPD-GO coating from smaller sheets (10h ultrasonication) possess hydrophobic, thinner film and smooth surfaces. It is suggested that the corrosion performance of the coating from smaller GO sheets is improved due to the surface texture and compactness of the coating as compared to the larger GO sheets

Characterizing anomalies in distributed strain measurements of cast-in-situ bored piles

This paper describes the method of identifying typical defects of bored cast-in-situ piles when instrumenting using Distributed Optical Fiber Strain Sensing (DOFSS). The DOFSS technology is based on Brillouin Optical Time Domain Analyses (BOTDA), which has the advantage of recording continuous strain profile as opposed to the conventional discrete based sensors such as Vibrating Wire strain gauges. In pile instrumentation particularly, obtaining distributed strain profile is important when analysing the load-transfer and shaft friction of a pile, as well as detecting any anomalies in the strain regime. Features such as defective pile shaft necking, discontinuity of concrete, intrusion of foreign matter and improper toe formation due to contamination of concrete at base with soil particles, among others, may cause the pile to fail. In this study, a new technique of detecting such defects is proposed using DOFSS technology which can potentially supplement the existing non-destructive test (NDT) methods. Discussion on the performance of instrumented piles by means of maintained load test are also presented

Improvement of dielectric loss of doped Ba0.5Sr0.5TiO3 thin films for tunable microwave devices

Al2O3-Ba0.5Sr0.5TiO3 (Al2O3-BST) thin films, with different Al2O3 contents, were deposited on (100) LaAlO3 substrate by pulsed laser deposition (PLD) technique. The Al2O3-BST films was demosnstrated to be a suitable systems to fabricate ferroelectric thin films with low dielectric loss and higher figure of merit for tunable microwave devices. Pure BST thin films were also fabricated for comparison purpose. The films' structure and morphology were analyzed by X-ray diffractiopn and scanning electron microscopy, respectively; nad showed that the surface roughness for the Al2O3-BST films increased with the Al2O3 content. Apart from that, the broadening in the intensity peak in XRD result indicating the grain size of the Al2O3-BST films reduced with the increasing of Al2O3 dopant. We measured the dielctric properties of Al2O3-BST films with a home-made non-destructive dual resonator method at frequency ~ 7.7 GHZ. The effect of doped Al2O3 into BST thin films significantly reduced the dielectric constant, dielectric loss and tunability compare to pure BST thin film. Our result shows the figure of merit (K), used to compare the films with varied dielectric properties, increased with the Al2O3 content. Therefore Al2O3-BST films show the potential to be exploited in tunable microwave devices.Comment: 8 pages, 4 figures, 1 table. Accepted & tentatively for Feb 15 2004 issue, Journal of Applied Physic