Winding movement in power transformers: a comparison of FRA measurement connection methods

Frequency response analysis (FRA) is an effective diagnostic tool for detecting transformer winding movements. Various FRA traces can be measured from a set of transformer winding terminals each of which relate to a different test connection scheme. Practical considerations of test and analysis time dictate that only some of the connections are used, and currently there is no standard test connection. This paper presents a comparison of three FRA measurement connections widely employed in the industry today, namely: end-to-end voltage ratio, input admittance and transfer voltage ratio measurements. Using a simulation model of a 132/11 kV, 30 MVA transformer, FRA traces were generated under these connection schemes and their sensitivity towards three types of winding movement, namely: axial displacement, forced buckling and axial bending was studied. A correlation exists between the FRA measurement results of end-to-end voltage ratio, input admittance and transfer voltage ratio connection methods, provided that the HV neutral is grounded. Among the three connection methods assessed, the transfer voltage ratio connection method has the best sensitivity to axial displacement and forced buckling, whereas the end-to-end voltage ratio method has the best sensitivity towards axial bending     

Controlled Generation of Microspheres Incorporating Extracellular Matrix Fibrils for Three‐Dimensional Cell Culture

A growing body of evidence suggests that studying cell biology in classical two‐dimensional formats, such as cell culture plasticware, results in misleading, non‐physiological findings. This paper describes the optimization of a microsphere‐based system permitting 3D cell culture incorporating physiological extracellular matrix components. Bio‐electrospraying, the most advanced method currently available, is used to produce microspheres containing THP‐1 cells as a model cell line. The bio‐electrospraying para­meters of nozzle size, polymer flow rate, and voltage are systematically investigated in order to allow stable production of size‐controlled microspheres containing extracellular matrix material and human cells. The effect of bio‐electrospraying parameters, alginate type and cell concentration on cell viability are investigated using trypan blue and propidium iodide staining. Bio‐electrospraying has no effect on cell viability nor the ability of cells to proliferate. Cell viability is similarly minimally affected by encapsulation in all types of alginate tested (MVM, MVG, chemical and food‐grade). Cell density of 5 × 106 cells mL^?1 within microspheres is the optimum for cell survival and proliferation. The stable generation of microspheres incorporating cells and extracellular matrix for use in a 3D cell culture will benefit study of many diverse diseases and permit investigation of cellular biology within a 3D matrix.     

A Study of Process Optimization of Extraction of Oil from Fish Waste for Use as A Low-Grade Fuel

Waste oils are potentially advantageous over petroleum and virgin vegetable oil based fuels due to waste utilization, and an overall lowering of gases and most other emissions over the life cycle of fuel production, use, and disposal. Waste generated from fish processing plants varies from 10–50 wt% of landed fish depending on the type of fish, product and processing techniques. A portion of this waste contains fish oil and varies significantly depending on the species. The oil recovery process must maximize extraction of oil and at the same time be able to integrate into the existing infrastructure at fish plants. In this study, we have optimized the recovery process developed in our lab (based on a fishmeal processing) and tested with the waste of a variety of fish species. The oil had low impurities (<0.5 wt% moisture) and degradation products, and physical properties suitable for substitution of No. 6 fuel oils and marine distillate/residual fuels. Based on this, pilot scale experiments were performed to determine scale-up challenges and design specifications for eventual costs analysis (e.g. size, residence time, etc.), energy required and waste emissions.     

A Novel Technique for Forming Self-Assembled Nanotube Structures

A suspension containing multi-wall, hollow structured carbon nanotubes were suspended in polyethylene glycol and electrosprayed. The results present an operational map identifying a parametric window in which stable cone-jet mode exists. At an electric field strength of ∼0.26 kV/mm and corresponding flow rate of ∼1×10^-8 m³s^-1 the finest droplets were generated. These droplets once deposited were analysed using optical and transmission electron microscopy and are compared with those deposits created through a control method. The electrosprayed deposits were further examined using electron diffraction and dispersive X-ray spectroscopy that forms the discussion in this article.     

Coaxial Electrohydrodynamic Atomization of Ceramic Suspensions

In this work we demonstrate a novel method of preparing composite ceramic microstructures, using alumina–zirconia as an example. Suspensions of these two ceramics, containing a similar solids content, were simultaneously subjected to electrohydrodynamic atomization (EHDA) in the stable cone-jet mode and the resulting relics were analyzed by microscopical techniques before and after partial sintering at 1200°C. We show that the new method, coaxial EHDA (CEHDA), is capable of forming different annular microstructures, which are mainly controlled by the speed of the jetting.     

A novel ceramic printing technique based on electrostatic atomization of a suspension

A novel computer-controlled method of depositing ceramic droplets, according to a pre-determined architecture is described. A 21 vol% alumina suspension flowing through a nozzle was subjected to electrostatic atomization in the cone-jet mode at different applied voltages. By using a point-like ground electrode the resulting spray was focused and printed on a substrate placed between the nozzle and the ground electrode. The substrate was moved with the aid of a 2-axis computer controlled stepper motor driven system which enabled the forming of different ceramic architectures. As an example, the word CERAMIC was printed. At an applied voltage of 10 kV, droplet relics in the print were in the size range 30–60 μm. Electronic Publication     

Thermal performance of insulated roof slabs in tropical climates

Reinforced concrete roof slabs can be an ideal alternative to traditional roofs considering the better cyclone resistance that can be offered due to the self weight. However, the concrete slabs do not perform satisfactorily in warm humid tropical climatic conditions and tend to act as heated bodies for the occupants in free running spaces. As a solution, a robust roof slab insulation system is proposed and its thermal performance was determined experimentally using small and large-scale models. With comfort models developed for the people acclimatized to tropical climatic conditions, it is shown that insulated roof slabs could provide acceptable indoor conditions while providing many valuable benefits such as cyclone resistance, regaining of land lost for the house and the possibility of creation of roof top gardens.     

Flacourside,a new 4-oxo-2-cyclopentenylmethyl glucoside from the fruit juice of Flacourtia indica

A new glucoside ester, named flacourside, has been isolated together with known methyl 6-O-(E)-p-coumaroyl glucopyranoside and 6-O-(E)-p-coumaroyl glucopyranose from the n-butanol extract of fruit juice of the Flacourtia indica. The structure of flacourside has been determined to be 4-oxo-2-cyclopentenylmethyl 6-O-(E)-p-coumaroyl-β-d-glucopyranoside on the basis of spectroscopic studies.