Analysis and design of a half-bridge parallel resonant converter

A half-bridge parallel resonant converter (PRC) is analyzed in detail for both continuous-conduction-mode and discontinuous-conduction-mode operations to provide more straightforward and easy-to-use design tools. Closed-form solutions are derived for the PRC operating under steady-state conditions. Theoretical results obtained are presented in the form of normalized design graphs. They could be directly utilized in designing a half-bridge PRC, having up to 2:1 input voltage variation. They do not necessitate converting the obtained ratings, depending on the input voltage and load variations, to check the worst case values. A design example of a 500 kHz 150 W offline switching power supply is given for both modes of operation, and it is implemented for experimental verification.<>     

The magnetic properties of the MgCd ferrite system by Mössbauer spectroscopy

The Mg-Cd ferrite system has been studied in detail by means of Mössbauer effect at 80K. Mössbauer spectra for x = 0.0 to 0.6 suggest the existance of two hyperfine fields, one due to the Fe³⁺ octahedral ions (B-sites) and the other due to the Fe³⁺ tetrahedral ions (A-sites), while for x = 0.8 it shows relaxation behaviour and for x ≥ 0.9 it exhibits a paramagnetic quadrupole doublet. The variation of nuclear magnetic fields at the A and B sites are explained on the basis of supertransferred hyperfine interactions. It has been found that the QS increases from MgFe₂O₄ to CdFe₂O₄ as the cadmium concentration is increased.     

Synthesis,characterization and polycondensation of Bis-(4-hydroxybutyl) terephthalate

Summary Monomeric Bis-(4-hydroxybutyl) terephthalate has been synthesized and characterized. Titanium iso-propoxide has been found to be a superior catalyst for transesterification compared to metal acetates. Further polycondensation of Bis (HBT) yields poly (1,4-butylene terephthalate). The effect of various titanium derived catalysts on the polycondensation of Bis (HBT) has been studied. The catalytic efficiency of these derivatives is ascribed to their relative hydrolytic stability and the degree of interaction between the carbonyl oxygen and the metal.     

Variability of degree of high order compositeness in fats from the same biological species: Fats from geographic varieties ofpongamia glabra,Nerium thevetifolium andMoringa pterygosperma

Seed fats from four geographic varieties ofP. glabra (Sm 20.2, 27.1, 25.2 and 24.7), three ofN. thevetifolium (Sm 33.5, 36.3 and 33.1) and two ofM. pterygosperma (Sm 23.2 and 20.6) showed high order compositeness (HOC) indices of GS₃nil, GS₂U +5.2, −3.1, +5.2 and +9.0, GS₃nil, GS₂U +0.9, +7.0 and +2.0 and GS₃nil, GS₂U +2.0 and +7.3 respectively. Since geographic varieties are morphologically indistinguishable no fixed relationship can any longer be expected between the proportions of acids and glycerides in different specimens of fat from the same biological variety. Prediction of glyceride structures of different specimens of fat from the same variety can hence be made only to the extent of HOC ranges just as in the case of fats from different varieties or species. Fats from geographic varieties belonging to different biological species show different kinds of relationships between the component saturated and unsaturated acids. No quantitative or even qualitative correlation exists between the HOC indices and the proportions of saturated acids in fats from geographical varieties belonging to the same biological source.     

Heat transfer investigations for in-bed and freeboard vertical U-tubes in a fluidized bed at moderate temperatures

The heat transfer coefficients for a single U-tube immersed vertically in fluidized beds of silica sands ($\text{d}\text{?}{}_{\mathrm{p}}\text{= 222, 488, and 778 μ}\text{m}$) and for a bundle of six hair-pin shaped nested vertical tubes mounted in the freeboard have been measured as a function of fluidizing velocity at bed temperatures ranging from 365 to 535 K. Simultaneous measurements of bed voidage were also made in each case. The effects of bed temperature, fluidizing velocity and particle size on in-bed and freeboard heat transfer coefficients and voidage are examined and explained.     

The fate of Listeria monocytogenes during the manufacture of Camembert-type cheese: A comparison between raw milk and milk treated with high hydrostatic pressure

Camembert-type cheese was produced from: raw bovine milk; raw milk inoculated with 2 or 4 log CFU/ml Listeria monocytogenes; raw milk inoculated with L. monocytogenes and subsequently pressure-treated at 500 MPa for 10 min at 20 °C; or uninoculated raw milk pressure-treated under these conditions. Cheeses produced from both pressure-treated milk and untreated milk had the typical composition, appearance and aroma of Camembert. Curd and cheese made from inoculated, untreated milk contained large numbers of L. monocytogenes throughout production. An initial inoculum of 1.95 log CFU/ml in milk increased to 4.52 log CFU/g in the curd and remained at a high level during ripening, with 3.85 log CFU/g in the final cheese. Pressure treatment inactivated L. monocytogenes in the raw milk at both inoculum levels and the pathogen was not detected in any of the final cheeses produced from pressure-treated milk. Therefore high pressure may be useful to inactivate L. monocytogenes in raw milk that is to be used for the production of soft, mould-ripened cheese.

Industrial relevance

This paper demonstrates the potential of high pressure (HP) for treatment of raw milk to be used in the manufacture of soft cheeses. HP treatment significantly reduced the level of Listeria monocytogenes in the raw milk and so allowed the production of safer non-thermally processed camembert-like soft cheese.     

Low Complexity Preprocessing Approach for Wireless Physical Layer Secret Key Extraction Based on PCA

Achieving communication security, along with high computational efficiency, is one of the challenging issues in the advancement of modern resource constraint wireless networks. Wireless physical layer secure key extraction in conjunction with suitable preprocessing techniques may be a possible way out. Principal component analysis (PCA) is one of the dimensionality reduction techniques employed commonly in various domains for different applications. However, the physical layer secure key extraction employing PCA as dimensionality reduction is untouched so far. This paper presents a comprehensive study on PCA based wireless secret key extraction with real-time experimentation. In this work, we propose to apply PCA as a preprocessing technique to reduce the total number of numerical computations required in the key generation process, by cutting down the dimension of the input data set. We propose to select the extracted principal components to be processed further for key generation, based on their information content and cross-correlation. We analyzed the performance of the proposed in terms of bit disagreement rate, key randomness and pass ratio. The computational complexity of the proposed approach is derived and the effect of dimensionality reduction factor (\({\mathbf{R}}_{\mathbf{f}}\)) on the required numerical computations is analyzed. It is found that substantial improvement in bit disagreement performance is achieved along with a significant reduction in the required numerical computations. Remarkably, these outcomes are achieved by slightly modifying one of the blocks of the traditional key generation system. Furthermore, the practicability of the proposed technique is verified through real-time experimentation in different physical scenarios.

     

Dynamic shovel allocation approach to short-term production planning in open-pit mines

The complexity and uncertainties associated with mining operations often lead to deviations from short-term plans. A proactive approach will predict such deviations and help minimise opportunity losses, providing economic and operational gains. This paper presents an optimisation tool as a dynamic shovel allocation decision-maker for mining operation simulation models. The objectives of the optimisation tool are to provide shovel allocations to mining faces in order to maximise production, meet desired head grade and tonnage at the crushers, and minimise shovel movements. This paper presents the development and implementation of the optimisation tool with an iron ore mine case study.     

Identification,Phylogeny, and Comparative Expression of the Lipoxygenase Gene Family of the Aquatic Duckweed,Spirodela polyrhiza,during Growth and in Response to Methyl Jasmonate and Salt

Lipoxygenases (LOXs) (EC 1.13.11.12) catalyze the oxygenation of fatty acids and produce oxylipins, including the plant hormone jasmonic acid (JA) and its methyl ester, methyl jasmonate (MeJA). Little information is available about the LOX gene family in aquatic plants. We identified a novel LOX gene family comprising nine LOX genes in the aquatic plant Spirodela polyrhiza (greater duckweed). The reduced anatomy of S. polyrhiza did not lead to a reduction in LOX family genes. The 13-LOX subfamily, with seven genes, predominates, while the 9-LOX subfamily is reduced to two genes, an opposite trend from known LOX families of other plant species. As the 13-LOX subfamily is associated with the synthesis of JA/MeJA, its predominance in the Spirodela genome raises the possibility of a higher requirement for the hormone in the aquatic plant. JA-/MeJA-based feedback regulation during culture aging as well as the induction of LOX gene family members within 6 h of salt exposure are demonstrated.