Voltage regulation considerations for the design of hybrid distribution transformers

The future substation depends on finding a way to mitigate the effects of the drawbacks of the conventional legacy by employing the efficiency of the solid state switches [1]. This paper discusses the considerations of designing a distribution transformer that provides additional functions in regulating the voltage and controlling the reactive power that is injected in the distribution network, using a fractional rated converter attached partially with the windings of the transformer. This approach aims mainly to enhance the unit with more flexibility in controlling the voltage at the last mile of the network, in order to decrease the losses and meet the future expectations for low voltage networks modifications, and that by using a power electronic (PE) approach has less losses and more functionality (depending on the reliability of transformer and intelligence of PE). The design of a hybrid distribution transformer is detailed and its functionality in regulating the voltage is discussed as a combination between the features of one of the most reliable network devices, the transformer, and the effect of PE existence with less losses in both switching and conduction losses. Reduced ratings PE are used in this approach, whereby the solid state switches are controlled according to the immediate need for voltage control in low voltage (LV) networks

A unified numerical model of collisional depolarization and broadening rates due to hydrogen atom collisions

Interpretation of solar polarization spectra accounting for partial or complete frequency redistribution requires data on various collisional processes. Data for depolarization and polarization transfer are needed but often missing, while data for collisional broadening are usually more readily available. Recent work by Sahal-Br\'echot and Bommier concluded that despite underlying similarities in the physics of collisional broadening and depolarization processes, relationships between them are not possible to derive purely analytically. We aim to derive accurate numerical relationships between the collisional broadening rates and the collisional depolarization and polarization transfer rates due to hydrogen atom collisions. Such relationships would enable accurate and efficient estimation of collisional data for solar applications. Using earlier results for broadening and depolarization processes based on general (i.e. not specific to a given atom), semi-classical calculations employing interaction potentials from perturbation theory, genetic programming (GP) has been used to fit the available data and generate analytical functions describing the relationships between them. The predicted relationships from the GP-based model are compared with the original data to estimate the accuracy of the method.Comment: 10 pages, 7 figures, Accepted for publication in Astronomy & Astrophysic

PHARMACOKINETICS AND BIOAVAILABILITY OF TYLVALOSIN AFTER ORAL, INTRAMUSCULAR AND INTRAVENOUS ADMINISTRATION IN TURKEYS

Objective: Tylvalosin, is a new macrolide antibiotic, it is highly effective against a range of important diseases in many different veterinary species specially pigs and poultry. The pharmacokinetics and bioavailability of Tylvalosin were investigated in healthy turkeys.Methods: Tylvalosin was orally, intramuscularly, and intravenously administrated to turkeys in a single dose of (25 mg/kg b.w.), and the blood samples were analyzed by using a microbiological assay method.Results: After intravenous injection, the serum concentration-time curves were best described by a two compartment-open model. The distribution and elimination half–life t 0.5 α and t 0.5 β were (0.076±0.0014 h, 0.788±0.107 h), respectively. The volume of distribution Vdss was (1.155±0.183 L/kg), with body clearance Cl (B) of (1.489±0.143 ml/kg/h). Following oral administration, Tylvalosin was absorbed with t 0.5 ab (0.283±0.012 h) and eliminated, with t 0.5 el (5.309±0.542 h). The peak serum concentration was (0.637±0.018 µg/ml) at Tmax of (1.293±0.024 h). Following intramuscular administration, Tylvalosin was absorbed with t 0.5 ab (0.076±0.003 h) and eliminated with t 0.5 el (0.467±0.058 h). The peak serum concentration was (1.446±0.121 µg/ml) at Tmax of (0.282±0.008 h). The systemic bioavailability of Tylvalosin following oral administration was 33.84% and 14.06% after intramuscular administration.Conclusion: These results indicate that, after oral and intramuscular administration, Tylvalosin was rapidly absorbed and distributed to tissues of turkeys. However, repeated doses are necessary to maintain Tylvalosin serum concentration above the MIC for most susceptible microorganisms.Â

Propagation of cracks and dislocations in 2D quasicrystals

A closed-form solution is provided for the stress, strain and velocity fields due to a planar crack steadily propagating in an elastic quasicrystal with fivefold symmetry at speed lower than the bulk wave-speeds. The cases of a semi-infinite rectilinear crack and a Griffith crack which propagates maintaining a constant length, according to the Yoffe model, are considered. Crack face loading and remote loading conditions are taken into consideration. The dynamic theory of quasicrystal with inertia forces, but neglecting dissipative phonon activity, is assumed to govern the motion of the medium. The phonon and phason stress fields turn out to be square-root singular at crack tip. The energy release rate is positive for subsonic and subRayleigh crack propagation

Investigation of enzyme modified cheese production by two species of Aspergillus

Enzymatic biotransformation of dairy protein and fat is the basis of most commercial cheese flavour ingredient processes; such products are commonly referred to as enzyme modified cheese (EMC). EMCs have approximately 15 - 30 times the flavor intensity of natural cheese. They are available as pastes or spray-dried powders. Aspergillus oryzae and Aspergillus niger are two kinds of molds that were used in this study for production of enzyme modified cheese. The results showed that A. nigerand A. oryzae have lipase enzyme activities of about 43.3 and 10 U/g (U = 1 mol/min), respectively, while the proteolytic activity was 143 U/g for A. oryzea and 38 U/g for A. niger. The EMC produced using both A. oryzae and A. niger had the best score of flavor and odor after 3 days of storage;however the cheese produced by only A. oryzea had good flavor after this period of time and the cheese treated with A. niger only just had a strong odor. The results of this study showed that the mixture of A. oryzea and A. niger can be used to produce EMC in much shorter ripening period andwith better flavor

Comparison of Functional Outcome of Total Knee Replacement Between Cruciate Retaining and Cruciate Substituting Prosthesis in Cipto Mangunkusumo Hospital

Background.Total knee replacement is a procedure of choice in the management of severe osteoarthritis. Currently two types of prosthesis are widely used, cruciate retaining and cruciate substituting. Experts have not yet reached agreement regarding which one is better. This study is aimed to compare functional outcome between cruciate retaining and substituting prosthesis. Materials and methods.This study was a randomized single-blinded clinical trial. Patients with severe osteoarthritis were divided into two groups and evaluated before operation. First group underwent cruciate retaining total knee replacement, and the other cruciate substituting total knee replacement. Functional outcome was evaluated in 3 and 6 months after operation, regarding the knee flexion angle and International Knee Documentation Committee score.Results.There were 14 patients. Mean knee flexion angle of cruciate retaining in 3 and 6 months were 105.0 degrees and 113.3 degrees respectively, whereas cruciate substituting were 118.1 degrees and 126.2 degrees. International Knee Documentation Committee score of cruciate retaining in 3 and 6 months were 49.0 and 59.4 respectively, while cruciate substituting were 52.6 and 63.8. There were significant differences in flexion angles between cruciate retaining and cruciate substituting groups at 3 months (p=0.006) and 6 months (p=0.018). No significant difference was demonstrated in International Knee Documentation Committee score between cruciate retaining and cruciate substituting groups at 3 months (p=0.053) and 6 months (p=0.240).Conclusions.Functional outcome regarding the knee flexion angle of cruciate substituting group was 13.1 degrees better in 3 months and 12.9 degrees in 6 months compared to cruciate retaining group. Functional outcome based on International Knee Documentation Committee score score did not show significant differences between two groups whether 3 or 6 months after operation

Effective thermal properties of fibre reinforced materials

The thermal behaviour of an elastic matrix reinforced with synthetic micro or macro fibres subjected to a constant heat flow is investigated in the present work. Steady-state condition for the heat flux is considered and isotropic thermal conductivity for both the matrix and fibres is assumed. Owing to the geometry of the system, reference is made to bipolar cylindrical coordinates. Various boundary conditions can be considered on the contours of the fibres. In particular, for a matrix reinforced with two fibres taken as insulated inclusions, a vanishing heat flow across the contour of the fibres must be imposed. After the temperature field has benn determined analytically, a homogeneization procedure is performed in order to find the equivalent thermal properties of the fibre reinforced composite material

Couple stress effects in a thin film bonded to a half-space

This study investigates the contact mechanics of a thin film laying on an elastic substrate within the context of couple-stress elasticity. It aims to introduce the effects of material internal length scale, which has proven an effective way of modeling structures at micro to nano-scales, allowing to capture their size dependent behavior. Specifically, stress analysis for a thin film bonded to a couple stress elastic half-space is considered under plane strain loading conditions by assuming that both shear stress and couple tractions are exchanged between the thin film and the substrate. The problem is converted to a singular integral equation, which is solved by expanding the shear stress tractions as a Chebyshev series. The results show that the introduction of couple tractions decreases the shear stress tractions and the axial load in the thin film. When the characteristic length is sufficiently small, but still finite, the results for classical elastic behavior are approached

Indentation of a free beam resting on an elastic substrate with an internal lengthscale

The plane strain problem of a slender and weightless beam-plate loaded by a transversal point force in unilateral contact with a couple stress elastic foundation is investigated. The study aims to explore the consequences of the material internal lengthscale on the contact mechanics. In particular, compatibility between the beam and the foundation surface demands that both displacement and rotation match along the contact line. To this aim, couple tractions are exchanged besides the traditional contact pressure until separation between the beam and the foundation occurs. The problem is formulated making use of the Green's functions for a point force and a point couple acting atop of a couple stress elastic half-plane. A pair of coupled integral equations is thus derived, that governs the distribution of contact pressure and couple tractions, with one of them being immediately solved to provide an explicit relation between the two unknowns. In this sense, we retrieve the concept of a mechanically equivalent action, as it is the case of the Kirchhoff shear for plates. The remaining integral equation sets a cubic eigenvalue problem, whose linear term accounts for the microstructure. Its numerical solution is sought by expanding the equivalent contact pressure in series of Chebyshev polynomials vanishing at the contact region ends points, namely the lift-off points, and then applying a collocation strategy. The contact length, the distributions of contact pressure and couple tractions under the beam and the shearing force and bending moment along the beam are then obtained as a function of the material characteristic length. Results clearly indicate that accounting for the material internal lengthscale is mainly realized through exchange of the couple tractions, in the lack of which results much resemble those of the classical solution. Specifically, greater contact lengths and a stronger focusing effect about the loading point are encountered, which become very significant when the contact length approaches the internal lengthscale