Active power filters — Recent advances

Power electronic loads inject harmonic currents into the utility causing overheating of power transformers and neutral wires, the power system, unpredictable performance of protection systems etc. In addition, electric resonances in such loads can also cause other undesirable phenomena like voltage fluctuations, ratio frequency interference (RFI) etc. To mitigate these undesirable effects, a new class of power electronics equipment (Active Filters) is being considered. A review of present-day solutions in the area of active filters is conducted in this paper. Finally, this paper discusses the trends in the design of active filters and the factors influencing them.     

Velocity field in a twin-screw extruder

Velocity measurements inside the screw channels of a co-rotating, self-wiping, twin-screw extruder were carried out. A laser Doppler anemometer (LDA) system was used to measure tangential and axial velocity components in the translational region of one of the screws of a twin-screw extruder. The velocity measurements were carried out using heavy corn syrup at different screw speeds and for two forwards conveying elements differing in their pitch. It was found that velocity profiles in the translational region were substantially affected by the pitch of the screw element, however, screw speed (30–90 r.p.m.) did not have a significant effect on the shape of the velocity profiles. The range of velocity values in a 14 mm pitch screw element was wider than that in a 28 mm pitch screw element. Experimentally measured velocity profiles were compared with predictions of a one-dimensional model, which showed that the model underpredicted the velocity values, for the 14 mm pitch element.     

Carbohydrate crosslinked biocompatible polyurethanes: Synthesis,characterization, and drug delivery studies

A series of novel polyurethanes (PUs) with carbohydrate crosslinkers was synthesized. The drug loading and release kinetics were studied by using lamotrigine as a model drug. The polymers were designed in such a way that the drug release was tailored by differences in the stoichiometry of polymers. All the PUs were characterized for thermal and morphological properties by using differential scanning calorimetry and thermogravimetric analysis and scanning electron microscope , respectively. The encapsulation of drug inside PU matrix was confirmed via Fourier transform ‐ infrared (FT‐IR) spectra and scanning electron microscope . The kinetics and release mechanisms were observed to be a function of stoichiometric parameters such as type of crosslinker, polyol/crosslinker ratio and polyol/chain extender ratio. All the PUs were observed to be non‐cytotoxic in normal lung cell line L132. The synthesized PUs exhibited good mechanical strength, tunable release rates and biocompatibility that can be utilized in biomedical applications like wound dressing, biomedical implants , and drug delivery carriers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42223.     

Response of laying Japanese quails to graded levels of essential amino acids profile with reduced dietary protein

The effect on egg production of graded levels of ideal amino acids, combined with reduced protein in the diet, was investigated in 312 laying quails aged 6–18 weeks. The quails were offered six diets, each of which contained one of three levels of amino acids (85, 100 and 115% of essential amino acids (EAAs)) together with 5% or without fishmeal (FM) (3 × 2 factorial design). Each diet was offered to 26 replicated groups of two quails each. Hen‐day and hen‐housed egg production did not differ as a result of EAA level, protein type or their interaction during the overall period of egg production. Egg weight improved linearly (P < 0.01) with increased EAA levels, while egg mass output per bird per day remained similar at the 100 and 115% EAA levels. Quails fed higher (100 and 115%) EAA levels had an improved feed conversion ratio (P < 0.01) compared to birds fed 85% EAA. The gain in body weight during the laying period was higher (P < 0.01) at the 100 or 115% than at 85% EAA levels The ratio of egg mass or egg mass and live weight gain, together, to protein intake improved (P < 0.01) linearly with a decrease in EAA levels in the diets, while better (P < 0.01) energy efficiency (EE, energy intake: egg mass) and net EE (energy intake: egg mass plus gain) was obtained in higher EAA levels (100 or 115%). Protein and energy efficiencies remained similar due to protein type or interaction. Shape index, albumen index, yolk index, yolk colour and relative shell weight did not differ due to EAA levels, protein type or their interaction. Eggs laid from quails fed diets with 100% EAAs without FM and 115% EAAs with or without FM had higher shell thickness than those on 85% EAAs irrespective of protein type. The retention of nitrogen and calcium retention was higher (P < 0.01) at the 115% EAA level. The results indicated a dietary level of 100% EAA (185 g kg^?1 crude protein (CP)) with 12.13 MJ kg^?1 was suitable for laying quails of 6–18 weeks of age. Copyright © 2007 Society of Chemical Industry     

Influence of Exposure Time,Shear Stress,and Surfactants on Detachment of <Emphasis Type="Italic">Escherichia coli</Emphasis> O157:H7 from Fresh Lettuce Leaf Surfaces During Washing Process

Washing and sanitation of fresh produce are critical for detachment and inactivation of pathogenic and spoilage microorganisms. The overall goal of this study was to evaluate the influence of processing conditions such as washing time, shear stress, and a food grade surfactant on the detachment of Escherichia coli O157:H7 from lettuce leaf surfaces during a simulated washing process. A benchtop scale rotating disk washing device was designed to simulate the processing conditions used in commercial washing systems. Numerical simulations were carried out to calculate the flow profile and shear stress near the leaf surface. Removal of E. coli O157:H7 as a function of processing conditions in the rotating disk washing device was evaluated by enumeration of bacterial population using plate counting and changes in bioluminescence intensity and further confirmed by bioluminescence imaging. The results showed that shear stress was necessary to remove attached bacteria from inoculated leaf samples and simple incubation of inoculated leaves with wash water was not effective. Furthermore, detachment of bacteria from inoculated leaf samples increased with increasing shear stress and incubation time. Shear stress values in the range of 0 – 300 mPa were adequate to induce removal of approximately 1.5 log CFU/cm² of bacteria from inoculated samples. The addition of a surfactant increased the removal of bacteria from inoculated leaf samples by 0.5 log CFU/cm². Overall, these results may guide the design of new produce wash systems as well as current industrial practice related to flow conditions and use of surfactants during washing of fresh produce.     

Density of additively-manufactured, 316L SS parts using laser powder-bed fusion at powers up to 400 W

Selective laser melting is a powder-based, additive-manufacturing process where a three-dimensional part is produced, layer by layer, by using a high-energy laser beam to fuse the metallic powder particles. A particular challenge in this process is the selection of appropriate process parameters that result in parts with desired properties. In this study, we describe an approach to selecting parameters for high-density (>99 %) parts using 316L stainless steel. Though there has been significant success in achieving near-full density for 316L parts, this work has been limited to laser powers <225 W. We discuss how we can exploit prior knowledge, design of computational experiments using a simple model of laser melting, and single-track experiments to determine the process parameters for use at laser powers up to 400 W. Our results show that, at higher power values, there is a large range of scan speeds over which the relative density remains >99 %, with the density reducing rapidly at high speeds due to insufficient melting, and less rapidly at low speeds due to the effect of voids created as the process enters keyhole mode.     

Dual material gate junctionless tunnel field effect transistor

This paper proposes a junctionless tunnel field effect transistor (JLTFET) with dual material gate (DMG) structure and the performance was studied on the basis of energy band profile modulation. The two-dimensional simulation was carried out to show the effect of conduction band minima on the abruptness of transition between the ON and OFF states, which results in low subthreshold slope (SS). Appropriate selection of work function for source and drain side gate metal of a double metal gate JLTFET can also significantly reduce the subthreshold slope (SS), OFF state leakage and hence gives improved I _ON/I _OFF.     

Creep behaviour of δ-phase of U-Zr system by impression creep technique

In this study, the impression creep behaviour of δ-phase of U-50 wt.% Zr (U-72.29 at.% Zr) system was studied in the temperature range 525-575 °C at different stresses. The velocity of the punch at different stresses and temperatures were evaluated for the above alloy. The stress exponents and thermal activation parameters of the above alloy were determined. A power law behaviour is displayed with the stress exponents range from 6.5 to 7. The activation enthalpy for the δ-UZr₂ was found to be independent of stress with an average value of 106 kJ/mol.     

Exotica/FMDC: A workflow management system for mobile and disconnected clients

Workflow Management Systems (WFMSs) automate the execution of business processes in environments encompassing large numbers of users distributed over a wide geographic area and using heterogeneous resources. Current implementations allow the definition and controlled execution of complex and long lived business processes as the basis for an enterprise-wide collaborative system but, in most cases, the autonomy of the users is greatly restricted due to architectural and design considerations. In particular, existing systems are built around a centralized server. As a result, users need to maintain an uninterrupted connection with the server to perform the different tasks assigned to them. This is a severe restriction, especially when considering the emergence of mobile computing, and the increase in use of laptops and small computers which are connected to the network only occasionally and which will, undoubtedly, be the tool of choice for many users. This paper addresses the problem of supporting disconnected workflow clients in large workflow management systems while still preserving the correctness of the overall execution and allowing coordinated interactions between the different users regardless of their location.Recommended by: Daniel Barbara, Ravi Jain, Narayanan Krishnakumar     

Accuracy Assessment of Upwind Algorithms for Steady-state Computations

Upwind schemes have been evaluated for their accuracy based upon steady-state solutions of Euler and Navier–Stokes equations. It includes the flux-vector splitting schemes due to Steger–Warming and Van Leer, flux-difference splitting schemes due to Roe and Osher, and the hybrid schemes, AUSM (Advection Upstream Splitting method) and HUS (Hybrid Upwind Splitting). Computations for inviscid and viscous compressible flows that are well documented in literature have been carried out in a unified framework. Comparisons of lift, drag, skin-friction and heat-transfer coefficients have been established with reference computational and experimental results.