Reliability evaluation of power systems with high short‐circuit current reduction

Similar to other cities worldwide, the increasing amounts of short‐circuit current in Bangkok (Thailand) and the vicinity areas are becoming higher than the interrupting capacity (IC) of circuit breakers. To cope with the problem, the Electricity Generating Authority of Thailand (EGAT) has come up with the solutions of network reconfiguration, e.g. bus splitting and transmission line disconnecting. These solutions help reduce effectively the amounts of short‐circuit currents by increasing the equivalent system impedance. However, bus splitting and transmission line disconnecting tend to decrease the system reliability. One of the alternative approaches, the installation of high‐voltage direct current (HVDC) can help reduce the amounts of short‐circuit currents, while the system reliability is maintained. Therefore, this paper mainly presents the reliability evaluation method of the systems with HVDC installation, which requires AC/DC power flow calculation. To avoid system constraint violation, generation redispatch, load shedding, and DC power flow control are executed. The Monte Carlo simulation is used to repeatedly evaluate the system reliability until convergence. The proposed method is tested in (i) the IEEE Reliability Test System 79 (RTS79) to confirm the correctness of reliability evaluation and (ii) the system of EGAT Bangkok including its vicinity areas to show the readiness for real implementation. Comparison of reliability indices among all solutions of short‐circuit current reduction is presented and discussed. The results show that the proposed method is effective and the HVDC installation can increase the system reliability, depending on its installation location and capacity. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Sodium Cardanol Sulfonate Surfactant from Cashew Nut Shell Liquid

Sodium cardanol sulfonate surfactant was synthesized from cardanol from cashew nut shell liquid. Surfactant properties of cardanol sulfonate were determined and compared with dodecylbenzene sulfonate. Surface tension values were determined to be 32.25 mN/m for cardanol sulfonate at 20% w/v and 28.00 mN/m for dodecylbenzene sulfonate at 15% w/v. Critical micelle concentrations of dodecylbenzene sulfonate and cardanol sulfonate were found to be 0.435 and 0.372 mol/L, respectively. In comparison with dodecylbenzene sulfonate, the relative detergency of cardanol sulfonate was calculated to be 93.7% compared to dodecylbenzene sulfonate. Results suggest that cardanol sulfonate can be used as alternative anionic surfactant.

The effect of cetyl palmitate crystallinity on physical properties of gamma-oryzanol encapsulated in solid lipid nanoparticles

This present study was aimed at investigating the effect of the crystallinity of cetyl palmitate based solid lipid nanoparticles (SLNs) on the physical properties of γ-oryzanol-loaded SLNs. SLNs consisting of varying ratios of cetyl palmitate and γ-oryzanol were prepared. Their hydrodynamic diameters were in the range 210-280?nm and the zeta potentials were in the range -27 to -35?mV. The size of SLNs increased as the amount of cetyl palmitate decreased whereas no significant change of zeta potentials was found. Atomic force microscopy pictures indicated the presence of disc-like particles. The crystallinity of SLNs, determined by differential scanning calorimetry and powder x-ray diffraction, was directly dependent on the ratio of cetyl palmitate to γ-oryzanol and decreased with decreasing cetyl palmitate content in the lipid matrix. Varying this ratio in the lipid mix resulted in a shift in the melting temperature and enthalpy, although the SLN structure remained unchanged as an orthorhombic lamellar lattice. This has been attributed to a potential inhibition by γ-oryzanol during lipid crystal growth as well as a less ordered structure of the SLNs. The results revealed that the crystallinity of the SLNs was mainly dependent on the solid lipid, and that the crystallinity has an important impact on the physical characteristics of active-loaded SLNs.     

The preparation and antimicrobial effect of AgZrP/nylon 6,10 fibers used as dental hygiene materials

Silver zirconium phosphate (AgZrP) was incorporated into nylon 6,10 fibers by using a twin screw extruder to produce antimicrobial fibers. Monofilament fibers with various degrees of AgZrP loading were prepared by the melt‐spinning process. The surface concentration of AgZrP particles was found to be dependent on AgZrP loading. A poor interface between AgZrP and the polymeric matrix was observed, however, it did not affect the drawn process. The presence of AgZrP particles did not disturb the structure and slightly effected to the mechanical properties of the nylon fiber. The fiber with the highest draw ratio showed the highest degree of polymer chain orientation, a higher tensile strength and a higher modulus. The antimicrobial effect started when the silver ion concentration was high enough, The AgZrP fiber showed the highest antimicrobial effect on S. mutans, L. Casei, S. aureus, and C. albicans at 10, 15, 10, and 15%, respectively. The AgZrP fibers showed the significant antimicrobial effect on three strains of microorganisms except S. aureus. Antimicrobial activities of AgZrP were demonstrated and the results showed that AgZrP incorporated into the matrix of nylon 6,10 fibers can improve their antimicrobial property. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

An efficient method for the large scale isolation of naringin from pomelo (Citrus grandis) peel

An efficient and simple method was developed to isolate high-purity naringin, a bitter flavoured (to humans) flavanone glycoside with various pharmacological activities, from pomelo ( Citrus grandis Osbeck) peel in high yield. The process, which involves a simple methanol extraction followed by crystallisation in water with the addition of 14–15% (v/v) dichloromethane, gave four times higher yield compared to the same method with no dichloromethane addition and five times higher yield compared to the conventional direct hot water extraction. Through this process, albedo peels from four pomelo cultivars, Khao Taeng-gwa, Khao Yai, Khao Nam Pheung and Tong Dee, gave 24, 22, 20 and 16 mg of naringin g⁻¹ of peel dry weight, respectively. High Performance Liquid Chromatography and Nuclear Magnetic Resonance analysis of the obtained naringin indicated >98% purity. Large scale isolation was also demonstrated.     

Fast texture‐preserving bilateral filtering

A new method for fast bilateral filtering with texture‐preserving properties is presented. In general, the texture area is composed of several tiny regions that have almost similar intensity, and therefore bilateral filtering combines similar gray scales of the texture area to form a smooth region. Adaptive boundary filtering solves this problem by using image segmentation to define a new weighting boundary at each pixel filtering. With the new type of boundary, the output image is smoothed while preserving both edges and textures details. The drawback of this algorithm is that it is time consuming. In this paper, a histogram‐based filtering is proposed to improve the speed of this algorithm. However, as texture details are blurred when a small number of bins are used, it is unable to increase speed by using a small number of bins. Deciles‐based algorithm is therefore applied to overcome this limitation, as it can increase the speed while preserving the texture details. The new algorithm, named fast adaptive boundary filtering, increases the speed by more than 40% when compared with adaptive boundary filtering at a boundary threshold T = 40. The output image of new algorithm shows that it is similar to the output of adaptive boundary filtering. Moreover, the speed of new algorithm is compared with the normal 256‐bin histogram‐based bilateral filtering. From the experimental results, it is seen that the new algorithm has higher speed when it is processed with a small to moderate radius window. In addition, a better output image can be obtained from the new algorithm as it preserves both edges and textures. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Maximization of distributed generation by considering system operating limits and protection reach reduction as constraints

Increased distributed generation (DG) in systems always brings about the impacts on maintaining the operation of protection systems. This paper concentrates on the impact on the protection reach reduction and proposes a solution to eliminate this impact by using a suitable DG transformer in parallel with a grounding reactance at the neutral point of the transformer's winding. Based on this, a Tabu search algorithm is proposed to maximize DG when the system operating limits and the protection reach reduction are considered as constraints. In order to illustrate the effectiveness of this algorithm, a case study is performed through an IEEE 34 Node Test Feeder. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Application of mesoporous magnetic nanosorbent developed from macadamia nut shell residues for the removal of recalcitrant melanoidin and its fractions

ABSTRACT

A novel mesoporous magnetic nanosorbent developed from macadamia nut shell residues was applied as an adsorbent for the removal of dissolved organic carbon (DOC) associated with melanoidin and its fractions in a batch system. The most favored molecular fraction of the melanoidin for adsorption onto the nanosorbent was 1–5 kDa with adsorption capacity of 10.26 mg DOC g^?1 achieving 68.4% removal efficiency. The sorption behaviors were all well fitted to a pseudo-second-order kinetic model and Langmuir isotherm. Optimum operating conditions needed for the maximum uptake of 14.7 mg DOC g^?1 were found to be pH of 6.3, temperature of 41.7°C at the dosage of the magnetic nanosorbent of 877.7 ppm.     

Downlink media streaming with wireless fountain coding in wireline‐cum‐WiFi networks

This paper addresses the problem of streaming packetized media data in a combined wireline/802.11 network. Since the wireless channel is normally the bottleneck for media streaming in such a network, we propose that wireless fountain coding (WFC) be used over the wireless downlink in order to efficiently utilize the wireless bandwidth and exploit the broadcast nature of the channel. Forward error correction (FEC) is also used to combat errors at the application‐layer. We analytically obtain the moment generating function (MGF) for the wireless link‐layer delay incurred by WFC. With the MGF, the expected value of this wireless link‐layer delay is found and used by the access point (AP), who has no knowledge of the buffer contents of wireless receivers, to make a coding‐based decision. We then derive the end‐to‐end packet loss/late probability based on the MGF. We develop an integrated ns‐3/EvalVid simulator to evaluate our proposed system and compare it with the traditional 802.11e scheme which is without WFC capability but equipped with application‐ and link‐layer retransmission mechanisms. Through extensive simulations of video streaming, we show that streaming with WFC is able to support more concurrent video flows compared to the traditional scheme. When the deadlines imposed on video packets are relatively stringent, streaming with WFC also shows superior performance in terms of packet loss/late probability, video distortion, and video frame delay, over the traditional scheme. Copyright © 2011 John Wiley & Sons, Ltd.     

Mesoscale crystallization of calcium phosphate nanostructures in protein (casein) micelles

Aqueous micelles of the multi-protein calcium phosphate complex, casein, were treated at 60°C and pH 7 over several months. Although partial dissociation of the micelles into 12 nm sized amorphous calcium phosphate (ACP)/protein nanoparticles occurred within a period of 14 days, crystallization of the ACP nanoclusters into bundles of hydroxyapatite (HAP) nanofilaments was not observed until after 12 weeks. The HAP nanofilaments were formed specifically within the partially disrupted protein micelles suggesting a micelle-mediated pathway of mesoscale crystallization. Similar experiments using ACP-containing synthetic micelles prepared from ?-casein protein alone indicated that co-aligned bundles of HAP nanofilaments were produced within the protein micelle interior after 24 hours at temperatures as low as 35°C. The presence of Mg2(+) ions in the casein micelles, as well as a possible synergistic effect associated with the multi-protein nature of the native aggregates, could account for the marked inhibition in mesoscale crystallization observed in the casein micelles compared with the single-component b-casein constructs.