A multi-objective evaluation of the impact of the penetration of Distributed Generation

This paper proposes a methodology to consider the effects of the integration of DG on planning. Since DG has potential to defer investments in networks, the impact of DG on grid capacity is evaluated. A multi-objective optimization tool based on the meta-heuristic MEPSO is used, supporting an alternative approach to exploiting the Pareto front features. Tests were performed in distinct conditions with two well-known distribution networks: IEEE-34 and IEEE-123. The results combined minimization and maximization in order to produce different Pareto fronts and determine the extent of the impact caused by DG. The analysis provides useful information, such as the identification of futures that should be considered in planning. A future means a set of realizations of all uncertainties. MEPSO also presented a satisfactory performance in obtaining the Pareto fronts. © 2011 IEEE.

Multi-objective evolutionary particle swarm optimization in the assessment of the impact of distributed generation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Time-series-based maximization of distributed wind power generation integration

Energy policies and technological progress in the development of wind turbines have made wind power the fastest growing renewable power source worldwide. The inherent variability of this resource requires special attention when analyzing the impacts of high penetration on the distribution network. A time-series steady-state analysis is proposed that assesses technical issues such as energy export, losses, and short-circuit levels. A multiobjective programming approach based on the nondominated sorting genetic algorithm (NSGA) is applied in order to find configurations that maximize the integration of distributed wind power generation (DWPG) while satisfying voltage and thermal limits. The approach has been applied to a medium voltage distribution network considering hourly demand and wind profiles for part of the U.K. The Pareto optimal solutions obtained highlight the drawbacks of using a single demand and generation scenario, and indicate the importance of appropriate substation voltage settings for maximizing the connection of MPG.

Distributed generators as providers of reactive power support - A market approach

Traditionally, ancillary services are supplied by large conventional generators. However, with the huge penetration of distributed generators (DGs) as a result of the growing interest in satisfying energy requirements, and considering the benefits that they can bring along to the electrical system and to the environment, it appears reasonable to assume that ancillary services could also be provided by DGs in an economical and efficient way. In this paper, a settlement procedure for a reactive power market for DGs in distribution systems is proposed. Attention is directed to wind turbines connected to the network through synchronous generators with permanent magnets and doubly-fed induction generators. The generation uncertainty of this kind of DG is reduced by running a multi-objective optimization algorithm in multiple probabilistic scenarios through the Monte Carlo method and by representing the active power generated by the DGs through Markov models. The objectives to be minimized are the payments of the distribution system operator to the DGs for reactive power, the curtailment of transactions committed in an active power market previously settled, the losses in the lines of the network, and a voltage profile index. The proposed methodology was tested using a modified IEEE 37-bus distribution test system. © 1969-2012 IEEE.

Penetration of zona-free hamster, bovine and equine oocytes by stallion and bull spermatozoa pretreated with equine follicular fluid, dilauroylphosphatidylcholine or calcium ionophore A23187

Experiments evaluated the ability of follicular fluid (FF), dilauroylphosphatidylcholine (PC12) and the calcium ionophore A23187 (A23187) to induce capacitation in stallion and bull spermatozoa, determined by the ability of the spermatozoa to penetrate zona-free hamster, bovine and equine oocytes. Spermatozoa suspensions were incubated at 37 degreesC in one of the following treatments: 1) a modified Tyrode's medium (BGM3) alone, 2) BGM3 + FF; 3) BGM3 + PC12; 4) BGM3 + FF + PC12; 5) BGM3 + A23187; and 6) BGM3 + FF + A23187. Treated spermatozoa were incubated with zona-free hamster, bovine and equine oocytes for 3 h, after which oocytes were stained to assess spermatozoa penetration. The number of hamster oocytes penetrated by spermatozoa incubated in BGM3 alone (1/30) or in presence of FF (2/31) was significantly lower (P < 0.05) than by spermatozoa treated with PC12 or A23187 (16/30 and 17/30, respectively). Processing stallion spermatozoa either by a swim-up procedure or by centrifugation through a Percoll gradient increased the percentages of motile spermatozoa in the final sample, and spermatozoa collected by both processes penetrated similar numbers of zona-free hamster oocytes (P > 0.05). Although treating spermatozoa with PC12 or A23187 enabled both stallion and bull spermatozoa to penetrate oocytes, higher numbers of bovine oocytes were penetrated by bull spermatozoa (25/30) than by stallion spermatozoa (4/30) regardless of spermatozoal treatment. However, the number of zona-free hamster and equine oocytes penetrated by bull spermatozoa (25/30 and 12/18 respectively) and stallion spermatozoa (17/30 and 15/21 respectively) were similar (P > 0.05). We conclude that both PC12 and A23187 capacitate stallion and bull spermatozoa sufficiently to permit the acrosome reaction to occur, enabling spermatozoa to penetrate homologous and heterologous zona-free oocytes. (C) 2001 by Elsevier B.V.

Asymmetrical penetration of microwave in a conducting media and determination of microwave conductivity for very thin samples using electron spin resonance

Dyson's theory of conduction electron spin resonance (CESR) has been used in the limit d less than or equal to delta (d being the thickness of the sample and delta the skin depth of the microwave field) to obtain the microwave conductivity from the (A/B) ratio of the CESR absorbed power derivative. In this work we calculate the CESR absorbed power derivative using Kaplan's approach and show that the (A/B) ratio can be enhanced if asymmetrical penetration of microwave is used, which means that the microwave field enters into the sample from one of the faces. Therefore, the determination of the microwave conductivity from the (A/B) ratio of the CESR line can be performed for thinner samples. Experimentally, asymmetrical penetration can be obtained if one of the sample's faces is covered with a thin gold layer. The determination of microwave conductivity in conducting polymers films is among the possible applications of this method. (C) 2001 Elsevier B.V. Ltd. All rights reserved.

Penetration of 38% hydrogen peroxide into the pulp chamber in bovine and human teeth submitted to office bleach technique

This study evaluated the pulp chamber penetration of peroxide bleaching agent in human and bovine teeth after office bleach technique. All the teeth were sectioned 3 mm apical of the cement-enamel junction and were divided into 2 groups, A (70 third human molars) and B (70 bovine lateral incisors), that were subdivided into A1 and B1 restored by using composite resin, A2 and B2 by using glass ionomer cement, and A3 and B3 by using resin-modified glass ionomer cement; A4, A5, B4, and B5 were not restored. Acetate buffer was placed in the pulp chamber, and the bleaching agent was applied for 40 minutes as follows: A1-A4 and B1-B4, 38% hydrogen peroxide exposure and A5 and B5, immersion into distilled water. The buffer solution was transferred to a glass tube in which leuco crystal violet and horseradish peroxidase were added, producing a blue solution. The optical density of the blue solution was determined by spectrophotometer and converted into microgram equivalents of hydrogen peroxide. Data were submitted to analysis of variance and Dunnett, Kruskal-Wallis, and Tukey tests (5%). A higher level of hydrogen peroxide penetrated into the pulp chamber in resin-modified glass ionomer cements in bovine (0.79 +/- 0.61 mu g) and human (2.27 +/- 0.41 mu g) groups. The bleaching agent penetration into the pulp chamber was higher in human teeth for any experimental situation. The penetration of the hydrogen peroxide depends on restorative materials, and under the conditions of this study human teeth are more susceptible to penetration of bleaching agent into the pulp chamber than bovine teeth.

Optimal Contract Pricing of Distributed Generation in Distribution Networks

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Location and contract pricing of distributed generation using a genetic algorithm

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Penetration of a light-cured glass ionomer and a resin sealant into occlusal fissures and etched enamel.

PURPOSE: To evaluate the penetration of a light-cured glass ionomer and a resin sealant into occlusal fissures and etched enamel. MATERIALS AND METHODS: Forty-eight maxillary and mandibular caries-free premolars scheduled for extraction for orthodontic reasons were isolated, the occlusal surfaces subjected to prophylaxis and acid-etched with orthophosphoric acid prior to the application of the VariGlass VLC glass ionomer and Concise resin sealants. The teeth were extracted, two longitudinal median sectiors from each tooth were ground to a thickness of 80-100 microns, and the sealant penetration into the fissures evaluated. The sections were placed in nitric acid to dissolve the enamel so the lengths of the tags which had penetrated into the etched enamel could be measured at different sites on the walls of the fissures. RESULTS: Both sealants adapted well to the fissures but penetrated deeper into shallow, open fissures than into deep, constricted fissures. The VariGlass VLC tags into etched enamel were generally longer than the Concise projections.

Effect of capacitation of stallion sperm with polyvinylalcohol or bovine serum albumin on penetration of bovine zona-free or partially zona-removed equine oocytes

Experiments were conducted to study effects of macromolecules on stallion sperm capacitation and fertilization as determined by penetration of bovine zona-free and equine partially zona-removed oocytes. Stallion sperm were capacitated in TYH medium (modified Krebs-Ringer bicarbonate) supplemented with either 1 mg/mL of polyvinylalcohol (PVA) or 4 mg/ mL of BSA. Capacitation was induced with 8 bromoadenosine cyclic monophosphate (8BrcAMP; 0.5 mM) alone or in combination with 0.1 μM of ionomycin. Intraspecies gametes were co-incubated in TYH/PVA or TYH/ BSA for 18 to 20 h. For zona-free bovine oocytes, penetration rate (35%) with the combination of 8BrcAMP and ionomycin in PVA-containing medium was higher (P < 0.05) than any treatment in BSA-containing medium (5 to 6%). A similar study was conducted using equine oocytes with partially removed zonae. Sperm capacitated and used for in vitro fertilization (IVF) in PVA-containing medium had higher penetration rates (P < 0.01) than sperm in BSA-containing medium (54 vs. 11%). The effect of equine preovulatory follicular fluid on bovine oocyte penetration was assessed. Bovine oocytes were matured in tissue culture medium-199 with 0, 20, 50, or 100% equine preovulatory follicular fluid, and 1 IU/mL of equine chorionic gonadotropin. Stallion sperm were treated with 8BrcAMP + ionomycin in PVA- or BSA-containing media. The penetration rates of bovine zona-free oocytes by stallion sperm were again higher with PVA (47%) than BSA (18%; P < 0.01). Penetration rates of oocytes matured in 100% follicular fluid were higher (P < 0.05) than for oocytes matured with 0% follicular fluid. The effects of equine follicular fluid and PVA/BSA during sperm capacitation on standard bovine IVF were examined. Culture of bovine oocytes with equine follicular fluid did not affect oocyte maturation or penetration rates after IVF. Bovine sperm capacitated with heparin in PVA-containing medium yielded lower (P < 0.05) fertilization rates than those capacitated in BSA-containing medium when incubated with both zona-intact and zona-free bovine oocytes. In summary, PVA was superior to BSA for ionophore-induced capacitation of equine sperm for penetration of zona-free bovine oocytes or partially zona-removed equine oocytes, but not for standard bovine IVF with bovine sperm. Zona-free bovine oocytes may be useful for assaying in vitro capacitation and fertilization of stallion sperm. © 2003 American Society of Animal Science. All rights reserved.