Control design and dynamic performance analysis of a windturbine-induction generator unit

This paper presents the modeling and control design for a wind energy conversion scheme using induction generators. The scheme consists of a three-phase induction generator driven by a horizontal axis wind turbine and interfaced to the utility through a double overhead transmission line. A static VAr compensator was connected at the induction generator terminals to regulate its voltage. The mechanical power input was controlled using the blade pitch-angle. Both state and output feedback controllers are designed using MATLAB software to regulate the generator output. From the simulation results, the response of closed loop system exhibited a good damping and fast recovery under different type of large disturbances     

Optimisation of pressurised liquid extraction for antioxidative polyphenolic compound from Momordica charantia using response surface methodology

Pressurised liquid extraction (PLE) of antioxidant compounds from bitter gourd fruits (Momordica charantia) in aqueous ethanolic solvent was investigated using response surface methodology at laboratory scale to understand key impact of extraction variables. Extraction efficiency was optimised by measuring the yield of extraction, total phenolic content (TPC), total flavonoid content (TFC), ferric reducing/antioxidant power assay (FRAP) and radical scavenging activity (RSA). The optimal extraction conditions were reached at 80% ethanol concentration, 10‐min extraction time and at 160 °C. Under these extraction conditions, values of TPC (5.40 ± 0.30 g GAE per 100 g), TFC (1.50 ± 0.10 g QE per 100 g), FRAP (778.55 ± 10 μmol eq Fe (II) g^?1), yield (178.50 ± 5.50 mg g^?1 dc) and RSA (75.50 ± 4.50%) were achieved. Furthermore, statistical analysis revealed that antioxidative attributes of bitter gourd extract were strongly and positively correlated with extraction temperature and ethanol concentration rather than processing time. This study illustrated that PLE has the potential to extract antioxidant compounds from tropical fruit vegetables in an accelerated manner. Furthermore, influential parameters affecting the process could be optimised for further industrial intake.     

Development of specific cutting energy map for sustainable turning: a study of Al 6061 T6 from conventional to high cutting speeds

This study presents the development of a novel Specific Cutting Energy (SCE) based process map for turning of Al 6061 T6 alloy from conventional to high-sp     

Evaluation of cyclic plasticity models of multi-surface and non-linear hardening by an energy-based fatigue criterion

This study examines the performance of four constitutive models according to capacity in predicting metal fatigue life under proportional and non-proportional loading conditions. These cyclic plasticity models are the multi-surface models of Mroz and Garud, and the non-linear kinematic hardening models of Armstrong-Frederick and Chaboche. The range of abilities of these models is studied in detail. Furthermore, the plastic strain energy under multiaxial fatigue condition is calculated in the cyclic plasticity models by the stress-strain hysteresis loops. Using the results of these models, the fatigue lives that have set in the energy-based fatigue model are predicted and evaluated with the reported experimental data of 1% Cr-Mo-V steel in the literature. Consequently, the optimum model in the loading condition for this metal is chosen based on life factor.     

Halophytes: Potential source of ligno-cellulosic biomass for ethanol production

World reserves of petroleum are being consumed rapidly and expected to exhaust by the middle of this century. This realization has led to the introduction of various grades of ethanol supplemented fuel. However, ethanol demands met from sources used for food may cause food shortage. This necessitates exploiting saline lands to produce non-food ligno-cellulosic biomass which, may be converted into ethanol without compromising human food production. Halophytes which produce plenty of biomass using saline resources (water and soil) may be an important alternative. This study shows that species like Halopyrum mucronatum, Desmostachya bipinnata, Phragmites karka, Typha domingensis and Panicum turgidum found in the coastal region of Pakistan, have potential as bio-ethanol crops. These perennial grasses are salt tolerant with high growth rates to produce ligno-cellulosic biomass of good quality (26-37% cellulose, 24-38% hemi-cellulose and <10% lignin) for ethanol production.     

Chemical Composition and Antioxidant Activity of Seeds of Various Halophytic Grasses

Increasing population has resulted in overexploitation of conventional seeds. The limited supply of water and salinization of agricultural lands are threats to crop production. This creates food insecurity and results in ever‐increasing prices of crops and edible oils. Halophytes that produce high‐quality seeds can serve as sources of oil and edible products. We analyzed the chemical composition and antioxidant activity of seeds from 5 halophytic grasses, i.e., Aeluropus lagopoides, Eragrostis ciliaris, Eragrostis pilosa, Panicum antidotale, and Sporobolus ioclados. These seeds contained crude protein (10–29%), carbohydrates (32–55%), crude fiber (4–21%), minerals (3.8–9.2%), and oil (4–11%), indicating their nutritional potential. Oils of these seeds had suitable fatty‐acid composition with 62–82% unsaturation and only 17–24% saturation. Out of this, 91–94% of the total oil constituted by linoleic, oleic, and palmitic acids. High contents of total phenols (2.8–4.2 mg gallic acid equivalent [GAE] g^?1), flavonoids (0.5–1.3 mg Quercetin equivalent [QE] g^?1), and tannins (0.3–1.3 mg catechin equivalent [CE] g^?1) supported their high antioxidant activity (1,1‐Diphenyl‐2‐picryl‐hydrazyl (DPPH) activity in terms of half maximal inhibitory concentration‐IC₅₀ 1.1–5.86 mg mL^?1; 2,2′‐azino‐bis3‐ethylbenzothiazoline‐6‐sulphonic acid (ABTS) 18.8–72.8 mmol Trolox g^?1; ferric‐reducing antioxidant power 2.0–4.4 mmol Fe⁺² g^?1). The reverse phase‐high‐pressure liquid chromatography analysis identified the presence of bioactive phenolic antioxidants (mainly gallic acid, chlorogenic acid, coumaric acid, ferulic acid, kaempferol, and quercetin). Due to these characteristic composition and salt tolerability, these plants can serve as potential sources of industrial raw materials for food, edible oil, phytochemicals, and oliochemicals.     

Effect of soil contamination with heavy metals on soybean seed oil quality

Soybean (Glycine max L.) plants were subjected to different levels of cadmium (Cd²⁺) and mercury (Hg²⁺) stress supplied as CdCl₂, HgCl₂ separately and as binary mixture (CdCl₂ + HgCl₂). An exposure of increasing concentration of heavy metals significantly reduces the oil content when applied separately, while the interactive effect of heavy metal showed less decrease in oil content and showed antagonistic impact of heavy metal on oil content. The study also revealed considerable changes in major and minor fatty acids of the soybean seeds due to heavy metal exposure. There was a noteworthy decrease in the amounts of fatty acid such as oleic acid (18:1), linoleic acid (18:2), while the fatty acids such as palmitic acid (16:0), stearic acid (18:0) and linolineic acid (18:3) were markedly increased as a result of increasing concentration of heavy metals. The results suggested that the heavy metal exposures adversely affected the seed oil content and changes in the fatty acid composition of oil.