Wind turbine speed control of a contactless piezoelectric wind energy harvester

ABSTRACT

Wind turbine control is an important task to make the electricity generation secure in terms of energy demand and machine safety. It also yields to control the desired power level and optimized energy because of the assignment of turbine speed. The contactless piezoelectric wind energy harvester (CPWEH) used in this study has three piezoelectric layers located around the shaft with 120 degrees apart and they are buckled by the magnetic force without any physical contact. The superiority of this device is to generate energy for low wind speeds such as 1.5 m/s. However, for high speeds, high total harmonic distortions (THDs) govern the waveforms, thus controlling the turbine speed becomes necessary for optimizing the output power. Encouraged by this, a small low inertia dc generator is coupled with the wind turbine, and the generator terminals are connected to a resistor through a power switch to generate a braking torque that opposes to wind speed direction. By controlling the switch properly, turbine speed is ensured to remain within a certain band, which accordingly prevents the turbine from rotating very fast at damaging wind speeds. Several experiments are performed on the developed CPWEH with/without the presented control scheme which prove the existence of promising performance of our proposal.     

A novel automatic suspicious mass regions identification using Havrda & Charvat entropy and Otsu's N thresholding

Mass detection is a very important process for breast cancer diagnosis and computer aided systems. It can be very complex when the mass is small or invisible because of dense breast tissue. Therefore, the extraction of suspicious mass region can be very challenging. This paper proposes a novel segmentation algorithm to identify mass candidate regions in mammograms. The proposed system includes three parts: breast region and pectoral muscle segmentation, image enhancement and suspicious mass regions identification. The first two parts have been examined in previous studies. In this study, we focused on suspicious mass regions identification using a combination of Havrda & Charvat entropy method and Otsu's N thresholding method. An open access Mammographic Image Analysis Society (MIAS) database, which contains 59 masses, was used for the study. The proposed system obtained a 93% sensitivity rate for suspicious mass regions identification in 56 abnormal and 40 normal images.     

Visualisierung der Partikelbewegung in einem Abweiseradsichter

In spite of its great importance for the dry classification of fine powders, the processes in deflector wheel classifiers are to a large extent unknown. Therefore, in the present work a commercial available classifier was modified to gain an optical access to the deflector wheel. For the first time, the obtained photographs enable an observation of the gas flow and the particle motion between the blades of the deflector wheel. Especially the importance of particle‐particle‐ and particle‐blade‐collisions could be shown.     

Wax Ester Rich Oil From The Marine Crustacean,Calanus finmarchicus,is a Bioavailable Source of EPA and DHA for Human Consumption

Oil from the marine copepod, Calanus finmarchicus, which contains >86 % of fatty acids present as wax esters, is a novel source of n‐3 fatty acids for human consumption. In a randomized, two‐period crossover study, 18 healthy adults consumed 8 capsules providing 4 g of Calanus^® Oil supplying a total of 260 mg EPA and 156 mg DHA primarily as wax esters, or 1 capsule of Lovaza^® providing 465 mg EPA and 375 mg DHA as ethyl esters, each with an EPA‐ and DHA‐free breakfast. Plasma EPA and DHA were measured over a 72 h period (t = 1, 2, 4, 6, 8, 10, 12, 24, 48, and 72 h). The positive incremental area under the curve over the 72 h test period (iAUC_{0‐72 h}) for both EPA and DHA was significantly different from zero (p < 0.0001) in both test conditions, with similar findings for the iAUC_{0–24 h} and iAUC_{0–48 h}, indicating the fatty acids were absorbed. There was no difference in the plasma iAUC_{0–72 h} for EPA + DHA, or DHA individually, in response to Calanus Oil vs the ethyl ester condition; however, the iAUC_{0–48 h} and iAUC_{0–72 h} for plasma EPA in response to Calanus Oil were both significantly increased relative to the ethyl ester condition (iAUC_{0–48 h}: 381 ± 31 vs 259 ± 39 μg*h/mL, p = 0.026; iAUC_{0‐72 h}: 514 ± 47 vs 313 ± 49 μg*h/mL, p = 0.009). These data demonstrate a novel wax ester rich marine oil is a suitable alternative source of EPA and DHA for human consumption.     

Regio‐ and Enantioselective Sequential Dehalogenation of rac‐1,3‐Dibromobutane by Haloalkane Dehalogenase LinB

The hydrolytic dehalogenation of rac‐1,3‐dibromobutane catalyzed by the haloalkane dehalogenase LinB from Sphingobium japonicum UT26 proceeds in a sequential fashion: initial formation of intermediate haloalcohols followed by a second hydrolytic step to produce the final diol. Detailed investigation of the course of the reaction revealed favored nucleophilic displacement of the sec‐halogen in the first hydrolytic event with pronounced R enantioselectivity. The second hydrolysis step proceeded with a regioselectivity switch at the primary position, with preference for the S enantiomer. Because of complex competition between all eight possible reactions, intermediate haloalcohols formed with moderate to good ee ((S)‐4‐bromobutan‐2‐ol: up to 87 %). Similarly, (S)‐butane‐1,3‐diol was formed at a maximum ee of 35 % before full hydrolysis furnished the racemic diol product.     

Partialsynthesen von Cardenoliden und Cardenolid-Analogen. IX. Cardenolidderivate mit einer ungesättigten Aldehydfunktion am Lactonring

Partial Syntheses of Cardenolides and Cardenolide Analogues. IX. Cardenolide Derivatives with an Unsaturated Aldehyde Function at the Lactone Ring Oxidation of 22-allyl-digitoxigenin-3-acetate [ 1 ] and 22-allyl-digitoxin ( 4 ) with selenium dioxide resulted in the introduction of an oxygen function into the unsaturated C-22 substituent of the cardenolide molecule. The isolated compounds were the 22-(3′-oxo-prop-1′-en-1′-yl)-derivatives 3 and 6 of 1 and 4 , respectively. The molecular biological activity of 3 was estimated to be about six times higher than that of the parent compound 1 .     

An Efficient New Pyrimidine Synthesis – a pathway to octupoles

The condensation of N,N,N′-tris(trimethylsilyl)-amidines ( 6 , 11 , 22 ) with vinamidinium salts ( 1 , 7 ) in the presence of potassium fluoride is the method of choice for the synthesis of pyrimidines ( 8 , 12 , 20 , 23 ). Octupoles comprising 1,3,5-benzene ( 8 ) and triphenylamine ( 12 , 20 ) derivatives can be prepared in high yields.