4,059 research outputs found
A direct A.C. to A.C. regenerative frequency and voltage converter
No full textIncludes bibliographical references.The reliable variable speed operation of an a. c. machine over a wide speed range is a problem that has received attention for some time. In this thesis a system to permit such operation from a fixed frequency fixed voltage supply is proposed, under the name of the asynchronous modulation converter. This converter is of the cycloconverter family, but is force-commutated and is not synchronised with the supply frequency. The power switching element comprises a power transistor in a diode bridge, coupled to the control circuitry by opto-isolators. The output of the a-mod converter is produced by a "chopper" modulation process and this results in the harmonics present being at frequencies well removed from the fundamental. A feedback system to ensure smooth commutation of the output current from the power switches is described. This feedback system operates by sensing the rate of rise of the inductive voltage surge on the load when a switch is opened to operate a freewheel path switch
Folsomides cariocus Mendonça & Neves 2020, sp. nov.
No full textFolsomides cariocus sp. nov. Figs 2 ̅13 Type material. Holotype: Female: mounted on slide Nº 334 CM / MNRJ, Southeast Brazil, City of Rio de Janeiro, 30.V.2019, M.C. de Mendonça, G. Queiroz, T. Silveira, and A.C. Neves coll. Paratypes 1 specimen on slides Nº 225 CM / MNRJ, 18.II.2019; 1 specimen on slide Nº 228a CM / MNRJ, 18.II.2019; 5 specimens on slide Nº 228b CM / MNRJ, 18. II.2019, M.C. de Mendonça, G. Queiroz, T. Silveira, and A.C. Neves coll., at the same locality. All specimens were deposited in the Museu Nacional / Universidade Federal do Rio de Janeiro, Brazil. Type locality: Bed with compacted clay soil covered by undergrowth and no litter, where bee Epicharis analis Lepeletier, 1841 (Apidae) make roles for reproduction at Botanical Garden, State of Rio de Janeiro, Brazil (Fig. 1). Coordinates: 21°42’37.20’’S; 43°53’46.36’’O. Description. Total holotype body length: 0,84 mm. Paratypes body length: 0,62mm– 0,82 mm. Habitus slender and cylindrical, typical of the genus. Color of body white. Cuticle smooth, with primary granulation. Tergites of thorax and abdomen with 3,3/2,2,2,2,4 S-chaetae and 1,1/0,0,1 S-microchaetae formula. Eyes missing. PAO long and narrow (22 µm) with slight constriction in the anterior middle part and three chaetae on the posterior region. Close to the postantennal organ, one semicircular area without convexity on external part, without pigment and with a finer texture than the surrounding area (Figs. 2) Cephalic chaetae subequal, the anterior and posterior are a little longer (Fig. 3) Antennae slightly shorter than the head. Ratio antennae: head: = 1:1,4. Ant. IV with one subapical small organite on dorsal side, protected by curved chaeta and about eight sensilla (Fig. 4). Ant III with about 18 ordinary chaetae, two S-chaetae S3 and S4 (3µm); two guard S-chaetae S2 and S5 (7 µm) and with one short dorso-lateral sensillum S1 (3µm). Ant. II with about 16 ordinary chaetae, one ventro-external sensillum (5 µm) distally and 2 basal microchaetae, 1 dorsal and 1 ventral (Fig. 5). Ant. I with 11 ordinary chaetae, two subequal sensilla, one thicker (7µm) and one thinner (5 µm) on ventral side and two basal microchaetae, one dorsal and one ventral (Fig. 6). Ratio antennal segments: I: II: III: IV = 1: 1,5: 1,6: 2,7. Labral chaetae formula 2/5,5,4, anterior row inserted on papillae. Maxillary outer lobe with bifurcated palp and three sublobal hairs (Fig. 7). Labium with 3 proximal, 4 basomedial and 5 basolateral chaetae. Labial palps complete. Ventral head with 3+3 post-labial chaetae. Body chaetae smooth and subequal; some longer laterally. Th II with 5+5 axial mesochaetae, 1+1 lateral macrochaetae (32 µm); 2+2 lateral largest sensilla, (11 µm), 1+1 smaller (5 µm) and 1+1 dorsal sensilla (12 µm); Th. III with 3+3 axial mesochaetae, 1+1 lateral macrochaetae (30 µm), 2+2 lateral sensilla (11 µm) and 1+1 dorsal sensilla (12 µm) Thorax without ventral chaetae. Abd. I with 3+3 axial mesochaetae, 1+1 lateral macrochaetae (30 µm) little longer than dorsal chaetae (29 µm), 1+1 lateral sensilla and 1+1 dorsal sensilla (12 µm) (Fig. 8). Abd. II with 3+3 axial mesochaetae, 1+1 lateral macrochaetae (32 µm), 1+1 lateral sensilla situated almost on ventral side (11 µm) and 1+1 dorsal sensilla (12 µm). Abd. III with 3+3 axial mesochaetae, 1+1 lateral macrochaetae (30 µm), 1+1 dorsal sensilla (12 µm), 1+1 lateral sensilla (12 µm) and 1+1 lateral microsensilla (5 µm) both situated on latero-ventral side. Abd. IV with 4+4 axial mesochaetae, 1+1 lateral macrochaetae (31µm) and 1+1 dorsal macrochaetae (29 µm), 1+1 dorsal sensilla (15 µm) and 1+1 lateral sensilla situated on latero-ventral side (12 µm). Dorsal sensilla on Abd I̅IV situated in mid-tergal position and dorsal sensilla on Abd. IV situated behind to the dorsal macrochaeta. Abd. V with 2+2 axial mesochaetae and one unpaired axial mesochaeta, 1+1 lateral macrochaeta (34 µm) and 1+1 dorsal macrochaeta (34 µm), 3+3 dorsal sensilla (20 µm) and 1+1 ventral (18 µm). Abd. VI some macrochaetae (35–40 µm) distributed among few mesochaetae, three unpaired chaetae (a0: 30 µm: m0: 38 µm: p0: 20 µm) (Fig. 9). Appendages. Claws simple, without teeth (18 µm). Unguiculi reduced (4 µm) with a basal lamella and a short apical filament. Tita I, II, III with 20, 20, 21–22 chaetae, Femora I, II, III with 11, 11, 13 chaetae. Trochanter I, II, III with 8, 8, 6 chaetae. Tita I and II with unpaired chaetae B 4/5. Tita III with 7 chaetae in distal whorl with undifferentiated tenent chaetae (Fig. 10, 11). Ventral tube with 3+3 laterodistal and two posterior chaetae. Tenaculum with 3+3 teeth and no chaetae on corpus. Anterior furcal subcoxae with 5 chaetae, one longer than others and posterior subcoxae with 3 chaetae, one longer than others (Fig. 12). Manubrium (60µm) with 7+7 chaetae on posterior side and no chaeta on anterior side. Dens (30µm) with 3+3 anterior chaetae and no chaetae on posterior side. Mucro (10µm) bidentate, separated from dens (Fig.13). Ratio manubrium:dens:mucro as 1:3:6. Females genital plates with 1+1 microchaetae on anterior region. Etymology. The name of the new species cariocus derives from the word ‘’carioca’’ originated from the Tupi indigenous language that means house of white man and actually refers to people born in the city of Rio de Janeiro.Published as part of Mendonça, Maria Cleide De & Neves, Ana Carolina Da Rocha, 2020, New Brazilian species of Folsomides Stach (Collembola: Isotomidae), pp. 443-450 in Zootaxa 4896 (3) on pages 444-445, DOI: 10.11646/zootaxa.4896.3.5, http://zenodo.org/record/438401
Zane Grey with Orange A.C. baseball team
No full textThis photograph shows Ohio native Zane Grey with the Orange A.C. Baseball Team, ca. 1896-1904. Prior to becoming a well-known author of western novels, Zane Grey was also a dentist and a semi-professional baseball player, with teams including the Orange Athletic Club and the Newark (New Jersey) Colts
Experimental research on spatial distribution of overtopping
No full textThe overtopping empirical formulas calculate the discharge only at the top of the crest of a coastal protection structure. On the other hand, the tolerable overtopping discharges are defined at certain points behind the crest where the total overtopping is reduced. The scope of this thesis is to find an empirical formula to describe the distribution of overtopping at the space behind the crest. This thesis comes as a further investigation on the work conducted by v.Kester [2009] for regular waves. In this research, a physical model was developed on which irregular waves are tested. Because of the duration of the tests and the amount of collected water (significant lose of water during the test), a completely new measuring system was designed. Five influencing parameters (variables) are considered on this research: wave height, wave period/steepness, slope angle, crest freeboard and crest permeability. The entire overtopping process is analysed separately for the total overtopping discharge, the overtopping discharge directly behind the crest and the distribution of overtopping behind the structure. In the analysis of the data collected from the measurements, the impact of the varying parameters is investigated leading to useful conclusions and better understanding of the entire process. Additionally, the experimental findings are analysed and compared to the relative existing methods. Based on the TAW [2002] method which is proposed by the EurOtop Manual [2007], a prediction formula is developed. This formula is a generic version of TAW [2002] formula in which a new reduction factor ?c is introduced in order to describe the decay of the overtopping and thus predict the discharge at any certain distance behind the crest. Other relevant methods are also analysed (Juul Jensen [1984], Steenaard [2002], Besley [1999] and v.Kester [2009]) and conclusions for their applicability are drawn leading to suggested improvements or corrections. Apart from the distribution of overtopping, on this thesis the determination of crest freeboard (which is an ambiguous issue) is also investigated. Finally, suggestions of further research on this topic are discussed. The entire work has been perfomed in close cooperation with van Oord.Hydraulic EngineeringCivil Engineering and Geoscience
Flow over partially liquid filled cavity
No full textExperiments have been carried out to investigate the effect of liquid cavity filling on the behavior of the gas flow over a flat plate cavity. PIV measurements in the gas phase reveal that cavity filling can affect vortex shedding in the cavity mouth. Shear layer vortices can break-up into smaller vortices, thereby losing their periodic interaction with the aft wall and, hence, their sound producing potential. Expected is that this is one of the mechanisms causing sound mitigation in corrugated pipes with liquid addition, observed in literature
On modular lattices generated by chains
No full textDe La Maza, A.C. (reprint author). Instituto de Matematica y Fisica, Universidad de Talca. Casilla 747, Talca, Chile.We describe the free modular lattice generated by two chains and a single point, under the assumption that there are few meets
Teoria de controle de sistemas lineares multivariaveis : uma análise comparativa das teorias geométrica e polinomial
No full textLarge aperture A.C. interferometry
No full textThesis (M.S.)--University of Rochester. College of Engineering and Applied Science. Institute of Optics, 1977. This thesis was digitized by the Institute of Optics in 2014 and was determined to have lapsed into the public domain. If you are the author and have questions about the digitization of your work, please contact Kari Brick, Graduate Program Coordinator for the Institute of Optics, at [email protected]. Other contact information for the Institute is available at http://www.optics.rochester.eduOptical interferometry for testing of large optical components has been studied. Various designs of interferometers were investigated and evaluated with respect to their potential utilization for testing of a variety of relatively large optical components. A modified Twyman-Green Interferometer was designed and assembled. This optical system has the versatility and capability of testing the various optical components with clear apertures up to 200 mm. in diameter. This optical system allows the use of a laser source at visible wavelengths as well as 1.06 microns. A technique for measuring optical phase electronically was developed. The technique called phase lock interferomtry irivolves an electronic feedback loop that maintains the phase on a scanning detector. The voltage that is required in this loop to "track" fringes is a direct measure of optical phase. To obtain information at points of interest in the aperture, a dual galvanometer scanning system and the associated driver electronics were designed and built. To handle the large amounts of data obtained, computer software was developed that stored phase and point ion information and performed the necessary data interpretation and reduction to allow the user to receive easily interpretable results
Quantized current steps due to the a.c. coherent quantum phase-slip effect
No full text| openaire: EC/H2020/862660/EU//QUANTUM E-LEAPS Funding Information: This work was supported by European Union’s Horizon 2020 Research and Innovation Programme under grant agreement no. 862660/QUANTUM E-LEAPS and Engineering and Physical Sciences Research Council (EPSRC) grant no. EP/T004088/1. Publisher Copyright: © 2022, The Author(s), under exclusive licence to Springer Nature Limited.The a.c. Josephson effect predicted in 19621 and observed experimentally in 19632 as quantized ‘voltage steps’ (the Shapiro steps) from photon-assisted tunnelling of Cooper pairs is among the most fundamental phenomena of quantum mechanics and is vital for metrological quantum voltage standards. The physically dual effect, the a.c. coherent quantum phase slip (CQPS), photon-assisted tunnelling of magnetic fluxes through a superconducting nanowire, is envisaged to reveal itself as quantized ‘current steps’3,4. The basic physical significance of the a.c. CQPS is also complemented by practical importance in future current standards, a missing element for closing the quantum metrology triangle5,6. In 2012, the CQPS was demonstrated as superposition of magnetic flux quanta in superconducting nanowires 7. However, the direct flat current steps in superconductors, the only unavailable basic effect of superconductivity to date, was unattainable due to lack of appropriate materials and challenges in circuit engineering. Here we report the direct observation of the dual Shapiro steps in a superconducting nanowire. The sharp steps are clear up to 26 GHz frequency with current values 8.3 nA and limited by the present set-up bandwidth. The current steps were theoretically predicted in small Josephson junctions 30 years ago5. However, unavoidable broadening in Josephson junctions prevents their direct experimental observation8,9. We solve this problem by placing a thin NbN nanowire in an inductive environment.Peer reviewe
Stabiliteit van het achtertalud van een rubble mound golfbreker
No full textCivil Engineering and Geoscience
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