2,741 research outputs found
Erratum: Allen, G.R., Erdmann, M.V. & Purtiwi, P.D. (2017): Author Purtiwi, P.D. is spelled Pertiwi, P.D.
No full textAllen, G.R., Erdmann, M.V. & Purtiwi, P.D. (2017) Descriptions of four new species of damselfishes (Pomacentridae) in the Pomacentrus philippinus complex from the tropical western Pacific Ocean. Journal of the Ocean Science Foundation, 25, 47–76.
corrected spelling of third author’s name to:
Allen, G.R., Erdmann, M.V. & Pertiwi, P.D. (2017) Descriptions of four new species of damselfishes
(Pomacentridae) in the Pomacentrus philippinus complex from the tropical western Pacific Ocean. Journal of the Ocean Science Foundation, 25, 47–76
A class B switch-mode assisted linear amplifier
No full textA switch-mode assisted linear amplifier (SMALA) combining a linear (Class B) and a switch-mode (Class D) amplifier is presented. The usual single hysteretic controlled half-bridge current dumping stage is replaced by two parallel buck converter stages, in a parallel voltage controlled topology. These operate independently: one buck converter sources current to assist the upper Class B output device, and a complementary converter sinks current to assist the lower device. This topology lends itself to a novel control approach of a dead-band at low power levels where neither class D amplifier assists, allowing the class B amplifier to supply the load without interference, ensuring high fidelity. A 20 W implementation demonstrates 85% efficiency, with distortion below 0.08% measured across the full audio bandwidth at 15 W. The class D amplifier begins assisting at 2 W, and below this value, the distortion was below 0.03%. Complete circuitry is given, showing the simplicity of the additional class D amplifier and its corresponding control circuitry
The philosophy poetry of G.R. Derzhavin: the contrast of life and death
No full textThis article is devoted to the eshatological philosophical concept of the G.R. Derzhavins’ poetry. The author describes the presentation of the theme of death and its artistic transformation in the works of the poet as the reception of the Orthodox tradition, a kind of the cultural memory
The construction of Karen Karnak: The multi-author-function
No full textThis thesis is situated within the comparatively recent developments of Web 2.0 and the emergence of interactive WikiMedia, and explores the mode of authorship within a Read/Write culture compared to that of a Read/Only tradition. The hypothesis of this study is that the role of the audience has become merged with the author, and as such, represents new functions and attributes, distinct from a more conventional concept of authorship, in which the roles of audience and author are more separate. Read/Write and participatory culture, as defined by this study, is focused on collaboration, and includes the influences of D.I.Y. culture, Open-Source practices and the production of text by multiple authors. Multi-authorship presents a re-thinking of several concepts which support the notion of the individual author, since the focus of multi-authorship is not on attribution and ownership of a finished text, but on the continued malleability of a text. Modes of multi-authorship, demonstrated in the use of the pseudonyms Alan Smithee and Karen Eliot, represent declarative authors whose names signify multiple origins, whilst concurrently indicating a distinct body of work. The function of these names form an important context to this study, since primary research involves the construction of an experimental mode of multi-authorship utilising WikiMedia technology and the interaction of thirty nine participants, who are invited to create a body of work under the collective pseudonym Karen Karnak. The data generated by this experiment is analysed using aspects of Michel Foucault's author-function to identify and determine power structures inherent in the WikiMedia context. The interplay of power structures, including concepts such as identity, ownership and the body of work, affect the resulting mode of authorship and contribute to the construction of Karen Karnak, suggesting further areas of research into the emerging multi-author
Cascaded DC-DC converter connection of photovoltaic modules
No full textNew residential scale photovoltaic (PV) arrays are commonly connected to the grid by a single dc-ac inverter connected to a series string of pv panels, or many small dc-ac inverters which connect one or two panels directly to the ac grid. This paper proposes an alternative topology of nonisolated per-panel dc-dc converters connected in series to create a high voltage string connected to a simplified dc-ac inverter. This offers the advantages of a converter-per-panel approach without the cost or efficiency penalties of individual dc-ac grid connected inverters. Buck, boost, buck-boost, and Cuk converters are considered as possible dc-dc converters that can be cascaded. Matlab simulations are used to compare the efficiency of each topology as well as evaluating the benefits of increasing cost and complexity. The buck and then boost converters are shown to be the most efficient topologies for a given cost, with the buck best suited for long strings and the boost for short strings. While flexible in voltage ranges, buck-boost, and Cuk converters are always at an efficiency or alternatively cost disadvantage
Spectral properties of Andreev reflection from quantum turbulence in 3He-B: What do they tell about turbulent fluctuations?
No full textOne of the experimental techniques developed to measure quantum turbulence at low temperatures in 3He-B utilizes the Andreev reflection of thermal quasiparticle excitations from quantized vortices and vortex structures. We present the results of theoretical, numerical, and experimental study of Andreev scattering from quantum turbulence in 3He-B. We analyze the spectral properties of the Andreev reflection and compare these with the spectral properties of superfluid turbulence, and discuss the physical mechanisms responsible for the scaling of spectral densities. Finally, we discuss the relation between our findings and related observables in ordinary turbulence
Elophila obliteralis Walker
No full textElophila obliteralis Walker Isopteryx? obliteralis Walker, 1859: 399. Hydrocampa proprialis Fernald, 1888: 37. Type locality: U.S.A. Described by Munroe (1972) and Shaffer (1968). Imago (Figs. 24, 25): Male wingspan 10–13mm. Head dark fuscous; labial palpus tufted, porrect, pale fuscous; antenna dull fuscous. Thorax dark fuscous. Forewing predominantly dark fuscous; pale subbasal fascia and a postmedian fascia mixed whitish, orange and fuscous; discal spot white, ringed dark fuscous; termen chequered white and dark fuscous. Hindwing dark fuscous; an orange tornal spot preceded by whitish scales. Legs fuscous, darker on joints. Abdomen dark fuscous, paler on edge of each segment. Male genitalia (Fig. 96): Uncus long, spatulate, slightly broader beneath apex, gnathos narrow 2/3 length of uncus, bearing a series of spines on the dorsal edge, valva simple; aedeagus fairly broad, bent near apex and bearing a thick cornutus, the apex being surrounded with spines. Female genitalia (Fig. 146): Ostium wide, ostial chamber narrowing and then broadening into corpus bursae which bears sclerotised patches. Tympanal organs: Venulae widely separated, slightly divergent. Diagnosis: Distinguished by its lack of crosslines on the wings. Biology: Larva on a variety of aquatic plants, in the USA recorded from Nymphaea, Potamogeton, Lemna etc. Distribution: South Africa, presumed to have been introduced, either accidentally or deliberately, from North America. Material examined: SOUTH AFRICA: 7♂ 1♀ Gauteng: Rietondale 25˚ 45´S 28˚ 12´E associated with Azolla filiculoides and Eichhornia crassipes M.P. Hill, 1995, Transvaal; KNP Skukuza 25˚ 00´S 31˚ 35´E xii. 1993 Krüger & Dunning; BOTSWANA, 1♀ Mashati Tuli G.R. Limpopo River, 534m (AJK).Published as part of Agassiz, David J. L., 2012, The Acentropinae (Lepidoptera: Pyraloidea: Crambidae) of Africa, pp. 1-73 in Zootaxa 3494 on page 22, DOI: 10.11646/zootaxa.3494.1.1, http://zenodo.org/record/638078
Phase accumulated carrier pulse width modulation
No full textAn alternative approach to digital PWM generation uses an accumulator rather than a counter to generate the carrier. This offers several advantages. The resolution and gain of the pulse width modulator remain constant regardless of the module clock frequency and PWM output frequency. The PWM resolution also becomes fixed at the register width. Even at high PWM frequencies, the resolution remains high when averaged over a number of PWM cycles. An inherent dithering of the PWM waveform introduced over successive cycles blurs the switching spectra without distorting the modulating waveform. The technique also lends itself to easily generating several phase shifted PWM waveforms suitable for multilevel converter modulation. Several example waveforms generated using both simulation and FPGA hardware are presented
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