1,052 research outputs found
Quantum heat engines: limit cycles and exceptional points
We show that the inability of a quantum Otto cycle to reach a limit cycle is
connected with the propagator of the cycle being non-compact. For a working
fluid consisting of quantum harmonic oscillators, the transition point in
parameter space where this instability occurs is associated with a
non-hermitian degeneracy (exceptional point) of the eigenvalues of the
propagator. In particular, a third-order exceptional point is observed at the
transition from the region where the eigenvalues are complex numbers to the
region where all the eigenvalues are real. Within this region we find another
exceptional point, this time of second order, at which the trajectory becomes
divergent. The onset of the divergent behavior corresponds to the modulus of
one of the eigenvalues becoming larger than one. The physical origin of this
phenomenon is that the hot and cold heat baths are unable to dissipate the
frictional internal heat generated in the adiabatic strokes of the cycle. This
behavior is contrasted with that of quantum spins as working fluid which have a
compact Hamiltonian and thus no exceptional points. All arguments are
rigorously proved in terms of the systems' associated Lie algebras
Topology optimized permanent magnet systems
Topology optimization of permanent magnet systems consisting of permanent
magnets, high permeability iron and air is presented. An implementation of
topology optimization for magnetostatics is discussed and three examples are
considered. First, the Halbach cylinder is topology optimized with iron and an
increase of 15% in magnetic efficiency is shown, albeit with an increase of 3.8
pp. in field inhomogeneity - a value compared to the inhomogeneity in a 16
segmented Halbach cylinder. Following this a topology optimized structure to
concentrate a homogeneous field is shown to increase the magnitude of the field
by 111% for the chosen dimensions. Finally, a permanent magnet with alternating
high and low field regions is considered. Here a figure
of merit of 0.472 is reached, which is an increase of 100% compared to a
previous optimized design.Comment: 10 pages, 10 figure
The Potential for Dickeya dianthicola to be Vectored by Two Common Insect Pests of Potatoes
Dickeya dianthicola (Samson) causing blackleg and soft rot was first detected in potatoes grown in Maine in 2014. Previous work has suggested that insects, particularly aphids, may be able to vector bacteria in this genus between plants, but no conclusive work has been done to confirm this theory. In order to determine whether insect-mediated transmission is likely to occur in potato fields, two model potato pests common in Maine were used: the Colorado potato beetle (Leptinotarsa decimlineata Say) and the green peach aphids (Myzus persicae Sulzer). Olfactometry and recruitment experiments evaluated if either insect discriminates between infected and uninfected foliage. To determine whether other insect species may display discriminatory recruitment, pitfall traps and adhesive trap cards were set up beside infected and uninfected plants placed in the field. In the laboratory, beetles and aphids were fed plants infected with Dickeya dianthicola and then transferred onto uninfected plants to determine if bacteria would be transmitted between plants. Both plants and insects were sampled and tested using polymerase chain reaction (PCR) for Dickeya spp. In 2017 and 2018, a single potato field was divided into five rows of four plots with randomly assigned insecticide treatments to selectively suppress aphids and/or Colorado potato beetles. Disease spread was monitored among plants in 2017, and tubers were harvested in both years to test for Dickeya.
Neither Colorado potato beetles nor green peach aphids were attracted to infected foliage in either olfactometry or recruitment experiments. To the contrary, the presence of 2,3-butanediol, which is product of Dickeya fermentation, significantly reduced beetle attraction to the odor of potato foliage. Green peach aphids preferred uninfected foliage, but only when conspecifics were present. Flea beetle (Coleoptera: Chrysomelidae: Alticinae) captures by adhesive cards were affected by the infection status of provisioned potato plants, but the effect was inconsistent between the dates of trap deployment. Neither Colorado potato beetles nor green peach aphids acquired and transmitted D. dianthicola through feeding on infected plants in the laboratory. In the field, neither insect’s abundance correlated significantly with the spread of this disease.
This study did not find indications that D. dianthicola is vectored by either Colorado potato beetles or green peach aphids. Therefore, controlling these pests is unlikely to prevent blackleg outbreaks in potato fields. Instead, the efforts to limit spread of this disease should focus on sanitation, water management, and seed screening
The submerged structure and stratal architecture of the Neapolitan Yellow Tuff (NYT) caldera, offshore the Campi Flegrei, (Eastern Tyrrhenian Margin): new insights from high resolution seismics and gravity core data
The Campi Flegrei is an active volcanic area defined by a
quasi-circular depression that covers some 200 km2 of the coastal
zone of SW Italy, a large part of which develops off the Naples
(Pozzuoli) Bay (Fig. 1). The area has been active at least since 60
ka BP ( Pappalardo et al., 1999), and is structurally dominated by a
caldera, 6 km in diameter, associated with the eruption of the
Neapolitan Yellow Tuff (NYT), a 40 km3 Dense Rock Equivalent
(DRE) ignimbrite (Scarpati et al., 1993) dated at ca 15 ka BP
(Deino et al., 2004), that covered the district now occupied by the
city of Naples, the Campi Flegrei and a large area of the
continental shelf off the Pozzuoli Bay.
The volcanological evolution of the NYT caldera as been long
described on the basis of outcrop and subsurface studies onland
(Rosi & Sbrana, 1987; Orsi et al., 1996, 2004 and references
therein; Di Vito et al., 1999; Perrotta et al., 2006; Fedele et al.,
2011), but its offshore morphology, detailed structure and recent
stratigraphic setting are still poorly understood.
In this study we integrate geological and geophysical data of
different resolution/penetration obtained from high-resolution
reflection seismic profiles (Sparker and Chirp source) with gravity
core and swath bathymetry to better constrain the shallow
structure, stratigraphic architecture and latest Quaternary to
Holocene evolution of the submerged sector of the NYT caldera
off the Pozzuoli Bay.
Our data clearly image, for the first time, the offshore geometry
of the NYT caldera ring-fault zone, as well as the style and timing
of volcano-tectonic deformation associated with the late stage
evolution of the NYT inner caldera resurgence. Our interpretation
suggests that since 15 ka the offshore sector of NYT inner caldera
underwent significant deformation and uplift (with minor
subsidence episodes) that occurred at almost the same rate as the
post-glacial sea-level rise. Particularly, the inner Pozzuoli Bay
started to deform soon after 15 ka BP, when sea-level rise was
initially faster than uplift. This caused a general increase of the
accommodation space that was progressively filled up by
volcaniclastic sediments. Since ca. 8 ka BP, along with the mid
Holocene decrease in the rate of the sea-level rise, the early NYT
resurgent structure was then uplifted up to the sea-level or even to
partial subaerial exposure. From ca. 8 to 5 ka BP two distinct
layers of volcaniclastic resediments, mostly represented by gravity
flow deposits, formed throughout the Bay. A significant post-
Roman (post 2 ka BP) subsidence phase of ca 10 m is then
recorded offshore Pozzuoli by the drowning of the infralittoral
prograding wedge below the present-day fair-weather wave base.
REFERENCES
Deino AL, Orsi G, de Vita S, Piochi M (2004) The age of the Neapolitan Yellow
Tuff caldera-forming eruption (Campi Flegrei caldera—Italy) assessed by
40Ar/39Ar dating method. J. Volcanol. Geotherm. Res. 133, 157–170.
Di Vito M., Isaia R., Orsi G., Southon J., de Vita S., D’Antonio M., Pappalardo
L., Piochi M., 1999. Volcanism and deformation since 12,000 years at the
Campi Flegrei caldera (Italy), J. Volcanol. Geotherm. Res. 91 (2-4), 221-246.
Fedele L., Insinga D.D., Calvert A.T., Morra V., Perrotta A., Scarpati C., 2011.
40Ar/39Ar dating of tuff vents in the Campi Flegrei caldera (southern Italy):
toward a new chronostratigraphic reconstruction of the Holocene volcanic
activity. Bull. Volcanol. 73, 1323-1336.
Orsi G, de Vita S, Di Vito M, 1996. The restless, resurgent Campi Flegrei nested
caldera (Italy): constraints on its evolution and configuration. J. Volcanol.
Geotherm. Res. 74, 179–214.
Orsi G., Di Vito M.A. Isaia R., 2004. Volcanic hazard assessment at the restless
Campi Flegrei caldera. Bull. Volcanol. 66, 514–530.
Pappalardo L., Civetta L., D’Antonio M., Deino A., Di Vito M., Orsi G.,
Carandente A., de Vita S., Isaia R. & Piochi M., 1999. Chemical and Srisotopical
evolution of the Phlegrean magmatic system before the Campanian
Ignimbrite and the Neapolitan Yellow Tuff eruptions J. Volcanol. Geotherm.
Res. 91, 141-166.
Perrotta A., Scarpati C., Luongo G., Morra V., 2006. The Campi Flegrei caldera
boundary in the city of Naples. In: De Vivo B (ed) Volcanism in the
Campania Plain: Vesuvius, Campi Flegrei and Ignimbrites. Elsevier,
Amsterdam, pp 85–96 (in the series Developments in Volcanology, 9)
Scarpati C., Cole P., & Perrotta A., 1993. The Neapolitan Yellow Tuff- A large
volume multiphase eruption from Campi Flegrei, Southern Italy. Bull.
Volcan. 55, 343-35
Low cost external serial interface watchdog for SoCs and FPGAs automatic characterization tests
Manufacturers must characterize their design deeply when designing and producing devices like FPGAs and SoCs. Information collected through simulation and physical experiments is the primary data source for manufacturers that can then decide the optimal working ranges of multiple critical parameters such as operating voltage, frequency, temperatures, etc. With complex devices such as SoCs, and FPGAs with integrated PLLs and voltage regulators, each combination of voltage and frequency can be checked by communicating the desired parameters to the DUT, running a functional test, and observing the results. However once the ATE sends the desired parameters to the DUT through SPI or other serial interfaces, the DUT may freeze and stop to accept new commands entirely. This is particularly problematic for targeted characterization that may include a minimal number of boards and DUTs and where the ATE may simply be a simple laptop without any automatic DUT reset capabilities. This paper presents an external serial communication watchdog designed using an ESP32-based board. Our watchdog can detect the communications coming from the ATE, monitor the answers from the DUT, and restart it through power cycling in case of freezing
L'evoluzione del sistema di riparto di giurisdizione e la nullit\ue0 del provvedimento amministrativo.
Le origini e l'evoluzione del riparto di giurisdizione. Il riparto di giurisdizione nelle pronunce della Consulta degli inizi del XXI secolo. La nullit\ue0 del provvedimento amministrativo ed il riparto di giurisdizione
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