144,240 research outputs found
Binding energies of hydrogen-like impurities in a semiconductor in intense terahertz laser fields
A detailed theoretical study is presented for the influence of linearly
polarised intense terahertz (THz) laser radiation on energy states of
hydrogen-like impurities in semiconductors. The dependence of the binding
energy for 1s and 2p states on intensity and frequency of the THz radiation has
been examined.Comment: 14 pages, 4 figure
Observation of strong electron dephasing in disordered CuGeAu thin films
We report the observation of strong electron dephasing in a series of
disordered CuGeAu thin films. A very short electron dephasing
time possessing very weak temperature dependence around 6 K, followed by an
upturn with further decrease in temperature below 4 K, is found. The upturn is
progressively more pronounced in more disordered samples. Moreover, a ln
dependent, but high-magnetic-field-insensitive, resistance rise persisting from
above 10 K down to 30 mK is observed in the films. These results suggest a
nonmagnetic dephasing process which is stronger than any known mechanism and
may originate from the coupling of conduction electrons to dynamic defects.Comment: to appear in Phys. Rev. Let
Core-collapse supernovae ages and metallicities from emission-line diagnostics of nearby stellar populations
Massive stars are the main objects that illuminate H II regions and they
evolve quickly to end their lives in core-collapse supernovae (CCSNe). Thus it
is important to investigate the association between CCSNe and H II regions. In
this paper, we present emission line diagnostics of the stellar populations
around nearby CCSNe, that include their host H II regions, from the PMAS/PPAK
Integral-field Supernova hosts COmpilation (PISCO). We then use BPASS stellar
population models to determine the age, metallicity and gas parameters for H II
regions associated with CCSNe, contrasting models that consider either single
star evolution alone or incorporate interacting binaries. We find binary-star
models, that allow for ionizing photon loss, provide a more realistic fit to
the observed CCSN hosts with metallicities that are closer to those derived
from the oxygen abundance in O3N2. We also find that type II and type Ibc SNe
arise from progenitor stars of similar age, mostly from 7 to 45 Myr, which
corresponds to stars with masses < 20 solar mass . However these two types SNe
have little preference in their host environment metallicity measured by oxygen
abundance or in progenitor initial mass. We note however that at lower
metallicities supernovae are more likely to be of type II.Comment: 22 pages, 19 Figures, 6 Tables. Accepted by MNRAS. Comments welcom
Experimental investigation of a double-diffused MOS structure
Self-aligned polysilicon gate technology was applied to double-diffused MOS (DMOS) construction in a manner that retains processing simplicity and effectively eliminates parasitic overlap capacitance because of the self-aligning feature. Depletion mode load devices with the same dimensions as the DMOS transistors were integrated. The ratioless feature results in smaller dimension load devices, allowing for higher density integration with no increase in the processing complexity of standard MOS technology. A number of inverters connected as ring oscillators were used as a vehicle to test the performance and to verify the anticipated benefits. The propagation time-power dissipation product and process related parameters were measured and evaluated. This report includes (1) details of the process; (2) test data and design details for the DMOS transistor, the load device, the inverter, the ring oscillator, and a shift register with a novel tapered geometry for the output stages; and (3) an analytical treatment of the effect of the distributed silicon gate resistance and capacitance on the speed of DMOS transistors
Experimental investigation of a shielded complementary Metal-Oxide Semiconductor (MOS) structure
A shielded integrated complimentary MOS transistor structure is described which is used to prevent field inversion in the region not occupied by the gates and which permits the use of a thinner field oxide, reduces the chip area, and has provision for simplified multilayer connections. The structure is used in the design of a static shift register and results in a 20% reduction in area
Tooth profile analysiis of circular-cut, spiral-bevel gears
An analysis of tooth profile changes in the transverse plane of circular-cut, spiral-bevel crown gears is presented. The analysis assumes a straight-line profile in the mid-transverse plane. The profile variation along the centerline is determined by using expressions for the variation of the spiral angle along the tooth centerline, together with the profile description at the mid-transverse plane. It is shown that the tooth surface is a hyperboloid and that significant variations in the pressure angle are possible
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