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1.
For over 27 years, SCD has been manufacturing and developing a wide range of high performance infrared detectors, designed
to operate in either the mid-wave (MWIR) or the long-wave (LWIR) atmospheric windows. These detectors have been integrated
successfully into many different types of system including missile seekers, time delay integration scanning systems, hand-held
cameras, missile warning systems and many others. SCD’s technology for the MWIR wavelength range is based on its well established
2D arrays of InSb photodiodes. The arrays are flip-chip bonded to SCD’s analogue or digital signal processors, all of which
have been designed in-house. The 2D focal plane array (FPA) detectors have a format of 320×256 elements for a 30-μm pitch
and 480×384 or 640×512 elements for a 20-μm pitch. Typical operating temperatures are around 77–85 K. Five years ago SCD began
to develop a new generation of MWIR detectors based on the epitaxial growth of antimonide based compound semiconductors (ABCS).
This ABCS technology allows band-gap engineering of the detection material which enables higher operating temperatures and
multi-spectral detection. This year SCD presented its first prototype FPA from this program, an InAlSb based detector operating
at a temperature of 100 K. By the end of this year SCD will introduce the first prototype MWIR detector with a 640×512 element
format and a pitch of 15 μm. For the LWIR wavelength range SCD manufactures both linear Hg1−xCdxTe (MCT) detectors with a line of 250 elements and time delay and integration (TDI) detectors with formats of 288×4 and 480×6.
Recently, SCD has demonstrated its first prototype uncooled detector which is based on VOx technology and which has a format of 384×288 elements, a pitch of 25 μm, and a typical NETD of 50 mK at F/1. In this paper,
we describe the present technologies and products of SCD and the future evolution of our detectors for the MWIR and LWIR detection.
The paper presented there appears in Infrared Photoelectronics, edited by Antoni Rogalski, Eustace L. Dereniak, Fiodor F. Sizov, Proc. SPIE Vol. 5957, 59570S (2005). 相似文献
2.
Alexander L. Kholmetskii 《Foundations of Physics》2006,36(5):715-744
In this paper we pay attention to the inconsistency in the derivation of the symmetric electromagnetic energy–momentum tensor for a system of charged particles from its canonical form, when the homogeneous Maxwell’s equations are applied to the symmetrizing gauge transformation, while the non-homogeneous Maxwell’s equations are used to obtain the motional equation. Applying the appropriate non-homogeneous Maxwell’s equations to both operations, we obtained an additional symmetric term in the tensor, named as “compensating term”. Analyzing the structure of this “compensating term”, we suggested a method of “gauge renormalization”, which allows transforming the divergent terms of classical electrodynamics (infinite self-force, self-energy and self-momentum) to converging integrals. The motional equation obtained for a non-radiating charged particle does not contain its self-force, and the mass parameter includes the sum of mechanical and electromagnetic masses. The motional equation for a radiating particle also contains the sum of mechanical and electromagnetic masses, and does not yield any “runaway solutions”. It has been shown that the energy flux in a free electromagnetic field is guided by the Poynting vector, whereas the energy flux in a bound EM field is described by the generalized Umov’s vector, defined in the paper. The problem of electromagnetic momentum is also examined. 相似文献
3.
X. Rottenberg R. Jansen C. Van Hoof H. A. C. Tilmans 《Applied Physics A: Materials Science & Processing》2011,103(3):869-875
This paper presents a meta-material-based design method for bulk acoustic wave (BAW) resonators with enhanced characteristics
compared to those obtained with the typical bulk material implementation. We demonstrate the novel use of empty inclusions
(i.e., ‘holes’) in bulk materials for engineering their acoustic (mechanical) properties (e.g. Young’s modulus E, Poisson’s ratio ν and mass density ρ) to tune and achieve optimal acoustical performance/characteristics. Inclusions have been demonstrated before to produce
phononic band gaps for wave trapping. We focus on the propagation characteristics of the meta-materials brought into being
by these inclusions. We implement patterns of holes with different sizes and distributions, to effectively scatter acoustic
waves in bar-type BAW resonators and to devise the desired resonator properties, e.g., the resonant frequency. While the available
bulk material is homogeneous and isotropic, the bar consists of an equivalent non-homogeneous material that can for example
be distributed by design in order to shrink the overall resonator size, enhance electromechanical transduction coefficients
or reject spurious modes. Our paper compares two extraction methods for the equivalent material properties of a periodically
hole-punched material: the steady-state mechanical simulation of a unit cell and its ‘phase delay’ counterpart. We discuss
their validity and practical use for the design of bar resonators. 相似文献
4.
Mahendra K. Verma 《Pramana》2003,61(3):577-594
Energy cascade rates and Kolmogorov’s constant for non-helical steady magnetohydrodynamic turbulence have been calculated
by solving the flux equations to the first order in perturbation. For zero cross helicity and space dimensiond = 3, magnetic energy cascades from large length-scales to small length-scales (forward cascade). In addition, there are energy
fluxes from large-scale magnetic field to small-scale velocity field, large-scale velocity field to small-scale magnetic field,
and large-scale velocity field to large-scale magnetic field. Kolmogorov’s constant for magnetohydrodynamics is approximately
equal to that for fluid turbulence (≈ 1.6) for Alfvén ratio 05 ≤r
A ≤ ∞. For higher space-dimensions, the energy fluxes are qualitatively similar, and Kolmogorov’s constant varies asd
1/3. For the normalized cross helicity σc →1, the cascade rates are proportional to (1 − σc)/(1 + σc , and the Kolmogorov’s constants vary significantly with σcc. 相似文献
5.
In this paper we have obtained some new exact solutions of Einstein’s field equations in a spatially homogeneous and anisotropic
Bianchi type-V space-time with perfect fluid distribution along with heat-conduction and decaying vacuum energy density Λ
by applying the variation law for generalized Hubble’s parameter that yields a constant value of deceleration parameter. We
find that the constant value of deceleration parameter is reasonable for the present day universe. The variation law for Hubble’s
parameter generates two types of solutions for the average scale factor, one is of power-law type and other is of the exponential
form. Using these two forms, Einstein’s field equations are solved separately that correspond to expanding singular and non-singular
models of the universe respectively. The cosmological constant Λ is found to be a decreasing function of time and positive
which is corroborated by results from recent supernovae Ia observations. Expressions for look-back time-redshift, neoclassical
tests (proper distance d(z)), luminosity distance red-shift and event horizon are derived and their significance are described in detail. The physical
and geometric properties of spatially homogeneous and anisotropic cosmological models are discussed. 相似文献
6.
Results from Super-Kamiokande-I’s entire 1496 live days of solar neutrino data are presented, including the absolute flux,
energy spectrum, zenith angle (day/night) and seasonal variation. The possibility of MSW and vacuum oscillations is discussed
in light of these results. Results from the first 1289 days of Super-K-I’s atmospheric neutrino analysis are also presented,
including the evidence for νμ →ν
τ oscillations, against νμ → νsterile oscillations, and the current limits on proton decay. Finally, results based on 56 × 1019 protons on target are given for the K2K long-baseline neutrino oscillation experiment. 相似文献
7.
The thermoelectric performance of a thermoelement is ideally defined in terms of the so-called figure-of-meritZ = α2σ/λ, where α,σ and λ refer respectively to the Seebeck coefficient, electrical conductivity and thermal conductivity of the thermoelement
material. However, there are other parameters which are fairly good indicators of a material’s thermoelectric ‘worth’. A simple
yet useful performance indicator is possible with only two parameters — energy gap and lattice thermal conductivity. This
indicator can outline all potentially useful thermoelectric materials. Thermal conductivity in place of lattice thermal conductivity
can provide some additional information about the temperature range of operation. Yet another performance indicator may be
based on the slope of α vs. ln σ plots. α plotted against ln σ shows a linear relationship in a simplified model, but shows
a variation with temperature and carrier concentration. Assuming that such a relationship is true for a narrow range of temperature
and carrier concentration, one can calculate the slope m of α vs. ln σ plots against temperature and carrier concentrations.
A comparison between the variation ofZT and slopem suggests that such plots may be useful to identify potential thermoelectric materials. 相似文献
8.
This paper overviews the electro-optical and thermal performances of different types of infrared detectors manufactured by
Sofradir. The detector’s fabrication processes and detector’s performance are shortly described. New staring arrays are more
compact and offer system solutions required by infrared market. Special attention is directed to some reliability advantages
of new dewar design. Finally, the development trends for highest resolution infrared detector are discussed.
The paper presented there appears in Infrared Photoelectronics, edited by Antoni Rogalski, Eustace L. Dereniak, Fiodor F. Sizov, Proc. SPIE Vol. 5957, 59570U (2005). 相似文献
9.
The results of the experimental study of the formation kinetics of metastable phases during decomposition of supersaturated
solid solutions of quenched Al-Mg-Si alloys are presented. The process has been studied by measuring the electrical conductivity
at low temperatures (18–85°C) and by measuring the Young’s modulus using the acoustic method in the temperature range 120–220°C.
The method of measuring the Young’s modulus is characterized by a high precision and has made it possible to distinguish between
the successive stages of the decomposition due to the formation of Guinier-Preston zones, particles of the pre-β″/β″ and β′-phases.
The effective activation energies have been calculated using the obtained data on the characteristic durations of the stages
of the process at different temperatures. It has been shown that the activation energy of the formation and evolution of particles
in the β″-phase is considerably lower than the activation energy of diffusion of alloying element atoms at equilibrium conditions,
which is caused by the effect of long-lived quenching vacancies. This energy is close to the activation energy of migration
of the ν + Mg complex and, according to the obtained results, is equal to 0.58 eV. 相似文献
10.
Dirac is the founder of quantum mechanical representation theory. By virtue of the technique of integration within an ordered
product (IWOP) of operators we introduce s-parameterized form of quantum mechanical coordinate and momentum representations, which are complete. We then point out that
s-parameterized representation’s completeness relation is accompanied with operators’ s-ordering, the special cases s=1,0,−1 correspond to normal-ordering, Weyl ordering and antinormal-ordering, respectively. The s-parameterized form of the coherent state representation and the entangled state representation are also derived. In our view,
the operators’ s-ordering should be traced back to s-parameterized form of the completeness relation of quantum mechanical coordinate and momentum representations, which is more
fundamental. Many operator identities can be derived by virtue of the above mentioned s-parameterized representation’s completeness relations. 相似文献
11.
V.N. Strekalov V.I. Konov V.V. Kononenko S.M. Pimenov 《Applied Physics A: Materials Science & Processing》2003,76(4):603-607
A mechanism for photographitization of a free diamond surface is proposed. The quantum-kinetic rate of this process is determined.
The graphitization rate is close to zero if the activation energy of the graphitization process is taken as being equal to
the binding energy of a carbon atom with the surface (i.e. equal to the sublimation energy of a carbon atom). On the contrary,
if the activation energy is close to the energy of C–C bonds, the graphitization process may occur at a noticeable rate and
be observed under ‘relatively smooth’ experimental conditions. The temperature rise leads to a considerable increase in the
graphitization rates. Preliminary experimental data on the low-rate laser ablation of diamond are presented to support the
proposed model of photographitization.
An early stage of laser-induced graphitization in the bulk of diamond is also considered. It is found that the nucleation
of a ‘tiny graphite drop’ is possible in the bulk of the diamond inside the focal area of a laser beam; the ‘graphite drop’
growth causing the appearance of mechanical stresses in the surrounding regions. The maximum size of the graphite drop is
determined, which, when exceeded, leads to mechanical damage of the sample and to a change in the mechanism of laser graphitization.
An evident mechanical criterion for laser-induced damage of diamond is proposed.
Received: 2 October 2002 / Accepted: 5 October 2002 / Published online: 29 January 2003
RID="*"
ID="*"Corresponding author. E-mail: stvn@stankin.ru 相似文献
12.
We discuss the production of particles via interaction with the earth’s gravitational field. Explicit calculations are done
for high energy scalars passing through earth’s gravitational field. We show for example, that the width for the scalar processφ→3φ can become comparable with a typical weak decay width at an energy scale of a few TeV. (Similar conclusions can be drawn about
particles that ultimately couple to some scalar field.) We speculate that similar processes may be responsible for many of
the anomalies in the 10–104 TeV experimental data. 相似文献
13.
Recent observations on Type-Ia supernovae and low density (Ω
m
=0.3) measurement of matter including dark matter suggest that the present-day universe consists mainly of repulsive-gravity
type ‘exotic matter’ with negative-pressure often said ‘dark energy’ (Ω
x
=0.7). But the nature of dark energy is mysterious and its puzzling questions, such as why, how, where and when about the
dark energy, are intriguing. In the present paper the authors attempt to answer these questions while making an effort to
reveal the genesis of dark energy and suggest that ‘the cosmological nuclear binding energy liberated during primordial nucleo-synthesis
remains trapped for a long time and then is released free which manifests itself as dark energy in the universe’. It is also
explained why for dark energy the parameter
w=-\frac23w=-\frac{2}{3}
. Noting that w=1 for stiff matter and
w=\frac13w=\frac{1}{3}
for radiation;
w=-\frac23w=-\frac{2}{3}
is for dark energy because “−1” is due to ‘deficiency of stiff-nuclear-matter’ and that this binding energy is ultimately
released as ‘radiation’ contributing “
+\frac13+\frac{1}{3}
”, making
w=-1+\frac13=-\frac23w=-1+\frac{1}{3}=-\frac{2}{3}
. When dark energy is released free at Z=80,
w=-\frac23w=-\frac{2}{3}
. But as on present day at Z=0 when the radiation-strength-fraction (δ), has diminished to δ→0, the
w=-1+d\frac13=-1w=-1+\delta\frac{1}{3}=-1
. This, almost solves the dark-energy mystery of negative pressure and repulsive-gravity. The proposed theory makes several
estimates/predictions which agree reasonably well with the astrophysical constraints and observations. Though there are many
candidate-theories, the proposed model of this paper presents an entirely new approach (cosmological nuclear energy) as a
possible candidate for dark energy. 相似文献
14.
15.
A detailed analysis is presented for a novel scenario in which gamma-ray bursts are of intergalactic origin and arise from
the induced collapse of an isolated neutron star triggered by a primordial black hole. The energy released from the phase
transition of accreted nucleon matter into a quark-gluon plasma is transferred by degenerate neutrinos to the star’s surface,
where neutrinos annihilate into an electron-positron plasma and produce an inverted temperature layer that preserves a fire-ball
from undue baryonic pollution. Possible observational tests include the absence of apparent cosmological time dilation, the
location of γ-ray bursts primarily outside of galaxies, a specific shape of the log N-log S curve, with a large peak near red shift z∼10, the emission of ∼10−3 of the total energy in the form of 100-GeV photons, a bimodal distribution of durations, a very weak accompanying pulse of
gravitational radiation, etc.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 10, 642–647 (25 November 1999)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
16.
G. Y. Wolf 《Pramana》2006,66(4):781-790
One consequence of the chiral restoration is the mixing of parity partners. We look for a possible signature of the mixing
of vector and axial vector mesons in heavyion collisions. We suggest an experimental method for its observation. The dynamical
evolution of the heavy-ion collision is described by a transport equation of QMD-type evolving nucleons,N* and Δ resonances, Λ’s and gS baryons, and furthermore,π’s,η’sρ’sσ’sΩ’s and kaons with their isospin degrees of freedom. The input cross-sections and resonance parameters of the model are fitted
to the available nucleon-nucleon and pion-nucleon cross-sections 相似文献
17.
We report a new formalism to obtain solutions of Einstein-Maxwell’s equations for static spheres assuming the matter content
to be a charged perfect fluid of null-conductivity. Defining three new variablesu=4πεr
2,ν=4πpr
2
2 andw=(4π/3)(ρ+ε)r
2 whereε, ρ andε denote respectively energy densities of the electric, matter and free gravitational fields whereasp is the fluid pressure, Einstein’s field equations are rewritten in an elegant form. The solutions given by Bonnor [1], Nduka
[2], Cooperstock and De la Cruz [3], Mehra [4], Tikekar [5,6], Xingxiang [7], Patino and Rago [8] are all shown to possess
simple relations betweenu, v, andw whereas Pant and Sah’s [9] solution for which all the three functions,u, v, andw are constants is a trivial case of the present formalism, We have presented six new solutions with ε = 2ρ. For the first
three solutionsw andu are constants withv as a variable whereas the remaining three solutions satisfy the equation of state for isothermal gas;v =kw =-ku where (i)k is an arbitrary constant but not equal to 1 or 1/3 (ii)k = 1 and (iii)k = 1/3. We also obtained a generalization of Cooperstock and De la Cruz’s [3] solution which is regular for 2ρ > ε but singular
for 2ρ ≤ ε. 相似文献
18.
A new method for the analysis of electron transmission property in single-walled carbon nanotubes (SWCNTs) using Green’s function
is presented in this paper for the first time. Using the proposed method, a new relation for the transmission function through
a deformed SWCNT is obtained, which depends on the energy variations and the coupling matrices related to the mechanical deformations
applied to the structure of CNT. The obtained new relation is explained by the presented results in the literature. 相似文献
19.
Eric A Lord 《Pramana》1975,4(4):164-170
A new generalisation of Einstein’s theory is proposed which is invariant under conformal mappings. Two scalar fields are introduced
in addition to the metric tensor field, so that two special choices of gauge are available for physical interpretation, the
‘Einstein gauge’ and the ‘atomic gauge’. The theory is not unique but contains two adjustable parameters ζ anda. Witha=1 the theory viewed from the atomic gauge is Brans-Dicke theory (ω=−3/2+ζ/4). Any other choice ofa leads to a creation-field theory. In particular the theory given by the choicea=−3 possesses a cosmological solution satisfying Dirac’s ‘large numbers’ hypothesis. 相似文献
20.
Anil Kumar Yadav Farook Rahaman Saibal Ray 《International Journal of Theoretical Physics》2011,50(3):871-881
The dark energy models with variable equation of state parameter ω are investigated by using law of variation of Hubble’s parameter that yields the constant value of deceleration parameter.
Here the equation of state parameter ω is found to be time dependent and its existing range for this model is consistent with the recent observations of SN Ia data,
SN Ia data (with CMBR anisotropy) and galaxy clustering statistics. The physical significance of the dark energy models have
also been discussed. 相似文献