810 research outputs found
Screen printed flexible Bi2Te3-Sb2Te3 based thermoelectric generator
This paper reports the fabrication and testing of Bismuth Tellurium (Bi2Te3) – Antimony Tellurium (Sb2Te3) based thermocouples using screen printing technology. In this study, screen printable thermoelectric pastes were developed and the transport properties of cured material were measured. The dimension of each planer thermoleg is 39.3 mm × 3 mm with a thickness of 67 µm for Bi2Te3 leg and 62 µm for Sb2Te3 leg. A single thermocouple with this dimension can generate a voltage of 6 mV and a peak output power of 48 nW at a temperature difference of 20°C. The calculated Seebeck coefficient of a single thermocouple is in the range of 262 to 282 µV/K. The Seebeck coefficient at room temperature were measured to be -134 to -119 µV/K and 128 to 134 µV/K for Bi2Te3 and Sb2Te3 respectively. This work demonstrates that the low-cost screen printing technology and low-temperature materials are promising for the fabrication of flexible thermoelectric generators (TEGs)
Improving the dielectric and piezoelectric properties of screen-printed low temperature PZT/polymer composite using cold isostatic pressing
This paper reports an improvement in dielectric and piezoelectric properties of screen-printed PZT/polymer films for flexible electronics applications using Cold Isostatic Pressing (CIP). The investigation involved half and fully cured PZT/polymer composite pastes with weight ratio of 12:1 to investigate the effect of the CIP process on the piezoelectric and dielectric properties. It was observed that the highest dielectric and piezoelectric properties are achieved at pressures of 5 and 10 MPa for half and fully cured films respectively. The relative dielectric constants were 300 and 245 measured at 1 kHz for the half and fully cured samples. Using unoptimised poling conditions, the initial d33 values were 30 and 35 pC/N for the half and fully cured films, respectively. The fully cured sample was then poled using optimized conditions and demonstrated a d33 of approximately 44 pC/N which is an increase of 7% compared with non-CIP processed material
(e,3e) on helium at low impact energy: the strongly correlated three-electron continuum
Double ionization of the helium atom by slow electron impact (E0=106 eV) is studied in a kinematically complete experiment. Because of a low excess energy Eexc=27 eV above the double ionization threshold, a strongly correlated three-electron continuum is realized. This is demonstrated by measuring and calculating the fully differential cross sections for equal energy sharing of the final-state electrons. While the electron emission is dominated by a strong Coulomb repulsion, also signatures of more complex dynamics of the full four-body system are identified
Quark and Nucleon Self-Energy in Dense Matter
In a recent work we introduced a nonlocal version of the
Nambu--Jona-Lasinio(NJL) model that was designed to generate a quark
self-energy in Euclidean space that was similar to that obtained in lattice
simulations of QCD. In the present work we carry out related calculations in
Minkowski space, so that we can study the effects of the significant vector and
axial-vector interactions that appear in extended NJL models and which play an
important role in the study of the , and mesons. We study
the modification of the quark self-energy in the presence of matter and find
that our model reproduces the behavior of the quark condensate predicted by the
model-independent relation , where is the
pion-nucleon sigma term and is the density of nuclear matter. (Since
we do not include a model of confinement, our study is restricted to the
analysis of quark matter. We provide some discussion of the modification of the
above formula for quark matter.) The inclusion of a quark current mass leads to
a second-order phase transition for the restoration of chiral symmetry. That
restoration is about 80% at twice nuclear matter density for the model
considered in this work. We also find that the part of the quark self-energy
that is explicitly dependent upon density has a strong negative Lorentz-scalar
term and a strong positive Lorentz-vector term, which is analogous to the
self-energy found for the nucleon in nuclear matter when one makes use of the
Dirac equation for the nucleon. In this work we calculate the nucleon self
-energy in nuclear matter using our model of the quark self-energy and obtain
satisfactory results.Comment: 19 pages, 8 figures, 2 tables, revte
Multiple solutions and corresponding power output of a nonlinear bistable piezoelectric energy harvester
We examine multiple responses of a vibrational energy harvester composed of a vertical
beam and a tip mass. The beam is excited horizontally by a harmonic inertial force while
mechanical vibrational energy is converted to electrical power through a piezoelectric
patch. The mechanical resonator can be described by single or double well potentials
depending on the gravity force from the tip mass. By changing the tip mass we examine the
appearance of various solutions and their basins of attraction. Identification of
particular solutions of the energy harvester is important as each solution may provide a
different level of power output
The Composition of Cosmic Rays at the Knee
The observation of a small change in spectral slope, or 'knee' in the fluxes
of cosmic rays near energies 10^15 eV has caused much speculation since its
discovery over 40 years ago. The origin of this feature remains unknown. A
small workshop to review some modern experimental measurements of this region
was held at the Adler Planetarium in Chicago, USA in June 2000. This paper
summarizes the results presented at this workshop and the discussion of their
interpretation in the context of hadronic models of atmospheric airshowers.Comment: 36 pages, 10 figure
Running into New Territory in SUSY Parameter Space
The LEP-II bound on the light Higgs mass rules out the vast majority of
parameter space left to the Minimal Supersymmetric Standard Model (MSSM) with
weak-scale soft-masses. This suggests the importance of exploring extensions of
the MSSM with non-minimal Higgs physics. In this article, we explore a theory
with an additional singlet superfield and an extended gauge sector. The theory
has a number of novel features compared to both the MSSM and Next-to-MSSM,
including easily realizing a light CP-even Higgs mass consistent with LEP-II
limits, tan(beta) < 1, and a lightest Higgs which is charged. These features
are achieved while remaining consistent with perturbative unification and
without large stop-masses. Discovery modes at the Tevatron and LHC are
discussed.Comment: 15 pages, 5 figures; Typo in equation (4.5) corrected; submitted to
JHE
Constraints on Large Extra Dimensions with Bulk Neutrinos
We consider right-handed neutrinos propagating in (large) extra
dimensions, whose only coupling to Standard Model fields is the Yukawa coupling
to the left-handed neutrino and the Higgs boson. These theories are attractive
as they can explain the smallness of the neutrino mass, as has already been
shown. We show that if is bigger than two, there are strong
constraints on the radius of the extra dimensions, resulting from the
experimental limit on the probability of an active state to mix into the large
number of sterile Kaluza-Klein states of the bulk neutrino. We also calculate
the bounds on the radius resulting from requiring that perturbative unitarity
be valid in the theory, in an imagined Higgs-Higgs scattering channel.Comment: 24 pages, 4 figures, revtex4. v2: Minor typos corrected, references
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Spin-triplet superconducting pairing due to local (Hund's rule, Dirac) exchange
We discuss general implications of the local spin-triplet pairing among
fermions induced by local ferromagnetic exchange, example of which is the
Hund's rule coupling. The quasiparticle energy and their wave function are
determined for the three principal phases with the gap, which is momentum
independent. We utilize the Bogolyubov-Nambu-De Gennes approach, which in the
case of triplet pairing in the two-band case leads to the four-components wave
function. Both gapless modes and those with an isotropic gap appear in the
quasiparticle spectrum. A striking analogy with the Dirac equation is briefly
explored. This type of pairing is relevant to relativistic fermions as well,
since it reflects the fundamental discrete symmetry-particle interchange. A
comparison with the local interband spin-singlet pairing is also made.Comment: 16 pages, LaTex, submitted to Phys. Rev.
Synthesis and characterisation of carbon nanotubes grown on silica fibres by injection CVD
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