1,595 research outputs found
Improved alkaline electrochemical cell
Addition of lead ions to electrolyte suppresses zinc dendrite formation during charging cycle. A soluble lead salt can be added directly or metallic lead can be incorporated in the zinc electrode and allowed to dissolve into the electrolyte
China's energy economy: a survey of the literature
RePECThis paper reviews literature on China’s energy economics, focusing especially
on: i) the relationship between energy consumption and economic growth, ii) China’s
changing energy intensity, iii) energy demand and energy -capital and -labor substitution,
iv) the emergence of energy markets in China, vi) and policy reforms in the energy
industry. After reviewing the literature, the study presents the main findings and suggests
some topics for further study
Experimentally estimated dead space for GaAs and InP based planar Gunn diodes
The authors would like to thank the staff of the James Watt Nanofabrication Centre at the University of Glasgow for help in fabricating the devices which is reported in this paper. ‘Part of this work was supported by ESPRC through EP/H011862/ 1, and EP/H012966/1.Peer reviewedPublisher PD
Dark energy records in lensed cosmic microwave background
We consider the weak lensing effect induced by linear cosmological
perturbations on the cosmic microwave background (CMB) polarization
anisotropies. We find that the amplitude of the lensing peak in the BB mode
power spectrum is a faithful tracer of the dark energy dynamics at the onset of
cosmic acceleration. This is due to two reasons. First, the lensing power is
non-zero only at intermediate redshifts between the observer and the source,
keeping record of the linear perturbation growth rate at the corresponding
epoch. Second, the BB lensing signal is expected to dominate over the other
sources. The lensing distortion on the TT and EE spectra do exhibit a similar
dependence on the dark energy dynamics, although those are dominated by primary
anisotropies. We investigate and quantify the effect by means of exact tracking
quintessence models, as well as parameterizing the dark energy equation of
state in terms of the present value () and its asymptotic value in the
past (); in the interval allowed by the present constraints on dark
energy, the variation of induces a significant change in the BB
mode lensing amplitude. A Fisher matrix analysis, under conservative
assumptions concerning the increase of the sample variance due to the lensing
non-Gaussian statistics, shows that a precision of order 10% on both
and is achievable by the future experiments probing a large sky
area with angular resolution and sensitivity appropriate to detect the lensing
effect on the CMB angular power spectrum. These results show that the CMB can
probe the differential redshift behavior of the dark energy equation of state,
beyond its average.Comment: New version including substantial text change, three more figures and
two more table
Nonpolar resistance switching of metal/binary-transition-metal oxides/metal sandwiches: homogeneous/inhomogeneous transition of current distribution
Exotic features of a metal/oxide/metal (MOM) sandwich, which will be the
basis for a drastically innovative nonvolatile memory device, is brought to
light from a physical point of view. Here the insulator is one of the
ubiquitous and classic binary-transition-metal oxides (TMO), such as Fe2O3,
NiO, and CoO. The sandwich exhibits a resistance that reversibly switches
between two states: one is a highly resistive off-state and the other is a
conductive on-state. Several distinct features were universally observed in
these binary TMO sandwiches: namely, nonpolar switching, non-volatile threshold
switching, and current--voltage duality. From the systematic sample-size
dependence of the resistance in on- and off-states, we conclude that the
resistance switching is due to the homogeneous/inhomogeneous transition of the
current distribution at the interface.Comment: 7 pages, 5 figures, REVTeX4, submitted to Phys. Rev. B (Feb. 23,
2007). If you can't download a PDF file of this manscript, an alternative one
can be found on the author's website: http://staff.aist.go.jp/i.inoue
Interrelationships between serum 25-hydroxycalciferol and bone mass in adults on long term antiepileptic drug therapy
Impact ionisation electroluminescence in planar GaAs-based heterostructure Gunn diodes:Spatial distribution and impact of doping nonuniformities
When biased in the negative differential resistance regime, electroluminescence (EL) is emitted from planar GaAs heterostructure Gunn diodes. This EL is due to the recombination of electrons in the device channel with holes that are generated by impact ionisation when the Gunn domains reach the anode edge. The EL forms non-uniform patterns whose intensity shows short-range intensity variations in the direction parallel to the contacts and decreases along the device channel towards the cathode. This paper employs Monte Carlo models, in conjunction with the experimental data, to analyse these non-uniform EL patterns and to study the carrier dynamics responsible for them. It is found that the short-range lateral (i.e., parallel to the device contacts) EL patterns are probably due to non-uniformities in the doping of the anode contact, illustrating the usefulness of EL analysis on the detection of such inhomogeneities. The overall decreasing EL intensity towards the anode is also discussed in terms of the interaction of holes with the time-dependent electric field due to the transit of the Gunn domains. Due to their lower relative mobility and the low electric field outside of the Gunn domain, freshly generated holes remain close to the anode until the arrival of a new domain accelerates them towards the cathode. When the average over the transit of several Gunn domains is considered, this results in a higher hole density, and hence a higher EL intensity, next to the anode
Flow along tool-chip interface in orthogonal metal cutting
In recent papers it has been suggested that over part of the toolchip
contact zone the chip does not slide but sticks to the tool, chip
flow taking place by shear within the body of the chip. Sticking
contact is inconsistent with steady state cutting and in this paper a
slip-line field model of chip flow is presented which does not include
sticking contact and which is consistent with the relevant experimental
observations
Thermal profiles within the channel of planar gunn diodes using micro-particle sensors
The paper describes the use of a novel microparticle sensor (~3 μm diameter) and infra-red (IR) microscopy to measure the temperature profile within the active channel (typically 3 μm length and 120 μm width) of planar Gunn diodes. The method has enabled detailed temperature measurements showing an asymmetrical temperature profile along the active width of these devices. The asymmetrical temperature profile suggests a similar behaviour in the channel current density, which may contribute to the lower than expected RF output power
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