39,424 research outputs found
Design and Construction of the 3.2 Mev High Voltage Column for Darht II
A 3.2 MeV injector has been designed and built for the Darht II Project at
Los Alamos Lab. The installation of the complete injector system is nearing
completion at this time. The requirements for the injector are to produce a 3.2
MeV, 2000 ampere electron pulse with a flattop width of at least 2-microseconds
and emittance of less than 0.15 p cm-rad normalized. A large high voltage
column has been built and installed. The column is vertically oriented, is 4.4
meters long, 1.2 meters in diameter, and weights 5700 kilograms. A novel method
of construction has been employed which utilizes bonded mycalex insulating
rings. This paper will describe the design, construction, and testing completed
during construction. Mechanical aspects of the design will be emphasized.Comment: 3 pages, 4 figures, Linac 200
Nonconventional screening of the Coulomb interaction in FexOy clusters: An ab-initio study
From microscopic point-dipole model calculations of the screening of the
Coulomb interaction in non-polar systems by polarizable atoms, it is known that
screening strongly depends on dimensionality. For example, in one dimensional
systems the short range interaction is screened, while the long range
interaction is anti-screened. This anti-screening is also observed in some zero
dimensional structures, i.e. molecular systems. By means of ab-initio
calculations in conjunction with the random-phase approximation (RPA) within
the FLAPW method we study screening of the Coulomb interaction in FexOy
clusters. For completeness these results are compared with their bulk
counterpart magnetite. It appears that the onsite Coulomb interaction is very
well screened both in the clusters and bulk. On the other hand for the
intersite Coulomb interaction the important observation is made that it is
almost contant throughout the clusters, while for the bulk it is almost
completely screened. More precisely and interestingly, in the clusters
anti-screening is observed by means of ab-initio calculations
Fractal Markets Hypothesis and the Global Financial Crisis: Scaling, Investment Horizons and Liquidity
We investigate whether fractal markets hypothesis and its focus on liquidity
and invest- ment horizons give reasonable predictions about dynamics of the
financial markets during the turbulences such as the Global Financial Crisis of
late 2000s. Compared to the mainstream efficient markets hypothesis, fractal
markets hypothesis considers financial markets as com- plex systems consisting
of many heterogenous agents, which are distinguishable mainly with respect to
their investment horizon. In the paper, several novel measures of trading
activity at different investment horizons are introduced through scaling of
variance of the underlying processes. On the three most liquid US indices -
DJI, NASDAQ and S&P500 - we show that predictions of fractal markets hypothesis
actually fit the observed behavior quite well.Comment: 11 pages, 3 figure
Meeting Global Cooling Demand with Photovoltaics during the 21st Century
Space conditioning, and cooling in particular, is a key factor in human
productivity and well-being across the globe. During the 21st century, global
cooling demand is expected to grow significantly due to the increase in wealth
and population in sunny nations across the globe and the advance of global
warming. The same locations that see high demand for cooling are also ideal for
electricity generation via photovoltaics (PV). Despite the apparent synergy
between cooling demand and PV generation, the potential of the cooling sector
to sustain PV generation has not been assessed on a global scale. Here, we
perform a global assessment of increased PV electricity adoption enabled by the
residential cooling sector during the 21st century. Already today, utilizing PV
production for cooling could facilitate an additional installed PV capacity of
approximately 540 GW, more than the global PV capacity of today. Using
established scenarios of population and income growth, as well as accounting
for future global warming, we further project that the global residential
cooling sector could sustain an added PV capacity between 20-200 GW each year
for most of the 21st century, on par with the current global manufacturing
capacity of 100 GW. Furthermore, we find that without storage, PV could
directly power approximately 50% of cooling demand, and that this fraction is
set to increase from 49% to 56% during the 21st century, as cooling demand
grows in locations where PV and cooling have a higher synergy. With this
geographic shift in demand, the potential of distributed storage also grows. We
simulate that with a 1 m water-based latent thermal storage per household,
the fraction of cooling demand met with PV would increase from 55% to 70%
during the century. These results show that the synergy between cooling and PV
is notable and could significantly accelerate the growth of the global PV
industry
Meeting Global Cooling Demand with Photovoltaics during the 21st Century
Space conditioning, and cooling in particular, is a key factor in human
productivity and well-being across the globe. During the 21st century, global
cooling demand is expected to grow significantly due to the increase in wealth
and population in sunny nations across the globe and the advance of global
warming. The same locations that see high demand for cooling are also ideal for
electricity generation via photovoltaics (PV). Despite the apparent synergy
between cooling demand and PV generation, the potential of the cooling sector
to sustain PV generation has not been assessed on a global scale. Here, we
perform a global assessment of increased PV electricity adoption enabled by the
residential cooling sector during the 21st century. Already today, utilizing PV
production for cooling could facilitate an additional installed PV capacity of
approximately 540 GW, more than the global PV capacity of today. Using
established scenarios of population and income growth, as well as accounting
for future global warming, we further project that the global residential
cooling sector could sustain an added PV capacity between 20-200 GW each year
for most of the 21st century, on par with the current global manufacturing
capacity of 100 GW. Furthermore, we find that without storage, PV could
directly power approximately 50% of cooling demand, and that this fraction is
set to increase from 49% to 56% during the 21st century, as cooling demand
grows in locations where PV and cooling have a higher synergy. With this
geographic shift in demand, the potential of distributed storage also grows. We
simulate that with a 1 m water-based latent thermal storage per household,
the fraction of cooling demand met with PV would increase from 55% to 70%
during the century. These results show that the synergy between cooling and PV
is notable and could significantly accelerate the growth of the global PV
industry
Testing Lorentz Invariance by Comparing Light Propagation in Vacuum and Matter
We present a Michelson-Morley type experiment for testing the isotropy of the
speed of light in vacuum and matter. The experiment compares the resonance
frequency of a monolithic optical sapphire resonator with the resonance
frequency of an orthogonal evacuated optical cavity made of fused silica while
the whole setup is rotated on an air bearing turntable once every 45 s.
Preliminary results yield an upper limit for the anisotropy of the speed of
light in matter (sapphire) of \Delta c/c < 4x10^(-15), limited by the frequency
stability of the sapphire resonator operated at room temperature. Work to
increase the measurement sensitivity by more than one order of magnitude by
cooling down the sapphire resonator to liquid helium temperatures (LHe) is
currently under way.Comment: Presented at the Fifth Meeting on CPT and Lorentz Symmetry,
Bloomington, Indiana, June 28-July 2, 201
Fluid use in mountain bikers – self-reported practices.
BACKGROUND AND OBJECTIVES. Little is known of the fluid replacement habits of participants in mountain bike (MTB)endurance events. This survey set out to determine the current perceptions and practices of this group of endurance athletes.
Method. Four hundred and twelve participants in the 3-day 2006 Sani2C (MTB) race completed questionnaires that elicited information regarding their regular fluid intake practices during competitive MTB endurance events. This included their general approach to fluid replacement, their fluid intake practices (type, amount and frequency), urine output and hydration status. RESULTS. While 70% (N = 290) reported that they based their fluid intake practices on personal past experiences, less than half the group (N = 177, 43%) were aware of official sport-specific guidelines. Although 86% (N = 354) reported making use of commercially available sport-specific drinks, consumption of water alone was reported by 34% of respondents (N = 140). The majority (N = 225, 55%) of the mountain bikers reported drinking every 16 - 30 minutes during an endurance ride, while 35% (N =144) reported drinking every 0 - 15 minutes. Fifty-three per cent (N = 182) of the male respondents and 45% (N= 23) of female respondents reported a routine intake of ≥ 750 ml per hour during endurance rides. This included 2 women who reported regular intakes of between 1 500 and 2 000 ml/hr. Only 7 (2%) reported receiving medical care for dehydration following their participation in previous MTB rides. CONCLUSIONS. This survey indicates that although more than half of the mountain bikers did not acknowledge specific awareness of the official fluid replacement guidelines, over 80% reported drinking regularly during a race, and 52% (N = 212) reported a usual intake of ≥ 750 ml/hr during endurance races. Until scientific studies have carefully examined the hydration status and fluid replacement needs of mountain bikers, MTB cyclists are cautioned against the practice of over-hydrating.Web of Scienc
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