2,017 research outputs found
Development of Optimization Tool for Air Conditioning System Operation
This study aims to realize the optimization of the air-conditioning system operation. Although set values of air-conditioning systems are usually fixed, variable setting values are used in this study. It is possible that less energy consumption with greater comfort is achieved by selecting appropriate set values in consideration of situations which change from day to day. In this study, the optimization of air-conditioning system operation is carried out by selecting appropriate set values in terms of energy consumptions and the comfort. The prediction of building heat loads is necessary to realize the optimization in ever-changing environments. Therefore, a more robust optimization method which handles errors in the prediction was proposed, and the optimization tool for an air-conditioning system was developed. The developed optimization tool is incorporated into the Building and Energy Management System (BEMS), and it automatically changes setting values acquiring data including driving data from the BEMS. Experiments were conducted to clarify the effectiveness of the tool, and simulations in the case of a medium-scale office building were also done for the evaluation of the tool. Experiments prove that the evaluation value tends to improve by using the optimization tool. As the result of simulations, it is found out that the evaluation value improves by considering prediction errors and that the evaluation value is reduced by 12.1% at maximum
A Detailed Comparison of Multi-Dimensional Boltzmann Neutrino Transport Methods in Core-Collapse Supernovae
The mechanism driving core-collapse supernovae is sensitive to the interplay
between matter and neutrino radiation. However, neutrino radiation transport is
very difficult to simulate, and several radiation transport methods of varying
levels of approximation are available. We carefully compare for the first time
in multiple spatial dimensions the discrete ordinates (DO) code of Nagakura,
Yamada, and Sumiyoshi and the Monte Carlo (MC) code Sedonu, under the
assumptions of a static fluid background, flat spacetime, elastic scattering,
and full special relativity. We find remarkably good agreement in all spectral,
angular, and fluid interaction quantities, lending confidence to both methods.
The DO method excels in determining the heating and cooling rates in the
optically thick region. The MC method predicts sharper angular features due to
the effectively infinite angular resolution, but struggles to drive down noise
in quantities where subtractive cancellation is prevalent, such as the net gain
in the protoneutron star and off-diagonal components of the Eddington tensor.
We also find that errors in the angular moments of the distribution functions
induced by neglecting velocity dependence are sub-dominant to those from
limited momentum-space resolution. We briefly compare directly computed second
angular moments to those predicted by popular algebraic two-moment closures,
and find that the errors from the approximate closures are comparable to the
difference between the DO and MC methods. Included in this work is an improved
Sedonu code, which now implements a fully special relativistic,
time-independent version of the grid-agnostic Monte Carlo random walk
approximation.Comment: Accepted to ApJS. 24 pages, 19 figures. Key simulation results and
codes are available at https://stellarcollapse.org/MCvsD
Macroscopic proof of the Jarzynski-Wojcik fluctuation theorem for heat exchange
In a recent work, Jarzynski and Wojcik (2004 Phys. Rev. Lett. 92, 230602)
have shown by using the properties of Hamiltonian dynamics and a statistical
mechanical consideration that, through contact, heat exchange between two
systems initially prepared at different temperatures obeys a fluctuation
theorem. Here, another proof is presented, in which only macroscopic
thermodynamic quantities are employed. The detailed balance condition is found
to play an essential role. As a result, the theorem is found to hold under very
general conditions.Comment: 9 pages, 0 figure
Universal law for waiting internal time in seismicity and its implication to earthquake network
In their paper (Europhys. Lett., 71 (2005) 1036), Carbone, Sorriso-Valvo,
Harabaglia and Guerra showed that "unified scaling law" for conventional
waiting times of earthquakes claimed by Bak et al. (Phys. Rev. Lett., 88 (2002)
178501) is actually not universal. Here, instead of the conventional time, the
concept of the internal time termed the event time is considered for
seismicity. It is shown that, in contrast to the conventional waiting time, the
waiting event time obeys a power law. This implies the existence of temporal
long-range correlations in terms of the event time with no sharp decay of the
crossover type. The discovered power-law waiting event-time distribution turns
out to be universal in the sense that it takes the same form for seismicities
in California, Japan and Iran. In particular, the parameters contained in the
distribution take the common values in all these geographical regions. An
implication of this result to the procedure of constructing earthquake networks
is discussed.Comment: 21 pages, 5 figure
Nucleosynthesis in Outflows from the Inner Regions of Collapsars
We consider nucleosynthesis in outflows originating from the inner regions of
viscous accretion disks formed after the collapse of a rotating massive star.
We show that wind-like outflows driven by viscous and neutrino heating can
efficiently synthesize Fe-group elements moving at near-relativistic
velocities. The mass of 56Ni synthesized and the asymptotic velocities attained
in our calculations are in accord with those inferred from observations of
SN1998bw and SN2003dh. These steady wind-like outflows are generally proton
rich, characterized by only modest entropies, and consequently synthesize
essentially nothing heavier than the Fe-group elements. We also discuss
bubble-like outflows resulting from rapid energy deposition in localized
regions near or in the accretion disk. These intermittent ejecta emerge with
low electron fraction and are a promising site for the synthesis of the A=130
r-process peak elements.Comment: 35 pages, 6 figures, added discussion of the influence of nuclear
recombination on wind dynamics, to appear in Ap
Dual wavelength Q-switched cascade laser
A diode-cladding-pumped dual wavelength Q-switched Ho3+ -doped fluoride cascade fiber laser operating in the mid-infrared is demonstrated. Stable pulse trains from the 5|6 -> 5|7 and 5|7 -> 5|8 laser transitions were produced, and the µs-level time delay between the pulses from each transition was dependent on the pump power. At maximum pump power and at an acousto-optic modulator repetition rate of 25 kHz, the 5|8 -> 5|7 transition pulse operated at 3.005 µm, a pulse energy of 29 µJ, and a pulse width of 380 ns; the 5|7 -> 5|8 transition pulse correspondingly produced 7 µJ pulse energy and 260 ns pulse width at 2.074 µm. To the best of our knowledge, this is the first demonstration of a Q-switched fiber laser operating beyond 3 µm
Development and Verification for the Control Method Using Surplus Pressure of Primary Pumps in Chiller Plant Systems for Air Conditioning which Adopts Primary/Secondary Piping Systems PPT
The primary/secondary piping systems are often employed in large chiller plant Systems.
Normally, the primary flow becomes more than secondary flow, and the flow difference
returns to a chiller via decoupler, which is common to primary flow loop (chiller side) and
secondary flow loop (load side). It is a huge energy loss, because the primary pumps use their
head to lead much flow to the decoupler. Therefore, we have developed new control method
using surplus pressure of the primary pump to reduce the primary and secondary pumps'
energy. In this paper, we used this control method to the actual chiller plant buildings and
verified its effectiveness. As a result, cold water conveyances, both primary loop and
secondary loop, could be covered by only primary pumps during plant operating time, and the
water conveyance power energy was reduced approximately 80%
Hidden gauge structure and derivation of microcanonical ensemble theory of bosons from quantum principles
Microcanonical ensemble theory of bosons is derived from quantum mechanics by
making use of a hidden gauge structure. The relative phase interaction
associated with this gauge structure, described by the Pegg-Barnett formalism,
is shown to lead to perfect decoherence in the thermodynamics limit and the
principle of equal a priori probability, simultaneously.Comment: 10 page
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