1,242 research outputs found
Solar-powered adsorption refrigeration cycle optimization
Solar energy is an attractive energy source among various renewable energy resources in Malaysia as relatively high solar radiation is available throughout the year. This solar energy can be utilized for air-conditioning by using solar-powered adsorption refrigeration cycle. Intermittent nature of the solar radiation leads to a challenge for continuous air-conditioning operation. In the present study, a combination of solar-powered adsorption refrigeration system and thermal storage is studied. Activated carbon-ammonia and activated carbon-methanol are the working pairs of the adsorption reaction. Analytical calculation results show that activated carbon-methanol pair indicates higher coefficient of performance (COP) than activated carbon-ammonia pair, while adsorption chiller system with hot water thermal storage has higher COP than the system with ice thermal storage. For the activated carbon-methanol case with hot water thermal storage, the COP is 0.79. Since this COP analysis is based on the ideal case with uniform temperature distribution within the reactor beds, which achieves equilibrium states at the end of the reactions. In more realistic situation, the reaction process will be terminated before reaching to the equilibrium states because of the non-uniform temperature distribution and the time required for the reaction. Transient simulation in which heat transfer and reaction equation are combined will be performed to model actual reactors
Space laser interferometers can determine the thermal history of the early Universe
It is shown that space-based gravitational wave detectors such as DECIGO
and/or Big Bang Observer (BBO) will provide us with invaluable information on
the cosmic thermal history after inflation and they will be able to determine
the reheat temperature provided that it lies in the range preferred by
the cosmological gravitino problem, GeV. Therefore it is
strongly desired that they will be put into practice as soon as possible.Comment: 5 page
Prevalence of early warning signs and symptoms of mental illness amongst males and females in Jos, Nigeria
Background: Mental illness is a psychological, emotional and mental health problems that affects the physical, behavioral and occupational functioning of an individual. The understand of the signs and symptoms of the disorder in a typical setting and by ordinary people or even among the literate is often difficulty; talk more of the early warning signs and symptoms of the illness. This is because some Africans still attribute the causes of mental illness to supernatural sources such as witchcraft, evil people, wicked people and demonic attacks etc. It thus becomes imperative to take a look at the general symptoms of mental illness.Objective of Study: The aim of the study was to determine the prevalence of early warning signs and symptoms of mental illness among males and females in Jos.Result: A total of 657 participants took part in the study. Participants were randomly selected. They comprised of 390 males who fell within the age range 17-65 with a Mean age of 29.09 and a standard deviation of 10.05 and 267 females who fell within he age range 16-60 with a Mean age of 31.28 and a standard deviation of 17.08. The study found out that that there was a significant difference in the prevalence of the early warning signs and symptoms of mental illness among the males and females (X2 = 10.5 >P.05 = 7.87). A higher proportion of females (75.41%) presented with the early warning signs and symptoms of mental illness.Conclusion: The result shows that a higher proportion of the sample (66.61 presented with the early warning signs and symptoms of mental illness by both males and females indicates that the society is sitting on a time bomb. This is because if these individuals are not checked and manage at this early stage, they can become fully blown victims of mental illness in later years. Thus mental health professionals and good policy should move quickly to prevent mental illness in the society.Keywords: Early warning Signs, Symptoms, Mental Illnes
Fibrations of genus two on complex surfaces
We consider fibrations of genus 2 over complex surfaces. The purpose of this
paper is primarily to provide a geometric description of the possible
structures of the fibration on a neighborhood of a singular fiber. In
particular it is shown that the "geometric data" of the singular fiber
determines the fibration on its neighborhood up to a transversely holomorphic
-diffeomorphism. The method employed is quite flexible and it
applies to good extent to fibrations of arbitrary genus.Comment: This is the final version, June 201
Concept study of microgrid dispatch strategy for solar thermal power plant with thermal storage
Complex grid systems have been gradually replaced by smaller and simpler grid systems called Microgrids. Integration of a solar thermal power generation systems into Microgrids open a new horizon of renewable energy power generation to achieve the supply and demand balance of electricity. Microgrid dispatch strategy is a control method of energy balance between power generation and electricity consumption. A thermal storage integrated into the system buffers the intermittency of solar radiation used as the heat source of the power generation system. The daily starting time for the power generation is determined by the dispatch strategy in search of minimum power from the conventional grid and maximum electricity generation from the solar thermal power generation system. In the simulation stage, the heat energy available for power generation and amount of thermal energy saved in the thermal storage is calculated at each time step using measured solar radiation data as the heat source and load profile data as the consumption required. Based on the simulation result, the power generation starting time for the next day is determined. The effectiveness of the proposed dispatch strategy is demonstrated by obtaining the best starting time and identifying minimum power requiredfrom the conventional grid. The power supply from the conventional grid is reduced by 10% by applying the proposed methodology
Cluster Morphologies as a Test of Different Cosmological Models
We investigate how cluster morphology is affected by the cosmological
constant in low-density universes. Using high-resolution cosmological
N-body/SPH simulations of flat (\Omega_0 = 0.3, \lambda_0 = 0.7, \Lambda CDM)
and open (\Omega_0 = 0.3, \lambda_0 = 0, OCDM) cold dark matter universes, we
calculate statistical indicators to quantify the irregularity of the cluster
morphologies. We study axial ratios, center shifts, cluster clumpiness, and
multipole moment power ratios as indicators for the simulated clusters at z=0
and 0.5. Some of these indicators are calculated for both the X-ray surface
brightness and projected mass distributions. In \Lambda CDM all these
indicators tend to be larger than those in OCDM at z=0. This result is
consistent with the analytical prediction of Richstone, Loeb, & Turner, that
is, clusters in \Lambda CDM are formed later than in OCDM, and have more
substructure at z=0. We make a Kolmogorov-Smirnov test on each indicator for
these two models. We then find that the results for the multipole moment power
ratios and the center shifts for the X-ray surface brightness are under the
significance level (5%). We results also show that these two cosmological
models can be distinguished more clearly at z=0 than z = 0.5 by these
indicators.Comment: 30pages, 6figures, Accepted for publication in Ap
The Role of Collective Neutrino Flavor Oscillations in Core-Collapse Supernova Shock Revival
We explore the effects of collective neutrino flavor oscillations due to
neutrino-neutrino interactions on the neutrino heating behind a stalled
core-collapse supernova shock. We carry out axisymmetric (2D)
radiation-hydrodynamic core-collapse supernova simulations, tracking the first
400 ms of the post-core-bounce evolution in 11.2 solar mass and 15 solar mass
progenitor stars. Using inputs from these 2D simulations, we perform neutrino
flavor oscillation calculations in multi-energy single-angle and multi-angle
single-energy approximations. Our results show that flavor conversions do not
set in until close to or outside the stalled shock, enhancing heating by not
more than a few percent in the most optimistic case. Consequently, we conclude
that the postbounce pre-explosion dynamics of standard core-collapse supernovae
remains unaffected by neutrino oscillations. Multi-angle effects in regions of
high electron density can further inhibit collective oscillations,
strengthening our conclusion.Comment: v2: Added multi-angle calculations. Conclusions unchanged. 16 pages,
7 figures. Accepted to Phys. Rev. D after revisions: 15 Sept 2011 (major), 24
Jan 2012 (minor
Effect of Collective Neutrino Oscillations on the Neutrino Mechanism of Core-Collapse Supernovae
In the seconds after collapse of a massive star, the newborn proto-neutron
star (PNS) radiates neutrinos of all flavors. The absorption of electron-type
neutrinos below the radius of the stalled shockwave may drive explosions (the
"neutrino mechanism"). Because the heating rate is proportional to the square
of neutrino energy, flavor conversion of mu and tau neutrinos to electron-type
neutrinos via collective neutrino oscillations (CnuO) may in principle increase
the heating rate and drive explosions. In order to assess the potential
importance of CnuO for the shock revival, we solve the steady-state boundary
value problem of spherically-symmetric accretion between the PNS surface (r_nu)
and the shock (r_S), including a scheme for flavor conversion via CnuO. For a
given r_nu, PNS mass (M), accretion rate (Mdot), and assumed values of the
neutrino energies from the PNS, we calculate the critical neutrino luminosity
above which accretion is impossible and explosion results. We show that CnuO
can decrease the critical luminosity by a factor of at most ~1.5, but only if
the flavor conversion is fully completed inside r_S and if there is no matter
suppression. The magnitude of the effect depends on the model parameters (M,
Mdot, and r_nu) through the shock radius and the physical scale for flavor
conversion. We quantify these dependencies and find that CnuO could lower the
critical luminosity only for small M and Mdot, and large r_nu. However, for
these parameter values CnuO are suppressed due to matter effects. By
quantifying the importance of CnuO and matter suppression at the critical
neutrino luminosity for explosion, we show in agreement with previous studies
that CnuO are unlikely to affect the neutrino mechanism of core-collapse
supernovae significantly.Comment: 8 pages, 3 figures, accepted to MNRA
- …