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

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

Stochastic backgrounds of gravitational waves from extragalactic sources

Astrophysical sources emit gravitational waves in a large variety of processes occurred since the beginning of star and galaxy formation. These waves permeate our high redshift Universe, and form a background which is the result of the superposition of different components, each associated to a specific astrophysical process. Each component has different spectral properties and features that it is important to investigate in view of a possible, future detection. In this contribution, we will review recent theoretical predictions for backgrounds produced by extragalactic sources and discuss their detectability with current and future gravitational wave observatories.Comment: 10 pages, 9 figures, proceedings of the GWDAW 10 Conference, submitted to Class. & Quantum Gra

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

Binge drinking and sexual assault among women in Jos Metropolis, Nigeria

Background: Alcohol related sexual assault is a growing epidemic world wide that affects mainly women. There is urgent need to empower women to identify behaviors and situations that may predispose them to sexual victimization.Objectives: The study was carried out to determine the relationship between binge drinking and sociodemographic factors. It also assessed the relationship between binge drinking and sexual assault.Methods: The cross-sectional descriptive study was carried out in Jos North Local Government Area from March to July, 2017. Multistage sampling technique was employed to select 272 participants aged 18 years and above who consented after obtaining ethical approval.Results: The total numbers of participants were 272 females with an age range of 18-60 years. The mean age was 28.8 ± 8.6 years. The socio-demographic variables significantly associated with binge drinking were marital status (X2 = 9.847, DF = 2, p = 0.007), educational status (X2 = 10.684, DF = 3, p = 0.014) and employment status (X2= 5.122, DF = 1, p = 0.024). Binge drinking was significantly associated with sexual assault (X2 = 10.732, DF = 1, p = 0.001). Previously married were significantly more likely to binge drink compared with never married and married. Those with no formal education were more likely to binge drink compared to those with tertiary education while the unemployed were less likely to binge drink compared with the employed. The sexually assaulted (P = 0.01, OR = 2.429, CI = 1.419-4.157) were 2 times more likely to binge drink.Conclusion: There was a significant relationship between binge drinking with marital status, employment, lower level of education and sexual assault. Women should be provided with information about the safe level of alcohol consumption and the many consequences of heavy drinking including sexual assault.Keywords: Binge drinking, women, sexual assault, socio-demographic, Jo

Fallback Supernovae: A Possible Origin of Peculiar Supernovae with Extremely Low Explosion Energies

We perform hydrodynamical calculations of core-collapse supernovae (SNe) with low explosion energies. These SNe do not have enough energy to eject the whole progenitor and most of the progenitor falls back to the central remnant. We show that such fallback SNe can have a variety of light curves (LCs) but their photospheric velocities can only have some limited values with lower limits. We also perform calculations of nucleosynthesis and LCs of several fallback SN model, and find that a fallback SN from the progenitor with a main-sequence mass of 13 Msun can account for the properties of the peculiar Type Ia supernova SN 2008ha. The kinetic energy and ejecta mass of the model are 1.2*10^{48} erg and 0.074 Msun, respectively, and the ejected 56Ni mass is 0.003 Msun. Thus, SN 2008ha can be a core-collapse SN with a large amount of fallback. We also suggest that SN 2008ha could have been accompanied with long gamma-ray bursts and long gamma-ray bursts without associated SNe may be accompanied with very faint SNe with significant amount of fallback which are similar to SN 2008ha.Comment: 9 pages, 11 figures, 2 tables, accepted by The Astrophysical Journal, proofed and some references added in v

Flat-Band Ferromagnetism in Organic Polymers Designed by a Computer Simulation

By coupling a first-principles, spin-density functional calculation with an exact diagonalization study of the Hubbard model, we have searched over various functional groups for the best case for the flat-band ferromagnetism proposed by R. Arita et al. [Phys. Rev. Lett. {\bf 88}, 127202 (2002)] in organic polymers of five-membered rings. The original proposal (poly-aminotriazole) has turned out to be the best case among the materials examined, where the reason why this is so is identified here. We have also found that the ferromagnetism, originally proposed for the half-filled flat band, is stable even when the band filling is varied away from the half-filling. All these make the ferromagnetism proposed here more experimentally inviting.Comment: 11 pages, 13figure

Tunable Emergent Heterostructures in a Prototypical Correlated Metal

At the interface between two distinct materials desirable properties, such as superconductivity, can be greatly enhanced, or entirely new functionalities may emerge. Similar to in artificially engineered heterostructures, clean functional interfaces alternatively exist in electronically textured bulk materials. Electronic textures emerge spontaneously due to competing atomic-scale interactions, the control of which, would enable a top-down approach for designing tunable intrinsic heterostructures. This is particularly attractive for correlated electron materials, where spontaneous heterostructures strongly affect the interplay between charge and spin degrees of freedom. Here we report high-resolution neutron spectroscopy on the prototypical strongly-correlated metal CeRhIn5, revealing competition between magnetic frustration and easy-axis anisotropy -- a well-established mechanism for generating spontaneous superstructures. Because the observed easy-axis anisotropy is field-induced and anomalously large, it can be controlled efficiently with small magnetic fields. The resulting field-controlled magnetic superstructure is closely tied to the formation of superconducting and electronic nematic textures in CeRhIn5, suggesting that in-situ tunable heterostructures can be realized in correlated electron materials