Simulating soil carbon sequestration from long term fertilizer and manure additions under continuous wheat using the DailyDayCent model

Bangabandhu Fellowship on Science and ICT project, Ministry of Science and Technology, People’s Republic of Bangladesh. Open Access via Springer Compact AgreementPeer reviewedPublisher PD

Ingestion efficiency of Macrobrachium rosenbergii (de Man) larvae feeding on Artemia, Moina micrura Kurz and their combination

Ingestion efficiency of Macrobrachium rosenbergii (de Man) larvae feeding on Artemia alone (A), Moina alone (M) and a 50:50 mixture of Artemia and Moina (AM) at 1, 3, 5 and 7 organisms ml-1 densities was investigated in terms of individual ingestion rate (IIR), dry mass ingestion (DMI) and energy intake (EI). Irrespective of larval stages and test food densities, larvae showed a significantly higher IIR for diet A except for AM, as the IIR for A and AM were similar from stage V onwards. Compared with diet A, IIR of M were sevenfold to fourfold lower, up to stage V. However, the larvae showed a sharp increase in IIR thereafter and gradually the differences reduced to about 1.6-1.2 fold at later stages. Despite the lower IIR, both DMI and EI for Moina were higher from stage VIII onwards than values for Artemia. In case of mixed diet (AM), the larvae of all stages showed a food selectivity response

Distributed secondary voltage regulation for autonomous microgrid

© 2017 IEEE. This research addresses the control problem of microgrids and presents a robust distributed secondary control system for voltage regulation of an islanded microgrid with droop-controlled and inverter-based distributed generators (DGs). A consensus-based distributed control approach is proposed to restore the voltage and frequency of the islanded microgrid to the reference values for all DGs within a very short time. The proposed method is flexible to system topology variations which AIDS the plug-and-play operation of microgrid. An autonomous micogrid test system consisting of four DGs is constructed in MATLAB using SimPowerSystem Toolbox to test the proposed design method, and the simulation results show the effectiveness of the proposed control strategy. The performance of the proposed controller is shown through several test case studies

Nonparametric Bayesian Multiple Comparisons for Dependence Parameter in Bivariate Exponential Populations

A nonparametric Bayesian multiple comparisons problem (MCP) for dependence parameters in I bivariate exponential populations is studied. A simple method for pairwise comparisons of these parameters is also suggested. The methodology by Gopalan and Berry (1998) is extended using Dirichlet process priors, applied in the form of baseline prior and likelihood combination to provide the comparisons. Computation of the posterior probabilities of all possible hypotheses are carried out through a Markov Chain Monte Carlo, Gibbs sampling, due to the intractability of analytic evaluation. The process of MCP for the dependent parameters of bivariate exponential populations is illustrated with a numerical example

State-Space Modeling and Stability Analysis for Microgrids with Distributed Secondary Control

© 2018 IEEE. High penetration of renewable energies in power systems leads to the necessity of comprehensive modelling of a microgrid (MG) for its appropriate control. The distributed secondary control in the MG can be used for complementing the role of primary droop-based control. This paper presents a systematic way of developing a linearized small signal state space model with distributed secondary control as well as stability analysis of an islanded AC MG. The MG considered here, consists of three distributed generations (DGs) represented in the synchronous (DQ) reference frame. To show the effect of controller parameters on system stability, the eigenvalue analysis is presented here. The MATLAB/Simulink model of islanded MG with both primary and secondary control strategies is also developed to verify the outcomes of small-signal analysis. The simulation results show that the voltage controller simultaneously achieves the critical voltage restoration and accurate reactive power sharing

The Baryon Content of Extremely Low Mass Dwarf Galaxies

We investigate the gas content and baryonic Tully-Fisher relationship for extremely low luminosity dwarf galaxies in the absolute magnitude range -13.5 > Mr > -16. The sample is selected from the Sloan Digital Sky Survey and consists of 101 galaxies for which we have obtained follow-up HI observations using the Arecibo Observatory and Green Bank Telescope. This represents the largest homogeneous sample of dwarfs at low luminosities with well-measured HI and optical properties. The sample spans a range of environments, from dense groups to truly isolated galaxies. The average neutral gas fraction is f_gas=0.6, significantly exceeding that of typical gas-rich galaxies at higher luminosities. Dwarf galaxies are therefore less efficient at turning gas into stars over their lifetimes. The strong environmental dependence of the gas fraction distribution demonstrates that while internal processes can reduce the gas fractions to roughly f_gas=0.4, external processes are required to fully remove gas from a dwarf galaxy. The average rotational velocity of our sample is vrot=50 km/s. Including more massive galaxies from the literature, we fit a baryonic Tully-Fisher slope of M_baryon \propto vrot^(3.70+/- 0.15). This slope compares well with CDM models that assume an equal baryon to dark matter ratio at all masses. While gas stripping or other processes may modify the baryon to dark matter ratio for dwarfs in the densest environments, the majority of dwarf galaxies in our sample have not preferentially lost significant baryonic mass relative to more massive galaxies.Comment: 33 pages, 8 figures. Accepted to ApJ. Data available at http://www.ociw.edu/~mgeha/researc

The Nearby and Extremely Metal-Poor Galaxy CGCG 269-049

We present Hubble Space Telescope (HST) and Spitzer Space Telescope images and photometry of the extremely metal-poor (Z = 0.03 Z_sol) blue dwarf galaxy CGCG 269-049. The HST images reveal a large population of red giant and asymptotic giant branch stars, ruling out the possibility that the galaxy has recently formed. From the magnitude of the tip of the red giant branch, we measure a distance to CGCG 269-049 of only 4.9 +/- 0.4 Mpc. The spectral energy distribution of the galaxy between ~3.6 - 70 microns is also best fitted by emission from predominantly ~10 Gyr old stars, with a component of thermal dust emission having a temperature of 52 +/- 10 K. The HST and Spitzer photometry indicate that more than 60% of CGCG 269-049's stellar mass consists of stars ~10 Gyr old, similar to other local blue dwarf galaxies. Our HST H-alpha image shows no evidence of a supernova-driven outflow that could be removing metals from the galaxy, nor do we find evidence that such outflows occurred in the past. Taken together with CGCG 269-049's large ratio of neutral hydrogen mass to stellar mass (~10), these results are consistent with recent simulations in which the metal deficiency of local dwarf galaxies results mainly from inefficient star formation, rather than youth or the escape of supernova ejecta.Comment: 35 Pages, 7 Figures, accepted for publication in ApJ; new version corrects errors in Table 1, Figure 3, and related calculations in tex

Electrical performance of zinc oxide varistor using powders processed by different latex binders

The critical electrical parameters such as I-V characteristics, watt-loss and energy absorption capability etc. are the determinants for performance evaluation of ZnO varistors. In this regard there are a large number of contributing variables. Selection of proper binder in the processing of electro-ceramic powder is also a crucial factor. It imparts green strength, enhances compressibility and reduces density gradient within the green discs. Grain growth during sintering and subsequent microstructure of the varistor is also highly influenced by the binder system. It is envisaged that a disc with higher mechanical strength could be capable of withstanding more thermal stress due to temperature gradients. The energy absorption capability as well as high current performance can thus be enhanced. It was possible to generate varistor discs from the powder processed by the latex binder with better electrical performance than that of the powder processed with conventional binder of polyvinyl alcohol. Factorial analysis showed that the level of binder and solid concentration in the slurry had great influence on the energy absorption capability of ZnO varistor

Diffuse Ionized Gas in the Dwarf Irregular Galaxy DDO 53

The spectral characteristics throughout the dwarf irregular galaxy DDO 53 are studied. The results are very similar to those for other irregular galaxies: high excitation and low values of the [SII]/Halpha ratio. The most likely ionization source is photon leakage from the classical HII regions, without any other source, although the interstellar medium of the galaxy is quite perturbed. Moreover, the physical conditions throughout the galaxy do not change very much because both the photon leakage percentage and the ionization temperature are very similar. In addition, the determined metal content for two HII regions indicates that DDO 53 is a low-metallicity galaxy.Comment: 32 pages, 9 figures, 7 tables. AJ, in pres