714 research outputs found
Control Optimization of Combined Cooling and Power System with Prime Mover of Solid Oxide Fuel Cell-gas Turbine for Building Application
© 2017 The Authors. This paper presents a control strategy for a combined cooling and power (CCP) system using a prime mover of solid oxide fuel cell (SOFC) with bottoming cycle of gas turbine (GT) for building application. Dynamic simulation model of the CCP system was developed in TRNSYS 17, and the control strategy was developed for year-round operation in response to the changing climatic and loading conditions. The capacity ratio of cells in operation; the ratio of exhaust heat delivered to GT; and the ratio of cooling load shared between absorption and compression chillers were chosen as the decision variables in the control strategy. In order to minimize the system energy consumption, particle swarm optimization (PSO) was constructed in MATLAB and coupled with TRNSYS 17 for control optimization. It was found that with the proposed control strategy, the yearly energy saving of the SOFC-GT CCP system would be 6.89% compared to the reference case
On the apparent permeability of porous media in rarefied gas flows
The apparent gas permeability of the porous medium is an important parameter in the prediction of unconventional gas production, which was first investigated systematically by Klinkenberg in 1941 and found to increase with the reciprocal mean gas pressure (or equivalently, the Knudsen number). Although the underlying rarefaction effects are well-known, the reason that the correction factor in Klinkenberg's famous equation decreases when the Knudsen number increases has not been fully understood. Most of the studies idealize the porous medium as a bundle of straight cylindrical tubes, however, according to the gas kinetic theory, this only results in an increase of the correction factor with the Knudsen number, which clearly contradicts Klinkenberg's experimental observations. Here, by solving the Bhatnagar-Gross-Krook equation in simplified (but not simple) porous media, we identify, for the first time, two key factors that can explain Klinkenberg's experimental results: the tortuous flow path and the non-unitary tangential momentum accommodation coefficient for the gas-surface interaction. Moreover, we find that Klinkenberg's results can only be observed when the ratio between the apparent and intrinsic permeabilities is ; at large ratios (or Knudsen numbers) the correction factor increases with the Knudsen number. Our numerical results could also serve as benchmarking cases to assess the accuracy of macroscopic models and/or numerical schemes for the modeling/simulation of rarefied gas flows in complex geometries over a wide range of gas rarefaction. Specifically, we point out that the Navier-Stokes equations with the first-order velocity-slip boundary condition are often misused to predict the apparent gas permeability of the porous media; that is, any nonlinear dependence of the apparent gas permeability with the Knudsen number, predicted from the Navier-Stokes equations, is not reliable. Worse still, for some type of gas-surface interactions, even the ``filtered'' linear dependence of the apparent gas permeability with the Knudsen number is of no practical use since, compared to the numerical solution of the Bhatnagar-Gross-Krook equation, it is only accurate when the ratio between the apparent and intrinsic permeabilities is
A smoothing SQP method for nonlinear programs with stability constraints arising from power systems
Whole genome sequencing of a banana wild relative Musa itinerans provides insights into lineage-specific diversification of the Musa genus
Crop wild relatives are valuable resources for future genetic improvement. Here, we report the de novo genome assembly of Musa itinerans, a disease-resistant wild banana relative in subtropical China. The assembled genome size was 462.1 Mb, covering 75.2% of the genome (615.2Mb) and containing 32, 456 predicted protein-coding genes. Since the approximate divergence around 5.8 million years ago, the genomes of Musa itinerans and Musa acuminata have shown conserved collinearity. Gene family expansions and contractions enrichment analysis revealed that some pathways were associated with phenotypic or physiological innovations. These include a transition from wood to herbaceous in the ancestral Musaceae, intensification of cold and drought tolerances, and reduced diseases resistance genes for subtropical marginally distributed Musa species. Prevalent purifying selection and transposed duplications were found to facilitate the diversification of NBS-encoding gene families for two Musa species. The population genome history analysis of M. itinerans revealed that the fluctuated population sizes were caused by the Pleistocene climate oscillations, and that the formation of Qiongzhou Strait might facilitate the population downsizing on the isolated Hainan Island about 10.3 Kya. The qualified assembly of the M. itinerans genome provides deep insights into the lineage-specific diversification and also valuable resources for future banana breeding
A Cluster Method for the Ashkin--Teller Model
A cluster Monte Carlo algorithm for the Ashkin-Teller (AT) model is
constructed according to the guidelines of a general scheme for such
algorithms. Its dynamical behaviour is tested for the square lattice AT model.
We perform simulations on the line of critical points along which the exponents
vary continuously, and find that critical slowing down is significantly
reduced. We find continuous variation of the dynamical exponent along the
line, following the variation of the ratio , in a manner which
satisfies the Li-Sokal bound , that was so far
proved only for Potts models.Comment: 18 pages, Revtex, figures include
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Characteristics of regional new particle formation in urban and regional background environments in the North China Plain
Long-term measurements of particle number size distributions were carried out both at an urban background site (Peking University, PKU) and a regional Global Atmospheric Watch station (Shangdianzi, SDZ) from March to November in 2008. In total, 52 new particle formation (NPF) events were observed simultaneously at both sites, indicating that this is a regional phenomenon in the North China Plain. On average, the mean condensation sink value before the nucleation events started was 0.025 s−1 in the urban environment, which was 1.6 times higher than that at regional site. However, higher particle formation and growth rates were observed at PKU (10.8 cm−3 s−1 and 5.2 nm h−1) compared with those at SDZ (4.9 cm−3 s−1 and 4.0 nm h−1). These results implied that precursors were much more abundant in the polluted urban environment. Different from the observations in cleaner environments, the background conditions of the observed particle homogeneous nucleation events in the North China Plain could be characterized as the co-existing of a stronger source of precursor gases and a higher condensational sink of pre-existing aerosol particles. Secondary aerosol formation following nucleation events results in an increase of particle mass concentration, particle light scattering coefficient, and cloud condensation nuclei (CCN) number concentration, with consequences on visibility, radiative effects, and air quality. Typical regional NPF events with significant particle nucleation rates and subsequent particle growth over a sufficiently long time period at both sites were chosen to investigate the influence of NPF on the number concentration of "potential" CCN. As a result, the NPF and the subsequent condensable growth increased the CCN number concentration in the North China Plain by factors in the range from 5.6 to 8.7. Moreover, the potential contribution of anthropogenic emissions to the CCN number concentration was more than 50%, to which more attention should be drawn in regional and global climate modeling, especially in the polluted urban areas
Hot air drying characteristics and nutrients of apricot armeniaca vulgaris lam pretreated with Radio Frequency(RF)
[EN] Apricot pretreated with RF and then dried with convective hot air at 65℃, 3.0m/s in this research. RF pretreatment time of 20, 30, 40 and 50min were chosen. Results showed that, there is only falling rate period during apricot hot air drying, and the drying rate of apricot is improved significantly; Herdenson and Pabis model is suitable for apricot hot air drying; retentions of flavonoids, polyphenols and Vc in dried apricot were higher than those of fresh apricot; when RF treating time was chosen 30mins, nutrients retentions of Vc, flavonoid and polyphenols were 0.9543mg/100g, 5.4089mg/100g and 7.3382mg/100g, separately.The work was financially supported by the Fundamental Research Funds for the Central Universities of China (NO. GK201503072 and GK201601007).Peng, M.; Liu, J.; Lei, Y.; Yang, X.; Wu, Z.; Huang, X. (2018). Hot air drying characteristics and nutrients of apricot armeniaca vulgaris lam pretreated with Radio Frequency(RF). En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Politècnica de València. 1583-1590. https://doi.org/10.4995/IDS2018.2018.7524OCS1583159
Screening and Molecular Analysis of Single Circulating Tumor Cells Using Micromagnet Array
Immunomagnetic assay has been developed to detect rare circulating tumor cells (CTCs), which shows clinical significance in cancer diagnosis and prognosis. The generation and fine-tuning of the magnetic field play essential roles in such assay toward effective single-cell-based analyses of target cells. However, the current assay has a limited range of field gradient, potentially leading to aggregation of cells and nanoparticles. Consequently, quenching of the fluorescence signal and mechanical damage to the cells may occur, which lower the system sensitivity and specificity. We develop a micromagnet-integrated microfluidic system for enhanced CTC detection. The ferromagnetic micromagnets, after being magnetized, generate localized magnetic field up to 8-fold stronger than that without the micromagnets, and strengthen the interactions between CTCs and the magnetic field. The system is demonstrated with four cancer cell lines with over 97% capture rate, as well as with clinical samples from breast, prostate, lung, and colorectal cancer patients. The system captures target CTCs from patient blood samples on a standard glass slide that can be examined using the fluorescence in-situ hybridization method for the single-cell profiling. All cells showed clear hybridization signals, indicating the efficacy of the compact system in providing retrievable cells for molecular studies
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