Performance study of a novel solar solid dehumidification/regeneration bed for use in buildings air conditioning systems

In this paper, a novel solar solid dehumidification/regeneration bed has been proposed, and its three regeneration methods, i.e., simulated solar radiation regeneration, microwave regeneration, and combined regeneration of the microwave and simulated solar radiation, were experimentally investigated and compared, as well as the dehumidification performance. The degree of regeneration of the proposed system under the regeneration method combining both microwave irradiation and simulated solar radiation could reach 77.7%, which was 3.77 times higher than that of the system under the simulated solar regeneration method and 1.05 times higher than that of the system under the microwave regeneration. The maximum energy efficiency of the proposed system under the combined regeneration method was 21.7%, while it was only 19.4% for the system under microwave regeneration. All these proved that the combined regeneration method of the simulated solar and microwave radiation not only improved the regeneration efficiency of the system, but also enhanced the energy efficiency. For the dehumidification performance, the maximum transient moisture removal was 14.1 g/kg, the maximum dehumidification efficiency was 68.0% and the maximum speed of dehumidification was 0.294 g/(kgμs) when the inlet air temperature was at 26.09 °C and the air relative humidity was at 89.23%. By comparing the testing results with the semi-empirical results from the Page model, it was indicated that the Page model can predict the regeneration characteristics of the novel solar solid dehumidification/regeneration bed under the combined method of microwave and simulated solar regeneration. The results of this research should prove useful to researchers and engineers to exploit the potential of solar technologies in buildings worldwide

Approximate Common Knowledge Based on Uncertain Measure

This paper studies that how an uncertain event can be outlined as an approximate common knowledge. By replacing “know” with “know with certainty α” in standard definitions of common knowledge, approximate common knowledge with some certainty, defined iteratively and mutually, iteratively known and mutually known with some certainty, are explored. Examples are constructed to show that an event which is not common knowledge can be analyzed as an approximate common knowledge with some certainty. An application in the principal-agent model is investigated to show that approximate common knowledge based on uncertain measure can be applied to improve the behavior of an economic model

Optimal L∞(L2)L^\infty(L^2) and L1(L2)L^1(L^2) a posteriori error estimates for the fully discrete approximations of time fractional parabolic differential equations

We derive optimal order a posteriori error estimates in the $L^\infty(L^2)$ and $L^1(L^2)$-norms for the fully discrete approximations of time fractional parabolic differential equations. For the discretization in time, we use the $L1$ methods, while for the spatial discretization, we use standard conforming finite element methods. The linear and quadratic space-time reconstructions are introduced, which are generalizations of the elliptic space reconstruction. Then the related a posteriori error estimates for the linear and quadratic space-time reconstructions play key roles in deriving global and pointwise final error estimates. Numerical experiments verify and complement our theoretical results.Comment: 22 page

Cost-reduction implicit exponential Runge-Kutta methods for highly oscillatory systems

In this paper, two novel classes of implicit exponential Runge-Kutta (ERK) methods are studied for solving highly oscillatory systems. First of all, we analyze the symplectic conditions of two kinds of exponential integrators, and present a first-order symplectic method. In order to solve highly oscillatory problems, the highly accurate implicit ERK integrators (up to order four) are formulated by comparing the Taylor expansions of numerical and exact solutions, it is shown that the order conditions of two new kinds of exponential methods are identical to the order conditions of classical Runge-Kutta (RK) methods. Moreover, we investigate the linear stability properties of these exponential methods. Finally, numerical results not only present the long time energy preservation of the first-order symplectic method, but also illustrate the accuracy and efficiency of these formulated methods in comparison with standard ERK methods

Plasma-Assisted Combustion

As a promising technology, plasma-assisted combustion (PAC) has attracted many researchers to explore the effect of PAC on improving the combustion in propulsion devices, such as scramjet, detonation engines, internal engines, and so on. In this chapter, we aim to exhibit the influence of quasi-DC discharge plasma on the operating performance of scramjet combustor and find the internal mechanisms, which may contribute to the development of PAC technology in supersonic combustion. For case one, a plasma filament is generated upstream of fuel jet through quasi-DC discharge in a scramjet combustor; for case two, the plasma is formed across the backward facing step of a flame holding cavity to improve the flame stabilization of the cavity in the scramjet combustor. The two cases are investigated in detail through three-dimensional numerical simulation based on the dominant thermal blocking mechanism. Important parameters including temperature distribution, separation zone, water production, stagnation pressure loss, combustion efficiency, cavity drag, mass exchange rate, and cavity oscillating characteristics are obtained and analyzed. It shows that the quasi-DC discharge plasma does benefit for the improvement of the combustion in a scramjet combustor

Dexmedetomidine protects gastric mucosal epithelial cells against ischemia/reperfusion-induced apoptosis by inhibiting HMGB1-mediated inflammation and oxidative stress

Purpose: To investigate the role of dexmedetomidine in gastric ischemia/reperfusion injury using gastric mucosal epithelial cell (GES-1) model. Methods: GES-1 were subjected to oxygen-glucose deprivation conditions, followed by increasing dexmedetomidine concentrations (0.5, 1.0, or 1.5 μM) for 4 h of reoxygenation. Cell viability and apoptosis were determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide and flow cytometry, respectively. Oxidative stress and inflammation were analyzed by enzyme-linked immunosorbent assay (ELISA). Results: Oxygen-glucose deprivation conditions induced cytotoxicity in GES-1 by decreasing cell viability and increasing apoptosis. Dexmedetomidine treatment significantly increased the cell viability of hypoxia/reoxygenation-induced GES-1 (p < 0.01) but reduced apoptosis. Dexmedetomidine also attenuated the hypoxia/reoxygenation-induced increase in malondialdehyde and myeloperoxidase, but the decrease in superoxide dismutase and glutathione in GES-1. Moreover, upregulated tumor necrosis factor-α, interleukin (IL)-1β, and IL-18 in hypoxia/reoxygenation-induced GES-1 was downregulated by dexmedetomidine treatment. Dexmedetomidine also enhanced IL-10 levels and inhibited proinflammatory factor production (p < 0.01). High-mobility group box 1 (HMGB1) protein in GES-1 was upregulated by hypoxia/reoxygenation but decreased by dexmedetomidine. HMGB1 over-expression attenuated the dexmedetomidine-induced increase in cell viability and the decrease in apoptosis, oxidative stress, and inflammation in hypoxia/reoxygenation-induced GES-1 (p < 0.01). Conclusion: Dexmedetomidine protects GES-1 against ischemia/reperfusion-induced apoptosis, inflammation, and oxidative stress by inhibiting HMGB1, thus providing a potential strategy for treating gastric ischemia/reperfusion injury. Keywords: Dexmedetomidine; gastric mucosal epithelial cells; Ischemia/reperfusion; Apoptosis; Inflammation; Oxidative stress; High-mobility group box 1 (HMGB1

Study on dehumidification performance of a multi-stage internal cooling solid desiccant adsorption packed bed

In this paper, the solid desiccant adsorption packed bed with a three-stage internal cooling (ICSPB) has been proposed to improve the dehumidification efficiency and make a comparison with that of non-internal cooling. To investigate the performance of the ICSPB, the dehumidification capacity, dehumidification efficiency, water content of solid desiccant, moisture ratio of solid desiccant, temperature of solid desiccant and inlet and outlet air temperature difference were discussed in different conditions of inlet air and supplying water temperature. It was found that the dehumidification performance of the bed with internal cooling could be improved greatly in the low temperature and low humidity conditions, while in the high temperature and humid, the improvement was not obvious. With internal cooling, the dehumidification efficiency and the water content of the solid desiccant could be improved 59.69% and 110.7%, respectively, and the temperature of solid desiccant could be reduced 2.2◦C when the ICSPB operated at the inlet air temperature of 20◦C, inlet humidity of 55%, and water temperature of 14◦C. Moreover, the dehumidification performance at each stage of ICSPB was studied. It was found that, the first stage played the most important role in the dehumidification process. In addition, the calculation models that can be used to predict the moisture ratio and the temperature of solid desiccant were established on the test results

Investigation on the Solar Absorption Property of the Nanoporous Alumina Sheet for Solar Application

In order to improve the absorption performance of the aluminum sheet for solar application, the nanoporous alumina sheets with the pore diameters of 30 nm and 400 nm were prepared by the anodic oxidation method. The absorption properties of the nanoporous alumina sheets under different solar radiation intensity were studied and compared with the conventional polished aluminum sheet. The results showed that the average absorptivity of the aluminum sheets decreased with the increase of the radiation intensity. When the radiation intensity was 100 W/m2, the nanoporous alumina sheet with the 30 nm pore diameter had the highest average solar absorptivity of 0.39, which was 18% higher than that of the nanoporous alumina sheet with 400 nm pore diameter, and 50% higher than that of the polished aluminum sheet. The maximum instantaneous absorption efficiency of the nanoporous alumina sheet with 30 nm pore diameter was found at 0.92 when the radiation intensity was 100 W/m2. The testing results indicated that the nanoporous alumina sheet with the 30 nm pore diameter performed the best compared with the other two aluminum sheets. By error propagation analysis, the relative error of the average amount of heat absorption and the average absorptivity were acceptable