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Abstract This study evaluated the feasibility of ethanol production from expired rice by surface immobilization technology fermentation. The process was carried out using temperature tolerant active fresh yeast TH-AADY cells immobilized on cotton fiber placed in a reticular hollow sphere. A 320-ton pilot reactor with a multi-layer packed bed immobilized structure and multi-branch circulation path was used instead of the typical cylindrical immobilized reactor. The average values of the alcohol degree and fermentation efficiency of the immobilized yeast cells were 12.46% (v/v) and 83.72%, respectively, which were 0.45% (v/v) and 3.2% higher than those of a free-cell fermentation. The fermentation was repeated for 32 batches with good reusability and long-term stability. In addition, fermentation via cell immobilization created an extra benefit of 6.37% per ton of fuel alcohol based on the mean market price in China. The results obtained in this study indicate that ethanol production from expired rice using immobilized yeast in the new bioreactor is feasible and may meet the demands of industrial production based on the fermentation indexes and economic evaluation.

Abstract Wind-induced vibration (WIV) and power extraction performances of a circular cylinder with symmetrically installed fin-shaped rods (FSR) were experimentally and numerically investigated under different coverages. The FSR coverage which is expressed as an angle (α) is measured from the upstream edge to the downstream edge of the rod. The effect of FSR installation angle (θ) which is the angle from the stagnation point of cylinder to the upstream edge of the rod was also considered in this work. The FSR cylinder is exposed in uniform wind and allowed to vibrate in cross-flow direction. The output electric power is realized by piezoelectric patch. It is found that, for most cases, the output power of FSR cylinder increases monotonously with the rise of α for a given wind velocity (U). In addition, the tendency of output voltage varies with the wind velocity is highly similar to that of output power. The maximum values of output voltage and power are 19.70 V and 1.90 mW can be obtained when α= 20° (θ= 60°). The WIV responses of FSR cylinder show that the amplitudes of FSR cylinder increase with the rise of α for low installation angle (θ= 0°, 30°) and the maximum amplitudes exceed 2D (D: diameter of circular cylinder) can be observed for α= 40°/50° (θ= 30°) and α= 20° (θ= 60°). The reduced frequency of cylinder for θ= 0° and 30° does not sensitive to the coverage (α). It is worth noting that multiple frequencies can be captured for high coverage. Due to the boundary layer separating point moves in downstream direction with the increase of U and α, the vortex pattern switches from 2S to 2P.

Considering multiple transmit antennas in each distributed antenna unit (DAU), two power allocation (PA) schemes are proposed for energy efficiency (EE) maximization for downlink distributed multiple-input single-output (DMISO) systems with orthogonal frequency-division multiplexing (OFDM) over frequency-selective fading channels, where the power constraints for individual antenna units are addressed. The optimization problem for the maximization of the EE subject to per-antenna maximum power constraints is formulated. By means of linear programming, the optimization is simplified to as if for a DMISO system whose DAUs use a single antenna corresponding to the largest channel-gain-to-noise ratio (CGNR) for transmission. Using the block coordinate descent (BCD) method, an iterative optimal PA scheme to the simplified optimization problem is derived, where an efficient procedure for determining the number of effective subcarriers and the optimized PA is developed. Since the optimal scheme needs iterative calculations, a closed-form suboptimal PA scheme is also derived by sorting the total CGNR and using the principle of the BCD method. Interestingly, this suboptimal scheme has small performance loss in comparing with the optimal scheme, and its relative EE loss is decreased with the number of subcarriers. Moreover, these two schemes include the ones with single transmit antenna for distributed antenna systems as special cases. Computer simulations verify the effectiveness of the two proposed schemes, and the proposed optimal one can obtain the same performance as the existing optimal scheme for DMISO-OFDM but with lower complexity.

Heat recovery of air ventilation is a means of energy conversation in buildings. In the present paper, a plastic film heat recovery ventilator that works under cross-flow mode was developed. The thin film vibrates when airflow passes through the channels, which enhances heat exchange performance. Experiments, as well as theoretical analyses, were carried out to study the performance of such a unit. Results show that the effectiveness of the heat exchanger varies from 0.65 to 0.85 with airflow rate and the pressure drop is less than 20.0 Pa. Film vibration induced by airflow can improve heat transfer. The extent of the enhancement is proportional to film vibration intensity that increases with airflow rate while decreases with film thickness.

AbstractStratified thermal energy storage (TES) tanks are widely used in thermal power plants to enhance the electric power peak load shifting capability and integrate high renewable energy shares. In this study, a data‐driven surrogate modeling and optimization study of the unequal diameter radial diffuser previously proposed by the present authors is conducted. First, based on the orthogonal experimental design, numerical experiments are performed to generate the performance database. Then, the database is used to establish the data‐driven surrogate model via the support vector machine. Subsequently, the single‐objective optimization and multiobjective optimization of an unequal diameter radial diffuser are conducted using the genetic algorithm. For the single‐objective optimization, the optimal thermocline thickness is 0.829 m when the diameter ratio of the long baffle and the tank is 0.426, the diameter ratio of the short baffle and the long baffle is 0.823, and the distance between the two baffles is 228.51 mm. For multiobjective optimization, the obtained Pareto optimal solutions are obtained. Under the premise of maintaining excellent thermal stratification, the selected Point C can reduce the steel cost by 88.1%. The research results are helpful for designing efficient and economical unequal diameter radial diffusers for TES tanks.

Voluntary environmental management programs for firms have become an increasingly popular instrument of environmental policy. However, the literature’s conclusion on the effectiveness of suchprograms is ambiguous, and for the European region there is a lack of evidence based on a large control group. We seek to fill this gap with an evaluation of the Eco-Management and Audit Scheme (EMAS), introduced in 1995 by the European Union as a premium certification of continuous pro-environmental efforts above regulatory minimum standards. It is more demanding than other voluntary programsdue to annual public reports of the environmental performance and targets for improvements. We use official firm-level production census data on the German manufacturing sector, a major energy consumer and emitter in Europe. To account for the self-selection of firms, we combine the Coarsened Exact Matching approach with a Difference-in-Differences estimation. Our results do not suggest reductions of firms’ CO2 intensity and energy intensity neither before nor after certification. Moreover, program participants do not increase renewable energy consumption or investments into the protection of the environment and climate. Our results are robust to a variety of checks and call into question the effectiveness of the EMAS program concerning these particular outcome variables.

Abstract We report the enhanced performance and stability of polymer solar cells based on regioregular poly(3-hexylthiophene) (P3HT) and methanofullerene [6,6]-phenyl C 61 -butyric acid methyl ester (PCBM) blend using lithium benzoate (C 6 H 5 COOLi) as cathode buffer layer between the active layer and the Al cathode. The effects of the C 6 H 5 COOLi thickness on the performance of polymer solar cell are also investigated. Under 100 mW/cm 2 white light illumination, the device with 1 nm thick C 6 H 5 COOLi as cathode buffer layer exhibits power conversion efficiency (PCE) as high as 3.41±0.07% and the device stability is greatly extended. Compared to the solar cell with LiF/Al cathode, the PCE is increased ca. 9.4%. Introduction of C 6 H 5 COOLi buffer layer effectively increases the shunt resistance and improves the photo-generated charge collection. The improved performance may attribute to the dissociation of semi-conducting C 6 H 5 COOLi upon deposition to liberate Li with a low work function, which reduces the interface resistance of the active layer and the cathode and enhances the interior electric field that may result in efficient charge transportion. In addition, the C 6 H 5 COOLi layer may serve as an effective oxygen and moisture diffusion barrier for the organic solar cells. Therefore, C 6 H 5 COOLi is a promising candidate as an interlayer to improve the efficiency of electron collection and to reduce the ambience influence on the stability of polymer solar cells.

The China Southern Power Grid (CSG) interconnects four provincial power grids: Guangdong, Guangxi, Yunnan, and Guizhou. It is the only ac/dc hybrid grid in China with dual ac/dc transmission corridors in parallel. The practical high-voltage direct current (HVDC) control scheme of the CSG and its modeling is first presented. Both the stability and small-signal analysis environments of 2005 CSG are established using a commercial software package. Interarea oscillatory modes among the four provincial power grids are then investigated. On the basis of modal analysis, a hierarchical optimization scheme is implemented for the parameter setting of selected power system stabilizers (PSS) and HVDC damping controllers. Digital simulations show that proper coordination of the PSS and HVDC modulation controllers can effectively suppress the interarea oscillation in large-scale ac/dc hybrid power systems under a wide range of operating conditions.