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Abstract To alleviate the shortage of natural gas resource and ease carbon emissions, a novel solar-driven combined cooling, heating and power (CCHP) system is designed and optimized using the genetic algorithm in the work. Different from the process of direct combustion in a conventional CCHP system, natural gas is firstly converted into syngas by a solar-driven natural gas reforming step, which is consumed in an efficient tri-generation system. Energy, economic and environmental evaluations on five office buildings in different climate zones in China are implemented to validate the advantages of the proposed system. Results show that the annual maximum primary energy saving, total cost saving, and CO2 emission reduction are 69.76%, 49.80%, and 71.55%, respectively. The system located in severe cold zones, where solar energy is abundant and building requires more heat load in whole year, achieves the highest benefits in comparison with separate systems. Furthermore, the sensitivities on the price fluctuations of electricity, natural gas and solar field to the system profits are investigated, which indicates that the influence of electricity price on the system performance is the most significant. Thus, a promising method for reducing the natural gas consumption and improving the utilization efficiency of solar energy is provided.

People’s attention of transformer condition assessment is increasing in recent year and data mining is applied in transformer condition assessment with its obvious superiority in dealing with complex data and finding potential problems. In this paper, the process of the research on applying data mining to transformer condition assessment is summarized. The research results of data processing methods such as rough set theory, principal component analysis and colony algorithm as well as the research result of transformer condition assessment such as vector machine, neural network, Bayes network, association rules and fuzzy theory are introduced, analyzed and compared in detail. The advise on the choice and quantification of figure, the employ of the pattern recognition method, the blend of multi-information and visualization display are given.

In this study, Myriophyllum elatinoides growth under different nitrogen (N) concentrations (2, 250, 300, 350 and 400 mg L-1) and changes in rhizosphere bacterial community structure were investigated. High N (>300 mg L-1) concentrations caused reduction in M. elatinoides biomass. Growth tended to stabilize at 49 days. N concentration in roots were higher than that in stems and leaves under high N conditions. TN and NH4+ removal efficiencies reached 84.0% and 87.2%, respectively, in M. elatinoides surface flow constructed wetlands (SFCWs). Rhizosphere bacterial diversity increased over time. Proteobacteria, Firmicutes, Cyanobacteria, and Bacteroidetes dominated at the phylum level. Genera Turicibacter, Allochromatium, and Methylocystis increased at low N (<300 mg L-1) concentrations, while Pseudomonas increased at high N concentrations over the experimental period. Redundancy analysis showed that pH was strongly correlated with changes in rhizosphere bacterial community structure. These findings helped to insight into N removal mechanism in M. elatinoides.

Abstract To further improve the cycle efficiency with the heat transfer curves between higher than 350 °C heat resource and the evaporating working medium of the Kalina cycle and to reduce the exhaust temperature of heat resource, the dual-pressure vaporization Kalina cycle for cascade utilization of high-to-mid grade heat resource is proposed. The optimization was conducted for parameters in this modified Kalina cycle such as concentrations of work solution and basic solution, evaporation dew point temperature. Under the conditions of inlet temperatures of heat resource and cooling water of respectively 400 °C and 25 °C and the constraints of proper heat transfer pinch point temperature differences, the maximum evaporation pressure not exceeds 20 MPa, the vapour quality at the turbine outlet is greater than 0.85 and the exhaust temperature of heat resource is not lower than 90 °C, the optimum parameters are obtained that the work and basic concentrations are 0.45 and 0.272 respectively, the dew point temperature of evaporation is 300 °C, and the corresponding power recovery efficiency of the dual-pressure vaporization Kalina cycle reaches 27%, which is 17% higher than that of the Kalina cycle with optimum parameters.

AbstractBy using the data of 30 provinces from 1998 to 2016 in China, this paper estimates the water rebound effect in the agricultural crop farming by combining Slacks‐based Measure (SBM‐based) of Malmquist Index and Logarithmic Mean Divisia Index (LMDI) method. We find that the average water rebound effect is 70.3%, implying that over two‐thirds of the water saving from irrigation technology improvement is offset by higher water consumption. We find evidence on the regional heterogeneity in terms of the magnitude of rebound: Southwest is the highest, whereas Northwest is the lowest. The heterogeneous rebound effect across regions is mainly due to the difference in water endowment and irrigation land availability. Our results indicate that irrigation technology improvement is not necessarily sufficient for achieving agricultural water conservation. In particular, the difference in natural geography conditions across regions needs to be considered in designing water conservation policies at a sub‐regional level.

The coupling between unsteady heat release and acoustic perturbations can lead to self-sustained thermoacoustic oscillations, also known as combustion instability. When such combustion instability occurs, the pressure oscillations may become so intense that they can cause engine structural damage and costly mission failure. Thus there is a need to understand the coupling physics between acoustic waves and unsteady combustion and to identify a measure to quantify the interaction between the flame and acoustics. The present work studies linear and nonlinear response of a conical premixed laminar flame to oncoming acoustic disturbances. Unsteady heat release from the flame is assumed to be caused by its surface area variations, which results from the fluctuations of the oncoming flow velocity. The classical G-equation is used to track the flame front variation in real-time. Second-order finite difference method is then used to expand the flame model. Time evolution of the flame surface distortions is successfully captured. To quantify the dynamic response of the flame to the acoustic disturbances, system identification is then conducted to estimate the linear and nonlinear flame transfer function. Good agreement is obtained. Finally, transfer function of an actuated open–open thermoacoustic system is experimentally measured by injecting a broad-band white noise. The present work opens up new applicable way to measure heat-driven acoustics transfer function in a thermoacoustic system by simply implementing white noise.

Abstract As covering layers, barrier envelopes of VIPs are always exposed to severe environmental conditions, including high temperatures, alkaline environments and local stress concentration when used as thermal insulation material in concrete structures. This study investigated the time-dependent degradations of three types of commonly used envelopes (aluminium film, metallized film and metallized film coated with alkali-resistant (AR) fibreglass mesh) and VIPs covered by these three envelopes by simulating environmental conditions with four types of alkaline solutions (NaOH solution with pH = 7, 11, 13 and saturated Ca(OH)2), two different temperatures (20 °C and 60 °C) and local stress concentration. The results showed that stress and high temperature accelerated the degradation of envelopes and that such degradation became more serious with increased pH value and temperature. It was also observed that the thermal conductivity of VIPs increases quickly when they are exposed to higher alkalinity combined with high temperatures. After 6-week submerged in saturated Ca(OH)2 solution at 60 °C, the thermal conductivity of VIPs increased from 4.413 mW/m K to 13.049 mW/m K for aluminium foil, from 5.375 mW/m K to 10.982 mW/m K for metallized film, and from 5.786 mW/m K to 8.110 mW/m K for AR fibreglass mesh-reinforced film, respectively.

Abstract China has the advantage of learning from the mistakes made by nations that have developed their nuclear power energy system in the last century. Such mistakes encompass the lack of sustainable development of the nuclear energy and poor planning in the back-end of the nuclear fuel cycle. The present paper studies the evolution of a double strata cycle with fast reactor gradually replacing the LWR. It starts from 2035 and covers the historical development of nuclear energy in China to the year 2100. The paper studies the ADS impact on the NFC and estimates the number and the deploying schedule of the ADS reactors to limit the accumulation of minor actinides. The other aspects considered here are natural uranium resources, fuel utilization efficiency, proliferation and diversion risks, spent fuel production and overall materials flow. Additionally, perturbation calculations were performed to evaluate the impact of the uncertainty on key parameters. The results are discussed in view of the Chinese nuclear fuel cycle plan and their policy implications are thoroughly evaluated.

AbstractVegetation growth is affected by past growth rates and climate variability. However, the impacts of vegetation growth carryover (VGC; biotic) and lagged climatic effects (LCE; abiotic) on tree stem radial growth may be decoupled from photosynthetic capacity, as higher photosynthesis does not always translate into greater growth. To assess the interaction of tree‐species level VGC and LCE with ecosystem‐scale photosynthetic processes, we utilized tree‐ring width (TRW) data for three tree species: Castanopsis eyrei (CE), Castanea henryi (CH, Chinese chinquapin), and Liquidambar formosana (LF, Chinese sweet gum), along with satellite‐based data on canopy greenness (EVI, enhanced vegetation index), leaf area index (LAI), and gross primary productivity (GPP). We used vector autoregressive models, impulse response functions, and forecast error variance decomposition to analyze the duration, intensity, and drivers of VGC and of LCE response to precipitation, temperature, and sunshine duration. The results showed that at the tree‐species level, VGC in TRW was strongest in the first year, with an average 77% reduction in response intensity by the fourth year. VGC and LCE exhibited species‐specific patterns; compared to CE and CH (diffuse‐porous species), LF (ring‐porous species) exhibited stronger VGC but weaker LCE. For photosynthetic capacity at the ecosystem scale (EVI, LAI, and GPP), VGC and LCE occurred within 96 days. Our study demonstrates that VGC effects play a dominant role in vegetation function and productivity, and that vegetation responses to previous growth states are decoupled from climatic variability. Additionally, we discovered the possibility for tree‐ring growth to be decoupled from canopy condition. Investigating VGC and LCE of multiple indicators of vegetation growth at multiple scales has the potential to improve the accuracy of terrestrial global change models.