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Small-signal stability analysis of interconnected power systems involves the computation of many eigenvalues/eigenvectors of very large unsymmetric matrices. A new numerical linear algebra method for the partial eigensolution of large sparse matrices is described in this paper. The method converges to as many eigenvalues as the number of trial vectors utilized, in a reduced number of iterations. The results presented are limited to the study of low frequency oscillations in electrical power systems, but the proposed method is completely general.

This study examined the effects of climate change on rice production in 30 Chinese provinces spanning 1998–2017. The study used the pooled mean group technique to capture the long-run and short-run effects of changing climatic conditions on rice production. It further employed the Dumitrescu–Hurlin panel causality test to examine the path of causality between the key variables and rice production. The study found that, in the long run, average temperature negatively influenced rice production, but average rainfall had a positive effect on rice production. The results indicated that the cultivated area and fertilizer usage were positively related to rice production in the long run. The short-run results accentuated that average temperature favourably influenced nationwide rice production, whereas average rainfall had no substantial effect on national rice production. The cultivated area had a significant positive short-term relationship with rice production, although the impact of fertilizer usage on rice production was negligible in the short run. Besides, the results established a bidirectional causality between rice output and the cultivated area, but there was a one-way causality running from fertilizer usage to rice output. Finally, the results indicated that, except for rainfall, a unidirectional causality exists between temperature and rice production. The study, therefore, recommends that in the case of crop failure due to weather conditions, policymakers could implement a new pricing policy to mitigate the deterioration of the farmers’ income. The government must also develop and implement an insurance scheme that compensates farmers for catastrophes induced by rainfall deficiency.

Chemical composition, surface morphology characteristics, and mineralogical characteristics of feed coals from six power plants were studied in this paper, as well as alteration behavior of mineral phase, functional groups, and trace elements during combustion. The apparent morphology of feed coals is different in compactness and order, while sharing a similar lamellar shape. Quartz, kaolinite, calcite, and illite are the main minerals in feed coals. There are obvious differences in the calorific value and temperature range in volatiles stages or coke combustion stages for feed coals. Peak positions for the main functional groups in feed coals are similar. After burning at 800 ℃, most organic functional groups in feed coals were lost in products, but the group of -CH2 on the side chain skeleton of n-alkane and the aromatic hydrocarbon bond (Ar-H) still existed in the ash, and the vibration of Si-O-Si bond and Al-OH bond in inorganic functional groups was strengthened. During combustion, Pb and Cr in feed coals will be accumulated in the mineral residues, unburned carbon, and residual ferromanganese minerals, along with the loss of organic matter and sulfide or the decomposition of carbonate. Pb and Cr are more easily adsorbed by the fine-graded coal combustion products. Occasionally, the abnormal phenomenon occurred in a medium-graded ash but with the maximum adsorption of Pb and Cr, which is mainly caused by the collision and agglomeration of the combustion products, or the adsorption capacity of different mineral components. The effects of diameter, coal species and feed coal on the forms of Pb and Cr in combustion products were also analyzed in this study. The study has some guiding significance for understanding the behavior track and alteration mechanism of Pb and Cr during coal combustion.

Increased use of ethanol-blended gasoline (gasohol) and its potential release into the subsurface have spurred interest in studying the biodegradation of and interactions between ethanol and gasoline components such as benzene, toluene, ethylbenzene and xylene isomers (BTEX) in groundwater plumes. The preferred substrate status and the high biological oxygen demand (BOD) posed by ethanol and its biodegradation products suggests that anaerobic electron acceptors (EAs) will be required to support in situ bioremediation of BTEX. To develop a strategy for aromatic hydrocarbon bioremediation and to understand the impacts of ethanol on BTEX biodegradation under strictly anaerobic conditions, a microcosm experiment was conducted using pristine aquifer sand and groundwater obtained from Canadian Forces Base Borden, Canada. The initial electron accepter pool included nitrate, sulfate and/or ferric iron. The microcosms typically contained 400 g of sediment, 600 approximately 800 ml of groundwater, and with differing EAs added, and were run under anaerobic conditions. Ethanol was added to some at concentrations of 500 and 5000 mg/L. Trends for biodegradation of aromatic hydrocarbons for the Borden aquifer material were first developed in the absence of ethanol, The results showed that indigenous microorganisms could degrade all aromatic hydrocarbons (BTEX and trimethylbenzene isomers-TMB) under nitrate- and ferric iron-combined conditions, but not under sulfate-reducing conditions. Toluene, ethylbenzene and m/p-xylene were biodegraded under denitrifying conditions. However, the persistence of benzene indicated that enhancing denitrification alone was insufficient. Both benzene and o-xylene biodegraded significantly under iron-reducing conditions, but only after denitrification had removed other aromatics. For the trimethylbenzene isomers, 1,3,5-TMB biodegradation was found under denitrifying and then iron-reducing conditions. Biodegradation of 1,2,3-TMB or 1,2,4-TMB was slower under iron-reducing conditions. This study suggests that addition of excess ferric iron combined with limited nitrate has promise for in situ bioremediation of BTEX and TMB in the Borden aquifer and possibly for other sites contaminated by hydrocarbons. This study is the first to report 1,2,3-TMB biodegradation under strictly anaerobic condition. With the addition of 500 mg/L ethanol but without EA addition, ethanol and its main intermediate, acetate, were quickly biodegraded within 41 d with methane as a major product. Ethanol initially present at 5000 mg/L without EA addition declined slowly with the persistence of unidentified volatile fatty acids, likely propionate and butyrate, but less methane. In contrast, all ethanol disappeared with repeated additions of either nitrate or ferric iron, but acetate and unidentified intermediates persisted under iron-enhanced conditions. With the addition of 500 mg/L ethanol and nitrate, only minor toluene biodegradation was observed under denitrifying conditions and only after ethanol and acetate were utilized. The higher ethanol concentration (5000 mg/L) essentially shut down BTEX biodegradation likely due to high EA demand provided by ethanol and its intermediates. The negative findings for anaerobic BTEX biodegradation in the presence of ethanol and/or its biodegradation products are in contrast to recent research reported by Da Silva et al. [Da Silva, M.L.B., Ruiz-Aguilar, G.M.L., Alvarez, P.J.J., 2005. Enhanced anaerobic biodegradation of BTEX-ethanol mixtures in aquifer columns amended with sulfate, chelated ferric iron or nitrate. Biodegradation. 16, 105-114]. Our results suggest that the apparent conservation of high residual labile carbon as biodegradation products such as acetate makes natural attenuation of aromatics less effective, and makes subsequent addition of EAs to promote in situ BTEX biodegradation problematic.

Abstract In this paper, we estimate the energy efficiency of educational buildings with the case study of buildings in City University of Hong Kong by constructing an energy demand stochastic frontier model. The model is estimated by using the university statistical data from 2011 to 2015. For the consistent frequency of data among the variables, we have adopted the quadratic-match sum method to convert annual university report data into a monthly dataset. Our result shows the average energy efficiency is 0.87, implying that 13% of total energy consumption can be saved. We then calculate how much of the energy saving potential has been achieved by constructing the performance score, which increases from 0.08 to 0.17. It implies that the campus performs more efficiently in saving energy over time. We further develop econometric decomposition analysis based on the energy demand frontier model to identify the factors affecting energy consumption. It suggests that research activities account for a large share of overall energy consumption. Analysis on energy end-use shows university should improve efficiency in lab instrument as it is least efficient among the four usages. We expect this paper can provide the fundamental and methodological guideline for university-scale energy efficiency estimation.

Abstract Power-to-gas (PtG), as a promising technology proposed to store surplus renewable energy (RE), can hardly be commercialized for its low profitability. In this paper, three approaches are proposed in this paper to enhance the profitability of the PtG. Firstly, a cooperative union containing PtG is proposed and its sustainability analysis is undertaken based on Shapley Value method. Secondly, the PtG reaction heat, as an essential by-product of PtG which is valuable and therefore requires further study, is fully exploited for district heating in the operation of regional integrated energy system, which is solved by an improved SOCP method. Thirdly, a symbiosis cooperation mode is designed for wind power and PtG to enhance the benefit of PtG through optimization-based trading strategy, which is a MINLP model and solved by Big-M method. The results show that the daily profit of PtG is significantly increased with the cooperative union as the symbiosis cooperation mode can produce a 15.1% profit lift, meanwhile, exploitation of reaction heat can produce an 8.6% profit lift. Finally, our study reveals the conflict of interest between wind power and the cogeneration. A sensitivity study on the proportion of reaction heat used for district heating is performed to verify the mutually beneficial relation between PtG and the cogeneration. The findings of this paper can guide the commercialization of PtG.

This study aimed to examine whether the administration of losartan can prevent acute elevation of pulmonary arterial pressure (AEPAP) induced by endovascular ethanol injection and to assess its related mechanisms. Male swine were selected and performed with absolute ethanol endovascular injection. Saline was used as the negative control. Losartan was administered preoperatively. Pulmonary arterial pressure (PAP), femoral arterial pressure (FAP) and heart rate (HR) were monitored during operations. Venous plasma and pulmonary artery (PA) tissue were harvested for analyses. Protein level was detected by Western blotting and ELISA, whereas qRT-PCR was used in mRNA detection. H & E staining and immunohistochemistry were conducted to evaluate histopathology. Ethanol injection elevated PAP in swine. The concentration of RAS ligands was elevated in plasma (all P < 0.0001) but not in PA. The level of oxidative stress increased in both plasma and PA. MRNA level of AT1R (P < 0.01, 95% CI: 0.251-1.006), not AT2R increased in PA. Losartan failed to inhibit AEPAP after all sessions of ethanol injection, and partially reversed the ethanol-induced PA remodeling. The P38 MAPK was activated after ethanol injection and could be inhibited by losartan (P < 0.01, 95% CI: -0.391 to -0.164). Ethanol also promoted the translocation of the P40-PHOX/P47-PHOX/P67-PHOX complex and the activation of NOX, which was independent from RAS. Endovascular ethanol injection can induce AEPAP mainly by activating RAS and P38 MAPK signaling. Losartan can partially prevent AEPAP and vascular remodeling owing to the promotion of NOX activity by ethanol. Mechanism diagram of endovascular ethanol injection-induced acute elevation of pulmonary arterial pressure (AEPAP) partially prevented by losartan. RAS: Renin-angiotensin system; AGT: angiotensinogen; Ang I: angiotensin I; ACE: angiotensin I converting enzyme; Ang II: angiotensin II. AT1R: angiotensin II type 1 receptor. NOX2: NADPH oxidase 2. PA: pulmonary artery.

The alarming increase in extreme weather events, such as severe storms with torrential rain and strong winds, is a direct result of climate change. These events have led to discernible shifts in forest structure and the carbon cycle, primarily driven by a surge in tree mortality. However, the impacts caused by these severe storms on the production and carbon increment from coarse woody debris (CWD) are still poorly understood, especially in the Brazilian Atlantic Forest. Thus, the goal proposed by the study was to quantify the CWD volume, necromass, and carbon stock before and after the occurrence of a severe storm and to determine the importance of spatial, structural, and qualitative variables of trees in the CWD carbon increment. The increase in carbon by the storm was 2.01 MgC ha-1, with a higher concentration in the CWD less decomposed and smaller diameter class. The forest fragment plots showed distinct increments (0.05-0.35 MgC), being influenced by spatial (elevation, declivity, and slope angle) structural (basal area) and qualitative factors (trunk quality and tree health), intrinsic to the forest. Thus, it is concluded that severe storms cause a large increase in carbon in CWD, making it essential to understand the susceptibility of forests to the action of intense rains and strong winds to model and monitor the future impacts of these extreme weather events on Atlantic Forest and other tropical forests in the world.

Abstract Low efficiency of heat conduction and absorption is a key problem to restrict the application of phase change materials (PCMs). Foam metals, which work as random heat transfer networks, are often used to improve the thermal conductivity of PCMs. But further improvements are still required in engineering. Interestingly, random micro-channels also widely exist in natural heat and mass transfer systems (e.g., minor veins of leaves and blood capillaries) that always appear with ordered branching networks of macro-channels. But the ordered branching networks, which perform as efficient transfer networks, are rare in metal-foam-enhanced PCMs. Therefore, this work enhances the PCMs’ heat-absorption efficiency by constructing heat transfer networks mimicking leaf veins. Given the gap that there lack trusted design criteria to design the heat transfer networks, we propose an innovative optimization criterion mimicking the generating process of leaf veins. Combine the criterion with an original flexibility-oriented optimization framework, a generating design method is established. The optimization performance is discussed in point-area PCM structures. Compared with the metal-foam-enhanced PCM plate, the heat-absorption efficiency of the generating-based PCM plate is increased to 196.67% in concentrating heat from the PCMs, and the heat-absorption efficiency is also enhanced for more than 3.79 times in dispersing heat to the PCMs. With these improvements, the proposed method is applied in cooling high-power electronic devices which solves the overheating problem and prolongs the working time to 400.00%. Further applications can be expended to PCM-cooling systems, heat pump, collection and output of solar energy and waste heat, etc.