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Abstract Biodiesel production was catalyzed by a novel magnetic carbonaceous acid (Zr-CMC-SO3H@3Fe-C400) with both Bronsted and Lewis sites synthesized by a four-step method: (i) metal (Fe) ion chelation, (ii) calcination, (iii) metal (Zr) ion chelation and embedding, and (iv) sulfonation. It catalyzed the esterification of oleic acid with 97% biodiesel yield, transesterification of high acid value (AV) soybean oil with 95% biodiesel yield, and pretreatment of Jatropha oil with AV reduced from 17.2 to 0.7 mg KOH/g. Biodiesel yields (>90%) at 90 °C for 4 h reaction time were obtained for ten cycles by easy magnetic separation which showed potential practical applications in the field of green production. The synthesized catalyst was characterized with elemental analysis, XRD, ICP-OES, FT-IR, BET, VSM, SEM-EDX, HRTEM, TG-DSC and Boehm titration.

Abstract Reducing a building’s energy consumption and providing better indoor environmental quality (IEQ) are the two major issues that building professionals are facing all over the world. It is not easy, however, to simultaneously address both issues. Therefore, this study aimed to establish the optimal occupant behavior that can simultaneously reduce total energy consumption and improve the IEQ, using an energy simulation and optimization tool. This study also developed an integrated IEQ score by combining three different IEQ indices (i.e., thermal comfort, indoor air quality (IAQ), and visual comfort) for building users to easily understand the IEQ condition. To analyze the effects of occupant behavior by region, the education facility was selected as the target facility, and five target regions were selected considering the Koppen climate classification system and the C40 Cities Climate Leadership Group. Finally, a total of 5 × 1.01 × 1022 occupant behavior combinations can be generated in the five target regions. As a result, among the four target variables (i.e., total energy consumption, thermal comfort, IAQ, and visual comfort), the total energy consumption of the optimal solution was found to have changed most dramatically compared to that of the basic condition in terms of percentage (94.7%), due to its strong correlation with the overall occupant behavior (the highest correlation coefficient: 0.879). Therefore, it is shown that occupant behavior has more influence on the total energy consumption than on the three IEQ indices. Among the three IEQ indices, the IAQ of the optimal solution decreased most significantly compared to that of the basic condition (the highest reduction ratio: 4.04% in Ulsan), which indicates that the IAQ has more influences on the integrated IEQ score than thermal and visual comfort. The facility manager and the building user can operate the building for reducing total energy consumption and improving the IEQ considering occupant behavior, which can be used as the building management guideline in various regions.

A preliminary design efficiency-optimization of an axial-flow compressor, using one-dimensional flow theory, is studied in this paper. A model for the optimum design of a compressor stage, assuming a fixed distribution of axial velocities, is presented. The absolute inlet and exit angles of the rotor are taken as design variables. Analytical relations between the isentropic efficiency and the flow coefficient, the work coefficient, the flow angles and the degree of reaction of the compressor stage are obtained. The results are universal and can be extended to the optimal design of a multi-stage compressor. Numerical examples are provided to illustrate the effects of various parameters on the optimal performance of the compressor stage.

Since 2009, global financial crisis has eased gradually and world economy has begun to recover slowly. Meanwhile, both Brent and WTI (West Texas Intermediate) crude oil prices have entered into a new round of increase and volatility, and the abnormal price spreads between them have been identified. Under this circumstance, this paper employs the Markov regime switching model with dynamic autoregressive coefficients to explore the price regimes of Brent and WTI after the financial crisis. Then it analyzes the causes of the abnormal spreads between the two benchmark crude oil prices based on the statistical observations of their typical regime differences. The results show that there are three main regimes in both Brent and WTI crude oil price returns, i.e., sharply downward, slightly downward and sharply upward regimes for Brent whilst sharply downward, relatively stable and sharply upward regimes for WTI. Meanwhile, the typical price regimes of Brent and WTI are the “sharply upward” and “relatively stable” regimes after the financial crisis, respectively. Besides, their different movement regimes in recent years are mainly attributed to their different market fundamental situations and the dynamics in crude oil markets, which also lead to the occurrence of their abnormal price spreads.