Modeling Analysis of DC Magnetic Bias of Iron Core Reactor of APF

As one of the main power devices of active power filter (APF), iron core reactor DC magnetic bias would affect the performance of APF. Based on the study of DC magnetic bias mechanism of APF iron core reactor, the data model was established in this paper. The performance of APF device impacted by iron core reactor DC magnetic bias was analysed through the simulation in different DC current conditions, and optimization scheme was proposed to reduce DC magnetic bias to improve working performance of APF. To reduce DC magnetic bias, main circuit parameters and control characteristics were uniform, and reluctance of iron core was increased. Results of the simulations and experiments validated that the improved method could restrain reactor DC magnetic bias to reduce even harmonic current in APF output current, which could greatly optimize APF performance

Highly enhanced catalytic stability of copper by the synergistic effect of porous hierarchy and alloying for selective hydrogenation reaction

Supported copper has a great potential for replacing the commercial palladium-based catalysts in the field of selective alkynes/alkadienes hydrogenation due to its excellent alkene selectivity and relatively high activity. However, fatally, it has a low catalytic stability owing to the rapid oligomerization of alkenes on the copper surface. In this study, 2.5 wt% Cu catalysts with various Cu:Zn ratios and supported on hierarchically porous alumina (HA) were designed and synthesized by deposition–precipitation with urea. Macropores (with diameters of 1 μm) and mesopores (with diameters of 3.5 nm) were introduced by the hydrolysis of metal alkoxides. After in situ activation at 350 °C, the catalytic stability of Cu was highly enhanced, with a limited effect on the catalytic activity and alkene selectivity. The time needed for losing 10% butadiene conversion for Cu1Zn3/HA was ~40 h, which is 20 times higher than that found for Cu/HA (~2 h), and 160 times higher than that found for Cu/bulky alumina (0.25 h). It was found that this type of enhancement in catalytic stability was mainly due to the rapid mass transportation in hierarchically porous structure (i.e., four times higher than that in bulky commercial alumina) and the well-dispersed copper active site modified by Zn, with identification by STEM–HAADF coupled with EDX. This study offers a universal way to optimize the catalytic stability of selective hydrogenation reactions

System Design and Optimisation Study on a Novel CCHP System Integrated with a Hybrid Energy Storage System and an ORC

For achieving higher energy transferring efficiency from the resources to the load, the Combined Cooling, Heating, and Power (CCHP) systems have been widely researched and applied as an efficient approach. The key idea of this study is designing a novel structure of a hybrid CCHP system and evaluating its performance. In this research, there is a hybrid energy storage unit enhancing the whole system’s operation flexibility while supplying cooling, heating, and power. An ORC system is integrated into the CCHP system which takes responsibility of absorbing the low-temperature heat source for electricity generation. There are a few research studies focusing on the CCHP systems’ performance with this structure. In order to evaluate the integrated system’s performance, investigation and optimisation work has been conducted with the approaches of experimental studies and modelling simulation. The integrated system’s configuration, the model building process of several key components, the optimisation method, and the case studies are discussed and analysed in this study. The design of the integrated system and the control strategy are displayed in detail. Several sets of dynamic energy demand profiles are selected to evaluate the performance of the integrated system. The simulation study of the system supplying selected scenarios of loads is conducted. A comprehensive evaluation report indicates that the system’s efficiency during each study process differs while supplying different loads. The results include the power supplied by each component, the energy consumed by each type of load, and the efficiency improvements. It is found that the integrated system fully satisfies the selected domestic loads and various selected scenarios of loads with high efficiency. Compared to conventional power plants or CHP systems, the system efficiency enhancement comes from higher amount of recovery waste heat. Especially, the ORC system can absorb the low-temperature heat source for electricity generation. Compared to the original following electrical load (FEL) control strategy, the optimisation process brings overall efficiency improvements. The system’s overall efficiency was increased by from 3%, 3.18%, 2.85%, 17.11%, 8.89%, and 21.7% in the second case studies. Through the whole study, the main challenge lies within the design and the energy management of the integrated system

Active Power Filter DC Bus Voltage Piecewise Reaching Law Variable Structure Control

The DC bus voltage stability control is one key technology to ensure that Active Power Filter (APF) operates stably. The external disturbances such as power grid and load fluctuation and the system parameters changing may affect the stability of APF DC bus voltage and the normal operation of APF. The mathematical model of DC bus voltage is established according to power balance principle and a DC bus voltage piecewise reaching law variable structure control algorithm is proposed to solve the above problem, and the design method is given. The simulation and experiment results proved that the proposed variable structure control algorithm can eliminate the chattering problem existing in traditional variable structure control effectively, is insensitive to system disturbance, and has good robustness and fast dynamic response speed and stable DC bus voltage with small fluctuation. The above advantages ensure the compensation effect of APF

Is the Stock Market a Casino?

It has been 20 years since the inception of the Chinese stock market. However, the market is still being criticized as a casino. This article compares the stock return performance between lottery type and non-lottery type stocks. Through constructing a lottery index for each stock, we find that the average return for lottery type stocks is 10%~12% lower each year comparing with non-lottery type stocks. Firm size, liquidity, whether a company is an ST company and institutional holding moderate the relationship between our lottery index and future stock return. Specifically, we find that the relationship between our lottery index and future stock return is stronger among smaller stocks, illiquid stocks, ST stocks and stocks with lower institutional holding. Further analysis shows that the moderating role of firm size, liquidity, institutional holding and whether a stock is ST works mainly through its effect on lottery-type stocks rather than non-lottery stocks. Overall, our finding suggests that gambling is an important motivation that investors participate in the stock market, and the effect of gambling on Chinese stock market is profound

Determination of Biological and Molecular Attributes Related to Polystyrene Microplastic-Induced Reproductive Toxicity and Its Reversibility in Male Mice

Microplastics exist not only in the natural environment, but also in human tissue such as blood and even placenta. Polystyrene microplastic exposure can cause abnormal sperm quality in mice; however, the mechanism is unclear, and whether sperm abnormalities can be restored has not been reported. ICR mice were exposed to 5 μm polystyrene microplastics through the drinking water. After one spermatogenic cycle, mitochondrial damage was observed to explain the possible cause of sperm damage. After 1–2 spermatogenic cycles of recovery, whether the damaged sperm could be recovered was observed. The results show that polystyrene microplastics caused a decrease in the mitochondrial membrane potential, an imbalance of kinetic homeostasis, a change in genetic characteristics, mitophagy, and a decrease in the ATP content in mouse testicular tissue. Oxidative stress may be the cause of mitochondrial damage. After 1–2 spermatogenic cycles, mitochondrial damage was restored and sperm quality was improved. This study explored the mitochondrial causes of reproductive toxicity of polystyrene microplastics and the reversibility of reproductive toxicity, providing data for further research on the toxicity of microplastics and the prevention and treatment of its harm

Challenges and Resilience of First-Year Chinese International Students on Academic Probation

A substantial percentage of international students are placed on academic probation each year. This study explored the challenges and resilience characteristics of Chinese international students placed on academic probation in their first year of college. Semi-structured interviews were conducted with nine probationary Chinese international students, and the data were analyzed using a thematic analysis approach. The results indicated that challenges with daily routine, reduced adult supervision, inadequate academic preparation, and limited participation in the application process were the main factors that contributed to their academic probation. Proactivity, independence, and flexible thinking were important resilience characteristics that may have helped students cope positively with stresses relating to academic probation. Targeted institutional support could be strengthened. Implications, limitations, and suggestions for future research are also discussed

A multi-optimization model for the design of hydrogen supply chains

This paper presents a multi-objective optimization models which operating as time processes (2025-2035) for the design of hydrogen supply chain. The feasibility of the models are illustrated through a detail case study of Dalian, China. Furthermore, the case is evaluated with the total daily costs and CO2 emissions reduction constraints. The results show that with the increase of hydrogen demand, considering the environmental factors, SMR are mostly applied in hydrogen production link. Shahekou and Pulandian grids are suitable for the constructions of hydrogen production units. Tank trucks are the main modes of hydrogen transportation. The proposed design models can provide policy-makers with the selection of infrastructures pathways for strategic dynamic hydrogen development planning

Methyl Halide to Olefins and Gasoline over Zeolites and SAPO Catalysts:A New Route of MTO and MTG

Rational and efficient conversion of methane to more useful higher hydrocarbons is one of the most important topics of natural gas utilization.Although methane activation and its conversion to valuable compounds attract an increasing attention,methane conversion is often made in indirect way through the very energy-consuming step for syngas production from steam reforming of methane.Some promising results appeared to be of significance for the development of an alternative and potential route for the production of high value-added products from methane.Efficient conversion of methane to higher hydrocarbons could be realized via methyl halide as the intermediate.After the production of halomethane,they could be transformed to gasoline and light olefins over modified zeolites and SAPO molecular sieves.High conversion efficiency and selectivity indicated the feasibility of industrial application.The research gained recently growing interest from the point of view in both fundamental research and industrial application.The study on the reaction mechanism shed light on the possible route of C-C bond construction from methyl halide,which is the very important issue of the C1-reactant conversion to higher hydrocarbons.Hydrogen halide generation during methyl halide conversion did not exert apparent impact on the reaction mechanism and the structure stability of the catalysts.This review deals with the evolution of the field and comments the advantages to be explored and the drawbacks to be prevented for the development of new and sustainable methane-to-olefins（MTO） and methane-to-gasoline（MTG） routes via methyl halides

Lack of Pharmacokinetic Interaction between the Oral Anti-Influenza Prodrug Oseltamivir and Aspirin

Twelve volunteers completed a two-sequence, three-way crossover study of a single 900-mg aspirin dose and multiple doses of 75 mg of oseltamivir in the absence and presence of 900 mg of aspirin. The plasma and urine results demonstrated no pharmacokinetic interaction between oseltamivir and aspirin