A generalized multilevel inverter based on T-Type switched capacitor module with reduced devices

Conventional multilevel inverters have problems in terms of their complicated expansion and large number of devices. This paper proposes a modular expanded multilevel inverter, which can effectively simplify the expansion and reduce the number of devices. The proposed inverter can ensure the voltage balancing of the voltage-dividing capacitors. The cascading of the T-type switched capacitor module and the step-by-step charging method of the switched capacitors enable the inverter to achieve high output voltage levels and voltage gain. In addition, the inversion can be achieved without the H-bridge, which greatly reduces the total standing voltage of the switches. The nine-level inverter of the proposed topology can be realized with only ten switches, obtaining a voltage gain that is two times larger. The above merits were validated through theoretical analysis and experiments. The proposed inverter has good application prospects in medium- and low-voltage photovoltaic power generation

Effects of the turbulence model and the spray model on predictions of the n-heptane jet fuel–air mixing and the ignition characteristics with a reduced chemistry mechanism

Reynolds-averaged Navier–Stokes simulations with an improved spray model and a realistic chemistry mechanism are performed for turbulent spray flames under diesel-like conditions in a constant-volume chamber. Comprehensive numerical analyses including two turbulence models (the renormalisation group k–ε model and the standard two-equation k–ε model) with different model coefficients are made. The distribution of the fuel mixture fractions is a very important factor affecting the combustion process. In this study, we also use the entrainment gas-jet model, modifications of the the spray model coefficient and two turbulence models to investigate extensively the influence of the gas-jet theory model on the fuel–air mixture process. First, a non-reacting case is validated by comparing the liquid-phase penetration and the vapour-phase penetration and also the mixture fractions at different axis positions. Second, approriate methods are confirmed according to accurate mixture fraction distributions to validate the combustion process. Because of the large number of species and reactions, the calculation of chemically reacting flows is unaffordable, particularly for three-dimensional simulations. Hence, the dynamic adaptive chemistry method for efficient chemistry calculations is extended in this work to reduce the computational cost of the spray combustion process when a reduced chemistry mechanism is used. The results show that, in the evaporation case, the gas-jet theory model can be used to obtain a relatively accurate fuel vapour penetration length with different influential factors and that improved numerical methods can effectively reduce the mesh dependence for the spray evaporation process. It is demonstrated that the Schmidt number Sc and the turbulence models significantly influence the mixture fraction distribution. Very good agreement with available experimental data is found concerning the ignition delay time and the flame lift-off length for different oxygen concentrations owing to the accurate fuel mixture fraction

2DPSK Signal Detection Based on Cascaded Stochastic Resonance

In the case of poor channel environment, the detection and reception of digital signal often appear errors. In view of this situation, by reducing the error rate of coherent reception of 2D PSK signals, we propose a new method based on the detection efficiency and improved cascaded stochastic resonance theory.A cascaded bistable stochastic resonance model was established by using stochastic resonance theory. The nonlinear receiver was used to receive 2DPSK signal under small signal-to-noise ratio (SNR). The experimental results show that the spectrum peak of the output signal of cascade stochastic resonance system is 5.70 times that of the traditional model. The output error rate of cascaded nonlinear system model can be reduced by 92.31% compared to the traditional model when the input signal to noise ratio is -7dB. Consequently, the output signal of the system is more likely to be detected and the accuracy can be greatly improved

Environment-economy tradeoff for Beijing–Tianjin–Hebei’s exports

The trade of goods among regions or nations associated with large environmental consequences. Yet balancing economic gains and environmental consequences induced by trade is still hindered by a lack of quantification of these two factors, especially for the environmental problems those are more locally oriented, such as the atmospheric pollution. Based on an environmental input-output analysis for 2010, we contrast economic gains (value added) against atmospheric pollutant emissions (sulfur dioxide (SO2), nitric oxide (NOx), primary fine particulate matter (PM2.5) and non-methane volatile organic compounds (NMVOC)) and the widely concerned CO2 emissions associated with international and interprovincial exports from Beijing-Tianjin-Hebei (BTH), the most polluted area in China. Our results show that exports contributed 55-62% of BTH's production emissions and 54% of its total value added. BTH's large exports of metals and metal products, nonmetal mineral products, chemical and transportation and warehousing, generated a larger share of pollutant emissions (36-46% of BTH's total) than that of value added (17%) along the supply chain. Most of BTH's embodied emissions in exports go to neighboring provinces and the developed east coastal regions in China, although the economic returns are comparatively low. Among BTH, industrial production in Beijing and Tianjin lead to more pollutant emission than value added in Hebei, due to reliance on pollution-intensive product imports from Hebei. Our results call for refocusing and restructuring of BTH's industry and trade structures to balance the economic gains and environmental losses for each region

Inequalities in the commuting burden: Institutional constraints and job-housing relationships in Tianjin, China

Encouraging transport equality is vital in order to create a liveable city. However, the burden of commuting has become a key concern in urban areas, particularly in developing countries. Inequalities in the commuting burden are accompanied by inequalities in housing and employment, because these institutions have a significant impact on individuals' choices of accommodation and jobs, thus shaping commuting behaviour and causing imbalances in job-housing relationships. Therefore, this paper aims to analyse the role of employment and housing system constraints in the unequal commuting burden by using Tianjin as a case study. The results of the study show that the effects of institutional factors, such as Hukou and the Danwei system, help to explain imbalances in the job-housing relationship and the unequal commuting burden. Some commuters are employed by Danweis or have Tianjin Hukou, and can, therefore, live in Danwei housing, which means that Danweis provide effective solutions for some people in terms of their accommodation, enabling them to significantly decrease the time they spend commuting. Moreover, our study provides new evidence that institutional barriers constrain the job-housing balance in the case of high-skilled immigrants, while local residents and low-skilled immigrants can avoid institutional barriers by returning to Danwei housing and choosing to live in informal housing. In terms of suggesting measures for improving commuting inequalities, commuters generally wanted to eliminate the housing benefits resulting from the legacy of the Danwei system and for equal housing subsidies to be implemented. At the same time, they appealed for improvements to be made in terms of housing benefits, the quality of public transport and mixed housing-workplace planning. This study finds that institutional discrimination causes social inequalities in relation to the commuting burden, which could continue to worsen unless the influence of institutional factors is eliminated. The findings could be used to assist planners and decision makers in developing effective strategies to promote sustainable urban development

Comparison and Analysis of Electromagnetic Characteristics of Basic Structure of Wireless Power Coil for Permanent Magnet Motors in Electric Vehicles

The purpose of this paper is to compare and analyze the electromagnetic characteristics of the basic structure of the coil in the electromagnetic coupling mechanism for the wireless power supply of permanent magnet motors in electric vehicles. The electromagnetic coupling mechanism is one of the key technologies for wireless power transmission and the coil structure plays a key role in the transmission performance of the coupling mechanism, and different structures can achieve different performances. The central objective of coil structure studies is to investigate how the coupling coefficient can be increased to achieve greater transmitted power and higher efficiency. In this paper, we investigate two basic coil configurations, circular and square, by studying their flux density variations when used as transmitting coils and their electromagnetic coupling characteristics when used as receiving coils. Three couplers consisting of circular and square coils are also analyzed in simulations and experiments are carried out on couplings containing circular and square coils of the same area. The results of the study show that the qualitative analysis, simulation analysis and experimental results are in high agreement. The results of this paper are an important reference for the design and optimization of wireless power coils for permanent magnet motors in electric vehicles

Synergistic benefits of lime and 3,4-dimethylpyrazole phosphate application to mitigate the nitrous oxide emissions from acidic soils

Acidic soils cover approximately 50 % of the arable land with high N2O emission potential. 3,4-dimethylpyrazole phosphate (DMPP) inhibits N2O emission from soils; however, its efficiency is affected by acidity. Liming is used for soil conditioning to ameliorate the effects of acidity. In the present study, we investigated the effects of liming on the efficiency of DMPP in inhibiting N2O emission in acidic soils and the mechanisms involved. We evaluated the impact of liming, DMPP, and combined application and its microbial responses in two acidic soils from Zengcheng (ZC) and Shaoguan (SG) City, Guangdong Province, China. Soils were subjected to four treatments: un-limed soil (low soil pH) + urea (LU), un-limed soil + urea + DMPP (LD), limed soil (high soil pH) + urea (HU), and limed soil + urea + DMPP (HD) for analyses of the mineral N, N2O emissions, and full-length 16S and metagenome sequencing. The results revealed that, HU significantly decreased and increased the N2O emission by 17.8 % and 235.0 % in ZC and SG, respectively, compared with LU. This was caused by a trade-off between N2O production and consumption after liming, where microbial communities and N-cycling functional genes show various compositions in different acidic soils. LD reduced N2O emission by 23.5 % in ZC, whereas decreased 1.5 % was observed in SG. Interestingly, DMPP efficiency considerably improved after liming in two acidic soils. Compared with LU, HD significantly reduced N2O emissions by 61.2 % and 48.5 % in ZC and SG, respectively. Synergy of mitigation efficiency was observed by lime and DMPP application, which was attributed to the changes in the dominant nitrifiers and the increase in N2O consumption by denitrifiers. The combined application of lime and DMPP is a high-efficiency strategy for N2O mitigation can ensure agricultural sustainability in acidic arable soils with minimal environmental damage

Volatilization and leaching behavior of heavy metals in MSW incineration fly ash in a DC arc plasma furnace

Three fly ash samples collected from different waste incinerators were vitrified using a direct current arc plasma furnace at 1250-1400 degrees C. The influence of water-wash extraction and wrapping pretreatment on the volatilization and leaching behavior of heavy metals was investigated. Results showed: After thermal arc plasma treatment, the volume reduction and weight loss of fly ash were in the range of 68.7-82.2% and 23.8-56.7%, respectively. The residual fractions (wt.%) of heavy metals in slag are in the following sequence: Cr < Ni < Cd < Pb < Cu < Zn. Water-washing could reduce the volatilization rate of heavy metals due to some volatile salts removed by washing, while wrapping of fly ash could most effectively resist heavy metals against volatilizing, especially for Zn and Ni. The possible CaO - Al2O3 - SiO2 (CAS) ratio for successful melting of fly ash is suggested to be CaO in range of 20-48%, Al2O3 in range of 10-15%, and SiO2 in range of 40-65%. Moreover, toxicity characteristic leaching procedure results showed that the leaching of heavy metals in slags was much lower than the standard limit of toxicity characteristic leaching procedure (TCLP)