磁化黑洞吸积盘的演化及放能效率

采用等效电路模型讨论了两种不同类型的磁场对黑洞的旋转能量和角动量的提取机制: Blandford—Znajek(BZ)过程和磁耦合过程.在研究磁化吸积盘中心黑洞自转参量演化特征的基础上,详细比较了纯吸积过程、BZ过程和磁耦合过程对黑洞吸积盘放能效率的贡献.结果表明,磁耦合过程是提取黑洞旋转能量重要的新机制,其放能效率与BZ过程几乎相等.在黑洞自转不足特别大的情况,纯吸积过程的放能效率高于BZ过程和磁耦台过程的放能效率,但足当黑洞自转接近极端Kerr黑洞的自转状态时,放能效率主要由BZ过程和磁耦合过程贡献.

磁化黑洞吸积盘的统一模型及其放能效率

阐述了一种包括三种放能机制在内的磁化黑洞吸积盘的统一模型 .在广义相对论框架中导出满足Maxwell方程的磁耦合映射关系 ,在黑洞基本演化方程的基础上得出描述黑洞演化状态的特征函数 ,分析了黑洞自转参量演化的平衡点及特征 .讨论了统一模型的各参量对磁化黑洞吸积盘放能效率的影响 .计算表明 ,在黑洞视界面磁压满足冲压平衡条件下 ,黑洞吸积盘的最大放能效率可达 44 .5 %.

广义相对论有效势与伪牛顿有效势的比较

比较了在牛顿力学和广义相对论框架中有效势的特征 ,对比了广义相对论有效势和两种伪牛顿有效势(PW有效势和LC有效势 )所对应的最内稳定圆轨道半径和放能效率 .结果表明 ,PW有效势能很好地描述检验粒子在Schwarzschild黑洞赤道面上的轨道特征 ,LC有效势也能较好地模拟检验粒子在Kerr黑洞赤道面上的轨道特征 (顺行粒子向快转黑洞吸积的情况除外 ) .

Exerav as a Parameter for Buildina Enerav Assessment

The energy and environmental impacts resulting from the buildings sector are one of the impending problems which address the international action. The main strategies implemented to answer to this problem are the energy efficiency improvement, the CO2 emissions reduction and the renewable energy share increase in the energy mix. The key subject discussed in this paper is the ＂building energy impact＂, aimed to leading the building sector towards the energy efficiency improvement. The paper＇s aim is to show that an energy assessment is not able to give a consistent evaluation of building energy use, and it could be misleading. Therefore, the paper proposes the exergy assessment as complementary evaluation method, in order to achieve a complete description of the concept ＂building＇s energy impact on the environment＂. In the first section, we describe the parameters currently used for the building energy assessment, focusing on the primary energy index and the CO2 emissions index. In the second section, we introduce the exergy as a complementary index. This index is a possible answer to the problems previously identified. Finally, in the third section, we present three test-cases, analyzed through transient simulation software TRNSYS. The purpose of the test-cases analysis is to show the difference between energy and exergy assessment.

China’s Transition to a Low-Carbon Economy:2006-2010

China achieved major progress in low-carbon development during the period of the 11th Five Year Plan (2006-2010). The increasing trend of energy intensity and carbon intensity of the economy as seen prior to 2005 was reversed to a sharp decreasing trend, leading to a 19% decrease in energy intensity and 21% decrease in carbon intensity in five years. The enhanced energy efficiency, mostly due to efficiency improvement in power and manufacturing sector, is the major driver of the decrease in carbon intensity of the economy. The development of renewable energy, despite its impressive growth rate, played a minor role because of its small share in the energy mix of the country. Energy con-sumption and energy-related carbon emissions per unit of area in building continued to grow at a lesser rate, which, combined with the fast growth of total building volume, led to fast growth in total energy consumption and carbon emissions in the sector. Similar trend is observed in the transportation sector whose total energy use and carbon emissions continued to grow fast despite slight improvement in energy efficiency. Agricultural energy use experienced a slight change and forestry made a major contribution to carbon sinks. Policy and institutional innovations helped build a solid system of rules for low-carbon development. Improving cost effectiveness of the system remains a major challenge for the next five year plan period.

Study on the Refineries＇ Energy Efficiency Based on SFA- Model

The study on the enterprise＇s energy efficiency is one of the most important fields of energy efficiency research. Most studies used DEA and aggregate data to estimate the energy efficiency of enterprises. In this study, based on Cobb-Douglas production function, we make a SFA model which takes the energy input and CO2 emission into account. By using the SFA model, we calculate the refineries＇ total-factor energy efficiency with Sinopec refineries＇ micro-data from 2004 to 2009. Meanwhile, we do empirical study on the factors which influence the energy efficiency. In the last, we put forward some advices so as to improve energy efficiency.

Laminar Diffusion Flames of Methane in a Co-annular Jet of Oxygen-Enriched Air

Oxygen rich combustion is a mean to increase the energy efficiency and to contribute to CO2 capture. Influence of oxygen enriched air on the stability of methane flames from non premixed laminar jets has been investigated experimentally. The burner consists of two coaxial jets： methane flowing out of the inner, oxidizer from the outer. The flame behavior is studied according to the proportion of oxygen in the oxidizer jet, the oxidizer and the methane jets velocities. The flame is either anchored to the burner, lifted, stationary or not or blown-out. The addition of oxygen produces a decrease of the lift height, a reduction of the length of the reaction zone and an increase in the soot emission. These results have been reported into diagrams of stability where the flame configurations are connected to the competition between the dynamic effect of the injection velocity and the chemical effect of oxygen addition.

Factors Influencing the Energy Efficiency of Tourism Transport in China

Transport is a major component of energy consumption and 002 emissions in travelling. Understanding changes in the energy efficiency of tourism transport （EETT） and factors affecting this is important to the promotion of low-carbon tourism. This paper established a new method following the top to bottom principle and analyzed EETT variation characteristics and influencing factors from 1994 to 2013 in China. We found that the energy consumption of tourism transport （ECTT） increased from 178.21 PJ in 1994 to 565.82 PJ in 2013 at an average annual growth rate of 6.27%; CO2 emissions of tourism transport （CETT） went up from 14.96×10^6t to 47.94×10^6 t due to person-trip and trip distance growth. EETT went from 3.22×10^6 person-trips PJ^-1 in 1994 to 5.99×10^6 person-trips PJ^-1 in 2013 at an average annual growth rate of 4.90%, and the CO2 emissions of tourism transport unit person-trips （CETTU） shifted from 26.07 kg person-trips^-1 in 1994 to 14.01 kg person-trips^-1 in 2013. Energy intensity decline, scale effects and policy promotion were key factors that enhanced EETT. Meanwhile, trip mode changes and enjoyment-oriented transport hindered EETT. Based on our analysis, we suggest methods to decrease ECTT and CETT. and enhance EETT.

City-level emission peak and drivers in China

China is playing an increasing role in global climate change mitigation,and local authorities need more city-specifc information on the emissions trends and patterns when designing low-carbon policies.This study provides the most comprehensive COemission inventories of 287 Chinese cities from 2001 to2019.The emission inventories are compiled for 47 economic sectors and include energy-related emissions for 17 types of fossil fuels and process-related emissions from cement production.We further investigate the state of the emission peak in each city and reveal hidden driving forces.The results show that38 cities have proactively peaked their emissions for at least fve years and another 21 cities also have emission decline,but passively.The 38 proactively peaked cities achieved emission decline mainly by effciency improvements and structural changes in energy use,while the 21 passively emission declined cities reduced emissions at the cost of economic recession or population loss.We propose that those passively emission declined cities need to face up to the reasons that caused the emission to decline,and fully exploit the opportunities provided by industrial innovation and green investment brought by low-carbon targets to achieve economic recovery and carbon mitigation goals.Proactively peaked cities need to seek strategies to maintain the downward trend in emissions and avoid an emission rebound and thus provide successful models for cities with still growing emissions to achieve an emission peak.

An experimental research on single discharge machining of insulating ceramics efficiently with high energy capacitor

Insulating ceramics are applied to modern manufacturing industries for their improved material properties.But they are the difficult-to-machine materials because of their high rigidity,high brittleness and non-electrical conductivity.A new method which employs a high energy capacitor for electric discharge machining of insulating ceramics efficiently is presented in this paper,and the single discharge experiments have been carried out.The process uses the high voltage,large capacitor and high discharge energy,it is able to effectively machine insulating ceramics,and the single discharge crater volume of insulating ceramics can reach 17.63 mm3.The effects of polarity,peak voltage,capacitance,current-limiting resistance,tool electrode feed,tool electrode section area and assisting electrode thickness on the process performance such as the single discharge crater volume,the tool wear ratio and the assisting electrode wear ratio have been investigated.The microstructure of the discharge crater is examined with a scanning electron microscope(SEM).The results show that the discharge craters have sputtering appearance,the insulating ceramic materials are mostly removed by spalling,in the center region of the discharge some materials are removed by melting and vaporization,and the material removal is enhanced with the machining parameters increasing.

Dual effect of NH4F additive in the hydrothermal deposition of antimony selenosulfide thin film for high-performance solar cells

Hydrothermal deposition of antimony selenosulfide(Sb_(2)(S,Se_(3)))has enabled solar cell applications to surpass the 10%efficiency threshold.This deposition process involves the reaction of three precursor materials:Sb,S,and Se.However,this process generates an unfavourable gradient of Se and S anions in the Sb_(2)(S,Se)_(3)film,which limits further efficiency improvements.Herein,we demonstrate how NH_(4)F can be used as an additive to regulate the band gradient of the Sb_(2)(S,Se)_(3)and modify the surface of the CdS electron-transporting layer.On the one hand,NH_(4)F inhibits the decomposition of Na_(2)S_(2)O_(3)and selenourea,which optimizes the deposition process and allows for adjustment of the Se/S ratio and their distribution in the Sb_(2)(S,Se)_(3)film.On the other hand,hydrolysis of NH_(4)F induces dissolution and redeposition of CdS,thereby effectively improving the morphology and crystallinity of the CdS substrate.Finally,the dual effect of NH_(4)F enables improved surface morphology and energy alignment of the Sb_(2)(S,Se)_(3)film,thus yielding a maximum efficiency of 10.28%,a 12%improvement over the control device.This study demonstrates an effective strategy for simultaneously modifying a sulfide-based substrate and regulating the element distribution during the deposition of a metal chalcogenide film for optoelectronic device applications.

Achieving superior high-temperature sodium storage performance in a layered potassium vanadate

The high-temperature sodium-ion batteries(SIBs)used for large-scale energy storage have attracted extensive attention in recent years.However,the development of SIBs is still hampered mainly by their poor charge/discharge efficiency and stability,necessitating the search for appropriate electrodes.A simple potassium ion intercalation process is used herein to obtain the potassium vanadate(KV_(3)O_(8))nanobelts.When serving as the anode for SIBs at a high temperature(60℃),the KV_(3)O_(8) nanobelts display superior sodium storage performance with a high capacity of 414mA h g^(-1) at 0.1Ag^(-1),remarkable rate capability(220mAh g^(-1) at 20Ag^(-1)),and super-long cycle life(almost no capacity fading at 10Ag^(-1) over 1000 cycles).Moreover,the ex-situ X-ray powder diffraction reveals no structural changes throughout the whole charge/discharge process,which further confirms their outstanding stability,indicating KV_(3)O_(8) nanobelts are a promising candidate for high-temperature SIBs.

Reversible LiOH chemistry in Li-O_(2)batteries with free-standing Ag/δ-MnO_(2)nanoflower cathode

The low energy efficiency and poor cycle stability arising from the high aggressivity of discharge products toward organic electrolytes limit the practical applications of Li-O_(2)batteries(LOBs).Compared with the typical discharge product Li_(2)O_(2),LiOH shows better chemical and electrochemical stability.In this study,a free-standing cathode composed of hydrangea-likeδ-MnO_(2)with Ag nanoparticles(NPs)embedded in carbon paper(CP)(Ag/δ-MnO_(2)@CP)is fabricated and used as the catalyst for the reversible formation and decomposition of LiOH.The possible discharge mechanism is investigated by in situ Raman measurement and density functional theory calculation.Results confirm thatδ-MnO_(2)dominantly catalyzes the conversion reaction of discharge intermediate LiO_(2)*to LiOH and that Ag particles promote its catalytic ability.In the presence of Ag/δ-MnO_(2)@CP cathode,the LOB exhibits enhanced specific capacity and a high discharge voltage plateau under humid O_(2)atmosphere.At a current density of 200 mA g^(−1),the LOB with the Ag/δ-MnO_(2)@CP cathode presents an overpotential of 0.5 V and an ultra-long cycle life of 867 cycles with a limited specific capacity of 500 mA h g^(−1).This work provides a fresh view on the role of solid catalysts in LOBs and promotes the development of LOBs based on LiOH discharge product for practical applications.