Tailoring Carbon Distribution inα/γPhase of Ductile Iron and Its Effects on Thermal Conductivity

The effects of carbon distribution on the microstructure and thermal conductivity of ductile iron were investigated in the present study.The microstructure of as-cast and quenched ductile iron were characterized by OM and SEM.Results showed that the microstructure of as-cast ductile iron was composed of spheroidal graphite,ferrite with the volume of 80%,and a small amount of pearlite,and quenched ductile iron was composed of spheroidal graphite,coarse/fine acicular martensite(α_(M)phase)and high-carbon retained austenite(γphase).The volume fraction of retained austensite and its carbon content for direct quenched ductile iron and tepmered ductile iron were quantitatively analysed by XRD.Results revealed that carbon atoms diffused fromα_(M)phase toγphase during tempering at low temperatures,which resulted in carbon content in retainedγphase increasing from 1.2 wt%for the direct quenched sample to about 1.9 wt%for the tempered samples.Consequently,the lattice distortion was significantly reduced and gave rise to an increase of thermal conductivity for ductile iron.

Carbon allocation in Picea jezoensis:Adaptation strategies of a non-treeline species at its upper elevation limit

Understanding the physiological adaptations of non-treeline trees to environmental stress is important to understand future shifts in species composition and distribution of current treeline ecotone.The aim of the present study was to elucidate the mechanisms of the formation of the upper elevation limit of non-treeline tree species,Picea jezoensis,and the carbon allocation strategies of the species on Changbai Mountain.We employed the^(13)C in situ pulse labeling technique to trace the distribution of photosynthetically assimilated carbon in Picea jezoensis at different elevational positions(tree species at its upper elevation limit(TSAUE,1,700 m a.s.l.)under treeline ecotone;tree species at a lower elevation position(TSALE,1,400 m a.s.l.).We analyzed^(13)C and the non-structural carbohydrate(NSC)concentrations in various tissues following labeling.Our findings revealed a significant shift in carbon allocation in TSAUE compared to TSALE.There was a pronounced increase inδ^(13)C allocation to belowground components(roots,soil,soil respiration)in TSAUE compared to TSALE.Furthermore,the C flow rate within the plant-soil-atmosphere system was faster,and the C residence time in the plant was shorter in TSAUE.The trends indicate enhanced C sink activity in belowground tissues in TSAUE,with newly assimilated C being preferentially directed there,suggesting a more conservative C allocation strategy by P.jezoensis at higher elevations under harsher environments.Such a strategy,prioritizing C storage in roots,likely aids in withstanding winter cold stress at the expense of aboveground growth during the growing season,leading to reduced growth of TSAUE compared to TSALE.The results of the present study shed light on the adaptive mechanisms governing the upper elevation limits of non-treeline trees,and enhances our understanding of how non-treeline species might respond to ongoing climate change.

Distribution of soil carbon in different grassland types of the Qinghai-Tibetan Plateau

Accurate estimate of soil carbon storage is essential to reveal the role of soil in global carbon cycle. However, there is large uncertainty on the estimation of soil organic carbon(SOC) storage in grassland among previous studies, and the study on soil inorganic carbon(SIC) is still lack. We surveyed 153 sites during plant peak growing season and estimated SOC and SIC for temperate desert, temperate steppe, alpine steppe, steppe meadow, alpine meadow and swamp, which covered main grassland in the Qinghai Plateau during 2011 to 2012. The results showed that the vertical and spatial distributions of SOC and SIC varied by grassland types. The SOC amount mainly decreased from southeast to northwest, whereas the SIC amount increased from southeast to northwest. The magnitude of SOC amount in the top 50 cm across grassland types ranked by: swamp > alpine meadow >steppe meadow > temperate steppe > alpine steppe > temperate desert, while the SIC amount showed an opposite order. There was a great deal of variation in proportion of SOC and SIC among different grassland types(from 55.17 to 94.59 for SOC and 5.14 to 44.83 for SIC). The total SOC and SIC storage was 5.78 Pg and 1.37 Pg, respectively, in the top 50 cm of soil in Qinghai Province. The mixed linear model revealed that grassland types was the predominant factor in spatial variations of SOC amount while grassland types and soil p H accounted for those of SIC amount. Our results suggested that the community shift of alpine meadow towards alpine grassland induced by climate warming would decrease carbon sequestration capacity by 6.0 kg C m2.

Carbon Accumulation and Distribution in Ecosystems of Taiwania flousiana Plantation and Successive Rotation Plantation of Cunninghamia lanceolata

The 23-year-old T. flousiana plantation and successive rotation plantation of C. lanceolata at Shankou Forest Farm of Nandan County, Guangxi were tested by the method of plot investigation combining with biomass measurement. Carbon storage and spatial distribution of different components in the two forests were analyzed. The results indicated that carbon content in different organs of T. flousiana ranged from 426.0 to 503.9 g/kg, and the order was bark 〉stem 〉 root 〉 branch 〉 leaf. The carbon contents in shrub, herb and litter layers were452.9 , 408.0 and 428.9 g/kg, respectively. Carbon content in the soil （0 -80 cm）was 16.59 g/kg. The carbon content in different organs of C. lanceolata ranged from 464.5 to 508.9 g/kg, and the order was bark 〉 stem 〉 branch 〉 root 〉 leaf. The carbon contents in shrub, herb and litter layers were 456.2, 416.3 and 468.1 g/kg, respectively. Carbon content in the soil （0 -80 cm）was 15.77 g/kg. Total carbon storage amounts of T. flousiana plantation and successive rotation plantation of C. lanceolata were 245.83 and 213.52 t/hm^2, respectively. The carbon storage order of different structure layers from T. flousiana plantation and successive rotation plantation of C. lanceolata was soil layer （0 -8 0 cm） 〉 vegetation layer 〉 litter layer. Annual net productivity in the arbor layers of T. flousiana plantation and successive rotation plantation of C. lanceolata plantations was 10.75 and 17.13 t/（hm^2 · a） ; annual net carbon fixation amounts were estimated as 5.05 and 3.47 t /（hm^2 · a） ; annual net absorption C02 amounts were 18.53 and 12.73 t/（hm^2 · a） respectively.

Mapping carbon distribution in 35SiMn steel by energy-filtered transmission electron microscopy

In this study,the three-windows method,the jump-ratio method and the R-map method in energy-filtered transmission electron microscopy(EFTEM) have been applied to mapping carbon distribution in 35SiMn steel after a quenching-partitioning treatment.The carbon contamination is successfully suppressed by using EFTEM and plasma-cleaning TEM samples.Compared to the three-windows method and the jump-ratio method,the R-map method provides carbon distribution with less noises,and is insensitive to changes in sample thickness.We have demonstrated that the R-map method is a better way for carbon mapping in middle-carbon steel without the influence of carbon contamination.

Effect of Nickel Distributions Embedded in Amorphous Carbon Films on Transport Properties

Electrical properties of C/Ni films are studied using four mosaic targets made of pure graphite and stripes of nickel with the surface areas of 1.78,3.21,3.92 and 4.64%.The conductivity data in the temperature range of400-500 K shows the extended state conduction.The conductivity data in the temperature range of 150-300 K shows the multi-phonon hopping conduction.The Berthelot-type conduction dominates in the temperature range of 50-150 K.The conductivity of the films in the temperature range about 〈 50 K is described in terms of variable-range hopping conduction.In low temperatures,the localized density of state around Fermi level（F）for the film deposition with 3.92% nickel has a maximum value of about 56.2×10^（17）cm^（-3）eV^（-1） with the minimum average hopping distance of about 3.43 × 10^（-6） cm.

考虑风险和碳交易机制的微电网分布鲁棒优化调度

提高微电网风电的消纳能力是实现双碳目标的重要手段。该文构建了一种考虑极限场景和净负荷条件风险价值的微电网低碳分布鲁棒优化模型。首先,针对源-荷不确定性构造基于Wasserstein距离的概率分布模糊集,并考虑极限场景修正该模糊集,以提高模糊集的鲁棒性,减少场景数目,提高求解效率。其次,以包括供能成本、阶梯式碳交易成本和风险成本的微电网日运行成本最小为优化目标,建立分布鲁棒优化调度模型,并利用分段线性近似法和对偶理论将模型转换为线性规划问题求解。最后,通过算例仿真进行验证,结果表明,考虑极限场景的分布鲁棒优化方法具有较强的鲁棒性;引入阶梯式碳交易成本可以有效减少微电网的碳排放量,并提高风电的消纳能力;净负荷条件风险价值可以有效平衡微电网运行的经济性与风险性。

含整体煤气化燃料电池-碳捕集电厂的风火储系统分布鲁棒调度方法

整体煤气化燃料电池(integrated gasification fuel cell,IGFC)是与碳捕集技术高度适配的清洁、高效、稳定的绿色煤电技术,有望克服传统碳捕集技术在低浓度CO_(2)环境下产生的高成本、高能耗问题。该文构建含IGFC碳捕集电厂的风火储发电系统。研究IGFC碳捕集电厂的运行机理,对IGFC内部各环节建立数学模型,提出工况匹配时燃烧利用率和阴极空气利用率需要满足的运行条件,并针对该型碳捕集电厂的电碳特性进行分析。为计及风电出力的不确定性,构建风火储系统的两阶段分布鲁棒经济调度模型,引入k阶适应性理论,提出基于正交支撑子集策略的求解方法来获得鲁棒对等式。最后,在改进IEEE-30节点系统中进行算例分析,结果表明,该型碳捕集电厂可利用阳极碳富集的优势,实现系统低碳经济调度的目标,并验证所提优化方法能为可行解提供可解释性。

计及最恶劣场景概率和供需灵活性的综合能源系统分布鲁棒低碳优化调度

随着可再生能源渗透率的提升,其不确定性给综合能源系统(integrated energy system,IES)的经济性和鲁棒性带来了极大挑战。为了促进可再生能源消纳以及降低碳排放量,提出了一种基于数据驱动的分布鲁棒优化(distributionally robust optimization,DRO)调度策略。首先,构建了由有机朗肯循环(organic Rankine cycle,ORC)、氢燃料电池和电动汽车等构成的供需灵活响应模型,并引入阶梯碳交易机制来约束系统碳排放量。其次,为了能获取最恶劣情况下的场景概率分布,采用综合范数对风电输出场景的概率分布置信集合进行约束。然后,以在最恶劣场景概率分布下综合能源系统运行总成本最低为目标建立两阶段鲁棒优化模型,并通过列和约束生成(column and constraint generation,CCG)算法对模型进行迭代求解。最后,算例仿真结果表明了所提模型和求解方法的有效性,并分析了阶梯碳交易机制和供需灵活响应模型对提高系统灵活性和低碳经济性的影响。

考虑条件风险价值的交直流系统两阶段分布鲁棒低碳经济优化调度

考虑到海上风电出力的随机性以及日益突出的生态环境问题,以含柔性直流输电技术(voltagesource converter high voltage direct current,VSC-HVDC)的交直流系统为研究对象,提出了考虑条件风险价值(conditional valueatrisk,CVaR)的两阶段分布鲁棒低碳经济优化模型,构建了基于Kullback-Leibler(KL)散度的概率分布模糊集,同时利用条件风险价值量化了极端场景下的尾部风险,使得模型能够同时考虑概率分布不确定性以及处于最坏概率分布中极端场景下的尾部损失;此外,将阶梯型碳交易机制并入所提分布鲁棒模型中,通过合理利用柔性资源和储能装置,增强系统运行的灵活性,在兼顾运行风险的前提下,降低碳排放量的目标。再者,为了提高计算效率,在列和约束生成算法(column-and-constraint generation method,C&CG)和Multi-cut Benders分解算法的基础上提出了双循环分解算法。最后,在基于改进的IEEE RTS 79测试系统中验证了所提模型及算法的有效性。

考虑碳减排的共燃发电厂鲁棒可信性选址决策优化

基于“碳达峰、碳中和”战略目标,研究考虑碳减排的共燃发电厂选址决策问题.受天气状况、市场环境等外部因素的影响,生物质供应能力和生物质价格等参数具有不确定性,构造一个非精确可能性分布集来描述问题中的不确定参数,进而建立一个分布鲁棒可信性选址优化模型.通过推导鲁棒可信性目标和鲁棒可信性约束的等价形式,将原模型重构为一个可计算的混合整数线性规划模型.最后利用算例分析验证提出方法的有效性.

Biomass and Carbon Sequestration Potential of Poplar-Wheat Inter-cropping System in Irrigated Agro-ecosystem in India

An attempt has been made to assess the productivity as well as the carbon sequestration potential of this mixture. The grain as well as straw yields were significantly lower in poplar block plantations than in the open （14 to 64% and 13 to 66% grain and straw yield, respectively under one to six year plantation）. The annual productivity of poplars was recorded maximum after fourth year and later the annual wood increment decreased （42.4, 39.8 and 35.6 m^3/ha/yr after 4^th, 5^th and 6^th year, respectively）. The enrichment of soil through litter and roots enhanced the organic carbon in the surface layer of soil （0-15 cm） under poplar blocks as compared to open fields with wheat crop only. The carbon storage potential in agroforestry system was recorded very high in comparison to sole crop. The carbon storage in agroforestry system increased with the age of the plantation and the major contribution came from the timber, roots and litter （37.30 mg/ha after six years）. However, wheat crop yield decreased under poplar but this may be compensated by the poplar trees in terms of biomass, economic returns and the carbon sequestration potential.

考虑分时碳价的虚拟电厂分布鲁棒竞标方法

为了探索双碳目标下虚拟电厂(virtual power plants,VPP)低碳、经济的竞标策略,提出了一种基于分时碳价和分布鲁棒优化思想的VPP参与日前多类市场的竞标策略。从减小电力市场运营成本的角度,提出了一种与电价负相关的分时碳价,采用基准线法为VPP无偿分配碳配额,计算新能源发电的国家核证减排量;综合考虑碳交易市场、能量市场和调峰市场的情况,搭建了VPP参与多类市场的竞标模型;针对风电的不确定性,构建了基于数据驱动的分布鲁棒两阶段竞标模型,并采用列与约束生成算法求解。算例分析表明,分时碳价能够有效降低电力市场运营商的运行成本,提高VPP运营商的收益,所提的VPP竞标模型能给出不同市场的最优投标方案,而分布鲁棒能够兼顾经济性与鲁棒性。

计及绿证-碳交易的源荷分布鲁棒优化调度

针对电力系统面临风电消纳困难、调节能力短缺的问题,文章建立了计及绿证-碳交易的源荷分布鲁棒优化调度模型。首先,在电源侧引入绿色证书交易机制和碳交易机制以提升风电上网功率,在负荷侧引入高载能负荷以提高系统调节能力;其次,为了减小风电出力不确定的影响,采用数据驱动的分布鲁棒方法,通过风电出力历史数据构建概率分布不确定集,进而寻找最恶劣的场景进行优化,利用列约束生成算法求解;最后,基于IEEE 39节点系统进行算例验证。结果表明,通过整合源荷双侧可调节资源进行协同优化,可以在促进风电消纳的同时保证电力系统具有良好的调节能力。

考虑新能源出力的分布鲁棒低碳经济调度

为提高风电并网能力并降低碳排放,文中提出了一种考虑碳交易和电动汽车的两阶段分布鲁棒低碳经济调度模型。引入碳交易成本,通过电动汽车的储能技术和风力发电的协同配合来降低系统的碳排放量,提高系统对风电的消纳能力。考虑到风电的不确定性,利用历史风电出力数据的矩信息,采用基于通用矩不确定性的分布鲁棒优化方法,建立分布鲁棒模糊集以刻画不确定的风电出力特性。利用对偶原理和线性决策规则将分布鲁棒模型转换为二次规划模型,并通过CPLEX对模型进行求解。实验结果表明,所提方法使风电消纳量提高了11.35%,碳排放量减少了1579 t,验证了两阶段分布鲁棒模型的有效性和优越性。

Enhanced biological nutrient removal in modified carbon source division anaerobic anoxic oxic process with return activated sludge pre-concentration

A pilot-scale modified carbon source division anaerobic anoxic oxic(AAO) process with pre-concentration of returned activated sludge(RAS) was proposed in this study for the enhanced biological nutrient removal(BNR) of municipal wastewater with limited carbon source. The influent carbon source was fed in step while a novel RAS pre-concentration tank was adopted to improve BNR efficiency, and the effects of an influent carbon source distribution ratio and a RAS pre-concentration ratio were investigated. The results show that the removal efficiency of TN is mainly influenced by the carbon source distribution ratio while the TP removal relies on the RAS pre-concentration ratio. The optimum carbon source distribution ratio and RAS pre-concentration ratio are 60% and 50%, respectively, with an inner recycling ratio of 100% under the optimum steady operation of pilot test, reaching an average effluent TN concentration of 9.8 mg·L-1with a removal efficiency of 63% and an average TP removal efficiency of 94%. The mechanism of nutrient removal is discussed and the kinetics is analyzed. The results reveal that the optimal carbon source distribution ratio provides sufficient denitrifying carbon source to each anoxic phase, reducing nitrate accumulation while the RAS pre-concentration ratio improves the condition of anaerobic zone to ensure the phosphorus release due to less nitrate in the returned sludge. Therefore, nitrifying bacteria, denitrifying bacteria and phosphorus accumulation organisms play an important role under the optimum condition, enhancing the performance of nutrient removal in this test.

STUDY ON THE SEQUENCE STRUCTURE OF SBR BY ^(13)C-NMR METHOD Ⅱ. PEAK ASSIGNMENT FOR ALIPHATIC CARBONS SPECTRA

The study on ^(13)C-NMR spectra of aliphatic carbon region of emuision-processed and solution-processed (by lithium catalyst) SBR was carried out. The assignments for more than thirty odd peaks observed experimentally were made by using 'corresponding analysis' method, combined with the empirical parameters reported in literature. The peak intensifies were calculated based on BemouUian statistic assumption.

Seismic analysis of early-mid Miocene carbonate platform in the southern Qiongdongnan Basin, South China Sea

The southern uplift of the Qiongdongnan Basin is a deepwater area in which no wells have beens drilled. The Miocene-Quaternary strata in the Xisha Islands, which are located 40–100 km to the south, are composed of carbonate reef formations. Paleotectonic and paleogeographic analyses of the basin suggest that the southern uplift experienced favorable geological conditions for the development of carbonate reefs during the Miocene.The high-impedance carbonates have high amplitudes and low frequencies on seismic profiles. The reefs are distributed on paleotectonic highs and are thicker than the contemporaneous formations. A forward model of the variation in carbonate thickness based on lithological and velocity information from wells in nearby regions can simulate the seismic response of carbonates with different thicknesses. We identified several important controlling points for determining the thickness of carbonates from seismic profiles, including the pinchout point,the λ/4 thickness point, and the λ/2 thickness point. We depict a carbonate thickness map in the deepwater area of the southern Qiongdongnan Basin based on this model. The carbonate thickness map, the paleotectonic and paleogeographic background, and the seismic response characteristics of reefs suggest that the carbonates that developed on the southern uplift of the Qiongdongnan Basin during the Miocene were mainly an isolated carbonate platform peninsula and ramp deposits. It consisted of gentle ramp platform, steep slope platform,platform depression, gravity flow, and reef bank facies.

考虑阶梯型碳交易的风光储联合系统分布鲁棒优化调度

在“双碳”目标下,风、光等清洁能源的渗透率将不断提高,针对其发电具有不确定性给电力系统带来的调度难题,提出了风光储联合系统的两阶段分布鲁棒优化调度模型。为了减少系统的碳排放量,引入了阶梯型碳交易。模型中,第一阶段根据预测信息使系统的运行成本最低,第二阶段使用基于数据驱动的Wasserstein距离来构建出力误差的模糊集。并使用仿射策略对模型进行调整,使系统在满足模糊集中最恶劣分布的情况下,使调整成本最小。最后,使用了强对偶原理把模型转化为等效混合整数线性优化模型。通过算例分析及对比,验证了考虑阶梯型碳交易可以显著减少对传统机组的使用,以及分布鲁棒优化模型的适用性和优越性。

计及风光不确定性的电-热-氢综合能源系统分布鲁棒优化

为了提高可再生能源消纳,促进综合能源系统发展,该文提出一种计及风光不确定性的电-热-氢综合能源系统(EHH-IES)分布鲁棒优化方法。给出EHH-IES结构和氢储能(HES)耦合模型;基于分布鲁棒条件风险价值(DRCVaR)方法,以系统收益最大、全生命周期碳排放量最小和不确定性风险成本最小为目标,建立EHH-IES优化问题的博弈模型;应用拉格朗日对偶原理,将模型转换成半定规划问题并求解。算例结果表明,该优化方法可使EHH-IES总收益提高1.4%,全生命周期碳排放量减少2.9%,显著降低风光不确定性造成的经济风险。