Ultrasonic Plasma Engineering Toward Facile Synthesis of Single-Atom M-N4/N-Doped Carbon(M=Fe,Co) as Superior Oxygen Electrocatalyst in Rechargeable Zinc-Air Batteries

As bifunctional oxygen evolution/reduction electrocatalysts,transition-metal-based single-atom-doped nitrogen-carbon(NC)matrices are promising successors of the corresponding noblemetal-based catalysts,offering the advantages of ultrahigh atom utilization effciency and surface active energy.However,the fabrication of such matrices(e.g.,well-dispersed single-atom-doped M-N4/NCs)often requires numerous steps and tedious processes.Herein,ultrasonic plasma engineering allows direct carbonization in a precursor solution containing metal phthalocyanine and aniline.When combining with the dispersion effect of ultrasonic waves,we successfully fabricated uniform single-atom M-N4(M=Fe,Co)carbon catalysts with a production rate as high as 10 mg min-1.The Co-N4/NC presented a bifunctional potential drop ofΔE=0.79 V,outperforming the benchmark Pt/C-Ru/C catalyst(ΔE=0.88 V)at the same catalyst loading.Theoretical calculations revealed that Co-N4 was the major active site with superior O2 adsorption-desorption mechanisms.In a practical Zn-air battery test,the air electrode coated with Co-N4/NC exhibited a specific capacity(762.8 mAh g(-1))and power density(101.62 mW cm^(-2)),exceeding those of Pt/C-Ru/C(700.8 mAh g^(-1) and 89.16 mW cm^(-2),respectively)at the same catalyst loading.Moreover,for Co-N4/NC,the potential difference increased from 1.16 to 1.47 V after 100 charge-discharge cycles.The proposed innovative and scalable strategy was concluded to be well suited for the fabrication of single-atom-doped carbons as promising bifunctional oxygen evolution/reduction electrocatalysts for metal-air batteries.

Multi-electron reaction and fast Al ion diffusion of δ-MnO_(2) cathode materials in rechargeable aluminum batteries via first-principle calculations

Rechargeable aluminum batteries with multi-electron reaction have a high theoretical capacity for next generation of energy storage devices. However, the diffusion mechanism and intrinsic property of Al insertion into MnO_(2) are not clear. Hence, based on the first-principles calculations, key influencing factors of slow Al-ions diffusion are narrow pathways, unstable Al-O bonds and Mn^(3+) type polaron have been identified by investigating four types of δ-MnO_(2)(O3, O'3, P2 and T1). Although Al insert into δ-MnO_(2) leads to a decrease in the spacing of the Mn-Mn layer, P2 type MnO_(2) keeps the long(spacious pathways)and stable(2.007–2.030 A) Al-O bonds resulting in the lower energy barrier of Al diffusion of 0.56 e V. By eliminated the influence of Mn^(3+)(low concentration of Al insertion), the energy barrier of Al migration achieves 0.19 e V in P2 type, confirming the obviously effect of Mn^(3+) polaron. On the contrary, although the T1 type MnO_(2) has the sluggish of Al-ions diffusion, the larger interlayer spacing of Mn-Mn layer,causing by H_(2)O could assist Al-ions diffusion. Furthermore, it is worth to notice that the multilayer δ-MnO_(2) achieves multi-electron reaction of 3|e|. Considering the requirement of high energy density, the average voltage of P2(1.76 V) is not an obstacle for application as cathode in RABs. These discover suggest that layered MnO_(2) should keep more P2-type structure in the synthesis of materials and increase the interlayer spacing of Mn-Mn layer for providing technical support of RABs in large-scale energy storage.

Engineering single-atom Mn on nitrogen-doped carbon to regulate lithium-peroxide reaction kinetics for rechargeable lithium-oxygen batteries

Precision engineering of catalytic sites to guide more favorable pathways for Li_(2)O_(2) nucleation and decom-position represents an enticing kinetic strategy for mitigating overpotential,enhancing discharge capac-ity,and improving recycling stability of Li-O_(2) batteries.In this work,we employ metal-organic frameworks(MOFs)derivation and ion substitution strategies to construct atomically dispersed Mn-N_(4) moieties on hierarchical porous nitrogen-doped carbon(Mn SAs-NC)with the aim of reducing the over-potential and improving the cycling stability of Li-O_(2) batteries.The porous structure provides more chan-nels for mass transfer and exposes more highly active sites for electrocatalytic reactions,thus promoting the formation and decomposition of Li_(2)O_(2).The Li-O_(2) batteries with Mn SAs-NC cathode achieve lower overpotential,higher specific capacity(14290 mA h g^(-1) at 100 mAg^(-1)),and superior cycle stability(>100 cycles at 200 mA g^(-1))compared with the Mn NPs-NC and NC.Density functional theory(DFT)cal-culations reveal that the construction of Mn-N_(4) moiety tunes the charge distribution of the pyridinic N-rich vacancy and balances the affinity of the intermediates(LiO_(2) and Li_(2)O_(2)).The initial nucleation of Li_(2)O_(2) on Mn SAs-NC favors the O_(2)-→LiO_(2)→Li_(2)O_(2) surface-adsorption pathway,which mitigates the overpoten-tials of the oxygen reduction(ORR)and oxygen evolution reaction(OER).As a result,Mn SAs-NC with Mn-N_(4) moiety effectively facilitates the Li_(2)O_(2) nucleation and enables its reversible decomposition.This work establishes a methodology for constructing carbon-based electrocatalysts with high activity and selectivity for Li-O_(2)batteries.

Advanced characterization and calculation methods for rechargeable battery materials in multiple scales

The structure-activity relationship of functional materials is an everlasting and desirable research question for material science researchers,where characterization and calculation tools are the keys to deciphering this intricate relationship.Here,we choose rechargeable battery materials as an example and introduce the most representative advanced characterization and calculation methods in four different scales:real space,energy,momentum space,and time.Current research methods to study battery material structure,energy level transition,dispersion relations of phonons and electrons,and time-resolved evolution are reviewed.From different views,various expression forms of structure and electronic structure are presented to understand the reaction processes and electrochemical mechanisms comprehensively in battery systems.According to the summary of the present battery research,the challenges and perspectives of advanced characterization and calculation techniques for the field of rechargeable batteries are further discussed.

Statistical Change Detection in Water Cycle over Two Decades and Assessment of Impact of Urbanization on Surface and Sub-Surface Water Flows

Urbanization is termed as physical transformation of landscapes that alter the natural regime of the environment of its surrounding resulting in further changes in macro as well as micro climate of the region [1]. Urban areas are continually facing problems of water scarcity and urban flash floods. Recent news from IPCC report 2010, CIESIN’s Global Rural Urban Mapping Project [2] and World Water Vol. 7 2007, it is clear that urban land area has doubled and affected the hydrological cycle. The components of hydrological cycle affected are Infiltration, Runoff and Evaporation and the causing components are derived by studies as land use, land cover, water withdrawal and urban developments. Thus water availability, water recharge and water cycle are all destabilized in course or urban development. The paper is an attempt to correlate and identify the periodical changes in urban water cycle, during urbanization of Bhopal City, India, during last twenty years and above. The observations are based on GIS mapping of the study area from 1991 to 2009 using rational method of runoff and recharge calculations and statistical analysis of related built-up areas. Also change in natural course of drainages with the help of GIS imageries which have been detected during twenty years that help to observe the adaptation of natural system to urban course. Also the observations show an interesting relation which can be used for further research and sustainable development [3].

基于流量衰减分析的次降水入渗补给系数计算方法

次降水入渗补给系数是地下水资源量评价的重要参数,次降水对地下水的入渗补给受气候、地形、地质等多种因素影响。以湖北宜昌香溪河流域雾龙洞地下河系统为例,进行次降水入渗补给系数获取方法的探索。在泉流量衰减规律分析基础上,探索新方法进行次降水入渗补给系数计算,分析其规律特征及影响因素,对计算结果的科学合理性进行验证。研究结果表明:雾龙洞泉流量衰减服从分段指数衰减方程;研究区次降水入渗补给系数受次降水强度及降水前下垫面条件影响。基于泉流量衰减分析计算次降水入渗补给系数方法合理可行,该方法在岩溶水资源评价中有一定的推广应用价值。

降雨入渗补给灵敏度及其计算方法研究

对两类降雨入渗计算模型进行了研究:①简单的水量平衡模型;②数值模拟模型。这两类模型的假定条件和非饱和的理论概念差别很大。两类模型在非饱和区中的应用表明,在非饱和区均质土壤条件下,水量平衡模型计算的降雨入渗补给量与应用数值模拟模型计算所得结果基本相吻合。灵敏度分析表明了地下水位变动对降雨入渗补给的影响。假定地下水位不变所造成的误差可作为水文地质参数的一个函数来处理。本文研究成果在一定水文地质条件下的非饱和水流模型、饱和水流模型或排水模型系统计算中具有十分重要的参考应用价值。

水电站生态流量中的河道地下水补给需水计算

大坝建设拦断河流,可能造成下游减脱水,减脱水河道内要产生地表径流,首先应满足河道地下径流的补给需水要求。即首先将河道地下孔隙充满,地下水位抬升至河道表面,而地下水处于流动状态,是一个动态平衡过程。就NB/T 35091—2016《水电工程生态流量计算规范》中河道地下水补给需水计算部分,建立了一套河道地下水补给需水定量计算流程和方法,以马马崖一级水电站为例,进行了试算,可作为相关计算和研究的一个参考和借鉴。

云南省水富县大峡谷温泉岩溶承压水补给量分析计算

通过水文地质调查、同位素、水化学等分析方法对云南省水富县大峡谷温泉岩溶承压水的来源补给区进行定性分析,采用降水入渗补给系数法、地下水总补给模数法对补给区的岩溶地下水资源总量进行定量计算,利用水量平衡原理计算岩溶承压水的补给量。结果表明:温泉补给区主要是五角堡,补给源为大气降水,补给区多年平均地下水总量为621万m3,流量为0.20 m3/s。岩溶承压水分析计算为该区域的水资源开发、利用和保护提供依据。

肾-膀胱排泄的剂量学模型

计算有效剂量时 ,膀胱有 0 .0 5的组织权重因子值。为计算摄入放射性物质对膀胱壁产生的当量剂量 ,需要放射性物质经肾 膀胱排泄的剂量学模型。ICRP 5 3号出版物给出了该模型的数学表达式。不过 ,这些表达式只适用于能从体液直接经尿排泄的物质。本文导出了摄入放射性物质经体内若干器官、组织依次转移然后经尿排出时 ,其在肾尿路、膀胱内容物中衰变数的计算式 ,并以吸入99mTc标记的DTPA气溶胶为例 。

隧道漏水诱发的地层水位降深计算方法与工程应用

隧道大量漏、涌水将造成周边地层水位下降,进而诱发大面积地层沉陷,危及周边建(构)筑物、管线的运行安全。文章基于面井法,考虑大气降水补给影响,建立了隧道漏水诱发的周边地层水位降深计算方法,并进行了实例应用与分析。结果表明:(1)隧道漏水诱发的周边地层水位降深曲线呈对称"沉降槽"形,越靠近隧道中心处,水位降深越明显;(2)随漏水持续时间的延长,水位降深呈对数函数发展趋势;(3)依托工程隧道连续漏水30 d,周边50 m范围内地层水位下降将超过3 m,实际施工过程中应及时采取堵水措施。

地下水库研究的现状及展望

阐述我国地下水库近年来的研究现状,总结地下水库在分类、库容计算、水库回灌、水库防渗及水库选址等方面的研究进展。通过对当前地下水库研究内容、方法和结论的系统分析,指出该领域的一个重要发展方向是坑道型地下水库的水资源开发工程,并提出研究过程中需要综合考虑回灌水源的水质、水量问题。此外,地下水库的环境效益评价及地下水库水质的污染防护也是重要的研究内容。

房地产建设项目雨水池适宜容积计算模型

随着城市化进程加快,城市内涝问题越来越突出。为解决因下垫面硬化引起的城市内涝问题,探求建设项目中雨水池容积计算方法。本文以北京市房地产建设项目为研究对象,从北京市1953—2012年降雨数据中选取降雨量最大、平均和最小年的日降雨数据,并拟定中水同时用于绿化和道路浇洒,应用日水量平衡模型方法,对比分析雨水池可利用率和中水补给率变化趋势,综合考虑经济效益因素,确定雨水池适宜容积。应用多项式拟合法,得到雨水池适宜容积简易计算模型。结果表明:随着雨水池容积增加,雨水池可利用率增大(0~1),中水补给率减小(1~0);当雨水池容积增至一定程度,其可利用率与中水补给率的变化趋于平缓;3种年况的雨水池可利用率的关系为最大>平均>最小,中水补给率的关系为最大<平均<最小,为互补趋势;效益费用比随着雨水池容积增大而减小。经验证,模型符合工程建设要求,且具普遍性,可投入应用。为提高模型可靠性,应用时宜将模型计算结果与规范最低建设标准进行校核比对。本研究为今后雨水池设计提供了一种新的快捷简便算法,丰富了设计理论。

青海省民和县中川乡美一和美二村地下水位上升原因分析

民和县中川乡美一和美二村因为地下水位上升引发了一系列不良反应。根据研究区的地质环境条件,分区计算地下水补给量与排泄量,定量讨论地下水上升原因,结合研究区水位地质条件和工程环境定性讨论地下水位上升原因。综合分析认为,区内地下水位上升主要原因是修建防渗堤坝使堤内地下水排泄不畅,导致地下水位上升。

利用非稳定流求解潜水水文地质参数的降深比值6点法

利用Boulton井流公式求解潜水非稳定流条件下的水文地质参数,是涉及4个未知数的超越方程,无法通过常规的解析法直接获解.传统的图解法不但受图表束缚,而且求解过程繁复、成果精度存在人为误差.文中采用优化拟合方法,在工程适用参数范围内,用较为简单的函数完成了由图表给出的井函数数值关系的替代,并利用降深比值关系,通过选取水位降深曲线上的6个点,经整理获得了仅含1个未知量的表达式,经简单试算即可完成参数求解,结果更接近工程实际,且计算过程简捷,不依赖图表,便于实际工程应用.

软土地区地铁基坑浅层承压水控制及降压影响预测研究

针对地铁基坑,提出一种浅层承压水抽灌一体化设计理念,用以控制因地下水位下降引起的被保护建(构)筑物的环境变形。结合宁波市轨道交通工程实例,分析地铁基坑浅层承压水抽灌一体化设计在实际工程应用中的优势,通过现场试验,证明抽灌一体化的设计方法可有效减小基坑降压引起的周边地面沉降。同时对该地铁站进行数值模拟计算,得到抽灌一体化设计下的环境水位变化。通过理论推导,结合工程实测数据和数值计算结果,提出适用于宁波地区的减压降水引起的地面沉降预测公式。

边界元法在地下水补给量计算中的应用

本文是边界元法在地下水补给量计算中应用的一次尝试,它成功地把边界元法应用到考虑有垂向补给或排泄的实际水文地质问题中。文中详细地推导了考虑有垂向补给或排泄均质各向同性承压含水层非稳定流边界元法的计算公式,结合长春市八里堡群井开采试验的水位观测资料计算了河流边界的补给量;分析了目前边界元法在水文地质计算中出现的时间积分和面积积分问题,在这两个问题的解决上做了些改进;结合简单水文地质模型给出了边界元法的精确度。

高海拔寒区隧道端墙式洞门冻胀力影响的模型试验研究

为研究洞口水分迁移与补给条件下高海拔寒区隧道端墙式洞门结构的冻胀力学特征,以某寒区隧道为依托,采用模型箱整体降温和洞口局部升温的方式进行室内相似模型试验,以模拟隧道洞口段实际冻融环境,并结合数值模拟探究了高海拔寒区隧道端墙式洞门的冻胀力变化规律。结果表明:试验与数值计算结果变化趋势基本吻合,墙身冻胀力最大值位于底部,靠近洞腔拱脚位置,墙身内部冻胀力次之,与围岩接触部分的墙身冻胀力比与大气接触时大,数值计算及模型试验得到的冻胀力最大值分别为1.71 MPa、1.29 MPa。本研究可为川藏线寒区隧道洞门墙身设计提供一定的参考价值。

稳定流抽水试验求解越流参数的新方法

利用稳定流抽水试验资料求解越流补给条件下水文地质参数为涉及2个未知数的超越方程,常规的解析法无法直接获解。而目前工程上采用的图解法及试算法或是误差大,或是依赖图表、计算繁复。本文采用优化拟合方法,在工程适应参数范围内,用较为简单的函数实现了对由图表给出的越流补给条件下虚宗量零阶第二类修正贝塞尔函数的替代,并利用水位降深比值关系,经整理获得了可直接完成参数求解的计算式,计算过程简捷,不依赖图表,便于实际工程应用。

滇中地区岩溶水文地质特征

在简述滇中地区自然地理、岩溶水文地质基本特征的基础上,结合野外现场调查及室内岩石、水化学样品的测试分析,查明了研究区可溶岩地层的岩性组合状况、地质构造特征、地表水体分布情况、地下水的补给、径流、排泄条件,基本查明了岩溶的类型为HCO_3-Ca·Mg、HCO_3-Mg·Ca、HCO_3-Ca型,可溶岩在不同地区呈不同发育规律,并分析了在地下水的补给来源主要为大气降水。