Temperature-dependent photoluminescence on organic inorganic metal halide perovskite CH3NH3Pb I3-xClx prepared on ZnO/FTO substrates using a two-step method

Temperature-dependent photoluminescence characteristics of organic-inorganic halide perovskite CH3NH3Pb I3-xClx films prepared using a two-step method on ZnO/FTO substrates were investigated. Surface morphology and absorption characteristics of the films were also studied. Scanning electron microscopy revealed large crystals and substrate coverage. The orthorhombic-to-tetragonal phase transition temperature was-140 K. The films＇ exciton binding energy was 77.6 ± 10.9 meV and the energy of optical phonons was 38.8 ± 2.5 meV. These results suggest that perovskite CH3NH3Pb I（3-x）Clx films have excellent optoelectronic characteristics which further suggests their potential usage in perovskitebased optoelectronic devices.

Applying the Dynamic Two-Step Method to Forecast Remaining Oil Distribution of Lower Series ,Xiaermen Oilfield

The distribution of remaining oil is often described qualitatively. The remaining oil distributed in the whole reservoir is calculated according to the characteristics of the space distribution of the saturation of remaining oil. Logging data are required to accomplish this. However, many such projects cannot be completed. Since the old study of remaining oil distribution could not be quantified efficiently, the ＂dynamic two-step method＂ is presented. Firstly, the water cut of every flow unit in one well at one time is calculated according to the comprehensive water cut of a single well at one time. Secondly, the remaining oil saturation of the flow unit of the well at one time is calculated based on the water cut of the flow unit at a given time. The results show that ＂dynamic two-step method＂ has characteristics of simplicity and convenience, and is especially suitable for the study of remaining oil distribution at high water-cut stage. The distribution of remaining oil presented banding and potato form, remaining oil was relatively concentrated in faultage neighborhood and imperfect well netting position, and the net thickness of the place was great. This proposal can provide an effective way to forecast remaining oil distribution and enhance oil recovery, especially applied at the high water-cut stage.

The convergence ball and error analysis of the two-step Secant method

Under the assumption that the nonlinear operator has Lipschitz continuous divided differences for the first order,we obtain an estimate of the radius of the convergence ball for the two-step secant method.Moreover,we also provide an error estimate that matches the convergence order of the two-step secant method.At last,we give an application of the proposed theorem.

Solution of Nonlinear Integro Differential Equations by Two-Step Adomian Decomposition Method (TSAM)

The Adomian decomposition method (ADM) can be used to solve a wide range of problems and usually gets the solution in a series form. In this paper, we propose two-step Adomian Decomposition Method (TSAM) for nonlinear integro-differential equations that will facilitate the calculations. In this modification, compared to the standard Adomian decomposition method, the size of calculations was reduced. This modification also avoids computing Adomian polynomials. Numerical results are given to show the efficiency and performance of this method.

要素投入对中国工业碳生产率的影响研究——来自Heckman两阶段的经验数据

在清洁低碳、安全高效的能源体系建设过程中,中国工业行业作为碳排放和能源消费重要主体,需积极提升碳生产效率,为能源体系建设做出贡献。基于理论分析及Heckman两阶段模型,选取2019年中国工业41个细分行业的数据,构建了工业碳生产率影响实证模型,研究劳动力投入、资本、技术创新、能源消费结构对工业碳生产率的影响方式及程度。经实证,劳动力投入和技术创新显著促进工业碳生产率提升,资本对工业碳生产率无促进作用,能源消费结构对工业碳生产率的影响程度尚不明确。针对以上结论,提出通过培训等方式促进劳动力素质提升,避免劳动粗放投入造成资源错配;推动冗余资本流向人才培养、技术研发;积极开展技术创新等建议。

牧户参与草原生态旅游经营意愿及影响因素研究——基于Heckman两阶段模型的分析

本研究基于内蒙古额尔古纳市9个村落及生产队500份调研数据,通过构建Heckman两阶段模型识别影响牧户参与草原生态旅游经营的意愿及预期收益影响因素。结果表明:牧户是否愿意参与草原生态旅游经营和预期收益水平是两个不同阶段的选择,主要受户主受教育程度、经济效益认知、传统经营习惯的影响;牧户是否愿意参与经营受户主受教育程度、经济效益认知、环境效益认知、与邻里亲朋经营经验的交流程度、亲朋好友是否参与草原生态旅游经营、政府激励政策的显著正向影响,受户主年龄、传统经营习惯遵循程度的显著负向影响;牧户参与经营的预期收益水平受户主受教育程度、牧户拥有牲畜数量、人均草场面积、经济效益认知、社会效益认知、传统经营习惯遵循程度、是否参与合作组织的正向显著影响。本研究提出了提升牧户参与草原生态旅游的经营意愿、促进草原生态旅游可持续发展的政策建议。

A Novel Method of Fabricating a Well-Faceted Large-Crystal Diamond Through MPCVD

A novel method was developed to deposit a large crystal diamond with good facets up to 1000 μm on a tungsten substrate using a microwave plasma enhanced chemical vapor deposition （MPCVD）. This method consists of two steps, namely single-crystal nucleation and growth. Prior to the fabrication of the well-faceted, large crystal diamond, an investigation was made into the nucleation and growth of the diamond which were affected by the O2 concentration and substrate temperature. Deposited diamond crystals were characterized by scanning electron microscopy and micro-Raman spectroscopy. The results showed that the conditions of single-crystal nucleation were appropriate when the ratio of H2/CH4/O2 was about 200/7.0/2.0, while the sub- strate temperature Ts of 1000℃ to 1050℃ was the appropriate range for single-crystal diamond growth. Under the optimum parameters, a well-faeeted large crystal diamond was obtained.

In-depth understanding of ionic liquid assisted perovskite film formation mechanism for two-step perovskite photovoltaics

Ionic liquids(ILs)have been widely applied in the one-step fabrication of perovskite with noticeable enhancement in the device performance.However,in-depth mechanism of ionic-liquid-assisted perovskite film formation is not well understood for also important two-step perovskite fabrication method,with better control of crystallization behavior.In this work,we introduced ionic liquid methylammonium formate(MAFa)into organic salt to produce perovskite film via a two-step method.Systematic investigations on the influence of MAFa on the perovskite thin film formation mechanism were performed.Ionic liquid is shown to assist lowering the perovskite formation enthalpy upon the density functional theory(DFT)calculation,leading to an accelerated crystallization process evidenced by in-situ UV-Vis absorption measurement.A gradient up-down distribution of ionic liquid has been confirmed by timeof-flight SIMS.Importantly,besides the surface passivation,we found the HCOO-can diffuse into the perovskite crystals to fill up the halide vacancies,resulting in significant reduction of trap states.Uniform perovskite films with significantly larger grains and less defect density were prepared with the help of MAFa IL,and the corresponding device efficiency over 23%was obtained by two-step process with remarkably improved stability.This research work provides an efficient strategy to tune the morphology and opto-electronic properties of perovskite materials via ionic-liquid-assisted two-step fabrication method,which is beneficial for upscaling and application of perovskite photovoltaics.

A class of twostep continuity Runge-Kutta methods for solving singular delay differential equations and its convergence

An idea of relaxing the effect of delay when computing the Runge-Kutta stages in the current step and a class of two-step continuity Runge-Kutta methods （TSCRK） is presented. Their construction, their order conditions and their convergence are studied. The two-step continuity Runge-Kutta methods possess good numerical stability properties and higher stage-order, and keep the explicit process of computing the Runge-Kutta stages. The numerical experiments show that the TSCRK methods are efficient.

A Remarkable Chord Iterative Method for Roots of Uncertain Multiplicity

In this note we at first briefly review iterative methods for effectively approaching a root of an unknown multiplicity. We describe a first order, then a second order estimate for the multiplicity index m of the approached root. Next we present a second order, two-step method for iteratively nearing a root of an unknown multiplicity. Subsequently, we introduce a novel chord, or a two- step method, not requiring beforehand knowledge of the multiplicity index m of the sought root, nor requiring higher order derivatives of the equilibrium function, which is quadratically convergent for any , and then reverts to superlinear.

Explicit solutions to some nonlinear physical models by a two-step ansatz

Explicit solutions are derived for some nonlinear physical model equations by using a delicate way of two-step ansatz method.

谁主沉浮:电视问政中的政府长期回应性及其动力研究

电视问政是具有独特属性的问政形式。为了探究电视问政中政府长期回应性及其动力,本研究以南宁市的《向人民承诺——电视问政》节目为例,从上层压力、下层压力和短期回应质量三个方面提出研究假设,利用2014—2018年的编码数据,使用离散时间事件史分析和Heckman两阶段模型等方法进行了实证分析。结果表明,电视问政中政府的长期回应质量明显低于短期回应质量;短期回应质量较低的议题和上级领导重视程度更高的议题更容易在电视问政中被长期关注,而被问责过的议题则更不容易被长期关注;上级领导重视程度越高和媒体关注度越高的议题,政府的长期回应质量越好,短期内公众舆论的负面程度和问责压力则对政府的长期回应质量没有显著影响;同时,政府内部的改革可以促进长期回应质量的提升,议题解决所需的单位时间协调成本则会随着时间的增加而降低。异质性分析的结果表明,与短期回应更注重问责官员、推动议题解决不同,电视问政的长期回应更倾向于避免对政府或官员不利的议题,更注重宣传政绩。

Synthesis of CA_(6)/AlON composite with enhanced slag resistance

Different amounts of AlON have been introduced in calcium hexaaluminate(CA_(6)) using two approaches, that is, one-step and twostep methods, to improve the slag resistance of CA_(6). A one-step method can directly sinter the mixtures combining Al_(2)O_(3), CaCO_(3), and Al in flowing nitrogen, in which AlON clusters are always formed because of the poor wettability of Al by Al_(2)O_(3), leading to the high porosity of CA_(6)/AlON composite. In a two-step method, CA_(6)and AlON are prepared separately and then mixed and sintered in flowing nitrogen. Compared with the sample prepared by the one-step method, CA_(6)and AlON in composite by the two-step method are more uniformly distributed,and the optimized amount of AlON added is 10wt%. The slag corrosion and penetration test shows that the CA_(6)/AlON composite using the two-step method exhibits superior slag corrosion protection. The promoted effect of AlON on slag penetration and corrosion resistance is also discussed.

Ultrahigh fill-factor all-inorganic CsPbBr_(3)perovskite solar cells processed from two-step solution method and solvent additive strategy

All-inorganic CsPbBr_(3)perovskite solar cells(PSCs)have attracted more attentions due to the excellent environmental stability,however,the wide bandgap and relatively poor crystallinity of CsPbBr_(3)have been the main obstacle to improve their power conversion efficiency(PCE).Herein,we proposed an efficient and simple strategy of precursor additive in the two-step aqueous-solution method,the resulted CsPbBr_(3)film has achieved more uniform grain size,almost pure perovskite phase,smoother surface,less defects,enhanced light absorption and longer carrier lifetime.This is due to the rapid evaporation of additive(IPA and CH_(3)OH)in the CsBr/H_(2)O precursor leads to a relatively higher local CsBr concentration on the surface of PbBr_(2),which can provide more nucleation sites and accelerate the crystallization of perovskite.Further,when utilizing the optimal additive of 5%(in volume)IPA,the HTM-free carbonbased CsPbBr_(3)PSCs obtained a PCE improvement from 9.09%to 10.29%,and an ultrahigh fill factor(FF)of 85.21%.What is more,by adding 0.1 mol/L PbCl_(2)into the PbBr_(2)solution in the first step,the open circuit voltage of device has increased from 1.36 V to 1.48 V,the champion PCE reached 10.37%(steady output PCE of 10.17%),and the non-encapsulated device could maintain 85%of its initial efficiency after 50 d in the air.This work provides a cost-effective approach to grow CsPbBr_(3)film and boosts the efficiency benchmark of the CsPbBr_(3)PSCs to more than 10%,it is desirable that the highly efficient and stable CsPbBr_(3)PSCs can be developed in future.

新发展阶段居民家庭碳排放核算及影响因素研究

新发展阶段下“双碳”目标的提出,使得人们对碳排放的关注度不断提高,而家庭作为人类社会的基本单元,其生活消费所产生的碳排放也是全社会碳排放的重要组成部分。论文基于兰州市600户家庭的调查数据,采用碳排放系数法核算样本居民家庭消费碳排放量,运用Heckman样本选择模型探究影响兰州市居民家庭碳排放行为的因素。研究发现,从居民家庭碳排放特征来看,家庭生活用电和私家车是主要碳排放源,且家庭碳排放在空间上存在较大差异。同时,与其他地区碳排放特征的对比结果表明,兰州市与西北地区碳排放特征基本保持一致,与中、东部地区之间存在一定差异。从居民家庭碳排放影响因素来看,家庭生活质量对碳排放有显著影响;此外,家庭碳排放影响因素存在地区异质性。

政府补贴、所有权性质与企业研发决策

本文将企业研发行为分为"是否研发"和"投入多少"两个阶段,就政府补贴对不同所有制企业研发决策的影响进行研究.理论方面,构建企业研发决策的两阶段模型,讨论了补贴对企业研发投资的作用机制.实证方面,以中国工业企业为对象,选择Heckman两步法和2SLS分别处理了样本选择性偏误及变量间的内生性问题,对来自国有、私营和外资企业的分类样本进行了检验,结果表明:在不同的所有权性质下,政府补贴对企业研发投资的作用存在一定差别,国有企业面对优惠政策的倾斜和需要担负的社会责任,从事技术创新活动的概率较高,但由于特殊的产权关系和预算软约束等原因,缺乏扩大研发投入的动力;对于治理机制完善的外资企业和处于市场竞争弱势地位的私营企业而言,政府补贴的研发激励效果更为明显.

社会资本能持续缓解农户信贷约束吗

本文采用Heckman两步法从微观层面分析了当前农户所拥有的不同的社会资本是否能够缓解信贷约束,提高信贷可得性的问题。研究结果表明,农户社会资本中以血缘为基础的强关系减少,而以朋友为主的弱关系增加,虽然能在一定程度上缓解农户的信贷约束,但这种以弱关系为主的社会资本是需要农户投入资金进行维持的,并不完全是穷人的社会资本。此外,家庭收入主要来源于工商经营的农户以及人情支出越多的农户更可能发生融资行为;户主是男性以及社会地位和收入水平越高的农户受到的信贷约束越小。

“是否研发”与“投入多少”:兼论企业研发投资的两阶段决策

研发投资是企业提高技术创新能力和市场竞争力的重要途径。与以往研究不同,针对中国企业研发参与度小和投入强度低的现实,本文从企业属性、行业特征和外部冲击三个角度探究了研发投资的决定因素及作用机制,进而利用Heckman两步法建立选择和投资方程,以2007年中国工业企业的微观数据和工业行业的中观数据为样本,就企业研发决策的两面性问题进行了实证检验,发现企业研发行为的选择性偏误确实存在,是否研发与投入多少会受到不同因素的制约,来自所有制分组的回归结果显示,企业性质是影响研发投资的重要因素,国有、外资和私营企业在研发决策机制方面存在巨大差异。

中国城市规模的工资溢价效应变迁研究

大城市的企业是否支付更高的工资,历来是极具争议的问题,产生分歧的一个重要原因可能在于城市规模对劳动者工资产生的外部性发生着动态变化。本文通过匹配《中国城市统计年鉴》和中国工业企业数据,同时借助中国人口普查分区县数据,系统估计了2000—2009年间城市规模带来的制造业企业劳动力工资溢价情况。研究发现:(1)中国的大城市存在显著的工资溢价效应,但工资溢价从2000年到2009年呈下降趋势,这一结论在控制了企业劳动者的个体特征、企业的选择效应以及城市规模与劳动力工资之间反向因果关系后仍然成立;(2)城市规模的工资溢价效应呈现从西到东逐渐递减的特征,再次说明中国城市化进程存在发展滞后和户籍制度掣肘等问题;(3)城市规模的工资溢价效应不断下降的两个渠道可能是:城市规模对本市、周边企业的溢出效应不断下降和大城市企业的工资增长速度逐渐变慢。本文的研究结果对理解中国城市化进程以及推动中国城市化发展有着重要的学术价值。

资源禀赋与企业能力会影响企业质量认证吗?——来自225家农业龙头企业的证据

基于对225家农业龙头企业的调查数据,利用Heckman(赫克曼)两步法,从资源能力观的视角研究资源禀赋和企业能力对农业企业是否实施质量认证以及多重认证频度决策的影响。研究表明:(1)规模、技术、品牌、股权集中度、盈利能力和偿债能力等内在特征是影响企业是否实施质量认证的显著因素;(2)规模越大、技术水平和决策者素质越高、盈利能力、偿债能力和营运能力越强的企业越倾向于实施多重质量认证;(3)经营模式和经营战略对企业多重质量认证行为有显著影响,且不同经营模式的边际影响存在显著差异。总之,资源禀赋和企业能力的异质性较好地解释了在面临同样的外部环境时,不同企业之间质量认证行为的差异。