Temperature-dependent photoluminescence on organic inorganic metal halide perovskite CH_3NH_3Pb I_(3-)Cl_ 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.

A new two-step variational model for multiplicative noise removal with applications to texture images

Multiplicative noise removal problems have attracted much attention in recent years.Unlike additive noise,multiplicative noise destroys almost all information of the original image,especially for texture images.Motivated by the TV-Stokes model,we propose a new two-step variational model to denoise the texture images corrupted by multiplicative noise with a good geometry explanation in this paper.In the first step,we convert the multiplicative denoising problem into an additive one by the logarithm transform and propagate the isophote directions in the tangential field smoothing.Once the isophote directions are constructed,an image is restored to fit the constructed directions in the second step.The existence and uniqueness of the solution to the variational problems are proved.In these two steps,we use the gradient descent method and construct finite difference schemes to solve the problems.Especially,the augmented Lagrangian method and the fast Fourier transform are adopted to accelerate the calculation.Experimental results show that the proposed model can remove the multiplicative noise efficiently and protect the texture well.

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.

Arrhenius relationship and two-step scheme in AF hyperdynamics simulation of diffusion of Mg/Zn interface

The accelerating factor （AF） method is a simple and appropriate way to investigate the atomic long-time deep diffusion at solid-solid interface. In the framework of AF hyperdynamics （HD） simulation, the relationship between the diffusion coefficient along the direction of z-axis which is normal to the Mg/Zn interface and temperature was investigated, and the AF＇s impact on the diffusion constant （D0） and activation energy （Q^＊） was studied. Then, two steps were taken to simulate the atomic diffusion process and the formation of new phases： one for acceleration and the other for equilibration. The results show that： the Arrhenius equation works well for the description of Dz with different accelerating factors; the AF has no effect on the diffusion constant Do in the case of no phase transition; and the relationship between Q＊ and Q conforms to Q^＊=Q/A. Then, the new Arrhenius equation for AFHD is successfully constructed as Dz=Doexp[-Q/（ART）]. Meanwhile, the authentic equilibrium conformations at any dynamic moment can only be reproduced by the equilibration simulation of the HD-simulated configurations. Key words： accelerating factor method; Arrhenius equation; two-steps scheme; Mg/Zn interface; hyperdynamic simulation

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.

The Research on Biogas Power Generation by Two Step Method

The paper aims to demonstrate the system of SANYI biogas power generation by two-step method which can produce methane and generate electricity effectively and stably.So it can be stable synchronization meshwork energy source establishment and provide references to develop an effective and stable project of producing methane and generating electricity.

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.

General Convergence Analysis for Three-step Projection Methods and Applications to Variational Problems

First a general model for a three-step projection method is introduced, and second it has been applied to the approximation solvability of a system of nonlinear variational inequality problems in a Hilbert space setting. Let H be a real Hilbert space and K be a nonempty closed convex subset of H. For arbitrarily chosen initial points x0, y0, z0 ∈ K, compute sequences xn, yn, zn such thatT ： K→ H is a nonlinear mapping onto K. At last three-step models are applied to some variational inequality problems.

我国产前诊断机构空间可及性与公平性

目的评价我国产前诊断机构的空间可及性与公平性,以期为优化此类机构的空间规划布局提供参考。方法用两步移动搜索法和空间基尼系数对我国产前诊断机构的空间可及性和公平性进行评价。结果我国中东部地区和各省(自治区、直辖市)中心城市产前诊断服务的空间可及性与公平性均优于西部地区和偏远地区。结论建议适当增加西部地区和偏远地区的产前诊断机构与卫生技术人员数量,以优化我国产前诊断机构的规划布局。

Analysis of steel-concrete composite structure with overlap slab of Xingguang bridge

Finite element modeling methods of steel-concrete composite structure with overlap slab were investigated. A two-step finite element method was presented. It was applied to analyze an extra long span composite bridge. The conversion of structure system and the mechanical behavior of the bridge were analyzed with two different construction methods. The stresses of steel beams, precast slabs and in-situ-place concrete under the total load were compared. The results show that steel-concrete composite structure with overlap slab has many advantages, the construction method that the top in-situ concrete and the concrete in construction joints are cast respectively is rather reasonable than the one that the top in-situ concrete and the concrete in construction joints are cast at the same time, and the two-step finite element method is affective to such large-scale structures.

Suitability Evaluation of Rural Settlements Based on Accessibility of Production and Living： A Case Study of Tingzu Town in Hubei Prov- ince of China

Rural settlements are the main carriers of agriculture, rural areas and farmers; thus, optimizing the production and living space of rural settlements is highly significant to rural development. Taking the effective allocation of resources as the starting point, a suitability evaluation system of rural settlements, based on accessibility of production and living, was proposed in this study to provide scientific basis for the optimization of production and living space. The accessibility of production and living was measured by an im- proved two-step floating catchment area method, which considered proximity and availability based on the inclination of rural residents. The suitability evaluation system consisted of traditional suitability evaluation and newly proposed limiting factor identification based on the loss score proportion of suitability. Tingzu Town of Hubei Province, China, was chosen as the case study area. Based on the re- suits of the suitability evaluation system, corresponding suggestions on rural land consolidation, industry division, as well as the layout of health care and education facilities were proposed to optimize the production and living space of rural settlements in Tingzu Town. It is found that the suitability evaluation based on accessibility of production and living is more scientific and accurate than the traditional ones which significantly overestimate production and living convenience. Moreover, the limiting factor identification can help us put forward suggestions according to local conditions and bring about the highly targeted optimization of production and living space of rural settlements.

Deep postbuckling and nonlinear bending behaviors of nanobeams with nonlocal and strain gradient effects

In this paper, multi-scale modeling for nanobeams with large deflection is conducted in the framework of the nonlocal strain gradient theory and the Euler-Bernoulli beam theory with exact bending curvature. The proposed size-dependent nonlinear beam model incorporates structure-foundation interaction along with two small scale parameters which describe the stiffness-softening and stiffness-hardening size effects of nanomaterials, respectively. By applying Hamilton's principle, the motion equation and the associated boundary condition are derived. A two-step perturbation method is introduced to handle the deep postbuckling and nonlinear bending problems of nanobeams analytically. Afterwards, the influence of geometrical, material, and elastic foundation parameters on the nonlinear mechanical behaviors of nanobeams is discussed. Numerical results show that the stability and precision of the perturbation solutions can be guaranteed, and the two types of size effects become increasingly important as the slenderness ratio increases. Moreover, the in-plane conditions and the high-order nonlinear terms appearing in the bending curvature expression play an important role in the nonlinear behaviors of nanobeams as the maximum deflection increases.

Robust,fluorine-free and superhydrophobic composite melamine sponge modified with dual silanized SiO_(2) microspheres for oil-water separation

Massive oily wastewater discharged from industrial production and human daily life have been an urgent environmental and ecological challenge.Superhydrophobic materials have attracted tremendous attention due to their unique properties and potential applications in the treatment of wastewater.In this study,a novel superhydrophobic/superoleophilic composite melamine sponge modified with dual silanized SiO_(2) microspheres was fabricated simply by a two-step sol-gel method using vinyltriethoxysilane and hexadecyltrimethoxysilane as functional agent,which exhibited a water contact angle of 153.2°and a water sliding contact angle of 4.8°.Furthermore,the composite sponge showed the excellent oil adsorption performance and the compressive elasticity reaching up to 130 g·g^(-1) of dichloromethane and 33.1 kPa of compressive stress.It was worth noting that the composite sponge presented the excellent separation efficiency(up to 99.5%)in the processes of continuous oil/water separation.The robust superhydrophobic composite melamine sponge provided the possibility with the practical application for oil-water separation.

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.

Preparation and photocatalytic activity of Gd-doped TiO_2 nanofibre

In order to realize the photocatalysis of TiO2 in the sunlight and directly apply it to waste water treatment, the Gd-doped TiO2 nanofibre was synthesized using two-step synthesis method as follows: Firstly, potassium carbonate, titanium dioxide and proper gadolinium oxide （dopant） were calcined in the muffle at high temperature and the doped gadolinium K2Ti4O9 fibres were obtained; secondly, the fibre was heated using glycerol as solvent until Gd-doped TiO2 nanofibres were obtained. The synthesized samples were characterized using scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The results show that Gd-doped TiO2 nanofibre heat-treated by glycerol solvent can inhibit the agglomeration, so the grain diameter of the fibre is smaller than that without heat-treated with glycerol. Meanwhile, the diameter of the fibre decreases with the increase of the heating temperature and time. 97% 98% of Gd-doped TiO2 nanofibre is anatase. The photocatalysis results showed that the photocatalysis activity of Gd-doped TiO2 nanofibre is just a little lower than that of TiO2 powder.