基于Two-step Cluste的出行选择行为研究

为研究广佛城际交通出行者选择公共交通出行的意愿,根据2016年广佛城际交通发展调研数据,基于两步聚类方法,将总出行群体聚为两类,并运用熵权法选取9类指标分别对聚类前后的群体进行满意度评价,结果显示聚类后群体的满意度较低,表明聚类后的群体的出行需求更为集中。基于此,分别对聚类前后群体构建是否选择公共交通出行方式选择BNL (binart-nomial logit)模型,预测管理策略的效果,进一步验证将群体进行聚类的必要性,并为城际出行乘客提供更精准的服务。

Effects of the two-step ageing treatment on the microstructure and properties of 7B04 alloy pre-stretched thick plates

The effects of the two-step ageing parameters （temperature and time） on the mechanical properties and electrical conductivity of 7B04 （A1-Zn-Mg-Cu） pre-stretched thick plates were studied. The results reveal that the initial T1 ageing contributes a major increase of the tensile strength, and the 0.2% proof stress value reaches 482 MPa after ageing for 7 h at 115℃. Behavioral differences in the tensile properties of the alloy after the two-step ageing treatment were less with the first-step ageing at 115~C for different time periods （7, 14, and 21 h）. The effects of the second ageing parameters on the properties and microstructure of the 7B04 alloy were remarkable. TEM analysis of the samples aged at Temper I （7 h at 115℃ ＋ 12 h at 160℃） and Temper II （7 h at 115℃ ＋ 16 h at 165℃） indicates that two kinds of phases, i.e. 11＇ and 11 phases, precipitate from the matrix and efficiently improve the tensile strength of the alloy, and the grain boundary precipitates are coarse and discrete. There are obvious precipitate free zones （PFZs） along the grain boundary in the microstructure of the alloy after the two-step ageing treatment.

A two-step quantum secure direct communication protocol with hyperentanglement

We propose a two-step quantum secure direct communication （QSDC） protocol with hyperentanglement in both the spatial-mode and the polarization degrees of freedom of photon pairs which can in principle be produced with a beta barium borate crystal. The secret message can be encoded on the photon pairs with unitary operations in these two degrees of freedom independently. This QSDC protocol has a higher capacity than the original two-step QSDC protocol as each photon pair can carry 4 bits of information. Compared with the QSDC protocol based on hyperdense coding, this QSDC protocol has the immunity to Trojan horse attack strategies with the process for determining the number of the photons in each quantum signal as it is a one-way quantum communication protocol.

Design System of the Two-step Gear Reducer on Case-based Reasoning

The design of the two-step gear reducer is a tedious and time-consuming process. For the purpose of improving the efficiency and intelligence of design process, case-based reasoning（CBR） technology was applied to the design of the two-step gear reducer. Firstly, the current design method for the two-step gear reducer was analyzed and the principle of CBR was described. Secondly, according to the characteristics of the reducer, three key technologies of CBR were studied and the corresponding methods were provided, which are as follows： （a） an object-oriented knowledge representation method, （b） a retrieval method combining the nearest neighbor with the induction indexing, and （c） a case adaptation algorithm combining the revision based on rule with artificial revision. Also, for the purpose of improving the credibility of case retrieval, a new method for determining the weights of characteristics and a similarity formula were presented, which is a combinatorial weighting method with the analytic hierarchy process（AHP） and roughness set theory. Lastly, according to the above analytic results, a design system of the two-step gear reducer on CBR was developed by VC＋＋, UG and Access 2003. A new method for the design of the two-step gear reducer is provided in this study. If the foregoing developed system is applied to design the two-step gear reducer, design efficiency is improved, which enables the designer to release from the tedious design process of the gear reducer so as to put more efforts on innovative design. The study result fully reflects the feasibility and validity of CBR technology in the process of the design of the mechanical parts.

Hydrogen and syngas production from two-step steam reforming of methane using CeO_2 as oxygen carrier

CeO2 oxygen carrier was prepared by precipitation method and tested by two-step steam reforming of methane （SRM）. Two-step SRM for hydrogen and syngas generation is investigated in a fixed-bed reactor. Methane is directly converted to syngas at a H2/CO ratio close to 2 ： 1 at a high temperature （above 750 °C） by the lattice oxygen of CeO2; methane cracking is found when the reduction degree of CeO2 was above 5.0% at 850 °C in methane isothermal reaction. CeO2？δ obtained from methane isothermal reaction can split water to generate CO-free hydrogen and renew its lattice oxygen at 700 °C; simultaneously, deposited carbon is selectively oxidized to CO2 by steam following the reaction （C＋2H2O→CO2＋2H2）. Slight deactivation in terms of amounts of desired products （syngas and hydrogen） is observed in ten repetitive two-step SRM process due to the carbon deposition on CeO2 surface as well as sintering of CeO2.

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.

Alumina nanostructures prepared by two-step anodization process

Alumina nanostructures were obtained by two-step anodization process.The porous anodic aluminum oxide(AAO)membranes were anodized in oxalic acid,which was subsequently treated with chemical etching process with 1.0 mol/L sodiumhydroxide solution,or mixed solution of phosphoric acid(6.0%)and chromic acid(1.8%),respectively.Field emission scanningelectron microscopy(FE-SEM)and transmission electron microscopy(TEM)were employed to character the morphology andstructure of the obtained alumina nanostructure.It is found that alumina nanowires are generated in the acidic chemical etchingsolution,while nanotube structures are formed in the alkaline solution.The influence of acid and alkaline solution on aluminamorphologies in the chemical etching process was discussed.

Multi-agent controlled teleportation of multi-qubit quantum information via two-step protocol

Utilizing both the general quantum teleportation and the two-step protocol, a new method is presented by which multi-qubit quantum information can be teleported in a much easier way from a sender Alice to a receiver Bob via the control of many agents in a network than by Yang et al＇s method. In this method, only all the agents collaborate with Bob can the unknown states in Alice＇s qubits be fully reconstructed in Bob＇s qubits. Comparisons between the method and Yang et al＇s method are made. Results show that, in this method, the preparation difficulty of initial states and the identification difficulty of entangled states are considerably reduced, new method is more feasible in technique, and Hadamard operations are not needed at all.

A two-step transient liquid phase diffusion bonding process of T91 steels

In this study, a two-step heating process is introduced for transient liquid phase （ TLP） diffusion bonding fo r sound joints with T91 heat resistant steels. At first, a short-time higher temperature heating step is addressed to melt the interlayer, followed by the second step to complete isothermal solidification at a low temperature. The most critical feature of our new method is producing a non-planar interface at the T9／ heat resistant steels joint. We propose a transitional liquid phase bonding of T91 heat resistant steels by this approach. Since joint microstructures have been studied, we tested the tensile strength to assess joint mechanical property. The result indicates that the solidified bond may contain a primary solid-solution, similar composition to the parent metal and free from precipitates. Joint tensile strength of the joint is not lower than parent materials. Joint bend＇s strengths are enhanced due to the higher metal-to-metal junction producing a non-planar bond lines. Nevertheless, the traditional transient liquid phase diffusion bonding produces planar ones. Bonding parameters of new process are 1 260 °C for 0. 5 min and 1 230 °C fo r 4 min.

Two-step pyrolysis of ZIF-8 functionalized with ammonium ferric citrate for efficient oxygen reduction reaction

Zeolitic imidazolate frameworks（ZIFs） are widely employed in catalyst synthesis as parental materials for electrochemical energy storage and conversion. Herein, we have demonstrated a facile synthesis of highly efficient catalyst for oxygen reduction reaction in both alkaline and acidic medium, which is derived from ZIF-8 functionalized with ammonium ferric citrate via two-step pyrolysis in Ar and NHatmosphere.The results reveal that the catalytic activity improvement after NH3 pyrolysis benefits from mesoporedominated morphology and high utilization of Fe-containing active sites. The optimum catalyst shows excellent performance in zinc-air battery and polymer electrolyte membrane fuel cell tests.

Synthesis of polyurea from 1,6-hexanediamine with CO_2 through a two-step polymerization

Activation and transformation of CO_2 is one of the important issues in the field of green and sustainable chemistry. Herein, CO_2 as a carbonoxygen resource was converted to CO_2-polyurea with 1,6-hexanediamine through a two-step polymerization. The reaction parameters such as temperature, pressure and reaction time were examined; and several kinds of catalysts were screened in the absence and presence of NMP solvent. The formed oligomer and the final polyurea were characterized by FT-IR, VT-DRIFTS, NMR, XRD, AFM and their thermal properties were examined by TGA and DSC. It was confirmed that the final polyurea has a high thermal stability; the melting temperature is 269℃ and the decomposition temperature is above 300℃. It is a brittle polymer with a tensile strength of 18.35 MPa at break length of 1.64%. The polyurea has a stronger solvent resistance due to the ordered hydrogen bond in structure. The average molecular weight should be enhanced in the postpolymerization as the appearance, hydrogen bond intensity, crystallinity, melting point and the thermal stability changed largely compared to the oligomer. The present work provides a new kind of polyurea, it is expected to have a wide application in the field of polymer materials.

Two-Step Synthesis of Sulfur/Graphene Composite Cathode for Rechargeable Lithium Sulfur Batteries

Sulfur/graphene composites with different sulfur contents were prepared by two-step synthesis, where graphene was regarded as a carrier of sulfur active substance. The surface structure and crystal form of the composites obtained were characterized and compared by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM）. It was found that sulfur was partially coated by graphene. The graphene folds provided more nano-pores and electron transport channels for sulfur. From TGA results, the sulfur contents of the sulfur/graphene compositcs measured were about 42.32 wt%, 54.94 wt%, and 65.23 wt%. Electrochemical tests demonstrated that sulfur/graphene composite （x=54.94 wt%） cathode exhibited better capacity retention （40.13%） compared with the pure cathode （20.46%）, where an initial discharge capacity was up to 1 500 mAh.g-t and it remained about 600 mAh·g-1 after 30 cycles. Furthermore, the electrochemical reaction mechanism and the state of reaction interface for Li/S battery were analyzed by cyclic voltammogram and AC-impedance spectra. The results indicated that the sulfur/graphene composite with a sulfur content of 54.94 wt%, based on a two-step synthesis, contributed to improving electrochemical properties of lithium/sulfur battery

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.

Multiple-image encryption by two-step phase-shifting interferometry and spatial multiplexing of smooth compressed signal

A multiple-image encryption method based on two-step phase-shifting interferometry （PSI） and spatial multiplexing of a smooth compressed signal is proposed. In the encoding and encryption process, with the help of four index matrices to store original pixel positions, all the pixels of four secret images are firstly reordered in an ascending order; then, the four reordered images are transformed by five-order Haar wavelet transform and performed sparseness operation. After Arnold transform and pixels sampling operation, one combined image can be grouped with the aid of compressive sensing （CS） and spatial multiplexing techniques. Finally, putting the combined image at the input plane of the PSI encryption scheme, only two interferograms ciphertexts can be obtained. During the decoding and decryption, utilizing all the secret key groups and index matrices keys, all the original secret images can be successfully decrypted by a wave-front retrieval algorithm of two-step PSI, spatial de-multiplexing, inverse Arnold transform, inverse discrete wavelet transform, and pixels reordering operation.

A CLASS OF TWO-STEP TVD MACCORMACK TYPE NUMERICAL SCHEME FOR MHD EQUATIONS

In this paper, a new numerical scheme of Total Variation Diminishing (TVD) MacCormack type for MagnetoHydroDynamic (MHD) equations is proposed by taking into account of the characteristics such as convergence, stability, resolution. This new scheme is established by solving the MHD equations with a TVD modified MacCormack scheme for the purpose of developing a scheme of quick convergence as well as of TVD property. To show the validation, simplicity and practicability of the scheme for modelling MHD problems, a self-similar Cauchy problem with the discontinuous initial data consisting of constant states, and the collision of two fast MHD shocks, and two-dimensional Orszag and Tang's MHD vortex problem are discussed with the numerical results conforming to the existing results obtained by the Roe type TVD, the high-order Godunov scheme,and Weighted Essentially Non-Oscillatory (WENO) scheme. The numerical tests show that this two-step TVD MacCormack numerical scheme for MHD system is of robust operation in the presence of very strong waves, thin shock fronts, thin contact and slip surface discontinuities.

A New 3-D Sr(Ⅱ)Complex:Two-step Solvothermal Synthesis,Structure and Luminescent Properties

The title complex [HSr3（pda）3（H2O）3Cl]n（1, H2pda = pyridine-2,6-dicarboxylic acid） has been prepared under two-step solvothermal conditions. It has been characterized by X-ray single-crystal diffraction, IR, TGA-DSC and elemental analysis. The crystal belongs to the trigonal system, space group R-3 with a = 14.484（2）, b = 14.484（2）, c = 21.970（4） A, γ = 120 o, V = 3991.4（11） A3, C（21）H（16）ClN3O（1）5Sr3, Mr = 848.68, Z = 6, Dc = 2.118 g/cm^3, μ = 6.175 mm-1, F（000） = 2484, the final R = 0.0457 and w R = 0.1139. This complex possesses a 3-D structure constructed from [HSr3（pda）3（H2O）3Cl]2 units and connected by coordinated carboxylate groups of pda2-ligands. The topology symbol of this network is（4^（12）6~3）. Luminescent property of the title complex has been investigated at room temperature.

Influence of two-step cooling method on magnetic properties of Fe_(82)Mo_7B_(10)Cu_1 nanocrystalline alloy

Soft magnetic properties of Fe82Mo7B10Cu1 nanocrystalline alloy were studied as a function of cooling condition. The results show that higher permeability and relaxation frequency can be obtained by the two-step cooling method, and the pinning field of the sample obtained by this method is smaller than that of the furnace-cooled and water-quenched samples. This phenomenon was interpreted in terms of internal stress and the magnetic ordering of the residual amorphous phase. The two-step cooling treatment is an effective way to improve the soft magnetic properties of Fe82Mo7B10Cu1 nanocrystalline alloy.

TWO-STEP MECHANISM IN HETEROGENEOUS CATALYSIS AND DYNAMIC ANALYSIS

Recent development of the dynamic analysis technique has made it possible to measure separately kinetic parameters of a catalytic reaction as well as to study the effect of catalyst preparation parameters. But its application is still limned to first-order reaction. This work is aimed to demonstrate in some detail that,by comparison of the reaction rate expressions with the two-step mechanism used in catalytic kinetics and dynamic analysis, these methods can be extended to non-first-order reaction, and the kinetic parameters measured by dynamic techniques are interpreted for different reaction mechanisms.

Two-step growth of VSe_2 films and their photoelectric properties

We put forward a two-step route to synthesize vanadium diselenide(VSe_2), a typical transition metal dichalcogenide(TMD). To obtain the VSe_2 film, we first prepare a vanadium film by electron beam evaporation and we then perform selenization in a vacuum chamber. This method has the advantages of low temperature, is less time-consuming, has a large area, and has a stable performance. At 400?C selenization temperature, we successfully prepare VSe_2 films on both glass and Mo substrates. The prepared VSe_2 has the characteristic of preferential growth along the c-axis, with low transmittance.It is found that the contact between Al and VSe_2/Mo is ohmic contact. Compared to Mo substrate, lower square resistance and higher carrier concentration of the VSe_2/Mo sample reveal that the VSe_2 film may be a potential material for thin film solar cells or other semiconductor devices. The new synthetic strategy that is developed here paves a sustainable way to the application of VSe_2 in photovoltaic devices.

Novel two-step CdS deposition strategy to improve the performance of Cu2ZnSn(S,Se)4 solar cell

Kesterite Cu2ZnSn(S,Se)4(CZTSSe)solar cells have drawn worldwide attention for their promising photovoltaics performance and earth-abundant element composition,yet the record efficiency of this type of device is still far lower than its theoretical conversion efficiency.Undesirable band alignment and severe non-radiative recombination at CZTSSe/CdS heterojunction interfaces are the major causes limiting the current/voltage output and overall device performance.Herein,we propose a novel two-step CdS deposition strategy to improve the quality of CZTSSe/CdS heterojunction interface and thereby improve the performance of CZTSSe solar cell.The two-step strategy includes firstly pre-deposits CdS thin layer on CZTSSe absorber layer by chemical bath deposition(CBD),followed with a mild heat treatment to facilitate element inter-diffusion,and secondly deposits an appropriate thickness of CdS layer by CBD to cover the whole surface of pre-deposited CdS and CZTSSe layers.The solar energy conversion efficiency of CZTSSe solar cells with two-step deposited CdS layer approaches to 8.76%(with an active area of about 0.19 cm2),which shows an encouraging improvement of over 87.98%or 30.16%compared to the devices with traditional CBD-deposited CdS layer without and with the mild annealing process,respectively.The performance enhancement by the two-step CdS deposition is attributed to the formation of more favorable band alignment at CZTSSe/CdS interface as well as the effective decrease in interfacial recombination paths on the basis of material and device characterizations.The two-step CdS deposition strategy is simple but effective,and should have large room to improve the quality of CZTSSe/CdS heterojunction interface and further lift up the conversion efficiency of CZTSSe solar cells.