The effects of the acid leaching and alkali fusion on the leaching efficiency of Y,Eu,Ce,and Tb from the waste rare earth fluorescent powders were investigated in this paper.The results show that hydrochloric acid is ...The effects of the acid leaching and alkali fusion on the leaching efficiency of Y,Eu,Ce,and Tb from the waste rare earth fluorescent powders were investigated in this paper.The results show that hydrochloric acid is better than sulfuric acid in the first acid leaching,and NaOH is better than Na2CO3in the alkali fusion.In the first acid leaching,the Wloss is 20.94%when the waste rare earth fluorescent powders are acid leached in H?concentration 3 mol L-1and S/L ratio 1:3 for 4 h due to red powders dissolved.The better results of the alkali fusion can be got at 800℃ for 2 h when the NaOH is used.The blue powders and the green powders can be dissolved into NaAlO2and oxides such as rare earth oxide(REO).The REO can be dissolved in H?concentration 5 mol L-1,S/L1:10 for 3 h in the second acid leaching.The leaching rates of the Y,Eu,Ce,and Tb are 99.06%,97.38%,98.22%,and 98.15%,respectively.The leaching rate of the total rare earth is 98.60%.展开更多
In order to get atomic smooth rigid disk substrate surface, ultra-fined alumina slurry and nanometer silica slurry are prepared, and two steps chemical-mechanical polishing （CMP） of rigid disk substrate in the two s...In order to get atomic smooth rigid disk substrate surface, ultra-fined alumina slurry and nanometer silica slurry are prepared, and two steps chemical-mechanical polishing （CMP） of rigid disk substrate in the two slurries are studied. The results show that, during the first step CMP in the alumina slurry, a high material removal rate is reached, and the average roughness （Ra） and the average waviness （Wa） of the polished surfaces can be decreased from previous 1.4 nm and 1.6 nm to about 0.6 nm and 0.7 nm, respectively. By using the nanometer silica slurry and optimized polishing process parameters in the second step CMP, the Ra and the Wa of the polished surfaces can be further reduced to 0.038 nm and 0.06 am, respectively. Atom force microscopy （AFM） analysis shows that the final polished surfaces are ultra-smooth without micro-defects.展开更多
Cordierite materials were mineral materials via the two synthesized using natural step calcination process. The phase composition and microstructure of the specimens were analysized by X-ray diffraction （XRD） and sc...Cordierite materials were mineral materials via the two synthesized using natural step calcination process. The phase composition and microstructure of the specimens were analysized by X-ray diffraction （XRD） and scanning electron microscopy （SEM） , respectively. The sintering properties of cordierite materials were also characterized. The effect of two step calcination process on the reaction sintering properties of cordierite materials was investigated. The results show that the two step calcination process can significantly increase the reaction sintering properties of the cordierite materials. When the weight ratio of the presynthesized cordierite to the premixed raw mineral materials is 2 ：1, the cordierite materials obtained by the two step calcination process have the higher bulk density and the lower apparent porosity （2.18 g · cm^- 3 and 13.85% , respectively）. Furthermore, the addition of presynthesized cordierite clinker in the process of synthesizing cordierite materials can promote the growth of cordierite crystalline size.展开更多
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 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.展开更多
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 wi...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.展开更多
Two-step steam reforming of methane (SRM) is a novel chemical looping process towards the production of pure hydrogen and syngas (synthesis gas), consisting of a syngas production step and a water-splitting step. Rene...Two-step steam reforming of methane (SRM) is a novel chemical looping process towards the production of pure hydrogen and syngas (synthesis gas), consisting of a syngas production step and a water-splitting step. Renewable energy can be used to drive this process for hydrogen production, especially solar energy. CeO2-Fe2O3 complex oxide oxygen carrier was prepared by the impregnation method and characterized by means of X-ray diffractometer (XRD), Raman spectroscopy (Raman) and hydrogen programmed reduction (H2-TPR). CH4 temperature programmed and isothermal reactions were adopted to test syngas production reactivity, and water splitting reaction was employed to investigate water-splitting activity. Moreover, two-step SRM performance was evaluated by a successive redox cycle. The results showed that CO-uncontaminated H2 and highly selective syngas (with H2/CO ratio close to 2) could be respectively obtained from two steps, and CeFeO3 formation was found in the first redox cycle and proved to be enhanced by the redox treatment. After 10 successive cycles, obvious CeFeO3 phase was detected, which may be responsible for favorable successive redox cycle performances.展开更多
Two steps foaming (TSF) technique was proposed to prepare shaped Al alloy foam. Based on the thermal decomposition kinetics equation of titanium hydride, the relationship be-tween two steps thermal decomposition kinet...Two steps foaming (TSF) technique was proposed to prepare shaped Al alloy foam. Based on the thermal decomposition kinetics equation of titanium hydride, the relationship be-tween two steps thermal decomposition kinetics of titanium hydride and two steps foaming Al alloy melt was studied. Two steps thermal decomposition curve of titanium hydride under in-creasing and constant temperature was calculated respectively. The hydrogen mass needed in the second foaming step was also calculated. Results showed that the hydrogen mass of the second thermal decomposition of titanium hydride is enough for the second foaming step in the condition of as-received Al melt foaming. Experimental and theoretical results indicate that two steps foaming technique can be used to prepare Al alloy foam with high porosity, shaped com-ponents and sandwich with Al alloy foam core.展开更多
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 th...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.展开更多
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 di...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.展开更多
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 ab...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.展开更多
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 mo...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.展开更多
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 B...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.展开更多
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 ...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.展开更多
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 effi...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.展开更多
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 throu...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.展开更多
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 composi...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展开更多
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 re...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.展开更多
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 f...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.展开更多
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...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.展开更多
基金supported by the National Hi-Tech R&D Program of China (No. 2012AA063202)National Key Project of Scientific and Technical Support Program of China (Nos. 2011BAE13B07, 2012BAC02B01, and 2011BAC10B02)National Natural Science Foundation of China (Nos. 51174247 and 50972013)
文摘The effects of the acid leaching and alkali fusion on the leaching efficiency of Y,Eu,Ce,and Tb from the waste rare earth fluorescent powders were investigated in this paper.The results show that hydrochloric acid is better than sulfuric acid in the first acid leaching,and NaOH is better than Na2CO3in the alkali fusion.In the first acid leaching,the Wloss is 20.94%when the waste rare earth fluorescent powders are acid leached in H?concentration 3 mol L-1and S/L ratio 1:3 for 4 h due to red powders dissolved.The better results of the alkali fusion can be got at 800℃ for 2 h when the NaOH is used.The blue powders and the green powders can be dissolved into NaAlO2and oxides such as rare earth oxide(REO).The REO can be dissolved in H?concentration 5 mol L-1,S/L1:10 for 3 h in the second acid leaching.The leaching rates of the Y,Eu,Ce,and Tb are 99.06%,97.38%,98.22%,and 98.15%,respectively.The leaching rate of the total rare earth is 98.60%.
基金This project is supported by National Basic Research Program of China (973 Program, N0.2003CB716201)National Natural Science Foundation of China (No.50575131)Science Foundation of Shanghai Municipal Commission of Science and Technology, China(No.0452nm013).
文摘In order to get atomic smooth rigid disk substrate surface, ultra-fined alumina slurry and nanometer silica slurry are prepared, and two steps chemical-mechanical polishing （CMP） of rigid disk substrate in the two slurries are studied. The results show that, during the first step CMP in the alumina slurry, a high material removal rate is reached, and the average roughness （Ra） and the average waviness （Wa） of the polished surfaces can be decreased from previous 1.4 nm and 1.6 nm to about 0.6 nm and 0.7 nm, respectively. By using the nanometer silica slurry and optimized polishing process parameters in the second step CMP, the Ra and the Wa of the polished surfaces can be further reduced to 0.038 nm and 0.06 am, respectively. Atom force microscopy （AFM） analysis shows that the final polished surfaces are ultra-smooth without micro-defects.
文摘Cordierite materials were mineral materials via the two synthesized using natural step calcination process. The phase composition and microstructure of the specimens were analysized by X-ray diffraction （XRD） and scanning electron microscopy （SEM） , respectively. The sintering properties of cordierite materials were also characterized. The effect of two step calcination process on the reaction sintering properties of cordierite materials was investigated. The results show that the two step calcination process can significantly increase the reaction sintering properties of the cordierite materials. When the weight ratio of the presynthesized cordierite to the premixed raw mineral materials is 2 ：1, the cordierite materials obtained by the two step calcination process have the higher bulk density and the lower apparent porosity （2.18 g · cm^- 3 and 13.85% , respectively）. Furthermore, the addition of presynthesized cordierite clinker in the process of synthesizing cordierite materials can promote the growth of cordierite crystalline size.
基金the National High-Tech Research Development Program of China (No. 2003AA331100).
文摘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.
基金supported by the Natural Science Foundation of Jiangsu Provincial Universities, China (Grant No. 10KJB180004)
文摘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.
基金Project support by the National Natural Science Foundation of China (50574046, 50774038)the Natural Science Foundation of Yunnan Prov-ince (2008E030M)+1 种基金the Research Fund for the Doctoral Program of Higher Education of China (20095314120005)2010 Innovation Fund of Kunming University of Science and Technology
文摘Two-step steam reforming of methane (SRM) is a novel chemical looping process towards the production of pure hydrogen and syngas (synthesis gas), consisting of a syngas production step and a water-splitting step. Renewable energy can be used to drive this process for hydrogen production, especially solar energy. CeO2-Fe2O3 complex oxide oxygen carrier was prepared by the impregnation method and characterized by means of X-ray diffractometer (XRD), Raman spectroscopy (Raman) and hydrogen programmed reduction (H2-TPR). CH4 temperature programmed and isothermal reactions were adopted to test syngas production reactivity, and water splitting reaction was employed to investigate water-splitting activity. Moreover, two-step SRM performance was evaluated by a successive redox cycle. The results showed that CO-uncontaminated H2 and highly selective syngas (with H2/CO ratio close to 2) could be respectively obtained from two steps, and CeFeO3 formation was found in the first redox cycle and proved to be enhanced by the redox treatment. After 10 successive cycles, obvious CeFeO3 phase was detected, which may be responsible for favorable successive redox cycle performances.
基金supported by the National Natural Science Foundation of China(Grant Nos.50471031,50231010,50081002&19982001)Foundation of Excellent Doctoral Dissertation of Southeast University(Grant No.YBJJ0409)National Project 973(Grant No.2006CB601201).
文摘Two steps foaming (TSF) technique was proposed to prepare shaped Al alloy foam. Based on the thermal decomposition kinetics equation of titanium hydride, the relationship be-tween two steps thermal decomposition kinetics of titanium hydride and two steps foaming Al alloy melt was studied. Two steps thermal decomposition curve of titanium hydride under in-creasing and constant temperature was calculated respectively. The hydrogen mass needed in the second foaming step was also calculated. Results showed that the hydrogen mass of the second thermal decomposition of titanium hydride is enough for the second foaming step in the condition of as-received Al melt foaming. Experimental and theoretical results indicate that two steps foaming technique can be used to prepare Al alloy foam with high porosity, shaped com-ponents and sandwich with Al alloy foam core.
基金This project is supported by National Hi-tech Research and Development Program of China (863 Program, Grant No. 2008AA04Z115)Science and Technology Program of the Ministry of Construction of China (Grant No. 2008-K8-2)+1 种基金Jiangsu Provincial Natural Science Foundation of China (Grant No. BK2007042)Open Fund of State Key Lab of CAD&CG, Zhejiang University, China (Grant No. A0914)
文摘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.
基金supported by the National Natural Science Foundation of China (NO. 51004060)the Natural Science Foundation of Yunnan Province (NO. 2008E030M, 2010ZC108)+2 种基金the Research Foundation for the Doctoral Program of Higher Education of China (NO. 20095314120005)the Analysis and Test Foundation of Kunming University of Science and Technology (KUST)the 2010 Innovation Foundation of KUST
文摘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.
基金supported by the International Science and Technology Cooperation Program of Science and Technology Bureau of Changchun City,China(Grant No.12ZX68)
文摘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.
基金Project(BG2005009)supported by Jiangsu Provincial Hi-Tech Research Program
文摘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.
基金Project supported by the National Natural Science Foundation of China （Grant No 10304022）.
文摘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.
基金supported by the Natural Science Foundation of Henan Province(Grant No.152107000047)
文摘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.
基金supported by the National Natural Science Foundation of China(Grants 21573222,21622607,91545202 and U1532117)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB17020200)+1 种基金CAS Youth Innovation PromotionK.C.Wong Education Foundation in Ningbo University
文摘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.
基金the financial support from National Basic Research Program of China(2016YFA0602900)National Natural Science Foundation of China(21672204,21273222)+1 种基金Youth Innovation Promotion Association CAS(2016206)Jilin Provincial Science and Technology Program of China(20160203007GX)
文摘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.
基金Funded partly by the Science and Technology Support Program of Hebei(No.11215114D)
文摘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
文摘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.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61775121,61307003,61405122,and 11574311)Key R&D Program of Shandong Province,China(Grant No.2018GGX101002)+1 种基金the Natural Science Foundation of Shandong Province,China(Grant No.R2016FM03)the Fundamental Research Funds of Shandong University,China(Grant No.2015GN031)
文摘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.
基金supported by the National Natural Science Foundation of China(91833303,51872044,51372036,51202025 and 51602047)the Key Project of Chinese Ministry of Education(113020A)+3 种基金the 111 project(B13013)the Jilin Province Science and Technology Development Project(20180101175JC and 20140520096JH)the Fundamental Research Funds for the Central Universities(2412019FZ043)the Open Project of Key Laboratory for UV Emitting Materials and Technology of Ministry of Education(130028857).
文摘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.
