New types of aerial robots(NTARs)have found extensive applications in the military,civilian contexts,scientific research,disaster management,and various other domains.Compared with traditional aerial robots,NTARs exhi...New types of aerial robots(NTARs)have found extensive applications in the military,civilian contexts,scientific research,disaster management,and various other domains.Compared with traditional aerial robots,NTARs exhibit a broader range of morphological diversity,locomotion capabilities,and enhanced operational capacities.Therefore,this study defines aerial robots with the four characteristics of morphability,biomimicry,multi-modal locomotion,and manipulator attachment as NTARs.Subsequently,this paper discusses the latest research progress in the materials and manufacturing technology,actuation technology,and perception and control technology of NTARs.Thereafter,the research status of NTAR systems is summarized,focusing on the frontier development and application cases of flapping-wing microair vehicles,perching aerial robots,amphibious robots,and operational aerial robots.Finally,the main challenges presented by NTARs in terms of energy,materials,and perception are analyzed,and the future development trends of NTARs are summarized in terms of size and endurance,mechatronics,and complex scenarios,providing a reference direction for the follow-up exploration of NTARs.展开更多
Precision drilling with picosecond laser has been advocated to significantly improve the quality of micro-holes with reduced recast layer thickness and almost no heat affected zone.However,a detailed comparison betwee...Precision drilling with picosecond laser has been advocated to significantly improve the quality of micro-holes with reduced recast layer thickness and almost no heat affected zone.However,a detailed comparison between nanosecond and picosecond laser drilling techniques has rarely been reported in previous research.In the present study,a series of micro-holes are manufactured on stainless steel 304 using a nanosecond and a picosecond laser drilling system,respectively.The quality of the micro-holes,e.g.,recast layer,micro-crack,circularity,and conicity,etc,is evaluated by employing an optical microscope,an optical interferometer,and a scanning electron microscope.Additionally,the micro-structure of the samples between the edges of the micro-holes and the parent material is compared following etching treatment.The researching results show that a great amount of spattering material accumulated at the entrance ends of the nanosecond laser drilled micro-holes.The formation of a recast layer with a thickness of;5μm is detected on the side walls,associated with initiation of micro-cracks.Tapering phenomenon is also observed and the circularity of the micro-holes is rather poor.With regard to the micro-holes drilled by picosecond laser,the entrance ends,the exit ends,and the side walls are quite smooth without accumulation of spattering material,formation of recast layer and micro-cracks.The circularity of the micro-holes is fairly good without observation of tapering phenomenon.Furthermore,there is no obvious difference as for the micro-structure between the edges of the micro-holes and the parent material.This study proposes a picosecond laser helical drilling technique which can be used for effective manufacturing of high quality micro-holes.展开更多
Gecko-like robot（Geckobot）,an important branch of bionic robotics,is a robot that simulates gecko＇s capacity to climb walls and ceilings.The work environment of the traditional wall-climbing robot is greatly limite...Gecko-like robot（Geckobot）,an important branch of bionic robotics,is a robot that simulates gecko＇s capacity to climb walls and ceilings.The work environment of the traditional wall-climbing robot is greatly limited as the moving structure and adsorption principle of the robot have nothing to do with the real gecko.However,the adsorption principle and moving mode of the real gecko can provide a new way to break through the restrictions of the traditional wall-climbing robot.Inspired by the moving mechanism of geckos, this paper develops the Geckobot with motile body.Two types of Geckobots are addressed：one with compliant flat bar as the body,and the other with prismatic joint as the body.The compliant body not only resembles the moving mode of the real gecko body,but also simplifies the Geckobot＇s structure.The prismatic joint body is used to adapt the change of body length in ground-to-wall transition. The gait planning on the plane and the transition between perpendicular intersectional planes is discussed,with an emphasis on the analysis of the kinematics degree of freedom（DOF） and body posture.Central pattern generator（CPG） neural network is realized in LabVIEW and utilized to control Geckobot＇s movement.The CPG scheme in Lab VIEW is given,and how CPG is used to control Geckobot to turn or move forward is explored.Simulations are conducted in ADAMS to verify the feasibility of the structure design and gait planning and to acquire some parameters for practical Geckobot development.The experiment with Geckobot-Ⅰand Geckobot-Ⅱon their crawling capacity on the plane and the ground-to-wall transition finds that the robot can complete the crawling movement and ground-to-wall transition,verifying the feasibility of the structure design,gait planning and the CPG motion control.The Geckobot structure design approach,gait planning and the CPG motion control presented would be useful for the research on wall-climbing robots.展开更多
This article focused on the influences of fulvic acid and humic acid on aluminum speciation in drinking water. Factors including the concentration of residual chlorine and pH value had been concerned. Aluminum species...This article focused on the influences of fulvic acid and humic acid on aluminum speciation in drinking water. Factors including the concentration of residual chlorine and pH value had been concerned. Aluminum species investigated in the experiments included inorganic mononuclear, organic mononuclear, mononuclear, polymer, soluble, and suspended forms. It was found that the effects of fulvic acid and humic acid on aluminum speciation depended mainly on their molecular weight. Fulvic acid with molecular weight less than 5000 Dalton had little influence on aluminum speciation; while fulvic acid with molecular weight larger than 5000 Dalton and humic acid would increase the concentration of soluble aluminum significantly even at concentration below 0.5 mg/L （calculated as TOC）. Aluminum species, in the present of fulvic acid with molecular weight larger than 5000 Dalton and humic acid, were more stable than that in the present of fluvic acid with molecular mass less than 5000 Dalton, and varied little with reaction time. Within pH range 6.5-7.5, soluble aluminum increased notably in water with organic matter. As the concentration of residual chlorine increased, the effects of fulvic acid and humic acid became weak. The reactions between humic acid, fulvic acid with large molecular weight, and aluminum were considered to be a multi-dentate coordination process. With the consideration of aluminum bioavailability, reducing the concentration of fulvic acid and humic acid and keeping the pH value among 6.5-7.5 were recommended during drinking water treatment.展开更多
The properties of the passivation film formed on 316L stainless steel were studied by Electrochemical Impedance Spectroscopy （EIS）, Mott-Schottky and Voltammetry measurements in high- temperature acetic acid. The re...The properties of the passivation film formed on 316L stainless steel were studied by Electrochemical Impedance Spectroscopy （EIS）, Mott-Schottky and Voltammetry measurements in high- temperature acetic acid. The results show that the passivation film formed on 316L stainless steel is stable in 60% acetic acid solution from 25 ℃ to 85 ℃. As temperature increased, the polarization resistance decreased but the interface capacitance increased. There was hardly any relation between temperature and the intrinsic property semiconductor. The passivation film represents the p-semiconductor property in the potential interval of -0.5-0.1 V; represents the n-semiconductor property in the potential interval of 0.1-0.9 V; and represents the p-semiconductor property in the potential interval of 0.9-1.1 V. The voltammetry measurements show that the structure of the passivation film is stable when the temperature is lower than 55 ℃ and that its stability decreased when this temperature is exceeded.展开更多
Durability of traditional reactive powder concrete （RPC） with rich cement and high volume of fly-ash reactive powder concrete （FRPC） were studied. The X-diffraction and scanning electron microscope （SEM） measure...Durability of traditional reactive powder concrete （RPC） with rich cement and high volume of fly-ash reactive powder concrete （FRPC） were studied. The X-diffraction and scanning electron microscope （SEM） measurement was imployed to analyze the microstructure. The results show that both types of RPC have higher compressive strength, less volume shrinkage ratio and better carbonation-, chloride-, freezing-resistances than the conventional concrete. The results of X-diffraction indicate that they basically have C-S-H as the main composition without Ca（OH）2 crystal and ettringite. SEM results show that hydration products of FRPC is mainly Ⅲ-C-S-H which is piled up closely like densely arranged stone body and it has very compacted structure, in addition, Ca/Si ratio of C-S-H gel is lower than 1.5.展开更多
Doped Ceria nano-powders were synthesized via a Pechini-type gel rout. The specific surface area of Ce_(0.8)Sm_(0.2)O_(1.9) powder measured by the multilayer BET method is 41 m2.g^(-1). The electrical conductivities o...Doped Ceria nano-powders were synthesized via a Pechini-type gel rout. The specific surface area of Ce_(0.8)Sm_(0.2)O_(1.9) powder measured by the multilayer BET method is 41 m2.g^(-1). The electrical conductivities of Sm_2O_(3)-CeO_2 systems were measured by the ac impedance technique in air at temperatures ranging from 513 to 900 ℃. Typical impedance spectra consist of two depressed semicircles at reduced measuring temperature and one depressed semicircle at elevated measuring temperature respectively, from which the grain interior and grain boundary conductivities were calculated. The relationship between the conductivities of Sm_2O_3 doped CeO_2 (SDC) electrolyte and measuring temperature obeys Arrhenius equation. The grain interior conductivity of SDC varies slightly with improving sintering temperature, while the total conductivity increases with enhancing sintering temperature. The effective index has a significant effect on the ionic conductivity of ceria doped based electrolyte. When the effective index improves, the ionic conductivity increases and the apparent conductance activation energy decreases.展开更多
High coercivity was obtained in bulk RE(Dy) Fe C(B) alloys with RE=Nd, Pr and Mm. In the as cast state, the samples show a negligible coercivity H ci . Magnetic hardening takes place when annealing the as ...High coercivity was obtained in bulk RE(Dy) Fe C(B) alloys with RE=Nd, Pr and Mm. In the as cast state, the samples show a negligible coercivity H ci . Magnetic hardening takes place when annealing the as cast alloys at around 1173 K for several hours, which produces an H ci greater than 1200 kA·m -1 . Boron appears to be very important for achieving high coercivity, which is found to increase with increasing Dy content. SEM studies show a very small grain size at around 2 μm. X ray diffraction and TEM studies reveal the existence of multiphases after annealing. They are RE 2Fe 14 (B,C), RE 2Fe 3C x , alpha Fe(RE) and RE 2Fe 17 (B,C) in order of their amounts. The carbide RE 2Fe 3C x has a complicated hexagonal structure with a =0.468 nm and c =0.795 nm.展开更多
The Dy^3＋ -doped Fe3O4 samples were synthesized by sol-gel method, and the effects of dopant on the electrical and magnetic properties were investigated. According to XRD analysis, the high concentration doping of dy...The Dy^3＋ -doped Fe3O4 samples were synthesized by sol-gel method, and the effects of dopant on the electrical and magnetic properties were investigated. According to XRD analysis, the high concentration doping of dysprosium ions in Fe3O4 can not be obtained due to the difference of ionic radius, and Fe^3 ＋ ions are replaced by only a small amount of dysprosium ions. The magnetic property was characterized by VSM. The substitution results in the change of saturation magnetization, which may be due to the complex effects of increasing magnetization resulted from Dy^3＋ substitution and decreasing magnetization resulted from the impurity. The electrical property was characterized by four-probe method. With the increasing eoped content, magnetoresistance also increases, then decreases, and increases again. The spin-polarization of doped samples is lower than that of Fe3O4. Lower spin-polarization results in lower tunneling magnetoresistance. Fortunately, barrier was obtained by the second phase at the same time when sample was synthesized. The increase of appropriate barrier height leads to the change of tunneling magnetoresistance.展开更多
Nanometer Ni0.5Zn0.5Fe2O4 powders with spinel phase were prepared by the hydrothermal method using purified FeSO4 solution from sodium jarosite＇s slag as materials. The results show that the spinel phase of Ni0.5Zn0....Nanometer Ni0.5Zn0.5Fe2O4 powders with spinel phase were prepared by the hydrothermal method using purified FeSO4 solution from sodium jarosite＇s slag as materials. The results show that the spinel phase of Ni0.5Zn0.5Fe2O4 powders begins to form at a relatively low temperature （130 ℃） and a shorter holding time （1 h） when pH=8. The crystallization kinetics equation at 200℃ is ln[-ln（1-x）] =-0.78＋0.951n t. The growth activation energy of Ni0.5Zn0.5Fe2O4 grains is 41.6 kJ/moL in hydrothermal synthesis process. With the increase of sintering temperature, the density and diameter shrinkage of ferrite circulus increase, whereas its pores decrease. The results of magnetic measurements show that saturation magnetic flux density Bs increases and the coercivity Hc decreases with the increase of their sintering temperature. Magnetic parameters of all the investigated samples satisfy the character demand of high Bs, low Br and low Hc of soft magnetic ferrite materials.展开更多
Through coupling electromagnetic field equations with turbulent flow equations,the numerical prediction has been conducted on the flow field of molten steel and the trajectory of inclusion particle in the continuous c...Through coupling electromagnetic field equations with turbulent flow equations,the numerical prediction has been conducted on the flow field of molten steel and the trajectory of inclusion particle in the continuous casting mold effected by electromagnetic field.The difference between the maximum and the minimum of the shear stress on mold wall is used to scale the impingement strength of molten steel discharged from immersed nozzle to the solidifying shell on the narrow wall of mold.The flow field of molten steel in the mold is changed greatly and the impingement strength of the jet is reduced while electromagnetic field is applied.It is found that the successful control of flow field depends on the current and location of coil.At the same time,the new floating paths of inclusion particles are formed and the upward particles that are far away from the solidifying zone on the narrow wall of mold change their moving directions with the change of flow field,so that the particles can avoid being entrapped by the solidifying shell.展开更多
This paper investigates the structural stability of intermetallics R3Ni13-xCoxB2 （R=Y, Nd and Sm） with Nd3Ni13B2-type structure and the site preferences of the transition element Co by using a series of interatomic ...This paper investigates the structural stability of intermetallics R3Ni13-xCoxB2 （R=Y, Nd and Sm） with Nd3Ni13B2-type structure and the site preferences of the transition element Co by using a series of interatomic pair potentials. The space group remains unchanged upon substitution of Co for Ni in R3Ni13-xCoxB2 and the calculated lattice constants are found to agree with reports in literatures. The calculated cohesive energy curves show that Co atoms substitute for Ni with a strong preference for the 3g sites and the order of site preference is 3g, 4h and 6i. Moreover, the total and partial phonon densities of states are first evaluated for the R3Ni13B2 compounds with the hexagonal Nd3Nil3B2-type structure.展开更多
Temperature and excitation dependent photoluminescence(PL) of InGaN epilayer grown on c-plane Ga N/sapphire template by molecular beam epitaxy(MBE) has been systematically investigated. The emission spectra of the sam...Temperature and excitation dependent photoluminescence(PL) of InGaN epilayer grown on c-plane Ga N/sapphire template by molecular beam epitaxy(MBE) has been systematically investigated. The emission spectra of the sample consisted of strong multiple peaks associated with one stimulated emission(SE) located at 430 nm and two spontaneous emissions(SPE) centered at about 450 nm and 480 nm, indicating the co-existence of shallow and deep localized states.The peak energy of SE exhibiting weak s-shaped variation with increasing temperature revealed the localization effect of excitons. Moreover, an abnormal increase of the SPE intensity with increasing temperature was also observed, which indicated that the carrier transfer between the shallow and deeper localized states exists. Temperature dependent time-resolved PL(TRPL) demonstrated the carrier transfer processes among the localized states. In addition, a slow thermalization of hot carriers was observed in InGaN film by using TRPL and transient differential reflectivity, which is attributed to the phonon bottleneck effect induced by indium aggregation.展开更多
The nodular cast iron samples were prepared with the normal nodularizing process, in which the important antinodularizing elements Pb, Bi and Al were added respectively in order to research the influence of them on th...The nodular cast iron samples were prepared with the normal nodularizing process, in which the important antinodularizing elements Pb, Bi and Al were added respectively in order to research the influence of them on the nodularization of the graphites. The nodular graphites were extracted from the nodular cast iron by the electrolytic technique. The distribution of trace elements in nodular and deformed graphite were measured by Scanning Proton Microprobe (SPM). Most of the adding elements Pb, Bi and Al existed in matrix as impurities, a part of them intruded into the nodular graphites. A new suggestion of Ti antinodularizing properties had been proposed. The influence of Pb, Bi and Al on the nodularization was indirectly performed through Ti. Therefore, Ti is one of the most important antinodularizing elements.展开更多
The effects of Fe substitution for Co on the structural stability and the site preference of intermetallics Nd2CoT-xFex with a hexagonal Ce2NiT-type structure are studied by using a series of interatomic pair potentia...The effects of Fe substitution for Co on the structural stability and the site preference of intermetallics Nd2CoT-xFex with a hexagonal Ce2NiT-type structure are studied by using a series of interatomic pair potentials. In Nd2CoT-xFex, Fe atoms are substituted for Co atoms with a strong preference for the 6h sites and the order of site preference is 6h, 4e, 4f, 2a, and 12k. Calculated lattice parameters are found to be consistent with the reported results in the literature. The variation behaviour of the Curie temperature of Nd2CoT-xFex is explained qualitatively by the exchange interaction model. The properties related to lattice vibration, such as phonon density of states and Debye temperature, are first evaluated for the Nd2Co7 xFex compounds.展开更多
The effect of compressive deformation tested above the M_s temperature on the martensite morphology in Fe-Ni-C alloys has been studied.In the Fe-30Ni-0.12C alloy,the M_s temperature is -50℃ The cylindrical specimens ...The effect of compressive deformation tested above the M_s temperature on the martensite morphology in Fe-Ni-C alloys has been studied.In the Fe-30Ni-0.12C alloy,the M_s temperature is -50℃ The cylindrical specimens were compressively deformed at -40℃.The strain rates were 10,20,30 and 40%.X-ray analysis and metallographic examination showed that no strain-induced martensite was found.After quench- ing to -53℃,some thin plates and unusual morphologies of lenticular martensites with bent and/or broken mid-ribs were observed.In the Fe-30Ni-0.34C alloy,the M_s temperature is -120℃.Compressive deformation with different strain rates were carried out at room temperature. After quenching to the liquid nitrogen temperature, some bent thin plate matensites(unbroken)occur- red.The transformed twins in bent plate were also bent and nearly parallel to the γ-α'interfaces. Orientation relationship between austenite and bent martensite has been examined by means of trans- mission electron microscope.It was proved that these unusual morphologies are inherent in the compressive pre-deformed austenite.展开更多
Experiments were carried out on carburizing and temperature rising of the semi steel melt in a plasma induction furnace.Influence of many factors, such as power supply mode,position of the plasma torch and bottom b...Experiments were carried out on carburizing and temperature rising of the semi steel melt in a plasma induction furnace.Influence of many factors, such as power supply mode,position of the plasma torch and bottom blown gas stirring,on heating efficiency and melt temperature distribution was studied. Melt temperature could be effectively controlled by plasma heating,and carbon content of semi steel melt increased from 1.92 % to 4.58 %, and the utilization rate of carbon reached up to 61.57 % during carburizing of the melt.展开更多
The site preferences of the rare earth intermetallics Nd6Fe13-xTxSi（T = Co, Ni） are investigated by using interatomic pair potentials which are converted from a lattice-inversion method. Calculation shows that the o...The site preferences of the rare earth intermetallics Nd6Fe13-xTxSi（T = Co, Ni） are investigated by using interatomic pair potentials which are converted from a lattice-inversion method. Calculation shows that the order of the site preference of Co is 4d, 16 k, 16l1, and 16l2 and that of Ni is 16l2, 16l1, 16 k, and 4d in Nd6Fe13-xTxSi. Calculated lattice and positional parameters are found to agree with those reported in the literature. Furthermore, the phonon density of states for Nd6Fe13-xTxSiis also evaluated, and a qualitative analysis featuring the coordination and the relevant potentials is carried out.展开更多
Combining the characteristics of the black pulping liquor that contains a lot of lignin and other biomass resources, the technology of comprehensive waste utilization is employed. The reconstructive preparation of mod...Combining the characteristics of the black pulping liquor that contains a lot of lignin and other biomass resources, the technology of comprehensive waste utilization is employed. The reconstructive preparation of modified urea-formaldehyde glue by adding black pulping liquor and the application in extruding the medium density fibre board using this modified urea-formaldehyde glue is researched. Results show that when applying the preparation technology that alkaline reaction and then weak acid reaction, the appropriate preparation process is as follows： the adding urea process is divided into three stages （proportion 2 ： 1 ： 1） ; the pH value is 8.0, and the reaction time is 40 min in the addition reaction stage; the pH value will be naturally reduced to 3.5 -5.0, and the reaction time is 45 min in the aggregation reaction stage; the pH value is 8.0 in the urea complement stage. And the optimal condition of the reconstructive preparation the modified ureaformaldehyde glue is adding the condensed black pulping liquor after hydroxymethylation in the beginning of polycondensation reaction by 5% proportion. The application in extruding medium density fibre board with this modified urea-fosmaldehyde glue is proved feasible.展开更多
On the basis of an experiment in ultrasonic enhanced ammonia leaching of tailings, the effect of ultrasonic waves on copper dissolution was studied. The mechanism of ultrasonic enhanced tailing leaching was analyzed a...On the basis of an experiment in ultrasonic enhanced ammonia leaching of tailings, the effect of ultrasonic waves on copper dissolution was studied. The mechanism of ultrasonic enhanced tailing leaching was analyzed and a technique of ultrasonic enhanced pipe leaching of tailings was proposed. The results show that tailings with ultrasonic treatment can leach up to 89.5% of Cu, which is 13.5% more than those without the treatment. Ultrasonic technology is capable of improving leaching rates and the overall recovery of tailing leaching. Impact waves and micro jet streams can strip and erode affected surfaces of tailing particles to create new active surfaces and disturbances can intensify mass transfer processes in "dead zones". The technique of ultrasonic enhanced pipe leaching of tailings is a combination of existing agitation enhancement with ultrasonic enhancement and can improve mineral recovery.展开更多
基金supported in part by the National Key Research and Development Program of China(2022YFB4701800 and 2021ZD0114503)the National Natural Science Foundation of China(62103140,U22A2057,62173132,and 62133005)+3 种基金the Hunan Leading Talent of Technological Innovation(2022RC3063)the Top Ten Technical Research Projects of Hunan Province(2024GK1010)the Key Research and Development Program of Hunan Province(2023GK2068)the Science and Technology Innovation Program of Hunan Province(2023RC1049).
文摘New types of aerial robots(NTARs)have found extensive applications in the military,civilian contexts,scientific research,disaster management,and various other domains.Compared with traditional aerial robots,NTARs exhibit a broader range of morphological diversity,locomotion capabilities,and enhanced operational capacities.Therefore,this study defines aerial robots with the four characteristics of morphability,biomimicry,multi-modal locomotion,and manipulator attachment as NTARs.Subsequently,this paper discusses the latest research progress in the materials and manufacturing technology,actuation technology,and perception and control technology of NTARs.Thereafter,the research status of NTAR systems is summarized,focusing on the frontier development and application cases of flapping-wing microair vehicles,perching aerial robots,amphibious robots,and operational aerial robots.Finally,the main challenges presented by NTARs in terms of energy,materials,and perception are analyzed,and the future development trends of NTARs are summarized in terms of size and endurance,mechatronics,and complex scenarios,providing a reference direction for the follow-up exploration of NTARs.
基金Supported by National Basic Research Program of China(Grant No.2011CB013004)National Natural Science Foundation of China(Grant No.51005130)Research Fund of State Key Laboratory of Tribology,Tsinghua University(Grant no.SKLT12B06)
文摘Precision drilling with picosecond laser has been advocated to significantly improve the quality of micro-holes with reduced recast layer thickness and almost no heat affected zone.However,a detailed comparison between nanosecond and picosecond laser drilling techniques has rarely been reported in previous research.In the present study,a series of micro-holes are manufactured on stainless steel 304 using a nanosecond and a picosecond laser drilling system,respectively.The quality of the micro-holes,e.g.,recast layer,micro-crack,circularity,and conicity,etc,is evaluated by employing an optical microscope,an optical interferometer,and a scanning electron microscope.Additionally,the micro-structure of the samples between the edges of the micro-holes and the parent material is compared following etching treatment.The researching results show that a great amount of spattering material accumulated at the entrance ends of the nanosecond laser drilled micro-holes.The formation of a recast layer with a thickness of;5μm is detected on the side walls,associated with initiation of micro-cracks.Tapering phenomenon is also observed and the circularity of the micro-holes is rather poor.With regard to the micro-holes drilled by picosecond laser,the entrance ends,the exit ends,and the side walls are quite smooth without accumulation of spattering material,formation of recast layer and micro-cracks.The circularity of the micro-holes is fairly good without observation of tapering phenomenon.Furthermore,there is no obvious difference as for the micro-structure between the edges of the micro-holes and the parent material.This study proposes a picosecond laser helical drilling technique which can be used for effective manufacturing of high quality micro-holes.
基金supported by National Natural Science Foundation of China(Grant No.60535020)National Natural Science Funds for Distinguished Young Scholars of China(Grant No.60525314)
文摘Gecko-like robot（Geckobot）,an important branch of bionic robotics,is a robot that simulates gecko＇s capacity to climb walls and ceilings.The work environment of the traditional wall-climbing robot is greatly limited as the moving structure and adsorption principle of the robot have nothing to do with the real gecko.However,the adsorption principle and moving mode of the real gecko can provide a new way to break through the restrictions of the traditional wall-climbing robot.Inspired by the moving mechanism of geckos, this paper develops the Geckobot with motile body.Two types of Geckobots are addressed：one with compliant flat bar as the body,and the other with prismatic joint as the body.The compliant body not only resembles the moving mode of the real gecko body,but also simplifies the Geckobot＇s structure.The prismatic joint body is used to adapt the change of body length in ground-to-wall transition. The gait planning on the plane and the transition between perpendicular intersectional planes is discussed,with an emphasis on the analysis of the kinematics degree of freedom（DOF） and body posture.Central pattern generator（CPG） neural network is realized in LabVIEW and utilized to control Geckobot＇s movement.The CPG scheme in Lab VIEW is given,and how CPG is used to control Geckobot to turn or move forward is explored.Simulations are conducted in ADAMS to verify the feasibility of the structure design and gait planning and to acquire some parameters for practical Geckobot development.The experiment with Geckobot-Ⅰand Geckobot-Ⅱon their crawling capacity on the plane and the ground-to-wall transition finds that the robot can complete the crawling movement and ground-to-wall transition,verifying the feasibility of the structure design,gait planning and the CPG motion control.The Geckobot structure design approach,gait planning and the CPG motion control presented would be useful for the research on wall-climbing robots.
基金supported by the National Natural Science Foundation of China (No.50838005)the Changjiang Scholars and Innovative Research Team in University(No.IRT0853)the American Aluminum Foundation
文摘This article focused on the influences of fulvic acid and humic acid on aluminum speciation in drinking water. Factors including the concentration of residual chlorine and pH value had been concerned. Aluminum species investigated in the experiments included inorganic mononuclear, organic mononuclear, mononuclear, polymer, soluble, and suspended forms. It was found that the effects of fulvic acid and humic acid on aluminum speciation depended mainly on their molecular weight. Fulvic acid with molecular weight less than 5000 Dalton had little influence on aluminum speciation; while fulvic acid with molecular weight larger than 5000 Dalton and humic acid would increase the concentration of soluble aluminum significantly even at concentration below 0.5 mg/L （calculated as TOC）. Aluminum species, in the present of fulvic acid with molecular weight larger than 5000 Dalton and humic acid, were more stable than that in the present of fluvic acid with molecular mass less than 5000 Dalton, and varied little with reaction time. Within pH range 6.5-7.5, soluble aluminum increased notably in water with organic matter. As the concentration of residual chlorine increased, the effects of fulvic acid and humic acid became weak. The reactions between humic acid, fulvic acid with large molecular weight, and aluminum were considered to be a multi-dentate coordination process. With the consideration of aluminum bioavailability, reducing the concentration of fulvic acid and humic acid and keeping the pH value among 6.5-7.5 were recommended during drinking water treatment.
基金the National R&D Infrastructure and Facility Development Program of China(No.2005DKA10400)
文摘The properties of the passivation film formed on 316L stainless steel were studied by Electrochemical Impedance Spectroscopy （EIS）, Mott-Schottky and Voltammetry measurements in high- temperature acetic acid. The results show that the passivation film formed on 316L stainless steel is stable in 60% acetic acid solution from 25 ℃ to 85 ℃. As temperature increased, the polarization resistance decreased but the interface capacitance increased. There was hardly any relation between temperature and the intrinsic property semiconductor. The passivation film represents the p-semiconductor property in the potential interval of -0.5-0.1 V; represents the n-semiconductor property in the potential interval of 0.1-0.9 V; and represents the p-semiconductor property in the potential interval of 0.9-1.1 V. The voltammetry measurements show that the structure of the passivation film is stable when the temperature is lower than 55 ℃ and that its stability decreased when this temperature is exceeded.
文摘Durability of traditional reactive powder concrete （RPC） with rich cement and high volume of fly-ash reactive powder concrete （FRPC） were studied. The X-diffraction and scanning electron microscope （SEM） measurement was imployed to analyze the microstructure. The results show that both types of RPC have higher compressive strength, less volume shrinkage ratio and better carbonation-, chloride-, freezing-resistances than the conventional concrete. The results of X-diffraction indicate that they basically have C-S-H as the main composition without Ca（OH）2 crystal and ettringite. SEM results show that hydration products of FRPC is mainly Ⅲ-C-S-H which is piled up closely like densely arranged stone body and it has very compacted structure, in addition, Ca/Si ratio of C-S-H gel is lower than 1.5.
文摘Doped Ceria nano-powders were synthesized via a Pechini-type gel rout. The specific surface area of Ce_(0.8)Sm_(0.2)O_(1.9) powder measured by the multilayer BET method is 41 m2.g^(-1). The electrical conductivities of Sm_2O_(3)-CeO_2 systems were measured by the ac impedance technique in air at temperatures ranging from 513 to 900 ℃. Typical impedance spectra consist of two depressed semicircles at reduced measuring temperature and one depressed semicircle at elevated measuring temperature respectively, from which the grain interior and grain boundary conductivities were calculated. The relationship between the conductivities of Sm_2O_3 doped CeO_2 (SDC) electrolyte and measuring temperature obeys Arrhenius equation. The grain interior conductivity of SDC varies slightly with improving sintering temperature, while the total conductivity increases with enhancing sintering temperature. The effective index has a significant effect on the ionic conductivity of ceria doped based electrolyte. When the effective index improves, the ionic conductivity increases and the apparent conductance activation energy decreases.
文摘High coercivity was obtained in bulk RE(Dy) Fe C(B) alloys with RE=Nd, Pr and Mm. In the as cast state, the samples show a negligible coercivity H ci . Magnetic hardening takes place when annealing the as cast alloys at around 1173 K for several hours, which produces an H ci greater than 1200 kA·m -1 . Boron appears to be very important for achieving high coercivity, which is found to increase with increasing Dy content. SEM studies show a very small grain size at around 2 μm. X ray diffraction and TEM studies reveal the existence of multiphases after annealing. They are RE 2Fe 14 (B,C), RE 2Fe 3C x , alpha Fe(RE) and RE 2Fe 17 (B,C) in order of their amounts. The carbide RE 2Fe 3C x has a complicated hexagonal structure with a =0.468 nm and c =0.795 nm.
文摘The Dy^3＋ -doped Fe3O4 samples were synthesized by sol-gel method, and the effects of dopant on the electrical and magnetic properties were investigated. According to XRD analysis, the high concentration doping of dysprosium ions in Fe3O4 can not be obtained due to the difference of ionic radius, and Fe^3 ＋ ions are replaced by only a small amount of dysprosium ions. The magnetic property was characterized by VSM. The substitution results in the change of saturation magnetization, which may be due to the complex effects of increasing magnetization resulted from Dy^3＋ substitution and decreasing magnetization resulted from the impurity. The electrical property was characterized by four-probe method. With the increasing eoped content, magnetoresistance also increases, then decreases, and increases again. The spin-polarization of doped samples is lower than that of Fe3O4. Lower spin-polarization results in lower tunneling magnetoresistance. Fortunately, barrier was obtained by the second phase at the same time when sample was synthesized. The increase of appropriate barrier height leads to the change of tunneling magnetoresistance.
基金Project(50204001) supported by the National Natural Science Foundation of China
文摘Nanometer Ni0.5Zn0.5Fe2O4 powders with spinel phase were prepared by the hydrothermal method using purified FeSO4 solution from sodium jarosite＇s slag as materials. The results show that the spinel phase of Ni0.5Zn0.5Fe2O4 powders begins to form at a relatively low temperature （130 ℃） and a shorter holding time （1 h） when pH=8. The crystallization kinetics equation at 200℃ is ln[-ln（1-x）] =-0.78＋0.951n t. The growth activation energy of Ni0.5Zn0.5Fe2O4 grains is 41.6 kJ/moL in hydrothermal synthesis process. With the increase of sintering temperature, the density and diameter shrinkage of ferrite circulus increase, whereas its pores decrease. The results of magnetic measurements show that saturation magnetic flux density Bs increases and the coercivity Hc decreases with the increase of their sintering temperature. Magnetic parameters of all the investigated samples satisfy the character demand of high Bs, low Br and low Hc of soft magnetic ferrite materials.
基金This project is sponsored by China Academic Association
文摘Through coupling electromagnetic field equations with turbulent flow equations,the numerical prediction has been conducted on the flow field of molten steel and the trajectory of inclusion particle in the continuous casting mold effected by electromagnetic field.The difference between the maximum and the minimum of the shear stress on mold wall is used to scale the impingement strength of molten steel discharged from immersed nozzle to the solidifying shell on the narrow wall of mold.The flow field of molten steel in the mold is changed greatly and the impingement strength of the jet is reduced while electromagnetic field is applied.It is found that the successful control of flow field depends on the current and location of coil.At the same time,the new floating paths of inclusion particles are formed and the upward particles that are far away from the solidifying zone on the narrow wall of mold change their moving directions with the change of flow field,so that the particles can avoid being entrapped by the solidifying shell.
基金Project supported by the National Basic Research Program of China (Grant No. 2006CB605101)the National Natural Science Foundation of China (Grant No. 50971024)
文摘This paper investigates the structural stability of intermetallics R3Ni13-xCoxB2 （R=Y, Nd and Sm） with Nd3Ni13B2-type structure and the site preferences of the transition element Co by using a series of interatomic pair potentials. The space group remains unchanged upon substitution of Co for Ni in R3Ni13-xCoxB2 and the calculated lattice constants are found to agree with reports in literatures. The calculated cohesive energy curves show that Co atoms substitute for Ni with a strong preference for the 3g sites and the order of site preference is 3g, 4h and 6i. Moreover, the total and partial phonon densities of states are first evaluated for the R3Ni13B2 compounds with the hexagonal Nd3Nil3B2-type structure.
基金Project supported by the National Key Research Program of China(Grant No.2016YFB0501604)the National Natural Science Foundation of China(Grant Nos.10874127 and 61227902)
文摘Temperature and excitation dependent photoluminescence(PL) of InGaN epilayer grown on c-plane Ga N/sapphire template by molecular beam epitaxy(MBE) has been systematically investigated. The emission spectra of the sample consisted of strong multiple peaks associated with one stimulated emission(SE) located at 430 nm and two spontaneous emissions(SPE) centered at about 450 nm and 480 nm, indicating the co-existence of shallow and deep localized states.The peak energy of SE exhibiting weak s-shaped variation with increasing temperature revealed the localization effect of excitons. Moreover, an abnormal increase of the SPE intensity with increasing temperature was also observed, which indicated that the carrier transfer between the shallow and deeper localized states exists. Temperature dependent time-resolved PL(TRPL) demonstrated the carrier transfer processes among the localized states. In addition, a slow thermalization of hot carriers was observed in InGaN film by using TRPL and transient differential reflectivity, which is attributed to the phonon bottleneck effect induced by indium aggregation.
基金The project was supported by Academia Sinica and Joint Opcn Laboratc y of Nuclear Analytical Technuiques ,Acadcmis Sinica
文摘The nodular cast iron samples were prepared with the normal nodularizing process, in which the important antinodularizing elements Pb, Bi and Al were added respectively in order to research the influence of them on the nodularization of the graphites. The nodular graphites were extracted from the nodular cast iron by the electrolytic technique. The distribution of trace elements in nodular and deformed graphite were measured by Scanning Proton Microprobe (SPM). Most of the adding elements Pb, Bi and Al existed in matrix as impurities, a part of them intruded into the nodular graphites. A new suggestion of Ti antinodularizing properties had been proposed. The influence of Pb, Bi and Al on the nodularization was indirectly performed through Ti. Therefore, Ti is one of the most important antinodularizing elements.
基金Project supported by the National Natural Science Foundation of China (Grant No.50971024)
文摘The effects of Fe substitution for Co on the structural stability and the site preference of intermetallics Nd2CoT-xFex with a hexagonal Ce2NiT-type structure are studied by using a series of interatomic pair potentials. In Nd2CoT-xFex, Fe atoms are substituted for Co atoms with a strong preference for the 6h sites and the order of site preference is 6h, 4e, 4f, 2a, and 12k. Calculated lattice parameters are found to be consistent with the reported results in the literature. The variation behaviour of the Curie temperature of Nd2CoT-xFex is explained qualitatively by the exchange interaction model. The properties related to lattice vibration, such as phonon density of states and Debye temperature, are first evaluated for the Nd2Co7 xFex compounds.
文摘The effect of compressive deformation tested above the M_s temperature on the martensite morphology in Fe-Ni-C alloys has been studied.In the Fe-30Ni-0.12C alloy,the M_s temperature is -50℃ The cylindrical specimens were compressively deformed at -40℃.The strain rates were 10,20,30 and 40%.X-ray analysis and metallographic examination showed that no strain-induced martensite was found.After quench- ing to -53℃,some thin plates and unusual morphologies of lenticular martensites with bent and/or broken mid-ribs were observed.In the Fe-30Ni-0.34C alloy,the M_s temperature is -120℃.Compressive deformation with different strain rates were carried out at room temperature. After quenching to the liquid nitrogen temperature, some bent thin plate matensites(unbroken)occur- red.The transformed twins in bent plate were also bent and nearly parallel to the γ-α'interfaces. Orientation relationship between austenite and bent martensite has been examined by means of trans- mission electron microscope.It was proved that these unusual morphologies are inherent in the compressive pre-deformed austenite.
文摘Experiments were carried out on carburizing and temperature rising of the semi steel melt in a plasma induction furnace.Influence of many factors, such as power supply mode,position of the plasma torch and bottom blown gas stirring,on heating efficiency and melt temperature distribution was studied. Melt temperature could be effectively controlled by plasma heating,and carbon content of semi steel melt increased from 1.92 % to 4.58 %, and the utilization rate of carbon reached up to 61.57 % during carburizing of the melt.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11272048 and 50971024)the National Key Basic Research Program of China(Grant No.2011CB606401)
文摘The site preferences of the rare earth intermetallics Nd6Fe13-xTxSi（T = Co, Ni） are investigated by using interatomic pair potentials which are converted from a lattice-inversion method. Calculation shows that the order of the site preference of Co is 4d, 16 k, 16l1, and 16l2 and that of Ni is 16l2, 16l1, 16 k, and 4d in Nd6Fe13-xTxSi. Calculated lattice and positional parameters are found to agree with those reported in the literature. Furthermore, the phonon density of states for Nd6Fe13-xTxSiis also evaluated, and a qualitative analysis featuring the coordination and the relevant potentials is carried out.
基金Sponsored by the Ministerial Level Advanced Research Foundation(20060013)
文摘Combining the characteristics of the black pulping liquor that contains a lot of lignin and other biomass resources, the technology of comprehensive waste utilization is employed. The reconstructive preparation of modified urea-formaldehyde glue by adding black pulping liquor and the application in extruding the medium density fibre board using this modified urea-formaldehyde glue is researched. Results show that when applying the preparation technology that alkaline reaction and then weak acid reaction, the appropriate preparation process is as follows： the adding urea process is divided into three stages （proportion 2 ： 1 ： 1） ; the pH value is 8.0, and the reaction time is 40 min in the addition reaction stage; the pH value will be naturally reduced to 3.5 -5.0, and the reaction time is 45 min in the aggregation reaction stage; the pH value is 8.0 in the urea complement stage. And the optimal condition of the reconstructive preparation the modified ureaformaldehyde glue is adding the condensed black pulping liquor after hydroxymethylation in the beginning of polycondensation reaction by 5% proportion. The application in extruding medium density fibre board with this modified urea-fosmaldehyde glue is proved feasible.
基金Projects 2004CB619205 supported by the National Basic Research Program of China50574099 by the National Natural Science Foundation of China06JJ30024 by the Natural Science Foundation of Hunan Province
文摘On the basis of an experiment in ultrasonic enhanced ammonia leaching of tailings, the effect of ultrasonic waves on copper dissolution was studied. The mechanism of ultrasonic enhanced tailing leaching was analyzed and a technique of ultrasonic enhanced pipe leaching of tailings was proposed. The results show that tailings with ultrasonic treatment can leach up to 89.5% of Cu, which is 13.5% more than those without the treatment. Ultrasonic technology is capable of improving leaching rates and the overall recovery of tailing leaching. Impact waves and micro jet streams can strip and erode affected surfaces of tailing particles to create new active surfaces and disturbances can intensify mass transfer processes in "dead zones". The technique of ultrasonic enhanced pipe leaching of tailings is a combination of existing agitation enhancement with ultrasonic enhancement and can improve mineral recovery.
