When a redundant robot performs a fault-tolerant operation for locked joint failures, its fault tolerant properties should include dexterity and sudden change of joint velocity at the moment of locking failed joints a...When a redundant robot performs a fault-tolerant operation for locked joint failures, its fault tolerant properties should include dexterity and sudden change of joint velocity at the moment of locking failed joints and the dexterity during the post-failure. Firstly three fault-tolerant indexes, reduced condition number, sudden change of relative joint velocity and centrality are proposed, which can comprehensively evaluate the kinematical performance of a redundant robot during its entire fault-tolerant operations. Then, the influence of the initial postures of robot＇s end-effector on these fault-tolerant indexes is analyzed with a planar robot and a spatial robot. Simulation results show that for a given task the joint trajectory with the best comprehensive effect of fault tolerance can be determined by optimizing the initial posture of a robot.展开更多
At present,evaluation on reservoir damage induced by fracturing fluid mainly refers to The Evaluation Measurement for Properties of Water-based Fracturing Fluid:SY/T5107-2016(referred to as the industry standard below...At present,evaluation on reservoir damage induced by fracturing fluid mainly refers to The Evaluation Measurement for Properties of Water-based Fracturing Fluid:SY/T5107-2016(referred to as the industry standard below).However,the fracturing fluid displacing core process stipulated in the industry standard is not consistent with the fast invading process of fracturing fluid into the reservoir under high pressure during the actual fracturing construction.Besides,the influences of fracturing fluid residues,gel breaking mode,original water saturation and other factors are not taken into consideration in the experiments to evaluate the damage of fracturing fluids.Thus,the accuracy of evaluation results is influenced.In this paper,tight sandstone cores of the Lower Jurassic Ahe Formation(J1a)in Dibei area of Kuqa Depression of the Tarim Basin were selected as samples.The invading process of fracturing fluid into a tight sandstone reservoir was simulated by modifying experimental process and method.Then,the damage degree of fracturing fluid to gas reservoir was evaluated and the damage mechanisms of fracturing fluid were analyzed systematically.And the following research results were obtained.First,themodified evaluationmethod takes into account the influences of several factors,such as the originalwater saturation of gas reservoir,the instantaneous“breakdown”effect of high-pressure during fracturing and the fracturing fluid residues,so it can evaluate the damage degree of fracturing fluid to tight sandstone gas reservoirsmore objectively.Second,the evaluation results based on the industry standard showthat the damage degree of fracturing fluid to the permeability of tight sandstone gas reservoirs ismedium to strong,whereas the damage degree evaluated by themodifiedmethod is medium to weak.Third,the retention of fracturing fluid residues in fractures is the main cause of permeability damage.The residues can easily block fractures and fracture surface pores.Most of them retain in the pores in the surface layer of matrix cores(invasion depth less than 3 cm),so residues are filtered by matrix pores.Fourth,when fracturing fluid migrates inwards from the core surface,high molecular polymers retain in the form of thin-film lamellar,local flaky nodular and crystal inclusion in turn in the reservoir pores.Fifth,under the experimental conditions,salting-out crystals appear and are unevenly distributed in the cores.In fractures,salting-out crystals and high molecules are polymerized to form composite inclusions.In matrix pores,salting-out crystals and a small number of fragments(e.g.illite)are enclosed to form a complex.Sixth,migratory particles caused by speed sensitivity are usually combined with residues and high molecular polymers to form composite inclusions,thus blocking pores and fractures.展开更多
Lattice structures have attracted extensive attention in the field of engineering materials due to their characteristics of lightweight and high strength.This paper combines topology optimization with additive manufac...Lattice structures have attracted extensive attention in the field of engineering materials due to their characteristics of lightweight and high strength.This paper combines topology optimization with additive manufacturing to investigate how pore shape in Triply Periodic Minimal Surface(TPMS)structures affects mechanical properties and energy absorption performance.The periodic lattice structures(Triangle lattice,rectangle lattice and Rectangle lattice)and aperiodic mixed structures are designed,including a variety of lattice structures such as circle-circle and triangle-triangle(CCTT),triangle-triangle and rectangle-rectangle(TTRR),circle-circle and rectangle-rectangle(CCRR),triangle-circle-circle-triangle(TCCT),rectangle-triangle-triangle-rectangle(RTTR)and rectangle-circle-circle-rectangle(RCCR).The anisotropy of the unit cells is compared by using the homogenization method.The deformation modes,mechanical properties,and energy absorption efficiency of lattice structures are evaluated systematically by finite element analysis and compression experiments.The results demonstrate that the circle lattice exhibits significantly superior performance in Young’s modulus,compressive strength,toughness,and energy absorption characteristics compared to the triangle lattice and the rectangle lattice.Among aperiodic structures,TCCT shows better comprehensive mechanical properties,while TTRR exhibits relatively inferior performance.The periodic structures possess overall superior mechanical performance.This study demonstrates that the mechanical properties and energy absorption characteristics can be optimized by controlling the pore shape of TPMS lattice structures.This provides an important insight into lightweight structure design in the engineering field.展开更多
In this note, we estimate the maximum amplitude for the Solar Cycle 25. We use the curvature technique presented for earlier cycles by Verdes and coworkers. We further extrapolate the location of the solar maximum num...In this note, we estimate the maximum amplitude for the Solar Cycle 25. We use the curvature technique presented for earlier cycles by Verdes and coworkers. We further extrapolate the location of the solar maximum number of Sunspots, of which the prediction made is about 115 in the year 2025 and identify the arrival to the minimum in the year 2031, forecasting the main characteristics for the current Solar Cycle 25 and list a short comparison with a few other predictions.展开更多
Pneumatic actuators and electric actuators have almost been applied to all manufacturing industries. The two kinds of actuators can replace each other in most fields, such as the point to point transmission occasion a...Pneumatic actuators and electric actuators have almost been applied to all manufacturing industries. The two kinds of actuators can replace each other in most fields, such as the point to point transmission occasion and some rotating occasions. However, there are very few research results about the advantages and disadvantages of two kinds of actuators under the same working conditions so far. In this paper, a novel comprehensive assessment method, named as overall life cycle comprehensive assessment （OLCCA）, is proposed for comparison and assessment of pneumatic and electric actuators. OLCCA contains mechanical properties evaluation （MPE）, life cycle cost analysis based on users （LCCABOU） and life cycle environmental impact analysis （LCEIA） algorithm in order to solve three difficult problems： mechanical properties assessment, cost analysis and environmental impact assessment about actuators. The mechanical properties evaluation of actuators is a multi-objective optimization problem. The fuzzy data quantification and information entropy methods are combined to establish MPE algorithm of actuators. Two kinds of pneumatic actuators and electric actuators with similar bearing capacity and similar work stroke were taken for example to verify the correctness of MPE algorithm. The case study of MPE algorithm for actuators verified its correctness. LCCABOU for actuators is also set up. Considering cost complex structure of pneumatic actuators, public device cost even method （PDCEM） is firstly presented to solve cost division of public devices such as compressors, aftercooler, receivers, etc. LCCABOU method is also effective and verified by the three groups of pneumatic actuators and electric actuators. Finally, LCEIA model of actuators is established for the environmental impact assessment of actuators. LCEIA data collection method and model establishment procedure for actuators are also put forward. With Simapro 7, LCEIA comparison results of six actuators can be obtained： Fossil fuels are the major environmental factor of pneumatic and electric actuators; Environmental impact of electric actuator is large than one of pneumatic actuator under the similar mechanical properties and working conditions of pneumatic and electric actuators. The results are correct and correspond with the actual mechanical properties of actuators. This paper proposes a comprehensive evaluation method of the actuators, which can solve the critical problem that similar electromechanical products are very difficult to be compared with each other from the angle of performance, cost and environment impact.展开更多
The scarcity of housing increases as population continues to rise all over the world. Despite government efforts at providing houses, yearly demand keeps on exceeding available houses and hence the hike in rent, the c...The scarcity of housing increases as population continues to rise all over the world. Despite government efforts at providing houses, yearly demand keeps on exceeding available houses and hence the hike in rent, the cost of erecting houses and the cost of building materials. This ultimately calls for a decisive solution. This study therefore applied compliance to cost ratio (C-CR) analysis in evaluating the optimum properties of fired ceramic bricks. The optimum mix proportions of waste glass (WG) and wood saw dust (WSD) in fired bricks, that will be suitable for housing constructions were hence determined. Fired clay brick samples which contained varied proportions of WG and WSD were examined for physical, mechanical and thermal properties in line with standard procedures. The results were compared with existing standards and property evaluation index, compliance level and C-CR were applied in analyzing the results obtained. It was observed that with increasing WG content, compliance level increased. Also, cost ratio and experimental cost of each brick sample trended upward. Sample with mix proportion;20 wt% WG, 5 wt% WSD and 75 wt% clay had compliance level of 94% and C-CR index of 7.81, hence chosen as optimum mix proportion for masonry bricks.展开更多
This paper presents the NUBASE2012 evaluation that contains the recommended values for nuclear and decay properties of nuclides in their ground and excited isomeric （T1/2≥ 100 ns） states. All nuclides for which som...This paper presents the NUBASE2012 evaluation that contains the recommended values for nuclear and decay properties of nuclides in their ground and excited isomeric （T1/2≥ 100 ns） states. All nuclides for which some experimental information is known are considered. NUBASE2012 covers all up to date experimental data published in primary （journal articles） and secondary （mainly laboratory reports and conference proceedings） references, together with the corresponding bibliographical information. During the development of NUBASE2012, the data available in the ＂Evaluated Nuclear Structure Data File＂ （ENSDF） database were consulted, and critically assessed of their validity and completeness. Furthermore, a large amount of new and somewhat older experimental results that were missing in ENSDF were compiled, evaluated and included in NUI3ASE2012. The atomic mass values were taken from the ＂Atomic Mass Evaluation＂ （AME2012, second and third parts of the present issue）. In cases where no experimental data were available for a particular nuclide, trends in the behavior of specific properties in neighboring nuclei （TNN） were examined. This approach allowed to estimate, whenever possible, values for a range of properties, and are labeled in NUBASE2012 as ＂non-experimental＂ （flagged ＂#＂）. Evaluation procedures and policies that were used during the development of this database are presented, together with a detailed table of recommended values and their uncertainties.展开更多
A quercetin-bonded silica gel stationary phase （QUSP） containing natural flavonoid ligand was first prepared via γ-glycidoxypropyltrimethoxysilane （KH-560） as a coupling reagent for high-performance liquid chroma...A quercetin-bonded silica gel stationary phase （QUSP） containing natural flavonoid ligand was first prepared via γ-glycidoxypropyltrimethoxysilane （KH-560） as a coupling reagent for high-performance liquid chromatography. Its chemical structure was characterized by Fourier infrared spectroscopy, elemental analysis, thermal thermogravimetry and 13C cross polarization/magic angle spinning nuclear magnetic resonance （CP/MAS NMR）. The chromatographic property of QUSP was systematically evaluated by using neutral, basic and acidic aromatic com- pounds as probes. In order to clarify its retention mechanism, a comparative study of QUSP with conventional oc- tadecylsilyl-bonded stationary phase （ODS） was also carried out under the same conditions. The results showed that the new quercetin-bonded phase exhibited an excellent reversed-phase chromatographic property with relatively weak hydrophobicity. However, it has an advantage over ODS in the fast separation of polar aromatic compounds because the quercetin ligand could provide various sites besides hydrophobicity, such as hydrogen bonding, dipole-dipole, n-n staking and charge transfer interactions. QUSP was performed in the baseline separations of ion- ized polar basic or acidic compounds, including pyridines, anilines, pyrimidines, purines and phenols with symmet- ric peak shape in common mobile phases without buffer salt within relatively short time. The natural ligands from herbs are readily available and contain a variety of active sites, which facilitate the exploration of industrial chromatographic separation materials for green products.展开更多
基金National Natural Science Foundation of China (No.50775002)Academic Human Resources Devel-opment in Institution of Higher Learning Under the Jurisdiction of Beijing Municipality, China.
文摘When a redundant robot performs a fault-tolerant operation for locked joint failures, its fault tolerant properties should include dexterity and sudden change of joint velocity at the moment of locking failed joints and the dexterity during the post-failure. Firstly three fault-tolerant indexes, reduced condition number, sudden change of relative joint velocity and centrality are proposed, which can comprehensively evaluate the kinematical performance of a redundant robot during its entire fault-tolerant operations. Then, the influence of the initial postures of robot＇s end-effector on these fault-tolerant indexes is analyzed with a planar robot and a spatial robot. Simulation results show that for a given task the joint trajectory with the best comprehensive effect of fault tolerance can be determined by optimizing the initial posture of a robot.
基金Project supported by National Natural Science Foundation of China“Basic study on drying of tight gas reservoir and enhancing gas seepage capacity”(No.51534006).
文摘At present,evaluation on reservoir damage induced by fracturing fluid mainly refers to The Evaluation Measurement for Properties of Water-based Fracturing Fluid:SY/T5107-2016(referred to as the industry standard below).However,the fracturing fluid displacing core process stipulated in the industry standard is not consistent with the fast invading process of fracturing fluid into the reservoir under high pressure during the actual fracturing construction.Besides,the influences of fracturing fluid residues,gel breaking mode,original water saturation and other factors are not taken into consideration in the experiments to evaluate the damage of fracturing fluids.Thus,the accuracy of evaluation results is influenced.In this paper,tight sandstone cores of the Lower Jurassic Ahe Formation(J1a)in Dibei area of Kuqa Depression of the Tarim Basin were selected as samples.The invading process of fracturing fluid into a tight sandstone reservoir was simulated by modifying experimental process and method.Then,the damage degree of fracturing fluid to gas reservoir was evaluated and the damage mechanisms of fracturing fluid were analyzed systematically.And the following research results were obtained.First,themodified evaluationmethod takes into account the influences of several factors,such as the originalwater saturation of gas reservoir,the instantaneous“breakdown”effect of high-pressure during fracturing and the fracturing fluid residues,so it can evaluate the damage degree of fracturing fluid to tight sandstone gas reservoirsmore objectively.Second,the evaluation results based on the industry standard showthat the damage degree of fracturing fluid to the permeability of tight sandstone gas reservoirs ismedium to strong,whereas the damage degree evaluated by themodifiedmethod is medium to weak.Third,the retention of fracturing fluid residues in fractures is the main cause of permeability damage.The residues can easily block fractures and fracture surface pores.Most of them retain in the pores in the surface layer of matrix cores(invasion depth less than 3 cm),so residues are filtered by matrix pores.Fourth,when fracturing fluid migrates inwards from the core surface,high molecular polymers retain in the form of thin-film lamellar,local flaky nodular and crystal inclusion in turn in the reservoir pores.Fifth,under the experimental conditions,salting-out crystals appear and are unevenly distributed in the cores.In fractures,salting-out crystals and high molecules are polymerized to form composite inclusions.In matrix pores,salting-out crystals and a small number of fragments(e.g.illite)are enclosed to form a complex.Sixth,migratory particles caused by speed sensitivity are usually combined with residues and high molecular polymers to form composite inclusions,thus blocking pores and fractures.
基金supported by the National Natural Science Foundation of China(Grant 52175236).
文摘Lattice structures have attracted extensive attention in the field of engineering materials due to their characteristics of lightweight and high strength.This paper combines topology optimization with additive manufacturing to investigate how pore shape in Triply Periodic Minimal Surface(TPMS)structures affects mechanical properties and energy absorption performance.The periodic lattice structures(Triangle lattice,rectangle lattice and Rectangle lattice)and aperiodic mixed structures are designed,including a variety of lattice structures such as circle-circle and triangle-triangle(CCTT),triangle-triangle and rectangle-rectangle(TTRR),circle-circle and rectangle-rectangle(CCRR),triangle-circle-circle-triangle(TCCT),rectangle-triangle-triangle-rectangle(RTTR)and rectangle-circle-circle-rectangle(RCCR).The anisotropy of the unit cells is compared by using the homogenization method.The deformation modes,mechanical properties,and energy absorption efficiency of lattice structures are evaluated systematically by finite element analysis and compression experiments.The results demonstrate that the circle lattice exhibits significantly superior performance in Young’s modulus,compressive strength,toughness,and energy absorption characteristics compared to the triangle lattice and the rectangle lattice.Among aperiodic structures,TCCT shows better comprehensive mechanical properties,while TTRR exhibits relatively inferior performance.The periodic structures possess overall superior mechanical performance.This study demonstrates that the mechanical properties and energy absorption characteristics can be optimized by controlling the pore shape of TPMS lattice structures.This provides an important insight into lightweight structure design in the engineering field.
文摘In this note, we estimate the maximum amplitude for the Solar Cycle 25. We use the curvature technique presented for earlier cycles by Verdes and coworkers. We further extrapolate the location of the solar maximum number of Sunspots, of which the prediction made is about 115 in the year 2025 and identify the arrival to the minimum in the year 2031, forecasting the main characteristics for the current Solar Cycle 25 and list a short comparison with a few other predictions.
基金Supported by Doctoral Foundation of Henan Polytechnic University(Grant No.B2012-101)Opening Project of Key Laboratory of Precision Manufacturing Technology and Engineering of Henan Polytechnic University,China(Grant No.PMTE201318A)Henan Provincial Science and Technology Research Projects of Education Department of China(Grant No.14B460033)
文摘Pneumatic actuators and electric actuators have almost been applied to all manufacturing industries. The two kinds of actuators can replace each other in most fields, such as the point to point transmission occasion and some rotating occasions. However, there are very few research results about the advantages and disadvantages of two kinds of actuators under the same working conditions so far. In this paper, a novel comprehensive assessment method, named as overall life cycle comprehensive assessment （OLCCA）, is proposed for comparison and assessment of pneumatic and electric actuators. OLCCA contains mechanical properties evaluation （MPE）, life cycle cost analysis based on users （LCCABOU） and life cycle environmental impact analysis （LCEIA） algorithm in order to solve three difficult problems： mechanical properties assessment, cost analysis and environmental impact assessment about actuators. The mechanical properties evaluation of actuators is a multi-objective optimization problem. The fuzzy data quantification and information entropy methods are combined to establish MPE algorithm of actuators. Two kinds of pneumatic actuators and electric actuators with similar bearing capacity and similar work stroke were taken for example to verify the correctness of MPE algorithm. The case study of MPE algorithm for actuators verified its correctness. LCCABOU for actuators is also set up. Considering cost complex structure of pneumatic actuators, public device cost even method （PDCEM） is firstly presented to solve cost division of public devices such as compressors, aftercooler, receivers, etc. LCCABOU method is also effective and verified by the three groups of pneumatic actuators and electric actuators. Finally, LCEIA model of actuators is established for the environmental impact assessment of actuators. LCEIA data collection method and model establishment procedure for actuators are also put forward. With Simapro 7, LCEIA comparison results of six actuators can be obtained： Fossil fuels are the major environmental factor of pneumatic and electric actuators; Environmental impact of electric actuator is large than one of pneumatic actuator under the similar mechanical properties and working conditions of pneumatic and electric actuators. The results are correct and correspond with the actual mechanical properties of actuators. This paper proposes a comprehensive evaluation method of the actuators, which can solve the critical problem that similar electromechanical products are very difficult to be compared with each other from the angle of performance, cost and environment impact.
文摘The scarcity of housing increases as population continues to rise all over the world. Despite government efforts at providing houses, yearly demand keeps on exceeding available houses and hence the hike in rent, the cost of erecting houses and the cost of building materials. This ultimately calls for a decisive solution. This study therefore applied compliance to cost ratio (C-CR) analysis in evaluating the optimum properties of fired ceramic bricks. The optimum mix proportions of waste glass (WG) and wood saw dust (WSD) in fired bricks, that will be suitable for housing constructions were hence determined. Fired clay brick samples which contained varied proportions of WG and WSD were examined for physical, mechanical and thermal properties in line with standard procedures. The results were compared with existing standards and property evaluation index, compliance level and C-CR were applied in analyzing the results obtained. It was observed that with increasing WG content, compliance level increased. Also, cost ratio and experimental cost of each brick sample trended upward. Sample with mix proportion;20 wt% WG, 5 wt% WSD and 75 wt% clay had compliance level of 94% and C-CR index of 7.81, hence chosen as optimum mix proportion for masonry bricks.
文摘This paper presents the NUBASE2012 evaluation that contains the recommended values for nuclear and decay properties of nuclides in their ground and excited isomeric （T1/2≥ 100 ns） states. All nuclides for which some experimental information is known are considered. NUBASE2012 covers all up to date experimental data published in primary （journal articles） and secondary （mainly laboratory reports and conference proceedings） references, together with the corresponding bibliographical information. During the development of NUBASE2012, the data available in the ＂Evaluated Nuclear Structure Data File＂ （ENSDF） database were consulted, and critically assessed of their validity and completeness. Furthermore, a large amount of new and somewhat older experimental results that were missing in ENSDF were compiled, evaluated and included in NUI3ASE2012. The atomic mass values were taken from the ＂Atomic Mass Evaluation＂ （AME2012, second and third parts of the present issue）. In cases where no experimental data were available for a particular nuclide, trends in the behavior of specific properties in neighboring nuclei （TNN） were examined. This approach allowed to estimate, whenever possible, values for a range of properties, and are labeled in NUBASE2012 as ＂non-experimental＂ （flagged ＂#＂）. Evaluation procedures and policies that were used during the development of this database are presented, together with a detailed table of recommended values and their uncertainties.
基金Acknowledgements This work was supported by the National Natural Science Foundation of China （No. 21165012）, the Jiangxi Provincial Natural Science Foundation of China （No. 2010GZH0089） and the Jiangxi Provincial Education Commission Foundation of China （No. GJJ11274）.
文摘A quercetin-bonded silica gel stationary phase （QUSP） containing natural flavonoid ligand was first prepared via γ-glycidoxypropyltrimethoxysilane （KH-560） as a coupling reagent for high-performance liquid chromatography. Its chemical structure was characterized by Fourier infrared spectroscopy, elemental analysis, thermal thermogravimetry and 13C cross polarization/magic angle spinning nuclear magnetic resonance （CP/MAS NMR）. The chromatographic property of QUSP was systematically evaluated by using neutral, basic and acidic aromatic com- pounds as probes. In order to clarify its retention mechanism, a comparative study of QUSP with conventional oc- tadecylsilyl-bonded stationary phase （ODS） was also carried out under the same conditions. The results showed that the new quercetin-bonded phase exhibited an excellent reversed-phase chromatographic property with relatively weak hydrophobicity. However, it has an advantage over ODS in the fast separation of polar aromatic compounds because the quercetin ligand could provide various sites besides hydrophobicity, such as hydrogen bonding, dipole-dipole, n-n staking and charge transfer interactions. QUSP was performed in the baseline separations of ion- ized polar basic or acidic compounds, including pyridines, anilines, pyrimidines, purines and phenols with symmet- ric peak shape in common mobile phases without buffer salt within relatively short time. The natural ligands from herbs are readily available and contain a variety of active sites, which facilitate the exploration of industrial chromatographic separation materials for green products.
