Taking the test stopes during continuous mining induced roof caving of Tongkeng ore-body No.92 as example, the calculation flow of unloading analysis was established. According to the unloading region division method ...Taking the test stopes during continuous mining induced roof caving of Tongkeng ore-body No.92 as example, the calculation flow of unloading analysis was established. According to the unloading region division method of the affected zone theory, and the deterioration laws of mechanics parameters of unloading rock mass, the continuous mining process in underground mine was analyzed by the software MIDAS/GTS, the mechanical response of roof rock mass unloading was studied, and the differences were analyzed with the conventional simulation. The result shows that the maximum tensile stress, subsidence displacement and equivalent plastic strain of roof rock mass are 1.5 MPa, 20 cm and 1.5% in the unloading analysis, while 1.0 MPa, 13 cm and 0.9% in the conventional analysis. The values of unloading analysis, which are also closer to the actual situation, are greater than those of conventional analysis; the maximum step in continuous mining is 48 m, which shows that the induced treatment of the roof should be carried out after 2 mining steps展开更多
An InP-based one-dimensional photonic crystal quantum cascade laser is realized. With photo lithography instead of electron beam lithography and using inductively coupled plasma etching, four-period air-semiconductor ...An InP-based one-dimensional photonic crystal quantum cascade laser is realized. With photo lithography instead of electron beam lithography and using inductively coupled plasma etching, four-period air-semiconductor couples are defined as Bragg reflectors at one end of the resonator. The spectral measurement at 80K shows the quasi-continuous-wave operation with the wavelength of 5.36μm for a 22gm-wide and 2mm-long epilayer-up bonded device.展开更多
The hydrolysis process of Ru(III) complex (HL)[trans-RuC14L(dmso-S)] (L=l-methyl-l,2,4- triazole and dmso-S=S-dimethyl sulfoxide) (1), a potential antitumor complex similar to the well-known antitumor agent ...The hydrolysis process of Ru(III) complex (HL)[trans-RuC14L(dmso-S)] (L=l-methyl-l,2,4- triazole and dmso-S=S-dimethyl sulfoxide) (1), a potential antitumor complex similar to the well-known antitumor agent (Him)[trans-RuC14 (dmso-S)(im)] (NAMI-A, im=imidazole), was investigated using density functional theory combined with the conductor-like polarizable continuum model approach. Tile structural characteristics and the detailed energy profiles for the hydrolysis processes of this complex were obtained. For the first hydrolysis step, complex 1 has slightly higher barrier energies than the reported anticancer drug NAMI-A, and the result is in accordance with the experimental evidence indicating larger half-life for complex 1. For the second hydrolysis step, the formation of cis-diaqua species is thermodynamic preferred to that of trans isomers. In addition, on the basis of the analysis of electronic characteristics of species in the hydrolysis process, the trend in nucleophilic attack abilities of hydrolysis products by pertinent biomolecules is revealed and predicted.展开更多
Geotechnical stability analyses based on classical continuum may lead to remarkable underestimations on geotechnical safety.To attain better estimations on geotechnical stability,the micro-polar continuum is employed ...Geotechnical stability analyses based on classical continuum may lead to remarkable underestimations on geotechnical safety.To attain better estimations on geotechnical stability,the micro-polar continuum is employed so that its internal characteristic length(lc)can be utilized to model the shear band width.Based on two soil slope examples,the role of internal characteristic length in modeling the shear band width of geomaterial is investigated by the second-order cone programming optimized micro-polar continuum finite element method.It is recognized that the underestimation on factor of safety(FOS)calculated from the classical continuum tends to be more pronounced with the increase of lc.When the micro-polar continuum is applied,the shear band dominated by lc is almost kept unaffected as long as the adopted meshes are fine enough,but it does not generally present a slip surface like in the cases from the classical continuum,indicating that the micro-polar continuum is capable of capturing the non-local geotechnical failure characteristic.Due to the coupling effects of lc and strain softening,softening behavior of geomaterial tends to be postponed.Additionally,the bearing capacity of a geotechnical system may be significantly underestimated,if the effects of lc are not modeled or considered in numerical analyses.展开更多
Studied is the Super-continuum(SC) generation of a normal-dispersion photonic crystal fiber(PCF) using picosecond pulse excitation. In experimental analyses, a 237 nm broadband infrared continuum was generated pumped ...Studied is the Super-continuum(SC) generation of a normal-dispersion photonic crystal fiber(PCF) using picosecond pulse excitation. In experimental analyses, a 237 nm broadband infrared continuum was generated pumped at 1 550 nm(normal dispersion regime) by 1.6 ps pulses from an erbium-doped fiber laser. In addition, we conduct the numerical analyses of SC based on generalized nonlinear Schr dionger equation. The results have been applied to investigate the dominant physical processes underlie the generation of SC. We conclude that dispersion, self-phase modulation(SPM),four-wave-mixing(FWM) and Raman scattering are determinants of SC generation rather than fission of soliton in normal-dispersion PCF.展开更多
A novel control strategy for a continuous stirred tank reactor(CSTR)system,which has the typical characteristic of strongly pronounced nonlinearity,multiple operating points,and a wide operating range,is initiated fro...A novel control strategy for a continuous stirred tank reactor(CSTR)system,which has the typical characteristic of strongly pronounced nonlinearity,multiple operating points,and a wide operating range,is initiated from the point of hybrid systems.The proposed scheme makes full use of the modeling power of mixed logical dy- namical(MLD)systems to describe the highly nonlinear dynamics and multiple operating points in a unified framework as a hybrid system,and takes advantage of the good control quality of model predictive control(MPC) to design a controller.Thus,this approach avoids oscillation during switching between sub-systems,helps to relieve shaking in transition,and augments the stability robustness of the whole system,and finally achieves optimal(i.e. fast and smooth)transition between operating points.The simulation results demonstrate that the presented ap- proach has a satisfactory performance.展开更多
The ingot was prepared by direct-chill(DC)casting technology with different casting speeds under the influence of intensive melt shearing to explore the effect of casting speed and intensive melt shearing on the float...The ingot was prepared by direct-chill(DC)casting technology with different casting speeds under the influence of intensive melt shearing to explore the effect of casting speed and intensive melt shearing on the floating grains and negative centerline segregation.The results indicate that the application of intensive melt shearing in DC casting process can distribute the floating grains uniformly,reduce the area fraction of the floating grains,alleviate the negative centerline segregation,and improve the uniformity of temperature field in the sump.It is also suggested that under the influence of intensive melt shearing,the casting speed plays a crucial role in the amounts and distribution of floating grains.At low casting speed,the intensive melt shearing can significantly reduce the area fraction of the floating grains and distribute them uniformly throughout the ingot.However,this effect gradually disappears with the increase of casting speed.展开更多
An increased global supply of minerals is essential to meet the needs and expectations of a rapidly rising world population. This implies extraction from greater depths. Autonomous mining systems, developed through su...An increased global supply of minerals is essential to meet the needs and expectations of a rapidly rising world population. This implies extraction from greater depths. Autonomous mining systems, developed through sustained R&D by equipment suppliers, reduce miner exposure to hostile work environments and increase safety. This places increased focus on "ground control" and on rock mechanics to define the depth to which minerals may be extracted economically. Although significant efforts have been made since the end of World War II to apply mechanics to mine design, there have been both technological and organizational obstacles. Rock in situ is a more complex engineering material than is typically encountered in most other engineering disciplines. Mining engineering has relied heavily on empirical procedures in design for thousands of years. These are no longer adequate to address the challenges of the 21st century, as mines venture to increasingly greater depths. The development of the synthetic rock mass (SRM) in 2008 provides researchers with the ability to analyze the deformational behavior of rock masses that are anisotropic and discontinuous-attributes that were described as the defining characteristics of in situ rock by Leopold Mfiller, the president and founder of the International Society for Rock Mechanics (ISRM), in 1966. Recent developments in the numerical modeling of large-scale mining operations (e.g., caving) using the SRM reveal unanticipated deformational behavior of the rock. The application of massive parallelization and cloud computational techniques offers major opportunities: for example, to assess uncertainties in numerical predictions: to establish the mechanics basis for the empirical rules now used in rock engineering and their validity for the prediction of rock mass behavior beyond current experience: and to use the discrete element method (DEM) in the optimization of deep mine design. For the first time, mining-and rock engineering-will have its own mechanics-based Ulaboratory." This promises to be a major tool in future planning for effective mining at depth. The paper concludes with a discussion of an opportunity to demonstrate the application of DEM and SRM procedures as a laboratory, by back-analysis of mining methods used over the 80-year history of the Mount Lvell Copper Mine in Tasmania.展开更多
For a single cylinder engine, the total unbalanced inertial forces occur in the engine block, which results in engine’s vibration and deteriorated noise. In order to eliminate the unbalanced forces, counterweight and...For a single cylinder engine, the total unbalanced inertial forces occur in the engine block, which results in engine’s vibration and deteriorated noise. In order to eliminate the unbalanced forces, counterweight and primary balance shaft should be attached to the cylinder block so that engine durability and ride comfortability may be further improved. Traditionally one third of connecting rod assembly’s mass is treated as reciprocating mass, and two thirds as rotating mass when designing balance mechanism. In this paper, a new method based on the multibody dynamics simulation is introduced to separate the reciprocating mass and rotating mass of connecting rod assembly. The model consists of crankshaft, connecting rod, piston and the simulation is performed subsequently. According to the simulation results of the main bearing loads, the reciprocating mass and rotating mass are separated. Finally a new balance mechanism is designed and simulation results show that it completely balances inertial forces to improve the engine’s noise vibration and harshness performance.展开更多
This paper considers the scalar differential delay equation x(t) -μ x(t)-f(x(t-τ)), where f(x) is a decreasing continuous function. By proving that all solutions will beultimately in some interval, we give...This paper considers the scalar differential delay equation x(t) -μ x(t)-f(x(t-τ)), where f(x) is a decreasing continuous function. By proving that all solutions will beultimately in some interval, we give tile conditions under which the unique equilibrium pointof the differential delay equation is globally attractive.展开更多
The contribution of the resonant continuum to pairing correlations is investigated in the relativistic mean field theory plus Bardeen–Cooper–Schrieffer (BCS) approximation with a constant pairing strength. The reson...The contribution of the resonant continuum to pairing correlations is investigated in the relativistic mean field theory plus Bardeen–Cooper–Schrieffer (BCS) approximation with a constant pairing strength. The resonance states with their widths in the continuum are considered explicitly. The numerical study is performed in an effective Lagrangian with the parameter set NLSH for neutron-rich nucleus <SUP>84</SUP>Ni. The results show that the effect of the proper treatment of the resonant continuum on pairing correlations for nucleus close to neutron drip line is important. It is found that the problem of an unphysical particle gas could be overcome when the pairing correlation is performed by using the resonant states instead of the discretized states in the continuum.展开更多
Using transfer matrix method,the optical transmission properties of 1-D photonic crystals composed partially of negative refraction media are analyzed. The transmission spectra of periodic photonic crystal,chirped pho...Using transfer matrix method,the optical transmission properties of 1-D photonic crystals composed partially of negative refraction media are analyzed. The transmission spectra of periodic photonic crystal,chirped photonic crystal and apodized photonic crystal are numerically simulated respectively. By contrast with optical transmission properties of ordinary photo-nic crystals made of positive refraction media,the transmission spectra of apodized photonic crystal become unregular,the Bragg flat-headed area recurs but the peak of transmission does not change significantly. Futhermore,the band gap range of chirped photonic crystal diminishes gradually.展开更多
Overall dispersed side volumetric mass transfer coefficients for protein and amino acids were measured in continuous countercurrent PEG4000/KHP aqueous two-phase systems in a 57mm I.D. packed extraction column. A mode...Overall dispersed side volumetric mass transfer coefficients for protein and amino acids were measured in continuous countercurrent PEG4000/KHP aqueous two-phase systems in a 57mm I.D. packed extraction column. A model for overall dispersed side volumetric mass transfer coefficients was derived by describing the motion of the drops based upon Navier-Stokes equation combined with the relationship between mass transfer coefficients and the drop velocity. The model provides good predictions and can be successfully used in aqueous two-phase extraction. The average relative deviation between calculated values and experimental data ranges from 8% to 14%.展开更多
The development history and major technological innovations of the ultra-low pressure naphtha reforming technology with continuous catalyst regeneration in China were introduced.This technology had been adopted by the...The development history and major technological innovations of the ultra-low pressure naphtha reforming technology with continuous catalyst regeneration in China were introduced.This technology had been adopted by the 1.0 Mt/a CCR unit at the Guangzhou Company.The appropriate catalyst was selected to meet the demand of the unit capacity,the feedstock,and the product slate.The design parameters,including the reaction pressure,the octane number of C5+liquid product,the reaction temperature,the space velocity,the hydrogen/oil molar ratio,and the catalyst circulating rate,were chosen based on the study of process conditions and parameters.The commercial test results showed that the research octane number of C5+product reached 104 when the capacity of the CCR unit was 100%and 115%of the design value.The other technical targets attained or exceeded the expected value.展开更多
Michel Houellebecq is perhaps the most successful, the most famous and controversial of all current novelists writing in French. He has become a global publishing phenomenon: His books have been translated worldwide,...Michel Houellebecq is perhaps the most successful, the most famous and controversial of all current novelists writing in French. He has become a global publishing phenomenon: His books have been translated worldwide, film adaptations of his novels have been produced, and the author is the subject of a million-euro publishing deals and successive media scandals in France. The novels depict surprising forms of imaginary resources, a radiating end of the world, a post-nuclear anxiety, and depressive characters. Houellebecq shocks us leaving us in a world where the feelings of love, tenderness and goodwill have disappeared. The purpose of Houellebecq's novels is to alert about the real problems of the human society in the twenty-first century. Indeed, in the books we can easily recognize the essential features of contemporary society and the fact that the individual assumes a dehumanization process in which one has to cope with his solitude in a world of emptiness. This socio-cultural dimension is indeed the background of Houellebecq's novels, novels in which the protagonists seem to be wedged in a mechanism from which it is difficult to escape: reification and dehumanization on the one hand, "robotization" of love on the other. This article focuses on the analysis of the texts revealing the poignant characteristics of"L'Ere du vide" ("The Era of Emptiness") as described by Gilles Lipovetsky: Loneliness, the lack of love and its replacement by sexual relations.展开更多
Reinforced concrete(RC) load bearing wall is widely used in high-rise and mid-rise buildings. Due to the number of walls in plan and reduction in lateral force portion, this system is not only stronger against earthqu...Reinforced concrete(RC) load bearing wall is widely used in high-rise and mid-rise buildings. Due to the number of walls in plan and reduction in lateral force portion, this system is not only stronger against earthquakes, but also more economical. The effect of progressive collapse caused by removal of load bearing elements, in various positions in plan and stories of the RC load bearing wall system was evaluated by nonlinear dynamic and static analyses. For this purpose, three-dimensional model of 10-story structure was selected. The analysis results indicated stability, strength and stiffness of the RC load-bearing wall system against progressive collapse. It was observed that the most critical condition for removal of load bearing walls was the instantaneous removal of the surrounding walls located at the corners of the building where the sections of the load bearing elements were changed. In this case, the maximum vertical displacement was limited to 6.3 mm and the structure failed after applying the load of 10 times the axial load bored by removed elements. Comparison between the results of the nonlinear dynamic and static analyses demonstrated that the "load factor" parameter was a reasonable criterion to evaluate the progressive collapse potential of the structure.展开更多
This paper proposes a new continuity model for engineering in rock masses and a new schematic method for reporting the engineering of rock continuity. This method can be used to evaluate the mechanics of every kind of...This paper proposes a new continuity model for engineering in rock masses and a new schematic method for reporting the engineering of rock continuity. This method can be used to evaluate the mechanics of every kind of medium;and is a new way to determine the mechanical parameters used in engineering design in rock masses. In the numerical simulation, the experimental parameters of intact rock were combined with the structural properties of field rock. Theexperimental results for orthogonally-jointed rock are given. The results included the curves of the stress-strain relationship of some rock masses, the curve of the relationship between the dimension Δ and the uniaxial pressure-resistant strength σc of these rock masses, and pictures of the destructive procedure of some rock masses in uniaxial or triaxial tests, etc. Application of the method to engineering design in rock masses showed the potential of its application to engineering practice.展开更多
The particle simulation method is used to solve free-surface slurry flow problems that may be encountered in several scientific and engineering fields.The main idea behind the use of the particle simulation method is ...The particle simulation method is used to solve free-surface slurry flow problems that may be encountered in several scientific and engineering fields.The main idea behind the use of the particle simulation method is to treat granular or other materials as an assembly of many particles.Compared with the continuum-mechanics-based numerical methods such as the finite element and finite volume methods,the movement of each particle is accurately described in the particle simulation method so that the free surface of a slurry flow problem can be automatically obtained.The major advantage of using the particle simulation method is that only a simple numerical algorithm is needed to solve the governing equation of a particle simulation system.For the purpose of illustrating how to use the particle simulation method to solve free-surface flow problems,three examples involving slurry flow on three different types of river beds have been considered.The related particle simulation results obtained from these three examples have demonstrated that:1) The particle simulation method is a promising and useful method for solving free-surface flow problems encountered in both the scientific and engineering fields;2) The shape and irregular roughness of a river bed can have a significant effect on the free surface morphologies of slurry flow when it passes through the river bed.展开更多
A design of diode-pumped Nd.YAG laser with a single crystal that generates simultaneous laser action at the wavelengths of 1064 nm and 1319 nm was presented and continuous-wave (CW) of 588.9 nm was obtained for the ...A design of diode-pumped Nd.YAG laser with a single crystal that generates simultaneous laser action at the wavelengths of 1064 nm and 1319 nm was presented and continuous-wave (CW) of 588.9 nm was obtained for the first time by use of type-I critical phase-matching LBO crystal intracavity sumfrequency mixing. The maximum output power of 62 mW is achieved with an incident pump power of 1.8 W. The optical-to-optical conversion efficiency is up to 3.4% ,and the power instability in 24 h is better than ± 2.7 %.展开更多
基金Projects (50934006, 51074178) supported by the National Natural Science Foundation of ChinaProject (2010QZZD001) supported by the Fundamental Research Funds for the Central Universities of China
文摘Taking the test stopes during continuous mining induced roof caving of Tongkeng ore-body No.92 as example, the calculation flow of unloading analysis was established. According to the unloading region division method of the affected zone theory, and the deterioration laws of mechanics parameters of unloading rock mass, the continuous mining process in underground mine was analyzed by the software MIDAS/GTS, the mechanical response of roof rock mass unloading was studied, and the differences were analyzed with the conventional simulation. The result shows that the maximum tensile stress, subsidence displacement and equivalent plastic strain of roof rock mass are 1.5 MPa, 20 cm and 1.5% in the unloading analysis, while 1.0 MPa, 13 cm and 0.9% in the conventional analysis. The values of unloading analysis, which are also closer to the actual situation, are greater than those of conventional analysis; the maximum step in continuous mining is 48 m, which shows that the induced treatment of the roof should be carried out after 2 mining steps
文摘An InP-based one-dimensional photonic crystal quantum cascade laser is realized. With photo lithography instead of electron beam lithography and using inductively coupled plasma etching, four-period air-semiconductor couples are defined as Bragg reflectors at one end of the resonator. The spectral measurement at 80K shows the quasi-continuous-wave operation with the wavelength of 5.36μm for a 22gm-wide and 2mm-long epilayer-up bonded device.
基金This work was supported by the National Natural Science Foundation of China (No.20903027), the Natural Science Foundation of Guangdong Province (No.9452402301001941), and the Doctor Startup Fund of Guangdong Medical College (No.XB0802 and No.XB0804).
文摘The hydrolysis process of Ru(III) complex (HL)[trans-RuC14L(dmso-S)] (L=l-methyl-l,2,4- triazole and dmso-S=S-dimethyl sulfoxide) (1), a potential antitumor complex similar to the well-known antitumor agent (Him)[trans-RuC14 (dmso-S)(im)] (NAMI-A, im=imidazole), was investigated using density functional theory combined with the conductor-like polarizable continuum model approach. Tile structural characteristics and the detailed energy profiles for the hydrolysis processes of this complex were obtained. For the first hydrolysis step, complex 1 has slightly higher barrier energies than the reported anticancer drug NAMI-A, and the result is in accordance with the experimental evidence indicating larger half-life for complex 1. For the second hydrolysis step, the formation of cis-diaqua species is thermodynamic preferred to that of trans isomers. In addition, on the basis of the analysis of electronic characteristics of species in the hydrolysis process, the trend in nucleophilic attack abilities of hydrolysis products by pertinent biomolecules is revealed and predicted.
基金Projects(2017YFC0804602,2017YFC0404802)supported by the National Key R&D Program of ChinaProject(2019JBM092)supported by the Fundamental Research Funds for the Central Universities,China。
文摘Geotechnical stability analyses based on classical continuum may lead to remarkable underestimations on geotechnical safety.To attain better estimations on geotechnical stability,the micro-polar continuum is employed so that its internal characteristic length(lc)can be utilized to model the shear band width.Based on two soil slope examples,the role of internal characteristic length in modeling the shear band width of geomaterial is investigated by the second-order cone programming optimized micro-polar continuum finite element method.It is recognized that the underestimation on factor of safety(FOS)calculated from the classical continuum tends to be more pronounced with the increase of lc.When the micro-polar continuum is applied,the shear band dominated by lc is almost kept unaffected as long as the adopted meshes are fine enough,but it does not generally present a slip surface like in the cases from the classical continuum,indicating that the micro-polar continuum is capable of capturing the non-local geotechnical failure characteristic.Due to the coupling effects of lc and strain softening,softening behavior of geomaterial tends to be postponed.Additionally,the bearing capacity of a geotechnical system may be significantly underestimated,if the effects of lc are not modeled or considered in numerical analyses.
基金National Natural Science Foundation of China(60578043 , 60378011) Public Construction Foundation ofBeijing City(XK100130637)
文摘Studied is the Super-continuum(SC) generation of a normal-dispersion photonic crystal fiber(PCF) using picosecond pulse excitation. In experimental analyses, a 237 nm broadband infrared continuum was generated pumped at 1 550 nm(normal dispersion regime) by 1.6 ps pulses from an erbium-doped fiber laser. In addition, we conduct the numerical analyses of SC based on generalized nonlinear Schr dionger equation. The results have been applied to investigate the dominant physical processes underlie the generation of SC. We conclude that dispersion, self-phase modulation(SPM),four-wave-mixing(FWM) and Raman scattering are determinants of SC generation rather than fission of soliton in normal-dispersion PCF.
基金Supported by the National Natural Science Foundation of China (No.60404018) and the State Key Development Program for Basic Research of China (No.2002CB312200).
文摘A novel control strategy for a continuous stirred tank reactor(CSTR)system,which has the typical characteristic of strongly pronounced nonlinearity,multiple operating points,and a wide operating range,is initiated from the point of hybrid systems.The proposed scheme makes full use of the modeling power of mixed logical dy- namical(MLD)systems to describe the highly nonlinear dynamics and multiple operating points in a unified framework as a hybrid system,and takes advantage of the good control quality of model predictive control(MPC) to design a controller.Thus,this approach avoids oscillation during switching between sub-systems,helps to relieve shaking in transition,and augments the stability robustness of the whole system,and finally achieves optimal(i.e. fast and smooth)transition between operating points.The simulation results demonstrate that the presented ap- proach has a satisfactory performance.
基金the financial supports from the National Natural Science Foundation of China (51674078, 51374067)
文摘The ingot was prepared by direct-chill(DC)casting technology with different casting speeds under the influence of intensive melt shearing to explore the effect of casting speed and intensive melt shearing on the floating grains and negative centerline segregation.The results indicate that the application of intensive melt shearing in DC casting process can distribute the floating grains uniformly,reduce the area fraction of the floating grains,alleviate the negative centerline segregation,and improve the uniformity of temperature field in the sump.It is also suggested that under the influence of intensive melt shearing,the casting speed plays a crucial role in the amounts and distribution of floating grains.At low casting speed,the intensive melt shearing can significantly reduce the area fraction of the floating grains and distribute them uniformly throughout the ingot.However,this effect gradually disappears with the increase of casting speed.
文摘An increased global supply of minerals is essential to meet the needs and expectations of a rapidly rising world population. This implies extraction from greater depths. Autonomous mining systems, developed through sustained R&D by equipment suppliers, reduce miner exposure to hostile work environments and increase safety. This places increased focus on "ground control" and on rock mechanics to define the depth to which minerals may be extracted economically. Although significant efforts have been made since the end of World War II to apply mechanics to mine design, there have been both technological and organizational obstacles. Rock in situ is a more complex engineering material than is typically encountered in most other engineering disciplines. Mining engineering has relied heavily on empirical procedures in design for thousands of years. These are no longer adequate to address the challenges of the 21st century, as mines venture to increasingly greater depths. The development of the synthetic rock mass (SRM) in 2008 provides researchers with the ability to analyze the deformational behavior of rock masses that are anisotropic and discontinuous-attributes that were described as the defining characteristics of in situ rock by Leopold Mfiller, the president and founder of the International Society for Rock Mechanics (ISRM), in 1966. Recent developments in the numerical modeling of large-scale mining operations (e.g., caving) using the SRM reveal unanticipated deformational behavior of the rock. The application of massive parallelization and cloud computational techniques offers major opportunities: for example, to assess uncertainties in numerical predictions: to establish the mechanics basis for the empirical rules now used in rock engineering and their validity for the prediction of rock mass behavior beyond current experience: and to use the discrete element method (DEM) in the optimization of deep mine design. For the first time, mining-and rock engineering-will have its own mechanics-based Ulaboratory." This promises to be a major tool in future planning for effective mining at depth. The paper concludes with a discussion of an opportunity to demonstrate the application of DEM and SRM procedures as a laboratory, by back-analysis of mining methods used over the 80-year history of the Mount Lvell Copper Mine in Tasmania.
基金Supported by National Natural Science Foundation of China (No50575203)
文摘For a single cylinder engine, the total unbalanced inertial forces occur in the engine block, which results in engine’s vibration and deteriorated noise. In order to eliminate the unbalanced forces, counterweight and primary balance shaft should be attached to the cylinder block so that engine durability and ride comfortability may be further improved. Traditionally one third of connecting rod assembly’s mass is treated as reciprocating mass, and two thirds as rotating mass when designing balance mechanism. In this paper, a new method based on the multibody dynamics simulation is introduced to separate the reciprocating mass and rotating mass of connecting rod assembly. The model consists of crankshaft, connecting rod, piston and the simulation is performed subsequently. According to the simulation results of the main bearing loads, the reciprocating mass and rotating mass are separated. Finally a new balance mechanism is designed and simulation results show that it completely balances inertial forces to improve the engine’s noise vibration and harshness performance.
文摘This paper considers the scalar differential delay equation x(t) -μ x(t)-f(x(t-τ)), where f(x) is a decreasing continuous function. By proving that all solutions will beultimately in some interval, we give tile conditions under which the unique equilibrium pointof the differential delay equation is globally attractive.
文摘The contribution of the resonant continuum to pairing correlations is investigated in the relativistic mean field theory plus Bardeen–Cooper–Schrieffer (BCS) approximation with a constant pairing strength. The resonance states with their widths in the continuum are considered explicitly. The numerical study is performed in an effective Lagrangian with the parameter set NLSH for neutron-rich nucleus <SUP>84</SUP>Ni. The results show that the effect of the proper treatment of the resonant continuum on pairing correlations for nucleus close to neutron drip line is important. It is found that the problem of an unphysical particle gas could be overcome when the pairing correlation is performed by using the resonant states instead of the discretized states in the continuum.
文摘Using transfer matrix method,the optical transmission properties of 1-D photonic crystals composed partially of negative refraction media are analyzed. The transmission spectra of periodic photonic crystal,chirped photonic crystal and apodized photonic crystal are numerically simulated respectively. By contrast with optical transmission properties of ordinary photo-nic crystals made of positive refraction media,the transmission spectra of apodized photonic crystal become unregular,the Bragg flat-headed area recurs but the peak of transmission does not change significantly. Futhermore,the band gap range of chirped photonic crystal diminishes gradually.
基金Supported by the National Natural Science Foundation of China.
文摘Overall dispersed side volumetric mass transfer coefficients for protein and amino acids were measured in continuous countercurrent PEG4000/KHP aqueous two-phase systems in a 57mm I.D. packed extraction column. A model for overall dispersed side volumetric mass transfer coefficients was derived by describing the motion of the drops based upon Navier-Stokes equation combined with the relationship between mass transfer coefficients and the drop velocity. The model provides good predictions and can be successfully used in aqueous two-phase extraction. The average relative deviation between calculated values and experimental data ranges from 8% to 14%.
基金Financial support form the SINOPEC Research Program(No.107025)
文摘The development history and major technological innovations of the ultra-low pressure naphtha reforming technology with continuous catalyst regeneration in China were introduced.This technology had been adopted by the 1.0 Mt/a CCR unit at the Guangzhou Company.The appropriate catalyst was selected to meet the demand of the unit capacity,the feedstock,and the product slate.The design parameters,including the reaction pressure,the octane number of C5+liquid product,the reaction temperature,the space velocity,the hydrogen/oil molar ratio,and the catalyst circulating rate,were chosen based on the study of process conditions and parameters.The commercial test results showed that the research octane number of C5+product reached 104 when the capacity of the CCR unit was 100%and 115%of the design value.The other technical targets attained or exceeded the expected value.
文摘Michel Houellebecq is perhaps the most successful, the most famous and controversial of all current novelists writing in French. He has become a global publishing phenomenon: His books have been translated worldwide, film adaptations of his novels have been produced, and the author is the subject of a million-euro publishing deals and successive media scandals in France. The novels depict surprising forms of imaginary resources, a radiating end of the world, a post-nuclear anxiety, and depressive characters. Houellebecq shocks us leaving us in a world where the feelings of love, tenderness and goodwill have disappeared. The purpose of Houellebecq's novels is to alert about the real problems of the human society in the twenty-first century. Indeed, in the books we can easily recognize the essential features of contemporary society and the fact that the individual assumes a dehumanization process in which one has to cope with his solitude in a world of emptiness. This socio-cultural dimension is indeed the background of Houellebecq's novels, novels in which the protagonists seem to be wedged in a mechanism from which it is difficult to escape: reification and dehumanization on the one hand, "robotization" of love on the other. This article focuses on the analysis of the texts revealing the poignant characteristics of"L'Ere du vide" ("The Era of Emptiness") as described by Gilles Lipovetsky: Loneliness, the lack of love and its replacement by sexual relations.
文摘Reinforced concrete(RC) load bearing wall is widely used in high-rise and mid-rise buildings. Due to the number of walls in plan and reduction in lateral force portion, this system is not only stronger against earthquakes, but also more economical. The effect of progressive collapse caused by removal of load bearing elements, in various positions in plan and stories of the RC load bearing wall system was evaluated by nonlinear dynamic and static analyses. For this purpose, three-dimensional model of 10-story structure was selected. The analysis results indicated stability, strength and stiffness of the RC load-bearing wall system against progressive collapse. It was observed that the most critical condition for removal of load bearing walls was the instantaneous removal of the surrounding walls located at the corners of the building where the sections of the load bearing elements were changed. In this case, the maximum vertical displacement was limited to 6.3 mm and the structure failed after applying the load of 10 times the axial load bored by removed elements. Comparison between the results of the nonlinear dynamic and static analyses demonstrated that the "load factor" parameter was a reasonable criterion to evaluate the progressive collapse potential of the structure.
文摘This paper proposes a new continuity model for engineering in rock masses and a new schematic method for reporting the engineering of rock continuity. This method can be used to evaluate the mechanics of every kind of medium;and is a new way to determine the mechanical parameters used in engineering design in rock masses. In the numerical simulation, the experimental parameters of intact rock were combined with the structural properties of field rock. Theexperimental results for orthogonally-jointed rock are given. The results included the curves of the stress-strain relationship of some rock masses, the curve of the relationship between the dimension Δ and the uniaxial pressure-resistant strength σc of these rock masses, and pictures of the destructive procedure of some rock masses in uniaxial or triaxial tests, etc. Application of the method to engineering design in rock masses showed the potential of its application to engineering practice.
基金Project(11272359)supported by the National Natural Science Foundation of China
文摘The particle simulation method is used to solve free-surface slurry flow problems that may be encountered in several scientific and engineering fields.The main idea behind the use of the particle simulation method is to treat granular or other materials as an assembly of many particles.Compared with the continuum-mechanics-based numerical methods such as the finite element and finite volume methods,the movement of each particle is accurately described in the particle simulation method so that the free surface of a slurry flow problem can be automatically obtained.The major advantage of using the particle simulation method is that only a simple numerical algorithm is needed to solve the governing equation of a particle simulation system.For the purpose of illustrating how to use the particle simulation method to solve free-surface flow problems,three examples involving slurry flow on three different types of river beds have been considered.The related particle simulation results obtained from these three examples have demonstrated that:1) The particle simulation method is a promising and useful method for solving free-surface flow problems encountered in both the scientific and engineering fields;2) The shape and irregular roughness of a river bed can have a significant effect on the free surface morphologies of slurry flow when it passes through the river bed.
文摘A design of diode-pumped Nd.YAG laser with a single crystal that generates simultaneous laser action at the wavelengths of 1064 nm and 1319 nm was presented and continuous-wave (CW) of 588.9 nm was obtained for the first time by use of type-I critical phase-matching LBO crystal intracavity sumfrequency mixing. The maximum output power of 62 mW is achieved with an incident pump power of 1.8 W. The optical-to-optical conversion efficiency is up to 3.4% ,and the power instability in 24 h is better than ± 2.7 %.