Discussed in the article are the factors for the imperfect quality of piecing based on the principles and the key technologies of semiautomatic piecing. Furthermore, three measures including changing the shape of seed...Discussed in the article are the factors for the imperfect quality of piecing based on the principles and the key technologies of semiautomatic piecing. Furthermore, three measures including changing the shape of seed yarn tail, changing the feed speed and removing the damaged fibers are put forward. Experimental results prove that the former two, especial the second one, offers better piecing quality.展开更多
The principle of an automatic piecing device is presented, and the mathematic model of a specific combined mechanism of the automatic piecing device is analysed. The kinematics and dynamics equation of the combined me...The principle of an automatic piecing device is presented, and the mathematic model of a specific combined mechanism of the automatic piecing device is analysed. The kinematics and dynamics equation of the combined mechanism is established on the basis of the mathematic model. By the virtual prototype technology, the motion of this mechanism is simulated, whose result is post-processed by ADAMS. To improve the output motion, according to the simulation output and automatic piecing device's practical working condition, the optimisation of the cam mechanism is carried out by finite difference method. The simulation result of this combined mechanism turns out in accordance with its theoretical analysis of virtual prototype in this research, which, therefore, lays a principle basis for the further study of automatic piecing device.展开更多
一、阅读理解[核心素养·文化意识](2024·贵州铜仁一模) The brush pen, one of the “Four Treasures of the Study”, was invented thou-sands of years ago. However, the oldest pen was just a stick or a piece of bamb...一、阅读理解[核心素养·文化意识](2024·贵州铜仁一模) The brush pen, one of the “Four Treasures of the Study”, was invented thou-sands of years ago. However, the oldest pen was just a stick or a piece of bamboo. It was difficult for people to write well on thin silk.展开更多
Lithic miniaturization is a key adaptive and technological feature of human populations and one of the key cultural hallmarks in the Late Pleistocene of Eastern Asia.In northern China this form of stone tool technolog...Lithic miniaturization is a key adaptive and technological feature of human populations and one of the key cultural hallmarks in the Late Pleistocene of Eastern Asia.In northern China this form of stone tool technology is well represented,including by microblade technology.Lithic miniaturization has been identified in South China,though this technological feature has received little research attention in comparison to the north.Here,we examine three miniaturized lithic assemblages in South China,ranging from the terminal Pleistocene to middle Holocene.To examine technological variations in lithic miniaturization,the three assemblages were subject to comparative quantitative analyses,including principal component analysis(PCA),K-means clustering and the Zingg system.The three sites were found to exhibit varied temporal and geographic patterns of lithic miniaturization across South China,potentially related to fluctuating climatic conditions and changes in population dynamics since the Late Pleistocene.展开更多
1 Fold two pieces of paper in half from top to bottom.2 Take one piece of paper.In the center of the folded side,cut two 3-cm lines.v^Cut them 5 cm apart.3 Open the card and push the tab in from the back.
The jacket structure and transition piece comprise the supporting structure of a bottom-fixed offshore wind turbine(OWT)connected to the steel tower,which determines the overall structural dynamic performance of the e...The jacket structure and transition piece comprise the supporting structure of a bottom-fixed offshore wind turbine(OWT)connected to the steel tower,which determines the overall structural dynamic performance of the entire OWT.Ideally,optimal performance can be realized by effectively coordinating two components,notwithstanding their separate design processes.In pursuit of this objective,this paper proposes a concurrent design methodology for the jacket structure and transition piece by exploiting topology optimization(TO).The TO for a three-legged jacket foundation is formulated by minimizing static compliance.In contrast to conventional TO,two separated volume fractions are imposed upon the structural design domain of the jacket structure and transition piece to ensure continuity.A 5 MW(megawatt)OWT supported by a four-legged or three-legged jacket substructure is under investigation.The external loads are derived from various design load cases that are acquired using the commercial software platform DNV Bladed(Det Norske Veritas).Through a comparative analysis of the fundamental frequency and maximum nodal deformation,it was found that the optimized solution demonstrates a reduced weight and superior stiffness.The findings demonstrate the present concurrent design approach using TO can yield significant benefits by reducing the overall design cycle and enhancing the feasibility of the final design.展开更多
0 INTRODUCTION Changbaishan volcanism,located on the border of China and North Korea,has been a subject of extensive research due to its unique geological features and active volcanic history(Wan et al.,2024).Two prim...0 INTRODUCTION Changbaishan volcanism,located on the border of China and North Korea,has been a subject of extensive research due to its unique geological features and active volcanic history(Wan et al.,2024).Two primary models have been proposed to explain the origin of Changbaishan volcanism(CV).展开更多
Rhizoma Polygoni Bistortae has been widely used as an important medicinal herb in the Far East for a few thousand years, and it has gained more recognition in the last few decades. In the present study, we used a high...Rhizoma Polygoni Bistortae has been widely used as an important medicinal herb in the Far East for a few thousand years, and it has gained more recognition in the last few decades. In the present study, we used a high-performance capillary electrophoresis （HPCE） method for determination of the gallic acid （GA） in Quanshen （QS） pieces. The analysis of GA in QS pieces was successfully achieved in less than 6 min by capillary electrophoresis with UV detection at a wavelength of 290 nm. The background electrolyte was 20 mmol/L sodium borate solution （pH 9.00）. The separation was performed in an uncoated fused-silica capillary （52 cm^50 lam） with an effective length of 40 cm, and the applied voltage was 20 kV. Sample solutions were injected for l0 s at an atmospheric pressure of 5 KPa. The result showed good resolution and precision （the intra-day RSD was 0.37%）. The calibration curves of the standard solutions were linear in the range of 0.22-2.25 mg/mL, with correlation coefficients greater than 0.9990. The recovery of the method ranged from 100.6% to 107.9%, and the average recovery of GA was 105.9% with an RSD of 3.63%. HPCE is a powerful technology, and it is the first time to successfully apply such a method for the determination of GA in the traditional Chinese medicine.展开更多
The Song of Solomon is a series of love poems which contain 6 pieces of love poems and most part in the form of songs addressed by a man to a woman, and by the woman to the man, in order to express the love between th...The Song of Solomon is a series of love poems which contain 6 pieces of love poems and most part in the form of songs addressed by a man to a woman, and by the woman to the man, in order to express the love between them.Figures of speech are ways of making our language figurative. They can be divided into three parts, they are syntactical, semantic and phonetic rhetorical devices. These rhetorical devices can help us to heighten effect and to make the writing figuratively and vividly.These figures of speech used in the Song of Solomon make great contribution to the success description of these long songs.This essay will center on the figures of speech in the Song of Solomon.展开更多
For the purpose of analyzing the torsional vibration caused by the gravitational unbalance torque arisen in a spindle system when it is machining heavy work piece,a 10-DOF lumped parameter model was made for the machi...For the purpose of analyzing the torsional vibration caused by the gravitational unbalance torque arisen in a spindle system when it is machining heavy work piece,a 10-DOF lumped parameter model was made for the machine tool spindle system with geared transmission.By using the elementary method and Runge-Kutta method in Matlab,the eigenvalue problem was solved and the pure torsional vibration responses were obtained and examined.The results show that the spindle system cannot operate in the desired constant rotating speed as far as the gravitational unbalance torque is engaged,so it may cause bad effect on machining accuracy.And the torsional vibration increases infinitely near the resonant frequencies,so the spindle system cannot operate normally during these spindle speed ranges.展开更多
This paper presents a dual-platform scanner for dental reconstruction based on a three-dimensional(3D)laser-scanning method.The scanner combines translation and rotation platforms to perform a holistic scanning.A hybr...This paper presents a dual-platform scanner for dental reconstruction based on a three-dimensional(3D)laser-scanning method.The scanner combines translation and rotation platforms to perform a holistic scanning.A hybrid calibration method for laser scanning is proposed to improve convenience and precision.This method includes an integrative method for data collection and a hybrid algorithm for data processing.The integrative method conveniently collects a substantial number of calibrating points with a stepped gauge and a pattern for both the translation and rotation scans.The hybrid algorithm,which consists of a basic model and a compensation network,achieves strong stability with a small degree of errors.The experiments verified the hybrid calibration method and the scanner application for the measurement of dental pieces.Two typical dental pieces were measured,and the experimental results demonstrated the validity of the measurement that was performed using the dual-platform scanner.This method is effective for the 3D reconstruction of dental pieces,as well as that of objects with irregular shapes in engineering fields.展开更多
Compared with the traditional non-cutting measurement,machining tests can more accurately reflect the kinematic errors of five-axis machine tools in the actual machining process for the users.However,measurement and c...Compared with the traditional non-cutting measurement,machining tests can more accurately reflect the kinematic errors of five-axis machine tools in the actual machining process for the users.However,measurement and calculation of the machining tests in the literature are quite difficult and time-consuming.A new method of the machining tests for the trunnion axis of five-axis machine tool is proposed.Firstly,a simple mathematical model of the cradle-type five-axis machine tool was established by optimizing the coordinate system settings based on robot kinematics.Then,the machining tests based on error-sensitive directions were proposed to identify the kinematic errors of the trunnion axis of cradle-type five-axis machine tool.By adopting the error-sensitive vectors in the matrix calculation,the functional relationship equations between the machining errors of the test piece in the error-sensitive directions and the kinematic errors of C-axis and A-axis of five-axis machine tool rotary table was established based on the model of the kinematic errors.According to our previous work,the kinematic errors of C-axis can be treated as the known quantities,and the kinematic errors of A-axis can be obtained from the equations.This method was tested in Mikron UCP600 vertical machining center.The machining errors in the error-sensitive directions can be obtained by CMM inspection from the finished test piece to identify the kinematic errors of five-axis machine tool trunnion axis.Experimental results demonstrated that the proposed method can reduce the complexity,cost,and the time consumed substantially,and has a wider applicability.This paper proposes a new method of the machining tests for the trunnion axis of five-axis machine tool.展开更多
The heat transfer theory is used to set up the mathematical model to calculate the process thermal cycle of steel ingot, steel slab and steel piece. The finite difference method is used to set up difference equation t...The heat transfer theory is used to set up the mathematical model to calculate the process thermal cycle of steel ingot, steel slab and steel piece. The finite difference method is used to set up difference equation to calculate the heat transfer process. Using initial condition and boundary condition during thermal cycle, the iteration method is used to calculate the difference equation The varying law of temperature distribution with furnace temperature and heating time are obtained in the heating process of steel ingot, steel slab and in the annealing process of steel piece. The heating process of GCr15 steel ingot, M2 steel slab in re-heating furnace and the annealing process of H13 steel piece in the roller bottom furnace are designed. The new process is already used in production. Comparing with old process, practice has proved that the new process is scientific and reasonable, and meets the requirements of production. The new process can save energy and raise the productivity. The new processes win eulogy of the producer.展开更多
文摘Discussed in the article are the factors for the imperfect quality of piecing based on the principles and the key technologies of semiautomatic piecing. Furthermore, three measures including changing the shape of seed yarn tail, changing the feed speed and removing the damaged fibers are put forward. Experimental results prove that the former two, especial the second one, offers better piecing quality.
文摘The principle of an automatic piecing device is presented, and the mathematic model of a specific combined mechanism of the automatic piecing device is analysed. The kinematics and dynamics equation of the combined mechanism is established on the basis of the mathematic model. By the virtual prototype technology, the motion of this mechanism is simulated, whose result is post-processed by ADAMS. To improve the output motion, according to the simulation output and automatic piecing device's practical working condition, the optimisation of the cam mechanism is carried out by finite difference method. The simulation result of this combined mechanism turns out in accordance with its theoretical analysis of virtual prototype in this research, which, therefore, lays a principle basis for the further study of automatic piecing device.
文摘一、阅读理解[核心素养·文化意识](2024·贵州铜仁一模) The brush pen, one of the “Four Treasures of the Study”, was invented thou-sands of years ago. However, the oldest pen was just a stick or a piece of bamboo. It was difficult for people to write well on thin silk.
基金National Natural Science Foundation of China,No.42177424,No.42488201Youth Innovation Promotion Association of the Chinese Academy of Sciences,No.2020074National Key Research and Development Projects,No.2022YFF0801502。
文摘Lithic miniaturization is a key adaptive and technological feature of human populations and one of the key cultural hallmarks in the Late Pleistocene of Eastern Asia.In northern China this form of stone tool technology is well represented,including by microblade technology.Lithic miniaturization has been identified in South China,though this technological feature has received little research attention in comparison to the north.Here,we examine three miniaturized lithic assemblages in South China,ranging from the terminal Pleistocene to middle Holocene.To examine technological variations in lithic miniaturization,the three assemblages were subject to comparative quantitative analyses,including principal component analysis(PCA),K-means clustering and the Zingg system.The three sites were found to exhibit varied temporal and geographic patterns of lithic miniaturization across South China,potentially related to fluctuating climatic conditions and changes in population dynamics since the Late Pleistocene.
文摘1 Fold two pieces of paper in half from top to bottom.2 Take one piece of paper.In the center of the folded side,cut two 3-cm lines.v^Cut them 5 cm apart.3 Open the card and push the tab in from the back.
基金supports were received from the National Key Research and Development Program of China(2024YFE0208600)New Energy Joint Laboratory of China Southern Power Grid Corporation(GDXNY2024KF03)+2 种基金the National Natural Science Foundation of China(Grant No.U24B2090)National Key R&D Program(No.2022YFB4201300)Science and Technology Project of Huaneng Group(HNKJ24-H78).
文摘The jacket structure and transition piece comprise the supporting structure of a bottom-fixed offshore wind turbine(OWT)connected to the steel tower,which determines the overall structural dynamic performance of the entire OWT.Ideally,optimal performance can be realized by effectively coordinating two components,notwithstanding their separate design processes.In pursuit of this objective,this paper proposes a concurrent design methodology for the jacket structure and transition piece by exploiting topology optimization(TO).The TO for a three-legged jacket foundation is formulated by minimizing static compliance.In contrast to conventional TO,two separated volume fractions are imposed upon the structural design domain of the jacket structure and transition piece to ensure continuity.A 5 MW(megawatt)OWT supported by a four-legged or three-legged jacket substructure is under investigation.The external loads are derived from various design load cases that are acquired using the commercial software platform DNV Bladed(Det Norske Veritas).Through a comparative analysis of the fundamental frequency and maximum nodal deformation,it was found that the optimized solution demonstrates a reduced weight and superior stiffness.The findings demonstrate the present concurrent design approach using TO can yield significant benefits by reducing the overall design cycle and enhancing the feasibility of the final design.
基金support from the National Natural Science Foundation of China(No.42276049)。
文摘0 INTRODUCTION Changbaishan volcanism,located on the border of China and North Korea,has been a subject of extensive research due to its unique geological features and active volcanic history(Wan et al.,2024).Two primary models have been proposed to explain the origin of Changbaishan volcanism(CV).
基金supported by Beijing Kaiao Technology Development Co., Ltd., China and Beijing Friendship Hospital, Capital University of Medical Sciences Beijing
文摘Rhizoma Polygoni Bistortae has been widely used as an important medicinal herb in the Far East for a few thousand years, and it has gained more recognition in the last few decades. In the present study, we used a high-performance capillary electrophoresis （HPCE） method for determination of the gallic acid （GA） in Quanshen （QS） pieces. The analysis of GA in QS pieces was successfully achieved in less than 6 min by capillary electrophoresis with UV detection at a wavelength of 290 nm. The background electrolyte was 20 mmol/L sodium borate solution （pH 9.00）. The separation was performed in an uncoated fused-silica capillary （52 cm^50 lam） with an effective length of 40 cm, and the applied voltage was 20 kV. Sample solutions were injected for l0 s at an atmospheric pressure of 5 KPa. The result showed good resolution and precision （the intra-day RSD was 0.37%）. The calibration curves of the standard solutions were linear in the range of 0.22-2.25 mg/mL, with correlation coefficients greater than 0.9990. The recovery of the method ranged from 100.6% to 107.9%, and the average recovery of GA was 105.9% with an RSD of 3.63%. HPCE is a powerful technology, and it is the first time to successfully apply such a method for the determination of GA in the traditional Chinese medicine.
文摘The Song of Solomon is a series of love poems which contain 6 pieces of love poems and most part in the form of songs addressed by a man to a woman, and by the woman to the man, in order to express the love between them.Figures of speech are ways of making our language figurative. They can be divided into three parts, they are syntactical, semantic and phonetic rhetorical devices. These rhetorical devices can help us to heighten effect and to make the writing figuratively and vividly.These figures of speech used in the Song of Solomon make great contribution to the success description of these long songs.This essay will center on the figures of speech in the Song of Solomon.
基金Project(10033135-2009-11) supported by the Korean Ministry of Knowledge Economy (MKE) through HNK. Co,Ltd.
文摘For the purpose of analyzing the torsional vibration caused by the gravitational unbalance torque arisen in a spindle system when it is machining heavy work piece,a 10-DOF lumped parameter model was made for the machine tool spindle system with geared transmission.By using the elementary method and Runge-Kutta method in Matlab,the eigenvalue problem was solved and the pure torsional vibration responses were obtained and examined.The results show that the spindle system cannot operate in the desired constant rotating speed as far as the gravitational unbalance torque is engaged,so it may cause bad effect on machining accuracy.And the torsional vibration increases infinitely near the resonant frequencies,so the spindle system cannot operate normally during these spindle speed ranges.
基金the National Science Fund for Excellent Young Scholars(51722509)the National Natural Science Foundation of China(51575440)+1 种基金the National Key R&D Program of China(2017YFB1104700)the Shaanxi Science and Technology Project(2016GY-011)。
文摘This paper presents a dual-platform scanner for dental reconstruction based on a three-dimensional(3D)laser-scanning method.The scanner combines translation and rotation platforms to perform a holistic scanning.A hybrid calibration method for laser scanning is proposed to improve convenience and precision.This method includes an integrative method for data collection and a hybrid algorithm for data processing.The integrative method conveniently collects a substantial number of calibrating points with a stepped gauge and a pattern for both the translation and rotation scans.The hybrid algorithm,which consists of a basic model and a compensation network,achieves strong stability with a small degree of errors.The experiments verified the hybrid calibration method and the scanner application for the measurement of dental pieces.Two typical dental pieces were measured,and the experimental results demonstrated the validity of the measurement that was performed using the dual-platform scanner.This method is effective for the 3D reconstruction of dental pieces,as well as that of objects with irregular shapes in engineering fields.
基金Supported by National Nature Science Foundation of China(Grant No.51175461)Science Fund for Creative Research Groups of National Natural Science Foundation of China(Grant No.51221004)Program for Zhejiang Leading Team of S&T Innovation of China(Grant No.2009R50008)
文摘Compared with the traditional non-cutting measurement,machining tests can more accurately reflect the kinematic errors of five-axis machine tools in the actual machining process for the users.However,measurement and calculation of the machining tests in the literature are quite difficult and time-consuming.A new method of the machining tests for the trunnion axis of five-axis machine tool is proposed.Firstly,a simple mathematical model of the cradle-type five-axis machine tool was established by optimizing the coordinate system settings based on robot kinematics.Then,the machining tests based on error-sensitive directions were proposed to identify the kinematic errors of the trunnion axis of cradle-type five-axis machine tool.By adopting the error-sensitive vectors in the matrix calculation,the functional relationship equations between the machining errors of the test piece in the error-sensitive directions and the kinematic errors of C-axis and A-axis of five-axis machine tool rotary table was established based on the model of the kinematic errors.According to our previous work,the kinematic errors of C-axis can be treated as the known quantities,and the kinematic errors of A-axis can be obtained from the equations.This method was tested in Mikron UCP600 vertical machining center.The machining errors in the error-sensitive directions can be obtained by CMM inspection from the finished test piece to identify the kinematic errors of five-axis machine tool trunnion axis.Experimental results demonstrated that the proposed method can reduce the complexity,cost,and the time consumed substantially,and has a wider applicability.This paper proposes a new method of the machining tests for the trunnion axis of five-axis machine tool.
文摘The heat transfer theory is used to set up the mathematical model to calculate the process thermal cycle of steel ingot, steel slab and steel piece. The finite difference method is used to set up difference equation to calculate the heat transfer process. Using initial condition and boundary condition during thermal cycle, the iteration method is used to calculate the difference equation The varying law of temperature distribution with furnace temperature and heating time are obtained in the heating process of steel ingot, steel slab and in the annealing process of steel piece. The heating process of GCr15 steel ingot, M2 steel slab in re-heating furnace and the annealing process of H13 steel piece in the roller bottom furnace are designed. The new process is already used in production. Comparing with old process, practice has proved that the new process is scientific and reasonable, and meets the requirements of production. The new process can save energy and raise the productivity. The new processes win eulogy of the producer.
