A chatter experiment of micro-miniature turn-milling was carried out in this paper. In or- der to reduce the effect that the natural frequencies of workpieces brought to the chatter experiments of micro-miniature turn...A chatter experiment of micro-miniature turn-milling was carried out in this paper. In or- der to reduce the effect that the natural frequencies of workpieces brought to the chatter experiments of micro-miniature turn-milling, both positive and negative cone-shape workpieces were used . The chatter frequency of micro-miniature turn-milling process was obtained by the sampling and analyzing systems. Then by applying excitation experiments to the workpiece system and tool system respec- tively, the natural frequencies of these two systems were obtained. By comparing chatter frequency of micro-miniature turn-milling process with the natural frequencies of workpiece system and tool system, we found that chatter frequency of micro-miniature turn-milUng was close to the natural fre- quency of the low stiffness vibration body in the machine tool system. The funding could be useful for optimizing the structure of machine-tool and designing the machining process.展开更多
Through vector analysis the kinetic vector model is built in a machining cylinder surface through axial turn-milling. When building a kinetic vector model in the machining field, machining through axial turn-milling a...Through vector analysis the kinetic vector model is built in a machining cylinder surface through axial turn-milling. When building a kinetic vector model in the machining field, machining through axial turn-milling and using equilateral triangles and square prism surfaces, the kinetic vector model is given any equilateral polygon prismic surface. Kinetic tracks are simulated through these kinetic models respectively, thus it can be seen that the axial turn-milling is a very effective method in manufacturing any equilateral, polygon, prismic surface.展开更多
The printed circuit heat exchanger(PCHE) is receiving wide attention as a new kind of compact heat exchanger and is considered as a promising vaporizer in the LNG process. In this paper, a PCHE straight channel in the...The printed circuit heat exchanger(PCHE) is receiving wide attention as a new kind of compact heat exchanger and is considered as a promising vaporizer in the LNG process. In this paper, a PCHE straight channel in the length of 500 mm is established, with a semicircular cross section in a diameter of 1.2 mm.Numerical simulation is employed to investigate the flow and heat transfer performance of supercritical methane in the channel. The pseudo-boiling theory is adopted and the liquid-like, two-phase-like, and vapor-like regimes are divided for supercritical methane to analyze the heat transfer and flow features.The results are presented in micro segment to show the local convective heat transfer coefficient and pressure drop. It shows that the convective heat transfer coefficient in segments along the channel has a significant peak feature near the pseudo-critical point and a heat transfer deterioration when the average fluid temperature in the segment is higher than the pseudo-critical point. The reason is explained with the generation of vapor-like film near the channel wall that the peak feature related to a nucleateboiling-like state and heat transfer deterioration related to a film-boiling-like state. The effects of parameters, including mass flow rate, pressure, and wall heat flux on flow and heat transfer were analyzed.In calculating of the averaged heat transfer coefficient of the whole channel, the traditional method shows significant deviation and the micro segment weighted average method is adopted. The pressure drop can mainly be affected by the mass flux and pressure and little affected by the wall heat flux. The peak of the convective heat transfer coefficient can only form at high mass flux, low wall heat flux, and near critical pressure, in which condition the nucleate-boiling-like state is easier to appear. Moreover,heat transfer deterioration will always appear, since the supercritical flow will finally develop into a filmboiling-like state. So heat transfer deterioration should be taken seriously in the design and safe operation of vaporizer PCHE. The study of this work clarified the local heat transfer and flow feature of supercritical methane in microchannel and contributed to the deep understanding of supercritical methane flow of the vaporization process in PCHE.展开更多
Turn-milling which history dates from the end of the 20th century is one of the advanced metal cutting technologies. It could precisely machine hard materials as an alternative to turning for certain limitations. A se...Turn-milling which history dates from the end of the 20th century is one of the advanced metal cutting technologies. It could precisely machine hard materials as an alternative to turning for certain limitations. A series of orthogonal turn-milling surface veins experiments have been done on the turn-milling machining center by machining aluminum alloy,and then the nexus between the surface veins and the cutting regimes is studied. The mathematical model for surface vein direction angle is established,also the forming mechanics of surface vein direction is analyzed. Its variety regulation presents decreasing trend with as axial feed and cutter rotary speed increasing. For different eccentric distance of orthogonal turn-milling,the surface veins are different.展开更多
When machining D60 steel by high speed turn-milling under the different cooling and lubricating conditions, the cutting performance and the wear mechanism of the cermet cutter are researched. With water soluble coolin...When machining D60 steel by high speed turn-milling under the different cooling and lubricating conditions, the cutting performance and the wear mechanism of the cermet cutter are researched. With water soluble cooling fluid, the wear performance of the cermet cutter is bad, and does not adapt to the requirements of machining. However, when machining D60 by high speed turn-milling is under dry conditions, the wearing performance of the cermet cutter is very good and the cutting time lasts almost 3 hours. The wear mechanism of the cermet cutter under the water soluble cooling fluid is different from the dry condition. With the water soluble cooling fluid, a great deal of little chap units are formed since high frequency alternates heat stress. The crash and desquamate of these chap units is the main cause of the cutter wearing. Under dry cutting conditions, it is the main cause of cermet cutter wear in the felting phase intenerating causing rigid phase grains to fall.展开更多
DNA methylation has been extensively investigated in recent years,not least because of its known relationship with various diseases.Progress in analytical methods can greatly increase the relevance of DNA methylation ...DNA methylation has been extensively investigated in recent years,not least because of its known relationship with various diseases.Progress in analytical methods can greatly increase the relevance of DNA methylation studies to both clinical medicine and scientific research.Microflu-idic chips are excellent carriers for molecular analysis,and their use can provide improvements from multiple aspects.On-chip molecular analysis has received extensive attention owing to its advantages of portability,high throughput,low cost,and high efficiency.In recent years,the use of novel microfluidic chips for DNA methylation analysis has been widely reported and has shown obvious superiority to conventional methods.In this review,wefirst focus on DNA methylation and its applications.Then,we discuss advanced microfluidic-based methods for DNA methylation analysis and describe the great progress that has been made in recent years.Finally,we summarize the advantages that microfluidic technology brings to DNA methylation analysis and describe several challenges and perspectives for on-chip DNA methylation analysis.This review should help researchers improve their understanding and make progress in developing microfluidic-based methods for DNA methylation analysis.展开更多
Underground pumped storage power plant(UPSP)is an innovative concept for space recycling of abandoned mines.Its realization requires better understanding of the dynamic performance and durability of reservoir rock.Thi...Underground pumped storage power plant(UPSP)is an innovative concept for space recycling of abandoned mines.Its realization requires better understanding of the dynamic performance and durability of reservoir rock.This paper conducted ultrasonic detection,split Hopkinson pressure bar(SHPB)impact,mercury intrusion porosimetry(MIP),and backscatter electron observation(BSE)tests to investigate the dynamical behaviour and microstructure of sandstone with cyclical dry-wet damage.A coupling FEM-DEM model was constructed for reappearing mesoscopic structure damage.The results show that dry-wet cycles decrease the dynamic compressive strength(DCS)with a maximum reduction of 39.40%,the elastic limit strength is reduced from 41.75 to 25.62 MPa.The sieved fragments obtain the highest crack growth rate during the 23rd dry-wet cycle with a predictable life of 25 cycles for each rock particle.The pore fractal features of the macropores and micro-meso pores show great differences between the early and late cycles,which verifies the computational statistics analysis of particle deterioration.The numerical results show that the failure patterns are governed by the strain in pre-peak stage and the shear cracks are dominant.The dry-wet cycles reduce the energy transfer efficiency and lead to the discretization of force chain and crack fields.展开更多
Supercapacitor diode is a novel ion device that performs both supercapacitor energy storage and ion diode rectification functions.However,previously reported devices are limited by their large size and complex process...Supercapacitor diode is a novel ion device that performs both supercapacitor energy storage and ion diode rectification functions.However,previously reported devices are limited by their large size and complex processes.In this work,we demonstrate a screen-printed micro supercapacitor diode(MCAPode)that based on the insertion of a finger mode with spinel ZnCo_(2)O_(4) as cathode and activated carbon as anode for the first time,and featuring an excellent area specific capacitance(1.21 mF cm^(-2)at 10 mV s^(-1))and high rectification characteristics(rectification ratioⅠof 11.99 at 40 mV s^(-1)).Taking advantage of the ionic gel electrolyte,which provides excellent stability during repeated flexing and at high temperatures.In addition,MCAPode exhibits excellent electrochemical performance and rectification capability in"AND"and"OR"logic gates.These findings provide practical solutions for future expansion of micro supercapacitor diode applications.展开更多
基金Supported by National Defense Basic Scientific Research Project(A092000000)High Quality CNC Machine Tool and BasicManufacturing Equipment Scientific Major Project(2012ZX04010-061)
文摘A chatter experiment of micro-miniature turn-milling was carried out in this paper. In or- der to reduce the effect that the natural frequencies of workpieces brought to the chatter experiments of micro-miniature turn-milling, both positive and negative cone-shape workpieces were used . The chatter frequency of micro-miniature turn-milling process was obtained by the sampling and analyzing systems. Then by applying excitation experiments to the workpiece system and tool system respec- tively, the natural frequencies of these two systems were obtained. By comparing chatter frequency of micro-miniature turn-milling process with the natural frequencies of workpiece system and tool system, we found that chatter frequency of micro-miniature turn-milUng was close to the natural fre- quency of the low stiffness vibration body in the machine tool system. The funding could be useful for optimizing the structure of machine-tool and designing the machining process.
基金Sponsored by the National High Technology Research and Development Program of China(Grant No.2003AA424020), Important Scientech ProblemTackling Subject Foundation Under the State 9th 5 -Year Plan(Grant No.96 -A22 -01 -01) and Provincial Doctoral Science Foundation of LiaoningProvince, China(Grant No.2001102034).
文摘Through vector analysis the kinetic vector model is built in a machining cylinder surface through axial turn-milling. When building a kinetic vector model in the machining field, machining through axial turn-milling and using equilateral triangles and square prism surfaces, the kinetic vector model is given any equilateral polygon prismic surface. Kinetic tracks are simulated through these kinetic models respectively, thus it can be seen that the axial turn-milling is a very effective method in manufacturing any equilateral, polygon, prismic surface.
基金provided by Science and Technology Development Project of Jilin Province(No.20230101338JC)。
文摘The printed circuit heat exchanger(PCHE) is receiving wide attention as a new kind of compact heat exchanger and is considered as a promising vaporizer in the LNG process. In this paper, a PCHE straight channel in the length of 500 mm is established, with a semicircular cross section in a diameter of 1.2 mm.Numerical simulation is employed to investigate the flow and heat transfer performance of supercritical methane in the channel. The pseudo-boiling theory is adopted and the liquid-like, two-phase-like, and vapor-like regimes are divided for supercritical methane to analyze the heat transfer and flow features.The results are presented in micro segment to show the local convective heat transfer coefficient and pressure drop. It shows that the convective heat transfer coefficient in segments along the channel has a significant peak feature near the pseudo-critical point and a heat transfer deterioration when the average fluid temperature in the segment is higher than the pseudo-critical point. The reason is explained with the generation of vapor-like film near the channel wall that the peak feature related to a nucleateboiling-like state and heat transfer deterioration related to a film-boiling-like state. The effects of parameters, including mass flow rate, pressure, and wall heat flux on flow and heat transfer were analyzed.In calculating of the averaged heat transfer coefficient of the whole channel, the traditional method shows significant deviation and the micro segment weighted average method is adopted. The pressure drop can mainly be affected by the mass flux and pressure and little affected by the wall heat flux. The peak of the convective heat transfer coefficient can only form at high mass flux, low wall heat flux, and near critical pressure, in which condition the nucleate-boiling-like state is easier to appear. Moreover,heat transfer deterioration will always appear, since the supercritical flow will finally develop into a filmboiling-like state. So heat transfer deterioration should be taken seriously in the design and safe operation of vaporizer PCHE. The study of this work clarified the local heat transfer and flow feature of supercritical methane in microchannel and contributed to the deep understanding of supercritical methane flow of the vaporization process in PCHE.
基金Sponsored by Doctoral Science Foundation of Shenyang Ligong University (BS04007)
文摘Turn-milling which history dates from the end of the 20th century is one of the advanced metal cutting technologies. It could precisely machine hard materials as an alternative to turning for certain limitations. A series of orthogonal turn-milling surface veins experiments have been done on the turn-milling machining center by machining aluminum alloy,and then the nexus between the surface veins and the cutting regimes is studied. The mathematical model for surface vein direction angle is established,also the forming mechanics of surface vein direction is analyzed. Its variety regulation presents decreasing trend with as axial feed and cutter rotary speed increasing. For different eccentric distance of orthogonal turn-milling,the surface veins are different.
文摘When machining D60 steel by high speed turn-milling under the different cooling and lubricating conditions, the cutting performance and the wear mechanism of the cermet cutter are researched. With water soluble cooling fluid, the wear performance of the cermet cutter is bad, and does not adapt to the requirements of machining. However, when machining D60 by high speed turn-milling is under dry conditions, the wearing performance of the cermet cutter is very good and the cutting time lasts almost 3 hours. The wear mechanism of the cermet cutter under the water soluble cooling fluid is different from the dry condition. With the water soluble cooling fluid, a great deal of little chap units are formed since high frequency alternates heat stress. The crash and desquamate of these chap units is the main cause of the cutter wearing. Under dry cutting conditions, it is the main cause of cermet cutter wear in the felting phase intenerating causing rigid phase grains to fall.
基金support from the National Key R&D Program of China(Grant No.2018YFE0118700)the National Natural Science Foundation of China(NSFC Grant No.62174119)+1 种基金the 111 Project(Grant No.B07014)the Foundation for Talent Scientists of Nanchang Institute for Microtechnology of Tianjin University.
文摘DNA methylation has been extensively investigated in recent years,not least because of its known relationship with various diseases.Progress in analytical methods can greatly increase the relevance of DNA methylation studies to both clinical medicine and scientific research.Microflu-idic chips are excellent carriers for molecular analysis,and their use can provide improvements from multiple aspects.On-chip molecular analysis has received extensive attention owing to its advantages of portability,high throughput,low cost,and high efficiency.In recent years,the use of novel microfluidic chips for DNA methylation analysis has been widely reported and has shown obvious superiority to conventional methods.In this review,wefirst focus on DNA methylation and its applications.Then,we discuss advanced microfluidic-based methods for DNA methylation analysis and describe the great progress that has been made in recent years.Finally,we summarize the advantages that microfluidic technology brings to DNA methylation analysis and describe several challenges and perspectives for on-chip DNA methylation analysis.This review should help researchers improve their understanding and make progress in developing microfluidic-based methods for DNA methylation analysis.
基金the National Natural Science Foundation of China(Nos.52374147,42372328,and U23B2091)National Key Research and Development Program of China(No.2023YFC3804200)Xinjiang Uygur Autonomous Region Science and Technology Major Program(No.2023A01002).
文摘Underground pumped storage power plant(UPSP)is an innovative concept for space recycling of abandoned mines.Its realization requires better understanding of the dynamic performance and durability of reservoir rock.This paper conducted ultrasonic detection,split Hopkinson pressure bar(SHPB)impact,mercury intrusion porosimetry(MIP),and backscatter electron observation(BSE)tests to investigate the dynamical behaviour and microstructure of sandstone with cyclical dry-wet damage.A coupling FEM-DEM model was constructed for reappearing mesoscopic structure damage.The results show that dry-wet cycles decrease the dynamic compressive strength(DCS)with a maximum reduction of 39.40%,the elastic limit strength is reduced from 41.75 to 25.62 MPa.The sieved fragments obtain the highest crack growth rate during the 23rd dry-wet cycle with a predictable life of 25 cycles for each rock particle.The pore fractal features of the macropores and micro-meso pores show great differences between the early and late cycles,which verifies the computational statistics analysis of particle deterioration.The numerical results show that the failure patterns are governed by the strain in pre-peak stage and the shear cracks are dominant.The dry-wet cycles reduce the energy transfer efficiency and lead to the discretization of force chain and crack fields.
基金the financial support from the Key Project of National Natural Science Foundation of China(12131010)the National Natural Science Foundation of China(22279166)+2 种基金the Special Project for Marine Economy Development of Guangdong Province(GDNRC[2023]26)the International Cooperation Base of Infrared Reflection Liquid Crystal Polymers and Device(2015B050501010)the Guangdong Basic and Applied Basic Research Foundation(2022B1515120019)。
文摘Supercapacitor diode is a novel ion device that performs both supercapacitor energy storage and ion diode rectification functions.However,previously reported devices are limited by their large size and complex processes.In this work,we demonstrate a screen-printed micro supercapacitor diode(MCAPode)that based on the insertion of a finger mode with spinel ZnCo_(2)O_(4) as cathode and activated carbon as anode for the first time,and featuring an excellent area specific capacitance(1.21 mF cm^(-2)at 10 mV s^(-1))and high rectification characteristics(rectification ratioⅠof 11.99 at 40 mV s^(-1)).Taking advantage of the ionic gel electrolyte,which provides excellent stability during repeated flexing and at high temperatures.In addition,MCAPode exhibits excellent electrochemical performance and rectification capability in"AND"and"OR"logic gates.These findings provide practical solutions for future expansion of micro supercapacitor diode applications.
