Vortex-induced vibration(VIV)of an underwater manipulator in pulsating flow presents a notable engineering problem in precise control due to the velocity variation in the flow.This study investigates the VIV response ...Vortex-induced vibration(VIV)of an underwater manipulator in pulsating flow presents a notable engineering problem in precise control due to the velocity variation in the flow.This study investigates the VIV response of an underwater manipulator subjected to pulsating flow,focusing on how different postures affect the behavior of the system.The effects of pulsating parameters and manipulator arrangement on the hydrodynamic coefficient,vibration response,motion trajectory,and vortex shedding behaviors were analyzed.Results indicated that the cross flow vibration displacement in pulsating flow increased by 32.14%compared to uniform flow,inducing a shift in the motion trajectory from a crescent shape to a sideward vase shape.In the absence of interference between the upper and lower arms,the lift coefficient of the manipulator substantially increased with rising pulsating frequency,reaching a maximum increment of 67.0%.This increase in the lift coefficient led to a 67.05%rise in the vibration frequency of the manipulator in the in-line direction.As the pulsating amplitude increased,the drag coefficient of the underwater manipulator rose by 36.79%,but the vibration frequency in the cross-flow direction decreased by 56.26%.Additionally,when the upper and lower arms remained in a state of mutual interference,the cross-flow vibration amplitudes of the upper and lower arms were approximately 1.84 and 4.82 times higher in a circular-elliptical arrangement compared to an elliptical-circular arrangement,respectively.Consequently,the flow field shifted from a P+S pattern to a disordered pattern,disrupting the regularity of the motion trajectory.展开更多
The management of chronic wounds remains a substantial challenge for healthcare providers. Inadequate wound care can result in serious complications, including infection, which may ultimately lead to amputation or eve...The management of chronic wounds remains a substantial challenge for healthcare providers. Inadequate wound care can result in serious complications, including infection, which may ultimately lead to amputation or even death. While traditional excipients exhibit some efficacy in promoting wound healing, they are not sufficiently effective in preventing wound infections. As an antimicrobial metal, copper has a long history in the antimicrobial field, and at the same time, wound auxiliaries with copper ions have also been used in the treatment of chronic wounds. To address the limitations of conventional wound dressings, including insufficient antimicrobial properties and limited capacity to promote wound healing, this study introduces a highly adhesive hydrogel with superior mechanical stability for non-invasive wound treatment. The hydrogel was composed of carboxymethyl chitosan, tannic acid and copper ions. The tannic acid solution was subjected to dropwise addition of CuCl2 solution to produce precipitation, and tannic acid/copper ions (TA/Cu2+) composite nanoparticles were prepared. Through topological adhesion, the CMCS with pH sensitivity has the ability to establish adhesive connections with a wide range of materials. The benefits of CMCS/TA/Cu2+ hydrogel, as a kind of wound closure and repair material, include efficient wound closure, and resistance against bacterial invasion while maintaining cleanliness. Additionally, it exhibits excellent tensile and mechanical stability that can facilitate effective closure and repair in dynamic areas like joint wounds. This promising hydrogel adhesive has demonstrated potential as a material for wound closure and restoration.展开更多
Deep tight reservoirs exhibit complex stress and seepage fields due to varying pore structures,thus the seepage characteristics are significant for enhancing oil production.This study conducted triaxial compression an...Deep tight reservoirs exhibit complex stress and seepage fields due to varying pore structures,thus the seepage characteristics are significant for enhancing oil production.This study conducted triaxial compression and permeability tests to investigate the mechanical and seepage properties of tight sandstone.A digital core of tight sandstone was built using Computed Tomography(CT)scanning,which was divided into matrix and pore phases by a pore equivalent diameter threshold.A fluid-solid coupling model was established to investigate the seepage characteristics at micro-scale.The results showed that increasing the confining pressure decreased porosity,permeability,and flow velocity,with the pore phase becoming the dominant seepage channel.Cracks and large pores closed first under increasing pressure,resulted in a steep drop in permeability.However,permeability slightly decreased under high confining pressure,which followed a first-order exponential function.Flow velocity increased with seepage pressure.And the damage mainly occurred in stress-concentration regions under low seepage pressure.Seepage behavior followed linear Darcy flow,the damage emerged at seepage entrances under high pressure,which decreased rock elastic modulus and significantly increased permeability.展开更多
Chondrocyte senescence is a critical pathological hallmark of osteoarthritis(OA).Aberrant mechanical stress is considered a pivotal determinant in chondrocyte aging;however,the precise underlying mechanism remains elu...Chondrocyte senescence is a critical pathological hallmark of osteoarthritis(OA).Aberrant mechanical stress is considered a pivotal determinant in chondrocyte aging;however,the precise underlying mechanism remains elusive.Our findings demonstrate that SPI1 plays a significant role in counteracting chondrocyte senescence and inhibiting OA progression.SPI1 binds to the PERK promoter,thereby promoting its transcriptional activity.Importantly,PERK,rather than GCN2,facilitates eIF2αphosphorylation,activating the mitochondrial unfolded protein response(UPRmt)and impeding chondrocyte senescence.Deficiency of SPI1 in mechanical overload-induced mice leads to diminished UPRmt activation and accelerated OA progression.Intra-articular injection of adenovirus vectors overexpressing SPI1 and PERK effectively mitigates cartilage degeneration.In summary,our study elucidates the crucial regulatory role of SPI1 in the pathogenesis of chondrocyte senescence by activating UPRmt signaling through PERK,which may present a novel therapeutic target for treating OA.展开更多
Aramid papers (AP), made of aramid fibers, demonstrate superiority in electrical insulation applications. Unfortunately, the strength and electrical insulating properties of AP remain suboptimal, primarily due to the ...Aramid papers (AP), made of aramid fibers, demonstrate superiority in electrical insulation applications. Unfortunately, the strength and electrical insulating properties of AP remain suboptimal, primarily due to the smooth surface and chemical inertness of aramid fibers. Herein, AP are modified via the nacre-mimetic structure composed of aramid nanofibers (ANF) and carbonylated basalt nanosheets (CBSNs). This is achieved by impregnating AP into an ANF-CBSNs (A-C) suspension containing a 3D ANF framework as the matrix and 2D CBSNs as fillers. The resultant biomimetic composite papers (AP/A-C composite papers) exhibit a layered “brick-and-mortar” structure, demonstrating superior mechanical and electrical insulating properties. Notably, the tensile strength and breakdown strength of AP/A-C5 composite papers reach 39.69 MPa and 22.04 kV mm^(−1), respectively, representing a 155 % and 85 % increase compared to those of the control AP. These impressive properties are accompanied with excellent volume resistivity, exceptional dielectric properties, impressive folding endurance, outstanding heat insulation, and remarkable flame retardance. The nacre-inspired strategy offers an effective approach for producing highly promising electrical insulating papers for advanced electrical equipment.展开更多
This paper introduces a high-precision bandgap reference(BGR)designed for battery management systems(BMS),fea-turing an ultra-low temperature coefficient(TC)and line sensitivity(LS).The BGR employs a current-mode sche...This paper introduces a high-precision bandgap reference(BGR)designed for battery management systems(BMS),fea-turing an ultra-low temperature coefficient(TC)and line sensitivity(LS).The BGR employs a current-mode scheme with chopped op-amps and internal clock generators to eliminate op-amp offset.A low dropout regulator(LDO)and a pre-regula-tor enhance output driving and LS,respectively.Curvature compensation enhances the TC by addressing higher-order nonlinear-ity.These approaches,effective near room temperature,employs trimming at both 20 and 60°C.When combined with fixed cur-vature correction currents,it achieves an ultra-low TC for each chip.Implemented in a CMOS 180 nm process,the BGR occu-pies 0.548 mm²and operates at 2.5 V with 84μA current draw from a 5 V supply.An average TC of 2.69 ppm/℃ with two-point trimming and 0.81 ppm/℃ with multi-point trimming are achieved over the temperature range of-40 to 125℃.It accommo-dates a load current of 1 mA and an LS of 42 ppm/V,making it suitable for precise BMS applications.展开更多
With the increasingly prominent trend of globalization,English,as the common language of international communication,plays an increasingly important role in university education.As a key link in English teaching,the c...With the increasingly prominent trend of globalization,English,as the common language of international communication,plays an increasingly important role in university education.As a key link in English teaching,the college English audio-visual oral course not only imparts language knowledge and skills,but also shoulders the important task of cultivating students’critical thinking.As one of the essential core qualities of modern talents,critical thinking ability plays an irreplaceable role in students’in-depth understanding of English knowledge,improving intercultural communication ability and cultivating innovative thinking.This paper expounds the significance of cultivating students’critical thinking ability in college English audio-visual and oral teaching,and puts forward a series of innovative teaching strategies to cultivate students’critical thinking ability combined with practical teaching experience and cutting-edge education theory,in order to provide new ideas and practical guidance for the improvement of college English teaching quality and the development of students’comprehensive quality.展开更多
Repairing the endothelial barrier is essential for maintaining pulmonary fuid balance and regulating leukocyte infiltration during sepsis[1].Tissue kallikrein-related peptidases(KLKs)are secreted serine proteases invo...Repairing the endothelial barrier is essential for maintaining pulmonary fuid balance and regulating leukocyte infiltration during sepsis[1].Tissue kallikrein-related peptidases(KLKs)are secreted serine proteases involved in angiogenesis[2].However,their involvement in regulating endothelial regeneration remains largely unknown.展开更多
基金Supported by the National Natural Science Foundation of China(No.51905211)A Project of the“20 Regulations for New Universities”Funding Program of Jinan(No.202228116).
文摘Vortex-induced vibration(VIV)of an underwater manipulator in pulsating flow presents a notable engineering problem in precise control due to the velocity variation in the flow.This study investigates the VIV response of an underwater manipulator subjected to pulsating flow,focusing on how different postures affect the behavior of the system.The effects of pulsating parameters and manipulator arrangement on the hydrodynamic coefficient,vibration response,motion trajectory,and vortex shedding behaviors were analyzed.Results indicated that the cross flow vibration displacement in pulsating flow increased by 32.14%compared to uniform flow,inducing a shift in the motion trajectory from a crescent shape to a sideward vase shape.In the absence of interference between the upper and lower arms,the lift coefficient of the manipulator substantially increased with rising pulsating frequency,reaching a maximum increment of 67.0%.This increase in the lift coefficient led to a 67.05%rise in the vibration frequency of the manipulator in the in-line direction.As the pulsating amplitude increased,the drag coefficient of the underwater manipulator rose by 36.79%,but the vibration frequency in the cross-flow direction decreased by 56.26%.Additionally,when the upper and lower arms remained in a state of mutual interference,the cross-flow vibration amplitudes of the upper and lower arms were approximately 1.84 and 4.82 times higher in a circular-elliptical arrangement compared to an elliptical-circular arrangement,respectively.Consequently,the flow field shifted from a P+S pattern to a disordered pattern,disrupting the regularity of the motion trajectory.
文摘The management of chronic wounds remains a substantial challenge for healthcare providers. Inadequate wound care can result in serious complications, including infection, which may ultimately lead to amputation or even death. While traditional excipients exhibit some efficacy in promoting wound healing, they are not sufficiently effective in preventing wound infections. As an antimicrobial metal, copper has a long history in the antimicrobial field, and at the same time, wound auxiliaries with copper ions have also been used in the treatment of chronic wounds. To address the limitations of conventional wound dressings, including insufficient antimicrobial properties and limited capacity to promote wound healing, this study introduces a highly adhesive hydrogel with superior mechanical stability for non-invasive wound treatment. The hydrogel was composed of carboxymethyl chitosan, tannic acid and copper ions. The tannic acid solution was subjected to dropwise addition of CuCl2 solution to produce precipitation, and tannic acid/copper ions (TA/Cu2+) composite nanoparticles were prepared. Through topological adhesion, the CMCS with pH sensitivity has the ability to establish adhesive connections with a wide range of materials. The benefits of CMCS/TA/Cu2+ hydrogel, as a kind of wound closure and repair material, include efficient wound closure, and resistance against bacterial invasion while maintaining cleanliness. Additionally, it exhibits excellent tensile and mechanical stability that can facilitate effective closure and repair in dynamic areas like joint wounds. This promising hydrogel adhesive has demonstrated potential as a material for wound closure and restoration.
基金financially supported by the National Natural Science Foundation of China(Nos.42272153 and 42472195)the Research Fund of PetroChina Tarim Oilfield Company(No.671023060003)the Research Fund of China National Petroleum Corporation Limited(No.2023ZZ16YJ04).
文摘Deep tight reservoirs exhibit complex stress and seepage fields due to varying pore structures,thus the seepage characteristics are significant for enhancing oil production.This study conducted triaxial compression and permeability tests to investigate the mechanical and seepage properties of tight sandstone.A digital core of tight sandstone was built using Computed Tomography(CT)scanning,which was divided into matrix and pore phases by a pore equivalent diameter threshold.A fluid-solid coupling model was established to investigate the seepage characteristics at micro-scale.The results showed that increasing the confining pressure decreased porosity,permeability,and flow velocity,with the pore phase becoming the dominant seepage channel.Cracks and large pores closed first under increasing pressure,resulted in a steep drop in permeability.However,permeability slightly decreased under high confining pressure,which followed a first-order exponential function.Flow velocity increased with seepage pressure.And the damage mainly occurred in stress-concentration regions under low seepage pressure.Seepage behavior followed linear Darcy flow,the damage emerged at seepage entrances under high pressure,which decreased rock elastic modulus and significantly increased permeability.
基金supported by the Anhui Provincial Natural Science Foundation(Grant No.2308085MH250)the Natural Science Research Project of Anhui Educational Committee(Grant No.2023AH053327)the Scientific Research Fund Project of Anhui Medical University(2020xkj039).
文摘Chondrocyte senescence is a critical pathological hallmark of osteoarthritis(OA).Aberrant mechanical stress is considered a pivotal determinant in chondrocyte aging;however,the precise underlying mechanism remains elusive.Our findings demonstrate that SPI1 plays a significant role in counteracting chondrocyte senescence and inhibiting OA progression.SPI1 binds to the PERK promoter,thereby promoting its transcriptional activity.Importantly,PERK,rather than GCN2,facilitates eIF2αphosphorylation,activating the mitochondrial unfolded protein response(UPRmt)and impeding chondrocyte senescence.Deficiency of SPI1 in mechanical overload-induced mice leads to diminished UPRmt activation and accelerated OA progression.Intra-articular injection of adenovirus vectors overexpressing SPI1 and PERK effectively mitigates cartilage degeneration.In summary,our study elucidates the crucial regulatory role of SPI1 in the pathogenesis of chondrocyte senescence by activating UPRmt signaling through PERK,which may present a novel therapeutic target for treating OA.
基金supported by the National Natural Science Foundation of China(No.22278260)the Open Foundation of Key Laboratory of Auxiliary Chemistry and Technology for Chemical Industry(No.KFKT2021-14)Shaanxi Collaborative Innovation Center of Industrial Auxiliary Chemistry and Technology(No.KFKT2021-14).
文摘Aramid papers (AP), made of aramid fibers, demonstrate superiority in electrical insulation applications. Unfortunately, the strength and electrical insulating properties of AP remain suboptimal, primarily due to the smooth surface and chemical inertness of aramid fibers. Herein, AP are modified via the nacre-mimetic structure composed of aramid nanofibers (ANF) and carbonylated basalt nanosheets (CBSNs). This is achieved by impregnating AP into an ANF-CBSNs (A-C) suspension containing a 3D ANF framework as the matrix and 2D CBSNs as fillers. The resultant biomimetic composite papers (AP/A-C composite papers) exhibit a layered “brick-and-mortar” structure, demonstrating superior mechanical and electrical insulating properties. Notably, the tensile strength and breakdown strength of AP/A-C5 composite papers reach 39.69 MPa and 22.04 kV mm^(−1), respectively, representing a 155 % and 85 % increase compared to those of the control AP. These impressive properties are accompanied with excellent volume resistivity, exceptional dielectric properties, impressive folding endurance, outstanding heat insulation, and remarkable flame retardance. The nacre-inspired strategy offers an effective approach for producing highly promising electrical insulating papers for advanced electrical equipment.
基金supported by the National Natural Science Foundation of China(NSFC)under grant No.62204235。
文摘This paper introduces a high-precision bandgap reference(BGR)designed for battery management systems(BMS),fea-turing an ultra-low temperature coefficient(TC)and line sensitivity(LS).The BGR employs a current-mode scheme with chopped op-amps and internal clock generators to eliminate op-amp offset.A low dropout regulator(LDO)and a pre-regula-tor enhance output driving and LS,respectively.Curvature compensation enhances the TC by addressing higher-order nonlinear-ity.These approaches,effective near room temperature,employs trimming at both 20 and 60°C.When combined with fixed cur-vature correction currents,it achieves an ultra-low TC for each chip.Implemented in a CMOS 180 nm process,the BGR occu-pies 0.548 mm²and operates at 2.5 V with 84μA current draw from a 5 V supply.An average TC of 2.69 ppm/℃ with two-point trimming and 0.81 ppm/℃ with multi-point trimming are achieved over the temperature range of-40 to 125℃.It accommo-dates a load current of 1 mA and an LS of 42 ppm/V,making it suitable for precise BMS applications.
基金A Study on the Teaching Reform of College English Audio-Visual Oral Course Oriented towards the Cultivation of Critical Thinking Ability(2501032339)。
文摘With the increasingly prominent trend of globalization,English,as the common language of international communication,plays an increasingly important role in university education.As a key link in English teaching,the college English audio-visual oral course not only imparts language knowledge and skills,but also shoulders the important task of cultivating students’critical thinking.As one of the essential core qualities of modern talents,critical thinking ability plays an irreplaceable role in students’in-depth understanding of English knowledge,improving intercultural communication ability and cultivating innovative thinking.This paper expounds the significance of cultivating students’critical thinking ability in college English audio-visual and oral teaching,and puts forward a series of innovative teaching strategies to cultivate students’critical thinking ability combined with practical teaching experience and cutting-edge education theory,in order to provide new ideas and practical guidance for the improvement of college English teaching quality and the development of students’comprehensive quality.
基金supported by the National Natural Science Foundation of China(Grant Nos.:32171124,31871156,31971101,32271180,82272229,and 81471852)Hunan Provincial Natural Science Foundation of China(Grant No.:2021JJ31058).
文摘Repairing the endothelial barrier is essential for maintaining pulmonary fuid balance and regulating leukocyte infiltration during sepsis[1].Tissue kallikrein-related peptidases(KLKs)are secreted serine proteases involved in angiogenesis[2].However,their involvement in regulating endothelial regeneration remains largely unknown.
