Low-heat Portland(LHP)cement is a new type of Portland cement that has been widely used in recent years due to its low heat of hydration,which makes it exceptional in temperature control for mass concrete construction...Low-heat Portland(LHP)cement is a new type of Portland cement that has been widely used in recent years due to its low heat of hydration,which makes it exceptional in temperature control for mass concrete construction.However,limited studies have investigated the impact of temperature and magnesium oxide(MgO)content on LHP cement-based materials.This study utilizes thermodynamic simulations to study the hydration process,pore structure,and autogenous shrinkage of LHP cement pastes with different water-to-cement ratios(0.3,0.4,and 0.5),curing temperatures(5,15,20,and 30℃),and MgO contents(mass fractions of 2%,4%,and 5%).Higher curing temperature is found to promote the hydration reactions in cement paste.Moreover,the incorporation of 4%MgO moderately decreases both porosity and dimensional shrinkage in pastes.The microstructural evolution of different LHP pastes is examined through a comparative analysis,lending insights into LHP cement-based material applications.展开更多
An autonomous adaptive low-power instrument platform(AAL-PIP)chain of six stations has been newly established on East Antarctic Plateau along the 40°geomagnetic meridian,to investigate interhemispheric geomagneti...An autonomous adaptive low-power instrument platform(AAL-PIP)chain of six stations has been newly established on East Antarctic Plateau along the 40°geomagnetic meridian,to investigate interhemispheric geomagnetically conjugate current systems,waves,and other space weather phenomena in Polar Regions.These six stations,PG0 to PG5,which host low-power magnetometers(Fluxgate and Searchcoil),dual frequency GPS receivers,HF radio experiment,and run autonomously with solar power and two-way satellite communication,are designated at the geomagnetically conjugate(based on the International Geomagnetic Reference Field)locations of the West Greenland geomagnetic chain covering magnetic latitudes from 70°to 80°.We present the development,deployment,and operation of this chain,as well as the data collected by the chain and some preliminary scientific results showing evidence of interhemispheric asymmetries,which are important to better understand Solar Wind–Magnetosphere–Ionosphere(SWMI)coupling in Polar Regions.Recent investigations focus on magnetic impulse(MI)events,traveling convection vortices(TCVs),and ultra-low frequency(ULF)waves in the coupled southern and northern hemispheres.展开更多
Icing of wires is a product of rain, fog, and freezing rain, and is a common meteorological disaster in winter in Guizhou Province of China. It is extremely harmful to facilities such as power transmission and communi...Icing of wires is a product of rain, fog, and freezing rain, and is a common meteorological disaster in winter in Guizhou Province of China. It is extremely harmful to facilities such as power transmission and communication lines, and has caused huge economic loss up to 48.9566 billion dollars a year. Based on the meteorological records of Guizhou from 1967, we analyze the meteorological characteristics during the icing of wires, and obtain the temperature, wind speed and direction conditions of the ice accident. The icing of wires is carried out by supercooling raindrops, freezing of the clouds, freezing and spreading on the wires. Different types of supercooled raindrops and cloud freezing and freezing processes will form different types of ice accretion;wind direction and wind speed will affect the growth of ice accretion by changing the speed of sub-cooling raindrops and cloud falling. The weight of rain-type ice accretion is between 24 and 152 g, and the weight of smog-type ice is between 40 - 76 g. The average ice density of these two places can be calculated to be 0.2 - 0.5 g/cm3. The longer the icing of wires, the higher the ice disaster rate.展开更多
Wave breaking at the bow of a high-speed ship is of great importance to the hydrodynamic performance of high-speed ships,accompanied by complex flow field deformation.In this study,the smoothed particle hydrodynamics(...Wave breaking at the bow of a high-speed ship is of great importance to the hydrodynamic performance of high-speed ships,accompanied by complex flow field deformation.In this study,the smoothed particle hydrodynamics(SPH)method under the Lagrange framework is adopted to simulate the breaking bow wave of the KCS ship model.In order to improve the computational efficiency,the inflow and outflow boundary model is used to establish a numerical tank of current,and a numerical treatment for free surface separation is implemented.Numerical simulations are carried out at Fr=0.35,0.40,0.5,0.6,and different types of wave breaking such as spilling breaker,plunging breaker,and scars are captured by the SPH method,which is consistent with the experimental result,demonstrating that the present SPH method can be robust and reliable in accurately predicting the breaking bow wave phenomenon of high-speed ships.Furthermore,the wave elevation and velocity field in the bow wave region are analyzed,and the evolution of the bow wave breaking is provided.展开更多
Human-robot interaction(HRI)is becoming ubiquitous where both humans and robots perform tasks,while reliable robotic sensors are the prerequisite for efficient and safe HRI,especially in unstructured or dynamic enviro...Human-robot interaction(HRI)is becoming ubiquitous where both humans and robots perform tasks,while reliable robotic sensors are the prerequisite for efficient and safe HRI,especially in unstructured or dynamic environments.A wide spectrum of robotic sensors has been developed but most of them are limited to single or dual functionality,making it challenging to perceive complex environments.Here,we present a type of intrinsically soft robotic sensor with quadruple sensing functionalities integrated into a single device,including spatial approach sensing,thermal approach sensing,thermal touch sensing,and mechanical force sensing.Through such quadruple sensing functions,both thermal and mechanical stimulations can be well resolved in both contact and non-contact manners.More importantly,all components of the robotic sensors can be fully recycled for reuse upon the sensor's end of service,achieving superior cost-efficiency and eco-sustainability.As demonstrations,a close-loop intelligent HRI system is constructed via integrating our intrinsically soft sensors with pneumatic soft grippers and programmable robotic arms.A diversity of reliable HRI scenarios(e.g.,human-robot interfacing,object perception/classification,bedside clinical care,etc.)are successfully demonstrated leveraging the quadruple sensing functionalities.This study presents a new path to enrich robotic sensing functionality and enhance HRI reliability in complex environments.展开更多
Ionospheric irregularities can adversely affect the performance of Global Navigation Satellite System (GNSS). How-ever, this opens the possibility of using GNSS as an effective ionospheric remote sensing tool. Despite...Ionospheric irregularities can adversely affect the performance of Global Navigation Satellite System (GNSS). How-ever, this opens the possibility of using GNSS as an effective ionospheric remote sensing tool. Despite ionospheric monitoring has been undertaken for decades, these irregularities in multiple spatial and temporal scales are still not fully understood. This paper reviews Virginia Tech’s recent studies on multi-scale ionospheric irregularities using ground-based and space-based GNSS observations. First, the relevant background of ionospheric irregularities and their impact on GNSS signals is reviewed. Next, three topics of ground-based observations of ionospheric irregulari-ties for which GNSS and other ground-based techniques are used simultaneously are reviewed. Both passive and active measurements in high-latitude regions are covered. Modelling and observations in mid-latitude regions are considered as well. Emphasis is placed on the increased capability of assessing the multi-scale nature of ionospheric irregularities using other traditional techniques (e.g., radar, magnetometer, high frequency receivers) as well as GNSS observations (e.g., Total-Electron-Content or TEC, scintillation). Besides ground-based observations, recent advances in GNSS space-based ionospheric measurements are briefly reviewed. Finally, a new space-based ionospheric observa-tion technique using GNSS-based spacecraft formation flying and a differential TEC method is demonstrated using the newly developed Virginia Tech Formation Flying Testbed (VTFFTB). Based on multi-constellation multi-band GNSS, the VTFFTB has been developed into a hardware-in-the-loop simulation testbed with external high-fidelity global ionospheric model(s) for 3-satellite formation flying, which can potentially be used for new multi-scale ionospheric measurement mission design.展开更多
基金supported by the National Natural Science Foundation of China(Nos.51602229 and U2040222)the Opening Project of Key Laboratory of Advanced Civil Engineering Materials of Ministry of Education(Tongji University)+1 种基金the Joint Fund Project of Hubei Provincial Natural Science Foundation(No.2023AFD196)the Opening Funding of Henan Key Laboratory of Green Building Materials Manufacturing and Intelligent Equipment(No.2024LGSYS02),China.
文摘Low-heat Portland(LHP)cement is a new type of Portland cement that has been widely used in recent years due to its low heat of hydration,which makes it exceptional in temperature control for mass concrete construction.However,limited studies have investigated the impact of temperature and magnesium oxide(MgO)content on LHP cement-based materials.This study utilizes thermodynamic simulations to study the hydration process,pore structure,and autogenous shrinkage of LHP cement pastes with different water-to-cement ratios(0.3,0.4,and 0.5),curing temperatures(5,15,20,and 30℃),and MgO contents(mass fractions of 2%,4%,and 5%).Higher curing temperature is found to promote the hydration reactions in cement paste.Moreover,the incorporation of 4%MgO moderately decreases both porosity and dimensional shrinkage in pastes.The microstructural evolution of different LHP pastes is examined through a comparative analysis,lending insights into LHP cement-based material applications.
基金Support for the development and testing of this system has been provided through a Major Research Infrastructure (MRI) Grant ATM-922979 to Virginia Tech from the National Science Foundation, USAsupport has been provided by the National Science Foundation for the operation and scientific investigation of data from the deployed AAL-PIP stations along the Antarctic 40 magnetic meridian by Grants NSF ANT-08398585, PLR-1243398, PLR-1543364 and EAR-1520864+2 种基金Support at the University of Michigan was provided by NSF grant ANT-0838861supported by NSF grant PLR-1243225 to ASTRAfinancial support through the German Ministry for Economy and Technology and the German Center for Aviation and Space (DLR) under contract 50 OC 0302
文摘An autonomous adaptive low-power instrument platform(AAL-PIP)chain of six stations has been newly established on East Antarctic Plateau along the 40°geomagnetic meridian,to investigate interhemispheric geomagnetically conjugate current systems,waves,and other space weather phenomena in Polar Regions.These six stations,PG0 to PG5,which host low-power magnetometers(Fluxgate and Searchcoil),dual frequency GPS receivers,HF radio experiment,and run autonomously with solar power and two-way satellite communication,are designated at the geomagnetically conjugate(based on the International Geomagnetic Reference Field)locations of the West Greenland geomagnetic chain covering magnetic latitudes from 70°to 80°.We present the development,deployment,and operation of this chain,as well as the data collected by the chain and some preliminary scientific results showing evidence of interhemispheric asymmetries,which are important to better understand Solar Wind–Magnetosphere–Ionosphere(SWMI)coupling in Polar Regions.Recent investigations focus on magnetic impulse(MI)events,traveling convection vortices(TCVs),and ultra-low frequency(ULF)waves in the coupled southern and northern hemispheres.
文摘Icing of wires is a product of rain, fog, and freezing rain, and is a common meteorological disaster in winter in Guizhou Province of China. It is extremely harmful to facilities such as power transmission and communication lines, and has caused huge economic loss up to 48.9566 billion dollars a year. Based on the meteorological records of Guizhou from 1967, we analyze the meteorological characteristics during the icing of wires, and obtain the temperature, wind speed and direction conditions of the ice accident. The icing of wires is carried out by supercooling raindrops, freezing of the clouds, freezing and spreading on the wires. Different types of supercooled raindrops and cloud freezing and freezing processes will form different types of ice accretion;wind direction and wind speed will affect the growth of ice accretion by changing the speed of sub-cooling raindrops and cloud falling. The weight of rain-type ice accretion is between 24 and 152 g, and the weight of smog-type ice is between 40 - 76 g. The average ice density of these two places can be calculated to be 0.2 - 0.5 g/cm3. The longer the icing of wires, the higher the ice disaster rate.
基金The Guangdong Basic and Applied Basic Research Foundation(2024B1515020107)the National Natural Science Foundation of China(Grant Nos.52171329)+1 种基金the State Key Laboratory of Disaster Prevention&Mitigation of Explosion&Impact(Grant No.NOLGD-SKL-202201)the Fundamental Research Funds for the Central Universities,Sun Yat-sen University(Grant No.231gbi023).
文摘Wave breaking at the bow of a high-speed ship is of great importance to the hydrodynamic performance of high-speed ships,accompanied by complex flow field deformation.In this study,the smoothed particle hydrodynamics(SPH)method under the Lagrange framework is adopted to simulate the breaking bow wave of the KCS ship model.In order to improve the computational efficiency,the inflow and outflow boundary model is used to establish a numerical tank of current,and a numerical treatment for free surface separation is implemented.Numerical simulations are carried out at Fr=0.35,0.40,0.5,0.6,and different types of wave breaking such as spilling breaker,plunging breaker,and scars are captured by the SPH method,which is consistent with the experimental result,demonstrating that the present SPH method can be robust and reliable in accurately predicting the breaking bow wave phenomenon of high-speed ships.Furthermore,the wave elevation and velocity field in the bow wave region are analyzed,and the evolution of the bow wave breaking is provided.
基金financially supported by the Sichuan Science and Technology Program(2024YFFK0133 and 2023NSFSC1131)the National Natural Science Foundation of China(52203272)+1 种基金supported by the“Fundamental Research Funds for the Central Universities of China”Medical Interdisciplinary Research Key Project of Sichuan University(2022)。
文摘Human-robot interaction(HRI)is becoming ubiquitous where both humans and robots perform tasks,while reliable robotic sensors are the prerequisite for efficient and safe HRI,especially in unstructured or dynamic environments.A wide spectrum of robotic sensors has been developed but most of them are limited to single or dual functionality,making it challenging to perceive complex environments.Here,we present a type of intrinsically soft robotic sensor with quadruple sensing functionalities integrated into a single device,including spatial approach sensing,thermal approach sensing,thermal touch sensing,and mechanical force sensing.Through such quadruple sensing functions,both thermal and mechanical stimulations can be well resolved in both contact and non-contact manners.More importantly,all components of the robotic sensors can be fully recycled for reuse upon the sensor's end of service,achieving superior cost-efficiency and eco-sustainability.As demonstrations,a close-loop intelligent HRI system is constructed via integrating our intrinsically soft sensors with pneumatic soft grippers and programmable robotic arms.A diversity of reliable HRI scenarios(e.g.,human-robot interfacing,object perception/classification,bedside clinical care,etc.)are successfully demonstrated leveraging the quadruple sensing functionalities.This study presents a new path to enrich robotic sensing functionality and enhance HRI reliability in complex environments.
基金the AFOSR(Grant No.13-0658-09)Virginia Tech.Z.Xu and M.D.Hartinger were supported by NSF-1543364(Polar Experiment Network for Geospace Upper-atmosphere Investigations-PENGUIn:Interhemispheric Investigations along the 40-degree Magnetic Meridian)1744828(Collaborative Proposal:A High-Latitude Conjugate Area Array Experiment to Investigate Solar Wind-Magnetosphere-Ionosphere Coupling).
文摘Ionospheric irregularities can adversely affect the performance of Global Navigation Satellite System (GNSS). How-ever, this opens the possibility of using GNSS as an effective ionospheric remote sensing tool. Despite ionospheric monitoring has been undertaken for decades, these irregularities in multiple spatial and temporal scales are still not fully understood. This paper reviews Virginia Tech’s recent studies on multi-scale ionospheric irregularities using ground-based and space-based GNSS observations. First, the relevant background of ionospheric irregularities and their impact on GNSS signals is reviewed. Next, three topics of ground-based observations of ionospheric irregulari-ties for which GNSS and other ground-based techniques are used simultaneously are reviewed. Both passive and active measurements in high-latitude regions are covered. Modelling and observations in mid-latitude regions are considered as well. Emphasis is placed on the increased capability of assessing the multi-scale nature of ionospheric irregularities using other traditional techniques (e.g., radar, magnetometer, high frequency receivers) as well as GNSS observations (e.g., Total-Electron-Content or TEC, scintillation). Besides ground-based observations, recent advances in GNSS space-based ionospheric measurements are briefly reviewed. Finally, a new space-based ionospheric observa-tion technique using GNSS-based spacecraft formation flying and a differential TEC method is demonstrated using the newly developed Virginia Tech Formation Flying Testbed (VTFFTB). Based on multi-constellation multi-band GNSS, the VTFFTB has been developed into a hardware-in-the-loop simulation testbed with external high-fidelity global ionospheric model(s) for 3-satellite formation flying, which can potentially be used for new multi-scale ionospheric measurement mission design.
