Using experimental data reflected by the sea on specific radar cross-section （SRCS） at millimeter and centimeter waves, the approximations of the wind speed, angle of the sea surface radiation and polarization of th...Using experimental data reflected by the sea on specific radar cross-section （SRCS） at millimeter and centimeter waves, the approximations of the wind speed, angle of the sea surface radiation and polarization of the incident field can be calculated. The simulation model of the scattered signal has been proposed on the basis of the semi-Markov nested processes. For the first time it has been proved that for the description of reflections at spikes and pauses, it is possible to use finite atomic functions. The proposed model allows us to estimate the baekscatter intensity of millimeter and centimeter radio waves by the sea at grazing angle of surface radiation, as well as to simulate scattered signal.展开更多
Two-dimensional(2D)transition-metal dichalcogenide materials(TMDs)alloys have a wide range of applications in the field of optoelectronics due to their capacity to achieve wide modulation of the band gap with fully tu...Two-dimensional(2D)transition-metal dichalcogenide materials(TMDs)alloys have a wide range of applications in the field of optoelectronics due to their capacity to achieve wide modulation of the band gap with fully tunable compositions.However,it is still a challenge for growing alloys with uniform components and large lateral size due to the random distribution of the crystal nucleus locations.Here,we applied a simple but effective promoter assisted liquid phase chemical vapor deposition(CVD)method,in which the quantity ratio of promoter to metal precursor can be controlled precisely,leading to tiny amounts of transition metal oxide precursors deposition onto the substrates in a highly uniform and reproducible manner,which can effectively control the uniform distribution of element components and nucleation sites.By this method,a series of monolayer Nb_(1−x)W_(x)Se_(2)alloy films with fully tunable compositions and centimeter scale have been successfully synthesized on sapphire substrates.This controllable approach opens a new way to produce large area and uniform 2D alloy film,which has the potential for the construction of optoelectronic devices with tailored spectral responses.展开更多
Hands-on Mini Lab Wor k with a partner.Set a soup can on a piece of grid paper and trace around the base,as shown at the right.1.Estimate the number of centimeter cubes that would fit at the bottom of the can.Include ...Hands-on Mini Lab Wor k with a partner.Set a soup can on a piece of grid paper and trace around the base,as shown at the right.1.Estimate the number of centimeter cubes that would fit at the bottom of the can.Include parts of cubes.2.How many layers would it take to fill the cylinder?3.Ma ke a conjecture about how you could find the volume ofthe soup can.展开更多
WHEN am I ever going to use this?WORLD RECORDS.In 2000,Joyce Samuels blew a bubble gum bubble that had a diameter of 27.94 centimeters.1.What is the smallest unit of measure?2.Explain whether a ruler whose smallest in...WHEN am I ever going to use this?WORLD RECORDS.In 2000,Joyce Samuels blew a bubble gum bubble that had a diameter of 27.94 centimeters.1.What is the smallest unit of measure?2.Explain whether a ruler whose smallest increment is 0.5 centimeter could have been used to measure the bubble.展开更多
基金National Academy of Sciences of Ukraine(NASU)and Russian Foundation for Basic Research(RFBR)2012-2013(Project #12-02-90425)
文摘Using experimental data reflected by the sea on specific radar cross-section （SRCS） at millimeter and centimeter waves, the approximations of the wind speed, angle of the sea surface radiation and polarization of the incident field can be calculated. The simulation model of the scattered signal has been proposed on the basis of the semi-Markov nested processes. For the first time it has been proved that for the description of reflections at spikes and pauses, it is possible to use finite atomic functions. The proposed model allows us to estimate the baekscatter intensity of millimeter and centimeter radio waves by the sea at grazing angle of surface radiation, as well as to simulate scattered signal.
基金the National Science Foundation of China(Nos.61922005 and U1930105)the Beijing Municipal Natural Science Foundation(No.JQ20027)+2 种基金The National Natural Science Foundation of China(No.62005003)The General Program of Science and Technology Development Project of Beijing Municipal Education Commission(No.KM202110005008)The Basic Research Foundation of Beijing University of Technology(No.048000546320504).
文摘Two-dimensional(2D)transition-metal dichalcogenide materials(TMDs)alloys have a wide range of applications in the field of optoelectronics due to their capacity to achieve wide modulation of the band gap with fully tunable compositions.However,it is still a challenge for growing alloys with uniform components and large lateral size due to the random distribution of the crystal nucleus locations.Here,we applied a simple but effective promoter assisted liquid phase chemical vapor deposition(CVD)method,in which the quantity ratio of promoter to metal precursor can be controlled precisely,leading to tiny amounts of transition metal oxide precursors deposition onto the substrates in a highly uniform and reproducible manner,which can effectively control the uniform distribution of element components and nucleation sites.By this method,a series of monolayer Nb_(1−x)W_(x)Se_(2)alloy films with fully tunable compositions and centimeter scale have been successfully synthesized on sapphire substrates.This controllable approach opens a new way to produce large area and uniform 2D alloy film,which has the potential for the construction of optoelectronic devices with tailored spectral responses.
文摘Hands-on Mini Lab Wor k with a partner.Set a soup can on a piece of grid paper and trace around the base,as shown at the right.1.Estimate the number of centimeter cubes that would fit at the bottom of the can.Include parts of cubes.2.How many layers would it take to fill the cylinder?3.Ma ke a conjecture about how you could find the volume ofthe soup can.
文摘WHEN am I ever going to use this?WORLD RECORDS.In 2000,Joyce Samuels blew a bubble gum bubble that had a diameter of 27.94 centimeters.1.What is the smallest unit of measure?2.Explain whether a ruler whose smallest increment is 0.5 centimeter could have been used to measure the bubble.
