In recent years, researches of disseminating wireless network have been conducted for areas without network infrastructure such as disaster situation or military disputes. However, conventional method was to provide a...In recent years, researches of disseminating wireless network have been conducted for areas without network infrastructure such as disaster situation or military disputes. However, conventional method was to provide a communication infrastructure by floating large aircraft as UAV or hot-air balloon in the high air. Therefore, it was difficult to utilize previous method because it requires a lot of time and cost. But it is possible to save money and time by using a drone which is already used in many areas as a small UAV. In this paper, we design a drone that can provide wireless infrastructure using high speed Wi-Fi. After reaching the target area, the drone can provide Wi-Fi using wireless mesh network and transmit the situation of local area through attached camera. And the transmitted videos can be monitored in the control center or cell phone through application in real time. The proposed scheme provides wireless communication of up to 160 Mbps in a coverage of about 200 m and video transmission with a coverage of about 120 m, respectively.展开更多
We present capillary grip-induced stick-slip motion,a nanoscale tribological effect,where the role of a nanoscale confined water meniscus formed between a buckled sharp tip and a glass or mica surface is addressed by ...We present capillary grip-induced stick-slip motion,a nanoscale tribological effect,where the role of a nanoscale confined water meniscus formed between a buckled sharp tip and a glass or mica surface is addressed by shear dynamic force measurement.We obtained the effective elasticity,viscosity,conservative(elastic)and non-conservative(viscous)forces,energy dissipation,and lateral force using small oscillation,amplitude-modulation,and shear-mode quartz tuning fork-atomic force microscopy(QTFAFM).We distinguished the conservative and non-conservative forces by investigating the dependence of normal load and relative humidity,slip length,and stick-slip frequency.We found that the confined nanoscale water enhances the lateral forces via capillary grip-induced stick-slip on a rough surface,resulting in an increase of static lateral force(3-fold for both substrates)and kinetic lateral force(6-fold for glass,3-fold for mica).This work provides quantitative and systematic understanding of nanoscale tribology properties in humid ambient conditions and is thus useful for control of friction as well as characterization of tribology in nanomaterials and nanodevices.展开更多
文摘In recent years, researches of disseminating wireless network have been conducted for areas without network infrastructure such as disaster situation or military disputes. However, conventional method was to provide a communication infrastructure by floating large aircraft as UAV or hot-air balloon in the high air. Therefore, it was difficult to utilize previous method because it requires a lot of time and cost. But it is possible to save money and time by using a drone which is already used in many areas as a small UAV. In this paper, we design a drone that can provide wireless infrastructure using high speed Wi-Fi. After reaching the target area, the drone can provide Wi-Fi using wireless mesh network and transmit the situation of local area through attached camera. And the transmitted videos can be monitored in the control center or cell phone through application in real time. The proposed scheme provides wireless communication of up to 160 Mbps in a coverage of about 200 m and video transmission with a coverage of about 120 m, respectively.
基金the National Research Foundation of Korea(NRF)grant funded by the Korea government(Ministry of Science,ICT&Future Planning,MSIP)(Nos.2016R1A3B1908660 and 2017R1C1B5076655)(Ministry of Education and Science Technology,MEST)(No.2020R1I1A1A01070755).
文摘We present capillary grip-induced stick-slip motion,a nanoscale tribological effect,where the role of a nanoscale confined water meniscus formed between a buckled sharp tip and a glass or mica surface is addressed by shear dynamic force measurement.We obtained the effective elasticity,viscosity,conservative(elastic)and non-conservative(viscous)forces,energy dissipation,and lateral force using small oscillation,amplitude-modulation,and shear-mode quartz tuning fork-atomic force microscopy(QTFAFM).We distinguished the conservative and non-conservative forces by investigating the dependence of normal load and relative humidity,slip length,and stick-slip frequency.We found that the confined nanoscale water enhances the lateral forces via capillary grip-induced stick-slip on a rough surface,resulting in an increase of static lateral force(3-fold for both substrates)and kinetic lateral force(6-fold for glass,3-fold for mica).This work provides quantitative and systematic understanding of nanoscale tribology properties in humid ambient conditions and is thus useful for control of friction as well as characterization of tribology in nanomaterials and nanodevices.
