The interaction problem of an elastic structure and anincompressible viscous fluid is solved through a computationalprocedure proposed in this paper. The fluid region is considered tobe bounded though without free sur...The interaction problem of an elastic structure and anincompressible viscous fluid is solved through a computationalprocedure proposed in this paper. The fluid region is considered tobe bounded though without free surface boundary. The discrete fluiddomain is described by the stream- line upwind/Petrov-Galerkin finiteelement method. The arbitrary Lagrangian-Eulerian description isemployed to treat the moving interface between the structure and thefluid. The predictor-multicorrec- tor method is adopted to solve thecoupling finite element equations. The results of three numerical ex-amples show the effectiveness of the procedure.展开更多
Calcium sulfate hemihydrate (CaSO4·0.5H2O, HH) is one of the three most commonly phases of gypsum observed in natural precipitates. Calcium sulfate hemihydrate whisker is a kind of fibriform single crystal with t...Calcium sulfate hemihydrate (CaSO4·0.5H2O, HH) is one of the three most commonly phases of gypsum observed in natural precipitates. Calcium sulfate hemihydrate whisker is a kind of fibriform single crystal with the mean diameter of 1-3 μm and the mean aspect ratio of 30–80. HH whisker was the most promising reinforcement seemed to be calcium sulfate-based due to its high intensity, high corrosion-resistance, good thermal stability, non-poisonous and low price. Thus, HH whiskers combine both reinforcement and low price, may be both effective in improving mechanical performance and extending application area.展开更多
Assessment and emergency planning to cope with disaster risks are usually founded primarily on expert evaluations, in part because local governments and public bodies mainly finance the recovery activities. Local comm...Assessment and emergency planning to cope with disaster risks are usually founded primarily on expert evaluations, in part because local governments and public bodies mainly finance the recovery activities. Local communities affected by disasters are scarcely really involved in the processes of information collection, problem analysis, or design of emergency plans.However, the development of good practices for incorporating local people’s knowledge into disaster risk management, known as Community-Based Disaster Risk Management (CBDRM), is becoming more common. Scientific communities increasingly realize the importance of local knowledge, though in Georgia this is still uncommon. Georgia faces frequent natural disasters and threats to its fragile ecosystems caused by unsustainable natural resource management and agricultural practices, improper infrastructure and urban development, as well as by innate geological and climatic factors. In this context, the lack of communication between local communities and public administrations is absolutely deleterious. The article analyzes the effectiveness of participatory methods and tools for better comprehension of people’s vulnerability and responses. Fieldwork in mountain areas of Caucasus involved local communities to investigate the direct participation of local people in Disaster Risk Management and assess their availability and interest to engage in hazard mapping and risk responses.展开更多
This article discusses the physical and kinematical characteristics of planetary nebulae accompanying PG 1159 central stars.The study is based on the parallax and proper motion measurements recently offered by the Gai...This article discusses the physical and kinematical characteristics of planetary nebulae accompanying PG 1159 central stars.The study is based on the parallax and proper motion measurements recently offered by the Gaia space mission.Two approaches were used to investigate the kinematical properties of the sample.The results revealed that most of the studied nebulae arise from progenitor stars in the mass range 0.9-1.75 M⊙.Furthermore,they tend to live within the Galactic thick disk and move with an average peculiar velocity of 61.7±19.2 km s^(-1) at a mean vertical height of 469±79 pc.The locations of the PG 1159 stars on the H-R diagram indicate that they have an average final stellar mass and evolutionary age of 0.58±0.08 M⊙and 25.5±5.3×103 yr,respectively.We found a good agreement between the mean evolutionary age of the PG 1159 stars and the mean dynamical age of their companion planetary nebulae(28.0±6.4×103 yr).展开更多
Low noise amplifier (LNA) performs as the initial amplification block in the receive path in a radio frequency (RF) receiver. In this work an ultra-wideband 3.1 10.6-GHz LNA is discussed. By using the proposed circuit...Low noise amplifier (LNA) performs as the initial amplification block in the receive path in a radio frequency (RF) receiver. In this work an ultra-wideband 3.1 10.6-GHz LNA is discussed. By using the proposed circuits for RF CMOS LNA and design methodology, the noise from the device is decreased across the ultra wide band (UWB) band. The measured noise figure is 2.66 3 dB over 3.1 10.6-GHz, while the power gain is 14 ± 0.8 dB. It consumes 23.7 mW from a 1.8 V supply. The input and output return losses (S11 & S22) are less than –11 dB over the UWB band. By using the modified derivative superposition method, the third-order intercept point IIP3 is improved noticeably. The complete circuit is based on the 0.18 μm standard RFCMOS technology and simulated with Hspice simulator.展开更多
基金The project is supported by the National Natural Sciences Foundation of Chinathe Foundation for Development of Industrial Technology of China
文摘The interaction problem of an elastic structure and anincompressible viscous fluid is solved through a computationalprocedure proposed in this paper. The fluid region is considered tobe bounded though without free surface boundary. The discrete fluiddomain is described by the stream- line upwind/Petrov-Galerkin finiteelement method. The arbitrary Lagrangian-Eulerian description isemployed to treat the moving interface between the structure and thefluid. The predictor-multicorrec- tor method is adopted to solve thecoupling finite element equations. The results of three numerical ex-amples show the effectiveness of the procedure.
文摘Calcium sulfate hemihydrate (CaSO4·0.5H2O, HH) is one of the three most commonly phases of gypsum observed in natural precipitates. Calcium sulfate hemihydrate whisker is a kind of fibriform single crystal with the mean diameter of 1-3 μm and the mean aspect ratio of 30–80. HH whisker was the most promising reinforcement seemed to be calcium sulfate-based due to its high intensity, high corrosion-resistance, good thermal stability, non-poisonous and low price. Thus, HH whiskers combine both reinforcement and low price, may be both effective in improving mechanical performance and extending application area.
文摘Assessment and emergency planning to cope with disaster risks are usually founded primarily on expert evaluations, in part because local governments and public bodies mainly finance the recovery activities. Local communities affected by disasters are scarcely really involved in the processes of information collection, problem analysis, or design of emergency plans.However, the development of good practices for incorporating local people’s knowledge into disaster risk management, known as Community-Based Disaster Risk Management (CBDRM), is becoming more common. Scientific communities increasingly realize the importance of local knowledge, though in Georgia this is still uncommon. Georgia faces frequent natural disasters and threats to its fragile ecosystems caused by unsustainable natural resource management and agricultural practices, improper infrastructure and urban development, as well as by innate geological and climatic factors. In this context, the lack of communication between local communities and public administrations is absolutely deleterious. The article analyzes the effectiveness of participatory methods and tools for better comprehension of people’s vulnerability and responses. Fieldwork in mountain areas of Caucasus involved local communities to investigate the direct participation of local people in Disaster Risk Management and assess their availability and interest to engage in hazard mapping and risk responses.
文摘This article discusses the physical and kinematical characteristics of planetary nebulae accompanying PG 1159 central stars.The study is based on the parallax and proper motion measurements recently offered by the Gaia space mission.Two approaches were used to investigate the kinematical properties of the sample.The results revealed that most of the studied nebulae arise from progenitor stars in the mass range 0.9-1.75 M⊙.Furthermore,they tend to live within the Galactic thick disk and move with an average peculiar velocity of 61.7±19.2 km s^(-1) at a mean vertical height of 469±79 pc.The locations of the PG 1159 stars on the H-R diagram indicate that they have an average final stellar mass and evolutionary age of 0.58±0.08 M⊙and 25.5±5.3×103 yr,respectively.We found a good agreement between the mean evolutionary age of the PG 1159 stars and the mean dynamical age of their companion planetary nebulae(28.0±6.4×103 yr).
文摘Low noise amplifier (LNA) performs as the initial amplification block in the receive path in a radio frequency (RF) receiver. In this work an ultra-wideband 3.1 10.6-GHz LNA is discussed. By using the proposed circuits for RF CMOS LNA and design methodology, the noise from the device is decreased across the ultra wide band (UWB) band. The measured noise figure is 2.66 3 dB over 3.1 10.6-GHz, while the power gain is 14 ± 0.8 dB. It consumes 23.7 mW from a 1.8 V supply. The input and output return losses (S11 & S22) are less than –11 dB over the UWB band. By using the modified derivative superposition method, the third-order intercept point IIP3 is improved noticeably. The complete circuit is based on the 0.18 μm standard RFCMOS technology and simulated with Hspice simulator.
