The fresh snow density was observed with snow analyzer (Snow Fork) at Tianshan Station for Snowcover and Avalanche Research, Chinese Academy of Sciences from February 21 to March 5, 2009. Results show that fresh snow ...The fresh snow density was observed with snow analyzer (Snow Fork) at Tianshan Station for Snowcover and Avalanche Research, Chinese Academy of Sciences from February 21 to March 5, 2009. Results show that fresh snow density increases from the 5th h to the 291st h after the snowfall, with an average rate of increase of 4.0×10-4 g/(cm3·h) (R2 = 0.943). Analysis shows that fresh snow density is negatively correlated with the compac-tion rate of fresh snow (R2 = -0.960). Inversely, it is positively correlated with fresh snow viscosity (R2 = 0.896). In relation to meteorological factors, ground temperature rising at a depth of 40 cm is the major driving factor of snow density increase. The temperature increase in fresh snow layer and the decrease in depth hoar layer have the most prominent impacts on the snow density increase in the afternoon. Principal component analysis shows that the de-terminant factors of fresh snow density change can be grouped into 3 types as follows: 1) dynamic factor contributes about 69.71% to fresh snow density change, with a significant effect from the 5th h to the 106th h after the snowfall; 2) exogenous energy factor contributes about 20.91% to it, with a significant effect at the 130th h; and c) endoge-nous energy factor contributes about 9.38% to it, with a significant effect at the 130th h and the 195th h.展开更多
In this paper, the outage performance of opportunistic relay （OR） and equal gain transmissionbeamfomaing （EGT-BF） are studied in decode-and-ibrward （DF） relay networks over Nakagami-m fading channels, assuming m...In this paper, the outage performance of opportunistic relay （OR） and equal gain transmissionbeamfomaing （EGT-BF） are studied in decode-and-ibrward （DF） relay networks over Nakagami-m fading channels, assuming multiple relays are available in the networks. We derive the moment generation function （MGF） of the received signal-to-noise ratio （SNR） at the destination, then obtain the exact closedform solution of OR and the approximate closed form expression of EGT-BF in terms of outage probability respectively through numerical inversion of Laplace transform. Simulation results are given to verify the correctness of theoretical analysis. We also compare the outage performance of OR and EGT-BF with oth- er transmission strategies and find that when decoding results of relays are available at the destination, OR achieves high performance and is the optimal scheme to achieve the tradeoff between performance and overheads. When relay decoding information is unachievable, the performance of OR degrades significant- ly, and the EGT-BF is a more preferred scheme.展开更多
[ Objective] To explore the effect of expansion temperature on the release of seven kinds of Hoffmann components （CO, NNK, NH3, HCN,, BaP, crotonaldehyde and phenol） from the mainstream smoke of cigarette. [ Method]...[ Objective] To explore the effect of expansion temperature on the release of seven kinds of Hoffmann components （CO, NNK, NH3, HCN,, BaP, crotonaldehyde and phenol） from the mainstream smoke of cigarette. [ Method] The release amount of seven kinds of Hoffmann com-ponents from the mainstream smoke of cigarettes which were prepared from the cut tobacco treated under different expansion temperatures was de-termined. [ Result] Under the same expansion model, the temperature change produced certain impact on the release amount of NH~, phenol and BAP, while had no significant influence on that of CO, NNK, HCN and crotonaldehyde; under CO2 expansion model, the release amount of seven Hoffmann components was small; the reduction of expansion temperature was good for lowering the harmful index of cigarette to a certain extent. [ Conclusion] The study provides basis for optimizing the technical parameters of producinq less harmful cigarette.展开更多
Greenhouse gas emissions are the main cause of today's climate change. To address this problem, the world is in an era of new round energy transformation, and the existing energy structure is being reformed. In th...Greenhouse gas emissions are the main cause of today's climate change. To address this problem, the world is in an era of new round energy transformation, and the existing energy structure is being reformed. In this paper, according to the Chinese government's action plan for coping with climate change, the China's wind energy sustainable development goals and development route are discussed, and the countermeasures and suggestions are put forward. Wind energy is currently a kind of important renewable energy with matured technology which can be scale-up developed and put into commercial application, and in this transformation, wind energy will play a key role with other non-fossil energy sources. The development and utilization of wind energy is a systematic project, which needs to be solved from the aspects of policy, technology and management. At present, China is in the stage of transferring from "large wind power country" to "strong wind power country", opportunities and challenges coexist, and the advantages of China's socialist system could be fully used, which can concentrate power to do big things and make contribution in the process of realizing global energy transformation.展开更多
基金Under the auspices of National R & D Project of Social Welfare, Ministry of Science and Technology Development, China (No. GYHY200706008, GYHY200806011)West Light Foundation of Chinese Academy of Sciences (No. RCPY200902)
文摘The fresh snow density was observed with snow analyzer (Snow Fork) at Tianshan Station for Snowcover and Avalanche Research, Chinese Academy of Sciences from February 21 to March 5, 2009. Results show that fresh snow density increases from the 5th h to the 291st h after the snowfall, with an average rate of increase of 4.0×10-4 g/(cm3·h) (R2 = 0.943). Analysis shows that fresh snow density is negatively correlated with the compac-tion rate of fresh snow (R2 = -0.960). Inversely, it is positively correlated with fresh snow viscosity (R2 = 0.896). In relation to meteorological factors, ground temperature rising at a depth of 40 cm is the major driving factor of snow density increase. The temperature increase in fresh snow layer and the decrease in depth hoar layer have the most prominent impacts on the snow density increase in the afternoon. Principal component analysis shows that the de-terminant factors of fresh snow density change can be grouped into 3 types as follows: 1) dynamic factor contributes about 69.71% to fresh snow density change, with a significant effect from the 5th h to the 106th h after the snowfall; 2) exogenous energy factor contributes about 20.91% to it, with a significant effect at the 130th h; and c) endoge-nous energy factor contributes about 9.38% to it, with a significant effect at the 130th h and the 195th h.
基金Supported by the High Technology Research and Development Programme of China (No. 2007AA01Z2652009AA01Z247)the National Natural Science Foundation of China (No. 60972076)
文摘In this paper, the outage performance of opportunistic relay （OR） and equal gain transmissionbeamfomaing （EGT-BF） are studied in decode-and-ibrward （DF） relay networks over Nakagami-m fading channels, assuming multiple relays are available in the networks. We derive the moment generation function （MGF） of the received signal-to-noise ratio （SNR） at the destination, then obtain the exact closedform solution of OR and the approximate closed form expression of EGT-BF in terms of outage probability respectively through numerical inversion of Laplace transform. Simulation results are given to verify the correctness of theoretical analysis. We also compare the outage performance of OR and EGT-BF with oth- er transmission strategies and find that when decoding results of relays are available at the destination, OR achieves high performance and is the optimal scheme to achieve the tradeoff between performance and overheads. When relay decoding information is unachievable, the performance of OR degrades significant- ly, and the EGT-BF is a more preferred scheme.
文摘[ Objective] To explore the effect of expansion temperature on the release of seven kinds of Hoffmann components （CO, NNK, NH3, HCN,, BaP, crotonaldehyde and phenol） from the mainstream smoke of cigarette. [ Method] The release amount of seven kinds of Hoffmann com-ponents from the mainstream smoke of cigarettes which were prepared from the cut tobacco treated under different expansion temperatures was de-termined. [ Result] Under the same expansion model, the temperature change produced certain impact on the release amount of NH~, phenol and BAP, while had no significant influence on that of CO, NNK, HCN and crotonaldehyde; under CO2 expansion model, the release amount of seven Hoffmann components was small; the reduction of expansion temperature was good for lowering the harmful index of cigarette to a certain extent. [ Conclusion] The study provides basis for optimizing the technical parameters of producinq less harmful cigarette.
文摘Greenhouse gas emissions are the main cause of today's climate change. To address this problem, the world is in an era of new round energy transformation, and the existing energy structure is being reformed. In this paper, according to the Chinese government's action plan for coping with climate change, the China's wind energy sustainable development goals and development route are discussed, and the countermeasures and suggestions are put forward. Wind energy is currently a kind of important renewable energy with matured technology which can be scale-up developed and put into commercial application, and in this transformation, wind energy will play a key role with other non-fossil energy sources. The development and utilization of wind energy is a systematic project, which needs to be solved from the aspects of policy, technology and management. At present, China is in the stage of transferring from "large wind power country" to "strong wind power country", opportunities and challenges coexist, and the advantages of China's socialist system could be fully used, which can concentrate power to do big things and make contribution in the process of realizing global energy transformation.
