A wide terahertz tuning range from 0.96 THz to 7.01 THz has been demonstrated based on ring-cavity THz wave parametric oscillator with a KTiOPO_(4)(KTP)crystal.The tuning range was observed intermittently from 0.96 TH...A wide terahertz tuning range from 0.96 THz to 7.01 THz has been demonstrated based on ring-cavity THz wave parametric oscillator with a KTiOPO_(4)(KTP)crystal.The tuning range was observed intermittently from 0.96 THz to 1.87 THz,from 3.04 THz to 3.33 THz,from 4.17 THz to 4.48 THz,from 4.78 THz to 4.97 THz,from 5.125 THz to 5.168 THz,from5.44 THz to 5.97 THz,and from 6.74 THz to 7.01 THz.The dual-Stokes wavelengths resonance phenomena were observed in some certain tuning angle ranges.Through the theoretical analysis of the dispersion curve of the KTP crystal,the intermittent THz wave tuning range and dual-wavelength Stokes waves operation during angle tuning process were explained.The theoretical analysis was in good agreement with the experiment results.The maximum THz output voltage detected by Golay cell was 1.7 V at 5.7 THz under the pump energy of 210 mJ,corresponding to the THz wave output energy of5.47μJ and conversion efficiency of 2.6×10^(-5).展开更多
Due to the relatively short history of the development of the Chinese stock market,the investment philosophy and psychology of most individual investors are not particularly mature.Especially under the influence of pu...Due to the relatively short history of the development of the Chinese stock market,the investment philosophy and psychology of most individual investors are not particularly mature.Especially under the influence of public health emergencies,the individual investors’characteristic of the investment behavior in the stock market has become more obvious.This paper combines questionnaire and psychological experiments to study the factors that affect investment decisions of individual investors,and then takes COVID-19 as an example to analyze the impact of public emergencies on individual investors’investment decisions in the stock market.展开更多
Case Method originated in the 1920s and was initiated by Harvard Business School in the United States.At that time,it adopted a unique style of case study,which was based on real situations or events in business manag...Case Method originated in the 1920s and was initiated by Harvard Business School in the United States.At that time,it adopted a unique style of case study,which was based on real situations or events in business management,in this way,it is helpful to cultivate and develop students’active participation in class discussion.For investment students,specialized courses such as Investment Project Evaluation and corporate finance are concentrated in the upper grades,and in the freshman,sophomore phase has completed the Finance,finance,macroeconomics and other basic courses.On the basis of students’existing knowledge structure,the course“Investment Project Evaluation”needs to fully tap students’potential in learning and train students’practical problem-solving ability,to cultivate students’thinking ability of combining theoretical knowledge with practical cases,to avoid the teaching mode of“I tell you to listen”,and to guide students to think,analyze and solve problems actively.展开更多
Obtaining the accurate value estimation and reducing the estimation bias are the key issues in reinforcement learning.However,current methods that address the overestimation problem tend to introduce underestimation,w...Obtaining the accurate value estimation and reducing the estimation bias are the key issues in reinforcement learning.However,current methods that address the overestimation problem tend to introduce underestimation,which face a challenge of precise decision-making in many fields.To address this issue,we conduct a theoretical analysis of the underestimation bias and propose the minmax operation,which allow for flexible control of the estimation bias.Specifically,we select the maximum value of each action from multiple parallel state-action networks to create a new state-action value sequence.Then,a minimum value is selected to obtain more accurate value estimations.Moreover,based on the minmax operation,we propose two novel algorithms by combining Deep Q-Network(DQN)and Double DQN(DDQN),named minmax-DQN and minmax-DDQN.Meanwhile,we conduct theoretical analyses of the estimation bias and variance caused by our proposed minmax operation,which show that this operation significantly improves both underestimation and overestimation biases and leads to the unbiased estimation.Furthermore,the variance is also reduced,which is helpful to improve the network training stability.Finally,we conduct numerous comparative experiments in various environments,which empirically demonstrate the superiority of our method.展开更多
To mitigate the impacts of grassland degradation on the Qinghai–Tibetan Plateau(QTP), in recent decades China has been implementing large-scale conservation programs and has invested about 42 billion CNY(7 billion US...To mitigate the impacts of grassland degradation on the Qinghai–Tibetan Plateau(QTP), in recent decades China has been implementing large-scale conservation programs and has invested about 42 billion CNY(7 billion USD). However, these programs are faced with major challenges involving trade-offs between ecological function, livestock production and income of pastoralists.Scientific assessments, as well as technical and policy issues, have not fully captured the complex ecological,social and economic dynamics of the challenges facing grassland management on the QTP. Pastoral livestock production on the QTP is characterized by imbalance in both quality and quantity between livestock seasonal nutrient requirements and herbage production, which forces pastoralists to keep larger numbers of livestock for longer periods, leading to overgrazing. To solve these problems, an integrated crop-livestock system is promoted to improve the efficiency of livestock production and conserve natural grassland as well for a sustainable system for the QTP.展开更多
We have demonstrated a high-average-power,high-repetition-rate optical terahertz(THz)source based on difference frequency generation(DFG)in the GaSe crystal by using a near-degenerate 2μm intracavity KTP optical para...We have demonstrated a high-average-power,high-repetition-rate optical terahertz(THz)source based on difference frequency generation(DFG)in the GaSe crystal by using a near-degenerate 2μm intracavity KTP optical parametric oscillator as the pump source.The power of the 2μm dual-wavelength laser was up to 12.33 W with continuous tuning ranges of 1988.0–2196.2 nm/2278.4–2065.6 nm for two waves.Different GaSe cystal lengths have been experimentally investigated for the DFG THz source in order to optimize the THz output power,which was in good agreement with the theoretical analysis.Based on an 8 mm long GaSe crystal,the THz wave was continuously tuned from 0.21 to 3 THz.The maximum THz average power of 1.66μW was obtained at repetition rate of 10 kHz under 1.48 THz.The single pulse energy amounted to 166 pJ and the conversion efficiency from 2 μm laser to THz output was 1.68×10^(-6).The signal-to-noise ratio of the detected THz voltage was 23 dB.The acceptance angle of DFG in the GaSe crystal was measured to be 0.16°.展开更多
Often referred to as the“Third Pole,”China’s Qinghai-Tibetan Plateau developed large amounts of peatland owing to its unique alpine environment.As a renewable resource,peat helps to regulate the climate as well as ...Often referred to as the“Third Pole,”China’s Qinghai-Tibetan Plateau developed large amounts of peatland owing to its unique alpine environment.As a renewable resource,peat helps to regulate the climate as well as performing other important functions.However,in recent years,intensifying climate change and anthropogenic disturbances have resulted in peatland degradation and consequently made sustainable development of peatland more difficult.This review summarizes peatland ecological and economic functions,including carbon sequestration,biodiversity conservation,energy supplies,and ecotourism.It identifies climate change and anthropogenic disturbances as the two key factors attributing to peatland degradation and ecosystem carbon loss.Current problems in environmental degradation and future challenges in peatland management under the effects of global warming are also discussed and highlighted.展开更多
基金Project supported by the National Basic Research Program of China(Grant Nos.2015CB755403 and 2014CB339802)the National Key Research and Development Program of China(Grant No.2016YFC0101001)+2 种基金the National Natural Science Foundation of China(Grant Nos.61775160,61771332,and 61471257)China Postdoctoral Science Foundation(Grant No.2016M602954)Postdoctoral Science Foundation of Chongqing,China(Grant No.Xm2016021)
文摘A wide terahertz tuning range from 0.96 THz to 7.01 THz has been demonstrated based on ring-cavity THz wave parametric oscillator with a KTiOPO_(4)(KTP)crystal.The tuning range was observed intermittently from 0.96 THz to 1.87 THz,from 3.04 THz to 3.33 THz,from 4.17 THz to 4.48 THz,from 4.78 THz to 4.97 THz,from 5.125 THz to 5.168 THz,from5.44 THz to 5.97 THz,and from 6.74 THz to 7.01 THz.The dual-Stokes wavelengths resonance phenomena were observed in some certain tuning angle ranges.Through the theoretical analysis of the dispersion curve of the KTP crystal,the intermittent THz wave tuning range and dual-wavelength Stokes waves operation during angle tuning process were explained.The theoretical analysis was in good agreement with the experiment results.The maximum THz output voltage detected by Golay cell was 1.7 V at 5.7 THz under the pump energy of 210 mJ,corresponding to the THz wave output energy of5.47μJ and conversion efficiency of 2.6×10^(-5).
文摘Due to the relatively short history of the development of the Chinese stock market,the investment philosophy and psychology of most individual investors are not particularly mature.Especially under the influence of public health emergencies,the individual investors’characteristic of the investment behavior in the stock market has become more obvious.This paper combines questionnaire and psychological experiments to study the factors that affect investment decisions of individual investors,and then takes COVID-19 as an example to analyze the impact of public emergencies on individual investors’investment decisions in the stock market.
基金Achievement of teaching reform research project in Sichuan University of Science&Engineering[JG1963]。
文摘Case Method originated in the 1920s and was initiated by Harvard Business School in the United States.At that time,it adopted a unique style of case study,which was based on real situations or events in business management,in this way,it is helpful to cultivate and develop students’active participation in class discussion.For investment students,specialized courses such as Investment Project Evaluation and corporate finance are concentrated in the upper grades,and in the freshman,sophomore phase has completed the Finance,finance,macroeconomics and other basic courses.On the basis of students’existing knowledge structure,the course“Investment Project Evaluation”needs to fully tap students’potential in learning and train students’practical problem-solving ability,to cultivate students’thinking ability of combining theoretical knowledge with practical cases,to avoid the teaching mode of“I tell you to listen”,and to guide students to think,analyze and solve problems actively.
基金supported by the National Natural Science Foundation of China(No.62173272).
文摘Obtaining the accurate value estimation and reducing the estimation bias are the key issues in reinforcement learning.However,current methods that address the overestimation problem tend to introduce underestimation,which face a challenge of precise decision-making in many fields.To address this issue,we conduct a theoretical analysis of the underestimation bias and propose the minmax operation,which allow for flexible control of the estimation bias.Specifically,we select the maximum value of each action from multiple parallel state-action networks to create a new state-action value sequence.Then,a minimum value is selected to obtain more accurate value estimations.Moreover,based on the minmax operation,we propose two novel algorithms by combining Deep Q-Network(DQN)and Double DQN(DDQN),named minmax-DQN and minmax-DDQN.Meanwhile,we conduct theoretical analyses of the estimation bias and variance caused by our proposed minmax operation,which show that this operation significantly improves both underestimation and overestimation biases and leads to the unbiased estimation.Furthermore,the variance is also reduced,which is helpful to improve the network training stability.Finally,we conduct numerous comparative experiments in various environments,which empirically demonstrate the superiority of our method.
基金funded by the National Key Research and Development Program (2016YFC0501905)the Science and Technology Service Network Initiative of Chinese Academy of Sciences (KFJ-STS-ZDTP-013)
文摘To mitigate the impacts of grassland degradation on the Qinghai–Tibetan Plateau(QTP), in recent decades China has been implementing large-scale conservation programs and has invested about 42 billion CNY(7 billion USD). However, these programs are faced with major challenges involving trade-offs between ecological function, livestock production and income of pastoralists.Scientific assessments, as well as technical and policy issues, have not fully captured the complex ecological,social and economic dynamics of the challenges facing grassland management on the QTP. Pastoral livestock production on the QTP is characterized by imbalance in both quality and quantity between livestock seasonal nutrient requirements and herbage production, which forces pastoralists to keep larger numbers of livestock for longer periods, leading to overgrazing. To solve these problems, an integrated crop-livestock system is promoted to improve the efficiency of livestock production and conserve natural grassland as well for a sustainable system for the QTP.
基金National Basic Research Program of China(973)(2014CB339802,2015CB755403)National key research and development projects(2016YFC0101001)+5 种基金National Key Technology R&D Program of China(2014BAI04B05,2015BAI01B01)National Natural Science Foundation of China(NSFC)(61107086,61471257,81402067)Natural Science Foundation of Tianjin City(14JCQNJC02200)Postdoctoral Science Foundation of Chongqing(Xm2016021)Joint Incubation Project of Southwest Hospital(SWH2016LHJC-04,SWH2016LHJC-01)Science and Technology Support Program of Tianjin(13ZCZDSF02300)
文摘We have demonstrated a high-average-power,high-repetition-rate optical terahertz(THz)source based on difference frequency generation(DFG)in the GaSe crystal by using a near-degenerate 2μm intracavity KTP optical parametric oscillator as the pump source.The power of the 2μm dual-wavelength laser was up to 12.33 W with continuous tuning ranges of 1988.0–2196.2 nm/2278.4–2065.6 nm for two waves.Different GaSe cystal lengths have been experimentally investigated for the DFG THz source in order to optimize the THz output power,which was in good agreement with the theoretical analysis.Based on an 8 mm long GaSe crystal,the THz wave was continuously tuned from 0.21 to 3 THz.The maximum THz average power of 1.66μW was obtained at repetition rate of 10 kHz under 1.48 THz.The single pulse energy amounted to 166 pJ and the conversion efficiency from 2 μm laser to THz output was 1.68×10^(-6).The signal-to-noise ratio of the detected THz voltage was 23 dB.The acceptance angle of DFG in the GaSe crystal was measured to be 0.16°.
基金This study was financially supported by the National Natural Science Foundation of China(41671244)China Postdoctoral Science Foundation Grant(2016M600751)+2 种基金a fund from Chengdu Institute of Biology,Chinese Academy of Sciences(KXYS20S1501)It is also supported by the National Basic Research Program of China(2014CB846003)China’s QianRen Program and a merit scholarship program for foreign students from Quebec,Canada,to G.Yang.We also thank Dr.Yongheng Gao for providing us the photo of grassland in QTP,and Dr.Mei Wang for her constructive suggestion for im-proving this paper.
文摘Often referred to as the“Third Pole,”China’s Qinghai-Tibetan Plateau developed large amounts of peatland owing to its unique alpine environment.As a renewable resource,peat helps to regulate the climate as well as performing other important functions.However,in recent years,intensifying climate change and anthropogenic disturbances have resulted in peatland degradation and consequently made sustainable development of peatland more difficult.This review summarizes peatland ecological and economic functions,including carbon sequestration,biodiversity conservation,energy supplies,and ecotourism.It identifies climate change and anthropogenic disturbances as the two key factors attributing to peatland degradation and ecosystem carbon loss.Current problems in environmental degradation and future challenges in peatland management under the effects of global warming are also discussed and highlighted.
