Vector analysis technique and ecological sequential comparison methods were adopted to study tree growth response to the micronutrients, B, Mo, Cu, Zn, Fe, and Mn, in soils derived from various parent materials in the...Vector analysis technique and ecological sequential comparison methods were adopted to study tree growth response to the micronutrients, B, Mo, Cu, Zn, Fe, and Mn, in soils derived from various parent materials in the forest area of Taihu Lake region in southeast China. The results showed that the dry weight of individual current-year needle of Chinese fir (Cunninghamia lanceolata) grown on the soi1 derived from granite parent rock was increased by 8% and 13% in comparison with that grown on the soils derived from sandstone and ash-tuff parent rock, respectively. And such dry weight of loblolly pine (Pinus taeda) grown on the soil derived from sandstone parent rock was increased by 21% in comparison with that on the soil derived from ash-tuff parent rock. One of the reasons for those results was that micronutrients content in the soil derived from ash-tuff parent rock were not sufficient to meet the requirement of the growth of Chinese fir and loblolly pine, i.e., micronutrients in soil were deficient and/or induced deficient. The amounts of Cu, Zn, Fe, and Mn uptake by Chinese fir and loblolly pine were in agreement with the contents of available micronutrients in soil respectively, except for B and Mo. Meanwhile, there might exist an "antagonism" between the uptake of B versus Mo by trees, although more studies are needed to confirm it. Regression analysis indicated that amount of a soil available micronutrient was correlated to the type of parent material and its total amount in the forest floor, except for B. The F test identified that the correlation of each equation reached the significant level to different extents, respectively. The t test confirmed that amount of available forms was mainly depended on the type of parent material for Mo, Cu, Zn and Mn but on the forest floor for Fe. There was a feedback effect of forest stand on the amount of soil available micronutrients. The ability of accumulating available micronutrients in soil was better by the sawtooth oak (Quercus acutissima) stand than by the Chinese fir stand (except for B). The ability of accumulating available Zn, Fe, Mn and Mo in soil was better by the Chinese fir stand than by the loblolly pine stand, while as for available B and Cu, by the latter was better than by the former. When discussing the effect of forest stand on the amount of soil available micronutrients, not only the amount of micronutrient in the forest floor and the parent materials but also the amount of micronutrient taken up by current-year needles have to be considered.展开更多
Ionospheric feedback effect has been proposed as a key factor in the formation of the throat aurora.Theoretically,it acts through the ionospheric feedback instability(IFI)induced by localized ionospheric density enhan...Ionospheric feedback effect has been proposed as a key factor in the formation of the throat aurora.Theoretically,it acts through the ionospheric feedback instability(IFI)induced by localized ionospheric density enhancements.However,observations linking ionospheric density enhancements to throat auroras remain lacking.In this study,we selected 70 throat auroras from DMSP/SSUSI images spanning from 2005 to 2010,combined with reliable GPS total electron content(TEC)data.Statistical analysis of these events reveals that 50 throat auroras(~71.4%)were preceded by plume-like TEC enhancements.These enhanced TEC structures generally extended from low latitudes into the high-latitude noon sector(10–14 MLT,≥70°MLAT),persisting for an average of~30.8 minutes within this region and being parallel to subsequent throat auroras.Further,case studies of two typical events show that the electron precipitations of throat auroras occurred adjacent to the duskward boundaries of these enhanced TEC plumes.This spatial correlation between ionospheric density enhancements and auroral structures is consistent with the features of the IFI theory.Also,the density gradients along the boundaries favor the establishment of IFI.Therefore,these observations establish a clear link between ionospheric density enhancements and throat auroras,providing critical evidence for the ionospheric feedback mechanism in generating the throat aurora.Our findings also highlight the importance of ionospheric feedback effect in the solar wind-magnetosphere-ionosphere coupling.展开更多
This paper explores the investors＇ feedback to the price change by modelling the price- related dynamics of trading intensity. A component decomposition duration modeling approach, called the component autoregressive...This paper explores the investors＇ feedback to the price change by modelling the price- related dynamics of trading intensity. A component decomposition duration modeling approach, called the component autoregressive conditional duration （CACD） model, is proposed to capture the variation of trading intensity across time intervals between price change events. Based on the CACD model, an empirical analysis is carried out on the Chinese stock market that covers different market statuses. The empirical results suggest that the CACD model can capture the price-related dynamics of trading intensity, which supports the existence of the feedback effect and is robust across different market statuses. The authors also study how the investors react to the price change by examining the driven factors of the price-related dynamics of trading intensity. The authors find that the trading can be triggered by the fast rise in the price level and the high trading volume. Besides, investors are more sensitive to the price change direction in the sideways market than in the upward or downward markets.展开更多
Based on the students' capability of assessing peers' essays, this paper attempts to analyze the effectiveness of peer feed-back in EFL writing. Significant improvements can be made in writing proficiency, esp...Based on the students' capability of assessing peers' essays, this paper attempts to analyze the effectiveness of peer feed-back in EFL writing. Significant improvements can be made in writing proficiency, especially for the students who review others' essays. The reviewers may not only improve their peer's papers but also improve general writing skills and learn to self-evaluatetheir own writing.展开更多
Since the result of effect comparison is important for teacher's decision making,roles teacher feedback and peer review play respectively and collaboratively in tertiary-level EFL writing context should be address...Since the result of effect comparison is important for teacher's decision making,roles teacher feedback and peer review play respectively and collaboratively in tertiary-level EFL writing context should be addressed via quantitative study as this paper proposed.Quantitative data should be collected from students'first drafts,second drafts and written comments from teachers and peers.Gains for overall scores between the first and second drafts and correlation between suggestions and gains should be examined.展开更多
We consider the impulsive effect on the exponential synchronization of neural networks with leakage delay under the sampled-data feedback control. We use an appropriate Lyapunov-Krasovskii functional combined with the...We consider the impulsive effect on the exponential synchronization of neural networks with leakage delay under the sampled-data feedback control. We use an appropriate Lyapunov-Krasovskii functional combined with the input delay approach and some inequality techniques to derive sufficient conditions that ensure the exponential synchronization of the delayed neural network. The conditions are formulated in terms of the leakage delay, the sampling period, and the exponential convergence rate. Numerical examples are given to demonstrate the usefulness and the effectiveness of the results.展开更多
Traditional PID controllers are no longer suitable formagnetic-bearing-supported high-speed flywheels with significant gyroscopic effects. Becausegyroscopic effects greatly influence the stability of the flywheel roto...Traditional PID controllers are no longer suitable formagnetic-bearing-supported high-speed flywheels with significant gyroscopic effects. Becausegyroscopic effects greatly influence the stability of the flywheel rotor, especially at highrotational speeds. Velocity cross feedback and displacement cross feedback are used to overcomeharmful effects of nutation and precession modes, and stabilize the rotor at high rotational speeds.Theoretical analysis is given to show their effects. A control platform based on RTLinut and a PCis built to control the active magnetic bearing (AMB) system, and relevant results are reported.Using velocity cross feedback and displacement cross feedback in a closed loop control system, theflywheel successfully runs at over 20000 r/min.展开更多
The feedback control of a delayed dynamical system, which also includes various chaotic systems with time delays, is investigated. On the basis of stability analysis of a nonautonomous system with delays, some simple ...The feedback control of a delayed dynamical system, which also includes various chaotic systems with time delays, is investigated. On the basis of stability analysis of a nonautonomous system with delays, some simple yet less conservative criteria are obtained for feedback control in a delayed dynamical system. Finally, the theoretical result is applied to a typical class of chaotic Lorenz system and Chua circuit with delays. Numerical simulations are also given to verify the theoretical results.展开更多
The main shortcomings of direct sequence spread spectrum multiple ac-cess(DS-SSMA)communication systems are the near-far effect and multiaccess in-terferences,which impair the stability,capacity and application areas ...The main shortcomings of direct sequence spread spectrum multiple ac-cess(DS-SSMA)communication systems are the near-far effect and multiaccess in-terferences,which impair the stability,capacity and application areas of the commu-nication systems.In this paper,a new kind of multiuser detector——decorrelatingdetector with decision feedback is proposed.In linear channels,this detector can e-liminate the multiaccess interferences with low complexity.Computer simulationsverify the theoretical analysis in this paper.展开更多
Observation and feedback plays an important part in guiding normal teaching and especially contributes to achieving educational purposes in an organization.In this article,the role of observation and various kinds of ...Observation and feedback plays an important part in guiding normal teaching and especially contributes to achieving educational purposes in an organization.In this article,the role of observation and various kinds of observation will be clarified;the effectiveness of observation will be illustrated and the strengths and shortcomings of the existing system will be pointed out objectively.展开更多
In this paper, we consider a multi-relay cooperative communication network that consists of a source node transmitting to its destination with the help of multiple decode-and- forward (DF) relays. Specifically, the DF...In this paper, we consider a multi-relay cooperative communication network that consists of a source node transmitting to its destination with the help of multiple decode-and- forward (DF) relays. Specifically, the DF relays that succeed in decoding the source signal are allowed to re-transmit their decoded results simultaneously to the destination in a cooperative beamforming manner. In order to carry out the cooperative beamforming, the destination needs to send the quantized channel state information (CSI) to the relays through a limited feedback channel in the face of channel quantization errors (CQE). We propose a CQE oriented multi-relay beamforming (MRB) scheme, denoted CQE-MRB for short, for the sake of improving the throughput of relay-destination transmissions. An effective throughput defined as the difference between the transmission rate and the feedback rate is used to measure an outage probability of the source-destination transmission. Simulation results demonstrate that the outage performance of proposed CQEMRB scheme is improved substantially with an increasing number of relays. Moreover, it is shown that the number of channel quantization bits can be further optimized to minimize the outage probability of proposed CQE-MRB scheme.展开更多
基金Project supported by the National Natural Science Foundation of China (No. 39370563)by the NationalKey Basic Research Suppor
文摘Vector analysis technique and ecological sequential comparison methods were adopted to study tree growth response to the micronutrients, B, Mo, Cu, Zn, Fe, and Mn, in soils derived from various parent materials in the forest area of Taihu Lake region in southeast China. The results showed that the dry weight of individual current-year needle of Chinese fir (Cunninghamia lanceolata) grown on the soi1 derived from granite parent rock was increased by 8% and 13% in comparison with that grown on the soils derived from sandstone and ash-tuff parent rock, respectively. And such dry weight of loblolly pine (Pinus taeda) grown on the soil derived from sandstone parent rock was increased by 21% in comparison with that on the soil derived from ash-tuff parent rock. One of the reasons for those results was that micronutrients content in the soil derived from ash-tuff parent rock were not sufficient to meet the requirement of the growth of Chinese fir and loblolly pine, i.e., micronutrients in soil were deficient and/or induced deficient. The amounts of Cu, Zn, Fe, and Mn uptake by Chinese fir and loblolly pine were in agreement with the contents of available micronutrients in soil respectively, except for B and Mo. Meanwhile, there might exist an "antagonism" between the uptake of B versus Mo by trees, although more studies are needed to confirm it. Regression analysis indicated that amount of a soil available micronutrient was correlated to the type of parent material and its total amount in the forest floor, except for B. The F test identified that the correlation of each equation reached the significant level to different extents, respectively. The t test confirmed that amount of available forms was mainly depended on the type of parent material for Mo, Cu, Zn and Mn but on the forest floor for Fe. There was a feedback effect of forest stand on the amount of soil available micronutrients. The ability of accumulating available micronutrients in soil was better by the sawtooth oak (Quercus acutissima) stand than by the Chinese fir stand (except for B). The ability of accumulating available Zn, Fe, Mn and Mo in soil was better by the Chinese fir stand than by the loblolly pine stand, while as for available B and Cu, by the latter was better than by the former. When discussing the effect of forest stand on the amount of soil available micronutrients, not only the amount of micronutrient in the forest floor and the parent materials but also the amount of micronutrient taken up by current-year needles have to be considered.
基金supported by the National Natural Science Foundation of China(Grant Nos.424B2030&42030101)the Shandong Provincial Natural Science Foundation(Grant No.ZR2022MD034)+5 种基金the Xiaomi Young Talents Programthe Chinese Meridian Projectthe International Partnership Program of the Chinese Academy of Sciences(Grant No.183311KYSB20200003)funded by the Arctic Yellow River Earth System National Observation and Research Station(No.YRNORS-20242606)provided by the Massachusetts Institute of Technology’s Haystack Observatory under support from the US National Science Foundation(NSF)(Grant No.AGS-1952737)the NSF funding support through grants AGS-2033787 and AGS-2149698。
文摘Ionospheric feedback effect has been proposed as a key factor in the formation of the throat aurora.Theoretically,it acts through the ionospheric feedback instability(IFI)induced by localized ionospheric density enhancements.However,observations linking ionospheric density enhancements to throat auroras remain lacking.In this study,we selected 70 throat auroras from DMSP/SSUSI images spanning from 2005 to 2010,combined with reliable GPS total electron content(TEC)data.Statistical analysis of these events reveals that 50 throat auroras(~71.4%)were preceded by plume-like TEC enhancements.These enhanced TEC structures generally extended from low latitudes into the high-latitude noon sector(10–14 MLT,≥70°MLAT),persisting for an average of~30.8 minutes within this region and being parallel to subsequent throat auroras.Further,case studies of two typical events show that the electron precipitations of throat auroras occurred adjacent to the duskward boundaries of these enhanced TEC plumes.This spatial correlation between ionospheric density enhancements and auroral structures is consistent with the features of the IFI theory.Also,the density gradients along the boundaries favor the establishment of IFI.Therefore,these observations establish a clear link between ionospheric density enhancements and throat auroras,providing critical evidence for the ionospheric feedback mechanism in generating the throat aurora.Our findings also highlight the importance of ionospheric feedback effect in the solar wind-magnetosphere-ionosphere coupling.
基金supported by the National Science Foundation of China under Grant Nos.71201161 and71671183
文摘This paper explores the investors＇ feedback to the price change by modelling the price- related dynamics of trading intensity. A component decomposition duration modeling approach, called the component autoregressive conditional duration （CACD） model, is proposed to capture the variation of trading intensity across time intervals between price change events. Based on the CACD model, an empirical analysis is carried out on the Chinese stock market that covers different market statuses. The empirical results suggest that the CACD model can capture the price-related dynamics of trading intensity, which supports the existence of the feedback effect and is robust across different market statuses. The authors also study how the investors react to the price change by examining the driven factors of the price-related dynamics of trading intensity. The authors find that the trading can be triggered by the fast rise in the price level and the high trading volume. Besides, investors are more sensitive to the price change direction in the sideways market than in the upward or downward markets.
文摘Based on the students' capability of assessing peers' essays, this paper attempts to analyze the effectiveness of peer feed-back in EFL writing. Significant improvements can be made in writing proficiency, especially for the students who review others' essays. The reviewers may not only improve their peer's papers but also improve general writing skills and learn to self-evaluatetheir own writing.
文摘Since the result of effect comparison is important for teacher's decision making,roles teacher feedback and peer review play respectively and collaboratively in tertiary-level EFL writing context should be addressed via quantitative study as this paper proposed.Quantitative data should be collected from students'first drafts,second drafts and written comments from teachers and peers.Gains for overall scores between the first and second drafts and correlation between suggestions and gains should be examined.
基金supported by the Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(Grant No.2013R1A1A2A10005201)the UAE University(Grant No.NRF Project UAEU-NRF-7-20886)
文摘We consider the impulsive effect on the exponential synchronization of neural networks with leakage delay under the sampled-data feedback control. We use an appropriate Lyapunov-Krasovskii functional combined with the input delay approach and some inequality techniques to derive sufficient conditions that ensure the exponential synchronization of the delayed neural network. The conditions are formulated in terms of the leakage delay, the sampling period, and the exponential convergence rate. Numerical examples are given to demonstrate the usefulness and the effectiveness of the results.
文摘Traditional PID controllers are no longer suitable formagnetic-bearing-supported high-speed flywheels with significant gyroscopic effects. Becausegyroscopic effects greatly influence the stability of the flywheel rotor, especially at highrotational speeds. Velocity cross feedback and displacement cross feedback are used to overcomeharmful effects of nutation and precession modes, and stabilize the rotor at high rotational speeds.Theoretical analysis is given to show their effects. A control platform based on RTLinut and a PCis built to control the active magnetic bearing (AMB) system, and relevant results are reported.Using velocity cross feedback and displacement cross feedback in a closed loop control system, theflywheel successfully runs at over 20000 r/min.
基金Project supported by the Natural Science Foundation of Chongqing City,China(Grant No.2005BB8085)the Chongqing Municipal Education Commission Project,China(Grant No.KJ080622)
文摘The feedback control of a delayed dynamical system, which also includes various chaotic systems with time delays, is investigated. On the basis of stability analysis of a nonautonomous system with delays, some simple yet less conservative criteria are obtained for feedback control in a delayed dynamical system. Finally, the theoretical result is applied to a typical class of chaotic Lorenz system and Chua circuit with delays. Numerical simulations are also given to verify the theoretical results.
文摘The main shortcomings of direct sequence spread spectrum multiple ac-cess(DS-SSMA)communication systems are the near-far effect and multiaccess in-terferences,which impair the stability,capacity and application areas of the commu-nication systems.In this paper,a new kind of multiuser detector——decorrelatingdetector with decision feedback is proposed.In linear channels,this detector can e-liminate the multiaccess interferences with low complexity.Computer simulationsverify the theoretical analysis in this paper.
文摘Observation and feedback plays an important part in guiding normal teaching and especially contributes to achieving educational purposes in an organization.In this article,the role of observation and various kinds of observation will be clarified;the effectiveness of observation will be illustrated and the strengths and shortcomings of the existing system will be pointed out objectively.
基金supported by the National Natural Science Foundation of China (Grant Nos. 61522109, 61631020, 61671253 and 91738201)the Natural Science Foundation of Jiangsu Province (Grant Nos. BK20150040, BK20171446 and BRA2018043)
文摘In this paper, we consider a multi-relay cooperative communication network that consists of a source node transmitting to its destination with the help of multiple decode-and- forward (DF) relays. Specifically, the DF relays that succeed in decoding the source signal are allowed to re-transmit their decoded results simultaneously to the destination in a cooperative beamforming manner. In order to carry out the cooperative beamforming, the destination needs to send the quantized channel state information (CSI) to the relays through a limited feedback channel in the face of channel quantization errors (CQE). We propose a CQE oriented multi-relay beamforming (MRB) scheme, denoted CQE-MRB for short, for the sake of improving the throughput of relay-destination transmissions. An effective throughput defined as the difference between the transmission rate and the feedback rate is used to measure an outage probability of the source-destination transmission. Simulation results demonstrate that the outage performance of proposed CQEMRB scheme is improved substantially with an increasing number of relays. Moreover, it is shown that the number of channel quantization bits can be further optimized to minimize the outage probability of proposed CQE-MRB scheme.
