Dear Editor,Sleep and memory are highly linked across species.Sleep gates and stabilizes memory,critical for memory processing.Insufficient sleep impairs cognition acutely/chronically,in vertebrates and invertebrates[...Dear Editor,Sleep and memory are highly linked across species.Sleep gates and stabilizes memory,critical for memory processing.Insufficient sleep impairs cognition acutely/chronically,in vertebrates and invertebrates[1,2].While key elements are characterized[3,4],how a single molecule integrates sleep and memory remains unknown.展开更多
In this paper,the authors study the multilinear commutators generated by a class of multilinear singular integral operators with generalized kernels and Lipschitz functions.By establishing the sharp maximal estimates,...In this paper,the authors study the multilinear commutators generated by a class of multilinear singular integral operators with generalized kernels and Lipschitz functions.By establishing the sharp maximal estimates,the boundedness of this kind of multilinear commutators on product of weighted Lebesgue spaces can be obtained.展开更多
The long-lasting application of representative herbicide atrazine （ATR） has given rise to the accumulation of its residues in the groundwater. To investigate the impact of long-term ATR use on groundwater safety, th...The long-lasting application of representative herbicide atrazine （ATR） has given rise to the accumulation of its residues in the groundwater. To investigate the impact of long-term ATR use on groundwater safety, the residues of ATR and its metabolites, desethylatrazine （DEA）, deisopropylatrazine （DIA） and hydroxyatrazine （HA） were monitored in groundwater and top soil at the major corn growing region of Qian＇an and Gongzhuling in Jilin Province, China. The residues of the target compounds were analyzed by UPLC-MS/MS. The limits of detection （LODs） ofATR, DEA, DIA, and HA were 0.5, 0.5, 5, and 0.5 ng L-1 in groundwater and 0.33, 0.33, 3.3, and 0.33 μg kg-1 in soil. The target compounds were found in 94% of groundwater samples and 100% of soil samples. The compounds detected most frequently in groundwater were ATR （89%）, DEA （64%） and HA （17%）, whereas in soil were ATR （97%）, DEA （36%） and HA （97%）. DIA was not detected in any determined groundwater and soil sample. Average residues were 106.8 ng L-1 for ATR, 0.9 ng L-1 for DEA and 0.3 ng L-1 for HA in groundwater, whereas 11.1 μg kg-1 for ATR, 0.4 μg kg-1 for DEA and 7.8 μg kg-1 for HA in soil. ATR residues detected in groundwater samples were below standards for drinking water quality （GB5749-2006, 2 μg L-1）, while the total residues of ATR and its chloro-s-triazine metabolites （DEA and DIA） were below current WHO （World Health Organization） guideline value （GV, 0.1 mg L-1）. In addition, concentrations of HA in groundwater were determined below current WHO GV （0.2 mg L-1）. The results indicated that ATR is safe to be used in Jilin Province under the current application scheme. However, total residues of ATR and DEA were detected in nearly all wells, thus, it is necessary to pay attention on groundwater monitoring for ATR and its metabolites.展开更多
The state estimation strategy using the smooth variable structure filter （SVSF） is based on the variable structure and sliding mode concepts. As presented in its standard form with a fixed boundary layer limit, the ...The state estimation strategy using the smooth variable structure filter （SVSF） is based on the variable structure and sliding mode concepts. As presented in its standard form with a fixed boundary layer limit, the value of the boundary layer width is not precisely known at each step and may be selected based on a priori knowledge. The boundary layer width reflects the level of uncertainty in the model parameters and disturbance characteristics, where large values of the boundary layer width lead to robustness without optimality and small values of the boundary layer width provide optimality with poor robustness. As a solution and to overcome these limitations, an adaptive smoothing boundary layer is required to achieve greater robustness and suitable accuracy. This adapted value of the boundary layer width is obtained by minimizing the trace of the a posteriori covariance matrix. In this paper, the proposed new approach will be considered as another alternative to the extended Kalman filters （EKF）, nonlinear H∞ and standard SVSF-based data fusion techniques for the autonomous airborne navigation and self-localization problem. This alternative is based on strapdown inertial navigation system （SINS） and GPS data using the nonlinear SVSF with a covariance derivation and adaptive boundary layer width. Furthermore, the full mathematical model of the SINS/GPS navigation system considering the unmanned aerial vehicle （UAV） position, velocity and Euler angle as well as gyro and accelerometer biases will be used in this paper to estimate the airborne position and velocity with better accuracy.展开更多
In this paper, a methodology has been developed to address the issue of force fighting and to achieve precise position tracking of control surface driven by two dissimilar actuators.The nonlinear dynamics of both actu...In this paper, a methodology has been developed to address the issue of force fighting and to achieve precise position tracking of control surface driven by two dissimilar actuators.The nonlinear dynamics of both actuators are first approximated as fractional order models. Based on the identified models, three fractional order controllers are proposed for the whole system. Two Fractional Order PID（FOPID） controllers are dedicated to improving transient response and are designed in a position feedback configuration. In order to synchronize the actuator dynamics, a third fractional order PI controller is designed, which feeds the force compensation signal in position feedback loop of both actuators. Nelder-Mead（N-M） optimization technique is employed in order to optimally tune controller parameters based on the proposed performance criteria. To test the proposed controllers according to real flight condition, an external disturbance of higher amplitude that acts as airload is applied directly on the control surface. In addition, a disturbance signal function of system states is applied to check the robustness of proposed controller. Simulation results on nonlinear system model validated the performance of the proposed scheme as compared to optimal PID and high gain PID controllers.展开更多
基金supported by the National Natural Science Foundation of China(32371063,82341248,and 32071009)Guangdong Basic and Applied Basic Research Foundation(2024A1515011500)the Shenzhen Science and Technology Program(ZDSYS20200811142401005).
文摘Dear Editor,Sleep and memory are highly linked across species.Sleep gates and stabilizes memory,critical for memory processing.Insufficient sleep impairs cognition acutely/chronically,in vertebrates and invertebrates[1,2].While key elements are characterized[3,4],how a single molecule integrates sleep and memory remains unknown.
基金Supported by the National Natural Science Foundation of China(11671397,11571160,12071052)the Yue Qi Young Scholar of China University of Mining and Technology(Beijing)。
文摘In this paper,the authors study the multilinear commutators generated by a class of multilinear singular integral operators with generalized kernels and Lipschitz functions.By establishing the sharp maximal estimates,the boundedness of this kind of multilinear commutators on product of weighted Lebesgue spaces can be obtained.
基金financed by the Key Technologies R&D Program of China during the 11th Five-Year Plan period(2006BAK02A0407)
文摘The long-lasting application of representative herbicide atrazine （ATR） has given rise to the accumulation of its residues in the groundwater. To investigate the impact of long-term ATR use on groundwater safety, the residues of ATR and its metabolites, desethylatrazine （DEA）, deisopropylatrazine （DIA） and hydroxyatrazine （HA） were monitored in groundwater and top soil at the major corn growing region of Qian＇an and Gongzhuling in Jilin Province, China. The residues of the target compounds were analyzed by UPLC-MS/MS. The limits of detection （LODs） ofATR, DEA, DIA, and HA were 0.5, 0.5, 5, and 0.5 ng L-1 in groundwater and 0.33, 0.33, 3.3, and 0.33 μg kg-1 in soil. The target compounds were found in 94% of groundwater samples and 100% of soil samples. The compounds detected most frequently in groundwater were ATR （89%）, DEA （64%） and HA （17%）, whereas in soil were ATR （97%）, DEA （36%） and HA （97%）. DIA was not detected in any determined groundwater and soil sample. Average residues were 106.8 ng L-1 for ATR, 0.9 ng L-1 for DEA and 0.3 ng L-1 for HA in groundwater, whereas 11.1 μg kg-1 for ATR, 0.4 μg kg-1 for DEA and 7.8 μg kg-1 for HA in soil. ATR residues detected in groundwater samples were below standards for drinking water quality （GB5749-2006, 2 μg L-1）, while the total residues of ATR and its chloro-s-triazine metabolites （DEA and DIA） were below current WHO （World Health Organization） guideline value （GV, 0.1 mg L-1）. In addition, concentrations of HA in groundwater were determined below current WHO GV （0.2 mg L-1）. The results indicated that ATR is safe to be used in Jilin Province under the current application scheme. However, total residues of ATR and DEA were detected in nearly all wells, thus, it is necessary to pay attention on groundwater monitoring for ATR and its metabolites.
基金Supported by National Natural Science Foundation of China（60874044） Research Foundation for Key Disciplines of Beijing Municipal Commission of Education （XK100060422）
基金supported by the National Natural Science Foundation of China(No.61375082)
文摘The state estimation strategy using the smooth variable structure filter （SVSF） is based on the variable structure and sliding mode concepts. As presented in its standard form with a fixed boundary layer limit, the value of the boundary layer width is not precisely known at each step and may be selected based on a priori knowledge. The boundary layer width reflects the level of uncertainty in the model parameters and disturbance characteristics, where large values of the boundary layer width lead to robustness without optimality and small values of the boundary layer width provide optimality with poor robustness. As a solution and to overcome these limitations, an adaptive smoothing boundary layer is required to achieve greater robustness and suitable accuracy. This adapted value of the boundary layer width is obtained by minimizing the trace of the a posteriori covariance matrix. In this paper, the proposed new approach will be considered as another alternative to the extended Kalman filters （EKF）, nonlinear H∞ and standard SVSF-based data fusion techniques for the autonomous airborne navigation and self-localization problem. This alternative is based on strapdown inertial navigation system （SINS） and GPS data using the nonlinear SVSF with a covariance derivation and adaptive boundary layer width. Furthermore, the full mathematical model of the SINS/GPS navigation system considering the unmanned aerial vehicle （UAV） position, velocity and Euler angle as well as gyro and accelerometer biases will be used in this paper to estimate the airborne position and velocity with better accuracy.
文摘In this paper, a methodology has been developed to address the issue of force fighting and to achieve precise position tracking of control surface driven by two dissimilar actuators.The nonlinear dynamics of both actuators are first approximated as fractional order models. Based on the identified models, three fractional order controllers are proposed for the whole system. Two Fractional Order PID（FOPID） controllers are dedicated to improving transient response and are designed in a position feedback configuration. In order to synchronize the actuator dynamics, a third fractional order PI controller is designed, which feeds the force compensation signal in position feedback loop of both actuators. Nelder-Mead（N-M） optimization technique is employed in order to optimally tune controller parameters based on the proposed performance criteria. To test the proposed controllers according to real flight condition, an external disturbance of higher amplitude that acts as airload is applied directly on the control surface. In addition, a disturbance signal function of system states is applied to check the robustness of proposed controller. Simulation results on nonlinear system model validated the performance of the proposed scheme as compared to optimal PID and high gain PID controllers.
