Attention deficit hyperactivity disorder（ADHD）is a common childhood neuropsychiatric disorder that has been linked to the dopaminergic system. This study aimed to investigate the effects of regulation of the dopamin...Attention deficit hyperactivity disorder（ADHD）is a common childhood neuropsychiatric disorder that has been linked to the dopaminergic system. This study aimed to investigate the effects of regulation of the dopamine D4 receptor（DRD4） on functional brain activity during the resting state in ADHD children using the methods of regional homogeneity（Re Ho） and functional connectivity（FC）. Resting-state functional magnetic resonance imaging data were analyzed in 49 children with ADHD. All participants were classified as either carriers of the DRD44-repeat/4-repeat（4 R/4 R） allele（n = 30） or the DRD42-repeat（2 R） allele（n = 19）. The results showed that participants with the DRD4 2 R allele had decreased Re Ho bilaterally in the posterior lobes of the cerebellum, while Re Ho was increased in the left angular gyrus. Compared with participants carrying the DRD4 4 R/4 R allele, those with the DRD4 2 R allele showed decreased FC to the left angular gyrus in the left striatum, right inferior frontal gyrus, and bilateral lobes of the cerebellum. The increased FC regions included the left superior frontal gyrus, medial frontal gyrus, and rectus gyrus. These data suggest that the DRD4 polymorphisms are associated with localized brain activity and specific functional connections, including abnormality in the frontal-striatal-cerebellar loop. Our study not only enhances the understanding of the correlation between the cerebellar lobes and ADHD, but also provides an imaging basis for explaining the neural mechanisms underlying ADHD in children.展开更多
An analysis technique of steady state and stability for closed-loop PWM DC/DC switching converters is presented. Using this method, the closed-loop switching converter is transformed into an open-loop system. By means...An analysis technique of steady state and stability for closed-loop PWM DC/DC switching converters is presented. Using this method, the closed-loop switching converter is transformed into an open-loop system. By means of the fact that in steady state, the two boundary values are equal in one switching period. The exponential matrix is evaluated by precise time-domain-integration method, and then the related curve between feedback duty cycle and the input one is obtained. Not only can the steady-state duty cycle be found from the curve, but also the stability and stable domain of the system. Compared with other methods, it features with simplicity and less calculation, and fit for numerical simulation and analysis for closed-loop switching converters. The simulation results of examples indicate the correctness of the presented method.展开更多
The measurements on actual traffic have revealed the existence of meta-stable states with high flow. Such nonlinear phenomena have not been observed in the classic Nagel-Schreckenberg traffic flow model. Here we just ...The measurements on actual traffic have revealed the existence of meta-stable states with high flow. Such nonlinear phenomena have not been observed in the classic Nagel-Schreckenberg traffic flow model. Here we just add a constraint to the classic model by introducing a velocity-dependent randomization. Two typical randomization strategies are adopted in this paper. It is shown that the Matthew effect is a necessary condition to induce traffic meta-stable states, thus shedding a light on the prerequisites for the emergence of hysteresis loop in the fundamental diagrams.展开更多
The effect of too much overhead caused by fixed neighborhood state update cycle on the whole network performance has been greatly alleviated by a neighborhood state dynamic update(NSDU) algorithm proposed for MANET in...The effect of too much overhead caused by fixed neighborhood state update cycle on the whole network performance has been greatly alleviated by a neighborhood state dynamic update(NSDU) algorithm proposed for MANET in this paper.A local topology flapping metric(LTFM) has been established based on the changes of link connection to achieve the measurement of stability.The loop control theory has been adopted to establish the control model of the neighborhood state,so as to set up the mapping relationship with the topology change,based on which both the neighborhood state information exchange and the timeout of link with neighbors involved will be adjusted dynamically according to NSDU to ensure that the update cycle would regulate with the network environment in order to achieve the purpose of reducing the control overhead.The simulation results on NS2.34 with different nodes velocities,traffic generating rates and the network node densities shows that adopting NSDU,no matter based on a table-driven protocol or a on-demand one,would reduce the overhead effectively while hardly bring any obvious impacts on metrics of packet successful delivery rate and the average end-to-end delay as well.展开更多
In this investigation, a novel thermally coupled reactor （TCR） containing methyl formate （MF） production in the endothermic side and methanol synthesis in the exothermic side has been investigated. The interesting...In this investigation, a novel thermally coupled reactor （TCR） containing methyl formate （MF） production in the endothermic side and methanol synthesis in the exothermic side has been investigated. The interesting feature of this TCR is that productive methanol in the exothermic side could be recycled and used as feed of endothermic side for MF synthesis. Other important advantages of the proposed system are high production rates of hydrogen and MF. The configuration consists of two thermally coupled concentric tubular reactors. In these coupled reactors, autothermal system is obtained within the reactor. A steady-state heterogeneous model is used for simulation of the coupled reactor. The proposed model has been utilized to compare the performance of TCR with the conventional methanol reactor （CMR）. Noticeable enhancement can be obtained in the performance of the reactors. The influence of operational parameters is studied on reactor performance. The results show that coupling of these reactions could be feasible and beneficial. Experimental proof-of-concept is required to validate the operation of the novel reactor.展开更多
提出了一种基于改进线性扩张状态观测器(linear extended state observer,LESO)的电力电子负载自抗扰控制策略,解决了传统控制方法动态性能较差、对系统参数依赖等问题。建立LCL(line current loop)变换器在α-β坐标系下的数学模型,分...提出了一种基于改进线性扩张状态观测器(linear extended state observer,LESO)的电力电子负载自抗扰控制策略,解决了传统控制方法动态性能较差、对系统参数依赖等问题。建立LCL(line current loop)变换器在α-β坐标系下的数学模型,分析线性自抗扰控制(linear active disturbance rejection control,LADRC)中LESO的误差,对观测器控制输出部分的结构进行改进,以减小观测值中来自控制输出信号的误差。通过LESO求取指令电流微分,引入线性误差反馈控制率中,减小传统LADRC的固有误差。分析系统的频域特性,研究参数和控制策略对系统的影响。通过仿真和半实物仿真,验证了改进策略能明显改善传统LADRC跟踪动态信号时的波形畸变、相位滞后等问题,使变换器实现对各类负载的精确模拟。展开更多
针对当前视觉同时定位与建图(Simultaneous Localization and Mapping,SLAM)面对如纹理稀疏、光照变化强烈及图像模糊等挑战性场景时,普遍存在的前端特征跟踪鲁棒性不足的问题,提出了一个鲁棒的多相机定位系统,并对关键技术进行了深入...针对当前视觉同时定位与建图(Simultaneous Localization and Mapping,SLAM)面对如纹理稀疏、光照变化强烈及图像模糊等挑战性场景时,普遍存在的前端特征跟踪鲁棒性不足的问题,提出了一个鲁棒的多相机定位系统,并对关键技术进行了深入的研究与优化。该系统设计了一种优于主流方案的前端跟踪算法,通过融合惯性测量单元(Inertial Measurement Unit,IMU)测量数据实现特征点重投影预测,并对跟踪的灰度图进行动态校正,有效提升了复杂场景下特征跟踪的成功率和稳定性。此外,该系统利用多相机观测信息构建了具备3层自适应置信度加权算法的状态估计器,并将卷积神经网络运用于交叉回环检测,有效提高了回环检测的成功率与准确率。通过一系列公开数据集的实验,验证了该多相机定位算法在精度和稳定性方面已达到最先进技术水平,且在本地环境中的测试结果也证实了该系统在实际应用中的可行性与有效性。展开更多
基金supported by the Natural Science Foundation of Zhejiang Province, China (No. LY14H180006, LQ18H090009)the Natural Science Foundation of Jiangsu Province (BK20160142)
文摘Attention deficit hyperactivity disorder（ADHD）is a common childhood neuropsychiatric disorder that has been linked to the dopaminergic system. This study aimed to investigate the effects of regulation of the dopamine D4 receptor（DRD4） on functional brain activity during the resting state in ADHD children using the methods of regional homogeneity（Re Ho） and functional connectivity（FC）. Resting-state functional magnetic resonance imaging data were analyzed in 49 children with ADHD. All participants were classified as either carriers of the DRD44-repeat/4-repeat（4 R/4 R） allele（n = 30） or the DRD42-repeat（2 R） allele（n = 19）. The results showed that participants with the DRD4 2 R allele had decreased Re Ho bilaterally in the posterior lobes of the cerebellum, while Re Ho was increased in the left angular gyrus. Compared with participants carrying the DRD4 4 R/4 R allele, those with the DRD4 2 R allele showed decreased FC to the left angular gyrus in the left striatum, right inferior frontal gyrus, and bilateral lobes of the cerebellum. The increased FC regions included the left superior frontal gyrus, medial frontal gyrus, and rectus gyrus. These data suggest that the DRD4 polymorphisms are associated with localized brain activity and specific functional connections, including abnormality in the frontal-striatal-cerebellar loop. Our study not only enhances the understanding of the correlation between the cerebellar lobes and ADHD, but also provides an imaging basis for explaining the neural mechanisms underlying ADHD in children.
文摘An analysis technique of steady state and stability for closed-loop PWM DC/DC switching converters is presented. Using this method, the closed-loop switching converter is transformed into an open-loop system. By means of the fact that in steady state, the two boundary values are equal in one switching period. The exponential matrix is evaluated by precise time-domain-integration method, and then the related curve between feedback duty cycle and the input one is obtained. Not only can the steady-state duty cycle be found from the curve, but also the stability and stable domain of the system. Compared with other methods, it features with simplicity and less calculation, and fit for numerical simulation and analysis for closed-loop switching converters. The simulation results of examples indicate the correctness of the presented method.
文摘The measurements on actual traffic have revealed the existence of meta-stable states with high flow. Such nonlinear phenomena have not been observed in the classic Nagel-Schreckenberg traffic flow model. Here we just add a constraint to the classic model by introducing a velocity-dependent randomization. Two typical randomization strategies are adopted in this paper. It is shown that the Matthew effect is a necessary condition to induce traffic meta-stable states, thus shedding a light on the prerequisites for the emergence of hysteresis loop in the fundamental diagrams.
基金Sponsored by the Youth Science Fund Project of Heilongjiang University(Grant No.QL201127)the National Natural Science Foundation and Civil Aviation Administration of China(Grant No.61101122)+2 种基金the China Postdoctoral Science Foundation(Grant No.20100471079)the Heilongjiang Province Postdoctoral Science Foundation(Grant No.LBH-210127)the Fundamental Research Funds for the Central Universities(Grant No.HIT.NSRIF. 2010090)
文摘The effect of too much overhead caused by fixed neighborhood state update cycle on the whole network performance has been greatly alleviated by a neighborhood state dynamic update(NSDU) algorithm proposed for MANET in this paper.A local topology flapping metric(LTFM) has been established based on the changes of link connection to achieve the measurement of stability.The loop control theory has been adopted to establish the control model of the neighborhood state,so as to set up the mapping relationship with the topology change,based on which both the neighborhood state information exchange and the timeout of link with neighbors involved will be adjusted dynamically according to NSDU to ensure that the update cycle would regulate with the network environment in order to achieve the purpose of reducing the control overhead.The simulation results on NS2.34 with different nodes velocities,traffic generating rates and the network node densities shows that adopting NSDU,no matter based on a table-driven protocol or a on-demand one,would reduce the overhead effectively while hardly bring any obvious impacts on metrics of packet successful delivery rate and the average end-to-end delay as well.
文摘In this investigation, a novel thermally coupled reactor （TCR） containing methyl formate （MF） production in the endothermic side and methanol synthesis in the exothermic side has been investigated. The interesting feature of this TCR is that productive methanol in the exothermic side could be recycled and used as feed of endothermic side for MF synthesis. Other important advantages of the proposed system are high production rates of hydrogen and MF. The configuration consists of two thermally coupled concentric tubular reactors. In these coupled reactors, autothermal system is obtained within the reactor. A steady-state heterogeneous model is used for simulation of the coupled reactor. The proposed model has been utilized to compare the performance of TCR with the conventional methanol reactor （CMR）. Noticeable enhancement can be obtained in the performance of the reactors. The influence of operational parameters is studied on reactor performance. The results show that coupling of these reactions could be feasible and beneficial. Experimental proof-of-concept is required to validate the operation of the novel reactor.
文摘提出了一种基于改进线性扩张状态观测器(linear extended state observer,LESO)的电力电子负载自抗扰控制策略,解决了传统控制方法动态性能较差、对系统参数依赖等问题。建立LCL(line current loop)变换器在α-β坐标系下的数学模型,分析线性自抗扰控制(linear active disturbance rejection control,LADRC)中LESO的误差,对观测器控制输出部分的结构进行改进,以减小观测值中来自控制输出信号的误差。通过LESO求取指令电流微分,引入线性误差反馈控制率中,减小传统LADRC的固有误差。分析系统的频域特性,研究参数和控制策略对系统的影响。通过仿真和半实物仿真,验证了改进策略能明显改善传统LADRC跟踪动态信号时的波形畸变、相位滞后等问题,使变换器实现对各类负载的精确模拟。
