针对高压直流(high voltage direct current,HVDC)线路高阻接地故障时保护容易拒动的问题,提出一种基于单环定理的纵联保护方法。首先,将直流线路两侧电流突变量作为状态变量构造奇异值等价矩阵,根据单环定理进行谱分析从而实现区内外...针对高压直流(high voltage direct current,HVDC)线路高阻接地故障时保护容易拒动的问题,提出一种基于单环定理的纵联保护方法。首先,将直流线路两侧电流突变量作为状态变量构造奇异值等价矩阵,根据单环定理进行谱分析从而实现区内外故障识别;然后,通过广义S变换提取两极电流突变量特定频段暂态能量和的比值特征进行故障选极;最后,给出了纵联保护方案。仿真验证表明,所提保护原理判据简单,易于整定,各种故障情况下均能实现快速、有选择性动作。所提方法对不良数据具有较强的免疫能力,即使在线路末端发生高阻接地等最不利于保护动作的故障情况下仍能可靠动作。展开更多
Existing specific emitter identification(SEI)methods based on hand-crafted features have drawbacks of losing feature information and involving multiple processing stages,which reduce the identification accuracy of emi...Existing specific emitter identification(SEI)methods based on hand-crafted features have drawbacks of losing feature information and involving multiple processing stages,which reduce the identification accuracy of emitters and complicate the procedures of identification.In this paper,we propose a deep SEI approach via multidimensional feature extraction for radio frequency fingerprints(RFFs),namely,RFFsNet-SEI.Particularly,we extract multidimensional physical RFFs from the received signal by virtue of variational mode decomposition(VMD)and Hilbert transform(HT).The physical RFFs and I-Q data are formed into the balanced-RFFs,which are then used to train RFFsNet-SEI.As introducing model-aided RFFs into neural network,the hybrid-driven scheme including physical features and I-Q data is constructed.It improves physical interpretability of RFFsNet-SEI.Meanwhile,since RFFsNet-SEI identifies individual of emitters from received raw data in end-to-end,it accelerates SEI implementation and simplifies procedures of identification.Moreover,as the temporal features and spectral features of the received signal are both extracted by RFFsNet-SEI,identification accuracy is improved.Finally,we compare RFFsNet-SEI with the counterparts in terms of identification accuracy,computational complexity,and prediction speed.Experimental results illustrate that the proposed method outperforms the counterparts on the basis of simulation dataset and real dataset collected in the anechoic chamber.展开更多
BACKGROUND Major depressive disorder(MDD)tends to have a high incidence and high suicide risk.Electroconvulsive therapy(ECT)is currently a relatively effective treatment for MDD.However,the mechanism of efficacy of EC...BACKGROUND Major depressive disorder(MDD)tends to have a high incidence and high suicide risk.Electroconvulsive therapy(ECT)is currently a relatively effective treatment for MDD.However,the mechanism of efficacy of ECT is still unclear.AIM To investigate the changes in the amplitude of low-frequency fluctuations in specific frequency bands in patients with MDD after ECT.METHODS Twenty-two MDD patients and fifteen healthy controls(HCs)were recruited to this study.MDD patients received 8 ECT sessions with bitemporal placement.Resting-state functional magnetic resonance imaging was adopted to examine regional cerebellar blood flow in both the MDD patients and HCs.The MDD patients were scanned twice(before the first ECT session and after the eighth ECT session)to acquire data.Then,the amplitude of low-frequency fluctuations(ALFF)was computed to characterize the intrinsic neural oscillations in different bands(typical frequency,slow-5,and slow-4 bands).RESULTS Compared to before ECT(pre-ECT),we found that MDD patients after the eighth ECT(post-ECT)session had a higher ALFF in the typical band in the right middle frontal gyrus,posterior cingulate,right supramarginal gyrus,left superior frontal gyrus,and left angular gyrus.There was a lower ALFF in the right superior temporal gyrus.Compared to pre-ECT values,the ALFF in the slow-5 band was significantly increased in the right limbic lobe,cerebellum posterior lobe,right middle orbitofrontal gyrus,and frontal lobe in post-ECT patients,whereas the ALFF in the slow-5 band in the left sublobar region,right angular gyrus,and right frontal lobe was lower.In contrast,significantly higher ALFF in the slow-4 band was observed in the frontal lobe,superior frontal gyrus,parietal lobe,right inferior parietal lobule,and left angular gyrus.CONCLUSION Our results suggest that the abnormal ALFF in pre-and post-ECT MDD patients may be associated with specific frequency bands.展开更多
The paper quantitatively assesses the relationship between specific energy absorption rates (SAR) of radio frequency (RF) electromagnetic fields (EMF) and resulting intracorporal tissue temperature changes (ΔT) at wh...The paper quantitatively assesses the relationship between specific energy absorption rates (SAR) of radio frequency (RF) electromagnetic fields (EMF) and resulting intracorporal tissue temperature changes (ΔT) at whole body exposure of a small person to resonant RF EMF. Applied thermal modeling allowed accounting also for dynamic thermoregulatory responses. As expected from physical laws the correlation of all local SAR values and ΔT data was fairly good. However, at local level SAR proved to be only weakly associated with ΔT. Even if averaged, over any 10 g tissue the ratio ΔT10g/SAR10g still varied by almost two orders of magnitudes. Blood perfusion was found to play a major role in affecting local temperature changes and caused even net cooling. The results demonstrate that local SAR is a poor surrogate for local temperature change, and that conventional static thermal modeling underestimates body core temperature. Results demonstrated that recommended reference levels of RF EMF fail to reliably prevent from exceeding yet legally binding basic restrictions not only with regard to whole-body SAR but also with regard to whole-body temperature rise (ΔT). Consequently, from a legal point of view general presumption of conformity is no longer justified. While thermal basic restrictions were exceeded if related to the whole-body averaged value, compliance could not be excluded with regard to body-core related values. Further results might allow improving EMF limiting in terms of relating it more closely to the basic health-relevant parameter which is tissue temperature change.展开更多
Background:Patients with drug refractory temporal lobe epilepsy frequently accumulate cognitive impairment over time,suggesting loss of neurons induced by seizures.Our objective was to determine whether there is a tem...Background:Patients with drug refractory temporal lobe epilepsy frequently accumulate cognitive impairment over time,suggesting loss of neurons induced by seizures.Our objective was to determine whether there is a temporal association between changes in serum levels of neural injury markers and electroencephalographic(EEG)evidence of seizures and interictal spikes.Methods:We measured serum levels of neuron-specific enolase(NSE),a neuronal injury marker,relative to levels of S100β,a marker of glial injury,at 6 AM,9 AM,noon,3 PM,and 6 PM over the course of several days in 7 epilepsy patients undergoing continuous video-EEG monitoring and in 4 healthy controls.Results:All epilepsy patients exhibited significant deviations in NSE levels through time,and 4 of the epilepsy patients exhibited large sample entropy values and large signal variation metrics for NSE relative to S100β.Controls did not exhibit such changes.Correlation analysis revealed that NSE levels were significantly elevated after seizures.There was also a highly significant relationship between increased EEG spike frequency and an increase in serum NSE levels measured 24 h later.Conclusions:The detection of large but transient post-ictal increases in NSE suggests that even self-limited seizures may cause an injury to neurons that underlies cognitive decline in some patients.While this study used a small patient population,the pilot findings suggest that post-ictal assessment of serum NSE may serve as a biomarker for measuring the efficacy of future acute neuroprotective strategies in epilepsy patients.展开更多
As future improvement to the energy density and power density of supercapacitors relies on the availability of new materials, worldwide research has been undertaken to address this need. The recent advancement in new ...As future improvement to the energy density and power density of supercapacitors relies on the availability of new materials, worldwide research has been undertaken to address this need. The recent advancement in new materials used for fabricating supercapacitors is reviewed in this paper. Among the newly emerged materials covered in this review are the activated graphene, conductive polymers, CNT （carbon nantotubes）, AC （activated carbons）, carbon additives and metal oxides for EDLC （electric double layer capacitors） and pseudocapacitors applications.展开更多
文摘针对高压直流(high voltage direct current,HVDC)线路高阻接地故障时保护容易拒动的问题,提出一种基于单环定理的纵联保护方法。首先,将直流线路两侧电流突变量作为状态变量构造奇异值等价矩阵,根据单环定理进行谱分析从而实现区内外故障识别;然后,通过广义S变换提取两极电流突变量特定频段暂态能量和的比值特征进行故障选极;最后,给出了纵联保护方案。仿真验证表明,所提保护原理判据简单,易于整定,各种故障情况下均能实现快速、有选择性动作。所提方法对不良数据具有较强的免疫能力,即使在线路末端发生高阻接地等最不利于保护动作的故障情况下仍能可靠动作。
基金supported by the National Natural Science Foundation of China(62061003)Sichuan Science and Technology Program(2021YFG0192)the Research Foundation of the Civil Aviation Flight University of China(ZJ2020-04,J2020-033)。
文摘Existing specific emitter identification(SEI)methods based on hand-crafted features have drawbacks of losing feature information and involving multiple processing stages,which reduce the identification accuracy of emitters and complicate the procedures of identification.In this paper,we propose a deep SEI approach via multidimensional feature extraction for radio frequency fingerprints(RFFs),namely,RFFsNet-SEI.Particularly,we extract multidimensional physical RFFs from the received signal by virtue of variational mode decomposition(VMD)and Hilbert transform(HT).The physical RFFs and I-Q data are formed into the balanced-RFFs,which are then used to train RFFsNet-SEI.As introducing model-aided RFFs into neural network,the hybrid-driven scheme including physical features and I-Q data is constructed.It improves physical interpretability of RFFsNet-SEI.Meanwhile,since RFFsNet-SEI identifies individual of emitters from received raw data in end-to-end,it accelerates SEI implementation and simplifies procedures of identification.Moreover,as the temporal features and spectral features of the received signal are both extracted by RFFsNet-SEI,identification accuracy is improved.Finally,we compare RFFsNet-SEI with the counterparts in terms of identification accuracy,computational complexity,and prediction speed.Experimental results illustrate that the proposed method outperforms the counterparts on the basis of simulation dataset and real dataset collected in the anechoic chamber.
基金Supported by the Natural Science Foundation of China,No.81901373the Intelligent Medicine Research Project of Chongqing Medical University,No.ZHYX202126.
文摘BACKGROUND Major depressive disorder(MDD)tends to have a high incidence and high suicide risk.Electroconvulsive therapy(ECT)is currently a relatively effective treatment for MDD.However,the mechanism of efficacy of ECT is still unclear.AIM To investigate the changes in the amplitude of low-frequency fluctuations in specific frequency bands in patients with MDD after ECT.METHODS Twenty-two MDD patients and fifteen healthy controls(HCs)were recruited to this study.MDD patients received 8 ECT sessions with bitemporal placement.Resting-state functional magnetic resonance imaging was adopted to examine regional cerebellar blood flow in both the MDD patients and HCs.The MDD patients were scanned twice(before the first ECT session and after the eighth ECT session)to acquire data.Then,the amplitude of low-frequency fluctuations(ALFF)was computed to characterize the intrinsic neural oscillations in different bands(typical frequency,slow-5,and slow-4 bands).RESULTS Compared to before ECT(pre-ECT),we found that MDD patients after the eighth ECT(post-ECT)session had a higher ALFF in the typical band in the right middle frontal gyrus,posterior cingulate,right supramarginal gyrus,left superior frontal gyrus,and left angular gyrus.There was a lower ALFF in the right superior temporal gyrus.Compared to pre-ECT values,the ALFF in the slow-5 band was significantly increased in the right limbic lobe,cerebellum posterior lobe,right middle orbitofrontal gyrus,and frontal lobe in post-ECT patients,whereas the ALFF in the slow-5 band in the left sublobar region,right angular gyrus,and right frontal lobe was lower.In contrast,significantly higher ALFF in the slow-4 band was observed in the frontal lobe,superior frontal gyrus,parietal lobe,right inferior parietal lobule,and left angular gyrus.CONCLUSION Our results suggest that the abnormal ALFF in pre-and post-ECT MDD patients may be associated with specific frequency bands.
文摘The paper quantitatively assesses the relationship between specific energy absorption rates (SAR) of radio frequency (RF) electromagnetic fields (EMF) and resulting intracorporal tissue temperature changes (ΔT) at whole body exposure of a small person to resonant RF EMF. Applied thermal modeling allowed accounting also for dynamic thermoregulatory responses. As expected from physical laws the correlation of all local SAR values and ΔT data was fairly good. However, at local level SAR proved to be only weakly associated with ΔT. Even if averaged, over any 10 g tissue the ratio ΔT10g/SAR10g still varied by almost two orders of magnitudes. Blood perfusion was found to play a major role in affecting local temperature changes and caused even net cooling. The results demonstrate that local SAR is a poor surrogate for local temperature change, and that conventional static thermal modeling underestimates body core temperature. Results demonstrated that recommended reference levels of RF EMF fail to reliably prevent from exceeding yet legally binding basic restrictions not only with regard to whole-body SAR but also with regard to whole-body temperature rise (ΔT). Consequently, from a legal point of view general presumption of conformity is no longer justified. While thermal basic restrictions were exceeded if related to the whole-body averaged value, compliance could not be excluded with regard to body-core related values. Further results might allow improving EMF limiting in terms of relating it more closely to the basic health-relevant parameter which is tissue temperature change.
基金NS064571 from the NIH/NINDS(CLH),grant UL1TR000135 from the NIH/NCATSthe Mayo Clinic Center for MS and Autoimmune Neurology,and a generous gift from the Albert and Mary Jane Staton Family.
文摘Background:Patients with drug refractory temporal lobe epilepsy frequently accumulate cognitive impairment over time,suggesting loss of neurons induced by seizures.Our objective was to determine whether there is a temporal association between changes in serum levels of neural injury markers and electroencephalographic(EEG)evidence of seizures and interictal spikes.Methods:We measured serum levels of neuron-specific enolase(NSE),a neuronal injury marker,relative to levels of S100β,a marker of glial injury,at 6 AM,9 AM,noon,3 PM,and 6 PM over the course of several days in 7 epilepsy patients undergoing continuous video-EEG monitoring and in 4 healthy controls.Results:All epilepsy patients exhibited significant deviations in NSE levels through time,and 4 of the epilepsy patients exhibited large sample entropy values and large signal variation metrics for NSE relative to S100β.Controls did not exhibit such changes.Correlation analysis revealed that NSE levels were significantly elevated after seizures.There was also a highly significant relationship between increased EEG spike frequency and an increase in serum NSE levels measured 24 h later.Conclusions:The detection of large but transient post-ictal increases in NSE suggests that even self-limited seizures may cause an injury to neurons that underlies cognitive decline in some patients.While this study used a small patient population,the pilot findings suggest that post-ictal assessment of serum NSE may serve as a biomarker for measuring the efficacy of future acute neuroprotective strategies in epilepsy patients.
文摘As future improvement to the energy density and power density of supercapacitors relies on the availability of new materials, worldwide research has been undertaken to address this need. The recent advancement in new materials used for fabricating supercapacitors is reviewed in this paper. Among the newly emerged materials covered in this review are the activated graphene, conductive polymers, CNT （carbon nantotubes）, AC （activated carbons）, carbon additives and metal oxides for EDLC （electric double layer capacitors） and pseudocapacitors applications.
