检索结果-南通市图书馆

Anthropomorphic Control of a dexterous Artificial Hand via Task dependent Temporally Synchronized Synergies

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Bionic Engineering 2014年第2期11卷 236-248页

作者： Benjamin A. Kcnt john Lavery Erik d. Engeberg department of Mechanical Engineering University of Akron Akron OH 44325 USA department of Biomedical Engineering University of Akron Akron OH 44325 USA

despite the recent influx of increasingly dexterous prostheses, there remains a lack of sufficiently intuitive control methods to fully utilize this dexterity. As a solution to this problem, a control framework is proposed which allows the control of an arbitrary number of degrees of Freedom （dOF） through a single electromyogram （EMG） control input. Initially, the joint motions of nine test subjects were recorded while grasping and catching a cylinder. Inherent differences emerged depending upon whether the cylinder was grasped or caught. These data were used to form a distinct synergy for each task, described as the families of parametric functions of time that share a mutual time vector. These two Temporally Synchronized Synergies （TSS） were derived to reflect the task dependent control strategies adopted by the initial participants. These synergies were then mapped to a dexterous artificial hand that was subsequently controlled by two subjects with transradial amputations. The EMG signals from these subjects were used to replace the time vector shared by the synergies, enabling the subjects to perform both tasks with a dexterous artificial hand using only a single EMG input. After a ten minute training period, the subjects learned to use the dexterous artificial hand to grasp and catch the cylinder with 100.0% and 65.0% average success rates, respectively.

关键词： electromyogram dexterous hands grasp synergy prosthetics sliding mode control

Neural connectivity inference with spike-timing dependent plasticity network

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2021年第6期64卷 70-79页

作者： john MOON Yuting WU Xiaojian ZHU Wei d.LU department of Electrical Engineering and Computer Science University of Michigan

Knowing the connectivity patterns in neural circuitry is essential to understand the operating mechanism of the brain, as it allows the analysis of how neural signals are processed and flown through the neural system. With the recent advances in neural recording technologies in terms of channel size and time resolution, a simple and efficient system to perform neural connectivity inference is highly desired, which will enable the process of high dimensional neural activity recording data and reduction of the computational time and cost. In this work, we show that the spike-timing dependent plasticity(STdP) algorithm can be used to reconstruct neural connectivity patterns in a biological neural network, with higher accuracy and efficiency than statistic-based inference methods. The biologically inspired STdP learning rules are natively implemented in a second-order memristor network and are used to estimate the type and the direction of neural connections. When stimulated by the recorded neural spike trains, the memristor device conductance is modulated by the proposed STdP learning rules, which in turn reflects the correlation of the spikes and the possibility of neural connections. By compensating for the different levels of neural activity, highly reliable inference performance can be achieved. The proposed approach offers real-time and local learning, resulting in reduced computational cost/time and strong tolerance to variations of the neural system.

关键词： spike-timing dependent plasticity neural connectivity memristor online learning second-order memristor

Non-Abelian generalizations of the Hofstadter model:spin-orbit-coupled butterfly pairs

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Light(Science & Applications) 2020年第1期9卷 302-314页

作者： Yi Yang Bo Zhen john d.Joannopoulos Marin Soljacic department of Physics and Research Laboratory of Electronics Massachusetts Institute of TechnologyCambridgeMA 02139USA department of Physics and Astronomy University of PennsylvaniaPhiladelphiaPA 19104USA

The Hofstadter model,well known for its fractal butterfly spectrum,describes two-dimensional electrons under a perpendicular magnetic field,which gives rise to the integer quantum Hall *** by the real-space building blocks of non-Abelian gauge fields from a recent experiment,we introduce and theoretically study two non-Abelian generalizations of the Hofstadter *** model describes two pairs of Hofstadter butterflies that are spin–orbit *** contrast to the original Hofstadter model that can be equivalently studied in the Landau and symmetric gauges,the corresponding non-Abelian generalizations exhibit distinct spectra due to the non-commutativity of the gauge *** derive the genuine(necessary and sufficient)non-Abelian condition for the two models from the commutativity of their arbitrary loop *** zero energy,the models are gapless and host Weyl and dirac points protected by internal and crystalline ***(8-fold),triple(12-fold),and quadrupole(16-fold)dirac points also emerge,especially under equal hopping phases of the non-Abelian *** other fillings,the gapped phases of the models give rise to topological *** conclude by discussing possible schemes for experimental realization of the models on photonic platforms.

关键词： generalization gauge Abelian

Effects of mountain pine beetle-killed forests on source water contributions to streamflow in headwater streams of the Colorado Rocky Mountains

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers of Earth Science 2017年第3期11卷 496-504页

作者： Christine E. WEHNER john d. STEdNICK Watershed Science Program College of Natural Resources Colorado State University Fort Collins CO 80523-1472 USA

Natural or human-influenced disturbances are important to the health and diversity of forests, which in turn, are important to the water quantity and quality exported from a catchment. However, human-induced disturbances （prescribed fire and harvesting） have been decreasing, and natural disturbances （fires and insects） have been increasing in frequency and severity. One such natural disturbance is the mountain pine beetle （MPB）, （denclroctonus ponderosae） an endemic species. A recent epidemic resulted in the mortality of millions of hectares of lodgepole pine （Pinus contorta） forests in Colorado, USA. Beetle-induced tree mortality brings about changes to the hydrologic cycle, including decreased transpiration and interception with the loss of canopy cover. This study examined the effect of the mountain pine beetle kill on source water contributions to streamflow in snowmelt- dominated headwater catchments using stable isotopes （2H and ~80） as tracers. Study catchments with varying level of beetle-killed forest area （6% to 97%） were sampled for groundwater, surface water, and precipitation. Streams were sampled to assess whether beetle-killed forests have altered source water contributions to streamflow. Ground- water contributions increased with increasing beetle-killed forest area （p = 0.008）. Both rain and snow contributions were negatively correlated with beetle-killed forest area （p = 0.035 and p = 0.011, respectively）. As the beetle-killed forest area increases, so does fractional groundwater contribution to streamflow.

关键词： mountain pine beetle isotope tracers stream-flow generation headwaters

Glucose metabolism in amyotrophic lateral sclerosis:it is bitter-sweet

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Neural Regeneration Research 2022年第9期17卷 1975-1977页

作者： Titaya Lerskiatiphanich Jianina Marallag john d.Lee School of Biomedical Sciences Faculty of MedicineThe University of QueenslandSt LuciaBrisbaneQLDAustralia

A recent study by Mcdonald et al.(2021)focused on how peripheral glucose metabolism and handling are compromised in amyotrophic lateral sclerosis(ALS).dysfunctions in glucose and energy metabolism have been identified in transgenic mouse models and patients with ***,how these processes are altered and contribute to disease progression are not fully *** aforementioned study has identified several changes to glucose homeostasis in the transgenic SOd1G93A mouse model of ALS at the later stages of the ***,the authors found that despite insulin resistance being present,there was increased glucose uptake in ALS mice,and increased glycogen accumulation in the ***,there was evidence of glucagon resistance developing in these mice,which supports clinical *** perspective outlines the key aspects of glucose metabolism and demonstrates how multiple pathways relating to these processes are compromised in ALS.

关键词： metabolism amyotrophic homeostasis

Complement:a global immunometabolic regulator in amyotrophic lateral sclerosis

在线全文

学校读者我要写书评

暂无评论

Neural Regeneration Research 2021年第6期16卷 1210-1211页

作者： Martin W.Lo john d.Lee School of Biomedical Sciences Faculty of MedicineThe University of QueenslandSt LuciaQueenslandAustralia

Recently,Mcdonald et al.(2020)proposed that complement causes a metabolic switch to lipid consumption in amyotrophic lateral sclerosis(ALS),which raises the possibility of complement as a global immunometabolic *** ALS,neuromuscular degeneration occurs concurrently with complement-mediated inflammation,glucose intolerance,and elevated lipid ***,complement is being increasingly recognized as a metabolic regulator that can induce insulin resistance and alter fuel source ***,the authors propose that chronic complement activation may be driving metabolic reprogramming in ALS,which has broad implications for the field of immunometabolism and would be the first mechanistic explanation of the“lipid switch”in ***,it suggests that complement can drive a global shift in resources during inflammation,in which glucose is redirected from peripheral tissues to immune cells to support their inflammatory actions.

关键词： inflammation metabolism elevated

Proportional-integral-derivative control of nonlinear half-car electro-hydraulic suspension systems

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2013年第6期14卷 401-416页

作者： john E. d. EKORU Jimoh O. PEdRO School of Mechanical Aeronautical and Industrial Engineering University of the Witwatersrand Private Bag 03 WITS 2050 Johannesburg South Africa

This paper presents the development of a proportional-integral-derivative (PId)-based control method for application to active vehicle suspension systems (AVSS). This method uses an inner PId hydraulic actuator force control loop, in combination with an outer PId suspension travel control loop, to control a nonlinear half-car AVSS. Robustness to model uncertainty in the form of variation in suspension damping is tested, comparing performance of the AVSS with a passive vehicle suspension system (PVSS), with similar model parameters. Spectral analysis of suspension system model output data, obtained by performing a road input disturbance frequency sweep, provides frequency response plots for both nonlinear vehicle suspension systems and time domain vehicle responses to a sinusoidal road input disturbance on a smooth road. The results show the greater robustness of the AVSS over the PVSS to parametric uncertainty in the frequency and time domains.

关键词： Force control Proportional-integral-derivative (PId) control Nonlinear half-car Active vehicle suspension system (AVSS) Hydraulic actuator dynamics Model uncertainty

All-optical forward-viewing photoacoustic probe for high-resolution 3d endoscopy

在线全文

学校读者我要写书评

暂无评论

Light(Science & Applications) 2018年第1期7卷 337-345页

作者： Rehman Ansari Edward Z.Zhang Adrien E.desjardins Paul C.beard department Medical Physics and Biomedical Engineering University College LondonGower StreetLondon WC1E 6BTUK Wellcome/EPSRC Centre for Interventional and Surgical Sciences University College LondonCharles Bell House67-73 Riding House StreetLondon W1W 7EJUK

A miniature forward-viewing endoscopic probe that provides high-resolution 3d photoacoustic images is *** probe is of outer diameter 3.2mm and comprised of a transparent Fabry-Pérot(FP)polymer-film ultrasound sensor that is located at the distal end of a rigid optical fiber *** laser pulses are coupled simultaneously into all cores of the bundle and are transmitted through the FP sensor to provide wide-field tissue illumination at the distal *** resulting photoacoustic waves are mapped in 2d by sequentially scanning the input end of the bundle with an interrogation laser beam in order to individually address different points on the FP *** this way,the sensor acts as a high-density ultrasound array that is comprised of 50,000 individual elements,each of which is 12μm in diameter,within the 3.2mm diameter footprint of the *** fine spatial sampling that this affords,along with the wide bandwidth(f_(-3dB)=34 MHz)of the sensor,enables a high-resolution photoacoustic image to be *** measured on-axis lateral resolution of the probe was depth-dependent and ranged from 45-170μm for depths between 1 and 7 mm,and the vertical resolution was 31μm over the same depth *** system was evaluated by acquiring 3d images of absorbing phantoms and the microvascular anatomies of a duck embryo and mouse *** image fidelity was *** is anticipated that this type of probe could find application as a tool for guiding laparoscopic procedures,fetal surgery and other minimally invasive interventions that require a millimeter-scale forward-viewing 3d photoacoustic imaging probe.

关键词： optical millimeter resolution

Characterization of the Tomato Prosystemin Promoter:Organ-specific Expression,Hormone Specificity and Methyl Jasmonate Responsiveness by deletion Analysis in Transgenic Tobacco Plants

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Integrative Plant Biology 2012年第1期54卷 15-32页

作者： Hamlet Avilés-Arnaut john Paul délano-Frier Center of Research and Advanced Studies (Cinvestav) at Irapuato:Unit for Plant Biotechnology and Genetic Engineering

Tomato systemin is a bioactive peptide that regulates the systemic activation of wound-responsive genes. It is released from its 200 amino acid precursor called prosystemin. Initial tissue-localization and hormone-induced expression assays indicated that the tomato prosystemin gene （SIPS） accumulates mainly in floral tissues and in response to exogenous abscisic acid and methyl jasmonate （MeJA） treatments, respectively. Later, the promoter regions of the PS gene in tomato （Solanum lycopersicum L. cv. Castlemart）, pepper （Capsicum annuum） and potato （Solanum tuberosum） were isolated and an in silico analysis of the SIPS promoter revealed an over-representation of stress- and MeJA-responsive motifs. A subsequent 5＇ deletion analysis of the SIPS promoter fused to the/^-glucuronidase reporter （GUS） gene showed that the -221 to ＋40 bp proximal SIPS promoter region was sufficient to direct the stigma, vascular bundle-specific and MeJA-responsive expression of GUS in transgenic tobacco plants. Important ***-specific, light- and MeJA-responsive cis-elements were also present in this region. These findings provide relevant information regarding the transcriptional regulation mechanisms of the SIPS promoter operating in transgenic tobacco plants. They also suggest that its Ussue-specificity and inducible nature could have wide applicability in plant biotechnology.

关键词： cis-regulatory elements flower specific jasmonic acid methyl jasmonate promoter analysis prosystemin wound-responsive genes.