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Response of monkey glabrous skin mechanoreceptors to random noise sequences .3. Spectral analysis

SOMATOSENSORY AND MOTOR RESEARCH 1996年第3-4期13卷 235-244页

作者： Looft, FJ Department of Electrical and Computer Engineering Worcester Polytechnic Institute 100 Institute Road Worcester Massachusetts 01609 fjlooft@ee.wpi.edu

Spectral transfer functions for monkey glabrous skin tactile mechanoreceptors were computed and compared to the results from a dynamic stimulus state analysis for the same receptors. For both sets of experiments, a vibrotactile indenting punctate stimulus driven from a non-repeating-noise (NRN) signal source was used to activate afferents. In all cases, the spectral transfer function results were similar to those inferred from dynamic stimulus state analysis. However, a comparison between the laboratory data and the results from a simple neural model showed that the interpretation of spectral transfer functions is significantly enhanced when compared to the results from an instantaneous state (position, velocity, acceleration) analysis of the stimulus at the time of impulse initiation.

关键词： mechanoreceptors vibrotactile glabrous skin noise stimulus spectral analysis

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RESPONSE OF MONKEY GLABROUS SKIN MECHANORECEPTORS TO RANDOM-NOISE SEQUENCES .1. TEMPORAL RESPONSE CHARACTERISTICS

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SOMATOSENSORY AND MOTOR RESEARCH 1994年第4期11卷 327-344页

作者： LOOFT, FJ Department of Electrical and Computer Engineering Worcester Polytechnic Institute Massachusetts 01609 USA.

The response of slowly adapting (SA, Merkel cell), rapidly adapting (RA, Meissner), and Pacinian corpuscle (PC) mechanoreceptors in monkey glabrous skin were recorded while being activated with a vibrotactile indenting stimulus. For one set of experiments, the stimulator was driven by an 800-point (400-msec) pseudorandom-noise (PRN) sequence, repeated 40 times. For a second set of experiments, a non-repeating-noise (NRN) sequence was used. SA impulse patterns generated with the PRN sequence were highly regular and similar for all afferents tested. RA and PC response patterns were more varied, but exhibited basic intraclass similarities. SA and RA PRN stimulus impulse patterns were often nearly indistinguishable at low to medium discharge rates. At higher discharge rates, RA and SA discharge patterns differed, primarily because of the unambiguous suprathreshold velocity sensitivity and shorter recovery periods of RA afferents. PC impulse patterns were substantially different from SA and RA patterns, being clearly dependent on the stimulus velocity at all stimulus intensities. Input-output correlation analysis, coupled with PRN stimulus-response analysis, provided a basis for hypothesizing the basic dynamic encoder function of each type of mechanoreceptor.

关键词： MECHANORECEPTORS VIBROTACTILE GLABROUS SKIN PSEUDORANDOM NOISE

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The effect of receiver diversity combining on optimum energy allocation and energy efficiency of cooperative wireless transmission systems

The effect of receiver diversity combining on optimum energy...

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2007 IEEE International Conference on Acoustics, Speech and Signal Processing, ICASSP '07

作者： Jie, Yang Brown III, D. Richard Electrical and Computer Engineering Department Worcester Polytechnic Institute Worcester MA

ISBN: (纸本)1424407281

This paper considers the problem of how to efficiently allocate transmission energy in a cooperative wireless communication system with one source, one relay, and one destination. The relay assists the source via an orthogonal amplify-and-forward protocol. The channels are assumed to be flat fading and the destination combines the source and relay transmissions using either maximal ratio combining (MRC) or equal gain combining (EGC). We analyze the problem of minimizing average total (source plus relay) transmit energy under a fixed outage probability constraint. We show that the choice of receiver diversity combining technique affects both the optimum energy allocation and the overall energy efficiency of the cooperative communication system. Our results show that the ratio of optimum relay to source transmission energy tends to be greater for EGC than MRC. Our results also show that, while cooperative transmission with MRC is always the most efficient strategy, cooperative transmission with EGC tends to be more energy efficient than direct transmission when the outage probability constraint is small or when the relay experiences an advantaged channel to the destination. © 2007 IEEE.

关键词： Wireless networks

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Robot-Assisted Wide-Area Photoacoustic System

Robot-Assisted Wide-Area Photoacoustic System

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2023 IEEE International Ultrasonics Symposium, IUS 2023

作者： Gao, Shang Ma, Xihan Zhang, Haichong K. Worcester Polytechnic Institute Department of Robotics Engineering Worcester United States Worcester Polytechnic Institute Department of Biomedical Engineering Worcester United States Worcester Polytechnic Institute Department of Computer Science Worcester United States

ISBN: (纸本)9798350346459

Liver ischemia and reperfusion injury (IRI) is a vascular complication that can lead to hepatic functional impairment. IRI is relevant in liver transplantation and during liver surgery performed with intermittent vascular inflow occlusion. Detecting intraoperative liver oxygenation impairment and ischemia could help prevent IRI, which is challenging partially due to the multiple hepatic vascular inflows. We propose a robot-assisted wide-area photoacoustic (PA) imaging system to monitor the liver oxygenation level intraoperatively. PA imaging has been widely used for oxygenation detection in preclinical research. We used a robotic arm to actuate the 2D PA probe and scan across the liver surface. An accurate volumetric tomography can be reconstructed via registering 2D images to the recorded robot trajectory. An ex vivo porcine liver sample was scanned using the proposed system. The result suggested that the robot-assisted wide-area PA tomography has the potential to be incorporated into clinical practice to evaluate liver SO2 intraoperatively. © 2023 IEEE.

关键词： Photoacoustic effect

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FINITE-ELEMENT FORMULATION OF ACOUSTIC SCATTERING PHENOMENA WITH ABSORBING BOUNDARY-CONDITION IN THE FREQUENCY-DOMAIN

FINITE-ELEMENT FORMULATION OF ACOUSTIC SCATTERING PHENOMENA ...

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IEEE 1992 ULTRASONIC SYMP

作者： GAN, H LEVIN, PL LUDWIG, R Department of Electrical and Computer Engineering Worcester Polytechnic Institute Worcester 01609 MA United States

ISBN: (纸本)0780305620

This paper discusses a finite element formulation with an absorbing boundary condition to simulate acoustic scattering phenomena in a general situation, that is, including density as well as sound velocity variations of single and multi-scatterers of arbitrary two dimensional cross sections. In this model, a Galerkin finite element formulation is incorporated with an absorbing boundary operator which explicitly accounts for the open field problem by mapping the Sommerfeld radiation condition from the far field to the near field. By applying the absorbing boundary operator on the artificial boundary of the finite domain, the truncation errors as well as the artifactual reflected power is minimized without compromising the spatsity of the finite element matrix. We compare the numerical results with analytical solutions of cylindrical scatterers of different sizes and at different frequencies. Also, we demonstrate the flexibility of the model by simulating inhomogeneous scatterers and multi-scattering configurations. © 1992 IEEE.

关键词： Boundary conditions

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Assessment of Positioning Errors on V2V Networks Employing Dual Beamforming 88

Assessment of Positioning Errors on V2V Networks Employing D...

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88th IEEE Vehicular Technology Conference, VTC-Fall 2018

作者： Kanthasamy, Nivetha Du, Ruixiang Gill, Kuldeep S. Wyglinski, Alexander M. Cowlagi, Raghvendra Department of Electrical and Computer Engineering Worcester Polytechnic Institute WorcesterMA United States Department of Mechanical Engineering Worcester Polytechnic Institute WorcesterMA United States

ISBN: (纸本)9781538663585

In this paper, we present an analysis of Vehicle-to-Vehicle (V2V) Networks employing beamforming at both the transmitter and the receiver when positioning errors are present. Specifically, we will examine the performance of this system setup when the source of the positioning errors are from the Global Positioning System (GPS) measurements as well as from variations in the delays due to the overhead communication channels. To achieve adequate performance, beamforming requires precise location information of the transmitter and the receiver, and when accurate information is unavailable the system performance can potentially deteriorate. This is especially challenging in highly mobile vehicle networking environments where the operating conditions and location information varies rapidly in time. Simulation results are obtained showing Bit Error Rate (BER) values increasing by 99.9% when the exact GPS locations are known by the vehicles when compared to a 6.6m error in GPS location. © 2018 IEEE.

关键词： Global positioning system

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Performance evaluation of the RF receiver for precision positioning system

Performance evaluation of the RF receiver for precision posi...

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17th International Technical Meeting of the Satellite Division of the institute of Navigation, ION GNSS 2004

作者： Parikh, Hemish K. Michalson, William R. Duckworth, R. James Electrical and Computer Engineering Department Worcester Polytechnic Institute Worcester Polytechnic Institute ECE Department Worcester Polytechnic Institute WPI Bioengineering Institute Center for Untethered Healthcare

One of the major drivers for developing integrated navigation systems is the vision to provide first responders and healthcare providers, critical information where and when they need it. These integrated wireless devices of the future will assist the user with communications and incident management operations in the field in real time. The most important piece of such a system is clearly a ability to track and locate these wireless devices with high precision in a high-multipath environment. A previous paper presented a novel method for precise geolocation in indoor environments using an orthogonal frequency domain multiplexed (OFDM) signal consisting of many sinusoidal sub-carriers. Unlike the ultra wideband signals that are often proposed for performing precision location in high multipath environments, the proposed signal structure is easily adapted to conform to existing spectral allocations. Further, the signal structure is capable of being used in coded orthogonal frequency domain multiplexing (COFDM) systems for supporting communications and navigation concurrently on the same radio channel. This technique is also well suited for use on ad hoc wireless networks, allowing the precision location of wireless nodes with respect to one another. This OFDM-based technique was first demonstrated using audio frequency signals rather than RF signals and is currently being implemented at RF. The focus of this paper is the design and performance evaluation of the RF front end receiver structure being developed for precision location system using this multi-carrier technique. The effect on the precision of the location estimate due to RF receiver design imperfections will be assessed and design issues for future receiver design improvements will be reviewed.

关键词： Radio receivers

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Resource allocation for cooperative transmission in wireless networks with orthogonal users

Resource allocation for cooperative transmission in wireless...

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Conference Record of the Thirty-Eighth Asilomar Conference on Signals, Systems and computers

作者： Brown III, D. Richard Electrical and Computer Engineering Department Worcester Polytechnic Institute Worcester MA 01609

This paper investigates the problem of efficient power allocation in a wireless communication system with two cooperating sources and one destination. The sources in the system each transmit information to a single destination at a fixed SNR target and cooperate via an orthogonal amplify-and-forward protocol with two timeslots. We develop a framework for power allocation in this scenario around the concept of "cooperation ratios" and derive expressions for the transmit power required by each source to achieve their SNR targets as a function of these cooperation ratios. Numerical examples are presented for time-invariant channels as well as Rayleigh fading channels. Our results show that cooperation does not reduce required transmit powers when both sources have symmetric time-invariant channels to the destination. When sources have asymmetric time-invariant channels to the destination, total power is minimized when only the source with the stronger channel cooperates. In the case of Rayleigh fading channels, we demonstrate that mutual cooperation can minimize the average total required transmit power and can also lead to a reduction in average required transmit power for both sources. ©2004 IEEE.

关键词： Wireless telecommunication systems

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An efficient N-to-1 multipath routing protocol in wireless sensor networks

An efficient N-to-1 multipath routing protocol in wireless s...

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2nd IEEE International Conference on Mobile Ad-hoc and Sensor Systems, MASS 2005

作者： Lou, Wenjing Department of Electrical and Computer Engineering Worcester Polytechnic Institute Worcester MA 01609

ISBN: (纸本)0780394666

A typical task in a wireless sensor network is that every sensor node senses its local environment and, upon request, sends the data of interest back to a base station. Based on this many-to-one communication pattern, we first propose a distributed N-to-1 multipath discovery protocol which distinguishes from other multipath routing protocols in that it is able to find multiple node-disjoint paths from every sensor node to the base station simultaneously in one route discovery process. Then we propose a hybrid multipath data collection scheme which combines end-to-end multipath traffic dispersion and per-hop alternate path salvaging. Our simulation results show that the proposed N-to-1 multipath discovery protocol is highly efficient and the hybrid data collection scheme based on it provides a seamlessly more reliable and more secure data collection service in wireless sensor networks. © 2005 IEEE.

关键词： Wireless telecommunication systems

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A method for carrier frequency and phase synchronization of two autonomous cooperative transmitters

A method for carrier frequency and phase synchronization of ...

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2005 IEEE 6th Workshop on Signal Processing Advances in Wireless Communications, SPAWC 2005

作者： Brown III, D. Richard Prince, Gregary B. McNeill, John A. Department of Electrical and Computer Engineering Worcester Polytechnic Institute Worcester MA 01609

Cooperative communication protocols in which two or more sources transmit simultaneously in a single subchannel offer the potential for increased power efficiency and achievable rate with respect to orthogonal transmit cooperation. These protocols are, however, complicated by the fact that they require strict transmitter synchronization in order for the carrier signals from each source to arrive in phase and constructively combine at the intended destination. This paper develops an explicit method for synchronizing the carriers of two sources in a cooperative communication system with one destination. Unlike the prior work in this area, the approach described in this paper allows for source and/or destination mobility. The performance of the proposed carrier synchronization system is investigated for several channel models and practical design considerations are also discussed. © 2005 IEEE.

关键词： Transmitters

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