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11th European Conference on Artificial Life, ECAL 2011

作者： Misevic, Dusan Ofria, Charles Lenski, Richard E. Université Paris Descartes Paris France Program in Ecology Evolutionary Biology and Behavior Michigan State University East LansingMI United States Department of Computer Science and Engineering Michigan State University East LansingMI United States Department of Microbiology and Molecular Genetics Michigan State University East LansingMI United States

ISBN: (纸本)9780262297141

Many theories have sought to explain the evolution of sex, but the question remains unanswered owing to the scarcity of compelling empirical tests. Here we summarize the results of two of our published studies investigating the evolution of sex using digital organisms. We used these evolving programs to test the hypothesis that sexual reproduction is advantageous in changing environments. We found that sex evolved to be the dominant mode of reproduction only when the environment was changing rapidly and substantially. Additionally, we measured the effects of sexual reproduction on genetic architecture, specifically modularity and epistasis. We found that sex profoundly influences genome organization, increasing modularity and decreasing the effects of interactions between mutations. Our studies have contributed to understanding both the causes and consequences of sexual reproduction, while also demonstrating the efficacy and power of in silico approaches to these issues. © 2011 ECAL 2011: The 11th European Conference on Artificial Life. All rights reserved.

关键词： Cell proliferation

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Exploring Time-Scales of Closed-Loop Decoder Adaptation in Brain-Machine Interfaces

Exploring Time-Scales of Closed-Loop Decoder Adaptation in B...

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Annual International Conference of the IEEE engineering in Medicine and Biology Society

作者： Amy L. Orsborn Siddharth Dangi Helene G. Moorman Jose M. Carmena Berkeley - Unviversity of California Department of Electrical Engineering and Computer Sciences University of California Helen Wills Neuroscience Institute University of California Department of Electrical Engineering and Computer Sciences Helen Wills Neuroscience Institute and Program in Cognitive Science University of California

ISBN: (纸本)9781424441211

Performing closed-loop modifications of a brain-machine interface (BMI) decoder is a technique that shows great promise for improving performance. We compare two algorithms for implementing adaptations that update decoder parameters on different time-scales (discrete batches vs. online), and present experimental results of a non-human primate performing a standard center-out BMI task. To ensure that our experimental training models are representative of a broad range of paralyzed patients, our decoders were initially trained using neural activity recorded during subject observation of cursor movement. We find that both closed-loop adaptation algorithms can be used to boost BMI performance from 20-30% to 80%, yielding movement kinematics similar to natural arm movements. Based on insights derived from the performance of each algorithm, we propose that a hybrid of batch and online decoder adaptation may be the best approach.

关键词： Decoding Kinematics Training Educational institutions Adaptation models Kalman filters USA Councils

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Online correction of orientation estimates using spatial memory in a neuromorphic head direction system

Online correction of orientation estimates using spatial mem...

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IEEE International Symposium on Circuits and Systems (ISCAS)

作者： Tarek M. Massoud Timothy K. Horiuchi Electrical and Computer Engineering Department Institute of Systems Research University of Maryland College Park MD USA Electrical and Computer Engineering Department Institute of Systems Research Neuroscience and Cognitive Science Program University of Maryland College Park MD USA

Many animals are known to maintain an internal estimate of their orientation in the environment. In the absence of external sensory cues, this estimate inevitably exhibits drift. When sensory information is available, associations between sensory landmarks and the internal estimate can be used to correct for drift. In this paper we present a neuromorphic system to model such associations between sensory landmarks in the environment (as provided by sonar) and the activity of a hardware-based head direction cell system (HDS) that continuously integrates angular velocity signals to maintain an estimate of the orientation. These associations are shown to correct for drift errors that are encountered in the HDS.

关键词： High definition video Robot sensing systems Neurons Navigation Sonar detection Neuromorphics

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Adaptive Kalman filtering for closed-loop Brain-Machine Interface systems

Adaptive Kalman filtering for closed-loop Brain-Machine Inte...

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International IEEE/EMBS Conference on Neural engineering, CNE

作者： Siddharth Dangi Suraj Gowda Rodolphe Héliot Jose M. Carmena Department of Electrical Engineering and Computer Sciences University of California Berkeley CA USA CEA-LETI France Department of Electrical Engineering and Computer Sciences Helen Wills Neuroscience Institute and Program in Cognitive Science University of California Berkeley CA USA

Brain-Machine Interface (BMI) decoding algorithms are often trained offline, but this paradigm ignores both the non-stationarity of neural signals and the feedback that exists in online, closed-loop control. To address these problems, we have developed an Adaptive Kalman Filter (AKF), a Kalman filter variant that adaptively updates its model parameters during training. For a Kalman filter decoder, batch retraining methods require completely re-estimating the parameter matrices from sufficient data to perform regression accurately, even if only small changes are necessary. Conversely, the AKF is designed to update the decoder parameters continuously and more intelligently. We simulated a population of 41 neurons learning to control a 2D computer cursor. The AKF yielded significantly faster skill acquisition and better robustness to perturbation and neuron loss than a standard Kalman filter with periodic batch retraining.

关键词： Decoding Kalman filters Mathematical model Equations Kinematics Neurons Training

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Characteristics of low latitude nocturnal ionospheric irregularities over India-Arab longitudes during solar maximum

Characteristics of low latitude nocturnal ionospheric irregu...

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2011 30th URSI General Assembly and Scientific Symposium, URSIGASS 2011

作者： Chu, Fang-Dar Chen, Wei-Sheng Lee, Chien-Chih Hsu, Wei-Chih Lin, Huang-Tien Liao, Chia-Shu National Standard Time and Frequency Lab. of Telecommunication Laboratories Chunghwa Telecom. Co. Ltd. Yangmei City Taoyuan County 32601 Taiwan General Education Center Ching Yun University Zhongli City Taoyuan County 32097 Taiwan Department of Computer and Communication Engineering National Kaohsiung First University of Science and Technology Kaohsiung City 81164 Taiwan

ISBN: (纸本)9781424451173

This study investigated the low latitude nocturnal ionospheric irregularities at India-Arab longitudes using phase fluctuations of the global positioning system during solar maximum. The results showed that the low latitude irregularities in this region develop easier in equinoctial months and December-solstice months than in June-solstice months. In addition, the low latitude irregularities mainly come from the magnetic equator. Moreover, at the crest of equatorial anomaly the irregularities in June-solstice months maybe come from middle latitudes. Many details are discussed. © 2011 IEEE.

关键词： Cities and towns Fluctuations Global Positioning System Ionosphere Satellite broadcasting Satellites Time frequency analysis

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Autonomous passive light tracking utilizing single-wall carbon nanotube enhanced opto-thermo-mechanical elastomer actuators

Autonomous passive light tracking utilizing single-wall carb...

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International Conference on Solid State Sensors and Actuators (TRANSDUCERS)

作者： Ye Liu Chensha Li Chi-Wei Lo Hongrui Jiang Electrical and Computer Engineering Department University of Wisconsin Madison Madison WI USA Materials Science Program University of Wisconsin Madison Madison WI USA

We have developed novel opto-thermo-mechanical actuators by effectively distributing a significant amount of single-wall carbon nanotube (SWCNT, up to 0.7%w/w) into liquid crystal elastomer (LCE) matrices. These SWCNT/LCE actuators exhibit a great potential to be utilized in MEMS applications, as they respond to a wide spectrum of visible/near-infrared light, and possess a large reversible compressive strain (up to 35%) when stimulated. Autonomous and passive light tracking is demonstrated here as one of the applications. With a simple design, the actuators are able to adaptively tilt a solar cell towards the light source by a degree of ~15° (with an incident light intensity of 1.6 kW/m 2 ). As a result, the photocurrent output of the solar cell is significantly enhanced (up to 247.10%) without any other control system or external energy source.

关键词： Actuators Photovoltaic cells Photoconductivity Films Carbon nanotubes Light sources Micromechanical devices

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Self adaptive cluster based and weed inspired differential evolution algorithm for real world optimization

Self adaptive cluster based and weed inspired differential e...

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Congress on Evolutionary Computation

作者： Udit Halder Swagatam Das Dipankar Maity Ajith Abraham Preetam Dasgupta Department of Electronics and Telecommunication Engineering Jadavpur University Kolkata India Faculty of Computer Science and Electrical Engineering VSB - Technical University of Ostrava Czech Republic Machine Intelligence Research Labs (MIR Labs) Seattle WA USA

In this paper we propose a Self Adaptive Cluster based and Weed Inspired Differential Evolution algorithm (SACWIDE), the total population is divided into several clusters based on the positions of the individuals and the cluster number is dynamically changed by the suitable learning strategy during evolution. Here we incorporate a modified version of the Invasive Weed Optimization (IWO) algorithm as a local search technique. The algorithm strategically determines whether a particular cluster will perform Differential Evolution (DE) or the IWO algorithm (modified). The number of clusters in a particular iteration is set by the algorithm itself self-adaptively. The performance of SACWIDE is reported on the set of 22 benchmark problems of CEC-2011.

关键词： Clustering algorithms Optimization Iron Algorithm design and analysis Convergence Performance evaluation Heuristic algorithms

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An authentication protocol based on kerberos 5

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International Journal of Network Security 2011年第3期12卷 159-170页

作者： El-Emam, Eman Koutb, Magdy Kelash, Hamdy Faragallah, Osama S. Egyptian Space Program National Authority for Remote Sensing and Space Sciences El-Nozha El-Gedeeda Cairo Egypt Department of Industrial Electronics and Control Faculty of Electronic Engineering Menouf Egypt Department of Computer Science and Engineering Faculty of Electronic Engineering Menouf Egypt

We introduce some modifications to the widely deployed Kerberos authentication protocol. The principle's secret-key will be independent of the user password to overcome the weak passwords chosen by the network principal that are susceptible to password guessing attacks, the main drawback of the Kerberos protocol. Instead, the Kerberos Distribution Center saves a profile for every instance in its realm to generate the principle's secret-key by hashing the profile, and encrypting the output digest. Besides, the lifetime of the secret-key is controlled using the sys-tem clock. Triple-Des is used for encryption, SHA-256 for hashing, and Blum Blum Shub for random number gen-eration.

关键词： Authentication

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Interactive content-based texture image retrieval

Interactive content-based texture image retrieval

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International Conference on computer and Communication Technology (ICCCT)

作者： Pushpa B. Patil Manesh B. Kokare Department of Computer Science and Engineering BLDEAs V.P.Dr. P. G. Halakatti CET. Bijapur India Department of Electronic and Telecommunication S.G.G.S. Institute of Engineering and Technology Nanded India

Due to the semantic gap between low-level image features and high level concepts, content-Based image retrieval (CBIR) systems are incapable to provide the effective results to the user. To address this problem, we have presented a framework for effective image retrieval by proposing a novel idea of cumulative learning using Support Vector Machines (SVM). It creates a knowledge base model to increase the training samples by simply accumulating the samples based on user interactions. As we know relevance feedback (RF) is online process, so we have optimized the learning process by considering the most positive image selection on each feedback iteration. To learn the system we have used SVM. The main significances of our system are to address the small training sample and to reduce retrieval time. Experiments are conducted on 1856 texture images to demonstrate the effectiveness of the proposed framework.

关键词： Radio frequency Accuracy Image retrieval Wavelet transforms Training data Training

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Optimization of defect hole placement in resonant cavities

Optimization of defect hole placement in resonant cavities

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作者： Kang, Christopher Weiss, Sharon M. Vlasov, Yurii A. Assefa, Solomon Interdisciplinary Graduate Program in Materials Science Vanderbilt University Nashville TN 37235 United States Department of Physics and Astronomy Vanderbilt University Nashville TN 37235 United States Department of Electrical Engineering and Computer Science Vanderbilt University 37235 United States IBM T.J. Watson Research Center Yorktown Heights NY 10536 United States

We demonstrate the resonance wavelength and quality factor dependence of 50nm defect-hole placement within photonic crystal L3 microcavities. Proper placement of defect-holes leads to a 12% increase in photonic crysta... 详细信息

ISBN: (纸本)9781557529107

关键词： Photonic crystals

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