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991.
Development and Simulation of Sulfur‐doped Graphene Supported Platinum with Exemplary Stability and Activity Towards Oxygen Reduction 下载免费PDF全文
Drew Higgins Md Ariful Hoque Min Ho Seo Rongyue Wang Fathy Hassan Ja‐Yeon Choi Mark Pritzker Aiping Yu Jiujun Zhang Zhongwei Chen 《Advanced functional materials》2014,24(27):4325-4336
Sulfur‐doped graphene (SG) is prepared by a thermal shock/quench anneal process and investigated as a unique Pt nanoparticle support (Pt/SG) for the oxygen reduction reaction (ORR). Particularly, SG is found to induce highly favorable catalyst‐support interactions, resulting in excellent half‐cell based ORR activity of 139 mA mgPt ?1 at 0.9 V vs RHE, significant improvements over commercial Pt/C (121 mA mgPt ?1) and Pt‐graphene (Pt/G, 101 mA mgPt ?1). Pt/SG also demonstrates unprecedented stability, maintaining 87% of its electrochemically active surface area following accelerated degradation testing. Furthermore, a majority of ORR activity is maintained, providing 108 mA mgPt ?1, a remarkable 171% improvement over Pt/C (39.8 mA mgPt ?1) and an 89% improvement over Pt/G (57.0 mA mgPt ?1). Computational simulations highlight that the interactions between Pt and graphene are enhanced significantly by sulfur doping, leading to a tethering effect that can explain the outstanding electrochemical stability. Furthermore, sulfur dopants result in a downshift of the platinum d‐band center, explaining the excellent ORR activity and rendering SG as a new and highly promising class of catalyst supports for electrochemical energy technologies such as fuel cells. 相似文献
992.
Using a unified representation for a class of buffered-outlet two current-feedback operational amplifier (CFOAs)-based sinusoidal
oscillators, new circuits of this type can be systematically discovered. A catalogue of four circuit structures, each structure
realizing nine oscillator circuits, is presented. Moreover, using the RC:CR transformation, additional nine oscillator circuits
can be obtained from each structure. While each circuit requires five passive elements, some of the circuits enjoy one or
more of the following attractive features: use of grounded capacitors, feasibility of absorbing the parasitic components of
the CFOAs and orthogonal tuning of the frequency and the startup condition of oscillation. 相似文献
993.
Ertan Onur Yunus Durmus Mohamed Gamal Hawas Sonia Marcela Heemstra de Groot Ignas G. M. M. Niemegeers 《Wireless Personal Communications》2011,58(1):71-93
In this paper, we present a visionary concept referred to as Collaborative and Cognitive Network Platforms (CCNPs) as a future-proof solution for creating a dependable, self-organizing and self-managing communication substrate for effective ICT solutions to societal problems. CCNP creates a cooperative communication platform to support critical services across a range of business sectors. CCNP is based on the personal network (PN) technology which is an inherently cooperative environment prototyped in the Dutch Freeband PNP2008 and the European Union IST MAGNET projects. In CCNP, the cognitive control plane strives to exploit the resources to better satisfy the requirements of networked applications. CCNP facilitates collaboration inherently. Through cognition in the cognitive control plane, CCNP becomes a self-managed substrate. The self-managed substrate, in this paper, is defined as cognitive and collaborative middleware on which future applications run without user intervention. Endemic sensor networks may be incorporated into the CCNP concept to feed its cognitive control plane. In this paper, we present the CCNP concept and discuss the research challenges related to collaboration and cognition. 相似文献
994.
Karthik Nagarajan Brian Holland Alan D. George K. Clint Slatton Herman Lam 《Journal of Signal Processing Systems》2011,62(1):43-63
Machine-learning algorithms are employed in a wide variety of applications to extract useful information from data sets, and
many are known to suffer from super-linear increases in computational time with increasing data size and number of signals
being processed (data dimension). Certain principal machine-learning algorithms are commonly found embedded in larger detection,
estimation, or classification operations. Three such principal algorithms are the Parzen window-based, non-parametric estimation
of Probability Density Functions (PDFs), K-means clustering and correlation. Because they form an integral part of numerous
machine-learning applications, fast and efficient execution of these algorithms is extremely desirable. FPGA-based reconfigurable
computing (RC) has been successfully used to accelerate computationally intensive problems in a wide variety of scientific
domains to achieve speedup over traditional software implementations. However, this potential benefit is quite often not fully
realized because creating efficient FPGA designs is generally carried out in a laborious, case-specific manner requiring a
great amount of redundant time and effort. In this paper, an approach using pattern-based decomposition for algorithm acceleration
on FPGAs is proposed that offers significant increases in productivity via design reusability. Using this approach, we design,
analyze, and implement a multi-dimensional PDF estimation algorithm using Gaussian kernels on FPGAs. First, the algorithm’s
amenability to a hardware paradigm and expected speedups are predicted. After implementation, actual speedup and performance
metrics are compared to the predictions, showing speedup on the order of 20× over a 3.2 GHz processor. Multi-core architectures
are developed to further improve performance by scaling the design. Portability of the hardware design across multiple FPGA
platforms is also analyzed. After implementing the PDF algorithm, the value of pattern-based decomposition to support reuse
is demonstrated by rapid development of the K-means and correlation algorithms. 相似文献
995.
996.
Salah-ud-din Ghulam Mohi-ud-Din Atif Bin Mansoor Hassan Masood Mustafa Mumtaz 《Signal, Image and Video Processing》2011,5(4):477-483
The ever increasing demand of security has resulted in wide use of Biometric systems. Despite overcoming the traditional verification
problems, the unimodal systems suffer from various challenges like intra class variation, noise in the sensor data etc, affecting
the system performance. These problems are effectively handled by multimodal systems. In this paper, we present multimodal
approach for palm- and fingerprints by feature level and score level fusions (sum and product rules). The proposed multi-modal
systems are tested on a developed database consisting of 440 palm- and fingerprints each of 55 individuals. In feature level
fusion, directional energy-based feature vectors of palm- and fingerprint identifiers are combined to form joint feature vector
that is subsequently used to identify the individual using a distance classifier. In score level fusion, the matching scores
of individual classifiers are fused by sum and product rules. Receiver operating characteristics curves are formed for unimodal
and multimodal systems. Equal Error Rate (EER) of 0.538% for feature level fusion shows best performance compared to score
level fusion of 0.6141 and 0.5482% of sum and product rules, respectively. Multimodal systems, however, significantly outperform
unimodal palm- and fingerprints identifiers with EER of 2.822 and 2.553%, respectively. 相似文献
997.
As an attractive technique for peak-to-average power ratio (PAPR) reduction in orthogonal frequency division multiplexing (OFDM) systems, time domain interleaved partitioning partial transmit sequence (TD-IP-PTS) scheme uses circular convolution property of discrete Fourier transforms (DFT) so as to need only one inverse fast Fourier transform (IFFT) operation. However, the search and combination of phase factors still need higher computational complexity. In order to improve the problem, this paper detailedly analyzes the independence of phase factor vectors and optimizes the phase factor vectors in TD-IP-PTS. Furthermore, we find the characteristic of combination of phase factors and propose three methods respectively based on storage-unit, pipeline and select-path to implement the combination of phase factors in TD-IP-PTS. The simulation results show that TD-IP-PTS using independent and effective phase factor vectors has better PAPR performance and lower complexity than traditional IP-PTS. Moreover, among three proposed methods for combination of phase factors, the method based on select-path requires the least registers and delay time. This method is the most promising in practical applications. 相似文献
998.
Chi-Li Yu Jung-Sub Kim Lanping Deng Srinidhi Kestur Vijaykrishnan Narayanan Chaitali Chakrabarti 《Journal of Signal Processing Systems》2011,64(1):109-122
Applications based on Discrete Fourier Transforms (DFT) are extensively used in several areas of signal and digital image
processing. Of particular interest is the two-dimensional (2D) DFT which is more computation- and bandwidth-intensive than
the one-dimensional (1D) DFT. Traditionally, a 2D DFT is computed using Row-Column (RC) decomposition, where 1D DFTs are computed
along the rows followed by 1D DFTs along the columns. Both application specific and reconfigurable hardware have utilized
this scheme for high-performance implementations of 2D DFT. However, architectures based on RC decomposition are not efficient
for large input size data due to memory bandwidth constraints. In this paper, we propose an efficient architecture to implement
2D DFT for large-sized input data based on a novel 2D decomposition algorithm. This architecture achieves very high throughput
by exploiting the inherent parallelism due to the algorithm decomposition and by utilizing the row-wise burst access pattern
of the external memory. A high throughput memory interface has been designed to enable maximum utilization of the memory bandwidth.
In addition, an automatic system generator is provided for mapping this architecture onto a reconfigurable platform of Xilinx
Virtex-5 devices. For a 2K ×2K input size, the proposed architecture is 1.96 times faster than RC decomposition based implementation under the same memory
constraints, and also outperforms other existing implementations. 相似文献
999.
The Asymptotic Waveform Evaluation (AWE) technique is an extrapolation method that provides a reduced-order model of linear system and has already been successfully used to analyze wideband electromagnetic scattering problems. As the number of unknowns increases, the size of Method Of Moments (MOM) impedance matrix grows very rapidly, so it is a prohibitive task for the computation of wideband Radar Cross Section (RCS) from electrically large object or multi-objects using the traditional AWE technique that needs to solve directly matrix inversion. In this paper, an AWE technique based on the Characteristic Basis Function (CBF) method, which can reduce the matrix size to a manageable size for direct matrix inversion, is proposed to analyze electromagnetic scattering from multi-objects over a given frequency band. Numerical examples are presented to illustrate the computational accuracy and efficiency of the proposed method. 相似文献
1000.
Optical burst switching (OBS) is a promising technology for bridging the gap between optical wavelength switching and optical
packet switching. Optical signal transmission quality is subject to various types of physical impairment introduced by optical
fibers, switching elements, or other network components. The signal degradation due to physical impairment may be significant
enough such that the bit-error rate of received signals is unacceptably high at the destination, rendering the signal to not
usable. In this article, based on earlier study, we study the burst-scheduling problem in OBS networks using two control packets
for each data burst, taking into account physical impairment effects. We propose a burst-scheduling algorithm that accommodates
incoming bursts by primary path routing, deflection routing, and burst scheduling. We design an admission control mechanism
to use network resources efficiently. At an OBS node, the proposed algorithm schedules bursts for transmission by searching
for available resources as well as verifying signal quality. Our simulation results demonstrate that the proposed algorithm
is effective in terms of reducing the burst-blocking probability. 相似文献