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Synchronization in complex networks

Description: Synchronization processes in populations of locally interacting elements are in the focus of intense research in physical, biological, chemical, technological and social systems. The many efforts devoted to understand synchronization phenomena in natural systems take now advantage of the recent theory of complex networks. In this review, we report the advances in the comprehension of synchronization phenomena when oscillating elements are constrained to interact in a complex network topology. We also overview the new emergent features coming out from the interplay between the structure and the function of the underlying pattern of connections. Extensive numerical work as well as analytical approaches to the problem are presented. Finally, we review several applications of synchronization in complex networks to different disciplines: biological systems and neuroscience, engineering and computer science, and economy and social sciences.
Date: December 12, 2007
Creator: Arenas, A.; Diaz-Guilera, A.; Moreno, Y.; Zhou, C. & Kurths, J.
Partner: UNT Libraries Government Documents Department

Multithreading for Synchronization Tolerance in MatrixFactorization

Description: Physical constraints such as power, leakage and pin bandwidth are currently driving the HPC industry to produce systems with unprecedented levels of concurrency. In these parallel systems, synchronization and memory operations are becoming considerably more expensive than before. In this work we study parallel matrix factorization codes and conclude that they need to be re-engineered to avoid unnecessary (and expensive) synchronization. We propose the use of multithreading combined with intelligent schedulers and implement representative algorithms in this style. Our results indicate that this strategy can significantly outperform traditional codes.
Date: July 16, 2007
Creator: Buttari, Alfredo; Dongarra, Jack; Husbands, Parry; Kurzak, Jakub & Yelick, Katherine
Partner: UNT Libraries Government Documents Department

Techniques for synchronization of X-Ray pulses to the pump laser in an ultrafast X-Ray facility

Description: Accurate timing of ultrafast x-ray probe pulses emitted from a synchrotron radiation source with respect to the signal initiating a process in the sample under study is critical for the investigation of structural dynamics in the femtosecond regime. We describe schemes for achieving accurate timing of femtosecond x-ray synchrotron radiation pulses relative to a pump laser, where x-rays pulses of <100 fs duration are generated from the proposed LUX source based on a recirculating superconducting linac. We present a description of the timing signal generation and distribution systems to minimize timing jitter of the x-rays relative to the experimental lasers.
Date: May 6, 2003
Creator: Corlett, J.N.; Doolittle, L.; Schoenlein, R.; Staples, J.; Wilcox, R. & Zholents, A.
Partner: UNT Libraries Government Documents Department

Channel Modeling and Time Delay Estimation for Clock Synchronization Among Seaweb Nodes

Description: From simulations, tracking of the impulse response is feasible. Potential to benefit other functions such as ranging between two nodes. Potential to combine the features of different protocols to create a new and more realistic clock-synchronization protocol.
Date: July 8, 2012
Creator: Gagnon, P; Rice, J & Clark, G A
Partner: UNT Libraries Government Documents Department

Fermi Timing and Synchronization System

Description: The Fermi FEL will depend critically on precise timing of its RF, laser and diagnostic subsystems. The timing subsystem to coordinate these functions will need to reliably maintain sub-100fs synchronicity between distant points up to 300m apart in the Fermi facility. The technology to do this is not commercially available, and has not been experimentally demonstrated in a working facility. Therefore, new technology must be developed to meet these needs. Two approaches have been researched by different groups working with the Fermi staff. At MIT, a pulse transmission scheme has been developed for synchronization of RF and laser devices. And at LBL, a CW transmission scheme has been developed for RF and laser synchronization. These respective schemes have advantages and disadvantages that will become better understood in coming years. This document presents the work done by both teams, and suggests a possible system design which integrates them both. The integrated system design provides an example of how choices can be made between the different approaches without significantly changing the basic infrastructure of the system. Overall system issues common to any synchronization scheme are also discussed.
Date: July 19, 2006
Creator: Wilcox, R.; Staples, J.; Doolittle, L.; Byrd, J.; Ratti, A.; Kaertner, F.X. et al.
Partner: UNT Libraries Government Documents Department

Experimental Synchronization of Chaotic Attractors Using Control

Description: The focus of this thesis is to theoretically and experimentally investigate two new schemes of synchronizing chaotic attractors using chaotically operating diode resonators. The first method, called synchronization using control, is shown for the first time to experimentally synchronize dynamical systems. This method is an economical scheme which can be viably applied to low dimensional dynamical systems. The other, unidirectional coupling, is a straightforward means of synchronization which can be implemented in fast dynamical systems where timing is critical. Techniques developed in this work are of fundamental importance for future problems regarding high dimensional chaotic dynamical systems or arrays of mutually linked chaotically operating elements.
Date: December 1994
Creator: Newell, Timothy C. (Timothy Charles)
Partner: UNT Libraries

Emergence of Complexity from Synchronization and Cooperation

Description: The dynamical origin of complexity is an object of intense debate and, up to moment of writing this manuscript, no unified approach exists as to how it should be properly addressed. This research work adopts the perspective of complexity as characterized by the emergence of non-Poisson renewal processes. In particular I introduce two new complex system models, namely the two-state stochastic clocks and the integrate-and-fire stochastic neurons, and investigate its coupled dynamics in different network topologies. Based on the foundations of renewal theory, I show how complexity, as manifested by the occurrence of non-exponential distribution of events, emerges from the interaction of the units of the system. Conclusion is made on the work's applicability to explaining the dynamics of blinking nanocrystals, neuron interaction in the human brain, and synchronization processes in complex networks.
Date: May 2008
Creator: Geneston, Elvis L.
Partner: UNT Libraries

Synchronization of x-ray pulses to the pump laser in an ultrafast x-ray facility

Description: Accurate timing of ultrafast x-ray probe pulses emitted from a synchrotron radiation source with respect to a pump laser exciting processes in the sample under study is critical for the investigation of structural dynamics in the femtosecond regime. We describe a scheme for synchronizing femtosecond x-ray pulses relative to a pump laser. X-ray pulses of <100 fs duration are generated from a proposed source based on a recirculating superconducting linac [1,2,3]. Short x-ray pulses are obtained by a process of electron pulse compression, followed by transverse temporal correlation of the electrons, and ultimately x-ray pulse compression. Timing of the arrival of the x-ray pulse with respect to the pump laser is found to be dominated by the operation of the deflecting cavities which provide the transverse temporal correlation of the electrons. The deflecting cavities are driven from a highly stable RF signal derived from a modelocked laser oscillator which is also the origin of the pump l aser pulses.
Date: May 30, 2002
Creator: Corlett, J.N.; Barry, W.; Byrd, J.M.; Schoenlein, R. & Zholents, A.
Partner: UNT Libraries Government Documents Department

Surface Impedance and Synchronous Modes

Description: The concept of the surface impedance is applicable to the case, when obstacles on the surface of a vacuum chamber are small compared to characteristic dimensions of the problem. We apply this concept to the calculation of a synchronous mode that can propagate in a tube with slightly corrugated walls. We also show that such a mode can propagate in a pipe with a rough surface, or a perforated pipe with a large number of holes.
Date: July 20, 1999
Creator: Stupakov, Gennady
Partner: UNT Libraries Government Documents Department

Upgrade of NSLS timing system

Description: We report on the progress of the new NSLS timing system. There are three types of requirements for NSLS timing system: clocks, synchronization and trigger circuits. All ring revolution frequency clocks are generated using ECL and high speed TTL logic. The synchronization circuits allows to fill both storage rings with any bunch pattern. The triggers are generated by using commercially available digital delay generators. The delay unit`s outputs are ultrastable, with a resolution of 5 ps, and are programmed by computer via IEEE 488 interface. The block diagrams, description of all major timing components and the present status are provided in this paper.
Date: May 1, 1995
Creator: Singh, O.; Ramamoorthy, S.; Sheehan, J. & Smith, J.
Partner: UNT Libraries Government Documents Department

Measuring and adjusting the path length at CEBAF

Description: Accurately setting the path length around the machine is central to the proper operation of the CEBAF accelerator. The CEBAF main accelerator consists of two recirculating superconducting linacs operating at 1497 MHz fundamental frequency. The electron beam can recirculate up to five times through the two linacs before it is extracted to the experimental halls. In order to obtain maximum energy gain and minimum energy spread through the linacs, all passes should arrive at the beginning of the linacs in phase at the crest of the RF cycle. In this paper we explain how the arrival times of higher pass beams are measured with respect to the first pass to less than one degree of RF phase and how the path length around the machine is adjusted. Following a brief introduction to the CEBAF design and some local nomenclature, these topics will be discussed: differential RF phase measurements of time delay, the energy method of cresting the higher pass beams, results obtained with the measurement techniques, future plans and improvements to the devices, and finally, a set of conclusions. 3 refs., 5 figs., 1 tab.
Date: December 31, 1995
Creator: Krafft, G.A.; Crofford, M. & Douglas, D.R.
Partner: UNT Libraries Government Documents Department

What Scientific Applications can Benefit from Hardware Transactional Memory?

Description: Achieving efficient and correct synchronization of multiple threads is a difficult and error-prone task at small scale and, as we march towards extreme scale computing, will be even more challenging when the resulting application is supposed to utilize millions of cores efficiently. Transactional Memory (TM) is a promising technique to ease the burden on the programmer, but only recently has become available on commercial hardware in the new Blue Gene/Q system and hence the real benefit for realistic applications has not been studied, yet. This paper presents the first performance results of TM embedded into OpenMP on a prototype system of BG/Q and characterizes code properties that will likely lead to benefits when augmented with TM primitives. We first, study the influence of thread count, environment variables and memory layout on TM performance and identify code properties that will yield performance gains with TM. Second, we evaluate the combination of OpenMP with multiple synchronization primitives on top of MPI to determine suitable task to thread ratios per node. Finally, we condense our findings into a set of best practices. These are applied to a Monte Carlo Benchmark and a Smoothed Particle Hydrodynamics method. In both cases an optimized TM version, executed with 64 threads on one node, outperforms a simple TM implementation. MCB with optimized TM yields a speedup of 27.45 over baseline.
Date: June 4, 2012
Creator: Schindewolf, M; Bihari, B; Gyllenhaal, J; Schulz, M; Wang, A & Karl, W
Partner: UNT Libraries Government Documents Department

Integration Window Position Estimation in TR Receivers

Description: Transmitted-reference (TR) receivers avoid the stringent synchronization requirements that exist in conventional pulse detection schemes. However, the performance of such receivers is highly sensitive to precise timing acquisition and tracking as well as the length of their integration window. This window in TR receivers defines the limits of the finite integrator prior to the final decision making block. In this paper, we propose a novel technique that allows us to extract the timing information of the integration window very accurately in UWB-TR receivers in the presence of channel noise. The principles of the method are presented and the BER performance of a modified UWB-TR receiver is investigated by computer simulation. Our studies show that the proposed estimation technique adds value to the conventional TR receiver structure with modest increase in complexity.
Date: March 15, 2005
Creator: Nekoogar, F; Dowla, F & Spiridon, A
Partner: UNT Libraries Government Documents Department

Energy-Aware Time Synchronization in Wireless Sensor Networks

Description: I present a time synchronization algorithm for wireless sensor networks that aims to conserve sensor battery power. The proposed method creates a hierarchical tree by flooding the sensor network from a designated source point. It then uses a hybrid algorithm derived from the timing-sync protocol for sensor networks (TSPN) and the reference broadcast synchronization method (RBS) to periodically synchronize sensor clocks by minimizing energy consumption. In multi-hop ad-hoc networks, a depleted sensor will drop information from all other sensors that route data through it, decreasing the physical area being monitored by the network. The proposed method uses several techniques and thresholds to maintain network connectivity. A new root sensor is chosen when the current one's battery power decreases to a designated value. I implement this new synchronization technique using Matlab and show that it can provide significant power savings over both TPSN and RBS.
Date: December 2006
Creator: Saravanos, Yanos
Partner: UNT Libraries

A 10-Hz Terawatt Class Ti:Sapphire Laser System: Development and Applications

Description: We developed a two stage Ti:Sapphire laser system to generate 16 mJ/80fs laser pulses at the pulse repetition rate of 10 Hz. The key deriver for the present design is implementing a highly efficient symmetric confocal pre-amplifier and employing a simple, inexpensive synchronization scheme relying only on a commercial digital delay-generator. We characterized the amplified pulses in spatial-, spectral-, and temporal-domains. The laser system was used to investigate various nonlinear optical processes, and to modify the optical properties of metal- and semiconductor-surfaces. We are currently building a third amplifier to boost the laser power to the multi-terawatt range.
Date: January 12, 2010
Creator: Sharma, A. K.; Smedley, J.; Tsang, T. & Rao, T.
Partner: UNT Libraries Government Documents Department

Summary of beam quality diagnostics and control working group

Description: The working group on beam quality, diagnostics, and control at the 12th Advanced Accelerator Concepts Workshop held a series of meetings during the Workshop. The generation of bright charged-particle beams (in particular electron and positron beams), along with state-of-the-art beam diagnostics and synchronization were discussed.
Date: September 1, 2006
Creator: Lewellen, John & Piot, Philippe
Partner: UNT Libraries Government Documents Department

Super synchronization for fused video and time-series neural network training

Description: A key element in establishing neural networks for traffic monitoring is the ground truth data set that verifies the sensor data. The sensors we use have time series data gathered from loop and piezo sensors embedded in the highway. These signals are analyzed and parsed into vehicle events. Features are extracted from these sensors and combine to form the vehicle vectors. The vehicle vectors are combined together with the video data in a data fusion process thereby providing the neural network with its training set. We examine two studies, one by Georgia Tech Research Institute (GTRI) and another by Los Alamos National Laboratory (LANL) that use video information and have had difficulties in establishing the fusion process. That is to say, the correspondence between the video events recorded as the ground truth data and the sensor events has been uncertain. We show that these uncertainties can be removed by establishing a more precise and accurate time measurement for the video events. The principal that the video time information is inherently precise to better than a frame (1/30 s) and that by tracing the factors causing imprecision in the timing of events, we can achieve precisions required for unique vehicle identification we call super synchronization. In the Georgia data study there was an imprecision on the order of 3 seconds and in the LANL study an imprecision of early a second. In both cases, the imprecision had led to lack of proper identification of sensor events. In the case of the Georgia 120 study sensors were placed at various distances downstream, up to 250 meters, from the ground truth camera. The original analysis assumed that there was a fixed time offset corresponding to the downstream location. For this case we show that when we restrict the analysis to passenger cars and ...
Date: June 1, 1996
Creator: Elliott, C.J.; Pepin, J. & Gillmann, R.
Partner: UNT Libraries Government Documents Department

A Sampled Master Oscillator for the PEP-II B Factory

Description: A sampled phase-locked loop synchronizes the PEP-II B Factory rings to their SLAC Linac injector. The injection of both electrons and positrons into the separate rings and into their proper rf buckets requires phase shifting the linac rf with respect to the PEP rings. One of every three machine cycles provides the PEP ring an undisturbed reference while the other two thirds of the time the reference is unusable due to the injection scheme. The ring rf must be tunable about its nominal frequency for machine physics use. A sampled phase-locked loop handles the task of synchronizing the PEP-II rf to the linac while maintaining good phase noise. The input reference is sampled at 120 Hz and provides a ring rf signal with less than 0.1{degree} of rms phase jitter at 476 MHz.
Date: May 18, 1999
Partner: UNT Libraries Government Documents Department

Amplification of Beam Acceleration in a Plasma by Plasma Instability

Description: Although achieving of high accelerating field in a plasma has been demonstrated experimentally, a practical use of such a scheme for building a large accelerator is questionable. A novel scheme of beam acceleration by a plasma wave is considered in this article. The scheme is based on an initial excitation of a plasma wave by a probe beam with comparatively modest intensity. This seed excitation is then amplified by plasma instability, so that the test beam which follows the probe beam with a small delay will be accelerated by the plasma wave with an amplitude significantly exceeding the initial amplitude of the wave. Because of small interaction between the synchronization beam and the plasma, such a scheme allows one to excite a plasma over large length and, consequently, to build a large accelerator.
Date: September 1, 1998
Creator: Lebedev, Valeri
Partner: UNT Libraries Government Documents Department

Farm batch system and Fermi inter-process communication and synchronization toolkit

Description: Farms Batch System (FBS) was developed as a batch process management system for off-line Run II data processing at Fermilab. FBS will manage PC farms composed of up to 250 nodes and scalable to 1000 nodes with disk capacity of up to several TB. FBS allows users to start arrays of parallel processes on multiple computers. It uses a simplified resource counting method load balancing. FBS has been successfully used for more than a year at Fermilab by fixed target experiments and will be used for collider experiment off-line data processing. Fermi Inter-Process Communication toolkit (FIPC) was designed as a supplement product for FBS that helps establish synchronization and communication between processes running in a distributed batch environment. However, FIPC is an independent package, and can be used with other batch systems, as well as in a non-batch environment. FIPC provides users with a variety of global distributed objects such as semaphores, queues and string variables. Other types of objects can be easily added to FIPC. FIPC has been running on several PC farms at Fermilab for half a year and is going to be used by CDF for off-line data processing.
Date: February 20, 2001
Creator: Mandrichenko, I.V.
Partner: UNT Libraries Government Documents Department

RF cogging in the FNAL Booster Accelerator

Description: The Fermilab Booster operates at a Radio Frequency (RF) harmonic number of 84 with beam in all buckets. One or two bunches of beam are systematically lost in the 8 GeV extraction process as beam is swept across a magnetic septum during the extraction kicker rise time. The prompt radiation and component activation resulting from this localized high energy beam loss become serious concerns as Booster beam throughput must be increased more than tenfold to meet the requirements of RUN II, NUMI, and MiniBooNE experiments. Synchronizing a gap in the beam to the firing of the extraction kickers, a relatively easy and standard practice in many machines, can eliminate the problem. This seemingly simple operation is greatly complicated in the Booster by the need to synchronize extraction to beam already circulating in the Main Injector. Coupled with the inflexibility of the Booster resonant magnetic cycle, cycle to cycle variations, and constraints inherent in the accelerator physics, that requirement forces active control of the gap's azimuthal position throughout the acceleration process as the revolution frequency sweeps rapidly. Until recently, the complexities of actually implementing and demonstrating this process in the Booster had not been worked out. This paper describes a successful demonstration of gap cogging in the Booster.
Date: June 13, 2000
Creator: Webber, William A. Pellico and Robert C.
Partner: UNT Libraries Government Documents Department