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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

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

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

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

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

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

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

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

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

A deterministic, gigabit serial timing, synchronization and data link for the RHIC LLRF

Description: A critical capability of the new RHIC low level rf (LLRF) system is the ability to synchronize signals across multiple locations. The 'Update Link' provides this functionality. The 'Update Link' is a deterministic serial data link based on the Xilinx RocketIO protocol that is broadcast over fiber optic cable at 1 gigabit per second (Gbps). The link provides timing events and data packets as well as time stamp information for synchronizing diagnostic data from multiple sources. The new RHIC LLRF was designed to be a flexible, modular system. The system is constructed of numerous independent RF Controller chassis. To provide synchronization among all of these chassis, the Update Link system was designed. The Update Link system provides a low latency, deterministic data path to broadcast information to all receivers in the system. The Update Link system is based on a central hub, the Update Link Master (ULM), which generates the data stream that is distributed via fiber optic links. Downstream chassis have non-deterministic connections back to the ULM that allow any chassis to provide data that is broadcast globally.
Date: March 28, 2011
Creator: Hayes, T.; Smith, K.S. & Severino, F.
Partner: UNT Libraries Government Documents Department

From neural and social cooperation to the global emergence of cognition

Description: This article elaborates on a discussion of the emergence of intelligence via criticality as a consequence of locality breakdown, by using criticality for the foundation of a novel generation of game theory making the local interaction between players yield long-range effects.
Date: June 16, 2015
Creator: Grigolini, Paolo; Piccinni, Nicola; Svenkeson, Adam; Pramukkul, Pensri; Lambert, David & West, Bruce J.
Partner: UNT College of Arts and Sciences

Femtosecond Synchronization of Laser Systems for the LCLS

Description: The scientific potential of femtosecond x-ray pulses at linac-driven free-electron lasers such as the Linac Coherent Light Source is tremendous. Time-resolved pump-probe experiments require a measure of the relative arrival time of each x-ray pulse with respect to the experimental pump laser. An optical timing system based on stabilized fiber links has been developed for the LCLS to provide this synchronization. Preliminary results show synchronization of the installed stabilized links at the sub-20-femtosecond level. We present details of the implementation at LCLS and potential for future development.
Date: August 24, 2012
Creator: Byrd, John; /LBL, Berkeley; Doolittle, Lawrence; /LBL, Berkeley; Huang, Gang; /LBL, Berkeley et al.
Partner: UNT Libraries Government Documents Department

Using Pin as a Memory Reference Generator for Multiprocessor Simulation

Description: In this paper we describe how we have used Pin to generate a multithreaded reference stream for simulation of a multiprocessor on a uniprocessor. We have taken special care to model as accurately as possible the effects of cache coherence protocol state, and lock and barrier synchronization on the performance of multithreaded applications running on multiprocessor hardware. We first describe a simplified version of the algorithm, which uses semaphores to synchronize instrumented application threads and the simulator on every memory reference. We then describe modifications to that algorithm to model the microarchitectural features of the Itanium2 that affect the timing of memory reference issue. An experimental evaluation determines that while cycle-accurate multithreaded simulation is possible using our approach, the use of semaphores has a negative impact on the performance of the simulator.
Date: October 22, 2005
Creator: McCurdy, C
Partner: UNT Libraries Government Documents Department