Runway Scheduling Using Generalized Dynamic Programming

Science.gov (United States)

Montoya, Justin; Wood, Zachary; Rathinam, Sivakumar

2011-01-01

A generalized dynamic programming method for finding a set of pareto optimal solutions for a runway scheduling problem is introduced. The algorithm generates a set of runway fight sequences that are optimal for both runway throughput and delay. Realistic time-based operational constraints are considered, including miles-in-trail separation, runway crossings, and wake vortex separation. The authors also model divergent runway takeoff operations to allow for reduced wake vortex separation. A modeled Dallas/Fort Worth International airport and three baseline heuristics are used to illustrate preliminary benefits of using the generalized dynamic programming method. Simulated traffic levels ranged from 10 aircraft to 30 aircraft with each test case spanning 15 minutes. The optimal solution shows a 40-70 percent decrease in the expected delay per aircraft over the baseline schedulers. Computational results suggest that the algorithm is promising for real-time application with an average computation time of 4.5 seconds. For even faster computation times, two heuristics are developed. As compared to the optimal, the heuristics are within 5% of the expected delay per aircraft and 1% of the expected number of runway operations per hour ad can be 100x faster.

Review of ice and snow runway pavements

Directory of Open Access Journals (Sweden)

Greg White

2018-05-01

Full Text Available Antarctica is the highest, driest, coldest, windiest, most remote and most pristine place on Earth. Polar operations depend heavily on air transportation and support for personnel and equipment. It follows that improvement in snow and ice runway design, construction and maintenance will directly benefit polar exploration and research. Current technologies and design methods for snow and ice runways remain largely reliant on work performed in the 1950s and 1960s. This paper reviews the design and construction of polar runways using snow and ice as geomaterials. The inability to change existing snow and ice thickness or temperature creates a challenge for polar runway design and construction, as does the highly complex mechanical behaviour of snow, including the phenomena known as sintering. It is recommended that a modern approach be developed for ice and snow runway design, based on conventional rigid and flexible pavement design principles. This requires the development on an analytical model for the prediction of snow strength, based on snow age, temperature history and density. It is also recommended that the feasibility of constructing a snow runway at the South Pole be revisited, in light of contemporary snow sintering methods. Such a runway would represent a revolutionary advance for the logistical support of Antarctic research efforts. Keywords: Runway, Pavement, Snow, Ice, Antarctic

Analysis of wind data for airport runway design

Directory of Open Access Journals (Sweden)

Roberto Bellasio

2014-09-01

Full Text Available Purpose: To provide a methodology, and examples of application, for analyzing wind data for the correct orientation of airport runways. Design/methodology/approach: More than 90000 observed wind data have been analyzed for each one of the three airports used as case studies. Both observed and estimated gusts have been considered. Findings: If only observed data are considered, each single runway of the three airports used as case studies is correctly oriented. When estimated gusts are considered, the FAA requirements are not satisfied by a single runway in some airports (which anyway satisfy such requirements by using more runways. Practical implications: The correct orientation of runways minimize the crosswind components, then increase the safety of the airports. Originality/value: The paper provides a methodology to evaluate the orientation of existing runways and to design new runways. Such methodology is based on the analysis wind data, considering both observed values and estimated gusts.

Spot and Runway Departure Advisor (SARDA)

Science.gov (United States)

Jung, Yoon

2016-01-01

Spot and Runway Departure Advisor (SARDA) is a decision support tool to assist airline ramp controllers and ATC tower controllers to manage traffic on the airport surface to significantly improve efficiency and predictability in surface operations. The core function of the tool is the runway scheduler which generates an optimal solution for runway sequence and schedule of departure aircraft, which would minimize system delay and maximize runway throughput. The presentation also discusses the latest status of NASA's current surface research through a collaboration with an airline partner, where a tool is developed for airline ramp operators to assist departure pushback operations. The presentation describes the concept of the SARDA tool and results from human-in-the-loop simulations conducted in 2012 for Dallas-Ft. Worth International Airport and 2014 for Charlotte airport ramp tower.

Runway Scheduling for Charlotte Douglas International Airport

Science.gov (United States)

Malik, Waqar A.; Lee, Hanbong; Jung, Yoon C.

2016-01-01

This paper describes the runway scheduler that was used in the 2014 SARDA human-in-the-loop simulations for CLT. The algorithm considers multiple runways and computes optimal runway times for departures and arrivals. In this paper, we plan to run additional simulation on the standalone MRS algorithm and compare the performance of the algorithm against a FCFS heuristic where aircraft avail of runway slots based on a priority given by their positions in the FCFS sequence. Several traffic scenarios corresponding to current day traffic level and demand profile will be generated. We also plan to examine the effect of increase in traffic level (1.2x and 1.5x) and observe trends in algorithm performance.

Aircraft and ground vehicle friction correlation test results obtained under winter runway conditions during joint FAA/NASA Runway Friction Program

Science.gov (United States)

Yager, Thomas J.; Vogler, William A.; Baldasare, Paul

1988-01-01

Aircraft and ground vehicle friction data collected during the Joint FAA/NASA Runway Friction Program under winter runway conditions are discussed and test results are summarized. The relationship between the different ground vehicle friction measurements obtained on compacted snow- and ice-covered conditions is defined together with the correlation to aircraft tire friction performance under similar runway conditions.

Analysis of Runway Incursion Data

Science.gov (United States)

Green, Lawrence L.

2013-01-01

A statistical analysis of runway incursion (RI) events was conducted to ascertain relevance to the top ten challenges of the National Aeronautics and Space Administration Aviation Safety Program (AvSP). The information contained in the RI database was found to contain data that may be relevant to several of the AvSP top ten challenges. When combined with other data from the FAA documenting air traffic volume from calendar year 2000 through 2011, the structure of a predictive model emerges that can be used to forecast the frequency of RI events at various airports for various classes of aircraft and under various environmental conditions.

PROBABILISTIC MODEL FOR AIRPORT RUNWAY SAFETY AREAS

Directory of Open Access Journals (Sweden)

Stanislav SZABO

2017-06-01

Full Text Available The Laboratory of Aviation Safety and Security at CTU in Prague has recently started a project aimed at runway protection zones. The probability of exceeding by a certain distance from the runway in common incident/accident scenarios (take-off/landing overrun/veer-off, landing undershoot is being identified relative to the runway for any airport. As a result, the size and position of safety areas around runways are defined for the chosen probability. The basis for probability calculation is a probabilistic model using statistics from more than 1400 real-world cases where jet airplanes have been involved over the last few decades. Other scientific studies have contributed to understanding the issue and supported the model’s application to different conditions.

Current status of Joint FAA/NASA Runway Friction Program

Science.gov (United States)

Yager, Thomas J.; Vogler, William A.

1989-01-01

Tests with specially instrumented NASA B-737 and FAA B-727 aircraft together with several different ground friction measuring devices have been conducted for a variety of runway surface types and wetness conditions. This effort is part of the Joint FAA/NASA Aircraft Ground Vehicle Runway Friction Program aimed at obaining a better understanding of aircraft ground handling performance under adverse weather conditions and defining relationships between aircraft and ground vehicle tire friction measurements. Aircraft braking performance on dry, wet, snow-, and ice-covered runway conditions is discussed together with ground vehicle friction data obtained under similar runway conditions. For the wet, compacted snow- and ice-covered runway conditions, the relationship between ground vehicles and aircraft friction data is identified. The influence of major test parameters on friction measurements such as speed, test tire characteristics, and surface contaminant type are discussed. The test results indicate that use of properly maintained and calibrated ground vehicles for monitoring runway friction conditions should be encouraged particularly under adverse weather conditions. The current status of the runway friction program is summarized and future test plans are identified.

Temporal Precedence Checking for Switched Models and its Application to a Parallel Landing Protocol

Science.gov (United States)

Duggirala, Parasara Sridhar; Wang, Le; Mitra, Sayan; Viswanathan, Mahesh; Munoz, Cesar A.

2014-01-01

This paper presents an algorithm for checking temporal precedence properties of nonlinear switched systems. This class of properties subsume bounded safety and capture requirements about visiting a sequence of predicates within given time intervals. The algorithm handles nonlinear predicates that arise from dynamics-based predictions used in alerting protocols for state-of-the-art transportation systems. It is sound and complete for nonlinear switch systems that robustly satisfy the given property. The algorithm is implemented in the Compare Execute Check Engine (C2E2) using validated simulations. As a case study, a simplified model of an alerting system for closely spaced parallel runways is considered. The proposed approach is applied to this model to check safety properties of the alerting logic for different operating conditions such as initial velocities, bank angles, aircraft longitudinal separation, and runway separation.

Vertical Temperature Simulation of Pegasus Runway, McMurdo Station, Antarctica

Science.gov (United States)

2015-01-01

Polar Programs PSP Precision Spectral Pyranometer SPAWAR Space and Naval Warfare Systems Command ERDC/CRREL TR-15-2 ix Unit Conversion Factors...site was measured (M. Knuth*, pers. comm.) in 15-minute intervals from 29 October 2010 until 5 February 2011. Two broadband pyranometers (Eppley...Precision Spectral Pyranometer ) were mounted on a mast immediately adjacent to the runway. One measured downwelling radiation and the other upwelling

Economic utilization of general aviation airport runways

Science.gov (United States)

Piper, R. R.

1971-01-01

The urban general aviation airport economics is studied in detail. The demand for airport services is discussed, and the different types of users are identified. The direct cost characteristics of the airport are summarized; costs to the airport owner are largely fixed, and, except at certain large airports, weight is not a significant factor in airport costs. The efficient use of an existing airport facility is explored, with the focus on the social cost of runway congestion as traffic density at the airport build up and queues form. The tradeoff between aircraft operating costs and airport costs is analyzed in terms of runway length. The transition from theory to practice is treated, and the policy of charging prices only on aircraft storage and fuel is felt likely to continue. Implications of the study from the standpoint of public policy include pricing that spreads traffic peaks to improve runway utilization, and pricing that discriminates against aircraft requiring long runways and causes owners to adopt V/STOL equipment.

Biharmonic Submanifolds with Parallel Mean Curvature Vector in Pseudo-Euclidean Spaces

Energy Technology Data Exchange (ETDEWEB)

Fu, Yu, E-mail: yufudufe@gmail.com [Dongbei University of Finance and Economics, School of Mathematics and Quantitative Economics (China)

2013-12-15

In this paper, we investigate biharmonic submanifolds in pseudo-Euclidean spaces with arbitrary index and dimension. We give a complete classification of biharmonic spacelike submanifolds with parallel mean curvature vector in pseudo-Euclidean spaces. We also determine all biharmonic Lorentzian surfaces with parallel mean curvature vector field in pseudo-Euclidean spaces.

Biharmonic Submanifolds with Parallel Mean Curvature Vector in Pseudo-Euclidean Spaces

International Nuclear Information System (INIS)

Fu, Yu

2013-01-01

In this paper, we investigate biharmonic submanifolds in pseudo-Euclidean spaces with arbitrary index and dimension. We give a complete classification of biharmonic spacelike submanifolds with parallel mean curvature vector in pseudo-Euclidean spaces. We also determine all biharmonic Lorentzian surfaces with parallel mean curvature vector field in pseudo-Euclidean spaces

NASA tire/runway friction projects

Science.gov (United States)

Yager, Thomas J.

1995-01-01

The paper reviews several aspects of NASA Langley Research Center's tire/runway friction evaluations directed towards improving the safety and economy of aircraft ground operations. The facilities and test equipment used in implementing different aircraft tire friction studies and other related aircraft ground performance investigations are described together with recent workshop activities at NASA Wallops Flight Facility. An overview of the pending Joint NASA/Transport Canada/FM Winter Runway Friction Program is given. Other NASA ongoing studies and on-site field tests are discussed including tire wear performance and new surface treatments. The paper concludes with a description of future research plans.

Aircraft and ground vehicle friction measurements obtained under winter runway conditions

Science.gov (United States)

Yager, Thomas J.

1989-01-01

Tests with specially instrumented NASA B-737 and B-727 aircraft together with several different ground friction measuring devices have been conducted for a variety of runway surface types and wetness conditions. This effort is part of the Joint FAA/NASA Aircraft/Ground Vehicle Runway Friction Program aimed at obtaining a better understanding of aircraft ground handling performance under adverse weather conditions, and defining relationships between aircraft and ground vehicle tire friction measurements. Aircraft braking performance on dry, wet, snow-, and ice-covered runway conditions is discussed together with ground vehicle friction data obtained under similar runway conditions. For the wet, compacted snow- and ice-covered runway conditions, the relationship between ground vehicles and aircraft friction data is identified. The influence of major test parameters on friction measurements such as speed, test tire characteristics, and surface contaminant-type are discussed. The test results indicate that use of properly maintained and calibrated ground vehicles for monitoring runway friction conditions should be encouraged particularly under adverse weather conditions.

Evaluation of high pressure water blast with rotating spray bar for removing paint and rubber deposits from airport runways, and review of runway slipperiness problems created by rubber contamination

Science.gov (United States)

Horne, W. B.; Griswold, G. D.

1975-01-01

A high pressure water blast with rotating spray bar treatment for removing paint and rubber deposits from airport runways is studied. The results of the evaluation suggest that the treatment is very effective in removing above surface paint and rubber deposits to the point that pavement skid resistance is restored to trafficked but uncontaminated runway surface skid resistance levels. Aircraft operating problems created by runway slipperiness are reviewed along with an assessment of the contributions that pavement surface treatments, surface weathering, traffic polishing, and rubber deposits make in creating or alleviating runway slipperiness. The results suggest that conventional surface treatments for both portland cement and asphaltic concrete runways are extremely vulnerable to rubber deposit accretions which can produce runway slipperiness conditions for aircraft operations as or more slippery than many snow and ice-covered runway conditions. Pavement grooving surface treatments are shown to be the least vulnerable to rubber deposits accretion and traffic polishing of the surface treatments examined.

Parallel Auxiliary Space AMG Solver for $H(div)$ Problems

Energy Technology Data Exchange (ETDEWEB)

Kolev, Tzanio V. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Vassilevski, Panayot S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2012-12-18

We present a family of scalable preconditioners for matrices arising in the discretization of $H(div)$ problems using the lowest order Raviart--Thomas finite elements. Our approach belongs to the class of “auxiliary space''--based methods and requires only the finite element stiffness matrix plus some minimal additional discretization information about the topology and orientation of mesh entities. Also, we provide a detailed algebraic description of the theory, parallel implementation, and different variants of this parallel auxiliary space divergence solver (ADS) and discuss its relations to the Hiptmair--Xu (HX) auxiliary space decomposition of $H(div)$ [SIAM J. Numer. Anal., 45 (2007), pp. 2483--2509] and to the auxiliary space Maxwell solver AMS [J. Comput. Math., 27 (2009), pp. 604--623]. Finally, an extensive set of numerical experiments demonstrates the robustness and scalability of our implementation on large-scale $H(div)$ problems with large jumps in the material coefficients.

Runway Safety: It's Everybody's Business. We Want You to Put the Brakes on Runway Incursions

National Research Council Canada - National Science Library

Cardosi, Kim

2001-01-01

This booklet tell pilots and controllers what they can do to help prevent runway incursions by helping them to avoid situations that induce errors and alerting them to them to situations as extra vigilance is required...

Benefits Assessment for Single-Airport Tactical Runway Configuration Management Tool (TRCM)

Science.gov (United States)

Oseguera-Lohr, Rosa; Phojanamonogkolkij, Nipa; Lohr, Gary W.

2015-01-01

The System-Oriented Runway Management (SORM) concept was developed as part of the Airspace Systems Program (ASP) Concepts and Technology Development (CTD) Project, and is composed of two basic capabilities: Runway Configuration Management (RCM), and Combined Arrival/Departure Runway Scheduling (CADRS). RCM is the process of designating active runways, monitoring the active runway configuration for suitability given existing factors, and predicting future configuration changes; CADRS is the process of distributing arrivals and departures across active runways based on local airport and National Airspace System (NAS) goals. The central component in the SORM concept is a tool for taking into account all the various factors and producing a recommendation for what would be the optimal runway configuration, runway use strategy, and aircraft sequence, considering as many of the relevant factors required in making this type of decision, and user preferences, if feasible. Three separate tools were initially envisioned for this research area, corresponding to the time scale in which they would operate: Strategic RCM (SRCM), with a planning horizon on the order of several hours, Tactical RCM (TRCM), with a planning horizon on the order of 90 minutes, and CADRS, with a planning horizon on the order of 15-30 minutes[1]. Algorithm development was initiated in all three of these areas, but the most fully developed to date is the TRCM algorithm. Earlier studies took a high-level approach to benefits, estimating aggregate benefits across most of the major airports in the National Airspace Systems (NAS), for both RCM and CADRS [2]. Other studies estimated the benefit of RCM and CADRS using various methods of re-sequencing arrivals to reduce delays3,4, or better balancing of arrival fixes5,6. Additional studies looked at different methods for performing the optimization involved in selecting the best Runway Configuration Plan (RCP) to use7-10. Most of these previous studies were high

Adaptive integrand decomposition in parallel and orthogonal space

International Nuclear Information System (INIS)

Mastrolia, Pierpaolo; Peraro, Tiziano; Primo, Amedeo

2016-01-01

We present the integrand decomposition of multiloop scattering amplitudes in parallel and orthogonal space-time dimensions, d=d ∥ +d ⊥ , being d ∥ the dimension of the parallel space spanned by the legs of the diagrams. When the number n of external legs is n≤4, the corresponding representation of multiloop integrals exposes a subset of integration variables which can be easily integrated away by means of Gegenbauer polynomials orthogonality condition. By decomposing the integration momenta along parallel and orthogonal directions, the polynomial division algorithm is drastically simplified. Moreover, the orthogonality conditions of Gegenbauer polynomials can be suitably applied to integrate the decomposed integrand, yielding the systematic annihilation of spurious terms. Consequently, multiloop amplitudes are expressed in terms of integrals corresponding to irreducible scalar products of loop momenta and external ones. We revisit the one-loop decomposition, which turns out to be controlled by the maximum-cut theorem in different dimensions, and we discuss the integrand reduction of two-loop planar and non-planar integrals up to n=8 legs, for arbitrary external and internal kinematics. The proposed algorithm extends to all orders in perturbation theory.

Adaptive integrand decomposition in parallel and orthogonal space

Energy Technology Data Exchange (ETDEWEB)

Mastrolia, Pierpaolo [Dipartimento di Fisica ed Astronomia, Università di Padova,Via Marzolo 8, 35131 Padova (Italy); INFN, Sezione di Padova,Via Marzolo 8, 35131 Padova (Italy); Peraro, Tiziano [Higgs Centre for Theoretical Physics, School of Physics and Astronomy,The University of Edinburgh,James Clerk Maxwell Building,Peter Guthrie Tait Road, Edinburgh EH9 3FD, Scotland (United Kingdom); Primo, Amedeo [Dipartimento di Fisica ed Astronomia, Università di Padova,Via Marzolo 8, 35131 Padova (Italy); INFN, Sezione di Padova,Via Marzolo 8, 35131 Padova (Italy)

2016-08-29

We present the integrand decomposition of multiloop scattering amplitudes in parallel and orthogonal space-time dimensions, d=d{sub ∥}+d{sub ⊥}, being d{sub ∥} the dimension of the parallel space spanned by the legs of the diagrams. When the number n of external legs is n≤4, the corresponding representation of multiloop integrals exposes a subset of integration variables which can be easily integrated away by means of Gegenbauer polynomials orthogonality condition. By decomposing the integration momenta along parallel and orthogonal directions, the polynomial division algorithm is drastically simplified. Moreover, the orthogonality conditions of Gegenbauer polynomials can be suitably applied to integrate the decomposed integrand, yielding the systematic annihilation of spurious terms. Consequently, multiloop amplitudes are expressed in terms of integrals corresponding to irreducible scalar products of loop momenta and external ones. We revisit the one-loop decomposition, which turns out to be controlled by the maximum-cut theorem in different dimensions, and we discuss the integrand reduction of two-loop planar and non-planar integrals up to n=8 legs, for arbitrary external and internal kinematics. The proposed algorithm extends to all orders in perturbation theory.

Airports and Airfields, Airports within Johnson County as well as runway depicted with attribute information of both airport and runway., Published in Not Provided, Johnson County Government.

Data.gov (United States)

NSGIC Local Govt | GIS Inventory — Airports and Airfields dataset current as of unknown. Airports within Johnson County as well as runway depicted with attribute information of both airport and runway..

Weather and forecasting at Wilkins ice runway, Antarctica

International Nuclear Information System (INIS)

Carpentier, Scott

2010-01-01

Aviation forecasts for Wilkins ice runway in East Antarctica are developed within the conceptual framework of flow against a single dome shaped hill. Forecast challenges include the sudden onset of blizzards associated with the formation of an internal gravity wave; frontal weather; transient wake vortices and mesoscale lows; temperature limitations on runway use; and snow and fog events. These key weather aspects are presented within the context of synoptic to local scale climatologies and numerical weather prediction models.

A Runway Surface Monitor using Internet of Things

Science.gov (United States)

Troiano, Amedeo; Pasero, Eros

2014-05-01

The monitoring of runway surfaces, for the detection of ice formation or presence of water, is an important issue for reducing maintenance costs and improving traffic safety. An innovative sensor was developed to detect the presence of ice or water on its surface, and its repeatability, stability and reliability were assessed in different simulations and experiments, performed both in laboratory and in the field. Three sensors were embedded in the runway of the Turin-Caselle airport, in the north-west of Italy, to check the state of its surface. Each sensor was connected to a GPRS modem to send the collected data to a common database. The entire system was installed about three years ago, and up to now it shows correct work and automatic reactivation after malfunctions without any external help. The state of the runway surface is virtual represented in an internet website, using the Internet of Things features and opening new scenarios.

Spot and Runway Departure Advisor

Science.gov (United States)

Jung, Yoon Chul

2013-01-01

The Spot and Runway Departure Advisor (SARDA) is a research prototype of a decision support tool for ATC tower controllers to assist in manging and controlling traffic on the surface of an airport. SARDA employs a scheduler to generate an optimal runway schedule and gate push-back - spot release sequence and schedule that improves efficiency of surface operations. The advisories for ATC tower controllers are displayed on an Electronic Flight Strip (EFS) system. The human-in-the-loop simulation of the SARDA tool was conducted for east operations of Dallas-Ft. Worth International Airport (DFW) to evaluate performance of the SARDA tool and human factors, such as situational awareness and workload. The results indicates noticeable taxi delay reduction and fuel savings by using the SARDA tool. Reduction in controller workload were also observed throughout the scenario runs. The future plan includes modeling and simulation of the ramp operations of the Charlotte International Airport, and develop a decision support tool for the ramp controllers.

An assessment of predominant causal factors of pilot deviations that contribute to runway incursions

Science.gov (United States)

Campbell, Denado M.

The aim of this study was to identify predominant causal factors of pilot deviations in runway incursions over a two-year period. Runway incursion reports were obtained from NASA's Aviation Safety Reporting System (ASRS), and a qualitative method was used by classifying and coding each report to a specific causal factor(s). The causal factors that were used were substantiated by research from the Aircraft Owner's and Pilot's Association that found that these causal factors were the most common in runway incursion incidents and accidents. An additional causal factor was also utilized to determine the significance of pilot training in relation to runway incursions. From the reports examined, it was found that miscommunication and situational awareness have the greatest impact on pilots and are most often the major causes of runway incursions. This data can be used to assist airports, airlines, and the FAA to understand trends in pilot deviations, and to find solutions for specific problem areas in runway incursion incidents.

Portable, parallel, reusable Krylov space codes

Energy Technology Data Exchange (ETDEWEB)

Smith, B.; Gropp, W. [Argonne National Lab., IL (United States)

1994-12-31

Krylov space accelerators are an important component of many algorithms for the iterative solution of linear systems. Each Krylov space method has it`s own particular advantages and disadvantages, therefore it is desirable to have a variety of them available all with an identical, easy to use, interface. A common complaint application programmers have with available software libraries for the iterative solution of linear systems is that they require the programmer to use the data structures provided by the library. The library is not able to work with the data structures of the application code. Hence, application programmers find themselves constantly recoding the Krlov space algorithms. The Krylov space package (KSP) is a data-structure-neutral implementation of a variety of Krylov space methods including preconditioned conjugate gradient, GMRES, BiCG-Stab, transpose free QMR and CGS. Unlike all other software libraries for linear systems that the authors are aware of, KSP will work with any application codes data structures, in Fortran or C. Due to it`s data-structure-neutral design KSP runs unchanged on both sequential and parallel machines. KSP has been tested on workstations, the Intel i860 and Paragon, Thinking Machines CM-5 and the IBM SP1.

State-space-based harmonic stability analysis for paralleled grid-connected inverters

DEFF Research Database (Denmark)

Wang, Yanbo; Wang, Xiongfei; Chen, Zhe

2016-01-01

This paper addresses a state-space-based harmonic stability analysis of paralleled grid-connected inverters system. A small signal model of individual inverter is developed, where LCL filter, the equivalent delay of control system, and current controller are modeled. Then, the overall small signal...... model of paralleled grid-connected inverters is built. Finally, the state space-based stability analysis approach is developed to explain the harmonic resonance phenomenon. The eigenvalue traces associated with time delay and coupled grid impedance are obtained, which accounts for how the unstable...... inverter produces the harmonic resonance and leads to the instability of whole paralleled system. The proposed approach reveals the contributions of the grid impedance as well as the coupled effect on other grid-connected inverters under different grid conditions. Simulation and experimental results...

Strengthening air traffic safety management by moving from outcome-based towards risk-based evaluation of runway incursions

International Nuclear Information System (INIS)

Stroeve, Sybert H.; Som, Pradip; Doorn, Bas A. van; Bakker, G.J.

2016-01-01

Current safety management of aerodrome operations uses judgements of severity categories to evaluate runway incursions. Incident data show a small minority of severe incursions and a large majority of less severe incursions. We show that these severity judgements are mainly based upon the outcomes of runway incursions, in particular on the closest distances attained. As such, the severity-based evaluation leads to coincidental safety management feedback, wherein causes and risk implications of runway incursions are not well considered. In this paper we present a new framework for the evaluation of runway incursions, which effectively uses all runway incursions, which judges same types of causes similarly, and which structures causes and risk implications. The framework is based on risks of scenarios associated with the initiation of runway incursions. As a basis an inventory of scenarios is provided, which can represent almost all runway incursions involving a conflict with an aircraft. A main step in the framework is the assessment of the conditional probability of a collision given a runway incursion scenario. This can be effectively achieved for large sets of scenarios by agent-based dynamic risk modelling. The results provide detailed feedback on risks of runway incursion scenarios, thus enabling effective safety management. - Highlights: • Current evaluation of runway incursions is primarily based on their outcomes. • A new framework assesses collision risk given initiation of runway incursions. • Agent-based dynamic risk modelling can evaluate the risks of many scenarios. • A developed scenario inventory can represent almost all runway incursions. • The framework provides detailed feedback to safety management.

Evaluation of two transport aircraft and several ground test vehicle friction measurements obtained for various runway surface types and conditions. A summary of test results from joint FAA/NASA Runway Friction Program

Science.gov (United States)

Yager, Thomas J.; Vogler, William A.; Baldasare, Paul

1990-01-01

Tests with specially instrumented NASA Boeing 737 and 727 aircraft together with several different ground friction measuring devices were conducted for a variety of runway surface types and conditions. These tests are part of joint FAA/NASA Aircraft/Ground Vehicle Runway Friction Program aimed at obtaining a better understanding of aircraft ground handling performance under adverse weather conditions and defining relationships between aircraft and ground vehicle tire friction measurements. Aircraft braking performance on dry, wet, snow and ice-covered runway conditions is discussed as well as ground vehicle friction data obtained under similar runway conditions. For a given contaminated runway surface condition, the correlation between ground vehicles and aircraft friction data is identified. The influence of major test parameters on friction measurements such as speed, test tire characteristics, type and amount of surface contaminant, and ambient temperature are discussed. The effect of surface type on wet friction levels is also evaluated from comparative data collected on grooved and ungrooved concrete and asphalt surfaces.

A Robust Vision-based Runway Detection and Tracking Algorithm for Automatic UAV Landing

KAUST Repository

Abu Jbara, Khaled F.

2015-05-01

This work presents a novel real-time algorithm for runway detection and tracking applied to the automatic takeoff and landing of Unmanned Aerial Vehicles (UAVs). The algorithm is based on a combination of segmentation based region competition and the minimization of a specific energy function to detect and identify the runway edges from streaming video data. The resulting video-based runway position estimates are updated using a Kalman Filter, which can integrate other sensory information such as position and attitude angle estimates to allow a more robust tracking of the runway under turbulence. We illustrate the performance of the proposed lane detection and tracking scheme on various experimental UAV flights conducted by the Saudi Aerospace Research Center. Results show an accurate tracking of the runway edges during the landing phase under various lighting conditions. Also, it suggests that such positional estimates would greatly improve the positional accuracy of the UAV during takeoff and landing phases. The robustness of the proposed algorithm is further validated using Hardware in the Loop simulations with diverse takeoff and landing videos generated using a commercial flight simulator.

Runway Wake Vortex, Crosswind, and Visibility Detection with a Scintillometer at Schiphol Airport

NARCIS (Netherlands)

Dinther, van D.; Hartogensis, O.K.; Holtslag, A.A.M.

2015-01-01

We evaluate the performance and investigate the capability of a scintillometer to detect wake vortices, crosswind and visibility near an airport runway. An experiment is carried out at Schiphol airport (Amsterdam, The Netherlands), where an optical scintillometer is positioned alongside a runway. An

A parallel implementation of particle tracking with space charge effects on an INTEL iPSC/860

International Nuclear Information System (INIS)

Chang, L.; Bourianoff, G.; Cole, B.; Machida, S.

1993-05-01

Particle-tracking simulation is one of the scientific applications that is well-suited to parallel computations. At the Superconducting Super Collider, it has been theoretically and empirically demonstrated that particle tracking on a designed lattice can achieve very high parallel efficiency on a MIMD Intel iPSC/860 machine. The key to such success is the realization that the particles can be tracked independently without considering their interaction. The perfectly parallel nature of particle tracking is broken if the interaction effects between particles are included. The space charge introduces an electromagnetic force that will affect the motion of tracked particles in 3-D space. For accurate modeling of the beam dynamics with space charge effects, one needs to solve three-dimensional Maxwell field equations, usually by a particle-in-cell (PIC) algorithm. This will require each particle to communicate with its neighbor grids to compute the momentum changes at each time step. It is expected that the 3-D PIC method will degrade parallel efficiency of particle-tracking implementation on any parallel computer. In this paper, we describe an efficient scheme for implementing particle tracking with space charge effects on an INTEL iPSC/860 machine. Experimental results show that a parallel efficiency of 75% can be obtained

The simplified spherical harmonics (SPL) methodology with space and moment decomposition in parallel environments

International Nuclear Information System (INIS)

Gianluca, Longoni; Alireza, Haghighat

2003-01-01

In recent years, the SP L (simplified spherical harmonics) equations have received renewed interest for the simulation of nuclear systems. We have derived the SP L equations starting from the even-parity form of the S N equations. The SP L equations form a system of (L+1)/2 second order partial differential equations that can be solved with standard iterative techniques such as the Conjugate Gradient (CG). We discretized the SP L equations with the finite-volume approach in a 3-D Cartesian space. We developed a new 3-D general code, Pensp L (Parallel Environment Neutral-particle SP L ). Pensp L solves both fixed source and criticality eigenvalue problems. In order to optimize the memory management, we implemented a Compressed Diagonal Storage (CDS) to store the SP L matrices. Pensp L includes parallel algorithms for space and moment domain decomposition. The computational load is distributed on different processors, using a mapping function, which maps the 3-D Cartesian space and moments onto processors. The code is written in Fortran 90 using the Message Passing Interface (MPI) libraries for the parallel implementation of the algorithm. The code has been tested on the Pcpen cluster and the parallel performance has been assessed in terms of speed-up and parallel efficiency. (author)

Runway exit designs for capacity improvement demonstrations. Phase 2: Computer model development

Science.gov (United States)

Trani, A. A.; Hobeika, A. G.; Kim, B. J.; Nunna, V.; Zhong, C.

1992-01-01

The development is described of a computer simulation/optimization model to: (1) estimate the optimal locations of existing and proposed runway turnoffs; and (2) estimate the geometric design requirements associated with newly developed high speed turnoffs. The model described, named REDIM 2.0, represents a stand alone application to be used by airport planners, designers, and researchers alike to estimate optimal turnoff locations. The main procedures are described in detail which are implemented in the software package and possible applications are illustrated when using 6 major runway scenarios. The main output of the computer program is the estimation of the weighted average runway occupancy time for a user defined aircraft population. Also, the location and geometric characteristics of each turnoff are provided to the user.

Parallel magnetic resonance imaging as approximation in a reproducing kernel Hilbert space

International Nuclear Information System (INIS)

Athalye, Vivek; Lustig, Michael; Martin Uecker

2015-01-01

In magnetic resonance imaging data samples are collected in the spatial frequency domain (k-space), typically by time-consuming line-by-line scanning on a Cartesian grid. Scans can be accelerated by simultaneous acquisition of data using multiple receivers (parallel imaging), and by using more efficient non-Cartesian sampling schemes. To understand and design k-space sampling patterns, a theoretical framework is needed to analyze how well arbitrary sampling patterns reconstruct unsampled k-space using receive coil information. As shown here, reconstruction from samples at arbitrary locations can be understood as approximation of vector-valued functions from the acquired samples and formulated using a reproducing kernel Hilbert space with a matrix-valued kernel defined by the spatial sensitivities of the receive coils. This establishes a formal connection between approximation theory and parallel imaging. Theoretical tools from approximation theory can then be used to understand reconstruction in k-space and to extend the analysis of the effects of samples selection beyond the traditional image-domain g-factor noise analysis to both noise amplification and approximation errors in k-space. This is demonstrated with numerical examples. (paper)

Parallel symbolic state-space exploration is difficult, but what is the alternative?

Directory of Open Access Journals (Sweden)

Gianfranco Ciardo

2009-12-01

Full Text Available State-space exploration is an essential step in many modeling and analysis problems. Its goal is to find the states reachable from the initial state of a discrete-state model described. The state space can used to answer important questions, e.g., "Is there a dead state?" and "Can N become negative?", or as a starting point for sophisticated investigations expressed in temporal logic. Unfortunately, the state space is often so large that ordinary explicit data structures and sequential algorithms cannot cope, prompting the exploration of (1 parallel approaches using multiple processors, from simple workstation networks to shared-memory supercomputers, to satisfy large memory and runtime requirements and (2 symbolic approaches using decision diagrams to encode the large structured sets and relations manipulated during state-space generation. Both approaches have merits and limitations. Parallel explicit state-space generation is challenging, but almost linear speedup can be achieved; however, the analysis is ultimately limited by the memory and processors available. Symbolic methods are a heuristic that can efficiently encode many, but not all, functions over a structured and exponentially large domain; here the pitfalls are subtler: their performance varies widely depending on the class of decision diagram chosen, the state variable order, and obscure algorithmic parameters. As symbolic approaches are often much more efficient than explicit ones for many practical models, we argue for the need to parallelize symbolic state-space generation algorithms, so that we can realize the advantage of both approaches. This is a challenging endeavor, as the most efficient symbolic algorithm, Saturation, is inherently sequential. We conclude by discussing challenges, efforts, and promising directions toward this goal.

Real-time terminal area trajectory planning for runway independent aircraft

Science.gov (United States)

Xue, Min

The increasing demand for commercial air transportation results in delays due to traffic queues that form bottlenecks along final approach and departure corridors. In urban areas, it is often infeasible to build new runways, and regardless of automation upgrades traffic must remain separated to avoid the wakes of previous aircraft. Vertical or short takeoff and landing aircraft as Runway Independent Aircraft (RIA) can increase passenger throughput at major urban airports via the use of vertiports or stub runways. The concept of simultaneous non-interfering (SNI) operations has been proposed to reduce traffic delays by creating approach and departure corridors that do not intersect existing fixed-wing routes. However, SNI trajectories open new routes that may overfly noise-sensitive areas, and RIA may generate more noise than traditional jet aircraft, particularly on approach. In this dissertation, we develop efficient SNI noise abatement procedures applicable to RIA. First, we introduce a methodology based on modified approximated cell-decomposition and Dijkstra's search algorithm to optimize longitudinal plane (2-D) RIA trajectories over a cost function that minimizes noise, time, and fuel use. Then, we extend the trajectory optimization model to 3-D with a k-ary tree as the discrete search space. We incorporate geography information system (GIS) data, specifically population, into our objective function, and focus on a practical case study: the design of SNI RIA approach procedures to Baltimore-Washington International airport. Because solutions were represented as trim state sequences, we incorporated smooth transition between segments to enable more realistic cost estimates. Due to the significant computational complexity, we investigated alternative more efficient optimization techniques applicable to our nonlinear, non-convex, heavily constrained, and discontinuous objective function. Comparing genetic algorithm (GA) and adaptive simulated annealing (ASA

Benefits Assessment for Tactical Runway Configuration Management Tool

Science.gov (United States)

Oseguera-Lohr, Rosa; Phojanamongkolkij, Nipa; Lohr, Gary; Fenbert, James W.

2013-01-01

The Tactical Runway Configuration Management (TRCM) software tool was developed to provide air traffic flow managers and supervisors with recommendations for airport configuration changes and runway usage. The objective for this study is to conduct a benefits assessment at Memphis (MEM), Dallas Fort-Worth (DFW) and New York's John F. Kennedy (JFK) airports using the TRCM tool. Results from simulations using the TRCM-generated runway configuration schedule are compared with results using historical schedules. For the 12 days of data used in this analysis, the transit time (arrival fix to spot on airport movement area for arrivals, or spot to departure fix for departures) for MEM departures is greater (7%) than for arrivals (3%); for JFK, there is a benefit for arrivals (9%) but not for departures (-2%); for DFW, arrivals show a slight benefit (1%), but this is offset by departures (-2%). Departure queue length benefits show fewer aircraft in queue for JFK (29%) and MEM (11%), but not for DFW (-13%). Fuel savings for surface operations at MEM are seen for both arrivals and departures. At JFK there are fuel savings for arrivals, but these are offset by increased fuel use for departures. In this study, no surface fuel benefits resulted for DFW. Results suggest that the TRCM algorithm requires modifications for complex surface traffic operations that can cause taxi delays. For all three airports, the average number of changes in flow direction (runway configuration) recommended by TRCM was many times greater than the historical data; TRCM would need to be adapted to a particular airport's needs, to limit the number of changes to acceptable levels. The results from this analysis indicate the TRCM tool can provide benefits at some high-capacity airports. The magnitude of these benefits depends on many airport-specific factors and would require adaptation of the TRCM tool; a detailed assessment is needed prior to determining suitability for a particular airport.

Mitigation of low-frequency groundnoise from runways

NARCIS (Netherlands)

Eerden, F.J.M. van der; Salomons, E.M.; Beeks, A.A.F.M.

2007-01-01

With the extra runway at Amsterdam Schiphol Airport, introduced in 2003, the noise nuisance for local residents increased due to increased groundnoise. In a case study the effect of enhanced ground absorption on the propagation of low-frequency noise from aircraft ground operations, e.g. departing

Burrowing Owl and Other Migratory Bird Mitigation for a Runway Construction Project at Edwards AFB

OpenAIRE

Hoehn, Amber L.; Hagan, Mark; Bratton, Mark

2009-01-01

Edwards Air Force Base (AFB) scheduled the construction of a runway in the spring of 2007. The runway would be in an area that contained migratory birds and their habitat. The construction project would be near Edwards AFB main runway and had the potential not only to impact species protected under the Migratory Bird Treaty Act (MBTA), including the burrowing owl (Athene cunicularia), but also to increase bird and wildlife–aircraft strike hazards in the active flightline areas. To discourage ...

Exact and Heuristic Algorithms for Runway Scheduling

Science.gov (United States)

Malik, Waqar A.; Jung, Yoon C.

2016-01-01

This paper explores the Single Runway Scheduling (SRS) problem with arrivals, departures, and crossing aircraft on the airport surface. Constraints for wake vortex separations, departure area navigation separations and departure time window restrictions are explicitly considered. The main objective of this research is to develop exact and heuristic based algorithms that can be used in real-time decision support tools for Air Traffic Control Tower (ATCT) controllers. The paper provides a multi-objective dynamic programming (DP) based algorithm that finds the exact solution to the SRS problem, but may prove unusable for application in real-time environment due to large computation times for moderate sized problems. We next propose a second algorithm that uses heuristics to restrict the search space for the DP based algorithm. A third algorithm based on a combination of insertion and local search (ILS) heuristics is then presented. Simulation conducted for the east side of Dallas/Fort Worth International Airport allows comparison of the three proposed algorithms and indicates that the ILS algorithm performs favorably in its ability to find efficient solutions and its computation times.

76 FR 67018 - Notice to Manufacturers of Airport In-Pavement Stationary Runway Weather Information Systems

Science.gov (United States)

2011-10-28

...-Pavement Stationary Runway Weather Information Systems AGENCY: Federal Aviation Administration (FAA), U.S. DOT. ACTION: Notice to Manufacturers of In-Pavement Stationary Runway Weather Information Systems... Operations. This notice requests information from manufacturers of systems meeting the technical requirements...

Comprehensive and Highly Accurate Measurements of Crane Runways, Profiles and Fastenings.

Science.gov (United States)

Dennig, Dirk; Bureick, Johannes; Link, Johannes; Diener, Dmitri; Hesse, Christian; Neumann, Ingo

2017-05-13

The process of surveying crane runways has been continually refined due to the competitive situation, modern surveying instruments, additional sensors, accessories and evaluation procedures. Guidelines, such as the International Organization for Standardization (ISO) 12488-1, define target values that must be determined by survey. For a crane runway these are for example the span, the position and height of the rails. The process has to be objective and reproducible. However, common processes of surveying crane runways do not meet these requirements sufficiently. The evaluation of the protocols, ideally by an expert, requires many years of experience. Additionally, the recording of crucial parameters, e.g., the wear of the rail, or the condition of the rail fastening and rail joints, is not regulated and for that reason are often not considered during the measurement. To solve this deficit the Advanced Rail Track Inspection System (ARTIS) was developed. ARTIS is used to measure the 3D position of crane rails, the cross-section of the crane rails, joints and, for the first time, the (crane-rail) fastenings. The system consists of a monitoring vehicle and an external tracking sensor. It makes kinematic observations with the tracking sensor from outside the rail run, e.g., the floor of an overhead crane runway, possible. In this paper we present stages of the development process of ARTIS, new target values, calibration of sensors and results of a test measurement.

Computer-aided system for detecting runway incursions

Science.gov (United States)

Sridhar, Banavar; Chatterji, Gano B.

1994-07-01

A synthetic vision system for enhancing the pilot's ability to navigate and control the aircraft on the ground is described. The system uses the onboard airport database and images acquired by external sensors. Additional navigation information needed by the system is provided by the Inertial Navigation System and the Global Positioning System. The various functions of the system, such as image enhancement, map generation, obstacle detection, collision avoidance, guidance, etc., are identified. The available technologies, some of which were developed at NASA, that are applicable to the aircraft ground navigation problem are noted. Example images of a truck crossing the runway while the aircraft flies close to the runway centerline are described. These images are from a sequence of images acquired during one of the several flight experiments conducted by NASA to acquire data to be used for the development and verification of the synthetic vision concepts. These experiments provide a realistic database including video and infrared images, motion states from the Inertial Navigation System and the Global Positioning System, and camera parameters.

STEP: Self-supporting tailored k-space estimation for parallel imaging reconstruction.

Science.gov (United States)

Zhou, Zechen; Wang, Jinnan; Balu, Niranjan; Li, Rui; Yuan, Chun

2016-02-01

A new subspace-based iterative reconstruction method, termed Self-supporting Tailored k-space Estimation for Parallel imaging reconstruction (STEP), is presented and evaluated in comparison to the existing autocalibrating method SPIRiT and calibrationless method SAKE. In STEP, two tailored schemes including k-space partition and basis selection are proposed to promote spatially variant signal subspace and incorporated into a self-supporting structured low rank model to enforce properties of locality, sparsity, and rank deficiency, which can be formulated into a constrained optimization problem and solved by an iterative algorithm. Simulated and in vivo datasets were used to investigate the performance of STEP in terms of overall image quality and detail structure preservation. The advantage of STEP on image quality is demonstrated by retrospectively undersampled multichannel Cartesian data with various patterns. Compared with SPIRiT and SAKE, STEP can provide more accurate reconstruction images with less residual aliasing artifacts and reduced noise amplification in simulation and in vivo experiments. In addition, STEP has the capability of combining compressed sensing with arbitrary sampling trajectory. Using k-space partition and basis selection can further improve the performance of parallel imaging reconstruction with or without calibration signals. © 2015 Wiley Periodicals, Inc.

Nearly auto-parallel maps and conservation laws on curved spaces

International Nuclear Information System (INIS)

Vacaru, S.

1994-01-01

The theory of nearly auto-parallel maps (na-maps, generalization of conformal transforms) of Einstein-Cartan spaces is formulated. The transformation laws of geometrical objects and gravitational and matter field equations under superpositions of na-maps are considered. A special attention is paid to the very important problem of definition of conservation laws for gravitational fields. (Author)

Aircraft Configuration and Flight Crew Compliance with Procedures While Conducting Flight Deck Based Interval Management (FIM) Operations

Science.gov (United States)

Shay, Rick; Swieringa, Kurt A.; Baxley, Brian T.

2012-01-01

Flight deck based Interval Management (FIM) applications using ADS-B are being developed to improve both the safety and capacity of the National Airspace System (NAS). FIM is expected to improve the safety and efficiency of the NAS by giving pilots the technology and procedures to precisely achieve an interval behind the preceding aircraft by a specific point. Concurrently but independently, Optimized Profile Descents (OPD) are being developed to help reduce fuel consumption and noise, however, the range of speeds available when flying an OPD results in a decrease in the delivery precision of aircraft to the runway. This requires the addition of a spacing buffer between aircraft, reducing system throughput. FIM addresses this problem by providing pilots with speed guidance to achieve a precise interval behind another aircraft, even while flying optimized descents. The Interval Management with Spacing to Parallel Dependent Runways (IMSPiDR) human-in-the-loop experiment employed 24 commercial pilots to explore the use of FIM equipment to conduct spacing operations behind two aircraft arriving to parallel runways, while flying an OPD during high-density operations. This paper describes the impact of variations in pilot operations; in particular configuring the aircraft, their compliance with FIM operating procedures, and their response to changes of the FIM speed. An example of the displayed FIM speeds used incorrectly by a pilot is also discussed. Finally, this paper examines the relationship between achieving airline operational goals for individual aircraft and the need for ATC to deliver aircraft to the runway with greater precision. The results show that aircraft can fly an OPD and conduct FIM operations to dependent parallel runways, enabling operational goals to be achieved efficiently while maintaining system throughput.

Runway Incursion Prevention System: Demonstration and Testing at the Dallas/Fort Worth International Airport

Science.gov (United States)

Jones, Denise R.; Quach, Cuong C.; Young, Steven D.

2007-01-01

A Runway Incursion Prevention System (RIPS) was tested at the Dallas-Ft. Worth International Airport (DFW) in October 2000. The system integrated airborne and ground components to provide both pilots and controllers with enhanced situational awareness, supplemental guidance cues, a real-time display of traffic information, and warning of runway incursions in order to prevent runway incidents while also improving operational capability. A series of test runs was conducted using NASA s Boeing 757 research aircraft and a test van equipped to emulate an incurring aircraft. The system was also demonstrated to over 100 visitors from the aviation community. This paper gives an overview of the RIPS, DFW flight test activities, and quantitative and qualitative results of the testing.

A Self Consistent Multiprocessor Space Charge Algorithm that is Almost Embarrassingly Parallel

International Nuclear Information System (INIS)

Nissen, Edward; Erdelyi, B.; Manikonda, S.L.

2012-01-01

We present a space charge code that is self consistent, massively parallelizeable, and requires very little communication between computer nodes; making the calculation almost embarrassingly parallel. This method is implemented in the code COSY Infinity where the differential algebras used in this code are important to the algorithm's proper functioning. The method works by calculating the self consistent space charge distribution using the statistical moments of the test particles, and converting them into polynomial series coefficients. These coefficients are combined with differential algebraic integrals to form the potential, and electric fields. The result is a map which contains the effects of space charge. This method allows for massive parallelization since its statistics based solver doesn't require any binning of particles, and only requires a vector containing the partial sums of the statistical moments for the different nodes to be passed. All other calculations are done independently. The resulting maps can be used to analyze the system using normal form analysis, as well as advance particles in numbers and at speeds that were previously impossible.

Domain Specific Language for Geant4 Parallelization for Space-based Applications, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — A major limiting factor in HPC growth is the requirement to parallelize codes to leverage emerging architectures, especially as single core performance has plateaued...

Models for estimating runway landing capacity with Microwave Landing System (MLS)

Science.gov (United States)

Tosic, V.; Horonjeff, R.

1975-01-01

A model is developed which is capable of computing the ultimate landing runway capacity, under ILS and MLS conditions, when aircraft population characteristics and air traffic control separation rules are given. This model can be applied in situations when only a horizontal separation between aircraft approaching a runway is allowed, as well as when both vertical and horizontal separations are possible. It is assumed that the system is free of errors, that is that aircraft arrive at specified points along the prescribed flight path precisely when the controllers intend for them to arrive at these points. Although in the real world there is no such thing as an error-free system, the assumption is adequate for a qualitative comparison of MLS with ILS. Results suggest that an increase in runway landing capacity, caused by introducing the MLS multiple approach paths, is to be expected only when an aircraft population consists of aircraft with significantly differing approach speeds and particularly in situations when vertical separation can be applied. Vertical separation can only be applied if one of the types of aircraft in the mix has a very steep descent angle.

The simplified spherical harmonics (SP{sub L}) methodology with space and moment decomposition in parallel environments

Energy Technology Data Exchange (ETDEWEB)

Gianluca, Longoni; Alireza, Haghighat [Florida University, Nuclear and Radiological Engineering Department, Gainesville, FL (United States)

2003-07-01

In recent years, the SP{sub L} (simplified spherical harmonics) equations have received renewed interest for the simulation of nuclear systems. We have derived the SP{sub L} equations starting from the even-parity form of the S{sub N} equations. The SP{sub L} equations form a system of (L+1)/2 second order partial differential equations that can be solved with standard iterative techniques such as the Conjugate Gradient (CG). We discretized the SP{sub L} equations with the finite-volume approach in a 3-D Cartesian space. We developed a new 3-D general code, Pensp{sub L} (Parallel Environment Neutral-particle SP{sub L}). Pensp{sub L} solves both fixed source and criticality eigenvalue problems. In order to optimize the memory management, we implemented a Compressed Diagonal Storage (CDS) to store the SP{sub L} matrices. Pensp{sub L} includes parallel algorithms for space and moment domain decomposition. The computational load is distributed on different processors, using a mapping function, which maps the 3-D Cartesian space and moments onto processors. The code is written in Fortran 90 using the Message Passing Interface (MPI) libraries for the parallel implementation of the algorithm. The code has been tested on the Pcpen cluster and the parallel performance has been assessed in terms of speed-up and parallel efficiency. (author)

An effective approach to reducing strategy space for maintenance optimisation of multistate series–parallel systems

International Nuclear Information System (INIS)

Zhou, Yifan; Lin, Tian Ran; Sun, Yong; Bian, Yangqing; Ma, Lin

2015-01-01

Maintenance optimisation of series–parallel systems is a research topic of practical significance. Nevertheless, a cost-effective maintenance strategy is difficult to obtain due to the large strategy space for maintenance optimisation of such systems. The heuristic algorithm is often employed to deal with this problem. However, the solution obtained by the heuristic algorithm is not always the global optimum and the algorithm itself can be very time consuming. An alternative method based on linear programming is thus developed in this paper to overcome such difficulties by reducing strategy space of maintenance optimisation. A theoretical proof is provided in the paper to verify that the proposed method is at least as effective as the existing methods for strategy space reduction. Numerical examples for maintenance optimisation of series–parallel systems having multistate components and considering both economic dependence among components and multiple-level imperfect maintenance are also presented. The simulation results confirm that the proposed method is more effective than the existing methods in removing inappropriate maintenance strategies of multistate series–parallel systems. - Highlights: • A new method using linear programming is developed to reduce the strategy space. • The effectiveness of the new method for strategy reduction is theoretically proved. • Imperfect maintenance and economic dependence are considered during optimisation

Application of Artificial Neural Network to Predict the use of Runway at Juanda International Airport

Science.gov (United States)

Putra, J. C. P.; Safrilah

2017-06-01

Artificial neural network approaches are useful to solve many complicated problems. It solves a number of problems in various areas such as engineering, medicine, business, manufacturing, etc. This paper presents an application of artificial neural network to predict a runway capacity at Juanda International Airport. An artificial neural network model of backpropagation and multi-layer perceptron is adopted to this research to learning process of runway capacity at Juanda International Airport. The results indicate that the training data is successfully recognizing the certain pattern of runway use at Juanda International Airport. Whereas, testing data indicate vice versa. Finally, it can be concluded that the approach of uniformity data and network architecture is the critical part to determine the accuracy of prediction results.

Aircraft performance in slippery runway conditions : a simulation study of the accuracy and limitations of real-time runway friction estimation based on airplane onboard data.

Science.gov (United States)

2015-04-01

Runway overrun accidents occurring during landings in slippery conditions continue to occur frequently worldwide. After a : number of specific landing overrun accidents in the U.S., the National Transportation Safety Board (NTSB) issued a safety : re...

Functional Analysis for an Integrated Capability of Arrival/Departure/Surface Management with Tactical Runway Management

Science.gov (United States)

Phojanamongkolkij, Nipa; Okuniek, Nikolai; Lohr, Gary W.; Schaper, Meilin; Christoffels, Lothar; Latorella, Kara A.

2014-01-01

The runway is a critical resource of any air transport system. It is used for arrivals, departures, and for taxiing aircraft and is universally acknowledged as a constraining factor to capacity for both surface and airspace operations. It follows that investigation of the effective use of runways, both in terms of selection and assignment as well as the timing and sequencing of the traffic is paramount to the efficient traffic flows. Both the German Aerospace Center (DLR) and NASA have developed concepts and tools to improve atomic aspects of coordinated arrival/departure/surface management operations and runway configuration management. In December 2012, NASA entered into a Collaborative Agreement with DLR. Four collaborative work areas were identified, one of which is called "Runway Management." As part of collaborative research in the "Runway Management" area, which is conducted with the DLR Institute of Flight Guidance, located in Braunschweig, the goal is to develop an integrated system comprised of the three DLR tools - arrival, departure, and surface management (collectively referred to as A/D/S-MAN) - and NASA's tactical runway configuration management (TRCM) tool. To achieve this goal, it is critical to prepare a concept of operations (ConOps) detailing how the NASA runway management and DLR arrival, departure, and surface management tools will function together to the benefit of each. To assist with the preparation of the ConOps, the integrated NASA and DLR tools are assessed through a functional analysis method described in this report. The report first provides the highlevel operational environments for air traffic management (ATM) in Germany and in the U.S., and the descriptions of the DLR's A/D/S-MAN and NASA's TRCM tools at the level of details necessary to compliment the purpose of the study. Functional analyses of each tool and a completed functional analysis of an integrated system design are presented next in the report. Future efforts to fully

Fast Time and Space Parallel Algorithms for Solution of Parabolic Partial Differential Equations

Science.gov (United States)

Fijany, Amir

1993-01-01

In this paper, fast time- and Space -Parallel agorithms for solution of linear parabolic PDEs are developed. It is shown that the seemingly strictly serial iterations of the time-stepping procedure for solution of the problem can be completed decoupled.

Design and implementation of a novel modal space active force control concept for spatial multi-DOF parallel robotic manipulators actuated by electrical actuators.

Science.gov (United States)

Yang, Chifu; Zhao, Jinsong; Li, Liyi; Agrawal, Sunil K

2018-01-01

Robotic spine brace based on parallel-actuated robotic system is a new device for treatment and sensing of scoliosis, however, the strong dynamic coupling and anisotropy problem of parallel manipulators result in accuracy loss of rehabilitation force control, including big error in direction and value of force. A novel active force control strategy named modal space force control is proposed to solve these problems. Considering the electrical driven system and contact environment, the mathematical model of spatial parallel manipulator is built. The strong dynamic coupling problem in force field is described via experiments as well as the anisotropy problem of work space of parallel manipulators. The effects of dynamic coupling on control design and performances are discussed, and the influences of anisotropy on accuracy are also addressed. With mass/inertia matrix and stiffness matrix of parallel manipulators, a modal matrix can be calculated by using eigenvalue decomposition. Making use of the orthogonality of modal matrix with mass matrix of parallel manipulators, the strong coupled dynamic equations expressed in work space or joint space of parallel manipulator may be transformed into decoupled equations formulated in modal space. According to this property, each force control channel is independent of others in the modal space, thus we proposed modal space force control concept which means the force controller is designed in modal space. A modal space active force control is designed and implemented with only a simple PID controller employed as exampled control method to show the differences, uniqueness, and benefits of modal space force control. Simulation and experimental results show that the proposed modal space force control concept can effectively overcome the effects of the strong dynamic coupling and anisotropy problem in the physical space, and modal space force control is thus a very useful control framework, which is better than the current joint

Parallel Finite Element Particle-In-Cell Code for Simulations of Space-charge Dominated Beam-Cavity Interactions

International Nuclear Information System (INIS)

Candel, A.; Kabel, A.; Ko, K.; Lee, L.; Li, Z.; Limborg, C.; Ng, C.; Prudencio, E.; Schussman, G.; Uplenchwar, R.

2007-01-01

Over the past years, SLAC's Advanced Computations Department (ACD) has developed the parallel finite element (FE) particle-in-cell code Pic3P (Pic2P) for simulations of beam-cavity interactions dominated by space-charge effects. As opposed to standard space-charge dominated beam transport codes, which are based on the electrostatic approximation, Pic3P (Pic2P) includes space-charge, retardation and boundary effects as it self-consistently solves the complete set of Maxwell-Lorentz equations using higher-order FE methods on conformal meshes. Use of efficient, large-scale parallel processing allows for the modeling of photoinjectors with unprecedented accuracy, aiding the design and operation of the next-generation of accelerator facilities. Applications to the Linac Coherent Light Source (LCLS) RF gun are presented

A massively-parallel electronic-structure calculations based on real-space density functional theory

International Nuclear Information System (INIS)

Iwata, Jun-Ichi; Takahashi, Daisuke; Oshiyama, Atsushi; Boku, Taisuke; Shiraishi, Kenji; Okada, Susumu; Yabana, Kazuhiro

2010-01-01

Based on the real-space finite-difference method, we have developed a first-principles density functional program that efficiently performs large-scale calculations on massively-parallel computers. In addition to efficient parallel implementation, we also implemented several computational improvements, substantially reducing the computational costs of O(N 3 ) operations such as the Gram-Schmidt procedure and subspace diagonalization. Using the program on a massively-parallel computer cluster with a theoretical peak performance of several TFLOPS, we perform electronic-structure calculations for a system consisting of over 10,000 Si atoms, and obtain a self-consistent electronic-structure in a few hundred hours. We analyze in detail the costs of the program in terms of computation and of inter-node communications to clarify the efficiency, the applicability, and the possibility for further improvements.

A Screen Space GPGPU Surface LIC Algorithm for Distributed Memory Data Parallel Sort Last Rendering Infrastructures

Energy Technology Data Exchange (ETDEWEB)

Loring, Burlen; Karimabadi, Homa; Rortershteyn, Vadim

2014-07-01

The surface line integral convolution(LIC) visualization technique produces dense visualization of vector fields on arbitrary surfaces. We present a screen space surface LIC algorithm for use in distributed memory data parallel sort last rendering infrastructures. The motivations for our work are to support analysis of datasets that are too large to fit in the main memory of a single computer and compatibility with prevalent parallel scientific visualization tools such as ParaView and VisIt. By working in screen space using OpenGL we can leverage the computational power of GPUs when they are available and run without them when they are not. We address efficiency and performance issues that arise from the transformation of data from physical to screen space by selecting an alternate screen space domain decomposition. We analyze the algorithm's scaling behavior with and without GPUs on two high performance computing systems using data from turbulent plasma simulations.

Parallelization of the Physical-Space Statistical Analysis System (PSAS)

Science.gov (United States)

Larson, J. W.; Guo, J.; Lyster, P. M.

1999-01-01

Atmospheric data assimilation is a method of combining observations with model forecasts to produce a more accurate description of the atmosphere than the observations or forecast alone can provide. Data assimilation plays an increasingly important role in the study of climate and atmospheric chemistry. The NASA Data Assimilation Office (DAO) has developed the Goddard Earth Observing System Data Assimilation System (GEOS DAS) to create assimilated datasets. The core computational components of the GEOS DAS include the GEOS General Circulation Model (GCM) and the Physical-space Statistical Analysis System (PSAS). The need for timely validation of scientific enhancements to the data assimilation system poses computational demands that are best met by distributed parallel software. PSAS is implemented in Fortran 90 using object-based design principles. The analysis portions of the code solve two equations. The first of these is the "innovation" equation, which is solved on the unstructured observation grid using a preconditioned conjugate gradient (CG) method. The "analysis" equation is a transformation from the observation grid back to a structured grid, and is solved by a direct matrix-vector multiplication. Use of a factored-operator formulation reduces the computational complexity of both the CG solver and the matrix-vector multiplication, rendering the matrix-vector multiplications as a successive product of operators on a vector. Sparsity is introduced to these operators by partitioning the observations using an icosahedral decomposition scheme. PSAS builds a large (approx. 128MB) run-time database of parameters used in the calculation of these operators. Implementing a message passing parallel computing paradigm into an existing yet developing computational system as complex as PSAS is nontrivial. One of the technical challenges is balancing the requirements for computational reproducibility with the need for high performance. The problem of computational

Evaluasi Kekuatan Perkerasan Sisi Udara (Runway,Taxiway,Apron Bandara Juanda Dengan Metode Perbandingan ACN-PCN

Directory of Open Access Journals (Sweden)

R. Haryo Triharso Seno

2015-03-01

Full Text Available Fasilitas sisi udara merupakan fasilitas pergerakan pesawat. Fasilitas ini harus memenuhi kekuatan struktur untuk melayani pergerakan pesawat-pesawat yang beroperasi sesuai dengan perencanaan. Tujuan dari penyusunan makalah ini adalah untuk menganalisis apakah perkerasan fasilitas sisi udara di Bandar Udara Juanda saat ini sudah memenuhi batas PCN yang dipersyaratkan atau belum. Analisis dilakukan dengan cara mengevaluasi kekuatan perkerasan runway, taxiway, dan apron eksisting menggunakan metode perbandingan PCN–ACN yang didapat dari pabrik pembuat pesawat, perhitungan dengan software COMFAA dan perhitungan dari Canadian Department of Transportation. Data yang digunakan adalah data pergerakan pesawat termasuk jumlah pergerakan tahunan dan tipe pesawat. Data kekuatan perkerasan sisi udara diperlukan untuk proses analisis. Hasil dari evaluasi menunjukkan B773 memiliki nilai ACN yang melebihi nilai PCN sebesar 50% untuk apron dan 25% untuk runway/taxiway. Besar kelebihan nilai ACN ini tidak mempengaruhi kekuatan struktural karena frekuensi pergerakan yang hanya 45 pergerakan per tahun. Dampak lain adalah pada fungsional perkerasan yang menunjukkan berkurangnya kekesatan runway dari hasil sand patch test.

Long term performance of the reef runway at Honolulu International Airport

CSIR Research Space (South Africa)

Magoon, OT

2007-07-01

Full Text Available Completed in 1977, the Reef Runway embankment at Honolulu International Airport was created by placing and compacting millions of cubic meters of dredged coral fill material over an existing coral reef. The wave protection structure on the deeper...

Runway Detection From Map, Video and Aircraft Navigational Data

Science.gov (United States)

2016-03-01

3 Figure 4. Pinhole Camera Model to Project 3D Coordinates onto 2D...xii THIS PAGE INTENTIONALLY LEFT BLANK xiii LIST OF ACRONYMS AND ABBREVIATIONS 2D Two-dimensional 3D Three-dimensional HFOV Horizontal field of...algorithm [2], which selects runway-useful features, such as image intensity and gradient or Zernike Moments, and extracts them on a set of 57

Phase space simulation of collisionless stellar systems on the massively parallel processor

International Nuclear Information System (INIS)

White, R.L.

1987-01-01

A numerical technique for solving the collisionless Boltzmann equation describing the time evolution of a self gravitating fluid in phase space was implemented on the Massively Parallel Processor (MPP). The code performs calculations for a two dimensional phase space grid (with one space and one velocity dimension). Some results from calculations are presented. The execution speed of the code is comparable to the speed of a single processor of a Cray-XMP. Advantages and disadvantages of the MPP architecture for this type of problem are discussed. The nearest neighbor connectivity of the MPP array does not pose a significant obstacle. Future MPP-like machines should have much more local memory and easier access to staging memory and disks in order to be effective for this type of problem

Algorithms for a parallel implementation of Hidden Markov Models with a small state space

DEFF Research Database (Denmark)

Nielsen, Jesper; Sand, Andreas

2011-01-01

Two of the most important algorithms for Hidden Markov Models are the forward and the Viterbi algorithms. We show how formulating these using linear algebra naturally lends itself to parallelization. Although the obtained algorithms are slow for Hidden Markov Models with large state spaces...

46 CFR 116.940 - Guards in vehicle spaces.

Science.gov (United States)

2010-10-01

... 46 Shipping 4 2010-10-01 2010-10-01 false Guards in vehicle spaces. 116.940 Section 116.940... ARRANGEMENT Rails and Guards § 116.940 Guards in vehicle spaces. On a vessel authorized to carry one or more vehicles, suitable chains, cables, or other barriers must be installed at the end of each vehicle runway...

An overview of the joint FAA/NASA aircraft/ground runway friction program

Science.gov (United States)

Yager, Thomas J.

1989-01-01

There is a need for information on runways which may become slippery due to various forms and types of contaminants. Experience has shown that since the beginning of all weather aircraft operations, there have been landing and aborted takeoff incidents and/or accidents each year where aircraft have either run off the end or veered off the shoulder of low friction runways. NASA Langley's Landing and Impact Dynamics Branch is involved in several research programs directed towards obtaining a better understanding of how different tire properties interact with varying pavement surface characteristics to produce acceptable performance for aircraft ground handling requirements. One such effort, which was jointly supported by not only NASA and the FAA but by several aviation industry groups including the Flight Safety Foundation, is described.

Large parallel volumes of finite and compact sets in d-dimensional Euclidean space

DEFF Research Database (Denmark)

Kampf, Jürgen; Kiderlen, Markus

The r-parallel volume V (Cr) of a compact subset C in d-dimensional Euclidean space is the volume of the set Cr of all points of Euclidean distance at most r > 0 from C. According to Steiner’s formula, V (Cr) is a polynomial in r when C is convex. For finite sets C satisfying a certain geometric...

Scattering by multiple parallel radially stratified infinite cylinders buried in a lossy half space.

Science.gov (United States)

Lee, Siu-Chun

2013-07-01

The theoretical solution for scattering by an arbitrary configuration of closely spaced parallel infinite cylinders buried in a lossy half space is presented in this paper. The refractive index and permeability of the half space and cylinders are complex in general. Each cylinder is radially stratified with a distinct complex refractive index and permeability. The incident radiation is an arbitrarily polarized plane wave propagating in the plane normal to the axes of the cylinders. Analytic solutions are derived for the electric and magnetic fields and the Poynting vector of backscattered radiation emerging from the half space. Numerical examples are presented to illustrate the application of the scattering solution to calculate backscattering from a lossy half space containing multiple homogeneous and radially stratified cylinders at various depths and different angles of incidence.

Experimental Investigation of Concrete Runway Snow Melting Utilizing Heat Pipe Technology

Directory of Open Access Journals (Sweden)

Fengchen Chen

2018-01-01

Full Text Available A full scale snow melting system with heat pipe technology is built in this work, which avoids the negative effects on concrete structure and environment caused by traditional deicing chemicals. The snow melting, ice-freezing performance and temperature distribution characteristics of heat pipe concrete runway were discussed by the outdoor experiments. The results show that the temperature of the concrete pavement is greatly improved with the heat pipe system. The environment temperature and embedded depth of heat pipe play a dominant role among the decision variables of the snow melting system. Heat pipe snow melting pavement melts the snow completely and avoids freezing at any time when the environment temperature is below freezing point, which is secure enough for planes take-off and landing. Besides, the exportation and recovery of geothermal energy indicate that this system can run for a long time. This paper will be useful for the design and application of the heat pipe used in the runway snow melting.

Experimental Investigation of Concrete Runway Snow Melting Utilizing Heat Pipe Technology.

Science.gov (United States)

Chen, Fengchen; Su, Xin; Ye, Qing; Fu, Jianfeng

2018-01-01

A full scale snow melting system with heat pipe technology is built in this work, which avoids the negative effects on concrete structure and environment caused by traditional deicing chemicals. The snow melting, ice-freezing performance and temperature distribution characteristics of heat pipe concrete runway were discussed by the outdoor experiments. The results show that the temperature of the concrete pavement is greatly improved with the heat pipe system. The environment temperature and embedded depth of heat pipe play a dominant role among the decision variables of the snow melting system. Heat pipe snow melting pavement melts the snow completely and avoids freezing at any time when the environment temperature is below freezing point, which is secure enough for planes take-off and landing. Besides, the exportation and recovery of geothermal energy indicate that this system can run for a long time. This paper will be useful for the design and application of the heat pipe used in the runway snow melting.

Use of Parallel Micro-Platform for the Simulation the Space Exploration

Science.gov (United States)

Velasco Herrera, Victor Manuel; Velasco Herrera, Graciela; Rosano, Felipe Lara; Rodriguez Lozano, Salvador; Lucero Roldan Serrato, Karen

The purpose of this work is to create a parallel micro-platform, that simulates the virtual movements of a space exploration in 3D. One of the innovations presented in this design consists of the application of a lever mechanism for the transmission of the movement. The development of such a robot is a challenging task very different of the industrial manipulators due to a totally different target system of requirements. This work presents the study and simulation, aided by computer, of the movement of this parallel manipulator. The development of this model has been developed using the platform of computer aided design Unigraphics, in which it was done the geometric modeled of each one of the components and end assembly (CAD), the generation of files for the computer aided manufacture (CAM) of each one of the pieces and the kinematics simulation of the system evaluating different driving schemes. We used the toolbox (MATLAB) of aerospace and create an adaptive control module to simulate the system.

Laboratory and On-Site Tests for Rapid Runway Repair

Directory of Open Access Journals (Sweden)

Federico Leonelli

2017-11-01

Full Text Available The attention to rapid pavement repair has grown fast in recent decades: this topic is strategic for the airport management process for civil purposes and peacekeeping missions. This work presents the results of laboratory and on-site tests for rapid runway repair, in order to analyse and compare technical and mechanical performances of 12 different materials currently used in airport. The study focuses on site repairs, a technique adopted most frequently than repairs with modular elements. After describing mechanical and physical properties of the examined materials (2 bituminous emulsions, 5 cement mortars, 4 cold bituminous mixtures and 1 expanding resin, the study presents the results of carried out mechanical tests. The results demonstrate that the best performing material is a one-component fast setting and hardening cement mortar with graded aggregates. This material allows the runway reopening 6 h after the work. A cold bituminous mixture (bicomponent premixed cold asphalt with water as catalyst and the ordinary cement concrete allow the reopening to traffic after 18 h, but both ensure a lower service life (1000 coverages than the cement mortar (10,000 coverages. The obtained results include important information both laboratory level and field, and they could be used by airport management bodies and road agencies when scheduling and evaluating pavement repairs.

NASA diagonal-braked test vehicle evaluation of traction characteristics of grooved and ungrooved runway surfaces at Miami International Airport, Miami, Florida, 8-9 May 1973

Science.gov (United States)

Horne, W. B.

1977-01-01

Two runways were evaluated under artificially wetted conditions with the NASA diagonal-braked vehicle (DBV). Results of the evaluation which included a pavement drainage analysis, a pavement skid resistance analysis, and a DBV wet/dry stopping distance ratio analysis indicated that the ungrooved runway surfaces had poor water drainage characteristics and poor skid resistance under wet conditions at high speeds especially in rubbercoated areas of the runways. Grooving runways to a transverse 1-1/4 x 1/4 x 1/4 inch pattern greatly improved both the water drainage and pavement skid resistance capability of these asphaltic concrete surfaces.

Animated computer graphics models of space and earth sciences data generated via the massively parallel processor

Science.gov (United States)

Treinish, Lloyd A.; Gough, Michael L.; Wildenhain, W. David

1987-01-01

The capability was developed of rapidly producing visual representations of large, complex, multi-dimensional space and earth sciences data sets via the implementation of computer graphics modeling techniques on the Massively Parallel Processor (MPP) by employing techniques recently developed for typically non-scientific applications. Such capabilities can provide a new and valuable tool for the understanding of complex scientific data, and a new application of parallel computing via the MPP. A prototype system with such capabilities was developed and integrated into the National Space Science Data Center's (NSSDC) Pilot Climate Data System (PCDS) data-independent environment for computer graphics data display to provide easy access to users. While developing these capabilities, several problems had to be solved independently of the actual use of the MPP, all of which are outlined.

A worker attaches covers for the nose pitot boom before removing the unpiloted X-40 from the runway

Science.gov (United States)

2001-01-01

A worker attaches covers for the nose pitot boom before removing the unpiloted X-40 from the runway at Edwards Air Force Base, California, following its successful free-flight on March 14, 2001. The unpiloted X-40 is a risk-reduction vehicle for the X-37, which is intended to be a reusable space vehicle. NASA's Marshall Space Flight Center in Huntsville, Ala, manages the X-37 project. At Dryden, the X-40A underwent a series of ground and air tests to reduce possible risks to the larger X-37, including drop tests from a helicopter to check guidance and navigation systems planned for use in the X-37. The X-37 is designed to demonstrate technologies in the orbital and reentry environments for next-generation reusable launch vehicles that will increase both safety and reliability, while reducing launch costs from $10,000 per pound to $1,000 per pound. The X-37, carried into orbit by the Space Shuttle, is planned to fly two orbital missions to test reusable launch vehicle technologies.

Uncertainty Analysis for the Evaluation of a Passive Runway Arresting System

Science.gov (United States)

Deloach, Richard; Marlowe, Jill M.; Yager, Thomas J.

2009-01-01

This paper considers the stopping distance of an aircraft involved in a runway overrun incident when the runway has been provided with an extension comprised of a material engineered to induce high levels of rolling friction and drag. A formula for stopping distance is derived that is shown to be the product of a known formula for the case of friction without drag, and a dimensionless constant between 0 and 1 that quantifies the further reduction in stopping distance when drag is introduced. This additional quantity, identified as the Drag Reduction Factor, D, is shown to depend on the ratio of drag force to friction force experienced by the aircraft as it enters the overrun area. The specific functional form of D is shown to depend on how drag varies with speed. A detailed uncertainty analysis is presented which reveals how the uncertainty in estimates of stopping distance are influenced by experimental error in the force measurements that are acquired in a typical evaluation experiment conducted to assess candidate overrun materials.

Exploiting Stabilizers and Parallelism in State Space Generation with the Symmetry Method

DEFF Research Database (Denmark)

Lorentsen, Louise; Kristensen, Lars Michael

2001-01-01

The symmetry method is a main reduction paradigm for alleviating the state explosion problem. For large symmetry groups deciding whether two states are symmetric becomes time expensive due to the apparent high time complexity of the orbit problem. The contribution of this paper is to alleviate th...... the negative impact of the orbit problem by the specification of canonical representatives for equivalence classes of states in Coloured Petri Nets, and by giving algorithms exploiting stabilizers and parallelism for computing the condensed state space....

Space-charge-dominated beam dynamics simulations using the massively parallel processors (MPPs) of the Cray T3D

International Nuclear Information System (INIS)

Liu, H.

1996-01-01

Computer simulations using the multi-particle code PARMELA with a three-dimensional point-by-point space charge algorithm have turned out to be very helpful in supporting injector commissioning and operations at Thomas Jefferson National Accelerator Facility (Jefferson Lab, formerly called CEBAF). However, this algorithm, which defines a typical N 2 problem in CPU time scaling, is very time-consuming when N, the number of macro-particles, is large. Therefore, it is attractive to use massively parallel processors (MPPs) to speed up the simulations. Motivated by this, the authors modified the space charge subroutine for using the MPPs of the Cray T3D. The techniques used to parallelize and optimize the code on the T3D are discussed in this paper. The performance of the code on the T3D is examined in comparison with a Parallel Vector Processing supercomputer of the Cray C90 and an HP 735/15 high-end workstation

Los Angeles International Airport Runway Incursion Studies: Phase III--Center-Taxiway Simulation

Science.gov (United States)

Madson, Michael D.

2004-01-01

Phase III of the Los Angeles International Airport Runway Incursion Studies was conducted, under an agreement with HNTB Corporation, at the NASA Ames FutureFlight Central (FFC) facility in June 2003. The objective of the study was the evaluation of a new center-taxiway concept at LAX. This study is an extension of the Phase I and Phase II studies previously conducted at FFC. This report presents results from Phase III of the study, in which a center-taxiway concept between runways 25L and 25R was simulated and evaluated. Phase III data were compared objectively against the Baseline data. Subjective evaluations by participating LAX controllers were obtained with regard to workload, efficiency, and safety criteria. To facilitate a valid comparison between Baseline and Phase III data, the same scenarios were used for Phase III that were tested during Phases I and II. This required briefing participating controllers on differences in airport and airline operations between 2001 and today.

Parallel algorithms for mapping pipelined and parallel computations

Science.gov (United States)

Nicol, David M.

1988-01-01

Many computational problems in image processing, signal processing, and scientific computing are naturally structured for either pipelined or parallel computation. When mapping such problems onto a parallel architecture it is often necessary to aggregate an obvious problem decomposition. Even in this context the general mapping problem is known to be computationally intractable, but recent advances have been made in identifying classes of problems and architectures for which optimal solutions can be found in polynomial time. Among these, the mapping of pipelined or parallel computations onto linear array, shared memory, and host-satellite systems figures prominently. This paper extends that work first by showing how to improve existing serial mapping algorithms. These improvements have significantly lower time and space complexities: in one case a published O(nm sup 3) time algorithm for mapping m modules onto n processors is reduced to an O(nm log m) time complexity, and its space requirements reduced from O(nm sup 2) to O(m). Run time complexity is further reduced with parallel mapping algorithms based on these improvements, which run on the architecture for which they create the mappings.

A Robust Vision-based Runway Detection and Tracking Algorithm for Automatic UAV Landing

KAUST Repository

Abu Jbara, Khaled F.

2015-01-01

and attitude angle estimates to allow a more robust tracking of the runway under turbulence. We illustrate the performance of the proposed lane detection and tracking scheme on various experimental UAV flights conducted by the Saudi Aerospace Research Center

Streaming for Functional Data-Parallel Languages

DEFF Research Database (Denmark)

Madsen, Frederik Meisner

In this thesis, we investigate streaming as a general solution to the space inefficiency commonly found in functional data-parallel programming languages. The data-parallel paradigm maps well to parallel SIMD-style hardware. However, the traditional fully materializing execution strategy...... by extending two existing data-parallel languages: NESL and Accelerate. In the extensions we map bulk operations to data-parallel streams that can evaluate fully sequential, fully parallel or anything in between. By a dataflow, piecewise parallel execution strategy, the runtime system can adjust to any target...... flattening necessitates all sub-computations to materialize at the same time. For example, naive n by n matrix multiplication requires n^3 space in NESL because the algorithm contains n^3 independent scalar multiplications. For large values of n, this is completely unacceptable. We address the problem...

Large-scale parallel configuration interaction. I. Nonrelativisticand scalar-relativistic general active space implementationwith application to (Rb-Ba)+

DEFF Research Database (Denmark)

Knecht, Stefan; Jensen, Hans Jørgen Aagaard; Fleig, Timo

2008-01-01

We present a parallel implementation of a string-driven general active space configuration interaction program for nonrelativistic and scalar-relativistic electronic-structure calculations. The code has been modularly incorporated in the DIRAC quantum chemistry program package. The implementation...

An Implementation and Parallelization of the Scale Space Meshing Algorithm

Directory of Open Access Journals (Sweden)

Julie Digne

2015-11-01

Full Text Available Creating an interpolating mesh from an unorganized set of oriented points is a difficult problemwhich is often overlooked. Most methods focus indeed on building a watertight smoothed meshby defining some function whose zero level set is the surface of the object. However in some casesit is crucial to build a mesh that interpolates the points and does not fill the acquisition holes:either because the data are sparse and trying to fill the holes would create spurious artifactsor because the goal is to explore visually the data exactly as they were acquired without anysmoothing process. In this paper we detail a parallel implementation of the Scale-Space Meshingalgorithm, which builds on the scale-space framework for reconstructing a high precision meshfrom an input oriented point set. This algorithm first smoothes the point set, producing asingularity free shape. It then uses a standard mesh reconstruction technique, the Ball PivotingAlgorithm, to build a mesh from the smoothed point set. The final step consists in back-projecting the mesh built on the smoothed positions onto the original point set. The result ofthis process is an interpolating, hole-preserving surface mesh reconstruction.

Fast MR image reconstruction for partially parallel imaging with arbitrary k-space trajectories.

Science.gov (United States)

Ye, Xiaojing; Chen, Yunmei; Lin, Wei; Huang, Feng

2011-03-01

Both acquisition and reconstruction speed are crucial for magnetic resonance (MR) imaging in clinical applications. In this paper, we present a fast reconstruction algorithm for SENSE in partially parallel MR imaging with arbitrary k-space trajectories. The proposed method is a combination of variable splitting, the classical penalty technique and the optimal gradient method. Variable splitting and the penalty technique reformulate the SENSE model with sparsity regularization as an unconstrained minimization problem, which can be solved by alternating two simple minimizations: One is the total variation and wavelet based denoising that can be quickly solved by several recent numerical methods, whereas the other one involves a linear inversion which is solved by the optimal first order gradient method in our algorithm to significantly improve the performance. Comparisons with several recent parallel imaging algorithms indicate that the proposed method significantly improves the computation efficiency and achieves state-of-the-art reconstruction quality.

Enhanced 2D-DOA Estimation for Large Spacing Three-Parallel Uniform Linear Arrays

Directory of Open Access Journals (Sweden)

Dong Zhang

2018-01-01

Full Text Available An enhanced two-dimensional direction of arrival (2D-DOA estimation algorithm for large spacing three-parallel uniform linear arrays (ULAs is proposed in this paper. Firstly, we use the propagator method (PM to get the highly accurate but ambiguous estimation of directional cosine. Then, we use the relationship between the directional cosine to eliminate the ambiguity. This algorithm not only can make use of the elements of the three-parallel ULAs but also can utilize the connection between directional cosine to improve the estimation accuracy. Besides, it has satisfied estimation performance when the elevation angle is between 70° and 90° and it can automatically pair the estimated azimuth and elevation angles. Furthermore, it has low complexity without using any eigen value decomposition (EVD or singular value decompostion (SVD to the covariance matrix. Simulation results demonstrate the effectiveness of our proposed algorithm.

Behavior of aircraft antiskid braking systems on dry and wet runway surfaces - A velocity-rate-controlled, pressure-bias-modulated system

Science.gov (United States)

Stubbs, S. M.; Tanner, J. A.

1976-01-01

During maximum braking the average ratio of drag-force friction coefficient developed by the antiskid system to maximum drag-force friction coefficient available at the tire/runway interface was higher on dry surfaces than on wet surfaces. The gross stopping power generated by the brake system on the dry surface was more than twice that obtained on the wet surfaces. With maximum braking applied, the average ratio of side-force friction coefficient developed by the tire under antiskid control to maximum side-force friction available at the tire/runway interface of a free-rolling yawed tire was shown to decrease with increasing yaw angle. Braking reduced the side-force friction coefficient on a dry surface by 75 percent as the wheel slip ratio was increased to 0.3; on a flooded surface the coefficient dropped to near zero for the same slip ratio. Locked wheel skids were observed when the tire encountered a runway surface transition from dry to flooded, due in part to the response time required for the system to sense abrupt changes in the runway friction; however, the antiskid system quickly responded by reducing brake pressure and cycling normally during the remainder of the run on the flooded surface.

Evaluation of the Intel iWarp parallel processor for space flight applications

Science.gov (United States)

Hine, Butler P., III; Fong, Terrence W.

1993-01-01

The potential of a DARPA-sponsored advanced processor, the Intel iWarp, for use in future SSF Data Management Systems (DMS) upgrades is evaluated through integration into the Ames DMS testbed and applications testing. The iWarp is a distributed, parallel computing system well suited for high performance computing applications such as matrix operations and image processing. The system architecture is modular, supports systolic and message-based computation, and is capable of providing massive computational power in a low-cost, low-power package. As a consequence, the iWarp offers significant potential for advanced space-based computing. This research seeks to determine the iWarp's suitability as a processing device for space missions. In particular, the project focuses on evaluating the ease of integrating the iWarp into the SSF DMS baseline architecture and the iWarp's ability to support computationally stressing applications representative of SSF tasks.

Non-Cartesian parallel imaging reconstruction.

Science.gov (United States)

Wright, Katherine L; Hamilton, Jesse I; Griswold, Mark A; Gulani, Vikas; Seiberlich, Nicole

2014-11-01

Non-Cartesian parallel imaging has played an important role in reducing data acquisition time in MRI. The use of non-Cartesian trajectories can enable more efficient coverage of k-space, which can be leveraged to reduce scan times. These trajectories can be undersampled to achieve even faster scan times, but the resulting images may contain aliasing artifacts. Just as Cartesian parallel imaging can be used to reconstruct images from undersampled Cartesian data, non-Cartesian parallel imaging methods can mitigate aliasing artifacts by using additional spatial encoding information in the form of the nonhomogeneous sensitivities of multi-coil phased arrays. This review will begin with an overview of non-Cartesian k-space trajectories and their sampling properties, followed by an in-depth discussion of several selected non-Cartesian parallel imaging algorithms. Three representative non-Cartesian parallel imaging methods will be described, including Conjugate Gradient SENSE (CG SENSE), non-Cartesian generalized autocalibrating partially parallel acquisition (GRAPPA), and Iterative Self-Consistent Parallel Imaging Reconstruction (SPIRiT). After a discussion of these three techniques, several potential promising clinical applications of non-Cartesian parallel imaging will be covered. © 2014 Wiley Periodicals, Inc.

Unified Lambert Tool for Massively Parallel Applications in Space Situational Awareness

Science.gov (United States)

Woollands, Robyn M.; Read, Julie; Hernandez, Kevin; Probe, Austin; Junkins, John L.

2018-03-01

This paper introduces a parallel-compiled tool that combines several of our recently developed methods for solving the perturbed Lambert problem using modified Chebyshev-Picard iteration. This tool (unified Lambert tool) consists of four individual algorithms, each of which is unique and better suited for solving a particular type of orbit transfer. The first is a Keplerian Lambert solver, which is used to provide a good initial guess (warm start) for solving the perturbed problem. It is also used to determine the appropriate algorithm to call for solving the perturbed problem. The arc length or true anomaly angle spanned by the transfer trajectory is the parameter that governs the automated selection of the appropriate perturbed algorithm, and is based on the respective algorithm convergence characteristics. The second algorithm solves the perturbed Lambert problem using the modified Chebyshev-Picard iteration two-point boundary value solver. This algorithm does not require a Newton-like shooting method and is the most efficient of the perturbed solvers presented herein, however the domain of convergence is limited to about a third of an orbit and is dependent on eccentricity. The third algorithm extends the domain of convergence of the modified Chebyshev-Picard iteration two-point boundary value solver to about 90% of an orbit, through regularization with the Kustaanheimo-Stiefel transformation. This is the second most efficient of the perturbed set of algorithms. The fourth algorithm uses the method of particular solutions and the modified Chebyshev-Picard iteration initial value solver for solving multiple revolution perturbed transfers. This method does require "shooting" but differs from Newton-like shooting methods in that it does not require propagation of a state transition matrix. The unified Lambert tool makes use of the General Mission Analysis Tool and we use it to compute thousands of perturbed Lambert trajectories in parallel on the Space Situational

Compactness of the automorphism group of a topological parallelism on real projective 3-space: The disconnected case

OpenAIRE

Rainer, Löwen

2017-01-01

We prove that the automorphism group of a topological parallelism on real projective 3-space is compact. In a preceding article it was proved that at least the connected component of the identity is compact. The present proof does not depend on that earlier result.

The ASLOTS concept: An interactive, adaptive decision support concept for Final Approach Spacing of Aircraft (FASA). FAA-NASA Joint University Program

Science.gov (United States)

Simpson, Robert W.

1993-01-01

This presentation outlines a concept for an adaptive, interactive decision support system to assist controllers at a busy airport in achieving efficient use of multiple runways. The concept is being implemented as a computer code called FASA (Final Approach Spacing for Aircraft), and will be tested and demonstrated in ATCSIM, a high fidelity simulation of terminal area airspace and airport surface operations. Objectives are: (1) to provide automated cues to assist controllers in the sequencing and spacing of landing and takeoff aircraft; (2) to provide the controller with a limited ability to modify the sequence and spacings between aircraft, and to insert takeoffs and missed approach aircraft in the landing flows; (3) to increase spacing accuracy using more complex and precise separation criteria while reducing controller workload; and (4) achieve higher operational takeoff and landing rates on multiple runways in poor visibility.

A novel machine learning model to predict abnormal Runway Occupancy Times and observe related precursors

NARCIS (Netherlands)

Herrema, Herrema Floris; Treve, V; Desart, B; Curran, R.; Visser, H.G.

2017-01-01

Accidents on the runway triggered the development and implementation of mitigation strategies. Therefore, the airline industry is moving toward proactive risk management, which aims to identify and predict risk percursors and to mitigate risks before accidents occur. For certain predictions Machine

Aviation System Capacity Program Terminal Area Productivity Project: Ground and Airborne Technologies

Science.gov (United States)

Giulianetti, Demo J.

2001-01-01

Ground and airborne technologies were developed in the Terminal Area Productivity (TAP) project for increasing throughput at major airports by safely maintaining good-weather operating capacity during bad weather. Methods were demonstrated for accurately predicting vortices to prevent wake-turbulence encounters and to reduce in-trail separation requirements for aircraft approaching the same runway for landing. Technology was demonstrated that safely enabled independent simultaneous approaches in poor weather conditions to parallel runways spaced less than 3,400 ft apart. Guidance, control, and situation-awareness systems were developed to reduce congestion in airport surface operations resulting from the increased throughput, particularly during night and instrument meteorological conditions (IMC). These systems decreased runway occupancy time by safely and smoothly decelerating the aircraft, increasing taxi speed, and safely steering the aircraft off the runway. Simulations were performed in which optimal trajectories were determined by air traffic control (ATC) and communicated to flight crews by means of Center TRACON Automation System/Flight Management System (CTASFMS) automation to reduce flight delays, increase throughput, and ensure flight safety.

Parallel MR imaging.

Science.gov (United States)

Deshmane, Anagha; Gulani, Vikas; Griswold, Mark A; Seiberlich, Nicole

2012-07-01

Parallel imaging is a robust method for accelerating the acquisition of magnetic resonance imaging (MRI) data, and has made possible many new applications of MR imaging. Parallel imaging works by acquiring a reduced amount of k-space data with an array of receiver coils. These undersampled data can be acquired more quickly, but the undersampling leads to aliased images. One of several parallel imaging algorithms can then be used to reconstruct artifact-free images from either the aliased images (SENSE-type reconstruction) or from the undersampled data (GRAPPA-type reconstruction). The advantages of parallel imaging in a clinical setting include faster image acquisition, which can be used, for instance, to shorten breath-hold times resulting in fewer motion-corrupted examinations. In this article the basic concepts behind parallel imaging are introduced. The relationship between undersampling and aliasing is discussed and two commonly used parallel imaging methods, SENSE and GRAPPA, are explained in detail. Examples of artifacts arising from parallel imaging are shown and ways to detect and mitigate these artifacts are described. Finally, several current applications of parallel imaging are presented and recent advancements and promising research in parallel imaging are briefly reviewed. Copyright © 2012 Wiley Periodicals, Inc.

Airport object extraction based on visual attention mechanism and parallel line detection

Science.gov (United States)

Lv, Jing; Lv, Wen; Zhang, Libao

2017-10-01

Target extraction is one of the important aspects in remote sensing image analysis and processing, which has wide applications in images compression, target tracking, target recognition and change detection. Among different targets, airport has attracted more and more attention due to its significance in military and civilian. In this paper, we propose a novel and reliable airport object extraction model combining visual attention mechanism and parallel line detection algorithm. First, a novel saliency analysis model for remote sensing images with airport region is proposed to complete statistical saliency feature analysis. The proposed model can precisely extract the most salient region and preferably suppress the background interference. Then, the prior geometric knowledge is analyzed and airport runways contained two parallel lines with similar length are detected efficiently. Finally, we use the improved Otsu threshold segmentation method to segment and extract the airport regions from the salient map of remote sensing images. The experimental results demonstrate that the proposed model outperforms existing saliency analysis models and shows good performance in the detection of the airport.

Final Environmental Assessment for the Runway Extension and New Parking Apron at Tyndall Air Force Base, Florida

National Research Council Canada - National Science Library

2004-01-01

The Air Force prepared an Environmental Assessment (EA) of the potential environmental consequences of constructing a new heavy parking apron and runway extension at Tyndall Air Force Base (AFB), Florida...

Qualitative Simulation of Photon Transport in Free Space Based on Monte Carlo Method and Its Parallel Implementation

Directory of Open Access Journals (Sweden)

Xueli Chen

2010-01-01

Full Text Available During the past decade, Monte Carlo method has obtained wide applications in optical imaging to simulate photon transport process inside tissues. However, this method has not been effectively extended to the simulation of free-space photon transport at present. In this paper, a uniform framework for noncontact optical imaging is proposed based on Monte Carlo method, which consists of the simulation of photon transport both in tissues and in free space. Specifically, the simplification theory of lens system is utilized to model the camera lens equipped in the optical imaging system, and Monte Carlo method is employed to describe the energy transformation from the tissue surface to the CCD camera. Also, the focusing effect of camera lens is considered to establish the relationship of corresponding points between tissue surface and CCD camera. Furthermore, a parallel version of the framework is realized, making the simulation much more convenient and effective. The feasibility of the uniform framework and the effectiveness of the parallel version are demonstrated with a cylindrical phantom based on real experimental results.

76 FR 21938 - Potential Environmental Impacts of the Proposed Runway 13 Extension and Associated Actions for...

Science.gov (United States)

2011-04-19

... DEPARTMENT OF TRANSPORTATION Federal Aviation Administration Potential Environmental Impacts of the Proposed Runway 13 Extension and Associated Actions for the Devils Lake Regional Airport in Devils Lake, ND AGENCY: Federal Aviation Administration (FAA), Department of Transportation (DOT). ACTION...

Factors that Determine Depth Perception of Trapezoids, Windsurfers, Runways

Directory of Open Access Journals (Sweden)

Chia-Huei eTseng

2015-04-01

Full Text Available We report here a windsurfer1 illusion, a naturally occurring trapezoidal illusion in which the small endof the sail viewed at a distance appears to be pointed away from the observer even when it is closer.This naturally occurring illusion is so compelling that observers are unaware of their gross perceptualmisinterpretation of the scene. Four laboratory experiment of this kind of trapezoidal illusion investigatedthe joint effects of retinal orientation, head position, relative motion, and the relative direction ofgravity on automatic depth perception. Observers viewed two adjacent white trapezoids outlined on ablack background rotating back and forth +/- 20 deg on a vertical axis much like the sails of two adjacentwindsurfers. Observers reported which side of the trapezoids (long or short appeared to becloser to them (i.e., in front. The longer edge of the trapezoid was reported in front 76+/-2% of trials(windsurfer effect whether it was on the left or on the right. When the display was rotated 90 deg toproduce a runway configuration, there was a striking asymmetry: the long edge was perceived to bein front 97% when it was on the bottom but only 43% when it was on top (runway effect. The runwayeffect persisted when the head was tilted 90 deg or when displays on the ceiling were viewedfrom the floor. 95% of the variance of the variance in the strikingly different 3D perceptions producedby the same 2D trapezoid image was quantitatively explained by a model that assumes there are justthree additive bias factors that account for perceiving an edge as closer: Implicit linear perspective,lower position on the retina (based on an automatic assumption of viewing from above, and beinglower in world coordinates.

Secoond order parallel tensors on some paracontact manifolds | Liu ...

African Journals Online (AJOL)

The object of the present paper is to study the symmetric and skewsymmetric properties of a second order parallel tensor on paracontact metric (k;μ)- spaces and almost β-para-Kenmotsu (k;μ)-spaces. In this paper, we prove that if there exists a second order symmetric parallel tensor on a paracontact metric (k;μ)- space M, ...

Prioritizing risks via several expert perspectives with application to runway safety

International Nuclear Information System (INIS)

Rogerson, Ellen C.; Lambert, James H.

2012-01-01

Factor hierarchies have been widely used in the literature to represent the view of an expert of what factors most contribute to reliability or safety. The methods for rating and aggregating the influences across a set of expert-elicited factors to risk or reliability are well known as multiple criteria decision analysis. This paper describes a method for distinguishing levels of risk across a set of locations via the use of multiple factor hierarchies. The method avoids averaging across experts and is thus useful for situations where experts disagree and where an absence of expert consensus on the causative or contributing factors is important information for risk management. A case study demonstrates using seven expert perspectives on the airport-specific factors that can contribute to runway incursions. The results are described for eighty towered airports in the US. The expert perspectives include differing relative emphases across the following set of factors: airport geometry, operations, weather, geography, and days since last safety review. Future work is suggested to include human factors issues as pilot-and-controller communications styles at airports. - Highlights: ► We examine influential factors in seven expert perspectives on the problem domain. ► We assess eighty US airports with qualitative measurement scales for each risk factor. ► Results show robustness and sensitivity of the risk index to expert perspective. ► We examine factors of several types including runway geometry, operations, weather, and geography.

Analytical model for vibration prediction of two parallel tunnels in a full-space

Science.gov (United States)

He, Chao; Zhou, Shunhua; Guo, Peijun; Di, Honggui; Zhang, Xiaohui

2018-06-01

This paper presents a three-dimensional analytical model for the prediction of ground vibrations from two parallel tunnels embedded in a full-space. The two tunnels are modelled as cylindrical shells of infinite length, and the surrounding soil is modelled as a full-space with two cylindrical cavities. A virtual interface is introduced to divide the soil into the right layer and the left layer. By transforming the cylindrical waves into the plane waves, the solution of wave propagation in the full-space with two cylindrical cavities is obtained. The transformations from the plane waves to cylindrical waves are then used to satisfy the boundary conditions on the tunnel-soil interfaces. The proposed model provides a highly efficient tool to predict the ground vibration induced by the underground railway, which accounts for the dynamic interaction between neighbouring tunnels. Analysis of the vibration fields produced over a range of frequencies and soil properties is conducted. When the distance between the two tunnels is smaller than three times the tunnel diameter, the interaction between neighbouring tunnels is highly significant, at times in the order of 20 dB. It is necessary to consider the interaction between neighbouring tunnels for the prediction of ground vibrations induced underground railways.

The parallel volume at large distances

DEFF Research Database (Denmark)

Kampf, Jürgen

In this paper we examine the asymptotic behavior of the parallel volume of planar non-convex bodies as the distance tends to infinity. We show that the difference between the parallel volume of the convex hull of a body and the parallel volume of the body itself tends to . This yields a new proof...... for the fact that a planar body can only have polynomial parallel volume, if it is convex. Extensions to Minkowski spaces and random sets are also discussed....

The parallel volume at large distances

DEFF Research Database (Denmark)

Kampf, Jürgen

In this paper we examine the asymptotic behavior of the parallel volume of planar non-convex bodies as the distance tends to infinity. We show that the difference between the parallel volume of the convex hull of a body and the parallel volume of the body itself tends to 0. This yields a new proof...... for the fact that a planar body can only have polynomial parallel volume, if it is convex. Extensions to Minkowski spaces and random sets are also discussed....

A parallel algorithm for the initial screening of space debris collisions prediction using the SGP4/SDP4 models and GPU acceleration

Science.gov (United States)

Lin, Mingpei; Xu, Ming; Fu, Xiaoyu

2017-05-01

Currently, a tremendous amount of space debris in Earth's orbit imperils operational spacecraft. It is essential to undertake risk assessments of collisions and predict dangerous encounters in space. However, collision predictions for an enormous amount of space debris give rise to large-scale computations. In this paper, a parallel algorithm is established on the Compute Unified Device Architecture (CUDA) platform of NVIDIA Corporation for collision prediction. According to the parallel structure of NVIDIA graphics processors, a block decomposition strategy is adopted in the algorithm. Space debris is divided into batches, and the computation and data transfer operations of adjacent batches overlap. As a consequence, the latency to access shared memory during the entire computing process is significantly reduced, and a higher computing speed is reached. Theoretically, a simulation of collision prediction for space debris of any amount and for any time span can be executed. To verify this algorithm, a simulation example including 1382 pieces of debris, whose operational time scales vary from 1 min to 3 days, is conducted on Tesla C2075 of NVIDIA. The simulation results demonstrate that with the same computational accuracy as that of a CPU, the computing speed of the parallel algorithm on a GPU is 30 times that on a CPU. Based on this algorithm, collision prediction of over 150 Chinese spacecraft for a time span of 3 days can be completed in less than 3 h on a single computer, which meets the timeliness requirement of the initial screening task. Furthermore, the algorithm can be adapted for multiple tasks, including particle filtration, constellation design, and Monte-Carlo simulation of an orbital computation.

Changes in the Albedo of the Pegasus and Phoenix Runways, 2000-2017

Science.gov (United States)

2017-07-18

by the net heat transfer into the runway surface during the brief but intense peak of austral summer. The flux of downwelling shortwave solar energy...snow; and as ERDC/CRREL TR-17-10 2 mentioned above, the presence of melt water in the snow further reduces albedo and increases heating of the snow...interpolating over all possible angles, end member albedo cases (“white sky” and “black sky”) can be modeled . The actual albedo or “blue sky” albedo falls

PDDP, A Data Parallel Programming Model

Directory of Open Access Journals (Sweden)

Karen H. Warren

1996-01-01

Full Text Available PDDP, the parallel data distribution preprocessor, is a data parallel programming model for distributed memory parallel computers. PDDP implements high-performance Fortran-compatible data distribution directives and parallelism expressed by the use of Fortran 90 array syntax, the FORALL statement, and the WHERE construct. Distributed data objects belong to a global name space; other data objects are treated as local and replicated on each processor. PDDP allows the user to program in a shared memory style and generates codes that are portable to a variety of parallel machines. For interprocessor communication, PDDP uses the fastest communication primitives on each platform.

Exploiting Stabilizers and Parallelism in State Space Generation with the Symmetry Method

DEFF Research Database (Denmark)

Lorentsen, Louise; Kristensen, Lars Michael

2001-01-01

The symmetry method is a main reduction paradigm for alleviating the state explosion problem. For large symmetry groups deciding whether two states are symmetric becomes time expensive due to the apparent high time complexity of the orbit problem. The contribution of this paper is to alleviate th...... the negative impact of the orbit problem by the specification of canonical representatives for equivalence classes of states in Coloured Petri Nets, and by giving algorithms exploiting stabilizers and parallelism for computing the condensed state space.......The symmetry method is a main reduction paradigm for alleviating the state explosion problem. For large symmetry groups deciding whether two states are symmetric becomes time expensive due to the apparent high time complexity of the orbit problem. The contribution of this paper is to alleviate...

Fringe Capacitance of a Parallel-Plate Capacitor.

Science.gov (United States)

Hale, D. P.

1978-01-01

Describes an experiment designed to measure the forces between charged parallel plates, and determines the relationship among the effective electrode area, the measured capacitance values, and the electrode spacing of a parallel plate capacitor. (GA)

Streaming nested data parallelism on multicores

DEFF Research Database (Denmark)

Madsen, Frederik Meisner; Filinski, Andrzej

2016-01-01

The paradigm of nested data parallelism (NDP) allows a variety of semi-regular computation tasks to be mapped onto SIMD-style hardware, including GPUs and vector units. However, some care is needed to keep down space consumption in situations where the available parallelism may vastly exceed...

Behavior of aircraft antiskid braking systems on dry and wet runway surfaces. A slip-velocity-controlled, pressure-bias-modulated system

Science.gov (United States)

Stubbs, S. M.; Tanner, J. A.; Smith, E. G.

1979-01-01

The braking and cornering response of a slip velocity controlled, pressure bias modulated aircraft antiskid braking system is investigated. The investigation, conducted on dry and wet runway surfaces, utilized one main gear wheel, brake, and tire assembly of a McDonnell Douglas DC 9 series 10 airplane. The landing gear strut was replaced by a dynamometer. The parameters, which were varied, included the carriage speed, tire loading, yaw angle, tire tread condition, brake system operating pressure, and runway wetness conditions. The effects of each of these parameters on the behavior of the skid control system is presented. Comparisons between data obtained with the skid control system and data obtained from single cycle braking tests without antiskid protection are examined.

On synchronous parallel computations with independent probabilistic choice

International Nuclear Information System (INIS)

Reif, J.H.

1984-01-01

This paper introduces probabilistic choice to synchronous parallel machine models; in particular parallel RAMs. The power of probabilistic choice in parallel computations is illustrate by parallelizing some known probabilistic sequential algorithms. The authors characterize the computational complexity of time, space, and processor bounded probabilistic parallel RAMs in terms of the computational complexity of probabilistic sequential RAMs. They show that parallelism uniformly speeds up time bounded probabilistic sequential RAM computations by nearly a quadratic factor. They also show that probabilistic choice can be eliminated from parallel computations by introducing nonuniformity

Computations on the massively parallel processor at the Goddard Space Flight Center

Science.gov (United States)

Strong, James P.

1991-01-01

Described are four significant algorithms implemented on the massively parallel processor (MPP) at the Goddard Space Flight Center. Two are in the area of image analysis. Of the other two, one is a mathematical simulation experiment and the other deals with the efficient transfer of data between distantly separated processors in the MPP array. The first algorithm presented is the automatic determination of elevations from stereo pairs. The second algorithm solves mathematical logistic equations capable of producing both ordered and chaotic (or random) solutions. This work can potentially lead to the simulation of artificial life processes. The third algorithm is the automatic segmentation of images into reasonable regions based on some similarity criterion, while the fourth is an implementation of a bitonic sort of data which significantly overcomes the nearest neighbor interconnection constraints on the MPP for transferring data between distant processors.

Tyura Tam Space Launch Facility, Kazakhstan, CIS

Science.gov (United States)

1992-01-01

Located in Kazakhstan on the Syr Darya River, the Tyura Tam Cosmodrome has been the launch site for 72 cosmonaut crews. The landing runway of the Buran space shuttle can be seen in the left center. Further to the right, near the center is the launch site for the Soyuz. The mission control center is located 1,300 miles away near Moscow. In the lower right, is the city of Leninsk, seen as a dark region next to the river.

Simulation Exploration through Immersive Parallel Planes

Energy Technology Data Exchange (ETDEWEB)

Brunhart-Lupo, Nicholas J [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Bush, Brian W [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Gruchalla, Kenny M [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Smith, Steve [Los Alamos Visualization Associates

2017-05-25

We present a visualization-driven simulation system that tightly couples systems dynamics simulations with an immersive virtual environment to allow analysts to rapidly develop and test hypotheses in a high-dimensional parameter space. To accomplish this, we generalize the two-dimensional parallel-coordinates statistical graphic as an immersive 'parallel-planes' visualization for multivariate time series emitted by simulations running in parallel with the visualization. In contrast to traditional parallel coordinate's mapping the multivariate dimensions onto coordinate axes represented by a series of parallel lines, we map pairs of the multivariate dimensions onto a series of parallel rectangles. As in the case of parallel coordinates, each individual observation in the dataset is mapped to a polyline whose vertices coincide with its coordinate values. Regions of the rectangles can be 'brushed' to highlight and select observations of interest: a 'slider' control allows the user to filter the observations by their time coordinate. In an immersive virtual environment, users interact with the parallel planes using a joystick that can select regions on the planes, manipulate selection, and filter time. The brushing and selection actions are used to both explore existing data as well as to launch additional simulations corresponding to the visually selected portions of the input parameter space. As soon as the new simulations complete, their resulting observations are displayed in the virtual environment. This tight feedback loop between simulation and immersive analytics accelerates users' realization of insights about the simulation and its output.

Millimeterwave Space Power Grid architecture development 2012

Science.gov (United States)

Komerath, Narayanan; Dessanti, Brendan; Shah, Shaan

- ramp up space solar power level to over 5.6 TeraWatts by year 50 from project start. Runway-based launch and landing are required to achieve the launch productivity as well as the cost reductions to enable such a large deployment on schedule. Advancements in the certainty of millimeter wave conversion technology and runway-based space access, are seen to be the outstanding issues in proceeding to full-scale Space Solar Power.

A scalable method for parallelizing sampling-based motion planning algorithms

KAUST Repository

Jacobs, Sam Ade; Manavi, Kasra; Burgos, Juan; Denny, Jory; Thomas, Shawna; Amato, Nancy M.

2012-01-01

This paper describes a scalable method for parallelizing sampling-based motion planning algorithms. It subdivides configuration space (C-space) into (possibly overlapping) regions and independently, in parallel, uses standard (sequential) sampling-based planners to construct roadmaps in each region. Next, in parallel, regional roadmaps in adjacent regions are connected to form a global roadmap. By subdividing the space and restricting the locality of connection attempts, we reduce the work and inter-processor communication associated with nearest neighbor calculation, a critical bottleneck for scalability in existing parallel motion planning methods. We show that our method is general enough to handle a variety of planning schemes, including the widely used Probabilistic Roadmap (PRM) and Rapidly-exploring Random Trees (RRT) algorithms. We compare our approach to two other existing parallel algorithms and demonstrate that our approach achieves better and more scalable performance. Our approach achieves almost linear scalability on a 2400 core LINUX cluster and on a 153,216 core Cray XE6 petascale machine. © 2012 IEEE.

A scalable method for parallelizing sampling-based motion planning algorithms

KAUST Repository

Jacobs, Sam Ade

2012-05-01

This paper describes a scalable method for parallelizing sampling-based motion planning algorithms. It subdivides configuration space (C-space) into (possibly overlapping) regions and independently, in parallel, uses standard (sequential) sampling-based planners to construct roadmaps in each region. Next, in parallel, regional roadmaps in adjacent regions are connected to form a global roadmap. By subdividing the space and restricting the locality of connection attempts, we reduce the work and inter-processor communication associated with nearest neighbor calculation, a critical bottleneck for scalability in existing parallel motion planning methods. We show that our method is general enough to handle a variety of planning schemes, including the widely used Probabilistic Roadmap (PRM) and Rapidly-exploring Random Trees (RRT) algorithms. We compare our approach to two other existing parallel algorithms and demonstrate that our approach achieves better and more scalable performance. Our approach achieves almost linear scalability on a 2400 core LINUX cluster and on a 153,216 core Cray XE6 petascale machine. © 2012 IEEE.

Productive urbanisms : From Runways to Greenways

Energy Technology Data Exchange (ETDEWEB)

White, M [Toronto Univ., ON (Canada). Faculty of Architecture Landscape and Design; Sheppard, L [Waterloo Univ., Cambridge, ON (Canada). School of Architecture

2009-07-01

This paper reported on an international competition for urban development in Reykjavik, Iceland in 2007. Known as the Runways to Greenways proposal, the prototype depends on a strategy that considers energy use, ecology and land use when integrating public amenities. While Iceland is advanced in terms of its vast geothermal reserves, it is a country that uses the most energy per capita. There are 5 major geothermal power plants in Iceland which produce about 26 per cent of the country's electricity. Geothermal heating also meets the heating and hot water needs for nearly 87 per cent of the nation's buildings. However, Reykjavik continues to rely heavily on imported fossil fuel primarily for fishing, transport and heavy industries. A recent masterplan for the expansion of Reykjavik calls for the densification of the city. The objective was to propose a city that is self-sufficient in terms of energy, agriculture and water while addressing the development potentials of biotechnology and ecotechnology enterprises in Reykjavik. The integrated infrastructure calls for a symbiotic relationship between urbanism and nature, and between energy consumption and production in an effort to pair infrastructure, landscape, public infrastructure and architecture in a culturally, economically and environmentally productive urban realm. 9 refs., 12 figs.

Productive urbanisms : From Runways to Greenways

Energy Technology Data Exchange (ETDEWEB)

White, M. [Toronto Univ., ON (Canada). Faculty of Architecture Landscape and Design; Sheppard, L. [Waterloo Univ., Cambridge, ON (Canada). School of Architecture

2009-07-01

This paper reported on an international competition for urban development in Reykjavik, Iceland in 2007. Known as the Runways to Greenways proposal, the prototype depends on a strategy that considers energy use, ecology and land use when integrating public amenities. While Iceland is advanced in terms of its vast geothermal reserves, it is a country that uses the most energy per capita. There are 5 major geothermal power plants in Iceland which produce about 26 per cent of the country's electricity. Geothermal heating also meets the heating and hot water needs for nearly 87 per cent of the nation's buildings. However, Reykjavik continues to rely heavily on imported fossil fuel primarily for fishing, transport and heavy industries. A recent masterplan for the expansion of Reykjavik calls for the densification of the city. The objective was to propose a city that is self-sufficient in terms of energy, agriculture and water while addressing the development potentials of biotechnology and ecotechnology enterprises in Reykjavik. The integrated infrastructure calls for a symbiotic relationship between urbanism and nature, and between energy consumption and production in an effort to pair infrastructure, landscape, public infrastructure and architecture in a culturally, economically and environmentally productive urban realm. 9 refs., 12 figs.

A Parallel Saturation Algorithm on Shared Memory Architectures

Science.gov (United States)

Ezekiel, Jonathan; Siminiceanu

2007-01-01

Symbolic state-space generators are notoriously hard to parallelize. However, the Saturation algorithm implemented in the SMART verification tool differs from other sequential symbolic state-space generators in that it exploits the locality of ring events in asynchronous system models. This paper explores whether event locality can be utilized to efficiently parallelize Saturation on shared-memory architectures. Conceptually, we propose to parallelize the ring of events within a decision diagram node, which is technically realized via a thread pool. We discuss the challenges involved in our parallel design and conduct experimental studies on its prototypical implementation. On a dual-processor dual core PC, our studies show speed-ups for several example models, e.g., of up to 50% for a Kanban model, when compared to running our algorithm only on a single core.

MCBooster: a library for fast Monte Carlo generation of phase-space decays on massively parallel platforms.

Science.gov (United States)

Alves Júnior, A. A.; Sokoloff, M. D.

2017-10-01

MCBooster is a header-only, C++11-compliant library that provides routines to generate and perform calculations on large samples of phase space Monte Carlo events. To achieve superior performance, MCBooster is capable to perform most of its calculations in parallel using CUDA- and OpenMP-enabled devices. MCBooster is built on top of the Thrust library and runs on Linux systems. This contribution summarizes the main features of MCBooster. A basic description of the user interface and some examples of applications are provided, along with measurements of performance in a variety of environments

Web-based Weather Expert System (WES) for Space Shuttle Launch

Science.gov (United States)

Bardina, Jorge E.; Rajkumar, T.

2003-01-01

The Web-based Weather Expert System (WES) is a critical module of the Virtual Test Bed development to support 'go/no go' decisions for Space Shuttle operations in the Intelligent Launch and Range Operations program of NASA. The weather rules characterize certain aspects of the environment related to the launching or landing site, the time of the day or night, the pad or runway conditions, the mission durations, the runway equipment and landing type. Expert system rules are derived from weather contingency rules, which were developed over years by NASA. Backward chaining, a goal-directed inference method is adopted, because a particular consequence or goal clause is evaluated first, and then chained backward through the rules. Once a rule is satisfied or true, then that particular rule is fired and the decision is expressed. The expert system is continuously verifying the rules against the past one-hour weather conditions and the decisions are made. The normal procedure of operations requires a formal pre-launch weather briefing held on Launch minus 1 day, which is a specific weather briefing for all areas of Space Shuttle launch operations. In this paper, the Web-based Weather Expert System of the Intelligent Launch and range Operations program is presented.

SiGN-SSM: open source parallel software for estimating gene networks with state space models.

Science.gov (United States)

Tamada, Yoshinori; Yamaguchi, Rui; Imoto, Seiya; Hirose, Osamu; Yoshida, Ryo; Nagasaki, Masao; Miyano, Satoru

2011-04-15

SiGN-SSM is an open-source gene network estimation software able to run in parallel on PCs and massively parallel supercomputers. The software estimates a state space model (SSM), that is a statistical dynamic model suitable for analyzing short time and/or replicated time series gene expression profiles. SiGN-SSM implements a novel parameter constraint effective to stabilize the estimated models. Also, by using a supercomputer, it is able to determine the gene network structure by a statistical permutation test in a practical time. SiGN-SSM is applicable not only to analyzing temporal regulatory dependencies between genes, but also to extracting the differentially regulated genes from time series expression profiles. SiGN-SSM is distributed under GNU Affero General Public Licence (GNU AGPL) version 3 and can be downloaded at http://sign.hgc.jp/signssm/. The pre-compiled binaries for some architectures are available in addition to the source code. The pre-installed binaries are also available on the Human Genome Center supercomputer system. The online manual and the supplementary information of SiGN-SSM is available on our web site. tamada@ims.u-tokyo.ac.jp.

Simulation Exploration through Immersive Parallel Planes: Preprint

Energy Technology Data Exchange (ETDEWEB)

Brunhart-Lupo, Nicholas; Bush, Brian W.; Gruchalla, Kenny; Smith, Steve

2016-03-01

We present a visualization-driven simulation system that tightly couples systems dynamics simulations with an immersive virtual environment to allow analysts to rapidly develop and test hypotheses in a high-dimensional parameter space. To accomplish this, we generalize the two-dimensional parallel-coordinates statistical graphic as an immersive 'parallel-planes' visualization for multivariate time series emitted by simulations running in parallel with the visualization. In contrast to traditional parallel coordinate's mapping the multivariate dimensions onto coordinate axes represented by a series of parallel lines, we map pairs of the multivariate dimensions onto a series of parallel rectangles. As in the case of parallel coordinates, each individual observation in the dataset is mapped to a polyline whose vertices coincide with its coordinate values. Regions of the rectangles can be 'brushed' to highlight and select observations of interest: a 'slider' control allows the user to filter the observations by their time coordinate. In an immersive virtual environment, users interact with the parallel planes using a joystick that can select regions on the planes, manipulate selection, and filter time. The brushing and selection actions are used to both explore existing data as well as to launch additional simulations corresponding to the visually selected portions of the input parameter space. As soon as the new simulations complete, their resulting observations are displayed in the virtual environment. This tight feedback loop between simulation and immersive analytics accelerates users' realization of insights about the simulation and its output.

A parallel nearly implicit time-stepping scheme

OpenAIRE

Botchev, Mike A.; van der Vorst, Henk A.

2001-01-01

Across-the-space parallelism still remains the most mature, convenient and natural way to parallelize large scale problems. One of the major problems here is that implicit time stepping is often difficult to parallelize due to the structure of the system. Approximate implicit schemes have been suggested to circumvent the problem. These schemes have attractive stability properties and they are also very well parallelizable. The purpose of this article is to give an overall assessment of the pa...

PAREMD: A parallel program for the evaluation of momentum space properties of atoms and molecules

Science.gov (United States)

Meena, Deep Raj; Gadre, Shridhar R.; Balanarayan, P.

2018-03-01

The present work describes a code for evaluating the electron momentum density (EMD), its moments and the associated Shannon information entropy for a multi-electron molecular system. The code works specifically for electronic wave functions obtained from traditional electronic structure packages such as GAMESS and GAUSSIAN. For the momentum space orbitals, the general expression for Gaussian basis sets in position space is analytically Fourier transformed to momentum space Gaussian basis functions. The molecular orbital coefficients of the wave function are taken as an input from the output file of the electronic structure calculation. The analytic expressions of EMD are evaluated over a fine grid and the accuracy of the code is verified by a normalization check and a numerical kinetic energy evaluation which is compared with the analytic kinetic energy given by the electronic structure package. Apart from electron momentum density, electron density in position space has also been integrated into this package. The program is written in C++ and is executed through a Shell script. It is also tuned for multicore machines with shared memory through OpenMP. The program has been tested for a variety of molecules and correlated methods such as CISD, Møller-Plesset second order (MP2) theory and density functional methods. For correlated methods, the PAREMD program uses natural spin orbitals as an input. The program has been benchmarked for a variety of Gaussian basis sets for different molecules showing a linear speedup on a parallel architecture.

Predicting capacities of runways serving new large aircraft

Directory of Open Access Journals (Sweden)

K. Gopalakrishnan

2008-03-01

Full Text Available This paper presents a simplified approach for predicting the allowable load repetitions of New Large Aircraft (NLA loading for airfield runways based on Non-Destructive Test (NDT data. Full-scale traffic test results from the Federal Aviation Administration’s National Airport Pavement Test Facility (NAPTF were used to develop the NDT-based evaluation methodology. Four flexible test pavement sections with variable (unbound layer thicknesses were trafficked using six-wheel and four-wheel NLA test gears until the test pavements were deemed failed. Non-destructive tests using a Heavy Weight Deflectometer (HWD were conducted prior to the initiation of traffic testing to measure the pavement surface deflections. In the past, pavement surface deflections have been successfully used as an indicator of airport pavement life. In this study, the HWD surface deflections and the derived Deflection Basin Parameters (DBPs were related to functional performance of NAPTF flexible pavements through simple regression analysis. The results demonstrated the usefulness of NDT data for predicting the performance of airport flexible pavements serving the next generation of aircrafts.

Probing Very Bright End of Galaxy Luminosity Function at z >~ 7 Using Hubble Space Telescope Pure Parallel Observations

Science.gov (United States)

Yan, Haojing; Yan, Lin; Zamojski, Michel A.; Windhorst, Rogier A.; McCarthy, Patrick J.; Fan, Xiaohui; Röttgering, Huub J. A.; Koekemoer, Anton M.; Robertson, Brant E.; Davé, Romeel; Cai, Zheng

2011-02-01

We report the first results from the Hubble Infrared Pure Parallel Imaging Extragalactic Survey, which utilizes the pure parallel orbits of the Hubble Space Telescope to do deep imaging along a large number of random sightlines. To date, our analysis includes 26 widely separated fields observed by the Wide Field Camera 3, which amounts to 122.8 arcmin2 in total area. We have found three bright Y 098-dropouts, which are candidate galaxies at z >~ 7.4. One of these objects shows an indication of peculiar variability and its nature is uncertain. The other two objects are among the brightest candidate galaxies at these redshifts known to date (L>2L*). Such very luminous objects could be the progenitors of the high-mass Lyman break galaxies observed at lower redshifts (up to z ~ 5). While our sample is still limited in size, it is much less subject to the uncertainty caused by "cosmic variance" than other samples because it is derived using fields along many random sightlines. We find that the existence of the brightest candidate at z ≈ 7.4 is not well explained by the current luminosity function (LF) estimates at z ≈ 8. However, its inferred surface density could be explained by the prediction from the LFs at z ≈ 7 if it belongs to the high-redshift tail of the galaxy population at z ≈ 7. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs 11700 and 11702.

Towards a streaming model for nested data parallelism

DEFF Research Database (Denmark)

Madsen, Frederik Meisner; Filinski, Andrzej

2013-01-01

The language-integrated cost semantics for nested data parallelism pioneered by NESL provides an intuitive, high-level model for predicting performance and scalability of parallel algorithms with reasonable accuracy. However, this predictability, obtained through a uniform, parallelism-flattening......The language-integrated cost semantics for nested data parallelism pioneered by NESL provides an intuitive, high-level model for predicting performance and scalability of parallel algorithms with reasonable accuracy. However, this predictability, obtained through a uniform, parallelism......-processable in a streaming fashion. This semantics is directly compatible with previously proposed piecewise execution models for nested data parallelism, but allows the expected space usage to be reasoned about directly at the source-language level. The language definition and implementation are still very much work...

Parallel-In-Time For Moving Meshes

Energy Technology Data Exchange (ETDEWEB)

Falgout, R. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Manteuffel, T. A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Southworth, B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Schroder, J. B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2016-02-04

With steadily growing computational resources available, scientists must develop e ective ways to utilize the increased resources. High performance, highly parallel software has be- come a standard. However until recent years parallelism has focused primarily on the spatial domain. When solving a space-time partial di erential equation (PDE), this leads to a sequential bottleneck in the temporal dimension, particularly when taking a large number of time steps. The XBraid parallel-in-time library was developed as a practical way to add temporal parallelism to existing se- quential codes with only minor modi cations. In this work, a rezoning-type moving mesh is applied to a di usion problem and formulated in a parallel-in-time framework. Tests and scaling studies are run using XBraid and demonstrate excellent results for the simple model problem considered herein.

Parallel processing of two-dimensional Sn transport calculations

International Nuclear Information System (INIS)

Uematsu, M.

1997-01-01

A parallel processing method for the two-dimensional S n transport code DOT3.5 has been developed to achieve a drastic reduction in computation time. In the proposed method, parallelization is achieved with angular domain decomposition and/or space domain decomposition. The calculational speed of parallel processing by angular domain decomposition is largely influenced by frequent communications between processing elements. To assess parallelization efficiency, sample problems with up to 32 x 32 spatial meshes were solved with a Sun workstation using the PVM message-passing library. As a result, parallel calculation using 16 processing elements, for example, was found to be nine times as fast as that with one processing element. As for parallel processing by geometry segmentation, the influence of processing element communications on computation time is small; however, discontinuity at the segment boundary degrades convergence speed. To accelerate the convergence, an alternate sweep of angular flux in conjunction with space domain decomposition and a two-step rescaling method consisting of segmentwise rescaling and ordinary pointwise rescaling have been developed. By applying the developed method, the number of iterations needed to obtain a converged flux solution was reduced by a factor of 2. As a result, parallel calculation using 16 processing elements was found to be 5.98 times as fast as the original DOT3.5 calculation

A Parallel Strategy for High-speed Interpolation of CNC Using Data Space Constraint Method

Directory of Open Access Journals (Sweden)

Shuan-qiang Yang

2013-12-01

Full Text Available A high-speed interpolation scheme using parallel computing is proposed in this paper. The interpolation method is divided into two tasks, namely, the rough task executing in PC and the fine task in the I/O card. During the interpolation procedure, the double buffers are constructed to exchange the interpolation data between the two tasks. Then, the data space constraint method is adapted to ensure the reliable and continuous data communication between the two buffers. Therefore, the proposed scheme can be realized in the common distribution of the operation systems without real-time performance. The high-speed and high-precision motion control can be achieved as well. Finally, an experiment is conducted on the self-developed CNC platform, the test results are shown to verify the proposed method.

Comprehensive quantification of signal-to-noise ratio and g-factor for image-based and k-space-based parallel imaging reconstructions.

Science.gov (United States)

Robson, Philip M; Grant, Aaron K; Madhuranthakam, Ananth J; Lattanzi, Riccardo; Sodickson, Daniel K; McKenzie, Charles A

2008-10-01

Parallel imaging reconstructions result in spatially varying noise amplification characterized by the g-factor, precluding conventional measurements of noise from the final image. A simple Monte Carlo based method is proposed for all linear image reconstruction algorithms, which allows measurement of signal-to-noise ratio and g-factor and is demonstrated for SENSE and GRAPPA reconstructions for accelerated acquisitions that have not previously been amenable to such assessment. Only a simple "prescan" measurement of noise amplitude and correlation in the phased-array receiver, and a single accelerated image acquisition are required, allowing robust assessment of signal-to-noise ratio and g-factor. The "pseudo multiple replica" method has been rigorously validated in phantoms and in vivo, showing excellent agreement with true multiple replica and analytical methods. This method is universally applicable to the parallel imaging reconstruction techniques used in clinical applications and will allow pixel-by-pixel image noise measurements for all parallel imaging strategies, allowing quantitative comparison between arbitrary k-space trajectories, image reconstruction, or noise conditioning techniques. (c) 2008 Wiley-Liss, Inc.

Soil settlement analysis in soft soil by using preloading system and prefabricated vertical draining runway of Kualanamu Airport

Science.gov (United States)

Roesyanto; Iskandar, R.; Silalahi, S. A.; Fadliansyah

2018-02-01

The method of soil improvement, using the combination of prefabricated vertical drain (PVD) and preloading, was used to accelerate the process of consolidation and the consolidation settlement in the runway of Kualanamu International Airport, which was constructed on the soft soil sediment like silty clay. In this research, the investigated area was the runway of Kualanamu International Airport zone I which had 11 meter-thickness of soft soil. Geotechnic instruments surveyed was settlement plate. Monitoring was done toward the behavior of landfill such as basic soil settlement. The result were compared with the analysis of finite element method of full scale in Mohr-Coulomb model by verifying the vertical drain of asymmetric unit cell and equivalent plane strain unit cell condition. The results of the research showed that there were an interesting behavior between the data in field observation and finite element of Mohr-Coulomb model. It was also found that the result of soil settlement of finite element method of Mohr-Coulomb model was closed to the result of settlement plate monitoring.

Aircraft Accident Report. Runway Overrun During Landing American Airlines Flight 1420 McDonnell Douglas MD-82, N215AA Little Rock, Arkansas

National Research Council Canada - National Science Library

1999-01-01

This report explains the accident involving American Airlines flight 1420, a McDonnell Douglas MD-82, which crashed after it overran the end of runway 4R during landing at Little Rock National Airport...

Parallel imaging with phase scrambling.

Science.gov (United States)

Zaitsev, Maxim; Schultz, Gerrit; Hennig, Juergen; Gruetter, Rolf; Gallichan, Daniel

2015-04-01

Most existing methods for accelerated parallel imaging in MRI require additional data, which are used to derive information about the sensitivity profile of each radiofrequency (RF) channel. In this work, a method is presented to avoid the acquisition of separate coil calibration data for accelerated Cartesian trajectories. Quadratic phase is imparted to the image to spread the signals in k-space (aka phase scrambling). By rewriting the Fourier transform as a convolution operation, a window can be introduced to the convolved chirp function, allowing a low-resolution image to be reconstructed from phase-scrambled data without prominent aliasing. This image (for each RF channel) can be used to derive coil sensitivities to drive existing parallel imaging techniques. As a proof of concept, the quadratic phase was applied by introducing an offset to the x(2) - y(2) shim and the data were reconstructed using adapted versions of the image space-based sensitivity encoding and GeneRalized Autocalibrating Partially Parallel Acquisitions algorithms. The method is demonstrated in a phantom (1 × 2, 1 × 3, and 2 × 2 acceleration) and in vivo (2 × 2 acceleration) using a 3D gradient echo acquisition. Phase scrambling can be used to perform parallel imaging acceleration without acquisition of separate coil calibration data, demonstrated here for a 3D-Cartesian trajectory. Further research is required to prove the applicability to other 2D and 3D sampling schemes. © 2014 Wiley Periodicals, Inc.

Massively Parallel QCD

International Nuclear Information System (INIS)

Soltz, R; Vranas, P; Blumrich, M; Chen, D; Gara, A; Giampap, M; Heidelberger, P; Salapura, V; Sexton, J; Bhanot, G

2007-01-01

The theory of the strong nuclear force, Quantum Chromodynamics (QCD), can be numerically simulated from first principles on massively-parallel supercomputers using the method of Lattice Gauge Theory. We describe the special programming requirements of lattice QCD (LQCD) as well as the optimal supercomputer hardware architectures that it suggests. We demonstrate these methods on the BlueGene massively-parallel supercomputer and argue that LQCD and the BlueGene architecture are a natural match. This can be traced to the simple fact that LQCD is a regular lattice discretization of space into lattice sites while the BlueGene supercomputer is a discretization of space into compute nodes, and that both are constrained by requirements of locality. This simple relation is both technologically important and theoretically intriguing. The main result of this paper is the speedup of LQCD using up to 131,072 CPUs on the largest BlueGene/L supercomputer. The speedup is perfect with sustained performance of about 20% of peak. This corresponds to a maximum of 70.5 sustained TFlop/s. At these speeds LQCD and BlueGene are poised to produce the next generation of strong interaction physics theoretical results

K.I.S.S. Parallel Coding (lecture 2)

CERN Multimedia

CERN. Geneva

2018-01-01

K.I.S.S.ing parallel computing means, finally, loving it. Parallel computing will be approached in a theoretical and experimental way, using the most advanced and used C API: OpenMP. OpenMP is an open source project constantly developed and updated to hide the awful complexity of parallel coding in an awesome interface. The result is a tool which leaves plenty of space for clever solutions and terrific results in terms of efficiency and performance maximisation.

Flow and heat transfer in parallel channel attached with equally-spaced ribs, 2

International Nuclear Information System (INIS)

Kunugi, Tomoaki; Takizuka, Takakazu

1980-09-01

Using a computer code for the analysis of the flow and heat transfer in a parallel channel attached with equally-spaced ribs, calculations are performed when a pitch to rib-width ratio is 7 : 1, a rib-width to rib-height ratio is 2 : 1 and a channel-height to rib-height is 3 : 1. Assuming that the fluid properties and the heat-flux at the wall of this channel are constant, characteristics of the flow and heat transfer are analyzed in the range of Reynolds number from 10 to 250. The following results are obtained: (1) The separation region behind a rib grows downstream with the increase of Reynolds number. (2) The pressure drop of ribbed channel is greater than that of the smooth channel, and increases as Reynolds number increases. (3) The mean Nusselt number of ribbed channel is about 10 - 11 at the upper wall and about 7.5 at the lower wall in the range of Reynolds number from 10 to 250. (author)

Comparison study on flexible pavement design using FAA (Federal Aviation Administration) and LCN (Load Classification Number) code in Ahmad Yani international airport’s runway

Science.gov (United States)

Santoso, S. E.; Sulistiono, D.; Mawardi, A. F.

2017-11-01

FAA code for airport design has been broadly used by Indonesian Ministry of Aviation since decades ago. However, there is not much comprehensive study about its relevance and efficiency towards current situation in Indonesia. Therefore, a further comparison study on flexible pavement design for airport runway using comparable method has become essential. The main focus of this study is to compare which method between FAA and LCN that offer the most efficient and effective way in runway pavement planning. The comparative methods in this study mainly use the variety of variable approach. FAA code for instance, will use the approach on the aircraft’s maximum take-off weight and annual departure. Whilst LCN code use the variable of equivalent single wheel load and tire pressure. Based on the variables mentioned above, a further classification and rated method will be used to determine which code is best implemented. According to the analysis, it is clear that FAA method is the most effective way to plan runway design in Indonesia with consecutively total pavement thickness of 127cm and LCN method total pavement thickness of 70cm. Although, FAA total pavement is thicker that LCN its relevance towards sustainable and pristine condition in the future has become an essential aspect to consider in design and planning.

Thermally optimum spacing of vertical, natural convection cooled, parallel plates

Science.gov (United States)

Bar-Cohen, A.; Rohsenow, W. M.

Vertical two-dimensional channels formed by parallel plates or fins are a frequently encountered configuration in natural convection cooling in air of electronic equipment. In connection with the complexity of heat dissipation in vertical parallel plate arrays, little theoretical effort is devoted to thermal optimization of the relevant packaging configurations. The present investigation is concerned with the establishment of an analytical structure for analyses of such arrays, giving attention to useful relations for heat distribution patterns. The limiting relations for fully-developed laminar flow, in a symmetric isothermal or isoflux channel as well as in a channel with an insulated wall, are derived by use of a straightforward integral formulation.

Next stop: space

CERN Multimedia

Paola Catapano

2010-01-01

At 6:30 a.m. on 25 August, the runway at Geneva International Airport was more crowded than usual, as dozens of airport staff and a few CERN personnel gathered as close as possible to watch the landing of one of the world's largest aircraft, a USAF (US Air Force) C5 Super Galaxy. Having left Afghanistan (where it transported provisions for the US military contingent) the day before, it had spent a few hours at a US military base in Iraq before finally landing in Geneva on a very special mission: to load AMS-02, the Alpha Magnetic Spectrometer, into its huge cargo bay.   On 25 August, after an 11 hour-long flight, the US Air Force C-5 Galaxy carrying the Alpha Magnetic Spectrometer (AMS-02) experiment landed at the Kennedy Space Centre (KSC) in Florida, US. Weighing 7.5 tonnes and measuring 5 by 4 by 3 metres, AMS-02 is one of the most complex scientific instruments ever built for space. The experiment, assembled and tested at CERN, uses particle physics technologies but smaller and lighter (by pa...

NonLinear Parallel OPtimization Tool, Phase II

Data.gov (United States)

National Aeronautics and Space Administration — The technological advancement proposed is a novel large-scale Noninear Parallel OPtimization Tool (NLPAROPT). This software package will eliminate the computational...

Parallel optoelectronic trinary signed-digit division

Science.gov (United States)

Alam, Mohammad S.

1999-03-01

The trinary signed-digit (TSD) number system has been found to be very useful for parallel addition and subtraction of any arbitrary length operands in constant time. Using the TSD addition and multiplication modules as the basic building blocks, we develop an efficient algorithm for performing parallel TSD division in constant time. The proposed division technique uses one TSD subtraction and two TSD multiplication steps. An optoelectronic correlator based architecture is suggested for implementation of the proposed TSD division algorithm, which fully exploits the parallelism and high processing speed of optics. An efficient spatial encoding scheme is used to ensure better utilization of space bandwidth product of the spatial light modulators used in the optoelectronic implementation.

Parallel translation in warped product spaces: application to the Reissner-Nordstroem spacetime

International Nuclear Information System (INIS)

Raposo, A P; Del Riego, L

2005-01-01

A formal treatment of the parallel translation transformations in warped product manifolds is presented and related to those parallel translation transformations in each of the factor manifolds. A straightforward application to the Schwarzschild and Reissner-Nordstroem geometries, considered here as particular examples, explains some apparently surprising properties of the holonomy in these manifolds

Automatic parallelization of while-Loops using speculative execution

International Nuclear Information System (INIS)

Collard, J.F.

1995-01-01

Automatic parallelization of imperative sequential programs has focused on nests of for-loops. The most recent of them consist in finding an affine mapping with respect to the loop indices to simultaneously capture the temporal and spatial properties of the parallelized program. Such a mapping is usually called a open-quotes space-time transformation.close quotes This work describes an extension of these techniques to while-loops using speculative execution. We show that space-time transformations are a good framework for summing up previous restructuration techniques of while-loop, such as pipelining. Moreover, we show that these transformations can be derived and applied automatically

Kinematics analysis and simulation of a new underactuated parallel robot

Directory of Open Access Journals (Sweden)

Wenxu YAN

2017-04-01

Full Text Available The number of degrees of freedom is equal to the number of the traditional robot driving motors, which causes defects such as low efficiency. To overcome that problem, based on the traditional parallel robot, a new underactuated parallel robot is presented. The structure characteristics and working principles of the underactuated parallel robot are analyzed. The forward and inverse solutions are derived by way of space analytic geometry and vector algebra. The kinematics model is established, and MATLAB is implied to verify the accuracy of forward and inverse solutions and identify the optimal work space. The simulation results show that the robot can realize the function of robot switch with three or four degrees of freedom when the number of driving motors is three, improving the efficiency of robot grasping, with the characteristics of large working space, high speed operation, high positioning accuracy, low manufacturing cost and so on, and it will have a wide range of industrial applications.

Parallel field line and stream line tracing algorithms for space physics applications

Science.gov (United States)

Toth, G.; de Zeeuw, D.; Monostori, G.

2004-05-01

Field line and stream line tracing is required in various space physics applications, such as the coupling of the global magnetosphere and inner magnetosphere models, the coupling of the solar energetic particle and heliosphere models, or the modeling of comets, where the multispecies chemical equations are solved along stream lines of a steady state solution obtained with single fluid MHD model. Tracing a vector field is an inherently serial process, which is difficult to parallelize. This is especially true when the data corresponding to the vector field is distributed over a large number of processors. We designed algorithms for the various applications, which scale well to a large number of processors. In the first algorithm the computational domain is divided into blocks. Each block is on a single processor. The algorithm folows the vector field inside the blocks, and calculates a mapping of the block surfaces. The blocks communicate the values at the coinciding surfaces, and the results are interpolated. Finally all block surfaces are defined and values inside the blocks are obtained. In the second algorithm all processors start integrating along the vector field inside the accessible volume. When the field line leaves the local subdomain, the position and other information is stored in a buffer. Periodically the processors exchange the buffers, and continue integration of the field lines until they reach a boundary. At that point the results are sent back to the originating processor. Efficiency is achieved by a careful phasing of computation and communication. In the third algorithm the results of a steady state simulation are stored on a hard drive. The vector field is contained in blocks. All processors read in all the grid and vector field data and the stream lines are integrated in parallel. If a stream line enters a block, which has already been integrated, the results can be interpolated. By a clever ordering of the blocks the execution speed can be

Harmonic resonance assessment of multiple paralleled grid-connected inverters system

DEFF Research Database (Denmark)

Wang, Yanbo; Wang, Xiongfei; Blaabjerg, Frede

2017-01-01

This paper presents an eigenvalue-based impedance stability analytical method of multiple paralleled grid-connected inverter system. Different from the conventional impedance-based stability criterion, this work first built the state-space model of paralleled grid-connected inverters. On the basis...... of this, a bridge between the state-space-based modelling and impedance-based stability criterion is presented. The proposed method is able to perform stability assessment locally at the connection points of the component. Meanwhile, the eigenvalue-based sensitivity analysis is adopted to identify...

Parallel family trees for transfer matrices in the Potts model

Science.gov (United States)

Navarro, Cristobal A.; Canfora, Fabrizio; Hitschfeld, Nancy; Navarro, Gonzalo

2015-02-01

The computational cost of transfer matrix methods for the Potts model is related to the question in how many ways can two layers of a lattice be connected? Answering the question leads to the generation of a combinatorial set of lattice configurations. This set defines the configuration space of the problem, and the smaller it is, the faster the transfer matrix can be computed. The configuration space of generic (q , v) transfer matrix methods for strips is in the order of the Catalan numbers, which grows asymptotically as O(4m) where m is the width of the strip. Other transfer matrix methods with a smaller configuration space indeed exist but they make assumptions on the temperature, number of spin states, or restrict the structure of the lattice. In this paper we propose a parallel algorithm that uses a sub-Catalan configuration space of O(3m) to build the generic (q , v) transfer matrix in a compressed form. The improvement is achieved by grouping the original set of Catalan configurations into a forest of family trees, in such a way that the solution to the problem is now computed by solving the root node of each family. As a result, the algorithm becomes exponentially faster than the Catalan approach while still highly parallel. The resulting matrix is stored in a compressed form using O(3m ×4m) of space, making numerical evaluation and decompression to be faster than evaluating the matrix in its O(4m ×4m) uncompressed form. Experimental results for different sizes of strip lattices show that the parallel family trees (PFT) strategy indeed runs exponentially faster than the Catalan Parallel Method (CPM), especially when dealing with dense transfer matrices. In terms of parallel performance, we report strong-scaling speedups of up to 5.7 × when running on an 8-core shared memory machine and 28 × for a 32-core cluster. The best balance of speedup and efficiency for the multi-core machine was achieved when using p = 4 processors, while for the cluster

Circuit and bond polytopes on series–parallel graphs

OpenAIRE

Borne , Sylvie; Fouilhoux , Pierre; Grappe , Roland; Lacroix , Mathieu; Pesneau , Pierre

2015-01-01

International audience; In this paper, we describe the circuit polytope on series–parallel graphs. We first show the existence of a compact extended formulation. Though not being explicit, its construction process helps us to inductively provide the description in the original space. As a consequence, using the link between bonds and circuits in planar graphs, we also describe the bond polytope on series–parallel graphs.

Many-Body Mean-Field Equations: Parallel implementation

International Nuclear Information System (INIS)

Vallieres, M.; Umar, S.; Chinn, C.; Strayer, M.

1993-01-01

We describe the implementation of Hartree-Fock Many-Body Mean-Field Equations on a Parallel Intel iPSC/860 hypercube. We first discuss the Nuclear Mean-Field approach in physical terms. Then we describe our parallel implementation of this approach on the Intel iPSC/860 hypercube. We discuss and compare the advantages and disadvantages of the domain partition versus the Hilbert space partition for this problem. We conclude by discussing some timing experiments on various computing platforms

State-space Generalized Predicitve Control for redundant parallel robots

Czech Academy of Sciences Publication Activity Database

Belda, Květoslav; Böhm, Josef; Valášek, M.

2003-01-01

Roč. 31, č. 3 (2003), s. 413-432 ISSN 1539-7734 R&D Projects: GA ČR GA101/03/0620 Grant - others:CTU(CZ) 0204512 Institutional research plan: CEZ:AV0Z1075907 Keywords : parallel robot construction * generalized predictive control * drive redundancy Subject RIV: BC - Control Systems Theory http://library.utia.cas.cz/separaty/historie/belda-0411126.pdf

Building a parallel file system simulator

International Nuclear Information System (INIS)

Molina-Estolano, E; Maltzahn, C; Brandt, S A; Bent, J

2009-01-01

Parallel file systems are gaining in popularity in high-end computing centers as well as commercial data centers. High-end computing systems are expected to scale exponentially and to pose new challenges to their storage scalability in terms of cost and power. To address these challenges scientists and file system designers will need a thorough understanding of the design space of parallel file systems. Yet there exist few systematic studies of parallel file system behavior at petabyte- and exabyte scale. An important reason is the significant cost of getting access to large-scale hardware to test parallel file systems. To contribute to this understanding we are building a parallel file system simulator that can simulate parallel file systems at very large scale. Our goal is to simulate petabyte-scale parallel file systems on a small cluster or even a single machine in reasonable time and fidelity. With this simulator, file system experts will be able to tune existing file systems for specific workloads, scientists and file system deployment engineers will be able to better communicate workload requirements, file system designers and researchers will be able to try out design alternatives and innovations at scale, and instructors will be able to study very large-scale parallel file system behavior in the class room. In this paper we describe our approach and provide preliminary results that are encouraging both in terms of fidelity and simulation scalability.

Generalized Philosophy of Alerting with Applications for Parallel Approach Collision Prevention

Science.gov (United States)

Winder, Lee F.; Kuchar, James K.

2000-01-01

The goal of the research was to develop formal guidelines for the design of hazard avoidance systems. An alerting system is automation designed to reduce the likelihood of undesirable outcomes that are due to rare failures in a human-controlled system. It accomplishes this by monitoring the system, and issuing warning messages to the human operators when thought necessary to head off a problem. On examination of existing and recently proposed logics for alerting it appears that few commonly accepted principles guide the design process. Different logics intended to address the same hazards may take disparate forms and emphasize different aspects of performance, because each reflects the intuitive priorities of a different designer. Because performance must be satisfactory to all users of an alerting system (implying a universal meaning of acceptable performance) and not just one designer, a proposed logic often undergoes significant piecemeal modification before gamma general acceptance. This report is an initial attempt to clarify the common performance goals by which an alerting system is ultimately judged. A better understanding of these goals will hopefully allow designers to reach the final logic in a quicker, more direct and repeatable manner. As a case study, this report compares three alerting logics for collision prevention during independent approaches to parallel runways, and outlines a fourth alternative incorporating elements of the first three, but satisfying stated requirements. Three existing logics for parallel approach alerting are described. Each follows from different intuitive principles. The logics are presented as examples of three "philosophies" of alerting system design.

Hydroelastic response of a floating runway to cnoidal waves

International Nuclear Information System (INIS)

Ertekin, R. C.; Xia, Dingwu

2014-01-01

The hydroelastic response of mat-type Very Large Floating Structures (VLFSs) to severe sea conditions, such as tsunamis and hurricanes, must be assessed for safety and survivability. An efficient and robust nonlinear hydroelastic model is required to predict accurately the motion of and the dynamic loads on a VLFS due to such large waves. We develop a nonlinear theory to predict the hydroelastic response of a VLFS in the presence of cnoidal waves and compare the predictions with the linear theory that is also developed here. This hydroelastic problem is formulated by directly coupling the structure with the fluid, by use of the Level I Green-Naghdi theory for the fluid motion and the Kirchhoff thin plate theory for the runway. The coupled fluid structure system, together with the appropriate jump conditions are solved in two-dimensions by the finite-difference method. The numerical model is used to study the nonlinear response of a VLFS to storm waves which are modeled by use of the cnoidal-wave theory. Parametric studies show that the nonlinearity of the waves is very important in accurately predicting the dynamic bending moment and wave run-up on a VLFS in high seas

Hydroelastic response of a floating runway to cnoidal waves

Energy Technology Data Exchange (ETDEWEB)

Ertekin, R. C., E-mail: ertekin@hawaii.edu [Department of Ocean and Resources Engineering, University of Hawaii at Manoa, Honolulu, Hawaii 96822 (United States); Xia, Dingwu [Engineering Services, British Petroleum GoM, Houston, Texas 77079 (United States)

2014-02-15

The hydroelastic response of mat-type Very Large Floating Structures (VLFSs) to severe sea conditions, such as tsunamis and hurricanes, must be assessed for safety and survivability. An efficient and robust nonlinear hydroelastic model is required to predict accurately the motion of and the dynamic loads on a VLFS due to such large waves. We develop a nonlinear theory to predict the hydroelastic response of a VLFS in the presence of cnoidal waves and compare the predictions with the linear theory that is also developed here. This hydroelastic problem is formulated by directly coupling the structure with the fluid, by use of the Level I Green-Naghdi theory for the fluid motion and the Kirchhoff thin plate theory for the runway. The coupled fluid structure system, together with the appropriate jump conditions are solved in two-dimensions by the finite-difference method. The numerical model is used to study the nonlinear response of a VLFS to storm waves which are modeled by use of the cnoidal-wave theory. Parametric studies show that the nonlinearity of the waves is very important in accurately predicting the dynamic bending moment and wave run-up on a VLFS in high seas.

Parallel Nonlinear Optimization for Astrodynamic Navigation, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — CU Aerospace proposes the development of a new parallel nonlinear program (NLP) solver software package. NLPs allow the solution of complex optimization problems,...

Comparison of phase-constrained parallel MRI approaches: Analogies and differences.

Science.gov (United States)

Blaimer, Martin; Heim, Marius; Neumann, Daniel; Jakob, Peter M; Kannengiesser, Stephan; Breuer, Felix A

2016-03-01

Phase-constrained parallel MRI approaches have the potential for significantly improving the image quality of accelerated MRI scans. The purpose of this study was to investigate the properties of two different phase-constrained parallel MRI formulations, namely the standard phase-constrained approach and the virtual conjugate coil (VCC) concept utilizing conjugate k-space symmetry. Both formulations were combined with image-domain algorithms (SENSE) and a mathematical analysis was performed. Furthermore, the VCC concept was combined with k-space algorithms (GRAPPA and ESPIRiT) for image reconstruction. In vivo experiments were conducted to illustrate analogies and differences between the individual methods. Furthermore, a simple method of improving the signal-to-noise ratio by modifying the sampling scheme was implemented. For SENSE, the VCC concept was mathematically equivalent to the standard phase-constrained formulation and therefore yielded identical results. In conjunction with k-space algorithms, the VCC concept provided more robust results when only a limited amount of calibration data were available. Additionally, VCC-GRAPPA reconstructed images provided spatial phase information with full resolution. Although both phase-constrained parallel MRI formulations are very similar conceptually, there exist important differences between image-domain and k-space domain reconstructions regarding the calibration robustness and the availability of high-resolution phase information. © 2015 Wiley Periodicals, Inc.

Finding of No Significant Impact and Environmental Assessment for Flight Test to the Edge of Space

Science.gov (United States)

2008-12-01

Runway 22 or on Rogers Dry Lakebed at Edwards AFB. 17 On the basis of the findings of the Environmental Assessment, no significant impact to human...FLIGHT TEST CENTER Environmental Assessment for Flight Test to the Edge of Space Page 5-3 Bowles, A.E., S. Eckert, L . Starke, E. Berg, L . Wolski, and...Numbers. Anne Choate, Laura 20 Pederson , Jeremy Scharfenberg, Henry Farland. Washington, D.C. September. 21 Jeppesen Sanderson, Incorporated 22

Comparative eye-tracking evaluation of scatterplots and parallel coordinates

Directory of Open Access Journals (Sweden)

Rudolf Netzel

2017-06-01

Full Text Available We investigate task performance and reading characteristics for scatterplots (Cartesian coordinates and parallel coordinates. In a controlled eye-tracking study, we asked 24 participants to assess the relative distance of points in multidimensional space, depending on the diagram type (parallel coordinates or a horizontal collection of scatterplots, the number of data dimensions (2, 4, 6, or 8, and the relative distance between points (15%, 20%, or 25%. For a given reference point and two target points, we instructed participants to choose the target point that was closer to the reference point in multidimensional space. We present a visual scanning model that describes different strategies to solve this retrieval task for both diagram types, and propose corresponding hypotheses that we test using task completion time, accuracy, and gaze positions as dependent variables. Our results show that scatterplots outperform parallel coordinates significantly in 2 dimensions, however, the task was solved more quickly and more accurately with parallel coordinates in 8 dimensions. The eye-tracking data further shows significant differences between Cartesian and parallel coordinates, as well as between different numbers of dimensions. For parallel coordinates, there is a clear trend toward shorter fixations and longer saccades with increasing number of dimensions. Using an area-of-interest (AOI based approach, we identify different reading strategies for each diagram type: For parallel coordinates, the participants’ gaze frequently jumped back and forth between pairs of axes, while axes were rarely focused on when viewing Cartesian coordinates. We further found that participants’ attention is biased: toward the center of the whole plotfor parallel coordinates and skewed to the center/left side for Cartesian coordinates. We anticipate that these results may support the design of more effective visualizations for multidimensional data.

Visual Interfaces for Parallel Simulations (VIPS), Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Configuring the 3D geometry and physics of large scale parallel physics simulations is increasingly complex. Given the investment in time and effort to run these...

A PARALLEL EXTENSION OF THE UAL ENVIRONMENT

International Nuclear Information System (INIS)

MALITSKY, N.; SHISHLO, A.

2001-01-01

The deployment of the Unified Accelerator Library (UAL) environment on the parallel cluster is presented. The approach is based on the Message-Passing Interface (MPI) library and the Perl adapter that allows one to control and mix together the existing conventional UAL components with the new MPI-based parallel extensions. In the paper, we provide timing results and describe the application of the new environment to the SNS Ring complex beam dynamics studies, particularly, simulations of several physical effects, such as space charge, field errors, fringe fields, and others

Combinatorics of spreads and parallelisms

CERN Document Server

Johnson, Norman

2010-01-01

Partitions of Vector Spaces Quasi-Subgeometry Partitions Finite Focal-SpreadsGeneralizing André SpreadsThe Going Up Construction for Focal-SpreadsSubgeometry Partitions Subgeometry and Quasi-Subgeometry Partitions Subgeometries from Focal-SpreadsExtended André SubgeometriesKantor's Flag-Transitive DesignsMaximal Additive Partial SpreadsSubplane Covered Nets and Baer Groups Partial Desarguesian t-Parallelisms Direct Products of Affine PlanesJha-Johnson SL(2,

Micro-calibration of space and motion by photoreceptors synchronized in parallel with cortical oscillations: A unified theory of visual perception.

Science.gov (United States)

Jerath, Ravinder; Cearley, Shannon M; Barnes, Vernon A; Jensen, Mike

2018-01-01

A fundamental function of the visual system is detecting motion, yet visual perception is poorly understood. Current research has determined that the retina and ganglion cells elicit responses for motion detection; however, the underlying mechanism for this is incompletely understood. Previously we proposed that retinogeniculo-cortical oscillations and photoreceptors work in parallel to process vision. Here we propose that motion could also be processed within the retina, and not in the brain as current theory suggests. In this paper, we discuss: 1) internal neural space formation; 2) primary, secondary, and tertiary roles of vision; 3) gamma as the secondary role; and 4) synchronization and coherence. Movement within the external field is instantly detected by primary processing within the space formed by the retina, providing a unified view of the world from an internal point of view. Our new theory begins to answer questions about: 1) perception of space, erect images, and motion, 2) purpose of lateral inhibition, 3) speed of visual perception, and 4) how peripheral color vision occurs without a large population of cones located peripherally in the retina. We explain that strong oscillatory activity influences on brain activity and is necessary for: 1) visual processing, and 2) formation of the internal visuospatial area necessary for visual consciousness, which could allow rods to receive precise visual and visuospatial information, while retinal waves could link the lateral geniculate body with the cortex to form a neural space formed by membrane potential-based oscillations and photoreceptors. We propose that vision is tripartite, with three components that allow a person to make sense of the world, terming them "primary, secondary, and tertiary roles" of vision. Finally, we propose that Gamma waves that are higher in strength and volume allow communication among the retina, thalamus, and various areas of the cortex, and synchronization brings cortical

Rescue and Fire Fighting on RWY 06R/24L

Directory of Open Access Journals (Sweden)

Kristýna Vaňková

2016-04-01

Full Text Available Rescue and firefighting service is an important and essential part at the Václav Havel Airport Prague and it has to follow the requirements stated in Commission regulations (EU, regulations and laws of Czech Republic. Construction of parallel runway 06R/24L influences runway and taxiway system significantly. Consequences of these construction changes are changes of access routes and new places of potential interventions originates. Safety risks of inaccessible areas at the airport and inability to follow response time come with operations of the new runway. These risks are assessed and mitigated if necessary.

Contrasting safety assessments of a runway incursion scenario: Event sequence analysis versus multi-agent dynamic risk modelling

International Nuclear Information System (INIS)

Stroeve, Sybert H.; Blom, Henk A.P.; Bakker, G.J.

2013-01-01

In the safety literature it has been argued, that in a complex socio-technical system safety cannot be well analysed by event sequence based approaches, but requires to capture the complex interactions and performance variability of the socio-technical system. In order to evaluate the quantitative and practical consequences of these arguments, this study compares two approaches to assess accident risk of an example safety critical sociotechnical system. It contrasts an event sequence based assessment with a multi-agent dynamic risk model (MA-DRM) based assessment, both of which are performed for a particular runway incursion scenario. The event sequence analysis uses the well-known event tree modelling formalism and the MA-DRM based approach combines agent based modelling, hybrid Petri nets and rare event Monte Carlo simulation. The comparison addresses qualitative and quantitative differences in the methods, attained risk levels, and in the prime factors influencing the safety of the operation. The assessments show considerable differences in the accident risk implications of the performance of human operators and technical systems in the runway incursion scenario. In contrast with the event sequence based results, the MA-DRM based results show that the accident risk is not manifest from the performance of and relations between individual human operators and technical systems. Instead, the safety risk emerges from the totality of the performance and interactions in the agent based model of the safety critical operation considered, which coincides very well with the argumentation in the safety literature.

Options for Parallelizing a Planning and Scheduling Algorithm

Science.gov (United States)

Clement, Bradley J.; Estlin, Tara A.; Bornstein, Benjamin D.

2011-01-01

Space missions have a growing interest in putting multi-core processors onboard spacecraft. For many missions processing power significantly slows operations. We investigate how continual planning and scheduling algorithms can exploit multi-core processing and outline different potential design decisions for a parallelized planning architecture. This organization of choices and challenges helps us with an initial design for parallelizing the CASPER planning system for a mesh multi-core processor. This work extends that presented at another workshop with some preliminary results.

Final Environmental Assessment for the Proposed Runway 17-35 Closure at Albuquerque International Sunport, Albuquerque, New Mexico

Science.gov (United States)

2011-10-01

34’ ------------------- .... ___ -------------·····-------- --·-----------·---- D-28 U.S. SIEVE OPENING IN INCHES I U.S. SIEVE NUMBERS I HYDROMETER 6 4 3 2 1.5 1 3/4 112...Runway 17-35 Closure Location: Albuquerque International Sunport Number: 1-90703 D-29 U.S. SIEVE OPENING IN INCHES I U.S. SIEVE NUMBERS I HYDROMETER 6...Location: Albuquerque International Sunport ~ (!) Number: 1-90703 ~ D-30 U.S. SIEVE OPENING IN INCHES I U.S. SIEVE NUMBERS I HYDROMETER 6 4 3 2 1.5 1

Fundamental Parallel Algorithms for Private-Cache Chip Multiprocessors

DEFF Research Database (Denmark)

Arge, Lars Allan; Goodrich, Michael T.; Nelson, Michael

2008-01-01

about the way cores are interconnected, for we assume that all inter-processor communication occurs through the memory hierarchy. We study several fundamental problems, including prefix sums, selection, and sorting, which often form the building blocks of other parallel algorithms. Indeed, we present...... two sorting algorithms, a distribution sort and a mergesort. Our algorithms are asymptotically optimal in terms of parallel cache accesses and space complexity under reasonable assumptions about the relationships between the number of processors, the size of memory, and the size of cache blocks....... In addition, we study sorting lower bounds in a computational model, which we call the parallel external-memory (PEM) model, that formalizes the essential properties of our algorithms for private-cache CMPs....

Improving parallel imaging by jointly reconstructing multi-contrast data.

Science.gov (United States)

Bilgic, Berkin; Kim, Tae Hyung; Liao, Congyu; Manhard, Mary Kate; Wald, Lawrence L; Haldar, Justin P; Setsompop, Kawin

2018-08-01

To develop parallel imaging techniques that simultaneously exploit coil sensitivity encoding, image phase prior information, similarities across multiple images, and complementary k-space sampling for highly accelerated data acquisition. We introduce joint virtual coil (JVC)-generalized autocalibrating partially parallel acquisitions (GRAPPA) to jointly reconstruct data acquired with different contrast preparations, and show its application in 2D, 3D, and simultaneous multi-slice (SMS) acquisitions. We extend the joint parallel imaging concept to exploit limited support and smooth phase constraints through Joint (J-) LORAKS formulation. J-LORAKS allows joint parallel imaging from limited autocalibration signal region, as well as permitting partial Fourier sampling and calibrationless reconstruction. We demonstrate highly accelerated 2D balanced steady-state free precession with phase cycling, SMS multi-echo spin echo, 3D multi-echo magnetization-prepared rapid gradient echo, and multi-echo gradient recalled echo acquisitions in vivo. Compared to conventional GRAPPA, proposed joint acquisition/reconstruction techniques provide more than 2-fold reduction in reconstruction error. JVC-GRAPPA takes advantage of additional spatial encoding from phase information and image similarity, and employs different sampling patterns across acquisitions. J-LORAKS achieves a more parsimonious low-rank representation of local k-space by considering multiple images as additional coils. Both approaches provide dramatic improvement in artifact and noise mitigation over conventional single-contrast parallel imaging reconstruction. Magn Reson Med 80:619-632, 2018. © 2018 International Society for Magnetic Resonance in Medicine. © 2018 International Society for Magnetic Resonance in Medicine.

Parallel 3-D method of characteristics in MPACT

International Nuclear Information System (INIS)

Kochunas, B.; Dovvnar, T. J.; Liu, Z.

2013-01-01

A new parallel 3-D MOC kernel has been developed and implemented in MPACT which makes use of the modular ray tracing technique to reduce computational requirements and to facilitate parallel decomposition. The parallel model makes use of both distributed and shared memory parallelism which are implemented with the MPI and OpenMP standards, respectively. The kernel is capable of parallel decomposition of problems in space, angle, and by characteristic rays up to 0(104) processors. Initial verification of the parallel 3-D MOC kernel was performed using the Takeda 3-D transport benchmark problems. The eigenvalues computed by MPACT are within the statistical uncertainty of the benchmark reference and agree well with the averages of other participants. The MPACT k eff differs from the benchmark results for rodded and un-rodded cases by 11 and -40 pcm, respectively. The calculations were performed for various numbers of processors and parallel decompositions up to 15625 processors; all producing the same result at convergence. The parallel efficiency of the worst case was 60%, while very good efficiency (>95%) was observed for cases using 500 processors. The overall run time for the 500 processor case was 231 seconds and 19 seconds for the case with 15625 processors. Ongoing work is focused on developing theoretical performance models and the implementation of acceleration techniques to minimize the number of iterations to converge. (authors)

Analysis of single blow effectiveness in non-uniform parallel plate regenerators

DEFF Research Database (Denmark)

Jensen, Jesper Buch; Bahl, Christian Robert Haffenden; Engelbrecht, Kurt

2011-01-01

Non-uniform distributions of plate spacings in parallel plate regenerators have been found to induce loss of performance. In this paper, it has been investigated how variations of three geometric parameters (the aspect ratio, the porosity, and the standard deviation of the plate spacing) affects...

The Perspective Structure of Visual Space

Science.gov (United States)

2015-01-01

Luneburg’s model has been the reference for experimental studies of visual space for almost seventy years. His claim for a curved visual space has been a source of inspiration for visual scientists as well as philosophers. The conclusion of many experimental studies has been that Luneburg’s model does not describe visual space in various tasks and conditions. Remarkably, no alternative model has been suggested. The current study explores perspective transformations of Euclidean space as a model for visual space. Computations show that the geometry of perspective spaces is considerably different from that of Euclidean space. Collinearity but not parallelism is preserved in perspective space and angles are not invariant under translation and rotation. Similar relationships have shown to be properties of visual space. Alley experiments performed early in the nineteenth century have been instrumental in hypothesizing curved visual spaces. Alleys were computed in perspective space and compared with reconstructed alleys of Blumenfeld. Parallel alleys were accurately described by perspective geometry. Accurate distance alleys were derived from parallel alleys by adjusting the interstimulus distances according to the size-distance invariance hypothesis. Agreement between computed and experimental alleys and accommodation of experimental results that rejected Luneburg’s model show that perspective space is an appropriate model for how we perceive orientations and angles. The model is also appropriate for perceived distance ratios between stimuli but fails to predict perceived distances. PMID:27648222

Environmental Assessment for Repair of Airfield Pavement and Lighting, Runway 03R/21L Travis Air Force Base, Fairfield, California. Revision

Science.gov (United States)

2009-12-01

substandard: 211450 SM PROJECT: Repair Runway 03R-21L pavements, airfield lighting, fiber optic communication lines , markers, and drainage systems...bottomed swales, or basalt flow depression pools in unplowed grasslands. The fairy shrimp has been collected from early December to early May. It can...pool types where the species has been found include Northern Hardpan, Northern Claypan, Northern Volcanic Mud Flow, and Northern Basalt Flow vernal

A DIRECT METHOD TO DETERMINE THE PARALLEL MEAN FREE PATH OF SOLAR ENERGETIC PARTICLES WITH ADIABATIC FOCUSING

International Nuclear Information System (INIS)

He, H.-Q.; Wan, W.

2012-01-01

The parallel mean free path of solar energetic particles (SEPs), which is determined by physical properties of SEPs as well as those of solar wind, is a very important parameter in space physics to study the transport of charged energetic particles in the heliosphere, especially for space weather forecasting. In space weather practice, it is necessary to find a quick approach to obtain the parallel mean free path of SEPs for a solar event. In addition, the adiabatic focusing effect caused by a spatially varying mean magnetic field in the solar system is important to the transport processes of SEPs. Recently, Shalchi presented an analytical description of the parallel diffusion coefficient with adiabatic focusing. Based on Shalchi's results, in this paper we provide a direct analytical formula as a function of parameters concerning the physical properties of SEPs and solar wind to directly and quickly determine the parallel mean free path of SEPs with adiabatic focusing. Since all of the quantities in the analytical formula can be directly observed by spacecraft, this direct method would be a very useful tool in space weather research. As applications of the direct method, we investigate the inherent relations between the parallel mean free path and various parameters concerning physical properties of SEPs and solar wind. Comparisons of parallel mean free paths with and without adiabatic focusing are also presented.

Design strategies for irregularly adapting parallel applications

International Nuclear Information System (INIS)

Oliker, Leonid; Biswas, Rupak; Shan, Hongzhang; Sing, Jaswinder Pal

2000-01-01

Achieving scalable performance for dynamic irregular applications is eminently challenging. Traditional message-passing approaches have been making steady progress towards this goal; however, they suffer from complex implementation requirements. The use of a global address space greatly simplifies the programming task, but can degrade the performance of dynamically adapting computations. In this work, we examine two major classes of adaptive applications, under five competing programming methodologies and four leading parallel architectures. Results indicate that it is possible to achieve message-passing performance using shared-memory programming techniques by carefully following the same high level strategies. Adaptive applications have computational work loads and communication patterns which change unpredictably at runtime, requiring dynamic load balancing to achieve scalable performance on parallel machines. Efficient parallel implementations of such adaptive applications are therefore a challenging task. This work examines the implementation of two typical adaptive applications, Dynamic Remeshing and N-Body, across various programming paradigms and architectural platforms. We compare several critical factors of the parallel code development, including performance, programmability, scalability, algorithmic development, and portability

Demonstration of an optoelectronic interconnect architecture for a parallel modified signed-digit adder and subtracter

Science.gov (United States)

Sun, Degui; Wang, Na-Xin; He, Li-Ming; Weng, Zhao-Heng; Wang, Daheng; Chen, Ray T.

1996-06-01

A space-position-logic-encoding scheme is proposed and demonstrated. This encoding scheme not only makes the best use of the convenience of binary logic operation, but is also suitable for the trinary property of modified signed- digit (MSD) numbers. Based on the space-position-logic-encoding scheme, a fully parallel modified signed-digit adder and subtractor is built using optoelectronic switch technologies in conjunction with fiber-multistage 3D optoelectronic interconnects. Thus an effective combination of a parallel algorithm and a parallel architecture is implemented. In addition, the performance of the optoelectronic switches used in this system is experimentally studied and verified. Both the 3-bit experimental model and the experimental results of a parallel addition and a parallel subtraction are provided and discussed. Finally, the speed ratio between the MSD adder and binary adders is discussed and the advantage of the MSD in operating speed is demonstrated.

Development of parallel Fokker-Planck code ALLAp

International Nuclear Information System (INIS)

Batishcheva, A.A.; Sigmar, D.J.; Koniges, A.E.

1996-01-01

We report on our ongoing development of the 3D Fokker-Planck code ALLA for a highly collisional scrape-off-layer (SOL) plasma. A SOL with strong gradients of density and temperature in the spatial dimension is modeled. Our method is based on a 3-D adaptive grid (in space, magnitude of the velocity, and cosine of the pitch angle) and a second order conservative scheme. Note that the grid size is typically 100 x 257 x 65 nodes. It was shown in our previous work that only these capabilities make it possible to benchmark a 3D code against a spatially-dependent self-similar solution of a kinetic equation with the Landau collision term. In the present work we show results of a more precise benchmarking against the exact solutions of the kinetic equation using a new parallel code ALLAp with an improved method of parallelization and a modified boundary condition at the plasma edge. We also report first results from the code parallelization using Message Passing Interface for a Massively Parallel CRI T3D platform. We evaluate the ALLAp code performance versus the number of T3D processors used and compare its efficiency against a Work/Data Sharing parallelization scheme and a workstation version

Parallel grid generation algorithm for distributed memory computers

Science.gov (United States)

Moitra, Stuti; Moitra, Anutosh

1994-01-01

A parallel grid-generation algorithm and its implementation on the Intel iPSC/860 computer are described. The grid-generation scheme is based on an algebraic formulation of homotopic relations. Methods for utilizing the inherent parallelism of the grid-generation scheme are described, and implementation of multiple levELs of parallelism on multiple instruction multiple data machines are indicated. The algorithm is capable of providing near orthogonality and spacing control at solid boundaries while requiring minimal interprocessor communications. Results obtained on the Intel hypercube for a blended wing-body configuration are used to demonstrate the effectiveness of the algorithm. Fortran implementations bAsed on the native programming model of the iPSC/860 computer and the Express system of software tools are reported. Computational gains in execution time speed-up ratios are given.

New algorithms for parallel MRI

International Nuclear Information System (INIS)

Anzengruber, S; Ramlau, R; Bauer, F; Leitao, A

2008-01-01

Magnetic Resonance Imaging with parallel data acquisition requires algorithms for reconstructing the patient's image from a small number of measured lines of the Fourier domain (k-space). In contrast to well-known algorithms like SENSE and GRAPPA and its flavors we consider the problem as a non-linear inverse problem. However, in order to avoid cost intensive derivatives we will use Landweber-Kaczmarz iteration and in order to improve the overall results some additional sparsity constraints.

Self-calibrated correlation imaging with k-space variant correlation functions.

Science.gov (United States)

Li, Yu; Edalati, Masoud; Du, Xingfu; Wang, Hui; Cao, Jie J

2018-03-01

Correlation imaging is a previously developed high-speed MRI framework that converts parallel imaging reconstruction into the estimate of correlation functions. The presented work aims to demonstrate this framework can provide a speed gain over parallel imaging by estimating k-space variant correlation functions. Because of Fourier encoding with gradients, outer k-space data contain higher spatial-frequency image components arising primarily from tissue boundaries. As a result of tissue-boundary sparsity in the human anatomy, neighboring k-space data correlation varies from the central to the outer k-space. By estimating k-space variant correlation functions with an iterative self-calibration method, correlation imaging can benefit from neighboring k-space data correlation associated with both coil sensitivity encoding and tissue-boundary sparsity, thereby providing a speed gain over parallel imaging that relies only on coil sensitivity encoding. This new approach is investigated in brain imaging and free-breathing neonatal cardiac imaging. Correlation imaging performs better than existing parallel imaging techniques in simulated brain imaging acceleration experiments. The higher speed enables real-time data acquisition for neonatal cardiac imaging in which physiological motion is fast and non-periodic. With k-space variant correlation functions, correlation imaging gives a higher speed than parallel imaging and offers the potential to image physiological motion in real-time. Magn Reson Med 79:1483-1494, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Short term prediction of the horizontal wind vector within a wake vortex warning system

Energy Technology Data Exchange (ETDEWEB)

Frech, M.; Holzaepfel, F.; Gerz, T. [DLR Deutsches Zentrum fuer Luft- und Raumfahrt e.V., Wessling (Germany). Inst. fuer Physik der Atmosphaere; Konopka, J. [Deutsche Flugsicherung (DFS) GmbH, Langen (Germany)

2000-07-14

A wake vortex warning system (WVWS) has been developed for Frankfurt airport. This airport has two parallel runways which are separated by 518 m, a distance too short to operate them independently because wake vortices may be advected to the adjacent runway. The objective of the WVWS is to enable operation with reduced separation between two aircraft approaching the parallel runways at appropriate wind conditions. The WVWS applies a statistical persistence model to predict the crosswind within a 20 minute period. One of the main problems identified in the old WVWS are discontinuities between successive forecasts. These forecast breakdowns were not acceptable to airtraffic controllers. At least part of the problem was related to the fact that the forecast was solely based on the prediction of crosswind. A new method is developed on the basis of 523 days of sonic anemometer measurements at Frankfurt airport. It is demonstrated that the prediction of the horizontal wind vector avoids these difficulties and significantly improves the system's performance. (orig.)

Codimension two Kaehler submanifolds of space forms

International Nuclear Information System (INIS)

Ferreira, M.J.; Tribuzy, R.

2001-03-01

In this article we study isometric immersions from Kaehler manifolds whose (1,1) part of the second fundamental form is parallel, the ppmc isometric immersions. When the domain is a Riemann surface these immersions are precisely those with parallel mean curvature. P. J. Ryan has classified the Kaehler manifolds that admit isometric immersions, as real hypersurfaces, in space forms. We classify the codimension two ppmc isometric immersions into space forms. (author)

Unpacking the cognitive map: the parallel map theory of hippocampal function.

Science.gov (United States)

Jacobs, Lucia F; Schenk, Françoise

2003-04-01

In the parallel map theory, the hippocampus encodes space with 2 mapping systems. The bearing map is constructed primarily in the dentate gyrus from directional cues such as stimulus gradients. The sketch map is constructed within the hippocampus proper from positional cues. The integrated map emerges when data from the bearing and sketch maps are combined. Because the component maps work in parallel, the impairment of one can reveal residual learning by the other. Such parallel function may explain paradoxes of spatial learning, such as learning after partial hippocampal lesions, taxonomic and sex differences in spatial learning, and the function of hippocampal neurogenesis. By integrating evidence from physiology to phylogeny, the parallel map theory offers a unified explanation for hippocampal function.

A parallel algorithm for 3D dislocation dynamics

International Nuclear Information System (INIS)

Wang Zhiqiang; Ghoniem, Nasr; Swaminarayan, Sriram; LeSar, Richard

2006-01-01

Dislocation dynamics (DD), a discrete dynamic simulation method in which dislocations are the fundamental entities, is a powerful tool for investigation of plasticity, deformation and fracture of materials at the micron length scale. However, severe computational difficulties arising from complex, long-range interactions between these curvilinear line defects limit the application of DD in the study of large-scale plastic deformation. We present here the development of a parallel algorithm for accelerated computer simulations of DD. By representing dislocations as a 3D set of dislocation particles, we show here that the problem of an interacting ensemble of dislocations can be converted to a problem of a particle ensemble, interacting with a long-range force field. A grid using binary space partitioning is constructed to keep track of node connectivity across domains. We demonstrate the computational efficiency of the parallel micro-plasticity code and discuss how O(N) methods map naturally onto the parallel data structure. Finally, we present results from applications of the parallel code to deformation in single crystal fcc metals

Briefing highlights space weather risks to GPS

Science.gov (United States)

Tretkoff, Ernie

2011-07-01

Solar storms, which are expected to increase as the Sun nears the most active phase of the solar cycle, can disrupt a variety of technologies on which society relies. Speakers at a 22 June briefing on Capitol Hill in Washington, D. C., focused on how space weather can affect the Global Positioning System (GPS), which is used in a wide range of industries, including commercial air travel, agriculture, national security, and emergency response. Rocky Stone, chief technical pilot for United Airlines, noted that GPS allows more aircraft to be in airspace, saves fuel, and helps aircraft move safely on runways. “Improvements in space weather forecasting need to be pursued,” he said. Precision GPS has also “changed the whole nature of farming,” said Ron Hatch, Director of Navigation Systems, NavCom Technology/John Deere. GPS makes it possible for tractors to be driven in the most efficient paths and for fertilizer and water to be applied precisely to the areas that most need them. Space weather-induced degradation of GPS signals can cause significant loss to farms that rely on GPS. Elizabeth Zimmerman, Deputy Associate Administrator for the Office of Response and Recovery at the Federal Emergency Management Agency (FEMA), described how FEMA relies on GPS for disaster recovery. The agency is developing an operations plan for dealing with space weather, she said.

A general exact method for synthesizing parallel-beam projections from cone-beam projections via filtered backprojection

International Nuclear Information System (INIS)

Li Liang; Chen Zhiqiang; Xing Yuxiang; Zhang Li; Kang Kejun; Wang Ge

2006-01-01

In recent years, image reconstruction methods for cone-beam computed tomography (CT) have been extensively studied. However, few of these studies discussed computing parallel-beam projections from cone-beam projections. In this paper, we focus on the exact synthesis of complete or incomplete parallel-beam projections from cone-beam projections. First, an extended central slice theorem is described to establish a relationship between the Radon space and the Fourier space. Then, data sufficiency conditions are proposed for computing parallel-beam projection data from cone-beam data. Using these results, a general filtered backprojection algorithm is formulated that can exactly synthesize parallel-beam projection data from cone-beam projection data. As an example, we prove that parallel-beam projections can be exactly synthesized in an angular range in the case of circular cone-beam scanning. Interestingly, this angular range is larger than that derived in the Feldkamp reconstruction framework. Numerical experiments are performed in the circular scanning case to verify our method

Parallel Programming with Intel Parallel Studio XE

CERN Document Server

Blair-Chappell , Stephen

2012-01-01

Optimize code for multi-core processors with Intel's Parallel Studio Parallel programming is rapidly becoming a "must-know" skill for developers. Yet, where to start? This teach-yourself tutorial is an ideal starting point for developers who already know Windows C and C++ and are eager to add parallelism to their code. With a focus on applying tools, techniques, and language extensions to implement parallelism, this essential resource teaches you how to write programs for multicore and leverage the power of multicore in your programs. Sharing hands-on case studies and real-world examples, the

A parallel orbital-updating based plane-wave basis method for electronic structure calculations

International Nuclear Information System (INIS)

Pan, Yan; Dai, Xiaoying; Gironcoli, Stefano de; Gong, Xin-Gao; Rignanese, Gian-Marco; Zhou, Aihui

2017-01-01

Highlights: • Propose three parallel orbital-updating based plane-wave basis methods for electronic structure calculations. • These new methods can avoid the generating of large scale eigenvalue problems and then reduce the computational cost. • These new methods allow for two-level parallelization which is particularly interesting for large scale parallelization. • Numerical experiments show that these new methods are reliable and efficient for large scale calculations on modern supercomputers. - Abstract: Motivated by the recently proposed parallel orbital-updating approach in real space method , we propose a parallel orbital-updating based plane-wave basis method for electronic structure calculations, for solving the corresponding eigenvalue problems. In addition, we propose two new modified parallel orbital-updating methods. Compared to the traditional plane-wave methods, our methods allow for two-level parallelization, which is particularly interesting for large scale parallelization. Numerical experiments show that these new methods are more reliable and efficient for large scale calculations on modern supercomputers.

Parallel electric fields in a simulation of magnetotail reconnection and plasmoid evolution

International Nuclear Information System (INIS)

Hesse, M.; Birn, J.

1990-01-01

Properties of the electric field component parallel to the magnetic field are investigate in a 3D MHD simulation of plasmoid formation and evolution in the magnetotail, in the presence of a net dawn-dusk magnetic field component. The spatial localization of E-parallel, and the concept of a diffusion zone and the role of E-parallel in accelerating electrons are discussed. A localization of the region of enhanced E-parallel in all space directions is found, with a strong concentration in the z direction. This region is identified as the diffusion zone, which plays a crucial role in reconnection theory through the local break-down of magnetic flux conservation. 12 refs

Parallel Breadth-First Search on Distributed Memory Systems

Energy Technology Data Exchange (ETDEWEB)

Computational Research Division; Buluc, Aydin; Madduri, Kamesh

2011-04-15

Data-intensive, graph-based computations are pervasive in several scientific applications, and are known to to be quite challenging to implement on distributed memory systems. In this work, we explore the design space of parallel algorithms for Breadth-First Search (BFS), a key subroutine in several graph algorithms. We present two highly-tuned par- allel approaches for BFS on large parallel systems: a level-synchronous strategy that relies on a simple vertex-based partitioning of the graph, and a two-dimensional sparse matrix- partitioning-based approach that mitigates parallel commu- nication overhead. For both approaches, we also present hybrid versions with intra-node multithreading. Our novel hybrid two-dimensional algorithm reduces communication times by up to a factor of 3.5, relative to a common vertex based approach. Our experimental study identifies execu- tion regimes in which these approaches will be competitive, and we demonstrate extremely high performance on lead- ing distributed-memory parallel systems. For instance, for a 40,000-core parallel execution on Hopper, an AMD Magny- Cours based system, we achieve a BFS performance rate of 17.8 billion edge visits per second on an undirected graph of 4.3 billion vertices and 68.7 billion edges with skewed degree distribution.

Analysis of gamma irradiator dose rate using spent fuel elements with parallel configuration

International Nuclear Information System (INIS)

Setiyanto; Pudjijanto MS; Ardani

2006-01-01

To enhance the utilization of the RSG-GAS reactor spent fuel, the gamma irradiator using spent fuel elements as a gamma source is a suitable choice. This irradiator can be used for food sterilization and preservation. The first step before realization, it is necessary to determine the gamma dose rate theoretically. The assessment was realized for parallel configuration fuel elements with the irradiation space can be placed between fuel element series. This analysis of parallel model was choice to compare with the circle model and as long as possible to get more space for irradiation and to do manipulation of irradiation target. Dose rate calculation were done with MCNP, while the estimation of gamma activities of fuel element was realized by OREGEN code with 1 year of average delay time. The calculation result show that the gamma dose rate of parallel model decreased up to 50% relatively compared with the circle model, but the value still enough for sterilization and preservation. Especially for food preservation, this parallel model give more flexible, while the gamma dose rate can be adjusted to the irradiation needed. The conclusion of this assessment showed that the utilization of reactor spent fuels for gamma irradiator with parallel model give more advantage the circle model. (author)

Modeling and Control of Primary Parallel Isolated Boost Converter

DEFF Research Database (Denmark)

Mira Albert, Maria del Carmen; Hernandez Botella, Juan Carlos; Sen, Gökhan

2012-01-01

In this paper state space modeling and closed loop controlled operation have been presented for primary parallel isolated boost converter (PPIBC) topology as a battery charging unit. Parasitic resistances have been included to have an accurate dynamic model. The accuracy of the model has been...

Badlands: A parallel basin and landscape dynamics model

Directory of Open Access Journals (Sweden)

T. Salles

2016-01-01

Full Text Available Over more than three decades, a number of numerical landscape evolution models (LEMs have been developed to study the combined effects of climate, sea-level, tectonics and sediments on Earth surface dynamics. Most of them are written in efficient programming languages, but often cannot be used on parallel architectures. Here, I present a LEM which ports a common core of accepted physical principles governing landscape evolution into a distributed memory parallel environment. Badlands (acronym for BAsin anD LANdscape DynamicS is an open-source, flexible, TIN-based landscape evolution model, built to simulate topography development at various space and time scales.

Numerical simulation of Vlasov equation with parallel tools

International Nuclear Information System (INIS)

Peyroux, J.

2005-11-01

This project aims to make even more powerful the resolution of Vlasov codes through the various parallelization tools (MPI, OpenMP...). A simplified test case served as a base for constructing the parallel codes for obtaining a data-processing skeleton which, thereafter, could be re-used for increasingly complex models (more than four variables of phase space). This will thus make it possible to treat more realistic situations linked, for example, to the injection of ultra short and ultra intense impulses in inertial fusion plasmas, or the study of the instability of trapped ions now taken as being responsible for the generation of turbulence in tokamak plasmas. (author)

Space Gerontology

Science.gov (United States)

Miquel, J. (Editor); Economos, A. C. (Editor)

1982-01-01

Presentations are given which address the effects of space flght on the older person, the parallels between the physiological responses to weightlessness and the aging process, and experimental possibilities afforded by the weightless environment to fundamental research in gerontology and geriatrics.

Marginal Assessment of Crowns by the Aid of Parallel Radiography

Directory of Open Access Journals (Sweden)

Farnaz Fattahi

2015-03-01

Full Text Available Introduction: Marginal adaptation is the most critical item in long-term prognosis of single crowns. This study aimed to assess the marginal quality as well asthe discrepancies in marginal integrity of some PFM single crowns of posterior teeth by employing parallel radiography in Shiraz Dental School, Shiraz, Iran. Methods: In this descriptive study, parallel radiographies were taken from 200 fabricated PFM single crowns of posterior teeth after cementation and before discharging the patient. To calculate the magnification of the images, a metallic sphere with the thickness of 4 mm was placed in the direction of the crown margin on the occlusal surface. Thereafter, the horizontal and vertical space between the crown margins, the margin of preparations and also the vertical space between the crown margin and the bone crest were measured by using digital radiological software. Results: Analysis of data by descriptive statistics revealed that 75.5% and 60% of the cases had more than the acceptable space (50µm in the vertical (130±20µm and horizontal (90±15µm dimensions, respectively. Moreover, 85% of patients were found to have either horizontal or vertical gap. In 77% of cases, the margins of crowns invaded the biologic width in the mesial and 70% in distal surfaces. Conclusion: Parallel radiography can be expedient in the stage of framework try-in to yield some important information that cannot be obtained by routine clinical evaluations and may improve the treatment prognosis

Behaviour of parallel girders stabilised with U-frames

DEFF Research Database (Denmark)

Virdi, Kuldeep; Azzi, Walid

2010-01-01

Lateral torsional buckling is a key factor in the design of steel girders. Stability can be enhanced by cross-bracing, reducing the effective length and thus increasing the ultimate capacity. U-frames are an option often used to brace the girders when designing through type of bridges and where...... overhead bracing is not practical. This paper investigates the effect of the U-frame spacing on the stability of the parallel girders. Eigenvalue buckling analysis was undertaken with four different spacings of the U-frames. Results were extracted from finite element analysis, interpreted and conclusions...

Numerical simulation of Vlasov equation with parallel tools; Simulations numeriques de l'equation de Vlasov a l'aide d'outils paralleles

Energy Technology Data Exchange (ETDEWEB)

Peyroux, J

2005-11-15

This project aims to make even more powerful the resolution of Vlasov codes through the various parallelization tools (MPI, OpenMP...). A simplified test case served as a base for constructing the parallel codes for obtaining a data-processing skeleton which, thereafter, could be re-used for increasingly complex models (more than four variables of phase space). This will thus make it possible to treat more realistic situations linked, for example, to the injection of ultra short and ultra intense impulses in inertial fusion plasmas, or the study of the instability of trapped ions now taken as being responsible for the generation of turbulence in tokamak plasmas. (author)

Advances in randomized parallel computing

CERN Document Server

Rajasekaran, Sanguthevar

1999-01-01

The technique of randomization has been employed to solve numerous prob­ lems of computing both sequentially and in parallel. Examples of randomized algorithms that are asymptotically better than their deterministic counterparts in solving various fundamental problems abound. Randomized algorithms have the advantages of simplicity and better performance both in theory and often in practice. This book is a collection of articles written by renowned experts in the area of randomized parallel computing. A brief introduction to randomized algorithms In the aflalysis of algorithms, at least three different measures of performance can be used: the best case, the worst case, and the average case. Often, the average case run time of an algorithm is much smaller than the worst case. 2 For instance, the worst case run time of Hoare's quicksort is O(n ), whereas its average case run time is only O( n log n). The average case analysis is conducted with an assumption on the input space. The assumption made to arrive at t...

Building Blocks for the Rapid Development of Parallel Simulations, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Scientists need to be able to quickly develop and run parallel simulations without paying the high price of writing low-level message passing codes using compiled...

Large amplitude parallel propagating electromagnetic oscillitons

International Nuclear Information System (INIS)

Cattaert, Tom; Verheest, Frank

2005-01-01

Earlier systematic nonlinear treatments of parallel propagating electromagnetic waves have been given within a fluid dynamic approach, in a frame where the nonlinear structures are stationary and various constraining first integrals can be obtained. This has lead to the concept of oscillitons that has found application in various space plasmas. The present paper differs in three main aspects from the previous studies: first, the invariants are derived in the plasma frame, as customary in the Sagdeev method, thus retaining in Maxwell's equations all possible effects. Second, a single differential equation is obtained for the parallel fluid velocity, in a form reminiscent of the Sagdeev integrals, hence allowing a fully nonlinear discussion of the oscilliton properties, at such amplitudes as the underlying Mach number restrictions allow. Third, the transition to weakly nonlinear whistler oscillitons is done in an analytical rather than a numerical fashion

A parallel 3D particle-in-cell code with dynamic load balancing

International Nuclear Information System (INIS)

Wolfheimer, Felix; Gjonaj, Erion; Weiland, Thomas

2006-01-01

A parallel 3D electrostatic Particle-In-Cell (PIC) code including an algorithm for modelling Space Charge Limited (SCL) emission [E. Gjonaj, T. Weiland, 3D-modeling of space-charge-limited electron emission. A charge conserving algorithm, Proceedings of the 11th Biennial IEEE Conference on Electromagnetic Field Computation, 2004] is presented. A domain decomposition technique based on orthogonal recursive bisection is used to parallelize the computation on a distributed memory environment of clustered workstations. For problems with a highly nonuniform and time dependent distribution of particles, e.g., bunch dynamics, a dynamic load balancing between the processes is needed to preserve the parallel performance. The algorithm for the detection of a load imbalance and the redistribution of the tasks among the processes is based on a weight function criterion, where the weight of a cell measures the computational load associated with it. The algorithm is studied with two examples. In the first example, multiple electron bunches as occurring in the S-DALINAC [A. Richter, Operational experience at the S-DALINAC, Proceedings of the Fifth European Particle Accelerator Conference, 1996] accelerator are simulated in the absence of space charge fields. In the second example, the SCL emission and electron trajectories in an electron gun are simulated

A parallel 3D particle-in-cell code with dynamic load balancing

Energy Technology Data Exchange (ETDEWEB)

Wolfheimer, Felix [Technische Universitaet Darmstadt, Institut fuer Theorie Elektromagnetischer Felder, Schlossgartenstr.8, 64283 Darmstadt (Germany)]. E-mail: wolfheimer@temf.de; Gjonaj, Erion [Technische Universitaet Darmstadt, Institut fuer Theorie Elektromagnetischer Felder, Schlossgartenstr.8, 64283 Darmstadt (Germany); Weiland, Thomas [Technische Universitaet Darmstadt, Institut fuer Theorie Elektromagnetischer Felder, Schlossgartenstr.8, 64283 Darmstadt (Germany)

2006-03-01

A parallel 3D electrostatic Particle-In-Cell (PIC) code including an algorithm for modelling Space Charge Limited (SCL) emission [E. Gjonaj, T. Weiland, 3D-modeling of space-charge-limited electron emission. A charge conserving algorithm, Proceedings of the 11th Biennial IEEE Conference on Electromagnetic Field Computation, 2004] is presented. A domain decomposition technique based on orthogonal recursive bisection is used to parallelize the computation on a distributed memory environment of clustered workstations. For problems with a highly nonuniform and time dependent distribution of particles, e.g., bunch dynamics, a dynamic load balancing between the processes is needed to preserve the parallel performance. The algorithm for the detection of a load imbalance and the redistribution of the tasks among the processes is based on a weight function criterion, where the weight of a cell measures the computational load associated with it. The algorithm is studied with two examples. In the first example, multiple electron bunches as occurring in the S-DALINAC [A. Richter, Operational experience at the S-DALINAC, Proceedings of the Fifth European Particle Accelerator Conference, 1996] accelerator are simulated in the absence of space charge fields. In the second example, the SCL emission and electron trajectories in an electron gun are simulated.

Parallel Monte Carlo Search for Hough Transform

Science.gov (United States)

Lopes, Raul H. C.; Franqueira, Virginia N. L.; Reid, Ivan D.; Hobson, Peter R.

2017-10-01

We investigate the problem of line detection in digital image processing and in special how state of the art algorithms behave in the presence of noise and whether CPU efficiency can be improved by the combination of a Monte Carlo Tree Search, hierarchical space decomposition, and parallel computing. The starting point of the investigation is the method introduced in 1962 by Paul Hough for detecting lines in binary images. Extended in the 1970s to the detection of space forms, what came to be known as Hough Transform (HT) has been proposed, for example, in the context of track fitting in the LHC ATLAS and CMS projects. The Hough Transform transfers the problem of line detection, for example, into one of optimization of the peak in a vote counting process for cells which contain the possible points of candidate lines. The detection algorithm can be computationally expensive both in the demands made upon the processor and on memory. Additionally, it can have a reduced effectiveness in detection in the presence of noise. Our first contribution consists in an evaluation of the use of a variation of the Radon Transform as a form of improving theeffectiveness of line detection in the presence of noise. Then, parallel algorithms for variations of the Hough Transform and the Radon Transform for line detection are introduced. An algorithm for Parallel Monte Carlo Search applied to line detection is also introduced. Their algorithmic complexities are discussed. Finally, implementations on multi-GPU and multicore architectures are discussed.

Parallelization of the MAAP-A code neutronics/thermal hydraulics coupling

International Nuclear Information System (INIS)

Froehle, P.H.; Wei, T.Y.C.; Weber, D.P.; Henry, R.E.

1998-01-01

A major new feature, one-dimensional space-time kinetics, has been added to a developmental version of the MAAP code through the introduction of the DIF3D-K module. This code is referred to as MAAP-A. To reduce the overall job time required, a capability has been provided to run the MAAP-A code in parallel. The parallel version of MAAP-A utilizes two machines running in parallel, with the DIF3D-K module executing on one machine and the rest of the MAAP-A code executing on the other machine. Timing results obtained during the development of the capability indicate that reductions in time of 30--40% are possible. The parallel version can be run on two SPARC 20 (SUN OS 5.5) workstations connected through the ethernet. MPI (Message Passing Interface standard) needs to be implemented on the machines. If necessary the parallel version can also be run on only one machine. The results obtained running in this one-machine mode identically match the results obtained from the serial version of the code

Development of parallel algorithms for electrical power management in space applications

Science.gov (United States)

Berry, Frederick C.

1989-01-01

The application of parallel techniques for electrical power system analysis is discussed. The Newton-Raphson method of load flow analysis was used along with the decomposition-coordination technique to perform load flow analysis. The decomposition-coordination technique enables tasks to be performed in parallel by partitioning the electrical power system into independent local problems. Each independent local problem represents a portion of the total electrical power system on which a loan flow analysis can be performed. The load flow analysis is performed on these partitioned elements by using the Newton-Raphson load flow method. These independent local problems will produce results for voltage and power which can then be passed to the coordinator portion of the solution procedure. The coordinator problem uses the results of the local problems to determine if any correction is needed on the local problems. The coordinator problem is also solved by an iterative method much like the local problem. The iterative method for the coordination problem will also be the Newton-Raphson method. Therefore, each iteration at the coordination level will result in new values for the local problems. The local problems will have to be solved again along with the coordinator problem until some convergence conditions are met.

Parallel computing in plasma physics: Nonlinear instabilities

International Nuclear Information System (INIS)

Pohn, E.; Kamelander, G.; Shoucri, M.

2000-01-01

A Vlasov-Poisson-system is used for studying the time evolution of the charge-separation at a spatial one- as well as a two-dimensional plasma-edge. Ions are advanced in time using the Vlasov-equation. The whole three-dimensional velocity-space is considered leading to very time-consuming four-resp. five-dimensional fully kinetic simulations. In the 1D simulations electrons are assumed to behave adiabatic, i.e. they are Boltzmann-distributed, leading to a nonlinear Poisson-equation. In the 2D simulations a gyro-kinetic approximation is used for the electrons. The plasma is assumed to be initially neutral. The simulations are performed at an equidistant grid. A constant time-step is used for advancing the density-distribution function in time. The time-evolution of the distribution function is performed using a splitting scheme. Each dimension (x, y, υ x , υ y , υ z ) of the phase-space is advanced in time separately. The value of the distribution function for the next time is calculated from the value of an - in general - interstitial point at the present time (fractional shift). One-dimensional cubic-spline interpolation is used for calculating the interstitial function values. After the fractional shifts are performed for each dimension of the phase-space, a whole time-step for advancing the distribution function is finished. Afterwards the charge density is calculated, the Poisson-equation is solved and the electric field is calculated before the next time-step is performed. The fractional shift method sketched above was parallelized for p processors as follows. Considering first the shifts in y-direction, a proper parallelization strategy is to split the grid into p disjoint υ z -slices, which are sub-grids, each containing a different 1/p-th part of the υ z range but the whole range of all other dimensions. Each processor is responsible for performing the y-shifts on a different slice, which can be done in parallel without any communication between

Parallel Lines

Directory of Open Access Journals (Sweden)

James G. Worner

2017-05-01

Full Text Available James Worner is an Australian-based writer and scholar currently pursuing a PhD at the University of Technology Sydney. His research seeks to expose masculinities lost in the shadow of Australia’s Anzac hegemony while exploring new opportunities for contemporary historiography. He is the recipient of the Doctoral Scholarship in Historical Consciousness at the university’s Australian Centre of Public History and will be hosted by the University of Bologna during 2017 on a doctoral research writing scholarship.   ‘Parallel Lines’ is one of a collection of stories, The Shapes of Us, exploring liminal spaces of modern life: class, gender, sexuality, race, religion and education. It looks at lives, like lines, that do not meet but which travel in proximity, simultaneously attracted and repelled. James’ short stories have been published in various journals and anthologies.

Efficient Mosaicking of Spitzer Space Telescope Images

Science.gov (United States)

Jacob, Joseph; Makovoz, David; Eisenhardt, Peter

2007-01-01

A parallel version of the MOPEX software, which generates mosaics of infrared astronomical images acquired by the Spitzer Space Telescope, extends the capabilities of the prior serial version. In the parallel version, both the input image space and the output mosaic space are divided among the available parallel processors. This is the only software that performs the point-source detection and the rejection of spurious imaging effects of cosmic rays required by Spitzer scientists. This software includes components that implement outlier-detection algorithms that can be fine-tuned for a particular set of image data by use of a number of adjustable parameters. This software has been used to construct a mosaic of the Spitzer Infrared Array Camera Shallow Survey, which comprises more than 17,000 exposures in four wavelength bands from 3.6 to 8 m and spans a solid angle of about 9 square degrees. When this software was executed on 32 nodes of the 1,024-processor Cosmos cluster computer at NASA s Jet Propulsion Laboratory, a speedup of 8.3 was achieved over the serial version of MOPEX. The performance is expected to improve dramatically once a true parallel file system is installed on Cosmos.

Some aspects of radial flow between parallel disks

International Nuclear Information System (INIS)

Tabatabai, M.; Pollard, A.

1985-01-01

Radial flow of air between two closely spaced parallel disks is examined experimentally. A comprehensive review of the previous work performed on similar flow situations is given by Tabatabai and Pollard. The present paper is a discussion of some of the results obtained so far and offers some observations on the decay of turbulence in this flow. (author)

PROBING VERY BRIGHT END OF GALAXY LUMINOSITY FUNCTION AT z ∼> 7 USING HUBBLE SPACE TELESCOPE PURE PARALLEL OBSERVATIONS

International Nuclear Information System (INIS)

Yan Haojing; Yan Lin; Zamojski, Michel A.; Windhorst, Rogier A.; McCarthy, Patrick J.; Fan Xiaohui; Dave, Romeel; Roettgering, Huub J. A.; Koekemoer, Anton M.; Robertson, Brant E.; Cai Zheng

2011-01-01

We report the first results from the Hubble Infrared Pure Parallel Imaging Extragalactic Survey, which utilizes the pure parallel orbits of the Hubble Space Telescope to do deep imaging along a large number of random sightlines. To date, our analysis includes 26 widely separated fields observed by the Wide Field Camera 3, which amounts to 122.8 arcmin 2 in total area. We have found three bright Y 098 -dropouts, which are candidate galaxies at z ∼> 7.4. One of these objects shows an indication of peculiar variability and its nature is uncertain. The other two objects are among the brightest candidate galaxies at these redshifts known to date (L>2L*). Such very luminous objects could be the progenitors of the high-mass Lyman break galaxies observed at lower redshifts (up to z ∼ 5). While our sample is still limited in size, it is much less subject to the uncertainty caused by 'cosmic variance' than other samples because it is derived using fields along many random sightlines. We find that the existence of the brightest candidate at z ∼ 7.4 is not well explained by the current luminosity function (LF) estimates at z ∼ 8. However, its inferred surface density could be explained by the prediction from the LFs at z ∼ 7 if it belongs to the high-redshift tail of the galaxy population at z ∼ 7.

Massively-parallel best subset selection for ordinary least-squares regression

DEFF Research Database (Denmark)

Gieseke, Fabian; Polsterer, Kai Lars; Mahabal, Ashish

2017-01-01

Selecting an optimal subset of k out of d features for linear regression models given n training instances is often considered intractable for feature spaces with hundreds or thousands of dimensions. We propose an efficient massively-parallel implementation for selecting such optimal feature...

Acceleration and parallelization calculation of EFEN-SP_3 method

International Nuclear Information System (INIS)

Yang Wen; Zheng Youqi; Wu Hongchun; Cao Liangzhi; Li Yunzhao

2013-01-01

Due to the fact that the exponential function expansion nodal-SP_3 (EFEN-SP_3) method needs further improvement in computational efficiency to routinely carry out PWR whole core pin-by-pin calculation, the coarse mesh acceleration and spatial parallelization were investigated in this paper. The coarse mesh acceleration was built by considering discontinuity factor on each coarse mesh interface and preserving neutron balance within each coarse mesh in space, angle and energy. The spatial parallelization based on MPI was implemented by guaranteeing load balancing and minimizing communications cost to fully take advantage of the modern computing and storage abilities. Numerical results based on a commercial nuclear power reactor demonstrate an speedup ratio of about 40 for the coarse mesh acceleration and a parallel efficiency of higher than 60% with 40 CPUs for the spatial parallelization. With these two improvements, the EFEN code can complete a PWR whole core pin-by-pin calculation with 289 × 289 × 218 meshes and 4 energy groups within 100 s by using 48 CPUs (2.40 GHz frequency). (authors)

Computation and parallel implementation for early vision

Science.gov (United States)

Gualtieri, J. Anthony

1990-01-01

The problem of early vision is to transform one or more retinal illuminance images-pixel arrays-to image representations built out of such primitive visual features such as edges, regions, disparities, and clusters. These transformed representations form the input to later vision stages that perform higher level vision tasks including matching and recognition. Researchers developed algorithms for: (1) edge finding in the scale space formulation; (2) correlation methods for computing matches between pairs of images; and (3) clustering of data by neural networks. These algorithms are formulated for parallel implementation of SIMD machines, such as the Massively Parallel Processor, a 128 x 128 array processor with 1024 bits of local memory per processor. For some cases, researchers can show speedups of three orders of magnitude over serial implementations.

An Intrinsic Algorithm for Parallel Poisson Disk Sampling on Arbitrary Surfaces.

Science.gov (United States)

Ying, Xiang; Xin, Shi-Qing; Sun, Qian; He, Ying

2013-03-08

Poisson disk sampling plays an important role in a variety of visual computing, due to its useful statistical property in distribution and the absence of aliasing artifacts. While many effective techniques have been proposed to generate Poisson disk distribution in Euclidean space, relatively few work has been reported to the surface counterpart. This paper presents an intrinsic algorithm for parallel Poisson disk sampling on arbitrary surfaces. We propose a new technique for parallelizing the dart throwing. Rather than the conventional approaches that explicitly partition the spatial domain to generate the samples in parallel, our approach assigns each sample candidate a random and unique priority that is unbiased with regard to the distribution. Hence, multiple threads can process the candidates simultaneously and resolve conflicts by checking the given priority values. It is worth noting that our algorithm is accurate as the generated Poisson disks are uniformly and randomly distributed without bias. Our method is intrinsic in that all the computations are based on the intrinsic metric and are independent of the embedding space. This intrinsic feature allows us to generate Poisson disk distributions on arbitrary surfaces. Furthermore, by manipulating the spatially varying density function, we can obtain adaptive sampling easily.

Research on parallel algorithm for sequential pattern mining

Science.gov (United States)

Zhou, Lijuan; Qin, Bai; Wang, Yu; Hao, Zhongxiao

2008-03-01

Sequential pattern mining is the mining of frequent sequences related to time or other orders from the sequence database. Its initial motivation is to discover the laws of customer purchasing in a time section by finding the frequent sequences. In recent years, sequential pattern mining has become an important direction of data mining, and its application field has not been confined to the business database and has extended to new data sources such as Web and advanced science fields such as DNA analysis. The data of sequential pattern mining has characteristics as follows: mass data amount and distributed storage. Most existing sequential pattern mining algorithms haven't considered the above-mentioned characteristics synthetically. According to the traits mentioned above and combining the parallel theory, this paper puts forward a new distributed parallel algorithm SPP(Sequential Pattern Parallel). The algorithm abides by the principal of pattern reduction and utilizes the divide-and-conquer strategy for parallelization. The first parallel task is to construct frequent item sets applying frequent concept and search space partition theory and the second task is to structure frequent sequences using the depth-first search method at each processor. The algorithm only needs to access the database twice and doesn't generate the candidated sequences, which abates the access time and improves the mining efficiency. Based on the random data generation procedure and different information structure designed, this paper simulated the SPP algorithm in a concrete parallel environment and implemented the AprioriAll algorithm. The experiments demonstrate that compared with AprioriAll, the SPP algorithm had excellent speedup factor and efficiency.

Joint redundancy and imperfect preventive maintenance optimization for series–parallel multi-state degraded systems

International Nuclear Information System (INIS)

Nourelfath, Mustapha; Châtelet, Eric; Nahas, Nabil

2012-01-01

This paper formulates a joint redundancy and imperfect preventive maintenance planning optimization model for series–parallel multi-state degraded systems. Non identical multi-state components can be used in parallel to improve the system availability by providing redundancy in subsystems. Multiple component choices are available in the market for each subsystem. The status of each component is considered to degrade with use. The objective is to determine jointly the maximal-availability series–parallel system structure and the appropriate preventive maintenance actions, subject to a budget constraint. System availability is defined as the ability to satisfy consumer demand that is represented as a piecewise cumulative load curve. A procedure is used, based on Markov processes and universal moment generating function, to evaluate the multi-state system availability and the cost function. A heuristic approach is also proposed to solve the formulated problem. This heuristic is based on a combination of space partitioning, genetic algorithms (GA) and tabu search (TS). After dividing the search space into a set of disjoint subsets, this approach uses GA to select the subspaces, and applies TS to each selected sub-space.

Modelling and parallel calculation of a kinetic boundary layer

International Nuclear Information System (INIS)

Perlat, Jean Philippe

1998-01-01

This research thesis aims at addressing reliability and cost issues in the calculation by numeric simulation of flows in transition regime. The first step has been to reduce calculation cost and memory space for the Monte Carlo method which is known to provide performance and reliability for rarefied regimes. Vector and parallel computers allow this objective to be reached. Here, a MIMD (multiple instructions, multiple data) machine has been used which implements parallel calculation at different levels of parallelization. Parallelization procedures have been adapted, and results showed that parallelization by calculation domain decomposition was far more efficient. Due to reliability issue related to the statistic feature of Monte Carlo methods, a new deterministic model was necessary to simulate gas molecules in transition regime. New models and hyperbolic systems have therefore been studied. One is chosen which allows thermodynamic values (density, average velocity, temperature, deformation tensor, heat flow) present in Navier-Stokes equations to be determined, and the equations of evolution of thermodynamic values are described for the mono-atomic case. Numerical resolution of is reported. A kinetic scheme is developed which complies with the structure of all systems, and which naturally expresses boundary conditions. The validation of the obtained 14 moment-based model is performed on shock problems and on Couette flows [fr

Parallel genetic algorithms with migration for the hybrid flow shop scheduling problem

Directory of Open Access Journals (Sweden)

K. Belkadi

2006-01-01

Full Text Available This paper addresses scheduling problems in hybrid flow shop-like systems with a migration parallel genetic algorithm (PGA_MIG. This parallel genetic algorithm model allows genetic diversity by the application of selection and reproduction mechanisms nearer to nature. The space structure of the population is modified by dividing it into disjoined subpopulations. From time to time, individuals are exchanged between the different subpopulations (migration. Influence of parameters and dedicated strategies are studied. These parameters are the number of independent subpopulations, the interconnection topology between subpopulations, the choice/replacement strategy of the migrant individuals, and the migration frequency. A comparison between the sequential and parallel version of genetic algorithm (GA is provided. This comparison relates to the quality of the solution and the execution time of the two versions. The efficiency of the parallel model highly depends on the parameters and especially on the migration frequency. In the same way this parallel model gives a significant improvement of computational time if it is implemented on a parallel architecture which offers an acceptable number of processors (as many processors as subpopulations.

Practical parallel computing

CERN Document Server

Morse, H Stephen

1994-01-01

Practical Parallel Computing provides information pertinent to the fundamental aspects of high-performance parallel processing. This book discusses the development of parallel applications on a variety of equipment.Organized into three parts encompassing 12 chapters, this book begins with an overview of the technology trends that converge to favor massively parallel hardware over traditional mainframes and vector machines. This text then gives a tutorial introduction to parallel hardware architectures. Other chapters provide worked-out examples of programs using several parallel languages. Thi

STANDARD METHODS FOR THE DETERMINATION OF THE RUNWAY AND SEAKEEPING CHARACTERISTICS OF A SEAPLANE ON THE WATERS DURING FULL-SCALE TESTS

Directory of Open Access Journals (Sweden)

A. A. Khokhlov

2015-01-01

Full Text Available One of the main stages of the creation of seaplanes and amphibious aircraft are flight certification tests, including tests to determine their landing and sailing characteristics on the water. In accordance with aviation regulations (part 21 certification work is carried out according to the methods of determination of compliance (MOC, which are the main organizational and methodological document for testing. The paper discusses the main provisions of the standard methods for the determination of the runway and sea keeping characteristics of seaplanes and amphibians on water areas with full-scale tests.

Parallel rendering

Science.gov (United States)

Crockett, Thomas W.

1995-01-01

This article provides a broad introduction to the subject of parallel rendering, encompassing both hardware and software systems. The focus is on the underlying concepts and the issues which arise in the design of parallel rendering algorithms and systems. We examine the different types of parallelism and how they can be applied in rendering applications. Concepts from parallel computing, such as data decomposition, task granularity, scalability, and load balancing, are considered in relation to the rendering problem. We also explore concepts from computer graphics, such as coherence and projection, which have a significant impact on the structure of parallel rendering algorithms. Our survey covers a number of practical considerations as well, including the choice of architectural platform, communication and memory requirements, and the problem of image assembly and display. We illustrate the discussion with numerous examples from the parallel rendering literature, representing most of the principal rendering methods currently used in computer graphics.

Parallel computations

CERN Document Server

1982-01-01

Parallel Computations focuses on parallel computation, with emphasis on algorithms used in a variety of numerical and physical applications and for many different types of parallel computers. Topics covered range from vectorization of fast Fourier transforms (FFTs) and of the incomplete Cholesky conjugate gradient (ICCG) algorithm on the Cray-1 to calculation of table lookups and piecewise functions. Single tridiagonal linear systems and vectorized computation of reactive flow are also discussed.Comprised of 13 chapters, this volume begins by classifying parallel computers and describing techn

Asynchronous broadcast for ordered delivery between compute nodes in a parallel computing system where packet header space is limited

Science.gov (United States)

Kumar, Sameer

2010-06-15

Disclosed is a mechanism on receiving processors in a parallel computing system for providing order to data packets received from a broadcast call and to distinguish data packets received at nodes from several incoming asynchronous broadcast messages where header space is limited. In the present invention, processors at lower leafs of a tree do not need to obtain a broadcast message by directly accessing the data in a root processor's buffer. Instead, each subsequent intermediate node's rank id information is squeezed into the software header of packet headers. In turn, the entire broadcast message is not transferred from the root processor to each processor in a communicator but instead is replicated on several intermediate nodes which then replicated the message to nodes in lower leafs. Hence, the intermediate compute nodes become "virtual root compute nodes" for the purpose of replicating the broadcast message to lower levels of a tree.

MCBooster: a tool for MC generation for massively parallel platforms

CERN Multimedia

Alves Junior, Antonio Augusto

2016-01-01

MCBooster is a header-only, C++11-compliant library for the generation of large samples of phase-space Monte Carlo events on massively parallel platforms. It was released on GitHub in the spring of 2016. The library core algorithms implement the Raubold-Lynch method; they are able to generate the full kinematics of decays with up to nine particles in the final state. The library supports the generation of sequential decays as well as the parallel evaluation of arbitrary functions over the generated events. The output of MCBooster completely accords with popular and well-tested software packages such as GENBOD (W515 from CERNLIB) and TGenPhaseSpace from the ROOT framework. MCBooster is developed on top of the Thrust library and runs on Linux systems. It deploys transparently on NVidia CUDA-enabled GPUs as well as multicore CPUs. This contribution summarizes the main features of MCBooster. A basic description of the user interface and some examples of applications are provided, along with measurements of perfor...

Parallel sorting algorithms

CERN Document Server

Akl, Selim G

1985-01-01

Parallel Sorting Algorithms explains how to use parallel algorithms to sort a sequence of items on a variety of parallel computers. The book reviews the sorting problem, the parallel models of computation, parallel algorithms, and the lower bounds on the parallel sorting problems. The text also presents twenty different algorithms, such as linear arrays, mesh-connected computers, cube-connected computers. Another example where algorithm can be applied is on the shared-memory SIMD (single instruction stream multiple data stream) computers in which the whole sequence to be sorted can fit in the

PUMA: An Operating System for Massively Parallel Systems

Directory of Open Access Journals (Sweden)

Stephen R. Wheat

1994-01-01

Full Text Available This article presents an overview of PUMA (Performance-oriented, User-managed Messaging Architecture, a message-passing kernel for massively parallel systems. Message passing in PUMA is based on portals – an opening in the address space of an application process. Once an application process has established a portal, other processes can write values into the portal using a simple send operation. Because messages are written directly into the address space of the receiving process, there is no need to buffer messages in the PUMA kernel and later copy them into the applications address space. PUMA consists of two components: the quintessential kernel (Q-Kernel and the process control thread (PCT. Although the PCT provides management decisions, the Q-Kernel controls access and implements the policies specified by the PCT.

Development of parallel 3D discrete ordinates transport program on JASMIN framework

International Nuclear Information System (INIS)

Cheng, T.; Wei, J.; Shen, H.; Zhong, B.; Deng, L.

2015-01-01

A parallel 3D discrete ordinates radiation transport code JSNT-S is developed, aiming at simulating real-world radiation shielding and reactor physics applications in a reasonable time. Through the patch-based domain partition algorithm, the memory requirement is shared among processors and a space-angle parallel sweeping algorithm is developed based on data-driven algorithm. Acceleration methods such as partial current rebalance are implemented. The correctness is proved through the VENUS-3 and other benchmark models. In the radiation shielding calculation of the Qinshan-II reactor pressure vessel model with 24.3 billion DoF, only 88 seconds is required and the overall parallel efficiency of 44% is achieved on 1536 CPU cores. (author)

Fast electrostatic force calculation on parallel computer clusters

International Nuclear Information System (INIS)

Kia, Amirali; Kim, Daejoong; Darve, Eric

2008-01-01

The fast multipole method (FMM) and smooth particle mesh Ewald (SPME) are well known fast algorithms to evaluate long range electrostatic interactions in molecular dynamics and other fields. FMM is a multi-scale method which reduces the computation cost by approximating the potential due to a group of particles at a large distance using few multipole functions. This algorithm scales like O(N) for N particles. SPME algorithm is an O(NlnN) method which is based on an interpolation of the Fourier space part of the Ewald sum and evaluating the resulting convolutions using fast Fourier transform (FFT). Those algorithms suffer from relatively poor efficiency on large parallel machines especially for mid-size problems around hundreds of thousands of atoms. A variation of the FMM, called PWA, based on plane wave expansions is presented in this paper. A new parallelization strategy for PWA, which takes advantage of the specific form of this expansion, is described. Its parallel efficiency is compared with SPME through detail time measurements on two different computer clusters

A parallel graded-mesh FDTD algorithm for human-antenna interaction problems.

Science.gov (United States)

Catarinucci, Luca; Tarricone, Luciano

2009-01-01

The finite difference time domain method (FDTD) is frequently used for the numerical solution of a wide variety of electromagnetic (EM) problems and, among them, those concerning human exposure to EM fields. In many practical cases related to the assessment of occupational EM exposure, large simulation domains are modeled and high space resolution adopted, so that strong memory and central processing unit power requirements have to be satisfied. To better afford the computational effort, the use of parallel computing is a winning approach; alternatively, subgridding techniques are often implemented. However, the simultaneous use of subgridding schemes and parallel algorithms is very new. In this paper, an easy-to-implement and highly-efficient parallel graded-mesh (GM) FDTD scheme is proposed and applied to human-antenna interaction problems, demonstrating its appropriateness in dealing with complex occupational tasks and showing its capability to guarantee the advantages of a traditional subgridding technique without affecting the parallel FDTD performance.

Numerical simulation of Vlasov equation with parallel tools; Simulations numeriques de l'equation de Vlasov a l'aide d'outils paralleles

Energy Technology Data Exchange (ETDEWEB)

Peyroux, J

2005-11-15

This project aims to make even more powerful the resolution of Vlasov codes through the various parallelization tools (MPI, OpenMP...). A simplified test case served as a base for constructing the parallel codes for obtaining a data-processing skeleton which, thereafter, could be re-used for increasingly complex models (more than four variables of phase space). This will thus make it possible to treat more realistic situations linked, for example, to the injection of ultra short and ultra intense impulses in inertial fusion plasmas, or the study of the instability of trapped ions now taken as being responsible for the generation of turbulence in tokamak plasmas. (author)

A Programming Model for Massive Data Parallelism with Data Dependencies

International Nuclear Information System (INIS)

Cui, Xiaohui; Mueller, Frank; Potok, Thomas E.; Zhang, Yongpeng

2009-01-01

Accelerating processors can often be more cost and energy effective for a wide range of data-parallel computing problems than general-purpose processors. For graphics processor units (GPUs), this is particularly the case when program development is aided by environments such as NVIDIA s Compute Unified Device Architecture (CUDA), which dramatically reduces the gap between domain-specific architectures and general purpose programming. Nonetheless, general-purpose GPU (GPGPU) programming remains subject to several restrictions. Most significantly, the separation of host (CPU) and accelerator (GPU) address spaces requires explicit management of GPU memory resources, especially for massive data parallelism that well exceeds the memory capacity of GPUs. One solution to this problem is to transfer data between the GPU and host memories frequently. In this work, we investigate another approach. We run massively data-parallel applications on GPU clusters. We further propose a programming model for massive data parallelism with data dependencies for this scenario. Experience from micro benchmarks and real-world applications shows that our model provides not only ease of programming but also significant performance gains

A new parallelization algorithm of ocean model with explicit scheme

Science.gov (United States)

Fu, X. D.

2017-08-01

This paper will focus on the parallelization of ocean model with explicit scheme which is one of the most commonly used schemes in the discretization of governing equation of ocean model. The characteristic of explicit schema is that calculation is simple, and that the value of the given grid point of ocean model depends on the grid point at the previous time step, which means that one doesn’t need to solve sparse linear equations in the process of solving the governing equation of the ocean model. Aiming at characteristics of the explicit scheme, this paper designs a parallel algorithm named halo cells update with tiny modification of original ocean model and little change of space step and time step of the original ocean model, which can parallelize ocean model by designing transmission module between sub-domains. This paper takes the GRGO for an example to implement the parallelization of GRGO (Global Reduced Gravity Ocean model) with halo update. The result demonstrates that the higher speedup can be achieved at different problem size.

Decentralized Interleaving of Paralleled Dc-Dc Buck Converters: Preprint

Energy Technology Data Exchange (ETDEWEB)

Johnson, Brian B [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Rodriguez, Miguel [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Sinha, Mohit [University of Minnesota; Dhople, Sairaj [University of Minnesota; Poon, Jason [University of California at Berkeley

2017-09-01

We present a decentralized control strategy that yields switch interleaving among parallel connected dc-dc buck converters without communication. The proposed method is based on the digital implementation of the dynamics of a nonlinear oscillator circuit as the controller. Each controller is fully decentralized, i.e., it only requires the locally measured output current to synthesize the pulse width modulation (PWM) carrier waveform. By virtue of the intrinsic electrical coupling between converters, the nonlinear oscillator-based controllers converge to an interleaved state with uniform phase-spacing across PWM carriers. To the knowledge of the authors, this work represents the first fully decentralized strategy for switch interleaving of paralleled dc-dc buck converters.

Anticonvection device for a narrow space comprised between two parallel walls

International Nuclear Information System (INIS)

Costes, Didier.

1975-01-01

The invention relates to an anticonvection device providing strong limitations against the convection currents inside a space submitted to a vertical thermal gradient and more especially the space enclosed between the inner wall of a vessel generally cyclindrical in shape and of vertical axis, intended for a nuclear reactor, and the outer wall of a plug fitted together with said vessel. To this effect, said device is characterized in that it comprises a packing of a material of open porosity and thickness-wise elasticity, in the form of threads, fibers, knitted-cloths or sheets separated by distances shorter than the thickness of stagnancy under the temperature conditions inside said space [fr

Parallel heat transport in integrable and chaotic magnetic fields

Energy Technology Data Exchange (ETDEWEB)

Castillo-Negrete, D. del; Chacon, L. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-8071 (United States)

2012-05-15

The study of transport in magnetized plasmas is a problem of fundamental interest in controlled fusion, space plasmas, and astrophysics research. Three issues make this problem particularly challenging: (i) The extreme anisotropy between the parallel (i.e., along the magnetic field), {chi}{sub ||} , and the perpendicular, {chi}{sub Up-Tack }, conductivities ({chi}{sub ||} /{chi}{sub Up-Tack} may exceed 10{sup 10} in fusion plasmas); (ii) Nonlocal parallel transport in the limit of small collisionality; and (iii) Magnetic field lines chaos which in general complicates (and may preclude) the construction of magnetic field line coordinates. Motivated by these issues, we present a Lagrangian Green's function method to solve the local and non-local parallel transport equation applicable to integrable and chaotic magnetic fields in arbitrary geometry. The method avoids by construction the numerical pollution issues of grid-based algorithms. The potential of the approach is demonstrated with nontrivial applications to integrable (magnetic island), weakly chaotic (Devil's staircase), and fully chaotic magnetic field configurations. For the latter, numerical solutions of the parallel heat transport equation show that the effective radial transport, with local and non-local parallel closures, is non-diffusive, thus casting doubts on the applicability of quasilinear diffusion descriptions. General conditions for the existence of non-diffusive, multivalued flux-gradient relations in the temperature evolution are derived.

High-Performance Psychometrics: The Parallel-E Parallel-M Algorithm for Generalized Latent Variable Models. Research Report. ETS RR-16-34

Science.gov (United States)

von Davier, Matthias

2016-01-01

This report presents results on a parallel implementation of the expectation-maximization (EM) algorithm for multidimensional latent variable models. The developments presented here are based on code that parallelizes both the E step and the M step of the parallel-E parallel-M algorithm. Examples presented in this report include item response…

ColDICE: A parallel Vlasov–Poisson solver using moving adaptive simplicial tessellation

International Nuclear Information System (INIS)

Sousbie, Thierry; Colombi, Stéphane

2016-01-01

Resolving numerically Vlasov–Poisson equations for initially cold systems can be reduced to following the evolution of a three-dimensional sheet evolving in six-dimensional phase-space. We describe a public parallel numerical algorithm consisting in representing the phase-space sheet with a conforming, self-adaptive simplicial tessellation of which the vertices follow the Lagrangian equations of motion. The algorithm is implemented both in six- and four-dimensional phase-space. Refinement of the tessellation mesh is performed using the bisection method and a local representation of the phase-space sheet at second order relying on additional tracers created when needed at runtime. In order to preserve in the best way the Hamiltonian nature of the system, refinement is anisotropic and constrained by measurements of local Poincaré invariants. Resolution of Poisson equation is performed using the fast Fourier method on a regular rectangular grid, similarly to particle in cells codes. To compute the density projected onto this grid, the intersection of the tessellation and the grid is calculated using the method of Franklin and Kankanhalli [65–67] generalised to linear order. As preliminary tests of the code, we study in four dimensional phase-space the evolution of an initially small patch in a chaotic potential and the cosmological collapse of a fluctuation composed of two sinusoidal waves. We also perform a “warm” dark matter simulation in six-dimensional phase-space that we use to check the parallel scaling of the code.

ColDICE: A parallel Vlasov–Poisson solver using moving adaptive simplicial tessellation

Energy Technology Data Exchange (ETDEWEB)

Sousbie, Thierry, E-mail: tsousbie@gmail.com [Institut d' Astrophysique de Paris, CNRS UMR 7095 and UPMC, 98bis, bd Arago, F-75014 Paris (France); Department of Physics, The University of Tokyo, Tokyo 113-0033 (Japan); Research Center for the Early Universe, School of Science, The University of Tokyo, Tokyo 113-0033 (Japan); Colombi, Stéphane, E-mail: colombi@iap.fr [Institut d' Astrophysique de Paris, CNRS UMR 7095 and UPMC, 98bis, bd Arago, F-75014 Paris (France); Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan)

2016-09-15

Resolving numerically Vlasov–Poisson equations for initially cold systems can be reduced to following the evolution of a three-dimensional sheet evolving in six-dimensional phase-space. We describe a public parallel numerical algorithm consisting in representing the phase-space sheet with a conforming, self-adaptive simplicial tessellation of which the vertices follow the Lagrangian equations of motion. The algorithm is implemented both in six- and four-dimensional phase-space. Refinement of the tessellation mesh is performed using the bisection method and a local representation of the phase-space sheet at second order relying on additional tracers created when needed at runtime. In order to preserve in the best way the Hamiltonian nature of the system, refinement is anisotropic and constrained by measurements of local Poincaré invariants. Resolution of Poisson equation is performed using the fast Fourier method on a regular rectangular grid, similarly to particle in cells codes. To compute the density projected onto this grid, the intersection of the tessellation and the grid is calculated using the method of Franklin and Kankanhalli [65–67] generalised to linear order. As preliminary tests of the code, we study in four dimensional phase-space the evolution of an initially small patch in a chaotic potential and the cosmological collapse of a fluctuation composed of two sinusoidal waves. We also perform a “warm” dark matter simulation in six-dimensional phase-space that we use to check the parallel scaling of the code.

Minimal surfaces in symmetric spaces with parallel second ...

Indian Academy of Sciences (India)

Xiaoxiang Jiao

2017-07-31

Jul 31, 2017 ... space and its non-compact dual by totally real, totally complex, and invariant immersions. ... frame fields, let θ1,θ2 and ω1,...,ωn be their dual frames. ... where ˜∇ is the induced connection of the pull-back bundle f. −1. T(N), which is defined by. ˜∇X W = ¯∇ f∗ X W for W ∈ f. −1. T(N) and X ∈ T(M). Let f∗(ei ) ...

Fast robot kinematics modeling by using a parallel simulator (PSIM)

International Nuclear Information System (INIS)

El-Gazzar, H.M.; Ayad, N.M.A.

2002-01-01

High-speed computers are strongly needed not only for solving scientific and engineering problems, but also for numerous industrial applications. Such applications include computer-aided design, oil exploration, weather predication, space applications and safety of nuclear reactors. The rapid development in VLSI technology makes it possible to implement time consuming algorithms in real-time situations. Parallel processing approaches can now be used to reduce the processing-time for models of very high mathematical structure such as the kinematics molding of robot manipulator. This system is used to construct and evaluate the performance and cost effectiveness of several proposed methods to solve the Jacobian algorithm. Parallelism is introduced to the algorithms by using different task-allocations and dividing the whole job into sub tasks. Detailed analysis is performed and results are obtained for the case of six DOF (degree of freedom) robot arms (Stanford Arm). Execution times comparisons between Von Neumann (uni processor) and parallel processor architectures by using parallel simulator package (PSIM) are presented. The gained results are much in favour for the parallel techniques by at least fifty-percent improvements. Of course, further studies are needed to achieve the convenient and optimum number of processors has to be done

Fast robot kinematics modeling by using a parallel simulator (PSIM)

Energy Technology Data Exchange (ETDEWEB)

El-Gazzar, H M; Ayad, N M.A. [Atomic Energy Authority, Reactor Dept., Computer and Control Lab., P.O. Box no 13759 (Egypt)

2002-09-15

High-speed computers are strongly needed not only for solving scientific and engineering problems, but also for numerous industrial applications. Such applications include computer-aided design, oil exploration, weather predication, space applications and safety of nuclear reactors. The rapid development in VLSI technology makes it possible to implement time consuming algorithms in real-time situations. Parallel processing approaches can now be used to reduce the processing-time for models of very high mathematical structure such as the kinematics molding of robot manipulator. This system is used to construct and evaluate the performance and cost effectiveness of several proposed methods to solve the Jacobian algorithm. Parallelism is introduced to the algorithms by using different task-allocations and dividing the whole job into sub tasks. Detailed analysis is performed and results are obtained for the case of six DOF (degree of freedom) robot arms (Stanford Arm). Execution times comparisons between Von Neumann (uni processor) and parallel processor architectures by using parallel simulator package (PSIM) are presented. The gained results are much in favour for the parallel techniques by at least fifty-percent improvements. Of course, further studies are needed to achieve the convenient and optimum number of processors has to be done.

A SPECT reconstruction method for extending parallel to non-parallel geometries

International Nuclear Information System (INIS)

Wen Junhai; Liang Zhengrong

2010-01-01

Due to its simplicity, parallel-beam geometry is usually assumed for the development of image reconstruction algorithms. The established reconstruction methodologies are then extended to fan-beam, cone-beam and other non-parallel geometries for practical application. This situation occurs for quantitative SPECT (single photon emission computed tomography) imaging in inverting the attenuated Radon transform. Novikov reported an explicit parallel-beam formula for the inversion of the attenuated Radon transform in 2000. Thereafter, a formula for fan-beam geometry was reported by Bukhgeim and Kazantsev (2002 Preprint N. 99 Sobolev Institute of Mathematics). At the same time, we presented a formula for varying focal-length fan-beam geometry. Sometimes, the reconstruction formula is so implicit that we cannot obtain the explicit reconstruction formula in the non-parallel geometries. In this work, we propose a unified reconstruction framework for extending parallel-beam geometry to any non-parallel geometry using ray-driven techniques. Studies by computer simulations demonstrated the accuracy of the presented unified reconstruction framework for extending parallel-beam to non-parallel geometries in inverting the attenuated Radon transform.

Historical parallels of biological space experiments from Soyuz, Salyut and Mir to Shenzhou flights

Science.gov (United States)

Nechitailo, Galina S.; Kondyurin, Alexey

2016-07-01

Human exploitation of space is a great achievement of our civilization. After the first space flights a development of artificial biological environment in space systems is a second big step. First successful biological experiments on a board of space station were performed on Salyut and Mir stations in 70-90th of last century such as - first long time cultivation of plants in space (wheat, linen, lettuce, crepis); - first flowers in space (Arabidopsis); - first harvesting of seeds in space (Arabidopsis); - first harvesting of roots (radish); - first full life cycle from seeds to seeds in space (wheat), Guinness recorded; - first tissue culture experiments (Panax ginseng L, Crocus sativus L, Stevia rebaundiana B; - first tree growing in space for 2 years (Limonia acidissima), Guinness recorded. As a new wave, the modern experiments on a board of Shenzhou Chinese space ships are performed with plants and tissue culture. The space flight experiments are now focused on applications of the space biology results to Earth technologies. In particular, the tomato seeds exposed 6 years in space are used in pharmacy industry in more then 10 pharmaceutical products. Tissue culture experiments are performed on the board of Shenzhou spaceship for creation of new bioproducts including Space Panax ginseng, Space Spirulina, Space Stetatin, Space Tomato and others products with unique properties. Space investments come back.

The language parallel Pascal and other aspects of the massively parallel processor

Science.gov (United States)

Reeves, A. P.; Bruner, J. D.

1982-01-01

A high level language for the Massively Parallel Processor (MPP) was designed. This language, called Parallel Pascal, is described in detail. A description of the language design, a description of the intermediate language, Parallel P-Code, and details for the MPP implementation are included. Formal descriptions of Parallel Pascal and Parallel P-Code are given. A compiler was developed which converts programs in Parallel Pascal into the intermediate Parallel P-Code language. The code generator to complete the compiler for the MPP is being developed independently. A Parallel Pascal to Pascal translator was also developed. The architecture design for a VLSI version of the MPP was completed with a description of fault tolerant interconnection networks. The memory arrangement aspects of the MPP are discussed and a survey of other high level languages is given.

Parallel Atomistic Simulations

Energy Technology Data Exchange (ETDEWEB)

HEFFELFINGER,GRANT S.

2000-01-18

Algorithms developed to enable the use of atomistic molecular simulation methods with parallel computers are reviewed. Methods appropriate for bonded as well as non-bonded (and charged) interactions are included. While strategies for obtaining parallel molecular simulations have been developed for the full variety of atomistic simulation methods, molecular dynamics and Monte Carlo have received the most attention. Three main types of parallel molecular dynamics simulations have been developed, the replicated data decomposition, the spatial decomposition, and the force decomposition. For Monte Carlo simulations, parallel algorithms have been developed which can be divided into two categories, those which require a modified Markov chain and those which do not. Parallel algorithms developed for other simulation methods such as Gibbs ensemble Monte Carlo, grand canonical molecular dynamics, and Monte Carlo methods for protein structure determination are also reviewed and issues such as how to measure parallel efficiency, especially in the case of parallel Monte Carlo algorithms with modified Markov chains are discussed.

Resolutions of the Coulomb operator: VIII. Parallel implementation using the modern programming language X10.

Science.gov (United States)

Limpanuparb, Taweetham; Milthorpe, Josh; Rendell, Alistair P

2014-10-30

Use of the modern parallel programming language X10 for computing long-range Coulomb and exchange interactions is presented. By using X10, a partitioned global address space language with support for task parallelism and the explicit representation of data locality, the resolution of the Ewald operator can be parallelized in a straightforward manner including use of both intranode and internode parallelism. We evaluate four different schemes for dynamic load balancing of integral calculation using X10's work stealing runtime, and report performance results for long-range HF energy calculation of large molecule/high quality basis running on up to 1024 cores of a high performance cluster machine. Copyright © 2014 Wiley Periodicals, Inc.

Vlasov modelling of parallel transport in a tokamak scrape-off layer

International Nuclear Information System (INIS)

Manfredi, G; Hirstoaga, S; Devaux, S

2011-01-01

A one-dimensional Vlasov-Poisson model is used to describe the parallel transport in a tokamak scrape-off layer. Thanks to a recently developed 'asymptotic-preserving' numerical scheme, it is possible to lift numerical constraints on the time step and grid spacing, which are no longer limited by, respectively, the electron plasma period and Debye length. The Vlasov approach provides a good velocity-space resolution even in regions of low density. The model is applied to the study of parallel transport during edge-localized modes, with particular emphasis on the particles and energy fluxes on the divertor plates. The numerical results are compared with analytical estimates based on a free-streaming model, with good general agreement. An interesting feature is the observation of an early electron energy flux, due to suprathermal electrons escaping the ions' attraction. In contrast, the long-time evolution is essentially quasi-neutral and dominated by the ion dynamics.

Vlasov modelling of parallel transport in a tokamak scrape-off layer

Energy Technology Data Exchange (ETDEWEB)

Manfredi, G [Institut de Physique et Chimie des Materiaux, CNRS and Universite de Strasbourg, BP 43, F-67034 Strasbourg (France); Hirstoaga, S [INRIA Nancy Grand-Est and Institut de Recherche en Mathematiques Avancees, 7 rue Rene Descartes, F-67084 Strasbourg (France); Devaux, S, E-mail: Giovanni.Manfredi@ipcms.u-strasbg.f, E-mail: hirstoaga@math.unistra.f, E-mail: Stephane.Devaux@ccfe.ac.u [JET-EFDA, Culham Science Centre, Abingdon, OX14 3DB (United Kingdom)

2011-01-15

A one-dimensional Vlasov-Poisson model is used to describe the parallel transport in a tokamak scrape-off layer. Thanks to a recently developed 'asymptotic-preserving' numerical scheme, it is possible to lift numerical constraints on the time step and grid spacing, which are no longer limited by, respectively, the electron plasma period and Debye length. The Vlasov approach provides a good velocity-space resolution even in regions of low density. The model is applied to the study of parallel transport during edge-localized modes, with particular emphasis on the particles and energy fluxes on the divertor plates. The numerical results are compared with analytical estimates based on a free-streaming model, with good general agreement. An interesting feature is the observation of an early electron energy flux, due to suprathermal electrons escaping the ions' attraction. In contrast, the long-time evolution is essentially quasi-neutral and dominated by the ion dynamics.

Real-Time Straight-Line Detection for XGA-Size Videos by Hough Transform with Parallelized Voting Procedures.

Science.gov (United States)

Guan, Jungang; An, Fengwei; Zhang, Xiangyu; Chen, Lei; Mattausch, Hans Jürgen

2017-01-30

The Hough Transform (HT) is a method for extracting straight lines from an edge image. The main limitations of the HT for usage in actual applications are computation time and storage requirements. This paper reports a hardware architecture for HT implementation on a Field Programmable Gate Array (FPGA) with parallelized voting procedure. The 2-dimensional accumulator array, namely the Hough space in parametric form (ρ, θ), for computing the strength of each line by a voting mechanism is mapped on a 1-dimensional array with regular increments of θ. Then, this Hough space is divided into a number of parallel parts. The computation of (ρ, θ) for the edge pixels and the voting procedure for straight-line determination are therefore executable in parallel. In addition, a synchronized initialization for the Hough space further increases the speed of straight-line detection, so that XGA video processing becomes possible. The designed prototype system has been synthesized on a DE4 platform with a Stratix-IV FPGA device. In the application of road-lane detection, the average processing speed of this HT implementation is 5.4ms per XGA-frame at 200 MHz working frequency.

Parallel integer sorting with medium and fine-scale parallelism

Science.gov (United States)

Dagum, Leonardo

1993-01-01

Two new parallel integer sorting algorithms, queue-sort and barrel-sort, are presented and analyzed in detail. These algorithms do not have optimal parallel complexity, yet they show very good performance in practice. Queue-sort designed for fine-scale parallel architectures which allow the queueing of multiple messages to the same destination. Barrel-sort is designed for medium-scale parallel architectures with a high message passing overhead. The performance results from the implementation of queue-sort on a Connection Machine CM-2 and barrel-sort on a 128 processor iPSC/860 are given. The two implementations are found to be comparable in performance but not as good as a fully vectorized bucket sort on the Cray YMP.

Parallel Newton-Krylov-Schwarz algorithms for the transonic full potential equation

Science.gov (United States)

Cai, Xiao-Chuan; Gropp, William D.; Keyes, David E.; Melvin, Robin G.; Young, David P.

1996-01-01

We study parallel two-level overlapping Schwarz algorithms for solving nonlinear finite element problems, in particular, for the full potential equation of aerodynamics discretized in two dimensions with bilinear elements. The overall algorithm, Newton-Krylov-Schwarz (NKS), employs an inexact finite-difference Newton method and a Krylov space iterative method, with a two-level overlapping Schwarz method as a preconditioner. We demonstrate that NKS, combined with a density upwinding continuation strategy for problems with weak shocks, is robust and, economical for this class of mixed elliptic-hyperbolic nonlinear partial differential equations, with proper specification of several parameters. We study upwinding parameters, inner convergence tolerance, coarse grid density, subdomain overlap, and the level of fill-in in the incomplete factorization, and report their effect on numerical convergence rate, overall execution time, and parallel efficiency on a distributed-memory parallel computer.

On a model of three-dimensional bursting and its parallel implementation

Science.gov (United States)

Tabik, S.; Romero, L. F.; Garzón, E. M.; Ramos, J. I.

2008-04-01

A mathematical model for the simulation of three-dimensional bursting phenomena and its parallel implementation are presented. The model consists of four nonlinearly coupled partial differential equations that include fast and slow variables, and exhibits bursting in the absence of diffusion. The differential equations have been discretized by means of a second-order accurate in both space and time, linearly-implicit finite difference method in equally-spaced grids. The resulting system of linear algebraic equations at each time level has been solved by means of the Preconditioned Conjugate Gradient (PCG) method. Three different parallel implementations of the proposed mathematical model have been developed; two of these implementations, i.e., the MPI and the PETSc codes, are based on a message passing paradigm, while the third one, i.e., the OpenMP code, is based on a shared space address paradigm. These three implementations are evaluated on two current high performance parallel architectures, i.e., a dual-processor cluster and a Shared Distributed Memory (SDM) system. A novel representation of the results that emphasizes the most relevant factors that affect the performance of the paralled implementations, is proposed. The comparative analysis of the computational results shows that the MPI and the OpenMP implementations are about twice more efficient than the PETSc code on the SDM system. It is also shown that, for the conditions reported here, the nonlinear dynamics of the three-dimensional bursting phenomena exhibits three stages characterized by asynchronous, synchronous and then asynchronous oscillations, before a quiescent state is reached. It is also shown that the fast system reaches steady state in much less time than the slow variables.

About Parallel Programming: Paradigms, Parallel Execution and Collaborative Systems

Directory of Open Access Journals (Sweden)

Loredana MOCEAN

2009-01-01

Full Text Available In the last years, there were made efforts for delineation of a stabile and unitary frame, where the problems of logical parallel processing must find solutions at least at the level of imperative languages. The results obtained by now are not at the level of the made efforts. This paper wants to be a little contribution at these efforts. We propose an overview in parallel programming, parallel execution and collaborative systems.

Experimental Study and steady state stability analysis of CLL-T Series Parallel Resonant Converter with Fuzzy controller using State Space Analysis

Directory of Open Access Journals (Sweden)

C. Nagarajan

2012-09-01

Full Text Available This paper presents a Closed Loop CLL-T (capacitor inductor inductor Series Parallel Resonant Converter (SPRC has been simulated and the performance is analysised. A three element CLL-T SPRC working under load independent operation (voltage type and current type load is presented in this paper. The Steady state Stability Analysis of CLL-T SPRC has been developed using State Space technique and the regulation of output voltage is done by using Fuzzy controller. The simulation study indicates the superiority of fuzzy control over the conventional control methods. The proposed approach is expected to provide better voltage regulation for dynamic load conditions. A prototype 300 W, 100 kHz converter is designed and built to experimentally demonstrate, dynamic and steady state performance for the CLL-T SPRC are compared from the simulation studies.

Parallel computing works!

CERN Document Server

Fox, Geoffrey C; Messina, Guiseppe C

2014-01-01

A clear illustration of how parallel computers can be successfully appliedto large-scale scientific computations. This book demonstrates how avariety of applications in physics, biology, mathematics and other scienceswere implemented on real parallel computers to produce new scientificresults. It investigates issues of fine-grained parallelism relevant forfuture supercomputers with particular emphasis on hypercube architecture. The authors describe how they used an experimental approach to configuredifferent massively parallel machines, design and implement basic systemsoftware, and develop

Smoldyn on graphics processing units: massively parallel Brownian dynamics simulations.

Science.gov (United States)

Dematté, Lorenzo

2012-01-01

Space is a very important aspect in the simulation of biochemical systems; recently, the need for simulation algorithms able to cope with space is becoming more and more compelling. Complex and detailed models of biochemical systems need to deal with the movement of single molecules and particles, taking into consideration localized fluctuations, transportation phenomena, and diffusion. A common drawback of spatial models lies in their complexity: models can become very large, and their simulation could be time consuming, especially if we want to capture the systems behavior in a reliable way using stochastic methods in conjunction with a high spatial resolution. In order to deliver the promise done by systems biology to be able to understand a system as whole, we need to scale up the size of models we are able to simulate, moving from sequential to parallel simulation algorithms. In this paper, we analyze Smoldyn, a widely diffused algorithm for stochastic simulation of chemical reactions with spatial resolution and single molecule detail, and we propose an alternative, innovative implementation that exploits the parallelism of Graphics Processing Units (GPUs). The implementation executes the most computational demanding steps (computation of diffusion, unimolecular, and bimolecular reaction, as well as the most common cases of molecule-surface interaction) on the GPU, computing them in parallel on each molecule of the system. The implementation offers good speed-ups and real time, high quality graphics output

Non-Almost Periodicity of Parallel Transports for Homogeneous Connections

International Nuclear Information System (INIS)

Brunnemann, Johannes; Fleischhack, Christian

2012-01-01

Let A be the affine space of all connections in an SU(2) principal fibre bundle over ℝ 3 . The set of homogeneous isotropic connections forms a line l in A. We prove that the parallel transports for general, non-straight paths in the base manifold do not depend almost periodically on l. Consequently, the embedding l ↪ A does not continuously extend to an embedding l-bar ↪ A-bar of the respective compactifications. Here, the Bohr compactification l-bar corresponds to the configuration space of homogeneous isotropic loop quantum cosmology and A-bar to that of loop quantum gravity. Analogous results are given for the anisotropic case.

Diffraction of love waves by two parallel perfectly weak half planes

International Nuclear Information System (INIS)

Asghar, S.; Zaman, F.D.; Ayub, M.

1986-04-01

We consider the diffraction of Love waves by two parallel perfectly weak half planes in a layer overlying a half space. The problem is formulated in terms of the Wiener-Hopf equations in the transformed plane. The transmitted waves are then calculated using the Wiener-Hopf procedure and inverse transforms. (author)

An intrinsic algorithm for parallel Poisson disk sampling on arbitrary surfaces.

Science.gov (United States)

Ying, Xiang; Xin, Shi-Qing; Sun, Qian; He, Ying

2013-09-01

Poisson disk sampling has excellent spatial and spectral properties, and plays an important role in a variety of visual computing. Although many promising algorithms have been proposed for multidimensional sampling in euclidean space, very few studies have been reported with regard to the problem of generating Poisson disks on surfaces due to the complicated nature of the surface. This paper presents an intrinsic algorithm for parallel Poisson disk sampling on arbitrary surfaces. In sharp contrast to the conventional parallel approaches, our method neither partitions the given surface into small patches nor uses any spatial data structure to maintain the voids in the sampling domain. Instead, our approach assigns each sample candidate a random and unique priority that is unbiased with regard to the distribution. Hence, multiple threads can process the candidates simultaneously and resolve conflicts by checking the given priority values. Our algorithm guarantees that the generated Poisson disks are uniformly and randomly distributed without bias. It is worth noting that our method is intrinsic and independent of the embedding space. This intrinsic feature allows us to generate Poisson disk patterns on arbitrary surfaces in IR(n). To our knowledge, this is the first intrinsic, parallel, and accurate algorithm for surface Poisson disk sampling. Furthermore, by manipulating the spatially varying density function, we can obtain adaptive sampling easily.

ESPRIT-Forest: Parallel clustering of massive amplicon sequence data in subquadratic time.

Science.gov (United States)

Cai, Yunpeng; Zheng, Wei; Yao, Jin; Yang, Yujie; Mai, Volker; Mao, Qi; Sun, Yijun

2017-04-01

The rapid development of sequencing technology has led to an explosive accumulation of genomic sequence data. Clustering is often the first step to perform in sequence analysis, and hierarchical clustering is one of the most commonly used approaches for this purpose. However, it is currently computationally expensive to perform hierarchical clustering of extremely large sequence datasets due to its quadratic time and space complexities. In this paper we developed a new algorithm called ESPRIT-Forest for parallel hierarchical clustering of sequences. The algorithm achieves subquadratic time and space complexity and maintains a high clustering accuracy comparable to the standard method. The basic idea is to organize sequences into a pseudo-metric based partitioning tree for sub-linear time searching of nearest neighbors, and then use a new multiple-pair merging criterion to construct clusters in parallel using multiple threads. The new algorithm was tested on the human microbiome project (HMP) dataset, currently one of the largest published microbial 16S rRNA sequence dataset. Our experiment demonstrated that with the power of parallel computing it is now compu- tationally feasible to perform hierarchical clustering analysis of tens of millions of sequences. The software is available at http://www.acsu.buffalo.edu/∼yijunsun/lab/ESPRIT-Forest.html.

Accurate reaction-diffusion operator splitting on tetrahedral meshes for parallel stochastic molecular simulations

Energy Technology Data Exchange (ETDEWEB)

Hepburn, I.; De Schutter, E., E-mail: erik@oist.jp [Computational Neuroscience Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa 904 0495 (Japan); Theoretical Neurobiology & Neuroengineering, University of Antwerp, Antwerp 2610 (Belgium); Chen, W. [Computational Neuroscience Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa 904 0495 (Japan)

2016-08-07

Spatial stochastic molecular simulations in biology are limited by the intense computation required to track molecules in space either in a discrete time or discrete space framework, which has led to the development of parallel methods that can take advantage of the power of modern supercomputers in recent years. We systematically test suggested components of stochastic reaction-diffusion operator splitting in the literature and discuss their effects on accuracy. We introduce an operator splitting implementation for irregular meshes that enhances accuracy with minimal performance cost. We test a range of models in small-scale MPI simulations from simple diffusion models to realistic biological models and find that multi-dimensional geometry partitioning is an important consideration for optimum performance. We demonstrate performance gains of 1-3 orders of magnitude in the parallel implementation, with peak performance strongly dependent on model specification.

A novel two-level dynamic parallel data scheme for large 3-D SN calculations

International Nuclear Information System (INIS)

Sjoden, G.E.; Shedlock, D.; Haghighat, A.; Yi, C.

2005-01-01

We introduce a new dynamic parallel memory optimization scheme for executing large scale 3-D discrete ordinates (Sn) simulations on distributed memory parallel computers. In order for parallel transport codes to be truly scalable, they must use parallel data storage, where only the variables that are locally computed are locally stored. Even with parallel data storage for the angular variables, cumulative storage requirements for large discrete ordinates calculations can be prohibitive. To address this problem, Memory Tuning has been implemented into the PENTRAN 3-D parallel discrete ordinates code as an optimized, two-level ('large' array, 'small' array) parallel data storage scheme. Memory Tuning can be described as the process of parallel data memory optimization. Memory Tuning dynamically minimizes the amount of required parallel data in allocated memory on each processor using a statistical sampling algorithm. This algorithm is based on the integral average and standard deviation of the number of fine meshes contained in each coarse mesh in the global problem. Because PENTRAN only stores the locally computed problem phase space, optimal two-level memory assignments can be unique on each node, depending upon the parallel decomposition used (hybrid combinations of angular, energy, or spatial). As demonstrated in the two large discrete ordinates models presented (a storage cask and an OECD MOX Benchmark), Memory Tuning can save a substantial amount of memory per parallel processor, allowing one to accomplish very large scale Sn computations. (authors)

Endpoint-based parallel data processing in a parallel active messaging interface of a parallel computer

Science.gov (United States)

Archer, Charles J.; Blocksome, Michael A.; Ratterman, Joseph D.; Smith, Brian E.

2014-08-12

Endpoint-based parallel data processing in a parallel active messaging interface (`PAMI`) of a parallel computer, the PAMI composed of data communications endpoints, each endpoint including a specification of data communications parameters for a thread of execution on a compute node, including specifications of a client, a context, and a task, the compute nodes coupled for data communications through the PAMI, including establishing a data communications geometry, the geometry specifying, for tasks representing processes of execution of the parallel application, a set of endpoints that are used in collective operations of the PAMI including a plurality of endpoints for one of the tasks; receiving in endpoints of the geometry an instruction for a collective operation; and executing the instruction for a collective operation through the endpoints in dependence upon the geometry, including dividing data communications operations among the plurality of endpoints for one of the tasks.

An image-space parallel convolution filtering algorithm based on shadow map

Science.gov (United States)

Li, Hua; Yang, Huamin; Zhao, Jianping

2017-07-01

Shadow mapping is commonly used in real-time rendering. In this paper, we presented an accurate and efficient method of soft shadows generation from planar area lights. First this method generated a depth map from light's view, and analyzed the depth-discontinuities areas as well as shadow boundaries. Then these areas were described as binary values in the texture map called binary light-visibility map, and a parallel convolution filtering algorithm based on GPU was enforced to smooth out the boundaries with a box filter. Experiments show that our algorithm is an effective shadow map based method that produces perceptually accurate soft shadows in real time with more details of shadow boundaries compared with the previous works.

Power conditioning for large dc motors for space flight applications

Science.gov (United States)

Veatch, Martin S.; Anderson, Paul M.; Eason, Douglas J.; Landis, David M.

1988-01-01

The design and performance of a prototype power-conditioning system for use with large brushless dc motors on NASA space missions are discussed in detail and illustrated with extensive diagrams, drawings, and graphs. The 5-kW 8-phase parallel module evaluated here would be suitable for use in the Space Shuttle Orbiter cargo bay. A current-balancing magnetic assembly with low distributed inductance permits high-speed current switching from a low-voltage bus as well as current balancing between parallel MOSFETs.

Massively parallel Fokker-Planck calculations

International Nuclear Information System (INIS)

Mirin, A.A.

1990-01-01

This paper reports that the Fokker-Planck package FPPAC, which solves the complete nonlinear multispecies Fokker-Planck collision operator for a plasma in two-dimensional velocity space, has been rewritten for the Connection Machine 2. This has involved allocation of variables either to the front end or the CM2, minimization of data flow, and replacement of Cray-optimized algorithms with ones suitable for a massively parallel architecture. Calculations have been carried out on various Connection Machines throughout the country. Results and timings on these machines have been compared to each other and to those on the static memory Cray-2. For large problem size, the Connection Machine 2 is found to be cost-efficient

Compressing Data Cube in Parallel OLAP Systems

Directory of Open Access Journals (Sweden)

Frank Dehne

2007-03-01

Full Text Available This paper proposes an efficient algorithm to compress the cubes in the progress of the parallel data cube generation. This low overhead compression mechanism provides block-by-block and record-by-record compression by using tuple difference coding techniques, thereby maximizing the compression ratio and minimizing the decompression penalty at run-time. The experimental results demonstrate that the typical compression ratio is about 30:1 without sacrificing running time. This paper also demonstrates that the compression method is suitable for Hilbert Space Filling Curve, a mechanism widely used in multi-dimensional indexing.

Parallel phase model : a programming model for high-end parallel machines with manycores.

Energy Technology Data Exchange (ETDEWEB)

Wu, Junfeng (Syracuse University, Syracuse, NY); Wen, Zhaofang; Heroux, Michael Allen; Brightwell, Ronald Brian

2009-04-01

This paper presents a parallel programming model, Parallel Phase Model (PPM), for next-generation high-end parallel machines based on a distributed memory architecture consisting of a networked cluster of nodes with a large number of cores on each node. PPM has a unified high-level programming abstraction that facilitates the design and implementation of parallel algorithms to exploit both the parallelism of the many cores and the parallelism at the cluster level. The programming abstraction will be suitable for expressing both fine-grained and coarse-grained parallelism. It includes a few high-level parallel programming language constructs that can be added as an extension to an existing (sequential or parallel) programming language such as C; and the implementation of PPM also includes a light-weight runtime library that runs on top of an existing network communication software layer (e.g. MPI). Design philosophy of PPM and details of the programming abstraction are also presented. Several unstructured applications that inherently require high-volume random fine-grained data accesses have been implemented in PPM with very promising results.

Systematic approach for deriving feasible mappings of parallel algorithms to parallel computing platforms

NARCIS (Netherlands)

Arkin, Ethem; Tekinerdogan, Bedir; Imre, Kayhan M.

2017-01-01

The need for high-performance computing together with the increasing trend from single processor to parallel computer architectures has leveraged the adoption of parallel computing. To benefit from parallel computing power, usually parallel algorithms are defined that can be mapped and executed

Hydration of non-polar anti-parallel β-sheets

International Nuclear Information System (INIS)

Urbic, Tomaz; Dias, Cristiano L.

2014-01-01

In this work we focus on anti-parallel β-sheets to study hydration of side chains and polar groups of the backbone using all-atom molecular dynamics simulations. We show that: (i) water distribution around the backbone does not depend significantly on amino acid sequence, (ii) more water molecules are found around oxygen than nitrogen atoms of the backbone, and (iii) water molecules around nitrogen are highly localized in the planed formed by peptide backbones. To study hydration around side chains we note that anti-parallel β-sheets exhibit two types of cross-strand pairing: Hydrogen-Bond (HB) and Non-Hydrogen-Bond (NHB) pairing. We show that distributions of water around alanine, leucine, and valine side chains are very different at HB compared to NHB faces. For alanine pairs, the space between side chains has a higher concentration of water if residues are located in the NHB face of the β-sheet as opposed to the HB face. For leucine residues, the HB face is found to be dry while the space between side chains at the NHB face alternates between being occupied and non-occupied by water. Surprisingly, for valine residues the NHB face is dry, whereas the HB face is occupied by water. We postulate that these differences in water distribution are related to context dependent propensities observed for β-sheets

Parallel algorithms

CERN Document Server

Casanova, Henri; Robert, Yves

2008-01-01

""…The authors of the present book, who have extensive credentials in both research and instruction in the area of parallelism, present a sound, principled treatment of parallel algorithms. … This book is very well written and extremely well designed from an instructional point of view. … The authors have created an instructive and fascinating text. The book will serve researchers as well as instructors who need a solid, readable text for a course on parallelism in computing. Indeed, for anyone who wants an understandable text from which to acquire a current, rigorous, and broad vi

A parallel FE-FV scheme to solve fluid flow in complex geologic media

NARCIS (Netherlands)

Coumou, Dim; Matthäi, Stephan; Geiger, Sebastian; Driesner, Thomas

2008-01-01

Field data-based simulations of geologic systems require much computational time because of their mathematical complexity and the often desired large scales in space and time. To conduct accurate simulations in an acceptable time period, methods to reduce runtime are required. A parallelization

Parallelization Issues and Particle-In Codes.

Science.gov (United States)

Elster, Anne Cathrine

1994-01-01

"Everything should be made as simple as possible, but not simpler." Albert Einstein. The field of parallel scientific computing has concentrated on parallelization of individual modules such as matrix solvers and factorizers. However, many applications involve several interacting modules. Our analyses of a particle-in-cell code modeling charged particles in an electric field, show that these accompanying dependencies affect data partitioning and lead to new parallelization strategies concerning processor, memory and cache utilization. Our test-bed, a KSR1, is a distributed memory machine with a globally shared addressing space. However, most of the new methods presented hold generally for hierarchical and/or distributed memory systems. We introduce a novel approach that uses dual pointers on the local particle arrays to keep the particle locations automatically partially sorted. Complexity and performance analyses with accompanying KSR benchmarks, have been included for both this scheme and for the traditional replicated grids approach. The latter approach maintains load-balance with respect to particles. However, our results demonstrate it fails to scale properly for problems with large grids (say, greater than 128-by-128) running on as few as 15 KSR nodes, since the extra storage and computation time associated with adding the grid copies, becomes significant. Our grid partitioning scheme, although harder to implement, does not need to replicate the whole grid. Consequently, it scales well for large problems on highly parallel systems. It may, however, require load balancing schemes for non-uniform particle distributions. Our dual pointer approach may facilitate this through dynamically partitioned grids. We also introduce hierarchical data structures that store neighboring grid-points within the same cache -line by reordering the grid indexing. This alignment produces a 25% savings in cache-hits for a 4-by-4 cache. A consideration of the input data's effect on

I/O Parallelization for the Goddard Earth Observing System Data Assimilation System (GEOS DAS)

Science.gov (United States)

Lucchesi, Rob; Sawyer, W.; Takacs, L. L.; Lyster, P.; Zero, J.

1998-01-01

The National Aeronautics and Space Administration (NASA) Data Assimilation Office (DAO) at the Goddard Space Flight Center (GSFC) has developed the GEOS DAS, a data assimilation system that provides production support for NASA missions and will support NASA's Earth Observing System (EOS) in the coming years. The GEOS DAS will be used to provide background fields of meteorological quantities to EOS satellite instrument teams for use in their data algorithms as well as providing assimilated data sets for climate studies on decadal time scales. The DAO has been involved in prototyping parallel implementations of the GEOS DAS for a number of years and is now embarking on an effort to convert the production version from shared-memory parallelism to distributed-memory parallelism using the portable Message-Passing Interface (MPI). The GEOS DAS consists of two main components, an atmospheric General Circulation Model (GCM) and a Physical-space Statistical Analysis System (PSAS). The GCM operates on data that are stored on a regular grid while PSAS works with observational data that are scattered irregularly throughout the atmosphere. As a result, the two components have different data decompositions. The GCM is decomposed horizontally as a checkerboard with all vertical levels of each box existing on the same processing element(PE). The dynamical core of the GCM can also operate on a rotated grid, which requires communication-intensive grid transformations during GCM integration. PSAS groups observations on PEs in a more irregular and dynamic fashion.

From Runway to Orbit: Reflections of a NASA Engineer

Science.gov (United States)

Iliff, Kenneth W.; Peebles, Curtis L.

2004-01-01

In his remarkable memoir Runway to Orbit, Dr. Kenneth W. Iliff - the recently retired Chief Scientist of the NASA Dryden Flight Research Center- tells a highly personal, yet a highly persuasive account of the last forty years of American aeronautical research. His interpretation of events commands respect, because over these years he has played pivotal roles in many of the most important American aeronautics and spaceflight endeavors. Moreover, his narrative covers much of the second half of the first 100 years of flight, a centennial anniversary being celebrated this year. aerospace knowledge. He arrived at the then NASA Flight Research Center in 1962 as a young aeronautical engineer and quickly became involved in two of the seminal projects of modern flight, the X-15 and the lifting bodies. In the process, he pioneered (with Lawrence Taylor) the application of digital computing to the reduction of flight data, arriving at a method known as parameter estimation, now applied the world over. Parameter estimation not only enabled researchers to acquire stability and control derivatives from limited flight data, but in time allowed them to obtain a wide range of aerodynamic effects. Although subsequently involved in dozens of important projects, Dr. Iliff devoted much of his time and energy to hypersonic flight, embodied in the Shuttle orbiter (or as he refers to it, the world s fastest airplane). To him, each Shuttle flight, instrumented to obtain a variety of data, represents a research treasure trove, one that he has mined for years. This book, then, represents the story of Dr. Ken Iliff s passion for flight, his work, and his long and astoundingly productive career. It can be read with profit not just by scientists and engineers, but equally by policy makers, historians, and journalists wishing to better comprehend advancements in flight during the second half of the twentieth century. Dr. Iliff's story is one of immense contributions to the nation s repository of

QR-decomposition based SENSE reconstruction using parallel architecture.

Science.gov (United States)

Ullah, Irfan; Nisar, Habab; Raza, Haseeb; Qasim, Malik; Inam, Omair; Omer, Hammad

2018-04-01

Magnetic Resonance Imaging (MRI) is a powerful medical imaging technique that provides essential clinical information about the human body. One major limitation of MRI is its long scan time. Implementation of advance MRI algorithms on a parallel architecture (to exploit inherent parallelism) has a great potential to reduce the scan time. Sensitivity Encoding (SENSE) is a Parallel Magnetic Resonance Imaging (pMRI) algorithm that utilizes receiver coil sensitivities to reconstruct MR images from the acquired under-sampled k-space data. At the heart of SENSE lies inversion of a rectangular encoding matrix. This work presents a novel implementation of GPU based SENSE algorithm, which employs QR decomposition for the inversion of the rectangular encoding matrix. For a fair comparison, the performance of the proposed GPU based SENSE reconstruction is evaluated against single and multicore CPU using openMP. Several experiments against various acceleration factors (AFs) are performed using multichannel (8, 12 and 30) phantom and in-vivo human head and cardiac datasets. Experimental results show that GPU significantly reduces the computation time of SENSE reconstruction as compared to multi-core CPU (approximately 12x speedup) and single-core CPU (approximately 53x speedup) without any degradation in the quality of the reconstructed images. Copyright © 2018 Elsevier Ltd. All rights reserved.

Cooperative parallel adaptive neighbourhood search for the disjunctively constrained knapsack problem

Science.gov (United States)

Quan, Zhe; Wu, Lei

2017-09-01

This article investigates the use of parallel computing for solving the disjunctively constrained knapsack problem. The proposed parallel computing model can be viewed as a cooperative algorithm based on a multi-neighbourhood search. The cooperation system is composed of a team manager and a crowd of team members. The team members aim at applying their own search strategies to explore the solution space. The team manager collects the solutions from the members and shares the best one with them. The performance of the proposed method is evaluated on a group of benchmark data sets. The results obtained are compared to those reached by the best methods from the literature. The results show that the proposed method is able to provide the best solutions in most cases. In order to highlight the robustness of the proposed parallel computing model, a new set of large-scale instances is introduced. Encouraging results have been obtained.

Particle simulation on a distributed memory highly parallel processor

International Nuclear Information System (INIS)

Sato, Hiroyuki; Ikesaka, Morio

1990-01-01

This paper describes parallel molecular dynamics simulation of atoms governed by local force interaction. The space in the model is divided into cubic subspaces and mapped to the processor array of the CAP-256, a distributed memory, highly parallel processor developed at Fujitsu Labs. We developed a new technique to avoid redundant calculation of forces between atoms in different processors. Experiments showed the communication overhead was less than 5%, and the idle time due to load imbalance was less than 11% for two model problems which contain 11,532 and 46,128 argon atoms. From the software simulation, the CAP-II which is under development is estimated to be about 45 times faster than CAP-256 and will be able to run the same problem about 40 times faster than Fujitsu's M-380 mainframe when 256 processors are used. (author)

Vectoring of parallel synthetic jets: A parametric study

Science.gov (United States)

Berk, Tim; Gomit, Guillaume; Ganapathisubramani, Bharathram

2016-11-01

The vectoring of a pair of parallel synthetic jets can be described using five dimensionless parameters: the aspect ratio of the slots, the Strouhal number, the Reynolds number, the phase difference between the jets and the spacing between the slots. In the present study, the influence of the latter four on the vectoring behaviour of the jets is examined experimentally using particle image velocimetry. Time-averaged velocity maps are used to study the variations in vectoring behaviour for a parametric sweep of each of the four parameters independently. A topological map is constructed for the full four-dimensional parameter space. The vectoring behaviour is described both qualitatively and quantitatively. A vectoring mechanism is proposed, based on measured vortex positions. We acknowledge the financial support from the European Research Council (ERC Grant Agreement No. 277472).

Computational cost of isogeometric multi-frontal solvers on parallel distributed memory machines

KAUST Repository

Woźniak, Maciej

2015-02-01

This paper derives theoretical estimates of the computational cost for isogeometric multi-frontal direct solver executed on parallel distributed memory machines. We show theoretically that for the Cp-1 global continuity of the isogeometric solution, both the computational cost and the communication cost of a direct solver are of order O(log(N)p2) for the one dimensional (1D) case, O(Np2) for the two dimensional (2D) case, and O(N4/3p2) for the three dimensional (3D) case, where N is the number of degrees of freedom and p is the polynomial order of the B-spline basis functions. The theoretical estimates are verified by numerical experiments performed with three parallel multi-frontal direct solvers: MUMPS, PaStiX and SuperLU, available through PETIGA toolkit built on top of PETSc. Numerical results confirm these theoretical estimates both in terms of p and N. For a given problem size, the strong efficiency rapidly decreases as the number of processors increases, becoming about 20% for 256 processors for a 3D example with 1283 unknowns and linear B-splines with C0 global continuity, and 15% for a 3D example with 643 unknowns and quartic B-splines with C3 global continuity. At the same time, one cannot arbitrarily increase the problem size, since the memory required by higher order continuity spaces is large, quickly consuming all the available memory resources even in the parallel distributed memory version. Numerical results also suggest that the use of distributed parallel machines is highly beneficial when solving higher order continuity spaces, although the number of processors that one can efficiently employ is somehow limited.

Highly accelerated cardiac cine parallel MRI using low-rank matrix completion and partial separability model

Science.gov (United States)

Lyu, Jingyuan; Nakarmi, Ukash; Zhang, Chaoyi; Ying, Leslie

2016-05-01

This paper presents a new approach to highly accelerated dynamic parallel MRI using low rank matrix completion, partial separability (PS) model. In data acquisition, k-space data is moderately randomly undersampled at the center kspace navigator locations, but highly undersampled at the outer k-space for each temporal frame. In reconstruction, the navigator data is reconstructed from undersampled data using structured low-rank matrix completion. After all the unacquired navigator data is estimated, the partial separable model is used to obtain partial k-t data. Then the parallel imaging method is used to acquire the entire dynamic image series from highly undersampled data. The proposed method has shown to achieve high quality reconstructions with reduction factors up to 31, and temporal resolution of 29ms, when the conventional PS method fails.

Architectural Design Space Exploration of an FPGA-based Compressed Sampling Engine

DEFF Research Database (Denmark)

El-Sayed, Mohammad; Koch, Peter; Le Moullec, Yannick

2015-01-01

We present the architectural design space exploration of a compressed sampling engine for use in a wireless heart-rate monitoring system. We show how parallelism affects execution time at the register transfer level. Furthermore, two example solutions (modified semi-parallel and full...

Weighted semiconvex spaces of measurable functions

International Nuclear Information System (INIS)

Olaleru, J.O.

2001-12-01

Semiconvex spaces are intermediates between locally convex spaces and the non locally convex topological vector spaces. They include all locally convex spaces; hence it is a generalization of locally convex spaces. In this article, we make a study of weighted semiconvex spaces parallel to weighted locally convex spaces where continuous functions are replaced with measurable functions and N p family replaces Nachbin family on a locally compact space X. Among others, we examine the Hausdorffness, completeness, inductive limits, barrelledness and countably barrelledness of weighted semiconvex spaces. New results are obtained while we have a more elegant proofs of old results. Furthermore, we get extensions of some of the old results. It is observed that the technique of proving theorems in weighted locally convex spaces can be adapted to that of weighted semicovex spaces of measurable functions in most cases. (author)

Time-dependent density-functional theory in massively parallel computer architectures: the OCTOPUS project.

Science.gov (United States)

Andrade, Xavier; Alberdi-Rodriguez, Joseba; Strubbe, David A; Oliveira, Micael J T; Nogueira, Fernando; Castro, Alberto; Muguerza, Javier; Arruabarrena, Agustin; Louie, Steven G; Aspuru-Guzik, Alán; Rubio, Angel; Marques, Miguel A L

2012-06-13

Octopus is a general-purpose density-functional theory (DFT) code, with a particular emphasis on the time-dependent version of DFT (TDDFT). In this paper we present the ongoing efforts to achieve the parallelization of octopus. We focus on the real-time variant of TDDFT, where the time-dependent Kohn-Sham equations are directly propagated in time. This approach has great potential for execution in massively parallel systems such as modern supercomputers with thousands of processors and graphics processing units (GPUs). For harvesting the potential of conventional supercomputers, the main strategy is a multi-level parallelization scheme that combines the inherent scalability of real-time TDDFT with a real-space grid domain-partitioning approach. A scalable Poisson solver is critical for the efficiency of this scheme. For GPUs, we show how using blocks of Kohn-Sham states provides the required level of data parallelism and that this strategy is also applicable for code optimization on standard processors. Our results show that real-time TDDFT, as implemented in octopus, can be the method of choice for studying the excited states of large molecular systems in modern parallel architectures.

Time-dependent density-functional theory in massively parallel computer architectures: the octopus project

Science.gov (United States)

Andrade, Xavier; Alberdi-Rodriguez, Joseba; Strubbe, David A.; Oliveira, Micael J. T.; Nogueira, Fernando; Castro, Alberto; Muguerza, Javier; Arruabarrena, Agustin; Louie, Steven G.; Aspuru-Guzik, Alán; Rubio, Angel; Marques, Miguel A. L.

2012-06-01

Octopus is a general-purpose density-functional theory (DFT) code, with a particular emphasis on the time-dependent version of DFT (TDDFT). In this paper we present the ongoing efforts to achieve the parallelization of octopus. We focus on the real-time variant of TDDFT, where the time-dependent Kohn-Sham equations are directly propagated in time. This approach has great potential for execution in massively parallel systems such as modern supercomputers with thousands of processors and graphics processing units (GPUs). For harvesting the potential of conventional supercomputers, the main strategy is a multi-level parallelization scheme that combines the inherent scalability of real-time TDDFT with a real-space grid domain-partitioning approach. A scalable Poisson solver is critical for the efficiency of this scheme. For GPUs, we show how using blocks of Kohn-Sham states provides the required level of data parallelism and that this strategy is also applicable for code optimization on standard processors. Our results show that real-time TDDFT, as implemented in octopus, can be the method of choice for studying the excited states of large molecular systems in modern parallel architectures.

Time-dependent density-functional theory in massively parallel computer architectures: the octopus project

International Nuclear Information System (INIS)

Andrade, Xavier; Aspuru-Guzik, Alán; Alberdi-Rodriguez, Joseba; Rubio, Angel; Strubbe, David A; Louie, Steven G; Oliveira, Micael J T; Nogueira, Fernando; Castro, Alberto; Muguerza, Javier; Arruabarrena, Agustin; Marques, Miguel A L

2012-01-01

Octopus is a general-purpose density-functional theory (DFT) code, with a particular emphasis on the time-dependent version of DFT (TDDFT). In this paper we present the ongoing efforts to achieve the parallelization of octopus. We focus on the real-time variant of TDDFT, where the time-dependent Kohn-Sham equations are directly propagated in time. This approach has great potential for execution in massively parallel systems such as modern supercomputers with thousands of processors and graphics processing units (GPUs). For harvesting the potential of conventional supercomputers, the main strategy is a multi-level parallelization scheme that combines the inherent scalability of real-time TDDFT with a real-space grid domain-partitioning approach. A scalable Poisson solver is critical for the efficiency of this scheme. For GPUs, we show how using blocks of Kohn-Sham states provides the required level of data parallelism and that this strategy is also applicable for code optimization on standard processors. Our results show that real-time TDDFT, as implemented in octopus, can be the method of choice for studying the excited states of large molecular systems in modern parallel architectures. (topical review)

Parallel computing works

Energy Technology Data Exchange (ETDEWEB)

1991-10-23

An account of the Caltech Concurrent Computation Program (C{sup 3}P), a five year project that focused on answering the question: Can parallel computers be used to do large-scale scientific computations '' As the title indicates, the question is answered in the affirmative, by implementing numerous scientific applications on real parallel computers and doing computations that produced new scientific results. In the process of doing so, C{sup 3}P helped design and build several new computers, designed and implemented basic system software, developed algorithms for frequently used mathematical computations on massively parallel machines, devised performance models and measured the performance of many computers, and created a high performance computing facility based exclusively on parallel computers. While the initial focus of C{sup 3}P was the hypercube architecture developed by C. Seitz, many of the methods developed and lessons learned have been applied successfully on other massively parallel architectures.

Parallel Density-Based Clustering for Discovery of Ionospheric Phenomena

Science.gov (United States)

Pankratius, V.; Gowanlock, M.; Blair, D. M.

2015-12-01

Ionospheric total electron content maps derived from global networks of dual-frequency GPS receivers can reveal a plethora of ionospheric features in real-time and are key to space weather studies and natural hazard monitoring. However, growing data volumes from expanding sensor networks are making manual exploratory studies challenging. As the community is heading towards Big Data ionospheric science, automation and Computer-Aided Discovery become indispensable tools for scientists. One problem of machine learning methods is that they require domain-specific adaptations in order to be effective and useful for scientists. Addressing this problem, our Computer-Aided Discovery approach allows scientists to express various physical models as well as perturbation ranges for parameters. The search space is explored through an automated system and parallel processing of batched workloads, which finds corresponding matches and similarities in empirical data. We discuss density-based clustering as a particular method we employ in this process. Specifically, we adapt Density-Based Spatial Clustering of Applications with Noise (DBSCAN). This algorithm groups geospatial data points based on density. Clusters of points can be of arbitrary shape, and the number of clusters is not predetermined by the algorithm; only two input parameters need to be specified: (1) a distance threshold, (2) a minimum number of points within that threshold. We discuss an implementation of DBSCAN for batched workloads that is amenable to parallelization on manycore architectures such as Intel's Xeon Phi accelerator with 60+ general-purpose cores. This manycore parallelization can cluster large volumes of ionospheric total electronic content data quickly. Potential applications for cluster detection include the visualization, tracing, and examination of traveling ionospheric disturbances or other propagating phenomena. Acknowledgments. We acknowledge support from NSF ACI-1442997 (PI V. Pankratius).

Through the lens of a space tourist

Directory of Open Access Journals (Sweden)

Julia Tcharfas

2015-11-01

Full Text Available This essay attempts to contextualise the experience and documentation of the world’s first space tourist, a multi-millionaire American businessman Dennis Tito, who vacationed on the International Space Station in 2001. The essay brings together two parallel elements of this historical event: the political transformation of the Russian space programme which made the private flight possible and the cultural significance and impact of the event. The first space tourist is both a direct product of the newly commercialised space programme and a reflection of a new worldview, with new values and expectations.

Template based parallel checkpointing in a massively parallel computer system

Science.gov (United States)

Archer, Charles Jens [Rochester, MN; Inglett, Todd Alan [Rochester, MN

2009-01-13

A method and apparatus for a template based parallel checkpoint save for a massively parallel super computer system using a parallel variation of the rsync protocol, and network broadcast. In preferred embodiments, the checkpoint data for each node is compared to a template checkpoint file that resides in the storage and that was previously produced. Embodiments herein greatly decrease the amount of data that must be transmitted and stored for faster checkpointing and increased efficiency of the computer system. Embodiments are directed to a parallel computer system with nodes arranged in a cluster with a high speed interconnect that can perform broadcast communication. The checkpoint contains a set of actual small data blocks with their corresponding checksums from all nodes in the system. The data blocks may be compressed using conventional non-lossy data compression algorithms to further reduce the overall checkpoint size.

A parallel implementation of 3D Zernike moment analysis

OpenAIRE

Berjón Díez, Daniel; Arnaldo Duart, Sergio; Morán Burgos, Francisco

2011-01-01

Zernike polynomials are a well known set of functions that find many applications in image or pattern characterization because they allow to construct shape descriptors that are invariant against translations, rotations or scale changes. The concepts behind them can be extended to higher dimension spaces, making them also fit to describe volumetric data. They have been less used than their properties might suggest due to their high computational cost. We present a parallel implementation of 3...

Dynamic and Control Analysis of Modular Multi-Parallel Rectifiers (MMR)

DEFF Research Database (Denmark)

Zare, Firuz; Ghosh, Arindam; Davari, Pooya

2017-01-01

This paper presents dynamic analysis of a Modular Multi-Parallel Rectifier (MMR) based on state-space modelling and analysis. The proposed topology is suitable for high power application which can reduce line current harmonics emissions significantly. However, a proper controller is required...... to share and control current through each rectifier. Mathematical analysis and preliminary simulations have been carried out to verify the proposed controller under different operating conditions....

Empirical valence bond models for reactive potential energy surfaces: a parallel multilevel genetic program approach.

Science.gov (United States)

Bellucci, Michael A; Coker, David F

2011-07-28

We describe a new method for constructing empirical valence bond potential energy surfaces using a parallel multilevel genetic program (PMLGP). Genetic programs can be used to perform an efficient search through function space and parameter space to find the best functions and sets of parameters that fit energies obtained by ab initio electronic structure calculations. Building on the traditional genetic program approach, the PMLGP utilizes a hierarchy of genetic programming on two different levels. The lower level genetic programs are used to optimize coevolving populations in parallel while the higher level genetic program (HLGP) is used to optimize the genetic operator probabilities of the lower level genetic programs. The HLGP allows the algorithm to dynamically learn the mutation or combination of mutations that most effectively increase the fitness of the populations, causing a significant increase in the algorithm's accuracy and efficiency. The algorithm's accuracy and efficiency is tested against a standard parallel genetic program with a variety of one-dimensional test cases. Subsequently, the PMLGP is utilized to obtain an accurate empirical valence bond model for proton transfer in 3-hydroxy-gamma-pyrone in gas phase and protic solvent. © 2011 American Institute of Physics

Speeding Up the String Comparison of the IDS Snort using Parallel Programming: A Systematic Literature Review on the Parallelized Aho-Corasick Algorithm

Directory of Open Access Journals (Sweden)

SILVA JUNIOR,J. B.

2016-12-01

Full Text Available The Intrusion Detection System (IDS needs to compare the contents of all packets arriving at the network interface with a set of signatures for indicating possible attacks, a task that consumes much CPU processing time. In order to alleviate this problem, some researchers have tried to parallelize the IDS's comparison engine, transferring execution from the CPU to GPU. This paper identifies and maps the parallelization features of the Aho-Corasick algorithm, which is used in Snort to compare patterns, in order to show this algorithm's implementation and execution issues, as well as optimization techniques for the Aho-Corasick machine. We have found 147 papers from important computer science publications databases, and have mapped them. We selected 22 and analyzed them in order to find our results. Our analysis of the papers showed, among other results, that parallelization of the AC algorithm is a new task and the authors have focused on the State Transition Table as the most common way to implement the algorithm on the GPU. Furthermore, we found that some techniques speed up the algorithm and reduce the required machine storage space are highly used, such as the algorithm running on the fastest memories and mechanisms for reducing the number of nodes and bit maping.

Performance Analysis of a Threshold-Based Parallel Multiple Beam Selection Scheme for WDM FSO Systems

KAUST Repository

Nam, Sung Sik; Alouini, Mohamed-Slim; Ko, Young-Chai

2018-01-01

In this paper, we statistically analyze the performance of a threshold-based parallel multiple beam selection scheme for a free-space optical (FSO) based system with wavelength division multiplexing (WDM) in cases where a pointing error has occurred

Introduction to parallel programming

CERN Document Server

Brawer, Steven

1989-01-01

Introduction to Parallel Programming focuses on the techniques, processes, methodologies, and approaches involved in parallel programming. The book first offers information on Fortran, hardware and operating system models, and processes, shared memory, and simple parallel programs. Discussions focus on processes and processors, joining processes, shared memory, time-sharing with multiple processors, hardware, loops, passing arguments in function/subroutine calls, program structure, and arithmetic expressions. The text then elaborates on basic parallel programming techniques, barriers and race

Parallelism in matrix computations

CERN Document Server

Gallopoulos, Efstratios; Sameh, Ahmed H

2016-01-01

This book is primarily intended as a research monograph that could also be used in graduate courses for the design of parallel algorithms in matrix computations. It assumes general but not extensive knowledge of numerical linear algebra, parallel architectures, and parallel programming paradigms. The book consists of four parts: (I) Basics; (II) Dense and Special Matrix Computations; (III) Sparse Matrix Computations; and (IV) Matrix functions and characteristics. Part I deals with parallel programming paradigms and fundamental kernels, including reordering schemes for sparse matrices. Part II is devoted to dense matrix computations such as parallel algorithms for solving linear systems, linear least squares, the symmetric algebraic eigenvalue problem, and the singular-value decomposition. It also deals with the development of parallel algorithms for special linear systems such as banded ,Vandermonde ,Toeplitz ,and block Toeplitz systems. Part III addresses sparse matrix computations: (a) the development of pa...

Enhancing sedimentation by improving flow conditions using parallel retrofit baffles.

Science.gov (United States)

He, Cheng; Scott, Eric; Rochfort, Quintin

2015-09-01

In this study, placing parallel-connected baffles in the vicinity of the inlet was proposed to improve hydraulic conditions for enhancing TSS (total suspended solids) removal. The purpose of the retrofit baffle design is to divide the large and fast inflow into smaller and slower flows to increase flow uniformity. This avoids short-circuiting and increases residence time in the sedimentation basin. The newly proposed parallel-connected baffle configuration was assessed in the laboratory by comparing its TSS removal performance and the optimal flow residence time with those from the widely used series-connected baffles. The experimental results showed that the parallel-connected baffles outperformed the series-connected baffles because it could disperse flow faster and in less space by splitting the large inflow into many small branches instead of solely depending on flow internal friction over a longer flow path, as was the case under the series-connected baffles. Being able to dampen faster flow before entering the sedimentation basin is critical to reducing the possibility of disturbing any settled particles, especially under high inflow conditions. Also, for a large sedimentation basin, it may be more economically feasible to deploy the proposed parallel retrofit baffle in the vicinity of the inlet than series-connected baffles throughout the entire settling basin. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

Study on Parallel Processing for Efficient Flexible Multibody Analysis based on Subsystem Synthesis Method

Energy Technology Data Exchange (ETDEWEB)

Han, Jong-Boo; Song, Hajun; Kim, Sung-Soo [Chungnam Nat’l Univ., Daejeon (Korea, Republic of)

2017-06-15

Flexible multibody simulations are widely used in the industry to design mechanical systems. In flexible multibody dynamics, deformation coordinates are described either relatively in the body reference frame that is floating in the space or in the inertial reference frame. Moreover, these deformation coordinates are generated based on the discretization of the body according to the finite element approach. Therefore, the formulation of the flexible multibody system always deals with a huge number of degrees of freedom and the numerical solution methods require a substantial amount of computational time. Parallel computational methods are a solution for efficient computation. However, most of the parallel computational methods are focused on the efficient solution of large-sized linear equations. For multibody analysis, we need to develop an efficient formulation that could be suitable for parallel computation. In this paper, we developed a subsystem synthesis method for a flexible multibody system and proposed efficient parallel computational schemes based on the OpenMP API in order to achieve efficient computation. Simulations of a rotating blade system, which consists of three identical blades, were carried out with two different parallel computational schemes. Actual CPU times were measured to investigate the efficiency of the proposed parallel schemes.

Parallel Polarization State Generation.

Science.gov (United States)

She, Alan; Capasso, Federico

2016-05-17

The control of polarization, an essential property of light, is of wide scientific and technological interest. The general problem of generating arbitrary time-varying states of polarization (SOP) has always been mathematically formulated by a series of linear transformations, i.e. a product of matrices, imposing a serial architecture. Here we show a parallel architecture described by a sum of matrices. The theory is experimentally demonstrated by modulating spatially-separated polarization components of a laser using a digital micromirror device that are subsequently beam combined. This method greatly expands the parameter space for engineering devices that control polarization. Consequently, performance characteristics, such as speed, stability, and spectral range, are entirely dictated by the technologies of optical intensity modulation, including absorption, reflection, emission, and scattering. This opens up important prospects for polarization state generation (PSG) with unique performance characteristics with applications in spectroscopic ellipsometry, spectropolarimetry, communications, imaging, and security.

A proposed experimental search for chameleons using asymmetric parallel plates

International Nuclear Information System (INIS)

Burrage, Clare; Copeland, Edmund J.; Stevenson, James A.

2016-01-01

Light scalar fields coupled to matter are a common consequence of theories of dark energy and attempts to solve the cosmological constant problem. The chameleon screening mechanism is commonly invoked in order to suppress the fifth forces mediated by these scalars, sufficiently to avoid current experimental constraints, without fine tuning. The force is suppressed dynamically by allowing the mass of the scalar to vary with the local density. Recently it has been shown that near future cold atoms experiments using atom-interferometry have the ability to access a large proportion of the chameleon parameter space. In this work we demonstrate how experiments utilising asymmetric parallel plates can push deeper into the remaining parameter space available to the chameleon.

A proposed experimental search for chameleons using asymmetric parallel plates

Energy Technology Data Exchange (ETDEWEB)

Burrage, Clare; Copeland, Edmund J.; Stevenson, James A., E-mail: Clare.Burrage@nottingham.ac.uk, E-mail: ed.copeland@nottingham.ac.uk, E-mail: james.stevenson@nottingham.ac.uk [School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD (United Kingdom)

2016-08-01

Light scalar fields coupled to matter are a common consequence of theories of dark energy and attempts to solve the cosmological constant problem. The chameleon screening mechanism is commonly invoked in order to suppress the fifth forces mediated by these scalars, sufficiently to avoid current experimental constraints, without fine tuning. The force is suppressed dynamically by allowing the mass of the scalar to vary with the local density. Recently it has been shown that near future cold atoms experiments using atom-interferometry have the ability to access a large proportion of the chameleon parameter space. In this work we demonstrate how experiments utilising asymmetric parallel plates can push deeper into the remaining parameter space available to the chameleon.

Modelling and simulation of multiple single - phase induction motor in parallel connection

Directory of Open Access Journals (Sweden)

Sujitjorn, S.

2006-11-01

Full Text Available A mathematical model for parallel connected n-multiple single-phase induction motors in generalized state-space form is proposed in this paper. The motor group draws electric power from one inverter. The model is developed by the dq-frame theory and was tested against four loading scenarios in which satisfactory results were obtained.

Model-driven product line engineering for mapping parallel algorithms to parallel computing platforms

NARCIS (Netherlands)

Arkin, Ethem; Tekinerdogan, Bedir

2016-01-01

Mapping parallel algorithms to parallel computing platforms requires several activities such as the analysis of the parallel algorithm, the definition of the logical configuration of the platform, the mapping of the algorithm to the logical configuration platform and the implementation of the

Parallelization in Modern C++

CERN Multimedia

CERN. Geneva

2016-01-01

The traditionally used and well established parallel programming models OpenMP and MPI are both targeting lower level parallelism and are meant to be as language agnostic as possible. For a long time, those models were the only widely available portable options for developing parallel C++ applications beyond using plain threads. This has strongly limited the optimization capabilities of compilers, has inhibited extensibility and genericity, and has restricted the use of those models together with other, modern higher level abstractions introduced by the C++11 and C++14 standards. The recent revival of interest in the industry and wider community for the C++ language has also spurred a remarkable amount of standardization proposals and technical specifications being developed. Those efforts however have so far failed to build a vision on how to seamlessly integrate various types of parallelism, such as iterative parallel execution, task-based parallelism, asynchronous many-task execution flows, continuation s...

Space, time and group identity in Jubilees 8-9

African Journals Online (AJOL)

p1243322

This paper investigates this change in communication strategy and ... his orientation towards and organisation of space, as revealed in his ideas ..... two versions of the same tradition or the parallel development of an older, .... In the case of Numbers Israel ... with its chronological system of jubilees and heavenly space.

EXPOSE-E: an ESA astrobiology mission 1.5 years in space.

Science.gov (United States)

Rabbow, Elke; Rettberg, Petra; Barczyk, Simon; Bohmeier, Maria; Parpart, André; Panitz, Corinna; Horneck, Gerda; von Heise-Rotenburg, Ralf; Hoppenbrouwers, Tom; Willnecker, Rainer; Baglioni, Pietro; Demets, René; Dettmann, Jan; Reitz, Guenther

2012-05-01

The multi-user facility EXPOSE-E was designed by the European Space Agency to enable astrobiology research in space (low-Earth orbit). On 7 February 2008, EXPOSE-E was carried to the International Space Station (ISS) on the European Technology Exposure Facility (EuTEF) platform in the cargo bay of Space Shuttle STS-122 Atlantis. The facility was installed at the starboard cone of the Columbus module by extravehicular activity, where it remained in space for 1.5 years. EXPOSE-E was returned to Earth with STS-128 Discovery on 12 September 2009 for subsequent sample analysis. EXPOSE-E provided accommodation in three exposure trays for a variety of astrobiological test samples that were exposed to selected space conditions: either to space vacuum, solar electromagnetic radiation at >110 nm and cosmic radiation (trays 1 and 3) or to simulated martian surface conditions (tray 2). Data on UV radiation, cosmic radiation, and temperature were measured every 10 s and downlinked by telemetry. A parallel mission ground reference (MGR) experiment was performed on ground with a parallel set of hardware and samples under simulated space conditions. EXPOSE-E performed a successful 1.5-year mission in space.

Grasp planning for a reconfigurable parallel robot with an underactuated arm structure

Directory of Open Access Journals (Sweden)

M. Riedel

2010-12-01

Full Text Available In this paper, a novel approach of grasp planning is applied to find out the appropriate grasp points for a reconfigurable parallel robot called PARAGRIP (Parallel Gripping. This new handling system is able to manipulate objects in the six-dimensional Cartesian space by several robotic arms using only six actuated joints. After grasping, the contact elements at the end of the underactuated arm mechanisms are connected to the object which forms a closed loop mechanism similar to the architecture of parallel manipulators. As the mounting and grasp points of the arms can easily be changed, the manipulator can be reconfigured to match the user's preferences and needs. This paper raises the question, how and where these grasp points are to be placed on the object to perform well for a certain manipulation task.

This paper was presented at the IFToMM/ASME International Workshop on Underactuated Grasping (UG2010, 19 August 2010, Montréal, Canada.

Massively parallel mathematical sieves

Energy Technology Data Exchange (ETDEWEB)

Montry, G.R.

1989-01-01

The Sieve of Eratosthenes is a well-known algorithm for finding all prime numbers in a given subset of integers. A parallel version of the Sieve is described that produces computational speedups over 800 on a hypercube with 1,024 processing elements for problems of fixed size. Computational speedups as high as 980 are achieved when the problem size per processor is fixed. The method of parallelization generalizes to other sieves and will be efficient on any ensemble architecture. We investigate two highly parallel sieves using scattered decomposition and compare their performance on a hypercube multiprocessor. A comparison of different parallelization techniques for the sieve illustrates the trade-offs necessary in the design and implementation of massively parallel algorithms for large ensemble computers.

Integrable covariant law of energy-momentum conservation for a gravitational field with the absolute parallelism structure

International Nuclear Information System (INIS)

Asanov, G.S.

1979-01-01

It is shown the description of gravitational field in the riemannian space-time by means of the absolute parallelism structure makes it possible to formulate an integrable covariant law of energy-momentum conservation for gravitational field, by imposing on the energy-momentum tensor the condition of vanishing of the covariant divergence (in the sense of the absolute parallelism). As a result of taking into account covariant constraints for the tetrads of the absolute parallelism, the Lagrangian density turns out to be not geometrised anymore and leads to the unambiguous conservation law of the type mentioned in the N-body problem. Covariant field equations imply the existence of the special euclidean coordinates outside of static neighbourhoods of gravitationing bodies. In these coordinates determined by the tetrads of the absolute parallelism, the linear approximation is not connected with any noncovariant assumptions

Computer-Aided Parallelizer and Optimizer

Science.gov (United States)

Jin, Haoqiang

2011-01-01

The Computer-Aided Parallelizer and Optimizer (CAPO) automates the insertion of compiler directives (see figure) to facilitate parallel processing on Shared Memory Parallel (SMP) machines. While CAPO currently is integrated seamlessly into CAPTools (developed at the University of Greenwich, now marketed as ParaWise), CAPO was independently developed at Ames Research Center as one of the components for the Legacy Code Modernization (LCM) project. The current version takes serial FORTRAN programs, performs interprocedural data dependence analysis, and generates OpenMP directives. Due to the widely supported OpenMP standard, the generated OpenMP codes have the potential to run on a wide range of SMP machines. CAPO relies on accurate interprocedural data dependence information currently provided by CAPTools. Compiler directives are generated through identification of parallel loops in the outermost level, construction of parallel regions around parallel loops and optimization of parallel regions, and insertion of directives with automatic identification of private, reduction, induction, and shared variables. Attempts also have been made to identify potential pipeline parallelism (implemented with point-to-point synchronization). Although directives are generated automatically, user interaction with the tool is still important for producing good parallel codes. A comprehensive graphical user interface is included for users to interact with the parallelization process.

Data communications in a parallel active messaging interface of a parallel computer

Science.gov (United States)

Archer, Charles J; Blocksome, Michael A; Ratterman, Joseph D; Smith, Brian E

2013-11-12

Data communications in a parallel active messaging interface (`PAMI`) of a parallel computer composed of compute nodes that execute a parallel application, each compute node including application processors that execute the parallel application and at least one management processor dedicated to gathering information regarding data communications. The PAMI is composed of data communications endpoints, each endpoint composed of a specification of data communications parameters for a thread of execution on a compute node, including specifications of a client, a context, and a task, the compute nodes and the endpoints coupled for data communications through the PAMI and through data communications resources. Embodiments function by gathering call site statistics describing data communications resulting from execution of data communications instructions and identifying in dependence upon the call cite statistics a data communications algorithm for use in executing a data communications instruction at a call site in the parallel application.

Space Flight and Manual Control: Implications for Sensorimotor Function on Future Missions

Science.gov (United States)

Reschke, Millard F.; Kornilova, Ludmila; Tomilovskaya, Elena; Parker, Donald E.; Leigh, R. John; Kozlovskaya, Inessa

2009-01-01

Control of vehicles, and other complex mechanical motion systems, is a high-level integrative function of the central nervous system (CNS) that requires good visual acuity, eye-hand coordination, spatial (and, in some cases, geographic) orientation perception, and cognitive function. Existing evidence from space flight research (Paloski et.al., 2008, Clement and Reschke 2008, Reschke et al., 2007) demonstrates that the function of each of these systems is altered by removing (and subsequently by reintroducing) a gravitational field that can be sensed by vestibular, proprioceptive, and haptic receptors and used by the CNS for spatial orientation, navigation, and coordination of movements. Furthermore, much of the operational performance data collected as a function of space flight has not been available for independent analysis, and those data that have been reviewed are equivocal owing to uncontrolled environmental and/or engineering factors. Thus, our current understanding, when it comes to manual control, is limited primarily to a review of those situations where manual control has been a factor. One of the simplest approaches to the manual control problem is to review shuttle landing data. See the Figure below for those landing for which we have Shuttle velocities over the runway threshold.

A parallel buffer tree

DEFF Research Database (Denmark)

Sitchinava, Nodar; Zeh, Norbert

2012-01-01

We present the parallel buffer tree, a parallel external memory (PEM) data structure for batched search problems. This data structure is a non-trivial extension of Arge's sequential buffer tree to a private-cache multiprocessor environment and reduces the number of I/O operations by the number of...... in the optimal OhOf(psortN + K/PB) parallel I/O complexity, where K is the size of the output reported in the process and psortN is the parallel I/O complexity of sorting N elements using P processors....

Application Portable Parallel Library

Science.gov (United States)

Cole, Gary L.; Blech, Richard A.; Quealy, Angela; Townsend, Scott

1995-01-01

Application Portable Parallel Library (APPL) computer program is subroutine-based message-passing software library intended to provide consistent interface to variety of multiprocessor computers on market today. Minimizes effort needed to move application program from one computer to another. User develops application program once and then easily moves application program from parallel computer on which created to another parallel computer. ("Parallel computer" also include heterogeneous collection of networked computers). Written in C language with one FORTRAN 77 subroutine for UNIX-based computers and callable from application programs written in C language or FORTRAN 77.

Parallel Algorithms and Patterns

Energy Technology Data Exchange (ETDEWEB)

Robey, Robert W. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2016-06-16

This is a powerpoint presentation on parallel algorithms and patterns. A parallel algorithm is a well-defined, step-by-step computational procedure that emphasizes concurrency to solve a problem. Examples of problems include: Sorting, searching, optimization, matrix operations. A parallel pattern is a computational step in a sequence of independent, potentially concurrent operations that occurs in diverse scenarios with some frequency. Examples are: Reductions, prefix scans, ghost cell updates. We only touch on parallel patterns in this presentation. It really deserves its own detailed discussion which Gabe Rockefeller would like to develop.

The suppression of destructive sparks in parallel plate proportional counters

Energy Technology Data Exchange (ETDEWEB)

Cockshott, R.A.; Mason, I.M.

1984-02-01

The authors find that high energy background events produce localised sparks in parallel plate counters when operated in the proportional mode. These sparks increase dead-time and lead to degradation ranging from electrode damage to spurious pulsing and continuous breakdown. The problem is particularly serious in low energy photon detectors for X-ray astronomy which are required to have lifetimes of several years in the high radiation environment of space. For the parallel plate imaging detector developed for the European X-ray Observatory Satellite (EXOSAT) they investigate quantitatively the spark thresholds, spark rates and degradation processes. They discuss the spark mechanism, pointing out differences from the situation in spark chambers and counters. They show that the time profile of the sparks allows them to devise a spark suppression system which reduces the degradation rate by a factor of ''200.

Parallel local search for solving Constraint Problems on the Cell Broadband Engine (Preliminary Results

Directory of Open Access Journals (Sweden)

Salvator Abreu

2009-10-01

Full Text Available We explore the use of the Cell Broadband Engine (Cell/BE for short for combinatorial optimization applications: we present a parallel version of a constraint-based local search algorithm that has been implemented on a multiprocessor BladeCenter machine with twin Cell/BE processors (total of 16 SPUs per blade. This algorithm was chosen because it fits very well the Cell/BE architecture and requires neither shared memory nor communication between processors, while retaining a compact memory footprint. We study the performance on several large optimization benchmarks and show that this achieves mostly linear time speedups, even sometimes super-linear. This is possible because the parallel implementation might explore simultaneously different parts of the search space and therefore converge faster towards the best sub-space and thus towards a solution. Besides getting speedups, the resulting times exhibit a much smaller variance, which benefits applications where a timely reply is critical.

Totally parallel multilevel algorithms

Science.gov (United States)

Frederickson, Paul O.

1988-01-01

Four totally parallel algorithms for the solution of a sparse linear system have common characteristics which become quite apparent when they are implemented on a highly parallel hypercube such as the CM2. These four algorithms are Parallel Superconvergent Multigrid (PSMG) of Frederickson and McBryan, Robust Multigrid (RMG) of Hackbusch, the FFT based Spectral Algorithm, and Parallel Cyclic Reduction. In fact, all four can be formulated as particular cases of the same totally parallel multilevel algorithm, which are referred to as TPMA. In certain cases the spectral radius of TPMA is zero, and it is recognized to be a direct algorithm. In many other cases the spectral radius, although not zero, is small enough that a single iteration per timestep keeps the local error within the required tolerance.

Dealing with BIG Data - Exploiting the Potential of Multicore Parallelism and Auto-Tuning

CERN Multimedia

CERN. Geneva

2012-01-01

Physics experiments nowadays produce tremendous amounts of data that require sophisticated analyses in order to gain new insights. At such large scale, scientists are facing non-trivial software engineering problems in addition to the physics problems. Ubiquitous multicore processors and GPGPUs have turned almost any computer into a parallel machine and have pushed compute clusters and clouds to become multicore-based and more heterogenous. These developments complicate the exploitation of various types of parallelism within different layers of hardware and software. As a consequence, manual performance tuning is non-intuitive and tedious due to the large search space spanned by numerous inter-related tuning parameters. This talk addresses these challenges at CERN and discusses how to leverage multicore parallelization techniques in this context. It presents recent advances in automatic performance tuning to algorithmically find sweet spots with good performance. The talk also presents results from empiri...

Tuning iteration space slicing based tiled multi-core code implementing Nussinov's RNA folding.

Science.gov (United States)

Palkowski, Marek; Bielecki, Wlodzimierz

2018-01-15

RNA folding is an ongoing compute-intensive task of bioinformatics. Parallelization and improving code locality for this kind of algorithms is one of the most relevant areas in computational biology. Fortunately, RNA secondary structure approaches, such as Nussinov's recurrence, involve mathematical operations over affine control loops whose iteration space can be represented by the polyhedral model. This allows us to apply powerful polyhedral compilation techniques based on the transitive closure of dependence graphs to generate parallel tiled code implementing Nussinov's RNA folding. Such techniques are within the iteration space slicing framework - the transitive dependences are applied to the statement instances of interest to produce valid tiles. The main problem at generating parallel tiled code is defining a proper tile size and tile dimension which impact parallelism degree and code locality. To choose the best tile size and tile dimension, we first construct parallel parametric tiled code (parameters are variables defining tile size). With this purpose, we first generate two nonparametric tiled codes with different fixed tile sizes but with the same code structure and then derive a general affine model, which describes all integer factors available in expressions of those codes. Using this model and known integer factors present in the mentioned expressions (they define the left-hand side of the model), we find unknown integers in this model for each integer factor available in the same fixed tiled code position and replace in this code expressions, including integer factors, with those including parameters. Then we use this parallel parametric tiled code to implement the well-known tile size selection (TSS) technique, which allows us to discover in a given search space the best tile size and tile dimension maximizing target code performance. For a given search space, the presented approach allows us to choose the best tile size and tile dimension in

Neural Parallel Engine: A toolbox for massively parallel neural signal processing.

Science.gov (United States)

Tam, Wing-Kin; Yang, Zhi

2018-05-01

Large-scale neural recordings provide detailed information on neuronal activities and can help elicit the underlying neural mechanisms of the brain. However, the computational burden is also formidable when we try to process the huge data stream generated by such recordings. In this study, we report the development of Neural Parallel Engine (NPE), a toolbox for massively parallel neural signal processing on graphical processing units (GPUs). It offers a selection of the most commonly used routines in neural signal processing such as spike detection and spike sorting, including advanced algorithms such as exponential-component-power-component (EC-PC) spike detection and binary pursuit spike sorting. We also propose a new method for detecting peaks in parallel through a parallel compact operation. Our toolbox is able to offer a 5× to 110× speedup compared with its CPU counterparts depending on the algorithms. A user-friendly MATLAB interface is provided to allow easy integration of the toolbox into existing workflows. Previous efforts on GPU neural signal processing only focus on a few rudimentary algorithms, are not well-optimized and often do not provide a user-friendly programming interface to fit into existing workflows. There is a strong need for a comprehensive toolbox for massively parallel neural signal processing. A new toolbox for massively parallel neural signal processing has been created. It can offer significant speedup in processing signals from large-scale recordings up to thousands of channels. Copyright © 2018 Elsevier B.V. All rights reserved.

A possibility of parallel and anti-parallel diffraction measurements on ...

Indian Academy of Sciences (India)

However, a bent perfect crystal (BPC) monochromator at monochromatic focusing condition can provide a quite flat and equal resolution property at both parallel and anti-parallel positions and thus one can have a chance to use both sides for the diffraction experiment. From the data of the FWHM and the / measured ...

Parallel Geometries in Geant4 foundation and recent enhancements

CERN Document Server

Apostolakis, J; Cosmo, G; Howard, A; Ivanchenko, V; Verderi, M

2009-01-01

The Geant4 software toolkit simulates the passage of particles through matter. It is utilized in high energy and nuclear physics experiments, in medical physics and space applications. For many applications it is necessary to measure particle fluxes and radiation doses in parts of the setup where there are complex structures. To undertake this in a flexible way, Geant4 has tools to create and use additional, parallel, geometrical hierarchies within a single application. A separate, parallel geometry can be used for each one amongst shower parameterization, event biasing, scoring of radiation, and/or the creation of hits in detailed readout structures. We describe the existing basic capabilities of the Geant4 toolkit to create multiple geometries and the recent major enhancements undertaken to streamline, enhance and extend these. New functionality enables Geant4 developers to offer new embedded schemes for scoring (requiring no user C++ code); has simplified the implementation of processes or capabilities usi...

Parallel and orthogonal stimulus in ultradiluted neural networks

International Nuclear Information System (INIS)

Sobral, G. A. Jr.; Vieira, V. M.; Lyra, M. L.; Silva, C. R. da

2006-01-01

Extending a model due to Derrida, Gardner, and Zippelius, we have studied the recognition ability of an extreme and asymmetrically diluted version of the Hopfield model for associative memory by including the effect of a stimulus in the dynamics of the system. We obtain exact results for the dynamic evolution of the average network superposition. The stimulus field was considered as proportional to the overlapping of the state of the system with a particular stimulated pattern. Two situations were analyzed, namely, the external stimulus acting on the initialization pattern (parallel stimulus) and the external stimulus acting on a pattern orthogonal to the initialization one (orthogonal stimulus). In both cases, we obtained the complete phase diagram in the parameter space composed of the stimulus field, thermal noise, and network capacity. Our results show that the system improves its recognition ability for parallel stimulus. For orthogonal stimulus two recognition phases emerge with the system locking at the initialization or stimulated pattern. We confront our analytical results with numerical simulations for the noiseless case T=0

Parallel implementation of many-body mean-field equations

International Nuclear Information System (INIS)

Chinn, C.R.; Umar, A.S.; Vallieres, M.; Strayer, M.R.

1994-01-01

We describe the numerical methods used to solve the system of stiff, nonlinear partial differential equations resulting from the Hartree-Fock description of many-particle quantum systems, as applied to the structure of the nucleus. The solutions are performed on a three-dimensional Cartesian lattice. Discretization is achieved through the lattice basis-spline collocation method, in which quantum-state vectors and coordinate-space operators are expressed in terms of basis-spline functions on a spatial lattice. All numerical procedures reduce to a series of matrix-vector multiplications and other elementary operations, which we perform on a number of different computing architectures, including the Intel Paragon and the Intel iPSC/860 hypercube. Parallelization is achieved through a combination of mechanisms employing the Gram-Schmidt procedure, broadcasts, global operations, and domain decomposition of state vectors. We discuss the approach to the problems of limited node memory and node-to-node communication overhead inherent in using distributed-memory, multiple-instruction, multiple-data stream parallel computers. An algorithm was developed to reduce the communication overhead by pipelining some of the message passing procedures

A parallel coordinates style interface for exploratory volume visualization.

Science.gov (United States)

Tory, Melanie; Potts, Simeon; Möller, Torsten

2005-01-01

We present a user interface, based on parallel coordinates, that facilitates exploration of volume data. By explicitly representing the visualization parameter space, the interface provides an overview of rendering options and enables users to easily explore different parameters. Rendered images are stored in an integrated history bar that facilitates backtracking to previous visualization options. Initial usability testing showed clear agreement between users and experts of various backgrounds (usability, graphic design, volume visualization, and medical physics) that the proposed user interface is a valuable data exploration tool.

Haptic spatial matching in near peripersonal space.

Science.gov (United States)

Kaas, Amanda L; Mier, Hanneke I van

2006-04-01

Research has shown that haptic spatial matching at intermanual distances over 60 cm is prone to large systematic errors. The error pattern has been explained by the use of reference frames intermediate between egocentric and allocentric coding. This study investigated haptic performance in near peripersonal space, i.e. at intermanual distances of 60 cm and less. Twelve blindfolded participants (six males and six females) were presented with two turn bars at equal distances from the midsagittal plane, 30 or 60 cm apart. Different orientations (vertical/horizontal or oblique) of the left bar had to be matched by adjusting the right bar to either a mirror symmetric (/ \\) or parallel (/ /) position. The mirror symmetry task can in principle be performed accurately in both an egocentric and an allocentric reference frame, whereas the parallel task requires an allocentric representation. Results showed that parallel matching induced large systematic errors which increased with distance. Overall error was significantly smaller in the mirror task. The task difference also held for the vertical orientation at 60 cm distance, even though this orientation required the same response in both tasks, showing a marked effect of task instruction. In addition, men outperformed women on the parallel task. Finally, contrary to our expectations, systematic errors were found in the mirror task, predominantly at 30 cm distance. Based on these findings, we suggest that haptic performance in near peripersonal space might be dominated by different mechanisms than those which come into play at distances over 60 cm. Moreover, our results indicate that both inter-individual differences and task demands affect task performance in haptic spatial matching. Therefore, we conclude that the study of haptic spatial matching in near peripersonal space might reveal important additional constraints for the specification of adequate models of haptic spatial performance.

Aerospace News: Space Shuttle Commemoration. Volume 2, No. 7

Science.gov (United States)

2011-01-01

The complex space shuttle design was comprised of four components: the external tank, two solid rocket boosters (SRB), and the orbiter vehicle. Six orbiters were used during the life of the program. In order of introduction into the fleet, they were: Enterprise (a test vehicle), Columbia, Challenger, Discovery, Atlantis and Endeavour. The space shuttle had the unique ability to launch into orbit, perform on-orbit tasks, return to earth and land on a runway. It was an orbiting laboratory, International Space Station crew delivery and supply replenisher, satellite launcher and payload delivery vehicle, all in one. Except for the external tank, all components of the space shuttle were designed to be reusable for many flights. ATK s reusable solid rocket motors (RSRM) were designed to be flown, recovered, and the metal components reused 20 times. Following each space shuttle launch, the SRBs would parachute into the ocean and be recovered by the Liberty Star and Freedom Star recovery ships. The recovered boosters would then be received at the Cape Canaveral Air Force Station Hangar AF facility for disassembly and engineering post-flight evaluation. At Hangar AF, the RSRM field joints were demated and the segments prepared to be returned to Utah by railcar. The segments were then shipped to ATK s facilities in Clearfield for additional evaluation prior to washout, disassembly and refurbishment. Later the refurbished metal components would be transported to ATK s Promontory facilities to begin a new cycle. ATK s RSRMs were manufactured in Promontory, Utah. During the Space Shuttle Program, ATK supported NASA s Marshall Space Flight Center whose responsibility was for all propulsion elements on the program, including the main engines and solid rocket motors. On launch day for the space shuttle, ATK s Launch Site Operations employees at Kennedy Space Center (KSC) provided lead engineering support for ground operations and NASA s chief engineer. It was ATK s responsibility

Parallel implementation of the PHOENIX generalized stellar atmosphere program. II. Wavelength parallelization

International Nuclear Information System (INIS)

Baron, E.; Hauschildt, Peter H.

1998-01-01

We describe an important addition to the parallel implementation of our generalized nonlocal thermodynamic equilibrium (NLTE) stellar atmosphere and radiative transfer computer program PHOENIX. In a previous paper in this series we described data and task parallel algorithms we have developed for radiative transfer, spectral line opacity, and NLTE opacity and rate calculations. These algorithms divided the work spatially or by spectral lines, that is, distributing the radial zones, individual spectral lines, or characteristic rays among different processors and employ, in addition, task parallelism for logically independent functions (such as atomic and molecular line opacities). For finite, monotonic velocity fields, the radiative transfer equation is an initial value problem in wavelength, and hence each wavelength point depends upon the previous one. However, for sophisticated NLTE models of both static and moving atmospheres needed to accurately describe, e.g., novae and supernovae, the number of wavelength points is very large (200,000 - 300,000) and hence parallelization over wavelength can lead both to considerable speedup in calculation time and the ability to make use of the aggregate memory available on massively parallel supercomputers. Here, we describe an implementation of a pipelined design for the wavelength parallelization of PHOENIX, where the necessary data from the processor working on a previous wavelength point is sent to the processor working on the succeeding wavelength point as soon as it is known. Our implementation uses a MIMD design based on a relatively small number of standard message passing interface (MPI) library calls and is fully portable between serial and parallel computers. copyright 1998 The American Astronomical Society

Particularities of fully-parallel manipulators in 6-DOFs robots design: a review of critical aspects

Directory of Open Access Journals (Sweden)

Milica Lucian

2017-01-01

Full Text Available A whole range of industrial applications requires the presence of parallel mechanisms with six degrees of freedom (6-DOF which have been developed in the last fifteen years, and one of the reasons why they still are a current topic is that present-day computers are capable of performing real-time motion laws of great complexity associated with these types of parallel mechanisms. The present work underlines particularities of parallel manipulators and their importance in the design of 6-DOF robots. The paper reveals the progress made in the last twenty years in the development of 6-DOF parallel manipulators, which increasingly find a wide scope of applications in different industrial areas such as robotics, manufacture and assisted medicine. It also emphasizes the need to determine singular configurations and the effect of cinematic redundancy which can increase the working space of the manipulators by adding active joints in one or more branches of the manipulator. Throughout the work, there were outlined three types of singularities encountered in the modelling of different types of parallel manipulators, and three types of redundancy. Furthermore, an analysis was made of the dimension of the workspace for a series of parallel manipulators, highlighting a number of factors that influence its size.

Dense SDM (12-Core × 3-Mode) Transmission Over 527 km With 33.2-ns Mode-Dispersion Employing Low-Complexity Parallel MIMO Frequency-Domain Equalization

DEFF Research Database (Denmark)

Shibahara, Kohki; Lee, Doohwan; Kobayashi, Takayuki

2016-01-01

We propose long-haul space-division-multiplexing (SDM) transmission systems employing parallel multiple-input multiple-output (MIMO) frequency-domain equalization (FDE) and transmission fiber with low differential mode delay (DMD). We first discuss the advantages of parallel MIMO FDE technique in...

Parallel k-means++

Energy Technology Data Exchange (ETDEWEB)

2017-04-04

A parallelization of the k-means++ seed selection algorithm on three distinct hardware platforms: GPU, multicore CPU, and multithreaded architecture. K-means++ was developed by David Arthur and Sergei Vassilvitskii in 2007 as an extension of the k-means data clustering technique. These algorithms allow people to cluster multidimensional data, by attempting to minimize the mean distance of data points within a cluster. K-means++ improved upon traditional k-means by using a more intelligent approach to selecting the initial seeds for the clustering process. While k-means++ has become a popular alternative to traditional k-means clustering, little work has been done to parallelize this technique. We have developed original C++ code for parallelizing the algorithm on three unique hardware architectures: GPU using NVidia's CUDA/Thrust framework, multicore CPU using OpenMP, and the Cray XMT multithreaded architecture. By parallelizing the process for these platforms, we are able to perform k-means++ clustering much more quickly than it could be done before.

Usability Evaluation of Spot and Runway Departure Advisor (SARDA) Concept in Dallas/Fort Worth Airport Tower Simulation

Science.gov (United States)

Hayashi, Miwa; Hoang, Ty; Jung, Yoon C.; Gupta, Gautam; Malik, Waqar; Dulchinos, Victoria

2013-01-01

Spot and Runway Departure Advisor (SARDA) is a proposed decision-support tool for air traffic control tower controllers for reducing taxi delay and optimizing the departure sequence. In the present study, the tool's usability was evaluated to ensure that its claimed performance benefits are not being realized at the cost of increasing the work burden on controllers. For the evaluation, workload ratings and questionnaire responses collected during a human-in-the-loop simulation experiment were analyzed to assess the SARDA advisories' effects on the controllers' ratings on cognitive resources (e.g., workload, spare attention) and satisfaction. The results showed that SARDA reduced the controllers' workload and increased their spare attention. It also made workload and attention levels less susceptible to the effects of increases in the traffic load. The questionnaire responses suggested that the controllers generally were satisfied with the ease of use of the tool and the objectives of the SARDA concept, but with some caution. To gain more trust from controllers, the the reasoning behind advisories may need to be made more transparent to them.

Parallel magnetic resonance imaging

International Nuclear Information System (INIS)

Larkman, David J; Nunes, Rita G

2007-01-01

Parallel imaging has been the single biggest innovation in magnetic resonance imaging in the last decade. The use of multiple receiver coils to augment the time consuming Fourier encoding has reduced acquisition times significantly. This increase in speed comes at a time when other approaches to acquisition time reduction were reaching engineering and human limits. A brief summary of spatial encoding in MRI is followed by an introduction to the problem parallel imaging is designed to solve. There are a large number of parallel reconstruction algorithms; this article reviews a cross-section, SENSE, SMASH, g-SMASH and GRAPPA, selected to demonstrate the different approaches. Theoretical (the g-factor) and practical (coil design) limits to acquisition speed are reviewed. The practical implementation of parallel imaging is also discussed, in particular coil calibration. How to recognize potential failure modes and their associated artefacts are shown. Well-established applications including angiography, cardiac imaging and applications using echo planar imaging are reviewed and we discuss what makes a good application for parallel imaging. Finally, active research areas where parallel imaging is being used to improve data quality by repairing artefacted images are also reviewed. (invited topical review)

Human space flight and future major space astrophysics missions: servicing and assembly

Science.gov (United States)

Thronson, Harley; Peterson, Bradley M.; Greenhouse, Matthew; MacEwen, Howard; Mukherjee, Rudranarayan; Polidan, Ronald; Reed, Benjamin; Siegler, Nicholas; Smith, Hsiao

2017-09-01

Some concepts for candidate future "flagship" space observatories approach the payload limits of the largest launch vehicles planned for the next few decades, specifically in the available volume in the vehicle fairing. This indicates that an alternative to autonomous self-deployment similar to that of the James Webb Space Telescope will eventually be required. Moreover, even before this size limit is reached, there will be significant motivation to service, repair, and upgrade in-space missions of all sizes, whether to extend the life of expensive facilities or to replace outworn or obsolete onboard systems as was demonstrated so effectively by the Hubble Space Telescope program. In parallel with these challenges to future major space astronomy missions, the capabilities of in-space robotic systems and the goals for human space flight in the 2020s and 2030s offer opportunities for achieving the most exciting science goals of the early 21st Century. In this paper, we summarize the history of concepts for human operations beyond the immediate vicinity of the Earth, the importance of very large apertures for scientific discovery, and current capabilities and future developments in robot- and astronaut-enabled servicing and assembly.

Experiences in Data-Parallel Programming

Directory of Open Access Journals (Sweden)

Terry W. Clark

1997-01-01

Full Text Available To efficiently parallelize a scientific application with a data-parallel compiler requires certain structural properties in the source program, and conversely, the absence of others. A recent parallelization effort of ours reinforced this observation and motivated this correspondence. Specifically, we have transformed a Fortran 77 version of GROMOS, a popular dusty-deck program for molecular dynamics, into Fortran D, a data-parallel dialect of Fortran. During this transformation we have encountered a number of difficulties that probably are neither limited to this particular application nor do they seem likely to be addressed by improved compiler technology in the near future. Our experience with GROMOS suggests a number of points to keep in mind when developing software that may at some time in its life cycle be parallelized with a data-parallel compiler. This note presents some guidelines for engineering data-parallel applications that are compatible with Fortran D or High Performance Fortran compilers.

Sn transport calculations on vector and parallel processors

International Nuclear Information System (INIS)

Rhoades, W.A.; Childs, R.L.

1987-01-01

The transport of radiation from the source to the location of people or equipment gives rise to some of the most challenging of calculations. A problem may involve as many as a billion unknowns, each evaluated several times to resolve interdependence. Such calculations run many hours on a Cray computer, and a typical study involves many such calculations. This paper will discuss the steps taken to vectorize the DOT code, which solves transport problems in two space dimensions (2-D); the extension of this code to 3-D; and the plans for extension to parallel processors

Kennedy Space Center Spaceport Analysis

Science.gov (United States)

Wary, Samantha A.

2013-01-01

Until the Shuttle Atlantis' final landing on July 21, 2011, Kennedy Space Center (KSC) served as NASA's main spaceport, which is a launch and landing facility for rockets and spacecraft that are attempting to enter orbit. Many of the facilities at KSC were created to assist the Shuttle Program. One of the most important and used facilities is the Shuttle Landing Facility (SLF), This was the main landing area for the return of the shuttle after her mission in space. · However, the SLF has also been used for a number of other projects including straight-line testing by Gibbs Racing, weather data collection by NOAA, and an airfield for the KSC helicopters. This runway is three miles long with control tower at midfield and a fire department located at the end in care of an emergency. This facility, which was part of the great space race, will continue to be used for historical events as Kennedy begins to commercialize its facilities. KSC continues to be an important spaceport to the government, and it will transform into an important spaceport for the commercial industry as well. During my internship at KSC's Center Planning and Development Directorate, I had the opportunity to be a part of the negotiation team working on the agreement for Space Florida to control the Shuttle Landing Facility. This gave me the opportunity to learn about all the changes that are occurring here at Kennedy Space Center. Through various meetings, I discovered the Master Plan and its focus is to transform the existing facilities that were primarily used for the Shuttle Program, to support government operations and commercial flights in the future. This. idea is also in a new strategic business plan and completion of a space industry market analysis. All of these different documentations were brought to my attention and I. saw how they came together in the discussions of transitioning the SLF to a commercial operator, Space Florida. After attending meetings and partaking in discussions for

Influence of Paralleling Dies and Paralleling Half-Bridges on Transient Current Distribution in Multichip Power Modules

DEFF Research Database (Denmark)

Li, Helong; Zhou, Wei; Wang, Xiongfei

2018-01-01

This paper addresses the transient current distribution in the multichip half-bridge power modules, where two types of paralleling connections with different current commutation mechanisms are considered: paralleling dies and paralleling half-bridges. It reveals that with paralleling dies, both t...

GENESIS: a hybrid-parallel and multi-scale molecular dynamics simulator with enhanced sampling algorithms for biomolecular and cellular simulations.

Science.gov (United States)

Jung, Jaewoon; Mori, Takaharu; Kobayashi, Chigusa; Matsunaga, Yasuhiro; Yoda, Takao; Feig, Michael; Sugita, Yuji

2015-07-01

GENESIS (Generalized-Ensemble Simulation System) is a new software package for molecular dynamics (MD) simulations of macromolecules. It has two MD simulators, called ATDYN and SPDYN. ATDYN is parallelized based on an atomic decomposition algorithm for the simulations of all-atom force-field models as well as coarse-grained Go-like models. SPDYN is highly parallelized based on a domain decomposition scheme, allowing large-scale MD simulations on supercomputers. Hybrid schemes combining OpenMP and MPI are used in both simulators to target modern multicore computer architectures. Key advantages of GENESIS are (1) the highly parallel performance of SPDYN for very large biological systems consisting of more than one million atoms and (2) the availability of various REMD algorithms (T-REMD, REUS, multi-dimensional REMD for both all-atom and Go-like models under the NVT, NPT, NPAT, and NPγT ensembles). The former is achieved by a combination of the midpoint cell method and the efficient three-dimensional Fast Fourier Transform algorithm, where the domain decomposition space is shared in real-space and reciprocal-space calculations. Other features in SPDYN, such as avoiding concurrent memory access, reducing communication times, and usage of parallel input/output files, also contribute to the performance. We show the REMD simulation results of a mixed (POPC/DMPC) lipid bilayer as a real application using GENESIS. GENESIS is released as free software under the GPLv2 licence and can be easily modified for the development of new algorithms and molecular models. WIREs Comput Mol Sci 2015, 5:310-323. doi: 10.1002/wcms.1220.

HVI Ballistic Performance Characterization of Non-Parallel Walls

Science.gov (United States)

Bohl, William; Miller, Joshua; Christiansen, Eric

2012-01-01

The Double-Wall, "Whipple" Shield [1] has been the subject of many hypervelocity impact studies and has proven to be an effective shield system for Micro-Meteoroid and Orbital Debris (MMOD) impacts for spacecraft. The US modules of the International Space Station (ISS), with their "bumper shields" offset from their pressure holding rear walls provide good examples of effective on-orbit use of the double wall shield. The concentric cylinder shield configuration with its large radius of curvature relative to separation distance is easily and effectively represented for testing and analysis as a system of two parallel plates. The parallel plate double wall configuration has been heavily tested and characterized for shield performance for normal and oblique impacts for the ISS and other programs. The double wall shield and principally similar Stuffed Whipple Shield are very common shield types for MMOD protection. However, in some locations with many spacecraft designs, the rear wall cannot be modeled as being parallel or concentric with the outer bumper wall. As represented in Figure 1, there is an included angle between the two walls. And, with a cylindrical outer wall, the effective included angle constantly changes. This complicates assessment of critical spacecraft components located within outer spacecraft walls when using software tools such as NASA's BumperII. In addition, the validity of the risk assessment comes into question when using the standard double wall shield equations, especially since verification testing of every set of double wall included angles is impossible.

Fundamental Limits of Parallel Optical Wireless Channels: Capacity Results and Outage Formulation

KAUST Repository

Chaaban, Anas; Rezki, Zouheir; Alouini, Mohamed-Slim

2016-01-01

Multi-channel (MC) optical wireless communication (OWC) systems employing wave-division multiplexing for outdoors free-space optical communications, or multi-user timedivision multiple access for indoors visible-light communications, e.g., can be modeled as parallel channels. Multi-input multioutput OWC systems can also be transformed, possibly with some performance loss, to parallel channels using pre-/postcoding. Studying the performance of such MC-OWC systems requires characterizing the capacity of the underlying parallel channels. In this paper, upper and lower bounds on the capacity of constant parallel OWC channels with a total average intensity constraint are derived. Then, the paper focuses on finding intensity allocations that maximize the lower bounds given channel-state information at the transmitter (CSIT). Due to its nonconvexity, the KKT conditions are used to describe a list of candidate allocations. Instead searching exhaustively for the best solution, low-complexity near-optimal algorithms are proposed. The resulting optimized lower bound nearly coincides with capacity at high signal-to-noise ratio (SNR). Under a quasi-static channel model and in the absence of CSIT, outage probability upper and lower bounds are derived. Those bounds also meet at high SNR, thus characterizing the outage capacity in this regime. Finally, the results are extended to a system with both average and peak intensity constraints.

Fundamental Limits of Parallel Optical Wireless Channels: Capacity Results and Outage Formulation

KAUST Repository

Chaaban, Anas

2016-10-26

Multi-channel (MC) optical wireless communication (OWC) systems employing wave-division multiplexing for outdoors free-space optical communications, or multi-user timedivision multiple access for indoors visible-light communications, e.g., can be modeled as parallel channels. Multi-input multioutput OWC systems can also be transformed, possibly with some performance loss, to parallel channels using pre-/postcoding. Studying the performance of such MC-OWC systems requires characterizing the capacity of the underlying parallel channels. In this paper, upper and lower bounds on the capacity of constant parallel OWC channels with a total average intensity constraint are derived. Then, the paper focuses on finding intensity allocations that maximize the lower bounds given channel-state information at the transmitter (CSIT). Due to its nonconvexity, the KKT conditions are used to describe a list of candidate allocations. Instead searching exhaustively for the best solution, low-complexity near-optimal algorithms are proposed. The resulting optimized lower bound nearly coincides with capacity at high signal-to-noise ratio (SNR). Under a quasi-static channel model and in the absence of CSIT, outage probability upper and lower bounds are derived. Those bounds also meet at high SNR, thus characterizing the outage capacity in this regime. Finally, the results are extended to a system with both average and peak intensity constraints.

Parallel Architectures and Parallel Algorithms for Integrated Vision Systems. Ph.D. Thesis

Science.gov (United States)

Choudhary, Alok Nidhi

1989-01-01

Computer vision is regarded as one of the most complex and computationally intensive problems. An integrated vision system (IVS) is a system that uses vision algorithms from all levels of processing to perform for a high level application (e.g., object recognition). An IVS normally involves algorithms from low level, intermediate level, and high level vision. Designing parallel architectures for vision systems is of tremendous interest to researchers. Several issues are addressed in parallel architectures and parallel algorithms for integrated vision systems.

Large-scale parallel configuration interaction. II. Two- and four-component double-group general active space implementation with application to BiH

DEFF Research Database (Denmark)

Knecht, Stefan; Jensen, Hans Jørgen Aagaard; Fleig, Timo

2010-01-01

We present a parallel implementation of a large-scale relativistic double-group configuration interaction CIprogram. It is applicable with a large variety of two- and four-component Hamiltonians. The parallel algorithm is based on a distributed data model in combination with a static load balanci...

Pattern-Driven Automatic Parallelization

Directory of Open Access Journals (Sweden)

Christoph W. Kessler

1996-01-01

Full Text Available This article describes a knowledge-based system for automatic parallelization of a wide class of sequential numerical codes operating on vectors and dense matrices, and for execution on distributed memory message-passing multiprocessors. Its main feature is a fast and powerful pattern recognition tool that locally identifies frequently occurring computations and programming concepts in the source code. This tool also works for dusty deck codes that have been "encrypted" by former machine-specific code transformations. Successful pattern recognition guides sophisticated code transformations including local algorithm replacement such that the parallelized code need not emerge from the sequential program structure by just parallelizing the loops. It allows access to an expert's knowledge on useful parallel algorithms, available machine-specific library routines, and powerful program transformations. The partially restored program semantics also supports local array alignment, distribution, and redistribution, and allows for faster and more exact prediction of the performance of the parallelized target code than is usually possible.

Real-Time Adaptive Lossless Hyperspectral Image Compression using CCSDS on Parallel GPGPU and Multicore Processor Systems

Science.gov (United States)

Hopson, Ben; Benkrid, Khaled; Keymeulen, Didier; Aranki, Nazeeh; Klimesh, Matt; Kiely, Aaron

2012-01-01

The proposed CCSDS (Consultative Committee for Space Data Systems) Lossless Hyperspectral Image Compression Algorithm was designed to facilitate a fast hardware implementation. This paper analyses that algorithm with regard to available parallelism and describes fast parallel implementations in software for GPGPU and Multicore CPU architectures. We show that careful software implementation, using hardware acceleration in the form of GPGPUs or even just multicore processors, can exceed the performance of existing hardware and software implementations by up to 11x and break the real-time barrier for the first time for a typical test application.

A Risk Assessment Model for Reduced Aircraft Separation: A Quantitative Method to Evaluate the Safety of Free Flight

Science.gov (United States)

Cassell, Rick; Smith, Alex; Connors, Mary; Wojciech, Jack; Rosekind, Mark R. (Technical Monitor)

1996-01-01

As new technologies and procedures are introduced into the National Airspace System, whether they are intended to improve efficiency, capacity, or safety level, the quantification of potential changes in safety levels is of vital concern. Applications of technology can improve safety levels and allow the reduction of separation standards. An excellent example is the Precision Runway Monitor (PRM). By taking advantage of the surveillance and display advances of PRM, airports can run instrument parallel approaches to runways separated by 3400 feet with the same level of safety as parallel approaches to runways separated by 4300 feet using the standard technology. Despite a wealth of information from flight operations and testing programs, there is no readily quantifiable relationship between numerical safety levels and the separation standards that apply to aircraft on final approach. This paper presents a modeling approach to quantify the risk associated with reducing separation on final approach. Reducing aircraft separation, both laterally and longitudinally, has been the goal of several aviation R&D programs over the past several years. Many of these programs have focused on technological solutions to improve navigation accuracy, surveillance accuracy, aircraft situational awareness, controller situational awareness, and other technical and operational factors that are vital to maintaining flight safety. The risk assessment model relates different types of potential aircraft accidents and incidents and their contribution to overall accident risk. The framework links accident risks to a hierarchy of failsafe mechanisms characterized by procedures and interventions. The model will be used to assess the overall level of safety associated with reducing separation standards and the introduction of new technology and procedures, as envisaged under the Free Flight concept. The model framework can be applied to various aircraft scenarios, including parallel and in

Data communications in a parallel active messaging interface of a parallel computer

Science.gov (United States)

Archer, Charles J; Blocksome, Michael A; Ratterman, Joseph D; Smith, Brian E

2013-10-29

Data communications in a parallel active messaging interface (`PAMI`) of a parallel computer, the parallel computer including a plurality of compute nodes that execute a parallel application, the PAMI composed of data communications endpoints, each endpoint including a specification of data communications parameters for a thread of execution on a compute node, including specifications of a client, a context, and a task, the compute nodes and the endpoints coupled for data communications through the PAMI and through data communications resources, including receiving in an origin endpoint of the PAMI a data communications instruction, the instruction characterized by an instruction type, the instruction specifying a transmission of transfer data from the origin endpoint to a target endpoint and transmitting, in accordance with the instruction type, the transfer data from the origin endpoint to the target endpoint.

The STAPL Parallel Graph Library

KAUST Repository

Harshvardhan,; Fidel, Adam; Amato, Nancy M.; Rauchwerger, Lawrence

2013-01-01

This paper describes the stapl Parallel Graph Library, a high-level framework that abstracts the user from data-distribution and parallelism details and allows them to concentrate on parallel graph algorithm development. It includes a customizable

Some nonlinear space decomposition algorithms

Energy Technology Data Exchange (ETDEWEB)

Tai, Xue-Cheng; Espedal, M. [Univ. of Bergen (Norway)

1996-12-31

Convergence of a space decomposition method is proved for a general convex programming problem. The space decomposition refers to methods that decompose a space into sums of subspaces, which could be a domain decomposition or a multigrid method for partial differential equations. Two algorithms are proposed. Both can be used for linear as well as nonlinear elliptic problems and they reduce to the standard additive and multiplicative Schwarz methods for linear elliptic problems. Two {open_quotes}hybrid{close_quotes} algorithms are also presented. They converge faster than the additive one and have better parallelism than the multiplicative method. Numerical tests with a two level domain decomposition for linear, nonlinear and interface elliptic problems are presented for the proposed algorithms.

String interactions in a plane-fronted parallel-wave spacetime

International Nuclear Information System (INIS)

Gopakumar, Rajesh

2002-01-01

We argue that string interactions in a plane-fronted parallel-wave spacetime are governed by an effective coupling g eff =g s (μp + α ' )f(μp + α ' ) where f(μp + α ' ) is proportional to the light-cone energy of the string states involved in the interaction. This simply follows from generalities of a matrix string description of this background. g eff nicely interpolates between the expected result (g s ) for flat space (small μp + α ' ) and a recently conjectured expression from the perturbative gauge theory side (large μp + α ' )

[PVFS 2000: An operational parallel file system for Beowulf

Science.gov (United States)

Ligon, Walt

2004-01-01

The approach has been to develop Parallel Virtual File System version 2 (PVFS2) , retaining the basic philosophy of the original file system but completely rewriting the code. It shows the architecture of the server and client components. BMI - BMI is the network abstraction layer. It is designed with a common driver and modules for each protocol supported. The interface is non-blocking, and provides mechanisms for optimizations including pinning user buffers. Currently TCP/IP and GM(Myrinet) modules have been implemented. Trove -Trove is the storage abstraction layer. It provides for storing both data spaces and name/value pairs. Trove can also be implemented using different underlying storage mechanisms including native files, raw disk partitions, SQL and other databases. The current implementation uses native files for data spaces and Berkeley db for name/value pairs.

Parallelism and array processing

International Nuclear Information System (INIS)

Zacharov, V.

1983-01-01

Modern computing, as well as the historical development of computing, has been dominated by sequential monoprocessing. Yet there is the alternative of parallelism, where several processes may be in concurrent execution. This alternative is discussed in a series of lectures, in which the main developments involving parallelism are considered, both from the standpoint of computing systems and that of applications that can exploit such systems. The lectures seek to discuss parallelism in a historical context, and to identify all the main aspects of concurrency in computation right up to the present time. Included will be consideration of the important question as to what use parallelism might be in the field of data processing. (orig.)

Parallel trajectory similarity joins in spatial networks

KAUST Repository

Shang, Shuo

2018-04-04

The matching of similar pairs of objects, called similarity join, is fundamental functionality in data management. We consider two cases of trajectory similarity joins (TS-Joins), including a threshold-based join (Tb-TS-Join) and a top-k TS-Join (k-TS-Join), where the objects are trajectories of vehicles moving in road networks. Given two sets of trajectories and a threshold θ, the Tb-TS-Join returns all pairs of trajectories from the two sets with similarity above θ. In contrast, the k-TS-Join does not take a threshold as a parameter, and it returns the top-k most similar trajectory pairs from the two sets. The TS-Joins target diverse applications such as trajectory near-duplicate detection, data cleaning, ridesharing recommendation, and traffic congestion prediction. With these applications in mind, we provide purposeful definitions of similarity. To enable efficient processing of the TS-Joins on large sets of trajectories, we develop search space pruning techniques and enable use of the parallel processing capabilities of modern processors. Specifically, we present a two-phase divide-and-conquer search framework that lays the foundation for the algorithms for the Tb-TS-Join and the k-TS-Join that rely on different pruning techniques to achieve efficiency. For each trajectory, the algorithms first find similar trajectories. Then they merge the results to obtain the final result. The algorithms for the two joins exploit different upper and lower bounds on the spatiotemporal trajectory similarity and different heuristic scheduling strategies for search space pruning. Their per-trajectory searches are independent of each other and can be performed in parallel, and the mergings have constant cost. An empirical study with real data offers insight in the performance of the algorithms and demonstrates that they are capable of outperforming well-designed baseline algorithms by an order of magnitude.

Parallel trajectory similarity joins in spatial networks

KAUST Repository

Shang, Shuo; Chen, Lisi; Wei, Zhewei; Jensen, Christian S.; Zheng, Kai; Kalnis, Panos

2018-01-01

The matching of similar pairs of objects, called similarity join, is fundamental functionality in data management. We consider two cases of trajectory similarity joins (TS-Joins), including a threshold-based join (Tb-TS-Join) and a top-k TS-Join (k-TS-Join), where the objects are trajectories of vehicles moving in road networks. Given two sets of trajectories and a threshold θ, the Tb-TS-Join returns all pairs of trajectories from the two sets with similarity above θ. In contrast, the k-TS-Join does not take a threshold as a parameter, and it returns the top-k most similar trajectory pairs from the two sets. The TS-Joins target diverse applications such as trajectory near-duplicate detection, data cleaning, ridesharing recommendation, and traffic congestion prediction. With these applications in mind, we provide purposeful definitions of similarity. To enable efficient processing of the TS-Joins on large sets of trajectories, we develop search space pruning techniques and enable use of the parallel processing capabilities of modern processors. Specifically, we present a two-phase divide-and-conquer search framework that lays the foundation for the algorithms for the Tb-TS-Join and the k-TS-Join that rely on different pruning techniques to achieve efficiency. For each trajectory, the algorithms first find similar trajectories. Then they merge the results to obtain the final result. The algorithms for the two joins exploit different upper and lower bounds on the spatiotemporal trajectory similarity and different heuristic scheduling strategies for search space pruning. Their per-trajectory searches are independent of each other and can be performed in parallel, and the mergings have constant cost. An empirical study with real data offers insight in the performance of the algorithms and demonstrates that they are capable of outperforming well-designed baseline algorithms by an order of magnitude.

Advances in non-Cartesian parallel magnetic resonance imaging using the GRAPPA operator

International Nuclear Information System (INIS)

Seiberlich, Nicole

2008-01-01

This thesis has presented several new non-Cartesian parallel imaging methods which simplify both gridding and the reconstruction of images from undersampled data. A novel approach which uses the concepts of parallel imaging to grid data sampled along a non-Cartesian trajectory called GRAPPA Operator Gridding (GROG) is described. GROG shifts any acquired k-space data point to its nearest Cartesian location, thereby converting non-Cartesian to Cartesian data. The only requirements for GROG are a multi-channel acquisition and a calibration dataset for the determination of the GROG weights. Then an extension of GRAPPA Operator Gridding, namely Self-Calibrating GRAPPA Operator Gridding (SC-GROG) is discussed. SC-GROG is a method by which non-Cartesian data can be gridded using spatial information from a multi-channel coil array without the need for an additional calibration dataset, as required in standard GROG. Although GROG can be used to grid undersampled datasets, it is important to note that this method uses parallel imaging only for gridding, and not to reconstruct artifact-free images from undersampled data. Thereafter a simple, novel method for performing modified Cartesian GRAPPA reconstructions on undersampled non-Cartesian k-space data gridded using GROG to arrive at a non-aliased image is introduced. Because the undersampled non-Cartesian data cannot be reconstructed using a single GRAPPA kernel, several Cartesian patterns are selected for the reconstruction. Finally a novel method of using GROG to mimic the bunched phase encoding acquisition (BPE) scheme is discussed. In MRI, it is generally assumed that an artifact-free image can be reconstructed only from sampled points which fulfill the Nyquist criterion. However, the BPE reconstruction is based on the Generalized Sampling Theorem of Papoulis, which states that a continuous signal can be reconstructed from sampled points as long as the points are on average sampled at the Nyquist frequency. A novel

Space charge in nanostructure resonances

Science.gov (United States)

Price, Peter J.

1996-10-01

In quantum ballistic propagation of electrons through a variety of nanostructures, resonance in the energy-dependent transmission and reflection probabilities generically is associated with (1) a quasi-level with a decay lifetime, and (2) a bulge in electron density within the structure. It can be shown that, to a good approximation, a simple formula in all cases connects the density of states for the latter to the energy dependence of the phase angles of the eigen values of the S-matrix governing the propagation. For both the Lorentzian resonances (normal or inverted) and for the Fano-type resonances, as a consequence of this eigen value formula, the space charge due to filled states over the energy range of a resonance is just equal (for each spin state) to one electron charge. The Coulomb interaction within this space charge is known to 'distort' the electrical characteristics of resonant nanostructures. In these systems, however, the exchange effect should effectively cancel the interaction between states with parallel spins, leaving only the anti-parallel spin contribution.

Adaptive Controller for 6-DOF Parallel Robot Using T-S Fuzzy Inference

Directory of Open Access Journals (Sweden)

Xue Jian

2013-02-01

Full Text Available 6-DOF parallel robot always appears in the form of Stewart platform. It has been widely used in industry for the benefits such as strong structural stiffness, high movement accuracy and so on. Space docking technology makes higher requirements of motion accuracy and dynamic performance to the control method on 6-DOF parallel robot. In this paper, a hydraulic 6-DOF parallel robot was used to simulate the docking process. Based on this point, this paper gave a thorough study on the design of an adaptive controller to eliminate the asymmetric of controlled plant and uncertain load force interference. Takagi-Sugeno (T-S fuzzy inference model was used to build the fuzzy adaptive controller. With T-S model, the controller directly imposes adaptive control signal on the plant to make sure that the output of plant could track the reference model output. The controller has simple structure and is easy to implement. Experiment results show that the controller can eliminate asymmetric and achieve good dynamic performance, and has good robustness to load interference.

Vectorization, parallelization and porting of nuclear codes (vectorization and parallelization). Progress report fiscal 1998

International Nuclear Information System (INIS)

Ishizuki, Shigeru; Kawai, Wataru; Nemoto, Toshiyuki; Ogasawara, Shinobu; Kume, Etsuo; Adachi, Masaaki; Kawasaki, Nobuo; Yatake, Yo-ichi

2000-03-01

Several computer codes in the nuclear field have been vectorized, parallelized and transported on the FUJITSU VPP500 system, the AP3000 system and the Paragon system at Center for Promotion of Computational Science and Engineering in Japan Atomic Energy Research Institute. We dealt with 12 codes in fiscal 1998. These results are reported in 3 parts, i.e., the vectorization and parallelization on vector processors part, the parallelization on scalar processors part and the porting part. In this report, we describe the vectorization and parallelization on vector processors. In this vectorization and parallelization on vector processors part, the vectorization of General Tokamak Circuit Simulation Program code GTCSP, the vectorization and parallelization of Molecular Dynamics NTV (n-particle, Temperature and Velocity) Simulation code MSP2, Eddy Current Analysis code EDDYCAL, Thermal Analysis Code for Test of Passive Cooling System by HENDEL T2 code THANPACST2 and MHD Equilibrium code SELENEJ on the VPP500 are described. In the parallelization on scalar processors part, the parallelization of Monte Carlo N-Particle Transport code MCNP4B2, Plasma Hydrodynamics code using Cubic Interpolated Propagation Method PHCIP and Vectorized Monte Carlo code (continuous energy model / multi-group model) MVP/GMVP on the Paragon are described. In the porting part, the porting of Monte Carlo N-Particle Transport code MCNP4B2 and Reactor Safety Analysis code RELAP5 on the AP3000 are described. (author)

Harmonic analysis on symmetric spaces

CERN Document Server

Terras, Audrey

This text explores the geometry and analysis of higher rank analogues of the symmetric spaces introduced in volume one. To illuminate both the parallels and differences of the higher rank theory, the space of positive matrices is treated in a manner mirroring that of the upper-half space in volume one. This concrete example furnishes motivation for the general theory of noncompact symmetric spaces, which is outlined in the final chapter. The book emphasizes motivation and comprehensibility, concrete examples and explicit computations (by pen and paper, and by computer), history, and, above all, applications in mathematics, statistics, physics, and engineering. The second edition includes new sections on Donald St. P. Richards’s central limit theorem for O(n)-invariant random variables on the symmetric space of GL(n, R), on random  matrix theory, and on advances in the theory of automorphic forms on arithmetic groups.

Parallel-vector algorithms for particle simulations on shared-memory multiprocessors

International Nuclear Information System (INIS)

Nishiura, Daisuke; Sakaguchi, Hide

2011-01-01

Over the last few decades, the computational demands of massive particle-based simulations for both scientific and industrial purposes have been continuously increasing. Hence, considerable efforts are being made to develop parallel computing techniques on various platforms. In such simulations, particles freely move within a given space, and so on a distributed-memory system, load balancing, i.e., assigning an equal number of particles to each processor, is not guaranteed. However, shared-memory systems achieve better load balancing for particle models, but suffer from the intrinsic drawback of memory access competition, particularly during (1) paring of contact candidates from among neighboring particles and (2) force summation for each particle. Here, novel algorithms are proposed to overcome these two problems. For the first problem, the key is a pre-conditioning process during which particle labels are sorted by a cell label in the domain to which the particles belong. Then, a list of contact candidates is constructed by pairing the sorted particle labels. For the latter problem, a table comprising the list indexes of the contact candidate pairs is created and used to sum the contact forces acting on each particle for all contacts according to Newton's third law. With just these methods, memory access competition is avoided without additional redundant procedures. The parallel efficiency and compatibility of these two algorithms were evaluated in discrete element method (DEM) simulations on four types of shared-memory parallel computers: a multicore multiprocessor computer, scalar supercomputer, vector supercomputer, and graphics processing unit. The computational efficiency of a DEM code was found to be drastically improved with our algorithms on all but the scalar supercomputer. Thus, the developed parallel algorithms are useful on shared-memory parallel computers with sufficient memory bandwidth.

Parallel External Memory Graph Algorithms

DEFF Research Database (Denmark)

Arge, Lars Allan; Goodrich, Michael T.; Sitchinava, Nodari

2010-01-01

In this paper, we study parallel I/O efficient graph algorithms in the Parallel External Memory (PEM) model, one o f the private-cache chip multiprocessor (CMP) models. We study the fundamental problem of list ranking which leads to efficient solutions to problems on trees, such as computing lowest...... an optimal speedup of ¿(P) in parallel I/O complexity and parallel computation time, compared to the single-processor external memory counterparts....

Methods to model-check parallel systems software

International Nuclear Information System (INIS)

Matlin, O. S.; McCune, W.; Lusk, E.

2003-01-01

We report on an effort to develop methodologies for formal verification of parts of the Multi-Purpose Daemon (MPD) parallel process management system. MPD is a distributed collection of communicating processes. While the individual components of the collection execute simple algorithms, their interaction leads to unexpected errors that are difficult to uncover by conventional means. Two verification approaches are discussed here: the standard model checking approach using the software model checker SPIN and the nonstandard use of a general-purpose first-order resolution-style theorem prover OTTER to conduct the traditional state space exploration. We compare modeling methodology and analyze performance and scalability of the two methods with respect to verification of MPD

A Parallel Compact Multi-Dimensional Numerical Algorithm with Aeroacoustics Applications

Science.gov (United States)

Povitsky, Alex; Morris, Philip J.

1999-01-01

In this study we propose a novel method to parallelize high-order compact numerical algorithms for the solution of three-dimensional PDEs (Partial Differential Equations) in a space-time domain. For this numerical integration most of the computer time is spent in computation of spatial derivatives at each stage of the Runge-Kutta temporal update. The most efficient direct method to compute spatial derivatives on a serial computer is a version of Gaussian elimination for narrow linear banded systems known as the Thomas algorithm. In a straightforward pipelined implementation of the Thomas algorithm processors are idle due to the forward and backward recurrences of the Thomas algorithm. To utilize processors during this time, we propose to use them for either non-local data independent computations, solving lines in the next spatial direction, or local data-dependent computations by the Runge-Kutta method. To achieve this goal, control of processor communication and computations by a static schedule is adopted. Thus, our parallel code is driven by a communication and computation schedule instead of the usual "creative, programming" approach. The obtained parallelization speed-up of the novel algorithm is about twice as much as that for the standard pipelined algorithm and close to that for the explicit DRP algorithm.

Learning Joint-Sparse Codes for Calibration-Free Parallel MR Imaging.

Science.gov (United States)

Wang, Shanshan; Tan, Sha; Gao, Yuan; Liu, Qiegen; Ying, Leslie; Xiao, Taohui; Liu, Yuanyuan; Liu, Xin; Zheng, Hairong; Liang, Dong

2018-01-01

The integration of compressed sensing and parallel imaging (CS-PI) has shown an increased popularity in recent years to accelerate magnetic resonance (MR) imaging. Among them, calibration-free techniques have presented encouraging performances due to its capability in robustly handling the sensitivity information. Unfortunately, existing calibration-free methods have only explored joint-sparsity with direct analysis transform projections. To further exploit joint-sparsity and improve reconstruction accuracy, this paper proposes to Learn joINt-sparse coDes for caliBration-free parallEl mR imaGing (LINDBERG) by modeling the parallel MR imaging problem as an - - minimization objective with an norm constraining data fidelity, Frobenius norm enforcing sparse representation error and the mixed norm triggering joint sparsity across multichannels. A corresponding algorithm has been developed to alternatively update the sparse representation, sensitivity encoded images and K-space data. Then, the final image is produced as the square root of sum of squares of all channel images. Experimental results on both physical phantom and in vivo data sets show that the proposed method is comparable and even superior to state-of-the-art CS-PI reconstruction approaches. Specifically, LINDBERG has presented strong capability in suppressing noise and artifacts while reconstructing MR images from highly undersampled multichannel measurements.

An efficient parallel algorithm: Poststack and prestack Kirchhoff 3D depth migration using flexi-depth iterations

Science.gov (United States)

Rastogi, Richa; Srivastava, Abhishek; Khonde, Kiran; Sirasala, Kirannmayi M.; Londhe, Ashutosh; Chavhan, Hitesh

2015-07-01

This paper presents an efficient parallel 3D Kirchhoff depth migration algorithm suitable for current class of multicore architecture. The fundamental Kirchhoff depth migration algorithm exhibits inherent parallelism however, when it comes to 3D data migration, as the data size increases the resource requirement of the algorithm also increases. This challenges its practical implementation even on current generation high performance computing systems. Therefore a smart parallelization approach is essential to handle 3D data for migration. The most compute intensive part of Kirchhoff depth migration algorithm is the calculation of traveltime tables due to its resource requirements such as memory/storage and I/O. In the current research work, we target this area and develop a competent parallel algorithm for post and prestack 3D Kirchhoff depth migration, using hybrid MPI+OpenMP programming techniques. We introduce a concept of flexi-depth iterations while depth migrating data in parallel imaging space, using optimized traveltime table computations. This concept provides flexibility to the algorithm by migrating data in a number of depth iterations, which depends upon the available node memory and the size of data to be migrated during runtime. Furthermore, it minimizes the requirements of storage, I/O and inter-node communication, thus making it advantageous over the conventional parallelization approaches. The developed parallel algorithm is demonstrated and analysed on Yuva II, a PARAM series of supercomputers. Optimization, performance and scalability experiment results along with the migration outcome show the effectiveness of the parallel algorithm.

Sparse Probabilistic Parallel Factor Analysis for the Modeling of PET and Task-fMRI Data

DEFF Research Database (Denmark)

Beliveau, Vincent; Papoutsakis, Georgios; Hinrich, Jesper Løve

2017-01-01

Modern datasets are often multiway in nature and can contain patterns common to a mode of the data (e.g. space, time, and subjects). Multiway decomposition such as parallel factor analysis (PARAFAC) take into account the intrinsic structure of the data, and sparse versions of these methods improv...

Parallel inter channel interaction mechanisms

International Nuclear Information System (INIS)

Jovic, V.; Afgan, N.; Jovic, L.

1995-01-01

Parallel channels interactions are examined. For experimental researches of nonstationary regimes flow in three parallel vertical channels results of phenomenon analysis and mechanisms of parallel channel interaction for adiabatic condition of one-phase fluid and two-phase mixture flow are shown. (author)

Parallel paving: An algorithm for generating distributed, adaptive, all-quadrilateral meshes on parallel computers

Energy Technology Data Exchange (ETDEWEB)

Lober, R.R.; Tautges, T.J.; Vaughan, C.T.

1997-03-01

Paving is an automated mesh generation algorithm which produces all-quadrilateral elements. It can additionally generate these elements in varying sizes such that the resulting mesh adapts to a function distribution, such as an error function. While powerful, conventional paving is a very serial algorithm in its operation. Parallel paving is the extension of serial paving into parallel environments to perform the same meshing functions as conventional paving only on distributed, discretized models. This extension allows large, adaptive, parallel finite element simulations to take advantage of paving`s meshing capabilities for h-remap remeshing. A significantly modified version of the CUBIT mesh generation code has been developed to host the parallel paving algorithm and demonstrate its capabilities on both two dimensional and three dimensional surface geometries and compare the resulting parallel produced meshes to conventionally paved meshes for mesh quality and algorithm performance. Sandia`s {open_quotes}tiling{close_quotes} dynamic load balancing code has also been extended to work with the paving algorithm to retain parallel efficiency as subdomains undergo iterative mesh refinement.

Parallel Reservoir Simulations with Sparse Grid Techniques and Applications to Wormhole Propagation

KAUST Repository

Wu, Yuanqing

2015-09-08

In this work, two topics of reservoir simulations are discussed. The first topic is the two-phase compositional flow simulation in hydrocarbon reservoir. The major obstacle that impedes the applicability of the simulation code is the long run time of the simulation procedure, and thus speeding up the simulation code is necessary. Two means are demonstrated to address the problem: parallelism in physical space and the application of sparse grids in parameter space. The parallel code can gain satisfactory scalability, and the sparse grids can remove the bottleneck of flash calculations. Instead of carrying out the flash calculation in each time step of the simulation, a sparse grid approximation of all possible results of the flash calculation is generated before the simulation. Then the constructed surrogate model is evaluated to approximate the flash calculation results during the simulation. The second topic is the wormhole propagation simulation in carbonate reservoir. In this work, different from the traditional simulation technique relying on the Darcy framework, we propose a new framework called Darcy-Brinkman-Forchheimer framework to simulate wormhole propagation. Furthermore, to process the large quantity of cells in the simulation grid and shorten the long simulation time of the traditional serial code, standard domain-based parallelism is employed, using the Hypre multigrid library. In addition to that, a new technique called “experimenting field approach” to set coefficients in the model equations is introduced. In the 2D dissolution experiments, different configurations of wormholes and a series of properties simulated by both frameworks are compared. We conclude that the numerical results of the DBF framework are more like wormholes and more stable than the Darcy framework, which is a demonstration of the advantages of the DBF framework. The scalability of the parallel code is also evaluated, and good scalability can be achieved. Finally, a mixed

Classical optics and curved spaces

International Nuclear Information System (INIS)

Bailyn, M.; Ragusa, S.

1976-01-01

In the eikonal approximation of classical optics, the unit polarization 3-vector of light satisfies an equation that depends only on the index, n, of refraction. It is known that if the original 3-space line element is d sigma 2 , then this polarization direction propagates parallely in the fictitious space n 2 d sigma 2 . Since the equation depends only on n, it is possible to invent a fictitious curved 4-space in which the light performs a null geodesic, and the polarization 3-vector behaves as the 'shadow' of a parallely propagated 4-vector. The inverse, namely, the reduction of Maxwell's equation, on a curve 'dielectric free) space, to a classical space with dielectric constant n=(-g 00 ) -1 / 2 is well known, but in the latter the dielectric constant epsilon and permeability μ must also equal (-g 00 ) -1 / 2 . The rotation of polarization as light bends around the sun by utilizing the reduction to the classical space, is calculated. This (non-) rotation may then be interpreted as parallel transport in the 3-space n 2 d sigma 2 [pt

A nonrecursive order N preconditioned conjugate gradient: Range space formulation of MDOF dynamics

Science.gov (United States)

Kurdila, Andrew J.

1990-01-01

While excellent progress has been made in deriving algorithms that are efficient for certain combinations of system topologies and concurrent multiprocessing hardware, several issues must be resolved to incorporate transient simulation in the control design process for large space structures. Specifically, strategies must be developed that are applicable to systems with numerous degrees of freedom. In addition, the algorithms must have a growth potential in that they must also be amenable to implementation on forthcoming parallel system architectures. For mechanical system simulation, this fact implies that algorithms are required that induce parallelism on a fine scale, suitable for the emerging class of highly parallel processors; and transient simulation methods must be automatically load balancing for a wider collection of system topologies and hardware configurations. These problems are addressed by employing a combination range space/preconditioned conjugate gradient formulation of multi-degree-of-freedom dynamics. The method described has several advantages. In a sequential computing environment, the method has the features that: by employing regular ordering of the system connectivity graph, an extremely efficient preconditioner can be derived from the 'range space metric', as opposed to the system coefficient matrix; because of the effectiveness of the preconditioner, preliminary studies indicate that the method can achieve performance rates that depend linearly upon the number of substructures, hence the title 'Order N'; and the method is non-assembling. Furthermore, the approach is promising as a potential parallel processing algorithm in that the method exhibits a fine parallel granularity suitable for a wide collection of combinations of physical system topologies/computer architectures; and the method is easily load balanced among processors, and does not rely upon system topology to induce parallelism.

Evaluation of alias-less reconstruction by pseudo-parallel imaging in a phase-scrambling fourier transform technique

International Nuclear Information System (INIS)

Ito, Satoshi; Kawawa, Yasuhiro; Yamada, Yoshifumi

2010-01-01

We propose an image reconstruction technique in which parallel image reconstruction is performed based on the sensitivity encoding (SENSE) algorithm using only a single set of signals. The signal obtained in the phase-scrambling Fourier transform (PSFT) imaging technique can be transformed to the signal described by the Fresnel transform of the objects, which is known as the diffracted wave-front equation of the object in acoustics or optics. Since the Fresnel transform is a convolution integral on the object space, the space where the PSFT signal exists can be considered as both in the Fourier domain and in the object domain. This notable feature indicates that weighting functions corresponding to the sensitivity of radiofrequency (RF) coils can be approximately given in the PSFT signal space. Therefore, we can obtain two folded images from a single set of signals with different weighting functions, and image reconstruction based on the SENSE parallel imaging algorithm is possible using a series of folded images. Simulation and experimental studies showed that almost alias-free images can be synthesized using a single signal that does not satisfy the sampling theorem. (author)

Seeing or moving in parallel

DEFF Research Database (Denmark)

Christensen, Mark Schram; Ehrsson, H Henrik; Nielsen, Jens Bo

2013-01-01

a different network, involving bilateral dorsal premotor cortex (PMd), primary motor cortex, and SMA, was more active when subjects viewed parallel movements while performing either symmetrical or parallel movements. Correlations between behavioral instability and brain activity were present in right lateral...... adduction-abduction movements symmetrically or in parallel with real-time congruent or incongruent visual feedback of the movements. One network, consisting of bilateral superior and middle frontal gyrus and supplementary motor area (SMA), was more active when subjects performed parallel movements, whereas...

The numerical parallel computing of photon transport

International Nuclear Information System (INIS)

Huang Qingnan; Liang Xiaoguang; Zhang Lifa

1998-12-01

The parallel computing of photon transport is investigated, the parallel algorithm and the parallelization of programs on parallel computers both with shared memory and with distributed memory are discussed. By analyzing the inherent law of the mathematics and physics model of photon transport according to the structure feature of parallel computers, using the strategy of 'to divide and conquer', adjusting the algorithm structure of the program, dissolving the data relationship, finding parallel liable ingredients and creating large grain parallel subtasks, the sequential computing of photon transport into is efficiently transformed into parallel and vector computing. The program was run on various HP parallel computers such as the HY-1 (PVP), the Challenge (SMP) and the YH-3 (MPP) and very good parallel speedup has been gotten

Hypergraph partitioning implementation for parallelizing matrix-vector multiplication using CUDA GPU-based parallel computing

Science.gov (United States)

Murni, Bustamam, A.; Ernastuti, Handhika, T.; Kerami, D.

2017-07-01

Calculation of the matrix-vector multiplication in the real-world problems often involves large matrix with arbitrary size. Therefore, parallelization is needed to speed up the calculation process that usually takes a long time. Graph partitioning techniques that have been discussed in the previous studies cannot be used to complete the parallelized calculation of matrix-vector multiplication with arbitrary size. This is due to the assumption of graph partitioning techniques that can only solve the square and symmetric matrix. Hypergraph partitioning techniques will overcome the shortcomings of the graph partitioning technique. This paper addresses the efficient parallelization of matrix-vector multiplication through hypergraph partitioning techniques using CUDA GPU-based parallel computing. CUDA (compute unified device architecture) is a parallel computing platform and programming model that was created by NVIDIA and implemented by the GPU (graphics processing unit).

Writing parallel programs that work

CERN Multimedia

CERN. Geneva

2012-01-01

Serial algorithms typically run inefficiently on parallel machines. This may sound like an obvious statement, but it is the root cause of why parallel programming is considered to be difficult. The current state of the computer industry is still that almost all programs in existence are serial. This talk will describe the techniques used in the Intel Parallel Studio to provide a developer with the tools necessary to understand the behaviors and limitations of the existing serial programs. Once the limitations are known the developer can refactor the algorithms and reanalyze the resulting programs with the tools in the Intel Parallel Studio to create parallel programs that work. About the speaker Paul Petersen is a Sr. Principal Engineer in the Software and Solutions Group (SSG) at Intel. He received a Ph.D. degree in Computer Science from the University of Illinois in 1993. After UIUC, he was employed at Kuck and Associates, Inc. (KAI) working on auto-parallelizing compiler (KAP), and was involved in th...

Parallel Framework for Cooperative Processes

Directory of Open Access Journals (Sweden)

Mitică Craus

2005-01-01

Full Text Available This paper describes the work of an object oriented framework designed to be used in the parallelization of a set of related algorithms. The idea behind the system we are describing is to have a re-usable framework for running several sequential algorithms in a parallel environment. The algorithms that the framework can be used with have several things in common: they have to run in cycles and the work should be possible to be split between several "processing units". The parallel framework uses the message-passing communication paradigm and is organized as a master-slave system. Two applications are presented: an Ant Colony Optimization (ACO parallel algorithm for the Travelling Salesman Problem (TSP and an Image Processing (IP parallel algorithm for the Symmetrical Neighborhood Filter (SNF. The implementations of these applications by means of the parallel framework prove to have good performances: approximatively linear speedup and low communication cost.

Compiler Technology for Parallel Scientific Computation

Directory of Open Access Journals (Sweden)

Can Özturan

1994-01-01

Full Text Available There is a need for compiler technology that, given the source program, will generate efficient parallel codes for different architectures with minimal user involvement. Parallel computation is becoming indispensable in solving large-scale problems in science and engineering. Yet, the use of parallel computation is limited by the high costs of developing the needed software. To overcome this difficulty we advocate a comprehensive approach to the development of scalable architecture-independent software for scientific computation based on our experience with equational programming language (EPL. Our approach is based on a program decomposition, parallel code synthesis, and run-time support for parallel scientific computation. The program decomposition is guided by the source program annotations provided by the user. The synthesis of parallel code is based on configurations that describe the overall computation as a set of interacting components. Run-time support is provided by the compiler-generated code that redistributes computation and data during object program execution. The generated parallel code is optimized using techniques of data alignment, operator placement, wavefront determination, and memory optimization. In this article we discuss annotations, configurations, parallel code generation, and run-time support suitable for parallel programs written in the functional parallel programming language EPL and in Fortran.

Fabrication of Si-nozzles for parallel mechano-electrospinning direct writing

International Nuclear Information System (INIS)

Pan, Yanqiao; Huang, YongAn; Bu, Ningbin; Yin, Zhouping

2013-01-01

Nozzles with micro-scale orifices drive high-resolution printing techniques for generating micro- to nano-scale droplets/lines. This paper presents the fabrication and application of Si-nozzles in mechano-electrospinning (MES). The fabrication process mainly consists of photolithography, Au deposition, inductively coupled plasma, and polydimethylsiloxane encapsulation. The 6 wt% polyethylene oxide solution is adopted to study the electrospinning behaviour and the relations between fibre diameter and process parameters in MES. A fibre grid with 250 µm spacing is able to be direct written, and the diameters are less than 3 µm. To improve the printing efficiency, positioning accuracy and flexibility, a rotatable multi-nozzle is adopted. The distance between parallel lines reduces sharply from 4.927 to 0.308 mm with the rotating angle increasing from 0° to 87°, and the fibre grids with tunable distance are achieved. This method paves the way for fabrication of addressable Si-nozzle array in parallel MES direct writing. (paper)

Parallel computing: numerics, applications, and trends

National Research Council Canada - National Science Library

Trobec, Roman; Vajteršic, Marián; Zinterhof, Peter

2009-01-01

... and/or distributed systems. The contributions to this book are focused on topics most concerned in the trends of today's parallel computing. These range from parallel algorithmics, programming, tools, network computing to future parallel computing. Particular attention is paid to parallel numerics: linear algebra, differential equations, numerica...

Parallel Computing Strategies for Irregular Algorithms

Science.gov (United States)

Biswas, Rupak; Oliker, Leonid; Shan, Hongzhang; Biegel, Bryan (Technical Monitor)

2002-01-01

Parallel computing promises several orders of magnitude increase in our ability to solve realistic computationally-intensive problems, but relies on their efficient mapping and execution on large-scale multiprocessor architectures. Unfortunately, many important applications are irregular and dynamic in nature, making their effective parallel implementation a daunting task. Moreover, with the proliferation of parallel architectures and programming paradigms, the typical scientist is faced with a plethora of questions that must be answered in order to obtain an acceptable parallel implementation of the solution algorithm. In this paper, we consider three representative irregular applications: unstructured remeshing, sparse matrix computations, and N-body problems, and parallelize them using various popular programming paradigms on a wide spectrum of computer platforms ranging from state-of-the-art supercomputers to PC clusters. We present the underlying problems, the solution algorithms, and the parallel implementation strategies. Smart load-balancing, partitioning, and ordering techniques are used to enhance parallel performance. Overall results demonstrate the complexity of efficiently parallelizing irregular algorithms.

DICE/ColDICE: 6D collisionless phase space hydrodynamics using a lagrangian tesselation

Science.gov (United States)

Sousbie, Thierry

2018-01-01

DICE is a C++ template library designed to solve collisionless fluid dynamics in 6D phase space using massively parallel supercomputers via an hybrid OpenMP/MPI parallelization. ColDICE, based on DICE, implements a cosmological and physical VLASOV-POISSON solver for cold systems such as dark matter (CDM) dynamics.

OS and Runtime Support for Efficiently Managing Cores in Parallel Applications

OpenAIRE

Klues, Kevin Alan

2015-01-01

Parallel applications can benefit from the ability to explicitly control their thread scheduling policies in user-space. However, modern operating systems lack the interfaces necessary to make this type of “user-level” scheduling efficient. The key component missing is the ability for applications to gain direct access to cores and keep control of those cores even when making I/O operations that traditionally block in the kernel. A number of former systems provided limited support for these c...

The Glasgow Parallel Reduction Machine: Programming Shared-memory Many-core Systems using Parallel Task Composition

Directory of Open Access Journals (Sweden)

Ashkan Tousimojarad

2013-12-01

Full Text Available We present the Glasgow Parallel Reduction Machine (GPRM, a novel, flexible framework for parallel task-composition based many-core programming. We allow the programmer to structure programs into task code, written as C++ classes, and communication code, written in a restricted subset of C++ with functional semantics and parallel evaluation. In this paper we discuss the GPRM, the virtual machine framework that enables the parallel task composition approach. We focus the discussion on GPIR, the functional language used as the intermediate representation of the bytecode running on the GPRM. Using examples in this language we show the flexibility and power of our task composition framework. We demonstrate the potential using an implementation of a merge sort algorithm on a 64-core Tilera processor, as well as on a conventional Intel quad-core processor and an AMD 48-core processor system. We also compare our framework with OpenMP tasks in a parallel pointer chasing algorithm running on the Tilera processor. Our results show that the GPRM programs outperform the corresponding OpenMP codes on all test platforms, and can greatly facilitate writing of parallel programs, in particular non-data parallel algorithms such as reductions.

Sieving for pseudosquares and pseudocubes in parallel using doubly-focused enumeration and wheel datastructures

OpenAIRE

Sorenson, Jonathan P.

2010-01-01

We extend the known tables of pseudosquares and pseudocubes, discuss the implications of these new data on the conjectured distribution of pseudosquares and pseudocubes, and present the details of the algorithm used to do this work. Our algorithm is based on the space-saving wheel data structure combined with doubly-focused enumeration, run in parallel on a cluster supercomputer.

Workspace optimization and kinematic performance evaluation of 2-DOF parallel mechanisms

International Nuclear Information System (INIS)

Nam, Yun Joo; Park, Myeong Kwan

2006-01-01

This paper presents the kinematics and workspace optimization of the two different 2-DOF (Degrees-of-Freedom) planar parallel mechanisms: one (called 2-RPR mechanism) with translational actuators and the other (called 2-RRR mechanism) with rotational ones. First of all, the inverse kinematics and Jacobian matrix for each mechanism are derived analytically. Then, the workspace including the output-space and the joint-space is systematically analyzed in order to determine the geometric parameters and the operating range of the actuators. Finally, the kinematic optimization of the mechanisms is performed in consideration of their dexterity and rigidity. It is expected that the optimization results can be effectively used as a basic material for the applications of the presented mechanisms to more industrial fields

Immuno-Oncology-The Translational Runway for Gene Therapy: Gene Therapeutics to Address Multiple Immune Targets.

Science.gov (United States)

Weß, Ludger; Schnieders, Frank

2017-12-01

Cancer therapy is once again experiencing a paradigm shift. This shift is based on extensive clinical experience demonstrating that cancer cannot be successfully fought by addressing only single targets or pathways. Even the combination of several neo-antigens in cancer vaccines is not sufficient for successful, lasting tumor eradication. The focus has therefore shifted to the immune system's role in cancer and the striking abilities of cancer cells to manipulate and/or deactivate the immune system. Researchers and pharma companies have started to target the processes and cells known to support immune surveillance and the elimination of tumor cells. Immune processes, however, require novel concepts beyond the traditional "single-target-single drug" paradigm and need parallel targeting of diverse cells and mechanisms. This review gives a perspective on the role of gene therapy technologies in the evolving immuno-oncology space and identifies gene therapy as a major driver in the development and regulation of effective cancer immunotherapy. Present challenges and breakthroughs ranging from chimeric antigen receptor T-cell therapy, gene-modified oncolytic viruses, combination cancer vaccines, to RNA therapeutics are spotlighted. Gene therapy is recognized as the most prominent technology enabling effective immuno-oncology strategies.

Lead-Free Experiment in a Space Environment

Science.gov (United States)

Blanche, J. F.; Strickland, S. M.

2012-01-01

This Technical Memorandum addresses the Lead-Free Technology Experiment in Space Environment that flew as part of the seventh Materials International Space Station Experiment outside the International Space Station for approximately 18 months. Its intent was to provide data on the performance of lead-free electronics in an actual space environment. Its postflight condition is compared to the preflight condition as well as to the condition of an identical package operating in parallel in the laboratory. Some tin whisker growth was seen on a flight board but the whiskers were few and short. There were no solder joint failures, no tin pest formation, and no significant intermetallic compound formation or growth on either the flight or ground units.

Decoupled Sliding Mode Control for a Novel 3-DOF Parallel Manipulator with Actuation Redundancy

Directory of Open Access Journals (Sweden)

Niu Xuemei

2015-05-01

Full Text Available This paper presents a decoupled nonsingular terminal sliding mode controller (DNTSMC for a novel 3-DOF parallel manipulator with actuation redundancy. According to kinematic analysis, the inverse dynamic model for a novel 3-DOF redundantly actuated parallel manipulator is formulated in the task space using Lagrangian formalism and decoupled into three entirely independent subsystems under generalized coordinates to significantly reduce system complexity. Based on the dynamic model, a decoupled sliding mode control strategy is proposed for the parallel manipulator; the idea behind this strategy is to design a nonsingular terminal sliding mode controller for each subsystem, which can drive states of three subsystems to the original equilibrium points simultaneously by two intermediate variables. Additionally, a RBF neural network is used to compensate the cross-coupling force and gravity to enhance the control precision. Simulation and experimental results show that the proposed DNTSMC can achieve better control performances compared with the conventional sliding mode controller (SMC and the DNTSMC without compensator.

Patterns for Parallel Software Design

CERN Document Server

Ortega-Arjona, Jorge Luis

2010-01-01

Essential reading to understand patterns for parallel programming Software patterns have revolutionized the way we think about how software is designed, built, and documented, and the design of parallel software requires you to consider other particular design aspects and special skills. From clusters to supercomputers, success heavily depends on the design skills of software developers. Patterns for Parallel Software Design presents a pattern-oriented software architecture approach to parallel software design. This approach is not a design method in the classic sense, but a new way of managin

High performance parallel I/O

CERN Document Server

Prabhat

2014-01-01

Gain Critical Insight into the Parallel I/O EcosystemParallel I/O is an integral component of modern high performance computing (HPC), especially in storing and processing very large datasets to facilitate scientific discovery. Revealing the state of the art in this field, High Performance Parallel I/O draws on insights from leading practitioners, researchers, software architects, developers, and scientists who shed light on the parallel I/O ecosystem.The first part of the book explains how large-scale HPC facilities scope, configure, and operate systems, with an emphasis on choices of I/O har

Parallel transport of long mean-free-path plasma along open magnetic field lines: Parallel heat flux

International Nuclear Information System (INIS)

Guo Zehua; Tang Xianzhu

2012-01-01

In a long mean-free-path plasma where temperature anisotropy can be sustained, the parallel heat flux has two components with one associated with the parallel thermal energy and the other the perpendicular thermal energy. Due to the large deviation of the distribution function from local Maxwellian in an open field line plasma with low collisionality, the conventional perturbative calculation of the parallel heat flux closure in its local or non-local form is no longer applicable. Here, a non-perturbative calculation is presented for a collisionless plasma in a two-dimensional flux expander bounded by absorbing walls. Specifically, closures of previously unfamiliar form are obtained for ions and electrons, which relate two distinct components of the species parallel heat flux to the lower order fluid moments such as density, parallel flow, parallel and perpendicular temperatures, and the field quantities such as the magnetic field strength and the electrostatic potential. The plasma source and boundary condition at the absorbing wall enter explicitly in the closure calculation. Although the closure calculation does not take into account wave-particle interactions, the results based on passing orbits from steady-state collisionless drift-kinetic equation show remarkable agreement with fully kinetic-Maxwell simulations. As an example of the physical implications of the theory, the parallel heat flux closures are found to predict a surprising observation in the kinetic-Maxwell simulation of the 2D magnetic flux expander problem, where the parallel heat flux of the parallel thermal energy flows from low to high parallel temperature region.

Reduction of momentum transfer rates by parallel electric fields: A two-fluid demonstration

International Nuclear Information System (INIS)

Delamere, P.A.; Stenbaek-Nielsen, H.C.; Otto, A.

2002-01-01

Momentum transfer between an ionized gas cloud moving relative to an ambient magnetized plasma is a general problem in space plasma physics. Obvious examples include the Io-Jupiter interaction, comets, and coronal mass ejections. Active plasma experiments have demonstrated that momentum transfer rates associated with Alfven wave propagation are poorly understood. Barium injection experiments from the Combined Release and Radiation Effects Satellite (CRRES) have shown that dense ionized clouds are capable of ExB drifting over large distances perpendicular to the magnetic field. The CRRES 'skidding' distances were much larger than predicted by magnetohydrodynamic theory and it has been proposed that parallel electric fields were a key component in the skidding phenomenon. A two-fluid code was used to demonstrate the role of parallel electric fields in reducing momentum transfer between two distinct plasma populations. In this study, a dense plasma was initialized moving relative to an ambient plasma and perpendicular to B. Parallel electric fields were introduced via a friction term in the electron momentum equation and the collision frequency was scaled in proportion to the field-aligned current density. The simulation results showed that parallel electric fields decreased the decelerating magnetic tension force on the plasma cloud through a magnetic diffusion/reconnection process

Ghost neutrinos as test fields in curved space-time

International Nuclear Information System (INIS)

Audretsch, J.

1976-01-01

Without restricting to empty space-times, it is shown that ghost neutrinos (their energy-momentum tensor vanishes) can only be found in algebraically special space-times with a neutrino flux vector parallel to one of the principal null vectors of the conformal tensor. The optical properties are studied. There are no ghost neutrinos in the Kerr-Newman and in spherically symmetric space-times. The example of a non-vacuum gravitational pp-wave accompanied by a ghost neutrino pp-wave is discussed. (Auth.)

Is Monte Carlo embarrassingly parallel?

Energy Technology Data Exchange (ETDEWEB)

Hoogenboom, J. E. [Delft Univ. of Technology, Mekelweg 15, 2629 JB Delft (Netherlands); Delft Nuclear Consultancy, IJsselzoom 2, 2902 LB Capelle aan den IJssel (Netherlands)

2012-07-01

Monte Carlo is often stated as being embarrassingly parallel. However, running a Monte Carlo calculation, especially a reactor criticality calculation, in parallel using tens of processors shows a serious limitation in speedup and the execution time may even increase beyond a certain number of processors. In this paper the main causes of the loss of efficiency when using many processors are analyzed using a simple Monte Carlo program for criticality. The basic mechanism for parallel execution is MPI. One of the bottlenecks turn out to be the rendez-vous points in the parallel calculation used for synchronization and exchange of data between processors. This happens at least at the end of each cycle for fission source generation in order to collect the full fission source distribution for the next cycle and to estimate the effective multiplication factor, which is not only part of the requested results, but also input to the next cycle for population control. Basic improvements to overcome this limitation are suggested and tested. Also other time losses in the parallel calculation are identified. Moreover, the threading mechanism, which allows the parallel execution of tasks based on shared memory using OpenMP, is analyzed in detail. Recommendations are given to get the maximum efficiency out of a parallel Monte Carlo calculation. (authors)

Is Monte Carlo embarrassingly parallel?

International Nuclear Information System (INIS)

Hoogenboom, J. E.

2012-01-01

Monte Carlo is often stated as being embarrassingly parallel. However, running a Monte Carlo calculation, especially a reactor criticality calculation, in parallel using tens of processors shows a serious limitation in speedup and the execution time may even increase beyond a certain number of processors. In this paper the main causes of the loss of efficiency when using many processors are analyzed using a simple Monte Carlo program for criticality. The basic mechanism for parallel execution is MPI. One of the bottlenecks turn out to be the rendez-vous points in the parallel calculation used for synchronization and exchange of data between processors. This happens at least at the end of each cycle for fission source generation in order to collect the full fission source distribution for the next cycle and to estimate the effective multiplication factor, which is not only part of the requested results, but also input to the next cycle for population control. Basic improvements to overcome this limitation are suggested and tested. Also other time losses in the parallel calculation are identified. Moreover, the threading mechanism, which allows the parallel execution of tasks based on shared memory using OpenMP, is analyzed in detail. Recommendations are given to get the maximum efficiency out of a parallel Monte Carlo calculation. (authors)

Parallel algorithms for continuum dynamics

International Nuclear Information System (INIS)

Hicks, D.L.; Liebrock, L.M.

1987-01-01

Simply porting existing parallel programs to a new parallel processor may not achieve the full speedup possible; to achieve the maximum efficiency may require redesigning the parallel algorithms for the specific architecture. The authors discuss here parallel algorithms that were developed first for the HEP processor and then ported to the CRAY X-MP/4, the ELXSI/10, and the Intel iPSC/32. Focus is mainly on the most recent parallel processing results produced, i.e., those on the Intel Hypercube. The applications are simulations of continuum dynamics in which the momentum and stress gradients are important. Examples of these are inertial confinement fusion experiments, severe breaks in the coolant system of a reactor, weapons physics, shock-wave physics. Speedup efficiencies on the Intel iPSC Hypercube are very sensitive to the ratio of communication to computation. Great care must be taken in designing algorithms for this machine to avoid global communication. This is much more critical on the iPSC than it was on the three previous parallel processors

Parallel S/sub n/ iteration schemes

International Nuclear Information System (INIS)

Wienke, B.R.; Hiromoto, R.E.

1986-01-01

The iterative, multigroup, discrete ordinates (S/sub n/) technique for solving the linear transport equation enjoys widespread usage and appeal. Serial iteration schemes and numerical algorithms developed over the years provide a timely framework for parallel extension. On the Denelcor HEP, the authors investigate three parallel iteration schemes for solving the one-dimensional S/sub n/ transport equation. The multigroup representation and serial iteration methods are also reviewed. This analysis represents a first attempt to extend serial S/sub n/ algorithms to parallel environments and provides good baseline estimates on ease of parallel implementation, relative algorithm efficiency, comparative speedup, and some future directions. The authors examine ordered and chaotic versions of these strategies, with and without concurrent rebalance and diffusion acceleration. Two strategies efficiently support high degrees of parallelization and appear to be robust parallel iteration techniques. The third strategy is a weaker parallel algorithm. Chaotic iteration, difficult to simulate on serial machines, holds promise and converges faster than ordered versions of the schemes. Actual parallel speedup and efficiency are high and payoff appears substantial

Parallel simulation of tsunami inundation on a large-scale supercomputer

Science.gov (United States)

Oishi, Y.; Imamura, F.; Sugawara, D.

2013-12-01

finite difference calculation, (2) communication between adjacent layers for the calculations to connect each layer, and (3) global communication to obtain the time step which satisfies the CFL condition in the whole domain. A preliminary test on the K computer showed the parallel efficiency on 1024 cores was 57% relative to 64 cores. We estimate that the parallel efficiency will be considerably improved by applying a 2-D domain decomposition instead of the present 1-D domain decomposition in future work. The present parallel tsunami model was applied to the 2011 Great Tohoku tsunami. The coarsest resolution layer covers a 758 km × 1155 km region with a 405 m grid spacing. A nesting of five layers was used with the resolution ratio of 1/3 between nested layers. The finest resolution region has 5 m resolution and covers most of the coastal region of Sendai city. To complete 2 hours of simulation time, the serial (non-parallel) computation took approximately 4 days on a workstation. To complete the same simulation on 1024 cores of the K computer, it took 45 minutes which is more than two times faster than real-time. This presentation discusses the updated parallel computational performance and the efficient use of the K computer when considering the characteristics of the tsunami inundation simulation model in relation to the characteristics and capabilities of the K computer.

Design and Evaluation of the Terminal Area Precision Scheduling and Spacing System

Science.gov (United States)

Swenson, Harry N.; Thipphavong, Jane; Sadovsky, Alex; Chen, Liang; Sullivan, Chris; Martin, Lynne

2011-01-01

This paper describes the design, development and results from a high fidelity human-in-the-loop simulation of an integrated set of trajectory-based automation tools providing precision scheduling, sequencing and controller merging and spacing functions. These integrated functions are combined into a system called the Terminal Area Precision Scheduling and Spacing (TAPSS) system. It is a strategic and tactical planning tool that provides Traffic Management Coordinators, En Route and Terminal Radar Approach Control air traffic controllers the ability to efficiently optimize the arrival capacity of a demand-impacted airport while simultaneously enabling fuel-efficient descent procedures. The TAPSS system consists of four-dimensional trajectory prediction, arrival runway balancing, aircraft separation constraint-based scheduling, traffic flow visualization and trajectory-based advisories to assist controllers in efficient metering, sequencing and spacing. The TAPSS system was evaluated and compared to today's ATC operation through extensive series of human-in-the-loop simulations for arrival flows into the Los Angeles International Airport. The test conditions included the variation of aircraft demand from a baseline of today's capacity constrained periods through 5%, 10% and 20% increases. Performance data were collected for engineering and human factor analysis and compared with similar operations both with and without the TAPSS system. The engineering data indicate operations with the TAPSS show up to a 10% increase in airport throughput during capacity constrained periods while maintaining fuel-efficient aircraft descent profiles from cruise to landing.

Vectorization, parallelization and porting of nuclear codes. Vectorization and parallelization. Progress report fiscal 1999

Energy Technology Data Exchange (ETDEWEB)

Adachi, Masaaki; Ogasawara, Shinobu; Kume, Etsuo [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Ishizuki, Shigeru; Nemoto, Toshiyuki; Kawasaki, Nobuo; Kawai, Wataru [Fujitsu Ltd., Tokyo (Japan); Yatake, Yo-ichi [Hitachi Ltd., Tokyo (Japan)

2001-02-01

Several computer codes in the nuclear field have been vectorized, parallelized and trans-ported on the FUJITSU VPP500 system, the AP3000 system, the SX-4 system and the Paragon system at Center for Promotion of Computational Science and Engineering in Japan Atomic Energy Research Institute. We dealt with 18 codes in fiscal 1999. These results are reported in 3 parts, i.e., the vectorization and the parallelization part on vector processors, the parallelization part on scalar processors and the porting part. In this report, we describe the vectorization and parallelization on vector processors. In this vectorization and parallelization on vector processors part, the vectorization of Relativistic Molecular Orbital Calculation code RSCAT, a microscopic transport code for high energy nuclear collisions code JAM, three-dimensional non-steady thermal-fluid analysis code STREAM, Relativistic Density Functional Theory code RDFT and High Speed Three-Dimensional Nodal Diffusion code MOSRA-Light on the VPP500 system and the SX-4 system are described. (author)

Astrium suborbital spaceplane project: Demand analysis of suborbital space tourism

Science.gov (United States)

Le Goff, Thierry; Moreau, Antoine

2013-12-01

ASTRIUM is preparing the development of a safe and passenger friendly Suborbital Spaceplane, taking off and landing from a standard runway, powered by turbofans and using a rocket engine of proven design to reach 100 km altitude. This vehicle will be able to carry paying passengers to the edge of space and return them safely to their starting point. As a very new potentially adjacent B2C market, Astrium had decided at the beginning of this project to first conduct a full market analysis with the support of a worldwide survey based Research Company (IPSOS) in order to assess reality and credibility of this market. Two campaigns have been done, the first one in 2007 and the second one in 2010 after the international financial crisis. Last one has been also the opportunity to optimize quality of models by focusing in Asia region. This article describes the methodology used for this survey and unveils some results in term of size of this market and typology of the customers.

Parallel clustering algorithm for large-scale biological data sets.

Science.gov (United States)

Wang, Minchao; Zhang, Wu; Ding, Wang; Dai, Dongbo; Zhang, Huiran; Xie, Hao; Chen, Luonan; Guo, Yike; Xie, Jiang

2014-01-01

Recent explosion of biological data brings a great challenge for the traditional clustering algorithms. With increasing scale of data sets, much larger memory and longer runtime are required for the cluster identification problems. The affinity propagation algorithm outperforms many other classical clustering algorithms and is widely applied into the biological researches. However, the time and space complexity become a great bottleneck when handling the large-scale data sets. Moreover, the similarity matrix, whose constructing procedure takes long runtime, is required before running the affinity propagation algorithm, since the algorithm clusters data sets based on the similarities between data pairs. Two types of parallel architectures are proposed in this paper to accelerate the similarity matrix constructing procedure and the affinity propagation algorithm. The memory-shared architecture is used to construct the similarity matrix, and the distributed system is taken for the affinity propagation algorithm, because of its large memory size and great computing capacity. An appropriate way of data partition and reduction is designed in our method, in order to minimize the global communication cost among processes. A speedup of 100 is gained with 128 cores. The runtime is reduced from serval hours to a few seconds, which indicates that parallel algorithm is capable of handling large-scale data sets effectively. The parallel affinity propagation also achieves a good performance when clustering large-scale gene data (microarray) and detecting families in large protein superfamilies.

Parallel R-matrix computation

International Nuclear Information System (INIS)

Heggarty, J.W.

1999-06-01

For almost thirty years, sequential R-matrix computation has been used by atomic physics research groups, from around the world, to model collision phenomena involving the scattering of electrons or positrons with atomic or molecular targets. As considerable progress has been made in the understanding of fundamental scattering processes, new data, obtained from more complex calculations, is of current interest to experimentalists. Performing such calculations, however, places considerable demands on the computational resources to be provided by the target machine, in terms of both processor speed and memory requirement. Indeed, in some instances the computational requirements are so great that the proposed R-matrix calculations are intractable, even when utilising contemporary classic supercomputers. Historically, increases in the computational requirements of R-matrix computation were accommodated by porting the problem codes to a more powerful classic supercomputer. Although this approach has been successful in the past, it is no longer considered to be a satisfactory solution due to the limitations of current (and future) Von Neumann machines. As a consequence, there has been considerable interest in the high performance multicomputers, that have emerged over the last decade which appear to offer the computational resources required by contemporary R-matrix research. Unfortunately, developing codes for these machines is not as simple a task as it was to develop codes for successive classic supercomputers. The difficulty arises from the considerable differences in the computing models that exist between the two types of machine and results in the programming of multicomputers to be widely acknowledged as a difficult, time consuming and error-prone task. Nevertheless, unless parallel R-matrix computation is realised, important theoretical and experimental atomic physics research will continue to be hindered. This thesis describes work that was undertaken in

Fuzzy Logic Based Autonomous Parallel Parking System with Kalman Filtering

Science.gov (United States)

Panomruttanarug, Benjamas; Higuchi, Kohji

This paper presents an emulation of fuzzy logic control schemes for an autonomous parallel parking system in a backward maneuver. There are four infrared sensors sending the distance data to a microcontroller for generating an obstacle-free parking path. Two of them mounted on the front and rear wheels on the parking side are used as the inputs to the fuzzy rules to calculate a proper steering angle while backing. The other two attached to the front and rear ends serve for avoiding collision with other cars along the parking space. At the end of parking processes, the vehicle will be in line with other parked cars and positioned in the middle of the free space. Fuzzy rules are designed based upon a wall following process. Performance of the infrared sensors is improved using Kalman filtering. The design method needs extra information from ultrasonic sensors. Starting from modeling the ultrasonic sensor in 1-D state space forms, one makes use of the infrared sensor as a measurement to update the predicted values. Experimental results demonstrate the effectiveness of sensor improvement.

Airport Movement Area Closure Planner, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — This SBIR research develops an automation tool improving temporary and permanent runway closure management. The Movement Area Closure Planner (MACP) provides airport...

Implementation and performance of parallelized elegant

International Nuclear Information System (INIS)

Wang, Y.; Borland, M.

2008-01-01

The program elegant is widely used for design and modeling of linacs for free-electron lasers and energy recovery linacs, as well as storage rings and other applications. As part of a multi-year effort, we have parallelized many aspects of the code, including single-particle dynamics, wakefields, and coherent synchrotron radiation. We report on the approach used for gradual parallelization, which proved very beneficial in getting parallel features into the hands of users quickly. We also report details of parallelization of collective effects. Finally, we discuss performance of the parallelized code in various applications.

Continuous development of schemes for parallel computing of the electrostatics in biological systems: implementation in DelPhi.

Science.gov (United States)

Li, Chuan; Petukh, Marharyta; Li, Lin; Alexov, Emil

2013-08-15

Due to the enormous importance of electrostatics in molecular biology, calculating the electrostatic potential and corresponding energies has become a standard computational approach for the study of biomolecules and nano-objects immersed in water and salt phase or other media. However, the electrostatics of large macromolecules and macromolecular complexes, including nano-objects, may not be obtainable via explicit methods and even the standard continuum electrostatics methods may not be applicable due to high computational time and memory requirements. Here, we report further development of the parallelization scheme reported in our previous work (Li, et al., J. Comput. Chem. 2012, 33, 1960) to include parallelization of the molecular surface and energy calculations components of the algorithm. The parallelization scheme utilizes different approaches such as space domain parallelization, algorithmic parallelization, multithreading, and task scheduling, depending on the quantity being calculated. This allows for efficient use of the computing resources of the corresponding computer cluster. The parallelization scheme is implemented in the popular software DelPhi and results in speedup of several folds. As a demonstration of the efficiency and capability of this methodology, the electrostatic potential, and electric field distributions are calculated for the bovine mitochondrial supercomplex illustrating their complex topology, which cannot be obtained by modeling the supercomplex components alone. Copyright © 2013 Wiley Periodicals, Inc.

Parallelizing the spectral transform method: A comparison of alternative parallel algorithms

International Nuclear Information System (INIS)

Foster, I.; Worley, P.H.

1993-01-01

The spectral transform method is a standard numerical technique for solving partial differential equations on the sphere and is widely used in global climate modeling. In this paper, we outline different approaches to parallelizing the method and describe experiments that we are conducting to evaluate the efficiency of these approaches on parallel computers. The experiments are conducted using a testbed code that solves the nonlinear shallow water equations on a sphere, but are designed to permit evaluation in the context of a global model. They allow us to evaluate the relative merits of the approaches as a function of problem size and number of processors. The results of this study are guiding ongoing work on PCCM2, a parallel implementation of the Community Climate Model developed at the National Center for Atmospheric Research

Algorithms for parallel computers

International Nuclear Information System (INIS)

Churchhouse, R.F.

1985-01-01

Until relatively recently almost all the algorithms for use on computers had been designed on the (usually unstated) assumption that they were to be run on single processor, serial machines. With the introduction of vector processors, array processors and interconnected systems of mainframes, minis and micros, however, various forms of parallelism have become available. The advantage of parallelism is that it offers increased overall processing speed but it also raises some fundamental questions, including: (i) which, if any, of the existing 'serial' algorithms can be adapted for use in the parallel mode. (ii) How close to optimal can such adapted algorithms be and, where relevant, what are the convergence criteria. (iii) How can we design new algorithms specifically for parallel systems. (iv) For multi-processor systems how can we handle the software aspects of the interprocessor communications. Aspects of these questions illustrated by examples are considered in these lectures. (orig.)

Parallel processing for fluid dynamics applications

International Nuclear Information System (INIS)

Johnson, G.M.

1989-01-01

The impact of parallel processing on computational science and, in particular, on computational fluid dynamics is growing rapidly. In this paper, particular emphasis is given to developments which have occurred within the past two years. Parallel processing is defined and the reasons for its importance in high-performance computing are reviewed. Parallel computer architectures are classified according to the number and power of their processing units, their memory, and the nature of their connection scheme. Architectures which show promise for fluid dynamics applications are emphasized. Fluid dynamics problems are examined for parallelism inherent at the physical level. CFD algorithms and their mappings onto parallel architectures are discussed. Several example are presented to document the performance of fluid dynamics applications on present-generation parallel processing devices

Parallel discrete event simulation

NARCIS (Netherlands)

Overeinder, B.J.; Hertzberger, L.O.; Sloot, P.M.A.; Withagen, W.J.

1991-01-01

In simulating applications for execution on specific computing systems, the simulation performance figures must be known in a short period of time. One basic approach to the problem of reducing the required simulation time is the exploitation of parallelism. However, in parallelizing the simulation

Parallel Quasi Newton Algorithms for Large Scale Non Linear Unconstrained Optimization

International Nuclear Information System (INIS)

Rahman, M. A.; Basarudin, T.

1997-01-01

This paper discusses about Quasi Newton (QN) method to solve non-linear unconstrained minimization problems. One of many important of QN method is choice of matrix Hk. to be positive definite and satisfies to QN method. Our interest here is the parallel QN methods which will suite for the solution of large-scale optimization problems. The QN methods became less attractive in large-scale problems because of the storage and computational requirements. How ever, it is often the case that the Hessian is space matrix. In this paper we include the mechanism of how to reduce the Hessian update and hold the Hessian properties.One major reason of our research is that the QN method may be good in solving certain type of minimization problems, but it is efficiency degenerate when is it applied to solve other category of problems. For this reason, we use an algorithm containing several direction strategies which are processed in parallel. We shall attempt to parallelized algorithm by exploring different search directions which are generated by various QN update during the minimization process. The different line search strategies will be employed simultaneously in the process of locating the minimum along each direction.The code of algorithm will be written in Occam language 2 which is run on the transputer machine

Overview of the Force Scientific Parallel Language

Directory of Open Access Journals (Sweden)

Gita Alaghband

1994-01-01

Full Text Available The Force parallel programming language designed for large-scale shared-memory multiprocessors is presented. The language provides a number of parallel constructs as extensions to the ordinary Fortran language and is implemented as a two-level macro preprocessor to support portability across shared memory multiprocessors. The global parallelism model on which the Force is based provides a powerful parallel language. The parallel constructs, generic synchronization, and freedom from process management supported by the Force has resulted in structured parallel programs that are ported to the many multiprocessors on which the Force is implemented. Two new parallel constructs for looping and functional decomposition are discussed. Several programming examples to illustrate some parallel programming approaches using the Force are also presented.

Space Radar Image of Sydney, Australia

Science.gov (United States)

1994-01-01

This spaceborne radar image is dominated by the metropolitan area of Australia's largest city, Sydney. Sydney Harbour, with numerous coves and inlets, is seen in the upper center of the image, and the roughly circular Botany Bay is shown in the lower right. The downtown business district of Sydney appears as a bright white area just above the center of the image. The Sydney Harbour Bridge is a white line adjacent to the downtown district. The well-known Sydney Opera House is the small, white dot to the right of the bridge. Urban areas appear yellow, blue and brown. The purple areas are undeveloped areas and park lands. Manly, the famous surfing beach, is shown in yellow at the top center of the image. Runways from the Sydney Airport are the dark features that extend into Botany Bay in the lower right. Botany Bay is the site where Captain James Cook first landed his ship, Endeavour, in 1770. The image was acquired by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X-SAR) on April 20, 1994, onboard the space shuttle Endeavour. The area shown is 33 kilometers by 38kilometers (20 miles by 23 miles) and is centered at 33.9 degrees south latitude, 151.2 degrees east longitude. North is toward the upper left. The colors are assigned to different radar frequenciesand polarizations as follows: red is L-band, vertically transmittedand horizontally received; green is C-band, vertically transmitted and horizontally received; and blue is C-band, vertically transmittedand received. SIR-C/X-SAR, a joint mission of the German, Italianand United States space agencies, is part of NASA's Mission to Planet Earth. #####

The Galley Parallel File System

Science.gov (United States)

Nieuwejaar, Nils; Kotz, David

1996-01-01

Most current multiprocessor file systems are designed to use multiple disks in parallel, using the high aggregate bandwidth to meet the growing I/0 requirements of parallel scientific applications. Many multiprocessor file systems provide applications with a conventional Unix-like interface, allowing the application to access multiple disks transparently. This interface conceals the parallelism within the file system, increasing the ease of programmability, but making it difficult or impossible for sophisticated programmers and libraries to use knowledge about their I/O needs to exploit that parallelism. In addition to providing an insufficient interface, most current multiprocessor file systems are optimized for a different workload than they are being asked to support. We introduce Galley, a new parallel file system that is intended to efficiently support realistic scientific multiprocessor workloads. We discuss Galley's file structure and application interface, as well as the performance advantages offered by that interface.

THE CAVALIERI ESTIMATOR WITH UNEQUAL SECTION SPACING REVISITED

Directory of Open Access Journals (Sweden)

Markus Kiderlen

2017-06-01

Full Text Available The Cavalieri method allows to estimate the volume of a compact object from area measurements in equidistant parallel planar sections. However, the spacing and thickness of sections can be quite irregular in applications. Recent publications have thus focused on the effect of random variability in section spacing, showing that the classical Cavalieri estimator is still unbiased when the stack of parallel planes is stationary, but that the existing variance approximations must be adjusted. The present paper considers the special situation, where the distances between consecutive section planes can be measured and thus where Cavalieri’s estimator can be replaced by a quadrature rule with randomized sampling points. We show that, under mild conditions, the trapezoid rule and Simpson’s rule lead to unbiased volume estimators and give simulation results that indicate that a considerable variance reduction compared to the generalized Cavalieri estimator can be achieved.

Design considerations for parallel graphics libraries

Science.gov (United States)

Crockett, Thomas W.

1994-01-01

Applications which run on parallel supercomputers are often characterized by massive datasets. Converting these vast collections of numbers to visual form has proven to be a powerful aid to comprehension. For a variety of reasons, it may be desirable to provide this visual feedback at runtime. One way to accomplish this is to exploit the available parallelism to perform graphics operations in place. In order to do this, we need appropriate parallel rendering algorithms and library interfaces. This paper provides a tutorial introduction to some of the issues which arise in designing parallel graphics libraries and their underlying rendering algorithms. The focus is on polygon rendering for distributed memory message-passing systems. We illustrate our discussion with examples from PGL, a parallel graphics library which has been developed on the Intel family of parallel systems.

Performance analysis of a threshold-based parallel multiple beam selection scheme for WDM-based systems for Gamma-Gamma distributions

KAUST Repository

Nam, Sung Sik; Yoon, Chang Seok; Alouini, Mohamed-Slim

2017-01-01

In this paper, we statistically analyze the performance of a threshold-based parallel multiple beam selection scheme (TPMBS) for Free-space optical (FSO) based system with wavelength division multiplexing (WDM) in cases where a pointing error has

Automatic Loop Parallelization via Compiler Guided Refactoring

DEFF Research Database (Denmark)

Larsen, Per; Ladelsky, Razya; Lidman, Jacob

For many parallel applications, performance relies not on instruction-level parallelism, but on loop-level parallelism. Unfortunately, many modern applications are written in ways that obstruct automatic loop parallelization. Since we cannot identify sufficient parallelization opportunities...... for these codes in a static, off-line compiler, we developed an interactive compilation feedback system that guides the programmer in iteratively modifying application source, thereby improving the compiler’s ability to generate loop-parallel code. We use this compilation system to modify two sequential...... benchmarks, finding that the code parallelized in this way runs up to 8.3 times faster on an octo-core Intel Xeon 5570 system and up to 12.5 times faster on a quad-core IBM POWER6 system. Benchmark performance varies significantly between the systems. This suggests that semi-automatic parallelization should...

Aspects of computation on asynchronous parallel processors

International Nuclear Information System (INIS)

Wright, M.

1989-01-01

The increasing availability of asynchronous parallel processors has provided opportunities for original and useful work in scientific computing. However, the field of parallel computing is still in a highly volatile state, and researchers display a wide range of opinion about many fundamental questions such as models of parallelism, approaches for detecting and analyzing parallelism of algorithms, and tools that allow software developers and users to make effective use of diverse forms of complex hardware. This volume collects the work of researchers specializing in different aspects of parallel computing, who met to discuss the framework and the mechanics of numerical computing. The far-reaching impact of high-performance asynchronous systems is reflected in the wide variety of topics, which include scientific applications (e.g. linear algebra, lattice gauge simulation, ordinary and partial differential equations), models of parallelism, parallel language features, task scheduling, automatic parallelization techniques, tools for algorithm development in parallel environments, and system design issues

An Optimization Algorithm for Multipath Parallel Allocation for Service Resource in the Simulation Task Workflow

Directory of Open Access Journals (Sweden)

Zhiteng Wang

2014-01-01

Full Text Available Service oriented modeling and simulation are hot issues in the field of modeling and simulation, and there is need to call service resources when simulation task workflow is running. How to optimize the service resource allocation to ensure that the task is complete effectively is an important issue in this area. In military modeling and simulation field, it is important to improve the probability of success and timeliness in simulation task workflow. Therefore, this paper proposes an optimization algorithm for multipath service resource parallel allocation, in which multipath service resource parallel allocation model is built and multiple chains coding scheme quantum optimization algorithm is used for optimization and solution. The multiple chains coding scheme quantum optimization algorithm is to extend parallel search space to improve search efficiency. Through the simulation experiment, this paper investigates the effect for the probability of success in simulation task workflow from different optimization algorithm, service allocation strategy, and path number, and the simulation result shows that the optimization algorithm for multipath service resource parallel allocation is an effective method to improve the probability of success and timeliness in simulation task workflow.

Initial Concept for Terminal Area Conflict Detection, Alerting, and Resolution Capability on or Near the Airport Surface

Science.gov (United States)

Green, David F.; Otero, Sharon D.; Barker, Glover D.; Jones, Denise R.

2009-01-01

The Next Generation Air Transportation System (NextGen) concept for 2025 envisions the movement of large numbers of people and goods in a safe, efficient, and reliable manner. The NextGen will remove many of the constraints in the current air transportation system, support a wider range of operations, and deliver an overall system capacity up to 3 times that of current operating levels. In order to achieve the NextGen vision, research is necessary in the areas of surface traffic optimization, maximum runway capacity, reduced runway occupancy time, simultaneous single runway operations, and terminal area conflict prevention, among others. The National Aeronautics and Space Administration (NASA) is conducting Collision Avoidance for Airport Traffic (CAAT) research to develop technologies, data, and guidelines to enable Conflict Detection and Resolution (CD&R) in the Airport Terminal Maneuvering Area (ATMA) under current and emerging NextGen operating concepts. In this report, an initial concept for an aircraft-based method for CD&R in the ATMA is presented. This method is based upon previous NASA work in CD&R for runway incursion prevention, the Runway Incursion Prevention System (RIPS). CAAT research is conducted jointly under NASA's Airspace Systems Program, Airportal Project and the Aviation Safety Program, Integrated Intelligent Flight Deck Project.

Initial Concept for Terminal Area Conflict Detection, Alerting, and Resolution Capability On or Near the Airport Surface, Version 2.0

Science.gov (United States)

Otero, Sharon D.; Barker, Glover D.; Jones, Denise R.

2013-01-01

The Next Generation Air Transportation System (NextGen) concept for 2025 envisions the movement of large numbers of people and goods in a safe, efficient, and reliable manner. The NextGen will remove many of the constraints in the current air transportation system, support a wider range of operations, and deliver an overall system capacity up to 3 times that of current operating levels. In order to achieve the NextGen vision, research is necessary in the areas of surface traffic optimization, maximum runway capacity, reduced runway occupancy time, simultaneous single runway operations, and terminal area conflict prevention, among others. The National Aeronautics and Space Administration (NASA) is conducting Collision Avoidance for Airport Traffic (CAAT) research to develop technologies, data, and guidelines to enable Conflict Detection and Resolution (CD&R) in the Airport Terminal Maneuvering Area (ATMA) under current and emerging NextGen operating concepts. The term ATMA was created to reflect the fact that the CD&R concept area of operation is focused near the airport within the terminal maneuvering area. In the following, an initial concept for an aircraft-based method for CD&R in the ATMA is presented. This method is based upon previous NASA work in CD&R for runway incursion prevention, the Runway Incursion Prevention System (RIPS).

An Improved Parallel DNA Algorithm of 3-SAT

Directory of Open Access Journals (Sweden)

Wei Liu

2007-09-01

Full Text Available There are many large-size and difficult computational problems in mathematics and computer science. For many of these problems, traditional computers cannot handle the mass of data in acceptable timeframes, which we call an NP problem. DNA computing is a means of solving a class of intractable computational problems in which the computing time grows exponentially with problem size. This paper proposes a parallel algorithm model for the universal 3-SAT problem based on the Adleman-Lipton model and applies biological operations to handling the mass of data in solution space. In this manner, we can control the run time of the algorithm to be finite and approximately constant.

Simulation evaluation of TIMER, a time-based, terminal air traffic, flow-management concept

Science.gov (United States)

Credeur, Leonard; Capron, William R.

1989-01-01

A description of a time-based, extended terminal area ATC concept called Traffic Intelligence for the Management of Efficient Runway scheduling (TIMER) and the results of a fast-time evaluation are presented. The TIMER concept is intended to bridge the gap between today's ATC system and a future automated time-based ATC system. The TIMER concept integrates en route metering, fuel-efficient cruise and profile descents, terminal time-based sequencing and spacing together with computer-generated controller aids, to improve delivery precision for fuller use of runway capacity. Simulation results identify and show the effects and interactions of such key variables as horizon of control location, delivery time error at both the metering fix and runway threshold, aircraft separation requirements, delay discounting, wind, aircraft heading and speed errors, and knowledge of final approach speed.

Advances in non-Cartesian parallel magnetic resonance imaging using the GRAPPA operator

Energy Technology Data Exchange (ETDEWEB)

Seiberlich, Nicole

2008-07-21

This thesis has presented several new non-Cartesian parallel imaging methods which simplify both gridding and the reconstruction of images from undersampled data. A novel approach which uses the concepts of parallel imaging to grid data sampled along a non-Cartesian trajectory called GRAPPA Operator Gridding (GROG) is described. GROG shifts any acquired k-space data point to its nearest Cartesian location, thereby converting non-Cartesian to Cartesian data. The only requirements for GROG are a multi-channel acquisition and a calibration dataset for the determination of the GROG weights. Then an extension of GRAPPA Operator Gridding, namely Self-Calibrating GRAPPA Operator Gridding (SC-GROG) is discussed. SC-GROG is a method by which non-Cartesian data can be gridded using spatial information from a multi-channel coil array without the need for an additional calibration dataset, as required in standard GROG. Although GROG can be used to grid undersampled datasets, it is important to note that this method uses parallel imaging only for gridding, and not to reconstruct artifact-free images from undersampled data. Thereafter a simple, novel method for performing modified Cartesian GRAPPA reconstructions on undersampled non-Cartesian k-space data gridded using GROG to arrive at a non-aliased image is introduced. Because the undersampled non-Cartesian data cannot be reconstructed using a single GRAPPA kernel, several Cartesian patterns are selected for the reconstruction. Finally a novel method of using GROG to mimic the bunched phase encoding acquisition (BPE) scheme is discussed. In MRI, it is generally assumed that an artifact-free image can be reconstructed only from sampled points which fulfill the Nyquist criterion. However, the BPE reconstruction is based on the Generalized Sampling Theorem of Papoulis, which states that a continuous signal can be reconstructed from sampled points as long as the points are on average sampled at the Nyquist frequency. A novel

libstable: Fast, Parallel, and High-Precision Computation of α-Stable Distributions in R, C/C++, and MATLAB

Directory of Open Access Journals (Sweden)

Javier Royuela-del-Val

2017-06-01

Full Text Available α-stable distributions are a family of well-known probability distributions. However, the lack of closed analytical expressions hinders their application. Currently, several tools have been developed to numerically evaluate their density and distribution functions or to estimate their parameters, but available solutions either do not reach sufficient precision on their evaluations or are excessively slow for practical purposes. Moreover, they do not take full advantage of the parallel processing capabilities of current multi-core machines. Other solutions work only on a subset of the α-stable parameter space. In this paper we present an R package and a C/C++ library with a MATLAB front-end that permit parallelized, fast and high precision evaluation of density, distribution and quantile functions, as well as random variable generation and parameter estimation of α-stable distributions in their whole parameter space. The described library can be easily integrated into third party developments.

Parallelization of the FLAPW method

International Nuclear Information System (INIS)

Canning, A.; Mannstadt, W.; Freeman, A.J.

1999-01-01

The FLAPW (full-potential linearized-augmented plane-wave) method is one of the most accurate first-principles methods for determining electronic and magnetic properties of crystals and surfaces. Until the present work, the FLAPW method has been limited to systems of less than about one hundred atoms due to a lack of an efficient parallel implementation to exploit the power and memory of parallel computers. In this work we present an efficient parallelization of the method by division among the processors of the plane-wave components for each state. The code is also optimized for RISC (reduced instruction set computer) architectures, such as those found on most parallel computers, making full use of BLAS (basic linear algebra subprograms) wherever possible. Scaling results are presented for systems of up to 686 silicon atoms and 343 palladium atoms per unit cell, running on up to 512 processors on a CRAY T3E parallel computer

Parallelization of the FLAPW method

Science.gov (United States)

Canning, A.; Mannstadt, W.; Freeman, A. J.

2000-08-01

The FLAPW (full-potential linearized-augmented plane-wave) method is one of the most accurate first-principles methods for determining structural, electronic and magnetic properties of crystals and surfaces. Until the present work, the FLAPW method has been limited to systems of less than about a hundred atoms due to the lack of an efficient parallel implementation to exploit the power and memory of parallel computers. In this work, we present an efficient parallelization of the method by division among the processors of the plane-wave components for each state. The code is also optimized for RISC (reduced instruction set computer) architectures, such as those found on most parallel computers, making full use of BLAS (basic linear algebra subprograms) wherever possible. Scaling results are presented for systems of up to 686 silicon atoms and 343 palladium atoms per unit cell, running on up to 512 processors on a CRAY T3E parallel supercomputer.

Fault detection for hydraulic pump based on chaotic parallel RBF network

Directory of Open Access Journals (Sweden)

Ma Ning

2011-01-01

Full Text Available Abstract In this article, a parallel radial basis function network in conjunction with chaos theory (CPRBF network is presented, and applied to practical fault detection for hydraulic pump, which is a critical component in aircraft. The CPRBF network consists of a number of radial basis function (RBF subnets connected in parallel. The number of input nodes for each RBF subnet is determined by different embedding dimension based on chaotic phase-space reconstruction. The output of CPRBF is a weighted sum of all RBF subnets. It was first trained using the dataset from normal state without fault, and then a residual error generator was designed to detect failures based on the trained CPRBF network. Then, failure detection can be achieved by the analysis of the residual error. Finally, two case studies are introduced to compare the proposed CPRBF network with traditional RBF networks, in terms of prediction and detection accuracy.

Large-Scale, Parallel, Multi-Sensor Data Fusion in the Cloud

Science.gov (United States)

Wilson, B. D.; Manipon, G.; Hua, H.

2012-12-01

NASA's Earth Observing System (EOS) is an ambitious facility for studying global climate change. The mandate now is to combine measurements from the instruments on the "A-Train" platforms (AIRS, AMSR-E, MODIS, MISR, MLS, and CloudSat) and other Earth probes to enable large-scale studies of climate change over periods of years to decades. However, moving from predominantly single-instrument studies to a multi-sensor, measurement-based model for long-duration analysis of important climate variables presents serious challenges for large-scale data mining and data fusion. For example, one might want to compare temperature and water vapor retrievals from one instrument (AIRS) to another instrument (MODIS), and to a model (ECMWF), stratify the comparisons using a classification of the "cloud scenes" from CloudSat, and repeat the entire analysis over years of AIRS data. To perform such an analysis, one must discover & access multiple datasets from remote sites, find the space/time "matchups" between instruments swaths and model grids, understand the quality flags and uncertainties for retrieved physical variables, assemble merged datasets, and compute fused products for further scientific and statistical analysis. To efficiently assemble such decade-scale datasets in a timely manner, we are utilizing Elastic Computing in the Cloud and parallel map/reduce-based algorithms. "SciReduce" is a Hadoop-like parallel analysis system, programmed in parallel python, that is designed from the ground up for Earth science. SciReduce executes inside VMWare images and scales to any number of nodes in the Cloud. Unlike Hadoop, in which simple tuples (keys & values) are passed between the map and reduce functions, SciReduce operates on bundles of named numeric arrays, which can be passed in memory or serialized to disk in netCDF4 or HDF5. Thus, SciReduce uses the native datatypes (geolocated grids, swaths, and points) that geo-scientists are familiar with. We are deploying within Sci

A hybrid parallel architecture for electrostatic interactions in the simulation of dissipative particle dynamics

Science.gov (United States)

Yang, Sheng-Chun; Lu, Zhong-Yuan; Qian, Hu-Jun; Wang, Yong-Lei; Han, Jie-Ping

2017-11-01

In this work, we upgraded the electrostatic interaction method of CU-ENUF (Yang, et al., 2016) which first applied CUNFFT (nonequispaced Fourier transforms based on CUDA) to the reciprocal-space electrostatic computation and made the computation of electrostatic interaction done thoroughly in GPU. The upgraded edition of CU-ENUF runs concurrently in a hybrid parallel way that enables the computation parallelizing on multiple computer nodes firstly, then further on the installed GPU in each computer. By this parallel strategy, the size of simulation system will be never restricted to the throughput of a single CPU or GPU. The most critical technical problem is how to parallelize a CUNFFT in the parallel strategy, which is conquered effectively by deep-seated research of basic principles and some algorithm skills. Furthermore, the upgraded method is capable of computing electrostatic interactions for both the atomistic molecular dynamics (MD) and the dissipative particle dynamics (DPD). Finally, the benchmarks conducted for validation and performance indicate that the upgraded method is able to not only present a good precision when setting suitable parameters, but also give an efficient way to compute electrostatic interactions for huge simulation systems. Program Files doi:http://dx.doi.org/10.17632/zncf24fhpv.1 Licensing provisions: GNU General Public License 3 (GPL) Programming language: C, C++, and CUDA C Supplementary material: The program is designed for effective electrostatic interactions of large-scale simulation systems, which runs on particular computers equipped with NVIDIA GPUs. It has been tested on (a) single computer node with Intel(R) Core(TM) i7-3770@ 3.40 GHz (CPU) and GTX 980 Ti (GPU), and (b) MPI parallel computer nodes with the same configurations. Nature of problem: For molecular dynamics simulation, the electrostatic interaction is the most time-consuming computation because of its long-range feature and slow convergence in simulation space

Multicultural Ground Teams in Space Programs

Science.gov (United States)

Maier, M.

2012-01-01

In the early years of space flight only two countries had access to space. In the last twenty years, there have been major changes in how we conduct space business. With the fall of the iron curtain and the growing of the European Union, more and more players were able to join the space business and space science. By end of the last century, numerous countries, agencies and companies earned the right to be equal partners in space projects. This paper investigates the impact of multicultural teams in the space arena. Fortunately, in manned spaceflight, especially for long duration missions, there are several studies and simulations reporting on multicultural team impact. These data have not been as well explored on the team interactions within the ground crews. The focus of this paper are the teams working on the ISS project. Hypotheses will be drawn from the results of space crew research to determine parallels and differences for this vital segment of success in space missions. The key source of the data will be drawn from structured interviews with managers and other ground crews on the ISS project.

Enabling parallel simulation of large-scale HPC network systems

International Nuclear Information System (INIS)

Mubarak, Misbah; Carothers, Christopher D.; Ross, Robert B.; Carns, Philip

2016-01-01

Here, with the increasing complexity of today’s high-performance computing (HPC) architectures, simulation has become an indispensable tool for exploring the design space of HPC systems—in particular, networks. In order to make effective design decisions, simulations of these systems must possess the following properties: (1) have high accuracy and fidelity, (2) produce results in a timely manner, and (3) be able to analyze a broad range of network workloads. Most state-of-the-art HPC network simulation frameworks, however, are constrained in one or more of these areas. In this work, we present a simulation framework for modeling two important classes of networks used in today’s IBM and Cray supercomputers: torus and dragonfly networks. We use the Co-Design of Multi-layer Exascale Storage Architecture (CODES) simulation framework to simulate these network topologies at a flit-level detail using the Rensselaer Optimistic Simulation System (ROSS) for parallel discrete-event simulation. Our simulation framework meets all the requirements of a practical network simulation and can assist network designers in design space exploration. First, it uses validated and detailed flit-level network models to provide an accurate and high-fidelity network simulation. Second, instead of relying on serial time-stepped or traditional conservative discrete-event simulations that limit simulation scalability and efficiency, we use the optimistic event-scheduling capability of ROSS to achieve efficient and scalable HPC network simulations on today’s high-performance cluster systems. Third, our models give network designers a choice in simulating a broad range of network workloads, including HPC application workloads using detailed network traces, an ability that is rarely offered in parallel with high-fidelity network simulations

Parallelization of 2-D lattice Boltzmann codes

International Nuclear Information System (INIS)

Suzuki, Soichiro; Kaburaki, Hideo; Yokokawa, Mitsuo.

1996-03-01

Lattice Boltzmann (LB) codes to simulate two dimensional fluid flow are developed on vector parallel computer Fujitsu VPP500 and scalar parallel computer Intel Paragon XP/S. While a 2-D domain decomposition method is used for the scalar parallel LB code, a 1-D domain decomposition method is used for the vector parallel LB code to be vectorized along with the axis perpendicular to the direction of the decomposition. High parallel efficiency of 95.1% by the vector parallel calculation on 16 processors with 1152x1152 grid and 88.6% by the scalar parallel calculation on 100 processors with 800x800 grid are obtained. The performance models are developed to analyze the performance of the LB codes. It is shown by our performance models that the execution speed of the vector parallel code is about one hundred times faster than that of the scalar parallel code with the same number of processors up to 100 processors. We also analyze the scalability in keeping the available memory size of one processor element at maximum. Our performance model predicts that the execution time of the vector parallel code increases about 3% on 500 processors. Although the 1-D domain decomposition method has in general a drawback in the interprocessor communication, the vector parallel LB code is still suitable for the large scale and/or high resolution simulations. (author)

Parallelization of 2-D lattice Boltzmann codes

Energy Technology Data Exchange (ETDEWEB)

Suzuki, Soichiro; Kaburaki, Hideo; Yokokawa, Mitsuo

1996-03-01

Lattice Boltzmann (LB) codes to simulate two dimensional fluid flow are developed on vector parallel computer Fujitsu VPP500 and scalar parallel computer Intel Paragon XP/S. While a 2-D domain decomposition method is used for the scalar parallel LB code, a 1-D domain decomposition method is used for the vector parallel LB code to be vectorized along with the axis perpendicular to the direction of the decomposition. High parallel efficiency of 95.1% by the vector parallel calculation on 16 processors with 1152x1152 grid and 88.6% by the scalar parallel calculation on 100 processors with 800x800 grid are obtained. The performance models are developed to analyze the performance of the LB codes. It is shown by our performance models that the execution speed of the vector parallel code is about one hundred times faster than that of the scalar parallel code with the same number of processors up to 100 processors. We also analyze the scalability in keeping the available memory size of one processor element at maximum. Our performance model predicts that the execution time of the vector parallel code increases about 3% on 500 processors. Although the 1-D domain decomposition method has in general a drawback in the interprocessor communication, the vector parallel LB code is still suitable for the large scale and/or high resolution simulations. (author).

Explorations of the implementation of a parallel IDW interpolation algorithm in a Linux cluster-based parallel GIS

Science.gov (United States)

Huang, Fang; Liu, Dingsheng; Tan, Xicheng; Wang, Jian; Chen, Yunping; He, Binbin

2011-04-01

To design and implement an open-source parallel GIS (OP-GIS) based on a Linux cluster, the parallel inverse distance weighting (IDW) interpolation algorithm has been chosen as an example to explore the working model and the principle of algorithm parallel pattern (APP), one of the parallelization patterns for OP-GIS. Based on an analysis of the serial IDW interpolation algorithm of GRASS GIS, this paper has proposed and designed a specific parallel IDW interpolation algorithm, incorporating both single process, multiple data (SPMD) and master/slave (M/S) programming modes. The main steps of the parallel IDW interpolation algorithm are: (1) the master node packages the related information, and then broadcasts it to the slave nodes; (2) each node calculates its assigned data extent along one row using the serial algorithm; (3) the master node gathers the data from all nodes; and (4) iterations continue until all rows have been processed, after which the results are outputted. According to the experiments performed in the course of this work, the parallel IDW interpolation algorithm can attain an efficiency greater than 0.93 compared with similar algorithms, which indicates that the parallel algorithm can greatly reduce processing time and maximize speed and performance.

Parallel Monte Carlo reactor neutronics

International Nuclear Information System (INIS)

Blomquist, R.N.; Brown, F.B.

1994-01-01

The issues affecting implementation of parallel algorithms for large-scale engineering Monte Carlo neutron transport simulations are discussed. For nuclear reactor calculations, these include load balancing, recoding effort, reproducibility, domain decomposition techniques, I/O minimization, and strategies for different parallel architectures. Two codes were parallelized and tested for performance. The architectures employed include SIMD, MIMD-distributed memory, and workstation network with uneven interactive load. Speedups linear with the number of nodes were achieved

Parallel Implicit Algorithms for CFD

Science.gov (United States)

Keyes, David E.

1998-01-01

The main goal of this project was efficient distributed parallel and workstation cluster implementations of Newton-Krylov-Schwarz (NKS) solvers for implicit Computational Fluid Dynamics (CFD.) "Newton" refers to a quadratically convergent nonlinear iteration using gradient information based on the true residual, "Krylov" to an inner linear iteration that accesses the Jacobian matrix only through highly parallelizable sparse matrix-vector products, and "Schwarz" to a domain decomposition form of preconditioning the inner Krylov iterations with primarily neighbor-only exchange of data between the processors. Prior experience has established that Newton-Krylov methods are competitive solvers in the CFD context and that Krylov-Schwarz methods port well to distributed memory computers. The combination of the techniques into Newton-Krylov-Schwarz was implemented on 2D and 3D unstructured Euler codes on the parallel testbeds that used to be at LaRC and on several other parallel computers operated by other agencies or made available by the vendors. Early implementations were made directly in Massively Parallel Integration (MPI) with parallel solvers we adapted from legacy NASA codes and enhanced for full NKS functionality. Later implementations were made in the framework of the PETSC library from Argonne National Laboratory, which now includes pseudo-transient continuation Newton-Krylov-Schwarz solver capability (as a result of demands we made upon PETSC during our early porting experiences). A secondary project pursued with funding from this contract was parallel implicit solvers in acoustics, specifically in the Helmholtz formulation. A 2D acoustic inverse problem has been solved in parallel within the PETSC framework.

Parallel kinematics type, kinematics, and optimal design

CERN Document Server

Liu, Xin-Jun

2014-01-01

Parallel Kinematics- Type, Kinematics, and Optimal Design presents the results of 15 year's research on parallel mechanisms and parallel kinematics machines. This book covers the systematic classification of parallel mechanisms (PMs) as well as providing a large number of mechanical architectures of PMs available for use in practical applications. It focuses on the kinematic design of parallel robots. One successful application of parallel mechanisms in the field of machine tools, which is also called parallel kinematics machines, has been the emerging trend in advanced machine tools. The book describes not only the main aspects and important topics in parallel kinematics, but also references novel concepts and approaches, i.e. type synthesis based on evolution, performance evaluation and optimization based on screw theory, singularity model taking into account motion and force transmissibility, and others.   This book is intended for researchers, scientists, engineers and postgraduates or above with interes...

Optimization of tokamak plasma equilibrium shape using parallel genetic algorithms

International Nuclear Information System (INIS)

Zhulin An; Bin Wu; Lijian Qiu

2006-01-01

In the device of non-circular cross sectional tokamaks, the plasma equilibrium shape has a strong influence on the confinement and MHD stability. The plasma equilibrium shape is determined by the configuration of the poloidal field (PF) system. Usually there are many PF systems that could support the specified plasma equilibrium, the differences are the number of coils used, their positions, sizes and currents. It is necessary to find the optimal choice that meets the engineering constrains, which is often done by a constrained optimization. The Genetic Algorithms (GAs) based method has been used to solve the problem of the optimization, but the time complexity limits the algorithms to become widely used. Due to the large search space that the optimization has, it takes several hours to get a nice result. The inherent parallelism in GAs can be exploited to enhance their search efficiency. In this paper, we introduce a parallel genetic algorithms (PGAs) based approach which can reduce the computational time. The algorithm has a master-slave structure, the slave explore the search space separately and return the results to the master. A program is also developed, and it can be running on any computers which support massage passing interface. Both the algorithm and the program are detailed discussed in the paper. We also include an application that uses the program to determine the positions and currents of PF coils in EAST. The program reach the target value within half an hour and yield a speedup rate of 5.21 on 8 CPUs. (author)

Space division multiplexing chip-to-chip quantum key distribution

DEFF Research Database (Denmark)

Bacco, Davide; Ding, Yunhong; Dalgaard, Kjeld

2017-01-01

nodes of the quantum keys to their respective destinations. In this paper we present an experimental demonstration of a photonic integrated silicon chip quantum key distribution protocols based on space division multiplexing (SDM), through multicore fiber technology. Parallel and independent quantum...