Parallel Load Research Articles

Multi-Axis Load Cell Designs Employing Multiple Shear Beams

Binocular and parallel plate structure load cells are very successful designs for strain based measurements of shear loads. In this paper we use finite element methods (FEM) to investigate the suitability of these two load cell designs for use in a force plate and compare the sensitivity of these two force plates to that of the Heglund’s force plate. Each force plate is also sensitive to two moments with axis in the same plane as the force plate. If the force plate is to be used as a two component force-moment sensor, we determine which moment axis is best to use. Finally, a novel six-axis load cell is modelled by assembling three force plates together with rotational symmetry. The sensitivity of the six-axis load cell is calculated using FEM. Analysis of the six axis load cell predicts good measurement sensitivity and isotropy while maintaining low interference between measurement axes. Further benefits of the load cell design are discussed.

병렬펄스부하를 갖는 직류배전시스템을 위한 능동 공진 댐퍼에 대한 연구

An active resonance damper for a DC Distributed Power System(DPS) with parallel loads is presented. Each pulse power load in a DC DPS comprises both a resistive power load and a step-up converter. The step-up converter behave as constant power load(CPL) when tightly regulated and usually cause a negative impedance instability problem. Furthermore, when an input filter is connected to a large constant power load, the instability of DC bus voltage. In this paper, a bidirectional DC/DC converter with a reduced storage capacitor quantitatively are proposed as a active resonance damper, to mitigate the voltage instability on the bus. The validity of the proposed method was confirmed by simulation and experimental works.

Discontinuous Galerkin unsteady discrete adjoint method for real-time efficient tsunami simulations

An unsteady discrete adjoint implementation for a discontinuous Galerkin model solving the shallow water wave equations on the sphere is presented. Its use for tsunami simulations is introduced to reconstruct the initial condition automatically from buoy measurements. Based on this feature, a real-time tsunami model is developed, using several numerical tools such as a high-order discretization, hp-refinement, parallel dynamic load balancing and adjoint-based data assimilation. The model is able to reconstruct the tsunami source and accurately forecast its far-field propagation (e.g. from Japan to Chile, at a distance of about 17000km) in a computational time 20 times faster than the physical propagation time, to which the data collecting time needs to be added. The work presented constitutes a step towards an efficient nonlinear tsunami warning model. Additional features could be added for more complete realistic forecasts.

Dynamic load balancing algorithm for molecular dynamics based on Voronoi cells domain decompositions

We present a new algorithm for automatic parallel load balancing in classical molecular dynamics. It assumes a spatial domain decomposition of particles into Voronoi cells. It is a gradient method which attempts to minimize a cost function by displacing Voronoi sites associated with each processor/sub-domain along steepest descent directions. Excellent load balance has been obtained for quasi-2D and 3D practical applications, with up to 440⋅106 particles on 65,536 MPI tasks.

The structural behaviour of laminated-guadua panels under parallel plane loads

The Universidad Nacional de Colombia "Analysis, Design and Materials - GIES" research group tested two types of panels made from Guadua angustifolia Kunth and poly vinyl acetate (PVA) as a first step in studying the behaviour of laminated guadua frames having panels of the same material under seismic load: type 1 panels had a solid cross-section and type 2 panels a sandwich cross-section. Each type of panel had three different heights and 10 replicates were tested for each type and height (60 trials in total). Each panel's load compared to displacement curve was found; 0.34m and 0.63m type1 panels had initial elastic behaviour followed by inelastic behaviour while 0.98 m panels made of both types had an almost completely elastic behaviour until failure. All panels became crushed at their base; however, the main failure mechanism was warping.

Are small-scale grid-connected photovoltaic systems a cost-effective policy for lowering electricity bills and reducing carbon emissions? A technical, economic, and carbon emission analysis

This research discusses findings from technical simulations and economic models of 1kWp and 3kWp grid-connected photovoltaic (PV) systems supplying a rural home electricity load in parallel with the electricity network in Western Australia (WA). The technical simulations are based on electricity billing, consumption monitoring, an energy audit data, combined with 15min interval load and PV system performance for commercially available technologies and balance of system components, using long-term meteorological input data. The economic modelling uses 2010 market prices for capital costs, operational costs, electricity tariffs, subsidies, and is based on discounted cash flow analyses which generate a final net present value (NPV) for each system against network electricity costs (in Australian dollars, AUD) over a 15 year investment horizon. The results suggest that current market prices generate a negative NPV (a net private loss), even with the current government subsidies, which lead to higher home electricity costs than conventional network electricity use. Additionally, the private costs of carbon emission mitigation (AUD tCO2-e−1) for the grid-connected PV system simulations and models were around AUD 600-700 tCO2-e−1, a particularly expensive option when compared to existing large-scale renewable energy mitigation activities.

Load Sharing of Parallel Shaft Split Torque Transmission System

Parallel shaft split torque Transmission system Split torque Load sharing Abstract: The Newton method was applied to develop a system of equations of motion, the mathematical model includes stiffness of shaft supporting, position of gears, backlashes, time-varying stiffness, composite transmission errors, damping. The model was solved by variable step size forth/fifth-order Runge-Kutta method. The load sharing was affected obviously by asymmetry of gear backlashes, stiffness of shaft supporting and gear position

ParAFEMCap: A Parallel Adaptive Finite-Element Method for 3-D VLSI Interconnect Capacitance Extraction

Parasitic extraction is one of the key techniques in very large scale integration design that has been widely used to build the equivalent-circuit model of interconnects. In this paper, a parallel adaptive finite-element method (AFEM) for capacitance extraction of large-scale interconnects (ParAFEMCap) is developed to provide extremely high parallel scalability and numerical accuracy. First, the proposed ParAFEMCap has the potential of high parallel scalability by taking advantages of several advanced parallel techniques, such as parallel adaptive mesh refinement and dynamic load balancing. To the best of the authors' knowledge, this is the first capacitance extraction field solver that is able to run in parallel on hundreds and even thousands of CPU cores. Second, the proposed ParAFEMCap is based on the AFEM, which is proven to converge to the exact solution of the electromagnetic problems in a theoretically quasi-optimal rate. The solution precision of ParAFEMCap can easily be controlled by varying the threshold for the a posteriori error estimator, while the computational time can easily be reduced by increasing the number of CPU cores. Moreover, ParAFEMCap is shown to have the same linear computation complexity as those integral-equation methods, which make it very promising for capacitance extraction of large-scale interconnect problems. Numerical experiments will demonstrate that ParAFEMCap has the advantages of high computational efficiency and accuracy for solving the capacitance extraction problem of large-scale interconnects with complex multilayer structures.

The Practical Formula of Ground Vibration Attenuation Induced by the Parallel Vehicles on a Ring Road

In this paper, based on the transient moving load equivalent radius, multiple non-point source within as multiple small non-point source, ground vibration amplitude for multiple small non-point attenuation stack, on the basis of considering the ground more than car parallel, will vehicle load simplified as parallel concentrated load, according to the harmonic waves equivalent radius, considering different soil types of geometric attenuation coefficient, gives a practical formulas with ring road of ground vibration attenuation caused by parallel vehicles. And through the comparison between the Xi’an bell Tower ring road traffic vibration decays monitoring and calculation results, the practical formulas are verified.

The Practical Formula of Ground Vibration Attenuation Induced by the Parallel Vehicles on a Ring Road

In this paper, based on the transient moving load equivalent radius, multiple non-point source within as multiple small non-point source, ground vibration amplitude for multiple small non-point attenuation stack, on the basis of considering the ground more than car parallel, will vehicle load simplified as parallel concentrated load, according to the harmonic waves equivalent radius, considering different soil types of geometric attenuation coefficient, gives a practical formulas with ring road of ground vibration attenuation caused by parallel vehicles. And through the comparison between the Xi’an bell Tower ring road traffic vibration decays monitoring and calculation results, the practical formulas are verified.

ナイフカッティング法による塗膜付着エネルギー評価法

We propose a novel procedure for estimating coating–substrate adhesion energy using a knife-cutting method. This method presented the problem that the force exerted by a cutting blade to a specimen during coating removal is not fixed. That issue associated with the method has been resolved by detecting the “critical normal load.” The value of this load and that of the parallel load are used to ascertain the adhesion energy and the energy for the deformation of the removed part of the coating. The adhesion energy between an electro-deposited acrylic resin coating and a cold-rolled steel substrate was obtained using this procedure.

Research and implementation of scalable parallel computing based on Map-Reduce

As a parallel programming model, Map-Reduce is used for distributed computing of massive data. Map-Reduce model encapsulates the details of parallel implementation, fault-tolerant processing, local computing and load balancing, etc., provides a simple but powerful interface. In case of having no clear idea about distributed and parallel programming, this interface can be utilized to save development time. This paper introduces the method of using Hadoop, the open-source Map-Reduce software platform, to combine PCs to carry out scalable parallel computing. Our experiment using 12 PCs to compute N-body problem based on Map-Reduce model shows that we can get a 9.8x speedup ratio. This work indicates that the Map-Reduce can be applied in scalable parallel computing.

Grip force regulates hand impedance to optimize object stability in high impact loads

Anticipatory grip force adjustments are a prime example of the predictive nature of motor control. An object held in precision grip is stabilized by fine adjustments of the grip force against changes in tangential load force arising from inertia during acceleration and deceleration. When an object is subject to sudden impact loads, prediction becomes critical as the time available for sensory feedback is very short. Here, we investigated the control of grip force when participants performed a targeted tapping task with a hand-held object. During the initial transport phase of the movement, load force varied smoothly with acceleration. In contrast, in the collision, load forces sharply increased to very large values. In the transport phase, grip force and load force were coupled in phase, as expected. However, in the collision, grip force did not parallel load force. Rather, it exhibited a stereotyped profile with maximum ∼65 ms after peak load at contact. By using catch trials and a virtual environment, we demonstrate that this peak of grip force is pre-programmed. This observation is validated across experimental manipulations involving different target stiffness and directions of movement. We suggest that the central nervous system optimizes stability in object manipulation-as in catching-by regulating mechanical parameters including stiffness and damping through grip force. This study provides novel insights about how the brain coordinates grip force in manipulation involving an object interacting with the environment.

A parallel goal-oriented adaptive finite element method for 2.5-D electromagnetic modelling

SUMMARY We present a parallel goal-oriented adaptive finite element method that can be used to rapidly compute highly accurate solutions for 2.5-D controlled-source electromagnetic (CSEM) and 2-D magnetotelluric (MT) modelling problems. We employ unstructured triangular grids that permit efficient discretization of complex modelling domains such as those containing topography, dipping layers and multiple scale structures. Iterative mesh refinement is guided by a goal-oriented error estimator that considers the relative error in the strike aligned fields and their spatial gradients, resulting in a more efficient mesh refinement than possible with a previous approach based on the absolute errors. Reliable error estimation is accomplished by a dual weighted residual method that is carried out via hierarchical basis computations. Our algorithm is parallelized over frequencies, wavenumbers, transmitters and receivers, where adaptive refinement is performed in parallel on subsets of these parameters. Mesh sharing allows an adapted mesh generated for a particular frequency and wavenumber to be shared with nearby frequencies and wavenumbers, thereby efficiently reducing the parallel load of the adaptive refinement calculations. We demonstrate the performance of our algorithm on a large cluster computer through scaling tests for a complex model that includes strong seafloor topography variations and multiple thin stacked hydrocarbon reservoirs. In tests using up to 800 processors and a realistic suite of CSEM data parameters, our algorithm obtained run-times as short as a few seconds to tens of seconds.

Load Balance with Imperfect Information in Structured Peer-to-Peer Systems

With the notion of virtual servers, peers participating in a heterogeneous, structured peer-to-peer (P2P) network may host different numbers of virtual servers, and by migrating virtual servers, peers can balance their loads proportional to their capacities. The existing and decentralized load balance algorithms designed for the heterogeneous, structured P2P networks either explicitly construct auxiliary networks to manipulate global information or implicitly demand the P2P substrates organized in a hierarchical fashion. Without relying on any auxiliary networks and independent of the geometry of the P2P substrates, we present, in this paper, a novel load balancing algorithm that is unique in that each participating peer is based on the partial knowledge of the system to estimate the probability distributions of the capacities of peers and the loads of virtual servers, resulting in imperfect knowledge of the system state. With the imperfect system state, peers can compute their expected loads and reallocate their loads in parallel. Through extensive simulations, we compare our proposal to prior load balancing algorithms.

Parallel randomized load balancing: A lower bound for a more general model

We extend the lower bound of Adler et al. (1998) [1] and Berenbrink et al. (1999) [2] for parallel randomized load balancing algorithms. The setting in these asynchronous and distributed algorithms is of n balls and n bins. The algorithms begin by each ball choosing d bins independently and uniformly at random. The balls and bins communicate to determine the assignment of each ball to a bin. The goal is to minimize the maximum load, i.e., the number of balls that are assigned to the same bin. In Adler et al. (1998) [1] and Berenbrink et al. (1999) [2], a lower bound of Ω ( log n / log log n r ) is proved if the communication is limited to r rounds. Three assumptions appear in the proofs in Adler et al. (1998) [1] and Berenbrink et al. (1999) [2]: the topological assumption, random choices of confused balls, and symmetry. The topological assumption states that each ball’s decision is based only on collisions between choices of balls. The confused ball assumption states that if a ball obtains the same topological information from all its chosen bins, then the ball commits to one of the chosen bins by flipping a fair coin. The symmetry assumption states that all the balls run identical algorithms, the same assumption holds for the bins. We extend the proof of the lower bound so that it holds without these three assumptions. This lower bound applies to every parallel randomized load balancing algorithm we are aware of (Adler et al., 1998 [1]; Berenbrink et al., 1999 [2]; Stemann, 1996 [3]; Even and Medina, 2009 [4]).

Calculation of operating safety factors of a subsystem with parallel load elements as part of a technogenically dangerous object

Formulas for calculating safety factors and their limit values for a subsystem with two parallel load elements as part of a technogenically dangerous object are determined. An example of using the received results is represented.

A call to arms for task parallelism in multi‐scale materials modeling

AbstractSimulations based on multi‐scale material models enabled by adaptive sampling have demonstrated speedup factors exceeding an order of magnitude. The use of these methods in parallel computing is hampered by dynamic load imbalance, with load imbalance measurably reducing the achieved speedup. Here we discuss these issues in the context of task parallelism, showing results achieved to date and discussing possibilities for further improvement. In some cases, the task parallelism methods employed to date are able to restore much of the potential wall‐clock speedup. The specific application highlighted here focuses on the connection between microstructure and material performance using a polycrystal plasticity‐based multi‐scale method. However, the parallel load balancing issues are germane to a broad class of multi‐scale problems. Copyright © 2011 John Wiley & Sons, Ltd.

Brief view on control of grid‐interfacing AC‐DC‐AC converter and active filter under unbalanced and distorted voltage conditions

PurposeThe purpose of this paper is to consider both sides of a back‐to‐back AC‐DC‐AC interface.Design/methodology/approachThe paper presents a mathematical analysis, simulation, laboratory test in scaled model.FindingsThe two main findings comprised concept of control methods for grid AC‐DC‐AC converter applied in renewable energy sources with variable speed operation under distorted grid. Active filtering functionality in case of non‐linear current of a parallel load. Second, a control algorithm dedicated for two‐level AC‐DC converter applied in industrial networks with high‐order harmonics compensation working under hard conditions – balanced and unbalanced voltage dips.Research limitations/implicationsThe paper shows preliminary results for AC‐DC‐AC converter and active filter (AF) during voltage dips and for harmonics compensation. Control methods and/or topology should be improved and tested in scale and after at high‐power system.Practical implicationsPower quality supplied/received to/from the grid can be increased. In case of low‐cost system only AF can be applied to existing non‐linear receivers. Moreover, in case of full AC‐DC‐AC converter energy saving and production is possible.Originality/valuePresented control methods give satisfactory results. Paper presents laboratory results for grid and machine side two different power circuits during steady states and transients. Moreover, active filtering operation during voltage dips is presented.

A minute asymmetrical current injection based anti‐islanding method for three‐phase grid‐connected photovoltaic inverters

AbstractAn active anti‐islanding protection method based on the current control for a three‐phase grid‐connected photovoltaic inverter is proposed in this paper. The current of phase‐a is synchronous with the corresponding phase voltage at the point of common coupling in its positive half cycle, and a zero‐current zone is inserted at the end of the cycle in a negative half cycle. As for phase‐c, the zero‐current zone is inserted in the positive half cycle of the current, and the current in a negative half cycle of phase‐c is in phase with the corresponding phase voltage. Therefore, the currents of phase‐a and phase‐c in one cycle become slightly asymmetrical. Before the islanding takes place, the positive and negative half cycles of three‐phase voltages are symmetrical due to the operation of the grid voltage. While islanding takes place, a time difference between the positive and negative half cycles of the voltages of phase‐a and phase‐c will be generated and the islanding is detected in accordance with the successive cycles fulfilling the conditions of islanding identification. In order to measure zero‐crossings of the voltages accurately, an finite impulse response filter is used to smooth out the voltage harmonics and noises. Simulations and experiments for three‐phase three‐wire power systems have been carried out. The results verify that the proposed method can detect the islanding for a parallel RLC load or induction motors when the voltage frequency is within the range of the non‐detection zone. It is seen from the analysis of the detecting principle that there is no influence of temporal voltage frequency fluctuation on the proposed method even if a large load connected to a weak power system frequently starts up or stops. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.