Parallel Load Research Articles

A shaped First Wall for ITER

The ITER First Wall is being redesigned to address a number of issues identified during the 2007 design review. One of the main improvements concerns the handling of parallel plasma heat loads. The design must be optimised for maximum leading edge protection with acceptable power flux distribution, which is achieved by shaping the First Wall panels. The conceptual design presented in the paper can accommodate both inboard and outboard limiter plasmas for a total power in the discharge of 7.5MW at 7.5MA and allows the abandonment of the original dedicated port limiters.

Schottky Diode Based on Microcrystalline Silicon Deposited at 165°C for RFID Application

The design and fabrication of high efficiency low cost electronics components for commercial and industrial applications is very challenging. In this paper we introduce a fabrication of Schottky diode dedicated to high frequency rectification. The devices are prepared on Corning glass substrate with a configuration Au /µc-Si:H /Al and by using microcrystalline silicon as semiconductor. Photolithographic masks are used for diodes fabrication. Two processes are carried out to optimize Schottky diode characteristics. Silicon films are deposited in an usual RF PECVD reactor at low temperature (165°C). Current - voltage (I-V) characteristics are measured and plotted to determine the different parameters of Schottky contact such as ideality factor and rectifying ratio. At 13.56 MHz which is common in RFID frequency application, this Schottky diode in association with parallel load capacitor can be used to build an efficient rectifier.

Research on parallel load sharing principle of piezoelectric six-dimensional heavy force/torque sensor

In working process of huge heavy-load manipulators, such as the free forging machine, hydraulic die-forging press, forging manipulator, heavy grasping manipulator, large displacement manipulator, measurement of six-dimensional heavy force/torque and real-time force feedback of the operation interface are basis to realize coordinate operation control and force compliance control. It is also an effective way to raise the control accuracy and achieve highly efficient manufacturing. Facing to solve dynamic measurement problem on six-dimensional time-varying heavy load in extremely manufacturing process, the novel principle of parallel load sharing on six-dimensional heavy force/torque is put forward. The measuring principle of six-dimensional force sensor is analyzed, and the spatial model is built and decoupled. The load sharing ratios are analyzed and calculated in vertical and horizontal directions. The mapping relationship between six-dimensional heavy force/torque value to be measured and output force value is built. The finite element model of parallel piezoelectric six-dimensional heavy force/torque sensor is set up, and its static characteristics are analyzed by ANSYS software. The main parameters, which affect load sharing ratio, are analyzed. The experiments for load sharing with different diameters of parallel axis are designed. The results show that the six-dimensional heavy force/torque sensor has good linearity. Non-linearity errors are less than 1%. The parallel axis makes good effect of load sharing. The larger the diameter is, the better the load sharing effect is. The results of experiments are in accordance with the FEM analysis. The sensor has advantages of large measuring range, good linearity, high inherent frequency, and high rigidity. It can be widely used in extreme environments for real-time accurate measurement of six-dimensional time-varying huge loads on manipulators.

Effect of Relative Humidity on Mechanical Properties of Birch Laminated Veneer Lumber

Laminated Veneer Lumber (LVL) panels made from birch (Betula platyphylla Suk.) veneers were tested for physical and mechanical strength properties in this study. The static bending test were conducted on the LVL, and bending test and shear test were conducted on veneer and three-lamination LVL. The effects of the relative humidity on the modulus of elasticity (MOE) and bending strength (MOR) of birch LVL with vertical load and parallel load were investigated. There were four relative humidities including 40%, 50%, 60% and 70%. The results showed that the MOE and MOR of LVL would diminished with the increase of relative humidity, the bending strength of veneer sample decreased as the relative humidity increased, and there was noticeable effect of relative humidity on shear strength of PF resin.

An improved method for the measurement of adhesion energy by using a nano-cutting machine

A novel procedure is proposed which improves the application of the knife-cutting method to estimate adhesion energy. The origin of a previously reported difficulty in determining the force exerted by the cutting blade to the specimen in removing the coatings is identified and a method to overcome this difficulty is developed. The essential point of the method is to detect the “critical normal load”. The value of this load and that of the parallel load are used to obtain the adhesion energy and the energy for the deformation of the removed part of the coating.

A parameter study of a hybrid Laplacian mean-curvature flow denoising model

This article presents results of a parameter study for a new denoising model, using parallel computing and advanced dynamic load balancing techniques for performance improvement of implementations. A denoising model is suggested hybridizing total variation and Laplacian mean-curvature; the fourth-order model and its numerical procedure introduce a number of parameters. As a preliminary step in the model development, a parameter study has been undertaken in order to discover solitary and interactive effects of the parameters on model accuracy. Such a parameter study is necessarily time-consuming due to the huge number of combinations of the parameter values to be tested. In addition, the study has to be performed on various images, thereby increasing the overall investigation time. The performance of this first parallel implementation of a new hybrid model for image denoising is evaluated when the application is running on heterogeneous environments. The hybrid model is simulated on a general-purpose Linux cluster for which the parallel efficiency exceeds 96%.

Analysis and Design of a CMOS UWB LNA With Dual-$RLC$-Branch Wideband Input Matching Network

A wideband low-noise amplifier (LNA) based on the current-reused cascade configuration is proposed. The wideband input-impedance matching was achieved by taking advantage of the resistive shunt-shunt feedback in conjunction with a parallel LC load to make the input network equivalent to two parallel RLC-branches, i.e., a second-order wideband bandpass filter. Besides, both the inductive series- and shunt-peaking techniques are used for bandwidth extension. Theoretical analysis shows that both the frequency response of input matching and noise figure (NF) can be described by second-order functions with quality factors as parameters. The CMOS ultra-wideband LNA dissipates 10.34-mW power and achieves <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> below -8.6 dB, <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">22</sub> below -10 dB, <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> below -26 dB, flat <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> of 12.26 ± 0.63 dB, and flat NF of 4.24 ± 0.5 dB over the 3.1-10.6-GHz band of interest. Besides, good phase linearity property (group-delay variation is only ±22 ps across the whole band) is also achieved. The analytical, simulated, and measured results agree well with one another.

Thermo-mechanical analysis of the fire performance of dowelled timber connection

As timber is a combustible material, fire safety is a significant obstacle for the development of timber usage in buildings. Among the various structural components, the connections are often the weakest elements in a timber construction. In fire as well as in normal conditions, they govern the load-bearing capacity of the structure. However, a lack of knowledge is pointed out for the design of connections in normal conditions and even more in fire conditions. In this paper, a three-dimensional finite element approach is developed to investigate the performance of dowelled timber connections in fire. The 3D mechanical model and the thermo-physical model for each connection component are described. For the mechanical model, the plastic behaviour of the materials is considered using the Von Mises criterion for steel and the Hill criterion for timber. Then a thermal and mechanical validation of the proposed model is achieved by comparison with the experimental results in normal and fire situations. The analysis is then focused on the behaviour of dowelled timber connections in a fire situation. Thus, timber-to-timber and steel-to-timber connections with fasteners of 12 to 20 mm in diameter are studied considering a load in direct tension parallel to the grain. A parametric analysis, based on the numerical model, is done to evaluate the influence of the timber thickness on the reduction of the load-bearing capacity of the connections. This influence is evaluated considering the time of fire resistance to deduct simple design methods.

Parallel adaptation of general three-dimensional hybrid meshes

A new parallel dynamic mesh adaptation and load balancing algorithm for general hybrid grids has been developed. The meshes considered in this work are composed of four kinds of elements; tetrahedra, prisms, hexahedra and pyramids, which poses a challenge to parallel mesh adaptation. Additional complexity imposed by the presence of multiple types of elements affects especially data migration, updates of local data structures and interpartition data structures. Efficient partition of hybrid meshes has been accomplished by transforming them to suitable graphs and using serial graph partitioning algorithms. Communication among processors is based on the faces of the interpartition boundary and the termination detection algorithm of Dijkstra is employed to ensure proper flagging of edges for refinement. An inexpensive dynamic load balancing strategy is introduced to redistribute work load among processors after adaptation. In particular, only the initial coarse mesh, with proper weighting, is balanced which yields savings in computation time and relatively simple implementation of mesh quality preservation rules, while facilitating coarsening of refined elements. Special algorithms are employed for (i) data migration and dynamic updates of the local data structures, (ii) determination of the resulting interpartition boundary and (iii) identification of the communication pattern of processors. Several representative applications are included to evaluate the method.

Design and Realization of a GA-Optimized VHF/UHF Antenna With "On-Body" Matching Network

This letter presents a VHF/UHF loaded wire antenna with an on-body matching network for broadband or multiband wireless applications. A genetic algorithm (GA) is used to optimize antenna structure and the on-body matching network. The designed 1.47-m antenna with a lossless LC parallel circuit load and a 0.32-m sleeve pedestal can work from 30 to 520 MHz. In the working band, the measured voltage standing-wave ratio (VSWR) and the gain of the loaded antenna with the on-body matching network are less than 2 and greater than 0 dBi, respectively. The efficiency of the on-body matching network is greater than 35% over the frequency range of 30 ˜ 520 MHz, greater than 38% over 60 ˜ 200 MHz, and greater than 42% over 210 ˜ 520 MHz.

Advances in parallel partitioning, load balancing and matrix ordering for scientific computing

We summarize recent advances in partitioning, load balancing, and matrix ordering for scientific computing performed by members of the CSCAPES SciDAC institute.

High Voltage Subnanosecond Monocycle Active Former Based on Compression Energy Unit

Compact high voltage subnanosecond monocycle former (MF) was tested. The device was designed on base of energy compression device and operated in a travelling wave mode. MF consists of high impedance and forming lines, which discharged for the load in parallel. As a result, the monocycle with pulse duration ∼ 1 ns and typical peak-to-peak amplitude ∼ 250 kV was formed without additional peaking of the nanosecond pulse rise time. Some pulses reached the maximum amplitude ∼ 270 kV. The parallel discharge circuit, and a spiral shape of forming line allowed keeping small dimensions of MF, and save enough electrical strength to operate with pulse repetition rate up to 100 pps.

An Optimizing Compiler for Parallel Chemistry Simulations

Well designed domain specific languages have three important benefits: (1) the easy expression of problems, (2) the application of domain specific optimizations (including parallelization), and (3) dramatic improvements in productivity for their users. In this paper we describe a compiler and parallel runtime system for modeling the complex kinetics of rubber vulcanization and olefin polymerization that achieves all of these goals. The compiler allows the development of a system of ordinary differential equations describing a complex vulcanization reaction or single-site olefin polymerization reaction--a task that used to require months--to be done in hours. A specialized common sub-expression elimination and other algebraic optimizations sufficiently simplify the complex machine generated code to allow it to be compiled--eliminating all but 8.0% of the operations in our largest program and enabling over 60 times faster execution on our largest benchmark codes. The parallel runtime and dynamic load balancing scheme enables fast simulations of the model.

De-convolution of bulk and interfacial contributions based on impedance spectroscopy with external load resistance

De-convolution of impedance spectra is often ambiguous, mainly due to overlapped contributions, or when a prevailing interfacial contribution raises uncertainties about much smaller bulk contributions at higher frequencies. This can be avoided by performing impedance spectroscopy with a parallel external load resistance, which might exert selective decrease in interfacial contributions, with much smaller changes on high frequency contributions. By suitable selection of a parallel load resistance one obtained clearer interpretation for incompletely resolved high capacitance contributions, especially when the frequency range of the equipment does not reach sufficiently low frequencies. This method is discussed in detail and applied to de-convolution of impedance spectra of selected study cases. This includes ionic, or mixed conductors based on Yb 2Ti 2O 7, CGO and strontium titanate. One also provides guidelines for selection of suitable ranges of external resistors.

Analysis of CLL Voltage-Output ResonantConverters Using Describing Functions

A new AC equivalent circuit for the CLL voltage-output resonant converter is presented, that offers improved accuracy compared with traditional FMA-based techniques. By employing describing function techniques, the nonlinear interaction of the parallel inductor, rectifier and load is replaced by a complex impedance, thereby facilitating the use of AC equivalent circuit analysis methodologies. Moreover, both continuous and discontinuous rectifier-current operating conditions are addressed. A generic normalized analysis of the converter is also presented. To further aid the designer, error maps are used to demonstrate the boundaries for providing accurate behavioral predictions. A comparison of theoretical results with those from simulation studies and experimental measurements from a prototype converter, are also included as a means of clarifying the benefits of the proposed techniques.

A new analytical method for parallel, diffusion-type load balancing

We propose a new proof technique which can be used to analyse many parallel load balancing algorithms. The technique is designed to handle concurrent load balancing actions, which are often the main obstacle in the analysis. We demonstrate the usefulness of the approach by analysing various natural diffusion-type protocols. Our results are similar to, or better than, previously existing ones, while our proofs are much easier. The key idea is to first sequentialise the original, concurrent load transfers, analyse this new, sequential system, and then to bound the gap between both.

Coupler Winding Ratio Selection for Effective Narrowband Power-Line Communications

Coupling losses caused by impedance mismatches are often underestimated and neglected by power-line communications researchers and manufacturers. Further, the variations in network topology combined with unknown cable and load impedances obscure the requirements for impedance adaptation, causing researchers and manufacturers to default to a guessed impedance level and a fixed winding ratio. Attempting to clarify said requirements, this paper approaches the transmitter-to-receiver chain using a simplified lumped-parameter model, which distinguishes between the influences of series (cable) and parallel (load) power-line impedances. Using apparent power transfer to the receiver as criterion, the influence of both the transmitter and receiver coupler winding ratios are investigated for 50- modems at frequencies below 1 MHz. Live measurements indicate that the results are useful regardless of power-line topology, yielding gains up to 10 dB.

A study of the concurrent execution of parallel and sequential applications on a non-dedicated cluster

Computers of a non-dedicated cluster are often idle (users attend meetings, have lunch or coffee breaks) or lightly loaded (users carry out simple computations to support problem solving activities). These underutilised computers can be employed to execute parallel applications. Thus, these computers can be shared by parallel and sequential applications, which could lead to the improvement of their execution performance. However, there is a lack of experimental study showing the applications’ performance and the system utilization of executing parallel and sequential applications concurrently and concurrent execution of multiple parallel applications on a non-dedicated cluster. Here we present the result of an experimental study into load balancing based scheduling of mixtures of NAS Parallel Benchmarks and BYTE sequential applications on a very low cost non-dedicated cluster. This study showed that the proposed sharing provided performance boost as compared to the execution of the parallel load in isolation on a reduced number of computers and better cluster utilization. The results of this research were used not only to validate other researchers’ result generated by simulation but also to support our research mission of widening the use of non-dedicated clusters. Our promising results obtained could promote further research studies to convince universities, business and industry, which require a large amount of computing resources, to run parallel applications on their already owned non-dedicated clusters.

Three dimensional adaptive mesh refinement on a spherical shell for atmospheric models with lagrangian coordinates

One of the most important advances needed in global climate models is the development of atmospheric General Circulation Models (GCMs) that can reliably treat convection. Such GCMs require high resolution in local convectively active regions, both in the horizontal and vertical directions. During previous research we have developed an Adaptive Mesh Refinement (AMR) dynamical core that can adapt its grid resolution horizontally. Our approach utilizes a finite volume numerical representation of the partial differential equations with floating Lagrangian vertical coordinates and requires resolving dynamical processes on small spatial scales. For the latter it uses a newly developed general-purpose library, which facilitates 3D block-structured AMR on spherical grids. The library manages neighbor information as the blocks adapt, and handles the parallel communication and load balancing, freeing the user to concentrate on the scientific modeling aspects of their code. In particular, this library defines and manages adaptive blocks on the sphere, provides user interfaces for interpolation routines and supports the communication and load-balancing aspects for parallel applications. We have successfully tested the library in a 2-D (longitude-latitude) implementation. During the past year, we have extended the library to treat adaptive mesh refinement in the vertical direction. Preliminary results are discussed. This research project is characterized by an interdisciplinary approach involving atmospheric science, computer science and mathematical/numerical aspects. The work is done in close collaboration between the Atmospheric Science, Computer Science and Aerospace Engineering Departments at the University of Michigan and NOAA GFDL.

Suitability of the pulse adjustment technique to control single DC/DC choppers feeding vehicular constant power loads in parallel with conventional loads

The increasing use of power electronic and motor drives in land vehicles, marine vessels and aircraft, for lots of applications such as propulsion, braking, steering, and actuation is creating particular problems when the power distribution system is in the form of multi-converter dc electrical systems. This is because of many power electronic loads and associated controllers which have a 'constant power' characteristic resulting in negative incremental input impedance. The effect of such loads in a dc system is to cause instability. The purpose of this paper is first to identify the most appropriate theoretical techniques for analysis of this nonlinear instability, and then to devise a novel technique for damping the instabilities and ensuring stable operation of system. We call this new control technique, Pulse Adjustment. In spite of its simplicity it offers a very fast and smooth response. Simulation and experimental results are presented to verify the proposed technique.