Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

http://ieeexplore.ieee.org/iel5/5/31047/01444179.pdf

Fundamentals of acoustics

random data analysis and measurement procedures is available in our digital library an online access to it is set as public so you can get it instantly. Our book servers spans in multiple countries, allowing you to get the most less latency time to download any of our books like this one. Merely said, the random data analysis and measurement procedures is universally compatible with any devices to read.

Random Data Analysis And Measurement Procedures

Piezo-actuated stages have become more and more promising in nanopositioning applications due to the excellent advantages of the fast response time, large mechanical force, and extremely fine resolution. Modeling and control are critical to achieve objectives for high-precision motion. However, piezo-actuated stages themselves suffer from the inherent drawbacks produced by the inherent creep and hysteresis nonlinearities and vibration caused by the lightly damped resonant dynamics, which make modeling and control of such systems challenging. To address these challenges, various techniques have been reported in the literature. This paper surveys and discusses the progresses of different modeling and control approaches for piezo-actuated nanopositioning stages and highlights new opportunities for the extended studies.

Modeling and Control of Piezo-Actuated Nanopositioning Stages: A Survey

A piezoelectric actuator consists of ceramic material that expands or contracts when a positive or a negative potential voltage signal is applied. The displacement of a piezoelectric actuator is commonly controlled using a voltage input due to its ease of implementation. However, driving a piezoelectric actuator using a voltage input leads to the non-linear hysteresis and creep. Hysteresis and creep are undesirable characteristics which lead to large errors when a piezoelectric actuator is used in positioning applications. The amount of hysteresis and creep could be minimized to a large extent when a piezoelectric actuator is driven using a charge input. Another method which substantially reduces hysteresis and creep involves the insertion of a capacitor in series with a piezoelectric actuator which is driven using a voltage input. A review of voltage, charge and capacitor insertion methods for driving piezoelectric actuators is presented in this paper. Experimental results, for a piezoelectric actuator driven using the above three methods, are presented to validate the facts presented in this review.

A review, supported by experimental results, of voltage, charge and capacitor insertion method for driving piezoelectric actuators

Noise is an environmental pollutant with recognized impacts on the psychological and physiological health of humans. Many porous materials are often limited by low sound absorption over a broad frequency range, delicacy, excessive weight and thickness, poor moisture insulation, high temperature instability, and lack of readiness for high volume commercialization. Herein, an efficient and robust lamella-structure is reported as an acoustic absorber based on self-assembled interconnected graphene oxide (GO) sheets supported by a grill-shaped melamine skeleton. The fabricated lamella structure exhibits ≈60.3% enhancement over a broad absorption band between 128 and 4000 Hz (≈100% at lower frequencies) compared to the melamine foam. The enhanced acoustic absorption is identified to be structure dependent regardless of the density. The sound dissipation in the open-celled structure is due to the viscous and thermal losses, whereas it is predominantly tortuosity in wave propagation and enhanced surface area for the GO-based lamella. In addition to the enhanced acoustic absorption and mechanical robustness, the lamella provides superior structural functionality over many conventional sound absorbers including, moisture/mist insulation and fire retardancy. The fabrication of this new sound absorber is inexpensive, scalable and can be adapted for extensive applications in commercial, residential, and industrial building structures.

/pdf/graphene-oxide-based-lamella-network-for-enhanced-sound-4ja09aylz8.pdf

Graphene Oxide-Based Lamella Network for Enhanced Sound Absorption

The Furuta pendulum, or rotational inverted pendulum, is a system found in many control labs. It provides a compact yet impressive platform for control demonstrations and draws the attention of the control community as a platform for the development of nonlinear control laws. Despite the popularity of the platform, there are very few papers which employ the correct dynamics and only one that derives the full system dynamics. In this paper, the full dynamics of the Furuta pendulum are derived using two methods: a Lagrangian formulation and an iterative Newton-Euler formulation. Approximations are made to the full dynamics which converge to the more commonly presented expressions. The systemdynamics are then linearised using a Jacobian. To illustrate the influence the commonly neglected inertia terms have on the system dynamics, a brief example is offered.

/pdf/on-the-dynamics-of-the-furuta-pendulum-2appox1mp1.pdf

On the dynamics of the furuta pendulum

Vibration isolation using six degree-of-freedom quasi-zero stiffness magnetic levitation

Driven by the need to reduce the sound transmitted into aircraft cabins from the power plant, this thesis investigates the active control of sound transmitted through structure into coupled enclosures. In particular, it examines alternatives to conventional microphone and accelerometer error sensors. This study establishes a design framework for the development and analysis of an active noise control system which can be applied to any complex vibro-acoustic system. The design approach has focused on using techniques presently used in industry to enable the transfer of the active noise control technology from the research stage into practical noise control systems. The structural and acoustic sub-systems are modelled using FEA to estimate the in vacuo structural modal response of the structure and the acoustic pressure modal response (with rigid boundary conditions) of the interior cavity. The acoustic and structural systems are then coupled using modal coupling theory. Within this framework, two novel error sensors aimed at overcoming observability problems suffered by traditional microphone and accelerometer sensors are investigated: namely, acoustic energy density sensors and shaped radiation modal vibration sensors. Acoustic Energy Density Sensors The principles of the measurement of energy density are discussed and the errors arising from its measurement using two and three-microphone sensor configurations are considered for a one-dimensional reactive sound field and a plane wave sound field. The error

https://digital.library.adelaide.edu.au/dspace/bitstream/2440/37893/9/01front.pdf

Benjamin S. Cazzolato

Papers

A review, supported by experimental results, of voltage, charge and capacitor insertion method for driving piezoelectric actuators

Graphene Oxide-Based Lamella Network for Enhanced Sound Absorption

On the dynamics of the furuta pendulum

Vibration isolation using six degree-of-freedom quasi-zero stiffness magnetic levitation

Sensing systems for active control of sound transmission into cavities