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

Worldwide commercial interest in carbon nanotubes (CNTs) is reflected in a production capacity that presently exceeds several thousand tons per year. Currently, bulk CNT powders are incorporated in diverse commercial products ranging from rechargeable batteries, automotive parts, and sporting goods to boat hulls and water filters. Advances in CNT synthesis, purification, and chemical modification are enabling integration of CNTs in thin-film electronics and large-area coatings. Although not yet providing compelling mechanical strength or electrical or thermal conductivities for many applications, CNT yarns and sheets already have promising performance for applications including supercapacitors, actuators, and lightweight electromagnetic shields.

/pdf/carbon-nanotubes-present-and-future-commercial-applications-1nhq3xy4hh.pdf

Carbon Nanotubes: Present and Future Commercial Applications

The unique electrical, mechanical and physical properties of two-dimensional materials make them attractive candidates in flexible nanoelectronic systems. Here Akinwande et al. review the literature on two-dimensional materials in flexible nanoelectronics, and highlight barriers to their full implementation.

/pdf/two-dimensional-flexible-nanoelectronics-4fvhvf1sg7.pdf

Two-dimensional flexible nanoelectronics.

The lateral and vertical integration of ZnO piezoelectric nanowires allows for voltage and power outputs sufficient to power nanowire-based sensors.

http://www.nanoscience.gatech.edu/zlwang/paper/2010/10_NN_01.pdf

Self-powered nanowire devices.

One-dimensional (1D) ZnO nanostructures have been studied intensively and extensively over the last decade not only for their remarkable chemical and physical properties, but also for their current and future diverse technological applications. This article gives a comprehensive overview of the progress that has been made within the context of 1D ZnO nanostructures synthesized via wet chemical methods. We will cover the synthetic methodologies and corresponding growth mechanisms, different structures, doping and alloying, position-controlled growth on substrates, and finally, their functional properties as catalysts, hydrophobic surfaces, sensors, and in nanoelectronic, optical, optoelectronic, and energy harvesting devices.

/pdf/one-dimensional-zno-nanostructures-solution-growth-and-30xs4d6be7.pdf

One-dimensional ZnO nanostructures: Solution growth and functional properties

Background: The piezoelectric microvibratory stage as a microelectromechanical system (MEMS) actuator can tilt around the X  /  Y axis and translate along the Z axis. However, when the vibratory stage is tilted around the X axis, it also has an undesirable tilting angle around the Y axis. It means that the X axis tilting and the Y axis tilting are not independent; therefore, it is significant to eliminate the coupling of two motions.
Aim: The coupling of X  /  Y tilting motion is studied theoretically and decoupled by optimization of structural parameters.
Approach: A structural model was established to analyze the reasons of the X  /  Y tilting coupling. Reasonable structure parameters of L-shaped piezoelectric beam were designed to eliminate the off-axis errors caused by X  /  Y tilting coupling.
Results: The reason of X  /  Y tilting coupling is that the stiffness of the L-shaped piezoelectric support beam mismatch in the X axis and Y axis directions. The appropriate width ratio of the two segments of the L-shaped piezoelectric beam can reduce the off-axis error effectively.
Conclusions: The test results show that the piezoelectric MEMS vibratory stage can achieve X  /  Y tilting motion with the relative off-axis error only at 1%.

Improved MEMS piezoelectric vibratory stage with reduced off-axis error

The invention provides a PDMS microlens array and a method for preparing the PDMS microlens array by concave mold liquid molding, and belongs to the technical field of microlens array manufacturing. The method for preparing the PDMS microlens array by concave mold liquid molding comprises the steps: a liquid surface layer is formed on the surface of a substrate, wherein the material of the liquid surface layer is a curable material; the open side surface of the PDMS sheet having circular holes arranged in an array is brought into contact with the liquid surface layer and a post-cured liquid surface layer is maintained so that a concave surface corresponding to the position of each circular hole is formed on the liquid surface layer; a microlens array concave mold is obtained by stripping the PDMS sheet from the cured liquid surface layer; and a PDMS microlens array is prepared from the microlens array concave mold. The microlens array concave mold is prepared by the method of concave mold liquid molding, which has the advantages of simple process, easy operation and low cost. The prepared PDMS microlens array has high quality of external surface profile forming and good imaging effect.

PDMS microlens array and method for preparing PDMS microlens array by concave mold liquid molding

A study on the dynamic response of a projectile penetrating concrete is conducted. The evolutional process of projectile mass loss and the effect of mass loss on penetration resistance are investigated using theoretical methods. A projectile penetration model considering projectile mass loss is established in three stages, namely, cratering phase, mass loss penetration phase, and remainder rigid projectile penetration phase.

/pdf/a-mass-loss-penetration-model-to-investigate-the-dynamic-4texpk2s81.pdf

A Mass Loss Penetration Model to Investigate the Dynamic Response of a Projectile Penetrating Concrete considering Mass Abrasion

Simulation of micro/nano electroporation for cell transfection

This work reports a 4-cm-long piezoelectric microrobot with agile steering abilities on water surface. Two unique accomplishments are demonstrated: (1) A 0.88g soft robot uses two pairs of flapping hydrofoils (equal frequency but with phase offsets) to generate adjustable thrusts that cause smoothly steering on water surface (first in published papers). The robot's angular velocity ranges from -6°/s (clockwise) to +6°/s (counterclockwise), and the turning resolution is 0.4°/s; (2) The soft robot that made of fully flexible structures has a forward skating speed up to 2cm/s, and carries loads of three times its weight with the speed of 4mm/s. As such, the new method could open up new opportunities for microrobots working on water surface.

Bei Peng

Papers

Improved MEMS piezoelectric vibratory stage with reduced off-axis error

PDMS microlens array and method for preparing PDMS microlens array by concave mold liquid molding

A Mass Loss Penetration Model to Investigate the Dynamic Response of a Projectile Penetrating Concrete considering Mass Abrasion

Simulation of micro/nano electroporation for cell transfection

A Piezoelectric Water Skating Microrobot Steers Through Ripple Interference