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

1. Interaction. The interactions learners have with each other build interpersonal skills, such as listening, politely interrupting, expressing ideas, raising questions, disagreeing, paraphrasing, negotiating, and asking for help. 2. Interdependence. Learners must depend on one another to accomplish a common objective. Each group member has specific tasks to complete, and successful completion of each member’s tasks results in attaining the overall group objective.

将“Cooperative Learning”融入课堂——浅谈英语素质教育

When there are many people who don't need to expect something more than the benefits to take, we will suggest you to have willing to reach all benefits. Be sure and surely do to take this problem based learning an approach to medical education that gives the best reasons to read. When you really need to get the reason why, this problem based learning an approach to medical education book will probably make you feel curious.

Problem-Based Learning: An Approach to Medical Education

Probability, Reliability and Statistical Methods in Engineering Design

Although the off-road mobility characteristics of wheeled or tracked vehicles are generally recognized as being inferior to those of man and cursorial animals, the complexity of the joint-coordination control problem has thus far frustrated attempts to achieve improved vehicular terrain adaptability through the application of legged locomotion concepts. Nevertheless, the evident superiority of biological systems in this regard has motivated a number of theoretical studies over the past decade which have now reached a state of maturity sufficient to permit the construction of experimental computer-controlled adaptive walking machines. At least two such vehicles are known to have recently demonstrated legged locomotion over smooth hard-surfaced terrain. This paper is concerned with an extension of the present theory of limb coordination for such machines to the case in which the terrain includes regions not suitable for weight-bearing and which must consequently be avoided by the control computer in deciding when and where to successively place the feet of the vehicle. The paper includes a complete problem formalization, a heuristic algorithm for solution of the problem thus posed, and a preliminary evaluation of the proposed algorithm in terms of a computer simulation study.

Adaptive Locomition of a Multilegged Robot over Rough Terrain

Dynamic capability equations (DCE) provide a new description of robot acceleration and force capabilities. These refer to a manipulator's ability to accelerate its end-effector and to apply forces to the environment at the end-effector. The key features in the development of these equations are that they combine the analysis of end-effector accelerations, velocities, and forces, while addressing the difference in units between translational and rotational quantities. The equations describe the magnitudes of translational and rotational acceleration and force guaranteed to be achievable in every direction, from a particular configuration, given the limitations on the manipulator's motor torques. They also describe the effect of velocities on these capabilities contributed by the Coriolis and centrifugal forces, as well as the reduction of actuator torque capacity due to motor speed. This article focuses on nonredundant manipulators with as many actuators as degrees of freedom.

/pdf/the-dynamic-capability-equations-a-new-tool-for-analyzing-1qj6m49vc0.pdf

The dynamic capability equations: a new tool for analyzing robotic manipulator performance

The focus of this paper is to develop a software-hardware platform that addresses one of the most costly, acute health conditions, pressure ulcers — or bed sores. Caring for pressure ulcers is extremely costly, increases the length of hospital stays and is very labor intensive. The proposed platform collects information from various sensors incorporated into the bed, analyzes the data to create a time-stamped, whole-body pressure distribution map, and commands the bed's actuators to periodically adjust its surface profile to redistribute pressure over the entire body. These capabilities are combined to form a cognitive support system, that augments the ability of a care giver, allowing them to provide better care to more patients in less time. For proof of concept, we have implemented algorithms and architectures that cover four key aspects of this platform: 1) data collection, 2) modeling & profiling, 3) machine learning, and 4) acting.

http://qolt.utdallas.edu/files/pdfs/BMEI11_Smart.pdf

A smart bed platform for monitoring & Ulcer prevention

Investigates the problem of manipulator design for increased dynamic performance. Optimization techniques are used to determine the design parameters which improve manipulator performance. The dynamic performance of a manipulator is characterized by the inertial and acceleration properties of the end-effector. Our study of inertial and acceleration properties have provided separate descriptions of the characteristics associated with linear and angular motions. This allows a more physically meaningful interpretation of these properties and provides simple models for their analysis. The article presents these models, discusses the design optimization criteria, and formulates the optimization problem. The approach is illustrated in the selection of design parameters of a parallel mechanism.

Optimization of the inertial and acceleration characteristics of manipulators

This paper addresses the improvement of navigability for a six-legged robot through the development of a simple method for measuring heading and drift errors. More specifically, the navigation scheme utilizes both a magnetic compass and landmark navigation to correct these errors with every step, hence limiting error propagation. The approach is aimed at operation in unknown environments. Elaborate data processing in the control algorithm is avoided by using modular sensors capable of processing their own inputs. The robot controller uses the well-known tripod gait, implemented here using the hexapod inverse kinematics. Experimental results show significant improvements in the hexapod's navigability for turning and walking maneuvers.

Navigability of multi-legged robots

Background. This article presents a method for describing the dynamic performance of multilegged robots. It involves examining how well the legged system uses ground contact to produce acceleration of its body; these abilities are referred to as its force and acceleration capabilities. These capabilities are bounded by actuator torque limits and the no-slip condition. Method of Approach. The approach followed here is based on the dynamic capability equations, which are extended to consider frictional ground contact as well as the changes in degrees-of-freedom that occurs as the robot goes into and out of contact with the ground. Results. The analysis describes the maximum translational and rotational accelerations of the main-body that are guaranteed to be achievable in every direction without causing slipping at the contact points or saturating an actuator. Conclusion. This analysis provides a description of the mobility and agility of legged robots. The method is illustrated using a hexapod as an example.

Alan Bowling

Papers

The dynamic capability equations: a new tool for analyzing robotic manipulator performance

A smart bed platform for monitoring & Ulcer prevention

Optimization of the inertial and acceleration characteristics of manipulators

Navigability of multi-legged robots

Dynamic Performance, Mobility, and Agility of Multilegged Robots