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

Probability Distributions.- Linear Models for Regression.- Linear Models for Classification.- Neural Networks.- Kernel Methods.- Sparse Kernel Machines.- Graphical Models.- Mixture Models and EM.- Approximate Inference.- Sampling Methods.- Continuous Latent Variables.- Sequential Data.- Combining Models.

Pattern Recognition and Machine Learning

The lithium metal battery is strongly considered to be one of the most promising candidates for high-energy-density energy storage devices in our modern and technology-based society. However, uncontrollable lithium dendrite growth induces poor cycling efficiency and severe safety concerns, dragging lithium metal batteries out of practical applications. This review presents a comprehensive overview of the lithium metal anode and its dendritic lithium growth. First, the working principles and technical challenges of a lithium metal anode are underscored. Specific attention is paid to the mechanistic understandings and quantitative models for solid electrolyte interphase (SEI) formation, lithium dendrite nucleation, and growth. On the basis of previous theoretical understanding and analysis, recently proposed strategies to suppress dendrite growth of lithium metal anode and some other metal anodes are reviewed. A section dedicated to the potential of full-cell lithium metal batteries for practical applicatio...

Toward Safe Lithium Metal Anode in Rechargeable Batteries: A Review.

A review on the key issues for lithium-ion battery management in electric vehicles

https://las493energy.files.wordpress.com/2014/11/2005_vetter_jpowsourc.pdf

Ageing mechanisms in lithium-ion batteries

Limiting mechanism on rapid charging NiMH batteries

Computer simulation of battery performance, especially from first principles, can provide valuable information for understanding how a battery performs under dynamic conditions. This paper describes recent progress made in incorporating both oxygen and hydrogen recombinant cycles in a computational fluid dynamics based numerical model to simulate nickel metal hydride (Ni-MH) traction battery performance. It is important to show that the incorporation of the hydrogen recombinant cycle is useful and how that affects simulation results in predicting and validating, for example, fast charging of an 85 Ah Ni-MH battery system made of AB 2 -hydride based cells. From our previous studies, we have found that in cells of such a battery, the hydrogen recombinant cycle is critically related to cell performance, particularly in fast charging behavior at 1-3C rates. Using the experimental data collected in our laboratory, we validated the model and showed comparisons between results from predictions made with and without the hydrogen recombinant cycle. Implications of the simulation results in the understanding of the limiting mechanism in the fast charging conditions are also discussed.

Numerical Simulation on Fast Charging Nickel Metal Hydride Traction Batteries

We studied the self-discharge and charge retention characteristics of an 85 Ah nickel metal hydride (Ni-MH) traction battery and proposed the most likely mechanisms associated with the passive capacity loss via self-discharge. The mechanistic explanation is evident through the analysis of the internal cell pressure profile and the corresponding individual electrode potential variation in the aging process. Three different stages, each associated with a predominant mechanism for self-discharge, were identified at room temperature, corresponding to a short (10-100 s), an intermediate (10 min-25 h), and a long (2 days-several months) period of aging. All three stages involved reactions with hydrogen gas, which led to the capacity loss. Most of the capacity loss was temporary and could be recovered from subsequent recharge. The effect from oxygen evolution and recombination only showed in the beginning of the self-discharge process and diminished after about 4 h of aging from the fully charged state. Through the remaining part of the intermediate stage, the residual hydrogen gas continued to reduce the positive electrode capacity via a partial discharge. In the final stage of the long aging period, the capacity loss was probably caused by a minute leakage current. From this study, we derived the charge retention as a function of aging time, which can be used for capacity prediction. Good agreement between the predicted value and the test result was found.

Self-Discharge and Charge Retention in AB 2-Based Nickel Metal Hydride Batteries

Lithium–sulfur batteries are very promising for next-generation energy storage. However, most studies use flooded electrolytes to achieve a high specific capacity at the expense of lowering the spe...

Dual Functional Ni3S2@Ni Core–Shell Nanoparticles Decorating Nanoporous Carbon as Cathode Scaffolds for Lithium–Sulfur Battery with Lean Electrolytes

Hawaii is an attractive proving ground for electric and hybrid vehicles (EHV) evaluation. Envisioning and embracing the needs for environmental-friendly advanced transportation technology developments, the Hawaii Center for Advanced Transportation Technologies (HCATT) and the Electrochemical Power Systems Laboratory (EPSL) at the Hawaii Natural Energy Institute (HNEI) of the University of Hawaii, are working together to promote and facilitate EHV development in Hawaii. This paper reports some of the recent activities in EHV evaluation, battery modeling, and fleet testing in the HCATT program. The fleet of EHV in this program includes battery-powered EV (BEV) and battery-fuel cell hybrid electric vehicles (HEV). We will present vehicle test results, battery modeling and simulation tool developments, and data analysis approaches that we developed and used in the program.

/pdf/vehicle-evaluation-battery-modeling-and-fleet-testing-25hszssjlz.pdf

Bor Yann Liaw

Papers

Limiting mechanism on rapid charging NiMH batteries

Numerical Simulation on Fast Charging Nickel Metal Hydride Traction Batteries

Self-Discharge and Charge Retention in AB 2-Based Nickel Metal Hydride Batteries

Dual Functional Ni3S2@Ni Core–Shell Nanoparticles Decorating Nanoporous Carbon as Cathode Scaffolds for Lithium–Sulfur Battery with Lean Electrolytes

Vehicle Evaluation, Battery Modeling, and Fleet-testing Experiences in Hawaii A Roadmap to Understanding Evaluation Data and Simulation