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

The long-standing popularity of thermoelectric materials has contributed to the creation of various thermoelectric devices and stimulated the development of strategies to improve their thermoelectric performance. In this review, we aim to comprehensively summarize the state-of-the-art strategies for the realization of high-performance thermoelectric materials and devices by establishing the links between synthesis, structural characteristics, properties, underlying chemistry and physics, including structural design (point defects, dislocations, interfaces, inclusions, and pores), multidimensional design (quantum dots/wires, nanoparticles, nanowires, nano- or microbelts, few-layered nanosheets, nano- or microplates, thin films, single crystals, and polycrystalline bulks), and advanced device design (thermoelectric modules, miniature generators and coolers, and flexible thermoelectric generators). The outline of each strategy starts with a concise presentation of their fundamentals and carefully selected examples. In the end, we point out the controversies, challenges, and outlooks toward the future development of thermoelectric materials and devices. Overall, this review will serve to help materials scientists, chemists, and physicists, particularly students and young researchers, in selecting suitable strategies for the improvement of thermoelectrics and potentially other relevant energy conversion technologies.

Advanced Thermoelectric Design: From Materials and Structures to Devices

The growth of a vapor bubble in a superheated liquid is controlled by three factors: the inertia of the liquid, the surface tension, and the vapor pressure. As the bubble grows, evaporation takes place at the bubble boundary, and the temperature and vapor pressure in the bubble are thereby decreased. The heat inflow requirement of evaporation, however, depends on the rate of bubble growth, so that the dynamic problem is linked with a heat diffusion problem. Since the heat diffusion problem has been solved, a quantitative formulation of the dynamic problem can be given. A solution for the radius of the vapor bubble as a function of time is obtained which is valid for sufficiently large radius. This asymptotic solution covers the range of physical interest since the radius at which it becomes valid is near the lower limit of experimental observation. It shows the strong effect of heat diffusion on the rate of bubble growth. Comparison of the predicted radius‐time behavior is made with experimental observations in superheated water, and very good agreement is found.

The growth of vapor bubbles in superheated liquids. report no. 26-6

Two-dimensional (2D) materials have attracted tremendous research interest since the breakthrough of graphene. Their unique optical, electronic, and mechanical properties hold great potential for harnessing them as key components in novel applications for electronics and optoelectronics. Their atomic thickness and exposed huge surface even make them highly designable and manipulable, leading to the extensive application potentials. What's more, after acquiring the qualification for being the candidate for next-generation devices, the assembly of 2D materials monomers into mass or ordered structure is also of great importance, which will determine their ultimate industrialization. By designing the monomers and regulating their assembling behavior, the exploration of 2D materials toward the next-generation circuits can be spectacularly achieved. In this review, we will first overview the emerging 2D materials and then offer a clear guideline of varied physical and chemical strategies for tuning their properties. Furthermore, assembly strategies of 2D materials will also be included. Finally, challenges and outlooks in this promising field are featured on the basis of its current progress.

Exploring Two-Dimensional Materials toward the Next-Generation Circuits: From Monomer Design to Assembly Control

https://espace.library.uq.edu.au/view/UQ:e38288a/UQe38288a_OA.pdf

High-performance SnSe thermoelectric materials: Progress and future challenge

Deposition of amyloid in the heart can lead to cardiac dilation and impair its pumping ability. This ultimately leads to heart failure with worsening symptoms of breathlessness and fatigue due to the progressive loss of elasticity of the myocardium. Biomarkers linked to clinical deterioration can be crucial in developing effective treatments. However, to date progression of cardiac amyloidosis is poorly characterized, and there is an urgent need to identify key features that can predict the disease progression and cardiac tissue function. In this proof of concept study, we estimate a group of new markers based on mathematical models of the left ventricle derived from routine clinical magnetic resonance imaging and follow-up scans from the National Amyloidosis Centre at the Royal Free in London. Using mechanical modelling and statistical classification, we show that it is possible to predict disease progression. Our predictions agree with clinical assessments in a double-blind test in six out of the seven sample cases studied. Importantly, we find that multiple factors need to be used in the classification, which includes mechanical, geometrical and shape features. No single marker can yield reliable prediction given the complexity of the growth and remodelling process of diseased hearts undergoing high-dimensional shape changes. Our approach is promising in terms of clinical translation but the results presented should be interpreted with caution due to the small sample size.

/pdf/analysis-of-cardiac-amyloidosis-progression-using-model-2zb0n9tlvl.pdf

Analysis of cardiac amyloidosis progression using model-based markers

Three-dimensional (3D) gallbladder (GB) geometrical models are essential to GB motor function evaluation and GB wall biomechanical property identification by employing finite element analysis (FEA) in GB disease diagnosis with ultrasound systems. Methods for establishing such 3D geometrical models based on static two-dimensional (2D) ultrasound images scanned along the long-axis/sagittal and short-axis/transverse cross-sections in routine GB disease diagnosis at the beginning of emptying phase have not been documented in the literature so far. Based on two custom MATLAB codes composed, two images were segmented manually to secure two sets of the scattered points for the long- and short-axis GB cross-section edges; and the points were best fitted with a piecewise cubic spline function, and the short-axis cross-section edges were lofted along the long-axis to yield a 3D geometrical model, then GB volume of the model was figured out. The model was read into SolidWorks for real surface generation and involved in ABAQUS for FEA. 3D geometrical models of seven typical GB samples were established. Their GB volumes are with 15.5% and − 4.4% mean errors in comparison with those estimated with the ellipsoid model and sum-of-cylinders method but can be correlated to the latter very well. The maximum first principal in-plane stress in the 3D models is higher than in the ellipsoid model by a factor of 1.76. A numerical method was put forward here to create 3D GB geometrical models and can be applied to GB disease diagnosis and GB shape analysis with principal component method potentially in the future.

/pdf/ultrasound-image-based-human-gallbladder-3d-modelling-along-4jtmliwo7b.pdf

Ultrasound Image Based Human Gallbladder 3D Modelling along with Volume and Stress Level Assessment

Strain energy-based constitutive laws with damage effect were proposed by using existing both uniaxial tensile test and tubular biaxial inflation test data on the human great saphenous vein (GSV) segments. These laws were applied into GSV coronary artery bypass grafts (CABG) by employing a thin-walled vessel model to evaluate their passive biomechanical performance under coronary artery physiological conditions at a fixed axial pre-stretch. At a peak systolic pressure in 100–150 mmHg, a 20–33% GSV diameter dilation was predicted with the law based on tubular biaxial inflation test data and agreed well with 25% dilation in clinical observation in comparison with as small as 2–4% dilation estimated with the law based on uniaxial tensile test data. The constitutive law generated by tubular biaxial inflation test data was mostly suitable for GSV CABG under coronary artery physiological conditions than that based on uniaxial tensile test results. With these laws, the fibre ultimate stretch was extracted from uniaxial tensile test data and the structural sub-failure/damage threshold of 1.0731 was decided for the human GSV. GSV fibres could exhibit damage effect but unlikely undergo a structure failure/break, suggesting a damage factor might exist during CABG arterialization. The damage in GSV tissue might initiate or contribute to early remodelling of CABG after implantation.

Constitutive laws with damage effect for the human great saphenous vein.

Constitutive modelling of skins that account for damage effects is important to provide insight for various clinical applications, such as skin trauma and injury, artificial skin design, skin aging, disease diagnosis, surgery, as well as comparative studies of skin biomechanics between species. In this study, a new damage model for human and animal skins is proposed for the first time. The model is nonlinear, anisotropic, invariant-based, and is based on the Gasser– Ogden–Holzapfel constitutive law initially developed for arteries. Taking account of the mean collagen fibre orientation and its dispersion, the new model can describe a wide range of skins with damage. The model is first tested on the uniaxial test data of human skin and then applied to nine groups of uniaxial test data for the human, swine, rabbit, bovine and rhino skins. The material parameters can be inversely estimated based on uniaxial tests using the optimization method in MATLAB with a root mean square error ranged between 2.15% and 12.18%. A sensitivity study confirms that the fibre orientation dispersion and the mean fibre angle are among the most important factors that influence the behaviour of the damage model. In addition, these two parameters can only be reliably estimated if some histological information is provided. We also found that depending on the location of skins, the tissue damage may be brittle controlled by the fibre breaking limit (i.e., when the fibre stretch is greater than 1.13–1.32, depending on the species), or ductile (due to both the fibre and the matrix damages). The brittle damages seem to occur mostly in the back, and the ductile damages are seen from samples taken from the belly. The proposed constitutive model may be applied to various clinical applications that require knowledge of the mechanical response of human and animal skins. Keywords—Skin, Damage, Fibre orientation, Fibre orientation dispersion, Constitutive model, Inverse problem. INTRODUCTION The human skin not only has important protective functions against mechanical trauma such as friction, impact, pressure, cutting and shearing, but also plays a vital role in active thermo-regulation, wound-healing, and acts as the nonslip intermediate surface when one grips, lifts, or presses. The skin consists of three layers: the epidermis, the dermis, and subcutaneous tissues. The epidermis is the top renewable layer of 0.1– 1.5 mm thickness. The dermis is the middle layer with 1–4 mm thickness, which has two sub-layers: the papillary layer and the reticular layer. The dermis consists of 77% collagen and 4% elastin (fat-free dry weight), vasculature, nerve bundles, hair follicles, veins and sweat glands. The subcutaneous tissue is underneath the dermis and with fat to store energy for the body. The skin is in tension in normal physiological conditions and its tension level depends on individual maturation and aging, wound healing state, dysfunction or diseases such as the Ehlers–Danlos syndrome. Studying biomechanical property of human skin is useful in cosmetic product development, plastic surgery, surgical practice and skin disease pathology as well as artificial skin design. Commonly used methods to identify skin biomechanical properties can be classified as in vivo and in vitro methods. In vivo methods are mainly adopted in daily clinical practice. With this method one can generate a stretch, shear, torsion, compression, indentation, or wave deformation, in order to compute the stress components or the material properties (e.g., Young’s moduli). However, with this approach, only up to 30% maximum extension can be obtained; the full nonlinear behaviour of skins cannot be accounted for in the damage models. In vitro methods provide alternative approaches, where skin Address correspondence to Wenguang Li, School of Engineering, University of Glasgow, Glasgow G12 8QQ, UK. Electronic mail: Wenguang.Li@Glasgow.ac.uk, Xiaoyu.Luo@Glasgow.ac.uk Annals of Biomedical Engineering, Vol. 44, No. 10, October 2016 ( 2016) pp. 3109–3122 DOI: 10.1007/s10439-016-1603-9 0090-6964/16/1000-3109/

/pdf/erratum-to-an-invariant-based-damage-model-for-human-and-2czbwgxrv9.pdf

Erratum to: An Invariant-Based Damage Model for Human and Animal Skins.

In reality, a solar panel with concentrator is
subject to variable sunlight radiation, wind
speed and environmental air temperature in a
day, accordingly the solar output power is
changed in a wide range of 2W-13W, causing
a degraded electric performance [1-3]. Thus it
is necessary to characterise optical and
thermal behaviour of a crossed compound
parabolic concentrator (CCPC) with solar cell
in its design stage to optimise its configuration.
Presently, the CCPC optical and thermal
performance characterisation is usually based
on steady-state physics models, see [4-8], for
example, thus ignored unsteady variation of air
flow and heat transfer in concentrator. In this
contribution, we investigate the optical and
thermal performance of an isolated CCPC with
solar cell from the solar panel in [6,7] by
means of ANSYS CFX. The CCPC with solar
cell is subject to a variable sunlight radiation
intensity, wind speed and air temperature from
6am to 17pm a day which were measured in
[6] on 20th March 2009.

Wenguang Li

Papers

Analysis of cardiac amyloidosis progression using model-based markers

Ultrasound Image Based Human Gallbladder 3D Modelling along with Volume and Stress Level Assessment

Constitutive laws with damage effect for the human great saphenous vein.

Erratum to: An Invariant-Based Damage Model for Human and Animal Skins.

Unsteady optical and thermal behaviour of crossed compound parabolic concentrator with solar cell