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Increased Light, Moderate, and Severe Clear-Air Turbulence in Response to Climate Change

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Advances in Atmospheric Sciences 2017年第5期34卷 576-586页

作者： Paul D. williams Department of Meteorology University of Reading Reading RG6 6BB United Kingdom

Anthropogenic climate change is expected to strengthen the vertical wind shears at aircraft cruising altitudes within the atmospheric jet streams. Such a strengthening would increase the prevalence of the shear instabilities that generate clear-air turbulence. Climate modelling studies have indicated that the amount of moderate-or-greater clear-air turbulence on transatlantic flight routes in winter will increase significantly in future as the climate changes. However,the individual responses of light,moderate,and severe clear-air turbulence have not previously been studied,despite their importance for aircraft operations. Here,we use climate model simulations to analyse the transatlantic wintertime clear-air turbulence response to climate change in five aviation-relevant turbulence strength categories. We find that the probability distributions for an ensemble of 21 clear-air turbulence diagnostics generally gain probability in their right-hand tails when the atmospheric carbon dioxide concentration is doubled. By converting the diagnostics into eddy dissipation rates,we find that the ensembleaverage airspace volume containing light clear-air turbulence increases by 59%(with an intra-ensemble range of 43%–68%),light-to-moderate by 75%(39%–96%),moderate by 94%(37%–118%),moderate-to-severe by 127%(30%–170%),and severe by 149%(36%–188%). These results suggest that the prevalence of transatlantic wintertime clear-air turbulence will increase significantly in all aviation-relevant strength categories as the climate changes.

关键词： turbulence climate change aviation jet stream

Extended Evolutionary Fast Learn-to-Walk Approach for Four-Legged Robots

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Journal of Bionic Engineering 2007年第4期4卷 255-263页

作者： Muh. Anshar Mary-Anne williams Innovation and Technology Research Laboratory Faculty of Information Technology University of Technology Sydney City Campus 15 Broadway Ultimo NSW 2007 Australia

Robot locomotion is an active research area. In this paper we focus on the locomotion of quadruped robots. An effective walking gait of quadruped robots is mainly concerned with two key aspects, namely speed and stability. The large search space of potential parameter settings for leg joints means that hand tuning is not feasible in general. As a result walking parameters are typically determined using machine learning techniques. A major shortcoming of using machine learning techniques is the significant wear and tear of robots since many parameter combinations need to be evaluated before an optimal solution is found. This paper proposes a direct walking gait learning approach, which is specifically designed to reduce wear and tear of robot motors, joints and other hardware. In essence we provide an effective learning mechanism that leads to a solution in a faster convergence time than previous algorithms. The results demonstrate that the new learning algorithm obtains a faster convergence to the best solutions in a short run. This approach is significant in obtaining faster walking gaits which will be useful for a wide range of applications where speed and stability are important. Future work will extend our methods so that the faster convergence algorithm can be applied to a two legged humanoid and lead to less wear and tear whilst still developing a fast and stable gait.

关键词： legged-robots locomotion learning genetic convergence walking gaits

Thoughts on the Jiaodong Gold Province of China:Towards a Tectonic Model

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Acta Geologica Sinica(English Edition) 1999年第1期73卷 1-7页

作者： williams.FYFE Department of Earth Sciences University of Western OntarioLondon OntarioCanada N6A 5B7

Abstract The Jiaodong gold province is situated in the eastern Sino-Korean Platform within the so-called Jiaoliao Uplift. The basement rocks are Archaean and Proterozoic metamorphic rocks. Mesozoic sedimentary and volcanic cover occur within extensional basins. Intrusive rocks are dominated by Mesozoic granitoid, with intermediate-acid and basic dyke swarms. The structures form an E-W-trending anticlinorium in the basement complex, and large-scale NE-SW- and NNE-SSW-trending fault zones of Mesozoic age. The gold mineralization is associated with the Mesozoic faults and related secondary fractures in the granites or granite-basement contacts. The mineralization types are quartz-vein type and wall-rock alteration type. Wall-rock alteration is very well developed around the ore zones. Alteration minerals include quartz, sericite (and fuchsite), pyrite, calcite, chlorite, hematite, rutile and graphite. The ore assemblage is uniform in all deposits, including pyrite, chalcopyrite, galena, sphalerite, arsenopyrite, pyrrhotite, gold, electrum, hessite, petzite, magnetite, molybdenite, tetrahedrite and wolframite. Mesozoic collision and subduction between the South China and North China continental blocks contributed to formation of the Mesozoic granitoid intrusions. The granitic magma is considered to be derived from partial melting of the crust through underplating processes. Gold was remobilised from basement rocks and deposited in fracture zones by the high-temperature fluids associated with these processes.

关键词： Jiaodong gold fluids faults granitoid subduction collision

On sustaining the ecology and livestock industry of the Bayanbuluk Grasslands

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Journal of Arid Land 2010年第1期2卷 57-63页

作者： Adrian R williams Pendragon Dryland Management Services

A short visit to the Bayanbuluk Grassland in the Tianshan Mountains, Xinjiang, PRC, revealed a number of environmental and livestock production problems, including grassland degradation, loss of grassland biodiversity, soil erosion and flash flooding downstream, decreased pasture productivity, and poor livestock nutrition (especially in winter) leading to stock losses and flocks and herds of low productivity. This paper describes those problems and then suggests some solutions. Short duration, high intensity grazing could be one of the solutions to both improving grassland condition and improving livestock nutrition. Local production of fodder crops for feeding in winter and spring deserves testing, using adapted strains of Alfalfa (Medicago sativa) and trialling fodder root crop production. It is important to realise that the land management objectives of scientists, administrators, herders and farmers may be similar, and that there are opportunities for land improvement through working together.

关键词： Bayanbuluk Grasslands Tianshan Mountains reversing grassland degradation improving livestock productivity

Combining X-ray microtomography with computer simulation for analysis of granular and porous materials

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Particuology 2010年第2期8卷 81-99页

作者： Roberto Moreno-Atanasio Richard A. williams Institute of Particle Science and Engineering School of Process Environmental and Materials Engineering University of Leeds Leeds LS2 9JT UK

The use of X-ray microtomographic （XMT） methods in analysing particulate systems has expanded rapidly in recent years with the availability of affordable desk-top apparatus. This review presents a summary of the major applications in which computer simulations are explicitly coupled with XMT in the area of granular and porous materials. We envisage two main ways of establishing the coupling between both techniques, based on the transference or exchange of information by using physical or geometrical parameters （i.e. a parametric link through fitting to a process model） or through the direct use of3D XMT digital images （i.e. comparing image pixels and features directly）. Examples of coupled applications are shown for the study of transport properties of rocks, particle packing, mechanical loading and sintering. Often, the link between XMT and computer simulations is based on visual comparisons and we conclude that the use of quantitative parameters such as the number of interparticle contacts, force networks or granule shape to link both techniques is still underrepresented in the literature. Strategies to provide a more robust and quantitative approach to optimise the information obtained from such tomography analyses are proposed. 2010 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

关键词： X-ray microtomographyGranular flowComputer modellingLattice Boltzmann methodDiscrete element method

Energy Release Rates for Interface Cracks in Multilayered Structures

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Computer Modeling in Engineering & Sciences 2019年第8期120卷 261-272页

作者： Changwei Huang Philip A.williams Department of Civil Engineering Chung Yuan Christian UniversityTaoyuan 32023Taiwan Simutech Solution Corporation 14FNo.90Section 2Nanjing E.Rd.Taipei 10406Taiwan

This paper examines the evolution of the interfacial deflection energy release rates in multilayered structures under four-point *** J-integral and the extended finite element method(XFEM)are adopted to investigate the evolution of the interfacial deflection energy release rates of composite *** results not only verify the accuracy of analytical solutions for the steady-state interfacial deflection energy release rate,but also provide the evolutionary history of the interfacial deflection energy release rate under different crack *** addition,non-dimensional parametric analyses are performed to discuss the effects of normalized ratios of the crack length,the elastic modulus,and the thickness on the interfacial deflection energy release *** results demonstrate that the elastic modulus ratio and thickness ratio have a distinct influence on the interfacial deflection energy release rate for multilayered ***,an unstable interfacial crack tends to occur for elastic multilayer beams with higher elastic modulus on the upper sub-beam under bending *** unstable interfacial fracture shows a decreasing interfacial deflection energy release rate with an increasing interfacial crack length.

关键词： Interfacial deflection energy release rate four-point bending J-integral extended finite element method

Effect of Cultivation on Soil Organic Matter and Aggregate Stability

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Pedosphere 2005年第2期15卷 255-262页

作者： A.williams P.VENEMAN Department of Plant Soil and Insect Sciences University of Massachusetts MA 01003 (USA) Department of Plant Amherst

Agricultural sustainability relates directly to maintaining or enhancing soil quality. Soil quality studies in Canada during the 1980’s showed that loss of soil organic matter (SOM) and soil aggregate stability was standard features of non-sustainable land management in agroecosystems. In this study total soil organic carbon (SOC), particulate organic matter (POM), POM-C as a percentage of total SOC, and aggregate stability were determined for three cultivated fields and three adjacent grassland fields to assess the impact of conventional agricultural management on soil quality. POM was investigated using solid-state 13C nuclear magnetic resonance (NMR) to determine any qualitative differences that may be attributed to cultivation. Results show a highly significant loss in total SOC, POM and aggregate stability in the cultivated fields as compared to the grassland fields and a significant loss of POM-C as a percentage of total SOC. Integrated results of the NMR spectra of the POM show a loss in carbohydr

关键词： aggregate stability cultivation NMR particulate organic matter soil organic matter

Lattice approaches to packed column simulations

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Particuology 2008年第6期6卷 404-411页

作者： Richard Caulkin Mike Fairweather Richard A. williams Institute of Particle Science and Engineering School of ProcessEnvironmental and Materials EngineeringUniversity of Leeds

This work presents a review of the findings into the ability of a digitally based particle packing algorithm, called DigiPac, to predict bed structure in a variety of packed columns, for a range of generic pellet shapes frequently used in the chemical and process engineering industries. Resulting macroscopic properties are compared with experimental data derived from both invasive and non-destructive measurement techniques. Additionally, fluid velocity distributions, through samples of the resulting bed structures, are analysed using lattice Boltzmann method （LBM） simulations and are compared against experimental data from the literature.

关键词： Packing algorithm Bed structure Packed columns Macroscopic properties Lattice Boltzmann simulations

Biocompatibility pathways and mechanisms for bioactive materials:The bioactivity zone

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Bioactive Materials 2022年第4期7卷 306-322页

作者： David F.williams Wake Forest Institute of Regenerative Medicine 391 Technology Way.Winston-SalemNorth Carolina27101USA

This essay analyzes the scientific evidence that forms the basis of bioactive materials,covering the fundamental understanding of bioactivity phenomena and correlation with the mechanisms of biocompatibility of *** is a detailed assessment of performance in areas such as bone-induction,cell adhesion,immunomodulation,thrombogenicity and antimicrobial *** is the modulation of biological activity by characteristics of the interfacial region that incorporates the material surface and the immediate local host *** the term‘bioactive material’is widely used and has a well understood general meaning,it would be useful now to concentrate on this interfacial region,considered as‘the bioactivity zone’.Bioactivity phenomena are either due to topographical/micromechanical characteristics,or to biologically active species that are presented in the bioactivity *** of topographical/micromechanical effects are the modulation of the osteoblast-osteoclast balance,nanotopographical regulation of cell adhesion,and bactericidal *** of bioactivity by biologically active species include their influence,especially of metal ions,on signaling pathways in bone formation,the role of cell adhesion molecules and bioactive peptides in cell attachment,macrophage polarization by immunoregulatory molecules and antimicrobial *** much experimental data exists to demonstrate the potential of such phenomena,there are considerable barriers to their effective clinical *** essay shows that there is solid scientific evidence of the existence of bioactivity mechanisms that are associated with some types of biomaterials,especially when the material is modified in a manner designed to specifically induce that activity.

关键词： Bioactivity Host response Biomaterial Medical technology Cell signaling