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Antarctic-wide annual ice flow maps from Landsat 8 imagery between 2013 and 2019

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International Journal of Digital Earth 2021年第5期14卷 597-618页

作者： Qiang Shen Hansheng Wang c.K.Shum Liming Jiang Houtse Hsu Fan Gao Yingli Zhao State Key Laboratory of Geodesy and Earth’s Dynamics Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhanPeople’s Republic of China Division of Geodetic Science School of Earth SciencesThe Ohio State UniversityColumbusOhioUSA college of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijingPeople’s Republic of China

Ice velocity constitutes a key parameter for quantifying ice-sheet discharge rates and is thus crucial for improving the coupled models of the Antarctic ice sheet towards accurately predict its contribution to future global sea-level ***,in Antarctica,high-resolution and continuous ice velocity estimates remain elusive,which is key to unravel Antarctica’s present-day ice mass balance ***,we present a suite of newly estimated Antarctic-wide,annually-sampled ice velocity products at 105-m grid-spacing observed by Landsat 8 optical images *** first describe a procedure that can automatically calibrate and integrate ice displacement maps to generate Antarcticwide seamless ice velocity *** annual ice velocity mosaics are assembled using a total of 250,000 displacement maps inferred from more than 80,000 Landsat 8 images acquired between December 2013 and April *** new annual Antarctic ice velocity data product exhibits an improved quantification of near-decadal Antarctic-wide ice flow,and an opportunity to investigate ice dynamics at a higher spatial resolution and annual sampling,as compared to existing data *** studies confirmed improved accuracy and consistency of this new data product,when compared with independently estimated optical and radar ice velocity data products,as well as in situ data.

关键词： Antarctica ice velocity Landsat 8

Introduction and evaluation of a novel hybrid brattice for improved dust control in underground mining faces: A computational study

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International Journal of Mining Science and Technology 2015年第4期25卷 537-543页

作者： Kurnia Jundika c. Sasmito Agus P. Hassani Ferri P. Mujumdar Arun S. Mechanical Engineering Department Universiti Teknologi PETRONAS Department of Mining and Materials Engineering McGill University

A proper control and management of dust dispersion is essential to ensure safe and productive underground working environment. Brattice installation to direct the flow from main shaft to the mining face was found to be the most effective method to disperse dust particle away from the mining face. However,it limits the movement and disturbs the flexibility of the mining fleets and operators at the tunnel. This study proposes a hybrid brattice system- a combination of a physical brattice together with suitable and flexible directed and located air curtains- to mitigate dust dispersion from the mining face and reduce dust concentration to a safe level for the working operators. A validated three-dimensional computational fluid dynamic model utilizing Eulerian–Lagrangian approach is employed to track the dispersion of dust particle. Several possible hybrid brattice scenarios are evaluated with the objective to improve dust management in underground mine. The results suggest that implementation of hybrid brattice is beneficial for the mining operation: up to three times lower dust concentration is achieved as compared to that of the physical brattice without air curtain.

关键词： Dust dispersion Hybrid brattice Underground mine Ventilation

LASER cLADDED TicN cOATINGS ON THE SURFAcE OF TITANIUM

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Acta Metallurgica Sinica(English Letters) 2007年第3期20卷 210-216页

作者： Y.L. Yang D. Zhang H.S. Kou c. S. Liu college of Science Northeastern University Shenyang 110004 China college of Material and Metallurgy Northeastern University Shenyang 110004 China

Laser cladded coatings of TicN were produced on the surface of titanium. To obtain the optimal techniques, several conditions were tested by varying the laser scanning rate. The choice of shielding gas was also studied. The cladded coatings were then evaluated from the surface mechanics point of view based on their microhardness. The microstructure of some interesting samples was investigated by optical micrographs （OM）. The results showed that under the condition of fixed pulse frequency and pulse width, the laser scanning rate and the shielding gas are the main factors influencing the components of coatings. TicN coatings were decompounded and oxidized during the cladding process in the condition of no shielding gas of N2. X-ray diffraction results indicated that the composite coatings composed of TicN, Tic, Ti2N, and TiO2 were produced using appropriate techniques. The results indicated that the best condition in terms of the surface microhardness is obtained when the scanning rate is 1.5mm/s, the pulse frequency is 15Hz, the pulse width is 3.0ms, and N2 is chosen as the shielding gas. The microhardness of the composite coatings is about 1331kg · mm^-2, which is about 4 times that of the substrate. The optical micrographs indicated that the cladding zone is made up of TicN, TiO2 and some interdendritic Ti, but the diffusion zone mainly consists of the dendrites phase, and the cladded depth is about 80μm, which is more than 2 times that of the laser nitrided sample. There were no microcracks or air bubbles in the cladded sample, which was cladded using the above optimal techniques.

关键词： laser cladding TicN coating titanium

Structural study of the cdc25 domain from Ral-specific guanine-nucleotide exchange factor RalGPS1a

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Protein & cell 2011年第4期2卷 308-319页

作者： Wei Peng Jiwei Xu Xiaotao Guan Yao Sun Xuejun c.Zhang Xuemei Li Zihe Rao National Laboratory of Biomacromolecules Institute of BiophysicsChinese Academy of SciencesBeijing 100101China

The guanine-nucleotide exchange factor(GEF)RalGPS1a activates small GTPase Ral proteins such as RalA and RalB by stimulating the exchange of Ral bound GDP to GTP,thus regulating various downstream cellular ***1a is composed of an Nterminal cdc25-like catalytic domain,followed by a PXXP motif and a c-terminal pleckstrin homology(PH)*** cdc25 domain of RalGPS1a,which shares about 30%sequence identity with other cdc25-domain proteins,is thought to be directly engaged in binding and activating the substrate Ral *** we report the crystal structure of the cdc25 domain of *** bowl shaped structure is homologous to the cdc25 domains of SOS and *** most remarkable difference between these three cdc25 domains lies in their active sites,referred to as the helical hairpin *** with previous enzymological studies,the helical hairpin of RalGPS1a adopts a conformation favorable for substrate binding.A modeled RalGPS1a-RalA complex structure reveals an extensive binding surface similar to that of the SOS-Ras ***,analysis of the electrostatic surface potential suggests an interaction mode between the RalGPS1a active site helical hairpin and the switch 1 region of substrate RalA distinct from that of the SOS-Ras complex.

关键词： RalGPS1a RalA cdc25 domain crystal structure

Natural cerebrolysin induces neuronal differentiation in bone marrow mesenchymal stem cells

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Neural Regeneration Research 2009年第3期4卷 178-185页

作者： Zhengzhi Wu Yinghong Li Andrew c. J. Huang Ming Li Min Yang Manyin chen Shenzhen Hospital Southern Medical University Shenzhen 518035 Guangdong Province China Larry Hillblom Islet Research center David Geffen School of Medicine UCLA Los Angeles CA 90024 USA

BAcKGROUND： Bone marrow mesenchymal stem cells （MScs） have been shown to differentiate into neuronal-like cells through the use of several factors, such as 2-mercaptoethanol, dimethyl sulfoxide, or monothioglycero However, these factors are not suitable for human use due to toxicity. Theoretically speaking, traditional chinese medicine could be used as potential and safe factors. OBJEcTIVE： To investigate the effect of natural cerebrolysin on neuronal-like differentiation of MScs, based on protein and mRNA analyses. DESIGN, TIME AND SETTING： A parallel controlled, in vitro experiment was performed at the Institute of Integrated chinese and Western Medicine, Shenzhen Hospital, Southern Medical University, between June 2006 and April 2008. MATERIALS： Natural cerebrolysin was provided by Shenzhen Institute of Integrated chinese and Western Medicine, china. It primarily consisted of Renshen （Radix Ginseng）, Tianma （Rhizoma Gastrodiae）, and Yinxingye （Ginkgo Leaf） at a proportion of 1：2：2. Natural cerebrolysin extract （1：20） was prepared using conventional water extraction methodology. Each gram of extract equaled 20 grams of the crude drug. Twelve adult, male, New Zealand rabbits were included, six of which underwent intragastric administration of natural cerebrolysin extract （0.976 g/kg per day） for 1 month for natural cerebrolysin-containing serum. The remaining six rabbits received intragastric administration of equal volumes of physiological saline for normal blank serum. METHODS： Sprague Dawley male rats, 6-8 weeks old, were used to harvest tibial and femoral bone marrow. Isolation and purification of MScs were established from the whole bone marrow by removing the non-adherent cells in primary and passage cultures. For cellular identification, MScs from four to five passages were co-cultured with LG-DMEM media containing 10% natural cerebrolysin. Simultaneously, MScs cultured in/G-DMEM media containing 10% blank rabbit serum served as the control group. MAIN OUTcO

关键词： natural cerebrolysin bone marrow mesenchymal stem cells differentiation neuronal-like cells

Geomechanical characterization of volcanic rocks using empirical systems and data mining techniques

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Journal of Rock Mechanics and Geotechnical Engineering 2018年第1期10卷 138-150页

作者： T.Miranda L.R.Sousa A.T.Gomes J.Tinoco c.Ferreira University of Minho GuimarasPortugal State Key Laboratory of Geomechanics and Deep Underground Engineering China University of Mining and TechnologyBeijingChina University of Porto PortoPortugal

This paper tries to characterize volcanic rocks through the development and application of an empirical geomechanical system. Geotechnical information was collected from the samples from several Atlantic Ocean islands including Madeira, Azores and canarias archipelagos. An empirical rock classification system termed as the volcanic rock system(VRS) is developed and presented in detail. Results using the VRS are compared with those obtained using the traditional rock mass rating(RMR) system. Data mining(DM) techniques are applied to a database of volcanic rock geomechanical information from the *** algorithms were developed and consequently approaches were followed for predicting rock mass classes using the VRS and RMR classification systems. Finally, some conclusions are drawn with emphasis on the fact that a better performance was achieved using attributes from VRS.

关键词： Volcanic rocks Geomechanical characterization Volcanic rock system(VRS) Data mining(DM)

Multi-scale drivers of soil resistance predict vulnerability of seasonally wet meadows to trampling by pack stock animals in the Sierra Nevada,USA

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Ecological Processes 2020年第1期9卷 364-377页

作者： Joy S.Baccei Mitchel P.Mcclaran Tim J.Kuhn Stephen c.Hart Environmental Systems Graduate Group University of CaliforniaMercedCA 95343USA Uc Merced Vernal Pools and Grassland Reserve UC Merced Natural Reserve SystemMercedCA 95343USA School of Natural Resources and the Environment University of ArizonaTucsonAZ 85721USA Resources Management and Science Yosemite National ParkEl PortalCA 95318USA Department of Life&Environmental Sciences and Sierra Nevada Research Institute University of CaliforniaMercedCA 95343USA.

Background:Meadow ecosystems have important ecological functions and support socioeconomic services,yet are subject to multiple stressors that can lead to rapid *** the Sierra Nevada of the western USA,recreational pack stock(horses and mules)use in seasonally wet mountain meadows may lead to soil trampling and meadow degradation,especially when soil water content is high and vegetation is ***:In order to improve the ability to predict meadow vulnerability to soil disturbance from pack stock use,we measured soil resistance(SR),which is an index of vulnerability to trampling disturbance,at two spatial scales using a stratified-random sampling *** then compared SR to several soil and vegetation explanatory variables that were also measured at the two spatial scales:plant community type(local scale)and topographic gradient class(meadow scale).Results:We found that local-scale differences in drivers of SR were contingent on the meadow scale,which is important because multiple spatial scale evaluation of ecological metrics provides a broader understanding of the potential controls on ecological processes than assessments conducted at a single spatial *** also found two contrasting explanatory models for drivers of SR at the local scale:(1)soil gravimetric water content effects on soil disaggregation and(2)soil bulk density and root mass influence on soil *** resistance was insufficient to sustain pack stock use without incurring soil deformation in wet plant communities,even when plant cover was maximal during a major ***:Our study provides new information on seasonally wet meadow vulnerability to trampling by pack stock animals using multi-scale drivers of SR,including the contrasting roles of soil disaggregation,friction,and *** work aims to inform meadow management efforts in the Sierra Nevada and herbaceous ecosystems in similar regions that are subject to seasonal soil saturation and livestock u

关键词： Hydrogeomorphic classification Hydrologic regime Pack stock Plant communities Soil properties Soil strength

Spread of common native and invasive grasses and ruderal trees following anthropogenic disturbances in a tropical dry forest

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Ecological Processes 2017年第1期6卷 394-407页

作者： Xavier A.Jaime Skip J.Van Bloem Frank H.Koch Stacy A.c.Nelson Department of Ecosystem Science and Management Texas A&M University2138 TAMUCollege StationTX 77843-2138USA Belle W.Baruch Institute of coastal Ecology and Forest Science Clemson UniversityPO Box 596GeorgetownSC 29442USA USDA Forest Service Southern Research Station3041 East Cornwallis RoadResearch Triangle ParkNC 27709USA center for Geospatial Analytics Department of Forestry and Environmental ResourcesNorth Carolina State UniversityRaleighNC 27695USA.

Introduction:A fundamental challenge to the integrity of tropical dry forest ecosystems is the invasion of nonnative grass *** grasses compete for resources and fuel anthropogenic *** 2012,a bulldozer from the Puerto Rico Electric Power Authority cleared a 570-m trail from a state road into a mature dry forest section of Guánica Forest to control a *** monitored colonization by a non-native invasive grass(Megathyrsus maximus),a highly invasive tree(Leucaena leucocephala),and a native grass(Uniola virgata),as well as natural regeneration,along the bulldozer *** determined whether bulldozing facilitated colonization by these species into the forest and the extent of ***:Distance from propagule source and temporal variations strongly influenced colonization by our three focal *** maximus invaded along the trail from source populations by the state *** establishment of new colonies of *** seedlings went as far as 570 m inside the forest(i.e.,at the end of the bulldozer trail),but we found most new colonies within 270 m of the *** leucocephala exhibited a similar spreading *** disturbance,Uniola virgata was distributed widely across the forest,but the highest densities were found in areas near the latter portion(>401 m)of the bulldozer ***,the species formed new clumps along more than half of the trail(250 to 570 m),apparently colonizing from undisturbed patches ***:Bulldozing facilitated the invasion of non-native *** projected community assemblage will be more fire-prone than before since *** carries fire across the landscape better than ***,emphasizing the capacity of invasive plant colonization to alter local ecological processes after only a single wildfire and bulldoze *** results provide a valuable baseline for short-term vegetation response to anthropogenic disturbances in tropical semi-deciduous dry forests.

关键词： Tropical dry forest Grass invasions Bulldozing Wildfire Leucaena leucocephala Megathyrsus(Panicum)maximus Uniola virgata

A statistical model to predict total column ozone in Peninsular Malaysia

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Frontiers of Earth Science 2016年第1期10卷 63-73页

作者： K. c. TAN H. S. LIM M. Z. MAT JAFRI School of Physics Universiti Sains Malaysia Penang 11800 Malaysia

This study aims to predict monthly columnar ozone in Peninsular Malaysia based on concentrations of several atmospheric gases. Data pertaining to five atmo- spheric gases （cO2, 03, cH4, NO2, and H2O vapor） were retrieved by satellite scanning imaging absorption spectro- metry for atmospheric chartography from 2003 to 2008 and used to develop a model to predict columnar ozone in Peninsular Malaysia. Analyses of the northeast monsoon （NEM） and the southwest monsoon （SWM） seasons were conducted separately. Based on the Pearson correlation matrices, columnar ozone was negatively correlated with HzO vapor but positively correlated with cOz and NO2 during both the NEM and SWM seasons from 2003 to 2008. This result was expected because NO/is a precursor of ozone. Therefore, an increase in columnar ozone concentration is associated with an increase in NO2 but a decrease in H/O vapor. In the NEM season, columnar ozone was negatively correlated with H20 （-0.847）, NO2 （0.754）, and cO2 （0.477）; columnar ozone was also negatively but weakly correlated with cH4 （-0.035）. In the SWM season, columnar ozone was highly positively correlated with NO2 （0.855）, cO2 （0.572）, and cH4（0.321） and also highly negatively correlated with H2O（-0.832）. Both multiple regression and principal component analyses were used to predict the columnar ozone value in Peninsular Malaysia. We obtained the best-fitting regression equations for the columnar ozone data using four independent variables. Our results show approxi- mately the same R value （≈0.83） for both the NEM and SWM seasons.

关键词： ozone ScIAMAcHY principal componentanalysis Peninsular Malaysia