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LiDAR mapping of ground damage in a heading re-orientation case study

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International Journal of Mining Science and Technology 2021年第1期31卷 67-74页

作者： Nicole Evanek Brent Slaker Anthony Iannacchione tim Miller National Institute for Occupational Safety and Health Pittsburgh Mining Research DivisionPittsburghPA 15236USA University of Pittsburgh PittsburghPA 15260USA East Fairfield Coal Company North LimaOH 44452USA

The Subtropolis Mine is a room-and-pillar mine extracting the Vanport limestone near Petersburg,Ohio,*** February of 2018,mine management began implementing a heading re-orientation to better control the negative effects of excessive levels of horizontal *** conditions in the headings improved,but as expected,stress-related damage concentrated within *** mine operator has worked to lessen the impact of the instabilities in the outby crosscuts by implementing several engineering *** the implementation of each control,conditions were monitored and analyzed using observational and measurement techniques including 3D LiDAR *** the heading re-orientation,several 3D LiDAR surveys have been conducted and analyzed by researchers from the National Institute for Occupational Safety and Health(NIOSH).This study examines(1)the characteristics of each 3D LiDAR survey,(2)the change in the detailed strata conditions in response to stress concentrations,and(3)the change detection techniques between 3D LiDAR surveys to assess entry ***,the 3D LiDAR surveys proved to be a useful tool for characterizing ground instability and assessing the effectiveness of the engineering controls used in the heading re-orientation at the Subtropolis Mine.

关键词： Ground control Limestone Horizontal stress Stress control layout Crosscut Windows

Day length constrains the time budget of aphid predators

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Insect Science 2019年第1期26卷 164-170页

作者： Jens Joschinski tim Kiess Jochen Krauss Department of Animal Ecology and Tropical Biology BiocentreUniversity of WEirzburgWEtrzburgGermany

Phenology shifts and range expansions cause organisms to experience novel day length-temperature *** on the temporal niche,organisms may benefit or suffer from changes in day length,thus potentially affecting phenological adaptation. We assessed the impact of day length changes on larvae of Chrysoperla carnea (Stephens) and Episyrphus balteatus (De Geer),both of which prey on *** *** are night-active,whereas those of *** appear to be *** subjected both species in climate chambers to day lengths of 16 :8 L :D and,to circumvent diapause responses,20 :4 L :*** recorded development times and predation rates of both species. *** grew 13%faster in the 16 :8 L :D treatment and preyed on significantly more *** contrast,*** grew 13% faster in the 20 :4 L :D treatment and higher predation rates in 20 :4 L :D were marginally *** results show that day length affects development and predation,but that the direction depends on species. Such differences in the use of day length may alter the efficiency ofbiocontrol agents in a changing climate.

关键词： Chiysoperla carnea climate change Episyrphus balteatus insect timing phenology photoperiod

Three-type MJO Initiation processes over the Western Equatorial Indian Ocean

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Advances in Atmospheric Sciences 2015年第9期32卷 1208-1216页

作者： MEI Shuangli tim LI CHEN Wen Center for Monsoon System Research Institute of Atmospheric PhysicsChinese Academy of Sciences University of Chinese Academy of Sciences International Laboratory on Climate and Environment Change and Key Laboratory of Meteorological Disaster of Ministry of Education Nanjing University of Information Science and Technology International Pacific Research Center Department of MeteorologySchool of Ocean and Earth Science and TechnologyUniversity of Hawaii at Manoa

Thirty strong Madden–Julian Oscillation（MJO） events in boreal winter 1982–2001 are selected to investigate the triggering processes of MJO convection over the western equatorial Indian Ocean（IO）.These MJO events are classified into three types,according to their dynamic and thermodynamic precursor signals in *** Type I,a remarkable increase in low-level moisture occurs,on average,7 days prior to the convection *** low-level moistening is mainly due to the advection of the background mean moisture by easterly wind anomalies over the equatorial *** Type II,lower-tropospheric ascending motion anomalies develop,on average,4 days prior to the *** cause of this ascending motion anomaly is attributed to the anomalous warm advection,set up by a suppressed MJO phase in the equatorial *** Type III,there are no clear dynamic and thermodynamic precursor signals in *** convection might be triggered by energy accumulation in the upper layer associated with Rossby wave activity fluxes originated from the midlatitudes.

关键词： MJO Indian Ocean dynamic precursor signal thermodynamic precursor signal

Contrast of Evolution Characteristics of Boreal Summer and Winter Intraseasonal Oscillations over Tropical Indian Ocean

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Journal of Meteorological Research 2019年第4期33卷 678-694页

作者： Qingchi ZHANG tim LI Jia LIU Key Laboratory of Meteorological Disaster Ministry of Education(KLME)/Joint International Research Laboratory of Climate and Environmental Change(ILCEC)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD)Nanjing University of Information Science&TechnologyNanjing 210044China International Pacific Research Center and Department of Atmospheric Sciences University of Hawaii at ManoaHonoluluHawaii 96822USA

A most striking summer–winter difference of evolution of the intraseasonal oscillation(ISO)over the equatorial Indian Ocean is a quasi-stationary oscillation in boreal summer but eastward propagation in boreal *** feature is consistent with the observational fact that maximum ISO variance appears only in the eastern Indian Ocean in boreal summer while it appears across the entire basin in boreal *** cause of the distinctive propagation and initiation characteristics is investigated through the diagnosis of observational and reanalysis data for the period of 1982–*** is found that when the ISO convection appears over eastern Indian Ocean,a positive(negative)moisture tendency appears to the east of the convection in boreal winter(summer).It is the moisture tendency difference that is responsible for different propagation behavior in the summer and winter.A further diagnosis of the moisture budget indicates that the major difference lies in anomalous moisture advection by the mean *** addition,air–sea interaction also plays a *** boreal winter ISO starts over western Indian Ocean,boreal summer ISO is initiated over central–eastern equatorial Indian Ocean,due to boundary layer *** moisture increase is caused primarily by the horizontal advection of mean specific humidity by anomalous easterlies induced by preceding suppressed-phase ISO over eastern Indian ***,a delayed SST feedback also plays a *** overall difference of ISO evolution between the summer and winter is regulated by the seasonal mean state including the mean SST and water vapor content.

关键词： intraseasonal oscillation seasonality convection initiation and propagation planetary boundary layermoistening air-sea interaction

Strengthening of the Walker Circulation under Global Warming in an Aqua-Planet General Circulation Model Simulation

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Advances in Atmospheric Sciences 2015年第11期32卷 1473-1480页

作者： tim LI ZHANG Lei Hiroyuki MURAKAMI AORC/IPRC and Department of Atmospheric Sciences University of Hawaii International Laboratory on Climate and Environment Change and Key Laboratory of Meteorological Disaster Nanjing University of Information Science and Technology Climate Research Department Meteorological Research Institute

Most climate models project a weakening of the Walker circulation under global warming scenarios. It is argued, based on a global averaged moisture budget, that this weakening can be attributed to a slower rate of rainfall increase compared to that of moisture increase, which leads to a decrease in ascending motion. Through an idealized aqua-planet simulation in which a zonal wavenumber-1 SST distribution is prescribed along the equator, we find that the Walker circulation is strengthened under a uniform 2-K SST warming, even though the global mean rainfall-moisture relationship remains the same. Further diagnosis shows that the ascending branch of the Walker cell is enhanced in the upper troposphere but weakened in the lower troposphere. As a result, a ＂double-cell＂ circulation change pattern with a clockwise （anti-clockwise） circulation anomaly in the upper （lower） troposphere forms, and the upper tropospheric circulation change dominates. The mechanism for the formation of the ＂double cell＂ circulation pattern is attributed to a larger （smaller） rate of increase of diabatic heating than static stability in the upper （lower） troposphere. The result indicates that the future change of the Walker circulation cannot simply be interpreted based on a global mean moisture budget argument.

关键词： Walker circulation global warming aqua-planet simulation

Impact of 10-60-Day Low-Frequency Steering Flows on Straight Northward-Moving Typhoon Tracks over the Western North Pacific

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Journal of Meteorological Research 2018年第3期32卷 394-409页

作者： Qiao LIU tim LI Weican ZHOU Key Laboratory of Meteorological Disaster Ministry of Education/Joint International Research Laboratory of Climate and Environmental ChangeCollaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science & Technology International Pacific Research Center and Department of Atmospheric Sciences School of Ocean and Earth Science and Technology University of Hawaii

This study investigates the impact of low-frequency(intraseasonal and interannual) steering flows on straight northward-moving(defined as a meridional displacement two times greater than the zonal displacement) typhoons over the western North Pacific using observational data. The year-to-year change in the northward-moving tracks is affected by the interannual change in the location and intensity of the subtropical high. A strengthened northward steering flow east of 120°E and a weakened easterly steering flow south of the subtropical high favor more frequent straight northward tracks. Examining each of the individual northward-moving typhoons shows that they interact with three types of intraseasonal(10-60-day) background flows during their northward journey. The first type is the monsoon gyre pattern, in which the northward-moving typhoon is embedded in a closed cyclonic monsoon gyre circulation. The second type is the wave train pattern, where a cyclonic(anticyclonic) vorticity circulation is located to the west(east) of the northward-moving typhoon center. The third type is the mid-latitude trough pattern, in which the northward-moving typhoon center is located in the maximum vorticity region of the trough.

关键词： intraseasonal steering flow interannual steering flow straight northward-moving typhoon

Microscale study of frictional properties of graphene in ultra high vacuum

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Friction 2015年第2期3卷 161-169页

作者： Diego MARCHETTO tim FESER Martin DIENWIEBEL Fraunhofer-Institute for Mechanics of Materials Microtribology CenterμTCWöhlerstr.1179108 FreiburgGermany Karlsruhe Institute of Technology Institute for Applied Materials-Computational Materials Science IAM-CMSKaiserstr.1276131 KarlsruheGermany

We report on the frictional properties of epitaxial graphene on SiC in ultra high *** have been performed using a microtribometer in the load regime of 0.5 to 1 *** observed that a ruby sphere sliding against graphene results in very low friction coefficients ranging from 0.02 to *** friction and also the stability of the graphene layer is higher than that under similar conditions in ambient *** friction shows a load *** it was found that graphene masks the frictional anisotropy which was observed on the SiC surface.

关键词： graphene SiC friction vacuum microtribology anisotropy

Asymmetry of Atmospheric Responses to Two-Type El Nino and La Nina over Northwest Pacific

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Journal of Meteorological Research 2019年第5期33卷 826-836页

作者： Mingcheng CHEN tim LI Xiaohui WANG Key Laboratory of Meteorological Disaster Ministry of Education(KLME)/Joint International Research Laboratory of Climate and Environmental Change(ILCEC)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD)Nanjing University of Information Science&TechnologyNanjing 210044China International Pacific Research Center and Department of Atmospheric Sciences School of Ocean and Earth Science and TechnologyUniversity of Hawaii at ManoaHonoluluHI96822USA

The mechanism for asymmetric atmospheric responses to the central Pacific(CP) El Ni?o and La Ni?a over the western North Pacific(WNP) is studied in this paper. The negative anomalies of rainfall over the key region of WNP are explained by diagnosing the column-integrated equations of moisture and moist static energy(MSE). It is revealed that the nonlinear advection of moist enthalpy is critical to introduce negative rainfall anomalies over the region. The anomalous easterly(westerly) in La Ni?a(CP El Ni?o) causes negative advection of anomalous moist enthalpy, inducing negative heating anomaly and an anticyclone anomaly in the WNP, which weakens(strengthens) the cyclone(anticyclone) in La Ni?a(CP El Ni?o). The MSE budget analysis shows a larger nonlinear term in CP El Ni?o than in eastern Pacific(EP) El Ni?o, inconsistent with the amplitudes of sea surface temperature anomalies. The reason is that the nonlinear term transforms to positive above 700 h Pa in EP El Ni?o, offsetting the negative advection below 700 h Pa and thus making the nonlinear term smaller. The nonlinear term is negative at low levels in CP El Ni?o, resulting in a larger nonlinear term. The stronger precipitation anomalies in the WNP during EP El Ni?o can be attributed to the linear moist enthalpy advection. The mean easterly wind at mid levels causes a larger(smaller) positive moist enthalpy advection in CP(EP) El Ni?o, due to a larger(smaller) moist enthalpy gradient, resulting in a positive(negative) linear moist enthalpy advection, which weakens(strengthens) the negative precipitation anomalies in the key region.

关键词： asymmetry La Nina eastern Pacific(EP) El Nino central Pacific(CP) El Nino moist enthalpy

Dependence of Tropical Cyclone Intensification on the Latitude under Vertical Shear

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Journal of Meteorological Research 2018年第1期32卷 113-123页

作者： Mingyu BI Xuyang GE tim LI Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters/Key laboratory of Meteorological Disaster Nanjing University of Information Science &Technology International Pacific Research Center/Department of Atmospheric Sciences University of Hawaii at Manoa

The sensitivity of tropical cyclone（TC） intensification to the ambient rotation effect under vertical shear is investigated. The results show that the vortices develop more rapidly with intermediate planetary vorticity, which suggests an optimal latitude for the TC development in the presence of vertical shear. This is different from the previous studies in which no mean flow is considered. It is found that the ambient rotation has two main effects. On the one hand,the boundary layer imbalance is largely controlled by the Coriolis parameter. For TCs at lower latitudes, due to the weaker inertial instability, the boundary inflow is promptly established, which results in a stronger moisture convergence and thus greater diabatic heating in the inner core region. On the other hand, the Coriolis parameter modulates the vertical realignment of the vortex with a higher Coriolis parameter, favoring a quicker vertical realignment and thus a greater potential for TC development. The combination of these two effects results in an optimal latitude for TC intensification in the presence of a vertical shear investigated.

关键词： tropical cyclone intensification vertical shear Coriolis parameter