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Analysis of the damage mechanism of strainbursts by a global-local modeling approach

Journal of Rock Mechanics and Geotechnical Engineering 2022年第6期14卷 1671-1696页

作者： Jun Wang derek B.Apel Artur Dyczko Andrzej Walentek Stanislaw Prusek Huawei Xu Chong Wei School of Mining and Petroleum Engineering University of AlbertaEdmontonAlbertaT6G 2R3Canada Jastrze˛bska Spółka We˛glowa S.A.Group Aleja Jana Pawła II 4Jastrze˛bie-Zdrój44-330Poland Central Mining Institute Plac GwarkówKatowice140-166Poland

Strainburst is the most common type of *** research of strainburst damage mechanisms is helpful to improve and optimize the rock support design in the burst-prone *** this study,an improved global-local modeling approach was first adopted to study strainburst damage *** extracted stresses induced by multiple excavations from a three-dimensional(3D)global model established by fast Lagrangian analysis of continua in 3 dimensions(FLAC3D)are used as boundary conditions for a two-dimensional(2D)local model of a deep roadway built by universal distinct element code(UDEC)to simulate realistic stress loading paths and conduct a detailed analysis of rockburst damage from both micro and macro *** results suggest that the deformation and damage level of the roadway gradually increase with the growth of surrounding rock stress caused by the superposition of mining-or excavation-induced stresses of the panel and nearby *** significant increase of surrounding rock stresses will result in more accumulated strain energy in two sidewalls,providing a necessary condition for the strainburst occurrence in the dynamic *** strainburst damage mechanism for the study site combines three types of damage:rock ejection,rock bulking,and *** the strainburst,initiation,propagation,and development of tensile cracks play a crucial role in controlling macroscopic failure of surrounding rock masses,although the shear crack always accounts for the main proportion of damage *** deformation and damage level of the roadway during a strainburst positively correlate with the increasing peak particle velocities(PPVs).The yielding steel arch might not dissipate kinetic energy and mitigate strainburst damage effectively due to the limited energy absorption *** principles to control and mitigate strainburst damage are proposed in this *** study presents a systematic framework to investigate strainburst damage mechanisms

关键词： Strainburst Numerical modeling Damage mechanism Finite difference method(FDM) Discrete element method(DEM) Underground mining

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Sexual signal conspicuity is correlated with tail autotomy in an anoline lizard

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Current Zoology 2022年第1期68卷 129-132页

作者： Kelly LinWUTHRICH derek STOCK Janelle B.TALAVERA Breanna J.PUTMAN Lindsey SWIERK Department of Biological Sciences Binghamton UniversityState University of New YorkBinghamtonNY 13902USA Department of Biology California State UniversityNorthridgeCA 91330-8303USA Department of Biology California State UniversitySan BernardinoCA 92407USA Department of Ecology and Evolutionary Biology University of California621 Young Drive SouthLos AngelesCA 90095-1606USA Department of Herpetology and Urban Nature Research Center Natural History Museum of Los Angeles CountyLos AngelesCA 90007USA School of Forestry and Environmental Studies Yale UniversityNew HavenCT 06511USA Amazon Conservatory for Tropical Studies IquitosLoreto 16001Peru The Morpho Institute Kansas CityMO 64113USA

Sexual selection favors conspicuous signals that animals can use to communicate with conspecifics and/or to attract ***,natural and sexual selection are often in opposition,as conspicuous sexual signals can also be detected by eavesdropping predators,forcing these signals to also evolve in light of natural selection(Andersson 1994).

关键词： signal evolve selection

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Revaluating coal permeability-gas pressure relation under various gas pressure differential conditions

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International Journal of Coal Science & Technology 2023年第4期10卷 203-216页

作者： Chunguang Wang Hongxu Wang derek Elsworth Guanglei Cui Bingqian Li Meng Zhou Wenxin Li Jiyuan Zhang College of Energy and Mining Engineering Shandong University of Science and TechnologyQingdao 266590China Energy and Mineral Engineering GeosciencesG3 Centerand EMS Energy InstitutePennsylvania State UniversityUniversity ParkPAUSA Key Laboratory of Ministry of Education On Safe Mining of Deep Metal Mines Northeastern UniversityShenyang 110004China Pingdingshan Tianan Coal Mining Co. LTDPingdingshanHenan 467003China School of Petroleum Engineering China University of Petroleum(East China)Qingdao 266580China

Identifying changes in coal permeability with gas pressure and accurately codifying mean efective stresses in laboratory samples are crucial in predicting gas-fow behavior in coal reservoirs. Traditionally, coal permeability to gas is assessed using the steady-state method, where the equivalent gas pressure in the coal is indexed to the average of upstream and downstream pressures of the coal, while ignoring the nonlinear gas pressure gradient along the gas fow path. For the fow of a compressible gas, the traditional method consistently underestimates the length/volume-averaged pressure and overestimates mean efective stress. The higher the pressure diferential within the sample, the greater the error between the true mean pressure for a compressible fuid and that assumed as the average between upstream and downstream pressures under typical reservoir conditions. A correction coefcient for the compressible fuid pressure asymptotes to approximately 1.3%, representing that the error in mean pressure and efective stress can be on the order of approximately 30%, particularly for highly pressure-sensitive permeabilities and compressibilities, further amplifying errors in evaluated reservoir properties. We utilized this volume-averaged pressure and efective stress to correct permeability and compressibility data reported in the literature. Both the corrected initial permeability and the corrected pore compressibility were found to be smaller than the uncorrected values, due to the underestimation of the true mean fuid pressure, resulting in an overestimation of reservoir permeability if not corrected. The correction coefcient for the initial permeability ranges from 0.6 to 0.1 (reservoir values are only approximately 40% to 90% of laboratory values), while the correction coefcient for pore compressibility remains at approximately 0.75 (reservoir values are only approximately 25% of laboratory value). Errors between the uncorrected and corrected parameters are quantifed un

关键词： Gas compressibility Coal permeability Pressure diferential Mean gas pressure

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Management of Peak Loads in an Emerging Electricity Market

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Energy Engineering 2022年第6期119卷 2637-2654页

作者： Edwin N.Mbinkar derek Ajesam Asoh Jerome Ndam Mungwe Livinus Songyuh Emmanuel Lamfu Laboratoire de Génie Electrique Mécatronique et Traitement du SignalENSPYUniversitéde YaoundéIYaoundeCameroun Department of Electrical and Electronic Engineering National Higher Polytechnic Institute(NAHPI)University of BamendaBamendaCameroon Department of Electrical and Power Engineering Higher Technical Teacher Training College(HTTTC)University of BamendaBamendaCameroon Mekin Hydroelectric Development Corporation MeyomessalaCameroon ENEO Cameroun S.A. DoualaCameroon

An electricity market is a trading platform provided by the actors in the electricity sector to sell and buy electricity while maintaining the stability of the transmission network and minimizing energy *** management of electrical energy for rational use consists of all the operations that the consumers can carry out in order to minimize their electricity bill,while the producers optimize their benefits and the transmission *** reduction of active and reactive power consumption and the smoothing of daily and yearly load profiles are the main objectives in this *** developed countries already have properly functioning electricity markets,but developing countries are still in their infancy of deregulated electricity *** major tools used in smoothing the load profiles include decentralized generation,energy storage and demand response.A load power smoothing control strategy is proposed to smooth the load power fluctuations of the distribution *** required power change is determined by evaluating the power fluctuation rate of the load,and then the required power change is allocated to some generators or to some stored ***,the consumers are made to curtail their power *** ideas proposed in this work provide important opportunities for energy policy makers and *** ideas would only be feasible if there exists real-time communication among the actors in the electricity *** results indicate that as much as 1100 Megawatt-hours of energy can be stored for smoothing the load profile,when applied to the Southern Interconnected Grid of the Cameroon power system;and that Time of Use(TOU)pricing could be used instead of rotating blackouts in case of energy shortage.

关键词： Peak load electricity markets decentralized generation energy storage demand response

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Performance of the Enhanced Liver Fibrosis Score,Comparison with Vibration-controlled Transient Elastography Data,and Development of a Simple Algorithm to Predict Significant Liver Fibrosis in a Community-based Liver Service:A Retrospective Evaluation

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Journal of Clinical and Translational Hepatology 2023年第4期11卷 800-808页

作者： Tina Reinson Janisha Patel Mead Mathews derek Fountain Ryan M.Buchanan Christopher DByrne Nutrition and Metabolism Faculty of MedicineUniversity of SouthamptonSouthamptonUK National Institute for Health and Care Research Southampton Biomedical Research CenterUniversity Hospital SouthamptonSouthamptonUK Hepatology Department University Hospital SouthamptonSouthamptonUK St Mary’s Surgery SouthamptonUK Core Minutes Ltd RingwoodUK Clinical and Experimental Sciences Faculty of MedicineUniversity of SouthamptonSouthamptonUK

Background and Aims:Liver fibrosis is a key risk factor for cirrhosis,hepatocellular carcinoma and end stage liver *** National Institute for Health and Care Excellence guidelines for assessment for advanced(≥F3)liver fibrosis in people with nonalcoholic fatty liver disease recommend the use of enhanced liver fibrosis(ELF)test,followed by vibration-controlled transient elastography(VCTE).Performance of ELF at predicting significant(≥F2)fibrosis in real-world practice is *** assess the accuracy of ELF using VCTE;investigate the optimum ELF cutoff value to identify≥F2and≥F3;and develop a simple algorithm,with and without ELF score,for detecting≥***:Retrospective evaluation of patients referred to a Community Liver Service for VCTE,Jan-Dec *** included:body mass index(BMI),diabetes status,alanine aminotransferase(ALT)levels,ELF score and biopsy-validated fibrosis stages according to ***:Data from 273 patients were available.n=110 patients had *** showed fair performance for≥F2 and≥F3,area under the curve(AUC)=0.70,95%confidence interval(CI)0.64-0.76 and AUC=0.72,95%CI:0.65-0.79 ***≥F2 Youden's index for ELF=9.85 and for≥F3,ELF=*** ALT,BMI,and HbA1c(ALBA algorithm)to predict≥F2 showed good performance(AUC=0.80,95%CI:0.69-0.92),adding ALBA to ELF improved performance(AUC=0.82,95%CI:0.77-0.88).Results were independently ***:Optimal ELF cutoff for≥F2 is 9.85 and 9.95 for≥***,BMI,and HbA1c(ALBA algorithm)can stratify patients at risk of≥*** is improved by adding ALBA.

关键词： Primary health care Retrospective evaluation Liver disease Diabetes Nonalcoholic fatty liver disease

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Improving modeling of low-altitude particulate matter emission and dispersion:A cotton gin case study

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Journal of Environmental Sciences 2023年第11期133卷 8-22页

作者： Zijiang Yang Michael N.Evans Michael D.Buser Cathleen J.Hapeman Alba Torrents derek P.Whitelock Department of Civil and Environmental Engineering University of Maryland College Park1173 Glenn L.Martin HallCollege ParkMaryland 20742United States Department of Geology University of Maryland College Park1212B Chemistry BuildingCollege ParkMaryland 20742United States Earth System Science Interdisciplinary Center 1120 Geology BuildingUniversity of MarylandCollege ParkMaryland 20742United States United States Department of Agriculture Agricultural Research ServiceOffice of National Programs5601 Sunnyside Ave(GWCC 4–2282)BeltsvilleMaryland 20705United States United States Department of Agriculture Agricultural Research ServiceHenry A.Wallace Beltsville Agricultural Research Center10300 Baltimore AvenueBeltsvilleMaryland 20705United States United States Department of Agriculture Agricultural Research ServiceSouthwestern Cotton Ginning Research LaboratoryPO Box 578Mesilla ParkNew Mexico 88047United States

Monitoring and modeling of airborne particulate matter(PM)from low-altitude sources is becoming an important regulatory target as the adverse health consequences of PM become better ***,application of models not specifically designed for simulation of PM from low-altitude emissions may bias *** address this problem,we describe the modification and validation of an air dispersion model for the simulation of lowaltitude PM dispersion from a typical cotton ginning *** found that the regulatory recommended model(AERMOD)overestimated pollutant concentrations by factors of 64.7,6.97 and 7.44 on average for PM 2.5,PM 10,and TSP,*** concentrations were negatively correlated with height(p<0.05),distance from source(p<0.05)and standard deviation of wind direction(p<0.001),and positively correlated with average wind speed(p<0.001).Based on these results,we developed dispersion correction factors for AERMOD and cross-validated the revised model against independent observations,reducing overestimation factors to 3.75,1.52 and 1.44 for PM 2.5,PM 10 and TSP,*** reductions in model error may be obtained from use of additional observations and refinement of dispersive correction *** generally,the correction permits the validated adjustment and application of pre-existing models for risk assessment and development of remediation *** same approach may also be applied to improve simulations of other air pollutants and environmental conditions of concern.

关键词： Air quality Particulate matter Air dispersion modelling Cotton gin

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Effect of obesity on post-operative outcomes following colorectal cancer surgery

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World Journal of Gastrointestinal Oncology 2022年第7期14卷 1324-1336页

作者： derek Mao David E Flynn Stephanie Yerkovich Kayla Tran Usha Gurunathan Manju D Chandrasegaram Faculty of Medicine and Health The University of SydneySydney 2050New South WalesAustralia Department of General Surgery The Prince Charles HospitalBrisbane 4032QueenslandAustralia of Medicine The University of QueenslandBrisbane 4006QueenslandAustralia Department of Pathology The Prince Charles HospitalBrisbane 4032QueenslandAustralia Department of Anaesthesia The Prince Charles HospitalBrisbane 4032QueenslandAustralia

BACKGROUND Colorectal cancer(CRC)resection is currently being undertaken in an increasing number of obese *** studies have yet to reach a consensus as to whether obesity affects post-operative outcomes following CRC *** To evaluate the post-operative outcomes of obese patients following CRC resection,as well as to determine the post-operative outcomes of obese patients in the subgroup undergoing laparoscopic *** Six-hundred and fifteen CRC patients who underwent surgery at the Prince Charles Hospital between January 2010 and December 2020 were categorized into two groups based on body mass index(BMI):Obese[BMI≥30,n=182(29.6%)]and non-obese[BMI<30,n=433(70.4%)].Demographics,comorbidities,surgical features,and post-operative outcomes were compared between both *** outcomes were also compared between both groups in the subgroup of patients undergoing laparoscopic surgery[n=472:BMI≥30,n=136(28.8%);BMI<30,n=336(71.2%)].RESULTS Obese patients had a higher burden of cardiac(73.1%vs 56.8%;P<0.001)and respiratory comorbidities(37.4%vs 26.8%;P=0.01).Obese patients were also more likely to undergo conversion to an open procedure(12.8%vs 5.1%;P=0.002),but did not experience more postoperative complications(51.6%vs 44.1%;P=0.06)or high-grade complications(19.2%vs 14.1%;P=0.11).In the laparoscopic subgroup,however,obesity was associated with a higher prevalence of post-operative complications(47.8%vs 39.3%;P=0.05)but not high-grade complications(17.6%vs 11.0%;P=0.07).CONCLUSION Surgical resection of CRC in obese individuals is safe.A higher prevalence of post-operative complications in obese patients appears to only be in the context of laparoscopic surgery.

关键词： Colorectal cancer Obesity Body mass index Post-operative outcomes Clavien-Dindo

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Digital Servo Control of a Robotic Excavator

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Chinese Journal of Mechanical Engineering 2009年第2期22卷 190-197页

作者： GU Jun SEWARD derek School of Mechanical ＆ Electronic Engineering Soochow University Suzhou 215021 China Engineering Department Lancaster University Lancaster LA1 4YR UK

An electro-hydraulic control system is designed and implemented for a robotic excavator known as the Lancaster University Computerised and Intelligent Excavator （LUCIE）. The excavator is being developed to autonomously dig trenches without human intervention. Since the behavior of the excavator arm is dominated by the nonlinear dynamics of the hydraulic actuators and by the large and unpredictable external disturbances when digging, it is difficult to provide adequate accurate, quick and smooth movement under traditional control methodology, e.g., PI/PID, which is comparable with that of an average human operator. The data-based dynamic models are developed utilizing the simplified refined instrumental variable （SRIV） identification algorithm to precisely describe the nonlinear dynamical behaviour of the electro-hydraulic actuation system. Based on data-based model and proportional-integral-plus （PIP） methodology, which is a non-minimal state space method of control system design based on the true digital control （TDC） system design philosophy, a novel control system is introduced to drive the excavator arm accurately, quickly and smoothly along the desired path. The performance of simulation and field tests which drive the bucket along straight lines both demonstrate the feasibility and validity of the proposed control scheme.

关键词： robotic excavator nonlinear dynamics data-based model true digital control (TDC) proportional-integral-plus (PIP)

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Dynamic analysis of heat extraction rate by supercritical carbon dioxide in fractured rock mass based on a thermal-hydraulic-mechanics coupled model

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International Journal of Mining Science and Technology 2022年第2期32卷 225-236页

作者： Chunguang Wang Xingkai Shi Wei Zhang derek Elsworth Guanglei Cui Shuqing Liu Hongxu Wang Weiqiang Song Songtao Hu Peng Zheng College of Energy and Mining Engineering Shandong University of Science and TechnologyQingdao 266590China New-energy Development Center of Sinopec Shengli Oilfield Dongying 257001China Energy and Mineral Engineering and G3 Center Penn State UniversityUniversity ParkPA 16802USA Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines Northeastern UniversityShenyang 110004China Shandong Provincial Geo-Mineral Engineering Co. LtdJinan 250013China Qingdao Wofu New Energy Science and Technology Co. LtdQingdao 266010China

Heat production from geothermal reservoirs is a typical heat transfer process involving a cold working fluid contacting a hot rock *** to the thermal-physical characteristics of water,supercritical CO_(2)(scCO_(2))has a higher heat storage capacity over a wide temperature-pressure range and may be favored as a heat transfer *** characteristic of scCO_(2)-based heat extraction is that the hydraulic-thermal properties of the scCO_(2) vary dramatically and dynamically with the spatial pressure gradient during unsteady-state flow along *** highly nonlinear behavior presents a challenge in the accurate estimation of heat extraction efficiency in scCO_(2)-based *** this paper,a thermal-h ydraulic-mechanical(THM)coupled model is developed by considering deformation of the fractured reservoir,non-Darcy flow and the varying thermal-physical properties of scCO_(2).The proposed model is validated by matching the modeling temperature distribution with published *** results show that during continuous injection of scCO_(2),the fracture first widens and then narrows,ultimately reopening over the long *** sequential fracture deformation behaviors are in response to the combined impacts of mechanical compression and thermally-induced *** controlling the injection parameters of the scCO_(2),it is found that the heat extraction rate is positively correlated to its pore pressure or mass flow *** heat extraction rate can be significantly enhanced,when the inlet temperature of scCO_(2) is below its critical *** a result,the heat increment recovered per unit mass of scCO_(2) decreases as the hot rock is gradually ***,the heat increment recovered per unit mass of scCO_(2) decreases by increasing the inlet temperature of scCO_(2) or its mass flow rate,but increases as the outlet pressure ***,multi-linear regression indicates that controlling the inlet temperature of the scCO_(2) can sig

关键词： Supercritical CO_(2) Heat extraction Hot rock Geothermal energy Fracture-matrix interaction

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Do cratons preserve evidence of stagnant lid tectonics?

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Geoscience Frontiers 2018年第1期9卷 3-17页

作者： derek Wyman School of Geosciences The University of Sydney

Evidence for episodic crustal growth extending back to the Hadean has recently prompted a number of numerically based geodynamic models that incorporate cyclic changes from stagnant lid to mobile lid tectonics. A large part of the geologic record is missing for the times at which several of these cycles are inferred to have taken place. The cratons, however, are likely to retain important clues relating to similar cycles developed in the Mesoarchean and Neoarchean. Widespread acceptance of a form of plate tectonics by ～3.2 Ga is not at odds with the sporadic occurrence of stagnant lid tectonics after this time. The concept of scale as applied to cratons, mantle plumes and Neoarchean volcanic arcs are likely to provide important constraints on future models of Earth's geodynamic evolution. The Superior Province will provide some of the most concrete evidence in this regard given that its constituent blocks may have been locked into a stagnant lid relatively soon after their formation and then assembled in the next global plate tectonic interval. Perceived complexities associated with inferred mantle plume — volcanic arc associations in the Superior Province and other cratons may be related to an over estimation of plume size. A possible stagnant lid episode between ～2.9 Ga and ～2.8 Ga is identified by previously unexplained lapses in volcanism on cratons, including the Kaapvaal, Yilgarn and Superior Province cratons. If real, then mantle dynamics associated with this episode likely eliminated any contemporaneous mantle plume incubation sites, which has important implications for widespread plumes developed at ～2.7 Ga and favours a shallow mantle source in the transition zone. The Superior Province provides a uniquely preserved local proxy for this global event and could serve as the basis for detailed numerical models in the future.

关键词： Archean Mantle overturn Superior Province Mantle plumes Stagnant lid tectonics

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