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Effects of overburden characteristics on dynamic failure in underground coal mining

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International Journal of Mining Science and Technology 2017年第1期27卷 121-129页

作者： Lawson Heather E. Tesarik douglas Larson Mark K Abraham Habte NIOSH Office of Mine Safety and Health ResearchGround Control BranchSpokane WA 99207USA

Dynamic failures, or ‘‘bumps", remain an imperative safety concern in underground coal mining, despite significant advancements in engineering controls. The presence of spatially discrete, stiff roof units are one feature that has been linked to these events. However, an empirical stratigraphic review indicates that no significant difference exists in the relative commonality of discrete units between bumping and non-bumping deposits. Instead an apparent relationship exists between reportable bumping and the overall stiffness of the host rock. However, this initial study is too simplistic to be conclusive; to weight the relative impact of changes in a single variable, such as the thickness or location of sandstone members, it must be examined in isolation—i.e., in a setting where all other variables are held *** modelling provides this setting, and the effects of variability in a stiff discrete member in a hypothetical longwall mining scenario are investigated within the context of three stratigraphic ‘‘types",Compliant, Intermediate and Stiff. A modelling experiment examines changes in rupture potential in stiff roof units for each stratigraphic type as discrete unit thickness and location are manipulated through a range of values. Results suggest that the stiff-to-compliant ratio of the host rock has an impact on the relative stress-inducing effects of discrete stiff members. In other words, it is necessary to consider both the thickness and the distance to the seam, within the context of the host rock, to accurately anticipate areas of elevated rupture-induced hazard; acknowledging the presence of a discrete unit within the overburden in general terms is an insufficient indicator of risk. This finding helps to refine our understanding of the role of individual stiff, strong roof members in bumping phenomena, and suggests that a holistic view of overburden lithology and site-specific numerical modelling may be necessary to improve miner safety.

关键词： Dynamic failure Coal mining Bumps Bounces

Forest composition and red oak (Quercus sp.) response to elevation gradients across greentree reservoirs

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Forest Ecosystems 2023年第5期10卷 607-617页

作者： Cassandra Hug Pradip Saud Keith McKnight douglas C.Osborne College of Forestry Agriculturaland Natural ResourcesUniversity of Arkansas at MonticelloMonticelloAR71656USA USFWS/Lower Mississippi Valley Joint Venture TylerTX75707USA Five Oaks Ag Research and Education Center HumphreyAR72073USA

Elevation gradients within forested wetlands have long been recognized for their role in defining species composition through factors such as hydrology and soil *** reservoirs(GTRs)are leveeimpounded tracts of bottomland hardwood forest flooded throughout the winter months to provide habitat for overwintering *** flooding of GTRs alters the forest composition due to flood frequency,depth,and duration in combination with slight changes in *** evaluate the effect of elevation gradients,soil properties,and management techniques in the overstory species composition and red oak(Quercus spp.)species abundance,we inventoried 662 plots across 12 independent GTRs in eastern *** the lower elevations ranging from 50.98 to 54.99 m above sea level,the importance value index(IVI)was highest for nuttall oak(Quercus texana)and overcup oak(Quercus lyrata),whereas IVI shifted to cherrybark oak(Quercus pagoda)in the higher elevations ranging from 54.99 to 58.00 *** diversity did not differ by elevation gradient,soil property,or management technique within *** diversity,using non-metric multi-dimensional scaling(NMDS)analysis,indicated site-specific variability significantly correlated with the environmental predictors,including elevation(R^(2)=0.57),easting(R^(2)=0.47),soil texture(R^(2)=0.21),and pH(R^(2)=0.12).Red oak species-specific mixed-effects modeling of abundance response using Poisson distribution suggested an inverse correlation of nuttall oak and a direct correlation of cherrybark oak abundance with ***,willow oak(Quercus phellos)abundance was not significantly affected by elevation but was by silt loam soil texture and restoration management *** findings will aid management efforts to reduce the dominance of less desirable species that are prominent under specific environmental conditions and promote the dominance of more desirable *** GTR sustainability is increas

关键词： Bottomland hardwoods Diversity Forested wetland Overstory Red oak Soil Thinning and management

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奇异金属用“汤”导电?

环球科学 2024年第9期 50-55页

作者：道格拉斯·纳特尔森林清(译) 美国莱斯大学不详

奇异金属违反了传统的电学规则。科学家一直在尝试寻找新模型,以解释这类特殊材料的特性。铜、铂、铝和金等金属在人类历史上发挥了非常重要的作用,而使对应的历史时代以它们的名字命名,如青铜时代和铁器时代。这些材料具有导电特性,在... 详细信息

奇异金属违反了传统的电学规则。科学家一直在尝试寻找新模型,以解释这类特殊材料的特性。铜、铂、铝和金等金属在人类历史上发挥了非常重要的作用,而使对应的历史时代以它们的名字命名,如青铜时代和铁器时代。这些材料具有导电特性,在现代社会中扮演着同样重要的角色——现在基本上所有技术都离不开它们,而正是这些技术的出现,我们才进入了信息时代。

关键词：导电特性青铜时代铁器时代信息时代奇异材料的特性

Scalp reconstructive flaps

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Plastic and Aesthetic Research 2022年第1期9卷 420-433页

作者： Craig Cameron Brawley douglas Sidle Department of Otolaryngology-Head and Neck Surgery Northwestern University Feinberg School of MedicineChicagoIL 60611USA

Scalp reconstruction requires keen insight into underlying anatomy and surgical *** reconstructive surgeon must consider a plethora of complexities to devise a safe and cosmetically maximized *** purpose of this article is to review scalp reconstruction techniques and the current literature in the framework of the reconstructive ladder,with special emphasis on local flap consideration,design,and execution.

关键词： Scalp reconstruction scalp defects local flaps scalp flaps reconstructive ladder

Estimation of age in forensic anthropology:historical perspective and recent methodological advances

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Forensic Sciences Research 2019年第1期4卷 1-9页

作者： douglas H.Ubelaker Haley Khosrowshahi Department of Anthropology Smithsonian InstitutionWashingtonDCUSA

Estimation of age represents a central focus of forensic anthropological analysis of human skeletal remains and of the living. Advances registered in recent research include the topics of taphonomic impact, new anatomical areas of interest, histology, population variation, the dental pulp chamber, technology, mathematical approaches, biochemical analysis and techniques specifically targeting the living. This article reviews the historical development of age estimation methods and considers likely future directions.

关键词： Age estimation forensic sciences forensic anthropology history recent advances

Empirical rock physics relationships on carbonate dry-frame elastic properties

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Petroleum Science 2021年第3期18卷 783-806页

作者： Zi-Zhen Wang Gautier Njiekak douglas RSchmitt Rui-He Wang Key Laboratory of Unconventional Oil&Gas Development(China University of Petroleum(East China)) Ministry of EducationQingdao 266555China School of Petroleum Engineering China University of Petroleum(East China)Qingdao 266555China Department of Physics University of AlbertaEdmontonCanada Department of Earth Atmosphericand Planetary SciencePurdue UniversityWest LafayetteUSA

Laboratory tests were conducted to analyze the ultrasonic velocity response to the pressure change in dry carbonate rocks from the Weyburn oilfield,***-four samples are from seven wells with helium porosities ranging from 1%to 29%.Thin-section images,SEM and mercury intrusion porosimetry were performed to show their inner structures and pore throat size distributions.P-and S-wave velocities(V_(p) and V_(s))measurements were first done under hydrostatic loading and then while unloading,with confining pressures varying between 3 and 35 *** results indicate that V_(p) and V_(s) in these samples follow a linear relation independent of the pressure *** ratio V_(p)/V_(s) is more responsive to pressure change irrespective of the pore ***-third of the carbonate samples show abnormal V_(p)/V_(s) reduction with the increase in the effective *** pressure dependence of velocities(PDV)of Weyburn carbonate rocks varies widely even for samples from the same formation with similar sedimentary *** with loosely packed crystals and/or relatively large dominant pore diameter have higher *** exponential empirical model V=A−Ce^(DPe) was tested;therein,V is the elastic wave velocity,Pe is the effective confining pressure,and A,C and D are the best fitting coefficients determined by curve *** model gives good fits for most of the Weyburn carbonate *** a statistical point of view,there is no difference between the V_(p)-and V_(s)-derived exponential coefficient D.

关键词： Velocity Carbonate rocks Pressure dependence Pore structure

The Role of International Community in Resolving Criss in Africa: Case of Rwandan Genocide1994

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The Role of International Community in Resolving Criss in Af...

作者： douglas GAKUMBA 外交学院

学位级别：硕士

Rwanda is a small land locked country in Eastern Africa bordered by neighbors of ***, Uganda, Burundi and Tanzania. It was relatively unknown before deadly violencebreak out in1994. It came into the international attention when over one million Tutsis andpolitically moderate Hutus were butchered in just one hundred days, making the Rwandangenocide the fastest, most well-organized killing spree of the twentieth century. In1994on April6th, a Hutu President Juvenal Habyarimana, and all others on board werekilled when the airplane he was travelling with was shot down by a ground missile whilelanding at Kigali airport. He was from the meeting in Arusha, Tanzania. The massacre ofRwanda’s minority Tutsi which was prepared well in advance by Hutu extremist began hoursafter the president’s deaths. On7April ten Belgian UN peacekeepers were killed. By doingthis the extremist who seemed to have done their assignment well, knew the UN would giveup the peacekeeping mission and pull out from Rwanda, and they were right. Within the following three months by using local garden equipment like machetes, hoes,pangs and other low-tech arms, the Hutus slaughtered over one million Tutsis in an attempt tofinish them all. The well prepared and coordinated government attempt to cruelly finish theTutsi population obviously meets the definition of genocide adopted by the UN GeneralAssembly in1948. By signing the convention, members of the UN have committedthemselves to prevent and punish the crime of genocide. If parties who have signed theGenocide Convention have committed to prevent and punish the crime of genocide, why didthe international community just watched when the Rwandan genocide was happening? This thesis will analyze the response of the international community with more attention tothe United Nations and the United States, to the Rwandan genocide. Why the UNpeacekeepers already in Rwanda did give up? Why did the US, the world’s most powerfulcountry in the world refus

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Mobilizing and integrating big data in studies of spatial and phylogenetic patterns of biodiversity

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Plant Diversity 2016年第6期38卷 264-270页

作者： douglas E.Soltis Pamela S.Soltis Florida Museum of Natural History University of Florida Genetics Institute University of Florida Department of Biology University of Florida

The current global challenges that threaten biodiversity are immense and rapidly *** biodiversity challenges demand approaches that meld bioinformatics,large-scale phylogeny reconstruction,use of digitized specimen data,and complex post-tree analyses(*** modeling,niche diversification,and other ecological analyses).Recent developments in phylogenetics coupled with emerging cyberinfrastructure and new data sources provide unparalleled opportunities for mobilizing and integrating massive amounts of biological data,driving the discovery of complex patterns and new hypotheses for further *** developments are not trivial in that biodiversity data on the global scale now being collected and analyzed are inherently *** ongoing integration and maturation of biodiversity tools discussed here is transforming biodiversity science,enabling what we broadly term"next-generation"investigations in systematics,ecology,and evolution(i.e.,"biodiversity science").New training that integrates domain knowledge in biodiversity and data science skills is also needed to accelerate research in these *** biodiversity science is crucial to the future of global *** cannot simply react to continued threats to biodiversity,but via the use of an integrative,multifaceted,big data approach,researchers can now make biodiversity projections to provide crucial data not only for scientists,but also for the public,land managers,policy makers,urban planners,and agriculture.

关键词： Biodiversity Big data Niche modeling Bioinformatics Phylogeny

Mitigating osteonecrosis of the jaw(ONJ) through preventive dental care and understanding of risk factors

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Bone Research 2020年第1期8卷 14-25页

作者： Jason TWan douglas MSheeley Martha JSomerman Janice SLee National Institute of Dental and Craniofacial Research National Institutes of HealthBethesdaMDUSA Laboratory for Oral Connective Tissue Biology National Institute of Arthritis and Musculoskeletal and Skin DiseasesNational Institutes of HealthBethesdaMDUSA

It is well established that alterations in phosphate metabolism have a profound effect on hard and soft tissues of the oral cavity. The present-day clinical form of osteonecrosis of the jaw(ONJ) was preceded by phosphorus necrosis of the jaw, ca. 1860. The subsequent removal of yellow phosphorus from matches in the early 20 th century saw a parallel decline in "phossy jaw" until the early 2000 s, when similar reports of unusual jaw bone necrosis began to appear in the literature describing jaw necrosis in patients undergoing chemotherapy and concomitant steroid and bisphosphonate treatment. Today, the potential side effect of ONJ associated with medications that block osteoclast activity(antiresorptive) is well known, though the mechanism remains unclear and the management and outcomes are often unsatisfactory. Much of the existing literature has focused on the continuing concerns of appropriate use of bisphosphonates and other antiresorptive medications, the incomplete or underdeveloped research on ONJ, and the use of drugs with anabolic potential for treatment of osteoporosis. While recognizing that ONJ is a rare occurrence and ONJ-associated medications play an important role in fracture risk reduction in osteoporotic patients, evidence to date suggests that health care providers can lower the risk further by dental evaluations and care prior to initiating antiresorptive therapies and by monitoring dental health during and after treatment. This review describes the current clinical management guidelines for ONJ, the critical role of dental-medical management in mitigating risks, and the current understanding of the effects of predominantly osteoclast-modulating drugs on bone homeostasis.

关键词： drugs metabolism alterations