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The current perspective of the PA 1957 gas well pillar study and its implications for longwall gas well pillars

International Journal of Mining Science and Technology 2021年第1期31卷 117-126页

作者： Peter Zhang daniel Su Chris Mark CDC NIOSH Pittsburgh Mining Research DivisionPittsburghPA 15236USA Mine Safety and Health Administration PittsburghPA 15217USA

Many states rely upon the Pennsylvania 1957 Gas Well Pillar Study to evaluate the coal barrier surrounding gas *** study included 77 gas well failure cases that occurred in the Pittsburgh and Freeport coal seams over a 25-year *** the time,coal was mined using the room-and-pillar mining method with full or partial pillar recovery,and square or rectangle pillars surrounding the gas wells were left to protect the *** study provided guidelines for pillar sizes under different overburden depths up to 213 m(700 ft).The 1957 study has also been used to determine gas well pillar sizes in longwall mines since longwall mining began in the 1970 *** original study was developed for room-and-pillar mining and could be applied to gas wells in longwall chain pillars under shallow ***,under deep cover,severe deformations in gas wells have occurred in longwall chain ***,with a better understanding of coal pillar mechanics,new insight into subsidence movements induced by retreat mining,and advances in numerical modeling,it has become both critically important and feasible to evaluate the adequacy of the 1957 study for longwall gas well *** this paper,the data from the 1957 study is analyzed from a new perspective by considering various factors,including overburden depth,failure location,failure time,pillar safety factor(SF),and floor *** pillar SF and floor pressure are calculated by considering abutment pressure induced by full pillar recovery.A statistical analysis is performed to find correlations between various factors and helps identify the most significant factors for the stability of gas wells influenced by retreat *** analyzing the data from the 1957 study,the guidelines for gas well pillars in the 1957 study are evaluated for their adequacy for roomand-pillar mining and their applicability to longwall *** modeling is used to model the stability of gas wells by quantifying the mining-induced s

关键词： Gas well pillar Pennsylvania 1957 gas well pillar study Room-and-pillar mining Longwall mining

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A Two-Player Coalition Cooperative Scheme for the Bodyguard Allocation Problem

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Journal of Computer Science & Technology 2018年第4期33卷 823-837页

作者： Jose Alberto Fernandez-Zepedu daniel Brubeck-Salcedo daniel Fajardo-Delgado Hector Zatarain-Aceves Department of Computer Science Center for Scientific Research and Higher Education of Ensenada Ensenada BC 22860 Mexico Department of Systems and Computation Instituto Technol6gico de Ciudad Guzmdn Guzmdn JAL 49100 Mexico

We address the bodyguard allocation problem （BAP）, an optimization problem that illustrates the conflict of interest between two classes of processes with contradictory preferences within a distributed system. While a class of processes prefers to minimize its distance to a particular process called the root, the other class prefers to maximize it; at the same time, all the processes seek to build a communication spanning tree with the maximum social welfare. The two state-of-the-art algorithms for this problem always guarantee the generation of a spanning tree that satisfies a condition of Nash equilibrium in the system; however, such a tree does not necessarily produce the maximum social welfare. In this paper, we propose a two-player coalition cooperative scheme for BAP, which allows some processes to perturb or break a Nash equilibrium to find another one with a better social welfare. By using this cooperative scheme, we propose a new algorithm called FFC-BAPs for BAP. We present both theoretical and empirical analyses which show that this algorithm produces better quality approximate solutions than former algorithms for BAP.

关键词： bodyguard allocation problem coalitional game graph algorithm Nash equilibrium

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Soil spatial variability impact on the behavior of a reinforced earth wall

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Frontiers of Structural and Civil Engineering 2020年第2期14卷 518-531页

作者： Adam HAMROUNI daniel DIAS Badreddine SBARTAI Laboratory InfraRES Mohammed Cherif Messaadia UniversitySoukAhras 41000Algeria School of Automotive and Transportation Engineering Hefei University of TechnologyHefei 230009China Antea Group Antony 92160France Department of Civil Engineering University of AnnabaAnnaba 23000&LMGHU LaboratoryUniversity of SkikdaSkikda 21000Algeria

This article presents the soil spatial variability effect on the performance of a reinforced earth *** serviceability limit state is considered in the *** cases of isotropic and anisotropic non-normal random fields are implemented for the soil *** K arhunen-Loeve expansion method is used for the discretization of the random *** finite difference models are considered as deterministic *** Monte Carlo simulation technique is used to obtain the deformation response variability of the reinforced soil retaining *** influences of the spatial variability response of the geotechnical system in terms of horizontal facing displacement is presented and *** results obtained show that the spatial variability has an important influence on the facing horizontal displacement as well as on the failure probability.

关键词： reinforced earth wall geosynthetic random field spatial variability Monte Carlo simulation

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Energy model based on solar potential and the production of electrical energy through living plants’photosynthesis

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Clean Energy 2024年第3期8卷 116-126页

作者： Raymond daniel Rodriguez Martinez Department of Industrial Production Faculty of EngineeringUniversidad Metropolitana1073 CaracasVenezuela

Developing a sustainable energy model is imperative considering the current trend towards decarbonizing sectors *** this purpose,Venezuela was used as a reference to propose an energy model focused on taking advantage of plant photosynthesis through microbial-vegetable fuel cells together with an agro-photovoltaic system to enhance energy and agricultural *** production from the cells was estimated using an average power density of 264 mW/m^(2) over 4%of the areas destined for crops in the entire Venezuelan region,obtaining an annual production of 19.889 GWh/*** contrast,the energy production of the agro-photovoltaic system was modelled using PVsyst software on 50%of the area used for the cells distributed throughout the states of Anzoátegui,Guárico,Monagas and Portuguesa according to their meteorological conditions,solar irradiation and agricultural activity,resulting in 3703417 GWh/*** resulting whole system proved to be able to cover>10 times the installed electricity generation capacity at a national level and,together with the tremendous scalability of the microbial fuel cells,it shows that Venezuela has a high potential for the production and distribution of clean energy.

关键词： ecosystems microbial fuel cell microorganisms renewable sustainability

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TRANSFORMATIONS FOR THE PRIZE-COLLECTING STEINer TREE PROBLEM AND THE MAXIMUM-WEIGHT CONNECTED SUBGRAPH PROBLEM TO SAP

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Journal of Computational Mathematics 2018年第3期36卷 459-468页

作者： daniel Rehfeldt Thorsten Koch Department of Mathematics Technische Universitat Berlin Germany Zuse Institute Berlin and Technische Universitat Berlin Germany

Transformations of Steiner tree problem variants have been frequently discussed in the literature. Besides allowing to easily transfer complexity results, they constitute a central pillar of exact state-of-the-art solvers for well-known variants such as the Steiner tree problem in graphs. In this article transformations for both the prize-collecting Steiner tree problem and the maximum-weight connected subgraph problem to the Steiner arborescence problem are introduced for the first time. Furthermore, the considerable implications for practical solving approaches will be demonstrated, including the computation of strong upper and lower bounds.

关键词： Prize-collecting Steiner tree problem Maximum-weight connected subgraphproblem Graph transformations Dual-ascent heuristics.

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Static/dynamic friction and wear of some selected polymeric materials for conformal tribo-pairs under boundary lubrication conditions

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Friction 2013年第3期1卷 232-241页

作者： daniel NILSSON Braham PRAKASH Bosch Rexroth Mellansel AB MellanselSweden Division of Machine Elements Department of Engineering Sciences and MathematicsLuleåUniversity of TechnologyLuleåSweden

This work is aimed at investigating the friction and wear performance of different polymeric materials having potential for hydraulic system components under lubricated sliding conditions against a steel counter face.A pin-on-disc test configuration was used for the experimental *** different polymeric materials selected for these studies were commercial polyimides(PI),polyether ether ketone(PEEK),and *** of these materials were bulk materials whereas others were used as coatings applied on to the cast iron *** tribological characteristics of the polymers were compared with a reference grey cast *** frictional characteristics were evaluated in both static and dynamic *** results have shown that by using polymeric materials it is possible to reduce breakaway friction by an order of magnitude compared to grey cast ***,the breakaway friction increased significantly after the wear *** polymeric materials having lowest breakaway friction have shown the highest wear with the exception of the PEEK-PTFE coating which showed low *** with graphite fillers also showed low wear but it resulted in relatively high *** carbon fibre reinforced materials resulted in unstable friction as well as higher wear compared to the PI materials with graphite fillers.

关键词： polymer tribology static friction dynamic friction and lubricated wear

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Vegetation cover and occurrence of salamanders in the western Mediterranean

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Integrative Zoology 2022年第3期17卷 456-467页

作者： daniel ESCORIZA Axel HerNANDEZ GRECO Institute of Aquatic EcologyUniversity of GironaGironaSpain Department of Environmental Sciences Faculty of Sciences and TechnicsUniversity Pasquale Paoli of CorsicaCorteFrance

The Mediterranean region possesses a rich diversity of salamanders,which also exhibit a high degree of ecological *** is assumed that the presence of salamanders is dependent on the level of vegetation cover in terrestrial habitats,but the strength of this association is likely to vary among *** this study,we investigated the patterns of habitat utilization for Mediterranean salamanders based on 589 records of 33 *** tested the hypothesis that the association between salamander presence and vegetation density varies among genera or reproductive modes(*** vs aquatic).The results show that vegetation cover has similar influences on terrestrial and aquatic groups but important differences are identified for lotic and lentic aquatic *** findings also indicate that the aquatic lotic,terrestrial,and small-body species deviate significantly from that expected from the background range of variation.

关键词： amphibian conservation habitat remote sensing salamander

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Targeting proliferation and survival pathways in head and neck cancer for therapeutic benefit

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Chinese Journal of Cancer 2012年第7期31卷 319-326页

作者： daniel E. Johnson Departments of Medicine and Pharmacology & Chemical Biology University of Pittsburgh Cancer InstitutePittsburgh Pennsylvania 15213 USA

Head and neck squamous cell carcinomas (HNSCC) are common human malignancies with poor clinical outcomes. The 5-year survival rates for patients with advanced stage HNSCC have not changed appreciably in the past few decades, underscoring a dire need for improved therapeutic options. Recent studies have elucidated a key signaling axis, the EGFR-STAT3-Bcl-XL signaling axis, that is aberrantly activated in a majority of HNSCC and contributes to the proliferation and survival of malignant cells. Considerable effort is being placed on developing highly specific inhibitors of different components of this pathway. This review highlights the progress that is being made towards achieving potent inhibition of the EGFR-STAT3-Bcl-XL signaling axis in HNSCC and the promising therapeutic strategies that are currently under development for this disease.

关键词：治疗效果头颈部癌症存活增殖鳞状细胞癌头部恶性肿瘤

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Beyond the code:the role of histone methylation in cancer resistance and therapy

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Signal Transduction and Targeted Therapy 2024年第7期9卷 2837-2839页

作者： daniel Noerenberg Frederik Damm Charité–Universitätsmedizin Berlin corporate member of Freie Universität BerlinHumboldt Universität zu Berlinand Berlin Institute of HealthDepartment of HematologyOncologyand Cancer ImmunologyBerlinGermany German Cancer Consortium(Deutsches Konsortium für Translationale Krebsforschung DKTK)Partner SiteBerlinGermany

In a recently published paper in Nature,Yamagishi et *** a comprehensive exploration on the mechanistic basis and subsequent emergence of resistance of targeting histone H3 lysine trimethylation(H3K27me3)using the EZH... 详细信息

关键词： EZH2 resistance

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Challenges to Coordination: Understanding Intergovernmental Friction During Disasters

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International Journal of Disaster Risk Science 2019年第3期10卷 306-316页

作者： daniel P.Aldrich Department of Political Science School of Public Policy and Urban Affairs Northeastern UniversityBoston

While idealized crisis response involves smooth coordination between relevant actors, friction between levels of government and between the state and civil society in responding to catastrophe may be more *** article builds a theory of cross-level friction during and after crisis by analyzing the conditions when discord is most likely. With a medium-N dataset(N = 18) of disaster responses from, among other countries, Chile, Haiti, Japan,North America, the Philippines, and Somalia, I carry out quantitative and qualitative analysis of cases with a variety of levels of friction to investigate the conditions that lead to misalignment. Tobit regression, qualitative comparative analysis, and case studies that take into account levels of economic development, government structure, nongovernmental organization density, and levels of damage demonstrate that low levels of development, lower levels of economic costs from the crisis, and poor planning and logistical infrastructure correlate with a higher likelihood of friction between disaster response *** not definitive, these findings come with theoretical and practical implications as climate change makes extreme weather events and future disasters more likely and more powerful.

关键词： Bottom up culture Case studies Disaster coordination Qualitative comparative analysis Tobit regression analysis Top down institutions

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