检索结果-南通市图书馆

Calibration of discrete element modeling: Scaling laws and dimensionless analysis

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Particuology 2022年第3期20卷 55-62页

作者： Yucang Wang peter Mora Yunpei Liang State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing UniversityChongqing 400044China College of Petroleum Engineering and Geosciences King Fahd University of Petroleum and MineralsSaudi Arabia

In this paper,dynamic similarity conditions are derived for discrete element simulations by non-dimensionalising the governing *** conditions must be satisfied so that the numerical model is a good representation of the physical *** a pure mechanical system,if three independent ratios of the corresponding quantities between the two models are set,then the ratios of other quantities must be chosen according to the similarity *** scalability of linear and non-linear contact laws is also *** tests of 3D uni-axial compression are carried out to verify the theoretical *** example is presented to show how to calibrate the model according to laboratory data and similarity ***,it is impossible to reduce computer time by scaling up or down certain parameters and continue to uphold the similarity *** results in this paper provide guidelines to assist discrete element modelers in setting up the model parameters in a physically meaningful way.

关键词： Discrete element method Dimensionless analysis Dynamic similarity Parameter calibration ESyS_Particle

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

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

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

Lactate-avid regulatory T cells:metabolic plasticity controls immunosuppression in tumour microenvironment

在线全文

学校读者我要写书评

暂无评论

Signal Transduction and Targeted Therapy 2021年第5期6卷 1418-1419页

作者： Gabriele Multhoff peter Vaupel Radiation Immuno-Oncology Project Group TranslaTUM–Central Institute for Translational Cancer ResearchKlinikum rechts der IsarTU MünchenMunichGermany Department of Radiation Oncology Klinikum rechts der IsarTU MünchenMunichGermany Department of Radiooncology and Radiotherapy Tumour Pathophysiology GroupUniversity Medical Centre MainzMainzGermany

The excellent article by Watson et al.1 points the way ahead to the important role of lactic acid/lactate-anion and glucose on the immunosuppressive activity of lactate-and glucose-affine metabolically distinct subset... 详细信息

关键词： tumour al. microenvironment

Flow frictional characteristics of microencapsulated phase change material suspensions flowing through rectangular minichannels

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2006年第4期49卷 445-456页

作者： Frank Dammel peter Stephan Chair of Technical Thermodynamics Darmstadt University of Technology Germany

An experimental investigation was conducted on the laminar flow frictional characteristics of suspensions with microencapsulated phase change material (MEPCM) in water flowing through rectangular copper minichannels. The MEPCM was provided at an average particle size of 4.97 μm, and was mixed with distilled water to form suspen- sions with various mass concentrations ranging from 0 to 20%. The experiment was per- formed to explore the effect of MEPCM mass concentration on friction factor and pressure drop in the minichannels. The Reynolds number ranged from 200 to 2000 to provide laminar and transitional flows. It was found that the experimental data for the suspensions with 0 and 5% concentration agree well with the existing theoretical data for an incom- pressible, fully developed, laminar Newtonian flow. For the suspensions with mass con- centrations higher than 10%, there is an obvious increase in friction factor and pressure drop in comparison with laminar Newtonian flow.

关键词： microencapsulated phase change material suspension, friction factor, rectangular minichannel.

PARALLEL STOCHASTIC NEWTON METHOD

在线全文

学校读者我要写书评

暂无评论

Journal of Computational Mathematics 2018年第3期36卷 404-425页

作者： Mojmir Mutny peter Richtarik Department of Informatics ETH Zurich Zurich Switzerland School of Mathematics University of Edinburgh Edinburgh ETH9 3FD UK Computer Electrical and Mathematical Sciences & Engineering Department KA UST Saudi Arabia

We propose a parallel stochastic Newton method （PSN） for minimizing unconstrained smooth convex functions. We analyze the method in the strongly convex case, and give conditions under which acceleration can be expected when compared to its serial counterpart. We show how PSN can be applied to the large quadratic function minimization in general, and empirical risk minimization problems. We demonstrate the practical efficiency of the method through numerical experiments and models of simple matrix classes.

关键词： Optimization Parallel methods Newton's method Stochastic algorithms.

USP20 links feeding-induced cholesterol synthesis and energy expenditure

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China(Life Sciences) 2021年第2期64卷 337-338页

作者： Xu Xiao peter Tontonoz Department of Pathology and Laboratory Medicine and Department of Biological Chemistry University of CaliforniaLos AngelesCA 90095USA

Processes that regulate energy expenditure have been the subject of intense study in recent years,both for their physiological importance and for their potential to be targeted for the treatment of metabolic *** novo ... 详细信息

关键词： synthesis energy steps

Target blood pressure in diabetes patients with hypertension——What is the accumulated evidence in 2011?

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2011年第8期12卷 611-623页

作者： peter M.NILSSON Department of Clinical Sciences Lund UniversityUniversity Hospital

There is overwhelming evidence that hypertension is an important risk factor for both macrovascular and microvascular complications in patients with diabetes,but the problem remains to identify appropriate goals for preventive therapies.A number of guidelines (the European Society of Cardiology (ESC)/European Association for the Study of Diabetes (EASD) 2007,the Joint National Committee (JNC)-Ⅶ 2003,the American Diabetes Association (ADA) 2011) have for example advocated a blood pressure goal of less than 130/80 mmHg,but this suggestion has been challenged by findings in recent trials and meta-analyses (2011).The European Society of Hypertension (ESH) therefore recommends a systolic blood pressure goal of "well below" 140 *** on evidence from both randomized controlled trials (hypertension optimal treatment (HOT),action in diabetes and vascular disease:preterax and diamicron MR controlled evaluation (ADVANCE),action to control cardiovascular risk in diabetes (ACCORD)) and observational studies (ongoing telmisartan alone and in combination with ramipril global endpoint trial (ONTARGET),international verapamil-trandolapril study (INVEST),treat to new targets (TNT),and the National Diabetes Register (NDR)),it has been shown that the benefit for stroke reduction remains even at lower achieved blood pressure levels,but the risk of coronary events may be uninfluenced or even increased at lower systolic blood pressure *** a recent meta-analysis,it was therefore concluded that the new recommended goal should be 130-135 mmHg systolic blood pressure for most patients with type 2 *** risk factors should also be controlled with a more ambitious strategy applied in the younger patients with shorter diabetes duration,but a more cautious approach in the elderly and frail patients with a number of vascular or non-vascular *** patients from East Asia,such as China,the stroke risk is relatively higher than the risk of coronary *** must al

关键词： Blood pressure Cardiovascular Diabetes Goal Hypertension Treatment

GUN4 Is Required for Posttranslational Control of Plant Tetrapyrrole Biosynthesis

在线全文

学校读者我要写书评

暂无评论

Molecular Plant 2009年第6期2卷 1198-1210页

作者： Enrico peter Bernhard Grimm Institute of Biology/Plant Physiology Humboldt University Philippstr. 13 Building 12 D 10115 Berlin Germany

In aerobic photosynthetic organisms, GUN4 binds the chlorophyll intermediates protoporphyrin and Mg protoporphyrin, stimulates Mg chelatase activity, and is implicated in plastidic retrograde signaling. GUN4 expression is most abundant in young and greening tissues and parallels the activity of 5-aminolevulinic acid （ALA） ALA and Mg porphyrin biosynthesis during photoperiodic growth. We explored function and mode of action of GUN4 using GUN4- deficient and overexpressing plants. GUN4 overexpression leads to a general activation of the enzymes of chlorophyll biosynthesis. During photoperiodic growth GUN4 deficiency prevents ALA synthesis and chlorophyll accumulation. All these metabolic changes do not correlate with altered gene expression or changes of protein abundance in tetrapyrrole biosynthesis. While ALA feeding fails to compensate GUN4 deficiency during light-dark growth, this approach results in chlorophyll accumulation under continuous dim light. A new model defines the involvement of GUN4 in posttranslational regulation of ALA and Mg porphyrin synthesis, to sustain chlorophyll synthesis, namely under varying environmental conditions.

关键词： Tetrapyrrole biosynthesis chlorophyll Mg porphyrin branch photo-oxidation chloroplasts

A product version of the Hilton-Milner-Frankl theorem

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China Mathematics 2024年第2期67卷 455-474页

作者： peter Frankl Jian Wang Alfréd Rényi Institute of Mathematics Hungarian Academy of SciencesBudapest H-1053Hungary Department of Mathematics Taiyuan University of TechnologyTaiyuan 030024China

Two families F and G of k-subsets of {1, 2,..., n} are called non-trivial cross t-intersecting if|F ∩ G|≥t for all F ∈ F, G ∈ G and | ∩ {F : F ∈ F}| < t, | ∩ {G : G ∈ G}| < t. In the present paper,we determine the maximum product of the sizes of two non-trivial cross t-intersecting families of k-subsets of{1, 2,..., n} for n≥4(t + 2)2k2, k≥5, which is a product version of the Hilton-Milner-Frankl theorem.

关键词： extremal set theory cross t-intersecting family product version non-trivial