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Influence of residual stresses on failure pressure of cylindrical pressure vessels

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Chinese Journal of Aeronautics 2013年第6期26卷 1415-1421页

作者： m.Jeyakumar T.christopher Department of mechanical Engineering Sardar Raja College of EngineeringAlangulamTirunelveli 627 808India Department of mechanical Engineering Government College of EngineeringTirunelveli 627 007India

The utilization of pressure vessels in aerospace applications is *** this work,fnite element analysis（FEA）has been carried out using ANSYS software package with 2D axisymmetric model to access the failure pressure of cylindrical pressure vessel made of ASTm A36 carbon steel having weld-induced residual *** fnd out the effect of residual stresses on failure pressure,frst an elasto-plastic analysis is performed to fnd out the failure pressure of pressure vessel not having residual *** a thermo-mechanical fnite element analysis is performed to assess the residual stresses developed in the pressure vessel during *** one more elasto-plastic analysis is performed to assess the effect of residual stresses on failure pressure of the pressure vessel having residual *** analysis indicates reduction in the failure pressure due to unfavorable residual stresses.

关键词： Aerospace engineering ASTm A36 Finite element analysis Pressure vessels Welding residual stress

Jet flows from bubbles during subcooled pool boiling on micro wires

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Science China(Technological Sciences) 2005年第4期48卷 385-402页

作者： D. m. christopher Laboratory of Phase Change and Interfacial Transport Phenomena Department of Thermal Engineering Tsinghua University Beijing 100084 China

An experimental investigation was conducted on subcooled nucleate boiling on ultra-small wires having diameters of 25―100 μm. High-speed photography and laser PIV (Particle Image Velocimetry) technology were used to visually observe the bubble dynamics. For highly subcooled boiling at moderate heat fluxes, the bubbles generally remained attached to the micro heating wires and bubble-top jet flows were clearly observed. Smaller bubbles usually had stronger bubble-top jet flows, while larger bubbles seemed to produce multi-jet flows. The structures of the bubble-top jet flows, as well as multi-jet flows, were proposed from the experimental observation. A model was developed to describe jet flow phenomena from bubbles on micro wires. Numerical simulations for bubbles having diameter of 0.03 and 0.06 mm showed that both the bubble-top and multi-jet flows were induced by a strong marangoni effect due to high temperature gradients near the wire. The predicted velocity magnitudes and flow structures agreed very well with experimental measurements. The bubble size relative to the wire is an important factor affecting the jet flow structure. For a 0.03 mm bubble on a 0.1 mm wire, only a bubble-top jet flow forms, while a complex multi-jet flow pattern forms around the bubble with a weak bubble-top jet and two side jet flows for a 0.06 mm bubble.

关键词： subcooled boiling, bubble, multi-jet, jet flow, PIV, marangoni, CFD.

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青藏高原腹地发现最早细石叶技术遗址

中国科学：地球科学 2024年第5期54卷 1588-1601页

作者：靳英帅张晓凌王社江葛俊逸何伟达娃谭韵瑶杨紫衣 christopher mORGAN 高星中国科学院脊椎动物演化与人类起源重点实验室中国科学院古脊椎动物与古人类研究所北京100044 中国科学院大学北京100049 西藏自治区文物保护研究所拉萨850000 那曲市文化和旅游局那曲852000 University of Nevada Reno 87557USA

细石叶技术产品是青藏高原发现最丰富的史前人类文化遗物,代表了早期人类在高原的大规模迁徙.然而,经过系统发掘、具有可靠年代数据的细石叶技术遗址在青藏高原发现较少,高原腹地更为缺乏,这对理解细石叶技术人群在高原大规模迁徙扩散... 详细信息

细石叶技术产品是青藏高原发现最丰富的史前人类文化遗物,代表了早期人类在高原的大规模迁徙.然而,经过系统发掘、具有可靠年代数据的细石叶技术遗址在青藏高原发现较少,高原腹地更为缺乏,这对理解细石叶技术人群在高原大规模迁徙扩散的时间和过程带来了诸多障碍.本文研究报道了青藏高原腹地海拔4600m处新发现的细石叶技术遗址——尼阿底遗址第3地点.技术-类型学分析结果显示,尼阿底遗址第3地点细石叶的生产主要包括楔形石核和半锥形石核两种技术,与旧石器时代晚期中国华北地区的细石叶技术特征接近.光释光测年(OSL)和碳十四测年(^(14)C)的结果表明,尼阿底遗址第3地点的年代为11000~10000a BP.尼阿底遗址第3地点作为目前青藏高原腹地发现的最早的细石叶技术遗址,为了解拥有细石叶技术的狩猎采集者到达高原腹地的时间及其可能的扩散路线提供了重要信息.另外,通过对整个高原细石叶技术发展的分析,结合分子生物学的成果对比显示,细石叶技术人群迁移进入高原可能与人类对高原的长期占领以及现代藏族人的形成有密切联系.

关键词：青藏高原腹地尼阿底遗址第3地点细石叶技术早全新世高海拔适应

Updates on treatment of irritable bowel syndrome

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World Journal of Gastroenterology 2008年第17期14卷 2639-2649页

作者： christopher W Hammerle Christina m Surawicz Department of medicine University of Colorado Health Sciences Center Harborview medical Center University of Washington

Irritable bowel syndrome （IBS） is a highly prevalent gastrointestinal disorder characterized by abdominal pain and discomfort in association with altered bowel habits. It is estimated tD affect 10%-15% of the Western population, and has a large impact on quality of life and （in）direct healthcare costs. IBS is a multifactorial disorder involving dysregulation within the brain-gut axis, and it is frequently associated with gastrointestinal motor and sensory dysfunction, enteric and central nervous system irregularities, neuroimmune dysregulation, and postinfectious inflammation. As with other functional medical disorders, the treatment for IBS can be challenging. Conventional therapy for those with moderate to severe symptoms is largely unsatisfactory, and the development of new and effective drugs is made difficult by the complex pathogenesis, variety of symptoms, and lack of objective clinical findings that are the hallmark of this disorder. Fortunately, research advances over the past several decades have provided insight into potential mechanisms responsible for the pathogenesis of IBS, and have led to the development of several promising pharmaceutical agents. In recent years there has been much publicity over several of these new IBS medications （alosetron and tegaserod） because of their reported association with ischemic colitis and cardiovascular disease. While these agents remain available for use under restricted prescribing programs, this highlights the need for continued development of safe and effective medication for IBS. This article provides a physiologicallybased overview of recently developed and frequently employed pharmaceutical agents used to treat IBS, and discusses some non-pharmaceutical options that may be beneficial in this disorder.

关键词： Irritable bowel syndrome Treatment Pharmacotherapy Challenges Opportunities

CO2 degassing and melting of metasomatized mantle lithosphere during rifting-Numerical study

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Geoscience Frontiers 2019年第4期10卷 1409-1420页

作者： Weronika Gorczyk christopher m. Gonzalez University of Western Australia Centre for Exploration TargetingSchool of Earth SciencesARC Centre of Excellence for Core to Crust Fluid SystemsPerthWestern AustraliaAustralia School of Earth Atmosphere and EnvironmentMonash University ClaytonMelbourneVICAustralia

:Reactivation of metasomatized mantle lithosphere may occur during continental extension,which is an important component of plate *** lower most part of the metasomatized domains in the subcontinental mantle lithosphere can be locally enriched in ***,partial melting of these metasomatized domains may play a crucial role in the global carbon ***,little is known about this process and up until now few numerical constraints are *** we address this knowledge gap and use a 2-D high resolution petrological-thermomechanical model to assess lithospheric ***2 degassing and *** test 4 lithospheric thicknesses:90,110,130 and 200 km with a 10 km thick metasomatized layer at the base using CO2 of 2 wt.%in the bulk *** carbonate enriched layer is stable below^3 GPa(>110 km)for a temperature of 1300℃;therefore,we only observe degassing patterns for lithospheric models that are 130 km and 200 km *** metasomatized layer for the 130 km thick lithosphere mostly comprises carbonatite melting,whereas in the 200 km thick scenario propagation of melt development from kimberlites to carbonatites occurs as the metasomatic mantle is exhumed during *** numerical models fit well into natural rifting zones of the European Cenozoic Rift System for young(shallow)and of the North Atlantic Rift for old(thick)lithosphere.

关键词： Rifting mantle CO2 degassing Carbonate melting

Heat Transfer in the microlayer Under a Bubble During Nucleate Boiling

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Tsinghua Science and Technology 2010年第4期15卷 404-413页

作者： David m.christopher 张璐 Key Laboratory for Thermal Science and Power Engineering of ministry of Education Department of Thermal Engineering Tsinghua University

many studies have shown that a very thin liquid microlayer forms under vapor bubbles during nucleate boiling. The heat transfer from the surface to the bubble is then significantly affected by this mi- crolayer and the curved region leading into the microlayer. Various models have been developed to predict the microlayer shape and the heat transfer along the curved interfacial region, but they tend to have incon- sistent boundary conditions or unrealistic results. This paper presents a theoretical model to predict the mi- crolayer thickness and the heat transfer rates for a variety of conditions. The results show how the wall su- perheat, the Hamaker constant, the bubble radius, and the accommodation coefficient at the interface affect the evaporation heat transfer rates and the microlayer shape for a large range of conditions for water and FC 72. The microlayer results are then shown to compare well with predictions made by solving the Na- vier-Stokes equations in the microlayer.

关键词： nucleate boiling bubble growth heat transfer microlayer

Experimental Study of High moisture Content Gas Flow Across a Cylinder at moderate Reynolds Numbers

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Tsinghua Science and Technology 2003年第5期8卷 598-604页

作者： D.m.christopher 郭亮 Department of Thermal Engineering

The Nusselt number for cross flow of a mixture of air and vapor over a cylinder was measured at moderate Reynolds numbers (30007000) for temperatures from 300℃ to 700℃ and for vapor mass fractions of 0.180.35. Results are also presented for a set of three cylinders aligned perpendicular to the flow for the same range of conditions. The effect of the vapor concentration and temperature on the convection coefficients was investigated to develop a modified Zhukauskas correlation. The results show that the Nusselt number increases as the moisture content increases and that the increase is more than could be accounted for by typical models for the property variations of mixtures. The exponent of the vapor concentration term in the modified correlation is 0.145 for the entire data set indicating the importance of the property variation due to the moisture content.

关键词： high moisture content cross flow convection coefficients heat exchangers

Dynamic Bubble Behaviour during microscale Subcooled Boiling

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Chinese Physics Letters 2005年第11期22卷 2881-2884页

作者：王昊彭晓峰 David m. christopher Laboratory of Phase-Change and Interracial Transport Phenomena Department of Thermal Engineering Tsinghua University Beijing 100084

Bubble cycles, including initiation, growth and departure, are the physical basis of nucleate boiling. The present investigation, however, reveals unusual bubble motions during subcooled nucleate boiling on microwires 25 or 100μm in diameter. Two types of bubble motions, bubble sweeping and bubble return, are observed in the experiments. Bubble sweeping describes a bubble moving back and forth along the wire, which is motion parallel to the wire. Bubble return is the bubble moving back to the wire after it has detached or leaping above the wire. Theoretical analyses and numerical simulations are conducted to investigate the driving mechanisms for both bubble sweeping and return. marangoni flow from warm to cool regions along the bubble interface is found to produce the shear stresses needed to drive these unusual bubble movements.

关键词： Dynamic Bubble Behaviour during microscale Subcooled Boiling

Strategies towards statistically robust interpretations of in situ U-Pb zircon geochronology

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Geoscience Frontiers 2016年第4期7卷 581-589页

作者： christopher J.Spencer christopher L.Kirkland Richard J.m.Taylor The Institute of Geoscience Research(TIGeR) Department of Applied GeologyWestern Australian School of MinesCurtin UniversityWA 6102Australia Centre for Exploration Targeting-Curtin Node Department of Applied GeologyWestern Australian School of MinesCurtin UniversityWA 6102Australia Australian Research Council Centre of Excellence for Core to Crust Fluid SystemsPerthWA 6102Australia

Zircon U-Pb geochronology has become a keystone tool across Earth science, arguably providing the gold standard in resolving deep geological time. The development of rapid in situ analysis of zircon （via laser ablation and secondary ionization mass spectrometry） has allowed for large amounts of data to be generated in a relatively short amount of time and such large volume datasets offer the ability to address a range of geological questions that would otherwise remain intractable （e.g. detrital zircons as a sedi- ment fingerprinting method）. The ease of acquisition, while bringing benefit to the Earth science com- munity, has also led to diverse interpretations of geochronological data. In this work we seek to refocus U -Pb zircon geochronology toward best practice by providing a robust statistically coherent workflow. We discuss a range of data filtering approaches and their inherent limitations （e.g. discordance and the reduced chi-squared; mSWD）. We evaluate appropriate mechanisms to calculate the most geologically appropriate age from both 238U/206pb and 207pb/206pb ratios and demonstrate the cross over position when chronometric power swaps between these ratios. As our in situ analytical techniques become progressively more precise, appropriate statistical handing of U-Pb datasets will become increasingly pertinent.

关键词： Zircon Geochronology U-Pb Geostatistics mSWD