The Structure of A Turbulent Jet in A Crossflow-Effect of Jet-Crossflow Velocity     

李行伟  匡翠萍  陈国谦 《中国海洋工程》2002,(1)

A comprehensive numerical study on the three-dimensional structure of a turbulent jet in crossflow is performed. The jet-to-crossflow velocity ratio (R) varies in the range of 2 - 16; both vertical jets and inclined jets without excess streamwise momentum are considered. The numerical results of the Standard two-equation k-ε model show that the turbulent structure can be broadly categorised according to the jet-to-crossflow velocity ratio. For strong to moderate jet discharges, i.e. R> 4, the jet is characterized by a longitudinal transition through a bent-over phase during which the jet becomes almost parallel with the main freestream, to a sectional vortex-pair flow with double concentration maxima; the computed flow details and scalar mixing characteristics can be described by self-similar relations beyond a dimensionless distance of around 20-60. The similarity coefficients are only weakly dependent on R. The cross-section scalar field is kidney-shaped and bifurcated, vvith distinct double concentr  相似文献   

Changes of precipitation extremes over South Korea projected by the 5 RCMs under RCP scenarios     

Joong-Bae Ahn  Sera Jo  Myoung-Seok Suh  Dong-Hyun Cha  Dong-Kyou Lee  Song-You Hong  Seung-Ki Min  Seong-Chan Park  Hyun-Suk Kang  Kyo-Moon Shim 《Asia-Pacific Journal of Atmospheric Sciences》2016,52(2):223-236

The change of extreme precipitation is assessed with the HadGEM2-AO - 5 Regional Climate Models (RCMs) chain, which is a national downscaling project undertaken cooperatively by several South Korean institutes aimed at producing regional climate change projection with fine resolution (12.5 km) around the Korean Peninsula. The downscaling domain, resolution and lateral boundary conditions are held the same among the 5 RCMs to minimize the uncertainties from model configuration. Climatological changes reveal a statistically significant increase in the mid-21st century (2046- 2070; Fut1) and the late-21st century (2076-2100; Fut2) precipitation properties related to extreme precipitation, such as precipitation intensity and average of upper 5 percentile daily precipitation, with respect to the reference period (1981-2005). Changes depending on the intensity categories also present a clear trend of decreasing light rain and increasing heavy rain. In accordance with these results, the change of 1-in-50 year maximum precipitation intensity over South Korea is estimated by the GEV method. The result suggests that the 50-year return value (RV50) will change from -32.69% to 72.7% and from -31.6% to 96.32% in Fut1 and from -31.97% to 86.25% and from -19.45% to 134.88% in Fut2 under representative concentration pathway (RCP) 4.5 and 8.5 scenarios, respectively, at the 90% confidence level. This study suggests that multi-RCMs can be used to reduce uncertainties and assess the future change of extreme precipitation more reliably. Moreover, future projection of the regional climate change contains uncertainties evoked from not only driving GCM but also RCM. Therefore, multi-GCM and multi-RCM studies are expected to provide more robust projection.  相似文献   

Projections of high resolution climate changes for South Korea using multiple-regional climate models based on four RCP scenarios. Part 1: surface air temperature     

Myoung-Seok Suh  Seok-Geun Oh  Young-Suk Lee  Joong-Bae Ahn  Dong-Hyun Cha  Dong-Kyou Lee  Song-You Hong  Seung-Ki Min  Seong-Chan Park  Hyun-Suk Kang 《Asia-Pacific Journal of Atmospheric Sciences》2016,52(2):151-169

We projected surface air temperature changes over South Korea during the mid (2026-2050) and late (2076-2100) 21st century against the current climate (1981-2005) using the simulation results from five regional climate models (RCMs) driven by Hadley Centre Global Environmental Model, version 2, coupled with the Atmosphere- Ocean (HadGEM2-AO), and two ensemble methods (equal weighted averaging, weighted averaging based on Taylor’s skill score) under four Representative Concentration Pathways (RCP) scenarios. In general, the five RCM ensembles captured the spatial and seasonal variations, and probability distribution of temperature over South Korea reasonably compared to observation. They particularly showed a good performance in simulating annual temperature range compared to HadGEM2-AO. In future simulation, the temperature over South Korea will increase significantly for all scenarios and seasons. Stronger warming trends are projected in the late 21st century than in the mid-21st century, in particular under RCP8.5. The five RCM ensembles projected that temperature changes for the mid/late 21st century relative to the current climate are +1.54°C/+1.92°C for RCP2.6, +1.68°C/+2.91°C for RCP4.5, +1.17°C/+3.11°C for RCP6.0, and +1.75°C/+4.73°C for RCP8.5. Compared to the temperature projection of HadGEM2-AO, the five RCM ensembles projected smaller increases in temperature for all RCP scenarios and seasons. The inter-RCM spread is proportional to the simulation period (i.e., larger in the late-21st than mid-21st century) and significantly greater (about four times) in winter than summer for all RCP scenarios. Therefore, the modeled predictions of temperature increases during the late 21st century, particularly for winter temperatures, should be used with caution.  相似文献   

Evaluation of multiple regional climate models for summer climate extremes over East Asia     

Changyong Park  Seung-Ki Min  Donghyun Lee  Dong-Hyun Cha  Myoung-Seok Suh  Hyun-Suk Kang  Song-You Hong  Dong-Kyou Lee  Hee-Jeong Baek  Kyung-On Boo  Won-Tae Kwon 《Climate Dynamics》2016,46(7-8):2469-2486

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Baryte and calcite cements in the 'breccias' of Ogmore-by-Sea, South Wales     

CHRIS W. LEE 《Geology Today》1991,7(4):133-136

Each year many hundreds, if not thousands, of Earth-science students visit the coastline at Ogmore-by-Sea, mid-Glamorgan. They study the excellent exposures of Lower Carboniferous Limestone, with their well-preserved coral and other shelly faunas, together with the presumed late Triassic 'breccias'* that rest unconformably on top. A study of the cements within the breccias may give an insight into syndepositional mineralization and the formation of sedimentary basins linked to the opening of the Atlantic in early Mesozoic times.  相似文献   

A three-dimensional large-scale cloud model: testing the role of radiative heating and ice phase processes     

J. L. LEE  K. N. LIOU  S. C. OU 《地球，A辑:动力气象学与海洋学》1992,44(3):197-216

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Geochemistry of ultramafic xenoliths in Cenozoic alkali basalts from Jiangsu province, eastern China and their geological implication     

SHAO-WEI HUANG  YUNG-TAN LEE  JU-CHIN CHEN  KUNG-SUAN HO  MENG-LUNG LIN  YEN-TSUI HU  REN-YI HUANG 《Journal of Earth System Science》2013,122(3):777-793

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Stardust impact analogs: Resolving pre‐ and postimpact mineralogy in Stardust Al foils     

Penelope J. WOZNIAKIEWICZ  Hope A. ISHII  Anton T. KEARSLEY  Mark J. BURCHELL  John P. BRADLEY  Mark C. PRICE  Nick TESLICH  Martin R. LEE  Mike J. COLE 《Meteoritics & planetary science》2012,47(4):708-728

Abstract– The grains returned by NASA’s Stardust mission from comet 81P/Wild 2 represent a valuable sample set that is significantly advancing our understanding of small solar system bodies. However, the grains were captured via impact at ～6.1 km s^?1 and have experienced pressures and temperatures that caused alteration. To ensure correct interpretations of comet 81P/Wild 2 mineralogy, and therefore preaccretional or parent body processes, an understanding of the effects of capture is required. Using a two‐stage light‐gas gun, we recreated Stardust encounter conditions and generated a series of impact analogs for a range of minerals of cometary relevance into flight spare Al foils. Through analyses of both preimpact projectiles and postimpact analogs by transmission electron microscopy, we explore the impact processes occurring during capture and distinguish between those materials inherent to the impactor and those that are the product of capture. We review existing and present additional data on olivine, diopside, pyrrhotite, and pentlandite. We find that surviving crystalline material is observed in most single grain impactor residues. However, none is found in that of a relatively monodisperse aggregate. A variety of impact‐generated components are observed in all samples. Al incorporation into melt‐derived phases allows differentiation between melt and shock‐induced phases. In single grain impactor residues, impact‐generated phases largely retain original (nonvolatile) major element ratios. We conclude that both surviving and impact‐generated phases in residues of single grain impactors provide valuable information regarding the mineralogy of the impacting grain whilst further studies are required to fully understand aggregate impacts and the role of subgrain interactions during impact.  相似文献   

玩具业中重金属的等离子体发射光谱分析     

LEE Davidowski  ZOE Grosser  LAURA Thompson 《岩矿测试》2009,28(2):203-205

为了支持玩具业,许多实验室需要分析各种复杂基体中的金属含量。人们关心的主要元素是铅,但很多其他有毒元素也具有潜在的威胁,尤其对于儿童。这些重金属元素包括锑、砷、钡、镉、铬、硒、汞和铅,累积在人体中将产生不利的影响。一些塑料和木制玩具,特别是表面色彩鲜艳的玩具被证实含有更高水平的铅和其他元素,儿童因接触易摄入,相关法规对产品表面含有这些元素的材料作了一些限制。为了保证玩具和其他物品的生产、流通和销售,有必要检测其中的重金属含量。不同的管理机构对各类样品中的元素提供了限量要求。在玩具安全性的欧洲标准EN71第3部分(已纳入ISO8124-3),其中在“特定元素的迁移”一节给出了玩具材料中元素迁移的  相似文献   

Fossil-Winged Fruits of Fraxinus(Oleaceae) and Liriodendron(Magnoliaceae) from the Duho Formation,Pohang Basin,Korea     

Seung-Ho JUNG  Seong-Joo LEE 《《地质学报》英文版》2009,83(5):845-852

Abstract: A total of 16 specimens of fossil-winged fruits were found from the Middle Miocene marine deposits, Duho Formation, Pohang Basin, Korea. They were identified into two structurally different groups: 15 specimens into a winged fruit of Fraxinus, and one specimen of Liriodendron. The most samaras (13 specimens) were identified as Fraxinus oishii, which is characterized by narrowly ovate or ovate–elliptic shapes that are 2.7–3.6 cm in length and 0.7–1 cm in width (l/w ratio=3.4–4). The apexes of the Fraxinus oishii samara are round or slightly emarginated, and a seed of the samara is always located at the base, of which the general shape is narrow rhombic-ellipsoidal. The seed is 1.2–2 cm long and 0.5–0.7 cm wide. Two specimens are different from the samara of Fraxinus oishii. They have a 6.6 length/width ratio (3.3 cm long and 0.5 cm wide), and thus, are temporarily classified into the Fraxinus sp. One specimen was recognized as a winged seed of Liriodendron meisenense. The wing is broadly lanceolate to elliptic in shape, has a smooth, acute apex, and is approximately 3 cm long and 0.7 cm wide. Samaras of Fraxinus oishii and Liriodendron meisenense were early reported from the Middle Miocene deposits from North Korea, but these specimens are the first discovery in South Korea. Further study of the Duho Formation may connect flora relationships between North and South Korea.  相似文献