For decades,some geological formations have been drilled with a drilling fluid that exerted a bottom-hole pressure less than the formation pressure,allowing formation fluids-oil,gas and water-to flow from the reservoi...For decades,some geological formations have been drilled with a drilling fluid that exerted a bottom-hole pressure less than the formation pressure,allowing formation fluids-oil,gas and water-to flow from the reservoir into the well bore while drilling proceeds.A growing number of Iranian case histories have shown that when UBD is applied in the right reservoir with the proper planning,well productivity can be orders of magnitude greater than with a conventional well drilled into the same formation.Wells drilled underbalanced have been proven to add展开更多
Understanding by design(UbD)是设计优质教学单元的有效工具,在美国等国家教育界得到了广泛的应用。针对目前农林院校学生在课堂上普遍缺乏学习积极性、学习效果差的现状,UbD理论以三个步骤为设计依据,对环境微生物学课程中的微生物特...Understanding by design(UbD)是设计优质教学单元的有效工具,在美国等国家教育界得到了广泛的应用。针对目前农林院校学生在课堂上普遍缺乏学习积极性、学习效果差的现状,UbD理论以三个步骤为设计依据,对环境微生物学课程中的微生物特性与功能教学单元进行了UbD模式的设计与应用。初步应用UbD教学效果表明,UbD教学模式有效地消除了课堂上的“法蒂玛”现象,显著提高了学生课堂参与度和师生互动的频率,激发了学生的学习积极性和求知欲,不仅使学生学习成绩提高,更主要的是使有关教学内容得到深入持久的理解与运用,实现了素质教育,达到了提高其综合能力的目的,教师也从UbD模式教案的设计与教学应用过程中,提升了专业知识水平并掌握了教学技巧。展开更多
UbD(Understanding by Design)即理解为先的教学模式提出的逆向设计,分别从预期结果、评估证据、设计学习体验和教学活动三个阶段强调单元教学设计程序。为落实单元教学设计,本文将理解为先的设计模式与问题式教学相结合,在问题情境下...UbD(Understanding by Design)即理解为先的教学模式提出的逆向设计,分别从预期结果、评估证据、设计学习体验和教学活动三个阶段强调单元教学设计程序。为落实单元教学设计,本文将理解为先的设计模式与问题式教学相结合,在问题情境下使教学内容结构化,以促进学生的知识理解和迁移,落实地理学科核心素养的发展。展开更多
Both evolution of the Asian monsoon system and the Cenozoic global cooling are thought to be closely linked to the Himalayan—Tibetan orogen. The South China Sea (SCS) with its high sedimentation rates of carbonate\|r...Both evolution of the Asian monsoon system and the Cenozoic global cooling are thought to be closely linked to the Himalayan—Tibetan orogen. The South China Sea (SCS) with its high sedimentation rates of carbonate\|rich hemipelagic sediments offers a unique opportunity to study the variability of the East Asian monsoon, the erosion and weathering of tectonic orogens as well as its possible impact on global and regional climate.Leg 184, the first deep\|sea drilling leg to the seas off China, cored 17 holes at 6 sites in the northern and southern parts of the SCS and recovered 5463m of sediment. The drilling of hemipelagic sediments was exceptionally successful, with core recovery averaging 83%～101%. The 32Ma sequence of deep\|sea sediments recovered during Leg 184 covers almost the entire environmental history of the SCS since its opening. The abnormally high sediment accumulation rates in the Oligocene section are correlative with the incipient sea floor spreading. The bathyal nature of the Oligocenefauna implies that rifting occurred in the Eocene or earlier. Faunal changesfrom the early to late Oligocene are indicative of basin deepening, a trend thatis even more evident in the Miocene section. Sediment deformation, abruptlithologic changes, and a hiatus occur near the Oligocene/Miocene boundary,representing one of the most significant events in the tectonic andenvironmental history of the SCS.展开更多
Force analysis using a compact tension model, as recommended by ASTM, was carried out on a crack stop hole. The stress before, and after, drilling the hole was compared in terms of stress concentration and stress grad...Force analysis using a compact tension model, as recommended by ASTM, was carried out on a crack stop hole. The stress before, and after, drilling the hole was compared in terms of stress concentration and stress gradient. The optimum drilling location and diameter were studied through analysis of different locations and diameters. By analyzing the effects of flank holes and an additional hole, drilling advice was proposed and fatigue testing of the cracks in a steel bridge deck with a crack stop hole was conducted. The results show that the stress at the crack tip with a crack stop hole decreased, and the major principal stress around the hole was distributed accordingly. The optimum position of the crack stop hole centre was where the centre of the crack stop hole was situated behind the crack and the hole edge coincided with the crack tip. Therefore, hole diameters larger than 8 mm, or those weakening the section by 10%, were suggested as the best diameters. In terms of multi-hole crack stopping, a flank hole was not recommended. The optimum horizontal position of flank holes was at a distance of 1/4 of a single hole diameter from, and in front of, the single hole. Besides, the experiment showed that crack stop hole could only prevent cracks from growing and had no influence on crack growth rate.展开更多
文摘For decades,some geological formations have been drilled with a drilling fluid that exerted a bottom-hole pressure less than the formation pressure,allowing formation fluids-oil,gas and water-to flow from the reservoir into the well bore while drilling proceeds.A growing number of Iranian case histories have shown that when UBD is applied in the right reservoir with the proper planning,well productivity can be orders of magnitude greater than with a conventional well drilled into the same formation.Wells drilled underbalanced have been proven to add
文摘Understanding by design(UbD)是设计优质教学单元的有效工具,在美国等国家教育界得到了广泛的应用。针对目前农林院校学生在课堂上普遍缺乏学习积极性、学习效果差的现状,UbD理论以三个步骤为设计依据,对环境微生物学课程中的微生物特性与功能教学单元进行了UbD模式的设计与应用。初步应用UbD教学效果表明,UbD教学模式有效地消除了课堂上的“法蒂玛”现象,显著提高了学生课堂参与度和师生互动的频率,激发了学生的学习积极性和求知欲,不仅使学生学习成绩提高,更主要的是使有关教学内容得到深入持久的理解与运用,实现了素质教育,达到了提高其综合能力的目的,教师也从UbD模式教案的设计与教学应用过程中,提升了专业知识水平并掌握了教学技巧。
文摘UbD(Understanding by Design)即理解为先的教学模式提出的逆向设计,分别从预期结果、评估证据、设计学习体验和教学活动三个阶段强调单元教学设计程序。为落实单元教学设计,本文将理解为先的设计模式与问题式教学相结合,在问题情境下使教学内容结构化,以促进学生的知识理解和迁移,落实地理学科核心素养的发展。
文摘Both evolution of the Asian monsoon system and the Cenozoic global cooling are thought to be closely linked to the Himalayan—Tibetan orogen. The South China Sea (SCS) with its high sedimentation rates of carbonate\|rich hemipelagic sediments offers a unique opportunity to study the variability of the East Asian monsoon, the erosion and weathering of tectonic orogens as well as its possible impact on global and regional climate.Leg 184, the first deep\|sea drilling leg to the seas off China, cored 17 holes at 6 sites in the northern and southern parts of the SCS and recovered 5463m of sediment. The drilling of hemipelagic sediments was exceptionally successful, with core recovery averaging 83%～101%. The 32Ma sequence of deep\|sea sediments recovered during Leg 184 covers almost the entire environmental history of the SCS since its opening. The abnormally high sediment accumulation rates in the Oligocene section are correlative with the incipient sea floor spreading. The bathyal nature of the Oligocenefauna implies that rifting occurred in the Eocene or earlier. Faunal changesfrom the early to late Oligocene are indicative of basin deepening, a trend thatis even more evident in the Miocene section. Sediment deformation, abruptlithologic changes, and a hiatus occur near the Oligocene/Miocene boundary,representing one of the most significant events in the tectonic andenvironmental history of the SCS.
基金Projects(51278166,51478163)supported by the National Natural Science Foundation of ChinaProject(2015B17414)supported by the Fundamental Research Funds for the Central Universities,China
文摘Force analysis using a compact tension model, as recommended by ASTM, was carried out on a crack stop hole. The stress before, and after, drilling the hole was compared in terms of stress concentration and stress gradient. The optimum drilling location and diameter were studied through analysis of different locations and diameters. By analyzing the effects of flank holes and an additional hole, drilling advice was proposed and fatigue testing of the cracks in a steel bridge deck with a crack stop hole was conducted. The results show that the stress at the crack tip with a crack stop hole decreased, and the major principal stress around the hole was distributed accordingly. The optimum position of the crack stop hole centre was where the centre of the crack stop hole was situated behind the crack and the hole edge coincided with the crack tip. Therefore, hole diameters larger than 8 mm, or those weakening the section by 10%, were suggested as the best diameters. In terms of multi-hole crack stopping, a flank hole was not recommended. The optimum horizontal position of flank holes was at a distance of 1/4 of a single hole diameter from, and in front of, the single hole. Besides, the experiment showed that crack stop hole could only prevent cracks from growing and had no influence on crack growth rate.
