UHPC材料是一种新型纤维增强水泥基复合材料,利用其力学性能高的特点建造桥梁后可以实现桥梁结构轻型化。国内公路和市政桥梁中均已有应用先例,而铁路桥梁主体结构未见应用。兰州至张掖高速铁路十八里堡特大桥拟建造56 m UHPC组合简支梁...UHPC材料是一种新型纤维增强水泥基复合材料,利用其力学性能高的特点建造桥梁后可以实现桥梁结构轻型化。国内公路和市政桥梁中均已有应用先例,而铁路桥梁主体结构未见应用。兰州至张掖高速铁路十八里堡特大桥拟建造56 m UHPC组合简支梁桥,以解决大跨度混凝土桥梁地震响应大这一技术难题,十八里堡特大桥UHPC简支梁的建造应用将拓宽国内铁路桥梁建设中主体结构只有钢和混凝土两种建筑材料的限制。该桥已完成设计研究分析,研究结果表明:(1)拟建造应用的56 m UHPC简支梁仅为同等跨度普通混凝土梁梁重的72%;(2)提出UHPC组合薄壁简支梁剪力键的主要构造形式;(3)提出UHPC组合简支梁的主要施工方法;(4)建立UHPC组合简支梁双层梁有限元计算模型,分析UHPC薄壁箱梁受力特征,计算分析UHPC与普通混凝土组合梁相对收缩效应和相对徐变效应。展开更多
Petrographic and geochemical characteristics of the Upper Triassic sandstones in the western Ordos Basin were studied to provide insight into weathering characteristics,provenance,and tectonic implications.Petrographi...Petrographic and geochemical characteristics of the Upper Triassic sandstones in the western Ordos Basin were studied to provide insight into weathering characteristics,provenance,and tectonic implications.Petrographic features show that the sandstones are characterized by low-medium compositional maturity and textural maturity.The CIA and CIW values reveal weak and moderate weathering history in the source area.The geochemical characteristics together with palaeocurrent data show that the northwestern sediments were mainly derived from the Alxa Block with a typical recycled nature,while the provenance of the western and southwestern sediments were mainly from the Qinling-Qilian Orogenic Belt.The tectonic setting discrimination diagrams signify that the parent rocks of sandstones in the western and southern Ordos Basin were mainly developed from continental island arc,which is closely related to the evolution of the QinlingQilian Orogenic Belt.However,the sandstones in the northwestern Ordos Basin show complex features,which may be resulted from a typical recycling process.Overall evidence from petrography,geochemistry and sedimentology,together with previous researches suggest the Kongtongshan and Helanshan areas were the southwestern and northwestern boundary of the Ordos Basin,respectively,and there was no clear boundary between the Hexi Corridor Belt and Ordos Basin,where a large,uniform sediment dispersal system developed during the Late Triassic.展开更多
目的探讨755 nm皮秒激光治疗雀斑伴黄褐斑的疗效及安全性。方法自2018年6月至2020年12月,中国医学科学院北京协和医学院整形外科医院激光美容中心对73例FitzpatrickⅢ、Ⅳ型雀斑伴黄褐斑患者,采用755 nm皮秒激光治疗。术前、术后3个月采...目的探讨755 nm皮秒激光治疗雀斑伴黄褐斑的疗效及安全性。方法自2018年6月至2020年12月,中国医学科学院北京协和医学院整形外科医院激光美容中心对73例FitzpatrickⅢ、Ⅳ型雀斑伴黄褐斑患者,采用755 nm皮秒激光治疗。术前、术后3个月采用VISIA分别对色斑清除的程度、黄褐斑面积和严重指数(melasma area and severity index,MASI)评分进行评估。结果73例患者获随访3个月,所有患者雀斑的平均清除评分为(2.53±0.50)分。黄褐斑MASI评分由治疗前(10.62±0.19)分降低为治疗后的(10.38±0.19)分,2例(4.8%)出现轻度炎症后色素沉着,其余患者无明显不良反应发生。结论755 nm皮秒激光是治疗雀斑伴有黄褐斑安全有效的方法,可有效去除患者皮肤的雀斑,治疗过程耐受良好,未观察到严重不良反应,同时诱发原有黄褐斑加重的风险性相对较小。展开更多
文摘UHPC材料是一种新型纤维增强水泥基复合材料,利用其力学性能高的特点建造桥梁后可以实现桥梁结构轻型化。国内公路和市政桥梁中均已有应用先例,而铁路桥梁主体结构未见应用。兰州至张掖高速铁路十八里堡特大桥拟建造56 m UHPC组合简支梁桥,以解决大跨度混凝土桥梁地震响应大这一技术难题,十八里堡特大桥UHPC简支梁的建造应用将拓宽国内铁路桥梁建设中主体结构只有钢和混凝土两种建筑材料的限制。该桥已完成设计研究分析,研究结果表明:(1)拟建造应用的56 m UHPC简支梁仅为同等跨度普通混凝土梁梁重的72%;(2)提出UHPC组合薄壁简支梁剪力键的主要构造形式;(3)提出UHPC组合简支梁的主要施工方法;(4)建立UHPC组合简支梁双层梁有限元计算模型,分析UHPC薄壁箱梁受力特征,计算分析UHPC与普通混凝土组合梁相对收缩效应和相对徐变效应。
基金the National Natural Science Foundation of China [Grant No. 41802119 and 41602212]Natural Science Foundation of Shaanxi [Grant No. 2019JQ-088]+1 种基金Special Projects of China Geological Survey [Grant No. 12120113039900 and 12120114009201]Doctor’s fund of Xi’an University of Science and Technology [Grant No. 2017QDJ051]
文摘Petrographic and geochemical characteristics of the Upper Triassic sandstones in the western Ordos Basin were studied to provide insight into weathering characteristics,provenance,and tectonic implications.Petrographic features show that the sandstones are characterized by low-medium compositional maturity and textural maturity.The CIA and CIW values reveal weak and moderate weathering history in the source area.The geochemical characteristics together with palaeocurrent data show that the northwestern sediments were mainly derived from the Alxa Block with a typical recycled nature,while the provenance of the western and southwestern sediments were mainly from the Qinling-Qilian Orogenic Belt.The tectonic setting discrimination diagrams signify that the parent rocks of sandstones in the western and southern Ordos Basin were mainly developed from continental island arc,which is closely related to the evolution of the QinlingQilian Orogenic Belt.However,the sandstones in the northwestern Ordos Basin show complex features,which may be resulted from a typical recycling process.Overall evidence from petrography,geochemistry and sedimentology,together with previous researches suggest the Kongtongshan and Helanshan areas were the southwestern and northwestern boundary of the Ordos Basin,respectively,and there was no clear boundary between the Hexi Corridor Belt and Ordos Basin,where a large,uniform sediment dispersal system developed during the Late Triassic.
文摘目的探讨755 nm皮秒激光治疗雀斑伴黄褐斑的疗效及安全性。方法自2018年6月至2020年12月,中国医学科学院北京协和医学院整形外科医院激光美容中心对73例FitzpatrickⅢ、Ⅳ型雀斑伴黄褐斑患者,采用755 nm皮秒激光治疗。术前、术后3个月采用VISIA分别对色斑清除的程度、黄褐斑面积和严重指数(melasma area and severity index,MASI)评分进行评估。结果73例患者获随访3个月,所有患者雀斑的平均清除评分为(2.53±0.50)分。黄褐斑MASI评分由治疗前(10.62±0.19)分降低为治疗后的(10.38±0.19)分,2例(4.8%)出现轻度炎症后色素沉着,其余患者无明显不良反应发生。结论755 nm皮秒激光是治疗雀斑伴有黄褐斑安全有效的方法,可有效去除患者皮肤的雀斑,治疗过程耐受良好,未观察到严重不良反应,同时诱发原有黄褐斑加重的风险性相对较小。
