期刊文献+
共找到600篇文章
< 1 2 30 >
每页显示 20 50 100
Missing Data Imputations for Upper Air Temperature at 24 Standard Pressure Levels over Pakistan Collected from Aqua Satellite 被引量:4
1
作者 Muhammad Usman Saleem Sajid Rashid Ahmed 《Journal of Data Analysis and Information Processing》 2016年第3期132-146,共16页
This research was an effort to select best imputation method for missing upper air temperature data over 24 standard pressure levels. We have implemented four imputation techniques like inverse distance weighting, Bil... This research was an effort to select best imputation method for missing upper air temperature data over 24 standard pressure levels. We have implemented four imputation techniques like inverse distance weighting, Bilinear, Natural and Nearest interpolation for missing data imputations. Performance indicators for these techniques were the root mean square error (RMSE), absolute mean error (AME), correlation coefficient and coefficient of determination ( R<sup>2</sup> ) adopted in this research. We randomly make 30% of total samples (total samples was 324) predictable from 70% remaining data. Although four interpolation methods seem good (producing <1 RMSE, AME) for imputations of air temperature data, but bilinear method was the most accurate with least errors for missing data imputations. RMSE for bilinear method remains <0.01 on all pressure levels except 1000 hPa where this value was 0.6. The low value of AME (<0.1) came at all pressure levels through bilinear imputations. Very strong correlation (>0.99) found between actual and predicted air temperature data through this method. The high value of the coefficient of determination (0.99) through bilinear interpolation method, tells us best fit to the surface. We have also found similar results for imputation with natural interpolation method in this research, but after investigating scatter plots over each month, imputations with this method seem to little obtuse in certain months than bilinear method. 展开更多
关键词 Missing Data Imputations Spatial Interpolation AQUA Satellite upper level Air Temperature AIRX3STML
下载PDF
IMPACTS OF UPPER-LEVEL COLD VORTEX ON THE RAPID CHANGE OF INTENSITY AND MOTION OF TYPHOON MERANTI(2010) 被引量:9
2
作者 李英 郭丽霞 +1 位作者 许映龙 胡姝 《Journal of Tropical Meteorology》 SCIE 2012年第2期207-219,共13页
Typhoon Meranti originated over the western North Pacific off the south tip of the Taiwan Island in 2010.It moved westward entering the South China Sea,then abruptly turned north into the Taiwan Strait,got intensified... Typhoon Meranti originated over the western North Pacific off the south tip of the Taiwan Island in 2010.It moved westward entering the South China Sea,then abruptly turned north into the Taiwan Strait,got intensified on its way northward,and eventually made landfall on Fujian province.In its evolution,there was a northwest-moving cold vortex in upper troposphere to the south of the Subtropical High over the western North Pacific(hereafter referred to as the Subtropical High).In this paper,the possible impacts of this cold vortex on Meranti in terms of its track and intensity variation is investigated using typhoon best track data from China Meteorological Administration,analyses data of 0.5×0.5 degree provided by the global forecasting system of National Centers for Environmental Prediction,GMS satellite imagery and Taiwan radar data.Results show as follows:(1)The upper-level cold vortex was revolving around the typhoon anticlockwise from its east to its north.In the early stage,due to the blocking of the cold vortex,the role of the Subtropical High to steer Meranti was weakened,which results in the looping of the west-moving typhoon.However,when Meranti was coupled with the cold vortex in meridional direction,the northerly wind changed to the southerly at the upper level of the typhoon;at the same time the Subtropical High protruded westward and its southbound steering flow gained strength,and eventually created an environment in which the southerly winds in both upper and lower troposphere suddenly steered Meranti to the north;(2)The change of airflow direction above the typhoon led to a weak vertical wind shear,which in return facilitated the development of Meranti.Meanwhile,to the east of typhoon Meranti,the overlapped southwesterly jets in upper and lower atmosphere accelerated its tangential wind and contributed to its cyclonic development;(3)The cold vortex not only supplied positive vorticity to the typhoon,but also transported cold advection to its outer bands.In conjunction with the warm and moist air masses at the lower levels,the cold vortex increased the vertical instability in the atmosphere,which was favorable for convection development within the typhoon circulation,and its warmer center was enhanced through latent heat release;(4)Vertical vorticity budget averaged over the typhoon area further shows that the intensification of a typhoon vorticity column mainly depends on horizontal advection of its high-level vorticity,low-level convergence,uneven wind field distribution and its convective activities. 展开更多
关键词 upper-level cold vortex TYPHOON INTENSIFICATION north turning Taiwan strait
下载PDF
Impact of Mid-and Upper-Level Dry Air on Tropical Cyclone Genesis and Intensification:A Modeling Study of Durian(2001) 被引量:5
3
作者 Yaping WANG Yongjie HUANG Xiaopeng CUI 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2018年第12期1505-1521,共17页
The impact of mid-and upper-level dry air,represented by low relative humidity(RH)values,on the genesis of tropical cyclone(TC)Durian(2001)in the South China Sea was investigated by a series of numerical experiments u... The impact of mid-and upper-level dry air,represented by low relative humidity(RH)values,on the genesis of tropical cyclone(TC)Durian(2001)in the South China Sea was investigated by a series of numerical experiments using the Weather Research and Forecasting model.The mid-level RH was lowered in different regions relative to TC Durian(2001)’s genesis location.Results suggest that the location of dry air was important to Durian(2001)’s genesis and intensification.The rapid development of the TC was accompanied by sustained near-saturated mid-and upper-level air,whereas low humidity decelerated its development.Water vapor budget analysis showed that moisture at mid and upper levels was mainly supplied by the vertical convergence of moisture flux and the divergence terms,and consumed by the condensation process.The horizontal convergence of moisture flux term supplied moisture in the air moistening process but consumed moisture in the air drying process.With a dryer mid-and upper-level environment,convective and stratiform precipitation were both inhibited.The upward mass fluxes and the diabatic heating rates associated with these two precipitation types were also suppressed.Generally,convection played the dominant role,since the impact of the stratiform process on vertical mass transportation and diabatic heating was much weaker.The vorticity budget showed that the negative vorticity convergence term,which was closely related to the inhibited convection,caused the vorticity to decrease above the lower troposphere in a dryer environment.The negative vorticity tendency is suggested to slow down the vertical coherence and the development rate of TCs. 展开更多
关键词 tropical cyclone formation mid-and upper-level dry air WRF water vapor budget convective and STRATIFORM precipitation
下载PDF
Evaluation of Airway Obstruction at Soft Palate Level in Male Patients with Obstructive Sleep Apnea/Hypopnea Syndrome:Dynamic 3-Dimensional CT Imaging of Upper Airway 被引量:10
4
作者 肖英 陈雄 +4 位作者 史河水 杨阳 何烈纯 董家琪 孔维佳 《Journal of Huazhong University of Science and Technology(Medical Sciences)》 SCIE CAS 2011年第3期413-418,共6页
This study examined the dynamic characteristics of upper airway collapse at soft palate level in patients with obstructive sleep apnea/hypopnea syndrome(OSAHS) by using dynamic 3-Dimensional(3-D) CT imaging.A tota... This study examined the dynamic characteristics of upper airway collapse at soft palate level in patients with obstructive sleep apnea/hypopnea syndrome(OSAHS) by using dynamic 3-Dimensional(3-D) CT imaging.A total of 41 male patients who presented with 2 of the following symptoms,i.e.,daytime sleepiness and fatigue,frequent snoring,and apnea with witness,were diagnosed as having OSAHS.They underwent full-night polysomnography and then dynamic 3-D CT imaging of the upper airway during quiet breathing and in Muller's maneuver.The soft palate length(SPL),the minimal cross-sectional area of the retropalatal region(mXSA-RP),and the vertical distance from the hard palate to the upper posterior part of the hyoid(hhL) were compared between the two breathing states.These parameters,together with hard palate length(HPL),were also compared between mild/moderate and severe OSAHS groups.Association of these parameters with the severity of OSAHS [as reflected by apnea hypopnea index(AHI) and the lowest saturation of blood oxygen(LSaO2)] was examined.The results showed that 31 patients had severe OSAHS,and 10 mild/moderate OSAHS.All the patients had airway obstruction at soft palate level.mXSA-RP was significantly decreased and SPL remarkably increased during Muller's maneuver as compared with the quiet breathing state.There were no significant differences in these airway parameters(except the position of the hyoid bone) between severe and mild/moderate OSAHS groups.And no significant correlation between these airway parameters and the severity of OSAHS was found.The position of hyoid was lower in the severe OSAHS group than in the mild/moderate OSAHS group.The patients in group with body mass index(BMI)≥26 had higher collapse ratio of mXSA-RP,greater neck circumference and smaller mXSA-RP in the Muller's maneuver than those in group with BMI26(P0.05 for all).It was concluded that dynamic 3-D CT imaging could dynamically show the upper airway changes at soft palate level in OSAHS patients.All the OSAHS patients had airway obstruction of various degrees at soft palate level.But no correlation was observed between the airway change at soft palate level and the severity of OSAHS.The patients in group with BMI≥26 were more likely to develop airway obstruction at soft palate level than those with BMI26. 展开更多
关键词 obstructive sleep apnea/hypopnea syndrome upper airway obstruction soft palate level dynamic computed tomography 3-Dimensional imaging
下载PDF
Two-level percutaneous endoscopic lumbar discectomy for highly migrated upper lumbar disc herniation: A case report 被引量:4
5
作者 Xin-Bo Wu Zi-Hua Li +1 位作者 Yun-Feng Yang Xin Gu 《World Journal of Clinical Cases》 SCIE 2020年第1期168-174,共7页
BACKGROUND The technique of percutaneous endoscopic lumbar discectomy(PELD)as a transforaminal approach has been used to treat highly migrated lower lumbar disc herniations.However,due to the different anatomic charac... BACKGROUND The technique of percutaneous endoscopic lumbar discectomy(PELD)as a transforaminal approach has been used to treat highly migrated lower lumbar disc herniations.However,due to the different anatomic characteristics of the upper lumbar spine,conventional transforaminal PELD may fail to remove the highly migrated upper lumbar disc nucleus pulposus.Therefore,the purpose of this study was to describe a novel surgical technique,two-level PELD,for the treatment of highly migrated upper lumbar disc herniations and to report its related clinical outcomes.CASE SUMMARY A 60-year-old male presented with a complaint of pain at his lower back and right lower limb.The patient received 3 mo of conservative treatments but the symptoms were not alleviated.Physical examination revealed a positive femoral nerve stretch test and a negative straight leg raise test for the right leg,and preoperative visual analog scale(VAS)score for the lower back was 6 points and for the right leg was 8 points.Magnetic resonance imaging(MRI)demonstrated L2-L3 disc herniation on the right side and the herniated nucleus pulposus migrated to the upper margin of L2 vertebral body.According to physical examination and imaging findings,surgery was the primary consideration.Therefore,the patient underwent surgical treatment with two-level PELD.The pain symptom was relieved and the VAS score for back and thigh pain was one point postoperatively.The patient was asymptomatic and follow-up MRI scan 1 year after operation revealed no residual nucleus pulposus.CONCLUSION Two-level PELD as a transforaminal approach can be a safe and effective procedure for highly migrated upper lumbar disc herniation. 展开更多
关键词 upper lumbar disc herniations Two-level percutaneous endoscopic lumbar discectomy Highly migrated disc herniations Case report
下载PDF
Paleocommunity Replacements of Benthic Brachiopod in the Middle-Upper Devonian in the Longmenshan Area,Southwestern China:Responses to Sea Level Fluctuations 被引量:1
6
作者 CHENYuanren LIXianghui 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2005年第3期313-324,共12页
Twelve paleocommunities dominated by benthic brachiopod are recognized in the Givetian-Frasnian stages of the Devonian in the Longmenshan area, southwestern China, in which two kinds of brachiopod community replacemen... Twelve paleocommunities dominated by benthic brachiopod are recognized in the Givetian-Frasnian stages of the Devonian in the Longmenshan area, southwestern China, in which two kinds of brachiopod community replacement are classified. One is the abrupt replacement, represented by abrupt alternation between the Leiorhynchus community and Zhonghuacoelia-Striatopugnax community in the Frasnian Tuqiaozi Formation. The other is the gradual one, developed in the Givetian Guanwushan Formation, which had been completed by the shift of the Independatrypa lemma-Uncinulus heterocostellis-Emanuella takwanensis community via the Sinospongophyllum irregulare-Pseudomicroplasma fongi community to the Clathrocoilona spissa-Hexagonaria composite reef community. According to analyses of the paleocommunities, either the abrupt or gradual paleocommunity replacement of the Middle-Upper Devonian in the Longmenshan area is suggested as a response to the 5th-order sea level fluctuation due to the replacements of the paleocommunities in a tracts-system of depositional sequence. It is supposed that changes of paleocommunity diversity, one of the results of paleocommunity replacement, are depended on the range and magnitude of sea level fluctuation, but there is not a linear relationship between them. Furthermore, a suggestion is proposed that the concept of paleocommunity succession seem to be abandoned in the paleocommunity analysis because it almost never be practiced to recover the information of community succession in the geological record at present. 展开更多
关键词 community replacement BRACHIOPOD benthic paleocommunity sea level fluctuation Middle Devonian upper Deovnian LONGMENSHAN Sichuan
下载PDF
高、低空急流耦合对山东“利奇马”台风暴雨增幅影响的诊断研究
7
作者 张端禹 王俊超 +2 位作者 王晓芳 崔春光 叶金桃 《大气科学》 CSCD 北大核心 2024年第2期445-462,共18页
受登陆北上台风“利奇马”等影响,2019年8月9~12日山东省出现连续暴雨,其中10日夜间出现降雨峰值。利用中国气象局上海台风研究所(Shanghai Typhoon Institute of China Meteorological Administration,简称CMA-STI)热带气旋最佳路径数... 受登陆北上台风“利奇马”等影响,2019年8月9~12日山东省出现连续暴雨,其中10日夜间出现降雨峰值。利用中国气象局上海台风研究所(Shanghai Typhoon Institute of China Meteorological Administration,简称CMA-STI)热带气旋最佳路径数据、山东省自动气象站逐时降雨量、常规观测资料、中国风云二号地球静止气象卫星(FY-2G)0.1°×0.1°逐小时云顶相当黑体亮温和美国环境预报中心(National Center of Environmental Prediction,简称NCEP)1°×1°逐6 h再分析等资料,主要运用纬向风局地变化方程与大气动能方程,诊断分析降雨明显增幅与高、低层风场变化的关系。结果表明:(1)暴雨主要影响系统有高低空急流、500 hPa西风槽、850 hPa台风倒槽及“利奇马”本体环流等。10日200 hPa中纬度大尺度西南风急流东南移影响鲁西北,当天08:00(北京时,下同)850 hPa因双台风活动而形成的大尺度东南风急流突然北伸越过山东省。台风倒槽对流云与本体环流对流云先、后北移经鲁中,累积效应造成该地区10日夜间雨量最大。(2)10日20:00850 hPa章丘站东北侧出现了过程最快东风增幅,纬向运动方程诊断结果表明,东风平流是东风增加最主要原因,地转偏向力项则不利于东风增加。(3)10日20:00章丘站200 hPa西南风风力明显加大形成急流,10日08:00至11日08:00青岛站850 hPa维持东南风低空急流。同时位于高空急流右后侧与低空急流左前方是鲁中附近10日夜间降雨增幅的重要原因。章丘200 hPa与青岛850 hPa都是在最大风力之前12 h动能增加最快。动能方程诊断表明,最有利于鲁西北高空急流形成的是位能平流项,最有利于鲁东南低空急流形成的是动能垂直通量散度项。(4)10日20:00至13日08:00“利奇马”本体环流一直在影响山东,暴雨期间山东中部地形的动力作用也一直存在,而降雨的峰值是出现在10日夜间,说明10日20:00前后高、低空急流的耦合可能是山东暴雨增幅的主要影响因子。其主要作用至少有加强山东中部的垂直运动、整层水汽输送与静力不稳定度等方面。 展开更多
关键词 登陆北上台风 降水增幅机理 高空西南风急流 低空东南风急流 动能诊断
下载PDF
宋代民众的诉讼与官府的审理——读《名公书判清明集》的几点认识
8
作者 许怀林 《河北大学学报(哲学社会科学版)》 2024年第3期1-12,共12页
“好讼”是宋代比较普遍的民情,这一现象在《名公书判清明集》中有具体印证。凭借大量的案例,再联系历史实情,可知“好讼”源于官吏贪腐、豪强奸恶,也是民众学法懂法、有文明维权意识的表现。江西农耕经济旺盛,耕地紧俏,因而争夺田产所... “好讼”是宋代比较普遍的民情,这一现象在《名公书判清明集》中有具体印证。凭借大量的案例,再联系历史实情,可知“好讼”源于官吏贪腐、豪强奸恶,也是民众学法懂法、有文明维权意识的表现。江西农耕经济旺盛,耕地紧俏,因而争夺田产所有权的讼案很多。审理纠纷时因官员品德才干差异,有的贪财,甚至“自紊其法”,遂判决不公正。诸多关于教化与刑罚并举的判词,启发我们加深对《白鹿洞书院揭示》的理解,朱熹强调圣贤教人之道,也告诫生徒若不听教育,必将实施“学规”,予以惩罚。《名公书判清明集》是研究断代史、社会史、法制史等的珍贵资料,至今不失其借鉴警示意义。 展开更多
关键词 诉讼 《名公书判清明集》 “在上者自紊其法” 民众学法 “学规”
下载PDF
土质边坡的单元失效概率与失效模式研究 被引量:1
9
作者 彭普 李泽 +2 位作者 张小艳 申林方 许芸 《工程力学》 EI CSCD 北大核心 2024年第1期193-207,共15页
土质边坡系统失效概率与土体抗剪强度参数以及地下水位息息相关,在传统边坡可靠度分析中一般只考虑了土体抗剪强度参数的变异性,忽略了地下水位随机性带来的影响。该文将有限元离散技术、上限法理论、相关非高斯随机场模拟方法以及随机... 土质边坡系统失效概率与土体抗剪强度参数以及地下水位息息相关,在传统边坡可靠度分析中一般只考虑了土体抗剪强度参数的变异性,忽略了地下水位随机性带来的影响。该文将有限元离散技术、上限法理论、相关非高斯随机场模拟方法以及随机规划理论结合起来研究随机地下水位作用下考虑参数空间变异性的边坡系统失效概率。采用有限单元离散边坡土体,将边坡地下水位作为随机变量并考虑土体抗剪参数的空间变异性,基于塑性极限分析上限法构建边坡可靠度分析的随机规划模型;采用基于蒙特卡洛的迭代方法进行求解,得到边坡稳定性系数和速度场;根据边坡中单元的失效信息首次采用AP聚类分析方法来估算边坡的系统失效概率,发展了边坡系统可靠度分析理论。对一个经典的边坡算例进行了系统分析并与极限平衡分析方法、有限元方法结果进行对比,结果表明:随机地下水位作用下考虑参数空间变异性时,边坡存在多种失效模式,AP聚类分析方法可以根据失效单元的位置信息识别出边坡所有失效模式以及对应的失效概率;基于Matlab编制了高效的上限法并行程序,大大提高了计算效率。 展开更多
关键词 边坡 可靠度 空间变异性 随机地下水位 上限法
下载PDF
随机误差传递的高空气象秒级数据快速校验方法
10
作者 韦丽英 梁建平 +2 位作者 谢非 黄梅艳 覃晓玲 《山地气象学报》 2024年第2期78-82,88,共6页
【目的】为保证气象预报结果的准确性。【方法】提出了考虑随机误差传递的高空气象秒级数据快速校验方法。对高空气象秒级数据进行预处理,包括数据中心化处理、特征点提取。数据中心化的处理方式为实施各组数据的加权平均处理,获得新的... 【目的】为保证气象预报结果的准确性。【方法】提出了考虑随机误差传递的高空气象秒级数据快速校验方法。对高空气象秒级数据进行预处理,包括数据中心化处理、特征点提取。数据中心化的处理方式为实施各组数据的加权平均处理,获得新的数据组作为基准数据;特征点提取使用的处理方法为遍历法,需要遍历全部数据点。考虑数据获取过程中的随机误差传递情况,对预处理后的高空气象秒级数据实施空间一致性检查、内部一致性检查。应用集合经验模态分解EEMD(Ensemble Empirical Mode Decomposition)算法与对比源反演CSI(Contrast Source Inversion)算法构建基于CSI-EEMD的高空气象秒级数据快速校验模型,实施数据得到快速校验。【结果】测试结果表明,该方法能够实现4个气象站数据的快速校验,校验结果的均方根误差与平均绝对误差均低于0.1,实现了数据的质量控制。【结论】将该方法应用于气象站数据校验中,可以实现精准度的数据校验,具有一定的实用价值。 展开更多
关键词 随机误差传递 特征点提取 高空气象秒级数据 一致性检查 数据校验
下载PDF
1969—2020年夏季山东极端暴雨事件的时空特征及其影响环流分型
11
作者 曹倩 黄菲 +1 位作者 欧阳婧怡 曲颖慧 《中国海洋大学学报(自然科学版)》 CAS CSCD 北大核心 2024年第4期1-12,共12页
利用山东省84个气象台站的逐日降水资料、美国国家环境预测中心和国家大气研究中心(National Centers for Environmental Prediction and National Center for Atmospheric Research, NCEP/NCAR)逐日再分析资料以及中国气象局(CMA)热带... 利用山东省84个气象台站的逐日降水资料、美国国家环境预测中心和国家大气研究中心(National Centers for Environmental Prediction and National Center for Atmospheric Research, NCEP/NCAR)逐日再分析资料以及中国气象局(CMA)热带气旋资料中心的CMA最佳路径数据集,对1969—2020年夏季(6—8月)发生在山东的857例极端暴雨事件(Extreme rainstorm events, EREs)的时空分布特征及影响环流分型进行了分析。结果表明:山东夏季EREs主要集中在7和8月,8月极端暴雨降水量占当月总降水量的比值最大,可达53.5%。山东夏季极端暴雨降水量以及极端暴雨发生日数呈现不显著的增加趋势,8月的增加趋势最明显。使用经验正交函数分解对影响山东夏季EREs的大气环流系统进行分型,发现影响山东夏季出现EREs的环流系统主要有4类,其中,影响ERE最多的环流系统是北方气旋型,约占事件总频次的33.1%;其次是高空急流型,占比约11.3%;南方气旋型和热带气旋型的环流型影响相当,出现的概率分别为9.7%和9.4%。 展开更多
关键词 极端暴雨事件 环流型 南方气旋 北方气旋 高空急流
下载PDF
阿拉伯海超级气旋风暴“查帕拉”(2015)快速加强过程中环境场特征
12
作者 柳龙生 刘莲 高拴柱 《热带气象学报》 CSCD 北大核心 2024年第1期40-51,共12页
利用美国联合台风警报中心(JTWC)发布的北印度洋热带气旋数据、NOAA 0.25°×0.25°逐日OISST资料以及ERA5提供的0.25°×0.25°逐小时的再分析资料分析了阿拉伯海超级气旋风暴“查帕拉”(2015)快速加强过程中... 利用美国联合台风警报中心(JTWC)发布的北印度洋热带气旋数据、NOAA 0.25°×0.25°逐日OISST资料以及ERA5提供的0.25°×0.25°逐小时的再分析资料分析了阿拉伯海超级气旋风暴“查帕拉”(2015)快速加强过程中的环境场特征,结果表明:较常年平均偏暖3.0~3.5℃的暖水区,为“查帕拉”的快速加强提供了水汽和能量条件;“查帕拉”北侧的副热带西风急流和南侧的高空出流通道的建立是其快速加强的重要高空强迫条件,高层辐散风的增强促进质量流出形成强上升运动,这也伴随着旋转风动能的快速增长;在“查帕拉”快速增强时段,高层150 hPa以上存在显著的正位涡异常,高层的正位涡异常能够调整引起低层气旋性环流加强,同时中层400 hPa有显著的正位涡平流输入,正涡度在垂直方向快速增长,300 hPa附近显著增暖,内核区的垂直对流运动达到最强。 展开更多
关键词 查帕拉 快速加强 高空出流 涡度 位涡
下载PDF
基于UDEC的顶板定向长钻孔瓦斯抽采技术研究
13
作者 吴洋洋 毕寸光 《能源与环保》 2024年第3期35-39,46,共6页
为有效解决主焦煤业2301工作面采空区瓦斯涌出量大、易造成上隅角瓦斯超限等问题,设计使用顶板超长定向高位钻孔对采空区瓦斯进行抽采。高位钻孔的层位选择直接影响瓦斯抽采效果,基于UDEC数值模拟软件研究了采空区垂向“三带”分布,计... 为有效解决主焦煤业2301工作面采空区瓦斯涌出量大、易造成上隅角瓦斯超限等问题,设计使用顶板超长定向高位钻孔对采空区瓦斯进行抽采。高位钻孔的层位选择直接影响瓦斯抽采效果,基于UDEC数值模拟软件研究了采空区垂向“三带”分布,计算出顶板裂隙带高度为17~35 m,且在顶板上方8~17 m处为关键层,在顶板上方17~35 m区域内布孔有助于保护成孔不受破坏。顶板定向高位长钻孔抽采瓦斯能够有效提高抽采效率,瓦斯抽采效果明显,实现了“以孔代巷”的目的。通过考察顶板定向长钻孔瓦斯抽采纯量、瓦斯浓度以及与底板穿层钻孔抽采效果进行对比,并实测抽采后残存瓦斯含量变化情况,验证了顶板定向长钻孔瓦斯抽采了优势,保障了矿井安全生产。顶板定向高位长钻孔替代高抽巷技术具有较强的可行性及广阔的应用前景。 展开更多
关键词 高位钻孔 瓦斯抽采 上隅角 UDEC数值模拟 采空区“三带”
下载PDF
高速公路ATB-30粗粒式沥青碎石上基层施工技术及应用
14
作者 何晓阳 《价值工程》 2024年第9期157-159,共3页
高速公路路面结构施工质量关系着公路运营期交通安全,随着高速公路网的逐步完善,路面施工技术得到了快速发展,需要结合工程实际情况开展施工,而沥青路面作为上部结构层,其施工的优劣更能直接决定道路使用寿命及行车舒适度。本文以山西... 高速公路路面结构施工质量关系着公路运营期交通安全,随着高速公路网的逐步完善,路面施工技术得到了快速发展,需要结合工程实际情况开展施工,而沥青路面作为上部结构层,其施工的优劣更能直接决定道路使用寿命及行车舒适度。本文以山西省西纵高速右玉至平鲁段路基路面第SG4合同段路面施工为工程依托,根据500m试验段总结得出的施工参数,进一步提炼形成了ATB-30粗粒式沥青碎石上基层成套施工技术,并在右玉至平鲁段后续路面工程施工中取得了成功应用,各项检测指标均满足设计及规范要求,颇具施工借鉴意义。 展开更多
关键词 ATB-30 粗粒式沥青碎石 上基层 施工参数
下载PDF
肝硬化伴上消化道出血患者外周血APRI的表达水平及临床意义
15
作者 张小晴 石秀芳 《检验医学与临床》 2024年第5期667-670,共4页
目的 探讨肝硬化并发上消化道出血患者外周血天门冬氨酸氨基转移酶(AST)和外周血血小板(PLT)比率指数(APRI)的表达水平及临床意义。方法 选取该院在2018年12月至2021年11月收治的肝硬化患者89例作为研究对象,按照是否并发上消化道出血... 目的 探讨肝硬化并发上消化道出血患者外周血天门冬氨酸氨基转移酶(AST)和外周血血小板(PLT)比率指数(APRI)的表达水平及临床意义。方法 选取该院在2018年12月至2021年11月收治的肝硬化患者89例作为研究对象,按照是否并发上消化道出血分为出血组(44例)和非出血组(45例)。检测并比较两组患者外周血凝血酶原时间(PT)、纤维蛋白原(FIB)、清蛋白-胆红素(ALBI)及APRI水平,绘制受试者工作特征(ROC)曲线分析APRI及FIB对肝硬化患者并发上消化道出血的预测价值。比较出血组不同临床资料患者的外周血APRI表达水平。结果 出血组外周血APRI表达水平高于非出血组,而FIB水平低于非出血组,差异均有统计学意义(P<0.05)。ROC曲线分析结果显示,APRI预测肝硬化患者并发上消化道出血的曲线下面积(AUC)为0.714,灵敏度和特异度分别为71.1%和75.0%。出血组肝功能不同Child-Pugh分级患者APRI表达水平表现为A级患者<B级患者<C级患者,差异均有统计学意义(P<0.05);出血组的APRI表达水平表现为重度患者>中度患者>轻度患者,差异均有统计学意义(P<0.05);出血组6个月内死亡患者的APRI表达水平高于存活患者(P<0.05)。结论 肝硬化并发上消化道出血患者的外周血APRI表达水平明显升高,具有一定的预测价值,且外周血APRI表达水平与病情严重程度及预后有关,是潜在的疾病标志物。 展开更多
关键词 天门冬氨酸氨基转移酶和外周血血小板比率指数 肝硬化 上消化道出血 临床意义 表达水平
下载PDF
沿空留巷工作面新老采空区瓦斯综合抽采技术
16
作者 王树军 李乾荣 《能源与环保》 2024年第1期76-79,85,共5页
近年来沿空留巷应用愈加普遍,但在应用中挡矸支架在方便挂模注模的同时,形成抽屉式的半封闭空间,容易积聚瓦斯。此外,由于无煤柱隔离,首采面到末采面会逐渐形成一个大采空区。老采空区瓦斯受到二次甚至多次采动影响,连通新采空区积聚瓦... 近年来沿空留巷应用愈加普遍,但在应用中挡矸支架在方便挂模注模的同时,形成抽屉式的半封闭空间,容易积聚瓦斯。此外,由于无煤柱隔离,首采面到末采面会逐渐形成一个大采空区。老采空区瓦斯受到二次甚至多次采动影响,连通新采空区积聚瓦斯一并快速涌出,导致瓦斯超限风险频发,甚至酿成瓦斯事故。为此,进一步优化了长钻孔瓦斯治理技术,一方面,采用走向高位钻孔抽采裂隙带瓦斯;另一方面,施工倾向高位钻孔至老采空区顶板裂隙带,持续抽采新老采空区瓦斯,最大限度降低采空区及其顶板裂隙带瓦斯存量。通过新老采空区瓦斯综合抽采,工作面瓦斯治理效果显著。 展开更多
关键词 沿空留巷 高位钻孔 上隅角 采空区瓦斯
下载PDF
武汉软土地区地铁隧道长期沉降规律及原因分析
17
作者 柯洋 代帅 李谋思 《城市勘测》 2024年第3期204-208,共5页
以武汉地铁8号线出入段线矩形隧道为分析对象,将近5年的地铁运营监测沉降数据与隧道沿线工程地质条件、地下水及周边施工进行对比分析,系统研究地铁隧道长期沉降规律。结果表明,出入段线隧道最大累计沉降106.1 mm,且沿线形成了三个大的... 以武汉地铁8号线出入段线矩形隧道为分析对象,将近5年的地铁运营监测沉降数据与隧道沿线工程地质条件、地下水及周边施工进行对比分析,系统研究地铁隧道长期沉降规律。结果表明,出入段线隧道最大累计沉降106.1 mm,且沿线形成了三个大的沉降槽。隧道结构下卧软弱土层较厚且分布不均、地下水位及上盖物业开发是导致出入段线长期沉降的主要原因。轨道交通结构的长期沉降问题,需要结合“设计—施工—运营”统筹考虑。 展开更多
关键词 地铁隧道 软土地区 长期沉降 地下水位 上盖物业
下载PDF
成庄矿高位定向长钻孔瓦斯抽采技术
18
作者 侯利军 《晋控科学技术》 2024年第3期42-44,47,共4页
为了有效地解决采场和上隅角的瓦斯涌出过多等问题,以晋城蓝焰煤业股份有限公司成庄矿101采区为研究对象,采用ZYWL-6000DS定向钻机进行高位定向钻进,最大孔深600 m。根据“O”型圈原理和现场条件,优化了高位钻孔的布置高度。对高位定向... 为了有效地解决采场和上隅角的瓦斯涌出过多等问题,以晋城蓝焰煤业股份有限公司成庄矿101采区为研究对象,采用ZYWL-6000DS定向钻机进行高位定向钻进,最大孔深600 m。根据“O”型圈原理和现场条件,优化了高位钻孔的布置高度。对高位定向钻孔抽气监测结果进行了分析,发现该钻孔具有服务年限长、瓦斯抽采效果好等优点,单孔的瓦斯抽采纯量可达17.9~18.2 m3/min。随着回采工作面的推进,上隅角的瓦斯含量降低到了0.2%~0.4%,说明在高位钻孔下,瓦斯抽采效果明显,为回采工作的顺利进行提供了强有力保证。 展开更多
关键词 瓦斯抽采 高位定向钻孔 上隅角
下载PDF
国土空间规划体系下三明市建宁县的多级规划联编研究
19
作者 徐浩铭 《福建建筑》 2024年第3期25-29,共5页
新时期国土空间规划体系下,为了进一步提高规划编制效率、节省编制经费,全国各地陆续开展了不同等级、不同区域的规划联编工作。三明市建宁县作为闽赣两省交界的山区县,资源禀赋和地理特征在福建省内具有较强的代表性。同时,作为人口小... 新时期国土空间规划体系下,为了进一步提高规划编制效率、节省编制经费,全国各地陆续开展了不同等级、不同区域的规划联编工作。三明市建宁县作为闽赣两省交界的山区县,资源禀赋和地理特征在福建省内具有较强的代表性。同时,作为人口小县,社会经济发展水平和政府财力较沿海发达地区相比也较为有限,具有很强的联编现实需求。基于近年来建宁县在县、镇、村三级规划联编上创新性的实践,探索多级规划联编及上下传导的相关经验,为福建省乃至全国其他地区提供相关的理论支撑和经验借鉴。 展开更多
关键词 国土空间规划体系 多级联编 上下传导 建宁县
下载PDF
ON THE RELATIONSHIPS BETWEEN THE UNUSUAL TRACK OF TYPHOON MORAKOT(0908)AND THE UPPER WESTERLY TROUGH 被引量:2
20
作者 费建芳 李波 +1 位作者 黄小刚 程小平 《Journal of Tropical Meteorology》 SCIE 2012年第2期187-194,共8页
In this paper,by carrying out sensitivity tests of initial conditions and diagnostic analysis of physical fields,the impact factors and the physical mechanism of the unusual track of Morakot in the Taiwan Strait are d... In this paper,by carrying out sensitivity tests of initial conditions and diagnostic analysis of physical fields,the impact factors and the physical mechanism of the unusual track of Morakot in the Taiwan Strait are discussed and examined based on the potential vorticity(PV)inversion.The diagnostic results of NCEP data showed that Morakot's track was mainly steered by the subtropical high.The breaking of a high-pressure zone was the main cause for the northward turn of Morakot.A sensitivity test of initial conditions showed that the existence of upper-level trough was the leading factor for the breaking of the high-pressure zone.When the intensity was strengthened of the upper-level trough at initial time,the high-pressure zone would break ahead of time,leading to the early northward turn of Morakot.Conversely,when the intensity was weakened,the breaking of the high-pressure zone would be delayed.Especially,when the intensity was weakened to a certain extent,the high-pressure zone would not break.The typhoon,steered by the easterly flow to the south of the high-pressure zone,would keep moving westward,with no turn in the test.The diagnostic analysis of the physical fields based on the sensitivity test revealed that positive vorticity advection and cold advection associated with the upper-level trough weakened the intensity of the high-pressure zone.The upper-level trough affected typhoon's track indirectly by influencing the high-pressure zone. 展开更多
关键词 TYPHOON unusual track potential vorticity(PV)inversion upper-level trough
下载PDF
上一页 1 2 30 下一页 到第
使用帮助 返回顶部