期刊文献+
共找到1,829篇文章
< 1 2 92 >
每页显示 20 50 100
Baoziwan-Majiashan Area of Jiyuan Oilfield Analysis of Reservoir Characteristics and Main Control Factors in Long 4 5 Section
1
作者 Zhengxi Cui Zhipeng Zhang Mingling Shen 《Open Journal of Yangtze Oil and Gas》 2024年第2期48-64,共17页
Based on the sheet, scanning electron microscope and high pressure mercury analysis method, this paper takes Jiyuan oilfield-Ma Jia mountain district 4 5 sandstone reservoir as the research object, from the reservoir ... Based on the sheet, scanning electron microscope and high pressure mercury analysis method, this paper takes Jiyuan oilfield-Ma Jia mountain district 4 5 sandstone reservoir as the research object, from the reservoir petrology, pore type and porosity, permeability, the system analyzed the reservoir characteristics and its control factors. The results show that the sandstone in the 4 5 section of Baoziwan-Majiashan area of Jiyuan oilfield is fine in size and high in filling content. The pore types were dominated by intergranular pores and dissolved pores, with a low face rate. The reservoir property is relatively poor, with mean porosity of 11.11% and mean permeability of 1.16 × 10<sup>−</sup><sup>3</sup> µm<sup>2</sup>. In the low porous, low otonic background, the development of relatively high pore hypertonic areas. Compaction and cementation should play a destructive role in reservoir properties, and dissolution should play a positive role in reservoir properties. Compaction adjusts the migration of clay minerals and miscellaneous bases in the original sediment in the study area, greatly reducing the porosity and permeability of the reservoir;the development of the cement cement, carbonate cementation and some quartz secondary compounds reduces the storage space;the dissolution effect, especially the secondary dissolution pores of the reservoir, which obviously improves the properties of the reservoir. 展开更多
关键词 Ordos Basin Jiyuan area Reservoir Characteristics Reservoir Control Factor Long 4 5 section
下载PDF
Relationship between sonographically measured median nerve cross-sectional area and presence of peripheral neuropathy in diabetic subjects 被引量:8
2
作者 Fredrick ANDrew Attah Christianah Mopelola Asaleye +3 位作者 Adeleye Dorcas Omisore Babatope Ayodeji Kolawole Adeniyi Sunday Aderibigbe Mathew Alo 《World Journal of Diabetes》 SCIE CAS 2019年第1期47-56,共10页
BACKGROUND Neuropathy is a common complication of diabetes mellitus resulting from direct damage by hyperglycemia to the nerves and/or ischemia by microvascular injury to the endoneurial vessels which supply the nerve... BACKGROUND Neuropathy is a common complication of diabetes mellitus resulting from direct damage by hyperglycemia to the nerves and/or ischemia by microvascular injury to the endoneurial vessels which supply the nerves. Median nerve is one of the peripheral nerves commonly affected in diabetic neuropathy. The median nerve size has been studied in non-Nigerian diabetic populations. In attempt to contribute to existing literature, a study in a Nigerian population is needed.AIM To evaluate the cross-sectional area(CSA) of the median nerve using B-mode ultrasonography(USS) and the presence of peripheral neuropathy(PN) in a cohort of adult diabetic Nigerians.METHODS Demographic and anthropometric data of 85 adult diabetes mellitus(DM) and 85 age-and sex-matched apparently healthy control(HC) subjects were taken. A complete physical examination was performed on all study subjects to determine the presence of PN and modified Michigan Neuropathy Screening Instrument(MNSI) was used to grade its severity. Venous blood was taken from the study subjects for fasting lipid profile(FLP), fasting blood glucose(FBG) and glycated haemoglobin(HbA1 c) while their MN CSA was evaluated at a point 5 cm proximal to(5 cmCATL) and at the carpal tunnel(CATL) by high-resolution Bmode USS. Data was analysed using SPSS version 22.RESULTS The mean MN CSA was significantly thicker in DM subjects compared to the HC at 5 cmCATL(P < 0.01) and at the CATL(P < 0.01) on both sides. The presence of diabetic peripheral neuropathy(DPN) further increased the MN CSA at the CATL(P < 0.05) but not at 5 cmCATL(P > 0.05). However, the severity of DPN had no additional effect on MN CSA 5 cm proximal to and at the CATL. There was no significant association between MN CSA and duration of DM and glycemic control.CONCLUSION Thickening of the MN CSA at 5 cmCATL and CATL is seen in DM. Presence of DPN is associated with worse thickening of the MN CSA at the CATL but not at5 cmCATL. Severity of DPN, duration of DM, and glycemic control had no additional effect on the MN CSA. 展开更多
关键词 MEDIAN nerve cross-sectional area SONOGRAPHY DIABETICS Peripheral NEUROPATHY
下载PDF
Ultrasonographic measurement of median nerve cross-sectional area reference values in a healthy Han population from Guiyang,China 被引量:3
3
作者 Jun Chen Shan Wu Jun Ren 《Neural Regeneration Research》 SCIE CAS CSCD 2011年第24期1883-1887,共5页
High-resolution ultrasonography was used to analyze the nerve cross-sectional area (CSA) of the median nerve at 7 sites: the wrist crease, pisiform bone, hamate bone, 6 cm proximal to the tip of the wrist crease, p... High-resolution ultrasonography was used to analyze the nerve cross-sectional area (CSA) of the median nerve at 7 sites: the wrist crease, pisiform bone, hamate bone, 6 cm proximal to the tip of the wrist crease, proximal forearm (where the nerve enters the pronator teres muscle), 4 cm proximal to the tip of the medial epicondyle, and mid-humerus (mid-point between elbow crease and axilla) in 200 healthy volunteers from Guiyang, China. Results showed similar CSA values between the left and right sides, but the CSA 6 cm proximal to the tip of the wrist crease, proximal forearm, 4 cm proximal to tip of the medial epicondyle, and mid-humerus in males was greater than that of females. Moreover, CSA values at the wrist crease, pisiform bone, and hamate bone were greater in the middle-aged and old groups when compared to the young group, and correlated with body mass and height. Thus, reference values of median nerve CSA of the upper limbs can facilitate the analysis of abnormal nerve conditions. 展开更多
关键词 ULTRASONOGRAPHY median nerve cross-sectional area Guiyang Han nationality
下载PDF
Does the ratio of the carpal tunnel inlet and outlet cross-sectional areas in the median nerve reflect carpal tunnel syndrome severity? 被引量:6
4
作者 Li Zhang Aierken Rehemutula +3 位作者 Feng Peng Cong Yu Tian-bin Wang Lin Chen 《Neural Regeneration Research》 SCIE CAS CSCD 2015年第7期1172-1176,共5页
Although ultrasound measurements have been used in previous studies on carpal tunnel syndrome to visualize injury to the median nerve, whether such ultrasound data can indicate the severity of carpal tunnel syndrome r... Although ultrasound measurements have been used in previous studies on carpal tunnel syndrome to visualize injury to the median nerve, whether such ultrasound data can indicate the severity of carpal tunnel syndrome remains controversial. The cross-sectional areas of the median nerve at the tunnel inlet and outlet can show swelling and compression of the nerve at the carpal. We hypothesized that the ratio of the cross-sectional areas of the median nerve at the carpal tunnel inlet to outlet accurately reflects the severity of carpal tunnel syndrome. To test this, high-resolution ultrasound with a linear array transducer at 5–17 MHz was used to assess 77 patients with carpal tunnel syndrome. The results showed that the cut-off point for the inlet-to-outlet ratio was 1.14. Significant differences in the inlet-to-outlet ratio were found among patients with mild, moderate, and severe carpal tunnel syndrome. The cut-off point in the ratio of cross-sectional areas of the median nerve was 1.29 between mild and more severe(moderate and severe) carpal tunnel syndrome patients with 64.7% sensitivity and 72.7% specificity. The cut-off point in the ratio of cross-sectional areas of the median nerve was 1.52 between the moderate and severe carpal tunnel syndrome patients with 80.0% sensitivity and 64.7% specificity. These results suggest that the inlet-to-outlet ratio reflected the severity of carpal tunnel syndrome. 展开更多
关键词 nerve regeneration peripheral nerve injury ultrasonography carpal tunnel syndrome diagnosis cross-sectional area classification clinical laboratory technique electrodiagnosis median nerve 973 Program neural regeneration
下载PDF
Modeling and Analysis of Transitional Tube with Constant Sectional Area along Derivative Central Route 被引量:1
5
作者 MENG Xiang-bao TONG Bao-guo +1 位作者 PAN Zi-jian LI Hai-xing 《Computer Aided Drafting,Design and Manufacturing》 2011年第2期19-24,共6页
Firstly, sample square-circular transition tube along straight central route was modeled on CATIA software. The parameters are as follows: let the tube length is L, and the constant cross section area is S, and S = ... Firstly, sample square-circular transition tube along straight central route was modeled on CATIA software. The parameters are as follows: let the tube length is L, and the constant cross section area is S, and S = πR^2 = a2, in which R stands for the circle radius on one end, and a the square side length on the other end; set up the coordinate system with OX axis on the central route in which the origin O is on centroid of the square end and assume the cross section size at x as the square shaped with all four comers filleted in radius r which is proportional to x, that is, the linear slope of r is R/L, thus, both values r and square side length ax can be attained on the constant cross section area assumption. Secondly, some sample polygonal-circular transition tubes along straight, circular and helical central route were implemented similarly. Thirdly, numerical analysis of stress and displacement of these tubes were carried out on MSC/PATRAN software which are important to the distribution of turbulent flow and the layout of these transitional tube structures. 展开更多
关键词 parametric modeling transitional tube constant cross section area finite element analysis CATIA application
下载PDF
Optimal Minimum Number of CT Slices Required to Measure Cross Sectional Areas of Small Pulmonary Vessels
6
作者 Shingo Sakamoto Shoichiro Matsushita +8 位作者 Akiyuki Kotoku Hayato Tomita Yuki Saito Shinji Saruya Shin Matsuoka Tsuneo Yamashiro Atsuko Fujikawa Kunihiro Yagihashi Yasuo Nakajima 《Open Journal of Medical Imaging》 2015年第2期71-77,共7页
The cross-sectional area (CSA) of small pulmonary vessels can be quantified by CT, which is a reliable method of evaluating vascular alterations in such vessels. However, the optimal number of slices required for accu... The cross-sectional area (CSA) of small pulmonary vessels can be quantified by CT, which is a reliable method of evaluating vascular alterations in such vessels. However, the optimal number of slices required for accurate quantitation remains unknown. We evaluated relationships among all slices at 10-mm interval and all slices at 3-cm interval, 6-cm interval, and 3-slices and found the closest correlation (0.939) between all slices at 10-mm intervals and 3-cm intervals. Thus, all slices at 3-cm intervals are suitable for accurately measuring CSA. 展开更多
关键词 COMPUTED Tomography cross-sectional area PULMONARY VESSELS Quantitative Analysis
下载PDF
Cause of over Water Quality Standard and Control Measures of State-controlled Sections in Northern Water-deficient Area of Jiangsu 被引量:5
7
作者 胡永定 韩宝平 +1 位作者 钱新 袁兴程 《Meteorological and Environmental Research》 CAS 2010年第2期91-94,99,共5页
Taking state-controlled section of Xuzhou Peiyan river as an example,the current water quality was monitored,and the cause of over water quality standard was analyzed.The results showed that the pollutants of Peiyan r... Taking state-controlled section of Xuzhou Peiyan river as an example,the current water quality was monitored,and the cause of over water quality standard was analyzed.The results showed that the pollutants of Peiyan river were mainly from the urban river segment,and the immediate cause of over standard was tributary pollutants in urban river segment with the runoff into rivers.So we should strengthen the maintenance of drainage control and gate-han,accelerate the construction of urban wastewater treatment facilities and supporting pipe network,promote rural decentralized sewage treatment,prevent and control livestock and poultry pollution,pesticides and fertilizers pollution,and intercept non-point source pollution by using eco-technology. 展开更多
关键词 State-controlled sections Cause analysis Control measures Water-deficient area China
下载PDF
Saddle-Dolomite-Bearing Fracture Fillings and Records of Hot Brine Activity in the Jialingjiang Formation,Libixia Section,Hechuan Area of Chongqing City 被引量:1
8
作者 HUANG Keke ZHONG Yijiang +2 位作者 HUANG Sijing LI Xiaoning FENG Mingshi 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2016年第1期195-208,共14页
Most vein minerals deposited in fractures of the Jialingjiang Formation from Libixia section, Hechan area include a large amount of saddle dolomite and accompanying celestite, calcite and fluorite. This study analyzed... Most vein minerals deposited in fractures of the Jialingjiang Formation from Libixia section, Hechan area include a large amount of saddle dolomite and accompanying celestite, calcite and fluorite. This study analyzed the nature, source, evolution of the fluids by plane-light petrography, fluid-inclusion methods, cathodoluminescence images, and stable isotopic compositions. The homogenization temperatures of two-phase aqueous fluid inclusions in dolomite range between 100 and 270℃. Combined with the jlSO data, it is suggested that the fluid responsible for the precipitation of fracture fillings have δ18O values between 10%o and 18‰ (relative to SMOW). The saddle dolomite and the accompanying minerals were the result of activity of dense brines at elevated temperatures. Moreover, analysis shows that the fluid was derived from a mixture of marine-derived brine and deeper circulating flow. This fluid was enriched in Sr during diagenesis and formed celestite in fracture and for regional mineralization. Dissolution of saddle dolomite was attributed to the cooling of Mg/Ca-decreased fluids, which may relate to a leaching of gypsum to celestite in surrounding carbonates. 展开更多
关键词 Libixia section Jialingjiang Formation saddle dolomite hot brine Hechuan area CHONGQING
下载PDF
Method of Fault Area & Section Location for Non-solidly Earthed Distribution System 被引量:28
9
作者 ZHENG Guping JIANG Chao LI Gang QI Zheng YANG Yihan 《中国电机工程学报》 EI CSCD 北大核心 2012年第13期I0014-I0014,197,共1页
中国中压配电网以架空线为主,多为小电流系统,单相接地故障占到电网故障总数的80%以上,但中国配网自动化系统基本上没有小电流接地故障定位功能,使配网自动化系统在提高可靠性的作用上大打折扣。给出一种小电流接地故障区段定位新... 中国中压配电网以架空线为主,多为小电流系统,单相接地故障占到电网故障总数的80%以上,但中国配网自动化系统基本上没有小电流接地故障定位功能,使配网自动化系统在提高可靠性的作用上大打折扣。给出一种小电流接地故障区段定位新方法,在线路上配置广域相量测量固定测点,获取小电流电网单相接地故障特征信息。基于测点相邻矩阵区段起始测点标识向量和故障路径标识向量概念,提出确定故障区间边界节点算法。物理模拟实验和挂网测试表明:该故障分区分段定位方法能够在线求解小电流接地故障段边界节点,缩小线路维护巡视范围。确定故障区间边界节点算法还可用于确定故障区相关负荷开关,为线路维护和馈线自动化提供依据。 展开更多
关键词 断层破碎带 配电自动化系统 单相接地故障 小电流系统 小电流接地 架空线路 电压分布 故障监测
下载PDF
Tomography for Q of the Eastern Section of the Tianshan Area from High-frequency Attenuation of S-wave
10
作者 Li Jin Zhou Longquan +1 位作者 Wang Huilin Xiang Yuan 《Earthquake Research in China》 CSCD 2018年第1期28-39,共12页
Based on the waveform data of 5,076 local earthquakes recorded at 25 stations in Xinjiang during the period from 2009 to 2014 and the observation reports provided by the Xinjiang Digital Seismic Network,a data set of ... Based on the waveform data of 5,076 local earthquakes recorded at 25 stations in Xinjiang during the period from 2009 to 2014 and the observation reports provided by the Xinjiang Digital Seismic Network,a data set of 19,140 attenuation factors t*is obtained by fitting the high-frequency attenuation of S-wave spectra with a genetic algorithm. The spatial distribution of Q_S is determined by inverting the t*data with seismic tomography. The results show that the average Q0 in eastern Tianshan is 520,and there is a significant correlation between the Q_S value distribution or attenuation characteristics it disclosed and the surface structure of the study area. The Q_S value is lower in the intersection area of the mountain basin which is located on the north and south sides of the Tianshan Mountains,and the high Q_S distribution is more concentrated inside the Tianshan orogenic belt. The M≥6. 0 earthquakes have been basically located in the Low-Q_S region since 1900. 24 high heat flow points in eastern Tianshan are located at the north and south of Tianshan Mountains where low Q_S exists,indicating a negative correlation. In addition,there is a positive correlation between the velocity structure and the attenuation structure in the study area,which reflects the consistency of the 2-D attenuation structure with the velocity structure and the two-dimensional density structure. 展开更多
关键词 Eastern section of the TIANSHAN area HIGH-FREQUENCY ATTENUATION of S-WAVE ATTENUATION operator t* Q TOMOGRAPHY
下载PDF
Effect of combined spinal and epidural anesthesia on the level of pain media, stress indicators and inflammatory factors in patients undergoing high altitude cesarean section
11
作者 Tian Shun Huang Cui-yuan +1 位作者 Pu Le-hua Tian Yu 《Journal of Hainan Medical University》 2019年第17期71-75,共5页
Objective: To discuss the effect of combined spinal and epidural anesthesia on the levels of pain media, stress indicators and inflammatory factors in patients undergoing high altitude cesarean section. Methods: Eight... Objective: To discuss the effect of combined spinal and epidural anesthesia on the levels of pain media, stress indicators and inflammatory factors in patients undergoing high altitude cesarean section. Methods: Eighty patients who underwent cesarean section in our hospital from January 2017 to April 2019 were enrolled in the hospital. They were divided into two groups according to the patient's anesthesia. Fourty patients receiving epidural anesthesia were included in the control group, and another 40 patients received lumbar stiffness. The combined anesthesia patient was included in the observation group. Changes in pain mediators [Serum neuropeptide Y (NPY), endorphin (β-EP), substance P (SP)], stress indicators [Serum cortisol (Cor), C-peptide (C-P), advanced oxidative protein product (AOPP)], inflammatory factor levels [Hypersensitive C-reactive protein (hs-CRP), tumor necrosis factor-alpha (TNF-α)], and immunoglobulin levels [Serum IgA, IgG, IgM] were compared between the two groups. Results: Before anesthesia, there were no significant difference in pain media, stress index, inflammatory factor level and immunoglobulin level between the two groups (P>0.05). At 12 h after operation, the two groups of patients were NPY, β-EP, SP, Cor. The levels of C-P, AOPP, hs-CRP and TNF-α were higher than those before operation (P<0.05). The levels of IgA, IgG and IgM were lower than those before operation (P<0.05). Among them, observation group NPY, β-EP, SP, Cor, C-P, AOPP, hs-CRP and TNF-α were significantly lower than those of the control group (P<0.05). The serum levels of IgA, IgG and IgM were significantly higher than those of the control group (P<0.05). Conclusion: Combined spinal and epidural anesthesia can more effectively alleviate maternal pain in high altitude cesarean section, more effectively reduce the inflammatory stress response of patients, promote the humoral immune function of patients, and is beneficial to the early recovery of maternal postoperative, and has high clinical value. 展开更多
关键词 COMBINED SPINAL and EPIDURAL anesthesia High ALTITUDE area CESareaN section surgery PAIN Stress Inflammation
下载PDF
新疆生产建设兵团石河子地区心房颤动流行病学调查研究
12
作者 张强 唐闽 +5 位作者 邝雅杰 刘丹 赵雪燕 赵媛媛 张琳 奴尔巴合提 《中国全科医学》 CAS 北大核心 2024年第33期4162-4167,共6页
背景心房颤动(简称房颤)是临床上较为常见的心律失常,具有高患病率、高致残率、高治疗费的特点,严重影响患者生活质量,国内不同地区以及不同人群中的房颤患病率有很大差异,目前新疆生产建设兵团地区对于房颤的患病率无较大规模流行病学... 背景心房颤动(简称房颤)是临床上较为常见的心律失常,具有高患病率、高致残率、高治疗费的特点,严重影响患者生活质量,国内不同地区以及不同人群中的房颤患病率有很大差异,目前新疆生产建设兵团地区对于房颤的患病率无较大规模流行病学调查。目的了解新疆生产建设兵团石河子地区房颤的患病率、相关的危因素、规范化的治疗状况,为本地区房颤预防、管理、治疗提供可靠数据支持。方法采用横断面年龄比例1∶10分层随机抽样调查2021年5月—2023年6月新疆生产建设兵团石河子地区18个农牧团场及市区18岁及以上常住居民63079人。采用问卷收集患者基线资料、房颤流行病学、知晓率及治疗情况。将患者分为房颤组(n=737)与非房颤组(n=62342)。采用多因素Logistic回归分析探究房颤发生的影响因素。结果共纳入新疆生产建设兵团第八师石河子地区居民63079人,平均年龄(54.9±15.3)岁。筛查出房颤患者737人,患病率为1.17%,根据年龄校正后患病率为1.12%。筛查人群中房颤知晓率仅为1.62%(1021/63079),其中确诊房颤人群中房颤知晓率52.78%(389/737)。18~39岁、40~49岁、50~59岁、60~69岁、70~79岁、≥80岁房颤患病率分别为0.05%(5/9964)、0.32%(29/9076)、0.62%(135/21686)、1.28%(151/11810)、3.05%(207/6776)、5.57%(210/3767);男性和女性房颤患病率分别为1.60%(441/27591)、0.83%(296/35488);汉族、回族、维吾尔族、哈萨克族、其他民族房颤患病率分别为1.20%(720/60014)、0.70%(7/1007)、0.62%(7/1130)、1.67%(2/120)、1.41%(1/171);城市区域及农牧团场区域房颤患病率分别为0.79%(350/44504)、2.08%(387/18575)。房颤组与非房颤组年龄、性别、年龄段分布、居住区域、受教育程度比较,差异有统计学意义(P<0.05)。房颤组吸烟、饮酒、高血压、冠心病、2型糖尿病、高脂血症、慢性心力衰竭、脑血管疾病、心脏瓣膜病、慢性肺部疾病、睡眠呼吸暂停综合征、甲状腺功能异常、外周血管疾病、肿瘤比例高于非房颤组(P<0.05)。多因素Logistic回归分析结果显示,年龄、性别、饮酒、高血压、心脏瓣膜病、慢性心力衰竭、甲状腺功能异常、睡眠呼吸暂停综合征、肿瘤为房颤发生的影响因素(P<0.05)。新发现房颤85例(11.53%)、阵发性房颤257例(34.87%)、持续性房颤178例(21.16%)、永久性房颤217例(29.44%);口服抗凝药物360例、行房颤射频消融术或一站式治疗23例,本地区房颤治疗率51.96%。房颤患者中规范化治疗、未规范化治疗和未治疗分别为360例(48.85%)、21例(2.85%)、356例(48.30%),新发现房颤、阵发性房颤、持续性房颤、永久性房颤的规划化治疗率分别为11.11%、28.89%、24.72%、35.28%,不同类型房颤规划化治疗率比较,差异有统计学意义(χ^(2)=18.918,P=0.004)。结论新疆生产建设兵团石河子地区房颤患病率基本持平于全国水平,危险因素与国内外研究相近,但人群中房颤知晓率、及房颤规范化治疗率明显偏低,情况不容乐观。 展开更多
关键词 心房颤动 流行病学研究 患病率 石河子地区 横断面研究
下载PDF
煤矿掘进巷道断面尺寸变化对噪声传播的影响
13
作者 杨明 贾改妮 +2 位作者 全星苑 张学博 刘毛毛 《中国安全科学学报》 CAS CSCD 北大核心 2024年第4期77-86,共10页
为研究煤矿掘进巷道长空间内断面尺寸变化对噪声传播的影响,采用仿真模拟方法研究巷道内噪声传播,分析煤矿掘进巷道断面积大小、断面形状及断面面积突变率的变化对巷道内噪声传播影响。结果表明:煤矿掘进巷道内断面面积大小、断面形状... 为研究煤矿掘进巷道长空间内断面尺寸变化对噪声传播的影响,采用仿真模拟方法研究巷道内噪声传播,分析煤矿掘进巷道断面积大小、断面形状及断面面积突变率的变化对巷道内噪声传播影响。结果表明:煤矿掘进巷道内断面面积大小、断面形状及断面面积突变率均会影响巷道内噪声的传播,当噪声源功率、频率相同时,声压级衰减随巷道截面积增大而增大;对于给定的断面面积(18 m2),当断面形状不同时,声压级衰减也不同,且断面形状为拱形时会产生明显的声聚焦效应,不利于噪声衰减;当断面面积发生突变时,巷道内的声压级分布会有所变化,其中断面面积由大变小时不利于噪声的衰减,断面面积由小变大时仅影响突变后的声场,而对巷道内整体声压级影响并不明显;巷道内噪声衰减现场测试与数值模拟结果基本一致,验证了搭建的模型及模拟结果的可靠性。 展开更多
关键词 煤矿掘进巷道 断面形状 噪声传播 掘进机 断面面积突变率
下载PDF
国家文化公园主体功能区识别路径构建——以长江国家文化公园湖北段为例的实证研究
14
作者 贺慧 张彤 +2 位作者 张庆昊 董凤千 张学标 《中国园林》 CSCD 北大核心 2024年第7期38-44,共7页
国家文化公园是国家公园建设模式的重要创新,其主体功能区划定是落实总体建设要求、保障基础工程有效实施的重要基础,但目前仍存在识别路径、技术方法模糊不清的问题。尝试在解读主体功能区内涵的基础上,以系统耦合思维构建“文化生态... 国家文化公园是国家公园建设模式的重要创新,其主体功能区划定是落实总体建设要求、保障基础工程有效实施的重要基础,但目前仍存在识别路径、技术方法模糊不清的问题。尝试在解读主体功能区内涵的基础上,以系统耦合思维构建“文化生态双维度耦合-保护利用双象限评价-空间功能四分区重构”的主体功能区识别路径,对长江国家文化公园的湖北段进行实证研究。结果表明,主体功能区呈现出以提供基础条件的管控保护区为基底、以文化引领的主题展示区为核心、以文旅融合区和传统利用区为外延圈层的空间分布特征,与大运河国家文化公园主体功能区布局模式相符。期望在丰富国家文化公园理论研究的同时,助力长江国家文化公园的科学布局与规划编制。 展开更多
关键词 风景园林 国家文化公园 主体功能区 湖北段
下载PDF
鄂尔多斯盆地陇东地区延长组层序地层再认识及地质意义
15
作者 惠潇 侯云超 +4 位作者 陈修 龙盛芳 喻建 赵俊峰 刘永涛 《沉积学报》 CAS CSCD 北大核心 2024年第5期1553-1567,共15页
【目的】最新三维地震资料显示延长组存在大量强反射同相轴前积现象,与传统“平起平落、等厚分布”的地层方案差异较大,为重新认识延长组地层格架提供了新视角。【方法】通过岩心观察、井震标定及三维地震解释,结合地震反演技术,对鄂尔... 【目的】最新三维地震资料显示延长组存在大量强反射同相轴前积现象,与传统“平起平落、等厚分布”的地层方案差异较大,为重新认识延长组地层格架提供了新视角。【方法】通过岩心观察、井震标定及三维地震解释,结合地震反演技术,对鄂尔多斯盆地陇东地区的地震相、层序地层及沉积体系等进行系统研究。【结果】延长组地震强反射连续同相轴可指示湖泛面凝缩层沉积。不同方向的地震相特征差异较大,平行物源方向的地震剖面包括中等振幅中等连续性亚平行结构、强振幅强连续性前积结构、弱振幅差连续性乱岗状结构三类,其中前积结构“穿层”最明显;垂直物源方向包括强振幅强连续性平行结构、强—中振幅中连续性丘状结构、弱振幅差连续性乱岗状结构三类地震相。陇东地区延长组湖盆充填演化经历了多期快速湖侵、缓慢湖退的震荡过程,可划分为多期湖侵—湖退体系域(T-R)组成的三级层序单元,呈透镜状依次向湖中心进积叠置,发育“斜坡富泥、两端富砂”的沉积序列。【结论】新的层序格架与传统等厚沉积模式存在三个方面的差异:一是烃源岩标志层没变,单井之间的对应关系变;二是延长组湖盆范围没变,湖盆充填演化过程变;三是砂岩总体分布规律没变,砂层之间的连通性变。 展开更多
关键词 层序地层 T-R体系域 凝缩层 前积 延长组 陇东地区
下载PDF
基于节段模型测力方法的塔式起重机风荷载特性研究
16
作者 李寿科 雷佳妍 +4 位作者 杨易归 林斌 郭凡 彭雄 孙洪鑫 《铁道科学与工程学报》 EI CAS CSCD 北大核心 2024年第7期2884-2896,共13页
塔式起重机被广泛应用于铁道工程和土木工程施工过程,属于高耸结构体系,风荷载是塔式起重机结构设计的控制性荷载。为完善《塔式起重机设计规范》(GB/T 13752—2017)和《建筑结构荷载规范》(GB 50009—2012)中的塔式起重机斜风向设计风... 塔式起重机被广泛应用于铁道工程和土木工程施工过程,属于高耸结构体系,风荷载是塔式起重机结构设计的控制性荷载。为完善《塔式起重机设计规范》(GB/T 13752—2017)和《建筑结构荷载规范》(GB 50009—2012)中的塔式起重机斜风向设计风荷载计算方法,解决风向、吊臂、平衡臂位置等因素对塔式起重机遮挡和干扰引起的设计风荷载计算问题。选取平头塔式起重机为研究对象,对塔身、吊臂、平衡臂进行多工况的节段模型测力风洞试验,研究湍流强度、节段干扰和遮挡等因素对塔式起重机节段风荷载特性的影响规律,研究不同风向下节段阻力系数分布规律,对比标准化阻力系数与当前主要规范的异同,进而探讨节段斜风向标准化阻力系数计算方法。研究结果表明湍流强度对节段阻力系数影响较小,可忽略,而平衡臂和吊臂相邻节段的干扰会减小测试节段的阻力系数;在斜风向下,由于吊臂和平衡臂之间存在相邻节段干扰,国内外规范方法的计算值均会大于干扰工况的节段风洞试验值;当前主要国家规范规定的垂直风向塔身、吊臂、平衡臂阻力系数与风洞试验测得的阻力系数值较为接近,基于风洞试验结果给出典型风向的塔式起重机各节段的风荷载系数取值可用于结构设计;基于风洞试验测试结果推导的塔式起重机斜风向风荷载计算方法具有较好的拟合效果。研究成果可推荐相关工程应用,可为相关规范的修改或补充提供参考。 展开更多
关键词 塔式起重机 风洞试验 节段模型 阻力系数 有效投影面积 角度风荷载
下载PDF
腰椎管狭窄与马尾神经冗余关系的MRI形态学定量分析
17
作者 刘英 郭家川 +1 位作者 李旭雪 陈君蓉 《医学影像学杂志》 2024年第9期123-126,共4页
目的探讨应用MRI分析腰椎管狭窄与马尾神经冗余(redundant nerve roots,RNRs)之间的关系。方法选取我院临床诊断为腰椎管狭窄患者155例的MRI资料。根据矢状位T2WI马尾神经形态将患者分为RNRs阳性组和RNRs阴性组,测量并记录狭窄节段椎管... 目的探讨应用MRI分析腰椎管狭窄与马尾神经冗余(redundant nerve roots,RNRs)之间的关系。方法选取我院临床诊断为腰椎管狭窄患者155例的MRI资料。根据矢状位T2WI马尾神经形态将患者分为RNRs阳性组和RNRs阴性组,测量并记录狭窄节段椎管硬膜囊横截面积及硬膜囊前后径,统计分析RNRs阳性组和RNRs阴性组之间硬膜囊横截面积、硬膜囊前后径、椎管狭窄程度的差异,进一步分析RNAs阳性组椎管不同狭窄程度间马尾神经冗余长度的差异。结果腰椎管狭窄患者中马尾神经冗余的发生率为34.2%。RNRs阳性组平均年龄大于RNRs阴性组,腰椎管最窄层面平均硬膜囊横截面积及硬膜囊前后径均小于RNRs阴性组,椎管狭窄程度大于RNRs阴性组,差异均有统计学意义(P均<0.05)。RNRs阳性组女性发生率较男性稍高(56.6%vs 43.4%),但差异无统计学意义(P>0.05);RNRs阳性组椎管不同狭窄程度间马尾神经冗余长度差异具有统计学意义(P<0.05)。结论RNRs是一种特殊的影像学表现,常见于较严重的腰椎管狭窄患者,能够被MRI清晰地展现,为腰椎管狭窄症的明确诊断提供了重要的依据。 展开更多
关键词 腰椎管狭窄 硬膜囊横截面积 马尾神经冗余 磁共振成像
下载PDF
玛西斜坡区风城组高含盐致密储集层流体识别
18
作者 毛锐 白雨 +1 位作者 王盼 黄志强 《新疆石油地质》 CAS CSCD 北大核心 2024年第3期279-285,共7页
准噶尔盆地玛西斜坡区二叠系风城组发育碱湖沉积的高含盐致密储集层,其油水关系复杂,流体识别难度大。利用岩性扫描测井资料构建饱含盐水地层热中子宏观俘获截面,并利用测井热中子宏观俘获截面与饱含盐水地层热中子宏观俘获截面的差值... 准噶尔盆地玛西斜坡区二叠系风城组发育碱湖沉积的高含盐致密储集层,其油水关系复杂,流体识别难度大。利用岩性扫描测井资料构建饱含盐水地层热中子宏观俘获截面,并利用测井热中子宏观俘获截面与饱含盐水地层热中子宏观俘获截面的差值构建含油性敏感因子,再利用氯元素相对产额与总孔隙度比值构建含盐度敏感因子,将含油性敏感因子与含盐度敏感因子交会形成流体识别图版。实例应用表明,利用该流体识别图版可以对储集层流体性质进行准确判断,为试油选层提供依据。 展开更多
关键词 准噶尔盆地 玛西斜坡区 风城组 致密储集层 热中子宏观俘获截面 岩性扫描测井 流体识别
下载PDF
基于黄金分割搜索的电压暂降域快速识别方法
19
作者 雷敏 汤迪虎 +2 位作者 兰征 李勇 吴艺松 《湖南工业大学学报》 2024年第2期25-32,共8页
针对大型复杂电网中敏感负荷的电压暂降域难以准确识别的问题,提出一种基于黄金分割搜索的电压暂降域快速识别方法。首先,求得网络中发生各类短路故障时敏感负荷节点的电压暂降幅值解析式,并引入节点判定向量和线路关联向量,以及相应的... 针对大型复杂电网中敏感负荷的电压暂降域难以准确识别的问题,提出一种基于黄金分割搜索的电压暂降域快速识别方法。首先,求得网络中发生各类短路故障时敏感负荷节点的电压暂降幅值解析式,并引入节点判定向量和线路关联向量,以及相应的判定准则,实现对所有线路临界点的快速分类计算;接着详细阐述了传统插值法存在的问题,并提出一种由黄金分割搜索改进的插值法,以期为正割迭代提供更优的初值点,提高临界点计算的准确度;因考虑到拟合的二次曲线难免存在偏差,故使用故障点法作为补充算法,用以计算有求解困难的线路;最后,以IEEE30节点标准测试系统为例,验证了该方法能在保证计算精度的前提下,简化电压暂降域的求解过程,提高算法的收敛速度,并广泛适用于大型复杂电网。 展开更多
关键词 电压暂降 敏感负荷 临界点 暂降域 黄金分割搜索
下载PDF
大型耙吸挖泥船结构设计要点
20
作者 荆海东 杨青 谢昊 《船海工程》 北大核心 2024年第1期82-86,共5页
为实现大型耙吸挖泥船结构设计安全、合理、可靠,以某大型耙吸挖泥船为例,分析大型耙吸挖泥船结构设计特点,从结构设计、强度评估、疲劳评估和振动评估等角度论证其设计要点,通过对泥舱结构设计分析,给出泥舱设计的关键节点,对关键节点... 为实现大型耙吸挖泥船结构设计安全、合理、可靠,以某大型耙吸挖泥船为例,分析大型耙吸挖泥船结构设计特点,从结构设计、强度评估、疲劳评估和振动评估等角度论证其设计要点,通过对泥舱结构设计分析,给出泥舱设计的关键节点,对关键节点进行强度分析和疲劳分析,结果表明,该船局部关键区域应力水平较高,低周疲劳在关键区域的疲劳中占据主要地位,建立三维有限元模型计算挖泥船固有频率,对比该大型耙吸挖泥船激励频率与固有频率,结果表明,船体总振动固有频率通常可以避开激励频率,生活楼固有频率与激励频率较为接近。 展开更多
关键词 大型耙吸挖泥船 结构设计 中剖面设计 关键区域 强度评估 疲劳评估 振动控制
下载PDF
上一页 1 2 92 下一页 到第
使用帮助 返回顶部