期刊文献+
共找到11,184篇文章
< 1 2 250 >
每页显示 20 50 100
Changes in neurological and pathological outcomes in a modified rat spinal cord injury model with closed canal 预览
1
作者 Xin Sun Xing-Zhen Liu +4 位作者 Jia Wang Hai-Rong Tao Tong Zhu Wen-Jie Jin Kang-Ping Shen 《中国神经再生研究:英文版》 SCIE CAS CSCD 2020年第4期697-704,共8页
Most animal spinal cord injury models involve a laminectomy,such as the weight drop model or the transection model.However,in clinical practice,many patients undergo spinal cord injury while maintaining a relatively c... Most animal spinal cord injury models involve a laminectomy,such as the weight drop model or the transection model.However,in clinical practice,many patients undergo spinal cord injury while maintaining a relatively complete spinal canal.Thus,open spinal cord injury models often do not simulate real injuries,and few previous studies have investigated whether having a closed spinal canal after a primary spinal cord injury may influence secondary processes.Therefore,we aimed to assess the differences in neurological dysfunction and pathological changes between rat spinal cord injury models with closed and open spinal canals.Sprague-Dawley rats were randomly divided into three groups.In the sham group,the tunnel was expanded only,without inserting a screw into the spinal canal.In the spinal cord injury with open canal group,a screw was inserted into the spinal canal to cause spinal cord injury for 5 minutes,and then the screw was pulled out,leaving a hole in the vertebral plate.In the spinal cord injury with closed canal group,after inserting a screw into the spinal canal for 5 minutes,the screw was pulled out by approximately 1.5 mm and the flat end of the screw remained in the hole in the vertebral plate so that the spinal canal remained closed;this group was the modified model,which used a screw both to compress the spinal cord and to seal the spinal canal.At 7 days post-operation,the Basso-Beattie-Bresnahan scale was used to measure changes in neurological outcomes.Hematoxylin-eosin staining was used to assess histopathology.To evaluate the degree of local secondary hypoxia,immunohistochemical staining and western blot assays were applied to detect the expression of hypoxia-inducible factor 1α(HIF-1α)and vascular endothelial growth factor(VEGF).Compared with the spinal cord injury with open canal group,in the closed canal group the Basso-Beattie-Bresnahan scores were lower,cell morphology was more irregular,the percentage of morphologically normal neurons was lower,the percentages of HIF-1α-and VEGF-immunorea 展开更多
关键词 Basso-Beattie-Bresnahan scores CLOSED SPINAL CANAL HIF-1α hypoxia MODEL nerve regeneration open SPINAL CANAL rat secondary INJURY SPINAL cord INJURY VEGF
在线阅读 下载PDF
中国大运河遗产本体演化的历史学解释 预览
2
作者 肖爱玲 《太原师范学院学报:社会科学版》 2019年第4期1-7,共7页
1994年世界遗产委员会将遗产运河、线路等特定类型的遗产列入《世界遗产名录》,中国的京杭大运河占居突出地位。从中国大运河近二十年的申遗过程来看,国际社会对遗产运河的认识呈不断深化的趋势。中国大运河遗产本体由京杭运河叠加隋唐... 1994年世界遗产委员会将遗产运河、线路等特定类型的遗产列入《世界遗产名录》,中国的京杭大运河占居突出地位。从中国大运河近二十年的申遗过程来看,国际社会对遗产运河的认识呈不断深化的趋势。中国大运河遗产本体由京杭运河叠加隋唐运河、浙东运河而成为中国大运河即是这一现象的直观表达。从概念史角度来看,运河、南北(大)运河、京杭(大)运河与中国大运河之间存在名实差异,中国大运河是一个具有当代意义的地理名词。 展开更多
关键词 运河 京杭运河 中国大运河 中国大运河遗产
在线阅读 下载PDF
明清河北运河城市变迁研究——以东光县为例
3
作者 郑民德 《运河学研究》 2019年第1期143-155,共13页
明清时期的东光县是京杭运河沿岸重要的漕运码头、河工重地、商业中心,其兴起、发展、衰落与运河均有着密切关系,同时大运河也给东光留下了不计其数的物质与非物质文化遗产。作为河北省运河城市的重要组成部分,东光的政治、经济、文化... 明清时期的东光县是京杭运河沿岸重要的漕运码头、河工重地、商业中心,其兴起、发展、衰落与运河均有着密切关系,同时大运河也给东光留下了不计其数的物质与非物质文化遗产。作为河北省运河城市的重要组成部分,东光的政治、经济、文化都带有浓厚的运河色彩,通过对运河历史文化的深入挖掘,不但有助于'运河文化带''运河经济带'建设,而且对于河北省运河文化建设的系统发展及文化遗产的保护与利用、运河旅游业发展都有着重要意义。 展开更多
关键词 运河 东光县 运河文化带
U形渠道量水平板水力性能试验研究 预览
4
作者 王文娥 张维乐 胡笑涛 《农业工程学报》 EI CAS CSCD 北大核心 2019年第13期84-90,共7页
根据北方灌区渠道底坡缓且灌溉水流多泥沙的现状,该文针对U型渠道设计了平板量水装置。为了探索不同尺寸悬垂薄平板在明渠水流冲击作用下的水力学特性,确定流量与平板偏转角度之间的关系。分析水流流态,将渠道运动水流分为3部分,对平板... 根据北方灌区渠道底坡缓且灌溉水流多泥沙的现状,该文针对U型渠道设计了平板量水装置。为了探索不同尺寸悬垂薄平板在明渠水流冲击作用下的水力学特性,确定流量与平板偏转角度之间的关系。分析水流流态,将渠道运动水流分为3部分,对平板部分水流应用闸孔淹没出流公式,建立流量计算模型,得出流量与角度的半经验关系式。对流量系数计算模型中的待定系数进行估计,得到了统一形式的流量公式。U型平板测流范围为9~44L/s,经验证,计算流量与实测流量之间最大相对误差为6.9%,平均相对误差为3.2%,其中收缩比0.547、0.439平板测流相对误差均小于5%,满足灌区量水要求。同一收缩比板型,相对水头损失随着流量增大而减小,不同收缩比板型,相对水头损失随着板型收缩比增大而增大,除收缩比0.715平板在小流量(本试验大约为10L/s)测流时,相对水头损失比在10%以上,其余平板测流时相对水头损失均小于10%,其中收缩比为0.439和0.337平板最大水头损失不超过上游总水头6%。经过综合分析,选择0.547到0.439为平板最佳收缩比测流范围。研究可为灌区量水设施的改进提供依据。 展开更多
关键词 流量 渠道 角度 渠道闸孔出流 流量系数 水头损失
在线阅读 下载PDF
扬州唐罗城形制与运河的关系——兼谈隋唐淮南运河过扬州唐罗城段位置
5
作者 汪勃 《中国国家博物馆馆刊》 CSSCI 北大核心 2019年第2期6-19,共14页
扬州唐罗城因河而市、因市而城,既是一座因运河而生的城池,也是一座因地制宜规划而成的城市。本文介绍了扬州唐罗城的城墙和城壕、中轴线、城内格局以及相关运河概况,探讨了隋唐时期淮南运河过扬州唐罗城段之位置,认为扬州唐罗城四至范... 扬州唐罗城因河而市、因市而城,既是一座因运河而生的城池,也是一座因地制宜规划而成的城市。本文介绍了扬州唐罗城的城墙和城壕、中轴线、城内格局以及相关运河概况,探讨了隋唐时期淮南运河过扬州唐罗城段之位置,认为扬州唐罗城四至范围和中轴线与隋唐及其以前开凿的运河有关,扬州唐罗城的形成与其周边水系的发展变化相辅相成;隋唐时期扬州城的形制既受当时两京形制影响,又具有以运河为中心围筑城池、交通水陆并行等诸多南方城市的特色,还带有从中古封建封闭型里坊制城市,向以近世经济生活为主的开放式城市格局过渡的特征;隋唐时期淮南运河过扬州唐罗城段之位置,或即在扬州唐罗城中轴线的汶河一线,然尚不能排除在汶河西侧二道河一线的可能性。唐扬州城因其处运河咽颐的特殊地理位置,随着水运贸易的繁荣而逐渐发展成为一座国际性的大都会。 展开更多
关键词 扬州城 唐罗城 四至范围 中轴线 运河 淮南运河
清代运河河政制度研究——以山东运河道为对象的历史考察 预览
6
作者 窦重沂 郑民德 《德州学院学报》 2019年第3期1-5,共5页
清代山东运河道上连河东河道总督,下辖管河六厅,直接管理山东运河河务,以及附属河流、湖泊、闸座、泉源等水利设施。不仅担负着挑挖河道、防洪抢险、维修水利设施、经营河库等重任,还要控制闸坝,调节运河水源,使南粮顺利入京,在河政体... 清代山东运河道上连河东河道总督,下辖管河六厅,直接管理山东运河河务,以及附属河流、湖泊、闸座、泉源等水利设施。不仅担负着挑挖河道、防洪抢险、维修水利设施、经营河库等重任,还要控制闸坝,调节运河水源,使南粮顺利入京,在河政体制中占有重要地位。 展开更多
关键词 运河道 河政 运河 山东
在线阅读 下载PDF
Seasonal Effect on Biomarkers of Exposure to Petroleum Hydrocarbons in the Coasts of North Western Suez Gulf,Egypt 预览
7
作者 Omayma E.Ahmed Mustafa M.Emara +2 位作者 Nazik A.Farid1 Enas A.El-Sabagh Eman M.Kamal 《地球与环境科学(英文)》 2019年第1期38-48,共11页
Petroleum hydrocarbons of surface water were collected from eight loca-tions of from the coasts of north western Suez Gulf,Egypt.The extracted petroleum hydrocarbons were determined by gas chromatography-flame ionizat... Petroleum hydrocarbons of surface water were collected from eight loca-tions of from the coasts of north western Suez Gulf,Egypt.The extracted petroleum hydrocarbons were determined by gas chromatography-flame ionization detector and quantified by integrating the areas of both the resolved and unresolved components.The results confirm that the con-centration is relatively higher than the recommended in the regulations of the Egyptian low of Environment of No.4/1994 of petroleum products.At various locations.The dissolved petroleum hydrocarbons ranged from 5.639 to 74.8 and 1.868 to 65.698 mg/ml for summer and winter sea-sons,respectively.This indicates that chronic oil pollution,in addition to hydrocarbon concentrations,the diagnostic indices used shows that the hydrocarbons in the area were comes from biogenic,petrogenic and anthropogenic sources.FT-IR spectrometric analysis confirms die petro-genic nature of pollutants. 展开更多
关键词 EGYPT Oil HYDROCARBON PHYSICOCHEMICAL Diagnostic Gas chromatography Suez CANAL
在线阅读 免费下载
巴基斯坦运河水源电厂供水可靠性分析
8
作者 王勇 马惠群 《工程建设》 2019年第9期45-47,共3页
以巴基斯坦某电厂为例,介绍了以运河为主要水源的电厂供水可靠性分析。基于水文站断流天数、年数据、97%保证率的流量等参数分析,提出运河闭闸时取地下水的供水方案,满足电厂需求。
关键词 供水 运河 断流 97%保证率
灵渠“四贤信仰”研究 预览
9
作者 董素云 《西北民族大学学报:哲学社会科学版》 CSSCI 2019年第4期62-71,共10页
在灵渠运河两千两百余年的历史发展过程中,随着其水利工程不断发展与完善,其附属建筑祠庙也在不断修建。在灵渠运河流域众多祠庙中,纪念对灵渠工程具有重大贡献历史人物的"四贤祠"是独具灵渠信仰文化特色的典型代表。"四... 在灵渠运河两千两百余年的历史发展过程中,随着其水利工程不断发展与完善,其附属建筑祠庙也在不断修建。在灵渠运河流域众多祠庙中,纪念对灵渠工程具有重大贡献历史人物的"四贤祠"是独具灵渠信仰文化特色的典型代表。"四贤"祭祀在灵渠运河发展过程中具有重要的功能和意义;"四贤祠"是灵渠运河维修与持续发挥功用所产生的,对"四贤"的祭祀属于民间信仰的一种。 展开更多
关键词 运河 灵渠 四贤祠 “四贤”信仰 祠庙研究
在线阅读 下载PDF
Improvement of Mechanical Stability for Single Unit Recording Based on Skull Cap in Living Chinchilla 预览
10
作者 Peng-yu REN Bo-wen +2 位作者 Shi-yao DONG Ming WU Peng HAN 《当代医学科学(英文)》 SCIE CAS 2019年第1期166-172,共7页
Three-point head fixation was constructed to provide mechanical stability for single unit recording(SUR)on vestibular sensory system in living chinchilla previously.However,it is no more qualified to this work when th... Three-point head fixation was constructed to provide mechanical stability for single unit recording(SUR)on vestibular sensory system in living chinchilla previously.However,it is no more qualified to this work when the stimulation intensity becomes large because of frequent unit losing and neuron damage,which strongly implies that the mechanical stability has been broken during the stimulation.Here,we constructed a novel hea0 fixation(skull cap assistant head fixation)provided by skull cap on the basis of three-point head fixation in order to improve the mechanical stability for SUR under the stimulation with large magnitude.The large area bone connection is the feature and advantage of this improved method,which directly fixes the tested local nervous tissue and microelectrode in an intact stable system through skull cap except two ear bars and a tube face mask.Our data exhibited that skull cap assistant head fixation could significantly improve the success rate of neural response activity recording in the population of semicircular canal neurons under the stimulation with large intensity(amplitudd 00 deg/s).Based on the analysis of neural response activity and noise base-line during stimulation,our data further indicated that this method could significantly improve the mechanical stability for SUR during high-speed motion stimulation on vestibular system in living chinchilla.Skull cap assistant head fixation extends the application of SUR on vestibular neuron in linear response range and provides a solid foundation for electrophysiological research on vestibular sensory system in fhrther studies. 展开更多
关键词 single unit RECORDING SKULL CAP mechanical stability IMPROVEMENT semicircular CANAL neurons
在线阅读 下载PDF
Non-Invasive management of invasive cervical resorption associated with periodontal pocket: A case report 预览
11
作者 Abdullah Alqedairi 《世界临床病例杂志》 2019年第7期863-871,共9页
BACKGROUND Invasive cervical resorption (ICR), a commonly misdiagnosed condition, is an aggressive form of external tooth resorption that contributes to periodontal tissue inflammation and deepening of the periodontal... BACKGROUND Invasive cervical resorption (ICR), a commonly misdiagnosed condition, is an aggressive form of external tooth resorption that contributes to periodontal tissue inflammation and deepening of the periodontal pockets. Herein we report the case of a patient, exhibiting ICR and elaborate the effects of a non-surgical approach in the amelioration of this condition. CASE SUMMARY A 21-year-old female reporting intermittent pain at the upper left side, multiple restorations, no trauma history, and having received orthodontic treatment was studied. Localized erythematous swelling was noted at the buccal interdental papilla between the left maxillary first molar and second premolar. The diseased pulp and tissue in resorption were removed and the root canal system including the defect were sealed using gutta percha/AH Plus and mineral trioxide aggregate (MTA). At the one-year recall, the tooth showed no symptoms and responded normally to percussion and palpation. The surrounding periodontium exhibited a normal color and the probing depth was normal. Radiographic examination showed a restoration of crestal alveolar bone and good adaption to MTA. CONCLUSION Non-surgical root canal treatment in conjunction with resorption defect orthograde repair with MTA was found to be an effective treatment option in the elimination of ICR. Early diagnoses are recommended in order to employ nonsurgical approaches for management of ICR instead of surgical interventions. 展开更多
关键词 INVASIVE CERVICAL RESORPTION Mineral TRIOXIDE aggregate NON-SURGICAL root canal PERIODONTAL Case report
在线阅读 免费下载
Efficacy. ProTaper Next. removing filling materials from oval-Shaped canal during root canal retreatment 预览
12
作者 Hui Liu 《探索-牙科学》 2019年第1期12-15,共4页
AIM:. Assess. efficacy. removing. filling material from oval-Shaped canals. Pro-Taper Next rotary files.Methods:60 extracted human mandibular premolars. instrumented up. a size F2. ProTaper UniversalThen filled. gutta... AIM:. Assess. efficacy. removing. filling material from oval-Shaped canals. Pro-Taper Next rotary files.Methods:60 extracted human mandibular premolars. instrumented up. a size F2. ProTaper UniversalThen filled. gutta-Percha ", AH-Plus sealer using. continuous wave. condensation technique.Then. teeth. divided. 3 groups(N = 20).. Filling material. removed. hand files(H)ProTaper UniversalREtreatment(PTUR), ProTaper Next(PTN)... Debris extruded. apical foramen. collected, weighted.. Working time. recorded.Then. teeth. split longitudinally Observed. 展开更多
关键词 PROTAPER NEXT Root CANAL RETREAT NiTi FILES Removal of filling material
在线阅读 免费下载
基于老大运河清淤工程实践浅谈精细化监管 预览
13
作者 韩红波 李文学 《江苏水利》 2019年第6期63-66,共4页
河道清淤工程实施过程中对水下清淤效果的检测、淤泥运输监管及淤泥卸场的监管历来是工程管理监管中的难点与薄弱点,随着环保要求的提高及市民环保意识的提升,使得关于清淤开挖、淤泥运输、淤泥堆放等清淤工作的关注度越来越广泛,这些... 河道清淤工程实施过程中对水下清淤效果的检测、淤泥运输监管及淤泥卸场的监管历来是工程管理监管中的难点与薄弱点,随着环保要求的提高及市民环保意识的提升,使得关于清淤开挖、淤泥运输、淤泥堆放等清淤工作的关注度越来越广泛,这些问题也成为热点与重点。基于老大运河清淤工程中“挖、运、卸”的精细化监控管理介绍,是工程实施中的有效探索。 展开更多
关键词 清淤 运河 精细化 管理
在线阅读 下载PDF
Post-inflammatory acquired atresia of the external auditory canal 预览
14
作者 Michel Kmeid Jade Nehme 《中华耳科学杂志:英文版》 CSCD 2019年第4期149-154,共6页
Acquired atresia of the external auditory canal(EAC)is a rare cause of conductive hearing loss.It has been traditionally classified into 4 categories:traumatic,post-operative,neoplastic and inflammatory.Post-inflammat... Acquired atresia of the external auditory canal(EAC)is a rare cause of conductive hearing loss.It has been traditionally classified into 4 categories:traumatic,post-operative,neoplastic and inflammatory.Post-inflammatory acquired auditory canal atresia is thought to be the result of chronic and repetitive infectious bouts affecting the auditory canal.Nevertheless,the underlying pathophysiology of this disorder is yet to be fully elucidated.Current data fail to clearly state the impact that certain underlying systemic disorders may have on the EAC.The possible association to metabolic disturbances such as iron deficiency is also emphasized.In the light of these findings,this analysis can be used to improve the classification of this entity thereby standardizing the assessment of therapeutic approaches. 展开更多
关键词 Stenosing external otitis Meatal atresia External auditory canal Conductive hearing loss CANALOPLASTY
在线阅读 下载PDF
北方某城市运河下段周边地下水PAHs污染特征 预览
15
作者 徐庆勇 《城市地质》 2019年第3期26-32,共7页
有机污染特征研究可为采取有效的地下水污染防治措施提供科学依据,对饮水安全、可持续发展、生态平衡具有重要意义。选取北方某城市运河下段,根据实测数据,评价了河段周边地下水PAHs类有机物的污染程度,分析了有机污染特征及成因。结果... 有机污染特征研究可为采取有效的地下水污染防治措施提供科学依据,对饮水安全、可持续发展、生态平衡具有重要意义。选取北方某城市运河下段,根据实测数据,评价了河段周边地下水PAHs类有机物的污染程度,分析了有机污染特征及成因。结果表明:地下水中16项PAHs测试指标全部检出,但大多为微量检出,仅个别指标在个别井中超标,污染程度总体为轻度污染。典型河段地下水有机污染具有丰富度高、主要污染物少、污染程度低、毒性不强及浅层井水质污染重于深层井的特征。 展开更多
关键词 运河 地下水 PAHS 有机污染 城市 检出率 超标率 检测
在线阅读 下载PDF
明清长芦盐业与运河交通述论
16
作者 裴一璞 《运河学研究》 2019年第1期156-165,共10页
明清长芦盐业的发展与运河交通密不可分,运河促进长芦盐业管理中心的转移,奠定今日长芦盐业格局;促进芦盐管理职能的完善;扩大芦盐的行销范围及对外影响。然而运河交通也为芦盐走私提供了方便之门,增加了政府缉私难度。总体言之,运河交... 明清长芦盐业的发展与运河交通密不可分,运河促进长芦盐业管理中心的转移,奠定今日长芦盐业格局;促进芦盐管理职能的完善;扩大芦盐的行销范围及对外影响。然而运河交通也为芦盐走私提供了方便之门,增加了政府缉私难度。总体言之,运河交通对长芦盐业发展的推动作用居主导地位。 展开更多
关键词 明清 长芦盐业 运河 交通
Hydraulic Geometry Relation for Navigable Canals Considering Ship Speed
17
作者 毛礼磊 陈一梅 《上海交通大学学报:英文版》 EI 2019年第3期299-304,共6页
Definition of hydraulic geometry of navigable canals and its expression are studied in this paper.The hydrodynamic and morphologic characteristics of navigable canals are analyzed on the basis of the data collected fr... Definition of hydraulic geometry of navigable canals and its expression are studied in this paper.The hydrodynamic and morphologic characteristics of navigable canals are analyzed on the basis of the data collected from field surveys conducted at two segments of the Grand Canal in Jiangsu Province,China.The channel morphologic factor and the ship hydrodynamic factor are adopted to describe the hydraulic geometry relation of navigable canals.The correlation analysis shows that the ship hydrodynamics can be a dominant factor influencing the channel evolution with larger determination coefficient.Furthermore,the undetermined index in the proposed hydraulic geometry relation is also discussed,which indicates that the index related to the intensity of water flow(qualitatively reflected by the integrated ship flow intensity)is within a range of 0.5 to 1.0. 展开更多
关键词 CROSS-SECTIONAL morphology hydraulic GEOMETRY navigable CANAL SHIP speed water flow INTENSITY
直肠周围间隙和盆底解剖
18
作者 胡祥 《中国实用外科杂志》 CSCD 北大核心 2019年第7期663-667,共5页
在直肠肛管手术中;为了达到根治性和保存完整的泌尿生殖器官功能;对局部解剖的理解极为重要。掌握直肠肛管的基本结构、直肠周围间隙、筋膜层次和盆底解剖;有助于选择手术入路和剥离层面;达到规范的全直肠系膜切除(TME)、侧方淋巴结清... 在直肠肛管手术中;为了达到根治性和保存完整的泌尿生殖器官功能;对局部解剖的理解极为重要。掌握直肠肛管的基本结构、直肠周围间隙、筋膜层次和盆底解剖;有助于选择手术入路和剥离层面;达到规范的全直肠系膜切除(TME)、侧方淋巴结清扫及神经保护等。 展开更多
关键词 直肠 肛管 筋膜 解剖 手术
Ordered space-time structures: Quantum carpets from Gaussian sum theory
19
作者 HuiXin Xiong XueKe Song +2 位作者 HuaiYang Yuan DaPeng Yu ManHong Yung 《中国科学:物理学、力学、天文学英文版》 SCIE EI CAS CSCD 2019年第7期55-62,共8页
The term 'quantum carpet' can be observed in many closed quantum systems, where the evolution of a wave function exhibits a carpet-like pattern. Quantum carpet mechanisms are also akin to the classical interfe... The term 'quantum carpet' can be observed in many closed quantum systems, where the evolution of a wave function exhibits a carpet-like pattern. Quantum carpet mechanisms are also akin to the classical interference patterns of light. Although the origins of quantum carpets have previously been studied by various researchers, many interesting details are still worth exploring. In this study, we present a unified framework for simultaneously analyzing three different features of quantum carpets: full revival,fractional revival, and diagonal canal. For the fractional revival feature, a complete formula is presented to explain its formation through Gaussian sum theory, in which all essential features, including phases and amplitudes, are captured analytically. We also reveal important relationships between the interference terms of diagonal canals and their geometric interpretations such that a better understanding of the development of diagonal canals can be supported. 展开更多
关键词 QUANTUM CARPETS fractional REVIVAL DIAGONAL CANAL Gaussian sum THEORY
基于悬垂平板偏转角的明渠流量估算模型及验证 预览
20
作者 王文娥 张维乐 +4 位作者 胡笑涛 谢祥薇 杜村 何君岩 徐茹 《农业工程学报》 EI CAS CSCD 北大核心 2019年第19期168-175,共8页
针对平板量水设施缺乏适用性广泛的流量计算模型,该文从2个角度提出流量估算模型,首先分析绕轴自由旋转薄平板在水中的受力,根据升力简化为竖直方向静水压力设想,提出压力体计算假设,根据动量定理与力矩平衡公式得到了流量、角度、水深... 针对平板量水设施缺乏适用性广泛的流量计算模型,该文从2个角度提出流量估算模型,首先分析绕轴自由旋转薄平板在水中的受力,根据升力简化为竖直方向静水压力设想,提出压力体计算假设,根据动量定理与力矩平衡公式得到了流量、角度、水深三者的理论关系式,通过U型和矩形渠道进行试验,验证假设合理性;根据闸孔出流流量公式针对矩形渠道建立闸孔出流半径验计算模型,拟合得出半径验流量公式。对于第1种模型,对于U型渠道,2种压力体假设均适用于流量计算,除流量小于10 L/s时,相对误差超过10%,其他均小于10%,流量大于17 L/s时误差均在5%左右;对于矩形渠道,仅假设1适用流量计算,假设2不成立,应用假设1计算压力体时,当流量较小(10 L/s左右)时的个别工况误差会偏大,大部分工况下计算误差均小于10%;对于闸孔出流计算模型,计算流量与实测流量之间最大误差不超过18%,大部分工况下计算误差在10%以下。当悬垂薄平板与明渠横断面等大时,来流量与偏转角度存在单值对应关系,角度随着来流量的增大而增大;同一流量下,板前后水深比、板前与下游水深比分别与偏转角度呈现出单独的函数关系,板前后水深比、板前与下游水深比随着平板偏转角度的增大而减小,但减小幅度变缓。对于不同流量,板前后水深比、板前与下游水深比随着角度增大而增大,但增大幅度变缓。研究可为灌区量水设施设计及应用提供新思路。 展开更多
关键词 渠道 角度 流量 绕流阻力 受力方向 闸孔出流
在线阅读 下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部 意见反馈