期刊文献+
共找到55,884篇文章
< 1 2 250 >
每页显示 20 50 100
Endoscopic trans-esophageal submucosal tunneling surgery:A new therapeutic approach for diseases located around the aorta ventralis 预览
1
作者 Ying Xiong Qian-Qian Chen +3 位作者 Ning-Li Chai Shun-Chang Jiao En-Qiang Ling Hu 《世界胃肠病学杂志:英文版》 SCIE CAS 2019年第1期85-94,共10页
AIM To assess the efficiency of endoscopic trans-esophageal submucosal tunneling surgery(EESTS)technique for diseases located around the aorta ventralis.METHODS Nine pigs were assigned to EESTs.The procedures were as ... AIM To assess the efficiency of endoscopic trans-esophageal submucosal tunneling surgery(EESTS)technique for diseases located around the aorta ventralis.METHODS Nine pigs were assigned to EESTs.The procedures were as follows:First,a long esophageal submucosal tunnel was established.Second,full-thickness myotomy was created.Third,an endoscope was entered into the abdominal cavity through a muscle incision and the endoscope was around the aorta ventralis.Eventually,celiac trunk ganglion neurolysis,partial hepatectomy and splenectomy,partial tissue resection in the area of the posterior peritoneum,and endoscopic submucosal dissection(ESD)combined with lymph node dissection were performed.The animals were given antibiotics for 5 d and necropsied 7 d after surgery.RESULTS In all surgeries,one pig died from intraperitoneal hemorrhage after doing partial splenectomy,while the other pigs were alive after successfully operating other surgeries.For surgery of celiac trunk ganglion damage,at necropsy,there was no exudation in the abdominal cavity.Regarding surgery of partial hepatectomy,the wound with part healing was observed in the left hepatic lobe,and no bleeding or obvious exudation was seen.In surgery of partial splenectomy,massive hemorrhage was observed on the splenic wound surface,and the metal clips could not stop bleeding.After surgery of retroperitoneal tissue resection,mild tissue adhesion was observed in the abdominal cavity of one animal,and another one suffered from severe infection.For surgery of ESD and lymph node dissection,a moderate tissue adhesion was observed.CONCLUSION EESTS is a feasible and safe technique for diseases located around the aorta ventralis. 展开更多
关键词 ENDOSCOPIC trans-esophageal SUBMUCOSAL TUNNELING SURGERY Diseases around the AORTA ventralis ENDOSCOPIC SUBMUCOSAL TUNNELING technique Abdominal SURGERY Animal model
在线阅读 免费下载
关于土压平衡盾构施工监理控制的要求 预览
2
作者 朱佑洪 《现代交通技术研究》 2019年第2期94-99,共6页
随着社会经济的发展城市人口增多、规模变大现有的城市交通已经不能满足城市发展的需要、经济发达的城市逐步修建地下工程,轨道盾构施工技术普遍应用于地铁工程中。盾构在地下工程施工中越来越得到重视,盾构施工前盾构机的安装,始发、... 随着社会经济的发展城市人口增多、规模变大现有的城市交通已经不能满足城市发展的需要、经济发达的城市逐步修建地下工程,轨道盾构施工技术普遍应用于地铁工程中。盾构在地下工程施工中越来越得到重视,盾构施工前盾构机的安装,始发、掘进、接收等施工时我们工程监理人控制中的重点。其盾构井下安装中盾构机内外拼装焊接质量,是在盾构隧道区间中重中之重,并将影响盾构区间的质量,当然盾构机前期的研发制作也是相关人员控制的重要质量,如施工中控制不妥,必将产生地表隆起或下沉,管片破裂一致成型隧道漏渗严重,其相关后果必将造成隧道的质量问题,并最终影响地下隧道的使用寿命。 展开更多
关键词 盾构安装 始发 掘进 接收 盾构管片破裂风险控制
在线阅读 下载PDF
煤矿斜井施工技术分析 预览
3
作者 张志龙 《建筑技术开发》 2019年第12期39-40,共2页
在矿山的建设过程中,斜井是其非常重要的组成部分,由于地址情况、施工工艺以及施工条件的影响,导致其施工难度较大,存在较多的不安全因素。为了保障煤矿斜井施工的顺利进行,就需要对整个施工过程进行系统全面的分析研究,并采取有针对性... 在矿山的建设过程中,斜井是其非常重要的组成部分,由于地址情况、施工工艺以及施工条件的影响,导致其施工难度较大,存在较多的不安全因素。为了保障煤矿斜井施工的顺利进行,就需要对整个施工过程进行系统全面的分析研究,并采取有针对性的斜井施工技术,确保各项施工措施的顺利实施以及确保斜井的施工质量符合要求。 展开更多
关键词 煤矿 斜井 掘进
在线阅读 下载PDF
煤矿掘进巷道锚杆支护技术研究 预览
4
作者 路瑞龙 《当代化工研究》 2019年第7期164-165,共2页
本文阐述了煤矿矿井的掘进巷道支护发展现状以及在矿井掘进工作中进行巷道锚杆支护的作用,并在巷道锚杆孔位和支护设计等角度分析了锚杆支护进行设计及施工方面的要求,某种程度上提高了煤矿矿井作业的安全性。
关键词 矿井 锚杆支护 掘进
在线阅读 下载PDF
基于Matlab的势垒与隧道效应可视化教学探讨 预览
5
作者 李立 张皓晶 +2 位作者 邱龙斌 吴杨峰 姚蕊 《云南大学学报:自然科学版》 CAS CSCD 北大核心 2019年第A01期39-43,共5页
势垒贯穿和隧道效应是理工科大学量子力学教学的一个重点和难点.在传统的教学中,教师往往只是基于对粒子的波函数的推导和解析,由于推导和解析过程的繁琐和困难,导致了教学效果不佳,学生对于势垒贯穿和隧道效应的认识仅仅停留在表面,而... 势垒贯穿和隧道效应是理工科大学量子力学教学的一个重点和难点.在传统的教学中,教师往往只是基于对粒子的波函数的推导和解析,由于推导和解析过程的繁琐和困难,导致了教学效果不佳,学生对于势垒贯穿和隧道效应的认识仅仅停留在表面,而没有从物理的本质中去认识该部分内容,因此,本文基于Matlab强大的计算和可视化功能,将势垒贯穿和隧道效应的教学可视化,使得教学过程更加直观和具体,让学生从本质上理解该部分内容,从而为后面的学习打下坚实的基础. 展开更多
关键词 势垒 隧道效应 MATLAB 可视化
在线阅读 下载PDF
Advances in the study of the host-guest interaction by using coronene as the guest molecule
6
作者 Jianqiao Li Yuxin Qian +1 位作者 Wubiao Duan Qingdao Zeng 《中国化学快报:英文版》 SCIE CAS CSCD 2019年第2期292-298,共7页
Host-guest chemistry in two-dimensional (2D) networks has gained much interest for the new functionalities and potential applications, such as separation technology, photogenic crystals and biomimetic surfaces. Nanopo... Host-guest chemistry in two-dimensional (2D) networks has gained much interest for the new functionalities and potential applications, such as separation technology, photogenic crystals and biomimetic surfaces. Nanoporous supramolecular networks are assembled by a range of non-covalent forces like hydrogen bonds, van der Waals interactions and coordinate bonds, to immobilize guest molecules of different sizes and shapes. In this review, we mainly presented the effect of coronene on the host-guest architecture. Coronene (COR) is chosen to be the promising guest molecule and it can embed, cover, or change the host networks in different host-guest systems. All of the research in the review was finished with assistance of scanning tunneling microscope (STM). These studies were called upon impose controlling on host-guest systems and revealed the behaviors of COR clusters as guest molecules. 展开更多
关键词 HOST-GUEST chemistry CORONENE Molecular TEMPLATE 2D SELF-ASSEMBLY Scanning TUNNELING microscopy(STM)
大跨度框架下穿多股道顶进施工时铁路线路加固技术研究 预览
7
作者 魏亚茹 《价值工程》 2019年第19期162-165,共4页
龙象公路在象山煤矿东侧下穿侯西铁路、运煤专线及编组站专用线等5条铁轨,公路设置2-14m框架下穿铁路。针对本项目为大跨度框架下穿铁路5股道顶进施工,施工难度高,安全压力大。通过采取纵横抬梁法+吊轨梁对既有铁路5股道进行线路加固,... 龙象公路在象山煤矿东侧下穿侯西铁路、运煤专线及编组站专用线等5条铁轨,公路设置2-14m框架下穿铁路。针对本项目为大跨度框架下穿铁路5股道顶进施工,施工难度高,安全压力大。通过采取纵横抬梁法+吊轨梁对既有铁路5股道进行线路加固,并顶进中运用了石蜡、黄油及塑料薄膜组成复合滑动层,滚杠、定向滑轮等措施,减小了框构桥顶进施工时的摩阻力,加快了施工进度,提高了顶进过程的安全性。 展开更多
关键词 大跨度框架 顶进施工 线路加固技术 减摩措施
在线阅读 下载PDF
煤矿软岩巷道掘进支护技术探讨 预览
8
作者 荆彦军 《当代化工研究》 2019年第7期17-18,共2页
掘进支护技术在软岩巷道施工建设中的应用效果,对整个巷道的稳固性和作业人员的人身安全起着重要作用,对保证煤矿企业的安全生产也具有重要意义。在对软岩巷道进行掘进支护过程中,出现了很多问题,比如软岩强度不高导致围岩应力水平较高... 掘进支护技术在软岩巷道施工建设中的应用效果,对整个巷道的稳固性和作业人员的人身安全起着重要作用,对保证煤矿企业的安全生产也具有重要意义。在对软岩巷道进行掘进支护过程中,出现了很多问题,比如软岩强度不高导致围岩应力水平较高,岩层中存在吸水膨胀特性的黏土矿物质会对软岩巷道的支护结构产生影响。所以为了降低围岩变形对巷道掘进支护工作带来的不利影响,需要采用一些方法措施来提高围岩强度和支护表力。目前在软岩巷道掘进作业中最常用的支护技术就是锚杆联合支护与锚网喷支护,合理掘进支护方式的选择要根据当地矿井的地质特点来决定。 展开更多
关键词 软岩巷道 掘进 支护技术
在线阅读 下载PDF
Modified criterion for prediction of tunnel deformation in non-squeezing ground conditions 预览
9
作者 Ako Daraei Shokrollah Zare 《现代交通学报:英文版》 2019年第1期11-24,共14页
The strength factor-based criterion for tunnel deformation prediction proposed by Hoek in 2000 is reckoned to be the most practical criterion among the tunnel deformation criteria since 1980s.In view of the fact that ... The strength factor-based criterion for tunnel deformation prediction proposed by Hoek in 2000 is reckoned to be the most practical criterion among the tunnel deformation criteria since 1980s.In view of the fact that Hoek’s criterion was obtained based on case studies under squeezing ground conditions,it has a limited range of applications,applicable mainly in squeezing tunnels.In this work,this criterion was modified by taking into consideration the conditions of eight unstable stations in three non-squeezing tunnels in Iran to amplify its application range.Relative displacements and strength factor(defined as a strength-to-stress ratio)were obtained in unstable stations first.Then,the parametric values were plotted on a Cartesian coordinate’s plane.By using the optimal regression line passing through all points,a criterion for prediction of tunnel deformation was proposed finally.A comparison made between the measured values and the ones predicted by the new criterion shows that the variance accounted for was 77%and the root mean square error was 2%,an acceptable accuracy and a small error implying the effectiveness of the new criterion in tunnel deformation prediction.In addition,the results show that the strength factor of 0.38 can be used to determine the boundary between squeezing and non-squeezing conditions;the behavior and type of failure of the tunnel would be predictable by use of the strength factor. 展开更多
关键词 Strength factor TUNNEL DEFORMATION Monitoring Failure type TUNNELING
在线阅读 下载PDF
基于GNS3的IPSec-VPN仿真设计与实现 预览
10
作者 吴志森 《九江职业技术学院学报》 2019年第1期21-23,17共4页
利用GNS3网络模拟器构建IPSec-VPN网络,实现密钥管理和交换、认证和数据篡改的安全机制。通过Ping工具和Wireshark对数据包进行测试和验证分析,保证了同一网络不同站点之间进行数据交换时对数据包是加密的。
关键词 GNS3 VPN IPSEC 隧道
在线阅读 免费下载
Method of Hill Tunneling via Weighted Simplex Centroid for Continuous Piecewise Linear Programming
11
作者 Zhiming Xu Yu Bai +1 位作者 Kuangyu Liu Shuning Wang 《清华大学学报自然科学版(英文版)》 EI CAS CSCD 2019年第3期301-316,共16页
This paper works on a heuristic algorithm with determinacy for the global optimization of Continuous PieceWise Linear(CPWL) programming. The widely applied CPWL programming can be equivalently transformed into D.C. pr... This paper works on a heuristic algorithm with determinacy for the global optimization of Continuous PieceWise Linear(CPWL) programming. The widely applied CPWL programming can be equivalently transformed into D.C. programming and concave optimization over a polyhedron. Considering that the super-level sets of concave piecewise linear functions are polyhedra, we propose the Hill Tunneling via Weighted Simplex Centroid(HTWSC) algorithm, which can escape a local optimum to reach the other side of its contour surface by cutting across the super-level set. The searching path for hill tunneling is established via the weighted centroid of a constructed simplex. In the numerical experiments, different weighting methods are studied first, and the best is chosen for the proposed HTWSC algorithm. Then, the HTWSC algorithm is compared with the hill detouring method and the software CPLEX for the equivalent mixed integer programming, with results indicating its superior performance in terms of numerical efficiency and the global search capability. 展开更多
关键词 global optimization PIECEWISE linear CONCAVE minimization cutting plane METHOD HILL TUNNELING
EJM340/4-2掘锚一体机在凉水井矿的应用
12
作者 王佃武 《煤矿机械》 北大核心 2019年第3期118-120,共3页
针对采掘衔接紧张、掘进技术落后的现状,凉水井矿采用掘支运平行作业理念,结合4-2煤的地质条件和巷道规格,引入国产掘锚一体机,优化掘、支、运工艺,提高掘进自动化和智能化水平,实现了掘进效率的大幅提升。
关键词 掘锚一体机 掘进 平行作业
快速通过陷落柱大断面全锚喷浆支护的应用 预览
13
作者 刘孟凯 《江西煤炭科技》 2019年第2期7-8,13共3页
山西霍宝干河煤矿2-106掘进工作面副巷掘进过程中遇2个陷落柱,经过对地质条件的分析,采用大断面全锚喷浆支护,支护强度达到了设计要求,有效降低了巷道维修工作量,节约业大量的人力、物力,取得了良好经济、社会效益。
关键词 煤巷掘进 大断面 过陷落柱 锚喷支护
在线阅读 免费下载
Analytical modeling of the junction evolution in single-molecule break junctions: towards quantitative characterization of the time-dependent process
14
作者 Zhi-Chao Pan Jin Li +5 位作者 Lijue Chen Yongxiang Tang Jia Shi Junyang Liu Jie-Lou Liao Wenjing Hong 《中国科学:化学英文版》 SCIE EI CAS CSCD 2019年第9期1245-1256,共12页
The conductance through single-molecule junctions characterized by the break junction techniques consists of the through-space tunneling and through-molecule tunneling conductance, and the existence of through-space t... The conductance through single-molecule junctions characterized by the break junction techniques consists of the through-space tunneling and through-molecule tunneling conductance, and the existence of through-space tunneling between the electrodes makes the quantitative extraction of the intrinsic molecular signals of single-molecule junctions challenging. Here, we established an analytic model to describe the evolution of the conductance of a single molecule in break junction measurements. The experimental data for a series of oligo(aryleneethynylene) derivatives validate the proposed model, which provides a modeling insight into the conductance evolution for the opening process in a "real" break junction experiment. Further modulations revealed that the junction formation probability and rupture distance of the molecular junction, which reflect the junction stability, will significantly influence the amplitude and position of the obtained conductance peak. We further extend our model to a diffusion and a chemical reaction process, for which the simulation results show that the break junction technique offers a quantitative understanding of these time-dependent systems, suggesting the potential of break junction techniques in the quantitative characterization of physical and chemical processes at the single-molecule scale. 展开更多
关键词 break JUNCTIONS SINGLE-MOLECULE CONDUCTANCE modeling through-space TUNNELING
掘进巷道破碎带顶板支护的实践 预览
15
作者 王金强 《山东煤炭科技》 2019年第3期3-5,共3页
巷道在掘进期间经常遇断层构造,受到构造应力的影响,前后顶板会出现破碎、局部冒顶现象,降低了巷道掘进效率,加大了顶板支护难度。对此,在承揽施工5402巷过断层带期间,根据矿方初步设计及主要存在的问题及实际生产需要提出了有效的顶板... 巷道在掘进期间经常遇断层构造,受到构造应力的影响,前后顶板会出现破碎、局部冒顶现象,降低了巷道掘进效率,加大了顶板支护难度。对此,在承揽施工5402巷过断层带期间,根据矿方初步设计及主要存在的问题及实际生产需要提出了有效的顶板控制措施,保证安全高效掘进施工。 展开更多
关键词 掘进 破碎带 支护
在线阅读 下载PDF
General way to define tunneling time
16
作者 舒正 郝小雷 +1 位作者 李卫东 陈京 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第5期27-31,共5页
With the development of attosecond science, tunneling time can now be measured experimentally with the attoclock technique. However, there are many different theoretical definitions of tunneling time and no consensus ... With the development of attosecond science, tunneling time can now be measured experimentally with the attoclock technique. However, there are many different theoretical definitions of tunneling time and no consensus has been achieved.Here, we bridge the relationship between different definitions of tunneling time based on a quantum travel time in onedimensional rectangular barrier tunneling problem. We find that the real quantum travel time tRe is equal to the Bohmian time tBohmian, which is related to the resonance lifetime of a bound state. The total quantum travel time τt can perfectly retrieve the transversal time tx and the Büttiker–Landauer time τBL in two opposite limits, regardless of the particle energy. 展开更多
关键词 TUNNELING TIME Buttiker–Landauer TIME Bohmian TIME
双层车站密贴下穿既有隧道案例分析及隧道沉降变形特征
17
作者 杜文 王永红 +3 位作者 李利 朱连臣 朱浩天 王有旗 《岩土力学》 EI CAS CSCD 北大核心 2019年第7期2765-2773,共9页
长春地铁1号线卫星广场站下穿轻轨3号线工程中,下穿段负一层顶板与轻轨隧道底板密贴接触,形成"叠合板结构"。施工中,先注浆加固下穿段土体,然后采用六导洞PBA法配合千斤顶顶升支撑修建下穿段,具体方法为:于1^#+4^#导洞冠梁上... 长春地铁1号线卫星广场站下穿轻轨3号线工程中,下穿段负一层顶板与轻轨隧道底板密贴接触,形成"叠合板结构"。施工中,先注浆加固下穿段土体,然后采用六导洞PBA法配合千斤顶顶升支撑修建下穿段,具体方法为:于1^#+4^#导洞冠梁上布置液压千斤顶,对上层板形成两端临时支撑;再于3^#+5^#、2^#+4^#导洞内各施作一组钢管混凝土立柱及纵梁,对下层板形成永久支撑,纵梁兼做负一层顶板。然后逐步移除千斤顶、拆除导洞初支、浇筑负一层顶板,实现上下层板密贴;最后修建剩余下穿段结构。为评估施工对轻轨隧道的影响,建立数值模型验算轻轨隧道底板弯矩,结果为安全;数值结果表明,底板沉降经历了先下沉、后抬升、再下沉的复杂过程,最终沉降曲线为单凹槽状。实测数据表明:沉降曲线可划分为振荡型、掉落型两种;曲线类型与测点位置有很大关系,震荡型曲线测点位于下穿段两端,掉落型曲线测点位于下穿段中部,分别受千斤顶、5^#及6^#导洞开挖控制;底板中线最终沉降为单凹槽状,最大沉降量与数值结果相符;变形缝差异沉降在千斤顶作用下一直处于可控状态。 展开更多
关键词 隧道 地铁下穿 叠合板结构 液压顶升 沉降
Comparison of tunneling currents in graphene nanoribbon tunnel field effect transistors calculated using Dirac-like equation and Schrodinger’s equation 预览
18
作者 Endi Suhendi Lilik Hasanah +3 位作者 Dadi Rusdiana Fatimah A. Noor Neny Kurniasih Khairurrijal 《半导体学报:英文版》 EI CAS CSCD 2019年第6期43-47,共5页
The tunneling current in a graphene nanoribbon tunnel field effect transistor(GNR-TFET) has been quantum mechanically modeled. The tunneling current in the GNR-TFET was compared based on calculations of the Dirac-like... The tunneling current in a graphene nanoribbon tunnel field effect transistor(GNR-TFET) has been quantum mechanically modeled. The tunneling current in the GNR-TFET was compared based on calculations of the Dirac-like equation and Schrodinger’s equation. To calculate the electron transmittance, a numerical approach-namely the transfer matrix method(TMM)-was employed and the Launder formula was used to compute the tunneling current. The results suggest that the tunneling currents that were calculated using both equations have similar characteristics for the same parameters, even though they have different values. The tunneling currents that were calculated by applying the Dirac-like equation were lower than those calculated using Schrodinger’s equation. 展开更多
关键词 graphene NANORIBBON TUNNEL field effect transistor tunneling current SCHRODINGER EQUATION Dirac-like EQUATION
在线阅读 下载PDF
Use of virtual reality in underground roof fall hazard assessment and risk mitigation 预览
19
作者 E.Isleyen H.S.Duzgun 《矿业科学技术学报:英文版》 CSCD 2019年第4期603-607,共5页
Virtual reality(VR)simulations are some of the alternative practice environments for safety education.Trainees gain experience under the most realistic conditions without being exposed to any real hazard.Virtual reali... Virtual reality(VR)simulations are some of the alternative practice environments for safety education.Trainees gain experience under the most realistic conditions without being exposed to any real hazard.Virtual reality also serves as a tool to expedite the decision-making process where quick decisions and actions are necessities for a safe operation.One example of such a situation in underground mines is the failure risks in a tunnel face after blasting.Ground support systems must be installed based on the stand-up time to ensure the safe access of personnel and equipment to the working area.Generally,a competent person inspects the area to identify risks and determines the required support systems.However,training of a competent person requires large amount of time and effort.This study presents virtual reality simulations developed for improving the assessment of the roof fall hazards and taking necessary measures for mitigating the risk related to roof fall.The virtual reality simulation involves decision-making tasks for a particular scenario in which participants can experience creating a safe working environment in a timely manner.First,they are asked to identify the potential hazard in a tunnel after blasting,namely,rock fall,wedge failure or groundwater inflow.If the hazard identification is successful,participants are requested to install rock bolts as a safety measure by selecting the bolt pattern(e.g.bolt length and spacing).Finally,participants evaluate the roof fall hazard by viewing displacements around the opening,before and after the support measures.This study illustrates the benefits of VR in safety training as well as enhancing the decision-making process to enhance safety. 展开更多
关键词 Virtual reality Hazard assessment TUNNELING
在线阅读 下载PDF
产业政策、盈余信息质量与审计意见 预览
20
作者 曾慧宇 《商业经济与管理》 CSSCI 北大核心 2019年第6期82-96,共15页
宏观经济政策对微观企业行为影响是当前经济和管理学领域的一个热点话题。文章以2006—2015年沪深两市A股上市公司为样本,理论分析与实证检验了宏观产业政策对微观企业审计意见的影响及其内在机理。实证结果发现,产业政策显著降低了受... 宏观经济政策对微观企业行为影响是当前经济和管理学领域的一个热点话题。文章以2006—2015年沪深两市A股上市公司为样本,理论分析与实证检验了宏观产业政策对微观企业审计意见的影响及其内在机理。实证结果发现,产业政策显著降低了受支持企业被出具非标准审计意见的概率,并且路径分析揭示,产业政策对审计意见的影响通过提高受支持企业的盈余信息质量得以实现,在通过双重差分(DID)控制潜在的内生性之后,仍表明产业政策能显著提高受支持企业的盈余信息质量。进一步探究其内在机理发现,产业政策会降低受支持企业的融资约束程度,从而降低企业市场融资动机下的盈余操纵行为,进而提升其盈余信息质量;同时产业政策会通过降低受支持企业大股东的掏空行为,从而降低其为掩盖掏空而进行的盈余操纵,进而提升盈余信息质量。这些发现揭示了产业政策影响审计意见的内在机理,不但为产业政策的积极经济后果提供了支持证据,也丰富了审计意见研究的相关理论。 展开更多
关键词 产业政策 审计意见 盈余信息质量 融资约束 大股东掏空
在线阅读 免费下载
上一页 1 2 250 下一页 到第
使用帮助 返回顶部 意见反馈