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压缩性对计算空化装置噪声的影响 预览
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作者 Amir.Bashirzadeh Tabrizi Bin-xin Wu 《风机技术》 2019年第1期29-36,I0008共9页
通过应用混合方法可以简化噪声预测。计算流体动力学计算可以通过求解可压缩或不可压缩的Navier-Stokes方程来确定噪声源的流场变量来完成。正确的假设取决于物理情况和马赫数。虽然在诸如空化孔的空化装置中,通常我们处理的是低马赫数... 通过应用混合方法可以简化噪声预测。计算流体动力学计算可以通过求解可压缩或不可压缩的Navier-Stokes方程来确定噪声源的流场变量来完成。正确的假设取决于物理情况和马赫数。虽然在诸如空化孔的空化装置中,通常我们处理的是低马赫数流量,但是空化是一种声学现象并且可能受到可压缩性的影响。在这项研究中,使用大涡模拟(LES)和Ffowcs Williams-Hawkings(FW-H)公式研究了压缩性在计算空化单孔孔口产生的噪声中的作用。这项工作的结果表明,压缩性在计算空化孔口产生的噪声方面具有重要作用,尤其是在研究低频空化状态下产生的噪声。 展开更多
关键词 ORIFICE LES COMPRESSIBLE Simulation Noise DEVELOPED CAVITATION Super CAVITATION
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The Influences of the Nozzle Throat Length and the Orifice Grooving Degree on Internal Flow Field for a Multi-Entry Fan Nozzle Based on FLUENT 预览
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作者 Wei Deng Ruirui Zhang +3 位作者 Gang Xu Longlong Li Qin Tang Min Xu 《工程(英文)(1947-3931)》 2019年第11期777-790,共14页
Spray nozzle is a key component in equipment for plant protection and water-saving irrigation. The fan nozzle is a kind of spray nozzle, which is widely used in agriculture and forestry for irrigation and control of d... Spray nozzle is a key component in equipment for plant protection and water-saving irrigation. The fan nozzle is a kind of spray nozzle, which is widely used in agriculture and forestry for irrigation and control of diseases, insects, and weeds. In consideration of the increasing velocity of the flow field, when the hydraulic pressure remains unchanged and the flow path becomes narrow, and because the increase of the velocity of spray drops can increase the penetrability of spray drops into the plant canopy, a kind of new fan nozzle with multi entries and simple inner structure was designed and the influences of its structure parameters on the inner flow field were analyzed using FLUENT software. The experimental results showed that the influence of the throat length on the inner flow field of the nozzle was insignificant, while the orifice grooving degree had a significant effect on inner flow field of the nozzle. The larger the grooving degree was, the smaller the pressure and velocity of internal flow field of the nozzle. The nozzle throat length had little influence on the velocity change of internal flow field. Positive correlation was shown between throat length and flow field velocity. 展开更多
关键词 FAN NOZZLE ORIFICE Spray FLUENT Multi-Entry Inner Flow Field
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Criteria for Beverloo’s scaling law
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作者 张晟 林平 +3 位作者 杨光辉 万江锋 田园 杨磊 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第1期628-633,共6页
Beverloo’s scaling law can describe the flow rate of grains discharging from hoppers.In this paper,we show that the Beverloo’s scaling law is valid for varying material parameters.The flow rates from a hopper with d... Beverloo’s scaling law can describe the flow rate of grains discharging from hoppers.In this paper,we show that the Beverloo’s scaling law is valid for varying material parameters.The flow rates from a hopper with different hopper and orifice sizes(D,D0)are studied by running large-scale simulations.When the hopper size is fixed,the numerical results show that Beverloo’s law is valid even if the orifice diameter is very large and then the criteria for this law are discussed.To eliminate the effect of walls,it is found that the criteria can be suggested as D-D0≥40 d or D/D0≥2.Interestingly,it is found that there is still a scaling relation between the flow rate and orifice diameter if D/D0 is fixed and less than 2.When the orifice diameter is close to the hopper size,the velocity field changes and the vertical velocities of grains above the free fall region are much larger.Then,the free fall arch assumption is invalid and Beverloo’s law is inapplicable. 展开更多
关键词 Beverloo’s LAW ORIFICE diameter HOPPER size DISCRETE element method
Bubble formation and evolution behavior from vertical wall orifice 预览
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作者 Zhao-Wei Ma Xiao-Ling Wu +4 位作者 Qin Zhang Guo Yang Gui-Min Liu Hua Li Wei Liu 《核技术:英文版》 SCIE CAS CSCD 2019年第12期94-102,共9页
Bubble formation is an integral part of the twophase flow science.Through numerical simulation and experiments using different air flow rates and orifice diameters,the present study aims at investigating the behavior ... Bubble formation is an integral part of the twophase flow science.Through numerical simulation and experiments using different air flow rates and orifice diameters,the present study aims at investigating the behavior of bubble formation and evolution from vertical wall orifice in quiescent pure water.For the experiments,the images of the bubble formation process under different working conditions were recorded using a high-speed camera and analyzed the entire process.The bubble formation process can be divided into three stages,namely nucleation,stable growth,and necking.According to the obtained results,bubble forms only when the air-phase pressure exceeds the threshold pressure at wall orifice.Due to the influence of the threshold pressure and buoyancy,the bubble volume decreases with an increase in the wall orifice diameter for the same flow rate.Moreover,the volume of fluid method is applied to simulate bubble formation in a three-dimensional model and the"buffer volume"is considered in the simulation model.The simulation results matched well with the experimental data,which proves the existence of threshold pressure and the periodic pressure fluctuation at the wall orifice. 展开更多
关键词 Bubble formation Vertical wall orifice Threshold pressure Pressure fluctuation
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Controlling the size of fragrance microcapsules using designed agitator paddles: Experiment and CFD simulation
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作者 Hongbin Zhao Xuening Fei +3 位作者 Baolian Zhang Shuxing Zhao Guangmin Li Lingyun Cao 《中国颗粒学报:英文版》 SCIE EI CAS CSCD 2019年第2期38-45,共8页
Controlling the size of fragranee microcapsules using designed agitator paddles was investigated and studied by CFD simulation. First, different fluid flows were established by varying stirring speeds, reactor scales,... Controlling the size of fragranee microcapsules using designed agitator paddles was investigated and studied by CFD simulation. First, different fluid flows were established by varying stirring speeds, reactor scales, and agitator paddle design, and the effects of each on particle size and distribution of prepared microcapsules were determined. The experimental results showed that the pattern design of orifices in the plate paddles control the flow field well. Narrow particle-size distributio ns of the microcapsules were obtained. The fluid flow characteristics including fluid velocity field, turbulent kinetic energy field, and shear stress distribution for thedifferent agitator paddle types in different reaction kettles were simulated using CFD tech no logy. The correlations between simulated data and experime ntal results were an alyzed. Significantly, the simulated average flow velocity was found to show good negative linear correlation w让h the average particle size of prepared microcapsules, with a correlation of y =-2.166x + 42.626. 展开更多
关键词 FRAGRANCE MICROCAPSULE MELAMINE-FORMALDEHYDE Particle SIZE Orifice stirring PADDLE CFD simulation
Short-term efficacy of natural orifice specimen extraction surgery for low rectal cancer 预览
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作者 Jun-Hong Hu Xing-Wang Li +4 位作者 Chen-Yu Wang Jun-Jie Zhang Zheng Ge Bing-Hui Li Xu-Hong Lin 《世界临床病例杂志》 2019年第2期122-129,共8页
BACKGROUND This case-control study compared the short-term clinical efficacy of natural orifice specimen extraction surgery(NOSES)using a prolapsing technique and the conventional laparoscopic-assisted approach for lo... BACKGROUND This case-control study compared the short-term clinical efficacy of natural orifice specimen extraction surgery(NOSES)using a prolapsing technique and the conventional laparoscopic-assisted approach for low rectal cancer.AIM To further explore the application value of the transanal placement of the anvil and to evaluate the short-term efficacy of NOSES for resecting specimens of low rectal cancer,as well as to provide a theoretical basis for its extensive clinical application.METHODS From June 2015 to June 2018,108 consecutive laparoscopic-assisted low rectal cancer resections were performed at our center.Among them,26 specimens were resected transanally using a prolapsing technique(NOSES),and 82 specimens were resected through a conventional abdominal wall small incision(LAP).A propensity score matching method was used to select 26 pairs of matched patients,and their perioperative data were analyzed.RESULTS The baseline data were comparable between the two matched groups.All 52 patients underwent the surgery successfully.The operative time,blood loss,number of harvested lymph nodes,postoperative complication rate,circumferential margin involvement,postoperative follow-up data,and postoperative anal function were not statistically significant.The NOSES group had shorter time to gastrointestinal function recovery(2.6±1.0 d vs 3.4±0.9 d,P=0.006),shorter postoperative hospital stay(7.1±1.7 d vs 8.3±1.1 d,P=0.003),lower pain score(day 1:2.7±1.8 vs 4.6±1.9,day 3:2.0±1.1 vs 4.1±1.2,day 5:1.7±0.9 vs 3.3±1.0,P<0.001),a lower rate of additional analgesic use(11.5%vs 61.5%,P=0.001),and a higher satisfaction rate in terms of the aesthetic appearance of the abdominal wall after surgery(100%vs 23.1%,P<0.001).CONCLUSION NOSES for low rectal cancer can achieve satisfactory short-term efficacy and has advantages in reducing postoperative pain,shortening the length of postoperative hospital stay,and improving patients’satisfaction in terms of a more aesthetic appearance of the abdominal wall. 展开更多
关键词 Natural ORIFICE SPECIMEN EXTRACTION SURGERY Low RECTAL cancer Laparoscopy Prolapsing technique No auxiliary INCISION
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浅谈制浆造纸厂臭气的流量测量 预览
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作者 仵旭宇 陈盼 张智建 《中国造纸》 CAS 北大核心 2019年第A01期214-217,共4页
硫酸盐法制浆在工业生产中经常会碰到大量程比流量测量的问题,受管道口径、使用温度和压力等工艺参数的影响,使流量计的选型有些困难。结合现场实际应用情况,比较了几种大量程比流量计的特点和应用场合,主要介绍了项目中采用孔板配合双... 硫酸盐法制浆在工业生产中经常会碰到大量程比流量测量的问题,受管道口径、使用温度和压力等工艺参数的影响,使流量计的选型有些困难。结合现场实际应用情况,比较了几种大量程比流量计的特点和应用场合,主要介绍了项目中采用孔板配合双变送器分段测量大量程比流量的方法。 展开更多
关键词 大量程比 流量计 孔板 双变送器
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白鹤滩拱坝#3底孔顺河向拉应力成因分析
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作者 张昕 刘晓青 +1 位作者 赵兰浩 王浩杰 《水电能源科学》 北大核心 2019年第1期91-94,共4页
以白鹤滩拱坝#3底孔为例,先采用子模型法分析施工期工况下孔口的应力分布情况;再从荷载作用和结构形式角度对孔口顶、底板顺河向拉应力的产生原因进行了三维有限元分析;最后,采用复变函数理论求出孔口附近顺河向应力的解析解,分析其拉... 以白鹤滩拱坝#3底孔为例,先采用子模型法分析施工期工况下孔口的应力分布情况;再从荷载作用和结构形式角度对孔口顶、底板顺河向拉应力的产生原因进行了三维有限元分析;最后,采用复变函数理论求出孔口附近顺河向应力的解析解,分析其拉应力产生的原因。结果表明,泊松比效应是产生孔口顺河向拉应力的主要原因;上游悬臂结构是产生孔口顺河向拉应力的次要原因;弹性状态下配置钢筋对顺河向拉应力大小无明显影响。 展开更多
关键词 拱坝 孔口 顺河向拉应力 悬臂结构 弹性力学 泊松比效应
Endoscopic applications of magnets for the treatment of gastrointestinal diseases 预览
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作者 Bing Hu Lian-Song Ye 《世界胃肠内镜杂志:英文版(电子版)》 2019年第12期548-560,共13页
Endoscopic treatment of gastrointestinal diseases has developed rapidly in recent years,due to its minimally invasive nature.One of the main contributing factors for this progress is the improvement of endoscopic inst... Endoscopic treatment of gastrointestinal diseases has developed rapidly in recent years,due to its minimally invasive nature.One of the main contributing factors for this progress is the improvement of endoscopic instruments,which are essential for facilitating safe and effective endoscopic interventions.However,the slow learning curve required in the implementation of many advanced endoscopic procedures using standard devices is associated with a high risk of complications.Other routine procedures may also be complicated by unexpected difficulties.Based on the ferromagnetic properties of many objects,both internal and external magnetic devices have been developed and applied for multiple endoscopic interventions.The applications of magnets,mainly including compression,anchoring and traction,facilitate many difficult procedures and make it feasible to operate procedures that were previously impossible.Other novel endoscopic applications,such as magnetic nanoparticles,are also under development.In this article,we reviewed published studies of endoscopic applications of magnets for the treatment of gastrointestinal diseases such as precancerous lesions and cancer,obstruction,stricture,congenital and acquired malformations,motility disorders,and ingestion of foreign bodies.Since several endoscopic applications of magnets may also be relevant to surgery,we included them in this review. 展开更多
关键词 ANASTOMOSIS ENDOSCOPES Endoscopic submucosal dissection MAGNETS Natural orifice endoscopic surgery TRACTION
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A Civil Engineering Senior Design Research Effort to Ascertain Discharge Coefficients of Different Orifice Geometries 预览
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作者 Abdalla Alajmi Sayed Sayed Ali +6 位作者 Mohammad Alkhudhari Jumana Alqaffas Zack Carrasco Jocelyn Payan Martin Pasamba Tadeh Zirakian David Boyajian 《土木工程与建筑:英文版》 2019年第3期204-208,共5页
The present researched topic was conceived from a senior design course for Civil Engineering students at CSUN (California State University), Northridge. In this work, experimental trials were performed and compared to... The present researched topic was conceived from a senior design course for Civil Engineering students at CSUN (California State University), Northridge. In this work, experimental trials were performed and compared to establish theoretical values of the discharge coefficient. The discharge coefficient is a dimensionless number used to characterize the flow and pressure loss behavior of nozzles and orifices in fluid systems. A group of low-income undergraduate students with diverse backgrounds designed multiple 3D printed orifices where each 3D printed orifice had a specific shape. Utilizing the methods of technical problem solving, the undergraduates found experimental discharge coefficient values for the following orifices: borda, short-tubed, and sharp-edged. Implementing ethics of engineering practice and utilizing university resources, this study is a representation of the collaborative work of minorities and females that want to expand their knowledge within their respective discipline of Civil Engineering. 展开更多
关键词 Education ORIFICE 3D-printing theory test
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加氢装置紧急泄压限流孔板孔径校核方法 预览
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作者 邵丹丹 艾明 周琴 《山东化工》 CAS 2019年第18期110-111,共2页
本文介绍了一种加氢装置紧急泄压限流孔板孔径的校核计算方法,采用该方法可验证测试孔板孔径是否可达到规定的泄压速率,并进一步计算实际需要的孔板孔径。
关键词 加氢 紧急泄压 孔板 校核计算
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对“醒脑开窍”针刺体系中神–脑–窍的认识
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作者 余亮 樊小农 《中国针灸》 CAS CSCD 北大核心 2019年第8期883-886,共4页
石学敏院士创新性提出"窍闭神匿,神不导气"是中风病的总病机,并创立"醒脑开窍"针刺法,以"脑腑"立论,"治神"思想是其核心内涵,立足于"醒脑""醒神""调神"。临床... 石学敏院士创新性提出"窍闭神匿,神不导气"是中风病的总病机,并创立"醒脑开窍"针刺法,以"脑腑"立论,"治神"思想是其核心内涵,立足于"醒脑""醒神""调神"。临床应用中也拓展到了不同的疾病种类,尽管配穴不同,但其治疗法则始终不离神、脑、窍。笔者通过引用古代文献及借鉴现代不同学者的观点,阐述石学敏院士"治神"思想指导下的神、脑、窍的含义及其相互关系,有助于对石学敏院士学术思想的理解和传承。 展开更多
关键词 醒脑开窍 中风
核电厂核岛设备冷却水系统流量整定 预览
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作者 田崇喜 《科技视界》 2019年第4期283-284,共2页
核岛设备冷却水系统是核电站重要的一回路辅助系统。本文介绍实际调试过程中流量预整定试验的原理和方法,希望对相关人员有借鉴意义。
关键词 设备冷却水系统 流量预整定试验 孔板
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DFR/DFR1压力-流量控制柱塞泵原理分析及研究 预览
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作者 雷欣瑞 王强 +1 位作者 闫尚荣 雷凯栋 《液压气动与密封》 2018年第1期74-76,80共4页
以DFR/DFR1压力-流量控制柱塞泵为研究对象,对其FR流量控制阀与DR压力控制阀的工作原理进行了重点分析;并采取试验对分析结果进行验证与对比。
关键词 DFR/DFR1压力-流量控制 柱塞泵 压力切断 阻尼
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孔口对混凝土重力坝抗爆性能的影响分析 预览
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作者 范鹏鹏 赵小华 +1 位作者 王高辉 杨广栋 《水电与抽水蓄能》 2018年第1期85-90,共6页
为满足防洪、发电、灌溉等需求,混凝土重力坝坝体往往设有很多孔口。当爆炸荷载在这些孔口附近起爆时,势必会对大坝造成一定程度的破坏。本文应用Euler-Lagrangian耦合方法,建立了库水、含孔口坝体、炸药、基岩和空气的全耦合模型,对比... 为满足防洪、发电、灌溉等需求,混凝土重力坝坝体往往设有很多孔口。当爆炸荷载在这些孔口附近起爆时,势必会对大坝造成一定程度的破坏。本文应用Euler-Lagrangian耦合方法,建立了库水、含孔口坝体、炸药、基岩和空气的全耦合模型,对比分析了挡水坝段(不含孔口坝段)和含孔口坝段在水下爆炸荷载作用下的毁伤特征,研究了孔口的存在对大坝毁伤发展过程和破坏模式的影响。结果表明:当坝体含有孔口时,大坝的整体抗爆性能显著降低,在水下爆炸荷载作用下,大坝将在孔口处形成贯穿上下游的裂缝,导致孔口以上的大坝失去挡水作用。 展开更多
关键词 混凝土重力坝 孔口 水下爆炸 毁伤发展过程 全耦合模型
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1000MW超超临界锅炉水冷壁壁温调整方案 预览
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作者 栗润喆 汪忠国 《锅炉制造》 2018年第6期25-26,31共3页
本文介绍了1000MW超超临界锅炉调整水冷壁壁温超温的方法,通过实际运行经验为同类型锅炉设计改进提供依据。
关键词 水冷壁 壁温 节流孔
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孔板泄洪洞宣泄含沙水流脉动壁压特性研究 预览
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作者 刘昉 丁瑞琳 +1 位作者 张建赫 谷欣玉 《天津大学学报:自然科学与工程技术版》 CSCD 北大核心 2018年第8期879-886,共8页
通过模型试验的方法研究了在不同含沙量下孔板泄洪洞脉动壁压的幅值特性、时空相关特性和频域特性.试验结果表明,脉压均方根在不同含沙量下的沿程分布规律相似,含沙量及水流来流条件均对脉压强度的大小产生重要影响,存在临界含沙量... 通过模型试验的方法研究了在不同含沙量下孔板泄洪洞脉动壁压的幅值特性、时空相关特性和频域特性.试验结果表明,脉压均方根在不同含沙量下的沿程分布规律相似,含沙量及水流来流条件均对脉压强度的大小产生重要影响,存在临界含沙量使脉压强度变化趋势发生改变;水流含沙后,时间和空间相关系数均比清水时降低,说明泥沙的加入使得水流大涡旋平均尺度有所减小;在各含沙量条件下脉动壁压的优势频率均属低频范畴,含沙水流归一化功率谱密度曲线存在其他频率的峰值,进一步验证了漩涡平均尺度的减小. 展开更多
关键词 孔板 含沙水流 脉动壁压 幅值 时空相关 频域
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新经自然腔道内镜手术感染控制的研究进展 被引量:2
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作者 刘亚萍 王东 李兆申 《中华消化内镜杂志》 CSCD 北大核心 2018年第3期221-224,共4页
近年来,随着微创技术的进步和人们对微创要求的不断提高,无痕手术逐渐成为微创技术追求和发展的重点。在此背景下,经单孔腹腔镜手术和经自然腔道内镜手术( natural orifice translu minal endoscopic surgery, NOTES)应运而生,并... 近年来,随着微创技术的进步和人们对微创要求的不断提高,无痕手术逐渐成为微创技术追求和发展的重点。在此背景下,经单孔腹腔镜手术和经自然腔道内镜手术( natural orifice translu minal endoscopic surgery, NOTES)应运而生,并成为目前微创发展前沿的两个主要方向。 展开更多
关键词 经自然腔道内镜手术 感染控制 ENDOSCOPIC ORIFICE SURGERY 微创技术 腹腔镜手术
经肛门拖出标本的腹腔镜右半结肠切除1例报告 预览 被引量:1
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作者 茹东跃 刘楠 +2 位作者 刘奇 陈德兴 张虹 《中国微创外科杂志》 CSCD 北大核心 2018年第11期1043-1044,共2页
经自然腔道取标本手术(natural orifice specimen extraction surgery,NOSES)是使用腹腔镜、软内镜等设备完成腹腔内手术,经自然腔道(直肠或阴道)取出标本的腹壁无辅助切口手术,与常规腔镜手术最大的区别在于标本经自然腔道取出,腹... 经自然腔道取标本手术(natural orifice specimen extraction surgery,NOSES)是使用腹腔镜、软内镜等设备完成腹腔内手术,经自然腔道(直肠或阴道)取出标本的腹壁无辅助切口手术,与常规腔镜手术最大的区别在于标本经自然腔道取出,腹壁仅存留几处微小的trocar瘢痕。 展开更多
关键词 右半结肠切除 腹腔镜 标本 ORIFICE surgery 腹腔内手术 肛门 切口手术
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Robotic transoral vestibular parathyroidectomy:Two case reports and review of literature 预览
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作者 Yasar Ozdenkaya Cenk Ersavas Naciye Cigdem Arslan 《世界临床病例杂志》 2018年第12期542-547,共6页
Advances in preoperative localization studies and demands for scarless surgery have promoted the investigation for remote techniques in parathyroid surgery.Transoral vestibular approach seems to provide the most comfo... Advances in preoperative localization studies and demands for scarless surgery have promoted the investigation for remote techniques in parathyroid surgery.Transoral vestibular approach seems to provide the most comfortable and safest access to the neck.In this paper,we report our initial experience with robotic transoral vestibular parathyroidectomy(RTVP)in four patients with primary hyperparathyroidism.The surgery was performed with the Da Vinci system through three trocars introduced from the lower lip vestibule.The procedure was converted to open in two patients due to inappropriate preoperative localization.The mean operative time was 169 min.No postoperative complications were seen.Patients were discharged on postoperative day 1.RTVP is a feasible and safe technique,which allows better surgical exposure and manipulation of the instruments.The advantages of transoral vestibular approach can be enhanced by robotics.Further studies are needed to analyze complications and costs. 展开更多
关键词 TRANSORAL VESTIBULAR SURGERY PARATHYROID ADENOMA Natural orifice transendoluminal SURGERY Robotics PARATHYROIDECTOMY
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新型冠状病毒肺炎防控与诊疗专栏