Effect of cyclotron resonance on ‘hot’ dispersion in a staggered double metallic grating sheet beam travelling wave tube

Based on the beam wave synchronous interaction in transverse and longitudinal directions at the same time and starting from Maxwell’s equation and linear Vlasov equation, the beam–wave interaction ‘hot’ dispersion equation considering both cyclotron resonance and Cherenkov resonance in a staggered double metallic grating traveling wave tube is deduced.Through the reasonable selection for geometric and electrical parameters, the numerical calculation and analysis of the ‘hot’ dispersion equation shows that the beam–wave interaction gain and frequency band with the cyclotron resonance enhancement effect are higher than those with only Cherenkov resonance radiation.

Effect of Empowering Education on Refined Nursing of Patients with Internal Double J Tubes after Surgery for Ureteral Stricture

Objective: To investigate the effect of the theory of enabling education on the fine management of patients with internal double J tubes after ureteral stricture. Methods: Eighty patients with built-in double J tubes after ureteral stricture were selected from the urology department of a grade a hospital in Guangzhou. The patients were divided into control group and observation group by random number method, with 40 patients in each group. The control group received refined nursing after surgery, while the observation group received refined nursing including the theory of empowerment education after surgery on the basis of the control group. Results: After the intervention, the observation group had a higher standard rate of quality indicators, higher self-efficacy score than the control group (P ≤ 0.05), lower scores of ureteral stent-related symptoms, urinary system symptoms, pain symptoms, total health status, job performance, additional problems and total scores than the control group (P ≤ 0.05), and statistically significant differences were found in the total health status dimension and total scores (P ≤ 0.01). The nursing satisfaction survey, the scores of clinical nursing, health education, psychological counseling and nurse-patient communication were all higher than those in the control group (P ≤ 0.05), and the differences in health education and nurse-patient communication were statistically significant (P ≤ 0.01). Conclusion: The theory of enabling education can improve patients’ self-nursing level, promote the implementation of refined nursing quantitative indicators and nursing measures, relieve the poor symptoms of ureteral stricture patients, and improve patients’ satisfaction with nursing work.

A staggered double vane circuit for a W-band traveling-wave tube amplifier

Based on the combination of a staggered double vane slow wave structure （SWS） and round electron beam, a 200-W W-band traveling-wave tube （TWT） amplifier is studied in this paper. The main advantages of round beam operation over the sheet beam is that the round beam can be formed more easily and the focus requirement can be dramatically reduced. It operates in the fundamental mode at the first spatial harmonic. The geometric parameters are optimized and a transition structure for the slow wave circuit is designed which can well match the signal that enters into and goes out from the tube. Then a TWT model is established and the particle-in-cell （PIC） simulation results show that the tube can provide over 200-W output power in a frequency range of 88 GHz-103 GHz with a maximum power of 289 W at 95 GHz, on the assumption that the input power is 0.1 W and the beam power is 5.155 kW. The corresponding conversion efficiency and gain at 95 GHz are expected to be 5.6% and 34.6 dB, respectively. Such amplifiers can potentially be used in high power microwave-power-modules （MPM） and for other portable applications.

Remote Control System of 37 mm Double Tube Antiaircraft Gun for Hunan Weather Modification

Hunan Weather Modification Center and Suizhou Dafang Precision Electromechanical Engineering Co.,Ltd. of Hubei commonly transformed and installed 83 double tube antiaircraft guns( 37 mm) of Hunan Province in order to realize remote control of computer. After transformation,loading capacity of ammunition feeding machine became large,which could shorten the time of filling shells in the case of short airspace time;one shell launch volume was more,which could improve hail suppression effect; the degree of automation was greatly improved,which could save manpower by more than 50%. It fully embodied the modernization level of Hunan weather modification operation.

Experimental study on the seismic behavior of high strength concrete fi lled double-tube columns

To study the seismic behavior of high strength concrete fi lled double-tube(CFDT) columns,each consisting of an external square steel tube and an internal circular steel tube,quasi-static tests on eight CFDT column specimens were conducted.The test variables included the width-to-thickness ratio(β1) and the area ratio(β2) of the square steel tube,the wall thickness of the circular steel tube,and the axial force(or the axial force ratio) applied to the CFDT columns.The test results indicate that for CFDT columns with a square steel tube with β1 of 50.1 and 24.5,local buckling of the specimen was found at a drift ratio of 1/150 and 1/50,respectively.The lateral force-displacement hysteretic loops of all specimens were plump and stable.Reducing the width-to-thickness ratio of the square steel tube,increasing its area ratio,or increasing the wall thickness of the internal circular steel tube,led to an increased fl exural strength and deformation capacity of the specimens.Increasing the design value of the axial force ratio from 0.8 to 1.0 may increase the fl exural strength of the specimens,while it may also decrease the ultimate deformation capacity of the specimen with β1 of 50.1.

Techno-economic analysis of single U-tube and double U-tube heat exchangers in Chongqing area

On the basis of practical projects in Chongqing,the thermal performance of heat exchangers (single U-tube type and double U-tube type) of the ground-source heat pump (GSHP) system in the hot summer was obtained and analyzed. The data obtained from test could match with the result deduced from theoretical calculation. From the test results,the cooling capacity of double U-tube is 1.6 times that of single U-tube. Taking cost per depth per watt Clq as the evaluation standard,Clq of single U-tube is 4.69 RMB$/W,and Clq of double U-tube is 3.14 RMB$/W. The double U-tube heat exchangers usage should be prioritized.

Numerical simulation on thixo-co-extrusion of double-layer tube with A356/AZ91D

Based on analysis of the main forming methods for double-layer tube,a new short-term forming process called thixo-co-extrusion was put forward in producing double-layer tube by combining the semi-solid forming technology and multi-billet extrusion technology.By means of forward extrusion with shaft,a finite element model of thixo-co-extrusion with A356/AZ91 was constructed by ABAQUS FEM software.The distributions of temperature field and velocity field as well as the contact force during thixo-co-extrusion were studied.The diffusion on the interfaces between inner and outer metals was analyzed.The simulation results show that,in the beginning of thixo-co-extrusion,the uneven wall thickness can appear.To thickness ratio of 5:5,a double layer tube with good inner and outer wall combination can be realized if VA356 is 0.12 m/s and VAZ91 is 0.20 m/s.

Double aortic arch and nasogastric tubes: A fatal combination

Double aortic arch is a common form of complete vascular ring that encircles both the trachea and the esophagus, and presents with various respiratory and esophageal symptoms, usually in the pediatric population. We present a case of double aortic arch in an adult patient that manifested as massive upper gastrointestinal bleeding after prolonged nasogastric intubation.

Virtues of Using a Double Lumen Tube for Anesthesia in Patients with Endobronchial Tumours Requiring Open Lung Resection or Bronchoplastic Procedures

Objective The benefits and risks of using double lumen tube (DLT) in open thoracotomy are not well studied and the relative contraindication for using it in cases of endobronchial tumours is not proven. In this study, we compared our experience with using DLT versus single lumen tube (SLT) for anesthesia in patients requiring an open thoracotomy for resection of endobronchial tumours. Methods A prospective observational study was performed in a single tertiary care university hospital in patients with endobronchial tumours anesthetized with single and double lumen tubes for open thoracotomy procedures over a period from 2010 till 2018. Results One hundred and six patients with endobronchial tumours were studied. There were 76 males. Median age was 32 years (14 - 62). In 96 cases, endobronchial pathology was a typical carcinoid. 58 patients were anesthetized using a DLT and 48 using a SLT. Four cases of near miss from potentially fatal intraoperative tumour migration occurred in the SLT group (p = 0.025). There was only one case of mild tumour bleeding from the DLT group and time of insertion was longer (16.2 vs. 4.5 min p Conclusions We conclude that it is safe to place a double lumen endo tracheal tube for patients with endobronchial tumours requiring open lobectomies or bronchoplastic procedures. An additional benefit of DLT use is increasing surgical satisfaction by reducing spillage and tidal volume loss during surgical anastomosis of the open airway.

An advanced turbulator with blades and semi-conical section for heat transfer improvement in a helical double tube heat exchanger

In present work,a helical double tube heat exchanger is proposed in which an advanced turbulator with blades,semi-conical part,and two holes is inserted in inner section.Two geometrical parameters,including angle of turbulator’s blades(θ) and number of turbulator’s blades(N),are considered.Results indicated that firstly,the best thermal stratification is achieved at θ=180°.Furthermore,at the lowest studied mass flow rate(m = 8 × 10^(-3) kg/s),heat transfer coefficient of turbulator with blade angle of 180° is 130.77%,25%,and 36.36% higher than cases including without turbulator,with turbulator with blade angle of θ =240°,and θ =360°,respectively.Moreover,case with N=12 showed the highest overall performance.At the highest studied mass flow rate(m = 5.842 × 10^(-2) kg/s),heat transfer coefficient for case with N=12 is up to 54.76%,27.45%,and 6.56% higher than cases including without turbulator,with turbulator with N=6,and with turbulator with N=9,respectively.

Simulation Analysis of Flow Characteristics in the Vortex Diode with Double Tangential Tube

The paper analyzed flow characteristics in vortex diode with double tangential tube by numerical simulation. Compared to traditional vortex diode with one tangential tube, the structure of double tangential tube can reduce the forward resistance and improve overall performance. The symmetrical design adopted in vortex diode with double tangential tube;the internal flow field in chamber showed symmetrical distribution in the reverse flow, which can improve the flow stability and accelerate the convergence speed in simulation.

Wind Tunnel Validation of Double Multiple Streamtube Model for Vertical Axis Wind Turbine

The performance and annual energy output have to be predicted to maximize the economic benefits from a wind turbine. Mathematically predicting the performance of Darrieus type lift based turbines are challenging due to the inconsistent angle of attack, blade wake interaction and local induced velocities giving rise to complex flow physics. A reliable and validated mathematical model is therefore essential to optimize the various design parameters prior to manufacture. The objective of the current study is to evaluate widely employed aerodynamic models based on their prediction accuracy, limitations, and computational requirements. Double multiple stream tube models have been discussed in detail and the predictions are experimentally validated through the wind tunnel test of three-bladed H-Darrieus rotor in terms of torque and power coefficient. The possible sources for the deviation between the predicted and measured values have been discussed and concluded with potential solutions.

Design of a re-entrant double-staggered ladder circuit for V-band coupled-cavity traveling-wave tubes

The re-entrant double-staggered ladder slow-wave structure is employed in a high-power V-band coupled-cavity traveling-wave tube. This structure has a wide bandwidth, a moderate interaction impedance, and excellent thermal dissipation properties, as well as easy fabrication. A well-matched waveguide coupler is proposed for the structure. Combining the design of attenuators, a full-scale three-dimensional circuit model for the V-band coupled-cavity traveling- wave tube is constructed. The electromagnetic characteristics and the beam wave interaction of this structure are investigated. The beam current is set to be 100 mA, and the cathode voltage is tuned from 16.8 kV to 15.8 kV. The calculation results show that this tube can produce a saturated average output power over 100 W with an instantaneous bandwidth greater than 1.25 GHz in the frequency ranging from 58 GHz to 62 GHz. The corresponding gain and electronic efficiency can reach over 32 dB and 6.5%, respectively.

钢管混凝土双块式轨枕无砟轨道结构疲劳性能试验研究

新型钢管混凝土(CFT)双块式轨枕克服了桁架钢筋双块式轨枕存在的生产制造复杂、存放易锈蚀、运营阶段易开裂等问题,可广泛应用于高速铁路和城市轨道交通无砟轨道结构。为检验CFT双块式轨枕无砟轨道结构的疲劳性能,采用11根预制CFT双块式轨枕现浇制作足尺无砟轨道结构节段模型,开展橡胶隔振垫式减振轨道和现浇整体式轨道节段的疲劳试验,揭示其疲劳损伤特性,分析典型疲劳加载循环次数后静载作用下轨道结构应变和变形分布及其演化规律。研究结果表明:1.5倍静轴重的疲劳荷载累计作用500万次后,减振节段及整浇节段CFT双块式轨枕无砟轨道结构混凝土均未出现肉眼可见的裂缝,轨枕与现浇道床整体工作性能良好,疲劳性能满足规范要求;停机开展静载试验过程中轨道结构各测点混凝土横向应变值随荷载增大而近似线性增大,最大拉压应变值均远小于混凝土的极限应变值,工作状态良好;轨道整浇节段道床板中处于整体受拉的状态,可见设置层间连接钢筋实现了道床与底座的共同工作;疲劳试验过程中轨道结构测点竖向位移值总体随着静载的增大而逐渐增大,位移量级较小,满足规范要求,减振轨道节段竖向位移值及其变化率大于整浇轨道节段。研究结果可供类似研究及钢管混凝土双块式轨枕无砟轨道结构工程应用参考。

地浸砂岩型铀矿松散岩层单动双管取心钻具的研制与试验

为解决单管钻具取心工艺方法在深部目的层/矿层等松散岩层取心中存在的取心质量差、取心效率低和操作难度大的问题,开展了地浸砂岩型铀矿松散岩层单动双管钻具的研制和试验。通过设计和改进单动机构、断心结构、液力退心机构和快拆机构,研制了两类分别具有可直接液力退心和快速拆卸功能的SD型单动双管钻具。试验结果表明:SD110型双管钻具可在免拆内管的情况下实现地表快速液力退心,提高双管钻具退心效率;SDKC110型钻具可快速拆装更换内管,实现退心和钻进平行作业。与单管钻具相比,SD系列单动双管钻具在松散岩层的平均回次长度提高28.62%,平均机械钻速提高11.61%;与常规单动双管钻具相比,退心操作时间降低了32.69%。SD系列单动双管钻具适用于在松散破碎地层进行取心钻进应用,可有效提高岩心采取效率和岩心质量。

神经重症患者留置双腔胃肠营养管护理专家共识

目的形成神经重症患者留置双腔胃肠营养管护理专家共识,推动护士规范、安全、有效地实施双腔胃肠营养管喂养,满足患者营养需求。方法检索、评价和汇总神经重症患者胃肠营养管护理的相关证据,提取相关的推荐意见,形成专家共识初稿,通过1轮专家函询和2轮专家论证会,结合专家意见修改、完善各条目内容,形成专家共识终稿。结果最终形成的专家共识包括神经重症患者双腔胃肠营养管喂养的操作性定义、置管适应证、置管禁忌证、置管及维护、拔管指征5个方面。结论形成的专家共识实用性较强,可为神经重症患者双腔胃肠营养管的临床护理实践和质量控制提供指导依据。

改良鼻胃肠双腔管两步置管法在神经外科重症患者中的应用

目的探索一种改良的鼻胃肠双腔管置管两步法,可以床旁徒手完成置管应用于神经外科重症患者;方法收集需行肠内营养的神经外科重症患者120例,采用随机数表法分为传统鼻肠管组(对照组)和改良鼻肠双腔管组(改良组),各60例,分别记录入组时的APACHEⅡ评分及GCS评分、年龄、体质量指数(BMI),收集每例患者鼻肠管置管操作时间,置管前心率及置管过程中的最高心率变化,置管前和置管后14 d的鼻窦CT、胸部CT及营养指标,判断是否出现鼻窦炎、吸入性肺炎、消化道出血、营养液潴留及心律失常等并发症。结果2组入组时APACHEⅡ评分,GCS评分,年龄,BMI比较,差异均无统计学意义(t=1.0598,1.2073,0.3104,0.9268;P=0.2914,0.2297,0.7568,0.3559,P均>0.05)。改良组置管时间(54.4±13)min,对照组置管时间(49.4±12.9)min,改良组置管时间略长于对照组(t=2.1334,P=0.035,P<0.05)。置管过程中,改良组和对照组在心率变化方面比较,差异无统计学意义(P>0.05)。改良组控制鼻窦炎(20.0%,12/60)方面优于对照组(36.7%,22/60)(P<0.05),改良组控制肺炎(26.7%,16/60)方面优于对照组(46.7%,28/60)(P<0.05),改良组控制胃液潴留(5.0%,3/60)方面优于对照组(16.7%,10/60)(P<0.05);2组胃肠道出血及心律失常方面比较,差异无统计学意义(P>0.05)。经过14 d的肠内营养治疗后,改良组白蛋白、前白蛋白、血红蛋白及淋巴细胞计数均好于对照组。结论改良的鼻胃肠双腔管两步置管法可在床头徒手完成,与传统方法比较,尽管置管时间略有延长,但鼻窦炎、吸入性肺炎的发生率明显降低,不增加置管相关并发症发生,同时改良组营养指标明显优于对照组。该两步法安全、有效、便捷,值得临床推广。

圆中空夹层不锈钢管水泥砂浆短柱轴压性能研究

海洋工程平台塔架结构中,圆形截面中空双钢管是主要受力构件,工程界十分关注其受压性能和耐腐蚀性能。为研究圆中空夹层不锈钢管水泥砂浆短柱的轴压力学性能,以外不锈钢管壁厚、内碳素钢管直径和是否含夹层水泥砂浆为试验变量,共设计了12个短柱试件。分析各试件的破坏情况、荷载-位移曲线、承载力、变形能力及应变特征,研究不同变量对极限承载力的影响规律。结果表明:试件破坏形态为外钢管端部或中部局部屈曲破坏;随着不锈钢管壁厚的增大,试件的轴压承载力近似呈线性增长;夹层水泥砂浆对试件力学性能影响较大,可有效提高试件承载力,抑制外不锈钢管的变形,提高试件延性;对于含夹层水泥砂浆的试件,承载力随空心率增大而减小,不含夹层水泥砂浆的试件,承载力随空心率增大而增大。根据国内外规范以及相关学者提出的理论公式,计算了试件的极限承载力,并与试验承载力进行了对比分析,给出了设计建议。

新型钢管混凝土枕式无砟轨道动力响应试验研究

采用钢管混凝土构件连接轨枕块形成钢管混凝土轨枕,基于钢管混凝土轨枕设计城市轨道交通用钢管混凝土枕式无砟轨道结构。为掌握钢管混凝土枕式无砟轨道结构在城市轨道交通列车运行条件下的力学性能,验证结构设计的安全性、合理性,分别在减振地段、普通地段铺设钢管混凝土枕式无砟轨道,通过行车试验,测试分析不同列车行驶速度下无砟轨道钢轨、轨枕、道床结构的动力响应。研究结果表明:在列车车速为40、60和80 km/h运行条件下,轮轨垂向力最大值为86.18 kN,横向力最大值为13.99 kN,脱轨系数最大值为0.21,轮重减载率最大值为0.23,测试值均明显小于相应的安全限值,无砟轨道结构满足行车安全性要求;在列车动荷载作用下,钢管混凝土轨枕钢管压应力最大值为3.55 MPa,拉应力最大值为3.77 MPa;轨枕块压应力最大值为1.32 MPa;道床钢筋压应力最大值为2.30 MPa,拉应力最大值为3.54 MPa;道床底压应力最大值0.22 MPa。这些动力响应结果均满足材料的的限值,表明结构保持了良好的力学性能,结构设计合理可行。

特制双导管结构在使用换管器更换气管导管中的应用价值

目的:探讨特制双导管结构在使用换管器更换气管导管过程中的应用价值。方法:选取60例围麻醉期需要更换气管导管的患者为研究对象,根据使用换管器不同分为对照组和试验组,每组各30例。对照组采用常规气管导管换管;试验组采用特制双导管换管。比较两组患者换管指标[一次插管成功率、插管时间、换管器折痕发生率、术后24 h咽痛(VAS评分)、声嘶发生情况]、换管过程中血流动力学[平均动脉压(MAP)、心率(HR)]及不良事件发生情况。结果:试验组患者换管一次插管成功率高于对照组(P<0.05);插管时间短于对照组(P<0.05);换管器折痕发生率低于对照组(P<0.05)。术后24 h,试验组患者咽痛VAS评分低于对照组(P<0.05);两组患者声嘶发生率无统计学差异(P>0.05)。两组患者在换管过程的MAP、HR比较,差异无统计学意义(P>0.05),且均无低氧血症等不良事件发生。结论:特制双导管结构能提高换管器换管一次性成功率,减少换管时间和并发症的发生。