Double balloon device compared to oxytocin for induction of labour after previous caesarean section

Objective: To assess cervical changes, duration of oxytocin infusion, mode of delivery and complications after cervical ripening using a double balloon device in women with a previous caesarean section. Methods: Longitudinal study including 80 women with a previous caesarean section, no previous vaginal delivery and an unfavourable cervix (Bishop

Layered double hydroxides as electrode materials for flexible energy storage devices

To prevent and mitigate environmental degradation,high-performance and cost-effective electrochemical flexible energy storage systems need to be urgently developed.This demand has led to an increase in research on electrode materials for high-capacity flexible supercapacitors and secondary batteries,which have greatly aided the development of contemporary digital communications and electric vehicles.The use of layered double hydroxides(LDHs)as electrode materials has shown productive results over the last decade,owing to their easy production,versatile composition,low cost,and excellent physicochemical features.This review highlights the distinctive 2D sheet-like structures and electrochemical characteristics of LDH materials,as well as current developments in their fabrication strategies for expanding the application scope of LDHs as electrode materials for flexible supercapacitors and alkali metal(Li,Na,K)ion batteries.

Double Intervention in Single Sitting: Percutaneous Device Closure and Permanent Pacemaker Implantation in a Patient with Atrial Septal Defect

Context: Atrial septal defect may rarely be associated with other cardiac diseases such as arrhythmia, and may require additional intervention. Case report: A 16-year-old boy presented with effort dyspnea, tiredness, and fatigue. The electrocardiograph revealed right bundle branch block, atrioventricular block, and left axis deviation. Ostium secundum type of atrial septal defect was detected by transthoracic echocardiography and was confirmed by transesophageal echocardiography. The patient was advised to undergo percutaneous device closure. Permanent pacemaker implantation was also suggested considering the risk of fatal arrhythmias associated with atrioventricular block. Consequently, patient underwent percutaneous atrial septal defect closure and implantation of pacemaker in a single sitting. Both the procedures were successful, after which the patient showed remarkable symptomatic improvement. Conclusion: In atrial septal defect patients with unexplained atrioventricular block, closure of atrial septal defect and implantation of pacemaker in single sitting appear to be an attractive modality.

Dependence of Plasma Parameters on Plate Separation and Filament Location in a Double Plasma Device

A pair of stainless steel (ss) plates separates the source and target regions of a double plasma device. Two sets of tungsten filaments, placed at different distances from the ss plates, are then used to produce plasma alternately and the plasma parameters in the source and target regions for different discharge voltage, discharge current and plate separation are measured using Langmuir probes. It is found that plasma density and electron temperature are considerably affected and respond differently to changes in the plate separations and the position of the filaments.

Design of an Ultrafast Frequency Doubling Photonic Device

Ultrashort pulses complicate the frequency conversion in a nonlinear crystal, where group velocity mismatch becomes the main obstacle due to dispersion. We present a design for group velocity compensated second harmonic generation in a modulated nonlinear structure, embedded in a liquid crystal box. In this structure, nonlinear crystals act as sources of signal and liquid crystals compensate for group velocity mismatch originating from nonlinear crystals. There are the advantages of the flexible, controllable birefringence of liquid crystals. Meanwhile, a method calculating the parameters of this type of structure is presented. To make it clear, an example is provided. Furthermore, the structure can also be shaped as a waveguide to support integration into other optical devices, applicable to all-optical processing systems.

Treatment of gastrointestinal bleeding in left ventricular assist devices:A comprehensive review

Left ventricular assist devices(LVAD)are increasingly become common as life prolonging therapy in patients with advanced heart failure.Current devices are now used as definitive treatment in some patients given the improved durability of continuous flow pumps.Unfortunately,continuous flow LVADs are fraught with complications such as gastrointestinal(GI)bleeding that are primarily attributed to the formation of arteriovenous malformations.With frequent GI bleeding,antiplatelet and anticoagulation therapies are usually discontinued increasing the risk of life-threatening events.Small bowel bleeds account for 15%as the source and patients often undergo multiple endoscopic procedures.Treatment strategies include resuscitative measures and endoscopic therapies.Medical treatment is with octreotide.Novel treatment options include thalidomide,angiotensin converting enzyme inhibitors/angiotensinⅡreceptor blockers,estrogen-based hormonal therapies,doxycycline,desmopressin and bevacizumab.Current research has explored the mechanism of frequent GI bleeds in this population,including destruction of von Willebrand factor,upregulation of tissue factor,vascular endothelial growth factor,tumor necrosis factor-α,tumor growth factor-β,and angiopoetin-2,and downregulation of angiopoetin-1.In addition,healthcare resource utilization is only increasing in this patient population with higher admissions,readmissions,blood product utilization,and endoscopy.While some of the novel endoscopic and medical therapies for LVAD bleeds are still in their development stages,these tools will yet be crucial as the number of LVAD placements will likely only increase in the coming years.

Fabrication of Fuze Micro-electro-mechanical System Safety Device

Fuze micro-electro-mechanical system（MEMS） has become a popular subject in recent years.Studies have been done for the application of MEMS-based fuze safety and arm devices.The existing researches mainly focused on reducing the cost and volume of the fuze safety device.The reduction in volume allows more payload and,thus,makes small-caliber rounds more effective and the weapon system more affordable.At present,MEMS-based fuze safety devices are fabricated mainly by using deep reactive ion ething or LIGA technology,and the fabrication process research on the fuze MEMS safety device is in the exploring stage.In this paper,a new micro fabrication method of metal-based fuze MEMS safety device is presented based on ultra violet（UV）-LIGA technology.The method consists of SU-8 thick photoresist lithography process,micro electroforming process,no back plate growing process,and SU-8 photoresist sacrificial layer process.Three kinds of double-layer moveable metal devices have been fabricated on metal substrates directly with the method.Because UV-LIGA technology and no back plate growing technology are introduced,the production cycle is shortened and the cost is reduced.The smallest dimension of the devices is 40 μm,which meets the requirement of size.To evaluate the adhesion property between electroforming deposit layer and substrate qualitatively,the impact experiments have been done on the device samples.The experimental result shows that the samples are still in good condition and workable after undergoing impact pulses with 20 kg peak and 150 μs duration and completely met the requirement of strength.The presented fabrication method provides a new option for the development of MEMS fuze and is helpful for the fabrication of similar kinds of micro devices.

Technical Note and Brief Overview of the Materials Science and Technology along with Designing Aspects for Development of Spintronic Devices with Optimum Efficiency

One of the major challenges in designing and fabricating Spintronic devices is the choice of both, Materials and the Technology, along with understanding the intricacies of the Designing aspects. In this communication, we have attempted to briefly discuss these factors, with an aim to draw the attention of the Materials Scientists and Technologists to this serious challenge, in the direction of which, though a lot of research and development work has been done, still needs more concerted efforts to be made in order to make the Spintronic devices that can offer good efficiency for maximizing their usefulness.

Current status of device-assisted enteroscopy: Technical matters, indication, limits and complications

Enteroscopy, defined as direct visualization of the smallbowel with the use of a fiberoptic or capsule endoscopy, has progressed considerably over the past severalyears. The need for endoscopic access to improvediagnosis and treatment of small bowel disease hasled to the development of novel technologies one ofwhich is noninvasive, the video capsule, and a type of invasive technique, the deviceassisted enteroscopy.In particular, the device-assisted enteroscopy consiststhen of three different types of instruments all able toallow, in skilled hands, to display partially or throug-hout its extension (if necessary) the small intestine.Newer devices, double balloon, single balloon and spiral endoscopy, are just entering clinical use. The aim of this article is to review recent advances in small bowelenteroscopy, focusing on indications, modifications toimprove imaging and techniques, pitfalls, and clinical applications of the new instruments. With new technologies, the trials and tribulations of learning new endo-scopic skills and determining their role in the diagnosisand treatment of small bowel disease come. Identification of small bowel lesions has dramatically improved.Studies are underway to determine the best strategy toapply new enteroscopy technologies for the diagnosisand management of small bowel disease, particularly obscure bleeding. Vascular malformations such as angiectasis and small bowel neoplasms as adenocar cinomaor gas trointestinal stromal tumors. Complete entero-scopy of the small bowel is now possible. However, because of the length of the small bowel, endoscopic examination and the rapeutic maneuvers require significant skill, radiological assistance, the use of deep sedation with the assistance of the anesthetist. Prospective ran-domized studies are needed to guide diagnostic testing and the rapy with these new endoscopic techniques.

Design and experiment of the pneumatic double disc precision seed metering device for Chinese flowering cabbage

Single seed metering devices for Chinese flowering cabbage planting machines have suffered such deficiencies as low efficiency,poor accuracy,and instability.To overcome these limitations,a pneumatic double disc precision seed metering device was designed.This innovative device can simultaneously plant four rows,considering the specific agricultural requirements and the geometric characteristics for Chinese flowering cabbage seeds.The precise parameters of the key component seed disc were derived through theoretical calculation.In addition,a detailed account was given for the working principle and workflow of the seed metering device.The discrete element method and EDEM software were employed to optimize the seed disc by exploring the effects of seed disc rotational speed and interleaving seed slots on seed viability.Orthogonal rotation experiments were conducted to evaluate the impact of seed disc rotational speed and negative pressure.While rates of qualified seeding,double seeding and missing seeding were adopted as test indicators.Testing results show that,at a seed disc rotational speed of 41.5 r/min and a negative pressure of 3.80 kPa,the average qualified seeding rate is 90.13%,the average missing seeding rate is 3.30%,and the average double seeding rate is 6.02%.These values satisfy the agricultural requirements for planting Chinese flowering cabbage.The findings can also provide valuable insights for the structural optimization and design of precision seed metering devices for Chinese flowering cabbage.

双粒竖直勺盘式花生精量穴播器节本增效优化设计与应用

根据目前新疆地区花生双粒播种需求,针对现有穴播器结构复杂、维修困难及精量穴播合格率低等问题,通过单粒取种、双粒排种的方式,设计了一种双粒竖直勺盘式花生精量穴播器。通过阐述穴播器结构组成及工作原理,清晰阐明了花生从取种到投种整个工作过程,同时对穴播器关键部件取种盘和隔板的结构参数进行了设计。为验证穴播器结构尺寸及性能的可靠性,选取转速、取种窝眼宽度、开口角度为试验因素,以双粒率、漏播率、重播率为试验指标,进行三因素三水平正交试验,并运用Design-Expert软件进行试验分析及参数优化等,得出最优排种组合为转速26.04 r/min、取种窝眼宽度8.8 mm、开口角度52.96°。此时双粒率94.68%、漏播率2.85%、重播率2.47%,符合国家标准。

气吸双行错置式玉米密植精量排种器设计与试验

针对大豆-玉米复合密植播种模式下传统气吸式排种器单行种盘高转速作业导致充种时间短、气流稳定性差,难以实现高速精量密植播种的问题,设计了一种气吸双行错置式玉米密植精量排种器,阐述了排种器结构与工作原理,对其工作过程及关键部件进行理论分析,构建充种和投种环节的种子力学模型,确定排种盘内外环型孔排布、投种轮、气室等关键结构参数,并开展单、双气道内负压分布、型孔内气流场特性分析,基于DEM-CFD耦合方法对排种器的排种过程进行仿真分析,以作业速度、气室结构和负压为试验因素,充种合格指数、重充指数和漏充指数为评价指标,优选出最优气室结构。通过台架试验开展不同气吸式排种器排种性能对比试验。试验结果表明,在作业速度为5~10 km/h的高速密植工况下,气吸双行错置式密植精量排种器排种合格指数均大于88.7%,且作业速度为10 km/h时,相较于常用单圆环气吸式排种器合格指数提高5.5个百分点,漏播指数降低5.6个百分点;田间试验结果表明,在作业速度为5 km/h下,播种合格指数为95.7%,重播指数为1.6%,漏播指数为2.8%。提出的气吸双行错置式玉米密植精量排种器在高速作业时拥有良好的排种性能,能够满足大豆-玉米高速精量密植播种要求。

高速精量播种机阿基米德螺线型弧面双齿盘覆土装置设计与试验

针对现有重型精量播种机在高速作业时存在覆土装置影响播种均匀性、种沟内种子被“架空”等问题,基于阿基米德螺线切刃曲线与挤压式覆土原理相结合的思路,设计了一种阿基米德螺线型弧面双齿盘覆土装置,实现了覆土厚度适宜且均匀一致,降低覆土作业对播种均匀性影响的目的。本研究对覆土装置的结构参数、覆土量进行分析,确定了影响覆土效果的主要参数取值范围;利用EDEM离散元仿真技术建立了覆土装置-种子-土壤间的离散元模型,对关键参数进行仿真优化,确定弧面双齿盘的最优参数组合;通过田间试验对该装置的作业性能进行了验证。研究结果表明:影响弧面双齿盘作业性能的主要结构参数为阿基米德螺线型弧面双齿盘的中心间距、安装倾角、入土深度。当弧面双齿盘的中心间距为142.6mm、安装倾角为20°、入土深度为55mm时,该装置通过性能良好,覆土厚度均匀一致,平均厚度为47mm,合格粒距标准差、变异系数与空白对照组分别相差0.22mm、1.81个百分点,对播种均匀性影响小,满足精量播种的农艺要求。

基于单片机控制的异形件双轨供料装置的设计

在电子电路板制造行业,部分非标异性元件需要人工完成供料工序,再对接快速贴片机(Surface Mount Technology,SMT)完成整个生产工序,效率低下,无法满足电子产品组装行业的发展需求。为此设计了一种基于单片机控制的散料异形件供料器,包括2套振动装置和直线导轨,振动装置呈螺旋形上升与直线轨道连接,2个直线导轨并行工作,直线振动器可使导轨部件振动使导槽内的散料移动,当散料移动至导槽的末端时,插件机吸夹嘴定点取料从而进行自动贴插件。与传统的手工贴插件相比,散料经本装置供料后,自动贴装品质更加得到保证。实践结果表明,该装置兼容现有的SMT设备及插件机设备,实现了供料器的全自动工作,提高了生产效率;所需员工从5人减少至1人,生产节拍从5 s/件降低至1 s/件,次品率从3‰大幅度下降至1‰。

车端侧滚减振装置对高速双层动车组动力学性能的影响分析

双层动车组设置较大的二系横向阻尼来抑制一次蛇行引起的共振,而较大的二系横向阻尼会使车辆的横向平稳性变差。针对某型高速双层动车组横向平稳性差的问题,基于车端侧滚减振装置的工作原理建立了车端侧滚减振装置在车体滚摆和摇头运动状态下的数学模型,并将AMEsim软件中建立的减振器仿真模型与台架试验进行验证。最后通过建立车端侧滚减振装置与被试车辆的联合仿真模型,在不改变车辆现有悬挂参数的基础上对车端侧滚减振装置的关键参数进行优化选取。仿真结果表明,车端侧滚减振装置可以在不影响车辆垂向平稳性、保证曲线运行安全性的前提下有效改善双层动车组的横向平稳性。

具有双螺旋结构的超弹性柔性导体研究

柔性电子器件由于其稳定、高导电性和高拉伸性等特点而受到广泛的关注。本文制备了一种由热塑性聚氨酯(TPU)线和铜(Cu)丝组成的双螺旋柔性导体(DHFC),导体初始电导率为5.71×10^(7) S/m。通过增大螺旋直径,使其拉伸性能增加,DHFC可恢复的最大形变量可达6706%。在弹性应变范围内,DHFC在重复形变(1000次循环的拉伸,应变为2200%)下表现出较高的稳定性,电阻的增加可以忽略不计。此外,由于导体外部涂有水性聚氨酯(WPU)而使其具有优异的防水性能,在水中所测的电阻值与在空气环境中所测的电阻值基本一致。

基于改性粉煤灰材料的双滤筒VOCs吸附装置开发

针对挥发性有机物(VOCs)污染,基于改性粉煤灰材料的理化性质设计了一种新型VOCs高效吸附装置。采用改性粉煤灰为吸附剂,其成本低廉且再生操作简单;内外双滤桶设计大大增加了被处理气体和吸附剂的接触面积;旋转上升的气流设计使气压分配均匀,避免沟流的出现,减小死层厚度,提高吸附剂的利用率;设有再生装置,吸附剂可与滤筒整体更换,避免散料运输时造成二次污染。本装置贴近工业生产气体处理实际,是一种可实现VOCs高效捕集及回收、吸附剂反复利用的VOCs处理新工艺。

高频双频Buck变换器平面集成磁件优化设计

针对目前开关器件和磁性元件性能不足导致双频Buck变换器的效率和功率密度低的问题,研究了一种高效高功率密度的双频Buck变换器。变换器将工作在连续导通(CCM)模式,采用解耦合的平面集成电感器完成系统磁元件的集成,结合磁件的集成方法、有限的PCB层数和变换器的特性给出双频Buck变换器的参数,然后,提出了一种双频Buck变换器平面磁件的设计方法,并完成系统磁元件的优化设计。最后,基于第3代半导体SiC器件以及平面集成磁件,设计了额定功率200 W、开关频率400 kHz的双频Buck变换器。结果表明:该变换器峰值效率将达到96.1%,功率密度为46.1 W/in^(3)(1 in=25.4 mm),验证了双频Buck变换器设计方法的正确性和有效性。

双轨道弹射式水稻精量直播排种器设计与试验

针对现有排种器存在投种不顺及大播量成穴性较差等问题,本文设计了一种双轨道弹射式水稻精量直播排种器。基于理论分析设计了关键部件,利用DEM-MBD耦合仿真技术得到了弹簧力参数及因素取值范围,明确了转速超过35 r/min后排种器的性能显著下降。以合格率、漏播率及重播率为性能评价指标开展台架正交试验,研究转速、调节深度及稻种球度对排种器工作性能的影响,建立排种性能评价指标的回归预测模型。试验结果表明:排种轮转速为23.06 r/min、型孔深度为8.99 mm、稻种球度为52.7%时,排种器合格率为88.58%、漏播率为4.43%、重播率为6.99%,排种器工作性能最佳。为验证排种器工作性能及优化后参数的准确性,开展了田间试验,试验结果与优化后结果保持一致,回归方程预测结果误差小于2%,验证了试验可行性及参数准确性,在最优参数下排种器穴径合格率为100%、平均穴径为3.62 cm、穴径变异系数为18.45%、平均穴距为22.98 cm、穴距变异系数为8.43%、平均穴粒数为11.08、穴粒数变异系数为17.56%。所设计的排种器具有较好的播种性能、较高的穴径合格率及较低的变异系数,表明该排种器具有良好的成穴性能。

液体火箭发动机热试车启动中导流锥对燃气管路流动特性影响研究

双推力室液体火箭发动机启动过程中,若出现两支管流量分配不均等现象,极易引起点火失败,造成重大损失。因此,燃气管路分叉处内部流动特性和在分叉处布置导流锥对改善流动特性影响的研究具有重要意义。本文针对某双推力室液体火箭发动机热试车启动过程中的燃气管路,以试验数据作为边界条件,开展了瞬态流动数值仿真研究。结果表明,火箭发动机热试车启动过程中,燃气管路流动呈现出4个典型阶段,分别为点火前的平稳期、点火后的一次上升期、下降期和二次上升期。在启动过程中,无导流锥时,导流罩进口存在预旋回流区、一侧出口存在滞止回流区,导流罩与燃气支管衔接处内侧存在转弯回流区,三者相互作用是造成两支管间压力分布不对称及出口质量流量分配不平衡的主要原因;有导流锥时,预旋回流区被导流锥约束而缩小,滞止回流区消失。有导流锥与无导流锥时相比,在启动过程中约0.2 s与0.6 s时刻,两支管对称测点压差均值分别降低约80.0%与80.0%,两支管出口质量流量差值分别降低约55.0%与80.8%。导流锥有效改善了流动特性,使得两支管压力分布的对称性提高,流量分配平衡性增强。导流锥对双推力室液体火箭发动机稳定性提高有重要作用。