Two Phase Pressure Drop Performance of Refrigerant in a Small Horizontal Smooth Tube with 2.5 mm inside Diameter

Two-phase flow pressure drop measurements were made during the phase change heat transfer process of R22 in a small horizontal smooth tube with 2.5 mm inside diameter. Conclusions can be drawn that the quality corresponding to the pressure gradient peak value of small tubes became higher than that of large tubes. The effect of quality to pressure drop becomes weak as the mass flux increases. The experiment data were compared with the predicated values of the state-of-the-art correlations from the open literature. The comparisons between the data and the predictions indicate that most of the state-of-the-art correlations fails to predict the experimental data. Chisholm model shows a relatively better predictive ability than the other empirical correlations although it has a mean deviation of 26.7%. But the predicated values of Chisholm model are lower by 50% than the experimental data when the quality becomes larger.

Placement of a Long Intestinal Tube in Patients with Early Postoperative Small Bowel Obstruction under Fluoroscopic Guidance

Objective To investigate the placement of a long tube into the small intestine under fluoroscopic guidance and to evaluate its decompression effect on early postoperative small bowel obstruction(EPSBO).Methods Fifty-four patients with EPSBO requiring decompression between April 2010 and July 2014 were enrolled in the study.Insertion of a long tube was guided by fluoroscopy.We first used the guide wire to pass the pylorus and then used the 10 Fr feeding tube as an exchangeable tube to put the superstiff wire into the duodenum.Finally the long tube could be passed over the guide wire through the pylorus into the intestine.The total procedure time,the radiation exposure time,and the incidence of complications were evaluated.Results The long tubes passed into the jejunum on initial insertion for all patients,so the success rate of this technique was 100%.The long tube was inserted into ileum in 18 patients.The mean total procedure time was 34.4±8.6 minutes,and the mean radiation exposure time 18.9±6.8 minutes.A total of 47 patients(87%) experienced full recovery following long-tube decompression and without the need for surgical intervention.Conclusions Using the wire-exchange technique,it is easy to place a long tube into the small bowel under fluoroscopic guidance.This decompression method is safe and effective for management of EPSBO.

Forming characteristics of thin-walled tube bending process with small bending radius

Currently requirements of thin-walled tube with small bending radius cause the defects such as wrinkling, overthinning and cross-section distortion more prone to occur in bending process. Based on the analysis of the forming characteristics by analytical and experimental methods, a complete 3D elastic-plastic FEM model of the process was developed using ABAQUS/Explicit code, including bending process, balls retracting and unloading process, and thus the plastic deformation characteristics with small bending radius were investigated. The main results show that: 1) The utmost deformation feature of the NC bending process is its continuous progressive deformation. 2) The occurring conditions of the defects such as wrinkling and tension instability in the process are obtained. The wrinkling is traditional on the double compressive stresses state and the tension instability is on the double tension stresses state. 3) The enhanced non-uniform deformation in thin-walled tube with small bending radius is demonstrated by comparing the stress/ strains distributions under the 1.5D and 1D bending conditions. 4) For ID small bending process, a new method-'stepped mandrel retraction' is proposed to improve the bending quality in experiment according to the FE simulation. The simulation results are verified by experiment.

High-Quality Three-Dimensional Computed Tomography Angiography of Abdominal Viscera with Small Focal Spot, Low Tube Voltage, and Iterative Model Reconstruction Technique

Purpose: To evaluate the quality of three-dimensional (3D) CT angiography images of the abdominal viscera with small focal spot, low tube voltage, and iterative model reconstruction technique (IMR). Materials and Methods: Seven patients with suspected disease of the pancreatobiliary system had undergone CT with high-quality CTA protocol in the present study. There were 5 men and 2 women, ranging in age from 52 to 80 years (mean: 64 years). Results: Depiction of abdominal small artery, small portal vein was possible in all cases. In two cases that we were able to compare, it was superior to standard CTA in small vascular depiction in CTA made clearly in high quality protocol. Conclusions: Although the use of small focal spot, low tube voltage, and IMR can produce higher-quality images of abdominal vessels than standard CTA, this improvement is not significant at elevated radiation doses.

Numerical simulation of small section rectangular tube in parallel welding

The welding temperature field and deformation of parallel arrangement small-section rectangular tubes is calculated by using a non-contact model. After comparing the computed results with the experimentally measured results, it shows that there exist big errors when applying this model to the numerical simulation of small-section rectangular tube＇ s welding temperature field and deformation. Based on a simple analysis of the errors, a contact model is presented. The heat transfer and stress analysis between small-section rectangular tubes and clamping fixture are simulated by using direct constraints method, and then the laws of the temperature distribution, which coincide with experiment, are obtained. A further numerical analysis of the stress and deformation are made, it shows that a ＂T＂ shaped stress-field is formed in the vicinity of the weld. As the stress-field departs from the centroid of tubes＇, this leads to the small rectangular tubes not only have a longitudinal deflection, but also have a transverse bending and deformation.

Small interfering RNA targeting PGC-1α inhibits VEGF expression and tube formation in human retinal vascular endothelial cells

AIMTo determine whether small interfering RNA (siRNA) of PGC-1α could inhibit vascular endothelial growth factor (VEGF) expression and tube formation in human retinal vascular endothelial cells (hRVECs).METHODShRVECs transfected with peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) siRNA were incubated for 24h and then placed into a normoxic (20%, O2) or hypoxic (1%, O2) environment for another 16h. PGC-1α mRNA and protein levels were detected by real-time PCR and Western blot. VEGF mRNA and protein levels were detected by real-time PCR and ELISA. Cell proliferation was evaluated by BrdU incorporation assay. Forty-eight hours after siRNA transfection, hRVECs were planted into Matrigel-coated plates and cultured under normoxic (20%, O2) or hypoxic (1%, O2) conditions for another 48h. The tube formation of hRVECs was observed under an optical microscope and quantified by counting the number of branch points and calculating the total tube length.RESULTSPGC-1α mRNA and protein levels were significantly reduced by PGC-1α siRNA, and VEGF mRNA and protein levels also decreased significantly. The percentage of BrdU-labeled cells in siPGC-1α groups were significantly decreased compared with control siRNA groups under normoxia and hypoxia in cell proliferation assay. In the tube formation assay, PGC-1α siRNA treated cells formed significantly fewer tubes.CONCLUSIONBlocking PGC-1α expression can inhibit VEGF expression in hRVECs and inhibit their ability to form tubes under both normoxic and hypoxic conditions.

National Survey of Attitudes and Practices of Endotracheal Tube Management in Infants and Small Children in Japan

Background: Surveys of pediatric endotracheal tube (ETT) management previously reported that specialists in pediatric anesthesia and intensive care medicine preferred to use uncuffed ETTs for children younger than 8 to 10 years of age. The aim of this study was to reveal the most recent attitudes and clinical practices of pediatric ETT management in Japan. Methods: The attitudes and clinical practices of pediatric ETT management were investigated using the data sheets of each institution and each patient. The data sheets contained information on patient characteristics and type of hospital, surgical procedures, devices used for intubation, and ETT information including types, size, depth, intracuff pressure (ICP), interval of ICP measurement, laryngeal packing, ETT exchange, airway complications, and reintubations. Results: The response rate of this survey was 66.7%. More than half of children older than 2 years of age were intubated with cuffed ETTs;83.5% of cuffed ETTs were used with the cuffs inflated, and ICP was measured in 80.7% of cuffed ETTs. More than half of ICP measurements were only taken at the time of intubation. Post-extubation stridor was rarely observed in cuffed (0.4%) or uncuffed ETTs (1.2%). The pediatric ETT management questionnaire revealed age-based size selection, differences in pressure of air leakage between cuffed (15 - 20 cmH2O) and uncuffed ETTs (20 - 30 cmH2O) of different sizes, the depthmarking method of insertion length. Continuous measurement of ICP was not common. Conclusion: This study revealed widespread use of cuffed ETTs in children older than 2 years of age, rarely occurrence of post-extubation stridor, inflation of cuffs, and practice of ICP measurement.

Correlations of Two-phase Friction of Refrigerant in Horizontal Smooth Tube with 2.5 mm inside Diameter

Two-phase flow pressure drop measurements are made during phase change heat transfer process of R-22 in small horizontal smooth tubes with 2.5 mm inside diameter. Conclusions are drawn that the quality corresponding to pressure gradient peak value of small tubes became higher than that of large tubes and that effects of quality on pressure drop become weak as the increase of mass flux. The experiment data are compared with predicted values of the state-of-the-art correlations from the open literature, which indicates that most of the state-of-the-art correlations fail to predict the present experimental data. Chisholm model shows a relatively better predictive ability than the other empirical correlations because it has the lowest mean deviation of 26.7%. But the predicted values of Chisholm model are 50% lower than experimental data when quality becomes higher. In this regard, an new empirical correlation based on Chisholm model is developed and this modified Chisholm correlation can describe 95% of the present data with ±20% mean deviations.

Effects of process parameters on numerical control bending process for large diameter thin-walled aluminum alloy tubes

Numerical control(NC) bending experiments with different process parameters were carried out for 5052O aluminum alloy tubes with outer diameter of 70 mm, wall thickness of 1.5 mm, and centerline bending radius of 105 mm. And the effects of process parameters on tube wall thinning and cross section distortion were investigated. Meanwhile, acceptable bending of the 5052O aluminum tubes was accomplished based on the above experiments. The results show that the effects of process parameters on bending process for large diameter thin-walled aluminum alloy tubes are similar to those for small diameter thin-walled tubes, but the forming quality of the large diameter thin-walled aluminum alloy tubes is much more sensitive to the process parameters and thus it is more difficult to form.

A case of postoperative recurrent intussusception associated with indwelling bowel tube

Intussusception is quite uncommon in adults.We report a rare case of a 76-year-old man with small bowel intussusception induced by two indwelling bowel tubes,the first a jejunal feeding tube and the second an ileus tube.After complete reduction of the first intussusception caused by the jejunal feeding tube and adhesion,reintussusception occurred due to the postoperative adhesion and ileus tube inserted into the bowel after the previous operation for intussusception.Finally,the part of the jejunum with re-intussusception and adhesion,including the place where the previous reduced intussusception had occurred,was resected.This case is a reminder that when there is no mucosal lesion other than an indwelling bowel tube or a hard adhesion/ inflammation around intussusception,the patient should be operated on without delay for resection of the intussusception to prevent re-intussusception,even if the resected bowel is predicted to be long.

Novel Formula for Calculation of the Optimal Insertion Depth for Cuffed Endotracheal Tubes in Pediatric Major Surgery

Background: Accurate determination of the optimal insertion depth of a pediatric endotracheal tube (ETT) is quite important. The aim of this study was to create an easily available formula that can be used to determine the optimal insertion depth for a cuffed ETT even without depth marking with clear definitions of the upper and lower limits for the tip of ETT in the trachea in clinical practice. Methods: Eighty children under 12 years of age were enrolled. The depth marking of the cuffed ETT was placed at the vocal cords and both lungs were then auscultated using a stethoscope. The upper limit was radiographically defined as the position of the tip of the cuffed ETT being between the clavicles. The lower limit was defined as a distance of 5 mm above the carina. The relationship between the insertion depth and patient characteristics was analyzed to create a formula for optimal ETT insertion depth. Results: Sixty-nine ETTs were optimally placed in the trachea. There were good correlations between the optimal insertion depth of ETTs and patients characteristics (height (R = 0.92);BSA (R = 0.92);weight (R = 0.91);age (R = 0.88)). Using these patient characteristics, we created the following three formulas for calculation of the optimal insertion depth for pediatric cuffed ETTs: insertion depth (cm) = height (cm)/11 + 5.5, weight (kg)/3 + 9.5 or 11 + 3/4 × age (years). The rates of appropriate tube placement of both pediatric cuffed ETTs were 87.5% (Hi-Contour) and 85.0% (Microcuff). Conclusions: Our formula and graphs may be easy to determine the optimal insertion depth of cuffed ETT even without depth marking in clinical practice.

房间空调器小管径室外换热器流路优化

随着空调器的快速发展和国际铜价的持续升高,制冷空调行业采用的换热器在向着小体积、低成本发展的过程中往往面临着性能衰减的技术瓶颈。为突破此瓶颈,以一款冷暖型房间空调器翅片管式室外换热器为研究对象,将其换热管外径由7 mm减小至5 mm并在此基础上优化其流路,最终实现Φ5 mm换热器性能达到初始样机水平并有效降低换热器成本。首先,分别在5种标准工况下测试初始样机性能;然后,利用CoilDesigner软件来分析小管径化对换热器性能的影响,仿真结果表明,在不改变流路布置的情况下,Φ5 mm换热器的换热能力略有提升,但制冷剂侧压降增大4~7倍;进一步地,有针对性地设计了5种流路布置方案来探究分路数、分路汇合位置等因素对换热器传热及压降特性的影响规律,总结了小管径翅片管式换热器流路优化的思路,并设计了3种Φ5 mm管径室外换热器流路优化方案。仿真评估3种方案的可行性后制作样机进行性能测试,实验结果表明:方案(3)性能与原换热器相当,同时其材料成本可降低34.6%。

小径管X射线焊缝图像缺陷识别算法

针对小径管X射线焊缝图像缺陷检测精确率低的现状,通过对图像进行特征分析并结合稀疏字典学习,提出一种基于图像分割的小径管焊缝图像缺陷检测算法.首先,对小径管焊缝图像进行两步图像分割获得感兴趣区域;其次,提取焊缝缺陷,得到缺陷疑似局部图像;最后,提出以不同类型原子间相关性最小为目标的小径管焊缝缺陷字典矩阵数学模型并使用K-SVD算法进行求解,利用该字典矩阵实现圆形缺陷、线形缺陷和噪声的分类鉴别.为提高系统实时性,使用并行编程对图像分割算法进行加速.结果表明,改进后缺陷字典矩阵对圆形缺陷识别成功率为0.974,线形缺陷识别成功率为0.967,且具有较快的识别速度,实现了小径管焊缝图像缺陷的有效识别.

核电站小径薄壁管的超声检测方法

为了对核电站中的小径薄壁管实施有效检测,介绍了水浸聚焦横波法和水浸聚焦纵波直入射法,分析确定了探头的工艺参数,并在含有局部磨损、环形磨损、轴向裂纹、周向裂纹、通孔等缺陷的样管上进行了对比检测。结果表明,两种超声检测方法对于不同缺陷的检出、定量各有优劣,其中水浸聚焦纵波直入射法对于磨损、肿胀、通孔等缺陷的检出能力较强,缺陷定量精确;水浸聚焦横波法对于裂纹检出能力较强,但难以定量;两种方法结合、相互验证,可大幅提升缺陷的检出能力。

用于高温管道的二重动力吸振器设计及力学性能试验

针对传统减振支撑难以解决核电机组中小支管的无规则振动问题,设计了一种基于金属橡胶材料的环形二重三向动力吸振器,其中质量块总质量为0.084 kg,矩形弹簧和金属橡胶固定在质量块与工装夹具之间。首先,构建二重动力吸振器动力学模型。其次,利用质量感应法确定小支管的等效质量,并结合定点理论优化吸振器刚度、阻尼比。最后,对小支管二重动力吸振器系统进行谐响应仿真分析。仿真结果表明:二重动力吸振器对X、Y、Z 3个方向的吸振效果均大于95%。分别对有无安装二重动力吸振器的小支管进行激振试验,正弦激励幅值为5 N,频率为0~150 Hz。数据表明,二重动力吸振器对于小支管主要振动方向Y、Z吸振效果达到95%以上,X方向的吸振效率达到75%以上。

深度学习对放疗影像进行盆腔肠管自动勾画的可行性研究

目的研究基于深度学习对放疗影像进行盆腔肠管自动勾画的可行性。方法随机选取2019—2021年在复旦大学附属中山医院接受放疗的直肠癌患者100例,随机选取其中60例作为训练模型病例,另40例作为测试病例。以手动肠管勾画为标准,基于深度学习自动分割软件AccuContour中的原始小肠模型,分别在60个模型病例中随机选取60、40、20(2组)个病例训练肠管勾画,获得4个训练模型Rec60、Rec40、Rec20A和Rec20B。使用40例测试病例评估原始模型与Rec60模型的Dice相似性系数(Dice similarity coefficient,DSC)、95%Hausdorff距离(95%Hausdorff distance,HD95)和平均对称表面距离(average symmetric surface distance,ASSD),并分别评估5组自动勾画的DSC。使用SPSS软件对几何参数进行配对t检验。结果训练后的勾画更接近手动勾画的肠管,能够较好地分辨肠管边界,可区分小肠与结肠。Rec60的平均DSC、HD95和ASSD分别较原始模型高0.16(P<0.001)、低12.4(P<0.001)和低5.14(P<0.001)。关于DSC,经配对t检验,4个训练模型与原始模型的差异均有统计学意义,Rec60与Rec40之间差异无统计学意义,Rec60和Rec40与Rec20A和Rec20B之间差异有统计学意义,Rec20A与Rec20B之间差异无统计学意义。结论对于放疗影像的自动勾画,模型训练能够有效提高肠管勾画的准确性。在AccuContour软件中40个及以上病例的训练集能够训练出盆腔肠管勾画的最优模型。

多通道平行流扁管-紧凑式翅片相变蓄热器蓄/放热性能

工业余热浪费严重、利用率较低且实际应用过程中受到时间和空间的限制,需要高效蓄热技术和装置来解决此类问题。提出一种将多通道平行流扁管与紧凑式翅片相结合的新型相变蓄热器,以水为载热流体,月桂酸为相变材料。实验研究了载热流体注入方式、流量、入口温度对蓄热器蓄/放热性能的影响,并分析小温差下蓄热器的传热特性。结果显示,该蓄热器相变材料填充率为82.5%,紧凑式翅片的采用极大强化了相变材料侧换热过程,蓄/放热性能优良。当载热流体入口温度分别为45℃和41℃时,相变材料约在270 min和75 min完成相变,最小蓄/放热温差可达2℃,最小温差时的平均蓄热比功率为25.18 W/kg,平均取热比功率为20.23 W/kg。

基于小管密封法的土壤有机质测定探究

为探究土壤有机质测定工作质量的提升路径,在参考已有研究文献的基础上,以小管密封法为基础进行土壤有机质测定,通过实验确定在消解温度170℃和消解时间30 min时,土壤有机质测定实验可取得相对较高的准确性。同时,本次设计的小管密封法在准确性方面明显优于传统的化学氧化法,表明该实验方法具有一定的实际应用价值。

小导管帷幕注浆法在巷道过断层破碎带的应用

在巷道掘进过程中遇涌水的断层破碎带,需先治水再掘进,常用方法为先工作面预注浆,再采用超前管棚+U型钢联合支护。但在含有大量淤泥、砂砾充填物的断层破碎带中,由于预注浆孔难以成型,而影响注浆效果。为解决此问题,马坑铁矿采用“花管”状的小导管作为超前管棚及注浆通道,对小导管进行注浆,加固巷道的围岩,使形成稳定的帷幕,并在马坑铁矿西矿段100m阶段上盘运输巷成功应用。

评估高浓度对比剂联合低管电流在克罗恩病CTE检查的图像质量及辐射剂量

目的这项研究通过比较不同浓度对比剂联合不同管电流在克罗恩病患者的腹部CT血管成像质量及肠壁相对强化值,从而探讨高浓度对比剂联合低管电流扫描方式在克罗恩病患者小肠CT造影的应用价值。方法52例连续患者随机分为低浓度组(A组)和高浓度组(B组),两组患者均行CTE检查,扫描时应用相同的管电压、注射速率、对比剂用量,将动脉期扫描数据作为研究对象,A组(碘浓度为300mg/mL的碘普罗胺)使用自动mAs,B组(碘浓度为400mg/mL的碘美普尔)使用0.6倍自动mAs;比较A组和B组有效辐射剂量及肠系膜上动脉起始段的图像质量客观评价指标(强化程度、信噪比、对比噪声比)、主观评价指标,病灶区域肠壁强化进行以CT值测量为基础的客观评价。结果B组较A组有效剂量降低约40%;B组在动脉期肠系膜上动脉起始段的CT值(366.9±56.5)及相对强化值(321.4±56.4)均高于A组在动脉期肠系膜上动脉起始段的CT值(286.1±36.2)及相对强化值(240.9±36.6),差异有统计学意义(P<0.001);B组在动脉期肠系膜上动脉起始段的CNR(30.4±8.9)及SNR(36.4±10.0)均高于A组在动脉期肠系膜上动脉起始段的CNR(22.0±5.4)及SNR(27.3±6.3),差异有统计学意义(P<0.001);B组在动脉期病变肠壁的CT值(111.7±13.8)及相对强化值(72.5±12.8)均高于A组在动脉期病变肠壁的CT值(94.1±18.2)及相对强化值(48.2±20.7),并且B组在动脉期病变肠壁的相对强化CT值>50HU;A、B两组图像质量主观评分分别为(4.04±0.445)、(4.15±0.464),A、B两组图像质量主观评价无统计学意义(P>0.05)。结论在克罗恩病患者CTE检查中应用高浓度对比剂注射方案联合低管电流,能大幅度降低了患者接受的辐射剂量,对肠系膜上动脉起始段强化程度更高、图像质量更佳,对病变肠壁强化更明显。