Large Diameter Research Articles

Multiscale 3D printing via active nozzle size and shape control.

Three-dimensional (3D) printers extruding filaments through a fixed nozzle encounter a conflict between high resolution, requiring small diameters, and high speed, requiring large diameters. This limitation is especially pronounced in multiscale architectures featuring both bulk and intricate elements. Here, we introduce adaptive nozzle 3D printing (AN3DP), a technique enabling dynamic alteration of nozzle diameter and cross-sectional shape during printing. The AN3DP nozzle consists of eight independently controllable, tendon-driven pins arrayed around a flexible, pressure-resistant membrane. The design incorporates a tapered angle optimized for extruding shear-thinning inks and a pointed tip suitable for constrained-space printing, such as conformal and embedded printing. AN3DP's efficacy is demonstrated through the fabrication of components with continuous gradients, eliminating the need for discretization, and achieving enhanced density and contour precision compared to traditional 3D printing methods. This platform substantially expands the scope of extrusion-based 3D printers, thus facilitating diverse applications, including bioprinting cell-laden and hierarchical implants with bone-like microarchitecture.

Study on Spray Characteristics and 0-D Model of Marine Injector with Large Orifice Diameter

ABSTRACT Low carbon, cleanliness and efficiency are the three key challenges facing the development of diesel engines. Biodiesel is a crucial step in the transition from fossil fuels to zero-carbon fuels. This study was carried out to investigate the effects of injection pressure and ambient pressure on the biodiesel spray characteristics of a marine large orifice diameter injector. Injection mass has a nonlinear relationship with short injection duration and a linear relationship with long injection duration. Increasing the injection pressure shortens the nonlinear stage and enhances the linear effect. When the injection pressure is increased from 35 MPa to 140 MPa, the injection delay is shortened by 10% (2.5 ms), and the diameter nozzle has almost unaffected on the injection delay. The Arai model was revised based on experimental data to improve its prediction effect on sprays with large nozzle diameters. The new model considers the effects of fuel density and ambient density on penetration before and after breakup, respectively. The penetration of the new model is still proportional to time of after start of injection (t) before the breakup and proportional to t0.6 after the breakup. Increasing the ambient pressure enhances the influence of injection conditions on dimensionless penetration. Compared with the Arai model, the new model reduces the sensitivity of the dimensionless penetration to the injection pressure. Research on biodiesel spray and spray models under large nozzle diameter conditions will be of great help to the application of low-carbon and clean fuels in marine diesel engines.

Mechanism investigation and model assessment of methane flow condensation in minichannels based on numerical simulation

Cryogenic refrigerants represented by methane differ significantly in thermophysical properties from working fluids at ambient temperature. Thus, examining their small-scale heat transfer and flow characteristics is essential for designing compact condensers within the cryogenic field. The numerical simulation of methane condensation in minichannels is conducted, and the process of phase-change mass and energy transfer is investigated by programming. Detailed condensation flow field information is obtained, and surface tension and gravity influences are elucidated. Synergy analysis indicates that the synergy near the tube wall still needs to be improved. Heat transfer performance is proved to be dependent on the relative significance of turbulence intensity and condensate film thickness. The tube inclination exerts a more noticeable influence on the condensation heat transfer for large diameters, which is supported by the dominance of gravity in the condensation heat transfer mechanism at larger diameters. At higher vapor quality and mass flux, the heat transfer enhancement governed by surface tension is more significant. The condensate at the bottom is mainly formed by the accumulation of condensate sliding off the tube top driven by gravity as the diameter increases, reducing the heat transfer region. The mass flux augments the frictional pressure drop more noticeably at high vapor quality. The prediction performance of empirical correlations is evaluated, and all the selected correlations underestimate the frictional pressure drop of methane. Moreover, the figure of merit analysis demonstrates that the pressure drop produced by diameter reduction is more substantial than heat transfer enhancement, suggesting the requirement to assess the pressure drop loss in practical applications.

Sandstone breaking performances and mechanisms of swirling abrasive waterjet during radial jet drilling process

Radial jet drilling (RJD) is one of the emerging hydrocarbon drilling technologies. And, the swirling abrasive waterjet (SAWJ) is expected to drill larger diameter laterals during RJD. Here, the performances and mechanisms of SAWJ breaking sandstone were studied by laboratory experiments. Results showed that the SAWJ could drill a smooth (surface roughness was 0.043 mm) & large (diameter was in 52.0–73.0 mm) circular hole on sandstone. The hole depth/volume increased as the jetting pressure, abrasive mass concentration and exposure time increased. Conversely, they decreased as the standoff distance increased. The optimal parameter combination under our experimental conditions was 30 MPa, 0 mm, 12% and 1 min. The SAWJ sandstone breaking mechanism were the erosion of cements, the integrally peeled off and broken of crystal grain. Failure mode of sandstone was mainly the tensile fracture. The key findings will provide guidance for the application of SAWJ in RJD technology.

Heat transfer performance and optimal design of shallow coaxial ground heat exchangers

The heat transfer performance of coaxial ground heat exchangers (GHEs) can be strongly influenced by their structure parameters and improved by the optimal design. To improve the heat transfer efficiency, this study proposed a coaxial GHE with large pipe diameters and thick inner pipe insulation for shallow ground source heat pump systems, which had heat transfer rates of more than 120 W/m in 12 h during both heat injection and extraction experiments. The validated three-dimensional CFD model was used to numerically investigate the influence of various structural parameters on the heat transfer efficiency considering the thermal short-circuiting effect. The thermal short-circuiting effect could be alleviated with thicker inner pipe insulation, while the decreasing annular space occupied by the insulation would reduce the borehole heat transfer rates, thus, an inner pipe with a 35 mm-thick insulation obtained the optimal heat transfer rate. The inner pipe diameter increase contributed to a more severe thermal short-circuiting and poor heat transfer performance. Increasing the outer pipe diameter improved the heat transfer efficiency and an optimal outer pipe diameter of 155 mm existed when considering the heat transfer performance and its efficiency. Therefore, increasing the inner pipe insulation thickness and outer pipe diameters can be regarded as an efficient method to improve the thermal performance of coaxial GHEs.

Determining a Reliability Centered Maintenance (RCM) analysis model for large diameter prestressed concrete water pipelines

Which maintenance task to perform on an asset is generally known but the schedule of when to perform the task may not be well defined. If the task is performed early, while it may benefit the asset, it may also be expending resources that could be better used elsewhere. If the task is not performed soon enough, the asset may fail, or the asset may require more extensive maintenance be performed. Reliability Centered Maintenance (RCM) is an analysis process used to determine the most effective maintenance strategies. RCM analysis can help an agency establish the most cost effective maintenance strategies for an asset and help establish the best schedule for implementing those strategies. The ultimate goal of an RCM is to determine the required function of an asset with the required reliability at the lowest operation and maintenance costs by identifying revealing indicators of potential failures to establish a condition based strategy; essentially, predicting failures and identifying procedures to minimize the risk of the failure. This paper reviews potential models for predicting the progression of distress of prestressed concrete pipe segments for use in an RCM analysis and proposes a regression model operators can use to forecast when to perform maintenance activities. The paper further considers the condition of the drinking water infrastructure in the United States, developing the case for evaluating predictive models to forecast when a pipeline may reach a specified limit state. The results of this study suggest that RCM analyses for large diameter water pipelines can improve reliability, reduce maintenance costs, and extend the useful life of a pipeline regardless of age or material. Further, using a regression style model with gathered data can be used to forecast when specific maintenance thresholds may be reached, prompting predictive maintenance actions.

Prognostic factors for surgical treatment of radiation-induced scleral necrosis after brachytherapy for uveal melanoma.

Radiation-induced scleral necrosis (RISN) is a less frequent complication of brachytherapy for uveal melanoma, and may require surgical treatment in selected cases. We aimed to identify the prognostic factors for RISN treatment. All patients with brachytherapy for uveal melanoma treated at our institution between 01/1999 and 12/2016 who developed RISN were followed until 02/2021. Various parameters were evaluated through univariable and multivariable Cox regression analysis. The surgical intervention due to RISN was the principal outcome event of this study. Of 115 patients in the final cohort, 51 individuals (44%) underwent RISN treatment (conjunctival revision [n = 2], patching [n = 46] or enucleation [n = 3]) at median 1.80 months after RISN occurrence. Significant RISN characteristics were summarized into a novel RISN severity scale - Grade I: largest diameter ≤ 5 mm and no progression; Grade II: largest diameter > 5 mm or any progression during the follow-up; Grade III: presence of uveal prolapse; and Grade IV: leakage through open eyewall perforation. In the multivariable analysis, the RISN severity scale (aHR = 2.37 per grade increase, p = 0.01) and the time between brachytherapy and RISN occurrence (<15 months, aHR = 6.33, p < 0.0001) were independently associated with the study endpoint. The RISN severity scale showed high diagnostic accuracy for prediction of RISN treatment (AUC = 0.869). In our series, about the half of RISN cases underwent surgical treatment. The presented novel severity scale for RISN might become a helpful tool for clinical management of individuals with RISN. We recommend external validation of the diagnostic accuracy of the presented scale.

Microsphere-assisted hyperspectral imaging: super-resolution, non-destructive metrology for semiconductor devices

As semiconductor devices shrink and their manufacturing processes advance, accurately measuring in-cell critical dimensions (CD) becomes increasingly crucial. Traditional test element group (TEG) measurements are becoming inadequate for representing the fine, repetitive patterns in cell blocks. Conventional non-destructive metrology technologies like optical critical dimension (OCD) are limited due to their large spot diameter of approximately 25 μm, which impedes their efficacy for detailed in-cell structural analysis. Consequently, there is a pressing need for small-spot and non-destructive metrology methods. To address this limitation, we demonstrate a microsphere-assisted hyperspectral imaging (MAHSI) system, specifically designed for small spot optical metrology with super-resolution. Utilizing microsphere-assisted super-resolution imaging, this system achieves an optical resolution of 66 nm within a field of view of 5.6 μm × 5.6 μm. This approach effectively breaks the diffraction limit, significantly enhancing the magnification of the system. The MAHSI system incorporating hyperspectral imaging with a wavelength range of 400–790 nm, enables the capture of the reflection spectrum at each camera pixel. The achieved pixel resolution, which is equivalent to the measuring spot size, is 14.4 nm/pixel and the magnification is 450X. The MAHSI system enables measurement of local uniformity in critical areas like corners and edges of DRAM cell blocks, areas previously challenging to inspect with conventional OCD methods. To our knowledge, this approach represents the first global implementation of microsphere-assisted hyperspectral imaging to address the metrology challenges in complex 3D structures of semiconductor devices.

Bending forming of lightweight large diameter thin-walled aluminum alloy aviation tube

To improve the forming quality of lightweight aviation tubes, the influence of different tube specifications, forming requirements and process parameters on bending forming of large diameter thin-walled (LDTW) LF2M aluminum alloy tubes (AATs) was studied. A finite element analysis model for LDTW AAT bending was established and verified. The results show that with the increase of mandrel extension length [Formula: see text], the wall-thinning ratio tends to increase. With the increase of [Formula: see text], the overall wall-thickening ratio decreases. With the increase of [Formula: see text], the ovality decreases first and then increases. The bending radius has a great influence on wall thickness variation. It has great significance to guide the bending forming of lightweight LDTW aluminum alloy aviation tube.

Value of radiofrequency ablation for treating locally recurrent thyroid cancer: a systematic review and meta-analysis for 2-year follow-up.

To evaluate the safety and efficacy of radiofrequency ablation (RFA) in treating locoregional recurrent thyroid cancer (LRTC) after a 2-year follow-up time. PubMed, Embase and Cochrane Library were searched from inception until 20 September 2022 to find studies reporting the safety and efficacy of RFA in LRTC patients after a 2-year follow-up. Two radiologists performed the data extraction and methodological quality assessment according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We analyzed 6 studies, 229 LRTC patients with 319 locally recurrent tumors were treated with RFA. The mean follow-up time of each study was ≥24 months. The pooled changes in the largest diameter and volume were 7.22 mm (95% confidence interval (CI), 6.35-8.09 mm) and 164.28 mm3 (95% CI, 87.78-240.77 mm3), respectively; the pooled volume reduction rate was 95.03% (95% CI, 87.56-102.49%). The total complete disappearance rate after treatment was 92% (95% CI, 83-100%). The pooled decrease of serum thyroglobulin levels was 0.02 ng/ml (95% CI, -0.00-0.04 ng/ml). The pooled proportion of recurrence rate was 6% (95% CI, 0-13%). The pooled complication rate was 5% (95% CI, 0-10%). The major complications were voice change and hoarseness, only one patient developed permanent vocal cord paralysis; minor complications were cough and pain. Ultrasound-guided RFA is an effective and safe treatment for LRTC based on 2-year follow-up results.

Experience in endoscope choice for neuroendoscopic lavage for intraventricular hemorrhage of prematurity: a systematic review.

Intraventricular hemorrhage (IVH) of prematurity occurs in 20-38% of infants born < 28 weeks gestational age and 15% of infants born in 28-32 weeks gestational age. Treatment has evolved from conservative management and CSF diversion of temporizing and shunting procedures to include strategies aimed at primarily clearing intraventricular blood products. Neuroendoscopic lavage (NEL) aims to decrease the intraventricular blood burden under the same anesthetic as temporizing CSF diversion measures in cases of hydrocephalus from IVH of prematurity. Given the variety of neuroendoscopes, we sought to review the literature and practical considerations to help guide neuroendoscope selection when planning NEL. We conducted a systematic review of the literature on neuroendoscopic lavage in IVH of prematurity to examine data on the choice of neuroendoscope and outcomes regarding shunt rate. We then collected manufacturer data on neuroendoscopic devices, including inflow and outflow mechanisms, working channel specifications, and tools compatible with the working channel. We paired this information with the advantages and disadvantages reported in the literature and observations from the experiences of pediatric neurosurgeons from several institutions to provide a pragmatic evaluation of international clinical experience with each neuroendoscope in NEL. Eight studies were identified; four neuroendoscopes have been used for NEL as reported in the literature. These include the Karl Storz Flexible Neuroendoscope, LOTTA® system, GAAB system, and Aesculap MINOP® system. The LOTTA® and MINOP® systems were similar in setup and instrument options. Positive neuroendoscope features for NEL include increased degrees of visualization, better visualization with the evolution of light and camera sources, the ability to sterilize with autoclave processes, balanced inflow and outflow mechanisms via separate channels, and a working channel. Neuroendoscope disadvantages for NEL may include special sterilization requirements, large outer diameter, and limitations in working channels. A neuroendoscope integrating continuous irrigation, characterized by measured inflow and outflow via separate channels and multiple associated instruments, appears to be the most commonly used technology in the literature. As neuroendoscopes evolve, maximizing clear visualization, adequate inflow, measured outflow, and large enough working channels for paired instrumentation while minimizing the footprint of the outer diameter will be most advantageous when applied for NEL in premature infants.

Complications associated with loop ileostomy: analysis of risk factors.

Loop ileostomy is a common surgical procedure but is associated with complications such as outlet obstruction (OO), parastomal hernia (PH), and high-output stoma (HOS). This study aimed to identify risk factors for these complications, as well as their causal relationships. The study included 188 consecutive patients who underwent loop ileostomy between April 2016 and September 2021. Clinical factors and postoperative stoma-related complications (OO, HOS, and PH) were analyzed retrospectively. Stoma-related factors were evaluated using specific measurements from computed tomography (CT) scans. The incidence, clinical course, and risk factors for the stoma-related complications were investigated. OO was diagnosed in 28 cases (15.7%), PH in 60 (32%), and HOS in 57 (31.8%). A small longitudinal stoma diameter at the rectus abdominis level on CT and a right-sided stoma were significantly associated with OO. Creation of an ileostomy for anastomotic leakage was independently associated with HOS. Higher body weight and a large longitudinal stoma diameter at the rectus abdominis level on CT were significantly associated with PH. There was a significant relationship between the occurrence of OO and HOS. However, the association between OO and PH was marginal. This study identified key risk factors for OO, HOS, and PH as complications of loop ileostomy and their causal relationships. Our findings provide insights that may guide the prevention and management of complications related to loop ileostomy.

The efficacy and safety of additional pulmonary vein antrum substrate ablation after cryo-ablation in patients with persistent atrial fibrillation

Abstract Background Cryo-ablation for persistent atrial fibrillation (PeAF) has been reported to be safe and comparable to radiofrequency (RF) ablation, but the outcome was not satisfactory. AF drivers mapping after pulmonary vein isolation (PVI) was reported to be widely identified in left atrium (LA). On the other hand, extensive drivers ablation is considered to have limited durability of PVI compared to cryo-ablation. Purpose This study sought to investigate the efficacy and safety of additional PV antrum substrate ablation after PVI by cryo-ablation in patients with PeAF. Methods A total of 122 consecutive patients (90 men, 32 women) who underwent ablation between January 2021 and July 2023 for PeAF, except for patients with long standing ≥10years AF, or large LA diameter ≥55mm, or low left ventricular ejection fraction (LVEF) ≤35% with organic heart disease, were divided into three groups; cryo-ablation alone (Cryo group; 30 patients), RF ablation alone guided by AF drivers mapping (RF group; 52 patients), or cryo-ablation plus RF for AF drivers (Cryo+RF group; 40 patients). AF drivers mapping was performed by real-time phase mapping system or complex fractionated electrograms (Figure1). The outcome of freedom from atrial tachy-arrhythmia lasting longer than 30 seconds without anti-arrhythmic drugs after three months blanking period of a single procedure was compared among groups. Results Baseline characteristics of patients (68±9.2 years old, LVEF 57±9.9 %, LA diameter 43±5.4 mm, persistent AF duration 9.4±18 months, long standing ≥1year AF 17 patients) were similar in three groups. The incident of recurrence of atrial tachy-arrhythmia in Cryo+RF group was significantly lower compared with Cryo group (15% vs. 37%; p=0.014) and RF group (15% vs. 25%; p=0.28) (Figure2). There was no serious complication in three groups. Conclusion Additional drivers RF ablation after cryo-ablation for PeAF is safe and associated with a significant reduction in atrial tachy-arrhythmia recurrence.Figure 1Figure 2

Intelligent circumferential deformation prediction of structures in PCCP-E with a large diameter under internal water overpressure based on prototype experiments and Inception-ResNet-LSTM

Prestressed Concrete Cylinder Pipe (PCCP) is extensively employed in long-distance water transmission projects, owing to its notable pressure-bearing capacity and durability. Nonetheless, the operation under overpressure conditions poses a risk of structural damage and functional failure to PCCP during its service life. Consequently, accurate prediction of the deformation characteristics of overpressure operation with the structural deformation data under standard water pressure is of great importance for ensuring the safety and reliability of the project. However, it is a challenge to obtain spatiotemporal features for traditional algorithms. As a consequence, a novel deep learning model, i.e. Inception-ResNet-LSTM, is put forward to forecast PCCP deformation. It integrates the Inception, ResNet, and Long Short-Term Memory (LSTM). Based on the prototype experiments, the monitoring was undertaken on the deformations of the inner and outer concrete layers, the steel cylinders, and the prestressed steel wire under internal water pressures of 0 MPa, 0.2 MPa, 0.4 MPa, 0.6 MPa, 0.8 MPa, 1.0 MPa, and 1.15 MPa. In the case study, the deformation data of different structures are input into Inception-ResNet-LSTM to establish a model. For all the structures, the R2 (coefficient of determination) of the Inception-ResNet-LSTM model exceeds 0.97. Based on the results, it is demonstrated that the model has captured the spatiotemporal features from the monitoring data. In comparison to models based on DL and ML algorithms, Inception-ResNet-LSTM demonstrates superior performance, exhibiting heightened accuracy and enhanced generalization capabilities. It provides a new method for PCCP deformation estimation under overpressure.

Pressure propagation mechanism of open-cell aluminium foam within a pipe under hypervelocity impact

Low-density open-cell aluminium (Al) foam exhibits a different deformation mode under hypervelocity impacts compared to being subjected to medium-low speed and quasi-static compression. In this case, material flows between cells in the form of metal jets and propagates forward. This paper establishes the open-cell Al foam model based on Voronoi tessellation. Using numerical methods, one-dimensional hypervelocity constant velocity impact experiments of 1–6 km/s inside a closed pipe are conducted on Al foam with different internal structure parameters (average cell diameter: 2–3.5 mm; ligament width: 0.251–1 mm). Propagation mechanism of pressure waves in foams and the key factors affecting the propagation velocity are investigated. Three zones are divided according to the condition of jet distribution along the impact direction: unaffected zone, jet influence zone, and particle accumulation zone. The variation of the length of different zones with impact velocity is discussed: higher velocities result in longer jet influence zones but shorter particle accumulation zones. Meanwhile, length of zones is closely related to the width of Al foam ligament and cell pore diameter: the larger the diameter of cell pores and the smaller the width of ligaments, the longer the length of the jet influence zone. Time dependence is exhibited in the length of jet influence zone for the large cell pore diameter specimens(≥0.03 cm). Particle pressures are extracted using the one-dimensional averaging method, which propagates forward significantly lower than in dense materials. Dominant factors affecting the pressure wave propagation of open-cell Al foam, i.e., the internal unloading space, are obtained by combining two-dimensional hypervelocity impact simulation experiments with different boundary conditions. A strong correlation between metal jet distribution and particle pressure propagation is observed.

Design and development of a novel multirotor configuration with counter-rotating coaxial propellers

In this study, a novel multirotor configuration has been developed, which utilizes a coaxial counter-rotating propeller with a large diameter at the center and four propellers with smaller diameters on four arms in an X configuration. The research pursues two main objectives. The first objective is to establish a development method for multirotors based on the well-known V-method approach in system development. The proposed method enables the design team to analyse and evaluate the multirotor at each stage of the design process, from the system to the component level, and improve the design with greater speed and accuracy. Additionally, the proposed approach can be integrated with various optimization methods, if necessary, to achieve an optimal design. The second objective is to provide the proof-of-concept of the novel multirotor configuration. This objective is pursued across different evaluation sections, from evaluating individual components to fully evaluating the multirotor, to assess the performance of this novel configuration and identify its advantages and disadvantages. The results of various evaluations demonstrate the proposed development process's practicality and proves that the novel configuration is operational and competitive with conventional multirotors in various applications.

Influence of precast microbial reinforcement on lateral responses of monopiles

Microbially Induced Calcium Carbonate Precipitation (MICP) provides an environmentally friendly solution for reinforcing large diameter monopiles for offshore wind turbines (OWTs). This study presents an investigation into the lateral responses of monopiles with precast microbial reinforcement using a low-pH one-phase method. Both static and cyclic loading tests were carried out. The results of static loading tests show that the failure mode of the bio-reinforced monopile was an overall overturn failure. The lateral bearing capacity was increased by 50% and the bending moment was reduced by about 25% with the bio-reinforcement. Further investigation was conducted on the secant stiffness, damping ratio, and accumulated deformation of the bio-reinforced monopile under various cyclic loadings. With the bio-reinforcement, the accumulated deformation under one-way cyclic loading can be reduced by 30%–60%. The influences of cyclic loading parameters and loading sequence on pile stiffness were clarified. The growth ratio of pile stiffness due to bio-reinforcement under one-way loading was between 1.65 and 2.82, and decreased with increasing load amplitude. The ratio was smaller under two-way loading. Three competing factors on pile stiffness were identified: cyclic compaction of the unreinforced sandy soil, weakening of the bio-reinforced soil and soil subsidence around the bio-reinforced soil.

Relationship Between Diameter and Pelvic Vein Reflux

Introduction: Diameter has been a complementary measurement in the evaluation of venous valvular insufficiency of superficial veins of the lower extremity. Small veins with reflux or large veins without reflux may indicate alternative treatments. Awareness of pelvic vein reflux is increasing. The pelvic vein diameter-reflux relationship was investigated. Methods: Findings of lower extremity ultrasound (US) and/or clinical conditions—pelvic pain, dyspareunia and dysmenorrhoea—were indications for pelvic/abdominal venous US. Complete US examination included renal, internal iliac and gonadal/ovarian veins. Diameters of the largest right or left pelvic veins were compared with presence of reflux. Intravaginal US was completed in 104 women, age 46 ± 11 (standard deviation) (range 25-76) years old. Pelvic symptoms were reported by 30 (29%) patients. The other patients had pelvic-related recurrent varicose veins or suspected pelvic source of lower extremity venous reflux. Positive and negative predictive values (PPV, NPV) and other statistics at the 90-95% level were calculated relating diameter to pelvic vein reflux. Results: Pelvic vein reflux was detected in 54 (52%) women. Pelvic vein diameters were larger in refluxing, 8.4 ± 1.9 (5.1-14.0) mm, than in nonrefluxing veins, 5.2 ± 1.0 (3.4-8.3) mm ( P &lt; .001 by t test). Diameters ≥6.3 mm had 91% (49/54) sensitivity and 92% (49/53) PPV. Diameters ≤6.3 mm had 94% specificity (47/50) and 89% (47/53) NPV. All veins with diameter ≥8.4 mm ( n = 21) had reflux. All veins with diameter ≤5.0 mm ( n = 27) did not have reflux. Conclusions: Probabilities of pelvic vein reflux were estimated based on diameters. Diameter-reflux agreement solidifies diagnosis. An explanation for contradiction between small diameter and reflux or large diameter and no reflux is recommended.

Harnessing fuzzy logic for building structural health during large diameter tunnelling in urban area

Building structural health is constantly jeopardized by tunnel construction, which thus is in a sustained demand for holistic risk assessment and management approaches. In this study, we propose an enhanced consulting fuzzy model with limited information losses to evaluate the static and dynamic risks of building health deterioration during tunnelling. The model integrates three main strategies including, (i) reducing influence of experts’ bias in the ranking processes; (ii) expanding the space of uncertainties in fuzzy environment, and (iii) controlling risk aversion settings through the prospect theory. The construction of the largest diameter (15.3 m) tunnel in China is adopted as a case study to demonstrate the application of the proposed model in assessing the risk statuses of surrounding buildings. Through the proposed model, the risk index can indicate beneficial or detrimental effects of tunnelling and the degree of risk factors delineates priority actions for risk management. The results enable the development of operational risk abatement procedures to enhance the state of practice of large diameter tunnel construction in complex geological conditions.

The effectiveness of minimally invasive surgical techniques for treating patients with chronic venous insufficiency in the stage of trophic disorders: comparative study

Introduction. Despite the active introduction of minimally invasive techniques into modern phlebology, the problem of surgical treatment of chronic venous insufficiency (CVI) in the stage of trophic disorders is still far from being finally resolved, especially problems of horizontal reflux. Aim. Тo comparatively evaluate the results of using various tactics of minimally invasive surgical treatment in patients with lower extremitiesʹs CVI in the stage of trophic disorders.Materials and methods. A study at 139 patients with CVI at the stage of trophic disorders was carried out. Group 1 (n = 79) included patients who underwent endovasal laser coagulation of the trunks of the great and small saphenous veins (GSV and SSV) with microfoam sclerotherapy of varicose perforating veins. In group 2 (n = 60) – method of intervention was determined by the diameter of Cockettʹs perforants.Results. Indicators of the early postoperative period in the study groups were comparable. After 2 months, no cases of relapse in the GSV and SSV were registered. Recurrence of horizontal reflux was observed only in 6 (7.6%) people in group 1. In long-term postoperative follow-up, decrease in the severity of the disease according to the VCSS scale was found in both groups (p &lt; 0.001). The persistence of pathological reflux along was observed in 16 (22.5%) patients of group 1. Moreover, in 62.5% and 68.75% cases of relapses, the perforants had, respectively, a large diameter and high blood flowʹs speed.Discussion. In general, minimally invasive techniques used demonstrated comparable clinical results and high efficiency. At the same time, the importance of preoperative assessment and taking into account the properties of perforants has been proven.Conclusion. The claimed method should be considered as an effective and safety method of obliteration of incompetent perforating veins at severe forms of CVI.