Connecting Tube Research Articles

Seismic Behavior of Assembly Joint with CFST Column and H-shaped Steel Beam

Existing concrete-filled steel tubular (CFST) structures are mostly based on cast-in-situ concrete construction technology. The beam-column joint emphasizes the horizontal connection, while the vertical connection of columns is mostly based on a steel tube connection instead of a precast CFST column connection; this is detrimental to the control of the concrete pouring quality and the full assembly of the structure. Thus, the investigation of an assembly joint that enables the full connection between the beam and CFST column is the key to the improvement of the construction quality and the promotion of the development of the assembled structure. This work proposes an assembly joint between an H-shaped steel beam and a CFST column, and the seismic behavior of the joint was investigated by low-cycle loading experiment. The finite element model of the joint was then established by the numerical analysis method. After verifying the rationality of the finite element model, the influences of both the endplate thickness and the bolt diameter on the energy dissipation performance of the joint were investigated via parametric analysis. The results reveal that with the increase of the endplate thickness and the bolt diameter within a certain range, both the bearing capacity and energy dissipation capacity of the joint will be improved. Moreover, the cooperative bearing mechanism of the column connector and concrete can be fully exerted. Thus, these conclusions indicate the feasibility of the use of the proposed assembly joint in practical engineering applications. Finally, the mechanical mechanism of the assembly joint was studied, and the calculation formula of the joint bending capacity was proposed.

The simulation analysis of sealing performance of cone-cone premium tubing connection under combined loads

Under the complex downhole loads, premium tubing connections often suffer from seal failure and threaded connection failure, leading to tubing string leakage and even safety accidents. Therefore, this paper focuses on the cone-cone premium tubing connection, simulating the make-up process and downhole load conditions, establishing three dimensional finite element models of premium tubing connections, analyzing the distribution of equivalent stress and contact pressure on sealing surface, shoulder and thread. The results show that the stress is mainly concentrated on the shoulder and sealing surface under the make-up torque. The equivalent stress on the shoulder shows a trend of increasing first and then stabilizing. The equivalent stress at the sealing surface tends to be stable first and then decreases. Under the combined loads, the overall equivalent stress of connection increases. The contact pressure decreases slightly in the area of sealing surface and the shoulder inflection point. It may cause joint failure and leakage, when the internal pressure is over 80MPa and the axial compressive load is greater than 800kN, which will lead to the maximum equivalent stress of the threaded part exceed 5.5% of the yield strength.

Experimental and theoretical investigation of prefabricated separated core tube flange column connection joint

This paper suggests a separated core tube flange connection column joint to ensure the horizontal shear performance of box section steel columns at the flange connection to meet the performance requirements of column-to-column connection in high-rise buildings and the effective connection of steel columns at the joints. Low cycle reciprocating loading tests were conducted on three specimens with different parameters (separated core tube and stiffeners) to study the seismic mechanical performance of the connection and the finite element analysis (FEA) of separated core tube column connection joint was performed. The result of the experimental study shows that the separated core tube connection joints have fuller hysteresis curves and higher energy dissipation performance, as well as less high-strength bolt tension at the same interlayer displacement angle. This investigation provides experimental evidence of the deformation compatibility of the separated core tube connection. The mechanical properties of the separated core tube connection is basically the same as that of the welded connection, which can realize the rigid connection of the steel box section column. According to the numerical simulation, the failure mode and mechanism of the connection were obtained. Based on the results of tests and the finite element numerical model, further analysis to the rotational performance of the separated core tube flange connection joint in elasto-plastic phase and yield-hardening phase is carried out, and a three-stage bearing capacity calculation theory of the joint in the seismic process is proposed, which was verified by the test and FEA.

Experimental and Numerical Investigations on Seismic Behavior of RC Beam to PVC-CFRP Confined Concrete Column Exterior Joint with Steel Tube Connector

Recently, substantial investigations were developed on a polyvinyl chloride (PVC)-carbon fiber-reinforced polymer (CFRP) confined concrete (PFCC) structure owing to its superior mechanical behavior and durability. However, a convenient and effective joint configuration between the PFCC columns and reinforced concrete (RC) beams still requires in-depth study. In the present work, the seismic performance of an RC beam to PFCC column exterior joint with steel tube connector (STC) is systematically studied. Eleven joint specimens are fabricated and tested, with the steel ratio of STC, reinforcement ratio of the frame beam, axial compression ratio, stirrup ratio of the joint and CFRP strips spacing as the design parameters. The experimental results, that is, 8 the failure modes, hysteretic response, ductility, strength, stiffness and energy dissipation, are analyzed. All specimens exhibit joint shear failure, although the joints with STC exhibit significantly better performance those of ordinary joint. In addition to reducing the axial compression ratio, the reinforcement ratio of the frame beam or increasing the stirrup ratio of the joint can also produce a positive effect. Furthermore, the numerical analysis of the exterior joints is performed; the calculated skeleton curves agree well with the test results, and additional parametric studies (i.e., the diameter, height and concrete strength of the joint) are carried out based on the verified numerical model.

Design and application of a new heat-and-moisture exchanger with anti-splash sputum suctioning function

In the emergency department, open endotracheal suctioning for mechanically ventilated patients with endotracheal intubation will lead to the spread of respiratory droplets and aerosols, polluting the surrounding environment and medical staff. The traditional heat-and-moisture exchanger has the effect of warming and humidifying, and can block pathogenic microorganisms, but it does not have the function of inserting a sputum suction tube. When the heat-and-moisture exchanger is pulled out for sputum suction, it is easy to cause sputum splash, which pollutes the surrounding environment and medical personnel. The addition of closed sputum suction devices will increase the economic burden on patients. Thus, the medical staff of emergency department of the First People's Hospital of Tongxiang City of Zhejiang Province designed a new type of heat-and-moisture exchanger with anti-splash sputum suctioning function and obtained the National Utility Model Patent of China (ZL 2021 2 0017615.0). The new heat-and-moisture exchanger is mainly composed of a receiving cavity, a connecting tube, a sputum suction tube intubation tube, a sealing valve, etc. The disposable sputum suction tube can be used to insert sputum suction, and at the same time, it can prevent the secretion from splashing to ensure sealing. The patent combines the humidification and pathogen blocking functions of the heat-and-moisture exchanger with the anti-splash sputum suctioning function, which is suitable for use in the emergency and critical care medicine departments and has clinically practical value.

A Novel Low-Cost Technique to Allow for Jet Ventilation.

Traditional jet ventilation requires the use of a catheter that is inserted either through an endotracheal tube or laryngoscope. Specially designed laryngoscopes with a built-in luer lock adapter to which the high-pressure tubing may be attached exist but are not always available. We present our experience with an adapter which allows connection of the high-pressure tubing to the suction side port of suitable laryngoscopes that is easily assembled using readily available materials in the operating room. We designed a jet ventilator adapter using a high-pressure jet ventilation tubing assembly and a 3-way stopcock extension set which we have used for the past 13 years. A retrospective case series of all adult patients who underwent direct laryngoscopy and/or bronchoscopy using this jet ventilation adapter between January 2017 and August 2021 was performed. A total of 100 consecutive patients underwent laryngoscopy and bronchoscopy using jet ventilation between January 2017 and August 2021 was identified. The mean age was 56.3 years, and the mean BMI was 31.2. The most common diagnoses were idiopathic subglottic/tracheal stenosis (46.4%), acquired tracheal stenosis (34.1%), and acquired subglottic stenosis (14.8%). The median duration of the surgical procedure was 53 minutes with an interquartile range of 23. The CO2 laser was used in all cases. There was no disconnection of the adapter, episodes of postoperative respiratory compromise, or extraluminal air on chest radiography for any of our cases. Oxygen saturations remained above 90% intraoperatively for all cases. Our simple jet ventilator adapter connects the jet ventilator to the suction side port of suitable laryngoscopes and eliminates the need for a jet ventilation catheter or specialized laryngoscope at a minimal cost.

A Scoping Review of the Use of Improvised External Ventricular Drains in Africa

Poor access to neurosurgical equipment is one of the problems limiting service delivery in Africa. Improvised surgical devices have long been used in Africa as replacements for high-cost standard versions. In this study, we aimed to see if improvised external ventricular drains (EVD) are being used, how these devices are made, and what their outcomes are. The PRISMA extension for scoping reviews was used in conducting this study. A search was conducted from inception to July 2022. PubMed, Ovid Embase, and African Journal Online were searched. Three studies were identified and used. The methods of making the EVD devices were compared and the incidence proportions of improvised EVD-related infections were calculated. The standard ventricular catheter was replaced by cheaper alternatives like a size 6/8 feeding tube or a 14-gauge central line catheter. The connecting tube had low-cost alternatives, and in a study, was replaced by a fluid infusion set. Aggregated outcomes from the three identified studies show that just over half of the sample survived post-EVD insertion (54%). The incidence proportion of EVD-related infections was 24%. This study describes the experience of African centers with an improvised version of the EVD devices and their outcomes. This will serve as a baseline for more research into the use of improvised EVD devices in low-resource settings.

Effects of manifold design parameters on flow uniformity in parallel mini-channels

Flow maldistribution in parallel mini-channels is a critical obstacle to the efficient design of mini-channel heat sinks. The flow maldistribution is known to cause dryout incipience in some channels, which triggers critical heat flux, eventually leading to physical burnout and catastrophic device failure. Hence, enhancing flow uniformity by reducing flow maldistribution is critical. While several attempts have been made to reduce flow maldistribution, most have focused on providing strategic frameworks for enhancing flow uniformity in channels. The present study develops a new predictive tool for quantitatively assessing flow maldistribution in parallel channels based on the parametric effect. Five parameters are considered: channel height, channel width, header length, connection tube diameter, and total volumetric flow rate. Thirty-six different heat sinks are numerically investigated to study the influence of each parameter on flow uniformity in channels. A decrease in channel height, channel width, and total volumetric flow rate and an increase in header length and connection tube diameter reduces the maldistribution factor enhancing channel flow uniformity. By analyzing the effects of these parameters on the flow uniformity in channels, a new correlation for the maldistribution factor constructed with dimensionless groups, including the design parameters, is proposed, which fits the numerical predictions for the maldistribution factor with excellent accuracy, evidenced by a root-mean-squared-error of 1.0%. The parametric assessment of the effects of the different parameters on the flow maldistribution using the new correlation shows that the magnitude of the relative influence of each variable on flow maldistribution can be expressed in the following order: header length > channel height > connection tube diameter > total volumetric flow rate > channel width.

Fluid dynamic assessment of positive end-expiratory pressure in a tracheostomy tube connector during respiration.

High-flow oxygen therapy using a tracheostomy tube is a promising clinical approach to reduce the work of breathing in tracheostomized patients. Positive end-expiratory pressure (PEEP) is usually applied during oxygen inflow to improve oxygenation by preventing end-expiratory lung collapse. However, much is still unknown about the geometrical effects of PEEP, especially regarding tracheostomy tube connectors (or adapters). Quantifying the degree of end-expiratory pressure (EEP) that takes patient-specific spirometry into account would be useful in this regard, but no such framework has been established yet. Thus, a platform to assess PEEP under respiration was developed, wherein three-dimensional simulation of airflow in a tracheostomy tube connector is coupled with a lumped lung model. The numerical model successfully reflected the magnitude of EEP measured experimentally using a lung phantom. Numerical simulations were further performed to quantify the effects of geometrical parameters on PEEP, such as inlet angles and rate of stenosis in the connector. Although sharp inlet angles increased the magnitude of EEP, they cannot be expected to achieve clinically reasonable PEEP. On the other hand, geometrical constriction in the connector can potentially result in PEEP as obtained with conventional nasal cannulae.Graphical abstract

Axial tensile test and design method of special-shaped rigid flange

Unlike the conventional flange with 90°-connecting angle, the new type of special-shaped rigid flange adopting non-90°-connecting angle can effectively reduce the joint region dimensions of steel tube connection in some conditions. Three special-shaped rigid flanges that adopt 45°, 60° and 75°-connecting angles were designed and tested under axial tensile load to investigate the mechanical characteristics and design method. The slip and open deformations occurred between two flange plates under axial tensile load, and the connecting bolts bore non-uniform tensile and shear forces along the bolt elliptical circle, which increase from the short axis to the long axis of elliptical flange plate. In addition, the nonlinear finite element model, whose accuracy was validated by the test results, were built to further inspect the bearing capacity and force-transfer mechanism. The results reveal that the bolt tensile forces are larger than the design values, and the corresponding modified factor was proposed. The stress developments of different fan-shaped sectors were analyzed, and the sectors located on the short axis are suggested to be selected for strength design of flange plate. The stiffener of these sectors has larger load allocation factor, and should be chosen for the strength design of stiffener weld lines. Lastly, the design method of special-shaped rigid flange under axial tensile load was provided, in which the combined tensile and shear forces should be considered for the connecting bolts and weld lines.

Experimental Development of Composite Bicycle Frame

This article focuses on the development of a carbon composite bicycle frame using various experimental methods of structural analysis. Two types of frame specimen were used. The complete frame specimen was tested in accordance with ISO test load cases with the addition of an ergometer test in order to refine the operational strain envelope of such a frame. Resistive strain gauges and optical Fiber Bragg Grating (FBG) sensors were used for this analysis. The FBG sensors were embedded inside the head tube joints during the manufacturing process. The head connection was designed as a geometrically precise form–connection of wound composite tubes, reinforced with a wrap of high-strength unidirectional carbon tapes and carbon fabrics. Additional structural strength laboratory tests were conducted using simplified frame specimens, in order to evaluate the range of the limit case strain ranges. The digital image correlation method was used for the evaluation of the strain distribution in the head tube area. Resistive strain gauges were used for local strain analysis in critical areas. The acoustic emission method was used to detect structural defects before they could influence the stiffness response of the frame. It was found that the joints of the frame tubes are crucial for the strength and safety of the frame. Therefore, attention was also focused on the strengthening of the head tube joint, and on its experimental verification. A positive effect on the strength of the reinforced frame was found by doubling the thickness of the carbon fabric in the head tube joint area.

Difficult Ventilation in an Infant After Successful Intubation.

Manufacturing defects in the connector of the endotracheal tube are not frequently encountered in emergency and planned intubations. In cases where they are encountered, however, they may cause partial or complete airway obstruction in sick infants with limited reserves, giving rise to a life-threatening situation following the intubation. For this reason, endotracheal tubes must be checked carefully before use. To this end, a stylet can be passed through the tube to check for a defect in the tube lumen or tube connector as part of a routine check of an endotracheal tube. This report features a patient who experienced a complete airway obstruction following intubation due to a manufacturing defect in the connector of the endotracheal tube.

Experimental evaluation and component model for single anchored blind-bolted concrete filled tube connections under direct tension

This paper presents an experimental programme of single anchored blind-bolted concrete filled square steel tube connections under tension to understand the joint behaviour, with emphasis on combined failure mode. A total of eight full-scale specimens were fabricated and tested. Parameters including infill concrete, length and diameter of anchored blind-bolt, tube wall thickness and concrete strength were considered. The experimental programme is accompanied by bolt preload tests and a range of material tests for all the elements in the connection. Primarily, three failure modes of the connection were identified, viz., tube wall deformation, bolt fracture and combined failure. It was observed that, apart from the beneficial effect of bolt anchorage length in enhancing the connection performance, the combined failure mode may be preferred over other failure modes for higher ductility and collapse prevention. Concrete strength is identified as the primary influential factor determining the failure modes. A component model based on spring theory is developed for prediction of global force-deformation behaviour of the bolted connection. Based on this analytical model, the strength and stiffness of such a complex connection can be predicted with good accuracy.

Broadband acoustic double-zero-index cloaking with coupled Helmholtz resonators

Acoustic double-zero-index metamaterials (DZIM) characterized by extremely large phase velocity along with no phase changes of the wave propagation inside the materials have received tremendous attention due to the fascinating physics and potential applications. However, due to the requirement of the degeneracy of dipolar and monopolar resonances and the available resonance-induced losses, the realization of highly efficient and broadband near-zero index metamaterials is still facing challenges. Here we report that by coupling two identical Helmholtz resonators with a connecting channel, acoustic DZIM can be realized. Owing to the presence of a connecting tube, the system can generate the dipolar mode that is independently tunable and the monopolar mode that is virtually unchanged. It thereby makes the mass density (ρ) and the reciprocal of the bulk modulus (1/B) simultaneously crossing zero possible. We numerically obtain the transmission and phase, and then calculate the effective mass density and bulk modulus, which agree remarkably well with the experimental results. Finally, we successfully cloak a rectangle block inside a two-dimensional waveguide grafted by the designed acoustic DZIM array of unit cells. A broadband cloaking is experimentally demonstrated at 1865–1925 Hz, which can offer potential possibilities for vast practical applications.

Monotonic loading performance of GFRP beam-column joints connected with slotted-hole bolts.

Nowadays there are many types of glass fiber reinforced polymer(GFRP) composite beam and column joints, such as standard connection, bolted through connection, angle steel connection, tube connection and so on, most of which connected by high-strength bolts with round holes. In this paper, monotonic loading tests on GFRPcomposite beam and column joints connected by slotted-hole bolts were conducted. To compare the performance of different joints, two groups of specimens were used in this study; one of group was the beam-column joints connected by the angle steel, and other group was connected by the tube connection. Specimens with different bolt holes, side plate reinforcement condition, and different bolt pre-tightening forces were studied. Failure modes, bending moment curves, plastic rotation, and yield stiffness of the two groups of joints were compared. Results showed thatthe ultimate bending moment bearing capacity of specimens with side plates could be increased by 30%. Under the same conditions, the bearing capacity of the tube joints was about 10% larger than that of the angle steel joints. Although the bearing capacity of joints was not increased by using slotted holes, plastic rotation capacity and yield stiffness of joints with slotted-hole bolts were 1.1 times than that of the ordinary round-hole bolts joints.

Integration of robotic in the reprocessing and transfer of endoscopes

Background and study aims Optimal hygiene is crucial for patients undergoing flexible endoscopy. Reprocessing is currently influenced by manual procedures performed by endoscopy staff. To overcome this limitation, we designed and evaluated the integration of robotic application for an automated endoscope processing pathway. Methods We used an endoscope reprocessing pass through machine with drying cabinet and a Franka Emika Panda robot. The robot was programmed to interact with its environment in a compliant way, guaranteeing desired contact force thresholds and therefore ensuring safety of both robot and medical equipment. Results In an initial phase we tested the robots’ ability to handle a modified tray holding an endoscope as well as certain challenges (correct positioning, connection of tubing, undesired collisions). We added another Panda robot arm resulting in a device featuring two independent manipulators and tested the accuracy of each individual step. We evaluated 50 consecutive processing and transfer procedures, simulating the average daily throughput of an endoscopic unit. The endoscopes were removed in adapted tray using a specially designed lifting device and placed in an endoscope storage and venting cabinet. The mean time for the handling of the scope was 104.2 ± 1.2 seconds and an accuracy of 100 % (0 failures in 50 attempts) was achieved.Conclusions To the best of our knowledge, this is the first description and evaluation of an automated compliant robotic assistance in the processing of endoscopes. Further development could help to overcome shortcomings of the man handled endoscope processing and could lead to reproducible, standardized and certified endoscope processing.

Vibration damping performance of the electrohydraulic self-leveling unit of the tracked platform of robotic bricklaying combine

The study proposes the use of a semi-active hydro-pneumatic spring damper unit for damping pressure pulsations in the servohydraulic leveling system of an electrohydraulic self-leveling unit of a tracked platform of a robotic bricklaying combine (RBC). The semi-active hydro-pneumatic spring damper unit consisted of a gas spring in the hydro-pneumatic accumulator and a controlled hydraulic damping valve. A model of a hydro-pneumatic accumulator with a connection tube was presented, using lumped hydraulic elements in the form of resistance, inductance, and capacitance (RLC). This model was transformed into a form of frequency impedance, from which the amplitude and phase characteristics were determined. The complex impedance of the throttle valve was determined, in which the real part is resistance and the imaginary part is reactance. Finally, the damping performance characteristics of a semi-active hydro-pneumatic spring damper unit were analyzed.

Polydopamine inner wall-coated hypodermic needle as microextraction device and electrospray emitter for the direct analysis of illicit drugs in oral fluid by ambient mass spectrometry

In this article, polydopamine inner wall-coated hypodermic needles (PDA-HNs) are evaluated as both microextraction devices and electrospray ionization (ESI) emitters for determining selected illicit drugs (methamphetamine, cocaine, and methadone) in oral fluid samples. The PDA film, located in the inner wall of the needle, allows the extraction of the analytes at alkaline pH, where their hydrophobic character is promoted. The extracted analytes are finally eluted in a methanol/formic acid mixture that also acts as ESI solution. For this purpose, a dedicated interface based on the connection of a PEEK tube with the needle hub is proposed. This assembly allows delivering the ESI solution by the infusion syringe pump of the mass spectrometer, providing an efficient ESI on the tip of the needle. The double use of the PDA-HNs as microextraction devices and ESI emitters permits the determination of the target analytes with limits of detection and precision (expressed as relative standard deviation) values better than 2.4 μg/L and 17.6%, respectively. The accuracy was evaluated by analyzing independent spiked oral fluid samples, obtaining good results.

Online hyphenation of centrifugal partition chromatography with countercurrent chromatography (CPC-CCC) and its application to the separation of saturated alkylresorcinols

Centrifugal partition chromatography (CPC) and countercurrent chromatography (CCC) are two preparative techniques mainly used for the isolation and purification of natural products. While CPC benefits from a larger sample capacity, CCC typically provides better peak resolutions and hereby higher purities. In this study, we aimed to combine both advantages by the direct linking of CPC and CCC which was achieved by installation of switching valves and connection tube. The hyphenated CPC-CCC setup was tested with major alkylresorcinols which were obtained from a transesterified and hydrogenated rye extract. Injections of 1- and 5-g samples into the individual CCC system confirmed the limited sample capacity because of immediate flooding with the 5-g sample (total loss of stationary phase). In comparison, the CPC system was stable with 5- and 10-g samples but the peak resolution with 1-g sample was poorer than with the CCC system. Injections of 5- and 10-g samples into the CPC-CCC system were successful. However, a sample load of 10 g resulted in lower purities of the alkylresorcinols (80% or less) due to peak tailing. By contrast, injection of 5-g sample provided high amounts of ~ 1.2 g alkylresorcinols with purities of > 95%.Graphical abstract

Study on thermal performances of a horizontal ground heat exchanger geothermal system with different configurations and arrangements

Horizontal ground heat exchanger (HGHE) is a low-cost shallow geothermal exploitation method compared with vertical ones, but it needs more land area. Optimizing geometrical configurations and arrangements of ground heat exchangers is desirable to enhance heat exchange per unit land area. However, a comprehensive study on different HGHE configurations and arrangements considering atmosphere-soil-HGHE interaction is still inadequate. To this end, thermal performances of four configurations, including slinky, spiral, multi-tube with serial connection and tiled tubes, are compared based on a 3D numerical model for HGHE considering atmosphere conditions variation and humidity migration. Effects of main geometrical parameters on HGHE performance and economical efficiency are investigated for these four configurations. Finally, different tube arrangements of multi-tube HGHE are designed and their thermal performances are analyzed. Results indicated that longer HGHE tube length has better thermal performance but lower economical efficiency, thus being not advisable for the HGHE design. Among these four configurations, multi-tube with serial connection shows the best thermal performance. Increasing the tube spacing is beneficial for reducing the tube mutual interference and enhance the heat exchange per unit land area, which is recommendable. Results are expected to provide meaningful suggestions for the HGHE design.