Target Tube Research Articles

Coupling vibration analysis of heat exchanger tube bundles under different stiffness conditions

A two-dimensional tube bundles fluid–structure coupling model was developed using the CFD approach, with a rigid body motion equation and the Newmark integral method. The numerical simulations were performed to determine the vibration coupling properties between various tube bundles of stiffness. Take the corner square tube bundles with a pitch ratio of 1.28 as the research object. The influence of adjacent tubes with different stiffness on the vibration of the central target tube was analyzed. The research results show that the vibration characteristic of tube bundles is affected by the flow field dominant frequency and the inherent frequency of tube bundles. The vibration of adjacent tube bundles significantly impacts the amplitude and frequency of the central target tube. The equal stiffness and large stiffness tubes upstream or downstream inhibit the vibration displacement of the target tube to some extent. The low-stiffness tubes upstream or downstream significantly enhanced the amplitude of the target tube. The findings can be used to provide a basis for reasonable design and vibration suppression of shell-and-tube heat exchangers.

A seven-channels microwave interferometer measurement system for measuring electron density distribution in hypervelocity transient plasma flow

When a hypersonic vehicle is flying in the near space region, the strong friction between the vehicle and the air can cause the air to ionize. As a result, the plasma sheath around the vehicle and the wake flow field behind it are formed, significantly affecting the electromagnetic (EM) scattering characteristics of the vehicle and resulting in the communication blackout. Therefore, the investigation of electron density distribution of the plasma sheath and wake flow field is of the great significance in the detection, communication, etc. of the hypersonic target. In order to meet the requirements for on-ground electron density distribution measurement of the transient plasma flow fields, the feasibility of measuring electron density profile with seven-channel microwave interferometer measurement system is demonstrated in this work. The wake plasma is modeled as a non-uniform multilayer medium, and the full-wave simulation software FEKO is used to calculate the phase-shift information of EM wave transmitting through non-uniform single-layered dielectric plate, uniform and non-uniform multi-layered dielectric plates. According to the simulation results, the dielectric constant of the substrate is retrieved and compared with the preset result. The retrieved results show that it is feasible that the dielectric constant distribution of non-uniform multi-layered dielectric plate is measured by utilizing the proposed microwave interferometer system with one transmission port and seven receptions. The amplitude-phase dynamic range analysis of the proposed Ka-band microwave measurement system is also carried out. The key technologies including large instantaneous amplitude-phase dynamic range and ray tracking inversion algorithm for two-dimensional (2-D) electron density distribution are also developed. Finally, the complete scheme of Ka-band seven-channel microwave interferometer measurement system is introduced. The system includes one lens antenna to generate the required plane wave and seven open-ended waveguide receiving antennas which are asymmetrically arranged to improve the lateral spatial resolution of the system. The system exhibits the amplitude dynamic range and the phase dynamic range of over 65 dB and 180° under 1 MHz IF bandwidth respectively. The plasma electron density distributions are measured by utilizing the proposed seven-channel microwave interferometer system in the ballistic range and multi-functional shock tube. The response time of the system is smaller than 1μs, satisfying the requirement for the two-dimensional distribution measurement of the transient plasma flow field generated by the ballistic range and multi-functional shock tube. The differences between experimental and numerical results are less than 0.5 order of magnitude, and the variations in transient plasma generated in both ballistic target and shock tube equipments are well detected. The measurement range of plasma electron density is 10<sup>10</sup>－10<sup>13</sup> cm<sup>–3</sup> and the spatial resolution is better than 15mm. In addition, the proposed ray tracing method is also used to invert the two-dimensional (2D) electron density distributions of both square layered model and cylindrical layered model under identical experimental state. The results are in consistent with each other, indicating that the proposed ray tracing method can be used in the inversion of 2D electron density distribution of plasma with different shapes.

Thermoelastic impact modeling for projectile–target–muzzle components during penetration start of motion

This paper presents the thermoelastic shock wave model components of projectile, target, and muzzle tube during the initial start of penetration. The penetration model is combined using pressure and temperature (e.g., mechanical and thermal shock) that act separately at the moment of penetration (a few microseconds) into a homogeneous or first-layer armor body. The armor’s shape and material will be investigated based on contact principal stress. The reciprocal influence between the penetrator and the armor in the aspect of the projectile nose shape will also be demonstrated. Moreover, the penetrator thermoelastic material’s durability will be examined, based on von Mises criterion. The examination for the initial elastic contact stress impact will be performed by using the explicit solution to temperature-displacement coupling equilibrium, based on commercial finite elements modeling. In addition, a modified impact contact stress model based on both mechanical and thermal energies was proposed and found to agree with the literature. Brief conceptual analysis of projectile–shield interactions was examined. Finally, shooting tube muzzle thermoelastic analysis was performed alongside a literature comparison, which was found to agree qualitatively and quantitatively. Muzzle tube material impact analysis was performed. Finally, it was concluded that muzzle tubes obey the rule that a shorter cylinder length tube develops higher muzzle tube principal stresses.

Early Versus Late Feeding After Percutaneous Endoscopic Gastrostomy Placement in Trauma and Burn

IntroductionTiming to resume feeds after percutaneous endoscopic gastrostomy (PEG) placement continues to vary among US trauma surgeons. The purpose of this study was to assess differences in meeting nutritional therapy goals and adverse outcomes with early versus late enteral feeding after PEG placement. MethodsThis retrospective review included 364 trauma and burn patients who underwent PEG placement. Data included patient characteristics, time to initiate feeds, rate feeds were resumed, % feed volume goals on postoperative days 0-7, and complications. Statistical analysis was performed comparing two groups (feeds ≤ 6 h versus > 6 h) and three subgroups (< 4 h, 4-6 h, ≥ 6 h) based on data quartiles. Chi-square/Fisher’s exact test, independent-samples t-test, and one-way analysis of variance were used to analyze the data. ResultsMean time to initiate feeds after PEG was 5.48 ± 4.79 h. Burn patients received early feeds in a larger proportion. A larger proportion of trauma patients received late feeds. The mean % of goal feed volume met on postoperative day 0 was higher in the early feeding group versus the late (P < 0.001). There were no differences in adverse events, even after subgroup analysis of those who received feeds < 4 h after PEG placement. ConclusionsPatients with early initiation of feeds after PEG placement achieve a higher percentage of goals on day 0 without an increased rate of adverse events. Unfortunately, patients routinely fall short of their target tube feeding goals.

An atmospheric pressure plasma device with multiple ring electrodes for decontamination of flexible tubing with variable scales

AbstractPlasma bacteria decontamination devices for the inner surface of medical tubes have to consider more practical application problems, such as the processing compatibility for medical tubes of variable scales, a reasonable and effective design model for plasma electrode parameters, and so on. This paper proposes a novel multisegment‐casing ring‐ring jet (MSC‐RRJ) without embedding the electrode into the target tube, obtaining the variable tube length processing capability. And through establishing an effective design model based on electric field distribution properties, ensuring the electric field strength margin in each segment of MSC‐RRJ to achieve the processing capability of variable tube diameters. A prototype device is developed based on the proposed MSC‐RRJ electrode and design method being verified by killing Staphylococcus aureus and Escherichia coli.

Influence of Foreign Body Blockage in Water Cooling Wall on Flow and Heat Transfer

The ultra (super) critical units, as mainstream thermal power units, often need to participate in deep peak shaving. The variable load and high frequency peak regulation will lead to the partial increase of the temperature of the water-cooled wall and the phenomenon of local over-temperature. Aiming at this situation, the numerical investigation on the water-cooled wall of the #5 boiler in She-yang-gang was performed. The results show that the welding nodules and the foreign bodies in the water-cooled tube have a significant effect on the wall temperature. Moreover, with the increase of the blocking ratio (β), the mass flow in the tube decreases significantly, and the mass flow in the adjacent tubes rising. Further the increase of the mass flow is noteworthy in the nearest tubes. When the β of the target tube is higher than 0.4 the possibility of exceeding the maximum temperature limit of water-cooled wall tube material increases. The deposition of foreign body on the inner wall of the tube weakens the convective heat transfer between the inner wall and the fluid, which makes the wall temperature rise faster than other places. The more serious the deposition, the more obvious this phenomenon is.

Mechanical properties and interface morphology of magnetic pulse-welded Al–Fe tubes with preset geometric features

A dissimilar metal tube joint fabricated by magnetic pulse welding (MPW) usually has uneven mechanical properties and an uneven morphology along the welding direction due to the small discontinuous matching range of the collision parameters. In this work, inclined, concave, and convex wall features were prefabricated on the target tube to improve the uniformity of the mechanical properties. The effects of the types of features and the prefabricated angle on the collision parameters, the axial distribution of the strength, and the interfacial morphology were investigated by simulations, shear tests, and microscopic observations, respectively. The results show that the collision parameters were increased with the increase of the prefabricated angle under the three types of features. Compared with the case without features, the increment of the collision parameters was found to be the greatest under the convex wall feature, and the smallest under the concave wall feature. With the increase of the prefabricated angle under the three types of features, the average shear strength tended to be reduced. When the prefabricated feature was the concave wall with a prefabricated angle of 5°, the quality of the joint was the best; it had an average shear strength of 46.46 MPa, an increase of 87%, and a low standard deviation of 4.96 MPa, a decrease of by 81%, as compared with that without geometric features. The transition layer was found to be the largest under the concave wall feature, and the maximum thickness decreased with the increase of the prefabricated angle.

Trajectory prediction of three-dimensional forming tube based on Kalman filter

This article focuses on the prediction of forming trajectory and process optimization during the forming process for the variable curvature tubes. Firstly, through cubic B-spline interpolation, the geometric characteristics of the axis of the target tube are obtained. The whole tube is “separated and then integrated,” and the relationship between geometric parameters and processing parameters is established to obtain the initial process parameters. Based on the extended Kalman filter (EKF) algorithm, the motion model and observation model of tube forming are presented section by section, and the relevant calculation and analysis are carried out. The forming trajectory has been predicted; moreover, the processing parameters are optimized during the processing process, in which the effectiveness of the processing optimum scheme is illustrated.

Video synopsis algorithm based on two-stage target tubes grouping

Video synopsis generates a concentrated video that can be browsed quickly. With the increase of condensation ratio, more pseudo collisions between target tubes will occur. To solve this problem, this paper proposed a video synopsis algorithm based on two-stage target tubes grouping. In the first stage, using the hypergraph to analyze the collision relationship between target tubes, and the target tubes are grouped according to the hyper-edges. In the second stage, a clustering algorithm based on equal distance nearest neighbor sampling is proposed to group the target tubes. Then, selecting target tubes according to the selection principle of quantity priority between groups and length priority within groups (QPB-LPG) . Finally, these target tubes are rearranged to generate concentrated videos with smaller pseudo collisions. The experimental results show that this algorithm can significantly reduce the pseudo collision between target tubes without reducing the frame condensation ratio and frame compact rate compared with existing video concentration algorithms, and the feasibility of the method is fully verified.

Actor and Action Modular Network for Text-Based Video Segmentation.

Text-based video segmentation aims to segment an actor in video sequences by specifying the actor and its performing action with a textual query. Previous methods fail to explicitly align the video content with the textual query in a fine-grained manner according to the actor and its action, due to the problem of semantic asymmetry. The semantic asymmetry implies that two modalities contain different amounts of semantic information during the multi-modal fusion process. To alleviate this problem, we propose a novel actor and action modular network that individually localizes the actor and its action in two separate modules. Specifically, we first learn the actor-/action-related content from the video and textual query, and then match them in a symmetrical manner to localize the target tube. The target tube contains the desired actor and action which is then fed into a fully convolutional network to predict segmentation masks of the actor. Our method also establishes the association of objects cross multiple frames with the proposed temporal proposal aggregation mechanism. This enables our method to segment the video effectively and keep the temporal consistency of predictions. The whole model is allowed for joint learning of the actor-action matching and segmentation, as well as achieves the state-of-the-art performance for both single-frame segmentation and full video segmentation on A2D Sentences and J-HMDB Sentences datasets.

Lagrangian approximations for stochastic reachability of a target tube

We consider the problem of stochastic reachability of a target tube for a discrete-time, stochastic dynamical system with bounded control authority. We propose grid-free algorithms to compute under- and over-approximations of the stochastic reach set, and a corresponding feedback-based controller associated with a given likelihood. Our approach employs set-theoretic (Lagrangian) techniques for nonlinear systems with affine stochastic disturbances. With available set computation tools, these algorithms can only be implemented on linear systems. We use the law of total probability to partition the potentially unbounded disturbance set, and compute minimal and maximal reach sets via a robust approach. We propose a heuristic to partition the disturbance set using an ellipsoid when the disturbance is Gaussian, and a polyhedron otherwise. For linear dynamics and convex and compact sets, we employ existing tools from support functions and robust linear programming to efficiently approximate the stochastic reach set. We synthesize an admissible controller using the disturbance minimal reach sets by solving a series of linear programs. We demonstrate our approach on systems with linear dynamics (time-invariant and time-varying) and arbitrary disturbances (as well as Gaussian), including trajectory following for a Dubin’s vehicle and space vehicle rendezvous and docking.

Backward Reachability for Polynomial Systems on a Finite Horizon

A method is presented to obtain an inner-approximation of the backward reachable set of a given target tube, along with an admissible controller that maintains trajectories inside this tube. The proposed optimization algorithms are formulated as nonlinear optimization problems, which are decoupled into tractable subproblems and solved by an iterative algorithm using the polynomial S-procedure and sum-of-squares techniques. This framework is also extended to uncertain nonlinear systems with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathcal {L}_2$</tex-math></inline-formula> disturbances and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathcal {L}_{\infty }$</tex-math></inline-formula> parametric uncertainties. The effectiveness of the method is demonstrated on several nonlinear robotics and aircraft systems with control saturation.

Stochastic reachability of a target tube: Theory and computation

Probabilistic guarantees of safety and performance are important in constrained dynamical systems with stochastic uncertainty. We consider the stochastic reachability problem, which maximizes the probability that the state remains within time-varying state constraints (i.e., a “target tube”), despite bounded control authority. This problem subsumes the stochastic viability and terminal hitting-time stochastic reach-avoid problems. Of special interest is the stochastic reach set, the set of all initial states from which it is possible to stay in the target tube with a probability above a desired threshold. We provide sufficient conditions under which the stochastic reach set is closed, compact, and convex, and provide an underapproximative interpolation technique for stochastic reach sets. Utilizing convex optimization, we propose a scalable and grid-free algorithm that computes a polytopic underapproximation of the stochastic reach set and synthesizes an open-loop controller. This algorithm is anytime, i.e., it produces a valid output even on early termination. We demonstrate the efficacy and scalability of our approach on several numerical examples, and show that our algorithm outperforms existing software tools for verification of linear systems.

An Autonomous Positioning Method of Tube-to-Tubesheet Welding Robot Based on Coordinate Transformation and Template Matching

In order to change the positioning method “teach-playback” for tube-to-tubesheet welding by robots, this letter proposes an autonomous positioning method based on coordinate transformation and template matching. The coordinate trans-formation between the robot coordinate system (RCS) and the drawing coordinate system (DCS) has been established. The CCD camera will move to the position of target tube by the coordinate transformation of robot. This is coarse positioning. An improved template matching algorithm is used in machine vision. It can automatically create a template for each image instead of using a template to match the images of all the tubes. The welding torch will accurately locate the target tube by the result of template match. This is fine positioning. Finally, the comparative test showed that the proposed method is superior to the method of Ref [27]. The detection errors in x and y directions are within ±0.18 mm.

Photon Doppler velocimetry measurements of the impact velocity during electromagnetic pulse welding of copper-steel tubular joints

Tubular copper to steel joints were manufactured by electromagnetic pulse welding, during which the impact velocity was measured with photon Doppler velocimetry. The reduction in inner diameter and the remaining cross-sectional area of the target tube were determined after welding. Tube-to-tube configurations with an internal support exhibited a larger remaining cross-sectional area, compared to the configuration without internal support. Moreover, for the tube-to-rod configuration, the initial velocity drop immediately after impact dropped down to zero, whereas for the tube-to-tube configurations, a velocity drop to an intermediate level was found. The velocity and acceleration increased with an increase of the discharge energy. The acceleration was positive up to at least 9 μs, with an expected turning point situated between 9 μs and 11 μs. The acceleration was still positive at the moment of impact at a stand off distance of 1.0 mm and 1.5 mm, but was likely negative at 2.0 mm.

Probing Magnetic Pulse Welding of Thin-Walled Tubes

Magnetic pulse welding is a solid-state joining technology, based on the use of electromagnetic forces to deform and to weld workpieces. Since no external heat sources are used during the magnetic pulse welding process, it offers important advantages for the joining of dissimilar material combinations. Although magnetic pulse welding has emerged as a novel technique to join metallic tubes, the dimensional consistency of the joint assembly due to the strong impact of the flyer tube onto the target tube and the resulting plastic deformation is a major concern. Often, an internal support inside the target tube is considered as a solution to improve the stiffness of the joint assembly. A detailed investigation of magnetic pulse welding of Cu-DHP flyer tubes and 11SMnPb30 steel target tubes is performed, with and without an internal support inside the target tubes, and using a range of experimental conditions. The influence of the key process conditions on the evolution of the joint between the tubes with progress in time has been determined using experimental investigations and numerical modelling. As the process is extremely fast, real-time monitoring of the process conditions and evolution of important responses such as impact velocity and angle, and collision velocity, which determine the formation of a metallic bond, is impossible. Therefore, an integrated approach using a computational model using a finite-element method is developed to predict the progress of the impact of the flyer onto the target, the resulting flyer impact velocity and angle, the collision velocity between the flyer and the target, and the evolution of the welded joint, which are usually impossible to measure using experimental observations.

Effect of Process Parameters on Wavy Interfacial Morphology During Magnetic Pulse Welding

Abstract Magnetic pulse welding (MPW) is a solid-state welding process that bonds similar and dissimilar metals using a high velocity collision. In this paper, effects of impact velocity, target tube thickness, and mandrel inclusion on the interfacial morphology were investigated through the welding of tubular parts, Al6060T4 (flyer) to Cu-ETP (target), by electromagnetic compression. The hypothesis tested in this research is that a “well-supported target,” i.e., either a thick target or the support of a mandrel, allows for vortices to be created at the interface during MPW provided that the impact velocity is sufficient. The mandrel used in the experiments was polyurethane with a Shore hardness of 92A, which was pre-stressed via a washer and nut. The impact velocity was measured via photon Doppler velocimetry (PDV) and used for the setup of numerical simulations. A 2D axisymmetric numerical model was implemented in LS-DYNA to predict the interfacial morphology. Thermal analyses in the numerical model were used to predict the local melting locations and compared with experimental observations. Both experimental and numerical results showed that the interfacial wavelength increased with an increase in the impact velocity and target thickness. Similarly, a thin target with mandrel support also caused an increase in the wavelength. Vortices were only generated with appropriate impact velocities and well-supported targets, i.e., again either a thick target or the support of a mandrel.

Magnetic pulse welding of copper to steel tubes–Experimental investigation and process modelling

Abstract Magnetic pulse welding allows joining of metallic tubes by a short electromagnetic pulse and the resulting high strain rate impact and plastic deformation. Since melting of materials is avoided, magnetic pulse welding is an efficient method for joining of dissimilar materials. However, the process occurs very fast with little opportunity for real-time monitoring and control, which is also difficult due to the presence of a high amplitude electromagnetic field. A novel attempt is presented here to examine the underlying phenomena for magnetic pulse welding of copper flyer tubes to steel target tubes by computational process modeling and a focused experimental investigation. A coupled electromagnetic and mechanical finite-element model was created to compute the electromagnetic field and pressure distribution, and the progressive nature of flyer tube impact velocity on the target tube. The consequent progress of the angle of impact and contact length are examined for a range of standoff distances between the flyer and target tubes, the target tube wall thickness. The computed results are validated extensively with corresponding experimentally measured results. Overall, the coupled theoretical and experimental investigation provided a useful quantitative insight of magnetic pulse welding of copper and steel tubes, which is expected to help in the advancement of practical application of the process.

Alumina film sputter deposition on mold steel by large-area electron beam irradiation

During the large-area EB irradiation, plasma generation is confirmed by collision of electrons with vaporized workpiece materials above the substrate surface due to its high energy density. This phenomenon would cause the sputtering of target material when it is set near the substrate surface. Thus, there is a possibility for coating a target material on the substrate surface by the large-area EB irradiation. The simultaneous sputter deposition of target material with melting and resolidification of workpiece surface by the large-area EB would improve the adhesion strength between the coated film and the workpiece surface. In this study, a new ceramics coating method with sputtering of target tube by large-area EB irradiation is proposed. Ceramic target tube made of alumina is put on the substrate surface of mold steel, and the large-area EB is irradiated to the substrate surface. The alumina film with thickness of several micro meter can be formed on the substrate surface. Moreover, the film formation mechanism is discussed by changing material property of a jig supporting the alumina target tube. The spectrum of plasma generated on the substrate surface during the EB irradiation is also analyzed. It is made clear that the magnetic property of jig greatly influences on the film formation. Furthermore, main components of plasma generated on workpiece surface during the process are components of steel in the case of low number of EB irradiation, while much more alumina component as a film is detected in the case of high number of EB irradiation.

Control design with guaranteed transient performance: An approach with polyhedral target tubes

In this paper a novel approach is presented for control design with guaranteed transient performance for multiple-input multiple-output discrete-time linear polytopic difference inclusions. We establish a theorem that gives necessary and sufficient conditions for the state to evolve from one polyhedral subset of the state-space to another. Then we present an algorithm which constructs a time-varying output feedback law which guarantees that the state evolves within a time-varying polyhedral target-tube specifying the system’s desired transient performance. We present generalisations involving constraints on the control, and a bounded additive disturbance term. Our formulation is very general and includes reference tracking with any desired transient behaviour in the face of disturbances, as specified, for example, by the most popular step response specifications. The approach is demonstrated by an example involving the control of water levels in two coupled tanks.