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Tube electromagnetic bulging has been given much attention due to its superior advantages in the field of light alloy processing. However, the conventional tube electromagnetic bulging process exhibits some critical issues that restrict its wide industrial applications. This includes non-uniform axial deformation and poor forming performance such as wall thickness thinning. This article proposes a cost-effective solution for such issues through simultaneous radial and axial electromagnetic force loading using an auxiliary driving coil. In this regard, the influence of the auxiliary coil geometrical parameters on the electromagnetic force distribution and tube forming performance is investigated using electromagnetic-structure coupling model of the bulging process. The robustness of the new proposed method is validated by comparing its electromagnetic force distribution and tube forming performance with the traditional cylindrical coil method, currently used by industry practice. Numerical results show that the introduction of the auxiliary coil may effectively weaken the radial electromagnetic force at the end of the tube and solve the uneven axial deformation issue. Based on the obtained results, the maximum uniform deformation area is increased from 6.9mm to 35.1mm. The tube relative wall thinning issue is reduced and the relative wall thickness reduction of the pipe is found to be 0.01661. The axial electromagnetic force can be further improved by adjusting the geometrical parameters of the coil and the proposed electromagnetic bulging can effectively increase the uniform deformation range of the tube.

In the conventional electromagnetic tube expansion, axial distribution of the electromagnetic force is not uniform along the workpiece. This results in uneven axial deformation of the deformed tube and restricts the full industrial implementation of this technology. In an attempt to overcome this issue, this article proposes a new method based on dual-coil electromagnetic tube compression. In this regard, an electromagnetic-structure finite element coupling model is developed to emulate the real electromagnetic tube compression process. Influence of the proposed dual-coil structure parameters on the electromagnetic force distribution is analyzed. Results show that the proposed dual-coil electromagnetic tube compression method can effectively solve the problem of uneven axial deformation in the conventional electromagnetic tube compression. The proposed method is expected to promote wide industrial applications of the electromagnetic tube forming technology.

The suspension system of the lower limb prosthesis has the main role of maintaining the contact with the residual limb. Therefore, the contact area should be safe and permanent as the prosthesis could be wearable. The way the contact area of the socket should be suited to the residual limb has to be appropriate for each person because of stump volume variation during some practical activities. The paper presents a new solution for the lower limb prosthesis system that consists in a thin wall tube network inflated with dry air working with controlled pressure. The network has to surround the entire area of the stump, so that it could be adapted to the variable volume. The thin wall tube is made of biocompatible material expanded polytetrafluoroethylene (ePTFE), whose elasticity affords to be suitable to the active surface of the stump. Meantime, the air pressure inside provides the working contact force. The experimental set-up points out the values for working pressure and contact force developed by using a mechatronic system with force and pressure sensors controlled with Arduino.

The condenser is a shell and tube-type heat exchanger that functions to condense the turbine output steam. To improve the performance of the condenser can by changing the tube size in the condenser design. This study, modeling with variations in tube diameter is carried out to determine its effect on condenser performance, such as heat transfer coefficient, effectiveness, and distribution of speed, pressure, and temperature. The study was simulated on CFD software using four variations of STHE tube diameter sizes. The highest temperature value on the cold fluid side obtained is 332.34 K at the variation of l = 600 mm; d = 25 mm, and the lowest cold fluid temperature value is 311.07 K at variation l = 600 mm; d = 10 mm. The highest heat transfer coefficient value of cold fluid is obtained at 1547.17 (W/m2K) at a variation of l = 600 mm; d = 25 mm, and the lowest heat transfer coefficient value of cold fluid is obtained 667.85 (W/m2K) at variation l = 600 mm; d = 10 mm. The highest effectiveness value was obtained at 0.2156 at variation l = 600 mm; d = 25 mm and the lowest effectiveness value is 0.0738 at variation l = 600 mm; d = 10 mm. From the research, it can be concluded that the addition of the width to the diameter of the tube has an impact on a more significant decrease in speed, a greater pressure drop, and a more significant temperature distribution. In addition, it also affects increasing the value of the heat transfer coefficient and effectiveness.

A W-band traveling-wave tube (TWT) by utilizing the folded waveguide slow wave structure (FWSWS) combined with the pencil beam is designed to develop the high power millimeter-wave radiation source. The particle-in-cell (PIC) simulation results show that this TWT can produce over 158W output power in the range from 90GHz to 97GHz. The maximum output power of the TWT can reach 293W at the typical frequency of 94GHz, which corresponds to a gain of 37.68dB and an interaction efficiency of 8.15%.

A controllable polymer solution-coating method was used to fabricate polycarbonate (PC) tube waveguide with broadband terahertz (THz) transmission capability. Highly uniform 3-mm-bore PC tube waveguides with three different wall thicknesses of 30.0μm, 57.0μm and 80.0μm were prepared. The measured transmission bandwidths are 1.4 THz, 1.7 THz and 1.9 THz, respectively. The lowest transmission loss of the waveguide sample with 80μm wall thickness is 0.15 dB/cm at 1.0 THz. A metal/dielectric hollow THz waveguide based on PC dielectric tube was also fabricated in this study. The transmission loss of the silver/PC hollow waveguide is 0.13 dB/cm at 300 GHz. It is expected to be decreased to 0.007 dB/cm by further optimization of the PC tube wall thickness.

In this paper, we present the results of design and development of the multiple-tunnel meander-line slow-wave structure (SWS) for a high-power traveling-wave tube (TWT) with multiple sheet electron beam operating at millimeter band. Electromagnetic parameters of the SWS with different number of beam tunnels are simulated. The results of 3-D PIC modeling of small-signal and large-signal hot-test operation are presented. Technologies for fabrication of the multiple-tunnel SWS are discussed.

To satisfy the requirement of the RF output in mega-watts level of the 170GHz gyrotrons. A design of a two-stage depressed collector with the radial magnetic field for 1MW, 170GHz gyrotrons for increasing the efficiency and the power capacity of the tube has been presented. The simulation results indicate that the total efficiency of the tube with the design could increase from 31% to 89% significantly.

This study focused on assessing the geothermal subcooling potential for the air conditioning system using CO 2 that operates in the transcritical state. In this study, the relationship between the parameters such as the subcooling quantity, the cooler pressure, and the mass flow rate was determined for the best operating conditions. The cooling capacity and COP (Coefficient of Performance) are also compared under different conditions: Without geothermal subcooling, with geothermal subcooling using a bare tube, and with geothermal subcooling using a water-covered tube. The results of study showed that, using geothermal subcooling with the water-covered tube may achieve the highest COP of 5.69 while using the bare tube of 4.71 compared to 4.53 without using geothermal subcooling. When reducing the capacity of the system, the COP decreases significantly. The COP tends to decrease when increasing the subcooling quantity in both cases. The mass flow rates were also analyzed in this study. When the mass flow rate is reduced, the subcooling quantity tends to decrease. However, in the case of the geothermal subcooling by a bare tube, the subcooling quantity decreases more than that by a water-covered tube. The results showed that although geothermal subcooling is highly effective, it is important to control the cooler pressure within the allowable range for the maximum energy efficiency.

Thermal energy storage (TES) effectively contributes in the energy efficiency improving and the energy supply/demand discrepancy eliminating of solar thermal technology. Among the different types of TES, phase change materials (PCMs) exhibit a high thermal energy density per unit mass. The present work numerically investigates the melting process of PCM (RT82) in a quadruple tube heat exchanger (QTHX). ANSYS (Fluent) version 18.2 software program is used to develop a 2D numerical model for the melting process of the QTHX, and pure conduction and natural convection are considered in the simulation. Two models of QTHXs are studied with respect to the PCM position in the tubes. In model (a), the PCM inserted in the first tube and the third tube while in model (b), the PCM inserted in the second tube and the fourth tube. Moreover, the melting process of the QTHX is compared with a triplex tube heat exchanger (TTHX) and double pipe heat exchanger (DPHX). The computational results indicated that the melting rate of model (b) was achieved in a 63.2% of that of model (a). In addition, the results indicated that PCM was melted earlier in the QTHX compared to TTHX and DPHX. The numerical model was validated with a previous experimental work. Numerical results show a consistent agreement with the experimental results.

ICEAA 2021, International Conference on Electromagnetics in Advanced Applications, Honolulu, Hawai, ETATS-UNIS, 09-/08/2021 - 13/08/2021; Vacuum tube magnetic levitation transportation is a novel rail transportation technology with high-speed operation under a specific environment without wheel resistance, and with low air resistance and noise. Operation of a maglev train system in a tube is currently studied [1] ; it consists in a complex system integrating both high-power electrical equipment and low-power, sensitive signalling and control command equipment [2] . The resulting electromagnetic compatibility problem to ensure coexistence and proper operation of both types of equipment relies on the determination of the main electromagnetic emission sources of the maglev train [3] . Prior analysis of the characteristics of these emissions is of great significance to ensure the electromagnetic compatibility of the maglev transportation system.

Jumper tubes are widely used in the field of ocean engineering as a key component of oil and gas transportations. In order to improve the mixing conditions in the offshore pipelines, a blind tee is usually installed upstream of the measuring instrument to replace the elbow connections. The purpose of this research is to study the influence of the blind tees on the internal mixing conditions of the jumper tube. To this end, the three-dimensional flow fields inside the jumper tubes are solved with the Computational Fluid Dynamics (CFD) method, and the internal flow characteristics of the jumper tubes with blind tees installed at different positions are analyzed. The absolute axial vorticity is used to characterize the mixing conditions of the fluid in the jumper, and the vorticities at fifty-nine sections inside the jumper tube are extracted and compared under different configurations. The results show that compared to the traditional jumpers, the cross-sectional vorticity at the position where a blind tee is installed increases by range between 22% and 136%, and the corresponding dissipation speed decreases as well. It also reveals that the effect of installing blind tees at all elbow positions is not as good as that of using a single blind tee to increase the vorticity at some specific positions, especially for the outlet of the jumper tube.

With the rapid economic development, people lead significantly better life. Due to busy work, people work at the desk for at least eight hours a day, and computers are indispensable for most workers and students. Long-term computer use or excessive indoor temperature will result in ultra-high CPU temperature, which will incur serious problems like slight computer failure or shorter service life due to damage of computer accessories in severe cases. A good radiator is easy to use with low noise, thus deeply favored by users. This design has the following advantages: 1) The water circulation and condenser tube achieve strong heat dissipation; two cooling fans are installed on the partition for bigger air flow; 2) The universal positioning tube can move to any position, thereby solving the problem of local overheating. 3) The whole device is an all-in-one machine, which is small and easy to carry.

The serious leakage in the tube bundles of a heat exchanger was found in a plant. By using the Macro and Micro morphology of cracks, chemical composition analysis, metallographic inspection and corrosion products energy dispersive spectroscopy (EDS) analysis, the leakage failure cause of the tube bundles was analyzed. It has been proved that the branch-shape cracks are generated from the outer wall of the tube bundles. Both ends of the crack were even and there was no significant plastic deformation. The crack propagation zone was covered with thick corrosion products. The results of EDS show high levels of oxygen and sulfur in the region, which showed that sulfide stress corrosion is the main cause of tube cracking.

This paper presents the development of 3D printed models of a lumbar puncture simulator and an epidural puncture simulator. For the lumbar puncture simulator two “pops” or losses of resistance were simulated when the needle penetrates 1) the ligamentum flavum ligament through the epidural space and 2) the dura mater which is a membrane of the thecal. A plastic tube inserted inside a silicone rubber tube gave the most realistic and second “pop.” The lumbar puncture simulator also included a partial plastic tube (with a foam insert) and a partial rubber tube that surrounded the plastic tube to simulate the first “pop.” For the epidural puncture simulator the needle does not enter as far as the lumbar puncture and only goes through the ligamentum flavum and then enters the epidural space. The simulators are being integrated into the Simulation Based Learning Experiences (SBLEs) in the College of Nursing.

The numerical simulation of the braided corrugated hose is always researched without considering the metallic braided tube, making the results of the study not match the actual situation. To address the problem, the entire braided corrugated hose model is established, and the axial mechanical properties of braided corrugated hose are studied, while the effect of the metallic braided tube on the bellows is also considered. Main conclusions are as follows: the axial stiffness of the braided corrugated hose is non-linear, in the early stages, the deformation is mainly small displacements and the axial stiffness consists of metallic braided tube and bellows respectively, in the later stages, the axial stiffness consists mainly of the contact stiffness between braided tube and bellows. For the bellows, the maximum equivalent stress and strain occur in the area where contact with metallic braided tube, with a maximum stress of 1055MPa. The maximum contact pressure between the metallic braided tube and the bellows is 151.54MPa and the friction stress is 27.717MPa. It is found that the contact characteristic between the metallic braided tube and the bellows has a great influence on the axial mechanical properties of the braided corrugated hose by compared the relationship between the axial stiffness and contact pressure.

The steam generator is an important heat transfer equipment in nuclear power plant. Its main component is the tube sheet with thousands of U-shaped heat transfer tubes. The inspection robot repairs the heat transfer tubes by positioning various types of tools to the specific heat transfer pipe, greatly reducing human intervention in the nuclear environment. Based on a brief overview of the research status of inspection robots used in steam generators, the mechanical structure of the body, tube-holding mechanism, collision detection, and trajectory planning are analyzed, problems and challenges are summarized, and the future development trend is prospected.

Since the hydrostatic pressure resistance ability of class III flextensional transducer is usually poorer, we did some researches on the common hydrostatic pressure resistance ability of deep water transducer to improve it. The hydrostatic pressure resistance ability of class III flextensional transducer can be improved that the way of overflow fills the acoustic compliance tube. With the simulating calculation of class III flextensional transducer using finite element software, a transducer prototype was made and a fitness to the transducer of small size acoustic compliance tube was designed. The conclusion is that the hydrostatic pressure resistance ability of acoustic compliance tube is over 3MPa. The transducer has two resonance peak at 760Hz and 2000Hz, with TVR 115dB and 125.1dB. TVR should be over 113dB between 680Hz and 3000Hz. The transducer still can work normally with hydrostatic pressure of 3MPa. The results showed that the hydrostatic pressure resistance ability of overflow class III flextensional transducer which fills the acoustic compliance tube was improved, and the transducer had the high-power transmitting ability in board band of frequencies.

Taking the heat exchange tube in the condenser as the research object, the three-dimensional finite element model of the heat exchange tube and the Internal and external fluid of pipe is established, and the bidirectional fluid-solid coupling calculation of the heat exchange tube is carried out. The time-domain and frequency-domain curves of lift, drag and displacement of the heat exchange tube and the time-domain and frequency-domain curves of the pressure pulsation in the tube are obtained. At the same time, the acoustic simulation calculation is carried out for the vibration noise of the heat exchange tube. The time domain and frequency domain curves of sound pressure near the heat exchange tube are obtained. The simulation results show that the frequency of pressure pulsation corresponds to the frequency of lift and drag. The flow velocity in the tube studied in this paper will affect the amplitude and waveform of the pressure pulsation but will not affect its frequency. The sound pressure frequency of the upper and lower sides of the heat exchange tube only corresponds to the lift frequency, and the sound pressure frequency on the left and right side corresponds to the lift and drag frequencies.

The temperature characteristics of underwater acoustic transducer include temperature variation characteristics, temperature balance characteristics, temperature influence characteristics and other factors. During the long time and high power use of underwater acoustic transducer, the temperature characteristics have become one of the main factors affecting the normal work of the transducer. Since the air environment and water environment are both stable free fields, it is of great scientific significance and engineering value to study the temperature characteristics of the underwater acoustic transducer based on the air environment for improving the long time and high power working ability of the underwater acoustic transducer. The research on the temperature characteristics of the tube underwater acoustic transducer based on the air environment is carried out. The research results are of certain value by means of theoretical analysis, simulation calculation and experimental verification. The formulas for calculating the heating power and cooling power of the tube transducer are obtained. The heat balance temperature of the tube transducer in air environment is simulated. The temperature characteristics and temperature balance characteristics of the tube transducer in the air environment are measured. The heat dissipation technology is used to reduce the temperature equilibrium temperature of the tube transducer in the air environment. It lays a certain technical foundation for the analysis of the temperature characteristics of the tube transducer in multiple environments and the effective realization of the heat dissipation technology of the transducer.

Continuous mixing and conveying technologies for processing solid-liquid mixtures and highly viscous fluids are required in the manufacture of food and medicine. A device featuring such a technology, namely the peristaltic continuous mixing conveyor, has been developed by the authors previously. This device, imitating the movement of intestines, is capable of mixing and conveying content by inflating a rubber tube using air pressure. Herein, we aim to estimate the degree of mixing of the contents via machine learning using data from pneumatic factor sensors installed in this device. However, the low measurement accuracy of these sensors when dealing with compressible fluids makes the mixing degree estimation difficult. Therefore, in this study, to improve the measurement accuracy of the sensing system, we installed an accelerometer that could directly measure the behavior of the rubber tube inside the device without any contact with the contents being required. Upon operation of the device with various objects within it, the sensor angle of the rubber tube was obtained from the accelerometer values for each input. The sensor angle at steady state after air supply was 22.5° greater for the rigid bodies than for the mixtures of powder and liquid. For the powder-liquid mixtures, a linear relationship was demonstrated between the percent concentration of mass and the sensor angle at a steady state. The results suggest that the content of the device can be determined with greater accuracy by using the attitude angle obtained from the accelerometer than from the conventional pneumatic factor sensors.

Pressure pulsation is the key problem causing pipeline vibration and reducing pipeline system reliability and service life. Detection technology plays a significant role in preventing pipeline malfunction. This work provides a cost-effective and realizable sensor for pressure detection. We combine the metamaterials structure with conductive fabric to monitor tube state. When the tube’s inner pressure changes, the metamaterials will bend. A resistive flexible conductive fabric is installed to measure inner pressure. This sensor has the efficiency of easy fabrication. We described the relationship between inner pressure and the bending property of the sensor. The experimental results show that the sensor detects pipeline inner pressure accurately. And the experimental data is consistent with the simulation results. The authors provide a convenient and economical approach to pressure detection.

We reproduce chemical reactions of blood vessels by a flexibly deformable collagen tube device. The device is composed of an unfixed collagen hydrogel tube, enabling the reproduction of both macro and micro scale deformation of the vessel tissue. In addition, the device is easily perfused because the collagen hydrogel tube is directly attached to silicone tubes. We succeeded in demonstrating the chemical deformation of vessel tissue and endothelial cells by inflammatory mediators. Moreover, the drug testing was presented by anti-inflammatory chemicals. We believe that our flexible culturing device could help the construction of functional blood vessels reproducing in vivo chemical reactions in high similarity, and contribute to biomedical researches and pharmacokinetic testing.

In view of the traditional welding location of tube plate by CAD drawing welding gun positioning, positioning position is not accurate, in the heat exchanger production process, the heat exchange tube welding is prone to quality problems, proposed a tube plate welding seam positioning correction algorithm based on Canny image edge segmentation algorithm. Two global threshold segmentation methods are used to reduce the inaccuracy of edge segmentation information caused by artificial high and low thresholds. In the process of tube plate welding, the welding seam identification accuracy of the connection between the heat exchange tube and the tube plate is improved, and the welding machine is helped to find the accurate position of the inner and outer circle of the heat exchange tube.

There is need to recognize the direction of injection tube, which plays a key role in the automatic assembly systems. A boundary correction and Support Vector Machine (SVM) based direction recognition method is proposed to automatically determine the direction of injection tube. First, the Moore neighborhood is utilized to detect and extract the contour boundary of tube image, which is pre-processed after captured by camera; Then, the contour image is performed by boundary correction and normalization, and the direction of the injection tube is recognized by the trained SVM; Finally, the mechanical arm is employed to adjust the plastic pipe realizing the injection tube automatic assembly system. Experimental results show that the proposed method can effectively and accurately recognize the direction of the injection pipe, and it has been applied into practice production achieving good results.

Based on the theoretical simulation of Geiger-Miieller (GM) tube in the model of GJ4105 with Monte Carlo software Geant4, the response of GM counter tube to the wide energy range of y rays and the detection efficiency curve are analyzed. Some factors that influence energy response are analyzed, which provides the basis for the optimal design of structure and performance of GM tube.

The single pulsating heat pipe and the main pulsating heat pipe are structurally coordinated with each other , So as to form a coupled pulsating heat pipe heat exchanger, using a constant temperature water bath as heat resource and the air as cooling resource.High purity distilled water and anhydrous ethanol were used as working fluids of main pulsating heat pipe and cooperating pulsating heat pipe respectively. By changing the constant temperature water bath temperature, the wall temperature characteristics and heat transfer performance of the pulsating heat pipe were studied experimentally, and compared with the heat transfer characteristics of the pulsating heat pipe without working medium under the same conditions. The results show that the pulsating heat pipe with ethanol as working fluid can operate stably under the action of multi heat source and multi cold source, which is established by cooperating with the main pulsating heat pipe structure, and further enhances the heat transfer performance of the main pulsating heat pipe. At the same time, the mechanism of heat transfer enhancement and mutual excitation between coupled pulsating heat pipes is proposed and qualitatively analyzed under the effect of external field of mutual variable load, so as to maximize the heat transfer performance of coupled pulsating heat pipe heat exchanger. In order to provide reference experience, methods and means for strengthening the phase change heat transfer process in the tube by using pulsating heat pipe as load external field.

The paper is devoted to mathematical modeling and improving a secondary treatment of molten steel at metallurgical plants. The process includes immersion of a cylindrical vessel into a ladle with molten steel to rise up a batch of steel using vacuum. After that, a cored wire with addition is injected into the melt inside the vessel through a guiding tube. Also argon starts blowing from a wall in the vessel to intensify mixing. Presented 3D mathematical model is based on the conservative laws of physics and includes Navier-Stokes equations as well as Euler-Lagrange ones. The model calculates coefficients of addition and hydrogen variations as criterion of homogeneity. Moreover coordinates of wire's end are determined by predicting 3D dynamics of wire as flexible system of rods. Numerical experiments are conducted using the set of technological parameters as well as moving guiding tube and fixed one. It is found that optimal consumption of inert gas is 150 1/m and optimal wire speed is in range 0,3 - 0,5 m/s in considered conditions. The model can help to further investigate the process in other configurations.

Disaster robots that can work safely and quickly in complex and fragile environments are required for collecting information from debris for initial response and recovery work. Various snake-like robots have been proposed that can be inserted into a confined space. However, their propulsion mechanisms, such as the wheel, the continuous track, and the vibrating inclined cilia, must be in physical contact with the environment and may induce secondary disasters like a further break and fall of debris. This paper introduces a snake-like robot with a two radial-layer structure that can be propelled not only on an arbitrary trajectory but also without establishing contact with the environment by sliding its two coaxial tubes alternately and switching their stiffness by internal pressurization. This newly invented variable stiffness mechanism has a hollow structure that allows both simplicity of design and positive pressure activation. A prototype model was developed for proof of principle, and the average pulling forces required to actuate either the inner or the outer tube when the other tube is bent at 1/225 and fixed were measured to be namely 67.6 N and 5.66 N, respectively. This evaluation experiment validated the proposed principle of contactless propulsion mechanism. In the future, it might be possible to verify whether non-contact propulsion can be conducted in the air as well, thereby requiring the verification of a theoretical model.

The digital tube displays abnormally during the use of a certain computer. Through analysis, it is found that the abnormal current display of the digital tube is caused by abnormal current sampling and amplification. The silver layer of the R2 resistance surface electrode inside the sensor is corroded and disconnected by sulfur-containing substances, causing the resistance to increase and fail, resulting in an abnormal zero point, and finally the current display of the digital tube is abnormal. Replace the sensor, the current value displayed by the digital tube is consistent with the output current value of the power module, and the problem is solved. The research in this article enriches the research on power supply current sampling, and provides theoretical support and basis for subsequent development and design and solving practical problems.

Wear analysis has been carried out on aluminum tube in parallel triangular tube bundle with P/D ratio of 1.45 and the baffle plate placed at the mid-span of the bundle. The cross-flow velocity of water ranges from 0.18 m/s to 0.55 m/s. For each flow velocity, tests were performed on five different flow velocities and three-time spans (tube-baffle interaction) i.e., 30, 60, and 90 min. The experiments were designed in a unique way to study the relationship between cross flow velocity and tube baffle interaction time with wear produced on the tube surface. This is the first study of its kind in which wear analysis of a flexible tube has been done in the water tunnel to simulate the real environment of the heat exchanger tubes. The vibration response of the monitored tube was acquired using a tri-axial wireless accelerometer. A Scanning Electron Microscope (SEM) was used for the measurement of wear sizes. It was observed that the transverse amplitude rises significantly at higher velocities as compared to streamwise amplitude results in significant wear in the transverse direction. The wear sizes also tend to increase with the cross-flow velocity and become prominent at higher velocities. A similar trend has been observed for the wear area and wears volume. Also with the increase in the tube-baffle interaction span, the wear scar tends to be deeper and wider significantly at higher velocities.

With rapid development of renewable energies and dc loads in distribution grids, converting ac distribution grids into dc operation has become a promising method to utmost utilize the present ac distribution grid in large cities. This paper reports a numerical investigation of thermo-electric fields of a three-core 10-kV ac cross-linked polyethylene (XLPE) cable and cable joint in the dc operation. DC conduction current for the XLPE and silicon rubber (SiR) was evaluated at different temperatures and electric fields. The thermo-electric field simulation was performed by COMSOL Multiphysics according to the measured data. The obtained result showed that the threshold of XLPE at 65 °C is 3.1 MV/m, whereas the threshold of SiR at 60 °C is 2.2 MV/m. It was found that the maximum electric field of the cable operated in dc voltage up to 12.5 kV was below the threshold of 3.1 MV/m. The maximum electric field in the cable joint appeared at the high voltage screen tube, whereas the maximum electric field at the high voltage screen tube was less than the threshold of SiR at a temperature difference of 25 °C. Moreover, the maximum transmission power of the three-core 10-kV AC XLPE cables running at the ±10-kV bipolar dc operation was 1.36 times of the power in the ac operation. It was elucidated that the three-core ac 10-kV XLPE cable could be operated reliably at ±10 kV in bipolar dc topology with sufficient safety margin. It is beneficial to upgrade the ac distribution grid to the dc distribution grid.

The paper presents the computed data on water flow and heat transfer through a staggered tube bank typical for subsea cooling. The numerical study of unsteady buoyancy-induced flow through cooling units that could be used also as ocean thermal energy extractors have been performed for Gr = 2×105. Three computational models of the cooler are considered: the tube bank without any bounding walls, the tube bank with vertical bounding walls and the tube bank with the side walls and the bottom wall. The direct numerical simulation is applied to model the draft water flow and heat transfer at the Prandtl number of 6.09. Tube bank external heat transfer enhancement in the presence of the bounding walls is reported and discussed.

Proper operation of steam generators in nuclear power plants is critical for the nuclear safety. In this research is developed simplified mathematical model of steam generator PGV-1000, used in eastern-type pressurized water reactors WWER-1000. The mathematical model uses an interpolation between the primary quantities in the primary loop, which can be used to solve the heat transfer problem under non-nominal operational conditions. The accumulation of deposits over the tube bundle and the tube failure in the tube bundle are analyzed.

Three dimensional unsteady computations have been carried out to study the absorption of Hydrogen in a metal hydride based cylindrical hydrogen storage reactor having cooling tubes with longitudinal fins. The results of the simulations have been compared with a base case having the exact configuration of a cooling tube but without fins. An optimization study is performed by varying the geometric parameters of the longitudinal cooling fins, such as their length and thickness. Both the rate of absorption and material mass added for this have been scrutinized to arrive at an optimal design. The variation of average bed temperature and hydrogen concentration with time have been presented for different cases of fin geometry. Instantaneous contours of hydrogen concentration have also been presented in this work.

When a gun fires, wear (including erosion) and fatigue cause inevitable damage to the gun barrel. Wear of gun bore gradually results in the decrease of gas pressure, projectile velocity, and accuracy. In contrast, fatigue failure of gun barrel is difficult to detect and measure. In this paper, low cycle fatigue behavior of simulated gun barrel was investigated by using a specially designed apparatus on MTS Landmark. Strain gages were mounted on the outer surface of the tube sample to monitor external strain. Crack propagation was nondestructively inspected by using Zeiss, Xradia 520 Versa. It is found that there is an inherent relationship between external strain and crack propagation. This finding suggests that the fatigue fracture could be prevented by monitoring the external strain on the gun barrel.

The article is focused on the development of a single-circuit vacuum tube generator 1 MW, 0.44 MHz with self-excitation which can be used for industrial applications, for example as a power source for generation of a radio-frequency induction plasma of high-enthalpy gases (air, nitrogen, etc.). A generator model in soft Matlab Simulink has been created. The vacuum tube GU-98A which produced by industry was chosen as the main element of the generator. The nonlinear characteristics of the vacuum tube (namely, the dependences of the anode current and the grid current on the anode and grid voltages) were approximated by analytical functions. The generator load which is an inductor with plasma was represented in the generator circuit as an active-inductive element with constant parameters. The article presents the parameters of effective operating modes of the tube generator and recommendations for the selection of its main elements.

In this paper, a novel fabrication method is proposed for microfluidic tube with a large diameter, circular cross-section and a thin wall. These properties make the tubes especially suitable for fluid density sensors and Coriolis mass flow sensors, because of the resulting low tube mass, low pressure drop and low pressure-dependence of the tube shape. A demonstrator sensor was fabricated and first measurement results of fluid density and mass flow are presented. The low-cost fabrication method is based on electroplating technology and results in tubes with a near-perfect circular cross section. Diameters ranging from 120 m to 1 mm and wall thicknesses from 8 m to 60 m have been achieved. For the demonstrator sensor presented in this paper a freely suspended tube was realized with a total length of 37 mm, a diameter of 600 m, and a wall thickness of 20 m. Density measurements were performed on nitrogen, ethanol, water, isopropyl alcohol (IPA), and various mixtures at 21°C-23°C lab temperature. Mass flow rate was measured up to 30 g/h with less than 30 mbar pressure drop thanks to the large tube diameter.

The unique characteristics of the thin-walled stainless steel tube itself put forward higher requirements on the processing technology. For example, because the thin-walled parts are easy to be affected by the vibration in the processing process, resulting in the machining tolerance is difficult to control, so the processing process puts forward higher requirements on the processing tools, tooling and technology. Based on this, this paper makes a more in-depth study on the processing process of thin-walled stainless steel pipe. Firstly, the processing and production methods and specific types of stainless steel pipe are analyzed, including the preparation of stainless steel tube blank, the determination of the length of tube blank, etc. Then, the processing technology of thin-walled stainless steel pipe is studied, and the related processes such as piercing process, capillary rolling, defect, leveling and finishing are analyzed in detail.

Coal-Fired Power Plant Boiler 600 MW has been operated more than 20 years. Secondary superheater outlet (SSH Outlet) tube bursts had been occurred on this unit. Long-term overheated failure mode was observed at failed tubes on three occasions which was on September 2017, April 2018, and December 2019. The design tubes are called SA-213 T91. On April 2018 and December 2019, the powerplant operator has joined hand with two different public university research institute which are called institution-1 and institution-2 to conduct tests to find the root cause of the failure by hardness test, microstructural examination, creep test and the remaining life analysis. The results of the hardness test on the fail tube on April 2018 and December 2019 were 170.84±1.98 Harness Vickers (HV) and 168–219 HV respectively compared to the new material hardness which are on the average of 258HV. On April 2018, creep tests were resulted that expected time to failure on 750°C and 72.93Mpa was 3.6hours; on 750°C and 93.46 Mpa was 0.4hours; on 650°C and 148.73Mpa was 4.3hours; on 650°C and 186.14 Mpa was 0.7hours; 550°C and 261.80Mpa was 9.6hours; 550°C and 316.05Mpa was 1.7hours. On December 2019, creep tests were resulted that expected time to failure on 680°C and 82.1Mpa was 16.290hours; on 650°C and 152Mpa was 0.84hours; last on 550°C and 201Mpa was 0.269hour. In order to operate more than 25 years, the stress should be less than 89.3Mpa according to ASME II PART D 2019. 6.9mm thickness tube has been resulted hoop stress 62Mpa. Welded metal approached resulted that tube remaining life of 570°C evaluated temperature was 54.4years. 600°C evaluated temperature resulted remaining life was 5.98years. In order to ensure that boiler was not overheated, Metal temperature monitoring and Coal blending has been applied to achieve the best result among bad conditions.

In the process of large-diameter rescue drilling using the air reverse circulation drilling process, the through hole in the main shaft of the top drive head of the vehicle-mounted drilling rig and the punching pipe assembly are often blocked. In order to solve the common technology in the construction process The problem is that this article analyzes and locates the cause of the blockage on the basis of a brief introduction to the air reverse circulation drilling process, and then proposes the design of a large diameter replaceable flushing pipe assembly. In the design process, the key breakthrough was made in the four groups of packing and the rotating seal of the flushing tube in the lower packing box of the flushing tube assembly, and a replaceable and vulnerable module was designed at the gooseneck tube, which greatly reduced the use cost. Engineering application results show that the application of the large-diameter replaceable flushing pipe assembly and slag discharge pipeline designed in this paper makes the slag discharge smooth during the air reverse circulation drilling process of the cluster type DTH hammer, the drilling efficiency is improved, and the labor intensity of workers is greatly reduced.

Based on Abaqus/Explicit platform, the 3-D FE model of rotary draw bending(RDB) for H96 waveguide tube has been established in this paper and validated by experiment, then the influence of process parameters on wall thickness variation of H96 waveguide tube in rotary draw bending was investigated. The results show that: wall thinning ratio and thickening ratio will decrease with the increase of the clearance between cores and tube. As the growth of the friction coefficient between pressure die and tube, wall thinning ratio gradually decreases while wall thickening ratio fluctuates ups and downs. As the increase of the friction coefficient between wiper die and tube, wall thickening ratio will reduce, but the wall thinning ratio increases first and then decreases. When the clearance between bending die and tube increases, wall thinning ratio slowly decreases while wall thickening ratio firstly decreases and then increases.

The vibration response of the launcher is one of the important sources of the initial disturbance of the missile launch. Based on the theory of multi-body dynamics and finite element analysis, a rigid-flexible coupling model of a vehicle-mounted missile launcher is established, and the vibration response of the launching tube is simulated. Using the method of replacing the rigid and flexible body models of the key components, the order of the main factors affecting the subsidence of the launch tube is obtained, and the conclusion that the subsidence can be reduced by increasing the rigidity of the frame and chassis is proposed.

The reasons of frequent tube burst of the high temperature reheater in a supercritical 600 MW unit were systematically investigated via the examination of macroscopic inspection, chemical composition, mechanical properties, microstructures, scanning electron microscope and energy disperse spectroscopy detection. It is demonstrated that the tube burst of the high temperature reheater results from not only design factors, but also manufacture quality. Due to the absence of solid solution treatment in spare elbow, the inner dislocations and residual stress increase obviously, which accelerates the precipitation of carbide containing Cr and the formation of Cr depleted zone on grain boundary(GB) subsequently, leading to the decrease of GB corrosion resistance and the final leakage of high temperature reheater tube induced by intergranular corrosion.

As with any heat exchanger, the function of a nuclear steam generator is compromised by operational changes that increase the resistance to heat transfer between the primary and secondary fluids, lowering the efficiency and leading to thermal performance degradation. This type of performance degradation, the underlying causes, industry experience, and plant operational consequences had been discussed by ERRI and DEI reference documentations. After 6-10 years operation the steam pressure degradation of most plants occurred. The steam pressure of steam generator (SG) in Ningde nuclear power plant (NPP) decreased after the unit was in commercial operation. It decreased by 1 bar in first fuel cycle, and it was down by 0.5 bar at the second and third cycle. And the same type of nuclear power plant in France had no similar status. It was also different with the situations of American units. In this paper it concludes that the main cause of steam pressure loss is the sludge or fouling which accumulated at tubes and supporting plates at the second loop. The eddy current imaging and video inspection results showed that the sludge or deposit were found at the cold side tubes nearby the tube supporting plate one, the sludge amount at hot side tubes was smaller than the cold tubes. In general, there were no deposit signals at the upper tube bundle. And the total amount of sludge on SG tubes was fewer, which was possibly contradiction with the fouling factor. The bundle flushes equipment have been applied at Ningde NPP unit 1, the sludge amount was five times larger than the normal tube sheet flush. This special bundle flush applications reduce the sludge in the SGs, avoid the corrosion of heat transfer tubes and ensure the SGs safety. It is a pity that the SG thermal performance was not recovered quickly after this special flush. The sludge nearby the TSP1 was not the main cause of steam pressure loss. At present, the project team is studying polyacrylic acid (PAA) and chemical cleaning to expand the scope of washing and cleaning effect, and further recover the thermal performance of steam generator.

This paper presents a single-switch AC-DC LED tube light drier with coupled-inductor and power-factor-correction (PFC) for indoor lighting applications. The presented LED tube light driver including input-current shaping feature integrates an inverse buck-boost converter with coupled-inductor and a lossless snubber. A prototype circuit has been successfully developed and implemented for supplying an 18W(60V/0.3A)-rated LED tube light with an input utility-line voltage of 110 V. Satisfactory results have demonstrated the functionality of the presented AC-DC LED tube light driver and its suitability for indoor lighting applications.

A strain sensor with high flexibility using ionic liquid is proposed for sensing movements of human body. The resistance strain sensor is constructed from a silicon tube filled fully with a mixture of aqueous sodium chloride and glycerin sealed gold-coated electrodes. When an external force is applied to the sensor, the silicon tube deforms resulting in a change in the sensor resistance value. The proposed sensor was fabricated and experimentally characterized under several working conditions. Good performance was demonstrated in detecting the movement of human leg and fingers. The proposed simple sensor has high potential in wearable applications.

Tissue engineering is trying to use modular tissue micro-rings to construct artificial biological microtubes as substitute of autologous tissue tubes to alleviate the shortage of donor sources. However, because of the lack of effective assembly strategies, it is still challenging to achieve high-speed fabrication of biological microtubes with high cell density. In this paper, we proposed a robotic-based magnetic assembly strategy to handle this challenge. We first encapsulated magnetic alginate microfibers into micro-rings formed by cell self-assembly to enhance the controllability. Afterwards, a 3D long-stroke manipulator with visual servoing system was designed to achieve magnetic pick-and-place operations of micro-rings for 3D assembly. Moreover, we developed a mathematical model of the motion of micro-ring in solution environments. Based on visual feedback, we analyzed the feasibility of automatic assembly and following response of micro-rings with the moving magnets, which shows our proposed method has great potential to achieve high-speed bio-assembly. Finally, we successfully assembled multi-micro-rings into a biological microtube with high cell density.

In this paper, the thermal impact on a metamaterial absorber (MMA) used in traveling-wave tube is investigated. This MMA has three layers, where the dielectric layer, SiC, is middle layer with metallic layers, copper, are top layer and bottom layer. The thermal impact on this MMA is studied with a comprehensive consideration of all thermal-sensitive parameter of MMA structure. The simulation results reveal the performance of MMA in a high temperature circumstances. When temperature rising from 300 K to 600 K, the absorbing frequency of the proposed MMA shifts from 27.60 GHz to 26.79 GHz. These results indicate the MMA has a potential application in TWT.

At present, there are many researches on the thermal characteristics of traveling wave tube, but few researches and discussions on the measurement of its internal temperature field are involved. Moreover, it is difficult to monitor the internal temperature of traveling wave tube. In related research, an RBF neural network model based on ANSYS slow wave structure simulation data has been proposed. Data outside the slow wave structure is input into the model to calculate its internal thermal characteristics. On this basis, a simplified model of slow wave structure was designed in this study. The real data outside the model tube measured by the infrared temperature measurement system was input into the inversion model to get the internal temperature, and the error is small compared with the real internal temperature.