Air Gap Research Articles

Gamma-irradiated janus electrospun nanofiber membranes for desalination and nuclear wastewater treatment

This study presents the fabrication of double-layer electrospun nanofibrous membranes (DL-ENMs) using polyvinylidene fluoride (PVDF) and polyether sulfone (PES) based polymers with different degrees of hydrophilicity (PES, sulfonated PES, and PES with hydroxyl terminals). A comparative analysis was carried out with single-layer electrospun nanofiber membranes (SL-ENM) with a total thickness of about 375 μm. Using feed solutions, including sodium chloride, sodium nitrate, and simulated nuclear wastewater (SNWW), the performance of DL-ENMs was evaluated for desalination and radionuclide decontamination by direct contact membrane distillation (DCMD) and air gap membrane distillation (AGMD) techniques. The results showed that DL-ENMs, especially those incorporating a sulfonated PES-based hydrophilic layer, exhibited superior permeate fluxes, reaching values of 72.72 kg/m2.h and 73.27 kg/m2.h in the DCMD using aqueous feed solutions of NaCl and NaNO3, respectively, and 70.80 kg/m2.h and 41.96 kg/m2.h using aqueous feed solutions of SNWW in DCMD and AGMD, respectively. Both SL-ENMs and DL-ENMs exhibited high rejection efficiencies and decontamination factors for the feed solutions (>99.9%). In addition, the prepared ENMs were exposed to gamma radiation to evaluate their applicability in real-life applications. The result of irradiation revealed the negative impact of gamma radiation on the fluorine content of PVDF which could be a critical point in using PVDF as a hydrophobic material for decontaminating nuclear wastewater by membrane distillation.

The impact of different air gap defects in polypropylene coaxial cables on electric field distortion

The internal cable will have different air gaps due to various physical influences, and partial discharge caused by air gap defects is the main cause of cable insulation aging. To avoid serious consequences caused by air gap defects, it is crucial to analyze the extent of the impact of early-stage air gaps on the electric field in the cable. In this paper, COMSOL Multiphysics software is used to build a three-dimensional model of the cable, and the insulation material is polypropylene. Different positions and sizes of air gap defects are designed in the model. The electric field distribution inside the cable is obtained through the finite element algorithm, and the degrees of distortion of the electric field under different air gap sizes, positions, and shapes are compared. The results show that the size of the air gap affects the change in the electric field. Air gaps closer to the copper core position produce greater electric field distortion. Additionally, air gaps with larger curvature also result in greater electric field distortion. Based on the conclusion of this study, the influence degree caused by different air gap defects can be determined and provide a basis for the analysis of such faults.

Microstrip antenna with reflector and air gap for short range communication in 900 MHz band

This paper proposes a microstrip antenna that was made of a microstrip fed slot with a complimentary stub on a single dielectric medium. This antenna was integrated with a reflector and air gap for the application of short range communication (SRC) in a 900 MHz band. Analyses were made on the dimension of the reflector and the height of the air gap towards the antenna performance. Besides, an antenna field test was done for the propagation distance of the proposed antenna. As a result, with the antenna size of 13,770 mm2 , the measured return loss was -10.79 dB and the directivity gain was 7.44 dBi. Besides, with the effective isotropic radiated power (EIRP) of 7.44 dBm, it was predicted that at 100 m, the received signal would be around 60 to 70 dBm. Therefore, a high gain was produced by using a reflector with air gap and a compact size was achieved if compared to conventional high gain antenna designs such as Yagi Uda. Thus, it is suitable for a communication device such as the SRC application.

Online Magneto-Thermal Coupled Model of PMECCs Using Measured Boundaries

Online modeling of the magneto-thermal coupled field (MCF) in permanent magnet eddy current couplings (PMECCs) has long been challenging since it exists in the copper layer and cannot be directly measured. This article proposes an online magneto-thermal coupled model (OMCM) to reconstruct the MCF using measured boundaries. The magnetic field (MF), eddy current field (ECF), and temperature field (TF) in the MCF are coupled in an identical space-time united discretization system. Virtual boundary nodes are added to the system, which can adapt to different boundary conditions in electromagnetic and thermal analysis. The measured data of single-point sensors are spanned to continuous boundary conditions. An approximate solution of the MCF is derived based on the measured boundaries and the general solutions of Laplace's equation and Poisson's equation in magneto-thermal analysis. The three-dimensional distribution of the MF, ECF, and TF at each spatial node and time segment can be simultaneously calculated in matrix form by the OMCM. Furthermore, the output torque is estimated and compared with the conventional methods. A verification process is carried out to assess the reconstructed results, showing that the OMCM can yield results close to the verification sensors for various slips and air gaps.

Electrical discharge reproduction in rod-barrier-plane system

The present paper deals with new modeling to reproduce the electric discharge in the rod-plane air gap system with rubber insulating barrier under AC and impulse voltage. This model considers the randomness character of discharge evolution which is governed by the electric field. The discharges shape obtained by this model are compared with ones given by experimental tests. The established model reproduces correctly the forms of discharges obtained by experimental tests under AC voltage. It is found that the behavior of the electrical discharge depends not only on the dimension (thickness and width) of the insulating barriers but on its positions in the air gap as well. It is to highlight that the mode of applied voltage is of key importance barrier. Experimental investigation shows that the developed arc can evolve on 1 to 4 channels. The generated discharges in AC voltage distinguish by the formation of a multiple-channel arc. Whereas, the discharge under lightning impulse voltage found to progress in a single channel whatever the barrier position and dimensions. The model confirms that electric field is the most important factor in the behavior of the rod-insulating barrier-plane system submitted to high voltage.

Investigation of torque and sensitivity analysis of a two-phase hybrid stepper motor

Abstract Stepper motors are extensively used in various automated systems, notably hybrid stepper motors (HSMs), renowned for their high torque density. Optimizing and improving their performance and torque density is highly beneficial. The first step in motor optimization is to perform a sensitivity analysis to identify the parameters most significantly affecting motor performance and torque density. Using Ansys Maxwell, a finite element method (FEM) software, we modeled and analyzed a commercially available HSM. After validating the computer model’s accuracy, we investigated the motor’s sensitivity to various parameters and discussed their effects on performance. Our findings highlight the significance of parameters such as air gap, magnet diameter, wire-turn numbers in the coils, and the shapes of the rotor and stator teeth in influencing HSM sensitivity—conversely, factors like magnet height and stator pole thickness exhibit negligible impact on motor performance.

Dynamic propagation velocity of a positive streamer in a 3 m air gap under lightning impulse voltage

Streamers represent an important stage in the initiation of gap discharge. In this work, we used an eight-frame intensified charge-coupled device camera to capture the streamer development process when a lightning impulse voltage of 95%–100% U 50% was applied in a 3 m rod–plate gap and the streamer velocity was analyzed. Analysis of the observations shows that streamer velocity can be defined by three stages: rapid velocity decline (stage 1), rapid velocity rise (stage 2) and slow velocity decline (stage 3). The effects of electrode shape, applied voltage and gap breakdown or withstanding on streamer velocity were analyzed. The electrode with a larger radius of curvature will result in a higher initial velocity, and a higher voltage amplitude will cause the streamer to propagate faster at stage 3. Gap withstanding or breakdown has no obvious effect on streamer velocity. In addition, the experimental results are compared with previous results and the statistical characteristics of the primary streamer discharge are discussed.

A fast and plug-and-play mechanical connector for microfluidic chips

This article introduces a fast and plug-and-play mechanical connector for microfluidic chips. With this connection device, fast and pluggable connection between microfluidic chips and liquid storage tanks can be achieved, allowing microfluidic flow between the storage tank and the chip and between chips while ensuring airtightness and avoiding liquid leakage. The reason for liquid leakage and the maximum sealing pressure are theoretically analyzed from the perspective of surface tension. The relationship between different liquids (surface tension coefficient), air gap distance, and leakage pressure is explored. Furthermore, the effect of fast connection method and capillary connection method on liquid flow inside the chip is compared. The experiment shows that the flow rate using the fast connection method can reach at least 70% of that using the capillary connection method, and can gradually increase to 96% with increasing pressure and flow rate.

Nanosecond photography observation of the discharge process across the 220 kV/500 kV insulators in lightning impulse

Long air gap discharge is the basis for the study of lightning protection and external insulation design of high voltage lines. However, there is a lack of detailed and comprehensive observation of the long air gap discharge process at the ns-level, as well as higher voltage insulator discharge observations. In this paper, the lightning impulse discharge/flashover tests are conducted on 220 kV glass insulators and 500 kV glass/composite insulators. Firstly, the U50% test is performed to determine the U50% value of each insulator under standard lightning impulse, and 1.1U50%, slightly higher than U50%, is applied to ensure the breakdown of the insulator. Subsequently, emICCD is utilized with a very short exposure time (minimum 10 ns) to obtain repeated single shots of discharge images under different delays, exposure times and light intensity gain. These images were spliced together based on time sequence to create a continuous discharge process. The discharge processes of 220 kV glass insulator and 500 kV glass/composite insulator are compared and analyzed. The results show that in the early stage of discharge, the discharge processes at the low voltage end of both 220 kV and 500 kV glass insulators are more intense. Additionally, the downward leader is faster than the upward leader in the discharge process of 500 kV composite insulators.

Magnetic Field Distortion Analysis and Suppression for the Minimum Unit Winding Segmented Moving-Magnet Linear Motor

Segmented power supply is frequently utilized for long-stroke moving-magnet linear synchronous motors to lessen the issue of large loss and heating brought on by long-stroke power supply. However, the driving mode of partial excitation in segmented power supply brings some problems, such as unbalanced parameters of three-phase, the transient inductance of winding changing with secondary position, and distortion of armature reaction magnetic field. This paper proposes a new topology with the minimum unit winding segmented to solve the problems of unbalanced inductance parameters and distortion of armature reaction magnetic field in winding segmented permanent magnet linear synchronous motors (WS-PMLSM). An analytical model of inductance distortion in the end coils of a moving-magnet PMLSM is established and compared with the non-end coil inductance to summarize the mechanism of inductance unbalance in WS-PMLSM. Based on the model of winding transient inductance changing with secondary position, the changing law of transient inductance is expounded. An analytical method of the air gap magnetic field based on virtual winding is proposed, and the formation mechanism of magnetic field distortion caused by partial excitation is revealed. Aiming at the topology of the minimum unit winding segmented moving-magnet PMLSM, an optimized drive strategy of n+3 is proposed.

МАТЕМАТИЧНА МОДЕЛЬ МАГНІТОЕЛЕКТРИЧНОЇ МАШИНИ

A mathematical model is proposed for the calculation of electromagnetic parameters of magnetoelectric machines using an analytical method. Permanent magnets are abstracted as equivalent solenoids with constant current represented as current loops. The model differs from known models by the presence of double linear current loops in the stator for the analysis of magnetoelectric machines with a two-layer winding. Additionally, the proposed model considers linear current loops of equivalent solenoids instead of point current loops for a more accurate calculation. The current loops of the stator and rotor are defined at the boundaries of the air gap of the electric machine, i.e., on the smooth slotless surfaces of the magnetic cores. The current loops are expressed for the first time as a product of three variables: current strength, linear current density coefficient, and spatial distribution coefficient. The inductance of stator slots and the resistance of the winding are taken into account using known analytical expressions from classical electric machine theory. The rotor rotation frequency is presented as a function of time. For magnetoelectric machines of specified dimensions and a given variable rotor rotation frequency, the distribution of magnetic field induction, vector magnetic potential, currents, winding spatial distribution coefficients, and electric field intensity of permanent magnets are calculated using the mathematical model. References 7, table 1, figures 4.

Analysis and Design of Adjustable-Gap Double-Side Axial Flux Permanent Magnet Hysteresis Damper

In this paper, a novel adjustable gap double-side axial flux permanent magnet hysteresis damper (AGDSAPHD) is proposed, of which the torque can be adjusted by changing the air gap and the magnetic field angle between the upper and lower stators at the same time. To analyze and design, a modified vector Jiles-Atherton (JA) hysteresis model is used for simulating the magnetic flux distribution and the hysteresis torque of AGDSAPHD. The eddy currents in the AGDSAPHD are analyzed, which have a great influence on the output torque when the rotational speed is fast. A splitting method used in the rotor of the AGDSAPHD is proposed to reduce the effect of eddy currents. The heat distribution of the AGDSAPHD is calculated to determine its slip power and operating mode. A prototype is built and tested to verify the reliability of the analysis. The experiments prove that the modified vector JA model has high computational accuracy in calculating the hysteresis effects of the AGDSAPHD. A splitting method used in the rotor can greatly reduce the eddy current torque. AGDSAPHD has a greater torque adjustment range and better temperature stability than the traditional one.

Mechanical and hygrothermal properties of hemp-silica bio-composites

This research investigated the development of a fast-drying silica-based binder for hemp concrete products with enhanced mechanical and thermal properties. Hemp-silica bio-composites were prepared by mixing hemp shivs with a two-component binder system composed of liquid sodium silicate and tributyl citrate (TBC). Compressive strength, thermal conductivity, moisture buffering value, cyclic moisture resistance and microstructure of hemp-silica composites were analysed, and the results were compared with those of hemp-lime concrete. Hemp-silica blocks with shiv-liquid sodium silicate mass ratio of 1:3.75 and TBC content of 37.5 wt% of sodium silicate dry matter produced a compressive strength of 0.56 MPa only after 3 days of drying and 1.92 MPa after 28 days. These were higher than hemp-lime blocks at the same density range. Hemp-silica panels showed a thermal conductivity of 0.101 W/mK and an excellent moisture buffering value of 3.49. Hemp silica formed an open porosity with large air gaps between the particles and a water-resistance silica-based layer on the shiv surface producing a higher moisture resistance compared to hemp-lime systems. This paper focuses on the development of a novel fast-drying binder system with a potential for use in conjunction with other lingnocellular plant aggregates to form low-carbon and efficient multifunctional building materials.

Geant4 Simulation of Scatter Radiation Removal: Comparison and Validation of Anti-scatter Grid and Air Gap for X-ray Mammography

Abstract: X-ray mammography modality provides excellent low-contrast resolution images with low scatter radiation, making it the gold standard in diagnosing breast cancer. Anti-scatter grid and air gap techniques are typically used to further minimize the scatter radiation and improve image quality. Thus, Geant4 simulation was used to investigate the effectiveness of these techniques in removing scatter radiation in X-ray mammography. The effectiveness of an anti-scatter grid was evaluated using the Bucky factor, where it linearly increased with increasing the anti-scatter grid ratio. It was found that increasing the grid frequency affects the Bucky factor depending on the design of the grid ratio. This research proved that designing an anti-scatter grid with high grid frequency (80 lp/mm), low grid ratio (2:1), and proper orientation minimized common anti-scatter grid artifacts. The effectiveness of the air gap technique was also evaluated using the air gap dose factor. It increased non-linearly with increasing magnification. This research validated that using smaller pixel sizes and small focal spot sizes improved spatial resolution with magnification. Our simulation validated that the anti-scatter grid and air gap were effective techniques in removing scatter radiation. By comparing these techniques, the anti-scatter grid was more effective in removing scatter radiation at the expense of increasing the radiation absorbed dose with the exception of 2.0 magnification. It’s recommended to be extremely cautious when using 2.0 magnification or a grid ratio higher or equal to 8:1. These parameters may cause the radiation absorbed dose to be increased by several folds. Keywords: Geant4, Gate, X-ray mammography, Scatter removal, Anti-scatter grid, Air gap.

Assessing Rotor Position Impact on the PMSM Perforamance and the Dynamic Simulation with Control Position for Wind Energy Conversion

In this paper, two parts are presented. First for the design and dimensioning of PMSM machine, we must know the distribution of the magnetic field in each part of the magnetic system and in particular at the air gap in which the energy conversion takes place. Generally, Maxwell’s partial differential equations supplemented by material’s law are used to describe the magnetic field problems. However, a numerical calculation is necessary, especially with the complex geometry of these devices. Secondly, we develop a machine Park model in relative unit to simulate a simple closed loop control imposed on the position of the PMSM rotor used in the wind energy conversion chain and this control is used to define the phase voltage have enabled to evaluate the performance of the machine.

Analysis of Multi-Objective Optimization Design of Interior Double Radial and Tangential Combined Magnetic Pole Permanent Magnet Drive Motor for Electric Vehicles

A new type of interior combined pole permanent magnet drive motor is proposed in this paper, which aims to improve the power and comfort of electric vehicles. In view of the complex magnetic circuit structure and rich harmonic magnetic field of the motor, the initial magnetic pole parameters of the rotor are determined by the equivalent magnetic circuit method. Then, aiming at the complex magnetic circuit and rich harmonic magnetic field, a multi-objective optimization method based on the Taguchi method and response surface method is proposed to reduce the cogging torque, high harmonic content in air gap magnetic flux density and increase the output torque. Based on the finite element analysis of the electromagnetic performance of the new type interior combined magnetic pole permanent magnet drive motor before and after optimization, it can be seen that the improved rotor structure can effectively reduce the torque ripple and increase the torque density. Finally, a prototype was developed and experiments were conducted, and experimental results verified the correctness of the proposed multi-objective optimization algorithm.

PENGARUH VARIABEL CELAH UDARA TERHADAP FLUKS MAGNET PADA GENERATOR PERMANEN MAGNETIK AXIAL FLUKS

Generators that use permanent magnets do not require initial excitation to produce voltage. where the generator design is an axial flux type using a ceramic type permanent magnet (NdFeB), and uses two flanking stator rotors. For electricity use, the AC voltage is changed to DC voltage using a rectifier for charging the accumulator. The air gap in an axialflux generator is the distance between the rotor and stator. The air gap is also a place for the magnetic field to move through the coils in the stator which ultimately produces a magnetic flux value which will influence the amount of induced voltage produced. The faster the rotation produced, the greater the voltage produced, but the frequency value will also increase, so that this generator is only limited to 400 rpm rotation, at a frequency value of 50 Hz, producing an effective voltage of ± 22 V with an air gap distance ( δ) is 2 mm, the frequency measurement has an error of 10-20 Hz and an error percentage of 5-10%, with the results of the induced current measurement having the same voltage

Air gap flux density measurement of PMSLM based on TMR sensing external stray magnetic field and CNN-LSTM

This paper presents a new non-invasive air gap flux density measurement method for permanent magnet synchronous linear motor (PMSLM) using tunneling magnetoresistance (TMR) sensor and convolutional neural networks-long short-term memory (CNN-LSTM) regression modeling. First, the analytical and finite element models of the air gap magnetic field of PMSLM are established as the data basis. Second, TMR sensor is used to measure the external stray magnetic density. Gramian Angular Field method combined with image similarity matching technology are used to obtain the optimal measurement position of the TMR sensor. Then, a new deep learning regression method as CNN-LSTM is introduced to establish a high-precision mapping model to realize non-invasive high-precision measurement of the air gap magnetic density by “substituting external to internal.” Finally, PMSLM prototype experimental platform with TMR sensor hardware acquisition circuit is built. Comparison confirmatory experiments with Gauss meter can verify the effectiveness and superiority of the proposed method.

Commissioning and clinical implementation of an independent dose calculation system for scanned proton beams.

Experimental patient-specific QA (PSQA) is a time and resource-intensive process, with a poor sensitivity in detecting errors. Radiation therapy facilities aim to substitute it by means of independent dose calculation (IDC) in combination with a comprehensive beam delivery QA program. This paper reports on the commissioning of the IDC software tool myQAiON (IBA Dosimetry) for proton therapy and its clinical implementation at the MedAustron Ion Therapy Center. The IDC commissioning work included the validation of the beam model, the implementation and validation of clinical CT protocols, and the evaluation of patient treatment data. Dose difference maps, gamma index distributions, and pass rates (GPR) have been reviewed. The performance of the IDC tool has been assessed and clinical workflows, simulation settings, and GPR tolerances have been defined. Beam model validation showed agreement of ranges within±0.2mm, Bragg-Peak widths within±0.1mm, and spot sizes at various air gaps within±5% compared to physical measurements. Simulated dose in 2D reference fields deviated by-0.3%±0.5%, while 3D dose distributions differed by 1.8% on average to measurements. Validation of the CT calibration resulted in systematic differences of 2.0% between IDC and experimental data for tissue like samples. GPRs of 99.4±0.6% were found for head, head and neck, and pediatric CT protocols on a 2%/2mm gamma criterion. GPRs for the adult abdomen protocol were at 98.9% on average with 3%/3mm. Root causes of GPR outliers, for example, implants were identified and evaluated. IDC has been successfully commissioned and integrated into the MedAustron clinical workflow for protons in 2021. IDC has been stepwise and safely substituting experimental PSQA since February 2021. The initial reduction of proton experimental PSQA was about 25% and reached up to 90% after 1 year.

Investigating the impact of Trombe wall parameters on thermal performance and room temperature in the Iraqi climate

AbstractTrombe wall serves as an effective passive heating element, and its performance is heavily reliant on local climate conditions. This study involved both experimental and numerical analyses of a full‐scale test room equipped with a Trombe wall under Iraqi climate conditions. To facilitate this investigation, an experimental test room was constructed in Kirkuk city with dimensions of 4.0 m × 3.0 m × 2.75 m. In addition, a numerical simulation method based on computational fluid dynamics was developed and a computer code was created to investigate the performance of the system. The accuracy of the developed numerical approach was validated against experimental data collected from the test room. This analysis was conducted specifically for the period of February 17–18, which represents the coldest month of winter in the study area. The performance of the system was assessed with respect to various parameters; air gap width variations (2, 4, 6, and 10 cm), massive wall thickness ranging from 15 to 35 cm with 5 cm increments, channel width options (3, 5, 10, 15, and 20 cm), and vent heights ranging from 5 to 20 cm in 5 cm increments. Furthermore, an investigation of the impact of replacing the air in the air gap with inert gases, specifically argon, krypton, and a mixture of these gases with air was conducted, as well. The outcomes indicate that both the channel width and vent height do not have a significant impact on the system's performance. However, the width of the air gap has a modest effect on system performance, and the best performance was observed with a smaller gap width, specifically 2 cm. The most significant impact on room temperature is observed when the storage wall thickness is varied. In the case of wall thickness of 15 cm, there is a notably higher fluctuation in room temperature between the maximum and minimum values, reaching approximately 16°C. For a wall thickness of 35 cm, however, this fluctuation is significantly reduced to about 3°C. The system efficiency as determined after 24 h of operation period improved significantly when the air was replaced by an inert gases or a mixture of gases in the air gap. Compared to air, the increase in efficiency is about 14.8% for argon, 17.7% for krypton, and 20.6% for the mixture of gases.