Air Gap Size Research Articles

The Interface Motion and Hydrodynamic Shear of the Liquid Slosh in Syringes.

Interface motion and hydrodynamic shear of the liquid slosh during the insertion of syringes upon autoinjector activation may damage the protein drug molecules. Experimentally validated computational fluid dynamics simulations are used in this study to investigate the interfacial motion and hydrodynamic shear due to acceleration and deceleration of syringes. The goal is to explore the role of fluid viscosity, air gap size, syringe acceleration, syringe tilt angle, liquid-wall contact angle, surface tension and fill volume on the interface dynamics caused by autoinjector activation. A simplified autoinjector platform submerged in water is built to record the syringe and liquid motion without obstruction of view. The syringe kinematics is imported to the simulations based on OpenFOAM InterIsoFoam solver, which is used to study the effects of various physical parameters. The simulations agree with experiments on the air-liquid interface profile and interface area. The interfacial area and the volume of fluid subject to high strain rate decrease with the solution viscosity, increase with the air gap height, syringe velocity, tilt angle and syringe wall hydrophobicity, and hardly change with the surface tension and liquid column height. The hydrodynamic shear mainly occurs near the syringe wall and entrained bubbles. For a given dose of drug solution, the syringe with smaller radius and larger length will generate less liquid slosh. Reducing the air volume and syringe wall hydrophobicity are also helpful to reduce interface area and effective shear. The interface motion is reduced when the syringe axis is aligned with the gravitational direction.

Comparison of Air-Gaps Effect in a Small Cavity on Dose Calculation for 6 MV Linac.

Background: Many authors stated that cavities or air-gaps were the main challenge of dose calculation for head and neck with flattening filter medical linear accelerator (Linac) irradiation.Objective: The study aimed to evaluate the effect of air-gap dose calculation on flattening-filter-free (FFF) small field irradiation.Material and Methods: In this comparative study, we did the experimental and Monte Carlo (MC) simulation to evaluate the presence of heterogeneities in radiotherapy. We simulated the dose distribution on virtual phantom and the patient’s CT image to determine the air-gap effect of open small field and modulated photon beam, respectively. The dose ratio of air-gaps to tissue-equivalent was calculated both in Analytical Anisotropic Algorithm (AAA) and MC.Results: We found that the dose ratio of air to tissue-equivalent tends to decrease with a larger field size. This correlation was linear with a slope of -0.198±0.001 and -0.161±0.014 for both AAA and MC, respectively. On the other hand, the dose ratio below the air-gap was field size-dependent. The AAA to MC dose calculation as the impact of air-gap thickness and field size varied from 1.57% to 5.35% after the gap. Besides, patient’s skin and oral cavity on head and neck case received a large dose discrepancy according to this study. Conclusion: The dose air to tissue-equivalent ratio decreased with smaller air gaps and larger field sizes. Dose correction for AAA calculation of open small field size should be considered after small air-gaps. However, delivered beam from others gantry angle reduced this effect on clinical case.

Research on Magnetic Field Simulation of Cylindrical Linear Synchronous Motor

In order to obtain the influence of different structures and frequencies on the thrust of cylindrical permanent magnet linear synchronous motor, the transient simulation of magnetic field of cylindrical permanent magnet linear synchronous motor is carried out by using Ansoft software, and the correctness of the simulation is verified by experiments. Through simulation, the characteristics of the linear motor under different voltage frequency, air gap size, and permanent magnet width and its influence on the linear motor thrust are obtained.

Effect of Air Gap on Electrical Tree in Epoxy Resin Under High Frequency Bipolar Square-Wave Voltage.

Insulation fails quickly under high-frequency AC high voltage, especially bipolar square-wave voltage with a high dV/dt. It is of great significance to study the failure mechanism of epoxy casting insulation under such kind of voltage. In this paper, pin-plane epoxy casting insulation samples with air gaps were prepared, and the relation between the electrical trees under the high frequency bipolar square-wave voltage and the air gap conditions and voltage frequencies (1~20 kHz) were studied. Results indicated that, with the presence of air gaps, the electrical trees were bush-type and had a relatively slow growth rate, which was different from the fast-growing branch-type trees in the samples without air gap. The electrical tree characteristics related with the size of air gap and voltage frequency were also studied. The electrical tree grew faster under higher voltage frequency or with a smaller air gap. Results proved that discharge introduced a lot of defects for the surface layer of the epoxy resin samples and hence induced the possibility of multi-directional expansion of electrical trees. In addition, the resulting heat accumulation and unique charge transport synergistically affected the electrical tree characteristics under the high frequency bipolar square-wave voltage.

Contactless Measurement of Sheet Resistance of Nanomaterial Using Waveguide Reflection Method.

Conductive nanomaterials are widely studied and used. The four-point probe method has been widely used to measure nanomaterials’ sheet resistance, denoted as . However, for materials sensitive to contamination or physical damage, contactless measurement is highly recommended if not required. Feasibility of evaluation using a one-port rectangular waveguide working on the microwave band in a contact-free mode is studied. Compared with existed waveguide methods, the proposed method has three advantages: first, by introducing an air gap between the waveguide flange and the sample surface, it is truly contactless; second, within the specified range of , the substrate’s effect may be neglected; third, it does not require a matched load and/or metallization at the sample backside. Both theoretical derivation and simulation showed that the magnitude of the reflection coefficient decreased monotonously with increasing . Through calibration, a quantitative correlation of and was established. Experimental results with various conductive glasses showed that, for in the range of ~10 to 400 Ohm/sq, the estimation error of sheet resistance was below ~20%. The potential effects of air gap size, sample size/location and measurement uncertainty of are discussed. The proposed method is particularly suitable for characterization of conductive glass or related nanomaterials with in the range of tens or hundreds of Ohm/sq.

An Exploration of Relationships among Thermal Insulation, Area Factor and Air Gap of Male Chinese Ethnic Costumes.

The present study investigated total and local thermal insulations of 39 sets of male Chinese ethnic costumes. Total and local clothing area factor, air gap size and air volume were determined by a 3D body scanner. Relationships between thermal insulation and air gap for the whole body, as well as local body parts, were explored. Correlations of both the total and local clothing area factor with the intrinsic insulation were also developed. Results demonstrated that the clothing total thermal insulation first increased with the increasing air gap size/air volume, followed by a decrease when the air gap size/air volume exceeded 37.8 mm/55.8 dm3. Similarly, it was also found that parabolic relationships widely existed between the local thermal insulation and local air gap at each body part. Our research findings provide a comprehensive database for predicting both global and local thermal comfort of male Chinese minority groups.

Investigation of the effect of air gap size on the spatial resolution in proton- and helium radio- and tomography

PurposeProton computed (transmission) tomography (pCT) refers to the process of imaging an object by letting protons pass through it, while measuring their energy after, and their position and (optionally) direction both before and after their traversal through that object. The so far experimental technique has potential to improve treatment planning of proton therapy by enabling the direct acquisition of a proton stopping power map of tissue, thus removing the need to obtain it by converting X-ray CT attenuation data and thereby eliminating uncertainties which arise in the mentioned conversion process. The image reconstruction in pCT requires accurate estimates of the proton trajectories. In experimental pCT detector setups where the direction of the protons is not measured, the air gap between the detector planes and the imaged object worsens the spatial resolution of the image obtained. In this work we determined the mean proton paths and the corresponding spatial uncertainty, taking into account the presence of the air gap. MethodsWe used Monte Carlo simulations of radiation transport to systematically investigate the effect of the air gap size between detector and patient on the spatial resolution of proton (ion) computed tomography for protons with an energy of 200MeV and 250MeV as well as for helium ions (He-4) with an energy of 798MeV. For the simulations we used TOPAS which itself is based on Geant4. ResultsFor all particles, which are detected at the same entrance and exit coordinate, the average ion path and the corresponding standard deviation was computed. From this information, the dependence of the spatial resolution on the air gap size and the angular confusion of the particle beam was inferred. ConclusionThe presence of the airgap does not pose a problem for perfect fan beams. In realistic scenarios, where the initial angular confusion is around 5mrad and for typical air gap sizes up to 10cm, using an energy of 200MeV a spatial resolution of about 1.6mm can be achieved. Using protons with E=250MeV a spatial resolution of about 1.1mm and using helium ions (He-4) with E=798MeV even a spatial resolution below 0.7mm respectively is attainable.

The air gap between bolus and skin affects dose distribution in helical and direct tomotherapy

AbstractAim:To modify the final dose delivered to superficial tissues and to modulate dose distribution near irradiated surface, different boluses are used. Air gaps often form under the bolus affecting dose distribution. This study aimed to evaluate the effect of an air gap under the bolus radiation on dose delivery.Materials and methods:To evaluate the impact of the air gap, both helical tomotherapy (HT) and direct tomotherapy (DT) were performed in a simulation study.Results:The maximum dose to bolus in DT plans was bigger than that used in HT plans. The maximum dose delivered to the bolus depended on the air gap size. However, the maximum dose to bolus in all HT plans was within the acceptable value range. Acceptable value was set to up to 107% of the prescription dose. In the simulation performed in this study, the acceptable air gap under bolus was up to 15 mm and below 5 mm in HT and DT plans, respectively.Conclusions:HT technique is a good choice, but DT technique can be also used if the bolus position can be reproduced accurately. Thus, the reproducibility of the bolus position between planning and treatment is very important.

Study of the Sound Absorption Properties of 3D-Printed Open-Porous ABS Material Structures.

Noise pollution is a negative factor that affects our environment. It is, therefore, necessary to take appropriate measures to minimize it. This article deals with the sound absorption properties of open-porous Acrylonitrile Butadiene Styrene (ABS) material structures that were produced using 3D printing technology. The material’s ability to damp sound was evaluated based on the normal incidence sound absorption coefficient and the noise reduction coefficient, which were experimentally measured by the transfer function method using an acoustic impedance tube. The different factors that affect the sound absorption behavior of the studied ABS specimens are presented in this work. In this study, it was discovered that the sound absorption properties of the tested ABS samples are significantly influenced by many factors, namely by the type of 3D-printed, open-porous material structure, the excitation frequency, the sample thickness, and the air gap size behind the sound-absorbing materials inside the acoustic impedance tube.

Detection of Small Defects in Composite Insulators Using Terahertz Technique and Deconvolution Method

After a long-term operation, defects may occur in composite insulators and threat the safe operation of power transmission. To secure the power transmission system, it would be beneficial to detect the defects in their initial stage. In this article, the terahertz technique combined with a deconvolution method was proposed, and a terahertz time-domain spectroscopy system was built. To validate the method proposed, three types of defects, namely, single air gap defect, inclusion defect, and double-layer air gap defect were artificially prepared and tested. According to the test results, it was found that compared with the traditional terahertz method, the air gap size that could lead to pulse overlapping was reduced from 1.22 to 0.57 mm. After the deconvolution process, air gap defect as small as 0.173 mm could be distinguished due to the shape characteristics of unipolar pulse. It was also found that when the defect was damp, the obtained waveform near the defect became smooth. The results of this article demonstrate that terahertz time-domain spectroscopy (THz-TDS), combined with the deconvolution method, can have high potential in the detection of defects in composite insulators.

Bandgap analysis of a tunable elastic-metamaterial-based vibration absorber with electromagnetic stiffness

Vibration is a mechanical phenomenon and exists throughout society. The vibrations in daily life would cause emotional discomfort as well as physical fatigue. Vibration even can give a life threat depending on its magnitude. Vibration is one of the significantly important factors to consider for the safety of the overall society, and therefore study of vibration reduction is indispensable. This paper presents a novel tunable electromagnetic vibration absorber based on an elastic metamaterial. The electromagnetic vibration absorber is a lattice structure dynamic model comprising elastic metamaterial unit cells having negative refractive index property and interconnected by springs. To verify the tunability of the elastic-metamaterial-based vibration absorber, the electromagnetic stiffness change in a finite element (FE) model of the electromagnet was analyzed through a parametric study of the air gap size, internal composition of the electromagnet, and amount of current. The conditions under which the electromagnet generates the highest electromagnetic stiffness were also explored. Each different value of electromagnetic stiffness obtained from the parametric studies was used for FE analysis of the dynamic model to investigate the influence on bandgap variations. The results reveal that the variation of electromagnetic stiffness has an effect on the location and bandwidth of bandgap. Moreover, vibration reduction was achieved due to the structural aspects of the dynamic model and the negative refractive index property of the elastic metamaterial. It is demonstrated that the elastic metamaterial vibration absorber is tunable in real time with the change of electromagnetic stiffness and has vibration reduction effect in various frequency ranges.

Air-gap-embedded robust hazy films to reduce the screen-door effect in virtual reality displays.

We report a way to make an air-gap-embedded flexible film to reduce the screen-door effect (SDE) in virtual reality (VR) displays. Oxygen plasma was treated with a polyethylene terephthalate substrate to produce wavelength-scale micropatterns. These micropatterns induce an effective haze, but it is easily destroyed by a very small external scratch. Such a problem could be solved by coating the patterns with poly(dimethylsiloxane) (PDMS). The viscosity of PDMS, controlled by the ratio of the base and curing agents, plays a key role in determining the size of air-gaps at the valleys of micropatterns. As the ratio of base agent increases to 40, the average haze abruptly increased from 0.9% to 88.6% in visible wavelengths, while the average total transmittance maintained was between 89.8 and 91.7%. The origin of air-gap-induced haze is confirmed by numerical simulations. The hazy film remarkably reduced the SDE of the VR display from 30.27% to 4.83% for red color, from 21.82% to 2.58% for green, and from 26.02% to 3.38% for blue, as the size of air-gaps increases from 0 to 406 ± 91 nm. No defects were found after 10 000 bending cycles with a bending radius of 3 mm.

Analysis of magnetic field distribution in a transverse-flux linear motor with superconducting windings

The influence of permanent magnet excitation on HTS coil in transverse-flux linear motor is analyzed. Numerical analysis using finite-element method is carried for two commonly used magnet arrays - alternating and Halbach. The influence of magnet arrangements on critical current density of HTS winding operating in temperature of liquid nitogen of 77 K is examined. The goal is to find optimal air gap size and magnet span to assure the best performance of the motor where anisotropy of superconductor is taken into account.

Quantitative Detection of Interfacial Air Gap in Insulation Equipment Based on Terahertz Wave Contrast Method

The nondestructive testing of internal defects in power grid equipment has always been a spotlight of research. Since terahertz wave has good application in the nondestructive detection fields, we apply terahertz wave to detect the interfacial air gap of insulation equipment. At present, terahertz wave is difficult to measure the thickness of the internal air gap. Hence, this paper presents a method for quantitative measurement of internal air gap based on the waveform database. In addition, the propagation characteristics of the terahertz wave in medium are analyzed. Furthermore, based on the value of $n(\omega)$ and $\kappa (\omega)$ , the calculation formula of the transmission and reflection coefficients is simplified. After obtaining the reflected wave of the single outer layer material, we quantitatively calculate the time-domain reflection wave of interface. According to the principle of terahertz detection based on photoconductive antenna, the detection of multiple reflection waves is analyzed. To verify the superposition characteristics of multiple waves, the terahertz reflection waves of samples with interfacial air gap are tested. By comparing the measured waves and the artificially calculated waves, we prove that the superposition of the waveform is approximately linear. Based on the good coincidence between artificially generated waveform and measured waveform, we propose a method of quantitatively diagnosing the interface air-gap defect. Indeed, the deviation between the test results and the actual air-gap size is small.

Numerical simulation of the induction heating process of a disk profile

This paper presents the developed parametric 3D model of disk heating. The numerical results reflect the change in the temperature profile of the heated pattern depending on the current value, current frequency, air gap size, workpiece thickness, workpiece diameter, heating time, number of inductor turns used and geometrical position elements of the systems “inductor - disk”. The results can be used for parametric studies and setting up the operation mode of installations for various sizes of disks.

Suspension Force Error Source Analysis and Multidimensional Dynamic Model for a Centripetal Force Type-Magnetic Bearing

The traditional modeling methods on suspension force of magnetic bearings are mainly based on static fields analysis, and lack of consideration for the effect of real-time temperature and rotation speed. However, the action area of Maxwell force and the air gap size in the calculation formula of the suspension force dynamically change with temperature rise and rotation speed. Therefore, the accuracy of model results on suspension force is compromised. In this article, taking the centripetal force type-magnetic bearing as an example, the error sources that affect the accuracy of the suspension force are analyzed meticulously. Then, based on the suspension force error sources results, a dynamic model involving multiple dimensional variables is proposed, which includes control current, displacement, temperature, and rotational speed. Superior to the traditional static models, the temperature and rotation speed are integrated into the proposed multidimensional model besides the traditional current and displacement. To prove the validity of suspension force error sources analysis and the accuracy of the proposed model, the dynamic stiffness experiments are carried out. The experiment results show that the multidimensional model is more practical and has higher precision than the traditional static model.

Revisiting an airgap split-optics mitigation for beam filamentation in high power lasers.

We extend the split-optic approach for mitigating filamentation in a thick optical component previously proposed for small beams to conditions relevant to high-power lasers. The split-optic approach divides a thick optic into two thinner optics separated by an airgap to reduce filamentation through diffraction management. Our numerical study focuses on filamentation of a flat-top beam with intensity modulation noise sources passing through a split-optic system. The improvement in the distance to collapse in glass is shown to be potentially substantial (>30%), yet has limited increase with the airgap size, unlike the common understanding when considering a collapse of a whole beam or a sole perturbation on a beam. The improvement in the collapse distance in glass asymptotes to an upper bound value that depends mainly on the beam mean intensity and its contrast for any airgap size above some value that depends mainly on the shortest spatial periods comprising the excitation noise source. Examining the difference in the simulation results for a periodic versus a randomly generated perturbation source-term suggests that the observed effect is governed by the statistical interference dynamics of the beam while propagating through the airgap.

Experimental analysis of a PCM integrated solar chimney under laboratory conditions

The objective of this work is to experimentally investigate the impact of integrating a Phase Change Material (PCM) on the performance of two different laboratory solar chimney prototypes, rendering it a viable option for yearlong use. It has been stated that solar chimneys can provide constant ventilation and increase air quality in a building. This study aims to provide a different approach in means of improving the current performance of solar chimneys as, nowadays, it is mostly pursued through the modification of the inclination, the air gap size or the inlet/outlet dimensions. The solar chimney prototype mainly analysed in this work is built with 2 cm plywood plates with a thermal conductivity of 0.15 W/mK with a volume of 3.50×1.00×0.30 m. After a 6 h charge period, a mean ventilation rate above 70 m3/h can be achieved with a relative low gain of 550 W/m2 provided by a series of 7 halogen lamps directed towards an effective collector area of 3.00 m2. The results obtained in this work show that PCM integration provides a higher ventilation rate and a slower decrease during ventilation only phases (6 h discharge), where the halogen lamps do not provide any energy to the solar chimney. Overall, the implementation of paraffinic PCMs in solar chimneys could be an economically viable option for hybrid design solutions to create a healthy indoor environment within residential buildings through renewable solar energy.

Effects of clothing ease and body postures on the air gap and clothing coverage

PurposeThe purpose of this paper is to determine the effects of clothing ease and body postures on the size and distribution of the air gap as well as the body coverage with the clothing.Design/methodology/approachVisual and quantitative analyses were conducted using a 3D body scanner and Geomagic Software. The air gap size and clothing area factor (fcl) in three test coverall and seven selected postures were calculated and compared.FindingsThe results indicated that both the clothing ease and body postures had a strong effect on the air gap and clothing coverage, especially the more complex the postures, the wider the range of influence. Nevertheless, these effects varied over body regions, being stronger at the lower body than the upper body. The air gap size at the left side of the body was generally larger than the right side. It was also found that the clothing coverage was linearly correlated with the air gap size and could be employed as an indicator to evaluate clothing protective capabilities.Practical implicationsThe findings suggested that greater attention should be paid to the protection and flexibility at the lower body and asymmetrical distribution of the air gap should be considered in the future air gap modeling.Originality/valueThe outcomes provided useful information to improve the protective clothing and develop more realistic air gap models to simulate the heat and mass transfer.

The effect of an air gap on a 2D monolithic silicon detector for relative dosimetry

Purpose: to evaluate the impact of an air gap on the Magic Plate (MP512) response and optimize this gap for relative dosimetry in photon and electron beams. Materials and methods: MP512 is a 2D monolithic silicon detector manufactured on a p-type substrate. The array consists of 512 pixels with 0.5 × 0.5 mm2 size and 2 mm pitch with an overall dimension of 52 × 52 mm2. The signal ratio (SR) as a function of beam size and the percentage were measured with MP512 in 6 MV and 10 MV photon beams. The enhanced dynamic wedge (EDW) beam profile measurements were performed for 6 MV photon beams. In this work the signal ratio is defined as the ratio of central axis MP512 reading for field sizes ranging from 0.5 × 0.5 cm2 to 10 × 10 cm2 and for the reference square field of side 10 cm at a depth of 10 cm in solid water phantom. The measurements were performed with an air gap immediately above the detector array of 0.5, 1.0, 1.2, 2.0 and 2.6 mm, respectively. The PDD was measured for field sizes 2× 2 cm2, 5× 5 cm2 and 10× 10 cm2 by scanning the MP512 from the depth of 0.5 cm to 10 cm. The beam profiles were measured for Varian linac enhanced dynamic wedge (EDW) angles of 15̂, 45̂ and 60̂ for field size 5× 5 cm2. The PDD for 6, 12 and 20 MeV electron beams were performed for a standard applicator providing 10× 10 cm2 field size. Results: the signal ratio measured with MP512 reduces with increasing air gap above the detector. The strongest effect of the air gap size was observed for small fields of 0.5× 0.5 cm2 and 1× 1 cm2 while the effect was negligible within ± 2% (1 standard deviation) for field sizes larger than 4× 4 cm2. The signal ratio measured with MP512 with air gaps of 0.5 mm and 1.2 mm showed a good agreement with signal ratio measured with the EBT3 film (within ± 2%) and MOSkinTM for 6 MV and 10 MV, respectively. Similar results were observed for the PDD measurement for field size 5× 5 cm2 and 10× 10 cm2. The PDD measured with M512 was in good agreement with Markus Ionization chamber (IC) within ± 1.6% (1 standard deviation) for 6 MV and ± 1.5% (1 standard deviation) for 10 MV. The PDD discrepancy for 2× 2 cm2 was within ± 3% of the EBT3 for both photon energies. The EDW dose profile matched well with the EBT3 for the air gap of 0.5 mm within ± 2% (1 standard deviation) for all wedge angles. The PDD measured by electron beams demonstrated no significant effect of the air gap size above MP512 for all energies. The results showed similar variations (within ± 3%) compared to Markus IC for both 0.5 mm and 2.6 mm gap. Conclusion: the MP512 diode array was demonstrated to be suitable as an in-phantom dosimeter for QA in small radiation treatment fields. The study shows that air gap size has a significant effect on small field photon beam dosimetry due to a loss of electronic equilibrium. The small air gaps of 0.5 mm and 1.2 mm were the best air gaps for 6 MV and 10 MV, respectively. The effect of the air gap in electron beam fields is not significant due to the fact that an electronic equilibrium is fully established.