Central Beam Research Articles

Analysis of the uranium chemical state by XPS: Is what you see real?

X-ray photoelectron spectroscopy (XPS) is an efficient technique for recognizing the state of elements. However, the effects of X-ray irradiation on change in the chemical state are sometimes ignored, which may impair the understanding of the environmental behavior of these elements. This study determined the change in the U 4f spectra induced by X-ray irradiation during XPS detection. For U(VI) on non-semiconductors, X-ray irradiation led to a negative shift of U 4f7/2 to ∼ 380.8 eV due to the break of the uranyl molecules, but not resulting in U(IV) species. However, owing to the photocatalytic reduction of U(VI), the irradiation of U(VI) loaded semiconductors rapidly induced the negative shift of U 4f7/2 peak to ∼ 379.8 eV, which is the characteristic of U(IV). Moreover, apparent photo-reduction occurred even if the samples were far from the center of the X-ray beam (>3971 μm). Based on these findings, methods for reducing potential error due to X-ray irradiation are suggested, including using the minimum scan time, measuring uranium-containing samples first or independent of other samples, and using X-ray of lower intensity. The results indicated that X-ray induced alteration to the chemical states must be considered when using X-ray techniques.

200 kV Ion Accelerator facility at Kurukshetra University, India

The air insulated high current medium energy 200 kV Ion Accelerator, with the terminal voltage in the range of 30–200 kV has been successfully operational at Ion Beam Centre, KU, Kurukshetra, India. A unique and imperative feature of this High Voltage Engineering Europa machine is the availability of only a single charge state, switching magnet with five exit ports and large area implantation using (-hollow cathode ion source). Ar+, B+, N+, Au+, H+, Ag+, Ni+ etc are the typically implanted ions. At present, only one beam line having beam rastering system is working specifically for material science research. The accelerator is consistently being used for conducting experiments using a wide variety of ion and target combination for research in diverse disciplines like materials science, atomic physics etc.. Ion beam sputter erosion experiments have been conducted successfully using different ion beams with varying current and energy. With the continued interest of researchers in this field, our accelerator’s use and research output is likely to many-fold in the near future.

Investigation on the influence of point loads on the deflection behaviour of G+5 frame structure

Nowadays, multi-storey structure portal frames are most commonly used worldwide. Multistory frames are used in structural systems in all metropolitan cities, future cities, and important businesses. The present study the effect of various point loads varying from 22 to 32 kN in steps of 2 were applied on the center of horizontal beams of the frame structure. The deflection behaviour in form of deflection, reaction, beading moments under point loading were discussed analytically according to stiffness matrix method and the results are validated with the help of simulation using STAAD Pro software. Results revealed that the analytical method using manual calculations in excel sheet provides approximately similar results as obtained by the costly simulation technique using STAAD Pro software. Therefore, the implementation of this excel sheet can be recommended for standard analysis of portal frame structures based on the outcomes of this study.

Determination of geometric information and radiation field overlaps on the skin in percutaneous coronary interventions with computer-aided design-based X-ray beam modeling.

PurposeThis study aimed to develop a method for the determination of the source‐to‐surface distance (SSD), the X‐ray beam area in a plane perpendicular to the beam axis at the entrance skin surface (Ap ), and the X‐ray beam area on the actual skin surface (As ) during percutaneous coronary intervention (PCI).Materials and MethodsMale and female anthropomorphic phantoms were scanned on a computed tomography scanner, and the data were transferred to a commercially available computer‐aided design (CAD) software. A cardiovascular angiography system with a 200 × 200 mm flat‐panel detector with a field‐of‐view of 175 × 175 mm was modeled with the CAD software. Both phantoms were independently placed on 40 mm thick pads, and the examination tabletop at the patient entrance reference point. Upon panning, the heart center was aligned to the central beam axis. The SSD, Ap , and As were determined with the measurement tool and Boolean intersection operations at 10 gantry angulations.ResultsThe means and standard deviations of the SSD, Ap , and As for the male and female phantoms were 573 ± 15 and 580 ± 15 mm, 8799 ± 1009 and 9661 ± 1152 mm2, 10495 ± 602 and 11913 ± 600 mm2, respectively. The number of As overlaps for the male and female phantoms were 15/45 and 21/45 view combinations, respectively.ConclusionsCAD‐based X‐ray beam modeling is useful for the determination of the SSD, Ap , and As . Furthermore, the knowledge of the As distribution helps to reduce the As overlap in PCI.

Time-resolved dosimetry with pencil-beam scanning for quality assurance/quality control in particle therapy.

This study aimed to measure dose in a scanning carbon beam‐irradiation field with high sampling rate that is sufficient for identifying spots and verifying the characteristics of the scanning beam that cannot generally be derived from the dose. To identify the spot, which is the smallest control unit of beam information during irradiation, effecting measurements with a sampling time of 10 μs or shorter is necessary. The provided dose within a specific time is referred to as time‐resolved dose (TRD). We designed a circuit for time‐resolved dosimetry using a fast‐data acquisition unit (SL1000, Yokogawa Electric Co.), which can measure 100 000 samples per second. Moreover, we used converters to enable a connection between an ionization chamber (IC) and the SL1000. TRD was measured successfully using point irradiation and two‐dimensional irradiation patterns in a scanned carbon beam. Based on the moving time of the spot obtained from the position monitor, the dose delivered to the IC from each spot position (spot dose) was interpreted. The spot dose, displacement of the chamber from the beam's center axis, and beam size were derived using TRD and position monitor outputs, which were measured concurrent with TRD. Spot dose up to a radius of 8 mm area from the IC's center were observed. Using the spot‐dose equations and simulation, we show that the spot dose of each position varies depending on the beam size and displacement of the IC's center from the beam's center axis. We devise an interpretation method for the characteristics that may apply to quality assurance, such as the verification of the trend for the beam axis and isocenter to coincide, as well as beam‐size verification.

Cyclic loading test of reinforced concrete frames protected with brace-type friction dampers

In this study, cyclic loading tests were conducted on reinforced concrete (RC) portal frames with brace-type friction dampers. The boundary conditions that could reproduce the axial forces exerted on the beams were adopted. To resist the axial force acting on the RC member, a damper connection method was employed by using steel inserted through the center of the RC member. The purpose of this study was to a) understand the behavior of the damper connection and the RC frame with brace-type friction dampers based on experimental tests and b) to confirm the effectiveness of the new connection method. According to the test results, the proposed connection method achieved effective damper connections in the RC frames. For the RC frame specimens with dampers, it was confirmed that the damper reached its sliding force and started to dissipate energy at an early stage with story drift ratios smaller than those at RC beam yielding. The welded part of the gusset plate and the steel inserted through the center of the RC beam were broken. When the welded part inside the beam broke and the axial deformation of the beam increased, the sliding displacement of the damper decreased. Therefore, a reliable jointing method of this part needs to be established.

Orbital angular momentum transfer in molecular magnets

We study the propagation of probe pulses carrying orbital angular momentum (OAM) in a crystal of molecular magnets characterized by a double-$\mathrm{\ensuremath{\Lambda}}$ light-matter coupling scheme. The model is based on the four-wave mixing (FWM) of applied fields interacting with the magnetic dipole moment of the molecular magnets. We consider the light-matter interaction under the situation where a weak probe field carries an optical vortex and investigate the exchange of optical vortices between different frequencies via the FWM in the microwave region. The propagation of OAM beams with nonzero radial indices is then explored. It is found that the conservation of both azimuthal and radial indices is satisfied over the swapping of OAM states of light. Superimposing two initially weak OAM modes with different topological charges creates specific vortex beams with a very characteristic form. The resulting beam contains a central vortex as well as several singly charged peripheral vortices distributed at the same radial distance from the center of the light beam. This complex pattern of vortices arises because the intensity radius of two interfering OAM modes is different. It is shown that the boundary region of intensity dominance of two OAM modes can be controlled by the molecular magnets parameters and strong cw electromagnetic fields. Our proposed scheme may provide a route to study the solid systems suitable for quantum technologies as well as for OAM exchange devices for quantum information processing.

Post-compression of long-wave infrared 2picosecond sub-terawatt pulses in bulk materials.

We have experimentally demonstrated the post-compression of a long-wave infrared (9.2 μm) 150 GW peak power pulse from 2 ps to less than 500 fs using a sequence of two bulk materials with negative group velocity dispersion (GVD). The compression resulted in up to 1.6-fold increase of the peak power and up to 2.8-fold increase of the intensity in the center of a quasi-Gaussian beam. The partial decoupling of the self-phase modulation and chirp compensation stages by using two materials with significantly different ratios of nonlinear refractive index to GVD provides accurate optimization of the compression mechanism and promises a viable path to scaling peak powers to supra-terawatt levels. During the preparatory study, we measured, for the first time to our knowledge, the nonlinear refractive indices of NaCl, KCl, and BaF2 for picosecond pulses in the long-wave infrared region.

Assessment of visual feedback system for reproducibility of voluntary deep inspiration breath hold in left-sided breast radiotherapy

IntroductionDeep inspiration breath-hold (DIBH) for left-sided breast cancer radiotherapy reduces the dose exposure of the heart and left anterior descending coronary artery. DIBH requires the patient to maintain an adequate breath-hold position during their daily radiotherapy fraction. This study aimed to assess the reproducibility of the breath-hold position by implementing DIBH with visual feedback (VF) system. MethodsForty-three patients who underwent left-sided radiotherapy with DIBH were reviewed. Data from 35 patients who underwent DIBH with VF (VF-DIBH) were compared with data from 8 patients who underwent DIBH with audio coaching (AC-DIBH). Reproducibility during radiotherapy was evaluated using the portal images obtained. Images were acquired daily during the tangential field treatment with DIBH. The distances between the field edge and chest wall at the central beam axis were manually measured on the portal image and digital reconstruction radiograph (DRR). The displacements of the chest wall during radiotherapy were assessed by subtracting the measurement made on the portal image from the DRR measurement. The overall average distances for the VF-DIBH and AC-DIBH cohorts were compared to assess reproducibility. The statistical analysis was performed using Mann–Whitney U tests (p < 0.05). ResultsThe mean chest wall displacement (±2 SD) was 0.59 ± 3.64 mm for VF-DIBH and 2.09 ± 4.96 mm for AC-DIBH, respectively. This value differed significantly between the VF-DIBH and AC-DIBH cohorts (p < 0.001). ConclusionIn DIBH radiotherapy, the implementation of VF was confirmed to improve breath-hold position reproducibility, and the utility of VF for DIBH was demonstrated.

A simulation study of ionizing radiation acoustic imaging (iRAI) as a real-time dosimetric technique for ultra-high dose rate radiotherapy (UHDR-RT).

Electron-based ultra-high dose rate radiation therapy (UHDR-RT), also known as Flash-RT, has shown the ability to improve the therapeutic index in comparison to conventional radiotherapy (CONV-RT) through increased sparing of normal tissue. However, the extremely high dose rates in UHDR-RT have raised the need for accurate real-time dosimetry tools. This work aims to demonstrate the potential of the emerging technology of Ionized Radiation Acoustic Imaging (iRAI) through simulation studies and investigate its characteristics as a promising relative in vivo dosimetric tool for UHDR-RT. The detection of induced acoustic waves following a single UHDR pulse of a modified 6 MeV 21EX Varian Clinac in a uniform porcine gelatin phantom that is brain-tissue equivalent was simulated for an ideal ultrasound transducer. The full 3D dose distributions in the phantom for a 1×1 cm2 field were simulated using EGSnrc (BEAMnrc∖DOSXYZnrc) Monte Carlo (MC) codes. The relative dosimetry simulations were verified with dose experimental measurements using Gafchromic films. The spatial dose distribution was converted into an initial pressure source spatial distribution using the medium-dependent dose-pressure relation. The MATLAB-based toolbox k-Wave was then used to model the propagation of acoustic waves through the phantom and perform time-reversal (TR)-based imaging reconstruction. The effect of the various linear accelerator (linac) operating parameters, including linac pulse duration and pulse repetition rate (frequency), were investigated as well. The MC dose simulation results agreed with the film measurement results, specifically at the central beam region up to 80% dose within approximately 5% relative error for the central profile region and a local relative error of<6% for percentage dose depth. IRAI-based FWHM of the radiation beam was within approximately 3mm relative to the MC-simulated beam FWHM at the beam entrance. The real-time pressure signal change agreed with the dose changes proving the capability of the iRAI for predicting the beam position. IRAI was tested through 3D simulations of its response to be based on the temporal changes in the linac operating parameters on a dose per pulse basis as expected theoretically from the pressure-dose proportionality. The pressure signal amplitude obtained through 2D simulations was proportional to the dose per pulse. The instantaneous pressure signal amplitude decreases as the linac pulse duration increases, as predicted from the pressure wave generation equations, such that the shorter the linac pulse the higher the signal and the better the temporal (spatial) resolutions of iRAI. The effect of the longer linac pulse duration on the spatial resolution of the 3D constructed iRAI images was corrected for linac pulse deconvolution. This correction has improved the passing rate of the 1%/1mm gamma test criteria, between the pressure-constructed and dosimetric beam characteristics, to as high as 98%. A full simulation workflow was developed for testing the effectiveness of iRAI as a promising relative dosimetry tool for UHDR-RT radiation therapy. IRAI has shown the advantage of 3D dose mapping through the dose signal linearity and, hence, has the potential to be a useful dosimeter at depth dose measurement and beam localization and, hence, potentially for in vivo dosimetry in UHDR-RT.

Extension and validation of a GPU-Monte Carlo dose engine gDPM for 1.5 T MR-LINAC online independent dose verification.

To extend and validate the accuracy and efficiency of a graphics processing unit (GPU)-Monte Carlo dose engine for Elekta Unity 1.5 T Magnetic Resonance-Linear Accelerator (MR-LINAC) online independent dose verification. Electron/positron propagation physics in a uniform magnetic field was implemented in a previously developed GPU-Monte Carlo dose engine-gDPM. The dose calculation accuracy in the magnetic field was first evaluated in heterogeneous phantom with EGSnrc. The dose engine was then commissioned to a Unity machine with a virtual two photon-source model and compared with the Monaco treatment planning system. Fifteen patient plans from five tumor sites were included for the quantification of online dose verification accuracy and efficiency. The extended gDPM accurately calculated the dose in a 1.5 T external magnetic field and was well matched with EGSnrc. The relative dose difference along central beam axis was less than 0.5% for the homogeneous region in water-lung phantom. The maximum difference was found at the build-up regions and heterogeneous interfaces, reaching 1.9% and 2.4% for 2 and 6MeV mono-energy photon beams, respectively. The root mean square errors for depth-dose fall-off region were less than 0.2% for all field sizes and presented a good match between gDPM and Monaco GPUMCD. For in-field profiles, the dose differences were within 1% for cross-plane and in-plane directions for all calculated depths except dmax. For penumbra regions, the distance-to-agreements between two dose profiles were less than 0.1cm. For patient plan verification, the maximum relative average dose difference was 1.3%. The gamma passing rates with criteria 3% (2mm) for dose regions above 20% were between 93% and 98%. gDPM can complete the dose calculation for less than 40 s with 5 × 108 photons on a single NVIDIA GTX-1080Ti GPU and achieve a statistical uncertainty of 0.5%-1.1% for all evaluated cases. A GPU-Monte Carlo package-gDPM was extended and validated for Elekta Unity online plan verification. Its calculation accuracy and efficiency make it suitable for online independent dose verification for MR-LINAC.

Gaussian fitting algorithm with multi‐geometric parameters for rotated elliptical beam profiling using pixel ion chamber

A high-precision rotated elliptical beam profiling method based on pixel ion chamber is proposed in this paper. This method aims to improve the accuracy by modeling the transverse profile of rotated beam as an ellipse with additional correlation coefficient and eliminating the fitting error due to the volume averaging effect of pixel ion chamber. In pencil beam scanning (PBS) proton therapy systems, the transverse beam profile model is generally represented as a standard Gaussian distribution. Considering the elliptical spots, two-dimensional (2D) joint Gaussian distribution characterized with the correlation coefficient ρ is adopted in this study. Gaussian-type particle distribution with white noise was generated and processed in MATLAB to simulate the secondary particle collection in the pixel ion chamber. The simulated pixel ion chamber is a commercially available ion chamber which consists of 12×12small square pixels (3.75×3.75mm2 ) with a 0.05mm interval. The simulated signals were preprocessed by filtering with the noise threshold and extracting the maximum simply connected domain (MSCD) of the signal. Then, five geometric parameters that identify the transverse beam profiles were fitted under different signal-to-noise ratio (SNR) conditions: the center of the beam (x0 , y0 ), the spot size (σmajor , σminor ), and the rotation angle θ formed between the major axes of elliptical spot and the x axes of the ion chamber. First, the simulated signals were preprocessed by filtering with the noise threshold and extracting the MSCD of the signal. Second, a rectification curve of systematic error in fitted spot size versus the prescribed spot size was used to predict the systematic error due to the volume averaging effect. Finally, the effects of fitting errors on therapeutic dose were evaluated in terms of gamma index and relative dose difference. When the SNR is not less than 20dB, the relative fitting error of spot size and the absolute fitting error of angle θ are less than 1% and 6.1°, respectively. The fitting error of beam center increases with spot size and will not exceed 0.22mm when spot size reaches up to 12mm. At a SNR equal to 20dB, neither cold nor hot spots were presented in dose distribution calculated with the fitted spot parameters. The improved Gaussian fitting algorithm performs well when SNR is not less than 20dB. This method can effectively distinguish the nominal beam and rotated elliptical beam. An ideal systematic error curve can be predicted and used to correct the fitted spot size, thus eliminating the systematic error due to the volume averaging effect of the pixel ion chamber. The fitting error of spot size cannot be fully corrected, but it is negligible and shows little effect on the overall therapeutic dose.

A Novel Approach for Design and Simulation of Equivalent Continuum Model of Lattice Structures Used in Tunnels and Caverns

Developing a continuum model of a lattice structure means expressing a complicated structure into a simpler one, and this is done by determining equivalent stiffness of the original structure, which can further be used to transform into desired simpler geometry for multiple benefits. Objective of this paper is to find a reliable method for determination of equivalent stiffness of lattice girder, comparing all the techniques suggested by various researchers. In present work the actual lattice girder structures and their equivalents were analysed using Finite Element Method tool Strand7. The primary focus is on lattice girder, which is a primary rock support system employed in tunnels and caverns. The equivalent stiffness so obtained is used as input parameter in numerical analysis tool STRAND7 for analysis of equivalent lattice beam. The maximum deflection and bending stress at centre of equivalent lattice beam were calculated and compared. In an attempt to develop a more accurate equivalent beam model a novel approach which is modification of the Method-B has been developed by authors. This Noval approach is the most convenient approach to develop an equivalent section with an extremely uncompromised representation of stress development and deformation characteristic. In this approach, the focus was made on the physical resemblance of a proposed equivalent beam with the actual lattice girder, leading us to adopt a beam of I-cross-section. This approach yielded similar stress and deflections in the equivalent beam as that of the actual lattice girder.

Uji Kesesuaian Berkas Cahaya Kolimasi pada Pesawat Sinar-X di Politeknik Al-Islam Bandung

Background : Suitability test for light collimation are tests to ensure that x-ray aircraft meet radiation safety requirements and provide precise and accurate diagnostic or diagnostic information. Suitability test for light collimation is carried out on x-ray aircraft at Al-Islam Bandung Politeknik.Methods: The research method used in quantitative experimental method. The suitability test was carried out with a collimator test tool and beam alignment test tool placed on the tape then performed an experiment using an exposure factor of 75 Kv, 200 mA and 8 mAs with FFD 100 cm.Results: Based on the tests that have been carried out, it is known that there is a discrepancy in the width of the collimation beam. The large discrepancy between the light field area and the radiation field area, that is, the edge X₁ 0.3 cm, the edge X₂ 0.5 cm, the edge Y₁ 0.5 cm, the edge Y₂ 0.1 cm. So the value of ∆X is 0.8% FFD, the value of ∆Y is 0.6% FFD, and the value of ∆X + ∆Y is 1.4% FFD. While the deviation of the central point is less or right than 3⁰. These results indicate that the discrepancy in the width of the light beam collimation and center point deviations is still within the tolerance limits.Conclusions: There is a discrepancy between the X-ray light field and the collimated light field, but it is still within the limit of the test value to the passing value of the predefined test.

Uncertainty in tissue equivalent proportional counter assessments of microdosimetry and RBE estimates in carbon radiotherapy

Microdosimetry is an important tool for assessing energy deposition distributions from ionizing radiation at cellular and cellular nucleus scales. It has served as an input parameter for multiple common mathematical models, including evaluation of relative biological effectiveness (RBE) of carbon ion therapy. The most common detector used for microdosimetry is the tissue-equivalent proportional counter (TEPC). Although it is widely applied, TEPC has various inherent uncertainties. Therefore, this work quantified the magnitude of TEPC measurement uncertainties and their impact on RBE estimates for therapeutic carbon beams. Microdosimetric spectra and frequency-, dose-, and saturation-corrected dose-mean lineal energy (****) were calculated using the Monte Carlo toolkit Geant4 for five monoenergetic and three spread-out Bragg peak carbon beams in water at every millimeter along the central beam axis. We simulated the following influences on these spectra from eight sources of uncertainty: wall effects, pulse pile-up, electronics, gas pressure, W-value, gain instability, low energy cut-off, and counting statistics. Statistic uncertainty was quantified as the standard deviation of perturbed values for each source. Bias was quantified as the difference between default lineal energy values and the mean of perturbed values for each systematic source. Uncertainties were propagated to RBE using the modified microdosimetric kinetic model (MKM). Variance introduced by statistic sources in and averaged 3.8% and 3.4%, respectively, and 1.5% in across beam depths and energies. Bias averaged 6.2% and 7.3% in and and 4.8% in These uncertainties corresponded to 1.2 ± 0.9% on average in RBEMKM. The largest contributors to variance and bias were pulse pile-up and wall effects. This study established an error budget for microdosimetric carbon measurements by quantifying uncertainty inherent to TEPC measurements. It is necessary to understand how robust the measurement of RBE model input parameters are against this uncertainty in order to verify clinical model implementation.

Self-splitting and propagation factors of a superimposed Hermite-Gaussian correlated Schell-model beam in turbulent atmosphere

A novel type of superimposed Hermite-Gaussian correlated Schell-model (SHGCSM) laser beam is first represented in terms of theory and then produced experimentally. Similar to a Hermite-Gaussian correlated Schell-model (HGCSM) beam, the SHGCSM beam demonstrates self-splitting features when it propagates in free space, over time the primary single beam spot that is initially seen gradually develops into four or two beam spots when it is in the far-field. The SHGCSM beam splits itself faster than the HGCSM beam when the other beam parameters are fixed, which has lower intensity at the center of beam at an intermediate distance. The four or two spots are more independent with each other, which can be used in attacking multiple targets. Compared with the propagation M2-factor of the HGCSM [Opt. Express 23, 10 (2015)], it has a lower propagation M2-factor in the non-Kolmogorov turbulence. The SHGCSM beam is unaltered to a lesser extent by turbulence compared with a HGCSM beam, which is beneficial for studies on atmospheric optical communications.

Cut-out resonators for tuned vibration suppression of plates

This research investigates a concept for cut-out resonators that exploit a small area of active mass of a host plate structure for sake of tuned, low frequency vibration attenuation. Integrated computational and experimental studies reveal that embedding the resonators at locations offering high bending moment gradient and arranging the central resonator beam along a nodal line of bending moment best excite the first resonator eigenmode for targeted vibration suppression. These results are independent of plate boundary conditions and do not require periodic resonators to achieve notable vibration suppression outcomes. These design concepts may guide the development of resonators for vibration absorption of plates with arbitrary boundary conditions.

Numerical investigation of molten pool dimension, temperature field and melting flow during pulsed laser welding of Ti-6Al-4V alloy sheets with different thicknesses

In this paper, a transient numerical model of pulsed laser welding is performed to predict the weld depth and width, temperature distribution, and melt flow. The material was made of Ti-6Al-4V with different thicknesses of laser beam energy, and an asymmetric temperature field was obtained. Three different thermal models were used to consider the laser beam energy. The results showed that the combination of Gaussian surface heat flux and heat source provides an accurate prediction of the dimensions and shape of the molten pool. The Marangoni flow due to the surface tension gradient at the surface of the molten pool had the greatest effect on the liquid metal flow. The analysis of the temperature field and dimensions of the weld bead was performed by changing the laser parameters such as welding speed and average power. The results showed that the heat affected zone and molten pool are directed toward the thin sheet. By increasing the movement speed of the laser beam, the molten pool became conical and did not penetrate completely. Also, increasing the average power has the greatest effect on the dimensions of the molten pool, temperature distribution, and liquid metal flow. Increasing the average power from 180 to 240 W increases the maximum temperature in the center of the laser beam by ∼1000 °C.

Experimental study on the factors affecting torque of beam-type implant torque wrenches

BackgroundScrew breakage and loosening are the most common mechanical complications associated with implant treatment, and they may occur due to excess or inadequate screw tightening torque. When fastening and fixing the implant superstructure, screws are tightened using a torque wrench, which is essential for an accurate tightening force. However, the characteristics of the torque wrench have not been fully verified. Therefore, we aimed to clarify the factors affecting the torque with a focus on beam-type torque wrenches, which are the main types of wrenches.MethodsThe torque values generated by beam-type torque wrenches from eight manufacturers were measured using a torque gauge. To investigate the influence of the location of the beam relative to the scale, measurements were performed with a scale aligned with the trailing edge, center, and leading edge of the beam respectively. Additionally, measurements were taken at 90°, 60°, and 30° to examine the effect of the angle at which the examiner read the torque value. Under each condition, a single examiner applied the recommended torque to each manufacturer's screws five times in a clockwise direction. The average measured torque, standard deviation, bias, and coefficient of variation were calculated and compared accordingly.ResultsWrenches from six manufacturers demonstrated excellent accuracy for measurements at the center of the beam (bias within ± 4%). For measurements at 90°, equipments from five manufacturers displayed excellent accuracy (bias within ± 7%), and seven showed excellent repeatability (coefficient of variation ≤ 2%).ConclusionThe scale should be aligned with the center of the beam and read from 90° while using a torque wrench. The accuracy and repeatability torques generated by the wrenches differed according to the manufacturer, scale width, scale line width, beam width, and distance between the scale and beam center. Based on these results, we suggest that a torque wrench must be selected after determining the difference in the structure of the torque wrench.

A Novel Demultiplexing Scheme for Vortex Beams in Radio Communication Systems

The orbital angular momentum (OAM) based communication is a promising technology in the wireless communication system for its improving spectrum efficiency. However, for the OAM demultiplexing, it requires a very large aperture size in the receiving end due to the OAM beam divergence and the amplitude null in the beam center, which restricts the full development of OAM based communication. In this paper, we propose a novel partial arc sampling receiving (PASR) scheme based on the augmented dynamic mode decomposition (ADMD) to solve this issue. We explore the use of the phase delay coordinates in the conventional DMD to sort the arbitrary OAM modes with arc sampling receiving. Simulation results demonstrate the accuracy and robustness of the proposed approach in sorting both integral and fractional OAM modes with the PASR scheme. Our work offers a practical approach for demultiplexing OAM beams in radio communication systems with fewer receiving devices, especially for the long-distance transmission case.