Arc Beam Research Articles

Dosimetric optimization for dynamic mixed beam arc therapy (DYMBARC).

Non-coplanarity and mixed beam modality could be combined to further enhance dosimetric treatment plan quality. We introduce dynamic mixed beam arc therapy (DYMBARC) as an innovative technique that combines non-coplanar photon and electron arcs, dynamic gantry and collimator rotations, and intensity modulation with photon multileaf collimator (MLC). However, finding favorable beam directions for DYMBARC is challenging due to the large solution space, machine component constraints, and optimization parameters, posing a highly non-convex optimization problem. To establish DYMBARC and solve the pathfinding challenge by employing direct aperture optimization (DAO) to determine the table angles and gantry angle ranges of photon and electron arcs for different clinically motivated cases. The method starts by generating a grid of beam directions based on user-defined resolutions along the gantry and table angle axes for each beam quality considered. Beam directions causing collisions or entering through the end of CT are excluded. For electrons, a fixed source-to-surface distance of 80cm is used to reduce in-air scatter. Electron beam energies with insufficient range to reach the target or beam directions impinging on the table before reaching the patient are excluded. The remaining beam directions form the pathfinding solution space. Promising photon and electron MLC-defined apertures, with associated monitor unit (MU) weights, are iteratively added using a hybrid-DAO algorithm. This algorithm combines column generation to add apertures and simulated annealing to further refine aperture shapes and weights. Apertures are added until the requested number of paths are formed and the user-defined maximum total gantry angle range is reached. Paths are resampled to a finer gantry angle resolution and subject to DAO for simultaneous optimization of beam intensities along the photon/electron arcs. Subsequent final dose calculation and MU weight reoptimization result in a deliverable DYMBARC plan. DYMBARC plans are created for three clinically motivated cases (brain, breast, and pelvis) and compared to DYMBARC variants: colli-DTRT (dynamic collimator trajectory radiotherapy) using non-coplanar photon arcs; and Arc-MBRT (mixed beam radiotherapy) using photons and electrons but restricted to coplanar setup. Additionally, a manually defined volumetric modulated arc therapy (VMAT) setup serves as a reference clinical technique. Dose distributions, dose-volume histograms, and dosimetric endpoints are evaluated. Dosimetric validation with radiochromic film measurements (gamma evaluation, 3% / 2mm (global), 10% dose threshold) is performed on a TrueBeam system in developer mode for one case. While maintaining similar target coverage and homogeneity, DYMBARC reduced mean doses to organs-at-risk compared to VMAT by an average of 3.2, 0.5, and 2.9Gy for the brain, breast, and pelvis cases, respectively. Similar or smaller mean dose reductions were observed for Arc-MBRT or colli-DTRT, compared to VMAT. Electron contributions to the mean planning target volume dose ranged from 2% to 34% for DYMBARC and from 11% to 40% for Arc-MBRT. Measurement validation showed>99.7% gamma passing rate. DYMBARC was successfully established using a dosimetrically optimized pathfinding approach, combining non-coplanarity with mixed beam modality. DYMBARC facilitated the determination of photon and electron contributions on a case-by-case basis, enhancing more personalized treatment modalities.

Design of hyperbolic quasi-zero stiffness metastructures coupled with nonlinear stiffness for low-frequency vibration isolation

Quasi-zero stiffness (QZS) metastructures with simple structures exhibit a high low-frequency vibration isolation performance, but the bearing capacity and working regions are limited due to the linear positive stiffness elements. In this study, a novel hyperbolic QZS metastructure coupled with nonlinear stiffness is designed by combining a pair of cosine-shaped beams and arc-shaped beams for low-frequency vibration isolation. Finite element models (FEM) and experimental analysis are utilized to examine the static characteristics of the metastructure, revealing a wide QZS region and significant load-bearing capacity. The metastructure can achieve effective vibration isolation properties through reasonably designing the unit cells. The influence of geometrical parameters on the QZS region is investigated to optimize and realize desirable QZS features. The dynamic equation and response of the vibration isolation system are determined using the harmonic balance method. Moreover, the corresponding displacement transmissibility is confirmed by numerical simulation. The results of the dynamic sweep frequency experiment further verify the validity of the theoretical analysis model. The hyperbolic QZS metastructure system possesses good vibration isolation performance due to the introduction and compensation of a nonlinear positive stiffness arc beam element. The proposed hyperbolic QZS metastructure provides a significant route for the stiffness compensation of metastructures.

Graded arc beam in light needle microscopy for axially resolved, rapid volumetric imaging without nonlinear processes.

High-speed three-dimensional (3D) imaging is essential for revealing the structure and functions of biological specimens. Confocal laser scanning microscopy has been widely employed for this purpose. However, it requires a time-consuming image-stacking procedure. As a solution, we previously developed light needle microscopy using a Bessel beam with a wavefront-engineered approach [Biomed. Opt. Express13, 1702 (2022)10.1364/BOE.449329]. However, this method applies only to multiphoton excitation microscopy because of the requirement to reduce the sidelobes of the Bessel beam. Here, we introduce a beam that produces a needle spot while eluding the intractable artifacts due to the sidelobes. This beam can be adopted even in one-photon excitation fluorescence 3D imaging. The proposed method can achieve real-time, rapid 3D observation of 200-nm particles in water at a rate of over 50 volumes per second. In addition, fine structures, such as the spines of neurons in fixed mouse brain tissue, can be visualized in 3D from a single raster scan of the needle spot. The proposed method can be applied to various modalities in biological imaging, enabling rapid 3D image acquisition.

Особенности фазовых и структурных превращений в композиционных материалах на основе систем несмешивающихся компонентов при воздействии концентрированных потоков энергии

The features of phase and structural transformations in composite materials based on systems of immiscible components Al – Be, Al – Be – Mg, Fe – Cu, Fe – Cu – Pb under the influence of concentrated heat sources — electric arc, electron and laser beams — are considered. It is shown that when materials of the Al – Be, Al – Be – Mg systems are exposed to an electric arc plasma and an electron flow, they are melted and subsequently cooled by grain grinding, formation of a zone of thermal influence and crystallization of the resulting new structures and phases. In zone of thermal influence, the enrichment of the aluminum matrix with Be particles is observed due to the thermal diffusion processes of their movement. When plasma is exposed to an arc discharge, pulsed and continuous laser radiation, as well as the flow of electrons on the composition Fe – Cu, Fe – Cu – Pb, a change in the morphology of the near-surface layer is observed: the irradiated material in the melt zone is exfoliated and in the process of crystallization the stratified phases are fixed in a solid state. The mechanism of stratification formation is associated with the limited solubility of the elements that make up the composition in the liquid and solid states.

Machine learning-based ensemble prediction model for the gamma passing rate of VMAT-SBRT plan

PurposeThe purpose of this study was to accurately predict or classify the beam GPR with an ensemble model by using machine learning for SBRT(VMAT) plans. MethodsA total of 128 SBRT VMAT plans with 330 arc beams were retrospectively selected, and 216 radiomics and 34 plan complexity features were calculated for each arc beam. Three models for GPR prediction and classification using support vector machine algorithm were as follows: (1) plan complexity feature–based model (plan model); (2) radiomics feature–based model (radiomics model); and (3) an ensemble model combining the two models (ensemble model). The prediction performance was evaluated by calculating the mean absolute error (MAE), root mean square error (RMSE), and Spearman’s correlation coefficient (SC), and the classification performance was measured by calculating the area under the receiver operating characteristic curve (AUC), accuracy, specificity, and sensitivity. ResultsThe MAE, RMSE and SC at the 2 %/2 mm gamma criterion in the test dataset were 1.4 %, 2.57 %, and 0.563, respectively, for the plan model; 1.42 %, and 2.51 %, and 0.508, respectively, for the radiomics model; and 1.33 %, 2.49 %, and 0.611, respectively, for the ensemble model. The accuracy, specificity, sensitivity, and AUC at the 2 %/2 mm gamma criterion in the test dataset were 0.807, 0.824, 0.681, and 0.854, respectively, for the plan model; 0.860, 0.893, 0.624, and 0.877, respectively, for the radiomics model; and 0.852, 0.871, 0.710, and 0.896, respectively, for the ensemble model. ConclusionsThe ensemble model can improve the prediction and classification performance for the GPR of SBRT (VMAT).

Calibration and error analysis of an arc detector for wide-angle X-ray scattering (WAXS)

In wide-angle X-ray scattering (WAXS) experiments, the use of a one-dimensional arc detector can effectively expand the angle range of collected diffraction or scattering signals. In practice, the relative positions between the centers of arc detector, sample and beam spot may overlap or misalign. Therefore, it is necessary to calibrate the instrument parameters and detection angle of the arc detector. The calibration is routinely performed by standard samples. In this contribution, the equations for angle calibration and error evaluation are constructed based on three standard diffraction peaks, and the corresponding simulation and experiment are performed to verify the feasibility of the calibration. The results indicate that the larger the coverage and the more uniform the dispersion of the three standard diffraction peaks distributed on the detector, the smaller the calibration error.

Особенности формирования сварных соединений алюминиевого сплава АК9, полученного селективным лазерным плавлением

The problem of obtaining high-quality plate welds made of AL9 alloy and powder by selective laser melting is viewed. Welded butt joints of plates of AK9CH alloy with a thickness of 3.0 mm were made by melting welding (automatic argon arc and electron beam welding) and friction stir welding. After welding the base metal of the AK9 alloy plates and their welded joints were subjected to X-ray transmission, computed tomography, metallographic analysis and mechanical tests for static tension and static three-point bending. X-ray inspection of welded joints made by automatic argon arc and electron beam welding revealed multiple porosity inside welds. The nuclei of pores in the weld metal are spherical micropores, formed in the parent metal during selective laser melting. The diameter of these micropores is 150...200 microns. In the welding bath during fusion welding, micropores develop up to 420...1070 microns in diameter in case of argon arc welding and 215...420 microns in case of electron beam welding. Metallographic analysis of cross-sections of welded joints performed by fusion welding revealed a characteristic pore distribution in the weld metal. So in case of argon arc welding, the largest pores were located near the front surface of the weld. In the fusion zone at the border of the weld and the base metal, pores with a diameter of 80.220 microns were located in the form of chains along the entire thickness of the plates being welded. When testing welded joints for static tension, the destruction of joints occurred precisely in this zone. The strength coefficient of the AK9 alloy joints obtained by fusion welding is as follows: for automatic argon arc welding 0.46, for electron beam welding - 0.66. It is established that the problem of porosity of welded joints is eliminated when using solid -phase welding for jointing (friction stir welding). The strength coefficient of the jointing of the AK9CH alloy plates made by friction stir welding is at the level of 0.81.0.86 of the time resistance of the base metal. The destruction of welded joints occurs along the mixing zone. In the weld zone during friction stir welding, as a result of dynamic recrystallization, a fine-grained equiaxed structure with an average grain size of 4.5...6.2 microns was formed with virtually no pores. The parent metal is represented by a cellular structure in which there are pores up to 168 microns in size.

Elucidation of the visualization process and its influencing factors for the preparation of microcircuits based on arc-beam laser-induced forward transfer

Arc beam laser-induced forward transfer (AB-LIFT) based on an arc beam is a promising micro additive manufacturing process to efficiently prepare high-performance metal microcircuits by transferring metal microdroplets. Therefore, elucidating the transfer mechanism of arc-beam-induced microdroplets is crucial to controlling the printing process. In this paper, a dark-field imaging system is developed to visually analyze the transfer process of metal microdroplets, and the injection mechanism of Gaussian and arc-beam laser-induced forward transfer is analyzed. Meanwhile, by studying the deposition behavior of laser-induced forward transfer micro drops with an arc beam at a single pulse energy, it is concluded that the factors affecting the laser-induced forward transfer with an arc beam mainly include the center angle and diameter of the arc beam. Then the effects of the center angle and diameter of the arc beam and the laser parameters on the preparation of microcircuits by AB-LIFT are systematically investigated, and a set of process methods for the effective preparation of high-performance microcircuits is proposed.

Peridynamic analysis of curved elastic beams

Peridynamics is an extended continuum theory which operates with non-local deformation measures as well as long range internal force/moment interactions. The aim of this paper is to present and to analyze peridynamic governing equations for elastic curved beams. To this end the strain energy density is formulated as a function of two non-local deformation measures including the axial deformation and curvature. Applying the Lagrangian formalism, peridynamic equations of motion are derived. To analyze curved beams of finite length peridynamic boundary conditions are required. Examples of boundary conditions including simple support and clamped edge are presented by introducing a fictitious domain. Solutions to PD equations of motion are presented for various problems including static analysis of simply supported and clamped arc beams as well as modal analysis of a slender ring and a simply supported arc beam. To validate peridynamic formulations, solutions for displacements, natural frequencies and vibration modes are compared with those by the classical beam theory. A very good agreement between the non-local and the classical theories is observed for the case of the small horizon sizes which shows the capability of the derived equations of motion and proposed boundary conditions.

Quantification of six-degree-of-freedom motion during beam delivery in spine stereotactic body radiotherapy using intra-irradiation cone-beam computed tomography imaging technique

PurposeQuantifying intra-fractional six-degree-of-freedom (6DoF) residual errors or motion from approved patient setups is necessary for accurate beam delivery in spine stereotactic body radiotherapy. However, previously reported errors were not acquired during beam delivery. Therefore, we aimed to quantify the 6DoF residual errors and motions during arc beam delivery using a concurrent cone-beam computed tomography (CBCT) imaging technique, intra-irradiation CBCT. MethodsConsecutive 15 patients, 19 plans for various treatment sites, and 199 CBCT images were analyzed. Pre-irradiation CBCT was performed to verify shifts from the initial patient setup using the ExacTrac system. During beam delivery by two or three co-planar full-arc rotations, CBCT imaging was performed concurrently. Subsequently, an intra-irradiation CBCT image was reconstructed. Pre- and intra-irradiation CBCT images were rigidly registered to a planning CT image based on the bone to quantify 6DoF residual errors. Results6DoF residual errors quantified using pre- and intra-irradiation CBCTs were within 2.0 mm/2.0°, except for one measurement. The mean elapsed time (mean ± standard deviation [min:sec]) after pre-irradiation CBCT to the end of the last arc beam delivery was 6:08 ± 1:25 and 7:54 ± 2:14 for the 2- and 3-arc plans, respectively. Root mean squares of residual errors for several directions showed significant differences; however, they were within 1.0 mm/1.0°. Time-dependent analysis revealed that the residual errors tended to increase with elapsed time. ConclusionThe errors represent the optimal intra-fractional error compared with those acquired using the pre-, inter-beam, and post-6DoF image guidance and can be acquired within a standard treatment timeslot.

Mechanical model of needle-punched (NP) carbon/carbon (C/C) composites with isogeometric beams-extended springs at mesoscale

The NP C/C composites have strong load-bearing capacity in ultra-high temperature environments, become an indispensable material for aircraft production, which is widely used in aerospace sector. The NP preform transfers the fibers in the XY plane to the Z direction through the NP process, which overcomes the disadvantage of easy delamination of the C/C composites. However, the stiffness and strength in the layers of C/C composites are reduced by introducing defects. In this paper, a mesoscale mechanical model is proposed. Isogeometric circular arc beam element (CABE) is established to characterize the fiber bundles of NP C/C composites, and extended spring element(ESE) is established to characterize the matrix within layers, matrix and chopped fiber felt between layers, and chopped fiber felt at pinhole defects of NP C/C composites. By comparing the tensile, compression and bending tests with the simulation, the correctness of the mechanical model is fully confirmed.

Novel Process Approach for Additive Manufacturing Using Inductive Wire Melting by Forced Droplet Detachment

To date, no AM technology for large-volume metallic components has been established on an industrial scale like Laser Powder Bed Fusion (LPBF). This contribution presents a new process approach to fabricate larger metallic structures from steel by inductive melting of a continuously fed wire. The presented method is characterized by the comparatively low energy input in contrast to comparable processes for AM, such as arc, laser, or electron beam. Previously published work is based on the principle of a melt reservoir of low-melting alloys and droplet delivery using gas pressure or vibration. In contrast, the approach described here is to transfer the material directly from the end of the wire to the substrate by continuous drop deposition. However, to avoid a stochastic material transition, a suitable process strategy has to be chosen. This challenge is met by a pulsed coil current and the resulting periodically varying Lorentz forces in order to achieve regular and forced droplet detachment. Tests confirm the principle of controlled droplet detachment and reveal the great potential of this technological approach.

Evaluation of surface image guidance and Deep inspiration Breath Hold technique for breast treatments with Halcyon

PurposeTo evaluate the accuracy/agreement of a three-camera Catalyst Surface Guided Radiation Therapy (SGRT) system on a closed-gantry Halcyon for Free-Breathing (FB) and Deep Inspiration Breath Hold (DIBH) breast-only treatments. MethodsThe SGRT positioning agreement with Halcyon couch and cone-beam computed tomography (CBCT) was evaluated on phantom and by evaluation of 2401 FB and 855 DIBH breast-only treatment sessions. The DIBH agreement was evaluated using a programmable moving support. Dose agreement was evaluated for manual SGRT-assisted beam interruption and Halcyon arc beam interruption. ResultsGeometrical phantom agreement was < 0.4 mm. Couch and SGRT agreement for an anthropomorphic phantom resulted in 95% limits of agreement in Right-Left/Feet-Head/Posterior-Anterior (RL/FH/PA) directions of respectively ± 0.4/0.8/0.5 mm and ± 1.1/1.1/0.6 mm in the virtual and real isocenter.FB-SGRT-assisted patient positioning compared to CBCT positioning resulted in RL/FH/PA systematic differences of −0.1/0.1/2.0 mm with standard deviations of 2.7/2.8/2.4 mm. This mean systematic difference had three origins: a) couch sag/isocenter difference of ≤ 0.5 mm. b) Average reconstructed FB-CBCT images do not visually represent the average respiratory position. c) CBCT-based positioning focused on the inner thoracic interface, which can introduce a mean positioning difference between SGRT and CBCT.Manual SGRT-assisted beam interruption and arc interruptions resulted in mean gamma passing rates > 97% (0.5%/0.5 mm) and mean absolute differences < 0.3%. ConclusionsAccuracy was comparable with breast-only C-arm SGRT techniques, with different tradeoffs. Depending on the patient’s morphology, real-time tracking accuracy in the real isocenter can be reduced. This study demonstrates possible discordances between SGRT and CBCT positioning for breast.

Wire-Feeding Based Additive Manufacturing of the Ti–6Al–4V Alloy. Part I. Microstructure

In recent years, metal additive manufacturing (AM), also known as 3D printing, is grown massively in the industry. The ability of AM to build parts directly from the digital representation makes it an excellent alternative compared to traditional manufacturing technologies, such as milling, welding, casting, rolling, stamping, forging and turning for rapidly making highly customized parts. Currently, a number of different powder- and wire-based AM technologies are developed for 3D printing of metals. A number of potential benefits of AM are noted, including the allowance of design freedom, complex parts’ production, the material waste and part weight reductions, material use minimization; it also saves the time and money of the production cycle times. Due to the feasibility of the economically producing large-scale metal components with relatively high deposition rate, low machinery cost, high material efficiency, and shortened lead time as compared to the powder-based AM, the wire-based AM significantly attracted in the industry and academia due to its ability to produce the large components of the medium geometric complexity. During this AM process, the wire is fed by the controlled rate into the melt pool produced by the electric arc, laser or electron beam as the heat source. In the past few decades, the basic research and development efforts are devoted to the wire-based 3D printing parts made of Ti–6Al–4V alloy, which has been widely investigated and used in different fields such as aerospace, automotive, energy, marine industries and in addition to the prosthetics and the orthopaedic implants. Numerous studies in recent years on the influence of the 3D printing parameters have shown a significant difference in the mechanism and kinetics of the microstructure formation in the Ti–6Al–4V alloy samples compared to traditional technologies. It is well investigated that the mechanical properties of such alloy are dependent on the solidification macro- and microstructure, which is controlled by the thermal conditions during 3D printing. In the present review, the main microstructural characteristics, which determine the mechanical properties of the two-phase Ti–6Al–4V alloy, are analysed for the samples obtained by wire-feed 3D printing with various sources used for the wire melting, namely, the electric arc, the laser, and the electron beam. At first, the review introduces the links between the process parameters, resultant microstructures, especially, the morphology, the size and the quantitative ratio of the α and β grains in the as-printed Ti–6Al–4V alloy samples. However, the metallic products manufactured by a vast majority of the AM processes need to be post-processed by heat treatment and/or hot isostatic pressing, which are also discussed in this review.

Wire-Feeding Based Additive Manufacturing of the Ti–6Al–4V Alloy. Part II. Mechanical Properties

Currently, the interest in the application of metal additive manufacturing (AM), also known as 3D printing, is grown massively in the various fields of the industry and surgery. AM has significant multiple advantages compared to traditional subtractive technologies for making highly customized parts with complex geometries without causing noteworthy extra costs. Now, several powder-based AM technologies for metals’ 3D printing are in progress, in particular, selective laser sintering (SLS), selective laser melting (SLM), and electron-beam melting (EBM). In the past few decades, increasing research and developments are devoted to the wire-feeding-based 3D printing production of parts made of the Ti–6Al–4V alloy, which is widely investigated in different fields such as aerospace, automotive, energy, and marine industries as well as the prosthetics and the production of orthopaedic implants. Due to the feasibility of economical producing large-scale metal components with relatively high deposition rate, low machinery cost, high material efficiency, and shortened lead-time compared to powder-based AM, wire-feeding-based AM (WFAM) is attracting significant attention in the industry and academia owing to its ability for the production of the large components of the medium geometric complexity. In recent years, three options of WFAM are intensively researched, which differ by the wire-melting heating sources: wire + arc additive manufacturing (WAAM); wire-laser AM (WLAM), and wire electron-beam additive manufacturing (WEBAM). The purpose of the present review is systematic analysis of the mechanical properties of the Ti–6Al–4V alloy samples 3D-printed by WFAM with various heating melting sources, namely, arc, laser, and electron beam. Particularly, considering the literature data for the period of 2013–2020, such important properties as yield strength, tensile strength, elongation, and hardness are analysed for the samples in the as-printed and post-processed conditions.

Asymmetry spin-polarization Fermi arc and topological chiral beam splitter with the triply degenerate point in metamaterial.

Dirac points (DPs) and Weyl points (WPs) have received much attention in photonic crystals (PhCs) and three-dimensional (3D) metamaterials research due to the robust surface states and Fermi arcs. In this work, two pairs of triply degenerate points (TDPs) have been proposed in a 3D metamaterial by breaking the time reversal symmetry (T) with an external magnetic field. Based on these TDPs, two pairs of asymmetric surface states with spin-polarization are revealed, and a topological chiral beam splitter is demonstrated showing the different propagating directions of the right-handed polarization (RCP) and left-handed polarization (LCP) lights. Remarkably, we can achieve unidirectional propagation with RCP or LCP even excited by a linear source owing to the asymmetry surface state. Our work provides a new, to the best of our knowledge, platform to study spin-polarization surface states and the enhanced spin photonic Hall effect in the metamaterials.

Fabrication of high-performance copper circuits using laser-induced forward transfer with large receiving gaps based on beam modulation technology

Laser-induced forward transfer (LIFT) technology has been widely used to print 2D/3D structural patterns in the micron level of metals due to its contactless and maskless advantages. Still, it cannot meet the practical needs of the industry due to its drawbacks, such as low efficiency and a small receiving gap. This study proposes a new LIFT by modulating a Gaussian beam into an Arc beam using a liquid crystal on silicon spatial light modulator (LCOS-SLM) to achieve stable preparation of high-performance Cu circuits at large receiving gaps. First, the laser-induced monomer transfer modes of Gaussian beams and arc beams are studied. Then the effects of laser energy density, scanning velocity, and reception gap on the microcircuits prepared by Gaussian beam laser-induced forward transfer (GB-LIFT) and Arc beam laser-induced forward transfer (AB-LIFT) are studied systematically, and suitable process parameters are found. The transfer process of action of AB-LIFT is revealed. Under the optimized process parameters, the flight distance of AB-LIFT is up to 120 μm, which is about twice that of GB-LIFT, when the laser energy density is 1.94 μJ, and the scanning velocity is 3 mm/s. And the height of the microcircuit can be controlled by the number of depositions. It is demonstrated that the AB-LIFT can achieve stable transfer with large receiving gaps and efficiently prepare continuous Cu circuits with high bonding strength and low resistance. The minimum resistivity (7.46 μΩ∙cm) obtained by selecting optimized process parameters is about 4 times that of Cu bulk (1.76 μΩ∙cm). The application of the AB-LIFT method based on the beam modulation technique in microcircuit defect repair is verified.

Scaling-up ultrasonic vibration assisted additive manufacturing to build 316 L 3 m3 waste container flange

Directed-energy deposition is a 3D printing method that uses a focused energy source, such as a plasma arc, laser, or electron beam to melt a material that is simultaneously deposited by a nozzle. As with other additive manufacturing processes, this technology is used to add material to existing components, for repairs, or to build new parts. Direct-energy deposition additive manufacturing techniques have gained much attention from the industry to build/repair in-service components. However, this process undergoes complex dynamics of melting and solidification raising challenges to the effective control of grain structure causing potential structural failure. This research study was conducted to investigate the potential of using high-intensity ultrasonic to control the solidification process and scaling up the system to manufacture large components. From the feasibility study, it was noted that ultrasonic can assist in the refinement of the grain structure and also reduce anomalies such as porosities. Under the feasibility study, a range of frequencies and power configurations were considered to ease the scale-up of the system. Based on the studied ultrasonic configurations, the 40 kHz 60 W configuration was finalized to use in the scale-up. It was also noted the reduction of hot cracks in the ultrasonic-assisted additive manufacturing due to the constitutional supercooling during solidification by lowering the temperature gradient in the bulk of the melt pool. Furthermore, it was also noted that the grain orientation is perpendicular to the direction of vibration which potentially can be used to control the orientation of the grains as required. This new finding provides new applications to exploit the ultrasonic-assisted additive manufacturing process.

Proton Arc Therapy vs Interstitial HDR Brachytherapy in Gynecologic Cancer with Parametrial/pelvic Side Wall Extension.

PurposeTo investigate whether volumetric-modulated proton arc therapy (VPAT) plans generate comparable doses to organs at risk (OARs) compared with interstitial high–dose-rate (iHDR) brachytherapy for patients with gynecologic cancer with disease extension to parametrial/pelvic side wall, who are not eligible for the aggressive procedure.Materials and MethodsVPAT delivers proton arc beams by modulated energies at the beam nozzle while maintaining the same incident energy to the gantry during the arc rotation. Plans of 10 patients previously treated with iHDR brachytherapy for high-risk clinical treatment volumes (HRCTV; 31.8–110.6 cm3; lateral dimensions, 4.2–5.6 cm) were selected and compared with VPAT plans. VPAT plans for each patient were designed using a 152- to 245-MeV range of energy-modulated proton beams.ResultsHRCTV coverage of the VPAT plans was comparable to that of the iHDR plans, with V150% showing no statistical differences. On average, the V100% and V90% of VPAT plans were higher than those of the iHDR plans, 95.0% vs 91.9% (P = .02) and 98.6% vs 97.5% (P = .02), respectively. D100 was also 17% higher for the VPAT plans (P = .03). On average, the D2cm3 of bladder, rectum, and small bowels in the VPAT plans were considerably lower than those in iHDR plans (by 17.4%, 35.2%, and 65.6%, respectively; P < .05 for all OARs).ConclusionVPAT–generated plans were dosimetrically superior to those with HDR brachytherapy with interstitial needles for locally advanced gynecologic cancer with parametrial/pelvic side wall disease extension. Dosimetrically, VPAT provides a noninvasive alternative to iHDR brachytherapy with a superior dosimetric profile.

Construction optimization and settlement analysis of Pile Beam Arc method in subway station

Subway stations are generally built in areas with dense buildings, heavy traffic, or dense pipelines. In this case, the control of land subsidence and building deformation is very strict. The Pile Beam Arc (PBA) method has its unique advantages in these aspects, and it is especially suitable for northern China. In this research, the Zhongjie subway station of Shenyang Metro Line 1 is taken as the research object, and MIDAS GTS NX software is used to simulate the various stages of the PBA method construction of the subway station. In this paper, the optimal construction scheme of the subway station is analyzed by numerical simulation. This study also uses the monitoring data provided by the construction site to analyze the influence and distribution law of the subway station on the ground surface deformation in each construction stage. In this paper, the results of numerical simulation are compared with the field monitoring data, and the most dangerous construction stage is obtained. The conclusions of this study can provide accurate supporting scheme and control measures for the subsequent construction.