Double Arc Research Articles

Effect of Transition Curve on Gear Bending Strength

Transition curve is very important to bending strength and life of gear. In order to improve the bending strength of gear, the shape of three kinds of transition curve (ordinary fillet cutter tip, single circle arc cutter tip and double circle arc cutter tip) was analyzed respectively, the relationship of double circle arc cutter tip parameters was established, the relation model of sensitive part of gear and stress concentration factor ( J and γ) was determined, the effect of different transition curves of gear on bending strength ( ) was explored. The results of analysis show that the bending strength of gear cut by double circle arc cutter tip increases by 10% comparing with that of gear cut by ordinary fillet cutter tip. It provides theories foundation for the design of high bending strength gear.

Profile Surface Construction and Pressure Angle Analysis of a New Type of Globoidal Indexing Cam

This paper presents a new type of globoidal indexing cam mechanism with steel ball. The characteristic of this mechanism has double circular arc section for cam raceway. Due to this kind of cam raceway section the mechanism can realize approximate rolling transmission. According to rotary transform tensor theory profile surface equation of globoidal cam is established. Meshing equation is built through meshing theory, and profile surface equation is determined by meshing equation. Based on profile surface equation 3D geometric model for globoidal cam is established. MATLAB software is used to calculate three-dimensional coordinate points, these coordinate points are imported into Pro/E software, and finally 3D model for globoidal cam is established by three-dimensional modeling function of Pro/E software. Pressure angle equation of globoidal cam is also established. On the condition that the other parameters remain unchanged the variation law of values of pressure angle depended on cam angle and indexing plate rotary radius is obtained respectively.

WE-E-BRA-01: Treatment of Moving Tumors: An Inter-Modality Comparison under Realistic Clinical Conditions

Purpose: To compare the effect of respiration on delivered dose for different treatment techniques under realistic clinical conditions. Methods and Materials: Twenty MOSFETs were inserted into a soft resin tumormodel positioned in a anatomical respiring phantom. The phantom motion was programmed using the trajectory of a real patient. A 4DCT was taken, and treatment plans created using different treatment techniques: Conformai plan (Eclipse), step‐and‐shoot IMRT (Pinnacle), step‐and‐shoot IMRT (XiO), dynamic IMRT (Eclipse), complex dynamic IMRT (Eclipse), hybrid IMRT (60% conformai, 40% dynamic IMRT [Eclipse]), VMAT (single arc [Eclipse]), VMAT (double arc [Eclipse]) and complex VMAT (Eclipse). The complex plans were created by artificially pushing the optimizer to give complex MU sequences. Each plan was treated 5 times (10 times for VMAT), each irradiation starting at a random point in the respiratory cycle. The effect of fractionation was calculated by randomly summing the measured doses. The maximum deviation for each point per fraction, and the probability of 95% of the tumor having dose deviations less than 2% and 5% were calculated as a function of number of fractions. Results: After 5 fractions, measured dose deviations were less than 2% with 95% probability for all plans except the complex IMRT, step‐and‐shoot IMRT (XiO), complex VMAT, and single‐arc VMAT. Reducing the dose rate of the complex IMRT plans to 200MU/min reduced the dose deviations to less than 2%. Dose deviations were less than 5% after 5 fractions for all plans except the complex VMAT plan. Conclusions: For most treatment techniques, the dose deviations averaged out after several fractions. Treatments with unusually complicated MLC had larger dose deviations. Dose deviations are reduced for IMRT treatments by reducing the dose rate. Using two arcs instead of one is effective for RapidArc treatments.

3D Modeling and Simulation of a New Type of Globoidal Indexing Cam Mechanism

This paper presents 3D modeling and simulation for a new type of globoidal indexing cam mechanism with steel ball. The characteristic of this mechanism is that cam raceway section is double circular arc section, and this characteristic is helpful to realize approximate rolling transmission. Profile surface equation of globoidal cam is established according to rotary transform tensor theory and meshing theory. Coordinate points of profile surface is obtained by MATLAB software. 3D model of parts of globoidal indexing cam mechanism with steel ball is built by Pro/E software. In Pro/E software these parts are assembled, and kinematics simulation is performed. Through kinematics simulation angular displacement, angular velocity and angular acceleration of indexing plate are obtained. Finally dynamic simulation of this mechanism is performed by ADMAS software, and contact force between cam and roller is obtained.

SU-GG-T-121: An Initial Study of Dose Distribution in the Junction of SmartArc and 3D Superclavical Fields for Head and Neck Tumors

Purpose: It has been common practice in head and neck radiotherapy to combine IMRT and 3d fields for larynx protection. Half beam block technique ensures a smooth dose distribution in the junction volume. The newly emerged VMAT technique, such as SmartArc, has proved in a variety of cases to achieve similar, or even better, dosimetrictumor coverage and critical organ protection compared with IMRT with the advantage of less needed MU and shorter delivery time. However, dose distribution of junction of VMAT fields with other fields is still an underexplored area. This abstract will present the result of our study on this topic and discuss issues exiting if VAMT is to replace IMRT for head and neck cases in combination with 3D fields. Method and Materials:Treatment planning was performed using Pinnacle version 9.0 planning system on Varian's 21EX Linac treatment machine with constant jaw. Coplanar double arc of 360° was selected in combination with 2 superclavical 3D fields. Control point spacing of the arc beams was set at the default 4°. Results: Dose distribution in the conjunction volume is very sensitive to the collimator angle. With the commonly preferred collimator angle of 45°, dose in the junction volume can be as high as double the prescription dose. Decreasing the collimator angle improved dose uniformity in the junction, but the tumor coverage in proximity to the junction could be compromised. 0° degree angle proved to produce the best tumor coverage and junction dose uniformity. Best jaw match requires a collimator angle of 90°, but it proved to product the coldest tumor coverage from the VMAT fields. Conclusion: More study and efforts are needed to resolve the issue of dose uniformity in the junction volume if VMAT fields are to be combined with 3D fields for head and neck tumors.

Computational Analysis of a Double Nozzle Structure Plasma Cutting Torch

Double arcing phenomenon is a limit to increasing the capacity of the plasma cutting torch. In an attempt to enhance the ability of being invulnerable to the double arcing, a double nozzle structure is introduced in this paper. The reason why the double nozzle structure is less vulnerable to the double arcing phenomenon than single nozzle structure is explored. Double nozzle structure allows the longer nozzle which may cause stronger shock wave. In order to evaluate the influence of shock wave on the cutting ability, the influence of nozzle length on the double nozzle structure plasma arc is investigated. The modeling results show that the longer nozzle produces the stronger shock wave outside the nozzle outlet, but the energy flux and momentum flux become concentrated after the shock wave and increases with the increasing of nozzle length. So the double nozzle structure improves the cutting ability of the plasma torch and meanwhile be less vulnerable to the double arcing phenomenon.

Study on Virtual Simulation Machining of Double Circular Arc Profile Spiral Bevel Gear

Following spatial mesh principle, the gear cutting meshing equation was established in the paper through analyzing the relation between the machining principle of the double circular arc profile spiral bevel gear and the movement of the machine tool. The parameters of cutter head and the machine tool’s movement were then obtained through the equation. VERICUT was applied to build the three-dimensional virtual simulation machining model by which the gear geometry parameters, cutter parameters and machining tool movement parameters were calculated for a given gear to be processed and virtual simulation machining proceeded to prove the validity of the model.

A Numerical Simulating Study of Mechanical Characteristics of Superposed Deformation in Daba Mountain Foreland

In this article, the mechanical characteristics, the interference patterns of superposed folds, and the feature of united arc-shaped structure in Daba mountain foreland are studied using nonlinear finite element numerical method. In addition, the developed procedure of a series of arc-shaped structure with time is demonstrated, and a group of boundary conditions adapted to the superposed deformation in this region is obtained. The study shows the following: 1 The creep materials selected in our model are deformed greatly with time, but the variation of stress field is small and slow, which makes it possible to study the tectonic deformation through principal stress trajectory. 2 The major interference patterns of superposed folds in Daba mountain foreland are roughly perpendicular, mitred, and syntropic superpositions. 3 The formation of Daba arc-shaped structure is believed to be due to the action of northeastern boundary forces, as well as the two tectonic convergences at east and west part, but another arc-shaped structure in eastern Sichuan basin assembled with Daba mountain forming a convergent double arc is believed to be due to the action of the boundary forces from southeastern orientation.

Volumetric Intensity-Modulated Arc Therapy Vs. Conventional IMRT in Head-and-Neck Cancer: A Comparative Planning and Dosimetric Study

Volumetric intensity-modulated arc therapy (RA) allows for rapid delivery of highly conformal dose distributions. In this study, planning and dosimetry of RA were compared with conventional intensity-modulated radiation therapy (IMRT) plans of head-and-neck cancer patients. Computed tomography scans of 12 patients who had completed IMRT for advanced tumors of the naso-, oro- and hypopharynx were replanned using RA using either one or two arcs. Calculated doses to planning target volume (PTV) and organs at risk (OAR) were compared between IMRT and RA plans. Dose distributions for single arc (n = 8) and double arc (n = 4) plans were verified using film dosimetry in three to five coronal planes using a quality assurance phantom. RA plans allowed for a mean reduction in number of monitor units (MU) by nearly 60%, relative to seven field sliding window IMRT plans. RA plans achieved similar sparing of all OAR as IMRT. Double arc RA provided the best dose homogeneity to PTV with a lower standard deviation of PTV dose (1.4 Gy), vs. single arc plans (2.0 Gy) and IMRT (1.7 Gy). Film measurements showed good correspondence with calculated doses; the mean gamma value was 0.30 (double arc) and area of the film with a gamma exceeding 1 was 0.82%. RA is a fast, safe, and accurate technique that uses lower MUs than conventional IMRT. Double arc plans provided at least similar sparing of OAR and better PTV dose homogeneity than single arc or IMRT.

The Realization of Low Stress and Nonangular Distortion by Double-Sided Double Arc Welding

Control welding residual stress and distortion is extremely important in manufacturing industry. Double-sided double arc welding (DSDAW), which can control residual stress and angular distortion, is developed. Because arc distance between fore and rear torches is the key effective factor of angular distortions in DSDAW, its effects are not clear on the stress and angular distortions. In this study, numerical simulation is used to predict the transient temperature and welding distortion and stress with different arc distances. Meanwhile, the transient temperature and angular distortion are measured. The calculated results are in good agreement with the experimental results. The effects of arc distance on the angular distortion and stress are investigated. Lower stress and nonangular distortion is obtained at arc distances of 0 mm and 50 mm.

Field-aligned currents of postnoon auroral arcs

[1] On 9 January 2008, postnoon (at about 15–16 magnetic local time [MLT]) poleward moving auroral arcs were observed over Svalbard during slightly negative interplanetary magnetic field (IMF) Bz and the IMF By gradually changing from near zero to about −3 nT. The arcs appeared from the western (dayside) horizon and developed toward the east coming to the postnoon sector. The steerable 32-m antenna of the European Incoherent Scatter (EISCAT) radar was directed at an elevation angle of 45° to the north-west at about 45° to geomagnetic west, allowing for measurement of azimuthal (along east-west) plasma flow in a range of latitudes. On the basis of this radar configuration, a new method has been developed and applied for calculating the field-aligned currents (FACs) in the vicinity of the arcs. The arcs were located in the region of the postnoon convection reversal, and the background upward FAC had a density of about 1 μA/m2. The optical arcs were of the order of 30–40 km wide and coincided with peaks of upward FAC. The return downward FAC and the southward electric field were observed poleward of the arcs. Equatorward of the arcs, secondary weaker arcs were detected so that the postnoon arcs appear to have a double structure. These features are surprisingly similar to the electric field and current patterns of morning Sun-aligned arcs. We suggest that the double arc structure can be explained by the nonlinear ionospheric feedback that results in splitting of the elongated magnetospheric plasma structures associated with the arcs.

Hypersingular integral equation for multiple curved cracks problem in plane elasticity

The complex variable function method is used to formulate the multiple curved crack problems into hypersingular integral equations. These hypersingular integral equations are solved numerically for the unknown function, which are later used to find the stress intensity factor, SIF, for the problem considered. Numerical examples for double circular arc cracks are presented.

Dynamic angio-MRI demonstration of persistent left superior vena cava in the absence of the right superior vena cava

This condition is a rare anomaly. Combination with other congenital malformations including coarctation of the aorta, double aortic arc, transposition of great vessels and dextrocardia was reported. We performed an MRI evaluation. MRI was first obtained at cardiac level using a gated Black Blood and Cine technique, useful to confirm the enlarged coronary sinus, and then using a dynamic angiographic technique. By means of the latter modality, each frame was obtained in 5 s and was useful to demonstrate the contrast bolus through the venous, cardiac, pulmonary and systemic levels. It was possible to demonstrate the persistence of the left superior vena cava in the absence of the right superior vena cava.

Stability of Double Wires Narrow-gap Gas Metal Arc Welding

Some special parameters of double wires narrow gap GMAW (NG-GMAW) welding can be adjusted individually, such as the angle and distance between the two wires along the welding direction and the distance between the wire and the sidewall of the groove. These parameters have great influence on the welding stability. Experiments results show that when the distance between the two wires is less than 15 mm or greater than 50 mm, the two welding arcs are in one molten pool or two independent molten pools, and the welding process is very stable. When the distance is 20～30 mm, the molten pool is transforming from single one to two independent one. Under the action of unbalanced electromagnetic force, the arc is compelled to break frequently and the stable welding process is destroyed. When the two wires are parallel along the welding direction, the welding process is stable; if the front wire is inclined to the rear wire, the wandering of the front arc is aggravated. The distance between the wire and the groove sidewall has great influence on the arc modality. When the distance is 2.5 mm, the arc burns stably between the wire and the sidewall as well as the bottom of the groove. But if the distance is less than 1.5 mm, the arc burns between the sidewall or bottom randomly, and the welding stability deteriorates.

Type 4 capitellum fractures: Diagnosis and treatment strategies

Background:Fractures of the capitellum are rare injuries of the elbow usually seen in the adolescents. This fracture is often missed in the emergency room if a proper radiograph is not available. Recent reports have described many modalities of treatment favoring headless screw for fixation. The facility for headless screw fixation, however, is not available in most centers. This paper presents the diagnosis and management of type 4 capituller fractures (Mckee) with gadgets available in a district hospital.Materials and Methods:Between 2004 and 2007 three patients with right sided type IV capetullar fracture were treated in a district hospital. There were two boys aged 15 and 17 and one 33 years old lady. In one case, the fracture was missed in the emergency room. A double arc sign in the lateral views of the X-rays of the elbow was seen in all the cases. In each case a preoperative CT scan was done and a diagnosis of Mckee type IV fracture of the capitellum was made. Under tourniquet, using extended lateral approach, open reduction and internal fixation was done using 4mm partially threaded AO cancellous screws (n=2) and 2.7 mm AO screws (n=1), under vision from posterior to anterior direction from the posterior aspect of lateral condyle of humerus avoiding articular penetration.Results:All the fractures united uneventfully. At the end of one year follow-up, two cases had excellent elbow function; implants were removed and there were no signs of AVN or arthritis. The third case had good elbow ROM at 11 months without AVN.Conclusion:Double arc sign on lateral X-rays of the elbow along with pre-operative CT scan evaluation is important to avoid a missed diagnosis and analysis of type IV capitellur fracture. Fixation with non-cannulated ordinary AO screws using extended Kocher's lateral approach has given good results.

Heat flux characteristics in an atmospheric double arc argon plasma jet

In this study, the axial evolution of heat flux excited by a double arc argon plasma jet impinging on a flat plate is determined, while the nonstationary behavior of the heat flux is investigated by combined means of the fast Fourier transform, Wigner distribution, and short-time Fourier transform. Two frequency groups (<1 and 2–10 kHz) are identified in both the Fourier spectrum and the time-frequency distributions, which suggest that the nature of fluctuations in the heat flux is strongly associated with the dynamic behavior of the plasma arc and the engulfment of ambient air into different plasma jet regions.

Numerical simulation of three-dimension stress field in double-sided double arc multipass welding process

A new high-efficiency method for welding thick plates of low-alloy high-tensile steel which does not require back chipping – double-sided arc welding (DSAW) – is provided in this paper. Backing run adopts double-sided pulse gas tungsten arc welding, and other passes adopt double-sided gas metal arc welding. Three-dimensional numerical models of DSAW with 50 mm plates are developed to predict the stress distribution by using finite-element analysis, computer parallel processing technology and multiple jobs design, and are compared with single arc welding (SAW). The analysis of the interpass stresses indicates that the stresses of the back and cover pass are to be regarded as the key point in multipass welding. To verify the calculated results, the residual stresses and transient temperature of back run weld measured individually agree approximately with the calculated results, which illustrates that the backing run and residual stresses of DSAW are lower than those of SAW.

Characterization of an atmospheric double arc argon-nitrogen plasma source

In the framework of studies devoted to hazardous waste destruction, an original dc double anode plasma torch has been designed and tested, which produces an elongated, weak fluctuation and reproducible plasma jet at atmospheric pressure. The arc instabilities and dynamic behavior of the double arc argon-nitrogen plasma jet are investigated through the oscillations of electrical signals by combined means of fast Fourier transform and Wigner distribution. In our experiment, the restrike mode is identified as the typical fluctuation behavior in an argon-nitrogen plasma jet. The Fourier spectra and Wigner distributions exhibit two characteristic frequencies of 150 Hz and 4.1 kHz, which reveals that the nature of fluctuations in the double arc argon-nitrogen plasma can be ascribed to the undulation of the power supply and both arc roots motion on the anode channels. In addition, the microscopic properties of the plasma jet inside and outside the arc chamber are investigated by means of optical emission spectroscopy, which yields excitation, electronic, rotational, and vibrational temperatures, as well as the electron number density. The results allow us to examine the validity criteria of a local thermodynamic equilibrium (LTE) state in the plasma arc. The measured electron densities are in good agreement with those calculated from the LTE model, which indicates that the atmospheric double arc argon-nitrogen plasma in the core region is close to the LTE state under our experimental conditions.

Fundamental studies on in-process controlling angular distortion in asymmetrical double-sided double arc welding

It is extremely important to reduce and control residual angular deformation from the welding processes which has negative effects on fabrication accuracy in the manufacturing industry. A new method, asymmetrical double-sided double arc welding (ADSAW), is studied due to control residual angular distortion. Because arc distance between fore and rear torches and welding parameters are the key effective factors of angular distortions in ADSAW, but it is not clear about the effects of them on the angular distortions. In this study, experiments are carried out to investigate the thermal character and the effects of arc distance and welding parameters on the angular distortion in ADSAW. Meanwhile, a 3-D thermal elastic plastic finite element model is developed to simulate transient temperature and welding deformation with different arc distance and heat input. The simulated results are in a good agreement with the experimental measurements. The influence on welding deformation of the arc distance and heat input is investigated. In addition, the distortion mechanism and control strategy of angular distortion are clarified through numerical simulation.

Electrical and spectroscopic diagnostic of an atmospheric double arc argon plasma jet

An atmospheric argon plasma jet generated by an original dc double anode plasma torch has been investigated through its electrical and spectroscopic diagnostics. The arc instabilities and dynamic behavior of the argon plasma are analyzed using classical tools such as the statistical method, fast Fourier transform (FFT) and correlation function. The takeover mode is identified as the fluctuation characteristic of the double arc argon plasma jet in our experiment. The FFT and correlation analysis of electrical signals exhibit the only characteristic frequency of 150 Hz, which originates from the torch power and is independent of any change in the operating parameters. No high frequency fluctuations (1–15 kHz) are observed. This indicates that the nature of fluctuations in an argon plasma jet is induced mainly by the undulation of the tri-phase rectified power supply. It is found that each arc root attachment is diffused rather than located at a fixed position on the anode wall. Moreover, the emission spectroscopic technique is performed to determine the electron temperature and number density of the plasma jet inside and outside the arc chamber. Along the torch axis, the measured electron temperature and number density of the double arc argon plasma drop from 12 300 K and 7.6 × 1022 m−3 at the divergent part of the first anode nozzle, to 10 500 K and 3.1 × 1022 m−3 at the torch exit. In addition, the validity criteria of the local thermodynamic equilibrium (LTE) state in the plasma arc are examined. The results show that the measured electron densities are in good agreement with those calculated from the LTE model, which indicates that the double arc argon plasma at atmospheric pressure is close to the LTE state under our experimental conditions.