Radial Edge Research Articles

Performance evaluation and optimization of the MiniPET-II scanner

This paper presents results of the performance of a small animal PET system (MiniPET-II) installed at our Institute. MiniPET-II is a full ring camera that includes 12 detector modules in a single ring comprised of 1.27×1.27×12mm3 LYSO scintillator crystals. The axial field of view and the inner ring diameter are 48mm and 211mm, respectively. The goal of this study was to determine the NEMA-NU4 performance parameters of the scanner. In addition, we also investigated how the calculated parameters depend on the coincidence time window (τ=2, 3 and 4ns) and the low threshold settings of the energy window (Elt=250, 350 and 450keV). Independent measurements supported optimization of the effective system radius and the coincidence time window of the system. We found that the optimal coincidence time window and low threshold energy window are 3ns and 350keV, respectively. The spatial resolution was close to 1.2mm in the center of the FOV with an increase of 17% at the radial edge. The maximum value of the absolute sensitivity was 1.37% for a point source. Count rate tests resulted in peak values for the noise equivalent count rate (NEC) curve and scatter fraction of 14.2kcps (at 36MBq) and 27.7%, respectively, using the rat phantom. Numerical values of the same parameters obtained for the mouse phantom were 55.1kcps (at 38.8MBq) and 12.3%, respectively. The recovery coefficients of the image quality phantom ranged from 0.1 to 0.87. Altering the τ and Elt resulted in substantial changes in the NEC peak and the sensitivity while the effect on the image quality was negligible. The spatial resolution proved to be, as expected, independent of the τ and Elt. The calculated optimal effective system radius (resulting in the best image quality) was 109mm. Although the NEC peak parameters do not compare favorably with those of other small animal scanners, it can be concluded that under normal counting situations the MiniPET-II imaging capability assures remarkably good image quality, sensitivity and spatial resolution.

Sci—Fri AM: Imaging — 05: Cone‐beam computed tomography for breast biopsy analysis: Simulations

To determine the feasibility and potential utility of cone beam CT on breast biopsies. CBCT simulations were done with a setup which emulates an MX-20 digital specimen radiography system (Faxitron X-Ray Corporation, Chicago, IL), albeit a DQE = 1 was assumed. The phantom consisted of a 5mm diameter cylinder with a length of 5mm, made up of a homogeneous 50:50 mixture of fibrous and fatty tissue. Small cancerous spheres (lesions) with diameters ranging from 5 to 500 μm were embedded. Projections were acquired at magnification 5 using 26 kV-0.3 mA-3.8 sec beams. Images were reconstructed using a varied number of projections (50, 100, 150, 300). Values of contrast and SNR were calculated between the lesions and nearby regions. Noise was estimated by generating 10 images for each task. Scatter was found to be negligible. The 50 μm spheres were only visible when at least 150 projections were used, but the 100 μm ones were visible regardless of the number. SNR increased with the number of projections, whereas contrast was insensitive. For ≥100 μm spheres contrast ranged from 0.26 on the outer radial edge to 0.28 nearer the center. The SNRs for 100 μm spheres were above 5 for reconstructions composed of ≥100 projections. Cancerous lesions within a fibrous biopsy may be detectable. The findings from this simulation study suggest that CBCT for breast biopsy characterization via the MX-20 system could be of potential use to see structures on the order of 100 μm.

Experimental observation of the skin effect on plasma uniformity in inductively coupled plasmas with a radio frequency bias

Electromagnetic effects such as the skin effect, standing wave effect, and edge effect have been mainly studied in large-area, high-frequency gas discharges. In this study, we show that the skin effect can be a major factor of plasma uniformity in a high-density plasma, even if the discharge regime is in a small electrode area and under moderate excitation frequency. When a radio frequency (RF) bias power was applied to an inductively coupled plasma (ICP), the plasma density near the radial edge was largely increased and the plasma uniformity was significantly enhanced in the high-density plasma regime. This change could be understood by considering the enhanced electric field in the radial edge, the so-called skin effect. The time-dependent behavior of the plasma density and electron temperature by the bias power was also studied. When the RF bias power was applied to the ICP, the electron temperature abruptly increased due to electron heating, while variations of plasma density depending on the radial position were observed with the RF bias power in the high-density plasma of the ICP.

Characterizing Diesel Fuel Spray Cone Angle From Back-Scattered Imaging by Fitting Gaussian Profiles to Radial Spray Intensity Distributions

Quantifying fuel spray properties including penetration, cone angle, and vaporization processes sheds light on fuel-air mixing phenomenon, which governs subsequent combustion and emissions formation in diesel engines. Accurate experimental determination of these spray properties is a challenge but imperative to validate computational fluid dynamic (CFD) models for combustion prediction. This study proposes a new threshold independent method for determination of spray cone angle when using Mie back-scattering optical diagnostics to visualize diesel sprays in an optically accessible constant volume vessel. Test conditions include the influence of charge density (17.6 and 34.9 kg/m3) at 1990 bar injection pressure, and the influence of injection pressure (990, 1370, and 1980 bar) at a charge density of 34.8 kg/m3 on diesel fuel spray formation from a multi-hole injector into nitrogen at a temperature of 100 °C. Conventional thresholding to convert an image to black and white for processing and determination of cone angle is threshold subjective. As an alternative, an image processing method was developed, which fits a Gaussian curve to the intensity distribution of the spray at radial spray cross-sections and uses the resulting parameters to define the spray edge and hence cone angle. This Gaussian curve fitting methodology is shown to provide a robust method for cone angle determination, accounting for reductions in intensity at the radial spray edge. Results are presented for non-vaporizing sprays using this Gaussian curve fitting method and compared to the conventional thresholding based method.

3-D Formal Resolution of Maxwell Equations for the Computation of the No-Load Flux in an Axial Flux Permanent-Magnet Synchronous Machine

This paper presents a 3-D analytical model of an axial flux permanent-magnet synchronous machine, based on formal resolution of Maxwell equations. This method requires much less computation time than conventional 3-D finite elements, and is therefore suitable for optimization purposes. In a first part, the mathematical procedure used to compute the machine no-load flux is described in detail. This method is 3-D, and then takes into account the radial edge effects of the machine, as well as the curvature effects by a resolution in cylindrical coordinates. Moreover, the originality of this method lies in the fact that it is totally analytical. The obtained results are verified using 3-D finite elements, and compared with simpler analytical models of axial flux machines, taken from the literature. This work puts in evidence the advantages of the proposed model. In particular, it is shown that the radial edge effects are important for a correct estimation of the no-load flux. On the contrary, the curvature effects are a second-order phenomenon.

Fluid simulation of the phase-shift effect in hydrogen capacitively coupled plasmas: II. Radial uniformity of the plasma characteristics

A two-dimensional fluid model, including the full set of Maxwell equations, has been developed and applied to investigate the effect of a phase shift between two power sources on the radial uniformity of several plasma characteristics in a hydrogen capacitively coupled plasma. This study was carried out at various frequencies in the range 13.56–200 MHz. When the frequency is low, at 13.56 MHz, the plasma density is characterized by an off-axis peak when both power sources are in-phase (φ = 0), and the best radial uniformity is obtained at φ = π. This trend can be explained because the radial nonuniformity caused by the electrostatic edge effect can be effectively suppressed by the phase-shift effect at a phase difference equal to π. When the frequency rises to 60 MHz, the plasma density profiles shift smoothly from edge-peaked over uniform to centre-peaked as the phase difference increases, due to the pronounced standing-wave effect, and the best radial uniformity is reached at φ = 0.3π. At a frequency of 100 MHz, a similar behaviour is observed, except that the maximum of the plasma density moves again towards the radial edge at the reverse-phase case (φ = π), because of the dominant skin effect. When the frequency is 200 MHz, the bulk plasma density increases significantly with increasing phase-shift values, and a better uniformity is obtained at φ = 0.4π. This is because the density in the centre increases faster than at the radial edge as the phase difference rises, due to the increasing power deposition Pz in the centre and the decreasing power density Pr at the radial edge. As the phase difference increases to π, the maximum near the radial edge becomes obvious again. This is because the skin effect has a predominant influence on the plasma density under this condition, resulting in a high density at the radial edge. Moreover, the axial ion flux increases monotonically with phase difference, and exhibits similar profiles to the plasma density. The calculation results illustrate that the radial uniformity of the various plasma characteristics is strongly dependent on the applied frequency and the phase shift between both power sources, which is important to realize, for controlling the uniformity of the plasma etch and deposition processes.

Study of critical buckling loads and modes of cross-ply laminated annular plates

Buckling of composite annular plates under uniform internal and external radial edge loads have been investigated using energy method. Trefftez rule is used in the stability equations. The symmetric buckling of symmetric cross-ply laminates is considered. In this paper, buckling behavior for the three laminates (90/0)2s, (90/02/90)s and (902/02)s are studied. Influence of some parameters such as thickness, stacking sequence, type of supports and the ratio of hole to sheet radius on buckling loads and modes are investigated. The results of the energy method are compared with the results of numerical method. Based on the results, in the plates with clamped boundary conditions the symmetric buckling assumption is not accurate, contrary to other boundary conditions.

Segmentation of left ventricle in short-axis echocardiographic sequences by weighted radial edge filtering and adaptive recovery of dropout regions

In this paper, we present a weighted radial edge filtering algorithm with adaptive recovery of dropout regions for the semi-automatic delineation of endocardial contours in short-axis echocardiographic image sequences. The proposed algorithm requires minimal user intervention at the end diastolic frame of the image sequence for specifying the candidate points of the contour. The region of interest is identified by fitting an ellipse in the region defined by the specified points. Subsequently, the ellipse centre is used for originating the radial lines for filtering. A weighted radial edge filter is employed for the detection of edge points. The outliers are corrected by global as well as local statistics. Dropout regions are recovered by incorporating the important temporal information from the previous frame by means of recursive least squares adaptive filter. This ensures fairly accurate segmentation of the cardiac structures for further determination of the functional cardiac parameters. The proposed algorithm was applied to 10 data-sets over a full cardiac cycle and the results were validated by comparing computer-generated boundaries to those manually outlined by two experts using Hausdorff distance (HD) measure, radial mean square error (rmse) and contour similarity index. The rmse was 1.83 mm with a HD of 5.12 ± 1.21 mm. We have also compared our results with two existing approaches, level set and optical flow. The results indicate an improvement when compared with ground truth due to incorporation of temporal clues. The weighted radial edge filtering algorithm in conjunction with adaptive dropout recovery offers semi-automatic segmentation of heart chambers in 2D echocardiography sequences for accurate assessment of global left ventricular function to guide therapy and staging of the cardiovascular diseases.

Long-range correlations and edge transport bifurcation in fusion plasmas

Recently, a European transport project has been carried out among several fusion devices for studying the possible link between the mean radial electric field (Er), long-range correlation (LRC) and edge bifurcations in fusion plasmas. The main results reported in this paper include: (i) the discovery of low-frequency LRCs in potential fluctuations which are amplified during the development of edge mean Er using electrode biasing and during the spontaneous development of edge sheared flows in stellarators and tokamaks. Evidence of nonlocal energy transfer and the geodesic acoustic mode modulation on local turbulent transport have also been observed. The observed LRCs are consistent with the theory of zonal flows described by a ‘predator–prey’ model. The results point to a significant link between the LRC and transport bifurcation. (ii) Comparative studies in tokamaks, stellarators and reversed field pinches have revealed significant differences in the level of the LRC. Whereas the LRCs are clearly observed in tokamaks and stellarators, no clear signature of LRCs was seen in the RFX-mod reversed field pinch experiments. These results suggest the possible influence of magnetic perturbations on the LRC, in agreement with recent observations in the resonant magnetic perturbation experiments at the TEXTOR tokamak. (iii) The degree of the LRCs is strongly reduced on approaching the plasma density-limit in tokamaks and stellarators, suggesting the possible role of collisionality or/and the impact of mean Er × B flow shear on zonal flows.

The Effects of the Cooling Gallery Position on the Piston Temperature Field and Thermal Stress

The effects of cooling gallery position on the piston temperature field and thermal stress are studied. A finite element model of 1015 engine piston is developed using Pro/E software and finite element analyses are achieved through ANSYS code. Numerical simulations are performed to find the temperature and thermal stress change rules with regard to the cooling gallery position. The results demonstrate that the axial direction position of cooling gallery has obvious effects on the piston temperature while the radial direction position of cooling gallery affects the piston thermal stress a lot. The highest position of cooling gallery should be as the same line as the top of the first ring groove. The distance between cooling gallery and piston radial edge should be more than a certain value to decrease the temperature gradient and thermal stress concentration.

Le greffon vascularisé radial de Zaidemberg. Bases anatomiques et expérience clinique

In 1991, Carlos Zaidemberg described a new technique to repair scaphoid non-unions with a vascularized bone graft harvested from the radial styloid process. An anatomic study based on 30 dissections after colorized latex injection established the constancy of the radial styloid process's artery, while showing that its origin, course and length were subject to variations. In a retrospective series of 38 cases over a period of 10 years, the vascularized bone graft was indicated for: (1) scaphoid non-union with the presence of avascular changes of the proximal fragment (23 cases); (2) failed prior reconstruction with bone graft and internal fixation (nine cases); (3) degenerative styloid-scaphoid arthritis (three cases); (4) fracture on Preiser dystrophy (three cases). The five steps of the simplified operative technique without dissection of the vascular pedicle include: (1) longitudinal dorso-radial approach, identification of the periosteal portion of the radial styloid process artery; (2) incision of the first and second compartments, longitudinal arthrotomy under the second compartment; (3) styloidectomy and transversal resection of the scaphoid non-union and sclerotic bone; (4) elevation of the vascularized bone graft; (5) transversal and radial insertion of the vascularized bone graft, osteosynthesis by two or three K-wire touching the scaphoid's radial edge. Scaphoid union was obtained in 33 cases out of 38. The only postoperative complications were two transient radial paresthesia. The standardized surgical procedure using vascularized bone graft harvested from the radial styloid process provides an efficient scaphoid reconstruction.

Influence of boundary stress singularities on the vibration of clamped and simply-supported sectorial plates with arbitrary radial edge conditions

This paper extends previous studies made for sectorial plates having re-entrant (i.e., interior) corners causing stress singularities, to provide accurate frequencies when the circular edge is either clamped or simply-supported. An extensive review of the literature is also given herein spanning nearly the past two decades explaining the free vibration characteristics of sectorial plates. In this work, the classical Ritz method is employed with two sets of admissible functions assumed for the transverse vibratory displacements. These sets include: (1) mathematically complete algebraic–trigonometric polynomials which guarantee convergence to exact frequencies as sufficient terms are retained and (2) corner functions which account for the bending moment singularities at the re-entrant vertex corner of the radial edges having arbitrary edge conditions. Extensive convergence studies summarized herein confirm that the corner functions substantially enhance the convergence and accuracy of non-dimensional frequencies for sectorial plates having either a clamped or hinged circumferential edge and various combinations of clamped, hinged, and free conditions on the radial edges. Accurate (to at least four significant figure) frequencies and normalized contours of the transverse vibratory displacement are presented for the spectra of sector angles [90°, 180° (semi-circular), 270°, 300°, 330°, 350°, 355°, 360° (complete circular)] causing a re-entrant vertex corner of the radial edges. For sector angles of 360°, a clamped–clamped, clamped–hinged, clamped–free, hinged–free or free–free radial crack ensues. One general observation is the substantial reduction in the first six frequencies as the sector angle increases for all plates, except in the first two modes of plates having free–free radial edges.

Modeling of chromatographic lipophilicity of food synthetic dyes estimated on different columns

The retention behavior of some food synthetic dyes has been studied by RP-HPLC on chemically bonded C18, C8, C16 and CN stationary phases. Using methanol-ammonium acetate (0.08 mol/L, pH=6.76) as mobile phase, a linear behavior of retention parameters throughout the methanol fraction variance was obtained in all cases (r>0.99). The patterns of chromatographic behavior of the compounds illustrate high similarities between the C18, C8 and C16 columns, respectively. Highly significant correlations were obtained between experimental lipophilicity indices log k(w) and phi(0) estimated on C18 and C8 stationary phases and some computed log P-values. An extensive investigation made for quantitative structure-property (lipophilicity) relationships of studied dyes, using descriptors from Dragon software, multiple linear regression and genetic algorithm, revealed that the molecular descriptors appearing in the best models combine 2-D and 3-D aspects of the molecular structure. The most significant descriptors can be classified as radial distribution function, GETAWAY (autocorrelation), 3D-MoRSE signal, Burden eigenvalues and edge adjacency descriptors.

A Novel Eye Gaze Tracking Technique Based on Pupil Center Cornea Reflection Technique

For several common drawbacks of existing gaze tracking systems using single camera and single light source:Low accuracy,restricted head movement and tedious calibration,this paper presents a novel gaze tracking method based on pupil center cornea reflection (PCCR) technique.Pupil location for gaze tracking has been well investigated and all methods worked on near-infrared images.This makes the eye details small and accuracy is affected.This paper addresses these problems by proposed radial distance pupil edge filter algorithm (RDPEF) and triple-channel pseudo-color map (TCPCM).Our pupil tracker improves the accuracy of gaze feature extraction.The 2-D mapping-based gaze estimation methods have two common drawbacks.This paper addresses these problems by proposed head position compensation method and individual difference transformation model.The advantage of the proposed method based on 2-D mapping-based gaze estimation is that it can estimate the gaze of user accurately under natural head movement.Furthermore,it minimizes the calibration procedure to only one calibration point for a new individual.The proposed methods will improve the accuracy and usability of the gaze tracking using single camera and single light source,and provides an effective low-cost gaze tracking for human-computer interaction.

반경방향의 모서리 균열을 갖고 내면이 경사기능재료(FGM)로 코팅된 두꺼운 실린더의 겉보기 파괴인성해석

This study analyzes the apparent fracture toughness of a thick-walled cylinder with a functionally graded material (FGM) coating at the inner surface of the cylinder. The cylinder is assumed to have a single radial edge crack emanating from its inner surface. The crack surfaces and the inner surface of the cylinder are subjected to an internal pressure. The incompatible eigenstrain developed in the cylinder due to nonuniform coefficient of thermal expansion as a result of cooling from sintering temperature is taken into account. Based on a method of evaluating stress intensity factor introduced in our previous study, an approach is developed to calculate apparent fracture toughness. The approach is demonstrated for a cylinder with a TiC/ FGM coating and some numerical results of apparent fracture toughness are presented graphically. The effects of material distribution profile, cylinder wall thickness, application temperature, and coating thickness on the apparent fracture toughness are investigated in details. It is found that all of these factors play an important role in controlling the apparent fracture toughness of the cylinder.

Die Behandlung der veralteten skapholunären Dissoziation mittels eines Knochen-Band-Knochen-Transplantats nach Cuénod

Correction of chronic scapholunate dissociation by replacement of the biomechanically most important dorsal part of the scapholunate ligament using a bone-ligament-bone autograft taken from the carpometacarpal joint II and, additionally, a modified dorsal capsulodesis. Nonfixed chronic scapholunate dissociation without useful remnants of the ligament in which loss of the dorsal part of the scapholunate ligament is the crucial pathophysiological moment. Chronic scapholunate dissociation with fixed deformity. Osteoarthritis. Dorsal incision. Approach to the wrist using the capsular flap described by Berger. Reduction of deformity and temporary transfixation of the scaphoid to the capitate as well as to the lunate. Creation of a trough at the ulnar edge of the dorsal aspect of the scaphoid and another trough at the radial edge of the dorsal aspect of the lunate. Fixation of an exactly fitting bone-ligament-bone autograft taken from the trapezoidometacarpal joint II with 1.2-mm screws into the troughs. Fixation of a part of the dorsal intercarpal ligament which is based on the scaphoid to the lunate using a bone anchor. Immobilization using a below-elbow cast including the metacarpophalangeal joint of the thumb for 8 weeks; removal of Kirschner wires 10 weeks postoperatively; after Kirschner wire removal physiotherapy to improve range of motion. Twelve out of 16 male patients were available for a clinical and radiologic examination after a mean follow-up time of 6.3 years (minimum 1.6, maximum 7.3 years). Clinical results were excellent. The modified Mayo Wrist Score averaged 87 points (minimum 65, maximum 100 points). Eleven patients had an excellent or good result, none of the patients showed a poor result. The DASH Score (Disability of the Arm, Shoulder and Hand) was 13 points on average (minimum 0, maximum 42 points). All patients would have the same operation again. Radiologically, a stretching of the bone-ligament-bone autograft was found in six cases. A symptomatic SLAC (scapholunate advanced collapse) wrist with the need for a salvage operation could not be observed.

Analysis of dynamic stress intensity factors of thick-walled cylinder under internal impulsive pressure

Dynamic stress intensity factors are evaluated for thick-walled cylinder with a radial edge crack under internal impulsive pressure. Firstly, the equation for stress intensity factors under static uniform pressure is used as the reference case, and then the weight function for a thick-walled cylinder containing a radial edge crack can be worked out. Secondly, the dynamic stresses in uncracked thick-walled cylinders are solved under internal impulsive pressure by using mode shape function method. The solution consists of a quasi-static solution satisfying inhomogeneous boundary conditions and a dynamic solution satisfying homogeneous boundary conditions, and the history and distribution of dynamic stresses in thick-walled cylinders are derived in terms of Fourier–Bessel series. Finally, the dynamic stress intensity factor equations for thick-walled cylinder containing a radial edge crack subjected to internal impulsive pressure are given by dynamic weight function method. The finite element method is utilized to verify the results of numerical examples, showing the validity and feasibility of the proposed method.

An intrinsic source of radial electric field and edge flows in tokamaks

We propose a new mechanism for radial electric fields and edge flows in tokamaks that will also serve as an intrinsic momentum source in systems without an up–down symmetry. An essential feature of toroidal plasmas is that charge-dependent ∇B and curvature drifts would lead to a vertical polarization of the discharge if it were not for the Pfirsch–Schlüter currents that neutralize the resulting charge separation. However, in the presence of collisions, there is a residual vertical electric field that drives an E × B flow in the direction of increasing major radius, regardless of the orientation of the fields and currents. This flow is excluded from the hot core and is localized to the more collisional edge plasma. It has many features in common with the edge flows observed in tokamaks such as C-Mod. In an up–down symmetric geometry it carries no net toroidal angular momentum; however, its viscous interaction with asymmetric boundaries leads to a net momentum input to the plasma. Both this momentum input, and the residual vertical electric field, the source of these flows, may play an important role in the ∇B direction-dependence of the power threshold for the L–H transition.

Uniform InGaAs quantum dot arrays fabricated using nanosphere lithography

We demonstrate the fabrication of optically active uniform InGaAs quantum dot arrays by combining nanosphere lithography and bromine ion-beam-assisted etching on a single InGaAs/GaAs quantum well. A wide range of lateral dot sizes was achieved from an oxygen plasma nanosphere resizing process. The increased lateral confinement of carriers in the dots results in low temperature photoluminescence blueshifts from 0.5 to 11 meV. Additional quantization was achieved using a selective wet-etch process. Our model suggests the presence of a 70 nm dead layer in the outer InGaAs radial edge, which we believe to be a result of defects and dislocations introduced during the dry-etch process.

Experimental observation of the inductive electric field and related plasma nonuniformity in high frequency capacitive discharge

To elucidate plasma nonuniformity in high frequency capacitive discharges, Langmuir probe and B-dot probe measurements were carried out in the radial direction in a cylindrical capacitive discharge driven at 90MHz with argon pressures of 50 and 400mTorr. Through the measurements, a significant inductive electric field (i.e., time-varying magnetic field) was observed at the radial edge, and it was found that the inductive electric field creates strong plasma nonuniformity at high pressure operation. The plasma nonuniformity at high pressure operation is physically similar to the E-H mode transition typically observed in inductive discharges. This result agrees well with the theories of electromagnetic effects in large area and/or high frequency capacitive discharges.