Symmetric Angle Research Articles

Effect of LAB on the Stress Rupture Properties and Fracture Characteristic of DD6 Single Crystal Superalloy

The slabs of the second generation single crystal superalloy DD6 were cast using bi-seeded crystals with symmetric twist low angle grain boundaries. The influence of low angle boundary (LAB) on the stress rupture properties of the alloy was investigated at 760 °C/758 MPa, 850 °C/550 MPa and 980 °C/250 MPa. SEM was used to study the fracture surface and the failure mechanism. The results show that when the misorientation angle of LAB is relatively small it has a less effect on the stress rupture properties of the alloy. The stress rupture properties decrease with the misorientation increase on the same test conditions. The fracture characteristic of specimen shows intergranular rupture trend with the misorientation increases on the same conditions or with increasing of temperature and decreasing of stress for the same misorientation of LAB.

Abstract 2571: Quantitative Analysis of Cobalt Alloy Clip Artifacts in 64 channel Three Dimensional CT Angiography and Introducing Strategies for Minimizing Metallic Artifacts

Objective Clip artifacts on postoperative CT scans after aneurysmal clipping, can create confusion, especially in cases of cobalt alloy clips. Mathematic analysis of the parameters influencing the degree of clip artifact in 64-channel 3 dimensional CT angiography (3D CTA) was conducted to develop methods for minimizing metallic artifacts. Materials and Methods CT images from 60 cases with single straight Sugita cobalt alloy clips (Mizuho Ikakogyo Co., Tokyo) were analyzed. The degree of the angle between the imaging acquisition gantry angle and clip blade on the CT axial scan (x, y) and on the lateral scout view (z) was measured as independent variables. The length of the clip blade was also measured. Analysis of whether the spring of the clip was included in the 5mm thick scan slide was performed. The dependent variables were the maximal diameter of the white artifact, degree of the symmetrical angle of the streak artifact and the maximal diameter of clip artifact in 3D volume rendering. Univariate and multivariate analysis was conducted to elucidate relationship between each parameters and each type of clip artifacts. Results The degree of the angle between z axis and clip blade was negatively correlated with the amount of white artifact (p<0.0001, R=-0.589) and positively with the streak artifact (angle of the streak artifact: p<0.0001, R=0.636; number of the streak artifact: p<0.0001, R=0.505). When the spring of the clip was included parallel in scan section, the amount of white artifact was increased (p<0.0001). On multiple linear regression analysis, angle of clip blade to z axis was the major parameter influencing all kinds of artifacts (white artifact: p<0.005, angle of the streak artifact: p<0.0001, number of the streak artifact: p<0.0001). Conclusions Metallic artifact was increased when the degree of angle between the clip blade and z axis became near to zero. Clip artifacts after aneurysmal clipping could be minimized with simple maneuvers such as minimal changes of the scan gantry angle on the lateral scout view if the clip blade was parallel to the gantry angle or the clip spring portion was included in the scan cross section.

ALTERATION OF THE END-PLANE ANGLE IN PRESS-FIT CYLINDRICAL STEM RADIAL HEAD PROSTHESIS: AN IN VITRO STUDY

Many studies comparing the morphology of native radial head with the prosthesis have been published. However, there is limited information regarding the postoperative alignment of the articular surface following the radial head replacement. The purpose of this study is to evaluate the alteration of the end-plane angle in the modular radial head prosthesis with a press-fit cementless cylindrical stem. The study used 36 cadaveric radii. The press-fit size prosthesis with cylindrical stem was inserted into each specimen. The end-plane angles of the radial head before and after prosthetic replacement, were measured in coronal and sagittal planes with a digital inclinometer. The data were analyzed by paired t-test. From paired t-test, there were statistically symmetrical end-plane angles before and after radial head replacement in both coronal and sagittal planes (p-value < 0.01). The mean of radial head end-plane angle alteration in the coronal plane was 3.62° (SD, 2.76°) (range, 0.3°-8.9°). In the sagittal plane, the mean of alteration was 5.85° (SD, 3.56°) degrees (range, 0.3° - 14.2°). The modular radial head prosthesis with cylindrical stem is in vitro able to restore the native end-plane angles of radial heads statistically when used in a press-fit fashion.

Predicting The Tensile Properties Of Woven Kenaf/Polyethylene terephthalate (PET)Fiber Reinforced Polyoxymethylene (POM) Hybrid Laminate Composite

The analytical design of the hybrid composite predicts its tensile properties at different fiber orientation using classical lamination theory. The critical volume fraction of the high elongation fiberyields 0.39 which defines the composite of minimum strength. The high elongation fiber (PET) contributes more in raising the hybrid composite strengthwhile the low elongation fiber (Kenaf) increases the composite modulus more inthe longitudinal direction. Six layers hybrid composite laminates were analyzed. The stacking sequence used was symmetric angle ply (0 0 , 45 0 , 90 0 ) with an overall thickness of 12mm .The thermal expansion coefficient of the laminate increases more than that of the individual ply. The overall analytical results confirm that thehybrid composite tensile properties haveincreased significantly as compared to single fiber reinforced composite.

Strain–Stress Analysis of AlGaN/GaN Heterostructures With and Without an AlN Buffer and Interlayer

Abstract: The strain–stress analysis of AlxGa1−xN/GaN (x = 0.3) heterostructures with and without a high‐temperature HT‐AlN interlayer (IL) grown on sapphire (Al2O3) substrates and AlN buffer/Al2O3 templates via metal organic chemical vapour deposition (MOCVD) was carried out based on the precise measurement of the lattice parameters by using high‐resolution X‐ray diffraction (HRXRD). The a‐ and c‐lattice parameters were measured from the peak positions that were obtained by rocking the theta axis at the vicinity of the symmetric and asymmetric plane reflection angles, followed by the in‐plane and out‐of‐plane strains. Then, the biaxial and hydrostatic components were extracted from the total strain values that were obtained and were then discussed in the present study as the effect of the HT‐AlN buffer and IL. The AlN buffer layer (BL) affects the strain values of the AlGaN ternary layer (TL). A further effect was realized by inserting an AlN IL between GaN BL and AlGaN TL. However, the experimental results also show that an AlN IL changes the strain behaviour in the a‐ and c‐directions of the AlGaN TL from the tensile to compressive and the compressive to tensile type, respectively. These similar behaviours were observed in hydrostatic strain, biaxial strain and stress. Their reasons are explained with an effective a‐lattice parameter, post‐growth cooling and lattice and thermal mismatches.

An extended stress-based method for orientation angle optimization of laminated composite structures

Orientation optimization plays an important role in the lay-up design of composite structures. Earlier orientation optimization methods face the main problem of huge number of design variables. Recently, a patch concept is proposed to reduce the number of design variables. However, the traditional stress-based method can not deal with patch orientation optimization of composite structures. In this paper, we propose an extended stress-based method to deal with such problems. The considered problems are to minimize the mean compliance under multiple load cases or to maximize the eigenvalues of a composite structure. Four numerical examples are solved to demonstrate the efficiency of the new method. It is shown that the new method has the ability to deal with constraints on orientation angle, such as symmetric, antisymmetric and discrete orientation angle constraints. The iteration is less time-consuming because no sensitivity analysis is needed and a quick convergence rate can be achieved.

Experimental and Theoretical Analysis of Carbon Fiber Filament Wound Tubes with Symmetric Winding Angle under Tensional Loading

Carbon fiber composite tubes with symmetric winding angles were experimented under tensional loading and theoretically calculated using classical laminate theory. The experimental result showed that the axial stiffness of filament wound tubes without woven fiber was a little higher than that of filament wound tubes with woven fibers. In addition, the theoretical calculation results of axial stiffness had a good agreement with the experimental results of filament wound tubes without woven fiber.

Asymmetric dihedral angle offsets for large-size lunar laser ranging retroreflectors

The distribution of two-dimensional velocity aberration is off-centered by 5 to 6 microradians in lunar laser ranging, due to the stable measurement geometry in the motion of the Earth and the Moon. The optical responses of hollow-type retroreflectors are investigated through numerical simulations, especially focusing on large-size, single-reflector targets that can ultimately minimize the systematic error in future lunar laser ranging. An asymmetric dihedral angle offset, i.e. setting unequal angles between the three back faces, is found to be effective for retroreflectors that are larger than 100 mm in diameter. Our numerical simulation results reveal that the optimized return energy increases approximately 3.5 times more than symmetric dihedral angle cases, and the optimized dihedral angle offsets are 0.65–0.8 arcseconds for one angle, and zeroes for the other two angles.

Elastic stable intramedullary nailing of tibial shaft fractures in children

Tibial fractures in the skeletally immature patient are usually treated without surgery. Elastic stable intramedullary nailing (ESIN) is commonly used for other diaphyseal fracture locations. Its advantages are minimally invasive surgery with a short hospitalisation duration, primary bone union and early weight bearing. The purpose of this study was to assess the use of ESIN in displaced tibial fractures in children over 6years old and in cases of polytrauma. This study was carried out over a 6-year period. The protocol consisted in ESIN of shaft tibial fractures in children over 6. Frontal and sagittal angulation, shortening and lengthening were measured on days 0, 2, 15, 30 and 45. At 6months, 1 and 2years, the femoro-tibial axis and eventual shortening or lengthening were assessed. The study involved 86 children (average age 11.8years). As early as day 30, all patients had normal knee mobility and symmetrical foot progress angle. At 2-year follow-up, frontal angulation and leg length discrepancy had decreased and affected 2% of patients. Four patients (5%) suffered from superficial infections. There were no cases of osteomyelitis or refracture. The fixation of paediatric diaphyseal tibial fractures with ESIN is a rapid, well-codified and effective method for treating long-bone closed fractures in children. Advantages over other fixation techniques include a lower infection rate, a lower refracture rate, ease of management, and an aesthetically pleasing scar.

Analysis and control of self-excited induction generator-converter systems for battery charging applications

A method has been developed for the analysis of operation of self-excited induction generators (SEIGs) supplying battery charging loads through three-phase semi-converters by representing the battery circuit as equivalent resistance and reactance in the equivalent circuit of these generators. Such equivalent values are functions of the dc charging voltage and current and the control angle set in the converter. The solution for this circuit has been carried out using the genetic algorithm technique instead of using higher-order polynomials for the loop or nodal equations of the circuit. Apart from the conventional phase angle control, other firing control schemes namely negative firing angle control, extinction angle control and symmetrical angle control have been considered for the operation of the converter. The relative performance of these control schemes, for the various modes of operation of SEIG-converter systems such as constant and variable speed, has been brought out. Experimental results obtained on a three-phase SEIG charging suitable batteries through an IGBT-based semi-converter, controlled with all these schemes, confirm the usefulness of the proposed system and the validity of its analysis.

Multipactor Effect Analysis and Design Rules for Wedge-Shaped Hollow Waveguides

A numerical model for predicting the multipactor breakdown effect in wedge-shaped hollow waveguides is presented in this paper. The computation of electromagnetic fields is based on the boundary integral-resonant mode expansion method, which provides the modal chart of hollow waveguides with any arbitrary cross section. The advantage of using wedge-shaped waveguides with respect to conventional rectangular ones is the deviation of the resonant paths of the electrons toward regions with lower voltages, thus reducing the probability of multipactor threshold for certain input power. To validate this method, our results have been compared with simulations from previous theoretical studies. Once the simulation tool is validated, it is used to predict the multipactor threshold of wedge-shaped waveguides with different symmetric inclination angles of their horizontal plates. Finally, susceptibility curves as the ones already available for rectangular waveguides are presented. These charts are useful for designing innovative waveguide geometries with improved multipactor-free working power ranges.

Single Cell PCR과 현미경을 통한 바지락 및 백합 유생의 동정

Single cell PCR analysis and light and scanning electron microscopic techniques were utilized to identify free living bivalve larvae in the coastal waters of Tae-an, on the west coast of Korea. Through DNA sequencing, venerid clam larvae were isolated and identified as Ruditapes philippinarum (99% similarity) and Meretrix lusoria (99%). Under microscopic observation, the D-veliger stage of R. philippinarum exhibited symmetrical shoulder angles and an elliptical ventral form. In contrast, M. lusoria displayed asymmetrical shoulder angles and a round ventral form in the umbonal stage. Size of the R. philippinarum larvae was 156±22 ㎛ in length, 126±12 ㎛ in height, 92±14 ㎛ in width with a length: height ratio of 1.23. Meretrix lusoria was 202±44 ㎛ in length, 161±35 ㎛ in height, 96±38 ㎛ in width with a length: height ratio of 1.25. Experimental results indicate that morphological and molecular characteristics provide evidence for the larval identification of these two venerid clam larvae species in nature.

Internal dissipation of a polymer

The dynamics of flexible polymer molecules are often assumed to be governed by hydrodynamics of the solvent. However there is considerable evidence that internal dissipation of a polymer contributes as well. Here we investigate the dynamics of a single chain in the absence of solvent to characterize the nature of this internal friction. We model the chains as freely hinged but with localized bond angles and threefold symmetric dihedral angles. We show that the damping is close but not identical to Kelvin damping, which depends on the first temporal and second spatial derivative of monomer position. With no internal potential between monomers, the magnitude of the damping is small for long wavelengths and weakly damped oscillatory time dependent behavior is seen for a large range of spatial modes. When the size of the internal potential is increased, such oscillations persist, but the damping becomes larger. However underdamped motion is present even with quite strong dihedral barriers for long enough wavelengths.

SU-GG-T-225: Gantry-Angle Dependence of a 2D Ion Chamber Array for IMAT QA

Purpose: Gantry‐angle dependence of dose measurement for intensity‐modulated arc therapy (IMAT) quality assurance (QA) using a two‐dimensional ion chamber array may be significant. A new device, the gantry angle sensor, has been provided to compensate for this dependence. However, the default correction factors (CF) assume that the ion chamber angular response is symmetrical, uniform across all chambers, and independent of field size. Our goal was to test these three assumptions, and verify the use of the default CF. Method and Materials: The Matrixx ion chamber array (IBA Dosimetry, Inc.) was irradiated every 5° gantry rotation with a 27×27cm2 static field. The central ion chamber CF = calculation/measurement. To test the asymmetry, dose was delivered over 360°, and compared for symmetrical angles. To test for chamber response uniformity, CFs for off‐axis chambers were calculated and compared to the central ion chamber. To test for field size dependence, the dose delivery was repeated with 10×10cm2 and 2×2cm2 fields, and the central ion chamber CF recalculated. Results: The measured chamber response is asymmetrical with gantry angle. The median difference between the default and measured central ion chamber CFs is 1.2% (range: −0.3%–8.5%) from Gantry 0–180°, and 2.9% (range: 0.7%–7.6%) from Gantry 180–360°. The asymmetry appears to arise from both the device itself (median 1.4%, range 0.1%–3.4%) and from the device holder (median 1.7%, range 0.5%–4.8%). The central‐axis and peripheral CFs varied by up to 10%. There was no observed field size dependence at 10×10cm2, but differences of up to 4.7% were seen with the 2×2cm2 field.Conclusion: The CF table for gantry angle dependence of an ion chamber array should account for asymmetry, nonuniformity of chamber response, and field size effect for small fields. Clinics are recommended to verify their own CFs.

Entanglement of photons due to nonlinear optical response of quantum wells

We show that many-body correlations among excitons originating from the Pauli exclusion principle in a quantum well embedded inside a microcavity provide a possibility to produce pairs of entangled photons by ultrashort laser pulses with a yield of $\sim 10^{-2}$. The quantum-field theoretical two-particle density matrix in second quantization is used to calculate entanglement for arbitrary emission angles. %At time scales where the heavy-light hole splitting is resolved the resonances corresponding to different two-exciton %states develop, which allow for a simple kinematic theory relating the %states of the outgoing photons with the respective two-exciton states. Largest response can be expected at symmetric emission angles for resonances with the heavy-heavy and light-light two-exciton states with remarkably nontrivial dependence of entanglement on the emission angles and on the ellipticity parameters of the excitation. We show that the angle dependence can be tailored by means of the microcavity. Interestingly, the emitted entangled 2-photon states are always in a triplet state.

Linear stone cutting tests with chisel tools for identification of cutting principles and predicting performance of chain saw machines

Different natural stone quarries are visited for collection of stone samples, determination of geological conditions, specifications and operational conditions of the chain saw machines and recording machine cutting performance with a data acquisition system. The samples are tested with a linear cutting test rig using chisel-type cutting tools with 0°, 15°, 30° and 45° sideways angles at different depths of cut and tool spacings, to determine stone cuttability, cutting characteristics of chain saw machines and effect of unsymmetric and symmetric sideways angles and different cutting patterns on cutting performance (tool forces, specific energy, optimum cutting geometry). A deterministic model is suggested for predicting performance of chain saw machines using the results of linear stone cutting experiments, and the laws of kinematics. The results of experimental studies and in-situ investigations indicate that the cutting action of chain saw machines can be successfully simulated by linear cutting experiments and the suggested model is proven, though requiring some additional study, to be a useful and reliable tool for selection, design, and performance prediction and optimization of chain saw machines.

Charles Crussard's early contributions: Recrystallization in situ and a Grain Boundary study with J. Friedel and B. Cullity

Abstract Charles Crussard's discovery of what he called Recrystallization in situ in 1944 is compared with what Egon Orowan and Robert Cahn named Polygonization. The context of the previous research is recalled in order to show the novelty of these contributions. Progress in accurate deformation and observation techniques such as tensile machines and X-ray methods were important, as were theoretical models about plausible microscopic mechanisms. With Jacques Friedel and Barney Cullity, Ch. Crussard also wrote a pioneering article on grain boundaries, which contains an experimental study of the relative energies of both symmetrical and asymmetrical grain boundaries observed in aluminium together with the first atomistic calculation of energies of symmetrical low and high angle tilt boundaries in several metals. This less well-known contribution is also recalled.

Analysis for Transverse Sensitivity of the Microaccelerometer

For the microaccelerometer, strong axial response and weak cross-axial one are always expected. This paper presents a general analysis about transverse sensitivity of the microaccelerometer. The analysis model is developed, where the influence of response stiffness and damping in different axes, as well as symmetrical decline angles of 3 degrees of freedom system is considered. Moreover, multi-freedom vibration equations based on the analysis model are established. And the equations are solved on condition that damping force is ignored. Finally, the theoretical analysis about transverse sensitivity is accomplished, and some effective methods, which are beneficial to reduce cross disturbance, are provided.

Meniscus and viscous forces during separation of hydrophilic and hydrophobic surfaces with liquid-mediated contacts

Adhesion due to the formation of meniscus bridges has been of interest since the early 20th century. Extensive studies have been carried out analytically and numerically. Adhesive or repulsive forces contributed by meniscus and adhesive viscous forces can be significant and become one of the main reliability issues when the contacting surfaces are smooth and/or when the normal load is small, as is common for micro/nanodevices. Previous numerical studies mainly focus on static meniscus analysis for hydrophilic surfaces. More recently, analysis of meniscus and viscous forces during separation of both hydrophilic and hydrophobic surfaces with symmetric and asymmetric contact angles have been carried out. These studies are useful to understand the relative roles of meniscus and viscous forces during the separation process. In this paper, a comprehensive review of analytical and numerical modeling of the meniscus and viscous forces are presented. The analyses for both forces during normal and tangential separation of hydrophilic and hydrophobic smooth or rough surfaces with symmetric and asymmetric contact angles, and viscous forces during tangential separation are presented. The analyses provide a fundamental understanding of the physics of the separation process and insight into the relationships between meniscus and viscous forces. Implications of these analyses in macro/micro/nanotechnologies are discussed.

Vibrational Spectroscopic Study on Ion Solvation and Ion Association of Lithium Tetrafluoroborate in 4‐Ethoxymethyl‐ethylene Carbonate

AbstractSolvation and association interactions in solutions of lithium tetrafluoroborate/4‐ethoxymethyl‐ethylene carbonate (EEC) have been studied as a function of concentration of lithium tetrafluoroborate by infrared and Raman spectroscopy. Strong interactions between Li+ and solvent molecules or BF4− anions were observed. Splitting of the ring symmetric angle deformation band, the carbonyl stretching band and the skeletal ring vibrational band suggests that the interaction between Li+ ions and EEC molecules take place via the oxygen atom on the carbonyl group. The apparent solvation numbers of Li+, varying from 4.32 to 1.26 with increasing the solution concentrations, were deduced. Band‐fitting to the B–F stretching band of BF4− anion permits detailed assess of ion pairing. The spectroscopically free BF4− anion, contact ion pair and contact ion dimmers coexist in concentrated solutions.