Favorable Angle Research Articles

Stable 2D magnetotelluric strikes and impedances via the phase tensor and the quadratic equation

A combination of the magnetotelluric phase tensor and the quadratic algorithm provides a fast and simple solution to the problem of a 2D impedance tensor distorted by 3D electrogalvanic effects. The strike direction is provided by the phase tensor, which is known to provide unstable estimates for noisy data. We obtain stable directions in three steps. First, we use bootstrapping to find the most stable estimate among the different periods. Second, this value is used as the seed to select the neighbor strikes assuming continuity over periods. This second step is repeated several times to compute variances. The third step, which we call prerotating, consists of rotating the original impedance tensor to a most favorable angle for optimal stability and then rotating it back for compensation. The procedure is developed as a progressing algorithm through its application to the gradually more difficult data sets COPROD2S1, COPROD2, far-hi, and BC87, all available for testing new ideas. Alternately, using the Groom-Bailey terminology, the quadratic algorithm provides the amplitudes and phases independently of the strike direction and twist. The amplitudes and phases still need to be tuned up by the correct shear. The correct shear is obtained by contrasting the phases from the phase tensor and from the quadratic equation until they match for all available periods. The results are the undistorted impedances. Uncertainties are computed using formulas derived for the quadratic equation. We use the same data sets as for the strike to illustrate the recovery of impedances and their uncertainties.

Nodal Arrangement of HOMO Controls the Turning On/Off the Electronic Coupling in Isomeric Polypyrene Wires

The charge transfer along π-conjugated wires is largely governed by the interchromophoric electronic coupling that depends on the geometry (e.g., interchromophoric dihedral angle) and electronic structure of the chromophores. Herein, we demonstrate that stabilization of the cationic charge (hole) in polypyrene cation radicals and the extent of hole delocalization can be easily controlled by modulating the nodal arrangement of the HOMO. For example, 2,2′-linked para-polypyrenes show nonexistent electronic coupling owing to a nodal arrangement of HOMO that is unfavorable for orbital overlap, despite a favorable interchromophoric dihedral angle. A repositioning of the linkage between two pyrenes from para to meta positions produces a far less favorable interchromophoric dihedral angle, yet the electronic coupling turns on due to a favorable nodal arrangement of HOMO, which allows interchromophoric orbital overlap. This surprising finding has been demonstrated through the synthesis and systematic examination ...

Biomechanical Evaluation of Different Plating Methods Used in Mandibular Angle Fractures With 3-Dimensional Finite Element Analysis: Favorable Fractures

The aim of the present study was to evaluate the performances of 5 different plating techniques for fixation of favorable mandibular angle fractures using the 3-dimensional finite element analysis (FEA) method. Five different miniplate placement configurations were considered for the fixation of favorable mandibular angle fractures. The following models were created: a double parallel miniplate (M1) placed at the halfway point of the mandibular angle height; a one-third superior-positioned miniplate (M2); a single miniplate (M3) placed at the halfway point of the mandibular angle height (one-half middle-positioned); a one-third inferior-positioned miniplate (M4); and an X-shape miniplate (M5). The M1 and M4 miniplates showed the lowest mechanical stress compared with the other configurations, whereas the M3 and M5 miniplates showed the highest stress levels. For favorable mandibular angle fractures, the authors suggest the M1 miniplate or, if used alone, the M4 miniplate is adequate for rigid fixation.

The magnitude and distribution pattern of stress on implant, teeth, and periodontium under different angulations of implant placement for en masse retraction: A finite element analysis

Context: This study was undertaken to evaluate the magnitude of reactionary stresses and their pattern of distribution on implant, teeth, cortical bone, cancellous bone, and periodontal ligament (PDL) so as to determine the most favorable angle for the placement of mini implant and the most favorable force system for en masse retraction. Aims: The aim of this study is to obtain the ideal force system for en masse retraction using mini implant and to determine most favorable angle for implant insertion. Materials and Methods: DENTASCAN was used to fabricate a three-dimensional finite element model of the maxilla. Three models were constructed with different implant angulations, i.e., 45°, 60°, and 75°. Each model was applied 150, 200, 250, and 300 g of load. The results were analyzed using ANSYS software. Results: Maximum stress was observed at the head of implant at the point of attachment with the retraction spring. In cortical bone and cancellous bone, stress was distal to bone-implant interface. In PDL, maximum stress developed at the apex of lateral incisor root. Conclusion: For en masse retraction, the most favorable angulations for implant placement are 60°, and ideal force system is in the range of 200–250 g. Force levels above 300 g will possibly produce deleterious effects on PDL, cancellous bone, and teeth.

Steady-state numerical modeling of size effects in micron scale wire drawing

Wire drawing processes at the micron scale have received increased interest as micro wires are increasingly required in electrical components. It is well-established that size effects due to large strain gradient effects play an important role at this scale and the present study aims to quantify these effects for the wire drawing process. Focus will be on investigating the impact of size effects on the most favourable tool geometry (in terms of minimizing the drawing force) for various conditions between the wire/tool interface. The numerical analysis is based on a steady-state framework that enables convergence without dealing with the transient regime, but still fully accounts for the history dependence as-well as the elastic unloading. Thus, it forms the basis for a comprehensive parameter study. During the deformation process in wire drawing, large plastic strain gradients evolve in the contact region. This creates a need for a higher order plasticity theory to accurately predict the material behaviour across the multiple scales involved. The present study reveals that the contribution from an energetic (recoverable) length parameter is limited, while the corresponding dissipative contribution dominates and tends to shift the drawing force to a higher level. As a direct consequence, the strain gradient hardening effect reduces the most favourable tool angle of a sharp tool with up to 50% (in terms of the required drawing force), whereas a circular shaped tool is proven less sensitive to scaling effects. By considering the contact force profile between tool and material it becomes clear that the strain gradients have a smoothing effect and both the magnitude and position of the peak pressure are affected significantly. A round tool is found to reduce the peak force, while the location of the peak is found to move from outlet to inlet depending on the tool geometry.

Endoscopic transorbital route to the cavernous sinus through the meningo-orbital band: a descriptive anatomical study.

OBJECTIVE Exposure of the cavernous sinus is technically challenging. The most common surgical approaches use well-known variations of the standard frontotemporal craniotomy. In this paper the authors describe a novel ventral route that enters the lateral wall of the cavernous sinus through an interdural corridor that includes the removal of the greater sphenoid wing via a purely endoscopic transorbital pathway. METHODS Five human cadaveric heads (10 sides) were dissected at the Laboratory of Surgical NeuroAnatomy of the University of Barcelona. To expose the lateral wall of the cavernous sinus, a superior eyelid endoscopic transorbital approach was performed and the anterior portion of the greater sphenoid wing was removed. The meningo-orbital band was exposed as the key starting point for revealing the cavernous sinus and its contents in a minimally invasive interdural fashion. RESULTS This endoscopic transorbital approach, with partial removal of the greater sphenoid wing followed by a "natural" ventral interdural dissection of the meningo-orbital band, allowed exposure of the entire lateral wall of the cavernous sinus up to the plexiform portion of the trigeminal root and the petrous bone posteriorly and the foramen spinosum, with the middle meningeal artery, laterally. CONCLUSIONS The purely endoscopic transorbital approach through the meningo-orbital band provides a direct view of the cavernous sinus through a simple and rapid means of access. Indeed, this interdural pathway lies in the same sagittal plane as the lateral wall of the cavernous sinus. Advantages include a favorable angle of attack, minimal brain retraction, and the possibility for dissection through the interdural space without entering the neurovascular compartment of the cavernous sinus. Surgical series are needed to demonstrate any clinical advantages and disadvantages of this novel route.

Joint direction finding and array calibration method for MIMO radar with unknown gain phase errors

A novel method for joint direction finding and array calibration in multiple-input multiple-output (MIMO) radar with unknown array gain phase errors is proposed. The transmit array and receive array are innovatively arranged along different axes, which are orthogonal to each other. After the trilinear decomposition, the influenced transmit direction matrix and receive direction matrix are combined to estimate the angles, and the gain phase errors can be calculated subsequently. The proposed algorithm is suitable for both uniform linear array (ULA) and non-ULA, and it can achieve favourable angle and gain phase errors estimation without any auxiliary sensors and any information of the gain phase errors. Furthermore, it has better estimation performance and lower complexity than the eigenstructure method. Simulation results verify the usefulness of the approach.

The arc characteristics of cold metal transfer welding with AZ31 magnesium alloy wire

The arc characteristics of cold metal transfer (CMT) welding with AZ31 magnesium alloy wire were investigated. A high-speed CCD camera and an electrical signal acquisition system were used to obtain welding arc images and electrical signals respectively. For DC-CMT, stable welding process could be achieved when wire feed speed (WFS) was no more than 5m/min and for pulsed-CMT, WFS should be no more than 4m/min. The welding arc was formed between weld pool and molten droplet and exhibited as an asymmetrical bell shape. Evaporation of molten droplet gave itself a recoil force, pushing it away from wire axis. At mid to upper power range, repelled droplet transfer process was observed. Molten droplets deviated from wire axis and detached from wire tip under the influence of the recoil force of droplet evaporation, falling outside the weld pool and compromising arc stability. The WFS of 4m/min under pulsed-CMT mode could gain good clad appearance and a favorable contact angle, which could be capable of realizing multi-pass cladding of magnesium alloys.

The southern hemisphere of 67P/Churyumov-Gerasimenko: Analysis of the preperihelion size-frequency distribution of boulders ≥7 m

We calculate the size-frequency distribution of the boulders on the southern hemisphere of comet 67P Churyumov-Gerasimenko (67P), which was in shadow before the end of April 2015. We compare the new results with those derived from the northern hemisphere and equatorial regions of 67P, highlighting the possible physical processes that lead to these boulder size distributions. Methods. We used images acquired by the OSIRIS Narrow Angle Camera (NAC) on 2 May 2015 at a distance of 125 km from the nucleus. The scale of this dataset is 2.3 m/px; the high resolution of the images, coupled with the favorable observation phase angle of 62◦, provided the possibility to unambiguously identify boulders ≥7 m on the surface of 67P and to manually extract them with the software ArcGIS. We derived the size-frequency distribution of the illuminated southern hemisphere. Results. We found a power-law index of −3.6 ± 0.2 for the boulders on the southern hemisphere with a diameter range of 7−35 m. The power-law index is equal to the one previously found on northern and equatorial regions of 67P, suggesting that similar boulder formation processes occur in both hemispheres. The power-law index is related to gravitational events triggered by sublimation and/or thermal fracturing causing regressive erosion. In addition, the presence of a larger number of boulders per km2 in the southern hemisphere, which is a factor of 3 higher with respect to the northern hemisphere, suggests that the southernmost terrains of 67P are affected by a stronger thermal fracturing and sublimating activity, hence possibly causing larger regressive erosion and gravitational events.

Performance Analysis of Centroid and SVD Features for Personnel Recognition Using Multistatic Micro-Doppler

In this letter, we investigate the use of micro-Doppler signatures experimentally recorded by a multistatic radar system to perform recognition of people walking. Three different sets of features are tested, taking into account the impact on the overall classification performance of parameters, such as aspect angle, types of classifier, different values of signal-to-noise ratio, and different ways of exploiting multistatic information. High classification accuracy of above 98% is reported for the most favorable aspect angle, and the benefit of using multistatic data at less favorable angles is discussed.

First evidences for 19F(α, p)22Ne at astrophysical energies

19F experimental abundances is overestimated in respect to the theoretical one: it is therefore clear that further investigations are needed. We focused on the 19F(α, p)22 Ne reaction, representing the main destruction channel in He-rich environments. The lowest energy at which this reaction has been studied with direct methods is EC.M. ≈ 0.91 MeV, while the Gamow region is between 0.39 ÷ 0.8 MeV, far below the Coulomb barrier (3.8 MeV). For this reason, an experiment at Rudjer Boskovic Institute (Zagreb) was performed, applying the Trojan Horse Method. Following this method we selected the quasi-free contribution coming from 6Li(19F,p22 Ne)2 H at Ebeam=6 MeV at kinematically favourable angles, and the cross section at energies 0 < EC.M. < 1.4 MeV was extracted in arbitrary units, covering the astrophysical region of interest.

Navigation-based tibial rotation at 90° of flexion is associated with better range of motion in navigated total knee arthroplasty.

In clinical practice, people with better femorotibial rotation in the flexed position often achieve a favourable postoperative maximum flexion angle (MFA). However, no objective data have been reported to support this clinical observation. In the present study, we aimed to investigate the correlation between the amount of intraoperative rotation and the pre- and postoperative flexion angles. Fifty-five patients with varus osteoarthritis undergoing computer-assisted posterior-stabilized total knee arthroplasty (TKA) were enrolled. After registration, rotational stress was applied towards the knee joint, and the rotational angles were recorded by using a navigation system at maximum extension and 90° of flexion. After implantation, rotational stress was applied for a second time, and the angles were recorded once more. The MFA was measured before surgery and 1month after surgery, and the correlation between the amount of femorotibial rotation during surgery and the MFA was statistically evaluated. Although the amount of tibial rotation at maximum extension was not correlated with the MFA, the amount of tibial rotation at 90° of flexion after registration was positively correlated with the pre- and postoperative MFA (both p<0.005). However, no significant relationship was observed between the amount of tibial rotation after implantation and the postoperative MFA (n.s.). The results showed that better femorotibial rotation at 90° of flexion is associated with a favourable postoperative MFA, suggesting that the flexibility of the surrounding soft tissues is an important factor for obtaining a better MFA, which has important clinical relevance. Hence, further evaluation of navigation-based kinematics during TKA may provide useful information on MFA. Diagnostic studies, development of diagnostic criteria in a consecutive series of patients, and a universally applied "gold" standard, Level II.

Influence of crack surface friction on crack initiation and propagation: A numerical investigation based on extended finite element method

Rock strengths are directly influenced by the open or closed flaws widely distributed in rock masses. Extensive studies have been conducted on the propagations of open flaws in rocks. However, few concerns are paid on the propagation of closed flaws, the influence of the surface friction on the initiation and propagation of closed flaws should be investigated systematically. In present article, the crack initiation and propagation in rock like material subjected to compressive loads have been investigated. The effects of crack surface friction on crack initiation and propagation have been quantified with the help from extended finite element method which is efficient and accurate. Based on the analysis on stress distribution and propagation patterns, following results are obtained: Firstly, minor effects are exerted by crack surface friction on the stress distribution around the flaws when the flaws inclination angle is 30° and 45°. However, as the inclination angle increases to 60°, the effects are much more significant. Secondly, as the inclination angle ranges from 30° to 60°, the most favorable angle for crack propagation is 45°. Thirdly, the initiation location and angle of the wing cracks will not be influenced by the frictions. However, the propagation length will be greatly influenced by the friction and the inclination angle.

Optimal input cross-power spectra in shake table testing of asymmetric structures

The study considers earthquake shake table testing of bending-torsion coupled structures under multi-component stationary random earthquake excitations. An experimental procedure to arrive at the optimal excitation cross-power spectral density (psd) functions which maximize/minimize the steady state variance of a chosen response variable is proposed. These optimal functions are shown to be derivable in terms of a set of system frequency response functions which could be measured experimentally without necessitating an idealized mathematical model to be postulated for the structure under study. The relationship between these optimized cross-psd functions to the most favourable/least favourable angle of incidence of seismic waves on the structure is noted. The optimal functions are also shown to be system dependent, mathematically the sharpest, and correspond to neither fully correlated motions nor independent motions. The proposed experimental procedure is demonstrated through shake table studies on two laboratory scale building frame models.

Feasibility of endovascular repair of splenic artery aneurysms using stent grafts

Percutaneous transcatheter embolization of splenic artery aneurysms (SAAs) has been widely accepted as the first line of treatment in patients with symptoms, rupture, or large aneurysm size. Although embolization can usually be performed safely, ischemic complications, such as splenic infarct or abscess, occur in some patients. This study evaluated the feasibility and outcomes of endovascular SAA repair (ESAAR) using stent grafts, which may allow treatment while preserving flow to the spleen. We reviewed the clinical data of all consecutive patients who underwent ESAAR using stent grafts. Brachial access was used except for patients with favorable angle of origin from the aorta. To overcome tortuosity and provide support, a coaxial system with a hydrophilic sheath was used. Low-profile 0.018-inch stent grafts were used for distal SAAs with a 10-mm to 15-mm length of proximal and distal segment of splenic artery measuring 4 to 11 mm in diameter. Follow-up included clinical examination and computed tomography imaging within 4 to 6 months after the procedure and yearly thereafter. End points were morbidity, stent graft patency, and freedom from endoleaks and reinterventions. ESAAR was attempted in 10 patients, four males and six females, with median age of 64 years (range, 48-77 years). Median SAA size was 2.8 cm (range, 2-5.7 cm). Nine patients were asymptomatic, and one had pancreatitis and gastrointestinal bleeding. The arterial access site was the brachial artery in six patients and the femoral artery in four. Two patients had brachial and femoral access to facilitate splenic artery stenting. Technical success of ESAAR using stent grafts was 80% (8 of 10). In two patients with distal SAAs, stent graft placement was not possible due to excessive vessel tortuosity, and treatment was by coil embolization. One patient developed brachial artery thrombosis, which was treated surgically. There were no ischemic complications in patients treated by ESAAR with stent grafts. Median length of stay was 1 day. One patient treated by coil embolization developed splenic infarct, which required readmission for pain control. Median follow-up was 9 months. Follow-up imaging in all successfully stented patients revealed patent stent grafts, no endoleak, and no aneurysm sac enlargement. No reinterventions were required. ESAAR using self-expandable stent grafts offers a viable alternative to coil embolization in selected patients with SAAs. Distal SAAs with excessive vessel tortuosity may result in technical failure requiring embolization. Among patients who underwent successful ESAAR, there were no ischemic complications, stent graft occlusions, endoleaks, or sac enlargement.

Lateral Tibiocalcaneal Angle As a Determinant for Percutaneous Achilles Tenotomy for Idiopathic Clubfeet.

The aim of the present study was to evaluate the clinical value of using the lateral tibiocalcaneal (LTiC) angle, measured on a lateral radiograph made with the foot and ankle in maximal dorsiflexion, instead of the ankle dorsiflexion (ADF) angle, measured on physical examination, as a determining indicator of the need for percutaneous Achilles tenotomy after Ponseti serial cast treatment of idiopathic clubfoot. We identified patients with idiopathic clubfoot who had been treated at our institution between March 2006 and June 2012. After exclusion of patients with Diméglio grade-I clubfoot and those followed for less than two years, 125 idiopathic clubfeet were evaluated. The clubfeet were grouped according to their LTiC and ADF angles, after which we evaluated the clinical outcomes of each group and investigated the prognostic effects of each angle-based decision regarding whether to perform percutaneous Achilles tenotomy. Patients with a favorable LTiC angle (≤80°) showed no sagittal relapse even though none underwent percutaneous Achilles tenotomy. In contrast, patients with an unfavorable LTiC angle (>80°) had a high chance of sagittal relapse if percutaneous Achilles tenotomy had not been performed, even when they had a favorable ADF angle (≥15°). The LTiC-angle-based decision showed the most significant prognostic value in multivariate analyses of relapse-free and surgery-free survival rates. The LTiC angle measured on simple radiographs is a more objective and prognostic indicator of the need for percutaneous Achilles tenotomy, as compared with the ADF angle measured on physical examination, in patients with idiopathic clubfoot. Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Interfacial Tension Dependence on Nanoparticle Surface Modification for Stabilization of CO&lt;sub&gt;2 &lt;/sub&gt;Foam in EOR: An Overview

Foam Flooding have been suggested to replace gas injection in Enhanced Oil Recovery (EOR) method since it will improve the volumetric sweep efficiency due to its low mobility. This paper aims to review on the relationship of Interfacial Tension (IFT) of the CO2foams and nanoparticle surface modification. Generally, in foam flooding technique, surfactant is used to stabilize the CO2foams. However, the concern about the stability of the surfactant-stabilized CO2foam has been rising due to high surfactant adsorption on the rock surface and they also tend to degrade at high temperature. Hence, nanoparticle has been introduced to generate more stable CO2foam by adsorption of nanoparticles at the fluid-fluid interface. Based on the review, the stability of CO2foam generated by nanoparticles is due to the strong adhesion energy at the fluid-fluid interface where the interfacial tension between aqueous phase and CO2gas phase inside the foam is one of the key parameter. It also has been identified that the main factors that influenced the interfacial tension at the fluid-fluid interface are the nanoparticles concentration and the degree of hydrophilicity of nanoparticles. The correct amount of nanosolid particles present at the fluid-fluid interface and the optimum degree of hydrophilicity with favorable contact angles less than 90 degree will increase the interfacial tension that lead to increase in adhesion energy and high stability foam can be generated.

Development and Testing of a Passive Variable-Pitch Propeller

A novel approach to passive propeller blade pitch variation is investigated. To effect passive pitch changes, the propeller blades are allowed to pivot freely about a radial axis, and aerodynamic pitching moments are tailored to give favorable blade pitch angles over a wide range of advance ratios. Computational modeling of the system indicated that a large expansion of the efficient operating envelope is possible, compared to a fixed-pitch propeller. Wind-tunnel experiments corroborated the computational results and demonstrated that the propeller maintained near-peak efficiency by passively adjusting blade pitch angles by over 15 deg to the match changing advance ratio. The passive variable-pitch propeller was then successfully demonstrated in flight on an unmanned aerial vehicle. Using tailored aerodynamics in place of active control allows this performance improvement to be realized at a fraction of the weight and complexity of a traditionally actuated variable-pitch propeller. The concept enables the benefits to be realized on platforms for which a traditional constant-speed variable-pitch propeller is not viable, such as on small general aviation aircraft or on unmanned platforms.

Biomechanical Comparison of 2 Different Pedicle Screw Systems During the Surgical Correction of Adult Spinal Deformities

Study DesignA biomechanical spine model was used to evaluate the impact of screw design on screw–vertebra interface loading during simulated surgical corrections of adult scoliosis. ObjectivesTo evaluate differences in screw–vertebra interface forces during adult scoliosis correction between favored angle (FA) screws with extension tabs and standard polyaxial screws while varying deformity severity and curve rigidity. Summary of Background DataPedicle screws enable surgeons to safely and effectively realign spinal deformities. The risk of perioperative screw pullout increases when presented with adult deformities that have less flexible spines and lower bone mineral density. An FA screw with reduction tabs is believed to enable surgical techniques permitting load distribution on multiple screws, thereby reducing screw pullout potential. MethodsThe researchers constructed 3 finite element spine models from adult scoliosis patients. Mechanical properties of intervertebral discs were modeled to reflect less flexible adult spines and their stiffness was varied to evaluate impact on screw–vertebra forces. Models simulated scoliosis surgery according to clinical data using FA or polyaxial screws. Forces measured at the screw–vertebra interface were monitored and compared for each patient with FA and then polyaxial screws. ResultsSimulations using FA screws reduced screw–vertebra interface forces significantly compared with polyaxial screws. Favored angle screws caused 18%, 14%, and 16% reductions in peak forces and 29%, 35%, and 22% reductions in average forces compared with polyaxial screws for patients 1, 2, and 3, respectively. Favored angle screws also provided consistent relative reduction in average forces by 28% when varying properties of intervertebral discs among 8, 10, and 12 MPa. ConclusionsUsing a virtual finite element platform, FA screws reduced screw–vertebra interface forces encountered during simulated correction of less flexible adult scoliosis compared with standard polyaxial screws. These results show a potential benefit of using this modified screw design to reduce screw–vertebra forces and potential intraoperative pullout failures.

Influence of sperm impact angle on successful fertilization through mZP oscillatory spherical net model

According to the available literature, penetrating sperm creates an oblique path trough Zona pellucida (ZP) – the most outer surface of oocytes. Considering fertilization process as an oscillatory phenomenon, the influence of sperm impact angle relative to the oscillatory behavior of mouse ZP is described by using the discrete continuum mechanical model in the form of a spherical net model.A parametric frequency analysis of oscillatory behavior of knot material particles in the mouse ZP (mZP) spherical net model is conducted by using generalized Lussajous curves. The influence of impact angles of sperm cells on the corresponding knot mass particles’ resultant trajectory is discussed. Favorable sperm impact angles for successful fertilization are identified.