Pitch Rotation Research Articles

Quantifying the Sensitivity of Target Dose on Intrafraction Displacement in Intracranial Stereotactic Radiosurgery

PurposeMask-immobilized stereotactic radiosurgery (SRS) using a gating window is an emerging technology. However, the amount of intracranial tumor motion that can be tolerated during treatment while satisfying clinical dosimetric goals is unknown. The purpose of this study was to quantify the sensitivity of target dose to tumor motion. Methods and MaterialsIn clinical SRS plans, where a nose marker was tracked as surrogate for target motion, translational and rotational target movements were simulated using nose-marker displacements of ±0.5 mm, ±1.0 mm, or ±1.5 mm. The effect on minimum dose to 99% of the target (D99) and percent target coverage by prescription dose was quantified using mixed-effect modeling with variables: displacement, target volume, and location. ResultsThe effect on dose metrics is statistically larger for translational displacements compared with rotational displacements, and the effect of pitch rotations is statistically larger compared with yaw rotations. The mixed-effect model for translations showed that displacement and target volume are statistically significant variables, for rotation the variable target distance to rotation axis is additionally significant. For mean target volume (12.6 cc) and translational nose-marker displacements of 0.5 mm, 1.0 mm, and 1.5 mm, D99 decreased by 2.2%, 7.1%, and 13.0%, and coverage by 0.4%, 1.8%, and 4.4%, respectively. For mean target volume, mean distance midpoint-target to pitch axis (7.6cm), and rotational nose-marker displacement of 0.5 mm, 1.0 mm, and 1.5 mm, D99 decreased by 1.0%, 3.6%, and 6.9%, and coverage by 0.2%, 0.8%, and 1.9%, respectively. For rotational yaw axis displacement, mean distance midpoint-target axis (4.2cm), D99 decreased by 0.3%, 1.2%, and 2.5%, and coverage by 0.1%, 0.2%, and 0.5%, respectively. ConclusionsSimulated target displacements showed that sensitivity of tumor dose to motion depends on both target volume and target location. Suggesting that patient- and target-specific thresholds may be implemented for optimizing the balance between dosimetric plan accuracy and treatment prolongation caused by out-of-tolerance motion.

Contrasting thrust generation mechanics and energetics of flapping foil locomotory states characterized by a unified - scaling

Self-propelled flapping foils with distinct locomotion-enabling kinematic restraints exhibit a remarkably similar Strouhal number ( $St$ )-Reynolds number ( $Re$ ) dependence. This similarity has been hypothesized to pervade diverse forms of oscillatory self-propulsion and undulatory biolocomotion; however, its genesis and implications on the energetic cost of locomotion remain elusive. Here, using high-resolution simulations of translationally free and restrained foils that self-propel as they are pitched, we demonstrate that a generality in the $St$ - $Re$ relationship can emerge despite significant disparities in thrust generation mechanics and locomotory performance. Specifically, owing to a recoil reaction induced passive heave, the fluid's inertial response to the prescribed rotational pitch, the principal source of thrust in unidirectionally free and towed configurations, ceases to produce thrust in a bidirectionally free configuration. Rather, the thrust generated from the leading edge suction mechanics self-propels a bidirectionally free pitching foil. Owing to the foregoing distinction in the thrust generation mechanics, the $St$ - $Re$ relationships for the bidirectionally and unidirectionally free/towed foils are dissimilar and pitching amplitude dependent, but specifically for large reduced frequencies, converge to a previously reported unified power law. Importantly, to propel at a given mean forward speed, the bidirectionally free foil must counteract the out-of-phase passive heave through a more intense rotational pitch, resulting in an appreciably higher power consumption over the range $10 \leq Re \leq 10^3$ . We highlight the critical role of thrust in introducing an offset in the $St$ - $Re$ relation, and through its amplification, being ultimately responsible for the considerable disparity in the locomotory performance of differentially constrained foils.

Pulsed laser deposition of large-sized superlattice films with high uniformity

Oxide superlattices often exhibit emergent physical properties that are desirable for future information device applications. The most common growth technique for fabrication of oxide superlattices is pulsed laser deposition (PLD), which is convenient yet powerful for the growth of various oxide superlattices. However, the sample size prepared by PLD is rather small confined by the plasmon plume, which greatly limits its potential for device applications. Here, we design a PLD system that is capable of fabricating large-sized oxide superlattices with high uniformity. Specifically, during growth, the laser beam scans the target surface by combining the pitch and yaw angle rotation of the high reflective mirror and the linear motion of the focus lens. A SiC susceptor is placed in between the sample holder and the substrate to improve the large area infrared heating efficiency. Using such a system, droplet-free 10 × 10 mm2 [(LSMO)12/(PCMO)6]7 superlattices are epitaxially grown with the same period of superlattices across the whole sample areas. The high uniformity of the superlattices is further illustrated by near identical physical properties of all regions of the superlattice films. The present PLD system can be used to grow various kinds of oxide superlattices with the area size as large as 2 in., which is highly useful for device applications of oxides.

Effect and correction of control delay in longitudinal dynamics of insect hovering flight.

Sensor-to-actuator delay is inevitable in any complex control system, be it one for a free-flying insect or a mimicking insectlike robotic flyer. In this work, we analyze the effects of control delay (latency) on the hovering performance of a model insect flyer, as exemplified by the hummingbird hawkmoth Re∼3000, and determine how control coefficients or gains may be modified to ameliorate the adverse effects of latency. The analyses are based on a simplified or reduced dynamic model of the hovering flyer. The longitudinal dynamics of the hovering flyer comprises the coupled forward (backward) and vertical translations and pitch rotation of the flyer, with kinematical wing actions being governed by proportional-differential (PD) closed-loop control. Keeping to the same PD control coefficients as a stable reference zero-delay case, the flight system becomes overly responsive at a small control delay, eventually diverging when delay approaches around one wing cycle. Stable hovering may be regained for control delay of up to several wingbeats by suitably reducing or softening the PD control coefficients. The results of the analyses are validated by a series of time-based simulations using the simplified dynamic model and a high-fidelity three-dimensional computational fluid dynamics with fluid structure-body interaction model of the hovering flyer. The simulations also show that noncyclic asymptotic oscillations about the mean equilibrium hovering state are enhanced with larger control delay. The analyses and simulations have helped us to gain a better understanding of the effects of control latency in insect free flight, which may be relevant for the design of mimetic insect flyers.

Bioinspired Helicoidal Composite Structure Featuring Functionally Graded Variable Ply Pitch.

Composite laminated materials have been largely implemented in advanced applications due to the high tailorability of their mechanical performance and low weight. However, due to their low resistance against out-of-plane loading, they are prone to generate damage as a consequence of an impact event, leading to the loss of mechanical properties and eventually to the catastrophic failure of the entire structure. In order to overcome this issue, the high tailorability can be exploited to replicate complex biological structures that are naturally optimised to withstand extreme impact loading. Bioinspired helicoidal laminates have been already studied in-depth with good results; however, they have been manufactured by applying a constant pitch rotation between each consecutive ply. This is in contrast to that observed in biological structures where the pitch rotation is not constant along the thickness, but gradually increases from the outer shell to the inner core in order to optimise energy absorption and stress distribution. Based on this concept, Functionally Graded Pitch (FGP) laminated composites were designed and manufactured in order to improve the impact resistance relative to a benchmark laminate, exploiting the tough nature of helicoidal structures with variable rotation angles. To the authors’ knowledge, this is one of the first attempts to fully reproduce the helicoidal arrangement found in nature using a mathematically scaled form of the triangular sequence to define the lamination layup. Samples were subject to three-point bending and tested under Low Velocity Impact (LVI) conditions at 15 J and 25 J impact energies and ultrasonic testing was used to evaluate the damaged area. Flexural After Impact (FAI) tests were used to evaluate the post-impact residual energy to confirm the superior impact resistance offered by these bioinspired structures. Vast improvements in impact behaviour were observed in the FGP laminates over the benchmark, with an average reduction of 41% of the damaged area and an increase in post-impact residual energy of 111%. The absorbed energy was similarly reduced (−44%), and greater mechanical strength (+21%) and elastic energy capacity (+78%) were demonstrated in the three-point bending test.

A Study of Vehicle Vibration with Multiple Degrees of Freedom Using OCTAVE and ANSYS

Vibration vehicle models provide a great opportunity to integrate vehicle-based vibrations into a mechanical engineering vibrations course. This paper documents and discusses an approach to a multiple-degree-of-freedom (MDOF) in regards to pitch and bounce of the vehicle body with dampening and stiffness observed. The approach utilizes hand calculations, OCTAVE, and ANSYS to solve speed-bump induced vibration and to calculate vibrations modes. The problem involves a bicycle-model approach to a vehicle’s response when subject to a speed bump, or a sudden impulse load upon the forward-face of the model. These responses are captured and analyzed on pitch and bounce of the model at the center-of-gravity and the front/rear sides of the model. Graphical models capture responses of the loading conditions and the modal equations of the model providing a method of studying and understanding vibrational responses under provided stiffness. Using ANSYS as an approach of the model to capture damping response, further graphical models can be captured and used to describe motions of the vehicle model’s center-of-gravity, frontward and rearward wheel assembly, and the pitch (rotation) of the center-of-gravity to the introduced responses. A successful study with analysis of each graphical element and further dissemination of the results is concluded.

Three-dimensional evaluation of long-term skeletal relapse following Le Fort I maxillary advancement surgery: a 2-year follow-up study

The aim of this study was to assess relapse following Le Fort I (LFI) maxillary advancement with superior or inferior repositioning at 2 years of follow-up. A total of 50 patients (26 female, 24 male; age range 15–56 years) with skeletal class II or III, who underwent bimaxillary surgery with LFI maxillary advancement in combination with either superior or inferior repositioning and also mandibular advancement/setback, were recruited. Preoperative (T0), immediate postoperative (T1), and 2-year postoperative (T2) cone beam computed tomography scans were acquired. Data were imported into a validated module to assess the skeletal movement (T0–T1) and relapse (T1–T2). Overall, the majority of the translational and rotational movements showed a relapse of <1 mm and <1°. Patients undergoing maxillary advancement with inferior repositioning in combination with mandibular advancement showed the highest amount of translational relapse in a superior (0.86 ± 0.85 mm, P < 0.0001) and posterior direction (−0.65 ± 1.11 mm, P < 0.0001). In relation to patients who received a bone graft, inferior repositioning with mandibular setback showed the highest maxillary relapse in a superior direction (1.20 ± 1.56 mm, P = 0.0719) with counterclockwise pitch rotation (2.15 ± 0.64°, P = 0.3759). Amongst the non-grafted procedures, superior repositioning with mandibular setback exhibited the highest relapse in a medial direction (1.38 ± 2.78 mm, P = 0.3981). Maxillary advancement was found to be a highly stable procedure with a lack of superoinferior stability in patients undergoing inferior repositioning.

Design and validation of an MRI-compatible mechatronic system for needle delivery to localized prostate cancer.

Prostate cancer is the most common non-cutaneous cancer among men in the United States and is the second leading cause of cancer death in American men. (Siegel et al. [2019] CA: A Cancer J Clin.69(1):7-34.) Focal laser ablation (FLA) has the potential to control small tumors while preserving urinary and erectile function by leaving the neurovascular bundles and urethral sphincters intact. Accurate needle guidance is critical to the success of FLA. Multiparametric magnetic resonance images (mpMRI) can be used to identify targets, guide needles, and assess treatment outcomes. The purpose of this work was to design and evaluate the accuracy of an MR-compatible mechatronic system for in-bore transperineal guidance of FLA ablation needles to localized lesions in the prostate. The mechatronic system was constructed entirely of non-ferromagnetic materials, with actuation controlled by piezoelectric motors and optical encoders. The needle guide hangs between independent front and rear two-link arms, which allows for horizontal and vertical translation as well as pitch and yaw rotation of the guide with a 6.0cm range of motion in each direction. Needles are inserted manually through a chosen hole in the guide, which has been aligned with the target in the prostate. Open-air positioning error was evaluated using an optical tracking system (0.25mm RMS accuracy) to measure 125 trajectories in free space. Correction of systematic bias in the system was performed using 85 of the trajectories, and the remaining 40 were used to estimate the residual error. The error was calculated as the horizontal and vertical displacement between the axis of the desired and measured trajectories at a typical needle insertion depth of 10cm. MR-compatibility was evaluated using a grid phantom to assess image degradation due to the presence of the system, and induced force, heating, and electrical interference in the system were assessed qualitatively. In-bore positioning error was evaluated on 25 trajectories. Open-air mean positioning error at the needle tip was 0.80±0.36mm with a one-sided 95% confidence interval of 1.40mm. The mean deviation of needle trajectories from the planned direction was 0.14±0.06∘ . In the MR bore, the mean positioning error at the needle tip was 2.11±1.05mm with a one-sided 95% prediction interval of 3.84mm. The mean angular error was 0.49±0.26∘ . The system was found to be compatible with the MR environment under the specified gradient-echo sequence parameters used in this study. A complete system for delivering needles to localized prostate tumors was developed and described in this work, and its compatibility with the MR environment was demonstrated. In-bore MRI positioning error was sufficiently small for targeting small localized prostate tumors.

Self-Induced Roll–Yaw Oscillations of an Aircraft Model in a Wind Tunnel

Wind tunnel oscillatory testing is a technique conventionally used for the measurement of dynamic aerodynamic loads on subscale aircraft models. Oscillatory testing is commonly used for identification of dynamic stability derivatives for flight mechanics models. Model oscillation is normally driven by a rig drive mechanism, or with the use of its control surfaces. This paper presents a new test technique in which self-induced coupled roll and yaw oscillations are driven purely by the aircraft’s natural modes of motion when constrained in translation and in pitch rotation. This method does not require external mechanisms to drive the motion, nor the use of aircraft control surface inputs to sustain the oscillation. Without these sources of error, it is potentially advantageous for identification of dynamic stability derivatives using parameter estimation techniques. The mechanics of and requirements for this self-induced oscillation are discussed. Computational simulation and dynamic wind tunnel tests of a subscale BAe Hawk model are used to demonstrate the self-induced roll–yaw oscillations and their results are compared. Effects of varying parameters such as wind tunnel speed and the addition of spring stiffness onto the aircraft rotation axes on the frequency and stability of the oscillation are investigated.

A Biomechanical Analysis of Muscle Force Changes After Bilateral Sagittal Split Osteotomy.

A basic procedure affecting maxillofacial geometry is the bilateral sagittal split osteotomy. During the surgery, the bony segments are placed in a new position that provides the correct occlusion. Changes in the geometry of the mandible will affect the surrounding structures and will have a significant impact on the functioning of the masticatory system. As a result of the displacement of the bone segment, the biomechanical conditions change, i.e., the load and the position of the muscles. The primary aim of this study was to determine the changes in the values of the muscular forces caused by mandible geometry alteration. The study considered the translation and rotation of the distal segment, as well as rotations of the proximal segments in three axes. Calculations were performed for the unilateral, static loading of a model based on rigid body mechanics. Muscles were modeled as spring elements, and a novel approach was used to determine muscle stiffness. In addition, an attempt was made, based on the results obtained for single displacements separately, to determine the changes in muscle forces for geometries with complex displacements. Based on the analysis of the results, it was shown that changes in the geometry of the mandibular bone associated with the bilateral sagittal split osteotomy will have a significant effect on the values of the masticatory muscle forces. Displacement of the distal segment has the greatest effect from −21.69 to 26.11%, while the proximal segment rotations affected muscle force values to a less extent, rarely exceeding 1%. For Yaw and Pitch rotations, the opposite effect of changes within one muscle is noticed. Changes in muscle forces for complex geometry changes can be determined with a high degree of accuracy by the appropriate summation of results obtained for simple cases.

A novel CAD/CAM composite occlusal splint for intraoperative verification in single-splint two-jaw orthognathic surgery

BackgroundPrevious computer-generated splints were designed and produced without modification than the traditional occlusal splints, which did not facilitate surgeon's intraoperative judgment in the single-splint two-jaw orthognathic surgery. Modifications of the digital occlusal splint can be achieved using computer-aided design and computer-aided manufacturing (CAD/CAM) software. This study reported the design, clinical application and validation of a novel CAD/CAM occlusal splint. MethodsThe maxillary and mandibular segments were fixed into the final occlusal splint and moved to the planned position according to the 3-dimensional simulation. The composite occlusal splint has 4 orthogonal bars to facilitate intraoperative assessment of the dental and skeletal midline, facial soft tissue midline, occlusal plane, upper tooth show, facial symmetry and facial bone position. To validate the surgical outcome, 5 parameters including pitch, roll and yaw rotations, midline deviation and chin position were measured on the virtual plan and the postoperative cone-beam computed tomography images to quantify the difference. ResultsThe results showed no significant differences in the 5 parameters between the simulation and postoperative images. The root-mean-square difference between the conventional splints and CAD/CAM surgical splint ranged from 0.18 to 0.31 mm by superimposition of the two image models. All patients were satisfied with the treatment outcomes. Overall, this novel occlusal splint is ideal for verification of the maxillomandibular position during surgery. ConclusionThe novel composite occlusal splint provided useful and informative check to verify the maxillomandibular complex (MMC) position and facial appearance in single-splint two-jaw orthognathic surgery.

Kinematic Analysis and Optimal Design of a Novel Schönflies-Motion Parallel Manipulator With Rotational Pitch Motion for Assembly Operations

Abstract This paper presents a novel Schönflies-motion Parallel Manipulator with RotationalPitch motion (SPM-RP) based on a single-platform fully parallel mechanism. An analysis of the position, workspace, velocity, and singularity of the SPM-RP is carried out in detail, and a dimensionless Jacobian is proposed to evaluate the manipulability of the SPM-RP. The analysis shows that the SPM-RP is with position-decoupled kinematics, a large singularity-free workspace, and excellent manipulability. The SPM-RP is actuated by four parallel prismatic actuators, enabling the manipulator to provide the identical kinematic performance at all generic cross sections perpendicular to the prismatic joint axes within its workspace. This paper thus proposes a reduced design optimization formulation, where the traditional optimization over the entire workspace is reduced to the optimization on a representative workspace cross section of the SPM-RP. According to this approach, the design optimization of the SPM-RP is carried out by maximizing its manipulability over the total orientation workspace, which is crucial for precision assembly. Based on the achieved optimal design, an SPM-RP prototype is developed. The mobility, orientation capability, total orientation workspace, and repeatability of the optimal design are tested and verified by the developed SPM-RP prototype. Experiments show that the SPM-RP can achieve a large total orientation workspace with excellent precision performance.

Assessment of setup errors of IGRT combined with a six degrees of freedom bed for patients with primary rectal cancer

Objective: To investigate the effect of six degree of freedom (6-DOF) bed combined with cone beam computed tomography (CBCT) in the on-line correction of setup errors in patients with primary rectal cancer. Methods: The clinicopathological data of 17 patients with primary rectal cancer in Department of Radiotherapy, Third Hospital of Peking University from July 2013 to January 2014 were collected. There were 14 males and 3 females, a median age of 65 years. The difference of CBCT and 6-DOF bed combined with CBCT online correction of patients with positioning error were retrospectively analyzed. Results: Before position correction, the first CBCT verification of setup errors in the three translation directions including X (left and right), Y (in and out) and Z (up and down) directions were (0.06±0.25) cm, (0.13±0.40) cm and (-0.28±0.31) cm, respectively. The setup errors of RX (rotation pitch), RY(rolling) and RZ (left and right rotation) directions were (0.62±1.15)°, (-0.19±0.99)°, and (-0.34 ± 0.84)°, respectively . After correction of IGRT combined with six freedom of bed, the setup errors of translation X, Y and Z were (0.01±0.09) cm, (-0.01±0.05) cm and (-0.03±0.08) cm, respectively, and the setup errors of rotation RX, RY and RZ directions were (-0.16±0.40)°, (0.36±0.31)°and (-0.01±0.25)°, respectively. There were significant differences in translation direction (X, Y and Z direction) and rotation direction (Rx, RY and RZ) before and after 6-DOF bed combined with CBCT correction (all P<0.05). In the translation direction, the higher frequency range of Z-direction error value was 0.20-0.79 cm. In the rotation direction, the frequency range of error in Rx direction was 0.20°-2.99°. There was no significant difference between bone mode and gray scale model registration (P>0.05). With the progress of radiotherapy, the setup errors of X, Z, Rx, RY and RZ directions increased except Y direction. Conclusions: In radiotherapy, six freedom bed combined with CBCT is helpful to correct the setup errors of patients with primary rectal cancer. Six freedom bed may be used to correct the setup errors of patients with primary rectal cancer online. Image-guided radiation therapy (IGRT) is recommended for bone pattern registration in patients with rectal cancer.

Enhanced trajectory estimation of mobile laser scanners using aerial images

Multipath effects and signal obstruction by buildings in urban canyons can lead to inaccurate GNSS measurements and therefore errors in the estimated trajectory of Mobile Laser Scanning (MLS) systems; consequently, derived point clouds are distorted and lose spatial consistency. We obtain decimetre-level trajectory accuracy making use of corresponding points between the MLS data and aerial images with accurate exterior orientations instead of using ground control points. The MLS trajectory is estimated based on observation equations resulting from these corresponding points, the original IMU observations, and soft constraints on the pitch and yaw rotations of the vehicle. We analyse the quality of the trajectory enhancement under several conditions where the experiments were designed to test the influence of the number and quality of corresponding points and to test different settings for a B-spline representation of the vehicle trajectory. The method was tested on two independently acquired MLS datasets in Rotterdam by enhancing the trajectories and evaluating them using checkpoints. The RMSE values of the original GNSS/IMU based Kalman filter results at the checkpoints were 0.26 m, 0.30 m, and 0.47 m for the X-, Y- and Z-coordinates in the first dataset and 1.10 m, 1.51 m, and 1.81 m in the second dataset. The latter dataset was recorded with a lower quality IMU in an area with taller buildings. After trajectory adjustment these RMSE values were reduced to 0.09 m, 0.11 m, and 0.16 m for the first dataset and 0.12 m, 0.14 m, and 0.18 m for the second dataset. The results confirmed that, if sufficient tie points between the point cloud and aerial imagery are available, the method supports geo-referencing of MLS point clouds in urban canyons with a near-decimetre accuracy.

Clinical concordance with Image Gently guidelines for pediatric computed tomography: a study across 663,417 CT scans at 53 clinical facilities.

Managing patient radiation dose in pediatric computed tomography (CT) examinations is essential. Some organizations, most notably Image Gently, have suggested techniques to lower dose to pediatric patients and mitigate risk while maintaining image quality. We sought to validate whether institutions are observing Image Gently guidelines in practice. Dose-relevant data from 663,417 abdomen-pelvis and chest CT scans were obtained from 53 facilities. Patients were assigned arbitrary age cohorts with a minimum size of n=12 patients in each age group, for statistical purposes. All pediatric (<19years old) cohorts at a given facility were compared to the adult cohort by a Kruskal-Wallis test for each of the four scan parameters - (1) x-ray tube kilovoltage (kV), (2) tube-current-by-exposure-time product (tube mAs), (3) scan pitch and (4) tube rotation time - to assess whether the distribution of values in the pediatric cohorts differed from the adult cohort. The same was repeated with volume CT dose index (CTDIvol) and size-specific dose estimate (SSDE) to assess whether pediatric cohorts received less dose than adult cohorts. A P-value of <0.05 was deemed significant. Across the 150 pediatric cohorts, 134 had scan parameters that were more child-sized than their adult counterparts. In 128 of these 134 pediatric cohorts, the CTDIvol was less than the adult counterpart. In 111 of these 128 pediatric cohorts, the SSDE was less than the adult counterpart. The study reaffirms that in practice, Image Gently's suggestions of lowering tube mAs and peak kilovoltage are commonly employed and effective at reducing pediatric CT dose.

Changes in muscle length and orientation after orthognathic surgeries using a bilateral sagittal split osteotomy as an example

Purpose: The aim of the present study was to analyze the changes in the angular positions and lengths of the mandibular elevator muscles due to the displacement of bone segments after bilateral sagittal split osteotomy. Additionally, the impact of changes in mandibular geometry on the values of occlusal forces and mandibular condyle loading was considered. The combined geometric and force analysis makes a valuable contribution to the operating conditions of the system affected by the changes. Methods: The considerations were based on elementary principles of analytical geometry and the analysis was performed for two craniofacial geometries. Results: For the rotation of the proximal segment, the greatest differences in angular position concern the masseter muscle during roll rotation (11.7). Significant changes in muscle length occurred during pitch rotation and amounted to 3.7 mm. Translation of the distal segment by 10 mm changed the angle of the pterygoid muscle by 30.2 in the coronal plane and 18.7 in the sagittal plane, simultaneously changing its direction to that of the opposite. Posterior translation (10 mm) caused an elongation of the muscle by 4.7 mm and anterior translation caused a shortening by 2.6 mm. For the mandible with elongated geometry, lower values of occlusion forces and increased reaction forces in the condyle were observed. Conclusions: The analysis revealed significant changes in the orientation and length of the masticatory muscles, and thus, their potential impact on the functioning conditions of the masticatory system.

Identifying optimal rotating pitch angles in composites with Bouligand structure

The Bouligand structure is a typical helicoidal architecture found in various crustaceans in which each layer rotates by a small angle relative to the adjacent one. We present a theoretical analysis to relate the rotation pitch angle to the mechanical performance (interlaminar shear property in this case) of laminas mimicking the Bouligand architecture. For a given laminate, there exists an optimal pitch angle that yields the lowest shear stress. Theoretical models are compared against experimental tests carried out on 32-layer helicoidal carbon fibre laminates with pitch angles of 6°, 9.1°, 12°, 25.7°. The 9.1° is the predicted optimal angle. The results show that this particular architecture with a pitch angle of 9.1° indeed attains the highest load-bearing capability and delays any catastrophic delamination. This provides a fundamental basis to the design of helicoidal structures mimicking the Bouligand architecture.

Updating headings in 3D navigation.

This study investigated to what extent humans can encode spatial relations between different surfaces (i.e., floor, walls, and ceiling) in a three-dimensional (3D) space and extend their headings on the floor to other surfaces when locomoting to walls (pitch 90°) and the ceiling (pitch 180°). In immersive virtual reality environments, participants first learned a layout of objects on the ground. They then navigated to testing planes: south (or north) walls facing Up, or the ceiling via walls facing North (or South). Participants locomoted to the walls with pitch rotations indicated by visual and idiothetic cues (Experiment 1) and only by visual cues (Experiment 2) and to the ceiling with visual pitch rotations only (Experiment 3). Using the memory of objects' locations, they either reproduced the object layout on the testing plane or did a Judgements of Relative Direction (JRD) task ("imagine standing at object A, facing B, point to C") with imagined headings of south and north on the ground. The results showed that participants who locomoted onto the wall with idiothetic cues showed a better performance in JRD for an imagined heading from which their physical heading was extended (e.g., imagined heading of North at the north wall). In addition, the participants who reproduced the layout of objects on the ceiling from a perspective extended from the ground also showed a sensorimotor alignment effect predicted by an extended heading. These results indicate that humans encode spatial relations between different surfaces and extend headings via pitch rotations three-dimensionally, especially with idiothetic cues.

Hydraulic Resistance of Flows in Tubes with Inserted Straight and Twisted Tapes

The results of an experimental study of hydraulic resistance of a laminar flow with air stream macrovortices in a long tube with inserted straight and twisted tapes are presented. It was found that there is a minimum in the relationship of the hydraulic resistance coefficient with the rotation pitch of the tape inserted into the tube. An empirical equation, recommended for use in a wide tape rotation pitch variation range, has been derived for calculating hydraulic resistance.

Corner Reflector Based Misalignment-Tolerant Chipless RFID Tag Design Methodology.

Chipless RFID is a relatively new and rapidly growing field that faces some practical implementation challenges. One of these challenges is extreme sensitivity to small misalignments between the tag and the reader antenna. These tilts and translations can lead to erroneous responses which can then be interpreted as incorrect IDs or sensing parameter values in identification and sensing applications, respectively. While there has been some work to mitigate this limitation through reading and post-processing methods, the problem has yet to be sufficiently addressed from the tag design perspective. This work proposes a misalignment-tolerant chipless RFID tag design methodology that utilizes trihedral corner reflector bases loaded with resonators to produce tags that are tolerant of pitch and yaw rotations up to ±40° and roll rotations up to ±180° (i.e., orientation independence as it is commonly defined in the chipless RFID field). This approach allows for linearly polarized monostatic reading schemes to be used and provides for a large radar cross-section and resonance depth, which increases the detectability of the tag response.