Structurally Integrated Antennas on a Joined-Wing Aircraft

This research is a foundational study of conformal, load-bearing antenna arrays embedded into the wing structure of a joined-wing aircraft. It is a multidisciplinary effort that touches on the aerodynamic structural and electromagnetic design considerations that stem from this unique type of sensor integration. The antenna performance Finite Element Model (FEM) and control surface effectiveness are investigated. The theory describing an ensemble of dipole antenna elements that conform to the shape of a section of the joined wing is developed. The far held flee space radiation pattern of the sensor is then analyzed for a wing that is deflected due to typical aerodynamic loading. This pattern is compared to the same antenna when the wing is not deformed. A FEM of the antenna elements is created and incorporated into the hill FEM of the joined-wing aircraft allowing its structural impact to be realized. Based on the positioning of these large sensor arrays control surfaces are placed and examined to achieve the proper handling capabilities necessary for this type of aircraft

A Magnetic Actuated Fully Insertable Robotic Camera System for Single Incision Laparoscopic Surgery

Minimally Invasive Surgery (MIS) is a common surgical procedure which makes tiny incisions in the patients anatomy, inserting surgical instruments and using laparoscopic cameras to guide the procedure. Compared with traditional open surgery, MIS allows surgeons to perform complex surgeries with reduced trauma to the muscles and soft tissues, less intraoperative hemorrhaging and postoperative pain, and faster recovery time. Surgeons rely heavily on laparoscopic cameras for hand-eye coordination and control during a procedure. However, the use of a standard laparoscopic camera, achieved by pushing long sticks into a dedicated small opening, involves multiple incisions for the surgical instruments. Recently, single incision laparoscopic surgery (SILS) and natural orifice translumenal endoscopic surgery (NOTES) have been introduced to reduce or even eliminate the number of incisions. However, the shared use of a single incision or a natural orifice for both surgical instruments and laparoscopic cameras further reduces dexterity in manipulating instruments and laparoscopic cameras with low efficient visual feedback. In this dissertation, an innovative actuation mechanism design is proposed for laparoscopic cameras that can be navigated, anchored and orientated wirelessly with a single rigid body to improve surgical procedures, especially for SILS. This design eliminates the need for an articulated design and the integrated motors to significantly reduce the size of the camera. The design features a unified mechanism for anchoring, navigating, and rotating a fully insertable camera by externally generated rotational magnetic field. The key component and innovation of the robotic camera is the magnetic driving unit, which is referred to as a rotor, driven externally by a specially designed magnetic stator. The rotor, with permanent magnets (PMs) embedded in a capsulated camera, can be magnetically coupled to a stator placed externally against or close to a dermal surface. The external stator, which consists of PMs and coils, generates 3D rotational magnetic field that thereby produces torque to rotate the rotor for desired camera orientation, and force to serve as an anchoring system that keeps the camera steady during a surgical procedure. Experimental assessments have been implemented to evaluate the performance of the camera system

The influence of different connecting rod configurations on the stability of the Ilizarov Frame: A biomechanical study

Background: The Ilizarov external fixator (IEF) is frequently used in trauma and elective orthopaedics. Many of its biomechanical variables (ring size; wire diameter; wire number; half pins versus wires; etc.) and their influence on stability and stiffness have been investigated. There is however a paucity in the literature regarding the influence of the connecting rod numbers and configurations between the rings on IEF stability. Objectives: Primarily to compare the stability between four and three rod IEF configurations. Secondarily to assess the difference in stability between symmetrical and asymmetrical spacing of the IEF rods. Methods: A custom jig was designed to facilitate mounting of a basic two ring IEF in a hydraulic press. Controlled centre and off centre (thus simulated bending) axial loading was then applied across the frame. The configurations were loaded up to 4000 Newtons. The frame deformation was plotted and the data was then analysed and interpreted. Results: Negligible differences were observed between different four and three rod configurations as long as the applied force at the loading point (LP) was within the area of support (AOS) created by the rods. The different four rod constructs were always more stable than the three rod constructs during bending. Conclusions: There is comparable stiffness between a four rod and a three rod IEF construct as long as the loading point (LP) is within the area of support (AOS) created by the rods. A four rod IEF is stiffer than a three rod IEF in bending

An automated approach for the aerodynamic design of close-coupled propulsion/airframe configurations

Reducing aircraft emissions is a key element in mitigating the environmental impact of aviation. Within this context, different novel aircraft propulsion configurations have been proposed. A common feature of many of these novel configurations is the closer integration of the propulsive system and the aircraft airframe with an expected increase of the aerodynamic coupling. Therefore, is necessary to assess the performance of the aerodynamic installation of the propulsive system of these configurations with a systematic approach. A systematic and automated methodology for the design and performance evaluation of embedded propulsion systems is defined. This methodology is demonstrated with a Boundary Layer Ingestion propulsive fuselage concept. This approach covers the geometry design of the selected configuration, an automatic aerodynamic numerical computation and a novel performance evaluation for the design. A Design Space Exploration was performed to characterize the relative importance of the individual parameters of the geometry and their correlation with the key performance metrics. Finally, a multi-objective optimization was carried to demonstrate the capabilities of this approach

Developments in circular external fixators: a review

Circular external fixators (CEFs) are successfully used in orthopedics owing to their highly favorable stiffness characteristics which promote distraction osteogenesis. Although there are different designs of external fixators, how these features produce optimal biomechanics through structural and component designs is not well known. Therefore, the aim of this study was to conduct a review on CEFs following the PRISMA statement. A search for relevant research articles was performed on Scopus and PubMed databases providing the related keywords. Furthermore, a patent search was conducted on the Google Patent database. 126 records were found to be eligible for the review. Different designs of CEFs were summarized and tabulated based on their specific features. A bibliometric analysis was also performed on the eligible research papers. Based on the findings, the developments of CEFs in terms of materials, automation, adjustment methods, component designs, wire-clamping, and performance evaluation have been extensively discussed. The trends of the CEF design and future directions are also discussed in this review. Significant research gaps include a lack of consideration towards ease of assembly, effective wire-clamping methods, and CEFs embedded with online patient-monitoring systems, among others. An apparent lack of research interest from low-middle and low-income countries was also identified

Characterisation and State Estimation of Magnetic Soft Continuum Robots

Minimally invasive surgery has become more popular as it leads to less bleeding, scarring, pain, and shorter recovery time. However, this has come with counter-intuitive devices and steep surgeon learning curves. Magnetically actuated Soft Continuum Robots (SCR) have the potential to replace these devices, providing high dexterity together with the ability to conform to complex environments and safe human interactions without the cognitive burden for the clinician. Despite considerable progress in the past decade in their development, several challenges still plague SCR hindering their full realisation. This thesis aims at improving magnetically actuated SCR by addressing some of these challenges, such as material characterisation and modelling, and sensing feedback and localisation. Material characterisation for SCR is essential for understanding their behaviour and designing effective modelling and simulation strategies. In this work, the material properties of commonly employed materials in magnetically actuated SCR, such as elastic modulus, hyper-elastic model parameters, and magnetic moment were determined. Additionally, the effect these parameters have on modelling and simulating these devices was investigated. Due to the nature of magnetic actuation, localisation is of utmost importance to ensure accurate control and delivery of functionality. As such, two localisation strategies for magnetically actuated SCR were developed, one capable of estimating the full 6 degrees of freedom (DOFs) pose without any prior pose information, and another capable of accurately tracking the full 6-DOFs in real-time with positional errors lower than 4~mm. These will contribute to the development of autonomous navigation and closed-loop control of magnetically actuated SCR

Aerodynamic and Acoustic Interaction Effects of Adjacent Propellers in Forward Flight

Distributed electric propulsion systems are an emerging technology with the potential of revolutionizing the design and performance of aircraft. When propellers are located in close proximity, they can be subjected to aerodynamic interactions, which affect the far-field noise. In this paper, we study an array of three co-rotating and adjacent propellers to describe both the aerodynamic and acoustic installation effects. A scale-resolving CFD simulation based on the Lattice-Boltzmann/Very-Large-Eddy-Simulation method is used to solve the flow field around the propellers. An acoustic analogy integral approach calculates the far-field noise. Findings show that the helical vortical structures, generated at the tip of each blade undergo a flow deformation at the location of interaction. This causes the loading of each blade to vary during the rotation. Consequently, the unsteady loading noise becomes a dominant noise generation mechanism, driving the noise levels and directivity. It is also shown that introducing a non-zero relative phase angle between the propellers results in a reduction of the unsteady thrust, leading to a mitigation of the unsteady-loading tonal components along the rotation axis. Additionally, the relative phase angle causes constructive/destructive acoustic interference, as demonstrated by analyzing the noise emitted simultaneously by the three propellers

Fracture fixation of complex tibial plateau fractures

Bi-condylar tibial plateau fractures with the highest frequency in 40-to-60-year-old patients accounts for 35% of all tibial plateau fractures. Surgical treatment of this fracture remains challenging due to the multi-planar articular comminution and the subsequent severe soft tissue injuries. Preoperative planning is meaningfully affected by recognition of the exact location of the fracture fragments, in particular the posteromedial fragment created by the coronal split. Despite the 50% incidence rate of this crucial fracture line, it has been disregarded in the established fracture classifications like the AO or Schatzker systems as well as in the previous biomechanical studies. For this reason, there is still a controversy regarding an ideal fixation strategy for the complex tibial plateau fractures. Therefore, through both experimental and the numerical investigations, this study aimed to develop a coronal fracture model based on the clinical data to ultimately address this concern. The experiments focused on comparison of the structural stability between the coronal fracture model and the traditional Horwitz model. The numerical simulations, which were established based on the validation of these fracture models, evaluated the effects of the fracture morphology on the stress distributions within the implant. Both study parts revealed that the coronal split remarkably reduced the global axial stiffness and displacement of the bone-implant structure, significantly destabilized the medial side of the tibia, as well as noticeably changed the stress distributions within the locking plates and screws. Furthermore, the lateral locking plate cannot adequately stabilize this fracture, and a double plating method including a supplemental medial plate is required. Consequently, it is highly recommended to apply the coronal fracture model of bi-condylar tibial plateau fractures for biomechanical tests, which aimed to compare different fixation methods, as well as for numerical studies, which focused on finding the optimum plate position, screw direction or plate design.Bicondyläre Tibiaplateaufrakturen machen 35% aller Tibiaplateaufrakturen aus, mit der höchsten Häufigkeit im Alter von 40-60 Jahren. Die chirurgische Behandlung dieser Fraktur bleibt aufgrund der multiplanaren Gelenkzertrümmerung sowie der nachfolgenden schweren Weichteilverletzungen eine Herausforderung. Das Erkennen der genauen Lage der Frakturfragmente wird bei der präoperative Planung, insbesondere durch die koronale Spaltung des entstandenen posteromedialen Fragments, erheblich beeinträchtigt. Trotz einer Inzidenzrate von 50% für diese kritische Frakturlinie wurde sie in den etablierten Frakturklassifikationen wie dem AO- oder Schatzker-System sowie in früheren biomechanischen Studien nicht berücksichtigt. Aus diesem Grund gibt es nach wie vor eine Kontroverse über eine ideale Fixationsstrategie für komplexe Tibiaplateaufrakturen. Daher zielte diese Studie, die aus experimentellen und numerischen Teilen besteht, darauf ab, auf der Grundlage der klinischen Daten ein koronales Frakturmodell zu entwickeln, um diesem Anliegen letztlich Rechnung zu tragen. Der experimentelle Teil konzentrierte sich auf den Vergleich der strukturellen Stabilität zwischen dem koronalen Frakturmodell und dem traditionellen Horwitz-Modell. Im numerischen Teil, der auf der Grundlage der Validierung dieser Bruchmodelle erstellt wurde, werden die Auswirkungen der Bruchmorphologie auf die Spannungsverteilungen innerhalb der Implantatkomponenten bewertet. Beide Teile dieser Studie zeigten, dass die koronale Bruchlinie die globale axiale Steifigkeit und Verschiebung der Knochen-Implantat-Struktur bemerkenswert reduziert, die mediale Seite der Tibia signifikant destabilisiert und die Spannungsverteilung innerhalb der Verriegelungsplatten und -schrauben merklich verändert hat. Außerdem kann die laterale Verriegelungsplatte diese Fraktur nicht ausreichend stabilisieren, so dass eine doppelte Verplattung einschließlich einer zusätzlichen medialen Platte erforderlich ist. Daher wird dringend empfohlen, das koronale Frakturmodell für bikondyläre Frakturen des Tibiaplateaus anzuwenden, sowohl bei biomechanischen Tests, bei denen verschiedene Fixationsmethoden verglichen werden, als auch für numerische Studien, bei denen es darum geht, die optimale Plattenposition, Schraubenrichtung oder das optimale Plattendesign zu finden

3D conformal antennas for radar applications

Embedded below the radome of a missile, existing RF-seekers use a mechanical rotating antenna to steer the radiating beam in the direction of a target. Latest research is looking at replacing the mechanical antenna components of the RF seeker with a novel 3D conformal antenna array that can steer the beam electronically. 3D antennas may oer signicant advantages, such as faster beamsteering and better coverage but, at the same time, introduce new challenges resulting from a much more complex radiation pattern than that of 2D antennas. Thanks to the mechanical system removal, the new RF-seeker has a wider available space for the design of a new 3D conformal antenna. To take best benets of this space, dierent array shapes are studied, hence the impact of the position, orientation and conformation of the elements is assessed on the antenna performance in terms of directivity, ellipticity and polarisation. To facilitate this study of 3D conformal arrays, a Matlab program has been developed to compute the polarisation pattern of a given array in all directions. One of the task of the RF-seeker consists in estimating the position of a given target to correct the missile trajectory accordingly. Thus, the impact of the array shape on the error between the measured direction of arrival of the target echo and its true value is addressed. The Cramer-Rao lower bound is used to evaluate the theoretical minimum error. The model assumes that each element receives independently and allows therefore to analyse the potential of active 3D conformal arrays. Finally, the phase monopulse estimator is studied for 3D conformal arrays whose quadrants do not have the same characteristics. A new estimator more adapted to non-identical quadrants is also proposed