Academic literature on the topic 'Lateral convexity'

The surface anatomies of the face and neck and their supporting structures that can be palpated have been described in Chapter 20. It is now time to move to the structures that lie under the skin but which cannot be identified by touch starting with the neck and moving up on to the face and scalp. The cervical vertebral column comprises the seven cervical vertebrae and the intervening intervertebral discs. These have the same basic structure as the thoracic vertebrae described in Section 10.1.1. Examine the features of the cervical vertebra shown in Figure 23.1 and compare it with the thoracic vertebra shown in Figure 10.3. You will see that cervical vertebrae have a small body and a large vertebral foramen. They also have two distinguishing features, a bifid spinous process and a transverse foramen, piercing each transverse process; the vertebral vessels travel through these foramina. The first and second vertebrae are modified. The first vertebra, the atlas, has no body. Instead, it has two lateral masses connected by anterior and posterior arches. The lateral masses have concave superior facets which articulate with the occipital condyles where nodding movements of the head take place at the atlanto-occipital joints. The second cervical vertebra, the axis, has a strong odontoid process (or dens because of its supposed resemblance to a tooth) projecting upwards from its body. This process is, in fact, the body of the first vertebra which has fused with the body of the axis instead of being incorporated into the atlas. The front of the dens articulates with the back of the anterior arch of the atlas; rotary (shaking) movements of the head occur at this joint. The seventh cervical vertebra has a very long spinous process which is easily palpable. The primary curvature of the vertebral column is concave forwards and this persists in the thoracic and pelvic regions. In contrast, the cervical and lumbar parts of the vertebral column are convexly curved anteriorly. These anterior curvatures are secondary curvatures which appear in late fetal life. The cervical curvature becomes accentuated in early childhood as the child begins to support its own head and the lumbar curve develops as the child begins to sit up.

Vertebral endplates of the lumbosacral spine have various degrees of concavity and/or convexity. Little information is available in the literature on accurate measurement of morphometry of the vertebral endplates of the lumbosacral spine and on biomechanical significance of the curvature. In this study, lumbar vertebral endplate curvatures in anterior-posterior and medial-lateral directions were measured. Human males-females, chimpanzees and canine lumbar endplates were scanned and quantified. Finite Element Analysis (FEA) was performed on endplates and the effects of location of maximum curvature depth on the stress distribution were investigated.

The paper begins with a brief overview of historical building coverings. Thermadapt™ thermally adaptive buildings are introduced as a completely new class of shingles, siding and roofing. These elements physically change shape in response to thermal loading. In hot weather with high solar loading, the panels curl up and away from the building. As the temperature cools and the sun sets, the Thermadapt™ elements lie close to the building. In cool temperatures, the elements lie flat agains the building transferring solar energy. In extremely cold temperatures, high convexity inherently forms in the elements, forming a pocket of trapped dead air which forms a highly effective layer of insulation. Thermadapt™ elements are analytically modeled using Classical Laminated Plate Theory (CLPT). Although Thermadapt™ elements may use materials like shape memory alloys, cost concerns drive the use of coefficient of thermal expansion mismatch as the basic driving mechanism. A series of experiments were performed on a variety of Thermadapt™ elements using high CTE mismatch pairs of structural materials including graphite-epoxy and aluminum and Invar and aluminum pairings. Analytical estimates are shown to predict the performance of the Thermadapt™ panels with great accuracy with curvature levels measured and predicted in excess of 5 deg/m/°C. Analytical predictions using CLPT employed a lateral constraint, driving lateral curvature, κy, to zero by the use of stiff lateral constraint mechanisms like edge rolls and lateral corrugations. This constraint was shown to increase deflections by roughly 33% over the unconstrained elements which were simply allowed to encounter equal curvatures in x and y directions, or “doming.”

Knowledge of the movements of the whole spine and lumbosacral joint is important for evaluating clinical pathologic conditions that may potentially produce unstable situations in human body movements. At present there are few studies that report systematic three-dimensional (3D) movement and force analysis of the whole spine. In this paper, a fully discretized bio-fidelity 3D musculoskeletal simulation model for biomechanical (kinematic) analysis of scoliosis for a patient with right thoracolumbar scoliosis is presented. It is important to note that this method can be used for modeling various types of scoliosis. It should be noted that this is the first time that such a detailed model of this kind has been constructed according to known literature. The combined loading conditions acting on the intervertebral joints and corresponding angles between vertebrae were analyzed during lateral bending through the motion capturing and musculoskeletal modeling of two female subjects, one with normal spine and the other with scoliosis. The scoliosis subject who participated in this study has thoracolumbar scoliosis with convexity to the right. Since lateral bending is one of the typical tasks used by clinicians to determine the severity of scoliosis condition, the motion data of the subjects in lateral bending while standing was captured. These motion data were assigned to train the musculoskeletal multi-body models for the inverse and forward dynamics simulations. The mobility of the ribcage, joint angle, as well as joint force were analyzed using the developed simulation model. According to the results obtained the combined loadings at the lumbar joints in the scoliosis model are considerably higher than the loads of the normal model in this exercise. This research has investigated the effect of thoracolumbar scoliosis on spinal angles and joint forces in lateral bending by the application of motion data capturing and virtual musculoskeletal modeling. The results of this study contribute to a better understanding of human spine biomechanics and help future investigations on scoliosis to understand its development as well as improved treatment processes.

The vertebral endplates of the lumbosacral spine have various degrees of concavity and/or convexity. Several investigators including Seenivasan G., Goel, V. K., 1994, Liebschner et al, 2003, etc have performed finite element analysis on the vertebral bones, but the endplate curvatures are not included. Therefore, the effect of morphological details of the endplate curvatures on the stress distribution is unknown. Differences in these curvatures will increase stress in some regions and decrease stress elsewhere as the spine is compressed. In our previous study [Kale et al, 2003], lumbar vertebral endplate curvatures in the anterior-posterior and medial-lateral directions on human cadaver lumbar vertebrae were measured. The measurements were carried out using a reverse engineering instrument, built at Rutgers University [Hsieh et al, 2002]. Six sets of measurements (on human male-female L4 lower to S1 upper endplates) were performed. The data was later used in a linear elastic cylindrical model containing cortical shell and trabecular core. The model then was modified to a more accurate model, with more realistic, characteristic kidney shaped cross section (obtained from equation by Mizrahi et al, 1993) and linearly varying height. The endplates were assigned curvatures extracted from our human cadaver data. FEA, done on both the models, showed that the endplate curvatures and their location had significant effect on the stress distribution in the vertebral bone. In the current study we have extended our bone model into a motion segment and have investigated the effects of the curvatures on the stresses in the motion segment.

Abstract In this paper, we propose an MPC-based motion planning algorithm, including a decision-making module, an obstacle-constraints generating module, and an MPC-based planning module. The designed decision module effectively distinguishes between structured and unstructured roads and processes them separately, so that the algorithm is more robust in different environments. Besides, the movement of obstacles is considered in the decision-making and obstacle constraints generating module. By processing obstacles with lateral and longitudinal speed separately, obstacle avoidance can be done in scenarios with moving obstacles, including moving obstacles crossing the road. Instead of treating the vehicle as a mass point, we explicitly consider the geometric constraints by modeling the vehicle as three intersecting circles when generating obstacle constraints. This ensures that the vehicle is collision-free in motion planning, especially when the vehicle turns. For non-convex obstacle constraints, we propose an algorithm that generates up to two alternative linear constraints to convexify the obstacle constraints for improving computational efficiency. In MPC, we consider the vehicle kino-dynamic constraints and two generated linear constraints. Therefore, the proposed method can achieve better real-time performance and can be applied to more complicated traffic scenarios with moving obstacles. Simulation results in three different scenarios show that motion planning can achieve satisfactory performance in both structured and unstructured roads with moving obstacles.

In this paper, we verify the enhancement of IREC, which is a computer algorithm for interactive design support system, to support global design features as design attributes. IREC (Interactive Reduct Evolutional Computation) is a method to evolve designs based on users’ personal preferences. The method works through an interaction between the user and a computer system. The computer system with IREC generates design samples consisting of random attributes and the user evaluates and scores each samples depending on his/her psychological preferences. The system estimates the design attributes that the user pays more attention to (favored features) with reduct in Rough set theory and reflects it to generate new design samples. This interaction continues until the samples converge to a satisfactory design. So far design parameters such as coordinate of nodes for spline curve have been regarded as design attributes. However, design attributes consist of not only detailed local parameters but also global features such as convexity, softness etc. In earlier design process, designers first drew a rough sketch to determine the outline of a design, and designed the details later. Therefore it is important to introduce global features to accelerate the convergence and to increase user friendliness. We develop G-IREC (Global feature based IREC) which allows to introduce global features in IREC. This method is applied to design an automobile side-view shape model. The effectiveness of the method is demonstrated by comparing the results of the experiments carried out.