A class of scaled Bessel sampling theorems

Sampling theorems for a class of scaled Bessel unitary transforms are presented. The derivations are based on the properties of the generalized Laguerre functions. This class of scaled Bessel unitary transforms includes the classical sine and cosine transforms, but also novel chirp sine and modified Hankel transforms. The results for the sine and cosine transform can also be utilized to yield a sampling theorem, different from Shannon's, for the Fourier transform

A Systematic Review of Weight Perception in Virtual Reality: Techniques, Challenges, and Road Ahead

Weight is perceived through the combination of multiple sensory systems, and a wide range of factors – including touch, visual, and force senses – can influence the perception of heaviness. There have been remarkable advancements in the development of haptic interfaces throughout the years. However, a number of challenges limit the progression to enable humans to sense the weight in virtual reality (VR). This article presents an overview of the factors that influence how weight is perceived and the phenomenon that contributes to various types of weight illusions. A systematic review has been undertaken to assess the development of weight perception in VR, underlying haptic technology that renders the mass of a virtual object, and the creation of weight perception through pseudo-haptic. We summarize the approaches from the perspective of haptic and pseudo-haptic cues that exhibit the sense of weight such as force, skin deformation, vibration, inertia, control–display ratio, velocity, body gestures, and audio–visual representation. The design challenges are underlined, and research gaps are discussed, including accuracy and precision, weight discrimination, heavyweight rendering, and absolute weight simulation. This article is anticipated to aid in the development of more realistic weight perception in VR and stimulated new research interest in this topic

Analysis of upper body biomechanics and control in manual wheelchair users

Manual wheelchair propulsion involves repetitive shoulder range of motion and muscular activities. It is an important form of mobility for many people with lower limb disabilities who depend upon their upper body to provide means of locomotion for completion of their activities of daily living. As a result of greater than normal usage of the upper limbs, shoulder and wrist pain and pathology are common among manual wheelchair users. This study provides a biomechanical analysis of the manual wheelchair mobility in control subjects during their functional activities of daily living. Non-experienced wheelchair users were recruited per this study for their feature of novice as they could determine their own self-selected speed and pattern of propulsion and to limit any variability that would be existed by a study group with multiple inter-individual differences. In the context of manual wheelchair propulsion, biomechanics of upper body involves the study of how a manual wheelchair user imparts power to the wheels to achieve mobility. In general, the primary goal of biomechanical analysis of manual wheelchair propulsion is to generate knowledge that can be used to improve performance and/or prevent injuries. The main objectives of this study were to investigate the impact of trunk and upper limb biomechanics associated with diverse wheelchair configurations in terms of adjusting vertical displacement (seat-to-floor height) and horizontal displacement (rear wheel axle position). A marker-based 3D motion analysis technique was used with more recently to the six degrees of freedom (6DOF) analysis, as an integrated feature in the software that was used to collect the motion capture data (Qualisys Track Manager, QTM, Qualisys, Sweden). Three-dimensional kinematics of trunk and upper limb joints were investigated during physiological range of motion (ROM), activities of daily living (ADL), and functional wheelchair mobility that includes starting up from the rest, propulsion and stopping a wheelchair during manual propulsion ii The contribution of the shoulder complex muscles was investigated through the analysis of the surface electromyographic (sEMG) patterns of six stabilising muscles activity during physiological range of motion, activities of daily living and functional wheelchair mobility. Also, the interrelationship between the users’ anthropometric characteristics and the biomechanics of their upper body were investigated in terms of kinematics, surface electromyography and spatiotemporal parameters during manual wheelchair propulsion. This study showed an interrelationship between diverse wheelchair configurations of adjustable wheelchair rear wheel axle position and seat height and upper body kinematic behaviour, muscles recruitment and spatiotemporal patterns during manual wheelchair mobility. It was observed that changing rear wheel axle position posteriorly and raising the seat-to-floor distance (i.e. raising the seat height position) are correlated with higher upper body kinematics and release phase muscle activities and lower pushing patterns and push muscle activities during functional wheelchair mobility and so could be linked with higher risk of musculoskeletal disorders. As the number of manual wheelchair users is developing around the world, it becomes very essential to increase the understanding of the biomechanics of upper body to enhance the performance and decrease the risk of injury. It is hoped that this knowledge will help both manufacturers and clinicians when designing and prescribing wheelchairs that are more proper to the users' functional features, needs and expectations, accordingly profiting users' independence and quality of life

A method to estimate the oblique arch folding axis for thumb assistive devices

People who use the thumb in repetitive manipulation tasks are likelyto develop thumb related impairments from excessive loading at the base jointsof the thumb. Biologically informed wearable robotic assistive mechanisms canprovide viable solutions to prevent occurring such injuries. This paper tests thehypothesis that an external assistive force at the metacarpophalangeal joint willbe most effective when applied perpendicular to the palm folding axis in termsof maximizing the contribution at the thumb-tip as well as minimizing the pro-jections on the vulnerable base joints of the thumb. Experiments conducted usinghuman subjects validated the predictions made by a simplified kinematic modelof the thumb that includes a foldable palm, showing that: 1) the palm folding an-gle varies from 71.5◦to 75.3◦(from the radial axis in the coronal plane) for thefour thumb-finger pairs and 2) the most effective assistive force direction (fromthe ulnar axis in the coronal plane) at the MCP joint is in the range 0◦<ψ<30◦for the four thumb-finger pairs. These findings provide design guidelines for handassistive mechanisms to maximize the efficacy of thumb external assistance

Medical Robotics

The first generation of surgical robots are already being installed in a number of operating rooms around the world. Robotics is being introduced to medicine because it allows for unprecedented control and precision of surgical instruments in minimally invasive procedures. So far, robots have been used to position an endoscope, perform gallbladder surgery and correct gastroesophogeal reflux and heartburn. The ultimate goal of the robotic surgery field is to design a robot that can be used to perform closed-chest, beating-heart surgery. The use of robotics in surgery will expand over the next decades without any doubt. Minimally Invasive Surgery (MIS) is a revolutionary approach in surgery. In MIS, the operation is performed with instruments and viewing equipment inserted into the body through small incisions created by the surgeon, in contrast to open surgery with large incisions. This minimizes surgical trauma and damage to healthy tissue, resulting in shorter patient recovery time. The aim of this book is to provide an overview of the state-of-art, to present new ideas, original results and practical experiences in this expanding area. Nevertheless, many chapters in the book concern advanced research on this growing area. The book provides critical analysis of clinical trials, assessment of the benefits and risks of the application of these technologies. This book is certainly a small sample of the research activity on Medical Robotics going on around the globe as you read it, but it surely covers a good deal of what has been done in the field recently, and as such it works as a valuable source for researchers interested in the involved subjects, whether they are currently “medical roboticists” or not

The benefits of an additional practice in descriptive geomerty course: non obligatory workshop at the Faculty of Civil Engineering in Belgrade

At the Faculty of Civil Engineering in Belgrade, in the Descriptive geometry (DG) course, non-obligatory workshops named “facultative task” are held for the three generations of freshman students with the aim to give students the opportunity to get higher final grade on the exam. The content of this workshop was a creative task, performed by a group of three students, offering free choice of a topic, i.e. the geometric structure associated with some real or imagery architectural/art-work object. After the workshops a questionnaire (composed by the professors at the course) is given to the students, in order to get their response on teaching/learning materials for the DG course and the workshop. During the workshop students performed one of the common tests for testing spatial abilities, named “paper folding". Based on the results of the questionnairethe investigation of the linkages between:students’ final achievements and spatial abilities, as well as students’ expectations of their performance on the exam, and how the students’ capacity to correctly estimate their grades were associated with expected and final grades, is provided. The goal was to give an evidence that a creative work, performed by a small group of students and self-assessment of their performances are a good way of helping students to maintain motivation and to accomplish their achievement. The final conclusion is addressed to the benefits of additional workshops employment in the course, which confirmhigherfinal scores-grades, achievement of creative results (facultative tasks) and confirmation of DG knowledge adaption