Virtual-reality neuropsychological tests offer a novel way to assess real-life executive functioning within the context of standardized test conditions whilst maximizing ecological validity. Given the limited empirical evidence base for many of these virtual-reality tests, the current study aimed to further examine the relative ecological validity, sensitivity to brain-injury and diagnostic accuracy of the virtual-reality based Jansari assessment of Executive Functions (JEF). To do this, the test was compared to seven standard tests of executive function, in a New Zealand sample of 27 brain-injured and 28 non brain-injured participants matched for age, gender and education. The JEF’s ecological validity was supported, with JEF total percent scores exhibiting large correlations with participants’ independently reported levels of everyday functioning, as measured by the Dysexecutive Questionnaire: Independent-Rater (DEX-IR) and Patient Competency Rating Scale-Relative (PCRS-R) (both rs = 0.606, p < 0.001). Compared to the standard executive function test variables included in the current study, the JEF’s associations with the everyday functioning measures were the largest, but only significantly larger than the respective correlations of some standard executive function test variables. These results indicated that the JEF is trending towards being relatively more ecologically valid than most of the standard executive function tests included in the study. The JEF also exhibited good sensitivity to brain-injury and diagnostic accuracy for discriminating brain-injured from non brain-injured participants, which was generally consistent with most of the standard tests, but only significantly better than some. These results provide empirical support for the JEF’s clinical utility, particularly in the assessment of brain-injured persons’ functional abilities. It also suggests that both virtual-reality and standard executive function tests have a place in the routine neuropsychological test batteries used to assess brain-injured persons.

This thesis studies the acquisition of spatial knowledge, through the use of virtual reality, and the role that audio can have in this type of learning. Two versions of a simulator were developed, one with the presence of audio and the other one without. 26 participants, divided into two groups (one group per version), were tested the simulator. The goal is to understand if the version with audio would lead to greater learning than the other. The results show that there was no difference between the groups and that they have learned in the same way. Both groups have subjects who suffered nausea or dizziness, with a greater presence in the group with the audio. Future work could consider trying to reduce the problem of these symptoms to have a clearer analysis.

A growing body of literature suggests that Virtual Reality is a successful tool for exposure therapy for anxiety disorders. Virtual Reality (VR) researchers posit the construct of presence, interpreting an artificial stimulus as if it were real, as the mechanism that enables anxiety to be felt during virtual reality exposure therapy (VRE). However, empirical studies on the relation between presence and anxiety in VRE have yielded mixed findings. The current study tested the following hypotheses 1) Presence is related to in session anxiety and treatment outcome; 2) Presence mediates the extent that pre-existing (pre-treatment) anxiety is experienced during exposure with VR; 3) Presence is positively related to the amount of phobic elements included within the virtual environment. Results supported presence as the mechanism by which anxiety is experienced in the virtual environment as well as a relation between presence and the phobic elements, but did not support a relation between presence and treatment outcome

published_or_final_version / Architecture / Master / Master of Architecture

published_or_final_version / abstract / toc / Education / Master / Master of Science in Information Technology in Education

published_or_final_version / Architecture / Master / Master of Philosophy

Τα περιβάλλοντα εικονικής παραγματικότητας είναι ένα κατάλληλο μέσο προκειμένου κάποιος να μπορέσει να εκπαιδευτεί και να εξασκηθεί εκ του ασφαλούς σε καταστάσεις που στον πραγματικό κόσμο θα ήταν δύσκολο και ίσως επικίνδυνο για αυτόν που εκπαιδεύεται αλλά και για όσους άλλους εμπλέκονται στην εκπαιδευτική διαδικασία. Μία τέτοια κατάσταση είναι και η εκδήλωση σεισμικής δραστηριότητας σε μία σχολική τάξη. Στόχος της συγκεκριμένης διπλωματικής εργασίας είναι η δημιουργία ενός εκπαιδευτικού εικονικού περιβάλλοντος για την προσομοίωση του φαινομένου του σεισμού και η χρήση εικονικών χαρακτήρων (avatars) για την δημιουργία ενός ρεαλιστικού σεναρίου που θα λάβει χώρα μέσα στο εικονικό περιβάλλον. Στα πλαίσια της συγκεκριμένης διπλωματικής εργασίας ορίζεται η έννοια της εικονικής πραγματικότητας, περιγράφονται τα συστήματα εικονικής πραγματικότητας καθώς και ο εξοπλισμός hardware ο οποίος είναι απαραίτητος για τη δημιουργία και χρήση εφαρμογών εικονικής πραγματικότητας. Επίσης περιγράφονται οι εφαρμογές της σε όλες της φάσεις και τους τομείς της ζωής μας καθώς και η υπάρχουσα κατάσταση στον Ελλαδικό χώρο. Για το εικονικό περιβάλλον που έχει δημιουργηθεί με τη χρήστη του 3D Studio Max, που είναι μια εικονική τάξη, περιγράφονται τα αντικείμενα που υπάρχουν σε αυτή καθώς και ο τρόπος εξαγωγής αυτής και των αντικειμένων της σε κατάλληλο λογισμικό εικονικής πραγματικότητας Virtools προκειμένου να καθοριστεί η περαιτέρω συμπεριφορά τους. Επιπλέον δίνεται έμφαση στην εισαγωγή εικονικών χαρακτήρων (avatars), στο εικονικό περιβάλλον που έχει δημιουργηθεί. Περιγράφεται αναλυτικά η εισαγωγή του εικονικού χαρακτήρα στο περιβάλλον της εικονικής τάξης καθώς και τρόποι και τεχνικές όσον αφορά τη συμπεριφορά των εικονικών χαρακτήρων με τη βοήθεια των animations. Δίνεται η δυνατότητα στο χρήστη να ελέγξει ο ίδιος και να καθορίσει της κινήσεις του εικονικού χαρακτήρα μέσα στο εικονικό περιβάλλον και να τον κινεί μέσα στον εικονικό χώρο όπως θα συνέβαινε στην πραγματικότητα. Ακόμα, έχει δημιουργηθεί ένα συμβάν σεισμού όπου συγκεκριμένος εικονικός χαρακτήρας αντιδρά λάθος κατά τη διάρκεια του φυσικού φαινομένου με στόχο η συγκεκριμένη αντίδραση να είναι παράδειγμα προς αποφυγή σε αυτούς που το παρακολουθούν (μαθητές) και να εξοικιωθούν με το ενδεχόμενο εκδήλωσης σεισμού στην τάξη. Γίνεται προσπάθεια απομυθοποίησης του φαινομένου του σεισμού με ευχάριστο και ασφαλή τρόπο. / Environments of virtual reality are a suitable means in order that somebody it can be educated and practiced from sure in situations that in the real world would be difficult and perhaps dangerous for the one that is educated but also for those who other they are involved in the educational process. A such situation is also the event of seismic activity in a school order. Objective of particular diplomatic work is the creation of educational virtual environment for the simulation of this phenomenon of earthquake and the use of virtual characters (avatars) for the creation of realistic script that will take place in the virtual environment. In the frames of particular diplomatic work is fixed the significance of s virtual reality, is described the systems of virtual reality as well as the equipment hardware which is essential for the creation and use of applications of virtual reality. Also are described her applications in all phases and the sectors of our life as well as the existing situation in the Hellenic space. For the virtual environment that has been created with the user of the 3 D Studio Max, that is a virtual order, are described the objects that exist in this as well as the way of export of this and her objects in suitable software of virtual reality Virtools so that is determined their further behavior. Moreover is given accent in the import of virtual characters (avatars), in the virtual environment that has been created. Are analytically described the import of virtual character in the environment of virtual order as well as ways and techniques with regard to the behavior of virtual characters with the help animations. Is given the possibility in the user checks himself and of determining her movements of virtual character in the virtual environment and him of moving in the virtual space as it would happen actually. Still, has been created a incident of earthquake where concrete virtual character reacts error at the duration of natural phenomenon in order the particular reaction is example to reject in those where watching (students) and familiarize with the possibility of event of earthquake in the order. Becomes effort of demystification of phenomenon of earthquake with pleasant and sure way.

Haptic simulation of medical procedures is an active area of research in engineering and medicine. Analogous to flight simulators for pilots, surgery simulators can allow medical students and doctors to practice procedures in a risk free and well monitored virtual environment. The quality of interaction that a surgery simulator can generate is dependent upon many components. In this thesis, careful attention is paid to the haptic display of viscous effects. / Viscous terms, defined here as terms that are dependent upon velocity, are typically computed 'using a discrete time backwards difference estimation of the velocity. It is well known that differentation has the tendency to amplify high frequency noise, and as a result, the backwards difference estimation generates considerable errors when applied to the quantized position readings from a digital encoder. Prior to this work, the only feasible method to improve velocity estimation was to use a variety of observation or filtering techniques, all of which inevitably add phase delay. In this thesis, the backwards difference operation was analyzed in detail. It was found that feedback viscosity simulation is very non-robust to noise, and oscillations exist in the presence of quantization noise regardless of the physical parameters of the plant. / A typical haptic interface for surgery simulation consists of a mechanical linkage driven by electric motors. These linkages are controlled with a computer using a discrete-time force update law that generates a prescribed force given the user's position in the medical virtual environment. It is clear from the literature that a haptic interface must have some level of physical dissipation to enable a passive rendering due to the inherent instability associated with time delayed systems. However, dissipation in typical haptic interfaces is a byproduct of their design, and is neither controllable nor easily identifiable. A prototype haptic interface is presented in this thesis that uses eddy current brakes to add high bandwidth programmable dissipation to an existing motor linkage. The new hardware has been optimized experimentally to maximize damping and minimize inertia given conventional machining and available material constraints. / A new paradigm in the control of haptic interfaces is time-domain passivity control. Passive systems are desirable in haptics because a passive system is globally stable, passivity theory applies to linear and nonlinear systems alike, and a user cannot extract energy from a passive system. Passivity controllers monitor the energy flow in the device and add virtual damping to remove any energy that violates the passivity constraint. Unfortunately, the amount of virtual damping available to a given device is limited by the physical dissipation that it exhibits. If the device is directly driven and light, such as the pantograph, the available virtual damping is insufficient to maintain the passivity constraint. The eddy current brakes allow programmable physical damping to be used in place of virtual damping which has been shown with experiments to improve the stable impedance range of a haptic interface. / It is clear from the literature that most tissues in a human body exhibit viscoelastic behavior. Simulation of viscoelastic objects requires that the velocity of interaction be known. Because typical haptic interfaces use digital encoders to sample position, the estimated velocity signal is noisy, delayed or both. Eddy current brakes are viscous actuators by nature, as they generate a resistive force proportional to the velocity. To take advantage of this fact, viscoelastic decomposition algorithms were developed that can output viscous components to the eddy current brakes and elastic components to the motors. This technique reduces or eliminates the use of a velocity estimation signal in the feedback loop which improves passivity, reduces motor saturation effects, and allows for a wider stable range of mechanical impedances than conventional haptic interfaces can achieve.

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