Search results for "Simulation"
showing 10 items of 5095 documents
Effects of whole-body vertical shock-type vibration on human ability for fine manual control
1991
The effects of vertical (z-axis) whole-body shock-type vibration on the ability for fine manual control were examined. The amplitudes and frequency of the shocks was varied, but a constant frequency-weighted acceleration of 1.25 m/s2 r.m.s. was maintained. The examination of the shock's effects was carried out using an experimental system that simulated the actual workplace of earth-moving machinery. Control was measured using a first-order pursuit tracking-test, in which a seated subject was asked to use both hands to direct a cursor on a monitor using a steering wheel. Although the magnitude of shocks (peak amplitude of 6-10 m/s2) and the number of shocks per unit time (shock cycle of 10-…
Muscle-tendon interaction and elastic energy usage in human walking
2005
The present study was designed to explore how the interaction between the fascicles and tendinous tissues is involved in storage and utilization of elastic energy during human walking. Eight male subjects walked with a natural cadence (1.4 ± 0.1 m/s) on a 10-m-long force plate system. In vivo techniques were employed to record the Achilles tendon force and to scan real-time fascicle lengths for two muscles (medial gastrocnemius and soleus). The results showed that tendinous tissues of both medial gastrocnemius and soleus muscles lengthened slowly throughout the single-stance phase and then recoiled rapidly close to the end of the ground contact. However, the fascicle length changes demonstr…
Crystalens HD Intraocular Lens Analysis Using an Adaptive Optics Visual Simulator
2013
PURPOSE To compare visual and optical quality of the Crystalens HD intraocular lens (IOL) with that of a monofocal IOL. METHODS The wavefront aberration patterns of the monocular Akreos Adapt AO IOL and the single-optic accommodating Crystalens HD IOL were measured in a model eye. The Crystalens IOL was measured in its nonaccommodative state and then, after flexing the haptic to produce 1.4 mm of movement, in its accommodative state. Using an adaptive optics system, subjects' aberrations were removed and replaced with those of pseudophakes viewing with either lens. Monocular distance visual acuity (DVA) at high (100%), medium (50%), and low (10%) contrast and contrast sensitivity (CS) were …
Axis Rotation and Visually Induced Motion Sickness: The Role of Combined Roll, Pitch, and Yaw Motion
2011
A well-known phenomenon in aviation and in virtual environments such as simulators or computer games is motion sickness (MS). The amount of sensory conflict is thought to be responsible for the severity of MS, which should increase with the complexity of the simulated motion. The focus of the present study is on the direction and complexity of simulated body rotations in the genesis and severity of visually induced MS. The methods utilized for this study are as follows: Three simulated rollercoaster rides including translational movement in the fore-aft axis and additional rotational motion either in pitch only, along the pitch and roll axes, or in pitch, roll, and yaw were generated. The a…
Physiological responses and parasympathetic reactivation in rescue interventions: The effect of the breathing apparatus.
2018
This study aimed to assess the effect of wearing a breathing apparatus during a simulated rescue intervention on psychophysiological responses and parasympathetic reactivation of firefighters. Thirty-four firefighters participated in this study which consisted of four experimental sessions conducted randomly: a maximal fitness test and three rescue interventions performed (a) with personal protective clothing (PPC); (b) with PPC and the full self-contained breathing apparatus (SCBA), including cylinder, full-face piece, and breathing regulator; and (c) with PPC and only the cylinder of the self-contained breathing apparatus (SCBAc). Physiological (heart rate [HR], breathing frequency [BF]) …
Segment coupling and coordination variability analyses of the roundhouse kick in taekwondo relative to the initial stance position.
2016
The initial stance position (ISP) has been observed as a factor affecting the execution technique during taekwondo kicks. In the present study, authors aimed to analyse a roundhouse kick to the chest by measuring movement coordination and the variability of coordination and comparing this across the different ISP (0°, 45° and 90°). Eight experienced taekwondo athletes performed consecutive kicking trials in random order from every of the three relative positions. The execution was divided into three phases (stance, first swing and second swing phase). A motion capture system was used to measure athletes' angular displacement of pelvis and thigh. A modified vector coding technique was used t…
Artificial Versus Video-Based Immersive Virtual Surroundings: Analysis of Performance and User's Preference.
2018
Introduction. Immersive virtual reality (VR) laparoscopy simulation connects VR simulation with head-mounted displays to increase presence during VR training. The goal of the present study was the comparison of 2 different surroundings according to performance and users’ preference. Methods. With a custom immersive virtual reality laparoscopy simulator, an artificially created VR operating room (AVR) and a highly immersive VR operating room (IVR) were compared. Participants (n = 30) performed 3 tasks (peg transfer, fine dissection, and cholecystectomy) in AVR and IVR in a crossover study design. Results. No overall difference in virtual laparoscopic performance was obtained when comparing …
Investigating centre of mass stabilisation as the goal of posture and movement coordination during human whole body reaching
2000
In the light of experimental results showing significant forward centre of mass (CoM) displacements within the base of support, this study investigated if whole body reaching movements can be executed whilst keeping the CoM fixed in the horizontal axis. Using kinematic simulation techniques, angular configurations were recreated from experimental data imposing two constraints: a constant horizontal position of the CoM and an identical trajectory of the hand to grasp an object. The comparison between recorded and simulated trials showed that stabilisation of the CoM was associated with greater backward hip displacements, which became more marked with increasing object distance. This was in c…
Modeling the impact of soft tissue on axial transmission measurements of ultrasonic guided waves in human radius
2008
Recent in vitro and simulation studies have shown that guided waves measured at low ultrasound frequencies (f=200 kHz) can characterize both material properties and geometry of the cortical bone wall. In particular, a method for an accurate cortical thickness estimation from ultrasound velocity data has been presented. The clinical application remains, however, a challenge as the impact of a layer of soft tissue on top of the bone is not yet well established, and this layer is expected to affect the dispersion and relative intensities of guided modes. The present study is focused on the theoretical modeling of the impact of an overlying soft tissue. A semianalytical method and finite-differ…
Fatigue-related changes in technique emerge at different timescales during repetitive training
2017
Training consisting of numerous repetitions performed as closely as possible to ideal techniques is common in sports and every-day tasks. Little is known about fatigue-related technique changes that emerge at different timescales when repeating complex actions such as a karate front kick. Accordingly, 15 karatekas performed 600 kicks (1 pre-block and 9 blocks). The pre-block comprised 6 kicks (3 with each leg) at maximum intensity (K-100%). Each block comprised 60 kicks (10 with each leg) at 80% of their self-perceived maximum intensity (K-80%) plus 6 K-100%. In between blocks, the participants rested for 90 seconds. Right leg kinematics (peak joint angles, peak joint angular velocities, pe…