Catálogo de publicaciones - libros

A wavelet analysis based multi-resolution representation method is adopted to establish mathematical description of three-dimensional anthropometric head data in this paper. This method provides flexible description of shapes at different resolution levels. Three-dimensional anthropometric data analysis can then be performed with coarse resolutions, which preserve the major shape components but ignore micro shape components. In a case study of 510 3D head scans, quantitative approximation errors, which reflect the approximation of the low-resolution surface to the original one, have been investigated and demonstrated with respect to various decomposition levels.

This paper presents a computational procedure for deriving and solving the governing dynamical equations of multi-body human systems subjected to impact. The procedure is developed on the basis of the assumption that the duration of the impact is very short, during which the configuration of the system remain the same, although the velocities of the system have undergone significant changes. These assumptions lead to a set of linear algebraic equations for the velocity increments. These equations may then be solved to obtain initial conditions for the analysis of the subsequent motion of the multi-body human system. A calculating task of ejecting seat problem is presented to illustrate and validate the procedure.

Compared with the previous video standard, the performance of H.264 has improved significantly because of multi-block-size motion estimation. However, encoder using above technology is very time-consuming. Making full use of the spatiotemporal correlation of video and similar motion between the different-size block, according to the central-biased characteristic of motion vector, a fast motion estimation algorithm for H.264 is proposed in this paper. By effective prediction of search window center point, adaptive selection of search patterns and termination of the search process, the proposed algorithm speedups 123-186 times than full search algorithm and 4.6-5.9 times than the fast motion estimation algorithm recommended in H.264 while maintains similar rate distortion performance.

The objective of this study is to validate two three-dimensional motion systems used capture human movement; the Lumbar Motion Monitor (LMM) and optical motion capture. Marras et al. captured the accuracy and reliability of optical motion capture and the LMM in a 1992 validation study, and found several benefits of using the LMM for ergonomic evaluations. However, since 1992, several advances have been made in the field of digital human modeling and optical motion capture, and it is believed that a modern validation of the two systems could serve others in academic and industry alike when choosing a methodology toward capturing ergonomic data. The purpose of this research is to validate the methods of collecting dynamic data and predicting injury risk in humans during lifting procedures.

The current research sought to construct a computational model of human navigation for virtual three dimensional environments. The model was implemented within the ACT-R cognitive architecture [1]. The navigation model incorporates visual search, encoding object features and spatial relationships, motion, obstacle avoidance, and incidental visual memory.

In this paper, we have proposed a unified data based approach which aims to predict both reach envelops and reach discomfort for a digital human model. Reach envelops can be obtained by applying the existing reach posture data to a new subject according to simulation scenario. Four reach surfaces are proposed according to the radial distance from the shoulder. The discomfort of a target on each surface needs to be defined at first. Then, the discomfort of an intermediate distance between two reach distances is interpolated. The proposed approach is illustrated by the data of a previous study. In this study, 38 young and elderly subjects were instructed to reach 94 targets for each from a seated position, covering a large reachable space.

In order to retrieve similar motion data from Mocap database, each human joint’s motion clip is regarded as a bag, while each of its segments is regarded as an instance. 3D temporal-spatial features are extracted and data driven decision trees are automatically constructed to reflect the influence of each point during the comparison of motion similarity. At last we use the method of multiple instance retrieval to complete motion retrieval. Experiment results show that our approaches are effective for motion data retrieval.

In this paper, a novel approach is presented for motion retrieval based on double-reference inde(DRI) in Motion Capture(Mocap) database. Due to high dimensionality of motion’s feature, the Isomap nonlinear dimensionality reduction is used. For handling new motion data, Isomap is generalized based on the estimation of underlying eigenfunctions. Then DRI is build based on selecting a small set of representative motion clips in the database. So we can get candidate set by abandoning most unrelated motion clips to reduce the number of costly similarity measure significantly. Experimental results show that our methods are effective for motion data retrieval in large database.

This paper proposed a layered fuzzy model of facial expression generation, in which the layers of physiological model at low level, emotional model at middle level and social rules at high level determine the fuzzy facial expression generation. In the layered fuzzy facial expression generation system, facial expressions of 26 emotions can be fuzzily generated, as well as social expressions and instinctive expressions. Experiment results indicated that the model of layered fuzzy facial expression generation works well in displaying lifelike facial expressions.

A inverse dynamical model for slip gait developed by using Kane’s method of dynamics is described in this paper. The modeling was based on two separate sub-systems: anti-slip and anti-fall. Both sub-systems were modeled as an open kinematic chain and formulated using the same equations, so that the whole slip and fall process could be simulated using the same equations by switching input data. In the simulation, only kinematic data need to be input to obtain the joint moments and horizontal ground reaction force in the whole slip and fall process. The kinematic input data were acquired from one health male subject who was asked to perform the normal and slip gait. The anthropometric data for each body segment in the skeletal model was calculated using the body height, weight and the national standards on inertia parameters regression equations. The kinematic and kinetic results from the simulation are discussed in the paper which are well consistent with the conclusions in previous studies .