The health and financial cost of falls has spurred research to differentiate the characteristics of fallers and non-fallers. Postural stability has received much of the attention with recent studies exploring various measures of entropy. This study compared the discriminatory ability of several entropy methods at differentiating two paradigms in the center-of-pressure (COP) of elderly individuals: 1.) eyes open (EO) versus eyes closed (EC) and 2.) fallers (F) versus non-fallers (NF). Methods were compared using the area under the curve (AUC) of the receiver-operating characteristic (ROC) curves developed from logistic regression models. Overall, multiscale entropy (MSE) and composite multiscale entropy (CompMSE) performed the best with AUCs of 0.71 for EO/EC and 0.77 for F/NF. When methods were combined together to maximize the AUC, the entropy classifier had an AUC of for 0.91 the F/NF comparison. These results suggest researchers and clinicians attempting to create clinical tests to identify fallers should consider a combination of every entropy method when creating a classifying test. Additionally, MSE and CompMSE classifiers using polar coordinate data outperformed rectangular coordinate data, encouraging more research into the most appropriate time series for postural stability entropy analysis.

No abstract

A generalized scaling law, based on the classical fracture mechanics approach, is developed to predict the bond strength of adhesive systems. The proposed scaling relationship depends on the rate of change of debond area with compliance, rather than the ratio of area to compliance. This distinction can have a profound impact on the expected bond strength of systems, particularly when the failure mechanism changes or the compliance of the load train increases. Based on the classical fracture mechanics approach for rate-independent materials, the load train compliance should not affect the force capacity of the adhesive system, whereas when the area to compliance ratio is used as the scaling parameter, it directly influences the bond strength, making it necessary to distinguish compliance contributions. To verify the scaling relationship, single lap shear tests were performed for a given pressure sensitive adhesive (PSA) tape specimens with different bond areas, number of backing layers, and load train compliance. The shear lag model was used to derive closed-form relationships for the system compliance and its derivative with respect to the debond area. Digital image correlation (DIC) is implemented to verify the non-uniform shear stress distribution obtained from the shear lag model in a lap shear geometry. The results obtained from this approach could lead to a better understanding of the relationship between bond strength and the geometry and mechanical properties of adhesive systems.

No abstract

No abstract

Currently robot designers are ever more inspired by nature to develop and design legged robots to mimic the walking style of insects over uneven and rough surfaces. In this work, walking behavior and method of a kind of spider Araneus diadematus are investigated. Image processing techniques are used to obtain kinematic parameters of the spider's legs. The positions of defi ned points on the spider's legs were recorded in terms of time. After extracting the necessary data, a linkage mechanism of the legs was designed. By using the position of defi ned points on spider's legs as input to our model and implementation of trigonometric relations, parameters such as angle, angular velocity, and angular acceleration of each link were obtained. Then, a model of linkage mechanism for the spider's legs in SIMULINK environment of MATLAB was created. By allocating mechanical properties of linkages such as mass and moment of inertia to the model, quantities of torque in joints, which were needed for producing the traversed path of spider's legs, were obtained. These quantities can be used for selection and control of actuators in the novel robotic system in order to mimic the spider's walking style. INTRODUCTIONToday there exist many challenges to fabricate robots that mimic insect's movements. The reason behind this requirement is that wheeled robots are unable to go over different obstacles like uneven surfaces. Wheeled robots have higher effi ciency in terms of energy consumption and their control is also easy. On the other hand, legged robots due to the fact that they can move over uneven surfaces that are closer to human's real world environment would be more effective. Based on these advantages, the tendency of engineers towards fabrication of legged robots which are inspired from insect walking has noticeably increased. In this regards, several investigations on different insects such as cockroaches [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15], ants [16][17][18][19][20][21], and crickets [22][23][24][25][26][27][28][29][30] have been carried out. Mean while another insect which has shown a higher level of fl exibility and performance during walking, has been the spider which has high mobility over uneven and irregular surfaces. Note that the animals move the greatest distance while using minimum energy [31]. Therefore, it is very important to carry out an accurate study on the spider's walking and its mobility. Also it is crucial to determine and analyze parameters involved in its movements in order to develop the model for fabrication of legged robots.In this paper, fi rst the traversed path of the spider's legs will be investigated. Then, the position of defi ned points on the spider's legs and parameters relating to its movement will be determined using image processing methods. By using this data as input to an equivalent linkage mechanism of spider's legs and employing trigonometric relations, the angle between each linkage with respect to horizontal axis will be obtained. Then, by using numerical ...

No abstract

No abstract