Optimization of the Seating Position in a Human-Powered Vehicle

Until recently, most of the human-powered vehicles (HPV) were designed focusing solely on its aerodynamics characteristic. In many of these HPV designs, the rider seating position was arbitrarily chosen without consideration of its effect on the rider\u27s comfort and cycling effectiveness. Also, there is no guarantee that the seating position is related to maximum power output. Too (1991) used an experimental approach to determine that the rider will produce the maximum anaerobic power when the seat tube angle of a bicycle is at 75° whereas Hull and Gonzalez (1990) used an engineering approach to optimize the cycling biomechanics. However several factors. including aerodynamic effects, were not considered in both studies. The objective of this study was, therefore, to find the optimal rider\u27s seating position in HPV for either aerobic or anaerobic performance. The method is based on modeling a mechanism equivalent to the hip, knee, and ankle joints. All physical constraints on the motion of these three joints as well as the HPV design constraints are mathematically described. Nonlinear programming techniques were used to reach an optimal solution for either aerobic or anaerobic designs. To test the validity of the model, it was compared to the experimental results of the anaerobic cycling power test presented by Too (1991)

Temporal sparse feature auto-combination deep network for video action recognition

In order to deal with action recognition for large‐scale video data, we present a spatio‐temporal auto‐combination deep network, which is able to extract deep features from short video segments by making full use of temporal contextual correlation of corresponding pixels among successive video frames. Based on conventional sparse encoding, we further consider the representative features in adjacent nodes of the hidden layers according to activation states similarities. A sparse auto‐combination strategy is applied to multiple input maps in each convolution stage. An information constraint of the representative features of hidden layer nodes is imposed to handle the adaptive sparse encoding of the topology. As a result, the learned features can represent the spatio‐temporal transition relationships better and the number of hidden nodes can be restricted to a certain range. We conduct a series of experiments on two public data sets. The experimental results show that our approach is more effective and robust in video action recognition compared with traditional methods

On 2D Viscoelasticity with Small Strain

An exact two-dimensional rotation-strain model describing the motion of Hookean incompressible viscoelastic materials is constructed by the polar decomposition of the deformation tensor. The global existence of classical solutions is proved under the smallness assumptions only on the size of initial strain tensor. The proof of global existence utilizes the weak dissipative mechanism of motion, which is revealed by passing the partial dissipation to the whole system.Comment: Different contributions of strain and rotation of the deformation are studied for viscoelastic fluids of Oldroyd-B type in 2

Optimization Of The Seating Position In A Human-Powered Vehicle

An aerobic and an anaerobic designs for a human-powered vehicle (HPV) are considered. In both cases the rider's seating position is an important design factor for either maximizing the vehicle's speed or minimizing the rider's energy requirement. The rider's seating position affects not only the aerodynamic performance of the vehicle, but more importantly the rider's physical performance. The goal of this study is to use optimization methods to improve the HPV design. The paper starts by deriving equation for torque produced by the hip and knee joints during pedaling. These equations include inertial and gravity effects. In the aerobic design the objective function is to reduce both the average and maximum variation of the torques on the hip and knee joints. In the anaerobic design, the objective function is to maximize the average of the torques on the hip and knee joints. Hip and joint torques are function of the vehicle's speed and the aerodynamic coefficient as well as the road conditions. The design variables are: 1. the seat inclination angle 2. the seat to pedal angle 3. the seat to pedal distance 4. the crank length. The search for optimal solution in both cases is constrained by: 1. the motion limits of hip and knee joints 2. conditions to ensure that the seat to crank position results in full rotation of the crank. 3. visibility of the road that limits how far the seat can be inclined for safe driving. The results have been verified by comparing it to the experimental data of Too [ 1991] for maximum anaerobic performance of a stationary bike. Both experimental and analytical techniques produced close values of the seat to pedal angles