Touch-down and take-off characteristics of the long jump performance of world level above- and below-knee amputee athletes

The aims of this study were to establish the take-off characteristics of long jump performance of disabled amputee athletes, and to establish to what extent amputee athletes conform to a model of performance defined for elite able-bodied athletes. The jumps of 8 male below-knee (trans-tibial) and 8 male above-knee (trans-femoral) amputee athletes who competed in the finals of the long jump at the 1998 World Disabled Championships were recorded in the sagittal plane on video (50 Hz). Approach speed was measured using a laser Doppler system. The best jump for each athlete was digitized, and kinematic data from the key instants of touch-down (TD), maximum knee flexion (MKF) and take-off (TO) were obtained. Amputees demonstrated a lower approach speed and jumped less far than able-bodied athletes although below-knee amputees performed better than above-knee amputees. For each amputee group there was a significant (p < 0.05) linear relationship between approach speed and distance jumped. With the exception of their slower horizontal speed and greater negative vertical speed at touch-down, below-knee amputees demonstrated characteristics of technique that were similar to elite able-bodied long jumpers. Above-knee amputees at touchdown had a more upright trunk, smaller hip and knee angles and consequently a smaller leg angle. This was attributed to the difficulty of taking off on the last stride on the prosthetic limb. Consequently, above-knee amputees were less able to gain vertical velocity during the compression (TD-MKF) phase, but were able to compensate for this by using a greater hip range of motion during the extension (MKF-TO) phase. It was concluded that below-knee amputees displayed the same basic jumping technique as elite able-bodied long jumpers, but above-knee amputees did not. These findings have implications for the training and technical preparation of amputee long jumpers.     

Touch-down and take-off characteristics of the long jump performance of world level above- and below-knee amputee athletes

The aims of this study were to establish the take-off characteristics of long jump performance of disabled amputee athletes, and to establish to what extent amputee athletes conform to a model of performance defined for elite able-bodied athletes. The jumps of 8 male below-knee (trans-tibial) and 8 male above-knee (trans-femoral) amputee athletes who competed in the finals of the long jump at the 1998 World Disabled Championships were recorded in the sagittal plane on video (50 Hz). Approach speed was measured using a laser Doppler system. The best jump for each athlete was digitized, and kinematic data from the key instants of touch-down (TD), maximum knee flexion (MKF) and take-off (TO) were obtained. Amputees demonstrated a lower approach speed and jumped less far than able-bodied athletes although below-knee amputees performed better than above-knee amputees. For each amputee group there was a significant (p < 0.05) linear relationship between approach speed and distance jumped. With the exception of their slower horizontal speed and greater negative vertical speed at touch-down, below-knee amputees demonstrated characteristics of technique that were similar to elite able-bodied long jumpers. Above-knee amputees at touchdown had a more upright trunk, smaller hip and knee angles and consequently a smaller leg angle. This was attributed to the difficulty of taking off on the last stride on the prosthetic limb. Consequently, above-knee amputees were less able to gain vertical velocity during the compression (TD-MKF) phase, but were able to compensate for this by using a greater hip range of motion during the extension (MKF-TO) phase. It was concluded that below-knee amputees displayed the same basic jumping technique as elite able-bodied long jumpers, but above-knee amputees did not. These findings have implications for the training and technical preparation of amputee long jumpers.     

On the optimal design of a plate submitted to a rupture criterion

In Structural Optimization one often finds the problem of minimizing the weight of a plate under some geometric constraints and considering that it must not rupt. We study in this paper the dependence on the thickness of a solution $\text{h}{}^1$ of the three-dimensional optimization problem, namely the convergence of $\text{h}{}^1$ to a solution of the two-dimensional optimization problem. We expose the results in the case of a clamped plate and we extend these results to the case when the plate is not clamped on its entire boundary.     

Receding-horizon optimal control of the current profile evolution during the ramp-up phase of a tokamak discharge

The control of the toroidal current density spatial profile in tokamak plasmas will be absolutely critical in future commercial-grade reactors to enable high fusion gain, non-inductive sustainment of the plasma current for steady-state operation, and magnetohydrodynamic (MHD) instability-free performance. The evolution in time of the current profile is related to the evolution of the poloidal magnetic flux, which is modeled in normalized cylindrical coordinates using a partial differential equation (PDE) usually referred to as the magnetic flux diffusion equation. The control objective during the ramp-up phase is to drive an arbitrary initial profile to approximately match, in a short time windows during the early flattop phase, a predefined target profile that will be maintained during the subsequent phases of the discharge. Thus, such a matching problem can be treated as an optimal control problem for a PDE system. A distinctive characteristic of the current profile control problem in tokamaks is that it admits interior, boundary and diffusivity actuation. A receding-horizon control scheme is proposed in this work to exploit this unique characteristic and to solve the associated open-loop finite-time optimal control problem using different optimization techniques. The efficiency of the proposed scheme is shown in simulations.     

立定跳远自动测距系统的设计

本文讨论了立定跳远自动测距仪的原理、开发过程和实现结果。选择三套方案，进行了可行性、经济性等对比分析，最终选中了以单片机为基础的开发原理。其中主要包括：三种方案的对比以及最后确定；以单片机为基础，原理的讨论，程序存储器(ROM)、数据存储器(RAM)、I／O口的扩展，在原理图的硬件电路基础上，用汇编语言编制程序，并用Proview32调试、仿真程序，对程序结构进行了优化。     

A three-dimensional criterion for the determination of optimal grip points

Multifingered grasping has aroused remarkable interest because it makes possible the manipulation of objects of different shapes and sizes. However, manipulating and picking up objects in unstructured environments requires accurate contact-point selection. Generally, such processes are subject to external forces which are difficult to predict and may change during task execution.In this paper, an optimization criterion is proposed which is meant to select the optimal grip points in a three-dimensional problem for any number of contact points. This method may be applied to three-dimensional objects of any shape (curved or polygonal) and does not require that the external forces acting on the object be known. A grasp quality index is presented which has been obtained by minimizing the grasping forces required to balance a generalized external disturbance. The optimization criterion has led to the formulation of a single optimization problem with non-linear constraints. Finally, the paper presents the results obtained in searches for the optimal grip points on some two- and three-dimensional objects.     

On the weighting factors of the quadratic criterion in optimal control

By the introduction of the time integral of the output variable of a second-order system, the optimal feedback control law with respect to the quadratic performance criterion gives the conventional proportional-integral-derivative (PID) control. Some comparisons between the weighting factors of the quadratic criterion and the parameters of the PID controller are given. The values of the weighting factors corresponding to the classical methods of Cohen-Coon and Ziegler-Nichols are calculated ; negative values of the weighting factors are obtained.     

Determine the optimal carrier selection for a logistics network based on multi-commodity reliability criterion

From the perspective of supply chain management, the selected carrier plays an important role in freight delivery. This article proposes a new criterion of multi-commodity reliability and optimises the carrier selection based on such a criterion for logistics networks with routes and nodes, over which multiple commodities are delivered. Carrier selection concerns the selection of exactly one carrier to deliver freight on each route. The capacity of each carrier has several available values associated with a probability distribution, since some of a carrier's capacity may be reserved for various orders. Therefore, the logistics network, given any carrier selection, is a multi-commodity multi-state logistics network. Multi-commodity reliability is defined as a probability that the logistics network can satisfy a customer's demand for various commodities, and is a performance indicator for freight delivery. To solve this problem, this study proposes an optimisation algorithm that integrates genetic algorithm, minimal paths and Recursive Sum of Disjoint Products. A practical example in which multi-sized LCD monitors are delivered from China to Germany is considered to illustrate the solution procedure.     

Necessary conditions for optimal design of structures with a nonsmooth eigenvalue based criterion

Necessary conditions of optimality for maximizing the buckling load for single or multimodal structures are derived using generalized gradients. The possible design dependence of the pre-buckling displacement is taken into account and implies the appearance of a number of adjoint problems not normally present in, for example, standard vibration problems. The relation to other equivalent forms of the necessary conditions are pointed out and the formulae are demonstrated on simple example problems.     

Inverse optimal adaptive stochastic gain assignment for a class of nonlinear systems with Markovian jump

This paper deals with the inverse optimal adaptive stochastic gain assignment problem for a class of Markovian jump nonlinear systems with constant unknown parameters. The Wiener noises have bounded but unknown covariance. It is shown that a sufficient condition to solve this problem is the existence of a Lyapunov function for a corresponding auxiliary system. By employing backstepping technique and common Lyapunov function method, an adaptive control law is designed, which solves this problem for a class of Markovian jump nonlinear systems in strict-feedback form. A numerical example is given to illustrate the theoretical analysis result.     

Improving emergency services efficiency during Islamic pilgrimage through optimal allocation of facilities

The proper allocation of facilities within Islamic holy places is barely studied. These places annually witness millions of pilgrims and guests. The number of people during pilgrimage has been growing recently and is expected to grow further in the future. Different facilities should be optimally allocated to properly serve this large number of people and efficiently respond to their requests. In this paper, we target the problem of optimally allocating facilities within the largest Islamic holy place, Arafat. We evaluate the current allocation with respect to distance, coverage, and cover inequality metrics. Average-case and worst-case values of the three metrics are considered for evaluation. Results show that the current allocation strategy is far from being optimal. For the three considered metrics, we use crowdedness-based techniques to allocate facilities within the area of Arafat. Optimal allocations are first obtained by solving integer programming (IP) models. Thereafter, two widely used metaheuristics, genetic algorithms (GA) and simulated annealing, are experimented and evaluated. Results show that the optimal solution could be easily obtained for coverage and cover inequality metrics. For the distance metric, the computation time of the IP technique is large and GA appears as a good candidate to balance between computation time and solution quality. Finally, we study allocating facilities from a multiobjective perspective. Both scalar-weighted formulation and nondominated sorting genetic algorithm II techniques are considered. Results show that the latter technique outperforms the former technique in the number of generated Pareto-optimal allocations as well as the quality of these allocations.     

An optimal controller arising from minimization of a quadratic performance criterion of indefinite form

The problem of minimizing energy loss in automatic steering of ships is considered. Two ship types are analyzed-a high-speed containership and a large oil tanker. Making use of the sufficiency conditions for existence of a stable closed-loop system, it is shown that there is no theoretical difficulty in using an exact performance criterion for energy losses due to steering with an indefinite form, rather than an approximate criterion which fits the positive semidefiniteness condition of standard linear regulator (LR) theory.     

A review of the minimum maximum criterion for optimal bitallocation among dependent quantizers

In this paper, we review a general framework for the optimal bit allocation among dependent quantizers based on the minimum maximum (MINMAX) distortion criterion. The pros and cons of this optimization criterion are discussed and compared to the well-known Lagrange multiplier method for the minimum average (MINAVE) distortion criterion. We argue that, in many applications, the MINMAX criterion is more appropriate than the more popular MINAVE criterion. We discuss the algorithms for solving the optimal bit allocation problem among dependent quantizers for both criteria and highlight the similarities and differences. We point out that any problem which can be solved with the MINAVE criterion can also be solved with the MINMAX criterion, since both approaches are based on the same assumptions. We discuss uniqueness of the MINMAX solution and the way both criteria can be applied simultaneously within the same optimization framework. Furthermore, we show how the discussed MINMAX approach can be directly extended to result in the lexicographically optimal solution. Finally, we apply the discussed MINMAX solution methods to still image compression, intermode frame compression of H.263, and shape coding applications     

Constraints on the synthesis of optimal manufacturing systems

In this paper the formalism of set theory is used to determine the constraints which bear upon the synthesis of optimal manufacturing systems to perform given work loads.     

Identifying the optimal method of predicting the utilization of cluster resources and grid nodes

A method of determining the optimal model of predicting the queue of tasks of computing clusters and grid nodes is discussed. It is shown that it is possible to use the PREDICTOR statistical prediction software.     

Design of optimal strategies in the problems of discrete system control by the probabilistic criterion

A modification was proposed for the relations of the method of dynamic programming in the problems of optimal stochastic control of the discrete systems by the probabilistic performance criterion. It enabled one to simplify the process of finding the optimal Markov strategy and obtain a suboptimal solution. Its efficiency was verified by the examples of maneuver optimization of the stationary satellite in the neighborhood of a geostationary orbit. An explicit form of the optimal control for the bilinear system with probabilistic terminal criterion was determined using the results obtained.     

Dependence of the optimal phase demodulator on statistical parameters

In this note we show that the filtering phase error variance for the optimal phase demodulator is independent of plant noise spectral density and depends only on output noise-to-signal ratio for the optimal phase demodulator. Hence, our Monte Carlo results are complete.     

On some iterative methods for the determination of optimal paths through a network

Some iterative methods for the determination of optimal path through a network are discussed, and their rates of convergence are compared. This research was supported in part by Comitato di Ingegneria, C.N.R.