5 results on '"Pensini, M."'
Search Results
2. COMBINING IMAGE PROCESSING OPERATORS AND NEURAL NETWORKS IN A FACE RECOGNITION SYSTEM
- Author
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Giancarlo Mauri, Paola Flocchini, Maria Pia Pensini, Francesco Gardin, Paolo Stofella, Flocchini, P, Gardin, F, Mauri, G, Pensini, M, and Stofella, P
- Subjects
Supervisor ,Artificial neural network ,business.industry ,Computer science ,Image Processing ,Face Recognition System ,Neural Network ,INF/01 - INFORMATICA ,Image processing ,Facial recognition system ,Tree (data structure) ,Artificial Intelligence ,Pattern recognition (psychology) ,Systems architecture ,Computer Vision and Pattern Recognition ,Artificial intelligence ,Noise (video) ,business ,Software - Abstract
This paper describes a system able to recognize human faces from different perspectives, and which have different expressions. It possibly presents some kind of noise in their representation. The problem of face recognition has been approached using a complex architecture based on a hierarchy of neural networks, with a particular self-referencing structure. The system, in fact, is structured as a tree in which nodes correspond to neural networks, each one having different tasks. Each leaf is a recognition module composed by some networks with different characteristics depending on the different preprocessing operators used. These networks are coordinated by a supervisor in a self-referencing structure. During the training phase, the supervisor, called Meta-Net, observes the behaviour of recognition nets and learns which net is more able in which task, while during the test phase it decides, given an input image, which weights to assign to each network and modifies their output in order to obtain the final result. This architecture shows a high generalization capability and allows the recognition of images with different kinds of noise better than what each single network can do, as confirmed by a preliminary experimental evaluation.
- Published
- 1992
3. Neuromuscular fatigue profile in endurance-trained and power-trained athletes.
- Author
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Garrandes F, Colson SS, Pensini M, Seynnes O, and Legros P
- Subjects
- Adaptation, Physiological physiology, Adult, Electromyography, Exercise Test, France, Humans, Male, United Kingdom, Exercise physiology, Muscle Contraction physiology, Muscle Fatigue physiology
- Abstract
Purpose: This study examined the effects of training background on the relationship between the neuromuscular fatigue profile and maximal voluntary torque production in isometric, concentric, and eccentric contraction modes., Methods: Before and after three sets of 31 isokinetic concentric knee extensions at 60 degrees .s(-1), voluntary and electrically induced contractions were recorded in 14 endurance-trained (ENDU) men (seven cyclists: age 25 +/- 2 yr, mass 70 +/- 8 kg, height 175 +/- 5 cm; and seven triathletes: age 27 +/- 4 yr, mass 71 +/- 5 kg, height 179 +/- 6 cm) and seven explosive power-trained men (EXPLO: age 24 +/- 1 yr, mass 73 +/- 5 kg, height 179 +/- 4 cm). Maximal knee-extension torque, activation level (twitch interpolation technique), electromyographic activity of agonist and antagonist muscles, and twitch contractile properties were assessed., Results: At preexercise, the maximal voluntary isometric and concentric torques of EXPLO were greater than those of ENDU (P < 0.05). After the fatiguing exercise, significant isometric (18%; P < 0.01) and concentric (25%; P < 0.05) torque decreases in EXPLO were associated with, respectively, twitch torque (Pt) and maximal rate of twitch development (+dPt/dt) reductions (P < 0.01) and with an increase in the antagonist coactivation level (P < 0.01). No modification was observed for ENDU. Interestingly, the coactivation level was also increased (P < 0.01) in eccentric contraction for EXPLO, although the maximal eccentric torque decrease (P < 0.01) could not be specifically attributed to any group., Conclusion: The fatiguing exercise induced central and peripheral adaptations, but the mechanisms differed regarding the contraction mode. At pre- and postfatiguing exercise, it seems that the neuromuscular profile depends on the subject's training background and the contraction modes used to assess fatigue.
- Published
- 2007
- Full Text
- View/download PDF
4. Activation of human plantar flexor muscles increases after electromyostimulation training.
- Author
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Maffiuletti NA, Pensini M, and Martin A
- Subjects
- Adult, Electric Stimulation, Electromyography, Humans, Male, Torque, Volition physiology, Exercise physiology, Isometric Contraction physiology, Muscle, Skeletal physiology
- Abstract
Neuromuscular adaptations of the plantar flexor muscles were assessed before and subsequent to short-term electromyostimulation (EMS) training. Eight subjects underwent 16 sessions of isometric EMS training over 4 wk. Surface electromyographic (EMG) activity and torque obtained under maximal voluntary and electrically evoked contractions were analyzed to distinguish neural adaptations from contractile changes. After training, plantar flexor voluntary torque significantly increased under isometric conditions at the training angle (+8.1%, P < 0.05) and at the two eccentric velocities considered (+10.8 and +13.1%, P < 0.05). Torque gains were accompanied by higher normalized soleus EMG activity and, in the case of eccentric contractions, also by higher gastrocnemii EMG (P < 0.05). There was an 11.9% significant increase in both plantar flexor maximal voluntary activation (P < 0.01) and postactivation potentiation (P < 0.05), whereas contractile properties did not change after training. In the absence of a change in the control group, it was concluded that an increase in neural activation likely mediates the voluntary torque gains observed after short-term EMS training.
- Published
- 2002
- Full Text
- View/download PDF
5. Electrical and mechanical H(max)-to-M(max) ratio in power- and endurance-trained athletes.
- Author
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Maffiuletti NA, Martin A, Babault N, Pensini M, Lucas B, and Schieppati M
- Subjects
- Adult, Electric Stimulation, Electromyography, Humans, Male, Muscle Contraction physiology, Muscle Relaxation physiology, Reference Values, Tibial Nerve physiology, H-Reflex physiology, Muscle, Skeletal physiology, Physical Education and Training, Physical Endurance
- Abstract
The aim of this study was to compare the mechanical and electromyographic (EMG) characteristics of soleus motor units activated during maximal H reflex and direct M response among subjects with different histories of physical activity. Power-trained athletes produced stronger twitches, with a higher rate of twitch tension buildup and relaxation, than their endurance counterparts for both maximal H-reflex and maximal M-wave responses. The maximal H-reflex-to-maximal M-wave ratios for both force output (twitch) and EMG wave amplitude were significantly lower in power-trained than endurance-trained athletes. However, power-trained athletes exhibited a significantly greater twitch-to-EMG ratio for the reflexly activated motor units with respect to the entire motor pool, whereas endurance-trained athletes had comparable twitch-to-EMG ratios for both reflexly and directly activated units. Power training increases the force output of the whole ensemble of the motor units, thereby compensating for the lower efficacy of the reflex transmission between Ia spindle afferent input and soleus alpha-motoneuron. On the other hand, the lower level of force evoked by the reflexly activated units in endurance-trained athletes is associated with a greater motor pool reflex excitability. Therefore, endurance-trained athletes produce the necessary force by recruitment of more slow-twitch units than do other subjects for comparable levels of force and type of task.
- Published
- 2001
- Full Text
- View/download PDF
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