-The amount and pattern of litterfall, its nutrient return, initial chemistry of leaf litter, and dynamics of N, P and K associated with leaf-litter decomposition were studied in 33-year-old plantations of two coniferous trees, Chinese fir (Cunninghamia lanceolata, CF) and Fokienia hodginsii (FH), and two broadleaved trees, Ormosia xylocarpa (OX) and Castanopsis kawakamii (CK), and compared with that of an adjacent natural forest of Castanopsis kawakamii (NF, ~150 year old) in Sanming, Fujian, China. Mean annual total litterfall over 3 years of observations was 5.47 Mg·ha -1 in the CF, 7.29 Mg·ha -1 in the FH, 5.69 Mg·ha -1 in the OX, 9.54 Mg·ha -1 in the CK and 11.01 Mg·ha -1 in the NF respectively; of this litterfall, leaf contribution ranged from 58% to 72%. Litterfall in the OX, CK, and NF showed an unimodal distribution pattern, while for the CF and FH, the litterfall pattern was multi-peak. The highest annual Ca and Mg returns were noticed in the FH and in the CK, respectively. The amounts of N, P, and K which potentially returned to the soil were the highest in the NF. The loss of dry matter in leaf litter exhibited a negative exponential pattern during the 750-day decomposition. Using the model x t = A + Be -kt , the annual dry matter decay constants (k) ranged from 1.157 in CF to 4.619 in OX. Initial lignin concentration and lignin/N ratios showed significantly negative correlations with k (r = -0.916, P = 0.011; r = -0.473, P = 0.041), whereas initial N concentration showed low positive correlations (r = 0.225, P = 0.038). Using the model x t = A + Be -kt , the decay constant of N (k N ) ranged from 0.769 in CF to 4.978 in OX; the decay constant of P (k P ) ranged from 1.967 in the OX to 4.664 in the NF; and the decay constant of K (k K ) seemed very similar among these forests (5.250-5.992). The decay constants of nutrients during leaf-litter decomposition can be arranged in the sequence of k K > k P > k N , except for leaf litter of OX wherelitterfall / nutrient return / litter decomposition / reafforestation / natural forest / Cunninghamia lanceolata / Fokienia hodginsii / Ormosia xylocarpa / Castanopsis kawakamii Résumé -Chute de feuilles, retour de nutriments et décomposition des feuilles de la litière dans quatre plantations en comparaison avec une forêt naturelle en Chine subtropicale. La quantité et la dynamique de chute de litière, le retour des nutriments, la composition chimique initiale des feuilles de la litière et la dynamique de N, Pet K associée à la décomposition de la litière ont été étudiés dans 2 plantations de conifères (Cunninghamia lanceolata, CF and Fokienia hodginsii, FH) âgées de 33 ans et 2 peuplements feuillus (Ormosia xylocarpa, OX et Castanopsis kawakamii, CK), comparativement à une forêt naturelle adjacente de Castanopsis kawakamii, NF, âgée d'environ 150 ans à Sanming, Fujian, Chine. Sur 3 années d'observations, la moyenne annuelle de chute de litière a été de 5,47 Mg·ha -1 pour CF, 7,29 Mg·ha -1 pour FH, 5,69 Mg·h -1 pour OX, 9,54 Mg·hg -1 pour CK et 11,01 Mg·h...

No abstract

This paper investigates the coordination of multiple robots with pre-specified paths, considering motion safety and minimizing the traveling time. A method to estimate possible collision point along the local paths of the robots is proposed. The repulsive potential energy is computed based on the distances between the robots and the potential collision points. This repulsive potential energy is used as the cost map of the probabilistic roadmap (PRM), which is constructed in the coordination space for multiple robots taking into account both motion time cost and safety cost. We propose a search method on the PRM to obtain the Pareto-optimal coordination solution for multiple robots. Both simulation and experimental results are presented to demonstrate the effectiveness of the algorithms.

This paper investigates task allocation for multiple robots by applying the game theory-based negotiation approach. Based on the initial task allocation using a contract net-based approach, a new method to select the negotiation robots and construct the negotiation set is proposed by employing the utility functions. A negotiation mechanism suitable for the decentralized task allocation is also presented. Then, a game theory-based negotiation strategy is proposed to achieve the Pareto-optimal solution for the task reallocation. Extensive simulation results are provided to show that the task allocation solutions after the negotiation are better than the initial contract net-based allocation. In addition, experimental results are further presented to show the effectiveness of the approach presented.

No abstract

In this paper, we proposed a novel master-slave robotic catheterization system with force feedback for VIS (Vascular Interventional Surgery). The force feedback to the operator on the master side is the key factor to improve the safety during VIS. The developed system used the MR (magneto rheological) fluid to realize force feedback, and it used the developed multidimensional monitoring interface to realize the visualization of force feedback, the developed multidimensional monitoring interface can monitor the motion information of the catheter and contact force between catheter tip or side wall and blood vessel wall, and the motion data of the catheter was collected and generated diagram for reference to surgeon. We have developed a force sensor array to detect the contact force between catheter tip or side wall and blood vessel wall. The force information was detected by the developed contact force sensor array when the catheter contacted with the blood vessel. The force feedback and multidimensional information monitoring interface evaluation experiments were done, the tracking characteristic evaluation experiments were also carried out, the experimental results indicated that the developed novel robotic catheterization system with force feedback and visualization of force feedback is effective for VIS, it can improve the safety during VIS.

No abstract

No abstract