We investigated the distribution and frequency of damage to tree stands adjacent to low-volume roads according to the type of hillside materials involved（soil or rock） and hillside gradient in mountainous forests of...We investigated the distribution and frequency of damage to tree stands adjacent to low-volume roads according to the type of hillside materials involved（soil or rock） and hillside gradient in mountainous forests of northern Iran. A total of 80 plots were systematically and randomly sampled to record damaged trees（bending,crushing and wounding） by class of hillside gradient and materials at the edge of road. Tree wounding and crushing at rock slopes was significantly greater than at hillsides with a mix of clay soil（p ／ 0.05）. Damage on hillsides with slope gradients[45% were 2, 8.5 and 2.3 times more frequent than on hillsides with slope gradient／15% for bending, crushing and wounding, respectively. The damage distribution varied according by type and the most frequent damage was tree wounding（p ／ 0.05）. The damage distribution was measured at distances of 4, 5 and 8 m from the road fillslope for tree bending, crushing and wounding, respectively. Using hydraulic excavators and physical barriers（wooden obstruction and synthetic holder） during earthworks for road construction could reduce these damage.展开更多
Suffix trees are the key data structure for text string matching, and are used in wide application areas such as bioinformatics and data compression. Ukkonen algorithm is deeply investigated and a new algorithm, which...Suffix trees are the key data structure for text string matching, and are used in wide application areas such as bioinformatics and data compression. Ukkonen algorithm is deeply investigated and a new algorithm, which decreases the number of memory operations in construction and keeps the result tree sequential, is proposed. The experiment result shows that both the construction and the matching procedure are more efficient than Ukkonen algorithm.展开更多
Regularized Boolean operations have been widely used in 3D modeling systems. However, evaluating Boolean operations may be quite numerically unstable and time consuming, especially for iterated set operations. A novel...Regularized Boolean operations have been widely used in 3D modeling systems. However, evaluating Boolean operations may be quite numerically unstable and time consuming, especially for iterated set operations. A novel and unified technique is proposed in this paper for computing single and iterated set operations efficiently, robustly and exactly. An adaptive octree is combined with a nested constructive solid geometry （CSG） tree by this technique. The intersection handling is restricted to the cells in the octree where intersection actually occurs. Within those cells, a CSG tree template is instanced by the surfaces and the tree is converted to planebased binary space partitioning （BSP） for set evaluation; Moreover, the surface classification is restricted to the ceils in the octree where the surfaces only come from a model and are within the bounding-boxes of other polyhedrons. These two ways bring about the efficiency and scalability of the operations, in terms of runtime and memory. As all surfaces in such a cell have the same classification relation, they are classified as a whole. Robustness and exactness are achieved by integrating plane-based geometry representation with adaptive geometry predicate technique in intersection handling, and by applying divide-and-conquer arithmetic on surface classification. Experimental results demonstrate that the proposed approach can guarantee the robustness of Boolean computations and runs faster than other existing approaches.展开更多
文摘We investigated the distribution and frequency of damage to tree stands adjacent to low-volume roads according to the type of hillside materials involved（soil or rock） and hillside gradient in mountainous forests of northern Iran. A total of 80 plots were systematically and randomly sampled to record damaged trees（bending,crushing and wounding） by class of hillside gradient and materials at the edge of road. Tree wounding and crushing at rock slopes was significantly greater than at hillsides with a mix of clay soil（p ／ 0.05）. Damage on hillsides with slope gradients[45% were 2, 8.5 and 2.3 times more frequent than on hillsides with slope gradient／15% for bending, crushing and wounding, respectively. The damage distribution varied according by type and the most frequent damage was tree wounding（p ／ 0.05）. The damage distribution was measured at distances of 4, 5 and 8 m from the road fillslope for tree bending, crushing and wounding, respectively. Using hydraulic excavators and physical barriers（wooden obstruction and synthetic holder） during earthworks for road construction could reduce these damage.
基金supported by the National Natural Science Foundation of China(6050203260672068).
文摘Suffix trees are the key data structure for text string matching, and are used in wide application areas such as bioinformatics and data compression. Ukkonen algorithm is deeply investigated and a new algorithm, which decreases the number of memory operations in construction and keeps the result tree sequential, is proposed. The experiment result shows that both the construction and the matching procedure are more efficient than Ukkonen algorithm.
基金supported by the Natural Science Foundation of China under Grant No.61202154 and No.61133009the National Basic Research Project of China under Grant No.2011CB302203+2 种基金Shanghai Pujiang Program under Grant No.13PJ1404500the Science and Technology Commission of Shanghai Municipality Program under Grant No.13511505000the Open Project Program of the State Key Lab of CAD&CG of Zhejiang University under Grant No.A1401
文摘Regularized Boolean operations have been widely used in 3D modeling systems. However, evaluating Boolean operations may be quite numerically unstable and time consuming, especially for iterated set operations. A novel and unified technique is proposed in this paper for computing single and iterated set operations efficiently, robustly and exactly. An adaptive octree is combined with a nested constructive solid geometry （CSG） tree by this technique. The intersection handling is restricted to the cells in the octree where intersection actually occurs. Within those cells, a CSG tree template is instanced by the surfaces and the tree is converted to planebased binary space partitioning （BSP） for set evaluation; Moreover, the surface classification is restricted to the ceils in the octree where the surfaces only come from a model and are within the bounding-boxes of other polyhedrons. These two ways bring about the efficiency and scalability of the operations, in terms of runtime and memory. As all surfaces in such a cell have the same classification relation, they are classified as a whole. Robustness and exactness are achieved by integrating plane-based geometry representation with adaptive geometry predicate technique in intersection handling, and by applying divide-and-conquer arithmetic on surface classification. Experimental results demonstrate that the proposed approach can guarantee the robustness of Boolean computations and runs faster than other existing approaches.
