ABSTRACT
The user-based collaborative filtering (CF) algorithm is one of the most popular approaches for making recommendation. Despite its success, the traditional user-based CF algorithm suffers one serious problem that it only measures the influence between two users based on their symmetric similarities calculated by their consumption histories. It means that, for a pair of users, the influences on each other are the same, which however may not be true. Intuitively, an expert may have an impact on a novice user but a novice user may not affect an expert at all. Besides, each user may possess a global importance factor that affects his/her influence to the remaining users. To this end, in this paper, we propose an asymmetric user influence model to measure the directed influence between two users and adopt the PageRank algorithm to calculate the global importance value of each user. And then the directed influence values and the global importance values are integrated to deduce the final influence values between two users. Finally, we use the final influence values to improve the performance of the traditional user-based CF algorithm. Extensive experiments have been conducted, the results of which have confirmed that both the asymmetric user influence model and global importance value play key roles in improving recommendation accuracy, and hence the proposed method significantly outperforms the existing recommendation algorithms, in particular the user-based CF algorithm on the datasets of high rating density.
Subject(s)
Algorithms , Databases as Topic , Humans , Principal Component AnalysisABSTRACT
OBJECTIVE: To investigate the therapeutic effect of reverse radial hypothenar flap for finger soft tissue defect. METHODS: From Mar. 2006 to Mar. 2010, 13 cases (14 fingers) with finger soft tissue defects were treated with reverse radial hypothenar flaps pedicled with ulnar palmar digital artery of little finger. The defects were 1.9 cm x 1.5 cm -4.0 cm x 2.0 cm in size. The flap size ranged from 1.5 cm x 2.0 cm to 4.0 cm x 2.0 cm. RESULTS: All the flaps survived completely with primary healing both in donor and recipient area. 12 cases (13 fingers) were followed up for 1-3 years. The flaps color was similar to the unaffected fingers. Cicatricial contracture happened in one case due to contracture of palmar fascia. The two-point discrimination distance on flap was 3.2-5.3mm. The active and passive movement of finger joints was evaluated as excellent in 12 fingers, good in one finger. There was no complaint about the feeling at the donor site. Two months after operation, all patients could go back to work. CONCLUSIONS: The reverse radial hypothenar flap is very suitable for finger soft tissue defect with less morbidity to donor site.
