Improving Social Recommender Systems

Recommender systems play a significant role in reducing information overload for people visiting online sites, but their accuracy could be improved by using data from online social networks and electronic communication tools.     

Repair of left ventricular aneurysm: long-term results of linear repair versus endoaneurysmorrhaphy

BACKGROUND: Recently, endoaneurysomorrhaphy has been proposed as a more physiologic repair of postinfarction left ventricular aneurysm than is linear repair. There are only a few studies comparing the short-term and long-term results of the two techniques. METHODS: Clinical outcomes and echocardiographic measurements of left ventricular volume and sphericity in 27 patients who underwent endoaneurysmorrhaphy were compared with those in 20 patients who had linear repair. RESULTS: The two groups were matched with respect to age, gender, comorbid risk factors, functional class, urgency of the operation, and concomitant procedures. Preoperatively, left ventricular ejection fraction was lower in the endoaneurysmorrhaphy group (0.25 +/- 0.08 versus 0.30 +/- 0.09; p = 0.03). Follow-up was available in 44 patients (94%) and ranged from 2 to 86 months (mean, 41.0 +/- 26.5 months). Thirty-day operative mortality, perioperative complications, 5-year survival, and freedom from cardiac death were similar. Early postoperative percentage increase in left ventricular ejection fraction was greater after endoaneurysmorrhaphy (0.51 +/- 0.64 versus 0.18 +/- 0.48; p = 0.036). Long-term functional improvement was significantly better in the endoaneurysmorrhaphy group: At the time of last follow-up, 88% of patients were in New York Heart Association class I/II, compared with 53% after linear repair (p = 0.01). There were no measurable differences between the groups with respect to left ventricular ejection fraction (0.28 +/- 0.11 versus 0.27 +/- 0.11; p = 0.90), left ventricular volume (171.6 +/- 59.1 versus 169.9 +/- 54.4 mL; p = 0.94), and sphericity index (0.61 +/- 0.09 versus 0.61 +/- 0.12; p = 1.0). CONCLUSIONS: Despite having a similar effect on left ventricular geometry, endoaneurysmorrhaphy resulted in a greater increase in postoperative left ventricular ejection fraction and a substantially improved long-term clinical outcome.     

N-tuple features for OCR revisited

N-tuple features for optical character recognition have received only scattered attention since the 1960s. Our main purpose is to show that advances in computer technology and computer science compel renewed interest. N-tuple features are useful for printed character classification because they indicate the presence or absence of a given rigid configuration of n black and white pixels in a pattern. Desirable n-tuples fit each pattern of a specified (positive) training set of characters in at least p different shift positions, and fail to fit each pattern of a specified (negative) training set by at least n-q pixels in each shift position. We prove that the problem of finding a distinguishing n-tuple is NP-complete, by examining a natural subproblem with binary strings called the missing configuration problem. The NP-completeness result notwithstanding, distinguishing n-tuples are found automatically in a few seconds on contemporary workstations. We exhibit a practical search algorithm for generating, from a small training set, a collection of n-tuples with low class-conditional correlation and with specified design parameters n, p, and q. The generator, which is available on the Internet, is empirically shown to be effective through a comparison with a benchmark generator. We show experimentally that the design parameters provide a useful tradeoff between distinguishing power and generation time, and also between the conditional probabilities for the positive and negative classes. We explore the feature probabilities obtainable for various dichotomies, and show that the design parameters control the feature probabilities     

Constructability and Economics of FRP Reinforcement Cages for Concrete Beams

This paper presents a quantitative economic analysis and a qualitative constructability analysis of three-dimensional fiber-reinforced plastic (FRP) reinforcement cages for concrete beams. Material, labor, and life-cycle costs are provided, and construction practice aspects are discussed. The results of the analyses indicate that prefabricated FRP cages can offer benefits to the construction industry. Although the initial costs of the FRP materials are likely to be higher than those of steel rebar, there is a significant potential for cost savings due to reduced maintenance and labor costs, as a result of the corrosion resistance of the FRP and the increased construction productivity. When direct life-cycle costs are considered, FRP reinforcements already constitute, in many cases, an economically competitive alternative to conventional steel reinforcement in adverse environments. If, in addition, the indirect cost savings as well as quality and safety issues are considered, the FRP reinforcement may be even more competitive.     

AHP-Based Equipment Selection Model for Construction Projects

Selection of equipment for construction projects, a key factor in the success of the project, is a complex process. Current models offered by the literature fail to provide adequate solutions for two major issues: the systematic evaluation of soft factors, and the weighting of soft benefits in comparison with costs. This paper presents a selection model based on analytic hierarchy process (AHP), a multiattribute decision analysis method, with a view to providing solutions for these two issues. The model has the capacity to handle a great number of different criteria in a way that truly reflects the complex reality, to incorporate the context and unique conditions of the project, and to allow for manifestation of user experience and subjective perception. The model was implemented in an in-house developed system that was improved and validated through testing by senior professionals. The main academic contribution of the study is in the modification of AHP to correspond with the nature of equipment selection and in its utilization as an effective means for the formalization of knowledge possessed by competent, experienced practitioners. On the practical side, the proposed model offers an efficient, convenient tool that forces the users into orderly, methodical thinking, guides them in making logical, consistent decisions, and provides a facility for all necessary computations.