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Abstract: Complex variability is a significant problem in predicting construction crew productivity. Neural Networks using supervised learning methods like Feed Forward Back Propagation (FFBP) and General Regression Neural Networks (GRNN) have proved to be more advantageous than statistical methods like multiple regression, considering factors like the modelling ease and the prediction accuracy. Neural Networks using unsupervised learning like Self Organizing Maps (SOM) have additionally been introduced as methods that overcome some of the weaknesses of supervised learning methods through their clustering ability. The objective of this article is thus to compare the performances of FFBP, GRNN and SOM in predicting construction crew productivity. Related data has been collected from 117 plastering crews through a systematized time study and comparison of prediction performances of the three methods showed that SOM have a superior performance in predicting plastering crew productivity. [Copyright &y& Elsevier]

Abstract: A Self Organizing Map (SOM), is a machine learning method that represents high-dimensional data in low-dimensional form without losing topological relations of the data. After an unsupervised learning process, it organizes the data on the basis on similarity. In the current study, a SOM based algorithm has been developed which not only produces 2-D maps to analyze the relationship between various factors and crew productivity, but also predicts productivity under given conditions. Validation of the model has been achieved both by using artificial data set and data from 144 concrete pouring, 101 formwork and 101 reinforcement crews. The results show that maps which are produced by the model are satisfactory in clustering the data and prediction performance of the model is superior to similar artificial neural network models. [Copyright &y& Elsevier]

Abstract: Broadcast-based DSM multiprocessors are nowadays an attractive platform for parallel computing due to their advantages in terms of scalability and programmability. In order to obtain high performance out of these systems, network latency reduction techniques should be developed, which requires the knowledge of the relationship between latency and other important DSM parameters. In this paper, self organizing maps (SOM) are used to investigate the effect of DSM parameters on network latency for a multiprocessor architecture interconnected by the Simultaneous Optical Multiprocessor Exchange Bus (SOME-Bus). An event-based discrete simulator using OPNET Modeler is developed for simulating a SOME-Bus system containing 64-nodes. Two thousand data points have been collected in order to create the dataset used in this study. 2-dimensional (2D) maps are produced by using SOM to display the relationship between network latency and other parameters such as the miss rate to a modified block (P m), fraction of write misses (P w), probability of having an upgrade ownership request message (P uor), probability of having a cache full (P cf) and ratio of the mean thread run time to mean message transfer time (T/R). The results show that the most dominant DSM parameter effecting network latency is T/R, while P cf has the minimum affect on network latency among other parameters. The individual effect of P m, P w and P uor on network latency depends on the values of all other parameters. [Copyright &y& Elsevier]