On the Approximability of Numerical Taxonomy (Fitting Distances by Tree Metrics)

Fitting Distances by Tree Metrics with Increment Error

The L p-min increment t and L p-min increment ultrametric t problems are two popular optimization problems arising from distance methods for reconstructing phyloge-netic trees. This paper gives the following results: 1. An O(n 2) approximation algorithm with ratio-3 for L 1-min increment t. 2. A ratio-O(n 1=p) approximation algorithm for L p-min increment ultrametric t. 3. The neighbor-joining ...

investigation of effective parameters on the rigidity of light composite diaphragms (psscb) by fem

در این رساله با معرفی سقف های psscb متشکل از ترکیب ورق های فولادی ذوزنقه ای و تخته های سیمانی الیافی به عنوان سقف های پیش ساخته (سازگار با سیستم سازه ای قاب های فولادی سبک) به بررسی پارامترهای موثر بر صلبیت سقف، پرداخته می شود. در تحقیق حاضر ابتدا به مدل سازی دو نمونه سقف آزمایش شده، به روش اجزاء محدود با استفاده از نرم افزار تحلیلی abaqus ver 6.10 پرداخته شده است. نمونه های ساخته شده تحت اعما...

the role of task-based techniques on the acquisition of english language structures by the intermediate efl students

this study examines the effetivenss of task-based activities in helping students learn english language structures for a better communication. initially, a michigan test was administered to the two groups of 52 students majoring in english at the allameh ghotb -e- ravandi university to ensure their homogeneity. the students scores on the grammar part of this test were also regarded as their pre...

Fitting Distances by Least Squares

On approximating planar metrics by tree metrics

We combine the results of Bartal [Proc. 37th FOCS, 1996, pp. 184–193] on probabilistic approximation of metric spaces by tree metrics, with those of Klein, Plotkin and Rao [Proc. 25th STOC, 1993, pp. 682–690] on decompositions of graphs without small Ks,s minors (such as planar graphs) to show that metrics induced by such graphs (with unit lengths on the edges) can be probabilistically approxim...