Logistic Regression at TREC4: s Probabilistic Retrieval from Full Text Document Collection

l w The Berkeley experiments for TREC4 extend those of TREC3 in three ways: for ad-hoc retrieva e retain the manual reformulations of the topics and experiment with limited query expansion g f based upon the assumption that top documents are relevant (this experiment was an interestin ailure); for routing retrieval we introduce a logistic regression which assumes relevance weights to h r be only one clue among several in predicting probability of relevance. Finally, for Spanis etrieval we retrain the basic logistic regression equations to apply to the statistical distributions of r Spanish words. In addition we apply two approaches to Spanish stemming, one which attempts to esolve verb variants into a standardized form, the other of which eschews stemming in favor of a 1 massive stop word list of variants of common words. . Introduction and history of Berkeley TREC participation For the past several years the UC Berekd ley Text Retrieval Research Group has been eveloping an approac..

Term importance, Boolean conjunct training, negative terms, and foreign language retrieval: probabilistic algorithms at TREC-5

The Berkeley experiments for TREC-5 extend those of TREC-4 in numerous ways. For routing retrieval we experimented with the idea of term importance in three ways -- training on Boolean conjuncts of the most important terms, filtering with the most important terms, and, finally, logistic regression on presence or absence of those terms. For ad-hoc retrieval we retained the manual reformulations of the topics and experimented with negative query terms. The ad-hoc retrieval formula originally devised for TREC-2 has proven to be robust, and was used for the TREC-5 ad-hoc retrieval and for our Chinese and Spanish retrieval. Chinese retrieval was accomplished through development of a segmentation algorithm which was used to augment a Chinese dictionary. The manual query run BrklyCH2 achieved a spectacular 97.48 percent recall over the 19 queries evaluated before the conference. 1. Introduction From the beginning of the TREC conference series, the UC Berkeley Text Retrieval Research Group ha..

Effect of nonmetallic solutes on the stability of {10–12} tension twin boundary of zirconium: a first-principles study

Effect of nonmetallic solutes on {10–12} tension twin boundary (TB) are investigated using first-principles calculations. Fourteen kinds of interstitial sites near the {10–12} tension TB for four nonmetallic solutes such as C, N, O, and H are considered. The results show that the C and O atoms are much easier to segregate from the {10–12} tension TB to the octahedral site 1, causing the {10–12} tension TB more stable. The N atom is much easier to segregate from the {10–12} tension TB to the octahedral site 4, causing the {10–12} tension TB more stable. The H atom is much easier to segregate from the {10–12} tension TB to these 14 interstitial positions, causing the {10–12} tension TB more stable. The effect of C, N, or O atom on the stability of {10–12} tension TB is greater than that of H atom