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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Porovnání přežití, růstu a celkové efektivity chovu u juvenilních ryb amura bílého (Ctenopharyngodon idella) v průběhu přezimování v rybnících a RAS. / Comparison of survival, growth rate and overall breeding of grass carp (Ctenopharyngodon idella) juveniles in pond and recirculating aquaculture system during winter time.

PECHER, Petr January 2016 (has links)
The study compared survival and growth rate in grass carp (Ctenopharyngodon idella) juveniles in pond and recirculation aquaculture system (RAS) during winter time. The juveniles of grass carp were stocked to 5 tanks and three ponds during 2013 and 2014. In the RAS, the fish were fed by dry pellets and rearing was in constant temperature. In the pond, the temperature and feeding were only natural. In the RAS, the survival rate was significantly higher 97.79 % 0.52 % compared to 10.94 % 11.42 % in the pond. At the end of experiment, the weight of fish, Specific growth rate (SGR) and Fulton coefficient (FK) was significantly higher in RAS in comparison with the pond. The results showed that the rearing of grass carp is more effective in RAS in comparison with pond during winter time.
2

A STUDY OF TIES AND TIME-VARYING COVARIATES IN COX PROPORTIONAL HAZARDS MODEL

Xin, Xin 12 September 2011 (has links)
In this thesis, ties and time-varying covariates in survival analysis are investigated. There are two types of ties: ties between event times (Type 1 ties) and ties between event times and the time that discrete time-varying covariates change or "jump"(Type 2 ties). The Cox proportional hazards model is one of the most important regression models for survival analysis. Methods for including Type 1 ties and time-varying covariates in the Cox proportional hazards model are well established in previous studies, but Type 2 ties have been ignored in the literature. This thesis discusses the effect of Type 2 ties on Cox's partial likelihood, the current default method to treat Type 2 ties in statistical packages SAS and R (called Fail before Jump in this thesis), and proposes alternative methods (Random and Equally Weighted) for Type 2 ties. A simulation study as well as an analysis of data sets from real research both suggest that both Random and Equally Weighted methods perform better than the other two methods. Also the effect of the percentages of Type 1 and Type 2 ties on these methods for handling both types of ties is discussed. / NSERC

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