Aggregation of Affine Estimators

We consider the problem of aggregating a general collection of affine estimators for fixed design regression. Relevant examples include some commonly used statistical estimators such as least squares, ridge and robust least squares estimators. Dalalyan and Salmon (2012) have established that, for this problem, exponentially weighted (EW) model selection aggregation leads to sharp oracle inequalities in expectation, but similar bounds in deviation were not previously known. While results indicate that the same aggregation scheme may not satisfy sharp oracle inequalities with high probability, we prove that a weaker notion of oracle inequality for EW that holds with high probability. Moreover, using a generalization of the newly introduced $Q$-aggregation scheme we also prove sharp oracle inequalities that hold with high probability. Finally, we apply our results to universal aggregation and show that our proposed estimator leads simultaneously to all the best known bounds for aggregation, including $\ell_q$-aggregation, $q \in (0,1)$, with high probability

Effect of air on vibration of structures

This research primarily studies the effect of air on vibration of structures. Theoretical solutions based on various physics are derived and compared with experimental results to determine how air modifies the vibrational behavior of structures. This work may help in determining the characteristics of structural vibrations — from acoustic behavior to earthquake response - in practical buildings. The work consists of several primary components: derivation of theories that predict the effect of air on structural vibrations and vice-versa, design of experiments, and determination of the importance of air in structural vibrations and the applicability of different physics under various vibrational frequencies. Two types of physics - acoustic theory and fluid dynamics theory - are applied to derive solutions for damping ratios of air. Experiments such as an unbaffled plate experiment, a pendulum experiment and a baffled plate experiment are designed and conducted to observe the damping effect of air. Experimental results illustrate the applicability of the theories. Finite element analysis is performed to provide a computational basis with which to compare the observed vibrational frequencies. The main question in this research is whether air has a great effect on structural vibrations. The results show that air has a damping effect on vibrating buildings that can be important under certain conditions. The results also reveal that when calculating the damping effects due to air, different physics should be applied under different vibrational conditions. A dimensionless factor is derived to determine under which regimes acoustic theory is applicable, and under which regimes fluid dynamics theory is applicable

Study on Problems Faced by Xinjiang Organic Producers and Solutions

Presently the behavioral features of the organic producers could be concluded as the fact that they are quite confident of the prospects for organic agriculture, while heavily dependent on the guidance and support of the local governments; are in great demand for technological innovation, while in the distinguished intimacy and poor pricing capacity. Such problems as low economic benefit, the imperfect marketing network and serious external economy, are threatening the healthy development of organic agriculture in Xinjiang. In this essay, it is suggested that the government should, taking full advantage of its rich natural resources, pay great attention to the organic development in the local region; establish an efficient organic marketing network; apply the innovation mechanism as a proper compensation for the external economy; promote organic circle economy.organic agriculture, problems, policy inspiration, Xinjiang, Farm Management,