Non-responses caused by refusals became the main reason for surveys’ failure to provide representative data. Refusals do not occur randomly and they distort representation of certain social groups and subgroups in survey data. Criteria for external validity are seldom mentioned in publications dealing with nonresponse bias in surveys. We propose the method for estimating certain biases of sampling by calculating indicators based on sample data, which could be compared with reliable statistical data from some independent source.
In this paper we show that for a given co-authorship network we could construct a recommender system for searching collaborators with similar research interests defined via keywords and topic modelling. We suggest new link embedding method and evaluate our model on National Research University Higher School of Economics (NRU HSE) co-authorship network.
The calibration problem is considered for the accelerometer unit by means of a high-precision motion simulator. The guaranteed approach is proposed to solve the calibration problem.
In this paper we consider the behavior of Kalman Filter state estimates in the case of distribution with heavy tails .The simulated linear state space models with Gaussian measurement noises were used. Gaussian noises in state equation are replaced by components with alpha-stable distribution with different parameters alpha and beta. We consider the case when "all parameters are known" and two methods of parameters estimation are compared: the maximum likelihood estimator (MLE) and the expectation- maximization algorithm (EM). It was shown that in cases of large deviation from Gaussian distribution the total error of states estimation rises dramatically. We conjecture that it can be explained by underestimation of the state equation noises covariance matrix that can be taken into account through the EM parameters estimation and ignored in the case of ML estimation.
Wide application of radiofrequency (RF) and microwave (MW) heating of dielectric materials is restrained by the relatively small specific RF losses and inhomogeneity of the MW energy penetration in the treated objects. These disadvantages may be overcome by using applicators based on slow-wave structures which support modes in which the phase velocity is less than the free-space velocity of light These structures concentrate the electromagnetic field relatively homogeneously along the system axis. Diverse applications have been found including food heating, disinfecting agricultural products, and electro-coagulation.