Structure Identifiability of an NDS with LFT Parametrized Subsystems

Requirements on subsystems have been made clear in this paper for a linear time invariant (LTI) networked dynamic system (NDS), under which subsystem interconnections can be estimated from external output measurements. In this NDS, subsystems may have distinctive dynamics, and subsystem interconnections are arbitrary. It is assumed that system matrices of each subsystem depend on its (pseudo) first principle parameters (FPPs) through a linear fractional transformation (LFT). It has been proven that if in each subsystem, the transfer function matrix (TFM) from its internal inputs to its external outputs is of full normal column rank (FNCR), while the TFM from its external inputs to its internal outputs is of full normal row rank (FNRR), then the NDS is structurally identifiable. Moreover, under some particular situations like there are no direct information transmission from an internal input to an internal output in each subsystem, a necessary and sufficient condition is established for NDS structure identifiability. A matrix valued polynomial (MVP) rank based equivalent condition is further derived, which depends affinely on subsystem (pseudo) FPPs and can be independently verified for each subsystem. From this condition, some necessary conditions are obtained for both subsystem dynamics and its (pseudo) FPPs, using the Kronecker canonical form (KCF) of a matrix pencil.Comment: 16 page

Separation of dissipation from diffusion

We study velocity correlations induced by diffusion and dissipation in a simple dissipative dynamical system. We observe that diffusion, as a result of time reversible microscopic processes, leads to correlations with different spatial parity from those caused by dissipation, consisting of time irreversible microscopic processes. The velocity correlations observed conflict with the ``molecular chaos'' assumption of the Boltzmann equation. To account for the apparent correlation structures in our simple model system, we propose that they indicate geometric distortion of the phase space.Comment: 4 pages, 5 figure

Consumer Perception of Organic Food in Urumqi

The market for organic products in Urumqi is at the beginning of its development. The objective of this paper is to gain knowledge about consumers attitudes toward organic food in Urumqi which is the capital of Xinjiang Uygur Autonomous Region. The consumers attitudes were collected by means of a face-to-face survey. Attitudes, purchasing frequency, supply satisfaction and beliefs about organic food were studied with a sample of 720 consumers. The data obtained from the survey were analyzed with univariate analysis, chi-square test, ANOVA and correlation analysis. About 44.9% of Urumqi consumers had never heard of organic food. Urumqi consumers who know organic food consider organically-grown products as very healthy, of good quality and tasty. Consumers are not very familiar with the supply of organic food in the market. One reason might be that there was very little advertisement about organic products. Some groups of consumers have more positive attitudes towards organic food, and they express an increased willingness to pay higher prices for these food. Therefore, marketing strategies for organic food should be targeted towards such groups. According to the research results, an important task for the producers will be to increase consumers knowledge of what organic food is and how to differentiate it in the marketplace.Urumqi, Consumer behavior, Organic food, Food Consumption/Nutrition/Food Safety,