Partial C*-dynamics and Rokhlin dimension

We develop the notion of the Rokhlin dimension for partial actions of finite groups, extending the well-established theory for global systems. The partial setting exhibits phenomena that cannot be expected for global actions, usually stemming from the fact that virtually all averaging arguments for finite group actions completely break down for partial systems. For example, fixed point algebras and crossed products are not in general Morita equivalent, and there is in general no local approximation of the crossed product $A\rtimes G$ by matrices over A. Using decomposition arguments for partial actions of finite groups, we show that a number of structural properties are preserved by formation of crossed products, including finite stable rank, finite nuclear dimension, and absorption of a strongly self-absorbing $C^*$ -algebra. Some of our results are new even in the global case. We also study the Rokhlin dimension of globalizable actions: while in general it differs from the Rokhlin dimension of its globalization, we show that they agree if the coefficient algebra is unital. For topological partial actions on spaces of finite covering dimension, we show that finiteness of the Rokhlin dimension is equivalent to freeness, thus providing a large class of examples to which our theory applies.

Are Soybean Yields Getting a Free Ride from Climate Change? Evidence from Argentine Time Series Data

We analyze the influence of climate change on soybean yields in a multivariate time-series framework for a major soybean producer and exporter—Argentina. Long-run relationships are found in partial systems involving climatic, technological, and economic factors. Automatic model selection simplifies dynamic specification for a model of soybean yields and permits encompassing tests of different economic hypotheses. Soybean yields adjust to disequilibria that reflect technological improvements to seed and crops practices. Climatic effects include (a) a positive effect from increased CO2 concentrations, which may capture accelerated photosynthesis, and (b) a negative effect from high local temperatures, which could increase with continued global warming.

Lects in Helsinki Finnish - a probabilistic component modeling approach

This article examines Finnish lects spoken in Helsinki from the 1970s to the 2010s with a probabilistic model called Latent Dirichlet Allocation. The model searches for underlying components based on the linguistic features used in the interviews. Several coherent lects were discovered as components in the data, which counters the results of previous studies that report only weak covariation between features that are assumed to be present in the same lect. The speakers, however, are not categorical in their linguistic behavior and tend to use more than one lect in their speech. This implies that the lects should not be considered in parallel with seemingly uniform linguistic systems such as languages, but as partial systems that constitute a network.

Dynamic reduction in the calculation of bridge structures

In modern bridge construction, on the one hand, there are increasing trends towards increasing bridge spans, which requires reducing the weight of structures. On the other hand, the use of structural elements made of various composite materials is expanding, which allows to significantly reduce the weight of the bridge structures as a whole. However, the creation of new forms of span structures of bridges requires more detailed calculations in order to optimize such forms, in particular the role of calculating the dynamic impact, because with increasing spans and weight loss, increases design flexibility and sensitivity to dynamic loads. In the present paper, the problems of solving an incomplete algebraic problem of eigenvalues and eigenvectors are considered. To increase the accuracy of the calculation and exclude the use of high-order matrices, a method of sequential reduction of the stiffness and equivalent mass matrices is proposed. The method is based on the construction of partial systems using a static transformation, followed by the solution of its own problem for the partial system. In the process of solving this problem through the eigenvectors of the system, the minor unknowns are reduced to the main ones. Dynamic reduction showed high calculation accuracy..

Gatekeeping and Journalism

One of the oldest social science theories applied to the study of communication, the gatekeeping approach emphasizes the movement of bits of information through channels, with an emphasis on decision points (gates) and decision-makers (gatekeepers). Forces on both sides of a gate can either help or hinder the information’s passage through a channel. The gatekeeping process shapes and produces various images of reality, not only because some bits of information are selected and others rejected, but because communication agents put information together in different ways. In addition, the timing and repetition of information can affect the prominence of events or topics and can influence the probability of future information diffusion. Gatekeeping was originally modeled as a series of linear processes within the mass media, but in the late 20th century the flow of information through the mass and social media began to interact. Information is now understood to flow among journalists, among social media users, and among agents of both types of media. All such communication agents are gatekeepers. In addition, we can study these networked interconnections as one level of analysis, with the supra-gatekeepers (such as Facebook or Twitter) adding their own gatekeeping processes over and beyond those of their own clients of the mass media. In addition to looking at various pairwise relationships between gatekeepers, gatekeeping theory should go beyond to instead consider the entire web of gatekeepers as a whole or system. A system is composed of elements (gatekeepers), interactions (relationships among them), and a goal or function. Multiple functions have been proposed by 20th-century scholars (such as socialization, entertainment, or surveillance) for the mass media, but scholars should now consider the function(s) of the gatekeeping system (mass and social media, as well as supra-gatekeepers) as a whole. Although each type of medium can be analyzed as its own system, such analysis would not facilitate new thinking about the various ways in which these partial systems affect one another and how the whole system functions beyond the simple addition of its parts.

Mathematical model of a drive mechanism with a crank device of a crank press

The most important link in the forging equipment is a crank mechanism. Their significant drawback is the unbalanced inertia forces of the moving masses of the crank mechanism, which cause vibration. The analysis of the phenomena occurring in the mechanism and the assessment of the technological process are based on the theory of chains, which allows analytically analyzing the dynamic characteristics of systems with a large number of degrees of freedom, based on the analysis of one structural element. The study of the process of force interaction inevitably comes down to the construction of a mathematical model of mechanisms, the formative movement of which leads to its formation. One of the partial systems makes an irregular programmed motion, meaning the crank drive mechanism. In addition, unwanted vibrations caused by kinematic excitation are superimposed on this drive. According to numerous papers on this topic, significant dynamic errors arise due to vibration accelerations. One of the main tasks in reducing the vibration activity and, accordingly, the level of acoustic emission of the process under study is to ensure the required law of motion of the instrument. On this basis, the study of the stability of formative movements is of particular importance. This question is complicated by the fact that in the processing, there is a change in the process parameters and, consequently, in the characteristics of the friction coupling. The latter circumstance presupposes the evolution of the system under study, and therefore the need for process control.