Delay-induced blow-up in a planar oscillation model

In this paper we study a system of delay differential equations from the viewpoint of a finite time blow-up of the solution. We prove that the system admits blow-up solutions, no matter how small the length of the delay is. In the non-delay system every solution approaches to a stable unit circle in the plane, thus time delay induces blow-up of solutions, which we call “delay-induced blow-up” phenomenon. Furthermore, it is shown that the system has a family of infinitely many periodic solutions, while the non-delay system has only one stable limit cycle. The system studied in this paper is an example that arbitrary small delay can be responsible for a drastic change of the dynamics. We show numerical examples to illustrate our theoretical results.

The value within multiform commodities: North African phosphates and global markets in the interwar period

Phosphates mined in France’s North African empire fed interwar Europe’s voracious appetite for chemical fertilizers. In critique of histories vesting commodities themselves with the agency to make the modern world, I trace not the substance but the value embedded within it. By following value, I argue that the ‘commodity’ is not a stable unit of analysis. Rather, commodities are multiform. They can acquire myriad properties when the value embedded within them changes across time and place. During the interwar period, phosphates’ character as a commodity transmuted in relation to flows of other goods, movements of labour, global financial exigencies and imperial considerations. As phosphates assumed new forms, the geographic scales over which they operated changed too. Through North African phosphates, I explore value-making processes that perpetuated capital-intensive farming, allowing for a history not of the commodity-as-substance but of the commodity-as-historical-object whose analytical boundaries and forms shifted across contexts.

IMPLEMENTATION OF THE MAIN CONTENT LINES IN THE PRACTICE OF MODERN PRESCHOOL EDUCATION

Рассмотрены и проанализированы содержательные линии предшкольного образования через призму задач дошкольного детства. Материалом исследования послужили многолетние наблюдения автора за деятельностью старших дошкольников и их родителями в учебно-методическом центре по предшкольному образованию детей на базе Института детства Томского государственного педагогического университета. Принципиальность содержательных линий предшколы заключается, прежде всего, не в том, что-бы подготовить ребенка именно к школе, а в том, чтобы сформировать у него важнейшие психические качества и способности – произвольность, воображение, память, творчество, толерантность, коммуникабельность, самостоятельность и т. д. Именно эти качества формируют функциональную грамотность детей, а значит, дают им возможность легче адаптироваться в будущей школьной жизни. Данное положение задает вектор деятельности педагогов предшколы, который должен быть ориентирован не на усвоение ребенком конкретной учебной информации, а на формирование полноценной гармоничной личности. В контексте рассматриваемой проблемы содержательная линия – это направления структурирования обучающего курса, в котором каждая содержательная линия понимается как устойчивая единица смысловой целостности педагогически целесообразных курса, предмета, технологии. Вместе с тем нельзя рассматривать данную устойчивую единицу автономно, она всегда взаимосвязана с другими составляющими данного курса или конкретного звена системы и может определять направление иного характера или уровня работы. Такое понимание содержательных линий предшкольного образования позволяет строить целостную работу не только с ребенком, но и с его родителями. The article considers and analyzes the content lines of preschool education through the prism of preschool childhood tasks. The research material is based on the author’s long-term observations of the activities of senior preschool children and their parents in the educational and methodological center for preschool education of children at the Institute of childhood of Tomsk State Pedagogical University. The principle of the content lines of preschool is, first of all, not to prepare the child for school, but to form in him the most important mental qualities and abilities-arbitrariness, imagination, memory, creativity, tolerance, sociability, independence, etc. These are qualities that shape children’s functional literacy, which means that they can more easily adapt to future school life. This provision sets the vector direction of activity of preschool teachers, which should be focused not on the child’s assimilation of specific educational information, but on the formation of a full-fledged harmonious personality. In the context of the considered problem the author proceeds from the understanding that content lines are the directions of structuring a training course, in which each content line is understood as a stable unit of semantic integrity of a pedagogically appropriate course, subject, and technology. But at the same time, this stable unit cannot be considered independently, it is always interconnected with other components of this course or a specific link in the system and can determine the direction of a different nature or level of work. This understanding of the content lines of preschool education allows you to build a holistic work not only with the child, but also with his parents.

Considering Network Effects in the Design and Analysis of Field Experiments on State Legislatures

Recent work on legislative politics has documented complex patterns of interaction and collaboration through the lens of network analysis. In a largely separate vein of research, the field experiment—with many applications in state legislatures—has emerged as an important approach in establishing causal identification in the study of legislative politics. The stable unit treatment value assumption (SUTVA)—the assumption that a unit’s outcome is unaffected by other units’ treatment statuses—is required in conventional approaches to causal inference with experiments. When SUTVA is violated via networked social interaction, treatment effects spread to control units through the network structure. We review recently developed methods that can be used to account for interference in the analysis of data from field experiments on state legislatures. The methods we review require the researcher to specify a spillover model, according to which legislators influence each other, and specify the network through which spillover occurs. We discuss these and other specification steps in detail. We find mixed evidence for spillover effects in data from two previously published field experiments. Our replication analyses illustrate how researchers can use recently developed methods to test for interference effects, and support the case for considering interference effects in experiments on state legislatures.

Social Mobility in an Era of Family Instability and Complexity

Families play a central role in the study of social mobility—they are units of analysis for measuring social class as well as settings that shape the intergenerational transmission of resources. The American family has undergone important changes since the mid-twentieth century. Divorce, nonmarital childbearing, and cohabitation increased dramatically. The rise in divorce and cohabitation made the family a less stable unit of socialization and led to a proliferation of step and blended family arrangements with complex configurations of residential and biological ties. As a result of these changes, less than half of children spend their entire childhood in an intact, two-biological parent household, and families are no longer defined solely by shared residence or biology. The instability and complexity of family life requires stratification scholars to rethink how they measure origin and destination class and to consider how parents in nontraditional families transmit class-specific resources to the next generation.

Definição automática de áreas censitárias na freguesia de Algés

AUTOMATIC STATISTICAL AREA DEFINITION IN ALGÉS PARISH. Portugal, along with many other countries, conducts a population census every 10 years. This way of counting the population offers a detailed photography of the country where many socio-economic variables are captured. In this study, it is assumed that census will be the way of population data collection and therefore the discussion deals with the issue of geographical aggregation of individuals and households enumerated. In this context, a methodological proposal for an automatic census area creation in the parish of Algés is described. The minimum geographic unit for completing the aggregations is the building since it was the smallest and stable unit for this purpose. The building layer was obtained in the municipal GIS of Oeiras and is based on large scale cartography (1:1000). Mainly, because the building layer is not contiguous, the study starts with the construction of a Thiessen polygon layer. This layer is drawn with the buildings layer centroids and having the master plan classes as barriers. The Thiessen polygon layer associated with the building attributes assumed a key role in this process and considering the range of possible data aggregation alternatives the zone boundaries are drawn concerning with some principles of consistence and homogeneity. To achieve a measurement of homogeneity for the statistical areas the variables used were the number of households, floors and type of building (residential, commercial, both). The automatic statistical area definition deals with the aggregation of the basic geographic units (Thiessen polygon layer), seeking for new optimized areas, considering the characteristics of the building and having a reference number of households around 100. To demonstrate the methodology used for the automatic statistical area definition, three simulation results are presented in this article.