Simulations of Yarn Unwinding from Packages

Yarn unwinding from stationary packages has an important role in many textile processes. In order to achieve high unwinding velocity that can lead to increased production rate, it is necessary to develop packages with a suitable geometry, dimensions, and winding type. The optimal design of the package leads to an optimal form of the balloon and low and uniform tension at high unwinding speed. In this work I will show a simple mathematical model which can be used for simulating the unwinding process. Using experimental values I will find a relation between the angular velocity of the yarn around the axis and the tension. This will allow me to calculate the oscillations of the tension in the yarn during the unwinding from packages of different geometries and with different winding angles. I will find an optimal design for a package of a new generation

The Effect of Winding Angle on Unwinding Yarn

In the production of fabric, the unwinding of thread occurs in the warping and weft insertion processes. In order to achieve low and constant tension of thread or yarn it is necessary to optimize the process of unwinding. Computer simulations are now in use for this purpose, so it is important to obtain a mathematical description of yarn motion. This article is devoted to the derivation of boundary conditions that considerably affect the form of the balloon. In this way, a mathematically well defined model of yarn unwinding will be obtained which could be solved by using the tools of numerical mathematics. The unwinding of yarn from an optimally designed package can be simulated and this knowledge can be used to find an optimal design of packages

Constraction process supervision risk management

Management of risks related to the construction project costs, timing, and quality of work carried out\ud is permanent activity in the construction process. In order to manage this complex activity with\ud significant financial inputs and environmental impacts, appropriate risk management is required. The\ud investor, as key participant in the construction process, has to supervise the construction process in\ud order to adequately manage those financially and technically demanding activities. The role of\ud supervision is very complex, but one can identify its key function - reduction of risks, that could lead\ud to the development of a construction project in an inappropriate way, resulting in project performance\ud failure. In order to ensure more systematic and better decision-making process, and improved risk\ud management in the construction process, a comprehensive risk management framework that could be\ud applied for supervision of building construction was analysed. The main intention of my work was\ud development of conceptual framework enabling quantitative analysis in risk identification and\ud management. During the development of such framework a register of risks which should be managed\ud during the construction supervision was drafted. After that a basic analytical framework, which can be\ud used for quantitative management of uncertainty and risks in construction, was developed. During the\ud development of those analytical tools important missing element for the adequate quantitative risk\ud management was identified: there is no available information or register containing the history of\ud identified unforeseen events and their consequences, which is probably the main obstacle that hinders\ud the shift to quantitative risk management. Despite the lack of data a decision-making model was\ud developed with a scope of validation of the approach. It was developed for a complex set of uncertain\ud events. It is based upon the conditional probabilities using Bayes' Theorem. As a practical example of\ud quantitative conditional probability network, taking into consideration evidence-based statistic, a\ud model was set for uncertainty management in concrete placing

Shock in the Yarn during Unwinding from Packages

Tension in the yarn and its oscillations during the over-end unwinding of the yarn from stationary packages depend on the unwinding speed, the shape and the winding type of the package, the air drag coefficient, and also the coefficient of friction between the yarn and the package. The yarn does not leave the surface package immediately at the unwinding point. Instead, it first slides on the surface and then lifts off to form the balloon. The problem of simulating the unwinding process can be split into two smaller subproblems: the first task is to describe the motion of the yarn in the balloon; the second one is to solve the sliding motion. In spite of the seemingly complex form of the equations, they can be partially analytically solved as we show in the paper

Orientation and mathematics in the pre-school education

The thesis deals with orientation as one of the important areas of child development in the pre-school period. The theoretical part defines the orientation in general as well as the orientation in education. Besides, it also covers the history of orientation, and how the development of the mode of orientation has changed over time. Since the thesis focuses primarily on pre-school children, orientation and mathematics, the latter part of the theoretical work presents the role of the educator and the child in learning mathematics, and the mathematical learning environment. It is explained how to organize experiences to children, and it includes various examples of activities. The aim of the thesis is to determine how children with the help of orientation instruments (models, maps) orient themselves in space, which instruments related to the spatial relations a child uses (e.g.: on, in, under ...), and how successfully children resolve the tasks of spatial relationships. It was found that the active participation of children and the use of objects have a positive effect on learning

Usage of copulae and validation of internal models

Magistrsko delo se osredotoča na kapitalske zahteve za zavarovalnice in pozavarovalnice in zakaj jih potrebujemo. Prikazana je razlika med uporabo in implementacijo standardne formule ter lastnega internega modela. Natančneje pogledamo tudi notranje modele in potek do njihove validacije. Pri tem pogledamo še kopule in njihovo uporabo v validaciji.The master thesis focuses on capital modelling of insurance and reinsurance companies and why do we need it. It shows difference between usage and implementation of standard formula and own internal model. Another look is made at internal models and the way to their validation. We focus on copulas and their use in validation