Study of dynamics of charge trapping in a-Si:H/SiN TFTs

In this paper we present the study of the failure mechanism responsible for long-term degradation that ultimately leads to instability in a-Si:H/SiN TFTs. The experimental data points we obtain by monitoring in-situ the drain current during gate bias stress (forward and reverse bias) and relaxation could not be fitted with the models existent in the literature. A new model that we have christened "Progressive Degradation Model" (PDM) emerged. The model makes use of Heimann-Warfield theory of trapping/detrapping front. PDM achieves a consistent fit to any bias condition showing that the degradation can be modelled quantitatively yielding the number of traps involved, their position and the charge dispersion coefficient. According to PDM the degradation of electrical response is a combined effect of a fast interface traps generation and a slow charge trapping at the created defect sites in a-SiN:H transitional region

Electrical instability of A-Si:H/SiN thin film transistors : a study at room temperature and low voltage stress

The thesis shows the results of four years of research into the electrical stability of a-Si:H/SiN TFTs. Various methods of investigation of a-Si:H/SiN TFTs have been carried out in this thesis towards understanding the causes of degradation that shortens the transistor lifetime and narrows the transistor application area. The research aims to cast light on the mechanism responsible for a-Si:H/SiN TFTs degradation during short and long period of voltage stress at room temperature

INVERSE KINEMATICS IN THE SUCCESS OF THE THROW

The paper analyses the problematic of the human arm’s movement in order to get a successful direct throw in basketball. For the human arm we analyzed the mechanic model of the double pendulum, formed by the arm and the forearm, with the hand being immobilized by the forearm. The classic equations of throwing the ball (dependent on the initial speed and throwing angle vector) have been correlated with the corresponding equations of the arms’ movement. After imposing the mathematical conditions necessary for the ball to get into the basket, meaning certain inequality-type restrictions, we determined the kinematic dependents between the human arms’ movement and the trajectory of the ball. The numeric analysis for several initial values of the throw allowed the assessment, through validation or non-validation, of the kinematic conditions for the success of the throw, and also several discussions regarding the influences of various kinematic parameters upon the throw

Advanced product design principles applied for developing a reconfigurable multi-station welding workbench

The research results presented in the paper are part of a larger approach concerning the improvement of product design process sustainability by enhancing the effectiveness and efficiency of Product Design activities. As case study, an applied educational project is exemplified as result sample, particularly referring to applying such advanced design principles in developing a reconfigurable multi-station welding workbench, intended to solve the problem of the lack of space which usually most of the welding workshops have to confront with

Enhancing product structure design for an automation mechanism, by involving axiomatic design theory

The research presented in the paper is part of a larger approach concerning the enhancing of Product Development Sustainability by involving advanced design theories for effectiveness and efficiency of Product Design and CAD/CAE/CAM activities. The particular idea is to apply some principles from the Axiomatic Design theory within Concept Design and System Level Design stages, in order to enhance the Product Structure Design and to streamline the CAD activities and to study how a decomposition model obtained by applying AD theory affects the capture of Design Intent into a 3D CAD parametric product model structure. An applied project is exemplified as a case study, particularly referring to developing the Product Structure Design activities for the mechanical structure of an automated dimensional sorting system. Related discussions, conclusions and some further research directions are included

Enhancing product structure design for an automation mechanism, by involving axiomatic design theory

The research presented in the paper is part of a larger approach concerning the enhancing of Product Development Sustainability by involving advanced design theories for effectiveness and efficiency of Product Design and CAD/CAE/CAM activities. The particular idea is to apply some principles from the Axiomatic Design theory within Concept Design and System Level Design stages, in order to enhance the Product Structure Design and to streamline the CAD activities and to study how a decomposition model obtained by applying AD theory affects the capture of Design Intent into a 3D CAD parametric product model structure. An applied project is exemplified as a case study, particularly referring to developing the Product Structure Design activities for the mechanical structure of an automated dimensional sorting system. Related discussions, conclusions and some further research directions are included

Aspects to be considered in case of variable surfaces modelling

Proper triangulation will bring benefits regarding the numerical conditioning of nodes within the point cloud but will also allow certain nodes to be able to move around those that are neighboring them. In this way, surface features as chained regions or curves will have a certain degree of freedom which will allow them to slide one towards another. At a more careful evaluation there is a major drawback in terms of lack of possibility to take into consideration the operations which depend upon approximate shapes inside the ideal shape evaluation process. In order to be able to control the accuracy of the process there is an impetuous need for all surfaces to be described functionally. Any triangulation procedure has to be able to allow control over the analyzed surface topology and any other after modifications: dividing the surface along an incorporated curve in order to define a new edge or sticking two surfaces together in order to form a mutual boundary edge

Influence of Machining Conditions on Micro-Geometric Accuracy Elements of Complex Helical Surfaces Generated by Thread Whirling

Complex surfaces such as helical ones are commonly used in machinery. Such surfaces can be obtained by various machining processes, one of these processes being thread whirling. The influence of machining conditions needs to be better understood to develop a more precise prediction of the specific resulting errors involved in thread whirling. This paper firstly presents the theoretical conditions which generate micro-deviations on whirled surfaces. A theoretical model which considers the geometrical parameters describing the whirling head and cutters and the process’s whole kinematics was developed. The threaded surface was described as a complex compound surface resulting from intersecting successive ruled helical surfaces corresponding to the cutting edges of the set of cutters from the whirling head. Numerical simulation results were exemplified and validation experiments were both designed and performed. Empirical mathematical models were established to highlight the influence of the input factors such as thread pitch and external diameter, the ratio between the diameter of cutters’ top edge disposal and the thread’s external diameter, the rotary speed of the whirling head, and the rotary speed of the workpiece on some accuracy elements and roughness parameters of the threaded surface

Aspects to be considered in case of variable surfaces modelling

Proper triangulation will bring benefits regarding the numerical conditioning of nodes within the point cloud but will also allow certain nodes to be able to move around those that are neighboring them. In this way, surface features as chained regions or curves will have a certain degree of freedom which will allow them to slide one towards another. At a more careful evaluation there is a major drawback in terms of lack of possibility to take into consideration the operations which depend upon approximate shapes inside the ideal shape evaluation process. In order to be able to control the accuracy of the process there is an impetuous need for all surfaces to be described functionally. Any triangulation procedure has to be able to allow control over the analyzed surface topology and any other after modifications: dividing the surface along an incorporated curve in order to define a new edge or sticking two surfaces together in order to form a mutual boundary edge