The impacts of outliers on different estimators for GARCH processes: an empirical study

The Maximum likelihood estimation (MLE) is the most widely used method to estimate the parameters of a GARCH(p,q) process. This is owed to the fact that the MLE, among other properties, is asymptotically efficient. Even though the MLE is sensitive to outliers, which can occur in time series. In order to abate the influence of outliers, robust estimators are introduced. Afterwards an Monte Carlo study compares the introduced estimators. --GARCH,Robust-Estimates,M-Estimates

The impacts of outliers on different estimators for GARCH processes: an empirical study

The Maximum likelihood estimation (MLE) is the most widely used method to estimate the parameters of a GARCH(p,q) process. This is owed to the fact that the MLE, among other properties, is asymptotically efficient. Even though the MLE is sensitive to outliers, which can occur in time series. In order to abate the influence of outliers, robust estimators are introduced. Afterwards an Monte Carlo study compares the introduced estimators

Detecting outliers in time series

In parametric time series analysis there is the implicit assumption of no aberrant observations, so-called outliers. Outliers are observations that seem to be inconsistent with the assumed model. When these observations are included to estimate the model parameters, the resulting estimates are biased. The fact that markets have been affected by shocks (i.e. East Asian crisis, Dot-com bubble, sub-prime mortgage crisis) make the assumption that no outlier is present questionable. This paper addresses the problem of detecting outlying observations in time series. Outliers can be understood as a short transient change of the underlying parameters. Unfortunately tests designed to detect structural breaks cannot be used to find outlying observations. To overcome this problem a test normally used to detect structural breaks is modified. This test is based on the cumulative sum (CUSUM) of the squared observations. In comparison to a likelihood-ratio test neither the underlying model nor the functional form of the outliers have to be specified. In a simulation study the finite sample behaviour of the proposed test is analysed. The simulation study shows that the test has reasonable power against a variety of alternatives. Moreover, to illustrate the behaviour of the proposed test we analyse the returns of the Volkswagen stock

Communication and Stochastic Processes in Some Bacterial Populations: Significance for Membrane Computing

Intercellular communication between bacterial cells belonging to the same population is well documented in Microbiology, sporulation and cannibalism in B. Subtilis and genetic competence and fratricide in S. pneumoniae being deeply studied in the last years. The investigation of individual cell behavior has revealed that populations of these bacteria sometimes bifurcate into phenotypically distinct, but genetically identical, subpopulations by random switching mechanisms. The probabilistic nature of the random switching mechanisms, the occurrence of some biochemical processes related to it at plasma membrane and the need to study the processes at the level of each individual cell make intercellular communication and stochastic processes very suitable to be modeled by P systems

Optical Characterization of Charge Transfer Excitons in Transition Metal Dichalcogenide Heterostructures

Two-dimensional materials such as graphene, boron nitride and transition metal dichalcogenides have attracted significant research interest due to their unique optoelectronic properties. Transition metal dichalcogenides (TMDCs) are a family of two-dimensional semiconductors which exhibit strong light-matter interaction and show great promise for applications ranging from more efficient LEDs to quantum computing. One of the most intriguing qualities of TMDCs is their ability to be stacked on top of one another to tailor devices with specific properties and exploit interlayer phenomena to develop new characteristics. One such interlayer interaction is the generation of charge transfer excitons which span the interface between two different TMDC monolayers. This work aims to study the intrinsic optical properties of charge transfer excitons in TMDC heterostructures. We must first start by investigating methods to protect and isolate our sample of interest from its chemical and electrostatic environment. We demonstrate that near intrinsic photoluminescence (PL) linewidth and exciton emission homogeneity from monolayer TMDCs can be achieved using a combination of BN encapsulation and passivation of substrate hydroxyl groups. Next, we develop clean stacking techniques and incorporate low defect density source crystals to maintain intrinsic properties and ensure a sufficiently high quality heterostructure interface to study characteristics of charge transfer excitons in 2D TDMCs. Strong photoluminescence emission from charge transfer excitons is realized and is shown to persist to room temperature. Charge transfer exciton lifetime is measured to be two orders of magnitude longer than previously reported. Using these high quality heterostructures, we study the behavior of charge transfer excitons under high excitation density. We observe the dissociation of charge transfer excitons into spatially separated electron-hole plasmas under optical excitation. We then probe properties of charge transfer exciton emission enhancement due resonant coupling to surface plasmon modes of gold nanorods

Case study using analysis of variance to determine groups’ variations

This paper aims to present the analysis of a part manufactured in three shifts, which has a specific characteristic dimension, using DFSS (Design for Six Sigma) ANOVA (Analysis of Variance) method. In every shift, the significant characteristic, “SC”, dimension should be produced within the given tolerance. The question that arises is: “Does the shift have any influence on the “SC” dimension realization?” By using the one way ANOVA method, one can observe the variation between the means of each of the three shifts. Afterwards, specific action can be undertaken to adjust, if necessary, the differences between the shifts

MANAGEMENTUL EDUCATIONAL ÎN ROMÂNIA DE AZI

Le management de l’éducation , bien qu’il soit l’objet des controverses, peut être définicomme la science et l’art d’instruire les ressources humaines, l’art de former despersonnalités, conformément à des fins acceptées par la société, par la communauté, par lesindividus. Cette science envisage un ensemble de principes et de fonctions, de normes et deméthodes de conduite qui assurent la réalisation des objectifs du système éducatif