Towards Informative Statistical Flow Inversion

This is the accepted version of 'Towards Informative Statistical Flow Inversion', archived originally at arXiv:0705.1939v1 [cs.NI] 14 May 2007.A problem which has recently attracted research attention is that of estimating the distribution of flow sizes in internet traffic. On high traffic links it is sometimes impossible to record every packet. Researchers have approached the problem of estimating flow lengths from sampled packet data in two separate ways. Firstly, different sampling methodologies can be tried to more accurately measure the desired system parameters. One such method is the sample-and-hold method where, if a packet is sampled, all subsequent packets in that flow are sampled. Secondly, statistical methods can be used to ``invert'' the sampled data and produce an estimate of flow lengths from a sample. In this paper we propose, implement and test two variants on the sample-and-hold method. In addition we show how the sample-and-hold method can be inverted to get an estimation of the genuine distribution of flow sizes. Experiments are carried out on real network traces to compare standard packet sampling with three variants of sample-and-hold. The methods are compared for their ability to reconstruct the genuine distribution of flow sizes in the traffic

Structure, dynamics and bifurcations of discrete solitons in trapped ion crystals

We study discrete solitons (kinks) accessible in state-of-the-art trapped ion experiments, considering zigzag crystals and quasi-3D configurations, both theoretically and experimentally. We first extend the theoretical understanding of different phenomena predicted and recently experimentally observed in the structure and dynamics of these topological excitations. Employing tools from topological degree theory, we analyze bifurcations of crystal configurations in dependence on the trapping parameters, and investigate the formation of kink configurations and the transformations of kinks between different structures. This allows us to accurately define and calculate the effective potential experienced by solitons within the Wigner crystal, and study how this (so-called Peierls-Nabarro) potential gets modified to a nonperiodic globally trapping potential in certain parameter regimes. The kinks' rest mass (energy) and spectrum of modes are computed and the dynamics of linear and nonlinear kink oscillations are analyzed. We also present novel, experimentally observed, configurations of kinks incorporating a large-mass defect realized by an embedded molecular ion, and of pairs of interacting kinks stable for long times, offering the perspective for exploring and exploiting complex collective nonlinear excitations, controllable on the quantum level.Comment: 25 pages, 10 figures, v2 corrects Fig. 2 and adds some text and reference

Middle managers’ role in organizational commitment and organizational citizenship behaviours

“Any motivated behavior, either preparatory or consummatory, must be understood to be a channel through which many basic needs may be simultaneously expressed or satisfied. Typically an act has more than one motivation.” (Maslow 1943, p.370) Written before organizational behaviour had been named let alone studied as a separate discipline, Abraham Maslow warned of the dangers of assuming that an individual behaviour can be explained simply by a single motivation. This dissertation will argue that where organizations operate in the context of continuing downsizing over long periods it is necessary to consider more than just positive affect employee motivations, such as organizational commitment. It may also prove important to consider more ambivalent motivations such as those involved in impression management. Since the early days of organizational behaviour researchers have sought to explain the degree of attachment shown by workers towards their organization. A great deal has been learned regarding two related constructs, organizational commitment and organizational citizenship behaviours. This research contributes to the theoretical framework underlying these two constructs. Empirical studies have shown associations between organizational commitment and aspects of an organization’s culture, for example organizational values and vision/mission. The underlying process has been explained by use of social exchange theory (Blau, 1964). Similarly, studies have shown an association between organizational citizenship behaviours and two other constructs besides organizational commitment, the individual’s perception of support from the organization and from the individual’s manager respectively. The resulting, widely accepted, models explain citizenship behaviours through two ‘pathways’, one via support from the organization, the other via support from their manager. Provision of such support is met by positive reciprocation by the individual. The research reported here assumes that any relationship between an individual employee and their organization may, and is likely to, be influenced by the actions of their direct report manager. A systematic literature review showed comparatively little research into the role of the manager and his/her role in influencing organizational commitment. This led to two empirical studies of middle managers’ role in influencing organizational commitment in their teams. Throughout this thesis the term middle manager is used interchangeably with direct report manager or line-manager. These terms are expressly taken to exclude both senior managers (those in a position to determine or contribute significantly to organizational level factors e.g. vision/mission and HR policies) and the first line supervisor with only task and team leader responsibilities. The first study found that the managers in the sample preferred the term engagement to commitment and that they focused largely on those citizenship behaviours of their direct reports that contributed directly to major performance measures i.e. key performance indicators. The second study in a different organization set out to explore whether or not this finding was repeated and irrespective of this, what techniques if any the managers used to influence both organizational commitment and citizenship behaviours in their teams. In addition to repeating the use of qualitative methods this study also incorporated some quantitative methods (surveys) in order to identify the direct reports’ levels of the relevant constructs. While the survey results showed that levels of both commitment and citizenship were high, unexpectedly and contrary to current models, the levels of perceived organizational and manager support were low. This runs counter to the prediction of social exchange theory. Nevertheless, it is argued that the current data can be explained, if one adds a third pathway to the model via impression management. This in turn can be attributed to an individual’s heightened job insecurity in times of downsizing and a consequent attempt to demonstrate one’s value to the manager/organization. It is further argued that any citizenship behaviours that may arise from impression management may not fully exploit the potential contributions from individuals. The techniques used by middle managers to encourage both organizational commitment and citizenship behaviours in their teams are reported and suggestions for further research are discussed

Development of an efficient method for simulating fixed-bed adsorption dynamics using Ideal Adsorbed Solution Theory

Otto-von-Guericke-Universität Magdeburg, Fakultät für Verfahrens- und Systemtechnik, Dissertation, 2016von M. Sc. Héctor Octavio Rubiera LandaLiteraturverzeichnis: Seite 195-22