Search

NLDA Bachelor Eindstudie, The detection range of radar systems is highly influenced by atmospheric conditions. Current research tries to estimate these atmospheric conditions, based on received AIS signals power. In this bachelor thesis it was tried to answer the following research question: how can the signal behaviour of received AIS signals be explained with the use of a signal receive model? Therefore, an AIS signal model is created based on a simple one-way transmission equation. Consequently this model is tested for different scenario’s. Results show that for the case under 5 kilometers and the case beyond line of sight the variance of the estimated gain was the smallest. For the case under line of sight the propagation factor probably ensures a bigger uncertainty and therefore a bigger variance. The error of the measured power and simulated power was the lowest for the case beyond line of sight. After that the error of the case under line of sight was the lowest. The error for the case under 5 kilometers was the highest. This could be explained by the different data sets and antenna setups used. Finally, it was found out that the location of the antenna setup affects the results significantly. Antenna setup with direct line of sight ensures no free space loss in the first 5 kilometers. The cause of this phenomenon is unknown and needs further research.

Esophageal perforations nearby the cardia are a clinical disorder of various causes. Perforations occur most often following diagnostic or interventional endoscopy but spontaneous perforations (Boerhaave syndrome) are less frequent. Due to the heterogeneous etiology there is a broad range of therapeutic options. In most cases the esophageal perforation site can be covered by an endoscopic stent. Recent endoscopic procedures are the intraluminal application of an endoscopic vacuum-assisted closure system (endo-VAC) or clipping of the esophageal defect. Surgical procedures include direct suturing with external coverage of the defect or transhiatal blunt dissection of the esophagus without primary reconstruction. All endoscopic and surgical procedures often require an additional drainage of the mediastinum and if necessary of the thoracic and abdominal cavities. The clinical presentation ranges from a simple perforation without concomitant esophageal pathology to a defect of considerable length with pleural perforation and associated septic multiple organ failure. The severity of the septic course is the crucial parameter for the choice of the procedure. An early multiple organ failure indicates an insufficient drainage of the septic focus and is indicative for surgical resection. The overall mortality is given as 12 % in the current literature and primarily depends on the localization and the etiology of the perforation. The highest mortality rates are observed with Boerhaave syndrome. The most important prognostic variable is the time interval between perforation and initiation of therapy whereby the mortality rises up to 20 % if the interval exceeds 24 h. Due to the complex therapy and the poor prognosis esophageal perforations should be treated in specialized centers.