AbstractStatistical analysis of defensive players in football has lagged behind that of offensive players, special teams, and coaching decisions, largely because data on individual defensive players has historically been lacking. With the introduction of player tracking data from the NFL, researchers can now tackle these problems. However, event and strategy annotations in the NFL’s tracking data are limited, especially when it comes to describing what defensive players do on each play. Moreover, methods for creating these annotations typically require extensive human labeling, which is difficult and expensive. Because of the importance of the passing game and the limited prior research on the defensive side of passing, we provide annotations for the pass coverage types of cornerbacks using unsupervised learning techniques, which require no training data. We define a set of features from the tracking data that distinguish between “man” and “zone” coverage. We use mixture models to create clusters corresponding to each group, allowing us to provide probabilistic assignments to each coverage type (or cluster). Additionally, we quantify each feature’s influence in distinguishing defensive pass coverage types. Our work makes possible several potential avenues of future NFL research into defensive backs and pass coverage strategies.

Utility of the reverse double-drift region (DDR) structure has been studied for fabricating the gallium nitride impact avalanche transit time (IMPATT) diode operating at 1.0 terahertz (THz). Static and largesignal simulations have been carried out in order to verify the THz capabilities of conventional (normal) and reverse DDR structures. It is revealed that IMPATT operation is only possible in a reverse GaN DDR structure due to the lower value of series resistance of it as compared to the normal GaN DDR structure. Normal DDR GaN IMPATT cannot be operational at THz regime. Earlier, the authors had calculated the series resistance of conventional GaN DDR IMPATT diode designed to operate at 1.0 THz, however. They did not take into account the current crowing and spreading resistance at the ohmic metal contacts. That is why, the results were misleading. Those results lead to the conclusion that conventional THz GaN DDR IMPATT may produce sufficient effective negative resistance since the series resistance of it remains within the range of 1.5-2.0 Ω. In this paper, authors have proposed a reverse DDR IMPATT structure exclusively for GaN material and THz frequency bands. By using this reverse DDR structure, p + -GaN ~ Ni/Au contact can obtain a sufficient contact area, so that the anode-contact resistance can be minimized. A nonsinusoidal voltage-excited large-signal model developed by the authors has been used to study the static (DC) and large-signal properties of conventional and reverse DDR structures at 1.0 THz. The present study on the evaluation of THz source seems to open a new horizon for THz researchers and scientists.

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