Objective: The objective of this study is to develop a novel algorithm on a mobile system that can warn drivers about the possibility of a collision with a pedestrian. The constraints of the algorithm are near-real-time detection speed and a good detection rate.
Method: Histogram of gradients (HOG)-based detection is widely used in pedestrian safety applications; however, it has low detection speed for real-time systems. Hence, it has no direct usage for mobile systems. In order to achieve near-real-time detection speed, partial Haar transform predetections are applied to an image before HOG detection. The partial and HOG detections are merged and a score-based confidence level is defined for the final detection phase. In this way, the outcome is prioritized and different warning levels can be issued to warn the driver before a possible pedestrian collision.
Results: The proposed algorithm provides an increase in detection speed (from 46 to 76 fps) and detection rate (from 80 to 91%) with respect to HOG-based pedestrian detection. It also improves confidence of the results by multidetection merging and score assignment to detections.
Conclusions: Performance improvement of the algorithm is compared with respect to state-of-the-art detectors/algorithms. Based on the detection rate and detection speed performance, it can be concluded that the proposed algorithm is suitable to be used for mobile systems to warn drivers about the possibility of collision with a pedestrian. 相似文献
We test the hypothesis that echolocation behavior can be used to find the border between bat habitats. Assuming that bats
react to background targets in “edge space” but not in “open space”, we determined the border between these two habitat types
for commuting individuals of the parti-colored bat Vespertilio murinus. We recorded sequences of bats’ echolocation signals while they flew parallel to the walls of large buildings and to the
ground and determined the signals’ average bandwidth, duration, and pulse interval. These parameters varied systematically
with the estimated horizontal and vertical distances between the bats and the background. A distinct effect of horizontal
distance to the background on echolocation behavior was found for horizontal distances of less than 6 m, thus indicating the
border between edge and open space. Only a few bats flew at vertical distances below 5 m. However, enough passages at vertical
distances of 5 m and above indicated that the vertical border is somewhere below a distance of 5 m. Within edge space, V. murinus reacted to the background by reducing signal duration, increasing bandwidth at closer distances, and often emitting one signal
per wing beat. In open space, signal parameters did not vary as a function of distance to the background. There, V. murinus emitted the longest signals with the narrowest bandwidth and often made one or two wing beats without emitting a pulse. With
our data we support with statistical methods the hypothesis that echolocation behavior reveals the border between the habitat
types “edge” and “open space”. 相似文献
In the annual bumblebee Bombus terrestris, the onset of queen-worker conflict over male production is seasonally and socially constrained. Workers will do better if they start to reproduce (the so-called competition phase) only after ascertaining that larvae are committed to gyne development but before the season ends because they gain more by rearing sister-gynes than their own sons. Here, we tested two nonmutually exclusive hypotheses as to what triggers the onset of worker reproduction: Workers can directly monitor larval development and/or workers eavesdrop on the queen signal that directs gyne development. Exposing workers to gyne larvae through a double mesh did not advance the competition phase compared to control colonies. However, when workers, but not the queen, were allowed contact with gyne larvae, both the competition phase and gyne production were advanced. Thus, while larvae do not emit a volatile pheromone that discloses their developmental route, the physical contact of workers with such larvae triggers early competition phase. However, workers exclusively exposed to worker larvae (colonies prevented from producing gyne larvae) started to reproduce at the same time as control colonies. Replacing the resident queen with an older queen (from gyne-rearing colonies) advanced the competition phase, irrespective of worker age. The results are consistent with the hypothesis that workers eavesdrop on the queen pheromones. This is adaptive because it allows workers a broader time-window for reproduction and thus to gain fitness from rearing both sister-gynes and sons before the season ends without affecting colony development. 相似文献
In ant societies, workers do not usually reproduce but gain indirect fitness benefits from raising related offspring produced
by the queen. One of the preconditions of this worker self-restraint is sufficient fertility of the queen. The queen is, therefore,
expected to signal her fertility. In Camponotus floridanus, workers can recognize the presence of a highly fertile queen via her eggs, which are marked with the queen's specific hydrocarbon
profile. If information on fertility is encoded in the hydrocarbon profile of eggs, we expect workers to be able to differentiate
between eggs from highly and weakly fertile queens. We found that workers discriminate between these eggs solely on the basis
of their hydrocarbon profiles which differ both qualitatively and quantitatively. This pattern is further supported by the
similarity of the egg profiles of workers and weakly fertile queens and the similar treatment of both kinds of eggs. Profiles
of queen eggs correspond to the cuticular hydrocarbon profiles of the respective queens. Changes in the cuticular profiles
are associated with the size of the colony the queen originates from and her current egg-laying rate. However, partial correlation
analysis indicates that only colony size predicts the cuticular profile. Colony size is a buffered indicator of queen fertility
as it is a consequence of queen productivity within a certain period of time, whereas daily egg-laying rate varies due to
cyclical oviposition. We conclude that surface hydrocarbons of eggs and the cuticular profiles of queens both signal queen
fertility, suggesting a major role of fertility signals in the regulation of reproduction in social insects. 相似文献
Every year between one and two million African children under five die of malaria. If one adds to this the contribution of malaria to all-cause infant mortality then clearly the burden of the disease is catastrophic — a disaster quietly happening each and every year. New tools are needed urgently to support those currently available for control of the disease. An effective vaccine remains elusive. This article outlines the potential contribution to malaria control services of satellite information, which is being used by resource managers in other sectors. In particular, it highlights the lessons which can be learned from early warning systems in other areas, especially those designed to respond to famine. An appendix provides a brief introduction to satellite data and their interpretation. 相似文献