The recycling of plastic products becomes increasingly attractive not only from an environmental point of view, but also economically. For recycled (engineering) plastic products with the highest possible quality, plastic sorting technologies must provide clean and virtually mono-fractional compositions from a mixture of many different types of (shredded) plastics. In order to put this high quality sorting into practice, the labeling of virgin plastics with specific fluorescent markers at very low concentrations (ppm level or less) during their manufacturing process is proposed. The emitted fluorescence spectra represent optical fingerprints" - each being unique for a particular plastic - which we use for plastic identification and classification purposes. In this study we quantify the classification performance using our prototype measurement system and 15 different plastic types when various influence factors most relevant in practice cause disturbances of the fluorescence spectra emitted from the labeled plastics. The results of these investigations help optimize the development and incorporation of appropriate fluorescent markers as well as the classification algorithms and overall measurement system in order to achieve the lowest possible classification error rates.
The conservation and efficient use of natural and especially strategic resources like oil and water have become global
issues, which increasingly initiate environmental and political activities for comprehensive recycling programs. To
effectively reutilize oil-based materials necessary in many industrial fields (e.g. chemical and pharmaceutical industry,
automotive, packaging), appropriate methods for a fast and highly reliable automated material identification are required.
One non-contacting, color- and shape-independent new technique that eliminates the shortcomings of existing methods is
to label materials like plastics with certain combinations of fluorescent markers ("optical codes", "optical fingerprints")
incorporated during manufacture. Since time-resolved measurements are complex (and expensive), fluorescent markers
must be designed that possess unique spectral signatures. The number of identifiable materials increases with the number
of fluorescent markers that can be reliably distinguished within the limited wavelength band available.
In this article we shall investigate the reliable detection and classification of fluorescent markers with specific
fluorescence emission spectra. These simulated spectra are modeled based on realistic fluorescence spectra acquired
from material samples using a modern VNIR spectral imaging system. In order to maximize the number of materials that
can be reliably identified, we evaluate the performance of 8 classification algorithms based on different spectral
similarity measures. The results help guide the design of appropriate fluorescent markers, optical sensors and the overall
Smoking is the most significant source of preventable morbidity and premature mortality worldwide (WHO-2008). One
of the many effects of nicotine is vasoconstriction which is triggered by the autonomic nervous system. The constriction
of blood vessels e.g. of the skin's vascular bed is responsible for a decrease of the supply with oxygen and nutrients and
a lowering of the skin temperature. We used infrared imaging to quantify temperature decreases caused by cigarette
smoking in the extremities of smokers and also monitored heart rate as well as blood pressure. The results - including
thermograms showing "temporary amputations" of the fingertips due to a significant temperature drop - can help increase
the awareness of the dangers of smoking and the success of withdrawal programs.
Surprisingly, in our control persons (3 brave non-smoking volunteers who smoked a cigarette) we also found
temperature increases suggesting that vasodilation (widening of blood vessels) was provoked by cigarettes. To verify this
unexpected finding and eliminate effects from the 4000 chemical compounds in the smoke, we repeated the experiment
following a stringent protocol ruling out physiological and psychological influences with 9 habitual smokers and 17 nonsmokers
who all chew gums with 2 mg of nicotine.
Task-optimized digital image processing techniques (target detection, image-registration and -segmentation) were
applied to the acquired infrared image sequences to automatically yield temperature plots of the fingers and palm. In this
paper we present the results of our study in detail and show that smokers and non-smokers respond differently to the
administration of nicotine.