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With the emergence of autonomous functions in road vehicles, there has been increased use of Advanced Driver Assistance Systems comprising various sensors to perform automated tasks. Light Detection and Ranging (LiDAR) is one of the most important types of optical sensor, detecting the positions of obstacles by representing them as clusters of points in three-dimensional space. LiDAR performance degrades significantly when a vehicle is driving in the rain as raindrops adhere to the outer surface of the sensor assembly. Performance degradation behaviors include missing points and reduced reflectivity of the points. It was found that the extent of degradation is highly dependent on the interface material properties. This subsequently affects the shapes of the adherent droplets, causing different perturbations to the optical rays. A fundamental investigation is performed on the protective polycarbonate cover of a LiDAR assembly coated with four classes of material-hydrophilic, almost-hydrophobic, hydrophobic, and superhydrophobic. Water droplets are controllably dispensed onto the cover to quantify the signal alteration due to the different droplets of various sizes and shapes. To further understand the effects of droplet motion on LiDAR signals, sliding droplet conditions are simulated using numerical analysis. The results are validated with physical optical tests, using a 905 nm laser source and receiver to mimic the LiDAR detection mechanism. Comprehensive explanations of LiDAR performance degradation in rain are presented from both material and optical perspectives. These can aid component selection and the development of signal-enhancing strategies for the integration of LiDARs into vehicle designs to minimize the impact of rain.
RESUMO
INTRODUCTION: Locked-in syndrome (LIS) results from a brainstem lesion in the pons. Ischemic stroke is the most common etiology of LIS. People with LIS have poor mobility with serious complications due to immobilization. Benefits of exercise after stroke have been widely reported. However, little is known about what and how much exercise should be prescribed for these patients. OBJECTIVES: To explore and evaluate the effect of exercise on the physical recovery of people with LIS after stroke. METHODS: We searched the following databases (last searched August 2017): EMBASE, MEDLINE, PubMed, CINAHL, AMED, PEDro, Cochrane Central Register of Controlled Trials, REHABDATA, Google Scholar, WANFANG, CNKI, and CQVIP. Handsearching of relevant journals and reference lists was also performed. The Oxford Centre for Evidence-Based Medicine was used to assess the evidence level of the included studies. RESULTS: We identified 5 papers from 207 papers involving 35 cases; 26 cases had various degrees of improvement in physical performance after exercise; 9 cases had no change. Five types of exercises and prescriptions were adopted. Study designs and interventions were heterogeneous. All studies contained mixed rehabilitation interventions. A total of 8 different outcome measurement tools have been reported in the studies. CONCLUSION: Studies indicate a positive trend of effect of exercise for physical recovery of people with LIS after stroke including the improvement of muscle strength, tone, walking ability, and activity in daily living. Mixed physical exercises were used. The effects were not significant. No adverse event has been reported. The quality of the existing evidence is relatively low since the papers were either case series or case studies. Further studies are needed on exercise types and dosages for better prescriptions for people with LIS after stroke. This may help to extend their lives with better control of the complications and to improve their quality of life.
