Indoor Visible Light Communication:A Tutorial and Survey

Abstract With the advancement of solid-state devices for lighting, illumination is on the verge of being completely restructured. This revolution comes with numerous advantages and viable opportunities that can transform the world of wireless communications for the better. Solid-state LEDs are rapidly replacing the contemporary incandescent and fluorescent lamps. In addition to their high energy efficiency, LEDs are desirable for their low heat generation, long lifespan, and their capability to switch on and off at an extremely high rate. The ability of switching between different levels of luminous intensity at such a rate has enabled the inception of a new communication technology referred to as visible light communication (VLC). With this technology, the LED lamps are additionally being used for data transmission. This paper provides a tutorial and a survey of VLC in terms of the design, development, and evaluation techniques as well as current challenges and their envisioned solutions. The focus of this paper is mainly directed towards an indoor setup. An overview of VLC, theory of illumination, system receivers, system architecture, and ongoing developments are provided. We further provide some baseline simulation results to give a technical background on the performance of VLC systems. Moreover, we provide the potential of incorporating VLC techniques in the current and upcoming technologies such as fifth-generation (5G), beyond fifth-generation (B5G) wireless communication trends including sixth-generation (6G), and intelligent reflective surfaces (IRSs) among others

Signals and Images in Sea Technologies

Life below water is the 14th Sustainable Development Goal (SDG) envisaged by the United Nations and is aimed at conserving and sustainably using the oceans, seas, and marine resources for sustainable development. It is not difficult to argue that signals and image technologies may play an essential role in achieving the foreseen targets linked to SDG 14. Besides increasing the general knowledge of ocean health by means of data analysis, methodologies based on signal and image processing can be helpful in environmental monitoring, in protecting and restoring ecosystems, in finding new sensor technologies for green routing and eco-friendly ships, in providing tools for implementing best practices for sustainable fishing, as well as in defining frameworks and intelligent systems for enforcing sea law and making the sea a safer and more secure place. Imaging is also a key element for the exploration of the underwater world for various scopes, ranging from the predictive maintenance of sub-sea pipelines and other infrastructure projects, to the discovery, documentation, and protection of sunken cultural heritage. The scope of this Special Issue encompasses investigations into techniques and ICT approaches and, in particular, the study and application of signal- and image-based methods and, in turn, exploration of the advantages of their application in the previously mentioned areas

MODIS. Volume 2: MODIS level 1 geolocation, characterization and calibration algorithm theoretical basis document, version 1

The EOS Moderate Resolution Imaging Spectrometer (MODIS) is being developed by NASA for flight on the Earth Observing System (EOS) series of satellites, the first of which (EOS-AM-1) is scheduled for launch in 1998. This document describes the algorithms and their theoretical basis for the MODIS Level 1B characterization, calibration, and geolocation algorithms which must produce radiometrically, spectrally, and spatially calibrated data with sufficient accuracy so that Global change research programs can detect minute changes in biogeophysical parameters. The document first describes the geolocation algorithm which determines geodetic latitude, longitude, and elevation of each MODIS pixel and the determination of geometric parameters for each observation (satellite zenith angle, satellite azimuth, range to the satellite, solar zenith angle, and solar azimuth). Next, the utilization of the MODIS onboard calibration sources, which consist of the Spectroradiometric Calibration Assembly (SRCA), Solar Diffuser (SD), Solar Diffuser Stability Monitor (SDSM), and the Blackbody (BB), is treated. Characterization of these sources and integration of measurements into the calibration process is described. Finally, the use of external sources, including the Moon, instrumented sites on the Earth (called vicarious calibration), and unsupervised normalization sites having invariant reflectance and emissive properties is treated. Finally, algorithms for generating utility masks needed for scene-based calibration are discussed. Eight appendices are provided, covering instrument design and additional algorithm details

Index to 1985 NASA Tech Briefs, volume 10, numbers 1-4

Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1985 Tech Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

Head tracking two-image 3D television displays

The research covered in this thesis encompasses the design of novel 3D displays, a consideration of 3D television requirements and a survey of autostereoscopic methods is also presented. The principle of operation of simple 3D display prototypes is described, and design of the components of optical systems is considered. A description of an appropriate non-contact infrared head tracking method suitable for use with 3D television displays is also included. The thesis describes how the operating principle of the displays is based upon a twoimage system comprising a pair of images presented to the appropriate viewers' eyes. This is achieved by means of novel steering optics positioned behind a direct view liquid crystal display (LCD) that is controlled by a head position tracker. Within the work, two separate prototypes are described, both of which provide 3D to a single viewer who has limited movement. The thesis goes on to describe how these prototypes can be developed into a multiple-viewer display that is suitable for television use. A consideration of 3D television requirements is documented showing that glassesfree viewing (autostereoscopic), freedom of viewer movement and practical designs are important factors for 3D television displays. The displays are novel in design in several important aspects that comply with the requirements for 3D television. Firstly they do not require viewers to wear special glasses, secondly the displays allow viewers to move freely when viewing and finally the design of the displays is practical with a housing size similar to modem television sets and a cost that is not excessive. Surveys of other autostereoscopic methods included within the work suggest that no contemporary 3D display offers all of these important factors

Index to NASA Tech Briefs, 1975

This index contains abstracts and four indexes--subject, personal author, originating Center, and Tech Brief number--for 1975 Tech Briefs

Plasma needle : exploring biomedical applications of non-thermal plasmas

The plasma needle is a novel design of a radio-frequency discharge in helium/air mixtures at atmospheric pressure. The discharge contains neutral, excited and ionized particles, and emits ultraviolet (UV) light. It operates at low electric power and close to ambient temperature; it combines chemical activity with non-destructive character. Therefore it is expected that the plasma needle will be used in future in (micro) surgery, e.g. in wound healing and in controlled tissue removal through cell detachment or apoptosis, avoiding necrosis and in°ammation reactions. Focus of this study is both on optimization of needle design and on assessment of effects of plasma activity on living cells. This work is a pio- neering study of the effects of non-thermal plasma on biological samples. The design of the plasma needle was adjusted in such a way that instead of operating in a closed reactor, now the treatments could be performed in open air. Thus, larger samples could be treated and handling times were reduced. Then, a characterization of the needle was performed using electrical as well as optical diagnostics (Chapter 3). It was found that the needle operated at voltages of 140 Vrms and higher. A model was made to determine the resistance of the plasma and from this an estimation of the electron density could be made. The latter can be regarded as an indirect measure for plasma reactivity. Results from optical emission spectroscopy showed that reactive oxygen species, such as O¢ and OH¢, were produced in the plasma. Furthermore, UV emission was detected. Both the radicals and the UV are known to interact with cells and tissues. For applications, the amount of radicals that reach the sample or that are generated in the sample is important. For this reason, radicals were detected in liquid that was treated with plasma using a chemical technique (Chapter 4). It involved a fluorescent probe: the probe was dissolved in liquid and after reaction with specific radicals it became fluorescent. Radical density in the liquid depended on plasma conditions, treatment time, and amount of liquid used, but it was always in the micromolar range. These concentrations were found to be comparable with physiological concentrations that were stated in literature. Basic cell reactions after plasma treatment were determined by experiments on cultured Chinese hamster ovarian (CHO K1) cells (Chapter 5). One of these reactions was cell detachment: cells detached from their environment but remained alive after treatment. Other reactions included a small percentage of apoptosis and, when high plasma powers were used, necrosis. A comparison with the effect of UV light from UV lamps was made (Chapter 7). The main effect of UV treatment was necrosis, but only above a certain threshold value. For mammalian cells, this threshold was reasonably high. Thus, the ef- fects of plasma treatment could not be explained by the action of the UV light from the plasma. Quantitative experiments were performed on cultured bovine aortic endothelial cells (BAEC) and rat smooth muscle cells (A7r5) (Chapter 6). These two cell types constitute walls of blood vessels. It was shown that treatment times of less than one minute cause detachment of the cells if the layer thickness of the liquid that covered the cells was low (around 0.1 mm). This suggests that at short treatment times, the penetration depth of the plasma into the sample is limited. The percentage of necrotic cells was low after treatment. No difference was found in the detachment behavior of both cell types. Finally, pilot experiments were performed on carotid arteries of C57BL/6 and Swiss mice ex vivo (Chapter 8). They were studied using a two-photon laser scanning microscope (TPLSM). Cell nuclei, elastin bands, and collagen could be visualized. Preliminary results indicate that induced changes are not strongly dependent on applied energy if no heating e®ects are induced. Apparent effects were limited to the adventitia, probably due to a low penetration depth of active plasma species. In conclusion, we can state that the plasma needle is a non-destructive tool that can be ap- plied with precision. It has a superficial action and causes little damage to the tissue. The level of damage can be controlled to achieve a desired therapeutic effect. Both on cultured cells and on ex vivo arteries interesting effects were found that confirm the hypothesis that the plasma needle will have a future in surgery

Aeronautical engineering: A continuing bibliography with indexes (supplement 284)

This bibliography lists 974 reports, articles, and other documents introduced into the NASA scientific and technical information system in Oct. 1992. The coverage includes documents on design, construction, evaluation, testing, operation, and performance of aircraft (including aircraft engines) and associated components, equipment, and systems. It also includes research and development in aerodynamics, aeronautics, and ground support equipment for aeronautical vehicles