Different Levels Of Illumination Research Articles

Open-circuit voltages across two junctions in n +−p−p + solar cells under high illumination levels

A theory using ambipolar diffusion equations is given for evaluating the generalized current density through the n +−p and p−p + junctions under illuminated conditions. The open-circuit voltages at the two junctions were obtained by imposing the condition of zero current flow through each of the junctions. The Dember potential which arises out of the non-uniform carrier concentrations in the base region was evaluated and was included in the total open-circuit voltage of the cell. The above voltages were determined for different solar cell thicknesses and different levels of illumination and were compared with the results obtained by earlier workers. A decrease in the thickness of the cell led to an increase in the junction voltages, as is normally expected. Saturation of the above voltages was seen at very high levels of illumination, with carrier generation rates near 10 24 cm −3 s −1. The effect of band gap narrowing on these voltages was incorporated by using the expressions given by Lanyon and Tuft for ΔE g in terms of the carrier concentrations. At very high levels of illumination the carrier concentration rapidly increased and led to a large amount of band gap narrowing; this resulted in a decrease in the open-circuit voltage with an increase in illumination level.

Spread of potentials along the network of horizontal cells in the retina of the turtle

The spread of potentials along electrically-coupled horizontal cell networks in the turtle retina was studied at different levels of illumination. The mean values of the stationary space constant,λ sr measured by the steady-state responses to a bar of light moved along the retina, is about 0.13 mm for the L II, horizontal cell response and 0.35 mm for the L 1 response.λ sr is quite stable in the physiological range of membrane potentials. The dynamic space constant,λ( t), measured at different intervals after the onset of the light bar, transiently increased during the rising phase of the on-response. Such a transient change ofλ( t) is absent or less apparent for depolarizing responses to the offset of the light bar. Ba 2+ ions strongly enhanced the transient increase ofλ( t) for hyperpolarizing responses without affectingλ( t) for depolarizing responses. Possible mechanisms of the transient increase of the dynamic space constant are discussed.

Performance of a Reading Test under Different Levels of Illumination

This is the second report of a series describing experiments designed to explore and define relationships between illumination level and the performance of tasks having selected realistic components of typical office tasks. The first report described an experiment involving proofreading of paragraphs for misspelled words.1 In that experiment, performance improved with increased illumination at different rates for a group of young and a group of older subjects and for different print qualities. The experiment described in this report involved reading for information.

Theory of photo-capacitance in amorphous silicon MIS structures

Abstract A theoretical treatment is presented in which the small-signal, space-charge capacitance, C sc, in a-Si MIS structures is calculated for varying levels of illumination. Bulk recombination and a sufficient density of states at the insulator-semiconductor interface to pin the Fermi level and produce a significant surface band-bending are assumed. It is shown that the trapping state density as a function of energy in the mobility gap can be derived from measurement of C sc at different levels of illumination. The method is particularly applicable in cases where the surface-state density is large enough to preclude field-effect measurements.

Development of Lighting Standards for the Visually Impaired

This article reviews the history of the development of lighting standards for the visually impaired. All available literature on how different levels of illumination affect visual acuity and visibility among persons with visual impairments is reviewed. And the implications of this research for meeting the needs of visually impaired children in the classroom are discussed.

Low temperature photoconductivity in arsenic-chalcogenide glasses

Measurements are presented on photoconductivity, at different levels of illumination, in several AsSe alloys, at temperatures down to about 100°K. These results, as well as earlier results from the litterature, are presented in a form different from and mathematically simpler than, the hitherto conventional form. The complementary nature of photoconductivity and photoluminescence is discussed and a common parameter is found.

Proofreading under different levels of illumination : Smith, S.W., and Rea, M.S.Journal of the Illuminating Engineering Society, Oct 1978, 8.11, 47–52

Proofreading under different levels of illumination : Smith, S.W., and Rea, M.S.Journal of the Illuminating Engineering Society, Oct 1978, 8.11, 47–52

Effect of variation in light intensity on sheep movement through narrow and wide races

The movement of flocks of 14 Border Leicester x Merino sheep through narrow and wide races was observed. A high partition across the race allowed light intensity to be varied independently on each side. The effects of various combinations of four levels of illumination, 1.4, 88, 350 and 1400 lux (i.e. dark, low, medium and bright, respectively) were examined. Different light intensities had little effect on the movement of sheep. Sheep moved more readily through or into brightly lit areas, and this response was clearly dependent upon the behaviour of the first sheep leading the flock. There was no evidence to suggest that the degree of contrast between different levels of illumination or the direction of change in light intensity, e.g. dark to bright vs bright to dark, were important. The results suggest that strong contrasts in light cannot be used to attract sheep to move along a race. However, they confirm that shearing sheds should be well lit to encourage sheep movement into and within the shed

Behavioural conflict in two strains of rat: Home cage preference versus dark preference

When confronted with a novel situation rats show a tendency either to stay in a dark place or to retreat to a familiar place, if available. To produce a conflict between these two tendencies the rat's home cage was connected by a runway to a dark but unfamiliar compartment. Three groups of rats were tested in this apparatus with different levels of illumination in the home cage. Tryon Maze Bright rats showed a strong preference for the home cage which was independent of the illumination level. This preference was also found in Wistar rats. With a very high level of illumination in the home cage, however, Wistar rats showed a preference for the home cage only in the first few trials or a series of repeated trials. In later trials they spent more time in the dark part of the apparatus. The results were regarded as an indication that in a novel situation rats primarily search for a familiar place. When such a place is available they tolerate aversive stimulation present in this place.

Proofreading under Different Levels of Illumination

The subjects' task in this experiment involved proofreading of paragraphs for misspelled words. Four young and four older subjects served in the experiment. It is concluded that age, print quality and illumination level significantly affect performance. Results indicate that performance improves with illumination but by varying degrees for different conditions. Further, increased illumination and good print quality are more important for older subjects than for young subjects.

Measurement of Luminance Factor

AbstractLuminance factor of a diffusing material is defined as the ratio of the luminance of the surface of the material to that of a perfect (Lambertian) diffuser under specified conditions of illuminance and angle of view. Measurement of this quantity has always been rather difficult, involving visual photometric measurements at widely different levels of illuminance. A physical method of measuring luminance factor is described which has given more repeatable results and better interlaboratory agreement than the former visual method.

Performance of Complex Tasks under Different Levels of Illumination: Part I—Needle Probe Task

This is the first in a series of research reports that describe the relationship between illumination level and the performance of complex tasks having selected realistic components. The task described in this article required subjects to insert a fine tipped probe into the eye-holes of ten needles in rapid succession. Results of the needle probe task and of different tasks reported by other investigators are compared.

Light intensity as a factor in the regulation of the density of symbiotic zooxanthellae in Aiptasia tagetes (Coelenterata, Anthozoa)

Experiments designed to investigate the effect of different levels of illumination on the density of symbiotic zooxanthellae in the anemone Aiptasia tagetes (Duch. & Mich.) are described.The anemones are found to regulate the densities of their zooxanthella populations to fixed levels which are dependent upon ambient light intensity.Regulation is continuous and results from the interaction of increase in algal numbers, growth of host tissues, population of new host tissues by symbionts and extrusion of zooxanthellae by the host.The nature of the process by which zooxanthellae are selected for extrusion is discussed and a scheme is outlined indicating the pathways through which the level of the algal population in Aiptasia, and other coelenterates, is believed to be controlled.

Proportional effect of light on entrained circadian rhythms of birds and mammals

Circadian rhythms of locomotor activity of two species of finches,Fringilla coelebs andCarduelis chloris, and four rodent species,Mesocricetus auratus, Glis glis, Eutamias sibiricus andFunambulus sp., were studied under the influence of 12∶12 h light-dark (LD) cycles with different levels of illumination during L and D. The LD intensity-ratio (Zeitgeber amplitude) was approximately constant at different mean levels of light intensity per cycle (Zeitgeber level). Theproportional effect of light, measured as the influence of mean light intensity per cycle (geometric mean) on the phase-angle differences between activity onset and light-on (in day-active species) or light-off (in night-active species) showed large interspecific variability. The variations—in extent and direction—were congruous with the effects of light on the free-running rhythms in the same species suggesting a functional relationship between effects of light on free-running and entrained circadian rhythms.

Chloroplast structure in mature apple leaves grown under different levels of illumination and their response to changed illumination

The thickness of grana within chloroplasts of mature apple leaves increased with depth in the palisade layer. Growth of trees under shade resulted in thicker grana. Transfer of trees from light to shade, and vice versa , suggested that grana thickness changed in response to decreased but not increased light intensity.

Locomotory patterns of fish ( Lepomis gibbosus) under different levels of illumination

The fish, Lepomis gibbosus, displayed a characteristic pattern of turnings under various illumination levels. The steady state locomotory pattern of these fish under standard light (1 lx) and bright light (1·2 lx) changed to a new pattern in dim light (0·6 lx) and darkness (<0·6 lx). Present observations suggest that the level of illumination has a definite effect on the turning behaviour, and pumpkinseed displayed left- or right-handedness in their movements. Blinded pumpkinseed showed the same frequency distribution of turnings (‘jumps’) as did normal fish under standard, dim light and darkness. It may be concluded that for any change in steady-state pattern of turning, light perception per se is more pertinent than optical perception.

Maze exploration in the rat under different levels of illumination

Male hooded rats were tested in an enclosed symmetrical Y-maze, constructed entirely of clear Perspex, for 3 min on each of four successive days. The maze was illuminated by either a 15-W red bulb (group R) or a 150-W white bulb (group W). Section entry scores were similar for both groups on day 1; there was a marked decline on subsequent days for group W but not for group R. Defaecation scores were higher for group W on all trials. The results are discussed in relation to comparisons of behaviour in elevated and enclosed mazes.

Responses to Light of Young Atlantic Salmon (Salmo salar) and Brook Trout (Salvelinus fontinalis)

Responses of young Atlantic salmon (Salmo salar L.) and of brook trout (Salvelinus fontinalis (Mitchill)) to different levels of illumination and to overhanging and submerged cover were compared in the laboratory. At surface illuminations between 0.4 and 160 ft-c trout were either slightly photopositive or showed no preference for light or dark areas, while salmon were photopositive. At illuminations above 300 ft-c both species were photonegative when the light area had a smooth, unbroken substrate. Under these conditions starvation induced salmon into the light, but trout remained photonegative, although slightly less so than well-fed trout. With submerged cover (plants, broken flowerpots, etc.) in the light area, salmon were strongly photopositive, while trout were photonegative. Salmon were less photopositive, but still preferred the light area, with submerged cover in both dark and light areas, in most experiments trout maintained position at the edge of the shadow caused by overhead cover, looking out into the light area from the dark.The significance of these results to habitat segregation by the two species where they are sympatric in nature is discussed.

Effect of Different Levels of Illumination on the Life Cycle of the Face Fly12

During the first attempts by other investigators to establish laboratory colonies of the face fly, Musca autumnalis DeGeer, it appeared that the illumination level might have some influence upon successful colonization. Research by Fales et al. (1961), the first to successfully establish a laboratory colony in the United States, indicated that a high level of illumination was necessary for rearing the face fly indoors. If this were so, it was desirable to determine whether colonies could be maintained under lower levels of illumination and, if so, the effect upon the fly’s life cycle. To evaluate this point, face flies were reared under different levels of illumination and their life cycles compared.

Effect of Intertrial Interval and Illumination upon Spontaneous Alternation and Running Time in Armadillidium vulgare.

IWAHARA (1) has shown that spontaneous alternation in a simple T-maze in Armadillidium vulgare is little affected by intertrial intervals (0″and 120″) and that the running time in the maze is also not significantly different whether trials are massed or spaced. Thus it was reasoned that the nonsignificant effect of intertrial interval upon alternation may be due to the fact that the accumulation of reactive inhibition which is supposed to affect alternation, is relatively independent of massing of the trials in this animal.The purpose of the present study is to repeat the IWAHARA study with broader variations of intertrial intervals, with more extended trials and, in addition, with three different levels of illumination. In Experiment I six groups of 17 animals each were run on a factorial design with 0″, 120″, and 300″intertrial intervals, and two levels of illumination (250 lux and less than 1 lux). Two groups with a 0″-interval were given 30 trials, while other four groups 20 trials. In Experiment II two groups were run only twice with a 24 hour-interval one under light and another under dark illumination. In Experiment III was run another group with a 120″-interval from the light starting point to the dark goal. No particular reinforcement was given.The results were: (1) spontaneous alternation (about 40%) was again little affected by intertrial intervals whether alternation was computed on the first two trials or on the total trials, and it was independent of an increase of trial numbers, (2) the animal ran faster with massed trials but slower with an increase of trials, and under the dark illumination, (3) it was fastest with the dark goal, (4) running time was not significantly different whether the animal alternated or repeated the preceding responses, and finally (5) significant individual differences were found with respect to position preferences and running time but not with respect to spontaneous alternation. The results were discussed in connection with previous studies.