Light Scenario Research Articles

Preferred luminance distributions in open-plan offices in relation to time-of-day and subjective alertness

ABSTRACT Dynamic lighting is one of the new trends in lighting research; providing the right lighting level at the right time could possibly increase the alertness and performance of office workers. However, they might have preferences that deviate from this “healthy” lighting. Simultaneously, the building environment becomes increasingly automated, with occupancy-based control as one of the most well-known examples to reduce offices’ lighting energy consumption. Nevertheless, preferences for lighting levels in the unoccupied area of the multi-occupant office space have not been addressed yet. Therefore, we studied luminance distribution preferences in relation to time of day and subjective alertness (SA) in a single occupancy scenario. Participants (N = 30) set the surrounding and background lighting six times a day as we first probed for SA. Our results clearly showed that a subset preferred varying luminance distributions; participants had fluctuating feelings of alertness, too. Preferences deviated sometimes from the typical dynamic lighting scenarios, suggesting that they do not always prefer healthy lighting. Moreover, we identified an effect of SA on the preferences, both with and without controlling for time of day. Hence, this study showed that we need to address these two factors when we want to provide satisfactory lighting conditions in case the office is not fully occupied. These are likely to affect other lighting preferences and therefore deserve more attention from research. Because we identified large individual differences, we suggest personalizing dynamic scenarios as the focus of future research.

Interplay of scalar and fermionic components in a multi-component dark matter scenario

We explore the multi-component dark matter (DM) scenario considered in a simple extension of the standard model with an inert scalar doublet and a singlet fermionic field providing the two DM candidates. The DM states are made stable under the unbroken Z_2times Z_2' discrete symmetry. An additional gauge singlet scalar field is introduced to facilitate the interaction of the dark fermion with the visible sector. Presence of a charged fermionic field having the same Z_2 charge as that of the inert scalar field allows exploring the dark matter mass regions otherwise disallowed, like in the standard Inert Doublet Model (IDM) scenarios. With these arrangements, it is shown that the light DM scenario and the desert region in the intermediate mass range of DM in the standard IDM case can be made compatible with the relic density bounds and direct detection limits. Further, detailed parameter space study is carried out keeping the coexistence of both the scalar and fermionic components in focus, showing that sizable parameter space regions are available for the entire mass range of 10 mathrm GeV le M_{DM}le 2000 GeV.

Multifeature fusion for robust human detection in thermal infrared imagery

Despite all the significant advances in human detection in various environmental conditions, it is still a challenging task. Most of the human detection algorithms mainly use color information, which is not robust to lighting changes and varying colors under which such a detector should operate namely day and nighttime. This problem is further amplified with infrared (IR) imagery, which only contains grayscale information. The proposed algorithm for human detection uses intensity distribution, gradient, and texture features for effective detection of humans in IR imagery. For the detection of intensity, histogram information is obtained in the grayscale channel. For extracting gradients, we utilize the histogram of oriented gradients for better information in the various lighting scenarios. For extracting texture information, center-symmetric local binary pattern gives rotational invariance as well as lighting invariance for robust features under these conditions. Various binning strategies help keep the inherent structure embedded in the features, which provide enough information for robust detection of the humans in the scene. The features are then classified using an AdaBoost classifier to provide a tree-like structure for detection in multiple scales. The algorithm has been trained and tested on IR imagery and has been found to be fairly robust to viewpoint changes and lighting changes in dynamic backgrounds and visual scenes.

Methods for assessing the effects of spatial luminance patterns on perceived qualities of concert lighting

This paper presents experimental approaches for evaluating concert lighting from the viewpoints of audience members and performers in Cambridge King's College Chapel. We develop image zoning and abstraction techniques to quantify and interpret photometric data acquired under four different electric lighting conditions. Assessed by 78 participants, these lighting scenarios are compared across six different viewing positions using a set of structured questionnaires. Ordered logistic regression modelling shows that the ratios and functions describing uniformity, brightness and light patterns are common explanatory variables for predicting perceived visual clarity, visual uniformity, brightness and spatial intimacy. Uniformity-related attributes are observed to be among the strongest variables for all these perceived qualities, except for visual clarity, which is better explained by acuity-related measures. These experimental results confirm the applicability of our approaches, highlighting the importance of combining multiple methods and integrating complex architectural situations into the process of understanding luminous appearance.

Modeling the interaction of light and nutrients as factors driving lake eutrophication

Eutrophication is a major problem in the field of water environments at present, and its main driving factors are light and nutrients. In this paper, the process of eutrophication in small artificial lake is studied, according to the principle of water optics and conservation of mass, the light and the nitrogen and phosphorus in water nutrients were selected as influencing factors, and 16 different scenarios of light-nutrients interaction conditions were designed by orthogonal experiment. Then water eutrophication model was used to analyze the process of eutrophication under different light-nutrient scenarios. According to the comparison of simulation results, if the concentration of nutrients is increased under low light conditions, the growth of algae will be inhibited; And if the light condition is set to a fixed value, the simulation results under different nitrogen and phosphorus concentrations in the water show that the effect of phosphorus on algae growth is greater than that of nitrogen; In addition, comparing the growth of algae under different light and phosphorus scenarios, it can be seen that the light-driven effect is more significant than that of phosphorus. By simulating all the design scenarios and analyzing the results, it can be found that the algae growth rate reaches a maximum when the light intensity and the nitrogen and phosphorus concentration increase to a certain range; while continuing to increase the light and nutrient concentration exceeds a certain threshold range, the rate of algae growth will be inhibited.

Impact of urban street lighting on road users’ perception of public space and mobility behavior

Refitting public spaces with light-emitting diode (LED) technology in lieu of conventional luminaires bears the risk of compromising lighting quality that road users have already adapted to; this is because the LED technology has been well tested indoors, but it has not been necessarily evaluated outdoors. Further insight into the effects of street lighting on road users is necessary to resolve potential deficiencies of available technologies. This study compares the effects of three different lighting scenarios (conventional lighting, state-of-the-art LED, optimized LED) on road users via surveys (N = 598 persons) and observations (N = 1341 persons) in the city of Vienna. In terms of the uniformity of street illumination and the comfort it provides, the results show the positive effects of LED street lighting both on surveyed pedestrians and vehicle drivers. The observations of pedestrian walking behavior revealed an unexpected result—no significant differences were noted apart from a more centric walking path along the sidewalk under LED illumination, particularly with the optimized LED luminaire.

A study on the implementation of dimmable street lighting according to vehicle traffic density

In this study, illuminance and luminance intensity that comply with road lighting classifications are determined by taking into account the vehicle traffic density. As the vehicle traffic density increases, illuminance and luminance intensities increases, while lower intensities are achieved with decreasing vehicle traffic density and energy saving is also succeeded. As a result of the saving, the negative impact of carbon emissions, which is a harmful effect for the environment, is also greatly reduced. When the number of vehicles on the road decreases at certain hours, the savings rate can be further increased with the lighting scenario loaded on the controller card by reducing the lighting comfort.

3D MODELLING AND MEDIEVAL LIGHTING RECONSTRUCTION FOR RUPESTRIAN CHURCHES

Abstract. The aim of this research is to define a method, able to analyse the systems of illumination in the medieval period, through a 3D virtual model reconstruction. It specifically needs to deepen the interactions between natural and artificial illumination in confined spaces. The study describes and examines the best survey technique to obtain a 3D model reconstruction, according to the achievement of such lighting scenarios, and the most suitable tools for lighting analysis. Thus, it is possible to carry out accurate interpretations of the past starting from historical sources and scientific data about lighting. This method was validated on a case study of a rupestrian church in Matera. The rupestrian contexts are less investigated in relation to mediaeval artificial lighting even if there are recognitions and comparative studies of widespread contexts, not only in Puglia and Basilicata, but also in Mediterranean area (e.g. in Cappadocia and Cyprus) which allow identifying evidences related to artificial lighting systems. The architectural signs (hole, niches, etc.) for ancient luminaries can be studied in 3D and lighting prospective. Lastly, the virtual model of the rupestrian church was imported into an opensource visualisation software (3D Heritage Online Presenter) to be appreciable on line and to promote historical heritage knowledge.

Outdoor microalgae cultivation at different biomass concentrations — Assessment of different daily and seasonal light scenarios by modeling

An efficient microalgae outdoor cultivation is hindered by the fluctuation of the photon flux density (PFD) during one day and the natural day-night-rhythm. As the light intensity is not directly adjustable, the adjustment of biomass concentration is often used for the indirect distribution of available photons to an appropriate number of cells.For this study, repeated fed batch cultivations were conducted in 28 L flat panel airlift reactors in Stuttgart, Germany between August and October 2015. The influence of the initial biomass concentration (1.5–9 g L−1) on the productivity of Chlorella sorokiniana was investigated.Two models (basing on different underlying assumptions) were developed, which used the results of a previous laboratory study to explain the effects of different PFD courses on the productivity outdoors. Both models were validated by using the results of the outdoor cultivation. With the model based on the light yield, an adequate prediction of the productivity was achieved. This leads to an assessment of the outdoor process with paradigmatic courses of the PFD.The application of the model on recorded outdoor PFD courses proved that not only the amount of photons has an impact on the productivity, but also their distribution during the day. Longer photoperiods with lower maximum PFD values (summer) lead to a higher productivity compared to shorter photoperiods with higher maximum PFD values (spring/fall). Additionally, the biomass concentration should be at least as low as 1.5 g L−1; this leads on the one hand to an improved light yield, as there is less self-shading of the algae culture, on the other hand, there is less night biomass loss at lower biomass concentrations.

Evaluating the effectiveness of image quality metrics in a light field scenario

In this contribution, an objective metric for quality evaluation of light field images is presented. The method is based on the exploitation of the depth information of a scene, that is captured with high accuracy by the light field imaging system. The depth map is estimated both from the original and impaired light field data. Then, a similarity measure is applied, and a mapping is performed to link the depth distortion with the perceived quality. Experimental test performed by comparing state-of-art metrics with the proposed one, demonstrate the effectiveness of the proposed metric.

Resource Management of LTE-U Systems for Channel Utilization and User Satisfaction

Deploying long term evolution (LTE) system into unlicensed spectrum for offloading faces two challenges: 1) the metrics of instantaneous performance to characterize user satisfaction are no longer applicable due to non-contiguously available channel and 2) in a light traffic scenario, the channel utilization is low due to the added padding bits of simultaneously scheduled users. To tackle these two issues, dynamically configuring channel occupancy duration (COD) and flexibly allocating subcarriers are needed to design for the LTE system operating in unlicensed spectrum (LTE-U system). In this paper, the channel utilization in the COD and a unified user satisfaction are first defined to characterize the performance of LTE-U system. Then, a time-frequency two-dimention optimization problem is formulated to maximize the weighted sum of the two defined performance indexes. To achieve the tradeoff between the two performance indexes, a control factor is introduced. By using Lyapunov optimization and Dinkelback theory, an optimal time-frequency resource management algorithm is developed. The results show that the proposed algorithm outperforms the baselines, as the algorithm can flexibly balance the two performance indexes of the LTE-U system for diverse applications.

Deep Learning Based Automated Attendance System

Abstract A significant portion of the time allocated to a faculty for teaching purposes is consumed on the task of taking attendance of the students. This is an issue because it takes the valuable time of teachers which could be spent on more productive tasks such as teaching and interacting with students. In excess to the increase in chaos and loss of decorum in the classroom environment, the presence of proxy attendance also plagues the existing method of manual attendance keeping. To counter these issues, this paper proposed the Deep Learning Assisted Attendance System (DPAAS); which keeps track of students attending a particular class with the help of a continuous stream of pictures captured from a video streaming device located inside a classroom connected to the remote server. The proposed DPAAS method reduces the amount of time spent by the faculty on taking attendance, and leads to a reduction in chaos inside a classroom. DPASS is proposed handles the issues in existing systems such as multi-class identification for multiple individuals in a classroom, occlusion and differing light scenarios. The DPAAS methodology compares the results of the state of art algorithms, and uses the best fit architecture which provides the lowest false rate on evaluation. There is no need of user interaction in the proposed DPAAS. Experimental results show that the proposed DPAAS method gives 94.66% accuracy which is better than the other existing methods.

A spatial-frequency-temporal domain based saliency model for low contrast video sequences

The last few decades have witnessed rapid development of visual saliency detection, as it can detect object-of-interest from clutter environments to substantially facilitate a wide range of applications. However, traditional visual saliency detection models primarily rely on image features, which may face great challenges in low contrast video stream captured from low lighting scenarios. This paper proposes a dynamic multimodal fusion based visual saliency detection model towards low contrast videos, which combines saliency information from spatial, frequency, and temporal domains. In spatial domain, superpixel covariance is utilized to compute the region dissimilarity under low lighting scenarios; in frequency domain, the amplitude spectrum tuned method is used to suppress the background noise; in temporal domain, the incremental learning is employed to efficiently update background model from high dimensional video streams. Extensive experiments have been conducted to validate the effectiveness of the proposed model.

Design and development of a low-cost mask-type eye tracker to collect quality fixation measurements in the sport domain

The aim of the study was to build a low-cost mask-type eye tracker with accuracy and precision levels similar to those reported for commercial eye tracking devices. To this end, head-mounted hardware was designed and developed, while open-source software was modified for digital image capture, manipulation, and fixation analysis. An image recognition application was also included with different lighting scenarios. Moreover, parallax and viewing perspective errors were controlled to ensure the quality of data collection. The device was wireless and lightweight (99 g) to allow for natural movement and avoid participant discomfort. After calibration of a 9-target monocular grid, spatial accuracy and precision of the eye tracker was evaluated by 30 participants, at four different lighting setups, both before and after a climbing task. Validity tests showed high levels of accuracy in all conditions as evidenced by a systematic error for a 13-target grid of <0.5°. The reliability tests also showed consistent measurements with no differences in accuracy recorded between participants, lighting conditions, and visual behaviors for the pre- versus post-climbing task. These results suggest that the present eye tracker reports spatial accuracy similar to other commercial systems with levels of high quality. Altogether, this innovative user interface is suitable for research purposes and/or performance analysis in physical activity and sport-related activities. Also, features of this mask-type eye tracking system make it a suitable perceptual user interface to investigate human–computer interactions in a large number of other research fields including psychology, education, marketing, transportation, and medicine.

СУЧАСНЕ ОСВІТЛЕННЯ В ДИЗАЙНІ МУЗЕЙНИХ ЕКСПОЗИЦІЙ

In modern design practice lighting plays an important role. Lighting means intensification of visual and psychological effect of museum exposition. Light plays an active role in perception of exhibit, revealing its shape, texture and color. Natural light is used to create a broad background, and artificial – to focus attention on specific information. The best way is the combination of artificial and natural light. This balance is possible due to technological achievement. New ways of lighting create the conditions for better preservation of objects.Lighting techniques give the possibility to make the exposure dynamic, without resorting to mechanical kinematic schemes. Since the motion of light attracts the attention of the viewer more than the movement of objects, this fact became the basis for development of a number of interesting schemes of dynamic lighting. Stands and showcases with dynamic illumination leave a brighter footprint in memory.The choice of the lighting system is closely linked with the architecture of the museum building and with the system of museum lighting (natural, artificial and combined). In this case, it is necessary to take into account the complexity of specifics of the museum exposition – the need to create the best illumination of exhibits and at the same time to protect them from the harmful effects of light rays. Lighting systems are based on the composition and properties of exhibited museum objects and the acceptable level of lighting for various categories of exhibits.Artificial lighting must be carried out mainly by sources of light, whose radiation in the spectrum is close to the daytime. For illumination special lighting fittings, which are usually hidden from visitors (behind suspended ceilings, embedded in furniture or exhibition equipment) should be used.Nowadays there is a wide arsenal of lighting means aimed to increase the visual and psychological effect of museum exposition, various types of lighting fixtures and lamps used to illuminate expositions. Among the lighting products, the leading role belongs to LED technologies. These technologies are characterized by qualities that are decisive in the organization of the museum environment. This is the ability to give white light to each exhibit, high light output at low power consumption, fire safety, the possibility of tape mounting of light sources, the implementation of programmable light scenarios with a change in color gamut. The latest technologies in lighting systems play an important role in design of museum exposition.

Examining bus driver behavior as a function of roadway features under daytime and nighttime lighting conditions: Driving simulator study

Numerous studies in the literature have established a relationship between driver behavior and roadway characteristics. However, investigating bus driver behavior as a function of roadway features under different lighting conditions has been a missing link. This research aims at investigating the main and interaction effects of three roadway features – shoulder width, guardrail existence, and roadway geometry – on bus driver behavior under daytime and nighttime lighting conditions. In this regard, using driving simulator, 40 professional bus drivers were recruited to drive on 30 different segments, including the combination of 3 shoulder widths, 5 curve radii, and 2 guardrail states, under daylight and dark lighting scenarios. By examining adopted speed and lateral positioning, it was found that bus driver behavior is noticeably affected by guardrail existence on the segments having a narrow shoulder. Interestingly, the results revealed that the presence of guardrail is negatively associated with driving speed on these segments; also, it causes drivers to travel close to the centerline of the road. Regarding the correlation of lighting conditions with driver behavior, it was found that while bus drivers consistently adopt higher speeds in daylight condition, as opposed to darkness, their lateral positioning is not significantly affected by lighting condition. This finding implies that lateral movements can be more attributed to roadway characteristics, rather than visibility of the road. The study suggests that driver behavior in darkness could be associated with contributing factors in different ways, which such differences cannot be uncovered by focusing merely on one aggregate analysis.

Effects of surface reflectance and lighting design strategies on energy consumption and visual comfort

Globally, artificial lighting accounts for a considerable part of electrical energy consumption in buildings. Hence, there is a need to design appropriate lighting scenarios for buildings in a way to reduce energy while meeting visual comfort requirements. This research aims to investigate the effects of applying different design strategies on lighting energy use and visual comfort level. Surface finishing reflectance, type, number and mounting height of luminaires are variables in the study. Lighting design software DIALux evo 7.0 provides simulations of a real scale room according to different scenarios whose models were calibrated and validated using experimental field data. The findings indicate that the type of luminaire is the most decisive parameter in quantity and quality of light in an indoor environment. However, increasing the indoor surface reflectance plays a key role in improving energy efficiency and visual comfort. The results show the possibility of electrical energy savings up to 45% by increasing surface reflectance properties. Finally, this paper stresses that there is no single design solution to guarantee both low energy demand and high visual quality, therefore integrating different strategies based on the type of task and the occupant’s activities is highly recommended.

Video Analytics Usage in Transportation Agencies: Nationwide Survey and Maryland Feasibility Study

This paper summarizes the findings from a study conducted by the University of Maryland Center for Advanced Transportation Technology (CATT) regarding the potential to extract meaningful traffic information from existing Maryland Department of Transportation-State Highway Administration (MDOT-SHA) closed-circuit television (CCTV) video feeds via image processing. It describes the survey that was developed and administered by CATT between March 10 and June 8, 2017, focusing on transportation agencies’ current use cases and future plans for video analytics. Feedback from 21 agencies (9 of which are using video analytics) indicates a general excitement about the technology, although a persistent theme throughout the responses is that most current solutions are not yet able to provide satisfactory quantitative results (e.g., traffic counts, speeds, turning movements), especially in low light and high glare scenarios. Additionally, the report summarizes the vendor evaluation procedure that was undertaken, which includes identifying suitable video analytics vendors, developing a testbed of representative video clips from MDOT-SHA cameras under various conditions, asking the vendors to demonstrate their product capabilities on the testbed, and analyzing results. With proper camera positioning and calibration, the two vendors who participated achieved results within 5% to 15% of manual counts, and 4% to 7% of probe speeds in the northbound travel direction during a one-hour test clip. However, only one vendor produced results for the more challenging southbound direction, and the estimates were far less accurate (within 25% of manual counts and 20% of probe speeds). Accordingly, it appears that the estimation accuracy is highly sensitive to factors such as camera angle, resolution, and visibility.

Influence of light availability on the specific density, size and sinking loss of Anabaena flos-aquae and Scenedesmus obliquus

Harmful algal blooms in eutrophic waters pose a serious threat to freshwater ecosystems and human health. In-situ light availability control is one of the most commonly used technologies to suppress algae in lakes and reservoirs. To develop a better understanding of the effects of light on algal growth, specific density, colony size and sinking loss, Anabaena flos-aquae (cyanobacteria) and Scenedesmus obliquus (green algae) were evaluated in varying light scenarios. The results showed that the specific density and colony size of these two species varied during growth, and there were obvious differences among the light scenarios. At the end of exponential phase, S. obliquus incubated under light-limited condition maintained a higher specific density and formed larger aggregates, whereas A. flos-aquae formed a longer filament length. Both species exhibited higher sinking loss rates with lower light availability. These results implied that the sinking loss rate was not always constant but should be considered as a variable response to the change of light availability, and in-situ light availability control might result in a significant increase of the sinking loss of algae due to the change of size and specific density, thereby further affecting the algal biomass in the water column.

RACH Preamble Repetition in NB-IoT Network

NarrowBand-Internet of Things (NB-IoT) is a radio access technology recently standardized by 3GPP. To provide reliable connections with extended coverage, a repetition transmission scheme is applied in both Random Access CHannel (RACH) procedure and data transmission. In this letter, we model RACH in the NB-IoT network taking into account the repeated preamble transmission and collision using stochastic geometry. We derive the exact expression of RACH success probability under time correlated interference, and validate the analysis with different repetition values via independent simulations. Numerical results have shown that the repetition scheme can efficiently improve the RACH success probability in a light traffic scenario, but only slightly improves that performance with very inefficient channel resource utilization in a heavy traffic scenario.