Academic literature on the topic 'Empirical lighting models'

Study of light at night has increased in recent decades due to the recognition of its impact on the environment, potential health concerns, as well as both the financial and carbon cost of energy waste. The advent of more extensive and improved ground-based measurements together with quantifiable satellite data has revolutionised the field, and provided data to test improved theoretical models. However, “closing the loop” and finding a detailed connection between these measurements requires knowledge of the “city emission function”, the angular distribution of upwelling radiation with zenith distance. Simplified analytical functions have been superseded by more complex models involving statistical approximation of emission sources and obstructions and inversion techniques now permit the estimation of emission functions from the observed sky brightness measurements. In this paper, we present an efficient GIS-based method to model public lighting using real-world photometric data and high-resolution digital elevation maps of obstructions such as buildings and trees at a 1 m scale. We discuss the results of this work for a sample of Irish towns as well as a city area. We also compare our results to previous emission functions as well as to observed asymmetries in emission detected by satellites such as SUOMI VIIRS.

Purpose Lighting in building sectors (consumes the highest energy in commercial buildings and the second highest in residential buildings in India) has very much potential for energy conservation in buildings. With the use of daylighting system, energy consumption in lighting can be lowered up to 30 to 40 per cent. Design/methodology/approach An experimental effort has been made in this paper to explore the internal wall coloring effect on the performance of tubular light pipe. Trace-pro software has been used and validated. With the help of this software, light pipe has been designed and simulated in a ray tracing mode. Assessment of four globally used prediction models has also been conducted to compare the performances in different seasons for light pipes in the composite climate of New Delhi. Findings It has been conducted based on three statistical indicators as mean bias error, root mean square error and R2. Using regression, an empirical model for average internal illuminance has been developed as a function of light reflectance value (LRV) and solar altitude angle. Trace-pro results confirmed that maximum internal illuminance can be obtained with wall surfaces coated with high LRV color. Finally, by using of a single light pipe system for a test room with the artificial lighting system and applying continuous dimming control, the amount of electrical energy has been saved up to 38.5 per cent per year. Originality/value After going through the literature, it has been identified that there has been no paper published which explores the effect of colors of the internal walls on the performance of the light pipe. Along with this, the comparison between existing empirical performance models and find out which model gives the best result in different seasons has been carried out for New Delhi, India.

In marketing terms, the phenomenon of price war is regarded as the result of over-competition and retaliatory reaction in order to win market share. Based on the available literature, three refined models of price war antecedents has been identified: the imperfect monitoring model, the cyclical model, and the learning model. This article was written as part of a recent empirical observation of four Indonesian lighting companies who consider themselves to be currently engaged in price war. Based on the proposition made earlier by Heil and Helsen (2001), this study was prepared as a qualitative survey using an open-ended questionnaire method. The study found that price war is a result of competitive interaction in periods where demands are declining and induced by intra-brand competition. In conclusion, propositions to manage activities in conditions of price war are presented.

In recent years, the number of artificial light sources has tremendously increased with the development of lighting technology and the economy. Nighttime light pollution has been an increasing environmental problem, resulting in negative impacts on human health and the ecological environment. Detailed knowledge of light pollution is important for the planning and management of urban lighting. In this study, light pollution in Nanjing, China was monitored and analyzed using field observations and a 130-m resolution Luojia 1-01 nighttime light imagery. Combined with in situ observations and satellite imagery, a variety of empirical models were established for estimating ambient illuminance at night. Cross-validation was employed to assess the performance of these models, indicating that the third-degree polynomials model had the best performance (MAE = 5.06 lx, R2 = 0.81). The developed third-degree polynomial model was then applied to the Luojia 1-01 image to map the nighttime illuminance in Nanjing. The nighttime illuminance depicted the spatial pattern of the light environment over Nanjing and also indicated some heavily light-polluted areas. Some lit areas were residential areas, whose high brightness had negative effects on residents and need particular attention. This study provides a quantitative and objective reference for the light pollution management in Nanjing, and also a reference for light pollution survey in other regions.

Light Emitting Diodes (LEDs) are quickly evolving as the dominant lighting solution for a wide variety of applications. With the elimination of incandescent light bulbs and the toxic limitations of fluorescent bulbs, there has been a dramatic increase in the interest in high-brightness light emitting diodes (HB-LEDs). Getting the light out of the die, with reliable color, while maintaining appropriate thermal control over a long service life is a challenge. These issues must be understood and achieved to meet the needs of unique applications, such as solidstate-lighting, automotive, signage, and medical applications. These applications have requirements for 15–25 years of operation making their reliability of critical importance. The LUXEON Rebel has been accepted as an industry leading LED product, widely used in Mean-Time-Between-Failure (MTBF) sensitive applications. Customers use various mounting platforms, such as FR4 Printed Circuit Board (PCB), FR4 PCB with thermal via's, Aluminum & Copper Metal Core printed Circuit Boards (MCPCB), Super MCPCB, etc. As in other LEDs, when mounting to a platform where a large Coefficient of Thermal Expansion (CTE) exists between the LED & the PCB, Solder fatigue could become an issue that may affect system level lifetime. In this paper we have examined extreme cases and how a solder joint can impact system level reliability. We have modeled the conditions and formed a means to predict system level reliability. We have compared the prediction modeling with empirical tests for validation of the models. It is vital to understand system level reliability factors to build lighting solutions that match the application and customer expectations. It is impractical to test LEDs and other components for 50k hours ~5 years since the device evolution is much faster than that – on average one LED generation every 12–18 month. Hence we need models and prediction methods …..

School travel has been a significant source of safety concerns for children, parents, and public authorities. It will continue to be a source of concerns as long as severe accidents continue to emerge during pupils’ commute to school. This study provides an empirical analysis of the factors influencing the injury severities of the accidents that occurred on trips to or from school in Scotland. Using 9-year data from the STATS19 public database, random parameter binary logit models with allowances for heterogeneity in the means were estimated in order to investigate injury severities in urban and rural areas. The results suggested that factors such as the road type, lighting conditions, vehicle type, and age of the driver or casualty constitute the common determinants of injury severities in both urban and rural areas. Single carriageways and vehicles running on heavy oil engines were found to induce opposite effects in urban and rural areas, whereas the involvement of a passenger car in the accident decomposed various layers of unobserved heterogeneity for both area types. The findings of this study can inform future policy interventions with a focus on traffic calming in the proximity of schools.

Based on a new approach for the prediction of the Daylight Factor (DF), using existing empirical models, this research work presents an optimization of window size and daylight provided by the glazed apertures component for a building located in a hot and dry climate. The new approach aims to improve the DF model, considering new parameters for daylight prediction such as the orientation, sky conditions, daytime, and the geographic location of the building to fill in all the missing points that the standard DF, defined for an overcast sky, presents. The enhanced DF model is considered for the optimization of window size based on Non dominated Sorting Genetic Algorithm (NSGA II), for heating and cooling season, taking into account the impact of glazing type, space reflectance and artificial lighting installation. Results of heating and cooling demand are compared to a recommended building model for hot and dry climate with 10% Window to Wall Ratio (WWR) for single glazing. The optimal building model is then validated using a dynamic convective heat transfer simulation. As a result, a reduction of 48% in energy demand and 21.5% in CO2 emissions can be achieved. The present approach provides architects and engineers with a more accurate daylight prediction model considering the effect of several parameters simultaneously. The new proposed approach, via the improved DF model, gives an optimal solution for window design to minimize building energy demand while improving the indoor comfort parameters.

Increased industrial energy efficiency (EE) has become one of the main environmental actions to mitigate carbon dioxide (CO2) emissions, contributing also to industrial competitiveness, with several implications on the production system and cost management. Unfortunately, literature is currently lacking empirical evidence on the impact of energy efficiency solutions on production. Thus, this work primarily aims at investigating the economic and production-related influence on the reduction in industrial energy consumption, considering the cross-cutting technologies HVAC, motors, lighting systems and air compressor systems. The analysis is performed using data from previous studies that characterized the main EE measures for the cross-cutting technologies. Four logistic models were built to understand how costs and production influence energy efficiency across such cross-cutting technologies. In this way, motivating industries to implement measures to reduce electrical consumption, offering an economic cost–benefit analysis and optimizing industry processes so that the reduction in electricity consumption adds to industrial energy efficiency were the aims of this study. The results of this work show through the adjusted indicators that senior management is mainly responsible for energy savings. The operational measures of each piece of equipment can be oriented in the industry towards a specific maintenance process for each technology, becoming an active procedure in industrial productions to obtain EE. Additionally, maintenance planning and control is essential to the reliability of the reduced energy consumption of cross-cutting technologies. This article concludes with managerial implications and suggestions for future research in this field.

At present, when designing a Light Emitting Diode (LED) luminaire, different strategies of development are followed depending on the size of the company. Since on LED datasheets there is only limited information provided, companies designing LED luminaires spend a lot of effort gathering the required input of LED details to be able to design reliable products. Small and medium size enterprises (SMEs) do not have the bandwidth to gather such input and solely rely on empirical approaches leading to approximated luminaire designs, while larger companies use advanced hardware and software tools to characterize parts, design versions, and finally optimize all design steps. In both cases, considerable time and money is spent on prototyping, sampling, and laboratory testing. Digitalization of the complete product development (also known as Industry 4.0 approach) at all integration levels of the solid state lighting (SSL) supply chain would provide the remedy for these pains. The Delphi4LED European project aimed at developing multi-domain compact models of LED (for a consistent, combined description of electronic, thermal, and optical properties of LEDs) as digital twins of the physical products to support virtual prototyping during the design of luminaires. This paper provides an overview of the Delphi4LED approach aimed at supporting new, completely digital workflows both for SMEs and larger companies (Majors) along with some comparison with the traditional luminaire design. Two demonstration experiments are described: One to show the achievable benefits of the approach and another one to demonstrate the ease of use and ability to be accommodated in a larger scale product design for assessing design choices like e.g., number and type of LEDs versus electrical/thermal conditions and constraints, in a tool agnostic manner.

Melatonin is fundamental to the lighting, display, and architectural industries as the primary biomarker used in circadian theory. Billions of dollars are being spent on research, product development, and marketing based on the impact of visible light on melatonin produced by the pineal gland. It has now been shown that the mitochondria produce melatonin in many cells in quantities which are orders of magnitude higher than that produced in the pineal gland. This subcellular melatonin does not necessarily fluctuate with our circadian clock or release into the circulation system, but instead has been proposed to be consumed locally in response to the free radical density within each cell, in particular in response to Near Infrared (NIR) exposure. The main point of this review hypothesizes that the subcellular melatonin is being produced in response to the NIR photons which make up the majority of natural sunlight. Given the number of cells and quantity of subcellular melatonin identified to date, it is reasonable to propose that the body produces and maintains a melatonin reservoir that is separate and apart from the circulatory melatonin generated by the pineal gland. To understand how sunlight may support or stimulate this antioxidant reservoir, it becomes necessary to quantify the free radical density in various parts of the human body. To do this, it is necessary to move away from two-dimensional empirical approaches and develop three-dimensional bio-optical models based on the underlying biological processes at play. Three-dimensional Mechanistic Bio-optical Models (MBM) of the skin, eye, and brain based on non-sequential optical ray tracing and Electron Spin Resonance (ESR) data clearly indicate that the NIR portion of natural sunlight provides the primary stimulus during the day to the majority of the cells in the human body, impacting over 60% of the cells in an adult body and 100% of the cells in the fetus and young children. It is also shown that optically, the human body, under the assumption of natural sunlight, has developed optical mechanisms to gather and localize NIR photons in the most sensitive areas of the human body: blood vessels, retina, brain, skin, and even the fetus. That assumption is no longer valid in modern societies where the majority of our time is spent exposed to visible only lighting and displays, which emit zero NIR photons. Based on an optical and biological review of the literature and the MBM results, it is proposed that the NIR portion of natural sunlight stimulates an excess of antioxidants in each of our healthy cells and that the cumulative effect of this antioxidant reservoir is to enhance the body’s ability to rapidly and locally deal with changing conditions throughout the day. In this approach the role of circulatory melatonin produced by the pineal gland is to provide an efficient method of delivering supplemental melatonin during periods of low cellular activity and solar stimulus to damaged or aging cells in both diurnal and nocturnal animals. While circulatory melatonin may be the “Hormone of Darkness”, subcellular melatonin may be the “Hormone of Daylight”.

Актуальність теми. Актуальною задачею комп’ютерної графіки являється отримання реалістичних зображень, котрі активно користуються попитом в промисловості, ігровій індустрії та кіно. Фотореалістичне зображення характеризується такими ефектами, як м’які тіні, напівтіні, каустика, динамічне розмиття, глибина різкості, нечіткі відбиття, блиск, напівпрозорість. Серед існуючих підходів фотореалістичної візуалізації методи трасування променів являються найбільш точними, оскільки вони базуються на фізичній моделі поширення світла. Існує багатий спектр різноманітних методів трасування променів, отже з’являється необхідність у вибірці найбільш ефективних точних методів трасування променів, котрі будуть в середній мірі коректно працювати для широкого ряду статичних (в майбутньому і динамічних) сцен, що проходять візуалізацію. Об’єктом дослідження є процес фізично обґрунтованого рендерингу і процес трасування променів. Предметом дослідження є способи трасування променів та методи розрахунку індексу передачі кольору. Мета роботи: дослідження методів PBR (Physical Based Rendering), їх одночасного використання для отримання максимального ефекту реалізму; оцінка здатності джерела світла виявляти всі частоти його кольорового спектру у порівнянні з контрольним світлом. Наукова новизна, а точніше – інноваційне рішення полягає в тому, що розроблений рушій реалізує обчислення індексу передачі кольору (CRI - Color Rendering Index) з високим рівнем точності відносно очікуваних значень контрольних джерел світла. Практична цінність проведених досліджень полягає у розробці нового PBRE, який для рендерингу сцен використовує емпіричні моделі освітлення; реалізовані такі моделі BRDF, як Ламберта, Орена Найара, Торренса Спарроу, дзеркального відбиття, дзеркального пропускання і виміряного BRDF. Реалізована підтримка декількох технік трасування променів: трасування Уайтеда і трасування шляху. Розраховуються кольори з використанням спектральних даних і колірний простір CIE XYZ в сценах PBR для досягнення високої передачі кольору. TTFD також підтримує обчислення індексу передачі кольору (CRI – Color Rendering Index). Цей показник описує здатність джерела світла точно відображати всі частоти його колірного спектра в порівнянні з ідеальним еталонним світлом аналогічного типу. Структура та обсяг роботи. Магістерський дипломний проект складається зі вступу, чотирьох розділів та висновків. У вступі подано загальну характеристику роботи, зроблено оцінку сучасного стану проблеми, обґрунтовано актуальність напрямку досліджень, сформульовано мету і задачі досліджень, показано наукову новизну отриманих результатів і практичну цінність роботи. У першому розділі розглянуто принципи колориметрії та радіометрії. Вони складають основу деяких основних ключових особливостей TTFD. Зокрема, розрахунок кольору і методи освітлення / затінення, реалізовані в TTFD, використовують поняття, представлені даному розділі. У другому розділі розглянуто трасування променів: фотореалістичний рендеринг (візуалізація). Коротка класифікація алгоритмів трасування променів. Вирішення рівняння рендеринга. У третьому розділі наведено особливості реалізації розробленої системи. У четвертому розділі представлено підходи до тестування системи в цілому та окремих модулів. У висновках представлені результати проведеної роботи. Робота представлена на 116 аркушах, містить посилання на список використаних літературних джерел. Ключові слова: фізичний рендеринг (PBR), трасування променів, індекс передачі кольору, емпіричні моделі освітлення, модель Уайтеда, трасування шляху.
Relevance of the topic. The actual task of computer graphics is to obtain realistic images that are actively in demand in industry, gaming and film industry. A photorealistic image is characterized by such effects as soft shadows, partial shade, caustic, dynamic blur, depth of field, fuzzy reflection, shine, translucency. Among the existing approaches of photorealistic visualization, ray tracing methods are the most accurate because they are based on a physical model of light propagation. There is a wide range of different ray-tracing methods, and therefore there is a need to select the most efficient, accurate ray-tracing methods that will, in average, work correctly for a wide range of static (future dynamic) scenes, and are being visualized. The object of the research is the process of physically sound rendering and the ray tracing process. The subject of research is the methods of ray tracing and methods for calculating the color rendering index. Objective: to study the methods of PBR (Physical Based Rendering), their simultaneous use to obtain the maximum effect of realism; assessment of the ability of a light source to detect all the frequencies of its color spectrum compared to the control light. The scientific novelty, or rather, an innovative solution, is that the engine developed implements the calculations of the color rendering index (CRI - Color Rendering Index) with a high degree of accuracy relative to the expected values of the control light sources. The practical value of the research is the development of a new PBRE, which employs empirical lighting models for rendering scenes; BRDF models such as Lambert, Oren Nayar, Torrens Sparrow, specular reflection, specular transmission and measured BRDF are implemented. Implemented support for several ray tracing techniques: Traced by Wyted and path tracing. Colors are calculated using spectral data and CIE XYZ color space in PBR scenes to achieve high color rendering. TTFD also supports Color Rendering Index (CRI) calculations. This indicator describes the ability of a light source to accurately reflect all the frequencies of its color spectrum compared to ideal reference light of a similar type. Structure and scope of work. Master thesis project consists of introduction, four chapters and conclusions. The introduction presents a general description of the work, assesses the current state of the problem, substantiates the relevance of the research area, formulates the goals and objectives of the research, shows the scientific novelty of the results and practical value of the work. The first section discusses the principles of colorimetry and radiometry. They form the basis of some key TTFD key features. In particular, color calculations and lighting / shading methods implemented in TTFD use the concept presented in this section. The second section deals with ray tracing: photorealistic rendering (visualization). Brief classification of ray tracing algorithms. Solution of the rendering equation. The third section presents the features of the implementation of the developed system. The fourth section presents approaches to testing the system as a whole and individual modules. The findings present the results of this work. The work is presented on 116 pages, contains links to the list of references used.
Актуальность темы. Актуальной задачей компьютерной графики является получение реалистичных изображений, которые активно пользуются спросом в промышленности, игровой индустрии и кино. Фотореалистичное изображение характеризуется такими эффектами, как мягкие тени, полутени, каустика, динамическое размытие, глубина резкости, нечеткие отражение, блеск, полупрозрачность. Среди существующих подходов фотореалистичной визуализации методы трассировки лучей являются наиболее точными, поскольку они базируются на физической модели распространения света. Существует богатый спектр различных методов трассировки лучей, следовательно появляется необходимость в выборке наиболее эффективных точных методов трассировки лучей, которые будут в средней степени правильно работать для широкого ряда статических (в будущем и динамических) сцен, проходят визуализацию. Объектом исследования является процесс физически обоснованного рендеринга и процесс трассировки лучей. Предметом исследования являются способы трассировки лучей и методы расчета индекса цветопередачи. Цель работы: исследование методов PBR (Physical Based Rendering), их одновременного использования для получения максимального эффекта реализма; оценка способности источника света выявлять все частоты его цветового спектра по сравнению с контрольным светом. Научная новизна, а точнее - инновационное решение, заключается в том, что разработан двигатель реализует вычисления индекса цветопередачи (CRI - Color Rendering Index) с высокой степенью точности относительно ожидаемых значений контрольных источников света. Практическая ценность проведенных исследований состоит в разработке нового PBRE, который для рендеринга сцен использует эмпирические модели освещения; реализованы такие модели BRDF, как Ламберта, Орена Найара, Торренса Спарроу, зеркального отражения, зеркального пропускания и измеренного BRDF. Реализована поддержка нескольких техник трассировки лучей: трассировки Уайтеда и трассировки пути. Рассчитываются цвета с использованием спектральных данных и цветовое пространство CIE XYZ в сценах PBR для достижения высокой цветопередачи. TTFD также поддерживает вычисления индекса цветопередачи (CRI - Color Rendering Index). Этот показатель описывает способность источника света точно отражать все частоты его цветового спектра по сравнению с идеальным эталонным светом аналогичного типа. Структура и объем работы. Магистерский дипломный проект состоит из введения, четырех глав и выводов. Во введении представлена общая характеристика работы, произведена оценка современного состояния проблемы, обоснована актуальность направления исследований, сформулированы цели и задачи исследований, показано научную новизну полученных результатов и практическую ценность работы. В первом разделе рассмотрены принципы колориметрии и радиометрии. Они составляют основу некоторых основных ключевых особенностей TTFD. В частности, расчет цвета и методы освещения / затенения, реализованные в TTFD, используют понятие, представленные данном разделе. Во втором разделе рассмотрены трассировки лучей: фотореалистичный рендеринг (визуализация). Краткая классификация алгоритмов трассировки лучей. Решение уравнения рендеринга. В третьем разделе приведены особенности реализации разработанной системы. В четвертом разделе представлены подходы к тестированию системы в целом и отдельных модулей. В выводах представлены результаты проведенной работы. Работа представлена на 116 листах, содержит ссылки на список использованных литературных источников.

Biologists study on the biological behavior of various marine creatures in situ using underwater observation systems. However, darkness in an underwater environment is always one of the most difficult problems to overcome in order to clearly monitor the life of underwater creatures. In this research, a light-following scheme is proposed with the lighting device installed on a separate Pan/Tilt platform as a slave while the main Pan/Tilt camera platform works as a master. A dynamic model of Pan/Tilt platform was developed using the Lagrange’s equation. In order to achieve high speed manipulation of the Pan/Tilt platforms in underwater environment, hydrodynamic forces have to be considered. Scientists had done a great deal of researches on the hydrodynamic forces of underwater motion bodies. Most of the researches employed the semi-empirical equation based on the experimental study. The coefficients (Cd Cm) of drag and added-mass which were solved by experimental study were the research point of hydrodynamic modeling in previous researches. However, these modeling methods can be employed for the underwater bodies with the simple geometry dimension. Two hydrodynamic torque models which represent the degree of freedoms (DOFs) of panning and tilting respectively had been developed employing CFD software. The selection of turbulence models, i.e., K-E, K-W, SST, RSM and LES, was firstly accomplished using the case of turbulence flow over flat plane. The hydrodynamic torque models are obtained with the simulations results for a certain range of position and velocity values for each of DOFs. The maximum velocity for simulation was set at 60 rpm for each axis. The geometry model which represents the space relationship between the master (camera) and slave (light) and the control algorithms would be elaborated in a separate paper.

Abstract As part of the quality assurance process in industrial production, employees make hundreds of decisions every day based on their experience and the given inspection specifications. The detection of quality deviations currently depends on the individual competence of the persons involved in the production process. With the automatic recognition of textured surfaces in camera images, valuable information can be given to support these persons in their decisions. For the design of augmented reality systems, the cognitive decision-making processes are first described in a model-based way and the requirements for design of the decision-making process are defined. The different lighting environments in the industrial process represent one of the important requirements of the augmented reality system, to function independently of the lighting. The good perceptibility of the information is the basic requirement for the recognition of contents. When implementing an augmented reality system, it is problematic to consider the different illuminance levels in a room. Depending on the task at hand, usually, the light at a machine is weaker and brighter in the quality control area. It is important that user-centered implementation is observed. Manual intervention by the end user in the augmented reality system is necessary to compensate for differences in brightness. This paper examines different lighting environments and the degree to which the user can clearly see content. An empirical evaluation is conducted to examine the clarity of content in AR. The aim is to find out how the difference in contrast at different lighting situations influences the differences in brightness of colors. The colors are chosen to display content but also to emphasize content. As a result, a usage recommendation can be made for grey values as well as for different color values. The consequence of this investigation is then used for the further development of sample solutions for the design of an augmented reality system. The focus lies on the user-centered development process and thus the integration of user requirements into the technical implementation should be ensured. The perceptibility of the information in an augmented reality system should not only play a role technically, but also physically. The perception of information is omnipresent, so one can perceive our environment. With the help of the study, a natural and easy perception of information should take place, which supports the recognition of important information in the everyday working environment.