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Lighting Fact Sheets
Published in John L. Fetters, The Handbook of Lighting Surveys & Audits, 2018
Visual comfort probability (VCP) is a rating of lighting systems that is expressed as a percentage of people who, when viewing from a specified location and in a specified direction, will find the lighting system acceptable in terms of discomfort glare. The IESNA minimum recommendation for office interiors is 70, and the recommendation for computer applications is 80.
V
Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
visual perception instrument resources with analysis and display of the data collected. virtual machine a process on a multitasking computer that behaves as if it were a stand-alone computer and not part of a larger system. virtual memory main memory as seen by the processor, i.e., as defined by the processorgenerated addresses, in contrast with real memory, which is the memory actually installed or that is immediately addressable. The virtual memory corresponds to the secondary storage, and data is automatically transferred to and from real memory as needed. In paged virtual memory, secondary memory is divided into fixed-size pages that are automatically moved to and from page frames of real memory; the division is not logical and is usually invisible to the programmer. In segmentation, the divisions (known as segments) are logical and of variablesized units that are much larger than pages: 16-24 KB versus 0.5-4 KB. Many machines combine both paging and segmentation. Since secondary memory is much larger than main memory, virtual memory presents the programmer with the view of a main memory that appears to be larger than it actually is. Virtual memory also facilitates automatic transfer of data, protection, accommodation of growing structures, efficient management of main-memory, and longterm storage. virtual memory interrupt interrupt that occurs when an attempt is made to access an item of virtual memory that is not loaded into main memory. virtual page number in a paged virtual memory system, this is the part of the memory addresses that points to the page that is accessed, while the rest of the address points to a particular part of that page. virtual path a concept used to describe the unidirectional transport of virtual channels that are associated by a common identifier value. virtual reality three or more dimensionality of computer-generated images, which gives the user a sense of presence (i.e., a first-person experience) in the scene. virtual register one of a bank of registers used as general purpose registers to hold the results of speculative instruction execution until instruction completion. Virtual registers are used to prevent conflicts between instructions that would normally use the same registers. See also speculative execution. virtually addressed cache a cache memory in which the placement of data is determined by virtual addresses rather than physical addresses. This scheme has the advantage of decreasing memory access times by avoiding virtual address translation for most accesses. The disadvantage is that data stored in the cache may have different virtual addresses in different processes (aliasing). visible associated with the wavelength region that can be seen by the human eye; often considered to range from about 400 to 700 nanometers. visible light electromagnetic radiation in the visible portion of the spectrum, roughly 400 to 700 nanometers. visual comfort probability (VCP) this rating is based in terms of the percentage of people who will be expected to find the given lighting system acceptable when they are seated in most undesirable locations. visual display unit a common means of input/ouput to/from a computer. Consists of a CRT and a keyboard. visual perception the perception of a scene as observed by the human visual system: it may
Modelling the Probability of Discomfort Due to Glare at All Levels: The Case of Outdoor Lighting
Published in LEUKOS, 2023
Joffrey Girard, Céline Villa, Roland Brémond
Instead of predicting a mean level of discomfort, some authors have a probabilistic approach. The Visual Comfort Probability (VCP) proposed by Guth (1963) estimates the percentage of people feeling that the discomfort glare is acceptable, that is, with a discomfort below the BCD threshold. Guth used a formula obtained at the BCD, and proposed a nomogram computed from the dataset of the participants’ responses, which gives the percentage of people who are above the BCD as a function of G.