Rectangular Room Research Articles

Evaluation and Design of Natural Ventilation for Houses in Thailand*

This research paper presents guidelines for evaluation and design of natural ventilation forsuburban houses in Thailand which is a part of building energy code development for residential buildings.The initial studies find that it is possible for natural ventilation to achieve thermal comfort conditions inplace of mechanical air-conditioning systems, especially in winter. The experimental research is dividedinto two parts: environmental arrangement and building opening. By measuring air conditions flowingthrough different generic types of environment, it is found that the best environment is that coveredwith large trees. Computational fluid dynamics studies on generic houses discover that cross ventilationis more effective than two-side ventilation, and is much more effective than one-side ventilation. Ingeneral, increasing the size of openings improves the effectiveness of natural ventilation. However, theoptimum effective opening area in rectangular rooms is found to be 20 percent of functional floor area.The findings from this research lead to the house evaluation method by factors of orientation and sizeof building openings. The method is successfully tested with different types of houses.

Predicting Airflow in Naturally-ventilated Generic Houses

This article reports the results of continuing research into the impact of the opening orientation andopening size on the natural ventilation of generic detached houses. The CFD simulation of 72 ventilation casesis generalized from actual houses surveyed in the suburban areas of Bangkok. It is discovered that largeropening in general allows higher indoor air velocities than smaller opening. In most cases, the Venturi effectproves to be efficient in terms of indoor air velocities up to approximately 1:1.5 proportion of inlet to outletopening area. In terms of air distribution, it is found that the opening size and the ratio of inlet to outlet openingarea do not have much impact on the uniformity in small square rooms. In large rectangular rooms, the Venturieffect improves the uniformity in two- and three-sided ventilation cases. In cross ventilation cases, however, theuniformity depends on the opening size. The results lead to the prediction of airflow and comfort which isdemonstrated by an example of application on an actual building.

Modeling of Path Arrival Rate for In-Room Radio Channels With Directive Antennas

We analyze the path arrival rate for an inroom radio channel with directive antennas. The impulse response of this channel exhibits a transition from early separate components followed by a diffuse reverberation tail. Under the assumption that the transmitter's (or receiver's) position and orientation are picked uniformly at random we derive an exact expression of the mean arrival rate for a rectangular room predicted by the mirror source theory. The rate is quadratic in delay, inversely proportional to the room volume, and proportional to the product of beam coverage fractions of the transmitter and receiver antennas. Making use of the exact formula, we characterize the onset of the diffuse tail by defining a "mixing time" as the point in time where the arrival rate exceeds one component per transmit pulse duration. We also give an approximation for the power-delay spectrum. It turns out that the power-delay spectrum is unaffected by the antenna directivity. However, Monte Carlo simulations show that antenna directivity does indeed play an important role for the distribution of instantaneous mean delay and rms delay spread

Room and window geometry influence for daylight harvesting maximization – Effects on energy savings in an academic classroom

Lighting systems have a fundamental role for the overall buildings energy consumption. Therefore, remarkable efforts are required for optimizing the lighting systems energy use and for finding new daylight harvesting solutions. In this paper, the impacts on daylight harvesting provided by different room and window geometries and their effects on energy savings are presented. An academic classroom with only one window is chosen as case study and it is supposed that the window orientation is modified according to the four cardinal points. A climate-based approach was chosen for the multiple simulations, carried out via DIVA software, by assuming: square and rectangular classroom geometries with the same total area; square and rectangular window shapes having Window to Floor Ratios (WFRs) equal to 8% and 12%; two different dimmable lighting systems, in order to quantify the energy savings, by considering fluorescent and LED dimmable lamps. The daylight analysis, performed by evaluating both the Daylight Factor (DF) and the Daylight Autonomy (DA), showed that room and window geometries have high influence on daylight harvesting maximization, allowing remarkable energy savings (up to 48.5%) with respect to non-dimmable lighting system. In particular, the best energy result, equal to 467.5 kWh/yr, was obtained with rectangular room and window geometries coupled with LED lamps and WFR equal to 12%.

Study of the Effect of Splaying Wall to Modify Acoustic Modes Distribution in Small Room

Modes are known as ones of the important acoustical issues in small room. These phenomena could drastically change the spectral and temporal characteristic of sound. Studies have been done in optimizing rectangular room dimension, optimizing source and listener position, and optimizing low frequency with acoustic panel. To follow the best room ratio, a built room has to be cut a lot. This paper is studied the effect of splaying wall in attempt to shift the modes without trimming too much space. Axial room modes from different room ratios – including random, splay wall, Bolt, Louden, Cox – were calculated and compared. Low frequency characteristic of small rooms were observed aided by FEM simulation so that SPL result could be graph and statistically analyzed. It was found that splaying some walls from the random room dimension could distribute the modes evenly, similar with Cox’, though the SPL standard deviation was raised. Further research will be continued through psychoacoustic evaluation.

The difficulties of simulating the acoustics of an empty rectangular room with an absorbing ceiling

In this study, simulations of a scale model of an unfurnished rectangular room with an absorbing ceiling using an energy-based geometrical acoustic model and a phased geometrical acoustic model are compared to measurements. This room can represent a typical classroom or office. This comparison concluded that the phased model can capture more details of the sound field, particularly at low frequencies. For accurate predictions, precise surface descriptions are needed for the phased GA method, which are not always available. The main drawback of the phased model is a longer calculation time.

Exact Line-of-Sight Probability for Channel Modeling in Typical Indoor Environments

The probability of line-of-sight (LOS) propagation is crucial for channel modeling and small-cell network evaluation. In this letter, by taking the layout of building structures into account, an analytical LOS probability model is proposed for typical indoor scenarios, which have rectangular rooms and corridors. The proposed model is validated through Monte Carlo simulations. Numerical results show that the proposed model estimates the network performance accurately and efficiently.

Radiation protection measures: Implications on the design of neurosurgery operating rooms

ObjectiveTo describe pros and cons of some radiation protection measures and the implications on the design of a neurosurgery operating room. Material and methodsConcurring with the acquisition and use of an O-arm device, a structural remodelling of our neurosurgery operating room was carried out. The theatre was enlarged, the shielding was reinforced and a foldable leaded screen was installed inside the operating room. Radiation doses were measured in front of and behind the screen. ResultsThe screen provides whole-body radiation protection for all the personnel inside the theatre (effective dose <5μSv at 2.5m from the gantry per O-arm exploration; 0.0μSv received behind the screen per O-arm exploration; and undetectable cumulative annual radiation dose behind the screen), obviates the need for leaded aprons and personal dosimeters, and minimises the circulation of personnel. Enlarging the size of the operating room allows storing the equipment inside and minimises the risk of collision and contamination. Rectangular rooms provide greater distance from the source of radiation. ConclusionFloor, ceiling and walls shielding, a rectangular-shaped and large enough theatre, the presence of a foldable leaded screen, and the security systems precluding an unexpected irruption into the operating room during irradiation are relevant issues to consider when designing a neurosurgery operating theatre.

Stochastic Dosimetry Based on Low Rank Tensor Approximations for the Assessment of Children Exposure to WLAN Source

In this study, the exposure of a female eight-year old child to a WLAN access point located in an unknown position in a realistic indoor environment was investigated. A stochastic dosimetry approach based on low rank tensor approximation was used to develop surrogate models to quickly estimate the specific absorption rate in all the possible positions of the WLAN source and the child. Results showed that, for all the possible positions in the room, the exposure values were significantly below the limits of the International Commission of Non-Ionizing Radiation Protection guidelines for general public exposure. The variation of the positions of the source and the child greatly influenced the exposure, resulting in quartile coefficient of dispersion values always higher than 65%. The WLAN source positions, among all the possible ones, that minimize the exposure of the child staying in the rectangular room were found to be on the sides of the smaller wall of the room.

Effects of absorption placement on sound field of a rectangular room: A statistical approach

Room resonances create dramatic fluctuations in the distribution of sound pressure throughout the listening region of a room. Previous studies indicate that the addition of sound absorbing material decreases room resonances and shifts its modal characteristics. The present study proposes an approach which qualifies the effects that the additional absorption in a listening room may have on the sound fields and the frequency responses. Finite element analysis was employed for modelling the low-frequency responses of a room. The study analyses frequency responses at various listening positions involving different amounts and different placement of sound absorbents on room surfaces by observing standard deviation for linearity across a chosen frequency range. Two-dimensional sound field plots at listening height were also used to examine the spatial changes of room resonances caused by the additional absorption. The present study applied a modified statistical approach to evaluate both the sound field and the frequency responses of a room. The results were then applied to re-evaluate the effects of the absorbers location on the listening region through the proposed approach.

HR LOD based HBIM to detect influences on geometry and shape by stereotomic construction techniques of brick vaults

The use of construction techniques in cloister vaults in noble buildings, as covering elements for square or rectangular rooms, is widespread across Europe. The geometric continuity at the intrados makes generally possible the execution all over the span of frescoes, stucco and decorations, with a great diffusion of a great variety of solutions. The construction of brick vaults, from the late Middle Age, was sped up by limiting the centring to the wooden planks arches that were instrumental in the profile determination. Starting from laser scanning, photogrammetric and thermographic techniques, the punctual reconstruction of the geometry and construction techniques allowed to recognise and understand the constructive richness, the multiplicity and unicity of each vaulted element, made of recurrent elements and specific features, thus sketching a mixed pattern of workers and highlighting the constructive knowledge of ‘stereotomy’ applied to the brick block vaults. Nowadays, the availability of several BIM-based modelling procedures and tools based on high detailed surveys allows to identify and reconstruct the shape, drawing reliable assumptions about the construction methods and the execution time. The research methodology here proposed intends to tackle an updatable geographic catalogue, able to transfer the construction richness, inheriting the historic lesson of French ‘repertoires’ to generate modern HBIM vault libraries (abaci). The paper focuses on a well-documented case, the Magio Grasselli palace in Cremona in which the cloister vaults of two main rooms, and others, show different construction systems embodied by the geometry. The methodology has shown how the cloister vault typology can be turned to a dome construction in the same vault, and how ‘stereotomy’, the capacity of skilled workers to control the space, modified the typical geometry, made by the ‘generative’ construction process used for the cloister vault (intended as the intersection of 2 barrel vaults), turning it into a dome in the upper part, giving back a sort of morphing, merging the two different generative rules (dome and vault) as described hereafter and creating unexpected scenic effect.

An Agent-based Pedestrian Evacuation Modeling from a Rectangular Room Using Cellular Automata and Fuzzy Inference System

An Agent-based Pedestrian Evacuation Modeling from a Rectangular Room Using Cellular Automata and Fuzzy Inference System

A Novel Method for Determining Optimum Dimension Ratios for Small Rectangular Rooms

A new method for determining optimum dimension ratios for small rectangular rooms has been presented. In a theoretical model, an exact description of the room impulse response was used. Based on the impulse response, a frequency response of a room was calculated to find changes in the sound pressure level over the frequency range 20–200 Hz. These changes depend on the source and receiver positions, thus, a new metric equivalent to an average frequency response was introduced to quantify the overall sound pressure variation within the room for a selected source position. A numerical procedure was employed to seek a minimum value of the deviation of the sound pressure level response from a smooth fitted response determined by the quadratic polynomial regression. The most smooth frequency responses were obtained when the source was located at one of the eight corners of a room. Thus, to find the best possible dimension ratios, in the numerical procedure the optimal source position was assumed. Calculation results have shown that optimum dimension ratios depend on the room volume and the sound damping inside a room, and for small and medium volumes these ratios are roughly 1 : 1.48 : 2.12, 1 : 1.4 : 1.89 and 1 : 1.2 : 1.45. When the room volume was suitably large, the ratio 1 : 1.2 : 1.44 was found to be the best one.

Statistical Modeling, Simulation, and Experimental Verification of Wideband Indoor Mobile Radio Channels

This paper focuses on the modeling, simulation, and experimental verification of wideband single‐input single‐output (SISO) mobile fading channels for indoor propagation environments. The indoor reference channel model is derived from a geometrical rectangle scattering model, which consists of an infinite number of scatterers. It is assumed that the scatterers are exponentially distributed over the two‐dimensional (2D) horizontal plane of a rectangular room. Analytical expressions are derived for the probability density function (PDF) of the angle of arrival (AOA), the PDF of the propagation path length, the power delay profile (PDP), and the frequency correlation function (FCF). An efficient sum‐of‐cisoids (SOC) channel simulator is derived from the nonrealizable reference model by employing the SOC principle. It is shown that the SOC channel simulator approximates closely the reference model with respect to the FCF. The SOC channel simulator enables the performance evaluation of wideband indoor wireless communication systems with reduced realization expenditure. Moreover, the rationality and usefulness of the derived indoor channel model is confirmed by various measurements at 2.4, 5, and 60 GHz.

Sex differences and the effect of instruction on reorientation abilities by humans.

This study examined whether differences in the amount of information provided to men and women, in the form of verbal instruction, influenced their encoding during a reorientation task. When a navigator needs to orient, featural (e.g., colour or texture) and geometry (e.g., metric information) are used to determine which direction to begin traveling. The current study used a spatial reorientation task to examine how men and women use featural and geometric cues and whether the content of the task's instructions influenced how these cues were used. Participants were trained to find a target location in a rectangular room with distinctive objects situated at each corner. Once the participants were accurately locating the target, various tests manipulating the spatial information were conducted. We found both men and women encoded the featural cues, and even though the features provided reliable information, participants generally showed an encoding of geometry. However, when participants were not provided with any information about the spatial aspects of the task in the instructions, they failed to encode geometry. We also found that women used distant featural cues as landmarks when the featural cue closest to the target was removed, whereas men did not. Yet, when the two types of cues were placed in conflict, both sexes weighed featural cues more heavily than geometric cues. The content of the task instructions also influenced how cues were relied upon in this conflict situation. Our results have important implications for our understanding of how spatial cues are used for reorientation.

Orientation in Virtual Reality Does Not Fully Measure Up to the Real-World

Adult participants learned to reorient to a specific corner inside either a real or virtual rectangular room containing a distinct featural object in each corner. Participants in the virtual-reality (VR) condition experienced an immersive virtual version of the physical room using a head-mounted display (HMD) and customized manual wheelchair to provide self-movement. Following a disorientation procedure, people could reorient by using either the geometry of the room and/or the distinct features in the corners. Test trials in which the different spatial cues were manipulated revealed participants encoded features and geometry in both the real and VR rooms. However, participants in the VR room showed less facility with using geometry. Our results suggest caution must be taken when interpreting the nuances of spatial cue use in virtual environments. Reduced reliability of geometric cues in VR environments may result in greater reliance on feature cues than would normally be expected under similar real-world conditions.

Intrinsic rectification in common-gated graphene field-effect transistors

Terahertz rectifying antennas (rectennas) couple micron-size antennas and high-speed diodes to convert the incident electro-magnetic radiation to useable DC power. At such frequencies, the device acting as the diode requires both a nonlinear electrical behavior and a very low parasitic capacitance. Due to their low-capacitance planar structure and high carrier mobility values, several graphene devices based on various rectification mechanisms have been previously proposed as the rectifying device in the terahertz range. In this paper, we report an asymmetric behavior in micrometer-scale rectangular CVD-grown graphene field-effect transistors (GFETs), both at 77K and room temperature (295K). The asymmetry with a measured ION/IOFF ratio as high as 1.85 is shown to originate from the slight change in graphene conductivity induced by drain-gate voltage variations. This is confirmed by simulations using a simple drift-diffusion transport model. The conclusions can be directly applied to optimize diode-connected GFETs. This nonlinear effect may also be of interest for graphene interconnect considerations as well as circuit designs using GFETs.

Theoretical model of reverberation decay in a rectangular room—Potential for predicting flutter echo

Reverberation is the most important factor governing the acoustic design of a room. It is known that non-exponential reverberation decay may occur in a room with unevenly distributed sound absorption, namely, with non-diffuse sound field. We propose the theoretical model of reverberation decay in non-diffuse sound fields. The reverberation decay is characterized by absorption and scattering properties of the surfaces of a room. As a first step for developing reverberation theory of non-diffuse sound field, the proposed model deals with rectangular rooms, because rectangular rooms are very common in any kind of buildings and architecture. Spatial absorption coefficients for three orthogonal directions are defined as the parameters which characterize the energy decay curve in the rectangular room. Within this model, the reverberation in such rectangular room becomes a combination of exponential and power law decay. The power law dependence as a function of time has a singularity. This issue is resolved within the model. The model was verified by comparison with the results of computer simulation using sound ray tracing method. Theoretical solutions of the proposed model agree well with the results of the computer simulation. Potential for predicting flutter echo by this model is also discussed.

Experimental characterization of the Green’s function in a room using sparse reconstruction principles

Measuring the Green’s function over the entire volume of a room would typically require an unfeasible number of measurements, due to requirements on spatial sampling. To alleviate the need for excessive measurements, sparse reconstruction methods can be employed, as they make it possible to reconstruct a seemingly undersampled signal. The present study proposes a method for acquiring experimentally the Green’s function in a room by measuring directly the mode shapes of the room, based on the conception that any mode can be expanded into a number of propagating waves. If the modes are described in the wavenumber domain (as a plane-wave expansion), sparse reconstruction methods can be employed, under the implicit assumption that each mode shape is represented as the superposition of a small number of plane waves. In addition, it is assumed that the medium is source-free and homogeneous. The methodology is examined numerically and verified experimentally, based on measurements in a lightly damped rectangular room.

Where you are affects what you can easily imagine: Environmental geometry elicits sensorimotor interference in remote perspective taking

Imagined perspective switches are notoriously difficult, a fact often ascribed to sensorimotor interference between one’s to-be-imagined versus actual orientation. Here, we demonstrate similar interference effects, even if participants know they are in a remote environment with unknown spatial relation to the learning environment. Participants learned 15 target objects irregularly arranged in an office from one orientation (0°, 120°, or 240°). Participants were blindfolded and disoriented before being wheeled to a test room of similar geometry (exp.1) or different geometry (exp.2). Participants were seated facing 0, 120°, or 240°, and asked to perform judgments of relative direction (JRD, e.g., imagine facing “pen”, point to “phone”). JRD performance was improved when participants’ to-be-imagined orientation in the learning room was aligned with their physical orientation in the current (test) room. Conversely, misalignment led to sensorimotor interference. These concurrent reference frame facilitation/interference effects were further enhanced when the current and to-be-imagined environments were more similar. Whereas sensorimotor alignment improved absolute and relative pointing accuracy, sensorimotor misalignment predominately increased response times, supposedly due to increased cognitive demands. These sensorimotor facilitation/interference effects were sustained and could not be sufficiently explained by initial retrieval and transformation costs. We propose that facilitation/interference effects occurred between concurrent egocentric representations of the learning and test environment in working memory. Results suggest that merely being in a rectangular room might be sufficient to automatically re-anchor one’s representation and thus produce orientation-specific interference. This should be considered when designing perspective-taking experiments to avoid unintended biases and concurrent reference frame alignment effects.