Post-tensioned concrete structures have been gaining in popularity over the past few decades. When properly designed, such structures allow for longer span lengths, reduced cracking, and less reinforcement than reinfo...
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Sustainable design and constructability are two keys for efficient design and construction that are often addressed separately from each other in projects. This paper examines the integration of these two initiatives ...
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ISBN:
(纸本)0784406715
Sustainable design and constructability are two keys for efficient design and construction that are often addressed separately from each other in projects. This paper examines the integration of these two initiatives on the Pentagon renovation. The examination exposes a synergistic relationship between sustainable design and constructability. This relationship strives to efficiently utilize resources and reduce waste in the project. The integrated organizational structure and design-build performance based contracting strategies at the Pentagon have assisted in the implementation of sustainable design and constructability. Connections between the two initiatives were found at the conceptual level, system level, materials level and in the design implementation process. Importantly, the analysis of the Pentagon reveals that the potential to improve the sustainability and the constructability of a project is enhanced when the two initiatives are integrated and approached in a combined fashion.
The goal of this research is to examine human response to background noise, and relate results to indoor noise criteria. In an initial study by the authors, subjects completed perception surveys, typing tasks, and pro...
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ISBN:
(纸本)9781622762712
The goal of this research is to examine human response to background noise, and relate results to indoor noise criteria. In an initial study by the authors, subjects completed perception surveys, typing tasks, and proofreading tasks under typical heating, ventilating, and air-conditioning (HVAC) noise conditions. Results were correlated with commonly used indoor noise criteria systems including Noise Criteria (NC), Room Criteria (RC) and others. The findings suggested that the types of tasks used and the length of exposure can impact the results. To examine these two issues, the authors conducted a second study in which each test subject completed 38 total hours of testing over multiple days. Subjects were exposed to several background noise exposures over 20, 40, 80, and 240 minute trials. During the trials, subjects completed a variety of performance tasks and answered questions about their perception of the noise, the thermal environment, and various other factors. Findings from this study are being used to determine optimum testing conditions for on-going research examining the effects of tonal or fluctuating background noise on performance, annoyance, and spectral perception. Results are being used to evaluate the effectiveness of commonly used indoor noise criteria systems.
This experimental study investigated the use of active flows and passive materials for the removal of gaseous pollutants indoors. In this study, a commercial electromagnetic synthetic jet actuator (SJA) was characteri...
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The proposed ASHRAE Standard 152P, "Method of Test for Determining the Design and Seasonal Efficiencies of Residential Thermal Distribution Systems" (ASHRAE 2002), has recently completed its second public re...
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The proposed ASHRAE Standard 152P, "Method of Test for Determining the Design and Seasonal Efficiencies of Residential Thermal Distribution Systems" (ASHRAE 2002), has recently completed its second public review. As part of the standard development process, this study compares the forced air distribution system ratings to measured field results. Fifty-eight field tests were performed on cooling systems in eleven homes in the summers of 1998 and 1999. Seven of these houses had standard attics with insulation on the attic floor and a well-vented attic space. The other four houses had unvented attics where the insulation is placed directly under the roof deck, and the attic space is not deliberately vented. Each house was tested under a range of summer weather conditions at each particular site and, in some cases, the amount of duct leakage was intentionally varied. The comparison between predicted efficiencies and the measured results includes evaluation of the effects of weather;duct location, thermal conditions, duct leakage, and system capacity. The results showed that the difference between measured results and those calculated using proposed Standard 152P is about 5 percentage points on average if weather data, duct leakage, and air handler flow are well known. However, the accuracy of the standard is strongly dependent on having good measurements of duct leakage and system airflow. Given that the uncertainty in the measured results is typically also about 5 percentage points, the Standard 152P results are acceptably close to the measured data.
Particles in indoor environments may deposit on the surfaces of heat exchangers that are used in heating, ventilation and air conditioning (HVAC) systems. Such deposits can lead to performance degradation and indoor a...
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This study aims to analyze the effects of indoor environmental quality (IEQ) factors with simultaneous changes in illuminance and noise levels on building occupants’ physiological response and work performance. To th...
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The ability to retrieve accurate information from databases without an extensive knowledge of the contents and organization of each database is extremely beneficial to the dissemination and utilization of freight data...
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Spectrum estimation is a problem common to many fields of physics, science, and engineering, and it has thus received a great deal of attention from the Bayesian data analysis community. In room acoustics, the modal o...
Spectrum estimation is a problem common to many fields of physics, science, and engineering, and it has thus received a great deal of attention from the Bayesian data analysis community. In room acoustics, the modal or frequency response of a room is important for diagnosing and remedying acoustical defects. The physics of a sound field in a room dictates a model comprised of exponentially decaying sinusoids. Continuing in the tradition of the seminal work of Bretthorst and Jaynes, this work contributes an approach to analyzing the modal responses of rooms with a time-domain model. Room acoustic spectra are constructed of damped sinusoids, and the modelbased approach allows estimation of the number of sinusoids in the signal as well as their frequencies, amplitudes, damping constants, and phase delays. The frequency-amplitude spectrum may be most useful for characterizing a room, but in some settings the damping constants are of primary interest. This is the case for measuring the absorptive properties of materials, for example. A further challenge of the room acoustic spectrum problem is that modal density increases quadratically with frequency. At a point called the Schroeder frequency, adjacent modes overlap enough that the spectrum - particularly when estimated with the discrete Fourier transform - can be treated as a continuum. The time-domain, model-based approach can resolve overlapping modes and in some cases be used to estimate the Schroeder frequency. The proposed approach addresses the issue of filtering and preprocessing in order for the sampling to accurately identify all present room modes with their quadratically increasing density.
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