117,951 research outputs found
An investigation of fall protection systems in the roofing industry
No full textThesis Chair, Dr. Sang D. Choi.
This file was last viewed in Adobe Reader 7.0Construction is one of most dangerous industries in the United States. One of the most hazardous areas within the construction industry is roofing. Concern for safety in roofing construction has continued to spread, as a result of falls that make up the greatest rate of fatalities in the construction industry. Previous research has found that falls have been one of the leading categories under type of occupational death and that fall protection systems are not consistently used to prevent fall accidents in the roofing industry. Research is needed in order to analyze falls and other potential hazards in roofing. The main goal for this study is to analyze commercial and residential roofers’ behaviors, attitudes, and beliefs on the fall protection systems. A survey was distributed to commercial and residential roofers in the Midwest. Information collected from roofers was compared and analyzed to find differences between residential and commercial roofers. A total of 129 roofing contractors participated in this study. The results of the survey showed that while most of commercial roofers did use fall protection devices, a significant number of residential roofers did not comply with fall protection regulations and guidelines. Two main reasons of noncompliance with fall protection regulations and guidelines in roofing construction were found: (1) fall protection devices decrease productivity; (2) fall protection equipment makes roofers uncomfortable. Results from this study revealed that personal fall arrest system (PFAS) was the most prevalent fall protection device used among residential and commercial roofers. PFAS was also the most preferred fall protection equipment among the two groups of roofers. For both residential and commercial roofing, there is a significant (p = 0.05 and p = 0.01) negative relationship between enforcing roofers to wear or install fall protection devices and having falls from roofs. In both residential and commercial roofing, there is a very significant (p= 0.001 and p = 0.001) positive relationship between the enforcement and the actual usage of fall protection equipment. This thesis presents the results of the investigation of fall protection systems in roofing construction and recommendations that ultimately would reduce fall accidents
The computer simulation and prediction of rock fall
No full textThis thesis deals with the study of rock falls using a mathematical model, codified for computer use, entitled GeoFall. GeoFall, which was developed by the author, allows predictions to be made of rock fall trajectories, run out distances and kinetic energies for a rock of any arbitrary shape. Its main purpose is to assist in the design of remedial works. The mathematical model is based on rigid body mechanics, and analyses a fall in 2D space using a new theory of impact dynamics developed by Brach (1991). The main features and algorithms of the program are presented in this thesis. The performance of GeoFall was evaluated by comparing actual rock fall events described in several published papers with the output created by GeoFall. Also the output from GeoFall has been compared with the output from other rock fall simulation programs used to simulate the documented rockfalls. A new rock slope inventory system entitled the Rock Fall Risk Assessment System (RFRAS) has been developed by the author to determine the rock fall risk at specific rock fall sites. It consists of three phases of inspection, the slope survey, and the preliminary and detailed rating phases. The detailed rating phase uses 13 parameters that when assessed, evaluated and totalled, numerically differentiates slopes from the least to the most hazardous producing an overall rating in the range 21-1926. It not only allows the relative risk of rockfall between slopes to be assessed but it also categorises the rock fall risk and the potential number of future rockfalls. It has been tested on 18 slopes at ten locations in County Durham. The final part of the thesis details a new laboratory based procedure that can be used to determine the coefficients of restitution for any type of rock material. The normal coefficient of restitution has been determined for seven different types of rock, and the tangential coefficient of restitution has been determined for a local sandstone. Some tentative correlations between the normal coefficient of restitution and the rocks physical properties, such as its Unconfined Compressive Strength (UCS) have been presented
The density, construction and drag coefficient of electrostatic volcanic ash aggregates.
No full textRecent laboratory experiments have demonstrated that electrostatic charges generated during the fragmentation of volcanic pumice cause rapid aggregation of the silicate particles produced. Here, we present measurements of the mass and component particle size distribution of individual, electrostatically bound aggregates produced during these experiments. Particles produced by fracturing pumice aggregated as they fell ∼1.5 m within an enclosed fall chamber. Aggregate mass measurements indicate aggregate densities of ∼200 kg m−3 or less. The component particle size analysis demonstrates exponential-type cumulative distributions which are dominated (on a volume basis) by particles ∼10–40 μm in diameter and contain few particles >70 μm. By representing these particles as disks of 5 μm thickness the calculated aggregate densities are in agreement with those derived from the aggregate mass measurements and indicate a relatively constant aggregate density with size (in contrast with previous results from fall velocities). Combining the density measurements with fall velocity data allows the drag coefficient of aggregates to be determined. Empirical equations developed to describe the particle size distribution within aggregates are used to derive relative aggregation coefficients for the electrostatic aggregation process. Our results can be used within numerical models of volcanic plumes in order to improve their representation of electrostatic aggregation processes
Advances in the Development of the Experiment to Test the Weak Equivalence Principle in Free Fall
No full textAbstract. We describe specific advances in the analysis and development of an experiment to test the Weak Equivalence Principle in free fall
inside a capsule (Einstein elevator) released from a stratospheric balloon. The accuracy goal of the experiment is a few parts in 10^15.
The attainment of this accuracy would improve the present results in testing the Equivalence Principle by two orders of magnitude.
The measurement technique calls for a detector with two sensing masses of different materials, spinning about the detector horizontal
axis, to free fall inside the capsule/cryostat for about 25 s. We focus here on the effects on the measurement accuracy of gravity gradients
produced by nearby masses, which are non-corotating with the detector. The results of our study on gravity gradients generated by the
distributed mass of the capsule/cryostat yield requirements on: (a) the size of the cryostat; (b) the tolerable verticality error of the capsule
during the fall; and (c) the centering of the center of masses of the detector’s sensing masses. These analyses on the mass distribution of
the experiment carrier have moved the project towards viable design options for the capsule/cryostat
Geomorphic Mapping and Paleoterrain Generation for use in Modeling Holocene (8, 000–1, 500 yr) Agropastoral Landuse and Landscape Interactions in Southeast Spain
No full textPoster presented at the American Geophysical Union 2006, San Francisco.See: American Geophysical Union, Fall Meeting 2006, abstract# GC51A-0453
Diffusive author(s), cohesive author: Analysis of S/N (1994)
No full textThis study indicates the ways in which various aspects of the author(s) are brought forth in Dumb type’s performance art, the S/N production. Previous research has suggested a non-hierarchical organization of Dumb type and the absence of a “privileged author” in Dumb type’s collaborative work, S/N. However, the results that I have investigated from member’s interviews on the creative process of S/N along with my analysis of the recorded images of S/N, indicate a different aspect of the author(s). First, S/N was created through, so to speak, the collective ideas of the members of Dumb type. Further, S/N has at least nine quotations from previous performances, installations, and printed writings, besides the work-in-progress technique. Explicating one of the “author functions” as given by Michel Foucault, each text has plural subjects of the author. However, it has been revealed from members’ interviews that Teiji Furuhashi had a decision-making role in selecting the members’ ideas within the performance. Since then, S/N has had plural subjects of creation; however, Furuhashi is one of the subjects of creation along with the “privileged author.” S/N has plural authors (diffusive authors) yet at the same time, it has a “privileged author,” Teiji Furuhashi (cohesive author)
Fall prevention methodology through the generation of 3rd Virtual Environments
No full textIn 2006 the construction industry accounted for 1,226 fatal occupational injuries. With nearly 21% of all occupational work related fatalities for each of the years between 2001 and 2006, the construction industry has consistently produced the most fatal work injuries than any other industry sector. As construction workers displayed the highest risk for fatal workplace falls during the years 1992-2006, these falls continue to be a leading cause of fatality in the industry. This research explores new strategies to mitigate construction work place injury and fatality through the identification of hazardous situations through the use of real-time Virtual Environment (VE) technologies. This investigation focuses on the identification of relevant conditions necessary to assess fall related hazards, integrative design of fall protection systems and the effective implementation of fall prevention management protocols.
The utilization of VE allows for the generation of 3D visual and anthropometric measurements of workers in real-time. A motion capture suit worn by human subjects enables the capturing and representation of the construction worker’s actual movement in the VE. Subsequently, new worker-environment profiles can be generated with respect to fall-related hazards by employing different scenarios in the VE. Human subjects will be exposed in these scenarios to generate visual and numerical motion data. By following this systematic process, this investigation proposes a methodology for data analysis and fall prevention strategies which can be used by safety experts to indentify potentially hazardous conditions within particular scenarios
A Study of Fall Detection: Review and Implementation
No full textThis thesis presents a research study on Fall detection with a comprehensive survey on available related literature and an evaluation experiment. Fall detection is a major challenge in the public health care domain, especially for the elderly, and reliable surveillance is a necessity to mitigate the effects of falls. The technology and products related to fall detection have always been in high demand within the security and the health-care industries. An
effective fall detection system is required to provide rgent support and to significantly reduce the medical care costs associated with falls. In this thesis, we initially give a comprehensive survey of different systems for fall detection and their underlying algorithms.
Fall detection approaches are divided into three main categories: wearable device based, ambience device based and vision based. These approaches are summarised and compared with each other and a conclusion is derived with some discussions on possible future work.
Then we present an evaluation of fall detection using optical flow. Optical flow is one of the widely used approaches in computer vision to estimate motion. The literature of optical flow is briefly reviewed and some of the methods are implemented with discussion on
experimental results. The best output yielding algorithm with respect to accuracy is used to setup an evaluation of fall detection. The evaluation compares our experimental results with the results obtained using other techniques. At the end we draw a conclusion in general on our research study and in particular on our contributions: Fall detection survey and Fall detection Evaluation. We also point out the futuristic direction of our research study with suggestions on possible areas with further development
A study on detection of risk factors of a toddler’s fall injuries using visual dynamic motion cues
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The research in this thesis is intended to aid caregivers’ supervision of toddlers to prevent accidental injuries, especially injuries due to falls in the home environment. There have been very few attempts to develop an automatic system to tackle young children’s accidents despite the fact that they are particularly vulnerable to home accidents and a caregiver cannot give continuous supervision. Vision-based analysis methods have been developed to recognise toddlers’ fall risk factors related to changes in their behaviour or environment. First of all, suggestions to prevent fall events of young children at home were collected from well-known organisations for child safety. A large number of fall records of toddlers who had sought treatment at a hospital were analysed to identify a toddler’s fall risk factors. The factors include clutter being a tripping or slipping hazard on the floor and a toddler moving around or climbing furniture or room structures.
The major technical problem in detecting the risk factors is to classify foreground objects into human and non-human, and novel approaches have been proposed for the classification. Unlike most existing studies, which focus on human appearance such as skin colour for human detection, the approaches addressed in this thesis use cues related to dynamic motions. The first cue is based on the fact that there is relative motion between human body parts while typical indoor clutter does not have such parts with diverse motions. In addition, other motion cues are employed to differentiate a human from a pet since a pet also moves its parts diversely. They are angle changes of ellipse fitted to each object and history of its actual heights to capture the various posture changes and different body size of pets. The methods work well as long as foreground regions are correctly segmented
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