In this thesis, we examine the Linear DC Motor in a configuration such that it provides the forces necessary to damp vibrations in a large flexible structure. The design is broken down into three steps where in each step, a feedback loop is placed around the actuator and/or the structure. The first loop is a motor compensation loop which effectively decouples the motor model from the structure model by removing the effect of the velocity of the structure on the motor's performance. The second loop stabilizes the relative position response of the combined actuator/structure model. This loop also shapes the magnitude response of the system, thus determining the bandwidth of the actuator. Two designs are developed: a narrow bandwidth design and a wide bandwidth design. The third loop is the vibration suppression design loop and can be designed a number of ways. In this thesis, we develop two decentralized designs and a centralized design. The final system is simulated to check design results. The various nonlinearities of the proof mass actuator are considered and their effect on results noted. These nonlinearites, the stroke and current limits, determine the effectiveness of each vibration suppression design. The linear model is checked for robustness to parameter uncertainty. Results for the various designs are tabulated and discussed. / M.S.

Blast resistance has recently become increasingly relevant for structural engineers. Blast loads are created by explosive devices that, upon detonation, create pressure loads that are much higher than most that a structure would ever experience. While there are many types of blast loads that are impossible to adequately prepare for, methods are presently being developed to mitigate these loads. This research investigates the possibility of using synthetic fiber ropes as a means of blast resistance. This is the third phase of a multi-stage research endeavor whose goal is to analyze Snapping-Cable Energy Dissipators (SCEDs) for reducing the effects of large-scale lateral loads. Finite element models of portal frames were developed using the commercial finite element program ABAQUS and dynamic models were run for varying blasts and frame systems. Blast pressures of 100, 2,000, and 4,000 psi were applied to a steel portal frame and comparisons were made between unbraced frames and frames braced with springs of different stiffnesses. Additional tests were run to examine the effects of strain rate dependent yield on the results of the models. Parallel research is being conducted on the specific material behavior of the synthetic fiber ropes so that the models developed for this research can be revised for a more accurate determination of the effects of the ropes on structural systems subjected to blast loads. / Master of Science

The work that is reported herein deals with system identification methods for large flexible structures. Proposed space missions for the future include the deployment of large flexible structures, e.g., NASA's proposed space station. These structures must be controlled to maneuver the structure to desired locations and to suppress unwanted vibration. Before controlling any structure, it is necessary to have an accurate model which may include accurate estimates of the structure's natural frequencies and mode shapes. System identification is an important process that precludes system control. Precision structures such as those proposed for the Space Based Laser or the Aerospace Plane require high performance control systems which will require robust, computationally efficient system identification algorithms. This work attempts to experimentally verify, develop, and compare existing identification algorithms to determine their properties and improve their efficiency towards potential applicability in a space environment. To this end, we consider the Temporal Correlation Method and the Eigensystem Realization Algorithm. The algorithms are implemented on the Astronautics Laboratory Grid structure, and the results of the algorithms are compared in the presence of damping, noise, and residual modes. In addition, the Temporal Correlation Method is shown to be a constrained version of the Eigensystem Realization Algorithm for cases of light damping. / Master of Science

This thesis presents a numerical study of the influence of varying story strength on the seismic performance of multi-story wood-frame shear wall buildings. In the prior FEMA P695 studies of these buildings, the non-simulated collapse limit-state was exceeded primarily in the first story. This observation raised interest in quantifying the influence of varying strength from story to story on seismic response. In this study, four distributions of strength are used as bounding cases. The Parabolic strength distribution (1) results from the ELF vertical force distribution method in ASCE 7 that assigns forces to each level based on weight and story height. The Triangular strength distribution (2) results from an assumed vertical force distribution that assigns lateral forces based on the seismic weight at each level. The Constant strength distribution (3) results from an assumed vertical force distribution that assigns a concentrated lateral force at the uppermost level based on the total seismic weight of all levels. The Baseline distribution (4) reflects a realistic vertical strength distribution resulting from the ELF vertical force distribution method. The FEMA P695 methodology, which quantifies seismic performance via adjusted collapse margin ratios, is employed in this study. The analytical models include P-Delta effects and utilize the 10-parameter hysteresis CASHEW model. It is observed that the Parabolic strength distribution allows for dissipation of energy over the height of the building, has less collapse risk than other strength distributions studied, and reduces occurrence of concentrated deformations in a single story from the onset of applied lateral force. / MS / Multi-story wood-frame buildings are becoming increasingly common, especially in areas like the western United States. Past earthquakes have shown that multi-story wood-frame buildings that have a soft and weak first story relative to upper stories are vulnerable to collapsing on the first story. This vulnerability has raised interest in understanding how the relative strength of each story of a wood building affects its performance in an earthquake. This thesis studies four strength distribution cases. The first three cases are called the Parabolic, Triangular and Constant strength distributions named after the shape of the building’s story to story strength profile. For example, the Triangular case has the least amount of strength on the top story, which increases linearly in the lower stories down to the first story, which has the greatest strength. The fourth case, called the Baseline case, is based on actual building designs. All four strength distribution cases have the same first story strength. Two evaluation methods are used to test the strength distribution cases. The first, known as a pushover analysis, applies lateral forces to the building until the roof reaches a specified displacement. The second, called an incremental dynamic analysis, subjects the building to increasingly intense earthquakes until a certain amount of displacement is reached in any story. The results of these analyses showed that the Parabolic strength distribution most effectively used the strength available in every story of the building to delay the onset of collapse and to distribute the location of the collapse story.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第25241号 / 工博第5200号 / 新制||工||1992(附属図書館) / 京都大学大学院工学研究科建築学専攻 / (主査)教授 大崎 純, 教授 西山 峰広, 准教授 藤田 皓平 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

Yes / Trips over obstacles are one of the main causes of falling in older adults, with vision playing an important role in successful obstacle negotiation. We determined whether a horizontal-vertical illusion, superimposed onto low-height obstacles to create a perceived increase in obstacle height, increased foot clearances during obstacle negotiation thus reducing the likelihood of tripping. Eleven adults (mean ± 1 SD: age 27.3 ± 5.1 years) negotiated obstacles of varying heights (3, 5, 7 cm) with four different appearance conditions; two were obstacles with a horizontal-vertical illusion (vertical stripes of different thickness) superimposed on the front, one was a plain obstacle and the fourth a plain obstacle with a horizontal black line painted on the top edge. Foot clearance parameters were compared across conditions. Both illusions led to a significant increase in foot clearance when crossing the obstacle, compared to the plain condition, irrespective of obstacle height. Superimposing a horizontal-vertical illusion onto low-height obstacles can increase foot clearance, and its use on the floor section of a double-glazing door frame for example may reduce the incidence of tripping in the home.

Thesis (Ed.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / This dissertation studied the implementation of Outlook 98, Microsoft's desktop information management software, at Saybrook University and Bancroft Valley Bank (fictitious names). The major research question was, What does the life cycle of Outlook 98 at Saybrook University and Bancroft National Bank tell us about the pattern of implementation at these two sites, and what roles do users' "technological frames" play in each site's implementation process? Employing a qualitative methodology and a conceptual framework based on Wanda Orlikowski's works on "technological frames" (nature of technology, technology strategy and technology in use) and an "episodic" (three-stage) pattern of adaptation, the author conducted unstructured and structured interviews, directly observed meetings and training sessions, and analyzed existing documents to ascertain participants' experience with Outlook 98. The findings corroborated Orlikowski's descriptions of the frames and episodic adaptation, and uncovered three new insights related to the technological frames. First, the frames first appeared in a pre-implementation stage, or what Zaltman, Duncan and Holbek (1973) call the "Formation of Attitudes Toward the Innovation" substage of an innovation's initiation stage. The users' spontaneous and vivid figurative language-similes and metaphors-presented images of motion, rest and calm, and momentary stasis before further motion in the various stages. Second, users at both sites experienced "antecedent intolerance," the author's term for a drastic change in their nature of technology frame, from an originally negative perception of the new software and a reluctance to use it to an eventual refusal to give it up. The shift in their frames was so complete that it represented not merely a modification of the original frames but a replacement of them. And third, the findings suggest two new domains of technological frames: a User/Change Agent domain (users' and change agents' perceptions of each other) and a Learning the Technology domain, which the author feels is so important that he proposes a new ASK Model of Learning, an approach to training that would address users' attitudes in the pre-implementation stage and first stage of use, skills in the second stage, and knowledge in the third stage. / 2999-01-01

Master of Science / Department of Architectural Engineering / Kimberly Waggle Kramer / Braced frames are a common seismic lateral force resisting system used in steel structures. Ordinary concentric braced frames (OCBFs) and special concentric braced frames (SCBFs) are two major types of frames. Brace layouts vary for both OCBFs and SCBFs. This report examines the inverted-V brace layout which is one common arrangement. OCBFs are designed to remain in the elastic range during the design extreme seismic event. As a result, OCBFs have relatively few special requirements for design. SCBFs are designed to enter the inelastic range during the design extreme seismic event while remaining elastic during minor earthquakes and in resisting wind loads. To achieve this, SCBFs must meet a variety of stringent design and detailing requirements to ensure robust seismic performance characterized by high levels of ductility. The design of steel seismic force resisting systems must comply with the requirements of the American Institute of Steel Construction’s (AISC) Seismic Provisions for Structural Steel Buildings. Seismic loads are determined in accordance with the American Society of Engineers Minimum Design Loads for Buildings and Other Structures. Seismic loads are very difficult to predict as is the behavior of structures during a large seismic event. However, a properly designed and detailed steel structure can safely withstand the effects of an earthquake. This report examines a two-story office building in a region of moderately high seismic activity. The building is designed using OCBFs and SCBFs. This report presents the designs of both systems including the calculation of loads, the design of frame members, and the design and detailing of the connections. The purpose of this report is to examine the differences in design and detailing for the two braced frame systems.

The main objective of this thesis is to provide a smooth video playout on the mobile device over wireless networks. The parameters that specify the wireless channel include: bandwidth variation, frame losses, and outage time. These parameters may affect the quality of the video negatively, and the mobile users may notice sudden stops during the playout video, i.e., the picture is momentarily frozen, followed by a jump from one scene to a different one. This thesis focuses on eliminating frozen pictures and reducing the amount of video data that need to be transmitted. In order to eliminate frozen scenes on the mobile screen, we propose three different techniques. In the first technique, the video frames are split into sub-frames; these sub-frames are streamed over different channels. In the second technique the sub-frames will be “crossed” and sent together with other sub-frames that are from different positions in the streaming video sequence. If some sub-frames are lost during the transmission a reconstruction mechanism will be applied on the mobile device to recreate the missing sub-frames. In the third technique, we propose a Time Interleaving Robust Streaming (TIRS) technique to stream the video frames in different order. The benefit of that is to avoid losing a sequence of neighbouring frames. A missing frame from the streaming video will be reconstructed based on the surrounding frames on the mobile device. In order to reduce the amount of video data that are streamed over limited bandwidth channels, we propose two different techniques. These two techniques are based on identifying and extracting a high motion region of the video frames. We call this the Region Of Interest (ROI); the other parts of the video frames are called the non-Region Of Interest (non-ROI). The ROI is transmitted with high quality, whereas the non-ROI is interpolated from a number of references frames. In the first technique the ROI is a fixed size region; we considered four different types of ROI and three different scenarios. The scenarios are based on the position of the reference frames in the streaming frame sequence. In the second technique the ROI is identified based on the motion in the video frames, therefore the size, position, and shape of the ROI will be different from one video to another according to the video characteristic. The videos are coded using ffmpeg to study the effect of the proposed techniques on the encoding size. Subjective and objective metrics are used to measure the quality level of the reconstructed videos that are obtained from the proposed techniques. Mean Opinion Score (MOS) measurements are used as a subjective metric based on human opinions, while for objective metric the Structural Similarity (SSIM) index is used to compare the similarity between the original frames and the reconstructed frames.

O presente trabalho teve como objetivo obter estimativas de parâmetros genéticos para escores de frame estimados por modelos propostos a partir da análise de dados de animais zebuínos (FRAME_GMA) e pelas equações propostas pela Federação Americana de Melhoramento de Gado de Corte (Beef Improvement Federation) (FRAME_BIF), bem como verificar as correlações entre escores de frame obtidos pelas duas metodologias e entre cada um dos escores e as variáveis independentes consideradas em avaliações genéticas de bovinos de corte da raça Nelore. Foram analisados dados de 12.728 animais provenientes de dois rebanhos da Agro-Pecuária CFM Ltda., com idades entre 490 a 610 dias. Os modelos de melhor ajuste para FRAME_GMA incluíram altura de garupa aos 18 meses, peso aos 18 meses e interação altura e peso. As estimativas de herdabilidade para FRAME_GMA e FRAME_BIF em análises uni-característica foram: 0,26 ± 0,03 e 0,23 ± 0,03, respectivamente; e, em análises bi-característica, essas estimativas foram 0,28 e 0,24, respectivamente. Os coeficientes de correlação fenotípica e genética de Pearson e de Spearman entre FRAME_GMA e FRAME_BIF para machos e fêmeas foram positivos e de alta magnitude, variando de 0,83 a 0,92. Os coeficientes de correlação fenotípica e genética entre cada escore de frame e as variáveis independentes altura de garupa, peso e idade na data da medida de altura foram sempre superiores para o FRAME_GMA em relação ao FRAME_BIF. Os parâmetros genéticos e os coeficientes de correlação indicam que o FRAME_GMA se adapta melhor ao conjunto de dados quando comparado ao FRAME_BIF. Outros estudos devem ser conduzidos para avaliar a aplicabilidade do modelo proposto a outras populações e em outras faixas etárias, bem como, estimativas de parâmetros genéticos para escores de frame na raça Nelore / This research was carried out to estimate genetic parameters for estimated frame scores for models proposed from the analysis of data of Nelore beef cattle (FRAME_GMA) and for the equations proposed by Beef Improvement Federation (FRAME_BIF), as well, to verify the correlations among frame scores obtained by the two methodologies and among each one of the scores and the independent variables considered in genetic evaluations of Nelore beef cattle. Data of 12,728 animals from Agro-Pecuária CFM Ltda. were analyzed, with ages between 490 and 610 days. The models of better adjustment for FRAME_GMA included hip height at 18 months, weight at 18 months and interaction height and weight. Estimates of heritability for FRAME_GMA and FRAME_BIF in single trait analysis were: 0.26 ± 0.03 and 0.23 ± 0.03, respectively; and, in mult trait analysis, these estimates were 0.28 and 0.24, respectively. The coefficients of phenotypic and genetic Pearson and Spearman correlations between FRAME_GMA and FRAME_BIF for males and females were positive and high magnitude, varying from 0.83 to 0.92. The coefficients of phenotypic and genetic correlation between each one of the frame scores and the independent variables hip height, weight and age at height measurement always went higher to FRAME_GMA than FRAME_BIF. The genetic parameters and the correlation coefficients indicate that FRAME_GMA was better than FRAME_BIF. Other studies were necessary to evaluate the applicability of the proposed model to other populations and in other age groups, as well, estimates of genetic parameters for frame scores in Nelore beef cattle