Browsing by Subject "constraints"
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Item Benefits and constraints associated with the use of an urban park reproted by the elderly in Hong Kong(Texas A&M University, 2006-04-12) Hung, KamThe purpose of this study was to identify benefits and constraints associated with the use of urban parks by a sample of elderly in Hong Kong. Before studying these topics, self-perception of aging of the elderly in Hong Kong was explored. In-depth interviews were conducted with 13 individuals inside and 12 outside the Tsuen Wan Jockey Club Tak Wah Park. Purposive sampling was used to select the sample. The interviews were semi-structured, based on an interview guide of open-ended questions. Results of the study suggested that although there are some differences in explanations of aging among different countries, some aging models and theories which have been developed in western countries can be employed to interpret the aging phenomenon in Hong Kong. Several constraints and health-related social and psychological benefits of attending a park were reported by the sample. Heterogeneity of leisure constraints among different age cohorts of the elderly was found in the study. Although similarities were found between the benefits reported in this study and those reported in western countries, the magnitude of benefits received from visiting parks may be different because of the different characteristics of elderly in different countries.Item Control of systems subject to uncertainty and constraints(2009-05-15) Villota Cerna, Elizabeth RoxanaAll practical control systems are subject to constraints, namely constraints aris?ing from the actuator?s limited range and rate capacity (input constraints) or from imposed operational limits on plant variables (output constraints). A linear control system typically yields the desirable small signal performance. However, the presence of input constraints often causes undesirable large signal behavior and potential insta?bility. An anti-windup control consists of a remedial solution that mitigates the e?ect of input constraints on the closed-loop without a?ecting the small signal behavior. Conversely, an override control addresses the control problem involving output con?straints and also follows the idea that large signal control objectives do not alter small signal performance. Importantly, these two remedial control methodologies must in?corporate model uncertainty into their design to be considered reliable in practice. In this dissertation, shared principles of design for the remedial compensation problem are identi?ed which simplify the picture when analyzing, comparing and synthesiz?ing for the variety of existing remedial schemes. Two performance objectives, each one related to a di?erent type of remedial compensation, and a general structural representation associated with both remedial compensation problems will be consid?ered. The e?ect of remedial control on the closed-loop will be evaluated in terms of two general frameworks which permit the uni?cation and comparison of all known remedial compensation schemes. The di?erence systems describing the performance objectives will be further employed for comparison of remedial compensation schemes under uncertainty considerations and also for synthesis of compensators. On the ba?sis of the di?erence systems and the general structure for remedial compensation, systematic remedial compensation synthesis algorithms for anti-windup and override compensation will be given and compared. Successful application of the proposed robust remedial control synthesis algorithms will be demonstrated via simulation.Item The Limits of Fire Support: American Finances and Firepower Restraint during the Vietnam War(2013-07-12) Hawkins, John MichaelExcessive unobserved firepower expenditures by Allied forces during the Vietnam War defied the traditional counterinsurgency principle that population protection should be valued more than destruction of the enemy. Many historians have pointed to this discontinuity in their arguments, but none have examined the available firepower records in detail. This study compiles and analyzes available, artillery-related U.S. and Allied archival records to test historical assertions about the balance between conventional and counterinsurgent military strategy as it changed over time. It finds that, between 1965 and 1970, the commanders of the U.S. Military Assistance Command, Vietnam (MACV), Generals William Westmoreland and Creighton Abrams, shared significant continuity of strategic and tactical thought. Both commanders tolerated U.S. Army, Marine Corps, and Allied unobserved firepower at levels inappropriate for counterinsurgency and both reduced Army harassment and interdiction fire (H&I) as a response to increasing budgetary pressure. Before 1968, the Army expended nearly 40 percent of artillery ammunition as H&I ? a form of unobserved fire that sought merely to hinder enemy movement and to lower enemy morale, rather than to inflict any appreciable enemy casualties. To save money, Westmoreland reduced H&I, or ?interdiction? after a semantic name change in February 1968, to just over 29 percent of ammunition expended in July 1968, the first full month of Abrams? command. Abrams likewise pursued dollar savings with his ?Five-by-Five Plan? of August 1968 that reduced Army artillery interdiction expenditures to nearly ten percent of ammunition by January 1969. Yet Abrams allowed Army interdiction to stabilize near this level until early 1970, when recurring financial pressure prompted him to virtually eliminate the practice. Meanwhile, Marines fired H&I at historically high rates into the final months of 1970 and Australian ?Harassing Fire? surpassed Army and Marine Corps totals during the same period. South Vietnamese artillery also fired high rates of H&I, but Filipino and Thai artillery eschewed H&I in quiet areas of operation and Republic of Korea [ROK] forces abandoned H&I in late 1968 as a direct response to MACV?s budgetary pressure. Financial pressure, rather than strategic change, drove MACV?s unobserved firepower reductions during the Vietnam War.