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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

The effect of movement strategy and elastic starting strain on shoulder resultant joint moment during elastic resistance exercise

Hodges, Gregory Neil 11 September 2006 (has links)
The purpose of this study was to compare the shoulder resultant joint moment (RJM) during a shoulder internal rotator exercise using elastic resistance employing four different movement strategies and two different starting elastic strains. Methods: Ten subjects aged 27.4 ± 2.6 yr (5 female and 5 male) with no previous shoulder pathology performed four sets of six repetitions of shoulder rotation though 180° using elastic resistance (Thera-Band® elastic band, blue) during two acceleration (medium and low) and two cadence (2s:2s, <1s:1s) strategies at 0% elastic starting strain. The acceleration movement strategies were also performed with starting strain of 30%. A mathematical model using Newtonian mechanics was used to compute the RJM. Elastic band recoil force was measured with a force transducer. Forearm acceleration was determined by a miniature uniaxial accelerometer secured at the wrist. Electrogoniometer data were collected to determine the range of motion (ROM) as well as the angle between the forearm and band which was used to determine elastic moment arm. Paired t-tests were used to identify joint angle specific RJM differences between conditions. Results: Angle specific comparisons revealed that RJM in the moderate acceleration movement strategy was significantly different from RJM in the low acceleration movement strategy through 150° (83%) of range of motion (p<0.05). Shoulder RJM was up to 111% higher in the moderate acceleration strategy (P < 0.01). Angle specific comparisons revealed RJM in the <1:1 cadence strategy was significantly different from RJM in the 2:2 cadence through 108° (60%) of the range of motion (p<0.05). RJM was up to 47% higher in the <1:1 cadence (p<0.01). RJM in the low acceleration strategy was significantly greater with 30% elastic start strain relative to 0% elastic start strain through 180º of angular excursion (p<0.001). The pattern and magnitude of neuromuscular loading was significantly different in higher acceleration movement strategies (moderate acceleration and fast cadence). Conclusions: These findings indicate that differential limb acceleration as a result of movement strategy significantly affects shoulder load during elastic resistance exercise. The pattern and magnitude of load was different in each movement strategy and could result in differential neuromuscular adaptation through training. Clinicians and exercise professionals should consider movement strategy/acceleration as an important factor when prescribing elastic resistance exercise for safety and efficacy.
12

The Effect of Pain on Balancing Behavior: Complexity Analysis of Mediolateral Force Trajectories

Leich Hilbun, A., Karsai, I., Perry, D. 01 June 2019 (has links)
Background: Postural instability is a prevalent and deleterious consequence of aging. It is unclear how the occurrence of chronic pain augments balance issues as age progresses. Research question: We investigated how postural stability is influenced by aging and chronic pain. Methods: Fifty-five participants with and without recent chronic pain balanced on one foot while performing three tasks, a standard balancing task with no challenge, a mental task in which participants answered arithmetic questions while balancing on one foot, and a knot-tying task in which participants tied knots in a ribbon while balancing on one foot. General linear models were used to assess the relationship between age, sex, BMI, and pain category for the three different balancing tasks. In addition, a multivariate analysis of variance was used to test the effect of age and pain category on Hurst exponents from all of three different balancing tasks. Results: Our results show that aging changes the control strategy of balancing from less persistent to more repetitive. The strong feedback elements intrinsic to healthy stability ensure quick reactions and strong capacity to compensate for balance checks; this reactive state changes into a less reactive and more predictable balance strategy with age while balancing on one foot. Mental tasks during balancing also decreased the feedback in balancing strategy. Balance strategy during the knot-tying task was correlated with age, but unaffected by chronic pain. Overall, the chronic pain group had a worse balance strategy while performing the mental task in comparison with healthy people, but were not differentiable from controls in the standard or knot-tying tasks. Significance: Scores from balancing while engaging in cognitive tasks may provide evidence of health decline, and contribute to our knowledge about how pain affects feedback mechanisms.
13

Modeling, Control and Prototyping of Alternative Energy Storage Systems for Hybrid Vehicles

Samuel Durair Raj, Kingsly Jebakumar 19 June 2012 (has links)
No description available.
14

Control of queueing delay in a buffer with time-varying arrival rate.

Awan, Irfan U., Guan, Lin, Woodward, Mike E. January 2006 (has links)
No / Quality of Service (QoS) is of extreme importance in accommodating the increasingly diverse range of services and types of traffic in present day communication networks and delay is one of the most important QoS metrics. This paper presents a new approach for constraining queueing delay in a buffer to a specified level as the arrival rate changes with time. A discrete-time control algorithm is presented that operates on a buffer (queue) which incorporates a moveable threshold. An algorithm is developed that controls the delay by dynamically adjusting the threshold which, in turn, controls the arrival rate. The feasibility of the system is examined using both theoretical analysis and simulation.
15

Reliability challenges for automotive aftertreatment systems: a state-of-the-art perspective

Soleimani, Morteza, Campean, Felician, Neagu, Daniel 02 November 2018 (has links)
Yes / This paper provides a critical review and discussion of major challenges with automotive aftertreatment systems from the viewpoint of the reliability of complex systems. The aim of this review is to systematically explore research efforts towards the three key issues affecting the reliability of aftertreatment systems: physical problems, control problems and fault diagnostics issues. The review covers important developments in technologies for control of the system, various methods proposed to tackle NOx sensor cross-sensitivity as well as fault detection and diagnostics methods, utilized on SCR, LNT and DPF systems. This paper discusses future challenges and research direction towards assured dependability of complex cyber-physical systems. / InPowerCare Project - JLR (Jaguar Land Rover)
16

Hybrid Electric Vehicle Control Strategy Based on Power Loss Calculations

Boyd, Steven J. 13 November 2006 (has links)
Defining an operation strategy for a Split Parallel Architecture (SPA) Hybrid Electric Vehicle (HEV) is accomplished through calculating powertrain component losses. The results of these calculations define how the vehicle can decrease fuel consumption while maintaining low vehicle emissions. For a HEV, simply operating the vehicle's engine in its regions of high efficiency does not guarantee the most efficient vehicle operation. The results presented are meant only to define a literal strategy; that is, an understanding as to why the vehicle should operate in a certain way under the given conditions. The literature review gives a background of hybrid vehicle control publications, and without the SPA HEV addressed or a hybrid analysis based on loss calculations between engine only and hybrid modes, there is a need for this paper. Once the REVLSE architecture and components are understood, the hybrid modes are explained. Then the losses for each hybrid mode are calculated, and both the conversion and assist efficiencies are detailed. The conversion efficiency represents the amount of additional fuel required to store a certain amount of energy in the battery, and this marginal efficiency can be higher than peak engine efficiency itself. This allows electric only propulsion to be evaluated against the engine only mode, and at low torques the electric motor is more efficient despite the roundtrip losses of the hybrid system. / Master of Science
17

Pressure compensator control – a novel independent metering architecture

Lübbert, Jan, Sitte, André, Weber, Jürgen 27 April 2016 (has links) (PDF)
This contribution presents an operating strategy for a novel valve structure for mobile machines’ working hydraulics which combines the flexibility and energetic benefits of individual metering with the functionality of common primary pressure compensation (IPC). The aim is to set up a system that uses a minimal amount of sensors and simple control algorithms. A control strategy theoretically described in /1/ is modified to facilitate the practical implementation on a mini excavator implement as a test rig. This test rig consists only of components that are currently available off-the-shelf to show that it is possible to develop an individual metering system under these economic restrictions. The novel is more energy efficient than common flow sharing systems but provides the same functionality. The control algorithm is experimentally evaluated in terms of functionality and energy consumption. Simulations show potential for further improvements.
18

Hydraulic Hybrid Excavator: Layout Definition, Experimental Activity, Mathematical Model Validation and Fuel Consumption Evaluation

Casoli, Paolo, Riccò, Luca, Campanini, Federico, Lettini, Antonio, Dolcin, Cesare 03 May 2016 (has links) (PDF)
Energy saving and fuel consumption reduction techniques are among the principal interests for both academic institutions and industries, in particular, system optimization and hybridization. This paper presents a new hydraulic hybrid system layout for mobile machinery implemented on a middle size excavator. The hybridization procedure took advantage of a dynamic programming (DP) algorithm, which was also utilized for the hybrid components dimensioning and control strategy definition. A dedicated experimental activity on test bench was performed on the main components of the energy recovery system (ERS). The JCMAS working cycle was considered as the reference test for a fuel consumption comparison between the standard and the hybrid excavator. A fuel saving up to 8% on the JCMAS cycle, and up to 11% during the digging cycle, has been allowed by the proposed hybrid system.
19

Energy Efficient Textile Drying

Brunzell, Lena January 2006 (has links)
<p>Traditionally, textiles were dried outdoors with the wind and the sun enhancing the drying process. Tumble dryers offer a fast and convenient way of drying textiles independent of weather conditions. Tumble dryers, however, consume large amounts of electrical energy. Over 4 million tumble dryers are sold each year in Europe and a considerable amount of energy is used for drying of clothes. Increasing energy costs and the awareness about environmental problems related to a large energy use has increased the demand for dryers with better energy efficiency. The aim with this thesis is to show how to improve the energy efficiency of domestic tumble dryers.</p><p>Two types of tumble dryers are available on the market today: the open cycle dryer and the closed cycle dryer. In the open cycle dryer room air is heated and led into the drying drum. The exhaust air leaves the dryer and is often evacuated outside the building. In the closed cycle dryer an internal airflow is recirculated inside the dryer. When the hot air has passed through the drying drum it is led through a heat exchanger where the water vapour is condensed before the air is heated again and led to the drum. The heat exchanger is cooled with room air.</p><p>Drying at low temperature has been shown to reduce the specific energy use for an open cycle tumble dryer. In Paper I a correlation between the specific energy use, the drying time and the heat supply was established for a specific load by using the exhaust air temperature. It was shown that the total drying time and specific energy use could be predicted from data during the first hour of the process. This result indicated a possibility to create a control system that makes it possible for the user to choose between low energy use or short drying time.</p><p>The focus of Paper II is to reduce the energy use for a closed cycle tumble dryer. Energy and mass balances were established in order to determine feasible improvements. Energy and mass flows in the dryer indicated that reducing leakage from the internal system of the dryer gave the largest reduction of specific energy use. Insulation of the back cover of the dryer and opening the internal system during the falling drying rate period also gave positive results on the energy use. In total a feasible reduction of the energy use of approximately 17% was calculated.</p>
20

Energy Efficient Textile Drying

Brunzell, Lena January 2006 (has links)
Traditionally, textiles were dried outdoors with the wind and the sun enhancing the drying process. Tumble dryers offer a fast and convenient way of drying textiles independent of weather conditions. Tumble dryers, however, consume large amounts of electrical energy. Over 4 million tumble dryers are sold each year in Europe and a considerable amount of energy is used for drying of clothes. Increasing energy costs and the awareness about environmental problems related to a large energy use has increased the demand for dryers with better energy efficiency. The aim with this thesis is to show how to improve the energy efficiency of domestic tumble dryers. Two types of tumble dryers are available on the market today: the open cycle dryer and the closed cycle dryer. In the open cycle dryer room air is heated and led into the drying drum. The exhaust air leaves the dryer and is often evacuated outside the building. In the closed cycle dryer an internal airflow is recirculated inside the dryer. When the hot air has passed through the drying drum it is led through a heat exchanger where the water vapour is condensed before the air is heated again and led to the drum. The heat exchanger is cooled with room air. Drying at low temperature has been shown to reduce the specific energy use for an open cycle tumble dryer. In Paper I a correlation between the specific energy use, the drying time and the heat supply was established for a specific load by using the exhaust air temperature. It was shown that the total drying time and specific energy use could be predicted from data during the first hour of the process. This result indicated a possibility to create a control system that makes it possible for the user to choose between low energy use or short drying time. The focus of Paper II is to reduce the energy use for a closed cycle tumble dryer. Energy and mass balances were established in order to determine feasible improvements. Energy and mass flows in the dryer indicated that reducing leakage from the internal system of the dryer gave the largest reduction of specific energy use. Insulation of the back cover of the dryer and opening the internal system during the falling drying rate period also gave positive results on the energy use. In total a feasible reduction of the energy use of approximately 17% was calculated.

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