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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.
371

Three dimensional kinetic analysis of asymmetrical lifting

Li, Jian-Chuan January 1996 (has links)
Manual lifting is dynamic in nature and involves asymmetrical loading of the human body. This study investigated kinematic and kinetic characteristics of asymmetrical lifting in three dimensions, and then constructed a 3-D biomechanical force model of the lower back which is capable of quantifying torsional stress on the human spine. Eleven healthy adult male manual workers were recruited as subjects and lifted a 1 Okg load placed at the sagittal plane (0°) and at 30°, 60° and 90° lateral planes to the right, from 150mm and 500mm initial lift heights, respectively, to an 800mm high bench in the sagittal plane. Subjects' spinal motions and the trajectorial movements of the load in three-dimensional space were monitored simultaneously by a Lumbar Motion Monitor and a V-scope Motion Analyzer. Generally, the spinal motion factors increased as a function of increasing task asymmetry and differed (p < 0.05) between the lower (150mm) and higher (500mm) levels in the sagittal plane. In all asymmetrical conditions the motion factors showed a dramatic increase at the 500mm level compared to the increase at the 150mm level. The rates of increase in the horizontal and frontal planes were greater than those in the sagittal plane. Task asymmetry had a significant effect on the spinal kinematic parameters in the frontal plane at the two lift heights, and only at the high level (500mm) in the horizontal plane, with exception of average acceleration . Initial lift height exerted a significant effect on peak velocity and acceleration in both frontal and horizontal planes and on range of motion in the horizontal plane. Kinetic characteristics of the object being lifted in three-dimensions increased with an increase in task asymmetry. The increase was more dramatic in the lateral direction in the horizontal plane. However, motion factors in the vertical direction dominated the full range of the lift, irrespective of task asymmetry and lift height. The kinetic measures differed (p < 0.05) between the lower ( 1 50mm) and the higher (500mm) levels in the vertical direction except for average force. Task asymmetry had a significant effect on dynamic measures in the anterior-posterior direction. Both task asymmetry and lift height had a significant effect on dynamic motion factors in the lateral direction. From insights gained in the empirical study a three-dimensional biomechanical force model of the lower back was constructed based on a mechanism of muscle force re-orientation in the lumbar region. Acknowledging that the lower back is designed to be able to rotate around its longitudinal axis, the proposed model accounts for compression and shear forces and a torsional moment. The model has similar predictability to Schultz and Andersson's (1981) model when the human trunk exerts only a flexion-extension moment in the sagittal plane, but additionally predicts dramatic increases in shear forces, oblique muscle forces and torsional moment under asymmetrical lifting conditions which the Schultz-Andersson model does not. The increase rates in these forces and moment are not linearly related over task asymmetric angle.
372

Characterisation of the effect of filler size on handling, mechanical and surface properties of resin composites

Elbishari, Haitham Idris January 2012 (has links)
Resin composites have been in the dental field for over forty years. They are now thought to be the most commonly used restorative material due to their aesthetic and mechanical properties. Although resin composites have high success rates as restorations, they do not offer all properties of an ideal restorative material. The aims of this research were to characterise the effects of variation in resin composite formulation on handling, mechanical; and physical properties. In particular the influence of the size and distribution of the inorganic components was investigated through the study of experimental formulations. Packing stress and viscosity were assessed with pentrometer principle at two different temperatures (23 and 37 ºC). It was found that filler size was strongly correlated with both packing stress and viscosity. Additionally, temperature has a dominant effect on packing stress and viscosity. Micro computed tomography [μCT] was used to investigate percentage of voids [% voids] in 3D dimensions. It was found that smaller filler size incorporated less % voids. In contrast filler size and disruption had a little effect on fracture toughness of resin composites. 3D surface topography was used to investigate the surface roughness before and after tooth brush abrasion. It was found filler size had a significant influence in both gloss retention and surface roughness (smaller filler size exhibited higher surface gloss). Finally, the effect of different storage media (distilled water, Coca Cola and red wine) on colour stability and gloss were investigated. It was found that dietary habits effect discolouration of resin composite restorations with the acidic drinks caused more staining.
373

Treatment of phthalic anhydride residue for improved handling and disposal

Van Staden, Karen 31 October 2005 (has links)
The handling and disposal of hot tarry liquid residues can be problematic in industry, in this case, a phthalic anhydride plant using naphthalene as feed stock. The residue from the plant contains an appreciable amount of phthalic anhydride which desublimates from the residue during draining, resulting in an unsafe working environment. In addition, the residue is a hot liquid that solidifies upon cooling, causing additional risks to personnel during handling and various problems associated with disposal. Research was conducted into finding a treatment method to reduce or eliminate the desublimation of phthalic anhydride from the residue and addressing the hot liquid residue, making the residue safer to handle and easy to dispose of. Laboratory experiments showed that the addition of Dicalite 4151 (a filter aid) in a concentration of 0,3 kg Dicalite 4151 per kg phthalic anhydride residue, resulted in the formation of a powdered residue. This was confirmed during plant trials where using the same concentration proved that a powdered residue could be obtained, while at the same time desublimation of the phthalic anhydride from the residue was negated by distilling the product from the residue mixture. An opportunity exists to test the use of filter aid in other residue producing industries to determine if the same results can be achieved. / Dissertation (MEng (Environmental Engineering))--University of Pretoria, 2005. / Chemical Engineering / unrestricted
374

Improving process flow for selected parts in a Port Elizabeth manufacturer of security products

Mosebi, Thapelo David January 2014 (has links)
South African SMMEs, just like their counterparts world-wide, play a very crucial role against the world economies. The competiveness of these SMMEs is therefore very important. Lean Manufacturing and its principles have been successfully applied by motor manufacturing industries over the years. Many other organisations has since followed suite and adopted lean manufacturing as an approach to optimise and better manage their resources while providing value to their customers. The objective of this study is to investigate how lean manufacturing techniques can be adopted by a specific SMME in a business of manufacturing security products for the banks to better manage its material flow and improve its competitiveness. The research uses observation method to gather information to develop the current value stream map and identify the wasteful procedures. The also involves the interviewing of staff members that are involved in the material handling within the organisation. The results from the two processes are explained and the future value stream map incorporating the lean techniques is developed and presented to the organisation.
375

Socio-economic importance, health and welfare aspects of donkeys (Equus asinus) used for carting in a peri-urban area of South Africa

Marufu, Madure January 2014 (has links)
The broad objective of the study was to determine the socio-economic importance, health and welfare aspects of donkeys used for carting in a peri-urban area. A survey was conducted among 71 donkey owners in Joza, a peri-urban area near Grahamstown in the Eastern Cape Province (ECP) of South Africa to investigate their perceptions on socio-economic importance, health and welfare aspects of donkeys used for transport. Two hundred and seventy-one donkeys used for carting were assessed through direct observation of health and behaviour parameters to determine their welfare status. Results revealed that donkeys are indeed of immense value to people, being used daily (54.93%) for income generation activities and at least once per month (7.08%) for domestic chores. Most of the respondents (32%) earned R 600.00 per week while 11% earned at least R 200.00 per week from carting using donkeys. Donkeys were used for carting of goods (90.14%) more than for manure (16.9%). Gender and age of owners significantly (P < 0.05) influence perceptions on source of income while education level influenced their perceptions on carting firewood, goods and water. Results on management practices and health problems encountered by working donkeys showed that most of the owners managed their animals poorly. Most donkeys were being beaten (74.65%) during work, made to travel long distances (43.66%), worked long hours (52.11%) without adequate water (59.10%) and feed supplements (83.10%). Wounds (95.97%), coughing (75.65%) and lameness (64.79%) were some of the health problems encountered by donkeys. Significant relationships (P ˂ 0.05) were observed between owners’ perceptions on management practices and health problems encountered by donkeys. Among the observed animals, 61% were thin and mostly apathetic (26.2%) than medium and fat animals. Responses to observer approaches were significantly associated with sex and body condition score (BCS), with stallions in good body condition being more aggressive. Donkeys having a BCS of 3-5 avoided chin contact either by kicking out or moving away. Results further showed that most of the donkeys were suffering from external injuries, with the hindquarters (39.85%), shoulder (32.10%) and spine (21.77%) being the mostly affected areas. The prevalence of wounds on tail-base, belly, flank and neck were seen in less than 13% of the animals. The prevalence of wounds was influenced by age and BCS of the animals. Young donkeys with good BCS were less affected than old donkeys. Lameness, poor coat condition, external parasites, abnormal mucous membrane and dental problems were observed in less than 30% of the animals. It was concluded that donkeys play a pivotal role economically and socially to the livelihoods of people in a peri-urban area (Joza) in terms of income generation and transportation. However, these animals are experiencing multiple health and welfare problems. Therefore, more access to veterinary services, training on donkey use and management, health and welfare promotion programs are of paramount importance in solving the problem of poor health and welfare in donkeys.
376

Future requirements for grain handling through Pacific Coast ports

Case, Alan Herbert January 1967 (has links)
Grain is the single most important export commodity shipped through four important Canadian ports on the Pacific Coast. Recent rapid growth in these exports have strained present facilities close to capacity. Therefore the necessity has arisen to study the problem of future requirements for grain handling facilities in British Columbia. Furthermore the over-all development of British Columbia ports has been widely discussed in recent years and because grain is such an important export, the problem of port development requires specific study of grain handling facilities. Investigation of future grain handling requirements relied on both library and field sources. Field work, mainly in the form of interviews with people in port administration and grain handling and selling were especially useful in gaining first-hand knowledge of the actual problems of grain exporting. Facts and opinions gained from field work were also invaluable to interpretation of a large mass of statistics that were available from various library sources. The results of the research have led to several conclusions. The most important is that the Pacific Coast of Canada requires new grain handling facilities in the near future. In addition improvements in handling are possible within existing facilities and throughout the extensive system of grain gathering which begins on the farms, hundreds of miles from the export point. In addition to the above findings there are several important secondary conclusions. First, the markets for grain are likely to continue growing in the foreseeable future. Because the markets of greatest growth are near the Pacific Ocean, Canada's West Coast ports are well situated to serve them. Second, the United States Pacific ports are also well situated to provide direct competition with Canada. If and when this competition becomes more direct, Canada will require the best facilities to keep its customers. Third, Canadian ports have definite advantages to ship operators over the United States ports in the form of lower charges for port use, but maintenance of efficiency in Canadian ports is essential to maintaining this advantage. Finally, the main Canadian Pacific ports are physically suitable for the expansion of grain handling facilities. / Business, Sauder School of / Graduate
377

Barriers to the adoption of safe beef cattle handling practices, equipment, and facilities in Iowa

Scott-Harp, DeAnn 01 May 2018 (has links)
Agriculture is one of the most hazardous industries in the United States, with a fatality rate that consistently surpasses other industries. Livestock handling activities are often found to be the second or third leading cause of on-farm injuries, with machinery and falls being cited as other leading causes. Among all livestock, cattle are responsible for the most injuries and fatalities on farms, and cattle-related nonfatal injuries have been shown to be some of the most costly, and result in more time off work than other injuries. Despite the fact that research has improved our understanding of cattle behavior and sensory functions, developed low-stress handling practices, and determined how facilities can be safer for workers and livestock, injury rates remain high. This project identified the types of equipment commonly used on beef farms, evaluated relationships between injuries and farm characteristics (such as herd size and equipment used), and assessed farmer perceptions of safety and obstacles to implementing changes. Most farms cited that they utilized equipment like alleyways (82.69%), a manual headgate (75.51%), a sorting/diverter gate (53.06%), and a manual squeeze chute (51.02%). However, it was found that having certain types of equipment had no influence on the likelihood of injuries. Herd size, on the other hand, was shown to be influential in that farms with larger than average herd size were shown to have a higher rate of injury. A final finding of this study was that farmers cited the cost of equipment, lack of necessity (their setup worked well already), and lack of time as being the main reasons they have not implemented changes on their operations. This study supports the idea that safe equipment and facilities are being implemented and used on most farms already, which suggests that the focus of future research should shift towards evaluating the influence that factors such as human behavior, handling practices, degree of training received, and training methods used have on the risk of worker injury.
378

Improving off-road vehicle handling using an active anti-roll bar

Cronje, Paul Hendrik 26 November 2009 (has links)
This thesis investigates the use of an active anti-roll bar as a means of improving the handling of an off-road vehicle. The active anti-roll bar consists of a stiff anti-roll bar and a hydraulic actuator at the one end between the anti-roll bar and the rear axle of the vehicle. The system is designed so that the anti-roll bar can be preloaded in both directions by the actuator. The displacement of the hydraulic actuator is close loop controlled to be a function of the lateral acceleration of the vehicle, which is measured by an accelerometer. For this study, full vehicle simulations were done in ADAMS/View to predict the response of the proposed solutions. A Land Rover Defender 110 was used as the test vehicle to verify the results of the simulations. Constant radius tests and the severe double-lane-change manoeuvre, which are standard handling tests, were used to determine the vehicle’s handling performance. Handling performance was quantified by measuring the body roll angle during the manoeuvre and noting the maximum roll angle. The effect of the active anti-roll bar on ride comfort was measured by driving over Belgian paving at a constant speed. The results show that the proposed system reduces the body roll angle to zero up to a lateral acceleration of 0.4 g during steady state handling and provided a 74% improvement in maximum body roll angle during a double-lane-change-manoeuvre at 70 km/h. The system has no detrimental effect on the ride comfort of the vehicle. / Dissertation (MEng)--University of Pretoria, 2008. / Mechanical and Aeronautical Engineering / unrestricted
379

Analýza rizik manipulace s materiálem / Materials handling risk analysis

Kašparová, Iva January 2009 (has links)
The process analysis provides a good way for identification (stock-taking) of the weak points in the firms in these days, when the waste is restricted, continual improvement is required and the crisis is one of the most frequent word in use. If such point was already found it is necessary to apply efficient remedial measure to provide against financial or information leakage. This master’s thesis is about Materials handling risk analysis.
380

Manipulace a materiálový tok ve výrobě ocelových konstrukcí / Manipulation and material flow in production of steel construction

Šíp, Ondřej January 2010 (has links)
This diploma thesis discourse about of material flow in production , following the deployment of workstations and handling equipement. It compares different methods of analysis on the basis of theoretical knowledge and processes them in calculation part. Within the problem it follows the expansion of production of a new machine and new areas.

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