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The heated flow within the silencers of heavy transport vehicles can easily reach temperatures of hundreds of degrees Celsius. The thermal loads can cause problems for certain components on a silencer. In this case it has been seen in previous testing that screw joints attaching suspension brackets onto the silencer tend to lose pretension when heat is applied. The goal with this project is to investigate possible causes of the pretension losses and gain a deeper understanding of the joint’sbehavior. The project starts with a pre study with the purpose of obtaining knowledge of what is usually taken into consideration when designing joints for heated applications thatcould cause pretension losses. This was followed by an experimental part. Two main tests are made, firstly a friction test to ensure that the friction properties ofthe studs used in previous clamping force measurements were up to specification. Comparisons to a second batch of studs is also conducted. The second test is an oven test were test specimens of the joint is heat cycled in different temperatures for different assembly torques. This, in order to gain a deeper understanding of the joints´plastic behavior. The test pieces are cycled a total of five cycles and clamping force measurements are made after the first and fifth cycle. Measurements of clamping force are conducted through both ultrasonic and micrometer measurements of screw elongation. The results of the oven test are compared to the results of a finite element simulation. The finite element model is a model of the same test piece as in the tests, it captures the clamping force losses due to plastic deformation of components at heat up. However, the finite element model has its´ limitations, especially in the way the threads are modelled. This is to be taken into consideration and possibly utilized when interpreting the results. The takeaways from the pre study are that creep and stress relaxation, as well asembedding is highly unlikely primary causes for the pretension losses. More instant effects like plasticity due to the applied load is deemed more likely. The friction tests concluded that both of the batches´ friction properties are up to specification, but onethe batches thread friction is on the lower side.The results from oven test shows a temperature dependency in the losses and clea rsigns pointing towards a plastic collapse. All of the clamping force seems to be lost at initial heat up, no further signs of losses after 5 cycles. In comparison with the finite element model the plastic tendencies shows yet again, but most of the losses is not captured in the simulation. By taking into account the known weaknesses of the model, the two threaded components, weld nut and flange nut, are considered to be possible subjects of plastic deformation causing the pretension losses. The two measurement techniques show big deviations between them. It is therefore hard to interpret the absolute results of the pretension losses. In order to that a furtherstudy of how to value the two techniques should be conducted.

<p> A review of movie projection principles and techniques as applied to conventional projectors and a description of general features, mechanism and film movement of the Rolling Loop Projector are presented.</p> <p> The characteristics of a film loop under static conditions with coplanar clamping planes are investigated in terms of loop shape, supporting forces and bending moments. An extension of this analysis is applicable to the case when the loop is fixed on a curved surface.</p> <p> The motion of a loop in the projector is simulated as it grows and rolls on a flat surface and a numerical technique is employed to find the point paths and the velocity and acceleration vectors of these points on the loop at various instants in a projection cycle.</p> <p> Some design criteria are derived from an examination of the results, and these are presented.</p> / Thesis / Master of Engineering (MEngr)

This diploma thesis deals with the structural design of the chucking jaws for RUMUL Cracktronic 160 testing machine. This apparatus is used in the fatigue laboratory of Institute of Machine Design FME BUT. Simplification, speed improvement and better test sample griping are expected gains of the new clamping system. Solidworks system is used to create 3D model of the jaws. Stress analysis is created by Finite element method in ANSYS Workbench software.

The overall aim of this thesis was to evaluate methods for urinary catheter handling in patients undergoing hip surgery. The intention was to gain knowledge in order to provide optimal and cost- effective care regarding urinary catheterisation in this group of patients. In Study I , 45 of the 86 catheterised patients (52%) contracted nosocomial urinary tract infections (UTIs). Diabetes was a risk factor for developing UTI, and cloxacillin as a perioperative antibiotic prophylaxis seemed to offer a certain protection. Study II was a randomised controlled trial on the effect of clamping (n = 55) or not (n = 58) of the indwelling urinary catheter before removal. No significant differences were found between the groups with respect to time to normal bladder function, need for recatheterisation, or length of hospital stay. Study III was a randomised controlled trial among patients with hip fracture and hip arthroplasty, in which the patients were randomised to intermittent (n = 85) or indwelling (n = 85) urinary catheterisation. No significant differences in nosocomial UTIs (9% vs. 12%) or cost-effectiveness were shown. The patients in the intermittent group regained normal bladder function significantly sooner after surgery. Fourteen percent of the patients in the intermittent group did not need any catheterisation. In Study IV , 30 patients were interviewed about their experiences of bladder emptying and urinary catheterisation. The patients’ views were described through the main category ‘An issue but of varying impact’. Both bladder emptying through micturition and bladder emptying through catheterisation were described as convenient, but also as uncomfortable and an intrusion on dignity. The patients were aware of risks and complications of urinary catheterisation. In conclusion, this thesis indicates that UTI is common in hip surgery patients. Clamping of indwelling catheters seems not necessary. There is no preference for either intermittent or indwelling urinary catheterisation according to the results of this thesis, either for the development of nosocomial UTI or, for cost-effectiveness, or from the patient perspective. Nurses should be aware that catheterisation might make the patients feel exposed, and it is essential that their practice reflect the best available evidence.

This paper studies a method for active electrohydraulic force compensation in industrial scale high power applications. A valve controlled cylinder moves a mass using the force of inertia to compensate for the reaction forces of an industrial process. Two strategies for force compensation are developed and investigated in a 160 ton clamping unit of an injection moulding machine to significantly reduce the excitation. Results of the different strategies are shown and evaluated. Advantages and drawbacks of the developed electrohydraulic force compensation are discussed.

Thesis (MCurr)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Intraventricular haemorrhage is associated with neurological morbidity and mortality in low birth weight infants. In spite of improvements in treatment to reduce the incidence of the haemorrhage, the condition continues to remain a major cause of long term morbidity in low birth weight infants. The evidence from the literature has shown that low birth weight infants might benefit from delayed cord clamping particularly in reducing the risk of intraventricular haemorrhage and its neurological consequences. The primary objective of this review was to assess the effects of delayed versus early cord clamping on intraventricular haemorrhage amongst low birth weight infants. The secondary objectives were to evaluate the effects of delayed versus early cord clamping on the Apgar scores, hyperbilirubinaemia and polycythaemia in infants. The following electronic databases were searched: CINAHL, MEDLINE (searched via PubMed) and Cochrane Central Register of Controlled Trials (CENTRAL). Other information was gathered from the reference lists of retrieved articles and relevant experts. The selection criteria entailed all randomised controlled trials comparing delayed versus early cord clamping following birth in infants with low birth weight. Two reviewers independently extracted the data and assessed the quality of the trials. Disagreements on studies for inclusion were resolved by discussion with the third reviewer. The review included five randomised controlled trials with 215 participants. The risk of intraventricular haemorrhage was significantly reduced in the delayed compared with early cord clamping (RR0.52, 95% CI 0.33 to 0.82, P=0.005). No statistically significant difference was shown between delayed versus early cord clamping for the risk of hyperbilirubinaemia (RR O.48, 95% CI -0.43 to 1.39, P=0.30). There was no data available for other comparisons: Polycythaemia and Apgar scores. There is growing evidence that delayed cord clamping might benefit low birth weight infants. In the included studies, delayed cord clamping for at least 30 seconds appear to have a potential in reducing the risk of intraventricular haemorrhage. The results of this review should however be interpreted with caution due to a limited number of studies with the absence of clinically important secondary outcomes in the included trials. Further research is required on large scale randomised controlled trials. / AFRIKAANSE OPSOMMING: Intraventrikulêre bloeding word geassosieer met neurologiese morbiditeit en mortaliteit in suigelinge met ’n lae geboortegewig. Ten spyte van die verbetering in die behandeling om die gevalle van bloeding te verminder, duur die toestand voort as ’n belangrike oorsaak van langtermyn morbiditeit in lae gewig geboortes. Bewyse uit die literatuur toon dat suigelinge met ’n lae geboortegewig voordeel mag trek uit vertraagde afklemming, veral deur die vermindering van die risiko van intraventrikulêre bloeding en die neurologiese gevolge daarvan. Die primêre doelwit van hierdie navorsing was om die effek van vertraagde, versus vroeë afklemming op intraventrikulêre bloeding onder suigelinge met ’n lae geboortegewig te bepaal. Die sekondêre doelwit is om die effekte van vertraagde, versus vroeë afklemming op die Apgar uitslae, hiperbilirubinaemia en polisitaemia by suigelinge te evalueer. Die volgende elektroniese databasisse is nagegaan: CINAHL, MEDLINE (soektog via PubMed); Cochrane Central Register of Controlled Trials (CENTRAL). Ander inligting is verkry uit die bronnelyste van nagevorsde artikels en van relevante deskundiges. Die seleksie kriteria behels alle ewekansige beheerde toetsing, insluitende toekomstige studies wat vertraagde, versus vroeë afklemming vergelyk by suigelinge met ’n lae geboortegewig. Twee resensente het onafhanklik data geneem en die kwalititeit van die toetse bepaal. Verskille oor insluiting van navorsing, is met ’n derde resensent deur middel van bespreking opgelos. Die navorsing het vyf ewekansige beheerde steekproewe met 215 deelnemers ingesluit. Die risiko van intraventrikulêre bloeding is beduidend verminder in die vertraagde gevalle, in teenstelling met vroeë afklemming (RR0.52, 95% CI 0.33 tot 0.82, P=0.005). Geen statistiese beduidende verskil is bewys tussen vertraagde teenoor vroeë afklemming ten opsigte van hiperbilirubinaemia nie (RR 0.48, 95% CI – 0.43 tot 1.39, P=0.30). Daar was geen data beskikbaar vir ander vergelykings nie: Polisytaemia en Apgar uitslae. Daar is groeiende bewyse dat vertraagde afklemming lae geboortegewig suigelinge mag beïnvloed. Dit wil in die ingeslote studies voor kom dat vertraagde afklemming van ten minste 30 sekondes die potensiaal het om die risiko van intraventrikulêre bloeding te verminder. Die uitslae van hierdie beskouing sal nietemin met omsigtigheid geïnterpreteer moet word, weens die beperkte aantal studies met die afwesigheid van klinies belangrike sekondêre uitkomste in die ingeslote proewe. Verdere navorsing word benodig op grootskaalse ewekansige beheerde proewe.

<p>Randomised controlled trials (RCT) have demonstrated a net benefit of carotid endarterectomy (CEA) in stroke prevention for patients with severe carotid artery stenosis as compared to best medical treatment. Results in routine clinical practice must not be inferior to those in the RCTs. The carotid arteries are clamped during CEA which may impair the cerebral perfusion. </p><p>The aim of this thesis was to assess population-based outcomes from CEA, investigate risk factors for perioperative complications/late mortality and to evaluate effects of carotid clamping during CEA. In the Swedish vascular registry 6182 CEAs were registered during 1994-2003. Data on all CEAs were retrieved, analysed and validated. In the validation process no death or disabling stroke was unreported. The perioperative stroke or death rate was 4.3% for those with symptomatic and 2.1% for asymptomatic stenosis (the latter decreasing over time). Risk factors for perioperative complications were age, indication, diabetes, cardiac disease and contralateral occlusion. Median survival time was 10.8 years for the symptomatic and 10.2 years for the asymptomatic group. </p><p>Tolerance to carotid clamping during CEA under general anaesthesia was evaluated in 62 patients measuring cerebral oximetry, transit time volume flowmetry and stump pressure. High internal carotid artery flow before clamping and low stump pressure was associated with decreased oxygenation after clamping suggesting shunt indication. </p><p>In 18 patients undergoing CEA, jugular bulb blood samples demonstrated significantly altered levels of marker for inflammatory activation (IL-6) and fibrinolytic activity (D-dimer and PAI-1) during carotid clamping as compared to radial artery levels. This indicates a cerebral ischaemia due to clamping although clinically well tolerated. </p><p>In conclusion, the perioperative outcome after CEA in Sweden compared well with the RCTs results. Tolerance to carotid clamping may be evaluated by combining stump pressure and volume flow measurements. Although clinically tolerated clamping may induce a cerebral ischaemic response.</p>

In this work characterisation methods and fuel cell hardwarewere developed for studying the components of the polymerelectrolyte fuel cell (PEFC). Humidifiers and other componentswere tested in order to develop reproducible and reliableexperimental techniques. A set-up for testing larger cells andstacks was developed. A new type of polymer electrolyte membrane fuel cell wasdeveloped for laboratory investigations. Current collectormaterial and gas flow channels can easily be modified in thisconstruction. The electrode potentials can be measured at thegas backing layers, thereby allowing measurement of contactresistances. The use of a reference electrode is alsopossible. Contact resistances were studied in situ as a function oftime, clamping pressure, gas pressure and current density.Ex-situ measurements were used to validate the in-situ contactresistance measurements. The validity and error sources of theapplied in-situ measurement methods with reference electrodesand potential probes were studied using both computersimulations and experiments. An in-house membrane electrode assembly (MEA) productionline was developed. In-house produced MEAs were utilised inboth membrane degradation and mass transport studies. The durability testing of PVDF based membranes membranes wasstudied both by fuel cell experiments and ex-situ testing.Raman spectra were measured for used membranes. A current distribution measurement method was developed. Theeffect of inlet humidification and gas composition at thecathode side was studied. In addition, two different flow fieldgeometries were studied. The results of current distributionmeasurements were used to validate a PEFC model. Methods for characterising gas diffusion layer (GDL)performance by fuel cell testing and ex-situ measurements weredeveloped. The performance of GDL materials was tested withvarying cell compression and cathode humidity. Porosity, poresize distribution and contact angle were determined. Electricalcontact resistance, thermal impedance and gas permeabilitieswere measured at different compression levels. Development work on a stack with stainless steel net wascarried out as well as characterisation studies of differentstack components. Thermal impedances and flow fieldpermeability were measured. Mass transport limitations in the cathodes were studied byvarying the electrode thickness, partial pressure and humidityof oxygen. <b>Keywords:</b>polymer electrolyte membrane fuel cell (PEFC),contact resistance, clamping pressure, stainless steel,membrane degradation, current distribution, gas diffusionlayer, stack, thermal impedance, permeability.

Randomised controlled trials (RCT) have demonstrated a net benefit of carotid endarterectomy (CEA) in stroke prevention for patients with severe carotid artery stenosis as compared to best medical treatment. Results in routine clinical practice must not be inferior to those in the RCTs. The carotid arteries are clamped during CEA which may impair the cerebral perfusion. The aim of this thesis was to assess population-based outcomes from CEA, investigate risk factors for perioperative complications/late mortality and to evaluate effects of carotid clamping during CEA. In the Swedish vascular registry 6182 CEAs were registered during 1994-2003. Data on all CEAs were retrieved, analysed and validated. In the validation process no death or disabling stroke was unreported. The perioperative stroke or death rate was 4.3% for those with symptomatic and 2.1% for asymptomatic stenosis (the latter decreasing over time). Risk factors for perioperative complications were age, indication, diabetes, cardiac disease and contralateral occlusion. Median survival time was 10.8 years for the symptomatic and 10.2 years for the asymptomatic group. Tolerance to carotid clamping during CEA under general anaesthesia was evaluated in 62 patients measuring cerebral oximetry, transit time volume flowmetry and stump pressure. High internal carotid artery flow before clamping and low stump pressure was associated with decreased oxygenation after clamping suggesting shunt indication. In 18 patients undergoing CEA, jugular bulb blood samples demonstrated significantly altered levels of marker for inflammatory activation (IL-6) and fibrinolytic activity (D-dimer and PAI-1) during carotid clamping as compared to radial artery levels. This indicates a cerebral ischaemia due to clamping although clinically well tolerated. In conclusion, the perioperative outcome after CEA in Sweden compared well with the RCTs results. Tolerance to carotid clamping may be evaluated by combining stump pressure and volume flow measurements. Although clinically tolerated clamping may induce a cerebral ischaemic response.