In recent years, a flurry of interest has been shown for a relatively old technology called magneto-rheological fluids, or MR fluids. Multiple types of devices have been designed to implement this versatile fluid, including linear dampers, clutches, work-piece fixtures, and polishing machines. The devices have been used in automobiles, washing machines, bicycles, prosthetic limbs, and even smart structures. This thesis focuses on another application of MR dampers, involving super-sport motorcycles. This paper introduces the topics of MR dampers and motorcycle suspensions, and why the two would be a good combination. A detailed history of MR fluids, MR dampers, and motorcycle suspension technologies is given next. After a broad outline of MR dampers and motorcycle suspensions, the method of designing and manufacturing MR dampers is discussed. The damper design for this research is presented in detail, along with the design procedure used to make it. Next, laboratory testing for it is covered, including the test equipment, test procedure, and the laboratory test results. Upon laboratory test completion, the field test setup and procedure are presented. The results of field tests with stock dampers and MR dampers with a variety of control systems is discussed. The MR dampers provided a more stable ride than that of the OEM dampers. By reducing suspension displacement, settling time, and suspension oscillations, the MR dampers were able to reduce suspension geometry instability. Lastly, concluding remarks are made on the research presented. Design flaws are discussed, as well as recommendations for future work in the same area. / Master of Science

<p dir="ltr"><i>Pseudomonas aeruginosa</i> (<i>P. aeruginosa</i>) is a Gram-negative bacterium responsible for many infections in immunocompromised humans. This multi-drug resistance human pathogen can form biofilms, which help protect it from not only clinical treatment but also from main homeostasis and metabolism. Understanding biofilm structures is critical to help combat biofilm formation and develop better ways to treat <i>P. aeruginosa</i> infections. A molecule that helps biofilm formation and virulence infections for <i>P. aeruginosa</i> is pyocyanin, which is believed to be correlated with the invasiveness of the bacteria and the stabilization of biofilms. To better understand the role of pyocyanin in assisting <i>P. aeruginosa</i> with survival, we applied optical imaging to study pyocyanin in biofilms and under blue light treatment. Using nonlinear optical imaging methods, we could successfully detect the aggregation of pyocyanin in biofilms. Furthermore, we discovered that pyocyanin protects <i>P. aeruginosa</i> from blue light inactivation. In addition, we found that blue light treatment alters the structure of pyocyanin, leading to irreversible changes that produce distinct spectra in UV-Vis and fluorescence signals. <i>These results provide new insights into how pyocyanin protects </i><i>P. aeruginosa</i> in blue light treatment. Further investigation would lead to better treatment strategies for more effective treatment of <i>P. aeruginosa</i> and biofilms for various infections.</p>

Investigations on the design of controllable magnetorheological (MR) fluid devices have focused heavily on low velocity and low frequency applications. The extensive work in this area has led to a good understanding of MR fluid properties at low velocities and frequencies. However, the issues concerning MR fluid behavior in impact and shock applications are relatively unknown. To investigate MR fluid properties in this regime, MR dampers were subjected to impulsive loads. A drop-tower test facility was developed to simulate the impact events. The design includes a guided drop-mass released from variable heights to achieve different impact energies. Five drop-heights and two fundamental MR damper configurations were tested. The two configurations were a double-ended piston and a mono-tube with nitrogen accumulator. To separate the dynamics of the MR fluid from the dynamics of the current source, each damper received a constant supply current before the impact event. A total of five supply currents were investigated for each impact velocity. After reviewing the results, it was concluded that the effect of energizing the MR fluid only leads to "controllability" below a certain fluid velocity for the double-ended design. In other words, until the fluid velocity dropped below some threshold, the MR fluid behaved as if it was not energized, regardless of the strength of the magnetic field. Controllability was defined when greater supply currents yielded larger damping forces. For the mono-tube design, it was shown that the MR fluid was unable to travel through the gap fast enough during the initial impact. Consequently, the damper piston and accumulator piston traveled in unison until the accumulator bottomed out. After which, the fluid was forced through the gap. In conclusion, the two designs were compared and general recommendations on designing MR dampers for impulsive loading were made. Possible directions for future research were presented as well. / Master of Science

Hydraulic energy absorbers may be described as high-loss centrifugal turbomachines arranged to operate as stalled torque converters. The device absorbs the kinetic energy of a vehicle in motion and dissipates the energy into water. A steady, single-phase, Computational Fluid Dynamics (CFD) simulation has been performed to investigate the flow field in a hydraulic energy absorber. It was determined that to better predict the performance of the energy absorber, more sophisticated modeling approaches may be needed. In this research, a steady, two-phase calculation with basic turbulence modeling was used as a first assessment. The two-phase model was used to investigate cavitation effects. Unsteady and advanced turbulence modeling techniques were then incorporated into single-phase calculations. The Multiple Reference Frame (MRF) Technique was used to model the interaction between the rotor and the stator. The calculations provided clearer details of the flow field without dramatically increasing the computational cost. It was found that unsteady modeling was necessary to correctly capture the close coupling between the rotor and the stator. The predicted torque in the unsteady calculations was 70% of the experimental value and twice of the result in the steady-state calculations. It was found that the inaccuracy of torque prediction was due to (1) high pressures in the regions with complicated geometrical boundaries and, (2) dynamic interactions between the rotor and the stator were not captured fully. It was also determined that the unrealistically low pressure values were not caused by the physical cavitation, but by the lack of proper boundary conditions for the model. Further integration of the modeling techniques studied would improve the CFD results for use in the design of the energy absorber. / Master of Science

This Diploma thesis deals with the design of device for measurement of vehicle shock absorbers. It describes shock absorbers and options for their diagnostics. In the next part describes design of device, strength analysis, modal analysis, and cost estimate. Transferring torque of device is realized by scotch yoke mechanism.

This thesis was made together with Syntronic, a leading design house specializing in advanced productand systems development. One of the major trends in vehicle industry today is the emergence of electricvehicles. One of the main challenges for the electric vehicles is the energy storage capacity whichtogether with powertrain, rolling- and wind resistance losses determines the vehicle range. Therefore,steps are taken in all areas from more efficient electronics to regenerative breaking which have beenwidely adopted, and the hunt for harvesting energy from other areas of the car is on its way. Energydissipated in heat from the shock absorbers can be harvested and some concepts of this have showngood results.The focus of this work was therefore to, based on previous studies, develop and evaluatea new type of shock absorber with integrated energy harvesting.A product development process was used to generate a new or develop a current concept for aregenerative shock absorber. From the product development process a compact hydraulic-electricsystem within the shock absorber were designed and evaluated on its regenerative capabilities with apeak efficiency of 32 percent while also providing an adjustable dampening coefficient. The conceptoffers a compact and affordable design by utilizing a vane pump integrated into the shock absorberpiston.

As the world’s need for electricity increases, so does its demand for sustainable energy with low to no greenhouse gas emissions. One of these renewable sources of energy is the Ocean which is one of the world’s largest and most predictable energy source, where the extraction of energy can be from waves or tidal current, with zero greenhouse gas emissions during production. A company which works with wave energy is Waves4Power which has developed the wave energy buoy WaveEL.WaveEL is comprised of a buoy which is eight meters in diameter with a 36 meters long vertical cylinder which goes through the buoy. In the cylinder is a piston that oscillates in pace with the waves and generates electricity. Between the piston and the cylinder wall is a gap where the water can move from one side of the piston to the other in pace with the piston’s oscillations. The gap is called the leakage clearance. The leakage clearance effect on the flow resistance is the focus of this master thesis as something which has not been studied before in scientific articles for similar wave energy buoys or in other fields.The aim of the master thesis is to improve the understanding of how the water flow, because of the leakage clearance in the WaveEL buoy, affects the force which the piston is subjected to, and in turn how much electricity can be generated. As it is a complex system the focus will be to determine the dynamic flow resistance parameter because of the leakage clearance and the changes to the dynamic flow resistance parameter as the dimensions of the piston is varied.The leakage clearance effect on the flow resistance has been studied with the help of Computational Fluid Dynamics (CFD) in the software COMSOL Multiphysics 6.0 in two different models. In the first model, model A, the piston is locked in different positions in the cylinder and the pressure at the bottom of the cylinder varies to reflect the motion of the waves. For the second model, model B, the piston is allowed to move vertically in the cylinder due to a set force which reflects the motion of the waves.The dynamic flow resistance parameter for model A is lower at higher Reynolds number and within an interval between 0.4 and 1.6 within the working area. Outside of the working area the dynamic flow resistance parameter is lower at a higher Reynolds number and higher than in the working area at an interval between 0.7 and 45.For model B, the dynamic flow resistance parameter has only been calculated for the working area and is within an interval of 0.1 and 7, the value for the dynamic flow resistance parameter is low when the Reynolds number is high. Dissimilar to model A where the piston is locked into position, the piston oscillates in model B. There is a phase shift between the velocity of the piston and the velocity of the water, which leads to the piston being subjected to a larger force than in model A at lower water velocities. This is one of the reasons why the dynamic flow resistance parameter is higher in model B than model A at low Reynolds number. As model B calculates the dynamic flow resistance parameter based on the relative velocity between the piston and the water, the dynamic flow resistance parameter becomes lower than for model A at higher Reynolds number.For the performed sensitivity analysis, the results shows that a more advantageous value on the dynamic flow resistance parameter can be achieved by altering the dimensions of the piston. A more advantageous result was achieved for example when the rounded edge on the piston became sharper or when the leakage clearance width was increased by 10%. If this master thesis work is to be extended, the studies should focus on elaborating model B either more in depth or with values derived from experiments from the WaveEL buoy for a more realistic model and thus determine a more accurate dynamic flow resistance parameter.The results from the sensitivity analysis justifies a future study where the dynamic flow resistance parameter should be investigated with greater variations of the piston diameters, as this can increase the flow resistance and thus generate more electricity. However, it should be investigated in relation to the cost of manufacture, to obtain the ultimate design which generates maximum electricity for a reasonable manufacturing cost. / Allt eftersom värdens elektricitetsbehov ökar, ökar också efterfrågan på förnybar energi med låga eller inga växthusgasutsläpp. En av dessa förnybara energikällor är havet som anses vara en av världens största och mest förutsägbara energikällor, där utvinningen av energi kan ske från vågor eller tidvattenströmmar, med noll växthusgasutsläpp under produktion. Ett av företagen som arbetar med vågenergi är Waves4Power som har utvecklat vågenergibojen WaveEL.WaveEL består av en boj som är åtta meter i diameter med en 36 meter lång vertikal cylinder som går igenom bojen. I cylindern finns en kolv som oscillerar i takt med vågorna och genererar elektricitet. Mellan kolven och cylinderväggen finns en spalt där vatten kan förflytta sig från ena sidan av kolven till den andra i takt med att kolven oscillerar, denna spalt kallas läckspalten. Läckspaltens påverkan på flödesmotståndet är någonting som tidigare inte har studerats i andra vetenskapliga artiklar för likartade vågenergibojar eller inom andra branscher och är därför fokus för detta examensarbete.Syftet med examensarbetet är att förbättra förståelsen hur vattenflödet till följd av läckspalten i WaveEL-bojen påverkar kraften som kolven utsätts för, vilket i sin tur påverkar hur mycket elektricitet som genereras. Eftersom det är ett komplext system kommer focus vara att fastställa den dynamiska flödesmotstånds parametern till följd av läckspalten och förändringarna i den dynamiska flödesmotstånds parametern när dimensionerna på kolven varieras.Läckspaltens påverkan på flödesmotståndet har studerats med hjälp av Computational Fluid Dynamics (CFD) med programvaran COMSOL Multiphysics 6.0 i två olika modeller. I den första modellen, modell A, är kolven låst i olika positioner i cylindern och trycket vid botten av cylindern varierar för att efterlikna vågrörelser. För den andra modellen, modell B, tillåts kolven röra sig vertikalt i cylindern genom en bestämd kraft som efterliknar vågrörelserna.Resultatet från modell A visar att flödesmotståndet befinner sig mellan 0,4 och 1,6 inom arbetsområdet och utanför arbetsområdet är den dynamiska flödesmotståndsparametern större än i arbetsområdet, här är den dynamiska flödesmotstånds parametern mellan 0,7 och 45. Oberoende av kolvens position i bojen sjunker den dynamiska flödesmotståndsparametern i takt med att Reynolds talet ökar.För modell B har den dynamiska flödesmotstånds parametern endast beräknas för arbetsområdet och ligger inom intervallet 0,1 och 7, där ett lågt värde på den dynamiska flödesmotstånds parametern fås när Reynolds talet är högt. Tillskillnad mot modell A där kolven är låst i sin position, oscillerar kolven i modell B. Det finns en fasvridning mellan kolvens och vattnets hastighet, vilket innebär att kolven utsätts för en större kraft i modell B än i modell A vid låga vattenhastigheter. Det är en av anledningarna till att den dynamiska flödesmotstånds parametern är högre i modell B vid låga Reynolds tal. Eftersom modell B beräknar ut den dynamiska flödesmotstånds parametern med hjälp av den relativa hastigheten mellan kolven och vattnet blir den dynamiska flödesmotståndsparametern lägre än för modell A högre Reynolds tal.För den genomförda känslighetsanalysen visar resultatet att ett mer fördelaktigt värde på den dynamiska flödesmotsstånds parametern kan uppnås vid förändring av kolvens dimensioner. Exempelvis uppnåddes ett mer fördelaktigt resultat när den avrundade kanten på kolven blev skarpare eller när bredden på läckspalten ökades med 10%. Om detta examensarbete ska utökas bör studierna fokusera på att utveckla modell B antingen mer på djupet eller med värden härledda från experiment från WaveEL-bojen för en mer realistisk modell och därmed en mer exakt bestämning av den dynamiska flödesmotstånds parametern.Resultatet från känslighetsanalysen motiverar en framtida studie där den dynamiska flödesmotstånds parametern bör undersökas med kraftigare dimensions variationer på kolven, eftersom detta kan komma att öka flödesmotståndet och således generera mer elektricitet. Dock behöver de undersökas i relation med tillverkningskostnaderna, för att hitta den ultimata design som genererar maximalt med elektricitet vid en rimlig tillverkningskostnad.

Denna rapport ämnar undersöka de vanligast förekommande typerna av teknologier för vågkraftverk (eng. Wave Energy Converter, WEC) teknologier för att jämföra de olika konceptens förmåga att absorbera vågenergi. Koncept som undersöks är punktabsorbatorer och oscillerande vattenkolumner. I denna rapport används de vanligt använda engelska översättningarna point absorber och oscillating water column (OWC). Beräkningar görs för de olika koncepten i liknande vågförhållanden för att kunna jämföra den energi som kan utvinnas. I rapporten sker beräkningar under optimala vågförhållanden. Vågorna antas vara linjära och vågkraftverken antas vara i fas med vågens svängningsrörelse. Den vågdata som använts är uppmätt utanför Belmullet i Irland. Beräkningar görs på vågor med en signifikant våghöjd på 1,25 m och en periodtid på 7,5 s. Det görs även beräkningar på den största uppmätta förekommande vågen. I huvudsak används effektberäkningar enligt en modell som Kjell Budal. Syftet är att grafiskt och numeriskt jämföra den teoretiska och faktiska maxeffekt som kan utvinnas ur respektive våg. Resultatet från undersökningen visar att den största bidragande faktorn till en hög energiutvinning beror på bojens volym. Volymen måste anpassas för de vågförhållanden som finns där bojen ska placeras.Vid beräkningar av en OWC med tvärsnittsarea på 19 m2 visar det sig att den effekt som kan utvinnas av en luftkammare med tillhörande turbin är ungefär 10 kW, 1/30 av de 300kW som kan utvinnas av en point absorber. En OWC består dock sällan utav en ensam luftkammare utan ofta i en array med ett flertal luftkammare med separata turbiner för att öka effekten. / This report intends to examine the most common types of wave energy converter technologies to compare the different concepts' ability to absorb wave energy. Concepts being investigated are point absorbers and oscillating water columns (OWC). Calculations are made for the different concepts in the same wave conditions to be able to compare the energy that can be extracted. In the report, calculations are made under optimal wave conditions. The waves are assumed to be linear and the wave energy converter is assumed to be in phase with the oscillating motion of the wave. The wave data used is measured outside Belmullet in Ireland. Calculations are made on waves with a significant wave height of 1.25 m and a period time of 7.5 s. Calculations are also made on the largest measured wave present. In essence, power calculations are used according to a model developed by Kjell Budal and with the help of this be able to graphically and numerically compare the theoretical and actual maximum power that can be extracted from each scale. The results from the survey show that the largest contributing factor to high energy recovery is due to the volume of the buoy. The volume must be adapted to the wave conditions that exist where the buoy is to be placed.When calculating an OWC with a cross sectional area of 19 m2, it turns out that the power that can be extracted from an air chamber with an associated turbine is approximately 10 kW, 1/30 of the 300 kW that can be extracted by one point absorber. However, an OWC rarely consists of a single air chamber but often in a construction with several air chambers with separate turbines to increase the power.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: As a renewable energy source, wave energy has the potential to contribute to the increasing global demand for power. In South Africa specifically, the country’s energy needs may easily be satisfied by the abundance of wave energy at the South-West coast of the country. Commercially developing and utilizing wave energy devices is not without its challenges, however. The ability of these devices to survive extreme weather conditions and the need to achieve cost-efficacy while achieving high capacity factors are but some of the concerns. Constant changes in wave heights, lengths and directions as well as high energy levels and large forces during storm conditions often lead to difficulties in keeping the complexity of the device down, avoiding over-dimensioning and reaching high capacity factors. The point absorber device developed as part of this research is based on an innovation addressing the abovementioned issues. An approach is followed whereby standard "offthe- shelf" components of a proven hydraulics technology are used. The size of the device is furthermore adaptable to different wave climates, and the need for a control system is not necessary if the design parameters are chosen correctly. These characteristics enable low complexity of the device, excellent survivability and an exceptionally high capacity factor. This may lead to low capital as well as low operationand maintenance costs. In this paper the working principle of this concept is presented to illustrate how it utilises the available wave energy in oceans. The results obtained from theoretical tests correlate well with the experimental results, and it is proven that the device has the ability to achieve high capacity factors. As the device makes use of existing, "off-the-shelf" components, cost-efficient energy conversion is therefore made feasible through this research. / AFRIKAANSE OPSOMMING: As ’n hernubare/ herwinbare energiebron bied golfenergie die potensiaal om by te dra tot die bevrediging van die stygende globale energie-navraag. In spesifiek Suid-Afrika kan die oorvloed van beskikbare golfenergie aan die Suid-Weskus van die land gebruik word om aan die land se energiebehoeftes te voldoen. Betroubaarheid en oorlewing in erge weerstoestande, koste-effektiwiteit en die behaal van hoë kapasiteitsfaktore is beduidende struikelblokke wat oorkom moet word in die poging om ’n golfenergie-omsetter wat kommersieël vervaardig kan word, te ontwikkel. Daarby dra voortdurende veranderings in golfhoogtes, -lengtes en -rigtings sowel as hoë energievlakke en groot kragte tydens storms by to die feit dat dit moeilik is om die kompleksiteit van die stelsel laag te hou. Dit terwyl daar voorkom moet word dat die toestel oorontwerp en verhoed word dat hoë kapsiteitsfaktore bereik word. Die puntabsorbeerder-toestel wat in hierdie navorsing ontwikkel is, bestaan uit ’n ontwerp wat spesifiek ontwikkel is om die bogenoemde probleme aanspreek. ’n Unieke benadering is gevolg waardeur standaard, maklik-bekombare komponente gebruik is en die komponent-groottes ook aangepas kan word volgens golfgroottes. Indien die ontwerpsdimensies akkuraat gekies word, is die moontlikheid verder goed dat ’n beheerstelsel nie geïmplementeer hoef te word nie. Hierdie eienskappe verseker lae stelselkompleksiteit, uitstekende oorlewingsvermoë en ’n uitstaande kapasiteitsfaktor. Lae kapitaal- sowel as onderhoudskostes is dus moontlik. Die doel van hierdie dokument is om die werking van die konsep voor te stel en teoreties sowel as prakties te evalueer. Die resultate van teoretiese toetse stem goed ooreen met eksperimentele resultate, en dit is duidelik dat die toestel hoë kapasiteitsfaktore kan behaal. Aangesien die toestel verder gebruik maak van bestaande komponente wat alledaags beskikbaar is, word die koste-effektiewe omsetting van golfenergie dus moontlik gemaak deur hierdie navorsing.

Carbon is the most well-known black material in the history of man. Throughout the centuries, carbon has been used as a black material for paintings, camouflage, and optics. Although, the techniques to make other black surfaces have evolved and become more sophisticated with time, carbon still remains one of the best black materials. Another well-known black surface is black silicon, reflecting less than 0.5% of incident light in visible spectral range but becomes a highly reflecting surface in wavelengths above 1000 nm. On the other hand, carbon absorbs at those and longer wavelengths. Thus, it is possible to combine black silicon with carbon to create an artificial material with very low reflectivity over a wide spectral range. Here we report our results on coating conformally black silicon substrate with amorphous pyrolytic carbon. We present a superior black surface with reflectance of light less than 0.5% in the spectral range of 350 nm to 2000 nm.