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Sur un nouveau micromètre à double image, ses possibilités et quelques questions connexes ...Müller, Paul. January 1948 (has links)
Thèse--Universit́e de Paris.
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Sur un nouveau micromètre à double image, ses possibilités et quelques questions connexes ...Müller, Paul. January 1948 (has links)
Thèse--Universit́e de Paris.
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The precision screw in scientific instruments of the 17th-19th centuries : with particular reference to astronomical, nautical and surveying instrumentsBrooks, Randall Chapman January 1989 (has links)
Published articles have been removed from the Appendices of the electronic copy of this thesis due to third party copyright restrictions. The complete version can be consulted at the University of Leicester Library.
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The effect of clearance upon friction and lubrication of large diameter hip resurfacing prosthesis using blood and combinations of bovine serum with aqueous solutions of CMC and hyaluronic acid as lubricantsAfshinjavid, Saeed January 2010 (has links)
In real life, immediately after joint replacement, the artificial joint is actually bathed in blood (and clotted blood) instead of synovial fluid. Blood contains large molecules and cells of size ~ 5 to 20 μm suspended in plasma and considered to be a non-Newtonian (pseudoplastic) fluid with density of 1060 Kg/m³ and viscosity ~ 0.01 Pas at shear rates of 3000 s⁻¹ (as obtained in this work). The effect of these properties on friction and lubrication is not fully understood and, so far to our knowledge, hardly any studies have been carried out regarding friction of metal-on-metal bearings with various clearances in the presence of lubricants such as blood or a fluid containing macromolecules such as hyaluronic acid (HA) which is a major component of synovial fluid increasing its viscosity and lubricating properties. In this work, therefore, we have investigated the frictional behaviour of a group of Smith and Nephew Birmingham Hip Resurfacing implants with a nominal diameter of 50mm and diametral clearances in the range ~ 80 μm to 300 μm, in the presence of blood (clotted and whole blood), a combination of bovine serum (BS) with hyaluronic acid (HA) and carboxymethyl cellulose (CMC, as gelling agent) adjusted to a range of viscosities (~0.001-0.2 Pas), and bovine serum with CMC adjusted to a similar range of viscosities. These results suggested that reduced clearance bearings have the potential to generate high friction especially in the presence of blood which is indeed the in vivo lubricant in the early weeks after implantation. Friction factors in higher clearance bearings were found to be lower than those of the lower clearance bearings using blood as the lubricant. Similar trends, i.e. increase in friction factor with reduction in diametral clearance, were found to be also the case using a combination of BS+CMC or BS+HA+CMC as lubricants having viscosities in the range 0.1-0.2 and 0.03-0.14 Pas, respectively. On the other hand, all the lubricants with lower viscosities in the range 0.001-0.0013 and 0.001-0.013 Pas for both BS+CMC and BS+HA+CMC, respectively, showed the opposite effect, i.e. caused an increase in friction factor with increase in diametral clearance. Another six large diameter (50mm nominal) BHR deflected prostheses with various clearances (~ 50-280μm after cup deflection) were friction tested in vitro in the presence of blood and clotted blood to study the effect of cup deflection on friction. It was found that the biological lubricants caused higher friction factors at the lower diametral clearances for blood and clotted blood as clearance decreased from 280μm to 50μm (after deflection). The result of this investigation has suggested strongly that the optimum clearance for the 50 mm diameter MOM BHR implants to be ≥150μm and <235μm when blood lubricant used, so as to avoid high frictions (i.e. avoid friction factors >0.2) and be able to accommodate a mixed lubrication mode and hence lower the risk of micro- or even macro-motion specially immediately after hip implantation. These suggested optimum clearances will also allow for low friction (i.e. friction factors of <0.2-0.07) and reasonable lubrication (dominantly mixed regime) for the likely cup deflection occurring as a result of press-fit fixation.
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Design of two-axis capacitive accelerometer using MEMSLee, Chun Ming 12 1900 (has links)
Approved for public release; distribution in unlimited. / MEMS technology is rapidly taking an important role in today's and future military systems. MEMS are able to lower the device size from millimeter to micrometer and maintain and sometimes surpass the performance of conventional devices. This thesis encompasses the knowledge acquired throughout the MEMS courses to design a two-axis capacitive accelerometer. The required acceleration and operating temperature range were Š50g in each axis and -40ʻC to +80 ʻC, respectively. The accelerometer was also needed to survive within a dynamic shocking environment with accelerations of up to 225g. The parameters of the accelerometer to achieve above specifications were calculated using lumped element approximation and the results were used for initial layout of it. A finite element analysis code (ANSYS) was used to perform simulations of the accelerometer under various operating conditions and to determine the optimum configuration. The simulated results were found to be within about 5% of the calculations indicating the validity of lumped element approach. The response of the designed accelerometer was 7 mV/g and with sensitivity of 1.3g at 3dB. It was also found that the accelerometer was stable in the desired range of operation including under the shock. Two axes sensing can be achieved using two identical accelerometers having their sensing axes perpendicular to each other. / Major, Taiwan Army
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The effect of clearance upon friction and lubrication of large diameter hip resurfacing prosthesis using blood and combinations of bovine serum with aqueous solutions of CMC and hyaluronic acid as lubricants.Afshinjavid, Saeed January 2010 (has links)
In real life, immediately after joint replacement, the artificial joint is actually bathed in blood
(and clotted blood) instead of synovial fluid. Blood contains large molecules and cells of size
~ 5 to 20 2m suspended in plasma and considered to be a non-Newtonian (pseudoplastic)
fluid with density of 1060 Kg/m3 and viscosity ~ 0.01 Pas at shear rates of 3000 s-1 (as
obtained in this work). The effect of these properties on friction and lubrication is not fully
understood and, so far to our knowledge, hardly any studies have been carried out regarding
friction of metal-on-metal bearings with various clearances in the presence of lubricants such
as blood or a fluid containing macromolecules such as hyaluronic acid (HA) which is a major
component of synovial fluid increasing its viscosity and lubricating properties. In this work,
therefore, we have investigated the frictional behaviour of a group of Smith and Nephew
Birmingham Hip Resurfacing implants with a nominal diameter of 50mm and diametral
clearances in the range ~ 80 2m to 300 2m, in the presence of blood (clotted and whole
blood), a combination of bovine serum (BS) with hyaluronic acid (HA) and carboxymethyl
cellulose (CMC, as gelling agent) adjusted to a range of viscosities (~0.001-0.2 Pas), and
bovine serum with CMC adjusted to a similar range of viscosities.
These results suggested that reduced clearance bearings have the potential to generate high
friction especially in the presence of blood which is indeed the in vivo lubricant in the early
weeks after implantation. Friction factors in higher clearance bearings were found to be lower
than those of the lower clearance bearings using blood as the lubricant. Similar trends, i.e.
increase in friction factor with reduction in diametral clearance, were found to be also the
case using a combination of BS+CMC or BS+HA+CMC as lubricants having viscosities in
the range 0.1-0.2 and 0.03-0.14 Pas, respectively. On the other hand, all the lubricants with
lower viscosities in the range 0.001-0.0013 and 0.001-0.013 Pas for both BS+CMC and BS+HA+CMC, respectively, showed the opposite effect, i.e. caused an increase in friction
factor with increase in diametral clearance.
Another six large diameter (50mm nominal) BHR deflected prostheses with various
clearances (~ 50-2802m after cup deflection) were friction tested in vitro in the presence of
blood and clotted blood to study the effect of cup deflection on friction. It was found that the
biological lubricants caused higher friction factors at the lower diametral clearances for blood
and clotted blood as clearance decreased from 2802m to 502m (after deflection).
The result of this investigation has suggested strongly that the optimum clearance for the 50
mm diameter MOM BHR implants to be ¿1502m and <2352m when blood lubricant used, so
as to avoid high frictions (i.e. avoid friction factors >0.2) and be able to accommodate a
mixed lubrication mode and hence lower the risk of micro- or even macro-motion specially
immediately after hip implantation. These suggested optimum clearances will also allow for
low friction (i.e. friction factors of <0.2-0.07) and reasonable lubrication (dominantly mixed
regime) for the likely cup deflection occurring as a result of press-fit fixation. / Smith & Nephew Orthopaedics Ltd.
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