Thesis (M.A.A.S.) -- Air University, 2004. / Title from PDF title page (viewed on April 23, 2009). "June 2004." Includes abstract. Includes bibliographical references (leaves 88-94).

No description available.

No description available.

Thesis (Ph. D.)--Johns Hopkins University, 2006. / Vita. Includes bibliographical references (p. 374-406).

This thesis presents the controller design and implementation of a high-precision 6-degree-of-freedom (6-DOF) magnetically levitated (maglev) positioner. This high-precision positioning system consists of a novel concentrated-field magnet matrix and a triangular single-moving part that carries three 3-phase permanent-magnet linear-levitation-motor armatures. Since only a single levitated moving part, namely the platen, generates all required fine and coarse motions, this positioning system is reliable and low-cost. Three planar levitation motors based on the Lorentz-force law not only generate the vertical force to levitate the triangular platen but control the platen??s position and orientation in the horizontal plane. All 6-DOF motions are controlled by magnetic forces only. The platen is regarded a pure mass system, and the spring and damping coefficients are neglected except for the vertical directions. Single-input single-output (SISO) digital lead-lag controllers are designed and implemented on a digital signal processor (DSP). This 6-DOF fully magnetically levitated positioner has a total mass of 5.91 kg and currently exhibits a 120 mm ?? 120 mm travel range. This positioner is highly suitable for semiconductor-manufacturing applications such as wafer steppers. Several experimental motion profiles are presented to demonstrate the maglev stage??s capability of accurately tracking any planar and 3-D paths.

The goal of this thesis is to develop a novel polishing tool system, which can be attached to a CNC machine tool and execute a precision polishing job for an axially symmetric free surface. The precision polishing job is to remove the error surface profile, left by the previous machining process, on the work to improve its form precision. The system mainly includes a mechanism of 3 degrees of freedom, a misalignment compensator mounted on the mechanism, and an oscillation-free connector between tool and driver. The mechanism was designed to meet the required motions of tool trajectories. These motions are to assure the tool can play three specific functions. The first one is to keep the tool axis maintain a constant angle with the normal of polished surface. The second one is to control the wear rate distribution of tool to reduce the effect of tool wear on polishing rate. The final one is to achieve the goal of uniform polishing quality at every spot of polished surface. The conceptual design of this mechanism is done based on a strategy of problem decomposition. The misalignment compensator is to reduce the effect of tool misalignment on the variation of polishing rate. The compensator allows a translational motion and is constrained by a spring. When the tool is mounted on the compensator, the study will show that with a proper spring constant the effect of tool misalignment can be significantly reduced. The study will indicate that the smaller the tool mass is the higher the compensation efficiency can be. The oscillation-free connector is to separate the tool and its driver so that the mass of driver is not included in tool, while the driving function retains. It is composed of two parts. One part is connected to tool and the other one is mounted on driver. These two parts are not joined together by any mean. However, the motions of two parts will interfere with each other. Thus, the driving function between tool and drive can be maintained. It is noted that the vibration of driver can be successfully isolated from the tool if a soft material is attached to one part.

This thesis presents the controller design and implementation of a high-precision 6-degree-of-freedom (6-DOF) magnetically levitated (maglev) positioner. This high-precision positioning system consists of a novel concentrated-field magnet matrix and a triangular single-moving part that carries three 3-phase permanent-magnet linear-levitation-motor armatures. Since only a single levitated moving part, namely the platen, generates all required fine and coarse motions, this positioning system is reliable and low-cost. Three planar levitation motors based on the Lorentz-force law not only generate the vertical force to levitate the triangular platen but control the platen??s position and orientation in the horizontal plane. All 6-DOF motions are controlled by magnetic forces only. The platen is regarded a pure mass system, and the spring and damping coefficients are neglected except for the vertical directions. Single-input single-output (SISO) digital lead-lag controllers are designed and implemented on a digital signal processor (DSP). This 6-DOF fully magnetically levitated positioner has a total mass of 5.91 kg and currently exhibits a 120 mm ?? 120 mm travel range. This positioner is highly suitable for semiconductor-manufacturing applications such as wafer steppers. Several experimental motion profiles are presented to demonstrate the maglev stage??s capability of accurately tracking any planar and 3-D paths.

Currently, the imprint lithography steppers are designed to only pattern one field of 26 x 33 mm at a time. This choice is based on the desire to mix-and-match to the standard optical lithography tools whose field size is also 26 x 33 mm. Throughput can be increased if more than one field can be imprinted simultaneously. The problem with adding a field to the imprinting template is that each field has overlay errors associated with it that are created when the template is manufactured and when the corresponding prior field is manufactured on the wafer. The current process is able to correct these template and wafer overlay errors using a precision stage and actuators that elastically deform the template. The same method cannot be used when there are two fields because the fields are not independent and interact with each other. Correcting the errors in one of the fields tend to increase the error in the second field. vii In this thesis, a new control method has been created to account for the dependent motion. A new template concept was also created to try to limit the interaction between the two fields. The new control algorithm was tested in simulation to see if it could correct the current 1-field setup as well as the new concept of having more than one field on a template. The control algorithm was also used to test applications where the overlay errors in only one direction need to be corrected. The control algorithm was tested on a solid single field template, the baseline case, and was able to achieve 1.3 nm overlay, which is consistent with the current method. The algorithm was then tested on the dual field concepts. The range of alignment errors needed to get 5 nm overlay are too tight for current manufacturing but the compliant concept did have more relaxed ranges than the solid dual field template. With more research, the compliant template concept might be changed to allow for wider ranges. The tests with correction in only one direction had promising data that should be investigated further. / text

Quality Control (QC) reference materials are widely used in microbiology to demonstrate the efficacy of testing methods and culture media. The current method for preparation of QC materials is by serial dilution of a microbial broth culture to obtain a suspension that contains an estimated number of colony forming units (cfu). Commercial reference material products are available with dried microbial cells, however, the numbers of cells are variable between batches as the production processes are reliant on cell suspensions of estimated cell number. This study developed a method to produce precise microbial reference materials with a accurate number of viable cells. Flow cytometry was used to count and dispense precise numbers of cells into a single droplet of fluid. The droplets were then mixed with a lyoprotectant solution and subjected to freeze-drying. The resultant freeze-dried pellets showed consistent average cfu counts between 28-33 cfu with a standard deviation < 3 cfu. The freeze-drying methodology and developed conditions of cell growth enabled > 90% of the cells to survive freeze-drying and remain viable for one year at a storage temperature below -18??C. The methodology for the production of freeze-dried pellet was applied to a range of genera including, different E. coli strains, Gram positive bacteria such as Listeria and Staphylococcus, the yeast Candida albicans and a spore-producing Bacillus cereus. The precision of cell numbers was comparable between different microbial genera and strains and a consistent standard deviation below 3 cfu was achieved. The same freeze-dried pellet method was used for the different micro-organisms, except for changes to preparation of cell suspensions. Different methods of broth culture were developed to ensure freeze-dried cell survival. A measurement of method reproducibility was obtained when 99 batches of pellets were produced, and within batch and between batch variation was determined.

Quality Control (QC) reference materials are widely used in microbiology to demonstrate the efficacy of testing methods and culture media. The current method for preparation of QC materials is by serial dilution of a microbial broth culture to obtain a suspension that contains an estimated number of colony forming units (cfu). Commercial reference material products are available with dried microbial cells, however, the numbers of cells are variable between batches as the production processes are reliant on cell suspensions of estimated cell number. This study developed a method to produce precise microbial reference materials with a accurate number of viable cells. Flow cytometry was used to count and dispense precise numbers of cells into a single droplet of fluid. The droplets were then mixed with a lyoprotectant solution and subjected to freeze-drying. The resultant freeze-dried pellets showed consistent average cfu counts between 28-33 cfu with a standard deviation < 3 cfu. The freeze-drying methodology and developed conditions of cell growth enabled > 90% of the cells to survive freeze-drying and remain viable for one year at a storage temperature below -18??C. The methodology for the production of freeze-dried pellet was applied to a range of genera including, different E. coli strains, Gram positive bacteria such as Listeria and Staphylococcus, the yeast Candida albicans and a spore-producing Bacillus cereus. The precision of cell numbers was comparable between different microbial genera and strains and a consistent standard deviation below 3 cfu was achieved. The same freeze-dried pellet method was used for the different micro-organisms, except for changes to preparation of cell suspensions. Different methods of broth culture were developed to ensure freeze-dried cell survival. A measurement of method reproducibility was obtained when 99 batches of pellets were produced, and within batch and between batch variation was determined.