Calibration of an instrument to calibrate accelerometers

The purpose of this research was to calibrate an instrument with which an accelerometer could be calibrated accurately. The instruments used were a piezoelectric shaker and a modified Michelson interferometer together with necessary electronic equipment. This equipment was used to calibrate a Kistler Model 808A accelerometer. Weight was added to the shaker in the second part of this experiment in order to determine its effect on the amplitude and frequency of oscillation of the shaker. Results show that this instrument may be used to calibrate an accelerometer quite accurately. The weight added to the shaker will effect only the amplitude of vibration and not the frequency of oscillation --Abstract, page ii

A study of the dynamic loading of hydrodynamically lubricated journal bearings

The analytical and experimental investigation presented here examined the response of a full journal bearing to a unidirectional dynamic load. Frequency response of the bearing at different eccentricity ratios was investigated. It was concluded that the response of the bearing varies with eccentricity. The experimental data obtained was compared to an analytical model which considered inertial, damping, and elastic characteristics of the lubricant film. An investigation of film pressure revealed that the pressure due to journal center acceleration is smaller than the hydrodynamic and squeeze-film pressures --Abstract, page 1

Predicting Natural Frequencies Of A Hydrodynamically Lubricated Journal Bearing With Constant Oil Supply Pressure

The analytical and experimental investigations reported here deal with the natural frequencies and system behavior of a full journal bearing subjected to a small sinusoidal load superimposed on a large unidirectional static load. The analysis, verified by experimentation, shows that the bearing can be regarded as two independent second-order systems acting perpendicular to each other. The variable coefficients of the equations of motion cause the bearing to behave as an underdamped system for low values of static eccentricity ratio to, and as an overdamped system for intermediate values of to. The bearing tends to be unstable above a particular to. Further analysis is needed to determine the effects resulting from changing the oil inlet pressure. © 1976 by ASME

Land subsidence along the Texas Gulf Coast due to oil and gas withdrawal

Land subsidence caused by groundwater withdrawal in the Houston-Galveston region is a well-documented phenomenon. Subsidence of up to 3m (10ft) has been calculated in the region since 1905. Hydrocarbon withdrawal is a plausible cause of subsidence where groundwater withdrawal has diminished and significant petroleum production has occurred for over 70 years. Sixteen fields were investigated by acquiring reservoir bottom hole pressure data (BHP) near bore-hole extensometers set up by the Harris-Galveston Coastal Subsidence District (HGCSD). All reservoirs were found to be well below hydrostatic pressure; a few of them were underpressured even before production began showing a possible hydraulic connection between fields. BHP data was used in a reservoir model and a boundary clay reservoir model to calculate subsidence. Subsidence under these fields is predicted to be as high as 0.30 m (~1.00 ft) in a nine-year period or 33.33 mm yr⁻¹ (1.3 in yr⁻¹) at the Goose Creek field and as low as 0.007 m (0.023 ft) in a twenty-year period or 0.33 mm yr⁻¹ (0.01 in yr⁻¹) at the Gillock field. Elevation benchmark data used in producing a cross section of a line of oil fields show connection of subsidence bowls above fields on two scales: A smaller local scale subsidence bowl on the order of 5 km (3.1 mi) and a more regional subsidence bowl on the order of 40 km (24.9 mi). Point estimation of the contribution to total subsidence from petroleum production and groundwater withdrawal show that the majority of the subsidence occurring presently in Harris and Galveston counties is from oil and gas withdrawal. Effects from clay equilibration caused by previous groundwater pumping were interpreted to be minimal. Implications of this study are: 1) hydrocarbon production, although not the major contributor to most land surface subsidence in this area, is significant and 2) depressurization and subsequently subsidence from oil and gas fields may be regional, connecting neighboring fields. This is inferred from the fact that some fields were already underpressured before production began in addition to benchmark data showing connection of subsidence bowls.Geological Science

Model based optimization for auto body dimensional control in design and assembly.

The focus of automobile consumers has forced manufacturers to increase efforts on quality improvement. One initiative at the forefront has been the improvement of dimensional relationships in the body build. Traditionally, statistical process control (SPC) has been used to monitor the process performance. However, the automobile assembly process is an information-intense process that overwhelms a sampling-based process control strategy such as SPC. Therefore, a model based approach to determine process adjustments is presented for two types of process improvement strategy: (1) run-by-run process adjustments and (2) individual cycle process adjustments. Also, a model for sheet metal joint design evaluation is presented as a model based evaluation technique. Run-by-run process adjustments are changes to a manufacturing process that are made on intervals called runs. Two models are developed in this dissertation for the purpose of run-by-run adjustments: (1) single input single output and (2) multiple input multiple output processes. The process performance data from the current run of production is used by the run-by-run optimization model to determine the adjustments necessary to keep the process on target. The results of the presented models clearly show an improvement in the number of parts produced outside specifications for the presented case studies. The second method of process adjustment is an individual cycle process adjustment model. Two models are presented that determine the necessary process adjustments for each individual assembly sequence, based on the data gathered from the incoming material. The two processes that are modeled in this dissertation are for the (1) sheet metal joining process and (2) multiple panel fitting operation. The goal in both presented models is to minimize the dimensional deviation of the assembly. Results from both models show that the models determined the necessary process adjustments to minimize the dimensional deviations. An added application of the individual cycle process adjustment model for sheet metaljoining is a design for manufacturability tool for sheet metal joint design. This work is a tool that can be used to isolate problem joints in a sheet metal assembly sequence. Problem joints are joints in an assembly sequence that are not robust to the incoming material dimensional deviation. Therefore, their isolation can be used as an indicator of a need to redesign the joints. Results from the examples given demonstrate the capabilities of the presented techniques.Ph.D.Applied SciencesAutomotive engineeringIndustrial engineeringMechanical engineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/130029/2/9712002.pd

Putative paraneoplastic pemphigus and myasthenia gravis in a cat with a lymphocytic thymoma

BackgroundParaneoplastic pemphigus (PNP) is a rare and severe autoimmune blistering skin disease of humans. It is associated mainly with haematopoietic neoplasia and a unique autoantibody profile. At this time and in animals, PNP has only been reported in dogs.ObjectivesTo report clinical, histological and immunological findings in a cat with suspected thymoma-associated PNP.AnimalAn 8-year-old female spayed Himalayan cat.ResultsThe cat presented with a thoracic mass diagnosed as a lymphocytic thymoma. Two weeks postremoval, the cat developed myasthenia gravis, which was controlled with prednisolone and pyridostigmine. The myasthenia gravis resolved, but the cat developed severe cutaneous erosions and ulcers primarily affecting the caudal ventral abdomen and perineum, but also the ventral chest, axillae and medial pinnae. Histopathological analysis revealed changes consistent with pemphigus vulgaris and erythema multiforme, a combination of lesions highly suggestive of PNP. Direct immunofluorescence revealed intercellular epidermal IgG deposition in the lower epidermis, especially in areas of suprabasal clefts. Indirect immunofluorescence revealed antikeratinocyte IgG to basal keratinocytes and bladder epithelial cells. Immunological results supported a diagnosis of PNP. Skin lesions were treated with prednisolone and chlorambucil and, after clinical remission was obtained, the drugs were tapered and eventually discontinued without further recurrence of skin lesions.Conclusions and clinical importanceIn this cat, clinical, microscopic and immunological findings were consistent with a diagnosis of PNP, with thymoma being the suspected cause.Peter B. Hill, Phil Brain, David Collins, Steve Fearnside and Thierry Olivr