ALTERNATIVES TO THE LOCAL PROPERTY TAX FOR EDUCATIONAL FINANCE

Public Economics,

High-speed, self-acting shaft seal (circumferential type)

Shaft riding circumferential seal is used with turbine engines under high pressure conditions. Construction of seal is discussed and schematic diagram to show operations is provided

High speed, self-acting shaft seal

A high-speed, self-acting circumferential type shaft seal for use in turbine engines is disclosed. One or more conventional circumferential ring seals having a central aperture are mounted in a housing. In three of the four embodiments of the invention, a helical groove and one or more dam seals are cut in the inner cylindrical surface of the one or more ring seals. In a fourth embodiment, two or more lift pads are disposed in surface contact with the inner cylindrical surface of the seal rings. To the outside of the lift pads, two dam seals are cut in the inner cylindrical surface of two of the ring seals. In each of the embodiments, a net outward radial force was produced during rotation of the turbine causing the ring seals to lift out of contact with the turbine shaft to minimize wear of the ring seals

Nonelastomeric Rod Seals for Advanced Hydraulic Systems

Advanced high temperature hydraulic system rod sealing requirements can be met by using seals made of nonelastomeric (plastic) materials in applications where elastomers do not have adequate life. Exploratory seal designs were optimized for advanced applications using machinable polyimide materials. These seals demonstrated equivalent flight hour lives of 12,500 at 350 F and 9,875 at 400 F in advanced hydraulic system simulation. Successful operation was also attained under simulated space shuttle applications; 96 reentry thermal cycles and 1,438 hours of vacuum storage. Tests of less expensive molded plastic seals indicated a need for improved materials to provide equivalent performance to the machined seals

Tribological properties of graphite-fiber-reinforced, partially fluorinated polyimide composites

Graphite-fiber-reinforced polyimide (GFRPI) composites were formulated from three new partially fluorinated polyimides and three types of graphite fiber. Nine composites were molded into pins and evaluated in a pin-on-disk tribometer. Friction coefficients, wear rates, pin wear surface morphology, and transfer film formation were assessed at 25 and 300 C. Also assessed was the effect of sliding speed on friction. Wear was up to two orders of magnitude lower at 25 C and up to one order of magnitude lower at 300 C than with previously formulated NASA GFRPI composites

Low wear partially fluorinated polyimides

Tribological studies were conducted on five different polyimide solid bodies formulated from the diamine 2,2-bis 4-(4-aminophenoxy)phenyl hexafluoropropane (4-BDAF) and the dianhydrides pyromellitic acid (PMDS) and benzophenonetetracarboxylic acid (BTDA). The following polyimides were evaluated 4-BDAF/PMDA, 4-BDAF/BTDA, 4-BDAF/80 mole percent PMDA, 20 mole percent BTDA, 4-BDAF/60 mole percent BTDA. Friction coefficients, polyimide wear rates, polyimide surface morphology and transfer films were evaluated at sliding speeds of 0.31 to 11.6 m/s and at temperatures of 25 C to 300 C. The results indicate that the tribological properties are highly dependent on the composition of the polyimide and on the experimental conditions. Two polyimides were found which produced very low wear rates but very high friction coefficients (greater than 0.85) under ambient conditions. They offer considerable potential for high traction types of application such as brakes

New circumferential seal design concept using self-acting lift geometries

Seal operating temperatures, leakage (pressurizing gas flow), torque, and wear of a conventional circumferential shaft seal were measured and compared to those of a conventional seal modified to have self-acting lift geometries. Both seal types had a 2.625-in diameter bore and were operated at a sliding velocity of 150 ft/sec with differential pressures ranging from 0 to 100 psi. Results of this investigation show that the self-acting seal operated at lower bulk carbon temperatures with half the torque and approximately one-tenth the wear of the conventional seal. Seal leakage of the self-acting seal was of order of 0.04 scfm for pressures above 60 psi which is well within the accepted range for gas turbine engine applications

Boundary lubrication and thermal stability studies with five liquid lubricants in nitrogen to 400 C

Steel friction and wear tests in nitrogen with paraffinic resins, synthetic paraffinic oil, glycol, and ester lubricants including thermal stability at high temperature

Anti Quorum Sensing Activity of Kayu Manis Leaves Extracts (Cinnamomun Burmannii Ness. Ex Bl.) Against Pseudomonas Aeruginosa

Quorum sensing is a communication system among bacterial cells which correlates with biofilm formation. Biofilm can protect bacteria from environment including antibiotic of which can cause higher antibiotic concentration of 100 up to 1000 times. Inhibition of quorum sensing is expected to inhibit the biofilm formation. The cinnamon bark (Cinnamomum burmanii Ness. Ex Bl.) has been known to have antibacterial and antibiofilm activities. Leaves are available abundantly which urges a research to find out the activity as anti quorum sensing against Pseudomonas aeruginosa. The succesive maceration of dried pulverized leaves produced hexane, ethyl acetate, and methanol extracts. Antibacterial activity was observed by microdillution method with MTT assay. Afterwards, the active extract was examined for anti quorum sensing activity by diffusion method in cetrimide Agar. Quorum sensing activity was shown by dark zone (opaque) growth around sample application, observed under UV light of 366 nm. TLC bioautography method was done to observe the active spots by using silica gel F254 as the stationary phase, chloroform-methanol (6:1 v/v) as the mobile phase, loading sample used was 1.25 mg and 30 min of plate contact duration. The ethyl acetate extract inhibited growth of P. aeruginosa with shown by MIC at 8 µg/µL Quorum sensing as well as growth inhibition activities were observed at loading samples 12,5 and 25 mg/wells, while at 6,25 mg the extract only exhibited quorum sensing inhibition. Presences of substances having phenolic, flavonoid, alkaloid and aldehyde/keton as functional groups were detected by TLC method of the extract but no active spot identified on bioautography

Motor Truck Transportation in Western South Dakota

Motor truck transportation has sprung into prominence with great rapidity during the past few years. Likewise the problems of this type of transportation of agricultural commodities have taken on increasing importance during this period. This report deals with only one phase of the problem of transportation of agricultural commodities in the state of South Dakota. The report logically divides itself into three parts. The first deals with the increasing use of motor trucks in the area covered by the study. The second part deals with a somewhat detailed study of the hauling of crops in the trade territory of one of our typical western South Dakota market centers. Here we get an idea of the distance that grain must move and the proportions hauled by various agencies engaged in the hauling of grain. The third part deals with some of the problems of commercial hauling or trucking in this same area. The area covered by the first and third parts of this study consists of nine counties located west of the Missouri river, namely: Butte, Haakon, Harding, Jackson, Jones, Mellette, Perkins, Tripp and Ziebach. Figure 1 will show the location of these counties. They were chosen to represent the various combinations of grazing and farming enterprises which are Common in this territory. These vary all the way from much grazing and little farming in the northwest counties to much farming and relatively little grazing in the southeast counties. For the second part the centrally located town of Philip, Haakon County was chosen. The reasons for choosing Philip were partly because of this central location in the area, it appearing to be a more or less typical town, and partly because of the fact that material for study was to be found in an unusually accessible form. The material for the section dealing with the growth of trucking was gathered largely from the records of the South Dakota Motor Vehicle department. These were supplemented by material gathered from the county treasurers of most of the nine counties involved. Material for the portion dealing with commercial hauling was obtained from the records of the South Dakota Railroad commission. The material for the study of the Philip market area was obtained from records made accessible by the Farmers Union Marketing association of that city. These records gave detailed information concerning every load of grain hauled into the elevator for the crop year 1929-1930. A number of other elevators in the larger area also gave valuable data for their own market areas