Advanced propeller research

Recent results of aerodynamic and acoustic research on both single rotation and counterrotation propellers are reviewed. Data and analytical results are presented for three propellers: SR-7A, the single rotation design used in the NASA Propfan Test Assessment (PTA) flight program; CRP-X1, the initial 5+5 Hamilton Standard counterrotating design; and F7-A7, the 8+8 counterrotating G.E. design used in the proof of concept Unducted Fan (UDF) engine. In addition to propeller efficiencies, cruise and takeoff noise, and blade pressure data, off-design phenomena involving formation of leading edge vortexes are described. Aerodynamic and acoustic computational results derived from 3-D Euler and acoustic radiation codes are presented. Research on unsteady flows which are particularly important for understanding counterrotation interaction noise, unsteady loading effects on acoustics, and flutter or forced response is described. The first results of 3-D unsteady Euler solutions are illustrated for a single rotation propeller at angle of attack and for a counterrotation propeller. Basic experimental and theoretical results from studies on the unsteady aerodynamics of oscillating cascades are outlined

The Evolution of the Mexican-Born Workforce in the United States

This paper examines the evolution of the Mexican-born workforce in the United States using data drawn from the decennial U.S. Census throughout the entire 20th century. It is well known that there has been a rapid rise in Mexican immigration to the United States in recent years. Interestingly, the share of Mexican immigrants in the U.S. workforce declined steadily beginning in the 1920s before beginning to rise in the 1960s. It was not until 1980 that the relative number of Mexican immigrants in the U.S. workforce was at the 1920 level. The paper examines the trends in the relative skills and economic performance of Mexican immigrants, and contrasts this evolution with that experienced by other immigrants arriving in the United States during the period. The paper also examines the costs and benefits of this influx by examining how the Mexican influx has altered economic opportunities in the most affected labor markets and by discussing how the relative prices of goods and services produced by Mexican immigrants may have changed over time.

Contrasting the beam interaction characteristics of selected lasers with a partially stabilised zirconia (PSZ) bio-ceramic

Differences in the beam interaction characteristics of a CO2 laser, a Nd:YAG laser, a high power diode laser (HPDL) and an excimer laser with a partially stabilised zirconia (PSZ) bio-ceramic have been studied. A derivative of Beer-Lambert’s law was applied and the laser beam absorption lengths of the four lasers were calculated as 33.55 x 10-3 cm for the CO2 laser, 18.22 x 10-3 cm for the Nd:YAG laser, 17.17 x 10-3 cm for the HPDL and 8.41 x 10-6 cm for the excimer laser. It was determined graphically that the fluence threshold values at which significant material removal was effected by the CO2 laser, the Nd:YAG laser, the HPDL and the excimer laser were 52 J/cm2, 97 J/cm2, 115 J/cm2 and 0.48 J/cm2 respectively. The thermal loading value for the CO2 laser, the Nd:YAG laser, the HPDL and the excimer laser were calculated as being 1.55 kJ/cm3, 5.32 kJ/cm3, 6.69 kJ/cm3 and 57.04 kJ/cm3 respectively

The For-Profit Postsecondary School Sector: Nimble Critters or Agile Predators?

Private for-profit institutions have been the fastest growing part of the U.S. higher education sector. For-profit enrollment increased from 0.2 percent to 9.1 percent of total enrollment in degree-granting schools from 1970 to 2009, and for-profit institutions account for the majority of enrollments in non-degree granting postsecondary schools. We describe the schools, students, and programs in the for-profit higher education sector, its phenomenal recent growth, and its relationship to the federal and state governments. Using the 2004 to 2009 Beginning Postsecondary Students (BPS) longitudinal survey we assess outcomes of a recent cohort of first-time undergraduates who attended for-profits relative to comparable students who attended community colleges or other public or private non-profit institutions. We find that relative to these other institutions, for-profits educate a larger fraction of minority, disadvantaged, and older students, and they have greater success at retaining students in their first year and getting them to complete short programs at the certificate and associate degree levels. But we also find that for-profit students end up with higher unemployment and “idleness” rates and lower earnings six years after entering programs than do comparable students from other schools, and that they have far greater student debt burdens and default rates on their student loans.

Somerset 1800 - 1830: an inquiry into social and economic conditions

Not availabl

The development and characteristics of a hand-held high power diode laser-based industrial tile grout removal and single-stage sealing system

As the field of laser materials processing becomes ever more diverse, the high power diode laser (HPDL) is now being regarded by many as the most applicable tool. The commercialisation of an industrial epoxy grout removal and single-stage ceramic tile grout sealing process is examined through the development of a hand-held HPDL device in this work. Further, an appraisal of the potential hazards associated with the use of the HPDL in an industrial environment and the solutions implemented to ensure that the system complies with the relevant safety standards are given. The paper describes the characteristics and feasibility of the industrial epoxy grout removal process. A minimum power density of approximately 3 kW/cm2 was found to exist, whilst the minimum interaction time, below which there was no removal of epoxy tile grout, was found to be approximately 0.5 s. The maximum theoretical removal rate that may be achievable was calculated as being 65.98 mm2/s for a circular 2 mm diameter beam with a power density of 3 kW/cm2 and a traverse speed of 42 mm/s. In addition, the characteristics of the single-stage ceramic tile grout sealing are outlined. The single-stage ceramic tile grout sealing process yielded crack and porosity free seals which were produced in normal atmospheric conditions. Tiles were successfully sealed with power densities as low as 550 W/cm2 and at rates of up to 420 mm/min. In terms of mechanical, physical and chemical characteristics, the single-stage ceramic tile grout was found to be far superior to the conventional epoxy tile grout and, in many instances, matched and occasionally surpassed that of the ceramic tiles themselves

Job Queues and Wages: New Evidence on the Minimum Wage and Inter-Industry Wage Structure

This paper uses job applications- data to test the existence of non-competitive, ex-ante rents in the labor market. We first examine whether jobs that pay the legal minimum wage face an excessively of labor as measured by the number of job applications received for the most recent positions filled by the firs. The results indicate that openings for jobs that pay the minimum wage attract significantly more job applications than jobs that pay either more or less than the minimum wage. This spike in the job application rate distribution indicates that ex-ante rents generated for employees by an above market-level minimum wage do not appear to be completely dissipated by employer actions. The second part of the paper uses a similar approach to examine whether jobs in high-wage industries pay above market-clearing wage rates. We find a weak, positive relationship between inter-industry applications differentials and inter-industry wage differentials. In addition, our results indicate that employer size has a sizeable positive effect on the job application rate even after controlling for the wage rate. The paper considers several possible explanations for these findings.

How Much Do Immigration and Trade Affect Labor Market Outcomes?

macroeconomics, trade, labor markets, immigration