Evaluation of an operating MOD-OA 200 kW wind turbine blade

Operating loads and structural damage were monitored during operation of the MOD-OA electric generating system. The turbine was damaged locally between stations 48 and 125 after 2.8 million rotations. Loads due to degraded yaw stiffness and fretting at rib station 48 were identified as primary to this distress. The repaired blades operated an additional 4.8 million rotations without problems

Reaction control system augmentation for V/STOL aircraft

Advantages and problems associated with augmentation of reaction controls are discussed. The current status of compact ejector technology and the expected performance of known efficient designs for reaction control applications are presented

Hingeless rotor theory and experiment on vibration reduction by periodic variation of conventional controls

The reduction of the n per rev. pitch-, roll- and vertical vibrations of an n-bladed rotor by n per rev. sinusoidal variations of the collective and cyclic controls is investigated. The numerical results presented refer to a four-bladed, 7.5-foot model and are based on frequency response tests conducted under an Army-sponsored research program. The following subjects are treated: extraction of the rotor transfer functions (.073R hub flapping and model thrust versus servo valve command, amplitude and phase), calculation of servo commands (volts) required to compensate .073R hub flapping (3P and 5P) and model thrust (4P), evaluation of the effect of the vibratory control inputs on blade loads, and theoretical prediction of the root flapbending moments generated by 0 to 5P perturbations of the feathering angle and rotor angle of attack. Five operating conditions are investigated covering advance ratios from approximately 0.2 to 0.85. The feasibility of vibration reduction by periodic variation on conventional controls is evaluated

The Erotics of History

The Erotics of History challenges long-standing notions of sexuality as stable and context-free—as something that individuals discover about themselves. Rather, Donald L. Donham argues that historical circumstance, local social pressure, and the cultural construction of much beyond sex condition the erotic. Donham makes this argument in relation to the centuries-old conversation on the fetish, applied to a highly unusual neighborhood in Atlantic Africa. There, local men, soon to be married to local women, are involved in long-term sexual relationships with European men. On the African side, these couplings are motivated by the pleasures of cosmopolitan connection and foreign commodities. On the other side, Europeans tend to fetishize Africans’ race, while a few search to become slaves in master/ slave relationships. At its most wide ranging, The Erotics of History attempts to show that it is history, both personal and collective, in reversals and reenactments, that finally produces sexual excitement

Mathematics Tracking: Policy Brief

Tracking is a long-standing practice in schools. Students are often placed in tracks beginning in upper elementary or middle school. The tracks in which students are placed in earlier grades set them up for the mathematics courses they are able to take in high school. The number of mathematics tracks for students can differ from school to school, but the policy of having mathematics tracks is common throughout schools in the United States. This policy brief will discuss the arguments for and against mathematics tracking policies, implications for educators and policymakers, and future directions

The Erotics of History

The Erotics of History challenges long-standing notions of sexuality as stable and context-free—as something that individuals discover about themselves. Rather, Donald L. Donham argues that historical circumstance, local social pressure, and the cultural construction of much beyond sex condition the erotic. Donham makes this argument in relation to the centuries-old conversation on the fetish, applied to a highly unusual neighborhood in Atlantic Africa. There, local men, soon to be married to local women, are involved in long-term sexual relationships with European men. On the African side, these couplings are motivated by the pleasures of cosmopolitan connection and foreign commodities. On the other side, Europeans tend to fetishize Africans’ race, while a few search to become slaves in master/ slave relationships. At its most wide ranging, The Erotics of History attempts to show that it is history, both personal and collective, in reversals and reenactments, that finally produces sexual excitement

Island Land Loss in the Chesapeake Bay: A Quantitative and Process Analysis

The rates and processes of land loss were studied for seven islands in the Chesapeake Bay: Barren, Bloodsworth, Hooper, James, Poplar, Smith and South Marsh Islands. Rates and patterns of land loss were quantified for the years 1848 to 1987 with the Metric Mapping technique which utilizes digitized data from historical maps and vertical aerial photographs. Processes of land loss were determined through field surveys and correlated with environmental factors. Two distinct island types were identified which exhibited different, long-term patterns of land loss. Small, upland islands, termed the Northern Group, showed rapid land loss along the main stem of the Bay primarily due to wave action driven by the predominant westerly winds. Land loss appeared to accelerate during periods of high storm frequency. The long-term averaged land loss rate for Northern Group islands is 1.9 ha/yr. The averaged erosion rate on the western side of the islands is 4.9 m/yr, compared to 0.68 m/yr on the eastern side of the islands. In contrast, the large, marshy islands of the Southern Group experienced uniform marsh edge erosion and interior marsh degradation. The Southern Group islands lost land at an averaged rate of 5. 6 ha/yr, with an averaged rate of marsh edge erosion of 1.2 m/yr. Land loss appeared to be weakly correlated to storm frequency. Interior marsh loss was not quantified for this study, however, so this study provides an underestimation of total land loss of coastal wetlands