Kinetic isolation tether experiment

Progress was made on the analysis of tether damping and on experimentation of the control system on the laboratory simulator. The damping analysis considers the dynamics of a long tether connecting two spacecraft in Earth orbit, one of the spacecraft having dominant mass. In particular, it considers the material damping of the tether. The results show that, with properly chosen tether material and braiding structure, longitudinal vibration of the tethered system is well damped. A particularly effective method of implementing attitude control for tethered satellites is to use the tether tension force to generate control torques by moving the tether attach point relative to the satellite center of mass. A scaled, one dimensional laboratory simulation of the KITE mission was built and preliminary experiments of the proposed attitude control system were performed. The simulator was built to verify theoretical predictions of attitude controllability, and to investigate the technological requirements in order to implement this concept. A detailed description of the laboratory apparatus is provided, and in addition, the results of the preliminary experiments are presented and discussed

Preserving the Dignity of the Irish in Translations

Focusing on the Anglicization of town names in Brian Friel’s Translations, this article analyzes the significance of translation, beyond names as agents of linguistic imperialism and functions or symbols of identity. Using a Christian lens to demonstrate the intrinsic dignity signified in a name combined with a colonization case study in the Danish West Indies attesting to the injuries of denying a given name, the irreversible damage of translating names into a non-native language is clear. At the same time, imposing Anglicized names on the Irish community allows opportunities for resistance, such as continuing the private use of the Irish names, even if they cannot be spoken in the public sphere. The example of Translations illustrates how the radical translation of names traumatizes and injures the dignity of Irish persons, beyond linguistic imperialism and the rupture of identity

Could Cheese Be the Missing, Hard, Stable Currency to Fortify Self-Sufficiency of Pastoralist Communities?

Traditional pastoral existence in Africa has always necessitated close, sustainable interaction with a harsh natural environment. Pastoralists, such as the indigenous Parakuyo Maasai of Tanzania traditionally depend on fresh cow’s milk as a staple. They are among the few African ethnic groups that still live as small, socially intact associations close to nature. Unfortunately, fresh milk is difficult to store and inevitably, times of plenty fluctuate with the times of hunger that threaten cultural retreat. Milk storage is particularly challenging in an arid climate without refrigeration and at such times, survival takes precedence over prosperity. We describe an ongoing pilot project that has attempted to address these hardships, facilitate traditional subsistence and the economic autonomy of the Parakuyo Maasai. We proposed that a simple solution is cheese production. The “Maasai-cheese” project (www.vsf.at) was implemented in 2011 and instructs sustainable cheese production on the Maasai boma using locally sourced assets, combining Austrian experience of cheese production with Maasai experience of arid dairy farming. Anticipated gains for the Maasai are becoming realised: (i) Family incomes can be assured during hardship. During the dry season Zebu cattle do not produce enough milk that can be sold or exchanged. However, cheese produced and matured earlier can be sold at this time; (ii) Antibiotic abuse in cattle can be drastically decreased. When cheese is a valuable commodity there is a strong disincentive to treat cattle with antibiotics, which prevent fermentation. (iii) Cheese is a sought-after commodity in Africa. This pilot initiative is being well received as the demand for cheese in Africa is enormous. In particular, technical know-how has been a limiting factor until now

Precision tethered satellite attitude control

Tethered spacecraft possess unique dynamic characteristics which make them advantageous for certain classes of experiments. One use for which tethers are particularly well suited is to provide an isolated platform for spaceborne observatories. The advantages of tethering a pointing platform 1 or 2 km from a space shuttle or space station are that, compared to placing the observatory on the parent spacecraft, vibrational disturbances are attenuated and contamination is eliminated. In practice, all satellites have some requirement on the attitude control of the spacecraft, and tethered satellites are no exception. It has previously been shown that conventional means of performing attitude control for tethered satellites are insufficient for any mission with pointing requirements more stringent than about 1 deg. This is due mainly to the relatively large force applied by the tether to the spacecraft. A particularly effective method of implementing attitude control for tethered satellites is to use this tether tension force to generate control torques by moving the tether attach point relative to the subsatellite center of mass. A demonstration of this attitude control technique on an astrophysical pointing platform has been proposed for a space shuttle flight test project and is referred to as the Kinetic Isolation Tether Experiment (KITE)

Control Software for a High-Performance Telerobot

A computer program for controlling a high-performance, force-reflecting telerobot has been developed. The goal in designing a telerobot-control system is to make the velocity of the slave match the master velocity, and the environmental force on the master match the force on the slave. Instability can arise from even small delays in propagation of signals between master and slave units. The present software, based on an impedance-shaping algorithm, ensures stability even in the presence of long delays. It implements a real-time algorithm that processes position and force measurements from the master and slave and represents the master/slave communication link as a transmission line. The algorithm also uses the history of the control force and the slave motion to estimate the impedance of the environment. The estimate of the impedance of the environment is used to shape the controlled slave impedance to match the transmission-line impedance. The estimate of the environmental impedance is used to match the master and transmission-line impedances and to estimate the slave/environment force in order to present that force immediately to the operator via the master unit

Endangered Sustainable Innovation: Indigenous Milk Hygiene and Preservation Techniques by Maasai Too Valuable to Lose

The indigenous Parakuyo Maasai communities of Tanzania are traditional pastoralists who depend on fresh cow’s milk as a staple food. However, the arid climate and a lack of clean water challenge milk production and conventional milk hygiene practices. By conducting informational interviews in eight Parakuyo Maasai regions and 13 districts of Tanzania we sought to identify the key indigenous plants preferred and establish their traditional manner of use. A semi-structured questionnaire was designed to: (i) determine the plants used, (ii) the parts used, (iii) methods of preparation and utensil smoking, (iv) therapeutic applications and associated health benefits of these plants, and (v) alternative uses; that may suggest why they are used and preferred. Twenty plants were identified as being the most valuable, comprising predominantly hard wood trees and shrubs with strong aromas and astringent tastes suggestive of a role played by secondary metabolites. The most frequently mentioned plants, in order of preference, were: Zanthoxylum chalybeum (prickly ash; overall preference 26.6 %), Olea europaea subsp. africana (African wild olive; 11.9 %), Combretum molle (velvet bush willow; 11.4 %), Cordia ovalis/monoica (satin saucer berry; 9.5 %) and C. sinensis (oldoroko; 7.3 %). Many of these plants are also used medicinally by these pastoralists for a variety of infectious diseases, suggesting possible antimicrobial properties. Plant choices also tended to vary by local geography and the purpose to which the calabashes were assigned, e.g. old or new calabashes and milk stored for children or mothers. Nevertheless, the expertise of selecting these plants and their innovative applications is transmitted solely by the oral tradition. Further, climatic change is adversely affecting herbaceous habitats in these regions and inter-tribal territorial strife and land-grabs necessitate that the pastoralists remain nomadic. Unless we document and attempt to understand this old indigenous and sustainable hygiene know-how, it may be too late

Cross-platform validation of notional baseline architecture models of naval electric ship power systems

To support efforts in assessing the relative merit of alternative power system architectures for future naval combatants, the Electric Ship Research and Development Consortium (ESRDC) has developed notional baseline models for each of the primary candidate architectures currently considered, medium-voltage DC (MVDC), conventional 60 Hz medium-voltage (MVAC), and high-frequency medium-voltage (HFAC). Initial efforts have focused on the development of a consistent set of component models, of which the system models can be comprised, and the basic definition of the system models. The broader objectives of the consortium, however, go beyond the definition of the baseline models. The focus is on the process by which the models are implemented in software and validated, the process by which the performance of the disparate system models are objectively and quantitatively assessed and compared, and, ultimately, the process by which the relative merits of the architectures may be assessed. This paper focuses specifically on cross-platform component validation.Center for Electromechanic

Diaphragm Pump With Resonant Piezoelectric Drive

A diaphragm pump driven by a piezoelectric actuator is undergoing development. This pump is intended to be a prototype of lightweight, highly reliable pumps for circulating cooling liquids in protective garments and high-power electronic circuits, and perhaps for some medical applications. The pump would be highly reliable because it would contain no sliding seals or bearings that could wear, the only parts subject to wear would be two check valves, and the diaphragm and other flexing parts could be designed, by use of proven methods, for extremely long life. Because the pump would be capable of a large volumetric flow rate and would have only a small dead volume, its operation would not be disrupted by ingestion of gas, and it could be started reliably under all conditions. The prior art includes a number piezoelectrically actuated diaphragm pumps. Because of the smallness of the motions of piezoelectric actuators (typical maximum strains only about 0.001), the volumetric flow rates of those pumps are much too small for typical cooling applications. In the pump now undergoing development, mechanical resonance would be utilized to amplify the motion generated by the piezoelectric actuator and thereby multiply the volumetric flow rate. The prime mover in this pump would be a stack of piezoelectric ceramic actuators, one end of which would be connected to a spring that would be part of a spring-and-mass resonator structure. The mass part of the resonator structure would include the pump diaphragm (see Figure 1). Contraction of the spring would draw the diaphragm to the left, causing the volume of the fluid chamber to increase and thereby causing fluid to flow into the chamber. Subsequent expansion of the spring would push the diaphragm to the right, causing the volume of the fluid chamber to decrease, and thereby expelling fluid from the chamber. The fluid would enter and leave the chamber through check valves. The piezoelectric stack would be driven electrically to make it oscillate at the resonance frequency of the spring and- mass structure. This frequency could be made high enough (of the order of 400 Hz) that the masses of all components could be made conveniently small. The resonance would amplify the relatively small motion of the piezoelectric stack (a stroke of the order of 10 m) to a diaphragm stroke of the order of 0.5 mm. The exact amplification factor would depend on the rate of damping of oscillations; this, in turn, would depend on details of design and operation, including (but not limited to) the desired pressure rise and volumetric flow rate. In order to obtain resonance with large displacement, the damping rate must be low enough that the energy imparted to the pumped fluid on each stroke is much less than the kinetic and potential energy exchanged between the mass and spring during each cycle of oscillation. To minimize the power demand of the pump, a highly efficient drive circuit would be used to excite the piezoelectric stack. This circuit (see Figure 2) would amount to a special-purpose regenerative, switching power supply that would operate in a power-source mode during the part of an oscillation cycle when the excitation waveform was positive and in a power-recovery mode during the part of the cycle when the excitation waveform was negative. The circuit would include a voltage-boosting dc-to-dc converter that would convert between a supply potential of 24 Vdc and the high voltage needed to drive the piezoelectric stack. Because of the power-recovery feature, the circuit would consume little power. It should be possible to build the circuit as a compact unit, using readily available components