Note: Landmark Preservation: The Problem of the Tax-Exempt Owner

This Note examines the effectiveness of the 1965 New York City Landmark Preservation Act with respect to its ability to confront the conflict between the desire to preserve the city\u27s history and the individual\u27s constitutional right to use and control her own property, with particular attention to the unprotected status of the tax-exempt property owner. The author argues that the legislation fails to mesh the two conflicting goals of preservation and just compensation to property owners. She suggests that in order to do so, perhaps a different standard of value should be placed on landmark preservation that focuses on non-economic measures, such as aesthetics and historical value. Finally, she concludes that the Landmarks Act will never work unless the community and the courts decide that the community is being served by preservation

Materials selection and design of microelectrothermal bimaterial actuators

A common form of MEMS actuator is a thermally actuated bimaterial, which is easy to fabricate by surface micromachining and permits out of plane actuation, which is otherwise difficult to achieve. This paper presents an analytical framework for the design of such microelectrothermal bimaterial actuators. Mechanics relationships for a cantilever bimaterial strip subjected to a uniform temperature were applied to obtain expressions for performance metrics for the actuator, i.e., maximum work/volume, blocked (force) moment, and free-end (displacement) slope. Results from finite-element analysis and closed form relations agree well to within 1%. The optimal performance for a given pair of materials and the corresponding thickness ratio were determined. Contours of equal performance corresponding to commonly used substrates (e.g., Si, SiO2) were plotted in the domain of governing material properties (thermal expansion coefficient and Young's modulus) to identify candidate materials for further development. These results and the accompanying methodology provide a rational basis for comparing the suitability of "standard" materials for microelectrothermal actuators, as well as identifying materials that might be suitable for further research

Low force electrical switching using gold coated vertically aligned multi-walled carbon nanotubes surfaces

Gold coated vertically aligned multi-walled carbon-nanotubes (Au/MWCNT) surfaces are investigated to determine the electrical contact performance under low force conditions with repeated load cycling. The multi-walled CNT's are synthesized on silicon planar and sputter coated with a gold film. These planar surfaces are mounted on the tip of a PZT actuator and mated with a coated Au hemispherical probe. The load is typical of MEMs devices, with a 4V supply, 1 and 10mA current, and applied force of 1mN. The contact resistance (Rc) is monitored with the repeated loading cycles (over 1000 and a million cycle) to determine reliability and durability testing. The surfaces are compared with a reference Au-Au contact under the same experimental conditions. This study shows the potential for the application of CNT surfaces as an interface in low force electrical contact applications

Gold coated carbon nanotube surfaces as low force electrical contacts for MEMS devices: part 1

An experimental investigation of a gold coated vertically aligned carbon nanotube surfaces is undertaken to determine the limits of the electrical contact performance over a large number of switching cycles under low force conditions and with current loading (1mA-50mA at 4V). The multi-walled CNT’s (MWCNT’s) are synthesized on a silicon planar and sputter coated with a gold film. The planar surfaces are mounted on the tip of a PZT actuator and mated with a coated Au hemispherical probe. The electrical load is selected to reflect typical MEMs relay loads with a 4V supply, 1 and 10mA current load with an applied force of 1mN. The surfaces tested maintain a stable contact resistance over 106 switching cycles. To determine the limits, the contact force is increased to 3mN under dry circuit conditions and the current increased at the 1mN load to 20mA-50mA. The surfaces are compared with a reference Au-Au contact under the same experimental conditions. For the surfaces investigated the current loading limit was determined to be 20mA where the contacts failed after 50x106 cycles

TDRSS S-shuttle unique receiver equipment

Beginning with STS-9, the Tracking and Date Relay Satellite system (TDRSS) will start providing S- and Ku-band communications and tracking support to the Space Shuttle and its payloads. The most significant element of this support takes place at the TDRSS White Sands Ground Terminal, which processes the Shuttle return link S- and Ku-band signals. While Ku-band hardware available to other TDRSS users is also applied to Ku-Shuttle, stringent S-Shuttle link margins have precluded the application of the standard TDRSS S-band processing equipment to S-Shuttle. It was therfore found necessary to develop a unique S-Shuttle Receiver that embodies state-of-the-art digital technology and processing techniques. This receiver, developed by Motorola, Inc., enhances link margins by 1.5 dB relative to the standard S-band equipment and its bit error rate performance is within a few tenths of a dB of theory. An overview description of the Space Shuttle Receiver Equipment (SSRE) is presented which includes the presentation of block diagrams and salient design features. Selected, measured performance results are also presented

The influence of toughening-particles in CFRPs on low velocity impact damage resistance performance

The role of particle-toughening for increasing impact damage resistance in carbon fibre reinforced polymer (CFRP) composites was investigated. Five carbon fibre reinforced systems consisting of four particle-toughened matrices and one system containing no toughening particles were subjected to low velocity impacts ranging from 25 J to 50 J to establish the impact damage resistance of each material system. Synchrotron radiation computed tomography (SRCT) enabled a novel approach for damage assessment and quantification. Toughening mechanisms were detected in the particle-toughened systems consisting of particle–resin debonding, crack-deflection and crack-bridging. Quantification of the bridging behaviour, increase in crack path length and roughness was undertaken. Out of the three toughening mechanisms measured, particle systems exhibited a larger extent of bridging suggesting a significant contribution of this toughening mechanism compared to the system with no particle

Fluidic packaging of microengine and microrocket devices for high pressure and high temperature operation

The fluidic packaging of Power MEMS devices such as the MIT microengine and microrocket requires the fabrication of hermetic seals capable of withstanding temperature in the range 20-600/spl deg/C and pressures in the range 100-300 atm. We describe an approach to such packaging by attaching Kovar metal tubes to a silicon device using glass seal technology. Failure due to fracture of the seals is a significant reliability concern in the baseline process: microscopy revealed a large number of voids in the glass, pre-cracks in the glass and silicon, and poor wetting of the glass to silicon. The effects of various processing and materials parameters on these phenomena were examined. A robust procedure, based on the use of metal-coated silicon substrates, was developed to ensure good wetting. The bending strength of single-tube specimens was determined at several temperatures. The dominant failure mode changed from fracture at room temperature to yielding of the glass and Kovar at 600/spl deg/C. The strength in tension at room temperature was analyzed using Weibull statistics; these results indicate a probability of survival of 0.99 at an operational pressure of 125 atm at room temperature for single tubes and a corresponding probability of 0.9 for a packaged device with 11 joints. The residual stresses were analyzed using the method of finite elements and recommendations for the improvement of packaging reliability are suggested

MEMS Materials and Processes: a research overview

An overview is provided of materials and processes research currently being conducted in support of MEMS device design at MIT. Underpinning research is being conducted in five areas: room temperature strength characterization, elevated temperature strength characterization, processing of Si/SiC hybrid structures, modeling of wafer bonding processes and development of high temperature fluid interconnections. Emphasis is placed on the key areas of materials science and engineering.Singapore-MIT Alliance (SMA

Space Launch System: SLS CubeSats, Now and the Future

No abstract availabl

Comparison studies of the mechanistic formation of polyhalogentaed dibenzo-p-dioxins and furans from the thermal degradation of 2-bromophenol and 2-chlorophenol

Emissions of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) and polybrominated dibenzo-p-dioxins and furans (PBDD/Fs) from hazardous waste incinerators, and many other sources for combustion have been considered environmentally hazardous and a major health threat. Recently, a growing number of materials containing brominated hydrocarbons, commonly used flame retardants, have been disposed in municipal and hazardous waste incinerators. This results in the increased potential for formation of PBDD/Fs and other hazardous combustion by-products. In contrast to chlorinated hydrocarbons, the reactions of brominated hydrocarbons have been studied only minimally. In fact, studies have shown that brominated phenols form higher yields of PBDD/Fs than the analogous chlorinated phenols form PCDD/Fs. For this study, the individual homogeneous, gas-phase oxidative and pyrolytic thermal degradations of 2-bromophenol and 2-chlorophenol were studied in a 1 cm i.d., fused silica flow reactor at a concentration of 88 ppm, with a reaction time of 2.0 s, and over a temperature range of 300 to 1000°C. In addition, 50:50 mixture of 2-chlorophenol and 2-bromophenol with a combined concentration of 88 ppm was studied under similar conditions. Also in order to compare previous work with 2-chlorophenol, the surface catalyzed gas-phase reactions for 2-bromophenol to form PBDD/Fs are described over a temperature range from 250 to 550°C. The results are compared and contrasted with each other in order to understand the roles oxygen, chlorine and bromine play in the formation of PCDD/Fs and PBDD/Fs. Reaction pathways to PCDD/F and PBDD/F products as well as all other products detected are proposed that are consistent with the experimental data for each condition. The presence of oxygen increases the formation of PBDFs and PCDFs. Presence of bromine increases the concentration of Cl radicals which in turn increases chlorination and formation of 4,6-dichlorodibenzofuran (4,6-DCDF). However the yields of the PCDFs and PBDFs are considerably less with the presence of both bromine and oxygen. The pool of ·OH and concentration of the chlorine atoms is reduced and thus prevents these furans from becoming major products