Flexure based mounts for sensitive payloads : a management and engineering study

Thesis (S.M. and S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.Includes bibliographical references (p. 51-52).With the cooperation of the Los Alamos National Laboratory and the Massachusetts Institute of Technology, an investigative and design study was performed to examine the history of the W80- 0 Area Aft Mount, understand its performance, and explore potential new designs. Simultaneously, professional and technical enhancement of the author was achieved. The historical organization of LANL influences the design space for this project, and understanding those relationships provides insight into concept generation and selection. In addition, the current organizational structure within the laboratory as well as with its customers provides additional constraints that must be managed technically. The new design concepts attempt to simulate the nonlinear load vs. displacement characteristics of the previously employed B3223 cellular silicone Pad Mount. New concepts separate the spring and damping characteristics of the cellular silicone into separate component parts. This uncoupled method should allow the new designs increased variability and control with respect to matching original Aft Area Mount performance in shock mitigation and deflection limiting.by Daniel K. Moon.S.M.and S.B

Introduction to Using the Window System

This document is a draft copy of a portion of the Lisp Machine window system manual. It is being published in this form now to make it available, since the complete window system manual is unlikely to be finished in the near future. The information in this document is accurate as of system 67, but is not guaranteed to remain 100% accurate. To understand some portions of this document may depend on background information which is not contained in any published documentation. This paper is a portion of a document which will explain how a programmer may make use of and extend the facilities in the Lisp machine known collectively as the Window System.MIT Artificial Intelligence Laborator

Tell Khaiber: An administrative centre of the Sealand period

Excavations at Tell Khaiber in southern Iraq by the Ur Region Archaeological Project have revealed a substantial building (hereafter the Public Building) dating to the mid-second millennium b.c. The results are significant for the light they shed on Babylonian provincial administration, particularly of food production, for revealing a previously unknown type of fortified monumental building, and for producing a dated archive, in context, of the little-understood Sealand Dynasty. The project also represents a return of British field archaeology to long-neglected Babylonia, in collaboration with Iraq's State Board for Antiquities and Heritage. Comments on the historical background and physical location of Tell Khaiber are followed by discussion of the form and function of the Public Building. Preliminary analysis of the associated archive provides insights into the social milieu of the time. Aspects of the material culture, including pottery, are also discussed

Age-associated reduction of cell spreading induces mitochondrial DNA common deletion by oxidative stress in human skin dermal fibroblasts: implication for human skin connective tissue aging

Abstract Background Reduced cell spreading is a prominent feature of aged dermal fibroblasts in human skin in vivo. Mitochondrial DNA (mtDNA) common deletion has been reported to play a role in the human aging process, however the relationship between age-related reduced cell spreading and mtDNA common deletion has not yet been reported. Results To examine mtDNA common deletion in the dermis of aged human skin, the epidermis was removed from full-thickness human skin samples using cryostat. mtDNA common deletion was significantly elevated in the dermis of both naturally aged and photoaged human skin in vivo. To examine the relationship between age-related reduced cell spreading and mtDNA common deletion, we modulated the shape of dermal fibroblasts by disrupting the actin cytoskeleton. Reduced cell spreading was associated with a higher level of mtDNA common deletion and was also accompanied by elevated levels of endogenous reactive oxygen species (ROS). Boosting cellular antioxidant capacity by using antioxidants was found to be protective against mtDNA common deletion associated with reduced cell spreading. Conclusion mtDNA common deletion is highly prevalent in the dermis of both naturally aged and photoaged human skin in vivo. mtDNA common deletion in response to reduced cell spreading is mediated, at least in part, by elevated oxidative stress in human dermal fibroblasts. These data extend current understanding of the mitochondrial theory of aging by identifying the connection between mtDNA common deletion and age-related reduction of cell spreading.http://deepblue.lib.umich.edu/bitstream/2027.42/112063/1/12929_2015_Article_167.pd

Extract-and-Adaptation Network for 3D Interacting Hand Mesh Recovery

Understanding how two hands interact with each other is a key component of accurate 3D interacting hand mesh recovery. However, recent Transformer-based methods struggle to learn the interaction between two hands as they directly utilize two hand features as input tokens, which results in distant token problem. The distant token problem represents that input tokens are in heterogeneous spaces, leading Transformer to fail in capturing correlation between input tokens. Previous Transformer-based methods suffer from the problem especially when poses of two hands are very different as they project features from a backbone to separate left and right hand-dedicated features. We present EANet, extract-and-adaptation network, with EABlock, the main component of our network. Rather than directly utilizing two hand features as input tokens, our EABlock utilizes two complementary types of novel tokens, SimToken and JoinToken, as input tokens. Our two novel tokens are from a combination of separated two hand features; hence, it is much more robust to the distant token problem. Using the two type of tokens, our EABlock effectively extracts interaction feature and adapts it to each hand. The proposed EANet achieves the state-of-the-art performance on 3D interacting hands benchmarks. The codes are available at https://github.com/jkpark0825/EANet.Comment: Accepted at ICCVW 202

Heterogeneous reactions involving HO2 radicals and atmospheric aerosols

The hydroxyl radical (OH), along with the closely coupled species the hydroperoxyl radical (HO2), have a profound effect on the concentration and distribution of most trace atmospheric species associated with climate change and poor air quality as they are essential to the daytime oxidizing capacity of the atmosphere. Tropospheric and mesospheric models that only consider gas-phase chemistry often over predict concentrations of HO2 indicating that heterogeneous reactions with aerosols could be a possible sink. In order to investigate the kinetics of such reactions, the HO2 uptake coefficient (γ(HO2), i.e. the probability that HO2 will collide and react within or on the surface of an aerosol) has been measured onto a variety of aerosols applicable to the troposphere, stratosphere and mesosphere using an aerosol flow tube experiment coupled to a highly sensitive HO2 detector, known as Fluorescence Assay by Gas Expansion (FAGE), and a Scanning Mobility Particle Sizer (SMPS). Deliquesced inorganic aerosols containing transition metal ions (TMI) have been shown to react rapidly with HO2. Measurements of γ(HO2) onto deliquesced inorganic aerosols doped with different concentrations of Cu(II), Fe(II), Mn(II), mixtures of Cu(II) and Fe(II) and I- are presented within this work. HO2 uptake onto deliquesced inorganic aerosols doped with transition metal ions may not be as significant as previously thought. The Thornton expression, used in global modelling studies of HO2 uptake, can predict γ(HO2) at a relative humidity (RH) of 65%, however at a RH of 43%, near the efflorescence point ((NH4)2SO4 = 37%), good agreement was only observed at higher concentrations of Cu(II) and Fe(II) (> 0.1 M) possibly indicating that HO2 solubility decreases as HO2 diffuses further into the bulk of the aerosol. It was expected that as deliquesced NaCl aerosols have a higher pH (7) that most HO2 accommodated within the aerosols will dissociated to the more reactive species O2-. This should result in high values of γ(HO2), however γ(HO2) onto Cu(II)-doped NaCl aerosols was measured to be lower than γ(HO2) onto Cu(II)-doped (NH4)2SO4 aerosols with a lower pH, possibly due to the formation of [Cu(Cl)4]2- complexes which are repelled into the bulk of the aerosol by enhanced concentrations of Cl- ions within the interfacial layer. Measurements of γ(HO2) onto Fe(II)-doped NaCl aerosols were relatively high and agreed with predictions made by the Thornton expression. When irradiated with UVA light, γ(HO2) onto Cu(II)-doped (NH4)2SO4 was lowered, however γ(HO2) onto Cu(II)-doped NaCl remained the same. When the effect of irradiating Fe(II)-doped (NH4)2SO4 aerosols on γ(HO2) was investigated, results indicated possible production of OH. Measurements of γ(HO2) onto mixed Cu(II) and Fe(II)-doped (NH4)2SO4 aerosols could not verify the Mao hypothesis that an electron transfer reaction occurs between Cu(I) and Fe(III) resulting in the conversion of HO2 to H2O, rather than H2O2. However, values of γ(HO2) did not simply equal the sum of γ(HO2) onto Cu or Fe-doped aerosols individually, indicating that the presence of both TMI in the aerosol does alter the chemistry of the aerosol in some way. Irradiation of Cu(II) and Fe(II)-doped aerosols resulted in an enhancement of γ(HO2), possibly indicating an alternative mechanism than that proposed by Mao, where HO2 is converted to H2O via a photochemical mechanism. The presence of I- within NaCl aerosols does not result in a change of γ(HO2), however when converted to I2 by reaction with Cu(II) an enhancement of γ(HO2) greater than when doped with Cu(II) alone was observed Measurements of γ(HO2) onto TiO2, a possible candidate aerosol for use within solar-radiation management (SRM) schemes, showed a positive dependence on Relative Humidity (RH) which correlated with the number of monolayers of water adsorbed onto the TiO2 nanoparticle. This dependence suggests a mechanism by which HO2 adsorbs to the surface of the TiO2 particle by forming complexes with water molecules bound to bridging OH groups. The TOMCAT chemical transport model was used by Professor Chipperfield to predict the possible effects of HO2 uptake (using an upper limit of γ(HO2) = 1) onto the surface of TiO2 nanoparticles on the stratospheric concentrations of HO2 and O3. The amount of TiO2 used was chosen to achieve a similar cooling to that following the Mt. Pinatubo eruption, but the model predicted a very small loss of both stratospheric HO2 and O3. Upon illumination of airborne TiO2 nanoparticles with UV light, significant quantities of HO2 was formed within the gas-phase, thought to be the first direct observations of radicals emitted from the surface of airborne particles. The reaction is dependent on the presence of gas-phase O2 and H2O within the system. The production of HO2 was shown to slow down as a function of time irradiated pointing towards a photochemical aging process occurring on the surface of the TiO2 particles. The dependence of HO2 production on O2 and H2O concentrations was determined, which shows a typical Langmuir adsorption saturation curve for O2 suggesting it is the gas-phase reactant in this process. The addition of H2O into the system inhibits the reaction and reduces the adsorption equilibrium coefficient for both species. Reduction of O2 by photogenerated electrons is likely to be the initial step in this process followed by reaction with a proton. Hydrogen extraction from hydroxyl bridging groups (OHbr) groups by O2- could explain the slow down observed in the rate of HO2 production. Production of gas-phase OH radicals was investigated and showed OH was produced only when large concentrations of TiO2 aerosols entered the aerosol flow tube, probably associated with the decomposition of H2O2 formed from reactive uptake. Although the production of HO2 by TiO2 aerosols initially would not be advantageous for its use within SRM schemes, the reaction ceases upon prolonged photocatalytic aging of the aerosol surface. Meteoric smoke particles (MSP) provide the only significant surfaces within the mesosphere for heterogeneous reactions to occur. To investigate whether such reactions could, in some part, be responsible for the ‘HOx Dilemma’ measurements of γ(HO2) onto analogues of MSP, forsterite, olivine and fayalite, were conducted at a RH of 10%. These experiments showed forsterite to have the lowest reactivity with HO2, similar to that of effloresced inorganic aerosols, and olivine and fayalite to have a similar reactivity that was more than an order of magnitude greater than that of forsterite, thus demonstrating that the presence of Fe within the MSP is required for significant reactivity with HO2. Electronic structure calculations, conducted by Professor Plane, predicts that the difference in reactivity is associated mechanistic and energetic differences between the binding of HO2 to Fe and Mg sites, however, the positive dependence of γ(HO2) with RH and similar values of γ(HO2) for olivine and fayalite suggests that OH bridging groups or complexing with water molecules adsorbed to such sites, as with TiO2 nanoparticles, are adsorption sites for HO2. Taking the measurements made in this work and the likely dependence of γ(HO2) on temperature and RH, a value of 0.2 for γ(HO2) was applied by Dr Sandy James in WACCM-CARMA. This modelling study predicted reductions in the HO2 volume mixing ratio of up to 40% in the polar vortex. Impact to HO2 budgets in the mesosphere was found to be dependent on latitude, giving agreement with the presence of MSPs in the polar night

The Determination of the Cross-sectional Shape and Area of Normal and Healing Ligaments Using Lasers

The reported biomechanical properties of soft tissues are often dependent on the method used to determine specimen cross-sectional area as this is an important factor in tissue stress calculations. Cross-sectional shape is also important, especially for documenting morphological changes in the tissue during healing. Successful measurement of these geometric characteristics, however, has been hindered by the complex geometry of many biological tissues, as well as concerns regarding the deformability of these tissues under mechanical contact. The overall objective of this thesis was to evaluate the cross-sectional shape and area of normal and healing ligaments using laser-based devices. Lasers allow for measurements without inducing mechanical contact and deformation. Initially, the effects of treatment with a bio-scaffold, small intestinal submucosa (SIS), on the cross-sectional shape and area of healing ligaments were evaluated using the laser micrometer system. However, due to limitations of currently available methods such as the inability to detect concavities, a new system was also developed and evaluated. The cross-sectional shape and area of non-treated healing and SIS-treated healing rabbit MCLs were assessed using a laser micrometer system 26 weeks after gap injury. No significant changes in shape were detected between SIS-treated and non-treated MCLs. However, SIS-treatment significantly reduced the cross-sectional area at 26 weeks after injury in comparison to the non-treated group. A charge coupled device (CCD) laser reflectance system was developed in order to determine the cross-sectional shape and area of tissues containing surface concavities. For this system, a CCD laser displacement sensor recorded distance measurements off a specimen while it rotated 360°. The area and shape could then be determined from this data. The system was evaluated using geometric shapes of known cross-sectional area before being applied to biological specimens.This work demonstrated that cross-sectional shape and area measurements can be used to quantify tissue healing and remodeling. Additionally, the CCD laser reflectance system successfully detected concavities on the surfaces of tissues and therefore is a viable approach to biological tissue measurement. However, this system does not offer much improvement in accuracy over the laser micrometer system for tissues that do not have significant concavities