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Comparison, at simulated altitude, of nitrogen tetroxide/monomethylhydrazine and hydrogen peroxide/monomethylhydrazine ignition pressure spiking characteristics
Two interferometer investigations of the polarization of Cassiopeia A employed beams of small dimensions as compared with the source. One was made at a wavelength of 9.8 cm and the other, which was more detailed, was made at a wavelength of 11.1 cm. Previous studies of the polarization of Cassiopeia A have covered either shorter wavelengths, where depolarization is small, or longer wavelengths where little polarized radiation remains. Comparison of the results of these studies with the new data near the 10-cm wavelength yields information on the rate of change of the radiation depolarization and the rotation of the plane of the electric vector as functions of wavelength. It is shown that the results can be explained in terms of a model of the source incorporating Faraday depolarization.
Configuration comparisons and systems evaluation for the orbital radar mapping mission of the planet Venus are discussed. Designs are recommended which best satisfy the science objectives of the Venus radar mapping concept. Attention is given to the interaction and integration of those specific mission-systems recommendations with one another, and the final proposed designs are presented. The feasibility, cost, and scheduling of these configurations are evaluated against assumptions of reasonable state-of-the-art growth and space funding expectations.
Decision making in early transportation planning must be responsive to complex value systems representing various policies and objectives. The assessment of alternative transportation concepts during the early initial phases of the system life cycle, when supportive research and technology development activities are defined, requires estimates of transportation, environmental, and socio-economic impacts throughout the system life cycle, which is a period of some 40 or 50 years. A unified methodological framework for comparing intercity passenger and freight transportation systems is described and is extended to include the comparison of long term transportation trends arising from implementation of the various R & D programs. The attributes of existing and future transportation systems are reviewed in order to establish measures for comparison, define value functions, and attribute weightings needed for comparing alternative policy actions for furthering transportation goals. Comparison criteria definitions and an illustrative example are included.
For a number of years Landsat data have been used to locate areas of iron oxide occurrences which might be associated with hydrothermal alteration zones. However, the usefulness of the Landsat data was restricted because of certain limitations of the spectral information provided by Landsat. A new generation multispectral scanner will, therefore, be carried by the fourth Landsat, which is to be launched in July, 1982. This instrument, called the Thematic Mapper (TM), will have seven channels and provide data with 30 m spatial resolution. Two of the spectral channels (1.6 micron and 2.2 micron) should allow detection of hydrous minerals. Possible applications of Landsat-D TM data for copper exploration were studied on the basis of a comparison of Landsat data with simulated TM data acquired using an aircraft scanner instrument. Three porphyr copper deposits in Arizona were selected for the study. It is concluded that the new Landsat-D TM scanner will provide Exploration geologists with a new improved tool for surveying mineral resources on a global basis.
A series of workshops were conducted for intercomparison of middle atmosphere data from a variety of sounding systems. The purposes were several: intercomparison of temperature data from various sources: characterization of any observed differences with an attempt to understand those differences, and to provide guidance to users of the data as to the validity of derived quantitites.
An Interagency (NASA/DOE/DOD) technical panel has been working in 1991 to evaluate nuclear thermal propulsion (NTP) concepts on a consistent basis, and to continue technology development project planning for a joint project in nuclear propulsion for Space Exploration Initiative (SEI). This paper summarizes the efforts of the panel to date and summarizes the technology plans defined for NTP. Concepts were categorized based on probable technology readiness data, and innovative 'proof-of-concept' tests and analyses were defined. While further studies will be required to provide a consistent comparison of all of the NTP concepts, the current status of the studies is presented.
The GEWEX Cloud System Study (GCSS, GEWEX is the Global Energy and Water Cycle Experiment) is a community activity aiming to promote development of improved cloud parameterizations for application in the large-scale general circulation models (GCMs) used for climate research and for numerical weather prediction. The GCSS strategy is founded upon the use of cloud-system models (CSMs). These are "process" models with sufficient spatial and temporal resolution to represent individual cloud elements, but spanning a wide range of space and time scales to enable statistical analysis of simulated cloud systems. GCSS also employs single-column versions of the parametric cloud models (SCMs) used in GCMs. GCSS has working groups on boundary-layer clouds, cirrus clouds, extratropical layer cloud systems, precipitating deep convective cloud systems, and polar clouds.
The GEWEX Cloud System Study (GCSS, GEWEX is the Global Energy and Water Cycle Experiment) is a community activity aiming to promote development of improved cloud parameterizations for application in the large-scale general circulation models (GCMs) used for climate research and for numerical weather prediction (Browning et al, 1994). The GCSS strategy is founded upon the use of cloud-system models (CSMs). These are "process" models with sufficient spatial and temporal resolution to represent individual cloud elements, but spanning a wide range of space and time scales to enable statistical analysis of simulated cloud systems. GCSS also employs single-column versions of the parametric cloud models (SCMs) used in GCMs. GCSS has working groups on boundary-layer clouds, cirrus clouds, extratropical layer cloud systems, precipitating deep convective cloud systems, and polar clouds.
No abstract available
Standard measures are defined as research measures (physiological, performance, or otherwise) that quantify the subject’s health and performance before, during, and after a spaceflight or a spaceflight analog mission. The Standard Measures Cross-Cutting Project (SMCCP) collects and analyzes standard measures that support assessment and quantification of health risks and efficacy of countermeasures and technologies required to prevent or mitigate adverse outcomes from exposure to the spaceflight environment. SMCCP uses the following spaceflight analogs: - Human Exploration Research Analog (HERA) in Houston, TX: 4-person isolation/confinement; nominal mission duration of 45 days; run by the Human Research Program (HRP). SMCCP uses weekly questionnaires to gather data on the crewmembers’ emotional and mental state and collects blood samples biweekly to measure crewmembers’ serum cortisol levels at the start, middle, and end of the mission. - Institute for Biomedical Problems (IBMP) Ground-Based Experimental Complex, called NEK, in Moscow, Russia: 6-person isolation/confinement; duration of 8 months; run by IBMP. Standard measures data collected during NEK are the same as for HERA above. - :envihab in Cologne, Germany: 12-person bed rest facility; closed environment; 30 to 60-day campaigns; run by the German Aerospace Center (DLR). For bedrest studies, SMCCP uses the international standard measures as documented in the International Academy of Astronautics publication titled Guidelines for Standardization of Bed Rest Studies in the Spaceflight Context (June 2014). These international standard measures evaluate potential changes in bone, muscle, cardiovascular, and visual systems, as well as changes in psychology and nutrition. The international standard measures complement those collected during studies by individual investigators and allow comparison of responses across different bed rest and countermeasures durations. In this presentation, we will review available SMCCP data collected during the recent isolation studies in HERA (C6) and NEK (SIRIUS-21), and during the SANS (SM1, SM2) bed rest studies in :envihab. These standard measures datasets are made available to concurrent investigators in the given mission or campaign via data sharing agreements and/or data sharing plans and to other investigators that have been granted retrospective access to the data (researchers with IRB approved protocols, risk custodians) to advance understanding of physiological and behavioral risks associated with these spaceflight analogs.
The dissolution of Pt in aqueous electrolytes has been studied for over forty years, most recently in the context of understanding the observed loss in electrochemically-active surface area (ECA) of cathode electrocatalysts in polymer electrolyte fuel cells. Despite extensive research, there are many unresolved issues regarding the dissolution of nano-particle Pt, such as the source of the observed potential dependence of potentiostatic and potential cycling dissolution rates. To help resolve these issues, in this paper we present results of measurements of the concentration of dissolved Pt and Pt dissolution rates for carbon-supported platinum nano-particles (Pt/C) in dilute perchloric acid, as a mimic of the PEFC cathode environment, as a function of potential and upper potential limit of potential cycling. Also presented, for comparison, are results of similar studies on polycrystalline platinum. In situ Pt L III X-ray absorption spectroscopy was used to determine the extent of oxidation, the coordination environment, and loss of Pt from the Pt nano-particles to elucidate the mechanism of Pt dissolution. Finally, based on the correlation of these studies with those presented in the literature, mechanisms for Pt dissolution under potentiostatic and potential cycling conditions are proposed.
A comparison between retrieved properties of the rain drop size distributions (DSDs) from multifrequency cloud radar observations and WRF Model results using either the Morrison or the Thompson bulk microphysics scheme is performed in order to evaluate the model’s ability to predict the rain microphysics. This comparison reveals discrepancies in the vertical profile of the rain DSDs for the stratiform region of the squall-line system observed on 12 June 2011 over Oklahoma. Based on numerical sensitivity analyses, this study addresses the bias at the top of the rain layer and the vertical evolution of the DSD properties (i.e., of D m and N$^{*}_{0}$). In this way, the Thompson scheme is used to explore the sensitivity to the melting process. Moreover, using the Thompson and Morrison schemes, the sensitivity of the DSD vertical evolution to different breakup and self-collection parameterizations is studied. Results show that the DSDs are strongly dependent on the representation of the melting process in the Thompson scheme. In the Morrison scheme, the simulations with more efficient breakup reproduce the DSD properties with better fidelity. Here, this study highlights how the inaccuracies in simulated D m and N$^{*}_{0}$ for both microphysics schemes can impact the evaporation rate, which is systematically underestimated in the model.
Ocean exploration sailing journeys from hundreds of years ago typically required large vessels and large crews (in comparison with today’s space capsules) to travel between the continents and around the world. Modern sailors of today are able to complete similar distant voyages, in small vessels, with a minimal crew, comparable in size to modern space travel crews. This paper uses a systems engineering approach (e.g. using the NASA Human Integration Design Handbook (HIDH), NASA-SP-2010-3407, 2010 and the “Advanced Life Support Baseline Values and Assumptions Document, (BVAD)” NASA-CR-2004-208941, 2004.), to examine and compare the logistics and sustainability aspects of a small crew traveling on Earth's oceans in sailing vessels versus humans traveling in space. The “Mālama Honua Worldwide Voyage” of the Hōkūleʻa, a replica of an ancient Hawaiian double hulled sailing canoe, will be used as a baseline minimalist case study. This is a good comparison case since the Polynesian exploration of the vast (and virtually empty) Pacific Ocean with limited resources is an analogue to human space travel. A modern sailboat is compared to the ancient Polynesian methods and then a space craft is assessed with similar functional decomposition methods. In 1992 during his second Space Shuttle mission (STS-52, Columbia) Astronaut Lacy Veach received a radio message from a student: "What are the similarities and differences between canoe and space travel?" Astronaut Charles Lacy Veach answered, "Both are voyages of exploration. Hōkūle‘a is in the past, Columbia is in the future." Navigator Nainoa Thompson added from the sailing canoe, "Columbia is the highest achievement of modern technology today, a voyaging canoe was the highest achievement of technology in its day." This paper is dedicated to the memory of two great Hawaiian astronauts: US Air Force Colonel Charles Lacy Veach and US Air Force Colonel Ellison Onizuka and to legendary waterman and Hōkūleʻa crew member Eddie Aikau who was lost at sea in 1978, at the beginning of a 30-day, 2,500-mile (4,000km) journey by the Hōkūleʻa to follow the ancient route of the Polynesian migration between the Hawaiian and Tahitian island chains.
Fractional free volume (FFV) is a commonly used metric for the development of structure–property relationships for polymer membranes. The most common method to calculate FFV uses Bondi's group contribution method, first introduced in 1964. While updated in 1997, there has not been a significant compilation of new structural motifs since the advent of linear microporous polymers. Here, in this study, we critically examined the assumptions in Bondi's original method and provide four recommendations to streamline and improve the accuracy of calculating van der Waals volume (V W ) for any group. Using these recommendations, we created an updated list of (V W ) values for structural groups commonly present in microporous polymers. The (V W ) and FFV values were then calculated for a database of 123 microporous and high free volume polymers from the literature, showing an average 7% decrease in (V W ) and corresponding increase in FFV by a factor of 24% when compared to prior group contribution correlations in the literature. The significant apparent increase in estimated FFV provides a new perspective to understand and interpret the role of free volume on the separation performance of linear microporous polymers. Additionally, standardization of the group contribution method allows for the direct comparison of FFV values across studies.
High-valent Fe IV =O species are common intermediates in biological and artificial catalysts. Heme and nonheme S=1 Fe IV =O sites have been synthesized and studied for decades but little quantitative experimental comparison of their electronic structures has been available, due to the lack of direct methods focused on the iron. This study allows a rigorous determination of the electronic structure of a nonheme Fe IV =O center and its comparison to an Fe IV =O heme site using 1s2p resonant inelastic X-ray scattering (RIXS) and Fe L-edge X-ray absorption spectroscopy (XAS). Further, variable temperature magnetic circular dichroism (VT-MCD) of the ligand field transitions, combined with nuclear resonance vibrational spectroscopy of the two S=1 Fe IV =O systems show that the equatorial ligand field decreases from a nonheme to a heme Fe IV =O site. Alternatively, RIXS and Fe L-edge XAS combined with MCD show that the Fe dπ orbitals are unperturbed in the Fe IV =O heme relative to the nonheme site because the strong axial Fe-O bond uncouples the Fe dπ orbitals from the porphyrin π-system. As a consequence, the thermodynamics and kinetics of the H-atom abstraction reactions are actually very similar for heme compound II and nonheme Fe IV =O active sites.
This paper describes design and logistical aspects of a decision analysis study to assess the performance of qualified firearms examiners working in accredited laboratories in the United States in terms of accuracy (error rate), repeatability, and reproducibility of decisions involving comparisons of fired bullets and cartridge cases. The purpose of the study was to validate current practice of the forensic discipline of firearms/toolmarks (F/T) examination. It elicited error rate data by counting the number of false positive and false negative conclusions. Preceded by the experimental design, decisions, and logistics described herein, testing was ultimately administered 173 qualified, practicing F/T examiners in public and private crime laboratories. The first round of testing evaluated accuracy, while two subsequent rounds evaluated repeatability and reproducibility of examiner conclusions. This project expands on previous studies by involving many F/T examiners in challenging comparisons and by executing the study in the recommended double-blind format.
The usefulness of the Earth Radiation Budget (ERB) data set in its present form was studied. Emphasis is placed on the comparison of wide-field-of-view measurements with integrated scanner observations at satellite altitudes. The purpose of making these comparisons is to check for the need of spectral corrections when processing the shortwave scanning radiometer data.