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At least 73 records · Page 4

Automatic Review of Abstract State Machines by Meta Property Verification

A model review is a validation technique aimed at determining if a model is of sufficient quality and allows defects to be identified early in the system development, reducing the cost of fixing them. In this paper we propose a technique to perform automatic review of Abstract State Machine (ASM) formal specifications. We first detect a family of typical vulnerabilities and defects a developer can introduce during the modeling activity using the ASMs and we express such faults as the violation of meta-properties that guarantee certain quality attributes of the specification. These meta-properties are then mapped to temporal logic formulas and model checked for their violation. As a proof of concept, we also report the result of applying this ASM review process to several specifications.

Arcaini, Paolo↗

Calibration for Thrust and Airflow Measurements in the CE-22 Advanced Nozzle Test Facility

CE-22 facility procedures and measurements for thrust and airflow calibration obtained with choked-flow ASME nozzles are presented. Six calibration nozzles are used at an inlet total pressure from 20 to 48 psia. Throat areas are from 9.9986 to 39.986 sq. in.. Throat Reynolds number varies from 1.8 to 7.9 million. Nozzle gross thrust coefficient (CFG) uncertainty is 0.25 to 0.75 percent, with smaller uncertainly generally for larger nozzles and higher inlet total pressure. Nozzle discharge coefficient (CDN) uncertainty is 0.15 percent or less for all the data. ASME nozzle calibrations need to be done before and after research model testing to achieve these uncertainties. In addition, facility capability in terms of nozzle pressure ratio (NPR) and nozzle airflow are determined. Nozzle pressure ratio of 50 or more is obtainable at 40 psia for throat areas between 20 and 30 sq. in.. Also presented are results for two of the ASME nozzles vectored at 10deg, a dead-weight check of the vertical (perpendicular to the jet axis) force measurement, a calibration of load cell forces for the effects of facility tank deflection with tank pressure, and the calibration of the metric-break labyrinth seal.

Werner, Roger A.↗

Introduction

It would be hard to argue against the fact that Integrated Computational Materials Engineering (ICME) is a fast growing discipline within material science and engineering. A quick scan of the proceedings from conferences such as Aeromat, Material Science and Technology, and the TMS Annual Meeting clearly shows it. What began a few years ago as one symposium has grown into multiple ICME related symposia at each of these conferences. As encouraging as the number of symposia being offered is the attendance at the symposia. For example, one of the ICME symposia at MS&T 10, the symposium in which this book is based, had five sessions which culminated in a panel discussion that was standing room only. In addition to the large, annual materials science and engineering conferences, smaller 1 to 2-day conferences/workshops sponsored by government agencies (e.g. AFRL and NIST) on specific aspects of ICME and by universities promoting their ICME work are regularly offered. And arguably the most significant news with regards to ICME and conferences is the July 2011 First World Congress on ICME. This five day TMS sponsored conference, specifically focused on ICME with an international advisory board of ICME leaders, shows how far ICME has spread across the globe. Evidence for the growth of ICME can also be found in Academia. The University Materials Council (UMC) is composed of department heads for material science and engineering from major U.S. and Canadian universities. Meeting twice a year to share best practices in order to strengthen both the engineering content [1] and the educational process, the UMC s agenda for their Spring 2010 meeting was dedicated to ICME [2]. This meeting was held in response to the growing awareness that the universities play a major role in the success of ICME and therefore need to develop ICME curriculum in order to meet that need. To aid educators in the development of ICME courses, NSF is funding a "Summer School" on ICME to be held at the University of Michigan in 2011 [3]. Northwestern University recently announced a MS Certificate Program in ICME [4]. Course work for this certificate begins in the Fall of 2011. Other signs that ICME is growing comes from the formation of ICME initiatives from work that did not start off with ICME in mind. One of the committees in ASM International is the Materials Properties Database Committee (MPDC). In the 2010 meeting of the MPDC, based on a study by ASM, the committee decided that it would create an ICME sub-committee in order to determine how ASM can meet the growing needs of the ICME community [5]. In 1999, the Air Force Research Laboratory (AFRL) created a consortium, the Metals Affordability Initiative (MAI), with members from both industry and government with a goal of reducing the cost and time to market of producing metal parts for aerospace applications [6].

Arnold, Steven M.↗

Formation of Tropopause Cirrus clouds by Typhoon-induced gravity waves during the Asian Summer Monsoon: A Case Study from the BATAL 2017 Campaign

Cirrus clouds in the Tropical Tropopause Layer (TTL) have a net warming impact on Earth’s climate and they regulate the amount of water vapor entering the lower stratosphere through dehydration process near the cold-point tropopause. During the Boreal summer, Asian Summer Monsoon (ASM) is an important source of cirrus clouds and humidity in the TTL owing to frequent deep convection. However, better representation of convection and TTL cirrus clouds in global climate models is needed for accurate assessment of their response to changing climate. In this study, we investigate the mechanisms involved in the formation of a tropopause cirrus cloud layer observed during the Balloon measurement campaigns of the Asian Tropopause Aerosol Layer (BATAL) over Hyderabad (17.47 °N, 78.58 °E), India on 23 August 2017. A subvisible cirrus cloud layer (optical thickness ~0.025) was detected by a backscatter sonde (COBALD) onboard a balloon near the cold-point tropopause (CPT, temperature~ -86.4 ° C, altitude~17.9 km) which was later confirmed by the CATS lidar on the ISS. Simultaneous measurements from an optical particle counter (Boulder Counter) revealed the presence of ice crystals smaller than 50 microns in this layer. The formation mechanism responsible for this tropopause cirrus is investigated using a technique combining three-dimensional back-trajectories, satellite observations, and ERA5 reanalysis data. Satellite observations revealed that the overshooting convection associated with a category-3 typhoon Hato, which hit Macau and Hong Kong on 23 August 2017 injected ice into the lower stratosphere. This caused a hydration patch that followed the ASM anticyclone subsequently moving towards Hyderabad. The presence of tropopause cirrus cloud layers in the cold temperature anomalies and updrafts along the back-trajectories indicated towards the role of typhoon-induced gravity waves in their formation. This case study highlights the role of typhoons in influencing the formation of tropopause cirrus clouds through stratospheric hydration and gravity waves in the ASM anticyclone.

Amit Kumar Pandit↗

Recent Trends in Transport of Surface Carbonaceous Aerosols to the Upper-Troposphere-Lower-Stratosphere Linked to Expansion of the Asian Summer Monsoon Anticyclone

Using MERRA-2 re-analyses, we have examined recent trends (2000-2019) in transport of surface carbonaceous aerosols (CA), i.e., organic carbon (OC) and black carbon (BC), to the upper troposphere (UT) and lower stratosphere (LS) during the Asian summer monsoon (ASM). We find a significant increased concentration of UTLS CA, linked to a linear trend in an expansion of the Asian Summer Monsoon Anticyclone (ASMA). Over core monsoon latitudes (25°-35°N), the trends in UTLS CA are enabled by increased upward transport from surface sources via an intensified monsoon meridional circulation, with increased latent heating over the southern Tibetan Plateau and foothill regions, enhanced by feedback processes associated with radiative heating by UTLS CA. In the extra-tropics, increased UTLS CA stems primarily from an extended source of increased wildfire emissions over eastern Siberia and northern Asia, coincident with a large-scale anomalous anticyclone with enhanced surface warming and drying near (80°-120°E, 55°-70°N). Here, carbonaceous aerosols are transported upward from the surface to the LS, likely by increased pyro-convection associated with enhanced wildfires, and enter the tropical UTLS via increased equator ward transport on the eastern flanks of anomalous upper-level anticyclones, coupled to the expanded ASMA. Overall, the increasing UTLS CA trends associated with expansion of the ASMA are consistent with a hydrostatic expansion of a warming troposphere, reflected in a rise in the tropical tropopause and consequential dynamical adjustments of the [ASM subtropical jetstream, modulating the climate of the greater ASM region.

interdecadal trends↗

The Chaotic Long-Term X-Ray Variability of 4U 1705-44

The low-mass X-ray binary 4U1705-44 exhibits dramatic long-term X-ray time variability with a time-scale of several hundred days. The All-SkyMonitor (ASM) aboard the Rossi X-ray Timing Explorer (RXTE) and the Japanese Monitor of All-sky X-ray Image (MAXI) aboard the International Space Station together have continuously observed the source from 1995 December through 2014 May. The combined ASM-MAXI data provide a continuous time series over 50 times the length of the time-scale of interest. Topological analysis can help us identify 'fingerprints' in the phase space of a system unique to its equations of motion. The Birman-Williams theorem postulates that if such fingerprints are the same between two systems, then their equations of motion must be closely related. The phase-space embedding of the source light curve shows a strong resemblance to the double-welled non-linear Duffing oscillator. We explore a range of parameters for which the Duffing oscillator closely mirrors the time evolution of 4U1705-44. We extract low period, unstable periodic orbits from the 4U1705-44 and Duffing time series and compare their topological information. The Duffing and 4U1705-44 topological properties are identical, providing strong evidence that they share the same underlying template. This suggests that we can look to the Duffing equation to help guide the development of a physical model to describe the long-term X-ray variability of this and other similarly behaved X-ray binary systems.

Rossi X-ray Timing Explorer (RXTE)↗

Discussion of the General Electric proposal to develop a computer program to select thermal coatings for passive temperature control of satellites

The General Electric Company, Missiles and Space Division, submitted/a proposal to NASA for the development of an IBM 7094 computer program which would select the exterior surface coatings for passively controlling spacecraft temperatures. G. E. claims that the "trial and error" procedures currently used can be accomplished more rationally and can therefore be programmed for a digital computer. In the ASME paper, 63-HT-41, which was presented at the ASME-AIChE Heat Transfer Conference at Boston in August, 1963, Costello, Harper, and Cline, described the procedures that have been used at G. E. to develop a coating selection program subject to the following restrictions: 1. Steady-state conditions prevail, 2. Heat transfer occurs by radiation only, 3. Temperatures are optimized at only one interior point in the spacecraft, an d 4. Only the solar absorptance of the external coatings is varied to optimize temperature. The emittance must remain constant at initially specified values. General Electric proposes to develop a generalized program in three steps: 1. The program would vary both solar absorptance and hemispherical emittance to obtain the optimum coating patterns; 2. Temperatures would be optimized at more than one interior point; and 3. The equations would be modified to account for both conduction and radiation heat transfer. In the development of the general program, the scope would be restricted to steady-state heat transfer. Since the thermal designs of most spacecraft are based primarily on nearly equilibrium conditions, the proposed program could have wide application. An obvious extension of the proposed program would be to account for transient temperatures.

IBM 7090 COMPUTER↗

X-ray all-sky monitors

Considerations for an all-sky monitor for the Ariel-5 mission are evaluated. The monitors with the best signal-to-noise utilize the pinhole-camera principle, and are also least expensive in hardware and data analysis costs. The sensitivity sufficient to sensibly monitor compact extragalactic sources requires a system with approximately 100 times the sensitivity of the Ariel-5 ASM. A system identical in size to the Ariel-5 ASM can be made with approximately 5 times better sensitivity, and can satisfy the minimum requirements for this mission if it spins. An all-sky monitor appears to be essential to assure that rare occurrences in compact objects can be observed with the pointed experiment, and to ascertain that large amounts of pointing time will not be wasted by observing at the wrong times.

Holt, S. S.↗

Features of a reattaching turbulent shear layer subject to an adverse pressure gradient

Experimental data have been obtained in an incompressible turbulent flow over a rearward-facing step with superimposed adverse pressure gradient. Mean velocities, Reynolds stresses and triple-products measured by a laser Doppler velocimeter are presented for two cases of adverse pressure gradient. Mixing lengths, eddy viscosities, production, convection, turbulent diffusion, and dissipation terms are extracted from the data. These data are compared with various mixing length and eddy-viscosity turbulence models. Numerical calculations incorporating the k-epsilon and the algebraic-stress turbulence models are compared with the data. When determining quantities of engineering interest, the modified algebraic-stress model (ASM) is a significant improvement over the unmodified ASM and the unmodified k-epsilon model

Driver, D. M.↗

Accomplishments of the NASA Johnson Space Center portion of the soil moisture project in fiscal year 1981

The NASA/JSC ground scatterometer system was used in a row structure and row direction effects experiment to understand these effects on radar remote sensing of soil moisture. Also, a modification of the scatterometer system was begun and is continuing, to allow cross-polarization experiments to be conducted in fiscal years 1982 and 1983. Preprocessing of the 1978 agricultural soil moisture experiment (ASME) data was completed. Preparations for analysis of the ASME data is fiscal year 1982 were completed. A radar image simulation procedure developed by the University of Kansas is being improved. Profile soil moisture model outputs were compared quantitatively for the same soil and climate conditions. A new model was developed and tested to predict the soil moisture characteristic (water tension versus volumetric soil moisture content) from particle-size distribution and bulk density data. Relationships between surface-zone soil moisture, surface flux, and subsurface moisture conditions are being studied as well as the ways in which measured soil moisture (as obtained from remote sensing) can be used for agricultural applications.

Paris, J. F.↗

Dual arm master controller development

The advanced servomanipulator (ASM) slave was designed with an anthropomorphic stance gear/torque tube power drives, and modular construction. These features resulted in increased inertia, friction, and backlash relative to tape driven manipulators. Studies were performed which addressed to human factor design and performance tradeoffs associated with the corresponding master controller best suited for the ASM. The results of these studies, as well as the conceptual design of the dual arm master controller, are presented.

Kuban, D. P.↗

Features of a reattaching turbulent shear layer in divergent channel flow

Experimental data have been obtained in an incompressible turbulent flow over a rearward-facing step in a diverging channel flow. Mean velocities, Reynolds stresses, and triple products that were measured by a laser Doppler velocimeter are presented for two cases of tunnel wall divergence. Eddy viscosities, production, convection, turbulent diffusion, and dissipation (balance of kinetic energy equation) terms are extracted from the data. These data are compared with various eddy-viscosity turbulence models. Numerical calculations incorporating the k-epsilon and algebraic-stress turbulence models are compared with the data. When determining quantities of engineering interest, the modified algebraic-stress model (ASM) is a significant improvement over the unmodified ASM and the unmodified k-epsilon model; however, like the others, it dramatically overpredicts the experimentally determined dissipation rate.

Driver, D. M.↗

Telerobotic technology for nuclear and space applications

Developments in telerobotics applicable to nuclear and space environments are discussed. The advanced servomanipulator (ASM) slave arm force-reflected servomanipulators designed for modular remote maintainability of the Advanced Integrated Maintenance System is examined. Consideration is given to the master controller, transporter, interface package, operator control station, and the control system for the ASM arm. A prototype of a telerobot capable of performing the activity of an astronaut during EVA is developed. The mechanical and control system features of the telerobot are described.

Herndon, J. N.↗

Long term integrity for space station power systems

A study was made of the High Temperature Design Codes ASME N47, British R5, and the French RCC-MR Rules. It is concluded that all these codes provide a good basis of design for space application. The new British R5 is the most complete since it deals with the problem of defects. The ASME N47 was subjected longer to practical application and scrutiny. A draft code is introduced, and a proposed draft for high temperature design in which attempts were made to identify gaps and improvements is suggested. The design is limited by creep characteristics. In these circumstances, life is strongly affected by the selected value of the factor of safety. The factor of safety of primary loads adopted in the codes is 1.5. Maybe a lower value of 1.25 is permissible for use in space. Long term creep rupture data for HAYNES 188 is deficient and it is suggested that extrapolation methods be investigated.

Leckie, F. A.↗

Turbulence modelling of flow fields in thrust chambers

Following the consensus of a workshop in Turbulence Modelling for Liquid Rocket Thrust Chambers, the current effort was undertaken to study the effects of second-order closure on the predictions of thermochemical flow fields. To reduce the instability and computational intensity of the full second-order Reynolds Stress Model, an Algebraic Stress Model (ASM) coupled with a two-layer near wall treatment was developed. Various test problems, including the compressible boundary layer with adiabatic and cooled walls, recirculating flows, swirling flows, and the entire SSME nozzle flow were studied to assess the performance of the current model. Detailed calculations for the SSME exit wall flow around the nozzle manifold were executed. As to the overall flow predictions, the ASM removes another assumption for appropriate comparison with experimental data to account for the non-isotropic turbulence effects.

Chen, C. P.↗

Application of materials database (MAT.DB.) to materials education

Finding the right material for the job is an important aspect of engineering. Sometimes the choice is as fundamental as selecting between steel and aluminum. Other times, the choice may be between different compositions in an alloy. Discovering and compiling materials data is a demanding task, but it leads to accurate models for analysis and successful materials application. Mat. DB. is a database management system designed for maintaining information on the properties and processing of engineered materials, including metals, plastics, composites, and ceramics. It was developed by the Center for Materials Data of American Society for Metals (ASM) International. The ASM Center for Materials Data collects and reviews material property data for publication in books, reports, and electronic database. Mat. DB was developed to aid the data management and material applications.

Liu, Ping↗

Development of an algebraic stress/two-layer model for calculating thrust chamber flow fields

Following the consensus of a workshop in Turbulence Modeling for Liquid Rocket Thrust Chambers, the current effort was undertaken to study the effects of second-order closure on the predictions of thermochemical flow fields. To reduce the instability and computational intensity of the full second-order Reynolds Stress Model, an Algebraic Stress Model (ASM) coupled with a two-layer near wall treatment was developed. Various test problems, including the compressible boundary layer with adiabatic and cooled walls, recirculating flows, swirling flows and the entire SSME nozzle flow were studied to assess the performance of the current model. Detailed calculations for the SSME exit wall flow around the nozzle manifold were executed. As to the overall flow predictions, the ASM removes another assumption for appropriate comparison with experimental data, to account for the non-isotropic turbulence effects.

Chen, C. P.↗

Implementation of algebraic stress models in a general 3-D Navier-Stokes method (PAB3D)

A three-dimensional multiblock Navier-Stokes code, PAB3D, which was developed for propulsion integration and general aerodynamic analysis, has been used extensively by NASA Langley and other organizations to perform both internal (exhaust) and external flow analysis of complex aircraft configurations. This code was designed to solve the simplified Reynolds Averaged Navier-Stokes equations. A two-equation k-epsilon turbulence model has been used with considerable success, especially for attached flows. Accurate predicting of transonic shock wave location and pressure recovery in separated flow regions has been more difficult. Two algebraic Reynolds stress models (ASM) have been recently implemented in the code that greatly improved the code's ability to predict these difficult flow conditions. Good agreement with Direct Numerical Simulation (DNS) for a subsonic flat plate was achieved with ASM's developed by Shih, Zhu, and Lumley and Gatski and Speziale. Good predictions were also achieved at subsonic and transonic Mach numbers for shock location and trailing edge boattail pressure recovery on a single-engine afterbody/nozzle model.

Abdol-Hamid, Khaled S.↗