Quantifying landscape change following catastrophic dam failures in Edenville and Sanford, Michigan, USA
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Harrison K. Martin↗
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Determinant Role of Aerosols From Industrial Sources in Hurricane Harvey's Catastrophe
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Bowen Pan↗
ELG spectroscopic systematics analysis of the DESI Data Release 1
Dark Energy Spectroscopic Instrument (DESI) uses more than 2.4 million Emission Line Galaxies (ELGs) for 3D large-scale structure (LSS) analyses in its Data Release 1 (DR1). Such large statistics enable thorough research on systematic uncertainties. In this study, we focus on spectroscopic systematics of ELGs. The redshift success rate (f goodz ) is the relative fraction of secure redshifts among all measurements. It depends on observing conditions, thus introduces non-cosmological variations to the LSS. We, therefore, develop the redshift failure weight (w zfail ) and a per-fibre correction (η zfail ) to mitigate these dependences. They have minor influences on the galaxy clustering. For ELGs with a secure redshift, there are two subtypes of systematics: 1) catastrophics (large) that only occur in a few samples; 2) redshift uncertainty (small) that exists for all samples. The catastrophics represent 0.26% of the total DR1 ELGs, composed of the confusion between [O ii] and sky residuals, double objects, total catastrophics and others. We simulate the realistic 0.26% catastrophics of DR1 ELGs, the hypothetical 1% catastrophics, and the truncation of the contaminated 1.31 < z < 1.33 in the A BACUS S UMMIT ELG mocks. Their P ℓ show non-negligible bias from the uncontaminated mocks. But their influences on the redshift space distortions (RSD) parameters are smaller than 0.2σ. The redshift uncertainty of DR1 ELGs is 8.5km s -1 with a Lorentzian profile. The code for implementing the catastrophics and redshift uncertainty on mocks can be found in https://github.com/Jiaxi-Yu/modelling_spectro_sys.
79 ASTRONOMY AND ASTROPHYSICS↗
Titanium-Oxygen Reactivity Study
A program has been conducted at Astronautics to investigate the likelihood of occurrence of the catastrophic oxidation of titanium alloy sheet under conditions which simulate certain cases of accidental failure of the metal while it is in contact with liquid or gaseous oxygen. Three methods of fracturing the metal were used; they consisted of mechanical puncture, tensile fracture of welded joints, and perforation by very high velocity particles. The results of the tests which have been conducted provide further evidence of the reactivity of titanium with liquid and gaseous oxygen. The evidence indicates that the rapid fracturing of titanium sheet while it is in contact with oxygen initiates the catastrophic oxidation reaction. Initiation occurred when the speed of the fracture was some few feet per second, as in both the drop-weight puncture tests and the static tensile fracture tests of welded joints, as well as when the speed was several thousand feet per second, as in the simulated micrometeoroid penetration tests. The slow propagation of a crack, however, did not initiate the reaction. It may logically be concluded that the localized frictional heat of rapid fracture and/or spontaneous oxidation (exothermic) of minute particles emanating from the fracture cause initiation of the reaction. Under conditions of slow fracture, however, the small heat generated may be adequately dissipated and the reaction is not initiated. A portion of the study conducted consisted of investigating various means by which the reaction might be retarded or prevented. Providing a "barrier" at the titanium-oxygen interface consisting of either aluminum metal or a coating of a petroleum base corrosion inhibitor appeared to be only partially effective in retarding the reaction. The accidental puncturing or similar rupturing of thin-walled pressurized oxygen tanks on missiles and space vehicle will usually constitute loss of function, and may sometimes cause their catastrophic destruction by explosive decompression regardless of the type of material used for their construction. In the case of tanks constructed of titanium alloys the added risk is incurred of catastrophic burning of the tanks. In view of this it is recommended that thin-walled tanks constructed of titanium alloys should not be used to contain liquid or gaseous oxygen.
Chafey, J. E.↗
Mechanism of Na2SO4-induced corrosion of molybdenum containing nickel-base superalloys at high temperatures. I - Corrosion in atmospheres containing O2 only. II - Corrosion in O2 + SO2 atmospheres
Kinetics of the Na2SO4-induced corrosion of the molybdenum-containing nickel-base superalloys, B-1900 and Udimet 700, coated with Na2MoO4, has been studied in oxygen atmosphere at temperatures ranging from 750 to 950 C. Because the gas turbine atmosphere always contains some SO2 and SO3, the effect of atmospheric SO2 content on corrosion of Udimet-700 has also been studied. It was found that in the O2 atmosphere the melt in the catastrophic corrosion phase consists of Na2MoO4 plus MoO3, with the onset of the catastrophic corrosion coinciding with the appearance of MoO3. In the presence of low levels of atmospheric SO2 (below 0.24 percent), the melt during catastrophic corrosion contains, in addition to Na2MoO4 and MoO3, some quantities of Na2SO4. At the levels of SO2 above 1 percent, no catastrophic corrosion was observed. At these SO2 levels, internal sulfidation appears to be the primary mode of degradation.
Misra, A. K.↗
The resurfacing controversy for Venus: An overview and a mechanistic perspective
Two remarkable aspects of the population of impact craters on Venus are that craters at all sizes are indistinguishable from a random population and that most craters have not been significantly modified by tectonic strain or by volcanic flows external to the crater rim, despite evidence from Magellan images that volcanic and tectonic features are widespread on Venus. One interpretation of these observations is that most of the surface dates from the end of a catastrophic global resurfacing event that ceased about 500 My ago, and that a small fraction of craters volcaniclly embayed or modified by deformation indicate that volcanic and tectonic activity subsequent to that time has been at much lower levels. A competing scenario, in which resurfacing occurs episodically in patches a few hundred kilometers in extent and there is a wider spectrum of surface ages, also appears to be consistent with the characteristics of impact craters on Venus. While geological and statistical studies of the crater population on Venus offer some promise for distinguishing between these two hypotheses, consideration of the possible mechanisms of catastrophic episodic resurfacing provides an independent perspective. Potential mechanisms for catastrophic resurfacing of Venus range from geologically sudden convective destabilization of the global lithosphere to strongly time-dependent heat flux and melt generation in the underlying mantle. For most of these mechanisms, resurfacing occurs implicitly or explicitly by volcanism. An alternative hypothesis is that, at least in the geologically recent history of Venus, the primary resurfacing mechanism has been tectonic deformation rather than volcanism. Because the rate of surface strain should be controlled by the temperature-dependent strength of the lower crust, a geologically rapid transition in surface strain rates should be the natural result of planetary cooling. This transition would occur at comparable times for areas of similar crustal thickness and heat flow, but would be delayed for regions of thicker or hotter crust. The end of the era of high rates of tectonic resurfacing could thus appear as a 'catastrophe' over the 80% of the planet with an elevation within 1 Km of the mean, while continued deformation would give rise to 'episodic' resurfacing to much younger times in the highlands, a result consistent with lower crater densities seen in highland regions.
Solomon, Sean C.↗
Space Shuttle Main Engine Quantitative Risk Assessment: Illustrating Modeling of a Complex System with a New QRA Software Package
During 1997, a team from Hernandez Engineering, MSFC, Rocketdyne, Thiokol, Pratt & Whitney, and USBI completed the first phase of a two year Quantitative Risk Assessment (QRA) of the Space Shuttle. The models for the Shuttle systems were entered and analyzed by a new QRA software package. This system, termed the Quantitative Risk Assessment System(QRAS), was designed by NASA and programmed by the University of Maryland. The software is a groundbreaking PC-based risk assessment package that allows the user to model complex systems in a hierarchical fashion. Features of the software include the ability to easily select quantifications of failure modes, draw Event Sequence Diagrams(ESDs) interactively, perform uncertainty and sensitivity analysis, and document the modeling. This paper illustrates both the approach used in modeling and the particular features of the software package. The software is general and can be used in a QRA of any complex engineered system. The author is the project lead for the modeling of the Space Shuttle Main Engines (SSMEs), and this paper focuses on the modeling completed for the SSMEs during 1997. In particular, the groundrules for the study, the databases used, the way in which ESDs were used to model catastrophic failure of the SSMES, the methods used to quantify the failure rates, and how QRAS was used in the modeling effort are discussed. Groundrules were necessary to limit the scope of such a complex study, especially with regard to a liquid rocket engine such as the SSME, which can be shut down after ignition either on the pad or in flight. The SSME was divided into its constituent components and subsystems. These were ranked on the basis of the possibility of being upgraded and risk of catastrophic failure. Once this was done the Shuttle program Hazard Analysis and Failure Modes and Effects Analysis (FMEA) were used to create a list of potential failure modes to be modeled. The groundrules and other criteria were used to screen out the many failure modes that did not contribute significantly to the catastrophic risk. The Hazard Analysis and FMEA for the SSME were also used to build ESDs that show the chain of events leading from the failure mode occurence to one of the following end states: catastrophic failure, engine shutdown, or siccessful operation( successful with respect to the failure mode under consideration).
Smart, Christian↗
NDE Evidence for the Damage Arrestment Performance of PRSEUS Composite Cube During High-Pressure Load Test
As an approach to light-weight, cost-effective and manufacturable structures required to enable the hybrid wing body aircraft, The Boeing Company, Inc. and NASA have developed the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) concept. A PRSEUS pressure cube was developed as a risk reduction test article to examine a new integral cap joint concept as part of a building block approach for technology development of the PRSEUS concept. The overall specimen strength exceeded the 18.4 psi load requirement as testing resulted in the cube reaching a final pressure load of around 48 psi prior to catastrophic failure. The cube pressure test verified that the joints and structure were capable of sustaining the required loads, and represented the first testing of joined PRSEUS structure. This paper will address the damage arrestment performance of the stitched PRSEUS structure. Following catastrophic failure of the cube, ultrasonic pulse-echo inspection found that the localized damage, surrounding a barely-visible impact damage site, did not change noticeably between just after impact and catastrophic failure of the cube, and did not play a role in the catastrophic failure event. Ultrasonic inspection of the remaining intact cube panels presented three basic types of indications: delaminations between laminae parallel to the face sheets, lying between face sheet and tear strap layers, or between tear strap and flange layers; delaminations above the noodles of stringers, frames or integral caps, lying within face sheet or tear strap layers; and delaminations between the laminae in the inner fillets of the integral caps, where pulloff stresses were expected to be highest. Delaminations of all three types were predominantly contained by the first row of stitches encountered. For the small fraction of delaminations extending beyond the first row of stitches, all were contained by the second stitch row.
Johnston, Patrick H.↗
Application of Fault Management Theory to the Quantitative Selection of a Launch Vehicle Abort Trigger Suite
The theory of System Health Management (SHM) and of its operational subset Fault Management (FM) states that FM is implemented as a "meta" control loop, known as an FM Control Loop (FMCL). The FMCL detects that all or part of a system is now failed, or in the future will fail (that is, cannot be controlled within acceptable limits to achieve its objectives), and takes a control action (a response) to return the system to a controllable state. In terms of control theory, the effectiveness of each FMCL is estimated based on its ability to correctly estimate the system state, and on the speed of its response to the current or impending failure effects. This paper describes how this theory has been successfully applied on the National Aeronautics and Space Administration's (NASA) Space Launch System (SLS) Program to quantitatively estimate the effectiveness of proposed abort triggers so as to select the most effective suite to protect the astronauts from catastrophic failure of the SLS. The premise behind this process is to be able to quantitatively provide the value versus risk trade‐off for any given abort trigger, allowing decision makers to make more informed decisions. All current and planned crewed launch vehicles have some form of vehicle health management system integrated with an emergency launch abort system to ensure crew safety. While the design can vary, the underlying principle is the same: detect imminent catastrophic vehicle failure, initiate launch abort, and extract the crew to safety. Abort triggers are the detection mechanisms that identify that a catastrophic launch vehicle failure is occurring or is imminent and cause the initiation of a notification to the crew vehicle that the escape system must be activated. While ensuring that the abort triggers provide this function, designers must also ensure that the abort triggers do not signal that a catastrophic failure is imminent when in fact the launch vehicle can successfully achieve orbit. That is, the abort triggers must have low false negative rates to be sure that real crew‐threatening failures are detected, and also low false positive rates to ensure that the crew does not abort from non‐crew‐threatening launch vehicle behaviors. The analysis process described in this paper is a compilation of over six years of lessons learned and refinements from experiences developing abort triggers for NASA's Constellation Program (Ares I Project) and the SLS Program, as well as the simultaneous development of SHM/FM theory. The paper will describe the abort analysis concepts and process, developed in conjunction with SLS Safety and Mission Assurance (S&MA) to define a common set of mission phase, failure scenario, and Loss of Mission Environment (LOME) combinations upon which the SLS Loss of Mission (LOM) Probabilistic Risk Assessment (PRA) models are built. This abort analysis also requires strong coordination with the Multi‐Purpose Crew Vehicle (MPCV) and SLS Structures and Environments (STE) to formulate a series of abortability tables that encapsulate explosion dynamics over the ascent mission phase. The design and assessment of abort conditions and triggers to estimate their Loss of Crew (LOC) Benefits also requires in‐depth integration with other groups, including Avionics, Guidance, Navigation and Control(GN&C), the Crew Office, Mission Operations, and Ground Systems. The outputs of this analysis are a critical input to SLS S&MA's LOC PRA models. The process described here may well be the first full quantitative application of SHM/FM theory to the selection of a sensor suite for any aerospace system.
Lo, Yunnhon↗
Extravehicular Activity on the Lunar Surface: Mapping Mitigation Risk Consequence for Crew Needing Assistance or Rescue
Extravehicular activity (EVA) on the lunar surface presents unique risks to crew with possibility for injury. Without appropriate assistance or rescue capability, inability to nominally ambulate and return to a lander, especially during early Artemis missions, could have catastrophic consequences. Mapping likelihood and consequence safety risk associated with identified injury scenarios establishes a baseline from which to assess potential mitigation solutions to ensure crew health and safety. Causes leading to the need for incapacitated crew rescue (ICR) during EVA on the lunar surface were previously identified and classified using an ICR/Acute Injury scenario spectrum. Severe scenarios are those when the affected astronaut requires either partial or full continuous assistance from the rescuer. Evaluation of these continual reliance conditions included calculating event probabilities (likelihoods) associated with an early Artemis mission and mapping them to established Exploration System Directorate (ESD) probability thresholds; safety consequences were analyzed and correlated to defined ESD personnel safety categories. These resulting likelihood and consequence values served as a baseline for assessing risk reduction of three mitigation capabilities: crew assistance (rescuer crew) only, walking assist devices, and a wheeled transport device. Of the twenty-five continual reliance conditions, ten were evaluated as “catastrophic” (Level 5, loss of life) during EVA on the lunar surface with probabilities ranging from moderate to very low during an early Artemis mission. Crew assistance only and walking assist devices showed similar potential for risk reduction, with four of the ten causes decreasing to Level 4. A wheeled transport device further increased risk reduction with six of the ten conditions decreasing to Level 4. Given the catastrophic consequence of several identified conditions, assessments should be performed to determine the feasibility of mitigation capabilities. It is currently unknown whether a rescuer astronaut could effectively provide continuous assistance to enable both crew to return safely to the lander from the standpoint of both suit geometry and human performance. Although resulting in an increase in resources, providing a wheeled transport provides the highest risk reduction potential, and walking assist devices may have prevention as well as mitigation benefits.
lunar surface↗
Resonant acoustic monitoring of damage in plug‐screw feeders
Abstract Plug‐screw feeders are critical in many industrial processes for compressing slurry materials via a rotating plug‐screw feeder. Over time, increasing plug‐screw feeder wear will eventually lead to catastrophic mechanical failure. Early detection of the wear state can prevent unplanned catastrophic failures resulting in operational shut‐downs, costly repairs, and most importantly the health and safety of workers. We present a theoretical basis for a noninvasive, in operando acoustic resonant technique to monitor the wear state of plug‐screw feeders. The technique is based on tracking the resonant acoustic modes of the plug‐screw feeder, which are sensitive to the plug‐screw feeder geometry, material, and operating conditions. We implemented a multivariate polynomial model to estimate the plug‐screw feeder wear state using multiple acoustic resonances by simulating the acoustic resonant modes for two categories of wear (tip and thread damage) that are common in plug‐screw feeders. Fitting multiple resonances to the polynomial model, we demonstrate accurate estimation of the total mass loss, as well as characterization of the type of damage (i.e., tip vs. thread). Current approaches for monitoring plug‐screw feeder wear rely on shutting down the operation and visually inspecting the plug‐screw feeder. The presented acoustic technique offers a noninvasive, in operando measurement approach that mitigates unplanned catastrophic failures. The acoustic resonance technique presented in the paper has a broad range of industrial applications including the Pharmaceutical, Mining, Integrated Biorefineries (IBR), and Additive Manufacturing industries, to name a few.
36 MATERIALS SCIENCE↗
2032 and 2036 risk enhancement from NEOs in the Taurid stream: Is there a significant coherent component to impact risk?
Impact risk is normally quantified by summing the product of the probability of an event and some measure of its consequences over the set of all possible events. The probability factor is considered to be more objective and is based on the size frequency distribution of Near Earth objects (NEOs) and an implicit assumption of randomness, which can be described as “stochastic risk”. Impact frequency does change with time, however, and there have been episodes in the deep geological past when the flux has been much higher. The hypothesis of “coherent catastrophism” suggests large variations on shorter timescales. It postulates the existence of a “Taurid resonant swarm” (TRS) of debris associated with Comet Encke that is stabilized by Jupiter and in a 7:2 resonance with it. The hypothetical cluster orbits in the broad Taurid stream, which crosses Earth's orbit twice a year at its nodes. Whereas the most extreme and fanciful versions of coherent catastrophism in recent geologic history have been comprehensively refuted, the possibility of a significant component of coherent (time-dependent) risk, associated with non-random correlated events, remains. This paper incorporates recently published data from observational campaigns associated with the Taurid stream. There is no evidence for objects in the Taurid stream that are above the global catastrophe threshold, but the possibility of a few large objects and a significant population of objects the size of the Chelyabinsk or Tunguska bodies has not been eliminated. Eyewitness accounts and comparison of airburst models to ground truth suggest that the Tunguska object was a Beta Taurid. The Tunguska event is probably an outlier when compared to the size frequency distributions under stochastic assumptions, but if there is a significant coherent component it may be representative of events that take place far more frequently, and risk assessments may have underestimated the contribution from airbursts. If so, the Earth will experience increased risk from objects this size, peaking in November 2032 and June 2036. We recommend targeted survey campaigns during these hypothetical TRS node crossings to quantify the population, search for potentially hazardous objects, and identify imminent impactors.
79 ASTRONOMY AND ASTROPHYSICS↗
Enhancing fatigue life by ductile-transformable multicomponent B2 precipitates in a high-entropy alloy
Catastrophic accidents caused by fatigue failures often occur in engineering structures. Thus, a fundamental understanding of cyclic-deformation and fatigue-failure mechanisms is critical for the development of fatigue-resistant structural materials. Here we report a high-entropy alloy with enhanced fatigue life by ductile-transformable multicomponent B2 precipitates. Its cyclic-deformation mechanisms are revealed by real-time in-situ neutron diffraction, transmission-electron microscopy, crystal-plasticity modeling, and Monte-Carlo simulations. Multiple cyclic-deformation mechanisms, including dislocation slips, precipitation strengthening, deformation twinning, and reversible martensitic phase transformation, are observed in the studied high-entropy alloy. Its improved fatigue performance at low strain amplitudes, i.e., the high fatigue-crack-initiation resistance, is attributed to the high elasticity, plastic deformability, and martensitic transformation of the B2-strengthening phase. This study shows that fatigue-resistant alloys can be developed by incorporating strengthening ductile-transformable multicomponent intermetallic phases.
36 MATERIALS SCIENCE↗
Simultaneously improved reversibility and hydrogen production of solid oxide cells through infiltrating air electrode
Among the various fuel cells, solid oxide cells (SOCs) are the unique type that can principally operate reversibly as either fuel cells to produce electricity or as an electrolyser to split water and produce green hydrogen (H 2 ). Nevertheless, the SOCs' reversibility presents enormous challenges that are manifested by the fast degradation through the cycling between fuel cell and electrolysis mode. While the La 0.8 Sr 0.2 MnO 3 /yttria-stabilized zirconia (LSM/YSZ) air electrode possesses significant advantages in terms of high electrical conductivity and high thermal stability under fuel cell mode, the SOCs with the LSM/YSZ air electrode experience rapid performance degradation with catastrophic electrode delamination shortly after switching from fuel cell to electrolysis mode. To prevent such catastrophic delamination and enable the electrolysis H 2 production, a chemical solution with the designed chemistry of SrFe 2 O 4-d was infiltrated into the LSM/YSZ air electrode. The infiltration immediately mitigates the catastrophic delamination, and the infiltrated cells exhibit significantly improved reversibility upon the electrochemical operation. Nanostructure examination reveals nanoscale cracks and second-phase nanograins formed in the air electrode from the baseline cell. By contrast, no delamination was observed at either the micron or the nanoscale for the infiltrated cell, which is attributed to the increased ion conductivity of the Fe-doped LSM mixed conductor induced by the significant interdiffusion between the LSM backbone and infiltrates. Here, this study presents a viable method for preventing electrode delamination while enhancing the durability of H 2 production and power generation for reversible fuel cell/electrolysis cell operation. It further opens new research directions of modifying the electrochemical activity of the electrode of inherently functional cells through the infiltration of the solutions with different chemistry.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Evolutionary NAS in Light of Model Stability for Accurate Continual Learning
Continual learning, the capability to learn new knowledge from streaming data without forgetting the previous knowledge, is a critical requirement for dynamic learning systems, especially for emerging edge devices such as self-driving cars and drones. However, continual learning is still facing the catastrophic forgetting problem. Previous work illustrate that model performance on continual learning is not only related to the learning algorithms but also strongly dependent on the inherited model, i.e., the model where continual learning starts. The better stability of the inherited model, the less catastrophic forgetting and thus, the inherited model should be elaborately selected. Inspired by this finding, we develop an evolutionary neural architecture search (ENAS) algorithm that emphasizes the Stability of the inherited model, namely ENAS-S. ENAS-S aims to find optimal architectures for accurate continual learning on edge devices. On CIFAR-10 and CIFAR-100, we present that ENAS-S achieves competitive architectures with lower catastrophic forgetting and smaller model size when learning from a data stream, as compared with handcrafted DNNs.
Du, Xiaocong↗
A preliminary assessment of the fluid erosional processes that shaped the Martian outflow channels
Catastrophic floods may be the mechanism which created Martian outflow channels and the distinctive assemblage of channel landforms, including regional and local anastomosing patterns, expanding and contracting reaches correlated with flow constrictions, streamlined uplands, inner channels with recessional headcuts, pendant forms on the downcurrent sides of flow obstacles, and scour marks around the obstacles. A terrestrial landscape which contains analogs to all the Martian outflow features is the Channeled Scabland of eastern Washington, formed by catastrophic flooding across differentially resistant basalt, loess and sedimentary rock. Both hydrodynamic theory and the properties of the boundary undergoing deformation need to be considered in studying the forms that result from catastrophic flooding.
Baker, V. R.↗
Role of molybdenum in the Na sub 2SO sub 4 induced corrosion of superalloys at high temperatures
Sodium sulfate induced corrosion of a molybdenum containing nickel-base superalloy, Udimet 700, was studied in laboratory furnace tests and in a high velocity (Mach 0.3) burner rig. The effect of SO2 content in the atmosphere on the corrosion behavior in the laboratory furnace tests was determined. Catastrophic corrosion occurs only when the melt contains MoO3 in addition to Na2SO4 and Na2MoO4. The conditions under which catastrophic corrosion occurs are identified and a mechanism is described to explain the catastrophic corrosion.
Misra, A. K.↗
Role of molybdenum in the Na2SO4 induced corrosion of superalloys at high temperature
Sodium sulfate induced corrosion of a molybdenum containing nickel-base superalloy, Udimet 700, was studied in laboratory furnace test and in a high velocity (Mach 0.3) burner rig. Tlhe effect of SO2 content in the atmosphere on the corrosion behavior in the laboratory furnace tests was determined. catastrophic corrosion occursonly when the melt contains MoO3 in addition to Na2SO4 and Na2MoO4. The conditions under which catastrophic corrosion occurs are identified and a mechanism is described to explain the catastrophic corrosion.
Misra, A. K.↗