Lateral spread of nuclear-electromagnetic cascades in iron
Lateral spread of nuclear-electromagnetic cascades in iron absorber from three-dimensional Monte Carlo simulation
Jones, W. V.↗
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Lateral spreading of Au contacts on InP
The contact spreading phenomenon observed when small area Au contacts on InP are annealed at temperatures above about 400 C was investigated. It was found that the rapid lateral expansion of the contact metallization which consumes large quantities of InP during growth is closely related to the third stage in the series of solid state reactions that occur between InP and Au, i.e., to the Au3In-to-Au9In4 transition. Detailed descriptions are presented of both the spreading process and the Au3In-to-Au9In4 transition along with arguments that the two processes are manifestations of the same basic phenomenon.
Fatemi, Navid S.↗
Lateral spread of sonic boom measurements from US Air Force boomfile flight tests
A series of sonic boom flight tests were conducted by the US Air Force at Edwards AFB in 1987 with current supersonic DOD aircraft. These tests involved 43 flights by various aircraft at different Mach number and altitude combinations. The measured peak overpressures to predicted values as a function of lateral distance are compared. Some of the flights are combined into five groups because of the varying profiles and the limited number of sonic booms obtained during this study. The peak overpressures and the lateral distances are normalized with respect to the Carlson method predicted centerline overpressures and lateral cutoff distances, respectively, to facilitate comparisons between sonic boom data from similar flight profiles. It is demonstrated that the data agrees with sonic boom theory and previous studies and adds to the existing sonic boom database by including sonic boom signatures, tracking, and weather data in a digital format.
Downing, J. Micah↗
Lateral-spread sonic-boom ground-pressure measurements from airplanes at altitudes to 75,000 feet and at mach numbers to 2.0
Measurements of shock wave overpressures from airplanes at altitudes to 75,000 feet & supersonic speed
HIGH ALTITUDE PRESSURE↗
Reversal in Spreading of a Tabbed Circular Jet Under Controlled Excitation
Detailed flow field measurements have been carried out for a turbulent circular jet perturbed by tabs and artificial excitation. Two "delta tabs" were placed at the nozzle exit at diametrically opposite locations. The excitation condition involved subharmonic resonance that manifested in a periodic vortex pairing in the near flow field. While the excitation and the tabs independently increased jet spreading, a combination of the two diminished the effect. The jet spreading was most pronounced with the tabs but was reduced when excitation was applied to the tabbed jet. The tabs generated streamwise vortex pairs that caused a lateral spreading of the jet in a direction perpendicular to the plane containing the tabs. The excitation, on the other band, organized the azimuthal vorticity into coherent ring structures whose evolution and pairing also increased entrainment by the jet. In the tabbed case, the excitation produced coherent azimuthal structures that were distorted and asymmetric in shape. The self-induction of these structures produced an effect that opposed the tendency for the lateral spreading of the streamwise vortex pairs. The passage of the distorted vortices, and their pairing, also had a cancellation effect on the time-averaged streamwise vorticity field. These led to the reduction in jet spreading.
Zaman, K. B. M. Q.↗
Reversal in Spreading of a Tabbed Circular Jet Under Controlled Excitation
Detailed flow field measurements have been carried out for a turbulent circular jet perturbed by tabs and artificial excitation. Two "delta tabs" were placed at the nozzle exit at diametricall opposite y locations. The excitation condition involved subharmonic resonance that manifested in a periodic vortex pairing in the near flow field. While the excitation and the tabs independently increased jet spreading, a combination of the two diminished the effect. The jet spreading was most pronounced with the tabs but was reduced when excitation was applied to the tabbed jet. The tabs generated streamwise vortex pairs that caused a lateral spreading of the jet in a direction perpendicular to the plane containing the tabs. ne excitation, on the other hand, organized the azimuthal vorticity into coherent ring structures whose evolution and pairing also increased entrainment by the jet. In the tabbed case, the excitation produced coherent azimuthal structures that were distorted and asymmetric in shape. The self-induction of these structures produced an effect that opposed the tendency for the lateral spreading of the streamwise vortex pairs. The passage of the distorted vortices, and their pairing, also had a cancellation effect on the time-averaged streamwise vorticity field. These led to the reduction in jet spreading.
Zaman, K. B. M. Q.↗
Characterization of multiple-bit errors from single-ion tracks in integrated circuits
The spread of charge induced by an ion track in an integrated circuit and its subsequent collection at sensitive nodal junctions can cause multiple-bit errors. The authors have experimentally and analytically investigated this phenomenon using a 256-kb dynamic random-access memory (DRAM). The effects of different charge-transport mechanisms are illustrated, and two classes of ion-track multiple-bit error clusters are identified. It is demonstrated that ion tracks that hit a junction can affect the lateral spread of charge, depending on the nature of the pull-up load on the junction being hit. Ion tracks that do not hit a junction allow the nearly uninhibited lateral spread of charge.
Zoutendyk, J. A.↗
A search for mini-clusters in Japan-USSR Joint Experiment at Pamir
A search for mini-clusters, very collimated shower clusters of hadrons and electromagnetic particles, is made for the hadron and gamma families observed by Japan-USSR joint carbon chamber at Pamir. The existence of anomalous correlation between hadrons and electromagnetic particles is found. The decascading method is applied to the families and it is found that 11 clusters which include hadrons as members have smaller spread, Er 3.5 GeV.m and larger lateral spread, E'R' 100 GeV.m, from the family center. In the simulated events, such clusters were found to be very rare.
Source record↗
Observations of liquid jets injected into a highly accelerated supersonic boundary layer
Experiments were conducted to observe the cross-sectional structure and streamwise growth of round transverse liquid jets injected into a highly accelerated boundary layer in supersonic flow. The accompanying shock structure was also visualized. In one case, a round jet of acetone was injected into a fully turbulent Mach 2.5 boundary layer that was subsequently accelerated and partially laminarized through a sharp Prandtl-Meyer expansion corner. In the second case, a jet was injected into the laminarized Mach 3.2 boundary layer downstream of the expansion corner at the same jet-to-freestream momentum ratio. The jet and shock structure in both cases were visualized using schlieren optics. Wall-flow patterns were visualized using paints. It was found that the lateral spreading of jets injected downstream of the expansion fan was augmented close to the wall and had a cross-sectional structure significantly different from that of the jet injected upstream: the upstream jet spreads rapidly at the expansion corner in both the lateral and vertical directions.
Johnson, Arthur W.↗
Waves produced from a harmonic point source in a supersonic boundary layer
The disturbance wave pattern produced by a harmonic point source in a compressible flat-plate boundary layer is computed using linear stability theory and direct numerical integration approach. Receptivity coefficients are computed for the spectrum of spanwise modes generated at the source. The effect of boundary layer growth on the development of linear waves is determined by using the method of multiple scales. Results are presented for Mach numbers of 0, 2, 4.5, and 7. It is found that disturbances spread in wedge-shaped regions behind the source and the wedge angle decreases with Mach number. The lateral spreading angle for the instability waves turns out to be quite close to the angle found experimentally for turbulence lateral contamination.
Balakumar, P.↗
Evolution of a Florida Cirrus Anvil
This paper presents a detailed study of a single thunderstorm anvil cirrus cloud measured on 21 July 2002 near southern Florida during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers--Florida Area Cirrus Experiment (CRYSTAL-FACE). NASA WB-57F and University of North Dakota Citation aircraft tracked the microphysical and radiative development of the anvil for 3 h. Measurements showed that the cloud mass that was advected downwind from the thunderstorm was separated vertically into two layers: a cirrus anvil with cloud-top temperatures of -45?C lay below a second, thin tropopause cirrus (TTC) layer with the same horizontal dimensions as the anvil and temperatures near -70?C. In both cloud layers, ice crystals smaller than 50 ?m across dominated the size distributions and cloud radiative properties. In the anvil, ice crystals larger than 50 ?m aggregated and precipitated while small ice crystals increasingly dominated the size distributions; as a consequence, measured ice water contents and ice crystal effective radii decreased with time. Meanwhile, the anvil thinned vertically and maintained a stratification similar to its environment. Because effective radii were small, radiative heating and cooling were concentrated in layers approximately 100 m thick at the anvil top and base. A simple analysis suggests that the anvil cirrus spread laterally because mixing in these radiatively driven layers created horizontal pressure gradients between the cloud and its stratified environment. The TTC layer also spread but, unlike the anvil, did not dissipate--perhaps because the anvil shielded the TTC from terrestrial infrared heating. Calculations of top-of-troposphere radiative forcing above the anvil and TTC showed strong cooling that tapered as the anvil evolved.
Garrett, T. J.↗
Comparison of Inflation Processes at the 1859 Mauna Loa Flow, HI, and the McCartys Flow Field, NM
Basaltic lavas typically form channels or tubes during flow emplacement. However, the importance of sheet flow in the development of basalt ic terrains received recognition over the last 15 years. George Walke r?s research on the 1859 Mauna Loa Flow was published posthumously in 2009. In this paper he discusses the concept of endogenous growth, or inflation, for the distal portion of this otherwise channeldominated lava flow. We used this work as a guide when visiting the 1859 flow to help us better interpret the inflation history of the McCartys flow field in NM. Both well preserved flows display similar clues about the process of inflation. The McCartys lava flow field is among the you ngest (approx.3000 yrs) basaltic lava flows in the continental United States. It was emplaced over slopes of <1 degree, which is similar to the location within the 1859 flow where inflation occurred. Although older than the 1859 flow, the McCartys is located in an arid environ ment and is among the most pristine examples of sheet flow morphologies. At the meter scale the flow surface typically forms smooth, undula ting swales that create a polygonal terrain. The literature for simil ar features includes multiple explanatory hypotheses, original breakouts from adjacent lobes, or inflation related upwarping of crust or sa gging along fractures that enable gas release. It is not clear which of these processes is responsible for polygonal terrains, and it is po ssible that one explanation is not the sole cause of this morphology between all inflated flows. Often, these smooth surfaces within an inflated sheet display lineated surfaces and occasional squeeze-ups alon g swale contacts. We interpret the lineations to preserve original fl ow direction and have begun mapping these orientations to better interpret the emplacement history. At the scale of 10s to 100s of meters t he flow comprises multiple topographic plateaus and depressions. Some depressions display level floors with surfaces as described above, while some are bowl shaped with floors covered in broken lava slabs. Th e boundaries between plateaus and depressions are also typically smoo th, grooved surfaces that have been tilted to angles sometimes approaching vertical. The upper margin of these tilted surfaces displays lar ge cracks, sometimes containing squeeze-ups. The bottom boundary with smooth floored depressions typically shows embayment by younger lavas. It appears that this style of terrain represents the emplacement of an extensive sheet that experiences inflation episodes within prefer red regions where lateral spreading of the sheet is inhibited, thereby forming plateaus. Depressions are often the result of non-inflation and can be clearly identified by lateral squeeze-outs along the pit walls that form when the rising crust exposes the still liquid core of the sheet. Our current efforts are focused on.
Bleacher, Jacob E.↗
Surface Textures and Features Indicative of Endogenous Growth at the McCartys Flow Field, NM, as an Analog to Martian Volcanic Plains
Basaltic lavas typically form channels or tubes, which are recognized on the Earth and Mars. Although largely unrecognized in the planetary community, terrestrial inflated sheet flows also display morphologies that share many commonalities with lava plains on Mars. The McCartys lava flow field is among the youngest (approx.3000 yrs) basaltic flows in the continental United States. The southwest sections of the flow displays smooth, flat-topped plateaus with irregularly shaped pits and hummocky inter-plateau units that form a polygonal surface. Plateaus are typically elongate in map view, up to 20 m high and display lineations within the glassy crust. Lineated surfaces occasionally display small < 1m diameter lava coils. Lineations are generally straight and parallel each other, sometimes for over 100 meters. The boundaries between plateaus and depressions are also lineated and tilted to angles sometimes approaching vertical. Plateau-parallel cracks, sometimes containing squeeze-ups, mark the boundary between tilted crust and plateau. Some plateau depressions display level floors with hummocky surfaces, while some are bowl shaped with floors covered in broken lava slabs. The lower walls of pits sometimes display lateral, sagged lava wedges. Infrequently, pit floors display the upper portion of a tumulus from an older flow. In some places the surface crust has been disrupted forming a slabby texture. Slabs are typically on the scale of a meter or less across and no less than 7-10 cm thick. The slabs preserve the lineated textures of the undisturbed plateau crust. It appears that this style of terrain represents the emplacement of an extensive sheet that experiences inflation episodes within preferred regions where lateral spreading of the sheet is inhibited, thereby forming plateaus. Rough surfaces represent inflation-related disruption of pahoehoe lava and not a a lava. Depressions are often the result of non-inflation and can be clearly identified by lateral squeeze-outs along the pit walls that form when the rising crust exposes the still liquid core of the sheet. The plains of Tharsis and Elysium, Mars, display many analogous features
Bleacher, Jacob E.↗
On the growth of turbulent regions in laminar boundary layers
Turbulent spots evolving in a laminar boundary layer on a nominally zero pressure gradient flat plate are investigated. The plate is towed through an 18 m water channel, using a carriage that rides on a continuously replenished oil film giving a vibrationless tow. Turbulent spots are initiated using a solenoid valve that ejects a small amount of fluid through a minute hole on the working surface. A novel visualization technique that utilizes fluorescent dye excited by a sheet of laser light is employed. Some new aspects of the growth and entrainment of turbulent spots, especially with regard to lateral growth, are inferred from the present experiments. To supplement the information on lateral spreading, a turbulent wedge created by placing a roughness element in the laminar boundary layer is also studied both visually and with probe measurements. The present results show that, in addition to entrainment, another mechanism is needed to explain the lateral growth characteristics of a turbulent region in a laminar boundary layer. This mechanism, termed growth by destabilization, appears to be a result of the turbulence destabilizing the unstable laminar boundary layer in its vicinity. To further understand the growth mechanisms, the turbulence in the spot is modulated using drag-reducing additives and salinity stratification.
Gad-El-hak, M.↗
Formation of perched lava ponds on basaltic volcanoes: Interaction between cooling rate and flow geometry allows estimation of lava effusion rates
Perched lava ponds are infrequent but distinctive topographic features formed during some basaltic eruptions. Two such ponds, each approximately 150 m in diameter, formed during the 1968 eruption at Napau Crater and the 1974 eruption of Mauna Ulu, both on Kilauea Volcano, Hawaii. Each one formed where a channelized, high volume flux lava flow encountered a sharp reduction of slope: the flow spread out radially and stalled, forming a well-defined terminal levee enclosing a nearly circular lava pond. We describe a model of how cooling limits the motion of lava spreading radially into a pond and compare this with the case of a channelized flow. The difference in geometry has a major effect, such that the size of a pond is a good indicator of the volume flux of the lava forming it. Lateral spreading on distal shallow slopes is a major factor limiting the lengths of lava flows.
Wilson, L.↗
Jets in Gamma-Ray Bursts
In the afterglows of several gamma-ray bursts (GRBs), rapid temporal decay, which is inconsistent with spherical (isotropic) blast-wave models, is observed. In particular, GRB 980519 had the most rapidly fading of the well-documented GRB afterglows, with t(sup -2.05 +/- 0.04) in optical as well as in X-rays. We show that such temporal decay is more consistent with the evolution of a jet after it slows down and spreads laterally, for which t(sup -P) decay is expected (where p is the index of the electron energy distribution). Such a beaming model would relax the energy requirements on some of the more extreme GRBs by a factor of several hundred. It is likely that a large fraction of the weak- (or no-) afterglow observations are also due to the common occurrence of beaming in GRBs and that their jets have already transitioned. to the spreading phase before the first afterglow observations were made. With this interpretation, a universal value of p approx. = 2.4 is consistent with all data.
Sari, R.↗
Ground testing at MSFC
The large-scale field collection of acoustic data and their analysis are described in this review. The entire sound-field program has the purpose of solving complex problems of excessive noise propagation associated with the static test firing of large space-booster powerplants. The site of data collection has been Mississippi Test Facility (MTF), where far-field sound-propagation and correlated meteorological measurements were initiated in 1962. The statistical evaluation of sound-measurement data shows that the polar distribution of sound in the springtime (at MTF) is determined mainly by the temperature field of the atmosphere. Greater deformation of sound-intensity polar distribution occurs in the autumn as a result of the influence of the wind field. The data on sound attenuation as a function of distance from its source revealed attenuation in excess of the expected magnitude. The excess was mainly between 1 and 10 kilometers from the source, with maximum attenuation (17 to 18 decibels) near 6 kilometers. Excess sound attenuation was compared with calculated sound dispersion. For all sound frequencies in all seasons the deviation between reference and empirical attenuation values formed a bell-shaped distribution on a semilogarithmic plot. The physical causes for the sound- attenuation behavior are considered to be atmospheric diffraction and scattering effects. Statistical analysis of sod-intensity extremes indicated amplification of the sound signals by focusing which could be expected along selected azimuths. Empirical amplification values showed the maximum occurring in winter (50 decibels at 22 kilometers). For the analysis of correlation between empirical sound data and local atmospheric sound- propagation conditions, #e concept of analytical classification of sound-velocity profiles has been developed. Examination of over a quarter-million individual sound-velocity profiles indicates that 33 profile types for heights up to 3 kilometers constitute the empirical possibilities of sound-propagation conditions in southeastern United States. Since the focusing qualities of each sound- velocity profile can be determined as a class characteristic, the overall probabilities of focusing occurrence can he obtained. The severity of focusing, as based upon lateral spread of focusing areas, has been determined. The data for MTF indicate focusing is most severe in winter, with the direction toward east being most affected. Sound propagation is a fluctuating phenomenon because atmospheric conditions vary continuously. A measuring system for analyzing the nonstationary sound-propagation phenomena has been established. The analysis of the acoustic fluctuation data is sup- posed to provide "dynamic” perturbation functions of sound, which are to be superimposed on the related characteristic sound-velocity-profile type. The ultimate result of the program will be the establishment of reliable contingency tables showing the relationship between atmospheric parameters and far-field sound intensities. These data will be the basis for more accurate sound-propagation forecasting for static firing tests.
STATIC TESTING↗
Some effects of airplane operations and the atmosphere on sonic-boom signatures.
Sonic boom phenomena, noting atmospheric dynamic effects, acceleration and lateral spread, variations in pressure signatures, etc
PRESSURE EFFECT↗