Single Abrupt Change Research Articles

Experimental and theoretical plasticity analyses of steel materials deformed under a nonlinear strain path

In this study, the macroscopic mechanical behavior of extra-deep drawing quality (EDDQ) and transformation-induced plasticity (TRIP1180) steels subjected to nonlinear-strain-path modes of deformation was investigated. For the nonlinear-strain-path experiments conducted on steels, an optimized experimental approach was proposed for deforming the material using two linear loading segments with a single abrupt change in the strain path. A specific medium-scale uniaxial tension specimen was designed for the pre-strain stage. The advantage of this approach over existing methods was that it enabled testing of various strain-path changes for steels with strengths greater than 1 GPa within a reasonable load range. In addition, this approach produced a more uniform strain field, which is important during the pre-strain stage. After the uniaxial pre-strain, various specimens were extracted from the uniformly deformed area for use in experiments involving changes in the strain path. To predict the material behavior under nonproportional loading, the homogeneous anisotropic hardening (HAH) distortional plasticity model was selected. The predictions of the HAH model were compared with the corresponding experimental results to assess the suitability of the constitutive model to accurately reproduce the observed effects of strain-path changes.

Advanced investigation on the change in the streamflow into the water source of the middle route of China's water diversion project

To alleviate water shortage in northern China, the middle route of the South to North Water Diversion Project (MRP) was constructed by the Chinese government. A dramatic reduction in the annual streamflow into Danjiangkou Reservoir (ASDR), the water source of MRP, during 1990 has raised some concerns on the MRP's operation. This paper employed an advanced segmented regression model with more recent data to have a clear picture and understand the changing pattern of the ASDR. Our study first revealed a zigzag changing pattern (decreasing‐increasing‐decreasing‐increasing) of ASDR during 1960–2013, which was supported by statistical criteria compared with a monotonic or single abrupt change. Particularly, the significantly decreasing trend from 1990s was reversed after 2000, and such change may relieve the concern about the water availability in the future. Sensitivity analysis showed that changes in streamflow were largely influenced by the combined effects of precipitation (P) and potential evapotranspiration (ET0) and were more sensitive to P than ET0. As ET0 is estimated from other primary variables, further analysis was conducted to understand the sensitivities of ET0 to its primary driving variables (wind speed, actual vapor pressure, temperature, and sunshine duration) and indicated that ET0 is mostly sensitive to actual vapor pressure during 1960–2013. The findings will assist the MRP's operation and management. Moreover, the results in this study also indicate that an adaptive water diversion plan, rather than the current plan with a constant annual amount of diversion water, might be a better option in the MRP's operation.

Variable growth modes in Late Cretaceous ammonoids: implications for diverse early life histories

Examination of ontogenetic changes in the septal angle of Late Cretaceous ammonoids (ten species representing seven superfamilies and four suborders) reveals four patterns: 1) a single abrupt change in septal angle; 2) two abrupt changes in septal angle; 3) cyclic fluctuations in septal angle throughout ontogeny; and 4) an almost constant septal angle throughout ontogeny. These various septal-angle patterns in Late Cretaceous ammonoids are in contrast with modern and fossil nautiloids, which have the common pattern displaying a single abrupt change in septal angles. Although the abrupt change of septal angles in nautiloids corresponds with the hatching event from the egg, change of septal angles in the examined ammonoids is hypothesized to correspond not to hatching but to the change from a planktic to a nektobenthic habit demarcated by the post-embryonic stage. Therefore, the variable patterns of septal angles within ammonoids suggest a diverse set of early life histories.

Event visibility in Austrian Sign Language (ÖGS)

This paper focuses on the phonological visibility of event structure of non-classifier predicates in Austrian Sign Language (ÖGS) as proposed in the Event Visibility Hypothesis (EVH) (Grose et al. 2006; Wilbur in press). The aim of this paper is to investigate the event structure of ÖGS predicate signs and to test the applicability of the EVH. The analysis provides evidence that the event structure of ÖGS predicates is also phonologically visible and that the two unrelated sign languages ASL and ÖGS use the same set of morphemes to mark telic and atelic event structures. The actual phonological realizations of these morphemes, however, are language dependent. The present paper adds to the EVH with a discussion of the observed inability of some predicates to be marked for telicity and with the analysis of mouth nonmanuals which are suggested to be sensitive to the event structure. These nonmanuals divide into two types: (1) continuous posture or P-nonmanuals, composed of a single facial posture which functions as an adverbial modifier of the event, and (2) discontinuous transition or T-nonmanuals, composed of a single abrupt change in the position of the articulator, which appear to emphasize the initial or final portion of the event structure.

Event visibility in Austrian Sign Language (ÖGS)

This paper focuses on the phonological visibility of event structure of non-classifier predicates in Austrian Sign Language (ÖGS) as proposed in the Event Visibility Hypothesis (EVH) (Grose et al. 2006; Wilbur in press). The aim of this paper is to investigate the event structure of ÖGS predicate signs and to test the applicability of the EVH. The analysis provides evidence that the event structure of ÖGS predicates is also phonologically visible and that the two unrelated sign languages ASL and ÖGS use the same set of morphemes to mark telic and atelic event structures. The actual phonological realizations of these morphemes, however, are language dependent. The present paper adds to the EVH with a discussion of the observed inability of some predicates to be marked for telicity and with the analysis of mouth nonmanuals which are suggested to be sensitive to the event structure. These nonmanuals divide into two types: (1) continuous posture or P-nonmanuals, composed of a single facial posture which functions as an adverbial modifier of the event, and (2) discontinuous transition or T-nonmanuals, composed of a single abrupt change in the position of the articulator, which appear to emphasize the initial or final portion of the event structure.

Assessment of the physiological effect of altered salinity on greenlip (Haliotis laevigata ) and blacklip (Haliotis rubra ) abalone using respirometry

The early physiological response (3 days) of greenlip (Haliotis laevigata Leach) and blacklip (H. rubra Leach) abalone to a single abrupt change in salinity was monitored using a multi-channel open-circuit respirometer. The range of salinity tolerance for both species in this trial was 25–40 ppt. Indications from other trials were that a margin of 2 ppt outside this range will cause mortality. Serum volume was increased by reduced salinity as much as 25% in the short term, with equilibration of the concomitant whole body weight increase (9.2±0.5%) occurring within 1 h. The serum volume appeared to be decreased at high salinity. There was little underlying change in basal oxygen usage levels, but significant behavioural changes that affected overall oxygen consumption. Both high and low salinity appeared to reduce activity. Animals in low salinity exhibit partial recovery of activity levels after 1 day in a manner similar to other stress responses. Animals at high salinity (40 ppt) did not show recovery of activity levels over 3 days. Overall, these results suggest that greenlip and blacklip abalone will have little trouble tolerating moderately low-salinity environments.

Nonequilibrium migration in human history.

A nonequilibrium migration model is proposed and applied to genetic data from humans. The model assumes symmetric migration among all possible pairs of demes and that the number of demes is large. With these assumptions it is straightforward to allow for changes in demography, and here a single abrupt change is considered. Under the model this change is identical to a change in the ancestral effective population size and might be caused by changes in deme size, in the number of demes, or in the migration rate. Expressions for the expected numbers of sites segregating at particular frequencies in a multideme sample are derived. A maximum-likelihood analysis of independent polymorphic restriction sites in humans reveals a decrease in effective size. This is consistent with a change in the rates of migration among human subpopulations from ancient low levels to present high ones.

Changes in the duration of economic expansions and contractions in the United States

This paper employs nonparametric change–point tests to business cycle duration data in the United States. The findings are consistent with recent studies citing longer expansions and shorter contractions since World War II. However, it is found that these shifts occurred much earlier. There is evidence of a single abrupt change–point to longer expansions that occurred in 1929. The shift towards shorter contractions was gradual: the transition began in 1918 and was completed in 1938.

Internal wave reflections and transmissions arising from a non‐uniform mesh. Part I: An analysis for the Crank–Nicolson linear finite element scheme

AbstractThis is the first of a series of three related papers dealing with some of the consequences of non‐uniform meshes in a numerical model. In this paper the accuracy of the Crank–Nicolson linear finite element scheme, which is applied to the linear shallow water equations, is examined in the context of a single abrupt change in nodal spacing. The (in)accuracy is quantified in terms of reflection and transmission coefficients. An incident wave impinging on the interface between two regions with different nodal spacings is shown to give rise to no reflected waves and two transmitted waves. The analysis is verified using three different wavelengths (2Δx, 4Δx 8Δx) in three ‘hot‐start’ numerical experiments with a mesh expansion factor of 2 and three experiments with a mesh contraction factor of 1/2. An energy flux analysis based on the concept of group velocity shows that energy is conserved across the interface.

North Atlantic sea-surface temperatures for the last 1.1 million years

Summary A 1.2 Ma time series of north-east Atlantic sea-surface temperature (SST) has been assembled from the spliced record of piston core K 708-7 (0.68-0 Ma) and hydraulic piston cores taken in nearby DSDP Hole 552A (1.2–0.68 Ma). A no-analogue fauna precludes making credible SST estimates in the interval 1.2–1.1 Ma, but the record above 1.1 Ma is suitable for SST estimates and related time-series analysis. The amplitude of SST variation is considerably higher in the Brunhes than in the upper Matuyama. This is due both to colder glacial SST minima after 0.85 Ma, and to increasingly warm interglacial SST maxima from 0.7 to 0.4 Ma. The dominant periodicity in the SST signal is centred near 95 000 years; it increases in amplitude by a factor of four from the bottom of the record to the top, with the largest increase occurring between 0.7 and 0.4 Ma. This suggests a relatively gradual evolution of ‘100 000-year’ power over half a million years of the late Quaternary, rather than a single abrupt change at 0.9 Ma. Significant, but progressively smaller, spectral peaks occur at periods of 54 000, 41 000, 31 000, 23 000 and 19 000 years. Both the 54 000-year and 31 000-year signals may be a response to insolation forcing by minor obliquity terms. Long-term δ 18 O records show small responses by the ice sheets at or near these two periods, indicating the probable initial response of the climate system to these insolation rhythms. In-phase relationships between δ 18 O and SST at these periods suggest that the ice sheets then impose these rhythms on the ocean with no lag. The mechanism by which such small insolation and ice-volume signals become enhanced in the SST record is not clear.

Sound velocities in calcareous oozes and chalks from sonobuoy data: Ontong Java Plateau, western equatorial Pacific

The Ontong Java Plateau, in the western equatorial Pacific Ocean, is blanketed by over 1 km of flatlying, highly stratified calcareous ooze, chalk, and limestone. Wide‐angle reflection data from 17 sonobuoys deployed over the plateau were analyzed for compressional wave velocities in these sediments. No particular velocity horizons stand out as prominent features that can be correlated from one sonobuoy station to the next. When the data from all stations are plotted together, a fairly consistent velocity‐depth relationship is derived: V = 1.56 + 2.97t with the standard error of estimate equal to 0.08, where V is the compressional wave velocity in kilometers per second at depth t and t is the depth below the sea floor in one‐way travel time of sound in seconds. When the velocity data are plotted against depth in kilometers below the sea floor, the velocity gradient is 1.4 s−1, which is considerably greater than that in most marine turbidites, silts, and clays that are buried to 1 km. The linear uniform velocity gradient is consistent with the type of lithology underlying the Ontong Java Plateau as determined by the Deep‐Sea Drilling Project. That is, there are gradual transitions from ooze to chalk to limestone with intervals of the different lithologies interbedded rather than a single abrupt change from ooze to chalk at one level and from chalk to limestone at a deeper level. A slight difference was seen between velocity profiles in calcareous sediments that had been deposited below and those that had been deposited above the lysocline (the depth below which calcareous ooze is markedly corroded). Sublysoclinal sediments have anomalously low acoustic velocities in the upper 200 m of strata but have normal velocities at greater burial depths. These observations suggest that calcareous sediments deposited below the lysocline lithify more slowly after burial than those deposited above the lysocline.

The Influence of Changes in Surface Roughness on the Development of the Turbulent Boundary Layer in the Lower Layers of the Atmosphere

Abstract This paper describes the development of a turbulent boundary layer in a neutral atmosphere downwind of an abrupt change of surface roughness. Both a single change and two subsequent changes are treated. For the treatment of a single abrupt change, a theory of Townsend forms the starting point. It is proved, according to this theory, that no surface layer adapted to the underlying surface roughness can exist behind the change. It is then shown how Townsend's theory can be modified in such a way that this discrepancy is removed. The modified theory gives nearly the same velocity profile as does the original. However, it leads to greatly different values of the surface shear stress behind the change, a matter of importance in calculating turbulent transport. It is shown that a correct evaluation of the height of the adapted layer is of importance for the determination of surface shear stress and roughness height from measured velocity profiles. The modified form of Townsend's theory is then extended...