A 217-year precipitation reconstruction in the Habahe area, Xinjiang, Northeast China

Evaluating long-term changes in precipitation resources is important for accurate hydrological evaluation and forecasting,water security and rational allocation of water resources.For this purpose in the Xinjiang Habahe area,tree-ring specimens were collected from Picea obovata,Larix sibirica,and Betula platyphylla to establish a tree-ring width chronology,which was used to analyse a correlation with the average temperature and precipitation per month for 1958-2016.Based on correlation coefficients for monthly temperature and precipitation with the chronology of tree-ring widths,radial tree growth was mainly restricted by precipitation,and tree-ring width chronology was significantly correlated with overall precipitation from the previous July to the next June(r=0.641,P<0.01).The above results were used to establish a transformation equation,and the overall precipitation from the previous July to the following June from 1800 to 2016 in Habahe was reconstructed after adjusted degrees of freedom,and obtain an explanatory rate of the variation up to 41.1%(40.0%).In addition to the reliability of the reconstructed values,the stability of the conversion function was determined via the“leave-one-out”method,which is commonly used in research on tree rings,and by cross-checking the conversion function with the reduced error value(RE),product mean test(t),with a sign test(ST).During the last 217 years,there were nine dry periods:1803-1829,1861-1865,1872-1885,1892-1905,1916-1923,1943-1954,1961-1966,1973-1981,and 2005-2011;and 12 wet periods:1830-1834,1836-1860,1866-1871,1886-1891,1906-1915,1925-1930,1934-1942,1955-1960,1967-1972,1982-1996,2000-2004,and 2012-2016.Comparisons of the reconstructions for neighboring regions and a spatial correlation analysis showed that the reconstructed sequence of the present precipitation data better represented the changes in precipitation in Habahe.Additionally,a power spectrum analysis revealed that precipitation over the past 217 years in Habahe Province exhibited 2-5 years of quasiperiodic variation.A power spectrum analysis and wavelet analysis indicated that El Niño-Southern Oscillation influenced the precipitation cycles.This reconstruction provides more information on high-frequency precipitation,which is an important supplement to the existing tree-ring reconstruction of precipitation in the study area.The reconstruction of regional high-resolution precipitation changes over the last several hundred years provides unique,important data for understanding regional differences in climate at the decadal-centennial scale.

Decreasing productivity of pine forests on the southern edge of the Mongolian Plateau as indicated by tree rings

Vegetation productivity on the southern edge of the Inner Mongolian Plateau,which plays a vital role in the ecological environment and in the arable and pasto-ral production in this region,can be characterized by the NDVI(normalized difference vegetation index).However,the observed NDVI data span only the last~40 years.The growth of Pinus tabulaeformis Carr.is strongly correlated with the NDVI,making it a valuable proxy for extend-ing the length of observed NDVI datasets.In this study,we reconstructed an NDVI series for 1776–2021 for the Daqing Mountains,based on a tree-ring width chronology.The reconstructed data accounted for 55%of the variance in the observed data,and its statistical characteristics and validation indicate that the reconstruction is dependable.Spatial correlation analysis demonstrated the consistency of climate signals in central Inner Mongolia in both the arable and pastoral zones.The results of superposed epoch analysis revealed a good temporal consistency between drought and flood events and the reconstructed NDVI sequence in this region.

A Compensation Controller Based on a Nonlinear Wavelet Neural Network for Continuous Material Processing Operations

Continuous material processing operations like printing and textiles manufacturing are conducted under highly variable conditions due to changes in the environment and/or in the materials being processed.As such,the processing parameters require robust real-time adjustment appropriate to the conditions of a nonlinear system.This paper addresses this issue by presenting a hybrid feedforward-feedback nonlinear model predictive controller for continuous material processing operations.The adaptive feedback control strategy of the controller augments the standard feedforward control to ensure improved robustness and compensation for environmental disturbances and/or parameter uncertainties.Thus,the controller can reduce the need for manual adjustments.The controller applies nonlinear generalized predictive control to generate an adaptive control signal for attaining robust performance.A wavelet-based neural network model is adopted as the prediction model with high prediction precision and time-frequency localization characteristics.Online training is utilized to predict uncertain system dynamics by tuning the wavelet neural network parameters and the controller parameters adaptively.The performance of the controller algorithm is verified by both simulation,and in a real-time practical application involving a single-input single-output double-zone sliver drafting system used in textiles manufacturing.Both the simulation and practical results demonstrate an excellent control performance in terms of the mean thickness and coefficient of variation of output slivers,which verifies the effectiveness of this approach in improving the long-term uniformity of slivers.

Sequential slip transfer of mixed-character dislocations across Σ3 coherent twin boundary in FCC metals: a concurrent atomistic-continuum study

Sequential slip transfer across grain boundaries(GB)has an important role in size-dependent propagation of plastic deformation in polycrystalline metals.For example,the Hall–Petch effect,which states that a smaller average grain size results in a higher yield stress,can be rationalised in terms of dislocation pile-ups against GBs.In spite of extensive studies in modelling individual phases and grains using atomistic simulations,well-accepted criteria of slip transfer across GBs are still lacking,as well as models of predicting irreversible GB structure evolution.Slip transfer is inherently multiscale since both the atomic structure of the boundary and the long-range fields of the dislocation pile-up come into play.In this work,concurrent atomistic-continuum simulations are performed to study sequential slip transfer of a series of curved dislocations from a given pile-up onΣ3 coherent twin boundary(CTB)in Cu and Al,with dominant leading screw character at the site of interaction.A Frank-Read source is employed to nucleate dislocations continuously.It is found that subject to a shear stress of 1.2 GPa,screw dislocations transfer into the twinned grain in Cu,but glide on the twin boundary plane in Al.Moreover,four dislocation/CTB interaction modes are identified in Al,which are affected by(1)applied shear stress,(2)dislocation line length,and(3)dislocation line curvature.Our results elucidate the discrepancies between atomistic simulations and experimental observations of dislocation-GB reactions and highlight the importance of directly modeling sequential dislocation slip transfer reactions using fully 3D models.