The tree-ring chronologies of Abies georgei Orr were developed for 3 sites at different elevations: the southern (2750 m), middle (3050 m), and northern (3400 m) parts of the Baimang Snow Mountains in northwestern Yunnan Province, China. The climate-growth response analysis indicated that trees at different elevations respond differently to environmental changes. The radial growth of trees found at the middle and high elevation sites was determined by temperature variables (mean, maximum, and minimum temperatures), particularly during the summer season (June to August), while moisture availability (precipitation and relative humidity) during spring (in March) was the crucial climate factor for tree growth at the low elevation site. The linear climate-growth model derived from the composite chronology of the 2 high elevation sites was verified with independent data from 1958 to 2005, and accounted for 33.4% of the mean temperature variation during summer (June to August). Based on this model, summer minimum temperature variations were reconstructed for the past 296 yr. The reconstruction revealed that cool climates mainly occurred in 1732-1743, 1758-1780, 1791-1824, 1836-1847, 1853-1862, 1908-1929, 1964-1976, and 1979-1993, while warm climates prevailed in 1718-1731, 1744-1756, 1781-1790, 1825-1835, 1883-1907, 1930-1963, and 1995 to present. Spectral analysis of the reconstruction using the multi-taper method (MTM) indicated the existence of some multidecadal (about 70 yr) and bidecadal (about 20 yr) cycles, which might correspond to the related cycles of solar activity, and significant peaks at about 2 to 8 yr, in agreement with the spectral mode of El Niño Southern Oscillation (ENSO)-type variability. KEY WORDS: Summer temperature · Climate reconstruction · Tree-ring · Northwestern YunnanResale or republication not permitted without written consent of the publisher Clim Res 47: 207-218, 2011 Tree-ring measurements provide a particularly valuable indicator of climatic history as they offer precise dating, extensive spatial availability, and climatologically high sensitivity (Fritts 1976, Schweingruber 1996. Tree-ring data play an important role in reconstructing the climate variability of the Northern Hemisphere and have been integrated worldwide into research on global change (Esper et al. 2002, Mann et al. 2008. The coniferous forests in northwestern Yunnan are ancient and diverse (Wu 1987), offering a compelling opportunity to explore tree-ring data, but few dendroclimatological studies have been conducted in this region. The earliest such study in this region was carried out at Haba Snow Mountains, in which Wu et al. (1988) reported a tree-ring chronology indicative of air temperature during the last 400 yr and suggested the existence of similar variations in the Tibetan Plateau. Based on the tree-ring data of the central Hengduan Mountains, variability in summer temperatures and spring droughts during the past several centuries have also been reconstructed (Fan et al. 2008, 2009a, Li et al. 2...

This paper presents a sequential coupled thermo-metallurgical-mechanical finite element model for low alloy steel quenching which can be used to predict temperature history, evolution of microstructure, internal stress and distortion. The main efforts are to develop a series of subroutines which consider the latent heat released due to phase transformation and numerical implementation of a thermo-metallurgical-mechanical constitute equation. The effectiveness of developed computational method is confirmed by a immersion quenching. Simulations of immersion quenching demonstrate that transformation induce plasticity has significant effect of the evolution of residual stress, distortion and can not be neglected for low alloy steel during immersion quenching.

The objective of this paper is to investigate the effects of solid-state phase transformation on welding residual stress in high stress low alloy steel. In this study, based on commercial finite element software, a sequentially coupled thermal, metallurgical, mechanical plane strain finite element model is developed. The main effort is to develop a series of subroutines which consider the heat transfer from welding arc and numerical implementation of a thermo-metallurgical-mechanical constitute equation. The effectiveness of developed computational method is confirmed by a butt welding simulation. Simulation of butt welding demonstrates that the distribution pattern of longitudinal residual stresses perpendicular to weld centerline at the upper surface of weldment has two peak and transformation plasticity has significant effect on the evolution of residual stress.