Holocene precipitationδ^18O as an indicator of temperature history in arid central Asia:an overview of recent advances

Holoceneδ^18O records from various archives(ice cores,cave stalagmites,and peat sediments)from the Xinjiang region of northwestern China,in arid central Asia(ACA),are all derived ultimately from local precipitationδ^18O(δ^18Op).Nevertheless,they have been proposed as indicators of different climatic parameters,such as wetness and temperature changes.This article summarizes previously reported records of moisture sources for the Xinjiang region and the results of modern observations conducted at an ice core site and a peat site in the Altai Mountains.The findings are used to propose that the overall positive trends in Holoceneδ^18O records from the various archives from the Xinjiang region primarily reflect the Holocene's long-term warming trend.It is concluded that more site-specific modern observations are needed to further elucidate the environmental significance of Holoceneδ^18O records from this region,especially for the separation of different seasonal temperature signals present withinδ^18O records.

Mesocosmic study on autogenous shrinkage of concrete with consideration of effects of temperature and humidity

A study on the autogenous shrinkage （AS） of concrete from a mesocosmic perspective was carried out using numerical simulation technology. The temperature history and the autogenous relative humidity （ARH）, two factors that have been shown to have occasional influence on this process in previous studies, were introduced into this study. According to these concepts, a program for simulation of the temperature field, humidity field, and stress field based on the equivalent age method and a fully automatic aggregate modeling tool were used. With the help of these programs, the study of a small concrete specimen provided some useful conclusions： the aggregate and the matrix show distinct distribution properties in the temperature field, humidity field, and stress field; the aggregate-matrix interface has a high possibility of becoming the location of the initial cracking caused by AS of concrete; the distribution of random aggregates is extremely important for mesoscopical analysis; and the temperature history is the main factor affecting the AS of concrete. On the whole, inherent mechanisms and cracking mechanisms of AS of concrete can be explained more reasonably and realistically only by considering the different characteristics of material phases and the effects of temperature and humidity.

An Energy Balance Simulation of the Universe

We have developed an energy balance equation for the universe. The two system parameters involved in the equation could be “fine-tuned” so that the predicted temperature histories all lead to what is observed in the present cosmic microwave background. We have shown that various combinations of these two parameters are possible;in particular, the present background temperature needs not be the remnant of a very hot temperature in the far distance past. We also solved for the propagation of vortex solitons in optical fibres as contrasting examples to show how electromagnetic wave could be transmitted in a particular waveform under strictly controlled conditions. To avoid singularity, all vortexes have a black centre. We conclude that while numerical techniques can be used to account for an infinite quantity, it is unlikely that such a quantity could exist in reality.

Methodology for predicting the life of plasma-sprayed thermal barrier coating system considering oxidation-induced damage

The lifespan of plasma-sprayed thermal barrier coating(TBC)systems is difficult to predict owing to the variety of microstructures and deterioration histories.In this study,we developed a novel TBC damage model to reflect deterioration histories;thus,it can be applied to various TBCs.Damage to TBCs is classifed into oxidation and mechanical damage;therefore,a detailed deterioration history can be reflected.In addition,by introducing a virtual S–N diagram,a life prediction model that can be applied to TBCs with various microstructures was established.We used the proposed damage and life prediction models in isothermal aging and thermal cycle tests with different aging cycles.The predicted lifespan of TBCs by using the proposed models was within 95%of the results obtained by performing actual tests in the temperature range of 1150–1350℃.