Study on Resistance Switching Properties of Na0.5Bi0.5TiO3Thin Films Using Impedance Spectroscopy

The Na0.5Bi0.5TiO3(NBT) thin films sandwiched between Au electrodes and fluorine-doped tin oxide (FTO) conducting glass were deposited using a sol–gel method. Based on electrochemical workstation measurements, reproducible resistance switching characteristics and negative differential resistances were obtained at room temperature. A local impedance spectroscopy measurement of Au/NBT was performed to reveal the interface-related electrical characteristics. The DC-bias-dependent impedance spectra suggested the occurrence of charge and mass transfer at the interface of the Au/NBT/FTO device. It was proposed that the first and the second ionization of oxygen vacancies are responsible for the conduction in the low- and high-resistance states, respectively. The experimental results showed high potential for nonvolatile memory applications in NBT thin films

Reconstruction of Time-Series MODIS LST in Central Qinghai-Tibet Plateau Using Geostatistical Approach

We present an approach for reconstructing land surface temperature (LST) time series over mountainous areas based on Regression Kriging (RK) technique and a data processing scheme for filtering out LST noise and artifacts. A total of 1462 eight-day composite Moderate Resolution Imaging Spectroradiometer LST images over central Qinghai-Tibet Plateau over 2003-2010 are reconstructed. The regression model includes four auxiliary predictors-latitude, longitude, elevation, and NDVI-which are proven to be a good estimator for the 8-day LST. Comparison of ground surface temperature (GST) measurements at eight meteorological stations with the raw and reconstructed LST series shows that the reconstruction strategy can effectively recover complete high-quality over-land LST maps and significantly improve the consistency between LST and GST.Department of Land Surveying and Geo-Informatic

Estimation of mass balance of Dongkemadi glaciers with multiple methods based on multi-mission satellite data

In the context of climate change and variability, the change of glaciers over Qinghai-Tibet Plateau (QTP) has substantial impact on regional water resource and supply in a large geographical area in Asia. In this study, the recent change of glaciers in the Dongkemadi region in the central QTP was estimated by using multi-date Landsat images acquired over 2000-2011 and altimetry data derived from ICESat over 2003-2008. The biased elevation sampling of ICESat footprints in different laser periods was corrected before trend fitting of elevation changes by estimating the gradients of elevation changes. The results show that glaciers experienced notable recession in the last decade, at a linear shrinking rate of 0.21km2 (0.26%) y-1 in area and a thinning rate of 0.56my-1. Mass balances based on ICESat (-421.2¡Ó83mmy-1 w.e) and area-volume scaling method (-487.2¡Ó96mmy-1) agree well with the in-situ measurements of Xiao Dongkemadi (-444.6mmy-1 w.e.), giving uncertainties with density assumptions. The results were compared with other studies, and indicate accelerated recession which may be linked with a significant warming trend in recent dDepartment of Land Surveying and Geo-Informatic