A NEW CLASS OF LUMINESCENT ORGANOMETALLICS -DIETHYNYLRHODACYCLOPENTADIENES

The main objective in this project is to develop a greater understanding of the unusual photophysical properties of 2,5-bis(arylethynyl)rhodacyclopentadienes. Three distinct and unusual photophysical properties were found in the 2,5-bis(arylethynyl)-rhodacyclopentadienes: (i) long-lived singlet excited states, from which some of them exhibit high-intensity fluorescence with nanosecond lifetimes; (ii) slow intersystem crossing rates (k values ≈ 108 s-1) compared to typical luminescent organometallic complexes (with k values ≈ 1012 s-1); and (iii) no phosphorescence was observed even at 77 K in a rigid glass. Many photophysical experiments such as e.g. low-temperature lifetime measurments, singlet oxygen sensitisation and time-resolved infrared (TRIR) have been carried out in order to investigate further and explain the unusual photophysical properties of this class of organometallic complexes. Five different types of ligand X on 2,5-bis(p-R-arylethynyl)-X-rhodacyclopentadienes [X = 4-[4-(N,N-di-n-hexylamino)phenylethynyl]phenylethynyl- (DHAPEPE-), trimethyl silylethynyl- (TMSE-), methyl- (Me-), η2-benzoato- and acetylacetonato- (acac-)] have been synthesised and the photophysical properties of the complexes were investigated. The TMSE-rhodacyclopentadienes gave the highest fluorescence quantum yields compared to the other series of rhodacyclopentadienes. Extended phenylene-ethynylene ligands (i.e. DHAPEPE-) did not impart any effects on the max values in absorption and emission but the quantum yields were lower than those for the TMSE-rhodacyclopentadienes. η2-Benzoato- and acac- ligands shifted the max values in absorption and emission to lower energy, which implies that they induce smaller energy gaps between the excited and ground states. The emissions from the η2-benzoato-rhodacyclopentadienes were quenched (especially for those with R = H and SMe substituents, which have quantum yields of less than 0.01). The first example of isomeric biphenyl-rhodacyclopentadiene by-product formation was found in the synthesis of acac-rhodacyclopentadienes. The isomeric biphenyl-rhodacyclopentadiene by-product with R = CO2Me was isolated and its molecular structure was confirmed by X-ray analysis. Its emission spectrum shows two emission bands with max values of 394 and 544 nm in degassed toluene solution. The fluorescent emission at 394 nm has a quantum yield of 0.03, whereas the phosphorescent emission at 544 nm has a quantum yield of 0.05. The unusual long lifetime (237.6 s) of the phosphorescence at room temperature indicates that the transition is from a ligand-centred (LC) * transition. In addition, the syntheses of 1,4-bis(p-R-phenyl)buta-1,3-diynes and novel 1,12-bis(p-R-phenyl)dodaca-1,3,9,11-tetraynes, which serve as the starting materials for the synthesis of the rhodacyclopentadienes, are also reported. Four novel 1,12-bis(p-R-phenyl)dodaca-1,3,9,11-tetraynes (where R = H, SMe, CO2Me and BMes2) have been synthesised and characterised. The formation of homo-coupling products was a major problem which reduced the yields of the 1,3,9,11-dodacatetraynes. The 1,3,9,11-dodacatetraynes were separated from their respective homo-coupling products using column chromatography, and the yields obtained were 30 – 46%

Quantity and quality of China's water from demand perspectives

China is confronted with an unprecedented water crisis regarding its quantity and quality. In this study, we quantified the dynamics of China's embodied water use and chemical oxygen demand (COD) discharge from 2010 to 2015. The analysis was conducted with the latest available water use data across sectors in primary, secondary and tertiary industries and input-output models. The results showed that (1) China's water crisis was alleviated under urbanisation. Urban consumption occupied the largest percentages (over 30%) of embodied water use and COD discharge, but embodied water intensities in urban consumption were far lower than those in rural consumption. (2) The 'new normal' phase witnessed the optimisation of China's water use structures. Embodied water use in light-manufacturing and tertiary sectors increased while those in heavy-manufacturing sectors (except chemicals and transport equipment) dropped. (3) Transformation of China's international market brought positive effects on its domestic water use. China's water use (116-80 billion tonnes (Bts))9 and COD discharge (3.95-2.22 million tonnes (Mts)) embodied in export tremendously decreased while its total export values (11-25 trillion CNY) soared. Furthermore, embodied water use and COD discharge in relatively low-end sectors, such as textile, started to transfer from international to domestic markets when a part of China's production activities had been relocated to other developing countries

Exploring Different Roles between Service Expectation and Technology Expectation In Citizen’s E-Government Continuance Adoption: An Extended Expectation-Confirmation Model

Although Chinese government has got remarkable achievement in e-Government development, the difficult issue that citizen use behaviour cannot last toward many e-Government services has long been troubling to government in different levels. Based on expectation-confirmation theory (ECT), this paper proposed an extended model by divide the expectation and perceived performance into two categories, service perspective and technology perspective, for understanding the different roles of those factors in the process of e-Government continuance adoption. The research plan of an empirical experiment toward the e-Government portal of Beijing, the capital of China for utilizing this extended model was also discussed briefly in the paper

XGrad: Boosting Gradient-Based Optimizers With Weight Prediction

In this paper, we propose a general deep learning training framework XGrad which introduces weight prediction into the popular gradient-based optimizers to boost their convergence and generalization when training the deep neural network (DNN) models. In particular, ahead of each mini-batch training, the future weights are predicted according to the update rule of the used optimizer and are then applied to both the forward pass and backward propagation. In this way, during the whole training period, the optimizer always utilizes the gradients w.r.t. the future weights to update the DNN parameters, making the gradient-based optimizer achieve better convergence and generalization compared to the original optimizer without weight prediction. XGrad is rather straightforward to implement yet pretty effective in boosting the convergence of gradient-based optimizers and the accuracy of DNN models. Empirical results concerning the most three popular gradient-based optimizers including SGD with momentum, Adam, and AdamW demonstrate the effectiveness of our proposal. The experimental results validate that XGrad can attain higher model accuracy than the original optimizers when training the DNN models. The code of XGrad will be available at: https://github.com/guanleics/XGrad.Comment: arXiv admin note: text overlap with arXiv:2302.0019

China\u27s inter-regional spillover of carbon emissions and domestic supply chains

In this study, we apply the inter-regional input–output model to explain the relationship between China’s inter-regional spillover of CO2 emissions and domestic supply chains for 2002 and 2007. Based on this model, we propose alternative indicators such as the trade in CO2 emissions, CO2 emissions in trade, regional trade balances, and comparative advantage of CO2 emissions. The empirical results not only reveal the nature and significance of inter-regional environmental spillover within China’s domestic regions but also demonstrate how CO2 emissions are created and distributed across regions via domestic production networks. The main finding shows that a region’s CO2 emissions depend on not only its intra-regional production technique, energy use efficiency but also its position and participation degree in domestic and global supply chains