Synthesis of Palladium-Based Electrocatalysis—From Pure Metal to Bimetallic Nanoparticles

This thesis focuses on synthesis and characterization of palladium-based nanoparticles. Background information of the research in this thesis is provided in Chapter 1. Preparation and characterization of pure palladium nanoparticles are presented in Chapter 2. A fast and convenient method to prepare ultra small Pd nanoparticles via Pluronic P123 reduction is discussed in detail. Impregnation method and poly method are also studied in this chapter. Chapter 3 reports the studies of these methods to prepare ultra small bimetallic (bimetallic means a mixture of two metals) palladium-based nanoparticles. Oleylamine-mediated method used Pd nanoparticles prepared via P123 reduction as precursor. Ultra small palladium-based nanoparticles are prepared in this way. With the assistance of trioctylphosphine complex as precursor, tiny palladium-based bimetallic nanoparticles can be prepared with certain structure. The structure of these bimetallic nanoparticles gives a better electrochemical activity than pure palladium nanoparticles. When loaded on mesoporous carbon, these tiny trioctylphosphine-assisted palladium nanoparticles displayed good thermal stability

Relationship between Ambulatory Pulse Pressure, Pulse Pressure Index and Coronary Artery Disease in Patients with Hypertension

Objective: To analyze the relationship between ambulatory pulse pressure, pulse pressure index, and coronary artery disease in patients with hypertension. Methods: From February 2018 to February 2019, a group of 100 patients with hypertension (control group) and a group of 100 patients with hypertension and coronary artery disease (experimental group) were selected to monitor and analyze dynamic pulse pressure and pulse pressure indicators. Results: In terms of clinical indicators, values of NPPI, 24hPP and 24hPPI in the experimental group were significantly higher than those in the control group. P < 0.05 indicates that there is statistical value in the data difference. Conclusion: In the clinical diagnosis of hypertension patients, ambulatory pulse pressure, pulse pressure index are highly correlated with the risk of coronary artery disease. Therefore, researchers should actively pay attention to the relevant indicators of patients to lay a solid foundation for the effective protection of patients’ health

Learning-Assisted Inversion for Solving Nonlinear Inverse Scattering Problem

Solving inverse scattering problems (ISPs) is challenging because of its intrinsic ill-posedness and the nonlinearity. When dealing with highly nonlinear ISPs, i.e., those scatterers with high contrast and/or electrically large size, the traditional iterative nonlinear inversion methods converge slowly and take lots of computation time, even maybe trapped into local wrong solution. To alleviate the above challenges, a learning-assisted (LA) inversion approach termed as the LA inversion method (LAIM) with advanced generative adversarial network (GAN) in virtue of a new recently established contraction integral equation for inversion (CIE-I) is proposed to achieve a good balance between the computational efficiency and the accuracy of solving highly nonlinear ISPs. The preliminary profiles composed of only small amount of low-frequency components can be got efficiently by the Fourier bases expansion of CIE-I inversion (FBE-CIE-I). The physically exacted information can be taken as the input of the neural network to recover super-resolution image with more high-frequency components. A weighted loss function composed of the adversarial loss, mean absolute percentage error (MAPE), and structural similarity (SSIM) is used under the pix2pix GAN framework. In addition, the self-attention module is used at the end of the generator network to capture the physical distance information between two pixels and enhance the inversion accuracy of the feature scatterers. To further improve the inversion efficiency, the data-driven method (DDM) is used to achieve real-time imaging by cascading U-net and pix2pix GAN, where U-net is used to replace FBE-CIE-I in the LAIM. Compared with other LA inversion, both the synthetic and experimental examples have validated the merits of the proposed LAIM and DDM

Core-sheath structured electrospun nanofibrous membranes for oil-water separation

In recent years, both the increasing frequency of oil spill accidents and the urgency to deal seriously with industrial oil-polluted water, encouraged material scientists to design highly efficient, cost effective oil-water separation technologies. We report on electrospun nanofibrous membranes which are composed of core-sheath structured cellulose-acetate (CA)-polyimide (PI) nanofibers. On the surface of the CA-PI fibers a fluorinated polybenzoxazine (F-PBZ) functional layer, in which silica nanoparticles (SNPs) were incorporated, has been applied. Compared with F-PBZ/SNP modified CA fibers reported before for the separation of oil from water, the PI-core of the core-shell F-PBZ/SNP/CA-PI fibers makes the membranes much stronger, being a significant asset in their use. Nanofibrous membranes with a tensile strength higher than 200 MPa, a high water contact angle of 160 degrees and an extremely low oil contact angle of 0 degrees were obtained. F-PBZ/SNP/CA-PI membranes seemed very suitable for gravity-driven oil-water separation as fast and efficient separation (>99%) of oil from water was achieved for various oil-water mixtures. The designed core-sheath structured electrospun nanofibrous membranes may become interesting materials for the treatment of industrial oil-polluted water

Evidence of elevation-dependent warming from the Chinese Tian Shan

The phenomenon in which the warming rate of air temperature is amplified with elevation is termed elevation-dependent warming (EDW). It has been clarified that EDW can accelerate the retreat of glaciers and melting of snow, which can have significant impacts on the regional ecological environment. Owing to the lack of high-density ground observations in high mountains, there is widespread controversy regarding the existence of EDW. Current evidence is mainly derived from typical high-mountain regions such as the Swiss Alps, the Colorado Rocky Mountains, the tropical Andes and the Tibetan Plateau–Himalayas. Rare evidence in other mountain ranges has been reported, especially in arid regions. In this study, EDW features (regional warming amplification and altitude warming amplification) in the Chinese Tian Shan (CTM) were detected using a unique high-resolution (1 km, 6-hourly) air temperature dataset (CTMD) from 1979 to 2016. The results showed that there were significant EDW signals at different altitudes on different timescales. The CTM showed significant regional warming amplification in spring, especially in March, and the warming trends were greater than those of continental China with respect to three temperatures (minimum temperature, mean temperature and maximum temperature). The significance values of EDW above different altitude thresholds are distinct for three temperatures in 12 months. The warming rate of the minimum temperature in winter showed a significant elevation dependence (p<0.01), especially above 3000 m. The greatest altitudinal gradient in the warming rate of the maximum temperature was found above 4000 m in April. For the mean temperature, the warming rates in June and August showed prominent altitude warming amplification but with different significance above 4500 m. Within the CTM, the Tolm Mountains, the eastern part of the Borokoonu Mountains, the Bogda Mountains and the Balikun Mountains are representative regions that showed significant altitude warming amplification on different timescales. This new evidence could partly explain the accelerated melting of snow in the CTM, although the mechanisms remain to be explored