Reversible Transition Between Thermodynamically Stable Phases with Low Density of Oxygen Vacancies on SrTiO3_3(110) Surface

The surface reconstruction of SrTiO$_3$(110) is studied with scanning tunneling microscopy and density functional theory (DFT) calculations. The reversible phase transition between (4$\times$1) and (5$\times$1) is controlled by adjusting the surface metal concentration [Sr] or [Ti]. Resolving the atomic structures of the surface, DFT calculations verify that the phase stability changes upon the chemical potential of Sr or Ti. Particularly, the density of oxygen vacancies is low on the thermodynamically stabilized SrTiO$_3$(110) surface.Comment: Accepted by Physical Review Letter

Research on fault law of rolling bearing under different fault levels and loads with HHT method

Bearing is one of the most important components of rotating machinery. The vibration signals are generally nonlinear and nonstationary while operating. The failed rolling bearing will damage to the machine, or cause a serious loss of property. There are a lot of methods about fault diagnosis of bearing, such as shock pulse method, resonance demodulation. Especially the HHT (Hilbert-Huang Transform) method with the adaptive advantage has gradually become a very promising method to extract the characteristics of nonlinear, nonstationary signal. In this paper the variant energy method was introduced in HHT to reduce the computation of the decomposed signal, which effectively improved the computation, and then an experimental platform was designed and established. The bearing fault categories can be diagnosed correctly in dealing with the vibration signals using this method and the fault law is discovered that the trend of the vibration signal fault characteristic frequency amplitude changes with the load increasing. The bearing failure mechanism provides beneficial reference for further research of nonlinear signal analysis

Ku Regulates the Non-Homologous End Joining Pathway Choice of DNA Double-Strand Break Repair in Human Somatic Cells

The repair of DNA double-strand breaks (DSBs) is critical for the maintenance of genomic integrity and viability for all organisms. Mammals have evolved at least two genetically discrete ways to mediate DNA DSB repair: homologous recombination (HR) and non-homologous end joining (NHEJ). In mammalian cells, most DSBs are preferentially repaired by NHEJ. Recent work has demonstrated that NHEJ consists of at least two sub-pathways—the main Ku heterodimer-dependent or “classic” NHEJ (C-NHEJ) pathway and an “alternative” NHEJ (A-NHEJ) pathway, which usually generates microhomology-mediated signatures at repair junctions. In our study, recombinant adeno-associated virus knockout vectors were utilized to construct a series of isogenic human somatic cell lines deficient in the core C-NHEJ factors (Ku, DNA-PKcs, XLF, and LIGIV), and the resulting cell lines were characterized for their ability to carry out DNA DSB repair. The absence of DNA-PKcs, XLF, or LIGIV resulted in cell lines that were profoundly impaired in DNA DSB repair activity. Unexpectedly, Ku86-null cells showed wild-type levels of DNA DSB repair activity that was dominated by microhomology joining events indicative of A-NHEJ. Importantly, A-NHEJ DNA DSB repair activity could also be efficiently de-repressed in LIGIV-null and DNA-PKcs-null cells by subsequently reducing the level of Ku70. These studies demonstrate that in human cells C-NHEJ is the major DNA DSB repair pathway and they show that Ku is the critical C-NHEJ factor that regulates DNA NHEJ DSB pathway choice

STUDY ON NONLINEAR DYNAMICS OF ASYMMETRICAL SUPPORTED ROTOR UNDER INFLUENCE OF HEELING ANGLE

This paper takes the support structure of a low-pressure rotor system of a marine gas turbine as the background.Considering the heel angle of the rotor system,a dynamic model of the rotor supported by asymmetric rolling bearing is established. The variable-step fourth-order Runge-Kutta method was used to solve the system’ s dynamic equations,and the nonlinear theory were used to analyze the simulation results. The study shows that the heel angle has no effect on the stability of the system at low rotational speeds. At high rotational speed,the heel angle mainly affects the 1/2 harmonic of the system,and the system has a single chaotic island or two chaotic islands. When the left or right tilt angle of the rotor system is the same,the heel angle has the same effect on the nonlinear dynamics of the system. The research results can provide a theoretical basis for the design,monitoring and fault diagnosis of the rotor system

Disinfection and Bactericidal Effect Using Photocatalytic Oxidation

This article first gives a brief review of the literature on disinfection and bactericidal effect using photocatalytic oxidation (PCO) technology. Photocatalytic chemistry of titanium dioxide has been extensively studied over the last 30 years for removal of organic and inorganic compounds from contaminated water and air. This review provides (1) background on PCO technology, (2) biological effect of PCO, (3) mechanism of cell and DNA damage photoinduced by PCO. Relevant research conducted in our laboratory is also presented. Finally, possible applications of the PCO for engineering controls of infectious diseases are discussed

Time-dependent Behaviour Analysis of Long-span Concrete Arch Bridge

This paper continues the previous study on clarifying the time-dependent behaviour of Beipanjiang Bridge ‒ a reinforced concrete arch bridge with concrete-filled steel tubular stiffened skeleton. The obtained prediction models and the Finite Element Models were used to simulate the long-term behaviour and stress redistribution of the concrete arch bridge. Three-dimensional beam elements simulated the stiffened skeleton and surrounding concrete. Then, a parameters study was carried out to analyse the time-dependent behaviour of the arch bridge influenced by different concrete creep and shrinkage models. The simulation results demonstrate that concrete creep and shrinkage have a significant influence on the time-dependent behaviour of the concrete arch bridge. After the bridge completion, the Comite Euro-International du Beton mean deviation of displacements obtained by 1990 CEBFIP Model Code: Design Code model and fib Model Code for Concrete Structures 2010 model are 3.4%, 31.9% larger than the results predicted by the modified fib Model Code for Concrete Structures 2010 model. The stresses between the steel and the concrete redistribute with time because of the concrete long-term effect. The steel will yield if the fib Model Code for Concrete Structures 2010 model is used in the analysis. The stresses in a different part of the surrounding concrete are non-uniformly distributed

Creep Characteristics Of Concrete Used In Long-Span Arch Bridge

The reinforced concrete arch bridge with concrete-filled steel tubular stiffened skeleton is extensively used in the mountainous area of southwest China due to their long span and high stability. Beibanjiang Bridge located in Shanghai- Kunming high-speed railway, which had a record span of 445 m, has recently been completed in 2016. However, concrete creep and shrinkage have pronounced effects on the long-term deflection and stress redistribution of this bridge. Several concrete creep and shrinkage specimens in the natural environment were made to predict the long-term behaviour of this bridge accurately. They were used to measure the concrete creep and shrinkage of the core concrete and surrounding concrete used in the arch bridge. The test results were compared to ACI209 R-92 Prediction of Creep, Shrinkage and Temperature Effects in Concrete Structures model, 1990 CEB-FIP Model Code 1990: Design Code model, fib Model Code for Concrete Structures 2010 model and Creep and Shrinkage Prediction Model for Analysis and Design of Concrete Structures-Model B3. Based on the numerical fitting method, the fib Model Code for Concrete Structures 2010 model was modified to suit the concrete creep and shrinkage experimental results. Then, the modified fib Model Code for Concrete Structures 2010 model was used to predict the timedependent behaviour of a concrete arch bridge

Research on intelligent diagnostic techniques for rolling bearings based on unbalanced data sets

In this paper, based on the combination of comprehensive sampling and one-dimensional convolutional neural network, a bearing fault intelligent diagnosis technique is proposed for the classification of rolling bearing vibration data. At first, the fault data set is expanded by ADASYN method. Then, the data is cleaned up by Tomek link under sampling technique, the risk of overfitting caused by overlap of different classes is reduced and the data of different categories is more apparent, and finally the normal data set and fault data set after comprehensive sampling are classified by one-dimensional convolutional neural network algorithm. Compared with random forests and support vector machines, the results show that the method has a high accuracy in identifying classifications and can effectively solve the classification problem of unbalanced bearing data