In this study we investigate biased random walk on branching trees in the varying environment. We have obtained the sufficient conditions for transience, positive recurrence, and null recurrence. Our main result enables the further study on the central limit theory for this kind of random walks.

SnSe and SnS are promising thermoelectric and optoelectronic materials. By means of the first-principle calculations, we systematically calculate the mechanical properties and electronic structures of SnSe and SnS and also investigate the effects of strain on these properties. We find that these properties are anisotropic. We calculate the strain-strain curve, Young's modulus, phonon dispersion, sound velocity, and the band structures under strain. We find that SnSe and SnS are auxetic materials with negative Poisson ratio which can be used in sensor and biomedicine. When strain is applied along the Z direction from -5% to 5%, the band gap of SnSe changes from 0.7eV to 1.03eV while the band gap of SnS changes from 0.85eV to 1.41eV, which indicates that strain is an effective method for improving the conversion efficiencies of SnSe and SnS as solar cell materials.

In this work, the fine structure of Sm I was calculated with the experimental fitting method, which is based on the non-relativistic atomic energy expressions with the relativistic correction. For the ground configuration[Xe]4f⁶6s², the results of different fitting procedures are compared with the experimental data, and the effects of various parameters on the energy levels are analyzed. For odd parity configurations 4f⁶6s6p+4f⁵5d6s², the 134 accurate known energy levels are obtained by using 22 fitted experimental energy levels. For even parity configurations 4f⁶6s²+4f⁶5d6s+4f⁶6s7s, the 65 accurate known energy levels are obtained by using 17 fitted experimental data. Five high-lying levels are assigned to even-parity 4f⁶(⁷F)6s7s ⁵F_J(J=1-5).

An undulating two-dimensional airfoil model is used to model the batoid fish swimming near a flat ground. The mechanisms of the thrust generation and its enhancement near the ground are investigated by using the vorticity dynamics theories. The lift-tuning way is found to satisfy the zero-lift when undulating airfoil is near the ground. The results show that, when the undulating airfoil is near the ground, the strength of the alternated vortices shedding from the trailing edge is enhanced and the distance between the two raws of vortices (reverse von Kármán vortex street) increases slightly. These two factors cause enhancement of the thrust. The lift adjustment relies on the angle of attack. The smaller distance between the airfoil and the ground, the bigger angle of attack is required to adjust the lift to zero. Furthermore, the ground effect (thrust increase) is enhanced by increasing amplitude and frequency of the undulating airfoil. The present study indicates that a batoid fish gains stronger thrust when it swims closer to a ground, but it should increase its angle of attack to maintain the distance to the ground.

Liquid crystal optical phased array (LCOPA) can be easily used for beam controlling and has a lot of advantages such as long-term stability, high speed, small size and weight compared with traditional devices. The phase distribution measurement of LCOPA is an important part of the LCOPA development process and a method for evaluating performance of the device. An orthogonal phase shift interferometry(OPSI) was used to measure the phase distribution of LCOPA. The feasibility and accuracy of the method was certificated by optical phase board experiments, and the phase distribution of LCOPA was measured by the proposed method. The experiment showed the briefness and accuracy of the proposed method. The phase information at ±2 grades of LCOPA was obtained.

Anisotropic growth of gold nanorods is often attributed to the adsorption of surfactant cetyltrimethyl ammonium bromide (CTAB) bilayer on gold facets. In this work, we performed DFT (density function theory) calculations to investigate possible binding sites of Br ions on Au(100), Au(110), and Au(111) facets. The CTAB bilayers on these facets were then constructed, and the structures of these interdigitated bilayers were studied by using molecular dynamics simulation. In addition, the dynamic properties of CTAB bilayer were investigated, and the results indicate that the outer layer exhibits noticeable lateral diffusion and undergoes fluctuation along surface normal. Both lateral diffusion and surface normal fluctuation of CTAB bilayer on Au(111) facet are more profound. The stability of CTAB bilayers on gold surfaces was estimated in terms of the required energy for dissociation of a CTA⁺ ion from the outer layer. The stability of CTAB bilayer on Au(111) is considerably weaker than on Au(100) and Au(110). Higher volatility and weaker stability may be due to lower packing density of CTAB bilayer on Au(111) facet, and both of them induce the growth tendency of gold nanoparticles along the (111) direction.

There is a high probability that cytochrome c interacts with the oxidized graphene via electron transfer reactions. We notice that the electron transfer coupling matrix element reveals the electronic interactions between two molecules. With this idea in mind, we applied the pathway tunneling model method to calculate the electron transfer coupling matrix element in the eight cytochrome c-graphene oxide systems with different conformations. Results indicate that the electron transfer coupling matrix element for system P8 is the greatest and the electronic interaction between cytochrome c and graphene oxide is the strongest.

Bone morphogenetic protein-2 (BMP-2) plays a key role in regeneration of tissues and organs. In this work, we use molecular dynamics (MD) simulation to investigate the adsorption of a BMP-2 molecule on the negatively and positively charged self-assembled monolayers (SAMs). The model monolayers are formed by placing alkanethiols, CH₃-(CH₂)₉-X, where the terminal functional group X is assigned to SO₃^- and N(CH₃)₃⁺. Simulation results show that the BMP-2 molecule can be adsorbed on both the negatively and positively charged SAMs, even though the net charge of BMP-2 is -8e. Interestingly, we find that the adsorption strength also depends on the distribution of charged amino acid residues on protein surface. Moreover, the active site of BMP-2 is oriented toward the surface when it is adsorbed on the positively charged surface, whereas the active site of BMP-2 is oriented toward the solution when it is adsorbed on the negatively charged surface. This work provides a perspective into the interactions of BMP-2 with differently charged SAMs.

This study takes the area surrounding Dongdao Island of the South China Sea as the study area, and uses a multi-band combination method to study the detection ability of water depth through WorldView-2 images. The single-band, dual-band, and multi-band models for water depth detection are built, and the detection ability and accuracy are evaluated. Results indicate that the multi-band model shows the best effect, the dual-band model the second, and the single-band model the last. For the single-band model, the depth detection ability order from the best to the worst is:green band, panchromatic band, blue band, and red band. The depth detection accuracy of the front view image is higher than that of the back view image. Panchromatic band plays an important role in water depth detection.

Based on 426 peasant household questionnaire data in Puding County in China, we analyzed the factors influencing household income by using stepwise method under a multiple regression model. The results are presented as follows. 1) Education has significant positive influence on household income. The farmers receiving higher education prefer higher income occupations, which affects the household income level. 2) The proportion of assets operating income has positive effect on household income. Farmers' assets operating income is mainly from business and also from farmland and woodland renting. 3) The increase of the proportion of policy income reflects the weakening of farmers' comprehensive production capacity. Therefore, the policy income has negative effect on household income. 4) Productive expenditure has significant positive effect on household income, which shows that agriculture is still the important source of household income. Moreover, accessing internet has a certain effect on increasing household income.

Based on the statistics of top grade hotel industry from Qunar.com, we study the temporal and spatial evolution and its influencing factors of top grade hotel industry in central district of Urumqi, using the methods of standard deviational ellipse (SDE), kernel density, nearest neighbor analysis, and ordinal regression. The results are given as follows. 1) The spatial distribution of new hotel industry shows different characteristics in the three different periods:before 2000, 2000-2010, and after 2010. The gravity center of new hotel industry tends to move northward. 2) Before 2000, the new hotel industry was mainly located around commercial circles and resulted in three spatial agglomeration zones. From 2000 to 2010, the new hotel industry was mainly located around commercial circles, transportation hubs, and culture and sport facilities. After 2010, the new hotel industry was mainly located around commercial circles and transportation hubs. 3) Before 2000, the new hotel industry showed the characteristics of spatial dispersion. After 2000, the new hotel industry showed the characteristics of spatial agglomeration, which became more significant. 4) Different influencing factors have different impacts on different types of top grade hotel industry.

The stress perturbation induced by 2004 Sumatra earthquake has greatly changed seismicity around Sumatra and its vicinity, including Southwest China. In this study, we calculated the co-seismic stress changes induced by this earthquake using a layered spherically symmetric earth model and a 3D laterally heterogeneous earth model. Both the calculations are based on the fault slip model, which fits well with the GPS observation and has been widely quoted by other researchers, and the equivalent body force finite element method is applied to deal with the co-seismic fault slip effect. The entire volume of a spherical shell from earth surface to core-mantle boundary is included in our investigation, and boundary conditions can be easily assigned to the two boundaries. In the spherical symmetric model, there are 67.6% of aftershocks occurring in regions of positive Coulomb stresses. In the lateral heterogeneous model, 72.3% of aftershocks occurring in regions of positive Coulomb stresss. The aftershocks in the northern part of west Andaman fault have good correlation with the main faults which have positive Coulomb stress. So the aftershocks were apparently controlled by adjacent main faults.

A robust synthetic aperture radar (SAR) target recognition method based on multi-scale Gabor feature extraction and sparse representation is proposed. Firstly, SAR images are segmented and filtered in different directions by using multi-scale Gabor filter to enhance the local features. Then, based on sparse representation model, the sparse dictionary is constructed by using the training samples as atoms. By using the sparse solving algorithms, the testing samples are represented by selecting the optimal atom set. Finally, the testing samples are recognized according to the l₁ norm of non-negative sparse representation coefficient. Experimental results show the effectiveness and robustness of the proposed method.

In this study, the variable bit rate BAQ algorithm is proposed based on adaptive rate allocation among blocks of SAR raw data. Compared with FDBAQ and SA-BAQ, the proposed rate selection scheme is completely automatic, without the optimization process using priori data. Compared with the traditional BAQ algorithm, the proposed method evidently improves signal-to-noise ratio (SNR) and decreases the phase error of SAR image at the expense of only slight increase of complexity. Besides, the new method realizes fraction bit rate, which increases the flexibility of the compression application for SAR raw data.

As an important method for information searching and filtering, the mobile health care system has successfully improved service efficiency of existing medical resources. To enhance accuracy and effect of the information recommendation, a new recommendation algorithm based on multi-bipartite network is proposed. Evaluation criteria of users are enriched as "interested", "uninterested", and "unknown". Moreover, a genre layer is appended so that the information confidence propagates on a new multi-bipartite network iteratively. Finally, we prove that multi-bipartite network iterative algorithm enhances service effect of mobile health care system.

The distribution and evolution of filamentation of femtosecond laser pulses with the chessboard-like and grid-like phase plates, respectively, in air are numerically studied. It is demonstrated that the filamentation can be controlled by using the two phase plates. More clearly separated and more stable filaments are formed by using the chessboard-like phase plate, while longer filaments are formed by using the grid-like phase plate.

The existing recognition system structure is too complicated and the cost is too high. In this work we design a UHF reader/writer system composed of discrete components. It uses the software to replace the hardware to realize the function of data coding of the UHF system, which reduces the complexity of the system and the cost. The design of anti-collision algorithm improves the recognition rate of the system. The simulation results show that the system has a certain distant recognition function, which meets the needs of the system.