Abstract:
Time sequence signals of instantaneous longitudinal and normal velocity components at different longitudinal and normal positions in a turbulent boundary layer have been finely measured simultaneously by IFA300 constant temperature anemometer and double-sensor hot-wire probe with sampling resolution higher than the frequency that corresponds to the smallest time scale of Kolmogorov dissipation scale before/after introducing artificial periodic blow/suction perturbation. The period-phase-average technique is applied to extract the periodic waveforms of artificial perturbation from instantaneous time sequence signals of longitudinal and normal turbulence background. Experimental investigation is carried out on the attenuation characteristics of periodic perturbation wave with different frequency along longitudinal direction and normal direction in a turbulent boundary layer. The amplitude distributions of longitudinal and normal disturbing velocity component for different perturbation frequencies are measured at different downstream and normal positions in turbulent boundary layer. The amplitude growth rate of artificial periodic perturbation wave is calculated according to flow instability theory. The experimental results are compared and in consistent with the theoretical and numerical results.

Abstract:
We show how single top production in conjunction with a variety of additional final states provides a sensitive probe of new physics. We investigate several new physics scenarios such as lepto-phobic W' model, and exotic B' model, and then perform detailed simulation analyses in s-, and tW-associated production channels.

Abstract:
Applying the well-known Feynman-Kac formula of inhomogeneous case, an interesting and rigorous mathematical proof of generalized Jarzynski's equality of inhomogeneous multidimensional diffusion processes is presented, followed by an extension of the second law of thermodynamics. Then, we explain its physical meaning and applications, extending Hummer and Szabo's work ({\em Proc. Natl. Acad. Sci. USA} {\bf 98}(7), 3658--3661 (2001)) and Hatano-Sasa equality of steady state thermodynamics ({\em Phys. Rev. Lett.} {\bf 86}, 3463--3466 (2001)) to the general multidimensional case.

Abstract:
We investigate a neutral gauge boson X originated from a hidden U(1) extension of the standard model as the particle dark matter candidate. The vector dark matter interacts with the standard model fermions through heavy fermion mediators. The interactions give rise to t-channel annihilation cross section in the XX to ff process, which dominates the thermal relic abundance during thermal freeze-out and produces measurable gamma-ray flux in the galactic halo. For a light vector dark matter, if it predominantly couples to the third generation fermions, this model could explain the excess of gamma rays from the galactic center. We show that the vector dark matter with a mass of 20 ~ 40 GeV and that annihilate into the bb and tautau final states provides an excellent description of the observed gamma-ray excess. The parameter space aimed at explaining the gamma-ray excess, could also provide the correct thermal relic density and is compatible with the constraints from electroweak precision data, Higgs invisible decay, and collider searches. We also show the dark matter couplings to the nucleon from the fermion portal interactions are loop-suppressed, and only contribute to the spin-dependent cross section. So the vector dark matter could easily escape the stringent constraints from the direct detection experiments.

Abstract:
In this paper, we study the Cauchy problem of a time-dependent drift-diffusion-Poisson system for semiconductors. Existence and uniqueness of global weak solutions are proven for the system with a higher-order nonlinear recombination-generation rate R. We also show that the global weak solution will converge to a unique equilibrium as time tends to infinity.

Abstract:
The forcing relation of braids has been introduced for a 2-dimensional analogue of the Sharkovskii order on periods for maps of the interval. In this paper, by making use of the Nielsen fixed point theory and a representation of braid groups, we deduce a trace formula for the computation of the forcing order.

Abstract:
Let $X$ be a smooth projective variety of Albanese fiber dimension 1 and of general type. We prove that the translates through 0 of all components of $V^0(\omega_X)$ generate $\Pic^0(X)$. We then study the pluricanonical maps of $X$. We show that $|4K_X|$ induces a birational map.

Abstract:
With the development of new energy technology, there are increasing applications of grid-connected photovoltaic power generation system. However, there is little research on development of electromechanical model of large scale photovoltaic power station. The computational speed will be very slow if electromagnetic transient model is used for stability study because of its complexity. Therefore, study on electromechanical transient model of grid-connected photovoltaic power generation system is of great meaning. In this paper, electromagnetic transient model of photovoltaic power generation system is introduced first, and then a general electromechanical transient model is proposed. These two kinds of simulation model are set up in PSCAD. By comparing the simulation results of two models, the correctness and validity of the electromechanical transient model is verified. It provides reference model for efficient simulation and modeling of grid-connected photovoltaic power station in large-scale power systems.

CAPTCHA is a completely automated program designed to distinguish whether
the user is a computer or human. As the problems of Internet security are
worsening, it is of great significance to do research on CAPTCHA. This article
starts from the recognition of CAPTCHAs, then analyses the weaknesses in its
design and gives corresponding recognition proposals according to various
weaknesses, finally offers suggestions related to the improvement of CAPTCHAs.
Firstly, this article briefly introduces the basic steps during the decoding
process and their principles. And during each step we choose methods which are
better adapted to the features of different CAPTCHA images. Methods chosen are
as followings: bimodal method in binarization, improved corrosion algorithm in
denoising, projection segmentation method in denoised image processing and SVM
in recognition. Then, we
demonstrate detailed process through the samples taken from the online
registration system of ICBC, show the recognition effect and correct the
results according to the statistical data in the process. This article decodes
CAPTCHAS from three other large banks in the same way but just provides the
recognition results. Finally, this article offers targeted suggestions to the
four banks based on the recognition effect and analysis process stated above.

Visual method including binocular stereo
vision method and monocular vision method of the relative position and pose
measurement for space target has become relatively mature, and many researchers
focus on the method based on three-dimension measurement recently. ICP
alignment, which is the key of three-dimension pattern measurement method, has
the problem of low efficiency in large data sets. Considering this problem, an
improved ICP algorithm is proposed in this paper. The improved ICP algorithm is
the combination of the original ICP algorithm and KD-TREE. The experimental
comparison between the improved ICP algorithm and the traditional ICP algorithm
in efficiency has been given in this paper, which shows that the improved ICP
algorithm can get much better performance.