Unambiguous Tracking Method Based on Combined Correlation Functions for sine/cosine-BOC CBOC and AltBOC Modulated Signals

Unambiguous tracking for Binary Offset Carrier (BOC) modulated signals is an important requirement of modern Global Navigation Satellite System (GNSS) receivers. An unambiguous tracking method based on combined correlation functions for even/odd order sine/cosine-BOC, Composite BOC(CBOC) and Alternate BOC(AltBOC) modulated signals is proposed. Firstly, a unitary mathematical formulation for all kinds of BOC modulations is introduced. Then an unambiguous tracking method is proposed based on the formulation and the idea of pseudo correlation function (PCF) method. Finally, the tracking loop based on the proposed method is designed. Simulation results indicate that the proposed method can remove side peaks while retaining the sharp main peak for all kinds of BOC modulations. The tracking performance for AltBOC is examined and the results show that the proposed method has better performance in thermal noise and long-delay multipath mitigation than the traditional unambiguous tracking methods

The effects of local voids and imperfections of surrounding rock on the performance of existing tunnel lining

Local voids and imperfections may exist around the tunnel due to reasons such as inadequate back infill behind the lining, insufficient local lining thickness, ground water erosion, and other imperfect construction related activities. Such local voids and imperfections generally will lead to local contact loss and discontinuity in the ground-lining interaction. This paper evaluates the effect of local voids and imperfections developing around the tunnel vault area on the mechanical performance of tunnel lining. Based on field investigation results, a series of voids and imperfections with different geometries are defined to reflect cases resulting from different causes. Numerical parametric analyses were performed to investigate how those voids and imperfections influence the internal force and the safety factor of the lining, and the reinforced concrete lining were modelled with the smeared crack model to examine the development of cracking directions and patterns. Furthermore, the numerical approach was verified by comparing with field investigations and measurements. This study aims to investigate the most unsafe situation due to local voids and imperfections around the tunnel, and the modelled cracking feature shows a way to preliminary evaluate the possible local voids and imperfections behind tunnel lining based on field observation

Spintronic properties of one-dimensional electron gas in graphene armchair ribbons

We have investigated, using effective mass approach (EMA), magnetic properties of a one-dimensional electron gas in graphene armchair ribbons when the electrons of occupy only the lowest conduction subband. We find that magnetic properties of the one-dimensional electron gas may depend sensitively on the width of the ribbon. For ribbon widths $L_x=3Ma_0$, a critical point separates ferromagnetic and paramagnetic states while for $L_x=(3M+1)a_0$ paramagnetic state is stable ($M$ is an integer and $a_{0}$ is the length of the unit cell). These width-dependent properties are a consequence of eigenstates that have a subtle width-dependent mixture of $\mathbf{K}$ and $\mathbf{K'}$ states, and can be understood by examining the wavefunction overlap that appears in the expression for the many-body exchange self-energy. Ferromagnetic and paramagnetic states may be used for spintronic purposes.Comment: 5 pages, 6 figure

Topological Phase Transition and Electrically Tunable Diamagnetism in Silicene

Silicene is a monolayer of silicon atoms forming a honeycomb lattice. The lattice is actually made of two sublattices with a tiny separation. Silicene is a topological insulator, which is characterized by a full insulating gap in the bulk and helical gapless edges. It undergoes a phase transition from a topological insulator to a band insulator by applying external electric field. Analyzing the spin Chern number based on the effective Dirac theory, we find their origin to be a pseudospin meron in the momentum space. The peudospin degree of freedom arises from the two-sublattice structure. Our analysis makes clear the mechanism how a phase transition occurs from a topological insulator to a band insulator under increasing electric field. We propose a method to determine the critical electric field with the aid of diamagnetism of silicene. Diamagnetism is tunable by the external electric field, and exhibits a singular behaviour at the critical electric field. Our result is important also from the viewpoint of cross correlation between electric field and magnetism. Our finding will be important for future electro-magnetic correlated devices.Comment: 4 pages,5 figure

On the energy of charged black holes in generalized dilaton-axion gravity

In this paper we calculate the energy distribution of some charged black holes in generalized dilaton-axion gravity. The solutions correspond to charged black holes arising in a Kalb-Ramond-dilaton background and some existing non-rotating black hole solutions are recovered in special cases. We focus our study to asymptotically flat and asymptotically non-flat types of solutions and resort for this purpose to the M{\o}ller prescription. Various aspects of energy are also analyzed.Comment: LaTe