Beijing Institute of Technology , is a co-educational public university, located in Beijing, China. Established in 1940 in Yan'an, the university is now under the direct administration of the Ministry of Industry and Information Technology.As a member university of National Key Universities, “Project 211” and “Project 985”, it has been given priority for development from the Chinese government, the Commission of Science, Technology and Industry for National Defense, the Ministry of Education and the Beijing Government. Wikipedia.
Beijing Institute of Technology | Date: 2017-01-18
The present disclosure is to provide a divided-aperture laser differential confocal Brillouin-Raman spectrum measuring method and the device thereof, which belongs to microscopic spectrum imaging field. By using the abandoned Rayleigh scattering light in the traditional confocal Raman spectrum detection, a divided-aperture laser differential confocal microscopy is constructed to realize high resolution imaging of three-dimensional geometrical structure of the measured sample. In addition, the characteristic that the zero-crossing point of the divided-aperture laser differential confocal imaging device accurately corresponds to the focus of objective is used to control the spectrum detector to accurately capture the excited Raman spectrum information excited at the focus of the objective, thereby achieving the detection of micro-area geometrical structure and spectrum information of the measured sample with high-spatial resolution, that is achieving mapping-spectrum with high-spatial resolution, and balancing resolution and measuring range. By complementing the advantages of confocal Raman spectrum detecting technology and confocal Brillouin spectrum detecting technology, the confocal spectrum detecting solution which detects the Raman spectrum and Brillouin spectrum at the same time is designed, the multi-property parameters of materials are measured and decoupled in composite.
Wei Hao H.,Beijing Institute of Technology
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011
Recently, the so-called Elko spinor field has been proposed to be a candidate of dark energy. It is a non-standard spinor and has unusual properties. When the Elko spinor field is used in cosmology, its unusual properties could bring some interesting consequences. In the present work, we discuss the cosmological coincidence problem in the spinor dark energy models by using the dynamical system method. Our results show that the cosmological coincidence problem should be taken to heart in the investigations of spinor dark energy models. © 2010 Elsevier B.V.
Wei H.,Beijing Institute of Technology
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2012
Recently, Geng et al. proposed to allow a non-minimal coupling between quintessence and gravity in the framework of teleparallel gravity, motivated by the similar one in the framework of General Relativity (GR). They found that this non-minimally coupled quintessence in the framework of teleparallel gravity has a richer structure, and named it "teleparallel dark energy". In the present work, we note that there might be a deep and unknown connection between teleparallel dark energy and Elko spinor dark energy. Motivated by this observation and the previous results of Elko spinor dark energy, we try to study the dynamics of teleparallel dark energy. We find that there exist only some dark-energy-dominated de Sitter attractors. Unfortunately, no scaling attractor has been found, even when we allow the possible interaction between teleparallel dark energy and matter. However, we note that w at the critical points is in agreement with observations (in particular, the fact that w=-1 independently of ξ is a great advantage). © 2012 Elsevier B.V.
Wei H.,Beijing Institute of Technology
Nuclear Physics B | Year: 2011
In the present work, motivated by the work of Cai and Su [Phys. Rev. D 81 (2010) 103514], we propose a new type of interaction in dark sector, which can change its sign when our universe changes from deceleration to acceleration. We consider the cosmological evolution of quintessence and phantom with this type of interaction, and find that there are some scaling attractors which can help to alleviate the cosmological coincidence problem. Our results also show that this new type of interaction can bring new features to cosmology. © 2010 Elsevier B.V.
Beijing Institute of Technology | Date: 2015-10-18
The invention relates to a method that low complexity suppression of PAPR in FRFT-OFDM system, which belongs to the field of broadband wireless digital communications technology and can be used to reduce the PAPR in FRFT-OFDM system. The method is based on fractional random phase sequence and fractional circular convolution theorem, which can effectively reduce the PAPR of system. The method of the invention has the advantages of simple system implementation and low computational complexity. In this method, the PAPR of the system can be effectively reduced while keeping the system reliability. When the number of candidate signals is the same, the PAPR performance of the proposed method was found to be almost the same as that of SLM and better than that of PTS. More importantly, the proposed method has lower computational complexity than that of SLM and PTS.
Beijing Institute of Technology | Date: 2016-07-22
The present invention provides an electrospray ionization source, which includes: a capillary, including a spray tip; a first electrode which provides the spray tip with a spray voltage; and a second electrode. The electrical potential difference between the first electrode and the second electrode forms a separation electric field, which allows the electric field separation and electrospray ionization of the sample to be accomplished simultaneously, thereby improving the sensitivity of detection.
Beijing Institute of Technology | Date: 2015-11-30
The present invention relates to a method of measuring optical fiber link chromatic dispersion by fractional Fourier transformation (FRFT), belonging to the technical field of optical communication. The method of the present invention performs coherent demodulation for an optical pulse signal output from the optical fiber link to obtain a complex field of the optical pulse signal, then performs FRFT on the complex field; according to the energy focusing effect of the chirp signal in the fractional spectrum, calculates an optimal fractional order of the FRFT, and then calculates chromatic dispersion of the optical fiber link according to the optimal fractional order. The method can be applied to an optical fiber communication system consisting of different types of optical fibers, to perform monitoring of optical fiber link chromatic dispersion.
Beijing Institute of Technology | Date: 2016-06-01
A wearable augmented reality (AR) or virtual reality (VR) display apparatus includes an optical waveguide; an optical free-form surface; and a microdisplay; wherein optical free-form surface is optically coupled to the waveguide through an inclined optical path.
Beijing Institute of Technology | Date: 2015-11-30
The present invention proposes a method for monitoring the nonlinear effect of an optical fiber link by fractional Fourier transformation, FRFT, by calculating an optimal fractional order of the FRFT of the frequency-domain signal propagating through an optical fiber link, calculating the chromatic dispersion of an optical fiber link based on the optimal fractional order, compensating for chromatic dispersion to the signal, calculating an optimal fractional order of the FRFT for the time-domain signal following the compensation for chromatic dispersion, calculating the time-domain chirp caused by the nonlinear effect of an optical fiber link based on the optimal fractional order, and monitoring the nonlinear effect of an optical fiber link based on the absolute value of the calculated time-domain chirp. The method can be used for quantitatively monitoring the nonlinear effect of an optical fiber link in an optical fiber communication system consisting of different types of optical fibers.
Beijing Institute of Technology | Date: 2016-07-13
The present disclosure relates to a divided-aperture laser differential confocal LIBS and Raman spectrum-mass spectrum microscopic imaging method and device. In the present disclosure, the divided-aperture differential confocal imaging technology is combined with the spectrum technology and the mass spectrum detecting technology, high-spatial resolution form imaging is performed on a sample by utilizing a minute focusing spot of a divided-aperture differential confocal microscope processed by using the super-resolution technique, a mass spectrum detection is performed on charged molecules or atoms in a sample microzone by using a mass spectrum detecting system, a microzone spectrum detection is performed on spectrum excited by the focusing spot of a divided-aperture differential confocal microscope system by using a spectrum detecting system, and high-spatial resolution and high-sensitivity imaging and detection of complete composition information and form parameter of the sample microzone are implemented by using complementary advantages and structural fusion in laser multi-spectrum detection.