Parametric studies on generation of short CO2 laser pulses for IR-laser chemistry

Results of parametric studies on short CO₂ laser pulse generation by laser induced dielectric breakdown in a plasma shutter cell are described. From the rise time of such short pulses obtained, threshold breakdown intensity (I_th) has been estimated for different gases. The technique is further extended to obtain 40 ns pulses on two-frequency emission from a single TEA CO₂ laser. Pressure dependent studies of I_th are utilised to model the process of such laser induced plasma.     

CNN-aided multiple PU spectrum sensing in uncalibrated massive antennas SU system

This paper deploys the Convolutional Neural Network (CNN) to learn and set the statistical test in Spectrum Sensing (SS) task of multiple primary user (PU) sources in massive uncalibrated antennas of secondary users (SU) sharing the same spectrum resources. The proposed deep learning-based SS method (DL-SS) is based on the CNN architecture that has the capability of extracting features of the sample covariance matrices (SCMs) that are given as the network input, improving the overall performance and robustness. The proposed CNN-SS method is compared with nine recent multiple-antennas SS methods, namely the arithmetic–geometric detector (AGM), John’s detector (JD), sphericity detector (SD), generalized likelihood test (GLRT), locally most powerful invariant test (LMPIT), maximum–minimum eigenvalue detector (MME), covariance detector (CAV), Hadamard detector (HD) and volume detector (VD) methods; besides, the proposed method is also compared with five recent state-of-art CNN-based SS methodologies. Performance-complexity trade-off of the proposed and reference SS methods are corroborated via Monte Carlo Simulations (MCS). The proposed CNN-SS method under uncalibrated massive antennas reveals substantial benefits w.r.t. the reference methods and is competitive with others CNN-SS methodologies, both in terms of complexity and performance, achieving detection probability of $P_d=0.9$ $(@SNR=-20\mathrm{dB})$ under very low false alarm probability $P_f=0.1$. Under different figures of merit, the performance of the CNN-based SS detector has revealed to be indubitably superior regarding the state-of-art SS detectors. However, the proposed CNN-based SS detector presents relative computational complexity increases. Hence, to be effective, such a superior operational performance requires a very efficient processing structure in the SU base stations.     

利用马赫-增德尔干涉仪改善光纤激光器输出激光性能的研究

本文设计了马赫-曾德尔干涉仪(MZI)在实验上改善1.5μm光纤激光器的输出性能,研究了MZI分束镜的反射率以及锁定MZI透过率对抑制激光输出噪声的影响。在MZI运转于最佳状态时,1.5μm光纤激光器的功率稳定性由±0.20%提升至±0.09%,激光的强度噪声在10 kHz^35 kHz分析频率范围内得到了抑制,在分析频率为15 kHz处,强度噪声降低了约8 dB,为制备1.5μm非经典光场提供了优质激光光源。     

Effects of size and location of distal tear on hemodynamics and wave propagation in type B aortic dissection

Applied Mathematics and Mechanics - The type B aortic dissection (TBAD) is a perilous disease with high morbidity and mortality rates. The hemodynamics of TBAD in different scenarios has been...     

Spectral properties in supersymmetric matrix models

We formulate a general sufficiency criterion for discreteness of the spectrum of both supersymmmetric and non-supersymmetric theories with a fermionic contribution. This criterion allows an analysis of Hamiltonians in complete form rather than just their semiclassical limits. In such a framework we examine spectral properties of various (1+0) matrix models. We consider the BMN model of M-theory compactified on a maximally supersymmetric pp-wave background, different regularizations of the supermembrane with central charges and a non-supersymmetric model comprising a bound state of N D2 with m D0. While the first two examples have a purely discrete spectrum, the latter has a continuous spectrum with a lower end given in terms of the monopole charge.     

Hedging the Risk of Delayed Data in Defaultable Markets

We investigate hedging the risk of delayed data in certain defaultable securities through the local risk minimization approach. From a financial point of view, this indicates that in addition to the risk of default, investors also face incomplete accounting data. In our analysis, the delay is modelled by a random time change, and different levels of information, including the full market’s, management’s, and investors’ information, are distinguished. We obtain semi-explicit solutions for pseudo locally risk minimizing hedging strategies from the perspective of investors where the results are presented according to the solutions of partial differential equations. In obtaining the main results of this paper, we apply a filtration expansion theorem that determines the canonical decomposition of stopped special semimartingales in an enlarged filtration of investors’ information.     

The 3-D stress intensity factor for a half plane crack in a transversely isotropic solid due to the motion of loads on the crack faces

Three-dimensional analysis of a half plane crack in a transversely isotropic solid is performed. The crack is subjected to a pair of normal point loads moving in a direction perpendicular to the crack edge on its faces. Transform methods are used to reduce the boundary value problem to a single integral equation that can be solved by the Wiener-Hopf technique. The Cagniard-de Hoop method is employed to invert the transforms. An exact expression is derived for the mode I stress intensity factor as a function of time and position along the crack edge. Some features of the solution are discussed through numerical results. The project supported by the Guangdong Provincial Natural Science Foundation and the Science Foundation of Shantou University     

Infrared radiation modeling of NO,OH, CO,H2O,and CO2 for emissivity/radiance prediction at high temperature

In the present study, infrared radiation modeling of NO, OH, CO, H₂O, and CO₂ molecules was devised based on a line-by-line method by utilizing a structured radiation analysis package, SPRADIAN07, coupled with up-to-date spectroscopic parameters and recent high-resolution radiation databases. An infrared calculation module was newly implemented in SPRADIAN07 for simulating the emissivity/radiance of NO and OH. The line positions of NO and OH molecules were determined by diagonalizing the Hamiltonian matrices of each molecule. The Einstein coefficients were obtained from either radiation databases or available calculated temperature-related line intensities. H₂O, CO₂, and CO were also modeled based on the high-resolution radiation databases, HITEMP2010 and CDSD-4000. When the line-by-line calculations were performed using the radiation databases, a parallel computing technique based on PC clusters was adopted for fast and efficient evaluation. The line-by-line model devised in the present study was validated by comparing the results with existing measurements. The simulations with room air absorption composed of H₂O and CO₂ were also carried out. The spectra taken from a plasma torch and those from a rocket plume were calculated by utilizing the present radiation model. It was shown that the calculated spectra are in good agreement with observed ones.