针对矿井视频监控图像受噪声干扰影响大,采用常规的图像采样和压缩方法存在图像模糊和传输时间过长等问题,提出了一种矿井视频监控图像分块压缩感知方法。该方法通过建立矿井视频监控图像分块压缩感知模型,在井下图像采集节点利用稀疏...针对矿井视频监控图像受噪声干扰影响大,采用常规的图像采样和压缩方法存在图像模糊和传输时间过长等问题,提出了一种矿井视频监控图像分块压缩感知方法。该方法通过建立矿井视频监控图像分块压缩感知模型,在井下图像采集节点利用稀疏随机矩阵进行压缩采样,然后在地面监控中心利用正交匹配追踪(OMP)算法重构图像。研究结果表明,采用本文算法的重构图像误差小、重构时间短,所需信号采样点数少;与扰频Hadamard矩阵相比,采用稀疏随机矩阵和高斯随机矩阵作为观测矩阵对图像信号重构的峰值信噪比(PSNR)提高4 d B^5 d B;本文算法与基于小波基的算法相比,信号重构的PSNR提高1 d B^4 d B,重构时间缩短至少80%以上。展开更多
Piezoelectricity is pivotal for applications in micro/nanoelectromechanical systems(MEMS/NEMS).Inducing such a property in 2D systems via the reduction of the dimensionality of their corresponding 3D bulk is here expl...Piezoelectricity is pivotal for applications in micro/nanoelectromechanical systems(MEMS/NEMS).Inducing such a property in 2D systems via the reduction of the dimensionality of their corresponding 3D bulk is here explored.Based on DFT theory and Gaussian-type-localized basis sets,the structural,electronic,mechanical,and piezoelectric properties of both 3D and 2D rare earth monochalcogenides RmX(Rm=Tm,Yb,Lu,and X=S,Se,Te)are investigated using the CRYSTAL code.Most intriguingly,the 2D LuX compounds display a buckled structure,where the Lu and X atoms protrude from the monolayer surface leading to an additional out-of-plane piezoelectric effect;(e_(31)=2104.84,1770.28,1689.79 pC/m,and d31=56.37,49.76,and 147.90 pm/V for LuS,LuSe,and LuTe,respectively).Such piezoelectric response is two orders of magnitude larger than the one of recently reported 2D ferroelectric MXenes,and is nearly thirty times larger than the commonly used AlN and GaN bulk structures.Furthermore,the reduced elastic constants obtained,when compared to other 2D materials,confirm the flexibility and softness of the considered 2D systems.展开更多
A DFT conformational and vibrational analysis of a single molecule of cisplatin (cis-[Pt(NH3)2Cl2]) was performed by means of PW91 functional and LANL08 ECP basis set for the Pt atom. 3-21G and 3-21G* Basis sets were ...A DFT conformational and vibrational analysis of a single molecule of cisplatin (cis-[Pt(NH3)2Cl2]) was performed by means of PW91 functional and LANL08 ECP basis set for the Pt atom. 3-21G and 3-21G* Basis sets were used for the remaining atoms. All the initially chosen conformations were found to converge to the global minimum conformation of C2v symmetry with H atoms lying in the coordination plane and pointing to the Cl atoms. The computational results were compared with the newest experimental structural data and with the vibrational spectroscopic data for cisplatin, obtained by other workers. The chosen level of theory was found to describe satisfactory the molecular structure (r. m. s. of the relative deviations ≤ 6%) and the harmonic vibrational frequencies (r. m. s. of the relative deviations ≤ 5%) of cisplatin.展开更多
The electron momentum spectra of outer va- lence orbitals 9a1+5b2 of thiophene (C4H4S) have been stud- ied by binary (e, 2e) electron momentum spectroscopy (EMS), at an impact energy of 1200 eV plus binding energy, an...The electron momentum spectra of outer va- lence orbitals 9a1+5b2 of thiophene (C4H4S) have been stud- ied by binary (e, 2e) electron momentum spectroscopy (EMS), at an impact energy of 1200 eV plus binding energy, and symmetric non-coplanar kinematics. The experimental mo- mentum profile of the summed orbitals is compared with the theoretical momentum distributions calculated using Har- tree-Fock (HF) and density functional theory (DFT) methods with various basis sets. The experimental measurement is well described by the HF and DFT calculations, and the cal- culations using the larger basis sets including diffuse and polarization functions give better descriptions of experi- ments.展开更多
文摘针对矿井视频监控图像受噪声干扰影响大,采用常规的图像采样和压缩方法存在图像模糊和传输时间过长等问题,提出了一种矿井视频监控图像分块压缩感知方法。该方法通过建立矿井视频监控图像分块压缩感知模型,在井下图像采集节点利用稀疏随机矩阵进行压缩采样,然后在地面监控中心利用正交匹配追踪(OMP)算法重构图像。研究结果表明,采用本文算法的重构图像误差小、重构时间短,所需信号采样点数少;与扰频Hadamard矩阵相比,采用稀疏随机矩阵和高斯随机矩阵作为观测矩阵对图像信号重构的峰值信噪比(PSNR)提高4 d B^5 d B;本文算法与基于小波基的算法相比,信号重构的PSNR提高1 d B^4 d B,重构时间缩短至少80%以上。
文摘Piezoelectricity is pivotal for applications in micro/nanoelectromechanical systems(MEMS/NEMS).Inducing such a property in 2D systems via the reduction of the dimensionality of their corresponding 3D bulk is here explored.Based on DFT theory and Gaussian-type-localized basis sets,the structural,electronic,mechanical,and piezoelectric properties of both 3D and 2D rare earth monochalcogenides RmX(Rm=Tm,Yb,Lu,and X=S,Se,Te)are investigated using the CRYSTAL code.Most intriguingly,the 2D LuX compounds display a buckled structure,where the Lu and X atoms protrude from the monolayer surface leading to an additional out-of-plane piezoelectric effect;(e_(31)=2104.84,1770.28,1689.79 pC/m,and d31=56.37,49.76,and 147.90 pm/V for LuS,LuSe,and LuTe,respectively).Such piezoelectric response is two orders of magnitude larger than the one of recently reported 2D ferroelectric MXenes,and is nearly thirty times larger than the commonly used AlN and GaN bulk structures.Furthermore,the reduced elastic constants obtained,when compared to other 2D materials,confirm the flexibility and softness of the considered 2D systems.
文摘A DFT conformational and vibrational analysis of a single molecule of cisplatin (cis-[Pt(NH3)2Cl2]) was performed by means of PW91 functional and LANL08 ECP basis set for the Pt atom. 3-21G and 3-21G* Basis sets were used for the remaining atoms. All the initially chosen conformations were found to converge to the global minimum conformation of C2v symmetry with H atoms lying in the coordination plane and pointing to the Cl atoms. The computational results were compared with the newest experimental structural data and with the vibrational spectroscopic data for cisplatin, obtained by other workers. The chosen level of theory was found to describe satisfactory the molecular structure (r. m. s. of the relative deviations ≤ 6%) and the harmonic vibrational frequencies (r. m. s. of the relative deviations ≤ 5%) of cisplatin.
基金The authors would like to acknowledge the help of Prof.Zhu Qihe.This work was supported by the National Natural Science Foundation of China(Grant Nos,19854002,19774037&10274040)the Research Fund for the Doctoral Program of Higher Education under Grant No.1999000327.
文摘The electron momentum spectra of outer va- lence orbitals 9a1+5b2 of thiophene (C4H4S) have been stud- ied by binary (e, 2e) electron momentum spectroscopy (EMS), at an impact energy of 1200 eV plus binding energy, and symmetric non-coplanar kinematics. The experimental mo- mentum profile of the summed orbitals is compared with the theoretical momentum distributions calculated using Har- tree-Fock (HF) and density functional theory (DFT) methods with various basis sets. The experimental measurement is well described by the HF and DFT calculations, and the cal- culations using the larger basis sets including diffuse and polarization functions give better descriptions of experi- ments.
