Unification of fundamental forces is the dream of physics. Nevertheless, unfortunately gravitational force operators to be isolated in its geometrical content from other forces. This encourages some researchers to pro...Unification of fundamental forces is the dream of physics. Nevertheless, unfortunately gravitational force operators to be isolated in its geometrical content from other forces. This encourages some researchers to propose the so-called gravimagnetic field to unify gravity with other forces and to explain some cosmological problems at the early universe. This motivates to construct a new model to confirm the existence of gravitomagnetic and a corresponding magnetic field associated with any field. Using the formal Newton definition of force and considering the magnetic force to be related to the time varying mass, the magnetic force is shown to be equal to the centrifugal force. This equality is typical when treating a particle as string. Using also the definition of force in terms of potential and electric force only, energy is shown to be conserved. The Newton force can be defined also in terms of four-dimensional potential with the time varying part related to the magnetic potential. When the particle is treated as a string, energy conservation holds, while for ordinary particle, the Lagrangian is conserved. The energy conservation holds for special relativity also for energy per unit mass. The definition of acceleration for forces that obeys inverse square law shows also the magnetic force is equal to the centrifugal force.展开更多
In this study, Si-doped Cu<sub>2</sub>ZnSnS<sub>4</sub> compounds (Cu<sub>2</sub>ZnSn<sub>1-x</sub>Si<sub>x</sub>S<sub>4</sub>, 0 ≤ x ≤ 1) were...In this study, Si-doped Cu<sub>2</sub>ZnSnS<sub>4</sub> compounds (Cu<sub>2</sub>ZnSn<sub>1-x</sub>Si<sub>x</sub>S<sub>4</sub>, 0 ≤ x ≤ 1) were prepared by solid state reaction method for use of materials for photovoltaic cells. The structural and spectroscopic properties of the as-prepared compounds were studied by X-ray diffraction (XRD), <sup>119</sup>Sn, <sup>29</sup>Si and <sup>65</sup>Cu Magic Angle Spinning nuclear magnetic resonance (MAS NMR) and Raman spectroscopy. The Si-substitution in the Sn-site induces three different types of XRD patterns which depend largely on the Si content in the compound. For 0 ≤ x ≤ 0.5, XRD analysis reveals the presence of a pure tetragonal phase of solid solution with I-42m as a space group. Mixed tetragonal and orthorhombic phases were observed for 0.5 < x < 0.8, followed by a pure orthorhombic structure with a space group Pmn2<sub>1</sub> at high content of Si (x ≥ 0.8). <sup>119</sup>Sn MAS NMR spectra show the presence of Sn/Si disorder as a function of the Si content. The <sup>65</sup>Cu MAS NMR spectra of the quadratic solid solution confirm the presence of the two copper sites (Cu-2a and Cu-2c) at 780 ppm while in the case of the orthorhombic solid solution samples, a very broad band is observed. The optical properties were investigated of all compounds by UV-Vis diffuse reflectance and the obtained optical band gap values (1.31 to 2.43 eV) confirm a semiconductor character.展开更多
文摘Unification of fundamental forces is the dream of physics. Nevertheless, unfortunately gravitational force operators to be isolated in its geometrical content from other forces. This encourages some researchers to propose the so-called gravimagnetic field to unify gravity with other forces and to explain some cosmological problems at the early universe. This motivates to construct a new model to confirm the existence of gravitomagnetic and a corresponding magnetic field associated with any field. Using the formal Newton definition of force and considering the magnetic force to be related to the time varying mass, the magnetic force is shown to be equal to the centrifugal force. This equality is typical when treating a particle as string. Using also the definition of force in terms of potential and electric force only, energy is shown to be conserved. The Newton force can be defined also in terms of four-dimensional potential with the time varying part related to the magnetic potential. When the particle is treated as a string, energy conservation holds, while for ordinary particle, the Lagrangian is conserved. The energy conservation holds for special relativity also for energy per unit mass. The definition of acceleration for forces that obeys inverse square law shows also the magnetic force is equal to the centrifugal force.
文摘In this study, Si-doped Cu<sub>2</sub>ZnSnS<sub>4</sub> compounds (Cu<sub>2</sub>ZnSn<sub>1-x</sub>Si<sub>x</sub>S<sub>4</sub>, 0 ≤ x ≤ 1) were prepared by solid state reaction method for use of materials for photovoltaic cells. The structural and spectroscopic properties of the as-prepared compounds were studied by X-ray diffraction (XRD), <sup>119</sup>Sn, <sup>29</sup>Si and <sup>65</sup>Cu Magic Angle Spinning nuclear magnetic resonance (MAS NMR) and Raman spectroscopy. The Si-substitution in the Sn-site induces three different types of XRD patterns which depend largely on the Si content in the compound. For 0 ≤ x ≤ 0.5, XRD analysis reveals the presence of a pure tetragonal phase of solid solution with I-42m as a space group. Mixed tetragonal and orthorhombic phases were observed for 0.5 < x < 0.8, followed by a pure orthorhombic structure with a space group Pmn2<sub>1</sub> at high content of Si (x ≥ 0.8). <sup>119</sup>Sn MAS NMR spectra show the presence of Sn/Si disorder as a function of the Si content. The <sup>65</sup>Cu MAS NMR spectra of the quadratic solid solution confirm the presence of the two copper sites (Cu-2a and Cu-2c) at 780 ppm while in the case of the orthorhombic solid solution samples, a very broad band is observed. The optical properties were investigated of all compounds by UV-Vis diffuse reflectance and the obtained optical band gap values (1.31 to 2.43 eV) confirm a semiconductor character.
