17 research outputs found
Magnetic-field-induced splitting of Rydberg Electromagnetically Induced Transparency (EIT) and Autler-Townes (AT) spectra in Rb vapor cell
We theoretically and experimentally investigate the Rydberg
electromagnetically induced transparency (EIT) and Autler-Townes (AT) splitting
of Rb vapor under the combined influence of a magnetic field and a
microwave field. In the presence of static magnetic field, the effect of the
microwave field leads to the dressing and splitting of each state,
resulting in multiple spectral peaks in the EIT-AT spectrum. A simplified
analytical formula was developed to explain the EIT-AT spectrum in a static
magnetic field, and the calculations are in excellent agreement with
experimental results.We further studied the enhancement of the Rydberg atom
microwave electric field sensor performance by making use of the splitting
interval between the two maximum absolute states under static magnetic
field. The traceable measurement limit of weak electric field by EIT-AT
splitting method was extended by an order of magnitude, which is promising for
precise microwave electric field measurement.Comment: 12 pages, 4 figure
Microwave electrometry with Rydberg atoms in a vapor cell using microwave amplitude modulation
We have theoretically and experimentally studied the dispersive signal of the
Rydberg atomic electromagnetically induced transparency (EIT) - Autler-Townes
(AT) splitting spectra obtained using amplitude modulation of the microwave
(MW) field. In addition to the two zero-crossing points, the dispersion signal
has two positive maxima with an interval defined as the shoulder interval of
the dispersion signal . The relationship of MW field
strength and are studied at the MW
frequencies of 31.6 GHz, 22.1 GHz, and 9.2 GHz respectively. The results show
that can be used to character the much weaker
than the interval of two zero-crossing points and the traditional EIT-AT splitting interval , the minimum measured by
is about 30 times smaller than that by . As an example,
the minimum at 9.2 GHz that can be characterized by is 0.056 mV/cm, which is the minimum value characterized by
frequency interval using vapour cell without adding any auxiliary fields. The
proposed method can improve the weak limit and sensitivity of
measured by spectral frequency interval, which is important in the direct
measurement of weak
Support Strength Criteria and Intelligent Design of Underground Powerhouses
The proper design of underground powerhouse support is the key engineering technique to guarantee the safe construction and operation of underground works. By regression analysis of the surrounding rock support parameters of 29 underground powerhouses with a span of 18.0–34.0 m, the empirical formula of the relationship between the support strength of anchor bar, strength-stress ratio, and plant span and the relationship among the support strength of the anchor cable, strength-stress ratio, and plant span are proposed. Furthermore, an intelligent design model for the anchor support of the underground powerhouse was trained by a BP (back propagation) neural network. Research shows that the support strength index of the anchor bolt and the anchor cable of these 29 plants are all distributed around 1.0. Therefore, a support strength index of 0.8–1.2 can be used as a reference for practical engineering support design. Finally, the reliability of the intelligent design model for the anchor support of the underground powerhouse was verified by comparison with actual engineering and support strength index. This shows that the intelligent design model can provide a reference for engineering design and construction
Effect of fiber microstructure studied by Raman spectroscopy upon the mechanical properties of carbon fibers
Effect of fiber microstructure studied by Raman spectroscopy upon the mechanical properties of carbon fiber
Evolution of microstructure and electrical property in the conversion of high strength carbon fiber to high modulus and ultrahigh modulus carbon fiber
Evolution of microstructure and electrical property in the conversion of high strength carbon fiber (HSCF) to high modulus carbon fiber (HMCF) and ultrahigh modulus carbon fiber (UHMCF) was investigated. Longitudinal grooves on fiber surfaces became less well-defined during high temperature graphitization. The tensile modulus of carbon fibers was affected by fiber crystalline structure and it increased with decreases in the value of interlayer spacing and improvements in the value of crystallite thickness. Increases in the crystallite size almost had little effect on the tensile strength. However, a lower interlayer spacing and a higher preferred orientation could result in a higher tensile strength. The crystal structure of carbon fibers became much more ordered during high temperature graphitization. It was found that the electrical resistivity gradually decreased from 14.69 x 10(-4) Omega.cm to 9.70 x 10(-4) Omega.cm and 8.80 x 10(-4) Omega.cm, respectively, in the conversion of HSCF to HMCF and UHMCF