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Ultrasound has found application in many different sectors, especially the evaluation industry to investigate component structural integrity, including the icing load on transmission line. In many cases, a liquid coupling medium is used to efficiently transfer energy between the transducer and the sample under investigation. There are some materials which are not suitable for liquid coupling, either through material properties or the complexity of the environmental condition. The alternative of using an air-coupled approach is inherently challenging due to a large acoustic impedance mismatch between the transducer and air, resulting in low system signal-to-noise ratio (SNR). A segmented annular array system has been designed for non-contact inspection applications, which provides control of the depth focussing with beam steering on the central axis. Assessment of the inspection capability of the developed array system was undertaken through manual scans of icing defect structures with a reasonable quality images have been acquired.

The transmission tower line system includes towers, wires, ground wires, insulator strings and so on. To study the changes of transmission lines under wind load is of great significance. This article explains how to automatically establish a transmission tower line system and the system simulation under wind loads. The establishment of the tower line system takes the towers, wires and insulator strings in consideration, discusses the simplified method and the connection method of the wires. The establishment process of the tower line system is studied in detail. Finally, the changes of wires of the tower line system under wind loads are simulated.

The operation experience of transmission line large cross project shows that the traditional anti-aeolian-vibration devices had poor adaptability to complex terrain and micro meteorological conditions, and they were difficult to meet the application requirements of super large cross project at this stage. A zero-natural-frequency damper was designed by introducing nonlinear energy sink in this paper, and the solid prototypes were processed. According to the actual design parameters of conductor using in a large cross project, the anti-vibration effect was tested by using the indoor simulation test span. The test results showed that the anti-vibration effect of the scheme based on the zero-natural-frequency damper could meet the needs of practical engineering. The installation of this damper could improve conductors’ and fittings’ adaptability to complex terrain and enhance the wind and anti-vibration ability of transmission line.

We demonstrate microwave-to-optical conversion using six-wave mixing in cold $^{87}\mathrm{Rb}$ atoms where the microwave field couples to two Rydberg states and propagates collinearly with the converted optical field. Our experiment is performed with a free-space microwave field, and we achieve a conversion efficiency of about $5%$ for the microwave photons entering the conversion medium. In addition, we theoretically investigate all-resonant six-wave mixing and outline a realistic experimental scheme for reaching an efficiency close to 70%.

To avoid a series of shortcomings of the traditional complex analytical mechanism, this paper selects the algorithm suitable for the transmission line galloping prediction model according to the characteristics of the traverse movement and the characteristics of the related galloping history data. After mining effective information from the selected and preprocessed data, the one class SVM algorithm is used to carry out unsupervised learning of the galloping history data. The Bagging algorithm is used in the ensemble learning algorithm to learn the classifier, avoiding the over fitting, and improving the anti-noise ability of the machine learning algorithm and the noise ability of the machine learning algorithm. The generalization ability, using the K folding cross validation method to verify the data of the galloping monitoring platform of the China Electric Power Research Institute, and using Fl-score to describe the performance of the traverse galloping early warning model, and verify the effectiveness of the machine learning method used in this paper in the aspect of galloping prediction.

We present an experimental demonstration of converting a microwave field to an optical field via frequency mixing in a cloud of cold $^{87}$Rb atoms, where the microwave field strongly couples to an electric dipole transition between Rydberg states. We show that the conversion allows the phase information of the microwave field to be coherently transferred to the optical field. With the current energy level scheme and experimental geometry, we achieve a photon conversion efficiency of ~0.3% at low microwave intensities and a broad conversion bandwidth of more than 4 MHz. Theoretical simulations agree well with the experimental data, and indicate that near-unit efficiency is possible in future experiments., Comment: 5 pages, 4 figures

A statistical analysis of the laser excitation of cold and randomly distributed atoms to Rydberg states is developed. We first demonstrate with a hard-ball model that the distribution of energy level shifts in an interacting gas obeys L\'evy statistics in any dimension $d$ and for any interaction $\ensuremath{-}{C}_{p}/{R}^{p}$ under the condition $d/pl1$. This result is confirmed with a Monte Carlo rate equations simulation of the actual laser excitation in the particular case $p=6$ and $d=3$. With this finding, we develop a statistical approach for the modeling of probe light transmission through a cold atom gas driven under conditions of electromagnetically induced transparency involving a Rydberg state. The simulated results are in good agreement with experiment.

We perform spectroscopic measurements of electromagnetically induced transparency (EIT) in a strongly interacting Rydberg gas, and observe a significant spectral shift of the transparency from the single-atom EIT resonance as well as a spectral dephasing of the same order. We characterize the shift and dephasing as a function of atomic density, probe Rabi frequency, and principal quantum number of Rydberg states, and demonstrate that the observed spectral shift and dephasing are reduced if the size of a Gaussian atomic cloud is increased. We simulate our experiment with a semi-analytical model, which gives results in good agreement with our experimental data., 6 pages, 5 figures

We study the lensing effect experienced by a weak probe field under conditions of electromagnetically induced transparency (EIT) involving a Rydberg state. A Gaussian coupling beam tightly focused on a laser-cooled atomic cloud produces an inhomogeneity in the coupling Rabi frequency along the transverse direction and makes the EIT area acting like a gradient-index medium. We image the probe beam at the position where it exits the atomic cloud, and observe that a red-detuned probe light is strongly focused with a greatly enhanced intensity whereas a blue-detuned one is de-focused with a reduced intensity. Our experimental results agree very well with the numerical solutions of Maxwell-Bloch equations., 7 pages, 4 figures

This work experimentally demonstrates a new method of optimizing the transport of cold atoms via modulating the velocity profile imposed on a magnetic quadrupole trap. The trap velocity and corresponding modulation are controlled by varying the currents of two pairs of anti-Helmholtz coils. Cold 87Rb atoms are transported in a non-adiabatic regime over 22 mm in 200 ms. For the transported atoms their final-vibration amplitude dependences of modulation period number, depth, and initial phase are investigated. With modulation period n=5, modulation depth K=0.55, and initial phase =0, cold atom clouds with more atom numbers, smaller final-vibration amplitude, and lower temperature are efficiently transported. Theoretical analysis and numerical simulation are also provided, which are in good agreement with experimental results.