Despite the rapidly growing popularity of laser vision correction (LVC) in the correction of myopia, its quantitative evaluation has not been thoroughly investigated. In this paper, an acoustic radiation force–optical coherence elastography (ARF-OCE) system was proposed to evaluate LVC by measuring the residual stromal bed (RSB) elasticity, because it is directly relevant to the RSB thickness that is critical to maintaining normal corneal function. As expected, the Young’s modulus of the RSB was calculated, then its relationship with the RSB thickness was determined. More significantly, a specific thickness was revealed in which the Young’s modulus changed dramatically, which may imply that there is a high risk of complication caused by over-cutting of the cornea. To the best of our knowledge, this is the first ARF-OCE imaging of the RSB, which may help to determine the safe RSB thickness and thus may help us to quantitatively assess LVC surgery.
The magnetron injection gun (MIG) is an essential component of the gyrotron traveling wave tube (gyro-TWT). Although the electron beam status influences the performance of the device, it cannot be measured directly in the experiment. An online evaluation module (OEM) for the experiment is developed to calculate the instant beam parameters of MIG. The OEM, by reconstructing the geometry of the MIG and related magnetic field distribution, can obtain the electron beam status under the operating parameters through the online simulation. The beam velocity spread of thermal emission with instant temperature and surface roughness are also considered. The validation is done in a W-band gyro-TWT, and the beam performance is evaluated in the experiment. With a pitch factor of 1.06 electron beam, the velocity spread affected by the electric-magnetic mismatch, thermal emission, and roughness is 1.00%, 0.56%, and 0.43%, respectively. The other beam parameters are also presented in the developed module. The OEM could guide and accelerate the testing process and ensure the safe and stable operation of the device.
An output system, consisting of a waveguide taper, a 90° waveguide bend, a corrugated waveguide horn, and an RF output window, which can output a Gaussian-like beam rather than a circular waveguide TE 0, 1 mode in a broadband for a Ka-band gyrotron traveling-wave tube (gyro-TWT) has been developed and tested. The conversion process in each section is displayed, and the working principles are discussed in detail. The output mode purity at different frequencies is investigated by analyzing the measured radiation pattern, and the results show that the Gaussian mode contents of the output field is at least 98.5% from 32 to 39 GHz. The high-power performance of the proposed output system is investigated by replacing the traditional output structure of a Ka-band gyro-TWT, and the results show that the device work stable with a maximum power of 150 kW. The obtained Gaussian-like beam at the output window is directly usable for low-loss transmission as well as for effective antenna feed; no extra oversized mode converters are needed. The results obtained demonstrate the possibility of developing a compact, high-efficiency, and low-cost high-power millimeter-wave system based on the gyro-TWT.
From basic prombles in quantum, the central and basic position of reciprocal principle is put forward from the argument between Einstein and Bohr, defferences are discussed at the central of reciprocalism and the height of natural philosophy.
In this article, we propose and measure a high-power Ku-band gyrotron traveling wave tube (gyro-TWT) with external coupling feedback to generate wide-band multifrequency signals. With varying the beam current, pitch factor, coupling coefficient, and feedback loop length, strong oscillations from single-frequency to multifrequency regimes of the self-excitation TE $_{11}$ mode are observed in the zero-driven state. Particle-in-cell (PIC) simulation shows the gyro-TWT can achieve a maximum output power of 192.86 kW and 56.67 MHz interval between main spectral components in the range of 14.85–17.46 GHz. It was confirmed by a proof-of-principle experiment based on a Ku-band gyro-TWT with an external feedback loop, which yielded 2.6 GHz multifrequency signals with an interval of 54 MHz and maximum output power of 174.25 kW at a duty cycle of 1%. The generated multifrequency radiation signals may have potential applications in microwave wireless communication, jamming of radar systems, and microwave frequency combs.
Uniform constraint qualifications play a very important role in the algorithms for solving mathematical programs with equilibrium constraints. In this paper, we discuss a uniform constraint qualification which is needed in some algorithms for solving mathematical programs with equilibrium constraints and give some properties of this uniform constraint qualification.
The technique of mode conversion between rectangular TE 10 and TE n0 (n = 2, 3,...) modes is studied in this article. The mode conversion was mainly realized by coupling apertures. To compensate for the junction discontinuity and, thus, enhance the performances, rectangular septa were introduced in the mode converters. Rectangular recesses were added to suppress the potential competing modes. As two examples, the design of rectangular TE 20 and TE 50 mode converters operating in the terahertz band is presented in this article. To verify the design, two identical rectangular TE 20 mode converters joined back-to-back were manufactured by nanocomputer numerical control (CNC) machining and the performances of the converters were characterized by using a vector network analyzer. The measured transmission coefficients were in good agreement with the simulated ones and showed a good flatness response with a 3-dB bandwidth of ~70.7 GHz (220.0-290.7 GHz). The average measured value of S 21 was about -2.0 dB and the in-band port reflection S 11 was around -10.0 dB.
The Faraday rotator is an important component used to separate the launching and receiving electromagnetic waves in the transmission line for millimetre wave radar systems. It has lower insertion loss, higher isolation and power capabilities as compared with the waveguide isolators. In this study, a HE 11 mode corrugated horn for the microwave performance measurement of a Ka‐band Faraday rotator was designed, fabricated and cold tested. The corrugated horn has a high conversion efficiency of above 99% over a bandwidth of 4 GHz. It is short in length, at 44 mm and produces a well‐formed linearly polarised HE 11 mode. The polarised wave has a well‐defined primary lobe and a −26.7 dB side‐lobe and also achieves a cross‐polarisation of −57.4 dB. The measured microwave reflection coefficient of the corrugated horn was in good agreement with simulation results and the back‐to‐back transmission coefficient is above −0.7 dB over a bandwidth of 7 GHz for a distance of 2 mm between the horns. Except high conversion efficiency, broad bandwidth, low side‐lobes and low cross‐polarisation, this corrugated horn is short, simple and suitable for the microwave measurement of Faraday rotator.
On the basis of the squeezed vacuum state in quantum optics, the concept of excited state for the squeezed vacuum state is presented by means of the nature of bosonic inverse operators. The quantum zero?point fluctuations both for charge and current in a mesoscopic RLC circuit are also derived.It is found that fluctuations depend explicitly on circuit units,squeezed parameter and quantum numbers of excited state. The quantum noise of this circuit at an absolute zero temperature is obtained.
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