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Optically pumped gas molecular terahertz (THz) lasers are promising for generating high-power and high-beam-quality coherent THz radiation. However, for pulsed gas THz lasers, the temporal behavior of the output THz pulse has rarely been investigated. In this study, the temporal behavior of a pulsed gas THz pumped by a fundamental-mode TEA CO

Lint percentage of seed cotton is one of the important bases for pricing in the trading segment. Unfortunately, the conventional methods of lint percentage are manually operated, which relies on the abundant experience of experts, and restrained by personal, physical and environmental factors. Up to date, the calculation of the lint percentage of seed cotton has not fully automated. In this paper, we proposed a non-destructive detection method for automatically obtaining lint percentage of seed cotton based on optical penetration imaging and machine vision, for the first time to our knowledge. The cotton seed image was obtained by the penetration imaging setup with a LED white backlight source. To accurately identify the number of cotton seeds, the image features of the cotton seed was studied and three key features was been found, which are the circumference, area, and greyscale value, respectively. A calculation system based on the three key features was presented to process the images and then automatically calculate the lint percentage of seed cotton. The first step of the system is to segment the original image using adaptive thresholding followed by morphological operations. Afterwards, the number of cotton seed was obtained by the three key features of the cotton seed. Then, the lint percentage was achieved by a professional industry formula. The suggested lint percentage detection methods were verified by the experiments with two seed cotton varieties samples of H219 and ZHM19. The experimental results indicated that the detection average accuracy of the developed system for seed cotton varieties H219 and ZHM19 were 96.33% and 95.40%

The paper proposed and verified a method of object edge detection based on the innovative defect spot working mode of the position-sensitive detector (PSD). With the output characteristics of the PSD in the defect spot mode and the size transformation properties of a focused beam, edge-detection sensitivity could be improved. Calibration experiments with the piezoelectric transducer (PZT) and object edge-detection experiments indicate that the object edge-detection sensitivity and accuracy of our method could reach 1 and 20 nm, respectively. Therefore, this method can be widely used in high-precision alignment, geometric parameters measurement, and other fields.

A high efficient, intense and compact pulsed D2O terahertz laser is presented, which is pumped by a multi-transverse mode TEA CO2 laser. For D2O gas as the active medium, with the cavity length of 120 cm, pulse energy of the THz laser has been investigated as the variation of pump energy and gas pressure. When the pump energy was 1.41 J, the maximum single pulse energy of 6.2 mJ was achieved at the wavelength of 385 μm. Photon conversion efficiency as high as 36.5% was obtained when laser operated at the maximum output energy. As the pump energy was raised from 0.57 to 1.41 J, the optimum pressure was slightly changed from 400 to 700 Pa. The THz pulse consisted of a spike pulse with pulse width of 120 ns and a tail pulse with pulse width of about 170 ns. The peak power of the spike pulse is about 44.3 kW. Comparing with the occurring time and pulse width of pump pulse, 70 ns delay and 10ns broadening were observed in the THz spike pulse.

This paper is concerned with the exponential state estimation problem for a class of discrete-time fuzzy cellular neural networks with mixed time delays. The main purpose is to estimate the neuron states through available output measurements such that the dynamics of the estimation error is globally exponentially stable. By constructing a novel Lyapunov-Krasovskii functional which contains a triple summation term, some sufficient conditions are derived to guarantee the existence of the state estimator. The linear matrix inequality approach is employed for the first time to deal with the fuzzy cellular neural networks in the discrete-time case. Compared with the present conditions in the form ofM-matrix, the results obtained in this paper are less conservative and can be checked readily by the MATLAB toolbox. Finally, some numerical examples are given to demonstrate the effectiveness of the proposed results.

We demonstrate a highly efficient and compact terahertz cavity oscillator that is based on z-cut crystal quartz used as the dichroic beam splitter, for the first time to the best of our knowledge. With D(2)O gas as the active medium, pumped with a multitransverse mode TEACO(2) laser, experimental verification was also presented to demonstrate the advantages of this cavity oscillator. With the cavity length of 120 cm, 7.4 mJ pulse energy at pulse repetition frequency of 6 Hz, pulse width of 90 ns, and peak power of 82.2 kW were achieved at a wavelength of 385 μm. Photon conversion efficiency (PCE) of 44% was obtained at the maximum output level from this terahertz cavity oscillator. Furthermore, to our knowledge, this PCE is the highest efficiency ever reported in D(2)O gas, 385 μm terahertz cavity laser systems. The beam quality or M(2) factor was found to be about 1.77.

This paper is concerned with the stability analysis problem for a class of discrete-time stochastic recurrent neural networks with mixed time delays. Based on the delay partitioning idea, a novel Lyapunov-Krasvskii functional is introduced. A new stability criterion is obtained by utilizing a free-weighting matrix method and some inequalities, which is characterized in terms of linear matrix inequalities (LMIs).

An efficient, compact pulsed D2O terahertz (THz) super-radiant laser pumped by a TEA (transversely excited atmospheric pressure) CO2 laser is presented. The pulse energy of the THz laser has been discussed as a function of CO2 laser pump energy, D2O gas pressure, and pump absorption. A pulse width of about 110 ns and the maximum pulse energy of about 1.3 mJ have been achieved at 385 μm, with pumping by a 378 mJ fundamental transverse mode TEA CO2 laser, and the photon conversion efficiency of 29% has been achieved. We have also studied the temporal behavior features such as the decay time, the full width at half-maximum, and the pulse broadening of the THz laser pulse compared with the pump pulse and the residual pump pulse at the optimum pressure.