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【Background and objective】 Water-fertilizer integrated drip irrigation has advantages over traditional methods, including even fertilization, saving water and fertilizer, and precise control. However, emitter clogging is a problem limiting its widespread use. While emitter clogging is affected by various factors, the role of irrigation water temperature is poorly understood. This paper is to investigate the combined impact of temperature and working pressure on emitter blockage in a water-fertilizer integrated irrigation system. 【Method】 We used the plain channel emitter; the short-cycle intermittent irrigation clogging tests were conducted under temperature ranging from 15 to 30 ℃, and working pressures at 50 kPa (low) an 100 kPa (normal). Ammonium phosphates were used as the fertilizer and tap water as the irrigation water. Average water flow in the emitter was monitored; at the end of the experiment, the geometrical structure and composition of the clogging materials were analyzed using SEM; the blocking position in the emitter was also measured. 【Result】 Ammonium phosphate had a significant effect on clogging; irrigation reduced the average relative flow in the emitter by 15.03%~34.02%. Temperature rise increased the average relative flow, and the increase under the low pressure was greater than under the normal pressure. Irrigation increased the average relative flow by 18.55% under low pressure and 14.88% under normal pressure. The temperature did not affect the main components of the clogging material. The mechanisms underlying the blockage involve physical blockage by flocculation and replacement of ions in formation of the flocculation. However, increasing temperature weakened the flocculation and reduced surficial complexity of the blockage materials. In the emitter, the blockage was mainly located at the transition zone, the channel head, and the tail of the channel, which accounted for 29.75%, 22.31%, and 22.31% of the blockage, respectively. Changing temperature did not affect the blockage location. Therefore, it is recommended to optimize the structure of the transition zone, the channel head, and the tail of the channel to alleviate the blockage. 【Conclusion】 Increasing temperature can reduce flocculation thereby alleviating emitter blockage to some extent, regardless of working pressure.

Yubin, Z., Zhengying, W., Lei, Z., Qinyin, L., & Jun, D. (March-April, 2017). Improved online sequential extreme learning machine for simulation of daily reference evapotranspiration. Water Technology and Sciences (in Spanish), 8(2), 127-140. The traditional extreme learning machine has significant disadvantages, including slow training, difficulty in selecting parameters, and difficulty in setting the singularity and the data sample. A prediction model of an improved Online Sequential Extreme Learning Machine (IOS-ELM) of daily reference crop evapotranspiration is therefore examined in this paper. The different manipulation of the inverse of the matrix is made according to the optimal solution and using a regularization factor at the same time in the model. The flexibility of the IOS-ELM in ET0 modeling was assessed using the original meteorological data (Tmax, Tm, Tmin, n, Uh, RHm, φ, Z) of the years 1971–2014 in Yulin, Ankang, Hanzhong, and Xi’an of Shaanxi, China. Those eight parameters were used as the input, while the reference evapotranspiration values were the output. In addition, the ELM, LSSVM, Hargreaves, Priestley-Taylor, Mc Cloud and IOS-ELM models were tested against the FAO- 56 PM model by the performance criteria. The experimental results demonstrate that the performance of IOS-ELM was better than the ELM and LSSVM and significantly better than the other empirical models. Furthermore, when the total ET0 estimation of the models was compared by the relative error, the results of the intelligent algorithms were better than empirical models at rates lower than 5%, but the gross ET0 empirical models mainly had 12% to 64.60% relative error. This research could provide a reference to accurate ET0 estimation by meteorological data and give accurate predictions of crop water requirements, resulting in intelligent irrigation decisions in Shaanxi.

In supersonic plasma spraying system (SAPS), heat transfer from arc plasma is characterized by several distinct features, such as transport of dissociation and ionization energy and of electrical charges in addition to mass transport. The thermodynamic and transport properties of plasma jet were influenced by several main parameters such as primary gas flow rate, the H2 vol.% and current intensity A. This paper first analyzes the effect of these parameters on the temperature and velocity of plasma jet theoretically. Further, the loading particles were melted and accelerated by plasma jet. Effects of several main parameters such as carrier gas flow rate, the H2 vol.%, the current intensity, the voltage and the spraying distance on temperature and velocity of in-flight particle were studied experimentally. The average maximum temperature and velocity of in-flight particle at any given parameters were systematically quantified. Optimal SAPS process parameters were given in this paper. In general, increasing the particles impacting velocity and surface temperature can improve the maximum spreading factor and decrease the coating porosity.

Through numerical simulation, key issues concerning the plasma jet features as well as the sizes of nozzle for supersonic atmosphere plasma spraying (SAPS) were analyzed in this paper. Numerical results were compared with the experimental measurements and a good agreement has been achieved. Due to the effect of mechanical compression, the increasing sizes of r1, r2, r3 and r4 (r1, r2, r3 and r4 are the sizes of nozzle) lead to a decrease in temperature and velocity of plasma jet. But large size of r5 can increase the external temperature and velocity of plasma jet, which benefit particles accelerating at the far downstream region. A new nozzle was designed based on the simulation results. Compared to the temperature and velocity of plasma jet in the original nozzle, the maximum temperature and velocity of plasma jet in new structure are increased by about 9.8% and 44.5%, which is a benefit to the particles to reach a higher speed and surface temperature.