Blade icing can affect wind turbines to generate electricity. In severe cases, 30% of power generation is lost in a year, and safety problems in the vicinity of wind power plants are also caused. Researchers have designed anti-icing and de-icing technologies to reduce these effects, and excellent ice-detecting devices are a prerequisite for using anti-icing and de-icing technologies. Ultrasonic attenuation technology can effectively and reliably detect the presence of ice without affecting the aerodynamic performance of the blade, providing a reliable guarantee for anti-icing and de-icing systems. Deicing and anti-icing systems are divided into active and passive, active heating blades are still the most effective anti-icing and de-icing methods, but their energy consumption is too high. Although there are many existing de-icing methods, there are not many practical uses. This article introduces them separately and lists their advantages and disadvantages. The use of ultrasonic anti-icing and de-icing is an economical and reliable means that has been proven to be used for anti-icing and de-icing of blades. However, under normal circumstances, a single anti-icing de-icing system cannot completely solve the problem of icing of the blades. This paper suggests using both ultrasonic and hydrophobic coatings to cope with more icing conditions. K E Y W O R D Santi-icing and deicing technology, fan blade, hydrophobic coating, ice detection technology, ultrasonic deicing | INTRODUCTIONWith the rapid development of the world economy, lots of countries are increasingly demanding energy resources. Owing to release a lot of greenhouse gases, chemicals and toxins substances from the combustion of the fossil fuels such as coal and oil, 1 People began to look for renewable energy to provide energy consumption, such as wind energy, 2-4 hydrogen energy, 5-7 solar energy, 8-10 biogas and biomass energy. 11-15 With the wind power growing rapidly, generate electricity by using wind turbines is economical and environmentally friendly. 16 As can be seen in Figure 1, China's total installed capacity of wind turbines in 2016 is much higher than in other countries.China has the largest wind power market in the country, and the installed capacity of wind power is growing steadily year by year. The high density of air is conducive to the development of wind energy resources in cold regions. Figure 2 shows wind resource changes in different seasons. The wind speed from June to August is significantly lower than other months. There are also data showing that wind resources in cold regions are 10% higher than other regions. 17,18

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Turbulent mixing driven by cloud/fog‐top radiative and evaporative cooling (hereafter top‐driven diffusion), including top‐down mixing and top‐cooling entrainment, is critical for the development of cloud/fog. Previous work mainly focused on impacts of top‐driven diffusion on stratocumulus‐topped planetary boundary layer (PBL) and radiation fog over land. However, its exact role in sea fog process is yet unclear. Using the Weather Research and Forecasting (WRF) model with the updated Yonsei University (YSU) PBL scheme, in which the ysu_topdown_pblmix option is responsible for the parameterization of the top‐driven diffusion, the present study investigates respective effects of the top‐cooling entrainment and top‐down mixing on an advection fog event over the Yellow Sea that occurred on 20–21 May 2014. Evaluation of the modeling results confirms that the top‐driven diffusion significantly improves the sea fog simulation. The top‐cooling entrainment allows more relatively quiescent air above the fog top to mix into the sea fog layer, leading to a higher mixed layer with increased temperature and decreased humidity. With the enhancement of buoyant turbulence, the warming and dehumidifying moderately lift the sea fog bottom and reduce the false fog area. The top‐down mixing performs quite well in reproducing a stable structure near the fog top, which results from the added turbulent mixing determined by a revised K profile. Note that the effect of top‐driven diffusion shows high sensitivities to shortwave radiation and vertical resolution. Besides the fog‐top cooling, the fog‐droplet sedimentation is necessary to be included in the top‐cooling entrainment.

The data assimilation method to improve the sea fog forecast over the Yellow Sea is usually three-dimensional variational assimilation (3DVAR), whereas ensemble Kalman filter (EnKF) has not yet been applied to this weather phenomenon. In this paper, two sea fog cases over the Yellow sea, one spread widely and the other spread narrowly along the coastal area, are studied in detail by a series of numerical experiments with 3DVAR and EnKF based on the Grid-point Statistical Interpolation (GSI) system and the Weather Research and Forecasting (WRF) model. The results show that the assimilation effect of EnKF outperforms that of 3DVAR: for the widespread-fog case, the probability of detection and equitable threat scores of the forecasted sea fog area are improved respectively by ~57.9% and ~55.5%; the sea fog formation of the other case completely mis-forecasted by 3DVAR was produced successfully by EnKF. These improvements of EnKF relative to 3DVAR benefit from its flow-dependent background error covariances, resulting in more realistic depiction of sea surface wind for the widespread-fog case and better moisture distribution for the other case in the initial conditions. More importantly, the correlation between temperature and humidity in the background error covariances of EnKF plays a vital role in the response of moisture to the assimilation of temperature, which leads to a great improvement in the initial moisture conditions for sea fog forecast. Extra sensitivity experiments of EnKF indicate that the forecast result is sensitive to ensemble inflation and localization factors, in particular, highly sensitive to the latter.

The data assimilation method to improve sea fog forecast over the Yellow Sea is usually three-dimensional variational assimilation (3DVAR), whereas ensemble Kalman filter (EnKF) has not yet been applied on this weather phenomenon. In this paper, two sea fog cases over the Yellow sea, one spread widely and the other spread narrowly along the coastal area, are studied in detail by a series of numerical experiments with 3DVAR and EnKF based on the Grid-point Statistical Interpolation (GSI) system and the Weather Research and Forecasting (WRF) model. The results show that the assimilation effect of EnKF outperforms that of 3DVAR: for the widespread-fog case, the probability of detection and equitable threat scores of the forecasted sea fog area get improved respectively by ~57.9% and ~55.5%; the sea fog of the other case completely mis-forecasted by 3DVAR is produced successfully by EnKF. These improvements of EnKF relative to 3DVAR are benefited from its flow-dependent background error, resulting in more realistic depiction of sea surface wind for the widespread-fog case and better moisture distribution for the other case in the initial conditions. More importantly, the correlation between temperature and humidity in the background error of EnKF plays a vital role in the response of moisture to the assimilation of temperature, which leads to a great improvement on the initial moisture conditions for sea fog forecast.

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Among the China Seas, the Yellow Sea has the highest occurrence frequency of sea fog that can be categorized into widespread sea fog and coastal sea fog. In this paper, we study a typical coastal sea fog along the Shandong Peninsula that is accompanied by sea-land breezes. Based on a series of numerical experiments conducted by the Weather Research and Forecasting model with high spatial resolution, the impacts of the sea–land breezes on the formation and development of sea fog are investigated in detail. The land breeze can act as an accelerator that enhances humidification and cooling near the coast which promotes sea fog formation during the nighttime, resulting from nearshore vapor convergence and offshore cool-air transportation jointly by the descending branch and low-level breeze of the land breeze circulation. During the daytime, the sea breeze acts as a reducer that inhibits sea fog development, including the contraction of fog area caused by onshore advection of the sea breeze on cloud liquid water, and the restraint of fog vertical growth due to warming and drying by the descending branch of the sea breeze circulation.

Material experiment system of hydraulic servo system is subject to load disturbance and load disturbance is a function of standard mechanical parameters of rock samples. Rock mass is very discrete, anisotropy, composition is not single and inelastic[. Traditional tester can't get the complete stress-strain curve of rock[ material, in order to solve the shortage of the traditional hydraulic servo system, in this paper, the fuzzy PID control is successfully applied to the hydraulic servo system, through the experiments and get good effect.