A scheme to detect sand/dust weather applying meteorological radars

Sandy dust weather occur frequently in arid and semi-arid areas. It is important to actually detect the sandy dust grain concentration or the visibility of the sandy dust weather for weather forecasting. In this paper, based on numerical calculation of the effective detection distance of different radar detecting the sandy-dust weather with different strength, a scheme to detect sand/dust weather applying existed meteorological radar stations is proposed in this paper. The scheme can be efficient to detect sandy dust weather, for it makes a good supplement to the current deficiencies in detecting sandy dust weather and it’s a cost-saving detection way by using the existed meteorological radars. In addition, the effect of charges carried by sand/dust grains and the relative humidity on the effective detection distance of radar is also investigated, and it shows that these effects will not change the proposed scheme. It will be promising to detect the sandy dust weather in the way of disastrous weather precaution by using this scheme.

Study on Influencing Factors of Helicopter Brownout Evolution Based on CFD-DEM

The gas-solid two-phase flow model is constructed based on the Euler-Lagrangian framework. The SST k−ω two-equation turbulence model and the soft ball model are coupled by computational fluid dynamics (CFD) and a discrete element model (DEM). Brownout is then simulated by the above method with sliding mesh. As the calculation examples show, the simulations and experiments of the Lynx rotor and the Caradonna–Tung rotor are compared. The coupling method is verified through calculation of the rotor lift coefficient, blade section pressure coefficient and tip vortex shedding position. The results show that when the helicopter is hovering at a height of 0.52R from the ground, it will cause brownout and the pilot’s vision will be obscured by sand. When the hovering height is 1R, the phenomenon of brownout is not serious. The movement speed of most sand dust is about 12 m/s, and the height of the sand dust from the ground will gradually increase over time. Large particles of sand are more difficult to be entrained into the air than the small particles, and the particles with a radius of 50 um are basically accumulated on the ground. Moreover, the slotted-Tip rotor has an effect on restraining brownout.

Efficient Sandstorm Image Enhancement Using the Normalized Eigenvalue and Adaptive Dark Channel Prior

A sandstorm image has features similar to those of a hazy image with regard to the obtaining process. However, the difference between a sand dust image and a hazy image is the color channel balance. In general, a hazy image has no color cast and has a balanced color channel with fog and dust. However, a sand dust image has a yellowish or reddish color cast due to sand particles, which cause the color channels to degrade. When the sand dust image is enhanced without color channel compensation, the improved image also has a new color cast. Therefore, to enhance the sandstorm image naturally without a color cast, the color channel compensation step is needed. Thus, to balance the degraded color channel, this paper proposes the color balance method using each color channel’s eigenvalue. The eigenvalue reflects the image’s features. The degraded image and the undegraded image have different eigenvalues on each color channel. Therefore, if using the eigenvalue of each color channel, the degraded image can be improved naturally and balanced. Due to the color-balanced image having the same features as the hazy image, this work, to improve the hazy image, uses dehazing methods such as the dark channel prior (DCP) method. However, because the ordinary DCP method has weak points, this work proposes a compensated dark channel prior and names it the adaptive DCP (ADCP) method. The proposed method is objectively and subjectively superior to existing methods when applied to various images.

Current State of Granulometric Composition of Irrigated Meadow-Serozem Soils of Azerbaijan

The article deals with the granulometric composition of irrigated-meadow-gray soils (Irrigic Calcisols). Along with the granulometric composition, the ratio of sand, dust and silt fractions was taken into account. The results of the analysis show that the uneven distribution of dependent silt particles supplied with irrigation water causes a variety in the granulometric composition of irrigated soils. At the same time, the differences in the granulometric composition of irrigated lands and raw soils were identified, and the reasons were studied.

Viability of Bacillus subtilis Cells in Airborne Bioaerosols on Face Masks

The coronavirus disease 2019 (COVID-19) pandemic is a general health crisis and has irreversible impacts on human societies. Globally, all people are at risk of being exposed to the novel coronavirus through transmission of airborne bioaerosols. Public health actions, such as wearing a mask, are highly recommended to reduce the transmission of infectious diseases. The appropriate use of masks is necessary for effectively preventing the transmission of airborne bioaerosols. The World Health Organization (WHO) suggests washing fabric masks or throwing away disposable masks after they are used. However, people often use masks more than once without washing or disposing them. The prolonged use of a single mask might—as a result of the user habitually touching the mask—promote the spread of pathogens from airborne bioaerosols that have accumulated on the mask. Therefore, it is necessary to evaluate how long the living components of bioaerosols can be viable on the masks. Here, we evaluated the viability of airborne Bacillus subtilis (B. subtilis) in bioaerosols filtered on woven and anti-droplet (non-woven) face masks. As a simulation of being simultaneously exposed to sand dust and bioaerosols, the viability rates of bioaerosols that had accumulated on masks were also tested against fine dust and airborne droplets containing bacteria. The bioaerosols survived on the masks immediately after the masks were used to filter the bioaerosols, and the bacteria significantly proliferated after one day of storage. Thereafter, the number of viable cells in the filtered bioaerosols gradually decreased over time, and the viability of B. subtilis in bioaerosols on the masks varied, depending on the mask material used (woven or non-woven). Despite the reduction in viability, bioaerosols containing living components were still found in both woven and anti-droplet masks even after six days of storage and it took nine days not to have found them on masks. The number of viable cells in bioaerosols on masks significantly decreased upon exposure of the masks to fine dust. The results of this study should provide useful information on how to appropriately use masks to increase their duration of effectiveness against bioaerosols.

Reaction products of Sm2Zr2O7 with calcium-magnesium-aluminum-silicate (CMAS) and their evolution

During flight, many silicates (sand, dust, debris, fly ash, etc.) are ingested by an engine. They melt at high operating temperatures on the surface of thermal barrier coatings (TBCs) to form calcium-magnesium-aluminum-silicate (CMAS) amorphous settling. CMAS corrodes TBCs and causes many problems, such as composition segregation, degradation, cracking, and disbanding. As a new generation of TBC candidate materials, rare-earth zirconates (such as Sm2Zr2O7) have good CMAS resistance properties. The reaction products of Sm2Zr2O7 and CMAS and their subsequent changes were studied by the reaction of Sm2Zr2O7 and excess CMAS at 1350 °C. After 1 h of reaction, Sm2Zr2O7 powders were not completely corroded. The reaction products were Sm-apatite and c-ZrO2 solid solution. After 4 h of reaction, all Sm2Zr2O7 powders were completely corroded. After 24 h of reaction, Sm-apatite disappeared, and the c-ZrO2 solid solution remained.