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Gas flotation for oily wastewater treatment is based on the attachment of gas bubbles to oil droplets to produce lighter aggregates that rise to the wastewater surface. It is a feasible, promising, and effective method for oily wastewater treatment due to its high separation efficiency with no secondary contamination, cost-effectiveness, and simple operation. This review focuses on separating oil from emulsions by gas flotation using microbubbles (MBs) and nanobubbles (NBs), which offer the advantages of small bubble size, large specific surface area, and slow rising velocity. The properties of different types of gas bubbles and their generation methods were discussed. Different gas flotation system designs and operational parameters were summarized for dissolved gas flotation, induced gas flotation, and electrolytic flotation (EF). The review illustrated that oil removal efficiency in MB- and NB-based gas flotation was affected by various factors including initial oil concentration, pH, temperature, flotation time, and oil droplet size. Key words: gas flotation, microbubble, nanobubble, oil-in-water emulsion, oily wastewater treatment La flottation gazeuse pour le traitement des eaux usées contaminées par les hydrocarbures est basée sur la fixation des bulles de gaz aux gouttelettes d'hydrocarbures pour produire des agrégats plus légers qui remontent àla surface des eaux usées. Il s'agit d'une méthode réalisable, prometteuse et efficace pour le traitement des eaux usées contaminées par les hydrocarbures en raison de sa grande efficacité de séparation sans contamination secondaire, de sa rentabilité et de sa simplicité d'utilisation. Cette synthèse se concentre sur la séparation des hydrocarbures des émulsions par flottation gazeuse en utilisant des microbulles et des nanobulles qui offrent les avantages d'une petite taille de bulle, d'une grande surface spécifique et d'une vitesse d'ascension lente. Les propriétés des différents types de bulles de gaz et leurs méthodes de génération ont été discutées. Les différentes conceptions de systèmes de flottation gazeuse et les paramètres opérationnels ont été résumés pour la flottation par gaz dissous, la flottation par gaz induit et la flottation électrolytique. La synthèse a montré que l'efficacité de l'élimination des hydrocarbures par la flottation gazeuse àbase de microbulles et de nanobulles était affectée par divers facteurs, notamment la concentration initiale d'hydrocarbures, le pH, la température, le temps de flottation et la taille des gouttelettes d'hydrocarbures. [Traduit par la Rédaction] Mots-clés : flottation gazeuse, microbulles, nanobulles, émulsion d'huile dans l'eau, traitement des eaux usées contaminées aux hydrocarbures, 1 Introduction Oily wastewater is generated from oil spill incidents and many other sources, such as food processing, oil refining, textile and leather industries, metal rolling and finishing, paper deinking, [...]

Under rainy conditions, atmospheric settling particles have significant depolarization effects on radar waves and thus affect the target detection performance. This paper establishes an extended target detection model for fully polarized radar under complex rainy conditions and proposes two polarization and waveform optimization methods by taking into account the transmission effect of rainfall. If the rainfall information is known, the polarization and waveform for transmitting and receiving are optimized by maximizing the system Signal-to-Clutter/Noise Ratio (SCNR). While the rainfall information is absent, the optimal transmitting polarization and waveform are obtained by directly compensating the transmission effect from non-rainfall optimization results using fully polarized radar observation parameters. Using measured data from the T-72 tank, The experimental results verify the effectiveness and robustness of the two methods in real scenarios and 4 dB on the improvement of SCNR can be achieved. [ABSTRACT FROM AUTHOR]

Accurate marine wind detection under all-weather conditions is crucial for maritime activities. The joint detection of lidar and radar is supposed to be a potential way to carry out the all-weather sensing of wind. However, their performance analysis has not been well studied, particularly in the far sea area, where the wind-tracing particles are quite different from those inland. Based on the particle distributions above the sea surface under different weather conditions, this study investigated the scattering and attenuation effects of lidar and radar waves in open sea areas with the Mie theory and T-matrix method. Then, the maximum detection range and velocity accuracies of lidar/radar were comprehensively analyzed based on detection principles to optimize the combination of lidar and radar. According to the simulation results, it was difficult to maintain the detection capability of a single lidar/radar under all-weather conditions, and 1.55 μ m lidar and W-band radar presented a promising joint detection scheme, as they exhibited optimal weather adaptability in clear sky and precipitation conditions, respectively. [ABSTRACT FROM AUTHOR]