Boiling of binary mixtures on superhydrophobic surfaces with artificial cavities

This study experimentally investigates bubble behaviour from an isolated artificial cavity on a superhydrophobic substrate, the working fluid is a binary mixture of Novec649 and Novec7000 with mole fractions between 0.05 - 99.5 as well as their pure counterparts. The results show an earlier onset of bubble departure as well as deceasing trends in bubble departure diameter in the presence of the binary mixture compared to pure cases. The bubble departure diameter is at its minimum and fastest growth rate at a mole fraction of approximately 0.50. Theoretical models from literature were tested and satisfactory agreement with different models were achieved depending on the concentration.</p

Experimental Investigation of Bubble Oscillation and Leaping Driven by Thermocapillary Effects with Non-condensable Gas

Boiling phase-change plays a crucial role in heat transfer as it can dissipate higher heat fluxes than single phase. Bubble nucleation, growth, motion (oscillation or leaping), coalescence and departure, govern the boiling and the heat transfer performance on wires. Many factors affect the bubble mechanisms and interactions taking place, which include the nature of the fluid, experimental conditions, thermocapillary effects, etc. This work investigates the bubble oscillation and leaping phenomena caused by thermocapillary effects in the presence of oxygen and air as non-condensable gases during boiling on a platinum micro-wire. More in particular, the bubble oscillation performance is compared under various bulk temperatures and heat fluxes for two different non-condensable gases. It is observed that for a similar fluid bulk temperature, the lower the heat flux the longer the bubble displacement. Moreover, bubble oscillation phenomenon is influenced by the concentration of non-condensable gas dissolved in the liquid showing larger harmonic periods and shorter waiting times with decrease in the contact line pinning force by approximately 7–44% in the presence of air when compared to nitrogen. Last during oscillations, bubble leaping phenomenon was observed as a consequence of the interaction between the jet flows above the oscillating bubble

A Study on Particle Swarm Algorithm Based on Restart Strategy and Adaptive Dynamic Mechanism

Aiming at the problems of low path success rate, easy precocious maturity, and easily falling into local extremums in the complex environment of path planning of mobile robots, this paper proposes a new particle swarm algorithm (RDS-PSO) based on restart strategy and adaptive dynamic adjustment mechanism. When the population falls into local optimal or premature convergence, the restart strategy is activated to expand the search range by re-randomly initializing the group particles. An inverted S-type decreasing inertia weight and adaptive dynamic adjustment learning factor are proposed to balance the ability of local search and global search. Finally, the new RDS-PSO algorithm is combined with cubic spline interpolation to apply to the path planning and smoothing processing of mobile robots, and the coding mode based on the path node as a particle individual is constructed, and the penalty function is selected as the fitness function to solve the shortest collision-free path. The comparative results of simulation experiments show that the RDS-PSO algorithm proposed in this paper solves the problem of falling into local extremums and precocious puberty, significantly improves the optimization, speed, and effectiveness of the path, and the simulation experiments in different environments also show that the algorithm has good robustness and generalization

Application of a Multi-Strategy Improved Sparrow Search Algorithm in Bridge Crane PID Control Systems

To address the anti-swing issue of the payload in bridge cranes, Proportional–Integral–Derivative (PID) control is a commonly used method. However, parameter tuning of the PID controller relies on empirical knowledge and often leads to system overshoot. This paper proposes an Improved Sparrow Search Algorithm (ISSA) to optimize the gains of PID controllers, alleviating adverse effects on payload oscillation and trolley positioning during the operation of overhead cranes. First, tent map chaos mapping is introduced to initialize the sparrow population, enhancing the algorithm’s global search capability. Then, by integrating sine and cosine concepts along with nonlinear learning factors, the updating mechanism of discoverer positions is dynamically adjusted, expediting the solving process. Finally, the Lévy flight strategy is employed to update follower positions, thereby enhancing the algorithm’s local escape capability. Additionally, a fitness function containing overshoot penalties is proposed to address overshoot issues. Simulation results indicate that the overshoot rates of all algorithms remain less than 3%. Moreover, compared with the Sparrow Search Algorithm (SSA), Particle Swarm Optimization (PSO), Simulated Annealing (SA), and Whale optimization Algorithm (WOA), the optimized PID control system with the ISSA algorithm exhibits superior control performance and possesses certain robustness and adaptability

Concentration and distribution of 17 organochlorine pesticides (OCPs) in seawater from the Japan Sea northward to the Arctic Ocean

Seventeen classic organochlorine pesticides in surface seawater were studied in terms of their composition pattern as well as their distribution pattern in the areas covering the Japan Sea, Okhotsk Sea, Bering Sea, Chukchi Sea and Arctic Ocean. Their concentrations varied, but roughly two levels were seen with one ranging between 0.1 and 1 ng L-1 for most HCH isomers and the other lower than 0.1 ng L-1 for other chemicals. Of the 17 target compounds, HCHs were dominant with a total concentration percentage generally more than 50%, and a relatively high concentration percentage of heptachlor and aldrine was also observed at scattered stations. The historical long-term trend of several target chemicals in the five sea zones considered was discussed in comparison with previous reports. Inter-sea zone comparison was carried out for individual chemicals by comparing the concentration variation in all five sea zones. A higher variation in concentration was generally found in the northern sea zones, namely the Bering Sea, Chukchi Sea and Arctic Ocean, for most target compounds. The sum concentration of the 17 target chemicals displayed a general trend of increasing northward from the Japan Sea to the Okhotsk Sea to the Bering Sea to the Arctic Ocean. Different latitudinal trends were found for alpha-HCH and gamma-HCH, and the reason of this difference was discussed by considering their divergence of thermodynamic properties, which could contribute to a slightly different fractionation effect during their northward transport driven by atmospheric long range transport. The source of the HCHs was identified by analyzing the alpha-HCH/gamma-HCH ratio, which was less than 4 without exception, indicating a component characteristic featuring a mixture of technical HCHs and lindane. In addition, the vertical distribution of alpha-HCH, gamma-HCH and their ratio at station B80 was discussed. Different patterns were found in the upper 300 m while in layers from 300 m downward to 3500 m the patterns were fairly comparable. The vertical profiles were used to correlate the water mass distribution, based on which four layers were tentatively classified at station B80.National Natural Science Foundation of China [40776040, 40306012, 40776003]; National High Technology Research and Development Program of China [2007AA09Z121]; Ocean Public Welfare Scientific Research Project ; State Oceanic Administration of China [200805095]; Fujian Provincial Department of Science Technology [2005Y021]; Chinese Arctic and Antarctic Administration, State Oceanic Administration of Chin

Heavy metals in surface sediments from mangrove zone in Zhangjiang River estuary, South China

Conference Name:International Conference on Environmental Science and Information Application Technology (ESIAT 2009). Conference Address: Wuhan, PEOPLES R CHINA. Time:JUL 04-05, 2009.Concentrations of selected heavy metals (Cr, Cu, Zn, As, Cd, Hg and Ph) in surface sediments from 18 sites were examined in Zhangjiang Estuary Mangrove National Natural Reserve (ZEMNNR), which is the largest natural mangrove forest at the north of tropic of Cancer in China. The ranges of heavy metals expressed in mu g/g sediment dry weight were as following: Cr (48.14 to 110.01), Cu (18.15 to 43.18), Zn (119.53 to 136.13), As (12.05 to 16.16), Cd (0.25 to 0.58), Hg (ND to 0.10) and Ph (55.61 to 67.71). Slight distribution changes implicate inflow from Zhangjiang River offered most Zn, As, Cd, Hg and Ph; While for Cr and Cu, anthropogenic activities might he another important source. The levels of Ph exceed sediment quality criteria ( I Class) and may show a potential risk to ecosystems. The values of 1,,,, indicate that Zhangjiang estuary mangrove zone is moderately polluted by Ph and slightly polluted by Cd, As and Cr

Magmatic crystallization drives zircon Zr isotopic variations in a large granite batholith

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