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Objective This study investigated the efficacy of different concentrations of cholesterol-loaded cyclodextrin (CLC) on cryopreservation in boar sperm quality. Methods In this study, we treated boar sperm with different concentrations of CLC before freezing and analyzed the sperm cholesterol concentration, plasma membrane, acrosome integrity rate and total motility rate before and after freeze-thawing. We also investigated the levels of reactive oxygen species (ROS), malondialdehyde (MDA), adenosine triphosphate (ATP), and structural- and oxidative-damage related proteins in all groups after thawing. Results The results revealed that the cholesterol concentration of the CLC-treated groups was higher than that of the control group, both before freezing and after thawing (p

Heat transfer enhancement based upon micro-disturbing structures becomes increasingly important for thermal protection of air-breathing propulsion systems. To explore the influence mechanism of different structures on heat transfer in regenerative cooling channels of scramjet engines, flow structures and heat transfer of supercritical-pressure n-Decane in mini-channels with dimple and micro-rib arrays are numerically investigated. Results indicate effective heat transfer enhancement inside the channels depends more on efficient transverse turbulence disturbance rather than longitudinal or perpendicular turbulence disturbance. Severe thermal stratification generates strong shear layers in channels, where transverse secondary flows bring much intenser flow mixing than longitudinal secondary flows, especially in transcritical temperature region where the best heat transfer enhancement is obtained. With same characteristic dimensions, longitudinal micro-disturbing structures like dimples have lower flow resistance, but transverse micro-disturbing structures like micro-ribs achieve stronger heat transfer enhancement. Besides, the performance of micro-ribs is much more sensitive to the dimensional change. Therefore, micro-ribs have larger working excursion for enhancing performance factor than dimples. With optimal structure parameters: hr = e = 0.3 mm, pr = 3 mm, hd = 0.225 mm, dd = 1.5 mm, overall performance factor in micro-ribbed channel is 1.14 times of that in dimpled channel. Those conclusions provide effective support for optimization design for the regenerative cooling structures.

Summary: During the operation of proton exchange membrane fuel cell (PEMFC), about half of the energy is dissipated as heat. To enhance the energy efficiency of fuel cell electric vehicle (FCEV), we hereby propose a waste heat recovery system for low-temperature energy harvesting of FCEV. A comprehensive fluid-thermal-electrical multiphysics model is established to predict the performance of the proposed thermoelectric generator (TEG) system. Subsequently, a practical prototype of TEG system is developed. Transient and steady-state experimental results from the prototype validated the feasibility and power generation efficiency of the TEG system. At a temperature difference of 40°C, the highest open circuit voltage and power output of each TEG are 6.2V and 0.33W respectively, the results affirmatively demonstrate that the TEG system can recover the low temperature waste heat from PEMFC, thus providing valuable guidance for the design of the future PEMFC thermal management system in FCEV.

Hydrogen fueled parallel wall-jet combustion is considered to be one of the most promising drag reduction technologies in supersonic combustors, researchers mainly focus on its drag reduction mechanism, while balancing its combustion efficiency and drag reduction performance is of great significance for engine performance and energy conservation. In this paper, combustion performance of hydrogen fueled parallel wall-jet is numerically investigated. Kinetic reaction rate and scalar dissipation rate are defined to decouple the chemical reaction and mixing processes. Results indicate that although hydrogen fueled parallel wall-jet combustion is a nonequilibrium chemical reaction process, the combustion process is dominated by mixing due to the much larger magnitude order of kinetic reaction rate. The investigation also reveals that, compared to the effects of mainstream total temperature, mainstream Mach number presents a more significant effect on combustion efficiency. Moreover, combustion efficiency increase first brings negative and then brings beneficial effects on drag reduction performance, which is due to the different sensibilities of the two skin friction determinants viscosity and velocity gradient to combustion efficiency. It is found that, viscosity is more sensitive to combustion efficiency, with combustion efficiency increases by 5.4 %, viscosity increases by 4.15 %, while velocity gradient only decreases by 2.19 %.

The investigation of film cooling in CH4/O2 rocket engines holds paramount importance in the advancement of rocket propulsion. However, the wall heat flux is always overestimated in numerical simulation processes. Hence, this article proposes a numerical framework that employs the Reynolds averaged Navier–Stokes method to simulate the single-element gaseous CH4/gaseous O2 combustion chamber, which is the basis for rocket engine simulations. The coupled wall function that considers chemical reaction effects is introduced to enhance the accuracy of wall heat flux prediction. The impact of utilizing a coupled wall treatment on the prediction of wall heat flux and its fundamental parameters are examined. In addition, a single-element combustion chamber experiment is performed to validate the simulation. The results demonstrate that the implementation of the coupled wall function hardly influences the main flow characteristics, whereas the wall heat flux calculated with general wall functions shows an overestimation, which can be reduced by the coupled wall function. Finally, the case with a coupled wall function can improve the cooling efficiency with greater accuracy and the cooling systems with optimized design. The proposed numerical framework and the findings of the study provide profound insights that can improve the design and optimization of rocket engines.

Abstract Amorphous carbon films have attracted substantial interest due to their exceptional mechanical and tribological properties. Previous studies revealed that the amorphous carbon films exhibited lower coefficient of friction (COF) because of the transformation in bond structure from sp3-C to sp2-C during friction processes. However, the mechanism for such a transformation during friction is not well understood. This study is conducted to get an insight into the metastable transformation in amorphous carbon film during friction by means of experiments and molecular dynamics (MD) simulation. Relevant wear tests showed that wear of the film changed from an abrasive wear mode to a mixture of abrasion and adhesive wear, resulting in a decrease in growth rate of the wear rate after the running-in stage. It is worth noting that the sp3-C atoms were increased during the running-in stage when the films contained lower sp3/sp2 ratios. However, the formed sp3-C atoms could only be short-lived and gradually transformed to sp2-C atoms with the graphitization generated on the wearing surface of the films. The radial distribution function and translational order parameter indicated that the films’ high sp3/sp2 ratio led to an increased sp2-C proportion on the wear scar after friction, which caused an increased structural ordering.

One of the effective methods to simultaneously achieve the thermal protection and friction reduction requirement of a scramjet engine is the usage of fuel film cooling. As the combustion process inside the combustor proceeds, the oxygen concentration in the burnt gas gradually decreases and will influence the thermal and friction characteristics of the hydrocarbon film. Therefore, the effects of oxygen concentration in the mainstream on the hydrocarbon film are evaluated by numerical simulations based on RANS framework. The results indicate that the cooling performance of the hydrocarbon film is not sensitive to the oxygen concentration, although the fuel film burns more intense as the oxygen concentration increases. While the friction reduction performance is sensitive to the oxygen concentration. Specifically, about 10% friction reduction can be obtained for 10% oxygen in the mainstream compared to that of inert cases, and the wall friction can be further reduced by 30% for 20% oxygen. Further analysis reveals that the mechanism of the above two drag reductions is different. For weak boundary layer combustion, the decrease of the molecular viscosity contributes to the reduction of friction. While for significant boundary layer combustion, a lower near-wall velocity gradient is the main reason.

Hydrocarbon fueled supersonic film is considered to be one of the most effective methods for achieving thermal protection and drag reduction meanwhile in scramjet combustors. In this paper, the effects of film and mainstream inflow parameters on thermal protection and drag reduction characteristics for hydrocarbon fueled supersonic film with combustion are numerically investigated. The results indicate that, based on the traditional supersonic film without chemical reaction, combustion brings beneficial effects on thermal protection and drag reduction characteristics mainly depend on the relative proportion and location of exothermic chemical reactions in the boundary layer. It is found that, film inflow parameters only change the reaction energy spatial distribution through changing mainstream energy addition by mixing. However, mainstream inflow parameters directly change reaction conditions, therefore influencing the reaction path, and bringing greater effects on the characteristics. It is worth mentioning that, with film inlet height increases under a constant film equivalence ratio, combustion brings more benefits for both thermal protection and drag reduction characteristics based on the traditional film. Moreover, mainstream Mach number increasing or total temperature decreasing can even inhibit the exothermic reactions, which only brings beneficial effects on thermal protection characteristics, however, barely has effects on drag reduction characteristics.

The Shuffled Complex Evolution—University of Arizona (SCE-UA) is a classical algorithm in the field of hydrology and water resources, but it cannot solve constrained optimization problems directly. Using penalty functions has been the preferred method to handle constraints, but the appropriate selection of penalty parameters and penalty functions can be challenging. To enhance the universality of the SCE-UA, we propose the Constrained Shuffled Complex Evolution Algorithm (CSCE) to conveniently and effectively solve inequality-constrained optimization problems. Its performance is compared with the SCE-UA using the adaptive penalty function (SCEA) on 14 test problems with inequality constraints. It is further compared with seven other algorithms on two test problems with low success rates. To demonstrate its effect in hydrologic model calibration, the CSCE is applied to the parameter optimization of the Xinanjiang (XAJ) model under synthetic data and observed data. The results indicate that the CSCE is more advantageous than the SCEA in terms of the success rate, stability, feasible rate, and convergence speed. It can guarantee the feasibility of the solution and avoid the problem of deep soil tension water capacity (WDM)

For hydrocarbon-fueled turbojet engines with a precooling technology, the precooling technology with a low-temperature endothermic fuel is a great potential way to solve the problem of sharp reduction of the specific impulse caused by the insufficient heat sink of the hydrocarbon fuel. To study the heat transfer and flow characteristics of a precooler with a fuel endothermic reaction, methanol is chosen as the low-temperature endothermic fuel, and the numerical model of a precooler of tube bank arranged in-line is built, which considers the methanol with a cracking reaction. The results indicate that the methanol cracking reaction can enhance the cooling effect to the air by increasing the heat transfer temperature difference. When the cracking rate is not more than 20%, the cooling effect to the air increases and the cracking rate decreases with the methanol mass flow rate. When the longitudinal pitch-to-diameter ratio varies between 1.25 and 2.50, the cooling effect and the cracking rate increase with its increase, which is not conducive to the compactness of the precooler. When the transverse pitch-to-diameter ratio varies between 1.25 and 2.00, the cooling effect and cracking rate increase with its decrease but bring significant pressure loss.

Adequate understanding of the combustion and heat transfer characteristics are considered key points for the development of methane engines. In this paper, a methane combustion chamber with 7-elements is simulated under RANS frame with EDC combustion model, and the focus is paid to the influence of injector geometric parameters on combustion and heat transfer processes. The pertinent geometric parameters include the injector-wall distance, the diameter of injectors, the GOX post wall thickness, and the GOX post recess length. The results show that the combustion and wall heat transfer characters are dominated by two types of composite vortex structures in the chamber. The distance between the injectors and the recess length can modify both the intensity and form of the composite vortex structures, leading to a significant change in the combustion and heat transfer process in the chamber. While the thickness of the post wall thickness has little influence on the vortex structure, therefore, the impacts on the combustion and the heat transfer process are also negligible. The diameter of injectors can change the flame anchoring state by increasing the velocity of the propellants, and the case with lifted flame leads to a rather severe thermal environment.

The quantity and quality of water resources are of vital importance to the sustainable development of the social economy. Accordingly, research on the water resources carrying capacity (WRCC) has received wide attention from scholars. The WRCC system comprises multiple complex and nonlinear interactions related to society, economy, water resources and the water environment. A full understanding of its internal mechanism is conducive to the further improvement of the regional WRCC. In this study, the system dynamics (SD) model is applied to establish the dynamic feedback system of the WRCC. The quantitative and qualitative evaluation of WRCC is conducted by coupling the analytic hierarchy process (AHP), entropy weight method and multiobjective linear weighting function. Furthermore, the coupling coordination degree model is introduced to rate the coordination of the WRCC system. Five typical scenarios designed for distinct purposes are simulated by the constructed SD model in Guangzhou from 2021 to 2030. The results indicate that the rapid economic development scenario performs worst in terms of WRCC (0.39 in 2030) and coupling coordination degree (0.28 in 2030), the water environment protection scenario and water conservation scenario are considerably effective for improving WRCC and promoting its coordinated development, and the comprehensive scenario performs best in both aspects. Pearson correlation analysis shows that there is a strong positive correlation between WRCC and coupling coordination degree, with a correlation coefficient of 0.91. Thus, to further enhance WRCC, we must attach great importance to regional coordinated development. In view of the problems existing in Guangzhou, several feasible suggestions are put forward for improving water use efficiency, reducing pollutant emissions and developing high-tech industries. This research can provide a scientific reference for promoting regional sustainable development.

In order to rapidly predict the performance of hydrocarbon-fueled regeneratively cooled scramjet engine in system design, a quasi-one-dimensional model has been developed. The model consists of a supersonic combustor model with finite-rate chemistry and a cooling channel model with real gas working medium, which are governed by two sets of ordinary differential equations separately. Additional models for wall friction, heat transfer, sonic fuel injection, and mixing efficiency are also included. The two sets of ordinary differential equations are coupled and iteratively solved. The SUNDIALS code is used since the equations for supersonic combustion flow are stiff mathematically. The cooling channel model was verified by electric heating tube tests, and the supersonic combustor model was verified by experimental results for both hydrogen and hydrocarbon-fueled scramjet combustors. Three cases were comparatively studied: (1) scramjet combustor with an isothermal wall, (2) scramjet combustor with an adiabatic wall, and (3) scramjet combustor with regenerative cooling. Results showed that the model could predict the axial distributions of flow parameters in the supersonic combustor and cooling channel. Differences on ignition delay time and combustion efficiency for the three cases were observed.

Rapid economic development and continuous population expansion have placed increasing pressure on the regional water environment. Maintaining a good water environment is the foundation for the sustainable development of human society. Therefore, an overall understanding of the regional water environment carrying capacity (WECC) is of great significance to promote regional sustainable development. In this study, a novel integrated model framework is proposed to comprehensively evaluate and predict the WECCs of 9 cities in the Guangdong-Hong Kong-Macao Greater Bay Area by coupling the entropy weight method, multi-objective linear weighting function, cloud model and Markov chain. Furthermore, an obstacle degree model is used to explore the major factors affecting the WECC in the study area. The results indicate that the WECCs of 9 cities from 2013 to 2018 show an overall improving trend, and the highest average WECC appears in Shenzhen (0.59) with a good state, while those of the other eight cities are in a medium state. From 2021 to 2030, it is predicted that the WECCs of the 9 cities will present gradual and specific changes, with the WECC of Shenzhen developing from a good to an excellent state, the WECCs of Guangzhou, Zhuhai, Huizhou, Dongguan and Jiangmen developing from medium to good, and the WECCs of Foshan, Zhongshan and Zhaoqing maintaining medium states for a long time. The main factors obstructing the WECC in the Greater Bay Area are water resources per capita, ecological water use rate, wastewater discharge per million yuan GDP and proportion of the tertiary industry, which should give priority in future development. This framework may contribute significantly to providing an effective scientific reference for regional water environmental planning and management.

This paper proposes a new laser parameter measuring method based on cone-arranged fibers to further improve the measurable spot size, allowable incident angle range, and spatial sampling resolution. This method takes a conical array composed of flexible fibers to sample and shrink the cross-section spot of the laser beam, facilitating low-distortion shooting with a charge-coupled diode (CCD) camera, and adopts homogenized processing and algorithm analysis to correct the spot. This method is experimentally proven to achieve high-accuracy measurements with a decimeter-level spot-receiving surface, millimeter-level resolution, and high tolerance in order to incite skew angle. Comparing the measured spot under normal incidence with the real one, the root mean square error (RMSE) of their power in the bucket (PIB) curves is less than 1%. When the incident angle change is between −8° and 8°, the RMSE is less than 2% and the measurement error of total power is less than 5% based on the premise that the fiber’s numerical aperture (NA) is 0.22. The possibility of further optimizing the measurement method by changing the fiber parameters and array design is also reported.

Microcystis-dominated blooms cause environmental and ecological impacts worldwide. However, it is sometimes challenging to correctly identify Microcystis and its related genera. Radiocystis fernandoi Komárek et Komáková-Legnerová 1993, characterized by large cells and correspondingly large colonies with gas vesicles, has been frequently found in cyanobacterial blooms in Brazil. However, its molecular and phylogenetic identity is unknown because no valuable DNA sequences are available in GenBank. In this study, a strain with R. fernandoi morphology was successfully isolated from a cyanobacterial bloom sample in Lake Erhai, a subtropical plateau lake in China. Molecular characterization and phylogenetic analyses based on 16S rRNA and cpcBA genes revealed that the strain is different from the type species of the genus Radiocystis but formed a well-supported clade with the Microcystis species. The comparative results of the ITS region between 16S–23S rRNA genes also showed that the strain had very similar secondary structures to the species of Microcystis, supporting it as a new member of the genus Microcystis. Therefore, we propose the transfer of Radiocystis fernandoi into Microcystis fernandoi comb. nov. The correct identification and further taxonomic procedure for the bloom-forming cyanobacterial genera, such as Microcystis, Radiocystis, and Sphaerocavum, are also discussed in this study.

A compact air-breathing jet hybrid-electric engine coupled with solid oxide fuel cells (SOFC) is proposed to develop the propulsion system with high power-weight ratios and specific thrust. The heat exchanger for preheating air is integrated with nozzles. Therefore, the exhaust in the nozzle expands during the heat exchange with compressed air. The nozzle inlet temperature is obviously improved. SOFCs can directly utilize the fuel of liquid natural gas after being heated. The performance parameters of the engine are acquired according to the built thermodynamic and mass models. The main conclusions are as follows. 1) The specific thrust of the engine is improved by 20.25% compared with that of the traditional jet engine. As pressure ratios rise, the specific thrust increases up to 1.7 kN/(kg·s−1). Meanwhile, the nozzle inlet temperature decreases. However, the temperature increases for the traditional combustion engine. 2) The power-weight ratio of the engine is superior to that of internal combustion engines and inferior to that of turbine engines when the power density of SOFC would be assumed to be that predicted for 2030. 3) The total pressure recovery coefficients of SOFCs, combustors, and preheaters have an obvious influence on the specific thrust of the engine, and the power-weight ratio of the engine is strongly affected by the power density of SOFCs.

In order to extend the cooling capacity of thermal protection in various advanced propulsion systems, dimple as an effective heat transfer enhancement device with low-pressure loss has been proposed in regenerative cooling channels of a scramjet. In this paper, numerical simulation is conducted to investigate the effect of the dimple depth-diameter ratio on the flow and heat transfer characteristics of supercritical hydrocarbon fuel inside the cooling channel. The thermal performance factor is adopted to evaluate the local synthetically heat transfer. The results show that increasing the dimple depth-diameter ratio h/dp can significantly reduce wall temperature and enhance the heat transfer inside the cooling channel but simultaneously increase pressure loss. The reason is that when h/dp is rising, the recirculation zones inside dimples would be enlarged and the reattachment point is moving downstream, which enlarge both the high Nu area at rear edge of dimple and the low Nu area in dimple front. In addition, when fluid temperature is nearer the fluid pseudocritical temperature, local acceleration caused by dramatic fluid property change would reduce the increment of heat transfer and also reduce pressure loss. In this study, the optimal depth-diameter ratio of dimple in regenerative cooling channel of hydrocarbon fueled is 0.2.

(1) Background: Cortisol and melatonin (MT) act in regulating follicular development. We hypothesized that abnormal levels of cortisol, MT, and steroids in theca interna cells might be involved in the development of follicular cysts in sows. (2) Methods: To test this hypothesis, we measured the mRNA levels of enzymes involved in steroid hormone synthesis, the glucocorticoid receptor (GR), and melatonin receptors (MTRs) in theca interna cells of cystic and normal porcine follicles. (3) Results: The concentrations of estradiol, progesterone, and cortisol were greater in cystic follicles than in control ones (p = 0.034, p = 0.020, p = 0.000), but the concentration of MT was significantly lower (p = 0.045). The levels of GR, 11β-HSD1, and 11β-HSD2 were higher in cystic follicles than in control l follicles. MT types 1 and 2 were significantly lower in cystic follicles (p < 0.05). The mRNA expression levels of genes encoding the steroid hormone synthesis enzymes, steroidogenic acute regulatory protein (StAR), recombinant cytochrome P45011A1 (CYP11A1), and 3β-hydroxysteroid dehydrogenase (3β-HSD) in theca interna cells of cystic follicles were significantly higher than in control follicles. Thus, there was disruption of hormone secretion in the fluid of cystic follicles in sows. (4) Conclusions: The levels of steroid hormones, cortisol and MT are disrupted in porcine cystic follicles.

Supersonic film cooling is an efficient method to cool the engine with extremely high heat load. In order to study supersonic film cooling in a real advanced engine, a two-dimensional model of the hypersonic inlet in a scramjet engine with supersonic film cooling in the isolator is built and validated through experimental data. The simulation results show that the cooling effect under different coolant injection angles does not show clear differences; a small injection angle can ensure both the cooling effect and good aerodynamic performances (e.g., flow coefficient) of the hypersonic inlet. Under selected coolant injection angle and inlet Mach number, the cooling efficiency increases along with the injection Mach number of the coolant flow, only causing a little total pressure loss in the isolator. Along with the increase of the inlet Mach number of the hypersonic inlet, the cooling efficiency does not present a monotonic change because of the complex shock waves. However, the wall temperature shows a monotonic increase when the inlet Mach number increases. The mass flow rate of coolant flow should be increased to cool the engine more efficiently according to the mass flow rate of the main stream when the inlet Mach number increases.