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The air blow-out method of extracting bromine from seawater or brine is widely used at home and abroad. The key parameter in this unit operation is the vapor-liquid equilibrium data (T, x, y) for brominebrine system, which were obtained with the Bubble Equilibrium equipment at 10 and 20℃ in this paper. The experimental equilibrium data were carried out by using Margules Equation for liquid phase and ideal equation for gas phase, and the nonlinear least square method was used to regress the parameters of Margules model for the system. It showed good consistency for the calculated data from Margules model and the experimental data.

Bromine has a strong resource dependence. With the sharp decline of the total amount and grade of traditional brine resources, the difficulty of mining is increasing day by day, and the shortage of bromine supply and demand has become a normal situation. Therefore, it is urgent to find new sources of bromine resources and develop corresponding extraction technologies. Bromine-containing waste salt is a new source of bromine. The mature technology achievements of bromine extraction in underground brine, concentrated seawater and other water are transferred to the field of bromine extraction from bromine-containing waste salt, which realizes the closed-loop recycling of resources and extends the industrial chain, and has a good application prospect.

The initial distribution of gas and liquid is one of the key factors that determine the operation efficiency of packed towers. The development of a gas distributor for ultra-large air blow-out bromine extraction plant can improve operation efficiency, save energy and reduce consumption. In order to develop the gas distributor for ultra-large air blow-out bromine extraction plant, the guidelines for evaluating gas distributors are clarified in this paper, and six kinds of commonly gas distributor are compared in detail. Considering gas distribution inhomogeneity, liquid foam entrainment rates and distributor pressure drop, the double tangential circulation type gas distributor is the first choice in the ultra-large air blow-out method bromine extraction plant.

In this paper, the existence and nonexistence of energy minimizer of the Kirchhoff–Schrodinger energy function with prescribed L 2 -norm in dimension four are considered. The energy infimum values are completely classified in terms of coefficient and exponent of the nonlinearity. The sharp existence results of global constraint minimizers for both the subcritical and critical exponent cases are obtained, and the criticality is in the sense of both Sobolev embedding and Gagliardo–Nirenberg inequality. Our results also show the delicate difference between the case without a trapping potential function and the one with potential function.

Information about evapotranspiration (ET) is essential for managing water resources, especially in areas with limited water and no irrigation facilities. In this study, based on ET observations made using an eddy covariance system, the variation of ET and its control factors are investigated on monthly and annual scales in the context of China’s Loess Plateau. Monthly ET is determined by the reference ET (ET0) and surface conductance (gs), where ET0 is an indicator of both the energy available for ET and the atmospheric demand for evaporation and gs represents the environmental stress that limits ET. The correlations among volumetric soil water content (SWC), leaf area index (LAI), and monthly ET are weak across all the studied ecosystems. ET shows large inter-annual variability in the Loess Plateau, with a coefficient of inter-annual variation of 19.5%. The environmental variables of ET0, precipitation (P), SWC, LAI, and gs also show notable inter-annual variability. P is the original factor forcing the inter-annual variability of ET. LAI and gs are important for regulating ET and reduce the correlation between ET and SWC. Different ecosystems use different biological processes to regulate ET under conditions of water stress: for natural vegetation, gs responds directly to SWC and surface air vapor pressure (e) and controls ET by regulating transpiration; for cropland, LAI responds directly to SWC and e and determines gs, thereby regulating ET. The present results suggest that LAI is useful for characterizing the physiological constraints on cropland ET but is not suitable for estimating the ET of semi-arid natural vegetation. Parameterizing gs with e could give better estimates of ET for natural vegetation.

Global surface evapotranspiration is one of the most significant components of the response of the water cycle to a warming climate. However, trends in surface evapotranspiration differ considerably from the trend in climate warming according to recent studies, with some studies even showing an opposing trend. The reason for this difference in the response of surface evapotranspiration to climate warming is still not completely understood. We validated the gridded FLUXNET evapotranspiration dataset and the Global Land Surface Assimilation Dataset (GLDAS) against evapotranspiration data observed in northern China using the eddy covariance system. The response of surface evapotranspiration to an increase in temperature varied with the type of climate (classified by the amount of precipitation) and the trend of surface evapotranspiration with warming showed similar features to the transitions between these climate types. The climate type with precipitation in the range of 250–350 mm was the most sensitive to the effects of warming on evapotranspiration. In more humid climates, surface evapotranspiration increased with increasing temperature, whereas in drier climates surface evapotranspiration decreased with increasing temperature. A similar response of evapotranspiration to increasing temperatures was also observed elsewhere in regions of climate transition. There are two main mechanisms of evapotranspiration: (1) an increase in temperature resulting in a direct increase in potential evapotranspiration; and (2) an increase in temperature resulting in a loss of soil moisture due to the increase in evapotranspiration, which in turn will indirectly suppress surface evapotranspiration due to the loss of vegetation.

Energy partitioning between grassland sensible (H) and latent (LE) heat fluxes is critical in determining boundary layer development, the hydrological cycle, weather and climate. In this report, we describe the seasonal and inter-annual variability of the Bowen ratio (β) over semi-arid grassland of the Loess Plateau in the north boundary belt of the summer monsoon of China. β was directly measured by an eddy covariance system over a 6-year period (2007–2012), during which the studied grassland experienced a large range in precipitation, extending from 555.5 mm (2007) to 262.8 mm (2011). The annual Bowen ratio (βa) based on annual energy budgets ranged from 0.90 (2007) to 1.93 (2011) with an annual mean value of 1.32, while the annual midday (10:00–16:00 GMT + 8) β ranged from 2.07 (2007) to 4.19 (2011) with an annual mean value of 3.02. The mean midday β during the dry years (3.66, 2009, 2010 and 2011) was higher than that observed during the wet years (2.39, 2007, 2008 and 2012). The 6-year annual mean values of the bulk surface resistance (Rs), aerodynamic resistance (Ra) and climatological resistance (Ri) varied from 272.27 to 410.10 s m−1, 31.62–34.89 s m−1 and from 64.5 to 87.13 s m−1, respectively, with annual mean values of 337.08, 32.83 and 73.05 s m−1, respectively. The normalized difference vegetable index (NDVI) had a direct influence on β as mediated by Rs, and there was a logarithmic function between ET/ETeq and Rs in the semi-arid grassland. A positive trend between β and the surface resistance (Rs*) normalized by the climatological and aerodynamic resistance was observed at this site. Moreover, the annual effective precipitation frequency was significantly related to the midday β during the growing and non-growing seasons, which indicated that the annual effective precipitation, not the annual precipitation, indirectly affected the annual β through its effect on the shallow soil water content (SWC). The results suggested that inter-annual variations in β was primarily controlled by an annual effective precipitation frequency and seasonal variations in β was directly affected by NDVI as mediated by Rs over the semi-arid grassland in the Chinese Loess Plateau.

Global surface evapotranspiration is one of the most significant components of the response of the water cycle to a warming climate. However, trends in surface evapotranspiration have varied widely from the trend in climate warming according to recent studies, and some studies have even shown an opposing trend. The reason for this difference in the response of surface evapotranspiration to climate warming is still not completely understood. We validated the gridded FLUXNET evapotranspiration dataset and the Global Land Data Assimilation System (GLDAS) against evapotranspiration data observed in Northern China by eddy covariance systems. The response of evapotranspiration to increases in temperature varies with climate type in Northern China and there is a correlation with the amount of precipitation. Climate types with a mean annual precipitation of 200–400 mm (P250 and P350) are a sensitive interval in which the climatological trend of evapotranspiration changes from negative to positive and the response of evapotranspiration to an increase in temperature is less obvious. In more humid climates, evapotranspiration increases with increasing temperature, whereas in drier climates evapotranspiration decreases with increasing temperature. Similar transition zones for surface evapotranspiration are also seen in other regions. This is a new understanding of global changes in surface evapotranspiration and can explain the different trends in the response of surface evapotranspiration to temperature reported previously. Although the methods and data used are different from these earlier studies, the differences between precipitation-based climate types are clearer. These transition zones can be explained by the different mechanisms for the effect of temperature on evapotranspiration. Temperature directly affects the potential evapotranspiration and an increase in temperature will increase the potential evapotranspiration. However, this increase in evapotranspiration can result in a decrease in the soil moisture content, which will restrict the growth of vegetation, which in turn reduces surface evapotranspiration. In humid climates, where the soil moisture is high, the direct temperature effect is dominant and an increase in temperature will enhance surface evapotranspiration. In drier climates where the soils are deficient in water, reduced vegetation growth means that evapotranspiration is limited and an increase in temperature weakens surface evapotranspiration due to soil moisture stress. The prominent effect of the summer monsoon in Northern China results in a wide range of precipitation over a large spatial area and the climate transition zone is clearly defined. Thus, the effect on evapotranspiration of different climate types classified according to the amount of precipitation is significant in this area. This has deepened our understanding of the mechanisms influencing evapotranspiration in similar areas. In the areas where transition between climate types is obvious, the response of surface evapotranspiration to climate warming is complex and there is large spatial variation in the warming trend for evapotranspiration. Therefore, the variation in regional evapotranspiration cannot be determined by the variation in the point or local evapotranspiration. This will significantly affect the assessment of regional water resources and drought monitoring in these transitional areas. For such areas, the analysis of trends in evapotranspiration should be at a fine resolution to meet the technical needs for the assessment of water resources and drought monitoring. The factors influencing surface evapotranspiration are complex. In addition to temperature and precipitation, other factors such as wind speed, solar radiation and atmospheric humidity also affect surface evapotranspiration to varying degrees. The results of this study were affected by these factors, resulting in a certain degree of dispersion and bias in the results, which will in turn affect the objective quantitation analysis.

Land–atmosphere-coupling parameters usually relate to particular climatic conditions and seldom consider the influence of the inter-annual variability of precipitation. This results in large uncertainty in the estimation of land-surface physical variables. In the current study, observed data for five land–atmosphere-coupling parameters (surface albedo, soil thermal conductivity, aerodynamic roughness length, and the bulk transfer coefficients of momentum and sensible heat) were analysed and related to the inter-annual variability of precipitation on the Loess Plateau, China, from April 2006 to March 2013. This is an area with sparse vegetation. The results demonstrate that the land–atmosphere-coupling parameters are very sensitive to the inter-annual variability of precipitation. The surface albedo increased with increasing duration of snow cover. The other four parameters increased when annual effective precipitation (yearly sum of daily rainfall > 4 mm or daily snowfall > 0.1 mm) increased, and the sensitivity decreased when annual effective precipitation increased. Empirical relations between the five land–atmosphere-coupling parameters and the inter-annual variability of precipitation were derived via regression, with R2 values of 0.67, 0.85, 0.93, 0.99, and 0.95, respectively. The land-surface physical variables calculated with dynamic land–atmosphere-coupling parameters (considering the inter-annual variability of precipitation) were much closer to the observed data than those calculated with static land–atmosphere-coupling parameters. The relative error was reduced by > 80% in years with low precipitation. This indicates that the inter-annual variability of precipitation has a significant impact on the land-surface physical variables. The results demonstrate that land–atmosphere-coupling parameters, which take into account inter-annual variability of precipitation, provide a more realistic representation of the land surface.

Deep seawater is a high-quality resource with development potential. Therefore, deep processing of deep seawater can achieve greater economic benefits. In this paper, the deep seawater concentrate after membrane separation was used as the raw material, and the deep-sea refined salt was prepared by the solution crystallization technology. By controlling the process conditions, a deep-sea refined salt product that meets the requirements of the standard was prepared.

On the basis of information from the project “Land-surface Processes and their Experimental Study on the Chinese Loess Plateau”, we analyzed differences in land-surface water and heat processes during the main dry and wet periods of the semiarid grassland growing season in Yuzhong County, as well as the influences of these environmental factors. Studies have shown that there are significant differences in changes of land-surface temperature and humidity during dry and wet periods. Daily average normalized temperature has an overall vertical distribution of “forward tilting” and “backward tilting” during dry and wet periods, respectively. During the dry period, shallow soil above 20-cm depth is the active temperature layer. The heat transfer rate in soil is obviously different during dry and wet periods. During the dry period, the ratio of sensible heat flux to net radiation (H/Rn) and the value of latent heat flux to net radiation (LE/Rn) have a linear relationship with 5-cm soil temperature; during the wet period, these have a nonlinear relationship with 5-cm soil temperature, and soil temperature of 16°C is the critical temperature for changes in the land-surface water and heat exchange trend on a daily scale. During the dry period, H/Rn and LE/Rn have a linear relationship with soil water content. During the wet period, these have a nonlinear relationship with 5-cm soil water content, and 0.21 m3 m−3 is the critical point for changes in the land-surface water and heat exchange trend at daily scale. During the dry period, for vapor pressure deficit less than 0.7 kPa, H/Rn rises with increased vapor pressure deficit, whereas LE/Rn decreases with that increase. When that deficit is greater than 0.7 kPa, both H/Rn and LE/Rn tend to be constant. During the wet period, H/Rn increases with the vapor pressure deficit, whereas LE/Rn decreases. The above characteristics directly reflect the effect of differences in land-surface environmental factors during land-surface water and heat exchange processes, and indirectly reflect the influences of cloud precipitation processes on those processes.

In fact, in arid environment such as desert, dew plays an important role to some vegetation and ecosystem[1]. Dew can help the vegetation restore from excessive water loss state[2]. In addition, dew is an important water source for some microorganism[3], insects and small animals. In particular, the distribution of dew may influence on remotely sensed measurements[4] and remote sensing parameters such albedo[5-6]. It also effects bright temperature and the backward reflection at microwave band[7]. Therefore, remote sensing data processing is closely related to the dew variation and it is helpful to understand variation characteristics of dew to processing remote sensing data.

There have been few studies conducted on the changes in actual ET over the Loess Plateau, due to the lack of reliable ET data. Based on ET data simulated by the Community Land Model, the present study analyzed the changes in ET over the Loess Plateau. The results showed the domain-average ET to have decreased in the past 31 years, at a rate of 0.78 mm year−1. ET fluctuated much more strongly in the 1990s than in the 1980s and 2000s, and, apart from in autumn, ET decreased in all seasons. In particular, ET in summer comprised about half of the annual ET trend and had the sharpest trend, dominating the interannual decline. ET also decreased more sharply in the semiarid than semihumid regions. The declining trend of ET was attributed to declining precipitation and air humidity. Locally, the ET trend was closely related to local mean annual precipitation: in areas with precipitation less than 400 mm, ET showed a decreasing trend; in areas with precipitation larger than 600 mm, ET showed an increasing trend; and in areas with precipitation in the range of 400–600 mm could be classified as a transitional zone.

Evapotranspiration (ET) is a critical component in the hydrological cycle. However, its actual values appear to be difficult to obtain, especially in areas in which precipitation has high inter-annual variability. Here, we evaluated eight commonly used ET models in semi-arid and semi-humid areas of China. The order of overall performance from best to worst is as follows: the revised Priestley–Taylor model (PT-JPL, 0.71, 1.65 [18.37%], 4.72 [49.19%])a, the modified PT-JPL model (M1-PT-JPL, 0.67, −0.68 [7.56%], 3.87 [40.31%]), the Community Land Model (CLM, 0.68, −2.52 [28.01%], 5.10 [53.17%]), the modified PT-JPL model (M2-PT-JPL, 0.63, 0.57 [6.27%], 5.04 [52.52%]), the revised Penman–Monteith model (RS-PM, 0.62, 3.56 [37.40%], 6.11 [63.68%]), an empirical model (Wang, 0.59, −1.04 [11.57%], 5.61 [58.43%]), the advection-aridity model (AA, 0.55, 5.56 [61.78%], 7.45 [77.60%]), and the energy balance model (SEBS, 0.35, 5.11 [56.72%], 9.43 [98.18%]). The performance of all of the models is comparably poor in winter and summer, except for the PT-JPL model, and relatively good in spring and autumn. Because of the vegetation control on ET, the Wang, RS-PM, PT-JPL, M1-PT-JPL, and M2-PT-JPL models perform better for cropland, whereas the AA model, SEBS model and CLM perform better for grassland. The CLM, PT-JPL, and Wang models perform better in semi-arid region than in semi-humid region, whereas the opposite is true for SEBS and RS-PM. The AA, M1-PT-JPL, and M2-PT-JPL models perform similarly in semi-arid and semi-humid regions. When considering the inter-annual variability in precipitation, the Wang model has relatively good performance under only some annual precipitation conditions; the performance of the PT-JPL and AA models is reduced under conditions of high precipitation; the two modified PT-JPL models inherited the steady performance of the PT-JPL model and improved the performance under conditions of high annual precipitation by the modification of the soil moisture constraint. RS-PM is more appropriate for humid conditions. CLM and PT-JPL models could be effectively applied to all precipitation conditions because of their good performance across a wide annual precipitation range. Copyright © 2016 John Wiley & Sons, Ltd.