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In this paper, the combustion characteristics of kerosene-fueled supersonic combustor under the conditions of Mach number 2.0, the total temperature at 700 K and the total pressure at 520 kPa (simulated flight Mach number at 3.5) were studied by using the flame stabilizing method of cavity and strut from three aspects such as blockage ratios, kerosene equivalence ratios, location and quantity of injection holes. The results showed that: (A) The combustor with the strut realized the independent and stable combustion of kerosene. The combustion-induced back pressure in the block test with blockage ratio of 20% and 10% destroyed the inlet flow conditions; while the blockage ratio was 7.3% and 5%, the incoming flow conditions when kerosene was burned stably were not destroyed. (B) The kerosene Equivalence Ratio (ER) was more likely to be disturbed upstream than the induced back pressure when it rose, and an excessively high-ER would reduce the combustion efficiency; when the equivalence ratio was constant, the combustion efficiency of the blockage ratio of 7.3% was higher than the blockage ratio of 5%. The combustion efficiencies were 0.86 (ER = 0.13) and 0.78 (ER = 0.19) when the blockage ratio was 5%, respectively; the combustion efficiencies were 0.89 (ER = 0.16) and 0.82 (ER = 0.19) when the blockage ratio was 7.3%, respectively; the combustion efficiencies were 0.51 (ER = 0.25), 0.81 (ER = 0.3), 0.65 (ER = 0.34) and 0.62 (ER = 0.42) when the blockage ratio was 20%, respectively. (C) The porous injection provided behind the strut was beneficial to the atomization of kerosene and improved the combustion efficiency of kerosene; the second injection after the cavity would reduce the combustion efficiency due to insufficient oxygen and combustion space. This study expanded the working range of ramjet and provided a reference fuel injection scheme for Turbine-Based Combined Cycle (TBCC) engine.

Fusarium Head Blight (FHB) of wheat and small grain cereals caused by Fusarium graminearum and other Fusarium species is an economically cereal disease worldwide. Fusarium infections results in reduced yields and mycotoxin contamination of the grain, and the research on the toxin production and growth control of Fusarium is the key to prevent and control of mycotoxin contamination in wheat. In this study, the molecular identification of toxigenic potential and gas fumigation control of typical Fusarium strains isolated from FHB-infected wheat were studied. The results showed that the consequences of molecular identification of toxigenic potential were consistent with the actual production of toxins, which can be used for rapid identification of fungal toxicity. And the effects of the gas fumigants were different. Chlorine dioxide could kill Fusarium spores and mycelium in a short time (0.5 h) at relatively low concentration (300 ppm), while ozone could only kill Fusarium spores and had no obvious inhibitory effect on the growth of mycelium, even at a concentration of 1400 ppm. Taken together, gaseous ClO2 could significantly inhibit the growth of Fusarium, and it’s an ideal fumigant used to control this fungal contamination during the postharvest storage of grain.

Daihai Lake (DL), the third largest inland lake in Inner Mongolia, has shrunk severely given the conditions of no significant decrease in annual precipitation. On the basis of field surveys and Landsat remote sensing images, this study analyzed land use and land cover (LULC) changes in six periods of the DL watershed area during 1986–2019. Then, with the combination of the LULC results and the Soil Conservation Service–Curve Number method, we discussed the change characteristics and influence factors of the surface runoff in the watershed and the reason for DL shrinkage. From 1986 to 2019, the water area of DL decreased rapidly at a rate of −2.22 km2/year, and the area of farmland and grassland in the watershed changed strongly along the opposite trend. The surface runoff in the DL watershed was reduced by approximately 513.6 million m3 during the last 34 years. In addition to local rainfall, groundwater is also an important water supply to the lake and accounts for a greater proportion. The average recharge rate of groundwater to the lake is approximately 64.55 million m3 per year in the past 34 years. The area change of the DL is related to the runoff reduction, huge evaporation, and lake water use in thermoelectric power generation. The local precipitation cannot enter the groundwater in DLW. Large-scale exploitation of external groundwater for agricultural irrigation and industrial production is another important cause of lake degradation.

Firstly, a one-dimensional steady-state calculation model of the scramjet including forebody/inlet, combustor and nozzle/afterbody has been established. Secondly, based on the one-dimensional stead...

Groundwater is a major source of water supply in China. However, groundwater levels have declined in many regions of China due to groundwater over-extraction, leading to adverse impacts on the eco-environment in China. It is urgent to formulate policy for sustainable groundwater management. In this study, we described and discussed the role of scientific research in China when creating a policy of double-control groundwater management. We used examples of three regions with the groundwater over-extraction problem, i.e., the Sanjiang Plain of northeast China, North China Plain, and the Xilin River Basin of northwest China, to demonstrate the support of scientific research in developing the policy. In addition, it was found that that the interactions between science and policy need to be further improved for the management of groundwater in China. Therefore, we developed a control-loop theory to enhance the interactions between science and policy in China.

Understanding the adaptative behaviors of dominant desert-steppe species under varying levels of grazing-related environmental degradation is an important step in elucidating the survival strategies and environmental response mechanisms of desert plants. In this study, the Xilamuren desert steppe in Northwest China was used as a case study location to systematically investigate the adaptative traits of three dominant plant species (Stipa breviflora, Cleistogenes squarrosa, and Convolvulus ammannii) from the perspectives of plant morphology, leaf structure, and photosynthesis. As degradation intensified, the adaptive changes in the three dominant plant species manifested in the following ways: 1) adjustment of substance allocation strategy, such that biomass was preferentially concentrated in the leaves and roots for photosynthesis and resource acquisition; 2) miniaturization, including reduced plant height, reduced leaf size, and leaf narrowing; 3) thickening of the leaves, epidermis, and cuticle to increase water storage and resist illumination and temperature elevation and thickening of the midrib veins to increase water and nutrient transportation; and 4) increased water-use efficiency in Stipa breviflora, which showed a stronger capacity to adjust to water stress than Cleistogenes squarrosa and Convolvulus ammannii. The results suggested that the morphological, structural, and functional adjustments of desert plants were related to the development of drought-resistance mechanisms through water-use strategies, including increased water absorption and water-use efficiency and decreased water consumption. These results enrich the existing knowledge of the environmental adaptation mechanisms of dominant plants in desert steppes, providing a scientific basis for the restoration of desert steppe ecologies and the formulation of suitable grazing policies.

Previous studies indicate that vegetation and lakes in arid and semi-arid regions are closely related to climate change. However, the responses of vegetation and lakes to climate-related variables have rarely been contrastively studied. The Hulun Lake (HLL) and its surrounding grasslands in Northeast Inner Mongolia of China comprise a semi-arid region that has experienced intense climate change over the last several decades. This study aims to understand the key factors that control the variations in the lake area and vegetation cover over the last five decades in the HLL region, as well as contrastively investigate the different responses of the lake area and vegetation cover to climate-related variables. Analysis results indicate that the variations with increasing change rates in the HLL area were mainly controlled by precipitation fluctuation. Moreover, an increase or decrease in the air temperature and relative humidity could affect the response time of the HLL area to the change in precipitation. The Normalized Difference Vegetation Index (NDVI) variations from 1990 to 1999 around the HLL region were mainly controlled by the intense local grazing rather than climatic restrictions. The fluctuation in NDVI after 1999 reflects the response of the vegetation cover to climatic change. The correlation analysis shows that the variations in the HLL area were closely related to the multi-year tendency of precipitation amount and to the Standardized Precipitation Evapotranspiration Index (SPEI) with a long timescale. However, NDVI is sensitive to changes in short-term precipitation amount, such as seasonal precipitation, and in SPEI with a monthly timescale. The soil moisture at shallow depths (

The steppe located in the middle Inner Mongolia Plateau (IMP) has scarce water resources and fragile ecosystems and has an arid-semiarid monsoon characterized by low and uneven seasonal precipitation and high evaporation. Until now, problems relating to the hydrologic processes in the area remain poorly understood, and thus strategies for the exploitation and utilization of the area’s local water resource remain limited. This study aimed to investigate the recharge and discharge processes of soil water and the source and circulation of groundwater through geochemical methods. The local meteoric water line (LMWI) of our study area in the middle IMP was first proposed and compared with the local meteoric water line of Baotou in Inner Mongolia and Ulan Bator. The δ18O and δD values of precipitation showed an increasing trend from June to August and decreasing trend from August to late October. The H and O isotopes of soil water varied with time, location, and soil profile depth. Besides the geographical and climatic factors, the Cl concentrations of soil water can be affected remarkably by land use type and land cover change. In our monitoring period, variations in the Cl concentrations and δ18O and δD values of shallow soil water indicated that the evaporation of soil water was in the sequence August > June > October. Furthermore, the detailed evaporation proportions of soil water were estimated. The isotope compositions of groundwater plotted on the LMWI and there could be a rapid recharge mechanism of the groundwater.

This paper simulated the flying conditions of flight Mach number 2.6 ~ 3.8. Under the inflow state of the total temperature of 507 K ~ 820 K, the ignition test under low total temperature was carried out on the supersonic combustor by using the hydrogen-guided flame ignition method. When the total temperature was 820 K (simulated flight Ma = 3.8), the kerosene sprayed by the non-strut spray block could achieve a single stable combustion after removing the Pioneer hydrogen, and the fuel rich limit of the combustor was 0.4. When the total temperature was 700 K (simulated flight Ma = 3.4), when the non-strut spray block was used, the kerosene after removing Pioneer hydrogen could not be burned stably alone. In the test with blocking ratios of 20% and 10%, kerosene could be burned steadily alone, but the combustion-induced back pressure propagated upstream to the entrance of the isolator, destroying the inlet flow conditions. When the spray block with blocking ratio of 7.3% and 5% was used for the test, kerosene could be burned stably alone, and the incoming flow conditions were not destroyed. At a total temperature of 600 K (simulated flight Ma = 3.0) and 507 K (simulated flight Ma = 2.6), hydrogen and kerosene with a blocking ratio of 7.3% were used to achieve stable combustion, but the combustion-induced back pressure severely damaged the inlet flow conditions of the combustor. After the Pioneer hydrogen was removed, kerosene at both total temperature conditions could not be burned steadily. This study extended the lower limit of the working Mach number of the ramjet engine, and provided a reference flame stabilization method and fuel injection scheme for the kerosene combustion of the supersonic combustor, and provided some design suggestions for the low-Mach-Number combustor.

Multihop underwater acoustic local area networks (MUA-LANs), which can greatly improve the access ability of underwater networks, suffer from the lack of network access mechanism utilized by new nodes to join the networks. Existing network access mechanisms for terrestrial wireless LANs cannot be directly applied to MUA-LANs due to the multihop topologies of MUA-LANs and the acoustic channel features of limited bandwidth and high propagation delay. In this paper, we present a network access mechanism constituted by three phases of network discovery, relay path determining, and association for MUA-LANs. The basic idea of our network access mechanism is to let the nodes that have joined a network assist new nodes in accessing the network by multihop relay forwarding. We theoretically verify that the unbalanced energy consumption is serious in MUA-LANs. Therefore, we present a lifetime and energy efficiency-based relay path selection algorithm in relay path determining phase. This algorithm can significantly prolong the network lifetime and improve energy efficiency. In association phase, we employ a MAC address forwarding tables mechanism. By utilizing this mechanism, multihop relay forwarding can be realized easily. The simulation results have confirmed that the proposed network access mechanism can achieve excellent performance owing to the lifetime and energy efficiency-based relay path selection algorithm and the MAC address forwarding tables mechanism.

The Ignition combustion experiment in a supersonic combustor was carried out under the conditions with the incoming flow Ma = 2.0, the total temperature at 700 K and the total pressure at 520 KPa(corresponding to the flight Mach number at 3.5). Spray blocks without struts and with struts (with the blockage ratios as 20%, 10%, 7.3% and 5% respectively) were used in the supersonic combustor. The experimental result showed that when there was no strut in the combustor, kerosene could be ignited but was unable to burn stably alone after hydrogen was removed. The addition of struts achieved the independent and stable combustion of kerosene. However, due to the addition of struts, the combustion during the strut test using the blockage ratios at 20%, 10% and 7.3% induced the back pressure to be spread towards the upstream to the entrance of the isolator; When the blockage ratio of the strut was 5%, kerosene could burn stably alone, and the back pressure induced by combustion failed to be spread to the entrance of the combustor. In this paper, the stable flame mode using the cavity and struts was used to achieve stable ignition under the condition with Ma = 2.0, total temperature at 700 K and total pressure at 520 KPa.

The mode transition experiments in a dual-mode combustor were carried out under the conditions of total pressure 1.05 MPa, Mach number 2.0 and total temperature 1285 K, 1085 K and 885 K. The processes of mode transition of the combustor under different total temperature conditions were studied. The connection between the fuel equivalence ratio, the ratio of the peak pressure of the combustor to the inlet total pressure of the isolator, and different combustion modes was analyzed. The study showed that the lower the total temperature of the incoming flow and the higher the fuel equivalence ratio, the higher the dimensionless wall pressure, the more easily the shock train to disturb the upstream of the isolator, the more backward position of the choked thermal throat, and the closer the combustion tended to the ramjet mode; The results showed that there were pure scramjet mode, dual-mode scramjet mode, dual-mode ramjet mode and the combustion state caused the pressure disturbance that spread to the entrance of the isolator with the increase of the fuel equivalence ratio. The dimensionless peak pressures when mode transition occurred were 0.25, 0.40 and 0.5, and did not change with the change of the total temperature.

Multihop underwater acoustic sensor networks (UASNs) suffer from low throughput caused by low channel utilization and unreasonable bandwidth allocation. The existing media access control (MAC) protocols for UASNs mainly aim to improve channel utilization but neglect to optimize bandwidth, so that they cannot achieve high throughput in miltihop networks. We propose the idea of joint bandwidth optimization and MAC in this paper. We first present a system model to optimize bandwidth for miltihop UASNs. Both the complicated interference relations between links and the different transmission demands of nodes are modeled. Thus, it can accurately reflect the characteristics of miltihop UASNs. By analyzing a 1-D linear miltihop network, we find and formulate a maximum hop number which is determined by nodes’ traffic load and channel capacity. The other finding is that an optimal scheduling needs to allocate the bandwidth based on traffic load, and the nodes with more traffic load should be allocated more bandwidth. This finding inspire us to develop a distributed traffic-based scheduling MAC protocol. This protocol can optimize bandwidth allocation by letting the older packet to be transmitted preferentially. To improve channel utilization, multiple packets are allowed to be transmitted in each data transmission round. Simulation results have confirmed that our protocol can achieve excellent performance owing to its core idea of joint bandwidth optimization and MAC.

Determining vegetation variation and its influential factors in a desert steppe under the impacts of climate change and human activities is crucial and meaningful for improving the understanding of desertification and taking targeted measures in ecological restoration. As compared to a large spatial scale such as a region or a whole catchment, which are more common in published studies, a micro perspective at the pixel level is provided in this study to investigate the vegetation fractional coverage dynamics and build the correlations between vegetation fractional coverage and its multiple influential factors, including precipitation, temperature, soil water, groundwater and human activities in a desert steppe region in the Inner Mongolia Autonomous Region, China. The average vegetation fractional coverage in August for the years 2000–2011 is 0.38 in the study area. The interaction of rain (R = 0.80) and heat (R = −0.76) significantly determines the growth and distribution of the vegetation in the study area. Besides, the effects of some other factors on vegetation fractional coverage should not be neglected, including groundwater (R = 0.04), available water content of soil (R = 0.23) and livestock density (R = 0.28). From the perspective of centre dynamics for the years 2000–2011, the annual precipitation centre has better synchronism with the vegetation centre, while the movement of the temperature centre is more stable.