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Numerous interrelated factors (e.g., the labile C, soil NO3- concentration, and soil moisture content) are involved in controlling the microbial sources of N2O and the product stoichiometry of denitrification; however, the interactions among different factors are still poorly understood. Here, a fully robotized continuous flow soil incubation system (allowing simultaneous measurements of N-2 and N2O fluxes) was employed to investigate the interactive effects of a 51-day duration of moist spell, straw amendment, and the NO3- level on the rate and product stoichiometry (N2O/(N2O + N-2) ratio) of denitrification in heavily N loaded arable soils (i.e., paddy, vegetable, and orchard soils). The rewetting-induced N2O emissions mainly originated from bacterial denitrification in all soil types, with a clear shift to fungal denitrification (plus contingent nitrification) over time. The vegetable and orchard soils showed a higher share of bacterial N2O (62-70%) than that in the paddy soils (50-54%), which may be attributed to more labile-C driven bacterial activity induced by the greater manure and crop residue input therein. Interestingly, the inhibitory effect of high soil NO3- on N2O reduction in these soils was offset by a 51-day-long moist spell, regardless of the amendment of straw. To our knowledge, our study is the first to show that the inhibitory effect of high residual NO3- on N2O reduction is suppressed by a moist spell with a certain duration in heavily N loaded arable soils, suggesting that the water regime history should be considered when optimizing the N fertilizer application timing to mitigate soil N2O emissions.

In this study, the changing performance characteristics of a solid-fuel scramjet with a size-fixed aft channel for a long-duration operation were investigated using numerical methods. The results show that a solid-fuel scramjet with such a chamber configuration can continuously provide effective thrust over a long working period, followed by a long tail section of thrust. The effective working period lasts from the beginning of the operation to the moment when the bottom wall covered by the solid fuel is exposed to hot gas. The fluctuation in the thrust is significant due to the relatively large fluctuation in the equivalence ratio. The solid fuel utilization is relatively low; approximately 49% of the solid fuel remains after the effective working period. The configuration used in this study limits the mass flow rate passing through the front part of the cavity significantly, thereby forcing the core of the main recirculation zone to move downward rapidly, with undesirable effects on the equivalence ratio fluctuation and utilization of the front part of the solid fuel.

Burning rate modulation of solid fuel can improve the performance of solid fuel ramjet over a wider altitude or Mach number envelopes. To better control the burning rate of a solid fuel, the effect of magnetic fields on the regression rate of solid fuel was experimentally and numerically investigated. In this experiment, the regression rates of polymethyl methacrylate (PMMA) rods under different types of magnetic field gradients were measured. Meanwhile, the morphological changes in the flame during combustion were recorded by a complementary metal-oxide semiconductor (CMOS) camera. The experimental results indicated that the regression rate for PMMA varies regularly with various magnetic field gradients, with rates in the range from -32.5% to 10.8%. Simultaneously, the flame structure also changes. The numerical simulation that considered both gas-phase combustion and gas-solid heat transfer produced results that were in good agreement with the experiment. The results show that the change in the regression rate is a result of the magnetic force acting on the paramagnetic and diamagnetic materials. By changing the flow field, the magnetic force can change the flame shape and temperature distribution. This alters the heat exchanged between the gas and the fuel surface and thus, changes the burning rate. It was found that the burning rate of solid fuel can be adjusted regularly by applying different types of non-uniform magnetic fields, and it may be used in the solid fuel ramjet burning rate modulation.

Information about effects of conversion from rice fields to vegetable fields on denitrification process is still limited. In this study, denitrification rate and product ratio (i.e., N

The purpose of this paper is to study the combustion characteristics of paraffin-based fuel grain in a supersonic flow, as a preliminary to investigate its potential as fuel in a solid fuel scramjet. Paraffin-based fuel, due to its high regression rate, will pyrolyze more fuel gas in the solid fuel scramjet during the same period of time, indicating that its application would increase the combustion efficiency of the solid fuel scramjet. Based on the strength and energy density of the fuel, the paraffin-based fuel applied herein consists of 45% paraffin, 40% aluminum powder, and 15% hydroxyl-terminated polybutadiene. Due to the lack of regression rate law of the paraffin-based fuel, a regression rate model for the paraffin-based fuel was established. Experiments were carried out on the ground dedicated connected-pipe static test facility to verify the correctness of the model. The numerical results are in good agreement with the experimental results. The results show that in solid fuel scramjet, the regression rate of paraffin-based fuel is 2–3 times that of poly-methyl methacrylate fuel. The total combustion efficiency of a paraffin-based solid fuel scramjet increases with the combustion process.

Influenced by various random factors, such as a ship's size, arrival time and anchoring spot, the number of ships that can be practically accommodated by the anchorage of a coastal port is generall...

To satisfy the demand for thrust control on solid rocket motors and solid ramjet engines, numerical simulation of the effect of high-voltage electric fields on the combustion characteristics of polymethyl methacrylate (PMMA) under lateral inflow was undertaken. The mechanism of the effect of electric fields on the regression rate and mass flow rate of PMMA was analyzed. The results show that PMMA mass flow rate can increase by about 54% when subjected to positive voltages. The PMMA mass flow rate can not only increase by about 5.5% but also decrease by about 14% under the action of negative voltages. When the oxygen mass fraction is 54.5% at 0.101 MPa, the effect of electric fields on PMMA mass flow is weakened as the lateral velocity increases. When the inflow velocity is 1.95 m s−1 and oxygen mass fraction is 23.2%, the effect of electric fields on PMMA mass flow is decreased as the pressure rises. The effect of electric fields on PMMA regression rate is mainly due to the electric-field-induced volumetric body force. It will result in large-scale bulk flow movement, known as ionic wind, which changes the distribution of species and affects the heat of reaction, thus causing the changes in flame temperature, finally altering the thermal feedback to the solid phase.

The Internet of Things (IoT) has become a research hotspot in recent years. With the increase of smart devices which are connected in IoT, the privacy of IoT has become an important problem. Multi-recipient public key encryption (MRPKE) system plays an important role in protecting the privacy of those smart devices in IoT. At present, the existing ID-MRPKE schemes can only achieve the security in the random oracle model. To enhance the security level, a new ID-MRPKE is constructed by using the programmable hash function from multilinear maps. The security of the novel scheme can be proven in the standard model, instead of the random oracle. Furthermore, based on the k-level Multilinear-maps Decisional Deffie-Hellman (MDDH) assumption, we prove that the proposed scheme has the indistinguishability under the selective multi-identity attack and chosen plaintext attack (IND-sMID-CPA).

Fungi play an essential role in regulating the functioning of terrestrial ecosystems and are sensitive to climate change factors. Climate change incidents, such as N deposition and altered precipitation, create abiotic stress regarding the water use efficiency of soil and nutrient limitation impacting the activity of soil fungi. This study aimed to examine the combined effects of N fertilization and altered precipitation on soil fungal diversity and composition in the desert steppe. In the present study, we carried out a field experiment to assess the soil fungal diversity and composition of the desert steppe in response to N fertilizer (0 or 35 kg N ha−1 year−1) and precipitation changes (control, − 50% precipitation, or + 50% precipitation) in the desert steppe. The study was initiated in 2012, and plant and soil samples were collected after 5 years (August, 2017) of field treatments. High-throughput sequencing was applied to estimate the fungal diversity and composition. The soil fungal communities were dominated by Ascomycota (87.85% ± 1.26%), which primarily drove the fungal community composition. Decreased precipitation promoted strong shifts in fungal community composition under both N fertilizer levels. Increased precipitation significantly reduced Shannon-Wiener indices by 9.96%. The increasing relative abundances of fungal functional groups (lichenized saprotroph, animaland plant pathogens) resulted in a marked shift in fungal community composition from decreased precipitation to increased precipitation, which is attributed to the important role of the Ascomycota phylum in fungal communities. Structural equation modeling (SEM) indicated that C4 biomass was the predominant factor determining the Shannon-Wiener index for these fungi. Direct altered precipitation, indirect soil pH, and C4 biomass together controlled soil fungal community composition, with altered precipitation as the main driver. The interactive effects of N fertilizer and altered precipitation on grassland plant density, biomass, and soil properties may play an essential role in determining fungal diversity and community composition. Precipitation is a primary limiting factor that influences fungal community composition. Effects of N fertilizer on soil fungal community composition are highly dependent on changes in precipitation.

Due to great demands on solid rocket motors and solid ramjets for thrust control, a study of the effect of high-voltage electric fields on the regression rate of polymethyl methacrylate (PMMA) has been undertaken. The flame shape was recorded by a CMOS camera. The regression rate of PMMA was measured. A numerical model of fluid-solid coupling, which is based on experiment and considers physico-chemical phenomena associated with the flame-field interaction process, has been developed to explain experimental observations. In order to reduce the computational workload, the radiation loss, including the soot radiation is not considered in the numerical simulation. The mechanism of the effect of electric fields on the regression rate of PMMA is analysed. The numerical simulation shows that the change of the regression rate of a PMMA tip under the action of electric fields is consistent with experimental results. Studies show that electric fields can change the regression rate of PMMA, increasing it by about 38%. The regression rate on the burning surface is increased when subjected to positive electric fields. Under a negative electric field, part of the burning surface is subjected to an increased regression rate, and some thereof is subjected to a decreased regression rate. The effect of electric fields on the regression rate of PMMA is mainly due to the interaction of buoyancy and the electric field induced volumetric body forces.

This study proposes an embedded rocket ramjet, a novel combined ramjet engine, that can operate at high altitude and low pressure. The embedded rocket ramjet combustor is investigated experimentally and numerically to predict its characteristics. Experiments are performed in a direct-connect ground test facility to measures the wall pressure and total pressure at the combustor exit. Three-dimensional Navier–Stokes equations and species transport equations are solved numerically. A compressible reactive shear stress transport k-ω turbulence model with reduced chemical kinetics of a surrogate model for kerosene is used to study the flow characteristics and overall performance of the combustor. Test results show that the embedded rocket can significantly increase the combustor pressure. Numerical analysis shows that the embedded rocket increases the mixing efficiency, combustion efficiency, and thrust but decreases the specific impulse.

To ensure global food security, agriculture must increase productivity while reducing environmental impacts associated with chemical nitrogen (N) fertilisation. This necessitates towards more sustainable practices such as recycling organic waste to substitute chemical fertiliser N inputs. However, hitherto how such strategy controls the succession of microbial communities and their relationship with crop yields and environmental impacts have not been comprehensively investigated. We conducted a field experiment with vegetable production in China examining partial substitution (25–50%) of chemical fertiliser with organic forms (pig manure or municipal sludge compost) considering key sustainability metrics: productivity, soil health, environmental impacts and microbial communities. We demonstrate that partial organic substitution improved crop yields, prevented soil acidification and improved soil fertility. Treatments also reduced detrimental environmental impacts with lower N2O emission, N leaching and runoff, likely due to reduced inorganic nitrogen surplus. Microbial communities, including key genes involved in the N cycle, were dynamic and time-dependent in response to partial organic substitution, and were also important in regulating crop yields and environmental impacts. Partial organic substitution increased bacterial diversity and the relative abundance of several specific microbial groups (e.g. Sphingomonadales, Myxococcales, Planctomycetes, and Rhizobiales) involved in N cycling. Additionally, partial organic substitution reduced the number of bacterial ammonia oxidizers and increased the number of denitrifiers, with the proportion of N2O-reducers being more pronounced, suggesting a mechanism for reducing N2O emissions. Comprehensive economic cost-benefit evaluation showed that partial organic substitution increased economic benefit per unit area by 37–46%, and reduced agricultural inputs and environmental impacts per unit product by 22–44%. Among them, 50% substitution of pig manure was the most profitable strategy. The study is crucial to policy-making as it highlights the potential advantages of shifting towards systems balancing chemical and organic fertilisers with economic benefits for farmers, reduced environmental damage and an efficient way for organic waste disposal.

Chemical nitrogen fertilizer application in the peri-urban zone has benefited food supply, but excess nitrogen input has altered multiple ecosystem services and caused an array of ecosystem dis-services that have degraded air and water quality. Using sewage sludge compost and pig manure to partially substitute chemical fertilizer nitrogen may promote sustainable ecosystem services. However, few studies have been conducted to evaluate the values of associate ecosystem services with a unified standard. To comprehensively understand the effect of partial organic substitution on ecosystem services (supporting vegetable production and sequestering soil organic carbon) and ecosystem dis-services (greenhouse gas emissions and reactive nitrogen release), we attempted to evaluate the ecosystem service from the perspective of economic assessment. A field experiment was conducted in a peri-urban zone in eastern China, including the following six treatments at equal total nitrogen application rates: (1) no fertilizer nitrogen applied; (2) 25% sewage sludge compost substitution; (3) 25% pig manure substitution; (4) 50% sewage sludge compost substitution; (5) 50% pig manure substitution and (6) chemical fertilizer nitrogen only. The results showed that partial organic substitution significantly increased annual vegetable yield by 27.8%–35.3% and annual soil organic carbon sequestration rate by 129.2%–213.8%. Moreover, greenhouse gas emissions (methane and nitrous oxide) were significantly decreased by 28.6%–43.2%; nitrogen leaching and runoff were significantly decreased by 39.0%–49.5% and 26.8%–62.0%, respectively; and ammonia volatilization was increased by 2.4%–27.8%. Overall, partial substitution with organic fertilizer decreased total reactive nitrogen losses by 19.9%–39.8% compared with the 100% chemical fertilizer nitrogen treatment. Although additional labor and higher input costs were required, partial organic substitution could obtain a higher net economic benefit of 25198–90670 ¥ ha−1 yr−1 compared with the sole application of chemical fertilizer nitrogen. The results suggest that partial substitution of chemical fertilizer with organic fertilizer can sustain ecosystem services and reduce ecosystem dis-services in the peri-urban zone and increase economic profits for farmers.

Based on the bubble dynamic theory and the compressible two-phase flow solver of the open source software OpenFOAM, a numerical simulation study is carried out on the interactions of bubble clusters in a closed volume. The bubble dynamics and interactions of a single bubble, two bubbles, and four bubbles are investigated under the working conditions without and with the presence of a free surface. Through a parametric study, the qualitative patterns of the variations of the bubble collapse period, the volume compressibility, the bubble pressure peak value, and the breakdown, fusion, and separation phenomena with the parameters such as the bubble pressure, the radius size, the bubble spacing, and the distance from the free surface are obtained. The main factors affecting the bubble morphology and the dynamic characteristics are summarized from numerous parameter experiments. It is shown that, in the absence of a free surface, the main factors are the relative size of the bubbles, the pressure of the liquid, and the pressure differences among the bubbles, while in the presence of a free surface, the main factor is the pressure of the liquid between the upper surface of the bubble and the free surface.

Current estimates of global indirect N2O emissions are based on a relatively small dataset and remain a major source of uncertainly in the global N2O budget. Nitrogen (N)-enriched groundwater from agricultural fields may act as an important source of indirect N2O emissions as it discharges to adjacent watershed areas. During 2015–2017, dissolved N2O concentrations in groundwater were measured and indirect N2O emission factors (EF5g) calculated under three typical high-N land-use types (vineyard, vegetable field and paddy field) in eastern China. The average dissolved N2O concentrations in groundwater were 58.1 ± 40.4, 18.5 ± 11.5 and 0.72 ± 0.27 μg N L−1 for vineyard, vegetable field and paddy field, respectively. The dissolved N2O was over-saturated and was therefore a net source of N2O to the atmosphere. The indirect N2O emission factors (EF5g) of vineyard (0.0091) and vegetable (0.0092) fields were much higher than the current Intergovernmental Panel on Climate Change (IPCC) default value of 0.0025 which indicated that these land-uses may have led to indirect N2O emissions from the underlying groundwater. In contrast, the EF5g of the paddy field (0.0019) was slightly lower than the default EF5g proposed by IPCC (2006) and contributed minimal indirect N2O emissions to the atmosphere. However, the current IPCC method may have overestimated the contribution of groundwater N2O to the global N cycle because it took residual but not initial groundwater NO3−-N concentration into account when calculating EF5g. Therefore, we proposed the adoption of an improved method for calculating the EF5g and compared it to the current IPCC (2006) method using data from the present study and other published data. The results of the comparison showed that the improved method was more scientifically appropriate measurement for calculating EF5g.

An isogeometric scaled boundary finite element method (IGA-SBFEM) using the non-uniform rational B-splines (NURBS) is firstly performed to investigate the liquid sloshing in the half-full horizontal circular cylindrical with the internal bodies. The proposed method can effectively maintain the advantages of the SBFEM, which combines the advantages of the finite element method and the boundary element method with its own unique characteristics, with the analytical solutions in the radial direction, and also can accurately improve the description of geometry on the boundary by using the NURBS, which brings out the flexibility to describe the complex geometry and presents some key improvements compared to the traditional SBFEM. The detailed derivation and solutions for the sloshing problems based on IGA-SBFEM, and the sloshing frequencies and the corresponding mode shapes and the dynamic sloshing characteristics are also presented by combining the multimodal method. The numerical results validate that this proposed method can acquire higher accuracy, efficiency and convergence with significantly fewer degrees of freedom than those of the traditional SBFEM, and the total number of degrees of freedom of IGA-SBFEM and SBFEM is far less than those of FEM which should be discretized in the entire domain. A detailed parametric study for estimating the influences of the key parameters involving the arrangement, shape, number and size of the internal bodies on the natural sloshing frequencies, mode shapes and sloshing forces and some interesting conclusions have been obtained.

In the VANET systems, the leakage of some sensitive data or communication information will cause heavy losses for life and property. Then, a higher security level is required in the VANET systems. Meanwhile, fast computation powers are needed by devices with limited computing resources. Thus, a secure and lightweight privacy-preserving protocol for VANETs is urgent. In this paper, we first propose an identity-based signature that achieves unforgeability against chosen-message attack without random oracle. In order to reduce the computational cost, we design two secure and efficient outsourcing algorithms for the exponential operations, where a homomorphic mapping based on matrices conjugate operation is used to achieve the security of both exponent and base numbers. Furthermore, we construct a privacy-preserving protocol for VANETs by using outsourcing computing and the proposed IBS, where a proxy re-signature scheme is presented for authentications. In the VANET privacy-preserving protocol, TA authorizes RSU to act as an agent and RUS converts OBU's signature into TA's signature, which effectively hides the real identity of vehicle OBU. Meanwhile, TA has access to trace the real identity of OBU using its secret key when malicious messages are found. Then, the protocol provides anonymity, traceability, and privacy. In addition, with respect to the efficiency, our scheme does not need pairing operations and exponential operations. Thus, the calculation burdens for the VANET system can be significantly reduced.

The main contribution of this paper is to determine the allocation strategy of on-shore power supply (OPS), comprising additional power capacity of OPS and adopting patterns of OPS at berth, to realize the trade-off between total cost of OPS and carbon emissions of ships. Firstly, carbon emission formulations, adopting patterns of OPS and arrival patterns of ships are described. Then, in order to minimize total cost and carbon emissions, an integer programming model for OPS allocation problem is proposed. Next, a simulation-based solution method is developed to resolve the optimization model, which consists of inner simulation module and outer optimization module. The outer module enumerates all the allocation scenarios and evaluates the results from the inner module. The inner module introduces a simulation model to represent the stochastic operation system in the container terminal and outputs results to outer module. Finally, taking a port in China as an example, this paper designs and conducts a series of experiments and discovers that the sensitivity of results emphasizes the importance of electricity price on the optimal allocation. When electricity price is lower or larger than 0.3 $/kWh, the optimal power capacity is 9200 or 5230 kW, correspondingly.

Objectives This study aimed to investigate the effect of the widely used food emulsifier glycerin monostearate (GM) on testicular toxicity caused by the mixture of three commonly used phthalate esters (MPEs) in rats, and further to explore the underlying mechanism. Materials and Methods Thirty male Sprague–Dawley rats were randomly divided into three groups. Rats were orally treated with 160 mg/kg/d MPEs in the MPEs group; coinstantaneously treated with 160 mg/kg/d MPEs and 200 mg/kg/d GM in the MPEs + GM group; and treated with the excipient in the control group. The intervention lasted for 5 weeks. Testis weight, epididymis weight, testicular histopathology, and serum testosterone were detected for testicular toxicity evaluation. The testicular ultrastructure, the tight junction proteins zonula occluden (ZO)-1, and claudin were measured for the mechanism exploration. Results The body weight, epididymis, serum testosterone level, and anogenital distance in the MPEs + GM group were significantly decreased compared with control group (P Conclusions The results from this study indicated that GM aggravated MPEs’ testicular toxicity, which might relate to the injured mitochondria and damaged tight junctions in testicular tissue.

Based on the MODIS NDVI product data source of Xilingol from 2010 to 2019, we use the pixel dichotomous model to retrieve the vegetation coverage in our study. The spatiotemporal changes of the vegetation cover were analyzed in the model by using the meteorological data from researched sites or the vicinal meteorological stations for evaluating the meteorological influence on the vegetation cover changes. Based on this, an evaluation method was established to estimate the relative influences of the climate changes and anthropogenic activities. The main conclusions are as follows: (1) Fractional vegetation cover in Xilingol was decreased from the northeast to the southwest. (2) The overall trend in Xilingol fractional vegetation cover in the 10-year period shows a fluctuating increasing trend. (3) An opposite distribution pattern was detected between mean precipitation and mean temperature in the study site. (4) Compared with temperature, annual precipitation has a higher correlation with fractional vegetation cover in the study site and is the main climatic factor that affects vegetation growth in the study site. (5) During the 10-year period in the study site, anthropogenic human activities have slightly greater inhibitory effects on vegetation growth than promoting effects. (6) Climate change is a major factor to accelerate grassland degradation from 2010 to 2019 in vegetation degradation regions. The promotion effect of precipitation on vegetation coverage is obviously higher than the limitation of human activities, which leads to the increase of vegetation coverage in 2010–2019.

Crop residue amendment in conjunction with synthetic nitrogen (N) fertilization is a common agricultural practice that increases soil fertility and crop yield. However, such a practice may also change soil denitrification process. Here, we conducted an incubation experiment with a robotized continuous flow N-2 free incubation system (using helium (He) and oxygen (O-2)1 and measured fluxes of N2O and N, at a high resolution in an intensively managed soil to examine the interaction effect of straw amendment and N fertilization on soil denitrification. Four treatments were set consisting of (a) a nonamended treatment (Control); (b) a Straw treatment (2 g straw kg(-1) dry soil); (c) a KNO3 treatment (KNO3, 15 mM KNO3); and (d) a Straw + KNO3 treatment (2 g straw kg(-1) dry soil and 15 mM KNO3). During the oxic phase (80% He plus 20% 0 2 ) of the experiment (initial 2 days), flux rates of N2O were 0.54 and 0.38 kg N/ha day(-1) in the Control and KNO3 treatments, respectively. Meanwhile, straw amendment triggered N2O fluxes immediately after the onset of treatments, which was more evident in the Straw + KNO3 treatment. During the anoxic phase (100% He), both N2O and N-2 emissions increased in all treatments, with the effect being more pronounced in the Straw and Straw + KNO3 treatments. In line with the observed differences in gas fluxes, the abundances of nirK, nirS, and nosZ genes increased clearly in these treatments. Overall, the mean N2O/(N2O + N-2) ratio (0.69 +/- 0.03) in the Control treatment was significantly lower compared to the KNO3 treatment (18.8%) and higher than the straw-amended soils (31.9% and 17.4% compared to the Straw and Straw + KNO3 treatments, respectively). Taken together, our results suggest straw amendment significantly altered N2O and N-2 fluxes by decreasing the N2O/(N2O + N-2) ratio; however, the effects of straw amendment depended on soil nitrate content.

In this study, soil-borne N2, NO, and N2O emissions induced by land use conversion and water management were investigated in intact soil cores under a helium/oxygen atmosphere by a robotized incubation system in combination with the N2O 15N site preference signature and molecular-based microbial analysis. The experiment consisted of five treatments: i) paddy-flooded (PF); ii) orchard-wet (OW, 70% WFPS); iii) orchard-dry (OD, 43% WFPS); iv) vegetable-wet (VW, 70% WFPS); and v) vegetable-dry (VD, 43% WFPS). The vessels of each treatment received 200 mg urea-nitrogen (N) (equivalent to 210 kg of urea-N ha−1), and soil moisture in the OW and VW treatments was adjusted to a higher constant moisture to simulate a scenario after irrigation or rainfall. The results showed that total gaseous N losses during the incubation period were 25.33 ± 0.33 kg N ha−1 in the PF treatment, whereas smaller losses were recorded in the OD and VD treatments (4.28 ± 2.04 and 9.75 ± 3.75 kg N ha−1, respectively). The potential contribution of bacterial denitrification to N2O emissions in the OD and VD treatments was 11.1% and 15.4% higher, respectively, than that in the PF treatment (58.8% ± 0.5%). Furthermore, the corresponding N2O/(N2O + N2) ratio in the OD and VD treatments decreased by 50% and 73.8%, respectively, relative to the ratio in the PF treatment (0.42 ± 0.01). Such changes indicated the crucial role of altered soil properties caused by land use conversion in regulating the production and consumption of N2O. Relative to the normal moisture (dry) condition, enhanced soil moisture increased total gaseous N losses in the orchard and vegetable soils by 386.9% and 67.4%, accompanied by a higher N2O/(N2O + N2) product ratio, but decreased the share of bacterial N2O by 11.1% and 15.4%, respectively. The changes in the abundance and community composition of soil denitrifiers caused by land use conversion from rice paddies to orchards and vegetable fields could partly explain the differences in gaseous N loss therein. These findings highlight the influence of land use conversion on soil gaseous N emissions and demonstrate that increased moisture in upland soils reduced the dominance of bacterial denitrification in N2O production.

A new scramjet configuration using solid fuel as propellant is proposed, namely, the combined solid fuel scramjet. The combined solid fuel scramjet combustor has been investigated numerically to predict its characteristics. Two-dimensional axisymmetric Reynolds-averaged Navier–Stokes equations and species transport equations are solved numerically. Turbulence closure is achieved using the shear stress transport k-ω model. Three global one-step reaction mechanisms are used in this study. The experimental data in the published literature has been used to validate the accuracy of numerical model. The results of the numerical analysis show that secondary combustion occurs in the supersonic combustor. At the combustor outlet, the total pressure loss is about 0.65 and the combustion efficiency is about 48%. A subsonic recirculation zone is formed near the wall between the air inlet and the fuel-rich gas inlet, which is beneficial to mixing and flame holding. A normal shock wave is generated at the end of the expansion zone after the fuel-rich gas is injected into the combustor, and this is due to the strong pressure downstream induced by secondary combustion.

With the paradigm shift of 5G in terms of computing and infrastructure, 5G security is confronted with new challenges due to the promising introduction of Software Defined Networks (SDN), Network Function Virtualization (NFV) and Cloud Computing. While most of current works on 5G security are focused on high-level analysis of challenges and threats to satisfy the emerging use cases. Software Defined Security (SDS), as a new security paradigm which provides flexible and centralized security protection for varieties of networks especially for SDN and Cloud environment, can be a potential security solution in 5G. Lots of work have focused on the implementations and details of SDS, and most researchers, however, are focusing on the controller design and security policy design. There are few work on the placement strategy of Network Security Functions (NSFs) and devices, which plays a significant role in SDS to improve the optimize defence effects. Most of existing placement schemes are modelled as Integer Linear Programming (ILP) by considering the constrains in terms of resource, time, security and so on, and introduce various heuristic algorithm to reduce its computing complexity. While in this paper, we propose a placement scheme of NSFs and devices in SDS based on underlying routing characteristic and evaluate its performance defending virus attack. The proposed scheme adopts Group Routing Betweenenss Centrality (GRBC) as a metric and introduces a successive algorithm to compute the GRBC. Different to traditional Routing Betweenness Centrality which only considers the importance of single node, the proposed scheme can find the key group of nodes in a SDS underlying network, where the NSFs and security devices should be deployed. In the performance evaluation, we apply our scheme to the scenario of computer virus and worms control in SDS, and the results show that the proposed scheme can improve the performance of security functions in SDS system.

Phytogenic hillocks are a type of wind-deposited biological micro-topography exhibiting a bulging shape under plant clusters in arid regions. In this study, we quantitatively measured the phenotypic characteristics of phytogenic hillocks, the soil particle size distribution in phytogenic hillocks and bare surfaces, and the sediment particle size distribution in hillocks of three heights under different grazing treatments. The results showed that the proportion of dense cluster phytogenic hillocks in the no grazing treatment was higher than in the moderate grazing treatment, and the proportion of scattered cluster phytogenic hillocks under moderate grazing was higher than under no grazing. The total area of dense cluster phytogenic hillocks under no grazing was higher than under heavy grazing and under moderate grazing. For the scattered cluster phytogenic hillocks, the total area was greatest under moderate grazing, followed by heavy grazing and, finally, no grazing. For single hillocks, grazing had a significant impact on the width of dense cluster phytogenic hillocks, while the heavy grazing treatment had a significant impact on the height of scattered cluster phytogenic hillocks. The results for windblown sediment showed that the only significant difference among grazing treatments occurred at a height of 2–8 cm. Grazing changed the relationships among the phenotypic characteristics of phytogenic hillocks, the soil particle size of phytogenic hillocks, and the particle size of wind-deposited sediments. Our results suggested that grazing increased the proportion of scattered cluster phytogenic hillocks and caused the relationship between somewhat bare land and phytogenic hillocks to change from symbiosis to competition.

The collision and deposition behaviors of aluminum/alumina droplets on a solid wall play a crucial role in improving the engine performance of a solid rocket motor (SRM). This study employed a high temperature oxy-methane flame and a solid wall to simulate the environment of SRM. Micron-sized aluminum particles were axially added into the flame and they were melted and ignited before collision with the wall. The velocities of the particles were varied by adjusting the flow rates of gaseous reactant and the collision angle was adjusted by arranging the solid wall layout. The dynamic deforming process of micron-sized droplets colliding on a hot wall was observed by high speed photography. And thousands of droplets were tracked to examine the deposition probability on the hot wall. The results show that the collision velocity, angle and particle size codetermine the post-collision behaviors, which typically include rebound, deposition and splashing. The heat transfer between the droplet and wall plays an important role in the deposition process. By further considering the component of the condensed droplet, the dimensionless parameter of normal Weber number has been proposed to quantify the deposition rate. And an empirical formula has been obtained by employing the Weber number and collision angle.

In this study, the surface modification on graphene oxide (GO) was performed using octadecylamine (ODA). Furthermore, polybutylene terephthalate/GO (PBT/GO) composites were prepared to elucidate the role of GO surface modification on the mechanical performance, thermal stability and crystallization behavior. Results of Fourier transform infrared spectra (FT-IR), Raman spectrum, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and transmission electron microscope (TEM) revealed that ODA was successfully grafted on GO. Differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), tensile test, Izod impact strength test and TGA were carried out on the PBT/GO composites. Results indicated that the addition of raw GO can enhance the crystallization temperature and degree of crystallinity and can slightly improve the thermal stability and tensile strength of the composites. However, the impact strength and elongation at break were seriously decreased owing to the poor compatibility between the GO and PBT matrix. Once the modified GO was added, the crystallization temperature and degree of crystallinity were greatly increased. The tensile strength increased greatly while the elongation at break and Izod impact strength were efficiently maintained, these were evidently higher than those of PBT/raw GO. Moreover, thermal stability was greatly enhanced. SEM (scanning electron microscope) observation results on the impact-fractured surface clearly confirmed the improved compatibility between the modified GO and PBT matrix. A related mechanism had been discussed.

In recent years, many institutes and organizations have been made efforts into developing new networkarchitecture. Universal Identifier Network(UIN) is one of them which is designed to providebetter mobility, better security and better reliability. Multicast is the basic network layer service thatis designed to save bandwidth for the whole network. The deployment of existing multicast schemeis restricted because of low security and the lack of control in sources. In this paper we have designeda central-controllable and secure multicast(CCSM) system for UIN that aims to achieve bettersecurity and scalability. We design the group management protocol and multicast routing protocol.The former one restricts the group members’ joining with authentication and the latter one provides asecure way to install multicast entries on routers. We evaluate CCSM by comparing it with PIM-SM,and the results show that CCSM is more secure and reduces the multicast flow entries for the wholenetwork.

Cold-flow tests, thermal tests, and numerical simulation were performed to study the thrust-adjustment characteristics, and the thrust-vector-control characteristics, of a fluidic nozzle throat com...

Accelerated aging tests under pre-strain were conducted on HTPB-based composite solid propellant with the goal of investigating the effect of pre-strain aging on its damage properties. A statistical damage constitutive model based on continuum damage theory and statistical strength theory was established. The aging damage coefficient, making aging process of propellant equivalent to a form of damage, was introduced to correct the damage variable. Experimental results show that theoretical model has good agreement with experimental results and can accurately describe the mechanical behavior of propellant during pre-strain aging. Further analysis indicated that the damage effects caused by pre-strain can be identified from the equation of the aging damage coefficient. Aging time influences both tensile strength and shape characteristics of the stress-strain curve of propellant in the damage stage, while pre-strain only decreased the tensile strength. The strain damage threshold value decreased linearly over the aging period and with increasing pre-strain level during the aging process.