•The adiabatic shear failure process of solids was investigated for the first time by dynamic tests synchronically combined with high-speed photography and infrared temperature measurement.•The key ...characteristics of ASB, such as temperature, critical strain, propagation speed and cooling rate were systematically studied.•The experimental results shows that the apparent temperature rise might have occurred after ASB initiation, indicating it might not be the causation but the consequences of ASB.•The discovery might help to clarify the causality of ASB and serve as the starting point for further physical, mechanistic and mathematic studies of ASB.
One of the most important issues related to dynamic shear localization is the correlation among the stress collapse, temperature elevation and adiabatic shear band (ASB) formation. In this work, the adiabatic shear failure process of pure titanium was investigated by dynamic shear-compression tests synchronically combined with high-speed photography and infrared temperature measurement. The time sequence of important events such as stress collapse, ASB initiation, temperature rise and crack formation was recorded. The key characteristics of ASB, such as width, critical strain, temperature, propagation speed and cooling rate were systematically studied. The maximum propagation velocity of ASB is found in this work to be about 1900 m/s, about 0.6Cs (Cs is the shear wave speed). The maximum temperature within ASB is in the range of 350–650 °C, while the material close to ASB is also heated. The cooling rate of ASB is on the order of 106 °C/s, indicating that it needs a few hundreds of microseconds for the ASB to cool down to the ambient temperature. One important observation is that the apparent temperature rise occurs after ASB initiation, which indicates that it might not be the causation but the consequences of ASB. Further efforts are called for confirmation of this notion because of its significance.
This paper researches the almost sure exponential leader-following consensus (ASELFC) of linear and nonlinear multi-agent systems (MASs) under semi-Markovian switching topologies (SMSTs). Differing ...from existing researchworks of MASs under SMSTs, we remove the restriction that every topology has a directed spanning tree (DST) rooted in the leader. Only partial switching topologies are requested to have a DST. By employing Lyapunov analysis method and stochastic technique, sufficient conditions for ASELFC are obtained. Finally, the theoretical results are applied to solve the synchronization of Chaos systems by using an example of Chua's circuits.
•Enzyme activity decreased by erosion leading to an increase in the depositional plot.•Slope enhanced the difference in enzyme activity between the erosional and depositional plot.•Enzyme activity ...mitigated total soil CO2 emission in the erosion-deposition plots.
Soil C-acquiring enzymes are good indicators for the biological mechanism of soil nutrients and organic matter cycles. However, they have been used less frequently to assess the ecological stability and soil C cycle in eroding landscapes due to a lack of knowledge of the responses of C-acquiring enzyme activities to soil erosion and deposition. In the present study, a 3-year field simulation experiment was conducted to examine the variations in the activities of C-acquiring enzymes (β-1,4-xylosidase (βX), β-1,4-glucosidase (βG) and β-D-cellobiohydrolase (CBH)) from erosion-deposition plots with different slope gradients (5°, 10° and 20°) on the Loess Plateau in China (2016–2018). The activities of βX, βG and CBH were higher in the depositional plots than in the erosional plots, and those differences were enlarged with increasing slope gradients. Compared to the 5°-erosional plot, the activities of βX, βG and CBH respectively declined by 3.2–4.5%, 14.3–37.5% and 12.7–29.1% in the 10°-and 20°-erosional plots. The βX, βG and CBH activities were 2.2–18.1%, 17.3–32.1% and 14.8–86.2% higher in the 10°- and 20°-depositional plots than in the 5°-depositional plot. Moreover, the total soil CO2 emissions from the whole erosion-deposition plots decreased as slopes steepened. The displaced runoff and sediment depleted soil moisture, SOC, clay and microbial biomass in the erosional plots but enhanced these resources in the depositional plots, which can account for the changes in C-acquiring enzyme activities. The spatial distribution of enzyme activities affected soil CO2 emissions in a positive linear function. The sensitive responses of the C-acquiring enzyme activities and the controlling effects of C-acquiring enzyme activities on soil CO2 emissions during erosion and deposition processes, should be properly considered in assessing the biological mechanism for nutrition cycling in regions predominated with fragmented eroding landscapes.
This paper is concerned with stochastic stabilization problem for networked semi-Markovian jump systems with randomly occurring uncertainties and nonlinearities under event-triggered scheme. By ...employing the delay system method, the stochastic stability analysis and controller synthesis for semi-Markovian jump systems considering the effect of network-induced delay are presented. In order to reduce the frequency of data transmission and save network resources, sampled-data-based event-triggered scheme is utilized. Mode-dependent Lyapunov-–Krasovskii functional candidate is constructed and free-weighting matrix method is employed which can reduce some conservativeness of the results. Then, novel conditions are formulated to ensure the stochastic stability for stochastic semi-Markovian jump time-delay systems in terms of linear matrix inequalities(LMIs). Controller gain matrices and event-triggered matrices can be co-designed simultaneously based on the obtained sets of LMIs. Finally, simulations are given to illustrate the effectiveness of the results.
•An integrated production system of cattle, biogas and vegetables was evaluated.•The integrated system was compared with single product systems.•High sustainability was achieved in the integrated ...production system.
Based on the concept of comprehensive utilization of wastes, an eco-agricultural integrated production system of cattle, biogas, and greenhouse vegetables (IPSCBV) was constructed for a large-scale farm in Northwest China. In the present study, the production efficiency, environmental impact, economic viability, and sustainability of the IPSCBV were evaluated using emergy and economic analyses. The performance of the IPSCBV was compared with that of independent production systems for cattle and greenhouse vegetables using a variety of emergy indices, including the joint indices (transformity, emergy yield ratio, environmental loading ratio, and emergy sustainable index) calculated for the IPSCBV with multiple outputs and the weighted average indices for the independent production systems. The self-organization ability, emergy exchange status, and economic and environmental benefits of the integrated and independent production systems were evaluated using the feedback ratio of yield (FYR), emergy exchange ratio (EER), and greenhouse gases emission mitigation intensity (GEMI). The evaluation results using the new emergy-based indices showed that the IPSCBV had better emergy efficiency and higher sustainability, which resulted in less environmental stress than the independent production systems for cattle and greenhouse vegetables. The FYR of the IPSCBV system was 10.50% while that of the independent systems was only 0%. The GEMI in the IPSCBV reached 2.12kgCO2-eq/1014sej. The EER of the IPSCBV (0.62) was significantly lower than that of the independent greenhouse vegetable production system (3.02). That is, the price of the products underestimated their real (emergy-based) value which includes the free environmental resources and the system's inherent feedbacks. From an economic point of view, the IPSCBV may not provide a competitive economic input–output ratio in the short run. However, it serves as a promising eco-agricultural model for comprehensive utilization of wastes on large-scale farms associated with intensive management because of its better performance with respect to resource utilization, environmental emission mitigation, and sustainability.
This article restudies the tracking consensus problem of disturbed second-order multiagent systems via event-based sliding mode control (EB-SMC). A new framework of EB-SMC method is proposed with new ...distributed EB integral-type sliding manifolds, distributed EB-SMCs, and more efficient event-triggered detections where continuous communication among follower agents is not required. Moreover, event-triggered conditions with heterogeneous parameters are well-designed to improve the flexibility of parameters selection. By employing Lyapunov analysis method and SMC theory, new sufficient conditions for ensuring the reachability of sliding manifold is deduced to remove the conservatism. In light of EB-SMC technique, attractive features containing fast response, good transient performance, and robustness with respect to uncertainties can be inherited. Also, resource consumption and network occupation can be greatly reduced via event-triggered control with exclusion of Zeno phenomena. At last, a numerical example is shown to support our results.
The tracking consensus problem for stochastic Markovian multi-agent systems (MASs) with mismatched uncertainty is investigated in this study. A restrictive assumption for stochastic systems in ...existing results is removed in this study. Under the directed interacted topology, the sliding mode control method is utilised to achieve leader-following consensus for general linear MASs in the sense of mean square. Integral sliding mode surfaces are employed to tackle the mismatched uncertainties. Then, with the transition rates of Markov process being completely known or partly unknown, two kinds of distributed sliding mode protocols are given, respectively. Based on the sliding mode control theory, algebraic graph theory and stochastic differential equation theory, mean square stability of sliding mode dynamics are ensured by LMIs and reachability of sliding mode surfaces almost surely from the initial time are obtained. Finally, simulations are given to illustrate the effectiveness of the results.
► An improved process has been studied for sulfur removal under ultraviolet irradiation. ► We explore the sulfur removal effect of different model sulfur compounds. ► The sulfur removal with metal ...Complex of Chitosan Salicylal Schiffs Base was studied. ► Up to 98% of sulfur removal was achieved for model sulfur compounds and fuel.
Ultraviolet-assisted oxidative desulfurization (UODS) was applied to diesel, gasoline and petroleum product feedstock containing model sulfur compounds (thiophene, thiotolene, thioxene and benzothiophene). The influence of oxidant amount, volume of acetonitrile, reaction time and temperature on the sulfur removal efficiency from model sulfur compounds and real oils in the presence of ultraviolet was investigated in the presence of ultraviolet. By using the optimized conditions for UODS, desulfurization rates of thiophene and benzothiophene increased to 98.87% and 99.87%, respectively, and desulfurization rates of thiotolene and thioxene to 96.86% and 98.37%, respectively, which were achieved for model compounds in petroleum product feedstock. By using the same conditions, the removal of sulfur for real gasoline and diesel samples was 98.34% and 97.17%, respectively. For model compounds, real gasoline and diesel samples, sulfur removal without ultraviolet and on the same conditions was lower than that with ultraviolet, which shows that ultraviolet improved the efficiency of oxidative desulfurization. The results for sulfur removal from gasoline and diesel samples prove the feasibility of the proposed UODS procedure for sulfur removal from real oil samples.
This paper studies scaled-based practical consensus issue for multiagent systems with input time delay by a fully continuous communication-free integral-type event-triggered scheme. By choosing the ...proper scales, scaled consensus can be induced to synchronization, bipartite consensus or cluster consensus. By defining a continuous communication-free measurement error for the integral-type event-triggered mechanism, the new integral-type event-triggered condition is proposed which can not only reduce the energy consumption but also prolong the interevent time. Then, with time domain analysis method, the distributed integral-type event-triggered control problem for nonlinear general multiagent systems involving input time delay is investigated and then the second-order counterpart, with a calculated upper-bound for time-delay. Moreover, it is concluded that with such event-triggered protocols, practical scaled consensus can be achieved without the exhibition of Zeno behavior. At last, simulations are shown to support the results.
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