In this technical note, a new class of discrete-time networked nonlinear systems with mixed random delays and packet dropouts is introduced, and the H ∞ filtering problem for such systems is ...investigated. The mixed stochasitc time-delays consist of both discrete and infinite distributed delays and the packet dropout phenomenon occurs in a random way. Furthermore, new techniques are presented to deal with the infinite distributed delay in the discrete-time domain. Sufficient conditions for the existence of an admissible filter are established, which ensure the asymptotical stability as well as a prescribed H ∞ performance. Finally, examples are given to demonstrate the effectiveness of the proposed filter design scheme in this technical note.
Chitosan and its oligosaccharides, which are known to possess multiple functional properties, have attracted considerable interest due to their biological activities and potential applications in the ...food, pharmaceutical, agricultural and environmental industries. Many researchers have focused on chitosan as a potential source of bioactive materials in the past few decades. This review focuses on the biological activities of chitosan and chitooligosaccharides based on our and others’ latest research results, including hypocholesterolemic, antimicrobial, immunostimulating, antitumor and anticancer effects, accelerating calcium and iron absorption, anti-inflammatory, antioxidant and Angiotensin-I-converting enzyme (ACE) inhibitory activities and so on, which are all correlated with their structures and physicochemical properties. The bioactivities summarized here may provide novel insights into the functions of chitosan, its derivatives or oligosaccharides and potentially enable their use as functional-food components and additives.
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This article is concerned with the security control of a class of discrete-time linear cyberphysical systems (CPSs) subject to denial-of-service attacks. To enhance the inherent resistance of the CPS ...against damage and attacks, a multichannel network is employed for remote information interaction between the ingredients of the system. In this way, a complex interaction process will be formed between the signal sender and the smart malicious adversary. Specifically, in the context of using the multichannel network, the malicious adversary has to maximize the attack success probability within its energy constraint. As a counterpart, the system tries to mitigate the negative impact of such attacks on CPS control performance. For the purpose of designing a control strategy to cope with the attacks, this interaction process is formulated as a zero-sum stochastic game, while the Nash equilibrium solution of this problem is found with the help of the proposed learning algorithm, and the optimal mixed strategies for both attackers and defenders are derived. Furthermore, for the CPS driven by the obtained decision-making strategies, a Kalman filter-based active dynamic output feedback resilient controller is proposed. Finally, the effectiveness of the developed optimal defense strategies and the resilient controller is demonstrated by extensive case studies on the servo motor experimental platform.
This paper introduces the design and implementation of a plug-in free online 3-D interactive laboratory based on networked control system laboratory (NCSLab) framework. The system relying only on ...HTML5 provides full supports for control engineering experimentation. The users are allowed to design their own control algorithms and apply them to the remote test rigs. Using the web-based interface, multiple widgets such as real-time charts, virtual gauges, and live images are available to customize the monitoring interfaces. To enhance the sense of immersion, 3-D animations which are synchronized with the remote experimental processes are also provided. The users can watch and interact with the remote experiments through the 3-D replicas. Various HTML5 based toolkits are integrated seamlessly under the NCSLab framework. NCSLab provides visualized services for the whole process of control experimentation including remote monitoring, tuning, configuration, and control algorithm implementation. As the network delay could disturb the 3-D representation, a communication scheme using web protocols is also implemented. The feedback from teaching shows the general acceptance and effectiveness of NCSLab is notably high. As most existing online laboratories adopt either native applications or plug-ins, the methodologies and technologies used in NCSLab could be insightful for other online laboratories toward web-based cross-platform systems.
This research is devoted to the coordinated control of high-order fully actuated multiagent systems (HOFA-MASs). A predictive control strategy is developed to realize the coordination of HOFA-MASs ...and simultaneous stability and output consensus. In this strategy, a Diophantine equation is introduced to construct an incremental HOFA prediction model rather than a reduced-order one, then a cost function focused on coordinated relationship is minimized by the design of predictive control such that the optimal coordination controllers can be achieved with simple and easy computation. Further discussion derives a simple criterion to guarantee the simultaneous stability and output consensus of the closed-loop HOFA-MASs. Two experiments of formation control of three air-bearing simulators are given to demonstrate the availability of the predictive control strategy.
Several experiments and field observations have demonstrated seismic waves‐induced permeability increases. However, a few experiments have revealed significant decreases in the permeability of ...fractured sandstone after shaking produced by dynamic stresses. In this paper, we analyze the tidal responses of the water level in two wells (Junan and Dingyuan) situated on and near, respectively, the Tan‐Lu fault in China. The results sampled by a single well indicate that seismic waves could both increase and decrease the permeability. In addition, our results indicate that the earthquakes that decreased the permeability in a single well were distributed in certain azimuthal zones. Given the azimuthal distribution of distant earthquakes, the observed permeability decrease could be attributed to the seismic wave‐induced clogging of fractures that compose the flow paths in the shallow crust. Our research contributes to an enhanced overall understanding of the effects of earthquakes on the permeability of the shallow crust.
Plain Language Summary
Most hydrological phenomena caused by earthquakes can be explained by permeability changes. Many experiments and field observations have demonstrated coseismic increases in permeability. However, coseismic decreases in permeability have seldom been reported. In this paper, we analyze the tidal responses of the water level in two wells. The results indicate that seismic waves could both increase and decrease the permeability. In addition, we find that the earthquakes that decreased the permeability in a single well were distributed in certain azimuthal zones. Given the azimuthal distribution of distant earthquakes, the observed permeability decrease could be attributed to the seismic wave‐induced clogging of fractures that compose the flow paths in the shallow crust. Furthermore, we discuss the possible process of particle remobilization in a natural fracture network caused by seismic waves, as this process may be used to explain the azimuthal distribution of earthquakes that decreased the permeability. Our research contributes to an enhanced overall understanding of the effects of earthquakes on the crustal permeability. In the future, earthquake‐induced increases and decreases in permeability should be considered when discussing controls on permeability for exploring underground resources of groundwater, geothermal energy, oil and gas, and for safely storing nuclear and toxic waste underground.
Key Points
Seismic waves could decrease besides increase the crustal permeability
Decreases in permeability may depend on the earthquake azimuth
The decrease in the permeability could be attributed to the clogging of fractures
•Meta-mafic rocks in the central Liaodong Peninsula was emplaced at 2154Ma, and metamorphosed at 1897Ma.•These rocks were derived from a depleted mantle source with extremely minimal crustal ...contamination.•These rocks formed in a back-arc basin.
The central Liaodong Peninsula is located in the northwestern part of the Jiao-Liao-Ji Belt in the Eastern Block of the North China Craton. Surface rocks in this region are voluminous meta-mafic rocks, which mainly comprise amphibolite and metamorphic gabbro or diabase. We present zircon cathodoluminescence images, U–Pb dates, and Lu–Hf isotope data, as well as whole-rock geochemical data for these rocks, in order to constrain the tectonic nature and evolution of the Jiao-Liao-Ji Belt. Zircons from these meta-mafic rocks can be divided into two groups, with one having a typical magmatic origin and the other a metamorphic origin. Zircon U–Pb dating and Lu–Hf isotopic results show that the magmatic zircons have two peak ages at 2503 and 2154Ma, with the former have ɛHf=+7.1 to +8.1 and single-stage model ages (THf)=2.50–2.55Ga, indicating that these captured or inherited zircons formed at ca. 2.50Ga by partial melting of coeval juvenile crust. The younger magmatic zircons have ɛHf=+3.2 to +9.6, mainly varying from +7.4 to +9.6 (average=+8.7), and THf=2.15–2.34Ga (peak at 2.19Ga), suggesting that the meta-mafic rocks were emplaced at ca. 2.15Ga and derived by partial melting of depleted mantle. The metamorphic zircons yield a peak age of 1897Ma and have ɛHf=−4.5 to +6.8. These zircons can be further divided into three groups on the basis of Hf isotope data (i.e., ɛHf=−4.5 to −2.3, −0.6 to +1.0, and +3.1 to +6.8; THf=2.39–2.54, 2.26–2.39, and 2.03–2.11Ga, respectively), indicating they were derived by reworking of Neoarchean–Paleoproterozoic ancient crust and some Paleoproterozoic juvenile crust. Thus there existed two crustal growth events at 2.50 and 2.15Ga and one reworking event at ca. 1.90Ga in the Eastern Block. Geochemical data show that these meta-mafic rocks are characterized by: SiO2=47.3–49.8wt.%; TiO2=0.97–1.59wt.%;K2O=0.39–1.95wt.%; Na2O/K2O=1.03–4.85; Mg#=39–52; Cr=29–247ppm; and Ni=24.4–73.4ppm. These features, combined with low total rare earth element concentrations (ΣREE), relative enrichment in light REE, significant positive Rb, Ba, K, and P anomalies, and depletions in high-field strength elements (e.g., Nb, Ta, and Ti), indicate derivation by partial melting of depleted lithospheric mantle that had been metasomatized by subduction-derived fluids, with little or no crustal contamination during magma ascent. Given our dating results and the regional geological framework, we propose that the subduction in the eastern Longgang Block took place at least in age of 2.15Ga, and that the meta-mafic rocks in the central Liaodong Peninsula may have formed in a back-arc basin. However, the tectonic location of this magmatic arc and its relationship with the Nangrim Block need to be further studied to confirm this hypothesis.
Small antibacterial effectors, including lysozymes, lectins, and antimicrobial peptides, are key regulators of intestinal immunity. However, whether there is coordination among them during regulation ...is an interesting, but largely unknown, issue. In the present study, we revealed that small effectors synergistically regulate peptidoglycan-derived intestinal immunity in the kuruma shrimp, Marsupenaeus japonicus. A C-type lysozyme (LysC) was screened as a responsive factor for the intestine-bacteria interaction. LysC functions to restrict intestinal bacteria, mainly by cleaving Photobacterium damselae peptidoglycan to generate muropeptides which are powerful stimulators that induce anti-lipopolysaccharides factor B1 (AlfB1), an effective bactericidal peptide. The muropeptides also induce a C-type lectin (Ctl24), which recognizes peptidoglycan and coats bacteria. By counteracting LysC-mediated muropeptide release and AlfB1's bactericidal activity, Ctl24 prevents the continuous elimination of intestinal bacteria. Therefore, this study demonstrates a mechanism by which small immune effectors coordinate to achieve intestinal homeostasis, and provides new insights into peptidoglycan-derived intestinal immunity in invertebrates.
He’s frequency–amplitude formulation and its modifications mainly depend upon the residual calculation. A suitable choice of a residual leads to an ideal result. This paper discusses some effective ...methods for the residual calculation, and a modification with a free parameter is suggested to effectively estimate the frequency of a nonlinear oscillator. Furthermore, an energy-based residual calculation is also suggested, which is deduced from a variational principle.
Ischemic stroke remains a serious threat to human life. Generation of neuronal and vascular cells is an endogenous regenerative mechanism in the adult brain, which may contribute to tissue repair ...after stroke. However, the regenerative activity is typically insufficient for significant therapeutic effects after brain injuries. Pyruvate kinase isoform M2 (PKM2) is a key regulator for energy metabolism. PKM2 also has nonmetabolic roles involving regulations of gene expression, cell proliferation, and migration in cancer cells as well as noncancerous cells. In a focal ischemic stroke mouse model, recombinant PKM2 (rPKM2) administration (160 ng/kg, intranasal delivery) at 1 h after stroke showed the significant effect of a reduced infarct volume of more the 60%. Delayed treatment of rPKM2, however, lost the acute neuroprotective effect. We then tested a novel hypothesis that delayed treatment of PKM2 might show proregenerative effects for long-term functional recovery and this chronic action could be mediated by its downstream STAT3 signaling. rPKM2 (160 ng/kg) was delivered to the brain using noninvasive intranasal administration 24 h after the stroke and repeated every other day. Western blot analysis revealed that, 7 days after the stroke, the levels of PKM2 and phosphorylated STAT3 and the expression of angiogenic factors VEGF, Ang-1, and Tie-2 in the peri-infarct region were significantly increased in the rPKM2 treatment group compared with those of the stroke vehicle group. To label proliferating cells, 5-bromo-2′-deoxyuridine (BrdU, 50 mg/kg, i.p.) was injected every day starting 3 days after stroke. At 14 days after stroke, immunohistochemistry showed that rPKM2 increased cell homing of doublecortin (DCX)-positive neuroblasts to the ischemic cortex. In neural progenitor cell (NPC) cultures, rPKM2 (0.4–4 nM) increased the expression of integrin β1 and the activation/phosphorylation of focal adhesion kinase (FAK). A mediator role of FAK in PKM2-promoted cell migration was verified in FAK-knockout fibroblast cultures. In the peri-infarct region of the brain, increased numbers of Glut-1/BrdU and NeuN/BrdU double-positive cells indicated enhanced angiogenesis and neurogenesis, respectively, compared to stroke vehicle mice. Using Laser Doppler imaging, we observed better recovery of the local blood flow in the peri-infarct region of rPKM2-treated mice 14 days after stroke. Meanwhile, rPKM2 improved the sensorimotor functional recovery measured by the adhesive removal test. Inhibiting the STAT3 phosphorylation/activation by the STAT3 inhibitor, BP-1-102 (3 mg/kg/day, o.g.), abolished all beneficial effects of rPKM2 in the stroke mice. Taken together, this investigation provides the first evidence demonstrating that early treatment of rPKM2 shows an acute neuroprotective effect against ischemic brain damage, whereas delayed rPKM2 treatment promotes regenerative activities in the poststroke brain leading to better functional recovery. The underlying mechanism involves activation of the STAT3 and FAK signals in the poststroke brain.
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