Event-triggered output-feedback tracking of a class of nonlinear systems with unknown time delays

A single function approximation (SFA) approach for event-triggered output-feedback tracker design is presented for uncertain nonlinear time-delay systems in lower-triangular form. Contrary to the existing event-triggered output-feedback control methods dependent on multiple function approximators in the presence of lower-triangular nonlinearities, the proposed SFA approach provides the following advantages: (i) the simple observer structure independent of function approximators; (ii) one event-triggering condition based on only a tracking error; and (iii) the simple control scheme using one function approximator. Thus, the structural simplicity is allowed for implementing the observer and the event-triggering law in the sensor part and the adaptive tracker in the control part. Under the proposed SFA-based event-triggered control scheme, it is shown that the boundedness of closed-loop signals and the existence of a minimum inter-event time are guaranteed regardless of unknown time-delay nonlinearities and unmeasurable state variables.

     

Analysis of earthy and musty odors in water samples by solid-phase microextraction coupled with gas chromatography/ion trap mass spectrometry

A method for the determination of the earthy and musty odors geosmin, 2-methylisoborneol (2-MIB), 2-isobutyl-3-methoxy pyrazine (IBMP), 2-isopropyl-3-methoxy pyrazine (IPMP) and 2,4,6-trichloroanisole (2,4,6-TCA) in water by headspace solid-phase microextraction (HSSPME) combined with gas chromatography-ion trap mass spectrometry (GC-ITMS) is described. Several parameters of the extraction and desorption procedure were studied and optimized (such as types of fibers, extraction temperature, extraction time, desorption temperature, desorption time, ionic strength and elutropic strength and pH of samples). The method shows good linearity over the concentration range 1-500 ng l⁻¹ and gives detection limits of sub-part per trillion levels for all compounds. Good precision (5.9-9.8%) is obtained using IBMP as internal standard. Finally, the method was successfully applied to analyze earthy and musty odors in tap water and lake water.     

处理污泥焦颗粒内部孔结构在燃烧过程中变化

在管式炉反应器中进行了1种污泥定温燃烧试验,进行了5个不同燃烬率样品的液氮静态容量法等温物理吸附试验.发现不同燃烬率的污泥样品孔分布特性相似,其孔系统可能主要是由一端封闭的不透气的孔构成;随着燃烬率的增加,比表面积、平均孔径和孔体积等参数变化不同;样品颗粒内孔表面分形维数随燃烬率的增长呈先降低再升高的趋势.     

Search for pi(0)-->nu(mu)nu(mu) decays in the LSND detector

We observe a net beam excess of 8.7+/-6.3(stat)+/-2.4(syst) events, above 160 MeV, resulting from the charged-current reaction of nu(micro) and/or nu;(mu) on C and H in the LSND detector. No beam-related muon background is expected in this energy regime. Within an analysis framework of pi(0)-->nu(mu)nu;(mu), we set a direct upper limit for this branching ratio of Gamma(pi(0)-->nu(mu)nu;(mu))/Gamma(pi(0)-->all)<1.6 x 10(-6) at 90% confidence level.     

The charge structure and interaction mechanism on In-doped sulphur spinel

The charge structure and interaction mechanism on In-doped sulphur spinel FeIn_xCr_2−xS₄ are studied. The temperature dependence of magnetization μ_B, measured from 60 K to room temperature, suggests that FeIn_xCr_2−xS₄ (x=0.1$x=0.1$, 0.3) are ferrimagnetic. The Néel temperature is decreased with increasing non-magnetic In substitution as consequence of reduction of superexchange interaction for increased lattice parameter. FeIn_xCr_2−xS₄ is investigated by Mössbauer spectra from 4.2 K to room temperature. The asymmetric line broadening is observed for the sample FeIn_xCr_2−xS₄ and considered to be dynamic Jahn–Teller relaxation. The charge state of Fe ions is ferrous in character.     

Control of resonant peak depths of tunable long-period fiber gratings using overcoupling

We present a method to reduce changes in the resonant peak depth of a long-period fiber grating (LPFG) as the resonant band is tuned by varying the external refractive index. We theoretically analyze the effects of the initial coupling strength on the peak depth change as external refractive index is varied. By controlling the initial coupling strength, it is experimentally demonstrated that an optimum peak depth can be obtained over a range of operating wavelengths that will maximize the sensitivity and stability of LPFG based sensors and tunable filters.     

Insights into unusual stability of 5‐membered‐ring endocyclic benzyl carbocations in aqueous solution

The acyclic o‐oxygen benzyl carbocation 1 , the 6‐membered‐ring endocyclic o‐oxygen benzyl carbocation 2 , and the 5‐membered‐ring endocyclic o‐oxygen benzyl carbocation 3 were used as model compounds to get insights into the general phenomenon for the unusual stability of the 5‐membered‐ring endocyclic benzyl carbocations in aqueous solution. The hydride‐ion affinities of 1 , 2 , and 3 in gas phase, acetonitrile, and DMSO were calculated and compared by the density functional theory method, and 3 isodesmic reactions were designed to confirm their thermodynamic stability. What we found is that the 5‐membered‐ring endocyclic o‐oxygen stabilizes the benzyl carbocation 3 less than the acyclic o‐oxygen stabilizes the benzyl carbocation 1 in gas phase because of ring strain and through‐bond induction. However, the high solvation energies of the 5‐membered‐ring endocyclic o‐oxygen benzyl carbocation 3 not only offset the destabilizing effects of ring strain and through‐bond induction but also make it even more stable than the acyclic o‐oxygen benzyl carbocation 1 in polar solvents like acetonitrile, DMSO, and water.