On the existence of finite state supervisors for arbitrarysupervisory control problems

Given two prefix closed languages K, L ⊆ Σ*, where K ⊆ L represents the desired closed-loop behavior and L is the open-loop behavior, there exists a finite-state supervisor that enforces K in the closed loop if and only if there is a regular, prefix-closed language M ⊆ Σ*, such that: 1) MΣ_u∪L⊆M, and 2) M∪L=K. In this paper, we show that this is equivalent to: 1) the controllability of sup{P⊆K∪L¯|pr(P)=P} with respect to Σ*; and 2) the regularity of sup{P⊆K∪L¯|pr(P)=P}, where L¯=Σ*-L:and pr(·) is the set of prefixes of strings in the language argument. We use this property to investigate the issue of deciding the existence of a finite-state supervisor for different representations. We also present some properties of the language sup{P⊆K∪L¯|pr(P)=P}, along with implications to the synthesis of solutions to the supervisory control problem with the fewest states     

Impact of low lignin containing brown midrib sorghum mutants to harness biohydrogen production using mixed anaerobic consortia

Three low lignin containing bmr 3 derivatives, namely DRT 07K1, DRT 07K6 and DRT 07K15 developed through backcrossing were used along with the parent, bmr 3 source mutant (IS 21888) for evaluation of biohydrogen production. Results demonstrated that biohydrogen production varied amongst bmr derivatives under similar fermentation conditions. Significant negative correlation was observed between lignin content and fermentative biohydrogen production. All bmr derivatives with lower lignin content produced higher levels of biohydrogen compared to source bmr 3 (IS 21888) which has more lignin content. The maximum and a minimum biohydrogen production observed was 72 and 50 ml/g Total Volatile Solids (TVS) for the DRT 07K6 bmr3 derivative and bmr 3 (IS 21888) respectively. Acetate and butyrate were accounted >85% of volatile fatty acids, indicating acid type fermentations. Statistical analysis revealed that all bmr mutant derivatives with respect to source differ significantly in cumulative biohydrogen production, plant height, grain yield and lignin content. Biohydrogen production from biomass associated at least two different levels, one at lignin entanglement another at the polymeric nature of cellulose and hemicellulose. Further studies are necessary to determine the effect of biomass structure associated with different bmr traits on the microbial growth and biohydrogen production rate.     

Structure, dielectric, ferroelectric, and energy density properties of (1 − x)BZT–xBCT ceramic capacitors for energy storage applications

We investigate the dielectric, ferroelectric, and energy density properties of Pb-free (1 ? x)BZT–xBCT ceramic capacitors at higher sintering temperature (1600 °C). A significant increase in the dielectric constant, with relatively low loss was observed for the investigated {Ba(Zr_0.2Ti_0.8)O₃}_(1?x ){(Ba_0.7Ca_0.3)TiO₃} _x (x = 0.10, 0.15, 0.20) ceramics; however, electric breakdown was low (~140, 170, 134 kV/cm), and of which room temperature (300 K) charging curve energy density values are largest ~0.88, 0.94, and 0.87 J/cm³ with maximum high dielectric constant values ~7800, 8400, and 5200, respectively. Bulk ceramic BZT–BCT materials have shown interesting energy densities with good energy storage efficiency (~72 %) at high sintering temperature; they might be one of the strong candidates for high energy density capacitor applications in an environmentally protective atmosphere.     

Switchable Faraday shielding with application to reducing the pain of internal cardiac defibrillation while permitting external defibrillation

Switchable Faraday shielding is desirable in situations where electric field shielding is required at certain times and undesirable at other times. In this study, electrostatic finite element modeling was used to assess the effect of different shield geometries on the leakage of an internally applied field and penetration of an externally applied field. "Switching OFF" the shield by electrically disconnecting shield faces from each other was shown to significantly increase external field penetration. Applying this model to defibrillation, we looked at the effect of spacing and size of shield panels to maximize the ability to deliver an external defibrillation shock to the heart when shield panels are disconnected while providing acceptably low leakage of internal defibrillation shocks to avoid painful skeletal muscle capture when shield panels are connected. This analysis may be useful for designing internal defibrillator electrodes that preserve the efficacy of internal and external defibrillation while avoiding the significant morbidity associated with painful defibrillator shocks. Similar analysis could also guide optimizing the switchable Faraday shielding concept for other applications.     

Integral Abutment Bridges: Current Practice in United States and Canada

Integral abutment bridges have been gaining popularity among bridge owners as cost-effective alternatives to bridges with conventional joints. They reduce initial construction costs and long-term maintenance expenses, improve seismic resistance, and extend long-term serviceability. New York has been building them since the late 1970s, with a wide variety of details, and they have been performing well. For further improvement of New York's design practice, a comparative survey was undertaken across North America, focusing on design and construction of both substructures and superstructures. In all, 39 states and Canadian provinces responded, including 8 who said they had no experience with these bridges. Responses are analyzed and summarized in this paper. Overall, integral abutment bridges are performing as well as, if not better than, conventional bridges, but no uniform national standards exist for their design. Design practices and assumptions concerning limits of thermal movement, soil pressure, and pile design vary considerably among responding agencies. These decisions are based largely on past experience. Validity of these assumptions needs investigation by testing and analysis to ensure efficient and reliable design.     

Biohydrogen production from renewable agri-waste blend: Optimization using mixer design

Biohydrogen from untreated mixed renewable agri-waste using buffalo dung compost is reported. Corn husk (CH) supported 25% higher hydrogen (H₂) production and showed the maximum value (62.38%) with p value (1.2 × 10⁻⁶) revealing its significance at individual and interactive level, respectively, compared to ground nut shell (GNS) and rice husk (RH). Augmented-simplex-lattice design experimentation revealed that a partial supplementation of RH or GNS to CH improves H₂ yield. Multiple-linear-regression analysis indicated that a quadratic model (low p = 0.0023, high F value = 35.99 and R²_quadratic = 0.99) was more significant compared to other (linear, cubic and special cubic) models. Acetate and butyrate were accounted >80% of the volatile fatty acids (VFAs). A maximum accumulation of 65.78 ml H₂ g⁻¹ TVS was produced using agri-wastes in the ratio of CH:RH:GNS = 70:16:12.     

Delineation of salt-affected soils and waterlogged areas in the Indo-Gangetic plains using IRS-1C LISS-III data

Waterlogging and subsequent salinization and/alkalinization is the major land degradation problem in irrigated commands in the arid and semi-arid regions. The Linear Imaging Self-scanning Sensor (LISS-III) digital data acquired by the Indian Remote Sensing Satellite (IRS-1C) over part of the Indo-gangetic plains are digitally analysed for delineating salt-affected and waterlogged areas on a IBM RS-6000 system. A comparison with the IRS-1B LISS-II data, with comparable spectral bands and acquired very close to LISS-III data, reveals a relatively poor overall classification accuracy achieved from this data as compared to LISS-II data. This may be attributed to higher intra-class spectral variations resulting from high spatial resolution LISS-III data. The classifiers capable of exploiting the spectral variations in spatial domain, like segmentation, textural analysis, etc., need to be used for exploiting the full potential of IRS-1C LISS-III data for mapping salt-affected soils and other degraded lands.     

Effect of Zr on dielectric, ferroelectric and impedance properties of BaTiO3 ceramic

A polycrystalline sample of Zr-doped barium titanate (BaTiO₃) was prepared by conventional solid state reaction method. The effect of Zr (0·15) on the structural and microstructural properties of BaTiO₃ was investigated by XRD and SEM. The electrical properties (dielectric, ferroelectric and impedance spectroscopy) were measured in wide range of frequency and temperature. With substitutions of Zr, the structure of BaTiO₃ changes from tetragonal to rhombohedral. Lattice parameters were found to increase with substitution. The room temperature dielectric constant increases from ～ 1675 to ～ 10586 and peak dielectric constant value increases from ～ 13626 to ～ 21023 with diffuse phase transition. Impedance spectroscopy reveals the formation of grain and grain boundary in the material and found to decrease with increase in temperature.     

On the existence of supervisory policies that enforce liveness indiscrete-event dynamic systems modeled by controlled Petri nets

We consider discrete-state plants represented by controlled Petri nets (CtlPNs), where a subset of transitions can be prevented from firing by a supervisor. A transition in a CtlPN can fire at a marking if there are sufficient tokens in its input places and it is permitted to fire by the supervisor. A CtlPN is live if it is possible to fire any transition from every marking that is reachable under supervision. In this paper we derive a necessary and sufficient condition for the existence of a supervisory policy that enforces liveness in CtlPNs. We show this condition cannot be tested for an arbitrary CtlPN. However, for bounded CtlPNs or CtlPNs, where each transition is individually controllable, we show the existence of a supervisory policy which enforces that liveness is decidable. We also show the existence of a supervisory policy that enforces liveness is necessary and sufficient for the existence of a minimally restrictive supervisory policy     

On commoner's liveness theorem and supervisory policies that enforce liveness in free-choice Petri nets

A Petri net (PN) (Peterson, 1981; Reisig, 1985) is said to be live if it is possible to fire any transition from every reachable marking, although not necessarily immediately. A free-choice Petri net FCPN) is a PN, where every arch from a place to a transition is either the unique output arc from that place or it is the unique input arc to the transition. Commoner's Liveness Theorem (cf. Hack, 1972, Ch. 4; Reisig, 1985, Section 7.2) states that a FCPN is live if and only if every siphon contains a marked trap at the initial marking. A siphon (trap) is a collection of places P such that . We concern ourselves with marking-dependent supervisory policies that can prevent the firing of a transition. We characterize supervisory policies that enforce liveness in non-live FCPNs using observations that strongly parallel Commoner's Liveness Theorem. We use this characterization to establish the existence of supervisory policies that enforce liveness in a Class of FCPNs called independent, increasing free-choice petri nets (II-FCPNs).