Generalized hybrid control synthesis for affine systems using sequential adaptive networks

BACKGROUND: A generalized methodology for the synthesis of a hybrid controller for affine systems using sequential adaptive networks (SAN) is presented. SAN consists of an assembly of neural networks that are ordered in a chronological sequence, with one network assigned to each sampling interval. Using a suitable process model based on oxygen metabolism and an a priori objective function, a hybrid control law is derived that can use online measurements and the states predicted by SAN for computing the desired control action. RESULTS: The performance of the SAN–hybrid controller is tested for simulated fed‐batch production of methionine for three different process conditions. Simulations assume that online measurements of dissolved oxygen (DO) concentration are available. The performance of the SAN–hybrid controller gave an NRMSE of ～10^?4 in the absence of noise, ～10^?3 and ～10^?2 for ± 5% and ± 10% noise in the DO measurement and ～10^?2 for parameter uncertainty when compared with the ideal model prediction. CONCLUSIONS: The observed performance for unmeasured state prediction and control implementation shows that the proposed SAN–hybrid controller can efficiently compute the manipulated variable required to maintain methionine production along the optimized trajectory for different conditions. The test results show that the SAN–hybrid controller can be used for online real‐time implementation in fed‐batch bioprocesses. Copyright © 2009 Society of Chemical Industry     

Effect of Vertical Misfit on Screw Joint Stability of Implant-Supported Crowns

The passive fit between prosthesis and implant is a relevant factor for screw joint stability and treatment success. The aim of this study was to evaluate the influence of vertical misfit in abutment-implant interface on preload maintenance of retention screw of implant-supported crowns. The crowns were fabricated with different abutments and veneering materials and divided into 5 groups (n = 12): Gold UCLA abutments cast in gold alloy veneered with ceramic (Group I) and resin (Group II), UCLA abutments cast in titanium veneered with ceramic (Group III) and resin (Group IV), and zirconia abutments with ceramic veneering (Group V). The crowns were attached to implants by gold retention screws with 35-N cm insertion torque. Specimens were submitted to mechanical cycling up to 10⁶ cycles. Measurements of detorque and vertical misfit in abutment-implant interface were performed before and after mechanical cycling. ANOVA revealed statistically significant difference (P < 0.05) among groups for vertical misfit measured before and after mechanical cycling. The abutments cast in titanium exhibited the highest misfit values. Pearson correlation test did not demonstrate significant correlation (P > 0.05) between vertical misfit and detorque value. It was concluded that vertical misfit did not influence torque maintenance and the abutments cast in titanium exhibited the highest misfit values.     

District Metered Areas Design Under Different Decision Makers’ Options: Cost Analysis

Water loss is a big challenge for water supply companies worldwide, and the Water Network Partitioning (WNP) is an excellent tool for water loss management–particularly in the current difficult economic and financial conditions. WNP is a recent research line and consists in dividing the water distribution network into smaller zones called District Metered Areas (DMAs) with one (or more, in exceptional cases) supply point, to reduce the network complexity and/or allow pressure management. Since there are several possible future scenarios, such as the water demand and/or the infrastructure degradation forecasts, which may have different impacts on the hydraulic behaviour, in this paper a computational application, based on an optimization model, is proposed to achieve a compromise between robustness required for the DMAs design (using a baseline scenario) and different decision makers’ options (using other scenarios with a lower “probability” of occurrence), to reduce the total cost. The objective function reflects the minimization of the squared deviations between the total cost of the DMAs design and the minimum cost for each scenario forecasted for the project plan, multiplied by the weight or “probability” of occurrence for each of the scenarios. The performance of the computational application is illustrated with a case study, and the results are encouraging.     

Hydroxyapatite deposition study through polymeric process on commercially pure Ti surfaces modified by laser beam irradiation

Many techniques have been used to coat metallic substrate with bioceramics. The aim of this study was to study the physical-chemical characteristics of polyvinylidene fluoride (α-PVDF)/hydroxyapatite (HA) composite coating, obtained by casting method, on commercially pure titanium (α-CP Ti) substrate surface modified by laser beam irradiation. The preparation of coating was done for mixing α-PVDF pellets shape dissolved in dimethylacetamide (DMA) with HA/DMA emulsion. The mixture was poured onto the α-CP Ti sample and left to dry in an oven. CP Ti plates were coated with α-PVDF/HA composite film, in proportions of 100/00 and 60/40 in weight, and characterized by particle size analysis, scanning electron microscopy, energy dispersive spectroscopy (EDS), X-ray diffractometry, thickness measurement and contact angle. Uniform coating with a small thickness variation along the coated surface was successfully obtained.     

Stresses Analysis on a Rail Part

The EFVM （Vitoria Minas Railroad） is one of the main railways in Brazil. It transports freight trains of ore, 220 wagons each. These wagons have 2 boogies of 2 axles each and 32 metric tons on metre gauge. Elastic strains were measured on a special part of this railway due to these trains. The main load to evaluate stresses and strains was a G 16 Locomotive, a C-C kind from Vale, a Brazilian Company. The measurements were obtained by dynamic deflectometer installed on a main line of this railway, near Ipatinga, a city from Minas Gerais, one of Brazil states. This track was equipped to obtain stresses under an equal repeated static load A simulation of the stresses was made under critical strain by Ferrovia 1.0 software. It was also made an evaluation of unequal results from neighbor sleepers taking in comparison two equipped parts of this railway, one with compacted ballast and no compaction to the other. The results were strain limited, avoiding breakage or damage to the studied rails. This work analyses these measurements focusing on the improvement of track quality.     

The Difficulties of Designing Future Coastlines in the Face of Climate Change

This paper adopts two perspectives. The first is a framing process aimed at defining and examining the conditions for adopting adaptive coastal governance. The second applies to relevant themes of changing coastal policy, central to the testing of adaptive coastal governance, namely cooperative science, risk-sensitive planning, socially fair insurance cover and effective ways to design, finance and engage with local communities over actual coastal change. We illuminate both missions through case studies in North Norfolk (England) and Portugal, all notably affected by coastal change. In England and Portugal, there is a broad understanding and acceptance of the likely effects of climate change. This recognition encourages debates over risk-averse planning, the design of proactive insurance cover, creative relocation of endangered property and new ways of predicting and paying for coastal adjustment. Yet, moving from a basic willingness to engage with coastal change to actual practices of landscape adjustment through such policy shifts is proving very difficult. In this research, we find that coastal landscapes are lived experiences, resigned acceptances of inevitable change and hopeful imaginings. Coastal management institutions are not geared to resolving this incompatibility and this paper explains why.     

Effect of self-etching dual-curing universal adhesive system application on bond strength of dentin resinous liners dentin

Purpose: The aim of this study was to evaluate the influence of previous application of an adhesive system on bond strength of resinous liner materials to dentin. Methods: Ninety bovine incisors crowns had a 6 × 6 mm area of dentin exposed, with minimum of 2 mm thickness. They were embedded in acrylic resin, and the dentin was polished with P600 SiC sandpaper for 30 s to standardize the smear layer. The specimens were divided into 6 groups (n = 15) according to the application or not of a self-etching system (Futurabond U – Voco) and the type of resinous liner used: A+Ionoseal (adhesive and Ionoseal – Voco); Ionoseal (Ionoseal only); A+Vitrebond (adhesive and Vitrebond – 3M/ESPE); Vitrebond (Vitrebond only); A+Ionosit (adhesive and Ionosit – DMG) and Ionosit (Ionosit only). Adhesives were used following manufacturer’s instructions, and the liner materials were applied inside a 2-mm-depth matrix and light-cured for 20 s. The bond strength was measured by microtensile test, using a universal testing machine with a cross-speed of 1 mm/min. Data were analyzed using one-way ANOVA and Tukey’s test (p < 0.05). Results: The adhesive system application increased bond strength of all liners tested. Ionoseal presented the highest bond strength when the adhesive system was used and exhibited similar performance to Vitrebond without adhesive. Ionosit without adhesive showed the smallest bond strength compared with the other liners tested. Conclusion: The application of an adhesive system prior to the use of the resinous liners improved the bond strength to dentin and should be preconized.