Hybrid explicit model predictive control of a nonlinear process approximated with a piecewise affine model

The recently developed methods of explicit (multi-parametric) model predictive control (e-MPC) for hybrid systems provide an interesting opportunity for solving a class of nonlinear control problems. With this approach, the nonlinear process is approximated by a piecewise affine (PWA) hybrid model containing a set of local linear dynamics. Compared to linear-model-based MPC, a performance improvement is expected with the reduction of the plant-to-model mismatch; however at a cost of controller computation complexity. In order to reduce the computational load, so that desired horizon lengths may be used, we present an efficient sub-optimal solution. The feasibility of the approach for the application was evaluated in an experimental case study, where an output feedback, offset-free-tracking hybrid e-MPC controller was considered as a replacement for a PID-controller-based scheme for the control of the pressure in a wire-annealing machine.     

Effect of electron density on the catalysts for copolymerization of propylene oxide and CO<Subscript>2</Subscript>

Copolymerization of propylene oxide and carbon dioxide (CO₂) has been studied using different R-salophenCoOBzF₅ (OBzF₅ = pentaflorobenzoate, R = CH₃, H, Cl, Cl₂) based catalysts. The central moiety of the catalysts R-salophenCoOBzF₅ has been kept the same and effect of the catalyst electron density on the copolymerization reaction has been studied. It has been observed that introduction of an electron withdrawing group (like Cl, Cl₂) on the o-phenylenediamine backbone moiety of the catalyst makes it more selective for poly(propylene carbonate) synthesis. On the other hand, introduction of an electron donating group (like CH₃) makes the catalyst selective for cyclic carbonate conversion. The effect of different type of co-catalysts has also been investigated using tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, [PPN]⁺Cl^? ([PPN]⁺ = bis(triphenylphosphine)iminium), DMAP and tetrabutyl ammonium bromide.     

Electrocaloric properties of 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 ceramics with different grain sizes

We have investigated the electrocaloric (EC) properties of the ceramic 0.7Pb(Mg_1/3Nb_2/3)O₃–0.3PbTiO₃. A variety of samples with different median grain sizes, i.e., 1.0, 2.2 and 4.0?μm, and relative densities of about 96% were prepared using atmospheric sintering at 1200^oC for 2, 8 and 16?h. The ceramic material with a median grain size of 2.2?μm exhibited the highest value for the EC temperature change, i.e., 1.27?K at 60?kV?cm^?1, measured with a high-resolution calorimeter. This value is 25 and 19% higher than the value for the ceramics with the finer and the coarser grains, respectively.     

Liquid–Liquid Equilibrium Constant for Acetic Acid in an Epoxidized Soybean Oil–Acetic Acid–Water System

Dependency of the liquid–liquid equilibrium constant for acetic acid (A) in a system of epoxidized soybean oil–acetic acid–water from temperature and composition was experimentally determined. To estimate the liquid–liquid equilibrium constant for acetic acid (K _A), the interaction parameters of the Wilson, NRTL (non-random two liquid) and UNIQUAC (universal quasi chemical) models for the activity coefficient were calculated by fitting the experimental values of the equilibrium constant for acetic acid. The Marquardt method was used to fit the data. In spite of all applied simplifications, small deviations of the calculated values from those experimentally determined indicate the adequacy of all three models for the prediction of the liquid–liquid equilibrium constant for acetic acid. Comparison of the experimentally determined values of the equilibrium constant for acetic acid in the investigated system with those reported in the literature for the system with soybean oil, shows that the value of the liquid–liquid equilibrium constant for acetic aid in the system of epoxidized soybean oil–acetic acid–water is about 1.5 times higher than in the system of soybean oil–acetic acid–water for the same temperature and similar composition. For the investigated conditions, the influence of the changing of the oil phase composition on the equilibrium constant for acetic acid is more prominent than the influence of the temperature or the total acetic acid content in the system.     

Analysis of attainable reactor performance for the oxidative methane coupling process

In this work, a comparative analysis of attainable performance is presented for three different reactor structures including a fixed-bed reactor, and two different feeding structures of packed bed membrane reactors. For this purpose, three types of kinetic models, namely La₂O₃/CaO, Mn/Na₂WO₄/SiO₂, and PbO/Al₂O₃ have been used under a wide range of operating conditions. Thus, the effect of several variables such as operating temperature, membrane thickness, methane-to-oxygen ratio, feed flow rate, gas streams composition, and reactor length are investigated.Moreover, kinetic-analysis based on a proposed graphical approach enables determination of the suitable operational condition range and allows analysis of the feasible and optimal performance that corresponds to the effect of several dependent operating variables. The results show that tracking the optimum area of operation has a monotonic direction under some range of operating conditions, while it reflects qualitative trade-offs under some other ranges of operating conditions. For all investigated reactor concepts and catalysts, optimal operating conditions and the best corresponding performance are presented.     

AgBrI超细颗粒乳剂的电性能和感光性能

７０年代,人们对纳米粒子的“量子尺寸效应”和它的介观相特性进行了初步的研究．近２０年来,这一领域得到了迅速的发展．它们的发展在很大程度上推动了照相化学的发展,对揭示照相过程中潜影银簇、显影银丝等和超细粒子有关的特殊现象的本质及机理有着不可低估的作用．...     

Development and application of a simultaneous measurement method for gaseous ammonia and particulate ammonium in ambient air

Ammonia gas is one of the precursors contributing to the formation of secondary particulate ammonium via reactions with atmospheric acids, such as sulfuric and/or nitric acids, which are present in ambient air. In this study, a new instrument that is suitable for measuring ammonia gas and fine particulate ammonium (PM_2.5 NH₄⁺) concentrations simultaneously under ambient conditions was developed. A wetted frit sampler was connected in the back of a counter-current flow tube (CCFT) sampler, and the NH₃ gas and PM_2.5 NH₄⁺ samples were collected by CCFT and wetted frit samplers, respectively. An air sample was drawn through the samplers at a flow rate of 1.0 dm³ min^?1 and an absorption water flow rate of 120 mm³ min^?1. Then, the ammonium that formed in the absorption solution was detected by the indophenol method using a continuous flow analysis system. The estimated detection limits were 43 and 49 ng m^?3 for ammonia gas and PM_2.5 NH₄⁺, respectively. Notably, the ammonia gas was collected on the CCFT sampler with a collection efficiency of 98.5%, but most of the PM_2.5 NH₄⁺ passed through it and was captured on the wetted frit sampler with a collection efficiency of approximately 100%. The present method was applied to measure NH₃ gas and PM_2.5 NH₄⁺ at two urban sites: Osaka, Japan and Ho Chi Minh City, Vietnam. It was found that the simultaneous measurement method performed very well and that the measured concentrations were comparable with those obtained with the annular denuder method.

Copyright © 2016 American Association for Aerosol Research     

The synthesis and microwave dielectric properties of Mg3B2O6 and Mg2B2O5 ceramics

Single-phase Mg₃B₂O₆ and Mg₂B₂O₅ ceramics were synthesized and then structurally and dielectrically characterized. The highest Qxf value of 230,900 GHz was obtained for a Mg₃B₂O₆ ceramic with a density of 97% and 1000-μm grains. Considerably lower Qxf values (10,000–32,000 GHz) were determined for the Mg₂B₂O₅ ceramic. Mg₃B₂O₆ and Mg₂B₂O₅ exhibited permittivities (?) of 7.2 and 6.2–7.0, respectively. Both ceramics showed negative temperature coefficients of resonant frequency (τ_f) of ?18 to ?45 ppm/°C.     

Hydrogenation of phenylacetylene and 3-phenylpropyne using Rh(diene) complexes under homogeneous and heterogeneous conditions

Hydrogenation of phenylacetylene (PA) and 3-phenylpropyne (PP) was carried out using [Rh(diene)Cl]₂ complexes (diene is hexadiene (HD), cycloocta-1,5-diene (COD), norborna-2,5-diene (NBD)) in their immobilized forms and compared with hydrogenation in homogeneous arrangement. Immobilization brings significant increase of the catalytic activity and product selectivity in the step-wise hydrogenation to corresponding vinyl-resp. allyl-benzenes. Diene-ligand effect was apparent in PA hydrogenation; the product selectivity decreased in order Rh(HD) > Rh(NBD) > Rh(COD) and catalytic activity decreased in order Rh(HD) > Rh(COD) > Rh(NBD).     

Synthesis of carbon-rich hafnia thin films by pulsed laser deposition

Carbon-rich ceramics are an emerging class of materials with attractive high-temperature properties, including resistance to crystallization, dense microstructure, and low porosity. We explored direct synthesis of carbon-rich hafnia, which is known to form as a compact interlayer in the oxide scales of oxidized hafnium carbide. The material was synthesized by pulsed laser deposition, using pure HfO₂ targets in C₂H₂ background gas at low pressures. Stable films up to 700 nm thick and with high molar fractions (～0.1–0.45) of carbon were obtained. The predominant chemical bonding of Hf and O atoms is that of oxygen-deficient HfO₂, while carbon is present in elemental or hydrogenated forms. Annealing at 600 °C leads to loss of most of the hydrogen from the films, which is accompanied by enhanced sp² bonding of carbon. The films have amorphous, compact, and finely grained microstructure. Carbon molar fractions higher than ～0.2 inhibit microcrystallinity to at least 600 °C.