Simultaneous stabilization of MIMO systems via robustly stabilizinga central plant

In this note, a new formulation and solution to the simultaneous stabilization problem (SSP) is given. The new method is based on finding a central plant from a set of plants to be simultaneously stabilized. The theory of robust stabilization can then be applied to the central plant with a bounded perturbation, which encapsulates the plants to be stabilized, in order to solve the SSP     

Responses of single and group piles within MSE walls under static and cyclic lateral loads

To investigate the behavior of piles and the performance of the mechanically stabilized earth (MSE) walls under static and cyclic lateral loading, six reduced-scale model tests of single and group piles within the MSE walls were conducted inside a test box. In the single pile tests, a hollow aluminum tube as a pile was placed at a distance of 2D or 4D (D is pile diameter) behind the wall facing, while in the group pile tests, the piles were only placed at the distance of 2D with a spacing of 3.3D between the piles. The piles were subjected to static lateral loading only and cyclic lateral loading followed by static loading until failure. The test results showed that the lateral load capacity of each pile in the group pile test was approximately 60% that of the single pile, while the wall facing displacements and the geogrid strains in the group pile test were larger than those in the single pile test. The lateral pile capacity, the wall facing displacement, the strain in the geogrid, and the lateral earth pressure behind the wall facing in the static and cyclic loading tests were evaluated at the pile head displacement equal to 20%D.     

Long-range dipole–dipole energy transfer enhancement via addition of SiO2/TiO2 nanocomposite in PFO/MEH-PPV hybrid thin films

Different weight ratios of poly(9,9-dioctylfluorene-2,7-diyl) (PFO)/poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) hybrid thin films, with and without a SiO₂/TiO₂ nanocomposite (NC), were successfully prepared using a solution blending method. All samples were deposited onto glass substrates by a spin coating technique to produce homogeneous thin films. The effect of the SiO₂/TiO₂ NC on the enhancement of the energy transfer mechanism in the PFO/MEH-PPV hybrids was investigated. The energy transfer parameters were calculated on the basis of the absorption and emission measurements. The long-range dipole–dipole energy transfer (Förster type) between the acceptor and donor molecules was enhanced in the presence of the SiO₂/TiO₂ NC in the hybrid thin films. The addition of the SiO₂/TiO₂ NC in the PFO/MEH-PPV hybrids reduced the distance between the donor and acceptor molecules more than the individual addition of SiO₂ or TiO₂ nanoparticles. Moreover, the direct relationships between the acceptor contents and energy transfer parameters, such as the energy transfer radius (R_DA), energy transfer efficiency (η), and energy transfer probability (P_DA), were estimated using theoretical fittings. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47845.     

Antioxidant and antimicrobial activities of the methanol extracts from pummelo (Citrus grandis Osbeck) fruit albedo tissues

The present study was conducted to evaluate the antioxidant and antimicrobial properties of methanol (100 and 80% aqueous) extracts of pummelo fruits albedo (Citrus grandis Osbeck). The antioxidant and antibacterial activity for crude extracts and isolated compounds were evaluated using free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH) and Paper disc diffusion method. A 100% Methanol (MeOH) extract was steeped in water at different pH levels and partitioned with ethyl acetate (EtOAc) to give basic, acidic, neutral, and phenolic fractions. The neutral extract was found to possess maximum antioxidant and antibacterial activity. Thereafter, neutral extract was carried out on a silica gel column and eluted with hexane:EtOAc:acetone and preparative TLC (PTLC) to give oil buntan compound, linoleic acid methyl ester, β-sitosterol, sigmasterol, limonin, nomilin and meranzin hydrate were isolated. While, 80% MeOH extract was fractionated also using a silica gel column and PTLC to give isomeranzin hydrate, p-coumaric acid and caffeic acid compound. The extract concentration providing 50% inhibition (IC₅₀) was as follows; oil buntan compound 95 μg/mL, caffeic acid 45 μg/mL, p-coumaric acid 105 μg/mL, limonin + nomilin (mixture) 135 μg/mL was lower than that of synthetic antioxidant butylated hydroxyanisole (BHA) 40 μg/mL. The inhibitory zone (mm) of bacteria tested was 2.9–4.1 mm caffeic acid and 11.6–15.1 mm p-coumaric acid.     

LQG control design over lossy communication links

This paper investigates the problem of linear-quadratic Gaussian feedback control over unreliable communication channels with observation noise. We consider the problems of estimation and control under two different protocols. In one protocol, the transfer control protocol-like protocol, the estimation/control unit provides acknowledgments to successfully deliver the packets. In the other protocol, the user datagram protocol (UDP)-like protocol, no acknowledgments are permitted. We address the nonlinearity for the UDP protocol using the suboptimal approach. It is shown that there is a critical value at which the system becomes unstable. These unstable properties do not only depend on the rates of the control packets but also on the eigenvalues for the considered system. Simulation of two numerical examples is carried out in detail to illustrate the theoretical analysis.     

Developing a successful SemEval task in sentiment analysis of Twitter and other social media texts

We present the development and evaluation of a semantic analysis task that lies at the intersection of two very trendy lines of research in contemporary computational linguistics: (1) sentiment analysis, and (2) natural language processing of social media text. The task was part of SemEval, the International Workshop on Semantic Evaluation, a semantic evaluation forum previously known as SensEval. The task ran in 2013 and 2014, attracting the highest number of participating teams at SemEval in both years, and there is an ongoing edition in 2015. The task included the creation of a large contextual and message-level polarity corpus consisting of tweets, SMS messages, LiveJournal messages, and a special test set of sarcastic tweets. The evaluation attracted 44 teams in 2013 and 46 in 2014, who used a variety of approaches. The best teams were able to outperform several baselines by sizable margins with improvement across the 2 years the task has been run. We hope that the long-lasting role of this task and the accompanying datasets will be to serve as a test bed for comparing different approaches, thus facilitating research.     

Thermal Stability and Mechanical Properties of Organo-Soluble and Processable Polyimides for High-Temperature Materials

A new series of organo-soluble polyimides with pendant groups of methoxy or methyl of azomethine diamine were synthesized through two-step process by chemical imidization. Such polyimides were tested for thermal and mechanical properties. Their thermal stability was studied in terms of temperature at 10% weight loss which ranged between 475 and 498°C with T_g around 240–278°C. Activation energy, enthalpy of the polyimides were calculated and ranged 31.12–43.59?kJmol^?1 and 29.46–41.93?kJmol^?1. Thermal, mechanical, and thermodynamic parameters demonstrated that the resulting polyimides can hold excellent application in the fields of high-performance, advanced composites, and high-temperature microelectronics.     

Performance evaluation of different types of ground source heat exchangers in a hot and dry climate

Most of the energy consumption in a hot and dry area is used for the air-conditioning systems. This study aims to investigate the possibility of reducing the electricity consumption in air conditioners using ground cold energy to cool the hot fluid in the pipes. Several experiments were carried out to investigate the performance of the proposed system to be used in the weather conditions of Baghdad city (i.e., hot and dry). Two configurations of ground source heat exchangers (GSHEs) were developed and constructed. The first configuration comprised coil type with two different materials (copper and polyvinyl chloride [PVC]). The second configuration was the 3U type, which was made from copper, PVC, and galvanized. Three water flow rates were considered (5, 10, and 15 L/min) with water inlet temperatures (80°C, 70°C, and 60°C). The experiments' results showed that the type of material of the pipe has a significant influence on both the heat transfer effectiveness and the system performance. Copper tubes were the best type of heat exchanger (type coil) to be used in this regard. The highest recorded values of the heat exchange rate were 5.81, 4.81, 2.72, 1.60, and 1.32 kW with an inlet temperature of 80°C and a flow rate of 5 L/min for the case of copper coil, copper 3U, galvanized 3U, PVC profile, and PVC 3U, respectively. These findings can be used as a guideline for future studies of GSHEs, particularly for the applications fixed in unsaturated soils.     

Photocatalytic generation of useful hydrocarbons and hydrogen from acetic acid in the presence of lanthanide modified TiO2

Pure and Ln³⁺ modified TiO₂ photocatalysts (Ln³⁺ = Eu³⁺ or Sm³⁺ ions) synthesized by a sol-gel method as well as commercially available P25 were applied for photocatalytic generation of useful hydrocarbons and hydrogen from acetic acid. Structure and surface properties of the photocatalysts were characterized by XRD, UV-vis/DR, FT-IR and N₂ adsorption-desorption measurements. The main gaseous products of CH₃COOH decomposition were CH₄ and CO₂. Trace amounts of C₂H₆ and H₂ were also detected in the reaction mixture. Moreover, it was observed that the quantities of all identified gases increased with elongation of irradiation time. The most active photocatalysts towards CH₄ and H₂ generation were Ln³⁺/TiO₂ containing 0.05 mol % of Sm and Eu, respectively. The results revealed that the Ln³⁺ modification can improve the effectiveness of the photocatalysts compared to pure and commercially available TiO₂ provided that a proper amount of modifying ions is used.     

Pareto lexicographic α-robust approach and its application in robust multi objective assembly line balancing problem

Robustness in most of the literature is associated with min-max or min-max regret criteria. However, these criteria of robustness are conservative and therefore recently new criteria called, lexicographic α-robust method has been introduced in literature which defines the robust solution as a set of solutions whose quality or jth largest cost is not worse than the best possible jth largest cost in all scenarios. These criteria might be significant for robust optimization of single objective optimization problems. However, in real optimization problems, two or more than two conflicting objectives are desired to optimize concurrently and solution of multi objective optimization problems exists in the form of a set of solutions called Pareto solutions and from these solutions it might be difficult to decide which Pareto solution can satisfy min-max, min-max regret or lexicographic α-robust criteria by considering multiple objectives simultaneously. Therefore, lexicographic α-robust method which is a recently introduced method in literature is extended in the current research for Pareto solutions. The proposed method called Pareto lexicographic α-robust approach can define Pareto lexicographic α-robust solutions from different scenarios by considering multiple objectives simultaneously. A simple example and an application of the proposed method on a simple problem of multi objective optimization of simple assembly line balancing problem with task time uncertainty is presented to get their robust solutions. The presented method can be significant to implement on different multi objective robust optimization problems containing uncertainty.