Distance similarity matrix using ensemble of dimensional data reduction techniques: Vibration and aerocoustic case studies

Vibration and acoustic-based health-monitoring techniques are used in the literature to monitor structural health under dynamic environment. In this paper, we propose a damage detection and monitoring method based on a distance similarity matrix of dimensionally reduced data wherein redundancy therein is removed. The matrix similarity approach is generic in nature and has the capability of multiscale representation of datasets. To extract damage-sensitive features, dimensional reduction techniques are applied and compared. An ensemble method of dimensional reduction feature outputs is presented and applied to two case studies. The results supports why ensembles can often perform better than any single-feature extraction method. For the first case study, aeroacoustic datasets are collected from controlled scaled experimental tests of controlled known damaged subscale wing structure. For the second case study, a vibration experiment study is used for abrupt change detection and tracking. The results of the two case studies demonstrate that the proposed method is very effective in detecting abrupt changes and the ensemble method developed here can be used for deterioration tracking.     

Acrylic bone cements: Effects of the poly(methyl methacrylate) powder size and chitosan addition on their properties

The effect of the particle size of poly(methyl methacrylate) (PMMA) and the incorporation of chitosan (CH) on the mechanical and thermal properties and the biocompatibility of acrylic bone cements were investigated. Three groups of bone cements were prepared with different PMMA particles. Groups 1 (BC1) and 2 (BC2) contained ground and sieved PMMA with particle sizes in the ranges 50–150 μm and 1–50 μm, and group 3 (BC3) contained synthesized PMMA microspheres with a size of about 1 μm. The mechanical properties of the three groups were similar, but their curing properties were significantly affected. The presence of CH improved the mechanical and thermal properties. For the BC1 group, the compressive strength increased more than 10 MPa, and the curing temperature decreased 12°. The cement having the optimum properties (BC1) was applied to rats, where it enhanced the bone bonding ability, and bioactivity was observed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39662.     

Properties and phase segregation of crosslinked PCL‐based polyurethanes

Polyurethane (PU) films were prepared from different types of poly(ε‐caprolactone) glycols and hexamethylene diisocyanate without using any other ingredients such as solvent, catalyst, or chain extender. Polymers were stabilized by crosslinking formed as allophanate and/or biuret linkages during the curing process. The effects of different components on the product properties such as chemical structure, microphase segregation, mechanical strength, thermo‐mechanical, thermal properties, and surface hydrophilicities were investigated by FTIR‐ATR, atomic force microscope, mechanical tester, dynamic mechanical analyses, thermogravimetric analyzer, differential scanning calorimetry, and contact angle measurements. Phase separation of hard and soft segments significantly varied depending on the type and molecular weight of diol and triol. Films containing urethane‐urea bonds displayed the maximum phase separation and the highest mechanical strength. Polyols having higher molecular weight increased hydrophilicity while urea bonds caused a reverse effect resulted by bidentate hydrogen bonds. Results showed PUs with various properties can be synthesized via environmentally friendly process without using any solvent or catalyst. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39758.     

Analysis of ESCO activities using country indicators

Energy Service Companies (ESCOs) are private-sector instruments that offer energy-/emission-improvement (energy saving, energy efficiency, energy conservation and emission reduction) projects, or renewable-energy projects, in the developed and in some developing countries. There has been an increased interest for the provision of such energy services, driven by a restructuring of the gas and electricity sectors, and the push to mainstream sustainable forms of energy into the market. ESCOs are destined to deliver sustainable-energy solutions, especially in emerging markets. Literature reveals that energy/emission improvements of countries may be related to their innovation- and R&D-activity levels. In this work, we use a literature data on the activities and the sectors targeted by ESCOs in 38 countries, summarized in terms of the age of ESCO market (AEM), number of ESCO companies (NE), and total value of ESCO projects (VE). Along with the Global Innovation Index (GII) data of the countries, we investigate the relationships among the ESCO Indicators (EIs: AEM, NE, VE, sectors targeted by ESCOs), and the Country Indicators (CIs: GII and per-capita GDP, energy consumption, CO₂ emission). We observe noteworthy dependencies between the EIs and CIs. Using the simple trend equations we estimate the missing VEs in the original data. We also project, as a hint for the size and orientation of the upcoming Turkish ESCO market, the set of EIs and the distribution of the sectors that are likely to be targeted by ESCOs in Turkey.     

Preparation,modification, and characterization of acrylic cements

Acrylic cements with different compositions were prepared by mixing the solid part (composed of poly(methyl methacrylate), PMMA, and benzoyl peroxide, BPO) and the liquid part (composed of methyl methacrylate, MMA, and N,N‐dimethyl‐p‐toluidine, DMPT), modified by addition of hydroxyapatite (HA) and ammonium nitrate (AN) and characterized by measuring thermal and mechanical properties. Three sets of samples were prepared. For B‐group, the total amount of solid including HA was constant but the PMMA to HA ratio was varied. For C‐group, polymer/monomer ratio was constant and varying amounts of HA was added. For D‐group, polymer/monomer ratio was kept constant and AN was added in varying amounts. Effects of these composition changes on the properties of the cement such as setting time, curing temperature, tensile and compression strength, and deformation were examined. For B‐group samples, no linear change was observed in thermal (curing temperatures were all quite high) and mechanical (between 27 and 19 MPa for tensile, and 98 and 116 MPa for compression strength) properties upon change of HA content with change in solid/liquid ratio. For C and D‐group samples, a continuous decrease in curing temperature from 114 to 101°C and from 94 to 73°C was observed upon increasing HA and AN contents, respectively. Also, a linear relation was observed in compression strength (from 98 to 111 MPa) and in tensile strength (from 27 to 21 MPa) upon HA addition, and in the compression strength (from 103 to 85 MPa) and in the tensile strength (from 22 to 17 MPa) with NA addition. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3631–3637, 2006     

Agitation scale-up model for the suspension polymerization of vinyl chloride

Photodegradation and loss of UV stabilizer resulting from natural and accelerated exposure in stabilized linear low density polyethylene (LLDPE) are investigated by spectroscopic techniques. It is found that the processes governing the loss of UV stabilizer are quite different under the two modes of UV exposure. This result clearly demonstrates that predictions concerning polymer lifetime based on the disappearance of additives must be avoided. For a large number of stabilized samples, acceleration factors according to different criteria have been estimated. Examination of the natural photodegradation process of stabilized LLDPE through mechanical property changes establishes that stabilized LLDPE undergoes catastrophic breakdown of the elongation at break the instant the carbonyl IR band begins to develop.     

A New Approach for the Electrochemical Detection of Phenolic Compounds. Part I: Modification of Graphite Surface by Plasma Polymerization Technique and Characterization by Raman Spectroscopy

This paper describes the early stages of preparation of an electrochemical sensor for the detection of phenolic compounds. For this aim, graphite leads were modified by plasma polymerization (PlzP) technique utilizing the monomer N-vinylpyrrolidone (VP) with its conductive property as precursor. The influence of different experimental parameters such as plasma discharge power and exposure time was investigated to optimize the proposed electrode. After the modification process, graphite leads (electrodes) were investigated by differential pulse voltammetry. The voltammograms were recorded between 0 and +1.0 V at 16 mVs⁻¹. The surface characteristics of the PlzP-VP modified carbon lead surfaces were determined by Raman spectroscopy. It was clearly observed that VP monomer was polymerized to form polyvinylpyrrolidone that is a very well-known adsorbant for phenolics. As expected, it was clearly pointed out that the electrochemical conductivity of the modified carbon leads were varied due to adsorption of a model phenolic compound “gallic acid” at a certain concentration.     

Physical properties of parboiled wheat and bulgur produced using spouted bed and microwave assisted spouted bed drying

The main objective of this study was to compare the spouted bed and microwave assisted spouted bed drying on affecting physical properties of parboiled wheat and bulgur. Drying was performed at different temperatures (50 °C, 70 °C, 90 °C) and microwave powers (288 W, 624 W). Bulk and apparent density, bulk and apparent porosity, sphericity, color, microstructure and pore size distribution of parboiled wheat were investigated after drying. Yield and water absorption capacity were determined in bulgur samples. The effect of air temperature on physical properties of product except color was not significant in spouted bed drying. More porous structure was observed in wheat samples dried in microwave assisted spouted bed compared to air dried ones. Sphericity and bulk density were higher when high temperature was combined with high microwave power. In microwave assisted spouted bed drying, similar yield value but lower water absorption capacity of bulgur were observed as compared to spouted bed drying.     

Effects of ingredients on thermal and mechanical properties of acrylic bone cements

There is a very delicate relation between the amounts of all the ingredients present in the cement composition and the properties of the product. In this study, homogeneous poly(methyl methacrylate) (PMMA) microspheres were prepared by suspension polymerization technique, and used in cement formulations. Various acrylic cements with different compositions were prepared by using PMMA microspheres, methyl methacrylate (MMA) monomer, radiopaque agent of barium sulfate (BaSO₄), inorganic particles of hydroxyapatite (HA), initiator and chain stopping agent of 1‐dodecyl mercaptan (DDM). The effects of these additives on mechanical and thermal properties of the resultant cements were examined. Addition of 8% HA relative to the solid parts caused an increase in both tensile and compressive strengths from 20.40 to 25.20 MPa, and from 84.04 to 89.57 MPa, respectively, while curing temperature was decreased about 3 degrees. Chain stopping agent of DDM caused a sharp decrease about 30 degrees in the curing temperature. Radiopaque agent of barium sulfate caused inverse effect on mechanical and thermal properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009