Block copolymers of acrylonitrile and poly(dimethylsiloxane)s

The chemical redox system of ceric ammonium nitrate(Ce⁴⁺) and poly(dimethylsiloxane)s (PDMS) with monohydroxy (MH), dihydroxy (DH), and diamine(DA) chain ends was used to polymerize acrylonitrile (AN) to produce monohydroxy poly(dimethylsiloxane)s‐b‐polyacrylonitrile (MH.PDMS‐b‐PAN), dihydroxy poly(dimethylsiloxane)s‐b‐polyacrylonitrile (DH.PDMS‐b‐PAN), and α, ω‐diamine poly(dimethylsiloxane)s‐b‐polyacrylonitrile (DA.PDMS‐b‐PAN) block copolymers. The concentration, reaction time, and the type of poly(dimethylsiloxane) affect the yield and the molecular weight of the copolymers. The ratio of AN/ceric salt/PDMS has remarkably affects the properties of formed copolymers. DH.PDMS‐b‐PAN copolymers were also prepared by electroinduced polymerization in the presence of catalytic amount of Ce⁴⁺ in a divided electrochemical cell where Ce³⁺ is readily oxidized into Ce⁴⁺ at the anode. The products were characterized by Fourier transform infrared spectroscopy, ¹H‐NMR spectroscopy, DSC, and their surface properties were investigated through contact‐angle measurements. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Miscibility studies on poly(ethylene glycol)/dextran blends in aqueous solutions by dilute solution viscometry

Miscibility of poly(ethylene glycol) (PEG) with dextran (Dx) was investigated by dilute solution viscometry. Dilute solution viscosity measurements were made on ternary systems, polymer (1)/polymer (2)/solvent (H₂O), for four different average molecular weights of PEG and Dx. The intrinsic viscosity and viscometric interaction parameters were experimentally measured for the binary (solvent/polymer) as well as for the ternary systems by classical Huggins equation. Degree of miscibility of these polymer systems was estimated on the basis of the four following criteria: (1) the sign of the Δk_AB, (2) the sign of α, (3) the sign of ΔB, and (4) the sign of the μ. Based on the sign convention involved in these criteria, immiscibility was observed in most systems. The miscibility of all these systems in accordance with the interactions between the unlike polymer chains rather the polymer–solvent interactions were investigated depending on molecular weight of polymer sample. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 453–460, 2004     

USG辅助下的棉条质量监控与改进

探讨USG辅助下的棉条质量监控与改进。针对纺纱企业依靠数量相对较少的末道并条机集中加工纤维的特点,提出末道并条是改进棉条质量变异和进行质量控制的关键部位。通过引入Uster Sliver Guard,论述了该系统在末并工序进行自调匀整和棉条质量监控的重要性,并试验性地证明了使用该系统可以显著减少棉条长片段不匀及粗节,实现更可靠的纺纱质量控制。     

Photovoltaic and photophysical properties of a novel bis-3-hexylthiophene substituted quinoxaline derivative

We report on the photophysical properties and photovoltaic performance of a polythiophene derivative, poly-2,3-bis(4-tert-butylphenyl)-5,8-bis(4-hexylthiophen-2-yl)quinoxaline (PHTQ) as an electron donor in bulk heterojunction solar cells blended with the acceptor 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-methanofullerene (PCBM). Devices were composed of PHTQ and varying amounts of PCBM (1:1, 1:2, 1:3, 1:4 w-w ratio). The components were spin cast from ortho-dichlorobenzene (ODCB) and characterized by measuring current–voltage characteristics under simulated AM 1.5 conditions. Efficiencies up to 0.3% have been reached. Incident photon to current efficiency (IPCE) is reported and the nanoscale morphology was investigated with atomic force microscopy (AFM). Photoinduced absorption spectroscopy confirms the photoinduced charge transfer in such donor acceptor blends.     

An emphasis on dynamic mechanical properties of novel stilbene containing copolymer/organo-MMT nanocomposites fabricated via in situ interlamellar copolymerization

The objective of the present study is to synthesis and characterize the novel functional stilbene containing copolymer-clay nanocomposites, make clear the influence of organo-clay on peculiarities of the nanocomposites and emphasis on the dynamic mechanical properties. For this purpose, poly(acrylamide-co-trans-stilbene)-organo-MMT [poly(AAm-co-Stb)-O-MMT] nanocomposites were synthesized by in situ interlamellar solution copolymerization with organically modified montmorillonite (O-MMT) clay due to its superior properties gives to copolymer. The effect of different amounts of O-MMT clay incorporation to the nanocomposite structure and properties of copolymer/O-MMT clay nanocomposites were characterized by X-ray diffraction (XRD), Attenuated Total Reflectance-Fourier Transform Infrared, Thermogravimetric Analysis, Differential Scanning Calorimeter, Dynamic mechanic analysis (DMA) methods. XRD analysis showed the basal spacing of the O-MMT increased in nanocomposites and this indicated that the intercalation of the copolymer chain into the O-MMT interlayer performed and nanocomposites were obtained successfully. Additionally, copolymer/O-MMT nanocomposites exhibited improved thermal properties at higher temperatures than the pristine copolymer. DMA results enlightened the viscoelastic properties of synthesized materials. DMA results indicated that obtained nanocomposites have higher mechanical strength because of the interaction/compatibility in between copolymer chains and O-MMT. In the light of these results, this work has introduced new perspectives on design, fabrication and viscoelastic properties of certain organo-clay copolymer nanocomposites for the synthesis of new materials and potential industrial applications.     

PM2.5 concentration prediction using hidden semi-Markov model-based times series data mining

In this paper, a novel framework and methodology based on hidden semi-Markov models (HSMMs) for high PM_2.5 concentration value prediction is presented. Due to lack of explicit time structure and its short-term memory of past history, a standard hidden Markov model (HMM) has limited power in modeling the temporal structures of the prediction problems. To overcome the limitations of HMMs in prediction, we develop the HSMMs by adding the temporal structures into the HMMs and use them to predict the concentration levels of PM_2.5. As a model-driven statistical learning method, HSMM assumes that both data and a mathematical model are available. In contrast to other data-driven statistical prediction models such as neural networks, a mathematical functional mapping between the parameters and the selected input variables can be established in HSMMs. In the proposed framework, states of HSMMs are used to represent the PM_2.5 concentration levels. The model parameters are estimated through modified forward–backward training algorithm. The re-estimation formulae for model parameters are derived. The trained HSMMs can be used to predict high PM_2.5 concentration levels. The validation of the proposed framework and methodology is carried out in real world applications: prediction of high PM_2.5 concentrations at O’Hare airport in Chicago. The results show that the HSMMs provide accurate predictions of high PM_2.5 concentration levels for the next 24 h.     

Quasi-solid-state dye-sensitized solar cells with cyanoacrylate as electrolyte matrix

A quasi-solid-state dye-sensitized solar cells (DSSCs) employing a commercial glue (“SuperGlue^®”) as electrolyte matrix was fabricated. The cyano groups of the cyanoacrylate can form a supramolecular complex with tetrapropylammonium cations. This immobilizes the cations and therefore might lead to a favored anionic charge transport necessary for a good performance of the iodide/triiodide electrolytic conductor. Obtaining energy conversion efficiencies of more than 4% under 100 mW/cm² of simulated A.M. 1.5 illumination, the cyanoacrylate quasi-solid-state electrolyte is an ordinary and low-cost compound which has fast drying property and offers significant advantages in the fabrication of solar cells and modules as it is in itself is a very good laminating agent. The influences of different porous layer thicknesses of titanium oxide and various kinds of cations on DSSC performance and long-term stability are presented.     

A decomposition analysis of CO2 emissions from energy use: Turkish case

Environmental problems, especially “climate change” due to significant increase in anthropogenic greenhouse gases, have been on the agenda since 1980s. Among the greenhouse gases, carbon dioxide (CO₂) is the most important one and is responsible for more than 60% of the greenhouse effect. The objective of this study is to identify the factors that contribute to changes in CO₂ emissions for the Turkish economy by utilizing Log Mean Divisia Index (LMDI) method developed by Ang (2005) [Ang, B.W., 2005. The LMDI approach to decomposition analysis: a practical guide. Energy Policy 33, 867–871]. Turkish economy is divided into three aggregated sectors, namely agriculture, industry and services, and energy sources used by these sectors are aggregated into four groups: solid fuels, petroleum, natural gas and electricity. This study covers the period 1970–2006, which enables us to investigate the effects of different macroeconomic policies on carbon dioxide emissions through changes in shares of industries and use of different energy sources. Our analysis shows that the main component that determines the changes in CO₂ emissions of the Turkish economy is the economic activity. Even though important changes in the structure of the economy during 1970–2006 period are observed, structure effect is not a significant factor in changes in CO₂ emissions, however intensity effect is.