Preparation and characterization of sepiolite‐poly(ethyl methacrylate) and poly(2‐hydroxyethyl methacrylate) nanocomposites

Poly(ethyl methacrylate) (PEMA) and poly(2‐hydroxyethyl methacrylate) (PHEMA) nanocomposites with sepiolite in pristine and silylated form were prepared using the solution intercalation method and characterized by the measurements of XRD, TEM, FTIR‐ATR, TG/DTG, and DSC. The TEM analysis indicated that the volume fraction of fibers in sepiolite decreased and the fiber bundles dispersed in PEMA and PHEMA at a nanometer scale. These results regarding TEM micrographs were in agreement with the data obtained by XRD. The increase in thermal stability of nanocomposites of PEMA is higher than that of PHEMA according to the data obtained from TG curves. The DTG analysis revealed that sepiolite/modified sepiolite caused some changes, as confirmed by FTIR in the thermal degradation mechanism of the polymers. T_g temperatures of PEMA and PHEMA usually increased upon the addition of sepiolite/modified sepiolite. In addition, modification of sepiolite with 3‐APTS had a slight influence on thermal properties of the nanocomposites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Poly(styrene‐co‐maleic anhydride)‐graft‐fatty acids as novel solid–solid PCMs for thermal energy storage

A solid–solid phase change material (S‐SPCM) can store and release a specific amount of latent heat during its phase transition. In this regard, poly(styrene‐co‐maleic anhydride) (SMA)‐graft‐fatty acids (FA) copolymers were synthesized as novel S‐SPCMs for thermal energy storage (TES). The chemical structures of the SMA‐g‐FA copolymers were characterized by proton nuclear magnetic resonance (¹H NMR) and Fourier transform infrared (FT‐IR) spectroscopy techniques. The phase transformations of the copolymers form crystalline phase to amorphous phase were monitored using polarized optical microscopy (POM). The latent heat TES (LHTES) properties, thermal cycling reliability, and thermal stability of the S‐SPCMs were investigated by differential scanning calorimetry and thermogravimetric analysis methods. The SMA‐g‐FA copolymers produced as S‐SPCMs showed solid–solid phase transitions at about 40°C–60 °C range and had latent heat storage and release ability between 84 and 127 J/g, respectively. The S‐SPCMs had stable chemical structures and reliable LHTES characteristics even after 5,000 thermal cycling. They had reasonable thermal conductivity value changed in the range of 0.15–0.19 W/mK. Furthermore, it was concluded that the SMA‐g‐FA copolymers can be considered as promising S‐SPCMs for TES utilizations. POLYM. ENG. SCI., 59:E337–E347, 2019. © 2019 Society of Plastics Engineers     

Granulation in a Fluidized Bed II Effect of Binder Amount on the Final Granules

There are many parameters affecting the properties of the final granules prepared in a fluidized bed. In this study one of the product parameters, quantity of the binder, has been studied for its effect on the final granule size, size distribution and friability

Determination of granule size change as a function of binder quantity leaded us to study the growth mechanisms during fluidized bed granulation. Two mechanisms are suggested;

1) Snowballing of primary granules (nuclei)

2) Agglomeration of primary granules

It has been shown that there is a critical amount of binder at which the formation of the primary granules comes to an end if more binder is added to the system. Then granule growth occurs by agglomeration of the primary granules. The physical properties of the granules formed before and after this critical binder concentration varies significantly     

Safety implications of providing real-time feedback to distracted drivers

A driving simulator study was conducted to assess whether real-time feedback on a driver's state can influence the driver's interaction with in-vehicle information systems (IVIS). Previous studies have shown that IVIS tasks can undermine driver safety by increasing driver distraction. Thus, mitigating driver distraction using a feedback mechanism appears promising. This study was designed to test real-time feedback that alerts drivers based on their off-road eye glances. Feedback was displayed in two display locations (vehicle-centered, and IVIS-centered) to 16 young and 13 middle-aged drivers. Distraction was observed as problematic for both age groups with delayed responses to a lead vehicle-braking event as indicated by delayed accelerator releases. Significant benefits were not observed for braking and steering behavior for this experiment, but there was a significant change in drivers' interaction with IVIS. When given feedback on their distracted state, drivers looked at the in-vehicle display less frequently regardless of where feedback was displayed in the vehicle. This indicates that real-time feedback based on the driver state can positively alter driver's engagement in distracting activities, helping them attend better to the roadway.     

EUV lithographic radiation grafting of thermo-responsive hydrogel nanostructures

Nanostructures of the thermoresponsive poly(N-isopropyl acrylamide) (PNIPAAm) and of PNIPAAm-block-poly(acrylic acid) copolymers were produced on poly(tetrafluoroethylene-co-ethyelene) (ETFE) films using extreme ultraviolet (EUV) lithographic exposure with subsequent graft-polymerization. The phase transition of PNIPAAm nanostructures at the low critical solution temperature (LCST) at 32 °C was imaged by atomic force microscopy (AFM) phase contrast measurements in pure water. Results show a higher phase contrast for samples measured below the LCST temperature than for samples above the LCST, proving that the soft PNIPAAm hydrogel transforms into a much more compact conformation above the LCST. EUV lithographic exposures were combined with the reversible addition-fragment chain transfer (RAFT)-mediated polymerization using cyanoisopropyl dithiobenzoate (CPDB) as chain transfer agent to synthesize PNIPAAm block-copolymer nanostructures.     

Quasistatic analysis of cylindrical coplanar waveguide with multilayer dielectrics

CAD-oriented analytic formulas are given for calculating the quasistatic parameters of the cylindrical CPW with three dielectrics. The effects of the dielectric materials on the quasistatic characteristics are investigated by using conformal mapping techniques. The calculated results are compared with those obtained for a corresponding planar CPW and a cylindrical CPW with a single dielectric. The curvature effects on the quasistatic characteristics are discussed. Moreover, the present expressions can also be extended to the cylindrical CPW with multilayer dielectrics. © 1998 John Wiley & Sons, Inc. Int J RF and Microwave CAE 8: 303–314, 1998.     

Coated particle fuel to improve safety, design, economics in water-cooled and gas-cooled reactors

In the context of Inert Matrix Fuels (IMF), coated particles (CP)s may play an important role to reduce the problems connected to the plutonium (Pu) and minor actinides stockpiles. In addition, the coatings of the fuel kernels made of different low and high-density ceramic layers allow a safe containment of fission products in operational, accidental and disposal conditions. Pu-based CPs embedded in a ceramic matrix (e.g. graphite, like in HTR fuel elements) can be judged as a special cercer type. There is a wide variety of different coatings and kernel compositions that has not yet been explored beyond the HTR development. Thus it can be expected that the CP technology can be applied to other reactor systems, too. For getting full benefit of the fission product retention capability of the CPs, not only the particle design but also the core geometry as well as power densities etc. have to be adopted to each specific requirement.     

长丝的工艺优化

天然纤维的应用虽已有数千年历史,但仍无法满足当今世界人口的需求,所以合成纤维的发明无疑是20世纪最重要的发明之一。另一个重点是纺织行业的竞争,为了不断满足客户的新要求,长丝的生产工艺和其特性得到了多方面的改进,因而长丝工业也变得越来越重要。主要介绍了对长丝质量变化进行的测试和测试结果的分析。     

A study of photomodulated reflectance on staircase-like,n-doped GaAs/AlxGa1?xAs quantum well structures

In this study, photomodulated reflectance (PR) technique was employed on two different quantum well infrared photodetector (QWIP) structures, which consist of n-doped GaAs quantum wells (QWs) between undoped Al_xGa_1−xAs barriers with three different x compositions. Therefore, the barrier profile is in the form of a staircase-like barrier. The main difference between the two structures is the doping profile and the doping concentration of the QWs. PR spectra were taken at room temperature using a He-Ne laser as a modulation source and a broadband tungsten halogen lamp as a probe light. The PR spectra were analyzed using Aspnes’ third derivative functional form.Since the barriers are staircase-like, the structure has different ground state energies; therefore, several optical transitions take place in the spectrum which cannot be resolved in a conventional photoluminescence technique at room temperature. To analyze the experimental results, all energy levels in the conduction and in the valance band were calculated using transfer matrix technique, taking into account the effective mass and the parabolic band approximations. A comparison of the PR results with the calculated optical transition energies showed an excellent agreement. Several optical transition energies of the QWIP structures were resolved from PR measurements. It is concluded that PR spectroscopy is a very useful experimental tool to characterize complicated structures with a high accuracy at room temperature.