Prediction and quality control of the melt index during production of high-density polyethylene

In polyolefin processes the melt index (MI) is the most important control variable indicating product quality. Because of the difficulty in the on-line measurement of MI, a lot of MI estimation and correlation methods have been proposed. In this work a new dynamic MI estimation scheme is developed based on system identification techniques. The empirical MI estimation equation proposed in the present study is derived from the 1 ^st -order dynamic models. Effectiveness of the present estimation scheme was illustrated by numerical simulations based on plant operation data including grade change operations in high density polyethylene (HDPE) processes. From the comparisons with other estimation methods it was found that the proposed estimation scheme showed better performance in MI predictions. The virtual sensor model developed based on the estimation scheme was combined with the virtual on-line analyzer (VOA) to give a quality control system to be implemented in the actual HDPE plant. From the application of the present control system, significant reduction of transition time and the amount of off-spec during grade changes was achieved     

Improved accuracy of burn wound assessment using laser Doppler

The utility of the laser Doppler for determining burn depth has been questioned because of problems with technology and methodology. This study prospectively evaluates the ability of a new laser Doppler technique to predict burn healing time. Using the Periflux System 4000 laser Doppler, readings were taken on 305 burns (147 patients) on postburn day 3 or 4. Sixty-six wounds were used to derive a predictive function (phase I) and 152 wounds were used to test the function (phase II). Blood flow dynamics (flux), microvascular dilation capacity of the wounds to beat stress, and flow motion wave pattern (vasomotion) were studied using the laser Doppler, and seven parameters were evaluated to determine their relative contribution to the prediction of healing time. These parameters are hyperemic flux (flux value after heating to 42 degrees C), average hyperemic wave amplitude (AHWA), number of average flux units >100(F100), number readings with wave amplitude 75 (A5), average flux change (AFC), percentage of average flux increase, and relative flow capacity (RFC = AFC/average hyperemic flux). After readings were made, the wounds were observed and divided into two groups: those that healed in less than 14 days and those that healed or were grafted after 14 days. A step-wise discriminant analysis was used to assess the relative contribution of the Doppler-derived measures to healing time prediction. AHWA, F100, and RFC were included in the final discriminant function explaining 72% of the healing time variance (Wilks' lambda value 0.28; p value <0.0001). Predicted outcome = 0.05(AHWA) + 0.31(F100) + 5.0(RFC) - 2.3. With this derived function, there is 94% accuracy in the prediction of burn wound healing time compared with a physician predictive accuracy of 70%.     

Development of a physics analysis procedure for the prismatic very high temperature gas-cooled reactors

A new physics analysis procedure has been developed for a prismatic very high temperature gas-cooled reactor based on a conventional two-step procedure for the PWR physics analysis. The HELIOS and MASTER codes were employed to generate the coarse group cross sections through a transport lattice calculation, and to perform the 3-dimensional core physics analysis by a nodal diffusion calculation, respectively. Physics analysis of the prismatic VHTRs involves particular modeling issues such as a double heterogeneity of the coated fuel particles, a neutron streaming in the coolant channels, a strong core-reflector interaction, and large spectrum shifts due to changes of the surrounding environment and state parameters. Double heterogeneity effect was considered by using a recently developed reactivity-equivalent physical transformation method. Neutron streaming effect was quantified through 3-dimensional Monte Carlo transport calculations by using the MCNP code. Strong core-reflector interaction could be handled by applying an equivalence theory to the generation of the reflector cross sections. The effects of a spectrum shift could be covered by optimizing the coarse energy group structure. A two-step analysis procedure was established for the prismatic VHTR physics analysis by combining all the methodologies described above. The applicability of our code system was tested against core benchmark problems. The results of these benchmark tests show that our code system is very accurate and practical for a prismatic VHTR physics analysis.     

Kinetics of volume expansion during infusion of Ringer’s solution based on two volume model

In this work mathematical models were developed to represent the kinetics of volume changes of fluid spaces associated with infusion of Ringer’s solution. During infusion of Ringer’s solution, the human body is assumed to be characterized by the two-fluid space model which has second volume space in addition to the first volume so that fluid exchanges between these two spaces are possible. Various infusion types were tested to accommodate different medical situations. Volunteers were given Ringer’s solution and the changes in blood hemoglobin were detected. From the comparison with experimental data, the two-fluid space model was found to represent adequately the kinetics of human volume expansion during infusion of Ringer’s solution.     

Poly(butylene terephthalate)/organoclay nanocomposites prepared by in situ interlayer polymerization and its fiber (II)

Intercalated nanocomposites with poly(butylene terephthalate) (PBT) incorporated between the montmorillonite layers were synthesized from dimethyl terephthalate and 1,4-butane diol by using an in situ interlayer polymerization. The PBT nanocomposites were melt-spun at different organoclay contents to produce monofilaments. The samples were characterized by using wide angle X-ray diffraction, electron microscopy, thermal analysis, and tensile testing. The extent of the clay layer in the PBT was confirmed by using X-ray diffraction and electron microscopy, and the clay layer was found to be highly dispersed on a nanometer scale. The addition of only a small amount of organoclay was enough to improve the thermo-mechanical properties of the PBT hybrid fibers. The hybrids were extruded with various draw ratios (DRs) to examine the tensile mechanical property of the fibers. At DR=1, the ultimate tensile strength of the hybrid fibers increased with the addition of clay up to a critical content and then decreased. However, the initial modulus monotonically increased with increasing amount of organoclay in the PBT matrix. When the DR was increased from 1 to 6, for example, the strength and the initial modulus values of the hybrids containing 3 wt% organoclay decreased linearly.     

Phase Relationships in the ZrO2-Sc2O3 and ZrO2-In2O3 Systems

Zirconia-rich subsolidus phase relationships in the ZrO₂–Sc₂O₃ and ZrO₂–In₂O₃ systems were investigated. Phase inconsistencies in the ZrO₂–Sc₂O₃ system resulted from a diffusionless cubic-to-tetragonal ( t' ) phase transformation not being recognized in the past. Through three different measuring techniques, along with microstructural observations, the solubility limits of the tetragonal and cubic phases were determined.     

A kinetic model for polystyrene (PS) pyrolysis reaction

A mathematical model for the pyrolysis reaction of polystyrene (PS) in a semi-batch reactor has been presented. The thermal degradation of PS was flexibly modeled by a combination of random and specific chain-end scissions. Numerical simulation was used to investigate the effect of operating conditions on the PS products spectrum, the results of which were validated by the experimental data. It was found that as the reaction temperature increased (decreased), the monomer fraction in the products became lower (higher) while the trimer higher (lower). No significant variation in the product composition was, however, observed while constant temperature was maintained. These results indicate the reaction temperature is an effective manipulated variable for the control of products composition of PS pyrolysis. The calculation of the optimum temperature trajectories through the optimization study can thus be of interest for achieving productivity enhancement in plastics pyrolysis processes. This paper is dedicated to Professor Dong Sup Doh on the occasion of his retirement from Korea University.     

A novel part-based approach to mean-shift algorithm for visual tracking

Visual tracking is one of the most important problems considered in computer vision. To improve the performance of the visual tracking, a part-based approach will be a good solution. In this paper, a novel method of visual tracking algorithm named part-based mean-shift (PBMS) algorithm is presented. In the proposed PBMS, unlike the standard mean-shift (MS), the target object is divided into multiple parts and the target is tracked by tracking each individual part and combining the results. For the part-based visual tracking, the objective function in the MS is modified such that the target object is represented as a combination of the parts and iterative optimization solution is presented. Further, the proposed PBMS provides a systematic and analytic way to determine the scale of the bounding box for the target from the perspective of the objective function optimization. Simulation is conducted with several benchmark problems and the result shows that the proposed PBMS outperforms the standard MS.

     

Memory effects of all‐solution‐processed oxide thin‐film transistors using ZnO nanoparticles

Abstract— Non‐volatile memory effects of an all‐solution‐processed oxide thin‐film transistor (TFT) with ZnO nanoparticles (NPs) as the charge‐trapping layer are reported. The device was fabricated by using a soluble MgInZnO active channel on a ZrHfO^x gate dielectric. ZnO NPs were used as the charge‐trapping site at the gate‐insulator—channel interface, and Al was used for source and drain electrodes. Transfer characteristics of the device showed a large clockwise hysteresis, which can be used to demonstrate its memory function due to electron trapping in the ZnO NP charge‐trapping layer. This memory effect has the potential to be utilized as a memory application on displays and disposable electronics.     

Synthesis and characterization of novel blue azo‐dye derivatives containing acrylate group for dye‐based color filters

Abstract— Even though dyes have a fine resolution and good chromaticities, they are not widely used as coloring materials for color filters (CFs) due to their low thermal stability and chemical resistance. A series of azo‐dye derivatives, which consist of two cross‐linkable acrylate or methacrylate groups to improve thermal and chemical properties, have been synthesized and used to fabricate color filters. The spectral properties and chemical/thermal stabilities of the fabricated CFs were investigated by comparing dye‐based CFs, without a complicated dispersion process, but with pigment‐based CFs using dispersed pigment. Also, more properties including the development test and surface morphologies lithographic properties were studied. The synthesized azo dyes were characterized by elemental analysis, UV‐visible spectra, IR, mass, and ¹H‐NMR spectra.