A kinetic study on medium temperature desulfurization using a natural manganese ore

Natural manganese ores were selected as raw materials for the desulfurization sorbent because of economical efficiency and high reactivity on hydrogen sulfide. Initial reaction rates between H₂S and desulfurization sorbent of natural manganese ores were determined in a temperature range of 400-800°C using a thermobalance reactor. All reactions were first order with respect to H₂S and were expressed by the Arrhenius relation. When the sulfidation reaction was controlled by diffusion, the temperature dependence of the effective diffusivity was given by the Arrhenius equation. Activation energies and frequency factors were obtained from the product layer diffusion coefficient of various sorbents by plotting as an Arrhenius equation form. Several additives were mixed to improve the sulfidation capacity, and NiO was the best additive.     

Development of modified stokes expression to model the behavior of expanded beds containing polydisperse resins for protein adsorption

Expanded bed behavior was modeled by using the Richardson-Zaki correlation between the superficial velocity of the feed stream and the void fraction of the bed. A polydisperse material, Chelating excellose® (70-210 Μm in diameter, 1.21 g/cm³ in density), which has Ni²⁺ ions for the selective binding of histidine-tagged proteins, was used as the resin. A method to modify the Stokes expression to express the terminal settling velocity of the resins by introducing two empirical parameters, the effective diameter of the resins and an exponent for(ρ _p -ρ)/Μ term, was developed. Combined use of the Richardson-Zaki correlation and the modified Stokes expression was successful in modeling the bed expansion by incorporating physical properties of feed streams and the resins.     

Dynamic adhesive forces in rough contacting bodies including normal and sliding conditions

Using a high-resolution, high-dynamic bandwidth capacitive force transducer and two piezoelectric actuators, adhesive pull-off forces between nominally flat rough silicon surfaces were measured under various dynamic conditions in normal and tangential directions and environmental humidity levels. The upper specimen approached and retracted with a constant velocity in the vertical (normal) direction, while the lower specimen started moving in the horizontal (tangential) direction during the middle of the contact. The experiments were performed under 35 and 60% relative humidity conditions. It was found that sliding of the contacting surfaces led to a significant reduction in pull-off forces under low-humidity contact conditions, whereas it caused higher pull-off forces under partially wet contact conditions. Comparing the effects of sliding velocity and sliding distance on the measured pull-off force values, it was found that the sliding distance played an important role in the increase in pull-off forces.     

Optimization of the sulfolane extraction plant based on modeling and simulation

An optimization system, based on modeling and simulation, was developed for a sulfolane extraction plant. The primary objective of the operation of this plant is to increase benzene composition, which is mostly affected by the recycle streams in the plant. In this work the optimal recycle streams were identified and resulting product compositions were evaluated. In the optimization, suitable parametric models for each process unit were obtained first from the steady-state rigorous modeling and simulation of the sulfolane extraction plant. The parametric models were then employed to develop the optimization system based on the SQP scheme. Results of simulations show promise for further economic improvements over present operation states.     

Dynamics of the wet-end section in paper mills

A model representing the wet-end section of a paper mill has been developed to characterize its dynamic behavior during the grade change. The model is based on the mass balance relationships written for the simplified wetend white water network. From the linearization of the dynamic model, higher-order Laplace transfer functions were obtained followed by the reduction procedure to give simple lower-order models in the form of 1^st-order or 2^nd-order plus dead times. The dynamic response of the wet-end is influenced both by the white water volume and by the level of wire retention. Effects of key manipulated variables such as the thick stock flow rate, the ash flow rate and the retention aid flow rate on the major controlled variables were analyzed by numerical simulations. The simple dynamic model developed in the present study can be effectively used in the operation and control. This paper is dedicated to Professor Se Ki Moon on the occasion of his retirement from Hanyang University.     

Model algorithmic control of grade change operations in paper mills

In this work, the Model Algorithmic Control (MAC) method is applied to control the grade change operations in paper mills. The neural network model for the grade change operations is identified first and the impulse model is extracted from the neural network model. Results of simulations for MAC control of grade change operations are compared with plant operation data. The major contribution of the present work is the application of MAC in the industrial plants based on the identification of neural network models. We can confirm that the proposed MAC method exhibits faster responses and less oscillatory behavior compared to the plant operation data in the grade change operations.     

Study of Residual Stress and Surface Morphology Changes in Al2O3 Induced by Nd:YAG Laser Irradiation

In this study, the residual stress and surface morphology changes in alumina plates by the irradiation of a Q-switched Nd:YAG laser were investigated. The results of x-ray diffraction using the sin²ψ technique show that laser irradiation induces tensile residual stresses on the surface of the plates, which increase with the increasing energy density of the laser beam. Residual stress and surface morphology are sensitive to the irradiation conditions. The surface morphology of the plates systematically changed with the laser energy density and the presence of an aluminum foil or water on the plates. The physical reasons for these changes are discussed in this article.     

Prediction of the melt flow index using partial least squares and support vector regression in high-density polyethylene (HDPE) process

In polyolefin processes the melt flow index (MFI) is the most important control variable indicating product quality. Because of the difficulty in the on-line measurement of MFI, a large number of MFI estimation and correlation methods have been proposed. In this work, mechanical predicting methods such as partial least squares (PLS) method and support vector regression (SVR) method are employed in contrast to conventional dynamic prediction schemes. Results of predictions are compared with other prediction results obtained from various dynamic prediction schemes to evaluate predicting performance. Hourly MFIs are predicted and compared with operation data for the high density polyethylene process involving frequent grade changes. We can see that PLS and SVR exhibit excellent predicting performance even for severe operating situations accompanying frequent grade changes.     

The Role of Autophagy in Chemical Proteasome Inhibition Model of Retinal Degeneration

We recently demonstrated that chemical proteasome inhibition induced inner retinal degeneration, supporting the pivotal roles of the ubiquitin–proteasome system in retinal structural integrity maintenance. In this study, using beclin1-heterozygous (Becn1-Het) mice with autophagic dysfunction, we tested our hypothesis that autophagy could be a compensatory retinal protective mechanism for proteasomal impairment. Despite the reduced number of autophagosome, the ocular tissue morphology and intraocular pressure were normal. Surprisingly, Becn1-Het mice experienced the same extent of retinal degeneration as was observed in wild-type mice, following an intravitreal injection of a chemical proteasome inhibitor. Similarly, these mice equally responded to other chemical insults, including endoplasmic reticulum stress inducer, N-methyl-D-aspartate, and lipopolysaccharide. Interestingly, in cultured neuroblastoma cells, we found that the mammalian target of rapamycin-independent autophagy activators, lithium chloride and rilmenidine, rescued these cells against proteasome inhibition-induced death. These results suggest that Becn1-mediated autophagy is not an effective intrinsic protective mechanism for retinal damage induced by insults, including impaired proteasomal activity; furthermore, autophagic activation beyond normal levels is required to alleviate the cytotoxic effect of proteasomal inhibition. Further studies are underway to delineate the precise roles of different forms of autophagy, and investigate the effects of their activation in rescuing retinal neurons under various pathological conditions.