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81.
O Ok Park Won Sang Lee Yum Rak Oh Yang-Kyoo Han 《Korean Journal of Chemical Engineering》1994,11(2):96-103
Phase transition was observed in HSMA/PVA IPN gels having ionizable groups with 3-dimensional network structure in the mixed
solvents such as water-methanol. water-acetone or water-ethanol. In order to analyze this phenomena quantitatively, two adjustable
parameters related to gel properties were determined from the model based on Tanaka theory. One was the number of dissociated
counterions per effective chain (f). the other was the interaction parameters (xjj) between gel and water. As increasing the composition of water, swelling of the gels occurs in the mixed solvent; the gel
was shrunk instead when the water content was decreased, which was reversible regardless of the path of swelling and shrinking.
A degree of swelling or shrinking of the gel was dependent upon theseX
ijand f of the gel. With smallerX
n and larger f. more rapid phase transition was observed. Additionally, swelling and shrinking behavior of the gel in system
of two solvents and one polymer was influenced not only byx
ij between gel and solvents but also by xij between two solvents. 相似文献
82.
83.
84.
Hepatoprotective effects of different combinations of sweet orange,Unshiu mikan,and mini tomato juice powders against tert‐butyl hydroperoxide‐induced oxidative stress in HepG2 cells 下载免费PDF全文
85.
Sung?Kyun?KimEmail author Young?Rak?Son 《Journal of Mechanical Science and Technology》2004,18(10):1799-1808
Knowledge of airflow characteristics in nasal cavity is essential to understand the physiological and pathological aspects
of nasal breathing. Several studies have utilizedphysical models of the healthy nasal cavity to investigate the relationship
between nasal anatomy and airflow. Since the final goal of these works is their contribution to the diagnosisand treatment
of nasal diseases, the next step on this topic is naturally studies for disordered nasal cavities. In this paper, as the first
application, airflows in the normal and abnormal nasal cavities with adenoid vegetation are investigated experimentally by
PIV, and comparisons of both cases are appreciated. Dense CT data and careful treatment of model surface under the ENT doctor’s
advice provide more sophisticatedcavity model. The CBC PIV algorithm with window offset is used for PIV flow analysis. Average
and RMS distributions are obtained for inspirational and expirational nasal airflows. Airflow characteristics that are related
with the abnormalities in nasal cavity are presented. 相似文献
86.
J. Rak 《应用聚合物科学杂志》1968,12(4):711-717
A new preparation process, which preserves the original morphological state of polysaccharides in solution during removal of the solvent and so makes possible direct electron microscope investigations, has been developed. The process consists of lyophylization of the sample (in very low concentration of water solution) by freeze-drying, modified for the purpose of electron-microscopic examination. Water-soluble mixture of the polysaccharides of hemicelluloses isolated from the wood tissues of beech and the water solution of the mannan from Saccharomyces cerevisieae treated by means of the new preparation process (preparation with freeze-drying) and, for comparison, these same samples treated without the application of freeze-drying (by means of drying at laboratory temperature and atmospheric pressure, standard preparation process) are introduced as instance from many polysaccharides electron microscopic examined after this preparation process. This method allows one to make direct electron microscope investigations of the water-soluble polysaccharides in no way stained or otherwise shadowed with good resolutions of details in the supermolecular range. 相似文献
87.
Saruar Alam Goo‐Rak Kwon The Alzheimer's Disease Neuroimaging Initiative 《International journal of imaging systems and technology》2017,27(2):133-143
Early diagnosis of Alzheimer disease (AD) and mild cognitive impairment (MCI) is always useful. Preventive measures might have an impact on reducing AD risk factors. Structural magnetic resonance (MR) imaging, one of the vital sensitive biomarkers for cerebral atrophy in the brain, is used to extract volumetric feature by FreeSurfer and the CIVET toolbox. All of the structural magnetic resonance imaging (s‐MRI) data that we used were downloaded from the Alzheimer's disease Neuroimaging Initiative (ADNI) database (adni.loni.usc.edu) of imaging data. This novel approach is applied for the diagnosis of AD and MCI from healthy controls (HCs) combining extracted features with the MMSE (mini‐mental state examination) scores, applying a two sample t‐test to select a subset of features. The subset of features is fed to kernel principal component analysis (KPCA) module to project data onto the reduced principal component coefficients at higher dimensional kernel space to increase the linear separability. Then, the kernel PCA coefficients are projected into the more efficient linear discriminant space using linear discriminant analysis. A multi‐kernel learning support vector machine (SVM) is used on newly projected data for stratification of AD and MCI from HCs. Using this approach, we obtain 93.85% classification accuracy when detecting AD from HCs for segmented volumetric features (using FreeSurfer) with high sensitivity and specificity. When distinguishing MCI from HCs and AD using volumetric features after subcortical segmentation, the detection rate reaches 86.54% and 75.12%, respectively. 相似文献
88.
Christina M. Rost Zsolt Rak Donald W. Brenner Jon‐Paul Maria 《Journal of the American Ceramic Society》2017,100(6):2732-2738
Entropy‐stabilized oxides (ESOs) provide an alternative route to novel materials discovery and synthesis. It is, however, a challenge to demonstrate that the constituent elements in an entropy‐stabilized crystal are homogeneously and randomly dispersed among a particular sublattice, resulting in a true solid solution with no evidence of local order or clustering. In this work, we present the application and analysis of extended X‐ray absorption fine structure (EXAFS) on the prototype ESO composition MgxNixCoxCuxZnxO (x=0.2). In so doing, we can quantify the local atomic structure on an element‐by‐element basis. We conclude that local bond lengths between metal and oxygen vary around each absorbing cation, with notable distortion around the Cu–O polyhedra. By the second near neighbor (i.e., the cation‐cation pair), interatomic distances are uniform to the extent that the collected data can resolve. Crystal models that best fit the experimental scattering data include cations that are distributed randomly on an FCC sublattice with minimal positional disorder, with an interleaved FCC anion sublattice with oxygen ions displaced from the ideal locations to accommodate the distortions in the cation polyhedra. Density functional theory calculations of the ESO system yield a significant broadening in the positional distribution for the oxygen sublattice compared to that for the cation sublattice for all peaks, showing consistency with the conclusion from the experimental data that the distortion from an ideal rock salt structure occurs primarily through disorder in the oxygen sublattice. 相似文献
89.
The supermolecular structure of mixtures of crystalline polymers (low pressure and high pressure polyethylene, isotactic polypropylene) with an amorphous polymer (atactic polypropylene) from the point of view of the influence of the amorphous component on the morphology of the crystalline component has been investigated. The criterion of changes in the morphological state of larger supermolecular formations was the microscopic image of the samples obtained with an optical microscope, both between crossed nicols and in phase contrast. It has been established that the formation of typical spherulites depends on the amount of admixture of the amorphous polymer and also on the treatment of the samples. Upon crystallization in presence of a small amount of solvent (p-xylene), formation of typical spherulites of the crystalline component of the mixture can be observed while the same mixture in case of evaporation of the solvent presents a granulated refractive structure without typical spherulites, regardless of the rate of cooling. The probable role of the solvent is to facilitate mutual segregation of the microphases of both polymers in consequence of decrease in viscosity of the mixture. It has been further shown that even after briefly heating the mixture to a temperature of 220°C., before crystallization, spherulites do not form; on the contrary, spherulites originally present disappear and a structure consisting of smaller refractive formations of crystalline polymer is obtained. The formation of this structure, emerging after destruction of spherulites, might be attributed to an increase of interpenetration of both polymers and to an increase of the contact surfaces between components of the mixture. 相似文献
90.
Gun Hee Lee Nguyen Dat Vo Rak Young Jeon Seung Whan Han Seong Uk Hong Min Oh 《Korean Journal of Chemical Engineering》2018,35(9):1791-1799
In view of the scale up of a batch reactor for super absorbent polymer (SAP), a dynamic mathematical model of a commercial scale batch reactor was developed with mass balance, energy balance, and complex polymerization kinetics. The kinetic parameters of the polymerization were estimated on the basis of the established mathematical model and reference data. Simulation results were validated with less than 10% marginal error compared with reference data. A case study was executed in terms of dynamic simulation for eight different initial concentrations of initiator and monomer to analyze the influence of initial concentration and predict the operation condition for desired product. The results were compared with various reference data, and good agreement was achieved. From the results, we argue that the methodology and results from this study can be used for the scale up of a polymerization batch reactor from the early stage of design. 相似文献