• 펄프종이기술
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• 제35권4호
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• pp.42-47
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• 2003

Analysis of the elements affecting short circulation in highly integrated paper mills and identification of the interactions among these elements are very important tasks to prevent operational perturbations such as web breaks. In the present work a dynamic model for the short circulation is developed to analyze tuning methods for the outputs to follow set points during grade change operations. Steady state operation data are used to investigate dynamic characteristics of responses for input changes.

• 한국임상수의학회지
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• 제15권1호
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• pp.75-78
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• 1998

This study was performed to estimate the clinical signs and changes of biochemical parameters in rats with hepatic injury induced by the administration of 2, 2'-azobis(2- amidinopropane)dihydrochloride (AAPH) . Minor behavioral change, brittleness of skin hair and decreased volume of water and feed intake were observed in ra% 2 hours after AAPH administration compared to control group. Concentration of serum albumin showed lower than that of control group. However, concentration of total bilirubin has shown higher than that of control group. As time goes on, . serum LDH activity increased significantly compared to control group, but senun CPK activity did not change compared to control group. Passive hemanglutination of $\alpha $-fetoprotein was negative in all the treaDent groups and control group.

• 한국응용과학기술학회지
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• 제15권1호
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• pp.47-54
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• 1998

On contraction of the muscles, marked changes in X-ray reflections are observed, suggesting that conformational changes of contractile molecules and the movement of myosin heads during muscle contraction. The time needed to the peak tension after the onset of stimulation and the amount of peak tension depend on the number of twitch cycle. It was found that the successive twitches decreased not only the time needed to the peak tension after the onset of stimulation but also the time needed to the maximum change of the X-ray intensity. However, the difference of the time between the peak tension and the maximum intensity change($T_{i}-I_{i}$) is nearly the same at any twitch. Based on these results the causes of the decrease of $T_{i}$ and $I_{i}$, and physiological implication of $T_{i}-I_{i}$ are discussed.

• Bulletin of the Korean Chemical Society
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• 제15권1호
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• pp.64-74
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• 1994

The nonstoichiometric chalcogenides with NaCl-type structure were prepared and the physical and structural properties were studied. The homogeneous range and the structural change were studied based on X-ray powder diffractions using Rietveld-type full-profile fitting technique. Wide homogeneous ranges were observed in Y-S and Y-Se systems, and relatively narrow homogeneous ranges were observed in Yb-S and Yb-Se systems. Both in $Yb_{1-x}S\;and\;Yb_{1-x}Se$, a vacancy ordering transition occurred in (111) plane direction. The ordered superstructure had cubic symmetry(Fm$\bar{3}m) with doubled unit cell "a" parameter compared to the original NaCl-type. The superlattice developed in a continuous second-order transitiion was characterized by the reduced waved vector k= $(a^*+b^*+c^*)/2$. Y-S system had metallic, and YSe, YbSe system had semiconducting properties in their homogeneous ranges. It was observed that the change of electronic transport properties in extended homogeneous range did not depend on the relativeratio of metal to nonmetal, but on the quantities of vacancies.

• Bulletin of the Korean Chemical Society
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• 제21권4호
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• pp.434-440
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• 2000

We present the results of computer simulation for the steady shear flows of rodlike molecules using nonequi-librium molecular dynamics simulation (NEMD) method. The model particle is a rigid rod composed of lin-early connected 6-sites and the Lennard-Jones 12-6 potential governs interactions between sites in different molecules. The system of rodlike molecules exhibits the change of orientational structure, that is, isotropic-nematic transition at high shear rates. We elucidate the nature of the ordered system developed from an isotro-pic phase by steady shear through an analysis of various quantities: orientational order parameters, orientational pair correlation functions, orientational distribution function, and snapshots of configurations. The effects of temperature and density on the shear rate dependence of orientational structure are described.

• Bulletin of the Korean Chemical Society
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• 제8권6호
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• pp.441-444
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• 1987

The circular dichroism(CD) spectra of the optically active [$Co(acac)_2(diamine)]^+$ complexes were measured in the several protic and aprotic solvents, where acac = acetylacetonate anion and diamine = ethylenediamine and trimethylenediamine. The degree of the CD variation in protic solvents was enhanced as the dielectric constant decreases except n-butanol and benzylalcohol. And the degree of the CD variation in aprotic solvents was roughly increased as both dipole moment and dielectric constant decrease except aromatic solvents and the solvents having no dipole moment. It was deduced that the CD variations of the complexes have been due to the conformational change of acetylacetonate ligands coordinated to Co(III) ion.

• 한국기후변화학회지
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• 제8권1호
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• pp.57-62
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• 2017

Greenhouse gas (GHG) emissions of private industry of Chungcheongbuk-do were estimated. GHG emissions were classified by industry and GHG emissions ratio of each industry of Chungcheongbuk-do was found. Characteristics of GHG emissions of Chungcheongbuk-do and GHG mitigation technology were analyzed. To calculate GHG emissions, equations proposed through GHG emissions calculation guidelines published by Korean Energy Agency in 2009 were used. As a result, GHG emissions ratio of cement, semiconductor, paper and petrochemical industry was about 73%, 16%, 5%, and 2% respectively. GHG mitigation technologies of cement, semiconductor and waste were investigated. For cement, amine technology, for semiconductor, scrubber system and for waste, land fill gas utilization were analyzed.

• Bulletin of the Korean Chemical Society
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• 제16권3호
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• pp.252-256
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• 1995

Semiempirical MO calculations using the PM3 method are performed on the reactions of acetate esters with substituted phenolate anions. The mechanistic change from rate-limiting formation to breakdown of the anionic intermediate is shown to occur in the gas-phase, especially for meta-nitrophenyl acetate. However the mechanistic change-over takes place at a lower basicity ($pK_0$) of the anion nucleophile than found for the corresponding formate. This lowering of $pK_0$ has been ascribed to the electron donating effect of the methyl group in the acetate. For the reactions involving rate-limiting breakdown of the intermediate, the large Bronsted coefficients, ${\beta}_X({\beta}_{nuc})$, are expected in general, but the magnitude increases to a larger value and the pK0 is lowered accordingly, when an electron-donating nonleaving group, like $CH_3$, is present. This type of nonleaving group effect provides a necessary condition for the carbonyl addition-elimination mechanism with rate-limiting breakdown of the intermediate.

• Bulletin of the Korean Chemical Society
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• 제6권5호
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• pp.280-284
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• 1985

Kinetic measurements of the 5-nitrofurfural-hydrazine reaction in various pH ranges of aquous solution were carried out by ultraviolet spectrophotometry at $25^{\circ},\;35^{\circ}\;and\;45^{\circ}C$. The observed rate of the reaction varies with the change in pH, which gives characteristic "bell-type" rate acidity profile. The maximum rate is shown in the vicinity of pH 4. This reaction procceds with rate-determining attack of hydrazine on the 5-nitrofurfural at low pH and undergoes a change in rate-determining step to dehydration of the addition intermediate as pH increases. The reaction has a "reactant-like transition state" which precedes intermediate in low pH and "product-like transition state" which follows it in neutral pH. The geometry of 5-nitrofurfural-hydrazine intermediate was estimated with PCILO method associated with CNDO/2 scheme.

• Bulletin of the Korean Chemical Society
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• 제7권3호
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• pp.163-166
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• 1986

A new paraffin salt bridge was developed for the concentration cell in high pressure system. The emf values of the concentration cells were measured to calculate the activity coefficients of the electrolytic ions depending upon the pressure of the system. The activity coefficients of sodium, chloride and bromide ions increase with the temperature of the cell and decreased, nearly half at 2500 bars, $20^{\circ}C$, with the pressure. These results can be explained to be attributed to the volume change of the hydrated ion due to the electrostriction. The volume change decreased with pressure due to an increase in the degree of the hydration.