• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.4
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• pp.44-51
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• 2003

By blending of various low boiling point oxygenated agents to lower grade fuels, significant improvements were simultaneously obtained in smoke, CO, PM, SOF and BSEC. Especially, our trends were remarkably obtained by retarding injection timing, by decreasing boiling point and increasing blending contents of additives in case of oxygenated agents rather than non-oxygenated agents. Also, it was revealed that when 20vo1.% DMM added to high viscosity fuels and injection timing was retarded, NOx-smoke trade off relationship was much better than that of ordinary diesel fuel. Thus, lower grade fuels with high viscosity could be expected to be used efficiently and cleanly in diesel operation by blending low boiling point oxygenates.

• Journal of Pharmaceutical Investigation
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• v.20 no.3
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• pp.51-76
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• 1990

It is sometimes said lately that the pH of the human gastric juice is significantly different among individuals. Thus, the dissolution behavior of coated solid dosage forms should preferably be independent of the pH of the test solution. With these points as a background, the effect of pH on the dissolution velocity of coated tablets was studied to compare that of Pharmacoat with other gastric soluble film coating materials. Three viscosity types of Pharmacoat have been available(3, 6 and 15cP) until now. the 6cP type has been considered to be the most suitable for a tablet coating amongst the three types. The 3 cP type with a low degree of polymerization, is capable of providing high concentration, but the film strength is so inferior that sometimes cracking of the film may occur. On the other hand, in the case of the 15cP type, high polymer concentration cannot be achieved because of the high dgree of polymerization, and thus it is uneconomical for coating. Now, there is a strong demand to reduce the coating time even when HPMC is used in the 6cP type in order to reduce the coating cost. In order to improve this problem, we have concentrated our attention on reducing the viscosity value of HPMC to an allowable lower limit from 6cP. As a result of this study, it was found that the reduction of the viscosity value to around 4.5cP enabled the use of a higher solution concentration and an incidental shorter coating time without giving any substantial adverse effects on the properties of coated preparations. These experiment results are presented in the later part of this presentation. Based on this study, we have added the viscosity type of 4.5cP as one of the Pharmacoat products as Pharmacoat-645.

• Korea-Australia Rheology Journal
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• v.21 no.4
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• pp.225-233
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• 2009

In various attempts to relate the behaviour of highly-elastic liquids in complex flows to their rheometrical behaviour, obvious candidates for study have been the variation of shear viscosity with shear rate, the two normal stress differences $N_1$ and $N_2$, especially $N_1$, and the extensional viscosity $\eta_E$. In this paper, we shall be mainly interested in 'constant-viscosity' Boger fluids, and, accordingly, we shall limit attention to $N_1$ and $\eta_E$. We shall concentrate on two important flows - axisymmetric contraction flow and "splashing" (particularly that which arises when a liquid drop falls onto the tree surface of the same liquid). Modern numerical techniques are employed to provide the theoretical predictions. It is shown that the two obvious manifestations of viscoelastic rheometrical behaviour can sometimes be opposing influences in determining flow characteristics. Specifically, in an axisymmetric contraction flow, high $\eta_E$ can retard the flow, whereas high $N_1$ can have the opposite effect. In the splashing experiment, high $\eta_E$ can certainly reduce the height of the so-called Worthington jet, thus confirming some early suggestions, but, again, other rheometrical influences can also have a role to play and the overall picture may not be as clear as it was once envisaged.

• Journal of the Korean GEO-environmental Society
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• v.22 no.12
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• pp.59-63
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• 2021

This study presented the characteristics and additive effects of the grout with mixing ratio for developing of high-efficiency grouting technology under high depth conditions. The laboratory investigation were conducted with Portland cement (OPC) and micro cement (S8000-E) including viscosity experiments, particle size analysis experiments, Gel-Time experiments and uniaxial compressive strength experiments. As a result of the viscosity experiment, it was shown that OPC is advantageous in terms of viscosity, but S8000-E is suitable when considering the passage of rock joint intervals through particle size analysis. The Gel-Time experiment shows that it is not that difficult with injection as a grout material even when silica fume (SF) was applied. The strength of the cured material is improved as increase in the content of silica fium (SF). Within the range of the study, the optimal mixing ratio obtained through various experiments is S8000-E, w/c=70%, silica fium (SF)=6%, and 7 days.

• Korean Journal of Food Science and Technology
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• v.3 no.1
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• pp.19-24
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• 1971

The Korean rice, Nonglim # 6 was milled into brown rice and 92% polished one and packed with the kraft paper bags. The sample, bags were irradiated with the respective doses of 30, 50, 600 and 800 Krad and then were stored at $10^{\circ}C$ and 75% RH. Changes of fat acidity, amylase activity, viscosity of thus irradiated rice were examined during storage. The results were as follows. 1) Fat acidity increased slightly in the range of $30{\sim}50$ Krad but remarkably in the range of $600{\sim}800$ Krad. However, the rate of increase was low in comparison with the storage under the room temperature. 2) The amylase activity of both the low dose lot and the control decreased in the same rate during the storage. However the high dose lot had more remarkable decrease of the amylase activity from the beginning. 3) The viscosity by Brabender amylogram showed the slightly decreasing tendency in both the low $30{\sim}50$ Krad lot and the control lot of the polished rice powder during storage. On the other hand, the high dose lot of 600 or 800 Krad marked the similar decreasing rate but by far the lower values of the viscosity. 4) The results of the organoleptic test presented no differences between the low dose lot and the control lot, but the high dose lot and the control lot differed significantly only in the color.

• Composites Research
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• v.33 no.2
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• pp.39-43
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• 2020

Recently, fabrication process of thermoplastic polyamide-based composites with recyclability as well as impact, chemical, and abrasion resistance have been widely studied. In particular, thermoplastic reactive resin transfer molding (TRTM) in which monomer with low viscosity is injected and in-situ polymerized inside mold has received a great attention, because thermoplastic melts are hard to impregnate fiber preform due to their very high viscosity. However, it is difficult to optimize the processing conditions because of high reactivity and sensitivity to external environments of the used monomer, ε-caprolactam. In this study, viscosity as an important process parameter in TRTM was measured during in-situ anionic polymerization of ε-caprolactam and the solutions for problems caused by high polymerization rate and sensitivity to moisture and oxygen were suggested. Reliability of the improved measurement technique was verified by comparing the viscosity behavior at various environmental conditions including humidity and atmosphere, and it is expected to be helpful for optimization of TRTM process.

• Proceedings of the Korean Fiber Society Conference
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• 1990.06b
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• pp.36-37
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• 1990

In the past, facile dissolution of cellulose has been hampered by the lack of suitable nondegrading solvents. Recently, this problem has been solved in our laboratory by the discovery of an inexpensive, convenient solvent system, that is the mixture of $NH_3\;and\;NH_4SCN$, for cellulose. Also, the $cellulose/NH_3/NH_4SCN$ solution system has been found to form the anisotropic, i.e., liquid crystalline phase. It is believed that both the cholesterio and the nematic phase occur. This finding has prompted extensive on-going researoh on the formation of the liquid crystalline phase from an inexpensive natural source such as cellulose since the nematic phase is envisioned as an excellent precursor sources for products with desirable properties, for example, high modulus and high strength. This interest naturally leads to a desire to understand the theological properties of the nematic phase so that the transformation of the nematic phase to the solid state with desirable properties can be efficiently accomplished, ;From this point of view, the theological behavior of the $cellulose/NH3_/NH_4SCN$ system has been studied as a function of shear rate and shear stress over a wide range of solvent compositions, cellulose concentration, centrifugation and urea contents, Results indicate that the viscosity decreases with increasing shear rate. A marked shear thinning behavior and a quasi-Newtonian behavior were observed in the low shear rate region and in the high shear rate region, respectively for all solvent compositions. The $cellulose/NH_3/NH_4SCN$ solution system only exhibited the viscosity increase with increasing cellulose concentration and failed to show the viscosity drop generally observed at the point of incipience of liquid crystal formation, This may be due to the gel-like nature of the solution by the association of the rodlike molecules into bundles which may serve as crosslinking points giving the cellulose solution a network structure. Also, simply hydrogen bonding may be so restrictive of molecular mobility that a viscosity drop is blocked. In addition to the above results, yield stress and thixotropy were also observed in the $cellulose/NH_3/NB_4SCN$ solution system which are characteristics of liquid crystal and gel, The results of the effect of centrifugation on viscosity show that viscosity decreases by the application of centrifugation. This may be explained by the change of the piled polydomain structure to the dispersed polydomain structure due to the pressure gradient generated during centrifugation.ation.

• Journal of the Korea Institute of Building Construction
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• v.2 no.4
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• pp.145-152
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• 2002

High fluid concrete unlike OPC concrete is made with various material, and the phase of fresh concrete is considerably different. In order to understand fluidity phase and mix properties of high fluid concrete, concrete is required to access as suspension structure which consists of aggregate and paste. The focus of this paper is to analyze the test results and quantify the effect of mix proportions of mortar and fineness modulus of sand on the properties of fresh mortar. The effect of water-binder ratio. sand-binder ration. contents of ggbs (by mass of total cementitious materials). and various contents of water reducing agent on the yield stress and plastic viscosity of the mix is studied. Based on the experimental results, the fellowing conclusions can be drawn: (1) The mixing time needed for high fluid mortar was approximately two times more than that of ordinary portland mortar. (2) The fluidity phase of mortar could be explained by yield stress of mix and the fluidity of mortar. (3) As the content of ggbs increased, yield stress of mortar was decreased and plastic viscosity of it was increased. (4) For the high fluid mortar, it was appeared that sand-binder ratio should be below 1.5.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.2
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• pp.240-245
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• 2016

This paper describes the rheological behavior study such as viscosity and change of shear stress regarding marine lubricating oil according to the amount of Marine Gas Oil (MGO) dilution. The viscosity reduction due to fuel dilution is crucially important characteristic to decreasing engine durability because of the abrasion of piston ring or liner. The lubricating oil used in this paper was blended with magnetic stirrer diluted High Sulfur Diesel (HSD, 0.05 wt%) ratio of 3 %, 6 %, 10 %, 15 % and 20 %. The viscosity and shear stress of diluted lubricating oil were measured with the temperature range from $-10^{\circ}C$ to $80^{\circ}C$ using a rotary viscometer (Brookfield Viscometer). As the amount of MGO dilution increasing in lubricating oil, the viscosity and stress of those decreased, because the lubricating oil diluted MGO with low viscosity show the trends to decreased viscosity and shear stress. Especially, the viscosity and shear stress of lubricating oil radically decreased at low temperature ($0{\sim}-10^{\circ}C$) and doesn't effect in MGO dilution at over $40^{\circ}C$. As temperature risen, the reduction of the viscosity and shear stress in lubricating oil shows the Newtonian behavior. The lubricating oil was required to check up periodically to improve engine durability since the viscosity reduction by MGO dilution accelerating the engine abrasion.

• Korean Chemical Engineering Research
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• v.55 no.5
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• pp.690-697
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• 2017

In this study, styrene-isoprene-styrene (SIS)-styrene-butadiene-styrene (SBS) modified asphalt was prepared for waterproof-sheet to measure its properties including softening point, penetration, low temperature flexibility, viscosity and adhesion. Then the properties of SIS-SBS modified asphalt imparted with self-healing were optimized to seek for optimal compositions of SIS and SBS versus asphalt according to response surface methodology (RSM). As the content of SBS or SIS was increased, both properties of softening point and viscosity, measured at high temperature, were increased with a statistical significance. However, the increments of softening point and viscosity per unit content of SBS added, were observed to be greater than those per unit content of SIS added, respectively. It was due to the difference of thermal properties of SBS and SIS at high temperature that the cross-linking degree of SBS was increased by gelation accompanied with the increase of viscosity, while chain-entanglement of SIS was relatively reduced owing to a chain scission of poly(isoprene) blocks causing the decrease of viscosity. To the contrary, SIS-SBS modified asphalt showed a behavior of the least elasticity resulting in both the maximum of penetration and adhesion, measured at room temperature, as well as the lowest low temperature flexibility at the composition of SIS, 4 g and SBS, 8.5 g based on asphalt, 63 g.