• KSBB Journal
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• 제10권4호
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• pp.386-392
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• 1995

The high viscous ${\gamma}$-polyglutamic acid(${\gamma}$-PGA) from alkalophilic Alcaligenes sp. was purified and its solution property was investigated. The intrinsic viscosities for Na+ form and H+ form of ${\gamma}$-PGA were 31.1 and 0.38d$\ell$/g, respectively. The viscosity of H+-PGA was not influenced by pH or salts while that of Na+-PGA was influenced. The intrinsic viscosity of Na+-PGA solution decreased remarkably at the alkaline or acidic pH and showed the sharp decrease when salts were added. ${\gamma}$-PGA exhibited the property of the polyelectrolyte showing the .sharp decrease of intrinsic viscosity by the addition of NaCl, and intrinsic viscosity of dilute solution with the low concentration of NaCl was exponentially dependent on temperature and its temperature dependency increased with increasing NaCl concentration. The chain stiffness, coil overlap parameter and critical concentration of Na+-PGA were 0.08, 5.25 and 0.07g/d$\ell$, respectively.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
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• pp.367-370
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• 2003

In this study the effects of fluid viscosity on the pump performances of a conventional centrifugal pump were experimentally studied. The study aimed to compare the pump characteristics for water and high viscosity fluids. The Working fluids are water, aqueous sugar solution and glycerin solution. The pump characteristics of total head and efficiency with high viscosity fluids were different. The performance curves of efficiency for the sugar and glycerin solutions were decreased up to 8.1% and 12.9% than that of water.

• East Asian mathematical journal
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• 제27권1호
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• pp.11-21
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• 2011

In this paper, we try to extend the viscosity approximation technique to find a particular common zero of a finite family of accretive mappings in a Banach space which is strictly convex reflexive and has a weakly sequentially continuous duality mapping. The explicit viscosity approximation scheme is proposed and its strong convergence to a solution of a variational inequality is proved.

• 한국안전학회지
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• 제29권4호
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• pp.78-84
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• 2014

Viscosity agents were added to water to improve extinguishing performance of low pressure water mist suppression system on wood cribs fire, and a small scale wood cribs fire experiment was conducted to measure the extinguishing performance. CMC and agar were used for viscosity agent and as the amount of viscosity agent enlarges, it showed the increase of the viscosity of aqueous solution and the decrease of the fluidity. On wood cribs fire experiment, the extinguishing efficiency was improved with supplemental viscosity agent as it enhanced the adhesive time of aqueous solution on the wood, and therefore expanded the contact time of fire surface. The surface tension of aqueous solution was decreased with the addition of agar which to be assumed as an increase factor of extinguishing efficiency. By the extinguishing experimental result, the most effective extinguishing agent was CMC 0.6 wt.%, with the flame suppression time and the extinguishing time were reduced by 70s and 93s respectively at this concentration.

• International Journal of Industrial Entomology and Biomaterials
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• 제22권1호
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• pp.5-10
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• 2011

The effect of sample handling condition on the rheological measurement of regenerated silk fibroin formic acid solution using parallel plate geometry was investigated. In case of loading method, the loading by pouring sample solution resulted in the best reproducibility of rheological measurement. Loading with spoon showed a high variance of viscosity value at low shear rate region ($0.01{\sim}1sec^{-1}$) while loading with syringe exhibited a low reproducibility of viscosity at high shear region ($1{\sim}100sec^{-1}$) with a disappearance of shear thinning phenomenon. It was revealed that the sample loading with small extra amount lead to the most reproducible result. The sample loading with the exact amount for the measuring plate resulted in a lack of reproducibility of high shear viscosity, while the loading with large extra volume produced a limited consistency of low shear viscosity. It was turned out that 3 min. of waiting time before measurement was the optimum condition for reliable result. When the waiting time was less than 1 min., the low shear viscosity was obtained with a lack of consistency. On the other hand, the sample solution started drying when the waiting time increased up to 5 min.

• 폴리머
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• 제34권5호
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• pp.415-423
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• 2010

고검화도(98%이상)의 폴리(비닐 알코올)(PVA)를 디메틸설폭사이드(DMSO) 용매에 녹인 뒤 PVA 준희박 용액 대에서 농도 $C{\simeq}0.14\;g/mL$까지 점성도를 측정하였으며, 이 시스템을 매트릭스로 하여 폴리스티렌(PS) 라텍스 입자의 확산운동 지연을 동적 광산란법으로 조사하였다. PVA/DMSO계의 점성도를 고유점성도 $[{\eta}]$로 스케일된 환산농도 $C[{\eta}]$에 대하여 도시하였을 때 C$[{\eta}]$ >2에서는 분자량 의존성이 강하게 나타났으며, 그 원인은 PVA 용액 내에 존재하는 불균일 영역때문인 것으로 추정하였다. 그러나 매트릭스 내에서 탐침입자의 확산운동은 모든 측정농도에서 단일모드로 관찰되었고, 용액상 및 용매상에서의 확산계수의 비인 D/Do를 $C[{\eta}]$로 도시할 때 전체 농도 범위에서 분자량 의존성은 전혀 나타나지 않았으나 신장지수함수의 적용 한계는 C$[{\eta}]$ >2.5인 것으로 관찰되었다.

• 한국수산과학회지
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• 제28권4호
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• pp.397-400
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• 1995

Chitosan 용액의 물성학적 특성을 조사하기 위하여 chitosan 용액의 점도에 미치는 전단속도, 온도, 농도 및 염의 영향을 조사한 결과, chitosan 용액$(0.5\%)$의 유동곡선은 hysteresis loop가 나타나는 Bingham 유체와 일치하였고, $10^{\circ}C-40^{\circ}C$에서 Arrhenius 온도의존성을 나타내었다$(2\%,\;2.5\%,\;3\%\;chitosan$ 용액). 활성화 에너지는 3.25-8.35(kcal/g mol)로 전단속도가 높을수록 그리고 농도가 높을수록 증가하였다. Chitosan 용액의 겉보기점도는 농도가 증가할수록 지수적으로 증가하였고, 측정 온도가 높을수록 농도의존성은 낮았다. 한편 chitosan용액에 염을 첨가하였을 때 점도감소현상이 나타났으며, 염농도가 높아짐에 따라 점도의 감소폭은 줄어들었다 염의 종류에 따른 점도변화는 없었다

• 산업기술연구
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• 제20권A호
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• pp.39-44
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• 2000

Highly viscous biopolymer from alkali-tolerant Bacillus sp. was purified and its solution properties were investigated. The intrinsic viscosities for crude biopolymer and biopolymers purified by dialysis or CPC(cetylpyridinium chloride) treatment were 58.24, 73.60 and 42.18 dL/g, respectively. The intrinsic viscosity of biopolymer showed the maximum value at the neutral pH but it was decreased remarkably at the alkaline or acidic pH. Biopolymer exhibited the property of polyelectrolyte, showing the sharp decrease of intrinsic viscosity by the addition of NaCl. Intrinsic viscosity of dilute solution at the low NaCl concentration was exponentially dependent on temperature and its temperature dependency was increased with NaCl concentrations. The chain stiffness, coil overlap parameter, and critical concentration were 0.09, 5.25 and 0.07g/dL, respectively. Temperature dependency on intrinsic viscosity of biopolymer solution was different each other at $45^{\circ}C$. Flow activation energies at temperatures above $45^{\circ}C$ were constant, while those at temperatures below $45^{\circ}C$ increased with increase of added NaCl concentration.

• Preventive Nutrition and Food Science
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• 제4권2호
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• pp.85-87
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• 1999

A simple and rapid method to estimate the viscosity of chitosan using laboratory pipettes was developed. The voscosities of nine different chitosan samples, prepared ini 1 % acetic acid at a 1% concentration , were measured with a standard viscometer. Prior to measurement of flow time of 1% chitosan solution with a pipette, twelve pipettes were assorted into three groups with flow times of 4, 5 and 6 sec after measuring passage of 9 ml of 1% acetic acid througth a 10 ml pipette. With each group of pipettes. flow time of 1% chitosan solution was determined by measuring the delivery time of 5 ml of the 10ml solution through a 10 ml pipette. Results of regression analyses revealed high linear relationship(R2=0.9812, 0.9663, and 0.9754) between viscosities calculated with a viscometer and flow times measured with 4, 5 or 6 sec group pipettes. The viscosity of chitosan could be readily and accurately estimated from these linear regression equation by measuring flow times based on pipette delivery.

• Journal of Nutrition and Health
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• 제26권6호
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• pp.793-803
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• 1993

This study was designed to measure viscosity, osmolality and in vitro flow rates via nasogastric tubes for 6 types of commercially available and 9 hospital-blenderized enteral solutions and to examine the effect of viscosity and osmolaility of enteral formula on the flow rates in gravity drip administration. Each solution was infused through 18, 16, 14, 12 French sizes of silicone rubber tube. Flow rates were measured six times at $25^{\circ}C$ using formula bags and drip sets hung at a uniform height on a intravenous drip stand with tube uniformly positioned in collecting container. Viscosity ranged widely from 16.0 to 195.5 cps with mean, 64.61$\pm$64.42 for hospital-blenderized formula while mean viscosity of commercial formula was 7.60$\pm$4.84 cps. Mean osmolality of commercial formula and hospital-blenderized formula were 370$\pm$100.80, 540.33$\pm$89.37 mOsm/kg respectively. There was negative relationship between viscosity of formula and flow rates through tubes but no significant relationship between flow rates and osmolalty. Some of hospital-blenderized formula was too viscous to be infused througth tube with gravity drip administration and the recipe of formula requires to be modiifed. On the other hand, commercial formula with the low viscosity flows too rapidly with large bore size tubes. Smaller size of tube must be selected for hyperosmolar solution to decrease possible side effects associated with tube feeding. Two kinds of regression equations for flow rates obtained according to viscosity and tube sizes were also presented for the purpose of practical uses. In conclusion, this study emphasizes that viscosity of fomula, osmolality, patient's tolerance and comfort, caloric density should be considered in the selection of tubes for gravify drip administration.