• 한국식품영양과학회지
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• 제28권1호
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• pp.1-8
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• 1999

Starch was isolated from nine Korean sweet potato varieties(Shinmi, Seangmi, Yulmi, Shinyulmi, Sunmi, Jeungmi, Mokpo 26, Mokpo 29, and Mokpo 30) and analysed in its physicochemical properties in comparison with a commercial sweet potato starch(Kumokanyu) imported from China. Protein content in the isolated starch was highest(1.1%) in Mokpo 29 and lowest(0.3%) in Kumokanyu, whereas lipid content was equally less than 0.2%. Pasting analysis by Rapid Viscoanalyser(RVA) showed that Yulmi starch had the lowest pasting temperature(70.2oC) whereas Kumokanyu did the highest one (74.3oC). Under a differential scanning calorimetry(DSC), however, Kumokanyu showed the lowest onset temperature(61.8oC) and enthalpy(42.0 J/g) for crystal melting. Shinyulmi showed the highest peak viscosity of the starch paste, but shear thinning was significant like commercial potato starch. Kumokanyu, however, displayed the least peak visicosity but good shear stability. With the starch gels prepared at 4oC, Mokpo 29 showed the highest hardness, whereas Shinyulmi did the lowest one. Against repeated freeze thawing treatments, the starch gel of Kumokanyu was most stable, and among the Korean varieties, Yulmi, Shinyulmi, Jeungmi and Mokpo 26 had good stability. According to the chain distribution analysis, Shinyulmi and Mokpo 29 consisted of larger quanitites of shorter amylopectin chains than Kumokanyu, potato and corn starches.

• Preventive Nutrition and Food Science
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• 제13권3호
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• pp.249-252
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• 2008

Flow behaviors of sweet potato starch (SPS) pastes (5% w/w) were studied in the presence of various sugars (xylose, glucose, fructose and sucrose) and sugar alcohols (xylitol and sorbitol). The flow properties of SPS-sugar mixtures were determined from the rheological parameters of power law model. The vane method was also employed for determining yield stresses of SPS-sugar mixtures directly under a controlled low shear rate. At $25^{\circ}C$ all the samples showed shear-thinning behaviors ($n=0.35{\sim}0.44$) with yield stress. The consistency index (K) values of SPS-sugar mixtures increased in the following order: sorbitol> xylitol> control (no sugar)> sucrose> fructose> glucose> xylose, showing that the addition of sugar alcohols enhanced the K values. The yield stress values were reduced in the presence of ugars and sugar alcohols and they also increased with an increase in swelling power of starch granules in the SPS-sugar mixture systems.

• Steel and Composite Structures
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• 제11권6호
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• pp.435-454
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• 2011

Bonding composite materials to structural members for strengthening purpose has received a considerable attention in recent years. The major problem when using bonded FRP or steel plates to strengthen existing structures is the high interfacial stresses that may be built up near the plate ends which lead to premature failure of the structure. As a result, many researchers have developed several analytical methods to predict the interface performance of bonded repairs. In this paper, a numerical solution using finite - difference method is used to calculate the interfacial stress distribution in beams strengthened with FRP plate having a tapered ends with different thinning profiles. These latter, can significantly reduce the stress concentration. In the present theoretical analysis, the adherend shear deformations are taken into account by assuming a parabolic shear stress through the thickness of both beam and bonded plate. Numerical results from the present analysis are presented to demonstrate the advantages of use the tapers in design of strengthened beams.

• 한국가시화정보학회지
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• 제22권2호
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• pp.63-73
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• 2024

The injection of polymer can significantly reduce drag, particularly in the turbulent flow region where the mutual interaction between the polymer and turbulent vortices occurs. In this study, Taylor-Couette flow of PEO-in-water solutions with a rotating inner cylinder was analyzed. Despite the shear-thinning behaviour of PEO-in-water solutions being well-documented, for a given range of shear rates their viscosity remains nearly constant. By varying the polymer concentration, we analyzed the torque evolution of different solutions followed by the viscoelasticity effects of the polymer on the interphase transition points. The torque was analyzed using a dimensionless torque scaling method, which allows for the assessment of the fluid's momentum transport capabilities. It was observed that for low concentrations of PEO, the flow behaviour exhibited only minor differences in comparison to that of water, the Newtonian fluid. However, once the PEO concentration exceeded the polymer overlap concentration, the flow behaviour was significantly altered.

• 유기물자원화
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• 제25권4호
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• pp.41-50
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• 2017

점도, 임펠러 종류, 소비전력 등에 의해 영향을 받는 생물학적 폐기물 처리시설 및 에너지 생산 플랜트에서 적절한 교반 시스템의 설계는 필수적이다. 본 연구에서는 적절한 교반 시스템의 설계를 위해 음식물류폐기물을 이용하여 다양한 조건(운전 pH 및 농도)에서의 수소발효 시 유변학적 특성의 변화를 조사한 후, 이를 기반으로 교반강도를 설계하였다. 운전 pH에 따른 수소발효 실험에서 수소전환율은 $0.51{\sim}1.77mol\;H_2/mol\;hexose_{added}$였고, 가장 높은 수소전환율은 운전 pH 5.5에서 나타났다. 발효액은 전단속도가 증가함에 따라 점도가 감소하는 Shear thinning 거동을 보였다. 탄수화물이 분해되면서 발효 이후 점도는 초기 점도보다 감소하는 경향을 보였으나, 운전 pH의 변화에 따른 발효액의 점도 변화는 크지 않았다. 탄수화물 농도 10~50 g Carbo. COD/L에서 수소전환율은 $1.40{\sim}1.86mol\;H_2/mol\;hexose_{added}$로 운전 pH 조건이 수소전환율에 미친 영향과 비교했을 때 큰 차이는 없었다. 발효액의 Zero viscosity와 Infinite viscosity는 탄수화물 농도에 따라 각각 $10.4{\sim}346.2mPa{\cdot}s$와 $1.7{\sim}5.3mPa{\cdot}s$로 나타났는데, 10 g Carbo. COD/L와 20 g Carbo. COD/L에서 발효액의 점도 값은 거의 차이가 없었다. 실험 결과에 기초하여 교반강도를 설계한 결과, 기질농도 30 g Carbo. COD/L의 수소발효 초기 및 발효 후 교반강도는 각각 26.0, 10.0 rpm으로 약 2.5배 정도의 교반강도를 줄임으로써 에너지를 절약할 수 있을 것으로 사료된다.

• Fibers and Polymers
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• 제2권3호
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• pp.129-134
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• 2001

Liquid crystalline (LC) poly(ethylene terephthalate-co-2(3)-chloro-1,4-phenylene terephthalate) (50/50, mole/mole) [PECPT] was synthesized and blended with polycarbonate (PC). LC properties of PECPT and thermal, morphological, and rheological behaviors of the PECPT/PC blend were studied. PECPT showed the nematic LC phase and much longer relaxation time than poly(ethylene terephthalate) (PET). The apparent melt viscosity of PECPT was one third of that of FET. An abrupt torque change was observed during the blending process due to the orientation of LC domains. For the blends containing 10~30 wt% of PECPT, the complex viscosities were higher than that of PC. As PECPT content increases above 40 wt%, shear thinning was observed. The lowest complex viscosity was obtained at 40~50 wt%. Transesterification of PECPT and PC was confirmed by the selective chemical degradation of carbonate groups in PC.

• 순환기질환의공학회:학술대회논문집
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• 순환기질환의공학회 2002년도 제2회 학술대회 초록집
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• pp.3-18
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• 2002

Hemorheology plays an important role in atherosclerosis. Hemorheologic properties of blood include whole blood viscosity, plasma viscosity, hemaocrit, RBC deformability and aggregation, and fibrinogen concentration in plasma. Blood flow is determine by three parameters (pressure, lumen diameter, and whole blood viscosity), whole blood viscosity is one of the key physiological variables. However, the significance of whole blood viscosity has not yet not been fully appreciated. Whole blood viscosity has a unique property, non-Newtonian shear-thinning characteristics, which is primarily due to the presence of RBCs. Hence, RBC deformability and aggregation directly affect the magnitude of blood viscosity, and any factors or diseases affecting RBC characteristics influence blood viscosity. Therefore, on can see that whole blood viscosity is the causal mechanism by which traditional risk factors such as hypertension, hyperlipidemia, smoking, exercise, obesity, age, and gender are related to atherogenesis. In this regard, we included whole blood viscosity in the three key determinants of injurious pulsatile flow that results in mechanical injury and protective adaptation in the arterial system. Because whole blood viscosity is a potential predictor of cardiovascular diseases, it should be measured in routine cardiovascular profiles. Incorporating whole blood viscosity measurements into a standard clinical protocol could improve our ability to identify patients at risk for cardiovascular disease and its complications.

• Tribology and Lubricants
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• 제15권3호
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• pp.248-256
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• 1999

Many tribological components in automobile engine undergo high load and sliding speed with thin film thickness. The lubrication characteristics of the components are regarded as ether hydrodynamic lubrication or boundary lubrication, whereas in a working cycle they actually have both characteristics. Many modem engine lubricants have various additives for better performance which make boundary film formation even under hydrodynamic lubrication regime. Conventional Reynolds equation with the viewpoints of continuum mechanics concerns only bulk viscosity of lubricant, which means that its simulation does not give insights on boundary lubrication characteristics. However, many additives of modern engine lubricant provide mixed modes of boundary lubrication characteristics and hydrodynamic lubrication. Especially, high molecular weight polymeric viscosity index improvers form boundary film on the solid surface and cause non-Newtonian fluid effect of shear thinning. This study has performed the investigation about journal bearing system with the mixed concepts of boundary lubrication and hydrodynamic lubrication which happen concurrently in many engine components under the condition of viscosity index improver added.

• 한국관광식음료학회지:관광식음료경영연구
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• 제13권1호
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• pp.55-68
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• 2002

Flow properties of doenjang samples at various total solid contents (30, 32, 34, 36, 38, 40%) were evaluated in this study. Flow properties of doenjang samples was determined by using Haake concentric cylinderical viscometer and Instron testing machine with capillary extrusion viscometer, and consistency index(K), and flow behavior index(n) was also determined from power models, and yield stress was derived form Casson models and vanes methods. Doenjang samples showed shear-thinning (pseudoplastic) fluid with small magnitude of flow behavior index(n) (n=0.30-0.55). Casson yield stress was from 2.11 to 64.02(Pa). Vane yield stress was more effective than casson yield stress in property of reactivation. Apparent viscosity was decreased with the increase in temperature and activation energy was in the range of 6.58 to 10.70 kJ/mole. From the capillary extrusion method, K and n was increased with the increase in solid content with good correlation with. The result revealed that capillary extrusion method is useful for measuring the flow properties of doenjang.

• 한국인쇄학회:학술대회논문집
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• 한국인쇄학회 2007년도 추계 학술논문 발표회
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• pp.59-64
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• 2007

We have manufactured low-curable silver pastes for gravure printing out of roll to roll printing process. When printing, the pastes be used different silver powder shape because of the printing characteristics. The pastes were prepared with silver powder by silver powder shape, polyester resin, solvent and homogenized on a standard three-roller mill. And the pastes exhibited a shear-thinning flow at viscosity profile. Moreover the adhesive strength and resistivity of silver film had good characteristics. With the manufactured paste in this study, RFID antenna circuit had flexible is manufactured and it had $10^{-4}{\sim}10^{-5}{\Omega}{\cdot}cm$.