• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.9 no.1
• /
• pp.59-69
• /
• 2001

The rotor blade is modeled using a composite box beam with arbitrary wall. The active constrained damping layers are bonded to the upper and lower surfaces of the box beam to provide active and passive damping. A finite element model, based on a hybrid displacement theory, is used in the structural analysis. The theory is capable of accurately capturing the transverse shear effects in the composite primary structure, the viscoelastic and the piezoelectric layers within the ACLs. A reduced order model is derived based on the Hankel singular value. A linear quadratic Gaussian (LQG) controller is designed based on the reduced order model and the available measurement output. However, the LQG control system fails to stabilize the perturbed system although it shows good control performance at the nominal operating condition. To improve the robust stability of LQG controller, the loop transfer recovery (LTR) method is applied. Numerical results show that the proposed controller significantly improves rotor aeromechanical stability and suppresses rotor response over large variations in rotating speed by increasing lead-lag modal damping in the coupled rotor-body system.

• Applied Chemistry for Engineering
• /
• v.24 no.1
• /
• pp.104-111
• /
• 2013

Poymer blends of two degradable aliphatic polyesters, relatively expensive material polylactic acid (PLA) and relatively inexpensive material poly(butylene adipate-co-terephthalate) (PBAT), were used in this study. Three different kinds of modifiers were used with various amounts. Diisocyanate type methylenediphenyl 4,4'-diisocyanate (MDI) and hexamethylene diisocyanate (HDI) were used as modifiers and epoxy type coupling agents also used. The melt flow index (MFI) and dynamic viscoelasticity of various compositions of PLA/PBAT blends were studied. The mechanical property and morphology with respect to the fracture surface of PLA/PBAT blends were also investigated using tensile test and field emission scanning electronic microscopy, respectively. These tests were also used to verify the compatibility of PLA/PBAT and the effect of mechanical properties due to the use of modifiers. Tensile properties of PLA/PBAT blends modified with HDI were improved remarkably.

• Food Engineering Progress
• /
• v.15 no.2
• /
• pp.116-121
• /
• 2011

This study was aimed to analyze the changes in rheological properties of sausages added tenderizer made with over-matured used-up fruits such as kiwifruit, grape, and pear. The tenderizers were manufactured by various concentration of fruit extract and added to the sausage at different heating temperatures. Failure stress and stress relaxation of beef sausage mixed with different tenderizers were measured with Rheometer, and analyzed with 3-element Maxwell model. As a result of the rheological measurements, over-matured kiwifruit extract showed the best tenderness effect among other fruit extracts, and the more kiwi contents were added, the beef texture turned to softer. The instantaneous stress and elastic component of beef mixed with various tenderizers were decreased at higher concentrations and lower heating temperatures. This study was well expressed the numerical magnitude of viscoelastic components of beef sausages to determine the tenderizer effect.

• Elastomers and Composites
• /
• v.52 no.2
• /
• pp.114-130
• /
• 2017

Enhancing the properties of rubber, such as the tensile strength, modulus, and wear abrasion, by the addition of carbon black and silica as fillers is very important for improving the performance of rubber products. In this review, we summarize the general features of 'the reinforcement of rubber by fillers' and the equations for representing the reinforcement phenomena. The rubber reinforcement was attributed to enhancement of the following: the rubber, bound rubber, formation of networks, and combination between rubber chains and silica followed by entanglement. The reinforcement capability of silica species with different surface and networked states demonstrated the importance of the connection between the silica particles and the rubber chains in achieving high reinforcement. The model involving combination followed by entanglement can provide a plausible explanation of the reinforcement of rubber by carbon black and silica because the combination facilitates the concentration of rubber chains near the filler particles, and entanglement of the rubber chains around the filler particles enforces the resistance against deformation and breakage of rubber compounds, resulting in high reinforcement.

• Applied Biological Chemistry
• /
• v.31 no.1
• /
• pp.65-78
• /
• 1988

This study aims effective use of soymilk residue, by-product of soymilk production, and making noodles by mixing soymilk residue with wheat flour. The results of viscosity property, cooking test of dry noodles, texture test of cooked noodles, and sensory test of cooked noodles were as follows. The color of cooked noodles were slightly shifted to yellowness according to the mixing of soymilk residue. The mixing of soymilk residue resulted in the decrease of texture and the loss of solids due to the decrease of visccelasity. Na-alginate, Na-C.M.C., guar gum, and crude gluten were added to improve the texture of noodles mixed with soymilk residue. As the results, either Na-alginate or guar gum was very effective in increasing the viscosity of composite flour and either guar gum or crude gluten was very effective in improving cooking quality. The texture of noodles supplemented by Na-alginate 1.0%, Na-C.M.C. 2.0%, guar gum 0.5%, or crude gluten 2.0% was similar to that of wheat flour noodles. Complex additives mixed with two different additives were very effective in improving noodle-making characteristics. Especially, the properties of the soymilk residue mixed noodles supplemented by crude gluten 1.0% and Na-C.M.C. 1.0% or crude gluten 1.0% and gum 0.5% were nearly the same in the texture organoleptic properties compared with those of wheat flour noodles.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
• /
• 2000.06a
• /
• pp.26-86
• /
• 2000

마늘을 MAE(microwave-assisted extractiona)방법에 의하여 물, 30% 에탄올 및 50% 에탄올로 추출하고 그 특성을 비교하였다. 마늘과 각 용매의 비율은 1:2.5로 하여 마이크로웨이브 60W로 각각 5분 및 20분 동안 추출하였다. 마늘 올레오레진 수율은 50% 에탄올로 20분동안 추출한 추출물이 14.1%로 가장 높았으며 polyphenol함량도 물로 20분동안 추출한 경우가 579.0mg%로 가장 많은 함량을 나타내었다. 전자공여작용 효과 및 피르브산 함량도 물로 20분 동안 추출한 추출물이 각각 32.7% 및 마늘 1g당 13.4$\mu$molus로 가장 높게 나타났다. 각 용매에 대해 20분동안 추출한 추출물들을 37$^{\circ}C$에서 8일동안 저장하면서 피르브산 함량과 전자공여작용의 변화를 조사한 결과, 피르브산 함량은 물 추출물이 에탄올 추출물보다 높은 함량을 나타내었고 저장 시간이 증가할수록 그 함량은 감소하는 경향을 나타내었다. 전자공여작용도 물 추출물이 가장 높은 효과를 나타내었으며 추출시간에 비례하여 증가하다가 저장 6일째부터 감소하는 경향을 나타내었다. 각 용매에 대한 추출물의 색깔을 조사한 결과 물 추출물이 가장 밝고 옅은 갈색을 나타내었으며 30% 에탄올 추출물이 가장 어둡고 푸르스름한 노란색을 나타내었다. 또한 각 추출물들을 37$^{\circ}C$에서 10일간 저장하면서 갈색화 정도를 측정해 본 결과 물 추출물이 에탄올 추출물이 에탄올 추출물보다 갈색화가 많이 진행되었으며 0.1% cysteine을 첨가한 추출물과 에탄올 추출물의 갈색화는 비슷한 경향을 나타내었다. 마늘 추출물을 추출한 후에 0.1% cysteine을 첨가하여 저장한 것 보다 추출하기 전에 첨가하는 경우가 갈색화 억제 효과가 뚜렷하였다.문에 밀가루에 일부를 대용한 wheat flour dough를 사용하고 가정용 제빵기로 구워 최종 단계에까지의 제빵성 결과를 산출했다. amarans folur 5%의 대체에는 빵의 비용적이 비교적 증대했지만 그 이상 amarans flour을 대처하면 확연히 비용적은 감소했다. amarans flour 10% 대체에 hemicellulase 1250U 이상을 첨가하면 비용적은 눈에 띄게 증대했다. farinograph에 있어서 반죽의 안정성은 amarans flour 10% 대용에 현저히 감소했다. 반죽의 점탄성(아축응력, 탄성률, 점성계수)는 amarans flour 10%를 대용한 것이 무첨가한 것보다 많이 단단해졌음을 알 수 있었다. 혼합중의 반죽의 조사형 전자현미경 관찰로 amarans flour로 대체한 gluten이 단단해졌음을 알수 있었다. 유화제 stearly 칼슘, 혹은 hemicellulase를 amarans 10% 대체한 밀가루에 첨가하면 확연히 비용적을 증대시킬 수 있다는 사실을 알 수 있었다. quinoa는 명아주과 Chenopodium에 속하고 페루, 볼리비아 등의 고산지에서 재배 되어지는 것을 시료로 사용하였다. quinoa 분말은 중량의 5-20%을 quinoa를 대체하고 더욱이 분말중량에 대하여 0-200ppm의 lipase를 lipid(밀가루의 2-3배)에 대하여 품질개량제로서 이용했다. 그 결과 quinoa 대량 7.5%에서 비용적, gas cell이 가장 긍정적 결과를 산출했고 반죽의 조직구조가 강화되었다. 또 quinoa 대체에 의해 전분-지질 복합제의 흡열량이 증대된 것으로부터 전분-지질복합제의 형성 촉진이 시사되었다.이것으로 인하여 호화억제에 의한 노화 방지효과가 기대되었지만 실제로 빵의 노화는 현저히 진행되었다. 이것은 quinua 대체량 증가에 따른 반죽의 안정성이 저하되어 버린 것으로 생

• Journal of the Korean Society for Precision Engineering
• /
• v.30 no.5
• /
• pp.559-563
• /
• 2013

This study aims to quantify the effects of medication (Med) and deep brain stimulation (DBS) on resting rigidity in patients with Parkinson's disease. We tested 10 limbs of five patients under each of four treatment conditions: 1) baseline, 2) DBS, 3) Med, 4) DBS + Med. Rigidity at the wrist joint was assessed using the Unified Parkinson's Disease Rating Scale (UPDRS). The examiner randomly imposed flexion and extension movement on patient's wrist joint. Resistance to passive movement was quantified by viscoelastic properties. Not only rigidity score but also damping constant showed improvements in rigidity by DBS and Med treatments (p<0.05). This indicates that the viscosity can represent the change in rigidity due to DBS as well as Med, which was manifested by UPDRS score.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.42 no.11
• /
• pp.927-936
• /
• 2014

This paper presents development and verification of the progressive failure analysis upon the composite laminates. Strength and stiffness of the fiber-reinforced composite are analyzed by property degradation approach with emphasis on the material nonlinearity and continuum damage mechanics (CDM). Longitudinal and transverse tensile modes derived from Hashin's failure criterion are used to predict the thresholds for damage initiation and growth. The modified Newton-Raphson iterative procedure is implemented for determining nonlinear elastic and viscoelastic constitutive relations. Laminar properties of the composite are obtained by experiments. Prediction on the un-notched tensile (UNT) specimen is performed under the laminate level. Stress-strain curves and strength results are compared with the experimental measurement. It is concluded that the present nonlinear CDM approach is capable of predicting the strength and stiffness more accurately than the corresponding linear CDM one does.

• Applied Biological Chemistry
• /
• v.40 no.3
• /
• pp.225-231
• /
• 1997

Optimization theory was applied to a native and two imported soybeans. Failure stress and stress relaxation curve was measured with rheometer, and color was measured by colorimeter. The effects of each soybean upon the tofu texture were expressed through a non-linear canonical regression model and trace plot. Compared to the other imported soybeans, native soybean produced a higher strength in tofu texture, and showed the positive increase in viscoelastic properties such as instantaneous stress, equilibrium stress and relaxation time, whereas it had no effect on whiteness from reference blend, represented that native soy-bean showed the individual strength upon the selected rheological texture properties. Higher soaking ability in native soybean was selected as a new response for the optimization mixture process, and it contributed positively to the rheological properties of tofu. New soaking process control system during processing and desirability for the mathematical model should be applied for a better mixture design in varieties of soybeans.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.3A
• /
• pp.221-228
• /
• 2010

External bonding of carbon fiber reinforced polymer (CFRP) sheets has been widely accepted as a popular method for strengthening of deteriorated RC structures. The long-term behavior of CFRP-strengthened RC structure is often affected by that of the interface between CFRP sheets and concrete. This study aims at applying a viscoelastic model to describe the creep behaviour of the adhesive layer bonding CFRP sheet to concrete, the CFRP-concrete interface. Reviews of available models on concrete creep behavior have been first carried out and then new FE analysis model is proposed. The proposed FE analysis model based on the maxwell model has been verified by previous experimental results. It is shown that the creep effect of interfacial adhesive layer is very important on the long-term behavior of concrete structures strengthened with CFRP.