• Korea-Australia Rheology Journal
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• v.17 no.4
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• pp.181-190
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• 2005

Rheological characterisation of flocculated kaolinite pulps has been undertaken to elucidate particle interactions underpinning the dewatering behaviour induced by flocculation with polyethylene oxide (PEO), anionic polyacrylamide (PAM A) and their blends. Shear yield stress $(\tau_y)$ analysis indicated that polymer mediated particle interactions were markedly amplified upon shear of PEG based pulps. In contrast, PAM A based pulps showed a significant decrease in yield values upon shear. Steady stress measurements analysed using a modified Ellis model indicated subtle differences between the respective linear viscoelastic plateaus of the pulps. Furthermore, modified shear thinning behaviour was evident in PEG based pulps. Estimation of elastic and viscous moduli (G', G') was made using dynamic stress analysis for comparison with values determined from vane measurements. Despite a noticeable difference in the magnitude of G' between the two methods, similar trends indicating sheared PEG-based pulps to be more elastic than PAM based pulps, were observed. Floc microstructural observations obtained in support of rheological properties indicate that PEG flocculant induces significantly more compact particle aggregation within the clay pulps under shear consistent with the yield stress data, in contrast to PAM A, or indeed unsheared PEG based pulps. Consequentially, sheared PEG based pulps show significantly improved dewatering behaviour. The implications of the results, potential benefits and drawbacks of flocculation with PEG and PAM A are discussed with respect to improvements in current dewatering processes used in the minerals industry.

• Journal of KSNVE
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• v.9 no.2
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• pp.324-330
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• 1999

With the increase of track density, high rotational speed and the compatibility for various media such as CD-ROM, CD-R/RW, DVD-ROM/RAM/RW etc. in optical disk drive, the effective anti-vibration design is so crucial for robust operaton. Especailly when the drive is self-excited by unbalanced disk, internal sled base vibration and its external transmission to the case bring about so severe problem. Generally these two consideration points the practical anti-vibration design process to control thses two conflictive properties using finite element analysis. As an example of the design process, Duro 25 and 40 visco-elastic rubber mount was selected and analyzed. The stiffness obtained from FEM rubber model was well matched with the experiments. Also it was confirmed that the internal and external vibration induced from unbalanced disk have good agreement with experimental results. The proposed design process is adopted to the slim-type optical disk drive.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.349-353
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• 2004

A study on optimal placement of constrained layer damping treatment for vibration control of automotive panels is presented. The effectiveness of damping treatment depends upon design parameters such as choice of damping materials, locations and size of the treatment. This paper proposes a CAE (Computer Aided Engineering) methodology based on finite element analysis to optimize damping treatment. From the equivalent modeling technique, it is found that the best damping performance occurs as the viscoelstic patch is placed by means of the modal strain energy method of bare structural panels to identify flexible regions, which in turn facilitates optimizations of damping treatment with respect to location and size. Different configurations of partially applied damping layer treatment have been analyzed for their effectiveness in realizing maximum system damping with minimum mass of the applied damping material. Moreover, simulated frequency response function of the automotive roof with and without damping treatments are compared, which show the benefits of applying damping treatment. Finally, the optimized damping treatment configuration is validated by comparing the locations and the size of the treatment with that of an experimental modal test conducted on roof compartment.

• Korean Journal of Food Science and Technology
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• v.32 no.6
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• pp.1313-1318
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• 2000

총고형분 함량$(TS:\;50{\sim}57%)$을 달리하여 숙성시킨 고추장의 유동특성, 정적 및 동적점탄특성을 관찰하였다. 고추장의 TS가 증가함에 따라서 점조도 지수(K)와 겉보기 점도$({\eta}_{a.5})$는 증가하였으며 유동성 지수(n)는 1보다 훨씬 낮은 0.24-0.31의 범위를 나타내어 고추장은 shear-thinning 성질을 보여주었다. 고추장의 항복응력 측정에서는 고추장의 TS가 증가함에 따라 Casson 항복응력$({\sigma}_{oc})$은 증가하는 경향을 나타내었으며, 또한 고추장의 액상 매개체인 serum 점도$({\eta}_{se})$는 고추장의 TS와 매우 좋은 상관관계$(R^2=0.97)$를 나타내었다. 고추장의 동적점탄성 실험에서는 주파수$({\omega})$가 증가함에 따라 저장탄성률(G#)와 손실탄성률(G@)은 증가하였으며 양(+) 기울기로 G#수치가 G@수치보다 높게 나타났다. 이는 고추장이 약한 겔과 같은 구조적 특성을 갖고 있으며 또한 shear-thinning 거동을 가지고 있음을 나타낸다. 정적점탄성 실험에서 고추장의 총고형분 함량에 따라서 순간탄성 변형$(J_0)$과 지연탄성변형$(J_1)$은 총고형분 함량이 증가함에 따라서 감소하였으며 점도$({\eta}_N)$와 지연시간 $({\tau}_1)$은 증가하였다. 따라서 고추장은 농도가 증가함에 따라 보다 탄력적이며 안정된 구조를 형성하고 있음을 알 수 있었다.

• International Journal of Reliability and Applications
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• v.17 no.2
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• pp.137-147
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• 2016

The engine mount of a car subjected to a pre-load related to the weight of the engine, and acts to insulate the vibration coming from the engine by moving on large or small displacement depending on the driving condition of the car. The vibration insulation of the engine mount is an effect obtained by dissipating the mechanical energy into heat by the viscosity characteristic of the rubber and the microscopic behavior of the additive carbon black. Therefore, dynamic stiffness from the intrinsic properties of rubber filled with carbon black at the design stage is an important design consideration. In this paper, we introduced a hyper-elastic, visco-elastic and elasto-plastic model to predict the dynamic characteristics of rubber, and developed a fitting program to determine the material model parameters using MATLAB. The dynamic characteristics analysis of the rubber insulator of the ACTIVE MOUNT was carried out by using MSC.MARC nonlinear structural analysis software, which provides the dynamic characteristics material model. The analysis results were compared with the dynamic characteristics test results of the rubber insulator, which is one of the active mount components, and the analysis results were confirmed to be valid.

• Structural Engineering and Mechanics
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• v.47 no.1
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• pp.1-25
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• 2013

A combined thermal and mechanical action in roller compacted concrete (RCC) dam analysis is carried out using a three-dimensional finite element method. In this work a numerical procedure for the simulation of construction process and service life of RCC dams is presented. It takes into account the more relevant features of the behavior of concrete such as hydration, ageing and creep. A viscoelastic model, including ageing effects and thermal dependent properties is adopted for the concrete. The different isothermal temperature influence on creep and elastic modulus is taken into account by the maturity concept, and the influence of the change of temperature on creep is considered by introducing a transient thermal creep term. Crack index is used to assess the risk of occurrence of crack either at short or long term. This study demonstrates that, the increase of the elastic modulus has been accelerated due to the high temperature of hydration at the initial stage, and consequently stresses are increased.

• Journal of Dental Anesthesia and Pain Medicine
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• v.19 no.1
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• pp.11-19
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• 2019

Hyaluronic acid (HA) has long been studied in diverse applications. It is a naturally occurring linear polysaccharide in a family of unbranched glycosaminoglycans, which consists of repeating di-saccharide units of N-acetyl-D-glucosamine and D-glucuronic acid. It is almost ubiquitous in humans and other vertebrates, where it participates in many key processes, including cell signaling, tissue regeneration, wound healing, morphogenesis, matrix organization, and pathobiology. HA is biocompatible, biodegradable, muco-adhesive, hygroscopic, and viscoelastic. These unique physico-chemical properties have been exploited for several medicinal purposes, including recent uses in the adjuvant treatment for chronic inflammatory disease and to reduce pain and accelerate healing after third molar intervention. This review focuses on the post-operative effect of HA after third molar intervention along with its various physio-chemical, biochemical, and pharmaco-therapeutic uses.

• Archives of Plastic Surgery
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• v.46 no.2
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• pp.167-170
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• 2019

Full-thickness scalp burns secondary to hair coloring are rare; however, such defects can be large and complex reconstruction of hair-bearing tissue may be necessary. Many skin-stretching devices that use gradual traction have been applied to take advantage of the viscoelastic properties of the skin. A 21-year-old female patient was seen with a burn defect on her occipital scalp leading to exposed subcutaneous tissue after chemical application of hair coloring in a salon. The dimensions of the wound were $10cm{\times}5cm$, and a skin graft or flap would have been necessary to close the defect. Two long transfixing K-wires (1.4 mm) and paired 3-wire threads (23 gauge), which are readily available in most hospitals, were applied over a period of 12 days for trichophytic closure of the defect. The remaining scalp scars after primary trichophytic closure with this skin-stretching method were refined with hair follicle transplantation. This skin-stretching method is simple to apply and valuable for helping to close problematic areas of skin shortage that would otherwise require more complicated procedures. This case shows a relatively unknown complication of hair coloring and its treatment.

• Structural Engineering and Mechanics
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• v.78 no.5
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• pp.557-572
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• 2021

The current study considers free vibration of the spherical panel with magnetorheological (MR) fluids core and magneto-electro-elastic face sheets. The panel is subjected to electro-magnetic loads and also is located on an orthotropic visco-Pasternak elastic foundation. To describe the displacement components of the structure, the first-order shear deformation theory (FSDT) is used and the motion equations are extracted by employing Hamilton's principle. To solve the motion differential equations, Navier's method is selected as an exact analytical solution for simply supported boundary conditions. Effect of the most important parameters such as magnetic field intensity, loss factor, multi-physical loads, types of an elastic medium, geometrical properties of the panel, and also different material types for the face sheets on the results is considered and discussed in details. The outcomes of the present work may be used to design more efficient smart structures such as sensors and actuators.

• Korea Journal of Cosmetic Science
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• v.2 no.1
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• pp.33-46
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• 2020

Cosmetics are representative complex fluids, and there have been many studies focusing on the correlation between the rheological properties and sensory attributes. Various instrumental measurements have been suggested to evaluate the sensory attributes, and one of the most common instruments is Texture Analyzer (TA). Although it is reported that the adhesiveness measured by TA is related to the stickiness of cosmetics, there exists reproducibility problem because measurements with TA are sensitive to application conditions. In this study, an instrumental protocol using rotational rheometer has been set up to measure the stickiness of cosmetics. This protocol consists of two steps. The first step is a preconditioning step, and various types of shear deformations are applied to the samples. The next step is the extensional flow and the axial force is measured. When the amplitude of the shear flow corresponded to the linear viscoelastic region, the axial force is the same as those without preconditioning. On the other hand, an axial force decreases as variation nonlinearity increases. It is because the effects of microstructure changes caused by nonlinear deformation affects the extensional flow. It is worth noting that a new protocol facilitates to evaluate the stickiness of cosmetics in a more systematic way.