• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.2
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• pp.875-882
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• 2019

The effects of Triangle Groove Strips (TGS) on Vortex-induced Vibration (VIV) suppression of marine riser are numerically investigated using Computational Fluid Dynamics (CFD) method. The range of Reynolds number in simulations is 4.0 × 10⁴ < Re < 1.2 × 10⁵. The two-dimensional unsteady Reynolds-Averaged Navier-Stokes (RANS) equations and Shear Stress Transport (SST) k-ω turbulence model are used to calculate the flow around marine riser. The Newmark-β method is employed for evaluating the structure dynamics of marine riser. The effect of the height ratio (ε) of TGS on VIV suppression is evaluated. The amplitude responses, frequency responses, vortex patterns and the flow around the structures are discussed in detail. With the increase of the height ratio of TGS, the suppression effect of TGS on VIV suppression is improved firstly and then weakened. When ε=0.04, the suppression effect of TGS is the best. Compared with the VIV responses of smooth marine riser, the amplitude ratio is reduced by 38.9%, the peak of the lift coefficient is reduced by 69% and the peak of the drag coefficient is reduced by 40% when Re=6.0 × 10⁴. With the increase of Reynolds number, the suppression effect of TGS on VIV suppression is improved firstly and then weakened. When the Reynolds number is 7.0 × 10⁴, the amplitude ratio can be reduced by 40.1%. As to the large-amplitude vibration cases, the TGS show nice suppression effect on VIV.

• Journal of the East Asian Society of Dietary Life
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• v.16 no.1
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• pp.113-119
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• 2006

The physicochemical properties and sensory characteristics for the neck, belly and ham of crossbred pigs SW90 (slaughter weight $90\sim100\;kg$) and SW110(slaughter weight $110\sim120\;kg$) were evaluated to investigate their quality. The water holding capacity, freezing loss, thawing loss, pan boiling loss and water boiling loss were not significantly different between SW90 and SW110, but the thawing loss and water boiling loss of belly were higher than those of other parts(p<0.05). The surface color was not affect by slaughter weight, but the L* value of belly was higher than that of the other parts and a* value was lower than that of the neck and ham(p<0.05). The mechanical texture was not affect by slaughter weight, the hardness of belly was lower than that of the neck and ham, but the springiness, cohesiveness, gumminess, chewiness and shear force of neck and ham were lower than those of belly(p<0.05). The pH, VBN content and TBARS value was not significantly different by slaughter weight. The taste, aroma, texture, juiciness and palatability of SW110 were higher than those of SW90, and the sensory characteristics of belly were higher than those of neck and ham, but their difference was not significant.

• Nuclear Engineering and Technology
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• v.47 no.5
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• pp.523-533
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• 2015

Three-dimensional flow phenomena in a wire-wrapped 37-pin fuel assembly mock-up of a Japanese loop-type sodium-cooled fast reactor, Monju, were investigated with a numerical analysis using a general-purpose commercial computational fluid dynamics code, CFX. Complicated and vortical flow phenomena in the wire-wrapped 37-pin fuel assembly were captured by a Reynolds-averaged Navier-Stokes flow simulation using a shear stress transport turbulence model. The main purpose of the current study is to understand the three-dimensional complex flow phenomena in a wire-wrapped fuel assembly to support the license issue for the core design. Computational fluid dynamics results show good agreement with friction factor correlation models. The secondary flow in the corner and edge subchannels is much stronger than that in an interior subchannel. The axial velocity averaged in the corner and edge subchannels is higher than that averaged in the interior subchannels. Three-dimensional multiscale vortex structures start to be formed by an interaction between secondary flows around each wire-wrapped pin. Behavior of the large-scale vortex structures in the corner and edge subchannels is closely related to the relative position between the hexagonal duct wall and the helically wrapped wire spacer. The small-scale vortex is axially developed in the interior subchannels. Furthermore, a driving force on each wire spacer surface is closely related to the relative position between the hexagonal duct wall and the wire spacer.

• Polymer(Korea)
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• v.39 no.2
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• pp.219-224
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• 2015

In this work, the effect of fiber array direction including $0^{\circ}$, $0^{\circ}/90^{\circ}$, $0^{\circ}/45^{\circ}/-45^{\circ}$ was investigated for mechanical properties of basalt fiber-reinforced composites. Mechanical properties of the composites were studied using interlaminar shear strength (ILSS) and critical stress intensity factor ($K_{IC}$) measurements. The cross-section morphologies of basalt fiber-reinforced epoxy composites were observed by scanning electron microscope (SEM). Also, the surface properties of basalt fibers were determined by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). From the results, it was observed that acid treated basalt fiber-reinforced composites showed significantly higher mechanical interfacial properties than those of untreated basalt fiber-reinforced composites. These results indicated that the hydroxyl functional groups of basalt fibers lead to the improvement of the mechanical interfacial properties of basalt fibers/epoxy composites in the all array direction.

• Elastomers and Composites
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• v.44 no.2
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• pp.156-163
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• 2009

Our objective is to increase the flowability of Polypropylene(PP) compounds and achieve flow mark free surface in injection molded specimen. We have investigated flowabilities of PP compounds which were composed of PP, rubber, talc, and trace amount of additives. Flowability measurement was performed with four types PPs of which molecular weight distributions(MWD) and melt indexes(MI) were different. Rheological properties of the PP compounding materials, such as spiral flow(SF) length, MI, and shear viscosity, were evaluated. When PP with the broad MWD was used, there were remarkable cases where the spiral flow length of low MI PP compound was longer than that of higher MI PP compound. The PP compound having low MI but broad MWD PP has more flowability than the compound with only high MI.

• Food Science of Animal Resources
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• v.34 no.3
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• pp.307-315
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• 2014

pH adjustment would be of advantage in improving the water holding capacity of muscle proteins. The objective of this study was to evaluate the addition of fish sarcoplasmic protein (SP) solution, which was adjusted to pH 3.0 or 12.0, neutralized to pH 7.0, and lyophilized to obtain the acid- and alkaline-treated SP samples, on the functional properties of the chicken myofibrillar protein induced by microbial transglutaminase (MTG). The solubility of alkaline-treated SP was higher than that of the acid counterpart; however, those values of the two pH-treated samples were lower than that of normal SP (p<0.05). All SP solutions were mixed with myofibrillar proteins (MP) extracted from chicken breast, and incubated with MTG. The shear stresses of MP with acid- and alkaline-treated SP were higher than that of normal SP. The thermal stability of MP mixture reduced upon adding SP, regardless of the pH treatment. The breaking force of MP gels with acid-treated SP increased more than those of alkaline-treated SP, while normal SP showed the highest value. The MP gel lightness increased, but cooking loss reduced, with the addition of SP. Smooth microstructure of the gel surface was observed. These results indicated that adjusting the pH of SP improved the water holding capacity of chicken myofibrillar proteins induced by MTG.

• Magazine of the Korean Society of Agricultural Engineers
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• v.26 no.1
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• pp.29-37
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• 1984

This study was made to find several significant relations among various physical and mechanical properties including cone penetration resistance. The alluvial clay samples were taken at the Daebul Reclaimed Tideland in Samhomyeon, Yeongamgun, Jeonranamdo. The results of the study are summarized as follows; 1.Most samples belong to medium or high plastic, inorganic, silty clay(clay contents;32-64%, silt contents; 36-68%, sand contents; 0-3%). The specific gravities range from 2.70 to 2.73, the unit weights from 1.45 to 1. 75g/cm$^3$, the natural moisture contents from 45 to 77%, the liquid limits from 32 to 56%. It is certain that the foundation is weak because the natural moisture contents are much higher than the liquid limits. 2.It is known from the shear tests that the unconfined compression strenghs vary from 0.09 to 0. 38kg/cm2, the cohesions from 0.05 to 0. 21kg/cm2, the internal friction angles from 0 to 3˚. 3.The consolidation tests show that the initial void ratios range from 1.25 to 2.28, the compression indeices from 0.43 to 0.84, the preconsolidation loads from 0.21 to 0.74kg/cm$^2$. 4.Cone penetration resistances are usually less than 5kg/cm$^2$ from ground surface to the depth of about 8m, and from S to l0kg/cm$^2$ in the layer below about 8m to hard layer. 5.The cohesion and cone penetration resistance are in proportion to the depth of soil layer. 6.The correlations between various physical and mechanical properties including cone penetration resistance for the alluvial clay samples are as follows; a) Wn=0.944C+ l2.733 (r=0.829) b) LL=0. 728Cy+6. 991 (r=0. 873) c) PI=0.659Cy-8.168 (r=0.860) d) rt=0. 0077(272-Wn) =2.092-0. 0077Wn (r=0. 859) e) 60=0. 035wn-0 447 (r=0. 893) f) C=0.380qw+0.031 (r=0.816) g) qu=0.0707qc+0.029 (r=0.810) h) C=0.018Z+0.055 (r=O.802) I) qc=0. 415Z+1, 438 (r=0. 943)

• Journal of Adhesion and Interface
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• v.9 no.4
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• pp.1-11
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• 2008

In the present study, kenaf fibers were treated with sodium hydroxide using soaking and ultrasonic methods prior to biocomposite processing, respectively. The effect of alkali treatment on the kenaf-PLA interfacial adhesion and mechanical and thermal characteristics of kenaf/poly(lactic acid) biocomposites was investigated in terms of their interfacial shear strength, flexural properties, dynamic mechanical properties and thermal stability and also microscopic observations of kenaf fibers and the composite fracture surfaces. As a result, use of both soaking and ultrasonic methods for treating kenaf fiber surfaces played a role in increasing the fiber-matrix adhesion and the mechanical properties of the biocomposites. Their characteristics depended not only on the fiber surface treatment method but also on the treatment condition like alkali concentration and treatment time.

• Composites Research
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• v.25 no.3
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• pp.76-81
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• 2012

Atmospheric pressure plasma treatment on carbon nanotube (CNT) surfaces was performed to modify reinforcement effect and interfacial adhesion of carbon fiber reinforced CNT-phenolic composites. The surface changes occurring on CNT treated with plasma were analyzed by using Fourier transform infrared spectroscope (FT-IR). The significant improvement of wettability on CNT was confirmed by static contact angle test after plasma treatment. Such plasma treatment resulted in a decrease in the advancing contact angle from $118^{\circ}$ to $60^{\circ}$. The interfacial adhesion between carbon fiber and CNT-phenolic composites increased by plasma treatment based on apparent modulus test results during quasi-static tensile strength. Furthermore, the proposed database offers valuable knowledge for evaluating interfacial shear strength (IFSS).

• Journal of the Korean Geotechnical Society
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• v.30 no.11
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• pp.5-15
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• 2014

It is very important to design and construct slopes safely because damage cases are increasing due to slope failure. Recently, Limit Equilibrium Method (LEM) based programs are commonly used for slope designs. Though LEM can give factors of safety through simple calculation, it has a disadvantage that the sliding surface should be assumed in advance. On the other hand, the use of Finite Difference Method (FDM) is increasing since the factor of safety can be easily estimated by using shear strength reduction technique. Therefore the purpose of this study is to present a reasonable slope design methodology by comparing the two commonly used analysis approaches; LEM and FDM. To this end, the reinforcement effects of the two methods were compared in terms of the support pattern of soil nailing reinforced in the section where plane failure is anticipated. As a result, the reinforcement effects by nail angle and nail spacing turned out to be equal. Also it was found that the factor of safety increased in LEM, but not changed in FDM when the nail length increased.