• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.232-239
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• 2006

Guided wave techniques have been used for pipeline inspection because of the long range inspection capability of guided waves. One of main concerns of these technique is how ones decide the axial interval of sensors when they are utilized for pipeline inspection. This question is related to the characteristic of cylindrical guided wave propagation, especially wave attenuation. Thus, attenuation of fundamental longitudinal guided wave propagating liquid-filled steel pipes is numerically investigated in the paper. Several liquids such as water, diesel oil, castor oil etc. are considered for the filing materials in the pipes. Sink is considered for numerical models for abandoning standing wave modes; hence, the attenuation dispersion curves become much simpler. Those attenuation calculations can be utilized for guided-wave-based nondestructive testing of pipelines when one inspects pipelines, using monitoring sensors, which are installed outside pipes.

• Elastomers and Composites
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• v.52 no.1
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• pp.1-8
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• 2017

Hydrolysis resistance and mechanical property changes of polyketone (POK)/glass fiber (GF) composites were investigated for GF concentrations varying between 30 and 50%. The hydrolysis resistance of GF filled POK and polyamide66 (PA66, hydrolysis resistant grade) composites were compared. As shown by the experimental results, increasing the immersion time of the composites in a monoethylene glycol (MEG)/water solution at $120^{\circ}C$ had no impact or resulted in slightly decreased mechanical properties such as the tensile strength, tensile modulus, and strain at break in case of POK composites, whereas the mechanical properties of PA66 composites showed a significant drop. Increasing GF concentrations increased the tensile strength, tensile modulus, flexural strength, and flexural modulus of POK composites; however, impact strength did not show significant changes. Hydrolysis mechanisms of POK and PA66 are discussed.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.994-996
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• 1999

Hygrothermal aging at the elevated temperature induces the long-term degradation of the epoxy resin. We investigated the effects of hydrothermal stress on the dielectric breakdown phenomena of epoxy composite filled with natural zeolite. The cured specimens absorbed the moisture in the autoclave at $120^{\circ}C$. $T_g$ of the deteriorated composite by moisture absorption decreased. The dielectric breakdown strength decreased with the moisture absorption cycle. It was concluded that the thermal stress and the high water-vapour-pressure deteriorated the natural zeolite filled epoxy resin system, consequently and the tree growth rate increased.

• Journal of Power System Engineering
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• v.18 no.3
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• pp.36-41
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• 2014

The structure of a variable liquid column oscillator(a VLCO) is analogous to that of the tuned liquid column damper used to suppress oscillatory motion in large structures like tall buildings and cargo ships. The VLCO is a system absorbing high kinetic energy of accelerated motions of the multiple floating bodies in the effect of air springs occurred by installation of inner air chambers. Thus, VLCO can improve the efficiency of energy than wave energy converters of the activating object type made in Pelamis Company. In this research, the experiment was performed in two models of same draft. The one is that weights were filled, and the other is that water was filled. The numerical results were estimated by assuming that do not exist internal flow, and the results were compared with the results of experiments.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.208-213
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• 2002

A new method is presented for the isolation of resonances from scattered waves for elastic wave resonance scattering problems. The resonance scattering function consisting purely of resonance information is defined. Elastic wave resonance scattering from a water-filled cylindrical cavity imbedded in an aluminum matrix is numerically analyzed. The classical resonance scattering theory and the new method compute different magnitudes and phases of the resonances from each partial wave, and therefore. their total resonance spectra are quite different. The exact $\pi$ - radians phase shifts through the resonance and anti-resonance frequencies show that the proposed method properly extracts the vibrational resonance information of the scatterer compared to resonance scattering theory.

• Journal of Environmental Science International
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• v.13 no.12
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• pp.1131-1138
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• 2004

The starch-filled waterborne acrylate (SWAC) films were prepared. The structures and properties of SWAC films were investigated by infrared spectroscopy, thermogravimetric analysis, and strength test. The biode­gradability of SWAC film was also studied by determination of reduced sugar products after enzymatic hydrolysis. The surface morphology of the SWAC film was investigated by scanning electron microscopy (SEM). The results showed that the tensile strength and elongation of SWAC film decreased with the increase of starch content. The SWAC film showed significantly higher water absorbed content than waterbonre acrylate film. The biodegradability of SWAC film increased as the content of starch increased. The biodegradation of starch in SWAC film by ${\alpha}-amylase\;was\;about\;77{\%}$ of that of pure starch.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2000.10a
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• pp.272-277
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• 2000

This study is performed to evaluate the engineering properties of permeable polymer concrete with blast furnace slag and fly ash. The following conclusions are drawn; 1. The highest strength is achieved by 50% filled blast furnace slag powder and fly ash permeable polymer concrete, it is increased 36% by compressive strength, 119% by tensile strength and 217% by bending strength than that of the normal cement concrete, respectively. 2. The ultrasonic pulse velocity is in the range of 2,022 ∼ 2,139m/s. The highest pulse velocity is showed by 50% filled blast furnace slag powder and fly ash permeable polymer concrete. 3. The water permeability is in the range of 4.612∼5.913$\ell$/$\textrm{cm}^2$/h, and it is largely dependent upon the mix design.

• Computers and Concrete
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• v.11 no.4
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• pp.291-304
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• 2013

By considering the creep characteristics of concrete core under eccentric compression, a creep model of concrete filled steel tubes (CFT) columns under eccentric compressive loads is proposed based on the concrete creep model B3. In this proposed model, a discrete element method is introduced to transform the eccentric loading into axial loading. The validity of the model is verified by comparing the predicting results with the published creep experiments results on CFT specimens under compressive loading, together with the predicting values based on other concrete creep models, such as ACI209, CEB90, GL2000 and elastic continuation and plastic flow theory. By using the proposed model, a parameters study is carried out to analysis the effects of practical design parameters, such as concrete mix (e.g. water to cement ratio, aggregate to cement ratio), steel ratio and eccentricity ratio, on the creep of CFT columns under eccentric compressive loading.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.757-759
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• 2003

Understanding the area of the rice paddy fields is important, and suitable for it the remote sensing. SAR is effective to the monitor in Southeast Asia with the rainy season. The detection of the filled rice paddy fields by RADARSAT was tried in the north part of Bangkok Thailand, and in the Mekong river valley Cambodia, which ware the main rice production country in Southeast Asia. We get observation data by RADARSAT and fields all through a year around Bangkok. However, because the flood had occurred on the study area in 2002 observed, the detection only of the rice fields ware difficult.

• Magazine of the Korean Society of Agricultural Engineers
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• v.38 no.5
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• pp.95-105
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• 1996

This study was performed to evaluate the mechanical properties of permeable polymer concrete using fillers and unsaturated polyester resin. The following conclusions were drawn; 1. The unit weight was in the range of 1, 663~ l, 892kg/$cm^3$, the weights of those concrete were decreased 18~28% than that of the normal cement concrete. 2. The highest strength was achieved by fly ash filled permeable polymer concrete, it was increased 22% by compressive strength, 190% by tensile strength and 192% by bending strength than that of the normal cement concrete, respectively. 3. The external strength of permeable pipe was in the range of 3, 083~3, 793kg/m, the external strengths of those concrete were increased 2~26% than that of the normal cement concrete. Accordingly, these permeable polymer concrete pipe can be used to the members and structures which need external strength. 4. The static modulus of elasticity was in the range of $5.7{\times} 10^4 ~ 15.4{\times} 10{^4}kg/cm^2 $, which was approximately 35~64% of that of the normal cement concrete. Fly ash filled permeable polymer concrete was showed relatively higher elastic modulus. The poisson's number of permeable polymer concrete was less than that of the normal cement concrete. 5. The dynamic modulus of elasticity was in the range of $83{\times} 10^3 ~ 211{\times} 10{^3}kg/cm^2 $, which was approximately Ins compared to that of the normal cement concrete. Fly ash filled permeable polymer concrete was showed higher dynamic modulus. The dynamic modulus of elasticity were increased approximately 22~45% than that of the static modulus. 6. The ultrasonic pulse velocity was in the range of 2, 584 ~ 3, 587m/sec, . which was showed about the same compared to that of the normal cement concrete. Fly ash filled permeable polymer concrete was in the range of$0.58~8.88 {\ell}/cm^2/hr$, , and it was larglely dependent upon the mixing ratio. These concrete can be used to the structures which need water permeability.