• Smart Structures and Systems
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• v.15 no.2
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• pp.245-258
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• 2015

A methodology based on distributed fiber optic sensors is proposed to detect the lateral buckling for subsea pipelines in this study. Uncontrolled buckling may lead to serious consequences for the structural integrity of a pipeline. A simple solution to this problem is to control the formation of lateral buckles among the pipeline. This firms the importance of monitoring the occurrence and evolution of pipeline buckling during the installation stage and long-term service cycle. This study reports the experimental investigations on a method for distributed detection of lateral buckling in subsea pipelines with Brillouin fiber optic sensor. The sensing scheme possesses the capability for monitoring the pipeline over the entire structure. The longitudinal strains are monitored by mounting the Brillouin optical time domain analysis (BOTDA) distributed sensors on the outer surface of the pipeline. Then the bending-induced strain is extracted to detect the occurrence and evolution of lateral buckling. Feasibility of the method was validated by using an experimental program on a small scale model pipe. The results demonstrate that the proposed approach is able to detect, in a distributed manner, the onset and progress of lateral buckling in pipelines. The methodology developed in this study provides a promising tool for assessing the structural integrity of subsea pipelines.

• Geomechanics and Engineering
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• v.38 no.2
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• pp.125-137
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• 2024

In paste backfill mining, cemented coal gangue-fly ash backfill (CGFB) can effectively utilize coal-based solid waste, such as gangue, to control surface subsidence. However, given the pressurized water accumulation environment in goafs, CGFB is subject to coupling effects from water pressure and chloride ions. Therefore, studying the influence of pressurized water on the chlorine salt erosion of CGFB to ensure green mining safety is important. In this study, CGFB samples were soaked in a chloride salt solution at different pressures (0, 0.5, 1.5, and 3.0 MPa) to investigate the chloride ion transport characteristics, hydration products, micromorphology, pore characteristics, and mechanical properties of CGFB. Water pressure was found to promote chloride ion transfer to the CGFB interior and the material hydration reaction; enhance the internal CGFB pore structure, penetration depth, and chloride ion content; and fill the pores between the material to reduce its porosity. Furthermore, the CGFB peak uniaxial compression strain gradually decreased with increasing soaking pressure, whereas the uniaxial compressive strength first increased and then decreased. The resulting effects on the stability of the CGFB solid-phase hydration products can change the overall CGFB mechanical properties. These findings are significant for further improving the adaptability of CGFB for coal mine engineering.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.5 s.176
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• pp.1075-1083
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• 2000

The prediction of the inelastic behavior of the structure is an essential part of reliability assessment procedure, because most of the failures are induced by the inelastic deformation, such as creep and plastic deformation. During decades, there has been much progress in understanding of the inelastic behavior of the materials and a lot of inelastic constitutive equations have been developed. These equations consist of the definition of inelastic strain and the evolution of the state variables introduced to quantify the irreversible processes occurred in the material. With respect to the definition of the inelastic strain, the inelastic constitutive models can be categorized into elastoplastic model, unified viscoplastic model and separated viscoplastic model and the different integration methods have been applied to each category. In the present investigation, the generalized integration method applicable for various types of constitutive equations is developed and implemented into ABAQUS by means of UMAT subroutine. The solution of the non-linear system of algebraic equations arising from time discretization with the generalized midpoint rule is determined using line-search technique in combination with Newton method. The strategy to control the time increment for the improvement of the accuracy of the numerical integration is proposed. Several numerical examples are considered to demonstrate the efficiency and applicability of the present method. The prediction of the inelastic behavior of the structure is an essential part of reliability assessment procedure, because most of the failures are induced by the inelastic deformation, such as creep and plastic deformation. During decades, there has been much progress in understanding of the inelastic behavior of the materials and a lot of inelastic constitutive equations have been developed. These equations consist of the definition of inelastic strain and the evolution of the state variables introduced to quantify the irreversible processes occurred in the material. With respect to the definition of the inelastic strain, the inelastic constitutive models can be categorized into elastoplastic model, unified viscoplastic model and separated viscoplastic model and the different integration methods have been applied to each category. In the present investigation, the generalized integration method applicable for various types of constitutive equations is developed and implemented into ABAQUS by means of UMAT subroutine. The solution of the non-linear system of algebraic equations arising from time discretization with the generalized midpoint rule is determined using line-search technique in combination with Newton method. The strategy to control the time increment for the improvement of the accuracy of the numerical integration is proposed. Several numerical examples are considered to demonstrate the efficiency and applicability of the present method.

• Journal of the Korean Magnetic Resonance Society
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• v.24 no.4
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• pp.136-142
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• 2020

Apolipoprotein B-100 (apo B-100), the main protein component that makes up LDL (Low density lipoprotein), consists of 4,536 amino acids and serves to combine with the LDL receptor. The oxidized LDL peptides by malondialdehyde (MDA) or acetylation in vivo were act as immunoglobulin (Ig) antigens and peptide groups were classified into 7 peptide groups with subsequent 20 amino acids (P1-P302). The biomimetic peptide P99 (KGTYG LSCQR DPNTG RLNGE) out of B-group peptides carrying the highest value of IgM antigens were selected for structural studies that may provide antigen specificity. Circular Dichroism (CD) spectra were measured for peptide secondary structure in the range of 190-260 nm. Experimental results show that P99 has pseudo α-helice and random coil structure. Homonuclear (COSY, TOCSY, NOESY) 2D-NMR experiments were carried out for NMR signal assignments and structure determination for P99. On the basis of these completely assigned NMR spectra and proton distance information, distance geometry (DG) and molecular dynamic (MD) were carried out to determine the structures of P99. The proposed structure was selected by comparisons between experimental NOE spectra and back-calculated 2D NOE results from determined structure showing acceptable agreement. The total Root-Mean-Square-Deviation (RMSD) value of P99 obtained upon superposition of all atoms were in the set range. The solution state P99 has mixed structure of pseudo α-helix and β-turn(Gln[9] to Thr[13]). These NMR results are well consistent with secondary structure from experimental results of circular dichroism. Structural studies based on NMR may contribute to the prevent oxidation studies of atherosclerosis and observed conformational characteristics of apo B-100 in LDL using monoclonal antibodies.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.9
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• pp.1475-1481
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• 2019

Objective: The objective of the present study was to investigate pork quality from Hereford${\times}$Berkshire female and intact male pigs reared outdoors in an alternative production system. Methods: Berkshire purebred sows were artificially inseminated, once in the fall and again in the spring of the following year, with semen from Hereford boars and managed free of antibiotics in an outdoor hoop structure until the last month of pregnancy, after which they were moved to a pasture-based unit of 0.8 hectares with individual lots with a farrowing hut, shade, and water ad libitum. Piglets were weaned at 4 weeks of age and housed in a deep-bedded hoop structure, grouped by sex. Animals were harvested at market weight of 125 kg, approximately 200 days of age. Hot carcass weight was collected at the time of the harvest. After 24 hours of refrigeration, carcass characteristics were measured. Longissimus dorsi samples collected from the right side loin. Loins were cut into 2.54-cm thick chops and were used to measure marbling score, color score, drip loss, and ultimate pH. Sensory panel tests were conducted as well at North Carolina State University. For pork characteristics and sensory panel data, trial and sex were included in the statistical model as fixed effects. Hot carcass weight was included in the model as a covariate for backfat thickness. Results: Neither the subjective nor the objective color scores displayed any differences between the boars and the gilts. No difference was found for pH and marbling score between trials or sexes. Gilts had a thicker backfat measurement at the last lumbar and a narrower longissimus muscle area measurement when compared to the boars. The only difference in the sensory characteristics was found between the trials for texture and moisture scores. Conclusion: Consumers were not able to detect boar taint under the condition of this study, which is that the intact males were reared outdoors. Additional trials would be necessary; however, based on the results of the present study, outdoor rearing can be suggested as a solution to the issue of boar taint.

• Korean Journal of Materials Research
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• v.18 no.9
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• pp.503-506
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• 2008

The effect of silver nanoparticles (NPs) incorporation on the electronic properties of poly (3, 4-ethylenedioxythiphene) : poly(styrenesulfonate) (PEDOT : PSS) films was investigated. The surface of silver NPs was stabilized with trisodium citrate to control the size of silver NPs and prevent their aggregation. We obtained ca. 5 nm sized silver NPs and dispersed NPs in PEDOT : PSS solution. Sheet resistance, surface morphology, bonding state, and work function values of the PEDOT : PSS films were modified by silver NPs incorporation as well as annealing temperature. Sodium in silver NPs solution could lead to a decrease of work function of PEDOT : PSS; however, large content of silver NPs have an effect on the increase in work function, resulting from charge localization on the silver NPs and a decrease in the number of charge-trapping-related defects by chemical bond formation.

• Rapid Communication in Photoscience
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• v.4 no.3
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• pp.70-72
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• 2015

Oligomers of p-phenylene vinylene and its derivatives have drawn much attention due to their unusual emission characteristics of showing increased emission when they form into nanoparticles. We have investigated the optical properties of the oligo-(p-phenylene vinylene) and its cyano-substituted derivatives in solution and in nanoaggregate media by femtosecond and picosecond time resolved fluorescence as well as stationary spectroscopies. All the spectroscopic data are consistent with the conclusion that the cyano substitution on the ${\beta}$-position of oligo-(p-phenylene vinylene) leads to breakage of the otherwise planar structure of cyano-unsubstituted molecules, which opens up an extremely efficient, as fast as 100 fs, non-radiative relaxation channel of the excited state. Formation of the nanoaggregates reverts the effect to make the molecules planar and to block the non-radiative relaxation channel. Therefore, concerning the applications in organic electroluminescent devices and organic light emitting diodes, substitution by the cyano group is not advantageous, although such modification should be useful in respect of controlling fluorescence intensity in different media.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.8
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• pp.186-192
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• 1999

This paper introduces a study of a method for the forward kinematic analysis, which finds the 6 DOF motions and velocities from the given six cylinder lengths in the Stewart platform. From the viewpoints of kinematics, the solution for the inverse kinematic is easily found by using the vectors of the links which are composed of the joint coordinates in base and plate frames, to act contrary to the serial manipulator, but forward kinematic is difficult because of the nonlinearity and complexity of the Stewart platform dynamic equation with the multi-solutions. Hence we, first in this study, introduce the linear estimator using the Luenberger's observer, and the estimator using the nonlinear measured model for the forward kinematic solutions. But it is difficult to find the parameter of the design for the estimation gain or to select the estimation gain and the constant steady state error exists. So this study suggests the estimator with the estimation gain to be learned by the neural network with the structure of multi-perceptron and the learning method using back propagation and shows the estimation performance using the simulation.

• Journal of the Korean Electrochemical Society
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• v.8 no.1
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• pp.42-46
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• 2005

It has been known that the synthesis of the cathode materials for the lithium rechargeable batteries by the sol-gel process has many advantages over the conventional solid-state method. It has been, however, a continuing issue that new additional steps should be introduced to commercialize this process. In this work, spray drying was introduced to the existing sol-gel process as a continuous mass production method of the pre-heat treatment precursor materials. The precursors of $LiCoO_2$ and $LiNi_{0.8}Co_{0.2}O_2$ were continuously produced through spray drying from the solution containing stoichiometric amount of lithium, cobalt, and nickel sources as well as a chelating agent. The process variables, such as pH of the starting solution, spray drying conditions, and calcination conditions were optimized. The XRD pattern for the synthesized material indicated a good crystallinity with a layered structure.

• YAKHAK HOEJI
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• v.32 no.1
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• pp.86-94
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• 1988

Some rheological properties of subfractions for dextran in the molecular weights range from $3{\times}10^4$ to $2{\times}10^6$ was investigated at room temperature. The dependence of the viscosity on concentration, shear rate, pH & ionic strength, temperature and solvent effect was observed. From the experimental data the Mark-Houwink viscosity equation in water at $25^{\circ}C$ was determined for samples having the molecular weight ranging from $3{\times}10^4$ to $2{\times}10^6$ as$[{\eta}]=3.1{\times}10^{-3}\;Mw^{0.39}(in\;dl/g)$. The intrinsic stiffness of the dextran backbone was estimated by evaluating the 'characteristic ratio' $C_{\infty}$, which is below the 0.082. In the concentrated region, the viscosity was decreased with increasing shear rate and was exponentially decreased with raising temperature, the viscosity showed the maximum value at neutral condition. From the experimental data, it was concluded that dextran chain, linked by the ${\alpha}-1$, 6-glucosidic linkage, behaves like a flexible random coil chain in aqueous solution, dextran solutions were pseudoplastic power law fluids among the empirical models of non-Newtonian behavior. Urea was an active reagent which increases the viscosity and swells dextran while pyrididine and glycerol were inactive reagents. Also, it could be estimated that the formation of gel structure is promote to the neutral state, the molecular weight larger than $2{\times}10^5$, when electrolytic concentration is IN and Ureas is use to solvent.