• Corrosion Science and Technology
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• v.20 no.1
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• pp.26-36
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• 2021

Pipes operating in the seawater environment faces cavitation degradation and corrosion of the metallic component, as well as a negative synergistic effect. Cavitation degradation shows the mechanism by which materials deteriorate by causing rapid change of pressure or high-frequency vibration in the solution, and introducing the formation and explosion of bubbles. In order to rate the cavitation resistance of materials, constant conditions have been used. However, while a dynamic cavitation condition can be generated in a real system, there has been little reported on the effect of ultrasonic amplitude on the cavitation resistance and mechanism of composites. In this work, 3 kinds of epoxy coatings were used, and the cavitation resistance of the epoxy coatings was evaluated in 3.5% NaCl at 15 ℃ using an indirect ultrasonic cavitation method. Eleven kinds of mechanical properties were obtained, namely compressive strength, flexural strength and modulus, tensile strength and elongation, Shore D hardness, water absorptivity, impact test, wear test for coating only and pull-off strength for epoxy coating/carbon steel or epoxy coating/rubber/carbon steel. The cavitation erosion mechanism of epoxy coatings was discussed on the basis of the mechanical properties and the effect of ultrasonic amplitude on the degradation of coatings.

• Steel and Composite Structures
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• v.42 no.2
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• pp.173-190
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• 2022

With the development of spatial structures, the joints are becoming more and more complex to connect tubular members of spatial structures. In this study, an approach is proposed to establish high-efficiency finite element model of multiplanar KTX-joint with the weld geometries accurately simulated. Ultimate bearing capacity the KTX-joint is determined by the criterion of deformation limit and failure mechanism of chord wall buckling is studied. Size effect of fillet weld on the joint ultimate bearing capacity is preliminarily investigated. Based on the validated finite element model, a parametric study is performed to investigate the effects of geometric and loading parameters of KT-plane brace members on ultimate bearing capacity of the KTX-joint. The effect mechanism is revealed and several design suggestions are proposed. Several simple reinforcement methods are adopted to constrain the chord wall buckling. It is concluded that the finite element model established by proposed approach is capable of simulating static behaviors of multiplanar KTX-joint; chord wall buckling with large indentation is the typical failure mode of multiplanar KTX-joint, which also increases chord wall displacements in the axis directions of brace members in orthogonal plane; ultimate bearing capacity of the KTX-joint increases approximately linearly with the increase of fillet weld size within the allowed range; the effect mechanism of geometric and loading parameters are revealed by the assumption of restraint region and interaction between adjacent KT-plane brace members; relatively large diameter ratio, small overlapping ratio and small included angle are suggested for the KTX-joint to achieve larger ultimate bearing capacity; the adopted simple reinforcement methods can effectively constrain the chord wall buckling with the design of KTX-joint converted into design of uniplanar KT-joint.

• Journal of Photoscience
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• v.9 no.2
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• pp.403-405
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• 2002

To study photocatalytic mechanism of metal doped $Ti0_2$, we investigated photodecomposition effect, photocurrent effect and antibacterial effect. When aluminium content was 2 wt %, photodecomposition effect was better than the others. Silver doped thin films had high photocurrent efficiency and antibacterial effect. This reactions were caused by dissolved oxygen in solution and oxygen adsorbed on surface of thin films.

• Journal of Acupuncture Research
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• v.21 no.6
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• pp.51-62
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• 2004

Objective: To investigate the analgesic effect and its serotonergic mechanism, especially related with 5-HTI and 5-HT2 receptor, of electroacupuncture(EA) in the rat model of collagen-induced arthritis(CIA). Methods : Immunization of male Sprague-Dawley rats with bovine type II (C II) collagen emulsified in Freund's incomplete adjuvant, followed by a booster injection 14 days later, leads to development of arthritis in more than 70% of rats by 21 days postinjection. After three weeks of first immunization, EA stimulation(2 Hz, 0.07 mA, 0.3 ms) was delivered into Jogsamni($ST_{36}$) for 30 minutes. Analgesic effect was evaluated by tail flick latency(TFL). We compared the analgesic effect of EA with TFLs between pretreatment of normal saline and pretreatment of spiroxatrine (5-HT1 receptor antagonist, 1mg/kg, intraperitoneal) and spiperone (5-HT2 receptor antagonist, 1 mg/kg, intraperitoneal) in CIA. Results : 1. TFLs were gradually decreased in CIA as increasing severity of arthritis. 2. Jogsamni($ST_{36}$) EA stimulation in CIA increased TFLs and the effect lasted for 60 minutes. 3. Increased TFLs with Jogsamni($ST_{36}$) EA stimulation were inhibited by pretreatment of spiroxatrine and spiperone in CIA. Conclusions : Jogsamni($ST_{36}$) EA showed analgesic effects in CIA The analgesic effects of Jogsamni($ST_{36}$) EA were inhibited by spiroxatrine and spiperone pretreatment. These observations suggest that 5-HT1 and 5-HT2 serotonergic receptor, which involve the release of serotonin neurotransmitter, play an important roles in analgesic mechanism of EA stimulation.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2002.05a
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• pp.175-178
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• 2002

The proposed immune algorithm has an uncomplicated structure and memory-cell mechanism as the optimization algorithm which imitates the principle of humoral immune response, and has been used as methods to solve parameter optimization problems. Up to now, the applications of immune algorithm have been optimization problems with non-varying system parameters. Therefore, the effect of memory-cell mechanism, which is a merit of immune algorithm, is without. this paper proposes the immune algorithm using a memory-cell mechanism which can be the application of system with nonlinear varying parameters. To verified performance of the proposed immune algorithm, the speed control of nonlinear DC motor are performed. Computer simulation studies show that the proposed immune algorithm has a fast convergence speed and a good control performances under the varying system parameters.

• Journal of Pharmaceutical Investigation
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• v.28 no.3
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• pp.165-169
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• 1998

The effect of various vehicles on the permeation of a model drug, ketoprofen in solution formulation was evaluated using a flow-through diffusion cell system at $37^{\circ}C$. To investigate the mechanism of permeation rate enhancement, the effects of pretreatment with various vehicles on the permeation of the drug were evaluated using 5 mg/ml solution and saturated solution. The order of permeation rate of ketoprofen across hairless mouse skin after pretreatment with various vehicles was similar to the case where the vehicles and the drug were coadministered except ethanol and oleic acid. The results indicate that the mechanism of enhancement can be direct action of the vehicles on the barrier property of the skin and/or carrier mechanism.

• Toxicological Research
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• v.26 no.4
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• pp.237-243
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• 2010

Endocrine disrupting chemicals (EDCs) have been shown to interfere with physiological systems, i.e., adversely affecting hormone balance (endocrine system), or disrupting normal function, in the female and male reproductive organs. Although endocrine disruption is a global concern for human health, its impact and significance and the screening strategy for detecting these synthetic or man-made chemicals are not clearly understood in female and male reproductive functions. Thus, in this review, we summarize the interference of environmental EDCs on reproductive development and function, and toxicological mechanism(s) of EDCs in in vitro and in vivo models of male and female reproductive system. In addition, this review highlights the effect of exposure to multiple EDCs on reproductive functions, and brings attention to their toxicological mechanism(s) through estrogen receptors.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1530-1535
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• 2003

The automatic load transfer switch (ALTS) typically automatically transfers electrical loads from a normal electrical power source to an emergency electrical power source upon reduction or loss of normal power source voltage. It can also automatically re-transfer the load to the normal power source when the normal voltage has been restored within acceptable limits. The transfer operation of ALTS is accomplished by a spring-driven linkage mechanism. In this paper we build a dynamic model of driving mechanism for ALTS using ADAMS and checked the characteristics of the transfer operation. Finally we performed a detailed design of the driving mechanism through results of analysis and confirmed it to satisfy design requirements.

• Korean Journal of Materials Research
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• v.14 no.2
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• pp.83-89
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• 2004

SiC nanotubes were synthesized by SLS growth mechanism using various metal catalysts. Synthesized nanotubes had mean diameters of 20~50 nm and several $\mu\textrm{m}$ length. The kind of catalysts affected microstructures of SiC nanotubes by different diffusion routes. These differences are attributed to catalysts' physical properties and relative activities to the graphite substrate. Fe acted as a good catalyst of SLS growth mechanism. But in case of Ni, SiC nanotubes grew slowly. Optical property was measured by photoluminescence measurement. Relatively broad peak was obtained and mean peak positioned at about 430 nm. This result was the same as other nanocrystalline SiC materials, but was different from the results of bulk SiC probably due to quantum confinement effect and defect in the grown SiC nanotube.

• The Journal of Korea Robotics Society
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• v.17 no.2
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• pp.159-163
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• 2022

A linearly moving structure in the area where the friction force is dominant - such as ducts filled with grease in the nuclear power plant - experiences increase in friction since the contact surface gets larger as the structure proceeds. To solve this problem is critical for the pipe inspection robot to investigate further area and this makes the system more energy-efficient. In this paper, we propose a passively growing sheath that can be added to linearly moving structures using zipper mechanism. The mechanism enables the linearly moving structures to maintain rolling contact condition against external environment, which provides substantial reduction in kinetic friction. To analyze the effect of the mechanism's head shape, we establish a physical model and compare to the experimental results. Finally, we have shown that the passively growing sheath can be successfully applied to the pipe inspection robot for the nuclear power plant.