• Journal of Ocean Engineering and Technology
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• v.20 no.2 s.69
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• pp.52-58
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• 2006

The effect of various environmental conditions on the durability of E-glass fiber/vinylester resin composites have been investigated using the tensile test specimen of strand type. It was found that the durability test method performed by the stand type specimen was more convenient and reliable than other conventional test method. The weight gains increased with the immersion time in both water and alkaline solution, and the Weight gains at $50^{\circ}C$. were much bigger than those at $20^{\circ}C$ in both conditions. The tensile strength decreased with the pass of immersion time in all aqueous solution, and the tensile strength at $80^{\circ}C$ in alkaline solution decreased very steeply at beginning of immersion time. The decrement of tensile strength according to the immersion time in various environmental conditions was mainly caused by the degradation of interface and the damage of glass fiber surface.

• Journal of the Korean Wood Science and Technology
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• v.29 no.1
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• pp.22-30
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• 2001

Composites with various layer constructions involving the ratio of S/P were produced from wood strands(S) and particles(P) (Cryptomeria japonica D.Don) to measure various Young's moduli and anisotropy by ultrasonics. As a result, static Young's moduli of composites were almost same as dynamic Young's moduli obtained from natural frequency. However, these were smaller than those evaluated from ultrasonic wave propagation velocity. The differences between propagation velocity of the parallel(${\parallel}$) and perpendicular(${\bot}$) in-plane direction resulted in a tendency of anisotropy. The tendency of anisotropy was larger in three-layer constructions than in seven-layer constructions. The differences of strand surface layers showed larger values than those of particle surface layers. Also, composites with higher weight ratio of strand had a tendency to propagate rapidly in each direction. In contrast to these results, the propagation velocity in the thickness direction had a tendency to propagate rapidly in composites with particle surface layers and the lower weight ratio of strand.

• Geomechanics and Engineering
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• v.15 no.5
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• pp.1061-1070
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• 2018

The main purpose of retaining wall methods for deep excavation is to keep the construction site safe from the earth pressure acting on the backfill during the construction period. Currently used retaining wall methods include the common strut method, anchor method, slurry wall method, and raker method. However, these methods have drawbacks such as reduced workspace and intrusion into private property, and thus, efforts are being made to improve them. The most advanced retaining wall method is the prestressed wale system, so far, in which a load corresponding to the earth pressure is applied to the wale by using the tension of a prestressed (PS) strand wire. This system affords advantages such as providing sufficient workspace by lengthening the strut interval and minimizing intrusion into private properties adjacent to the site. However, this system cannot control the tension of the PS strand wire, and thus, it cannot actively cope with changes in the earth pressure due to excavation. This study conducts a preliminary numerical analysis of the field applicability of the controllable prestressed wale system (CPWS) which can adjust the tension of the PS strand wire. For the analysis, back analysis was conducted through two-dimensional (2D) and three-dimensional (3D) numerical analyses based on the field measurement data of the typical strut method, and then, the field applicability of CPWS was examined by comparing the lateral deflection of the wall and adjacent ground surface settlements under the same conditions. In addition, the displacement and settlement of the wall were predicted through numerical analysis while the prestress force of CPWS was varied, and the structural stability was analysed through load tests on model specimens.

• Journal of the Korean Society of Safety
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• v.13 no.1
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• pp.13-18
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• 1998

It is well known in the fracture mechanics community that the fracture toughness of brittle materials, such as ceramics, can be improved improves significantly when fibers are added into the material. This is because in presence of fibers the cracks cannot propagate as freely as it can in absence of them. Fibers bridge the gap between two adjacent surfaces of the crack and reduce the crack tip opening displacement, thus make it harder to propagate. Several investigators have experimentally studied how the length, diameter and volume fraction of fibers affect the fracture toughness of chopped strand reinforced matrix composite materials. In this paper, matrix used ALS, Arizona Lunar Simulant, types of fiber used carbon steels and stainless steels. To analyze quantitatively fiber reinforced ALS composites, experimental and analytical methods was progressed. Load-displacement curve is used to experimental method, and FEM analysis program using ABAQUS is used analytical method.

• Journal of the Korean Society of Safety
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• v.25 no.6
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• pp.70-74
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• 2010

For each strand of wirerope sling, the international standards, ISO-8794, EN-13414 specify that the splice shall have five series of load carrying tucks. At least three of the load carrying tucks shall be made with the whole strand. And, the breaking force of the splice shall not be less than 70% or 80% of that of rope. But, There are no prescriptions for splicing types against different efficiency of each splicing type being used many workplace. In this study, analysis the work limit load efficiency according to variation of number of tucks and splicing types by experimental method As a result, the number of tucks 3+2 had the highest breaking efficiency.

• Journal of Microbiology
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• v.37 no.3
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• pp.154-158
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• 1999

The arginine residue at position 243 (Arg 243) of the yeast transcription factor, Gcn4p, is invariably conserved among bZIP transcription factors. Using site-directed oligonucleotide saturation mutagenesis involving two-step polymerase chain reaction (PCR) amplification, random mutations were successfully introduced at the codon of 243 in the basic domain of Gcn4p. This mutant library was transformed ito Gcn4p defective yeast strain and selected for the transcriptionally active colonies. All colonies which were transcriptionally active had arginines in the codon 243. In this study, the strand preference by Taq polymerase during mutagenesis was also tested. Oligonucleotides were specially designed to test whether or not the polymerase was preferred using the strand as a template. A population of randomly mutated products were cloned into an appropriate vector and characterized by DNA sequencing analysis. Saturation mutagenesis which was performed efficiently by this method revealed a strong bias in terms of strand preference of Taq polymerase by an approximate ratio of 3 to 1 in this study.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1869-1871
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• 2001

DNA 센서의 중요한 역할 중의 하나는 염기서열을 분석함으로써 유전적인 질병이나 돌연변이를 찾아낸다는 점이다. 염기서열 분석법으로 질량, 광학, 전기 화학적 측정법 등이 있는데, 그 중 전기 화학적 측정방법이 타 방법에 비해 간편하고 비용도 저렴해서 전망이 매우 밝다. 전기 화학적 측정을 위해서는 전극의 표면 처리 공정과 전극 표면에서의 DNA immobilization, hybridization 공정 및 전기적 신호를 발생시키는 intercalator, 그리고 전기적 신호 검출을 위한 측정 장비가 필요하다. 본 논문에서는 전극의 표면 처리 물질로서 2-mercaptoethanol을 사용했고 double strand DNA의 intercalator로써 methylene blue를 사용했으며, methylene blue의 환원 전류값을 측정하여 double strand DNA를 bare Au 또는 single strand DNA와 구분할 수 있었다. 이러한 연구 결과를 토대로 하여 전기 화학적 신호 검출을 이용한 DNA 센서의 가능성과 개발 방향을 제시하고자 한다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.3
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• pp.207-215
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• 2004

The objective of the present study is to understand the strengthening effects of reinforced concrete beam applied external prestressing with strand or CFRP(Carbon Fiber Reinforced Plastic). In the present study, the structural tests was performed to find the effects of stiffness and ductility for the strengthening RC beam. The experimental results show that proposed methods can increase the bending capacity such as strength, stiffness of the beam significantly and the ranged between 57% and 75% of the load-carrying capacity of the control beam.

• Advances in Computational Design
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• v.4 no.3
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• pp.251-272
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• 2019

This study performed lateral load testing on seventeen wood wall frames in two sections. Section one included eight tests studying structural foam sheathing of shear walls subjected to monotonic loads following the ASTM E564 test method. In this section, the wood frame was sheathed with four different types of structural foam sheathing on one side and gypsum wallboard (GWB) on the opposite side of the wall frame, with Simpson HDQ8 hold down anchors at the terminal studs. Section two included nine tests studying wall constructed with oriented strand board (OSB) only on one side of the wall frame subjected to gradually applied monotonic loads. Three of the OSB walls were tied to the baseplate with Simpson LSTA 9 tie on each stud. From the test results for Section one; the monotonic tests showed an 11 to 27 percent reduction in capacity from the published design values and for Section two; doubling baseplates, reducing anchor bolt spacing, using bearing plate washers and LSTA 9 ties effectively improved the OSB wall capacity. In comparison of sections one and two, it is expected the walls with structural foam sheathing without hold downs and GWB have a lower wall capacity as hold down and GWB improved the capacity.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.1 s.256
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• pp.43-49
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• 2007

A new electric coil design methodology using the notion of topology optimization is developed. The specific design problem in consideration is to find optimal coil configuration that maximizes the Lorentz force under given magnetic field. Topology optimization is usually formulated using the finite element method, but the novel feature of this method is that no such partial differential equation solver is employed during the whole optimization process. The proposed methodology allows the determination of not only coil shape but also the number of coil turns which is not possible to determine by any existing topology optimization concept and to perform single coil strand identification algorithm. The specific applications are made in the design of two-dimensional fine-pattern focusing coils of an optical pickup actuator. In this method, the concept of equivalent magnetizing current is utilized to calculate the Lorentz force, and the optimal coil configuration is obtained without any initial layout. The method is capable of generating the location and shape of turns of coil. To confirm the effectiveness of the proposed method in optical pickup applications, design problems involving multipolar permanent magnets are considered.