• 소성∙가공
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• 제16권8호
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• pp.567-574
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• 2007

Double layered tube is assembled with an inner tube and an outer tube, similar in material or not, contacting closely and deforming simultaneously when subjected to external force. For the manufacturing of double layered tube, the hydroforming assembly technology has several advantages. Therefore in this study, hydroforming characteristics of double layered tube was investigated. The free bulge test was performed to produce formability diagrams of double layered tubes at various forming pressure and feeding amounts. The hexagonal shape hydroforming test was also performed to estimate the dimensional accuracies of double layered tube through the corner filling ratio and the gap between inner and outer tube. Besides experimental analyses, the analytical model that can predict internal pressure for the hydroforming of double-layered tube was proposed and experimentally validated.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.306-309
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• 2007

In this study, hydroforming characteristic of the double-layered tube was investigated in the hydroforming process. The double-layered tube can be made outer surface on the stainless steel by only one processing. The free bulging test was performed to analysis optimized pressure and axial feeding amount of the double layered tubes. And the experimental results between stainless/carbon and carbon/carbon double-layered tube were compared with the forming data. Moreover analysis model that can be hydroformability and predictable forming pressure of double-layered tube was presented.

• KIEAE Journal
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• 제7권5호
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• pp.87-92
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• 2007

As expansion of balconies at apartments has been legalized, the major function of the balconies as a thermal buffer zone is disappearing. This weakens the ability of window to insulate heat and multiplies surface condensation. Thus more and more residents require solutions to increasing surface condensation and aggravation in thermal comfort. This study intends to provide basic data by evaluating performance of triple layered Low-E windows, triple layered clear windows, double layered Low-E windows and double layered clear window used for expanded balconies and marketed within the country in terms of surface condensation and thermal environment through simulation. Results revealed that no surface condensation occurred at double layered Low-E windows and triple layered Low-E windows. Surface condensation took place at double layered clear windows and triple layered clear windows at a relative humidity of 60%. Thermal environment analysis suggested that double layered clear windows showed the most time falling into the range of comfort at $23^{\circ}C$. The figure were $22^{\circ}C$ for triple layered clear windows, $22^{\circ}C$ for double layered Low-E windows and $21^{\circ}C$ for triple layered Low-E windows.

• 한국세라믹학회지
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• 제39권10호
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• pp.919-927
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• 2002

표면층과 내부간의 기공구조가 다른 다공질체를 제조하기 위해 입자크기가 다른 두 종류의 분체를 이용하여 다공질 성형체를 제조하였다. 두 층간의 소결 수축율을 동일하게 제어하기 위해 성형밀도 변화에 따른 소결밀도 변화를 예측할 수 있는 Ford＇s equation을 도입하여 소결 수축율을 동일한 조건을 구하였다. 제조된 다공질체는 미세구조와 통기도를 조사함으로서 기공의 이중 구조화 여부를 평가하였다. SEM 관찰결과 기공크기가 다른 두 층으로 구성되어 있는 것을 확인하였다. 각 층의 통기도는 출발 입자크기와 기공율이 클수록 증가하였으며, 이중 기공구조를 갖는 시편의 통기도는 기공크기가 작은 층의 특성에 의존하였다.

• Steel and Composite Structures
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• 제31권6호
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• pp.641-653
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• 2019

In this paper, wave propagation is studied and analyzed in double-layered nanotubes systems via the nonlocal strain gradient theory. To the author's knowledge, the present paper is the first to investigate the wave propagation characteristics of double-layered porous nanotubes systems. It is generally considered that the material properties of nanotubes are related to the porosity and hygro-thermal effects. The governing equations of the double-layered nanotubes systems are derived by using the Hamilton principle. The dispersion relations and displacement fields of wave propagation in the double nanotubes systems which experience three different types of motion are obtained and discussed. The results show that the phase velocities of the double nanotubes systems depend on porosity, humidity change, temperature change, material composition, non-local parameter, strain gradient parameter, interlayer spring, and wave number.

• Investigative Magnetic Resonance Imaging
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• 제20권3호
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• pp.191-195
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• 2016

Among the various types of congenital meniscal anomalies, the double-layered lateral meniscus is extremely rare. The double-layered meniscus consists of both the upper additional and the lower normal meniscus. As the upper additional meniscus is mobile, it can be easily displaced, while the lower lateral meniscus is usually normal in shape and volume. A 42-year-old woman suffering from pain and locking of her left knee underwent Magnetic resonance imaging (MRI) examination and an arthroscopic surgery. A rare meniscal abnormality was seen in her left knee, which presented as a double-layered lateral meniscus with displacement. It was remarkable that the upper additional meniscus was displaced over the intercondylar eminence of the tibia and it mimicked a bucket-handle tear. Even though it is rare, it is necessary to consider the possibility of displaced double-layered meniscus in the differential diagnosis of a bucket-handle tear. Here, we report the MRI and arthroscopic findings of a displaced double-layered lateral meniscus, which was similar to the bucket-handle tear.

• 한국표면공학회지
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• 제54권1호
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• pp.30-36
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• 2021

In this study, double-layered anodizing films were formed on Al 5052 and Al 6061 alloys consecutively first in sulfuric acid and then in oxalic acid, and hardness, withstand voltage, surface roughness and acid resistance of the anodizing films were compared with single-layered anodizing films in sulfuric acid and oxalic acid electrolytes. Hardness of the double-layered anodizing film decreased with increasing ratio of inner layer to outer layer for both Al 5052 and Al 6061 alloys, suggesting that outer anodizing film formed in sulfuric acid electrolyte is damaged during the second anodizing in oxalic acid electrolyte. Withstand voltage of the double-layered anodizing films increased with increasing the thickness ratio of inner layer to outer layer. Surface roughness of the double-layered anodizing films were comparable with that of single-layered anodizing film formed in sulfuric acid but higher than that of single layer anodizing film formed in oxalic acid electrolyte. In acid resistance test, all of the double-layered and single-layered anodizing films showed good acid resistance more than 3 h without any visible gas evolution, which is attributable to sealing of pores. Based on the experimental results obtained in this work, it is possible to design a double-layered anodizing film with cost-effectiveness and improved physical and electrical properties by combining two consecutive anodizing processes of sulfuric acid anodizing and oxalic acid anodizing methods.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2015년도 추계 학술논문 발표대회
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• pp.107-108
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• 2015

Layered Double Hydroxides is known as a hydrotalcite-like material. It is a type of anionic clay with planar structure. It is composed of layer structure which is able to exchange anion between two layers which includes divalent ion and trivalent ion. Therefore, layered double hydroxide is applicable for eliminating harmful heavy metals and anionic substances which exist in the concrete. Because it is also able to be used as catalyst and has high possibility of utilization, It is getting an large amount of attention recently. In this study, an analysis on the structure of the layerd double hydroxide (LDH) which is possible to bind the anion was carried out.

• 한국지열·수열에너지학회논문집
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• 제7권2호
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• pp.43-50
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• 2011

This paper presents how to analyze heat transfer characteristics of double-layered soils. Thermal response tests were conducted to measure the ground thermal conductivities of Joomunjin sand and double layered soils filled in a steel box of which the size is $5m{\times}1m{\times}1m$. Double-layered soils were composed of Joomunjin sand and Kaoline clay. Each thermal conductivity of Joomunjin sand and Kaloine clay was measured by using Heat Flow Meter considering different void ratio. The ground thermal conductivity of double-layered soils was 15% smaller than that of Joomunjin sand.

• 소성∙가공
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• 제19권7호
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• pp.405-410
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• 2010

Double layered tube that has been used for transportation and oil piping system is occasionally exposed to elevated temperature. The change in stress state at elevated temperature is important for the safe design of double layered tube. In this study, the variation of stress state for hydroformed double layered tube of which inner tube is stainless steel and outer tube is mild steel has been analytically analyzed. To characterize the thermal stress at elevated temperature, analytical model to provide thermal stresses between outer tube and inner tube was developed by using theories of elasticity and Lame equation. The feasibility of analytical model is verified by finite element analysis using ANSYS $CLASSIC^{TM}$, commercially available code. The variation of thermal stress at various thickness combination of inner and outer tube has also been investigated by proposed analytical model.