• The Science & Technology
• /
• v.14 no.10 s.149
• /
• pp.29-30
• /
• 1981

• Journal of the Korean Society for Advanced Composite Structures
• /
• v.4 no.1
• /
• pp.15-24
• /
• 2013

This project investigated the use of two types of thermoplastic pipes, High-Density Polyethylene (HDPE) and Poly-vinyl Chloride (PVC), as cross-drains under highways. Pipes ranging from 0.3 m (12 in.) to 1.5 m (60 in.) in diameter were evaluated under deep fills, minimum cover, and construction loads. In addition to a comprehensive literature review, an analytical study into the allowable fill heights for thermoplastic pipes and a field study to observe the installation and performance of the pipe in service conditions were conducted. Based on the study findings, recommendations regarding how and when thermoplastic pipe should be installed are provided.

• Composites Research
• /
• v.16 no.3
• /
• pp.32-40
• /
• 2003

In recent years, the investigation on the development of fiber reinforced plastic(FRP) Re-Bar has been greatly increased due to the attractive physical and mechanical properties of FRP. The primary reason of such a tendency is in the fact that it does not ordinarily cause durability problems such as those associated with steel reinforcement corrosion. This study is an experimental investigation on the flexural behavior of one-way concrete slabs, which can be used to construct bridge deck, reinforced with GFRP Re-Bar bundle. The tensile tests of GFRP Re-Bar produced by domestic industry and third point bending tests of one-way slab specimens reinforced with GFRP Re-Bar bundle are peformed. For all slab specimens, load-deflection relations are predicted by using the ACI committee 440 and the results are compared with experimental ones. In order to establish the design criteria or guidelines of concrete flexural member reinforced with FRP Re-Bar, it is needed to evaluate the serviceability limit state as well as the strength limit state.

• Journal of Welding and Joining
• /
• v.9 no.1
• /
• pp.48-57
• /
• 1991

Welding of dissimilar materials is an area of growing importance in the automotive, aerospace, electronics medical and other domestic appliance industries. This study investigated the ultrasonic welding of dissimilar polymers. Two amorphous and two semicrystalline polymers were used, utilizing all possible welding combinations. For each combination of dissimilar materials, the weldabilitys of the joint was evaluated as a function of weld time, amplitude of vibration and pressure. The joint was also examined microscopically to analyze the melting and flow of the materials. It was generally around found that welding of amorphus polymers resulted in very poor joints. Welding of the amorphous polymers together and welding of the semicrystalline polymers together produced good joints.

• Journal of the Korean Society for Advanced Composite Structures
• /
• v.4 no.1
• /
• pp.25-32
• /
• 2013

In real world applications, the response of structures may be dependent on the rate of loading and thus can be affected by transient loading, especially when the rate of loading is significant. In such situations, the rate of loading may become a major issue to understand structures during earthquake excitation or under blast or high velocity impact. In some cases, the rate effect on structures under strong earthquake excitation cannot be ignored when attempting to understand inelastic behavior of structures. Many researchers developed the constitutive theories in cyclic plasticity and viscoplasticity. In this study, numerical simulation by cyclic visocoplasticity models is introduced and analyzed. Finally, the analytical results are compared with experimental results as a means to evaluate and verify the model.

• The Korean Journal of Rheology
• /
• v.6 no.2
• /
• pp.104-118
• /
• 1994

단섬유 보강 플래스틱 재료의 사출성형 충전공정에서 금형재의 유동장이 섬유 배향 상태를 형성하는데 중요한 역할을 할 뿐만 아니라 섬유의 배향상태가 역으로 유동장에 영향 을 미친다. 충전유동과 섬유 배향의 연계해석을 위하여 단섬유에 의한 추가적인 응력을 포 함하는 Dinh과 Armstrong의 이방성 구성방정식을 충전유동의 해석에 도입하였다. 평명방향 으로의 속도구배에 의한 응력을 고려하여 새롭게 유도된 압력 지배방정식과 에너지방정식을 유한요소법과 유한차분법을 이용하여 풀고 동시에 2차배향텐서의 변화방정식을 4차 Runge-kutta 방법을 이용하여 풀었다. 절점 게이트 주변의 확장유동영역과 라인게이트를 통한 수축유동영역에서 평면방향으로의 속도구배에 의한 응력이 유동장에 미치는 영향을 고 찰하였다. 확장유동영역에서는 평면방향으로의 속도구배에 의한 영향이 추가적인 유량으로 나타나면서 주어진 유량조건하에서 평면방향으로의 속도구배에 의한 응력을 고려하지 않은 경우보다 작은 압력구배를 나타냈다. 수축유동영역에서는 위와 반대의 결과를 보였다. 이러 한 경향은 섬유의 부피분율이증가하거나 모양비가 커짐에 따라 증가한다.

• Composites Research
• /
• v.12 no.2
• /
• pp.46-52
• /
• 1999

In this paper result of an analytical investigation pertaining to the elastic buckling behavior of orthotropic plate under combined in-plane shear and bending forces is presented. The existing analytical solution developed for the isotropic plates is extended so that the orthotropic material properties can be taken into account in the buckling analysis of web plate. For the solution of the problems Rayleigh-Ritz method is employed. Graphical form of results for finding the elastic buckling strength of orthotropic plate under combined in-plane shear and bending forces is presented. Brief discussion on the design criteria for the shear and bending interaction is also presented.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.14 no.3
• /
• pp.185-193
• /
• 1994

Conventional ultrasonic flaw detection system uses a large amplitude narrow pulse to excite a transducer. However, these systems are limited in pulse energy. An excessively large amplitude causes a dielectric breakage of the transducer, and an excessively long pulse causes decrease of the resolution. Using the pulse compression, a long pulse of pseudorandom signal can be used without sacrificing resolution by signal correlation. In the present work, the pulse compression technique was implemented into an ultrasonic system. Golay code was used as a pseudorandom signal in this system, since pair sum of autocorrelations has no sidelobe. The equivalent input pulse of the Golay code was derived to analyze the pulse compression system. Throughout the experiment, the pulse compression technique has demonstrated for its improved SNR(signal to noise ratio) by reducing the system's white noise. And the experimental data also indicated that the SNR enhancement was propotional to the square root of the code length used. The technique seems to perform particularly well with highly energy-absorbent materials such as polymers, plastics and rubbers.

• The Transactions of the Korea Information Processing Society
• /
• v.6 no.7
• /
• pp.1724-1737
• /
• 1999

Multimedia data service applications have to store and manipulate LOBs(unstructured large objects) composing multimedia data. As such, the tertiary storage devices such as an optical disk jukebox and a tape library that consist of a number of platters (the disks in case of an optical disk jukebox and the cartridge tapes in case of a tape library) have been considered essential for the storage system of a DBMS in order to efficiently support storage and management of vary large volume of data. Since the latency with tertiary storage is too long, the schemes for efficient retrieval of LOBs out of tertiary storage need to be investigated. In this paper, we investigated the tertiary I/O Considering the performance characteristics of the LOBs, we proposed various I/O scheduling heuristic algorithms that reduce latency in query processing with LOB retrieval from tertiary storage, and evaluated their performance through a detailed simulation.