• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.23 no.3
• /
• pp.247-254
• /
• 2010

Due to lightweight and high durability of glass-fiber reinforced polyester (GFRP) materials, they are promising alternatives to conventional construction materials such as steel, concrete and wood. As good application examples of GFRP materials, several types of temporary arch bridges were suggested and verified by finite element analyses in our previous study where snap-fit GFRP decks were applied. In this paper, we conduct a structural performance test to verify safety and serviceability of the temporary arch bridge, where snap-fit GFRP decks are assembled by bolts. The structural problems occurred in this test are also discussed and improvement of temporary arch bridges is suggested to resolve the occurred structural problems.

• Korean Journal of Plant Resources
• /
• v.35 no.6
• /
• pp.820-824
• /
• 2022

Ecologically sustainable means of development is the point to support environmental homeostasis. One of our roles is to find bio-degradable resources that can be substituted for petroleum-based products to effectively abide by the natural viability. To counter the issues of deforestation and preserve biodiversity, it is necessary to produce a non-wood crop that can fulfill the requirement for raw material from which several products can be produced. Kenaf (Hibiscus cannabinus), a member of the family Malvaceae, is showing sufficient potentiality along this road-map. Due to its rich fiber content, it has been used extensively in various fields for long, probably as early as 4,000 BC. At present, kenaf has been used as provider of paper, plastics, fiber glass, biofuel, activated carbon and epoxy composite. This obviously catch one's attention towards its capability to replace petroleum-based products as a whole. Moreover, the plant shows considerable relevance in decreasing pollutants by virtue of its enormous absorption capacity. These multiple applications of kenaf justify its credibility to be the best resource for the better world. The paper presents an overview on its numerous uses reported in the literature that we have investigated and its great potential as a valuable multipurpose crop.

• Composites Research
• /
• v.34 no.3
• /
• pp.155-160
• /
• 2021

Metamaterials are complexes of elements that can create properties not found in naturally occurring materials, such as changing the direction of forces, creating negative stiffness, or altering vibration and impact properties. In the case of wood pile metamaterials that are easy to manufacture and have excellent performance in reducing vibration and shock in the vertical direction, basic research on variables affecting shock transmission is needed to reduce shock. Although research on impact reduction according to geometrical factors is being conducted recently, studies on the effect of material variables on impact reduction are insufficient. In this paper, finite element analysis was carried out by variablizing the geometrical properties (lamination angle, diameter, length) and material properties (modulus of elasticity, specific gravity, Poisson's ratio) of wood pile cylinders. Through finite element analysis, the shape of the wooden pile cylinder delivering impact was confirmed, and the effect of each variable on the reduction of impact force and energy was considered through main effect diagram analysis, and frequency band analysis was performed through fast Fourier transform. proceeded In order to reduce the impact force and vibration, it was found that the variables affecting the contact area of t he cylinder have a significant effect.

• Journal of the Korean Wood Science and Technology
• /
• v.32 no.5
• /
• pp.29-38
• /
• 2004

In this study, we investigated the thermal properties of corn-starch filled polybutylene succinate-adipate (PBS-AD) bio-composites. Thermal analysis (TA) is used to describe the analytical method for measuring the chemical property and weight loss of composite materials as a function of temperature. The thermal stability of corn-starch was lower than that of pure PBS-AD. As corn-starch loading increased, the thermal stability and degradation temperature of the bio-composites decreased and the ash content increased. It can be seen that the degree of compatibility and interfacial adhesion of the bio-composites decreased because of the increasing mixing ratio of the corn-starch. As the content of corn-starch increased, there was no significant change in the glass transition temperature (T_g) and the melting temperature (T_m) for the bio-composites. The storage modulus (E') and loss modulus (E") of the corn-starch flour filled PBS-AD bio-composites were higher than those of PBS-AD, because of the incorporation of corn-starch increased the stiffness of the bio-composites. At higher temperatures, the decreased storage modulus (E') of bio-composites was due to the increased polymer chain mobility of the matrix polymer. From these results, we can expect that corn-starch has potential as a reinforcing filler for bio-composites. Furthermore, we recommend using a coupling agent to improve the interfacial adhesion between corn-starch and biodegradable polymer.

• The Journal of the Korea Contents Association
• /
• v.22 no.2
• /
• pp.147-161
• /
• 2022

This study examined changes in the ecological characteristics and design characteristics of Ban's exhibition space in three representative temporary exhibition halls and three permanent exhibition halls designed by Ban Shigeru since 2000. Through the investigation of the concepts and characteristics of ecological architecture, the design characteristics of exhibition space, the analysis framework of the design characteristics of exhibition space and the design elements of ecological architecture is obtained. The analysis results show that there are big changes between the temporary exhibition space and the permanent exhibition space in terms of building scale, space composition, function, materials and technology. On the one hand, the temporary exhibition space used recyclable materials, such as paper tubes, containers to be assembled on site into a single-layer space focused on display. The assembly method was simple and the construction period was short. After the exhibition, the exhibition space were dismantled. The materials were either transported to the next display site or recycled and reused. On the other hand, the permanent exhibition space used reinforced concrete as the main structure, and used a large amount of wood and glass materials to construct a multi-layered composite cultural space that separated the exhibition space and the leisure space. In terms of ecological characteristics, the building materials of the temporary exhibition space were recycled and no industrial wastes were generated after the demolition. The permanent exhibition hall uses eco-friendly wood for the roof and walls, so it is easy to replace and repair. Both types of exhibition halls are changing ecological architecture in a more sustainable direction by saving resources and energy through natural light and ventilation.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.28 no.2
• /
• pp.27-34
• /
• 2024

This study was conducted to examine the feasibility of using Fe-activated wood-derived biochar as a conductive filler for manufacturing cement-based strain sensor. To evaluate the compressive and electrical properties of cement composite with 3% Fe-activated biochar, three cubic specimens of size 50 x 50 x 50mm³ and three prismatic cement-based sensors of size 40 x 40 x 80mm³ were prepared respectively. The four-probe method of electrical resistance measurement was used for cement-based sensors. For cement-based sensors with FE-activated biochar, the conductive performance such as electrical resistance and impedance under different water content and repeated compression was investigated. Results showed that the fractional changes in the DC electrical resistivity of cement-based sensors increase with increasing time and the maximum fractional changes in the resistivity decrease with increasing the moisture contents during 900s. At moisture content of 7.5% range, the conductive performance of cement composite including 3% Fe-activated biochar as a conductive filler showed the most stable, while the strain detection ability tended to decrease somewhat as the repeated compressive stress increased between repeated compressive strain and fractional change in resistivity (FCR).

• Journal of Korean Association for Spatial Structures
• /
• v.20 no.2
• /
• pp.39-49
• /
• 2020

In this study, we will develop a hybrid cross-sectional shape of steel inserted type glued-laminated timber that can improve the strength of structural glued-laminated timber and maximize the ductility by using steel plate with excellent tensile and deformation ability. A total of three specimens were fabricated and the flexural performance test was carried out to evaluate the structural performance of the steel inserted type glued-laminated timber. In order to compare the effect of steel inserted glued-laminated timber, one structural glued-laminated timber test specimen composed of pure wood was manufactured. In addition, in order to evaluate the adhesion performance of the steel inserted, one each of a screw joint test specimen and a polyurethane joint test specimen was prepared. As a result, all the specimens showed the initial crack in the finger joint near the force point. This has been shown to be a cause of crack diffusion and strength degradation. The use of finger joints in the maximum moment section is considered to affect the strength and ductility of the glued-laminated timber beam. Polyurethane-adhesive steel inserted glued-laminated timber showed fully-composite behavior with little horizontal separation between the steel plate and glued-laminated timber until the maximum load was reached. This method has been shown to exhibit sufficient retention bending performance.

• Proceedings of the Korean Society of Dyers and Finishers Conference
• /
• 2011.03a
• /
• pp.79-79
• /
• 2011

최근 플라스틱 제품의 사용후 폐기에서 발생 되는 환경적인 문제점들이 대두 되고 있는 가운데, 이러한 제품에 대한 친환경적인 재료 설계에 대한 요구가 거세지고 있는 실정으로 플라스틱 업계의 사활이 걸릴 정도의 중요한 문제로 부각되고 있다. 본 연구에서는 이러한 플라스틱 제품의 치명적인 환경적인 문제점을 극복하고자, Matrix 물질이 되는 플라스틱에서 부터 친 환경적인 생분해성 수지를 사용하면서, 물성의 강화제로써 천연물 유래의 여러 종류의 섬유를 사용하고자 하였다.가장 보편화된 생분해성 플라스틱인 지방족 폴리에스테르 계통의 생분해성 수지와 Polylactic acid에 대해 검토를 하였다. 지방족 폴리에스테르 의 경우는 기존 플라스틱 제품과 비교해서 유연하고, 신장율이 높고, PLA 대비 내열 사용한계 온도도 높아서 물성적인 측면에서 상당한 장점을 가지고는 있으나 가격이 매우 고가이므로, 기존 플라스틱을 대체하는 것에는 문제점이 있다. 반면 PLA의 경우 지방족 폴리에스테르 대비 절반 이하의 가격이고 기계적 강도 또한 매우 높기 때문에 기존의 플라스틱을 대체할 수 있는 가장 유력한 물질로 대두 되고 있으나, 사출물과 같은 충격이 요구되는 제품에 있어서는 PLA 고유의 약한 취성이 가장 큰 단점으로 지적되고 있다. 본 연구에서는 이러한 PLA를 기반으로 PLA의 장점이 기계적 강성을 유지하면서, 취성을 보완하기 위해 PBS를 혼합 할 수 있는 기술을 개발하였으며, 또한 원재료의 Cost를 줄이고, PBS 혼합에 따른 PLA의 기계적 강도 감소를 보완하기 위해 천연물 유래의 Wood fiber, Starch, Bamboo fiber, Cellulose fiber, Paper fiber 와 같은 각종 천연 Filler를 사용하여 기계적 기계적 강도 감소를 최소화 하였다.

• The Korean Journal of Quaternary Research
• /
• v.17 no.2
• /
• pp.55-61
• /
• 2003

In the year 2000 we culminated a successful five year investigation of climate change by completing a preliminary east-west transect across Mongolia. An earlier tree-ring study at Tarvagatay Pass, Mongolia indicated unusual warming during the 20th century similar to other paleo-investigations of the northern hemisphere. This record had represented one of the few tree-ring records for central Asia. New data from several sites in western Mongolia confirmed the preliminary temperature. The highest twenty-year growth period for the composite record is from 1973-1994. The western Mongolian record was significantly correlated with the Taimyr Peninsula and two northern hemisphere temperature reconstructions reflecting large-scale temperature patterns while showing some important regional differences. These differences should prove useful for climate models. We have also developed a millennial length temperature-sensitive record at the Solongotyin Davaa site (formerly Tarvagatay Pass) using relict wood and living trees. Conspicuous features over the last 1000 years are a century scale temperature decline punctuated by the end of the Little Ice Age in the late-1800s and 20th century warming. The record also shows a cold period early in the 12th century and warm intervals late in the 10th, early in the 15th and at end of the 18th centuries. Despite a limited sample size before 900 AD, the long Solongotyin Davaa record is useful in indicating severe cold events and suggests some cold intervals nearly as severe. These tree ring series, spanning much of the circumpolar northern treeline, have been compiled to create a long-term reconstruction of the Earth's temperature over centuries. The new chronology, in addition to its value as a detailed record of Mongolian climate, provides independent corroboration for such hemispheric and global reconstructions and their indications of unusual warming during the 20th century.

• Composites Research
• /
• v.35 no.3
• /
• pp.153-160
• /
• 2022

Cellulose nanofibrils (CNF) based on wood pulp fibers are gained much attention as part of biocompatible hydrogels for biomedical applications such as tissue engineering scaffolds, biomedicine, and drug carrier. However, CNF hydrogels have relatively poor mechanical properties, impeding their applications requiring high mechanical integrity. In this work, we prepare 2,2,6,6-tetramethylipiperidin-oxyl (TEMPO) oxidated cellulose nanofibrils hydrogels mediated with metal cations, which form the metal-carboxylate coordination bonds for enhanced mechanical strength and toughness. We conduct the large amplitude oscillatory shear (LAOS) test and Live/dead cell assay for obtaining nonlinear viscoelastic parameters and cell viability, respectively. In particular, the cell proliferation and viability change depending on the type of metal salt, which also affected the rheological properties of the hydrogels.