• Proceedings of the KOSOMBE Conference
• /
• v.1997 no.05
• /
• pp.245-248
• /
• 1997

Excessive stress on the bone-stem interface may cause local micromotion that could produce midthigh pain, interface bone resorption and prevent bony ingrowth. It is important for clinician and prosthetic designer to develop an understanding of the load transfer mechanism, its associated stress pattern and its relationships with the particular mechanical characteristics of the femoral stem designs. Finite element method (FEM) is preeminently suited to provide information in this respect. The authors developed 3-dimensional numerical finite element models implanted with the straight stem which is composed of total 1170 elements of 8 nodes and with the curved stem which is composed of total 885 elements of 8 node, and analysed the relative micromotions between the straight stem and the curved stem in immediate postoperative stage of an uncemented total hip replacement in load simulating the single leg stance. The results showed that the rotational displacement was occupied over 90% of total micromotion in both types of stem and was peak at the proximal medial portion of the stem, but markedly less distally. The curved stem was more stable especially in terms of rotational stability. It is recommended that surgeons do not allow the patient weight bearing until bony ingrowth was achieved. In the future more attention should be drawn to increase initial rotational stability of the two types of femoral stem to prevent loosening from excessive micromotion.

• Geophysics and Geophysical Exploration
• /
• v.17 no.3
• /
• pp.147-154
• /
• 2014

For analyzing the distribution of chromite, magnetic survey was carried out on the chromium mineralized belt in Bophi Vum area, northwestern Myanmar. As a result, the magnetic susceptibility of chromite is lower than those of dunite and harzburgite, which are background rocks of chromite. Also, the locations of low magnetic anomaly zone and low magnetic susceptibility models of 3D magnetic inversion result are spatially well matched with those of chromite occurrences confirmed by the surface geological survey and trench survey. Some of low magnetic effects are expanded to the periphery area of chromite occurrences. Considering the magnetic susceptibility characteristics of various rocks in this area, the expanded low magnetic anomaly zones are estimated as the high potential areas bearing chromite. For confirming the potential area of chromite pointed by coarse magnetic survey, the additional detail exploration need to be carried out in future.

• Journal of the Korean Geosynthetics Society
• /
• v.14 no.1
• /
• pp.33-41
• /
• 2015

In this study, laboratory tests (flow, unit weight, unconfined compressive strength and bleeding tests) were performed to evaluate engineering properties of treated soil to improve pipe mixing method. As result, flow and bleeding properties are proportional to the water contents. The unit weight and unconfined compressive strength is decreased as the water contents increased. Comparing equipments contact pressure with bearing capacity of the mixed soil for dozer, backhoe and belt conveyor are immediately appliable. The applicable water content range is estimated from 80% to 200% by pipe mixing method using cement. Also, The design chart is developed from the results.

• Composites Research
• /
• v.32 no.6
• /
• pp.319-326
• /
• 2019

To address tremendous needs for developing efficiently heat dissipating material with lightweights, a new class of polymer possessing recyclable and malleable characteristics was synthesized for incorporating model functional hexagonal boron nitride (h-BN) filler. A good interfacial affinity between the polymer matrix and the filler along with shear force generated upon manufacturing the composite yielded the final product bearing highly aligned filler via simple hot pressing method. For this reason, the composite exhibited a high thermal conductivity of 13.8 W/mK. Moreover, it was possible to recover the h-BN from the composite without physical/chemical denaturation of the filler by chemically depolymerizing the matrix, thus the recovered filler can be re-used in the future. We believe this polymer could be beneficial as matrix for incorporating many other functional fillers, thus they may find applications in various polymeric composite related fields.

• Geomechanics and Engineering
• /
• v.4 no.3
• /
• pp.173-190
• /
• 2012

With recent growing interests in the Performance-Based Seismic Design and Assessment Methodology, more realistic modeling of a structural system is deemed essential in analyzing, designing, and evaluating both newly constructed and existing buildings under seismic events. Consequently, a shallow foundation element becomes an essential constituent in the implementation of this seismic design and assessment methodology. In this paper, a contact interface fiber section element is presented for use in modeling soil-shallow foundation systems. The assumption of a rigid footing on a Winkler-based soil rests simply on the Euler-Bernoulli's hypothesis on sectional kinematics. Fiber section discretization is employed to represent the contact interface sectional response. The hyperbolic function provides an adequate means of representing the stress-deformation behavior of each soil fiber. The element is simple but efficient in representing salient features of the soil-shallow foundation system (sliding, settling, and rocking). Two experimental results from centrifuge-scale and full-scale cyclic loading tests on shallow foundations are used to illustrate the model characteristics and verify the accuracy of the model. Based on this comprehensive model validation, it is observed that the model performs quite satisfactorily. It resembles reasonably well the experimental results in terms of moment, shear, settlement, and rotation demands. The hysteretic behavior of moment-rotation responses and the rotation-settlement feature are also captured well by the model.

• Advances in concrete construction
• /
• v.5 no.2
• /
• pp.117-143
• /
• 2017

The attack of environmental aggressive agents progressively reduces the structural reliability of buildings and infrastructures and, in the worst exposition conditions, may even lead to their collapse in the long period. A change in the material and sectional characteristics of a structural element, due to the environmental damaging effects, changes its mechanical behaviour and varies both the internal stress redistribution and the kinematics through which it reaches its ultimate state. To identify such a behaviour, the evolution of both the damaging process and its mechanical consequences have to be taken into account. This paper presents a computational approach for the analysis of reinforced and prestressed concrete elements under sustained loading conditions and subjected to given damaging scenarios. The effects of the diffusion of aggressive agents, of the onset and development of the corrosion state in the reinforcement and the corresponding mechanical response are studied. As known, the corrosion on the reinforcing bars influences the damaging rate in the cracking pattern evolution; hence, the damage development and the mechanical behaviours are considered as coupled phenomena. The reliability of such an approach is validated in modelling the diffusion of the aggressive agents and the changes in the mechanical response of simple structural elements whose experimental behaviour is reported in Literature. A second set of analyses studies the effects of the corrosion of the tendons of a P.C. beam and explores potentially unexpected structural responses caused by corrosion under different aggressive exposition. The role of the different types and of the different positions of the damaging agents is discussed. In particular, it is shown how the collapse mode of the beam may switch from flexural to shear type, in case corrosion is caused by a localized chloride attack in the shear span.

• Geomechanics and Engineering
• /
• v.19 no.6
• /
• pp.485-498
• /
• 2019

Pre-tensioned rock bolts can be classified into fully anchored, lengthening anchored and point anchored bolts based on the bond length of the resin or cement mortar inside the borehole. Bolts in varying anchoring methods may significantly affect the supporting effect of surrounding rock around a tunnel. However, thus far, the theoretical basis of selecting a proper anchoring method has not been thoroughly investigated. Based on this problem, 16 schemes were designed while incorporating the effects of anchoring length, pretension, bolt length, and spacing, and a systematic numerical experiment was performed in this paper. The distribution characteristics of the stress field in the surrounding rock, which corresponded to various anchoring scenarios, were obtained. Furthermore, an analytical approach for computing the active and passive strengthening index of the anchored surrounding rock is presented. A new fully anchoring method with pretension and matching technology are also provided. Then, an isolated loading model of the anchored surrounding rock was constructed. The physical simulation test for the bearing capacity of the model was performed with three schemes. Finally, the strengthening mechanism of varying anchoring methods was validated. The research findings in this paper may provide theoretical guidelines for the design and construction of bolting support in tunnels.

• Journal of Arbitration Studies
• /
• v.17 no.2
• /
• pp.141-165
• /
• 2007

This study aims to make a contribution to the promotion of trade and economic development of South Korea, and, at the same time, call attention to the increasing trend of investment agreements concluded within Free Trade Agreements (FTA) by examining theoretically FTAs and dispute resolution and investigating systematically the conclusion procedure of agreements, and the system, institutions, and jurisdiction of dispute resolution, and presenting these findings to the government and investors involved. The most problematic aspect in the legal process of arbitration involving disputes over investment is that of arguments concerning the right of jurisdiction. When a dispute arises, even though an investor files for arbitration at an ICSID institution, the parties become involved in another energy-consuming argument even before proceeding to the hearing and decision of the original plan in cases in which the respondent of the dispute files an objection to the decision rights of the arbitral tribunal. As the main basis for this type of plea, the point of non-existence of jurisdiction is first raised where the applicable dispute does not fall under the range of investments defined in individual investment contracts or investment agreements such as a Bilateral Investment Treaty (BIT). To avoid an open-ended definition of investment for the range of investments, articles concerning investments in the FTA and NAFTA between Canada and the USA adopt the limited closed-list method. Article 96 of the FTA between Japan and Mexico applied the same abovementioned method of limited form of definition regarding range of investments and concluded BITs between member countries of APEC applied a similar method as well. Instead of employing the previously used inclusive definition, the BITs concluded between countries of Latin America and the USA are equipped with limited characteristics of an investment. Furthermore, to correspond with this necessary condition the three following requirements are needed : 1) fixed investment funding; 2) expected profits resulting from such investments; 3) and the existence of fixed risk bearing.

• Journal of Forest and Environmental Science
• /
• v.25 no.1
• /
• pp.1-24
• /
• 2009

Teak (Tectona grandis) is one of the most valuable timber yielding species in the world, with predominant distribution in tropical or sub-tropical countries. However, natural teak available only in few countries like India, Myanmar, Laos People's Democratic Republic and Thailand. Teak grows well in deep, well-drained alluvial soils, fairly moist, warm, tropical climate with pH ranges from 6.5-7.5. Teak is cultivated in many Asian, African and South American countries for timber production. The global teak plantations are estimated to be three million hectare with major share in India (44%) followed by Indonesia (33%). India is considered as richest genetic resources of teak with large areas of natural teak bearing forests (8.9 million ha), plantations (1.5 million ha), clonal seed orchards (1000 ha) and seed production areas (5000 ha). The studies on diversity of teak populations showed that teak is an out crossing species with major portion of diversity present within the populations. The productivity and quality of teak timber varies depending upon the site and environmental conditions. Teak wood is moderately heavy, strong and tough,straight grained, coarse textured and ring porous with specific gravity varies from 0.55 to 0.70. The sapwood is white to pale yellow in colour and clearly demarcated while heartwood is dark brown or dark golden yellow in colour. Teak is one of the most durable timbers in the world, practically, impervious to fungus and white ant attack and resistant to decay. Teak wood is used in ship and boat constructions, furnitures and aesthetic needs. Genetic improvement programmes have been undertaken in countries like Thailand, India, Malaysia and Indonesia. The programme includes provenance identification and testing, plus tree selection and clonal multiplication, establishment of seed orchards and controlled hybridization. Several aspects like phenology, reproductive biology, fruit characteristics, silvicultural practices for cultivation, pest and diseases problems, production of improved planting stock, harvesting and marketing, wood properties and future tree improvement strategy to enhance productivity have been discussed in this paper.

• Journal of the Korean Geotechnical Society
• /
• v.21 no.2
• /
• pp.67-84
• /
• 2005

This research was conducted to evaluate the effectiveness of reinforcement for nearly saturated soft clay compaction. The effectiveness was investigated by roller compaction test using nearly saturated clay specimens. The nearly saturated condition was obtained by submerging clay in the water for 12 hours. High water content specimens were compacted in plane strain condition by a steel roller. A specimen was compacted by four 5 cm horizontal layers. Specimens were prepared fur both reinforced and unreinforced cases to evaluate the effectiveness of reinforcement. Used reinforcement is a composite consisted of both woven and non-woven geotextile. The composite usually provides drainage and tensile reinforcement to hi인 water-contented clay so that it increases bearing capacity. Therefore, large compaction load can be applied to reinforced clay and it achieves higher density effectively. The reinforcement also increases compaction efficiency because it reduces the ratio between shear and vertical forces during compaction process. The maximum vertical stress on the base of specimen usually decreased with higher compaction thickness. The reinforcement increases soil stiffness under the compaction roller and it initiates stress concentration. As a result, it maintains higher vertical stress level on the base of specimen that provides better compaction characteristics. Based on test results, it can be concluded that the reinforcement is essential to achieve effective compaction on soft clay.