• Geotechnical Engineering
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• v.13 no.1
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• pp.35-46
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• 1997

The isotropic single-hardening constitutive model has been applied to predict the behavior of soils during reorientation of principal stresses in the field. The predicted response by the model agrees well with the measured behavior for a series of torsion shear tests performed on hollow cylinder specimens of Ko consoildated clay along various stress -paths. This indicates that the soil behavior during reorientation of principal stresses can be predicted by using the model with application of simple informations given by isotropic compression tests and conventional consolidated-undxained triaxial compression tests. Isotropic elasto-plastic soil behavior has been served during primary loading from both the torsion shear tests and the predictions by the model. However, the directions of maj or principal strain increment given by the model have not coincided with the directions for tests during stress reversal, such as unloading and reloading, within isotropic yield surface for Ko consolidated stress. This indicates that kinematic hardening model instead of isotropic hardening model should be developed to predict the soil behavior during stress reversal. The experimental strain increment vectors in the work-space have been compared with the directions expected for associated and nonassociated flow rules.

• Journal of the Korean GEO-environmental Society
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• v.20 no.5
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• pp.31-38
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• 2019

Recently, there has been an increasing number of ground subsidence (sink-hole) in the downtown areas, and in such a case, it is important to minimize accidents and passages through prompt recovery. With respect to the present recovery method for ground subsidence, the methods of applying the back filling after excavating the ground subsidence or using the grouting injected materials to restore the ground are mostly used, but there has been few studies on materials used for recovering the ground subsidence. Therefore, in order to clarify the characteristics of back filling materials used in the ground subsidence, this study uses the environment-friendly hardening agent to improve the dredged clay, and then, the mixture ratio of hardening agent and mixture ratio of decomposed granite soil is changed to cure for 3, 7, 14 and 28 days to analyze the intensity characteristics of the unconfined compression, and it was compared with the unconfined compression intensity for the previously used cement, a hardening agent. In order to evaluate the characteristics of intensity on the back filling materials, the C.B.R test was carried out, and for the review on whether the back filling materials influence on corrosion of water and sewer pipes and others, the soil non-resistance test was carried out. As a result of the test, for the case of the recovery work of the ground subsidence that requires urgency, it is considered as prudent if the hardening agents of 12% are integrated to cure for 3 days or longer, and for not having the influence on the corrosion of the gas tube or water pipes, it is proposed to mix for 30% or more of the decomposed granite soil. Door model test were conducted To confirm the bearing capacity characteristics of the solidified layer.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.160-164
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• 2007

In the steel industry, there is a need to produce large forged parts for the automobile industries, the flight and shipping industries ad military industries. In the steel-industry application, a cogging technique for cast ingots is required, because the major parts are needed as one large body in order to obtain higher quality. Therefore, cogging process is the primary step in manufacturing of practically large open-die forging. In the cogging process, internal voids have to be eliminated as defects, The present work is concerned with the elimination of the internal voids in large ingots so as obtain sound products. In this study, hot compression tests were carried out to obtain the flow stress of cast microstructure at different temperature and strain rates. The FEM analysis are performed to investigate the overlap defect of cast ingots during cogging stage. The measure flow stress data were used to simulate the cogging process of cast ingot using the practical material properties. Also the analysis of void closure are performed by using the $DEFORM^{TM}$-3D. The calculated results of void closure behavior are compared with the measured results before and after cogging, which are scanned by the X-ray scanner. From this result, the criteria for deformation amounts effect on the void closure can be investigated by the comparison of practical experiment and numerical analysis.

• Journal of Korean Society of Steel Construction
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• v.10 no.3 s.36
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• pp.509-523
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• 1998

A consistent finite element formulation and analytic solutions are presented for stability of thin-walled circular arch. The total potential energy is derived by applying the principle of linearized virtual work and including second order terms of finite semitangential rotations. As a result, the energy functional corresponding to the semitangential moment is newly derived. Analytic solutions for the out-of-plane buckling of symmetric thin-walled curved beam subjected to pure bending or uniform compression with simply supported boundary conditions are obtained. For finite element analysis, the cubic Hermitian polynomials are utilized as shape functions and $16{\times}16$ stiffness matrix for curved beam elements and $14{\times}14$ stiffness matrix for straight beam elements are evaluated, respectively. In order to illustrate the accuracy of this study, analytical and numerical results for lateral buckling problems of circular arch are presented and compared with available analytical solutions.

• Korean Journal of Materials Research
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• v.3 no.1
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• pp.50-57
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• 1993

Abstract The sintering behavior of the mechanically alloyed AI-8wt%Fe power during vacuum hot pressing was investigated and high temperature deformation behavior of the sintered specimen was studied through compression tests at various strain rates in the temperature range between 35$0^{\circ}C$ and 45$0^{\circ}C$. In 'addition, thermal stablity of the sintered specimem was examined by hardness measurement after annealing the spcimem for 60 hours in the temperature range of 30$0^{\circ}C$ ~50$0^{\circ}C$. The compressive stress increased rapidly with strain and reached the maximum point at the strain about 3%. With slight decrement after reaching the maximum point, the flow stress became constant up to the strain of 30% and it was considered to be due to equilibrium between work hardening and dynamic recrystallization. The hardness of the 60 hrs annealed specimens began to decrease rapidly at 40$0^{\circ}C$ .

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.8
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• pp.1144-1151
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• 2009

Refrigeration systems can be incorporated with non-adiabatic capillary tubes to improve their efficiency. The non-adiabatic capillary tube is constructed by joining the capillary tube with suction pipe to allow heat transfer between them, which is called capillary tube-suction line heat exchanger(SLHX). There are various joining methods and they may influence the characteristics of the refrigeration cycle. The present work aims to analyze the effect of widely-used two joining methods on the refrigeration cycle. The results show that soldered SLHX has much less thermal resistance than tapered SLHX but slightly outperforms in terms of coefficient of performance(COP) and cooling capacity. The soldered SLHX increased COP and cooling capacity of a refrigerator by 5.09% and 14.77% while the tapered SLHX did by 5.05% and 14.75%, respectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.7
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• pp.1237-1245
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• 2006

This paper presented a hardware implementation of ARIA, which is a Korean standard l28-bit block cryptography algorithm. In this work, ARIA was designed technology-independently for application such as ASIC or core-based designs. ARIA algorithm was fitted in FPGA without additional components of hardware or software. It was confirmed that the rate of resource usage is about 19% in Altera EPXAl0F1020CI and the resulting design operates stably in a clock frequency of 36.35MHz, whose encryption/decryption rate was 310.3Mbps. Consequently, the proposed hardware implementation of ARIA is expected to have a lot of application fields which need high speed process such as electronic commerce, mobile communication, network security and the fields requiring lots of data storing where many users need processing large amount of data simultaneously.

• Polymer(Korea)
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• v.39 no.1
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• pp.144-150
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• 2015

Gellan gum as a natural polysaccharide has good heat resistance, acid resistance and enzymes resistance. However, one of the drawbacks of gellan gum might be the lower mechanical strength. In this work, gellan gum scaffolds were mixed with poly(lactic-co-glycolic acid) (PLGA) microsphere in order to improve mechanical properties. The gellan gum scaffolds with various contents of PLGA microsphere were prepared for the regeneration of disc tissues. To evaluate the mechanical strength of hybrid structure of gellan gum and PLGA microsphere, compression strength of the fabricated scaffolds was measured. MTT analysis, SEM observation, histological evaluation and RT-PCR were performed to confirm the effect on the cell growth and extracellular matrix secretion. As a result, it showed the best cell proliferation and extracellular matrix secretion in gellan gum sponge containing 50% PLGA microspheres. In conclusion, this study confirmed that the hybrid structure of gellan gum and PLGA microspheres was found suitable in regeneration of the intervertebral disc.

• Journal of Adhesion and Interface
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• v.10 no.2
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• pp.106-112
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• 2009

In the present work, novel biocomposites made with biodegradable Lyocell woven fabrics and poly (butylene succinate) were successfully fabricated for the first time. Lyocell/poly(butylene succinate) biocomposites with different fiber loadings of 0, 30, 40, 50 and 60 wt% were prepared by compression molding with a sheet interleaving manner. The effect of Lyocell fabric loading on the interlaminar shear strength, tensile and flexural properties, heat deflection temperature, thermal expansion behavior, and thermal stability of the biocomposites was investigated. The properties strongly depended on the fabric loading and the results were consistent with each other. It was demonstrated that the Lyocell fabrics played a remarkable role in improving the properties of poly(butylene succinate) resin by incorporating the fabrics into the resin. The greatest inter-laminar, tensile, flexural and thermal properties of the biocomposites were obtained with Lyocell fabrics of 50% by weight.

• Steel and Composite Structures
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• v.35 no.5
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• pp.627-634
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• 2020

The past years were marked by an increase in the use of wood waste in civil and mechanical constructions. Date palm waste remains also one of the most solicited renewable and recyclable natural resources in the composition of composite materials. In Algeria, a great amount of this type of plant wastes accumulates every year. In order to make use of this waste, a new wood-epoxy composite material based on date palm petiole particleboard is developed. It makes use of date palm petiole particleboard as reinforcement and epoxy resin as matrix. The size of the particles reinforcement are between 1~3 mm and proportion of reinforcement used is 37%. In this work, experimental and numerical studies are conducted in order to characterize the wood fibre-epoxy plates. Firstly, experimental modal analysis test was carried out to determine Young's modulus of the elaborated material. Then, in order to validate the results, compression test was conducted. Furthermore, additional information about the shear modulus of this material is obtained by performing an experimental modal analysis to extract the first torsional mode. Moreover, a finite element model is developed using ANSYS software to simulate the vibration behaviour of the plates. The results show a good agreement with the experimental modal analysis, which confirms the values of Young's modulus and shear modulus.