• Journal of the Korean Geosynthetics Society
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• v.9 no.3
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• pp.67-75
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• 2010

The tensile strength, permeability and discharge capacity of biodegradable plastic drain boards made with poly lactic acid (PLA) have been tested and verified prior to their usage at field. Based on test results, the tensile strength of biodegradable plastic drain board made with PLA has relatively lower tensile strain and tensile strength than those of plastic drain board. Performance of PLA filter having good permeability and low opening size is proper for the filter of vertical drain board. In case of improving stiffness of PLA filter, biodegradable plastic drain board also satisfies required discharge capacity as use of vertical drain board too.

• Magazine of the Korean Society of Agricultural Engineers
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• v.33 no.2
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• pp.82-93
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• 1991

The objective of this paper is to show that the soil-geotextile interaction needs to he addressed in addition to the usual tensile and modulus properties when the geotextile is being designed for a specific application. The soil-geotextile interaction can be directly assessed by standard direct shear test. The data presented here show that the shear strength paramaters describing the soil-geotextile interface can he greatly influenced by the type of the geotextile. In this investigation, we examined nine different geotextiles of varying construction and surface textures with two standard soil, under five loading conditions, and compared the shear strength and the frictional resistance with the corresponding values of soil itself The following conclusions were drawned from this study. 1. The shear stress-strain curve shows that there are the residual shear stresses at the soil-geotextile interface. Because of the hydraulic gradient between the soil and the geotextile, the excessive pore water can migrate into the geotextile and among the filaments and dissipate through the soil-geotextile interface. 2. The shear strength of the soil-geotextile interface is affected by the moisture content of the soil. At moisture content lower than the optimum water content of the Proctor compaction test, the shear strength of the soil-geotextile interface is greater. 3. The type and surface roughness of the geotextile have the greatest influence on the interface friction angle between the soil and the geotextile.

• Proceeding of KASS Symposium
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• 2006.05a
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• pp.233-238
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• 2006

This paper provides a new topology optimization technique which is intended to maximize the fundamental frequency with simultaneous consideration of other natural frequencies in the form of multi-frequency problems. The modal strain energy is considered as the objective function to be minimized and the initial volume of structures is used as the constraint function. The resizing algorithm based on the optimality criteria is adopted to update the hole size existing inside the material. From numerical tests, the proposed technique is found to be very effective to maximize the fundamental frequency of the structure and it can also successfully consider several higher mode effects into the optimum topology of structure through the introduction of weights.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.1
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• pp.9-13
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• 2009

A simple outline for teaching adaptive scheme based finite element method for planar problems as a part of computer aided teaching of structural engineering curriculum is presented. Displacement based finite element formulation for planar problems and representative strain value based adaptive scheme for mesh generation are considered. As examples, a cantilever beam with a concentrated load treated as a planar problem and stretching of a plate with a circular hole are analyzed with displacement based finite element method with adaptive meshes. The examples and outlines show how adaptive based finite element method may become an essential part of computer aided teaching of structural engineering.

• Journal of Korean Society of Forest Science
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• v.98 no.4
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• pp.357-362
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• 2009

Trials to find a method for overcoming the depletion of Tricholoma matsutake mycorrhiza from the artificially inoculated pine seedling (Pinus densiflora) when it is transplanted in situ were carried out. The culturing jars containing mycorrhizal seedlings were punched at the bottom to make the jar like a pot with keeping the soil structure of the original medium in vitro, and 8 kinds of irrigation solution were applied. Irrigation of distilled water caused disappearance of T. matsutake mycorrhizae, but biweekly irrigation of 2.5% PDMP (24 g potato dextrose broth, 3 g malt extract, 1 g peptone) solution or 0.5% Tween 80 solution until 3 months of acclimation could keep mycorrhizal association stronger. The percentage of mycorrhizal roots out of total length of roots was increased during the acclimation, and the acclimation rate reached up to 70%. Thus, we recommend that the mycorrhizal pine seedlings inoculated with T. matsutake would be acclimated before transplanting into the field.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.1
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• pp.238-246
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• 1998

Surface residual stresses as well as wall thickness and ovality changes after U-bending process on UNS N06690 row-1 heat exchanger tubes, were estimated. Surface residual stresses were measured by Hole Drilling Method(HDM), calculating the stresses from relieved strains of 3 rosette strain gages. After bending of the tubes, dimensional tolerances for wall thickness and ovality were satisfied with ASTM requirements. Residual stresses at the extrados were introduced with compressive stress(-) by bending operations, and its maximum value reached-319 MPa in axial direction at ${\phi}=0^{\circ}$ in position. Tensile residual stresses(+) of ${\sigma}_zz=45$ MPa,${\sigma}_zz=25$ MPa were introduced in the intrados surface at position of ${\phi}=0^{\circ}$ Maximum tensile residual stress of 170 MPa was detected on the flank side at position of ,${\phi}=95^{\circ}$i.e., at apex region. It appeared that higher stress gradients were generated at the irregular transition regions. In the trend of residual stress changes with U-bend position, the extrados is related with the changes of ovality and the intrados is related with the changes of wall thickness.

• Journal of the Korea Convergence Society
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• v.11 no.6
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• pp.209-213
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• 2020

In this study, the model A with the existing shape used at racing car and the model B with light weight were designed. The structural analysis with thermal deformation and stress were carried out. Model A shows that the maximum temperature is lower than model B. The cooling performance due to the shape of the disk without any other cooling conditions can be shown to be better for model A. Model A was seen to be superior in durability as the thermal stress reduced by almost twice as much as model B. The part where the greatest stress occurred appeared to be the hole jointed with the hub regardless of its shape. The analysis results at this study are seen to be useful at designing the shape of the actual vehicle brake disc. The analysis results obtained in this study can be applied at grasping the strength of the brake disk for racing car practically. By utilizing the analysis result of the brake disk for racing car, this study is seen as the convergence study that the aesthetic design and analysis are applied.

• Journal of Korean Association for Spatial Structures
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• v.5 no.3 s.17
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• pp.83-89
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• 2005

This paper provides the results of the investigation on the optimum topology of simply supported deep beam structures with multi-point load cases. In this study, the strain energy to be minimized is considered as the objective function and the initial volume of structures is used as the constraint function. The resizing algorithm based on the optimality criteria is adopted to update the hole size existing inside the material. In this study, the sensitivities of topology optimization parameters to the optimum topology of the deep bean structures is investigated and also the effect of filtering process on the optimum topology is thoroughly tested. From numerical tests, the optimum topology of the deep beam is closely related with the optimization parameters used in the iteration and the filtering process play important role in order to find the optimum topology of the deep beam.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.6
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• pp.175-182
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• 2006

In the design of composite structures, shear connectors such as headed stud, channel, perforated plate, etc, are commonly used to transfer longitudinal shear forces across the steel-concrete interface. Many researches have been conducted to improve the characteristics of different types of shear connector. This paper presents the results of 11 push-out tests performed on the new perforated rib connectors with shearing bars embedded in concrete slab under static loads. The results obtained from these tests are as following : 1) The bearing plate welded on both sides of perforated rib plate improves the stiffness and strength. 2) The capacity of perforated connectors is influenced primarily by the transverse reinforcements and shearing bars.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.10
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• pp.5974-5979
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• 2014

Lightweight parts with very uniform precision are manufactured by an indent method and the press technique has been improved. Upon assembly with an indent method, a deformation force due to the compressive force occurs between the pin and hole and the contact surface is affected by damage. Therefore, a 3 dimensional model was made using the CATIA program and the damage on the surface contacted with indent was estimated through the ANSYS program in this study. In the analysis result, the maximum load applied at the PCB plate was 21.3 N when the pin goes through the PCB plate. When PCB plate came out of the pin, the maximum load was 19.24 N. As the structural analysis result, the maximum equivalent stress of Pin 1 was 192.96MPa because the maximum stress occurs at Pin 1 among all parts of this study model. By examining the damage property of the contacted indent and applying this study result to the design of real indentation, the damage can be prevented and the durability can be estimated.