• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4C
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• pp.247-253
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• 2008

This paper investigates the mechanical characteristics of waste tire powder-added lightweight soil in which dredged soils, waste tire powder and bottom ash were reused. In this study, 5 groups of soil samples were prepared with varing contents of waste tire powder ranged from 0% to 100% at 25% intervals by the dredged soil weight. The mixed soil samples were subjected to unconfined compression and elastic wave tests to investigate their unconfined compressive strengths and dynamic properties. Test results showed that the unconfined compressive strength and unit weight decreased as the waste tire powder contents increased, but axial strain at failure increased. Also stress-strain relationship of waste tire powder-added lightweight soil showed a ductile behavior rather than a brittle behavior. The result of elastic wave tests indicated that the higher waste tire powder content, the lower elastic wave velocity and the lower shear modulus (G).

• Current Industrial and Technological Trends in Aerospace
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• v.8 no.2
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• pp.54-64
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• 2010

A spacecraft contends with various vibration from the launch to the on-orbit operation, which is one of the major considerations in spacecraft design. The weight reduction has been indispensable to decrease the launch cost, however it produces worse disturbances for the spacecraft equipments. Besides, the load requirements at observation payload interfaces have became severe to secure their pointing stability as their images are required with high resolution. As a possible solution, a vibration isolation system is introduced and it reduces the vibration from the launch vehicle or isolates the spacecraft equipments from their generating/transmitted vibration. In this paper, it is examined the design consideration needed for the accommodation of the vibration isolation systems through the survey of recent applications of vibration mitigation technologies to spacecrafts.

• Resources Recycling
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• v.21 no.3
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• pp.39-47
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• 2012

This study was conducted to optimize a mixing design of lightweight aerated concrete with the blast furnace slag(BFS) using Box-Behnken method, one of response surface designs. The lightweight aerated concrete with the BFS was made on the conditions of steam curing method at atmospheric pressure. The experimental factors were unit Water(W)/total powder($P_d$) ratio, BFS replacement percentage and Al powder addition based on the total powder (${P_d}^*$%). From the results of the response surface analysis, regression models for dried specific gravity and compressive strength of the lightweight aerated concrete were derived. When the target values for dried specific gravity and compressive strength of the lightweight aerated concrete were set at 0.72 and 4.42 MPa respectively, its optimized mixing conditions driven from the regression models were 0.62 of $W/P_d$ ratio, 35.5% of BFS replacement and 0.05% of Al powder addition. This experimental design model was found to be credible by measuring the dried specific gravity and compressive strength of the sample made from the above mixing conditions.

• Journal of the Korean Geosynthetics Society
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• v.17 no.2
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• pp.41-49
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• 2018

The purpose of this study is to fabricate a full scale road embankment using lightweight air foamed soil as a soil material on soft ground and to investigate its material characteristics and behavior in order to promote dredged soil utilization and minimize ground improvement. As a result of the laboratory test of the onsite mixed samples, the total unit weight of the specimens decreased almost linearly until curing 28 days. In particular, the total unit weight after 28 days of curing was reduced to about 81% of the slurry state before curing, which will be useful in the formulation of similar native soil materials in the future. The unconfined compressive strength began to decrease with the 14th day of curing as shown in the previous study. When the cement content is increased, the strength decreases sharply at a small strain change after the occurrence of the maximum compressive strength, and the maximum strength is exhibited in a range of a smaller axial strain than normal range. The settlement at the surface layer of the ground due to the lightweight embankment was about 1 / 2.75 of the soil embankment and was in agreement with the unit weight ratio (1 / 2.7) of the embankment materials. This indicates the cause and effect of the settlement due to the difference in self weight of the embankments. Also, the difference in settlement between soil and lightweight embankment increased with increasing depth. This shows that the difference in the point at which the settlement is terminated is clear. The ground horizontal displacement under the lightweight embankment was about 15~20% smaller than that of the soil embankment and the depth of occurrence was also 4.5~5.0m shallower in the lightweight embankment.

• Journal of the Microelectronics and Packaging Society
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• v.30 no.1
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• pp.90-94
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• 2023

Carbon fiber(CF) with excellent thermal conductivity and electrical conductivity is attracting attention as an alternative material because metal heating elements have problems such as high heat loss and fire risk. However, since CF is oxidized and disconnected at about 200℃ or higher, the application of heating elements is limited, and CF heating elements in the form of vacuum tubes are currently used in some commercial heaters. In this work, polyimide(PI) with high heat resistance was coated on the surface of carbon fiber by electrophoretic deposition to prevent oxidation of CF in the atmosphere without using a vacuum tube, and the coating thickness and heat resistance were investigated according to the applied voltage. The heater made by connecting the PI-coated CF heating elements in series showed stable heating characteristics up to 292℃, which was similar to the heating temperature result of the heat transfer simulation. The PI layer coated by the electrophoretic deposition method is effective in preventing oxidation of CF at 200℃ or higher and is expected to be applicable to various heating components such as secondary batteries, aerospace, and electric vehicles that require heat stability.

• Composites Research
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• v.37 no.3
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• pp.219-225
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• 2024

It is essential to develop a light-weight, high-performance structure for the deployable reflector antenna, which is the payload of a reconnaissance satellite, considering launch and orbital operation performance. Among them, the composite main reflector is a key component that constitutes a deployable reflector antenna. In particular, the development of a high-performance main reflector is required to acquire high-quality satellite images after agile attitude control maneuvers during satellite missions. To develop main reflector, the initial design of the main reflector was confirmed considering the structural performance according to the laminate stacking design and material properties of the composite main reflector that constitutes the deployable reflector antenna. Based on the initial design, four types of composite main reflectors were manufactured with the variable for manufacturing process. As variables for manufacturing process, the curing process of the composite structure, the application of adhesive film between the carbon fiber composite sheet and the honeycomb core, and the venting path inside the sandwich composite were selected. After manufacture main reflector, weight measurement, non-destructive testing(NDT), surface error measurement, and modal test were performed on the four types of main reflectors produced. By selecting a manufacturing process that does not apply adhesive film and includes venting path, for a composite main reflector with light weight and structural performance, we developed and verified a main reflector that can be applied to the SAR(Synthetic Aperture Rader) satellite.

• Journal of the Korean Society for Advanced Composite Structures
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• v.7 no.1
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• pp.1-8
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• 2016

In this paper, the full-size structural performance test for a lightweight soundproof tunnel composed of partitioned pipe truss members is carried out to investigate the structural performance. In addition, a nonlinear structural analysis of the same finite element model as the full-size testing model is performed to compare the test result. The test and analysis results showed that the lightweight soundproof tunnel ensures the structural safety against wind loads, snow loads and load combinations. As a result, the full-size test and analysis results meet all the design load conditions, hence the proposed lightweight soundproof tunnel is ready for the field application.

• Journal of the Korean Society for Advanced Composite Structures
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• v.7 no.1
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• pp.9-18
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• 2016

In this paper, the structural characteristics of a lightweight soundproof tunnel to reduce the dead load imposed on the bridge are investigated. Subsequently, the design procedure of soundproof tunnel structures is reviewed and a design practice for the lightweight soundproof tunnel is carried out according to the reviewed procedure. Next, design compatibility for the lightweight soundproof tunnel is verified through a detailed finite element analysis. The result for evaluation of design compatibility shows that the lightweight soundproof tunnel has structural safety in structural members, welding zones and foundation parts. It is also confirmed that serviceability and buckling safety is excellent.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.114-115
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• 2014

Recently, the construction structure repeats the brilliant development including the shper high rising, high functionalization, environmental friendliness, conversion to ubiquitous, and etc. upon with the construction industry development and it is continually soothed. Meanwhile, as to the construction structure of the modern society, the research for corresponding to the box-frame construction way where the response to the diversity of the life of the occupant is difficult is needed. Thus, the lightweight of the structure is the important factor in order to secure the functionality. Therefore, this research tries to study the water absorption ratio and flexural strenght of the magnesium oxide light weight matrix according to the powdery modified sulfur addition ratio.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.244-245
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• 2014

This is an experimental study on manufacturing of non-cement matrix. Materials like cement and blowing agent in foamed concrete is replaced by by-products from blast furnace slag and paper ash. Further, the experiment was performed by replacing alkali with red mud by (0, 5, 10, 15, 25, 35, 45) of weight of alkali (wt.%) in order to reduce the amount of expensive alkali acclerator. Sample Plain with density showed lowest. The compressive strength test result, showed a similar trend with density. And it showed that compressive strength of the RM-0.05 was highest.