• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.2
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• pp.17-22
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• 2015

In this paper, we study the calculation for the fracture area of the composite material specimens using digital image processing techniques. This study was able to calculate the area of the fracture region through the main operation step 7 on the basis of improved image. To extract the area in the original image, we have to use opening operation, close operation, the Hit-or-Miss operation and Bottom hat filter, Top hat filter, etc. In particular, to extract the area of the composite specimen discussed in this study, we have to use the combination of the operations and filters because it is non-isotropic material, or should develop a new algorithm based on it.

• Structural Engineering and Mechanics
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• v.77 no.6
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• pp.753-763
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• 2021

Feasibility studies of a reinforced concrete (RC) deep pile foundation system with the compressed air energy storage (CAES) technology were conducted in previous studies. However, those studies showed some technical limitations in its serviceability and durability performances. To overcome such drawbacks of the conventional RC energy pile system, various steel-concrete composite pile foundations are addressed in this study to be utilized as a dual functional system for an energy storage medium and load-resistant foundation. This study conducts finite element analyses to examine the applicability of various composite energy pile foundation systems considering the combined effects of structural loading, soil boundary forces, and internal air pressures induced by the thermos-dynamic cycle of compressed air. On this basis, it was clearly confirmed that the role of inner and outer tubes is essential in terms of reliable storage tank and better constructability of pile, respectively, and the steel tubes in the composite pile foundation can also ensure improved serviceability and durability performances compared to the conventional RC pile system.

• Composites Research
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• v.30 no.6
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• pp.393-398
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• 2017

The shrinkage distribution of a dental composite (Clearfil AP-X, Kuraray, Japan) used for dental restoration was observed using a digital image correlation method. In order to analyze the shrinkage distribution formed during and after light irradiation, digital images were taken with different photographing conditions for each period. Optimal photographing conditions during LED irradiation were obtained through a preliminary experiment in which the exposure time was applied from 0.15 ms to 0.55 ms in 0.05 ms intervals. The DIC analysis results showed that the strain was non-uniform. For the initial 20 s of light irradiation the composite resin shrank to the level of 50~60% of the final curing shrinkage. Such large shrinkage amount of the composite resin lump affected the tensile stress concentration near the adhesive region between the composite resin and the substrate.

• Advances in aircraft and spacecraft science
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• v.6 no.1
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• pp.69-86
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• 2019

This paper discusses the use of the Digital Image Correlation (DIC) technique for the displacement and strain measurements of a wet lay-up composite wing. As opposed to classical strain gages, DIC allows to conduct full field strain analysis of simple to complex structural parts. In this work, wing-up bending tests and measurements of the composite wing of the Dardo Aspect by CFM Air are carried out through an ad-hoc test rig and the Q-400 DIC system by Dantec Dynamics. Also, the results are used to validate a finite element model of the structure under investigation.

• Korean Journal of Materials Research
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• v.29 no.1
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• pp.23-29
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• 2019

Three-dimensional(3D) printing is a process for producing complex-shaped 3D objects by repeatedly stacking thin layers according to digital information designed in 3D structures. 3D printing can be classified based on the method and material of additive manufacturing process. Among the various 3D printing methods, digital light processing is an additive manufacturing technique which can fabricate complex 3D structures with high accuracy. Recently, there have been many efforts to use ceramic material for an additive manufacturing process. Generally, ceramic material shows low processability due to its high hardness and strength. The introduction of additive manufacturing techniques into the fabrication of ceramics will improve the low processability and enable the fabrication of complex shapes and parts. In this study, we synthesize silica composite material that can be applied to digital light processing. The rheological and photopolymeric properties of the synthesized silica composite are investigated in detail. 3D objects are also successfully produced using the silica composite and digital light processing.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.5
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• pp.1349-1359
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• 1998

In this paper, presented is the result of a digital implementation of a FM stereo composite signal generator. The chip utilizing DDFS(Direct Digital Frequency Synthesizer architecture is implemented using $1.0\mu\textrm{m}$ CMOS gate-array technology thereby replacing analog componentry. To verify the process of generating composite signals a conventional logic simulation method was used. The processed chip was mounted on an evaluation PCB to test and analyze to signals. According to the measurement result obtained by using a 12-bit DAC, the digital FM composite signal generator produces a 74DB spectrally pure signal over its entire tuning range, which is superior to that of analog counterpart by 14dB in it spectral reponse. And further enhancements of the spectral response is expected to be achieved by using a high resolution digital to analog converter, such as a 16-bit DAC. The resulting signals is superior to the signal of the analoy circuitry typically used, in major characteristics such as S/N ratios, accuracy, tuning stability, and signal seperation.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.5
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• pp.686-694
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• 2010

Continuing progress in high technology has created numerous industrial applications for new advanced composite materials. Among these materials, carbon fiber-reinforced plastic (CFRP) laminate composite is typically used for low-weight carrying structures that require high specific strength. In this study, the damage mechanism of a compact tension (CT) specimen of woven CFRP laminates is described in terms of strain and displacement changes and crack growth behavior. The digital image correlation (DIC) method (which is employed here as a computer vision technique) is analyzed. Acoustic emission (AE) characteristics are also acquired during fracture tests. The results demonstrate the usefulness of these methods in evaluating the damage mechanism for woven CFRP laminate composites. From the results, we show these methods are so useful in order to evaluate the damage mechanism for woven CFRP laminate composites.

• Journal of KSNVE
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• v.8 no.5
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• pp.832-840
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• 1998

Experimental studies on the adaptive vibration control of composite beams have been performed using a piezoelectric actuator and the neuro-controller. The variations in natural frequencies of the specimen and the actuation characteristics of the piezoelectric actuator according to the delamination in the bonding layer have been studied. In addition, the simulation of adaptive vibration control has been performed for the composite specimens with delaminated piezoelectric actuator using neuro-controller. The hardware for the adaptive vibration control experiment was prepared. A DSP(digital signal processor) has been used as a digital controller. Using neuro-controller, the adaptive vibration control experiment has been performed. The vibration control results using the neuro-controller show that the present neuro-controller has good performance and robustness with the system parameter variations.

• Journal of Broadcast Engineering
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• v.5 no.2
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• pp.159-166
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• 2000

This paper analyzed the transmission performance when we transmited digital TV signal through analog CATV network. We considered random noise, microreflection, and composite tripple beats as channel impairment factors, and random noise and CTB( Composite Tripple Beat) are modelled as Gaussian distribution and Weibull distribution respectively. Channel modellings for microreflections are classified as three cases, and we exploited carrier recovery and blind equalizer to minimize their effects. We developed a computer simulator for the digital transmission system using DVB-C specification to analyze digital transmission performance, and found BER values according to $E_{b}$/$N_{o}$ for each configuration.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.10
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• pp.809-815
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• 2014

The co-bonded dissimilar composite under a wide range of temperature change shows thermal distortion due to the differences in thermal expansion characteristics of the composite materials. Analysis of the thermal expansion characteristics of each composite is required for the design of co-bonded dissimilar composite structure with considering the shape distortion during the manufacturing process. In this work, digital image correlation (DIC) technique is introduced for measuring the thermal distortion characteristics of co-bonded dissimilar composite specimen, carbon/epoxy and silica/phenolic. The thermal distortion of co-bonded dissimilar composite specimen is numerically estimated and compared with the experiments. The estimated results is successfully validated using the measured results.