• Magazine of the Korea Concrete Institute
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• v.8 no.6
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• pp.235-243
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• 1996

The mechanical behavior ot concrete is strongly influenced by various scenarios of crack initiation and crack propagation. Recently. the study of the interface fracture and cracking in interfacial regions is emerged as an important field, in the context of the developement of high performance concrete composites. The crack path criterion for elastically homogeneous materials is not valid when the crack advances at an interface because. in this case, the consideration of the relative magnitudes of the fracture toughnesses between the constituent materials and the interface are involved. In this paper, a numerical method is presented to obtain the values of two interfacial fracture parameters such as the energy release rate and the phase angle at the tip of an existing interface crack. Criteria based on energy release rate concepts are suggested for the prediction of crack growth at the interfaces and an hybrid experimental-numerical study is presented on the two-phase beam composite models containing interface cracks to investigate the cracking scenarios in interfacial regions. In general, good agreement between the experimental results and the prediction from the criteria is obtained.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.12
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• pp.1013-1019
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• 2016

CFRP is the composite material manufactured by the hybrid resin on the basis of carbon fiber. As this material has the high specific strength and the light weight, it has been widely used at various fields. Particularly, the unidirectional carbon fiber can be applied with the layer angle. CFRP made with layer angle has the strength higher than with no layer angle. In this paper, the property of crack growth due to each layer angle was investigated on the crack propagation and fracture behavior of the CFRP compact tension specimen due to the change of layer angle. The value of maximum stress is shown to be decreased and the crack propagation is slowed down as the layer angle is increased. But the limit according to the layer angle is shown as the stress is increased again from the base point of the layer angle of $60^{\circ}$. This study result is thought to be utilized with the data which verify the probability of fatigue fracture when the defect inside the structure at using CFRP of mechanical structure happens.

• Journal of the Microelectronics and Packaging Society
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• v.19 no.2
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• pp.61-66
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• 2012

Bismuth(Bi) nanoparticles were synthesized at room temperature by a modified polyol process using bismuth(III) carbonate basic as precursor. In addition, some characteristics of the synthesis with respect to the exchange of a capping agent/surface stabilizer and solvent type were observed. When polyvinylpyrroldone was added, the finest Bi nanoparticles were synthesized in diethylene glycol(DEG), while the coarsest nanoparticles were formed in polyethylene glycol(PEG). The particle size immediately after synthesis was proportionate to final particle size which was determined by particle growth through coalescence and aggregation during drying. As a result, the finest Bi particles with the diameter range of several tens of nanometers - 300 nm were finally obtained in DEG. Regardless of the type of capping agent/surface stabilizer, extensive coalescence and aggregation behavior occurred in PEG, resulting in final products agglomerated with coarse particles.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.2
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• pp.352-356
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• 2011

Transparent conducting oxide films like ITO/Au/ITO and AZO/Au/AZO were fabricated with a sputter at a low-temperature of less then $70^{\circ}C$ and their crystallization and opto-electrical properties were studied. X-ray diffractiometry showed that single-ITO layer was amorphous, whereas, ITO of ITO/Au/ITO multi-layer was crystal. The ITO crystallization and its orientation depended on Au crystallization. Surface roughness of the ITO-multi-layers were in the range of 29-88% of that of ITO-single layer. ITO on amorphous gold layer had more rough surface than ITO on crystal gold. The gold layer between ITO improved electrical conductivity. Carrier density, mobility, resistivity and sheet resistance of ITO-single layer were $2.3{\times}10^{19}/cm^3$, $85{\times}cm^2$/Vs, $31{\times}10^{-4}{\Omega}cm$, and $310{\times}{\Omega}/cm^2$, respectively. Those of ITO/Au/ITO-multi-layers depended on Au-interlayer-thickness, which were in the range of $3.6{\times}10^{19}{\sim}4.2{\times}10^{21}/cm^3$, $43{\sim}85cm^2$/Vs, $0.17{\times}10^{-4}{\sim}25{\times}10^{-4}{\Omega}cm$, and $1.7{\sim}20{\times}{\Omega}/cm^2$, respectively. The sheet resistances of the single-layer ITO and the multi-layer ITO were 310 and $2.7{\sim}21{\Omega}/cm^2$, respectively. That of AZO/Au/AZO was $8.6{\Omega}/cm^2$, which was better than the single-layer ITO.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.3
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• pp.686-697
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• 2017

Rapid growth in mobile communication and the proliferation of smart devices have drawn significant utilization of machine generated data. Behavior tracking technology now are utilized in the various fields based on extracting data using the sensor and device. We deploy IoT based behavioral intervention system in Suwon mental health center to improve the effectiveness of non-medicine care for senior people. Using smart activity trackers and BLE scanner devices, we proposed a location-based behavioral intervention system and verify the integrity of the harvested data.

• The Journal of the Korea Contents Association
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• v.17 no.9
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• pp.523-535
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• 2017

Despite consumers' increasing awareness and interests in innovative wearable devices, the sales growth has been stagnant. To analyze this phenomenon, we investigate consumer preferences for various innovative features embedded in wearable devices. Conducting conjoint analysis on smartwatches, we empirically show that the curse of innovation can occur when the consumer's expected utility from the smartwatch falls short of his/her psychological cost associated with behavior change from smartwatch usage. Therefore, our findings provide managerial implications on the R&D strategy for new technologies and more importantly on the marketing strategy easing consumers' resistance to highly innovative products.

• Economic and Environmental Geology
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• v.42 no.5
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• pp.471-477
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• 2009

An experimental removal of dissolved uranium (U) exsiting as uranyl ion (${UO_2}^{2+}$) was carried out using Shewanella p., iron-reducing bacterium. By the microbial reductive reaction, initial U concentration ($50{\mu}M$) was constantly decreased, and most U were removed from solution after 2 weeks. Major mechanism that U was removed from the solution was adsorption, precipitation and mineralization on the microbe surface. Under the transmission electron microscopy, the U adsorbed on the microbe was observed as being crystallized and eventually enlarged to several ${\mu}m$ sizes of minerals by combining with individual microbes and organic exudates. It seems that such U growth and mineralization on the microbial surface could affect the U behavior in a radioactive waste disposal site. Thus, the biogechemical reaction of metal-reducing bacteria observed in this experiment could give an affirmative measure that the microbial activity may retard U movement in subsurface environment.

• Proceedings of the Korean System Dynamics Society
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• 2001.10a
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• pp.3-14
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• 2001

Since 1998, government-led Korean venture business boom now proceeds into the stage of market-oriented venture business growth. At such a moment, this research is to clarify the relations between the success factors of Korean venture businesses, based on domestic and foreign documentary surveys and inquiry surveys over domestic venture businesses. This research starts from the necessity to overcome the limits of the existing researches by uni-dimensional probing research into success factors of Korean venture businesses and to manifest the multi-dimensional relations between the success factors from the various viewpoints. And this research adopts System-Dynamics methodology to manifest and utilize relations among those factors, avoiding the existing metrical approaches. This research can be called a new approach to the current ecosystems of Korean venture in which whether venture businesses success in Korea is considered to depend on the list on the stock market. For this, this research implemented verification analysis through the simulations of each factor at various levels to build causality map which clarifies the causality of success factors of venture businesses through the System-Dynamics methodology and to utilize it as a way of supporting tool for decision-making of venture businesses. This research will be able to suggest the reactions depending on various internal and external situations. This research tried to manifest the causality map of each factor on the basis of inquiry surveys and documentary surveys to verify feedback among each factor by the SD methodology. This research will be a basis bolster up the still fragile substructure of venture businesses through an efficient analysis framework using the verification of SD methodology and resulting outcomes from this research.

• Korean Journal of Environmental Agriculture
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• v.21 no.1
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• pp.24-30
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• 2002

Ginseng (Panax ginseng C. A. Meyer) has been cultivated on raised beds with shading condition for 4 to 6 years because of its physiological characteristics. This shading condition maintains relatively stable soil environments protecting from rainfall and direct sunlight. Therefore, pesticides in ginseng growing soil are exposed to far different environment from the general cropping field. To study the behavior of pesticides under this condition, the effect of covering on the persistency of Procymidone in ginseng cultivating soil was investigated by using several shade materials. The most important factor affecting Procymidone persistency in soil under covering was water leakage rates of shade materials.

• Tunnel and Underground Space
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• v.27 no.3
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• pp.121-131
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• 2017

We studied the time-dependent behaviors of rock and concrete materials by conducting the static and dynamic long-term strength tests. In particular, acoustic emission(AE) signals generated while the tests were analyzed and used for the long-term stability evaluation. In the static subcritical crack growth test, the long-term behavior and AE characteristics of Mode I and Mode II were investigated. In the dynamic long-term strength test, the fatigue limit and characteristics of generation of AE were analyzed through cyclic four points bending test. The graph of the cumulative AE hits versus time showed a shape similar to that of the creep curve with the first, second and third stages. The possibility for evaluating the static and dynamic long-term stability of rock and concrete is presented from the log - log relationship between the slope of the secondary stage of cumulative AE hits curve and the delayed failure time.