• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.1
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• pp.308-316
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• 2015

The purpose of this study is to verify TOM(turn-of-the-month) effect in the Kosdaq market, and that to compare to TOM effect of KOSPI for supporting degree of identification and to find new features. For this study, as the study basis sample, we used the daily data of the KOSDAQ from January 1996 to December 2013 and verified the TOM effect through yearly, monthly, classification by event as financial crisis, different period of TOM in order to clarify the effect of the KOSPI and KOSDAQ. As a result, We find that the TOM effect in KOSDAQ is always present uniformly in yearly, monthly, event-specific, which unlike TOM period also in KOSPI and generally TOM effect in KOSDAQ market which has larger volatility was appeared more pronouncedly than KOSPI market, and particularly TOM effect of KOSDAQ was larger than that of KOSPI on financial crisis occasion. But TOM effect of KOSDAQ was less stable than KOSPI.

• Resources Recycling
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• v.18 no.4
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• pp.24-30
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• 2009

Rare earth based calcium aluminate phosphor ($CaAl_2O_4:Eu^{2+}$, $Nd^{3+}$) supported $TiO_2$ nanoparticles are synthesized by using sol-gel method, which are further characterized using powder X-ray diffraction (XRD), fourier transform infrared (FT-IR), diffuse reflectance UV-Visible spectroscopy (DRS UV-Vis) and transmission electron microscopy (TEM). The XRD pattern of as-prepared and sintered phosphor supported $TiO_2$ does not show the tendency to change the crystal structure from anatase to rutile phase up to $600^{\circ}C$. This indicates that the phosphor support might inhibit the densification and crystallite growth by providing dissimilar boundaries. The diffuse reflectance spectral (DRS) measurements showed shift towards longer wavelength indicating reduction in the band-gap energy as compared to free $TiO_2$. The FT-IR spectra of phosphor supported $TiO_2$ nanoparticles show shift in the peak positions to lower wavelengths. This indicates that the $TiO_2$ nanoparticles are not free, but covalently bonded to the phosphor support. TEM micrographs show presence of crystalline and spherical $TiO_2$ nanoparticles (8 - 15 nm diameter) dispersed uniformly on the surface of phosphor.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.6
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• pp.67-73
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• 2017

Recently, the demand for large diameter piles has been rapidly increased in order to secure the allowable bearing capacity of pile foundation due to the increase of large structures such as high rise buildings. In this study, to improve the shear capacity of a conventional PHC pile, a large diameter composite PHC pile strengthened by in-filled concrete and shear reinforcement was manufactured. All the piles were tested according to the shear strength test method of Korean Standard. As a result of the shear test, the F-type piles which are produced without shear reinforcement occurred abrupt horizontal cracks after flexural and inclined shear cracks occurred. On the contrary, the FT-type piles which are produced with shear reinforcement exhibited stable flexural and inclined shear cracks uniformly over the entire pile without abrupt horizontal cracks. Furthermore, the maximum load of the large diameter composite PHC pile improved to 2.9 times in the F series, and more than 3.3 times in the FT series compared to the conventional PHC pile. This result indicated that FT-type piles had excellent composite behavior due to the shear reinforcement and effectively prevented the unstable growth of inclined shear cracks.

• Journal of the Korean Magnetics Society
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• v.17 no.4
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• pp.156-161
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• 2007

To develop array magnetic sensors, specular-type giant magnetoresistive- spin valve (GMR-SV) film of Glass/Ta(5)MiFe(7)/IrMn(10)NiFe(5)/$O_2$/CoFe(5)/Cu(2.6)/CoFe(5)/$O_2$/NiFe(7)/Ta(5)(nm) was deposited by using a high-vacuum sputtering system. One of 15 way sensors in the area of $8{\times}8mm^2$ was Patterned a size of $20{\times}80{\mu}m^2$ in multilayer sample by Photo-lithography. All of 15 sensors with Cu electrodes were measured a uniform magnetic properties by 2-probe method. The highest magnetic sensitivity of MR and output voltage measured nearby an external magnetic field of 5 Oe were MS = 0.5%/Oe and ${\triangle}$V= 3.0 mV, respectively. An easy-axis of top-free layers of $CoFe/O_2/NiFe$ with shape anisotropy was perpendicular to one of bottom-pinned layers $IrMn/NiFe/O_2/CoFe$. When the sensing current increased from 1 mA to 10 mA, the output working voltage uniformly increased and the magnetic sensitivity was almost stable to use the nano-magnetic devices with good sensitive properties.

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.1
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• pp.36-42
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• 2007

Korean paddy soils have long been almost uniformly managed throughout the whole country with flooded, deep tillage, puddlling, transplanting, and uncovering after harvest. Management of soil organic carbon could be more important in the sources of green house gases. However, soil organic carbon dynamics were not been studied for Korean paddy soils. Therefore, we evaluated the changes in soil organic carbon (SOC) of paddy soils between 1999 and 2003 at the same locations nationwide except islands. Soil organic carbon tends to increase in Inceptisols, which is predominant soil order for Korean paddy soils, from 1999 to 2003. Soil organic carbon increases in topographically plain paddy soils was greater than in valley soils, and was considerably high in predominant types of paddy soils (i.e., well adapted paddy soils, sandy paddy soils, and poorly drained paddy soils) but low and stable in the saline paddy soils. We also found that clay paddy soils are greater in soil organic carbon than sandy paddy soils. Through this study, we concluded that a proper management of paddy soils could contribute to soil organic carbon storage, which imply that the Korean paddy soils could help to enhance carbon dioxide sequestration via soil organic matter into the soil.

• Korean Journal of Construction Engineering and Management
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• v.22 no.4
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• pp.3-10
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• 2021

According to the IPCC, humans are influencing the climate system. Such changes in the climate system can cause problems in the supply of food ingredients in the agricultural field by changing the existing growing environment. To solve this problem, vertical farms can be a good alternative for a stable supply of food ingredients. Although the vertical smart farm pays close attention to maintaining and managing the growing environment of crops, it is difficult to uniformly implement temperature, humidity, illumination, oxygen, and carbon dioxide concentrations in the building space. As a result of conducting computational fluid dynamics analysis to ensure air uniformity, a remarkable result is that it is advantageous to continuously spray suitable carbon dioxide CO2 concentrations for a long period of time for air uniformity in a vertical smart farm. Through this result, it is possible to efficiently plan a growing environment system optimized for a vertical smart farm. Based on this study, if efficient crops are produced by creating an optimized growing environment for vertical smart farms, it will be able to contribute to the development of the agricultural field.

• Journal of Intelligence and Information Systems
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• v.16 no.4
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• pp.85-97
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• 2010

Internet communities are a typical space for knowledge creation and use on the Internet as people discuss their common interests within the internet communities. When we define 'Knowledge Communities' as internet communities that are related to knowledge creation and use, they are categorized into 4 different types such as 'Search Engine,' 'Open Communities,' 'Specialty Communities,' and 'Activity Communities.' Each type of knowledge community does not remain the same, for example. Rather, it changes with time and is also affected by the external business environment. Therefore, it is critical to develop processes for practical use of such changeable knowledge communities. Yet there is little research regarding a strategic framework for knowledge communities as a source of knowledge creation and use. The purposes of this study are (1) to find factors that can affect knowledge creation and use for each type of knowledge community and (2) to develop a strategic framework for practical use of the knowledge communities. Based on previous research, we found 7 factors that have considerable impacts on knowledge creation and use. They were 'Fitness,' 'Reliability,' 'Systemicity,' 'Richness,' 'Similarity,' 'Feedback,' and 'Understanding.' We created 30 different questions from each type of knowledge community. The questions included common sense, IT, business and hobbies, and were uniformly selected from various knowledge communities. Instead of using survey, we used these questions to ask users of the 4 representative web sites such as Google from Search Engine, NAVER Knowledge iN from Open Communities, SLRClub from Specialty Communities, and Wikipedia from Activity Communities. These 4 representative web sites were selected based on popularity (i.e., the 4 most popular sites in Korea). They were also among the 4 most frequently mentioned sitesin previous research. The answers of the 30 knowledge questions were collected and evaluated by the 11 IT experts who have been working for IT companies more than 3 years. When evaluating, the 11 experts used the above 7 knowledge factors as criteria. Using a stepwise linear regression for the evaluation of the 7 knowledge factors, we found that each factors affects differently knowledge creation and use for each type of knowledge community. The results of the stepwise linear regression analysis showed the relationship between 'Understanding' and other knowledge factors. The relationship was different regarding the type of knowledge community. The results indicated that 'Understanding' was significantly related to 'Reliability' at 'Search Engine type', to 'Fitness' at 'Open Community type', to 'Reliability' and 'Similarity' at 'Specialty Community type', and to 'Richness' and 'Similarity' at 'Activity Community type'. A strategic framework was created from the results of this study and such framework can be useful for knowledge communities that are not stable with time. For the success of knowledge community, the results of this study suggest that it is essential to ensure there are factors that can influence knowledge communities. It is also vital to reinforce each factor has its unique influence on related knowledge community. Thus, these changeable knowledge communities should be transformed into an adequate type with proper business strategies and objectives. They also should be progressed into a type that covers varioustypes of knowledge communities. For example, DCInside started from a small specialty community focusing on digital camera hardware and camerawork and then was transformed to an open community focusing on social issues through well-known photo galleries. NAVER started from a typical search engine and now covers an open community and a special community through additional web services such as NAVER knowledge iN, NAVER Cafe, and NAVER Blog. NAVER is currently competing withan activity community such as Wikipedia through the NAVER encyclopedia that provides similar services with NAVER encyclopedia's users as Wikipedia does. Finally, the results of this study provide meaningfully practical guidance for practitioners in that which type of knowledge community is most appropriate to the fluctuated business environment as knowledge community itself evolves with time.

• Science of Emotion and Sensibility
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• v.22 no.1
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• pp.15-22
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• 2019

The purpose of this study is to develop a strain sensor based on a nanoweb by applying electrical conductivity to a polyurethane nanoweb through the use of Graphene. For this purpose, 1% Graphene ink was pour-coated on a polyurethane nanoweb and post-treated with PDMS (Polydimethylsiloxane) to complete a wearable strain sensor. The surface characteristics of the specimens were evaluated using a field emission scanning electron microscope (FE-SEM) to check whether the conductive material was well coated on the surface of the specimen. Electrical properties of the specimens were measured by using a multimeter to measure the linear resistance of the specimen and comparing how the line resistance changes when 5% and 10% of the specimens are tensioned, respectively. In order to evaluate the performance of the specimen, the gauge factor was obtained. The evaluation of the clothing was performed by attaching the completed strain sensor to the dummy and measuring the respiration signal according to the tension using MP150 (Biopac system Inc., USA) and Acqknowledge (ver. 4.2, Biopac system Inc., U.S.A.). As a result of the evaluation of the surface characteristics, it was confirmed that all the conductive nanoweb specimen were uniformly coated with the Graphen ink. As a result of measuring the resistance value according to the tensile strength, the specimen G, which was treated with just graphene had the lowest resistance value, the specimen G-H had the highest resistance value, and the change of the line resistance value of the specimen G and the specimen G-H is increased to 5% It is found that it increases steadily. Unlike the resistance value results, specimen G showed a higher gauge rate than specimen G-H. As a result of evaluation of the actual clothes, the strain sensor made using the specimen G-H measured the stable peak value and obtained a signal of good quality. Therefore, we confirmed that the polyurethane nanoweb treated with Graphene ink plays a role as a breathing sensor.

• Journal of the Korean Electrochemical Society
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• v.26 no.1
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• pp.1-10
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• 2023

The cathode, which is one of the four major components of a lithium secondary battery, is an important component responsible for the energy density of the battery. The mixing process of active material, conductive material, and polymer binder is very essential in the commonly used wet manufacturing process of the cathode. However, in the case of mixing conditions of the cathode, since there is no systematic method, in most cases, differences in performance occur depending on the manufacturer. Therefore, LiMn₂O₄ (LMO) cathodes were prepared using a commonly used THINKY mixer and homogenizer to optimize the mixing method in the cathode slurry preparation step, and their characteristics were compared. Each mixing condition was performed at 2000 RPM and 7 min, and to determine only the difference in the mixing method during the manufacture of the cathode other experiment conditions (mixing time, material input order, etc.) were kept constant. Among the manufactured THINKY mixer LMO (TLMO) and homogenizer LMO (HLMO), HLMO has more uniform particle dispersion than TLMO, and thus shows higher adhesive strength. Also, the result of the electrochemical evaluation reveals that HLMO cathode showed improved performance with a more stable life cycle compared to TLMO. The initial discharge capacity retention rate of HLMO at 69 cycles was 88%, which is about 4.4 times higher than that of TLMO, and in the case of rate capability, HLMO exhibited a better capacity retention even at high C-rates of 10, 15, and 20 C and the capacity recovery at 1 C was higher than that of TLMO. It's postulated that the use of a homogenizer improves the characteristics of the slurry containing the active material, the conductive material, and the polymer binder creating an electrically conductive network formed by uniformly dispersing the conductive material suppressing its strong electrostatic properties thus avoiding aggregation. As a result, surface contact between the active material and the conductive material increases, electrons move more smoothly, changes in lattice volume during charging and discharging are more reversible and contact resistance between the active material and the conductive material is suppressed.