• Composites Research
• /
• v.35 no.4
• /
• pp.283-287
• /
• 2022

Stretchable strain sensors have been developed for potential future applications including wearable devices and health monitoring. For practical implementation of stretchable strain sensors, their stability and repeatability are one of the important aspects to be considered. In this work, we utilized 3D printed polymer structures having kirigami patterns to improve the stretchability and reduce the hysteresis. The polymer structures were coated with graphene/carbon nanofiber hybrids to make a robust electrical network. The stretchable strain sensors showed a high gauge of 36 at a strain of 32%. Because of the kirigami structures and the robust graphene/carbon nanofiber coating, the sensors also exhibited stable resistance responses at various strains ranging from 1% to 30%.

• The Journal of Bigdata
• /
• v.7 no.1
• /
• pp.113-124
• /
• 2022

Various methods using machine learning and big data have been applied to prevent failures in Data Centers. However, there are many limitations to referencing individual equipment-based performance indicators or to being practically utilized as an approach that does not consider the infrastructure operating environment. In this study, the performance indicators of individual infrastructure equipment are integrated monitoring and the performance indicators of various equipment are segmented and graded to make a single numerical value. Data pre-processing based on experience in infrastructure operation. And an ensemble of RRCF (Robust Random Cut Forest) analysis and Prophet analysis model led to reliable analysis results in detecting anomalies. A failure analysis system was implemented to facilitate the use of Data Center operators. It can provide a preemptive response to Data Center failures and an appropriate tuning time.

• Journal of Korean Historical Folklife
• /
• no.45
• /
• pp.263-289
• /
• 2014

King Munjong(文宗), the eleventh King of the Goryeo Dynasty, was the son of King Hyeonjong(顯宗), the eighth king, and the younger stepbrother(異母弟) of King Jeongjong(靖宗), the 10th king. Although King Jeongjong had four sons, he abdicated the throne to King Munjong. King Taejo(太祖) had opened the possibility for sons other than the eldest son to succeed to the throne. When King Jeongjong died, his sons were children under the age of 10 years. In the early period of the Goryeo Dynasty, when kings had young sons, there were precedents of abdicating the throne to their grown-up younger brothers. In addition, King Jeongjong and Munjong had an identical blood background. During the period, Goryeo people also naturally accepted the fact that a former king's younger brother succeeded to the throne. In this background, King Munjong ascended the throne. However, King Munjong did not ascend the throne after identifying state affairs with politic power. Therefore, he needed to increase his authority as the king. Moreover, as the sons of King Jeongjong had grown up, they could stir up trouble in future succession to the throne. Therefore, King Munjong intended to concentrate power on himself and remove trouble in future succession to the throne by selecting his son as successor to the throne. After the installation of Wangtaeja(王太子, the Crown Prince), King Munjong expanded and organized Donggunggwan(東宮官, the establishment of Secretariat of Wangtaeja) and carried out various rituals related to Wangtaeja. The control system for Donggunggwan was completed institutionally in 1068. At this time, the newly organized Donggunggwan was operated as a miniature version of the central government office. In addition, the ritual for the installation of Taeja, which was held in 1054, complied with regulated procedures. After the ritual of the installation, a ceremony to congratulate on Jangheungjeol(長興節, the birthday of Wangtaeja) was held in 1056. In 1064, the wedding ritual of Taeja took place, and the ritual for Taeja regulated in Yeji(禮志) of "Goryeosa(高麗史)" was carried out. In addition, the installation of Wangtaeja was made known overseas, and the Taeja of Goryeo was proclaimed by the Kitan three times. Such various measures played an important role in strengthening the status of Taeja as the man of authority next to the king. Later, Taeja demonstrated his status as the man of authority following the king by participating in state affairs on behalf of King Munjong who was not able to move about freely in his later years.

• Journal of Korean Society of Steel Construction
• /
• v.24 no.5
• /
• pp.535-547
• /
• 2012

PSRC column is a concrete encased steel angle column. In the PSRC column, the steel angles placed at the corner of the cross-section resists bending moment and compression load. The lateral re-bars welded to steel angles resist the column shear and the bond between the steel angle and concrete. In the present study, current design procedures in KBC 2009 were applied to the flexure-compression, shear, and bond design of the PSRC composite column. To verify the validity of the design method and failure mode, simply supported 2/3 scaled PSRC and correlated SRC beams were tested under two point loading. The test parameters were the steel angle ratio and lateral bar spacing. The test results showed that the bending, shear, and bond strengths predicted by KBC 2009 correlated well with the test results. The flexural strength of the PSRC specimens was much greater than that of the SRC specimen with the same steel ratio because the steel angles were placed at the corner of the column section. However, when the bond resistance between the steel angle and concrete was not sufficient, brittle failures such as bond failure of the angle, spalling of cover concrete, and the tensile fracture of lateral re-bar occurred before the development of the yield strength of PSRC composite section. Further, if the weldability and toughness of the steel angle were insufficient, the specimen was failed by the fracture of the steel angle at the weld joint between the angle and lateral bars.

• Journal of Korea Foresty Energy
• /
• v.17 no.1
• /
• pp.47-55
• /
• 1998

In the search for broadband damping composites, it is desirable to have polymers with a broad and high loss region, covering the entire temperature and frequency range of interest. Interpenetrating polymer networks, IPN's, are materials composed of two or more crosslinked polymers intimately and irrevocably interwinded. The resulting distribution of microenviron-ments can result in a materials with a high mechanical loss broad end over that of either polymer component alone. In this study, several series of copolymer, crosslinked copolymer and copolymer/copolymer IPN's were synthesized for possible use as broadband damping materials. Then their dynamic tensile properties were measured and compared with the damping properties of sandwich composites. Dynamic mechanical analysis showed that the temperature of loss peak may be varied over a wide temperature range with formulation. The compatibility of IPN`s was depended on the compatibility of A and B polymers as well as crosslink density. The damping factor(tan ${\delta}_c$) of composites became greater when a polymer of approximate storage module(E`) range of 5X10$^7$ to 10$^9$ dyne/cm$^2$ and large tan ${\delta}$ at the same time was used. The damping properities of poly (2-EHA80-co-St20)/poly(2-EHA20-co-St80) IPN`s crosslinked with 3%-DEGDM were relatively better over a broad temperature range.

• Journal of Conservation Science
• /
• v.31 no.3
• /
• pp.309-318
• /
• 2015

The staff given with chair to Yi Gyeong-seok, senior official over 70 years old by King Hyeonjong of Joseon Dynasty is representative handcraft of Joseon Dynasty. Results of analysis on the metallic decoration show that the metallic ornament of the end part which is connected to the spade was made by rolling of iron plate and brass plating. The plated part is limited to the ornament of the end part connected to the spade and the plating was not applied to the spade. Brass including 20% zinc was used for the connecting part of guard while brass gilded iron was used for the spade. This suggests that the tone of the connecting part of the guard and the spade was not different for reason of visual harmonization. Potential applied plating method can be amalgam, dippping in molten brass, and brushing but the analysis result suggests that dipping in molten brass method is the most likely accepted method. The brass guard of knife was joined by tin-lead solder. Rivet used to fix the blade was made by pure iron as an optimum material which satisfies flexibility and strength.

• Journal of Korean Society of Steel Construction
• /
• v.29 no.3
• /
• pp.249-260
• /
• 2017

In order to investigate the structural performance of a novel prefabricated-SRC column using bolt-connected steel angles(PSRC column), eccentric axial loading tests were performed for six PSRC column specimens and two conventional SRC column specimens. The test parameters were the spacing and sectional configurations of lateral reinforcement, and eccentricity ratio of axial load. The test results showed that, due to high axial-stiffness of the angles located at the corners of the cross section, the compressive load-carrying capacity and deformation capacity of the PSRC specimens were greater than those of the SRC specimens in the large eccentricity ratio of axial load. Closely spaced lateral steel plates and Z-shaped lateral steel plates improved lateral confinement, which increased the load-carrying capacity of the PSRC specimens. The combined flexural and axial load-carrying capacity of the specimens by tests and nonlinear numerical analysis were greater than the predictions by current design codes. The numerical analysis agreed well with the test results including the initial stiffness, peak strength, and post-peak strength degradation.

• Journal of Korean Society of Steel Construction
• /
• v.25 no.6
• /
• pp.601-612
• /
• 2013

In the present study, details of the TSC beam-to-PSRC column connection for low and middle seismic zones were developed. For ease construction, the top and bottom flanges of the steel section of the TSC beam were discontinuous at the joint face on purpose, while the web passes through the joint. Thus, tensile resistance of the top and bottom flanges is not considered in the calculation of nominal strength of the connection. Cyclic loading tests on two interior connections and an exterior connection were performed to verify the seismic performance. The test parameter for two interior connections was the depth of the TSC beams: 600 and 700 mm including the slab depth. The test results showed that the nominal strength of the connections predicted by KBC 2009 correlated well with the test results. The connection specimens exhibited relatively good deformation and energy dissipation capacities, greater than the requirements for the ordinary and intermediate moment frames. Ultimately, the connection specimens were failed at the story drift ratios of 3.0 to 4.0 % due to local buckling and tensile fracture of the web of the TSC beam passing through the joint. By modifying the existing provisions of ASCE, the joint shear strength of the TSC beam-PSRC column connection was evaluated.

• Journal of Korean Society of Steel Construction
• /
• v.29 no.2
• /
• pp.147-158
• /
• 2017

The present study focused on the structural performance of newly developed prefabricated composite columns (PSRC composite column) using bolt-connected steel angles. Concentric axial loading tests were performed for four 2/3 scaled PSRC column specimens and two conventional SRC column specimens. The test parameters were the spacing and sectional configurations of lateral reinforcement, and width-to-thickness ratio of steel angles. The test results showed that the axial load-carrying capacity and deformation capacity of the PSRC column specimens were comparable to those of the conventional SRC column specimens. Closely spaced steel plates and Z-shaped steel plates for lateral reinforcement increased the deformation capacity of the PSRC column specimens. The load-carrying capacity was greater than the prediction by current design codes. Numerical analysis was performed for the specimens. The results agreed well with the test results in terms of initial stiffness, load-carrying capacity, except for strength degradation due to cover concrete spalling.

• Korean Journal of Soil Science and Fertilizer
• /
• v.37 no.2
• /
• pp.91-96
• /
• 2004

Accumulation of nitrate in edible crops is undesirable due to potential risks to human health. Since nitrate has a role in the osmotic regulation of plants, salt accumulation in soil is expected to stimulate nitrate accumulation in plants. Lettuce (Lactuca sativa L.) was grown in soils of different salinities, 9.69 and $4.49dS\;m^{-1}$, in a greenhouse, and the effect of soil salinity on nitrate accumulation in lettuce was investigated. Content of nitrate in the lettuce increased significantly as soil salinity increased under low light intensity and ample supply of nitrate in root media. Soluble sugar and oxalate contents in lettuce were also significantly higher in the soil of higher salinity. Phosphate, Cl, and $SO_4$ contents in lettuce were not significantly different in soils of different salinities. Among the cations, K content in lettuce was significantly higher in the soil of higher salinity, but Na, Ca, and Mg comtents were not much influenced. Comparing to the lettuce grown in low salinity soil, although the growth of lettuce was decreased by 9% in the soil of higher salinity, nitrate accumulation in the lettuce was increased by 18.6%. These results indicate that higher nitrate content in lettuce of higher salinity soil is a positive accumulation to adapt to the water stress condition. The nitrate accumulation of vegetables grown in plastic film houses is known to be due to the heavy fertilization and low light intensity, but salt accumulation in the soil, which can lower soil water potential, is expected to stimulate the nitrate accumulation further.