• Journal of the Korean Wood Science and Technology
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• v.30 no.2
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• pp.158-164
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• 2002

The properties of new porous carbon materials "Woodceramics" are affected by the characteristics of raw boards. To investigate of density profile and resin contents in impregnated boards, control board and 3 types of steam-injected boards were made by steam injection time, The wood species used for manufacturing boards was Sugi(Cryptomeria japonica). The results are as follows: 1) The density gradient of board after 10 minutes steam injection was the smallest and non-steamed board was largest. 2) The resin content and dimensional rise decreased with increase of board density, and were the largest in board after 10minutes steam injection but there was little difference between boards after 5 and 10 minutes steam injection.

• Earthquakes and Structures
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• v.22 no.3
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• pp.319-330
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• 2022

Retrofit of soft-story buildings due to seismic loads using Gap-Inclined-Brace (GIB) system is considered a new retrofit technique that aims to maintain both strength and stiffness of structure. In addition, it provides more ductility and less P-delta effect, and subsequently better performance is observed. In this paper, the effect of the eccentricity between GIB and the retrofitted column due to installation on the efficiency of the retrofitting system is studied. In addition, a modification in the determination method of GIB properties is introduced to reduce the eccentricity effect. Also, the effect of GIB system on the seismic response of mid-rise buildings with different heights considering soft-story at various heights has been studied. A numerical model is developed to study the impact of such system on the response of retrofitted soft-story buildings under the action of seismic loads. To achieve that goal, this model is used to perform a numerical investigation, by considering five case study scenarios represent several locations of soft-story of two mid-rise reinforced concrete buildings. At first, Non-linear static pushover analysis was carried out to develop the capacity curves for case studies. Then, Non-linear time history analyses using ten earthquake records with five peak ground accelerations is performed for each case study scenario before and after retrofitting with GIB. The results show that large GIB eccentricity reduce the ultimate lateral resistance and deformation capacity of the retrofitting system. Moreover, the higher the retrofitted building, the more deformation capacity is observed but without significant increase in ultimate lateral resistance.

• Journal of Energy Engineering
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• v.13 no.1
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• pp.12-19
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• 2004

A Molded Case Circuit Breaker (MCCB) is an electric control device to interrupt the abnormal currents which result from the over-loads or short-circuits. Its malfunction will result in severe accidents. In the development of the MCCB, higher current-rating and improved thermal performance become more and more important in providing the safe function and reliability for the modern devices requiring small scale and high performance. It is also very important to consider the factors of temperature rise in the design of MCCB. The major reasons of temperature rise in the MCCB result from the resistances, which are come from the connection and contact surfaces. These resistances are influenced by current, time, configuration of contact surfaces and applied voltage. In order to predict the temperature distribution inside MCCB, we have simulated the model with some assumptions and simplifications, using commercial code ICEPAK. To verify the results of temperature field analysis, the numerical results are compared with experimental ones for the same model. The results show a good agreement with actual temperature rise obtained by experiments.

• Earthquakes and Structures
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• v.11 no.3
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• pp.483-503
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• 2016

This study aims to evaluate seismic performance of existing low and mid-rise reinforced concrete buildings by comparing their displacement capacities and displacement demands under selected ground motions experienced in Turkey as well as demand spectrum provided in 2007 Turkish Earthquake Code for design earthquake with 10% probability of exceedance in 50 years for soil class Z3. It should be noted that typical residential buildings are designed according to demand spectrum of 10% probability of exceedance in 50 years. Three RC building sets as 2-, 4- and 7-story, are selected to represent reference low-and mid-rise buildings located in the high seismicity region of Turkey. The selected buildings are typical beam-column RC frame buildings with no shear walls. The outcomes of detailed field and archive investigation including approximately 500 real residential RC buildings established building models to reflect existing building stock. Total of 72 3-D building models are constructed from the reference buildings to include the effects of some properties such as structural irregularities, concrete strength, seismic codes, structural deficiencies, transverse reinforcement detailing, and number of story on seismic performance of low and mid-rise RC buildings. Capacity curves of building sets are obtained by nonlinear static analyses conducted in two principal directions, resulting in 144 models. The inelastic dynamic characteristics are represented by "equivalent" Single-Degree-of- Freedom (ESDOF) systems using obtained capacity curves of buildings. Nonlinear time history analysis is used to estimate displacement demands of representative building models idealized with (ESDOF) systems subjected to the selected ground motion records from past earthquakes in Turkey. The results show that the significant number of pre-modern code 4- and 7-story buildings exceeds LS performance level while the modern code 4- and 7-story buildings have better performances. The findings obviously indicate the existence of destructive earthquakes especially for 4- and 7-story buildings. Significant improvements in the performance of the buildings per modern code are also obvious in the study. Almost one third of pre-modern code buildings is exceeding LS level during records in the past earthquakes. This observation also supports the building damages experienced in the past earthquake events in Turkey.

• KIEAE Journal
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• v.10 no.5
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• pp.165-170
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• 2010

Super high-rise mixed use buildings require a longer period for construction. Especially finishing work takes up about 40% of the whole construction period. Thus, finishing work is becoming an important factor in determining the construction period along with earth work and frame work. As the expected returns added by the reduction of the period and cost in constructing super high-rise mixed use buildings are huge, the expectations are now increasing for the possible gains. In this respect, as the period of finishing work is easier to be shortened than that of frame work, the efforts to acquire the technical knowledge to reduce the finishing work period are now being required. Accordingly, in this study, we aimed at suggesting the basic data for designing an economic plan for finishing-work procedure by analyzing the productivity of each work type of finishing work procedure on the basis of the execution and results of a construction method as a time-flexible finishing work plan. For this, we categorized the work types of finishing work procedure into each work unit and provided a work-system for each of them. Also, with case studies, we calculated the detailed amounts of the work-loads, required materials, productivity, and productivity index of the main work types of finishing work procedure and each of their separate work units as well as analyzed the relationship between the value results to suggest a better way to improve its productivity.

• Journal of Environmental Health Sciences
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• v.34 no.4
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• pp.316-326
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• 2008

The Earth's temperature has risen $0.76^{\circ}C$ (degree) during last 100 years which Implies a sudden rise, compare with the 4oC (degrees) rise through out the past 20,000 years. If the volume of GHG (Greenhouse Gas) emission continues at the current level, the average temperature of the Earth will rise by $1^{\circ}C$ (degree) by 2030 with the further implication that the temperature of Earth will rise by $2{\sim}5^{\circ}C$ (degrees) every 100 years. Therefore, as we are aware that the temperature of the glacial epoch was $8{\sim}9^{\circ}C$ (degrees) lower than the present time, we can easily predict that the above temperature rises can be potentially disastrous for human life. Every country in the world recognizes theseriousness of the current climate change and adopted a convention on climate change in June 1992 in Rio. The COP1 was held in March 1995 in Berlin and the COP3 in Dec. 1997 in Kyotowhere the target (2008-2012) was determined and the advanced nations' reduction target (5.2%, average)was also agreed at this conference. Korea participated in the GHG reduction plan which required the world's nations to ratify the Kyoto Protocol. Ratification of the Kyotoprotocol and the followup requirement to introduce an international emissions trading scheme will require severe reductions in GHGs and considerable economic consequences. USA are still refusing to fully ratify the treaty as the emission reductions could severely damage the economies of these countries. In order to estimate the exact $CO_2$ emission, this study statistically analyzed $CO_2$ emission of each country based on the following variables : level of economic power and scientific development, the industrial system, productivity and energy efficiency.

• Journal of the Korean GEO-environmental Society
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• v.20 no.10
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• pp.5-14
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• 2019

Recently, earthquakes have occurred in our country and seismic stability of high-rise buildings in large cities is being a growing interest and thus the related studies have been increased. Also the grounds are considered indirectly in most of seismic designs and analyses and seismic researches based on 3D dynamic analysis are insufficient. In this study, therefore, 2D and 3D dynamic analyses were performed based on the SSI complete model including grounds and the behavior was compared and analyzed. For dynamic modeling, linear time history analyses were performed by using MIDAS GTS NX. For this purpose, a high-rise building was assumed to be constructed on top of the bedrock and surrounded by a surface layer. A sensitivity analysis was performed with the selected parameters. The dynamic behavior was compared and analyzed in terms of horizontal displacements, drift ratios, bending stresses, and weak parts. In most cases, 2D dynamic behavior was calculated to be larger than 3D's and thus it shows more conservative results with increasing number and size of weak parts.

• Journal of Ocean Engineering and Technology
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• v.35 no.6
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• pp.414-425
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• 2021

Overcrowding of high-rise buildings in urban zones change the airflow pattern in the surrounding areas. This causes building wind, which adversely affects the wind environment. Building wind can generate more serious social damage under extreme weather conditions such as typhoons. In this study, to analyze the wind speed and wind speed ratio quantitatively, we installed five anemometers in Haeundae, where high-rise buildings are dense, and conducted on-site monitoring in the event of typhoon OMAIS to determine the characteristics of wind over skyscraper towers surround the other buildings. At point M-2, where the strongest wind speed was measured, the maximum average wind speed in 1 min was observed to be 28.99 m/s, which was 1.7 times stronger than that at the ocean observatory, of 17.0 m/s, at the same time. Furthermore, when the wind speed at the ocean observatory was 8.2 m/s, a strong wind speed of 24 m/s was blowing at point M-2, and the wind speed ratio compared to that at the ocean observatory was 2.92. It is judged that winds 2-3 times stronger than those at the surrounding areas can be induced under certain conditions due to the building wind effect. To verify the degree of wind speed, we introduced the Beaufort wind scale. The Beaufort numbers of wind speed data for the ocean observatory were mostly distributed from 2 to 6, and the maximum value was 8; however, for the observation point, values from 9 to 11 were observed. Through this study, it was possible to determine the characteristics of the wind environment in the area around high-rise buildings due to the building wind effect.

• Journal of the Korean Society for Nondestructive Testing
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• v.18 no.1
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• pp.33-41
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• 1998

The response characteristics of the PZT transducers during glass capillary breakage were studied at the epicenter of the glass plate. The PZT transducers had been made by using EC-65 PZT ceramics(supplied by Edo co.) with a constant area and a various thickness. The theoretical displacement and velocity at the epicenter of glass plate with an air boundary condition were calculated by assuming the point load of 1N force strength and a rise time of 280 ns with a ramped functional dependence, and the 1st pulses of the PZT transducer may be considered as the vertical velocity incident on the electrode of the PZT ceramic. The responses of the PZT transducer may be depended on the thickness mode of the PZT ceramic below 0.33 in the ratio of the thickness to the diameter of PZT ceramic, but the reponse of the PZT transducer may be depended on the other modes of PZT transducer in the addition of the thickness mode of the PZT ceramic above 0.33. The full time of half maximum at the 1st pulse was nearly 280 ns without a variation of applied breakage load and the resonant frequency of the PZT transducer, and then may be considered as the rise time of a AE source. The maximum amplitude of the 1st pulse depended on the incident vertical velocity and capacitance of the PZT transducer. Therefore, the full time of half maximum and maximum amplitude of the 1st pulse may be considered as the rise time and strength of acoustic emission source respectively.

• Structural Engineering and Mechanics
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• v.49 no.3
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• pp.411-425
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• 2014

This paper presents the processing of nonlinear features associated with a damage event by quadratic time-frequency distributions for damage identification in a frame structure. A time-frequency distribution is a function which distributes the total energy of a signal at a particular time and frequency point. As the occurrence of damage often gives rise to non-stationary, nonlinear structural behavior, simultaneous representation of the dynamic response in the time-frequency plane offers valuable insight for damage detection. The applicability of the bilinear time-frequency distributions of the Cohen class is examined for the damage assessment of a frame structure from the simulated acceleration data. It is shown that the changes in instantaneous energy of the dynamic response could be a good damage indicator. Presence and location of damage can be identified using Choi-Williams distribution when damping is ignored. However, in the presence of damping the Page distribution is more effective and offers better readability for structural damage detection.