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        검색결과 15

        2.
        2021.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        PURPOSES : Pavement growth (PG) is a phenomenon whereby the overall length of a concrete pavement increases. The increase in length induces an axial compressive force in the concrete pavement slab, resulting in blow-up and damage of adjacent structures, such as a bridge. PG is influenced by several interacting factors, including climatic conditions, pavement materials, joint systems, incompressible particles (IP) infiltrating the joints or cracks in the slab, and an expansion caused by reactive aggregates in the concrete. However, it is difficult to predict PG and blow-up due to various complicated factors. Therefore, in this study, the pavement growth and blow-up analysis (PGBA) package program was developed to predict the PG and blow-up potential. The PGBA can consider the pavement configuration, expansion joint (EJ) configuration, climatic conditions, and design reliability. To evaluate the effects of influencing factors — such as climatic data, EJ configuration, pavement structures and materials, and design reliability — on PG and occurrence time of blow-up, a numerical example was demonstrated and a sensitivity analysis was performed. METHODS : To predict the PG, the concrete temperature was calculated using an appropriate analytical model. The trigger temperature for pavement growth(TTPG) was predicted using a statistical equation that considers pavement age, joint spacing, and precipitation. An analytical solution for estimating the concrete slab movement was performed. Through the calculated TTPG and the amount of PG, the service life of the EJ (width of EJ) can be predicted compared to the allowable width. In addition, by using analytical and finite elements, the safe temperature(Tsafe) for preventing blow-up occurrence was calculated. The blow-up occurrence was assumed to occur when the variation between the concrete temperature and TTPG was larger than Tsafe. RESULTS :As a result of the sensitivity analysis of maximum temperature and precipitation, the temperature and precipitation increase and the EJ service life and possibility of blow-up decrease. Sensitivity analysis was performed on the thermal expansion coefficient, pavement thickness, base layer type, concrete elastic modulus, and joint rotational stiffness in the concrete pavement structure and properties. In the PGBA program, the coefficient of thermal expansion and the type of base layer significantly affect the EJ life, as do the possibility of blowup and the elastic modulus. The joint rotational stiffness and pavement thickness had little effect on the EJ life but were found to affect the possible timing of blow-up. As a result of the PGBA sensitivity analysis of the width and spacing, which are the specifications of the EJ, the life of the EJ and the possibility of blow-up increased as the joint width increased; however, the EJ life and blow-up increased as the EJ interval reached a certain value. It was found that the possibility of a blow-up occurrence decreased. The results for the PGBA program in extreme weather conditions, the life span of EJs, and the possibility of blow-up in normal climates were reduced by over 50 %. CONCLUSIONS : As a result of PGBA sensitivity analysis, it was found that the substrate type, thermal expansion coefficient, precipitation, and alkali-silica reaction had the greatest influence on pavement expansion and blow-up.
        4,900원
        4.
        2019.05 KCI 등재 구독 인증기관 무료, 개인회원 유료
        2016 Gyeongju and 2017 Pohang earthquakes led Koreans to acknowledge that the Korean peninsula is not an earthquake-free zone anymore. Among various buildings crucial to after-shock recovery, general hospital buildings, especially existing old ones, are very significant so seismic retrofitting of those must be an important issue. Self-centering energy dissipative(SCED) brace is one of retrofitting methods, which consists of tendon with restoring force and friction device capable of dissipating seismic energy. The strength of the SCED brace is that the tendon forces a structure to go back to the original position, which means residual drift can be negligible. The residual drift is a very important parameter to determine usableness of general hospitals after shock. To the contrary, buckling-restrained braces(BRB) are also a very effective way to retrofit because they can resist both compressive and tensile, but residual drift may exist when the steel core yields. On this background, the seismic retrofitting effect of general hospitals reinforced with SCED braces was investigated and compared to that of the BRD in this study. As a result, although the floor acceleration cannot be reduced, the story drift and residual drift, and the shear demand of walls significantly decreased. Consequently, seismic retrofitting by SCED braces are very effective for domestic low-rise general hospitals.
        4,000원
        5.
        2018.05 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The main function of the general hospital building is to provide medical facilities and service. However, damage to the non-structural elements such as architectural, medical, mechanical and other components will interrupt those functions after the earthquake. Especially, it is considered that, damage to the non-structural elements is a serious event because it is directly associated with the lives of patients. Therefore, this study evaluated whether the certain non-structural elements of general hospital building has the seismic performance to provide hospital medical services after the earthquake. The evaluation is conducted by selecting the non-structural elements used in general hospital which are sensitive to acceleration, such as cooling towers, air handler, MRI and CT. As a result, the non-structural elements located on the upper floor without suitable support method did not meet the performance objective. Therefore, adequate anchorage against the seismic event is required for such non-structural elements that are acceleration-sensitives.
        4,000원
        6.
        2018.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Pohang earthquake occurred on November 15, 2017, with a magnitude of 5.4. The damage of the structure caused by the Pohang earthquake was the most significant in 4-story piloti-type buildings, where the damage patterns were different according to the location of columns and walls at the first story. One building with a staircase at a corner shows shear failure at columns, and Another building with a staircase in the middle shows no failure or shear failure at staircase walls. Therefore, two different piloti-type buildings were selected; one has a staircase at a corner and another has in the middle, and the seismic behavior of the buildings were examined by nonlinear dynamic analysis applying a ground motion measured at Pohang. Analytical model well simulated the actual behavior of the piloti-type buildings during the earthquake. Analysis results showed that walls have an insufficient shear strength wherever the location of the staircase is and columns with insufficient transverse reinforcement could be failed when the staircase is located at a corner. Conclusively, structural engineers should design columns and walls in piloti-type buildings to possess sufficient capacity according to the location of staircase.
        4,000원
        7.
        2016.12 구독 인증기관 무료, 개인회원 유료
        Demand for the development of non-antibiotic growth promoters (AGP) in animal production surged in recent years. However, elucidating the specific mechanisms and action of prebiotics, probiotics, and synbiotics as non-AGP in animals is still in progress. This work investigated and compared faecal microbiotas of weaned piglets under the administration of a basal diet (CON) and with prebiotic lactulose (LAC), probiotic Enterococcus faecium NCIMB 11181 (PRO), or their synbiotic combination (SYN). Although prebiotics and/or probiotics in the diet significantly increased alpha-diversity compared with CON values, no differences were detected in richness and diversity values among the treatment groups (LAC, PRO, and SYN). At phylum level, the Firmicutes to Bacteroidetes ratio increased in the treatment groups in comparison to the CON group, and the lowest abundance of Proteobacteria was found in LAC group. At family level, Enterobacteriaceae decreased in all treatments, especially more than 10-fold reduction in LAC group compared with CON group. At genus level, the highest abundance of Oscillibacter was detected in PRO group, the highest Clostridium in LAC group, and the highest Lactobacillus in SYN group; the abundance of Escherichia was lowest in LAC group. Clustering in the DAPC plots illustrated distinct separation of the feeding groups (CON, LAC, PRO, and SYN) from one another, showing that microbial communities had different compositions according to different feed additives. Effects of LAC and PRO treatments on the faecal microbiota suggest independent mechanisms; nonetheless, the impact of SYN might also be distinct from that when each are administered singly as LAC or PRO.
        4,000원
        11.
        2012.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        본 연구는 숲속에서의 태교활동이 임산부의 스트레스 감소에 미치는 효과를 규명하기 위하여 수행되었다. 피험자로는 과거 병력이 없는 51명의 임산부(28±3.0세)가 참가하였다. 실험 참가 전날 도시환경에서의 심리적·생리적 변화를 측정하였으며1박 2일의 숲태교 프로그램을 진행한 후 도시환경에서의 측정방법과 동일한 방법으로 비교측정이 이루어졌다. 심리지표로서BDHI(공격성 척도), BHOP(무망감 척도), STAI-X-1(상태불안 척도), DIS(역기능성 행동척도)에 관한 설문조사를 하였다.생리지표로서는 심박변동성과 코티솔을 측정하였다. 본 연구의 결과 1박 2일의 숲태교 프로그램에 참여한 후 임산부들의공격성과 불안감이 감소되고 부정적인 사고가 감소하여 심리적 안녕감이 증진되는 결과를 얻을 수 있었다. 이 결과를 통하여숲속에서의 태교활동이 산모의 임신 중 스트레스를 감소시키며 심리적 안녕감을 증가시킨다는 사실을 밝힐 수 있었다.
        4,000원
        12.
        2016.10 KCI 등재 서비스 종료(열람 제한)
        This study was conducted to examine how inhaling woody essential oil during work influences attention. The indoor experiment was conducted using woody essential oil that blends Hinoki cypress (Chamaecyparis obtusa (Siebold & Zucc.) Endl.) and pine (Pinus densiflora Siebold & Zucc.) and the control experiment was done with odorless air. The subjects were 19 high school and college students (male: 8, female: 11, average age: 19.47±3.20) and double-blind cross-over trial was conducted to identify the effect of essential oil on the body and attention. The subjects sat on the chair and closed their eyes for stabilization for 30 seconds. Then, they inhaled woody essential oil and odorless air for three minutes each. During each stimulation periods, the subjects calculated a multiplication of two digit-numbers in their minds and their heart rate variability (HRV) was measured. Physiological changes were measured using the total variation of LF/HF, which is an indicator of activities of sympathetic nerves and psychological changes were measured using the Semantic Differential Method (SD method) and the Profile of Mood States (POMS). As a result, inhaling woody essential oil increased total variation of LF/HF (diffrence of LF/HF in stimulation and LF/HF in rest; ΔLF/HF) compared to inhaling odorless air and led to the activation of sympathetic nerves. Also, it increased tranquility and reduced anger (A-H) and total mental disorder (TMD) among the psychological indicators. In case of calculations, it significantly increased the number of multiplications solved, number of correct answers, and percentage of correct answers. Overall, this study showed that inhaling woody essential oil during work effectively improved the subjects' attention.
        13.
        2015.10 KCI 등재 서비스 종료(열람 제한)
        This study evaluates the physiological and psychological relaxing effects of viewing the scenery in the Jangseong healing forest. Twenty-two university students (20.9 ± 1.3 years old) participated in the study. An experiment was conducted in the Jangseong healing forest, and a control experiment was performed in the city. The physiological indicators used in the study were the heart rate variability and heart rate of the participants. Subjective assessments (SD method, POMS, and STAI) were used as psychological indicators. The participants sat on a chair watching the scenery in the forest area and the urban area for 10 minutes each. The results indicate that viewing the scenery in the forest can increase parasympathetic nerve activity as compared with that in the city. In addition, the forest environment can enhance “comfortable,” “natural,” and “soothed” feelings; alleviate negative emotions; and reduce anxiety. The results clearly indicate that viewing the scenery in the Jangseong healing forest induced physiological and psychological relaxation.
        14.
        2013.08 KCI 등재 서비스 종료(열람 제한)
        This paper presents a robotic system that provides telepresence to the visually impaired by combining real-time haptic rendering with multi-modal interaction. A virtual-proxy based haptic rendering process using a RGB-D sensor is developed and integrated into a unified framework for control and feedback for the telepresence robot. We discuss the challenging problem of presenting environmental perception to a user with visual impairments and our solution for multi-modal interaction. We also explain the experimental design and protocols, and results with human subjects with and without visual impairments. Discussion on the performance of our system and our future goals are presented toward the end.