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        검색결과 204

        1.
        2024.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        PURPOSES : Concrete, which is a construction material, is the most widely used compression material; however, unlike steel, it exhibits nonlinear material characteristics. Therefore, to examine the behavior of structures under the nonlinear conditions of concrete materials, one must select an appropriate numerical-analysis technique and a reasonable material model. When performing the nonlinear numerical analysis of a structure using general-purpose structural analysis software, the stress–strain curve or the Mohr–Coulomb failure criterion is typically employed to consider the nonlinear material characteristics. In this study, an efficient nonlinear numerical analysis is conducted by defining the stress–strain curves and Mohr–Coulomb parameters applicable to Strand7 to examine and design the stability of reinforced concrete structures. METHODS : This study was conducted by improving existing data. Based on the tensile region of the concrete stress–strain curve presented in a simple shape and the results of the splitting test, the proposed Mohr–Coulomb parameter was improved based on regulations stipulated in the design standards of concrete structures. The characteristics and usability of the improved material models were examined using concrete splitting tensile and bending models. RESULTS : A yield area distribution similar to that of the reference data is obtained when the Mohr–Coulomb material model is used in the numerical analysis of the concrete splitting tension, thus confirming the validity of the model. In the Mohr–Coulomb material model, nonlinear resistance continues even after the maximum reaction force occurs. However, when the stress–strain curve material model is applied, at the moment the maximum reaction force occurs, the material yields and begins to be damaged. In addition, by applying the Mohr–Coulomb material model to the bending numerical-analysis model, the magnitude of stress in the tensile region from the initial stage exceeds the yield stress defined in the stress–strain curve. CONCLUSIONS : Based on a series of examples, the usability of the proposed concrete stress–strain curve and Mohr–Coulomb parameters is confirmed. However, to obtain numerical-analysis results that are consistent with the nonlinear behavior of actual structures, nonlinear testing of reinforced concrete structures shall be conducted and material models shall be improved.
        4,000원
        2.
        2023.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        PURPOSES : The wedge-type anchorage system requires a complex analysis of not only the tensile stress of the CFRP plate, but also the compressive stress and shear stress generated by the wedge action. The purpose of this study is to find a composite material failure theory that is suitable for analyzing the behavior of wedge-type anchorage system among various failure theories. METHODS : In this study, numerical analysis of various composite material failure theories was performed to analyze the anchorage strength and failure mode of the wedge-type anchorage system according to each failure theory, and compared with actual test results to determine the composite material failure theory most suitable for analyzing the behavior of a wedge-type anchorage system. RESULTS : Since the Maximum Stress failure theory shows similar results to the actual test in terms of failure mode and anchorage strength, there is no significant problem in applying it to the wedge-type anchorage system. However, it is judged to be difficult to apply under property conditions where interactions between stresses are highlighted. The Tsai-Hill and Tsai-Wu failure theories are considered unsuitable for application to wedge-type anchorage systems because the wedge angle conditions at which the most advantageous anchorage strength occurs are significantly different from other theories and the fracture type cannot be predicted. The Hashin-Rotem failure theory is considered to be the most appropriate to apply as a failure theory for the wedge-shaped anchorage system because the anchorage strength was slightly lower than the actual test results, but there was no significant difference, and the failure mode was consistent with the test results. The Hashin failure theory is judged to be unsuitable for application as a failure theory for the wedge-type anchorage system because the anchorage strength and failure mode were interpreted differently from the actual test results. CONCLUSIONS : The Hashin-Rotem failure theory was presented as the composite material failure theory most suitable for analyzing the behavior of wedge-type anchorage system.
        4,000원
        4.
        2022.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        지속적인 화석연료의 과도한 소비는 지구온난화와 기후환경 위기를 초래하고 있다. 이에 따라 화석연료의 대체 에너지 중 수소에너지가 주목받고 있는데, 수소에너지는 공해물질의 배출이 없고 자원적인 제약이 없다는 장점이 있다. 이에 따라 물의 전기분해를 이용하여 수소를 생산하는 수전해 시스템 및 수소에너지를 연료로 사용하여 전기를 생산하는 연료전 지 시스템과 관련된 다양한 연구가 진행되고 있다. 본 연구에서는 수전해 시스템과 연료전지의 핵심 소재 중 하나인 음이온 전도성 이오노머 소재를 대상으로 과량의 수화 상태를 반영하여 3D 이오노머 모델을 제작하였다. 최종적으로 과량의 수화상 태에서 이오노머의 구조적인 안정성과 성능 분석을 통해, 수전해 시스템과 연료전지의 핵심 소재인 음이온 전도성 이오노머 설계에 있어서 성능향상 인자를 제시하고자 하였다.
        4,200원
        5.
        2022.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Sarcoma is rare malignant tumors that develop from mesenchymal cells. Metastasis to the oral cavity is a rare occurrence. Undifferentiated Pleomorphic sarcoma(UPS), formerly known as Malignant fibrous histiocytoma(MFH), is rare spindle cell neoplasm that can have poorly prognosis with metastasis and local recurrence. This report describes a case of a 77-year-old man who was diagnosed with Undifferentiated Pleomorphic Sarcoma of the chest wall and underwent adjuvant radiation therapy after surgical resection. Although there was success of wide excision, two years later, he presented with metastasis to the several organs including tongue. We retrospectively analyzed results of Next Generation Sequencing(NGS), and we figured out RB1 gene mutation. Until now targeted therapy of RB1 gene mutation is not established. Surgeon needs to consider metastatic tumors through identifying patients’ chief complaints and past medical & dental history. We need to research through NGS, and take a step closer to find targeted therapy for tumors.
        4,000원
        6.
        2022.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        PURPOSES : Steel deck bridges are the preferred structural type for reducing dead load, and the use of thin-layer asphalt concrete with excellent adhesion to the steel deck and excellent deformation followability is increasing for bridge pavements. However, because these materials are constructed at a high temperature of 240 °C or higher to maintain high fluidity during construction, excessive thermal deformation and stress may be temporarily induced in the steel deck. Therefore, the stability of the structure must be assessed by considering the environmental conditions of the site during pavement construction. Herein, a method is presented for estimating the heat source equation, in which conduction and convection effects are removed using temperature measurement data, for modeling U-rib using plate elements. The validity of the study is assessed by deriving the equivalent heat source equation using the temperature data measured from the underside of the steel deck while constructing a 40-mm-thick goose asphalt concrete pavement layer on a 12-mm-thick steel deck. In addition, the practicality is verified by performing heat transfer and thermal stress analyses. METHODS : By comparing the temperature data measured during the construction of high-fluidity asphalt concrete with the results of repeated heat transfer numerical analysis, heat source data without field conduction and convection conditions are obtained. Subsequently, a heat source equation suitable for the heat source data is derived using the least-squares method. RESULTS : The results of the heat transfer analysis using the equivalent heat source equation calculated using the presented method are almost consistent with the measured temperature data. In addition, the behavioral characteristics of the structure that matches the behavior of the actual structure can be derived through thermal stress analysis, which considers heat conduction and convection to adjacent members. CONCLUSIONS : Even when the steel deck and U-rib member are modeled as plate elements, thermal effect analysis can be performed reasonably while considering field conditions.
        4,000원
        9.
        2020.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        모듈러 건축물은 철근콘크리트 및 철골 구조물에 비하여 상대적으로 경량이고, 단위 모듈간 기둥의 일체성을 기대하기 어려운 구조적 특성을 가진다. 이와 같은 구조적 특성은 모듈러 건축물의 높이가 높아짐에 따라 바람 및 지진과 같은 횡력저항성능에 직접적인 영향을 미친다. 본 연구에서는 횡력저항성능을 향상시키기 위해 긴장재를 활용한 모듈러 구조시스템을 제안하였다. 모듈러 구조시스템을 구성하는 주요 요소인 포스트텐션 기둥-바닥 접합부는 셀프 센터링 거동을 유도하기 위한 형상 및 상세를 가진다. 포스트텐션 기 둥-바닥 접합부의 이력 거동을 상세히 파악하기 위해 유한요소해석을 수행하였으며, 그 결과 초기 긴장력 및 보-기둥 접합부의 접합 조건에 따라 이력 거동은 확연한 차이를 보이는 것으로 나타났다.
        4,000원
        10.
        2020.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Gilles de la Tourette Syndrome (GTS) is a neuropsychiatric disorder defined by the motor and phonic tics affecting approximately 1% of the children worldwide. The symptoms of GTS typically arise at the age of 5 to 7 and generally improve with increasing age. Affected individuals can have a social stigma and poor quality of life, especially when tics are severe or accompanied by other neuropsychiatric disorders. Abnormalities in neurotransmitter signaling affecting basal ganglia circuits have been suggested as representatives of neurobiological mechanisms underlying GTS. While several evidences suggest GTS as an inherited disorder, the detailed genetic abnormalities responsible for the pathophysiology of GTS remain poorly understood. Currently, there is no satisfactory treatment option for moderate-to-severe GTS due to the limited efficacy, often complicated with side effects of available pharmacological drugs. Therefore, a number of animal models have been established to explore potential pathophysiological targets in GTS and to further screen candidate drugs. In this review, we revisit the experimental findings that describe the genetic and immunologic abnormalities in GTS as well as animal models established for studying GTS.
        4,900원
        13.
        2020.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Adsorption by granule activated carbon(GAC) is recognized as an efficient method for the removal of perfluorinated compounds(PFCs) in water, while the poor regeneration and exchange cycles of granule active carbon make it difficult to sustain adsorption capacity for PFCs. In this study, the behavior of PFCs in the effluent of wastewater treatment plant (S), the raw water and the effluents of drinking water treatment plants (M1 and M2) located in Nakdong river waegwan watershed was monitored. Optimal regeneration and exchange cycles was also investigated in drinking water treatment plants and lab-scale adsorption tower for stable PFCs removal. The mean effluent concentration of PFCs was 0.044 0.04 PFHxS g/L, 0.000 0.00 PFOS g/L, 0.037 0.011 PFOA g/L, for S wastewater treatment plant, 0.023 0.073 PFHxS g/L, 0.000 0.00 PFOS g/L, 0.013 0.008 PFOA g/L for M1 drinking water treatment plant and 0.023 0.073 PFHxS g/L, 0.000 0.01 PFOS g/L, 0.011 0.009 PFOA g/L for M2 drinking water treatment plant. The adsorption breakthrough behaviors of PFCs in GAC of drinking water treatment plant and lab-scale adsorption tower indicated that reactivating carbon 3 times per year suggested to achieve and maintain good removal of PFASs. Considering the results of mass balance, the adsorption amount of PFCs was improved by using GAC with high-specific surface area (2,500m2/g), so that the regeneration cycle might be increased from 4 months to 10 months even if powdered activated carbon(PAC) could be alternatives. This study provides useful insights into the removal of PFCs in drinking water treatment plant.
        4,300원
        17.
        2019.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Herbal medicine has been the basis for medical treatments through much of human history, and such traditional medicine is still widely practiced today. Modern medicine makes use of many plant-derived compounds as the basis for pharmaceutical drugs. In traditionally, Achyranthes aspera, Safflower (Carthamus tinctorius) seed and Acanthopanax senticosus have been used for the treatment and prevention of bone-related diseases. In this study, we investigated the pharmacological effect of mixture of Achyranthes aspera, Safflower (Carthamus tinctorius) seed and Acanthopanax senticosus and the other herbs. Two types of enzymes were used to enhance the extraction components of amino acid, mineral content, free sugar, and flavor recovery in extracting natural herbal mixtures(NME). We evaluated regulation of osteogenic differentiation in human bone marrow mesenchymal stem cells using alkaline phosphatase staining, alizarin red S staining and RT-PCR. The CCK-8 assay indicated that NME had no cytotoxicity but increased cell survival. In addition, NME promoted the mineralization and expression of osteogenic differention marker genes in human bone marrow mesenchymal stem cells. Therefore, NME has an effect of promoting proliferation and osteogenic differentiation of human mesenchymal stem cell.
        4,000원
        18.
        2019.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Nerve injury induced protein 1 (Ninjurin1) was originally described in neuroscience in which the expression of Ninjurin1 was regulated by Schwann cells and dorsal root ganglion neuronal cells of damaged nerve tissues. After the first discovery of Ninjurin1, the widespread expression of Ninjurin1 in adult and embryonic tissues have been observed including bone marrow, peripheral blood lymphocytes, thymus, and heart. Currently, the Ninjurin1 mediated positive regulation of pre-osteoclasts fusion and osteoclast development was reported. The bone homeostasis is dynamically balanced by bone-resorbing activity of osteoclast and bone-forming activity of osteoblast. Until now, the role of Ninjurin1 was never been described in osteoblastogenesis. Therefore, in this study, we have evaluated the expression and function of Ninjurin1 in osteoblast. The ample expression of Ninjurin1 was observed in bone marrow of mouse tibia sections but it was barely expressed in osteocytes. And also the expression levels of Ninjurin1 were gradually increased during osteoblast differentiation of calvarial pre-osteoblast, C2C12, and MC3T3-E1 cells. Importantly, the expression of Ninjurin1 was increased in the absence of osteogenic stimulus, BMP2, which suggests the cell density-dependent regulation of Ninjurin1. The controlled expression of Ninjurin1 by cell-density was evidently shown in not only pre-osteogenic osteoblast lineage cells but also in non-osteogenic cancer cells such as HeLa and A549 cells. In addition, the isoform-specific knockdown of Ninjurin1 remarkably reduced the alkaline phosphatase (ALP)-positive osteoblast differentiation. Thus, our results suggest a previously unappreciated mechanism of Ninjurin1 expression and also suggest its role on osteoblastogenesis.
        4,000원
        19.
        2019.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        As indoor activities continue to increase, the importance of indoor air is emphasized. Moreover, children's activities are emphasized as being vulnerable. In this study, vocal organic compounds (VOCs) and CO2 in the indoor air were analyzed among children aged 4 to 7 years attending day care centers in Seoul. In the case of VOCs, the average concentration measured during a period of 24 hours in an asthmatic home was 143.9 (μg/m3). The average concentration measured during a period of 24 hours in the asthma and rhinitis home was 146.7 (μg/m3). In CO2, the average concentration measured during a period of 24 hours in the asthmatic home was 665.9 (ppm). The average concentration measured during a period of 24 hours in the asthma and rhinitis home was 695.9 (ppm). In this study, asthma symptoms increased as the concentration of indoor pollutants increased. Exposure of VOCs (μg/ m3) and CO2 (ppm) among environmental factors shows that respiratory symptoms such as asthma can be induced.
        4,000원
        20.
        2019.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        휴전국인 우리나라는 의무복무제도를 시행하고 있다. 이에 취업 및 진학을 한 20대 초반의 사회 초년생은 군 입대 문제로 많은 고민과 큰 걱정을 하고 있다. 이에 군에 대한 부정적인 인식과 군 생활 적응은 사회가 같이 풀어야 할 문제이다. 따라서 방송사 등 문제 해결을 위해 다각적으로 노력하고 있으나 역부족이다. 실제 군 입대 후 스트레스 및 불안정 심리상태의 장병 비중이 높다. 따라서 본 연구는 군 생활에서 일상적인 방법을 통해 스트레스, 불안감을 감소시키고, 집중력을 향상 시키고자 실행하였다. 주의 집중력 증가 및 스트레스, 불안감의 변화를 측정하기 위해 SMR파 대역의 주파수를 직접 노출시킨 실험군과 그렇지 않은 대조군으로 실험을 진행하였다. 실험군과 대조군대한 대응표본 t-검정 결과는 신뢰수준 95%에서 t=2.487, p=0.042로 유의차가 인정되었다. 즉, 가상사격영상에서 특정 주파수를 제시한 실험군의 피실험자들이 스트레스 및 불안정 심리의 완화효과가 발생하였다. 본 실험의 결과를 활용하면 젊은 장병들의 군 생활 적응에 효과가 높은 것으로 사료된다. 추후 연구에서는 심전도와 뇌파의 상관관계의 확인이 필요하다.
        4,000원
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