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        검색결과 337

        43.
        2022.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Polyacrylonitrile (PAN)-based carbon fibers (CFs) and their composites, CF-reinforced plastics, have garnered significant interest as promising structural materials owing to their excellent properties and lightweight. Therefore, various processing technologies for fabricating these advanced materials using thermal energy have been intensively investigated and developed. In most cases, these thermal energy-based processes (heat treatment) are energy and time consuming due to the inefficient energy transfer from the source to materials. Meanwhile, advanced processing technologies that directly transfer energy to materials, such as radiation processing, have been developed and applied in several industrial sectors since the 1960s. Herein, general aspects of radiation processing and several key parameters for electron-beam (e-beam) processing are introduced, followed by a review of our previous studies pertaining to the preparation of low-cost CFs using specific and textile-grade PAN fibers and improvements in the mechanical and thermal properties of CF-reinforced thermoplastics afforded by e-beam irradiation. Radiation processing using e-beam irradiation is anticipated to be a promising method for fabricating advanced carbon materials and their composites.
        5,100원
        44.
        2021.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        본 연구는 스탠다드 국화 ‘백마’의 삽목기간(15, 30, 45일)과 단일처리 시기(정식 후 40, 50, 60, 70일 후)에 따른 버들눈 발생과 절화의 생육에 미치는 영향을 알아보기 위해 실시하였다. 삽목기간이 30일과 45일 처리는 15일 처리보다 초장이 길었고 뿌리수가 많았으나, 잎의 황화현상이 나타났다. 삽목기간이 길수록 정식 후 버들눈 발생률이 높았고, 삽목기간이 45 일 처리에서 버들눈의 발생률이 28.3%로 가장 높았다. 절화의 생육에서 절화장은 삽목기간 15일 처리에서 110.9cm로 가장 길었고, 삽목기간이 길수록 절화장이 짧았다. 절화의 엽수와 무게는 삽목기간 15일 처리에서 가장 양호하였다. 화폭, 설상화 수, 꽃 무게 등 꽃의 생육은 삽목기간이 길어질수록 불량하였고, 꽃목길이는 삽목기간 30일과 45일 처리에서 6.5~8.9cm 로 길게 나타나 절화의 품질이 떨어졌다. 개화소요일수는 다른 처리들보다 삽목기간 45일 처리에서 버들눈 발생으로 인하여 가장 짧았다. 단일처리 시기에 따른 절화의 버들눈 발생률은 정식 60일과 70일 후 단일처리에서 각각 20.1%와 45.8%로 나타나, 정식 40일과 50일 후 단일처리보다 높게 나타났다. 절화의 길이, 엽수, 무게 등의 절화 생육은 영양생장기간이 길었던 정식 70일 후 단일처리에서 가장 양호하였고, 정식 40일 후 단일처리에서 가장 불량하였다. 그러나 화폭, 설상화수, 꽃의 무게 등의 꽃의 생육은 정식 50일 후 단일처리에서 가장 우수하였다. 정식 60일과 70일 단일처리에서 꽃목에 유엽이 발생함에 따라 꽃목길이가 길어져 품질이 하락하였고, 개화소 요일수는 단일처리 시기가 늦을수록 지연되었다. 따라서 스탠다드 국화 ‘백마’의 버들눈은 삽목기간이 길어져 15일 이상된 노화된 삽목묘를 정식하거나 정식 후 단일처리 시기가 50일 이상으로 늦어질 경우에 많이 발생하며, 버들눈 발생으로 화폭, 설상화수, 꽃 무게, 꽃목길이 등 절화의 품질이 크게 하락하는 것으로 나타났다.
        4,000원
        45.
        2021.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This paper presents a periodic replacement policy for a system subject to shocks when the system is operating for a finite random horizon. The system is subject to shocks during operation, and each shock causes downgrading of the system performance and makes it more expensive to run by the additional running cost. Shocks arrive according to a nonhomogeneous or a renewal process, and we develop periodic replacement policies under a finite random operating horizon. The optimum periodic replacement interval which minimizes the total operating cost during the horizon is found. Numerical examples are presented to demonstrate the results.
        4,000원
        46.
        2021.11 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Background: Lunge exercises are lower extremity rehabilitation and strengthening exercises for patients and athletes. Most studies have shown the effectiveness of the forward and backward lunge exercises for treating patellofemoral pain and anterior cruciate ligament injuries (by increasing lower extremity muscle activity) and improving kinematics. Objects: However, it is not known how the two different lunge movements affect trunk muscle activities in healthy individuals. The purpose of this study was to investigate the electromyographic activity of the rectus abdominis and erector spinae muscles during forward and backward lunge exercises in healthy participants. Methods: Twelve healthy participants were recruited. Electromyographic activity of the rectus abdominis and erector spinae was recorded using surface electrodes during forward and backward lunges, and subsequently normalized to the respective reference voluntary isometric contractions of each muscle. Results: Activity of the erector spinae was significantly higher than that of the rectus abdominis during all stages of the backward lunge (p < 0.05). The activity of the erector spinae was significantly greater during the backward than forward lunge at all stages (p < 0.05). Conclusion: Backward lunging is better able to enhance trunk motor control and activate the erector spinae muscles.
        4,000원
        51.
        2021.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Background: Although recent studies using virtual reality have been actively conducted, studies on exercise therapy interventions and changes in muscle characteristics in patients with scoliosis are limited. Objectives: To investigate the effects of trunk and pelvic exercises program using virtual reality on the characteristics of paraspinal muscles in patients with scoliosis. Design: A randomized controlled trial. Methods: Thirty college students with scoliosis were randomly assigned to the trunk and pelvic exercise program using virtual reality group (VRG; n=15) and the general stretching exercise group (SG; n=15). The intervention was conducted three times a week for 8 weeks for 30 min per session. The recorded variables were muscle tone (F), muscle stiffness (S), and muscle elasticity (D). The collected data were analyzed after statistical processing. Results: In the cervical vertebrae, F showed significant differences in the amount of inter-group variation in the VRG compared that in the SG on the right side. The VRG showed significant increases in intra-group variation on both the right and left sides. S showed significant differences in the amount of inter-group variation in the VRG compared to that in the SG on the right side. With regard to the intra-group variation of F in the thoracic vertebrae, the right muscle in the VRG demonstrated significantly increased after the experiment, while D significantly increased in the left muscle in the VRG. Conclusion: Pelvic and trunk exercises program using virtual reality may be applied a better therapeutic intervention for patients with scoliosis.
        4,000원
        52.
        2021.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Pacific herring, Clupea pallasii, a keystone species with significant ecological and commercial importance, is declining globally throughout much of its range. While traditional fishing equipment methods remain limited, new sensitive and rapid detection methods should be developed to monitor fisheries resources. To monitor the presence and quantity of C. pallasii from environmental DNA (eDNA) extracted from seawater samples, a pair of primers and a TaqMan® probe specific to this fish based on mitochondrial cytochrome b (COB) sequences were designed for the real-time PCR (qPCR) assay. The combination of our molecular markers showed high specificity in the qPCR assay, which affirmed the success of presenting a positive signal only in the C. pallasii specimens. The markers also showed a high sensitivity for detecting C. pallasii genomic DNA in the range of 1 pg~100 ng rxn-1 and its DNA plasmid containing COB amplicon in the range of 1~100,000 copies rxn-1, which produced linear standard calibration curves (r2=0.99). We performed a qPCR assay for environmental water samples obtained from 29 sampling stations in the southeastern coastal regions of South Korea using molecular markers. The assay successfully detected the C. pallasii eDNA from 14 stations (48.2%), with the highest mean concentration in Jinhae Bay with a value of 76.09±18.39 pg L-1 (246.20±58.58 copies L-1). Our preliminary application of molecular monitoring of C. pallasii will provide essential information for efficient ecological control and management of this valuable fisheries resource.
        4,300원
        53.
        2021.09 구독 인증기관 무료, 개인회원 유료
        Associations between periodontal infection and cardiovascular disease have been documented. Porphyromonas gingivalis is a well-established periodontal pathogen, and tissue factor (TF) is a key initiator of the coagulation cascade. In this context, P. gingivalis has been reported to enhance TF expression in human endothelial cells. The present study investigated the underlying mechanisms of TF induction by P. gingivalis in human umbilical vein endothelial cells. P. gingivalis increased TF expression in a dose- and time-dependent manner. Not only live bacteria but also glutaraldehyde-fixed bacteria increased TF expression to the same extent. However, sonicates of P. gingivalis did not induce TF expression. Cytochalasin D and SMIFH2, which are inhibitors of actin polymerization and actin nucleation, respectively, inhibited the TF expression induced by P. gingivalis . Finally, TF production was decreased or increased in the presence of various signaling inhibitors, including mitogen-activated protein kinases. These results suggest that P. gingivalis induces endothelial TF expression by a bacterial internalization-dependent mechanism and through diverse signal transduction mechanisms.
        4,000원
        54.
        2021.08 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The purpose of this study was to analyze changes to body measurements and silhouettes after wearing an early 19th century women’s corset. Two types of corsets were tested. Changes in body size and silhouette were compared based on the levels of tightening strength of the corset. The tightening strength was adjusted in 4 steps by making the length of back fastening string 10-40 cm shorter than the standard. The silhouette was compared with the front silhouette and the side silhouette. The results were as follows. After wearing the experimental 19th century corsets, the chest circumference and front interscye length increased. However, the chest circumference did not increase proportionally to the tightening strength. The underbust circumference, waist circumference, and back interscye length also decreased. The waist width was decreased to create a slim front silhouette. The change in the body silhouette differed depending on the style of the experimental corset. The experimental corset made with the six-piece torso pattern changed the posture so that the shoulders were pulled back and the chest was pushed forward. The experimental corset with the side bodice pattern resulted in the subject’s shoulders reclining backward and the chest and abdomen extending forward. The results of this study show that women’s body sizes and silhouettes could be changed by wearing the early 19th century corsets, but the changes in body size and silhouette vary depending on the wearer's individual body type or corset style.
        5,100원
        55.
        2021.08 KCI 등재 구독 인증기관 무료, 개인회원 유료
        이 논문은 윌리엄 버틀러 예이츠의 「조각상」 , 「델픽 오라클을 위한 소식」 , 그리고 「긴다리 파리」 의 순서에 대한 중요성을 탐구하려한다. 본 연구자는 이 세 시의 순서는 예이츠의 위대한 예술에 대한 견해를 반영한다고 주장한다. 즉 예이츠는 위대한 예술은 비극으로 시작해서 기쁨 더 정확히 표현하자면 섹스로 끝난다고 쓴 적이 있다. 예이츠는 예술을 신혼 첫날밤의 기쁨 같은 존재에 비유하기도 했다. 「조각상」은 비극적인 시이고 「델픽 오라클을 위한 소식」은 섹스의 기쁨을 노래한 시인데 이 기쁨은 예이츠에게는 천국이요 유토피아의 세계이다. 이 두 시 다음에 「긴다리 파리」가 위치한 점을 눈여겨보아야 하는데 이 시 역시 비극과 섹스라는 같은 주제를 다루어 앞서 제시된 같은 주제를 확장하고 강화하려는 의도를 보여준다. 시를 통해 기쁨을 추구하려는 예이츠의 의도는 그의 정치적인 목적과 깊은 연관이 있다. 즉 아일랜드 국민을 유토피아로 이끄는 것이다. 여기서 시인이 꿈꾸는 유토피아는 고대 그리스보다 더 위대한 문명의 요람으로 세계에 우뚝 설 미래의 아일랜드이다.
        4,900원
        56.
        2021.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Porcine pleuropneumonia caused by Actinobacillus pleuropneumoniae is a highly contagious disease that leads to enormous economic losses in pig industry, worldwide. Of the many virulence factors produced by the causative bacterium, ApxA exotoxins have been considered as the most important contributor to the disease. The toxins are classified into four different types; ApxIA, ApxIIA, ApxIIIA and ApxIVA. Uniquely, ApxIVA is expressed across all serotypes of A. pleuropneumoniae only during in vivo infection in pigs. Active research focusing on resolving the precious roles and mechanisms of the toxins is still at its primitive stage. In this study, we report the development of monoclonal antibodies against the two major antigenic epitopes that were characterized in our previous study incorporating the in silico predictions and protein modeling analyses. Recombinant proteins of the selected epitopes were expressed and purified after molecular cloning of the corresponding partial genes in E. coli expression system. Subsequently, we generated hybridomas with lymphoid cells from the rats immunized with the recombinantly expressed proteins of Apx. Consequently, hybridomas exhibiting strong productivity of the monoclonal antibodies were selected for downstream verifications that tested for reactivity and specificity using Western blot and ELISA. Our results strongly suggest the potential application of the monoclonal antibodies developed in this study as useful reagents to further elaborate the mechanism of the A. pleuropneumoniae infection in pig.
        4,000원
        57.
        2021.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study analyzes the user-generated reviews of Paris-based Michelin three-star restaurants in terms of how they are discursively constructed. Using the reviews posted in Tripadvisor in 2019 as data, it examines how positive reviews (PR) and negative reviews (NR) are framed with distinct discursive practices. While PR and NR a re both characteriz ed by the discursive practice of highlighting professed culinary expertise of the reviewer, this feature is more foregrounded in NR, where the reviewer is generally more oriented to showing themselves as being entitled to write a review. In terms of communicative styles, PR is also characterized by a heavy use of symbolic and metaphoric language, while more ordinary style of language is used in NR, embedded in the context of critiquing specific items of dish or service. While PR and NR both tend to make references to Michelin star status as a basis of their evaluation, they were shown to differ in terms of the tones or keys used in describing chefs, and also in the way the target of evaluation is formulated. The findings shed light on how and why the members of foodie community construct the language the way they do, and have implications for genre analysis.
        8,000원
        59.
        2021.05 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Background: Flat feet can be identified by assessing the collapse of the medial longitudinal arch (MLA) and these conditions can trigger epidemiological changes in the feet. Many of previous studies compared the muscle activity of lower body in terms of intervention and dynamics to treat the structural defect of flat feet. However, few studies have investigated or analyzed the muscle activity of gastrocnemius muscle in the subjects with flat feet. Objects: This study investigated the differences in changes of medial and lateral plantar flexors in subjects with flat feet during bipedal heel-rise (BHR) task and analyzed the differences in muscle activity between two groups by measuring the electromyography (EMG) of abductor hallucis (AH), tibialis anterior (TA), medial gastrocnemius (MG), lateral gastrocnemius (LG). Methods: A total of Twenty one adult females participated in this experiment. Subjects were assigned to groups according to the navicular drop test. The task was applied to the leg, where the heel lifting action prevailed. The muscle activity of the medial and lateral feet plantar flexors was evaluated, and the % maximum voluntary isometric contractions (%MVIC) of these were compared. Results: For the difference between groups the muscle activity (%MVIC) of LG muscle was statistically significantly low in flat feet group compared to healthy feet group (flat feet: 64.57, healthy feet: 90.17; p < 0.05). Conclusion: The results of this study will contribute to identifying the muscle activities of medial and lateral feet plantar flexors among subjects with flat feet, which can cause abnormal epidemiological changes in the feet.
        4,000원
        60.
        2021.05 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Background: Flat-back posture refers to a posture in which the pelvis is tilted backward, the lumbar spine is bent, the upper thoracic spine is increasingly bent, and the lower thoracic spine is straight. Given that most of the day is spent sitting, we need to develop exercise programs and devices that are suitable for people who spend less time exercising than sitting. Objects: This study investigated the effects of resistance footrest exercise on spine posture angles in visual display terminal (VDT) workers with flat back. Methods: We measured the upper lumbar angle (ULA) and lower lumbar angle (LLA) using a flexible ruler for the ULA and LLA. Then, after 1 week of resistance footrest exercise designed to strengthen the lumbar spine musculature, we measured these angles again. We measured each angle three times and then compared measurements from before and after exercise. Results: There were no significant differences in the ULA following the strengthening exercise, but significant differences were observed in LLA. Conclusion: The resistance footrest exercise strengthened the muscles affecting the pelvic and lumbar lordotic angles, and increases in the LLA were changed. This suggests that the role of the lower lumbar spine in the lumbar lordotic curve is greater than that of the upper lumbar spine. In addition, considering the contemporary tendency to lead fairly sedentary lives, these results indicate that exercising while seated can be effective.
        4,000원
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