• Journal of Ginseng Research
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• v.47 no.2
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• pp.218-227
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• 2023

Background: Myocardial fibrosis (MF) is an advanced pathological manifestation of many cardiovascular diseases, which can induce heart failure and malignant arrhythmias. However, the current treatment of MF lacks specific drugs. Ginsenoside Re has anti-MF effect in rat, but its mechanism is still not clear. Therefore, we investigated the anti-MF effect of ginsenoside Re by constructing mouse acute myocardial infarction (AMI) model and AngII induced cardiac fibroblasts (CFs) model. Methods: The anti-MF effect of miR-489 was investigated by transfection of miR-489 mimic and inhibitor in CFs. Effect of ginsenoside Re on MF and its related mechanisms were investigated by ultrasonographic, ELISA, histopathologic staining, transwell test, immunofluorescence, Western blot and qPCR in the mouse model of AMI and the AngII-induced CFs model. Results: MiR-489 decreased the expression of α-SMA, collagenI, collagen III and myd88, and inhibited the phosphorylation of NF-κB p65 in normal CFs and CFs treated with AngII. Ginsenoside Re could improve cardiac function, inhibit collagen deposition and CFs migration, promote the transcription of miR-489, and reduce the expression of myd88 and the phosphorylation of NF-κB p65. Conclusion: MiR-489 can effectively inhibit the pathological process of MF, and the mechanism is at least partly related to the regulation of myd88/NF-κB pathway. Ginsenoside Re can ameliorate AMI and AngII induced MF, and the mechanism is at least partially related to the regulation of miR-489/myd88/NF-κB signaling pathway. Therefore, miR-489 may be a potential target of anti-MF and ginsenoside Re may be an effective drug for the treatment of MF.

• Steel and Composite Structures
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• v.47 no.6
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• pp.709-728
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• 2023

Experimental and analytical studies were conducted to clarify the influencing mechanisms of the longitudinal reinforcement on performance of axially loaded Reinforced Concrete-Filled Steel Tube (R-CFST) short columns. The longitudinal reinforcement ratio was set as parameter, and 10 R-CFST specimens with five different ratios and three Concrete-Filled Steel Tube (CFST) specimens for comparison were prepared and tested. Based on the test results, the failure modes, load transfer responses, peak load, stiffness, yield to strength ratio, ductility, fracture toughness, composite efficiency and stress state of steel tube were theoretically analyzed. To further examine, analytical investigations were then performed, material model for concrete core was proposed and verified against the test, and thereafter 36 model specimens with four different wall-thickness of steel tube, coupling with nine reinforcement ratios, were simulated. Finally, considering the experimental and analytical results, the prediction equations for ultimate load bearing capacity of R-CFSTs were modified from the equations of CFSTs given in codes, and a new equation which embeds the effect of reinforcement was proposed, and equations were validated against experimental data. The results indicate that longitudinal reinforcement significantly impacts the behavior of R-CFST as steel tube does; the proposed analytical model is effective and reasonable; proper ratios of longitudinal reinforcement enable the R-CFSTs obtain better balance between the performance and the construction cost, and the range for the proper ratios is recommended between 1.0% and 3.0%, regardless of wall-thickness of steel tube; the proposed equation is recommended for more accurate and stable prediction of the strength of R-CFSTs.

• Maritime Security
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• v.6 no.1
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• pp.137-161
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• 2023

This paper explores the limited role of alliances in preventing maritime territorial disputes among member states, using the ongoing conflict between Greece and Türkiye, two NATO allies, as a case study. Drawing on Institutionalist theory, we seek to explain the mechanisms that have contributed to the failure of the alliance to prevent this dispute, despite constant cooperation and transparency. Unlike land disputes, maritime territorial disputes are complex and multi-layered, with fluid boundaries that can change with climate or natural resource availability. Moreover, the lack of constant surveillance creates ambiguity about territorial encroachment thresholds. These factors have exacerbated the dispute between Greece and Türkiye, drawing other NATO members into the conflict and undermining the strength of the alliance. This paper concludes by providing policy implications for the Republic of Korea in its own potential maritime disputes, and contributes to the broader literature on the role of alliances in preventing territorial disputes.

• Steel and Composite Structures
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• v.50 no.1
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• pp.107-122
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• 2024

Following an internal column failure, adjacent double-span beams above the failed column will play a critical role in the load transfer and internal force redistribution within the remaining structure, and the span-to-depth ratios of double-span beams significantly influence the structural resistance capacity against progressive collapse. Most existing studies have focused on the collapse-resistant performances of single-story symmetric structures, whereas limited published works are available on the collapse resistances of multi-story steel frames with unequal spans. To this end, in this study, numerical models based on shell elements were employed to investigate the structural behavior of multi-story steel frames with unequal spans. The simulation models were validated using the previous experimental results obtained for single- and two-story steel frames, and the load-displacement responses and internal force development of unequal-span three-story steel frames under three cases were comprehensively analyzed. In addition, the specific contributions of the different mechanism resistances of unequal-span, double-span beams of each story were separated quantitatively using the energy equilibrium theory, with an aim to gain a deeper level of understanding of the load-resistance mechanisms in the unequal-span steel frames. The results showed that the axial and flexural mechanism resistances were determined by the span ratio and linear stiffness ratio of double-span beams, respectively.

• Composites Research
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• v.14 no.3
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• pp.18-31
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• 2001

Interfacial and microfailure properties of the modified steel, carbon and glass fibers/cement composites were investigated using electro-pullout test under tensile and compressive tests with acoustic emission (AE). The hand-sanded steel composite exhibited higher interfacial shear strength (IFSS) than the untreated and even neoalkoxy zirconate (Zr) treated steel fiber composites. This might be due to the enhanced mechanical interlocking, compared to possible hydrogen or covalent bonds. During curing process, the contact resistivity decreased rapidly at the initial stage and then showed a level-off. Comparing to the untreated case, the contact resistivity of either Zr-treated or hand-sanded steel fiber composites increased to the infinity at latter stage. The number of AE signals of hand-sanded steel fiber composite was much more than those of the untreated and Zr-treated cases due to many interlayer failure signals. AE waveforms for pullout and frictional signals of the hand-sanded composite are larger than those of the untreated case. For dual matrix composite (DMC), AE energy and waveform under compressive loading were much higher and larger than those under tensile loading, due to brittle but well-enduring ceramic nature against compressive stress. Vertical multicrack exhibits fur glass fiber composite under tensile test, whereas buckling failure appeared under compressive loading. Electro-micromechanical technique with AE can be used as an efficient nondestructive (NDT) method to evaluate the interfacial and microfailure mechanisms for conductive fibers/brittle and nontransparent cement composites.

• Tuberculosis and Respiratory Diseases
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• v.45 no.4
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• pp.705-713
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• 1998

Background: An association between diabetes and tuberculosis has long been implied. The severity of diabetes appears to correlate with the degree of tuberculous activity. Methods: A retrospective chart review of 82 patients with active pulmonary tuberculosis in diabetics (DMTB) and 83 patients with active pulmonary tuberculosis in nondiabetics (Non-DMTB) admitted to the Kyung Hee Medical Center between January 1995 and December 1996 was underiaken. Results: The sex ratio of DMTB was 58 : 24, and that of Non-DMTB was 62 : 21. Male patients predominated in both groups. The highest incidence of DMTB was 6th and 7th decades and that of Non-DMTB was 3rd and 4th decades. In case which the tuberculosis developed after diagnosis of diabetes, the prevalence of pulmonary tuberculosis was the highest in diabetes for 5-10 years. On chest X-ray findings, the moderate advanced tuberculosis cases were the most common (60.9% in DMTTB and 50.6% in Non-DMTB). There was no relation between the degree of tuberculosis activity on chest x-ray(minimal, moderate, and far advanced tuberculosis) and presence of diabetes. The incidence of lower lung field tuberculosis in DMTB was significantly higher than Non-DMTB(p<0.05). The multiple lobe involvement was the predominant chest roentgenographic finding in both groups. There was no significant difference of treatment response between DMTB and Non-DMTB. There was no relationship between initial HbA1c and the severity of pulmonary tuberculosis on chest X-ray. During treatment of pulmonary tuberculosis in excellently and well controlled diabetes, the cure rate of pulmonary tuberculosis was significantly higher than the poorly controlled diabetes and the rate of treatment failure was significantly lower than poorly controlled diabetes. (p<0.05). Conclusion: Poor control of blood glucose is related with increased rate of treatment failure in pulmonary tuberculosis with diabetes mellitus. Further investigation will be needed to study the mechanisms of treatment failure in poorly controlled diabetics with pulmonary tuberculosis.

• Tuberculosis and Respiratory Diseases
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• v.56 no.1
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• pp.77-84
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• 2004

Background : We hypothesized that there was a relationship between body weight change and bronchodilator response (BDR) in patients with chronic renal failure (CRF) on hemodialysis (HD). Several mechanisms such as pulmonary edema due to water retention or increased permeability of alveolar capillary may play a important role in pulmonary function impairment and bronchial hyperresponsiveness in patients with CRF on HD. But, no studies have been published concerning BDR in patients with CRF on HD. This study was aimed to know the immediate effect of hemodialysis on pulmonary function and BDR in patients with CRF on HD. Methods : This study included 30 patients with CRF on HD. We collected data including age, sex, height, pretibial and pedal pitting edema, interdialysis weight gain, postdialysis weight loss, underlying diseases, duration of HD, $FEV_1$, FVC, $FEV_1/FVC$, and BDR before and after HD. Results : Interdialysis weight gain of the patients was $3.4{\pm}1.0kg$, and postdialysis weight loss was $3.2{\pm}0.7kg$. Before HD,$FEV_1$, FVC, and $FEV_1/FVC$ of the patients were $89{\pm}22%$, $86{\pm}19%$ of predicted, and $87{\pm}10%$. After bronchodilator inhalation, these parameters were changed to $95{\pm}22%$, $90{\pm}19%$ of predicted, and $88{\pm}9%$ respectively. BDR was positive in 15 patients. After HD, $FEV_1$, FVC, and $FEV_1/FVC$ of the patients were $100{\pm}23%$, $94{\pm}18%$ of predicted, and $88{\pm}11%$. After bronchodilator inhalation, these parameters were changed to $102{\pm}23%$, $96{\pm}18%$ of predicted, and $89{\pm}8%$ respectively. BDR was positive in 9 patients. Conclusion : First, HD increases $FEV_1$, FVC, and $FEV_1/FVC$ but little affects BDR. Second, there is no correlation between postdialysis weight loss and increases in $FEV_1$, FVC, and $FEV_1/FVC$ after HD. Third, there is also no correlation not only between interdialysis weight gain and BDR before HD but between postdialysis weight loss and BDR after HD.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.4
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• pp.276-284
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• 2000

The acoustic emission (AE) behavior of reinforced concrete beams tested under flexural loading was investigated to characterize and identify the source of damage. This research was aimed at identifying the characteristic AE response associated with micro-crack development, localized crack propagation, corrosion, and debonding of the reinforcing steel. Concrete beams were prepared to isolate the damage mechanisms by using plain, notched-plain, reinforced, and corroded-reinforced specimens. The beams were tested using four-point cyclic step-loading. The AE response was analyzed to obtain key parameters such as the time history of AE events, the total number and rate of AE events, and the characteristic features of the waveform. Initial analysis of the AE signal has shown that a clear difference in the AE response is observed depending on the source of the damage. The Felicity ratio exhibited a correlation with the overall damage level, while the number of AE events during unloading can be an effective criterion to estimate the level of corrosion distress in reinforced concrete structures. Consequently, AE measurement characterization appears to provide a promising approach for estimating the level of deterioration in reinforced concrete structure.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.15 no.4
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• pp.83-96
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• 2020

Traditionally social problems had been largely left to be handled by non-profit organizations, not because of lack of interests in social causes but mostly because of lack of innovative ideas to solve them in commercially viable ways. This market failure has recently been fixed by social enterprises, which manage to provide both solutions for social issues and commercially viable business models. As a result, we have been witnessing a sudden spike of public interests in these social enterprises as well as a call for empirical investigation on social enterprises by prior studies. However, empirically investigating a social enterprise has been a challenging endeavor mostly due to the insufficient number of successful social enterprises. Answering to the call in this study, we empirically investigate Goyohan Taxi, a successful social enterprise that partners with visually impaired cabdrivers and offers a taxi service, by both longitudinally interviewing the founder and adopting in vivo observation throughout the entrepreneurial journey of Goyohan Taxi. Based on the single case study method, we find that Goyohan Taxi adopts two distinctive decision-making mechanisms, the de-escalation of commitment and the orthogonality of commercial and social goals. Although generalizability of the our finding is minimal due to the limitation of single case study method, our finding contributes to the research of social entrepreneurship by offering new avenue of research in decision-making process of social entrepreneurs.

• Journal of KIISE
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• v.43 no.11
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• pp.1233-1244
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• 2016

In the IoT network environments for LLNs(Low power and Lossy networks), IPv6 Routing Protocol for Low Power and Lossy networks(RPL) has been proposed by IETF(Internet Engineering Task Force). The goal of RPL is to create a directed acyclic graph, without loops. As recommended by the IETF standard, RPL route recovery mechanisms in the event of a failure of a node should avoid loop, loop detection, DIO Poisoning. In this process, route recovery time and control message might be increased in the sub-tree because of the repeated route search. In this paper, we suggested RPL route recovery method to solve the routing overhead problem in the sub-tree during a loss of a link in the RPL routing protocol based on IoT wireless networks. The proposed method improved local repair process by utilizing a route that could not be selected as the preferred existing parents. This reduced the traffic control packet, especially in the disconnected node's sub tree. It also resulted in a quick recovery. Our simulation results showed that the proposed RPL local repair reduced the recovery time and the traffic of control packets of RPL. According to our experiment results, the proposed method improved the recovery performance of RPL.