• Ocean and Polar Research
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• v.44 no.1
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• pp.13-27
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• 2022

The Yeongsan River estuary was altered by a sea dike built in 1981 and the sluice gates in the dike were extended recently in 2014. The construction has caused changes in water properties and hydrodynamics and also produced disturbances including hypoxia and algal blooms. We analyzed the water quality and chlorophyll-a data (2009-2018) collected seasonally at 3 stations (Sts. 1-3) along the channel of the estuary by the Marine Environmental Monitoring System. Variations in water quality and chlorophyll-a (an index of phytoplankton biomass) were examined and their stressors were also identified by statistics including correlation and multivariate principal component analyses (PCA). The water quality was mainly affected by freshwater discharge from the dike. Salinity, nutrients and chlorophyll-a were especially affected by the discharge and the effect enhanced during summer and at the upper region near the sea dike decreasing downstream. Three factors were extracted for each station in the PCA accounting for 66.07-72.42% of the variations. The first was an external factor associated with freshwater discharge and the second and third were seasonal or biological factors. The results indicate that the water quality is more affected by short-termed and episodic events such as freshwater discharge than seasonal events and the influence of freshwater discharge on water quality is more extensive than that previously reported. This suggests that the boundary of the estuary should be extended to take into account the findings of this study and a management strategy linked to the freshwater zone is required to manage the integrity and water quality of the Yeongsan River estuary.

• International conference on construction engineering and project management
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• 2022.06a
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• pp.269-276
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• 2022

The robustness of a supply chain (i.e., the ability to cope with external and internal disruptions and disturbances) becomes more critical in ensuring the success of a construction project because the supply chain of today's construction project includes more and diverse suppliers. Previous studies indicate that topological features of the supply chain critically affect its robustness, but there is still a great challenge in characterizing and quantifying the impact of network topological features on its robustness. In this context, this study aims to identify network measures that characterize topological features of the supply chain and evaluate their impact on the robustness of the supply chain. Network centrality measures that are commonly used in assessing topological features in social network analysis are identified. Their validity in capturing the impact on the robustness of the supply chain was evaluated through an experiment using randomly generated networks and their simulations. Among those network centrality measures, the PageRank centrality and its standard deviation are found to have the strongest association with the robustness of the network, with a positive correlation coefficient of 0.6 at the node level and 0.74 at the network level. The findings in this study allows for the evaluation of the supply chain network's robustness based only on its topological design, thereby enabling practitioners to better design a robust supply chain and easily identify vulnerable links in their supply chains.

• Structural Engineering and Mechanics
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• v.90 no.1
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• pp.19-26
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• 2024

In recent years, an increasing number of experimental studies have shown that the practical application of mature active control systems requires consideration of robustness criteria in the design process, including the reduction of tracking errors, operational resistance to external disturbances, and measurement noise, as well as robustness and stability. Good uncertainty prediction is thus proposed to solve problems caused by poor parameter selection and to remove the effects of dynamic coupling between degrees of freedom (DOF) in nonlinear systems. To overcome the stability problem, this study develops an advanced adaptive predictive fuzzy controller, which not only solves the programming problem of determining system stability but also uses the law of linear matrix inequality (LMI) to modify the fuzzy problem. The following parameters are used to manipulate the fuzzy controller of the robotic system to improve its control performance. The simulations for system uncertainty in the controller design emphasized the use of acceleration feedback for practical reasons. The simulation results also show that the proposed H∞ controller has excellent performance and reliability, and the effectiveness of the LMI-based method is also recognized. Therefore, this dynamic control method is suitable for seismic protection of civil buildings. The objectives of this document are access to adequate, safe, and affordable housing and basic services, promotion of inclusive and sustainable urbanization, implementation of sustainable disaster-resilient construction, sustainable planning, and sustainable management of human settlements. Simulation results of linear and non-linear structures demonstrate the ability of this method to identify structures and their changes due to damage. Therefore, with the continuous development of artificial intelligence and fuzzy theory, it seems that this goal will be achieved in the near future.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.36 no.2
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• pp.185-196
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• 1991

The rice culture, the most representative farming in humid regions of East Asia, have been playing a decisive role in supplying finance and staple food of the nations. This situation must be formed with exchange of techniques and interests in the matter betwen China, Korea and Japan. Especially Korea was obligated to playa bridge role because of geographical conditions, thereby the situations of agriculture were repeatedly reclaimed, and recovered by changes of cultures during external aggression, and internal disturbances. Thus, it is obvious that development of rice culture and its techniques was being undaunted in Korea. Nevertheless, in history of Korea, the documents of the government on chronicles of the dynasty were plentiful, while they were very poor in countryside and rural communities, so that it is very hard to search the transition process of rice culture and its techniques. Finally, the faming books that were begun editing from the early Chosun dynasty are here divided chronically and examined, and also the interrelationships are compared and discussed here. The objectives of this study were to discuss the following questions？ How were the dryfarming techniques, introduced from the ancient China by the end of Koryo dynasty, established to fit for our situations？ What were the basis for reestablishment of the techniques with originality？ How were they continued and changed through the internal and external wars in the Chosun dynasty？ What were suggested from these continuously results by the end of the Chosun dynasty?

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.6 s.52
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• pp.93-102
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• 2006

Control input's saturation of active control devices for large structures under large external disturbances are often occurred. It is more difficult to obtain the exact values of mass and stiffness as structures are higher. The modelling errors between mathematical models and real structures must be also included as parameter uncertainties. Therefore, in active vibration control of civil engineering structures like buildings and bridges, the robust saturation controller design method considering both control input's saturation and parameter uncertainties of system is needed. In this paper, stabilities of linear optimal controller LQR, modified bang-bang controller, saturated sliding mode controller, and robust saturation controller among various controllers which have been studied and applied to active vibration control of buildings are investigated. Especially, unstable phenomena of the LQR, the modified bang-bang controller and the saturated sliding mode controller when the control input is saturated or parameter uncertainties exist are presented to show the necessity of the robust saturation controller. The robust stability of the robust saturation controller are shown through a numerical example of a 2DOF linear vibrating system and an experimental test of the two-story structure with an active mass damper (AMD).

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.3
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• pp.225-231
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• 2020

Recently, there has been an increasing demand for SAR satellite as it can be operated regardless of the weather condition. In general, main reflector of the SAR is formed of multiple deployable panels to increase performance in the constrained payload envelope. By nature, deployable structure lacks structural stiffness and it is vulnerable to external disturbances and excitation. In particular, SAR satellites may have high levels of vibration occurring at the antenna reflecting surface due to higher angular rate requirements. During image capturing it is important to keep high surface accuracy of the reflector for the quality of images. In this research, a performance degradation of deployable SAR antenna due to structural deformation is analyzed. Panels for main reflectors are assumed to be flexible structures and multi-body simulation environment is established. Then, deflection of the panel is calculated while the satellite performs maneuvers. In addition, antenna gain and beam pointing error are analyzed to determine how these deflections affect antenna performance and mission.

• Journal of the Korea Society of Computer and Information
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• v.24 no.12
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• pp.25-33
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• 2019

This paper presents a novel evolutionary framework for optimizing a bio-inspired fully dynamic neurocontroller for the maneuverable flapping flight of a simulated bird-sized ornithopter robot which takes advantage of the morphological computation and mechansensory feedback to improve flight stability. In order to cope with the difficulty of generating robust flapping flight and its maneuver, the wing of robot is modelled as a series of sub-plates joined by passive torsional springs, which implements the simplified version of feathers attached to the forearm skeleton. The neural controller is designed to have a bilaterally symmetric structure which consists of two fully connected neural network modules receiving mirrored sensory inputs from a series of flight navigation sensors as well as feather mechanosensors to let them participate in pattern generation. The synergy of wing compliance and its sensory reflexes gives a possibility that the robot can feel and exploit aerodynamic forces on its wings to potentially contribute to the agility and stability during flight. The evolved robot exhibited target-following flight maneuver using asymmetric wing movements as well as its tail, showing robustness to external aerodynamic disturbances.

• The Journal of the Korea Contents Association
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• v.13 no.2
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• pp.370-377
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• 2013

Traumatic brain injury(TBI) is a brain damage caused by an external physical force. TBI patients have disturbances of functioning including attention, memory, reasoning,, executive function, and pragmatic language. The aim of this study was to develop the cognitive-pragmatic language ability assessment protocol for traumatic brain injury(CAPTBI) and to evaluate reliability and validity. This study was also conducted to investigate domains that contributed to differentiate between the normal and TBI groups. The CAPTBI data were obtained from 226 normal adults and 62 TBI patients(mean age=$43.95{\pm}11.92$, $46.37{\pm}11.87$, M:F=110:116, 48:14). The CAPTBI had high item internal consistency, test-retest reliability, construct validity, and concurrent validity. The normal group performed significantly better than the TBI group in all domains of the CAPTBI and the separate scores for 9 domains. All 9 domains were found to be significant variables to discriminate between the two groups. The most powerful variable was executive function followed by memory, organization, pragmatic language, problem-solving, attention, orientation, reasoning, and visuoperception in order. The CAPTBI could discriminate between the two groups accurately by 95.5%. This result demonstrated that 97.3% of normal adults and 88.7% of TBI patients could be discriminated by CAPTBI. In conclusion, The CAPTBI is appropriate for evaluating and identifying cognitive-pragmatic language disorders in TBI patients.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.7
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• pp.1694-1704
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• 2015

In this paper, a robust trajectory tracking control method of a wheeled mobile robot is newly proposed combining the PDC and the ISMC. The PDC is a relatively simple and easy control method for nonlinear system compared to the other non-linear control methods. And the ISMC can have robust and stable control characteristics against model uncertainties and disturbances from the initial time by placing the states on the sliding plane with desired nominal dynamics. Therefore, the proposed PDC+ISMC trajectory tracking control method shows robust trajectory tracking performance in spite of external disturbance. The tracking performance of the proposed method is verified through simulations. Even though the disturbance increases, the proposed method keeps the performance of the PDC method when there is no disturbance. However, the PDC trajectory tracking control method has increasing tracking error unlike the proposed method when the disturbance increases.

• Journal of Korean Society of Forest Science
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• v.107 no.4
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• pp.378-384
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• 2018

Chinese jujube (Ziziphus jujuba Mill.), a member of family Rhamnaceae, is an economically important species. It has high nutritional value in fruits, and its medicinal properties have led to extensive use in traditional oriental medicine. In this study, we investigated the genetic characteristics of 270 jujube germplasms collected from the six major jujube fruit production areas in Korea including Boeun and Gyeongsan, in order to understand the current situation on cultivated varieties of domestic jujube and to obtain useful data for selection of superior germplasms and establishing their breeding plans. The results of ISSR marker analysis revealed that the Shannon's information index of the 270 germplasms was 0.107 and the genetic similarity was as high as 0.935 showing the dominance of a specific cultivar or germplasm, and almost 67% (180) of them were identified at the same genotype with 'Bokjo'. The domestic commercial jujube populations could be characterized by very low genetic diversity and thus may be vulnerable to external disturbances. In addition, it seems that most of the jujube fruits in domestic market were largely produced through parthenocarpy.