• Journal of the Korean Society of Safety
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• v.35 no.4
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• pp.92-100
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• 2020

Along with the rapid development of industrial technology, the industrial structure has been continuously changed. Accordingly, safety technologies have been gradually developed to be applied into various industrial fields as well, not limited to a specific industry area. As a result, it became important to analyze and predict trends of safety technology development in order to establish technology strategies for industrial safety. In particular, since patents are easily accessible to gather the technology and business information, many studies have highlighted technology forecasting using patent information. Thus, this study proposes the patent analysis of monitoring trends of safety technologies of industry fields, taking into account both static and dynamic aspects through index and text analysis. First, patent documents containing safety-related keywords are collected from the WIPSON database for extracting technology information. Then, the development trends of safety technologies by industry fields are identified and analyzed through the analysis of indicators such as marketability, growth, and activation. The results of various indicator analyses of safety technologies are visualized to compare among industrial safety technologies for businesses and technology developers. Second, textmining algorithm is applied to identify trends of specific technology keywords of major industries extracted from patent index analysis. As a result, it is expected that the safety manager uses the patent analysis of safety technologies to provide safety technology information with safety-related companies and institutes. The extracted safety technologies are applicable to business practice and predict future promising technologies.

• Proceedings of the KIEE Conference
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• 2005.11b
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• pp.46-48
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• 2005

This paper discusses a probabilistic method for power system security assessment. The security analysis relates to the ability of the electric power systems to survive sudden disturbances such as electric short circuits or unanticipated loss of system elements. It consists of both steady state and dynamic security analyses, which are not two separate issues but should be considered together. In steady state security analysis including voltage security analysis, the analysis checks that the system is operated within security limits by OPF (optimal power flow) after the transition to a new operating point. Until now, many utilities have difficulty in including dynamic aspects due to computational capabilities. On the other hand. dynamic security analysis is required to ensure that the transition may lead to an acceptable operating condition. Transient stability, which is the ability of power systems to maintain synchronism when subjected to a large disturbance. is a principal component in dynamic security analysis. Usually any loss of synchronism may cause additional outages and make the present steady state analysis of the post-contingency condition inadequate for unstable cases. This is the reason for the need of dynamic studies in power systems. Probabilistic criterion can be used to recognize the probabilistic nature of system components while considering system security. In this approach. we do not have to assign any predetermined margin of safety. A comprehensive conceptual framework for probabilistic static and dynamic assessment is presented in this paper. The simulation results of the Western System Coordinating Council (WSCC) system compare an analytical method with Monte-Carlo simulation (MCS).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.718-723
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• 2017

When structural analysis modelling methods of practical fields are investigated, a slab is generally modeled by a finite element mesh using plate elements and a shear wall is modeled using a shell element or wall element for 3-D structural analysis. The point worthy of notice in this practice is that a shear wall is modelled using only one wall or shell element divided by floors and column lines to produce structural models. The modeling method like this can cause analysis errors according to the type of computer programs in use, and these errors reduce the reliability of the analysis results. Therefore, to secure the reliability of structural analysis, studies of the causes of errors and finding reasonable modeling methods are necessary. In this study, the causes of analysis errors according to the modelling methods of a shear wall, which are used in practical fields, were investigated and some considering matters for modelling a shear wall are presented to reduce the analysis errors on these analysis results.

• Journal of Power Electronics
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• v.18 no.2
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• pp.627-639
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• 2018

The fact that the reliability of IGBTs has become a more and more significant aspect of power converters has resulted in an increase in the research on the open circuit (OC) fault location of IGBTs. When an OC fault occurs, a zero-current phenomena exists and frequently appears, which can be found in a lot of the existing literature. In fact, fault variables have a very high correlation with the zero-current interval. In some cases, zero-current interval actually decides the most significant fault feature. However, very few of the previous studies really explain or prove the zero-current phenomena of the fault current. In this paper, the zero-current phenomena is explained and verified through mathematical derivation, based on two-level and three-level NPC static var generators (SVGs). Mathematical models of single OC fault are deduced and it is concluded that a zero-current interval with a certain length follows the OC faults for both two-level and NPC three-level SVGs. Both inductive and capacitive reactive power situations are considered. The unbalanced load situation is discussed. In addition, simulation and experimental results are presented to verify the correctness of the theoretical analysis.

• Korean Journal of Applied Biomechanics
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• v.16 no.3
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• pp.165-172
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• 2006

The purpose of this study was to determine effects of 12-week wearing of unstable shoe on the standing posture and gait mechanics. Nine healthy men were asked to wear the unstable shoes for 12-week and walk for 30 minute everyday. Their standing posture and gait mechanics were measured before and after treatment. Standing posture was measured for each side(anterior, posterior, lateral) for standing position. And gait analysis was measured joint angle of a right lower limb between first right heel contact and second right heel contact. Kinematic data were collected using video camera at 30 frame per seconds. Statistical analysis was paired t-test(p<.05) to compare before training with after that. A head tilt angle was significantly decreased for posterior side(p<.05). The angle of between center of line and surface was significantly decreased at midstance and take off during walking(p<.05). Ankle dorsiflexion significantly increased at heel contact2(p<.05) and ankle plantarflexion significantly increased at midstance and midswing(p<.05). The increase of ankle dorsiflexion showed that our results consisted with previous study. In conclusion, there was not large significant difference in static standing posture but joint angle of lower limb represented many changes with increasing of ankle motion during walking. These were of benefit to body by increasing leg muscle activity but it was necessary for man having a ankle problem to consider. Further studies concerning optimum outsole angle of unstable shoes are necessary.

• Wind and Structures
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• v.23 no.4
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• pp.313-350
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• 2016

Taipei 101 Tower, which has 101 stories with height of 508 m, is located in Taipei where typhoons and earthquakes commonly occur. It is currently the second tallest building in the world. Therefore, the dynamic performance of the super-tall building under strong wind actions requires particular attentions. In this study, Large Eddy Simulation (LES) integrated with a new inflow turbulence generator and a new sub-grid scale (SGS) model was conducted to simulate the wind loads on the super-tall building. Three-dimensional finite element model of Taipei 101 Tower was established and used to evaluate the wind-induced responses of the high-rise structure based on the simulated wind forces. The numerical results were found to be consistent with those measured from a vibration monitoring system installed in the building. Furthermore, the equivalent static wind loads on the building, which were computed by the time-domain and frequency-domain analysis, respectively, were in satisfactory agreement with available wind tunnel testing results. It has been demonstrated through the validation studies that the numerical framework presented in this paper, including the recommended SGS model, the inflow turbulence generation technique and associated numerical treatments, is a useful tool for evaluation of the wind loads and wind-induced responses of tall buildings.

• Journal of Korean Society of Steel Construction
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• v.24 no.3
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• pp.279-287
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• 2012

A double split tee connection is used as a connection that is suitable for ordinary moment frames or special moment frames according to the combination of variables of the thickness of the T-stub flange and the gauge distance of the high-strength bolts. In order to demonstrate safe structural behavior, a double split tee connection must meet the requirements for inter-story drift angles and the moment of connection, as defined in the Korea Building Code-Structural. In order to determine whether the these requirements are met, it is necessary to predict rotational stiffness and the ultimate plastic moment of the connection. Therefore, this study primarily aimed to propose an analytical model for predicting the rotational stiffness of a double split tee connection under a static load. Toward this end, a three-dimensional, non-linear finite element analysis was carried out. Then, the applicability of the proposed model was verified after comparing the test results of this study with other studies.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.1
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• pp.135-141
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• 2016

Recently, the needs for the development and application of marine robots are increasing as marine accidents occur frequently. However, it is very difficult to acquire the information by utilizing marine robots in the marine environment. Therefore, the needs for the researches of sensor networks which are composed of underwater, surface and aerial robots are increasing in order to acquire the information effectively as the information from heterogeneous robots has less limitation in terms of coverage and connectivity. Although various researches of the sensor network which is based on marine robots have been executed, all of the underwater, surface and aerial robots have not yet been considered in the sensor network. To solve this problem, a collaborative control method based on the acoustic information and image by the sonars of the underwater robot, the acoustic information by the sonar of the surface robot and the optical image by the camera of the static-floating aerial robot is proposed. To verify the performance of the proposed method, the collaborative control of a MUR(Micro Underwater Robot) with an OAS(Obstacle Avoidance Sonar) and a SSS(Side Scan Sonar), a MSR(Micro Surface Robot) with an OAS and a BMAR(Balloon-based Micro Aerial Robot) with a camera are executed. The test results show the possibility of real applications and the need for additional studies.

• Journal of the Korea Concrete Institute
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• v.27 no.1
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• pp.55-63
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• 2015

Prefabrication technologies are making bridge construction safer and less disruptive to the environment and traveling public, making bridge designs more constructible and, improving the quality and durability by shifting site work to a more controllable environment. Modular bridge substructures with concrete-filled steel tube (CFT) piers and composite pier caps were suggested to realize accelerated bridge construction. The precast segmental pier cap consists of a composite pier table and precast prestressed segments on the table. The pier table has embedded steel section to mitigate stress concentration at the connection by small tubes. Each bridge pier has four or six CFT columns which connect to the pier cap. Shear strength of the pier cap was obtained by extending vertical reinforcing bars from the table to the precast segment. Transverse prestressing was introduced to control tensile stresses by service loadings. Structural performance of the proposed modular system was evaluated by static tests. Design requirements of the composite pier cap were satisfied by continuous reinforcing bars and prestressing tendons. Standardized modular substructures can be effectively utilized for the fast replacement or construction of bridges.

• Physical Therapy Korea
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• v.21 no.2
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• pp.8-17
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• 2014

The purpose of this study was to examine the effects of hip joint mobilization (HJM) on walking ability, balance ability, and the joint range of motion in stroke patients to minimize the problems of the musculoskeletal system in patients with central nervous system diseases. All volunteers were randomly assigned to the HJM group ($n_1=14$) and the general neurodevelopment therapy (NDT) group ($n_2=16$). The HJM procedure involved applying Maitland mobilization techniques (distraction, lateral gliding, inferior gliding, and anterior gliding) by grade 3 to both hip joint. The mobilization process included mobilization and NDT for 15 min/day, 3 days a week for 4 weeks. The outcome measures were evaluated, including the hip joint passive range of motion (ROM) test and femur head anterior glide test (FHAG) using prone figure four test, dynamic and static balance abilities [timed up and go (TUG) test and center of pressure (COP) analysis], and walking ability [10-meter walking test (10MWT) and 6-min walking test (6MWT)]. Both the groups showed significant post-training differences in the hip joint ROM (FHAG and degree of hip extension) and 10MWT. The post-training improvements in the TUG test were significantly greater in patients of the HJM group than in the NDT group; however, there were no post-training improvements in COP in both groups. Patients in the HJM group showed post-training improvement in the 6MWT; however, statistically significant differences were not observed. Patients in the NDT group showed post-training improvements in the 6MWT. These results suggest that HJM improves hip joint ROM, dynamic balance ability, and walking speed in stroke patients. However, further studies are required to evaluate the long-term therapeutic efficacy of HJM in stroke patients.