• Ocean Systems Engineering
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• 제5권3호
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• pp.139-160
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• 2015

The global performance of the 5MW OC4 semisubmersible floating wind turbine in random waves was numerically simulated by using the turbine-floater-mooring fully coupled and time-domain dynamic analysis program FAST-CHARM3D. There have been many papers regarding floating offshore wind turbines but the effects of second-order wave-body interactions on their global performance have rarely been studied. The second-order wave forces are actually small compared to the first-order wave forces, but its effect cannot be ignored when the natural frequencies of a floating system are outside the wave-frequency range. In the case of semi-submersible platform, second-order difference-frequency wave-diffraction forces and moments become important since surge/sway and pitch/roll natural frequencies are lower than those of typical incident waves. The computational effort related to the full second-order diffraction calculation is typically very heavy, so in many cases, the simplified approach called Newman's approximation or first-order-wave-force-only are used. However, it needs to be justified against more complete solutions with full QTF (quadratic transfer function), which is a main subject of the present study. The numerically simulated results for the 5MW OC4 semisubmersible floating wind turbine by FAST-CHARM3D are also extensively compared with the DeepCWind model test results by Technip/NREL/UMaine. The predicted motions and mooring tensions for two white-noise input-wave spectra agree well against the measure values. In this paper, the numerical static-offset and free-decay tests are also conducted to verify the system stiffness, damping, and natural frequencies against the experimental results. They also agree well to verify that the dynamic system modeling is correct to the details. The performance of the simplified approaches instead of using the full QTF are also tested.

• Nuclear Engineering and Technology
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• 제53권9호
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• pp.3085-3099
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• 2021

Investigations of large commercial aircraft impact effect on nuclear power plant (NPP) buildings have been drawing extensive attentions, particularly after the 9/11 event, and this paper aims to numerically assess the damage and vibrations of NPP buildings subjected to aircrafts crash. In Part I of present paper, two shots of reduce-scaled model test of aircraft impact on NPP were conducted based on the large rocket sled loading test platform. In the present part, the numerical simulations of both scaled and prototype aircraft impact on NPP buildings are further performed by adopting the commercial program LS-DYNA. Firstly, the refined finite element (FE) models of both scaled aircraft and NPP models in Part I are established, and the model impact test is numerically simulated. The validities of the adopted numerical algorithm, constitutive model and the corresponding parameters are verified based on the experimental NPP model damages and accelerations. Then, the refined simulations of prototype A380 aircraft impact on a hypothetical NPP building are further carried out. It indicates that the NPP building can totally withstand the impact of A380 at a velocity of 150 m/s, while the accompanied intensive vibrations may still lead to different levels of damage on the nuclear related equipment. Referring to the guideline NEI07-13, a maximum acceleration contour is plotted and the shock damage propagation distances under aircraft impact are assessed, which indicates that the nuclear equipment located within 11.5 m from the impact point may endure malfunction. Finally, by respectively considering the rigid and deformable impacts mainly induced by aircraft engine and fuselage, an improved Riera function is proposed to predict the impact force of aircraft A380.

• 한국정보통신학회논문지
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• 제25권9호
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• pp.1144-1151
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• 2021

프레스 공정은 가열 또는 가열하지 않은 상태의 재료에 힘을 가해 원하는 형태로 변형시켜 제품을 만드는 압축 가공 과정이다. 짧은 시간의 연속 압축을 통해 제품을 생산하는 프레스 장비의 특성상 제품 불량은 연속적으로 발생하며 이러한 문제를 해결하기 위한 시스템은 다양한 기술을 이용하여 개발되고 있다. 본 논문은 불량을 탐지하는 인공지능 알고리즘을 기반으로 실시간 불량탐지 시스템을 제안한다. 프레스 장치에 각종 센서를 부착하여 장비의 상태와 불량과의 관계를 빅데이터 플랫폼을 기반으로 정의하고 수집한다. 수집된 데이터를 기반으로 인공지능 알고리즘을 개발하고 개발된 알고리즘을 임베디드 보드를 이용하여 구현함으로써 실제 현장에 적용하여 시스템의 실용성을 보이겠다.

• 한국응용과학기술학회지
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• 제35권4호
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• pp.1472-1479
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• 2018

본 연구는 지속적인 곡예 운동이 여자 체조, 프리스타일 스키어 및 피겨 스케이터 선수의 동적자세 유지 능력에 미치는 영향을 분석하고자 하였다. 이 연구에 참여한 피험자는 운동경력이 4-6년 된 운동선수로서 체조선수 7명, 프리스타일 스키어 선수8명, 피겨 스케이터 7명과 일반 여학생 10명을 통제집단으로 분류하였다. 동적자세의 운동능력을 비교하고자 뉴로컴사의 동적자세측정기를 이용하여 6가지 각 조건에 맞는 이른바, 시각계, 전정계 및 체성감각계가 동원되는 상황을 연출하면서 실험에 임하였다. 자료처리는 일원변량분석을 실시하였고, 사후검증으로는 집단 간의 차이를 보고자 Scheffe로 하였고, 통계학적 유의수준은 .05로 하였다. 연구결과 운동집단 간에는 조건 5에서 프리스타일 선수와 체조선수 간의 유의한 차이가 있었으며, 운동선수 집단과 일반인 여학생 간에는 조건 2, 3, 4, 5, 6에서 유의한 차이가 나타났다. 결론적으로 지속적인 곡예 운동은 평형기관계를 자극하여 동적자세 조절의 향상에 효과가 있는 것으로 사료된다.

• 대한통합의학회지
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• 제9권4호
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• pp.191-200
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• 2021

Purpose : Chronic ankle instability can lead to problems in balance and gait due to weakness of the ankle muscles and decreased proprioceptive sensation. Balance training that stimulates proprioceptors is necessary to improve ankle stability. We aimed to compare the effects of unstable support balance exercises using whole body sonic vibration and an aero-step (TOGU) on proprioception and balance in individuals with unilateral functional ankle instability. Methods : Thirty-six participants with unilateral functional ankle instability were randomly recruited and divided into two groups (group 1 = sonic whole body vibration, group 2= TOGU). Individuals in each group participated in training for 5 weeks, 40 minutes per session, 5 times per week, and performed weight-bearing exercises in five postures on different unstable support surfaces. Proprioception was measured by digital inclinometer (Dualer IQ), and balance was measured by force platform (Biodex balance system). Results : Significant differences were observed in proprioception before and after intervention within both group (p<.05). Significant differences were also observed in the balance index before and after intervention within both groups (p<.05). Conclusion : As a result of this study, it is suggested that for individuals with ankle instability, unstable support surface training using a whole body sonic vibrator and TOGU can have a positive effects on proprioception and balance ability.

• 한국해양공학회지
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• 제34권6호
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• pp.394-405
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• 2020

To assess the station-keeping performance of floating structures in the Arctic region, the ice load should be considered along with other environmental loads induced by waves, wind, and currents. However, present methods for performance evaluation in the time domain are not effective in terms of time and cost. An ice load generation module is proposed based on the experimental data measured at the KRISO ice model basin. The developed module was applied to a time domain simulation. Using the results of a captive model test conducted in multiple directions, the statistical characteristics of ice loads were analyzed and processed so that an ice load corresponding to an arbitrary angle of the structure could be generated. The developed module is connected to commercial dynamic analysis software (OrcaFlex) as an external force input. Station-keeping simulation in the time domain was conducted for the same floating structure used in the model test. The mooring system was modeled and included to reflect the designed operation scenario. Simulation results show the effectiveness of the proposed ice generation module and its application to station-keeping performance evaluation. Considering the generated ice load, the designed structure can maintain a heading angle relative to ice up to 4°. Station-keeping performance is enhanced as the heading angle conforms to the drift direction. It is expected that the developed module will be used as a platform to verify station-keeping algorithms for Arctic floating structures with a dynamic positioning system.

• 문화기술의 융합
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• 제7권2호
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• pp.269-273
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• 2021

미(美) 육군은 21세기 최초로 모술이라는 대도시에서 공격작전을 실시하여 5가지의 도시 지역작전의 교훈을 도출하였다. 이를 바탕으로, 미(美) 육군은 무기체계, 싸우는 개념 및 구조 등 미래 메가시티 작전을 준비하기 위해 박차를 가하고 있다. 한편, 한반도 도시화가 급격히 진행되고 있으며 이로 인해 메가시티도 늘어날 전망이며 이에 한국 육군도 미(美) 육군을 벤치마킹하여 메가시티 작전을 다음과 같이 준비할 필요가 있다. 첫째, 미래 메가시티 작전을 준비하는 집단지성 플랫폼을 구축해야 한다. 둘째, 메가시티에 최적화된 군사력 건설(무기체계, 싸우는 개념, 구조)이 필요하다. 마지막으로, 전승(全勝)을 구현하기 위한 메가시티 합성훈련장을 구축해야 한다. 결국, 대한민국 육군은 이런 작전 준비를 통해 미래 전쟁에서 최종 승리를 담보할 수 있을 것이다.

• The Journal of Korean Physical Therapy
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• 제34권5호
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• pp.212-217
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• 2022

Purpose: This study sought to investigate the effects of visual cue deprivation balance training by applying head control feedback to the balance function and the fall index in older people. Methods: The study was conducted on 26 older people at the S Hospital in Gyeongsansi. The patients were randomly divided into the experimental groupI (EGI, n=9), the experimental groupII (EGII, n=9), and the control group (CG, n=8). The three groups were trained for 30 minutes three times a week for four weeks. To assess the patients' static balance function, their limits of stability (LOS) was measured using the BioRescue system, (RM Ingenierie, France), composed of a pressure platform that can measure force in diverse ways, a computer, and a monitor. The dynamic balance function was measured using the Berg Balance Scale (BBS). Also, the fall index was measured to evaluate the risk of falling. A paired t-test was performed to compare pre- and post-training performance within the groups. One-way ANOVA was performed for comparing the three groups. A post hoc least significant difference (LSD) test was also performed. Results: The results of the LOS showed a significant difference after training in the EGI and EGII groups (p<0.05). As a result of the difference between the three groups, there was a significant difference after training (p<0.05). The results of the BBS showed a significant difference after training in the EGI group (p<0.05). As a result of the difference between the three groups, there was a significant difference after training (p<0.05). Conclusion: Visual cue deprivation balance training applying head control feedback is effective in improving the dynamic balance function in older people. It is also necessary to constantly maintain the head orientation by feedback and to properly control the head movement.

• International Journal of Internet, Broadcasting and Communication
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• 제14권1호
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• pp.85-94
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• 2022

Recently, consumers who prefer contactless consumption are increasing due to pandemic trends such as Corona 19. This is the driving force for developing the last mile-based logistics ecosystem centered on the online e-commerce market. Lastmile led to the continued development of the logistics industry, but increased the amount of cargo in urban area, and caused social problems such as overcrowding of logistics. The courier service in the logistics base area utilizes the process of visiting the delivery site directly because the courier must precede the loading work of the cargo in the truck for the delivery of the ordered product. Currently, it's carried out as automated logistics equipment such as conveyor belt in unloading or classification stage, but the automation system isn't applied, so the work efficiency is decreasing and the intensity of the courier worker's labor is increased. In particular, small-scale courier workers belonging to the sub-terminal unload at night at underdeveloped facilities outside the city center. Therefore, the productivity of the work is lowered and the risk of safety accidents is exposed, so robot-based loading technology is needed. In this paper, we have derived the top-level concept and requirements of robot-based loading system to increase the flexibility of logistics processing and to ensure the safety of courier drivers. We defined algorithms and motion concepts to increase the cargo loading efficiency of logistics sub-terminals through the requirements of end effector technology, which is important among concepts. Finally, the control technique was proposed to determine and position the load for design input development of the automatic conveyor system.

• PNF and Movement
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• 제22권2호
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• pp.201-211
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• 2024

Purpose: This study aimed to evaluate the effects of trunk stabilization exercises using a Reformer on trunk control, balance ability, and gait function in chronic stroke patients. Methods: The participants were 24 chronic stroke patients, randomly divided into two groups: trunk stabilization exercise using the Reformer group (TS-R, n = 12) and general trunk stabilization exercise group (GT-E, n = 12). Assessment methods included the Trunk Impairment Scale for trunk control, the AMTI force platform for static balance, the Timed Up and Go test for dynamic balance, and the Dynamic Gait Index for gait function. Assessments were conducted before and after the intervention. The intervention for the TS-R group consisted of bridging exercises using a Reformer, while the GT-E group performed bridging exercises on a mat. All interventions were performed for 17 minutes per session, five times a week, for a total of 20 sessions over four weeks. Statistical analysis was performed using repeated-measures ANOVA to analyze the interaction between groups and time. Results: The results of the repeated measures ANOVA indicated a significant interaction between the groups and time. The TS-R group showed statistically significant differences in all variables before and after the intervention. In contrast, the GT-E group did not show statistically significant differences in any variables before and after the intervention. Conclusion: The findings of this study suggest that trunk stabilization exercises using a reformer are effective in improving trunk control, balance ability, and gait function in chronic stroke patients.