• Ocean Systems Engineering
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• 제14권2호
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• pp.141-156
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• 2024

The turbine system converts the kinetic energy of water flow to electricity by rotating the rotor in a restricted waterway between the seabed and free surface. A turbine system's immersion depth and rotation direction are significantly critical in the turbine's performance along with the shape of the rotor. This study has investigated the hydrodynamic performance of the Savonius hydrokinetic turbine (SHT) according to the immersion depth and rotation direction using computational fluid dynamics (CFD) simulations. The instantaneous torque, torque coefficient, and power coefficients are calculated for the immersion ratios Z/D ranging [0.25, 3.0] and both clockwise (CW) and counterclockwise (CCW) rotations. A flow visualization around the rotor is shown to clarify the correlation between the turbine's performance and the flow field. The CFD simulations show that the CCW rotation produces a higher power at shallow immersion, while the CW rotation performs better at deeper immersion. The immersion ratio should be greater than the minimum of Z/D=1.0 to obtain the maximum power production regardless of the rotation direction.

• 한국세라믹학회지
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• 제41권4호
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• pp.344-347
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• 2004

The influence of spindle immersion depth on the determination of glass melt viscosity was examined in rotating cylinder method. The exact adjustment of spindle immersion depth into soda lime silicate standard glass melts could be peformed by self-constructed electric system. The results showed a slight dependence of viscosity value on the immersion depth change of spindle shaft. The viscosity error per unit length of spindle was 0.4%/mm under the present cylinder dimension.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.889-901
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• 2021

The tension of cables and motion response significantly affect safety of an immersed tunnel element in the immersion process. To investigate those, a hydrodynamic scale-model test was carried out and the model experiments was conducted under wind, current and wave loads simultaneously. The immersion standby (the process that the position of the immersed tunnel element should be located before the immersion process) and immersion process conditions have been conducted and illustrated. At the immersion standby conditions, the maximum force of the cables and motion is much larger at the side of incoming wind, wave and current, the maximum force of Element-6 (6 cables directly tie on the element) is larger than for Pontoon-8 (8 cables tie on pontoon of the element), and the flexible connection can reduce the maximum force of the mooring cables and motion of element (i.e. sway is expecting to decrease approximate 40%). The maximum force of the mooring cables increases with the increase of current speed, wave height, and water depth. The motion of immersed tunnel element increases with increase of wave height and water depth, and the current speed had little effect on it. At the immersion process condition, the maximum force of the cables decrease with the increase of immersion depth, and dramatically increase with the increase of wave height (i.e. the tension of cable F4 of pontoons at wave height of 1.5 m (83.3t) is approximately four times that at wave height of 0.8 m). The current speed has no much effect on the maximum force of the cables. The weight has little effect on the maximum force of the mooring cables, and the maximum force of hoisting cables increase with the increase of weight. The maximum value of six-freedom motion amplitude of the immersed tunnel element decreases with the increase of immersion depth, increase with the increase of current speed and wave height (i.e. the roll motion at wave height of 1.5 m is two times that at wave height of 0.8 m). The weight has little effect on the maximum motion amplitude of the immersed tunnel element. The results are significant for the immersion safety of element in engineering practical construction process.

• 디지털융복합연구
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• 제19권7호
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• pp.341-348
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• 2021

본 연구는 '신종 코로나바이러스' 이후 대학가에서 쓰이고 있는 온라인 화상 교육 플랫폼, 줌과 웹엑스를 중심으로 학습자들의 몰입도를 파악하고 몰입도 향상을 위한 디자인 개선방안을 제시하였다. 선행연구와 문헌조사를 통해 몰입의 구성요소와 온라인 원격 교육 플랫폼의 화면 구성요소를 파악하였고 설문조사와 심층 인터뷰를 통해 몰입도 개선 방안을 제시하였다. 연구 방법은 줌과 웹엑스를 통해 온라인 교육을 받는 20-30대 학부생, 대학원생 50명을 대상으로 2021년 4월 7일부터 12일까지 5일간 진행하였고, 그중 6명을 심층 인터뷰하였다. 실험 결과 학습자와 강의자의 소통이 가장 큰 요소로 도출되어 학습자와 강의자 간 소통을 원활히 할 수 있는 디자인 방안을 구텐베르크의 다이어그램을 토대로 제안하였다. 온라인 화상 교육이 COVID-19 이후에도 지속될 것이라 예측됨에 따라 지속적인 온라인 화상 교육 몰입도 연구가 필요하며, 몰입도 향상에 기여할 수 있기를 바란다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.733-742
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• 2020

Taking the cylindrical float of the floating fence of a floating litter collection device as the research object, based on the shallow immersion characteristics of the cylindrical float, the Morison equation is modified, and the interaction between regular waves and the partially immersed horizontal cylindrical float is discussed in combination with scale model test. The results show that the modified Morison equation can accurately predict the wave force of the horizontal cylindrical float and reveal the influence of amplitude, immersion depth and period on the wave force of the cylindrical float. For partially immersed cylindrical floats, the wave force increases with the increase in wave height and decays with the increase in period. The positive value distribution of the wave force is larger than that of the negative direction, and the difference between the positive and negative directions is mainly affected by the immersion depth.

• 한국지하수토양환경학회지:지하수토양환경
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• 제25권4호
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• pp.58-66
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• 2020

Since the typical horn-type ultrasonic equipment induces a reaction at the probe tip, the sonochemical reaction has a limitation that it occurs only in a specific area. As one of the ways to overcome this limitation, an ultrasonic device with multi-stepped horn equipped with several oscillators has been developed. The objective of this study was to investigate the sonochemical effects induced by acoustic cavitation system in 20 kHz multi-stepped ultrasonic horn using calorimetry, KI dosimetry and the luminol test. The sonochemical effects of multi-stepped ultrasonic horn were compared with that of the typical horn-type 20 kHz ultrasonic device. The effect of immersion depth and power on the sonochemical reaction was investigated in the ultrasonic system with multi-stepped ultrasonic horn. Higher calorimetric energy was obtained at higher immersion depth and power conditions. Sonochemical effects increased significantly when using the high immersion depth and input power. However, as the input power increased, the cavitation reaction zone concentrated around the ultrasonic horn. Additionally, the experiments to examine the effect of liquid temperature was conducted. The smaller sonochemical reaction was obtained for the higher liquid temperature. The effect on temperature seems to be closely related to liquid conditions such as viscosity and vapor pressure of water.

• 센서학회지
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• 제18권4호
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• pp.322-326
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• 2009

To estimate the measurement uncertainty for industrial platinum resistance thermometers(IPRTs) made with 3-wire connection, the immersion temperature profile was investigated using a liquid bath. Two types of IPRTs having lead wires made of silver and nickel were constructed and the immersion profiles were measured at temperatures from -50 $^{\circ}C$ to 250 $^{\circ}C$ using 3-wire and 4-wire method. As immersion depth and temperature increased, the resistances measured by 3-wire method increased linearly but not for 4-wire method. To calibrate a 3-wire IPRT, the immersion effect must be accounted for. We propose a linear equation to assess correctly the measurement uncertainty.

• 한국건축시공학회지
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• 제24권3호
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• pp.297-308
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• 2024

본 연구에서는 화재로 손상된 콘크리트의 손상 깊이 판정방법을 제안하고자 하였다. 고온에 노출된 콘크리트의 경우 내부 조직이 팽창하여 건전한 부위보다 손상부위의 공극이 다량 발생하고 미세균열이 발생됨에 따라 흡수율이 더 높아져 수중 침치후 건조를 하는과정에서 건전부위보다 손상부위의 늦은 건조속도와 이에 따른 명도차이에 의한 색상차이를 이용하여 손상 깊이를 측정하는 것이다. 수중 침지방법의 경우 배합별로 각각 38.7 및 37.5mm로 나타났는데, 기존 페놀프탈레인에 의한 중성화 측정 방법보다 손상깊이를 깊게 추정하는 것을 알 수 있었다. 이는 Portlandite(Ca(OH)₂)의 존재여부에 따라 발색이 되는 페놀프탈레인법에 비해 조직이완에 따른 흡수율 원리를 이용한 손상 깊이를 측정하는 방법이 더 민감도가 높아 얻어진 결과로 사료된다.

• International Journal of Internet, Broadcasting and Communication
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• 제15권2호
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• pp.181-186
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• 2023

With the development of VR technology, the visual immersion of VR games has been greatly enhanced nowadays. There has been an issue that has been troubling players in previous VR games, which is motion sickness. Therefore, VR games have been limited in terms of game mechanics, game duration, and game scale, greatly reducing the immersive experience of visual immersion. However, <Half-Life: Alyx> is different from previous VR games in that players can actually perform spatial displacement in the game scene, rather than being fixed in one place for 360-degree observation and interaction. At the same time, compared to traditional games, VR games no longer need to rely on screens, and the complete visual immersion enhances the fun and playability of the game. This research focuses on the VR game <Half-Life: Alyx> to explore its immersive factors in terms of visual perception. Through in-depth analysis of elements such as color, texture mapping, lighting, etc. in VR games, it was found that the game creates a strong sense of visual immersion in these aspects. Through analysis, it is helpful to gain a deeper understanding of the factors that contribute to visual immersion in VR games, which has certain reference value for game developers and related professionals.

• International Journal of Concrete Structures and Materials
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• 제18권2E호
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• pp.97-102
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• 2006

In this study, the effect of supplementary materials(GGBS, PFA, SF) on sulfuric acid corrosion resistance was assessed by measuring the compressive strength, corroded depth and weight change at 7, 28, 56, 91, 180 and 250 days of immersion in sulfuric acid solution with the pH of 0.5, 1.0, 2.0 and 3.0. Then, it was found that an increase in the duration of immersion and a decrease in the pH, as expected, resulted in a more severe corrosion irrespective of binders: increased corroded depth and weight change, and lowered the compressive strength. 60% GGBS mortar specimen was the most resistant to acid corrosion in terms of the corroded depth, weight change and compressive strength, due to the latent hydraulic characteristics and lower portion of calcium hydroxide. The order of resistance to acid was 60% GGBS>20% PFA>10% SF>OPC. In a microscopic examination, it was found that acid corrosion of cement matrix produced gypsum, as a result of decomposition of hydration products, which may loose the structure of cement matrix, thereby leading to a remarkable decrease of concrete properties.