• Smart Structures and Systems
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• 제21권1호
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• pp.27-35
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• 2018

In the water-filling and preloading test, the sensing cables were installed on the surface of steel spiral case and in the surrounding concrete to monitor the strain distribution of several cross-sections by using Brillouin Optical Time Domain Analysis (BOTDA), a kind of distributed optical fiber sensing (DOFS) technology. The average hoop strain of the spiral case was about $330{\mu}{\varepsilon}$ and $590{\mu}{\varepsilon}$ when the water-filling pressure in the spiral case was 2.6 MPa and 4.1 MPa. The difference between the measured and the calculated strain was only about $50{\mu}{\varepsilon}$. It was the first time that the stress adjustment of the spiral case was monitored by the sensing cable when the pressure was increased to 1 MPa and the residual strain of $20{\mu}{\varepsilon}$ was obtained after preloading. Meanwhile, the shrinkage of $70{\sim}100{\mu}{\varepsilon}$ of the surrounding concrete was effectively monitored during the depressurization. It is estimated that the width of the gap between the steel spiral case and the surrounding concrete was 0.51 ~ 0.75 mm. BOTDA based distributed optical fiber sensing technology can obtain continuous strain of the structure and it is more reliable than traditional point sensor. The strain distribution obtained by BOTDA provides strong support for the design and optimization of the spiral case structure.

• Structural Engineering and Mechanics
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• 제42권1호
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• pp.73-93
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• 2012

With an active structural involvement in spiral case structure (SCS) that is always the design and research focus of hydroelectric power plant (HPP), the compressible membrane sandwiched between steel spiral case and surrounding reinforced concrete was often assumed to be linear elastic material in conventional design analysis of SCS. Unfortunately considerable previous studies have proved that the foam material serving as membrane exhibits essentially nonlinear mechanical behavior. In order to clarify the effect of membrane (foam) material's nonlinear stress-strain behavior on SCS, this work performed a case study on SCS with a compressible membrane using the ABAQUS code after a sound calibration of the employed constitutive model describing foam material. In view of the successful capture of fitted stress-strain curve of test by the FEM program, we recommend an application and dissemination of the simulation technique employed in this work for membrane material description to structural designers of SCS. Even more important, the case study argues that taking into account the nonlinear stress-strain response of membrane material in loading process is definitely essential. However, we hold it unnecessary to consider the membrane material's hysteresis and additionally, employment of nonlinear elastic model for membrane material description is adequate to the structural design of SCS. Understanding and accepting these concepts will help to analyze and predict the structural performance of SCS more accurately in design effort.

• Advances in concrete construction
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• 제14권1호
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• pp.57-70
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• 2022

The spiral case concrete (SCC) used in the underground powerhouse of large hydropower stations is complex, difficult to pour, and has high requirements for temperature control and crack prevention. In this study, based on the closed-loop control theory of "multi-source sensing, real analysis, and intelligent control", a new intelligent cooling control system (ICCS) suitable for the SCC is developed and is further applied to the Wudongde large-scale underground powerhouse. By employing the site monitoring data, numerical simulation, and field investigation, the temperature control quality of the SCC is evaluated. The results show that the target temperature control curve can be accurately tracked, and the temperature control indicators such as the maximum temperature can meet the design requirements by adopting the ICCS. Moreover, the numerical results and site investigation indicate that a safety factor of the spiral case structure was sure, and no cracking was found in the concrete blocks, by which the effectiveness of the system for improving the quality of temperature control of the SCC is verified. Finally, an intelligent cooling control procedure suitable for the SCC is proposed, which can provide a reference for improving the design and construction level for similar projects.

• 한국정보전자통신기술학회논문지
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• 제15권5호
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• pp.315-320
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• 2022

일반적인 나선형 인덕터의 경우에 비대칭 구조를 가짐에 따라 포트의 방향에 영향을 받게 된다. 본 논문에서는 2층이면서 대칭 구조를 가질 수 있는 나선형 인덕터를 제안하고 시뮬레이션 및 주파수 특성을 분석하였다. 기존 단층 대칭형 인덕터가 3.9~4.2nH의 인덕턴스를 갖는 것과 비교하여 제안된 2층 대칭 나선형 인덕터는 포트에 변함없이 0.3~1.2GHz 범위에서 11~12nH의 인덕턴스, 800MHz에서 약 4.4의 품질계수, 약 2.7~2.8GHz의 자기공진주파수를 가진다. 이는 기존 일반적인 나선형 인덕터가 포트에 따라 큰 차이를 갖는 것과 비교하여 포트의 방향에 대한 영향이 적은 것을 확인할 수 있었다.

• 한국정보전자통신기술학회논문지
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• 제13권5호
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• pp.353-358
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• 2020

일반적인 나선형 인덕터의 경우에 비대칭 구조를 가짐에 따라 포트의 방향에 영향을 받게 된다. 본 논문에서는 단층이면서 대칭 구조를 가질 수 있는 나선형 인덕터를 제안하고 시뮬레이션 및 주파수 특성을 분석하였다. 일반적인 나선형 인덕터는 포트의 기준에 따라 주파수-인덕턴스 특성, 주파수-품질계수 특성, 자기공진주파수가 큰 차이를 보이는 반면에, 제안된 대칭 나선형 인덕터는 포트에 변함없이 2.7nH의 인덕턴스, 약 7.86의 품질계수, 약 14.1GHz의 자기공진주파수를 가진다. 이는 기존 일반적인 나선형 인덕터가 포트에 따라 큰 차이를 갖는 것과 비교하여 포트의 방향에 대한 영향이 적은 것을 확인할 수 있었다. 다만, 코일의 점유 면적에 비하여 상호 인덕턴스가 줄어들어 낮은 인덕턴스를 가지며, 인덕턴스 증가보다 코일의 저항이 더 증가하여 품질계수 또한 낮아짐을 확인할 수 있었다. 향후에는 2층 대칭 나선형 구조를 통하여 인덕턴스와 품질계수를 향상시킬 수 있을 것으로 기대된다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.272-273
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• 2007

This paper presents the characteristic of rectangular and octagonal spiral inductor using PGS(Patterned Ground Shield). We investigated variation of inductance and Q-factor with changing of turn number at fixed width, spacing and inner diameter. We confirmed that characteristic of inductance and Q-factor be appled PGS in rectangular and octagonal types spiral inductor by EM simulation tool. Inductance decreased irrespective of structure but Q-factor increased. When PGS not exist, Q-factor of Inductor is analogous at classification frequency but, rectangular is a few larger then octagonal in small turn number. The other side, When PGS is inserted, we confirmed that octagonal lager then rectangular in many turn number. Q-factor is improved in case of octagonal structure and small turn number by PGS effect.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.219-219
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• 2008

Energy harvesting from the environment has been of great interest as a standalone power source of wireless sensor nodes for ubiquitous sensor networks (USN). There are several power generating methods such as thermal gradients, solar cell, energy produced by human action, mechanical vibration energy, and so on. Most of all, mechanical vibration is easily accessible and has no limitation of weather and environment of outdoor or indoor. In particular, the piezoelectric energy harvesting from ambient vibration sources has attracted attention because it has a relative high power density comparing with other energy scavenging methods. Through recent advances in low power consumption RF transmitters and sensors, it is possible to adopt a micro-power energy harvesting system realized by MEMS technology for the system-on-chip. However, the MEMS energy harvesting system hassome drawbacks such as a high natural frequency over 300 Hz and a small power generation due to a small dimension. To overcome these limitations, we devised a novel power generator with a spiral spring structure. In this case, the energy harvester has a lower natural frequency under 200 Hz than a normal cantilever structure. Moreover, it has higher an energy conversion efficient because shear mode ($d_{15}$) is much larger than 33 mode ($d_{33}$) and the energy conversion efficiency is proportional to the piezoelectric constant (d). We expect the spiral type MEMS power generator would be a good candidate as a standalone power generator for USN.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.163-167
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• 2003

In this paper, an air-suspension type RF MEMS inductor is fabricated, and an appropriate de-embedding scheme for 3-dimenstional MEMS structure is applied and verified with inductance calculation algorithm. With the presented de-embedding method, parasitics from contanct pads and feeding lines are effectively and accurately de-embedded using open and short calibration procedure, and only spiral and posts can be characterized as a high-Q inductor structure. The validity of the de-embedding method is verified by the comparison of the measured and calculated inductances of two 1.5 and 2.5 turn square spiral inductors. The open-short de-embedded inductance error is below 5% each case in comparison with the calculated value based on H.M. Greenhouse's algorithm.

• 한국수자원학회논문집
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• 제52권4호
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• pp.235-243
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• 2019

급격한 기상변화로 인한 극한 강우와 집중폭우의 발생빈도 증가로 기존 수방시설의 한계 용량을 초과해 도심지 침수피해가 빈번하게 발생하고 있다. 최근 도시화 추세가 급격하게 빨라지면서 수방시설 등 사회기반시설에 대한 지하공간 개발의 필요성이 증가하고 있으며, 지하공간을 활용한 지하방수로와 지하저류지 기술이 급부상하고 있다. 본 연구에서는 지하유입시설의 대표적 형상인 접선식 유입구와 나선식 유입구에 대한 공기 배출효과를 분석하기 위해 유입유량 변화에 따른 수직갱 내부 공기공동(air-core)의 형상 크기를 계측했다. 나선식 유입구의 경우, 저유량 유입조건에서 와류 유도 효과를 개선하기 위해 유입부 바닥면에 계단형 다단식 구조를 도입했다. 수직갱 내부 공기공동의 전체적인 평균 단면적의 경우, 다단식 나선 유입구가 접선식 유입구보다 10% 정도 크게 나타나 고유량 유입조건에서 높은 공기 배출 효과와 유입효율을 나타냈다. 접선식 유입구의 경우, 유입구가 가지는 고유 성능을 유지할 수 있는 최대 유량 조건을 초과하면서 공기 배출 효과가 감소하기 시작했다. 또한, 실험에서 사용된 접선식 유입구와 다단식 나선 유입구 모형에 활용 가능한 기초자료를 제공하기 위해 수직갱 내부 위치에 따른 공기공동 단면적에 대한 실험식(empirical formula)을 제시했다.

• 천문학회지
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• 제25권1호
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• pp.11-21
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• 1992

Applying mass model to disk galaxy NGC 300, since the observed rotation curve of NGC 300 is flatter than Toomre's mass model n = 1, two cases are used; obtaining parameters $a^n$ and $b^n$ from the polynomial fitting of the observed rotation curve (case A) and from the least square fitting between the observed rotation curve and model rotation curve (case B). In any case, n bas a fixed value of 1. Brandt's mass model is also discussed. which has a shape parameter n = 1.4. Calculated total mass and total mass to luminosity ratio are $3.3{\times}10^{10}M_{\odot}$, l2.1 for case A and $2.8{\times}10^{10}M_{\odot}$, 10.3 for case B. In case of Brandt's model, the values are $4.2{\times}10^{10}M_{\odot}$ and 15.4. The rise in the local mass to luminosity ratio in the outer part of NGC 300 implies existence of massive halo. Other dynamical properties are also discussed.