• 한국임상보건과학회지
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• 제5권1호
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• pp.808-815
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• 2017

Purpose. To analyze the refractive status between urban and rural regions, of children in Korea, in the age group of 13. Methods. From October 2016 to January 2017, forty subjects( 20 male subjects, 20 female subjects; 13 years) were performed in refraction test using the Auto-Refraction. Myopia, hyperopia, astigmatism, and anisometropia were defined as spherical equivalent(SE)${\leq}-0.50$ diopters, SE ${\geq}+1.00D$, cylinder error ${\geq}0.75D$ and SE difference${\geq}1.00D$ between binocular eyes, respectively. Results. The refractive error by spherical equivalent among all subjects was myopia 76.25%, astigmatism 35%, emmetropia 16.25%, anisometropia 8.75%, and hyperopia 5%. The prevalence of myopia and astigmatism were much more common in urban than rural region although the difference was not statically significant. Emmetropia and astigmatism were much more common in rural region than urban although the difference was not statically significant. The prevalence of spherical equivalent was much common from -1.00 diopter to -4.00 diopter. On the other hand, the prevalence of myopia was much more than hyperopia. There was a statistical significance between OD and OS of rural region in the spherical equivalent power(p<.000). Also, There was a statistical significance between OD and OS of urban region in the spherical equivalent power(p<.004). Therefore, there was a significant statistical similarity between urban and rural regions on the OD and OS in the spherical equivalent power. On the other hand, There was a significant statistical similarity between urban and rural regions of the OD and OS in the astigmatism power(p<0.000). However, in the rural and urban regions there was not statistical significance in the OD and OS concerning the spherical equivalent power and astigmatism power (p>0.1). Conclusions. Myopia was the most common refractive error in Korea young children. while hyperopia was few. There was not a statistical significance as age between rural and urban at spherical equivalent power( P> 0.01). These results suggested that the analysis of the refractive status at young children can give the useful diagnosis data for the correction of visual acuity.

• 한국지진공학회논문집
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• 제7권1호
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• pp.9-16
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• 2003

건축구조물의 내진성능을 효율적으로 평가하기 위해서는 다자유도계 구조물을 등가 1자유도계로 표현하는 것이 필요하다. 본 연구는 다층 철근콘크리트 골조구조를 등가 1자유도계로 치환하는 방법을 제시하였다. 다층 철근콘크리트 모멘트 골조를 등가 1자유도계로 치환하여 모델화에 따른 비선형 시간이력해석을 통하여 다자유도계 구조물의 축약 방법의 타당성을 검토하는 것이 목적이다. 다층 골조구조의 정적 비선형 해석을 수행하여, 등가 1자유도계의 복원력 모델을 설정하였다. 다층 골조 구조의 비선형 시간이력해석 응답치와 등가 1자유도계의 시간이력해석 응답치를 비교하여, 등가 1자유도계 모델의 타당성을 검증하였다. 다층 철근콘크리트 골조구조를 등가 1자유도계로 치환하여 비선형 지진응답을 구하는 방법은 충분히 그 타당성이 있다는 것이 확인되었다. 다층 철근콘크리트 골조구조의 대표변위로서 1차모드참여 yector$_1$,$\beta${$_1$$\mu$}= 1인 높이가 등가 1자유도계의 응답을 가장 근사하게 나타내는 것을 알 수 있었다. 등가 1자유도계의 지진응답해석에 사용하는 복원력 모델의 이력곡선에 따라 응답파형에 차이가 생기므로, 실제 frame 구조의 복원력 특성을 반영한 이력모델을 선정하는 것이 중요하다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 봄 학술발표회 논문집
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• pp.569-576
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• 2003

Based on the equivalent uniform stress concept Presented by Seed and Idriss, sinusoidal cyclic loads which simplified earthquake loads have been applied in evaluating the liquefaction resistance strength experimentally. However, the liquefaction resistance strength of soil based on the equivalent uniform stress concept can not exactly reflect the dynamic characteristics of the irregular earthquake motion. The liquefaction assessment method which was invented by using the equivalent uniform stress concept is suitable for the severe earthquake region such as Japan or USA, so the proper method to Korea is needed. In this study, estimation of the resistance to liquefaction was conducted by applying real earthquake loading to the cyclic triaxial test. From the test results, the characteristics of the fine sand under moderate earthquake were analyzed and compared with the results under strong earthquakes. Typically real earthquake loads used in this study are divided into two types - impact type and vibration type. Furthermore, results of the liquefaction resistance strength based on the equivalent uniform stress concept and tile concept using real earthquake loading were compared.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.271-271
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• 2012

Many studies have been investigated on high density plasma source (Electron Cyclotron Resonance, Inductively Coupled Plasma, Helicon plasma) for large area source after It is announced that productivity of plasma process depends on plasma density. In this presentation, we will propose the new concept of the multiple source, which consists of a parallel connection of ICP sources and helicon plasma sources. For plasma uniformity, equivalent power (especially, equivalent current in ICP & Helicon) should distribute on each source. We design power feeding line as coaxial transmission line with same length of ground line in each source for equivalent power distribution. And we confirm the equivalent power distribution with simulation and experimental result. Based on basic study, we develop the plasma source for oxidation in semiconductor process. we will discuss the relationship between the processing parameters (With or WithOut magnet, operating pressure, input power ). In ICP, plasma density uniformity is uniform. In ICP with magnet (or Helicon) plasma density is not uniform. As a result, new design (magnet arrangement and gas distributor and etc..) are needed for uniform plasma density in ICP with magnet and Helicon.

• Steel and Composite Structures
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• 제37권4호
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• pp.447-462
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• 2020

In this paper, a simplified seismic design method for low-rise dual frame-steel plate shear wall (SPSW) structures is proposed in the framework of performance-based seismic design. The dynamic response of a low-rise structure is mainly dominated by the first-mode and the structural system can be simplified to an equivalent single degree-of-freedom (SDOF) oscillator. The dual frame-SPSW structure was decomposed into a frame system and a SPSW system and they were simplified to an equivalent F-SDOF (SDOF for frame) oscillator and an equivalent S-SDOF (SDOF for SPSW) oscillator, respectively. The analytical models of F-SDOF and S-SDOF oscillators were constructed based on the OpenSees platform. The equivalent SDOF oscillator (D-SDOF, dual SDOF) for the frame-SPSW system was developed by combining the F-SDOF and S-SDOF oscillators in parallel. By employing the lateral force resistance coefficients and seismic demands of D-SDOF oscillator, the design approach of SPSW systems was developed. A 7-story frame-SPSW system was adopted to verify the feasibility and demonstrate the design process of the simplified method. The results also show the seismic demands derived by the equivalent dual SDOF oscillator have a good consistence with that by the frame-SPSW structure.

• 한국전산구조공학회논문집
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• 제19권3호
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• pp.303-312
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• 2006

본 연구에서는 요소의 추가 및 제거 또는 부분적인 강성 변경이 있을 때, 이러한 강성 변경이 전체 구조물의 거동에 미치는 영향을 하중으로 표현한 강성등가하중을 제안한다. 강성등가하중에 의한 재해석은 초기 구조물을 대상으로 하므로 이미 계산된 강성행렬 및 역행렬을 다시 사용할 수 있어 재해석 효율을 크게 향상시킬 수 있다. 본 논문에서는 강성등가하중의 개념을 정의하고 간단한 병렬 스프링 구조물을 이용하여 강성등가하중 산정 가능성에 대하여 우선 기술한다. 다음으로 일반적인 골조 구조물에서 강성 변경에 대한 강성등가하중 산정 절차를 제안하고, 마지막으로 몇몇 강성 변경 사례에 대한 강성등가하중 산정 및 해석결과를 제시함으로써 제안된 기법을 검증한다. 강성등가하중은 향후 비선형해석, 구조물 거동및 응력 제어 등 다양한 문제에 활용될 수 있을 것으로 기대된다.

• 대한기계학회논문집A
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• 제31권12호
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• pp.1165-1172
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• 2007

The spacer grid set is a part of a nuclear fuel assembly. The set has a spring and the spring supports the fuel rods safely. Although material nonlinearity is involved in the deformation of the spring, nonlinearity has not been considered in design of the spring. Recently a nonlinear response structural optimization method has been developed using equivalent loads. It is called nonlinear response optimization equivalent loads (NROEL). In NROEL, the external loads are transformed to the equivalent loads (EL) for linear static analysis and linear response optimization is carried out based on the EL in a cyclic manner until the convergence criteria are satisfied. EL is the load set which generates the same response field of linear analysis as that of nonlinear analysis. Shape optimization of the spring is carried out based on EL. The objective function is defined by minimizing the maximum stress in the spring while mass is limited and the support force of the spring is larger than a certain value. The results are verified by nonlinear response analysis. ABAQUS is used for nonlinear response analysis and GENESIS is employed for linear response optimization.

• Imaging Science in Dentistry
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• 제30권1호
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• pp.16-22
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• 2000

Purpose : To evaluate the bone densities measured on copper-equivalent image of cross sectional view of mandibular edentulous premolar area obtained by multifuctional panoramic x-ray machine, PM 2002 CC with transversal slicing system. Materials and Methods: Panoramic cross sectional views with 8 mm focal layer of aluminum step and blocks, of hydroxyapatite (RA) step, 6 HA blocks and copper step wedge having 0.03 mm thickness of each step, and of 3 bone blocks cutted by 8 mm thickness mesiodistally and a dry mandible with copper step wedge were taken by using transversal slicing system in PM 2002 Cc. All reference-equivalent images were made and analyzed by NIH image program. Results: The average copper-equivalent value of cancellous bone of bone blocks on the panoramic cross sectional view was 0.026 ± 0.020 mm Cu. The calculated average bone density was 0.38g/cm². There was no significant difference (P>0.1) between the bone densities on intraoral digital view and on the panoramic digital cross sectional view. Conclusion: The copper-equivalent image of panoramic digital cross sectional view obtained by PM 2002 CC with very thin copper step wedge was supposed to be useful to measure the bone density of cancellous bone of mandible at the premolar edentulous area.

• 한국산업융합학회 논문집
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• 제14권3호
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• pp.121-125
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• 2011

EMTP-RV is the very powerful program to analyze the dynamic operation of the power system. To use this package in the large complex power system, it is very important to simplify the power system to simple equivalent network. In our study the 100 MVA STATCOM is placed at 345kV "MIGUM" which is the one of the 345kV substations of the Korean Electric Power System that is consist of more than 1000-bus. MIGUM substation is connected with 7 separated transmission lines to main Korean Electric power system. We developed a new method to simplify the network except the substation that we want to analysis. The power system outside the 345kV substation is modeled into the equivalent network. The loop network outside the substation can be modeled to simplified Thevenin equivalent network. The proposed method is applied to IEEE-14 Reliability Test System and the results shows the effectiveness of the method.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.749-752
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• 2002

In this study, we carried out the finite element analysis about screw that is the weakest part of the centrifuge for sewage management. Structural analysis was done with respect to the change of outer radius and thickness of screw blade and screw with sewage discharge hole. If the area of circular hole is equal to that of extended holes, maximum equivalent stress was compared between hole and extended hole. Centrifugal force on account of rotation of 4000 rpm was applied the screw. The results are as follows : 1 . When the larger radius and thickness of screw blade was used, the higher maximum equivalent stress is occurred. 2. When the larger radius of sewage discharge hale was used, the higher maximum equivalent stress is occurred. 3. When the longer parallel part length of extended hole was used, the higher maximum equivalent stress is occurred. 4. If the extended hole with the same discharging area which circular hole uses, the maximum equivalent stress is lower.