• 천문학회보
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• 제41권2호
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• pp.67.2-67.2
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• 2016

The Sun has diverse variations in solar atmosphere's layers due to solar activity. This solar variations can be recognized easily by sunspots which appear on the solar photosphere. Thus the sunspot on the photosphere is utilized by direct index of the solar activity. The other variation of the photosphere is center-to-limb variation (CLV). In this study, we analyze the relative intensity observed by SOHO, SDO. The data of photospheric intensity are from full disk images of SOHO/MDI intensity ($6768{\AA}$, from May 1994 to March 2011) and of SDO/HMI intensity ($6173-6174{\AA}$, from May 2010 to June 2016). As the result, we found the latitudinal variation of the intensity. The daily photospheric intensity showed the solar cyclic variation with sunspot number. It has a little difference of phase with sunspot number.

• Ocean Systems Engineering
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• 제7권3호
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• pp.225-246
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• 2017

Excessive dynamic-tension variations on the top-tensioned risers (TTRs) deteriorate the structural integrity and cause potential safety hazards. This phenomenon has become more remarkable in the development of deep-water fields with harsher environmental loads. The conventional prediction method of tension variations in hydro-pneumatic tensioner (HPT) has the disadvantage to underestimate the magnitude of cyclic loads. The actual excessive dynamic tension variations are larger when considering the viscous frictional fluid effects. In this paper, a suppression method of tension variations in HPT is modeled by incorporating the magneto-rheological (MR) damper and linear-force actuator. The mathematical models of the combined HPT and MR damper are developed and a force-control scheme is introduced to compensate the excessive tension variations on the riser tensioner ring. Numerical simulations and analyses are conducted to evaluate the suppression of tension variations in HPT under both regular- and irregular-wave conditions for a drilling riser of a tensioned-leg platform (TLP). The results show that significant reduction of tension variations can be achieved by introducing the proposed system. This research has provided a theoretical foundation for the HPT tension control and related structural protection.

• Computers and Concrete
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• 제17권3호
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• pp.353-386
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• 2016

Realistic assessment of the performance of reinforced concrete structural members like columns is needed for designing new structures or maintenance of the existing structural members. This assessment requires analytical capability of employing proper material models and cyclic rules and considering various load and displacement patterns. A computer application was developed to analyze the non-linear, cyclic flexural performance of reinforced concrete structural members under various types of loading paths including non-sequential variations in axial load and bi-axial cyclic load or displacement. Different monotonic material models as well as hysteresis rules, were implemented in a fiber-based moment-curvature and in turn force-deflection analysis, using proper assumptions on curvature distribution along the member, as in plastic-hinge models. Performance of the program was verified against analytical results by others, and accuracy of the analytical process and the implemented models were evaluated in comparison to the experimental results. The computer application can be used to predict the response of a member with an arbitrary cross section and various type of lateral and longitudinal reinforcement under different combinations of loading patterns in axial and bi-axial directions. On the other hand, the application can be used to examine analytical models and methods using proper experimental data.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전기물성,응용부문
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• pp.12-15
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• 2001

Polycrystalline diamond films are deposited by cyclic method. modulating the $H_2$ Plasma and $CH_4+H_2$ plasma during the growth step. Diamond quality is evaluated by FWHM and $I_D/I_G$ ratio obtained from Raman spectroscopic analysis. Structural defects and impurities generated during the growth step are characterized by cathodoluminescence, and the variations between band-A(430 nm) line and nitrogen-related(578 nm) line are investigated as a function of $T_E/T_G$. Furthermore, the correlations between preferential orientation. film morphologies and CL characteristics are also investigated.

• Steel and Composite Structures
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• 제7권5호
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• pp.391-404
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• 2007

This paper presents push-out tests of stud shear connectors to examine their fatigue behavior for developing a new composite bridge deck system. The fifteen push-out specimens of D16 mm stud welded on 9 mm steel plate were fabricated according to Eurocode-4, and a series of fatigue endurance test and residual strength test were performed. Additionally, the stiffness and strength variations by cyclic loading were compared. The push-out test, when the stiffness reduction ratio of the specimens was 0.95 under cyclic load, resulted in the failure of the studs. The stiffness variation of the push-out specimens additionally showed that the application of cyclic loads reduced the residual strength. The fatigue strength of the shear connectors were compared with the design values specified in the Eurocode-4, ASSHTO LRFD and JSSC codes. The comparison result showed that the fatigue endurance of the specimens satisfies the design values of these codes.

• Structural Engineering and Mechanics
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• 제55권5호
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• pp.913-929
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• 2015

The ratcheting and strain cyclic behaviour of joined conical-cylindrical shells under uniaxial strain controlled, uniaxial and multiaxial stress controlled cyclic loading are investigated in the paper. The elasto-plastic deformation of the structure is simulated using Chaboche non-linear kinematic hardening model in finite element package ANSYS 13.0. The stress-strain response near the joint of conical and cylindrical shell portions is discussed in detail. The effects of strain amplitude, mean stress, stress amplitude and temperature on ratcheting are investigated. Under strain symmetric cycling, the stress amplitude increases with the increase in imposed strain amplitude. Under imposed uniaxial/multiaxial stress cycling, ratcheting strain increases with the increasing mean/amplitude values of stress and temperature. The abrupt change in geometry at the joint results in local plastic deformation inducing large strain variations in the vicinity of the joint. The forcing frequency corresponding to peak axial ratcheting strain amplitude is significantly smaller than the frequency of first linear elastic axial vibration mode. The strains predicted from quasi static analysis are significantly smaller as compared to the peak strains from dynamic analysis.

• 한국정보통신학회논문지
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• 제17권9호
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• pp.2009-2019
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• 2013

본 논문에서는 cyclic moment 및 새로운 인자인 변형 cumulant를 기반으로 하여 아날로그 및 디지털 신호의 변조방식을 인식하는 알고리즘을 제안한다. 각 변조신호들은 cyclic moment 차수에 따라 서로 다른 cycle frequency 특성을 가진다. 이러한 특성을 분류인자로 하여 다양한 변조신호를 효과적으로 분류해 낼 수 있다. 또한 cycle frequency 특성이 같은 변조신호들 간의 분리를 위해서 진폭 및 위상 변화와 변형 cumulant를 decision tree의 분류인자로 사용하였다. 심볼 수, SNR, 주파수 옵셋을 고려하여 알고리즘 성능검증을 수행하였다. 약 819개의 심볼이 수집되었을 경우, 제안하는 자동변조인식 알고리즘은 SNR 10dB 이상, 주파수 옵셋 25% 이하 조건에서 평균 95% 이상의 정확도를 나타내었다.

• 터널과지하공간
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• 제9권4호
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• pp.350-363
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• 1999

주기전단하중 하의 암석 절리에 대한 역학적 거동을 규명하기 위해 정밀 주기전단시험 장치를 설계·제작하였다. 실험실에서 황등화강암과 여산대리석 인공 절리 시료로 펑면절리와 거친 절리에 대해 일련의 주기전단시험을 실시하였다. 시료에 대한 레이저 변위계를 이용한 3차원 거칠기 측정을통해 절리의 거칠기 특성을규명하였다. 주기전단시험 결과를 통해 주기전단 과정의 단계별 거동 특성과하중과제하시의 거동 차이, 전단거동의 이방성 등을고찰하였다. 거친 절리면의 역학적 거동 특성은 주로 2차 거칠기의 영향과 암석 재료의 높은 강도에 영향을 받았다. 주기전단시 거친 절리에 대한 돌출부 손상이 지수적인 거칢각 손상 법칙을 따름을 실험적으로 검증하였으며, 수직응력파 거칠기 종류, 하중 단계에 따라 돌출부들의 손상 기구가 다름을 확인하였다.

• Steel and Composite Structures
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• 제31권3호
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• pp.319-327
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• 2019

This paper describes an experimental study of steel beam-column connections with or without expanded beam flanges with different geometries. The objectives of this study are to elucidate the cyclic behavior of these connections, identify the location of the plastic hinge zone, and provide useful test data for future numerical simulations. Five connection specimens are designed and tested under cyclic load. The test setup consists of a beam and a column connected together by a connection with or without expanded beam flanges. A constant axial force is applied to the column and a time varying point load is applied to the free end of the beam, inducing shear and moment in the connection. Because the only effect to be studied in the present work is the expanded beam flange, the sizes of the beam and column as well as the magnitude of the axial force in the column are kept constant. However, the length, width and shape of the expanded beam flanges are varied. The responses of these connections in terms of their hysteretic behavior, failure modes, stiffness degradation and strain variations are experimentally obtained and discussed. The test results show that while the influence of the expanded beam flanges on hysteretic behavior, stiffness degradation and energy dissipation capacity of the connection is relatively minor, the size of the expanded beam flanges does affect the location of the plastic hinge zone and strain variations in these beam-column joints. Furthermore, in terms of ductility, moment and rotational capacities, all five connections behave well. No weld fracture or premature failure occurs before the formation of a plastic hinge in the beam.

• Nuclear Engineering and Technology
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• 제51권4호
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• pp.1109-1116
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• 2019

It is essential to predict the radioactivity distribution around the reactor cooling system (RCS) during obligatory cyclic operation of AP-1000. A home-developed program CPA-AP1000 is upgraded to predict the response of activated corrosion products (ACPs) in the RCS. The program is written in MATLAB and it uses state of the art MCNP as a subroutine for flux calculations. A pair of cyclic power profiles were superimposed after initial full power operation. The effect of cyclic operation is noticed to be more prominent for in-core surfaces, followed by the primary coolant and out-of-core structures. The results have shown that specific activity trends of $^{56}Mn$ and $^{24}Na$ promptly follow the power variations, whereas, $^{59}Fe$, $^{58}Co$, $^{99}Mo$ and $^{60}Co$ exhibit a sluggish power-following response. The investigations pointed out that promptly power-following response of ACPs in the coolant is vital as an instant radioactivity source during leakage incidents. However, the ACPs with delayed power-following response in the out-of-core components are perceived to cause a long-term activity. The present results are found in good agreement with those for a reference PWR. The results are useful for source term monitoring and optimization of work procedures for an innovative reactor design.