• 한국도로학회논문집
• /
• 제10권4호
• /
• pp.9-18
• /
• 2008

줄눈 콘크리트포장(JCP-Jointed Concrete Pavement)의 경우 포장단면 온 습도차에 의해 슬래브 내의 컬링이 발생하게 된다. 컬링에 의해서 발생하는 슬래브의 휨 형상 및 크기는 포장내 응력 및 평탄성에 영향을 미치기 때문에 포장의 구조적, 기능적 성능에 중요한 영향을 줄 수 있다. 슬래브의 휨 형상을 직접 측정하는 것은 시공초기에 포장내에 다량의 계측기를 매설하여야 하며, 시공초기부터 거동의 정교한 측정이 필요하고 고가의 실험비용 및 기술적 인 어려움을 갖고 있다. 본 연구에서는 현장에서 손쉽게 획득할 수 있는 프로파일 데이터(Profile Data)에 파워 스펙트럼 분석(Power Spectrum Density Analysis) 및 역 푸리에 변환(Inverse Fast Fourier Transform) 기법 등을 적용하여 임의의 시간에서 줄눈 콘크리트포장의 슬래브 휨 형상을 측정하는 방법을 개발하였다. 개발한 기법의 실효성을 검증하기 위하여 국내 중부내륙에 위치한 시험도로 줄눈 콘크리트 포장에서 시간대별 프로파일을 측정하고 이 데이터로부터 슬래브 휨 형상을 도출하여 그 결과를 검토하였다. 또한 동 시간대의 연속철근 콘크리트포장(CRCP- Continuous Reinforced concrete Pavement) 구간에서의 프로파일 데이터를 분석하고 이를 줄눈 콘크리트포장에서의 결과와 비교하여 개발한 슬래브 휨 형상 추출기법의 타당성을 검증하였다.

• 천문학회보
• /
• 제43권2호
• /
• pp.45.2-45.2
• /
• 2018

Twisted magnetic flux tubes (also called magnetic flux ropes) are believed to play a crucial role in solar eruptive phenomena. The evolution of a single flux rope with or without the influence of an overlying field of a simple geometry has been extensively studied and its physics is rather well understood. Observations show that interacting flux tubes are often involved in solar eruptions. It was Lau and Finn (1996) who intensively studied the interaction between two flux ropes, whose footpoints are anchored in two parallel planes. In this too simplified setting, the curvature of the flux rope axial fields is totally ignored. In our study, the footpoints of flux ropes are placed in a single plane containing a polarity inversion line as in the real solar active region. Our simulation study is performed for four cases: (1) co-axial field and co-axial current (co-helicity), (2) counter-axial field and co-axial current (counter-helicity), (3) co-axial field and counter-axial current (counter-helicity), and (4) counter-axial field and counter-axial current (co-helicity). Except case 3, each case is found to be related with certain eruptive features.

• Journal of Astronomy and Space Sciences
• /
• 제30권2호
• /
• pp.91-94
• /
• 2013

We use the outer gap model to explain the spectrum and the energy dependent light curves of the X-ray and soft ${\gamma}$-ray radiations of the spin-down powered pulsar PSR B1509-58. In the outer gap model, most pairs inside the gap are created around the null charge surface and the gap's electric field separates the opposite charges to move in opposite directions. Consequently, the region from the null charge surface to the light cylinder is dominated by the outflow current and that from the null charge surface to the star is dominated by the inflow current. We suggest that the viewing angle of PSR B1509-58 only receives the inflow radiation. The incoming curvature photons are converted to pairs by the strong magnetic field of the star. The X-rays and soft ${\gamma}$-rays of PSR B1509-58 result from the synchrotron radiation of these pairs. The magnetic pair creation requires a large pitch angle, which makes the pulse profile of the synchrotron radiation distinct from that of the curvature radiation. We carefully trace the pulse profiles of the synchrotron radiation with different pitch angles. We find that the differences between the light curves of different energy bands are due to the different pitch angles of the secondary pairs, and the second peak appearing at E > 10 MeV comes from the region near the star, where the stronger magnetic field allows the pair creation to happen with a smaller pitch angle.

• 한국대기환경학회지
• /
• 제15권3호
• /
• pp.281-289
• /
• 1999

A new E-$\varepsilon$ turbulence numerical model is proposed for analysing the turbulent air flow field within are urban street canyon. In this model the equations of eddy viscosity and energy dissipation ae reformed by considering the Kolmogorov time scale and streamline curvature effect. Application results of the new E-$\varepsilon$ model have been compared with those of standard E-$\varepsilon$ model and Yang and Shih's one, which are commonly used ones in engineering fields, and with field experiment results of DePaul and Sheih. The new model appears to be generally superior to other both models in the prediction of an air flow field within street canyon.

• 대한수학회지
• /
• 제61권2호
• /
• pp.309-339
• /
• 2024

Let M be a real hypersurface in the complex hyperbolic quadric Q^m*, m ≥ 3. The Riemannian curvature tensor field R of M allows us to define a symmetric Jacobi operator with respect to the Reeb vector field ξ, which is called the structure Jacobi operator R_ξ = R( · , ξ)ξ ∈ End(TM). On the other hand, in [20], Semmelmann showed that the cyclic parallelism is equivalent to the Killing property regarding any symmetric tensor. Motivated by his result above, in this paper we consider the cyclic parallelism of the structure Jacobi operator R_ξ for a real hypersurface M in the complex hyperbolic quadric Q^m*. Furthermore, we give a complete classification of Hopf real hypersurfaces in Q^m* with such a property.

• 천문학회보
• /
• 제40권1호
• /
• pp.66.3-67
• /
• 2015

Without scrutinizing reflection, the plasma comprising a coronal loop is usually regarded to reside within a flux rope. This picture seems to have been adopted from laboratory plasma pinches, in which a plasma of high density and pressure is confined in the vicinity of the flux rope axis by magnetic tension and magnetic pressure of the concave inward magnetic field. Such a configuration, in which the plasma pressure gradient and the field line curvature vector are almost parallel, however, is known to be vulnerable to ballooning instabilities (to which belong interchange instabilities as a subset). In coronal loops, however, ideal MHD (magnetohydrodynamic) ballooning instabilities are impeded by a very small field line curvature and the line-tying condition. We, therefore, focus on non-ideal (resistive) effects in this study. The footpoints of coronal loops are constantly under random motions of convective scales, which twist individual loop strands quite randomly. The loop strands with the axial current of the same direction tend to coalesce by magnetic reconnection. In this reconnection process, the plasma in the loop system is redistributed in such a way that a smaller potential energy of the system is attained. We have performed numerical MHD simulations to investigate the plasma redistribution in coalescence of many small flux ropes. Our results clearly show that the redistributed plasma is more accumulated between flux ropes rather than near the magnetic axes of flux ropes. The Joule heating, however, creates a different temperature distribution than the density distribution. Our study may give a hint of which part of magnetic field we are looking to in an observation.

• 지질공학
• /
• 제31권3호
• /
• pp.283-293
• /
• 2021

고해상 드론 기반의 지형 정보와 중력장 데이터를 이용하여 다짐지반의 모양과 균질성을 분석하였다. 지형과 수문 모형에서 계산된 지형요소 중 곡률은 다짐과정에서 발생한 지형의 변화를 효과적으로 보여 주었으며 이를 통해 불균질 다짐 영역을 확인할 수 있다. 지형 정보의 적정 해상도는 10 cm 정도였다. 성토지반의 공간적인 밀도변화를 분석하기 위해 중력장 해석을 수행하였으며 완전 부게이상의 변화로부터 불균질 다짐 영역과 지하 밀도구조 모델링을 통해 다짐도 차이에 의한 불균질 영역을 파악하였다. 연구결과로부터 지형요소와 중력장 해석법은 다짐된 지반의 균질성을 평가법이 될 수 있을 것으로 판단된다.

• Current Optics and Photonics
• /
• 제1권4호
• /
• pp.344-350
• /
• 2017

We present a new design approach and an example design for an image-space telecentric two-mirror system that has a fast f-number and a wide-field line image. The initial design of the telecentric mirror system is a conventional axially symmetric system, consisting of a flat primary mirror with fourth-order aspheric deformation and an oblate ellipsoidal secondary mirror to correct spherical aberration, coma, and field curvature. Even though in the optimized design the primary mirror is tilted, to avoid ray obstruction by the secondary mirror, the image-space telecentric two-mirror system shows quite good imaging performance, for a line imager.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1996년도 추계학술대회 논문집
• /
• pp.430-433
• /
• 1996

In This paper, we design the developed path generation method which is named that CBPM(Continuous path generation method Based artificial Potential field) that is able to be used in the obstacles environment. This CBPM is designed so that it puts together two obstacle avoidance algorithm-the continuous path generation method and the artificial potential field method. Here, the continuous path generation method generate the safety path using continuous path curvature. But, this method has demerits when used in obstacles environment in which are closely located. Another method which is named the artificial potential field method generates the path with the artificial potential field in the obstacles environment. But, APFM has local minima in certain places and unnecessarily calculates the path in which obstacles are not located. So, the developed path generation method, CBPM, is suggested and performances in many different obstacles environments are shown by using computer simulation.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 1997년도 추계학술대회논문집
• /
• pp.49-52
• /
• 1997

The kinematically admissible velocity field is developed for the analysis of the curving of an eccentric extrusion. The curving of product in extrusion is caused by the difference of the linearly distributed longitudinal velocity on the cross-section of the workpiece at the dies exit. The result of the analysis show that the curvature of product increases with the increase in eccentricity of gravity center of the cross-section of the workpiece at the die entrance from that of the cross-section at the die exit. It also increase with the die land dimension. By the DEFORMTM-3D analysis, the curving of T-shaped product in extrusion is changed by the eccentricity, die land length and the friction constant. The result of the analysis by DEFORMTM-3D software shows that the curvature of circular shaped product increases with the eccentricity. The two analysis and one experiment show the curving phenomenon in eccentric extrusion process.