• 대한기계학회논문집B
• /
• 제22권8호
• /
• pp.1073-1082
• /
• 1998

When thermal diffusivity is measured by laser flash method, the thermal diffusivity call be calculated front the assumption of the uniformly heated whole surface of the specimen. It has been known that the approximate 5% error is made by the non-uniform energy distribution on the specimen surface of laser pulse heat source. In this study, to obtain the highly-uniformed laser beam, which has both the low non-uniform heating error from non-uniform laser beam and the energy loss, research was carried out on no transmitting loss by optical fiber and high repetitions. In addition, heating error and thermal diffusivity were measured as the measuring positions were varied and compared with the results using the uniform and the non-uniform laser beams. In addition, dole to using the uniformalized laser beam, the whole surface of the specimen was heated uniformly and as a result, it was the thought that this was very effective to reduce the variations of the errors of the thermal diffusivity as the measuring positions were varied. It can be obtained that when the thermal diffusivity of POCO-AXM-5Q1 of SRM in NBS was measured with both the uniform and the non-uniform laser beams, the dispersion error of the former was from 2 to 2.5%, which was more improved than that of the latter.

• Wind and Structures
• /
• 제30권6호
• /
• pp.649-662
• /
• 2020

The existence of a dam has potential effects on the surrounding wind environment especially when it is located in mountainous areas. In this situation, the long-span bridge over the reservoir can easily be exposed to non-uniform incoming flows, affecting its wind-resistance performance. This paper presents a study on the aerostatic stability of such a bridge. Wind tunnel tests were first carried out to investigate the wind environment above a mountainous reservoir. The results show that the angle of attack and the wind speed along the bridge axis show obvious non-uniform characteristics, which is related to the inflow direction. When winds come from the south where the river is winding, the angle of attack varies along the span direction significantly. The finite element model for the bridge was established using ANSYS software, and effects of non-uniform wind loads on the aerostatic stability were computed. Non-uniform angle of attack and wind speed are unfavorable to the aerostatic stability of the bridge, especially the former. When the combined action of non-uniform angle of attack and wind speed is considered, the critical wind speed of aerostatic instability is further reduced. Moreover, the aerostatic stability of the bridge is closely related to the dam height.

• Structural Engineering and Mechanics
• /
• 제40권3호
• /
• pp.347-371
• /
• 2011

This paper focuses on post-buckling analysis of Timoshenko beams with various boundary conditions subjected to a non-uniform thermal loading by using the total Lagrangian Timoshenko beam element approximation. Six types of support conditions for the beams are considered. The considered highly non-linear problem is solved by using incremental displacement-based finite element method in conjunction with Newton-Raphson iteration method. As far as the authors know, there is no study on the post-buckling analysis of Timoshenko beams under uniform and non-uniform thermal loading considering full geometric non-linearity investigated by using finite element method. The convergence studies are made and the obtained results are compared with the published results. In the study, the relationships between deflections, end rotational angles, end constraint forces, thermal buckling configuration, stress distributions through the thickness of the beams and temperature rising are illustrated in detail in post-buckling case.

• Korean Chemical Engineering Research
• /
• 제62권1호
• /
• pp.27-35
• /
• 2024

메탄, 프로판 등을 주성분으로 하는 연료가스는 폭발위험장소에서 사용될 수 있으며, 누출로 인한 공정조건의 영향으로 불균일한 혼합기를 형성할 수 있다. 균일한 혼합기를 대상으로 측정된 문헌 데이터를 이용한 화재 폭발 위험성 평가, 손상 예측은 가스 누출에 의한 실제 폭발 사고와 다른 결과를 얻을 수 있다. 본 연구에서는 가스 누출시 나타날 수 있는 농도 변화에 있어서 불균일성 혼합기의 폭발압력, 화염속도 등의 폭발특성을 조사하였다. 길이 0.82 m의 스테인리스 재질의 밀폐 배관에서 수행하였으며 컬러 초고속 카메라 및 압력 센서를 사용하여 관찰하였다. 또한 배관 내의 시간에 따른 농도차이 변화에 대해 회귀분석 모델을 사용하여 불균일 혼합물의 정량화 방법을 제안하였다. 본 연구의 농도 불균일성 조건에 있어서 메탄 폭발 시 전파화염은 불균일성 농도가 높아짐에 따라 화염 면적의 증가가 관찰되었고 이는 난류 화염의 주름진 화염 구조와 유사하였다. 메탄의 최대압력까지 걸리는 소요시간은 불균일성이 클수록 감소하였고, 폭발압력은 불균일성이 클수록 증가하였다. 농도가 불균일한 메탄의 K_G(폭연지수)의 범위는 1.30~1.58 [MPa·m/s]으로서 메탄의 농도가 균일성에서 불균일성로 변화하면서 17.7% 증가하였다.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2000년도 춘계학술대회 논문집
• /
• pp.553-556
• /
• 2000

The paper deals with the dynamic response of non-uniform beams subjected to a moving mass. In the dynamic analysis, the effects of inertia force, elastic force, centrifugal force, Coriolis force and self weight due to moving mass are taken into account. Galerkin's mode summation method is applied for the discretized equations of notion. Numerical results for the dynamic response of the non-uniform beam under a moving mass having various magnitudes and velocities are investigated. Experimental results have a good agrement with predictions

• EDISON SW 활용 경진대회 논문집
• /
• 제5회(2016년)
• /
• pp.481-484
• /
• 2016

Jansen mechanism is basic principal of walking robot. Because that mechanism have many link, walking robot can walk like animals. One of the feature is that space is existed between leg of walking robot and ground surface. So, it can walk through the non-uniform ground surface that have obstacle. In this paper, I will suggest design of walking robot that can walk on non-uniform ground surface effectively based on Jansen mechanism.

• Nuclear Engineering and Technology
• /
• 제55권4호
• /
• pp.1310-1323
• /
• 2023

A reactor coolant pump (RCP) is essential for transporting coolant in the primary loop of pressurized water reactors. In the advanced passive reactor, the absence of a long pipeline between the steam generator and RCP serves as a transition section, resulting in a non-uniform flow field at the pump inlet. Therefore, the characteristics of the pump should be investigated under non-uniform flow to determine its influence on the pump. In this study, the pressure pulsation characteristics were examined in the time and frequency domains, and the sources of low-frequency and high-amplitude signals were analyzed using wavelet coherence analysis and numerical simulation. From computational fluid dynamics (CFD) results, non-uniform inflow has a great effect on the flow structures in the pump's inlet. The pressure pulsation in the pump at the rated flow increased by 78-128.7% under the non-uniform inflow condition in comparison with that observed under the uniform inflow condition. Furthermore, a low-frequency signal with a high amplitude was observed, whose energy increased significantly under non-uniform flow. The wavelet coherence and CFD analysis verified that the source of this signal was the low-frequency pulsating vortex under the steam generator.

• 한국콘텐츠학회논문지
• /
• 제12권3호
• /
• pp.55-66
• /
• 2012

무선 센서 네트워크에서 위치 측위 기술은 재난 감시, 환경 모니터링 등과 같은 응용에서 매우 필수적이다. 대표적인 Range-free 기반 위치 측위 기법인 DV-HOP은 균일한 네트워크 환경을 기반으로 위치를 측위하기 때문에 실제 배포 환경을 고려하지 않는다. 따라서 실제 배포 환경인 비 균일 네트워크에서는 위치 정확도가 낮다. 이러한 환경에서 정확도를 향상시키기 위해서는 많은 수의 앵커 노드를 필요로 하기 때문에, 많은 구축비용이 소모되는 문제점이 발생한다. 본 논문에서는 이러한 문제점을 해결하기 위해 비균일 환경을 고려한 위치 인식 기법을 제안한다. 제안하는 기법은 노드 배포 특성을 이용한 밀집 확률 방법과 정확도 향상을 위해 노드 간 거리를 보정하는 기법으로 구성된다. 이를 통해, 비 균일 무선 센서 네트워크 환경에서도 높은 정확도의 센서 측위가 가능하다. 성능평가 결과, 비 균일한 배포 환경에서도 제안하는 기법이 기존 기법에 비해 위치 측위 정확도가 평균 44% 상승하였다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년 학술대회 논문집 정보 및 제어부문
• /
• pp.422-424
• /
• 2006

This paper suggests an automatic spot-inspection algorithm for LCD modules. Usually, LCD module testing is classified by two categories. One is for uniform pattern testing and the other is Non-uniform testing. The uniform pattern testing is well defined and also fully automated in the factory. However non-uniform pattern testing is not defined well yet, so non-uniform testing is conducted by human operators. In this paper a spot-pattern, which is one of non-uniform pattern, inspection algorithms are proposed. The performance of the proposed algorithm is tested by extensive simulations using artificial slot-patterns and real ones in the LCD modules.

• International journal of advanced smart convergence
• /
• 제11권1호
• /
• pp.36-41
• /
• 2022

Recently, to improve the performance of the strongest channel gain user in non-orthogonal multiple access (NOMA) with a non-uniform source and symmetric superposition coding (SSC), a novel bit-to-symbol (BTS) mapping have been proposed. However, only the performance of the user with the stronger channel gain was analyzed. Thus, we compare the bit-error rate (BER) of the new BTS scheme with that of uniform sources, especially for the user with weakest channel gain. First, we show that the performance of the novel BTS scheme for the user with weakest channel gain also improves, compared to that of the uniform sources. Furthermore, the signal-to-noise (SNR) gain of the new BTS scheme over the uniform sourcesis calculated. As a consequence, the novel BTS scheme would improve the performance of the user with weakest channel gain as well as that with the stronger channel gain for SSC NOMA with a non-uniform source.