• Advances in nano research
• /
• 제12권3호
• /
• pp.231-251
• /
• 2022

Dynamic behavior of temperature-dependent Reddy functionally graded (RFG) nanobeam subjected to thermomagnetic effects under the action of moving point load is carried out in the present work. Both symmetric and sigmoid functionally graded material distributions throughout the beam thickness are considered. To consider the significance of strain-stress gradient field, a material length scale parameter (LSP) is introduced while the significance of nonlocal elastic stress field is considered by introducing a nonlocal parameter (NP). In the framework of the nonlocal strain gradient theory (NSGT), the dynamic equations of motion are derived through Hamilton's principle. Navier approach is employed to solve the resulting equations of motion of the functionally graded (FG) nanoscale beam. The developed model is verified and compared with the available previous results and good agreement is observed. Effects of through-thickness variation of FG material distribution, beam aspect ratio, temperature variation, and magnetic field as well as the size-dependent parameters on the dynamic behavior are investigated. Introduction of the magnetic effect creates a hardening effect; therefore, higher values of natural frequencies are obtained while smaller values of the transverse deflections are produced. The obtained results can be useful as reference solutions for future dynamic and control analysis of FG nanobeams reinforced nanocomposites under thermomagnetic effects.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
• /
• pp.111-116
• /
• 2002

The types of service using location Information are being various and extending it's domain as wireless internet technology is developing and it's application part is widespread, so it is prospected that LBS (Location-Based Services) will be killer application in wireless internet services. This location information is basic and high value-added information, and this information services make prior GIS (Geography Information System) to be useful to anybody. The acquisition of this location information from moving object is very important part for these LBS. After this, when LBS is familiar to everybody, we can predict that LBS system load is so heavy for the acquisition of so many subscribers and vehicles. Moving object database (MODB) system manages objects like subscribes and vehicles that are moving and have telecommunication terminal checked one's location. MODB is consists of 4 part, moving object location acquisition part, moving object location storage part, moving object query processing part, and moving object application p art. In this MODB system, acquisition of moving object location part must provide guarantee location information as well as reduce telecommunication overhead. In this paper, we study of problems in acquisition a huge number o f moving objects location and design some acquisition strategies to reduce telecommunication overhead. And after implementation these strategies, we estimate performance of this system and quality of information.

• 전력전자학회논문지
• /
• 제5권5호
• /
• pp.459-466
• /
• 2000

전정기관 자극용 회전자극기에 있어서 외란 관측기를 이용한 PMSM(permanent Magnet Synchronous Motor)의 강인한 정밀 속도 제어 방법에 대해서 제안한다. 본 제어기는 더욱 정확한 전정기관 평가를 가능하게 한다. 현기증을 유발시키기 위해서 지면에 수직인 회전축을 갖는 2D 자극기가 사용되어져 왔다. 그러나 정확한 현기증의 원인 규명을 위해서 회전축을 기울인 3D 자극기가 필요하다. 3D 자극기와 같이 기울임을 갖는 회 전자극기의 경우, 회전축에 대한 무게중심의 이격은 불평형 부하를 유발하게 된다. 이러한 경우에 대하여 강인한 속도 제어를 위한 외란 관측기를 이용하는 보상방법을 연구하였다 정확한 전정기관 자극을 위해 정밀한 속도 제어가 필요하며, 이러한 정밀 속도 제어에 있어서 외란의 영향을 제거하기 위해 데드비트 관측기와 같은 높은 이득을 갖는 관측기가 필요하다. 외란 관측기의 위치 제어에 대한 응용이 연구되어 졌다. 그러나 속도와 같은 노이즈가 많은 신호를 이용한 속도 제어에 있어서 데드비트 관측기는 노이즈 증폭 효과를 가져와 적용이 어렵다는 문제를 가지고 있다. 따라서 MA(Moving Average)처리를 이용하여 노이즈 효과를 저감한다. 이상의 제안된 알고리즘의 효과를 실험으로 보였다.

• Structural Engineering and Mechanics
• /
• 제82권1호
• /
• pp.31-40
• /
• 2022

In structural engineering, the material properties of the structures such as elastic modulus, shear modulus, density, and size may not be deterministic and may vary at different locations. The dynamic response analysis of such structures may need to consider these properties as stochastic. This paper introduces a stochastic finite element method (SFEM) approach to analyze moving loads problems. Firstly, Karhunen-Loéve expansion (KLE) is applied for expressing the stochastic field of material properties. Then the mathematical expression of the random field is substituted into the finite element model to formulate the corresponding random matrix. Finally, the statistical moment of the dynamic response is calculated by the point estimation method (PEM). The accuracy and efficiency of the dynamic response obtained from the KLE-PEM are demonstrated by the example of a moving load passing through a simply supported Euler-Bernoulli beam, in which the material properties (including elastic modulus and density) are considered as random fields. The results from the KLE-PEM are compared with those from the Monte Carlo simulation. The results demonstrate that the proposed method of KLE-PEM has high accuracy and efficiency. By using the proposed SFEM, the random vertical deflection of a high-speed railway (HSR) bridge is analyzed by considering the random fields of material properties under the moving load of a train.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2010년도 춘계 학술논문 발표대회 1부
• /
• pp.67-70
• /
• 2010

This study investigates the physical properties of the acrylic emulsion mortar according to variable composition set of redispersible emulsion powders. This materials have to be composed of many types of binders and chemical additives. So it is difficult to decide suitable mixing proportion of composition materials. The redispersible emulsion powders using "2, 4, 6, 8kg" of EVA polymers dispersion ranges are prepared with acrylic emulsion mortars and were tested for basic characteristics such as flexural, and compressive strength, wheel load. Through experiments we found that the improved formula to satisfy the standard of wheel load by EVA polymers, and the masration rangs between about 2.0% to 2.6% which the white portland cenmet and EVA polymers is good for resistauce wheel load.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
• /
• pp.401-405
• /
• 2017

연속가변 추력기는 비행체의 위치 또는 자세 변경 및 연소실 내부의 압력 조절을 위하여 정밀 추력 조절이 요구된다. 이를 위하여 연소실 내부의 노즐 목 근처에 설치된 핀틀 구조물을 앞/뒤로 움직여 추력을 조절하고, 핀틀 구조물을 움직이기 위하여 구동장치를 사용한다. 본 논문에서는 연속가변 추력기용 구동장치를 개발하였으며, 운용조건에서의 부하를 모사하기 위한 부하시험장비를 개발하였다. 또한, 개발된 부하시험장비를 이용하여 구동장치의 성능 시험을 수행하였다.

• Advances in Computational Design
• /
• 제4권3호
• /
• pp.307-326
• /
• 2019

A low computational cost semi-analytical method is developed, based on eigenfunction expansion, to study the vibration of rectangular plates subjected to a series of moving sprung masses, representing a bridge deck under multiple vehicle or train moving loads. The dynamic effects of the suspension system are taken into account by using flexible connections between the moving masses and the base structure. The accuracy of the proposed method in predicting the dynamic response of a rectangular plate subjected to a series of moving sprung masses is demonstrated compared to the conventional rigid moving mass models. It is shown that the proposed method can considerably improve the computational efficiency of the conventional methods by eliminating a large number of time-varying components in the coupled Ordinary Differential Equations (ODEs) matrices. The dynamic behaviour of the system is then investigated by performing a comprehensive parametric study on the Dynamic Amplification Factor (DAF) of the moving loads using different design parameters. The results indicate that ignoring the flexibility of the suspension system in both moving force and moving mass models may lead to substantially underestimated DAF predictions and therefore unsafe design solutions. This highlights the significance of taking into account the stiffness of the suspension system for accurate estimation of the plate maximum dynamic response in practical applications.

• 한국공간정보시스템학회 논문지
• /
• 제8권3호
• /
• pp.89-103
• /
• 2006

무선인터넷 기술의 발달과 응용의 확산으로 위치정보를 이용한 위치기반서비스 형태는 더욱더 다양해 지고 있다. 위치기반 서비스 중 특정지역에 진입하거나 벗어날 경우에 자동으로 정보를 제공하는 위치기반 경보서비스는 향후 LBS의 가장 중요한 서비스가 될 것으로 전망된다. 그러나 위치기반 경보서비스를 제공하기 위해서는 대상이 되는 이동체의 위치정보를 주기적으로 빈번하게 조회해야 한다. 이러한 방법은 이동성을 가지는 수많은 이동체의 위치정보를 지속적이면서도 대량으로 조회해야 함으로써 심각한 시스템의 부하와 비용증가를 초래한다. 지금까지 연구되고 있는 이동체를 위한 위치조회 방법은 위치기반 경보서비스를 제공 하기 위한 효율적인 위치조회 및 구조에는 적합하지 않다. 이에 본 논문에서는 위치기반 경보서비스를 제공하기 위해 대용량의 위치정보를 조회함에 있어서, 이동체의 이동 패턴을 이용하여 불필요한 위치정보 조회 회수를 줄임으로써 시스템의 부하를 줄이는 효율적인 이동체 조회 방법을 제시하고 기존의 방법과 비교 실험하고자 한다.

• 한국강구조학회 논문집
• /
• 제14권6호
• /
• pp.711-720
• /
• 2002

본 연구에서는 곡선교에서 주행차량에 의한 동적 응답을 보다 정밀하게 구현할 수 있는 3차원 해석 모형을 개발하였다. 원심력에 의한 차량의 롤링운동에 따른 차량의 쏠림현상을 구현하여 곡선교의 대표적인 응답특성인 편경사와 곡률반경에 따른 동적응답과 받침의 변화에 따른 동적 응답 특성을 규명하였으며, 2가지 지점조건에 대하여 주행차량에 의한 곡선교의 동적 특성을 비교 분석하였다. 또한 이와 함께 곡선교에서 어떤 파라미터가 하중 분배에 가장 효율적인가를 비교 분석하였다. 동적해석결과 받침이 외측에 배치된 경우가 중앙에 배치된 경우보다 더 유리하게 분석되었으며, 여러 가지 조건에 따라 하중분배 특성이 다르게 나타남을 알 수 있었다.

• Interaction and multiscale mechanics
• /
• 제3권4호
• /
• pp.321-331
• /
• 2010

A new technique is proposed for bridge structural damage detection based on spatial wavelet analysis of the time history obtained from vehicle body moving over the bridge, which is different from traditional detection techniques based on the bridge response. A simply-supported Bernoulli-Euler beam subjected to a moving spring-mass unit is established, with the crack in the beam simulated by modeling the cracked section as a rotational spring connecting two undamaged beam segments, and the equations of motion for the system is derived. By using the transfer matrix method, the natural frequencies and mode shapes of the cracked beam are determined. The responses of the beam and the moving spring-mass unit are obtained by modal decomposition theory. The continuous wavelet transform is calculated on the displacement time histories of the sprung-mass. The case study result shows that the damage location can be accurately determined and the method is effective.