• Industrial Engineering and Management Systems
• /
• 제6권2호
• /
• pp.94-105
• /
• 2007

Measurement technology plays an important role in discrete manufacturing industry. Probe-type coordinate measuring machines (CMMs) are normally used to capture the geometry of part features. The measured points are then fit to verify a specified geometry by using the least squares method (LSQ). However, it occasionally overestimates the tolerance zone, which leads to the rejection of some good parts. To overcome this drawback, minimum zone approaches defined by the ANSI Y14.5M-1994 standard have been extensively pursued for zone fitting in coordinate form literature for such basic features as plane, circle, cylinder and sphere. Meanwhile, complex features such as torus have been left to be dealt-with by the use of profile tolerance definition. This may be impractical when accuracy of the whole profile is desired. Hence, the true deviation model of torus is developed and then formulated as a minimax problem. Next, a relatively new and simple population based evolutionary approach, particle swarm optimization (PSO), is applied by imitating the social behavior of animals to find the minimum tolerance zone torusity. Simulated data with specified torusity zones are used to validate the deviation model. The torusity results are in close agreement with the actual torusity zones and also confirm the effectiveness of the proposed PSO when compared to those of the LSQ.

• Advances in concrete construction
• /
• 제5권3호
• /
• pp.221-240
• /
• 2017

The modeling of the mechanical behavior of quasi-brittle materials is still a challenge task, mainly in failure processes when fracture and plasticity phenomena become important actors in dissipative processes which occur in materials like concrete, as instance. Many homogenization-based approaches have been proposed to deal with heterogeneous materials in the last years. In this context, a computational homogenization modeling for concrete is presented in this work using the concept of Representative Volume Element (RVE). The material is considered as a three-phase material consisting of interface zone (ITZ), matrix and inclusions-each constituent modeled by an independent constitutive model. The Representative Volume Element (RVE) consists of inclusions idealized as circular shapes symmetrically and nonsymmetrically placed into the specimen. The interface zone is modeled by means of cohesive contact finite elements. The inclusion is modeled as linear elastic and matrix region is considered as elastoplastic material. A set of examples is presented in order to show the potentialities and limitations of the proposed modeling. The consideration of the fracture processes in the ITZ is fundamental to capture complex macroscopic characteristics of the material using simple constitutive models at mesoscopic level.

• Smart Structures and Systems
• /
• 제21권1호
• /
• pp.65-74
• /
• 2018

In this article, an analytic non-classical model for the free vibrations of nanobeams accounting for surface stress effects is developed. The classical continuum mechanics fails to capture the surface energy effects and hence is not directly applicable at nanoscale. A general beam model based on Gurtin-Murdoch continuum surface elasticity theory is developed for the analysis of thin and thick beams. Thus, surface energy has a significant effect on the response of nanoscale structures, and is associated with their size-dependent behavior. To check the validity of the present analytic solution, the numerical results are compared with those obtained in the scientific literature. The influences of beam thickness, surface density, surface residual stress and surface elastic constants on the natural frequencies of nanobeams are also investigated. It is indicated that the effect of surface stress on the vibrational response of a nanobeam is dependent on its aspect ratio and thickness.

• Computers and Concrete
• /
• 제3권1호
• /
• pp.65-77
• /
• 2006

This study reports the details of the finite element analysis of eleven shear critical partially prestressed concrete T-beams having steel fibers over partial or full depth. Prestressed concrete T-beams having a shear span to depth ratio of 2.65 and 1.59 and failing in the shear have been analyzed using 'ANSYS'. The 'ANSYS' model accounts for the nonlinear phenomenon, such as, bond-slip of longitudinal reinforcements, post-cracking tensile stiffness of the concrete, stress transfer across the cracked blocks of the concrete and load sustenance through the bridging of steel fibers at crack interface. The concrete is modeled using 'SOLID65'-eight-node brick element, which is capable of simulating the cracking and crushing behavior of brittle materials. The reinforcements such as deformed bars, prestressing wires and steel fibers have been modeled discretely using 'LINK8' - 3D spar element. The slip between the reinforcement (rebar, fibers) and the concrete has been modeled using a 'COMBIN39'-non-linear spring element connecting the nodes of the 'LINK8' element representing the reinforcement and nodes of the 'SOLID65' elements representing the concrete. The 'ANSYS' model correctly predicted the diagonal tension failure and shear compression failure of prestressed concrete beams observed in the experiment. The capability of the model to capture the critical crack regions, loads and deflections for various types of shear failures in prestressed concrete beam has been illustrated.

• 한국물환경학회지
• /
• 제21권1호
• /
• pp.79-83
• /
• 2005

Foraging behaviour of false dace, Pseudorasbora parva, was investigated in water flowing at various velocities with the existence of a cavity for rest. The pursuit comprised three succeeding processes such as, approaching, chasing and attacking. Angles between the fish body and the water flow direction and swimming speeds increased in the latter stages of approaching, chasing and attacking. All pursuit angles, swimming speeds and distances increased with flow velocity and peaked at the flow velocity of 7 cm/sec. At higher velocities, however, the fish avoided the use of much energy against the large drag force. The probability of capture and the feeding rate steadily decreased with increasing flow velocity. Under the fast flow, the fish adjusted their swimming speed to get the optimum velocity relative to the flowing water for the energetic budget. Fish spent more time in the cavity as flow velocity increased to avoid the energy expenditure necessitated by the high velocity.

• 한국컴퓨터그래픽스학회논문지
• /
• 제15권2호
• /
• pp.9-17
• /
• 2009

다수 캐릭터가 경쟁적으로 상호작용하는 애니메이션의 합성은 컴퓨터 게임, 애니메이션 등의 응용분야에서 종종 요구되는 중요한 문제이다. 하지만 상대의 예측하기 어려운 행동에 효과적으로 대응하는 전략적 경쟁 양상을 모사하는 것은 어려운 문제로 남아있다. 본 논문은 다수 에이전트 학습 분야에서 제안된 마르코프 게임 강화학습 알고리즘을 촬영된 동작 데이터로부터 생성된 행위 모델에 적용하여 사실적인 경쟁 애니메이션을 합성하는 방식을 제안한다. 추격-회피, 간격 유지, 총격전 등의 다양한 경쟁적 상황에 대하여 효과적인 전략을 학습하여 흥미로운 애니메이션을 합성하는 예제들을 통하여 본 논문이 제안하는 방법의 효용성을 보인다.

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제15권2호
• /
• pp.208-222
• /
• 2015

For the performance-efficient integration of IPs on an SoC utilizing heterochronous multi-clock domains, we propose a synchronization scheme that causes low latency overhead when data are crossing clock boundaries. The proposed synchronization scheme is composed of a clock predictor and a synchronizer. The clock predictor of a sender clock domain produces a predicted clock that is used in a receiver clock domain to detect possible synchronization failures in advance. When the possible synchronization failures are detected, a synchronizer at the receiver delays data-capture times to avoid the possible synchronization failures. From the simulation of the proposed scheme through SPICE modeling using a Chartered $0.18{\mu}m$ CMOS process, we verified the functionalities and timing behavior of the clock predictor and the synchronizer. The simulation results show that the clock predictor produces a predicted clock before a synchronization failure, and the synchronizer samples data correctly using the predicted clock.

• Steel and Composite Structures
• /
• 제26권3호
• /
• pp.273-287
• /
• 2018

Buckling and free vibration analysis of sandwich micro plate (SMP) integrated with piezoelectric layers embedded in orthotropic Pasternak are investigated in this paper. The refined Zigzag theory (RZT) is taken into consideration to model the SMP. Four different types of functionally graded (FG) distribution through the thickness of the SMP core layer which is reinforced with single-wall carbon nanotubes (SWCNTs) are considered. The modified couple stress theory (MCST) is employed to capture the effects of small scale effects. The sandwich structure is exposed to a two dimensional magnetic field and also, piezoelectric layers are subjected to external applied voltages. In order to obtain governing equation, energy method as well as Hamilton's principle is applied. Based on an analytical solution the critical buckling loads and natural frequency are obtained. The effects of volume fraction of carbon nanotubes (CNTs), different distributions of CNTs, foundation stiffness parameters, magnetic and electric fields, small scale parameter and the thickness of piezoelectric layers on the both critical buckling loads and natural frequency of the SMP are examined. The obtained results demonstrate that the effects of volume fraction of CNTs play an important role in analyzing buckling and free vibration behavior of the SMP. Furthermore, the effects of magnetic and electric fields are remarkable on the mechanical responses of the system and cannot be neglected.

• Computers and Concrete
• /
• 제20권5호
• /
• pp.617-625
• /
• 2017

Prestress force identification (PFI) is crucial to maintain the safety of prestressed concrete bridges. A synergic identification method has been proposed recently by the authors that can determine the prestress force (PF) and the excitation force simultaneously in prestressed concrete beams with good accuracy. In this paper, the ability of this method in the application with prestressed concrete box-girder bridges is demonstrated. A reasonable assumption is made to capture the similarity of the dynamic behavior of the prestressed concrete box-girder bridge and a beam under a certain loading scenario, and the feasibility of this method for application in a prestressed box-girder bridge is affirmed. A comprehensive laboratory test program is conducted, and the effects of PF, excitation, measuring time and uncertainties are studied. Results show that the proposed method can predict the PF and the excitation force in a prestressed concrete box-girder accurately and has a great robustness against uncertainties.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2008년도 춘계학술대회논문집
• /
• pp.142-143
• /
• 2008

In the present work, high-speed video images of the ground take-off flight of a live butterfly were captured and their dynamic motions during the first full-stroke were analyzed. To capture the dynamic images of the take-off motion, the experimental setup consisted of a high-speed camera, a Xenon lamp as a light source and a transparent chamber of $15^W{\times}15^L{\times}17^H$ $cm^3$ in physical size. The ambient temperature and supplementary lighting devices were precisely controlled. The weight and wing span of the butterfly tested in this study was 104 mg and 63.14 mm, respectively. The ground take-off images were captured with 4000 fps with a spatial resolution of (1024${\times}$512) pixels. The period of the first full-stroke was 80.5ms and the flapping speed of downstroke was 2 times faster than that of upstroke. As a result, butterflies used the fling and near-clap motion to generate lifting force and an interesting take-off behavior of early pronation and downstroke was observed.