• Korea-Australia Rheology Journal
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• 제14권3호
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• pp.93-105
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• 2002

Experimental methods for making quantitative measurements of velocity fields in non-Newtonian fluids are reviewed. Techniques based on light scattering spectroscopy - laser Doppler velocimetry and homodyne light scattering spectroscopy, techniques based on imaging the displacement of markers - including particle image velocimetry and molecular tagging velocimetry, and techniques based on nuclear magnetic resonance imaging are discussed. The special advantages and disadvantages of each method are summarized, and their applications to non-Newtonian flows are briefly reviewed. Example data from each technique are also included.

• Journal of Mechanical Science and Technology
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• 제20권3호
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• pp.310-318
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• 2006

In this study, we investigate the feasibility of in-situ crack propagation by using a double cleavage drilled compression (DCDC) specimen showing a slow crack velocity down to 0.03 mm/s under 0.01 mm/s of displacement control. Finite element analysis predicted that the DCDC specimens would show at least 4.3 fold delayed crack initiation time than conventional tensile fracture specimens under a constant loading speed. Using DCDC specimens, we were able to observe the in-situ crack propagation process in a particle reinforced transparent polymer composite. Our results confirmed that the DCDC specimen would be a good candidate for the in-situ observation of the behavior of particle reinforced composites with slow crack velocity, such as the self-healing process of micro-particle reinforced composites.

• 한국전기전자재료학회논문지
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• 제22권10호
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• pp.844-849
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• 2009

The moving behavior of particle with voltage biasing is studied by analyzing the displacement current generated in electrodes and the drift current by moving particles in cell gap. These currents are ascertained by optical reflectivity on the panel. We obtained the saturated current after a peak in threshold voltage which is coincide with reflectivity of 80%. These saturated optical reflectivity and its drift current offer optimum q/m of particles and driving voltage and can be analytically studied on grey scale methods. Especially regional analysis is useful to aging and driving voltage and the understanding of operating mechanism of charged particle type display.

• Structural Engineering and Mechanics
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• 제51권4호
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• pp.547-564
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• 2014

This study focuses on the application of an active tuned mass damper (ATMD) for controlling the seismic response of an 11-story building. The control action is achieved by combination of a fuzzy logic controller (FLC) and Particle Swarm Optimization (PSO) method. FLC is used to handle the uncertain and nonlinear phenomena while PSO is used for optimization of FLC parameters. The FLC system optimized by PSO is called PSFLC. The optimization process of the FLC system has been performed for an 11-story building under the earthquake excitations recommended by International Association of Structural Control (IASC) committee. Minimization of the top floor displacement has been used as the optimization criteria. The results obtained by the PSFLC method are compared with those obtained from ATMD with GFLC system which is proposed by Pourzeynali et al. and non-optimum FLC system. Based on the parameters obtained from PSFLC system, a global controller as PSFLCG is introduced. Performance of the designed PSFLCG has been checked for different disturbances of far-field and near-field ground motions. It is found that the ATMD system, driven by FLC with the help of PSO significantly reduces the peak displacement of the example building. The results show that the PSFLCG decreases the peak displacement of the top floor by about 10%-30% more than that of the FLC system. To show the efficiency and superiority of the adopted optimization method (PSO), a comparison is also made between PSO and GA algorithms in terms of success rate and computational processing time. GA is used by Pourzeynali et al for optimization of the similar system.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.188-197
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• 2010

This paper presents experimental results of a series of 1-g shaking table model tests performed on end-bearing single piles and pile groups to investigate the effect of particle size on the dynamic behavior of soil-pile systems. Two soil-pile models consisting of a single-pile and a $4{\times}2$-pile group were tested twice; first using Jumoonjin sand, and second using Australian Fine sand, which has a smaller particle size. In the case of single-pile models, the lateral displacement was almost within 1% of pile diameter which corresponds to the elastic range of the pile. The back-calculated p-y curves show that the subgrade reaction of the Jumoonjin-sand-model ground was larger than that of the Australian Fine-sand-model ground at the same displacement. This phenomenon means that the stress-strain behavior of Jumoonjin sand was initially stiffer than that of Australian Fine sand. This difference was also confirmed by resonant column tests and compression triaxial tests. And the single pile p-y backbone curves of the Australian fine sand were constructed and compared with those of the Jumoonjin sand. As a result, the stiffness of the p-y backbone curves of Jumunjin sand was larger than those of Australian fine sand. Therefore, using the same p-y curves regardless of particle size can lead to inaccurate results when evaluating dynamic behavior of soil-pile system. In the case of the group-pile models, the lateral displacement was much larger than the elastic range of pile movement at the same test conditions in the single-pile models. The back-calculated p-y curves in the case of group pile models were very similar in both sands because the stiffness difference between the Jumoonjin-sand-model ground and the Australian Fine-sand-model ground was not significantly large at a large strain level, where both sands showed non-linear behavior. According to a series of single pile and group pile test results, the evaluation group pile effect using the p-multiplier can lead to inaccurate results on dynamic behavior of soil-pile system.

• Geomechanics and Engineering
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• 제10권1호
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• pp.1-19
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• 2016

This paper presents the results of an intensive experimental investigation on cyclic behavior of various sands and structural materials interface. Comprehensive measurements of the horizontal displacement and shear stresses developed during testing were performed using an automated constant normal load (CNL) cyclic direct shear test apparatus. Two different particle sizes (0.5 mm-0.25 mm and, 2.0 mm-1.0 mm) of sands having distinct shapes (rounded and angular) were tested in a cyclic direct shear testing apparatus at two vertical stress levels (${\sigma}=50kPa$, and 100 kPa) and two rates of displacement ($R_D=2.0mm/min$, and 0.025 mm/min) against various structural materials (i.e., steel, concrete, and wood). The cyclic direct shear tests performed during this investigation indicate that (i) the shear stresses developed during shearing highly depend on both the shape and size of sand grains; (ii) characteristics of the structural materials are closely related to interface response; and (iii) the rate of displacement is slightly effective on the results.

• 설비공학논문집
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• 제19권4호
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• pp.299-306
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• 2007

Recently, the numerical analysis using person shape model for CFD (Computational Fluid Dynamic) has been researched widely for the thermal comfort and inhaled air quality of human body in the indoor environments. The purpose of this research is to examine the characteristic of airflow and thermal environment around human body by the experiment of displacement ventilation that assumes the indoor environment of natural convection. In this study, thermal manikin was used instead of real human body. The Airflow characteristic around human body was measured in precision by PIV (Particle Image Velocimetry). This experimental result will be used as data for CFD benchmark test using person shape model.

• Structural Engineering and Mechanics
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• 제89권4호
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• pp.383-397
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• 2024

To improve the vibration control performance and applicability of traditional particle tuned mass damper (PTMD) and realize the significant characteristic of lightweight design, this study proposes a novel particle tuned mass inerter system (PTMIS) by introducing inerter system (IS) to the PTMD. In the study, the motion equation of single degree of freedom (SDOF) structure attached with PTMIS is established first, then the variation law of the system's vibration reduction performance (VRP) is discussed through parameter analysis, and it is compared with the PTMD to analyze its VRP advantages. Finally, its vibration reduction (VR) mechanism from the perspective of core control force and energy analysis is explored, and its cavity relative displacement from the application perspective is analyzed. The results show that the PTMIS can remarkably improve the vibration control effectiveness of the PTMD. The reason is that the inerter can store energy and transfer the energy to the cavity and particles, which further stimulates the interaction between the two parts, thereby improving the nonlinear energy consumption effectiveness. Also, the IS can amplify the damping element's energy dissipation efficiency. In addition, the PTMIS can effectively reduce the working stroke of the PTMD, and through the analysis of the lightweight characteristics of the PTMIS, it is found that its lightweight advantage can reach nearly 100%.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.159-169
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• 2008

In general, it is considered that a pillar between closely-spaced tunnel is sensitive for stress concentration. Stability of a pillar is key factor for excavation of closely-spaced tunnel. In this paper, the study is focused on tracing the behaviors, displacement and plotting damages around tunnels that is modelled with Particle Flow Code, $PFC^{2D}$. Parametric study was performed with changing distance between center of tunnels and coefficient of earth pressure(K). Scaled-model tests were also carried out to validate a numerical analysis model. It was found that $PFC^{2D}$ could show dynamic visualized result in quite good agreement with the experimental test.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1998년도 봄 학술발표회 논문집
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• pp.53-59
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• 1998

A new algorithm using meshless particle method for the analysis of crack propagation problems is presented. The meshless particle method requires only a set of nodes and the description of boundaries in its formulation. The method is particulary useful for crack propagation problems due to the absence of any predefined element connectivity. Formulation procedures for the construction of displacement and shape functions are described. A numerical integration scheme and a strategy for the consideration of crack propagation are also described. Numerical examples show that the proposed method is very convenient and efficient in modeling crack problems and can guarantee the accuracy of solution in crack propagation analysis.