• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.3A
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• pp.195-202
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• 2005

The third generation cellular system requires the seamless macro/micro mobility support. Mobile IP provides a simple and scalable macro mobility solution but lacks the support for fast handoff control in micro-domain. However, A lot of micro-mobility protocols have been proposed to complement the Mobile IP capability by providing the fast, seamless, and local handoff control. Cellular If also provides the seamless mobility support in limited geographical area. But semi-soft handoff mechanism of Cellular IP produces the packet loss and the duplication problem due to the difference of propagation delay between the new path and the old path. In this paper, we present an efficient handoff mechanism in micro-domain. The proposed handoff mechanism uses the SCD (Suitable Cross Delay) in order to minimize the packet loss and the duplication problem during the handoff. Also, the proposed mechanism is verified by the performance evaluation through the NS-2 Simulation.

• Korean Journal of Materials Research
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• v.18 no.1
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• pp.38-44
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• 2008

The micro-structural changes, strength characteristics, and micro-fractural behaviors at the joint interface between a Sn-4.0wt%Ag-0.5wt%Cu solder ball and UBM treated by isothermal aging are reported. From the reflow process for the joint interface, a small amount of intermetallic compound was formed. With an increase in the isothermal aging time, the type and amount of the intermetallic compound changed. The interface without an isothermal treatment showed a ductile fracture. However, with an increase in the aging time, a brittle fracture occurred on the interface due mainly to the increase in the size of the intermetallic compounds and voids. As a result, a drastic degradation in the shear strength was observed. From a microshear test by a scanning electron microscope, the generation of micro-cracks was initiated from the voids at the joint interface. They propagated along the same interface, resulting in coalescence with neighboring cracks into larger cracks. With an increase in the aging time, the generation of the micro-structural cracks was enhanced and the degree of propagation also accelerated.

• Anatomy & Biological Anthropology
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• v.31 no.4
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• pp.133-142
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• 2018

3D histology is a imaging system for the 3D structural information of cells or tissues. The synchrotron radiation propagation phase contrast micro-CT has been used in 3D imaging methods. However, the simple phase contrast micro-CT did not give sufficient micro-structural information when the specimen contains soft elements, as is the case with many biomedical tissue samples. The purpose of this study is to develop a new technique to enhance the phase contrast effect for soft tissue imaging. Experiments were performed at the imaging beam lines of Pohang Accelerator Laboratory (PAL). The biomedical tissue samples under frozen state was mounted on a computer-controlled precision stage and rotated in $0.18^{\circ}$ increments through $180^{\circ}$. An X-ray shadow of a specimen was converted into a visual image on the surface of a CdWO4 scintillator that was magnified using a microscopic objective lens(X5 or X20) before being captured with a digital CCD camera. 3-dimensional volume images of the specimen were obtained by applying a filtered back-projection algorithm to the projection images using a software package OCTOPUS. Surface reconstruction and volume segmentation and rendering were performed were performed using Amira software. In this study, We found that synchrotron phase contrast imaging of frozen tissue samples has higher contrast power for soft tissue than that of non-frozen samples. In conclusion, synchrotron radiation propagation phase contrast cryo-microCT imaging offers a promising tool for non-destructive high resolution 3D histology.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1997.04a
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• pp.62-67
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• 1997

This paper reprdsents a new scheme of neural network control system analysis the robustues of robot manipulator using digital signal processors. Digtal signal processors, DSPs, are micro-processors that are particularly developed for fast numerical computations involving sums and products of variables. Digital version of most advanced control algorithms can be defined as sums and products of measured variables, thus it can be programmed and executed through DSPs. In additions, DSPs are a s fast in computation as most 32-bit micro-processors and yet at a fraction of their prices. These features make DSPs a viable computational tool in digital implementation of sophisticated controllers. Durng past decade it was proposed the well-established theorys for the adaptive control of linear systems, but there exists relatively little general theory for the adaptive control of nonlinear systems. The proposed neuro network control algorithm is one of learning a model based error back-propagation scheme using Lyapunov stability analysis method.

• Computers and Concrete
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• v.8 no.3
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• pp.327-341
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• 2011

Three-dimensional graphic objects created by MATLAB are exported to the AUTOCAD program through the MATLAB handle functions. The imported SAT format files are used to produce the finite element mesh for MSC.PATRAN. Based on the Monte-Carlo random sample principle, the material heterogeneity of cement composites with randomly distributed fibers is described by the WEIBULL distribution function. In this paper, a concept called "soft region" including micro-defects, micro-voids, etc. is put forward for the simulation of crack propagation in fiber-reinforced cement composites. The performance of the numerical model is demonstrated by several examples involving crack initiation and growth in the composites under three-dimensional stress conditions: tensile loading; compressive loading and crack growth along a bimaterial interface.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.1052-1055
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• 2001

In micro-drilling of brittle materials including glass, cracks occur at the exit surface. In drilling glass, the main type of crack is cone crack. Cone crack is generated by thrust force acting at the bottom surface of the workpiece. Cone crack size could be reduced by changing cutting conditions, but cone crack still existed. Two methods were proposed to prevent crack formation and perfect hole shapes were obtained. One method is attaching two glass plates with water and the other method is constraining two glass plates. The proposed methods eliminated tensile stress acting on the exit surface of glass and prevented crack propagation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.875-878
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• 2006

In the case of a vibration sensitive equipment, it require a vibration free environment to provide its proper function, therefore, it is very important to predict precisely vibration environment of microelectronics production facility due to adjacent blast work. However, it is not easy to evaluate a quantitative vibration response of structure due blast because it can be determined by the characteristics of vibration sources, propagation through rock and soil and dynamic properties of building. In this paper, vibration influence evaluation of micro-electronic Production building induced from adjacent blast activity was performed by real measurement data obtained on ground and structure at same time. And blast vibration allowable limit on ground was supposed by measurement data analysis in order to avoid operation error of precision equipments

• Transactions of Materials Processing
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• v.11 no.7
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• pp.608-613
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• 2002

An ultrasonic machining process is efficient and economical means for precision machining of glass and ceramic materials. However, the mechanism of the process with respect to the crack initiation and propagation and the stress development in the ceramic workpiece subsurface arc still not well understood. In this research, we have investigated the basic mechanism of ultrasonic machining of ultrasonic machining of glass by the experimental approach. For this purpose, we designed and fabricated the desktop micro ultrasonic machine. The feed is controlled precisely by using the constant load control system. During machining experiments, the effects of abrasive characteristics and machining conditions on the surface roughness and the material removal rate are measured and compared.

• Advances in biomechanics and applications
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• v.1 no.2
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• pp.111-126
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• 2014

The microarchitecture of trabecular bone plays a significant role in mechanical strength due to its load-bearing capability. However, the complexity of trabecular microarchitecture hinders the evaluation of its morphological characteristics. We therefore propose a new classification method based on static multiscale theory and dynamic finite element method (FEM) analysis to visualize a three-dimensional (3D) trabecular network for investigating the influence of trabecular microarchitecture on load-bearing capability. This method is applied to human vertebral trabecular bone images obtained by micro-computed tomography (micro-CT) through which primary trabecular bone is successfully visualized and extracted from a highly complicated microarchitecture. The morphological features were then analyzed by viewing the percolation of load pathways in the primary trabecular bone by using the stress wave propagation method analyzed under impact loading. We demonstrate that the present method is effective for describing the morphology of trabecular bone and has the potential for morphometric measurement applications.

• Journal of the korean Society of Automotive Engineers
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• v.13 no.1
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• pp.57-65
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• 1991

It is experimented under rotary bending stress that the spacing of two micro hole flaws is adjacent and that it is distant. In order to observe the behavior of fatigue crack propagation, two kinds of specimens are tested under constant stress and periodic overstressing. Although the crack occurs faster when two micro-hole flaws are adjacent than when they are distant, but there is no difference of the number of fracture cycles between two. The crack propagates slower under low-high block stress than under high-constant stress, and it propagates faster under high-low block stress than under low-constant stress. The influence of two-step block stress is serious right after the stress varies.