• Proceedings of the KSME Conference
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• 2003.04a
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• pp.119-124
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• 2003

In this study, retardation behavior of fatigue crack under single overloading of the mixed mode I+II state was experimentally investigated. To produce single overload in the mixed mode I+II state, the compact tension shear (CTS) specimen and loading device were used. The propagation tests for fatigue crack were performed under mode I loading overloading afterwards. We examined the observed deformation aspects, variation of fatigue life and crack propagation rate, and the aspects of retardation behavior from tests. The retardation effect of mixed-mode single overload on fatigue crack propagation behavior was smaller than that of mode I single overload. It has been confirmed that the retardation behavior did not immediately appear and the retardation length was short when the component of mixed-mode overload was changed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1508-1512
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• 2003

In this study, retardation behavior of fatigue crack under single overloading of the mixed mode state was experimentally investigated. To produce single overload in the mixed mode I+II state, the compact tension shear (CTS) specimen and loading device were used. The propagation tests for fatigue crack were performed under mode I and mixed-mode loading overloading afterwards. We examined the observed deformation aspects, the variation of fatigue life and crack propagation rate, and the aspects of retardation behavior from tests. The retardation effect of mixed-mode single overload on fatigue crack propagation behavior was smaller than that of mode I single overload. Also the loading modes of variable and constant amplitude loads have influence on the retardation behavior of fatigue cracks.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.201-204
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• 1999

Polarization mode dispersion (PMD) restrict the bend-width of single mode optical filer, and it is important parameter in the optical fiber having long-length. Although fiber has perfect circular symmetry, fiber bending, twisting and laws governing manufacture cause additional Polarization mode dispersion. The effect of polarization mode dispersion in general single mode fiber of long length is discussed in this paper. Measurement of PMD with random mode coupling were conducted in two kind of fibers using different laws governing manufacture and interferometric method.

• Korean Journal of Optics and Photonics
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• v.14 no.3
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• pp.298-305
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• 2003

We have calculated the single mode yield of index-coupled (IC) DFB lasers above threshold for several kL, and facet reflectivity combinations, and investigated the correlation between those results and the single mode yield as a function of f number at the threshold. As a result, there is little correlation between the single mode yield above threshold and the single mode yield as a function of f number at the threshold. The single mode yields above threshold for kL of 0.8 and 1.25 is larger than those for kL, of 2 and 3 due to the spatial hole burning effect. Also, we have investigated the effect of the reflectivity of the AR facet on the single mode yield for AR-HR and AR-CL combinations. For AR-HR combinations, the single mode yield increases as the reflectivity of the AR facet decreases. However, for AR-CL combinations, the reflectivity of the AR facet for the largest single mode yield exists. In the single mode yield calculations for IC DFB lasers in this paper, the single mode yield for kL of 0.8 with AR(1％)-HR combination is largest above threshold.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.359-364
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• 2004

In this study, experiments were tried on the mixed-mode I+II single overloading model which changes the loading mode of overload and fatigue load. Aspects of deformation field in front of the crack which is formed by mixed-mode I+II single overloading were experimentally studied. Then the shape and size of mixed-mode plastic zone were approximately calculated. The propagation behavior of fatigue crack was examined under the test conditions combined by changing the loading mode. The behavior of fatigue cracks were greatly affected by shapes of plastic deformation field and applying mode of fatigue load. Accuracy of prediction and evaluation for fatigue life may be improved by considering all aspects of deformation and behavior of fatigue cracks.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.11
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• pp.1976-1980
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• 2008

This paper deals the characteristic analysis of Switched Reluctance Motor(SRM) driven by single-pulse mode considering dc link voltage ripple. Two dimensional time-stepped Finite Element Method(FEM) is used to analyze the characteristic of SRM driven by single-pulse mode with dc link voltage ripple. The analysis results is verified by experimental test.

• Korean Journal of Optics and Photonics
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• v.14 no.3
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• pp.292-297
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• 2003

A diode-pumped single-mode Nd:YV $O_4$ green laser was developed. Frequency doubling of the laser was achieved by using an intracavity KTP generated green beam (532 nm). By comparing the diode laser spectrum with absorption spectrum of the Nd:YV $O_4$ crystal, we found optimal operating temperature of the diode laser. From output power measured for various mirror curvatures and cavity lengths, we found the optimal matching of TE $M_{00}$ mode with the pump beam gives the best efficiency. When the pump power was 1.9 W, 80 ㎽ of TE $M_{00}$ mode green beam was obtained. We tried to get a single longitudinal mode lasing as the fluctuation of the laser power was caused by the shift of longitudinal modes and the beating between the modes. We tested the intracavity etalon method and birefringent filter method for single mode operation. The etalon method resulted in the best single mode output power of 60 ㎽. The power fluctuation of the single-mode laser was reduced to 1/10 of that of the multi-mode laser.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.6
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• pp.109-116
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• 2004

In this study, when variable-amplitude load with various applying mode acts on the pre-crack tip, we examined how fatigue cracks behave. Hence aspects of the deformation caused by changing the applying mode of single overload and propagation behavior of fatigue crack were experimentally examined: What kinds of the deformation would be formed at pre-crack and its tip\ulcorner What aspects of the residual plastic deformation field would be formed in front of a crack\ulcorner How aspects of the plastic zone could be evaluated\ulcorner As applying mode of single overloading changes, the deformation caused by tensile and shear loading variously showed in each applying mode. The different aspects of deformation make influence on propagation behavior of cracks under constant-amplitude fatigue loading after overloading with various modes. We tried to examine the relationship between aspects of deformation and fatigue behavior by comparing the observed deformation at crack and crack propagation behavior obtained from fatigue tests.

• Korean Journal of Optics and Photonics
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• v.14 no.5
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• pp.521-529
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• 2003

For complex-coupled (CC) DFB lasers, we found that there might be little correlation between the single mode yields at threshold and above threshold. At threshold, the single mode yield considering f number of in-phase (IP) CC DFB lasers is the same as that of anti-phase (AP) CC DFB lasers. However, the single mode yield as a function of injection current above threshold of IP CC DFB lasers is much different from that of AP CC DFB lasers. In the case of IP CC DFB lasers, the single mode yield increases as the coupling coefficient ratio (CR) increases, while, in the case of AP CC DFB lasers, the single mode yield decreases rapidly regardless of CR as the injection current increases. In the case of AR-HR combinations, the effect of AR ref1ectivity on the single mode yield increases as the coupling strength decreases. As the coupling strength decreases, the CR at which the increase rate of the single mode yield starts to decrease, increases, and the maximum single mode yield increases. Single mode yields of AR-HR and AR-AR combinations are larger than those of AR-CL and CL-CL combinations.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.663-664
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• 2006

In the electronic, medical, aerospace and automobile industries, many products and parts are manufactured by joining. Recently, as these get smaller, micro joining is becoming more and more important. In this study, micro wire-to-micro wire parallel joining was performed using single mode fiber laser. Maximum power of the fiber laser is 100 W. The CCD(Charge- Coupled Device, CCD) camera to observe the specimen was made up. The objective was applied to micro joining system to make a small spot size of laser beam. In order to control the target position, micro-multi-axis-stage was set up. This paper presents results for the single mode fiber laser joining of micro wires.