• International Journal of Aeronautical and Space Sciences
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• v.15 no.2
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• pp.163-172
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• 2014

This paper proposes a novel guidance law based on the block backstepping sliding mode control and extended state observer (ESO), which also takes into account the autopilot dynamic characteristics of the near space interceptor (NSI), and the impact angle constraint of attacking the maneuvering target. Based on the backstepping control approach, the target maneuvers and the parameter uncertainties of the autopilot are regarded as disturbances of the outer loop and inner loop, respectively. Then, the ESO is constructed to estimate the target acceleration and the inner loop disturbance, and the block backstepping sliding model guidance law is employed, based on the estimated disturbance value. Furthermore, in order to avoid the "explosion of complexity" problem, first-order low-pass filters are also introduced, to obtain differentiations of the virtual control variables. The stability of the closed-loop guidance system is also proven, based on the Lyapunov theory. Finally, simulation results demonstrate that the proposed guidance law can not only overcome the influence of the autopilot dynamic delay and target maneuvers, but also obtain a small miss distance.

• The Journal of Society for e-Business Studies
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• v.10 no.2
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• pp.59-88
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• 2005

The recent development of IT, consolidation of communications and multimedia technology have brought enormous changes in many organizations. These changes are enabling the new educational environments such as distance learning and virtual education. Particularly e-Learning has grown rapidly in business training fields. In this regard, the primary purpose of this study is to investigate which factors of e-Learning influence education and training in business organizations through an empirical survey. The results show that most of hypotheses get significant support. Implications of these findings are discussed for researchers and practitioners.

• Structural Engineering and Mechanics
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• v.13 no.3
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• pp.313-328
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• 2002

Based on the orthotropic hypoelasticity formulation, a triaxial constitutive model of concrete is proposed. To account for increasing ductility in high confinement of concrete, the ductility enhancement is considered using so called the strain enhancement factor. It is also developed a three-dimensional finite element model for reinforced concrete structural members based on the proposed constitutive law of concrete with the smeared crack approach. The concrete confinement effects due to the beam-column joint are investigated through numerical examples for simple beam and structural beam member. Concrete at compression fibers in the vicinity of beam-column joint behaves dominant not only by the uniaxial compressive state but also by the biaxial and triaxial compressive states. For the reason of the severe confinement of concrete in the beam-column joint, the flexural critical cross-section is observed at a small distance away from the beam-column joint. These observations should be utilized for the economic design when the concrete structural members are subjected to high confinement due to the influence of beam-column joint.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.1
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• pp.92-103
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• 1999

The fuel spray behavior in the intake port of an electronic control port irijection gasoline engine has a strong influence on engine performance, exhaust emission and fuel consumption. Thus, in this study, fuel spray behavior and flow characteristics of the air assist gasoline spray injected into a suction flow in a simulated rectangular intake port have boon investigated. Macro-behavior of spray characteristics was investigated by means of visualization and the measurements of SMD and velocity were made by PDPA. For analysis the flow field with droplets size, droplets are classified five droplets size groups. As a result, the normal distance of suction flow increasing, the relatively large droplets distribution and SMD increase because small droplets easily follow suction flow. Near impinging wail, after impinging against the wall, secondary atomized small droplets of D < $30{\mu}m$ bound from the wall. And the increasement of suction flow progress to the large droplets of D > $100{\mu}m$ distribution. Therefore, SMD are apparently increased near impinging wall, Z/d = 9.0.

• Aerospace Engineering and Technology
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• v.11 no.2
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• pp.12-18
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• 2012

In this paper, impacts on the COMS MI images during the COMS eclipse period were analyzed and the method to eliminate the contaminated area was investigated. Main effect on the meteorological images during the eclipse is a stripping effect due to a strong stray light. The quantitative analyses were conducted during the COMS In-Orbit-Test period and the impacts of the stray light on the four infrared channels of the COMS MI according to the distance with respect to the Sun were examined. Based on the typical case of the stray light influence on the infrared channel of the MI, the intensity of contamination due to the stray light was investigated for each channel using the computed COMS eclipse information. The effectiveness of removal of a contaminated area by replacing the SWIR with the combined WINDOW channels was promising.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.3
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• pp.99-104
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• 2003

Alumina/zirconia-glass composites prepared by melt-infiltration were investigated to evaluate the influence of zirconia addition on mechanical and optical properties of the composites and glass penetration kinetics. The infiltration distance was parabolic with respect to time as described by the Washburn equation and the penetration rate constant, K, decreased due to the reduction In pore size as the amount of zirconia rose. The zirconia addition increased lightness ($L^*$) but reduced K, transmittance and color sharpness ($C^*$) It can be concluded that the zirconia addition was not effective to the mechanical properties of the composites due to the increase in porosity even though the toughness of the composites increased when zirconia was added up to 15 wt%.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.463-470
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• 2000

In tunnel excavation by blast beneath the surface structures in urban area, the characteristics of ground vibration induced by blast and its influence on surface structures are analyzed by the field test and the numerical analysis on dynamic behaviors of the structure. According to the field test on the propagating characteristics of blast vibration through the rock mass and the concrete foundation pile. the attenuation index of peak particle velocity with distance shows the range of 1.7∼2.0 for the rock mass and the range of 2.0∼2.3 for the concrete pile. This shows that the blast vibration reduces more rapidly in the concrete pile. It is known from the numerical analysis on dynamic behavior of the structure that the coefficient of response, velocity ratio of structure response to input wave, is different according to the story of the structure. It can be said from this research that the characteristics of the ground vibration and the dynamic behavior of the structure should be well evaluated and be considered as important factors for safe blasting design especially in underground excavation at shallow depth in urban area.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.939-948
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• 2006

The structural anisotropy and heterogeneity of rock mass, caused by discontinuities and weak zones, have a great influence on the deformation behavior of tunnel. Tunnel construction in these complex ground conditions is very difficult. No matter how excellent a geological investigation is, local uncertainties of rock mass conditions still remain. Under these uncertain circumstances, an accurate forecast of the ground conditions ahead of the advancing tunnel face is indispensable to safe and economic tunnel construction. This paper presents the effect of anisotropy and heterogeneity of the rock masses to be excavated by numerical analysis. The influences of distance from weak zone, the size or dimension, the different stiffness and the orientation of weak zones are analysedby 2-D and 3-D finite element analysis. By analysing these numerical results, the tunnel behavior due to excavation can be well understood and the prediction of rock mass condition ahead of tunnel face can be possible.

• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.130-132
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• 2002

Because of the continuous growth of energy consumption and also the tendency to site power lines and pipelines along the same route, the close proximity of power lines and buried metallic pipelines has become more and more frequent. Therefore there has been and still is a slowing concern about possible hazards resulting from the influence of power lines on metallic pipelines. Underground pipelines that run parallel to or in close proximity to power lines are subjected to induced voltages caused by the time-varying magnetic fields produced by the power line currents. The induced electro- motive force cause currents circulation in the pipeline and voltages between the pipeline and surrounding earth. This paper analyzes the induced voltage on the gas pipelines buried in parallel with 22.9kV distribution lines. Their magnitude depends on the length of parallelism and on the distance between distribution lines and pipeline.

• Journal of the Korean Ceramic Society
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• v.41 no.2
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• pp.131-135
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• 2004

The effect of Co additive on the microstructural evolusion of WC was investigated. A small amount of Co powder was placed on the top-center of the pure WC powder compact and then sintered at 1950$^{\circ}C$. During sintering some abnormally large WC grains of different size and shape observed depending on the distance from the liquid source. However, in the region far away from Co liquid source, it showed low densification and the grains of WC were very small and uniform in size. A small amount of Co liquid phase has a remarkable influence on the AGG of WC and it has been explained in terms of 2-D nucleation and growth mechanism.