• Wind and Structures
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• v.37 no.4
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• pp.315-329
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• 2023

We investigated the wind characteristics in the near-surface layer during the landfall of Typhoon Mujigae (2015) based on observations from wind towers in the coastal areas of Guandong province. Typhoon Mujigae made landfall in this region from 01:00 UTC to 10:00 UTC on October 4, 2015. In the region influenced by the eyewall of the tropical cyclone, the horizontal wind speed was characterized by a double peak, the wind direction changed by >180°, the vertical wind speed increased by three to four times, and the angle of attack increased significantly to a maximum of 7°, exceeding the recommended values in current design criteria. The vertical wind profile may not conform to a power law distribution in the near-surface layer in the region impacted by the eyewall and spiral rainband. The gust factors were relatively dispersed when the horizontal wind speed was small and tended to a smaller value and became more stable with an increase in the horizontal wind speed. The variation in the gust factors was the combined result of the height, wind direction, and circulation systems of the tropical cyclone. The turbulence intensity and the downwind turbulence energy spectrum both increased notably in the eyewall and spiral rainband and no longer satisfied the assumption of isotropy in the inertial subrange and the -5/3 law. This result was more significant in the eyewall area than in the spiral rainband. These results provide a reference for forecasting tropical cyclones, wind-resistant design, and hazard prevention in coastal areas of China to reduce the damage caused by high winds induced by tropical cyclones.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.9
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• pp.859-866
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• 2010

Nonlinear dynamics of pulsating instability-diffusional-thermal instability with Lewis numbers sufficiently higher than unity-in counterflow diffusion flames, is numerically investigated by imposing a Damkohler number perturbation. The flame evolution exhibits three types of nonlinear behaviors, namely, decaying pulsating behavior, diverging behavior (which leads to extinction), and stable limit-cycle behavior. The stable limit-cycle behavior is observed in counterflow diffusion flames, but not in diffusion flames with a stagnant mixing layer. The critical value of the perturbed Damkohler number, which indicates the region where the three different flame behaviors can be observed, is obtained. A stable simple limit cycle, in which two supercritical Hopf bifurcations exist, is found in a narrow range of Damkohler numbers. As the flame temperature is increased, the stable simple limit cycle disappears and an unstable limit cycle corresponding to subcritical Hopf bifurcation appears. The period-doubling bifurcation is found to occur in a certain range of Damkohler numbers and temperatures, which leads to extend the lower boundary of supercritical Hopf bifurcation.

• Korean Journal of Heritage: History & Science
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• v.49 no.4
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• pp.38-51
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• 2016

This study reports on human dietary reconstruction of Joseon Dynasty using stable isotope analysis. The stable carbon and nitrogen isotope values were measured of bone collagen extracted from 25 human bones from archaeological site in Myeongam-ri, Asan. Average values of ${\delta}^{13}C$ and ${\delta}^{15}N$ are $-19.7{\pm}0.5$‰(n=23) and $9.6{\pm}1.1$‰(n=23), respectively. The isotopic data indicates that Myeongam-ri individuals consumed $C_3$ plants mainly and assumed of dietary resourced from a terrestrial animal protein. Previous isotopic studies of the Joseon era suggested that dietary composition of Joseon population was not influenced by region and burial type. Also comparison of the isotopic results of male and female from double burials showed sex-dependent dietary patterns among individuals living in the same circumstances.

• Transactions on Control, Automation and Systems Engineering
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• v.4 no.1
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• pp.84-91
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• 2002

A new composite control method for a carriage balancing single inverted pendulum system is proposed and applied to swing up the pendulum and to stabilize it under the state constraint. The target inverted pendulum system has an extremely limited length of the cart(below 16cm). The proposed swing-up controller comprises a sliding mode control algorithm and an optimal control algorithm based on two regions: the region near the inverted unstable equilibrium position and the rest of the state space including the downward stable equilibrium position. The sliding mode controller uses a switching control action to converge along the specified path(hyperplane) derived from energy equation from a state around the path to desired state(standing position). An optimal control method is also used to guarantee the stability at unstable equilibrium position. Compared with the reported controllers, it is simpler and easier to implement. Experimental results are given to show the effectiveness of this controller.

• Journal of Photoscience
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• v.9 no.2
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• pp.118-121
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• 2002

A state of bacteriorhodopsin at high temperature was studied by various spectral measurements. The stability measurements indicated that the onset temperature of the denaturation was 70$^{\circ}C$ in the dark and 60$^{\circ}C$ under illumination. The reactivity of hydroxylamine with the Schiff's base also significantly increased in the temperature range between 60 and 70$^{\circ}C$. A spectral band at about 470 nm appeared in the temperature range higher than 60$^{\circ}C$. The circular dichroism spectra in the visible region started to change from a bilobed exiton type to a positive band at about 60$^{\circ}C$, suggesting that the two-dimensional configuration of bacteriorhodopsin molecules changed from crystalline to amorphous. All the measurements suggested a new state between 60 and 70$^{\circ}C$ in which bacteriorhodopsin is stable only in the dark.

• Journal of computational fluids engineering
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• v.13 no.4
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• pp.50-57
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• 2008

The prediction of hydrate pellet decomposition characteristics is required to design the regasification process of GTS (gas to solid) technology, which is considered as an economic alternative for LNG technology to transport natural gas produced from small and stranded gas wells. Mathematical model based on the conservation principles, the phase equilibrium relation, equation of gas state and phase change kinetics was set up and numerical solution procedure employing volume averaged fixed grid formulation and extended enthalpy method are implemented. Initially, porous methane hydrate pellet is at uniform temperature and pressure within hydrate stable region. The pressure starts to decrease with a fixed rate down to the final pressure and is kept constant afterwards while the bounding surface of pellet is heated by convection. The predicted convective heat and mass transfer accompanied by the decomposed gas flow through hydrate/ice solid matrix is reported focused on the comparison of spherical and cylindrical pellets having the same effective radius.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.1184-1186
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• 2002

Recently, according to the industrial development relative to multimedia, demand of display system is radically increase, thus development for power supply of back-lighting is advanced lively. Fluorescent lamp operated at high frequency by the electronic ballast provide benefits like unnoticeable flicker effect and higher luminous efficiency. This paper presents analysis of Push-Pull type resonant inverter for CCFL drive for stable characteristic and life improvement of fluorescent lamp operated at high frequency. Also it has proposed design procedure of Current-Fed type resonant inverter. On the basis of equivalent circuit, component characteristic and suitable region of operation frequency from simulation using Matlab and Pspice is predicted. Suitability of applied equivalent model and validity of design process from the experimental results with CCFL inverter.

• Journal of Sensor Science and Technology
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• v.6 no.1
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• pp.43-48
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• 1997

$Ca_{10}(PO_{4})_{6}(OH)_{2}$ humidity-sensitive devices were fabricated by a solid reaction method, and their humidity-sensitive characteristics were investigated. The impedance decreases with increasing relative humidity, and the good sensitivity is shown in which impedance changes by about $10^{2}\;{\Omega}$ over the region of $30{\sim}90\;%$. Also, It is shown that the humidity sensitivity is stable in temperature variations and long time exposures to the humidity. The sensitivity of the specimens is not affected by a heat treatment, and the hysteresis in one humidity cycle is negligible.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3282-3287
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• 2007

Lean combustion is one of the most promising method for increasing engine efficiency and reducing the exhaust emission from SI gas engines. Due to the possibility of partial burn and misfire, however, under lean burn operation, stable flame kernel formation and fast burn rate are needed to guarantee a successful subsequent combustion. Experiment data were obtained on a single-cylinder CNG fueled SI engine to investigate the effect of direct injection, spark timing and variation of injection timing. Experimental results show that lean burn limit is ${\lambda}$=1.3 with port injection, and expansion of lean burn limit ${\lambda}$=1.4 with direct injection method, due to increase of turbulence intensity in cylinder and stratified charge. Combustion duration in lean region is improved by using the variation of injection timing.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3183-3186
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• 2007

Taylor-Couette flow may appear when the angular velocity is different between two concentric rotating cylinders. This kind of Taylor-vortex flow can be easily seen in lots of engineering problems. In general the geometries of rotating cylinders are generally complex in these cases. In this study, we investigated Taylor-Couette flow when the outer cylinder has the slit along the annulus. The radius ratio and aspect ratio of the experimental model used was 0.825 and 48, respectively. The depth of slits is 5mm and total 18 slits are azimuthally located along the inner wall of outer cylinder. We used PIV method to measure the flow and applied index matching method to resolve the complex geometry effect. The results show the model with slit has no stable wavy vortex region above Re=143.