• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.191-197
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• 2002

The motion of a floating OWC chamber in waves is studied taking account of fluctuating.air pressure in the air chamber. An atmospheric pressure drop occurs across the upper opening of the chamber which causes not only hydrodynamic but also pneumatic added mass and damping forces to the floating chamber. A velocity potential in the water due to the free surface oscillating pressure patch is added to the conventional radiation-diffraction potential problem. The potential problem inside the chamber is formulated by making use of the Green integral equation associated with the Rankine Green function while the outer problem with the Kelvin Green function. The two integral equations are solved simultaneously by making use of a matching boundary condition at the lower opening of the chamber to the outer water region. The chamber motion in the frequency domain is calculated for various values of parameters related to the atmospheric pressure drop. The present methods can also be used for the analysis of air-cushion vehicle motion as well as for the design oj a floating owe wave energy absorber.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.6
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• pp.468-471
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• 2013

In this paper, we analyzed the effects of the number of TIPS-pentacene droplets and also the substrate temperature on the performance of OTFTs. As the number of the droplets increased, the mobility increased and reached the peak value and then reduced at the all temperatures. The peak mobility was $0.14{\pm}0.03cm^2/V{\cdot}sec$ at 3 droplets and $41^{\circ}C$, $0.19{\pm}0.02cm^2/V{\cdot}sec$ at 4 droplets and $46^{\circ}C$, and $0.35{\pm}0.10cm^2/V{\cdot}sec$ at 7 droplets and $51^{\circ}C$. The reason of existence of peak mobility can be found in matching the evaporation of solvent with the velocity of crystal formation. When two parameters were properly matched, the mobility produced the highest.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.6
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• pp.14-22
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• 2010

In this study, a large bus is tested for measuring the steering response based on the slarom test and step steer test. A full car model by using ADAMS/Car is established for computer simulation. For bus modeling, user defined templates are made and used in the simulation. Simulation results according to the slarom and step steer test are compared to the physical experiments, in which several sensors are installed to measure vehicle responses. The results obtained from the comparison show a good agreement with regard to the vehicle velocity and steering angle.

• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.173-174
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• 1996

We have mapped $17 deg^2$ region toward Galactic anticenter in $^{12}CO$ J = 1 - 0 using the 3 mm SIS receiver on the 14 m telescope at Taeduk Radio Astronomy Observatory (TRAO). The region mapped in this paper is the first target of the Galactic AntiCenter CO Survey Project (GACCOS) and was selected comparing with IRAS Sky Survey Atlas (ISSA) images at 100${\mu}m$. Molecular emission of the target area is found to be very extended and is well matching with the FIR emission boundary. There are several pieces of clouds, and as some of spectra show several peaks, there seem to be several clouds overlapped in some directions. The Velocity of Local Standard of Rest ($V_{LSR}$) of the CO emission of the mapped region ranges from -20 to +10 km/s. It is also found that the two cloudlets located around I = $180^{\circ}$ have $V_{LSR}$ = -20 km/s, which is very abnormal. The peak antenna temperature of 13 K arises near the H II Region S241.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.4
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• pp.63-71
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• 2002

In this paper, we present microwave characteristics of traveling-wave photodetectors (TWPD) using the finite-difference time-domain method (FDTD). Current and voltage in the time domain are calculated by the FDTD. Also, characteristic impedance and propagation constant in frequency domain are obtained from the time-domain data. As the thickness of i-layer gets thicker and the waveguide width gets narrower, TWPD's show less microwave loss and higher velocity. The 50Ω impedance matching design is achieved for 2.4${\mu}{\textrm}{m}$ waveguide width and 1.2${\mu}{\textrm}{m}$ thickness of i-layer at 100 GHz.

• International Journal of Precision Engineering and Manufacturing
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• v.7 no.2
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• pp.18-24
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• 2006

This paper proposes a LuGre Model-Based Neural Network (MBNN) friction compensation algorithm for a linear motor stage. For matching the friction phenomena in both the motion-start region and the motion-reverse region, the LuGre dynamic model is employed into the proposed compensation algorithm. After training of the model-based neural network is completed, the estimated friction for compensation is obtained. From the obtained result we find that the new structure gains advantage over the non-friction compensation system on the performance of the compensator in both regions. The proposed compensator is evaluated and compared experimentally with an uncompensated system on a microcomputer controlled linear motor tracking system in the final section of the paper. The experimental results show the improvement on the maximum velocity error and the root mean square tracking error in the motion-start region ranges from 34% to 53% and from 53% to 75% respectively, and in the motion-reverse region from 48% to 65% and from 79% to 90% respectively.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.3
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• pp.91-98
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• 2007

This paper presents the induced mathematical modeling equations for evaluating the operation stability with automatic transmission of heavy duty vehicle. This theoretical approach indicates that linearized governing equations of system can be converted into eigen-value problems. if the eigen-value has positive number, we can predict the engine operating point locates an unstable operating region. To be a stable state, the unstable operating point diverges toward a stable point which is able to maintain uniform velocity. Based on the previous theoretical analysis, we carry out dynamic simulation to show the behavior of engine operating point and torque converter in transient state. As a result of the dynamic simulation, the suggested theoretical method is found to be reasonable for evaluating the operation stability of a torque converter. In addition, the numerical results explain the engine stops and fluctuating phenomenon in reality.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.12
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• pp.1321-1328
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• 2003

In this paper, we demonstrate that the directivity of the CPW(Coplanar Waveguide) directional coupler with finite-extent backed conductor is enhanced by eliminating center region of backed conductor appropriately. If the backed conductor is removed at center region of couplers, the couplers have two backed conductors. If effective odd mode dielectric constant is decreased at center region, the electrical length for odd mode is changed and phase velocity is same at the directional couplers. Hence, directivity is improved. The eliminated length is solved by an odd and even mode analysis. The designed moderate CPW directional coupler with the proposed compensation structure has excellent directivity and matching characteristic at center frequency in simulation and measurement.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.4
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• pp.368-378
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• 2004

In this paper, we proposed the compensation structures for the enhanced directivity of CPW(Coplanar waveguide) directional couplers with finite-extent backed conductor. The proposed compensation structures are. realized by expanding the slot width between signal line and ground plane in center region of couplers. The CPW couplers with expanded slot have the same phase velocity for even and odd mode because of added inductance and changed capacitance appropriately, so the enhanced directivity is accomplished. The designed CPW directional couplers have good directivity and matching characteristic at center frequency in simulation and measurement.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.6
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• pp.998-1005
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• 2010

Rifling force has a torsion impulse effect on the gun tube and thus generates undesirable vibration of the gun tube about its bore axis, putting additional stress on the projectile. High rifling force at the muzzle of the gun tube may adversely influence the trajectory of the projectile. And, the service life of rifled gun barrels is known to depend on the rifling force. Rifling force along the path of the projectile in the longitudinal direction of the gun tube can be described with projectile mass, projectile velocity, gas pressure curve and rifling angle. Under the same conditions, the character of the rifling of the gun barrel decisively influences the rifling force curve. To reduce the above mentioned harmful effect, locally distinct maximum of rifling force has to be avoided and maximum rifling force needs to be minimized. The best way to minimize the maximum rifling force is to design a rifling angle function so that the rifling force curve has a near trapezoidal shape. In this paper a new approach to make the optimal rifling force curve is described. The rifling angle determining the rifling force is developed by combined Fourier series and polynomial function to satisfy both the convergence and boundary condition matching problems.