• Journal of Energy Engineering
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• v.15 no.1 s.45
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• pp.28-34
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• 2006

The convective heat transfer on the outer surface of tube arrays perpendicular to the flow direction was experimentally investigated. The test sections which include the aligned and staggered arrangements were made and the local heat transfer coefficients on the outer surface of the tube were measured after the Hour has been fully developed. The results showed that the local heat transfer coefficients of the staggered arrangement, which has transverse pitch of 0.075 m and longitudinal pitch of 0.08 m, were about 15% greater than that of the aligned arrangement. Also, the overall mom Nusselt number of the former was greater thu that of the latter.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.5
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• pp.626-634
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• 1998

Controllable pitch propeller(CPP) is usually adopted for easy and effective engine controls of a ship in a port. Unfortunately the torsional vibration may occur by a certain variation of engine torque and the major resonance peak may exist within the maximum continuous rating(MCR) In these cases an additional stress concentration on the oil passages such as longitudinal slots notches and circular holes of an oil distributor shaft(ODS) occurs by the torsional vibration of the CPP shaft. In this paper an analysis for the fatigue limit of an ODS system of the 5S70MC engine in a crude oil carrier is done by applying FEM and empirical formulas. Furthermore the additional stress on the ODS is investigated by analyzing the torsional vibration of the shaft system and a control method in which a tuning damper is adopted is introduced in the case of the additional stress exceeds the fatigue limit. The validity of analysis method is verified by comparing the results acquired by an actual measurement of the vibratory torque for the above ODS

• International Journal of Aeronautical and Space Sciences
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• v.6 no.2
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• pp.23-32
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• 2005

An experimental control system is proposed for the attitude control of a simplified 2-DOF helicopter model. The main rotor is a rigid one, and the fuselage is simply supported by a fixed hinge point where the longitudinal motion is decoupled from the lateral one since the translations and the rolling rotation are completely removed. The yaw trim of the helicopter is performed with a tail rotor, by which the azimuthal attitude can be adjusted on the rotatable post in the yaw direction. The robust sliding mode control tracking a given attitude angle is proposed based on the flight dynamics. A pitch damper is inserted for the control of pitching angle while the compensator to reaction torque is used for the control of azimuth angle. Several parameters of the system are selected through experiments. The results shows that the proposed control method effectively counteracts nonlinear perturbations such as main rotor disturbance, undesirable chattering, and high frequency dynamics.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.317-322
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• 2008

The objectives of this paper are to study the effects of thermal and geometric conditions on the performance of indoor heat exchanger with R410A for Gas Engine Driven Heat Pump (GHP) application and to find optimum design conditions of indoor heat exchanger by parametric analysis for the key parameters. In the air side, moisture out of the humid air condenses on the fin surface while the refrigerant (R410A) boils inside the smooth tube. Therefore this study uses Log Mean Enthalpy Difference (LMHD) method to analyze the heat transfer from the humid air to the refrigerant of R410A. The results show that fin pitch and longitudinal pitch have significant effect on the heat exchanger preformance. This study will provide the guideline for optimum design of indoor heat exchanger with R410A for GHP application.

• Journal of Magnetics
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• v.6 no.4
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• pp.109-118
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• 2001

A computer simulation, utilizing the Landau-Lifshitz-Gilbert equation, of ultra-high- density recording on continuous longitudinal media is carried out. The two important features of this work are the use of a planar-type head, which enables a high write field of 14183 Oe ts be generated at the center of the recording medium, and the media with very high coercivities up to 13010 Oe. From a systematic investigation, it is found that the optimum write field is higher than the medium coercivity by only 3400 Oe over a wide coercivity range. This new finding allows one to write an a medium with a very high coercivity by using a planar-type head. It is demonstrated that a reasonably good bit pattern with a bit density of 605 kfci is generated on the medium with a coercivity of l1720 Oe, and, combined with a high track pitch density of 100 ktpi, a recording density of 60 Gb/in$^2$can be obtained in a single layer medium. With an improved write- head designs even a higher recording density of 75 Gb/in$^2$may be possible since comparison of the results for the bit pattern from the present head profile and the ideal Lindholm profile indicates an increase in the track pitch density of about 27%. Even at this density, the thermal stability parameter (KV/kT) at room temperature is high enough (60) to provide ample room for thermal stability.

• Bulletin of the Society of Naval Architects of Korea
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• v.12 no.1
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• pp.47-58
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• 1975

The effect of the bow shape on the ship motion response among longitudinal regular waves, is investigated employing the strip theory. The two dimensional hydrodynamic forces such as added mass and damping are calculated by the integral equation method for arbitrary sections. Nine ship models are selected for investigation. They are U, UV and V bow ship forms of different block coefficient of 0.6, 0.7 and 0.8 with constant after body. The heave amplitude of the V bow ship is smaller than that of the U bow ship in the whole range of wave length except extremely short wave as were stated by the earlier investigators. This results holds also in the case of bow vertical motions such as vertical relative displacement, velocity and acceralation. As to the pitch amplitudes, the V bow ship gives smaller value in long waves but larger value in short waves. However, heave and pitch phase angles are practically not influenced by the form of the fore body sections. In the bow motions, a little difference in phase angle is appeared in the vicinity of the wave which has same ship length. With respect to the wave exiting force and moment unfovourable effects could be expected in V bow ships. And these tendency hold also in the wave bending moment.

• Journal of Advanced Navigation Technology
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• v.9 no.1
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• pp.28-33
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• 2005

In this paper, we developed the algorithm to control longitudinal and lateral motion of UAV(Unmanned Aerial Vehicle) with Infrared heat sensors and GPS(Global Positioning System) receiver. UAV was controlled to be flown horizontally and also turned coordinately maintaining the constant altitude. Accomplishing the flight test of UAV sevral times, we were able to develope low price controller to control bank angle for lateral motion, and also pitch angle and altitude for longitudinal motion simultaneously.

• Journal of the Korean Society for Railway
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• v.17 no.5
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• pp.321-327
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• 2014

In this paper, linear dynamic equations are derived from nonlinear dynamic equations of constrained multibody systems using the QR decomposition method. The derived linear equations are applied to a railway vehicle bogie. The vibration characteristics of the railway vehicle are investigated by calculating the natural mode and transfer function of the bogie frame in relation to rail-roughness input. The main modes of the bogie were found below 35Hz, and the local modes above 198Hz. The magnitude of the vertical transfer function varied with the forward velocity due to vertical and pitch modes, which were influenced by the forward velocity. The magnitude of the lateral transfer function was negligibly small, and the mode in the longitudinal direction was excited for longitudinal transfer function regardless of the forward velocity.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.4
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• pp.367-375
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• 2013

In this study, the characteristics of the heat transfer coefficient and pressure drop were numerically analyzed according to the axis ratio (AR), pitch, location of vortex generator, and bump phase of the tube surface about an elliptical fin-tube heat exchanger. The boundary condition for CFD analysis was decided as a tube surface temperature of 348 K and inlet air velocity of 1-5 m/s. RSM 7th turbulent model was chosen as the numerical analysis for the sensitivity level. The analysis results indicated that the AR and transverse pitch decreased whereas the heat transfer coefficient increased. On the other hand, there was little difference in the longitudinal pitch. Furthermore, the heat transfer rate was more favorable when the vortex generator was located in front of the tube. Also, the bump phase of the tube surface indicated that the pressure drop and heat transfer were more favorable with the circle type than with the serrated type.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.7
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• pp.85-91
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• 2005

Supersonic jet fighter aircraft must have been guaranteed appropriate for controllability and stability in HAoA(High Angle of Attack) region. Limit value of aircraft enter the deep stall at HAoA is related to problem of aircraft configuration design. But, In order to guarantee the aircraft safety in HAoA, control law is designed using digital Fly-By-Wire flight control system in modern versions of supersonic jet fighter aircraft. Also, In order to recovery if aircraft enter the deep stall or spin, anti-spin control law and MPO(Manual Pitch Override) mode is designed. AoA limiter and MPO is designed in longitudinal axis and HAoA departure prevention logic, roll command limiter, rudder fader and anti-spin logic is designed in lateral-directional axis. In this paper, we introduce the T-50 HAoA flight control law and propose that aircraft stability and adequate of these control law from HAoA flight test.