• Nuclear Engineering and Technology
• /
• v.46 no.4
• /
• pp.513-520
• /
• 2014

In this paper, three types of operational and industrial absorbers used at research reactors, including Ag-In-Cd alloy, $B_4C$, and Hf are selected for sensitivity analyses. Their integral effects on the main neutronic core parameters important to safety issues are investigated. These parameters are core excess reactivity, shutdown margin, total reactivity worth of control rods, thermal neutron flux, power density distribution, and Power Peaking Factor (PPF). The IAEA 10 MW benchmark core is selected as the case study to verify calculations. A two-dimensional, three-group diffusion model is selected for core calculations. The well-known WIMS-D4 and CITATION reactor codes are used to carry out these calculations. It is found that the largest shutdown margin is gained using the $B_4C$; also the lowest PPF is gained using the Ag-In-Cd alloy. The maximum point power densities belong to the inside fuel regions surrounding the central flux trap (irradiation position), surrounded by control fuel elements, and the peripheral fuel elements beside the graphite reflectors. The greatest and least fluctuation of the point power densities are gained by using $B_4C$ and Ag-In-Cd alloy, respectively.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.36 no.1
• /
• pp.62-71
• /
• 2008

Swirl injector with adjustable backhole length was analyzed to suppress high-frequency combustion instability in Liquid Rocket Engines. In order to analyze the effect of swirl injector as an acoustic absorber, swirl injector was regarded as a quarter-wave resonator and its damping capacity is verified in atmospheric temperature. Experiments were carried out with copied tubes on air core because the interior air core volume of injector has a direct effect on damping. From the experimental data, it is proved that increasing the number of injectors mounted at each anti-node point can increase acoustic damping effect. Also, when tuned injectors at 1L, 1T, 1L1T modes simultaneously are installed at each anti-node point of model chamber, the damping effect of tuned injectors with multi modes agree well with it of tuned injectors with single mode.

• Journal of the Korean Society for Railway
• /
• v.1 no.1 s.1
• /
• pp.1-9
• /
• 1998

Described in this paper is the result of a study on collision analysis of TGV-K using 1-dimensional model for crashworthy design. Crashworthy design of the front end is very important because majority of the impact energy (more than 70%) is absorbed by the crush of the front end when the train is collided with an obstacle like a tank lorry. Guideline for the crashworthy design can be described from the collision analysis of the whole train using a 1-dimensional model. Since the headstock of TGV-K is not designed in a crashworthy point of view, a conceptual design of the headstock to improve crashworthiness is suggested and evaluated using 1-dimensional collision analysis. The suggested design, which adopts an energy absorber and a crashworthy headstock, shows a good behaviour on the accident scenario of SNCF (collision at 110 km/h against a movable rigid mass of 15 ton).

• Proceedings of the KSR Conference
• /
• 1998.05a
• /
• pp.361-368
• /
• 1998

Described in this paper is the result of a study on collision analysis of TGV-K using 1-dimensional model for crashworthy design. Crashworthy design of the front end is very important because majority of the impact energy (more than 70%) is absorbed by the crush of the front end when the train is collided with an obstacle like a tank lorry. Guideline for the crashworthy design can be described from the collision analysis of the whole train using a 1-dimensional model. Since the headstock of TGV-K is not designed in a crashworthy point of view, a conceptual design of the headstock to improve crashworthiness is suggested and evaluated using 1-dimensional collision analysis. The suggested design, which adopts an energy absorber and a crashworthy headstock, shows a good behaviour on the accident scenario of SNCF (collision at 110 km/hr against a movable rigid mass of 15 ton).

• Ocean Systems Engineering
• /
• v.7 no.2
• /
• pp.89-106
• /
• 2017

The study explores a novel design of wave energy converter (WEC) that utilizes the interaction between an inside heaving vertical cylinder with an outside fixed hollow cylinder. This design originates from the oscillating water column (OWC) type WEC but replaces the pneumatic power take off (PTO) through the Wells turbine with the hydrodynamic PTO through the inside heaving cylinder. To effectively evaluate the maximum power output, the system has been modeled in the hydrodynamic software AQWA (developed by ANSYS Inc) that has accumulated extensive offshore industry users. Ranges of the PTO parameters have been examined to make sure that proper linear damping can be implemented to simulate the PTO force. Comparing the efficiency of the pneumatic PTO with the hydrodynamic PTO, it appears that the hydrodynamic PTO is more promising than the traditional Wells turbine for an OWC system.

• Proceedings of the KSR Conference
• /
• 2000.05a
• /
• pp.645-651
• /
• 2000

In this paper, numerically evaluated is the regulations for crashworthy design of the Korean standard urban train suggested by KRRI. The 4-car consist of K-EMU(Korean Electric Multiple Unit) train developed in recent is analyzed under various collision conditions such as normal coupling, heavy shunt, light and heavy collisions. The collision conditions are assumed as K-EMU collides against another stationary one at 5 kph, 10 kph, 25 kph and 32 kph. According to the numerical results and bibliographical study, it is necessary that the regulations by KRRI be complemented from crashworthy point of view. Furthermore, the K-EMU train is recommended to adopt a new coupler with an additional energy absorber or a mechanical fuse.

• Proceedings of the KSR Conference
• /
• 1998.11a
• /
• pp.545-552
• /
• 1998

A study on collision analysis of TGV-K using a 2-dimensional model is described to evaluate its crashworthiness. Two-dimensional analysis gives good information on overriding behaviour and impact forces applied to interconnecting devices such as side buffers, ball & socket joints, hooks, pins, and fingers. Since the headstock of TGV-K is not designed in a crashworthy point of view, its conceptual design fur KHST(Korean High Speed Train), under development, is suggested to improve crashworthiness. The suggested design, which adopts an energy absorber and a crashworthy headstock, is compared with the conventional headstock on dynamic behaviour to the vertical direction under the accident scenario of SNCF (collision at 110km/h against a movable rigid mass of 15 ton). It is concluded that the design modification make little difference in vertical motion. To evaluate validation of the 2-dimensional model, the results fur longitudinal motion is compared with those of 1-dimemsional one. It is found that the two results are in good agreements.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.21 no.4
• /
• pp.144-152
• /
• 2013

PRT(Personal Rapid Transit) system is a new transportation system which will meet increasing demands of traffic in Korea. It is also an environment-friendly transportation and automatically operated. For these reasons, researches on the PRT system are actively undergoing, but the PRT vehicles have different forms of subway, bus, etc. There are no design standards to evaluate structural integrity, yet. In this paper, Structural design specifications are derived, which are based on the performance test standard for EMU and the ASCE-APM standards. We also perform the static and fatigue analyses by FE simulation and suggest strategies to improve an initial structure design. In addition, we derived the design specifications for energy-absorbing structures to meet the conditions of the collision scenarios predefined from a view point of operation safety.

• Ocean Systems Engineering
• /
• v.4 no.1
• /
• pp.63-82
• /
• 2014

Declutching control is applied to a hemispherical wave energy converter with direct linear electric Power-Take-Off systems oscillating in heave direction in both regular and irregular waves. The direct linear Power-Take-Off system can be simplified as a mechanical spring and damper system. Time domain model is applied to dynamics of the hemispherical wave energy converter in both regular and irregular waves. And state space model is used to replace the convolution term in time domain equation of the heave oscillation of the converter due to its inconvenience in analyzing the controlled motion of the converters. The declutching control strategy is conducted by optimal command theory based on Pontryagin's maximum principle to gain the controlled optimum sequence of Power-Take-Off forces. The results show that the wave energy converter with declutching control captures more energy than that without control and the former's amplitude and velocity is relatively larger. However, the amplification ratio of the absorbed power by declutching control is only slightly larger than 1. This may indicate that declutching control method may be inapplicable for oscillating wave energy converters with direct linear Power-Take-Off systems in real random sea state, considering the error of prediction of the wave excitation force.

• Journal of Institute of Control, Robotics and Systems
• /
• v.4 no.6
• /
• pp.713-721
• /
• 1998

In this paper a new modeling and an optimal pole-placement control for the suspension system of Macpherson type are investigated. The rotational motion of the unsprung mass is emphasized in the new modeling. The two generalized coordinates selected in the new model are the vortical displacement of sprung mass and the angular displacement of control arm. Both variables are measured from their static equilibrium points. It is shown that the conventional model is a special case of the new model since the transfer function of the new model coincides with that of the conventional one if the lower support point of the shock absorber is located at the mass center of the unsprung mass. It is also shown that the resonance frequencies of the new model agree better with experimental results. Therefore, the new model is more general in the sense that it Provides an extra degree of freedom in determining the plant model for control system design. An optimal pole-placement control which combines LQ control and pole-placement technique is applied to the new model. Simulations are provided.