• Proceedings of the KSR Conference
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• 2008.06a
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• pp.2191-2194
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• 2008

This paper investigates the sound insulation performance of the fiber sandwich panels for a tilting train. Due to the high strength and low mass, fiber sandwich panels are widely used for aircraft structures, railway vehicle structures. These fiber sandwich panels show orthotropic behavior because of the fiber's structural characteristics. This orthotropy often reduces the critical frequency and makes negative effect on the sound insulation performance. In this study, transmission loss of the fiber panels is analyzed based on the equivalent orthotropic plate model. An analysis program is developed to calculate the transmission loss of the fiber sandwich panels. Using the program, the coincidence frequency ranges and their effects on the transmission loss are investigated.

• Journal of Mechanical Science and Technology
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• v.19 no.8
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• pp.1568-1575
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• 2005

The calculation of the transmission loss of the silencers with complicated internal structures by the conventional BEM combined with the transfer matrix method is incorrect at best or impossible for 3-dimensional silencers due to its inherent plane wave assumption. On this consideration, we propose an efficient practical means to formulate algebraic overall condensed acoustic equations for the whole acoustic structure, where particle velocities on the domain interface boundaries are unknowns, and the solutions are used later to compute the overall transfer matrix elements, based on the multi-domain BEM data. The transmission loss estimation by the proposed method is tested by comparison with the experimental one on an air suction silencer with perforated internal structures installed in air compressors. The method shows its viability by presenting the reasonably consistent anticipation of the experimental result.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.383-386
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• 2003

This paper deals with transmission loss of 3-dimensional rectangular plenum lined chamber. There are three kinds of rectangular plenum lined chamber: throughflow type, flow-reversal type, and end-in/side-out type. The combination of above three types of rectangular plenum lined chamber is used for the commercial HVAC system and automobile exhaust system. However, the ambiguity and complexity of sound absorbing material property and 3-dimensional property have impeded research. In this paper, the transmission loss of three kinds of rectangular plenum lined chamber is derived and calculated. The effect of increase of sound absorbing material is also considered. Analytical solution is calculated by using the locally-reacting property of sound absorbing material.

• Proceedings of the KSR Conference
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• 1998.05a
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• pp.265-272
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• 1998

In this paper, the intoner noise reduction for subway railroad vehicles was studied by improving transmission loss of carbody panels and side doors, and on-line tests were conducted to examine the exterior noise levels at various running conditions. Also the transmission loss for design candidates of the carbody specimen was measured in two reverberation rooms. From the results of the tests, side door gap is the most dominant factor affecting the Interior noise level of subway railroad cars with a sliding typed side door. The next one is revealed to transmission loss of a floor panel. To improve the transmission loss of the carbody, many activities were conducted such as, treatment of resilient and sound-absorbing materials and reducing the gap of the side door by adopting a brush and rubber, etc. The estimated interior noise level for modified car which is designed with improved carbody panels is lower than original car by about 5㏈.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.646-650
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• 2001

In this paper, it is presented that the effect of air gap insertion in testing the transmission loss of sound barrier using structural vibration system. In this study, we use the APAMAT based on the structure-borne-noise. The measured results show that air gap insertion improves transmission loss as results of test based on the air-borne-noise. The measured results are compared with the predicted transmission loss using the transfer matrix method. The predicted results were found to be in reasonable agreement with measured results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.374-379
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• 2013

Helmholtz resonators have high transmission loss in a narrow band at the resonance frequency. The transmission loss characteristics of resonators at high sound pressure levels can change due to variations of the impedance as a result of nonlinear behavior. Different sound pressure levels are applied to each resonator when resonators were arranged along the path. Therefore, impedance variation due to incident sound pressure level should be considered in order to predict the transmission loss.

• IEMEK Journal of Embedded Systems and Applications
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• v.6 no.3
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• pp.149-156
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• 2011

Transmission delay and packet loss induced by a communication network can degrade the control performance and, even make the system unstable. This paper presents a method for compensating transmission delay and packet loss in a networked control system for unmanned underwater vehicle. The proposed method is based on Lagrange interpolation in order to satisfy the requirements of simplicity and model-independency. In this work, the lost/delayed data are estimated in real time by only using the past data without requiring any mathematical model of the controlled system. Consequently, the proposed method can be implemented independent of the controlled system, and also it can achieve fast and accurate compensation performance. The performance of the proposed technique is evaluated by numerical simulations with an unmanned underwater vehicle.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.10a
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• pp.302-307
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• 2010

Development of light-weight high speed train (HST) based on distributed motor control with the top speed of 350 km/hr has engendered a need for abatement of the interior noise of the train cabin. The development of noise abatement measures is crucial at the design stage of the train car since the noise transmission characteristics of the car structure directly influences the cabin interior noise. Since the transmission loss measurement using the entire car structure is often not feasible, especially at the initial stages of the train development, investigation of transmission characteristics using small-scale reverberation chamber can furnish useful alternative source of predicting the noise level. In the present study, white noise is generated at source and transmission loss estimated by performing measurement of a specimen in a scaled reverberation chamber. Comparison of measured values with the previously derived numerical values show good agreement in the overall trend but appreciable quantitative differences still remain.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.7
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• pp.429-436
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• 2003

This paper presents a new approach for evaluating the transmission marginal loss factors (MLFs) considering the reactive power. Generally, MLFs are represented as the sensitivity of transmission losses, which is computed from the change of the generation at reference bus by the change of the load at the arbitrary bus-i. The conventional evaluation method for MLFs uses the only H matrix, which is a part of jacobian matrix. Therefore, the MLFs computed by the existing method, don't consider the effect of the reactive power, although the transmission losses are a function of the reactive power as well as the active power. To compensate the limits of the existing method for evaluating MLFs, the power factor at the bus-i is introduced for reflecting the effect of the reactive power in the evaluation method of the MLFs. Also, MLFs calculated by the developed method are applied to energy spot markets to reflect the impacts of reactive power. This method is tested with the sample system with 5-bus, and analyzed how much MLFs have an effect on the bidding/offer price, market clearing price(MCP), and settlement in the competitive energy spot market. This paper compared the results of MLFs calculated by the existing and proposed method for the IEEE 14-bus system, and the KEPCO system.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.192-194
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• 2001

The Transmission network provides physical transport, network security, and connection services. The five principles of Transmission pricing are economic efficiency, cost recovery, efficient regulation, simplicity and transparency, non-discrimination. The Transmission Charges are made up of transmission connection charge and transmission charge of network. The Transmission Losses will be considered through Marginal Transmission Loss Factors in the market operation. The transmission loss rentals are used for the reduction of the annual revenue requirement of the transmission network for the purpose of derivation of transmission use of network charge.