• Journal of the Society of Naval Architects of Korea
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• v.29 no.1
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• pp.123-134
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• 1992

The reduction of the airborne noise level is essential to the comfortability for mien and passengers in ships. In this paper, the acoustic characteristics on the multilayered acoustic panel with the Helmholtz resonator was described analytically and experimentally. The design software based on the Transfer Matrix Analysis(TMA) method for the acoustic enclosing panel was developed. According to the change of the design parameters of the panel, verious transmission losses were obtained using the developed software. As a result, it was verified that the acoustic characteristics of the composite panel was excellent in comparison with the conventional acoustic partitioning structures. This panel can be applicable to the acoustic enclosure system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.676-681
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• 2001

We usually divide the noise of exhaust system into pulsation noise and flow noise. Pulsation noise is the shock wave to occur when the burning gas of low pressure emits and include harmonic having basic frequency as the exhaust cycle of engine. Flow noise is the noise that is produced when gas flow emits into the atmosphere through the pipe and has the character of frequency like pink noise which has the high level of high frequency component. A muffler is divided into reflective type and absorptive type. We usually use the muffler compounding the property of them. In this study, it is the case of transfer matrix method that a muffler is compounded to analyze the elements of each section according to sound wave's proceed direction. But we use simple model. So, we use finite element method that takes short time to analyze. Acoustic analysis gives us transfer matrix to use FEA of SYSNOISE and we use STAR-CD for fluid analysis. We made database that is based on analytical results about the muffler of expansion type, extended type, offset type, reverse type, and perforated type and developed the muffler design system to perform work efficiently.

• ETRI Journal
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• v.42 no.6
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• pp.859-871
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• 2020

A spectrally encapsulated (SE) orthogonal frequency-division multiplexing (OFDM) precoding scheme for wireless short packet transmission, which can suppress the out-of-band emission (OoBE) while maintaining the advantage of the cyclic prefix (CP)-OFDM, is proposed. The SE-OFDM symbol consists of a prefix, an inverse fast Fourier transform (IFFT) symbol, and a suffix generated by the head, center, and tail matrices, respectively. The prefix and suffix play the roles of a guard interval and suppress the OoBE, and the IFFT symbol has the same size as the discrete Fourier transform symbol in the CP-OFDM symbol and serves as an information field. Specifically, as the center matrix generating the IFFT symbol is orthogonal, data and pilot symbols can be allocated to any subcarrier without distinction. Even if the proposed precoder is required to generate OFDM symbols with spectral efficiency in the transmitter, a corresponding decoder is not required in the receiver. The proposed scheme is compared with CP-OFDM in terms of spectrum, OoBE, and bit-error rate.

• ETRI Journal
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• v.39 no.3
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• pp.326-335
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• 2017

In the uplink transmission of massive (or large-scale) multi-input multi-output (MIMO) systems, large dimensional signal detection and its hardware design are challenging issues owing to the high computational complexity. In this paper, we propose low-complexity hardware architectures of Richardson iterative method-based massive MIMO detectors. We present two types of massive MIMO detectors, directly mapped (type1) and reformulated (type2) Richardson iterative methods. In the proposed Richardson method (type2), the matrix-by-matrix multiplications are reformulated to matrix-vector multiplications, thus reducing the computational complexity from $O(U^2)$ to O(U). Both massive MIMO detectors are implemented using a 65 nm CMOS process and compared in terms of detection performance under different channel conditions (high-mobility and flat fading channels). The hardware implementation results confirm that the proposed type1 Richardson method-based detector demonstrates up to 50% power savings over the proposed type2 detector under a flat fading channel. The type2 detector indicates a 37% power savings compared to the type1 under a high-mobility channel.

• ETRI Journal
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• v.39 no.3
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• pp.336-344
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• 2017

In this paper, we propose a convenient microwave orbital angular momentum (OAM) mode generation and multiplexing method operating in the 18 GHz frequency band, based on a $2{\times}2$ uniform circular array and a $4{\times}4$ Butler matrix. The three OAM modes -1, 0, and +1 were generated and verified using spatial S-parameter measurements; the measured back-to-back mode isolation was greater than 17 dB in the full 17 GHz to 19 GHz range. However, the radiated OAM beam centers were slightly dislocated and varied with both frequency and the mode index, because of the non-ideal characteristics of the Butler matrix. This resulted in mode isolation degradation and transmission distance limitations.

• Korean Journal of Optics and Photonics
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• v.5 no.1
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• pp.25-30
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• 1994

We derive a set of formuale which show one-to-one correspondence between the the unitary Jones matrices of transparent anisotropic media and the rotational transformations on the Poincare sphere. By using the formuale one can determine the vectorial representation of the rotational transformation on the Poincare sphere which specifies the direction of the axis and the angle of the rotation in terms of the three parameters specific to the corresponding unitary Jones matrix, and conversely the the three parameters of the uniatry Jones matrix in terms of the vectorial representation of the corresponding rotational transformation on the Poincare sphere. To understand the polarization transmission characteristics of an optical system consisting of transparent linear anisotropic media, start with the Jones calculus to get the unitary Jones matrix for the whole system and then convert it to a rotational transformation on the Poincare sphere, from which we can intuitively understand the effect of the optical system on the polarization state of the light passing through the system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11A
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• pp.852-861
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• 2009

We propose a complexity reduced Lattice Reduction(LR) scheme for MIMO detection under time varying fading environments. It is found that for successive MIMO transmission instances, the integer matrix P after LR decomposition remains the same or only a few elements of the matrix P are slightly changed. Based on this feature, we perform LR reduction by setting the initial values for P matrix for the decomposition to be the one obtained in the previous instance not starting from the identity matrix. Simulation results reveal that the proposed scheme drastically reduces overall complexity of LR reduction compared to the conventional scheme for various system parameters under time varying channels. We also show that the proposed scheme can be applied to Seysen LR as well as LLL(Lenstra, Lenstra, and Lavasaz)-LR.

• Journal of the Institute of Convergence Signal Processing
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• v.14 no.1
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• pp.45-50
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• 2013

Sensors have limited resources in sensor networks, so efficient use of energy is important. Representative clustering methods, LEACH, LEACHC, TEEN generally use direct transmission methods from cluster headers to a sink node to pass collected data. If clusters are located at a long distance from the sink node, the cluster headers exhaust a lot of energy in order to transfer the data. As a consequence, the life of sensors is shorten and re-clustering is needed. In the process of clustering, sensor nodes consume some energy and the energy depletion of the cluster headers meet another energy exhaustion. A method of transferring data from cluster headers to the sink using neighbor clusters is needed for saving energy. In this paper, we propose a novel routing method using a multi-hop transmission method in cluster sensor networks. This method uses the topology matrix which presents cluster topology. One-hop routing and two-hop routing are proposed in order to increase the energy efficiency.

• Applied Microscopy
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• v.38 no.2
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• pp.107-115
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• 2008

The filtration barrier of kidney consists of endothelial cell, glomerular capillary, glomerular basement membrane, mesangial matrix, and podocyte. In aged rats, the morphological changes were shown in various parts, including the glomerulus. These changes were thickening of basement membrane and mesangial matrix, crescent formation of glomerular capillary, deformity of foot processes, glomerular sclerosis and obsolescence. But these glomerular morphologies are partial images or few serial images analysis. In this study, we examined the morphological alteration of glomerulus in the young and aged rats by light microscopy, transmission electron microscopy and three dimensional reconstruction. We were found in aged rat glomerulus, expansion of urinary space and mesangial matrix, thickening and degrading of glomerular basement membrane, decreasing in podocyte foot processes, fragmentation of podocytic nucleus membrane. These observations indicate that may provide useful data for investigating the pathogenesis of age-related dysfunction of kidney.

• Korean Journal of Metals and Materials
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• v.49 no.12
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• pp.995-1000
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• 2011

The microstructure of Cu-24 wt.%Ag filamentary nanocomposite fabricated by a thermo-mechanical process has been investigated by transmission electron microscopy (TEM) observations. This study is focused on the stability of Ag filaments formed by cold drawing; the effects of thermal treatment on the precipitation behavior and distribution of Ag-rich precipitates were also investigated. The Ag filaments elongated along the <111> orientation were observed in Cu-rich ${\alpha}$ phase of the as-drawn specimen and the copper matrix and the silver filament have a cube on cube orientation relationship. Annealing at temperatures lower than $200^{\circ}C$ for the as-drawn specimen caused insignificant change of the fibrous morphology but squiggly interfaces or local breaking of the elongated Ag filaments were easily observed with annealing at $300^{\circ}C$. When samples were annealed at $400^{\circ}C$, discontinuous precipitation was observed in supersaturated Cu solid solution. Ag precipitates with a thickness of 7-20 nm were observed along the <112> direction and the orientation relationship between the copper matrix and the Ag precipitates maintained the same orientation relationship in the as-drawn specimen. The interface between the copper matrix and the Ag precipitates is parallel to {111} and micro-twins were observed in the Ag precipitates.