• Journal of Advanced Marine Engineering and Technology
• /
• v.39 no.3
• /
• pp.238-242
• /
• 2015

A steam jet vacuum system that will be implemented in a multi-effect desalination plant is numerically investigated. The objective of this study is to numerically investigate the performance characteristic of the steam jet vacuum system for the sea water distillation process. The effects of design parameter such as nozzle size and converging duct angle are discussed in order to get a better understanding of flow characteristics inside the steam ejector and subsequently pave the way for more optimum designs. The simulation results have been in good agreement with experimental data and have well reproduced the shock train phenomena of the throat region.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37B no.9
• /
• pp.741-749
• /
• 2012

Ad Hoc Self-Organizing TDMA (ASO-TDMA) has been proposed as a specification to support the multi-hop data communication service for ships over VHF band. It allows for organizing a multi-hop ad-hoc network in a distributed manner by sharing the radio resources among the ships navigating along the route. In this paper, Markov chain analysis is given to provide the average throughput performance for ASO-TDMA protocol Furthermore, the analytical results are verified with computer simulation, which shows that there exists the optimal transmission rate to maximize the average throughput as the subframe size and the number of ships are varying in each hop region.

• Korean Journal of Optics and Photonics
• /
• v.15 no.1
• /
• pp.28-33
• /
• 2004

An in-line fiber coupler, based on side-polished single-mode fibers covered with an intermediate coupling layer and a planar waveguide, is analyzed by modeling the interaction region as an equivalent multi-layered planar waveguide. The reflectance for the multi-layered structure with and without buffer layer is illustrated as a function of the refractive index and thickness of the overlay waveguides. When the refractive index of the overlay waveguides is greater than that of the fiber core, the conditions for the intermediate coupling layer to increase the power coupling from the fiber to the overlays is also explained. Through the experimental results using a LiNbO$_3$planar waveguide, we show that the theoretical analysis is reasonable and in good agreement with the measured values.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.16 no.4
• /
• pp.311-317
• /
• 2004

In the present study, the cooling characteristics of the multi-air conditioner (A/C) using an inverter scroll compressor are experimentally investigated for the number of the indoor units and the operating conditions (2$0^{\circ}C$, 24$^{\circ}C$, 26$^{\circ}C$) under the cooling standard conditions by KS C 9306. In the case of the simultaneous operation for 3 indoor units, the cooling capacity, the mass flow rate and the input power have a decreasing trend and COP has an increasing trend, with decreasing the difference in the operating temperature of the indoor unit and the room temperature. In the case of the simultaneous operation for 2 indoor units, the COP of the indoor unit with large cooling capacity is high when the operating temperature is high, but the COP of the indoor unit with low cooling capacity is high when the operating temperature is low. In the case of the single operation for one unit, when the large cooling capacity of the indoor unit is less than 50％ the compressor operates at the minimum operation frequency region and the COP decreases.

• KIEE International Transactions on Electrophysics and Applications
• /
• v.4C no.6
• /
• pp.288-294
• /
• 2004

In this paper, a ceramic antenna and diplexer are designed for dual-band handset ap plications. Basically, the antenna is designed by using the meander line configuration. The diplexer presented in this paper is composed of both low- and high-pass filters. We have designed the low- and high-pass filters with attenuation poles to improve the attenuation performances of the diplexer. The attenuation poles are located at each rejection frequency region so as to improve the shrinkage characteristic of the diplexer. In order to accomplish the volume effectiveness, the antenna and the diplexer have been designed and fabricated in a multi-layer structure. The diplexer designed with a multi-layer structure has inductors and capacitors, which are implemented by LTCC (Low Temperature Co-fired Ceramics) process technique. Design of the multi-layer antenna and diplexer has been achieved by employing the full 3-D EM simulation. The designed antenna and diplexer offer excellent return loss and broadband performances with highly isolated rejection performance.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.54 no.7
• /
• pp.332-338
• /
• 2005

PD(Partial Discharge) signal emitted from PD sources has their intrinsic features in the region of time and frequency STFT(Short Time Fourier Transform) shows time-frequency distribution at the same time. 2-Dimensional matrices(33$\times$77) from STFT for PD pulse signals are a good feature vectors and can be decreased in dimension by wavelet 2D data compression technique. Decreased feature vectors(13$\times$24) were used as inputs of Back-propagation ANN(Artificial Neural Network) for discrimination of Multi-PD sources(air discharge sources(3), surface discharge(1)). They are a good feature vectors for discriminating Multi-PD sources in the air.

• Journal of Power System Engineering
• /
• v.11 no.2
• /
• pp.44-50
• /
• 2007

The oxidation behavior of commercial pure titanium is investigated in the temperature range of $727^{\circ}C{\sim}950^{\circ}C$ in mixed gases. The weight change is measured by TGA during oxidation in mixed gases. The oxidation behavior indicated by weight gain or the growth of oxide layer is based on the linear rate law at high temperatures. The structure of the oxide scale formed during oxidation is analysed by optical microscopy, electron probe microanalyzer, scanning electron microscope and x-ray diffraction. Oxide scales have a $TiO_2$ structure, and are constituted with multi-layered or two layered porous external one and a dense internal one. Ti-O solid solution region is formed at the interface of metal and scale layer. The formation of oxide scale is influenced by the oxidation temperature, time, crystal structure and the condition of atmosphere.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.62 no.8
• /
• pp.1120-1124
• /
• 2013

Our objective of this study was to reduce radio frequency coil (RF) control time at 3 T MRI systems. A compressed method is proposed with a convex optimization and pseudo-inverse method in multi-channel RF coils. After applying the proposed methods, fields are homogenized with less field data. Even with 80% compression, the fields are well homogenized and localized, indicating that mapping requires only 20% of the original data. Detailed values are compared between each compressed result in and outside the region of interest at 3 T.

• Journal of the Optical Society of Korea
• /
• v.18 no.6
• /
• pp.783-787
• /
• 2014

This paper presents an improved vertical alignment nematic liquid crystal mode characterized by the protrusions or slits of the top substrate and additional stripe type common electrodes with polarity switching of the bottom substrate to improve multi-domain vertically aligned (MVA) and patterned vertically aligned (PVA) nematic modes. MVA and PVA modes have disadvantages such as an LC disclination in the vicinity of the middle region of electrodes between the top and bottom protrusions in MVA mode or the top and bottom slits in PVA mode. Therefore, the stripe type common electrode generating a horizontal electric field and the protrusion or slit producing some pretilt of liquid crystals (LCs) were used to improve the LC disclination, which influences the transmittance and response speed. The simulation results showed that the proposed VA mode has higher transmittance than the MVA and PVA modes. As a result, the proposed VA mode can improve the response speed and transmittance remarkably, which makes it useful for upgrading the LCD display quality.

• Proceedings of the IEEK Conference
• /
• 2003.11a
• /
• pp.461-464
• /
• 2003

This paper proposes the multi-level vector error diffusion for smear artifact reduction in the boundary regions. Smear artifact mainly results from a large accumulation of quantization error. Accordingly, to reduce these artifacts, the proposed method excludes the large quantization error in the error diffusion process by comparing the magnitude of the error vector with predetermined first threshold. In addition, if the vector norm of the difference between the error adjusted input vector and the primary co]or that has minimum vector norm for the error adjusted input vector is larger than second threshold, the error is excluded. As a result, the proposed method reduce smear artifact in the boundary region and produces visually pleasing halftone pattern.