• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.7
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• pp.689-695
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• 2012

The friction factor in a rod bundle and the loss coefficient at a spacer grid were examined. As a test section, 25 smooth rods, 9.5 mm in diameter and 2000 mm in length, were prepared and installed in a $5{\times}5$ square array in a square channel. In this case, the P/D (Pitch-to-Diameter ratio) was 1.35. In this work, plain (i.e., no mixing vanes), split-vane, and hybrid-vane spacer grids were tested. In a bare rod bundle (i.e., no spacer grid), the measured friction factors were in good agreement with the previous correlations. Among the spacer grids tested, the hybrid-vane spacer grid presented the largest friction factor in the rod bundle and loss coefficient. This may be because of the flow pattern change induced by large relative plugging of the flow cross section and mixing vane geometry. At Re=$5{\times}10^5$, the predicted loss coefficients of plain, splitvane, and hybrid-vane spacer grids were approximately 0.79, 0.80, and 0.88, respectively.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.107-112
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• 2006

The previous acquisition method of GPS receiver for reference station adopts not only the coherent integration method but also the non-coherent integration method in order to enhance sensitivity under noisy environment. However, under noisy environment, the previous GPS signal acquisition method causes the non-coherent integration loss which is a major factor among losses that can be caused during GPS signal acquisition. The non-coherent integration loss also increases with the strength of the received noise. This paper has intention of analyzing the performance of the GPS signal acquisition method proposed to effectively enhance sensitivity of DGPS reference receiver under noisy environment. This paper presents that the proposed GPS signal acquisition method suppresses the non-coherent integration loss through post-processing simulation. Furthermore, with regard to the mean acquisition time, it is shown that the number of search cells of the proposed GPS signal acquisition method is much fewer than that of the previous GPS signal acquisition method.

• Journal of IKEEE
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• v.26 no.1
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• pp.89-94
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• 2022

The W-band (75-110GHz) is a band that can utilize at least 10 times more bandwidth than the existing 5G band. Therefore, it is one of the bands suitable for future mobile communication that requires high speed and low latency, such as virtual and augmented reality. However, since the wavelength is short, it has a high path loss and is very sensitive to the atmospheric environment. Therefore, in order to develop a W-band communication system in the future, it is necessary to analyze the characteristics of path loss according to the channel environment. In this paper, to analyze the characteristics of the W-band path loss, the random forest technique was used, and the influence of the channel parameters according to the distance section was analyzed through the path loss data according to various channel environment parameters. As a result of the simulation, the distance has the highest influence on the path loss in the short distance, and the other channel environment factor is almost ignored. However, as the distance section became longer, the influence of distance decreased while the impact of clutter and rainfall increased.

• Journal of Power System Engineering
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• v.20 no.6
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• pp.71-79
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• 2016

This paper introduces the design method of the centrifugal turbo fan and the process of developing the design program of it. The developed design program confirmed the applicability by experimental performance data. Here, we proposed new velocity coefficients and considered various losses such as impeller inlet loss, vane passage flow loss, casing pressure loss, recirculation loss power, and disk friction loss power. Especially, the inlet and outlet widths of the impeller were newly determined by reflecting the experimental results. As a result, this fan design program shows a good performance result regardless of the types of impeller and is expected to be a very useful design tool.

• Proceedings of the KIEE Conference
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• summer
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• pp.1010-1012
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• 2004

AC loss is an important factor in the development of superconducting tapes and superconducting power applications. In this paper we measured and compared characteristics of BSCCO tape and YBCO Coated Conductor(YBCO CC). BSCCO tape was fabricated by PIT method. We measured critical current density and transport current loss of it. Also, YBCO CC tape consist of substrate. buffer, YBCO and metal layers. We measured critical current density on variations of external magnetic field and transport current loss of these cases. The results of measurement show that normalized critical current of YBCO CC is smaller then that of BSCCO tape in the external magnet field. According to the results. measured loss and calculated of the YBCO CC show the same tendency.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.5
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• pp.88-94
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• 2012

Development trend of modern HSDI diesel engine is now focusing on low fuel consumption and emission because of strong interest in global environmental protection. Two big branches of criteria for modern diesel engine development are down sizing and down speeding. Down sizing keeps engine operation condition to the direction of higher load and thus pursuing for better thermal efficiency. But this may cause degraded vehicle dynamic performance because of reduced back up torque. Down speeding keeps engine operation condition to the direction of slightly higher load and lower engine speed. Therefore reduction of back up torque can be limited within flat torque area. This study analyzed fuel economy effect of down speeding on a vehicle powered by HSDI diesel engine in aspect of engine friction work, intake and exhaust pumping work, exhaust hat loss and thermal loss of fuel leakage of fuel injection system. Contribution factor of each engine and vehicle related parameters under basic and down speeding condition were compared and work balance of down speeding during NEDC was analyzed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.3 s.106
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• pp.229-238
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• 2006

In this paper, developed study about isolator that after design and optimizes center strip to use 3-D simulator. We use the factor about the change and propose simple mode of the simulation. Design strip line that center frequency is 1.85 GHz by software that use 3-D finite element method(FEM) and confirmed variable. Developed isolator were shown that more than isolation 25 dB, reflection loss has the more than 25 dB and insertion loss does not 0.2 dB. We could confirm that compare with simulation and manufacture sample propertied agrees more than 90 %.

• Journal of Biosystems Engineering
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• v.43 no.4
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• pp.296-302
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• 2018

Purpose: The aim of this study was to determine appropriate threshing and selection conditions for sorghum harvesting using a rice combine-harvester. Methods: Sorghum harvesting performance was tested using an actual rice combine. Through this test, the grain loss rate and the composition of crops according to the engine and fan speeds of the combine were investigated. Furthermore, the optimal threshing and selection conditions were determined by carrying out a harvest test based on the opening size factor of the concave in a test field. Results: The grain loss rate for the sorghum using a concave ($18{\times}18mm$) of the rice combine was the lowest at 0.1% at a chaffer angle of $40^{\circ}$, engine speed of 2000 rpm, and fan speed of 20 m/s, but the sorting sieve clogged frequently. Furthermore, as the engine speed and fan speed increased, the grain loss rate also increased. The sorghum harvesting test results of the combine according to the concave opening size showed that the grain loss rate was 0.5% at a driving speed of 0.5 m/s, with a concave opening diameter of 13 mm, a chaffer angle of $40^{\circ}$, a concave sieve oscillation frequency of 4.8 Hz, a fan speed of 20 m/s, and an engine speed of 2000 rpm. Conclusions: Findings showed that sorghum could be harvested using a head feeding rice combine.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1222-1224
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• 2005

AC loss is an important factor in the development of superconducting tapes and superconducting power applications. In this paper, magnetization loss in YBCO coated conductor have been measured and compared with Brandt equation. Measurements of magnetization loss were performed under various angles of external magnetic field to consider the anisotropic characteristics of YBCO coated conductors. The results show that measured values of magnetization loss agreed well with the calculated value by using Brandt equation, especially at large degrees of incidence angle. The magnetization losses were strongly influenced by the direction of external magnet field as were expected.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.2
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• pp.107-112
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• 2013

In this paper, we discuss a 3-dimensional localization sensor node using EM waves (Electromagnetic waves) with RSSI (Received Signal Strength Indicator). Generally EM waves cannot be used in underwater environment, because the signal is highly attenuated by the water medium according to the distance. Although the signal quickly reduces in underwater, the reducing tendency is very clear and uniform. Hence EM waves have possibility as underwater distance sensors. The authors have verified the possibility by theory and several experiments, and developed calibration methods in case of linear and planer environment. For 3-dimensional localization in underwater, it must be known antenna's radiation pattern property in electric plane(called E-plane). In this paper, we proceed experiments to verify attenuation tendency with z axis movement, PLF (Polarization Loss Factor) and ILF (Inclination Loss Factor) with its theoretical approach.