• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.8
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• pp.25-31
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• 2018

Recently, research on the development of lightweight vehicle bodies is increasing continuously as a response to fuel economy regulations. To reduce the weight of a vehicle body, a conventional steel plate has been substituted by light weight material with high specific strength and the jointing of multi-materials is generally applied. On the other hand, the customer's demand for safety and emotional quality in NVH (Noise, Vibration and Harshness) is becoming increasingly important. Therefore, a light weight with proper strength and NVH quality is needed. In the view of light weighting and NVH quality, the application of a vibration proof steel plate can be an effective solution but the formability of a sandwich panel is different with a conventional steel sheet. Therefore, careful analysis of formability is required. This study aims to characterize the formability of a sandwich high-strength steel plate. The high-strength steel plates of different thicknesses with resistance spot welding and sealer bonding were analyzed using forming limits diagram through a cup drawing test.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.2
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• pp.221-228
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• 2020

A sonobuoy is dropped onto the surface of water to estimate the bearing of an underwater target. A Directional Frequency Analysis and Recording (DIFAR) sonobuoy has an error in the specific angular section due to the method of estimating bearing and noise, which causes an error in target localization using multiple sonobuoys. In addition, the position of the sonobuoy continues to move, but since a sonobuoy with a GPS is intermittently arranged, it is difficult to estimate the exact position of the sonobuoy. This also causes target localization performance degradation. In this paper, we propose a technique to improve the target localization performance by compensating for bearing errors using characteristics of the DIFAR sonobuoy and multiple-sonobuoy position errors based on the intermittently arranged active sonobuoy with a GPS.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.7
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• pp.3216-3223
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• 2012

Deep cement mixing method (DCM) is one of the most effective improving methods for deep soft ground. The strength of soft soil can be increased in a short period of time with less noise and vibration. However, it is necessary to determine the stress transferring and concentration ratio of the composite soft ground for estimating the settlement behaviors. In this study, a model test was undertaken to investigate the stress distribution of the improved soil. Results of the model test shows that stresses were concentrated mainly on the improved areas by DCM and the concentration ratios (35.4, 28.6, 27.02) were obtained using several different techniques. These were well in accordance with other previous research results (26.52, 32.5).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.1
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• pp.500-506
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• 2011

The deep mixing method, which is generally considered as a method for improving soft ground, is assessed in terms of its applicability for urban construction. Using small equipment tailored to perform deep mixing in congested urban areas, deep mixing was performed to reinforce the foundation ground of a retaining wall in a redevelopment site in Seoul. Strengths characteristics, construction vibrations and displacements induced to an adjacent old masonry wall were evaluated by laboratory tests and field monitoring. The results indicate that the strength of ground was improved appropriately whilst the vibrations and displacements induced by deep mixing were slight enough to satisfy the general requirements for construction works in urban environments. Therefore, it is concluded that deep mixing method can be a practical option for foundation methods in urban construction works where minimizing noise and vibrations is an important concern.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.6
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• pp.2729-2734
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• 2011

In this paper, an active replica Low-dropout(LDO) regulator with DC voltage matching circuit is presented. In order to match the voltage between replica and output of regulator, DC voltage matching circuit is designed. The active replica low dropout regulator has higher Power Supply Rejection(PSR) than that of conventional regulator. The designed DC voltage matching circuit can reduce the drawback that may be occurred in replica regulator. And using fully active element in regulator can reduce the chip area and heat noise with resistor. As results of HSPICE simulation with 0.35um CMOS parameter, the designed active replica LDO regulator achieves Power Supply Rejection, -28@10Hz better than -17@10Hz of conventional replica regulator without DC matching circuit. And the output voltage is 3V.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.6
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• pp.2830-2839
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• 2011

Because the puretone audiometer is an important medical instrument used to diagnose hearing loss, the IEC and ANSI has been published a specification with which audiometer should comply. This paper describes development of Linux based real-time spectrum analyzer which is dedicated to puretone audiometer. It can measure not only hearing level but also compliance of IEC standard for puretone audiometer such as frequency accuracy, harmonic distortion, pulsed tone, narrow band noise and linearity. We have verified our real-time spectrum analyzer through comparing to commercial product.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.2
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• pp.476-484
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• 2010

Recently, as the piezoelectric transformer technology develops, piezoelectric transformer may become a variable alternative to magnetic transformers in various applications. Because it was have to favorable characteristics such as electromagnetic-noise free, compact size, higher efficiency, and superior power density, linkage flux, noiseless, etc. its resonance frequency was used to output waveform of a sine wave. In this paper, the switching mode power supply of about 87.2[KHz] is driven by the multilayer thickness vibration mode piezoelectric transformer and the DC to DC converter drive circuit using an electrical equivalent circuit is proposed. Also, it was possible to drive power source device of the high-luminance LED by propose circuits.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.9
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• pp.5776-5782
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• 2014

Relay-assisted wireless communication systems have been studied widely to cope with shadow areas and extend the cell coverage. This paper proposes a space-frequency (SF) block coded single carrier-frequency division multiple access (SC-FDMA) transmission system in a relaying multi-path shadow area and present the performance comparison of SC-FDMA systems based on the signal-to-noise power ratio (SNR) between a relay and a destination station. The performance of relaying SC-FDMA systems can be improved by applying SF block code to the recovered signals of relays before re-transmitting them. The simulation result showed that the SNR performance of the proposed SF block coded relaying SC-FDMA system was approximately 5 dB better than the SNR performance of the single-path relaying SC-FDMA system at a symbol error rate (SER) of $10^{-2}$.

• Environmental Analysis Health and Toxicology
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• v.14 no.4
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• pp.175-187
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• 1999

To investigate the risk perception of environmental issues, two consequtive surveys were conducted to environmental professionals using a standardized questionnaire from September to October in 1999. The number of subjects were 72 for the first survey and 68 for the second one. The questionnaire was consisted of items such as the degree of environmental pollution in Korea, risk perception of some issues on human health and ecosystem, and seriousness of the problems in the real situation in Korea. For the degree of environmental pollution in Korea, the average risk rating in the second test (7.4 point) was significantly higher than that in the first test (7.2 point). The risk perception on the general human health and ecosystem, and the seriousness in Korea situation were analyzed in the order of ′air pollution′, ′water pollution′,′soil contamination′,′waste′,′toxic chemical pollutants′,′food contamination′,′ocean contamination′, ′odor pollution′, and ′noise pollution′. Also ′toxic chemical pollutants′ problem was perceived to be the highest risk on general human health or ecosystem, and on present situation in Korea. ′Automotive vehicle exhaust′ problem was perceived to be the most severe environmental problems among specific 30 items. ′Industrial source air pollution′,′toxic air pollutants′, and ′domestic and industrial source pollutants to surface water′ were relatively severe environmental problems comparing to other problems. The pollution issues were classified into four categories by two aspects of perception; risk in general setting and seriousness in Korea situation. If the issues were highly serious in Korea and low risk perception in general setting then it is named "the Korea-specific group". Those that were all high score in two aspects, named "the Common group". Those that were all low in two aspects, named "the Nonsignificant group". And the issues were high risk perception in general setting and low seriousness in Korean situation, named "the Latent group".

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.6
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• pp.2240-2245
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• 2010

Myocardial imaging in SPECT (Single Photon Emission Computed tomography) scan of the gamma-ray emitting radiopharmaceuticals to patients after intravenous radiopharmaceuticals evenly spread in the heart region of interest by recording changes in the disease caused by a computer using the PSA test is to diagnose. Containing information on the functional myocardial perfusion imaging is a useful way to examine non-invasive heart disease, but the argument by noise and low resolution of the physical landscape that is difficult to give. For this paper, the level of myocardial imaging by using the three algorithms to split the video into 3-D implementation of the partitioned area to help you read the proposed plan. To solve the difficulty of reading level, interest in using the sheet set, partitioned area of the left ventricle was ranked the partitioned area was modeled as a 3-D images.