• 전기학회논문지P
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• 제62권4호
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• pp.192-197
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• 2013

Road traffic noise barriers being used to reduce the noise, but the city surroundings inhibition, ecosystem disturbance, and it is difficult to maintain. Can enhance or complement the existing noise barrier performance, so that it is necessary to develop an electronic noise-reduction system In this paper, we proposed an electronic road noise reduction devices to reduce road noise for a DSP-based signal processing and analog signal input-output controller. In order to verify the control performance, we performed noise reduction experimentation of ANC by filtered-X LMS algorithm and traffic noise signal injection. The controller is equipped with noise reduction algorithms were tested on the characteristics of directional and omnidirectional speaker.

• 한국환경복원기술학회지
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• 제23권5호
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• pp.1-14
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• 2020

In order to improve the urban thermal environment, efforts are being made to increase green areas in cities that include park construction, planting, and green roofing. Among these efforts, urban parks play an important role not only in improving the urban thermal environment, but also in terms of ecosystem services (serving as resting places for citizens, providing cleaner air quality, reducing noise, etc.). Therefore, the purpose of this study is to suggest planning and management guidelines for urban parks that are effective in improving the thermal environment, by analyzing the urban surface temperature reduction performance of urban parks. To do this, first, land surface temperature was calculated by using Landsat 8 images. Second, the PCI (Park Cool Island) index was calculated to identify the temperature reduction performance of urban parks. Third, the characteristics of parks (area, shape, vegetation) and the surrounding spatial characteristics (land cover, building-related variables, etc.) were identified. Finally, the relationship between the PCI indices (PCI scale, PCI effect, PCI intensity) and the characteristics of the parks and their surroundings were analyzed. The results revealed that the parks consisting of a larger area, simple shape, and higher tree coverage ratio had increased PCI performance, and were advantageous for improving the urban thermal environment. Meanwhile, PCI performance was found to have decreased in areas with a higher impermeable area ratio and building coverage ratio. The outcomes of this study can be used to identify priority areas for planning and management of urban parks and can also be utilized as planning and management guidelines for improving urban thermal environment.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2012년도 춘계 학술논문 발표대회
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• pp.201-203
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• 2012

The establishment of the technology for evaluating friction resistance and pipe pressure and the relation of the fluid characteristics and pumpability of concrete is essential for the evaluation of concrete pumping performance for high speed construction of super-tall building. So, this study focuses on quantitative evaluation of concrete fluid characteristics and surface friction resistance under the change of concrete mix proportion and pumping condition. In this study, we measured the rheology of concrete and pipe pressure and surface friction characteristics when pumping. And, relations between the rheology characteristics of concrete and pumping performance was investigated by experiment. As the result of the experiment, high regression between the surface friction and pressure gradient was confirmed. And, prediction model to evaluate the friction resistance coefficient and pipe pressure reduction coefficient was suggested.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 추계학술대회 논문집
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• pp.159-159
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• 2009

In this work, nitrogen and oxygen functionalities was introduced to the graphite nanofibers (GNFs) and their effect on electrocatalytic performance of the GNF supports for direct methanol fuel cells (DMFCs) was invesigated. The nitrogen and oxygen groups were introduced through the urea treatments and acid treatment, respectively. And, PtRu catalysts deposited on modified GNFs were prepared by a chemical reduction method. The catalysts were characterized by means of elemental analysis, nitrogen adsorption, and X-ray photoelectron spetroscopy (XPS). The structure and morphological characteristics of the catalysts were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). As a result, the Pt-Ru nanoparticles were impregnated on GNFs with good formation in 3-5 nm. And, the cyclic voltammograms for methanol oxidation revealed that the methanol oxidation peak varied depending on changes of surface functional groups. It was thus considered that the PtRu deposition was related to the reduction of PtRu and surface characteristics of the carbon supports. The changes of surface functional groups were related to PtRu reduction, significantly affect the methanol oxidation activity of anode electrocatalysts in DMFCs.

• Nuclear Engineering and Technology
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• 제51권2호
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• pp.439-443
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• 2019

To improve the noise characteristics, software-based noise reduction algorithms are widely used in cadmium zinc telluride (CZT) pixelated semiconductor gamma camera system. The purpose of this study was to develop an improved median filtering algorithm using a thresholding method for noise reduction in a CZT pixelated semiconductor gamma camera system. The gamma camera system simulated is a CZT pixelated semiconductor detector with a pixel-matched parallel-hole collimator and the spatial resolution phatnom was designed with the Geant4 Application for Tomography Emission (GATE). In addition, a noise reduction algorithm with a median filter using an improved thresholding method is developed and we applied our proposed algorithm to an acquired spatial resolution phantom image. According to the results, the proposed median filter improved the noise characteristics compared to a conventional median filter. In particular, the average for normalized noise power spectrum, contrast to noise ratio, and coefficient of variation results using the proposed median filter were 10, 1.11, and 1.19 times better than results using conventional median filter, respectively. In conclusion, our results show that the proposed median filter using improved the thresholding method results in high imaging performance when applied in a CZT semiconductor gamma camera system.

• Industrial Engineering and Management Systems
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• 제13권4호
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• pp.454-462
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• 2014

Retention of possible churning customer is one of the most important issues in customer relationship management, so companies try to predict churn customers using their large-scale high-dimensional data. This study focuses on dealing with large data sets by reducing the dimensionality. By using six different dimension reduction methods-Principal Component Analysis (PCA), factor analysis (FA), locally linear embedding (LLE), local tangent space alignment (LTSA), locally preserving projections (LPP), and deep auto-encoder-our experiments apply each dimension reduction method to the training data, build a classification model using the mapped data and then measure the performance using hit rate to compare the dimension reduction methods. In the result, PCA shows good performance despite its simplicity, and the deep auto-encoder gives the best overall performance. These results can be explained by the characteristics of the churn prediction data that is highly correlated and overlapped over the classes. We also proposed a simple out-of-sample extension method for the nonlinear dimension reduction methods, LLE and LTSA, utilizing the characteristic of the data.

• 환경생물
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• 제34권4호
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• pp.272-280
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• 2016

Changes in land use and increase in urban energy consumption influence urban life. This study analyzed the characteristics and patterns of urban heat and presents management schemes to generate a comfortable and sustainable urban environment. The study aimed to demonstrate the positive effects of artificial ground greening on improving the microclimate through evapotranspiration using perennial herbs. We have designed a chamber that could control constant temperature and humidity, measure temperature reductions in each plant and changes in sensible heat and latent heat. This study identified Sedum kamtschaticum as the most effective plant in controlling temperature. At $22^{\circ}C$, $3.2^{\circ}C$ temperature reduction was observed, whereas four other plants showed a $1.5^{\circ}C$ reduction. At $25^{\circ}C$, $2.0^{\circ}C$ temperature reduction was observed. On the other hand, the use of Sedum sarmentosum resulted in the lowest effect. Zoysia japonica is the most commonly used ground covering plant, although the temperature reduction of Lysimachia nummularia was more effective at high temperature conditions. Sensible heat and latent heat were calculated to evaluate the thermal performance of energy. At a temperature >$30^{\circ}C$, L. nummularia and S. sarmentosum emitted high latent heat. In this study, we analyzed the thermal performance of green roof perennial plants; in particular, we analyzed the evapotranspiration and temperature reduction of each plant. Since the substrate depth and types, plant species, and seasonal change may influence temperature reduction and latent heat of green roofs, further studies are necessary.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.8-12
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• 2003

To protect digital communications and broadcasting that are expected to be increasingly used at frequencies above 1GHz, there is a need to determine permissible disturbance limits for frequency bands above 1GHz according to indicates that better correlates with interference level in digital systems. The quality of digital communications is expressed in terms of bit error rate(BER) or throughput. In this regard, it has been reported that degradation of BER or throughput can be estimated from the amplitude probability distribution (APD) of disturbance amplitude. Therefore, if the APD can simply be measured with a high accuracy, APD will be an optimal index for the assessment of interference in digital communications. In this paper, we show that a measurement method using statistic model of APD has compatibility about performance reduction estimation of WLAN. And through approach of this inspection, we propose numeral models about interference effects of peak value and time rate of spurious.

• 한국기계연구소 소보
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• 통권12호
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• pp.63-71
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• 1984

A new kind of bulb called Stern-End-Bulb(SEB) for the improvement of the after part of fine hull forms was developed. The reduction of wave resistance and the improvement of the powering performance for the ship with SEB were shown by the ship model tests, At the same time, the characteristics of wave in the vicinity of the stern and the mechanism of the resistance reduction by SEB were investigated. By the systematical variation of the SEB size, the optimum size of SEB was obtained.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1999년도 전력전자학술대회 논문집
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• pp.130-133
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• 1999

It is one of the most effective methods for improving the performance of electric railway vehicles to make better the wheel-railway adhesion characteristics. The purpose of this paper is to develop the equivalent reduction machine to experiment on the adhesion system. The experiment system makes it possible to change the wheel-rail adhesion force with various adhesion parameters, and therewith to test the adhesion control system with the reduction machine in a laboratory.