• The Journal of the Acoustical Society of Korea
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• v.4 no.3
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• pp.33-41
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• 1985

이 논문에서는 frequency-weighted MSE를 최소화하는 적응 pre-filter와 post-filter를 음성파형 부호화기에 적용했을 때의 성능을 분석한다. 먼저 여러 다양한 pre-filter와 post-filter에 의한 noise shaping 효과를 이론적으로 보여준다. 그리고 frequency-weighted SNR 척도를 사용하여 적응 pre-filter 와 post filter에 의한 성능면에서의 이득을 이론적으로 유도한다. 적응 pre-filter와 post-filter를 ADM과 ADPCM 부호화기에 적용해본 결과에 의하면 음성파형 부호화기의 성능을 FWSNR\sub SEG\ 척도로 약 3dB 정도 개선할 수 있음을 알 수있다. 또한 pre-filter와 post-filter를 사용하면 청각적으로 중요한 영향을 미치는 1kHz에서 3kHz 사이의 양자화 잡음을 효과적으로 줄일 수 있다.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.5
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• pp.655-659
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• 2005

Pre-filter system that was consisted of wasted-tire, non-woven fabrics, and sponge was developed as a primary treatment process prior to rainwater reservation or a pre-treatment process of rainwater reuse system for reclamation. By using this system, SS concentration, TOC, COD, and turbidity could decreased by 86.7%, 62.6%, 69.1% and 66.5%, respectively. From the results of particle size distribution of treated water, the particles over than $30{\mu}m$ of diameter were completely removed by pre-filter system. But 90% of particles less than $20{\mu}m$ of diameter were passed through pre-filter. Optimal depth of wasted-tire and non-woven fabrics were 15cm and 2.4cm, respectively. Pre-filter system was considered as an effective alternative for pre-treatment of rainwater including non-point pollutants and it could be also applied for the treatment of combined sewer overflow (CSO).

• Journal of Broadcast Engineering
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• v.11 no.2 s.31
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• pp.229-241
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• 2006

In this paper we propose and analyze a novel modulation and pre-equalization method to minimize signal processing time delay for the Equalization Digital On-Channel Repeater (EDOCR) in ATSC (Advanced Television Systems Committee) terrestrial digital TV system. The proposed modulation method uses Equi-Ripple (ER) filter coefficients instead of conventional Square Root Raised Cosine (SRRC) after coefficients for VSB (Vestigial Side Bands) pulse shaping. And the proposed pre-equalization method calculates pre-equalizer filter coefficients by using baseband signal as reference signal and demodulated repeater output signal, then generates a new VSB pulse shaping filter coefficients by convolutioning ER filter coefficients and pre-equalizer filter coefficients. The newly generated pulse shaping filter does not have minimized time delay by adjusting the number of pre-taps of the filter, but also compensates linear distortions caused by ER filter and mask filter.

• Land and Housing Review
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• v.10 no.2
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• pp.53-58
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• 2019

Particulate matter (PM) is designated as a group 1 carcinogen by the International Agency for Research on Cancer (IARC) of the World Health Organization (WHO). In South Korea, the health threat caused by PM is the most serious level internationally. Therefore, in order to solve the urban PM problem, it is important to develop the technology that can control PM efficiently. In this study, CFD(Computational Fluid Dynamics) simulation was performed for PM pre-filter (type 1-3 with different PM collecting room) to develop a high-efficiency PM collecting device. The complex flow field and the local flow phenomenon inside the PM collecting device were understood with CFD simulation by changing the shape and size of the pre-filter. The PM removal performance can be described with flow rate through the device and PM removal efficiency. The type-1 pre-filter with 5x5 size collecting room was confirmed to have the highest efficiency. Based on the analysis results, the optimal type of pre-filter could be developed and it would be applied as an element technology included in the PM collecting device.

• Journal of Advanced Navigation Technology
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• v.24 no.1
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• pp.53-60
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• 2020

In this paper, We have studied the structure of a Telemetry Transmitter capable of transmitting variable data rates. This paper proposed a structure combining variable pre-modulation filter with cutoff characteristic with variable input sample rate converter. Variable pre-modulation filter has the same characteristics as pre-modulation filter and is converted to a constant sampling rate without structural changes according to the variable input data rate. We propose a software program that actively controls variable pre-modulation filter and variable input sample rate converter to respond to real-time changing data.

• International Journal of Air-Conditioning and Refrigeration
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• v.17 no.3
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• pp.94-99
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• 2009

In the Korean subway station, three types of pre-filters, which include auto filter, electrostatic precipitator (ESP) and auto cleaning demister, are widely used. However, these devices have some problems such as the difficulty of maintenance and high operating cost. In this study, axial-flow cyclone separator was employed as a pre-filter inside a heating, ventilation, and air conditioning (HVAC) system. 3-dimensional computational fluid dynamics (CFD) analysis was performed on a single unit axial-flow cyclone and coupled unit axial-flow cyclone. Calculated and measured pressure drop of the designed axial-flow cyclone were found be comparable to other types of pre-filters and the observed cut-off diameter was less than 10 micron. Considering lower operating and maintenance cost, axial-flow cyclone was proved to be a better solution as a pre-filter.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.5
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• pp.40-47
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• 2009

A motion adaptive video noise reduction scheme is proposed by cascading a temporal filter and a spatial filter. After a noise-robust motion detection is performed with a pre-spatial filter, the strength of the motion adaptive temporal filter is controlled by the amount of temporal movement. In order to fully utilize the temporal correlation of video signal, noisy input image is processed first by the temporal filter, therefore, image details of temporally stationary region are quite well preserved while undesired noises are suppressed. In contrast to the pre-spatial filter used for the robust motion detection, the cascaded post-spatial filter removes the remained noises by considering the strength of the temporal filter and the spatial self-similarity search results obtained from the pre-spatial filter.

• International Journal of Control, Automation, and Systems
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• v.6 no.2
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• pp.204-213
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• 2008

In this paper, we present the practical application of an Unscented Kalman Filter (UKF) for an Indoor Mobile Localization System using ultrasonic sensors. It is true that many kinds of localization techniques have been researched for several years in order to contribute to the realization of a ubiquitous system; particularly, such a ubiquitous system needs a high degree of accuracy to be practical and efficient. Unfortunately, a number of localization systems for indoor space do not have sufficient accuracy to establish any special task such as precise position control of a moving target even though they require comparatively high developmental cost. Therefore, we developed an Indoor Mobile Localization System having high localization performance; specifically, the Unscented Kalman Filter is applied for improving the localization accuracy. In addition, we also present the additive filter named 'Pre-filtering' to compensate the performance of the estimation algorithm. Pre-filtering has been developed to overcome negative effects from unexpected external noise so that localization through the Unscented Kalman Filter has come to be stable. Moreover, we tried to demonstrate the performance comparison of the Unscented Kalman Filter and another estimation algorithm, such as the Unscented Particle Filter (UPF), through simulation for our system.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.37 no.4
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• pp.20-28
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• 2000

The error diffusion algorithm is good for reproducing continuous image to binary image. However the reproduction of edge characteristic is weak in power spectrum analysts of display error. In this paper, an error diffusion method which include pre-filter algorithm for edge characteristic enhancement is proposed Pre-filter algorithm is organized horizontal and vertical directional differential value and weighting function of pre-filter First, it is obtained the horizontal and vertical differential value from the peripheral pixels in original image using $3{\times}3$ Sobel operator Secondly weighting function of pre-filter is composed by function including absolute value and sign of differential value The improved Error diffusion algorithm using pre-filter, present a good result visually which edge characteristic is enhanced. The difference between orignal image and halftoning image is compared with edge-enhanced error diffusion algorithm by measuring the radially averaged power spectrum density.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.47 no.5
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• pp.24-32
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• 2010

In this study, we have proposed a pre-processing algorithm newly developed for improving the tracking efficiency of the optical flow method. The developed pre-processing algorithm consists of a median filter, binarization, morphology, canny edge, contour detecting and an approximation method. In order to evaluate whether the optical flow tracking capacity increases, this study applied the pre-processing algorithm to the Lucas-Kanade(LK) optical flow algorithm, and comparatively analyzed its images and tracking results with those of optical flow without the pre-processing algorithm and with the existing pre-processing algorithm(composed of median filter and histogram equalization). As a result, it was observed that the tracking performance derived from the LK optical flow algorithm with the pre-processing algorithm, shows better tracking accuracy, compared to the one without the pre-processing algorithm and the one with the existing pre-processing algorithm. It seems to have resulted by successful segmentation for characteristic areas and subdivision into inner and outer contour lines.