• Journal of the Korea Society of Computer and Information
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• v.28 no.2
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• pp.55-62
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• 2023

Radio waves must pass through the unstable atmosphere for successful wireless data transmission from space to ground stations. Data link algorithms required by the International Space Data Systems Advisory Committee (CCSDS) must be capable of detecting and resynchronizing cryptographic and receiver-side errors. However, error recovery is not part of the CCSDS requirements. This paper proposes an algorithm that enables robustness and error recovery against various noises. We experimented with environments such as Gaussian, Salt, Pepper, and S&P noise through noise reduction filters, filters that improve sharpness, and EDSR. In addition, we compare similar algorithms SES Alarmed and DSES Alarmed.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.755-758
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• 2002

This paper presents a second-generation CMOS current conveyor (CCII) consisting of a rail-to-rail complementary N- and P-channel differential input stage for the voltage input, a class AB push-pull stage for the current input, and current mirrors far the current outputs. The CCII was implemented using a double-poly triple-metal 0.6 ${\mu}$m n-well CMOS process, to confirm its operation experimentally. A prototype chip achieves a rail-to-rail swing ${\pm}$2.4 V under ${\pm}$2.5 V power supplies and shows the exact voltage and current following performances up to 100 MHz. Because of its high performances, the CCII proposed herein is quite useful for a building block of current-mode circuits. The applications of the proposed CCII to current-mode filters are also described.

• The Journal of the Acoustical Society of Korea
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• v.14 no.6
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• pp.68-73
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• 1995

In this paper, two new morphological pitch detectors, one in time-domain and the other in frequency-domain, are presented. The roles of structuring element in morphological filters are experimentally examined. As a result, it is shown that the new pitch detectors using suitable structuring elements are quite simple, computationally very efficient, and robust than the conventional pitch detectors.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.876-881
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• 1998

The compensation strategy of shunt active power filters is one of the most important link that determine its compensation characteristics. In this paper, a new interpretation of the instantaneous reactive power theory in three-phase circuits was proposed. A compensation strategy (ip, iq mode) was introduced on the basis of the new interpretation. This compensation strategy was compared with other two compensation strategies(P, q mode and UPF mode). When source voltage is distorted, a sinusoidal, the three compensation strategies are equivalent to each other. When source voltage is distorted, a sinusoidal source current may result only by using ip, iq mode. This is the advantage of ip, iq mode. The result is verified by simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.1
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• pp.81-88
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• 1997

Wavelength tunable, narrowbandwidth wvelength filters in compound semiconductor have been modeled, fabricated, and characterized. In order to obtain a narrow bandpass characteristics at 1.55.$\mu$m, a highly asymmertrical directional coupler structure composed of a strongly guided ridge waveguide and a weakly guided strip-loaded waveguide was used. The optimized filter structure modeling has been obtained by using the spectral index method, effective index method, and the coupled mode theory. Operation at a center wavelength a 1.537.mu.m with a bandwidth of 1.8nm and transfer efficiency of 50-70% is experimentally achieved. For the purpose of center wavelength tuning, the carrier injection in p-n diode structure has been theoretically investigated. It has been found that the tuning range of nanometer can be easily obtained by moderate amount carrier injection. We also found that the bandwidth becomes broad as the center wavelength tuning increases.

• Proceedings of the KIEE Conference
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• 1990.07a
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• pp.529-531
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• 1990

Because Filters do both the sampling or Sampled-and-Hold(S/H) operations, it result in the replication of the spectrum of input signal and (unless Nyquist's criterion is satisfied) induce aliasing distortion. In this paper, therefore, we designed AAF(Analog Anti-aliasing Filers) so as to remove high-frequency components from input signal for aliasing distortion prevention before input signal had been processed frequency seletion by filters. and then, researched characteristics of it.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.565-568
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• 2001

A novel control scheme compensating for source voltage unbalance and harmonic current for series active power filters is proposed, where the references for voltage unbalance and current harmonic and phase angle is derived from the positive sequence component of the source voltage obtained simply through digital all-pass filters, which makes the whole control algorithm simpler than other methods using p-q theory. In addition, the harmonic component of source current is compensated by harmonic component of load voltage and therefore fundamental component of source current is considered as separated terms for the control issue. The validity of the proposed scheme has been verified by experimental results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.7
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• pp.3117-3122
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• 2011

Skull A-P projections are the bi-product where the ESD (Entrance Surface Dose) for digital radiography is much higher than that conventional screen-film radiography. Therefore, the aim of this study was to reduce radiation doses to patients by using an added filter. This research focuses on the identification of the reduction of exposure to radiation based on the thickness of an added filter when applying the 'Skull A-P Projection' by using the 'Skull Phantom'. Also, an experiment was conducted to evaluate the qualitative decline of images through filtration. The measurement of one's exposed dose to radiation was executed by locating the 'Skull Phantom' on the position of the 'Skull AP,' while changing 16 kinds of added filters from 0.1 mmAl to 0.5 mmCu + 2.0 mmAl in terms of incident and penetrating doses. For the qualitative evaluation of images, a total number of 17 images have been acquired in the 'Skull Phantom' under the same conditions as those for the measurement of one's exposed dose. The acquired images have been evaluated by a radiological specialist. As a result, the images with a diagnostic value have been obtained by using such added filters as the compound filter of 0.2 mmCu +1.0 mmAl. The exposed dose absorbed on the 'Skull Phantom' is about 0.6 mGy. The value is only 12% of 5 mGy, the ESD value acquired on the 'Skull P-A Projection', which is recommended by the International Atomic Energy Agency (IAEA). As a result, depending on the parts of inspection, it is possible to reduce the patient's exposed dosage of radiation considerably by using an appropriate added filter.

• Journal of the Korean Chemical Society
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• v.26 no.1
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• pp.36-42
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• 1982

Filters were evaluated to use in the collection of ammonia and ammonium salts in the atmosphere. Ammonia from standard gas generator was collected on a glass fiber filter impregnated with a mixture of 3% boric acid and 25% glycerin. The collection efficiency by the impregnated filter was 96.4${\pm}$2.15% in pH control method and 97.4${\pm}$1.06% in the atmosphere for five measurements, respectively. Adsorption and desorption of gaseous ammonia were compared using three commercially available filters; glass fiber, quartz fiber and polycarbonate filters. Both glass and quartz fiber filters indicated some loss of ammonium salts and adsorption of ammonia, respectively. However, polycarbonate filter was found to be satisfactory for the collection of ammonium salts in the atmosphere. The minimum measurable concentration of ammonia was 0.83ppb (ca. 0.63${\mu}g$/$m^3$) by spectrophotometry of the indophenol method for the sample collected by 47mm${\phi}$ filter(20l/min, 60min). The sensitivity of the present method is about 20 folds higher than that of conventional method of bubbler collection followed by spectrophotometry, so that this method makes it possible to measure thevariation of ammoniacal concentrations in the atmosphere for a short time period of about 60 min.

• Proceedings of the Korean Environmental Health Society Conference
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• 2002.04a
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• pp.40.1-43
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• 2002

The purpose of this study was to evaluate a new sampling and analytical method for the determination of hexavalent chromium, Cr(VI) in mist from field plating operation. The Procedures of this new method (Shin & Paik's Method) are as the following: Airborne hexavalent chromium is collected on polyvinyl chloride (PVC) filter according to the National Institute for Occupational Safety and Health (NIOSH) Method 7600, and the filter sample is placed in a screw-capped vial and soaked with 2％ NaOH/3％ Na₂CO₃ solution immediately after sampling. The Cr(VI) sample is analyzed by ion chromatography/visible spectrophotometry (IC/VS) according to the U.S. Environmental Protection Agency (EPA) Method 218.6. The airborne Cr(VI) concentrations measured by this method were compared with those determined by three reference methods: One (NIOSH/EPA Method) consisted of sampling airborne Cr(VI) on PVC filters and storing the sample filters in screw-capped vials according to the NIOSH method, and analyzing Cr(VI) in samples using IC/VS according to the EPA method. The second method (Impinger Method/NaHCO₃) consisted of absorbing airborne Cr(VI) into 0.02 MN/sub a/Hco₃ solution in midget impinger, and analyzing the Cr(VI) in samples using IC/VS. The third method was the OSHA Method Id-215. Using these four different methods, four replicates of air samples were collected at an electroplating process and analyzed simultaneously. Two-way ANOVA and Paired t-test were used to test difference among values determined by the methods. There was no significant difference and a strong correlation (r/sup 2/=0.99) between Cr(VI) concentrations measured by the shin & Paik's Method and an impinger method (p＞0.05). However, Cr(VI) concentrations determined by Shin & Paik's Method were Significantly different form those by the NIOSH/EPA Method (p＜0.05) or the OSHA method (p＜0.05). The Cr(VI) concentrations of Shin & Paik's Method were Significantly higher than those of the NIOSH/EPA Method or the OSHA method. We concluded that the Shin & Paik's Method could prevent Cr(VI) losses caused by reduction and give more reliable results of airborne Cr(VI) concentrations in work environments.