• Proceedings of the KIEE Conference
• /
• 2003.11c
• /
• pp.920-923
• /
• 2003

An wearable electrocardiogram (ECG) monitoring system is a widely used non-invasive diagnostic tool for ambulatory patient who may be at risk from latent life-threatening cardiac abnormalities. In this paper, we have a portable ECG monitoring system with conductive fiber which was characterized by the small-size and the low power consumption. The system consists of conductive fibers, one-chip microcontroller, ECG preprocessing circuit, and monitoring software to be able to record and analyze in PC. ECG preprocessing circuit is made of pre-amplifier with gain of 10, band-pass filter with bandwidth of 0.5-120Hz and 2.5V offset circuit for A/D conversion. ECG signals obtained by sensor are included with corrupted noises such as a baseline wandering, 60 Hz power noise and interference noise by body movement. For cancellation corrupted noises in signals obtained by conductive fiber, we used the wavelet decomposition of wavelet transforms in MATLAB toolbox.

• Journal of the Optical Society of Korea
• /
• v.12 no.4
• /
• pp.226-231
• /
• 2008

40 Gbps WDM Systems using super-Gaussian RZ pulses have been studied by numerical simulation to optimize their performance. The assumption of standard single mode fiber is valid when existing WDM systems are required to upgrade their performance to 40Gbps. It is shown that the standard single mode fiber can transmit optical signals over 720 km (Q > 10) by optimizing optical and electrical filter characteristics at the receiver and by compensation of dispersion. However, it is also shown that ${\pm}0.3%$ dispersion compensation tolerance per span (80 km) could prohibit transmitting over 320km (Q > 10). In addition, a duty cycle of less than 0.4 degrades system performance significantly.

• Current Optics and Photonics
• /
• v.6 no.6
• /
• pp.634-641
• /
• 2022

A frequency stable and tunable optoelectronic oscillator (OEO) incorporating an optical phase shifter and a phase-shifted fiber Bragg grating (PS-FBG) is designed and analyzed. The frequency tunability of the OEO can be realized by using a tunable microwave photonic bandpass filter consisting of a PS-FBG, a phase modulator. The optical phase compensation loop is used to compensate for the phase variations of the RF signal from the OEO by adjusting an optical phase shifter. Simulation results demonstrate that the output RF signals of the OEO can be tuned in a frequency range of 118 MHz to 24.092 GHz. When the ambient temperature fluctuates within ±3.9 ℃, the frequency drifts of the output RF signals are less than 68 Hz, the side-mode suppression ratios are more than 69.39 dB, and the phase noise is less than -92.49 dBc/Hz at a 10 kHz offset frequency.

• Journal of Information Processing Systems
• /
• v.19 no.2
• /
• pp.164-172
• /
• 2023

Through theoretical proof and algorithm design, this paper numerically demonstrates that the three sampling methods of DDS are equivalent in amplitude-frequency characteristics. Depending on theoretical analysis, the article obtains the conclusion that 2 points are optimal when sampling at 2, 3, and 4 points. Built on the data results, this paper obtains the fractional form of the amplitude and phase of the DDS sampled signal; in addition, this paper also obtains the design parameters of the DDS post-stage filter. It also gives a control method for the calculation error when addressing this issue.

• Carbon letters
• /
• v.26
• /
• pp.74-80
• /
• 2018

The South Korean Ministry of the Environment has revised the laws relating to the management of interior air quality for multiple use facilities, and recommends maintaining carbon dioxide ($CO_2$) concentration in passenger vehicles below 1000 ppm during operation in urban areas of large cities. However, the interior $CO_2$ concentration of passenger vehicles can rapidly increase and exceed 5000 ppm within 30 min, as observed when two passengers are traveling in urban areas of the South Korean city of Jeonju with the air conditioner blower turned off and the actuator mode set to internal circulation mode. With four passengers, $CO_2$ concentration can reach up to 6000 ppm within 10 min. To counter this, when the actuator is set to external mode, $CO_2$ concentration can be maintained below 1000 ppm, even after a long period of running time. As part of the air conditioning system, alkali-treated activated carbon fiber filters are considered to be far superior to the commercial non-woven filters or combination filters currently commonly in use.

• Publications of The Korean Astronomical Society
• /
• v.19 no.1
• /
• pp.101-107
• /
• 2004

This paper describes the digital back-end system for getting the data to analyze the user observation mode by digitalize the analog data after receiving the space radio using the radio telescope, The received analog data will be digitalized by high-speed sampler with 1 Gsps for 4 channel frequency band of millimeter wave, and the digital data will be transported through the fiber-optic digital transmission system and WDM(wavelength division multiplex) to observation building, The wideband digital FIR(Finite Impulse Response) filters analyze the data for user observation mode to record the data in high-speed recorder with 1 Gbps. In this paper, we introduce the overall system configuration and features combined by various information and communication technology in radio astronomy briefly, which will be adopted by KVN(Korean VLBI Network).

• Korean Chemical Engineering Research
• /
• v.43 no.6
• /
• pp.691-695
• /
• 2005

Zeolite membranes on various supports such as filter paper, cotton fiber, and glass fiber filter were prepared by secondary growth hydrothermal synthesis. First, zeolite NaA (${\approx}0.5{\mu}m$) and silicalite-1 (${\approx}0.2{\mu}m$) crystals were synthesized as zeolite seed crystals, and they were attached to the surfaces of the supports via chemical bonding. Zeolite NaA or silicalite-1 membranes could be synthesized on the supports coated with the seed crystals. The prepared zeolite membranes were observed by scanning electron microscope and analyzed by X-ray diffraction.

• Journal of Korean Society for Atmospheric Environment
• /
• v.12 no.3
• /
• pp.341-350
• /
• 1996

We determined 6 polycyclic aromatic hydrocarbons (PAHs) fluranthene, pyrene, benz(a)anthracene, chrysene, benzo(a)pyrene, dibenzo(a,h)anthracene). A total of 129 samples has been collected from September 1990 to September 1994 on 2 different types of filters (quartz fiber filter, glass fiber filter) by a PM-10 high volume air sampler at the Kyung Hee University-Suwon campus. The organic components in the PM-10 were extracted by an ultrasonication process with benzene:ethanol(4:1, v/v) prior to the analysis by using a GC/FID. We had also investigated the decaying quantity of 6PAHs at the room temperature. For example, chrysene was decayed by 56.7% after 4 days and benzo(a)anthracene by 84.2% after 30 days. All of PAHs were almost completely decayed after a year. We extensively estimated the decay rates by regression analyses for existing 18 raw data sets. Based on the decay rate constants $(\beta)$, pyrene was rapidly decayed by 19.0 $\times 10^{-2}$/day; on the other hand, dibenzo(a,h)anthracene slowly by 0.7 $\times 10^{-2}$/day. Applying the decay rates of PAHs on stored and dated samples, we could reasonably determine annual and seasonal concentration average of PAHs in particulate matters smaller than 10 $\mu$m.

• Journal of Korean Society of Water and Wastewater
• /
• v.33 no.6
• /
• pp.437-446
• /
• 2019

Reverse osmosis seawater desalination facilities can extend the cleaning cycle and replacement time of the reverse osmosis membrane by pretreatment process. Selection of pretreatment process depends on water quality. It was attempted in this study to select approriate pretreatment process for the Masan bay, which was high in particles and organic content. For this purpose, performances of pretreatment processes such as filter adsorber (FA), pore controllable fiber (PCF), and ultrafiltration (UF) were compared based on the silt density index (SDI). The SDI value of the filtrate should be less than 3. The study results showed that UF can produce the filtrate quality satisfying the requirement. However, the transmembrane pressure (TMP) of UF increased quickly, reaching 0.6 bar within 4 days. In order to secure stable operation, FA and PCF were combined with UF. The study results showed that combination of PCF and UF was able to extend the filtration duration (more than 2 months) until to reach TMP of 0.6 bar.

• Membrane Journal
• /
• v.17 no.4
• /
• pp.381-386
• /
• 2007

Hollow fibers were made using the nickel slurry containing nickel particles and polymers by phase inversion method. And then, metallic filters were fabricated by sintering method at $1,150^{\circ}C$ under reduction condition. Metallic microfiltration membranes were prepared by coating nickel particles on the metallic filter. The properties of the metallic hollow fiber filters and microfiltration membranes such as pore size and strength were investigated. The metallic membrane showed good resistance against acid, base and chlorine. It was observed that the membrane exhibited good recovery rate by back washing.