• Applied Chemistry for Engineering
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• v.10 no.3
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• pp.445-449
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• 1999

Hydrophilic polyphosphazenes were synthesized from hydrophobic polyphosphazenes by adding methoxyethylenoxy side chains and cast by dip-coating method into membranes supported on porous polypropylene mesh filter sheet for metal separation testing. A solution of $Cr^{3+},\;Co^{2+},\;Mn^{2+}$ nitrates was used in diffusion experiments which were conducted from $25^{\circ}C$ to $60^{\circ}C$. lt was found that the ion transport properties were increased as the repeating number of ethylenoxy side chain increased. Membrane from trifluoroethoxy methoxyethoxyethoxyethoxy co-substituted polyphosphazenes was found to separate $Cr^{3+}$ ion from $Mn^{2-}$ and $Co^{2+}$ ions with separation factor of 4.5 at $60^{\circ}C$.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.3
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• pp.75-80
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• 2006

Since air pollution has become a globally critical issue and exhaust emissions from automobiles cause a major source of air pollution, many countries including advanced countries have stipulated stringent emission regulations. Particularly in diesel vehicles, NOx and particulate matters exhaust in significant amounts even though diesel vehicles provide merits in aspects of higher thermal efficiency and lower $CO_2$. To reduce Particulate matters and NOx, after-treatment technology such as filter trap, oxidation catalysts and EGR has been applied. This test was conducted on the effect of continuous regeneration diesel particulate filter and cooled-EGR, and 15ppm low sulfur diesel was used as a test fuel. Exhaust emissions, PM, NOx, CO, HC and Soots were measured and compared under D-13 and D-3 modes.

• Journal of Korean Society for Atmospheric Environment
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• v.4 no.2
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• pp.20-27
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• 1988

A simple two stage aerosol filter sampler which allows simultaneous and fractional collection of two different-size particles, coarse and fine, was constructed and applied to the collection of Seoul atmospheric particulate for inorganic analysis. The sampler consist of two 47-mm diameter filter holder, a pneumatic pump, and a flowmeter. Filtering rate normally runs around 20$\ell$/min for 8 hrs. Using the sampler, a series of seasonal aerosol samples were collected from June 1986 to March 1988 at Yonsei University campus, Seoul and subsequently analysed for ten environmentally important metals using an atomic absorption spectrometer and an inductively coupled plasma emission spectrometer. The analysed metals are Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb, V, and Zn. The analytical results showed the following order of metal abundance; Al > Fe > Zn > Pb > Mn > Cu > V > Ni > Cr > Cd. Based upon their size distribution pattern, the analyzed matals could be clasified into two groups, those present primarily in coarse particle and those in fine particle. Fe, Al, Mn, V, and Cr belong to the former group while the rest to the latter. Most metal concentration were highest in spring or winter, and lowest in autumn. Statistical analysis showed strong correlations between Al and Fe, Pb and Zn, and Cu and Mn.

• ETRI Journal
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• v.32 no.2
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• pp.214-221
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• 2010

Radio frequency (RF) subsampling can be used by radio receivers to directly down-convert and digitize RF signals. A goal of a cognitive radio/software defined ratio (CR/SDR) receiver design is to place the analog-to-digital converter (ADC) as near the antenna as possible. Based on this, a band-pass sampling (BPS) frontend for CR/SDR is proposed and verified. We present a receiver architecture based second-order BPS and signal processing techniques for a digital RF frontend. This paper is focused on the benefits of the second-order BPS architecture in spectrum sensing over a wide frequency band range and in multiband receiving without modification of the RF hardware. Methods to manipulate the spectra are described, and reconstruction filter designs are provided. On the basis of this concept, second-order BPS frontends for CR/SDR systems are designed and verified using a hardware platform.

• Journal of Environmental Health Sciences
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• v.23 no.1
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• pp.105-108
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• 1997

For the removal of heavy metals, Cd, Cu and Cr were used. The initial concentration of Cd and Cu were 1-10 ppm, the removal efficiency of Cd and Cu was 76.2-89.0% and 69.0-79.0%, respectively. The initial concentration of Cr were 1~5 ppm, and the-removal efficiency was low especially at high concentration. In general, the initial concentrations of heavy metals had no relation to the removal efficiency. At the beginning, the removal efficiency was very high, but it was maintained at constant concentration. The trends of accumulations of heavy metals in the stem increased in proportion to the initial concentration. The removal efficiency of heavy metals increased a little bit when nutrients existed in the solution. So that, the initial concentration of Cd and Cu were 1-10 ppm, the removal efficiency of Cd and Cu was 84.8-91.0% and 75.9-82.0%. The initial concentration of Cr were 1-5 ppm, the removal efficiency was 25.0-67.0%.

• Journal of radiological science and technology
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• v.37 no.4
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• pp.239-246
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• 2014

Filter absorbs low-energy X-ray to increase the average energy and reduces patient exposure dose. This study investigates if the materials of Mo and W could be used for the digital imaging device CR by conducting image assessment and dose measurement of SNR, FOM and histogram. In addition, measurement of beam quality was conducted depending on the material of the filter, and at the same time, a proper combination of filters was examined depending on the change in tube voltage (kVp). In regard to entrance skin dose, Mo filter showed the dose reduction by 42~56%, compared to Cu filter. Moreover, Mo filter showed higher transmission dose by around 1.5 times than that of Cu filter. In image assessment, it was found that W was unsuitable to be used as a filter, whereas Mo could be used as a filter to reduce dose without decline in image quality at the tube voltage of 80 kVp or higher. As tube voltage increased, 2.0 mm Al+0.1 mm Mo almost had a similar histogram width to that of 2.0 mm Al+0.2 mm Cu. Therefore, Mo filter can be used at relatively high tube voltage of 80 kVp, 100 kVp and 120 kVp. The SNR of 2.0 mm Al+0.1 mm Mo did not show any significant difference from those of 2.0 mm Al+0.2 mm Cu and 2.0 mm Al+0.1 mm Cu. As a result, if Mo filter is used to replace Cu filter in general radiography, where 80 kVp or higher is used for digital radiation image, patient exposure dose can be reduced significantly without decline in image quality, compared to Cu filter. Therefore, it is believed that Mo filter can be applied to chest X-ray and high tube voltage X-ray in actual clinical practice.

• KSBB Journal
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• v.22 no.2
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• pp.102-108
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• 2007

A sewage was treated using a vertical flow zeolite-filled reed bed. The sewage from the student dormitory of Changwon National University was fed into the reed bed for 10 minutes every 6 hours at the hydraulic load of $314L/m^3{\cdot}$day. The filtering height of the reed bed was 100 em and the zeolite mixture was filled in the reed bed. The mixture consisted of the same volume of two types of zeolite: 0.5$\sim$1 mm and 1$\sim$3 mm in diameter. Annual average removal efficiency was 88 89.9%, $COD_{Cr}$ 86.1 %, $COD_{Mn}$ 81.2%, T-N 34.0%, $NH_4^+$-N 97.3% and T-P 34.6%. T-N of effluent was mostly $NO_3^-$-N and the concentration of $NO_2^-$-N in effluent was lower than 0.1 mg/L. All removal efficiencies did not show a remarkable seasonal change. The ranking of phosphorous fractions fixed to the zeolite in column test was Ca-P > Fe-P > reductant soluble Fe-P > occluded P > saloid P > AI-P at all depths of the filter. All phosphorous fractions except for AI-P reduced at deeper filter layer, while their content ratios increased at deeper filter layer. Organic matter content was the highest at the highest layer (0$\sim$5 cm from the top of the filter) and only small differences were observed at the deeper filter layer than 5 em from the top. Organic matter content increased at all depths of the filter with the operating time.

• Journal of Electrical Engineering and Technology
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• v.13 no.6
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• pp.2479-2484
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• 2018

The filter bank multicarrier modulation (FBMC) technique is one of multicarrier modulation technique (MCM), which is mainly used to improve channel capacity of cognitive radio (CR) network and frequency spectrum access technique. The existing FBMC System contains serial to parallel converter, normal QAM modulation, Radix2 inverse FFT, parallel to serial converter and poly phase filter. It needs high area, delay and power consumption. To further reduce the area, delay and power of FBMC structure, a new clock gating technique is applied in the QAM modulation, radix2 multipath delay commutator (R2MDC) based inverse FFT and unified addition and subtraction (UAS) based FIR filter with parallel asynchronous self time adder (PASTA). The clock gating technique is mainly used to reduce the unwanted clock switching activity. The clock gating is nothing but clock signal of flip-flops is controlled by gate (i.e.) AND gate. Hence speed is high and power consumption is low. The comparison between existing QAM and proposed QAM with clock gating technique is carried out to analyze the results. Conversely, the proposed inverse R2MDC FFT with clock gating technique is compared with the existing radix2 inverse FFT. Also the comparison between existing poly phase filter and proposed UAS based FIR filter with PASTA adder is carried out to analyze the performance, area and power consumption individually. The proposed FBMC with clock gating technique offers low power and high speed than the existing FBMC structures.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.11
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• pp.175-182
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• 2012

The scattered radiation always occurs when X-ray strikes the object. To absorb the scattered X-rays, the antiscatter grids are used, however these grids images are superimposed in the projection radiography images. When those images are displayed on the monitor, moir$\acute{e}$ patterns are overlapped over the images and disturb the anatomical informations. Most of the researches performed to date removed the grid noises by calculating or observing those frequencies in one dimensional frequency domain, two dimensional wavelet transform or Fourier transform. Those methods filtered not only the grid noises but also diagnostic informations. In this paper, we proposed the combined wavelet packet-Fourier method to remove the grid artifact in CR images. For the phantom image, the proposed method achieved from 5.2 to 7.4 dB better than others in SNR and for CR images by rejecting the grid noise bands effectively while leaving the remaining bands unchanged, the loss of images could get minimal results.

• Journal of Preventive Medicine and Public Health
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• v.20 no.2 s.22
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• pp.341-351
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• 1987

For the purpose of the determination of the most proper sampling time on using spot urine which can represent the general status of electrolytes in 24 hour urine and for test of the validity of filter paper method which was developed recently in estimation of the amount of daily salt intake, the author investigated this study by different sampling time and various measuring methods in 21 healthy men and 12 women. The summarized results were as follows; 1) The mean excretion amount of urinary electrolytes were Na 3.93 g/l, K 1.47 g/l, and creatinine 1.08 g/l in male, and Na 3.83 g/l, K 1.86 g/l, and creatinine 0.99 g/l in female. 2) In using spot urine for estimation of the amount of daily salt intake, morning urine was the most approximate to that of 24 hour urine in both sexes. 3) There was validity in estimation of daily salt intake by filter paper method using spot urine instead of 24 hour urine. 4) The estimated amounts of daily salt intake in male was higher than the values in female as 16.04-16.22 g and 13.35-13.82 g respectively.