• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9C
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• pp.913-921
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• 2005

A complex bandpass sampling technique can provide a more flexible architecture for designing a software- defined radio(SDR) system, because it has several advantageous features of larger sampling range and lower minimum sampling frequency than a real bandpass sampling method. In spite of the potential advantages of the complex bandpass sampling, solid investigation for the direct downconversion of multiple signals by the complex sampling theory has not been reported yet. Thus, we propose in this paper a novel scheme for the downconversion of multiple signals using the complex bandpass sampling, and develop the formulae related to the complex bandpass sampling for practical usage, such as the valid sampling range, the intermediate frequency (If), and the minimum sampling frequency of the downconversion of multiple RE signals. Such derived formulae are verified from simulations.

• Journal of Plant Biology
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• v.29 no.1
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• pp.41-51
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• 1986

The plants of Nicotiana tabacum L. cv. NC2326 were germinated in 10 cm D$\times$20 cm H polyethylene pot, and sand-cultured with Hoagland solution near by the window of laboratory room(26$\pm$5$^{\circ}C$). The growing plants were sprayed with various concentrations of ABA around 9 : 00 a.m. once in every two days for 12 weeks in summer. As the results, frequency of stomatal number, stomatal opening, chlorophyll content, respiration rate, and protein content in the leaves were decreased with the increasing of concentrations of ABA, respectively. The plant growth was inhibited by exogenous ABA, but leaf abscission was not found during the experimental period. The ratio of three to one in chlorophyll a to b was not altered by exogenous ABA. All the stomata were closed within three minutes by 100 $\mu\textrm{g}$ ml-1 ABA and within seven minutes by 1-10 $\mu\textrm{g}$ ml-1 ABA after the spraying of ABA, and then reopended after a few hours in 1-10 $\mu\textrm{g}$ ml-1 ABA and after 24 hours in 100 $\mu\textrm{g}$ ml-1 ABA. The polar movement of chloroplast within the guard cells was found in the higher concentrations of 10 and 100 $\mu\textrm{g}$ ml-1 ABA, but not found in the lower concentrations than 1 $\mu\textrm{g}$ ml-1 ABA. During the night and weak light, it was fond that the inhibition of respiration rate by the higher concentration of ABA was owing to firstly the stomatal closure by the spraying of ABA and secondly the decrease of stomatal frequency by the inhibition of stomatal development with exogenous ABA for the long period of 12 weeks. In the band number of leaf protein by the electrophoresis, most of the protein bands were disappeared by the higher concentration of 100 $\mu\textrm{g}$ ml-1 ABA, but were not altered by the lower concentration of ABA in comparison with control.

• Journal of Broadcast Engineering
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• v.21 no.5
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• pp.803-815
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• 2016

In this paper, we design a direct radio frequency (RF) sampling receiver for multiband GNSS signals and demonstrate its performance. The direct RF sampling is a technique that does not use an analog mixer, but samples the passband signal directly, and all receiver processes are done in digital domain, whereas the conventional intermediate frequency (IF) receiver samples the IF band signals. In contrast to the IF sampling receiver, the RF sampling receiver is less complex in hardware, reconfigurable, and simultaneously converts multiband signals to digital signals with an analog-to-digital (AD) converter. The reconfigurability and simultaneous reception are very important in military applications where rapid change to other system is needed when a system is jammed by an enemy. For simultaneous reception of multiband signals, the sampling frequency should be selected with caution by considering the carrier frequencies, bandwidths, desired intermediate frequencies, and guard bands. In this paper, we select a sampling frequency and design a direct RF sampling receiver to receive multiband global navigation satellite system (GNSS) signals such as GPS L1, GLONASS G1 and G2 signals. The receiver is implemented with a commercial AD converter and software. The receiver performance is demonstrated by receiving the real signals.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.3 s.106
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• pp.307-316
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• 2006

In this paper the analytical method, namely advanced minimum coupling loss(A-MCL), was proposed in order to analyze the coexistence of OFDM-based systems beyond 3G(B3G) with point-to point(PP) fixed service(FS) microwave systems. Our proposed method is based on a power spectral density(PSD) analysis. So it can be easily applicable to analyze the coexistence of OFDM-based systems B3G using flexible spectrum usage(FSU) with other systems, where the conventional MCL method cannot allocate transmit power partially to some subcarriers which overlap the band of a victim system. By applying the conventional MCL method and the A-MCL method, interfering power levels at the receiver of a interfered system are respectively calculated. A-MCL can calculate interference power more accurately than MCL by the maximum value of 4.5 dB. Therefore it can be concluded that our prosed method, namely A-MCL, is applicable to a sharing analysis of OFDM-based systems B3G.

• Journal of Korean Society of Forest Science
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• v.32 no.1
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• pp.73-86
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• 1976

Two individuals ($sp_1$, $sp_2$) of purple and one individual ($sd_1$) of red hearted flower were selected from 18 years old Hibiscus syriacus trees obtained from the seeds treated with colchicine, and their morphological and physiological characteristics were investigated and following results were obtained. 1. The somatic chromosome number of the selected individuals, $sp_1$, $sp_2$, and $sd_1$ were 2n=160, while that of the check tree was 2n=80, indicating that the selected individuals, $sp_1$, $sp_2$ and $sd_1$ were tetraploid. 2. Peroxidase isoenzyme bands of high activity in selected individuals, $sp_1$, $sd_1$ and check tree were mostly in cathode, fixed band was f and v bands, and frequency of each band and their activity were not different between selected individuals, $sp_1$ and $sd_1$ and check tree. 3. The flowers of $sp_1$ individual were large in size and more dark purple than check tree's. The flowers of $sp_2$ individual were not increased in size, but they were dark purple and red heart at the base of the petal was expanded to 2/3 of the petal length. The flower of $sd_1$ individual was also large and some of the red lines from the petal base were extended to 2/3 of the petal length, which was much longer than those of the check tree. 4. Thickess of leaves, length of guard cells, diameter of pollens, wood fiber lengths and woody fiber widths were all increased in $sp_1$, $sp_2$ and $sd_1$ as compared to those of the check tree. 5. Survival percentage of cuttings was 80% with $sp_1$ and 36% with $sd_1$, and their growth performance were inferior to control in their second growing season.

• Journal of Navigation and Port Research
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• v.45 no.1
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• pp.26-32
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• 2021

In ocean field, the spread of the Fourth Industrial Revolution based on information and communication technology requires high precision and stable PNT&D (Position, Navigation, Timing and Data). As the IMO (International Maritime Organization) and IALA (The International Association of Marine Aids to Navigation and Lighthouse Authorities) are requiring backup systems due to mitigate vulnerabilities and the increase of dependency on GNSS (Global Navigation Satellite System), Korea is conducting a research & development of R-Mode. An DGPS (Differentiate Global Positioning System) reference station that uses MF, an existing maritime infrastructure, and AIS (Automatic Identification System) base stations that use 34 integrity station and VHF will be utilized in this study to avoid redundant investment. Because there are radio shadow areas that display low signal levels in the west sea, the establishment of new R-Mode reference and integrity station will be intended to resolve problems regrading the radio shadow area. Because the frequency has a characteristic in that radio wave transmits well along the ground (water surface) in low frequency band, simulation and measurement were conducted therefore this paper to propose candidate sites for R-Mode reference and integrity station resulted through p wave's propagation characteristics analysis. Using this paper, R-Mode reference and integrity station can be established at appropriate locations to resolve radio shadow areas in other regions.