• Korean Journal of Microbiology
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• v.50 no.4
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• pp.372-375
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• 2014

This experiment was undertaken to investigate proper conditions for protoplast isolation and genetic transformation of the white rot fungi, Polyporus brumalis. The protoplasts were formed from mycelia at a frequency of $1{\times}10^7/ml$ with 0.5% Usukizyme. The transformation vector (pHYgpt) was constructed using hygromycin resistance gene (hph) for the selectable maker. The yield was 100-160 transformants/${\mu}g$ DNA in a transformation mediated by 40% polyethylene glycol solution with aurintricarboxylic acid, heparin and supermidine. The genomic integration of the pHYgpt was confirmed by hph-specific PCR and the expected amplified band appeared only in the transformants. These results could be an efficient tool in gene engineering of the genus polyporus.

• Korean Journal of Materials Research
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• v.16 no.6
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• pp.360-366
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• 2006

A series of ZnO thin films were grown by radio-frequency (RF) magnetron sputtering with various RF powers on $SiO_2/Si$(100) substrates at $500^{\circ}C$. Thicknesses of the investigated ZnO films were fixed to about 250nm by changing the growth time based on the changes of growth rates with RF powers. All the ZnO thin films were grown with <0001> preferred orientation. Average grain sizes of about 250nm-thick ZnO films evaluated by FE-SEM, AFM, and TEM were increased by decreasing the RF power. Structural properties addressed by FWHM values of XRD (0002) omega rocking curves and their intensities were better for the smaller grain sized ZnO films grown with high RF powers, which implies small values of tilt for smaller grain sized ZnO films. However, optical properties addressed by intensities of band edge emissions from room temperature and low temperature photoluminescence were better for the larger grain sized ZnO films with low RF power, which implies grain boundaries acted as nonradiation recombination centers.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.3C
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• pp.314-319
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• 2010

The chirp spread spectrum (CSS) technique that spreads the data signal over a wider frequency band via chirp signal for transmission has attracted much attention in the field of wireless communications due to capability to resist multipath fading signals. However, there has been little mathematical analysis for the performance of CSS-based communication systems in the multipath fading environments. In this paper, we study the influence of the multipath channel on the direct modulation (DM) scheme with M-ary phase shift keying (MPSK). When a chirp signal is transmitted on the Rayleigh fading channel and affected by additive white Gaussian noise (AWGN), we derive the theoretical performance. From numerical results, it is confirmed that the analytic symbol error rate (SER) agrees closely with the empirical SER.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.9
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• pp.606-613
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• 2014

The Internet of Things (IoT), which has recently attracted attention as next-generation IT industry, is based on a wired and wireless network platform that can connect various Things. However, it is challenging to implement the IoT platform because of the heterogeneity of the network. Particularly, the ZigBee transmission may be significantly harmed due to Wi-Fi with the relatively much higher power, and this is one of the reason making the platform implementation difficult. In this paper, the ZigBee transmission is measured and analyzed by the BEB algorithm for finding the slot time when ZigBee can transmit, and an actual transmission happens stochastically depending on the network environment. The simulation results show that it guarantees high success rate of the ZigBee transmission by overcoming Wi-Fi interference in the 2.4 GHz frequency band.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.5A
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• pp.479-486
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• 2008

In this paper, an efficient training symbol design with m-sequence is proposed for the MIMO-OFDM based next generation wireless transmission system which supports gigabits per second data rate. In the traditional blute force method, the preamble design is based on the case by case comparison with the system requirements. This paper discusses a training symbol design methodology for the MIMO-OFDM system based on the m-sequence which has been widely used in the spread spectrum communication areas due to its good correlation characteristics. Also the step-by-step design and performance verification method within the limited search space is discussed. The proposed method targets the design of the training symbol which satisfies system requirements for the packet based MIMO-OFDM wireless communication system including automatic gain control(AGC), timing synchronization, frequency and sampling offset estimation, and MIMO channel estimation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.4
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• pp.325-336
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• 2013

FlashLinQ, one of the typical D2D communication systems developed by Qualcomm, considers a single-tone communication based distributed channel-aware link scheduling method to realize the link scheduling process with low control overheads. However, considering the frequency selective fading effect of practical multi-path channel, the single-tone based SIR estimation causes a critical scheduling error problem because the received single-tone signal has quite different channel gain at each sub-carrier location. In order to overcome this problem, we propose a novel link scheduling method based on CAZAC (Constant Amplitude Zero Auto-Correlation) sequence for D2D communication system. In the proposed method, each link has a unique offset value set for the generation of CAZAC sequences. CAZAC sequences with the cyclic offsets are transmitted using multiple sub-blocks in the entire bandwidth, and then each device can obtain nearly full-band SIR using a good cyclic cross-correlation property of CAZAC sequence.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.1
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• pp.115-125
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• 1998

This paper examined the feasibility of adding a new NGSO/MSS(Non-Geostationary orbit/Mobile satellite service) service link to a frequency band which is already allocated to fixed-service microwave(M/W) system. To achieve this goal, the NGSO/MSS handset performance under the influence of the M/W multiple stations and the influence of handsets on the M/W station were both analyzed. Sharing criterions were also obtained by means of coordination contour in the former case, and handset capacity in the latter case. As the results, it was proven that sharing was feasible only when the vertical distance between handset and trendline was above 4 km except front and back points of M/W antenna bore sight under influence of 9 hops(the distance between hops = 50 km) M/W system on the NGSO/MSS handset, and only when the capacity of handset was below $7.0\times10^{-14}$ handsets/ $m^{2}$ under influence of handsets on the M/W station.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.6 no.3
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• pp.15-23
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• 1995

The antenna height of the mobile communications lower than its typical surroundings causes multipath fading usually resulting in fast fluctuations of both signal strength and wave length in mobile radio communications. Therefore, there have been developed and used various wave be- havior prediction models, in some other foreign countries, based on the measurement data rather than on theoretical derivation. The main purpose of this paper is to examine the wave propagation characteristics particularly in Korean terrain with the measurements made in four types of different areas - a large city area, a small city area, a flat terrain area, and a mountain area. Those areas have been classified according to the terrain characteristics with which the particular area contains, such as scale and number of buildings, highways, trees, and so on. With the measured data of the field strength in the frequency band of pager system obtained from those four different areas, we compared the calculated ones from both Hata's and TIREM prediction models which are often applied in Korea.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.7
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• pp.1131-1137
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• 1999

In this paper, a novel design method of an apertured coupled microstrip patch antenna with the single feeding structure is proposed for dual resonance frequencies with mutually perpendicular polarizations. The characteristics of this antenna are experimentally investigated. In order to achieve this goal, a new type of square patch with double notches is used as a radiator and the crossed slot and the bended mictrostrip feeder are adopted for the dual polarizations in the aperture-coupled structure. For the application of the proposed antenna, a Ku-band Tx/Rx $2\times$ subarray antenna is designed and manufactured. Also, the applicability of the antenna as a ground terminal is examined through performance analysis. According to the measurement, the gain of the antenna is 10dBi at the center frequencies of Tx and Rx, the side lobe level is lower than -13dB, and the cross polarization lebel is below 17 dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.7
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• pp.998-1009
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• 1999

In this paper, a microstrip aperture-patch antenna and a microstrip ring antenna, which have single microstrip line feeding systems for the circular polarization, are designed, and experimental results are presented at X-band. The microstrip aperture-patch antenna is characterized by its wide operating frequency range, and the microstrip ring antenna is suitable for a basic radiator in the large array antenna due to its small size. Several design parameters for these antennas are considered and analyzed to improve antenna characteristics such as VSWR bandwidth and axial ratio. Initially, the sizes of the aperture and ring radiator are determined on a basis of the cavity model, then shapes of the patch within the aperture and the inner stub of the ring are optimized using Ensemble software. Measurement results show that the aperture-patch antenna has 25% of VSWR bandwidth and 1.2dB of axial ratio at the boresight, and the ring antenna has 6.7% of VSWR bandwidth and 1.6dB of axial ratio at the boresight.