• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.1
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• pp.44-53
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• 2000

In this paper, we propose a multicarrier CDMA system with an adaptive subchannel allocation method for forward links. In the proposed system, instead of transmitting identical DS waveforms over a number of subchannels in parallel, each user's DS waveform is transmitted over the user's favorite subchannel which has the largest fading amplitude among all the subchannels. The proposed system is shown to have performance gain over the conventional multicarrier DS/CDMA system. We also investigate how the performance is influenced when the signal is not perfectly allocated into the best subchannel.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.11
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• pp.12-17
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• 1999

In this paper, we proposed a novel CB-CPW(Conductor Backed CPW) for suppression of crosstalk caused by PPL(Parallel Plate Line) mode in the millimeter wave frequency. The proposed structure is formed by the GaAs main substrate attached on the Si lossy layer. The PPL mode can be suppressed by the Si lossy layer of conductivity ${\sigma}$, and it reduces the crostalk between the nearby transmission lines. Using 200 um thick Si substrate of ${\sigma}$ = 30S/m, as the lossy layer, the crosstalk can be suppressed below - 40 dB at 60 GHz. The proposed method is costly effective because inexpensive Si wafer is employed to suppress the PPL mode, and it can be used in the various types of millimeter wave applications.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.8 s.111
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• pp.739-745
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• 2006

This paper presents a method to control group delay tine using a resonance circuit. The group delay time adjuster(GDTA) that can control signal group delay time comprises a variable capacitance and a variable equivalent inductor. These are coupled in parallel at a node and also controlled by two bias voltages separately, A variable equivalent inductor is realized a transmission line terminated a variable capacitor. Group delay time can be controlled by change of capacitance and inductance, but the resonating frequency is fixed. When the proposed GDTA is fabricated on RFID Korean frequency band$(908.5{\sim}914 MHz)$, a group delay variation is obtained about 3 ns.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.9
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• pp.904-911
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• 2011

This paper deals with transmission characteristics of a new dual resonant structure for designing waveguide band-pass filter. The structure which has a pass-band between two adjacent stop-bands in a single body consists of circular ridged aperture and four armed conducting patch. The dual resonant behavior of the structure can be represented by a combination of LC series and parallel resonant circuits. Also these resonant properties can be easily controlled by varying the geometry of the aperture and four armed conducting patch. Actually, the structure is fabricated on the microstrip substrate by use of etching technique so that it is formed an iris type resonator which can be easily put into the transverse plane of the waveguide. We use WR-90 standard waveguide, adapters, and VNA(vector network analyzer) to measure the resonant characteristics of the structure. It is very useful to design and to improve the cutoff skirts characteristics in the waveguide band-pass filter design area.

• Applied Microscopy
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• v.34 no.4
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• pp.223-230
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• 2004

To identify the structural basis of mutations that affect synaptic transmission we have begun quantitative ultrastructural descriptions of synapses in cultured Drosophila embryonic neurons. In wild-type cultures, synapses are distinguished by the parallel arrangement of a thickened pre- and post synaptic membrane separated by a synaptic cleft. The presynaptic active zones and postsynaptic densities are defined by electron dense material close to the membrane. Presynaptic regions are also characterized by the presence of one or more electron dense regions, presynaptic densities, around which a variable number of small, clear core synaptic vesicles (mean $35.1{\pm}1.44$ nm in diameter) are clustered. Subsets of these vesicles are in direct contact with either the presynaptic density or the membrane and are considered morphologically docked. A small number of larger, dense core vesicles are also observed in most presynaptic profiles.

• Korean Journal of Plant Tissue Culture
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• v.27 no.6
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• pp.429-434
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• 2000

Isolated protoplasts from ginseng (Panax ginseng C. A. Meyer) callus tissue were cultured in modified MS media supplemented with various concentrations of dimethylsulfoxide (DMSO). The cell wall regeneration rate and cell division efficiency of the protoplasts were increased significantly by 1% DMSO treatment. However, there was no difference in the viability of protoplasts between the DMSO treatment and non-treatment. Transmission electron microscopy revealed that the microtubules were oriented in parallel manner to the plasmalemma after 3 days of culture in medium with 1% DMSO. Further, interconnected cellulose microfibrils were observed on the outer surface of the 3-day-cultured protoplasts by scanning electron microscopy These structures shown by electron microscopy were not observed in protoplasts cultured on DMSO-free media. This studies indicates that DMSO supplemented in culture media seemed to stimulate the cell wall regeneration and cell divisions of protoplasts by forming microtubule organizing centers (MTOC).

• Journal of the Microelectronics and Packaging Society
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• v.11 no.4 s.33
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• pp.7-11
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• 2004

In this paper, a $\lambda$/4 hairpin resonator is applied to reduce the size of planar resonators for a 2.4 GHz Band LTCC MLC bandpass filter. The $\lambda$/4 hairpin resonator operates as stepped impedance resonator (SIR) without changing the width of the planar resonator. It is composed of two sections those are parallel coupled line and transmission line. The characteristic impedance of two sections is different each other. The design formulas of the bandpass filter using the coupling element at the arbitrary position are derived from even and odd-mode analysis. The formulas can take account of the arbitrary coupling of lumped and/or distributed resonators. The advantage of this filter is its abilities to change freely the coupling structure between two resonators. Experimental bandpass filters for 2.4 GHz Band are implemented and their performances are shown.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.8
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• pp.1613-1621
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• 2015

This paper analyzes the rate adaptation scheme and suggests applicable strategy of the MCS(Modulation and Coding Scheme) for improving DCF throughput in the IEEE 802.11ad and 802.11ad wireless LAN. IEEE 802.11ac and 802.11ad wireless LAN provide MCS technique that dynamically adjusts modulation level and code rate to the time-varying channel conditions in order to obtain considerably high data rates. But these standards did not provide rate adaptation algorithm, so this paper surveyes rate adaptation algorithm and suggests MCS scheme applied to IEEE 802.11ac and 802.11ad wireless LAN. Specially A MAC(Medium Access Control) layer throughput is evaluated over error-prone channel in the IEEE 802.11ac-based wireless LAN. In this evaluation, DCF (Distributed Coordination Function) protocol and A-MPDU (MAC Protocol Data Unit Aggregation) scheme are used. Using theoretical analysis method, the MAC saturation throughput is evaluated with the PER (Packet Error Rate) on the condition that the number of station, transmission probability, the number of parallel beams and the number of frames in each A-MPDU are variables.

• Journal of Korean Society of Steel Construction
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• v.9 no.4 s.33
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• pp.515-521
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• 1997

The effects of heat treatment and fiber orientation on tensile strength and fatigue behavior were studied in a continuously reinforced. magnesium-based composite Following an earlier TEM investigation, specimens were thermally aged to modified the interfacial zone between the alumina fibers and the magnesium alloy matrix. From the tensile experimental results, the ultimate tensile strength of the aged specimens were lower than that of the as-fabricated due to weak fiber-matrix interfacial strength with chemical reaction during the thermal processing. The fatigue crack growth experiments were conducted with specimens having the fiber orientation normal to the crack growth direction (longitudinal) and also specimens with the fibers oriented parallel to the crack growth direction(transverse). A comparison of the fatigue crack growth behavior indicates that aged longitudinal specimens are more resistant to fatigue crack growth the as-fabricated longitudinal specimens. Conversely, as-fabricated transverse specimens are more resistant to fatigue crack growth than aged transverse specimens.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.9A
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• pp.1022-1030
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• 2004

The next generation cellular radio systems require high data rate transmission and large system capacity In order to meet these requirements, multiple antennas can be used at the base and mobile stations, forming MIMO(multiple-input, multiple-output) channels This paper considers a downlink MIMO system assuming a large number of base station antennas, a small number of mobile station antennas, and rich-scattering, quasi-stationary, and flat-fading channel environments When the channel state information is given at the base station in a single user system, a MIMO technique with SVD(singular value decomposition) and water-filling can achieve the maximal downlink channel capacity. In multi-user environments, however, SDMA(space division multiple acces) technique can be used to further increase the total channel capacity supported by the base station This paper proposes a MIMO SDMA technique which can transmit parallel data streams to each of multiple users. The proposed method. can achieve higher total channel capacity than SVD-based MIMO techniques or conventional SDMA using smart antennas.