Sang-Min Han

Synovial fluid CD34⁻ CD44⁺ CD90⁺ mesenchymal stem cell levels are associated with the severity of primary knee osteoarthritis.

To the best of our knowledge, no reports have directly compared synovial fluid (SF)- and synovial membrane (SM)-derived mesenchymal stem cells (MSCs) from primary knee osteoarthritis patients in terms of MSC proportion, either immediately after isolation or during culture. Any possible correlation between SM- and SF-MSC purity and osteoarthritis severity, also remains unclear. We therefore assessed quantitative and phenotypic differences in MSCs isolated from SF and SM. We also evaluated the correlation between sample MSC purity, and disease severity, in patients with osteoarthritis. The main result of the current study was that the mean SF-MSC proportion at passage 0 was negatively correlated with Kellgren-Lawrence (KL) grade (r = -0.565, P = 0.002). In addition, KL grade was a only significant independent negative predictor of SF-MSC proportion at passage 0 (β = -0.356, P = 0.039). Conclusively, the proportion of SF-MSCs in fresh samples, evaluated at the single cell level, was inversely correlated with osteoarthritis severity.

Resonant frequency of dielectric resonator

In this paper, an effective dielectric constant (EDC) has been introduced in an axial attenuation constant of dielectric waveguide model (DWM) method to calculate more accurately the resonant frequency of the TE/sub 01/spl delta// mode of a dielectric resonator (DR) in an MIC environment. The accuracy of this method is shown to be better than 1.5% error.

Planar Directional Beam Antenna Design for Beam Switching System Applications

In this paper, a planar directional beam-switchable antenna with four orthogonal beam directions is proposed. The proposed antenna is designed with two crossed active elements and two parasitic elements for each direction. The design methodology is described on the basis of the Yagi-Uda method for the active and parasitic elements, respectively. By adjusting the effective electric lengths of the parasitic elements, the roles of a director and a reflector are exchanged with each other. The planar four-way beam-switchable Yagi-Uda antenna is implemented. From the experimental results. The proposed design method is verified for orthogonal radiation beam switching.

A Reconfigurable Circularly Polarized Microstrip Antenna on a Cross-Shape Slotted Ground

A compact circular microstrip patch antenna with a switchable circular polarization(CP) is proposed at 2.4 GHz. An unequal cross-shaped slot on a ground plane is utilized as a perturbation. By switching pin diodes mounted on the slot, the CP sense of each antenna can be simply switched from left-handed(LH) CP to right-handed(RH) CP vice versa. Since the perturbation can be made on the ground plane and no bias circuit is required on the patch side, the bias circuit has not effect on the main beam radiation. From the experimental results, the impedance bandwidth and CP bandwidth of the proposed antenna have shown up to 150 MHz and 35 MHz, respectively. The peak gain of the proposed antenna is 1.7 dBi for both CP senses.

Low Phase Noise VCO Using Complimentary Bifilar Archimedean Spiral Resonator(CBASR)

In this paper, a novel voltage-controlled oscillator(VCO) using the complimentary bifilar archimedean spiral resonator(CBASR) is presented for reducing the phase noise characteristic. A CBASR has compact dimension, a sharp skirt characteristic in stopband, a low insertion loss in passband, and a large coupling coefficient value, which makes a high Q value and improve the phase noise of VCO. The proposed VCO has the oscillation frequency of 2.396~2.502 GHz in the tuning voltage of 0~5 V, the output power of 7.5 dBm and phase noise of -119.16~-120.2 dBc/㎐ at the offset frequency of 100 kHz in tuning range.

RF Spectrum Cognition Technologies for IoT Wireless Sensors

Abstract – In this paper, new spectrum sensing schemes based on analog/RF front-end processing are introduced for IoT wireless sensor networks. While the conventional approaches for wireless channel cognition have been issued in signal processing area, the RF spectrum cognition concept makes it feasible to achieve cognitive wireless sensor networks (C-WSNs). The spectrum cognition at RF processing is categorized as four kinds of sensing mechanisms. Two recent reseaches are described as promising candidates for the C-WSN. One senses spectrum by the frequency discriminating receiver, the other senses and detects from the frequency selective super-regenerative receiver. The introduced systems with simple and low-power RF architectures play dual roles of channel sensing and demodulation. simultaneously. Therefore, introduced spectrum sensing receivers can be one of the best candidates for IoT wireless sensor devices in C-WSN environments.Key Words : Cognitive radio, C-WSN(Cognitive wireless sensor network), IoT(Internet of things), Spectrum sensing, Wireless connectivity†Corresponding Author : Dept. of Information and Communi- cation Engineering, Soonchunhyang University, Korea E-mail : smhan@sch.ac.kr* Dept. of Electronic Engineering, Hoseo University, Korea Received : October 30, 2015; Accepted : December 24, 2015

Voltage Controlled Injection-Locked Oscillator Design at 2.4 GHz Band for Wideband Applications

In this paper, a voltage controlled injection-locked oscillator(VC-ILO) is proposed for wideband applications. From the control of the free-running frequency by a varactor diode, the wide frequency locking range can be obtained for low-level injected signals. The proposed VC-ILO is implemented on an FR-4 substrate with a thickness of 0.8 mm. The free-running frequencies of the oscillator is 2.39~2.52 GHz at the control voltage of 0~5 V. While the frequency locking range of over 50 MHz is presented for -10 dBm injected signal level at a fixed frequency, the locking range of over 90 MHz can be achieved for -30 dBm by controlling the free-running frequency.

A Switchable Circularly Polarized Microstrip Antenna using Asymmetric U-shaped Slotted Ground Structures

In this paper, a new microstrip antenna using asymmetric U-shaped slotted ground is proposed for a switchable circular polarization sense. The proposed antenna is achieved a circularly polarization from orthogonal E-field distributions with 90 degree phase difference due to the asymmetrical U-shaped slot. Moreover, the circular polarization sense of the proposed antenna can be easily switchable with changing the symmetric plane of the U-shaped slots. As a result, the proposed antenna is implemented by two PIN diodes with two different bias condition for ON/OFF states. The measured axial ratios are about 1.5 dB without the dependence of the polarization sense and 3-dB axial ratio bandwidth are achieved 29 MHz with respect to about 1.2 % at 2.46 GHz operating frequency.

A Dual-Band Asymmetrical Metamaterial Antenna for Orthogonal Radiation Patterns

Abstract A new metamaterial antenna with dual resonant modes is presented using an asymmetrical periodic arrangement for orthogonal radiation patterns. The proposed antenna produces two orthogonal modes by the asymmetrical periodic unit-cell arrangement. The orthogonal resonant mode provides perpendicular radiation patterns without changing the antenna polarization at each resonant mode. The fabricated antenna shows good agreements with the theoretical analysis of the electric-field. The experimental results shows the orthogonal radiation patterns along x- and y-axises, and gains are 3.34 and 3.86 dBi at each radiating resonant mode, respectively. Additionally, slotted ground structures are embedded on the back side of the antenna in order to reduce the size and enhance the radiation efficiency of 12 % and 27 %, respectively.Key Words : Composite right/left-handed transmission lines (CRLH-TLs), Magnetic monopole antennas, Microstrip patch antennas, Dual-band antennas, Orthogonal radiation patterns.