Hyo-Dal Park

Effects of green tea extract administration on the pharmacokinetics of clozapine in rats.

The pharmacokinetic interaction between clozapine, an atypical antipsychotic with metabolic complications, including weight gain, and green tea consumption has not been evaluated, although green tea is responsible for beneficial effects, including weight reduction, and is widely consumed in the world. Commercial green tea extract (175 mg kg−1) or saline was administered orally for 4 days before the oral administration of clozapine (20 mg kg−1) to rats. Plasma concentrations of clozapine were measured up to 5 h after clozapine administration, and then hepatic CYP1A2 expression and activity were determined. There was no significant difference in the elimination half‐life of clozapine between the green tea extract and saline groups. However, the time to reach peak concentration (Tmax) was significantly increased by green tea extract. The mean total area under the plasma concentration‐time curve (AUC0‐∞) and maximal peak plasma concentration (Cmax) of clozapine in the green tea extract group were significantly lower than those of controls. Green tea extract induced a ∼2‐fold increase in hepatic CYP1A2 levels, while the activity increased slightly (by 10% of control). Because of this reduction in AUC and Tmax of clozapine by green tea extract pretreatment, we suggest that both the rate and amount of absorption of clozapine may be reduced by green tea extract, although the hepatic elimination phase may not be significantly altered. Therefore, the clinical implications of the effects of green tea on the bioavailability of clozapine in patients should be further evaluated.

Poly-Harmonic Modeling and Predistortion Linearization for Software-Defined Radio Upconverters

This paper presents a new predistortion linearization scheme for single-sideband mixers to be used for removing unwanted harmonics and intermodulation products of the digital IF in an heterodyne transmitter. The proposed algorithm, called poly-harmonic predistortion linearization, relies on an orthogonal expansion in the frequency domain of the nonlinearities for the mixer modeling. It takes into account memory effects that are piece-wise quasi-memoryless and enables the independent cancellation of unwanted spurious sidebands of the digital IF harmonics. The poly-harmonic predistortion linearization scheme for the weak-nonlinear regime was implemented in a field-programmable gate array and experimentally investigated for the linearization of a four-path polyphase single-sideband upconverter. The ability of the poly-harmonic predistortion algorithm to linearize the four-path polyphase mixer for input signals with high envelope fluctuation is demonstrated. -70-dBc/-62-dBc/-60-dBc spurious rejection and 18-dB/10-dB/8-dB linearization improvement of the third-order distortions are achieved for a two-tone RF signal, a 64-tone 10-MHz bandwidth multisine signal and orthogonal frequency-division multiplexing signal, respectively. The combination of the polyphase multipath technique and the poly-harmonic predistortion linearization technique offers an attractive filterless approach for the development of multimode broadband software-defined radio.

Frequency-Tunable Waveguide Antenna With Miniaturized Aperture Using a Varactor-Loaded Split-Ring Resonator

We propose a frequency-tunable waveguide antenna with a size-reduced aperture. Up to now, waveguide antennas with split-ring resonators have exhibited narrow-frequency bandwidths. To expand the operating frequency band, the resonant frequency of a split-ring resonator is tuned by adjusting the capacitance of the gap. A capacitor-loaded split-ring resonator is simulated and experimentally tested to validate its performance, and a varactor-loaded split-ring resonator is then investigated. The effective capacitance of the varactor-loaded split-ring resonator is changed by varying the external dc voltage. The tunable frequency range extends from 1.96 to 2.36 GHz (a fractional frequency range of 18.5%). The simulations and experiments yield good results for the reflection coefficient, radiation pattern, and gain. The proposed antenna retains the 70% aperture reduction of previously developed split-ring-resonator-loaded waveguide antennas.

Pulsed load-pull based optimal load-modulation PA design methodology for average efficiency enhancement

A new load-modulation based power amplifier design scheme is proposed for average power added efficiency (PAE) enhancement. An algorithm for choosing the optimal operating conditions from load-pull data with swept input power is presented. The optimal conditions for the joint control of the inputs power and the tunable output matching network for dynamic load-modulation are extracted and demonstrated using a commercial 15W GaN HEMT transistor. Instead of the PAE peaking only at high output power, greater than 60% PAE over 10 dB output power range is predicted in simulation for class-AB operation. Pulsed-RF real time active load-pull measurements with 1.9μs pulse width and 1.2% duty rate are then performed for swept input power to approximate high peak-to-average power ratio operation. Additional pulsed-RF active load-pull measurements are further used at the selected optimal loads for verification. Greater than 60% PAE over 7 dB are observed using both measurement techniques.

A Frequency-Selecting Technique for Mobile Handset Antennas Based on Capacitance Switching

This paper introduces a mobile switchable antenna for long term evolution (LTE) of the 4th generation (4G), applicable to all mobile service bands. The validity of this antenna is assessed by design, realization, and measurement. A new frequency-selecting method is used in the proposed antenna, based on capacitance switching among four states. Due to the limited antenna space in existing terminals, it is quite di-cult to cover the entire low band with a single antenna. To overcome this di-culty, three single- pole double-throw (SPDT) switches, one 74HC04, and four capacitors are used. The resulting antenna covers the LTE (698{798MHz) and GSM (824{960MHz) bands in the low-band characteristic by realizing four capacitance states and at the same time covers the DCS (1710{1880 MHz)/PCS (1850{1990MHz)/WCDMA (1920{2170MHz) bands in the high-band characteristic. The antenna provides a gain of i1:04{6.00dBi, a radiation e-ciency of 32.73{74.99%, and omnidirectional characteristics in the H-plane. Because of this outstanding performance, it is expected that the new frequency - selecting technique will be applied in 4G mobile communication terminals.

Aperture-miniaturized antenna loaded with split ring resonator array

In this paper, a novel antenna having a miniaturized aperture is proposed. The substrate including a split-ring resonator (SRR) array has been inserted into a size-reduced open-ended waveguide. For a low return loss and high radiation efficiency, the ring arrangement has been optimized, and a stepped transition using H-plane discontinuity is proposed. The proposed antenna achieves a 70% aperture reduction compared to a conventional standard waveguide antenna. The return loss was deeply dropped at three frequencies, and a reasonable gain was presented. The aperture-miniaturized antenna can be used in many antenna applications such as near-field measurements.

Trajectory Prediction for Using Real Data and Real Meteorological Data

Trajectory prediction is basic work for 4D-trajectory modeling, conflict detection and air traffic flow management. This paper proposes a novel algorithm based distance calculation formula (vincenty formula) for trajectory prediction. We demonstrated through simulations with real flight plan and real meteorological data and experimental results show that our trajectory prediction exhibits good performance in real air traffic management environment.

Design and Fabrication of a Multi-Function Circuit to Implement Hybrid-Conversion RF Front-End for Broadband and Multiband System

In this paper, we propose a RF front-end architecture based on hybrid conversion which is available to receive both broadband and multiband DVB-H receiver, and a multi-function circuit for implementing the RF front-end is fabricated. A multi-function circuit is operated as a sub-harmonic mixer mode in the case of receiving a broadband VHF/UHF band, which show a conversion loss of -10.0 dB, noise figure of 7.0 dB and IIP3 of 2.0 dBm. On the other hand, it is performed as a attenuation mode with a insertion loss of -10.0 dB in receiving a multiband, L-band.

Design and Implementation of Broadband RF Amplifier for Microwave Receiver

In this paper, We proposed a broadband RF amplifier for Microwave band receiver. We also proposed a broadband RF amplifier, designed by using EM simulation for reliable amplification of the received signal. Connected to a source terminal to via, it minimizes those which are the active elements of source-side oscillation as the operating element in an ideal GND, and a constant gain characteristic in a broadband. The goal of this was to obtain stable amplification characteristics. For implementing this architecture, we designed the broadband(500 MHz ~ 7 GHz) RF amplifier by using commercial GaAs FET, which operate on 720 MHz, 4,595 MHz, and 6,035 MHz by impedance matching. The voltage gain is 10.635 dB ~ 14.407 dB(737.5 MHz ~ 6.0575 GHz), P1dB is 20 dBc of band(1st harmonic/2nd harmonic).

En-Route Trajectory calculation using Flight Plan Information for Effective Air Traffic Management

Trajectory modeling is foundational for 4D-Route modeling, conflict detection and air traffic flow management. This paper proposes a novel algorithm based Vincenty`s fomulas for trajectory calculation, combined with the Dijkstra algorithm and Vincenty`s formulas. Using flight plan simulations our experimental results show that our method of En-route trajectory calculation exhibits much improved performance in accuracy.