• Journal of Powder Materials
• /
• v.21 no.6
• /
• pp.429-433
• /
• 2014

This study investigated the magnetic properties and frequency dispersion of complex permeability of Ni-Zn-Co ferrites used for magnetic shielding in near field communication (NFC) system. The sintered specimens of $(Ni_{0.7}Zn_{0.3})_{1-x}Co_xFe_2O_4$ composition were prepared by the conventional ceramic processing. The coercive force and saturation magnetization were measured by vibrating sample magnetometer. The complex permeability was measured by RF impedance analyzer in the range of 1 MHz~1.8 GHz. The coercive force increased and saturation magnetization decreased with increasing the Co substitution. The real and imaginary parts of complex permeability decreased and the resonance frequency increased with Co substitution, which was attributed to the increase in crystal anisotropy field and reduction in saturation magnetization. The effect of Co substitution could be found in reducing the magnetic loss to nearly zero at the operating frequency of NFC (13.56 MHz).

• The Journal of Churna Manual Medicine for Spine and Nerves
• /
• v.1 no.2
• /
• pp.125-135
• /
• 2006

Objectives: The purpose of this study was to investigate the relationship among lumbar lordotic and obesity in Low Back Pain Patient Methods: The subjects of this study were patients with low back pain who visited Jung-Dong Oriental Hospital. X-ray were taken in lateral decubitus. The measurements of the Ferguson angles(FA) and the lumbar lordotic angles(LLA) were performed. We measured BMI and WHR has been accessed bio-impedance analyzer(inbody 3.0). This results were statistically analyzed using SPSS 12.0. Results 1. In female group. FA and LLA were significantly higher than male group. 2. LLA was shown to decrease to rise with increasing WHR and BMI 3. FA had no realtion with WHR and BMI Conclusions: This data shows that obesity related to mechanical structures such as lumbar curvature. Obesity can be a one of the stressor of lumbar spine, and one of the causing factor of low back pain.

• Journal of Powder Materials
• /
• v.23 no.2
• /
• pp.132-135
• /
• 2016

This study investigates the influence of sintering temperature on the magnetic properties and frequency dispersion of the complex permeability of Ni-Zn-Cu ferrites used for magnetic shielding in near-field communication (NFC) systems. Sintered specimens of $(Ni_{0.7}Zn_{0.3})_{0.96}Cu_{0.04}Fe_2O_4$ are prepared by conventional ceramic processing. The complex permeability is measured by an RF impedance analyzer in the range of 1 MHz to 1.8 GHz. The real and imaginary parts of the complex permeability depend sensitively on the sintering temperature, which is closely related to the microstructure, including grain size and pore distribution. In particular, internal pores within grains produced by rapid grain growth decrease the permeability and increase the magnetic loss at the operating frequency of NFC (13.56 MHz). At the optimized sintering temperature ($1225-1250^{\circ}C$), the highest permeability and lowest magnetic loss can be obtained.

• Polymer(Korea)
• /
• v.32 no.1
• /
• pp.85-89
• /
• 2008

Acrylate polymer gel electrolytes containing N-methoxymethyl-N-methylpyrrolidium bis (trifluoro - methansulfonyl) imide (MPSI) as an ionic liquid were synthesized by solution polymerization in the presence of carbonate solvent. ionic conductivity and mechanical properties of the polymer gel electrolytes were investigated by impedance analyzer and universal testing machine as a function of the amount of polymer, and ionic liquid and type of crosslinker. The maximum ionic conductivity of polymer gel electrolytes was 0.8 mS/cm at $25^{\circ}C$ with 15 wt% of polymer, 30 wt% of ionic liquid and 5 wt% of crosslinker. The mechanical analysis showed that the tensile strength of polymer gel electrolytes increased with additional polymer contents and had the maximum value of 0.5 MPa with a reasonable ionic conductivity.

• Journal of Korean Biological Nursing Science
• /
• v.22 no.1
• /
• pp.36-44
• /
• 2020

Purpose: The purpose of this study was to predict measuring site suited for abdominal skin fold thickness (ASFT) by measuring the distribution of abdominal subcutaneous fat thickness (AScFT) and ascertain the correlations among obesity indicators. Methods: The size of analysis materials was 124 secondary data measured by ultrasonic device, bioelectrical impedance analyzer and caliper. Data were analyzed using t-test, and Pearson's correlation. Results: The average of AScFT was 10.63± 6.79mm with its range 1.39-36.16 mm, and AScFT of female and of central parts were thicker than those of male and outer parts in the abdomen. The average of ASFT was 29.26±12.59 mm. Site 5 on Figure 1 was most similar to the average of AScFT in both sexes. Body mass index (BMI) and waist hip ratio (WHR) were 23.65±3.98 and 0.88±0.05 respectively. The body weight, BMI, WHR, visceral fat, ASFT vs AScFT revealed in significant correlation (r= .29, r= .55, r= .39, r= .33. r= .29). Conclusion: BMI and WHR seem more useful than other obesity indicators, when obesity control is necessary for Type 2 diabetes patients. Site 5 on Figure 1 is most suitable site to measure ASFT.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.12 no.6
• /
• pp.1003-1008
• /
• 2017

In this paper, we studied the design and fabrication of double T Structure with CPW antenna at around 5 GHz band.. To improve of frequency properties of antenna, Double T Structure with CPW antenna was simulated by HFSS(: High Frequency Structure Simulator). A double T Structure with CPW antenna was designed and fabricated by photolithograph on an FR4 substrate (dielectric constant of 4.4 and thickness of 1.6 mm). The fabricated A double T Structure with CPW antenna showed a center frequency, the minimum return loss and impedance were 5.29GHz, -34dB, and 390MHz, $49.6{\Omega}$ respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.19 no.10
• /
• pp.1129-1136
• /
• 2008

In this paper, a dual polarized broadband antenna fed by L-shaped strip for the Korea PCS band and W-CDMA band is presented. To analyze the characteristics of the designed antenna, we used commercial simulation tool(HFSS). The designed antenna was fabricated and measured using HP8753D vector network analyzer. The measured impedance bandwidth(VSWR<1.5) is 560 MHz and the measured average gain is 6.56 dBi. The measured isolation characteristic between two ports is -14 dB(min.) $\sim$ -40 dB(max.). These results are proper for the mobile communication application and repeater antenna.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.11 no.8
• /
• pp.637-645
• /
• 1998

The characteristics of waveguide, electrode and packaging fabricated for acousto-optic tunable filters(AOTF) used for optical communications were analyzed. A $Ti:LiNbO_3$in-diffusing method was employed for the formation of the optical waveguide with a dimension of width $8{\mu}m$, length $30000-50000{\mu}m$ and varying the thickness. The diffusion was carried at $1050^{\circ}C$ for 8 hours to pattern the optical waveguide. The resulted waveguide exhibited a single mode at 1550nm optical wavelength. The width of IDT, with 10 SAM periods, was $5000{\mu}m$ . Impedances of the electrodes deposited with Au were analyzed using a network analyzer; $48.1\Omega$ at the center frequency of 193MHz for electrode thickness of $1500{\AA}$ and $50.7\Omega$ at the center frequency of 192MHz for $1600\AA$. And the characteristics of packaged AOTF was analyzed. When the electrical frequency 177.1MHz was applied to the device, the mode conversion efficiency was measured as 63% at the optical wavelength 1515nm.

• Electrical & Electronic Materials
• /
• v.9 no.10
• /
• pp.1053-1059
• /
• 1996

The pulse-echo response of the piezoceramics PZT-polymer 3-3 type composite transducers with various PVA additions were investigated. The PZT powder was prepared by the molten salt synthesis method. The porous PZT specimens will be used as a filler to make 3-3 type comosite were prepared from a mixture of PZT and polyvinylalcohol(PVA) sphere by utilizing BURPS(Bumout Plastic Sphere) technique. It was shown that the transmitting and receiving sensitivity of 3-3 type piezoelectric composite transducers could be improved than that of solid PZT transducers. The reason is that 3-3 type piezoelectric composite have low dielectric constant, density and acoustic impedance. The distance between transducer and reflector was in good agreement with the distance calculated from the longitudinal velocity of the specimens and receiving time observed pulse-echo responses on the ultrasonic transducer analyzer.

• Bulletin of the Korean Chemical Society
• /
• v.30 no.1
• /
• pp.201-204
• /
• 2009

$BaTiO_3/SrTiO_3$ and $PbTiO_3/PbZrO_3$ superlattice thin films were fabricated on $Pt/Ti/SiO_2/Si$ substrate by the pulsed laser deposition process. The morphologies and physical properties of deposited films were characterized by using X-ray diffractometer, HR-SEM, and Impedance Analyzer. XRD data and SEM images of the films indicate that each layer was well deposited alternatively in the superlattice structure. The dielectric constant of $BaTiO_3/SrTiO_3$ superlattice thin film was higher than that of individual $BaTiO_3$ or $SrTiO_3$ film. Same result was obtained in the $PbTiO_3/PbZrO_3$system. The dielectric constant of a superlattice film was getting higher as the number of layer is increased.