• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.4
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• pp.279-285
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• 2017

In this paper, the resonator with a parallel plate capacitor is newly proposed around sub-microwave frequency band and applied to earlobe for non-invasive glucose monitoring the human biological tissue. The capacitor including the earlobe as dielectric material is connected to inductive slot in the ground plane of the microstrip line. Based on the simulation, one port resonator circuit is designed and fabricated as a prototype. Three step glucose concentration levels(0, 250, 500 mg/dL) was tested, and its reflection coefficients($S_{11}$) were measured. Owing to high Q resonator more than 100, resonant frequency shift of about 9 MHz per glucose level of 250 mg/dL has been successfully measured. This proves that the proposed sensor is applicable to a blood glucose sensor.

• Korean Journal of Materials Research
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• v.28 no.12
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• pp.719-724
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• 2018

Cordierite composed of an alumina-silica-magnesia compound has a low coefficient of thermal expansion(CTE) and excellent thermal shock resistance. It also has a low dielectric constant and high electrical insulation. However, due to low mechanical strength, it is limited for use in a ceramic heater. In this study, $ZrO_2$ is added to an 80 wt% cordierite-20 wt% mullite composition, and the effect of $ZrO_2$ addition on the mechanical strength and thermal shock resistance is investigated. With an increasing addition of $ZrO_2$, cordierite-mullite formed $ZrO_2$, $ZrSiO_4$ and spinel phases. With sintering conducted at $1400^{\circ}C$ with the addition of 5 wt% $ZrO_2$ to 80 wt% cordierite-20 wt% mullite, the most dense microstructure forms along with an excellent mechanical strength with a 3-point flexural strength of 238MPa. When this composition is quenched in water at ${\Delta}T=400^{\circ}C$, the 3-point flexural strength is maintained. Moreover, when this composition is cooled from $800^{\circ}C$ to air, the 3-point flexural strength is maintained even after 100 cycles. In addition, the CTE is measured as $3.00{\times}10^{-6}{\cdot}K^{-1}$ at $1000^{\circ}C$. Therefore, 80 wt% cordierite-20 wt% mullite with 5 wt% $ZrO_2$ is considered to be appropriate as material for a ceramic heater.

• Korean Journal of Food Science and Technology
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• v.49 no.1
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• pp.44-49
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• 2017

Subcritical water extraction can be used to selectively extraction compounds by varying the temperature-dependent dielectric constant of water. This study investigated subcritical water extraction of decursin and nodakenin yields from Angelica gigas Nakai (AN) quantitatively and qualitatively by HPLC, and HPLC-ESI/MS. Total phenolics, total flavonoid contents, and antioxidant activity were determined by DPPH and ABTS radical scavenging activity, including the effects of varying the extraction conditions of temperature ($110-200^{\circ}C$) and time (1-20 min) under high pressure (10 MPa). By subcritical water extraction under operating conditions of $120-130^{\circ}C$, the maximum yields of decursin ($6.64{\pm}0.42%$ in the dried material) and nodakenin ($3.71{\pm}0.28%$ in the dried material) were obtained. From $190-200^{\circ}C$ the maximum yields of total phenolics ($75.97{\pm}1.64mg$ gallic acid equivalent/g AN), flavonoids ($8.56{\pm}1.10mg$ quercetin equivalent/g AN), DPPH ($63.07{\pm}1.71%$), and ABTS ($72.32{\pm}2.82%$) were obtained.

• Korean Journal of Materials Research
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• v.18 no.4
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• pp.169-174
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• 2008

The structural and electrical properties of amorphous $BaSm_2Ti_4O_{12}$ (BSmT) films on a $TiN/SiO_2/Si$ substrate deposited using a RF magnetron sputtering method were investigated. The deposition of BSmT films was carried out at $300^{\circ}C$ in a mixed oxygen and argon ($O_2$ : Ar = 1 : 4) atmosphere with a total pressure of 8.0 mTorr. In particular, a 45 nm-thick amorphous BSmT film exhibited a high capacitance density and low dissipation factor of $7.60\;fF/{\mu}m2$ and 1.3%, respectively, with a dielectric constant of 38 at 100 kHz. Its capacitance showed very little change, even in GHz ranges from 1.0 GHz to 6.0 GHz. The quality factor of the BSmT film was as high as 67 at 6 GHz. The leakage current density of the BSmT film was also very low, at approximately $5.11\;nA/cm^2$ at 2 V; its conduction mechanism was explained by the the Poole-Frenkel emission. The quadratic voltage coefficient of capacitance of the BSmT film was approximately $698\;ppm/V^2$, which is higher than the required value (<$100\;ppm/V^2$) for RF application. This could be reduced by improving the process condition. The temperature coefficient of capacitance of the film was low at nearly $296\;ppm/^{\circ}C$ at 100 kHz. Therefore, amorphous BSmT grown on a TiN substrate is a viable candidate material for a metal-insulator-metal capacitor.