• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.188-191
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• 1993

Silicon flow sensor which can detect the magnitude and direction of two dimensional air flow was designed and fabricated by CMOS process and bulk micromachining technique. The flow sensor consists of three-layered dielectric diaphragm a heater at the center of the diaphragm and four thermopiles surrounding the heater at each side of diaphragm as sensing elements. This diaphragm structure contributes to improve the sensitivity due to excellent thermal isolation property of dielectric materials and its tiny thickness. The flow sensor has good axial symmetry to sense 2-D air flow with the optimized sensing position in the given structure. Measured sensitivity of our sensor is $18.7mV/(m/s)^{1/2}$.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.5
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• pp.113-120
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• 1994

Silicon flow sensor that can detect the velocity and direction of air flow was designed and fabricated by integrated circuit process and bulk micromachining technique. The flow sensor consists of three-layered dielectric diaphragm, a heater at the center of the diaphragm, and four thermopiles surrounding the heater at each side of diaphragm as sensing elements. This diaphragm structure contributes to improve the sensitivity of the sensor due to excellent thermal isolation property of dielectric materials and their tiny thickness. The flow sensor has good axial symmetry to sense 2-D air flow with the optimized sensing position in the proposed structure. The sensor is fabricated using CMOS compatible process followed by the anisotropic etching of silicon in KOH and EDP solutions to form I$\mu$ m thick dielectric diaphragm as the last step. TCR(Temperature Coefficient of Resistance) of the heater of the fabricated sensors was measured to calculate the operating temperature of the heater and the output voltage of the sensor with respect to flow velocity was also measured. The TCR of the polysilicon heater resistor is 697ppm/K, and the operating temperature of the heater is 331$^{\circ}C$ when the applied voltage is 5V. Measured sensitivity of the sensor is 18.7mV/(m/s)$^{1/2}$ for the flow velocity of smaller than 10m/s.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.10
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• pp.876-883
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• 2007

Numerical simulations are conducted for the design of a micro thermal mass air flow sensor (MAFS), which consists of a microfabricated heater and thermopiles on the silicon-nitride ($Si_3N_4$) thin membrane structure. It is important to find the proper locations of these thermal elements in the design of MAFS with improved sensitivity. Three heating modes of the micro-heater are considered: constant temperature, constant power and heating pulses. The analyses are focused on the membrane temperature profile near the sensing section. Considered are the practical flow velocities, ranging from 3 m/s to 35 m/s, and the corresponding Reynolds numbers from 1000 to 10000. The results show that one of optimum sensing locations is about $100{\mu}m$ away from the microheater. It is concluded that the heating mode and configurations of thermal elements are the main factors for the MAFS with higher sensitivity.

• Journal of Food Hygiene and Safety
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• v.3 no.4
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• pp.233-239
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• 1988

Vegetable mixed codiments, commercial products prepared using soybean,paste and natto, respectively as the ingredients, were used ina study to evaluate the efficacy of gamma irradiationas a means of decontamination and the emphasis was placed upon the determination of the effect of irradiation on the microbiological and some physicochemical properties of the samples. The number of microorganisms contaminated ranged from $10^{6}\;to\;10^{7}$ cells per gram in mesophilic total bacteria, which were composed of thermophilts and acid tolerant bacteria by over 90%. They were reduced by 3 to 4 log cycles with irradiation at 10 kGy. Gamma irradiation at 5 kGy could eliminate the microbial populations of yeasts and molds ($10^{2}\;to\;10^{3}$ cells per gram) and coliforms ($10^{6}\;to\;10^{6}$ cells per gram of natto condiments). However, total destruction of microorganisms in soybean-paste and natto condiments was shown to be possible at a dose-range more than 10 kGy. Irradiationup to 10 kGy was not detrimental to the physicochemical properties of the sample, such as pH. amino nitrogen, rancidity and color, even though some change was brought about in the content of sulfur-containing amino acids.