• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.451-454
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• 2006

Fiber optic distributed temperature sensing and thermal line sensor are applied in an observation borehole and a loom deep borehole heat exchanger. For the case of permanently installed system fiber optic DTS is very useful. By comparing with TLS, fiber optic DTS shows good accuracy and reliability. Ground water flow can give influences at heat exchange rate of the heat pump system. According to the hydraulic characteristics and temperature-depth profile, we consider that temperature-depth profile do not seem to be dependent on ground water flow. A permanent installation of fiber optic cable is expected as a reliable temperature measurement technique in a borehole heat exchanger system.

• 센서학회지
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• 제11권4호
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• pp.191-199
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• 2002

This paper presents the design concept, theoretical investigation, and fabrication of a six-degree of freedom (6-DOF) turbulent flow micro sensor utilizing the piezoresistive effect in silicon. Unlike other flow sensors, which typically measure just one component of wall shear stress, the proposed sensor can independently detect six components of force and moment on a test particle in a turbulent flow. By combining conventional and four-terminal piezoresistors in Si (111), and arranging them suitably on the sensing area, the total number of piezoresistors used in this sensing chip is only eighteen, much fewer than the forty eight piezoresistors of the prior art piezoresistive 6-DOF force sensor.

• 대한기계학회논문집B
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• 제31권10호
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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.

• 전기학회논문지
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• 제62권6호
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• pp.833-839
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• 2013

Cardiopulmonary resuscitation (CPR) is performed by thoracic compression and artificial ventilation for the patient under emergent situation to maintain at least the minimum level of respiration and blood circulation for life survival. Good quality CPR requires monitoring respiration, however, traditional respiratory air flow transducers cannot be used because the transducer elements are facing the whole area perpendicular to the flow axis. The present study developed a new air flow transducer conveniently applicable to CPR. Specially designed "sensing rod" samples the air velocity at 3 different locations of the flow cross-section, then transforms into average dynamic pressure by the Bernoulli's law. The symmetric structure of the sensing holes of the sensing rod enables bi-directional measurement simply by taking the difference in pressure by a commercial differential pressure transducer. Both inspiratory and expiratory flows were obtained with symmetric measurement characteristics. Quadratic curve fitting provided excellent calibration formula with a correlation coefficient>0.999 (P<0.0001) and the mean relative error<1%. The present results can be usefully applied to accurately monitor the air flow rate during CPR.

• 전자공학회논문지A
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• 제31A권5호
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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.

• 한국정보통신학회논문지
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• 제9권3호
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• pp.595-600
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• 2005

마이크로 흐름센서는 반도체 집적기술을 이용할 수 있어, 소형으로 제작이 가능하며 빠른 응답특성을 가져 다양한 분야에 응용되고 있다. 본 연구에서는 넓은 흐름의 세기 영역에서 정밀한 감도를 가지는 2차원의 마이크로 흐름센서를 실리콘 기판위에 적충시켜 제작하였다. 흐름센서의 중앙에 하나의 히터와 양측에 온도를 검출할 수 있는 3쌍의 감지막을 가진 새로운 센서 구조를 제안하고, 온도 검출에 대한 성능평가를 위하여 시간영역에서의 유한차분법을 이용하여 공기흐름의 세기 변화에 따른 온도분포를 계산하였다. 계산결과를 통하여 실제 흐름센서의 동작을 정량적으로 분석하였다.

• 한국항해항만학회지
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• 제32권9호
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• pp.717-722
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• 2008

We have proposed and demonstrated an gas-flow sensor using optical fiber bragg grating(FEG). The flow sensor has no electronics and no mechanical parts in its sensing part and the structure is th11s simple and immune to electromagnetic interference(EMI). The FEG sensor was consisted qf the sensing element and a coil heater. The metal coil was used to supply the current to the FEG. While some currents supply to the coil, the refractive index of the FEG under the coil is changed and thus the wavelength shift of fiber optic sensor was induced In this work, the wavelength shift according to flow-rate was experimentally studied and was used to evaluate the gas flow-rate in a gas tube. As a result, it was possible to measure the flow-rate in a linear range from 5 to $20{\ell}/min$ with a resolution of approximately $1{\ell}/min$ at the applied currents of 100 mA and 120 mA. The measured sensitivities were $15.3\;pm/\ell/min$ for 100 mA and $20.2\;pm/\ell/min$ for 120 mA.

• 대한기계학회논문집A
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• 제40권1호
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• pp.87-95
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• 2016

본 연구에서는 오픈센터 시스템과 부하 감지형 시스템의 해석모델을 개발하고 시스템의 특성과 효율을 분석하였다. 오픈 센터 방식의 메인 컨트롤 밸브의 압력과 유량 특성을 분석하기 위해 각각의 포트별로 시험을 수행하였다. 시스템의 특성 분석 전 단계에서 시험 결과와 해석 결과를 비교함으로써 해석모델의 신뢰성을 검토하였다. 신뢰성이 검증된 오픈 센터 방식의 메인컨트롤 밸브에 유량 분배 밸브를 추가하여 부하 감지형 메인 컨트롤 밸브의 해석모델을 개발하였다. 두 가지 시스템의 효율을 분석하기 위해 동일한 부하 조건에서 해석을 수행하였으며 각각의 부하 특성에 따른 효율을 검토하였다. 또한, 서로 다른 부하 조건에서 유량 분배 시스템의 특성을 분석함으로써 복합 동작에 대한 성능도 검토 하였다.

• 전기전자학회논문지
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• 제23권3호
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• pp.1033-1037
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• 2019

GaN-based sensors have been widely investigated thanks to its potential in detecting the presence of hydrogen. In this study, we fabricated hydrogen gas sensors with AlGaN/GaN heterojunction and investigated how the sensing performance to be affected by SiN surface passivation. The gas sensor employed a high electron mobility transistors (HEMTs) with 30 nm platinum catalyst as a gate to detect the hydrogen presence. SiN layer was deposited by inductively-coupled chemical vapor deposition as post-passivation. The sensors with SiN passivation exhibited hydrogen sensing characteristics with various gas flow rates and concentrations of hydrogen in inert background gas at $200^{\circ}C$ similar to the ones without passivation. Aside from quick response time for both sensors, there are differences in sensitivity and recovery time because of the existence of the passivation layer. The results also confirmed the dependence of sensing performance on gas flow rate and gas concentration.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권4호
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• pp.1519-1534
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• 2016

In this paper, we study how to optimize the data shuffle phase by leveraging the flow relationship in datacenter networks (DCNs). In most of the clustering computer frameworks, the completion of a transfer (a group of flows that can enable a computation stage to start or complete) is determined by the flow completing last, so that limiting the rate of other flows (not the last one) appropriately can save bandwidth without impacting the performance of any transfer. Furthermore, for the flows enter network late, more bandwidth can be assigned to them to accelerate the completion of the entire transfer. Based on these characteristics, we propose the flow chasing algorithm (FCA) to optimize the completion of the entire transfer. We implement FCA on a real testbed. By evaluation, we find that FCA can not only reduce the completion time of data transfer by 6.24% on average, but also accelerate the completion of data shuffle phase and entire job.