• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.5
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• pp.989-998
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• 2012

A ratio type of capacitance measurement circuit is proposed to measure an extremely small value of the fF capacitance on this paper. This measurement circuit is formed with a switched-capacitor integrator, a comparator, and logic circuit blocks to control the switches. It converts the measured ratio value between the known value of on-chip capacitor and the unknown value of capacitor to the digital signal. The fF capacitance with minimized error can be obtained by calculating this ratio. This proposed circuit is designed with standard CMOS $0.18{\mu}m$ process, and various HSpice simulations prove that this capacitance measurement circuit is able to measure the capacitance under 5fF with less than ${\pm}0.3%$ error rate.

• KIPS Transactions on Computer and Communication Systems
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• v.7 no.8
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• pp.203-210
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• 2018

Mobile traffic is increasing consistently, and mobile carriers are becoming more and more hard to meet this ever-increasing mobile traffic demand by means of additional installation of base stations. To overcome this problem, heterogeneous networks, which can reuse space and frequency by installing small cells such as femto cells in existing macro cells, were introduced. However, existing macro cell users are difficult to increase the spectral efficiency without the cooperation of femto owners. Femto owners are also reluctant to accommodate other mobile stations in their femto stations without proper incentive. In this paper, a method of obtaining the optimal incentive is proposed, which adopts a utility function based on the logarithm of throughput of mobile stations, and the incentive is calculated to maximize the utility of the entire network.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.9
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• pp.762-771
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• 2012

In this paper, we propose an adaptive power control scheme employing a self-optimization concept in femtocell systems, in order to improve system capacity, thereby reducing call-drop probability. In the proposed scheme, each femto base station(FBS) controls individual channel's transmission power base on two parameters; the neighboring cell's transmission power for each individual channel which is delivered from a femto-gateway and the received power strength from neighboring cells which is periodically measured by means of a spectrum sensing. Adaptive adjustment of individual channel's transmission power in accordance with femto mobile station(FMS) mobility features can also reduce undesirable handovers and evenly distribute traffic load over all femtocells. In addition, the manipulative control of channel's transmission power is able to keep the system coverage and the call-drop probability within an acceptable range, regardless of density of femtocells. Computer simulation shows that the proposed scheme outperforms existing schemes in terms of the system coverage and the call-drop probability.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1132-1132
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• 2004

• The Science & Technology
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• no.7 s.446
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• pp.29-31
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• 2006

• Proceedings of the Korean Society of Laser Processing Conference
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• 2006.06a
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• pp.69-73
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• 2006

• Proceedings of the Optical Society of Korea Conference
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• 2006.02a
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• pp.205-206
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• 2006

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2013.05a
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• pp.50-50
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• 2013

• Journal of Biomedical Engineering Research
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• v.42 no.4
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• pp.193-200
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• 2021

Flowmeter and oxygen sensors are listed in COVID-19 essential medical devices. This article reports a Teensy microcontroller-based Oxygen mass flow controller (MFC), core part of the oxygen respirator or extracorporeal membrane oxygenation (ECMO). The developed MFC consisting of the microcontroller, MEMS flow sensor, and solenoid valve was able to accurately control 0 to 100 sccm of oxygen flow rate. The pressure of vacuum chamber increased proportionally to the flow rate (0.998 of Pearson correlation coefficient). The experimental results proved that the developed MFC exhibits comparable performance to a commercial MFC in accuracy, settling time, linearity with pressure, and repeatability of oxygen mass flow control. It is expected that this simple and cheap MFC is utilized for oxygen therapy against the severe acute respiratory syndrome coronavirus 2.

• Proceedings of the Optical Society of Korea Conference
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• 2005.02a
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• pp.246-247
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• 2005