• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.8
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• pp.16-21
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• 2007

CMOS variable gain amplifier (VGA) IC designs for the structure monitoring systems of the telemetries were developed. A three stage cascaded VGA using a differential amplifier and a linear-in-dB controller is presented. A proposed VGA is a modified version of a conventional VGA such that the gain is controlled in a linear-in-dB fashion through the current ratio. The proposed VGA circuit introduced in this paper has a dynamic range of 77 dB with 1.5 dB gain steps. It also achieved a gain error of less than 1.5 dB over 77 dB gain range. The VGA can operate up to 10MHz dissipating 13.8 mW from a single 1.8 V supply. The core area of the VGA fabricated in a Magnachip $0.18{\mu}m$ standard CMOS process was about $430{\mu}m{\times}350{\mu}m$. According to measurement results, we can verify that the proposed method is reasonable with regard to the enhancement of dynamic range and the better linear-in-dB characteristics.

• Progress in Medical Physics
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• v.12 no.2
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• pp.125-131
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• 2001

We was investigate the dosimetric characteristics of the virtual wedge and it compared to the conventional fixed wedge. Also we was evaluate the quality factor of the experimental multi-channel dosimetry system for virtual wedge. Recently virtual wedge technique and wedge fraction methods are available through the computer controlled asymmetric collimator or the independent jaw in medical linear accelerator for radiation therapy. The dosimetric characteristics are interpreted by radiation field analyzer RFA-7 system and PTW-UNIDOS system. Experimental multi-channel dosimetry system for virtual wedge was consists of the electrometer, the solid detector and array phantom. The solid detectors were constructed using commercially diodes for the assessment of quality assurance in radiotherapy. And it was used for the point dose measuring and field size scanning. The semiconductor detector and ion chamber were positioned at a dmax, 5 cm, 10 cm, 20 cm depth and its specific ratio was determined using a scanning data. Wedge angles in fixed and virtual type are compared with measurements in water phantom and it is shown that the wedge angle 15$^{\circ}$, 30$^{\circ}$, 45$^{\circ}$were agree within 1$^{\circ}$ degree in 6, 10 MV photon beams. In PDD and beam flatness, experimental multi-channel disimetry system was capable of reproduceing the measured values usually to within $\pm$2.1% the statistical uncertainties of the data. It was used to describe dosimetric characteristics of virtual wedge in clinical photon beams. Also we was evaluate optimal use of the virtual wedge and improve the quality factor of the experimental multi-channel dosimetry system for virtual wedge.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.13 no.3
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• pp.47-65
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• 2014

VMS(Variable Message Sign) helps drivers to choose their path to destinations on roadways. Some types of VMS often provide traffic information with clearly visible and comprehensible graphical route diagrams. Currently many diagramed types of VMS are installed on urban arterial and highways. This type of VMS surely enhances drivers' ability to comprehend traffic route information while they are driving on the roadway. Nevertheless, some of them are presented with so much information and design elements and they sometimes lead to decline of drivers' comprehensible level for traffic information. Drivers would fail to decide their preferable route in this state of information overflow. The purpose of this paper is to develop a drivers preference model for effective design principle including size and height of displaying font, and the amount of information in the route diagram considering driving speed, sex and age of the driver. This model is developed using structural equation modeling techniques. This model considers driver's emotional factor and, human factor and design component of route diagram. To collect data, we built driving simulator which is able to replicate real driving condition. 72 people who participated in the simulation were selected considering gender and age. The developed model showed that the amount of information, and visibility are more influential factors to the drivers' preference of the route diagram on VMS than design elements such as the shape and the font of the diagram.

• The Journal of Engineering Geology
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• v.25 no.4
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• pp.587-598
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• 2015

We examined various existing threshold methods for the determination of the first arrival time of acoustic emission (AE), and developed a new variable threshold method that could determine the first arrival time of AE more accurately and more quickly than existing methods. The new method, a modification of an existing threshold method, does not fix the threshold, but applies variable thresholds for the AE signals according to noise analysis. Two- and three-dimensional models were established to test the effectiveness of the new method. It could determine source locations of AE in a two-dimensional model 38.3% more accurately than the pre-existing threshold methods. Its accuracy improvement over the existing methods in a three-dimensional model was about 15.2%. A practical test involved measuring the source locations of AE during three-point bending tests of granite cores. The new method placed the sources closer to the fracture plane than did the pre-existing methods, indicating its superior (and quicker) ability to determine the source locations of AE.

• Smart Media Journal
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• v.6 no.3
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• pp.89-94
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• 2017

The existing geofences provide only context-awareness service for entering or leaving the set region when a user sets a virtual region for his/her PoI(Point of Interest). Applying the mobile-geofence technology to the connected car technology, which is attracting attention as a next generation technology, it is possible to provide application service without additional infrastructure construction cost However, to do this, we need to expand and improve the functions of traditional geofence. In this paper, we propose and implement a flexible mobile-geofence in which the radii of each geofence applied to vehicles is changed according to context-aware in order to support connected cars technology based on the previously studied mobile three-dimensional geofence system. The proposed flexible mobile-geofence shows experimentally that the region of the geofence is changed according to context-aware of itself and its surroundings after applying a flexible decision algorithm by the flexible factor analysis. In the future, we are expected that the flexible mobile-geofence proposed in this paper will be applied not only to connected-cars technology but also to the application technology of V2X(Vehicle to Everything) for safe and efficient vehicle operation.

• Proceedings of KOSOMES biannual meeting
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• 2018.06a
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• pp.179-179
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• 2018

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.1201-1202
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• 2013

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.10a
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• pp.112-112
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• 2003

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.316-317
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• 2011

본 연구에서는 일반 사무 건물을 대상으로 주광을 이용 하여 작업 시 조도에 따른 사용자의 만족도를 높이고 가변 전기요금에 따른 요금을 절감 하는 최적의 조도를 설정하여 조광을 제어하는 방식으로 조명 에너지를 절감하는 기법을 제안한다.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.07a
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• pp.276-276
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• 2004