• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.1
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• pp.223-228
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• 2017

In this paper, we are proposing an optimal design of wideband pulsed type gamma-ray sensors. These sensors were manufactured based on the design results and after word electrical properties were analyzed. The sensor input parameters were derived on the basis of pulsed gamma-ray spectrum and time-dependent energy rate, and the output current which were derived on the basis of the sensor sensitivity control circuit. Pulsed gamma-ray sensors were designed using the TCAD simulators. The design results show that the optimal Epi layer thickness is 45um with the applied voltage 3.3V and the diameter is 2.0mm. The doping concentrations are as follows : N-type is an Arsenic as $1{\times}10^{19}/cm^3$, P-type is a Boron as $1{\times}10^{19}/cm^3$ and Epi layer is Phosphorus as $3.4{\times}10^{12}/cm^3$. The fabricated sensor was a leakage current, 12pA at voltage -3.3V and fully depleted mode at voltage -5V. A test result of pulsed radiation shows that the sensor gives out the optimal photocurrent.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.257-258
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• 2008

Hall-type current sensors have been widely used in many fields such as elevator and train system. To estimate lifetime of hall-type current sensors, an accelerated life test with real-time monitoring system simultaneously was designed and performed in high temperature environment with three different temperatures. From the experimental results, activation energy was about 0.9 eV, and acceleration factor was about 450 based on Arrhenius model. As a results, $B_{10}$ lifetime of hall-type current sensor is estimated to be 65,460 hours.

• Proceedings of the KIEE Conference
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• 2002.11a
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• pp.215-218
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• 2002

In this paper some of optical current transformers and optical potential transformers for extra high voltage system are introduced. The optical current transformer and optical potential transformer will be adopted in the near future, because of increasing demands of high accuracy and good reliability of current transformer and potential transformer. The application cases of optical current transformers and optical potential transformers are also introduced.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.251-256
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• 2006

In the work package 'Integrated Positioning' of the research project NAVIO (Pedestrian Navigation Systems in Combined Indoor/Outdoor Environements) we are dealing with the navigation and guidance of visitors of our University. Thereby start points are public transport stops in the surroundings of the Vienna University of Technology and the user of the system should be guided to certain office rooms or persons. For the position determination of the user different location sensors are employed, i.e., for outdoor positioning GPS and dead reckoning sensors such as a digital compass and gyro for heading determination and accelerometers for the determination of the travelled distance as well as a barometric pressure sensor for altitude determination and for indoor areas location determination using WiFi fingerprinting. All sensors and positioning methods are combined and integrated using a Kalman filter approach. Then an optimal estimate of the current location of the user is obtained using the filter. To perform an adequate weighting of the sensors in the stochastic filter model, the sensor characteristics and their performance was investigated in several tests. The tests were performed in different environments either with free satellite visibility or in urban canyons as well as inside of buildings. The tests have shown that it is possible to determine the user's location continuously with the required precision and that the selected sensors provide a good performance and high reliability. Selected tests results and our approach will be presented in the paper.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.3
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• pp.292-298
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• 2003

Most of the three phase inverters for adjustable speed drive of AC machines are equipped with two or three current sensors for measurement of three phase current. One method to reduce the number of current sensors is that single current sensor measures the DC link current, then three phase current is reconstructed using the measured value and the switching status. To improve the measurement accuracy, switching state should be maintained for more than minimum switching time. Many papers have been published, which focused on the readjustment of pulse width and compensation of voltage distortion. Those methods are suitable for space vector modulation. But there are some difficulties in applying these methods to carrier-based PWM which is widely used in industry. In this paper, new current measurement method and voltage compensation method are proposed which are suitable for carrier-based PWM, then, the validity of proposed method is confirmed through experiment.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.10
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• pp.4804-4822
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• 2017

Coverage problem is a research hot spot in directional sensor networks (DSNs). However, the major problem affecting the performance of the current coverage-enhancing strategies is that they just optimize the coverage of networks, but ignore the maximum number of sleep sensors to save more energy. Aiming to find an approximate optimal method that can cover maximum area with minimum number of active sensors, in this paper, a new scheduling algorithm based on learning automata is proposed to enhance area coverage, and shut off redundant sensors as many as possible. To evaluate the performance of the proposed algorithm, several experiments are conducted. Simulation results indicate that the proposed algorithm have effective performance in terms of coverage enhancement and sleeping sensors compared to the existing algorithms.

• Journal of KSNVE
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• v.7 no.3
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• pp.377-386
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• 1997

A cantilever type piezoceramic vibration sensor was developed that could make up for the short-comings of current vibration sensors, such as high price, low sensitivity, and complex structure. For the design, in conjunction with piezoelectric constitutive equations, we derived full analytic response equations of the piezoelectric bimorph sensor to external forces. The external forces were supposed to take the form of either step or sinusoidal force. Based on the results, actual piezoelectric vibration sensors were fabricated and tested for verification of the theoretical results. Further, comparison of the performance of the developed sensor was made with that of a commercially available representative vibration sensor so that quantitative evaluation of its sensitivity could be made. The sensor developed in this work showed excellent sensitivity and thermal stability in addition to the merits of simple structure and low fabrication cost in comparison with conventional mass-loaded piezoelectric sensors.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.6
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• pp.132-145
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• 2008

We propose a new technique for autonomous navigation and travelling of mobile robot based on ultrasonic sensors through the narrow labyrinth that leave only distance of a few centimeters on each side between the guides and the robot. In our current implementation the ultrasonic sensor system fires at a rate of 100 ms, that is, each of the 8 sensors fires once during each 100 ms interval. This is a very good firing rate, implemented here for optimal performance. This paper presents an extensively tested and verified solution to the problem of obstacle avoidance. Our solution is based on the optimal placement of ultrasonic sensors at strategic locations around the robot. Both the sensor location and the associated navigation algorithm are defined in such a way that only the accurate radial sonar data is used for accurate travelling.

• Smart Structures and Systems
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• v.13 no.6
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• pp.891-899
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• 2014

Over the past several decades, substantial amounts of sensors and sensing systems have been developed for civil infrastructure systems. This special issue focuses on state-of-the-art robotics and automation technologies, including construction automation, robotics, instrumentation, monitoring, inspection, control, and rehabilitation for civil infrastructure. The issue also covers construction informatics supporting sensing, analysis and design activities needed to operate smart and sustainable civil infrastructure. Examples include robotic systems applied to civil infrastructure and equipped with various sensing technologies, such as optical sensors, laser sensors, wireless sensors, multi-sensor fusion, etc. This special issue is published in an effort to disseminate current advances of various robotics and automation technologies for civil infrastructure and built environment.

• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.193-194
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• 2006