• Journal of information and communication convergence engineering
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• v.13 no.4
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• pp.270-274
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• 2015

In this paper, we propose an improved framework to analyze an N-ocular imaging system under fixed constrained resources such as the number of image sensors, the pixel size of image sensors, the distance between adjacent image sensors, the focal length of image sensors, and field of view of image sensors. This proposed framework takes into consideration, for the first time, the defocusing effect of the imaging lenses according to the object distance. Based on the proposed framework, the N-ocular imaging system such as integral imaging is analyzed in terms of depth resolution using two-point-source resolution analysis. By taking into consideration the defocusing effect of the imaging lenses using ray projection model, it is shown that an improved depth resolution can be obtained near the central depth plane as the number of cameras increases. To validate the proposed framework, Monte Carlo simulations are carried out and the results are analyzed.

• Structural Monitoring and Maintenance
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• v.1 no.3
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• pp.293-308
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• 2014

In the aeronautical environment, numerous regulatory and communication protocols exist that cover interconnection of on-board equipment inside the aircraft. Developed and implemented by the airlines since the 1960s, these communication systems are reliable, strong, certified and able to contact different sensors distributed throughout the aircraft. However, the scenario is slightly different in the structural health monitoring (SHM) field as the requirements and specifications that a global SHM communication system must fulfill are distinct. The number of SHM sensors installed in the aircraft rises into the thousands, and it is impossible to maintain all of the SHM sensors in operation simultaneously because the overall power consumption would be of thousands of Watts. This design of a new communication system must consider aspects as management of the electrical power supply, topology of the network for thousands of nodes, sampling frequency for SHM analysis, data rates, selected real-time considerations, and total cable weight. The goal of the research presented in this paper is to describe and present a possible integration scheme for the large number of SHM sensors installed on-board an aircraft with low power consumption. This paper presents a new communications system for SHM sensors known as the Bi-Instruction Link Bi-Operator (BILBO).

• Journal of Sensor Science and Technology
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• v.29 no.2
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• pp.105-111
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• 2020

Interest and demand for hydrogen sensors are increasing in the field of H₂ leakage detection during storage/transport/use and detection of H₂ dissolved in transformer oil for safety issues as well as in the field of breath analysis for non-invasively diagnosing a number of disease states for a healthy life. In this study, various ZnO-based sensors were synthesized by controlling the reduction in crystallite size, decoration of Pt nanoparticles, doping of electron donating atoms, and doping of various atoms with different ionic radii. The sensing response of the various prepared ZnO-based nanoparticles and quantum dots (QDs) for 10 ppm H₂ was investigated. Among the samples, the smallest-sized (3.5 nm) In³⁺-doped ZnO QDs showed the best sensing response, which is superior to those in previously reported hydrogen sensors based on semiconducting metal oxides. The higher sensing response of In-doped ZnO QDs is attributed to the synergic effects of the increased number of oxygen vacancies, higher optical band gap, and larger specific surface area.

• The Journal of the Acoustical Society of Korea
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• v.29 no.8
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• pp.483-490
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• 2010

In this paper, an Inter-Digital Transducer (IDT) type Lamb wave sensor is proposed to estimate the geometry and number of cracks on a plate structure, and its validity is checked through experiments. This IDT type sensor is more readily controllable than conventional patch type piezoelectric sensors to modify its operation frequency and directionality by altering its finger patterns. In this work, omni-directional annular IDT and highly directional rectangular IDT sensors are designed and fabricated. The IDT sensors are used to diagnose the length, number and orientation of cracks on an aluminum plate by measuring the amplitude and time of flight of Lamb waves. The results are analyzed to discuss the efficacy of the IDT sensors.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.5
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• pp.303-310
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• 2020

In this study, a method for selection of the location and number of monitoring sensors in a building structure using artificial neural networks is proposed. The acceleration-history values obtained from the installed accelerometers are defined as the input values, and the mass and stiffness values of each story in a building structure are defined as the output values. To select the installation location and number of accelerometers, several installation scenarios are assumed, artificial neural networks are obtained, and the prediction performance is compared. The installation location and number of sensors are selected based on the prediction accuracy obtained in this study. The proposed method is verified by applying it to 6- and 10-story structure examples.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.2
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• pp.307-315
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• 2017

Random number generator(RNG) is essential in cryptographic applications. As recently a system using small devices such as IoT, Sensor Network, SmartHome appears, the lightweight cryptography suitable for this system is being developed. However due to resource limitations and difficulties in collecting the entropy, RNG designed for the desktop computer are hardly applicable to lightweight environment. In this paper, we propose a lightweight RNG to produce cryptographically strong random number using sensors. Our design uses a Hankel matrix, block cipher as the structure and sensors values as noise source. Futhermore, we implement the lightweight RNG in Arduino that is one of the most popular lightweight devices and estimate the entropy values of sensors and random number to demonstrate the effectiveness and the security of our design.

• Proceedings of the Acoustical Society of Korea Conference
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• 1993.06a
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• pp.206-209
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• 1993

The main purpose of this paper is to verify the effectiveness of a high resolution direction finding method, so called the‘averaged MUSIC’. This method uses a new sample array covariance matrix that consists of diagonal components obtained by taking averages of the diagonal component values of the sample covariance matrix for the MUSIC. The paper shows that the proposed method performs higher resolved direction-of-arrival estimation and better resolution probability than the MUSIC in such cases as low signal-to-noise ratio, when the number of sensors used is finite, based on the statistical analysis.

• ETRI Journal
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• v.38 no.3
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• pp.551-559
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• 2016

In this paper, we propose a hybrid sensor calibration scheme for mobile crowdsensing applications. As the number of newly produced mobile devices containing embedded sensors continues to rise, the potential to use mobile devices as a sensor data source increases. However, because mobile device sensors are generally of a lower performance and cost than dedicated sensors, sensor calibration is crucial. To enable more accurate measurements of natural phenomena through the use of mobile device sensors, we propose a hybrid sensor calibration scheme for such sensors; the scheme makes use of mobile device sensors and existing sensing infrastructure, such as weather stations, to obtain dense data. Simulation results show that the proposed scheme supports low mean square errors. As a practical application of our proposed scheme, we built a temperature map of a city using six mobile phone sensors and six reference sensors. Thanks to the mobility of the sensors and the proposed scheme, our map presents more detailed information than infrastructure-based measurements.

• Electronics and Telecommunications Trends
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• v.33 no.6
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• pp.41-49
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• 2018

Mid-infrared optical sensors have a number of compelling advantages for remote sensing and the simultaneous measurement of mixtures. However, they still have difficulties in accurate detection owing to signal interferences among a large number of molecular fingerprints in the mid-infrared band, which result in very slow commercialization. Higher sensitivity and higher selectivity are required to overcome this obstruction in measurement technology. In this paper, we review and analyze the trends of mid-infrared sensor technologies enhancing the sensitivity and selectivity.

• Transactions of the Korean Society of Automotive Engineers
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• v.25 no.3
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• pp.309-316
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• 2017

In shuttle vans designed to transport children, the recognition of a child's approach and departure is very important. Ultrasonic sensors are generally used for a short distance around a vehicle. Although ultrasonic sensors are cheaper than other ADAS sensors, the number of sensors installed in a van should be optimized. In order to recognize the presence of a child around a shuttle van, this paper proposes the placement of ultrasonic sensors in the van. Considering the turning radius of the van and the distance from each sensor to a child, collision risk is classified as 'safe', 'warning', and 'danger'. The sensor placement and the recognition algorithm are verified in a virtual driving environment.