• Korean Journal of Remote Sensing
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• v.23 no.5
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• pp.365-373
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• 2007

Car navigation system is a key application in geographic information system and telematics. A recent trend of car navigation system is using real video captured by camera equipped on the vehicle, because video has more representation power about real world than conventional map. In this paper, we suggest a visual car navigation system that visually represents route guidance. It can improve drivers' understanding about real world by capturing real-time video and displaying navigation information overlaid directly on the video. The system integrates real-time data acquisition, conventional route finding and guidance, computer vision, and augmented reality display. We also designed visual navigation controller, which controls other modules and dynamically determines visual representation methods of navigation information according to current location and driving circumstances. We briefly show implementation of the system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.1
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• pp.68-78
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• 2013

In this paper, we propose an early spectrum sensing(ESS) as an advance preparation for radio-access trial, which enables multi-mode terminals to access the most appropriate radio-access system in a cloud-conceptual base station system where multiple radio access technologies(RATs) coexist. Prior to a random access to one of RATs, a multi-mode terminal conducts a spectrum sensing over entire frequency bands of whole RATs, then select the RAT with the lowest sensing power, that is likely to have the most available spectrum. Thus, an access failure caused by that the selected RAT has no available radio spectrum could be avoidable in advance. In computer simulation, we consider as various RATs as possible. First, circuit and packet systems are taken into consideration. In addition, the packet systems are classified according to the feasibility of carrier aggregation(CA). In case of terminal, three modes are considered with circuit-only, packet-only, and multi-mode. Subsequently, packet traffic is classified into real-time and non-real-time traffic with three different tolerable delay levels. The simulation includes a call process starting with a call generation and ending up with a resource allocation reflecting individual user's QoS requirements and evaluates the proposed scheme in terms of the successful access probability, system access time, system balancing factor and packet loss probability.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.6
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• pp.443-450
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• 2016

In this study, we propose a novel fiber optic sensor to show the measurement feasibility of distributed temperature and strains in a single sensing fiber line. Distributed temperature can be measured using optical time domain reflectometry (OTDR) with a Raman anti-Stokes light in the sensing fiber line. Moreover, the strain can be measured by fiber Bragg gratings (FBGs) in the same sensing fiber line. The anti-Stokes Raman back-scattering lights from both ends of the sensing fiber, which consists of a 4 km single mode optical fiber, are acquired and inserted into a newly formulated equation to calculate the temperature. Furthermore, the center wavelengths from the FBGs in the sensing fiber are detected by an optical spectrum analyzer; these are converted to strain values. The initial wavelengths of the FBGs are selected to avoid a cross-talk with the wavelength of the Raman pulsed pump light. Wavelength shifts from a tension test were found to be 0.1 nm, 0.17 nm, 0.29 nm, and 0.00 nm, with corresponding strain values of $85.76{\mu}{\epsilon}$, $145.55{\mu}{\epsilon}$, $247.86{\mu}{\epsilon}$, and $0.00{\mu}{\epsilon}$, respectively. In addition, a 50 m portion of the sensing fiber from $30^{\circ}C$ to $70^{\circ}C$ at $10^{\circ}C$ intervals was used to measure the distributed temperature. In all tests, the temperature measurement accuracy of the proposed sensor was less than $0.50^{\circ}C$.

• Smart Structures and Systems
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• v.16 no.2
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• pp.281-294
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• 2015

Bolted joint connection is the most commonly used connection element in structures and devices. The loosening due to external dynamic loads cannot be observed and measured easily and may cause catastrophic loss especially in an extreme requirement and/or environment. In this paper, an innovative Real-time Cross-Correlation Method (RCCM) for monitoring of the bolted joint loosening was proposed. We apply time reversal process on stress wave propagation to obtain correlation signal. The correlation signal's peak amplitude represents the cross-correlation between the loosening state and the baseline working state; therefore, it can detect the state of loosening. Since the bolt states are uncorrelated with noise, the peak amplitude will not be affected by noise and disturbance while it increases SNR level and increases the measured signals' reliability. The correlation process is carried out online through physical wave propagation without any other post offline complicated analyses and calculations. We implemented the proposed RCCM on a single bolt/nut joint experimental device to quantitatively detect the loosening states successfully. After that we implemented the proposed method on a real large structure (reaction wall) with multiple bolted joint connections. Loosening indexes were built for both experiments to indicate the loosening states. Finally, we demonstrated the proposed method's great anti-noise and/or disturbance ability. In the instrumentation, we simply mounted Lead Zirconium Titanate (PZT) patches on the device/structure surface without any modifications of the bolted connection. The low-cost PZTs used as actuators and sensors for active sensing are easily extended to a sensing network for large scale bolted joint network monitoring.

• Journal of Sensor Science and Technology
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• v.25 no.5
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• pp.344-348
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• 2016

We developed a 2-channel fiber-optic temperature sensor (FOTS) using a temperature sensing probe, a fiber-optic coupler, transmitting optical fiber, and an optical time domain reflectometer (OTDR). The temperature sensing probe is divided into a sensing probe and a reference probe for accurate thermometry. A sensing probe is composed of a silicon oil, a FC terminator, a brass pipe, and a singlemode optical fiber and the structure of a reference probe is identical with that of the sensing probe excluding a silicon oil. In this study, we measured the modified optical powers of the light signals reflected from the temperature sensing probe placed inside of the water with a thermal variation from 5 to $70^{\circ}C$. Although the optical power of the reference probe was constant regardless of the temperature change, the optical power of the sensing probe decreased linearly as the temperature increased. As experimental results, the FOTS using a subtraction method showed a small difference (i.e., hysteresis) in its response due to heating and cooling. The reversibility and reproducibility of the FOTS were also evaluated.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.5
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• pp.32-39
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• 2009

Compressed Sensing is a method to sample analog signals at a rate under the Nyquist rate. With this scheme, it is possible to represent signals with a relatively smaller number of measurements than that of the conventional sampling method, and the original signals are reconstructed with high probability from the acquired measurements using the linear programming. Compressed sensing allows measurement time and/or the amount of ADC (analog-to-digital converter) resources for the signal acquisitions to be reduced. In this paper, we presents the backgrounds of the compressed sensing, a way to acquire measurements from an analog signal with a random basis, and the signal recovery method. Also we introduce applications of compressed sensing in wireless communications.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.739-744
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• 2002

Recently we have discovered that sediments should be separated from lithosphere, and soil should be separated from biosphere, both sediment and soil will be mixed sediments-soil-sphere (Seso-sphere), which is using particulate mechanics to be solved. Erosion and sediment both are moving by particulate matter with water or wind. But ancient sediments will be erosion same to soil. Nowadays, real soil has already reduced much more. Many places have only remained sediments that have ploughed artificial farming layer. Thus it means sediments-soil-sphere. This paper discusses sediments-soil-sphere erosion modeling. In fact sediments-soil-sphere erosion is including water erosion, wind erosion, melt-water erosion, gravitational water erosion, and mixed erosion. We have established geographical remote sensing information modeling (RSIM) for different erosion that was using remote sensing digital images with geographical ground truth water stations and meteorological observatories data by remote sensing digital images processing and geographical information system (GIS). All of those RSIM will be a geographical multidimensional gray non-linear equation using mathematics equation (non-dimension analysis) and mathematics statistics. The mixed erosion equation is more complex that is a geographical polynomial gray non-linear equation that must use time-space fuzzy condition equations to be solved. RSIM is digital image modeling that has separated physical factors and geographical parameters. There are a lot of geographical analogous criterions that are non-dimensional factor groups. The geographical RSIM could be automatic to change them analogous criterions to be fixed difference scale maps. For example, if smaller scale maps (1:1000 000) that then will be one or two analogous criterions and if larger scale map (1:10 000) that then will be four or five analogous criterions. And the geographical parameters that are including coefficient and indexes will change too with images. The geographical RSIM has higher precision more than mathematics modeling even mathematical equation or mathematical statistics modeling.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2008.11a
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• pp.115-116
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• 2008

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.2
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• pp.93-101
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• 2016

This paper presents the results obtained using time-series-based methods for structural damage assessment. The methods are applied to a wind turbine blade structure subjected to fatigue loads. A 9 m CX-100 (carbon experimental 100 kW) blade is harmonically excited at its first natural frequency to introduce a failure mode. Consequently, a through-thickness fatigue crack is visually identified at 8.5 million cycles. The time domain data from the piezoelectric active-sensing techniques are measured during the fatigue loadings and used to detect incipient damage. The damage-sensitive features, such as the first four moments and a normality indicator, are extracted from the time domain data. Time series autoregressive models with exogenous inputs are also implemented. These features could efficiently detect a fatigue crack and are less sensitive to operational variations than the other methods.

• Korean Journal of Microbiology
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• v.50 no.2
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• pp.108-113
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• 2014

Pseudomonas aeruginosa and Vibrio vulnificus are Gram-negative human pathogens, which exert their virulence through quorum sensing (QS) regulation. The infection of these pathogens have been known to be mediated by biofilm formation in many cases and this study carried out the time-course analysis of biofilm formation depending on the QS regulation in P. aeruginosa and V. vulnificus. In P. aeruginosa, our results demonstrated that QS-deficient mutant better attached to surface at initial stage of biofilm formation, but poorly proceeded to the maturation of the biofilm structure, while wild type less attached at initial stage but developed highly structured biofilm at late stage. Because of this, the quantitative comparison of biofilm formation between wild type and the QS mutant showed the reversion; the QS mutant formed more biofilm until 10 h after inoculation than wild type, but wild type formed much more biofilm after 10 h than QS mutant. V. vulnificus has been reported to form more biofilm with the mutation on QS system. When we performed the same time-course analysis of the V. vulnificus biofilm formation, the reversion was not detected even with prolonged culture for 108 h and the QS mutant always forms more biofilm than wild type. These results indicate that the QS regulation negatively affects the attachment at early stage but positively facilitates the biofilm maturation at late stage in P. aeruginosa, while the QS regulation has a negative effect on the biofilm formation throughout the biofilm development in V. vulnificus. Based on our results, we suggest that the developmental stage of biofilm and bacterial species should be considered when the QS system is targeted for biofilm control.