• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.393-398
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• 2018

This work offers a promising approach for development of a temperature-responsive colorimetric display platform. For this purpose, uniform thermochromic microcapsules consisting of a cholesteric liquid crystal (CLC) core and a thin polyurethane shell layer were fabricated by conducting in-situ condensation polymerization at the interface of monodisperse CLC-in-water emulsion drops. Colloidal packing-driven microcapsule registry led to exact 2-dimensional positioning of CLC microcapsules into a holes-patterned flexible film stencil. Furthermore, we showed that the designated registry of different color types of CLC microcapsules on the stencil enabled development of a microwriting display technology capable of reversible text representation according to temperature change.

• Journal of Positioning, Navigation, and Timing
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• v.4 no.1
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• pp.1-7
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• 2015

In the case of an unmanned aerial vehicle (UAV) equipped with a GNSS sensor, a boundary line where the vehicle can actually exist can be calculated using a navigation error model, and safe navigation (e.g., precise landing and collision prevention) can be supported based on this boundary line. Therefore, for the safe operation of UAV, a model for the position error of UAV needs to be established in advance. In this study, the multipath error of a GNSS sensor installed at UAV was modeled through a flight test, and this was analyzed and compared with the error model of an existing manned aircraft. The flight test was conducted based on a scenario in which UAV performs hovering at an altitude of 40 m, and it was found that the multipath error value was well bound by the error model of an existing manned aircraft. This result indicates that the error model of an existing manned aircraft can be used in operation environments similar to the scenario for the flight test. Also, in this study, a scenario for the operation of multiple UAVs was considered, and the correlation between the multipath errors of the UAVs was analyzed. The result of the analysis showed that the correlation between the multipath errors of the UAVs was not large, indicating that the multipath errors of the UAVs cannot be canceled out.

• Korean Journal of Poultry Science
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• v.23 no.1
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• pp.9-17
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• 1996

This study was conducted to compare the survival rate of chick embryos among different eggshell window positions and to search for the most appropriate injection position. The eggshells were punctured at blunt-end, sharp-end and side-up with a sterilized fine forceps, respectively. The survival rate of sharp-end window was higher than the other window positions. Injection of Dulbecco’s modified eagle’s medium (DMEM) through blunt-end window (BE1) was impossible because inner cell membrane was obscure. The 2 ${\mu}$L DMEM was injected into 2.5 d-old embryo blood vessel through sharp end window. To prevent hemorrhages at the point of injection, the air bubbles were injected into the embryo blood vessel. The survival rate of chicks embryo in sharp end window was about 17.0％. Therefore, this sharp-end window system will be helpful for the production of germline chimera or transgenic chicken using primordial germ cells ( PGCs ).

• Journal of Advanced Navigation Technology
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• v.23 no.5
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• pp.408-414
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• 2019

We developed a surveillance tool for collision avoidance of unmanned aerial vehicles (UAVs) in urban areas. In our tool, users can visualize the safety distance on the actual 3D map of urban area. The estimated positions of UAVs are assumed to be obtained based on the long-term evolution (LTE) signals. The safety distance is defined to include two or more signals with bias. The safety distance calculation method used in this paper enables simulation similar to the actual urban areas where signals are frequently biased due to multipath. In the simulation, the parameters were set based on the measured values, and the change of the safety distance according to the number of faulty signals was simulated. As a result, increasing the number of faulty signals led to a longer safety distance as expected.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.11
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• pp.1528-1533
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• 2020

Recently, indoor location recognition technology using Wi-Fi fingerprints has been applied and operated in various industrial fields and public services. Along with the interest in machine learning technology, location recognition technology based on machine learning using wireless signal data around a terminal is rapidly developing. At this time, in the process of collecting radio signal data required for machine learning, the accuracy of location recognition is lowered due to distorted or unsuitable data for learning. In addition, when location recognition is performed based on data collected at a specific location, a problem occurs in location recognition at surrounding locations that are not included in the learning. In this paper, we propose a learning data preprocessing technique to obtain an improved position recognition result through the preprocessing of the collected learning data.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.91-96
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• 2006

Presently, cycle-slip detection is done between adjacent two points in many cycle-slip methods. Inherently, it is simple wavelet analysis. A new idea is put forward that the number of difference point can adjust by a parameter factor; we study this method to smooth raw data and detect cycle-slip with wavelet analysis. Taking CHAMP satellite data for example, we get some significant conclusions. It is showed that it is valid to detect cycle-slip in GPS phase measurement based on this wavelet function, and it is helpful to improve the precision of GPS data pre-processing and positioning.

• Journal of Advanced Navigation Technology
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• v.18 no.2
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• pp.134-141
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• 2014

Mobile robots use various sensors for navigation such as wheel encoder, vision sensor, sonar, and laser sensors. Dead reckoning is used with wheel encoder, resulting in the accumulation of positioning errors. For that reason wheel encoder can not be used alone. Too much information of vision sensors leads to an increase in the number of features and complexity of perception scheme. Also Sonar sensor is not suitable for positioning because of its poor accuracy. On the other hand, laser sensor provides accurate distance information relatively. In this paper we propose to extract the angular information from the distance information of laser range finder and use the Kalman filter that match the heading and distance of the laser range finder and those of wheel encoder. For laser scanner with one feature point error may increase much when the feature point is variant or jumping to a new feature point. To solve the problem, we propose to use two feature points and show that the positioning error can be reduced much.

• Journal of Advanced Navigation Technology
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• v.11 no.1
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• pp.1-8
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• 2007

Loran-C of ground transmitting station base that can prevent confusion of country navigation system and give BACK-UP function about electric wave navigation comparing utilization incapability state about GPS(Global Positioning System) infra that user is spreading rapidly over our society whole such as sea/aviation safety, vehicles navigation, minuteness agriculture, minuteness measurement in this treatise practical use of Loran-C navigation propose. Executed ASF(Additional Secondary Phase Factor) production and an application experiment Loran-C by location error improvement way to enhance practical use value. By the result Loran-C in conclusion that can improve location error 100~400m remarkably by 10~65m reach. Also, production extent is latitude when go composition medium and bends cotton at ASF revision table utilization of land area, this smell is judged to be suitable hardness 10 minutes. And notable location error improvement and numeric of GPS BACK-UP function are judged to be possible at a ASF revision table application to Korea Peninsula whole area hereafter.

• Journal of Satellite, Information and Communications
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• v.10 no.3
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• pp.38-43
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• 2015

This paper describes a GPS signal generator that can generate multiple satellite signals in real time at the RF level. It realizes the verified software algorithm on a FPGA. The algorithm models orbits and environmental errors such as ionospheric and tropospheric multipath. The position of a simulated receiver is one of simulation parameters. The hardware which consists of a digital logic board and an analog board can generate 16 simulated satellites signals at the same time. The users can generate spoofing signals and jamming signals as well as satellite signals by using the windows-based control software. In addition, the software provides GIS-based simulation scenarios editing tools. We verified the generator by using commercial receivers. As an application, we configured generators as indoor positioning systems and tested them in a building. To improve the accuracy of indoor systems is our further study.

• Journal of Advanced Navigation Technology
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• v.20 no.1
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• pp.29-36
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• 2016

Accuracy of GPS (global positioning system) deteriorates dramatically or positioning is impossible in urban area occasionally since high-rise buildings and elevated roads make the reception of navigation signal very difficult so that number of visible satellites decreases. In these cases, vertical error usually becomes much larger than the horizontal error due to the intrinsic geometry of GPS satellites. To obtain more accurate and reliable height information, this paper proposes a hybrid method that combines GPS and a low-cost barometric altimeter. In the proposed method, the sea-level pressure and the sea-surface temperature are applied to the output of the altimeter. Next, the difference between the ellipsoid and the geoid is compensated. Finally, a simple Kalman filter combines the compensated barometric altitude and the GPS height. By static and car experiments, performance of the proposed method is evaluated. By the experiment results, it can be seen that the proposed method improves the altitude accuracy considerably.