• The Journal of the Acoustical Society of Korea
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• v.38 no.3
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• pp.302-307
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• 2019

In modern Anti-Submarine Warfare, there are various ways to locate a submarine in a two-dimensional space. For more effective tracking and attack against a submarine the depth of the target is a critical factor. However, it has been difficult to find out the depth of a submarine until now. In this paper a possible solution to the depth estimation of submarines is proposed utilizing DIFAR (Directional Frequency Analysis and Recording) sonobuoy information such as contact bearings at or prior to CPA (Closest Point of Approach) and the target's Doppler signals. The relative depth of the target is determined by applying the Pythagorean theorem to the slant range and horizontal range between the target and the hydrophone of a DIFAR sonobuoy. The slant range is calculated using the Doppler shift and the target's velocity. the horizontal range can be obtained by applying a simple trigonometric function for two consecutive contact bearings and the travel distance of the target. The simulation results show that the algorithm is subject to an elevation angle, which is determined by the relative depth and horizontal distance between the sonobuoy and target, and that a precise measurement of the Doppler shift is crucial.

• Journal of the Korea Computer Graphics Society
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• v.29 no.3
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• pp.149-158
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• 2023

HMD, which is applied with the latest technology, minimizes motion sickness with high-resolution displays and fast motion recognition, and can accurately track location and motion. This can provide an environment where you can immerse yourself in a virtual three-dimensional space, and virtual reality contents such as disaster simulators and high-risk equipment learning spaces are developing using these characteristics. These advantages are also applicable in the field of basic science education. In particular, expanding the concepts of electric and magnetic fields in physics described by existing two-dimensional data into three-dimensional spaces and visualizing them in real time can greatly help improve learning understanding. In this paper, realistic physical education environments and contents based on three-dimensional virtual reality are developed and the developed learning contents are experienced by actual learning subjects to prove their effectiveness. A total of 46 middle school and college students were taught and experienced in real time the electric and magnetic fields expressed in three dimensions in a virtual reality environment. As a result of the survey, more than 85% of positive responses were obtained, and positive results were obtained that three-dimensional virtual space-based physical learning could be effectively applied.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.4
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• pp.335-344
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• 2014

To understand the drift-diffusion of HAB(Harmful Algal Bloom) in this paper, we used three-dimensional hydrodynamic model POM(Pringceton Ocean Model) and Lagrangian particle track module. First, the results of residual flow that considered tide, wind, temperature, salinity, and TWC(Tsushima Warm Current) effect was tend to northeast in the coastal area and the flow in the offshore region showed results similar to TWC. To understand of HAB's movement, released each area that southern Kamak bay(Case 1), Mijo coast(Case 2), and southern Mireukdo coast(Case 3) assumption that red tide occurred. The areas where the HAB occurs frequently. As a result of HAB occurred in southern Kamak Bay(Case 1), mainly drifts to Narodo coast and Yeoja bay that located on the west side. Case 2 was mainly drifts to Yokjido coast and Saryangdo coast Especially, HAB occurred in Mireukdo coast(Case 3) relatively many particles drift to eastward as the influence of the TWC.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.1
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• pp.18-23
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• 2001

In this paper, the several indexes represented by swimming characteristics of aquarcultured red seabream, Dchrysophrys majors in a farming water raft(10L×10W×5H) were measured by ultrasonic telemetry. The fishes tagged by pingers were tracked by the LBL method(Shin etc., 1994). The location of fishes were calculated by the hyperbolic method and the indexes were estimated by the least square method. The similarity was confirmed by the comparision between experiment and simulation on the swimming trajectory of fishes, the mean distance of individual from wall, the mean swimming speed and the mean distance between the nearest individuals. The obtained results are summerized as follows ; 1. The swimming trajectory of fishes tagged by the pingers and the swimming trajectory by the simulation for 120 minutes showed a simularity. 2. The mean swimming speed by the experiment and the simulation showed 39.2 ㎝/sec (1.4BL ㎝/sec) and 44.4 ㎝/sec (1.6BL ㎝/sec), respectively. 3. The mean swimming depth by the experiment and the simulation showed 238㎝ and 248 ㎝, respectively. 4. The mean distance of individuals from wall of the farming water raft by the experiment and the simulation showed 132 cm and 129 cm, respectively. 5. The mean distance between the nearest individuals by the experiment and the simulation showed 83 ㎝ and 61 ㎝, respectively.

• Journal of Bio-Environment Control
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• v.28 no.4
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• pp.279-285
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• 2019

To estimate daily canopy photosynthesis, accurate estimation of canopy light interception according to a daily solar position is needed. However, this process needs a lot of cost, time, manpower, and difficulty when measuring manually. Various modeling approaches have been applied so far, but it was difficult to accurately estimate light interception by conventional methods. The objective of this study is to estimate the spatial distributions of light interception and photosynthetic rate of paprika with time by using 3D-scanned plant models and optical simulation. Structural models of greenhouse paprika were constructed with a portable 3D scanner. To investigate the change in canopy light interception by surrounding plants, the 3D paprika models were arranged at $1{\times}1$ and $9{\times}9$ isotropic forms with a distance of 60 cm between plants. The light interception was obtained by optical simulation, and the photosynthetic rate was calculated by a rectangular hyperbola model. The spatial distributions of canopy light interception of the 3D paprika model showed different patterns with solar altitude at 9:00, 12:00, and 15:00. The total canopy light interception decreased with an increase of surrounding plants like an arrangement of $9{\times}9$, and the decreasing rate was lowest at 12:00. The canopy photosynthetic rate showed a similar tendency with the canopy light interception, but its decreasing rate was lower than that of the light interception due to the saturation of photosynthetic rate of upper leaves of the plants. In this study, by using the 3D-scanned plant model and optical simulation, it was possible to analyze the light interception and photosynthesis of plant canopy under various conditions, and it can be an effective way to estimate accurate light interception and photosynthesis of plants.

• Conservation Science in Museum
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• v.21
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• pp.41-52
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• 2019

The findings of a 2017 safety inspection of the Three-story Pagoda from the Goseonsa Temple site in Gyeongju suggested the possibility that the stone for the second story of the pagoda may have been rotated after the pagoda was disassembled for removal from its original site in 1975. The materials from the pagoda were investigated using photographs and other relevant data from both the Japanese colonial period and from around 1975. The analysis found that the materials of the pagoda were not changed after analleged reconstruction in 1943, but that during the process of relocating the pagoda in 1975 the body of the second story was indeed rotated counter clockwise by 90 degrees and one of the four stone elements making up the first-story roof was exchanged with a part from the second-story roof. In order to discover whether the materials had been incorrectly placed, each part of the pagoda was precisely measured and the elements of the roofs were virtually reconstructed using 3D scanning data. The investigation did not find any singularities with in the components of each roof; the four part sof the first-story roof were 75 to 76 centimeters thick and those for the second-story roof were 78 to 79 centimeters thick. The connections between each part of the roofs also appeared natural. This seems to indicate that there was indeed an undocumented repair of the pagoda at some point between its creation and 1943 and an error that took place during this repair was corrected in 1975. In addition, the study suggested a possibility that the body of the second story was rotated counter clockwised to a change in the locations of parts of the two roofs.

• Progress in Medical Physics
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• v.20 no.2
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• pp.51-61
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• 2009

A Compton camera, which is based on the geometrical interpretation of Compton scattering, is a very promising gamma-ray imaging device considering its several advantages over the conventional gamma-ray imaging devices: high imaging sensitivity, 3-D imaging capability from a fixed position, multi-tracing functionality, and almost no limitation in photon energy. In the present study, a Monte Carlo-based, user-friendly Compton imaging simulator was developed in the form of a graphical user interface (GUI) based on Geant4 and $MATLAB^{TM}$. The simulator was tested against the experimental result of the double-scattering Compton camera, which is under development at Hanyang University in Korea. The imaging resolution of the simulated Compton image well agreed with that of the measured image. The imaging sensitivity of the measured data was 2~3 times higher than that of the simulated data, which is due to the fact that the measured data contains the random coincidence events. The performance of a stacking-structure type Compton camera was evaluated by using the simulator. The result shows that the Compton camera shows its highest performance when it uses 4 layers of scatterer detectors.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.12
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• pp.1087-1092
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• 2010

A micro 3D-PTV system has been constructed using a single camera system. Two viewing holes were created behind the object lens of the microscopic system to construct a stereoscopic viewing image. A hybrid recursive PTV algorithm was used. A concept of epipolar line was adopted to eliminate many spurious candidates. Three-dimensional velocity vector fields were obtained by calculating the three-dimensional displacements of particles that were identified as being identical. The system consists of a laser light source (Ar-ion, 500 mW), one high-definition camera ($1028{\times}1024$ pixels, 500 fps), a circular plate with two viewing holes, and a host computer. The performance of the developed algorithm was tested using artificial images. The characteristic of the vector recovery ratio was investigated for the particle numbers. A micro backward-facing step channel ($H{\times}h{\times}W:\;36{\mu}m{\times}70{\mu}m{\times}3000{\mu}m$) was measured using the developed measurement system. The results were in good qualitative agreement with other results.

• Journal of the Korean Geographical Society
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• v.47 no.3
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• pp.426-439
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• 2012

The goal of this study is to propose a new method to capture the qualitative person spatial behavior. Beyond tracking or indexing the change of the location of a person, the changes in the relationships between a person and its environment are considered as the main source for the formal model of this study. Specifically, this paper focuses on the movement behavior of a person near the boundary of a region. To capture the behavior of person near the boundary of regions, a new formal approach for integrating an object's scope of influence is described. Such an object, a spatio-temporally extended point (STEP), is considered here by addressing its scope of influence as potential events or interactions area in conjunction with its location. The formalism presented is based on a topological data model and introduces a 12-intersection model to represent the topological relations between a region and the STEP in 2-dimensional space. From the perspective of STEP concept, a prototype analysis results are provided by using GPS tracking data in real world.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.43 no.6 s.312
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• pp.46-56
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• 2006

In this paper, we propose an improved reproduction algorithm for a realistic image of the real scene based on the optical characteristics of the light sources and the materials at the lighting environment. This paper is continuation of the previous study to improve the modeling method of the light sources and the materials and apply this to the real rear lamp of automobile. The backward ray tracing method is first used to trace the light ray from a light source, and also considers the physical characteristics of object surfaces and geometric properties of light radiation to estimate accurately the light energy incoming toward to human eyes. For experiments and verification of the proposed method, the simulation results are compared with the measured light stimuli. Accordingly, the simulation results show that the proposed algorithm can estimate light energy well and reproduce the visually similar image with a scene incident on a sight of viewer.