• Journal of Korean Society of Forest Science
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• v.110 no.1
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• pp.72-81
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• 2021

We developed smartphone application and web application server to acquire and effectively manage tree measurement information. Smartphone applications can measure tree height, diameter at breast height (DBH), azimuth, altitude, slope, and positional coordinates using augmented reality (Google AR core) and motion sensors. The web application server effectively manages and stores measurement information. To evaluate the accuracy of information acquired using a smartphone, 90 Korean pine trees (Pinus koraiensis) were randomly selected from a natural mixed forest, with a total of 90 representative trees randomly collected from a natural mixed forest. Then, height and DBH were measured using a Haglof Vertex Laser Hypsometer and caliper. Comparisons of the results indicated significant results at the 95% level and a very high average correlation of 0.972 for both tree height and DBH. In terms of DBH, the average errors were 0.6745 cm and 1.0139 cm for artificial coniferous and natural mixed forests, respectively.

• The Journal of the Acoustical Society of Korea
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• v.43 no.3
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• pp.324-334
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• 2024

The Wavefront Curvature Ranging (WCR) is an estimation method for a source range from the wavefront curvature of acoustic waves. The conventional method uses trigonometry to estimate the source range by assuming the sound speed as a constant. Because of this assumption, range error occurs in the ocean environment where the bottom reflection is clearly separated. In order to reduce the range error, Matched Wavefront Curvature Ranging (MWCR) was proposed applying the sound speed structure in the ocean environment and Maximum Likelihood Estimation (MLE). The range error was reduced in the results of the simulation on the proposed method. In the future, this method will be applicable to the sonar system if the reliability of ranging is confirmed by measured signal.

• Journal of Korean Society of Steel Construction
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• v.24 no.3
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• pp.267-278
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• 2012

In general, the H-shaped steel ribs or triangular lattice girders have been mostly used in constructing tunnels through the NATM construction method. The H-shaped steel rib has higher flexural and axial strength than the triangular lattice girder, but many unexpected gaps can occur in the concrete lining system after shotcreting if the H-shaped steel rib is used as the support system. To achieve better shotcreting quality, the triangular lattice girder was developed. However, in general, the triangle lattice girder has low flexural and axial strength. Likewise, the triangular lattice girder, which has circular sectional members, has so many fractures from welded points at the joints between the members. Finally, the new type of tetragonal lattice girder was developed to overcome those problems. In this study, the structural performance of the tetragonal lattice girders was evaluated through analytical and experimental studies. In the analytical studies, the four-point bending analysis, the traditional evaluation method to determine the flexural strength of the lattice girder, was performed. Moreover, the linear-elastic analysis and stability analysis of the arch structure made by the lattice girders were performed to measure structural performance. Experiments were likewise performed to compare the structural performances of the tetragonal girder with traditional triangular lattice girders.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.4
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• pp.408-416
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• 2010

A study on the calibration of an X-band HPS(Hongik Polarimetric Scatterometer) system for ground-based operation is presented in this paper. In order to calibrate the scatterometer system, the degree of its distortions are analyzed by comparison between theoretical- and measured-values using the theoretically well-known calibration targets such as a metal sphere, a trihedral corner reflector(CR) and a metal cylinder. The calibration works in the field conditions depend on the precise and stable measurements of those calibration target. we present a measurement technique, so-called, an automatic 2-D target-scanning technique, using the incidence-angle(${\xi}-$ and ${\phi}-$ directions) control of HPS system. Then, we used STCT(Single-Target Calibration Technique) and GCT(General Calibration Technique) to calibrate a distortion of the scatterometer system, and measured the polarimetric RCS(Radar Cross Section) and phase-difference of a trihedral-CR as a test-target to verify the accuracy of the calibration technique. Then, three different types(i.e., 10, 20, 30 cm) of trihedral-CR were used. we obtained the error ranges about ${\pm}1.0$dB, ${\pm}0.5$ dB in a polarimetric RCS and about $-20^{\circ}{\sim}0^{\circ}$ and ${\pm}5^{\circ}$ in the co-polarized phase-difference by using the GCT and STCT, respectively.

• Korean Journal of Ecology and Environment
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• v.55 no.4
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• pp.285-293
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• 2022

Sampling gears for collecting fish are diverse, and the community of fish varies according to the selection and characteristics of the sampling gears. The present study compared the characteristics of fish communities in Yedang reservoir using four sampling gears (kick net, cast net, gill net, and fyke net). The kick net and cast net were inefficient in collecting the number of individuals. However, they increased the species diversity of fish inhabiting the waterfront. Although not many individuals were collected, the gill net mainly collected large fish. The largest number of individuals was collected in the fyke net, and the dominance was high due to the high species selectivity. Through Self-Organizing Map (SOM) analysis, large fish were collected in the gill net, whereas small fish were collected in the fyke net. The characteristics and efficiency of the fish differed depending on the sampling gears. It is expected that researchers will need to use it appropriately according to the characteristics of the sampling gears when investigating the fish community.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.4
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• pp.27-35
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• 1991

This paper presents a numerical analysis procedure and a characteristics for vibration and buckling of the cylinderical panels. The panels with simply-simply or simply-clamped edge supports are subjectes to circumferential compressive or flexural stresses. The differential equations governing vibration and buckling for these panels are derived by using the fundamental differential equation of the Love-Timoshenko and are solved numerically via the Galerkin method. The panel with simply-clamped edge supports is used a trigonometric function or a eigen function of a beam as a trial function and the effects of trial functions on numerical solutions are displayed. Numerical results are presented to demonstrate the effects of the flexural parameters in natural frequencies and coefficients of critical buckling and some typical mode shapes of vibration and buckling are also presented.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.2
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• pp.63-70
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• 2009

This paper proposes a novel path finding approach of a mobile robot using RF strength in sensor network. In the experiments based on the proposed method, a mobile robot attempts to find its location, heading direction and the shortest path in the indoor environment. The experimental system consisting of mesh network shares node data and send them to base station. The triangulation and the proposed Grid method calculate the location and heading angle of the robot. In addition, the robot finds the shortest path by using the base station attached on it to receive data of environment around each node. Kalman filter reduces the straight line error when the robot estimates the strength of received signal. The experimental results show the effectiveness of the proposed algorithm.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.7
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• pp.158-168
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• 1995

연삭숫돌 선택은 공작물제거량, 숫돌의 소모량, 표면정도 및 공작물의 물리적,화학적 특성을 고려하여 설정하는 것을 기본으로 한다. 연삭가공은 구성인자의 상호관계가 복잡하여 이중에서 어느한 요소만을 고려하여 설정하기 어렵고 정량적 기준 또한 정해져있지 않아 현실적으로는 숙련자의 정성적이고 경험적 지식에 따른 주관적 척도에 의존하는 것이 대부분이다. 또한, 연삭숫돌은 작업조건중에서 대량생산을 제외하고는 되도록이면 현장에 구비되어 있는 작업가능한 연삭숫돌 중에서 선택하는 것이 바람직하다. 따라서 본시스템에서는 이와같은 점을 고려하여 최적 연삭숫돌선택을 퍼지이론에 기초한 현장 숙련자의 지식을 활용하므로써 연삭숫돌선택의 효율성을 도모하는 동시에 현장에 연삭숫돌이 구비되지 않은 경우도 고려하여 연삭숫돌설정에 우선순위를 제시하므로써 작업자에 연삭숫돌선택의 유연성을 부여하였다. 또한, 실용성있는 전문가시스템의 구축을 위해 정성적이고 경험적인 지식의 활용을 위한 지식표현으로 설문조사에서 얻은 테이타를 x$^{2}$-분포에 따른 추정신뢰구간을 구해, 이를 토대로한 비대칭 삼각퍼지함수의 결정법을 제시하고, 이를 이용해서 구축한 시스템의 실행결과의 타당성을 비교하고자 한다.

• Journal of Broadcast Engineering
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• v.16 no.4
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• pp.669-679
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• 2011

In this paper, we propose a POCS based irregularly sampled image interpolation method exploiting non-local block-based wavelet shrinkage denoising algorithm. The method provides convex sets to improve the performance. The Delaunay triangulation interpolation is first applied to interpolate the missing pixels of the irregularly sampled image into the regular grids. Then, the non-local block-based wavelet shrinkage denoising algorithm is applied, and the originally observed pixels are enforced. After iteration is performed, the denoising algorithm for non-edge areas is applied to acquire the final result. The experimental results show that the proposed method outperforms the conventional methods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.5A
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• pp.602-610
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• 2000

There has been increasing interest in broadband services to mobile terminals. Wireless ATM will be used to support broadband services for future generation mobile service. We propose an algorithm for handover in wireless ATM LANs. We have studied how to treat the loop cancellation and optimization of path extension handover scheme, and present path optimization algorithms : polyangular loop cancellation and triangular loop cancellation. We express the location of MT(mobile terminal) by direction angle, and the direction angles can be converted into direction vectors. Using direction vectors, we can find the current optimal path of MT. The analysis and the experimental results show that the proposed scheme provides the better performance than that of anchor rerouting scheme in average handover delay, handover disruption delay, and buffer requirements.