• The Journal of the Acoustical Society of Korea
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• v.41 no.2
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• pp.210-217
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• 2022

Passive source depth estimation has been studied for decades since the source depth can be used for target classification, target tracking, etc. The purpose of this paper is to solve the problem of ambiguity in the previous paper [S.-il. Cho et al. (in Korean), J. Acoust. Soc. Kr. 38, 120-127 (2019)] that source depth is estimated in two points. The patterns of phase shift of Channel Impulse Response(CIR) reflected in ocean surface and bottom is used for removing ambiguity of the source depth estimation, and after removing ambiguity, source depth is estimated at one point through the intersection of CIR. In order to extract CIR in case of unknown source signal and continuous signal or noise, Ray-based blind deconvolution is used. The proposed algorithm is demonstrated through numerical simulation in ocean waveguide.

• Journal of Agricultural Extension & Community Development
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• v.19 no.2
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• pp.211-240
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• 2012

The purpose of this study was to identify korean agricultural extension workers' Perception of role ambiguity according to restructuring of Agricultural Administrative Systems. The target population of this study was selected from 21 centers out of 156 centers. The subjects for study were 728 agricultural extension officers by the cluster sampling drawn from the sampled 21 agricultural extension centers in four clusters. A survey questionnaire was utilized to measure variables of this study. It consisted of role ambiguity scale and demographic items. In this study, role ambiguity scale was translated from the existing scale. Through a pilot test and final survey, reliability and validity of these scales were examined. The data were collected by mail. A total 420 questionnaires out of 728 from 21 agricultural extension centers were returned. After data cleaning, 410 responses were used for analysis. Both descriptive and inferential statistics were applied for data analysis. Major findings of the study were as follows. There were significant differences of the degree of role ambiguity among the local extension workers divided by four clusters. Especially, the degree of role ambiguity of restructured local administrative system were more higher than other clusters, comparatively. Thus, the factors causing the role ambiguity to agricultural extension officers need to be measured it in-depth.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.11
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• pp.935-940
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• 2002

For robot navigation and visual reconstruction, structure from motion (SFM) is an active issue in computer vision community and its properties arc also becoming well understood. In this paper, when using stereo image sequence and direct method as a tool for SFM, we present a new method for overcoming bas-relief ambiguity. We first show that the direct methods, based on optical flow constraint equation, are also intrinsically exposed to such ambiguity although they introduce robust methods. Therefore, regarding the motion and depth estimation by the robust and direct method as approximated ones. we suggest a method that refines both stereo displacement and motion displacement with sub-pixel accuracy, which is the central process f3r improving its ambiguity. Experiments with real image sequences have been executed and we show that the proposed algorithm has improved the estimation accuracy.

• Journal of Positioning, Navigation, and Timing
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• v.10 no.4
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• pp.297-305
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• 2021

Monocular depth estimation helps the robot to understand the surrounding environments in 3D. Especially, deep-learning-based monocular depth estimation has been widely researched, because it may overcome the scale ambiguity problem, which is a main issue in classical methods. Those learning based methods can be mainly divided into three parts: supervised learning, unsupervised learning, and semi-supervised learning. Supervised learning trains the network from dense ground-truth depth information, unsupervised one trains it from images sequences and semi-supervised one trains it from stereo images and sparse ground-truth depth. We describe the basics of each method, and then explain the recent research efforts to enhance the depth estimation performance.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.12
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• pp.139-146
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• 2020

The domain of entrepreneurship has been dotted across various paradigms. Identifying and examining entrepreneurial intention and propensity to it spontaneously require the insight from the lens of psychological approach. The aim of this study is to examine the influence and impact of psychological factors on entrepreneurial intention; as it is found that in Bangladeshi context several entrepreneurship studies are undertaken, still the exploratory research on interplay between the psychological factors (i.e., self-confidence, locus of control, need for achievement, and tolerance for ambiguity) and entrepreneurial intention has been merely found. The study has chosen Bangladeshi university students as the unit of analysis and the ultimate sample size in this research is n=265. The current paper is a quantitative study where sampling method is followed by convenience sampling technique, and study data is collected through survey questionnaire. Data has been compiled into SPSS whereas, for hypotheses assessment, Smart PLS software is applied. The results reflect that self-confidence, locus of control, and need for achievement are revealed as contributory determinants of entrepreneurial intention while tolerance for ambiguity is found as an insignificant predictor. The current research is expected to offer an in-depth understanding about the significance of psychological factors in examining entrepreneurial intention.

• Journal of Positioning, Navigation, and Timing
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• v.5 no.4
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• pp.221-233
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• 2016

This paper deals with performance assessment of the kinematic network-based GPS positioning technique with a view to using it for ellipsoidally referenced bathymetric surveys. To this end, two field trials were carried out on a land vehicle and a surveying vessel. Single-frequency GPS data acquired from these tests were processed by an in-house software which equips the network modeling algorithm with instantaneous ambiguity resolution procedure. The results reveals that ambiguity success rate based on the network model is mostly higher than 99.0%, which is superior to that of the single-baseline model. In addition, achievable accuracy of the technique was accessed at ${\pm}1.6cm$ and 2.7 cm with 95% confidence level in horizontal and vertical component respectively. From bathymetric survey at the West Nakdong River in Busan, Korea, 3-D coordinates of 2,011 points on its bed were computed by using GPS-derived coordinates, attitude, measured depth and geoid undulation. Note that their vertical coordinates are aligned to the geoid, the so-called orthometric height which is widely adopted in river engineering. Bathymetry was constructed by interpolating the coordinate set, and some discussion on its benefit was given at the end.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1851-1856
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• 2008

A numerical program based on computational fluid dynamics has been developed to simulate characteristics of an EHD induction micropump. The ambiguity of boundary conditions was removed by adopting an equation formulated for electric potential as the dependent variable. The calculations show that the dependency of frequency agrees well with the experiments and the previous analysis. The instability, caused by backflows, is getting stronger as the channel depth increases, which is consistent with experiments. The present study reveals that it is due to the limit in the penetration depth which the electric field can affect. Despite the disadvantage of large channel depth, there is a certain optimal depth for the maximum flow rate.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.42 no.1
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• pp.21-28
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• 2005

In this paper, we studied resolution to the FBP(Filtered Back-Propagation) tomographic image reconstruction algorithms. In order to analyze the resolution to the tomographic images, we derived ambiguity function to this algorithm which can be reconstructed from the improved FBP image reconstruction algorithm by using fixed coordinate system practically. Through simulation using this function, we determined the lateral and depth resolution quantitively and then analyzed respectively. Simulation results show that the lateral and depth resolution to the improved FBP image reconstruction algerian was determined $0.27\lambda\;and\;0.70\lambda$ at the 3dB, and also $0.89\lambda\;and\;0.96\lambda$ at the 6dB respectively. This results proved that improved FBP reconstruction algorithms for diffraction tomography of incident planar wave is useful to developed the tomographic image system, analyze the resolution to the tomographic images, we derived ambiguity function to this algerian which can be reconstructed from the improved FBP image reconstruction algorithm by using fixed coordinate system.

• Journal of Broadcast Engineering
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• v.26 no.1
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• pp.70-78
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• 2021

Estimating 3D information from a single image is one of the essential problems in numerous applications. Since a 2D image inherently might originate from an infinite number of different 3D scenes, thus 3D reconstruction from a single image is notoriously challenging. This challenge has been overcame by the advent of recent deep convolutional neural networks (CNNs), by modeling the mapping function between 2D image and 3D information. However, to train such deep CNNs, a massive training data is demanded, but such data is difficult to achieve or even impossible to build. Recent trends thus aim to present deep learning techniques that can be trained in a weakly-supervised manner, with a meta-data without relying on the ground-truth depth data. In this article, we introduce recent developments of weakly-supervised deep learning technique, especially categorized as scene 3D reconstruction and object 3D reconstruction, and discuss limitations and further directions.

• Speech Sciences
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• v.9 no.3
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• pp.211-221
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• 2002

The prosody can play a crucial role in differentiating ambiguous sentences to correctly reflect their intended syntactic structures. In what way do the speakers in Tokyo and Sendai dialects of Japanese use prosodic elements to differentiate syntactic ambiguities? Acoustic measurement was made of utterances of ambiguous sentences in Japanese to observe prosodic strategies for disambiguation. Materials were sentences of the type ADV-VP1-NP-VP2, ADV-NP1-NP2-VP2, where the ambiguity lies in locative adverbial modification, ADV modifying either VP1 or VP2. For this construction the Japanese create the same ambiguities. After defining the depth of a syntactic boundary, F0 of the phrase before and after the boundary, and duration of the syllable and pause before the boundary were measured. The results show that Tokyo dialects speakers use F0 after syntactic boundary, and Sendai dialects speakers use of the syllable and/or pause before the boundary.