• 한국음향학회지
• /
• 제41권2호
• /
• pp.210-217
• /
• 2022

수동 소나 시스템에서 음원 깊이 추정 분야는표적 식별, 추적 등 다양한 전술에 활용할 수 있기 때문에 많은 연구가 지난 수십년간 진행되어 왔다. 본 논문은 기존 논문[조성일 외, 한국음향학회지 제38권 제1호, 120-127(2019)]의 문제점이었던 음원 깊이가두 곳에서 추정되는 모호성을 해결하는데 목적이 있다. 해수면과 해저면에 반사되어 나타나는채널 임펄스 응답의 위상천이 패턴을 이용하여 모호성을 제거하며, 제거 후 하나의 깊이에서 채널 임펄스 응답의 교차점을 통해 음원의깊이를 추정한다. 음원에 대한 정보가 없고, 연속적인 신호 혹은 소음에서 채널 임펄스 응답을 추정하기 위해 음선 기반 블라인드 디컨벌루션 기법이 사용되며, 제안된 알고리즘은 시뮬레이션를 통하여 검증하였다.

• 농촌지도와개발
• /
• 제19권2호
• /
• pp.211-240
• /
• 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.

• 제어로봇시스템학회논문지
• /
• 제8권11호
• /
• pp.935-940
• /
• 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
• /
• 제10권4호
• /
• pp.297-305
• /
• 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
• /
• 제7권12호
• /
• pp.139-146
• /
• 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
• /
• 제5권4호
• /
• pp.221-233
• /
• 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.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2008년도 추계학술대회A
• /
• pp.1851-1856
• /
• 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.

• 대한전자공학회논문지TE
• /
• 제42권1호
• /
• pp.21-28
• /
• 2005

본 논문은 토모그라픽 영상시스템에 적합한 FBP 토모그라픽 영상복원 알고리즘의 분해능에 관하여 연구하였다. 고정좌표계를 이용하는 개선된 FBP 토모그라픽 영상복원 알고리즘으로부터 분해능을 분석할 수 있는 모호함수를 유도하였고, 이를 이용한 모의실험을 통하여 얻은 진폭분포로부터 측방향 및 축방향 분해능을 정량적으로 결정하였다. 개선된 FBP 토모그라픽 영상복원 알고리즘을 통해 기존의 SAM(Scanning Acoustic Microscope)시스템으로부터 얻을 수 있는 3dB와 6dB 축방향 분해능에 대해서도 각각 0.70 파장과 0.96 파장으로 SAM 영상의 3dB 축방향 분해능인 7 파장에 비하여 매우 개선된 분해능을 얻을 수 있음을 확인하였다. 평면 입사파의 회절 토모그라픽 영상복원을 위한 개선된 FBP 토모그라픽 영상복원 알고리즘은 미세하고 복잡한 다층 박막구조를 갖는 시료에 대하여 좋은 분해능을 갖는 토모그라픽 영상시스템을 개발하는데 유용하게 활용할 수 있도록 하였다.

• 방송공학회논문지
• /
• 제26권1호
• /
• pp.70-78
• /
• 2021

2차원 단일 영상에서 3차원 깊이 정보를 복원하는 기술은 다양한 한계 및 산업계에서 활용도가 매우 높은 기술임이 분명하다. 하지만 2차원 영상은 임의의 3차원 정보의 투사의 결과라는 점에서 내재적 깊이 모호성(Depth ambiguity)을 가지고 있고 이를 해결하는 문제는 매우 도전적이다. 이러한 한계점은 최근 인공지능 기술의 발달에 힘입어 2차원 영상과 3차원 깊이 정보간의 대응 관계를 학습하는 알고리즘의 발달로 극복되어 지고 있다. 이러한 3차원 깊이 정보 획득을 위한 인공지능 기술을 학습하기 위해서는 대응 관계를 나타내는 대규모의 학습데이터의 필요성이 절대적인데, 이러한 데이터는 취득 및 가공 과정에서 상당한 노동력을 필요로 하기에 제한적으로 구축이 가능하다. 따라서 최근의 기술 발전 동향은 대규모의 2차원 영상과 메타 데이터를 활용하여 3차원 깊이 정보를 예측하려는 약교사(Weakly-supervised) 인공지능 기술의 발전이 주를 이루고 있다. 본 고에서는 이러한 기술 발전 동향을 장면(Scene) 3차원 복원 기술과 객체(Object) 3차원 복원 기술로 나누어 요약하고 현재의 기술들의 한계점과 향후 나아갈 방향에 대해서 토의한다.

• 음성과학
• /
• 제9권3호
• /
• pp.211-221
• /
• 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.