• Journal of Astronomy and Space Sciences
• /
• 제24권4호
• /
• pp.409-416
• /
• 2007

이 논문에서는 톤 방식을 사용하는 통신해양기상위성의 위성 거리 측정의 거리 측정 모호성 및 성능을 위성이 천이궤도(transfer-station)와 운용궤도(on-station)에서 운용될 경우를 고려하여 해석하였다. 결과적으로 위성 거리 측정의 모호성은 사용하는 톤 신호의 주파수 비율이 낮고, 많은 톤 신호를 사용할수록 작아짐을 알 수 있었다. 또한, 동일한 톤 신호의 신호 대 잡음밀도 비에서는 작은 잡음 대역폭을 사용할수록 모호성 발생이 작아짐을 알 수 있었다. 요구된 통신해양기상위성의 거리 측정 성능을 위해서 천이궤도에서는 2Hz, 그리고 운용궤도에서는 1Hz 이하의 잡음 대역폭으로 운용하여야 함을 확인할 수 있었다.

• 한국군사과학기술학회지
• /
• 제14권4호
• /
• pp.590-597
• /
• 2011

The IDRS provides detection, classification and bearing/range estimation by performing wavefront curvature analysis on an intercepted active transmission from target. Especially, a estimate of the target bearing/range that significantly affects the optimal operation of own submarine is required. Target bearing/range can be estimated by wavefront curvature ranging which use the difference of time arrival at sensors. But estimation ambiguity occur in bearing/range estimation due to a number of peaks caused by high center frequency and limited bandwidth of the intercepted active transmission and distortion caused by noise. As a result the bearing/range estimation performance is degraded. To estimate target bearing/range correctly, bearing/range estimation method that eliminate estimation ambiguity is required. In this paper, therefore, for wavefront curvature ranging, NLS cost function with curve fitting method is proposed, which provide robust bearing/range estimation performance by eliminating estimation ambiguity. Through simulation the performance of the proposed bearing/range estimation methods are verified.

• Journal of electromagnetic engineering and science
• /
• 제13권4호
• /
• pp.251-258
• /
• 2013

A procedure for antenna parameter selections is proposed that considers the relationships between synthetic aperture radar performance and the antenna parameters of a parabola-type reflector antenna with a central flat dish. The effects of a central dish designed for weight reduction on the antenna beam pattern are also quantitatively analyzed using commercially available software based on the physical optics algorithm. The results of the theoretical analysis and simulation predict that a larger size of the central dish results in an increase in the sidelobe level, which is the reason for the increase in two important ambiguities, such as range ambiguity ratio (RAR) and azimuth ambiguity ratio (AAR). The dependence of RAR and AAR on Pulse repetition frequency is also analyzed and discussed.

• 말소리와 음성과학
• /
• 제9권2호
• /
• pp.61-68
• /
• 2017

The aim of this study is to investigate the prosodic aspects of ambiguous sentences in Korean produced by Chinese Korean Learners (L1: Chinese, L2: Korean). In Korean, sentence ambiguity can be caused by homonym or syntactically ambiguous structure. In spoken language however all ambiguity can be resolved by different prosodic features according to the meaning that they transmit. In this study we examined whether Chinese Korean Leaners also distinguish, in production, ambiguous sentences on the basis of prosodic characteristics. For this study 4 Korean natives speakers and 10 advanced Chinese Korean learners participated in the production test. The material analysed constituted 10 Korean sentences in which 6 sentences are lexically ambiguous and 4 sentences contain structural ambiguity. The results show that Korean native speakers produced ambiguous sentences by different prosodic structure depending on their semantic and syntactic structure. Chinese speakers also show distinct prosodic structure for different ambiguous sentences in most cases. But in the phonetic realization, the internal pitch range was greater for Korean native speakers than Chinese learners.

• 말소리와 음성과학
• /
• 제2권1호
• /
• pp.33-39
• /
• 2010

This study investigates the effect of pitch range reset in Korean listeners' processing of syntactically ambiguous participle structures. Unlike Japanese and English,in Korean, the downtrend or the reset of pitch range does not consistently differentiate Accentual Phrases (AP), a lower level of phrasing, from Intonational Phrases (IP), a higher level of phrasing. Therefore, we explore Korean listeners' comprehension patterns for syntactically ambiguous speech strings varying in 1) the relative height of F0 peaks across prosodic units, and 2) the types of prosodic phrasing, to see whether pitch range reset informs the recovery of syntactic structure even though it is not reflected in the intonational hierarchy in Korean. The results show that the hierarchical level of prosodic phrasing affects the parsing pattern of syntactic ambiguity. The pitch range reset also cued the location of syntactic boundaries, but this effect was confined to phrases across AP.

• 한국직업건강간호학회지
• /
• 제22권2호
• /
• pp.121-129
• /
• 2013

Purpose: This study is designed to verify affecting variables to turnover intention of nurses in general hospital. Methods: The data were from the self-reported questionnaire responses of 168 nurses in five general hospitals 300-400 beds in Seoul and Gyungi province and analyzed by frequency and percentage, t-test, ANOVA and Sheffe's test and stepwise multiple regression. Results: The means of turnover intention were $3.14{\pm}0.87$, job overload, $3.54{\pm}0.67$, role ambiguity, $2.87{\pm}0.71$ and burnout, $2.68{\pm}0.72$. A significant correlation was found among turnover intention and job overload (r=.24, p<.001), role ambiguity (r=.30, p<.001), and burn out (r=.58, p<.001). The factors that affect turnover intention from the result of multiple regression by the stepwise selection, were emotional exhaustion, role ambiguity, and diminished personal accomplishment. Conclusion: Based on the results, to reduce turnover intention of nurses, emotional support should be provided and also range of roles be clearly defined. In addition, it is needed to improve the working conditions for nurses to get a sense of accomplishment.

• 한국정보통신학회:학술대회논문집
• /
• 한국정보통신학회 2014년도 추계학술대회
• /
• pp.965-966
• /
• 2014

초음파를 이용한 거리 및 속도측정에서는 PRF(Pulse Repitition Frequency) 선정에 따른 거리 및 속도 모호성 문제가 큰 장애 요인 중의 하나이다. 따라서 이러한 장애 극복을 위한 신호파형 발생시 PRF 선정 방법과 측정 결과에 미치는 영향을 분석하였다.

• 제어로봇시스템학회논문지
• /
• 제18권10호
• /
• pp.977-987
• /
• 2012

One of the most significant errors in the pseudo-range measurement performance of GNSSes (Global Navigation Satellite Systems) is their multipath error for high-precision applications. Several schemes to mitigate this error have been studied. Most of them, however, have been focused on the GPS (Global Positioning System) L1 C/A (Coarse/Acquisition) signal that was designed in the 1970s and is still being used for civil navigation. Recently, several modernized signals that were especially conceived to more significantly mitigate multipath errors have been introduced, such as Time Multiplexed and Composite Binary Offset Carrier (TMBOC and CBOC, respectively) signals. Despite this advantage, however, a problem remains with the use of TMBOC and CBOC modulations: the ambiguity of BOC (Binary Offset Carrier)-modulated signal tracking. In this paper, a novel unambiguous multipath error mitigation scheme for these modernized signals is proposed. The proposed scheme has the same complexity as HRCs (High Resolution Correlators) but with low ambiguity. The simulation results showed that the proposed scheme outperformed or performed at par with the HRC in terms of their multipath error envelopes and running averages in the static and statistical channel models. The ranging error derived by the mean multipath error of the proposed scheme was below 1.8 meters in an urban area in the statistical channel model.

• 한국항해항만학회:학술대회논문집
• /
• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.1
• /
• pp.271-275
• /
• 2006

This paper describes the design and realization of full attitude system based on MEMS IMU and GPS carrier phase. The work can be divided into two parts: First, initial heading is determined by using two GPS receivers. And this paper discusses the usage of space geometry conditions to reduce the range of ambiguity search. The method presented in this paper was tested on the static. On the static condition, an accuracy better than 0.06 degrees for heading for 3.48m long baseline has been achieved. Integration of GPS and low cost MEMS IMU are used to realize the real-time heading attitude system. Second, level attitude (pitch and roll) is determined using the method of frequency-velocity for the feedback control. At the same time, the method using the attitude based on MEMS IMU to help determination of the range of ambiguity search is proposed. The results done on the sea show that an alternative means to provide real-time, cost-effective, accurate and reliable attitude information for attitude surveys. Though motivated by a big ships application, the design can be applied to other vehicles.

• 한국전자파학회논문지
• /
• 제29권6호
• /
• pp.464-472
• /
• 2018

최근 위성 SAR(Synthetic Aperture Radar) 시스템의 개발은 광역 관측을 수행하는 동시에, 고해상도 영상을 확보하는 방향으로 확장되고 있다. 일반적인 위성 SAR 시스템에서는 광역의 고해상도 영상을 획득하는 과정에서 방위 및 거리방향의 모호성 문제가 유발되어 영상 품질의 저하가 발생한다. 다중 입출력 장치를 사용하는 MIMO(Multiple Input Multiple Output) SAR 기술은 상호 상관성이 낮은 파형군을 적용하여 관측폭을 확장하면서도 영상 품질을 유지하는 기법으로 제안되고 있다. 본 논문에서는 상호 직교 특성을 갖는 다중 잡음 OFDM(Orthogonal Frequency Division Multiplex) 파형을 설계하고, 다중 파형 모드에서의 영상 품질 분석을 수행하여 광역 고해상도 SAR 모드에 적용 가능성을 제시한다.