• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2013년도 추계학술대회
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• pp.402-404
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• 2013

수중에서의 무선통신 채널환경은 수심이나 염분 등에 의해 전달 속도가 다르며 해면이나 해저에 의해 다중 경로의 영향을 받는다. 본 논문에서는 이러한 다중 경로를 갖는 채널에서의 전송율을 높이기 위해 MIMO(Multi-Input-Multi-Output) 시스템에서의 부호화 기법과 등화기가 결합하여 동작하는 터보 등화기를 갖는 시스템을 사용하였다. 또한 다중경로로 인한 위상 오차 추정은 decision directed 방식의 효율적인 방안을 제시하고 시뮬레이션 하였다. 시뮬레이션 결과 본 논문에서는 제안한 방식을 통해 위상 오차에 대한 영향을 최소화 할 수 있었다.

• Journal of Communications and Networks
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• 제6권1호
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• pp.19-25
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• 2004

In this paper, we present a trellis-based blind channel estimation and equalization technique coupling two kinds of adaptive Viterbi algorithms. First, the initial blind channel estimation is accomplished by incorporating the list parallel Viterbi algorithm with the least mean square (LMS) updating approach. In this operation, multiple trellis mappings are preserved simultaneously and ranked in terms of path metrics. Equivalently, multiple channel estimates are maintained and updated once a single symbol is received. Second, the best channel estimate from the above operation will be adopted to set up the whole trellis. The conventional adaptive Viterbi algorithm is then applied to detect the signal and further update the channel estimate alternately. A small delay is introduced for the symbol detection and the decision feedback to smooth the noise impact. An automatic switch between the above two operations is also proposed by exploiting the evolution of path metrics and the linear constraint inherent in the trellis mapping. Simulation has shown an overall excellent performance of the proposed scheme in terms of mean square error (MSE) for channel estimation, robustness to the initial channel guess, computational complexity, and channel equalization.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.598-601
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• 2006

The radio signal in GNSS was intentionally designed with two frequencies in order to combat the dispersion error caused by trans-ionospheric propagation. By measuring the path delay independently at the two, widely spaced GPS frequencies, L1 & L2, the TEC along the path from satellite to receiver can be measured directly. The issue with dual frequency measurement of the ionosphere is the calibration of L1/L2 interfrequency biases. L1/L2 interfrequency biases are generated because physical electric signal paths of L1 and L2 circuits are different from each other for both satellites and receiver. Conventionally L1/L2 interfrequency bias is estimated and broadcasted by 2D ionospheric model. In this paper, we estimated IFB (interfrequency bias) by 2D & 3D ionospheric models including real time filter methods and compared the result of those and concluded the merit of 3D tomography model to recover the problem of 2D thin shell model. We confirmed our conclusion by experimental data.

• 한국정보처리학회논문지
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• 제4권8호
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• pp.1975-1986
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• 1997

프로토콜이 방대화되고 복잡해짐에 따라 기존의 제어흐름 중심의 테스트는 프로토콜이 갖는 자료흐름, 전이조건, 지연 등의 복합요소를 테스트하는데 문제점을 갖는다. 따라서 본 연구에서는 자료흐름을 제어흐름에 통합하여 테스트 스위트를 생성함으로써 제어흐름 분석시 발생하는 비결정성 문제를 해결하고, 도달가능 트리를 이용하여 실행 불가능 경로를 제거한 후 실행가능 경로에 대한 테스트 스위트만을 생성하는 기법을 제안하고 이를 설계 및 구현하였다. 설계 및 구현된 도구는 기존 방법과 비교하여 UIO 길이를 줄이며 오류 가능성이 높은 특성 경로에 대한 부분적인 테스트가 필요한 경우에 효율적으로 사용할 수 있다. 또한 구현된 자동 테스트 스위트 생성도구의 활용으로 프로토콜 구현의 생산성을 높일 수 있으며 프로토콜 테스팅 환경의 기반을 제공한다.

• 한국농공학회논문집
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• 제52권6호
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• pp.135-144
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• 2010

This study was performed to suggest a soil loss reduction skill through estimating soil erosion from a small watershed including each type of sloping agriland by using GEOWEPP model. Experimental watershed at Gangwon province was selected for very typical sloping fields of highland agriculture in Alpine area. Runoff discharge and sediment load, hourly rainfall amount occurred during storm event were gauged, and weather data were obtained from Daegwallyeong meteorological station. The results of GEOWEPP model estimation showed that relative error values for total runoff discharge and sediment load were 3 %, -14.5 % respectively. Based on the result, soil erosion and waterway path map for each hillslope were made to select target hillslope. Several hillslopes of severe soil erosion were analyezed and then the optimal vegetative filter strip construction width and waterway path to plant grass were decided by using GEOWEPP Model.

• Journal of information and communication convergence engineering
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• 제16권2호
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• pp.130-134
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• 2018

Wireless capsule endoscopy (WCE) is considered as recent technology for the detection cancer cells in the human digestive system. WCE sends the captured information from inside the body to a sensor on the skin surface through a wireless medium. In WCE, the design of low-power consumption devices is a challenging topic. In the Shannon-Nyquist sampling theorem, the number of samples should be at least twice the highest transmission frequency to reconstruct precise signals. The number of samples is proportional to the power consumption in wireless communication. This paper proposes compressive sensing as a method to reduce power consumption in WCE, by means of a trade-off between samples and reconstruction accuracy. The proposed scheme is validated under channel constraints, expressed as the realistic human body path loss. The results show that the proposed scheme achieves a significant reduction in WCE power consumption and achieves a faster computation time with low signal error reconstruction.

• 한국소음진동공학회논문집
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• 제24권1호
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• pp.35-44
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• 2014

Sound pressure levels in the receiving room while testing airborne sound insulation performance are varied by the measuring points. This may increase the measurement error, then decrease the measurement reliability. With this reason the research has carried out on the method to reduce deviations of sound pressure level in the ISO type rectangular laboratory focusing on the measurement of airborne sound insulation performance. Tests were made to see the effect of sound absorption in the receiving room, loudspeaker locations, microphones locations and flanking transmission path. Consequently, it was resulted that sound absorption in the receiving room and the loudspeaker location have influence on the sound level deviations especially in the low frequency. The microphone location was very important to get measurement reliability. The effective measuring point, which the sound level difference with average sound pressure level is within 2 dB, could yield most reliable average sound pressure level. Therefore it is necessary to find the effective measuring points in the receiving room. Flanking transmission path should be sealed using sound absorber or magnet etc. to prevent from lowering the sound insulation performance.

• 농업과학연구
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• 제48권3호
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• pp.617-627
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• 2021

In the field of on-road motor vehicles, the level for autonomous driving technology is defined according to J3016, proposed by Society of Automotive Engineers (SAE) International. However, in the field of agricultural machinery, different standards are applied by country and manufacturer, without a standardized classification for autonomous driving technology which makes it difficult to clearly define and accurately evaluate the autonomous driving technology, for agricultural machinery. In this study, a method to classify the autonomy levels for autonomous agricultural machinery (ALAAM) is proposed by modifying the SAE International J3016 to better characterize various agricultural operations such as tillage, spraying and harvesting. The ALAAM was classified into 6 levels from 0 (manual) to 5 (full automation) depending on the status of operator and autonomous system interventions for each item related to the automation of agricultural tasks such as straight-curve path driving, path-implement operation, operation-environmental awareness, error response, and task area planning. The core of the ALAAM classification is based on the relative roles between the operator and autonomous system for the automation of agricultural machines. The proposed ALAAM is expected to promote the establishment of a standard to classify the autonomous driving levels of self-propelled agricultural machinery.

• 한국수소및신에너지학회논문집
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• 제34권6호
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• pp.748-757
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• 2023

Numerical analysis was conducted to confirm the characteristics of extinction behavior in NH₃/CH₄ counterflow symmetrical flames. Numerical simulations were run on CHEMKIN-PRO, using the OPPDIF code, with Okafor's mechanisms, which had the lowest error rate compared to Colson's experimental data in the our previous part I study. The chemical interactions of merged flames were examined by analyzing the production rate of major chemical species and key radicals with the volume fractional percentage of ammonia and global strain rate. The interaction phenomenon of the flames could be identified by observing the main chemical reaction path of the merged flames at the stagnation plane.

• Current Optics and Photonics
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• 제7권5호
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• pp.518-528
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• 2023

As an effective means of remotely detecting the spectral information of the object, the spectral calibration for the Savart polarization interference imaging spectrometer (SPIIS) is a basis and prerequisite of information quantification, and its experimental calibration scheme is firstly proposed in this paper. In order to evaluate the accuracy of the spectral information acquisition, the linear interpolation, cubic spline interpolation, and piecewise cubic interpolation algorithms are adopted, and the precision of the quadratic polynomial fitting is the highest, whose fitting error is better than 5.8642 nm in the wavelength range of [500 nm, 820 nm]. Besides, the inversed value of the spectral resolution for the monochromatic light is greater than the theoretical value, and the deviation between them becomes larger with the wavelength increasing, which is mainly caused by the structural design of the SPIIS, together with the rationality of the spectral restoration algorithm and the selection of the maximum optical path difference (OPD). This work demonstrates that the SPIIS has achieved high performance assuring the feasibility of its practical use in various fields.