• 한국정보통신학회논문지
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• 제17권1호
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• pp.1-7
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• 2013

본 논문에서는 강우 레이더간 간섭 현상과 강우 레이더의 스퓨리어스 방사 신호로부터 발생되는 인접 무선국에 대한 간섭 현상을 분석한다. 강우 레이더는 강우강도를 측정하고 강우를 예측하기 위하여 수평 지향각에서 운영되고 있으며, 높은 출력으로 동일 또는 인접대역의 통신기기 및 레이더간 간섭현상이 발생할 수 있다. S대역 주파수 영역의 전파 특성과 강우 레이더의 전파 간섭 보호비를 도출하여 강우 레이더간 간섭 현상과 인접 무선국의 간섭 영향을 분석한다. 아울러 인접 무선국에 대한 강우 레이더의 전파 간섭영향과 강우 레이더의 스퓨리어스 방사 특성으로부터 강우 레이더의 방사 스펙트럼 특성을 제안한다. 인접 무선국에 대한 간섭을 최소화하기 위해서는 105 dB 이상의 스퓨리어스 억압 특성을 가져야 하며, 레이더간 간섭을 최소화하기 위해서는 운용 시각 및 PRF를 다르게 설정하여 운용하여야 한다.

• Journal of Positioning, Navigation, and Timing
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• 제11권1호
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• pp.23-28
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• 2022

The eLoran system is a high-power terrestrial navigation system that is recognized as the most appropriate alternative to complement the GNSS's vulnerability to radio frequency interference. Accordingly, Korea has conducted eLoran technology development projects since 2016. The eLoran system developed in Korea provides 20 m positioning accuracy to maritime user in Incheon and Pyeongtaek harbor. To accurately calculate the position with the eLoran signal, it is necessary to apply a compensation method that mitigates the propagation delay. In this paper, we develop the compensation method to mitigate the eLoran signal propagation delay and evaluate the positioning performance in Incheon harbor. The propagation delay due to the terrain characteristics is pre-surveyed and stored in the user receiver. Real-time fluctuations in propagation delay compared to the pre-stored data are mitigated by the temporal correction generated at a nearby differential Loran station. Finally, two performance evaluation tests were performed to verify the positioning accuracy of the Korean eLoran system. The first test took place in December 2020 and the second in April 2021. As a result, the Korean eLoran service has been confirmed to provide 20 m location accuracy without GPS.

• Geomechanics and Engineering
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• 제9권5호
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• pp.645-667
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• 2015

Single treatment and staged treatments in vertical wells are widely applied in sandstone and mudstone thin interbedded (SMTI) reservoir to stimulate the reservoir. The keys and difficulties of stimulating this category of formations are to avoid hydraulic fracture propagating through the interface between shale and sand as well as control the fracture height. In this paper, the cohesive zone method was utilized to build the 3-dimensional fracture dynamic propagation model in shale and sand interbedded formation based on the cohesive damage element. Staged treatments and single treatment were simulated by single fracture propagation model and double fractures propagation model respectively. Study on the changes of fracture vicinity stress field during propagation is to compare and analyze the parameters which influence the interfacial induced stresses between two different fracturing methods. As a result, we can prejudge how difficult it is that the fracture propagates along its height direction. The induced stress increases as the pumping rate increasing and it changes as a parabolic function of the fluid viscosity. The optimized pump rate is $4.8m^3/min$ and fluid viscosity is $0.1Pa{\cdot}s$ to avoid the over extending of hydraulic fracture in height direction. The simulation outcomes were applied in the field to optimize the treatment parameters and the staged treatments was suggested to get a better production than single treatment.

• 한국통신학회논문지
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• 제28권7A호
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• pp.440-450
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• 2003

The reverse link of a spectrally overlaid macrocell/microcell cellular CDMA system supporting multimedia traffic is characterized in terms of the required signal power, interference, and capacity. Several narrowband subsystems are overlaid with a wideband subsystem in macrocells, while a single wideband subsystem is operated in a microcell with the same spectrum as the macrocell wideband subsystem. Using a typical propagation model the reverse link signal power and interference are characterized as the relative user signal power and the cross-tier interference factors between the macrocell and the microcell. The reverse link capacity of the overlay system is then analyzed. Analytical results show that the dominant parameters affecting the system performance are the spectral overlay ratio and the distance between the microcell and macrocell base stations. In particular, when the distance equals a half of macrocell radius, optimum performance can be achieved by minimizing the cross-tier interference factors. These results can be applied to CDMA multimedia network planning in heavily populated traffic areas.

• 한국ITS학회 논문지
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• 제6권3호
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• pp.122-137
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• 2007

본 논문은 주파수 자원을 효율적으로 이용하기 위하여 무선통신 업무가 인접 대역 혹은 동일 대역에 존재하는 경우 몬테 카를로 시뮬레이션 방법을 이용하여 양립성을 분석하였다. 간섭 시나리오를 설정하면 간섭원과 피 간섭원간의 간섭 확률을 몬테 카를로 방법으로 계산한 후 이를 미리 설정된 최대 허용 간섭 확률과 비교하여 활성화 간섭원 밀도, 간섭원 대역폭, 피 간섭원의 셀 반경, 간섭원과 피간섭원 사이의 거리, 충격 계수에 따라 양립 여부를 판단하였다. 이 때 전파 모델은 free space 모델, extended Hata 모델로 가정하였다.

• 한국광학회지
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• 제11권6호
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• pp.418-422
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• 2000

본 논문에서는 다중모드간섭(multimode interference: MMI) $1\times4$ 광파워 분리기를 유한 차분빔전파법(FD-BPM)을 이용하여 모델링하고 BK7 유리기판에 $Ag^+-Na^+$ 이온교환법을 이용하여 제작하였다. 제작된 MMI $1\times4$ 광파워 분리기의 분리비는 0.46dB이었다.

• 한국환경과학회지
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• 제18권8호
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• pp.911-918
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• 2009

Electromagnetic interference (EMI) is defined as the interaction phenomena of electromagnetic waves scattered from a large structure or complex terrain. In this study, the propagation of linear wave is modeled with ray theory, direct simulation Monte Carlo (DSMC), and some classical theories on flat plates. The wave physics of reflection, refraction, and diffraction are simulated for the investigation of front and back scattering of the one-dimensional plane wave from a tower with ray theory and DSMC, respectively. The effect of rotating disk idealized from the real wind-turbine blades is modeled with a simplified version of the classical electromagnetic theory as well as DSMC based on the ray theory.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1995년도 춘계공동학술대회논문집; 전남대학교; 28-29 Apr. 1995
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• pp.724-728
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• 1995

A new dynamic channel assignment (DCA) algorithm with rearrangement for cellular mobile communication systems is suggested. Our DCA algorithm is both traffic and interference adaptive, which is based on the mathematical formulation of the maximum packing under a realistic propagation model. In developing the algorithm, we adopt the Lagrangean relaxation technique that has been successfully used in the area of mathematical programming. Computational experiments of the algorithm reveal quite encouraging results. Although our algorithm primarily focuses on microcellular systems, it can be effectively applied to conventional cellular systems under highly nonuniform traffic distributions and interference conditions.

• 전자공학회논문지S
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• 제34S권11호
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• pp.148-155
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• 1997

Ths signal processing technqiue of FET type electrolyte sensors using the back propagation neural network was studied to reduce the interference effects of the different electrolytes. The FET-type electrolyte sensors, pH-ISFET, K-ISFET, and Ca-ISFET, were prepared to measure the pH, K, and Ca electrolytes. Neural network consisted of three layers was learned with 8 patterns and 9 patterns. The sensor output obtained with arbitrary concentrations was processed by the learned neural network. The errors obtained from calibration curve for pH, K, and Ca were .+-.0.039 pH, .+-.2.508 mmol/l, and .+-.1.807 mmol/l, respectively, without considering the interference effects. The errors of the network output for pH, K, and Ca were reduced to .+-.0.005 pH, .+-.0.436 mmol/l, and .+-.0.381 mmol/l in case of 9 patterns, respectively. the signal processing using the neural network can reduce the errors ofthe electrolyte sensor outputs caused by the interference effect, thereby providing effectiveness in the improvement of the sensor selectivity.

• Journal of the Optical Society of Korea
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• 제9권1호
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• pp.32-35
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• 2005

In light microscopy, spatial resolution is limited by diffraction effect. Confocal microscopy has improved resolutions in both lateral and axial directions, but these are still limited by diffraction effect. Confocal self-interference microscopy (CSIM) uses interference between two perpendicularly polarized beams to enhance lateral resolution. In previous research, we proposed a calcite plate with its optic-axis perpendicular to the propagation angle and one of the boundary surfaces of the plate. This type of plate is not widely used to our knowledge. In this paper, we change the calcite plate to more common one, which is commercially available. This calcite plate has its optic axis in the plane of incidence. We analyze the characteristics of this calcite plate and numerically compare the performances of CSIM in previous research and CSIM with the commercial calcite plate. Numerical results show improved performance when using the commercial calcite plate