• 한국대기환경학회지
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• 제23권6호
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• pp.689-698
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• 2007

Particular attention is paid to the validity of PM-10 measurement using beta attenuation method. In this study, the inter-comparison studies were undertaken for PM-10 sampler with different measuring methods. The three beta attenuation monitoring instruments (BAM1020, FH C-14, and DIGS-150) and filter based gravitational method using High Volume Air Sampler were collocated and mass concentrations were compared from August to November, 2006. The results of the investigation show that beta attenuation monitoring instruments are comparable with gravitational method within 10% of measurement error. For specific conditions under high humidity and high concentrations, the inter-comparison results also showed a relatively good agreement and this can be explained as the effect of inlet heating of beta attenuation instrument. Subsequently, this study shows that beta attenuation monitoring instruments can be equivalently used with reasonable validity when compared gravimetric method.

• 대기
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• 제23권4호
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• pp.513-517
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• 2013

In this study, it is first intended to simulate the vertical profile of atmospheric flow in a short wind tunnel. In order to accomplish it, proper devices are designed properly to reduce freestream flow momentum and it is confirmed from the measured velocity profile using hot-wire anemometer that momentum flux of the tunnel free stream can be reduced and desired atmospheric boundary can be created. Second, experiments are performed to identify influences of a surrounding structure measuring correct wind velocity by an anemometer, which are located nearby due to area limitation in actual airport and correction factors are proposed from experimental results. One of findings is that in order to limit the velocity attenuation due to a nearby structure under 10%, wind velocity measuring equipment should be installed at least 6 times of the structure height away from the structure of concern.

• 한국산학기술학회논문지
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• 제6권2호
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• pp.159-164
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• 2005

광 펄스가 대기 채널을 통해 전송될 때, 대기 교란은 광 펄스를 감쇠시키고 퍼지게 한다. 이러한 감쇠와 펄스 퍼짐은 광 수신 단에서 펄스 도착시간의 요동에 의해 발생된다. 이러한 펄스 퍼짐이 인접 펄스간의 부호 간 간섭을 일으킨다. 결국, 부호 간 간섭에 의해 인접한 펄스들은 중첩이 되고 비트 전송률 및 무중계 전송거리를 제한하게 된다. 따라서, 디지털 통신시스템에서는 감쇠보다 펄스 퍼짐이 더 중요한 인자가 된다. 이에, 본 논문에서는 시간적 모멘트 함수를 이용하여 대기 교란상태에서 교란 상태를 나타내는 굴절을 구조 함수로 부호 간 간섭을 구하고, 수치 해석을 통해 교란 상태에 따른 부호 간 간섭을 나타내고자 한다.

• Journal of information and communication convergence engineering
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• 제15권3호
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• pp.143-150
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• 2017

Absorption of microwave radio frequency signal by atmospheric rain is prevalent at frequencies above 10 GHz. This paper presents the studies on rain attenuation at 18 GHz for 3.2 km experimental link between Khumdang (Korea Telecom, KT station) and Icheon (National Radio Research Agency, RRA station). The received signal data for rain attenuation and rain rate were collected at 10 second intervals over a three year periods from 2013 to 2015. Out of several models, the paper present discussion and comparison of ITU-R P.530-16 model, Moupfouma model, Da Silva Mello model along with suitable rain attenuation prediction method. The limitation of research lies on the experimental system that is set up in only one location, however, the preliminary results indicate the application of suitable 1-minute rain attenuation model for specific site. The method provides useful information for microwave engineers and researchers in making decision over the choice of most suitable rain attenuation prediction in terrestrial links.

• 대한전자공학회논문지
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• 제8권4호
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• pp.17-24
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• 1971

직접광검파방식에 의하여 변조된 LASER광을 수중 1m 및 대기공간 1krn의 거리에 전송하여 검파했다. 이 검파를 자승검파법으로 해석했으며 이 실험에 사용한 검파장치의 설계와 구성을 밝혔다. 전파특성의 정량적 해석은 못했지만 기후조건에 따른 전파경향을 알아냈다. 기후변화에 따른 전파특성은 평균 25dB정도 감쇠했으며 수중에서의 감쇠계수는 약 0.4(m-1)이였다.

• 대한원격탐사학회지
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• 제10권2호
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• pp.63-82
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• 1994

Multitemporal analysis with remotely sensed data is complicated by numerous intervening factors, including atmospheric attenuation and occurrence of clouds that obscure the relationship between ground and satellite observed spectral measurements. A reconstruction system was developed to increase the discrimination capability for imagery that has been modified by residual dffects resulting from imperfect sensing of the target and by atmospheric attenuation of the signal. Utilizing temporal information based on an adaptive timporal filter, it recovers missing measurements resulting from cloud cover and sensor noise and enhances the imagery. The temporal filter effectively tracks a systematic trend in remote sensing data by using a polynomial model. The reconstruction system were applied to the AVHRR data collected over Korean Peninsula. The results show that missing measurements are typically recovered successfully and the temporal trend in vegetation change is exposed clearly in the reconstructed series.

• 전자공학회논문지D
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• 제34D권6호
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• pp.75-82
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• 1997

Today's wireless communication needs the super-high speed for picture transmission as well as voice. The optical communication with the very wide bandwidth is suitable for this demand. To fulfill the optical wireless communication, however, the atmospheric attenuation in rainy weather condition must be overcome. In the optical satellite up-link communication between geo-satellite and earth station, the factors of attenuation are turbulence, pointing error, scattering, and so on. The most serious factor for these is the scattering by rain. Under the weather conditiion of rain and cloud, in this paper, the atmospheic attenuation which affects the optical satellite up-link communication was considered, and the optimum idameter of the optical satellite transmitting antenna in the earth station versus elevation angles, data rates and rainfall rates was presented.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.65.4-65
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• 2001

In case of data transmission using the upper 10GHz frequency, rain results in attenuation of radio waves. And the most serious atmospheric effect in a satellite link is the rainfall. The attenuation of rainfall very seriously affects the quality of transmission line. Because the rain increases thermal noise and interference, and decreases the amplitude of the signal. KOWACO manages the VSAT system instead of VHF network for communication of rain and water-level data from 1998. The purpose of this system is to monitor the change of water-level and rain data during a flood duration. VHF system acquires the data by a call per a hour. But the satellite network obtains the data whenever event data occur. Thus the satellite network is more powerful than the VHF system. In study ...

• Journal of Multimedia Information System
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• 제6권3호
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• pp.155-164
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• 2019

We intended to confirm that microwave attenuation by tree leaves is strongly linked to water content in leaves. We sampled natural broadleaves, including Japanese cinnamon, and investigated their effects on the microwave (3 to 20 GHz) frequency characteristics using a network analyzer. Experiments determined that microwave attenuation by foliage increases as a linear function of frequency per unit weight (gram). As the frequency increases, the spatial resolution increases, but the phase difference (imaginary component) increases. So we solved the dispersion of phase difference by sweeping the frequency and taking the intermediate value. Based on these experimental results, we developed a microwave scanner on 10Ghz to describe foliage moisture as a image and to enable assessments of leaf condition. Photosynthesis is the process whereby plants synthesize oxygen and sugars from carbon dioxide and water, thereby converting light energy into chemical energy. Since water is a major parameter of photosynthesis, the quantity of water accumulated inside a leaf reflects leaf health. The equipment described here and related microwave technologies will help assess the capacity of leaves to absorb atmospheric carbon dioxide.

• 한국군사과학기술학회지
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• 제27권2호
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• pp.238-246
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• 2024

Modern military operations rely heavily on broadband communication and data transmission. Recently, the rising use of intelligent unmanned technology necessitates more frequencies. Free-space optical(FSO) communication can offer high-data-rate communications with high security and no need for licensing. Therefore, the FSO communication holds significant interest and potential in the defense industry. In this paper, we present design of a FSO communication terminal taking Korean domestic weather conditions into account. The domestic atmospheric attenuation is analyzed using several models and two-year meteorological information for a city in Korea, and this analysis is utilized to design the FSO communication terminal. The design results were verified using an FSO communication test bed, and we achieved an Ethernet bandwidth of approximately 1.86 Gbps at a distance of 1.3 km with the optical amplifier output power of the test bed set to about 20 dBm.