• Korean Journal of Remote Sensing
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• v.35 no.5_2
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• pp.851-859
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• 2019

The COMS satellites take image of the Korean Peninsula every 15 minutes, but due to the limitations of the observational channels, they tend to underestimate when estimating rainfall. In this study, we developed satellite-based rainfall estimation technology using COMS and GPM that can be used in the heavy rain on the Korean Peninsula. The time resolution and spatial resolution of COMS satellites and GPM satellites were matched to improve accuracy using GPM IMERG data. As a result, it showed that the number of correlations with the ASOS observations was more than 0.7, enabling the estimation of rainfalls that are more accurate than the estimates of rainfall by COMS satellites. It is believed that the application of the subsequent satellite(GK-2A) will provide more accurate rainfall estimation information in the future. Therefore, we expect greater utilization in disaster management for the ungauged areas.

• The Journal of the Acoustical Society of Korea
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• v.37 no.6
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• pp.404-411
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• 2018

This paper proposes a dolphin whistle mimicking underwater communication method using FSK (Frequency Shift Keying) and method to improve BER (Bit Error Rate) performance by using multipath gain combining. The proposed method divides whistle sound into short time intervals and transmits FSK modulated signal that ensures orthogonality of the symbol. Multipath gain can be obtained by using characteristic of mimicked signal frequency that varies with time. To demonstrate the performance of the proposed method, computer simulations and lake experiments were conducted. Computer simulation results show that an additional multipath gain is obtained by multipath. From lake experiments, when symbol length is 20 msec and modulation band is 900 Hz, the proposed FSK method with multipath combining gain obtains BER of 0.002, which is better than CSS (Chirp Spread Spectrum) with BER of 0.185. he proposed based on FSK method has higher imitation degree than the CSS method by analyzing mean cross-correlation value in the time - frequency domain of the imitated signal and actual whistle signal.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.11
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• pp.1477-1485
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• 2021

Recently, super-resolution has been intensively studied only on upscaling models with integer magnification. However, the need to expand arbitrary magnification is emerging in representative application fields of actual super-resolution, such as object recognition and display image quality improvement. In this paper, we propose a model that can support arbitrary magnification by using the weights of the existing integer magnification model. This model converts super-resolution results into the DCT spectral domain to expand the space for arbitrary magnification. To reduce the loss of high-frequency information in the image caused by the expansion by the DCT spectral domain, we propose a high-frequency attention network for arbitrary magnification so that this model can properly restore high-frequency spectral information. To recover high-frequency information properly, the proposed network utilizes channel attention layers. This layer can learn correlations between RGB channels, and it can deepen the model through residual structures.

• 지역과문화
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• v.7 no.2
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• pp.155-172
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• 2020

This study analyzed the factors to customer attitude on the goods and service introduced in UGC(User Generated Contents) and explored the difference between Korean and Chinese customers. For the first research question, the hypothetical factors were selected through literature review, the area of which are media consumption, social media and effect of advertising. In this study examined 4 independent variables: information, reliability, BJ attractiveness and customer innovation. Methodologies are confirmatory factor analysis, correlation analysis and multi regression. Result showed that reliability, BJ attractiveness and customer innovation are statistically significant. According to the β value, the biggest one is customer innovation, the second one is BJ attractiveness and the third one is reliability. The influence of information on customer attitude is not statistically significant. The result is well-aligned with the prior studies. The information factor's influence, however, is disputable because some prior studies shows that it is not significant when the research samples are recently developed channel such as mobile or social media commerce platforms. It is necessary to identify the root causes why the information factor is not significant in some research cases. For the second research question, this study used independent t-test between Korean and Chinese customers. The result shows that the difference in reliability, BJ attractiveness and attitude are stastically significant, and the ratings of Chinese customers are higher. This result caused by the difference of media commerce environment between Korea and China. Information and customer innovation didn't show significant difference.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.46 no.1
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• pp.1-9
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• 2009

In this paper, a 2.4 GHz doppler radar system consisting of a doppler radar sensor and a baseband module were designed to detect heart beat and respiration signal without direct skin contact. The doppler radar system emits RF signal of 2.4 GHz toward human chest, and then detects phase modulation of the reflected signal so as to investigate cardiopulmonary activities. The heartbeat and respiration signals acquired from I/Q channels of the doppler radar system are applied to the pre-processing circuit, the amplification circuit, and the offset circuit of the baseband module. The designed system was tested on mouse, rabbit and mankind, which have different range of heart rates and respiration signals, to evaluate detection accuracy of the system. ECG acquisition system and respiration transducer were used to generate the reference signal. In our experiments, a performance of detection were found to be high in the case that the subject stays still. In this paper, we confirmed that non-contact heart beat and respiration detection using the doppler radar has the possibility and limitation according to distance, cardiopulmonary activities, range of heart rates and respiration.

• Membrane Journal
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• v.16 no.4
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• pp.241-251
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• 2006

In this study, crosslinked copolyimides with random (r-) and block (b-) structure were fabricated using N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid and pentanediol as crosslinkers. Linear r- and b-sulfonated copolyimides were also fabricated for comparison. Ion exchange capacities of r- and b-copolyimides were very similar to each other owing to their strong dependence of sulfonic acid content. The physical crosslinking via dimerization of carboxylic acid groups induced a reduced average interchain distance in b-copolyimide without crosslinkers. Consequently, its water uptake and methanol permeability were lower than those of r-sulfonated copolyimides. Simultaneously, the reduced interchain distance increased the content of fixed-charged ions per unit volume. The high fixed-charged ion density contributed to an enhancement of proton conductivity In the b-sulfonated copolyimide. Crosslinking caused the reduction of average interchain distance between polymer chains irrespective of types of crosslinker and polymer structure, leading to low methanol permeability. On the contrary, their proton conductivity was improved owing to formation of effective hydrophilic channels responsible for proton conduction. In particular, this trend was observed in r-copolyimide containing a fixed charged ion.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.3
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• pp.1-8
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• 2009

DS-CDMA system has very low bandwidth efficiency, hence it is difficult to maintain high spreading gain for high speed data transmission. Offset stacked spreading CDMA(OSS-CDMA) is a transmission scheme where spreading codes with chip offsets are overlapped, then transmitted. This kind of system requires a code set that guarantees orthogonality between codes in the set of any cjip offset. An orthogonal complementary code set has a property that the crosscorrelation function between codes in the group is zero for all shifts, hence it can be used for an OSS-CDMA system. In an OCC-OSS CDMA system each user is assigned an orthogonal complementary code group. User data bit is spread by the given codes and overlapped, and the code sequences are transmitted with multicarrier. However, the offset stacked spread sequences are multilevel, and the number of symbol levels is increases as the spreading efficiency is increased. When the OSS sequence is transmitted with MPSK mapping, the signal constellation becomes dense, and the system is easily affected by channel impairments. In this paper, we propose a level clipping scheme on OSS sequence before MPSK modulated. Simulations have been carried out to investigate the BER performance of the OCC-OSS CDMA system in AWGN environment. The results show that proposed scheme outperform the scheme without level clipping.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.12
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• pp.1352-1370
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• 2010

In this paper, we investigated the shadow area of radio programs which are currently being broadcast via FM 102.5 MHz in Jeollabuk-do consisting of 6 cities and 8-guns. The field strength data of FM 102.5 MHz was used with criterion of shadow area. As a result, the field strength of the eastern mountainous area in Jeollabuk-do was very low. We also measured, compared and analyzed the field strength of 102.5 MHz(TBN-Jeonju), 100.7 MHz(KBS) and 99.1 MHz (MBC) in Jeollabuk-do. Based on the field strength data, we tried to find what correlation exists and how much influence is between difference of antenna output power and solution of shadow area. In result, enhancement of antenna output power is not solution in terms of reducing the shadow Area of 102.5 MHz(TBN-Jeonju). In addition, we measured, compared and analyzed the field strength of 102.5 MHz(TBN-Jeonju) and 106.9 MHz(EBS). In fact, the relay stations with 104.1 MHz, 104.9 MHz, 105.3 MHz and 107.5 MHz of EBS FM has a number of FM relay stations in the eastern mountainous area of Jeollabuk-do. As a result, we confirmed that EBS almost did not have shadow area in the eastern mountainous area of Jeollabuk-do based on the field strength data. As in the case of EBS and KBS, we suggest installing TBN-Jeonju FM relay station with the best solution to reducing the shadow area to extend the audible range of TBN-Jeonju.