• 한국농림기상학회지
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• 제8권2호
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• pp.61-67
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• 2006

내음성정도가 서로 다른 두 수종 먼나무와 붓순나무를 대상으로 높은 광도조건인 자연상태와 낮은 광도 조건인 비음 처리구로 나누어, 두 수종간의 적응 반응을 비교하였다. 두 수종의 묘목을 처리구에서 각각 1년간 비음처리하였을 때, 엽록소함량과 광합성계, 엽육세포내 $CO_2$농도, 수분이용효율의 특성을 조사하였다. 엽록소 함량은 두 수종모두 자연조건(full sunlight)일 때, 비음처리구에 비하여 낮은 엽록소 함량들(Chl a, Chl b, Chl a+b)을 나타냈으며, 붓순나무에서 특히 자연조건과 비음 처리구간의 엽록소 함량의 차이가 크게 나타났다. 한편, 중용수인 먼나무는 PPFD $1000\;{\mu}mol\;m^{-2}s^{-1}$ 이상 일 때, 자연조건(full sunlight)에서 높은 광합성율과 높은 수분이용효율을 보였지만, PPFD $1000\;{\mu}mol\;m^{-2}s^{-1}$ 이하에서는 비음처리구에서 자연조건에 비해 더 높은 광합성율과, 수분이용효율을 나타냈다. 이에 반해 붓순나무는 모든 광도에서 비음처리를 하지 않은 묘목이 비음처리를 한 묘목에 비해 낮은 광합성율과 수분이용효율을 나타냈다. 먼나무가 탄력적으로 광도변화에 따라 유동성 있는 반응을 보이는 것에 비해 내음성이 강한 붓순나무는 광환경 변화에 따른 민감성이 낮게 나타나는 것을 알 수 있었다.

• International Journal of Advanced Culture Technology
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• 제8권2호
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• pp.1-5
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• 2020

As the world gradually advances to an aging society, the quality of human life is valued. Among them, 'quality of sleep' is very closely related to quality of life. Recently, Korea expanded health insurance coverage for "sleep disorders". Particularly, as the number of sleep multiple tests and prescriptions for sleep aids has increased rapidly, much attention has been focused on the related medical service environment. Therefore, this study looked at an in-depth interview of 11 hospitals to see what treatment delivery system is being established when the government applies health insurance for 'sleep disorders'. In conclusion, the organizations with the most average number of sleep polyp tests per day were found to have more sleep polyp labs (hardware) and more full-time specialists. Also, the polysomnography lab (hardware) and the specialist's full-time status (software) did not necessarily result in a "positive pressure regulator prescription" that can solve "sleep apnea" caused by "sleep ailments". Rather, it was found that the number of days of sleep multiple laboratories (hardware), the number of full-time specialists (software) or the specialty majors (software) had a greater impact. In particular, the higher the specialist's full-time personnel (software) index (=6.000), the higher the sleep-inducing agent prescription rate(=1.000), and the lower the specialist's full-time personnel (software) index (=1.000), the higher the sleep-inducer's prescription rate(= 0.010) Was low. In addition, even if the professional full-time personnel(software) index was the same (=1.000), the hospital type was lower as it was closer to the public hospital(=0.067) and higher at the specialized hospital (= 0.933). In the case of university hospitals, when the full-time specialists (software) are in the same condition (= 1.000), the frequency of use of the sleep laboratory (=1.000) and the sleep test rate (= 1.000) were all the same.

• Journal of electromagnetic engineering and science
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• 제7권1호
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• pp.17-27
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• 2007

Jacket matrices which are defined to be $n{\times}n$ matrices $A=(a_{jk})$ over a field F with the property $AA^+=nI_n$ where $A^+$ is the transpose matrix of elements inverse of A,i.e., $A^+=(a_{kj}^-)$, was introduced by Lee in 1984 and are used for signal processing and coding theory, which generalized the Hadamard matrices and Center Weighted Hadamard matrices. In this paper, some properties and constructions of Jacket matrices are extensively investigated and small orders of Jacket matrices are characterized, also present the full rate and the 1/2 code rate complex orthogonal space time code with full diversity.

• ETRI Journal
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• 제28권1호
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• pp.87-90
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• 2006

In this letter, we propose a quasi-orthogonal space-time-frequency (QOSTF) block coded orthogonal frequency division multiplexing (OFDM) that can achieve full symbol rate with four transmit antennas. Since the proposed QOSTF-OFDM cannot achieve full diversity, we use a diversity advantage collection with zero forcing (DAC-ZF) decoder to compensate the diversity loss at the receiving side. Due to modulation advantage and collected diversity advantage, the proposed scheme exhibits a better bit-error rate performance than other orthogonal schemes.

• Journal of Communications and Networks
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• 제12권3호
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• pp.240-245
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• 2010

Jacket matrices, motivated by the complex Hadamard matrix, have played important roles in signal processing, communications, image compression, cryptography, etc. In this paper, we suggest a novel approach to design a simple class of space-time block codes (STBCs) to reduce its peak-to-average power ratio. The proposed code provides coding gain due to the characteristics of the complex Hadamard matrix, which is a special case of Jacket matrices. Also, it can achieve full rate and full diversity with the simple decoding. Simulations show the good performance of the proposed codes in terms of symbol error rate. For generality, a kind of quasi-orthogonal STBC may be similarly designed with the improved performance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권1호
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• pp.16-33
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• 2019

In this paper, a full-duplex NOMA relaying based underlay device-to-device (D2D) communication scheme is proposed, in which D2D transmitter assists cellular downlink transmission as a full-duplex relay. Specifically, D2D transmitter receives signals from base station and transmits the superposition signals to D2D receiver and cellular user in NOMA scheme simultaneously. Furthermore, we investigate the power allocation under the proposed scheme, aiming to maximize D2D link's achievable transmit rate under cellular link's transmit rate constraint and total power constraint. To tackle the power allocation problem, we first propose a power allocation method based on linear fractional programming. In addition, we derive closed-form expressions of the optimal transmit power for base station and D2D transmitter. Simulation results show that the performance of two solutions matches well and the proposed full-duplex NOMA relaying based underlay D2D communication scheme outperforms existing full-duplex relaying based D2D communication scheme.

• 한국산학기술학회논문지
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• 제12권12호
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• pp.5843-5848
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• 2011

EVRC에서는 채널 스펙트럼의 효율을 높이고 시스템의 소비 전력을 줄이기 위하여, 통화시간 중에서 사용자가 말을 할 때만 음성신호를 압축하여 전달하고, 말을 하지 않을 때는 음성신호를 전달하지 않는다. 또한, EVRC에서는 음성 프레임을 1, 1/2, 1/8의 세 가지 전송률로 구분하여 다르게 처리 하고 있으며, 예를 들어, 1/8 전송률은 입력 신호가 묵음구간인 것을 의미한다. 본 연구에서는 LSP 파라미터의 분포특성을 이용한 유성음 구간, 무성음 구간, 묵음 구간을 구분하는 방법을 사용하여, 유성음인 경우에 대해 1 rate으로 부호화하고, 무성음 구간의 경우는 1/2 rate, 묵음의 경우에는 1/8 rate으로 전송하는 방법에 대하여 제안하였다. 즉, EVRC에서 full rate으로 보내는 부분에 대해서는 기존의 방식을 그대로 적용하며, half rate은 유성음, 무성음을 구분하여 유성음일 경우 full rate으로 바꾸어 전송하였고, 묵음에 대해서는 EVRC 기본 rate을 적용하였다. 실험과정에서는, SNR, ASDM, 전송률을 측정하였으며, 제안한 알고리즘을 사용하는 경우 EVRC에 비해 음성품질이 향상됨을 증명하였다.

• 대한수학회지
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• 제57권5호
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• pp.1167-1186
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• 2020

This paper considers the case of pricing discretely-sampled variance swaps under the class of equity-interest rate hybridization. Our modeling framework consists of the equity which follows the dynamics of the Heston stochastic volatility model, and the stochastic interest rate is driven by the Cox-Ingersoll-Ross (CIR) process with full correlation structure imposed among the state variables. This full correlation structure possesses the limitation to have fully analytical pricing formula for hybrid models of variance swaps, due to the non-affinity property embedded in the model itself. We address this issue by obtaining an efficient semi-closed form pricing formula of variance swaps for an approximation of the hybrid model via the derivation of characteristic functions. Subsequently, we implement numerical experiments to evaluate the accuracy of our pricing formula. Our findings confirm that the impact of the correlation between the underlying and the interest rate is significant for pricing discretely-sampled variance swaps.

• 한국통신학회논문지
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• 제35권12C호
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• pp.1020-1028
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• 2010

릴레이는 차세대 이동통신 시스템에서 기지국의 서비스 커버리지 영역을 확대하고 음영지역을 해소하기 위해 반드시 필요한 기술이다. 하지만, 기존의 릴레이 관련 연구는 주로 반이중 모드, 즉 서로 다른 시간 혹은 주파수에서 송수신을 수행하도록 제한하고 있다. 반이중 릴레이는 구현이 쉬운 반면 릴레이 송수신 지원 구분이 필요하기 때문에 전체 시스템 용량이 줄어드는 단점이 있다. 본 논문에서는 다중 안테나를 갖는 전이중 릴레이의 다중 사용자 precoding 및 sum rate 정합 기반의 전력 할당 방식을 제안한다. 전이중 릴레이는 같은 주파수에서 동시에 송수신을 수행하기 때문에 릴레이의 송수신 안테나 사이에 발생하는 자기 간섭 문제를 해결해야 한다. 본 논문에서 제안하는 precoding 기법을 통해 다중 사용자 MIMO 전송이 가능하면서 동시에 전이중 릴레이의 자기 간섭을 제거할 수 있다. 또한, 릴레이가 기지국으로부터 수신하는 정보량과 단말국으로 전달하는 정보량이 동일하도록 하는 조건 하에서 전체 시스템 용량을 최대화하는 전력 할당 기법을 제안한다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.421-424
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• 2006

High nitrogen steels (HNS) exhibit both high strength and ductility during tensile deformation. In the present study the Fe-18Cr-14Mn-4Ni-0.9N high nitrogen steel was heat treated at $1000^{\circ}C$ and $1100^{\circ}C$ to produce $Cr_2N$ precipitates in austenite matrix and full austenite microstructures, respectively. Tensile tests of the heat treated specimens were performed at two different strain rates of 0.05/sec and 0.00005/sec. Each tensile curve of the specimens could be well characterized by the the modified Ludwik equation. Plastic deformation of the steel was adequately represented by the four parameters of the modified Ludwik equation. At 0.05/s strain rate, the specimen with the $Cr_2N$ precipitate exhibited higher strength than the full austenite specimen, while the full austenite specimen showed better mechanical properties at 0.00005/s strain rate. It was found that the $Cr_2N$ precipitates influences deformation behavior of the high nitrogen steel significantly.