• ETRI Journal
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• 제19권1호
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• pp.1-12
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• 1997

In this paper, we present an improved multicarrier direct sequence (DS) code division multiple access (CDMA) scheme by modifying the system originally proposed by Kondo and Milstein [13]. In this modified system, different spreading sequences multiplied by a data sequence modulate different carriers. This is to prevent the multiple access capability from reducing when the fading characteristics of different carrier frequencies are highly correlated. We have derived a formula which determines the mean values of the relative received signal strength in a single carrier DS CDMA rake system and in a multicarrier DS-CDMA system. We present results on the comparison of the bit error rate (BER) performance of the two systems including the effect of correlation between fading characteristics of different frequencies under various multipath fading conditions. The results indicate that with 50 users the modified multicarrier DS CDMA system can achieve an uncoded irreducible BER of $1.7{\times}10^{-3}$ with an average received signal-to-noise ratio per bit of 10dB, which is better that $3.0{\times}10^{-3}$ achieved by the single carrier DS CDMA rake system, and also show that if multicarrier CDMA system is used with respect to single carrier CDMA system, the SNR gain is up to 4.5 dB for the uncode BER of $10^{-3}$ being achieved.

• Asian-Australasian Journal of Animal Sciences
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• 제12권2호
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• pp.186-188
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• 1999

This study was conducted to investigate the effects of four levels (0, 10, 20, 40 %) of sugar-beet pulp (SB pulp) supplementation to Italian ryegrass hay (IRG hay) on the fiber degradability of IRG hay in the rumen of goats. The following results were obtained: Degradabilities of DM, NDF, ADF and hemicellulose of IRG hay in the rumen increased significantly (p<0.05) by 10 % level supplementation of SB pulp to IRG hay. This was probably due to the increased numbers (p<0.05) of total viable bacteria, pectin-fermenting, xylan-fermenting and cellulolytic bacteria in the rumen in the increased supply of degradable pectic substances and hemicellulose at 10% level supplementation of SB pulp pectin. In 40% supplementation of SB pulp, ruminal pH was lowered by the fermentation of increased amount of molasses from SB pulp, resulting in the depression of growth of fiber fermenting bacteria and hence the decrease in degradabilities of cell wall fractions. It was suggested from this study that the sugar-beet pulp supplementation to forages at the level of 10% in the total diet increased fiber degradation of forage in the rumen of goats.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.387-394
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• 2000

Theoretical and experimental study is conducted on the contact pressure distribution of a radial tire in motion under various camber angles. Tire construction is modelled by a spring bedded elastic ring, consisted of sidewall springs and a composite belt ring. The contact area is assumed to be a trapezoidal shape varying with camber angles and weighted load. The basic equation in a quasi-static form is derived for the deformation of a running belt with a constant velocity by the aid of Lagrange-Euler transformation. Galerkin's method and stepwise calculation are applied for solving the basic equation and the mechanical boundary condition along both sides of the contact belt part subjected to shearing forces transmitted from the sidewall spring. Experimental results on the contact pressure, measured by pressure sensors embedded in the surface of the drum tester, correspond well with the calculated ones for the test tire under various camber angles, running velocities and weighted loads. These results indicate that a buckling phenomenon of the contact belt in the widthwise direction occurs due to the effect of camber angle.

• Journal of Photoscience
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• 제9권2호
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• pp.158-161
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• 2002

UV-B radiation gives harmful effects on plants, such as production of several types of DNA lesions, and growth inhibition. On the other hand, plants have some protective mechanisms, including filtering effect due to accumulation of phenolic compounds in epidermal cells and reactivation of DNA lesions, which are enhanced by UV-B irradiation. We have investigated the mechanism of UV-B effects on plants using cucumber seedlings as plant materials. Cucumber plants were cultivated in an artificially lit growth chamber. Supplemental UV-B irradiation, of which intensity was almost equal to the level of natural sunlight, retarded the growth of first leaves. The growth retardation must result trom the inhibition of cell division and/or cell growth. Microscopical observation of leaf epidermis suggested that the growth retardation might be mainly caused by cell growth inhibition. The retardation was, however, restored within 2 or 3 days after the termination of UV-B irradiation. It is known that UV-B irradiation lowers the activity of photo system II (PS II). In the present experimental conditions, however, UV-B irradiation has little effect on PS II activity as estimated by chlorophyll fluorescence. The stomatal conductance, a major factor determining photosynthetic rate, of first leaves increased during the growth. The increase of stomatal conductance was suppressed by UV-B irradiation and restored by termination of the irradiation. It has not been clear, however, what mechanisms are involved in the suppression of increase of stomatal conductance.

• Asian-Australasian Journal of Animal Sciences
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• 제19권4호
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• pp.533-540
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• 2006

In this study, the possibility of green tea waste (GTW) as a new ingredient of byproducts-mixed silage was investigated. Characteristics of GTW were low in dry matter (DM) content (20%), and high in crude protein (30 to 36%) and tannins (8.5%). The GTW was added to mixed silages composed of tofu cake, rice straw and rice bran that are locally available in Japan. In experiment 1, the effect of GTW addition to silage made from various patterns of byproducts mixture based on tofu cake was studied. In experiment 2, the effect of GTW addition and storage temperature on fermentation characteristics, nutrient contents and in vitro ruminal gas production of byproducts-mixed silages were examined. In experiment 1, GTW addition on tofu cake accelerated acetic, propionic and butyric acid accumulation in the silage. When rice straw was mixed with tofu cake, DM content was increased from 47 to 56%, lactic acid was the main acid and the pH was decreased below 4.2. In this case, GTW addition to those mixtures did not affect acid concentrations of the silage. In experiment 2, GTW addition to the byproducts mixture increased lactic acid concentration, decreased the pH and DM loss of the silages. In GTW treatments, tannin concentration was lower in the silage stored at $30^{\circ}C$ than $15^{\circ}C$. Addition of GTW into the silage also increased in vitro ruminal gas production. It was concluded that addition of GTW into byproducts-mixed silage enhanced lactic acid fermentation when there were insufficient materials for lactic acid production. Utilization of GTW as an ingredient in mixed silages would be effective in enhancing fermentation characteristics, lowering tannin content and in vitro ruminal gas production.

• Asian Journal of Atmospheric Environment
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• 제10권4호
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• pp.179-189
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• 2016

Here we evaluated the effect of using water retentive pavement or WRP made from fly ash as material for main street in a real city block. We coupled computational fluid dynamics and pavement transport (CFD-PT) model to examine energy balance in the building canopies and ground surface. Two cases of 24 h unsteady analysis were simulated: case 1 where asphalt was used as the pavement material of all ground surfaces and case 2 where WRP was used as main street material. We aim to (1) predict diurnal variation in air temperature, wind speed, ground surface temperature and water content; and (2) compare ground surface energy fluxes. Using the coupled CFD-PT model it was proven that WRP as pavement material for main street can cause a decrease in ground surface temperature. The most significant decrease occurred at 1200 JST when solar radiation was most intense, surface temperature decreased by $13.8^{\circ}C$. This surface temperature decrease also led to cooling of air temperature at 1.5 m above street surface. During this time, air temperature in case 2 decreased by $0.28^{\circ}C$. As the radiation weakens from 1600 JST to 2000 JST, evaporative cooling had also been minimal. Shadow effect, higher albedo and lower thermal conductivity of WRP also contributed to surface temperature decrease. The cooling of ground surface eventually led to air temperature decrease. The degree of air temperature decrease was proportional to the surface temperature decrease. In terms of energy balance, WRP caused a maximum increase in latent heat flux by up to $255W/m^2$ and a decrease in sensible heat flux by up to $465W/m^2$.

• 한국측량학회:학술대회논문집
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• 한국측량학회 2010년 춘계학술발표회 논문집
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• pp.201-206
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• 2010

한국 측지 VLBI 시스템 건설 프로젝트는 2008년 11월에 공식적으로 시작되었으며, 2011년 말까지 완료하는 것을 목표로 하고 있다. 프로젝트의 공식 명칭은 한국 측지 VLBI 시스템(Korea VLBI system for Geodesy)이며 주목적은 한국측지 기준점을 유지 관리하는 것이다. KVG의 경우 수소 메이저 주파수 표준이 위치한 관측실은 안테나와 수십 m 떨어진 분리된 건물에 있다. 따라서 KVG는 위상 변동 효과가 축소된 기준신호를 안테나로 전달하는 라운드 trip 시스템을 갖출 것이다. KVG의 라운드 trip 시스템은 metal이나 광케이블을 모두 사용할 수 있을 뿐만 아니라 K5/VSSP32 샘플러를 이용하여 위상 변동을 직접적으로 측정하는 것도 가능하도록 설계되었다. 여기서는 라운드 trip 시스템의 기본원리와 KVG를 위한 새로운 타입의 라운드 trip 시스템을 소개할 것이다.

• 천문학회보
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• 제41권1호
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• pp.47.3-48
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• 2016

The zodiacal light (ZL), combination of the sunlight scattered by and the infrared light emitted by the interplanetary dust (IPD) particles, changes with time due to the asymmetric distribution of the particles with respect to the Earth's orbit. Especially, the variation of the ZL brightness toward the ecliptic poles are useful to probe the properties of the global distribution of the IPD because we can evade the effect of the small scale structures, such as the asteroidal dust bands. The ecliptic poles are frequently visited by the infrared (IR) space telescopes owing to their sun-synchronous orbits or for specific purposes. We collect and analyze the observations toward the ecliptic poles by COBE/DIRBE, AKARI, and MIRIS, covering the wavelengths from about 1 to $25{\mu}m$. The observed seasonal variations of the ZL are modeled with a simple IPD cloud model to derive cloud parameters. The parameters are compared with those of the empirical cloud models by Kelsall et al. (1998) and Kondo et al. (2016), and the discrepancies are discussed.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.235-240
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• 2006

Ionospheric scintillation induces a rapid change in the amplitude and phase of radio wave signals. This is due to irregularities of electron density in the F-region of the ionosphere. It reduces the accuracy of both pseudorange and carrier phase measurements in GPS/satellite based Augmentation system (SBAS) receivers, and can cause loss of lock on the satellite signal. Scintillation is not as strong at mid-latitude regions such that positioning is not affected as much. Severe effects of scintillation occur mainly in a band approximately 20 degrees on either side of the magnetic equator and sometimes in the polar and auroral regions. Most scintillation occurs for a few hours after sunset during the peak years of the solar cycle. This paper focuses on estimation of the effects of ionospheric scintillation on GPS and SBAS signals using a software receiver. Software receivers have the advantage of flexibility over conventional receivers in examining performance. PC based receivers are especially effective in studying errors such as multipath and ionospheric scintillation. This is because it is possible to analyze IF signal data stored in host PC by the various processing algorithms. A L1 C/A software GPS receiver was developed consisting of a RF front-end module and a signal processing program on the PC. The RF front-end module consists of a down converter and a general purpose device for acquiring data. The signal processing program written in MATLAB implements signal acquisition, tracking, and pseudorange measurements. The receiver achieves standalone positioning with accuracy between 5 and 10 meters in 2drms. Typical phase locked loop (PLL) designs of GPS/SBAS receivers enable them to handle moderate amounts of scintillation. So the effects of ionospheric scintillation was estimated on the performance of GPS L1 C/A and SBAS receivers in terms of degradation of PLL accuracy considering the effect of various noise sources such as thermal noise jitter, ionospheric phase jitter and dynamic stress error.

• 보건교육건강증진학회지
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• 제26권5호
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• pp.57-70
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• 2009

목적: 이 연구는 맞벌이 가정의 부친의 육아참가 발생과정을 인과관계모델로 구축하여 이 모델에 대한 데이터로의 적합성에 대해 검토하는 것을 목적으로 하였다. 방법: 조사대상은 I 현 A,B시, II현 C시의 어린이집 21곳과 유치원 4곳을 이용하는 2,006세대(A시:499세대, B시:1113세대, C시:98세대)의 부친으로 하였다. 조사내용은 부친의 연령, 학력, 자녀수, 막내자녀나이, 부모역할관, 1일 노동시간, 귀가시간, 육아참가로 구성하였다. 결과: 부친의 육아참가 발생과정 모델의 데이터로의 적합성에 대해 검토한 결과, 적합도 지표는 CFI=0.912, RMSEA=0.082였다. 경로계수를 살펴보면, 막내자녀나이에서 긍정적 부모역할관으로 향하는 경로계수는 0.08, 긍정적 부모역할관에서 육아참가로 향하는 경로계수는 0.19로 통계학적으로 유의하였다. 또한 저해요인으로서 상정한 귀가시간과 1일 노동시간은 부친의 긍정적/부정적 부모역할관으로부터 영향을 받지 않고, 육아참가에 직접효과를 나타내었다. 이때, 귀 시간에서 육아참가로 향하는 경로계수는 -0.43, 노동시간에서 육아참가로 향하는 경로계수는 -0.13, 귀가시간과 노동시간 간의 상관계수는 0.80이었다. 결론: 이상의 결과를 통해 본 연구에서 제기한 모델의 타당성을 증명하였고, 부친의 육아참가 발생 매커니즘에 관한 기초자료로 활용될 수 있음을 시사한다.