• Wind and Structures
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• v.15 no.6
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• pp.463-480
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• 2012

The effects of Reynolds number (Re), freestream turbulence intensity (Tu) and integral length scale (${\Lambda}$) on the drag coefficient ($C_d$) of a circular cylinder in cross flow were experimentally studied for $6.45{\times}10^3$ < Re < $1.82{\times}10^4$. With the help of orificed plates, Tu was fixed at approximately 0.5%, 5%, 7% and 9% and the normalized integral length scale (L/D) was varied from 0.35 to 1.05. Our turbulent results confirmed the general trend of decreasing $C_d$ with increasing Tu. The effectiveness of Tu in reducing $C_d$ is found to lessen with increasing ${\Lambda}$/D. Most interestingly, freestream turbulence of low Tu (${\approx}5%$) and large ${\Lambda}$/D (${\approx}1.05$) can increase the $C_d$ above the corresponding smooth flow value.

• 한국연소학회:학술대회논문집
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• 2005.10a
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• pp.132-137
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• 2005

The burning characteristics of interacting spherical droplet in a turbulent flow are numerically investigated. The transient combustion of 3-dimensionally arranged droplets, both the fixed streamwise droplet distances of 3 radii and 10 radii and different turbulence intensities, is studied. The results obtained from the present numerical analysis show that droplet vaporization rate for heptane droplet is insensitive to turbulence intensity, and that the transient flame configuration and retardation of droplet surface temperature augmentation with streamwise droplet spacing substantially influence vaporization process of interacting droplets. Single flame mode in which individual flames are merged into single flame, with decreasing streamwise droplet spacing, becomes faster. Therefore, vaporization rate of the second droplet with decreasing streamwise droplet spacing decreases remarkably with flame movement.

• Journal of Auto-vehicle Safety Association
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• v.12 no.3
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• pp.7-12
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• 2020

This paper has presented the headlight inspection standards and methods of two-wheeled motorcycles considering Korean Motor Vehicle Safety Standards (KMVSS), Korean Motor Vehicle Inspection Standards (KMVI) and the inspection standards of the International Motor Vehicle Inspection Committee (CITA). As a result of analyzing the headlight luminous intensity test result with fixed inspection equipment, 21% does not meet the inspection standard proposed in this study, and 33.3% in mobile inspection equipment does not meet. The average luminous intensity of motorcycle less than 50 cc is 8,340 cd, so all the lightweight small sized motor cycles do not meet the proposed headlight inspection standard.

• Asian-Australasian Journal of Animal Sciences
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• v.13 no.7
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• pp.883-887
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• 2000

One way of evaluating the effectiveness of a dairy breeding program is to measure response to selection. This may be direct or indirect. The objectives of this study were to estimate expected progress for direct selection on milk, fat and protein yields; to estimate the expected correlated responses on indirect selection for milk, fat and protein yields in Zimbabwean Holstein cattle and to establish the effect of selection intensity on responses. The Animal Model contained fixed effects of herd, year of calving, calving month, dry period, milking frequency and additive effects pertaining to cows, sires and dams. AIREML software package was used to analyse the data. The genetic and phenotypic parameters obtained in this study were used to compute direct and correlated responses to selection. Because of the higher heritabilities in first parity, genetic progress was found to be greater when selection was practised on first parity cows as compared to later lactations. It is therefore recommended that older cows in the herd be replaced with improved heifers so as to enhance genetic progress.

• KIEAE Journal
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• v.13 no.1
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• pp.133-140
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• 2013

The purpose of this study was to test the effectiveness of the light-shelf system combined with IT to save lighting energy in resident space. According to the multiple variables that affected intensity of illumination, various experiments were designed and conducted. The main findings of this study were following: (1)the optimal level of light-shelf system was formulated which met the appropriate range of intensity of illumination in living-room; (2)although the mixed light-shelf system indicated a high performance, it could often provide discomforts to residents according to the degree of exposure; (3)artificial lights using light-shelf system combined with IT showed a higher effectiveness than those using fixed light-shelf system displayed. This study provided initial information of light-shelf system formative processes that could contribute to the lighting energy diminution. Future studies should focus more on multiple approaches regarding different types of resident space planning.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.10
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• pp.103-109
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• 2003

We have proposed the 4-Dimensional Multiple-Subcarrier Modulation with fixed bias in Optical Wireless Communications. Here, the 4-D signal vectors are derived from the optimization technique of signal waveforms maximizing the minimum distance between signal points in an n-dimensional Euclidean sphere. The resulting vectors are used in generating the output amplitude of impulse generator in a Multiple-Subcarrier Modulation scheme. We have achieved that the normalized power requirement of the proposed system is maximum 3 dB and 3.3 dB smaller than those of normal QPSK, Reserved Subcarrier, and Minimum Power scheme, respectively. Also, in the range of 1.125 ∼ 1.25 of the normalized bandwidth, the proposed system has maximum 3 dB, 2 ∼ 4 dB, 0 ∼ 3 dB smaller bandwidth requirement compare to normal QPSK, Res. Subcarrier, Min. Power schemes, respectively.

• Korean Journal of Optics and Photonics
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• v.10 no.5
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• pp.405-412
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• 1999

We propose an effective algorithm, which can predict the detailed behavior of the intensity-modulated high speed optical signal after propagating through an optical fiber. The alogrithm is based on the SSF (Split Step Fourier) Method, however, the step size is automatically calibrated in each calculation step to reduce the number of calculations within given round-off error bound. Applying the algorithm to the 2.5 Gbps 100 km transmission and 10 Gbps 40 km transmission simulations, we achieved the calculation time reduction by maximum 1/120 and 1/56 of the calculation time by using the SSF fixed step algorithm previously known. The root-mean-square of the round-off error was kept within -30 dB compared to the signal level throughout the calculation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.6
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• pp.656-664
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• 1997

This paper introduces a fixed radio-relay link design simulator with which we can select the station site and the frequency and can predict the performance of the radio-relay links. The simulator analyzes the path profile, the fading effects, the availability, the rain attenuation and the interference of the cosidered radio path using the digital terrain data and the rain intensity data. The calculation algorithms used in this simulator are mostly from the recommendations of the ITU-R. All the modules of the simulator are performed in full GUI mode and the input and output parameters are displayed interactively. This simulator could be used to the fixed radio-relay link design and the LMDS design.

• The Journal of Asian Finance, Economics and Business
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• v.9 no.3
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• pp.23-31
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• 2022

The study investigates the effect of trade openness on the economic growth of agricultural countries. The information of export, import, gross domestic product (GDP), Gross Fixed Capital Formation (GFCF), and population of 72 agrarian nations generated by the World Bank from 2011 until 2020 is used for data examination. Then, before panel data analysis, a preferred model is chosen from among common-effects, fixed-effects, and random effects. The best model turns out to be a fixed-effect model. The result reports that from 2011 to 2020; 16 out of 72 nations have succeeded in experiencing positive economic growth, the value of GFCF was US$ 2,859.04 billion, and later grew by 19 percent to US$ 3,393.73 billion, the population tends to increase continuously year by year, and 2 out of 72 countries experienced export plus import exceed their GDP. Moreover, trade openness is positively associated with economic growth, with a coefficient of 3.81. Besides that, an increase in GFCF may boost economic growth by approximately 3.32 percent. On the contrary, one percent additional population significantly delivers around 25.46 percent negative economic growth. To sum up, the higher intensity of products or services sold and bought abroad may enhance the economic performance.

• Journal of Korea Multimedia Society
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• v.8 no.4
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• pp.509-515
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• 2005

This paper explores the throughput of DCF protocol with both the traffic intensity and MSDU size at the MAC layer in the 802.11a wireless LAN. By exploring the throughput of DCF protocol with the data rate of 6Mbps, 12 Mbps, 24 Mbps and 54 Mbps, we find the fact that the less the data rate be, the higher the throughput be. We also find, from the throughput calculation by means of traffic intensity and MSDU size, that the longer the MSDU size is, the higher the throughput is. We also found the traffic intensity that the throughput is at the maximum point with the fixed MSDU size.