• Title/Summary/Keyword: A/B Ratio

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Numerical Simulation of the Effect of Pressure Fluctuation on the Modulation of Equivalence Ratio at the Fuel Injection Hole (압력변동이 연료 분사구에서의 당량비 변동에 미치는 영향에 관한 수치 해석)

  • Kim, Hyeon-Jun;Hong, Jung-Goo;Shin, Hyun-Dong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.31 no.3 s.258
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    • pp.292-299
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    • 2007
  • In gas turbine technology, the flame stability is inherently greater in conventional diffusion type combustion over a wider range fuel to oxidizer ratio. However, premixed type combustion which has narrow flame stability region, is widely used due to environmental reason. It has been observed in experiments that combustion instability of low frequency (${\sim}10Hz$) results from the modulation of equivalence ratio at fuel injection hole when a pressure fluctuation propagates upwards along the channel of the burner under an unchoked fuel flow condition. In this study, a commercial program was used to determine how the fuel flow rate changed with respect to the pressure, velocity of the fuel flow and the mass fraction in a choked and an unchoked condition. The calculation focuses on the upstream of the dump plane to know how the forced pressure with the fuel injection conditions affects the modulation of the equivalence ratio. Therefore, it is found that pressure fluctuation leads to oscillation of mass flow rate and then results in equivalence ratio modulation under the unchoked fuel flow condition.

Effects of different Bacillus licheniformis and Bacillus subtilis ratios on nutrient digestibility, fecal microflora, and gas emissions of growing pigs

  • Kim, Yong Ju;Cho, Sung Bo;Song, Min Ho;Lee, Sung Il;Hong, Seok Man;Yun, Won;Lee, Ji Hwan;Oh, Han Jin;Chang, Se Yeon;An, Jae Woo;Go, Young Bin;Song, Dong Cheol;Cho, Hyun Ah;Kim, Hyeun Bum;Cho, Jin Ho
    • Journal of Animal Science and Technology
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    • v.64 no.2
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    • pp.291-301
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    • 2022
  • The objective of this study was to evaluate the effects of different mixing ratios of Bacillus licheniformis and Bacillus subtilis in diets on nutrient digestibility, fecal microflora, and odor gas emissions of growing pigs. A total of four crossbred ([Landrace × Yorkshire] × Duroc) barrows with average body weight (BW) of 41.2 ± 0.7 kg were randomly allotted four diets over four periods in a 4 × 4 Latin square design. Treatments were as follows: Control (CON, basal diet), CON + 0.2% probiotic complex (L4S6, B. licheniformis and B. subtilis at a 4:6 ratio), CON + 0.2% probiotic complex (L5S5, B. licheniformis and B. subtilis at a 5:5 ratio), CON + 0.2% probiotic complex (L6S4, B. licheniformis and B. subtilis at a 6:4 ratio). Dietary probiotic supplementation showed higher crude protein (CP) digestibility values and lower Escherichia coli counts in fecal samples than the CON group (p < 0.05). There was no significant difference in NH3 or H2S emission until day 3. The positive effect of H2S and NH3 emissions was detected earlier with the L4S6 and L5S5 compared to the L6S4, which had a lower ratio of B. subtilis. Both the L4S6 and L5S5 probiotic complexes significantly decreased the fecal H2S and NH3 emission in days 4 and 6 (p < 0.05). On day 7, all probiotic complexes decreased (p < 0.05) H2S and NH3 emissions than the CON group. Our results agreed that the dietary supplementation of Bacillus licheniformis and Bacillus subtilis complexes in growing pigs can significantly improve CP digestibility and reduce fecal E. coli counts, NH3 and H2S emissions. Notably, the higher mixing ratio of Bacillus subtilis in probiotic supplementation is more effective in reducing the odor of manure.

Low Spurious Image Rejection Mixer for K-band Applications

  • Lee, Moon-Que;Ryu, Keun-Kwan;Kim, Hyeong-Seok
    • KIEE International Transactions on Electrophysics and Applications
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    • v.4C no.6
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    • pp.272-275
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    • 2004
  • A balanced single side-band (SSB) mixer employing a sub-harmonic configuration is designed for up and down conversions in K-band. The designed mixer uses anti-parallel diode (APD) pairs to effectively eliminate even harmonics of the local oscillator (LO) spurious signal. To reduce the odd harmonics of LO at the RF port, we employ a balanced configuration for LO. The fabricated chip shows 12$\pm$2dB of conversion loss and image-rejection ratio of about 20dB for down conversion at RF frequencies of 24-27.5GHz. As an up-conversion mode, the designed chip shows 12dB of conversion loss and image-rejection ratio of 20 ~ 25 dB at RF frequencies of 25 to 27GHz. The odd harmonics of the LO are measured below -37dBc.

Characterization of Flowable Fill with Ferro-Nickel Slag Dust (페로니켈 슬래그 미분말을 이용한 유동성 뒤채움재 특성)

  • Lee, Kwan-Ho
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.5
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    • pp.16-21
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    • 2017
  • The aim of this study was to utilize ferronickel slag produced in the manufacture of stainless steel as a flowable backfill material for underground use using crushed fine powder. Experimental combinations were made using two components: Case A (sand) and Case B (soil). The optimal mixing ratio of Case A was sand (58.4%), ferronickel slag fine powder (21.6%), cement (1.8%), and water (18.2%). In the case of B, the optimal mixing ratio was determined to be soil (53.0%), ferronickel slag fine powder (20.0%), cement (1.7%), and water (25.3%). The uniaxial compressive strength of case A, which is a mixture of ordinary sand and ferronickel slag powder, was relatively larger than that of case B using soil. In addition, the strength of the specimen increased with increasing curing time. The uniaxial compressive strength tended to increase with increasing curing time. In addition, the unconfined compression strength of the fluid backfill material using common sand as the main material was relatively larger than that of the mixed material using soil as the main material. In case A, the uniaxial compressive strength ranged from 0.17-0.33 MPa, 0.21-0.39 MPa, and 0.19-0.40 MPa, respectively, at curing times of 7, 14, and 28 days. From the experimental results, it was concluded that the ratio of FNS powder and cement mixture was the most appropriate for Case A3. Case B, which used soil as the main material, showed a similar tendency to Case A. As a result of the dissolution test for evaluating the environmental harm of the FNS fine powder, there was no dissolution of substances harmful to the environment.

The Hearing Ability of the Dusky spinefoot Siganus fuscescens(Houttuyn)to Audible Sound 2. The Auditory Critical Ratio (가청음에 의한 독가시치의 청각 능력 2. 청각 임계비)

  • Lee, Chang-Heon;Moon, Jong-Wook;Seo, Du-Ok
    • Journal of Fisheries and Marine Sciences Education
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    • v.12 no.2
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    • pp.191-198
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    • 2000
  • An experiment was carried out to obtain the fundamental data on the auditory thresholds of fishes for catching method using audible frequency sound, the auditory thresholds of dusky spinefoot Siganus fuscescens(Houttuyn) were measured in the presence of masking noise in the spectrum level range of 74 - 83dB re $1{\mu}Pa/{\sqrt{Hz}}$ by heartbeat conditioning technique using pure tones coupled with a delayed electric shock. The auditory critical ratios were about 23 - 34dB at measurement frequency range. The ratio increased almost linearly with increasing frequency from 200 to 500Hz. The noise spectrum level at the start of masking was about 61 - 73dB within the measurement frequency range. This suggests that hearing of dusky spinefoot is masked in the natural environment with the noise spectrum level above 70dB. The sound pressure level of which the signal sound of 100Hz is recognized by dusky spinefoot under the white noise of 70dB is above 98dB and the critical ratio of them is above 23dB.

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The Change of Soil Physicochemical Properties by Mixture Ratio of Inorganic Soil Amendments (무기성 토양개량제들의 혼합비율에 따른 토양이화학성의 변화)

  • Kim, Young-Sun;Kim, Tack-Soo;Ham, Suon-Kyu
    • Asian Journal of Turfgrass Science
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    • v.23 no.2
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    • pp.271-278
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    • 2009
  • This study was conducted to investigate the effect of the mixture ratio of the inorganic soil amendments on the soil physicochemical properties. In this experiment, three kinds of soil amendments which had similar pH, EC and particle size, the A, B and C, were tested. The mixture ratio of soil amendment were 0%, 3%, 5%, 7% and 10% (V/V) incorporated with sand which met to the USGA(United State of Golf Association) particle standard. To analyze the effects of amendment on chemical soil properties, pH, EC(electrical conductivity) and CEC(cation exchangeable capacity) were measured. The porosity, bulk density and hydraulic conductivity also measured to analyze the changes of physical properties. In the chemical properties, pH was significantly related to the mixture ratios of amendments, A and C(P<0.05), CEC and EC also related to the ratios of C(P<0.01). When the results were applied to the USGA standard of the soil physical properties, the optimum mixture ratios of each amendment were 3% in A and B, and 7~10% in C. To analyze the corelation of mixture ratio versus to physical character, volume of porosity was significantly related to the ratio of B (P<0.05), and showed similar corelation in porosity and hydraulic conductivity with ratio of C(P<0.05). These results indicate that types and mixture ratio of inorganic soil amendments should affect on soil physio-chemical properties of root zone on USGA sand green.

A Study on Generalized Fibonacci Sequence (피보나치 수열의 일반화에 관한 고찰)

  • Yang, Young-Oh;Kim, Tae-Ho
    • Journal for History of Mathematics
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    • v.21 no.4
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    • pp.87-104
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    • 2008
  • In this paper we investigate several properties and characteristics of the generalized Fibonacci sequence $\{g_n\}$={a, b, a+b, a+2b, 2a+3b, 3a+5b,...}. This concept is a generalization of the famous Fibonacci sequence. In particular we find the identities of sums and the nth term $g_n$ in detail. Also we find the generalizations of the Catalan's identity and A. Tagiuri's identity about the Fibonacci sequence, and investigate the relation between $g_n$ and Pascal's triangle, and how fast $g_n$ increases. Furthermore, we show that $g_n$ and $g_{n+1}$ are relatively prime if a b are relatively prime, and that the sequence $\{\frac{g_{n+1}}{g_n}\}$ of the ratios of consecutive terms converges to the golden ratio $\frac{1+\sqrt5}2$.

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Evaluation of a Solar Flare Forecast Model with Value Score

  • Park, Jongyeob;Moon, Yong-Jae;Lee, Kangjin;Lee, Jaejin
    • The Bulletin of The Korean Astronomical Society
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    • v.41 no.1
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    • pp.80.1-80.1
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    • 2016
  • There are probabilistic forecast models for solar flare occurrence, which can be evaluated by various skill scores (e.g. accuracy, critical success index, heidek skill score, and true skill score). Since these skill scores assume that two types of forecast errors (i.e. false alarm and miss) are equal or constant, which does not take into account different situations of users, they may be unrealistic. In this study, we make an evaluation of a probabilistic flare forecast model [Lee et al., 2012] which use sunspot groups and its area changes as a proxy of flux emergence. We calculate daily solar flare probabilities from 2011 to 2014 using this model. The skill scores are computed through contingency tables as a function of forecast probability, which corresponds to the maximum skill score depending on flare class and type of a skill score. We use a value score with cost/loss ratio, relative importance between the two types of forecast errors. The forecast probability (y) is linearly changed with the cost/loss ratio (x) in the form of y=ax+b: a=0.88; b=0 (C), a=1.2; b=-0.05(M), a=1.29; b=-0.02(X). We find that the forecast model has an effective range of cost/loss ratio for each class flare: 0.536-0.853(C), 0.147-0.334(M), and 0.023-0.072(X). We expect that this study would provide a guideline to determine the probability threshold and the cost/loss ratio for space weather forecast.

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A Study of the Changes in Dress Wearers' Images in Relationto the Changes in the Size and Area Ratio of Polka Dots Relative to Coloration (색상대비 물방울무늬의 크기와 면적비 변화에 따른 원피스 드레스 착용자의 이미지 연구)

  • Kim, Sun-Mi;Jeong, Su-Jin
    • Journal of the Korean Society of Costume
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    • v.58 no.6
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    • pp.54-68
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    • 2008
  • The purpose of this study is to investigate the effect of dot pattern size(0.8, 1.8, 2.5, 5, 8), color combination(BG/R, Y/B), area-ratio on image formation. Sets of stimulus and response scales(7 point semantic) were used as experimental materials. The stimuli were 20 color pictures manipulated with the combination of dot pattern size, color combination, and area-ratio using computer simulation. The subjects were 240 female undergraduates living in Gyeongnam-do. Image factor of the stimulus was composed of 5 different components, visibility, attractiveness, cuteness, stability and high class image. In the cuteness, color combination, dot pattern size showed independent effect. In the stability, area-ratio, dot pattern size showed independent effect. Interaction effects of color and area-ratio combination was significant on cuteness. For visibility image 8cm yellow dot/blue background, for attractiveness image BG/R coloration, for cuteness image Y/B coloration and for stability image 0.8cm yellow dot/blue background were effective. According to the variation of dot pattern size, color combination and area-ratio, it was investigated that the images for a dress wearer were expressed diversely, were shown differently in image dimensions, and could be produced to different images.

Verification of Graphite Isotope Ratio Method Combined With Polynomial Regression for the Estimation of Cumulative Plutonium Production in a Graphite-Moderated Reactor

  • Kim, Kyeongwon;Han, Jinseok;Lee, Hyun Chul;Jang, Junkyung;Lee, Deokjung
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.19 no.4
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    • pp.447-457
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    • 2021
  • Graphite Isotope Ratio Method (GIRM) can be used to estimate plutonium production in a graphite-moderated reactor. This study presents verification results for the GIRM combined with a 3-D polynomial regression function to estimate cumulative plutonium production in a graphite-moderated reactor. Using the 3-D Monte-Carlo method, verification was done by comparing the cumulative plutonium production with the GIRM. The GIRM can estimate plutonium production for specific sampling points using a function that is based on an isotope ratio of impurity elements. In this study, the 10B/11B isotope ratio was chosen and calculated for sampling points. Then, 3-D polynomial regression was used to derive a function that represents a whole core cumulative plutonium production map. To verify the accuracy of the GIRM with polynomial regression, the reference value of plutonium production was calculated using a Monte-Carlo code, MCS, up to 4250 days of depletion. Moreover, the amount of plutonium produced in certain axial layers and fuel pins at 1250, 2250, and 3250 days of depletion was obtained and used for additional verification. As a result, the difference in the total cumulative plutonium production based on the MCS and GIRM results was found below 3.1% with regard to the root mean square (RMS) error.