• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.36 no.9
• /
• pp.923-930
• /
• 2012

The wall heat transfer of backward-facing step laminar flows with different Prandtl numbers and a pulsating inlet is investigated by unsteady simulations. The inlet is perturbed by the variation of frequency and amplitude. Temperature-dependent transport properties are adopted. Various characteristics of the wall heat transfer are explained by the variation of the thermal boundary layer. For Pr < 1, the wall heat transfer of temperature-dependent properties is decreased compared to that of constant properties, whereas it increases for Pr < 1. In addition, the wall heat transfer increases depending on the pulsating amplitude. However, the results of frequency variation for St < 0.2 show that the heat transfer is strongly enhanced at a specific frequency. In particular, the increase in the wall heat transfer is strongly related to the root mean square of the fluctuations of the reattachment length.

• The Mathematical Education
• /
• v.51 no.1
• /
• pp.1-19
• /
• 2012

In this study, contents of 'the 2007 revised curriculum handbook' and 16 kinds of mathematics textbooks were analyzed first. The purpose of this study is to examine the understanding state of students at general high schools by making questionnaires to survey the understanding state on contents of chapter of complex number based on above analysis. Results of research can be summarized as follows. First, the content of chapter of complex number in textbook was not logically organized. In the introduction of imaginary number unit, two kinds of marks were presented without any reason and it has led to two kinds of notation of negative square root. There was no explanation of difference between delimiter symbol and operator symbol at all. The concepts were presented as definition without logical explanations. Second, students who learned with textbook in which problems were pointed out above did not have concept of complex number for granted, and recognized it as expansion of operation of set of real numbers. It meant that they were confused of operation of complex numbers and did not form the image about number system itself of complex number. Implications from this study can be obtained as follows. First, as we came over to the 7th curriculum, the contents of chapter of complex number were too abbreviated to have the logical configuration of chapter in order to remove the burden for learning. Therefore, the quantitative expansion and logical configuration fit to the level for high school students corresponding to the formal operating stage are required for correct configuration of contents of chapter. Second, teachers realize the importance of chapter of complex number and reconstruct the contents of chapter to let students think conceptually and logically.

• Korean Journal of Veterinary Service
• /
• v.36 no.4
• /
• pp.227-232
• /
• 2013

The dried root of Angelica gigas (A. gigas) has been traditionally used as an oriental medicine, which is known to improve blood circulation and blood stasis. In the present study, leaves and stalks of A. gigas were used to investigate their effects on the innate immunity. The extracts were prepared from leaves and stalks of A. gigas and were fed to mice. The numbers of blood cells, total WBCs, neutrophils, lymphocytes, eosinophils and basophils were increased by 50% in mice fed with leaves extract of A. gigas compared to control mice. However, the numbers of blood cells were decreased when treated with stalks extract of A. gigas. The level of cholesterol and triglyceride in serum was markedly reduced in both mice group fed with leaves extract and stalks extract of A. gigas compared to control group (P<0.01). There was no significant change in the level of albumin, total protein, phosphate and calcium in serum. Activity of cationic peptide was found to be diffused in the testicles of mice fed with leaves extract of A. gigas compared to control group, which might be due to increased lysozyme in testicle. The lysoplate assay and immunohistochemistry assay suggest that the extract of leaves and stalks of A. gigas are immunogenic, but the effects might be related with acquired immune response rather than innate immunity.

• Journal of Mechanical Science and Technology
• /
• v.19 no.8
• /
• pp.1632-1648
• /
• 2005

The effects of Reynolds number on the non-nulling calibration of a typical cone-type five-hole probe have been investigated for the representative Reynolds numbers in turbomachinery. The pitch and yaw angles are changed from - 35 degrees to 35 degrees with an angle interval of 5 degrees at six probe Reynolds numbers in range between $6.60{\times}10^3\;and\;3.17{\times}10^4$. The result shows that not only each calibration coefficient itself but also its Reynolds number dependency is affected significantly by the pitch and yaw angles. The Reynolds-number effects on the pitch- and yaw-angle coefficients are noticeable when the absolute values of the pitch and yaw angles are smaller than 20 degrees. The static-pressure coefficient is sensitive to the Reynolds number nearly all over the pitch- and yaw-angle range. The Reynolds-number effect on the total-pressure coefficient is found remarkable when the absolute values of the pitch and yaw angles are larger than 20 degrees. Through a typical non-nulling reduction procedure, actual reduced values of the pitch and yaw angles, static and total pressures, and velocity magnitude at each Reynolds number are obtained by employing the calibration coefficients at the highest Reynolds number ($Re=3.17{\times}10^4$) as input reference calibration data. As a result, it is found that each reduced value has its own unique trend depending on the pitch and yaw angles. Its general tendency is related closely to the variation of the corresponding calibration coefficient with the Reynolds number. Among the reduced values, the reduced total pressure suffers the most considerable deviation from the measured one and its dependency upon the pitch and yaw angles is most noticeable. In this study, the root-mean-square data as well as the upper and lower bounds of the reduced values are reported as a function of the Reynolds number. These data would be very useful in the estimation of the Reynolds-number effects on the non-nulling calibration.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.9 no.1
• /
• pp.188-198
• /
• 2005

The Goldschmidt iterative algorithm for finding a floating point square root calculated it by performing a fixed number of multiplications. In this paper, a variable latency Goldschmidt's square root algorithm is proposed, that performs multiplications a variable number of times until the error becomes smaller than a given value. To find the square root of a floating point number F, the algorithm repeats the following operations: $R_i=\frac{3-e_r-X_i}{2},\;X_{i+1}=X_i{\times}R^2_i,\;Y_{i+1}=Y_i{\times}R_i,\;i{\in}\{{0,1,2,{\ldots},n-1} }}'$with the initial value is $'\;X_0=Y_0=T^2{\times}F,\;T=\frac{1}{\sqrt {F}}+e_t\;'$. The bits to the right of p fractional bits in intermediate multiplication results are truncated, and this truncation error is less than $'e_r=2^{-p}'$. The value of p is 28 for the single precision floating point, and 58 for the doubel precision floating point. Let $'X_i=1{\pm}e_i'$, there is $'\;X_{i+1}=1-e_{i+1},\;where\;'\;e_{i+1}<\frac{3e^2_i}{4}{\mp}\frac{e^3_i}{4}+4e_{r}'$. If '|X_i-1|<2^{\frac{-p+2}{2}}\;'$ is true, $'\;e_{i+1}<8e_r\;'$ is less than the smallest number which is representable by floating point number. So, $\sqrt{F}$ is approximate to $'\;\frac{Y_{i+1}}{T}\;'$. Since the number of multiplications performed by the proposed algorithm is dependent on the input values, the average number of multiplications per an operation is derived from many reciprocal square root tables ($T=\frac{1}{\sqrt{F}}+e_i$) with varying sizes. The superiority of this algorithm is proved by comparing this average number with the fixed number of multiplications of the conventional algorithm. Since the proposed algorithm only performs the multiplications until the error gets smaller than a given value, it can be used to improve the performance of a square root unit. Also, it can be used to construct optimized approximate reciprocal square root tables. The results of this paper can be applied to many areas that utilize floating point numbers, such as digital signal processing, computer graphics, multimedia, scientific computing, etc.

• The Korean Journal of Applied Statistics
• /
• v.20 no.2
• /
• pp.387-394
• /
• 2007

This paper considers several stratification strategies for multivariate and multipurpose survey with several quantitative stratification variables. We propose three methods of stratification based on, respectively, the method of cumulative frequency square root which is the most popular one in univariate stratification, cluster analysis, and factor analysis followed by cluster analysis. We then compare the efficiency of those methods using the Dong-Eup-Myun data of the holding numbers of farming machines, extracted from the 2001 Agricultural Census. It turned out that the method based on cluster analysis with factor analysis would be a relatively satisfactory strategy.

• Korean Journal of Medicinal Crop Science
• /
• v.19 no.2
• /
• pp.83-89
• /
• 2011

This studies were conducted to investigate the growth responses and yields of Astragalus membranaceus Bunge which were grown with organic cultivation using two organic fertilizers and two green manure crops of hairy vetch and rye in 2008 and 2009. The lengths of stems and roots were not clearly different between organic and conventional cultivations. The root diameters and the branch numbers were slightly thicker and more in all treatments of organic cultivation than that of conventional cultivation in 2008, although they were not significantly different between two cultivating methods in 2009. The dry weights of shoot and root were heavier on organic cultivation than those on conventional cultivation. The T/R ratios were commonly higher in organic culture, showing more clearly in 2008 than 2009. The yields were generally higher in organic cultivation than those in conventional cultivation in 2008 although the effect did not clear on yield in 2009. The organic cultivation using of organic fertilizers and green manure crops would be new method to have safety and qualitative products. The techniques of organic cultivation for Astragalus membranaceus Bunge would be studied more on utilizing the natural organic resources.

• Explosives and Blasting
• /
• v.8 no.1
• /
• pp.3-16
• /
• 1990

The cautious blasting works had been used with emulsion explosion electric M/S delay caps. Drill depth was from 3m to 6m with Crawler Drill $\varphi{70mm}$ on the calcalious sand stone(sort-moderate-semi hard Rock). The total numbers of feet blast were 88. Scale distance were induces 15.52-60.32. It was applied to propagation Law in blasting vibration as follows. Propagtion Law in Blasting Vibration $V=K(\frac{D}{W^b})^n$ where V : Peak partical velocity(cm/sec) D : Distance between explosion and recording sites (m) W : Maximum Charge per delay-period of eighit milliseconds or more(Kg) K : Ground transmission constant, empirically determind on th Rocks, Explosive and drilling pattern ets. b : Charge exponents n : Reduced exponents Where the quantity $D/W^b$ is known as the Scale distance. Above equation is worked by the U.S Bureau of Mines to determine peak particle velocity. The propagation Law can be catagrorized in three graups. Cabic root Scaling charge per delay Square root Scaling of charge per delay Site-specific Scaling of charge per delay Charge and reduction exponents carried out by multiple regressional analysis. It's divided into under loom and over loom distance because the frequency is verified by the distance from blast site. Empirical equation of cautious blasting vibration is as follows. Over 30m----under l00m----- $V=41(D/3\sqrt{W})^{-1.41}$ -----A Over l00m-----$V= 121(D/3\sqrt{W})^{-1.66}$-----B K value on the above equation has to be more specified for furthur understang about the effect of explosives, Rock strength. And Drilling pattern on the vibration levels, it is necessary to carry out more tests.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.15 no.4
• /
• pp.245-252
• /
• 1995

To select a carrier as Rhizobiwn inoculants for alfalfa, severeal Rhizobium inoculants were produced by adding or not sub-materials($CaCO_3$ and sucrose) to main materials(organic or inorganic materials). The root nodule bacteria, Rhizobium meliloti 1061 distributed from KAIST, and Vemal alfalfa was used in this experiment. The Rhizobium populations and inoculation effects of the Rhizobium inoculants produced in several materials were scrutinized at laboratory and greenhouse in Livestock Experiment Station, RDA from 1993 to 1994. Moisture contents of the caniers were varied from 32 to 50% on dry weight basis according to material characteristics and the pH ranges of these were varied from pH 4.56 to 10.06 according to raw material characteristics and preparations. Initial Rhizobium numbers of the carriers were higher in organic material-inoculants than in inorganic, and among the inoculants, the inoculant made of Bentonite+Vermiculite(l:3 w/w) was excellent because of high rhizobium population($7.8~8.3\times10^8/g$ inoculant) and high rhizobium reappearance of inoculant in severed different production time. The root nodules of the alfalfa inoculated with different inoculants were fast formed in the fermented sawdust with cattle dung (FSC) inoculant, and bentonite(B)+vermiculite(V) than others. Plant length of alfalfa was differentiated on 15 days after inoculation but was not nearly different between higher inoculants than rhizobium number $10^7/g$ inoculant. Total dry matter of alfalfa was yielded by 20.65, 20.34mg per pot in FSC + sucrose 0.5% and B + V + sucrose 1% inoculants respectively that were higher inoculation effect by 17 times compared with non-inoculation, 1.2 mg per pot.

• Journal of the Korean Professional Engineers Association
• /
• v.24 no.6
• /
• pp.97-105
• /
• 1991

The cautious blasting works had been used with emulsion explosion electric M/S delay caps. Drill depth was from 3m to 6m with Crawler Drill ø70mm on the calcalious sand stone (soft-moderate-semi hard Rock). The total numbers of fire blast were 88 round. Scale distance were induces 15.52-60.32. It was applied to propagation Law in blasting vibration as follows. Propagation Law in Blasting Vibration (Equation omitted) where V : Peak partical velocity(cm/sec) D : Distance between explosion and recording sites(m) W : Maximum Charge per delay-period of eighit milliseconds o. more(kg) K : Ground transmission constant, empirically determind on the Rocks, Explosive and drilling pattern ets. b : Charge exponents n : Reduced exponents Where the quantity D / W$^n$ is known as the Scale distance. Above equation is worked by the U.S Bureau of Mines to determine peak particle velocity. The propagation Law can be catagrorized in three graups. Cubic root Scaling charge per delay Square root Scaling of charge per delay Site-specific Scaling of charge per delay Charge and reduction exponents carried out by multiple regressional analysis. It's divided into under loom and over 100m distance because the frequency is verified by the distance from blast site. Empirical equation of cautious blasting vibration is as follows. Over 30 ‥‥‥under 100m ‥‥‥V=41(D/$^3$√W)$\^$-1.41/ ‥‥‥A Over 100 ‥‥‥‥under 100m ‥‥‥V=121(D/$^3$√W)$\^$-1.56/ ‥‥‥B K value on the above equation has to be more specified for furthur understang about the effect of explosives, Rock strength. And Drilling pattern on the vibration levels, it is necessary to carry out more tests.