• The Journal of the Acoustical Society of Korea
• /
• v.20 no.2
• /
• pp.3-9
• /
• 2001

In this paper, a random number generator for simulation of speech-waveform coders was designed. A random number generator having a desired probability density function and a desired power spectral density is discussed and experimental results are presented. The technique is based on Sondhi algorithm which consists of a linear filter and a memoryless nonlinearity. Several methods of obtaining memoryless nonlinearities for some typical continuous distributions are discussed. Sondhi algorithm is analyzed in the time domain using the diagonal expansion of the bivariate Gaussian probability density function. It is shown that the Sondhi algorithm gives satisfactory results when the memoryless nonlinearity is given in an antisymmetric form as in uniform, Cauchy, binary and gamma distribution. It is shown that the Sondhi algorithm does not perform well when the corresponding memoryless nonlinearity cannot be obtained analytically as in Student-t and F distributions, and when the memoryless nonlinearity can not be expressed in an antisymmetric form as in chi-squared and lognormal distributions.

• Communications for Statistical Applications and Methods
• /
• v.5 no.3
• /
• pp.633-644
• /
• 1998

혼합설계의 교호작용에 대한 F 검정이 유효하려면 다표본 구형성(multisample sphericity) 가정과 다변량 정규분포 가정이 만족되어야 한다. F 검정을 실시하기 위한 가정들이 위반된 조건하에서 혼합설계의 교호작용에 대한 검정법들의 1종오류가 비교되었다. 비교된 검정법들은 (1) F 검정(F), (2) 절사평균을 사용한 F 검정($F_T$)(3)$\varepsilon$-수정 F 검정($\varepsilon)$(4) 절사평균을 사용한 $\varepsilon$-수정 F 검정$(\varepsilon_T$) (5) CIGA검정(CIGA), (6) 절사평균을 사용한 CIGA검정($CIGA_T$)이었다. 결과는 CIGA와 $CIGA_T$는 1종오류를 대체로 잘 관리하나, F검정들과 ($\varepsilon$)검정들은 일부 조건에서 아주 작은 1종오류나 아주 큰 1종오류를 갖는 것으로 나타났다.

• Journal of Plant Biology
• /
• v.33 no.4
• /
• pp.237-242
• /
• 1990

Geographical distribution of diploid plant with AA genome (2n=16) and allotetraploid with AABB genome (2n=34) of Scilla scilloides Complex from Korea has been studied. The composition and frequencies of B chromosomes ere also investigated. Plants with AABB genome were predominant over AA genome plants. A mixed population of AA and AABB genome plants was found for the first time. Aneuploid plants have not been found. Chromosomes of AA genome were composed of three pairs of metacentric, two pairs of submetacentric, two pairs of subtlocentric and one pair of telocentric chromosomes, whereas BB genome was four pairs of metacentric and five pairs of subtelocentric chromosomes. B chromosomes were classified into two categories, isochromosome (F) and chromosome fragment (f). The frequencies of B chromosomes were 43% in AA genome plants and 44% in AABB genome plants. The number of B chromosome ranged from 1 to 3 and 1 to 7 in AA and AABB genome plants, respectively. B chromosome combinations were F and F+f in AA genome plants and F, F+f and f in AABB genome plants.

• Korean Journal of Optics and Photonics
• /
• v.13 no.5
• /
• pp.449-454
• /
• 2002

We have studied the effects of incoherent pumping on EIA at the transition between the $F_g=2$ ground state and the $F_e=3$ excited state in $^{85}Rb\;D_1$-line. Generally, the studies about EIA have been done in the cycling transition, where the population has no loss to other states. In the case of EIA by using the $^{85}Rb\;D_1$ transition line, the population is transferred to the other hyperfine state due to optical pumping. We incoherently pumped the atoms from $F_g=3\;to\;F_g=2$ with the pumping beam, which is resonant at the transition from $F_g=3\;to\;F_g=2$. We were able to observe the effects of incoherent pumping depending on the power and the polarization of the pumping beam.

• Korean Journal of Optics and Photonics
• /
• v.8 no.1
• /
• pp.19-25
• /
• 1997

Holographic zone plate (HZP) is fabricated by interfering a plane wave and a spherical wave in a dichromated gelatin (DCG) film obtained from Agfa 8E75HD plates. We have developed a simple theory for HZP considering optical nonlinearity of DCG material. Analysis of our theory for HZP shows that it has infinite focal points at distances f,f/2, f/3,,…. In experiment, we observed the corresponding focal points of up to f/6 when illuminating HZP by a plane wave. It is also shown that the beam profile around the first focal point measured by using a knife-edge scanning method has a Gaussian shape.

• Journal of Korean Society of Forest Science
• /
• v.90 no.3
• /
• pp.266-276
• /
• 2001

This study was conducted to clarify the taxonomic implications of F. chiisanensis Nakai based on morphology and flavonoids of four taxa of Fraxinus [F. chiisanensis Nakai, F. mandshurica Rupr., F. chinensis Roxb. var. rhynchophylla (Hance) Hemsl. and F. sieboldiana Blume] in Korea with one species of China and Japan (F. platypoda Oliv.). Morphologically F. chiisanensis was clearly distinguished from other taxa due to the presence of panicle from leafless lateral bud of previous year, apetalous flower, persistent calyx, and brownish naked bud. A survey of the foliar flavonoids of five species showed two distinctive chemical types. Unique flavones with flavonols, C-glycosylflavone and flavanone were detected in F. chiisanensis (chiisanensis type), while only flavonols, C-glycosylflavone, and flavanone were present in other four taxa (chinensis type). This study showed that F. chiisanensis was not a hybrid between F. mandshurica and F. chinensis var. rhynchophylla, but an endemic taxon distributed in southwestern Korea. Morphologically F. chiisanensis should be included into subgen. Fraxinus, sect. Melioides according to Chang and Qiu's classification. F. platypoda, a taxon of sect. Meliodies in China and Japan, was different from F. chiisanensis with respect of scaled bud, decurrent wing of samara and the lack of flavones (chinensis type). Since four American taxa of sect. Melioides contained flavones (chiisanensis type), they are more closely related with F. chiisanensis chemically.

• Pediatric Infection and Vaccine
• /
• v.13 no.2
• /
• pp.89-98
• /
• 2006

Purpose : The prevalence of serotypes can be changed with respect to age of the patients, regions and times of the surveillance. The aim of this study is to analyze changes in serotype distribution of pneumococcal isolates from Korean pediatric patients. Methods : Four hundred and sixty five strains of S. pneumoniae were isolated from various clinical specimens at the Seoul National University Children's Hospital during a 15 year-period, from 1991 to 2005, were subjected to serotype and penicillin susceptibility. The study period was divided into three 5 year-periods, 1991~1995(period I), 1996~2000(period II), and 2001~2005(period III). Results : Common serotypes were 19F, 23F, 19A, 6B, 14, 6A and 9V in decreasing orders of frequency, and these 7 serotypes accounted for 79% of total 465 strains. In the serotype distribution of invasive infection isolates from children <60 months of age, similar serotypes accounted for 70% of 101 strains. In total strains, the proportion of serotype 19A and 6A increased, while that of serotype 19F and 14 decreased. The majority(75~92%) of vaccine types and cross-reactive types from invasive infection isolates was penicillin-resistant, whereas 34.4% of non-vaccine types was penicillin-resistant. Conclusion : Distribution of serotypes of S. pneuomoniae isolated from Korean children has changed significantly over the last 15 years. The surveillance for pneumococcal serotypes should be continued to monitor changes in serotype distribution which are essential for the establishment of pneumococcal vaccine policy.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.12
• /
• pp.3208-3216
• /
• 1993

Heat transfer characteristics of the laminar oscillating flow in a circular pipe have been studied under the condition that the wall temperature of the pipe is distributed sinusoidally with the axial direction. The axial velocity was assumed to be uniform in radial direction and the temperature field was analyzed by means of the perturbation method. The results show that the difference between wall and section-time-averaged fluid temperature increases as the oscillating frequency increases and eventually converges to a constant value which is determined by the ratio of swept distance to the characteristic length of wall temperature distribution. Also it is shown that the dominant variable in the heat transfer process when swept distance ratio is greater than 1 is not thermal Womersley number(F) but thermal Womersley number multiplied by the square root of swept distance ratio. The variation of the time-averaged Nusselt number is obtained as a function of F. The results indicate that Nusselt number is proportional to $F_{\epsilon}^{1/2}$ when both of F and .epsilon. are much greater than 1.

• 한국연소학회:학술대회논문집
• /
• 2003.12a
• /
• pp.125-130
• /
• 2003

본 논문에서는 액체로켓엔진에서 터보펌프의 160kW급 터빈을 구동하고, 액체산소와 케로신을 추진제로 사용하는 가스발생기의 설계점 연소성능시험 결과에 대해 논의하였다. 충돌형 F-O-F 인젝터, 물냉각 채널을 가진 연소실, torch ignitor, turbulence ring 그리고 측정 링을 갖는 가스발생기에 대해 기술하였고, 점화, 연소, 종료 등의 시험 cyclogram에 대해 언급하였다. 설계점에서의 연소시험 및 turbulence ring 장착여부, 연소실 길이 변화에 따른 연소시험의 결과들에 대해 기술하였다. 연소시험 결과 가스발생기는 설계점에서 안정된 작동성을 보여주었고, 연소압력 및 온도 등의 성능이 예측치에 근접하는 결과를 보여 주었다. Turbulence ring은 출구에서의 가스온도를 균일하게 분포시켜 효과적인 혼합 장치임을 보여 주었고, 4-6msec 정도에서의 잔류시간에서는 연소효율의 차이가 크지 않음을 알 수 있었다. 가스발생기 출구에서의 온도는 공급되는 추진제의 O/F ratio에 따라 매우 민감하게 반응함을 알 수 있었다.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.26 no.1
• /
• pp.51-55
• /
• 1981

Seed proteins of 51 varieties of soybean were separated by disc electrophoresis. Nine varieties had Rf 0.79 electrophoretic band, and 42 varieties had Rf 0.83 band. The frequency for Rf 0.79 was 0.176 and the frequency for Rf 0.83 was 0.824. The F_1 seeds of crossed between Kumgangdaepp (Rf 0.79) and Uidu (Rf 0.83) possessed both bands. Analysis of 96 F_2 seeds showed a ratio of 22 : 53 : 21 (Rf 0.79 : Rf 0.79/Rf 0.83 : Rf 0.83), suggesting single gene control with two co dominant alleles.