• 한국수학교육학회지시리즈E:수학교육논문집
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• 제23권4호
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• pp.977-998
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• 2009

초등(elementary), 중등(secondary)교육에 이어지는 대학 및 직업 교육을 총칭하여 고등(tertiary) 교육이라고 한다. 본 연구는 미국에서의 고등(tertiary)수학과 한국에서의 고등수학 초기 발전과정을 비교 연구한다. 미국 대학에서의 수학 강좌개설의 역사를 살펴보면 하버드대 학장인 던스터가 1640년 산술과 기하를 예비졸업생들을 대상으로 지도한 기록이 남아있다[10]. 이 기록에 의하면 미국 대학과정의 수학은 1636년 설립된 하버드 대학에서 1640년부터 실질적인 강의가 시작되었다고 할 수 있다. 미국의 수학자로는 1870년 'Linear Associative Algebra'를 발간한 하버드의 벤자민 퍼스가 비로소 수학에 대한 학술적인 기여를 통하여 처음으로 유럽학계의 주목을 받는다. 미국의 경우 세 번째 연구중심대학으로 시작한 시카고대학의 성장과 함께 학술적으로 유럽 수학계의 인정을 받고 미국 수학연구의 존재를 학계에 알린 미국인 수학자로 G.D. 버코프를 꼽는다. 1912년 하버드대 수학과 교수로 부임하여 하버드대 수학과의 역할을 교육에서 연구로 바꾸는데 결정적인 역할을 한다. 즉, 미국 수학이 교육에서 연구 단계로 진화하는 과정에 무려 200년 이상이 걸렸다는 사실을 확인할 수 있다. 하버드에서 대학 과정이 설립될 즈음 조선에서의 고등수학의 상황은 어떠하였을까? 한반도에서는 조선산학과 구한말의 대학부 및 연희 전문학교 수물과를 거쳐 1945년 8월 2차 세계대전이 끝나면서 비로소 일제식민통치하에서 벗어난 1945년 4년제 대학에 수학과가 처음 설립된다. 일제 강점기에는 중학교와 전문학교 이과에서 일부 직업교육 또는 대학수학이 다루어졌다. 한국의 경우 경성대의 이임학이 1947년 막스 존의 미해결 문제를 풀며 한국 근대수학자의 존재를 서양에 알리게 된다. 본 연구에서는 미국과 한국의 초기 고등수학 발전과정을 수학자 중심으로 비교 연구하여 발전 단계를 진단한다.

• 천문학회보
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• 제40권1호
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• pp.59.1-59.1
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• 2015

We present hydrodynamic simulations of gas clouds that inflowing from the disk to a few hundred parsec region of the Milky Way. Realistic Galactic structures are included in our simulations by thousands of multipole expansions that describe 6.4 million stellar particles of a self-consistent Galaxy simulation (Baba, Saitoh & Wada, in prep.). We find that a hybrid multipole expansion model with two different basis sets and a thick disk correction well reproduces the overall structures of the Milky Way. We find that the nuclear ring evolves into 240 pc at T~1500 Myr, regardless of the initial size. For most of simulation runs, gas inflow rate to the nuclear region is equilibrated as ~0.02 Msun/yr, and thus accumulated gas mass and star formation activity is stabilized as $6{\times}10^7Msun$ and ~0.02M/yr, respectively. These stabilized values are in a good agreement with estimations for the CMZ. The nuclear ring is off-centered to the Galactic center by the lopsided central mass distribution of the Galaxy model, and thus an asymmetric mass distribution is arose accordingly. The lopsidedness also leads the nuclear ring to be tilted to the Galactic plane and to precess along the Galaxy rotation. In early evolutionary stage when gas clouds start to inflow and form the nuclear ring, the z-directional oscillations of the gas clouds results in the twisted, infinity-shaped nuclear ring. Since the infinity-shaped feature is transient only for first 100 Myr, the current infinity-shape observed in the CMZ may indicate that the CMZ forms quite recently.

• 한국지구과학회지
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• 제25권7호
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• pp.629-636
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• 2004

구름이 유입하는 경우 해양대기경계층의 발달을 분석하기 위하여, 울릉도에서 관측한 레윈존데 자료와 AWS 자료, 위성사진, 동해에 설치된 부이 자료를 이용하였다. 이 자료를 이용하여 열의 이류와 표층 열속, 구름 유입에 따른 복사에너지를 추정하였다. 혼합층 내의 열 변화 및 혼합층의 발달을 표층 열속과 구름에 의한 장파복사속으로 설명하였다. 열속의 변화를 알아보기 위해 벌크법을 이용하였다. 울릉도, 동해상의 부이, 포항에서 관측한 자료를 이용한 열수지 방정식으로 대기경계층의 열보존 관계를 분석하였다. 구름의 유입으로 인해 일몰 후 지면의 복사냉각이 방해되고, 구름에서 장파복사가 방출된다. 그로 인해 야간에 오히려 기온이 증가하였다. 또 남서쪽으로부터 따뜻한 공기가 이류되어, 하층 대기의 온도를 증가시켰다. 이러한 이유로 혼합층이 파괴되지 않고, 잔류층을 형성하며 남아있었다.

• 한국지구과학회지
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• 제23권3호
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• pp.207-220
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• 2002

이 연구에서는 최근 수행된 국제 비교 연구인 TIMSS-R과 PISA 2000에 나타난 우리 나라 학생들의 지구 과학영역에 대한 전체적인 성취도 및 성 차이 경향을 파악하였다. 이를 위해 1999년에 실시된 TIMSS-R에 포함된 33개의 지구 과학 관련 문항과 2000년에 실시된 PISA에 포함된 13개의 지구 환경 과학 문항에 대한 국제 및 국내 평균 정답율을 비교하였다. 분석 결과, 우리 나라 학생들은 문항 유형별로는 선택형 문항에서, 수행 영역별로는 단순 정보 이해문항에서 국제 평균 정답율에 비해 큰 차이를 보이며 높게 나타났다. 또한, 우리 나라 학생들은 그래프 해석, 표 해석등 자료 해석과 관련된 문항에서 국제 평균보다 특히 높은 정답율을 나타냈는데, 이러한 경향은 남학생들에게 더 두드러졌다. 한편, 우리 나라 학생들은 천문학 문항에서 상대적으로 가장 낮은 점수를 나타냈으며, 이는 특히 여학생에게 더 심하게 나타났다. 우리 나라 여학생들은 문항의 내용, 유형, 수행 영역 등 모든 부분에서 남학생들보다 낮은 정답율을 보여 심각한 성 차이를 드러냈다.

• Journal of Astronomy and Space Sciences
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• 제31권2호
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• pp.145-148
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• 2014

There was a research on the prolongation of solar cycle 23 by the solar cyclic variation of solar, interplanetary geomagnetic parameters by Oh & Kim (2013). They also suggested that the sunspot number cannot typically explain the variation of total solar irradiance any more. Instead of the sunspot number, a new index is introduced to explain the degree of solar activity. We have analyzed the frequency of sunspot appearance, the length of solar cycle, and the rise time to a solar maximum as the characteristics of solar cycle. Then, we have examined the predictability of solar activity by the characteristics of preceding solar cycle. We have also investigated the hemispheric variation of flare index for the periods that the leading sunspot has the same magnetic polarity. As a result, it was found that there was a good correlation between the length of preceding solar cycle and spotless days. When the length of preceding solar cycle gets longer, the spotless days increase. It is also shown that the shorter rise time to a solar maximum is highly correlated with the increase of sunspots at a solar maximum. Therefore, the appearance frequency of spotless days and the length of solar cycle are more significant than the general sunspot number as an index of declining solar activity. Additionally, the activity of flares leads in the northern hemisphere and is stronger in the hemisphere with leading sunspots in positive polarity than in the hemisphere with leading sunspots in negative polarity. This result suggests that it is necessary to analyze the magnetic polarity's effect on the flares and to interpret the period from the solar maximum to solar maximum as the definition of solar cycle.

• 천문학회지
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• 제24권1호
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• pp.55-70
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• 1991

Infrared emission maps are constructed at 12.5, 25, 60, and $100{\mu}m$ for dark globules B5, B34, B133, B134, B361, L134 and L1523 by using Infrared Astronomical Satellite data base. These clouds are selected on the basis of their appearance in Palomar print as dark obscuring objects with angular sizes in the range of 3 to 30 arcminutes. The short wavelength(12.5 and $25{\mu}m$) maps show the embedded infrared sources. We found many such sources only in B5, B361 and B34 regions, Diffuse component at 12.5 and $25{\mu}m$, possibly arising from the stochastically heated very small dust grains(a < $0.01{\mu}m$) by interstellar radiation field, is found in B361 and L1523 regions. Such emission is characterized by the limb brightening, and it is confirmed in L1523 and in B361. Infrared emissions at the long wavelengths(60 and $100{\mu}m$) are due to colder dusts with temperature less than 20 K. The distribution of color index determined by the ratio 60 to $100{\mu}m$ intensities shows monotonic decrease of dust temperature toward the center. The black body temperature determined from these ratios is found to lie between 16 and 23 K. Such temperature is possible for small(i.e., $a\;{\lesssim}\;0.01{\mu}m$) graphite grains if the grains are mainly heated by interstellar radiation field. Thus IRAS 100 and $60{\mu}m$ emissions are arising mainly from small grains in the colud. The distribution of such dust grains implied from the emissivity distributions at 100 and $60{\mu}m$ resembles that of isothermal sphere. This contrasts to earlier findings of much steeper distribution of dusts contributing visible extinction. These dust grains are mainly larger ones(i.e., $a{\simeq}0.1{\mu}m$). Therefore we conclude that the average grain size increase, toward the cloud center.

• 한국지구과학회지
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• 제27권7호
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• pp.804-815
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• 2006

Meteorologists define a drought as a period of common dry weather. This may sound straightforward, but it is not so in reality. In this study, we attempted to identify meteorological drought conditions over South Korea. To evaluate the temporal and spatial variability of drought, we calculated two commonly used drought indices, the percent of normal precipitation (PNP) and the Palmer drought severity index (PDSI) calculated from fifty-eight meteorological stations below the Korean Meteorological Administration (KMA). The yearly precipitation has been growing gradually, and the amplitude between maximum and minimum also grow more explicitly from 1960's. According to the analysis of percentile anomaly of monthly precipitation, major drought duration was $1927{\sim}1929,\;1937{\sim}1939,\;1942{\sim}1944,\;1967{\sim}1968,\;1976{\sim}1977,\;1982{\sim}1983,\;1988,\;and\;1994{\sim}1995$. The severe drought occurred most frequently in Mokpo, Daegu, Jeonju, Busan, and Gangneung; it tended to occur more frequently in south sector than in mid sector of Korea and in south west sector than in south east sector. According to the analysis of seasonal distribution, extreme droughts occurred frequently in winter at Seoul, Gangneung, Jeonju, Daegu, and Busan. Severe droughts in summer were formed frequently at Seoul, Gangneung, and Mokpo, while that for spring at Jeonju, Daegu, and Busan. The results of PDSI distribution for the $1994{\sim}1995$ drought period were one of the most severe and widely spreaded droughts; it occurred most frequently in the south sector of South Korea. The comparison of time series between PDSI and Normal Percent showed that they exhibit a strong compatibility for the entire study period; it implies that both drought indices are useful method to indicate drought severity.

• 대한한의학원전학회지
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• 제20권4호
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• pp.187-210
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• 2007

Dunong(鈍翁), Yun-Ji had born by a concubine, and his dream didn't come true for the restraint of his social position, so he tried to train younger men. His writings still remain 4 volumes of "Dunongyeonsocheonjimundap" and "Dunongdongmongmundap(鈍翁童蒙問答)", which may be called its primer. "Dunongyeonsocheonjimundap" is written in question-and-answer form between Chal-Hye-Ja(察慧子) who has a meager knowledge and Sim-Gyeong-Ong(心耕翁) who search for the truth. It is progressed from the law of nature to human's cultivation of the mind so as to reconfirm the recognition of the unity between the heaven and human beings and lead the interpretation and practice of the metaphysical proposition. It is characterized by making use of metrical compositions to induce plain tone of argument. "Dunongdongmongmundap", whereas, uses archaic writings to describe natural science including astronomy to the beginners. Dunong's scholarship is characterized by these: He explained the metaphysical propositions by approaching usual things including oriental medicine practically; He comprised the Confucian concepts intensively to examine the Oriental studies closely; He groped for the outlooks on the world of taking serious view of human being or human body. And his medical thought is characterized by these: He attached importance to the theory of viscera and bowels based on yin-yang and five phase theory; He suggested the concrete yin-yang theory with a viewpoint of qi-blood theory; He considered the concept of 'six' only as mutual rooting of yin and yang and five visceras and six vowels, and denied the traditional six qi concepts; He explained the ghost theories of the metaphysics based on the yin-yang theory to analogize points of sameness between the oriental medicine and the metaphysics; He emphasized restore yang theory. Therefore, we can say that he regarded the human body as small heaven-earth and grafted the abstract propositions into the actuals so as to put the metaphysical propositions in practice.

• 한국지구과학회지
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• 제35권5호
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• pp.313-323
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• 2014

We secured the high dispersion spectra of the symbiotic star CI Cyg. The HI, HeI, and HeII line profiles were analyzed using the relatively long exposure data including 1800 sec (Sep. 12, 1998, phase=0.90), 3600 sec (Aug. 12, 2002, ${\phi}=0.47$), and 1800 sec (Oct. 21, 2009, ${\phi}=0.54$). Although a minor outburst was reported in 2008, our three observation periods were generally known to be quiescent in earlier photometric studies. With the help of hydrodynamic simulations, we identified the two emission zones responsible for the blue- and red-shifted line components: (a) an accretion disk around a hot white dwarf star which consists of the outer cool HeI emission zone and the inner hot HeII emission part, and (b) a high density zone near the inner Lagrangian point responsible for the HeI line flux variation and the broadening of its line profile. The HeII line fluxes indicate that the HeII emission zone of the accretion disk is relatively stable, implying a constant gas inflow from the giant star throughout the quiescent period. The 2002 HeI data showed that the notable mass flow activity through the inner Lagrangian point occurred during this period and its flux intensity became strongest, whereas the HeII line width in the same period indicates that its flow activity forced the accretion disk to expand. The [OIII] lines were observed in 1998 but not detected in 2002 and 2009, implying the disappearance of the low density zone. Based on our kinematical studies upon the line profiles, we conclude that CI Cyg was stable in 1998 among the three observation periods selected in this research.

• 천문학회보
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• 제45권1호
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• pp.59.2-59.2
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• 2020

Disks around protostars are the birthplace of planets. The first step toward planet formation is grain growth from ㎛-sized grains to mm/cm-sized grains in a disk, particularly in dense regions. In order to study whether grains grow and segregate at the protostellar stage, we investigate the ALMA Band 3 (3.1 mm) and 7 (0.87 mm) dust continuum observations of the protostellar disk WL 17 in ρ Ophiuchus L1688 cloud. As reported in a previous study, the Band 3 image shows substructures: a narrow ring and a large central hole. On the other hand, the Band 7 image shows different substructures: a non-axisymmetric ring and an off-center hole. The two-band observations provide a mean spectral index of 2.3, which suggests the presence of mm/cm-sized large grains. Its non-axisymmetric distribution may imply dust segregation between small and large grains. We perform radiative transfer modeling to examine the size and spatial distributions of dust grains in the WL 17 disk. The best-fit model suggests that large grains (>1 cm) exist in the disk, settling down toward the midplane, whereas small grains (~10 ㎛) well mixed with gas are distributed off-center and non-axisymmetrically in a thick layer. The low spectral index and the modeling results suggest that grains rapidly grow at the protostellar stage and that grains differently distribute depending on sizes, resulting in substructures varying with observed wavelengths. To understand the differential grain distributions and substructures, we discuss the effects of the protoplanet(s) expected inside the large hole and the possibility of gravitational instability.