• 천문학회지
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• 제38권3호
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• pp.345-355
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• 2005

We present a photometric study of the star cluster system in the merging galaxy NGC 1487, based on the BI photometry obtained from the F450W and F814W images in the HST /WFPC2 archive data. We have found about 560 star cluster candidates in NGC 1487, using the morphological parameters of the objects. We have investigated several photometric characteristics of the clusters: color-magnitude diagrams (CMDs), color distribution, spatial distribution, age, size and luminosity function. The CMD of the bright clusters with 18.5 < B < 24 mag in NGC 1487 shows three major populations of clusters: a blue cluster population with $(B-I){\le}0.45$, an intermediate-color cluster population with $0.45<(B-I){\le}1.55$, and a red cluster population with (B - I) > 1.55. The intermediate-color population is the most dominant among the three populations. The brightest clusters in the blue and intermediate- color populations are as bright as $B{\approx}18mag$ ($M_B{\approx}-12mag$), which are three magnitudes brighter than those in the red population. The blue and intermediate-color clusters are strongly concentrated on the bright condensations, while the red clusters are relatively more scattered over the galaxy. The CMD of these clusters is found to be remarkably similar to that of the clusters in the famous interacting system M51. From this we suggest that the intermediate-color clusters were, probably, formed during the merging process which occurred about 500 Myrs ago.

• 대한기계학회논문집B
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• 제25권10호
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• pp.1311-1317
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• 2001

To investigate only the effects of the stratified mixture distribution on initial flame propagation and combustion characteristics, the instantaneous equivalence ratio in the spark plug gap and combustion pressure were measured simultaneously In a constant volume chamber, To induce the stratified propane-air mixture distribution near the spark plug, counter-flow typed mixture injection system was used under the constant mean equivalence ratio $\Phi$$\_$mean/= 1.0 The instantaneous equivalence ratio was measured by a single-shot Raman scattering with narrow-band KrF excimer laser. The measuring error was within the limit of $\pm$ 3.5% provided that the proposed method was applied to the measured Raman signals. Judging from mass fraction burned derived from the measured pressure, the optimum combustion characteristics were shown under the condition that the local equivalence ratio in the spark plug was near 1.28$\pm$0.04, and these characteristics were more remarkable at the initial stage of combustion.

• 한국농공학회지
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• 제19권1호
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• pp.4296-4311
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• 1977

This study was conducted to derive an Instantaneous Unit Hydrograph for the accurate and reliable unitgraph which can be used to the estimation and control of flood for the development of agricultural water resources and rational design of hydraulic structures. Eight small watersheds were selected as studying basins from Han, Geum, Nakdong, Yeongsan and Inchon River systems which may be considered as a main river systems in Korea. The area of small watersheds are within the range of 85 to 470$\textrm{km}^2$. It is to derive an accurate Instantaneous Unit Hydrograph under the condition of having a short duration of heavy rain and uniform rainfall intensity with the basic and reliable data of rainfall records, pluviographs, records of river stages and of the main river systems mentioned above. Investigation was carried out for the relations between measurable unitgraph and watershed characteristics such as watershed area, A, river length L, and centroid distance of the watershed area, Lca. Especially, this study laid emphasis on the derivation and application of Instantaneous Unit Hydrograph (IUH) by applying Nash's conceptual model and by using an electronic computer. I U H by Nash's conceptual model and I U H by flood routing which can be applied to the ungaged small watersheds were derived and compared with each other to the observed unitgraph. 1 U H for each small watersheds can be solved by using an electronic computer. The results summarized for these studies are as follows; 1. Distribution of uniform rainfall intensity appears in the analysis for the temporal rainfall pattern of selected heavy rainfall event. 2. Mean value of recession constants, Kl, is 0.931 in all watersheds observed. 3. Time to peak discharge, Tp, occurs at the position of 0.02 Tb, base length of hlrdrograph with an indication of lower value than that in larger watersheds. 4. Peak discharge, Qp, in relation to the watershed area, A, and effective rainfall, R, is found to be {{{{ { Q}_{ p} = { 0.895} over { { A}^{0.145 } } }}}} AR having high significance of correlation coefficient, 0.927, between peak discharge, Qp, and effective rainfall, R. Design chart for the peak discharge (refer to Fig. 15) with watershed area and effective rainfall was established by the author. 5. The mean slopes of main streams within the range of 1.46 meters per kilometer to 13.6 meter per kilometer. These indicate higher slopes in the small watersheds than those in larger watersheds. Lengths of main streams are within the range of 9.4 kilometer to 41.75 kilometer, which can be regarded as a short distance. It is remarkable thing that the time of flood concentration was more rapid in the small watersheds than that in the other larger watersheds. 6. Length of main stream, L, in relation to the watershed area, A, is found to be L=2.044A0.48 having a high significance of correlation coefficient, 0.968. 7. Watershed lag, Lg, in hrs in relation to the watershed area, A, and length of main stream, L, was derived as Lg=3.228 A0.904 L-1.293 with a high significance. On the other hand, It was found that watershed lag, Lg, could also be expressed as {{{{Lg=0.247 { ( { LLca} over { SQRT { S} } )}^{ 0.604} }}}} in connection with the product of main stream length and the centroid length of the basin of the watershed area, LLca which could be expressed as a measure of the shape and the size of the watershed with the slopes except watershed area, A. But the latter showed a lower correlation than that of the former in the significance test. Therefore, it can be concluded that watershed lag, Lg, is more closely related with the such watersheds characteristics as watershed area and length of main stream in the small watersheds. Empirical formula for the peak discharge per unit area, qp, ㎥/sec/$\textrm{km}^2$, was derived as qp=10-0.389-0.0424Lg with a high significance, r=0.91. This indicates that the peak discharge per unit area of the unitgraph is in inverse proportion to the watershed lag time. 8. The base length of the unitgraph, Tb, in connection with the watershed lag, Lg, was extra.essed as {{{{ { T}_{ b} =1.14+0.564( { Lg} over {24 } )}}}} which has defined with a high significance. 9. For the derivation of IUH by applying linear conceptual model, the storage constant, K, with the length of main stream, L, and slopes, S, was adopted as {{{{K=0.1197( {L } over { SQRT {S } } )}}}} with a highly significant correlation coefficient, 0.90. Gamma function argument, N, derived with such watershed characteristics as watershed area, A, river length, L, centroid distance of the basin of the watershed area, Lca, and slopes, S, was found to be N=49.2 A1.481L-2.202 Lca-1.297 S-0.112 with a high significance having the F value, 4.83, through analysis of variance. 10. According to the linear conceptual model, Formular established in relation to the time distribution, Peak discharge and time to peak discharge for instantaneous Unit Hydrograph when unit effective rainfall of unitgraph and dimension of watershed area are applied as 10mm, and $\textrm{km}^2$ respectively are as follows; Time distribution of IUH {{{{u(0, t)= { 2.78A} over {K GAMMA (N) } { e}^{-t/k } { (t.K)}^{N-1 } }}}} (㎥/sec) Peak discharge of IUH {{{{ {u(0, t) }_{max } = { 2.78A} over {K GAMMA (N) } { e}^{-(N-1) } { (N-1)}^{N-1 } }}}} (㎥/sec) Time to peak discharge of IUH tp=(N-1)K (hrs) 11. Through mathematical analysis in the recession curve of Hydrograph, It was confirmed that empirical formula of Gamma function argument, N, had connection with recession constant, Kl, peak discharge, QP, and time to peak discharge, tp, as {{{{{ K'} over { { t}_{ p} } = { 1} over {N-1 } - { ln { t} over { { t}_{p } } } over {ln { Q} over { { Q}_{p } } } }}}} where {{{{K'= { 1} over { { lnK}_{1 } } }}}} 12. Linking the two, empirical formulars for storage constant, K, and Gamma function argument, N, into closer relations with each other, derivation of unit hydrograph for the ungaged small watersheds can be established by having formulars for the time distribution and peak discharge of IUH as follows. Time distribution of IUH u(0, t)=23.2 A L-1S1/2 F(N, K, t) (㎥/sec) where {{{{F(N, K, t)= { { e}^{-t/k } { (t/K)}^{N-1 } } over { GAMMA (N) } }}}} Peak discharge of IUH) u(0, t)max=23.2 A L-1S1/2 F(N) (㎥/sec) where {{{{F(N)= { { e}^{-(N-1) } { (N-1)}^{N-1 } } over { GAMMA (N) } }}}} 13. The base length of the Time-Area Diagram for the IUH was given by {{{{C=0.778 { ( { LLca} over { SQRT { S} } )}^{0.423 } }}}} with correlation coefficient, 0.85, which has an indication of the relations to the length of main stream, L, centroid distance of the basin of the watershed area, Lca, and slopes, S. 14. Relative errors in the peak discharge of the IUH by using linear conceptual model and IUH by routing showed to be 2.5 and 16.9 percent respectively to the peak of observed unitgraph. Therefore, it confirmed that the accuracy of IUH using linear conceptual model was approaching more closely to the observed unitgraph than that of the flood routing in the small watersheds.

• 한국환경보건학회지
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• 제22권2호
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• pp.43-57
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• 1996

To characterize worker's exposure to glass fibers, to find the correlation between airborne total dust concentrations and fiber concentrations and to recommend an appropriate evaluation method for worker's exposure to fibrous dusts in glass wool industry, we carried out this study. Average respirable fiber levels at five factories were 0.013-0.056 f/cc, and fairly below the OSHA PEL, 1 f/cc. A factory showed the lowest airborne fiber level, 0.013 f/cc, which was different significantly from those of other factories of which average fiber concentration was 0.046 f/cc. The cutting and grinding operations of insulation products resulted in higher airborne fiber cocentrations than any other processes(p<0.05). To characterize airborne fiber dimension, fiber length and diamter were determined using phase contrast microscope. The geometric means of airborne fiber lengths were $42-105 \mu m$. One factory had airborne fibers whose length distribution(GM = $105 \mu m$) was different from those of other factories(GM = $42-50 \mu m$). The percentages of respirable fibers less thinner than 3 gm were 38.9-90.9% at four factories, and two factories of them had the higher percentages than others. The findings explain for variation of airborne fiber diameters between factories. On the other hand, between the processes were the difference of fiber-length distributions observed. The cutting and grinding operations showed shorter fiber-length distributions than the fiber forming one. However, fiber-diameter distributions or respirable fiber contents were similar in all processes. The airborne fiber concentrations and the dust concentrations had relatively weak correlation(r=0.25), thus number of fibers couldn't be expected reliably from dust amount. Fiber count is appropriate for assessing accurate exposures and health effects caused by fibrous dusts including glass fibers. Ministry of Labor have established occupational exposure limit to glass fibers as nuisiance dust, but should establish it on the basis of respirable fiber concentration to provide adequate protection for worker's health

• 한국식품저장유통학회지
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• 제21권4호
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• pp.512-519
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• 2014

본 연구는 계절별 배추 원료의 최적 절임 조건 및 저장성 연구를 위한 기초 자료 제공을 위하여 계절별 절임배추의 물리화학적 및 미생물학적 특성 조사와 이들 특성의 상관성을 조사하였다. 계절별(봄배추, 여름배추, 가을배추 및 겨울배추) 절임배추의 pH와 적정산도의 경우 가을배추 시료가 $6.02{\pm}0.04$와 $0.15{\pm}0.01%$로 다른 계절의 절임배추 시료보다 pH는 약간 높고 적정산도는 약간 낮았다. 가용성 고형분 함량은 월동배추가 $7.76{\pm}0.39%$로 가장 높았고, 염도 함량은 계절별로 유의적인 차이가 없었다. 총균수의 경우 여름배추가 다른 계절의 배추보다 유의적으로 많은 균수가 있었고 색도는 유의적인 차이가 없었다. 조직감의 경우 경도(firmness)는 봄배추가 가장 높은 $4.92{\pm}0.06kg_f$였고, 단단한 정도(hardness)는 여름 배추가 $11.71{\pm}0.53kg_f$로 가장 높게 측정되었다. 한편 계절별 절임배추의 품질 특성간 상관관계를 분석한 결과 계절별 절임배추와 가용성 고형분 함량, 경도와 1% 유의수준 유의적인 상관성이 있었다. 또 주성분 분석 결과 첫 번째 주성분(F1)과 두 번째 주성분(F2)는(은) 전체 데이터의 각각 35.59%와 27.28%의 설명력을 보여 주었고, 총설명력은 62.87%였다. 주성분 F1은 계절, 밝기, 가용성 고형분 함량, 배추 두께, 총균수와 젖산균 수였고, 주성분 F2는 절임배추의 피크 개수였다. 계절별 절임배추의 품질 특성을 바탕으로 계층적 군집분석 결과 봄배추, 여름배추 그리고 가을과 월동 배추로 3그룹으로 나뉘었다. 이상의 결과에서 계절별 절임배추의 경우 물리화학적 및 미생물학적 품질 특성에 차이가 있음을 확인하였고, 품질 균일화와 고품질의 절임배추를 연중 생산하기 위해서는 각 계절별 배추의 품질 특성과 절임 적성에 관한 많은 연구가 필요하다고 사료된다.

• 천문학회보
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• 제35권2호
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• pp.44-44
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• 2010

We study the effect of massive neutrinos on the evolution of the early mini-halos ($M\sim10^6h^{-1}M{\odot}at$ z~20) where the first stars may have formed. In the framework of the extended Press-Schechter formalism, we evaluate analytically the rates of merging of the mini-halos into zero-dimensional larger halos and one-dimensional mini-filaments. It is shown that the halo-to-filament merging rate increases with the neutrino mass fraction $f_v$ while the halo-to-halo merging rate decreases. Comparing the cases of $f_v$=0 and 0.10, the halo-to-filament merging rate for $f_v$=0.10 is 3 times larger than the other. The distribution of the epochs of the longest-axis collapse of these first filaments is also derived and found to reach a sharp maximum at z~8-9. Once the first mini-filaments form, they would provide bridges along which the matter and gas more rapidly accrete onto the constituent halos, causing the early formation of the first galaxies and rapid growth of their central blackholes. Furthermore, the longest axis collapse of these first mini-filaments would spur the supermassive blackholes to power the ultra-luminous high-z quasars.

• 한국결정성장학회지
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• 제18권4호
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• pp.169-173
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• 2008

본 연구에서는 자외선 영역에서 우수한 발광강도를 가지는 적색 형광체를 얻기 위하여 microwave 급속 열처리법으로 합성하여 $Eu^{3+}$와 $Bi^{3+}$가 도핑된 $YVO_4$의 발광특성을 관찰하였다. Microwave 급속 열처리시 입자의 크기는 매우 미세하며, 응집이 매우 심하였으나 열처리 유지시간이 증가할수록 입자 크기는 증가하고 응집현상은 개선되는 경향을 나타내었다. $YVO_4$: $Eu^{3+}$, $Bi^{3+}$ 적색 형광체의 발광 peak는 $Eu^{3+}$ ion의 영향에 의해 594.9 nm와 602.3 nm에서 $^5D_0{\longrightarrow}^7F_1$ 전자 천이에 의한 약한 발광 peak와 616.7 nm와 620.0 nm에서 $^5D_0{\longrightarrow}^7F_2$ 전자 천이에 의한 강한 발광 peak이 관찰 되었다. Microwave 급속 열처리법을 형광체 합성시 장시간 열처리 시간이 필요하지 않으면서 균일한 activator의 확산으로 인하여 발광특성을 향상시키는 것을 확인 할 수 있었다.

• 한국환경생태학회지
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• 제11권2호
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• pp.166-176
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• 1997

들메나무군집의 식생구조를 밝히기 위하여 민주지산지역의 해발 700~1,100m 사이 계곡부에 10m*10m 면적의 조사구 20개를 설정, 조사하였다. 전체 조사구에 대해 classification 기법중 TWINSPAN을 이용한 결과 6개의 군집으로 분리되었으며, 각 군집별로 종조성을 살펴본 결과 민주지산 지역의 들메나무군집은 신갈나무군집에서 천이가 진행되어 온 것으로 판단되며, 까칩가달, 고로쇠나무, 층층나무 등이 부수종을 이루고 있으나 경쟁수종이 형성되어 있니 장ㄴㅎ아 토지극상림으로 판단되었다. 흉고직경급별분석에서 들메나무는 전층위에서 고르게 출현하고 있고, 군집이 안정되어 있어 종다양도(Shannon's index 0.72~0.82)가 낮게 나타났으며, 각 조사구당 평군종수는 11.0종, 평균개체수는 111.5주였다.

• 항공우주의학회지
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• 제30권2호
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• pp.75-79
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• 2020

This study focuses on the comparative and quantitative analysis of the epidemiologic trends and aspects of severe fever with thrombocytopenia syndrome (SFTS) outbreaks between Korea and Japan from 2013 to 2017. The following factors were analyzed; cumulative incidence rate (CIR), cases-fatality rate (CFR), and the epidemic aspects, including cases related to gender, male-to-female morbidity ratio (MFMR), age, seasonal, and geographical distributions. We observed 607 SFTS cases with CIR in Korea during the period 2013 to 2017 were as 0.24 per 100,000 populations and with a 127 fatal-cases (F.C.s), corresponding to a CFR of 20.9%, respectively. During the same period in Japan, 319 SFTS cases with a CIR of 0.05 and with 60 F.C.s to a CFR of 18.8% observed. When compared, the CIR of SFTS in Korea was significantly higher than in Japan (P<0.01), but there were no significant differences levels of the CFR and MFMR between Korea and Japan. Also, a higher incidence of SFTS was observed in people aged over 50-years or elders in Korea and those of 60-years or elders in Japan (P<0.01). The seasonal distribution of SFTS outbreak cases showed that the incidence in summer through autumn in Korea (92.4% of total cases) was higher than in Japan (65.2%), while the outbreaks of SFTS in spring was much higher in Japan (31.0%) than in Korea (7.4%), (P<0.01). The regional distribution revealed no significant difference between the eastern area (44.8%) and the western area (46.8%) of the Korean peninsula except Jeju-island (8.4%). However, in Japan, the incidence only occurred in Chubu-Kinki-Chugoku (30.3%), Shikoku (25.7%), Kyushu (42.6%) and Okinawa (0.3%), which are the western and southern areas of Japan. These differences in SFTS occurrence may reflect the influences of vector/hosts, climate, and geographical and cultural characteristics between the two countries.

• 천문학회지
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• 제30권1호
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• pp.83-94
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• 1997

We have identified the candidates for the primordial galaxies in the process of formation in the Hubble Deep Field (hereafter HDF). In order to select these objects we have removed objects brighter than 29-th magnitude in the HDF images and smoothed the maps with the Gaussian filters with the FWHM of 0.8' and 4' to obtain the difference maps. This has enabled us to find. very faint diffuse structures close to the sky level. Peaks are identified in the difference map for each of three HDF chips with three filters (F450W, F606W, and F814W). They have the apparent AB magnitudes typically between 29 and 31. The objects identified in different wavelengths filters have a strong cross-correlations. The correlation lengths are about 0.8'. This means that an object found in one filter can be also found as a peak within 0.8' separation in another filter, thus telling the reality of the identified objects. This angular scale is also the size of the primordial galaxies which have strong color fluctuations on their surfaces. Their large-scale distribution quite resembles that of nearby galaxies, supporting the idea that these objects are ancestors of the present bright galaxies forming at statistically high density regions. Inspections on individual objects show that these primordial galaxy candidates have tiny multiple glares embedded in diffuse backgrounds. Their radial light distributions are quite different from that of nearby bright galaxies. We may be now looking at the epoch of galaxy formation.