• 한국작물학회지
• /
• 제36권4호
• /
• pp.370-381
• /
• 1991

$\ulcorner$농사직설$\lrcorner$ 단계에서는 품종보다는 품종군 또는 도종류로서의 조만, 치갱유, 또는 몇몇 지방 품종명이 소개되는 정도였으나, 우리나라의 도작기상이 ‘조한만수의’ 특징을 보일 뿐만 아니라 만하의 풍우 때문에 이들 재해를 회피하여 안전수확을 하는 것이 가장 중요하였으므로 15세기 이후의 도종발달은 조파조수집에 적응하고 내재해성을 갖는 쪽으로 서서히 진전되어 왔다. 시대경과에 따라 조도, 유망종, 유수색종, 내탈립종, 내풍성종, 내비성종의 분화와 이들의 정유율증대가 이루어져 왔음으로 알 수 있다.

• Wind and Structures
• /
• 제19권5호
• /
• pp.505-522
• /
• 2014

While effects of the atmospheric boundary layer flow on engineering infrastructure are more or less known, some local transient winds create difficulties for structures, traffic and human activities. Hence, further research is required to fully elucidate flow characteristics of some of those very unique local winds. In this study, important characteristics of observed vertical velocity profiles along the main wind direction for the gusty Bora wind blowing along the eastern Adriatic coast are presented. Commonly used empirical power-law and the logarithmic-law profiles are compared against unique 3-level high-frequency Bora measurements. The experimental data agree well with the power-law and logarithmic-law approximations. An interesting feature observed is a decrease in the power-law exponent and aerodynamic surface roughness length, and an increase in friction velocity with increasing Bora wind velocity. This indicates an urban-like velocity profile for smaller wind velocities and rural-like velocity profile for larger wind velocities, which is due to a stronger increase in absolute velocity at each of the heights observed as compared to the respective velocity gradient (difference in average velocity among two different heights). The trends observed are similar during both the day and night. The thermal stratification is near neutral due to a strong mechanical mixing. The differences in aerodynamic surface roughness length are negligible for different time averaging periods when using the median. For the friction velocity, the arithmetic mean proved to be independent of the time record length, while for the power-law exponent both the arithmetic mean and the median are not influenced by the time averaging period. Another issue is a large difference in aerodynamic surface roughness length when calculating using the arithmetic mean and the median. This indicates that the more robust median is a more suitable parameter to determine the aerodynamic surface roughness length than the arithmetic mean value. Variations in velocity profiles at the same site during different wind periods are interesting because, in the engineering community, it has been commonly accepted that the aerodynamic characteristics at a particular site remain the same during various wind regimes.

• 한국대기환경학회지
• /
• 제20권1호
• /
• pp.1-15
• /
• 2004

Sea/land circulation system is a representative mesoscale local circulation system in coastal area. In this study, wind fields around coastal area. Pohang, which is affected by this system was investigated and its detailed characteristic analysis was carried out. The following can be found out from the numerical simulation. Generally, at nighttime mountain winds prevail and land breeze toward the coastal area was well simulated During daytime, valley wind and sea breeze was simulated in detail. Especially, as a result of analyzing the land breeze path, it could be found along the coastline as it flows out through low land coastal area. In order to investigate the accuracy of model results. wind speed, temperature and wind direction of continuous typical sea/land breeze occurrence day was compared with observation data. Analyzing the characteristics of local circulation system was very hard because of horizontally sparse observation data but from the above result, a numerical simulation using RAMS, which satisfies the spatial high resolution, will provide more accurate results.

• 한국대기환경학회지
• /
• 제18권1호
• /
• pp.1-10
• /
• 2002

A three-dimensional numerical model which involved the nesting method was developed to reproduce the wind circulation of Kwangyang Bay area which comprises complicated mountains and sea topograph. The calculated results indicated geographical effects of Kwangyang Bay area, sea/land breezes and mount-valley wind which are local circular winds. We also noticed that the northern inland area of Kwangyang Bay formed the very complex wind systems under the influence of such geographic effects when a land breeze was not formed. A good agreement was found between predicted and observed values of temperature. In addition, the calculated results of the wind direction and the wind velocity are in accord with the observed values. They showed only a slight difference in between predicted and the observed values, when the sea breeze and the land breeze are changing.

• Journal of Ecology and Environment
• /
• 제43권4호
• /
• pp.438-453
• /
• 2019

Background: To investigate the trends of succession occurring at the Pinus thunbergii forests on the lowlands of Jeju Island, we quantified the species compositions and the importance values by vegetation layers of Braun-Blanquet method on the Pinus thunbergii forests. We used multivariate analysis technique to know the correlations between the vegetation group types and the location environmental factors; we used the location environment factors such as altitudes above sea level, tidal winds (distance from the coast), annual average temperatures, and forest gaps to know the vegetation distribution patterns. Results: According to the results on the lowland of Jeju Island, the understory vegetation of the lowland Pinus thunbergii forests was dominated by tall evergreen broad-leaved trees such as Machilus thunbergii, Neolitsea sericea, and Cinnamomum japonicum showing a vegetation group structure of the mid-succession, and the distribution patterns of vegetation were determined by the altitudes above sea level, the tidal winds on the distance from the coast, the annual average temperatures, and the forest gaps. We could discriminate the secondary succession characteristics of the Pinus thunbergii forests on the lowland and highland of Jeju Island of South Korea. Conclusions: In the lowland of Jeju Island, the secondary succession will progress to the form of Pinus thunbergii (early successional species)→Machilus thunbergii, Litsea japonica (mid-successional species)→Machilus thunbergii (late-successional species) sequence in the temperate areas with strong tidal winds. In the highland of Jeju Island, the succession will progress to the form of Pinus thunbergii (early successional species)→Neolitsea sericea, Eurya japonica (mid-successional species)→Castanopsis sieboldii (late-successional species) sequence in the areas where tidal winds are weak and temperatures are relatively low. However, local differences between lowland and highland of Jeju Island will be caused by the micro-environmental factors resulting from the topographic differences and the supply of tree seeds. From the characteristics of succession study, we could properly predict and manage the Pinus thunbergii forest ecosystem on lowland and highland of Jeju Island.

• 한국대기환경학회지
• /
• 제31권6호
• /
• pp.573-584
• /
• 2015

In this study, the atmospheric dispersion of radioactive material ($^{137}Cs$) was simulated with regard to its impact within a 50-km radius from the Kori Nuclear Power Plant (NKPP) based on two different types of models (the non-steady-state puff model CALPUFF and the lagrangian model HYSPLIT) during the spring of 2012 (May 2012). The dispersion distribution of $^{137}Cs$ calculated in the CALPUFF model was similar to that of the HYSPLIT model, but the magnitudes of differences in its spatio-temporal concentrations between the two models were different. The $^{137}Cs$ concentrations simulated by the CALPUFF were significantly lower than those of the HYSPLIT due to a limitation of puff models (e.g. puff size growth over time). The CALPUFF had the advantage of determining the dispersion of radioactive materials and their impacts on the surrounding regions, compared with the HYSPLIT that had high concentrations of $^{137}Cs$ in only small local areas with the movement of air masses along the local winds.

• Wind and Structures
• /
• 제8권5호
• /
• pp.357-372
• /
• 2005

Mean and extreme pressure distributions on a large cantilevered flat roof model are measured in a boundary layer wind tunnel. The largest peak suction values are observed from pressure taps beneath conical "delta-wing type" corner vortices that occur for oblique winds, then the characteristics and causes of the local peak suctions are discussed in detail. Power spectra of fluctuating wind pressures measured from some typical taps located at the roof edges under different wind directions are presented, and coherence functions of fluctuating pressures are also obtained. Based on these results, it is verified that the peak suctions are highly correlated with the conical vortices. Furthermore, according to the characteristics of wind loads on the roof, an aerodynamic solution to minimize the peak suctions by venting the leading edges and the corners of the roof is recommended. The experimental results show that the suggested strategy can effectively control the generation of the conical vortices and make a reduction of 50% in mean pressures and 25% in extreme local pressures at wind sensitive locations on the roof.

• 천문학논총
• /
• 제30권2호
• /
• pp.355-358
• /
• 2015

We have conducted a near-infrared monitoring campaign at the UK InfraRed Telescope (UKIRT), of the Local Group galaxy M33. The main aim was to identify stars in the very final stage of their evolution, and for which the luminosity is more directly related to the birth mass than the more numerous less-evolved giant stars that continue to increase in luminosity. The pulsating giant stars (AGB and red supergiants) are identified and their distributions are used to derive the star formation rate as a function of age. These stars are also important dust factories; we measure their dust production rates from a combination of our data with Spitzer Space Telescope mid-IR photometry. The mass-loss rates are seen to increase with increasing strength of pulsation and with increasing bolometric luminosity. Low-mass stars lose most of their mass through stellar winds, but even super-AGB stars and red superginats lose ~40% of their mass via a dusty stellar wind. We construct a 2-D map of the mass-return rate, showing a radial decline but also local enhancements due to agglomerations of massive stars. By comparing the current star formation rate with total mass input to the ISM, we conclude that the star formation in the central regions of M33 can only be sustained if gas is accreted from further out in the disc or from circum-galactic regions.

• 한국강구조학회 논문집
• /
• 제17권3호통권76호
• /
• pp.263-270
• /
• 2005

본 연구에서는 강풍을 받는 차량의 주행안정성을 증가시키기 위한 일련의 종합적인 대책을 제시하였다. 본 연구는 크게 세가지 부분으로 구성된다. 첫 번째로 차종별 속도제한 및 통행제한 기준을 마련하였다. 두 번째는 방풍대책의 필요여부를 판단할 설치 기준을 작성하는 것으로, 국부적인 지형의 보정을 통한 기상자료의 확률적인 모델을 이용하여 위험도를 판단하는 과정을 제시하였다. 세 번째는 풍속을 저감시킬 수 있는 효과적인 방풍벽을 제안하는 것으로 전산유체해석과 풍동실험을 통하여 풍속감소 효과, 경제성, 시각적 개방성을 고려한 방풍벽을 설계하였다. 아울러 현장실험을 통하여 4가지 방풍벽의 성능에 대한 검증을 하였다.

• 한국환경과학회지
• /
• 제26권5호
• /
• pp.621-638
• /
• 2017

Meteorological characteristics related to variations in ozone ($O_3$) concentrations in the Korean peninsula before, during, and after Typhoon Talas (1112) were analyzed using both observation data and numerical modeling. This case study takes into account a high $O_3$ episode (e.g., a daily maximum of ${\geq}90ppb$) without rainfall. Before the typhoon period, high $O_3$ concentrations in the study areas (e.g., Daejeon, Daegu, and Busan) resulted from the combined effects of stable atmospheric conditions with high temperature under a migratory anticyclone (including subsiding air), and wind convergence due to a change in direction caused by the typhoon. The $O_3$ concentrations during the typhoon period decreased around the study area due to very weak photochemical activity under increased cloud cover and active vertical dispersion under a low pressure system. However, the maximum $O_3$ concentrations during this period were somewhat high (similar to those in the normal period extraneous to the typhoon), possibly because of the relatively slow photochemical loss of $O_3$ by a $H_2O+O(^1D)$ reaction resulting from the low air temperature and low relative humidity. The lowest $O_3$ concentrations during the typhoon period were relatively high compared to the period before and after the typhoon, mainly due to the transport effect resulting from the strong nocturnal winds caused by the typhoon. In addition, the $O_3$ increase observed at night in Daegu and Busan was primarily caused by local wind conditions (e.g., mountain winds) and atmospheric stagnation in the wind convergence zone around inland mountains and valleys.