• Journal of Astronomy and Space Sciences
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• 제25권2호
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• pp.129-138
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• 2008

This study attempts to show how the geomagnetic indices, AU, AL and Dst, respond to the interplanetary parameters, more specifically, the solar wind electric field VBz during southward interplanetary magnetic field (IMF) period. The AU index does not seem to respond linearly to the variation of southward IMF. Only a noticeable correlation between the AU and VBz is shown during summer, when the ionospheric conductivity associated with the solar EUV radiation is high. It is highly likely that the effect of electric field on the eastward electrojet intensification is only noticeable whenever the ionospheric conductivity is significantly enhanced during summer. Thus, one should be very cautious in employing the AU as a convection index during other seasons. The AL index shows a significantly high correlation with VBz regardless of season. Considering that the auroral electrojet is the combined result of electric field and ionospheric conductivity, the intensification of these two quantities seems to occur concurrently during southward IMF period. This suggests that the AL index behaves more like a convection index rather than a substorm index as far as hourly mean AL index is concerned. Contrary to the AU index, the AL index does not register the maximum value during summer for a given level of VBz. It has something to do with the findings that discrete auroras are suppressed in sunlight hemisphere (Newell et al. 1996), thus reducing the ionospheric conductivity during summer. As expected, the Dst index tends to become more negative as VBz gets intensified. However, the Dst index (nT) is less than or equal to 15VBz(mV/m) + 50(Bz < 0). It indicates that VBz determines the lower limit of the storm size, while another factor(s), possibly substorm, seems to get further involved in intensifying storms. Although it has not been examined in this study, the duration of southward IMF would also be a factor to be considered in determining the size of a storm.

• 한국응용곤충학회지
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• 제29권2호
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• pp.123-131
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• 1990

숫검 은밤나방(Agrotis tokionis Butler) 유충 하면의 개시와 종료에 온도와 광주기가 어떠한 역할을 하는지 조사하였다. 자연조건에서 하면기간은 유충이 하면을 시작하는 시기가 늦을수록 짧아져서 조사짐단내 용화시기는 일치하는 경향을 보였다. 실험한 모든 광주기 및 온도 조건에서 유충의 발육속도에는 변화가 있었으나 하면개시에는 아무런 영향을 미치지 못하 였기 때문에 이 곤충의 하면은 내인성으로 추측되었다. 그러나 하면의 종료는 이상의 두가 지 환경조건의 변화에 영향을 받았다. 온도조건에 대한 반응에 따라 하면기간은 2시기로 나눌 수 있었는데 전기에는 평균온도가 높을수록 하면시간이 단축되었으나 후기에는 저온 일수록 짧아졌다. 또한 실험한 광주기에서는 단일조건 (LD 8 : 16)에서 하면기간이 가장 짧았다.

• Journal of Astronomy and Space Sciences
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• 제40권3호
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• pp.101-111
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• 2023

We conducted a statistical study of polar mesospheric summer echoes (PMSEs) in relation to magnetic local time (MLT), considering the geomagnetic conditions using the K-index (or K). Additionally, we performed a case study to examine the velocity profile, specifically for high velocities (≥ ~100 m/s) varying with high temporal resolution at high K-index values. This study utilized the PMSE data obtained from the mesosphere-stratosphere-troposphere radar located in Esrange, Sweden (63.7°N, 21°E). The change in K-index in terms of MLT was high (K ≥ 4) from 23 to 04 MLT, estimated for the time PMSE was present. During the near-midnight period (0-4 MLT), both PMSE occurrence and signal-to-noise ratio (SNR) displayed an asymmetric structure with upper curves for K ≥ 3 and lower curves for K < 3. Furthermore, the occurrence of high velocities peaked at 3-4 MLT for K ≥ 3. From case studies focusing on the 0-3 MLT period, we observed persistent eastward-biased high velocities (≥ 200 m/s) prevailing for ~18 min. These high velocities were accompanied with the systematic motion of profiles at 85-88 km, including large shear formation. Importantly, the rapid variations observed in velocity could not be attributed to neutral wind effects. The present findings suggest a strong substorm influence on PMSE, especially in the midnight and early dawn sectors. The large zonal drift observed in PMSE were potentially energized by local electromagnetic fields or the global convection field induced by the electron precipitation during substorms.

• Ocean and Polar Research
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• 제27권3호
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• pp.351-358
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• 2005

Reproductive condition of the tropical blacklip pearl oyster, Pinctada margaritifera collected during the period July through September 2003 from Chuuk Lagoon, Federated State of Micronesia was investigated using histology. The level of gonad development for each pearl oyster was determined with an average score of five microscopic fields, and the average score was used as the maturity index (ML). All wild pearl oysters collected in July did exhibit fully ripe eggs in their ovaries ($45{\sim}50{\mu}M$ in diameter), indicating that they were ready for spawning. In mid August most wild pearl oysters were in spawning and M1 dropped dramatically from mid- to late September, suggesting that the wild pearl oyster completed spawning during this period. In contrast, the cultivated pearl oysters collected in mid-September held ripe eggs in the ovaries and only a few of them spawned, indicating that gonad maturation of the cultivated pearl oyster was somewhat slower than that of the wild pearl oyster in Chuuk Lagoon during the summer period. Histological analysis also indicated that spawning of the pearl oyster is rather incomplete and they may spawn continuously during summer.

• 한국환경과학회지
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• 제20권10호
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• pp.1243-1263
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• 2011

This study was carried out to determine marine environments and phytoplankton community in Deukryang Bay during the period of summer in 1987-2010. Water temperature, salinity, pH and dissolved oxygen were shown in much yearly fluctuations. In August, water temperatures in surface and on bottom were the highest, compared with average surface (24.54$^{\circ}C$) and bottom (22.90$^{\circ}C$) water temperature for 18 years in Deukryang Bay. The main reason is assumed to longer duration of sunshine during the period of August. Although the amount of the rainfall in August was the highest, significant impact of marine environment did not show. Most of dissolved inorganic nitrogen and phosphate in Deukryang were lower concentration during summer and N:P ratio also showed below 18 in Redfield. In particular, extreme increasing of N:P ratio in August was occurred by intensive precipitation. Distribution of phytoplankton community was a consistent occurrence for 18 years. The genus of Chaetoceros, Cosinodisucs and Skeletonema were regarded as the represent diatom, whereas the highest occurrence of genus among dinofagellates was Ceratium. It is thought that the relationship between phytoplankton and nutrient has a strong positive signal, although nutrients persist a little concentration and much fluctuations in marine environments were observed. High availability in phytoplankton is contributed to consistently provide the food organism of shellfish. Consequently, recent decreasing production of shellfish and seed are probably associated with higher temperature during the period of summer. However, higher temperature is also occurred ago and after 2000. On the basis of geography, Deukryang Bay had a small mouth and long channel, which is attributed to decreasing genetic diversity. It is assumed that higher temperature and lower genetic diversity have a extreme impact of larvae and shellfish for reproduction in Deukryang. It is necessary to persistently monitor based on water quality and phytoplankton community.

• 한국해양환경ㆍ에너지학회지
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• 제7권3호
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• pp.137-145
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• 2004

제주해역의 상기 파랑분포 특성을 제3세대 파랑모델인 SWAN모델에 의한 시뮬레이션을 통해 고찰하였다. 제주해역은 한국 연안에서 파랑에너지 밀토가 상대적으로 큰 해역으로 파력발전에 적합한 후보지이며, 파력발전 효율은 해역의 파랑특성 인자들에 밀접히 연관되어 있다. 파랑분포는 한국해양연구원의 광역 장기 파랑추산 자료의 월평균 파랑특성을 경계조건으로 1 km 격자의 SWAN모델 시뮬레이션을 통해 획득하였으며, 파랑분포 해석은 유의파고, 평균 파향, 평균 과주기의 계절적ㆍ공간적 변화특성 고찰을 주목적으로 하였다. 유의파고는 겨울과 여름이 우세하며, 지역적으로는 제주도의 서쪽이 동쪽에 비해 유의파고가 높다. 유의파고의 최고치는 겨울에 북서쪽 해역에서 발생하며, 여름철의 남동쪽 해역이 다음으로 우세하고, 봄가을은 전체적으로 파고가 낮으나 분포가 비교적 균일하다. 파향의 분포는 회절의 영향을 받는 배후지역을 제외하면, 여름에는 북서 방향이 지배적이고, 겨울에는 남동 방향이 지배적이다. 파주기는 여름과 겨울철에 길고, 동쪽에 비해 서쪽 해역에서 길게 나타난다. 파주기의 최대치는 겨울에 서쪽 해역에서 발생하고, 여름에는 남쪽 해역의 파주기가 다소 우세하나 비교적 균일한 분포를 갖는다.

• 대기
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• 제17권2호
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• pp.115-123
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• 2007

The present study uses the GOES IR brightness temperature to examine the temporal and spatial variability of cloud activity over the region $25^{\circ}N-45^{\circ}N$, $105^{\circ}E-135^{\circ}E$ and analyzes the coherence of eastern Asian summer season rainfall in Weather Research and Forecast (WRF) model. Time-longitude diagram of the time period from June to July 2005 shows a signal of eastward propagation in the WRF model and convective index derived from GOES IR data. The rain streaks in time-latitude diagram reveal coherence during the experiment period. Diurnal and synoptic scales are evident in the power spectrum of the time series of convective index and WRF rainfall. The diurnal cycle of early morning rainfall in the WRF model agrees with GOES IR data in the Korean Peninsula, but the afternoon convection observed by satellite observation in China is not consistent with the WRF rainfall which is represented at the dawn. Although there are errors in strength and timing of convection, the model predicts a coherent tendency of rainfall occurrence during summer season.

• 한국물환경학회지
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• 제21권2호
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• pp.158-168
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• 2005

In this study, the discharging effluents from have been 9 municipal wastewater treatment plants surveyed for 1 year-period. Statistics including probability distribution, cumulative occurrence concentration and other statistical parameters were presented. In addition, treatment performance and its stability were also discussed. Most of the plants, have an operational problem of high soluble organic content in the secondary effluent which may be associated with the integrated treatment of human and livestock manures. Nitrogen concentration in the effluents were usually higher during the period of summer and winter. It was found that this is mainly due to lack of the proper C/N ratio during the summer, or/and the effects of low temperature and less dilution by dry weather during the winter. Phosphorus concentration is sharply increased in June. Discussion with plant operators told that it is due to the dissolution of phosphate from the sludge accumulated in the primary settling tanks from the early spring to june. During this period, usually, sludge treatment line is highly overloaded with flush-outs of the sediments also stored in the bottom of combined sewer due to the low flow during winter season. Most of the plants can meet new effluent discharge limits of the nitrogen and phosphorus, and total coliform without further treatment.

• 설비공학논문집
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• 제27권8호
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• pp.432-439
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• 2015

Current building procedures seek to minimize external air supplies to reduce the energy consumption of air conditioning, resulting in a high dependency on mechanical ventilation. We therefore studied an economizer-cycle system, whereby the introduction of external air saves energy. We analyzed different economizer-control methods, addressing mixed-air temperatures and outdoor-air fractions according to outdoor-air temperatures; also, we analyzed the energy consumption of the three economizer-cycle control types using detailed EnergyPlus simulation modeling. A differential enthalpy control method showed a lower energy consumption range from 5.8% to 6.2% than that of other methods during the simulated period. A differential dry-bulb control method showed a 12.7% lower energy consumption than the no-economizer method in the intermediate period, but also showed 7.1% more energy consumption during the summer period. When latent heat was not removed due to high summer humidity, we found a significant level of resultant energy consumption.

• 한국환경보건학회지
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• 제26권2호
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• pp.41-48
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• 2000

This study has been carried out to determine the seasonal characteristics of concentration of various ionic (CI-, NO3-, SO42-, Na+, NH+, K+, Ca2+) and heavy metallic (Pb, Mn, Cu, Ni) species in Pusan from August 1997 to April 1998. The concentrations of CI-, Na+, K+ were higher during summer with 2.98 ${\mu}{\textrm}{m}$/㎥. Seasonal variation of total concentration of but the concentration of NH4+ was higher during winter with 2.46${\mu}{\textrm}{m}$/㎥. Seasonal variation of total concentration of heavy metals(Pb, Cu, Mn, Ni) were 186.0 ng/㎥ in summer, 222.6 ng/㎥ in autumn, and 135.83 ng/㎥ in winter. Over the seasons inspected, the concentration of Mn was higher in coarse particles than fine particles and concentration of Ni was higher in fine particles than coarse particles. during yellow sand period, the concentration of TSP was increased about two times than that of other period. SO42-, Ca2+ concentrations were higher than other ionic components because of soil particles. The concentration of Ni showed 94.62ng/㎥ was increased about 4~5 times than other period. Principal component of the yellow sand, SO42-, Ca2+ could be discreased by rainfall and washout effect of atmospheric aerosol was higher in coarse particles than fine particles. Results from PCA(principal component analysis) showed that major pollutant was NaCl by seasalt particulate and (NH4)2SO4.