• The Journal of Engineering Geology
• /
• v.22 no.1
• /
• pp.27-37
• /
• 2012

To investigate the effect of aquifer disturbance on hydraulic properties while well drilling at unconsolidated aquifer, the following tests were conducted: the surge block and air-surging methods, which are well development methods used after well drilling; and step-drawdown tests and constant-rate pumping tests, which are used to assess changes in the aquifer after well drilling and development. The result of step-drawdown tests indicated that drawdown for a pumping-rate of $700m^3/day$ was 21.62 m after well development, decreasing 4.39 m from 26.01 m after well drilling. The skin factor used to identify the well properties decreased from 7.92 after well drilling to 5.04 after well development, respectively, which shows the improvement of well. Constant-rate pumping tests revealed a small increase in aquifer transmissivity after well development at MW-2, -3, and -4, centering around pumping well, from $1.684{\times}10^{-3}{\sim}4.490{\times}10^{-3}m^2/sec$ to $4.002{\times}10^{-3}{\sim}4.939{\times}10^{-3}m^2/sec$. MW-1, however, showed decline in hydraulic conductivity from $1.018{\times}10^{-2}m^2/sec$ to $6.988{\times}10^{-3}m^2/sec$, which was caused by a small decrease of aquifer permeability around monitoring well MW-1 due to latent factor of air interception and clogging in aquifer during surging. This finding indicates that fine particles have an effect on hydraulic properties at unconsolidated aquifers during well drilling; therefore, we consider that well drilling and development have an effect on hydraulic properties.

• Pediatric Infection and Vaccine
• /
• v.17 no.2
• /
• pp.91-100
• /
• 2010

Purpose : Recurrent otitis media (ROM) is usually defined as ${\geq}$3 distinct and well-documented episodes within 6 months or ${\geq}$4 episodes within 12 months. ROM is sufficiently important to warrant consideration of chemoprophylaxis, tympanostomy tube placement. There also is evidence that children with ROM are at risk for both hearing loss and speech delay. However, studies of ROM have been notably insufficient. In addition, even though environmental, racial, and sociocultural differences can affect risk factors, few studies have been conducted with regard to recurrent otitis media in Korea. Methods : This study was conducted from July 2009 to January 2010 with infants and children who were younger than 60 months old, who visited the out-patient clinics at Han-Il General Hospital and Kyunghee University Hospital. Data were collected by interview using a pre-formed sheet. Among a total of 892 infants and children, 457 were excluded, and the remaining 435 were allocated to 104 with ROM and 331 as a control group. Results : Attendance at daycare centers (P<0.001, OR=2.85), allergic rhinitis (P=0.026, OR=2.32), past history of bronchiolitis (P=0.003, OR=2.33), and low socioeconomic status (P=0.005, OR=2.00) were found to have a close significant correlation with ROM. Risk factors such as sex, having a sibling, breast-feeding, use of pacifiers, atopy, pneumococcal vaccination, influenza vaccination, smoking of parents, and indoor smoking are not relevant. Conclusion : Attendance at daycare centers, allergic rhinitis, past history of bronchiolitis, and low socioeconomic status have been identified as risk factors for ROM.

• Korean Journal of Environment and Ecology
• /
• v.27 no.3
• /
• pp.280-304
• /
• 2013

This study was carried out to investigate the flora of Mt. Gilsangsan (Ganghwa-Isl.). The vascular plants were collected 14 times (from March to November 2012), and were identified as 595 taxa; 122 families, 359 genera, 529 species, 7 subspecies, 51 varieties, 2 forms and 3 hybrids. The plant formation of Mt. Gisangsan is the deciduous broad-leaved and conifer mixed forest which is the common one in the middle part of Korean peninsula. All most mountain covered with young secondary forest which is mainly composed of Pinus and Quercus. The family represented by the largest number of species diversity were Asteraceae (11.%), Poaceae (10.7%), Cyperaceae (6.38%), Fabaceae (3.86%) and Rosaceae (3.52%) respectively. Korean endemic plants of this area were 12 taxa; Asarum misandrum, Clematis brachyura, Philadelphus schrenkii, Forsythia koreana, Polygonatum infundiflorum, etc. The red list of vascular plants according to IUCN valuation basis were examined, endangered species (EN) Abies koreana, Near Threatened species (NT) both Wikstroemia trichotoma and Sparganium erectum, Least Concern species (LC) Platycladus orientalis, Swertia diluta var. tosaensis and Iris minutoaurea and by Not Evaluate species (NE) Polygonatum infundiflorum. The floristic regional indicator plants found in this area were 45 taxa comprising two taxa of grade V and VI, nine taxa of grade III, three taxa of grade II, 29 taxa of gradeI. The naturalized plants were identified as 64 taxa and the percent of naturalized index (NI) was 10.7% of total 595 taxa vascular plants. Ecosystem disturbance wild plants were consisted of eight taxa; Rumex acetosella, Sicyos angulatus, Solanum carolinense, Ambrosia artemisiifolia, Ambrosia trifida, Aster pilosus, Hypochaeris radicata and Lactuca scariola. Furthermore, therophytes (26.5%), hemicryptophytes (26.0%), Geophyte (14.0%) showed high proportional ratio in life form spectrum.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.14 no.4
• /
• pp.224-229
• /
• 2011

Recently, the management of the marine invasive alien species introduced by ballast water has come to the core as an urgent task. Because, hazardous organisms cause harmful effects on the ecosystem. Hazardous organisms also negatively affect fisheries, commercial shipping activities, and marine resources. In this regard, IMO used to operate GloBallast, Ballast Water Risk Assessment System, in order to manage the introduction of invasive species by ballast water. GloBallast is constructed to assess the relative risk due to the movement of ballast water between nations, using the volume and the number of times of ballast water discharge, the environmental similarity between ports, and the abundance of hazardous species as the main factors. According to the results of the demo-operation of GloBallast, it was found out that the environmental similarity factor had affected most highly the results of risk assessment. Therefore, in this study, the correlation between the main factors used in GloBallast risk assessment were re-examined, and some methods were suggested in order to reflect these main factors in the risk assessment more reasonable.

• Journal of the Korean Chemical Society
• /
• v.50 no.5
• /
• pp.362-368
• /
• 2006

SH group modifying chemicals were used to characterize the eight cysteine residues of cabbage PLD. 5,5-dithiobis(2-nitrobenzoate)(DTNB) was used to titrate the SH group of cysteine residues . Based on the optical density at 412nm due to the reduced DTNB, 4 SH groups are found to be present in a native PLD while 8 SH groups in the denatured PLD whose tertiary structure was perturbed by 8M urea. The results imply that among the 8 cysteine residues of PLD, the half(4) are exposed on the surface whereas the other half are present at the interior of the enzyme tertiary structure. The PLD was inactivated by SH modifying reagents such as p-chloromercuribenzoate(PCMB), iodoacetate, iodoacetamide, and N-ethylmaleimide. At the addition of dithiothreitol(DTT) only the PCMB inhibited PLD activity was recovered reversibly. The micro-environment of the exposed SH group of cysteine residues was examined with various disulfide compounds with different functional groups and we found that anionic or neutral disulfides appear to be more effective than the positively charged cystamine for inactivating the PLD activity. The effect of redox state of cysteine residues on the PLD activity was further explored with H2O2. The oxidation of SH groups by H2O2 inhibited the PLD activity more than 70%, which was mostly recovered by DTT. From these results, we could confirm chemically that all the cysteine residues of PLD are present as in their reduced SH forms and the 4 SH groups exposed on the surface of the enzyme may play important roles in the regulation of PLD activity.

• Journal of Radiation Protection and Research
• /
• v.37 no.4
• /
• pp.167-172
• /
• 2012

Jeju Island is a significant area as a reference site of in situ gamma spectrometry because there are a number of open spaces which includes $^{137}Cs$ above a certain level. In this paper, the pasture within the Hallasan National Park was selected as one of the open spaces of Jeju Island. The homogeneity of $^{137}Cs$ at the site was assessed by analysis of variance on count and by radioactivity concentration obtained through in situ gamma spectrometry. For this purpose, the count of a total of 79 points at 3 sites were measured with less than count uncertainty of 5% for 2000 seconds. In the results of the analysis of variance, the 2 sites were homogeneous, and the remaining 1 site can be specified to be homogeneous through the adjustment of measuring range. The distribution of radioactivity concentration calculated by in situ gamma spectrometry were $53.7{\sim}93.2Bq\;kg^{-1}$, $30.5{\sim}61.0Bq\;kg^{-1}$ and $48.8{\sim}102Bq\;kg^{-1}$ at each site.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2006.05a
• /
• pp.1007-1011
• /
• 2006

본 연구에서는 어류 생태계 유지를 위해 필요한 생태학적 추천유량을 산정하고, 어류의 서식처 환경인 여울과 웅덩이의 형성조건을 검토함으로써 '작용'인 '흐름'과 '응답'인 '하상구조'와의 상관 관계를 규명하고자 하였다. 본 연구의 대상하천인 금호강에서는 하상변동이 활발한 자연 상태를 벗어나 하상의 이동성 상당히 둔화된 상태이며, 저수로내 여울과 웅덩이도 대표어종이 서식할 수 있는 자갈하상 구조에 변화가 일어나고 있는 것으로 분석되었다. 이것은 금호강 상류에 영천댐 건설의 영향이 어느 정도 미치고 있음을 유황분석 결과를 통해 간접적으로 파악할 수 있었다. 댐과 같은 수공구조물의 건설로 인하여 하도가 고정화된 상태에서 장기간에 걸치게 되면 여울과 웅덩이와 같은 하상구조가 축소되거나 소멸되어 금호강에서의 대표어종 서식처 환경에 영향을 미칠 것으로 추정된다. 금번 연구결과, 금호강에서 어류의 생식에 필요한 생태학적 추천유량 $8.2m^3/sec$가 필요하였으며, 어류의 서식처 환경인 여울과 웅덩이를 지속적으로 유지되기 위해서는 $250m^3/sec$ 이상의 유량이 연간 한번 이상 흘러야 하고, 2.5년 내지 3년 마다 약 $500m^3/sec$ 정도의 유량이 흐를 필요가 있다고 분석되었다. 본 연구 대상지점에서 흐름과 하상구조를 하천생태계와 연계해서 볼 때, 생태추천유량은 어디까지나 대표어종이 서식할 수 있는 최소조건에 불과하다. 대표어종이 장기간에 걸쳐 서식할 수 있는 하상구조가 존재하기 위해서는 대표어종이 선호하는 여울과 웅덩이가 필요하다. 결국 대표어종이 서식하기 위한 필요충분조건은 생태추천유량 확보와 아울러 대표어종이 선호하는 하상구조를 유지하기 위해서는 하도의 이동성을 유발할 유황변화가 필요하다는 것이 입증되었다.대상으로 연중 발생하는 큰 호우사상에 대해 임의의 강우관측소를 결측지점으로 가정하고 주변의 강우관측소로부터 각각의 방법을 이용해 가중치들을 산정하여 결측지점의 강우량 값을 보정하고자 하였다. 또한 각각의 방법을 이용하여 얻어진 결과에 대해 실측값과 보정값의 오차정도를 평균절대오차법(Mean Absolute Error)과 제곱평균제곱근오차법(Root Mean Squared Error)에 의해 산정하여 보정 방법간의 효율성을 검토하고자 하였다.9년, 그리고 2010년${\sim}$2019년까지 총 4구간으로 나누어 결과를 도출하였으며 예상한 바와 같이 후반기 20년 동안에 세 가지 지표가 취약해 지는 것을 확인할 수 있었고, 특히 2000년부터 2009년까지 10년 동안에는 더욱 취약해짐을 확인할 수 있었다.를 보임에 따라 그 정책적 효과는 때로 역기능적인 결과로 초래하였다. 그럼에도 불구하고 이 연구결과를 통하여 최소한 주식시장(株式市場)에서 위탁증거금제도는 그 제도적 의의가 여전히 있다는 사실이 확인되었다. 또한 우리나라 주식시장에서 통상 과열투기 행위가 빈번히 일어나 주식시장을 교란시킴으로써 건전한 투자풍토조성에 저해된다는 저간의 우려가 매우 커왔으나 표본 기간동안에 대하여 실증분석을 한 결과 주식시장 전체적으로 볼 때 주가변동율(株價變動率), 특히 초과주가변동율(超過株價變動率)에 미치는 영향이 그다지 심각한 정도는 아니었으며 오히려 우리나라의 주식시장은 미국시장에 비해 주가가 비교적 안정적인 수준을 유지해 왔다고 볼 수 있다.36.4%)와 외식을 선호(29.1%)${\lrcorner}$ 하기 때문에 패스트푸드를 이용하게 된 것으로 응답 하였으며, 남 여 대학생간에는 유의한 차이(p<0.05)가 인정되었다. 응답자의 체형은 ${\ulco

• Journal of Korea Water Resources Association
• /
• v.45 no.5
• /
• pp.445-454
• /
• 2012

The present study aims to investigate the long-term channel morphological changes derived from channelization, embankment and levee construction works in unregulated fluvial channel of the Jiseock River. Analyses of aerial photographs taken past (Year 1966) and recent (Year 2002) showed the temporally remarkable changes in channel planform such as channel shape, bar migration, vegetation encroachment in bar. During the period, the natural single threading changed into braided types together with decreasing sinuosity by 9.2%, increasing vegetation occupied bar ranged 97% of total bars area. Because such channel morphological changes are closely similar to those in dam downstream channels, we assume that both/either flow regime alteration and/or sediment transport discontinuity may be critical for the fixed channel and spread of vegetated bars even in unregulated river without dam reservoir upstream. We found more reduced frequency and magnitude of flooding water level comparing with past, but no significant alteration of inter annual water level variation. Bed material has been coarsened by 4~5 times and the riverbed has been degraded in overall channel but aggraded locally in conjunction reach of tributaries. The results indicates that reduced sediment dynamics in fluvial channel which derived by bed material coarsening, river bed degradation and unbalanced sediment transport capacity between tributary and mainstem can be a causal factor to trigger channel morphological changes even in unregulated rivers.

• Korean Journal of Environment and Ecology
• /
• v.24 no.5
• /
• pp.566-574
• /
• 2010

This study was carried out for the purpose of understanding the situation of the urban forest and presenting basic data bases for a proper management plan through the analysis of forest vegetation and soil characteristics. In three representative urban forests of Deajeon, we analyzed the differences of vegetation and soil properties in each geological location. The indices of ecological health such as Species Diversity and Maximum Species Diversity are increasing in the order of Namseon Park, Wolpyung Park and Mt. Bomun; the first is in the center of the city, the second is well-conserved inner-city park and the third is in the border of the city. In the soil analysis of Namseon Park where human disturbance is strong, the surface fuel bed was very thin just 0.5cm and the soil was harder than the other two urban forests, the soil hardness was $0.5{\sim}3.7kg/cm^2$. All three urban forests showed low $pH_{1:5}$ under 5.0 except Robinia pseudo-acasia association of Wolpyung and low exchangeable cation level. These results say that the urban forests of Deajeon have been being acidified severely and the eluviation of exchangeable cation is proceeding. The organic matter and the available phosphate level was lower than the average level of Korean forest. It means that nutrition supply is not sufficient. In Daejeon urban forests, the management plan of urban forest is necessary according to the analysis result of vegetation and soil.

• Korean Journal of Environment and Ecology
• /
• v.33 no.6
• /
• pp.686-694
• /
• 2019

This study was carried out to identify the long-term changes to beech forest due to climate change in Ulleung-do. To study the traits of the stand structure of beech forest with micro-topography, we investigated the distribution of the basal area, important values, and indicated species in a small ridge between Albong basin and Seongin-bong peak, and 1-ha stands (20 m × 20 m, 25 sites) dominated beech species including on the upper slope and valley parts. The result showed that the indicator species characterizing the vegetation communities were Tsuga sieboldii, Rhododendron brachycarpum, and Mitchella undulata in the small ridge and Celtis jessoensis, Dryopteris crassirhizoma, and Ulmus laciniata in the valley part. Moreover, the individuals with the total DBH < 10 cm were more predominant in the small ridge and upper slope than in the valley part, the individuals with DBH = 10-25 cm were predominant in the small slope, and individuals with DBH = 25-45 cm and DBH > 45 cm were predominant in the upper slope. The reason for the predominant distribution of beech stand with DBH<10 cm in all terrains is suggested to be germination by nutritional propagation rather than secondary succession caused by artificial disturbances and seed propagation.