• 한국지반공학회논문집
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• 제30권9호
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• pp.19-28
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• 2014

해성점토를 활용한 준설매립공사에서는 준설토의 거동분석이 선행되어야 한다. 본 연구에서는 침강압밀하는 준설토의 밀도와 간극비 변화를 관찰하기 위해 물리탐사기법을 적용하였다. 서해안에서 채취한 흙에 대한 기본물성시험을 실시하였고, 침강압밀시험기에 시료를 단계적으로 투기하여 시간에 따른 계면고와 탄성파의 변화를 관찰하였다. 흙의 침강압밀이 완료된 후 하방향의 투수시험을 실시하여 조간대의 영향이 준설토의 물리적 특성에 미치는 영향을 관찰하였다. 또한 초소형 전기저항탐침을 관입하여 깊이에 따른 시료의 전기비저항을 측정하였다. 모든 실험이 완료된 후, 시료를 채취하여 간극비를 계산하였다. 실험결과, ML 시료의 특성상 급격한 침강을 보여 침강압밀특성을 육안으로 관찰하기 어려웠으나, 단계투기가 계속될수록 탄성파의 속도는 증가하는 경향을 보였다. 하방향 투수에 따른 조간대 영향은 매우 적어 관찰할 수 없었다. 한편 탄성파 속도로 추정한 시료의 간극비는 단계투기에 따라 선형적으로 증가하는 경향을 나타내었다. 전기비저항으로부터 계산된 간극비는 깊이에 따라 반복적으로 증가, 감소하는 형태를 나타내었으며 이는 단계투기에 따라 층을 이루고 있는 시료의 영향으로 파악된다. 시료채취, 탄성파 속도, 그리고 전기비저항으로부터 구한 간극비를 비교한 결과, 서로 유사한 관계를 나타내었다. 본 연구는 물리탐사기법이 준설토의 간극비 관찰에 효과적으로 활용될 수 있음을 보여준다.

• 한국지반공학회논문집
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• 제33권4호
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• pp.35-46
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• 2017

미연소탄소 함량이 높은 플라이애쉬(High carbon contents fly ash, HCFA)는 콘크리트 혼화재로의 사용이 부적합하여 대부분 매립되고 있다. 이에 본 연구는 미연소탄소함량이 높은 플라이애쉬의 지반공학적 활용 방안을 모색하기 위하여 폴리프로필렌섬유(Polypropylene fiber, PP fiber)와 모래로 보강하여 일축압축시험과 벤더엘리먼트가 설치된 일차원 수정 압축실험을 진행하였다. 섬유의 보강효과로 섬유비가 증가함에 따라 일축압축강도(UCS), 일축압축강도시의 변형률과 동일 간극비 상에서의 최대전단탄성계수(Maximum Shear Modulus, $G_{max}$)가 증가하였다. 모래로 보강된 경우 혼합물의 UCS는 다소 증가하였으나 UCS 시의 변형률은 모래비의 영향을 받지 않았으며, 모래입자는 HCFA 입자간의 접촉을 방해하여 혼합물의 $G_{max}$를 감소시켰다. 그러나 20% 이상의 모래비에 대하여 동일 에너지로 다짐하였을 시, 조밀한 상태로 조성되며 그로 인한 보강 효과를 기대할 수 있었다. 섬유나 모래로 보강된 HCFA의 압축지수(Compression index, $C_c$)는 보강재의 종류와 관계없이 주로 초기 간극비에 의해 결정되었다.

• 한국양식학회지
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• 제8권2호
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• pp.85-98
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• 1995

서해연안의 양식장 환경조사의 일환으로 군장국가공단 건설사업 중 방조제 공사가 진행되고 있어 그 영향을 받을 것으로 예상되는 군산연안 간석지 양식장을 대상으로 1992년 5월부터 1993년 4월까지 저질환경을 조사하여 양식장환경을 진단하고 동시에 방조제공사의 영향을 고찰하였다. 1 조사지역의 입도조성은 입경 $0.064\leq0.25mm$의 미사가 $69\~98\%$를 나타내어 모래질이 우세한 지역으로 분류되었다. 2. 저질의 pH는 7.2-9.1의 범위를 나타내었는데 하층이 상층에 비해 높았으며 방조제 공사에 따라 점차 pH값이 증가하는 경향을 보였다. 3. 저질의 함수율은 $11.1\~28.1\%$의 범위로 점토가 많은 지역의 함수율이 높았다. 4. COD 값은 0-1.27mg/g 건니를 나타내어 양호한 상태를 보였으며 pH값과는 달리 방조제공사에 따라 COD값이 낮아지는 경향을 보였다. 5. 총유기물함량은 $0.84\~8.11\%$의 범위를 나타내었으며 하층이 상층에 비해 약간 높은 경향을 보였다. 6. 용존산소흡수량은 $0\~6.56mg/g$ 건니의 범위를 보였으며 겨울에서 봄에 낮은 값을, 여름에서 가을에 놀은 값을 보였다. 7. 총질소함량과 황화물은 각각 $0\~402{\mu}g/g$ 건니와 $0\~122{\mu}g/g$ 건니의 범위를 나타내었으며 여름과 겨울에 비교적 높게 나타났다. 그리고 층별로는 대체로 상층이 하층에 비해 약간 높게 나타났다.

• 한국수산과학회지
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• 제29권5호
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• pp.567-577
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• 1996

본 연구는 한국 연근해 갈치의 자원생태학적 특성치인 성장계수와 생잔율, 순간자연 및 어획사망계수, 어획개시연령 및 연령별 성장률을 추정하는 것이다. 갈치의 성장을 나타내는데는 세가지의 성장모델에 적합시켰으며, 이 중 차후의 자원평가연구를 목적으로 von Bertalanffy 성장식을 채택하였다. von Bertalanffy 성장계수는 EXCEL의 Solver를 사용하여 비선형회귀 방법에 의하여 다음과 같이 추정되었다. $L_\infty=46.01cm,\;K=0.3868,\;t_0=-0.3220$. 갈치의 연간생잔율 (S)은 0.277 (분산=0.00035)로 추정되었으며 순간자연사망 계수 (M)는 0.4411년으로 추정되었다. 근년의 순간어획사망계수 (F)는 0.843/년으로서 자연사망보다 어획에 의한 영향이 약 2배나 되고 있음을 암시하였다. 어획개시연령 $(t_c)$은 0.787세로 $50\%$ 성숙연령의다 훨씬 어린 연령이었다 마지막으로 갈치의 연령별 성장률이 추정되었다.

• 한국대기환경학회지
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• 제22권4호
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• pp.487-498
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• 2006

Total 438 precipitation samples were collected in Jeju City between 1997 and 2005, and their major ionic components were analyzed. The comparison tests using ion balance, electric conductivity and acid fraction were performed. It was found their correlation coefficients were in the range of 0.977$\sim$0.994, indicating the good quality of collected dam. The volume-weighted mean pH and electric conductivity were 4.8 and 23.0 $\mu$S/cm, respectively. with the ionic strength of 0.23$\pm$0.20 mM. The marine ($Na^+$, $Mg^{2+}$, and $CI^-$), anthropogenic (nss$SO_4{2-}$, $NO_3^-$, and $NH_4^+$) and soil (nss-$Ca^{2+}$) species have contributed to the ionic components of precipitation samples with 43$\sim$74%, 16$\sim$37% and $\sim$5%, respectively. The seasonal variations of $NO_3^-$ and nss-$SO_4^{2-}$ showed a distinct seasonality with higher concentrations in winter than summer, indicating an increase of fossil fuel consumption and a possibility of long-range transport of those pollutants from continental area along the dominant winter westerly. The levels of nss-$Ca^{2+}$ also were appeared the highest in winter and increased comparatively in spring season. possibly due to the soil influences including the Asian Dust. The acidification contribution of nss-$SO_4^{2-}$ and $NO_3^-$ showed 88$\sim$96%, and the free acidity was in the range of 6.0$\sim$40.1%. Interestingly, the backward trajectories for the case of upper 10% nss-$SO_4^{2-}$ and $NO_3^-$ levels have passed through the China continent before their arrival to Jeju. The precipitation of pH below 4.5 has been occurred frequently when the trajectory's path lied over the China continents. On the other hand, the air masses from the North Pacific area were characterized by lower 10% of nss-$SO_4^{2-}$- and $NO_3^-$ concentration, which demonstrated that air mass from the North Pacific was the cleanest among air masses moved to Jeju.

• 한국항행학회논문지
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• 제22권5호
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• pp.442-448
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• 2018

본 논문에서는 광대역 이동통신 시스템을 위한 LTE/LTE-A용 마이크로스트립 안테나를 설계 및 제작하였다. 제안된 안테나의 기판은 FR-4(er = 4.3)이고 크기는 $40mm{\times}50mm$이며 LTE/LTE-A 주파수대역인 2.3 GHz와 2.5 GHz의 대역에서 사용할 수 있는 특성을 갖도록 설계하였다 시뮬레이션은 CST Microwave Studio 2014을 사용하였으며 시뮬레이션 결과 이득은 2.3 GHz일 때 2.391 dBi, 2.5 GHz일 때 2.566 dBi이다. S-Parameter 또한 원하는 주파수 대역에서 -10 dB (VSWR 2:1) 이하의 결과를 볼 수 있었다. 광대역 이동통신 안테나는 소형화, 고성능, 초경량화 등이 되어 우수하고 저가의 시스템이 계속해서 개발되고 있으며 광대역 이동통신 시스템은 많은 사람들이 사용하고 있다. 시스템의 발달과 수요 증가에 따른 LTE/LTE-A 기술이 제안되고 있기 때문에 위의 조건에 만족하는 안테나 설계 및 제작하여 해당 시스템을 적용한 기술을 많은 이용자가 사용할 것으로 보인다.

• 대기
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• 제25권4호
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• pp.693-706
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• 2015

A shift of first fowering date (FFD) of spring blossoms (cherry, peach and pear) over the northest Asia under global warming is investiaged using dynamically downscaled daily temperature data with 12.5 km resolution. For the study, we obatained gridded daily data with Historical (1981~2010), and Representative Concentration Pathway (RCP) (2021~2100) 4.5 and 8.5 scenarios which were produced by WRFv3.4 in conjunction with HadGEM2-AO. A change on FFDs in 21st century is estimated by applying daily outputs of WRFv3.4 to DTS phonological model. Prior to projection on future climate, the performances of both WRFv3.4 and DTS models are evaluated using spatial distribution of climatology and SCR diagram (Normalized standard deviation-Pattern correlation coefficient-Root mean square difference). According to the result, WRFv3.4 and DTS models well simulated a feature of the terrain following characteristics and a general pattern of observation with a marigin of $1.4^{\circ}C$ and 5~6 days. The analysis reveals a projected advance in FFDs of cherry, peach and pear over the northeast Asia by 2100 of 15.4 days (9.4 days). 16.9 days (10.4 days) and 15.2 days (9.5 days), respectively, compared to the Historical simulation due to a increasing early spring (Februrary to April) temperature of about $4.9^{\circ}C$ ($2.9^{\circ}C$) under the RCP 8.5 (RCP 4.5) scenarios. This indicates that the current flowering of the cherry, peach and pear over analysis area in middle or end of April is expected to start blooming in early or middle of April, at the end of this century. The present study shows the dynamically downscaled daily data with high-resolution is helpeful in offering various useful information to end-users as well as in understanding regional climate change.

• Ocean and Polar Research
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• 제25권3호
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• pp.277-286
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• 2003

Nitrification performance of fixed film biofilters using coarse sand, loess bead, or styrofoam beads in biofilter columns 1 meter high and 30cm in diameter were studied at different hydraulic and organic matter loading rates. Synthetic wastewater was supplied to the culture tank in order to maintain desired TAN concentrations in inlet water to biofilters. All the biofilters were conditioned 5 months before start of sampling. TAN and $NO_2-N$ conversion rates increased with an increase in the hydraulic loading rate (HLR). However, the improvement in biofilter performance was not linearly correlated to HLR in styrofoam bead filters. This is mainly due to the characteristics of the styrofoam beads used. TAN conversion rates of sand filters increased with the increase of HLR up to $200m^3/m^2$. per day. No increase in the TAN conversion rate was observed at the highest HLR since flooding on the media surface took place. HLR had a significant impact on the TAN conversion rates in loess bead filter up to the highest HLR tested (P<0.05). TAN conversion rates were much less at organic matter loading rates of 9 and 18kg $O_2/m^3$ per day than those without the addition of organic matter in styrofoam bead filters. The addition of glucose resulted in a reduction of the TAN conversion rate from 540 to 284g $TAN/m^3$ per day. No significant difference of TAN conversion rates between the two organic matter loading rates was found (p<0.05). This indicates that the impact of organic matter on nitrification becomes less and less sensitive with an increase in the COD/TAN ratio. At an organic matter loading rate of 9kg $O_2/m^3$. per day, a great reduction of TAN conversion rates was observed in sand filters and loess bead filters. Clearly, organic matter can be one of the most Important Impacting factors on nitrification. $NO_2-N$ conversion rates showed a similar trend for TAN. Based on the TAN and nitrite conversion rates, styrofoam beads showed the best performance among the three filter media tested. Also, the low gravity and price of styrofoam beads make the handling easier and more cost-effective for commercial application. The results obtained at the highest organic matter loading rates can be used in the biofilter design in recirculating aquaculture system.

• Ocean and Polar Research
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• 제32권4호
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• pp.449-462
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• 2010

Ongoing port baseline surveys are essential for developing ballast water management procedures in order to control unwanted or potentially risky species. Seasonal distributional patterns of marine dinoflagellate Noctiluca scintillans internationally recognized as harmful species and the related environmental factors were surveyed at Incheon, Gwangyang and Ulsan seaports in Korea from 2007 to 2009. The above three seaports were chosen because of their status as the busiest in Korea and characterized by their different bioregions. Average temperature ranged from $2.08^{\circ}C$ in winter to $26.39^{\circ}C$ in summer at Incheon, $7.22^{\circ}C$ in winter to $25.77^{\circ}C$ in summer at Gwangyang, and $11.59^{\circ}C$ in winter to $21.67^{\circ}C$ in summer at Ulsan during the study period. Average salinity varied from 26.88 in winter to 31.25 in summer at Incheon, 22.83 in winter to 33.41 in summer at Gwangyang, and 30.04 in winter to 33.90 in summer at Ulsan. Noctiluca scintillans appeared consistently at all ports during the study period, indicating its eurythermal and euryhaline nature. The highest abundances (21,813 to 41,753 $inds{\cdot}m^{-3}$) of N. scintillans were observed in May 2008 and 2009 at the outer stations of Incheon port. Abundances of between 10,000 and 30,000 $inds{\cdot}m^{-3}$ were only observed at the innermost station of Ulsan in May, while abundances of between 10,000 and 40,000 $inds{\cdot}m^{-3}$ were frequently observed throughout all stations at Gwangyang during the study period, coinciding with consistently high concentration of chlorophyll-a (hereafter chl-a) ($4.32-8.24\;{\mu}g\;l^{-1}$) compared to other ports. Spatio-temporal variation of chl-a concentration was not significantly correlated with abundances of N. scintillans (p>0.01). However, relatively high chl-a concentrations were consistently recorded along with high abundances of N. scintillans throughout all stations at Gwangyang compared to other ports. Abundances of N. scintillans observed at the three surveyed ports did not significantly (p>0.01) affect the concentration of dissolved oxygen in the surface mixed layer, indicating that the species abundances were not enough to cause reduction of dissolved oxygen during the study period. Presented results indicated that the Gwangyang seaport may provide the most suitable environment for a wide range of N. scintillans blooming compared to other ports.

• Ocean and Polar Research
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• 제39권2호
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• pp.85-106
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• 2017

The Lago Sofia conglomerate in southern Chile is a deep-marine gravelly deposit, which is hundreds of meters thick and kilometers wide and extends laterally for more than 100 km, filling the foredeep trough of the Cretaceous Magallanes Basin. For understanding the depositional processes and environments of this gigantic deep-sea conglomerate, detailed analyses on sedimentary facies, architecture and paleoflow patterns were carried out, highlighting the differences between the northern (Lago Pehoe and Lago Goic areas) and southern (Lago Sofia area) parts of the study area. The conglomerate bodies in the northern part occur as relatively thin (< 100 m thick), multiple units intervened by thick mudstone-dominated sequences. They show paleoflows toward ENE and S to SW, displaying a converging drainage pattern. In the southern part, the conglomerate bodies are vertically interconnected and form a thick (> 400 m thick) conglomerate sequence with rare intervening fine-grained deposits. Paleoflows are toward SW. The north-to-south variations are also distinct in sedimentary facies. The conglomerate bodies in the southern part are mainly composed of clast-supported conglomerate with sandy matrix, which is interpreted to be deposited from highly concentrated bedload layers under turbidity currents. Those in the northern part are dominated by matrix- to clast-supported conglomerate with muddy matrix, which is interpreted as the products of composite mass flows comprising a turbidity current, a gravelly hyperconcentrated flow and a mud-rich debris flow. All these characteristics suggest that the Lago Sofia conglomerate was formed in centripetally converging submarine channels, not in centrifugally diverging channels of submarine fans. The tributaries in the north were dominated by mass flows, probably affected by channel-bank failures or basin-marginal slope instability processes. In contrast, the trunk channel in the south was mostly filled by tractive processes, which resulted in the vertical and lateral accretion of gravel bars, deposition of gravel dunes and filling of scours and channels, similar to deposits of terrestrial gravel-bed rivers. The trunk channel developed along the axis of foredeep trough and its confinement within the trough is probably responsible for the thick, interconnected channel fills. The large-scale architecture of the trunk-channel fills shows an eastward offset stacking pattern, suggesting that the channel migrated eastwards most likely due to the uplift of the Andean Cordillera.