Water uptake in to polyanhydride devices : kinetics of uptake and effects of model compounds incorporated, and device geometry on water uptake

Park, Eun-Seok,Maniar, Manoj,Shah, Jaymin 성균관대학교 약학연구소 1996 成均藥硏論文集 Vol.8 No.1

Polyanhydrides are known as surface eroding biodegradable polymers since they are hydrophobic, which is believed to prevent penetration of water into the bulk and hence only the labile bonds on the surface are hydrolyzed. We wanted to test the hypothesis that polyanhydrides, specifically poly(fatty acid dimer-sebacic acid; FAD-SA) undergo pure surface erosion. If P(FAD-SA) does indeed undergo pure surface erosion, very little water should be present in the device since the polymer is hydrophobic and hydrolyzed on contact with water. An understanding of water uptake is also necessary to predict the stability and release of the incorporated drug. The specific aims of this study were to establish the rate of water uptake into P(FAD-SA) devices of cylinder and disk shapes at various pH conditions, and to study the effect of loaded model drug compounds (having different molecular size, aqueous solubility and dissolution rate) on water uptake. The model compounds included: mannitol, inulin and stearic acid, loaded at 10%(w/w) in disk-shaped devices. Water uptake was estimated from the amount of tritiated water found in the devices after they were soaked and gently mixed with buffers (pH 1-9) containing tritiated water (1μCi/ml) at various time intervals. The results showed that water uptake by the devide is a function of pH (pH 9>pH 7.4≫pH 1-5). Significantly higher amount of water was taken up at pH 7.4 and 9.0 (8-9% (v/v) for cylindrical devices, 15-25% (v/v) for disk-shaped device in 2 weeks), compared to less than 5% (v/v) uptake between pH 1 and 5. Disk-shaped devices showed a faster uptake rate compared to cylinder-shaped devices due to their higher surface area to volume ratio. The loaded compounds had no significant effect on either the water uptake profile or water uptake kinetics at all pH values examined. From the large amount of water (up to 20% (v/v)) found in the devices at pH 7.4 and pH 9.0, it appears that P(FAD-SA) does not undergo pure surface erosion. The photomicrographs of the devices at various stages of water uptake showed channels on the rough surface indicative of bulk erosion rather than pure surface erosion.

표면 에너지가 물 윤활 현상에 미치는 영향에 대한분자시뮬레이션 연구

김현준 한국트라이볼로지학회 2023 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.39 No.6

This paper presents a molecular dynamics simulation-based numerical investigation of the influence of surface energy on water lubrication. Models composed of a crystalline substrate, half cylindrical tip, and cluster of water molecules are prepared for a tribological-characteristic evaluation. To determine the effect of surface energy on lubrication, the surface energy between the substrate and water molecules as well as that between the tip and water molecules are controlled by changing the interatomic potential parameters. Simulations are conducted to investigate the indentation and sliding processes. Three different normal forces are applied to the system by controlling the indentation depth to examine the influence of normal force on the lubrication of the system. The simulation results reveal that the solid surface's surface energy and normal force significantly affect the behavior of the water molecules and lubrication characteristics. The lubrication characteristics of the water molecules deteriorate with the increasing magnitude of the normal force. At a low surface energy, the water molecules are readily squeezed out of the interface under a load, thus increasing the frictional force. Contrarily, a moderate surface energy prevents expulsion of the water molecules due to squeezing, resulting in a low frictional force. At a high surface energy, although squeezing of the water molecules is restricted, similar to the case of moderate surface energy, dragging occurs at the soil surface–water molecule interface, and the frictional force increases.

통제할 수 있는 물에 대한 갈망: 지하수에서 지표수로- 국가 수자원 개발 계획의 변화, 1962-1972

박서현 한국생태환경사학회 2024 생태환경과역사 Vol.- No.12

산업화와 도시화로 인해 더 많은 물을 소비하게 된 우리의 일상은 하천으로부터 취수되는 지표수에 깊이 의존하고 있다. 지표수를 대량으로 취수하고 정수하여 공급하는 급수 시스템은 종종 지하수를 사용하는 우물과 비교하여 깨끗한 물을 편리하게 공급하는 근대적인 기술로 명명된다. 하지만 본 논문은 국가의 주요 용수원이 기술의 발전에 따라 지하수에서 지표수로 자연스럽게 바뀐 것이 아니라, 부처 간 경쟁과 논의 끝에 국가 차원에서 통제하기에 더 용이한 지표수로 변화하게 되었다고 주장한다. 1960년대 초에 미국의 기술 원조를 받아 이루어진 지하수 조사 사업을 토대로 농림부는 지하수를 용수원으로 확보하는 편이 가뭄에 대응하고 국가의 생산성을 늘리는 데 더 효과적이라고 판단했다. 하지만 전국각지에서 진행되는 지하수 개발을 중앙 정부가 일일이 감독하는 데 어려움이 있었고 실적 또한 초기의 기대에 비해 지지부진했다. 지하수 개발이 난항을 겪던 차에, 건설부에서 주관한 “4대강 유역종합개발계획”은 국가의 수자원 정책을 지표수 위주의 개발로 바꾸어 놓았다. 당시 건설부는 1965년부터 시행한 4대강 유역조사의 결과로 12개의 다목적 댐 건설을 제안했는데, 이 계획은 각 댐이 건설될 때마다 확보할 수 있는 용수의 양을 명확한 숫자로 보여주었다. 다시 말하면, 지표수 개발 계획은 물의 순환을 마치 국가가 완벽하게 관리하고 통제할 수 있는 대상으로 가시화하는데 기여했다. 본 논문은 이처럼 국가가 물을 통제할 수 있는 자원으로 구성하며 권력을 획득해 나가는 과정을 살피는 것이 국가가 자연에 개입할 때 발생하는 폭력을 깊이 있게 탐구하는 단초가 될 수 있음을 시사한다. As industrialization and urbanization have led us to consume more water, our daily lives are deeply dependent on surface water from rivers. Water supply systems that harvest, purify, and distribute surface water in large quantities are often considered as a modern technology, in comparison to wells using ground water. However, this paper argues that the country’s primary water source did not naturally shift from ground water to surface water with technological advance. Rather, the central government shifted from ground water to surface water-oriented development policies in order to facilitate water resource management at the national level. Based on ground water survey conducted with US technical assistance in the early 1960s, the government determined that securing ground water would be more effective in combating drought and increasing national productivity. However, oversight of ground water development across the country was challenging while the results failed to meet the initial expectations. As ground water development struggled, the Ministry of Construction proposed “Comprehensive Development Plan for the Four Major River Basins,” which shifted the nation’s water policy toward surface water development. Beginning in 1965, the ministry conducted surveys in the four major river basins and planned the construction of 12 multipurpose dams. The comprehensive basin development plan showed a clear number for the amount of water that could be secured by each dam, making national water planning much more easier. In response, the government abandoned the ground water-oriented water resources policy in favor of surface water development, contributing to the visualization of the water cycle as something under control of the state. This paper suggests that examining the process by which the state controls water as a resource and gains power can serve as a springboard for further exploration of the violence that occurs when the state intervenes in nature.

Comparative assessment of surface and ground water quality using geoinformatics

Giridhar, M.V.S.S.,Mohan, Shyama,Kumar, D. Ajay Techno-Press 2020 Advances in environmental research Vol.9 No.3

Water quality demonstrates physical, chemical and biological characteristics of water. The quality of surface and groundwater is currently an important concern with population growth and industrialization. Over exploitation of water resources due to demand is causing the deterioration of surface water and ground water. Periodic water quality testing must be carried out to protect our water resources. The present research analyses the spatial variation of surface water and groundwater in and around the lakes of Hyderabad. Twenty-Seven lakes and their neighboring bore water samples are obtained for water quality monitoring. Samples are evaluated for specific physico-chemical parameters such as pH, Total Dissolved Solids (TDS), Cl, SO₄, Na, K, Ca, Mg, and Total Hardness (TH). The spatial variation of water quality parameters for the 27 lakes and groundwater were analysed. Correlation and multiple regression analysis were carried out to determine comparative study of lake and ground water. The study found that most of the lakes were polluted and this had an impact on surrounding ground water.

지표수-지하수 연계 기반의 통합수자원 관리를 위한 단위유역 제안

김규범,황찬익 한국수자원학회 2020 한국수자원학회논문집 Vol.53 No.S-1

In South Korea, 850 standard watersheds and 7,807 KRF catchment areas have been used as basic maps for water resources policy establishment, however it becomes necessary to set up new standard maps with a more appropriate scale for the integrated managements of surface water-groundwater as well as water quantity-quality in the era of integrated water management. Since groundwater has a slow flow velocity and also has 3-D flow properties compared to surface water, the sub-catchment size is more effective than the regional watershed for the evaluation of surface water-groundwater interaction. The KRF catchment area, which has averagely a smaller area than the standard watershed, is similar to the sub-catchment area that generally includes the first-order or second-order tributaries. Some KRF catchment areas, which are based on the surface reach, are too small or large in a wide plain or high mountain area. Therefore, it is necessary to revise the existing KRF area if being used as a unit area for integrated management of surface-water and groundwater. A unit watershed with a KRF area of about 5 to 15 km2 can be effective as a basic unit for water management of local government considering a tributary composition and the location of groundwater wells, and as well it can be used as a basic tool for water demand-supply evaluation, hydrological observation system establishment, judgment of groundwater permission through a total quantity management system, pollution assessment, and prioritizing water policy, and etc. 현재 우리나라는 수자원단위지도의 표준유역(850개) 및 KRF의 집수구역(7,807개) 등의 기준 도면이 수자원 정책 수립의 기본 도면으로 활용되고 있으나, 물관리 일원화 시점에 맞추어 지표수-지하수의 연계 관리 및 수량-수질 통합관리를 위해서는 보다 적절한 규모의 표준 도면 설정이 필요해 보인다. 지표수에 비하여 지하수는 느린 이동 속도를 보이고 3차원 흐름 특성을 갖고 있으므로 지표수-지하수 연계 평가를 위해서는 광역적 규모의 유역 보다는 준 유역 규모가 보다 효과적인데, 표준유역보다 평균 면적이 작은 KRF 집수구역은 1차 또는 2차 지류를 포함하는 준 유역 규모에 해당한다. 그러나, KRF는 지표수 수계를 기준으로 구역을 구분하였기 때문에 넓은 평지 또는 높은 산악지역에서는 지나치게 작거나 큰 면적을 갖고 있다. 따라서, 지표수-지하수 연계 통합 관리에 적합한 단위 유역은 기존 KRF 집수구역을 수정하여 설정하는 것이 필요하다. 이로부터 설정될 개소 당 약 5 ~ 15 km2 면적의 단위 유역은 지류의 구성과 관정의 위치를 고려할 때 지방자치단체의 수자원 관리의 기본 단위가 될 수 있으며, 물 수요-공급 평가, 수문 계측 시스템의 배치, 지하수 허가 총량 기준, 오염의 평가, 정책의 우선 순위 결정 등 실질적인 수자원 통합관리의 기본 수단으로 활용 가능할 것이다.

천해역에 수표면 및 수중방류된 사각형제트의 흐름 거동

김대근,김동옥 대한상하수도학회 2011 상하수도학회지 Vol.25 No.5

In the present study, the flow behaviors of square jets surface discharged and submerged discharged into shallow water were each simulated using computational fluid dynamics, and the results were compared. As for the verification of the models, the results of the hydraulic experiment conducted by Sankar, et al. (2009) were used. According to the results of the verification, the present application of computational fluid dynamics to the flow analysis of square jets discharged into shallow water was valid. As for the wall jet, which is one form of submerged discharges, at the bottom wall boundary, the peak velocity of the jet rapidly moved from the center of the jet to the bottom wall boundary due to the restriction of jet entrainment and the no-slip condition of the bottom wall boundary, and, as for the surface discharge, because jet entrainment is limited on the free water surface, the peak velocity of the jet moved from the center of the jet to the free water surface. This is because jet entrainment is restricted at the bottom wall boundary and the surface so that the momentum of the central core of the jet is preserved for considerable time at the bottom wall boundary and the surface. In addition, due to the effect of the bottom wall boundary and the free water surface, the jet discharged into shallow water had a smaller velocity diminution rate near the discharge outlet than did the free jet; at a location where it was so distant from the discharge outlet that the vertical profile of the velocity was nearly equal (b/x =20~30), moreover, it had a far smaller velocity diminution rate than did the free jet due to the effect of the finite depth.

수증 전도도 변화에 따른 수표면 방전의 특성

박승록,김진규,김형표 한국조명전기설비학회 2004 조명·전기설비학회논문지 Vol.18 No.2

수표면을 전극으로 사용한 무성방전형 오존발생기를 제안하고 수중의 전도도 변화가 수표면 방전에 미치는 영향을 실험적으로 조사하였다. 수표면 방전에 중요한 영향을 줄 수 있는 요소로 방전공간내의 이온과 수중의 이온 및 극성분자등이 있다. 본 연구에서는 전도도를 변화시켜 수중에 존재하는 이온의 수를 조절함으로써 방전특성을 변화시키고자 하였다. 이를 위해 증류수내에 각각 다른양의 NaCl을 투입함으로써 전도도를 변화시켰고 이때의 전류-전압특성과 오존발생특성을 비교 조사하였다. 결과적으로 순수한 증류수를 사용한 경우보다 NaCl을 투입한 경우 안정된 방전을 발생시킬 수 있었고 투입하는 NaCl의 양을 늘여감에 따라 방전개시전압을 낮출 수 있었다. A silent type ozone generator using water surface electrode was proposed. And it was investigated experimentally that a variation of water conductivity affected to water surface discharge. Important factors affecting to water surface discharge are ions in discharge space and ions and polarized molecules in water and so on. In this study, It was intended to change the characteristics of discharge by controlling the number of ions in water. The number of ions in water could be controlled by changing the water conductivity. Water conductivity was controlled by quantity of inserted NaCl to distilled water. At this time, current-voltage characteristics and characteristics of ozone generation quantity were investigated in each case. As a result, when NaCl was inserted in distilled water, more stable discharge was generated. As the quantity of NaCl was increased, discharge starting voltage could be lowered.

대기 건식침적 측정을 위한 물표면 매체 포집기의 성능평가

이승묵,정장표 이화여자대학교 환경문제연구소 1998 이화환경연구 Vol.2 No.-

원형 모양의 물 표면 매체 포집 기기가 대기중의 가스와 입자들의 건식 침적 유동량을 측정하기 위하여 개발되었다. 포집 기기는 날카로운 모서리와 아크릴로 만들어진 판(지름 37cm, 깊이 0.5cm)에 순환시스템을 통하여 계속해서 물이 공급되어지는 구조로 설계되어 있다. 물 표면 매체 포집 기기의 성능을 평가하기 위하여 황산염, 칼슘 그리고 납의 유동량(flux)을 일리노이주(Illinois) 시카고(Chicago)에서 측정하였다. 대기중 입자상의 건식 침적 유동량을 측정하기 위하여 날카로운 모서리를 지닌 침적판 위에 놓여진 그리스 표면 매체를 물 표면 매체와 동시에 대기중에 노출하였다. 통계학적 분석 결과에 의하면 칼슘과 납의 유동량(flux)은 두표면 매체에서의 침적량이 동일한 것으로 분석 평가되어져 물과 그리스 표면 매체는 입자상의 침적에 대해서는 동일한 특성을 지니는 것으로 판명될 수 있었다. 황산염의 건식 침적의 경우, 가스상(SO₂) 과 입자상(SO₄())의 물질이 동시에 물로 침적될 수 있기 때문에 황산염을 시험대상 화합물로 선택하였다. (이산화황은 물 속에서 빠르게 가수 분해되고 황산염으로 산화된다). 이산화황(SO₂ )의 유동량을 물 표면 매체와 그리스 표면 매체사이의 황산염 유동량의 차이에 의하여 결정하였다. 저항모델(resistance model)을 사용하여 계산한 개별 이산화황 기체상 질량전달계수(individual SO₂gas phase mass transfer coefficient)와 대기중의 이산화황 농도를 곱하여 황산염 유동량을 예측하였다. 저항 모델은 질량 전달을 일련의 저항들을 통과하는 전기 및 열적 흐름과의 유사성과 연관지어서 개발한 모델이다. 물 표면 매체 포집기기를 사용하여 직접 측정한 이산화황 유동량을 저항 모델을 사용하여 예측된 유동량들과 잘 일치하였다. 이 결과는 물 표면 매체 포집기기가 대기중에서 가스상과 입자상의 물질로 동시에 존재하는 질소 화합물, PCBs, PAHs 및 수은과 같은 화합물질들의 침적을 측정하는데도 유용하게 쓰일 수 있는 가능성을 시사하고 있다. A circular water surface sampler was developed to measure the dry deposition flux of atmospheric gases and particle. The sampler consists of a sharp edged, acrylic plate, filled with water(37cm in diameter and 0.5cm deep) that is continuously replenished from a reservoir by a pump that maintains a constant water depth. To evaluate the water surface sampler, the flux of sulfate, calcium and lead were measured in Chicago. IL. A sharp edged greased surface was exposed to the atmosphere simultaneously with the water surface to measure the dry deposition flux of atmospheric particles. Calcium and lead fluxes were found to be statistically the same indicating that the water and greased surfaces had the same particulate phase deposition characteristics. Sulfate was also selected as the test compound because it can be deposited to water as both a gas(SO₂) and particulate(SO₄()) from the atmosphere(SO₂is quickly hydrolized and oxidized to SO₄() in water). The flux of SO₂was determined from the difference in the sulfate flux between the water surface and the greased surface. For each sample the calculated SO₂ flux was calculated as the product of the individual SO₂ gas phase mass transfer coefficient calculated using a resistance model multiplied by the ambient SO₂ concentration. A resistance model was developed by analogy to electrical or heat flow through a series of resistances. The SO₂ fluxes measured directly with the water surface sampler agreed well with those predicted with the resistance model. These findings indicate this sampler will be useful for measuring the deposition of other compounds which exist in both the gas and particulate phases like nitrogen, PCBs, PAHs and Hg.

Study of the wetting characteristics of water droplet on a heterogeneous pillared surface

고정안,권태우,매튜스탠리암브로시아,하만영 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.3

We investigated the wetting characteristics of a water droplet on a heterogeneous pillared surface at the nano-scale including contactangle, molecule inflow percentage and density fields and compared them with the wetting characteristics of a water droplet on a homogeneouspillared surface. Molecular dynamics simulations were employed to analyze the wetting behavior of water droplets on surfaceswith pillar structures by considering different potential energies including bond, angle, Lennard-Jones and Coulomb to calculate the interactingforces between water molecules and the surface. The heterogeneous surfaces considered had pillars with a different surfaceenergy than the base surface. It was found that the difference in surface energy between the base surface and pillar had little effect on thehydrophobicity of the surface at low pillar heights. However cases with pillar heights over H = 4.24 Å, the pillar surface energy has alarger effect on the molecule inflow percentage with the maximum differences in the range from 33.8% to 47.2% depending on the basesurface energy. At a pillar height of H = 16.96 Å, the pillar surface energy has a large effect on the contact angle of the water droplet withthe maximum differences in the range from -26.1% to -40.62% depending on the base surface energy. There was a large variation in thecontact angle of the droplet as the pillar height increased when there was a large difference in the surface energies between the base andthe pillars.

Measurement of the radon and thoron exhalation rates from the water surface of Yixin lake

Jiulin Wu,Shuaibin Liu,Tao Hu,Fen Lin,Ruomei Xie,Shuai Yuan,Haibo Yi,Yixiang Mo,Jiale Sun,Linquan Cheng,Huiying Li,Zhipeng Liu,Zhongkai Fan,Yanliang Tan Korean Nuclear Society 2024 Nuclear Engineering and Technology Vol.56 No.4

The importance of determining the radon exhalation rate from water surface is emphasized by the increased use of radon and its daughter products as tracers in large-scale circulation studies of the atmosphere. There were many methods to measure radon exhalation from water surface. With the development of radon exhalation rate measurement methods and instruments on the surface of the soil, the rock and building materials, so the radon exhalation rate from water surface can be more accurately measured by applying these improved methods and instruments. In this paper, a cuboid accumulation chamber surrounded by foam boards and a RAD7 were used to measure the radon exhalation rate on the water surface at three different positions by Yixin lake. Each measurement was performed 2 h. The radon exhalation rate from the water surface was about 6 × 10^-3 Bq m^-2s^-1. The thoron exhalation rate from the water surface also can be estimated, it is about 0.16 Bq m^-2s^-1. These results hint that the radon transmission from the lake bottom soil to water and then into the atmosphere.