• 한국환경과학회지
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• 제19권11호
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• pp.1315-1322
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• 2010

A membrane bioreactor (MBR) was designed using polyvinylidene fluoride(PVDF)-type hollow fiber membrane modules with a treatment capacity of 10 ton/day. A pilot plant was installed in a sewage treatment plant and was operated with an intermittent aeration method which avoids any concentration gradient of suspended solids (SS) in the MBR. For continuous operation, the pilot plant was first tested with influent (mixed liquor suspended solid:MLSS of 1000-2000 mg/L) of aeration tanks in the sewage treatment plant. The MBR was pre-treated with washing water, 10% ethanol solution, 5% NaOCl solution and finally washing water, one after another. To demonstrate the effect of the MBR on sewage treatment, compared with conventional activated sludge processes, we investigated the relationships among permeate amount (LMH), change in operation conditions, influent MLSS level and sludge production. It was found that the optimum aeration rate and suction pressure were $0.3\;m^3$/min and 30~31 cmHg, respectively. Under stable conditions in aeration, suction pressure, influent flow rate and drainage, the SS removal efficiency was more than 99.99% even when the MLSS loading rate changes. Compared with conventional activated sludge processes, the MBR was more effective in cost reduction by 27% based on permeate amount and by 51.5% on sludge production.

• 한국유체기계학회 논문집
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• 제9권3호
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• pp.36-43
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• 2006

Recently, micro hydropower and it's useful utilization are taking a growing interest as a countermeasure of global worming by carbon dioxide and exhaustion of fossil fuel. The purpose of this study is to investigate the possibility of extracting micro hydropower wasted by a valve in water supply system using micro cross-flow hydraulic turbine. In order to fulfill the functions of controlling flow rate and pressure in substitute for the valve, air and water are supplied into an air suction hole which is installed on the side wall of micro cross-flow hydraulic turbine. The results show that in case of supplying a lot of air into the air suction hole, about 50% of flow rate and relatively high value of loss coefficient are controlled by the turbine. Moreover, including high possibility of applying the micro cross-flow turbine to water supply system, extended application of the turbine to the water discharge system of drainage and irrigation canal.

• Geomechanics and Engineering
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• 제19권5호
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• pp.447-462
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• 2019

The vacuum preloading method has been used in many countries for ground improvement and land reclamation works. A sand cushion is required as a horizontal drainage channel for conventional vacuum preloading. In terms of the dredged-fill foundation soil, the treatment effect of the conventional vacuum preloading method is poor, particularly in Tianjin, China, where a shortage of sand exists. To solve this problem, straight-line vacuum preloading without sand is widely adopted in engineering practice to improve the foundation soil. Based on the engineering properties of dredged fill in Lingang City, Tianjin, this paper presents field instrumentation in five sections and analyzes the effect of a prefabricated vertical drain (PVD) layout and a vacuum pumping method on the soft soil ground treatment. Through the arrangement of pore water pressure gauges, settlement marks and vane shear tests, the settlement, pore water pressure and subsoil bearing capacity are analyzed to evaluate the effect of the ground treatment. This study demonstrates that straight-line vacuum preloading without sand can be suitable for areas with a high water content. Furthermore, the consolidation settlement and consolidation degree system is developed based on the grey model to predict the consolidation settlement and consolidation degree under vacuum preloading; the validity of the system is also verified.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1999년도 제17회 학술발표회 논문개요집
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• pp.160-160
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• 1999

To reduce the fouling of heat exchangers, the plasma polymerized films was coated on the heat exchangers, and an effect of plasma polymerized film on fouling of heat exchangers was investigated. Monomer and reactive gases were used as the precursors of plasma polymerization. Plasma polymerized films were deposited with process parameters of pressure, power, and ratio of gases. Plasma polymerized films could be served as functional layers of good wettability and high resistance to corrosion. Wettability of plasma polymerized film could be controlled by the ratio change gas mixture. Hydrophilicity of plasma polymerized films on heat exchanger in air conditioner can provide improvement in performance of heat exchanger which results from good water drainage, decrease of pressure drop. DC-plasma polymerized films improve resistance to corrosion whcih is related to deposit formation in heat exchangers. The difference in the build up of fouling deposits between bare substrate and plasma polymerized substrate was investigated by scanning electron microscopy (SEM). An effect of plasma polymerized film on fouling of heat exchangers was discussed in terms of surface properties such as wettability, surface chemical state.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 2003년도 춘계학술발표논문집
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• pp.80-92
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• 2003

The water retention of coating colors can be accurately measured by devices such as an AA-GWR water retention meter whose principle of measurement is based on pressure filtration of coatings under an externally applied air pressure over a certain period of time. It was hypothesized that such devices could be also used to determine the immobilization solids(IMS) of coating colors by determining a sudden drop in the rate of dewatering, that is, a sudden change in the drainage curves. To test this hypothesis, the immobilization solids of coating colors containing various thickeners and water retention additives at different levels were first accurately measured by a modified immobilization tester based on the well-known gloss drop method, and then their values were compared with those obtained by an AA-GWR water retention tester. They agreed very well and showed that the mean of the solids differences is 0.36% in the IMS points between both methods. This good agreement was not surprising because both test methods are based on the same end-point, that is, the immobilization solids point at which menisci begin to form at the coating surface. Theoretical considerations supporting this new method for measuring the immobilization solids of coating colors are presented and some recommendations for the test method are discussed. Also, the effect of various thickeners and water retention additives on the properties and printability of coated papers is discussed.

• 한국지반공학회지:지반
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• 제9권2호
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• pp.27-40
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• 1993

한 개의 공시체에 대해 일정한 크기의 높은 구속압력을 가하고, 단계별로 압밀배수시간을 조정하여 압밀비배수 삼축압축시헙을 할 수 있는 방법을 이 논문에서 제안하였다. 이 방법으로 시험하면 하나의 공시체로 여러 단계의 시험을 하여 강도정수를 구할 수 있음은 물론 시험시간이 종전의 다단계시험에 비해 현저히 절약된다. 이 시험에 대한 적합성을 증명하기 위하여 불교란 시료와 재성형시료에 대해 표준압축시험과 재래의 다단계시험을 수행하고 그 결과를 비교하였다. 여기서 제안하는 시험방법으로 결정된 강도정수는 다른 시험방법으로 얻은 강도정수와 잘 일치하였으며, 이 방법이 대단히 효과적이고 실용적이라는 것을 입증하였다.

• Geomechanics and Engineering
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• 제1권3호
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• pp.193-204
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• 2009

A 10.4-m high highway embankment retained behind mechanically stabilized earth (MSE) walls is under construction in the northeastern part of the Indian state of Bihar. The structure is constructed with compacted, micaceous, grey, silty sand, reinforced with polyester (PET) geogrids, and faced with reinforced cement concrete fascia panels. The connections between the fascia panels and the geogrids failed on several occasions during the monsoon seasons of 2007 and 2008 following episodes of heavy rainfall, when the embankment was still under construction. However, during these incidents the MSE embankment itself remained by and large stable and the collateral damages were minimal. The observational data during these incidents presented an opportunity to develop and calibrate a simple procedure for estimating rainfall induced pore water pressure development within MSE embankments constructed with backfill materials that do not allow unimpeded seepage. A simple analytical finite element model was developed for the purpose. The modeling results were found to agree with the observational and meteorological records from the site. These results also indicated that the threshold rainwater infiltration flux needed for the development of pore water pressure within an MSE embankment is a monotonically increasing function of the hydraulic conductivity of backfill. Specifically for the MSE embankment upon which this study is based, the analytical results indicated that the instabilities could have been avoided by having in place a chimney drain immediately behind the fascia panels.

• 한국지반환경공학회 논문집
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• 제6권2호
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• pp.15-20
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• 2005

도로 주변 절토사면 상부에 시공되는 산마루 측구는 상부로부터 흘러내리는 지표수를 원활히 배수시켜 절개면으로 유입되는 것을 방지한다. 국내의 경우 전 국토의 70%이상이 산악지로 구성되어 있어 도로 개설에 따른 절개면의 발생은 필연적이다. 여름 집중호우와 간극수압의 증가로 인하여 절개면의 불안정성은 증가된다. 그러나 절토사면 상부에 시공되어 있는 산마루측구는 품질관리의 어려움과 배수능력 부족 등의 문제점들이 있다. 따라서, 본 논문에서는 산마루 측구의 깊이와 투수계수에 따른 절토사면의 안전율 변화를 분석하였으며 적절한 측구 설치깊이를 결정하였다.

• Journal of Yeungnam Medical Science
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• 제38권1호
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• pp.74-77
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• 2021

Lymphorrhea is a rare but potentially severe complication that occurs after various surgical procedures. Untreated lymphorrhea may lead to wound dehiscence, infection, and prolonged hospital stay. Currently, there is no standard effective treatment. Early management usually includes leg elevation, drainage, and pressure dressing. However, these methods are associated with prolonged recovery and high recurrence rates. We report a case of lymphorrhea from a calf wound after endoscopic great saphenous vein (GSV) harvesting for coronary artery bypass grafting (CABG). The patient presented with intractable oozing from the postoperative wound on the right calf. Lymphorrhea persisted for 6 weeks despite negative-pressure wound therapy with a long-acting somatostatin. We performed unilateral pedal lymphangiography that confirmed wound lymphorrhea, followed by glue embolization. No recurrence was observed after 8 months of follow-up. This case report demonstrates the successful use of lymphangiography with glue embolization in the control of lymphorrhea after GSV harvesting for CABG.

• Geomechanics and Engineering
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• 제29권5호
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• pp.497-508
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• 2022

Tailings fluidization (i.e., tailings behave as being fluidized) under cyclic loading is one concern during the construction of tailings dams, especially in the shallow tailings layers. The primary goal of this study is to evaluate the responses of tailings under cyclic loadings and the tailings potential for fluidization. A series of cyclic triaxial undrained and drained tests were performed on medium and dense tailings samples under various cyclic stress ratios (CSR). The results indicated that axial strain and excess pore water pressure accumulated over time due to cyclic loading. However, the accumulations were dependent on CSR values, densities, and drainage conditions. The fluidization potential analysis in this study was then evaluated based on the obtained cyclic axial strain and excess pore water pressure. As a result, tailings samples were stable (unfluidized) under small CSR values, and the critical CSR values, where the tailings fluidized, varied depending on the density of tailings samples. Tailings fluidization is triggered as cyclic stress ratios reach critical values. In this study, the critical CSR values were found to be 0.15 and 0.40 for medium and dense samples, respectively.