• 한국소음진동공학회논문집
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• 제26권5호
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• pp.546-551
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• 2016

The objective of this study is to investigate the response delays between piezo-stack actuator and the displacement magnifier of jetting dispenser and to reduce its falling time in terms of displacement optimization. The dispenser is driven by the dual piezo-stack actuators with a hinge lever mechanism to precisely control flow rate of the working fluid (3000 cP). It is commonly found that piezo actuator-driven jetting dispensers involving viscous working fluids have displacement optimization problem for ideal performance. The response delay of the system is caused by the phenomenon that the displacement magnifier cannot exactly follow the motion of the piezo actuators. The response delay may lower the performance of the system due to the inaccurate discharge of working fluid or even damages to the system itself due to inharmonious motion of piezo actuators with lever system. To reduce its response delay, a new displacement profile obtained from displacement optimization is suggested; its performance is tested through finite element analysis; and experiments are carried out to verify the performance of the obtained displacement profile.

• 한국물환경학회지
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• 제32권6호
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• pp.537-545
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• 2016

In order to cope with the new and strict government regulations for turbid water discharge from construction sites, this study tested whether synthetic fiber filters can replace conventional best management practices. The filter efficiency was about 10 to 60% with a varying filter depth of 5 to 15cm, presuming extreme storm flow conditions to be in the range of 800 to 1500m/day of filtration rates. Fiber filter acts exactly like a granular filter, i.e. the separation efficiency is directly and inversely proportional to filter depth and rate, respectively. Based on the operational data, we suggested the Log-Log design relationship, which can be used to determine the filter depth and area. Compared to the widely used gravel filter which treats the turbid water at the construction site, about 20% higher efficiency was obtained under similar operating conditions. Cleaning the filter through a simple hand-washing method at the time of break-through, achieved about 90% soil recovery.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.151-154
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• 2003

AlN/Al/SiO$_2$/Si thin films for application to FBAR(Film Bulk Acoustic Resonator) devices were prepared by FTS(Facing Targets sputtering system) apparatus which provides a stable discharge at low gas pressures and can deposit high quality thin films because of the substrate located apart from the plasma. The AlN thin films were deposited on a $SiO_2(1{\mu}m)/Si(100)$ substrate using an Al bottom electrode. The process parameters were fixed such as sputering power of 200W, working pressures of 1mTorr and AlN thin film thickness of 800nm, respectively and crytallographic characteristics of AlN thin films were investigated as a function of $N_2$ gas flow rate$[N_2/(N_2+Ar)]$. Thickness of AlN thin films were measured by $\alpha$-step, the crystallographic characteristics and c-axis preferred orientation were evaluated by XRD.

• 한국정밀공학회지
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• 제33권11호
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• pp.927-935
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• 2016

A gerotor is suitable for miniature manufacturing because it has a high discharge per cycle and a simple structure, while also being widely used as lubrication oil of engines and the hydraulic source of automatic transmission. In the automobile industry, it has been necessary to continuously improve the flow rate and noise of internal gear pumps for better fuel efficiency through optimal gerotor design. In this study, to obtain an optimal gerotor with an ellipse-elliptical involute-ellipse combined lobe shape, an automatic program was developed for calculating performance parameters and drawing a gerotor profile. An oil pump was assembled with the optimal gerotor together with the port used at the actual field and CFD analysis was performed on this assembly using Ansys-CFX. A performance test for the oil pump was carried out and showed good agreement with the results obtained from the theoretical analysis and the CFD analysis.

• 한국물환경학회지
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• 제28권3호
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• pp.401-408
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• 2012

High-voltage dielectric discharges are an emerging technique in environmental pollutant degradation, which that are characterized by the production of hydroxyl radicals as the primary degradation species. The initiation and propagation of the electrical discharges depends on several physical, chemical, and electrical parameters such as 1st and 2nd voltage of power, gas supply, conductivity and pH. These parameters also influence the physical and chemical characteristics of the discharges, including the production of reactive species such as OH, $H_2O_2$ and $O_3$. The experimental results showed that the optimum 1st voltage and air flow rate for RNO (N-Dimethyl-4-nitrosoaniline, indicator of the generation of OH radical) degradation were 160 V (2nd voltage of is 15 kV) and 4 L/min, respectively. As the increased of the 2nd voltage (4 kV to 15 kV), RNO degradation, $H_2O_2$ and $O_3$ generation were increased. The conductivity of the solution was not influencing the RNO degradation and $H_2O_2$ and $O_3$ generation. The effects pH was not high on RNO degradation. However, the lower pH and the conductivity, the higher $H_2O_2$ and $O_3$ generation were observed.

• 상하수도학회지
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• 제22권6호
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• pp.697-704
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• 2008

Stormwater runoff from urban road area as non-point source has a tendency of including lots of pollutants at initial rain period. Recently, there are several cases of having installed treatment facilities for reducing pollution discharge from the impervious cover in urban area to prevent watershed environment from getting worse. The filtration type among non-point source treatment systems has been known as one of the most efficient system for treatment of non-point source pollutants. Therefore, various kinds of filter media such as expanded polypropylene(EPP), granular activated carbon, zeolite, perlite, illite, sand, gravel has been developed. This study was conducted to verify performance and hydraulic characteristics of filter media as measures for non-point source. The experiment was carried out to evaluate applicability and variation of 4 kind of most popular filter media(EPP, GAC, Zeolite, Perlite) in headloss with elapsed time and influent flow rate and to obtain data base that could be used to establish management plan for road runoff treatment. In experiment by tap water, it showed that EPP and perlite those are floatable materials showed stable operating performance and lower headloss than the others.

• 한국수자원학회논문집
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• 제37권6호
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• pp.509-515
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• 2004

본 연구에서는 국내에서 독자적으로 개발한 완전 연동형 SWAT-MODFLOW결합모형을 평가하였다. 결합모형은 함양량의 시공간적 변동성을 반영할 수 있어 기존 지하수 모델링에 있어서 함양량을 현실적으로 고려하지 못했던 부분이 크게 개선될 것으로 판단된다. 또한 SWAT의 지하수 모형성분은 집중형이므로 분포형 매개변수의 입력이 어렵고 지하수위의 변화 등을 고려하지 못하나 결합모형은 지하수부분에 MODFLOW모형을 탑재시킴으로써 완벽한 시간단계별 지하수위 분포를 재생해 낼 수 있었다. 마지막으로 하천네트워크-대수층간의 상호작용에 있어서 SWAT은 일방향만을 고려하나 결합모형은 양방향 상호작용을 모두 고려할 수 있어 실제적인 하천-대수층간의 경계유량을 고려할 수 있어 유역내 기저 유출량 및 총 유출량의 신뢰성이 크게 증대될 것으로 기대된다.

• 한국자동차공학회논문집
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• 제16권6호
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• pp.176-183
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• 2008

Performance of electrostatic diesel PM filtration systems (E-DPS) with different types has been tested using the carbon particles generated by spark discharge in laboratory. Among the five electrostatic precipitators, the multiple wires cylindrical E-DPS with the highest collection efficiency and relatively lower differential pressure at the flow rate of $1\;m^3$/min, as an applicable device to diesel engine as an after treatment system, has been combined with another collection cylinder to improve the collection efficiency of diesel particulate matters generated from diesel engines. The multiple wires cylindrical E-DPS combined with the cylindrical collector showed the collection efficiency of more than 60% at the engine speed of 2,000 rpm with the engine loads of 25 and 50%.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 C
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• pp.1555-1559
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• 1997

The thin films were obtained by plasma polymerization of phenyl isothiocyanate. Polymerizations were carried out in rf(13.56[MHz]) glow discharge generated in an inter-electrode capacitively coupled gas flow system. It was found that this monomer produces uniform films with a wide range of thicknesses, from hundreds of nanometers to tens of micrometers. The deposition rate appeared to be dependent on the substrate distance from the monomer inlet. The IR data revealed significant decrease in -NCS groups content in the polymer as compared with the monomer spectrum and indicated for the appearance of new absorption bands corresponding to the -CN and C-H aliphatic groups. The soluble fraction by GC was found to be composed of numerous low molecular-weight compounds.

• Nuclear Engineering and Technology
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• 제48권5호
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• pp.1280-1290
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• 2016

This paper presents an advanced estimation method for obtaining the probability density functions of a damage parameter for valve leakage detection in a reciprocating pump. The estimation method is based on a comparison of model data which are simulated by using a mathematical model, and experimental data which are measured on the inside and outside of the reciprocating pump in operation. The mathematical model, which is simplified and extended on the basis of previous models, describes not only the normal state of the pump, but also its abnormal state caused by valve leakage. The pressure in the cylinder is expressed as a function of the crankshaft angle, and an additional volume flow rate due to the valve leakage is quantified by a damage parameter in the mathematical model. The change in the cylinder pressure profiles due to the suction valve leakage is noticeable in the compression and expansion modes of the pump. The damage parameter value over 300 cycles is calculated in two ways, considering advance or delay in the opening and closing angles of the discharge valves. The probability density functions of the damage parameter are compared for diagnosis and prognosis on the basis of the probabilistic features of valve leakage.