• Carbon letters
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• 제1권3_4호
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• pp.154-157
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• 2001

Composite adsorbents were prepared by mixing water plant sludge with phenolic resin having the ratio of 1 : 1, 1 : 2, and 1 : 3 respectively, curing from $100^{\circ}C$ to $170^{\circ}C$ under $N_2$ atmosphere, and then activating with $N_2$ at $700^{\circ}C$. Thermal property, specific surface area and morphology of the composite adsorbents as well as their precursors were measured by TGA, BET and SEM respectively. Removal efficiency of the composite adsorbents to ${NH_4}^+$ and TOC was compared with those of commercial zeolite and activated carbon. The adsorbents presented very promising TOC removal efficiency of 98%, which was identical level to that of commercial activated carbon while they displayed removal efficiency, only 32%, of ${NH_4}^+$. Therefore, this composite adsorbent considered as the alternative material of commercial activated carbon, used as an expensive removal agent of organic substances and THM in water treatment plant and it also suggested a possibility of practical application in other processes.

• International Journal of Fluid Machinery and Systems
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• 제1권1호
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• pp.86-91
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• 2008

The effects of the diffuser vane on the performances of the multistage centrifugal pump were investigated experimentally, taking account of the interactions among the diffuser vane, the return vane, and the next stage impeller. It is very important to match well the diffuser vane with the return vane, for improving the hydraulic efficiency of the pump. The efficiency may be more improved by making the cross-sectional area of the channel from the diffuser vane outlet to the return vane inlet larger, as much as possible.

• 대한기계학회논문집B
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• 제29권12호
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• pp.1369-1376
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• 2005

Effective mixing gives strong advantageous impact on microfluidic applications since mixing is in general very slow process motivated by molecular diffusion transport only on the micro-scale. In this work, the mixing characteristics are analyzed in a Y-channel micromixer with obstacles. For the through analysis, our laboratory in-house unstructured grid CFD code is validated through solving a concentration transport in a uniform microchannel. The solutions well correspond to both exact solutions and those from MemCFD. Mixing in a Y-channel micromixer with obstacles is numerically investigated by the in-house code to search the optimal radius and layout of obstacles. From the simulations, the mixing efficiency appears to be proportional to the magnitude of the formation of lateral velocity component. It is also shown that the asymmetric layout and radius enlargement of obstacles greatly improves mixing efficiency.

• 대한기계학회논문집B
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• 제24권4호
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• pp.608-613
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• 2000

The present study has proposed a novel aerosol CVD utilizing an internal jet in the conventional MCVD reactor for the purpose of enhancing the deposition efficiency(and rate) and the uniformity of deposited film. The use of impingement of high temperature jet through a thin inner tube ensures the reduction of non-uniform particle deposition zone as well as higher thermophoretic particle deposition. It is shown that significant improvements have been achieved for both aspects of deposition efficiency and uniformity. As jet temperatures increase, the tapered length is reduced and deposition efficiency is significantly increased.

• Smart Structures and Systems
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• 제10권3호
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• pp.193-207
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• 2012

New insights into our previously proposed hybrid-type method for vibration control are highlighted in terms of energy analysis, such as the assessment of energy efficiency and system stability. The hybrid method improves the bang-bang active method by combining it with an energy-recycling approach. Its simple configuration and low energy-consumption property are quite suitable especially for isolated structures whose energy sources are strictly limited. The harmful influence of the external voltage is assessed, as well as its beneficial performance. We show a new chattering prevention approach that both harvests electrical energy from piezoelectric actuators and eliminates the displacement-offset of the equilibrium point of structures. The amount of energy consumption of the hybrid system is assessed qualitatively and is compared with other control systems. Experiments and numerical simulations conducted on a 10-bay truss can provide a thorough energy-efficiency evaluation of the hybrid suppression system having our energy-harvesting system.

• 한국소음진동공학회논문집
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• 제19권9호
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• pp.876-883
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• 2009

The radiation of sound from a rectangular plate with a guided edge condition is investigated. By taking this particular boundary condition into account, simple analytical forms of the average radiation efficiency and radiation power based on the modal approach can be found, where the cross-modal terms can average out for all possible point excitation locations. Design variables of the plate such as thickness, aspect ratio, and damping that are closely related to the sound radiation are mainly discussed. The radiation power of the guided plate is found to be governed by the piston mode as well as the critical frequency. While both the radiation efficiency and the radiation power seem to be influenced by thickness and a large aspect ratio, damping loss factor seems less important to the radiation power. It is also shown that no clear corner and edge mode regions may be found for the guided case, unlike the pinned.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2003년도 추계학술발표회
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• pp.565-569
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• 2003

One-year-long groundwater-level data have been collected from 18 wells in Cheon-an area. The result of barometric efficiency, autocorrelation, cross-correlation and statistical distribution evaluated from the measurement data shows that groundwater-level measurements from observation wells are the principal source of information about aquifer characteristics. Data from WA-2 has high barometric efficiency as well as steady decreasing auto-correlation coefficient, which means nonleaky confined aquifer, Most aquifers in this study show the unconfined properties so that barometric efficiencies are mostly low and the coefficients of cross-correlation between groundwater-level and precipitation are commonly high. This study showed that the long-term groundwater-level monitoring data without artificial stress such as pumping would give accurate information about aquifer characteristics.

• 한국해양공학회지
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• 제19권6호통권67호
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• pp.1-7
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• 2005

This paper deals with the design and aerodynamic analysis of a special-type impulse turbine, with an end plate for wave energy conversion. Numerical analysis was performed using a CFD code, FLUENT. The main idea of the proposed end plate was to minimize the adverse effect of tip clearance of turbine blade, and was borrowed from ducted propeller, with so-called penetrating end plate for special purpose marine vehicles. Results show that efficiency increases up to $5\%$, depending on the flow coefficient; a higher flow coefficient yields increased efficiency. Decrease of input coefficient CAwith an end plate is the main reason for higher efficiency. Performance of end plate at various design parameters, as well as flow conditions, was investigated; the advantages and disadvantages of the presentimpulse turbine were also discussed.

• KDI Journal of Economic Policy
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• 제39권1호
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• pp.83-102
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• 2017

Price control can restore efficiency in some cases, but an uncarefully designed policy fails to restore efficiency, yields side effects, or even exacerbates efficiency losses. This paper shows that the copyright royalty rule, which takes the greater of ad valorem royalties and perunit royalties, tends to fix the prices of final goods at a specific level. Such a rule weakens competition as it prevents prices from decreasing even when market conditions change, having negative effects on social welfare as well as consumer surplus. Counterfactual analyses using estimation results in the Korean online music service industry show that firms could have profitably reduced prices if the ad valorem rule had been applied instead, although they did not have an incentive to do so under the original combination rule.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 추계학술대회 논문집 학회본부
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• pp.453-455
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• 1995

In electrostatic airclean filter, the collection efficiency defends on particle charge in the ionizer section. The effect of electrostatic airclean filter condition (deposition of dust, variation of corona discharge current) on corona discharge characteristics was well studied. However, it seems not to be studied on corona discharge characteristics of electrostatic airclean filter respect to contaminated electrode which is caused by practical use. In this paper, Long-term(60days) effects are studied experimentally by two methods. The one is ozone concentration, the other is collection efficiency. Generation of ozone level was increased but collection efficiency was slightly reduced in long-term used electrostatic airclean filter.