• Proceedings of the Membrane Society of Korea Conference
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• 2002.07a
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• pp.59-101
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• 2002

PVDF is good material for a hollow fiber membrane with high porosity and excellent hydrophobicity. Asymmetric PVDF hollow fiber membranes were prepared by the Loeb-Sourirajan phase inversion method. Asymmetric PVDF hollow fiber membranes could be controlled in pore size and porosity using various additives(LiCl, ZnCl$_2$) and internal coagulants (water, EtOH/water, and DMAc/water mixture). $CO_2$removal efficiency of asymmetric PVDF hollow fiber membranes was 1.2 times high than that of commercialized PP hollow fiber membranes at MEA 5wt% solution. $CO_2$flux of asymmetric PVDF hollow fiber membranes was 2.5 times higher than that of commercialized PP hollow fiber membranes. $CO_2$removal efficiency and absorption rate of asymmetric PVDF hollow fiber membranes were 30 times higher than those of packed column at absorbent $H_2O$. $CO_2$flux of asymmetric PVDF hollow fiber membranes at MEA 5wt% solution was 48 times higher than that of pure water. In the case of MEA 5wt% solution used as an absorbent, the $CO_2$absorption rate and removal efficiency of PVDF hollow fiber membrane were 2.3 times higher than that of a packed column.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.60 no.4
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• pp.172-174
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• 2011

This paper is presented for robot vacuum cleaners using BLDC motors. Recently, BLDC motors which require smaller size, lower sound noise and higher efficiency have been placed in high value-added products including robot vacuum cleaners, vehicle cars and other industry applications. The DC motors have higher sound noise, higher height of the size and lower efficiency due to electro-magnetic structure using the brushes and the commutators. The proposed BLDC motors are appropriate for the motors adequate in regards to higher efficiency, longer life cycle time, and smaller height of the size when robot vacuum cleaners go to some lower height of the space like under sleeping beds and because it's power source is batteries. The paper shows the performance of the BLDC motors designed by the Finite Element Analysis(FEA) of the electro-magnetic field. This paper shows the mechanical structure and the prototype of the motor with the impeller. The performance characteristics of the BLDC motors with the hall sensor controller are verified by the experimental results.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.44 no.3
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• pp.63-69
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• 2012

The rice husk is one of the major agricultural residue in KOREA. In this paper, the effects of various pulping conditions on the properties of rice husk pulp and handsheets made of rice husk fiber were evaluated in order to utilize the rice husk as an alternative source for wood pulp. Two typical alkali pulping, such as soda pulping and Kraft pulping were applied with various conditions of the pulping processes. The higher effective alkali and higher pulping temperature resulted in the higher efficiency in removal of lignin and ash, which leaded to the higher strength properties of handsheets made of rice husk fiber, but the lower yield of rice husk pulp. The better efficiency in production of rice husk pulp and the stronger handsheets were obtained by the Kraft pulping.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.11
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• pp.5360-5376
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• 2017

In this paper, we study the cross-layer design for the AMC/HARQ-based wireless networks, and propose a new dynamic transmission-mode selection scheme to improve system spectrum efficiency. In the proposed scheme, dynamic thresholds for transmission-mode selection in each packet transmission and retransmission are jointly designed under the constraint of the overall packet error rate. Comparing with the existing schemes, the proposed scheme is inclined to apply higher modulation order at the first several (re)transmissions, which corresponds to higher-rate transmission modes thus higher average system spectrum efficiency. We also extend the cross-layer design to MIMO (Multi-input Multi-output) communication scenarios. Numerical results show that the proposed new dynamic transmission-mode selection scheme generally achieves higher average spectrum efficiency than the conventional and existing cross-layer design.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.823-825
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• 2009

We present multilayer transparent electrodes (MTEs) that resulted in organic light-emitting diodes (OLEDs) with the 90 % higher forward luminous efficiency and 30% higher external quantum efficiency (EQE) than conventional ITO based devices respectively. Optimization method of such MTE structure is investigated in consideration of both injection and optical structure.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.46 no.5
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• pp.61-68
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• 2014

The energy efficiency of papermaking process becomes more significant because of various new regulation of the energy consumption and the green house gas emission. In this study, the effects of wood powder addition on the drainage and the drying efficiency of the OCC based paper products, linerboard, were deeply investigated for improving energy efficiency. The fractionation of wood powder depending on the size were conducted. The bigger size of wood powder resulted in the higher bulk and the higher drainage efficiency, but the lower paper strength. The drying efficiency were in detail evaluated depending on the drying process level. In the first section of drying process until the 80% solid level, there were no significant changes in the drying efficiency by the addition of wood powder. However, after the 80 % solid level, the drying efficiency was greatly improved by the addition of wood powder. Those results showed the addition of wood powder could greatly affect not only the drainage in forming and wet pressing but also the drying process.

• Korea Journal of Hospital Management
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• v.22 no.2
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• pp.44-57
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• 2017

The objective of this study is to investigate financial integrity strategies for sustainable development of local public medical centers, and particularly focus on seeking ways to enhance its financial efficiency and publicness. The data which was collected from 33 local public medical centers was analyzed by Data Envelopment Analysis to measure its financial efficiency. Then, Matrix Analysis was used to examine the association of financial efficiency and publicness of local public medical centers with related factors. In the aspects of facilities and location, according to the results, the local public medical centers which have larger number of available hospital beds or located in bigger cities were examined to have higher degree of publicness. In the aspect of human resources, greater number of doctors made both financial efficiency and the degree of publicness decreased, whereas higher participation rate of educational program for doctors affects increasing its financial efficiency and publicness. Lastly, in the aspect of costs, higher labor, material, and administrative cost diminished financial efficiency, but enhanced the degree of publicness. Based on these results, this study concluded that enhancing the publicness of local public medical centers should be pursued by increasing the accessibility with better facilities and location, and also concurrently organizing rational expenditure structure with appropriate cost investment to the resources of local public medical centers. Also, it is necessary to enhance both financial efficiency and publicness simultaneously by improving the quality of health care services through the educational programs for medical staffs.

• Journal of Environmental Science International
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• v.22 no.7
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• pp.905-913
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• 2013

We compared the applicability and economical efficiency of peroxone process with those of ozone process in the existing water treatment plant on downstream of Nakdong River. After comparing the peroxone process for removing geosmin with the ozone process in lab scale test, peroxone process showed much higher removal efficiency than the ozone process at the same ozone dosage. Proper range of $H_2O_2/O_3$ ratio were 0.5~1.0 and the half-life of geosmin was about 5.5~6.8 min when the $H_2O_2/O_3$ ratio was set to 0.5 during 1~2 mg/L of ozone dosage. Peroxone process could reduce the ozone dosage about 50 to maximum 30% for the same geosmin removal efficiency compared to the ozone process in the pilot scale test. In case of 1,4-dioxane treatment, peroxone process could have 3~4 times higher efficiency than ozone process at the same ozone dosage. The results of estimating the economical efficiency of ozone and peroxone process for treating geosmin and 1,4-dioxane by using pilot scale test, in case of the removal target was set to 85% for these two materials, the cost of peroxane process could be reduced about 1.5 times compared to ozone process, and in the same production cost peroxone process could have 2~3 times higher removal efficiency than ozone process. The removal efficiency by peroxone process showed a large difference depending on the physicochemical characteristics of target materials and raw water, therefore detailed examination should be carried out before appling peroxone process.

• Membrane and Water Treatment
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• v.5 no.4
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• pp.281-293
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• 2014

The present work aimed to study the decolorization kinetics and characteristics of a selected azo dye under the influence of two key operational parameters including hydraulic retention time (HRT) and solid retention time (SRT). The decolorization efficiency and the two important criteria of k and normalized k (k/MLSS) were evaluated in lab-scale membrane sequencing batch reactors (MSBRs) at various HRTs of 48, 24 and 16 h (with constant SRT) and in addition, at various SRTs of infinity, 40 and 10 d (with constant HRT). According to the obtained results, both zero and first-order kinetics were properly fitted the decolorization profiles of the selected azo dye in all of the applied HRTs and SRTs. Increase of both HRT and SRT positively affected the decolorization efficiency. More MLSS concentrations corresponded to the lower HRTs and the higher SRTs resulted in higher decolorization rate constants (k). However, the effect of reducing the HRT was not compensated by increase of the MLSS concentration in order to reach higher decolorization efficiency. In addition, increase of the decolorization efficiency, as a consequence of the higher MLSS concentrations at longer SRTs, was restrained by decrease of the time-limited decolorization capability of biomass (represented by normalized k). Evaluation of both k and normalized k is suggested in order to have a more precise study on the decolorization kinetics and characteristics.

• Korean Journal of Environmental Biology
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• v.25 no.3
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• pp.228-238
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• 2007

Calcium plays an important role for the organisms' physiology, reproduction, and growth. Calcium amount and transfer efficiency along trophic levels were compared at two different geological areas, Limestone area (LS) and Granitic Gneiss area (GG) in 1992 and 1993. Biomass and calcium amount of plants, herbivores and carnivores were seasonally measured. The removal sweeping net method was used to collect the quantitative insect samples. Calcium content (mgCa $g^{-1}$ DM) and pH of soil were 4.85 and 7.3 at LS and 0.21 and 7.3 at GG. The calcium transfer efficiencies (%) at LS and CG were 0.2 and 4.2 from soil to plants, 0.002 and 0.02 from plants to herbivores, and 73 and 47 from herbivores to carnivores, respectively. As a whole, the high calcium content of the LS soil reduced the utilization of calcium by plants. The higher trophical levels were, the higher ecological efficiency of the biological levels was. The calcium transfer amount was higher at LS, but its efficiency was rather higher at GG.