• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.10
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• pp.908-916
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• 2000

In this paper, the characteristics of moisture ventilation in the lithium ion battery manufacturing dry room are studied numerically using standard $k-\varepsilon$ turbulence model. Both the steady-state and the unsteady behaviors of moisture ventilation are analyzed by considering local and uniform moisture generation. In order to evaluate the characteristics of moisture ventilation, three scales of ventilation efficiency and characteristic ventilation time are presented from the numerical results. It was shown that moisture distribution was dependent strongly on the flow field. The characteristics of moisture ventilation were improved by 20% and 40% in terms of the 1st scale of ventilation efficiency (SVE1) and the 2nd scale of ventilation efficiency (SVE2), respectively, through the modifications of design variables such as the addition of inlets, outlets and partition. A significant improvement in the characteristic ventilation time and the moisture exhaust efficiency was also made by these modifications.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.04a
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• pp.34-37
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• 2002

In this study, electrochemical characteristics variation and removal efficiency with initial pH and mineral compositions during electrokinetic remediation of lead contaminated soils were investigated. Test results showed that heavy metal transportation affected by soil characteristics and electrochemical characteristics varied during electrokinetic remediation. Therefore, in the application of enhanced electrokinetic remediation technique to increase removal efficiency, discrete selection of enhanced technique with characteristics of targeted soil were needed.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.6
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• pp.10-16
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• 2011

Diesel particulate filter is being recognized that it is the most effective technologies to reduce particulate matter. In this study, to determine the characteristics of the cell-open-type pDPF, we employed p-DPF to exhaust gas tunnel of diesel engine and surveyed filtration efficiency and BPT on the basis of PM which is exhausted from engine. In this paper the soot loading mass in DPF can be predicted from increase of differential pressure of DPF so that we can measure filtration efficiency and Balance Point Temperature (BPT) by soot loading mass. The result of the research showed that the filtration efficiency is 65% in ESC mode with 0.7mm hole diameter. For the results of the characteristics of filtration efficiency and BPT according to mass_exh, we found that if mass_exh increases, filtration efficiency increases and BPT decreases.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.31 no.2
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• pp.94-103
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• 2008

This study measured technology transfer efficiency for public institutes. The study made use of DEA being one of the non-parametric linear programming to evaluate technology transfer efficiency for public institutes and to measure technology efficiency, pure technical efficiency and scale efficiency. The measurement of the technology transfer efficiency for public institutes was as follows: The cause of the technology transfer inefficiency was affected by pure technical inefficiency more than by scale inefficiency. Public institutes' RTS(Return To Scale) value varied depending upon the features of the organizations than the features of the regions. Public research institutes' RTS value is more effective than universities' RTS value. We compared the RTS group with the RTS of Projected DMU groups. The RTS group had constant returns to scale effect while the RTS of the Projected DMU had increasing returns to scale effect. The technology transfer efficiency of public institutes varied depending upon the features of the organizations and regions : The technology transfer efficiency of public institutes were as follows : public research institutes at the metropolitan area, public research institutes at the local areas, universities at the metropolitan area and universities at the local areas. In other words, the technology transfer efficiency was affected by organizational characteristics more than by regional characteristics at the place where public institutes were located.

• International Journal of Aeronautical and Space Sciences
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• v.4 no.1
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• pp.26-33
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• 2003

Recess is a geometrical configuration shape that the exit surface of an inner injector is located at a certain length inward from that of an outer injector. It is known to have the characteristics that it can augment mixing efficiency and flame stabilization through internal mixing of propellant in it. So, various experiments, such as backlit stroboscopic photography, phase Doppler particle analyzer(PDPA) and mechanical patternator, were performed at several recess lengths to grasp its effect on the spray characteristics of spray angle, breakup length, atomization and' mixing. Recess length was normalized to dimensionless recess number and two principal mechanisms of impingement and swirl recovery were introduced to explain its influence on the spray characteristics. The effect of recess on SMD doesn't appear significantly near the recess number where mixing efficiency attains to the maximum, whereas mass distribution and mixing efficiency are changed considerably. Thus, it can be inferred that a certain optimum recess number exists, where mixing efficiency becomes the maximum.

• Korean Journal of Materials Research
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• v.21 no.10
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• pp.532-541
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• 2011

The Xe plasma flat lamp, considered to be a new eco-friendly LCD backlight, requires a further improvement of its luminance and luminous efficiency. To improve the performance of this type of lamp, it is necessary to understand the effects of the discharge variables on the luminous characteristics of the lamp. In this study, the luminous characteristics of a coplanartype Xe plasma flat lamp with a teeth-type electrode pattern were analyzed while varying the gas composition, gas pressure and input voltage. The effects of the phosphor layer on the discharge and the luminous characteristics of the lamp were also studied. The luminous efficiency of the coplanar-type Xe plasma flat lamp improved as the Xe input ratio and gas pressure increased. Higher luminous efficiency was also obtained when helium (He) was used as a buffer gas and when a phosphor layer was fabricated on the electrode region. In contrast, the luminous efficiency was reduced with increasing the input voltage. It was found that the infrared emissions from the lamp were affected by the Xe excitation rate in the plasma, the Xe gas density, the collisional quenching of excited Xe species by gas molecules, and the recombination rate between the Xe ions and electrons.

• Korean Journal of Materials Research
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• v.31 no.10
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• pp.586-591
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• 2021

This paper proposes a mathematical model that can calculate the luminescence characteristics driven by alternating current (AC) power using the current-voltage-luminance (I-V-L) properties of organic light emitting devices (OLED) driven by direct current power. Fluorescent OLEDs are manufactured to verify the model, and I-V-L characteristics driven by DC and AC are measured. The current efficiency of DC driven OLED can be divided into three sections. Region 1 is a section where the recombination efficiency increases as the carrier reaches the emission layer in proportion to the increase of the DC voltage. Region 2 is a section in which the maximum luminous efficiency is stably maintained. Region 3 is a section where the luminous efficiency decreases due to excess carriers. Therefore, the fitting equation is derived by dividing the current density and luminance of the DC driven OLED into three regions, and the current density and luminance of the AC driven OLED are calculated from the fitting equation. As a result, the measured and calculated values of the AC driving I-V-L characteristics show deviations of 4.7% for current density, 2.9 % for luminance, and 1.9 % for luminous efficiency.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.5
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• pp.884-891
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• 2007

Comparing with the conventional transformer without the air gap, a contact-less transformer with the large air-gap (4.8cm) between the long primary winding and the secondary winding has the increased leakage inductance and the reduced magnetizing inductance. By the increased leakage inductance and the reduced magnetizing inductance on the primary of the contact-less transformer, a good deal of the primary current circulates through magnetizing inductance, which results in a massive loss and the high voltage gain characteristics for load variations in contact-less power supply (CPS). To consider these characteristics, in this paper, the efficiency characteristics of the contact-less power supply using a series resonant converter is presented, described and verified through theoretical analysis, computer simulation and experimental test of 2.5kW prototype.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.8
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• pp.432-441
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• 2000

It is difficult to analyze the charging characteristics of the lead-acid battery, because of the influences by various non-linear and time-variant parameters. In this study, the charging characteristics of high capacity industrial lead-acid battery 630 Ah was investigated through experiments with respect to the variations of temperature and the aged state of battery during the charging process. The database of those characteristics is established from the results of experiments, and the fuzzy logic charging algorithm is suggested using them. The results of experiment shows that the industrial lead-acid batteries can be always fully charged within the saved charging time by the proposed charging control algorithm adapting to the variations of charging condition. This new charging concept will be useful for developing the advanced battery charger improving the efficiency of storing electricity.

• Korean Journal of Applied Biomechanics
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• v.13 no.1
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• pp.109-119
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• 2003

The purpose of this study was to investigate differences of the mechanical efficiency on the characteristics of the basketball wheelchairs(cambers & size of the handrims). Nine healthy and normal wheelchair basketball players who had no impairments to their upper extremities were volunteered to participate in this study. $VO_2$ was collected using automatic gas analyzer(vmax29). Gross efficiency, net efficiency and work efficiency were analyzed from the calculated external power output and energy expenditure. The results were followed. First, gross efficiency in the basketball wheelchairs was observed across the range from 4 to 10%. Gross efficiency in this study showed less values than that from the literature reviewed in the arm cranking(15%), racing wheelchair(above 30%), gait(27%) and cycling(18-23%). Second, the small size of handrim(61cm) at the 16 degrees of camber produced higher efficiency values than the large size of handrim(66cm) whereas the different sizes of handrim at the 20 degrees of camber did not show any pattern. Third, both faster speed($1.11^m/s{\rightarrow}1.39^m/s$) and increases in treadmill inclination produced increases in energy expenditure. The results of this study may provide not only better understanding of the mechanical efficiency with adequate camber degree and proper size of handrim but also fundamental information for manufacturing the wheelchair.