• Communications for Statistical Applications and Methods
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• v.31 no.3
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• pp.291-308
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• 2024

The current article discusses ratio type exponential estimators for estimating the mean of a finite population in sample surveys. The estimators uses robust regression's Huber M-estimation function, and their bias as well as mean squared error expressions are derived. It was campared with Kadilar, Candan, and Cingi (Hacet J Math Stat, 36, 181-188, 2007) estimators. The circumstances under which the suggested estimators perform better than competing estimators are discussed. Five different population datasets with a well recognized outlier have been widely used in numerical and simulation-based research. These thorough studies seek to provide strong proof to back up our claims by carefully assessing and validating the theoretical results reported in our study. The estimators that have been proposed are intended to significantly improve both the efficiency and accuracy of estimating the mean of a finite population. As a result, the results that are obtained from statistical analyses will be more reliable and precise.

• Journal of Korean Society for Atmospheric Environment
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• v.18 no.E2
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• pp.107-120
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• 2002

Dimethyl sulfide (DMS) is the major sulfur gas released from the ocean. The atmospheric DMS released from the ocean is oxidized mainly by hydroxyl (OH) radical during the day and nitrate (NO$_3$) radical at night to form sulfur dioxide (SO$_2$) as well as other stable products. The oxidation mechanism of DMS via OH has been known to proceed by two channels; abstraction and addition channels. The major intermediate product of the addition channel has been known to be dimethylsulfoxide (DMSO) based on laboratory chamber studies and field experiments. However, a branching ratio for DMSO formation is still uncertain. The reaction of DMSO with OH ultimately produces SO$_2$and dimethylsulfone. The major product of the abstraction channel has known to be SO$_2$from laboratory chamber studies. But overall conversion efficiency for DMS to SO$_2$from DMS oxidation is still inconsistent in the literature. Based on laboratory and field studies, the conversion efficiency from the abstraction channel is likely to be greater than 0.5, while that from the addition channel is likely to be greater than 0.6. Overall conversion efficiency from DMS to SO$_2$might be greater than 0.5 based on the above two values in the remote marine boundary layer (MBL). This high efficiency in the remote MBL is supported by strong coupling between DMS and SO$_2$measurements with high temporal resolution.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.36 no.4 s.107
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• pp.67-76
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• 2004

Because paper industry spends lots amount of water, the recycling of water is very important in economical as well as environmental aspects. In order to optimize the process water recycling system, the efficiency of unit operation for water circulation, such as save-all system, CDS and settling tank, plays an important role in. In this study, the sedimentation efficiency of process water was evaluated by SS measurement with the different amounts of flocculent addition. 3 different kinds of process water were collected from fine paper mill, and applied in laboratory sedimentation equipment for the measurement of settling efficiency of SS materials. The addition amounts of alum and PAC were resulted in optimum efficiency of sediments in the condition of 100 ppm of alum and 500 ppm of PAC respectively. In the comparison of sedimentation efficiency between alum and PAC, alum showed more economical and efficient results. The SS of spill water and the particle size of suspended materials treated by alum flocculents were below 50 ppm and about 1 $\mu$m. It would be considered that the spill water can be substituted to superclear water grade.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.4
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• pp.208-215
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• 2013

An experimental study of an ORC (Organic Rankine Cycle) system has been performed for small-scale applications in the range of a few kW for low-grade-recovery heat sources. The ORC system was equipped with a scroll expander. Experimental tests were carried out using this system, and showed good performance and reliability for the small-scale system. The effects of various operating conditions were selected as the main parameters for the performance of ORC system, such as the expander speeds and mass flow rates of R-134a for expander inlet temperatures ranging from $100^{\circ}C$ to $190^{\circ}C$, as well as the thermal power, thermal efficiency, expansion efficiency, and volumetric efficiency.

• Korea-Australia Rheology Journal
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• v.20 no.2
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• pp.79-88
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• 2008

In this study, we focus on the improvement of the filling efficiency in injection molding by application of ultrasonic vibration. While studies about the filling efficiency of typical filling processes in the injection molding have been widely performed, there have been only few studies about the filling efficiency of an ultrasonic process. The effect of the ultrasonic vibration is an important process condition, which influences the flow characteristics of polymer melt. This new condition even affects well-known injection conditions such as cavity pressure, injection temperature and mold temperature. For this study, we carried out a numerical analysis by appropriate modeling and analysis of the ultrasonic process in the filling process. To verify this numerical analysis, we compared the numerical results with the experimental data. Also, we analyzed the filling process in a thin cavity using this numerical analysis. To understand the flow characteristics of polymer melt in the ultrasonic process, we substituted real and complex vibration conditions with simplified and classified conditions according to the position of vibrating cavity surfaces and the phase difference between two opposing cavity surfaces. We also introduced MFR (melt flow ratio) as a new index to estimate the filling efficiency in the ultrasonic process.

• Journal of Electrical Engineering and Technology
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• v.12 no.5
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• pp.1934-1944
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• 2017

As a key component of high-voltage power conversion system for electric vehicles (EVs), bidirectional DC/DC (Bi-DC/DC) is required to have high efficiency and light weight. Conventional design methods optimize the Bi-DC/DC at the maximum power dissipation point (MPDP). For EVs application, the work condition of the Bi-DC/DC is not strict as the MPDP, where the design method using MPDP may not be optimal during travel of EVs. This paper optimizes the Bi-DC/DC converter targeting efficiency and weight based on the driving cycle. By analyzing the two-phase interleaved Bi-DC/DC for hybrid energy storage systems (HESS) of EVs, its power dissipation is calculated, and an efficiency model is derived. On this basis, weight models of capacitor, inductor and heat sink are built, as well as a dynamic temperature model of heat sink. Based on these models, a method using New European Driving Cycle (NEDC) for optimal design of Bi-DC/DC which simultaneously considered efficiency and weight is proposed. The simulation result shows that compare with conventional optimization methods revealed that the optimization approach based on driving cycle allowed significant weight reduction while meeting the efficiency requirements.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.7
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• pp.275-280
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• 2013

This paper presents an optimizing method for wireless charging system, specifically focused on the capsule endoscope applications. In order to increase the wireless power transfer efficiency of electro-magnetic resonance coupled coils, this paper investigates the impact factors of the power transfer efficiency in small battery capacity system and proposes a efficiency optimizing method based on frequency control. Simulation results show that the proposed efficiency optimal control method can effectively stabilize the wireless power transfer efficiency so as to successfully solve the main issue of transfer efficiency variation with distance and as well as parasitic element.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.09a
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• pp.347-350
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• 2002

The petrochemical products can cause soil and groundwater contamination during their transportation and the use of the products, and while being contained in underground storage tanks(USTs) throughout the leakage. To treat the contaminated soil, the bioventing method is suitable for the remediation of semi-volatile compounds, such as diesel and kerosene. Biofiltration is one of possible method to treat the off-gas produced in the process of the bioventing. This study is related to the usage, effectiveness of treatment, and feasibility of two types of biofilter system made of ceramic-compost and polymer respectively to treat diesel VOCs at constant retention time of 20 sec. Compost biofilter showed the average removal efficiency of 73 % when the inlet concentration increased to 20 ppmv. Increased the inlet concentration decreased the microbial activities as well as the removal efficiency. On the contrary, the removal efficiency of the polyurethane biofilter was maintained at 88 % at the inlet concentration of 13 ppmv during ten days and was obtained to 80 % at the inlet concentration of 30 ppmv in spite of the drop of the efficiency in the sudden increase of the inlet concentration. At the beginning of the experiment it showed low removal efficiency at low inlet concentration due to the low microbial activity, however, as experiments proceed the removal efficiency could be obtained more than 80% at high inlet concentration.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.3
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• pp.359-366
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• 2008

The series of experiments under the various conditions were carried out to evaluate the feasibility of dissolved air flotation (DAF) as an alternative of conventional gravity sedimentation (CGS) and to investigate the decrease of the loadings following to biological wastewater treatment processes in livestock wastewater system. On the basis of the experiment result between CGS and DAF processes, for the other water quality criteria as well as suspended solid the removal efficiency of DAF process was about 20~25 % better than CGS process on average. In addition, the particle removal efficiency of DAF process became higher in proportion as the increase of air to solid (A/S) ratio and the general wastewater treatment efficiency of DAF process was enough to meet the requirement of loading decrease to following biological process even at low A/S ratio range. Though DAF process is widely known as an solid separation unit, there was not the notable relationship between particle separation efficiency and several pollutant removal efficiencies like $COD_{Cr}$ and nutrients (T-N, T-P). Assume that the $COD_{Cr}$ was removed as the fraction of particle separation in this experiment, the removal efficiency of T-N and T-P were sensitive to removal efficiency of $COD_{Cr}$, especially.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.4
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• pp.369-376
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• 2010

The purpose of this study is to reprocess Waste-LCD(Liquid Crystal Display), to widely increase specific surface-area by foaming agent in the process of reprocessing and to use as a substrate of water treatment which is increased the ability of biological treatment, as well as to control non-point source pollutants produced by surface run off during rainfall with using this substrate, and to improve water quality of public watershed as developing substrate for water treatment to be able to purify second treated water which is exhausted at the wastewater treatment plant. The average removal efficiency of Waste-LCD that using the foaming technology was SS 71.2%, BOD 55.7%, COD 58.4%, T-N 29.5% and T-P was 50.3%. Almost Media, early stage showed low removal efficiency of SS and BOD. However, it became high when the microorganism adhered the Media. The variation of SS removal efficiency was high by inflow concentration of SS. The reason for the Media 4 showed high SS removal efficiency is that it has wide specific surface-area, and also it has a pore. All in all, it shows floating matter treatment ability not only inside but it also works outside of the substrate.