• Journal of Power Electronics
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• v.8 no.4
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• pp.309-316
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• 2008

In this paper, new topology is proposed that can dramatically reduce the converter power rating and increase the efficiency of total PV system. Since the output voltage of PV module has very wide voltage range, in general, the DC/DC converter is used to get constant high DC voltage. According to analysis of PV characteristics, in proposed topology, only 20% power of total PV system power is needed for DC/DC converter. DC/DC converter used in proposed topology has flat efficiency curve at all load range and very high efficiency characteristics. The total system efficiency is the product of that of converter and that of inverter. In proposed topology, because the converter efficiency curve is flat all load range, the total system efficiency at the low power range is dramatically improved. The proposed topology is implemented for 200kW PCS system. This system has only three DC/DC converters with 20kW power rating each other. It is only one-third of total system power. The experiment results show that the proposed topology has good performance.

• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.1
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• pp.142-156
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• 2015

A new method for ship Inner Shell optimization, which is called Parametric Inner Shell Optimization Method (PISOM), is presented in this paper in order to improve both hull performance and design efficiency of transport ship. The foundation of PISOM is the parametric Inner Shell Plate (ISP) model, which is a fully-associative model driven by dimensions. A method to create parametric ISP model is proposed, including geometric primitives, geometric constraints, geometric constraint solving etc. The standard optimization procedure of ship ISP optimization based on parametric ISP model is put forward, and an efficient optimization approach for typical transport ship is developed based on this procedure. This approach takes the section area of ISP and the other dominant parameters as variables, while all the design requirements such as propeller immersion, fore bottom wave slap, bridge visibility, longitudinal strength etc, are made constraints. The optimization objective is maximum volume of cargo oil tanker/cargo hold, and the genetic algorithm is used to solve this optimization model. This method is applied to the optimization of a product oil tanker and a bulk carrier, and it is proved to be effective, highly efficient, and engineering practical.

• Journal of the Korean Society of Safety
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• v.26 no.1
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• pp.8-14
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• 2011

Noise and vibration are likely to disturb the sensory system of human body leading to psychological stress and thereby property damage. In this research, a cut out switch(COS) with a built-in acoustic absorber along with a COS fuse broken was developed to reduce percussion noise. This new system is based on a design approach that combines existing absorber systems: expansion type, resonator type, and acoustic absorber type silencer The noise performance of the new system was simulated using the $SYSNOISE^{TM}$ software under optimized parameters: the diameter of perforated plate 2 mm, the plate thickness 3 mm, the width of expansion room 25 mm, the impinging vortex room 14 mm, and the noise absorbtion room 10 mm. The results showed that it reduced noise by approximately 41.1 dB compared to the current systems available in the market. Furthermore, it showed reduced noise by approximately 12 dB more than a product with an acoustic absorber of the Fault Tamer(USA).

• Journal of the Korean Institute of Gas
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• v.19 no.2
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• pp.45-53
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• 2015

In order to improve the performance of the visual inspection process, in addition to existing automatic visual inspection machine and human inspectors have developed a new process configuration using a Naive Bayes classifier. By applying the classifier, defect leakage and human inspector's work amount could be improved at the same time. New classification method called AMPB was applied instead of conventional methods based on MAP classification. By experimental results using the filter product for camera modules, it was confirmed that it is possible to configure the process at the level of leakage ratio 1.14% and human inspector's work amount ratio 75.5%. It is significant that the result can be applied in such a wide range as gas leak detection which is the collaboration process between inspection machine and human inspector's

• Communications for Statistical Applications and Methods
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• v.26 no.1
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• pp.1-9
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• 2019

Various probabilistic methods have been proposed for using interpopulation allele frequency differences to infer the ethnic group of a DNA specimen. The selection of the statistical method is critical because the accuracy of the statistical classification results vary. For the ancestry classification, we proposed a new ancestry evaluation method that estimate the combined ethnicity index as well as compared its performance with various classical classification methods using two real data sets. We selected 13 SNPs that are useful for the inference of ethnic origin. These single nucleotide polymorphisms (SNPs) were analyzed by restriction fragment mass polymorphism assay and followed by classification among ethnic groups. We genotyped 400 individuals from four ethnic groups (100 African-American, 100 Caucasian, 100 Korean, and 100 Mexican-American) for 13 SNPs and allele frequencies that differed among the four ethnic groups. Additionally, we applied our new method to HapMap SNP genotypes for 1,011 samples from 4 populations (African, European, East Asian, and Central-South Asian). Our proposed method yielded the highest accuracy among statistical classification methods. Our ethnic group classification system based on the analysis of ancestry informative SNP markers can provide a useful statistical tool to identify ethnic groups.

• Journal of English Language & Literature
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• v.57 no.6
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• pp.1017-1041
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• 2011

This study investigates Korean EFL learners' awareness and use of the English existential there-construction by examining data collected from 54 Korean EFL learners of English by means of a pragmalinguistic judgment task and a controlled discourse completion task. The results of the judgment task reveal that lower proficiency learners rated canonical sentences and existentials with a preposed locative best in the communicative situations where the use of existentials would have been most appropriate. A comparison of the ratings by more proficient learners and native speakers shows that existentials received highest ratings by both groups where they are the most natural option, while canonical sentences received significantly higher ratings by the learners. With regard to the production data, learners tended to avoid existentials, but rather relied on canonical sentences. Existentials were rarely used by lower proficiency learners and not used productively even by more proficient learners in the situations where existentials would have been the most natural option. These results suggest that Korean learners' difficulty with the use of existentials is not merely a product of performance limitations, but attributable to limited knowledge about existentials and their syntactic alternatives in terms of contextual appropriateness. Lower proficiency learners lack such knowledge, and more proficient learners, while showing better awareness of the use of existentials, have problems as to the placement of new information when engaging in writing tasks that place lower level of demands on attention to the information status of noun phrases compared to communicative, oral tasks.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.3
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• pp.135-141
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• 2010

Researchers continue to explore possibilities for expanding additive manufacturing (AM) technologies into direct product manufacturing. One limitation is in the materials available for use in AM that can meet the needs of end-use applications. Stereolithography (SL) is an AM technology well known for its precision and high quality surface finish capabilities. SL builds parts by selectively crosslinking or solidifying photo-curable liquid resins, and the resin industry has been continuously developing new resins with improved performance characteristics. This paper introduces a unique SL machine that can fabricate parts out of multiple SL materials. The technology is based on using multiple vats positioned on a rotating vat carousel that contain different photo-curable materials. To change the material during the process, the build platform is raised out of the current vat, a new vat with a different material is rotated under the platform, and the platform is submerged into the new vat so that the new material can be used. This paper introduces a new vat exchange mechanism, cleaning process, recoating process, resin leveling mechanism and process planning technologies for the implementation of multiple material SL. An overview of the system framework is provided and the system integration and control software is described. In addition, several multiple material test parts are designed, fabricated, and described.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.6
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• pp.623-630
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• 2013

This study was to evaluate hydrodynamic performance evaluation between an abroad product, a developed inflatable kayak and new developed kayaks. In order to test, inclining and turning trial test were carried out in the Ocean engineering Basin. Also, resistance test was carried out using a reduced scale model in the circulating water channel. In conclusion, stability of KONA was evaluated was the most greatest, the coefficient of resistance and center of gravity from RD-FK-12 were considerable, and turning performance of RD-FK-11 was greater than this of KONA and RD-FK-12.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.759-764
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• 2001

The separation performance of zigzag air classifier with angle of 90 degrees was studied using narrow size fractions of thin square samples and granular samples. The simulation results of air velocity inside the classifier indicated that the zigzag geometry induces a new pattern consisting of an upward flow and a circulation flow, Experimental results showed that overflow product recovery was described as an integral calculus of normal distribution as a function of dimensionless air velocity ( $V_{A}$ $V_{A50}$), where $V_{A}$ is superficial air velocity and $V_{A50}$ is the $V_{A}$ at the fifty percent recovery. The $V_{A}$ values were predicted using the equations derived from dynamics for a particle dropping in air. A monitoring system that utilizes changes in acoustic signals emitted during the process of air classification was developed to separate PET with desired recovery or grade. The technical feasibility of the on-line monitoring of the PET recovery and grade was demonstrated by measuring relative energy of the signals.signals.als.

• Journal of Korean Society for Quality Management
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• v.43 no.3
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• pp.341-358
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• 2015

Purpose: This paper presents graphic methods and desirability function approach to determine best vibration reducing configuration for Surion helicopter. Many flight tests were executed and nine vibration levels in cockpit, cabin, and engine room were measured in each test and analyzed to find optimal configuration. Methods: Graphic analysis methods such as matrix, scatter, and box plots are used to identify better vibration-reducing flight test conditions. As an integrated measure of the performance of 9 vibration levels desirability function approach is adopted. Results: Three vibration reducing configurations are found to be proper and one configuration is recommended. Conclusion: It is expected to be helpful to adopt graphic and desirability function methods presented in this paper in developing new products or systems like helicopters. For efficient and effective flight testing of helicopters, it will be necessary to have consistently homogeneous environment for flight testing and applying design of experiments techniques and analyzing test data.