• Journal of Power Electronics
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• v.14 no.5
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• pp.1057-1068
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• 2014

Phase-locked loops (PLL) based on the synchronous reference frame (SRF-PLL) have recently become the most widely-used for grid synchronization in three phase grid-connected inverters. However, it is difficult to study their performance since they are nonlinear systems. To estimate the performances of a SRF-PLL, a canonical small-signal linearized model has been developed in this paper. Based on the proposed model, several significant specifications of a SRF-PLL, such as the capture time, capture rang, bandwidth, the product of capture time and bandwidth, and steady-state error have been investigated. Finally, a noise model of a SRF-PLL has been put forward to analyze the noise rejection ability by computing the SNR (signal-to-noise ratio) of a SRF-PLL. Several simulation and experimental results have been provided to verify and validate the obtained conclusions. Although the proposed model and analysis method are based on a SRF-PLL, they are also suitable for analyzing other types of PLLs.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2007.11a
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• pp.152-155
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• 2007

The object of this research is to evaluate the priority of R&B project alternatives which were already screened by both feasibility and suitability of technological performance. This research is a selection model for R&D project alternatives after setting phase. And it is designed by CHP model which include individual and mutual weights. This model have 5 steps. (1) Setting Technology-Modules derived on the setting phase (2) Presenting the evaluation standards divided with 'M-Field' and 'T-Field' (3) Assessing the evaluation standard and technology modules (4) Obtaining and integrating the individually and mutually effective weights (5) Selecting the technology modules based on the priority of order by CHP. Through these steps, this model can suggest the evaluation way from specific technology levels to project level. And it can be guaranteed to perform the selected module set.

• The Journal of Korean Association of Computer Education
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• v.4 no.1
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• pp.119-126
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• 2001

In this paper, a highly effective learning model that can be applied to the 7th level-based curriculum, which will begin in high schools in the year 2002, will be proposed. Two learning models that have different perspectives on dividing the students into level groups(diagnostic evaluation model and formative evaluation model) were introduced, and teaching materials for each model were developed. After applying the teaching materials to actual classes, the achievement rate of the students was analyzed. According to the results of this research, the achievement rate of students is affected by the point of time at which they are divided into level groups, and formative evaluation proved to be the superior learning model dividing students into level groups.

• KIPS Transactions on Computer and Communication Systems
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• v.11 no.12
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• pp.461-468
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• 2022

Development of the big data industry, the cases of providing data utilization services on digital platforms are increasing. In this regard, research in data-related fields is being conducted to apply the FAIR principle that can be applied to the assessment of (meta)data quality, service, and function to data quality evaluation. Especially, the European Open Data Portal applies an assessment model based on FAIR principles. Based on this, a data maturity assessment is conducted and the results are disclosed in reports every year. However, public data portals do not conduct data maturity evaluations based on metadata. In this paper, we propose and evaluate a new model for data maturity evaluation on a big data platform built for multiple domestic public data portals and data transactions, FAIR principles used for data maturity evaluation in Europe's open data portals. The proposed maturity evaluation model is a model that evaluates the quality of public data portal datasets.

• Korean Journal of Construction Engineering and Management
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• v.19 no.2
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• pp.83-95
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• 2018

The aim of this paper is to develop a performance evaluation model for PPP (Public-Private Partnership) projects that appropriately reflects the important traits that are unique to PPP projects. To this end, 1) it defines a set of distinct perspectives involved in the PPP projects and their associated success factors that might differ amongst the perspectives; 2) it identifies the key performance indicators and suggests the performance evaluation criteria for each indicator; and 3) it builds a performance evaluation model by matching the success factors from each perspective with performance measure criteria as well as applies the model to the two selected BTO road projects in Korea. The process of model construction and its application confirms significant differences between the main stakeholder perspectives typically involved in PPP projects, which highlights the need for an evaluation model tailored for PPP projects by taking into account the distinct perspectives. The results from the PPP evaluation model developed in the study is compared against the results from the existing ex-post evaluation model for construction projects in general. The former shows a closer match with the results from the user satisfaction survey conducted. This new evaluation framework and the performance indicators entailed in it permits a balanced evaluation of PPP projects as it takes into account different perspectives involved in PPP projects as well as an understanding of the factors affecting the success of PPP projects. While the construction of the model is based on transport projects, it is applicable to different types of PPP projects through variation with the weight allocation amongst different success factors and/or additions or other adjustments to the performance evaluation criteria as required.

• The Journal of the Korea Contents Association
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• v.17 no.4
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• pp.541-549
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• 2017

This research investigates the quantitative screening methods for the Grant Funding system and seeks for the efficient evaluation of a number of proposals. We search foreign cases of Grand Funding, but we found no appropriate model for using in Korea. Thus, we had to develope our own model for better screening. First, we analyse the existing evaluation system and find some problems and challenges. Second, we suggest a quantitative screening system for Grant Funding with a numeric model, and operates a tedious simulation by using the previous data and our suggested model. Third, we test the suggested model and find the optimal model by using simulation method The number of data analysed for simulation is larger than 200 thousands. Last, we suggest some brief policy implications based on the results in the paper.

• Structural Engineering and Mechanics
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• v.63 no.5
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• pp.639-646
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• 2017

According to the multi-index system of dam safety assessment and the standard of safety, a comprehensive evaluation model for dam safety based on a cloud model is established to determine the basic probability assignment of the Dempster-Shafer theory. The Dempster-Shafer theory is improved to solve the high conflict problems via fusion calculation. Compared with the traditional Dempster-Shafer theory, the application is more extensive and the result is more reasonable. The uncertainty model of dam safety multi-index comprehensive evaluation is applied according to the two theories above. The rationality and feasibility of the model are verified through application to the safety evaluation of a practical arch dam.

• Journal of Information Technology Services
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• v.14 no.4
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• pp.105-120
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• 2015

Enterprise should determine the adoption and utilization of information systems would be a great help to increase management performance. So, it maintains continually the budget and the investment for informatization. However, there is a limit to clarify whether the investment in informatization is contributed to create business opportunities through corporate competitiveness certainty or not. We tend to recognize the information system as a simple means to support common business rather than being used to achieve the company's business performance and to remain competitive. It is not an easy problem for the quantitative evaluation and analysis on the effect of intangible, such as management performance measurement by introducing computerization project. Informatization level evaluation model for the harsh business environment, specifically the Small and Medium Enterprise is lacking. In this paper, we proposed the audit evaluation model of an Small and Medium Enterprise informatization level based on system quality, information quality, user satisfaction, and IT business contribution. The proposed audit evaluation model was evaluated in the information system users, and verified the suitability throughout the survey of the audit professionals.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.45 no.4
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• pp.31-41
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• 2022

As the environmental impacts of fossil fuel energy sources increase, the South Korean government has tried to change non-environmental-friendly enery sources to environmental-friendly energy sources in order to mitigate environmental effects, which lead to global warming and air pollution. With both a limited budget and limited time, it is essential to accurately evaluate the economic and environmental effects of renewable energy projects for the efficient and effective operation of renewable energy plants. Although the traditional economic evaluation methods are not ideal for evaluating the economic impacts of renewable energy projects, they can still be used for this purpose. Renewable energy projects involve many risks due to various uncertainties. For this reason, this study utilizes a real option method, the Geske compound model, to evaluate the renewable energy projects on Jeju Island in terms of economic and environmental values. This study has developed an economic evaluation model based on the Geske compound model to investigate the influences of flexibility and uncertainty factors on the evaluation process. This study further conducts a sensitivity analysis to examine how two uncertainty factors (namely, investment cost and wind energy production) influence the economic and environmental value of renewable energy projects.

• The Journal of the Acoustical Society of Korea
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• v.43 no.2
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• pp.253-259
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• 2024

This paper proposes a new speech enhancement model based on a complex nested U-Net with a dual-branch decoder. The proposed model consists of a complex nested U-Net to simultaneously estimate the magnitude and phase components of the speech signal, and the decoder has a dual-branch decoder structure that performs spectral mapping and time-frequency masking in each branch. At this time, compared to the single-branch decoder structure, the dual-branch decoder structure allows noise to be effectively removed while minimizing the loss of speech information. The experiment was conducted on the VoiceBank + DEMAND database, commonly used for speech enhancement model training, and was evaluated through various objective evaluation metrics. As a result of the experiment, the complex nested U-Net-based speech enhancement model using a dual-branch decoder increased the Perceptual Evaluation of Speech Quality (PESQ) score by about 0.13 compared to the baseline, and showed a higher objective evaluation score than recently proposed speech enhancement models.