• 한국가시화정보학회:학술대회논문집
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• 2001.12a
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• pp.151-163
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• 2001

A two color PIV technique has been developed for visualization of complex and high speed flow in a ramjet combustor. Two color PIV has the advantages that velocity distributions in high speed flowfields can be measured simply by varying the time interval between two different laser beams and a directional ambiguity problem can be solved by color separation, and then a signal-to-noise ratio can be increased through nearly perfect cross-correlation. As a basic research of the ramjet engine, a 2-D shaped combustor with two symmetric air intakes has been manufactured and an experimental study has been conducted using a two color PIV technique. The flow characteristics such as recirculation zones, intake air mixing and turbulent kinetic energy have been investigated varying inlet angles and dome heights. It was found that the primary recirculation zone is affected mainly by the dome height, whereas the secondary recirculation zone is influenced by the air inlet angle.

• Journal of Electrical Engineering and Technology
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• v.9 no.1
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• pp.170-177
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• 2014

This paper presents a new method of classification of the induction machine faults using Time Frequency Representation, Particle Swarm Optimization and artificial neural network. The essence of the feature extraction is to project from faulty machine to a low size signal time-frequency representation (TFR), which is deliberately designed for maximizing the separability between classes, a distinct TFR is designed for each class. The feature vectors size is optimized using Particle Swarm Optimization method (PSO). The classifier is designed using an artificial neural network. This method allows an accurate classification independently of load level. The introduction of the PSO in the classification procedure has given good results using the reduced size of the feature vectors obtained by the optimization process. These results are validated on a 5.5-kW induction motor test bench.

• Journal of Electrical Engineering and information Science
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• v.2 no.6
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• pp.7-13
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• 1997

Morphological Analysis of Korean has known to be a very complicated problem. Especially, the degree of part-of-speech(POS) ambiguity is much higher than English. Many researchers have tried to use a hidden Markov model(HMM) to solve the POS tagging problem and showed arround 95% correctness ratio. However, the lack of lexical information involves a hidden Markov model for POS tagging in lots of difficulties in improving the performance. To alleviate the burden, this paper proposes a method for combining multiword units, which are types of lexical information, into a hidden Markov model for POS tagging. This paper also proposes a method for extracting multiword units from POS tagged corpus. In this paper, a multiword unit is defined as a unit which consists of more than one word. We found that these multiword units are the major source of POS tagging errors. Our experiment shows that the error reduction rate of the proposed method is about 13%.

• Journal of the Korea Society of Computer and Information
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• v.23 no.9
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• pp.81-86
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• 2018

Software defect severity is very important in projects with limited historical data or new projects. But general software defect prediction is very difficult to collect the label information of the training set and cross-project defect prediction must have a lot of data. In this paper, an unclassified data set with defect severity is clustered according to the distribution ratio. And defect severity-based prediction model is proposed by way of labeling. Proposed model is applied CLAMI in JM1, PC4 with the least ambiguity of defect severity-based NASA dataset. And it is evaluated the value of ACC compared to original data. In this study experiment result, proposed model is improved JM1 0.15 (15%), PC4 0.12(12%) than existing defect severity-based prediction models.

• Asia pacific journal of information systems
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• v.31 no.4
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• pp.527-542
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• 2021

The government-driven open data policies are on the rise to protect consumers from misunderstandings and monitor the companies. However, in contract-based industries such as insurance, the contract-inherent characteristics make information asymmetry between consumers and companies. Our paper focuses on insurance contracts where the contingency has high uncertainty of occurrence, and the clauses may incur high costs of reading. Given those contracts, we hypothesized that the contract's clear statement decreases customer dissatisfaction and lowers the number of complaints. To empirically support the claim, we collected customers' complaint documents of insurance companies and insurance contracts from 2005 until 2017. Our econometric models showed that clearer statements and words significantly reduce the complaints after controlling for firm-specific heterogeneity and time-specific heterogeneity. We identify that insurance companies' complaint ratio significantly differ depending on the insurance contract, including specific clauses and words.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.1
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• pp.95-104
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• 2002

A two color PIV technique has been developed for visualization of complex and high speed flow in a ramjet combustor. Two color PIV has the advantages that velocity distribytions in high speed flowfields can be measured simply by varying the time interval between two different laser beams and a directional ambiguity problem can be solved by color separation, and then a singnal-to-noise ratio can be increased through nearly perfect cross-correlation. As a basic research of the ramjet engine, a 2-D shaped combustor with two symmetric air intakes has been manufactured and an experimental study has been conducted using a two color PIV technique. The flow characteristics such as recirculation zones and two intake air mixing have been investigated varying inlet angles and dome heights. It is found that the size and air mass ratio of reciculation zones are affected mainly by an inlet angle, but not much by a dome height.

• Journal of Environmental Policy
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• v.2 no.1
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• pp.51-75
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• 2003

The objective of this study is to analyze the problems of disposal and collection, including administrative management of agricultural PE waste and suggest effective management measurements. Information regarding problems of agricultural PE waste management were collected from field survey of farmers, regional governments and officials. On the national level, the low ratio of collection for optimal treatment of agricultural PE waste is a critical problem. , the negative discharging behavior of farmers, an illegal incineration and landfill of farmers and a lack of education and extension etc. An ambiguity of the management principle to agricultural PE waste, the differences in management among the regional governments, a lack of will of the regional governments and officials to realize SARD and lack of education and extension etc. are some of the problems in administrative management of agricultural PE waste collection. The major suggestions of this study are as follows : (1) to strengthen education and extension, (2) to adopt an improved economic incentive system and strong, lawful regulation simultaneously, (3) to use temporang collection and permanent collection site, and (4) to organize "OTC(Optimal Treatment Conference)" composed of farmers, regional cooperative, PE producers etc. for operating an effective management system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.5
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• pp.466-471
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• 2015

In this paper, the design technique of the wide swath TOPS(Terrain Observation by Progressive Scan) imaging mode is introduced. The TOPS mode overcomes the scalloping limitations imposed by ScanSAR mode by steering the antenna pattern along track direction during the acquisition of a burst. This paper reports the operation concept of TOPS imaging and mode design result to extract the SAR operational parameters. Finally, several analyzed results such as IRF(Impulse Response Function), NESZ(Noise Equivalent Sigma Zero) and DTAR(Distributed Target Ambiguity Ratio) are presented.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.10
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• pp.4873-4888
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• 2018

A joint blind parameter estimation algorithm based on minimum channel stability function aimed at the non-cooperative high-order modulated paired carrier multiple access (PCMA) signals is proposed. The method, which uses hierarchical search to estimate time delay, amplitude and frequency offset and the estimation of phase offset, including finite ambiguity, is presented simultaneously based on the derivation of the channel stability function. In this work, the structure of hierarchical iterative processing is used to enhance the performance of the algorithm, and the improved algorithm is used to reduce complexity. Compared with existing data-aided algorithms, this algorithm does not require a priori information. Therefore, it has significant advantage in solving the problem of blind parameter estimation of non-cooperative high-order modulated PCMA signals. Simulation results show the performance of the proposed algorithm is similar to the modified Cramer-Rao bound (MCRB) when the signal-to-noise ratio is larger than 16 dB. The simulation results also verify the practicality of the proposed algorithm.

• Nuclear Engineering and Technology
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• v.41 no.3
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• pp.327-334
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• 2009

Elastic wave is one of the most useful tools for non-destructive tests in nuclear power plants. Since the elastic properties are indispensable for analyzing the behaviors of elastic waves, they should be predetermined within an acceptable accuracy. Nuclear power plants are exposed to harsh environmental conditions and hence the structures are degraded. It means that the Young's modulus becomes unreliable and in-situ measurement of Young's modulus is required from an engineering point of view. Young's modulus is estimated from the group velocity of propagating waves. Because the flexural wave of a plate is inherently dispersive, the group velocity is not clearly evaluated in temporal signal analysis. In order to overcome such ambiguity in estimation of group velocity, Wigner-Ville distribution as the time-frequency analysis technique was proposed and utilized. To verify the proposed method, experiments for steel and acryl plates were performed with accelerometers. The results show good estimation of the Young's modulus of two plates.