• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1233-1243
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• 2015

The contrast enhancement is great challenge in the image processing when images are suffering from poor contrast problem. Therefore, in order to overcome this problem an automatic method is proposed for contrast enhancement of natural color images. The proposed method consist of two stages: in first stage lightness component in YIQ color space is normalized by sigmoid function after the adaptive histogram equalization is applied on Y component and in second stage automatic color contrast enhancement algorithm is applied on output of the first stage. The proposed algorithm is tested on different NASA color images, hyperspectral color images and other types of natural color images. The performance of proposed algorithm is evaluated and compared with the other existing contrast enhancement algorithms in terms of colorfulness metric and color enhancement factor. The higher values of colorfulness metric and color enhancement factor imply that the visual quality of the enhanced image is good. Simulation results demonstrate that proposed algorithm provides higher values of colorfulness metric and color enhancement factor as compared to other existing contrast enhancement algorithms. The proposed algorithm also provides better visual enhancement results as compared with the other existing contrast enhancement algorithms.

• Journal of Power Electronics
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• v.17 no.4
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• pp.1048-1057
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• 2017

An indirect matrix converter (IMC) is a modern power generation system that enables a direct ac/ac conversion without the need for any bulky and limited lifetime electrolytic capacitor. This system also allows four-quadrant operation, generation of sinusoidal output voltage waveforms with variable frequency and amplitude, and control of input power factor. This study proposes a pulse-width modulation-based sliding-mode controller to achieve unity input-power factor operation of the IMC independently of the active power exchanged with the grid, as well as a fast dynamic response. The designed equivalent control law determines, at each sampling period, the appropriate q-axis component of the modulated input current to be injected into the grid through the LC input filter. An integral term of the error is included in the expression of the sliding surface to increase the accuracy of the control method. A double space vector modulation method is used to synthesize the direction of the space vector of the input currents as required by the sliding-mode controller and the space vectors of the target output voltages. Simulation and experimental results are provided to show the effectiveness and evaluate the performance of the proposed control method.

• Bulletin of the Korean Space Science Society
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• 1992.10a
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• pp.21-21
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• 1992

The X-ray binary pulsar Her X-1 was observed with Ginga on 1988 August 28 during the orbital phase of 0.76 to 0.85 at the main-on phase of the 35 day cycle. During the observations the X-ray intensity varied by a factor of five or more on a time scale as short as 30 sec, due mostly to the soft X-ray absorption in the pre-eclipse phase. From the studies of pulse profiles and energy spectra, we revealed that there exists in the dipphase an unpulsed component which is "3% of the intensity at the non-absorbed high-level. We suggest that scattering of the source continuum by the optically thin hot corona is responsible for the unpoised component. In the spectral analysis, we find that the high-state non-absorbed spectra can be fitted by a power-law without absorption, and the spectra observed in the different abgorption states by two components of a power-law with the same photon index. An iron-K emission line is required in to the cases of fitting. The estimated equivalent width of the iron line varies from 0.18 to 0.51 key according to the change in the absorption column density along the line of sight. We suggest that the fluorescent iron line arises in a cool and relatively small region, like the Alfvensur face, and may be partially intercepted by the optically thick gas cloud passing across the line of sight.1 Korea Astronomy Observatorya The Institute of Space and Astronautical Science in Japan3 Korea Advanced Institute of Science and Technology

• Journal of the Korean Institute of Landscape Architecture
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• v.32 no.3
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• pp.91-105
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• 2004

Recently the function of a department store has changed to the concept of a multi-functional center because of the alternative stores such as discount stores, home shopping, and internet shopping. This means that the front plaza of a department store is not a personal or private space any more, but a public space. This study focuses on the special character of public space through the classification and preference types of department store front plazas. The major results of this study can be summarized as follows: (1) Components of front plaza of department store are classified by three factors. The first factor, named "space limit", has 14 elements ; the second, named "space decoration" has 16 elements ; third, named "activity", has 2 elements. The first preferred element is easily- used and easily- serviced wide space. The second preferred element is the equipment that is placed linearly along the street. The third preferred element is cultural events. (2) The comparison between the frequency and preference shows that the plazas could not satisfy the user-needs. (3) Preference factors of front plazas were examined to three characters such as familiarity, peculiarity, and openness. Familiarity, peculiarity, openness have a positive correlation in all types. Peculiarity especially influences the other two space - preference factors.

• Bulletin of the Korean Space Science Society
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• 2008.10a
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• pp.34.4-35
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• 2008

The significant I&T process gain represented by reduction in overall budget expenditure can be obtained from the use of efficient alignment technique for large space optical systems. Such process gain tends to increase rapidly with an increase in aperture and/or in number of optical elements within the system. However, in practice, the alignment of multiple optical components tends to be rather difficult task because of the multiple coupling effects among the elements within the target system. In order to understand and hence identify the complex interplay of the wavefront coupling effects from the alignment process, the original differential wavefront sampling(DWS) method was presented elsewhere in recent years. DWS uses partial differential of the wavefront of optical component and perturbation value of the optical component against a particular alignment factor. The straightforward application of DWS for an off-axis optical system revealed that it tends to give incorrect estimation of the given misalignment state. In this study, we added off-axis correction terms to the original DWS algorithm and investigated its alignment performance. The performance simulation result for a Korsch type space optical system shows that the modified DWS is capable of bringing the misaligned system into the target alignment tolerance only after 3 iterations. It also shows that this new improved algorithm can be used to estimate the source misalignment as well. We are planning to apply this method for the alignment of a 800mm Korsch type telescope in the near future. We discuss the computational technique, simulation results and implications in details.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.5
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• pp.770-778
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• 1994

In this paper, the photovoltaic inverter system with instantaneous sinusoidal current tracking control is proposed to improve the utilization factor of photovoltaic power system which would be connected utility interactive system. The proposed inverter is designed to track maximum power point by two-state value control method and utility interactive operation, and to decrease output harmonics component. Optimal operating region is described by state space averaging method, and present tracking condition of standard guide line. The experimental result shows the effectiveness of inverter system using the instantaneous control method.

• Nuclear Engineering and Technology
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• v.50 no.4
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• pp.589-598
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• 2018

To maintain safety and reliability of reactors, redundant sensors are usually used to measure critical variables and estimate their averaged time-dependency. Nonhealthy sensors can badly influence the estimation result of the process variable. Since online condition monitoring was introduced, the online cross-calibration method has been widely used to detect any anomaly of sensor readings among the redundant group. The cross-calibration method has four main averaging techniques: simple averaging, band averaging, weighted averaging, and parity space averaging (PSA). PSA is used to weigh redundant signals based on their error bounds and their band consistency. Using the consistency weighting factor (C), PSA assigns more weight to consistent signals that have shared bands, based on how many bands they share, and gives inconsistent signals of very low weight. In this article, three approaches are introduced for improving the PSA technique: the first is to add another consistency factor, so called trend consistency (TC), to include a consideration of the preserving of any characteristic edge that reflects the behavior of equipment/component measured by the process parameter; the second approach proposes replacing the error bound/accuracy based weighting factor ($W^a$) with a weighting factor based on the Euclidean distance ($W^d$), and the third approach proposes applying $W^d$, TC, and C, all together. Cold neutron source data sets of four redundant hydrogen pressure transmitters from a research reactor were used to perform the validation and verification. Results showed that the second and third modified approaches lead to reasonable improvement of the PSA technique. All approaches implemented in this study were similar in that they have the capability to (1) identify and isolate a drifted sensor that should undergo calibration, (2) identify a faulty sensor/s due to long and continuous missing data range, and (3) identify a healthy sensor.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.43 no.2 s.308
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• pp.82-86
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• 2006

The design of a pattern recognition system generally involves the three aspects: preprocessing, feature extraction, and decision making. Among them, a feature extraction method determines an appropriate subspace of dimensionality in the original feature space of dimensionality so that it can reduce the complexity of the system and help to improve successful recognition rates. Linear transforms, such as principal component analysis, factor analysis, and linear discriminant analysis have been widely used in pattern recognition for feature extraction. This paper shows that singular value decomposition (SVD) can be applied usefully in feature extraction stage of pattern recognition. As an application, a remote sensing problem is applied to verify the usefulness of SVD. The experimental result indicates that the feature extraction using SVD can improve the recognition rate about 25% compared with that of PCA.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.12 no.1
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• pp.1-5
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• 2012

Data reduction has been used widely in data mining for convenient analysis. Principal component analysis (PCA) and factor analysis (FA) methods are popular techniques. The PCA and FA reduce the number of variables to avoid the curse of dimensionality. The curse of dimensionality is to increase the computing time exponentially in proportion to the number of variables. So, many methods have been published for dimension reduction. Also, data augmentation is another approach to analyze data efficiently. Support vector machine (SVM) algorithm is a representative technique for dimension augmentation. The SVM maps original data to a feature space with high dimension to get the optimal decision plane. Both data reduction and augmentation have been used to solve diverse problems in data analysis. In this paper, we compare the strengths and weaknesses of dimension reduction and augmentation for classification and propose a classification method using data reduction for classification. We will carry out experiments for comparative studies to verify the performance of this research.

• Korean Institute of Interior Design Journal
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• no.34
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• pp.45-52
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• 2002

It is noted that the expressionistic feature appears as one of characteristic phenomena for representing the regional culture and economic level. In architecture, it seems to be difficult to define the expressionism in a concrete way because of lots of meanings the word originally has. In this study, the expressionistic feature is defined as a mode which impresses the users emotionally with strength or as a touching and stimulating one, contrary to the designing conception which pursues only the rationality and the functionality. These features can be expressed as designing methods such as organic form, adoption of natural design factor, decisive opening of space or its extreme closing, contrast of mutually opposite components, or application of basic design components.These methods described above are largely categorized into spatial form, openness, scale and design component and also are studied for each example within the scope of these categories. This study has significance in conceptualizing this expressionistic tendency and in analyzing some detailed aspects for expression.