• Proceedings of the IEEK Conference
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• 2003.11a
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• pp.381-384
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• 2003

Among digital halftoning methods, error diffusion is a procedure for generating high quality bilevel images from continuous-tone images but blurs the edge information in the bilevel images. To solve the problem, we propose the edge enhanced error diffusion using the edge information of the original images. The edge enchanted weights is computed by adding local characteristic weights and input pixels multiplied a constant. Also, we combined the edge enhanced method with the adaptive error diffusion using human spatial and frequency perception characteristic. The performance of the proposed method is compared with conventional method by measuring the edge correlation. The halftoned images applied the proposed method get more fine quality due to the enchanced edge and better quality in halftoned image. And the detailed edge is preserved in the halftoned images by the proposed method.

• ETRI Journal
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• v.17 no.2
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• pp.11-19
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• 1995

The plasma densities generated from a semiconductor bridge (SCB) device employing a capacitor discharge firing set have been measured by a novel diagnostic technique employing a microwave resonator probe. The spatial resolution of the probe is comparable to the separation between the two wires of the transmission lines (${\approx}$3 mm). This method is superior to Langmuir probes in this application because Langmuir probe measurements are affected by sheath effects, small bridge area, and unknown fraction of multiple ions. Measured electron densities are related to the land material and input energy. Although electron densities in the plasma generated by aluminum or tungsten-land SCB devices show a general tendency to increase steadily with power, at the higher energies, the electron densities generated from tungsten-land SCB devices are found to remain constant.

• Journal of Mechanical Science and Technology
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• v.17 no.1
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• pp.157-167
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• 2003

The exciplex fluorescence technique with the TMPD (tetamethyl-Ρ-phenylene-diamine) / naphthalene dopant system was applied in a combustion-type constant-volume spray chamber. A detailed set of calibration experiments has been performed in order to quantify the TMPD fluorescence signal. It has been demonstrated that the TMPD fluorescence intensity was directly proportional to concentration, was independent of the chamber pressure, and was not sensitive to quenching by either water vapor or carbon dioxide. Using a dual heated-jet experiment, the temperature dependence of TMPD fluorescence up to 1000 K was measured. The temperature field in the spray images was determined using a simple mixing model, and an iterative solution method was used to determine the concentration and temperature field including the additional effects of the laser sheet extinction. The integrated fuel vapor concentration compared favorably with the measured amount of injected fuel when all of the liquid fuel had evaporated.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.8
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• pp.1982-1988
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• 1995

Methane/Air premixed flames are studied numerically, using a detailed chemical model, to investigate the flame strech effects on the extinction in a counterflow. The finite difference method, time integration and modified Newton iteration are used, and adaptive grid technique and grid smoothing have been employed to adjust the grid system according to the spatial steepness of the solution profiles. Results show that the flame stretch, or the conventional nondimensionalized stretch having the tangential flow characteristics of the stretched flame alone cannot adequately describes the extinction phenomena. On the other hand, the local flame stretch having both the normal and tangential flow characteristics of the stretched flame can give a proper explanation to the extinction of the symmetric planar premixed flames stabilized in a counter flow. The extinction condition were found to be a constant local stretch regardless of the equivalence ratio.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.857-864
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• 2006

Due to the difficulties in numerical generation of random fields that satisfy not only the probabilistic distribution but the spectral characteristics as well. it is relatively hard to find an exact response variability of a structural response with a specific random field which has its features in the spatial and spectral domains. In this study. focusing on the fact that the random field assumes a constant over the domain under consideration when the correlation distance tends to infinity, a semi-theoretical solution of response variability is proposed for in-plane and plate bending structures. In this procedure, the probability density function is used directly resulting in a semi-exact solution for the random field in the state of random variable. It is particularly noteworthy that the proposed methodology provides response variability for virtually any type of probability density functions.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1080-1085
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• 2003

The flow of electrical current through a microscopic actual contact spot between two conductors is influenced by the flow through adjacent contact spots. A smoothed version of this interaction effect is developed and used to predict the contact resistance when the statistical size and spatial distribution of contact spots is known. To illustrate the use of the method, an idealized fractal rough surface is defined using the random midpoint displacement algorithm and the size distribution of contact spots is assumed to be given by the intersection of this surface with a constant height plane. With these assumptions, it is shown that including finer scale detail in the fractal surface, equivalent to reducing the sampling length in the measurement of the surface, causes the predicted resistance to approach the perfect contact limit.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.8
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• pp.678-688
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• 1990

In this paper, pSDF-based referance image is realized. Using BJTC(binary joint transform correlator) as the spatial plane correlator, optical pattern recognition for intraclass indentification is performed. Computer simulation shows that the correlation performance of BJTC is superior to that of JTC. Experimental results using BJTC reveal that correlation peak intensity is constant within the error range from 4.1% to 9.6% in intraclass indentification.

• Proceedings of the Korean Information Science Society Conference
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• 2000.04b
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• pp.643-645
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• 2000

This paper puts emphasis on navigation in virtual environment, which is one of the major interfaces for the interactivity between human and virtual environment in virtual reality circumstances and worlds. It proposes a new navigation method: 2d Map-Based navigation, which prevents user's spatial lost in 3D Virtual Environment. The 2D Map-Based Navigation is composed of three major processes, Constant Velocity Navigation, Collision Detection and Avoidance, and Path Adjustment. The 2D Map-Based Navigation can reduce user's difficulties and improve user's sense of presence and reality in the virtual environments. The experiment study proved that the 2D Map-Based Navigation is a very natural, straightforward and useful navigation interface in the virtual environment.

• Journal of Korean Society for Geospatial Information Science
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• v.4 no.2 s.8
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• pp.137-147
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• 1996

In this paper, the performances between maximum likelihood classifier based on statistical classification and multilayer perceptrons based on neural network approaches were compared and evaluated Experimental results from both neural network method and statistical method are presented. In addition, the nature of two different approches are analyzed based on the experiments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.5A
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• pp.726-742
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• 2000

A novel rte control algorithm consisting of two major components, i.e. a variable encoding frame rate method and a hybrid DCT/wavelet I-frame coding scheme, is proposed in this work for low bit rate video coding. Most existing rate control algorithms for low bit rate video focus on bit allocation at the macroblock level under a constant frame rate assumption. The proposed rate control algorithm is able to adjust the encoding frame rate at the expense of tolerable time-delay. Furthermore, an R-D optimized hybrid DCT/wavelet scheme is used for effective I-frame coding. The new rate-control algorithm attempts to achieve a good balance between spatial quality and temporal quality to enhance the overall human perceptual quality at low bit rates. It is demonstrated that the rate control algorithm achieves higher coding efficiency at low bit rates with a low additional computational cost. The variable frame rate method and hybrid I-frame coding scheme are compatible with the bi stream structure of H.263+.