• Journal of Powder Materials
• /
• v.7 no.3
• /
• pp.137-142
• /
• 2000

In order to analyze the densification behaviour of stainless steel powder compacts during hot isostatic pressing (HIP) at elevated temperatures, a power-law creep constitutive model based on the plastic deformation theory for porous materials was applied to the densification. Various densification mechanisms including interparticle boundary diffusion, grain boundary diffusion and lattice diffusion mechanisms were incorporated in the constitutive model, as well. The power-law creep model in conjunction with various diffusion models was applied to the HIP process of 316L stainless steel powder compacts under 50 and 100 MPa at $1125^{\circ}C$. The results of the calculations were verified using literature data. It could be found that the contribution of the diffusional mechanisms is not significant under the current process conditions.

• Bulletin of the Korean Mathematical Society
• /
• v.56 no.5
• /
• pp.1355-1376
• /
• 2019

We investigate the valuation of participating life insurance policies with default risk under a geometric regime-switching jump-diffusion process. We derive explicit formula for the Laplace transform of the price of participating contracts by solving integro-differential system and then price them by inverting Laplace transforms.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.32 no.5C
• /
• pp.542-549
• /
• 2007

Recently, many research activities in the image processing area are concentrated on developing new algorithms by finding the solution of the 'diffusion equation'. The diffusion algorithms are expected to be utilized in numerous applications including noise removal and image restoration, edge detection, segmentation, etc. In this paper, at first, it will be shown that the anisotropic diffusion algorithms have the similar structure with the adaptive FIR filters with cross-shaped 5-tap kernel, and this relatively small-sized kernel causes many iterating procedure for satisfactory filtering effects. Moreover, it will also be shown that lots of modifications which are adopted to the conventional Gaussian diffusion method in order to weaken the edge blurring nature of the linear filtering process increases another computational burden. We propose a new Median diffusion scheme by replacing the adaptive linear filters in the diffusion process with the AWM (Adaptive Weighted Median) filters. A diffusion-equation-based adaptation scheme is also proposed. With the proposed scheme, the size of the diffusion kernel can be increased, and thus diffusion speed greatly increases. Simulation results shows that the proposed Median diffusion scheme outperforms in noise removal (especially impulsive noise), and edge preservation.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.8 no.3 s.22
• /
• pp.51-55
• /
• 2005

In this paper, a near net shape technology using superplasticity and diffusion bonding characteristics was presented for application to various components of aircraft and missiles. Due to these special characteristics of some aerospace alloys, it is possible to produce complex components to shape very near final dimension with enhanced design freedom, reduced material usage, and overall saving of weight and cost. The high pressure vessel for a space launcher was fabricated with Ti-6Al-4V alloy by superplastic forming and diffusion bonding process and the failure characteristics are compared with conventionally fabricated vessel spin formed and TIG welded. The structural integrity of the superplastic forming and diffusion bonding process was successfully demonstrated.

• Journal of the Korean Geographical Society
• /
• v.28 no.2
• /
• pp.123-136
• /
• 1993

The growth of radidly improving computer and information technology has a profound impact upon economical, social and cultural sectors. With the progress of information technology, information-telecommunication services are produced. This service is used in sending the information to order service-users, and search the need information. This case study considers information-telecommunication service as a consumer-innovation. Information telecommunication services are provided by firms involved in collection. HiTEL(High-Telecommunication) service represents a subset of this group in that the collection, processing and transmission is primarily in an electronic from. The purpose of this paper is concerned with examining the spatial diffusion process, the issues, and behavior to used in HiTEL service one of the information-telecommunication services in Kwangju. HiTEL service is one of the typical information-telecommunication services, and is begun in Seoul and Kwangju area from October 1991, and diffusing several cities and regions now. Diffusion process of HiTEL services in Kwangju showed the irregular pattern in major residential areas, particularly Daewei-dong, Dongun-dong present higher adoption rate than other area, and where functioned as a diffusion center, the social and economic characteristics of residential area have a critical effect on diffusion process. The major adoption areas are recently built residential area, apartment districts, and diffusion direction shows two directions according to development of residental area; one is to south, another is from northeast to southwest. In order to understand the use-behavior of HiTEL service, questionary survey was carried out. Most adopters have a concern to actual life, as HiTEL, information of telephonenumber, and Daewoo Dial-Van compared with other information service. But the actual use-frequency of service is very low. In use of Kwangju regional information service, the use-frequency of operator is very low because of the lack of advertisement, the lack of providing information, and the low-concerns for regional information. But most of adopters need the providing of various regional information as regional news, education, medical and cultural events, housing, city-transportation, and job market. Thus, in order to increase and diffuse the HiTEL service, the establishment of diffusion strategies and the scheme for solution of related issues are very important. The direct diffusion strategies are the diffusion of information-mind, establishment of diffusion and education center, providing of regional information. The scheme for solution of related issues revealed in operating process are reduction of rental fee, development of the related technology and services.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.3 no.2
• /
• pp.85-93
• /
• 2005

Isotopes of alkali and alkaline earth metals (AM and AEM) are the main contributors to the heat load and the radiotoxicity of spent fuel (SF) . These components are separated from the SF and dissolved in a molten LiCl in an electrolytic reduction process. A mass transfer model is developed to describe the diffusion behavior of Cs, Sr, and Ba in the SF into the molten salt. The model is an analytical solution of Fick's second law of diffusion for a cylinder which is the shape of a cathode in the electrolytic reduction process. And the model is also applied to depict the concentration profile of the oxygen ion which is produced by the electrolysis of Li$_{2}$O. The regressed diffusion coefficients of the model correlating the experimentally measured data are evaluated to be greater in the order of Ba, Cs, and Sr for the metal ions and the diffusion of the oxygen ion is slower than the metal ions which implies that different mechanisms govern the diffusion of the metal ions and the oxygen ions in a molten LiCl.

• Journal of Agricultural Extension & Community Development
• /
• v.16 no.1
• /
• pp.201-235
• /
• 2009

This study analyzed the demographic characteristics, strengths and weaknesses related to information acquisition of local innovation diffusion types. This study use ordered probit model to find strengths and weaknesses of innovation diffusion type in rural area. The individual characteristics of 'formal extension type', 'situational reaction diffusion type', 'agriculturist connection type', and 'systematic approach type', all differentiated according to innovation diffusion type, were analyzed. Following Choi & Choe(2008), immediacy, accessibility, referability, applicability, and satisfaction were the highest in the situational reaction diffusion type, systematic approach type, formal extension type, and farmers connection type, in the order. And there existed organic contexts among individual characteristics. So this study tried to analyze strengths and weaknesses of innovation diffusion type with a focus on immediacy, which emerged as the most important variable in the process of interpreting innovation diffusion. And the strengths and weaknesses of each innovation diffusion type were presented.

• Communications for Statistical Applications and Methods
• /
• v.14 no.2
• /
• pp.267-280
• /
• 2007

In this paper, we consider the robust estimation for diffusion processes when the sample is observed discretely. As a robust estimator, we consider the minimizing density power divergence estimator (MDPDE) proposed by Basu et al. (1998). It is shown that the MDPDE for diffusion process is weakly consistent. A simulation study demonstrates the robustness of the MDPDE.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.28 no.11
• /
• pp.683-689
• /
• 2015

For the formation of $N^+$ doping, the antimony ions are mainly used for the fabrication of a BJT (bipolar junction transistor), CMOS (complementary metal oxide semiconductor), FET (field effect transistor) and BiCMOS (bipolar and complementary metal oxide semiconductor) process integration. Antimony is a heavy element and has relatively a low diffusion coefficient in silicon. Therefore, antimony is preferred as a candidate of ultra shallow junction for n type doping instead of arsenic implantation. Three-dimensional (3D) profiles of antimony are also compared one another from different tilt angles and incident energies under same dimensional conditions. The diffusion effect of antimony showed ORD (oxygen retarded diffusion) after thermal oxidation process. The interfacial effect of a $SiO_2/Si$ is influenced antimony diffusion and showed segregation effects during the oxidation process. The surface sputtering effect of antimony must be considered due to its heavy mass in the case of low energy and high dose conditions. The range of antimony implanted in amorphous and crystalline silicon are compared each other and its data and profiles also showed and explained after thermal annealing under inert $N_2$ gas and dry oxidation.

• Journal of Korea Multimedia Society
• /
• v.8 no.10
• /
• pp.1360-1368
• /
• 2005

PDP is the flat panel display, suitable for high definition television because of large-sire and high-brightness. It has many advantages such as fast response, wide viewing angle, low weight, and simple manufacturing process for fabrication. However, there are some disadvantages and one of them is the image quality degradation, which is dependent on the digital signal processing. Although image quality of PDP is improving by many researches and experimentations, it still isn't as good as that of CRT because of various factors. One of them is worm-like pattern generated by an error diffusion process. And the worm-like pattern is severely increased after an APL process. An increased worm-like pattern occur a drop of resolution in image and a change of CCT according to each grayscale. In this paper, a method for improvement of image quality using the error diffusion which considers the APL process is proposed. In the proposed method, the APL process is performed before the error diffusion process. Simulation results showed that the proposed method has better performances for resolution in images and CCT uniformity according to each grayscale than the conventional method.