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Chang Weon Song,Mi Young You,Damin Lee,Hyoung Seok Mun,Seohan Kim,Pung Keun Song 한국표면공학회 2020 한국표면공학회지 Vol.53 No.5
The change of the deposition behavior of diamond through a pretreatment process of the base metal prior to diamond deposition using HFCVD was investigated. To improve the specific surface area of the base material, sanding was performed using sandblasting first, and chemical etching treatment was performed to further improve the uniform specific surface area. Chemical etching was performed by immersing the base material in HCl solutions with various etching time. Thereafter, seeding was performed by immersing the sanded and etched base material in a diamond seeding solution. Diamond deposition according to all pretreatment conditions was performed under the same conditions. Methane was used as the carbon source and hydrogen was used as the reaction gas. The most optimal conditions were found by analyzing the improvement of the specific surface area and uniformity, and the optimal diamond seeding solution concentration and immersion time were also obtained for the diamond particle seeding method. As a result, the sandblasted base material was immersed in 20% HCl for 60 minutes at 100 °C and chemically etched, and then immersed in a diamond seeding solution of 5 g/L and seeded using ultrasonic waves for 30 minutes. It was possible to obtain optimized economical diamond film growth rates.
Chang Weon Song,Rongguang Jin,Nong Moon Hwang,Kwang Ho Kim 대한금속·재료학회 2019 ELECTRONIC MATERIALS LETTERS Vol.15 No.5
As a carbon source for hot filament chemical vapor deposition of boron-doped diamond (BDD), cost-effective acetone(C3H6O) was used instead of commonly used methane gas. In this case, tantalum filaments turned out to be more suitablethan tungsten filaments because tantalum is more oxidation-resistant and can be heated to much higher temperature withoutevaporation than tungsten. As the acetone flux was varied, the hydrogen flux was also varied so that the mixture of acetoneand hydrogen fluxes was fixed at 500 standard cubic centimeter per minute (sccm). Trimethyl borate (TMB) was used asa boron source. As the acetone flux was varied, the TMB flux was also varied so that the boron doping of 11,400 ppmwas maintained. As the flux of acetone was increased from 90 to 170 sccm, the grain size and the film thickness of BDDincreased. In this range of acetone fluxes, the films showed well-defined (111) facets, indicating that the high quality diamondwas deposited. When the acetone flux was increased to 210 sccm, the grain size decreased abruptly and the film thickness,which represents the deposition rate, decreased also. When the acetone flux was increased to 250 sccm, the grain size furtherdecreased, producing a cauliflower structure and the film thickness further decreased. The potential window, which is measuredas electrochemical properties of BDD, increased as the acetone flux increased from 90 to 170 sccm and did not changemuch between 170 and 250 sccm. From this experiment, it was confirmed that varying the flux of acetone could control themorphology, the growth rate and the electrochemical properties of the BDD film.
장혜숙,이상오,홍원선,민영일,정훈용,이영수,김해련,양석균,정성애,송병철,-- 대한소화기내시경학회 1997 Clinical Endoscopy Vol.17 No.6
Pyoderma gangrenosum is a painful, chronic, ulcerating skin disease of unknown cause. It commences as an erythematous papulopustule and rapidly evolves to form an area of frank ulceration with undermined, violaceous edges and a bright outer halo of erythema. Diagnosis is clinical, there being no accepted histological diagnostic criteria. An underlying systemic illness is present in more than 50 percent of patients. Pyoderma gangrenosum develops in 0.8-5.0 percent of patients with inflammatory bowel disease, which is the most frequent underlying disease of pyoderma gangrenosum. There is no report of pyoderma gangrenosum associated with Crohn's disease in Korea. We recently experienced two cases of pyoderma gangrenosum, a 52-year old man with Crohn's disease and a 30-year old man with ulcerative colitis. The cases are presented with the review of literature.
A Multiple Instance Learning Problem Approach Model to Anomaly Network Intrusion Detection
Weon, Ill-Young,Song, Doo-Heon,Ko, Sung-Bum,Lee, Chang-Hoon Korea Information Processing Society 2005 Journal of information processing systems Vol.1 No.1
Even though mainly statistical methods have been used in anomaly network intrusion detection, to detect various attack types, machine learning based anomaly detection was introduced. Machine learning based anomaly detection started from research applying traditional learning algorithms of artificial intelligence to intrusion detection. However, detection rates of these methods are not satisfactory. Especially, high false positive and repeated alarms about the same attack are problems. The main reason for this is that one packet is used as a basic learning unit. Most attacks consist of more than one packet. In addition, an attack does not lead to a consecutive packet stream. Therefore, with grouping of related packets, a new approach of group-based learning and detection is needed. This type of approach is similar to that of multiple-instance problems in the artificial intelligence community, which cannot clearly classify one instance, but classification of a group is possible. We suggest group generation algorithm grouping related packets, and a learning algorithm based on a unit of such group. To verify the usefulness of the suggested algorithm, 1998 DARPA data was used and the results show that our approach is quite useful.