Earticle

This study applies magnetic abrasive finishing to the precision machining of Ti-6Al-4V (Eli) bars and then assesses the finishing capabilities for application to high-precision machining. Because Ti-6AL-4V (Eli) is widely used in applications where it is exposed to the human body, the industrial grinding oil that is commonly used in the magnetic abrasive finishing process was replaced by vegetable oils; the processing performances of these different grinding oils were compared and verified. The characteristics of magnetic abrasive finishing were also investigated according to the temperature of the material. The experimental results show that olive oil yields a surface roughness improvement of 87%. Also, in terms of the roundness and the amount of material removal, the performance was excellent. This demonstrates the possibility of replacing the conventional industrial oil for grinding. Furthermore, when olive oil was used at different temperatures, the finishing characteristics at room temperature were the most excellent. SEM and EDX analyses of the machined components (before and after processing) showed that the material composition was not changed. Additionally, the magnetic abrasive tool composition was not found on the surface of the finished samples. In conclusion, the possibility of using vegetable oil as the grinding oil for high-precision machining of Ti-6Al-4V (Eli) bars via a magnetic abrasive finishing process at room temperature conditions was verified.

Purpose: This study provided the basic data for selecting the zirconia blocks by comparing the mechanical properties of the all ceramic crown between the domestic, import, translucent and shade blocks that were used in clinically. Methods: Currently, the most commercial block of five types(one import and two domestic block which is the translucent and shade) were used. It were elucidated by means of three point bending test, hardness test, FE-SEM observations and EDX analysis. The results were analyzed using a one-way ANOVA and Scheffe post hoc test for significant findings. Results: For flexural strength, LT specimen was the highest as 733.1 ㎫, followed by JT specimen(712.0 ㎫), ZT specimen(646.0 ㎫), LS specimen(553.1 ㎫), JS specimen(429.0 ㎫). One-way ANOVA showed statistically significant difference between groups for flexural strength(p<0.05). For hardness, ZT specimen was the highest as 1556.5 Hv, followed by JT specimen(1540.3 Hv), LT specimen(1512.3 Hv), JS specimen(1472.0 Hv), LS specimen(1353.3 Hv). One-way ANOVA showed statistically significant difference between groups for hardness(p<0.05). Conclusion: Domestic block was higher than import block for flexural strength, and translucent block was higher than shade block for flexural strength. However, all blocks showed clinically acceptable range. There was no significant difference in hardness between domestic and import blocks. And significant difference was observed in translucent and shade blocks.

The purpose of this study was to investigate the expansion of alkali-activated mortar based on ground granulated blast furnace slag containing reactive aggregate due to alkali-silica reaction. Also this study was particularly concerned with the behaviour of alkaline materials in the presence of reactive aggregates. The experimental program included expansion measurement of the mortar bar specimens and the determination of the morphology and composition of the alkali-silica reaction products by scanning electron microscopy(SEM), energy dispersive x-ray(EDX). According to the experimentation result, Although alkali-activated ground granulated blast furnace slag mortars showed expansion due to the alkali-slica reaction, the expansion exhibited less than 0.1% at 14 day. So it is safety. After the accelerated test, SEM analysis showed the presence of alkali-silica gel and rim around the aggregate and cement paste, According to the EDX, the reaction products decreased markedly as alkali-activated ground granulated blast furnace slag was used. In addition, the study on improving the quality of alkali-activated mortar bar by substituting other materials of mineral admixture is needed to assure of the durability properties of concrete.

최근 MOOC 플랫폼으로 많이 사용하고 있는 Open edX MOOC시스템은 Tutor 라 는 커맨드라인 도구의 개발로 설치 및 관리가 쉬워졌다. 본 논문에서는 도커 명령어 기반으로 만들어진 Tutor를 사용하여, Open edX MOOC 플랫폼을 설치하고, 추가 기능 구현을 위한 플러그인들을 설치하는 방법에 대해 소개하고자 한다.

본 논문은 웹 기반 코딩 플랫폼인 CodeWalks를 Open edX 학습관리시스템(LMS)과 통합하여 코딩 교육을 개선하는 방안을 제시하였다. 제안된 시스템은 RESTful API와 사용자 정의 XBlock을 활용하여 CodeWalks와 Open edX 간의 원활한 통신을 구현하였으며, 이를 통해 실시간 코딩 활동 모니터링, 포괄적인 학습자 분석, 자동화된 퀴즈 채점, 그리고 블록 기반 및 텍스트 기반 코딩 인터페이스의 통합과 같은 핵심 기능을 제공하였다. 또한, Open edX의 분석 모듈인 edX Insights와 Figures를 통합하여 학습자 진행 상황을 정밀하게 추적하고 분석할 수 있는 강력한 프레임워크를 구축하였다. 정량적 분석 결과, 제안된 시스템은 학습자의 참여도(31% 증가, p < 0.001), 과제 완료율(23% 상승, χ² = 45.2, p < 0.001), 오류율(41% 감소, p < 0.001), 블록 기반에서 텍스트 기반 코딩으로의 전환율(73% vs. 52%, χ² = 38.7, p < 0.001), 그리고 학습자 만족도(중앙값 4.4 vs. 3.7, U = 76,234, p < 0.001)에서 통계적으로 유의미한 개선을 보였다. 이 연구는 코딩 초보자들의 학습 어려움을 해결하고 개인화된 학습 환경을 제공함으로써, 더 효과적이고 접근성 높은 코딩 교육의 새로운 가능성을 제시하였다.

This paper proposes integrating the CodeWalks coding platform with Open edX LMS to enhance coding education. The system uses RESTful APIs and custom XBlocks for seamless communication, enabling real-time monitoring, comprehensive analytics, and automated assessment. Integration with edX Insights and Figures provides detailed learner progress tracking. Quantitative analysis reveals significant improvements in the experimental group: 31% increase in engagement rate (p < 0.001), 22% higher completion rate (χ² = 45.2, p < 0.001), 41% decrease in error rate (p < 0.001), improved transition to text-based coding (73% vs 52%, χ² = 38.7, p < 0.001), and higher learner satisfaction (median 4.4 vs 3.7, U = 76,234, p < 0.001). The integrated platform addresses challenges faced by coding novices and offers a personalized learning environment. This study contributes to effective online coding education and provides a foundation for future innovations in educational technology.

Scanning electron microscope/energy-dispersive X-ray spectroscopy (SEM/EDX) is a rapid, non-destructive, and multi-elemental analytical technique used for the elemental analysis and chemical characterization of the selected surface of the sample. In this study, the elemental concentration ratios of four cicada's exuviae including Cicadidae Periostracum [Cryptotympana atrata (Fabricius, 1775), Hyalessa maculaticollis (Motschulsky, 1866), Meimuna opalifera (Walker, 1850), and Platypleura kaempferi (Fabricius, 1794)] were analyzed using SEM/EDX for the first time. C, O, Cl, and K were found in all studied species. However, S and Mg were only found in H. maculaticollis and P. kaempferi, respectively. The results imply that this SEM/EDX technique could be used and applied as a crucial potential tool, analyze both microstructure and element, and manage the quality of the distributed medicinal medicines.

총기사고에 있어 발사자 식별을 위한 방법으로는 발사 용의자 피복에서 추진제화약 잔사를 검출 하는 방법과 손에 뇌관화약 잔사를 검출하여 확인하는 방법이 있다. 뇌관화약 잔사 검출방법은 손에 부 착된 뇌관화약 잔사 성분인 바륨(Ba), 안티몬(Sb), 납(Pb)을 확인하는 방법으로 중성자 방사화 분석법, 비 불꽃 원자흡수분광 광도법, SEM-EDX 분석법을 이용하고 있다. 본 연구는 M16 소총, 45구경, 38구경 권 총을 1발, 3발, 5발 발수로 사격하여 SEM-EDX 분석법을 이용 총기 별 사격 발수에 따른 뇌관화약 잔사 식별 가능여부를 확인하였다. 실험 결과 권총(45구경, 38구경)에서는 뇌관화약 잔사가 사격발수에 비례 하여 관찰되나 M16 소총은 비례하지 않았으며, 2combo 뇌관화약 잔사의 경우 Sb+Ba, Ba+Pb, Sb+Pb 순 으로 검출되었으며 탄피배출구와 손의 위치가 가까운 권총류에서 더 많은 뇌관화약 잔사가 검출되었다.

In the firearm accidents, identifying a suspect who shoot the gun can be confirmed by alternative methods of detection of primer GSR and propellant GSR. In the case of detection method of primer GSR, residues like Ba, Sb, Pb from shooter's hands can be analyzed by Netron activation analysis, Flameless atomic absorbtion spectroscopy and SEM-EDX. In this study, we shoot the guns which M16 rifle, 45-caliber pistol, 38-caliber revolver with 1,3,5 shootings respectively. Then the possibility of identifying a primer GSR versus number of shootings was researched by SEM-EDX. In the results, the ratio of quantity of primer GSR versus number of shootings is in direct proportion in cases of 45-caliber pistol, 38-caliber revolver but is irreguler in the case of M16 rifle. There were found in order of Sb+Ba, Ba+Pb, Sb+Pb in case of two compositions primer GSR and more primer GSR in pistol and revolver compared with M16 rifle because of short distance between the hand and the catridge extractor.

그라우팅 공법은 연약지반의 보강과 방수 및 지하수위저하 또는 상승과 진동으로 인한 침하 및 부등침하로 손상된 구조물의 지지력을 높이고 차수를 높이는 목적으로 사용된다. 본 연구는 보강섬유를 이용하여 그라우트재료의 강도와 경화시간을 증대시키기 위하여 고로슬래그 기반의 무시멘트 그라우트재를 개발하고자 하였다. 이와 관련하여 본 연구에서는 고로슬래그 3종 미분말의 알칼리 자극제인 수산화칼슘을 미분말 형태로 배합하여 사용하였고 수산화칼슘의 함유량은 고로슬래그 미분말 대비 10, 20, 30%까지 치환하여 사용하였다. 또한 보강섬유 유무에 따른 강도를 비교하기 위하여 각 섬유를 0.5%씩 추가하여 실험을 수행하였다. 보강섬유인 아라미드 및 탄소섬유 함유량이 증가함에 따라 일축압축강도가 증가하였는데 이는 그라우트재 내에 섬유에 의한 가교작용이 일축압축강도를 증가시킨 것으로 확인할 수 있다. 또한 알칼리자극제의 함유량이 증가할수록 일축압축강도가 증가하였으나 순수한 시멘트 100%일 때 보다는 낮은 강도를 확인할 수 있었다. 이는 알칼리자극제인 수산화칼슘이 고로슬래그 미분말과 반응했을 때 강도 증가에 영향을 미칠 수는 있으나, 시멘트와 비교하였을 때 미분말형태보다는 용액의 형태가 더 효과적이라는 것을 알 수 있다.

Grouting is used for reinforcement and waterproofing of soft ground to increase its bearing capacity, reduce the impacts of rising or lowering groundwater levels, and reduce subsidence due to vibration and general causes. This study investigated the enhancement of grout strength and hardening time by the addition of reinforcing fibers, and the development of non-cement grouting materials from blast furnace slag. An experiment was performed to measure the increase in grout strength resulting from the addition of 0.5% increments of aramid and carbon reinforcing fibers. The results show that the uniaxial compressive strength of grout increases with increasing content of reinforcing fiber. Comparison of three admixtures of finely powdered blast furnace slag and 10%, 20%, and 30% calcium hydroxide stimulating agent showed that the uniaxial compressive strength of the mixture increases with increasing content of alkaline stimulant; however, the strength was lower than for 100% pure cement. The reaction of calcium hydroxide with blast furnace slag powder, which increases the strength of the grout, is more effective if injected as a solution rather than a powder.

In this study, the composition and morphology of deposited dust particles with size ranging from a few to tens ㎛ were investigated using SEM/EDX (scanning electron microscopy with energy dispersive x-ray spectrometer). Then deposited dust particles were classified into 8 groups: quartz, aluminosilicates, ca-rich, Fe/Ti oxide, carbon-rich, industrial particle, Fe-rich, and biogenic particle. The sources of deposited dust were high in the order of aluminosilicates 41% > biogenic 18% > Fe-rich 11% > quartz and C-rich 8% > industrial 7% > Fe/Ti oxide 5% > Ca-rich 1%. In particular, the ratio of biogenic particles was relatively high due to influence of pollen. The ratio of carbon-rich was 11% at YM site, 10% at MD site, and 4% at MO site, and the site close to the large emission source was high.

대기 중에는 가스상 물질뿐만 아니라 액적 또는 고체의 미립자도 존재하고 있다. 이러한 입자상 물질은 다른 크기와 화학적 조성을 가지는 입자들로 혼합되어 있고, 그 성상은 시간에 따라 크게 변동한다. 따라서 대기 중 미세입자에 대한 발생원 추정 및 발생원 정보를 얻기 위해서는 개개의 입자에 대한 물리ㆍ화학적 정보를 얻는 것이 중요하다. 입자상 물질을 이해하기 위해서는 물리적인 특성(size, shape 등)과 화학적인 특성이 중요한 요소이다. 입자상 물질의 형상은 그 발생원에 따라 또는 존재에 따라 매우 다양하고 불규칙적이다. (중략)