• Polymer(Korea)
• /
• v.35 no.5
• /
• pp.390-394
• /
• 2011

Effects of silver nanoparticles on the polymerization rate and morphology of poly(vinyl acetate) (PVAc)/silver microspheres prepared by suspension polymerization of VAc were investigated. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction and atomic absorption spectrometry were used to characterize the morphology and properties of the PVAc/silver microspheres. Due to the change of hydrophilicity of silver nanoparticles, appearance of the microspheres having golf ball-like convave surfaces was observed. Under controlled concentration of surfactant, PVAc/silver microspheres with various hollow structures were synthesized. In the case of silver nanoparticles modified by surfactant, the polymerization rate increased slightly. PVAc/silver microspheres with a conversion up to 80% were prepared via suspension polymerization.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.19 no.3
• /
• pp.370-375
• /
• 2010

Tungsten carbide microshaft is used as micro punch, electrode of micro electro discharge machining, and micro tool because of its high hardness and rigidity. In this research, tungsten carbide microshaft was fabricated using electrochemical machining. $H_2SO_4$ solution was used as the electrolyte because it can dissolve tungsten carbide and cobalt simultaneously. Experimentally studied were the effects of electrolyte concentration, machining time, and machining voltage on material removal rate and the shape of the microshaft. To eliminate the effects of bubbles and metal corrosion layer on microshaft shape, the machining was performed below the electrolysis voltage. Three step electrochemical process was suggested to fabricate the straight tungsten carbide microshaft. As a result, a straight tungsten carbide microshaft of $30{\mu}m$ in diameter and $500{\mu}m$ in length was obtained through the proposed three step electrochemical process.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2020.05a
• /
• pp.508-511
• /
• 2020

미세먼지(PM10, PM2.5)는 배출가스 증가와 함께 빠르게 악화되어 왔으며, 다양한 화학성분 뿐만 아니라 금속 성분이 포함되어 있어 인체에 큰 유해성을 발생한다. 이에 정부는 미세먼지 저감 정책 및 법률을 통해 개선하고자 했지만, 2013년부터 그 효력을 잃기 시작하였다. 이에 본 연구에서는 미세먼지 저감 정책 및 법률을 수립하는데 있어 가장 중요한 요소인 미세먼지 농도를 예측하는 연구를 진행한다. 이전 연구들에서 미세먼지 영향 요소들이 시계열 기반의 데이터(기상인자와 대기오염 인자)인 것을 확인하였기에, 시계열 데이터에 좋은 성능을 보이는 LSTM 알고리즘을 사용하여 학습 후, 서울시 '구별' '시간단위' 미세먼지 농도 예측에 대한 예측 오차(RMSE, MAE) 성능을 비교하였다. 실험 결과 PM10의 경우 (7.2, 4.78), PM2.5의 경우 (4.7, 3.2)의 예측 오차를 보였으며, 금천구의 경우 PM10이 (5.3, 3.71), PM2.5에서 (3.5, 2.5)로 가장 좋은 성능을 보였다.

• 전기의세계
• /
• v.42 no.10
• /
• pp.10-13
• /
• 1993

마이크로 시스템은 감각 기관, 지능 기관, 운동 기관으로 구성되어 있으며 운동기관에 해당하는 액튜에이터의 마이크로화를 통하여 마이크로 시스템은 실현될 수 있다. 마이크로 시스템의 한예로 대두되고 있는 마이크로 로봇의 구현을 위해서는 마이크로 세계에서의 역학점 고려, 감각, 지능 기관의 극소화, 마이크로 부품 조립기술의 발달, 에너지 전달의 효율화 통신 기능 부여 등의 장벽을 극복해야 한다. 마이크로 시스템의 실용화는 큰 구동력을 필요로 하지 않는 미세광학, 세포 또는 고분자의 조작, STM 등의 미세 과학분야에 먼저 이루어질 것으로 예상하며 곧 구동력을 필요로 하는 국부 수술의 시행, 생체의 정보 취득, 인간의 범위가 닿지 않는 구조물의 결함 보수, 정보전용 로봇 등으로 전파되리라 본다.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.22 no.4
• /
• pp.377-385
• /
• 2002

Ultrasonic tests employing non-ionizing radiation are preferred in nondestructive examinations since they are safe and simple in use. The same principles of the techniques have been taken as valuable tools in medical area for the diagnoses of diseases, in other words, defects of the human body. The paper overviews the principles of the medical diagnosis based on nondestructive ultrasonic tests, and then evaluates experimentally the clinical potential of C scan images not popular in medicine, for detecting the micro fractures of the cortical bone. In the experiment the micro bone fractures were created on the femurs of porks by loading three point bending forces (2-4kN) with the speed of 1 mm/min. As the extent of the fracture was altered, not only X ray images but also ultrasonic C scan images using a focused ultrasonic probe resonated at 25 MHz were obtained. The results showed that ultrasonic C scan images were capable of detecting the micro bone fractures which were not possible to identify by conventional X ray images.

• Korean Chemical Engineering Research
• /
• v.53 no.4
• /
• pp.468-471
• /
• 2015

Microalgae have the advantages of being able to utilize the solar energy and culturing at a low cost. In particular, microalgae have a great potential in the production of biodiesel due to the high lipid content. Lipids produced from microalgae are converted to fatty acid methyl ester (FAME) by trans-esterification reaction and FAME is called a biodiesel in general. In addition, microalgae can also be utilized as a substrate for ethanol fermentation after saccharification reaction. In this study, three types of microalgae (Nanochloris, Dunaliella tertiolecta, Tetraselmis) were cultured and their lipid contents were compared. In addition, the effects of lighting period on the growth rate and lipid content were studied. Finally, the amounts of glucose produced from each saccharified microalgae were investigated. As a result, we demonstrated that D. tertiolecta has 43.6% higher lipid content and 22% higher glucose conversion than two others.

• Clinical and Experimental Reproductive Medicine
• /
• v.37 no.1
• /
• pp.83-88
• /
• 2010

Objective: Globozoospermia is observed in <0.1% of male infertile patients. The aim of this study is to report the successful clinical outcome in man with globozoospermia. Design: A case report. Method: A 36-year-old man and 32-year-old partner visited our fertility center with 6 years infertility duration. The semen analysis revealed globozoospermia combined with oligozoospermia which was stained with Diff-Quick method. ICSI (Intracytoplasmic sperm injection) was performed on 12 matured oocytes. Result: 5 injected oocytes were fertilized normally. 5 embryos were transferred on day 3 after oocyte retrieval. The patient became pregnant and delivered a healthy boy at 39 weeks of gestation. Conclusion: In case of globozoospermia, it has a low fertilization rate even though ICSI method is used. The favorable technique is still needed to increase the fertilization rate.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.32 no.2
• /
• pp.198-209
• /
• 2012

The present paper reviews the widely used surface microstructural investigation technique and micro/nano nondestructive evaluation(NDE) technique which is able to evaluate the surface and subsurface. In general, the micro/nano defects and microstructural state of surface have great influence on the mechanical, physical, and chemical properties of bulk materials. The investigation technique of surface microstructure is possible to evaluate the defects and microstructural state with high reliability. The various applications and developments of each inspection technique have been introduced. Consequently, it is thought that the technique developments and applications of micro/nano NDE in nondestructive industries are extensively possible hereafter.

• Korean Journal of Materials Research
• /
• v.2 no.3
• /
• pp.213-219
• /
• 1992

The microstructure, dopant distribution and electrical properties of the $As^{+}$ ion-implanted surface layer differ significantly depending on the methods of subsequent heat treatments, furnace annealing(FA) and rapid thermal annealing(RTA). The amorphous layer created by ion implantation was recrystallized during the thermal annealing through solid phase epitaxial (SPE) growth. The dopant distribution and electrical properties are discussed with respect to the TEM cross-sectional microstructure observed. The microstructure, dopant distribution and electrical properties depended upon especially the annealing time of the heat treatment.

• 한국신재생에너지학회:학술대회논문집
• /
• 2008.10a
• /
• pp.178-181
• /
• 2008

다양한 조성을 갖는 $CH_4+CO_2$ 혼합 기체 하이드레이트 샘플의 미세 구조 분석을 위하여 X-ray 회절 방법을 이용하였다. X-ray 회절 분석을 이용할 경우, 하이드레이트로의 전환율과 같은 정성적인 분석뿐 아니라 각 객체별 cage occupancy와 같은 정량적인 분석까지도 가능한 것으로 나타났다. 또한 이렇게 얻어진 X-ray 회절 분석 결과 및 refinement 결과를 $^{13}C$ 고체 NMR 방법과 교차 비교함으로써 측정 결과의 신뢰도를 높이려 하였다. 얻어진 분석 결과는 이후 가스 하이드레이트를 이용한 다양한 연구 분야에서 저장용량 평가 및 객체 점유율과 같은 미세 구조 정보를 얻는 데에 유용하게 사용될 것으로 전망된다.