76059 research outputs found
Sort by
Effect of titanium addition on mechanical properties of Mo-Si-B alloys
No full textIn this study, we investigated the effect of titanium addition on microstructure and mechanical properties in Mo-Si-B alloys. The Mo-Ti-Si-B alloy (Mo-3.9Ti-3Si-1B, wt%), which has alpha-Mo, Mo3Si, Mo5SiB2 and TiO2 phases, was fabricated by a powder metallurgy (PM) method. The starting materials were pulverized by using a high-energy ball milling and the resultant powder was subjected to a reduction process followed by cold isostatic pressing (CIP) compaction and pressureless sintering. In the microstructure, intermetallic compound phases were uniformly distributed in the alpha-Mo matrix. Some titanium atoms solved into the alpha-Mo matrix and the others formed a TiO2 phase caused by reaction with oxygen at the grain boundary. Fracture toughness of the Mo-Ti-Si-B sintered body was recorded as 10.42 MPa.mr(1/2), which is lower than that of the Mo-Si-B sintered body without addition of titanium. In the Mo-Ti-Si-B sintered body, the fracture mode is similar to the Mo-Si-B sintered body where intergranular fracture through the Mo grain boundary and transgranular fracture cross the intermetallic compound phase. The decrease of fracture toughness is due to the relatively large TiO2 at the grain boundary, promoting intergranular fracture.This work was supported by the Human Resources Program in Energy Technology of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea. (No. 20174030201750). This work was also supported by a research fund of the Agency for Defense Development (ADD), Republic of Korea (Project No. UD160078BD)
Effects of Macromonomeric Length of Ureidopyrimidinone-Induced Supramolecular Polymers on Their Crystalline Structure and Mechanical/Rheological Properties
No full textTo investigate the effect of the macromonomeric length of ureidopyrimidinone-based supramolecular polymers on their crystalline structure and mechanical/rheological properties, we synthesized ureidopyrimidinone-end functional poly(tetramethylene glycol), U(PTMG), with varied molecular weight (1k, 2k, and 3k gmol(-1)). From H-1 NMR, FT-IR, and specific viscosity analysis, we confirmed chain extension of U(PTMG)s by the quadruple hydrogen bonding of ureidopyrimidinone, indicating successful formation of U(PTMG) supramolecular polymers. We found that the U(PTMG) supramolecular polymers had dual-crystalline structures composed of PTMG and UPy crystals. The rigid UPy crystals, which had relatively high melting temperatures, were dominant with decreasing macromonomeric lengths of the U(PTMG) supramolecular polymers, whereas the chain-folded PTMG crystals were drastically reduced. As a result, the mechanical and rheological properties of the U(PTMG) supramolecular polymers became rigid and elastic, with decreasing macromonomer lengths of the U(PTMG) supramolecular polymers, due to their increased portions of UPy crystals.This work was financially supported by the Advanced Research Center Program (Grant No. NRF-2017R1A5A1015596) of the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT
Low pH treatment of starch industry effluent with bacteria from leaf debris for methane production
No full textCornstarch industry generates a huge amount of acidic effluent, that is, 5-11 M-3/Mt grinding, with a high load of chemical oxygen demand, 6000-19000 mg/L. The acidic effluent requires neutralization making the treatment process expensive. Methanogenesis under the acidic environment (pH 5-5.5) can reduce the cost of operation as well as treatment time. This research focuses on the evaluation of the optimum condition of COD reduction and methane generation simultaneously from leaf debris sludge using Box-Behnken model. Three 1 L bioreactors were seeded with 5000-10000 mg/L inoculum and operated at different pH 4.0-7.0 for 72 hr up to 10 cycles. The production of methane was found maximum 2980 ml after treating the wastewater from the starch industry at pH 5.57 and 9612.9 mg biomass load at 62.4 hr. The high reduction rate of around 97% shows there is ample opportunity for further research on low pH treatment of waste along with recovery as methane. (C) 2018 Water Environment Federatio
The Communication Requirements for Humanoid In-Robot Networks
No full textIn order to achieve human sensory and motor abilities, different from traditional robots, humanoid needs more sensors to receive environmental information, and more sophisticated artificial muscles to achieve similar human motion behavior. But as the number and accuracy of sensor and actuator increase, there will be a huge amount of data. In this paper, we construct a humanoid network framework based on human structure and function. The bit rate of data generated by sensor and actuator in IRN will be calculated. The results can be used as a reference for designing In-Robot Network protocols in the future.This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MOE: Ministry of Education) (No.2018R1D1A1A02048970)
An efficient Cu-CeO2 citrate catalyst for higher aliphatic ketone synthesis via alkali-free alkylation of acetone with butanol
No full textA remarkable effect of Cu-CeO2 citrate catalyst was examined for the alkylation of acetone with butanol for making jet-fuel range precursors under elevated reaction conditions, in which 2-heptanone and 6-undecanone were produced as major products with 3-heptene-2-one, 2-heptanol, and butyl butyrate in minor quantities. The catalytic performance was measured over 10 wt% Cu-CeO2 catalysts prepared by calcination at 400-800 degrees C with an interval of 100 degrees C followed by identical H-2 activation. Interestingly, the alkylation activity exhibited a volcano-shaped trend with respect to the calcination temperature as copper particle size and basicity played a vital role. The activity results revealed the optimum calcination temperature of 600 degrees C (namely, Cu-CeO2-600). When the catalysts prepared by two classical methods such as impregnation and co-precipitation were tested under an identical condition, the citrate method turned out to yield a highly stable nanocatalyst with the following features: the copper particles protected by CeO2, a high amount of surface copper species, and the basicity. These are responsible for sturdiness of Cu-CeO2-600 citrate catalyst in the production of higher aliphatic ketone.The authors gratefully acknowledge the financial support from the Basic Science Research Program through the National Research Foundation of Korea under the Ministry of Education, South Korea (NRF-2016R1A6A1A03013422) and from the New & Renewable Energy Core Technology Program through the Korea Institute of Energy Technology Evaluation and Planning (KETEP) under the Ministry of Trade, Industry & Energy, Republic of Korea (KETEP-20163010092210)
Surface-tensile-stress induced polishing-voids in cross-point phase-change-memory cells: corrosion mechanism and solution
No full textIn the fabrication of cross-point phase-change-memory-cells through atomic-layer-deposition of Ge-doped SbTe (Ge-ST) film followed by chemical-mechanical-polarization (CMP), a remarkable surface tensile stress was generated, originating from the surface stress induced by the pad down force and the surface structure tensile stress in a confined memory-cell structure. It was maximized at the position of the Si3N4-film spacer where the curvature becomes zero. The maximized surface tensile stress produced polishing induced voids via the generation mechanism of the stress corrosion cracking. The generation frequency and nanoscale size of the polishing induced voids rapidly increased at the maximum surface tensile stress during CMP. Then, they slightly decreased and saturated when the surface tensile stress reduced during further CMP. A design of a spacer using a SiO2-film spacer rather a Si3N4-film spacer could prevent the generation of the polishing induced voids, confirming that the generation mechanism of the polishing induced voids is associated with the stress corrosion cracking.This research was supported by the MOTIE (Ministry of Trade, Industry & Energy)(10085643) and KSRC (Korea Semiconductor Research Consortium) support program for the development of the future semiconductor device, Republic of Korea and the Brain-Korea 21 PLUS Program in 2017
Utility of Ultra-wide Fundus Photography in Patients with Acute Blunt Ocular Trauma
No full text목적: 응급실을 방문한 급성 안외상환자에서 광각안저촬영의 유용성에 대해 알아보고자 하였다.
대상과 방법: 2015년 6월부터 2016년 12월까지 안외상으로 응급실을 방문한 162명의 의무기록을 후향적으로 분석하였다. 응급실 진료에 광각안저촬영(Optos Optomap Panoramic 200MA; Optos PLC, Dunfermline, UK)검사가 도입된 2015년 12월 전과 후로 광각안저촬영을 하지 않고, 안저검사를 한 군(비촬영군)과 광각안저촬영검사를 시행받은 군(촬영군)으로 나누었다. 의무기록과 광각안저촬영에서 보이는 망막 소견에 대해 분석하고 망막 소견과 다른 안외상 소견과의 연관성도 조사하였다.
결과: 총 162명의 162안 중 92안에서 광각안저촬영을 시행하였고, 70안에서 광각안저촬영을 시행하지 않았다. 비촬영군의 망막 소견은 17안(24%)에서 주변부 망막진탕, 7안(10%)에서 황반부 망막진탕(Berlin’s edema), 3안(4%)에서 망막출혈이 있었다. 촬영군에서 발견된 망막 소견은 주변부 망막진탕 45안(49%), 황반부 망막진탕 10안(11%), 망막 및 유리체출혈 10안(11%), 망막열공 2안(2%)으로 촬영군에서 더 많은 외상관련 망막이상이 발견되었다. 주변부 망막진탕의 경우 두 군 간에 통계적으로 유의한 차이를 보였다(p=0.001).
결론: 광각안저촬영은 안검부종이 심하거나 환자 협조가 어려운 급성 안외상환자에서 망막 중심부 및 주변부 영상 촬영이 가능하여 외상 후의 초기 안저 상태 확인에 도움을 줄 수 있다.
Purpose: We explored the utility of ultra-wide fundus photography (UFP) to evaluate patients with blunt ocular trauma who visited our emergency room.
Methods: We retrospectively reviewed the records of 162 patients with blunt ocular trauma who visited the emergency room between June 2015 and December 2016. The patients were divided into two groups: those who underwent UFP and those who did not. We reviewed all medical records and took photographs to illustrate trauma-related retinal problems, and compared the two groups.
Results: Ninety-two eyes underwent UFP and 70 eyes did not. In the latter group, commotio retinae was detected in 17 eyes (24%), Berlin’s edema in seven (10%), and retinal hemorrhage in three (4%). In the former group, commotio retinae was detected in 45 eyes (49%), Berlin’s edema in 10 (11%), and retinal hemorrhage in 10 (11%). Retinal breaks were evident in only two eyes (2%). The frequency of commotio retinae significantly differed between the two groups.
Conclusions: UFP usefully detects abnormal retinal lesions in patients with acute blunt periorbital trauma, particularly in those with severe eyelid swelling and those who are in pain
The Discharge Mechanism Leading to the Tracking Progress in Polyvinyl-Chloride-Sheathed Flat Cord
No full textPurposes
This paper suggests the mechanism of the discharge phenomenon that leads to tracking progress.
Methods
For this purpose, a polyvinyl-chloride-sheathed flat cord (PVCSFC), which is widely used as a distribution cord, was employed and an artificial crack was intentionally made on the surface. Tracking was progressed using electrolyte droplets. The mechanism of the discharge phenomenon was suggested from the measurement and analysis of the current waveform.
Results
As carbonization progressed during the tracking progress, the frequency of scintillation discharge also significantly increased. The mechanism for scintillation discharge during the tracking progress was based on the change in the electric field of the dry band, initial electron, electron avalanche, photoionization, secondary electron generation (electron detachment, photoemission, and secondary electron emission avalanche), space charge due to positive ions, and formation of conductive channels.
Conclusions
This discharge mechanism could explain the physical phenomenon and change in the current waveform that occurs during the tracking progress.This work was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea (no. 20161210200560). In addition, this research was supported by Korea Electric Power Corporation (Grant number: R17XA05-19)
Mass composition of ultrahigh-energy cosmic rays with the Telescope Array Surface Detector data
No full textThe results on ultrahigh-energy cosmic rays (UHECR) mass composition obtained with the Telescope Array surface detector are presented. The analysis employs the Boosted Decision tree (BDT) multivariate analysis built upon 14 observables related to both the properties of the shower front and the lateral distribution function. The multivariate classifier is trained with Monte-Carlo sets of events induced by the primary protons and iron. An average atomic mass of UHECR is presented for energies 10(18.0)-10(20.0) eV. The average atomic mass of primary particles shows no significant energy dependence and corresponds to �� ln A �� = 2.0 +/- 0.1(stat.) +/- 0.44(syst:). The result is compared to the mass composition obtained by the Telescope Array with Xmax technique along with the results of other experiments. Possible systematic errors of the method are discussed.The Telescope Array experiment is supported by the Japan Society for the Promotion of Science (JSPS) through Grants-in-Aid for Priority Area 431, for Specially Promoted Research JP21000002, for Scientific Research (S) JP19104006, for Specially Promote Research JP15H05693, for Scientific Research (S) JP15H05741 and for Young Scientists (A) JPH26707011; by the joint research program of the Institute for Cosmic Ray Research (ICRR), The University of Tokyo; by the U.S. National Science Foundation Grants No. PHY-0601915, No. PHY-1404495, No. PHY-1404502, and No. PHY-1607727; by the National Research Foundation of Korea (2017K1A4A3015188, 2016R1A2B4014967, 2017R1A2A1A05071429, 2016R1A5A1013277); by IISN Project No. 4.4502.13, and Belgian Science Policy under IUAP VII/37 (ULB). The development and application of the multivariate analysis method is supported by the Russian Science Foundation Grant No. 17-72-20291 (INR). The foundations of Dr. Ezekiel R. and Edna Wattis Dumke, Willard L. Eccles, and George S. and Dolores Dore Eccles all helped with generous donations. The State of Utah supported the project through its Economic Development Board, and the University of Utah through the Office of the Vice President for Research. The experimental site became available through the cooperation of the Utah School and Institutional Trust Lands Administration (SITLA), U.S. Bureau of Land Management (BLM), and the U.S. Air Force. We appreciate the assistance of the State of Utah and Fillmore offices of the BLM in crafting the Plan of Development for the site. Patrick Shea assisted the collaboration with valuable advice on a variety of topics. The people and the officials of Millard County, Utah have been a source of steadfast and warm support for our work which we greatly appreciate. We are indebted to the Millard County Road Department for their efforts to maintain and clear the roads which get us to our sites. We gratefully acknowledge the contribution from the technical staffs of our home institutions. An allocation of computer time from the Center for High Performance Computing at the University of Utah is gratefully acknowledged. The cluster of the Theoretical Division of INR RAS was used for the numerical part of the work
Self-perceptions of body weight status according to age-groups among Korean women: A nationwide population-based survey
No full textWhile numerous studies have investigated body image, including body weight perception, most of which have focused on adolescents or young women, few studies have attempted to evaluate body weight perceptions in adult women according to age groups. This study was conducted to investigate the accuracy of self-perceived weight and actual body mass index (BMI) values among adult Korean women according to age. We used data from the 2016 Korean Study of Women’s Health Related Issues, a population-based, nationwide, cross-sectional survey. BMI was calculated from self-reported weight and height. Participants were asked to describe their body image by choosing one of the following descriptions: very underweight, underweight, about right, overweight, or obese. The proportions of women aged 20–29, 30–39, 40–49, 50–59, 60–69, and 70–79 years who underestimated their body weight relative to their actual BMI category were 12.6%, 15.1%, 22.2%, 34.0%, 45.6%, and 50.7%, respectively; those who overestimated their body weight comprised 18.7%, 17.8%, 14.3%, 10.8%, and 7.4%. In all BMI categories, the proportion of those who overestimated their weight status increased as age decreased, while those who underestimated their weight status increased as age increased. After adjusting for possible covariates, age was strongly associated with both underestimation and overestimation. The odds ratio for underestimating one’s weight status among women aged 70–79 yeas was 2.96 (95% CI: 2.10–4.18), and that for overestimation was 0.52 (95% CI: 0.35–0.79), compared to women aged 20–29 years. Age is the most important factor associated with weight perceptions among Korean women, affecting both underestimation and overestimation of weight status.The study was funded from the Center for Disease Control and Prevention, Korea (http://www.cdc.go.kr/CDC/main.jsp) (2015ER630300), and the National Cancer Center of Korea (http://www.ncc.re.kr) (#1610401). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript