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가열건조법에 의한 단위수량 추정에 미치는 혼화재료의 영향
문학룡 ( Wen¸ Xue-long ),김영득 ( Kim¸ Young Deuk ),황인성 ( Hwang¸ Yin-seong ),한천구 ( Han¸ Cheon-goo ),김광서 ( Kim¸ Kwang Soe ) 한국구조물진단유지관리공학회 2002 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.6 No.2
This study is intended to investigate the influence of admixture factor on estimation of water content in fresh concrete. According to the results, as the replacing ratio of blast furnace slag powder and fly ash increases, the difference between designed and estimated water content by heat drying method grows small before correction, but water content is estimated favorably in the range of ± 5kg/m<sup>3</sup>, compared with designed water content after correction. Estimated water content shows the difference of 20~30kg/m<sup>3</sup> with increase of AE agent in comparison with designed water content before correction, but it is similar to designed water. As the mixing ratio of AE agent increases, water content is estimated less than designed water content with increase of air content.
Xuelong Li,Heng Du,Jia Li,Xianliang Li,Qingchun Gao,Xiangyan Chen 대한신경과학회 2023 Journal of Clinical Neurology Vol.19 No.4
Background and Purpose By measuring a newly defined parameter, the carotid–cerebral pulse wave velocity (ccPWV), this study aimed to determine the association of intracranial artery calcification (IAC) with arterial stiffness as reflected by the pulse wave velocity between the carotid and middle cerebral arteries using transcranial Doppler sonography in patients with acute stroke. Methods We recruited 146 patients with ischemic stroke from our stroke center. Computed tomography of the head was used to assess the presence and severity of IAC. Arterial stiffness was evaluated using ccPWV. Data are presented as quartiles of ccPWV. A multivariable logistic regression model was used to assess the independent relationship between ccPWV and IAC. Results The IAC prevalence increased with the ccPWV quartile, being 54%, 76%, 83%, and 89% for quartiles 1, 2, 3, and 4, respectively (p<0.001) as did IAC scores, with median [interquartile range] values of 0 [0–2], 3 [2–4], 4 [2–5], and 5 [4–6], respectively (p<0.001). After additionally adjusting for age and hypertension, a significant correlation was only found between quartiles 3 and 4 of ccPWV and IAC scores. The odds ratio (95% confidence interval) for the IAC scores was 1.78 (1.28–2.50) (p=0.001) in quartile 4 of ccPWV and 1.45 (1.07–1.95) (p=0.015) in quartile 3 compared with quartile 1. Conclusions We found that in patients with acute ischemic stroke, ccPWV was positively related to the degree of IAC. Future longitudinal cohort studies may help to identify the potential role of IAC in the progression of cerebral arterial stiffness.
Short circuit fault‑tolerant LCC‑S wireless power transfer system
Xuelong Han,Yinyin Hou,Chundi Jiang,Yinzhong Ye 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.2
Short circuit faults (SCF) in full bridge inverter result in more serious failures if not promptly resolved. In this paper, a fast short circuit fault diagnosis method is proposed for wireless power transmission networks with inductance–doublecapacitances-series compensation circuits. Each arm of the bridge is connected in series with a sampling resistor. When a MOSFET or an IGBT is short circuited, the sampling resistor voltage is much larger than before. Based on this, the system built in this paper can quickly stop the pulse of the other switch in the same bridge. Then, the full bridge converter is transformed into a half bridge converter, which causes the output voltage to drop by half. To obtain a constant voltage output, a BOOST + WPT structure is proposed. When there is no fault, the boost does not work. When a SCF occurs, the pulse of the short circuited MOSFET or IGBT is stopped and the boost starts to work with 50% duty cycle on the MOSFET to keep the output voltage unchanged. The effect on the efficiency and constant voltage output with a sampling resistor is studied. The short circuit current is analyzed for different circuit parameters, and the voltage change on the capacitance is analyzed. Taking the output voltage drop by less than 1% as the bottom line, the selection criterion of the sampling resistor should be that the load resistance value is 100 times greater than the sampling resistor value. Finally, the experimental results with the input voltage of 30 V verified the correctness of the theoretical analysis and the feasibility of the proposed method.
Xuelong Wen,Fengbing Han,Yadong Gong 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.8
In this paper, coated micro-grinding tools with high wear resistance are successfully manufactured by vacuum multi-arc ion plating method, aiming at improving the grinding performance and prolonging the service life of micro-grinding tools. The principle of vacuum multi-arc ion plating is analyzed. Single factor coating experiment is conducted on the surface of specimens to investigate the effect of different preparation parameters on coating properties. It demonstrated during the present research that the interfacial reaction between metal titanium coating and diamond abrasive particles produces metallurgical bond. Meanwhile, the interpenetration between titanium coating and cobalt and nickel binder layer improves the binding force of the coating, which can firmly wrap diamond particles and slow down the shedding of diamond abrasive particles. When the arc current is 100 A, the voltage of the electromagnetic coil is 20 V and the deposition time is 2.5 h, coating properties with high wear resistance can be obtained.
Xuelong Wen,Yadong Gong,Chao Wang 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.12
Micro mill-grinding is a novel compound machining process. This article presented a novel micro mill-grinding tool fabricated by cold spray technology. Compound tools with various grit sizes were used in sidewall machining and slotting. It is proved the effect of micro mill-grinding is better in sidewall machining. The machined surface topography and roughness were measured and the results were compared with those of micro milling. It shows that the smaller the grit size is, the smaller the surface roughness is, and the surface textures by compound tools also get tinier and denser with the decrease of the grit size. The influences of processing parameters on sidewall machining were investigated. It is found that surface roughness increases with the increase of cutting depth and feed rate, but decreases with the increase of spindle speed. The plastic deformation was found in the experiments by different machining methods, but there was no microstructure alternation. The plastic deformation of the specimen surface layer is smaller with the high cutting speed and slow feed speed in micro mill-grinding. The microhardness of the processed surface in micro milling-grinding is larger than that in micro-milling. The major wear mode of the micro mill-grinding tools is grit shedding or coating peeling off.
Xuelong Yang,Xinping LONG,Yong Kang,Longzhou Xiao 한국유체기계학회 2013 International journal of fluid machinery and syste Vol.6 No.3
To improve annular jet pump (AJP) performance, new ways named constant rate of velocity/pressure change method (CRVC/CRPC) were adopted to design its diffuser. The design formulas were derived according to the assumption of linear velocity/pressure variation in the diffuser. Based on the two-dimensional numerical simulations, the effect of the diffuser profile and the included angle on the pump performance and the internal flow details has been analyzed. The predicted results of the RNG k-epsilon turbulence model show a better agreement with the experiment data than that of the standard and the realizable k-epsilon turbulence models. The AJP with the CRPC diffuser produces a linear pressure increase in the CRPC diffuser as expected. The AJP with CRPC/CRVC diffuser has better performance when the diffuser included angle is greater or the diffuser length is shorter. Therefore, the AJP with CRPC/CRVC diffuser is suitable for applications requiring space limitation and weight restriction.
( Xuelong Zhuang ),( Min Chang Shin ),( Byeong Jun Jeong ),( Seung Hwan Lee ),( Jung Hoon Park ) 한국화학공학회 2021 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.59 No.2
Recently, hybrid coal research is underway to upgrade low-grade coal. The hybrid coal is made by mixing low-grade coal with bioliquids such as molasses, sugar cane, and lignin. In the case of lignin used here, a large amount of lignin is included in the wastewater of the papermaking process, and thus, research on hybrid coal production using the same is attracting attention. However, since a large amount of metal ions are contained in the lignin wastewater from the papermaking process, substances that corrode the generator are generated during combustion, and the amount of fly ash is increased. To solve this problem, it is essential to remove metal ions in the lignin wastewater. In this study, metal ions were removed by ion exchange with a alumina hollow fiber membrane coated with K-Phillipsite (K-PHI) zeolite. The alumina hollow fiber membrane used as the support was prepared by the nonsolvent induced phase separation (NIPS) method, and K-PHI seeds were prepared by hydrothermal synthesis. The prepared K-PHI seed was seeded on the surface of the support and coated by secondary growth hydrothermal synthesis. The characteristic of prepared coating membrane was analyzed by Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), Energy Dispersive Spectroscopy (EDX), and the concentration of metal ions before and after ion exchange was measured by Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES). The extraction amount of K<sup>+</sup> is 86 mg/kg, and the extraction amount of Na<sup>+</sup> is 54.9 mg/kg. Therefore, K-PHI zeolite membrane has the potential to remove potassium and sodium ions from the solution and can be used in acidic lignin wastewater.
Xuelong Zhuang,신민창,정병준,황재연,최영찬,박정훈 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.6
To remove the main barrier for lignin valorization, which is the development of actual lignin separationtechnology, we studied the ceramic membrane nanofiltration process using a dense, ultra-thin -Al2O3 film-coatedporous -Al2O3 hollow fiber ( HF) membrane for the simultaneous separation of alkali metals (Na+, K+, etc) andconcentration of lignin from an alkaline media like black liquor with success as an advanced wastewater treatment process. The -AlOOH sol was prepared by sol-gel method and coated by dip-coating on -Al2O3 hollow fiber ( HF)support. After calcination at high temperature, the mean pore sizes of the HF support and the HF membranewere found to be 0.2 m and 1.6 nm. The rejection rate performance for various salts increased in the following order:Na2SO4<MgSO4<NaCl<KCl<CaCl2<MgCl2<AlCl3. Under the best condition, the removal rate of sodium and potassiumions reached about 92% and 85%, respectively, with 19.34% of the lignin being discharged. The HF membranepresents good performance stability during a five day nano-filtration process.