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498 results on '"Ma, Lun"'

151. A novel flame-anchorage micro-combustor: Effects of flame holder shape and height on premixed CH4/air flame blow-off limit

Author

Xiaoting Wang, Xu Hao, Ma Lun, Gang Chen, Qingyan Fang, and Cheng Zhang

Subjects
Materials science, 020209 energy, Flow (psychology), Heat recirculation, Energy Engineering and Power Technology, 02 engineering and technology, Mechanics, Combustion, Industrial and Manufacturing Engineering, 020401 chemical engineering, Limit (music), 0202 electrical engineering, electronic engineering, information engineering, Fluent, Combustor, 0204 chemical engineering, Microscale chemistry, Flammability
Abstract

Maintaining stable combustion is one of the major challenges for microscale combustors. In this study, a novel premixed CH4/air flame micro-combustor combining a flame holder, backward-facing step and preheating channel is developed to enhance the flame anchorage and extend the blow-off limits. The effects of flame holder shape (triangle and rectangle) and height (H = 0.0, 0.5, 1.0, 1.5 and 2.0 mm) on the combustion stability are studied numerically by FLUENT 16.0. The results show that this micro-combustor not only can considerably anchor the flame root owing to flow recirculation but also can further improve CH4 flammability owing to heat recirculation. Compared with the rectangle flame holder, the triangle flame holder achieves the higher blow-off limits owning to the larger recirculation zone and better preheating effect. As the flame holder height increases, (i) the recirculation zone sizes near the flame root decrease, weakening the flame-root anchorage ability, and (ii) the heat recirculation effect becomes stronger, improving CH4 flammability. Under the combined effects of flow recirculation and heat recirculation, the highest flame blow-off limits are attained when H = 0.5 mm. The flame holder with triangle shape and H = 0.5 mm attains the highest flame blow-off limits (10.3 m/s and 6.2 m/s at Φ = 0.7 and 0.5).

Published
2019
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158. Effect of Gallium and Indium Co-Substituting on Upconversion Properties of Er/Yb:Yttrium Aluminum Garnet Powders Prepared by the Co-Precipitation Method

Author

Zhengfa Hu, Qian Liu, Wei Zhang, Jie Luo, Zuyong Feng, Xia Sheng, Ma Lun, Xiu-ping Zhang, and Yunling Liang

Subjects
010302 applied physics, Materials science, Biomedical Engineering, Analytical chemistry, Infrared spectroscopy, chemistry.chemical_element, Bioengineering, Phosphor, General Chemistry, Yttrium, Condensed Matter Physics, 01 natural sciences, Photon upconversion, X-ray photoelectron spectroscopy, chemistry, 0103 physical sciences, General Materials Science, Gallium, Luminescence, Indium
Abstract

Gallium and Indium co-substituted Yb, Er:YAG was fabricated through the chemical co-precipitation method. The formation process and structure of the Ga3+ and In3+ substituted phosphor powders were characterized by the X-ray diffraction, thermo-gravimetry analyzer, infrared spectra, and X-ray photoelectron spectroscopy, and the effects of Ga3+ and In3+ concentration on the luminescence properties were investigated by spectrum. The results showed that the blue shift occurred after the substitution of Ga3+ and In3+ for Al3+ in matrix, and the intensity of emission spectrum was affected by the concentration of Ga3+ and In3+.

Published
2016

169. A novel autofocus algorithm based on maximum total variation criteria for SAR images

Author

Liao Gui-sheng and Ma Lun

Subjects
Autofocus, Synthetic aperture radar, Computational complexity theory, Computer science, business.industry, ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION, Phase (waves), Computer Science::Software Engineering, Electronic, Optical and Magnetic Materials, law.invention, Domain (software engineering), Image (mathematics), Azimuth, law, Computer vision, Artificial intelligence, Electrical and Electronic Engineering, Focus (optics), business, Algorithm
Abstract

A novel autofocus algorithm for synthetic aperture radar (SAR) based on total variation is presented in this paper. The method, which starts with a complex phasedegraded SAR image, after the phase errors model is introduced into the range-compressed phase-history domain, carries out phase errors correction by changing the focus till the total variation of the azimuth profile is maximized. Compared with the minimum entropy autofocus algorithm, the autofocus algorithm has less computational complexity and is easier to implement. The simulation and the processing results of the measured data show the validity of the proposed method.

Published
2007
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170. Reducing NOx Emissions for a 600 MWe Down-Fired Pulverized-Coal Utility Boiler by Applying a Novel Combustion System

Author

Gang Chen, Qingyan Fang, Xihuan Wang, Yiping Chen, Dangzhen Lv, Ma Lun, Cheng Zhang, and Xuenong Duan

Subjects
Nozzle, Combustion, Environmental Chemistry, Coal, Computer Simulation, Staged combustion, NOx, Environmental Restoration and Remediation, Nitrites, Air Pollutants, Nitrates, Pulverized coal-fired boiler, Waste management, business.industry, Environmental engineering, Boiler (power generation), Temperature, Reproducibility of Results, Numerical Analysis, Computer-Assisted, General Chemistry, Oxygen, Fly ash, Environmental science, business, Power Plants
Abstract

A novel combustion system was applied to a 600 MWe Foster Wheeler (FW) down-fired pulverized-coal utility boiler to solve high NOx emissions, without causing an obvious increase in the carbon content of fly ash. The unit included moving fuel-lean nozzles from the arches to the front/rear walls and rearranging staged air as well as introducing separated overfire air (SOFA). Numerical simulations were carried out under the original and novel combustion systems to evaluate the performance of combustion and NOx emissions in the furnace. The simulated results were found to be in good agreement with the in situ measurements. The novel combustion system enlarged the recirculation zones below the arches, thereby strengthening the combustion stability considerably. The coal/air downward penetration depth was markedly extended, and the pulverized-coal travel path in the lower furnace significantly increased, which contributed to the burnout degree. The introduction of SOFA resulted in a low-oxygen and strong-reducing atmosphere in the lower furnace region to reduce NOx emissions evidently. The industrial measurements showed that NOx emissions at full load decreased significantly by 50%, from 1501 mg/m3 (O2 at 6%) to 751 mg/m3 (O2 at 6%). The carbon content in the fly ash increased only slightly, from 4.13 to 4.30%.

Published
2015

171. Prediction of the impact of support structures on the aerodynamic performance of large wind farms.

Author

Ma, Lun, Nishino, Takafumi, and Antoniadis, Antonios F.

Subjects
*OFFSHORE wind power plants, *WIND power plants, *IMPACT craters, *ATMOSPHERIC boundary layer, *DRAG coefficient, *WIND turbines
Abstract

An extended theoretical model based on a two-scale coupled momentum balance method is proposed to estimate aerodynamic effects of wind turbine towers on the performance of both ideal (infinitely large) and more realistic (large but finite-size) wind farms. A key implication of the extended model is that a normalized support-structure drag, A S / A × C D * , where A and A S are the rotor swept area and support-structure frontal projected area, respectively, and C D * is an effective support-structure drag coefficient, may play an important role in the design of future large wind farms. For the infinitely large case, the theoretical model shows that the optimal turbine spacing should increase with the value of A S / A × C D * , whereas for the large finite case, this also depends on an additional parameter describing the response characteristics of the atmospheric boundary layer to the total farm drag. To validate the theoretical model for the infinitely large case, Wall-Modeled Large-Eddy Simulations of a periodic array of actuator disks with and without support structures are conducted. The results show a reasonably good agreement (within 10% in the prediction of power) with the theoretical model. [ABSTRACT FROM AUTHOR]

Published
2019
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172. Raman spectroscopy analysis of new copper‐cysteamine photosensitizer.

Author

Akafzade, Hussein, Sharma, Suresh C., Hozhabri, Nader, Chen, Wei, and Ma, Lun

Subjects
RAMAN spectroscopy, FOURIER transform infrared spectroscopy, SCANNING electron microscopy, INFRARED absorption, X-ray scattering, CALCIUM oxalate
Abstract

Raman spectroscopy and several microstructure analysis techniques have been used to better characterize recently synthesized copper‐cysteamine Cu3Cl(SR)2, where R = CH2CH2NH2. Nanoparticles of this new copper‐cysteamine have been identified as having potential applications in radiation detection and cancer treatment because of the fact that they can be activated by light, X‐rays, ultrasound, and microwave radiation to produce reactive oxygen species. Three samples were grown under different conditions, and their microstructure was examined by using Raman spectroscopy, Fourier transform infrared, scanning electron microscopy, energy dispersive X‐ray scattering, and X‐ray diffraction. The Raman spectroscopy and Fourier transform infrared measurements identify numerous Raman active and infrared absorption bonds with wavenumbers ranging from 200 to 3,500 cm−1. Scanning electron microscopy scans show well‐faceted crystals varying in size from approximately 10 nm to 4 μm, energy dispersive X‐ray scattering measurements identify relative elemental composition (C = 48%, N = 37.5%, S = 5%, Cl = 2.6%, Cu = 7%), X‐ray diffraction data show the crystal plane spacing varies from 0.8454 to 0.8616 nm. The microstructure observed for the three samples is consistent with variations in the growth conditions. [ABSTRACT FROM AUTHOR]

Published
2019
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173. A Novel Method for one-Stage Repair of the lip Vermilion Defects in Progressive Hemifacial Atrophy

Author

Feng, Shi, Ma, Lun-kun, Zhang, Zhi-yong, Tang, Xiao-jun, Xu, Xi, Zhao, Shan-baga, Liu, Bing-yang, Zang, Tian-ying, Li, Hong-wen, Liang, Ying-xiang, and Liu, Wei

Abstract

Background Progressive hemifacial atrophy often causes lip vermilion defects in patients. In this study, we described a one-stage repair method for lip defects in progressive hemifacial atrophy using a lip vermilion mucosal flap or combined dermal fat flap graft.Patients and Methods Patients diagnosed with progressive hemifacial atrophy with lip vermilion defects from 2010 to 2022 were included in this study. Based on the severity and location of the patient's lip defect, a lip vermilion mucosal flap was designed and transferred to the lip defect or combined with a hip dermal fat flap for one-stage repair of the lip morphology. Lip morphology and function of patients were followed up after surgery.Results A total of 22 patients were enrolled in this study, including 15 patients with lip defects on the upper lip alone and 7 patients with both upper and lower lip defects. Follow-up six months to two years postoperatively, all patients recovered uneventfully without complications. The repaired lips of the patient had a full and symmetrical morphology with no visible scarring. Two patients experienced transient dysesthesia of the lips postoperatively and both returned to normal after three months. All patients had good lip closure with normal dietary and speech function.Conclusions The method we described for repairing lip defects in progressive hemifacial atrophy can achieve satisfactory aesthetic and functional lip results. The distinct advantage of this approach is that the patients undergo only one-stage operation and it can be used to repair both upper and lower lip defects.

Published
2024
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174. Analysis of Obstructive Sleep Apnoea in Craniofacial Microsomia Based on Polysomnography

Author

Ma, Lun-kun, Zhang, Zhi-yong, Tang, Xiao-jun, Xu, Xi, Feng, Shi, Zhao, Shan-baga, Liu, Bing-yang, Zang, Tian-ying, Li, Hong-wen, and Liu, Wei

Abstract

Objective This study aimed to investigate the prevalence of obstructive sleep apnoea (OSA) in patients with craniofacial microsomia (CFM) through polysomnography (PSG) and the relationship with the severity of CFM.Methods This study reviewed patients of CFM with pre-operative PSG data between January 2005 and September 2023. Patients were grouped according to the Pruzansky-Kaban classification. OSA was diagnosed and severity was assessed by the obstructive apnea-hypopnea index. The Pediatric Sleep Questionnaire was used to investigate OSA-related signs and symptoms. The χ 2 test and Fisher's exact test were used to compare between groups. Univariate logistic regression was used to identify risk factors associated with OSA. A p-value less than 0.05 was considered statistically significant.Results A total of 121 patients with CFM were included in the study with 3 bilateral and 118 unilateral patients. In total, 86 patients (71.07%) were diagnosed with OSA. The prevalence of OSA in type IIa, type IIb and type III was 72.97%, 78.33%, and 47.62%. There was no statistically significant difference in the prevalence of OSA between type IIa and type IIb (p> .05). The difference in the prevalence of OSA between type III and type II was statistically significant (p< .05). Snoring was the most common symptom among the patients of CFM with OSA.Conclusions Patients with CFM have a higher incidence of OSA based on PSG in type II and type III patients. The incidence of OSA did not correlate positively with the severity of CFM, with type III patients having certain particularities.

Published
2024
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175. Enhancement of Afterglow in ZnS:Cu,Co Water-Soluble Nanoparticles by Aging

Author

Ma, Lun and Chen, Wei

Abstract

In addition to illuminations and lighting, water-soluble afterglow nanoparticles may also find applications in disease treatment and medical imaging. Afterglow efficiency and longevity are the key parameters for practical applications. It was observed that the afterglow efficiency of 3-mercaptopropionic acid stabilized water-soluble ZnS:Cu,Co afterglow nanoparticles can be improved by using much less S2–precursor (Na2S) in the synthesis. In addition, the afterglow intensity increased more than 7 times after the sample was aged for two weeks at room temperature. To figure out the mechanism for the enhancement, the nanoparticle structures and sizes were measured by X-ray diffraction and high-resolution transmission electron microscopy. The crystal structure and the particle sizes are almost the same for the samples before and after aging. The optical absorption spectra show not much difference for the two samples. However, the X-ray photoelectron spectroscopy measurement indicates that oxidation occurred on the surfaces of ZnS:Cu,Co nanoparticles due to the aging. The oxidation may lead to more S vacancies and electron traps that might be responsible for the afterglow enhancement.

Published
2024
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185. Sr3GdLi(PO4)3F: Sm3+ phosphor: preparation and luminescence properties evaluation.

Author

Deng, Sheng, Feng, Zuyong, Sheng, Xia, Pan, Yongman, Luo, Li, Zhang, Wei, Hu, Zhengfa, Hu, Peiju, and Ma, Lun

Subjects
LIGHT emitting diodes, PHOSPHORS, CHROMATICITY, FLUORESCENCE, PHOTOLUMINESCENCE
Abstract

A series of Sr3Gd1−xLi(PO4)3F: xSm3+ (x = 0.02, 0.04, 0.06, 0.08) phosphors were synthesized by a high-temperature solid state method. The Sm3+ activated Sr3GdLi(PO4)3F phosphors can be efficiently excited by the wavelengths in the range from 350 to 450 nm, which matches perfectly with that of the commercial near-UV LED chips. The optimal doping concentration of Sr3Gd1−xLi(PO4)3F: xSm3+ phosphors was determined to be x = 0.04, corresponding to the quantum efficiency of 2.23%, and the CIE chromaticity coordinates (x = 0.5172, y = 0.4641). The concentration quenching mechanism of Sm3+ in Sr3GdLi(PO4)3F host is mainly attributed to the dipole-dipole interaction, which was confirmed by the fluorescent lifetimes. The effect of temperature on the photoluminescence property of Sr3GdLi(PO4)3F: Sm3+ was investigated. 90% of the intensity is preserved at 150 °C. In addition, a white light emitting diode (WLED) lamp was fabricated by a 405 nm n-UV LED chip coated with Sr3Gd0.96Li(PO4)3F:0.04Sm3+ phosphor and commercial yellow phosphor (YAG: Ce3+) of a certain mass ratio. The present work indicates that the Sr3GdLi(PO4)3F: Sm3+ orange-red-emitting phosphors tend to be potential application in n-UV WLED. [ABSTRACT FROM AUTHOR]

Published
2018
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186. Thermal Management Technology of a Liquid Cooling Thin-disk Oscillator

Author

姜彦玲 Jiang Yan-ling, 佘江波 She Jiang-bo, 聂荣志 Nie Rong-zhi, 马仑 Ma Lun, 李伟 Li Wei, 赵朋飞 Zhao Peng-fei, and 杨鹏 Yang Peng

Subjects
Materials science, Computer cooling, Thin disk, business.industry, Optoelectronics, Thermal management of electronic devices and systems, business, Atomic and Molecular Physics, and Optics
Published
2016
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200. Elastic material constants for isotropic granular solids with particle rotation

Author

Ma Lun and Ching S. Chang

Subjects
Materials science, Applied Mathematics, Mechanical Engineering, Isotropy, Stiffness, Mechanics, Condensed Matter Physics, Granular material, Microstructure, Finite element method, Classical mechanics, Mechanics of Materials, Modeling and Simulation, medicine, Material constants, General Materials Science, Boundary value problem, medicine.symptom, Elasticity (economics)
Abstract

The granular material perceived as a collection of particles is modelled as a micropolar continua taking account of particle interaction and microstructure of the material. Explicit expressions of constitutive constants in terms of elastic inter-particle stiffness are derived for granular solids with Isotropie random fabric distribution. Based on the derived expressions for Isotropic material, six material constants are identified instead of two constants used in conventional elasticity. The derived constitutive constants in explicit terms of inter-particle contact properties provide a fundamental understanding of these constants and furnish useful inter-relations among these constants. The physical meaning of these material constants is discussed with emphasis on the role of particle spin. Finite element analysis incorporating these material constants is described and used to obtain solutions for boundary value problems. Examples are given for granular solids under boundary pressure to show the effects of inter-particle properties and material constants on the behavior of stress distribution and deformation in granular material.

Published
1992
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