课程文献中心 更多>>

关键词： 湿式离合器   带排转矩   表面张力   径向槽摩擦片   SAE#2台架  

摘要： 为了研究湿式离合器分离阶段带排转矩特性,根据流体力学理论和Navier-Stokes方程推导了润滑油流动压力和径向速度模型,在质量流量守恒条件下推导了油膜等效外径计算方程,同时改进了表面张力计算模型与径向槽摩擦片带排转矩模型。在SAE#2台架上测试了不同流量下湿式离合器带排转矩的大小,通过数值模拟将改进模型与试验数据进行对比,验证了模型的有效性。

关键词： 粉管   可信程度   磨煤机   皮托管   传感器数据   标准器   极限范围   三分之一  

摘要： 目前我国比较常见的风速计量检定设备都是采用皮托管以及微差压计,在此类标准器使用过程中,如果是测量较低风速会会产生差异和不确定性。特别是风速小的情况下,其测量差异可以达到实际数据的误差三分之一。如果校准的结果超出极限范围误差,那么最后数据的可信程度将快速降低。这对于后期的传感器数据记录实际准确数值有着较大的影响。关于这一方面,国内外均没有较为成熟的借鉴策略,对于减小低风速的不确定的研究方法仍旧欠缺科技性,因此在没有涉及专业领域的情况下,对于风速测点装置的改造是志在必行。本文主要就磨煤机出口粉管风速测点壳体改造为课题进行分析,并提出一些个人观点,以供参考。

关键词： “卢卡斯之谜”   分类资本流动   金融发展程度   资本账户开放  

摘要： “卢卡斯之谜”自提出以来,就成为开放宏观领域的一个重要谜题,如何合理解释资本流动方向逆转,成为国际经济学学科的一个重要挑战。对此本文采用154个国家1980-2011年的面板数据,对分类资本流动进行实证研究后发现,对外直接投资表现为从富国流向穷国,而股权类资本和债务类资本的流动方向发生逆转。进一步探究这两类资本存在流动方向逆转的原因,实证研究发现金融发展程度越高,人均相对收入水平越高的国家的股权类资本净流入越多,而对于债务类资本,资本账户开放程度越高,金融发展程度越高且人均相对收入水平越高的国家倾向于成为债务类资本的净流入国。

关键词： age-related macular degeneration   OCT angiography   type 3 neovascularization  

摘要： Purpose: To study B-scan flow overlay and en face flow optical coherence tomography angiography (OCT-A) images of Type 3 neovascularization (NV) and to characterize a staging system for Type 3 NV based on the OCT-A findings. Methods: We retrospectively collected data on consecutive treatment-naive eyes with Type 3 NV. All eyes underwent fluorescein angiography, indocyanine green angiography, structural spectral domain OCT, and OCT-A (AngioPlex). Localization and extension of abnormal flows detected by B-scan flow overlay and en face OCT-A images were assessed. Results: Of 24 eyes of 22 patients with Type 3 NV, B-scan flow overlay images showed that 4.2% had telangiectatic flow in the deep retinal layer without outer plexiform layer disruption (Stage 1), 8.3% had downward intraretinal flow and subretinal flow without retinal pigment epithelium disruption (Stage 2), and 87.5% had downward flow and retinal pigment epithelium disruption (Stage 3). Of the Stage 3 eyes, 95.2% showed flow signal penetrating at the site of the retinal pigment epithelium disruption on the B-scan flow overlay images. Conclusion: We showed the characteristics of Type 3 NV using B-scan flow overlay and en face OCT-A images. B-scan flow overlay OCT-A images seem useful to improve the detection and accurate diagnosis of Type 3 NV.

关键词： Redox reactions   Anions   Reaction products   Deposition   Minerals  

摘要： The mineralogical, morphological, and chemical characteristics of ash deposits during combustion of Zhundong lignite (<3 mm) in a 0.2 t d(-1) circulating fluidized bed (CFB) operating at relatively low temperatures, that is, 800-760 and 750-680 degrees C, were investigated. Two air-cooled probes were installed in the furnace dilute phase (P-1) and the cyclone outlet (P-2) to simulate ash deposition. The deposits along with the bottom ash and fly ash were collected and analyzed by using scanning electron microscopy energy-dispersive X-ray spectroscopy, X-ray diffraction, and inductively coupled plasma optical emission spectroscopy. Results showed that the P-1 deposit composed of melted Ca/Na sulfate particles at 800 degrees C but became granular Na/Ca/Mg aluminosilicate particles at 750 degrees C. Likewise, the P2 deposit comprised agglomerated particles rich in Na2SO4 and CaSO4 at 800 degrees C but became discrete Na2SO4 and NaCl particles at 750 degrees C. The bottom ash was enriched with (Ca,Na)(Si,Al)(4)O-8 and Na2SO4 at 800 degrees C but turned into Na2SO4, (Na,K)(Si3Al)O-8 at 750 degrees C. The Na content in the bottom ash correspondingly increased from 31.3 to 36.S mg g(-1), retaining more Na in the bottom ash at 750 degrees C. The fly ash also became discrete particles enriched in Na2SO4 and NaCl. The CFB combustion at 750-680 degrees C thus decreased the release of Na and the sintering propensity of ash particles and consequently lessened their deposition propensity.

关键词： Pressurized oxy-fuel combustion   Fluidized bed   Ignition   Char combustion   Burnout time  

摘要： Pressurized oxy-fuel combustion (POFC) is recognized as the second generation of oxy-fuel combustion for the reduction of CO2 emissions, which has gradually gained more and more attention recently. In this work, the influence of pressure on the combustion characteristics (i.e., ignition, volatiles combustion, char combustion) of a single lignite particle was investigated in a pressurized visualized fluidized bed combustor under O-2/N-2 and O-2/CO2 atmospheres. The combustion process was recorded by a color video camera, and the temperatures of volatiles flame and char particle were measured by pre-calibrated two-color pyrometry. The results indicated that increasing the overall pressure and increasing the oxygen volume fraction to a same partial pressure of oxygen will affect the ignition delay time (t(d)) differently. t d increased with the operating pressure at the same oxygen volume fraction, but decreased with the increase of oxygen volume fraction under atmospheric pressure. Pressurization significantly changes the coal flame shape and the volatiles flame becomes longer and thinner at a higher pressure. At the same oxygen volume fraction, higher flame and char temperatures and shorter burnout time (t(b)) of coal particle were observed under a higher pressure due to the better mass transfer of oxygen. With the same oxygen partial pressure, particle temperature is lower at high overall pressure than that at high oxygen volume fraction, which is probably a potential advantage of pressurized oxy-fuel combustion to resist agglomeration. Moreover, compared with atmospheric oxygen-combustion, the gasification of char particle in pressurized oxygen-combustion is more remarkable and cannot be neglected. (C) 2019 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

关键词： Deformation   Deposition   Coal   Syngas   Gasification  

摘要： Thermal cracking and char catalytic conversion of tar were carried out on a laboratory-scale circulating fluidized bed to provide theoretical support for the removal of tar. The used char and gas were characterized using a portable infrared analyzer, a specific surface area analyzer, proximate analysis, etc. Catalytic conversion of tar was more effective than thermal cracking. It could inhibit carbon deposition and improve the quality of syngas. The effect of temperature and tar amount on the catalytic conversion of tar during circulating fluidized-bed char gasification was investigated. The effect of temperature on the catalytic conversion of tar was remarkable. The efficiency of tar conversion (ETC) increased significantly with increasing temperature. A tendency for catalytic conversion of tar at different temperatures was revealed. As the amount of tar feeding increased, the ETC would decrease because of the carbon deposition. In this process, a maximum increase of low heating value (LHV) was discovered and so there was an optimum amount of tar treatment for a certain amount of char.

关键词： Morse-Smale flow   gradient-like flow   surface dynamics   heteroclinic trajectory   topological equivalence   topological classification   Seifert manifold  

关键词： Redox reactions   Atmospheric chemistry   Coal   Fuels   Gasification  

摘要： How to reduce nitrogen oxides in coal combustion process has always been a hot and difficult topic in the research process. In this paper, under the condition of circulating fluidized bed air equivalence ratio of 0.61 and gasification temperature of 970 degrees C, the partial gasification and combustion method is used to study the influence of the secondary air distribution modes on the gasification and combustion characteristics. Three aspects are discussed in this test: partial gasification characteristics, combustion characteristics, and coal-nitrogen migration and transformation characteristics. The experimental results show that under partial gasification conditions of the circulating fluidized bed, nearly 87% of the fuel nitrogen at the outlet of the circulating fluidized bed is converted into nitrogen in the coal gas, and the ratio of fuel nitrogen to N-2 is about 64.11%, the conversion rate of HCN is about twice that of NH3, and the combustion reactivity of partial gasification fuels increased at the outlet of circulated fluidized bed. Different secondary air distribution modes will affect the combustion process and the temperature distribution of the combustion chamber. When the secondary air is mixed with the high-temperature coal-based fuel in advance, the entire combustion reaction and the maximum temperature point in the combustion chamber will be moved up. When secondary air is injected simultaneously with high-temperature coal-based fuels, NOx emissions are approximately 90 mg/m(3) (@6% O-2), the conversion rate of fuel nitrogen to NOx is 2.09%, and when nearly half or all of the secondary air is directly premixed into the high-temperature coal-based fuel, the NOx emissions are about 70 mg/m(3) (@6% O-2), the conversion ratio of fuel nitrogen to NOx is reduced to about 1.63%.

关键词： Chronic granulomatous disease   gp91phox   p22phox   p47phox   CYBB   CYBA   NCF1   flow cytometry   NADPH oxidase   primary immunodeficiencies  

摘要： Purpose Chronic granulomatous disease (CGD) is an innate immune deficiency, primarily affecting the phagocytic compartment, and presenting with a diverse phenotypic spectrum ranging from severe childhood infections to monogenic inflammatory bowel disease. Dihydrorhodamine (DHR) flow cytometry is the standard diagnostic test for CGD, and correlates with NADPH oxidase activity. While there may be genotype correlation with the DHR flow pattern in some patients, in several others, there is no correlation. In such patients, assessment by flow cytometric evaluation of NADPH oxidase-specific (NOX) proteins provides a convenient and rapid means of genetic triage, though immunoblotting has long been used for this purpose. Methods and Results We describe the clinical utility of the NOX flow cytometry assay through assessment of X-linked and autosomal recessive CGD patients and their first-degree relatives. The assessment of specific NOX proteins was correlated with overall NADPH oxidase function (DHR flow), clinical phenotype and genotype. NOX-specific protein assessment is a valuable adjunct to DHR assessment and genotyping to classify and characterize CGD patients. Conclusions The atypical clinical presentation of some CGD patients can make genotype-phenotype correlation with DHR flow data challenging. Genetic testing, while useful for confirmation of diagnosis, can take several weeks, and in some patients does not provide a conclusive answer. However, NADPH-oxidase-specific protein flow assessment offers a rapid alternative to identification of the underlying genetic defect in cellular subsets, and can be utilized as a reflex test to an abnormal DHR flow. Further, it can provide insight into correlation between oxidative burst relative to protein expression in granulocytes and monocytes.