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Brazing of ceramic-to-ceramic and ceramic-to-metal joints in air

Kirsten BOBZIN, Thomas SCHLAEFER, Lidong ZHAO, Nils KOPP, Arne SCHLEGEL

《机械工程前沿（英文）》 2010年第5卷第2期页码 125-129 doi: 10.1007/s11465-010-0007-z

摘要： Reactive air brazing (RAB) is an emerging technology for the production of ceramic-to-ceramic and ceramic-to-metal joints. In this study, RAB was investigated with respect to the potential applications for solid oxide fuel cells (SOFCs) as one example of use. It was found that alumina could be well brazed by RAB with AgCu and AgCuTi brazes. Both braze composition and brazing temperature influenced significantly the wetting behavior and their mechanism of wetting. AgCu and AgCuTi braze alloys could also be used to produce brazed joints with the SOFC materials ceramic yttria stabilized zirconia and steel X1CrTiLa22. However, CuO reacts with the steel, forming a brittle oxide layer on the steel surface, which is undesirable for SOFC applications. The first trials with Ag0.5Al showed a promising solution.

关键词： reactive air brazing (RAB) X1CrTiLa22 Al₂O₃ yttria stabilized zirconia (YSZ) solid oxide fuel cell (SOFC)

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Combining innovative science and policy to improve air quality in cities with refining and chemicals

David T. Allen

《化学科学与工程前沿（英文）》 2017年第11卷第3期页码 293-304 doi: 10.1007/s11705-017-1660-0

摘要： In Houston, a combination of urban emissions from a city of 4 million people, coupled with emissions from extensive petroleum refining and chemical manufacturing, leads to conditions for photochemistry that are unique in the United States, and historically, the city had experienced some of the highest ozone concentrations recorded in the United States. Large air quality field studies (the Texas Air Quality Studies or TexAQS I and II) were conducted to determine root causes of the high ozone concentrations. Hundreds of air quality investigators, from around the world, deployed instruments on aircraft, on ships, and at fixed ground sites to make extensive air quality measurements; detailed photochemical modeling was used to interpret and assess the implications of the measurements. The Texas Air Quality Studies revealed that both continuous and episodic emissions of light alkenes, which came to be called highly reactive volatile organic compounds, played a critical role in the formation of ozone and other photochemical oxidants in the region. Understanding and quantifying the role of these emissions in regional air quality required innovations in characterizing emissions and in photochemical modeling. Reducing emissions required innovative policy approaches. These coupled scientific and policy innovations are described, and the result, substantially cleaner air for Houston, is documented. The lessons learned from the Houston air quality experience are relevant to cities with similar population and industrial profiles around the world.

关键词： ozone air quality highly reactive volatile organic compounds Houston

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Air pollution affects food security in China: taking ozone as an example

Zhaozhong FENG,Xuejun LIU,Fusuo ZHANG

《农业科学与工程前沿（英文）》 2015年第2卷第2期页码 152-158 doi: 10.15302/J-FASE-2015067

摘要： Air pollution is becoming an increasingly important environmental concern due to its visible negative impact on human health. However, air pollution also affects agricultural crops or food security directly or indirectly, which has not so far received sufficient attention. In this overview, we take ozone (O ) as an example to analyze the principles and extent of the impact of air pollution on food security in China based on a review of the literature. Current O pollution shows a clear negative impact on food security, causing around a 10% yield decrease for major cereal crops according to a large number of field studies around the world. The mean yield decrease of winter wheat is predicted to be up to 20% in China, based on the projection of future ground-level O concentration in 2020, if no pollution control measures are implemented. Strict mitigation of NO and VOC (two major precursors of O ) emissions is crucial for reducing the negative impacts of ground-level O on food security. Breeding new crop cultivars with tolerance to high ground-level O should receive serious consideration in future research programs. In addition, integrated soil-crop system management will be an important option to mitigate the negative effects of elevated ground-level O on cereal crop production and food quality.

关键词： air pollution ozone damage anthropogenic activity crop production mitigation of reactive N emission

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Relations between indoor and outdoor PM

Cong Liu, Yinping Zhang

《环境科学与工程前沿（英文）》 2019年第13卷第1期 doi: 10.1007/s11783-019-1089-4

摘要：

Factors impacting indoor-outdoor relations are introduced.

Sulfate seems a fine tracer for other non-volatile species.

Particulate nitrate and ammonium desorb during outdoor-to-indoor transport.

OC load increases during the transport due to sorption of indoor SVOCs.

关键词： Indoor air quality Exposure SVOC Reactive oxidative species Oxidative potential Chemical transport model

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Wide gap active brazing of ceramic-to-metal-joints for high temperature applications

K. Bobzin,L. Zhao,N. Kopp,S. Samadian Anavar

《机械工程前沿（英文）》 2014年第9卷第1期页码 71-74 doi: 10.1007/s11465-014-0291-0

摘要：

Applications like solid oxide fuel cells and sensors increasingly demand the possibility to braze ceramics to metals with a good resistance to high temperatures and oxidative atmospheres. Commonly used silver based active filler metals cannot fulfill these requirements, if application temperatures higher than 600°C occur. Au and Pd based active fillers are too expensive for many fields of use. As one possible solution nickel based active fillers were developed. Due to the high brazing temperatures and the low ductility of nickel based filler metals, the modification of standard nickel based filler metals were necessary to meet the requirements of above mentioned applications. To reduce thermally induced stresses wide brazing gaps and the addition of Al₂O₃ and WC particles to the filler metal were applied. In this study, the microstructure of the brazed joints and the thermo-chemical reactions between filler metal, active elements and WC particles were analyzed to understand the mechanism of the so called wide gap active brazing process. With regard to the behavior in typical application oxidation and thermal cycle tests were conducted as well as tensile tests.

关键词： wide gap active brazing nickel filler metals high temperature application WC Al₂O₃

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Construction of lentiviral vector carrying Rab9 gene and its expression in mouse brain

Youguo HAO, Min ZHANG, Jinzhi XU, Bitao BU, Jiajun WEI

《医学前沿（英文）》 2009年第3卷第2期页码 141-147 doi: 10.1007/s11684-009-0041-6

摘要： Rab proteins and their effectors facilitate vesicular transport by tethering donor vesicles to their respective target membranes. Rab9 mediates late endosome-to- -Golgi-network trafficking. To explore the possibility of Rab9-related gene therapy for neurodegenerative diseases, we packed Lentivirus encoding Rab9. The expressing plasmid pCDH1-MCF1-Rab9-EF1-copGFP was constructed by using molecular biological techniques. The Lentivirus encoding Rab9 cDNA was packed by Lifectamine-2000 mediated co-transfection of the plasmid pPACKH1- , pPACKH1- and pVSV- into 293T cells. DNA sequencing proved the successful construction of pCDH1-MCF1-Rab9-EF1-copGFP. After 72 hours, the expression of GFP could be detected in BV-2 cells. Western blotting revealed that the Rab9 gene expression in BALB/c mice brain was up-regulated significantly 4 weeks after injection with Lentivirus encoding Rab9, which evidenced a satisfactory increasing effect of this virus. Administration of Lenti-Rab9 to postnatal day 3 Niemann-Pick disease type C (NPC) mice reduced motor defects and prevented the weight loss associated with female NPC mice, as well as modulating the death rate of Purkinje neurons. It is concluded that the packaging of Lentivirus encoding Rab9 was successful. Lentivirus encoding Rab9 can increase the expression of Rab9 gene effectively, which might offer a novel means for the treatment of neurodegenerative diseases.

关键词： Rab9 lentivirus gene therapy gene transfer

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Application of cold spraying for flux-free brazing of aluminium alloy 6060

Kirsten BOBZIN, Lidong ZHAO, Thomas SCHLAEFER, Thomas WARDA,

《机械工程前沿（英文）》 2010年第5卷第3期页码 256-260 doi: 10.1007/s11465-010-0095-9

摘要： In the present study, samples of aluminium alloy 6060 were coated by cold spraying with a powder of brazing alloy Al12Si. The influence of the process gas temperature on particle velocities and coating build-up was investigated. The coated samples were heat-treated in air and under argon atmosphere to investigate the wetting behaviour of the deposited Al12Si and the diffusion processes between Al12Si coatings and substrates. Coated samples were brazed flux-free under argon atmosphere by an induction heating system. The microstructure of the coated, heat-treated, and brazed samples was investigated. The shear strength of the brazed joints was determined. The results show that the brazing alloy Al12Si could be very well deposited on the substrate by cold spraying. The particle velocity increased with increasing process temperature. Correspondingly, the thickness of Al12Si coatings increased with increasing process temperature. The heat treatments showed that a very good metallurgical bond between the Al12Si coatings and the substrate could be realized by the deposition using cold spraying. The coated samples could be well brazed without fluxes. The coating thickness and overlap width influenced the shear strength of the brazed joints. The highest shear strength of brazed joints amounts to 80 MPa.

关键词： aluminium alloy flux-free brazing cold spraying shear strength

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Influence of the filler materials on flux-free brazing of pure aluminium (1050)

Kirsten BOBZIN, Lidong ZHAO, Thomas SCHLAEFER, Thomas WARDA,

《机械工程前沿（英文）》 2010年第5卷第1期页码 47-51 doi: 10.1007/s11465-009-0079-9

摘要： In the present study, samples of pure aluminium (1050) were deposited by cold spraying with filler materials such as Al12Si, Al7Si, Al12Si-4%Cu, and the Al-Si-based filler material A, which was especially developed for flux-free brazing by the Surface Engineering Institute. Besides, pure Si powder was also sprayed. The coated samples were heat-treated under different conditions and were brazed under an argon atmosphere without fluxes or with the flux Nokolok by an induction heating system. The shear strength of the brazed joints was determined. The results show that the filler materials could be well deposited by cold spraying. A thin layer of brittle Si could also form due to the strong deformation of the substrate surface. The heat treatments showed that a very good metallurgical bond between the filler materials and the substrate could be realized by the deposition by cold spraying. The Al7Si deposited samples could not be brazed without fluxes under the given conditions. The samples deposited with other filler materials could be brazed without fluxes. The in-situ diffusion process made it possible to braze the Si-deposited samples at 580°C. The joints of the samples deposited with the filler material showed the highest shear strength of 41 MPa, whereas the values of the Al12Si and Si deposited samples were less than 20 MPa. The employment of the flux Nikolok significantly increased the shear strength of the Al12Si deposited samples to more than 53 MPa.

关键词： aluminium flux-free brazing cold spraying shear strength

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Flux-free brazing of Mg-containing aluminium alloys by means of cold spraying

BOBZIN Kirsten, ZHAO Lidong, ERNST Felix, RICHARDT Katharina

《机械工程前沿（英文）》 2008年第3卷第4期页码 355-359 doi: 10.1007/s11465-008-0055-9

摘要： In the present study, AlSi12 and AlSi10Cu4 were deposited onto Mg-containing aluminium alloys 6063 and 5754 by cold spraying. The influences of the two brazing alloys and spray parameters on coating formation were investigated. The microstructure of the coatings was characterized. Some coated samples were heat-treated at 590°C and 560°C in air to investigate the effect of the rupture of oxide scales on the diffusion of elements during heat-treatment. Some coated samples were brazed under argon atmosphere without any fluxes. The results show that AlSi12 had much better deposition behaviour than AlSi10Cu4. Due to the rupture of oxide scales, Cu and Si diffused into the substrate and a metallurgical bond formed between the brazing alloys and the substrates during heat-treatment. The coated samples could be brazed without any fluxes. Because the oxide scales prevented the formation of a metallurgical bond locally, the brazed samples had relatively low shear strengths of up to 43 MPa.

关键词： diffusion metallurgical substrate Mg-containing aluminium spraying

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Design and optimization of reactive distillation: a review

《化学科学与工程前沿（英文）》 2022年第16卷第6期页码 799-818 doi: 10.1007/s11705-021-2128-9

摘要： Reactive distillation process, a representative process intensification technology, has been widely applied in the chemical industry. However, due to the strong interaction between reaction and separation, the extension of reactive distillation technology is restricted by the difficulties in process analysis and design. To overcome this problem, the design and optimization of reactive distillation have been widely studied and illustrated for plenty of reactive mixtures over the past three decades. These design and optimization methods of the reactive distillation process are classified into three categories: graphical, optimization-based, and evolutionary/heuristic methods. The primary objective of this article is to provide an up-to-date review of the existing design and optimization methods. Desired and output information, advantages and limitations of each method are stated, the modification and development for original methodologies are also reviewed. Perspectives on future research on the design and optimization of reactive distillation method are proposed for further research.

关键词： reactive distillation process intensification design method reactive phase diagram optimization algorithm

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Passive convergence-permeable reactive barrier (PC-PRB): An effective configuration to enhance hydraulic

《环境科学与工程前沿（英文）》 2022年第16卷第12期 doi: 10.1007/s11783-022-1591-y

摘要：

● A novel PRB configuration based on passive convergent flow effect was proposed.

关键词： Passive convergence-permeable reactive barrier (PC-PRB) Permeable reactive barrier configuration Numerical simulation Hydraulic performance evaluation Sensitivity analysis

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Preparation of nZVI embedded modified mesoporous carbon for catalytic persulfate to degradation of reactive

《环境科学与工程前沿（英文）》 2021年第15卷第5期 doi: 10.1007/s11783-020-1372-4

摘要：

• The MCNZVI is prepared as an interesting material for PS activation.

关键词： MCNZVI Core-shell structure Reactive Black 5 Persulfate Mechanism

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GASEOUS REACTIVE NITROGEN LOSSES FROM ORCHARDS, VEGETABLES AND TEA PLANTATIONS

《农业科学与工程前沿（英文）》 2023年第10卷第2期页码 155-166 doi: 10.15302/J-FASE-2022477

摘要：

● Gaseous N emissions from orchards, vegetables and tea plantations (OVT) are reviewed.

关键词： fruit greenhouse gas green development fertilizer management climate change

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Tuned reactive power dispatch through modified differential evolution technique

S. BISWAS (RAHA), N. CHAKRABORTY

《能源前沿（英文）》 2012年第6卷第2期页码 138-147 doi: 10.1007/s11708-012-0188-8

摘要： This paper explores the capability of modified differential evolution (MDE) technique for solving the reactive power dispatch (RPD) problem. The proposed method is based on the basic differential evolution (DE) technique with a few modifications made into it. DE is one of the strongest optimization techniques though it suffers from the problem of slow convergence while global minima appear. The proposed modifications are tried to resolve the problem. The RPD problem mainly defines loss minimization with stable voltage profile. To solve the RPD problem, the generator bus voltage, transformer tap setting and shunt capacitor placements are controlled by the MDE approach. In this paper, IEEE 14-bus and IEEE 30-bus systems are chosen for MDE implementation. The applied modification show much improved result in comparison to normal DE technique. Comparative study with other soft-computing technique including DE validates the effectiveness of the proposed method.

关键词： reactive power dispatch (RPD) modified differential evolution (MDE) differential evolution algorithm with localizations around the best vector (DELB)

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Elevated C-reactive protein levels predict worsening prognosis in Chinese patients with first-onset stroke

Jiangtao YAN, Rutai HUI, Daowen WANG

《医学前沿（英文）》 2009年第3卷第1期页码 30-35 doi: 10.1007/s11684-009-0005-x

摘要： The role of high sensitivity C-reactive protein (hsCRP) in predicting prognosis after stroke in the Asian population has not been investigated. We hypothesized that elevated levels of hsCRP were associated with worsening prognosis after stroke in Chinese patients. Two hundred and ninety consecutive patients with first-onset stroke and 290 age- and gender-matched control subjects without any cerebrovascular disease were enrolled for study. Plasma hsCRP level was detected and subsequent vascular events and death were recorded in both groups over a 5-year period. Compared to control group, patients presenting with stroke had higher plasma hsCRP level (3.3 ± 3.8 1.3 ± 2.2 mg/L, < 0.01). Furthermore, in the group of patients with stroke, the mean plasma hsCRP level was higher in patients who developed subsequent vascular diseases or died as compared with the patients without further complications (4.4 ± 4.3 2.7 ± 3.3 mg/L, < 0.01). Compared to the lowest tertile of hsCRP level, the relative risk for vascular events or death in stroke patients was 2.91 in the highest tertile of hsCRP (95% CI, 1.54–5.50, = 0.001). This increase in relative risk for vascular events or death in stroke patients continued after adjustment for age, sex and other cardiovascular risk factors such as hypertension and diabetes ( : 2.771, 95% CI: 1.367–5.617, = 0.005). These findings indicate that increased hsCRP level is associated with worsening prognosis after stroke in Chinese patients and suggests that inflammation is correlated with stroke outcome.

关键词： C-reactive protein inflammation stroke