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排序方式: 共有403条查询结果,搜索用时 31 毫秒
11.
Waldemar Krieger Evren Bayraktar Otto Mierka Lutz Kaiser Robin Dinter Julian Hennekes Stefan Turek Norbert Kockmann 《American Institute of Chemical Engineers》2020,66(6):e16953
The implementation of traditional sensors is a drawback when investigating mass transfer phenomena within microstructured devices, since they disturb the flow and reactor characteristics. An Arduino based slider setup is developed, which is equipped with a computer-vision system to track gas–liquid slug flow. This setup is combined with an optical analytical method allowing to compare experimental results against CFD simulations and investigate the entire lifetime of a single liquid slug with high spatial and temporal resolution. Volumetric mass transfer coefficients are measured and compared with data from literature and the mass transfer contribution of the liquid film is discussed. 相似文献
12.
Inside Cover: Site‐Specific Immobilization of the Peptidoglycan Synthase PBP1B on a Surface Plasmon Resonance Chip Surface (ChemBioChem 23/2016)
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13.
Modeling of real physical processes by numerical methods is highly time-consuming and requires significant computational capacity. In some cases, tens or even hundreds of hours of high-power computing are needed to virtually model a real process that lasts one second. Processes that take many hours, such as drying, pose an even greater challenge. This problem can be solved in two ways: by using faster computers (such as computing clusters) or by significantly simplifying the modeled process (its geometry, physical phenomena, or the impact of individual factors). For this reason, all methods which speed up or minimize the number of simulations required to achieve the research objective should be analyzed. This article focuses on the latter approach, and it proposes a simple method for predicting the responses of a numerical model (values of any output parameter) to changes in input values (values of any input parameter). This method requires a base model, such as a numerical model which is qualitatively and quantitatively consistent with experimental observations, and a sensitivity analysis. This article discusses the mathematical and logical premises for the discussed model, and it proposes two methods for predicting numerical simulation results. Those methods are illustrated with examples which analyze the behavior of the Eulerian Multiphase Model and describe phase interactions based on Gidaspow's approach. The discussed example relies on data from a series of articles published by the authors in Drying Technology. This article was inspired by the observations made during a time-consuming process of modeling a spouted bed grain dryer, which was described in the above publications. The objective of this study was to discuss the advantages and possibilities created by sensitivity analyses of numerical models and to encourage their practical application. 相似文献
14.
15.
Karin Schwarz Hedda Ernst Waldemar Ternes 《Journal of the science of food and agriculture》1996,70(2):217-223
The non-polar fraction of thyme was examined for the occurrence of phenolic components and their antioxidative activity. In addition to carvacrol ( II ) and thymol ( III ), p -cymene-2,3-diol (I ; 2,3-dihydroxy-4-isopropyl-1-methylbenzene) was isolated for the first time from thyme. The structure of I was elucidated using 1H nuclear magnetic resonance (NMR), 13C NMR, and mass spectrometry. Antioxidative activity was investigated with the Rancimat method (100°C) and the Schaal test (60°C). Compound I exhibited the strongest antioxidative activity which was greater than that of α-tocopherol and butylated hydroxyanisole. Five thyme species were analysed by means of HPLC with electrochemical detection for the concentration of compounds I – III . The highest amounts of I – III were found in Thymus vulgaris L. 相似文献
16.
Justyna Zygmuntowicz Paweł Falkowski Marcin Wachowski Konrad Cymerman Paulina Piotrkiewicz Waldemar Kaszuwara 《International Journal of Applied Ceramic Technology》2020,17(4):1731-1741
In the present research, the influence of sintering temperature on the microstructure and properties of Al2O3–Cu–Ni hybrid composites prepared by the Pulse Plasma Sintering (PPS) technique were described. In this research, three temperatures have been selected: 1250°C, 1300°C, and 1350°C. SEM observations were carried out to determine the distribution of the metallic phase in the composite depending on the sintering temperature. The conducted experiments and microscopic observations enabled a better understanding of the phenomena occurring between the ceramic matrix and metallic phase in the obtained materials. The mechanical properties like a hardness and fracture toughness were measured. The technology applied allowed us to obtain ceramic-metal composites with a homogeneous microstructure. It was found that the sintering temperature influences the selected physical and mechanical properties of the composites produced. It was found that samples produced at 1300°C are characterized by the highest relative density and the mechanical properties. 相似文献
17.
Influence of Molybdenum Silicide Additions on High-Temperature Oxidation Resistance of Silicon Nitride Materials 总被引:2,自引:0,他引:2
Hagen Klemm Katja Tangermann Christian Schubert Waldemar Hermel 《Journal of the American Ceramic Society》1996,79(9):2429-2435
The influence of additions of molybdenum disilicide (MoSi2 ) on the microstructure and the mechanical properties of a silicon nitride (Si3 N4 ) material, with neodymium oxide (Nd2 O3 ) and aluminum nitride (AIN) as sintering aids, was studied. The composites, containing 5, 10, and 17.6 wt% MoSi2 , were fabricated by hot pressing. All materials exhibited a similar phase composition, detected by X-ray diffractometry. Up to MoSi2 additions of 10 wt%, mechanical properties such as strength, fracture toughness, or creep at 1400°C were not affected significantly, in comparison to that of monolithic Si3 N4 . The oxidation resistance of the composites, in terms of weight gain, degraded. After 1000 h of oxidation at 1400° and 1450°C in air, a greater weight gain (by a factor of approximately three) was obtained, in comparison to that of the material without MoSi2 . Nevertheless, after 1000 h of oxidation, the degradation in strength of the composites was considerably less severe than that of the material without MoSi2 . An additional layer was formed, caused by processes at the surface of the Si3 N4 material, preventing the formation of pores, cracks, or glassy-phase-rich areas, which are common features of oxidation damage in Si3 N4 materials. This surface layer, containing Mo5 Si3 and silicon oxynitride (Si2 ON2 ), was the result of reactions between MoSi2 , Si3 N4 , and the oxygen penetrating by diffusion into the material during the hightemperature treatment. 相似文献
18.
Maria Tynek Roman Pawłowicz Justyna Gromadzka Robert Tylingo Waldemar Wardencki Gyorgy Karlovits 《European Journal of Lipid Science and Technology》2012,114(3):357-366
The aim of the present study was to compare different rape varieties. For this purpose oil from six different varieties of rapeseeds was cold pressed under laboratory conditions. In the obtained rapeseed oils the fatty acids composition and minor components, characteristic values (acid value; AV and TOTOX), oxidative stability (DSC test), and volatiles were determined and a sensory evaluation was carried out. The highest oxidative stability was found for oil from sample 5 (IP = 158 min), which also has the lowest amount of C18:3 (7.8%), chlorophylls (0.083 mg/kg), and metals (Cu2+ 0.02 mg/kg and Fe2+ 0.08 mg/kg). This oil has also the lowest AV (0.17 mg KOH/g), which may be related to the lowest moisture content of the seeds prior to extraction. It was characterized by the highest rapeseed flavor intensity. The lowest induction period was observed for samples 3 and 6 (100 min). Although sample 3 had the same low level of metals as sample 5 and the highest concentration of tocopherols (635 mg/kg), PUFA (33.9%), and AV (1.37 mg KOH/g) it also had the lowest intensity of rapeseed flavor among the analyzed oils. Sample 6, despite its low percentage of PUFA (24.7%), conjugated diens and triens, and the lowest content of total volatiles (0.4Vs), had the highest concentration of metals (Cu2+ 0.04 mg/kg and Fe2+ 0.34 mg/kg). 相似文献
19.
The reliability and validity of self-reported assessment of exposure and outcome variables were examined for manual lifting activities among ten physiotherapists. In this study, the participants evaluated the effects of five lifting variables on perceived effort, twice separated by a one-week period. One hundred and sixty-two lifting conditions were evaluated by each subject. The exposure and outcome lifting variables were described in linguistic terms. Intra-class correlation coefficient (ICC(1,1)) analysis revealed a mean value of 0.62 for all lifting activities. The self-reported assessment was cross-validated with the NIOSH lifting index by mapping the linguistic variables into numerical ranges. Moderate correlations (r = 0.54 and 0.53, p<0.01) were obtained between perceived physical exertion/perceived risk and lifting index. The findings of this study provide preliminary indications that human-based methodologies may be further explored on experienced workers. 相似文献
20.
Erläuterung der Methoden zur Ermittlung mechanischer Spannungen unter besonderer Berücksichtigung der räumlichen Verhältnisse bei der Röntgenmessung. Darstellung der Verformungsgeometrie und der daraus abgeleiteten Meßverfahren. Vergleichende Gegenüberstellung des Röntgen-φ-Integralverfahrens mit dem Röntgen-ψ-Integralverfahren. 相似文献