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21.
Dynamics of milling processes with variable time delays 总被引:5,自引:0,他引:5
A milling-process model with a variable time delay associated with each cutting tooth is presented in this article. The source
of this variable time delay is the feed rate. The effect of the feed motion on the entry cutting angle, the exit cutting angle,
and the amplitude of feed mark is also discussed. Loss-of-contact effects are also considered. The system dynamics is described
by a set of delay differential equations with periodic coefficients and variable time delays. A semi-discretization scheme
is presented for analyzing the stability of periodic orbits of this system. The analysis provides evidence of period-doubling
bifurcations and secondary Hopf bifurcations. Good agreement is found between the numerical results obtained from this work
and the results of related experimental studies. 相似文献
22.
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24.
H. R. Schütte D. Gross H.-W. Liebisch U. Stephan 《Isotopes in environmental and health studies》2013,49(9-10):319-325
Es werden neuere Ergebnisse von Untersuchungen zur Biosynthese einiger Alkaloide und zum Stoffwechsel von Herbiziden mitgeteilt und diskutiert, die unter Verwendung von 14C, 3H und 15N durchgeführt wurden. 相似文献
25.
We numerically study the performance of the displacement based quantum receiver for the discrimination of weak 3- and 4-phase-shift keyed (PSK) coherent state signals. We show that due to the nontrivial asymmetry of the receiver structure, optimization of the prior probability increases the mutual information and achieves sub-shot-noise limit discrimination. Moreover, we estimate the cutoff rate for a 4-PSK signal and confirm that the prior probability optimization shortens the code length for a given decoding error criterion. Such consideration for the asymmetric channel matrix is essential in a study of the compassable quantum receiver. 相似文献
26.
为了多维度地培养学生的实践创新能力、终身学习能力及信息获取能力等核心素养,以具体实验为例,探讨结构性思维在生物化学实验教学中的综合应用。教学实践表明:结构性思维可使知识更有序、梯度更明确、更易表达,实验操作变得程序化,学生学习倾向主动,是一种多维度地培养学生核心素养的教学模式。 相似文献
27.
Olha Мykhailenko Sergiy Chetvernya Ivan Bezruk Yrii Buydin Nadija Dhurenko Olena Рalamarchuk Liudas Ivanauskas Victoriya Georgiyants 《Biomedical chromatography : BMC》2022,36(7):e5369
Iris genus plants are a valuable source of bioactive compounds, which are an important component for pharmaceutical development. The present article shows the potential for mineral nutrition with application of magnesium sulfate, iron chelates and potassium oxide affecting the phenolic compound contents in Iris hybrida ‘Tsikavynka’, I. hybrida ‘Tambo’ and I. hybridа ‘Widecombe Fire’. The effect of mineral processing was specific to plant organs and varied in the component composition. The Iris rhizomes had an increased total phenolic compound content after treatment (up to 10% of the total isoflavonoid content, up to 8% of phenolic acids, up to 5% of γ-pyrones and up to 13% of flavonoids), determined using UV–vis spectroscopy. A positive effect of nutrition on the biosynthesis and content of individual isoflavonoids (tectoridin, nigricin d -glucoside, genistin, iristectorigenin B, nigricin, irigenin and irisolidone) and xanthone mangiferin in Iris rhizomes by HPLC was established. In addition, an increase in the chlorogenic acid amount in Iris leaves was noted. The results demonstrate the sensitivity of Iris phenylpropanoid metabolism to mineral nutrition and can be used to predict medical plant cultivation with increased content of bioactive constituents. 相似文献
28.
Ty N. F. Roach 《Entropy (Basel, Switzerland)》2020,22(12)
Here, I discuss entropy and its use as a tool in fields of biology such as bioenergetics, ecology, and evolutionary biology. Statistical entropy concepts including Shannon’s diversity, configurational entropy, and informational entropy are discussed in connection to their use in describing the diversity, heterogeneity, and spatial patterning of biological systems. The use of entropy as a measure of biological complexity is also discussed, and I explore the extension of thermodynamic entropy principles to open, nonequilibrium systems operating in finite time. I conclude with suggestions for use of caliber, a metric similar to entropy but for time-dependent trajectories rather than static distributions, and propose the complementary notion of path information. 相似文献
29.
Nielen MW Lasaroms JJ Essers ML Oosterink JE Meijer T Sanders MB Zuidema T Stolker AA 《Analytical and bioanalytical chemistry》2008,391(1):199-210
The use of β-agonists as growth promoters in cattle breeding is forbidden in many countries for reasons of fair trade and
consumer protection. In recent years the use of liquid chromatography (LC) tandem mass spectrometry (MS/MS) has been shown
to be the method of choice for the control of β-agonists. In this study an LC-MS/MS multiresidue analysis method is presented
for trace analysis of 22 β-agonists. A truly generic concept has been designed based on mixed-mode solid-phase extraction
and positive electrospray ionisation LC-MS/MS operated in the multiple reaction monitoring mode. This method allows application
to a wide variety of sample matrices such as urine, feed and hair, following minor modifications to the analysis procedure
only. The method features fit-for-purpose sensitivity in urine as shown by CCα and CCβ values of less than 0.2 and less than
0.5 μg/l respectively, for all β-agonists studied (terbutaline and reproterol, less than 0.3 and less than 1.0 respectively).
Similar but semiquantitative application to feed and hair showed CCβ values of less than 10.0 and less than 5.0 μg/kg, respectively.
A further simplification and improvement is demonstrated using Ultra Performance LC (UPLC™) and fast-switching MS/MS. The
successful validation of this method following the latest EU requirements and its application to real samples demonstrate
that a new versatile tool has been achieved for veterinary control of β-agonists. 相似文献
30.
有氧和无氧分解是生物体代谢有机物的2种途径,前者一直是生物化学课程中物质代谢的教学核心和重点。厌氧消化是有机物经无氧分解生成甲烷和二氧化碳的途径,相比于有氧分解,其具有化学反应众多、中间产物多、途径复杂等特点,同时对维护自然生态平衡、物质循环和人类社会的绿色健康发展等具有重要作用。如此重要的途径长期以来一直没有在生物化学教材与教学内容中体现,亟需进行教学改革。利用布鲁姆教学目标分类理论将厌氧消化过程中的主要反应、氧化还原过程及电子传递、热力学变化及串联反应等知识进行系统介绍,对物质代谢的另一条无氧路径进行补充,丰富了学生代谢网络的知识框架,完善了生物化学教学体系,相关教学内容和经验可供同行参考借鉴,对相关课程教学改革具有重要价值。 相似文献