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排序方式: 共有67条查询结果,搜索用时 46 毫秒
31.
Recently, we proposed a chaos control strategy with weak Fourier signals optimized by using a genetic algorithm (GA) and demonstrated its merits in controlling Lorenz and Rössler systems (Physical Review E, 2004). In this continuation work, performance of various types of signals, namely periodic continuous, periodic discrete, and constant bias (non-periodic), applied to an autonomous (Rössler) system and a non-autonomous (Murali–Lakshmanan–Chua, MLC) system are investigated. An index of relative robustness is proposed for measuring the noise-resisting ability of the control signals. The results reveal that the constant signal has the strongest noise-resisting ability, the periodic pulse signal has the weakest, and the Fourier signal falls in between. Phase modulation generally shortens the transient time period and is additionally beneficial to non-autonomous systems in minimizing significantly the signal power. By searching with the present GA-optimization, it is demonstrated that the minimum-power signal for controlling the non-autonomous (MLC) system is the signal with a frequency exactly the same as that of the system forcing but with phase modulation. The effectiveness of the GA-optimized signals of extremely low power employed in alternatively switching control of non-autonomous systems is also demonstrated. 相似文献
32.
Yu-Hung?Chang Shang-Chieh?Ting Chieh-Cheng?Liu Jing-Tang?YangEmail author Chyi-Yeou?Soong 《Experiments in fluids》2011,51(5):1231-1243
An unconventional mechanism of ventral clap is exploited by hovering passerines to produce lift. Quantitative visualization
of the wake flow, analysis of kinematics and evaluation of the transient lift force was conducted to dissect the biomechanical
role of the ventral clap in the asymmetrical hovering flight of passerines. The ventral clap can first abate and then augment
lift production during the downstroke; the net effect of the ventral clap on lift production is, however, positive because
the extent of lift augmentation is greater than the extent of lift abatement. Moreover, the ventral clap is inferred to compensate
for the zero lift production of the upstroke because the clapping wings induce a substantial elevation of the lift force at
the end of the downstroke. Overall, our observations shed light on the aerodynamic function of the ventral clap and offer
biomechanical insight into how a bird hovers without kinematically mimicking hovering hummingbirds. 相似文献
33.
J. Fan Z.H. Lee W.C. Ng W.L. Khoa S.H. Teoh T.H. Soong Y.R. Qin Z.Y. Zhang X.P. Li 《Journal of magnetism and magnetic materials》2012
This study aimed to investigate the effect of low frequency and high amplitude pulse magnetic field (PMF) on Calcium ion channel current of cells. Measurements were done on the Human Embryonic Kidney 293 cells (HEK 293), which have only Calcium ion channels functioning. The whole cell current was measured by patch clamp method, with the clamped voltage ramping from −90 mV to +50 mV across the cell membrane. A PMF was generated by a 400-turn coil connected to a pulse current generator. The frequency of the pulse was 7 Hz, the width of the pulse was 3 ms, and the amplitude of the pulse, or the flux density, was ranging from 6 to 25 mT. The results showed that the profile of the whole cell Calcium channel current could be modified by the PMF. With the PMF applied, the phase shifting occurred: the onset of the channel opening took place several mili-seconds earlier than that without the PWF and correspondingly, the whole cell current reached its maximum earlier, and the current returned back to zero earlier as well. When the PWF was stopped, these effects persisted for a period of time, and then the current profile “recovered” to its original appearance. The decrease of the onset time and peak current time could be due to the local electric potential induced by the PWF and the direct interaction between PMF and ion channels/ions. The exact mechanisms of the observed effects of PMF on the cell are still unknown and need to be further studied. 相似文献
34.
Ronald Soong Yalda Liaghati Mobarhan Maryam Tabatabaei Monica Bastawrous Rajshree Ghosh Biswas Myrna Simpson Andre Simpson 《Magnetic resonance in chemistry : MRC》2020,58(5):411-426
NMR applied to living organisms is arguably the ultimate tool for understanding environmental stress responses and can provide desperately needed information on toxic mechanisms, synergistic effects, sublethal impacts, recovery, and biotransformation of xenobiotics. To perform in vivo NMR spectroscopy, a flow cell system is required to deliver oxygen and food to the organisms while maintaining optimal line shape for NMR spectroscopy. In this tutorial, two such flow cell systems and their constructions are discussed: (a) a single pump high-volume flow cell design is simple to build and ideal for organisms that do not require feeding (i.e., eggs) and (b) a more advanced low-volume double pump flow cell design that permits feeding, maintains optimal water height for water suppression, improves locking and shimming, and uses only a small recirculating volume, thus reducing the amount of xenobiotic required for testing. In addition, key experimental aspects including isotopic enrichment, water suppression, and 2D experiments for both 13C enriched and natural abundance organisms are discussed. 相似文献
35.
Bing Wu Sebastian von der Ecken Ian Swyer Chunliang Li Amy Jenne Franck Vincent Daniel Schmidig Till Kuehn Armin Beck Falko Busse Henry Stronks Ronald Soong Aaron R. Wheeler Andr Simpson 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(43):15516-15520
Microcoil nuclear magnetic resonance (NMR) has been interfaced with digital microfluidics (DMF) and is applied to monitor organic reactions in organic solvents as a proof of concept. DMF permits droplets to be moved and mixed inside the NMR spectrometer to initiate reactions while using sub‐microliter volumes of reagent, opening up the potential to follow the reactions of scarce or expensive reagents. By setting up the spectrometer shims on a reagent droplet, data acquisition can be started immediately upon droplet mixing and is only limited by the rate at which NMR data can be collected, allowing the monitoring of fast reactions. Here we report a cyclohexene carbonate hydrolysis in dimethylformamide and a Knoevenagel condensation in methanol/water. This is to our knowledge the first time rapid organic reactions in organic solvents have been monitored by high field DMF‐NMR. The study represents a key first step towards larger DMF‐NMR arrays that could in future serve as discovery platforms, where computer controlled DMF automates mixing/titration of chemical libraries and NMR is used to study the structures formed and kinetics in real time. 相似文献
36.
J.W. Blunt M.P. Hartshorn M.H.G. Munro Lee Tin Soong R.W. Vannoort 《Tetrahedron letters》1981,22(22):2143-2144
Lithium aluminium hydride reduction of methoxyalkynol(1) yields cyclopropane derivatives (2) and (3), both formed by loss of a methoxy group; a reaction scheme for their formation is presented. 相似文献
37.
Preparation of Cu nanoparticles with controlled particle size and distribution via reaction temperature and sonication 下载免费PDF全文
Sangyoon Lee Hakyung Jeong Youngwook Noh Soong Keun Hyun Dongjin Lee Changhyun Jin 《Surface and interface analysis : SIA》2017,49(5):405-409
This paper presents metallic copper nanoparticles (CuNPs) that differ according to the process parameters used, such as bath temperature and sonication. The effect of different reactions on the size and distribution of CuNPs that had been formed in ethylene glycol solvent were characterized by the X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses after extraction from the solvent. The optimal dimensional properties, including size, distribution, and agglomeration, of CuNPs were determined by controlling the reaction temperature. On the other hand, the mechanically induced sonication process enhances the formation of the selective CuNPs because of the many homogeneous interactions among precursors, reducing agents, and capping agents related to the nucleation and growth of CuNPs. The mechanics of the origin of the diverse CuNPs of different size and distribution are discussed. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
38.
Valentina?KlimenokEmail author Che?Soong?Kim Dmitry?Orlovsky Alexander?Dudin 《Queueing Systems》2005,49(2):187-213
The BMAP/PH/N/0 model with three different disciplines of admission (partial admission, complete rejection, complete admission) is investigated.
Loss probability is calculated. Impact of the admission discipline, variation and correlation coefficients of inter-arrival
times distribution, and variation of service times distribution on loss probability is analyzed numerically. As by-product,
it is shown by means of numerical results that the invariant property of the famous Erlang M/G/N/0 system, which was proven by B. A. Sevastjanov, is absent in case of the MAP input.
AMS subject classification: Primary 60K25, 60K20
This revised version was published online in June 2005 with corrected coverdate 相似文献
39.
Steven S. C. Chuang Yee Soong Richard P. Noceti Richard R. Schehl 《Reaction Kinetics and Catalysis Letters》1992,48(1):31-36
The presence of Cu on Rh/SiO2 inhibited H2 chemisorption at 303 K and suppressed CO hydrogenation. TPD study shows that chemisorption of H2 on Cu–Rh/SiO2 is an activated process at 303 K.
Cu Rh/SiO2 H2 303 CO. , H2 Cu–Rh/SiO2 303 .相似文献
40.
Vincent Moxley-Paquette Bing Wu Daniel Lane Monica Bastawrous Paris Ning Ronald Soong Peter De Castro Ivan Kovacevic Thomas Frei Juerg Stuessi Danijela Al Adwan-Stojilkovic Stephan Graf Franck Vincent Daniel Schmidig Till Kuehn Rainer Kuemmerle Armin Beck Michael Fey Wolfgang Bermel Falko Busse Marcel Gundy Holger Boenisch Hermann Heumann Ben Nashman Rudraksha Dutta Majumdar Andressa Lacerda André J. Simpson 《Magnetic resonance in chemistry : MRC》2022,60(3):386-397
Microcoils provide a cost-effective approach to improve detection limits for mass-limited samples. Single-sided planar microcoils are advantageous in comparison to volume coils, in that the sample can simply be placed on top. However, the considerable drawback is that the RF field that is produced by the coil decreases with distance from the coil surface, which potentially limits more complex multi-pulse NMR pulse sequences. Unfortunately, 1H NMR alone is not very informative for intact biological samples due to line broadening caused by magnetic susceptibility distortions, and 1H-13C 2D NMR correlations are required to provide the additional spectral dispersion for metabolic assignments in vivo or in situ. To our knowledge, double-tuned single-sided microcoils have not been applied for the 2D 1H-13C analysis of intact 13C enriched biological samples. Questions include the following: Can 1H-13C 2D NMR be performed on single-sided planar microcoils? If so, do they still hold sensitivity advantages over conventional 5 mm NMR technology for mass limited samples? Here, 2D 1H-13C HSQC, HMQC, and HETCOR variants were compared and then applied to 13C enriched broccoli seeds and Daphnia magna (water fleas). Compared to 5 mm NMR probes, the microcoils showed a sixfold improvement in mass sensitivity (albeit only for a small localized region) and allowed for the identification of metabolites in a single intact D. magna for the first time. Single-sided planar microcoils show practical benefit for 1H-13C NMR of intact biological samples, if localized information within ~0.7 mm of the 1 mm I.D. planar microcoil surface is of specific interest. 相似文献