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131.
Huang L Choy YS So RM Chong TL 《The Journal of the Acoustical Society of America》2000,108(2):624-631
Propagation of sound in a flexible duct is investigated both theoretically and experimentally. Strong coupling of sound and flexural waves on the duct wall is found when the wall-to-air mass ratio is of the order of unity. The axial phase speed of sound approaches the in vacuo speed of flexural waves (subsonic in this case) at low frequencies. However, a speed higher than the isentropic sound speed in free space (340 m/s) is found beyond a critical frequency which is a function of the mass ratio. Experiments using a duct with a finite section of tensioned membrane are compared with the propagating modes pertaining to the infinite membrane model. Satisfactory quantitative agreement is obtained and the measured phase speed ranges from 8.3 to 1348 m/s. In the moderate frequency range, the theory predicts high spatial damping rate for the subsonic waves, which is consistent with the experimental observation that subsonic waves become increasingly undetectable as the frequency increases. Substantial sound reflection is observed at the interface between the rigid and the flexible segments of the duct without cross-section discontinuity, which, together with the high spatial damping, could form a basis for passive control of low-frequency duct noise. 相似文献
132.
133.
Gyeonghee Nam Chu-Shik Kang Hun-Young So JongOh Choi 《Accreditation and quality assurance》2009,14(1):43-47
After a measurement, a measured value and a measurement uncertainty are produced as a measurement result. By a repeated measurement,
another measurement result is produced. Between the individual results of the two measurements, it is shown that there may
be a significant correlation. A correlation coefficient can be determined when a GUM-compliant uncertainty budget for a measurement
is available. Utilizing the correlations between the N individual results, an equation is derived to combine the N individual uncertainties of N measurements. Using the newly derived equation including the correlation coefficient, three measurement uncertainties of
three measurement results are combined as an example. The combined uncertainty is compared with the uncertainty of a measurement
which treats the three individual measurements as one process.
Papers published in this section do not necessarily reflect the opinion of the editors, the editorial board, or the publisher. 相似文献
134.
Dongling Zhou Dr. Wai-Pong To Dr. Glenna So Ming Tong Dr. Gang Cheng Dr. Lili Du Prof. Dr. David Lee Phillips Prof. Dr. Chi-Ming Che 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(16):6437-6444
Structurally robust tetradentate gold(III)-emitters have potent material applications but are rare and unprecedented for those displaying thermally activated delayed fluorescence (TADF). Herein, a novel synthetic route leading to the preparation of highly emissive, charge-neutral tetradentate [C^C^N^C] gold(III) complexes with 5-5-6-membered chelate rings has been developed through microwave-assisted C−H bond activation. These complexes show high thermal stability and with emission origin (3IL, 3ILCT, and TADF) tuned by varying the substituents of the C^C^N^C ligand. With phenoxazine/diphenylamine substituent, we prepared the first tetradentate gold(III) complexes that are TADF emitters with emission quantum yields of up to 94 % and emission lifetimes of down to 0.62 μs in deoxygenated toluene. These tetradentate AuIII TADF emitters showed good performance in vacuum-deposited OLEDs with maximum EQEs of up to 25 % and LT95 of up to 5280 h at 100 cd m−2. 相似文献
135.
Suji Lee Ryeong Ha Kwon Ju Hyung Kim Hyemin Na So-Jeong Lee Yu-Mi Choi Hyemyeong Yoon So Young Kim Yong-Suk Kim Sang Hoon Lee Seon Mi Yoo Heon-Woong Kim Chi-Do Wee 《Molecules (Basel, Switzerland)》2022,27(13)
In this study, thirty-eight isoflavone derivatives were comprehensively identified and quantified from the raw, steamed and fermented seeds of four selected soybean cultivars based on UPLC-DAD-QToF/MS results with reference to the previously reported LC-MS library and flavonoid database, and summarized by acylated group including glucosides (Glu), malonyl-glucosides (Mal-Glu), acetyl-glucosides (Ac-Glu), succinyl-glucosides (Suc-Glu) and phosphorylated conjugates (Phos) in addition to aglycones. Among them, Suc-Glu and Phos derivatives were newly generated due to fermentation by B. subtilis AFY-2 (cheonggukjang). In particular, Phos were characterized for the first time in fermented soy products using Bacillus species. From a proposed roadmap on isoflavone-based biotransformation, predominant Mal-Glu (77.5–84.2%, raw) decreased rapidly by decarboxylation and deesterification into Ac-Glu and Glu (3.5–8.1% and 50.0–72.2%) during steaming, respectively. As fermentation continued, the increased Glu were mainly succinylated and phosphorylated as well as gradually hydrolyzed into their corresponding aglycones. Thus, Suc-Glu and Phos (17.3–22.4% and 1.5–5.4%, 36 h) determined depending on cultivar type and incubation time, and can be considered as important biomarkers generated during cheonggukjang fermentation. Additionally, the changes of isoflavone profile can be used as a fundamental report in applied microbial science as well as bioavailability research from fermented soy foods. 相似文献
136.
We consider the angle of inclination (with respect to the horizontal) of the profile of a steady 2D inviscid symmetric periodic or solitary water wave subject to gravity. There is an upper bound of 31.15° in the irrotational case [1] and an upper bound of 45° in the case of favorable vorticity [13]. On the other hand, if the vorticity is adverse, the profile can become vertical. We prove here that if the adverse vorticity is sufficiently small, then the angle still has an upper bound which is slightly larger than 45°. 相似文献
137.
So Hee Yoon Jeong Hee Moon Yeon Ji Chung Myung Soo Kim 《Journal of mass spectrometry : JMS》2009,44(10):1532-1537
Product ion yields in postsource decay and time‐resolved photodissociation at 193 and 266 nm were measured for some peptide ions with lysine ([KF6 + H]+, [F6K + H]+, and [F3KF3 + H]+) formed by matrix‐assisted laser desorption ionization. The critical energy (E0) and entropy (ΔS?) were determined by RRKM fitting of the data. The results were similar to those found previously for peptide ions with histidine. To summarize, the presence of a basic residue, histidine or lysine, inside a peptide ion retarded its dissociation by lowering ΔS?. On the basis of highly negative ΔS?, presence of intramolecular interaction involving a basic group in the transition structure was proposed. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
138.
Cross-benzoin condensation catalyzed by NHC, prepared from chiral triazolium salts bearing a pyridine ring, afforded α-hydroxy ketones with reasonable chemical yields and enantioselectivities. A wide range of aliphatic and aromatic aldehydes were successfully used in the reaction. 相似文献
139.
Standing-wave total-internal-reflection fluorescence (SW-TIRF) microscopy uses a super-diffraction-limited standing evanescent wave to extract the high-spatial-frequency content of an object through a diffraction-limited optical imaging system. The effective point-spread function is better than a quarter of the emission wavelength. With a 1.45 numerical aperture objective and 532 nm excitation wavelength, a Rayleigh resolution of approximately 100 nm can be achieved, which is better than twice the resolution of conventional TIRF microscopy. This first experimental realization of SW-TIRF in an objective-launched geometry demonstrates the potential for extended resolution imaging at high speed by using wide-field microscopy. 相似文献
140.
Gas-liquid chromatography was applied in thermodynamic investigations of processes of complexation and enantioseparation by alpha- and [-cyclodextrins of chiral monoterpenoids. The distribution constants, stability constants and thermodynamic parameters enthalpy, entropy and free energy of the complexation processes were determined. It has been found that enantioseparation of monoterpenes by alpha- and beta-cyclodextrins is the result of formation of 1:2 stoichiometric complexes. When 1:1 stoichiometric complexes are formed, enantioselectivity is not observed. All investigated processes of complexation are enthalpy-driven regardless of the stoichiometry of the formed complexes. -deltaH, -TdeltaS and -deltaG of complexation process have higher values for bicyclic than for monocyclic monoterpenoids as well as for alpha-CD than for beta-CD. The first or second step of complexation may be responsible for enantioselectivity. 相似文献