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排序方式: 共有170条查询结果,搜索用时 31 毫秒
31.
Alexander I Balabanovich Ala M Balabanovich Jochen Engelmann 《Polymer International》2003,52(8):1309-1314
The flame‐retardant effect of 2‐methyl‐1,2‐oxaphospholan‐5‐one 2‐oxide (OP) and ammonium polyphosphate (APP) in poly(butylene terephthalate) (PBT) was studied by the limiting oxygen index and the UL94 test. A self‐extinguishing formulation (V‐0 rating) was achieved by the addition of 15 wt% APP and 10 wt% OP. The fire‐retardant effect was attributed to the condensed‐phase mechanism of intumescence. Mechanistic studies were performed using thermogravimetry, IR characterization of solid residues and GC–MS characterization of the gaseous and high‐boiling products. OP–APP was shown to cause ammonolysis of PBT, formation of aromatic nitriles in the high‐boiling products and phosphorus ester groups and polyphosphoric acid–phosphorus pentaoxide in the solid residue. Copyright © 2003 Society of Chemical Industry 相似文献
32.
PJ Ala EE Huston RM Klabe PK Jadhav PY Lam CH Chang 《Canadian Metallurgical Quarterly》1998,37(43):15042-15049
The long-term therapeutic benefit of HIV antiretroviral therapy is still threatened by drug-resistant variants. Mutations in the S1 subsite of the protease are the primary cause for the loss of sensitivity toward many HIV protease inhibitors, including our first-generation cyclic urea-based inhibitors DMP323 and DMP450. We now report the structures of the three active-site mutant proteases V82F, I84V, and V82F/I84V in complex with XV638 and SD146, two P2 analogues of DMP323 that are 8-fold more potent against the wild type and are able to inhibit a broad panel of drug-resistant variants [Jadhav, P. K., et al. (1997) J. Med. Chem. 40, 181-191]. The increased efficacy of XV638 and SD146 is due primarily to an increase in P2-S2 interactions: 30-40% more van der Waals contacts and two to four additional hydrogen bonds. Furthermore, because these new interactions do not perturb other subsites in the protease, it appears that the large complementary surface areas of their P2 substituents compensate for the loss of P1-S1 interactions and reduce the probability of selecting for drug-resistant variants. 相似文献
33.
Relief holograms are obtained on Agfa 8E56HD holographic emulsions by a Russian chemical-processing technique that is developed for their PE-2 holographic emulsion. We have shown that the three-dimensional surface profiles can easily be visualized by applying atomic force microscopy to measurement of the relief depth and relief spacing on holographic emulsions. The relief depth and thus diffraction efficiency decreases with increasing exposure time. 相似文献
34.
A.L. Nemmour F. Mehazzem A. Khezzar M. Hacil L. Louze R. Abdessemed 《Renewable Energy》2010,35(10):2375-2380
This paper presents a new non-linear control Algorithm based on the Backstepping approach for an isolated induction generator (IG) driven by a wind turbine. For this purpose and in order to reduce the complexity of the real induction machine mathematical model, the multi-scalar machine model is exploited. The machine delivers an active power to the load via a converter connected to a single capacitor on the dc-side. So, during the voltage build-up process, the necessary stator currents references to be injected by the converter are calculated from the desired active power to be sent to the load and the rotor flux magnitude. Simulation results show that the proposed control provides perfect tracking performances of the DC-bus voltage and the rotor flux magnitude to their reference trajectories. 相似文献
35.
Zidani F. Nait-Said M.S. Benbouzid M.E.H. Diallo D. Abdessemed R. 《Power Engineering Review, IEEE》2001,21(11):25-25
This letter presents a method for induction motor on-line rotor resistance estimation. This is important in vector control, if high-performance torque control is needed. For this purpose, a fuzzy logic technique is used to estimate the rotor resistance. The fuzzy estimator (FE) principle design is then presented, and simulations demonstrate the effectiveness of the proposed method. 相似文献
36.
Wisam Al-Faqheri Tzer Hwai Gilbert Thio Mohammad Ameen Qasaimeh Andreas Dietzel Marc Madou Ala’aldeen Al-Halhouli 《Microfluidics and nanofluidics》2017,21(6):102
Particle/cell separation in heterogeneous mixtures including biological samples is a standard sample preparation step for various biomedical assays. A wide range of microfluidic-based methods have been proposed for particle/cell sorting and isolation. Two promising microfluidic platforms for this task are microfluidic chips and centrifugal microfluidic disks. In this review, we focus on particle/cell isolation methods that are based on liquid centrifugation phenomena. Under this category, we reviewed particle/cell sorting methods which have been performed on centrifugal microfluidic platforms, and inertial microfluidic platforms that contain spiral channels and multi-orifice channels. All of these platforms implement a form of centrifuge-based particle/cell separation: either physical platform centrifugation in the case of centrifugal microfluidic platforms or liquid centrifugation due to Dean drag force in the case of inertial microfluidics. Centrifugal microfluidic platforms are suitable for cases where the preparation step of a raw sample is required to be integrated on the same platform. However, the limited available space on the platform is the main disadvantage, especially when high sample volume is required. On the other hand, inertial microfluidics (spiral and multi-orifice) showed various advantages such as simple design and fabrication, the ability to process large sample volume, high throughput, high recovery rate, and the ability for multiplexing for improved performance. However, the utilization of syringe pump can reduce the portability options of the platform. In conclusion, the requirement of each application should be carefully considered prior to platform selection. 相似文献
37.
Khalifeh Ala’ F. Al-Taee Majid A. Murshed Ayman N. 《Multimedia Tools and Applications》2017,76(24):26129-26152
Multimedia Tools and Applications - Video streaming over Internet has been gaining momentum and several quality adaptation schemes have been reported to improve quality of the streamed videos. Most... 相似文献
38.
María Elena Alañón María Consuelo Díaz‐Maroto María Soledad Pérez‐Coello 《International Journal of Food Science & Technology》2012,47(4):816-826
The analysis of the volatile profile of different oak chips carried out by gas chromatography–mass spectrometry after their isolation by accelerated solvent extraction permitted faster and thorough extractions, while the appearance of artefacts was avoided. Statistical analysis revealed that toasting treatment is the main factor for the volatile compounds with a great sensorial impact. Indeed, toasting process overrode the differences between species. Furthermore, it was evidenced that the toasting treatment is not a homogeneity process. Concentrations of furaneol, 2,3‐dihydro‐3,5‐dihydroxy‐6‐methyl‐4H‐pyran‐4‐one and 5‐hydroxymethylfurfural could be used to monitor the intensity of the toasting process. Differences in the volatile composition with respect to species were also found, being the most remarkable the high concentration of trans and cis‐β‐methyl‐γ‐octanolactone in oak chips from Quercus alba and Quercus petraea species. The differences found in the volatile composition of different commercial oak chips evidenced the necessity to know their chemical composition previously to predict their aromatic potential. 相似文献
39.
Vladimir Sankin Alexandr Andrianov Alexey Petrov Alexey Zakhar‘in Ala Lepneva Pavel Shkrebiy 《Nanoscale research letters》2012,7(1):560
We report on efficient terahertz (THz) emission from high-electric-field-biased SiC structures with a natural superlattice at liquid helium temperatures. The emission spectrum demonstrates a single line, the maximum of which shifts linearly with increases in bias field. We attribute this emission to steady-state Bloch oscillations of electrons in the SiC natural superlattice. The properties of the THz emission agree fairly with the parameters of the Bloch oscillator regime, which have been proven by high-field electron transport studies of SiC structures with natural superlattices. 相似文献
40.
Ala Abbas M. Emin Kutay Haleh Azari Robert Rasmussen 《Computer-Aided Civil and Infrastructure Engineering》2007,22(3):197-209
Abstract: This article investigates the effectiveness of different mathematical methods in describing the three-dimensional surface texture of Portland cement concrete (PCC) pavements. Ten PCC field cores of varying surface textures were included in the analysis. X-ray Computed Tomography (CT) was used to scan the upper portion of these cores, resulting in a stack of two-dimensional grayscale images. Image processing techniques were utilized to isolate the void pixels from the solid pixels and reconstruct the three-dimensional surface topography. The resulting three-dimensional surfaces were reduced to two-dimensional "map of heights" images, whereby the grayscale intensity of each pixel within the image represented the vertical location of the surface at that point with respect to the lowest point on the surface. The "map of heights" images were analyzed using four mathematical methods, namely the Hessian model, the Fast Fourier transform (FFT), the wavelet analysis, and the power spectral density (PSD). Results obtained using these methods were compared to the mean profile depth (MPD) computed in accordance with ASTM E1845 . 相似文献