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871.
872.
The design and performance of millimeter-wave microstrip/suspended-stripline end-coupled bandpass filters are presented. Filters in Ka-band (26.5 to 40 GHz) and W-band (75 to 110 GHz) using suspended-stripline and microstrip have been designed. Good agreement between the experimental results and those predicted theoretically was observed. Measured passband insertion losses of less than 1 and 0.5 dB have been achieved in W- and Ka-band, respectively. An extremely wideband waveguide-to-microstrip transition with an insertion loss of 0.25 dB over the full W-band is also presented. 相似文献
873.
Chemical unfolding of bovine testicular hyaluronidase (HAase) has been studied by fluorescence spectroscopy and Fourier transformed
infrared spectroscopy (FTIR). Thermodynamic parameters were determined for unfolding HAase from changes in the intrinsic fluorescence
emission intensity and the formations of several possible unfolding intermediates have been identified. This was further confirmed
by representation of fluorescence data in terms of ‘phase diagram’. The secondary structures of HAase have been assigned and
semiquantitatively estimated from the FTIR. The occurrence of conformational change during chemical unfolding as judged by
fluorescence and FTIR spectroscopy indicated that the unfolding of HAase may not follow the typical two-state model. 相似文献
874.
Radical cyclization of vinyl iodides in 6-(pi-exo)-exo-dig mode were effected by SmI2 to give exo-cyclic dienes fused to six-membered rings. 相似文献
875.
Wang Z Kai G Liu Y Liu J Zhang C Sun T Wang C Zhang W Yuan S Dong X 《Optics letters》2005,30(19):2542-2544
Coupling characteristics of dual-core photonic bandgap fibers with triangular photonic crystal cladding are investigated by use of a vector plane-wave expansion method and a vector finite-element method. We demonstrate the eigenmodes and the coupling length for two orthogonal polarizations. A decoupling phenomenon is found at a certain wavelength in this fiber configuration. The decoupling effect is attributed to the effect of surface modes on the eigenmodes. The decoupling wavelength decreases as the ratio of core radius to cladding air-hole pitch increases from 1.05 to 1.15. 相似文献
876.
Guoqing?MiaoEmail author Kai?Huang Yi?Yun Rongjue?Wei 《The European Physical Journal B - Condensed Matter and Complex Systems》2004,40(3):301-304
We present a granular-hydrodynamic model that captures the essence of convection in a fully vibrofluidized granular system. The steady temperature distribution is solved analytically. Numerical simulation shows that the convection always develops through a supercritical bifurcation, with its energy about
of the random (heat) one. A comparison calculation is performed for a normal fluid. The convection roll, or an active roll as we call it, has an angular velocity gradient from its interior to exterior. We conclude that active rolls are universal.Received: 25 March 2004, Published online: 9 September 2004PACS:
45.70.Mg Granular flow: mixing, segregation and stratification - 47.20.Bp Buoyancy-driven instability - 47.27.Te Convection and heat transfer 相似文献
877.
Mylon SE Chen KL Elimelech M 《Langmuir : the ACS journal of surfaces and colloids》2004,20(21):9000-9006
The stability and aggregation behavior of iron oxide colloids in natural waters play an important role in controlling the fate, transport, and bioavailability of trace metals. Time-resolved dynamic light scattering experiments were carried out in a study of the aggregation kinetics and aggregate structure of natural organic matter (NOM) coated hematite colloids and bare hematite colloids. The aggregation behavior was examined over a range of solution chemistries, by adjusting the concentration of the supporting electrolyte-NaCl, CaCl2, or simulated seawater. With the solution pH adjusted so that NOM-coated and bare hematite colloids were at the same zeta potential, we observed a significant difference in colloid stability which results from the stability imparted to the colloids by the adsorbed NOM macromolecules. This enhanced stability of NOM-coated hematite colloids was not observed with CaCl2. Aggregate form expressed as fractal dimension was determined for both NOM-coated and bare hematite aggregates in both NaCl and CaCl2. The fractal dimensions of aggregates formed in the diffusion-limited regime indicate slightly more loosely packed aggregates for bare hematite than theory predicts. For NOM-coated hematite, a small decrease in fractal dimension was observed when the solution composition changed from NaCl to CaCl2. For systems in the reaction-limited regime, the measured fractal dimensions agreed with those in the literature. Colloid aggregation was also studied in synthetic seawater, a mixed cation system to simulate estuarine mixing. Those results describe the important phenomena of iron oxide aggregation and sedimentation in estuaries. When compared to field data from the Mullica Estuary, U.S.A., it is shown that collision efficiency is a good predictor of the iron removal in this natural system. 相似文献
878.
879.
A ray model is developed and validated for the prediction of the insertion loss of barriers that are placed in front of a tall building in high-rise cities. The model is based on the theory of geometrical acoustics for sound diffraction at the edge of a barrier and multiple reflections by the barrier and fa?ade surfaces. It is crucial to include the diffraction and multiple reflection effects in the ray model, as they play important roles in determining the overall sound pressure levels for receivers located between the fa?ade and barrier. Comparisons of the ray model with indoor experimental data and wave-based boundary element formulation show reasonably good agreement over a broad frequency range. Case studies are also presented that highlight the significance of positioning the barrier relative to the noise-sensitive receivers in order to achieve improved shielding efficiency of the barrier. 相似文献
880.
In the short treatise De Motu (1684),which serves as a precursor to the Principia Mathematica (1687),Newton essentially deals with the following two problems. 相似文献