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71.
Adaptive quantizers for PCM and DPCM coding of speech have been of great interest, and several excellent quantization strategies have evolved [1], [2]. In this paper we propose another algorithm for the step-size change in a quantizer. In the present strategy the quantizer is always a linear one except for the fact that the step size can be changed by a fixed amount at each sampling instant. This fixed value is also the minimum allowed step size. Hence, we have the name incremental adaptive quantizer. The quantizer has been simulated on a computer and its performance has been compared with that of Jayant's adaptive quantizer (JAQ), both in PCM and DPCM coders. The figure of merit used in the comparison is the signal-to-noise ratio (SNR) with a correlated sequence as the input. The preliminary results indicate that the new design can perform very well. However, it has the drawback of not being able to respond to very fast changes in the input. It can be easily realized in an integrated form using ROM's. 相似文献
72.
This correspondence presents expressions for the Mean Error-Free Interval in a packet-oriented data transmission system. In particular, the case of transmission through a random-error channel is studied, with some results also given for more general noisy channels. 相似文献
73.
Attempts are made to correlate the structure and properties of dense and porous Yittria Stabilized Zirconia to establish optimal
thermo-elastic properties for better performance at elevated temperatures. Temperature and compositional dependence of isotropic
elastic bulk properties (Young's modulus, Poisson's ratio and Shear and Bulk moduli) are determined using the stiffness constants
reported in the literature. Anisotropy of Yittria Stabilized Zirconia increases with composition of Yittria dosage in Zirconia.
Optimal composition of 12 mole% Yittria stabilized Zirconia is slightly better than 8 mole% Yittria Stabilized Zirconia based
on the improved thermo-elastic properties for better performance at higher temperature (RT-400°C). However 15.5 mole% YSZ
seems to be more suitable from the view point of thermo-elastic performance at elevated temperatures (500–800°C). Polycrystalline
properties predicted are within 5% error limits of the experimental values for Young's modulus of 12 mole% Yittria Stabilized
Zirconia. Numerical prediction of Young's modulus of 12 mole% YSZ for 〈100〉 orientation is 362 GPa as compared to experimental
value of 370 GPa reported in literature. 相似文献
74.
Blends of fluorocarbon elastomer (FKM) and liquid crystalline polymer (LCP) have been prepared by the melt mixing technique. Processing studies indicated the increase in viscosity with the addition of LCP. The tensile strength, tear strength, and modulus of the elastomer are greatly improved by the addition of the LCP. Dynamic mechanical analysis (DMA) results showed that the shift in the glass transition temperature (Tg) of the elastomer with the addition of LCP and the storage modulus of the blends increased above the Tg of FKM, whereas decreases below the Tg of the elastomer were seen with up to 20 wt% LCP; this suggests that the LCP acts as an effective reinforcing agent above the Tg of FKM. From the thermogravimetric analysis (TGA) and differential thermogravimetry (DTG), we found that the thermal stability of the elastomer enhances by blending with the LCP. The weight loss and the weight loss rate of the FKM decrease enormously with the addition of LCP. From the X‐ray diffraction (XRD) study, it has been observed that the LCP acts as a nucleating agent by increasing the crystallinity of the blend. The failure mechanism of the blends was studied using a scanning electron microscope (SEM). It suggested that the failure occurred in the blends; mainly due to the pull out of the fibrils from the matrix phase and due to lower interfacial adhesion between the LCP phase and the elastomer. POLYM. COMPOS. 26:306–315, 2005. © 2005 Society of Plastics Engineers 相似文献
75.
76.
Avadhesh Kushwaha Melissa Jacob H. N. Shiva Kumar Shobharani Hiremath Sacchidanand Aradhya Michael A. Repka 《Drug development and industrial pharmacy》2015,41(7):1089-1094
Itraconazole (ITR) is a potent antifungal drug. However, poor aqueous solubility limits its permeation ability across the human nail plate. Therefore, in this project, ITR was converted to hydrochloride salt (ITR-HCl) to improve its solubility and to render it amenable to iontophoresis. ITR-HCl was characterized by spectroscopic methods and antifungal efficacy was evaluated in comparison to the base. In vitro and ex vivo transport studies (passive and iontophoresis) were carried out across the porcine hoof membrane and excised human cadaver toe using two different protocols; continuous delivery of drug for 24?h and pulsed delivery of drug for 3 days (8?h/day). The antifungal efficacy of ITR-HCL was comparable to ITR. Iontophoresis was found to be more effective than passive mode of delivery of ITR-HCL. In both iontophoresis as well as passive mode of delivery, the pulsed protocol resulted in more ungual and trans-ungual delivery of drug than continuous protocol. ITR-HCL could be delivered into and across the nail plate by iontophoresis. Human cadaver toe appears to be a good model to investigate the ungual delivery of drugs. 相似文献
77.
78.
79.
N. P. Liyanawaduge Shiva Kumar Singh Anuj Kumar V. P. S. Awana H. Kishan 《Journal of Superconductivity and Novel Magnetism》2011,24(5):1599-1605
The superconducting properties and AC/DC magnetic properties of YBa2Cu3−x
Zn
x
O7−δ
, (x=0.0, 0.01, 0.03, 0.05, 0.10 and 0.15) compounds were investigated. Samples were synthesized through solid-state reaction
route. X-ray diffraction data confirms the single-phase orthorhombic/tetragonal crystallization for the studied samples. Thermo-Gravimetric
Analysis (TGA) was done for pure and Zn-doped YBa2Cu3O7−δ
(YBCO) samples. Results reveal that at higher dopant levels the doped samples are more oxygen-deficient than the undoped
ones. The superconducting properties of YBa2Cu3−x
Zn
x
O7−δ
system always enhance with addition of oxygen to Cu–O chains, which causes enhancement of superconducting carrier density
together with orthorhombic structure. Zn substitution causes an overall reduction of superconducting condensation energy with
systematic degradation of superconducting properties like T
c and J
c. This occurs via induced non-homogeneity of hole carrier density created by extended nature of perturbation on electronic
structure in CuO2 planes and its weak-link type behavior. AC susceptibility measurement reveals that Zn doping reduces the inter-granular couplings.
Scanning Electron Microscope (SEM) images indicate that increment of average grain size with increasing of Zn concentration. 相似文献
80.
Pal P Rastogi SK Gibson CM Aston DE Branen AL Bitterwolf TE 《ACS applied materials & interfaces》2011,3(2):279-286
A novel fluorescent zinc sensor was designed and synthesized on ordered mesoporous silica material, MCM-41, with N-(quinolin-8-yl)-2-[3-(triethoxysilyl)propylamino]acetamide (QTEPA; 3) using a simple one-step molecular self-assembly of the silane. The solution and solid samples were characterized using solid-state nuclear magnetic resonance, transmission electron microscopy, diffuse-reflectance infrared Fourier transform, and thermogravimetric analysis techniques. The QTEPA-modified MCM-41 (4) shows 3-fold fluorescence emission enhancement and about a 55 nm red shift upon addition of 1 μM Zn(II) ions in a Tris-HCl (pH 7.22) aqueous buffer solution. The UV-vis absorption maximum is at 330 ± 5 nm, and the fluorescence emission maximum wavelength is at 468 nm, with an increase in quantum yield from 0.032 to 0.106 under the same conditions. The presence of other metal ions has no observable effect on the sensitivity and selectivity of 4. This system selectively detects Zn(II) ions with submicromolar detection to a limit of 0.1 μM. The MCM-41-based systems have the advantage that they can be employed in aqueous solutions without any aggregation. 相似文献