Comparison of satellite and cellular architectures for downlink broadcast data transmission

Traditional voice and video‐oriented networks such as the cellular and satellite networks are being increasingly used to carry data traffic. We endeavour to compare the downlink broadcast performance of the two architectures against each other on the basis of energy consumption, end‐to‐end delay and maximum stable throughput. The architectures are modelled as systems of Geo/G/1 queues. Queuing theory arguments and then sample‐path based comparisons are used to show that the satellite architecture while being more energy‐efficient has a higher delay and a lower maximum throughput. The variation of energy and delay with the total number of receiver nodes is also studied. Copyright © 2006 John Wiley & Sons, Ltd.     

Gas permeation properties of polyamide membrane prepared by interfacial polymerization

Interfacial polymerization technique has been widely employed to prepare reverse osmosis (RO) and nanofiltration (NF) membranes. The present study explores the possibility of preparing a polyamide membrane by interfacial polymerization and its utilization for the separation of CO₂ and H₂S from CH₄. A novel ultraporous substrate of polysulfone (PSF) was prepared by phase inversion technique from a solution containing 18% PSF and 4% propionic acid in dimethyl formamide (DMF) solvent. Thin film composite (TFC) polyamide membrane was synthesized on PSF substrate from the reaction between meta-phenylene diamine in an aqueous media and isophthaloyl chloride in hexane. The membrane prepared was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) to study intermolecular interactions, crystallinity, thermal stability and surface morphology, respectively. Gas permeabilities of pure CO₂, H₂S, CH₄, O₂, and N₂ gases were measured using the indigenously built permeation cell incorporated into a high-pressure gas separation manifold. At the feed pressure of 1 MPa, the membrane exhibited permeances of 15.2 GPU for CO₂ and 51.6 GPU for H₂S with selectivities of 14.4 and 49.1 for CO₂/CH₄ and H₂S/CH₄ systems, respectively. The observed N₂ permeance of 0.95 GPU was close to that of CH_4. The corresponding O₂ permeance was 5.13 GPU with a reasonably high O₂/N₂ selectivity of 5.4. The effect of feed pressure on polyamide membrane performance was examined. Further, molecular dynamics (MD) simulations were employed to compute the cohesive energy density (CED), solubility parameter (δ) and sorption of CO₂, H₂S, CH₄, O₂, and N₂ gases in polyamide membrane to corroborate theoretical study with experimentally determined gas transport properties.     

W/W型PAM-MMT乳液的制备及性能研究

为了提高以明胶为稳定剂分散聚合制备的聚丙烯酰胺“水包水”（W/W型PAM）乳液的絮凝性能，首先，采用阳离子单体甲基丙烯酰氧乙基三甲基氯化铵（methacrylatoethyl trimethyl ammonium chloride, DMC）对钠基蒙脱土（sodium-montmorillonite, Na-MMT）进行插层改性制备有机蒙脱土（organic montmorillonite, OMMT），通过X射线衍射（X-ray diffraction, XRD）测试得到插层改性后蒙脱土的层间距由1.25 nm增加至1.43 nm，说明DMC单体已经成功插层进入蒙脱土片层。然后，将OMMT引入以明胶为稳定剂的W/W型PAM乳液的体系中，以制备W/W型PAM-MMT乳液。通过透射电镜（transmission electron microscope, TEM）乳液微观形貌进行观察，得到乳液结构是由以蒙脱土颗粒为“交联点”的聚丙烯酰胺高分子网络和W/W型PAM乳液的混合体。研究了OMMT用量、明胶浓度、体系pH值以及阳离子单体DMC添加比例对合成W/W型PAM-MMT乳液性能的影响规律。结果显示：在适宜条件下合成的乳液均具有较好的储存稳定性和在水中的再分散性。乳液的表观黏度和絮凝性能都与OMMT和明胶用量呈正相关性；当pH值在明胶等电点（isoelectric point，IEP）时，得到的乳液的表观黏度最低，絮凝效果最好；随着DMC单体用量比例增大，乳液表观黏度减小，高岭土悬浮液的絮凝效果先增大后减小。     

Soil line transformation based relative radiometric normalization

Relative radiometric normalization is a prerequisite for multi‐temporal remotely sensed data analysis. Dark object subtraction (DOS) and pseudo‐invariant feature (PIF) methods are two commonly employed scene‐based methods for relative radiometric normalization. Both these methods have known limitations. The authors describe a soil line transformation method for multi‐date relative radiometric normalization, which circumvents the limitations of the DOS and PIF methods.     

Optimization of the continuously extruded unleavened flat bread (chapati) process

Processing variables such as size of die openings, production rate and initial moisture content on the discharge temperature and power input used in the continuous production of Indian unleavened flat bread (chapati) were studied. The extruder was a specially designed continuous chapati making system. The net specific energy (NSE) decreased with increasing size of die openings and moisture content. The total power efficiency increased with increasing production rate while NSE values remain unchanged. The discharge temperature decreased with increased moisture content of the dough and increased die opening size. The process variables were optimized for the continuous production of chapati, based on minimum specific energy and maximum puffing index. The optimum conditions were found to be a rate of 40 kg/h, a die opening of 1.4 mm height쐘 mm width and moisture contents of 60% and 75% (w.b.) for Resultant Atta and Atta, respectively. Sensory analysis showed that chapatis produced under the above conditions compared well with traditionally made chapatis in quality.     

An analytical approach to dynamic crosstalk in coupled interconnects

This paper deals with waveform analysis, crosstalk peak and delay estimation of CMOS gate driven capacitively and inductively coupled interconnects. Simultaneously switching inputs for the coupled interconnects are considered. A transmission line-based coupled model of interconnect is used for analysis. Alpha-power Law model of MOS transistor is used to represent the transistors in CMOS driver. Peaks and delays at far-end of victim line are estimated for conditions when the inputs to the two coupled interconnects are switching in-phase and out-of-phase. The comparison of analytically obtained results with SPICE simulations show that the proposed model captures noise peak and their timing; 90% propagation delay; transition time delay and waveform shape with good accuracy, such as not more than 5% error in crosstalk peak estimation.     

Equations for nucleation of hydrogen gas pores during solidification of aluminium seven weight percent silicon alloy

A statistical prediction model has been applied to the nucleation rate as a function of temperature for an Al7Si alloy based upon observations of pore formation during solidification in an XTGS. A normalised Gaussian function was developed ((1), (2), (3) and (4)) which may be used to describe pore nucleation in mathematical simulations of porosity formation during solidification.     

Evaluation of the methods for calculating the concentration-dependent diffusivity in binary systems

Boltzmann and Matano developed a procedure for the solution to Fick’s second law when the diffusivity is a function of concentration. The procedure requires the determination of the so-called Matano interface. The accuracy of the resulting solution depends heavily on the precise location of the Matano interface, the determination of which is laborious and often inaccurate. Three alternative procedures by Sauer and Freise, Wagner, and den Broeder, modifications to the original Boltzmann-Matano (B-M) method, were developed such that the diffusivity can be calculated without having to determine the location of the Matano interface. However, none of these derivations quantifies the extent to which the modified methods arrive at the same result as that obtained from the standard B-M analysis. This article serves to apply the B-M method, and the modification suggested by den Broeder, to various analytical concentration profiles containing different degrees of noise and to compare the results quantitatively. In addition to these analytical functions, concentration profiles obtained from interdiffusion experiments were studied. The two methods are shown to be equivalent in terms of the accuracy of the result. The advantages or disadvantages of one method over the other are illustrated with examples.     

Minimization of organic chemical load in direct dyes effluent using low cost adsorbents

The work is carried out to minimize the organic chemical load (unexhausted dye contents) in direct dyes effluent using low cost adsorbents. The studies are made with different direct dyes, i.e. Direct Red 28, Direct Yellow 12, Direct Orange 26 and Direct Blue 1 with various adsorbents. Three different bio/natural materials have been selected as adsorbents. These includes, Sugarcane bagasse pith (SB), Saw dust (SD)—the plant origin products, and Brick powder (BP)—a silica based material obtained from earth's crust on thermal heating. These substances are almost discarded waste products with the possibility of use as adsorbents. Experimental work for the dye removal from the effluent by activated charcoal (AC) has also been carried out and the results are compared with other adsorbents. The amount of unexhausted organic dye present in the effluent is measured as chemical oxygen demand (COD) before and after the treatment. Adsorbent Sugarcane bagasse pith shows good performance as compared to Saw dust and Brick powder. For understanding the behaviour of adsorbents Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) has also been carried out.     

Effect of ionizing radiation on antinutritional features of velvet bean seeds (Mucuna pruriens)

Impact of gamma irradiation on the antinutritional constituents of seeds of Mucuna pruriens was assessed on exposing to doses of 2.5, 5.0, 7.5, 10, 15 and 30 kGy. Except for 2.5 kGy, the rest showed significant dose-dependent increase in phenolics. Tannin concentration did not differ significantly up to 7.5 kGy, while it significantly increased at higher doses. Excluding 2.5 kGy, the rest of the treatments showed significant decreases in the phytic acid and complete degradation was attained at 15 and 30 kGy. The l-DOPA concentration showed a dose-dependent decline. A trace amount of hemagglutination activity was seen on human erythrocytes in raw seeds, which was completely absent on irradiation (>5 kGy). Concentration of Polonium-210, a natural radionuclide falls within the admissible limits for consumption. As Mucuna seeds serve as food, feed or as pharmaceuticals, it may be necessary to set the ionizing radiation to a specific dose to retain optimum levels or to eliminate phenolics, tannins, phytic acid and L-DOPA. As irradiation is a physical and cold process, it may be ideal and emerge as an important technique to improve the nutritional or pharmaceutical quality of Mucuna seeds and its products.