Optimal allocation of customers in a two server queue withresequencing

The problem of optimal allocation of customers in a two server queue with heterogeneous service rates and resequencing is addressed. The resequencing constraint ensures that the customers leave the system in the order in which they entered it. It is shown that the optimal policy that minimizes the average end-to-end delay of customers in the system is independent of the number of customers in the resequencing buffer. It is also shown that the faster server should be kept busy whenever possible     

Synthesis and characterisation of copolyesters from poly(ethylene terephthalate) and poly(hexamethylene terephthalate)

Copolyesters containing poly(ethylene terephthalate) and poly(hexamethylene terephthalate) (PHT) were prepared by a melt condensation reaction. The copolymers were characterised by infrared spectroscopy and intrinsic viscosity measurements. The density of the copolyesters decreased with increasing percentage of PHT segments in the backbone. Glass transition temperatures (T_g). melting points (T_m) and crystallisation temperatures (T_c) were determined by differential scanning calorimetry. An increase in the percentage of PHT resulted in decrease in T_g, T_m and T_c. The as-prepared copolyesters were crystalline in nature and no exotherm indicative of cold crystallisation was observed. The relative thermal stability of the polymers was evaluated by dynamic thermogravimetry in a nitrogen atmosphere. An increase in percentage of PHT resulted in a decrease in initial decomposition temperature. The rate of crystallisation of the copolymers was studied by small angle light scattering. An increase in percentage of PHT resulted in an increase in the rate of crystallisation.     

Structural, Dielectric, Pyroelectric and Ferroelectric Properties of Glass Nano Composite: Lithium Borate-Strontium Bismuth Vanadium Niobate

Transparent glasses in the system (100 - x) (Li₂O - 2B₂O₃) - x (SrO - Bi₂O₃ - 0.7 Nb₂O₅ - 0.3 V₂O₅) (10 ≤ x ≤ 60, in molar ratio) were fabricated via the melt quenching technique. The as-quenched samples were X-ray amorphous. Differential thermal analysis (DTA) confirmed the glassy nature of the as-quenched samples. Strontium bismuth vanadium niobate nanorods were grown by controlled heat-treatment of the as-quenched glasses at 783 K for 6 h. The formation of nanorod layered perovskite SrBi₂(Nb_0.7V_0.3)₂O_9-δ (SBVN) phase via an intermediate fluorite phase was confirmed by both X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). The dielectric constants of both the as-quenched and heat-treated samples (783 K/6 h) increased while the dielectric loss (D) decreased with increasing x (SBVN content). Interestingly, the dielectric constant of the glass nanocrystal composite (heat-treated at 783 K/6 h) exhibited an anomaly in the vicinity of the crystallization temperature of the host glass (Li₂B₄O₇) reaching a value as high as ≈10⁶ at 800 K. These glass nanocrystal composites were pyroelectric and ferroelectric at 300 K.

Communicated by George W. Taylor     

预测准确与否需要事实证明

欢迎进入硕果累累的一年--这是根据调查分析家们提供的数据所作的判断.2004年,半导体市场的增长率远远超过其13%左右的平均值.对2004年最乐观的预测如下:Future Horizons公司估计增长25.0%;VLSI Research公司估计增长24.5%;IC Insights公司估计增长23.0%;Gartner Dataquest公司估计增长21.1%;WSTS公司估计增长18.5%.     

Synthesis and characterisation of N-toluyl methacrylatoethyl carbamates,homopolymers and copolymers with methyl methacrylate

The paper describes the synthesis of N-2/4-toluyl methacrylatoethyl carbamates using 2/4-toluyl isocyanate and 2-hydroxyethyl methacrylate. Homopolymerisation and copolymerisation of these novel monomers with methyl methacrylate was carried out using benzoyl peroxide as an initiator and tetrahydrofuran as solvent. Photopolymerisation of N-4-toluyl methacrylatoethyl carbamate could be carried out without the use of photosensitiser. Structural characterisation of copolymers was done using ¹H-NMR. Thermal stability of copolymers was evaluated in a nitrogen atmosphere by dynamic thermogravimetry.     

Oxidation Behavior of Rh–30Ni–18Nb Refractory Superalloy

The isothermal-oxidation behavior of Rh–30Ni–18Nb refractory alloy was investigated up to a period of 312 hours in air from 1000 to 1350°C. A comparison of the oxidation behavior of this alloy with a conventional Ni-base superalloy (Inconel 713 C) shows an order-of-magnitude higher oxidation resistance. This experimental alloy oxidizes by forming alternate layers of Nb₂O₅ and RhO while NiO is on the surface in contact with air. Optical and scanning-electron microscopy (SEM) was used to study the microstructure and morphology for the characterization of the oxides. Thermal stability of the alloy for extended periods of exposure to air at 1400°C was studied using transmission-electron microscopy (TEM).     

Effect of structure on the thermal behaviour of ethynyl-terminated imide resins

A series of ethynyl-terminated aromatic imide monomers containing phosphine oxide in the backbone were synthesized by the reaction of tris(3-aminophenyl) phosphine oxide (TAP) or bis(3-aminophenyl)methyl phosphine oxide (BAP) with pyromellitic dianhydride (PMDA) or 3, 3′,4, 4′-benzophenone tetracarboxylic acid dianhydride (BTDA) or 4, 4′-perfluoroisopropylidenebis(phthalic anhydride), and 3-ethynyl aniline. Structural characterization was done by infrared, nuclear magnetic resonance spectroscopy and elemental analysis. Thermal characterization was done by differential scanning calorimetry and thermogravimetric analysis. The decomposition temperatures of cured resins were above 500°C in nitrogen atmosphere. Char yield at 800°C ranged from 52–63.5%.