Thermal and surface characterization of polyurethane–urea clay nanocomposite coatings

This paper reports synthesis and characterization of polyurethane–urea (PU‐urea) and the nanocomposites derived from the PU‐urea with silicate clays. Organophilic montmorillonite cotreated by cetyl trimethyl ammonium bromide (CTAB) was synthesized and used to prepare PU‐urea/montmorillonite nanocomposites coatings. PU‐ureas were prepared from polyethylene glycol (PEG), polypropylene glycol (PPG), trimethylol propane (TMP), and 4,4′‐diphenylmethane diisocyanate (MDI) by reacting excess diisocyanate with polyether glycols. The excess isocyanate of the prepolymers was cured with atmospheric moisture. The synthesized moisture cured PU‐urea and nanocomposites were characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetric (DSC), and angle resolved X‐ray photoelectron spectroscopy (AR‐XPS). The thermal stability of the PU‐urea nanocomposites was higher relative to the mother PU‐urea films. DSC results showed a slight enhancement in the soft segment glass transition temperature after 3 wt % clay loading. The surface properties showed an enrichment of the soft segment toward the surface. An enhancement in the hard segment composition in the nanocomposite coatings has resulted in enhancing the phase mixing process. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2393–2401, 2006     

Architectural design and FPGA implementation of radix-4 CORDIC processor

A new scaled radix-4 CORDIC architecture that incorporates pipelining and parallelism is presented. The latency of the architecture is n/2 clock cycles and throughput rate is one valid result per n/2 clocks for n bit precision. A 16 bit radix-4 CORDIC architecture is implemented on the available FPGA platform. The corresponding latency of the architecture is eight clock cycles and throughput rate is one valid result per eight clock cycles. The entire scaled architecture operates at 56.96 MHz of clock rate with a power consumption of 380 mW. The speed can be enhanced with the upgraded version of FPGA device. A speed-area optimized processor is obtained through this architecture and is suitable for real time applications.     

Effects of polymer molecular weight,concentration, and role of polyethylene glycol as additive on polyacrylonitrile homopolymer membranes

Polyacrylonitrile (PAN), is an important base polymer to cast porous membranes. In this work, a detailed study of the effects of molecular weight of PAN homopolymer and its concentration on the cast membrane has been undertaken. The effects of molecular weight of additive polyethylene glycol (PEG) and its concentration have also been investigated. The membranes are cast using dimethyl formamide as solvent using phase inversion technique. They are characterized in terms of porosity, water permeability, molecular weight cut off, average pore diameter, contact angle, and tensile strength at breaking point. Fourier transform infrared spectroscopy and scanning electron microscopy are used to characterize the chemical and morphological changes of the membrane surface. Further studies have been considered to evaluate the antifouling property of various membranes using filtration of bovine serum albumin solution. Membrane modified by PEG 400 membrane shows an improved separation performance and antifouling characteristics. POLYM. ENG. SCI., 54:2375–2391, 2014. © 2013 Society of Plastics Engineers     

Regime transition in viscous and pseudo viscous systems: A comparative study

A comprehensive quantitative study on the effect of liquid viscosity (1 ≤ µ_L ≤ 1149 mPa‐s) on the local flow phenomena of the gas phase in a small diameter bubble column is performed using ultrafast electron beam X‐ray tomography. The internal dynamic flow structure and the bubble size distribution shows a dual role of the liquid viscosity on the hydrodynamics. Further, the effect of solid concentration (C_s = 0.05, 0.20) on the local flow behavior of the gas phase is studied for the pseudo slurry viscosities similar to the liquid viscosities of the gas–liquid systems. The effects of liquid and pseudo slurry viscosities on flow structure, bubble size distribution, and gas phase distribution are compared. The bubble coalescence is significantly enhanced with the addition of particles as compared to the system without particles for apparently same viscosity. The superficial gas velocity at which transition from homogeneous bubbly to slug flow regime occurs is initiated by the addition of particles as compared to the particle free system for apparently same viscosity. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3079–3090, 2014     

A multiplicative model of software defect repair times

We hypothesize that software defect repair times can be characterized by the Laplace Transform of the Lognormal (LTLN) distribution. This hypothesis is rooted in the observation that software defect repair times are influenced by the multiplicative interplay of several factors, and the lognormal distribution is a natural choice to model rates of occurrence of such phenomenon. Conversion of the lognormal rate distribution to an occurrence time distribution yields the LTLN. We analyzed a total of more than 10,000 software defect repair times collected over nine products at Cisco Systems to confirm our LTLN hypothesis. Our results also demonstrate that the LTLN distribution provides a statistically better fit to the observed repair times than either of the two most widely used repair time distributions, namely, the lognormal and the exponential. Moreover, we show that the repair times of subsets of defects, partitioned according to the Orthogonal Defect Classification (ODC) scheme also follow the LTLN distribution. Finally, we describe how the insights that lead to the LTLN repair time model allow us to consider and evaluate alternative process improvement strategies.     

A note on the deformation of consolidating spherical shell

This paper presents the solutions of the problem of deformation of a consolidating spherical shell of poro-elastic material. Jana and Sanyal have treated the same problem and obtained approximate solutions using Laplace Transform technique. The loading conditions taken by them seem to be unrealistic. By considering boundary conditions which are physically realisable, solutions have been derived in this paper. To obtain the solutions truncated Hankel transform technique has been used and no approximation has been made.     

Architecture-Based Software Reliability Analysis: Overview and Limitations

With the growing size and complexity of software applications, research in the area of architecture-based software reliability analysis has gained prominence. The purpose of this paper is to provide an overview of the existing research in this area, critically examine its limitations, and suggest ways to address the identified limitations     

印度的能效与节能状况

能源是影响经济发展的重要因素，不仅对大部分的工业化国家，甚至对发展中国家和欠发达国家的正常运作都是必不可少的。一次性能源如煤炭、石油、天然气和生物质大多通过工业设备转化成电力、煤和精炼石油产品等二次性能源，这些二次性能源是构成现代社会工业、农业、交通和商业发展的基础。目前，世界平均能源消费量约为2．2吨煤／人，在工业化国家，人们能源使用量高达世界平均水平4到5倍以上，为发展中国家平均水平的9倍以上。     

Synthesis and Biological Evaluation of Imidazo[2,1‐b][1,3,4]thiadiazole‐Linked Oxindoles as Potent Tubulin Polymerization Inhibitors

A series of imidazo[2,1‐b][1,3,4]thiadiazole‐linked oxindoles composed of an A, B, C and D ring system were synthesized and investigated for anti‐proliferative activity in various human cancer cell lines; test compounds were variously substituted at rings C and D. Among them, compounds 7 ((E)‐5‐fluoro‐3‐((6‐p‐tolyl‐2‐(3,4,5‐trimethoxyphenyl)‐imidazo[2,1‐b][1,3,4]thiadiazol‐5‐yl)methylene)indolin‐2‐one), 11 ((E)‐3‐((6‐p‐tolyl‐2‐(3,4,5‐trimethoxyphenyl)imidazo[2,1‐b][1,3,4]thiadiazol‐5‐yl)methylene)indolin‐2‐one), and 15 ((E)‐6‐chloro‐3‐((6‐phenyl‐2‐(3,4,5‐trimethoxyphenyl)imidazo[2,1‐b][1,3,4]thiadiazol‐5‐yl)methylene)indolin‐2‐one) exhibited potent anti‐proliferative activity. Treatment with these three compounds resulted in accumulation of cells in G₂/M phase, inhibition of tubulin assembly, and increased cyclin‐B1 protein levels. Compound 7 displayed potent cytotoxicity, with an IC₅₀ range of 1.1–1.6 μM , and inhibited tubulin polymerization with an IC₅₀ value (0.15 μM ) lower than that of combretastatin A‐4 (1.16 μM ). Docking studies reveal that compounds 7 and 11 bind with αAsn101, βThr179, and βCys241 in the colchicine binding site of tubulin.     

Development of a new solid-state absorber material for dye-sensitized solar cell (DSSC)

In contrast to the conventional DSSC systems, where the dye molecules are used as light harvesting material, here a solid-state absorber was used as a sensitizer in conjunction with the dye. The materials like ZnO and Al₂O₃ : C, which will show optically stimulated luminescence (OSL) upon irradiation were used as extremely thin absorber layers. This novel architecture allows broader spectral absorption, an increase in photocurrent, and hence, an improved efficiency because of the mobility of the trapped electrons in the absorber material after irradiation, to the TiO₂ conduction band. Nanocrystalline mesoporous TiO₂ photoanodes were fabricated using these solid-state absorber materials and after irradiation, a few number of samples were co-sensitized with N719 dye. On comparing both the dye loaded photoanodes (ZnO/TiO₂ and Al₂O₃ : C/TiO₂), it can be concluded from the present studies that, the Al₂O₃ : C is superior to ZnO under photon irradiation. Al₂O₃ : C is more sensitive to photon irradiation than ZnO and hence there can be more trap centres produced in Al₂O₃ : C.