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1.
Software is the key technology in applications as diverse as accounting, hospital management, aviation, and nuclear power. Application advances in different domains such as these-each with different requirements-have propelled software development from small batch programs to large, real-time programs with multimedia capabilities. To cope, software's enabling technologies have undergone tremendous improvement in hardware, communications, operating systems, compilers, databases, programming languages, and user interfaces, among others. In turn, those improvements have fueled even more advanced applications. Improvements in VLSI technology and multimedia, for example, have resulted in faster, more compact computers that significantly widened the range of software applications. Database and user interface enhancements, on the other hand, have spawned more interactive and collaborative development environments. Such changes have a ripple effect on software development processes as well as on software techniques and tools. In this article, we highlight software development's crucial methods and techniques of the past 30 years 相似文献
2.
Ferroelectrically Gated Atomically Thin Transition‐Metal Dichalcogenides as Nonvolatile Memory 下载免费PDF全文
3.
Electrospinning of protein‐loaded fibers faces many challenges, e.g. burst release owing to segregation of the protein on the fiber surface, loss of activity due to electrospinning conditions, limitation of loading capacity etc. Core–shell electrospinning provides an effective way to electrospin fibers wherein the core can be loaded with bioactive molecules in friendly conditions of a compatible polymer solution, thereby protecting the molecules from the electrostatic field and organic solvent of shell solutions. The shell polymer, after the electrospinning, acts as a barrier to control the release of the loaded molecules. However, the limitation of loading capacity still remains due the prerequisite of using an additional polymer as additive to achieve the minimum viscosity of the core solution required for viscous drag by the shell solution being drawn by the electrostatic force. The work reported here aims to alleviate the need of a polymer additive by using aqueous protein solutions of very high concentration. High concentrations of protein solutions were successfully electrospun as the core of the protein–poly(lactide‐co‐glycolic acid) core–shell fibers. A partitioning effect was seen in the controlled release of hydrophilic proteins as they were retained in the aqueous core for longer times. Using lysozyme as a model protein, it was shown that the activity is significantly retained after electrospinning, compared with electrospinning in monolithic fibers. Moreover, the lysozyme activity was also comparable with the lysozyme released from core–shell fibers spun using poly(vinyl acetate) as additive in the core. Copyright © 2012 Society of Chemical Industry 相似文献
4.
Sandeep Kumar Tiwari Subbu S. Venkatraman 《Materials science & engineering. C, Materials for biological applications》2012,32(5):1037-1042
Electrospun polymeric fibers are attractive candidates in the development of scaffolds for the tissue engineering and for providing new systems for delivery of bioactive molecules. Co-axial fibers have emerged as an efficient tool to protect the core material from the adverse conditions of electrospinning process, to spin difficult-to-process fluids and to generate fibers with much more control of the delivery of encapsulated bioactive molecules. Currently, there is very little reported work on the optimization of the processing parameters of electrospinning, especially core–shell electrospinning. This study extends the understanding of the role of solution viscosity as a vital material parameter for electrospinning of fibers. The spinning solutions were characterized for viscosity and optical imaging of the compound Taylor cone for spinnability, and the fibers were imaged by Scanning Electron Microscopy (SEM). Our experimental results, using PLGA as the model polymer, confirm that the solution concentration be above the entanglement concentration (Ce) to obtain uniform beadless monolithic fibers; for core–shell fibers, the shell solution must fulfill the above criterion for spinnability and, further, the ratio of the viscosities of core and shell solutions (ηcore/ηshell) has to be greater than a threshold value to get a stable compound Taylor cone and therefore to obtain uniform beadless core–shell fibers. Addition of surfactant led to reduction of the threshold ηcore/ηshell (from 0.55 to 0.18) for the PVA–PLGA system. 相似文献
5.
Mechanical and thermal characterization of compression moulded polylactic acid natural fiber composites reinforced with hemp and lyocell fibers 下载免费PDF全文
This research evaluates the effects of PLA/PP blend ratio and Lyocell/hemp mixture ratio on the morphology, water absorption, mechanical and thermal properties of PLA‐based composites. The composites were fabricated with 30 mass % hemp using compression moulding. As a reference composites made from PP were also studied. Combining of hemp and Lyocell in PLA composite leads to the reduction of moisture absorption and can improve the impact, tensile, flexural properties when compared with PLA/hemp. Composite based on the PLA/PP blend‐matrix could not improve the tensile and flexural properties compared with PLA/hemp, however; the lighter composite with better impact properties was obtained. The crystallization temperature of the PLA‐PP/hemp increased compared with pure PLA. This result was also confirmed by the SEM micrographs. The moisture absorption of PLA‐PP/hemp was higher than PLA/hemp. Based on theoretical analysis of DMTA data, there was favorable adhesion in all composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40534. 相似文献
6.
Polyelectrolyte and silver nanoparticle modification of microfiltration membranes to mitigate organic and bacterial fouling 总被引:1,自引:0,他引:1
Diagne F Malaisamy R Boddie V Holbrook RD Eribo B Jones KL 《Environmental science & technology》2012,46(7):4025-4033
Membrane fouling remains one of the most problematic issues surrounding membrane use in water and wastewater treatment applications. Organic and biological fouling contribute to irreversible fouling and flux decline in these processes. The aim of this study was to reduce both organic and biological fouling by modifying the surface of commercially available poly(ether sulfone) (PES) membranes using the polyelectrolyte multilayer modification method with poly(styrenesulfonate) (PSS), poly(diallyldimethylammonium chloride) (PDADMAC), and silver nanoparticles (nanoAg) integrated onto the surface as stable, thin (15 nm) films. PSS increases the hydrophilicity of the membrane and increases the negative surface charge, while integration of nanoAg into the top PSS layer imparts biocidal characteristics to the modified surface. Fouling was simulated by filtering aqueous solutions of humic acid (5 and 20 mg L(-1)), a suspension of Escherichia coli (10(6) colony-forming units (CFU) mL(-1)), and a mixture of both foulants through unmodified and modified PES membranes under batch conditions. Filtration and cleaning studies confirmed that the modification significantly reduced organic and biological fouling. 相似文献
7.
Investigation and optimization of lubrication parameters in high speed turning of superalloy Inconel 718 总被引:2,自引:2,他引:0
Dinesh G. Thakur B. Ramamoorthy L. Vijayaraghavan 《The International Journal of Advanced Manufacturing Technology》2010,50(5-8):471-478
Dry machining is sometimes less effective when higher machining efficiency, better surface finish quality, and severe cutting conditions are required. For these situations, semi-dry operations utilizing very small amount of cutting fluids called minimum quantity lubrication is expected to become a powerful tool and played a significant role in a number of practical applications. It has been observed from the literature survey that a systematic research work has to be carried out to determine the optimum quantity of lubricant with appropriate cutting conditions for achieving better machinability characteristics of a material. Hence, an attempt has been made in this paper to enhance the machinability characteristics in high speed turning of superalloy Inconel 718 using quantity of lubricant, delivery pressure at the nozzle, frequency of pulses, direction of application of cutting fluid, cutting speed, and feed rate as the process parameters. Results indicated that the use of optimized minimum quantity lubrication parameters under pulsed jet mode leads to lower cutting force, cutting temperature, and flank wear. 相似文献
8.
9.
A high conversion light water reactor lattice has been analysed using the code DRAGON Version4. This analysis was performed to test the performance of the advanced self-shielding models incorporated in DRAGON Version4. The self-shielding models are broadly classified into two groups – “equivalence in dilution” and “subgroup approach”. Under the “equivalence in dilution” approach we have analysed the generalized Stamm’ler model with and without Nordheim model and Riemann integration. These models have been analysed also using the Livolant–Jeanpierre normalization. Under the “subgroup approach”, we have analysed Statistical self-shielding model based on physical probability tables and Ribon extended self-shielding model based on mathematical probability tables. This analysis will help in understanding the performance of advanced self-shielding models for a lattice that is tight and has a large fraction of fissions happening in the resonance region. The nuclear data for the analysis was generated in-house. NJOY99.90 was used for generating libraries in DRAGLIB format for analysis using DRAGON and A Compact ENDF libraries for analysis using MCNP5. The evaluated datafiles were chosen based on the recommendations of the IAEA Co-ordinated Research Project on the WIMS Library Update Project. The reference solution for the problem was obtained using Monte Carlo code MCNP5. It was found that the Ribon extended self-shielding model based on mathematical probability tables using correlation model performed better than all other models. 相似文献
10.
Chen Y.-F. Nishimoto M.Y. Ramamoorthy C.V. 《IEEE transactions on pattern analysis and machine intelligence》1990,16(3):325-334
A system for analyzing program structures is described. The system extracts relational information from C programs according to a conceptual model and stores the information in a database. It is shown how several interesting software tasks can be performed by using the relational views. These tasks include generation of graphical views, subsystem extraction, program layering, dead code elimination and binding analysis 相似文献