Isothermal and non-isothermal crystallization kinetics of hydroxyl-functionalized polypropylene

Hydroxyl-modified polypropylenes (PPOH) with side chains containing OH groups were synthesized by copolymerization of the propylene and undecenyloxytrimethylsilane monomers. The isothermal and non-isothermal crystallization behavior of the modified polypropylenes (PPOH) with side chains containing up to 6.8 mol% OH groups were compared with that of polypropylene (PP). The introduction of the OH-comonomer decreased the overall rate of isothermal crystallization compared with PP due to steric effects of the hydroxyl-containing side-chains that hindered packing of the PP backbone chains into a lamellar structure. However, a maximum reduction in the rate of crystallization occurred at an intermediate hydroxyl concentration as a consequence of a competition between the effects of the comonomer on the nuclei density and the thermodynamic barrier to crystallization. Steric hindrance by the comonomer side-chains also reduced the radial growth rate of the crystals in PPOH and produced a coarser crystal morphology than that for PP. PP and PPOH exhibited an identical α-monoclinic crystal structure, but the introduction of only ∼6.8 mol% comonomer reduced the fold-surface free energy of the crystals by 42%. For non-isothermal crystallization, the crystallization peak temperature (T_p) decreased for low concentrations of OH, but above a critical OH concentration, T_p increased, a result similar to the isothermal crystallization rate.     

Biofouling reduction of EPDM by radiation-assisted modification for water environment applications

Ethylene propylene diene elastomer (EPDM) harbors diverse microbiota that form biofilms. Such biofilms may contaminate water and can increase drag force impacting the hydrodynamic performance of a ship, once it is used as fenders. Here, the EPDM surface is modified by radiation-assisted grafting to prevent biofilm formation. Three different monomers, namely, methacrylic acid (MAA), isodecyl methacrylate (IDM), and lauryl methacrylate (LMA), are grafted on EPDM. The modified surfaces are characterized by Fourier transform infrared (FTIR) spectroscopy, surface wettability, mechanical and dynamic mechanical properties (DMA), and scanning electron microscopy (SEM). The modified surfaces are subjected to biofouling by prominent biofilm adherents, that is, Pseudomonas aeruginosa and Klebsiella pneumoniae. The standard plate count and resazurin fluorescence assays are performed to observe the microbial load on these surfaces. The MAA-grafted EPDM, which is hydrophilic in nature, shows a considerable decrease in bacterial adhesion compared to pure EPDM, but for IDM and LMA-grafted EPDM, it is the opposite. The deterioration of the surface with bacteria by environmental scanning electron microscopy (ESEM) supports the findings. The tensile property of the modified EPDM is observed to be within satisfactory limits. After such modification, the EPDM is expected to expand its application.     

Remanufacturing and energy savings

Remanufactured products that can substitute for new products are generally claimed to save energy. These claims are made from studies that look mainly at the differences in materials production and manufacturing. However, when the use phase is included, the situation can change radically. In this Article, 25 case studies for eight different product categories were studied, including: (1) furniture, (2) clothing, (3) computers, (4) electric motors, (5) tires, (6) appliances, (7) engines, and (8) toner cartridges. For most of these products, the use phase energy dominates that for materials production and manufacturing combined. As a result, small changes in use phase efficiency can overwhelm the claimed savings from materials production and manufacturing. These use phase energy changes are primarily due to efficiency improvements in new products, and efficiency degradation in remanufactured products. For those products with no, or an unchanging, use phase energy requirement, remanufacturing can save energy. For the 25 cases, we found that 8 cases clearly saved energy, 6 did not, and 11 were too close to call. In some cases, we could examine how the energy savings potential of remanufacturing has changed over time. Specifically, during times of significant improvements in energy efficiency, remanufacturing would often not save energy. A general design trend seems to be to add power to a previously unpowered product, and then to improve on the energy efficiency of the product over time. These trends tend to undermine the energy savings potential of remanufacturing.     

Debug-localize-repair: a symbiotic construction for heap manipulations

We present Wolverine2, an integrated Debug-Localize-Repair environment for heap manipulating programs. Wolverine2 provides an interactive debugging environment: while concretely executing a program via on an interactive shell supporting common debugging facilities, Wolverine2 displays the abstract program states (as box-and-arrow diagrams) as a visual aid to the programmer, packages a novel, proof-directed repair algorithm to quickly synthesize the repair patches and a new bug localization algorithm to reduce the search space of repairs. Wolverine2 supports “hot-patching” of the generated patches to provide a seamless debugging environment, and also facilitates new debug-localize-repair possibilities: specification refinement and checkpoint-based hopping. We evaluate Wolverine2 on 6400 buggy programs (generated using automated fault injection) on a variety of data-structures like singly, doubly, and circular linked lists, AVL trees, Red-Black trees, Splay Trees and Binary Search Trees; Wolverine2 could repair all the buggy instances within realistic programmer wait-time (less than 5 s in most cases). Wolverine2 could also repair more than 80% of the 247 (buggy) student submissions where a reasonable attempt was made.

     

Thermal and geometrical assessment of parabolic trough collector-mounted double-evacuated receiver tube system

Clean Technologies and Environmental Policy - This paper particularly aims to highlight the necessity of optimal geometrical design considerations of a parabolic trough collector (PTC)-mounted...     

Three-dimensional fuzzy graphene ultra-microelectrodes for subcellular electrical recordings

Microelectrode arrays (MEAs) have enabled investigation of cellular networks at sub-millisecond temporal resolution. However, current MEAs are limited by the large electrode footprint since reducing the electrode's geometric area to sub-cellular dimensions leads to a significant increase in impedance thus affecting its recording capabilities. We report a breakthrough ultra-microelectrodes platform by leveraging the outstanding surface-to-volume ratio of nanowire-templated out-of-plane synthesized three-dimensional fuzzy graphene (NT-3DFG). The enormous surface area of NT-3DFG leads to 140-fold reduction in electrode impedance compared to bare Au microelectrodes, thus enabling scaling down the geometric size by 625-fold to ca. 2 μm × 2 μm. The out-of-plane morphology of NT-3DFG leads to a tight seal with the cell membrane thus enabling recording of electrical signals with high signal-to-noise ratio (SNR) of > 6. This work highlights the possibility to push the limits of the conventional MEA technology to enable electrophysiological investigation at sub-cellular level without the need of any surface coatings. This presented approach would greatly impact our basic understanding of signal transduction within a single cell as well as complex cellular assemblies.

     

Comparative analysis of rockmass characterization techniques for the stability prediction of road cut slopes along NH-44A,Mizoram, India

The network of roads in hilly areas plays an important role in the socio-economic development of any country. Instability in road cut slopes is the most critical and common problem in the Northeast region of India. We conducted rockmass characterization of thirteen slopes from three regions, namely Lengpui, Phunchawng and Aizawl Zoo areas near the Aizawl city, on the basis of rock mass rating (RMR), geological strength index (GSI), kinematic analysis, and various slope mass rating techniques. Wedge failure was observed to be prominent in these regions, though some other modes of failure were present at the site. The stability of road cut slopes was found to vary from partially stable to completely unstable with regard to slope mass rating (SMR), Chinese slope mass rating (CSMR) and the continuous slope mass rating (CoSMR). A comparative analysis was also carried out among the findings of various rockmass characterization techniques to predict the stability of the road cut slopes along NH-44A highway.

     

Numerical simulation of adiabatic and isothermal cracks in functionally graded materials using optimized element-free Galerkin method

In the present work, element-free Galerkin method (EFGM) is modified and implemented to simulate thermoelastic fracture in functionally graded materials (FGMs). By solving the simple heat transfer problem, the temperature distribution over the domain can be obtained which is later used as an input to determine the displacement and stress fields. The crack surfaces are modeled under adiabatic and isothermal conditions. To capture stress fields around the crack tip, intrinsic enrichment criterion is used. A modified conservative M-integral technique has been used to extract the stress intensity factors (SIFs) for the simulated problems. A new algorithm to ensure equal number of nodes in support domain has been suggested. The optimum size of support domain is derived by performing an optimization of predefined EFGM parameters, namely, total number of nodes in problem geometry, Gauss quadrature, and number of nodes in support domain. Taguchi L-16 orthogonal array is used to obtain optimized values of these parameters. The results of analysis by optimized EFGM (OEFG) show about 80% reduction in computational time and an improvement in accuracy over EFGM. The present analysis shows that the results obtained by OEFG are in good agreement with those available in the literature.     

Effect of nitrogen and water uptake on yield of wheat

For 2 years, field experiments were conducted to study the direct and interactive effects of water and nitrogen uptake at different growth stages on grain yield of wheat, grown on coarse textured alluvial soil of Ludhiana. Twelve treatments comprising 3 irrigation regimes and 4 rates of N were imposed. The N and irrigation regimes showed significant interaction, especially during the drier year. Grain yield was better explained with water uptake and N uptake, when partitioned over different growth stages than with total uptake. The sensitivity factor for water uptake was higher at the reproductive stage ( = 1.60) than at the vegetative ( = 1.05) and maturation ( = 0.38) stages. Contrary, yield was more sensitive to N uptake during the vegetative stage than the reproductive and the maturation stages. Sensitivity of grain yield to water uptake was higher at higher N application rates. Yield predictability was much better (R² = 0.98) when N and water uptake at different growth stages were combined.