Influence of electron beam radiation on mechanical and thermal properties of styrene‐butadiene‐styrene block copolymer

Electron beam crosslinking of elastomers is a special type of crosslinking technique that has gained importance over conventional chemical crosslinking method, because the former process is fast, pollution free, and simple. The technique involves the impingement of high‐energy electrons generated from electron accelerators and the subsequent production of free radicals on target elastomers. These radicals result in crosslinking of elastomers via radical–radical coupling. In the process, some chain scission may also take place. In this work, a high‐vinyl (～ 50%) styrene‐butadiene‐styrene (S‐B‐S) block copolymer was used as the base polymer. An attempt was made to see the effect of electron beam radiation on the mechanical and thermal properties of the block copolymer. Radiation doses were varied from 25 to 300 kGy. Mechanical properties like tensile strength, elongation at break, modulus at different elongations, hardness, tear strength, crosslink density, and crosslink to chain scission of the irradiated samples were studied and compared with those of unirradiated ones. In this S‐B‐S block copolymer, a relatively low‐radiation dose was found effective in improving the level of mechanical properties. Differential scanning calorimeter and dynamic mechanical analyzer were used to study the thermal characteristics of the irradiated polymer. Influence of a stabilizer at different concentrations on the properties of S‐B‐S at varied radiation doses were also focused on. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Burr formation during drilling of mild steel at different machining conditions

This paper investigates burr generation while drilling of mild steel grade 350. The influences of feed, speed and point angle on burr height, thrust force, torque and chip ratio are investigated to correlate with burr height. It was found that, the burr height reduces gradually with the rise of speed at minimum feed and point angle. At maximum feed and point angle, initially the height rises with speed and then reduces as speed rises further. The maximum burr is 720 μm at 584 rpm. At maximum point angle and speed, the height rises initially and then reduces as the feed rises where the trend is opposite at minimum feed and speed. The maximum burr is 1223.15 μm at 0.25 mm/rev feed. The variation of burr height with point angle is similar to that with the variation of feed. The maximum burr is 1230 μm at 125°point angle. The trends of thrust forces, torques and chip ration with the variation of different parameters are not similar to that of burr height in most of the cases. The complex interaction between strain hardening and thermal softening plays the main role in burr formation for the considered material.     

Effect of Zn Doping on Structural and Magnetic Properties of Ba4Ni2−x Zn x Fe36O60 Hexaferrites

Polycrystalline Ba₄Ni_2?x Zn _x Fe₃₆O₆₀ (0.0 ≤x ≤ 1.4) hexagonal ferrite samples have been prepared by conventional solid-state reaction method. Structural and magnetic properties of the prepared samples were then analyzed by the X-ray diffraction technique and with superconducting quantum interface device (SQUID) magnetometer, respectively. Variations of lattice parameters, density, and porosity with Zn content were measured. Magnetic properties such as complex permeability, relative quality factor, loss factor, and saturation magnetization have been investigated as a function of Zn content. The study revealed that Zn content has a significant effect on structural and magnetic properties of the Ba₄Ni₂Fe₃₆ O ₆₀ hexaferrites.     

Synthesis of Secondary Amides from N‐Substituted Amidines by Tandem Oxidative Rearrangement and Isocyanate Elimination

In this work an efficient tandem process transforming N‐substituted amidines into secondary amides has been described. The process involves N‐acylurea formation by reaction of the substrate with bis(acyloxy)(phenyl)‐λ³‐iodane followed by isocyanate elimination. The periodinane reagents are obtained from the commercially available phenyliodine(III) diacetate [PhI(OAc)₂, (PIDA)] by ligand exchange with carboxylic acids. The N‐substituted amidine substrates are easily synthesized from readily available nitriles. The method is applicable for secondary amide synthesis, based on both aliphatic and (hetero)aromatic amines, including challenging amides consisting of sterically hindered acids and amines. Moreover, the protocol allows one to combine steric bulk with electron deficiency in the target amides (aniline based). Such compounds are difficult to synthesize efficiently based on classical condensation reactions involving carboxylic acids and amines. Overall, the synthetic protocol transforms a nitrile into a secondary amide in both aliphatic and (hetero)aromatic systems.

     

Safe amine based zinc dithiocarbamates for the vulcanization of carbon black reinforced natural rubber

Binary combination of three safe amine based synthesized zinc dithiocarbamates (ZDC), namely zinc (N‐benzyl piperazino) dithiocarbamate (ZBPDC), zinc (N‐ethyl piperazino) dithiocarbamate (ZEPDC), and zinc (N‐phenyl piperazino) dithiocarbamate (ZPPDC) with mercapto benzothiazole disulfide (MBTS) as an effective accelerator system for the vulcanization of carbon black (N330, N550, and N774) filled natural rubber (NR) composites are studied. A comparison between the safe amine based zinc dithiocarbamates with the unsafe zinc dimethyl dithiocarbamate (ZDMC) in the light of mechanical and aging resistance behavior, introduces the non carcinogenic rubber additives in the filled vulcanization of rubber. Both accelerator and filler have the major importance for improving the mechanical as well as aging resistance behavior of the resultant vulcanizate. Variation in the filler and also filler to oil ratio are done to optimize the mechanical properties. SEM studies of different types of filler with different amounts show that N330 at 30 phr loading composites forms more homogeneity and less aggregated structures. Natural rubber systems with N330 carbon black show the best results with respect to tensile strength, but after the aging N774 carbon black filled system indicates better retention in the tensile strength. ZPPDC‐MBTS accelerated vulcanizate shows the better age resistance behavior than ZDMC‐MBTS accelerated vulcanizate. From both the points of age resistance and mechanical properties, ZBPDC‐MBTS accelerator system is the suitable substitute for ZDMC‐MBTS accelerated system in the filled vulcanization of natural rubber composites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39988.     

Cell-graph coloring for cancerous tissue modelling and classification

In traditional cancer diagnosis process, pathologists manually examine biopsies to make diagnostic assessments. The assessments are largely based on visual interpretation of cell morphology and tissue distribution, lacking of quantitative measures. Therefore, they are subject to considerable inter-observer variability. To circumvent this problem, numerous studies aim at quantifying the characteristics of cancerous cells and tissues that distinguish them from their counterparts. Such quantification facilitates to design automated systems that operate on quantitative measures, and in turn, to reduce the inter-observer variability. There is a computational model available that relies solely on the topological features of cancerous cells in a tumor. Despite their complex dynamic nature, the self-organizing clusters of cancerous cells exhibit distinctive graph properties that distinguish the cancerous tissue from non-cancerous tissues; e.g. from a healthy tissue or an inflamed tissue. It is difficult to distinguish a cancerous tissue sample visually from an inflamed one. It is possible to construct a graph of the cells (cell graph) based on the location of the cells in the low-magnification image of a tissue sample surgically removed from a human patient. Assuming the cells present in a sample as the vertices of the cell graphs and the edges connecting those vertices/cells we can construct the cell graphs. There is a possibility of implementing the technique of using cell graphs to detect cancerous sample biopsies using some simple or a little bit complex computational techniques. Here possibly a new way is going to be introduced in this field, which is an application of graph coloring using the cell graphs to classify the normal, cancerous and inflamed sample biopsies. This work intends to automate the solution to the problem of identifying cancerous sample biopsies applying customized graph Coloring method solving by Genetic Algorithm on the cell graphs.     

An analysis of global edf schedulability for arbitrary-deadline sporadic task systems

Recent results on the global multiprocessor edf scheduling of sporadic task systems are, for the most part, applicable only to task systems in which each task’s relative deadline parameter is constrained to be no larger than its minimum inter-arrival separation. This paper introduces new analysis techniques that allow for similar results to be derived for task systems in which individual tasks are not constrained in this manner. For tasks with deadlines greater than their minimum inter-arrival separation, two models are considered, with and without an implicit intra-task job precedence constraint. The new analyses yield schedulability conditions that strictly dominate some previously proposed tests that are generally accepted to represent the current state of the art in multiprocessor edf schedulability analysis, and permits the derivation of an improved speed-up bound.

The partitioned dynamic-priority scheduling of sporadic task systems

A polynomial-time algorithm is presented for partitioning a collection of sporadic tasks among the processors of an identical multiprocessor platform. Since the partitioning problem is NP-hard in the strong sense, this algorithm is unlikely to be optimal. A quantitative characterization of its worst-case performance is provided in terms of resource augmentation.