Machining is basically defined as a process of gradual material removal used to finish materials of desired surface finish and dimensional accuracy. For achieving the desired surface finish and ...dimensional accuracy every machining operation faces several difficulties such as localization of heat in the cutting zone resulting in various problems such as tool wear, increase in surface roughness, etc. So in order to overcome these problems the most common technique is to use cutting fluids. Cutting fluids are generally used for cooling and lubricating the machining zone. But there are various environmental constraints on the use of cutting fluids during the machining. As the continuous use of these cutting fluids have an adverse effect on human health and environment. Therefore it becomes very essential to go for some new technique which can either reduce the use of lubricants or completely avoid them. Thus surface texturing proved to be one of the promising techniques which helped in the improvement of tribological properties of textured tools. The surface textures have different geometrical size, shape and are generally created either on the flank surface or on the rake surface of the cutting tool. The quality of texture greatly depends on the manufacturing processes which have been used. Thus it becomes very essential to have a complete understanding of the associated parameters of any process. The basic mechanisms in the improvement of tribological properties are debris entrapment, reduction in contact length and improvement in lubrication capacity, which finally helps in improvement in reducing the cutting forces, tool wear and surface roughness of the work material.
The current article presents an extensive literature survey carried out on the different aspects of textured cutting tools in machining processes – turning, drilling and milling. It includes the different techniques used in creating these textures on cutting tool, experimental setups, the mechanism how textured tool is performing better than conventional tool, different modelling and simulation techniques used and the effect of these textures on improvement in surface finish, reducing cutting forces, tool wear, friction and cutting temperature.
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•The progress in photoswitches based on spiropyran, oxazine, spirooxazine and chromenes is overviewed.•The photochromic molecules demonstrate excellent metal affinity towards heavy ...metal ions.•The photochromic molecules produce an excellent optical signal in the presence of specific metal ions.•The photosensitive nature of the metal complex allow for the release of metal ion triggered by light.
This review focuses on the recent growth in the photo triggered molecular receptors for heavy metal ions. The photochromic unit in such molecular receptors performs as a trigger unit to allow control over a range of the properties through an external stimulus. This review opens up with the new opportunities for the development of host molecular motifs for heavy metal ion sensing applications. The photochromic switches based on a chemical structure like spiropyran, chromenes and spirooxazines tagged with appropriate chromogenic or fluorogenic unit reported till date have been summarized and categorized by the selectivity of metal ion to achieve the suitable optical response. The review has relevance for designing new photoreversible switches with the interesting optical response for environmentally important heavy metal ions.
•A spirooxazine receptor was synthesized and structure was investigated through single crystal X-ray determination.•The optical response (color, absorbance and fluorescence change) of the ...spirooxazine receptor toward transition metal ions was investigated.•The spirooxazine receptor displayed highly sensitive and selective optical response toward Fe3+ ions.•Detection limit value suggested that the spirooxazine receptor can be used for detection of trace concentration of Fe3+ ions in aqueous solution.
A photochromic spirooxazine derivative was synthesized and evaluated for optical response toward heavy metal ions. The spirooxazine derivative was observed to selectively respond to the presence of Fe3+ ions and produced both chromogenic and fluorogenic response. The spirooxazine derivative produced a ∼100nm shift in the UV–visible spectrum and ∼90 fold enhancement in fluorescence intensity in the presence of one equivalent Fe3+ ions. A large stokes shift (110nm) was also observed on addition of one equivalent Fe3+ ions in methanol or methanol:water (1:1) solvent system.
The tool indexing problem (TIP) is the problem of allocating cutting tools to different slots in a tool magazine of Computer Numerically Controlled machine to reduce the processing time of jobs on ...the machine. This is one of the mostly encountered optimization problems in manufacturing systems. In TIP, the number of tools used by the machine is at most the number of slots available in the tool magazine. In this article, a customized harmony search (HS) algorithm, which utilizes a harmony refinement strategy for faster convergence, is presented to solve TIP. The harmony refinement method also helps to avoid getting stuck into local optima. The performance of the proposed method is tested on 27 instances taken from the literature and out of these it is found to improve the best known solutions for 16 instances. For the remaining instances, it gives the same results as found in the literature. Moreover, the performance of the proposed algorithm is tested on newly adapted 41 instances and for some of these instances the results obtained using the proposed algorithm are compared with that obtained using CPLEX.
Martensitic AISI 420 steel has widespread applications in the manufacturing of shafts of large vertical pumps, various dental and surgical instruments because of its better mechanical, heat and ...corrosion resistance properties. However, the machining of this steel possesses a great challenge because of its poor thermal conductivity. Therefore, the current study aims to study the performance of different coated carbide tool (multi-coated TiN-Al
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-TiN coated, single TiAlN coated) and uncoated carbide tool during the dry turning of martensitic AISI 420 steel at different cutting parameters (speed, feed, depth). The machining performances such tool wear, surface defect, residual stress, cutting force and chip morphology are assessed. Abrasion, built-up edge, adhesion and micro-cracks are the wear mechanism observed in the cutting tools. The uncoated tool showed minimum generation of residual stress on the machined surface followed by single TiAlN coated tool. The influence of tool coatings and machining parameters on the various geometrical characteristics of the sawtooth chip has been investigated. It is perceived that the TiAlN coated tool results in minimum frequency and maximum chip segmentation ratio of chips compared to other tools. Out of the different coated and uncoated carbide tools utilized during the turning of martensitic AISI 420 steel, the single-layer TiAlN coated tool performed superior in terms of reduction of tool wear, cutting forces and surface roughness compared to the other coated tools and uncoated tool. The results indicate an average percentage reduction in flank wear, surface roughness, feed force and tangential force of 70.5, 42.8, 24.1 and 20.7%, respectively, using the TiAlN coated tool compared to the uncoated tool. The current investigations recommend the TiAlN coated tool with a feed rate in the range of 0.10–0.25 mm/rev while machining martensitic AISI 420 steel because of its excellent overall performance characteristics.
Summary
The draft genome of the moss model, Physcomitrella patens, comprised approximately 2000 unordered scaffolds. In order to enable analyses of genome structure and evolution we generated a ...chromosome‐scale genome assembly using genetic linkage as well as (end) sequencing of long DNA fragments. We find that 57% of the genome comprises transposable elements (TEs), some of which may be actively transposing during the life cycle. Unlike in flowering plant genomes, gene‐ and TE‐rich regions show an overall even distribution along the chromosomes. However, the chromosomes are mono‐centric with peaks of a class of Copia elements potentially coinciding with centromeres. Gene body methylation is evident in 5.7% of the protein‐coding genes, typically coinciding with low GC and low expression. Some giant virus insertions are transcriptionally active and might protect gametes from viral infection via siRNA mediated silencing. Structure‐based detection methods show that the genome evolved via two rounds of whole genome duplications (WGDs), apparently common in mosses but not in liverworts and hornworts. Several hundred genes are present in colinear regions conserved since the last common ancestor of plants. These syntenic regions are enriched for functions related to plant‐specific cell growth and tissue organization. The P. patens genome lacks the TE‐rich pericentromeric and gene‐rich distal regions typical for most flowering plant genomes. More non‐seed plant genomes are needed to unravel how plant genomes evolve, and to understand whether the P. patens genome structure is typical for mosses or bryophytes.
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•A chromogenic substituted spiropyran was synthesized and evaluated for affinity towards anions.•The spiropyran derivative selectively detected cyanide ions in the presence of other ...anions.•The spiropyran derivative displayed high sensitivity towards cyanide ions.•DFT or TDDFT/B3LYP/6-31G(d) methods were used to investigate the photochromism and cyanide binding to the spiropyran derivative.
A nitrophenyl azo substituted spiropyran was synthesized and characterized spectroscopically. The substituted spiropyran derivative was evaluated for affinity towards different anions in MeCN:water (10mM HEPES buffer) at different pH. The spiropyran derivative selectively detected cyanide ions by displaying blue or purple color visible to the naked eye and through spectral changes. The 1H NMR spectra was used to confirm the binding of cyanide ion to the receptor. The nitrophenyl azo group amplified the observed change in color triggered by cyanide binding to the spiropyran derivative enabling high sensitivity.Theoretical methods were used to investigate the experimental observation at the molecular level.
The Single-Row Facility Layout Problem (SRFLP) is a well-known combinatorial optimization problem. The objective of SRFLP is to find out the arrangement of facilities with given lengths on a line so ...that the weighted sum of the distances between all pairs of facilities is minimized. This problem is known to be NP-hard. Hence, a population-based improvement heuristic algorithm with local search is presented in this article to solve SRFLP. The proposed algorithm works well also for the Single-Row Equidistant Facility Layout Problem (SREFLP), where the length of each facility is equal. The computational efficiency of the proposed algorithm is checked with the instances of sizes ranging from 5 to 300 available in the literature for SRFLP and SREFLP. The obtained results are compared to those from different state-of-the-art algorithms. The proposed algorithm achieves best known solutions to date for every instance considered in this article in reasonable computational time.
With majority of the medical journals having a rejection rate of more than 80% of submitted manuscripts, it does come as a shock and grief to the author who had a lot of expectations before ...submission. Though most of the literature available does mention how to overcome the lacunae in the manuscript before considering resubmission in another journal, none addresses the mental agony and setback the author faces and the way to overcome this setback. Every author should develop immunity and be adequately mentally prepared to overcome this misery. A question- answer session between an eager enthusiastic author, a highly experienced reviewer, and the final authority Editor is presented for guidance.
Forest trees are dominant components of terrestrial ecosystems that have global ecological and economic importance. Despite distributions that span wide environmental gradients, many tree populations ...are locally adapted, and mechanisms underlying this adaptation are poorly understood. Here we use a combination of whole-genome selection scans and association analyses of 544 Populus trichocarpa trees to reveal genomic bases of adaptive variation across a wide latitudinal range. Three hundred ninety-seven genomic regions showed evidence of recent positive and/or divergent selection and enrichment for associations with adaptive traits that also displayed patterns consistent with natural selection. These regions also provide unexpected insights into the evolutionary dynamics of duplicated genes and their roles in adaptive trait variation.
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