Microstructure and cutting performance investigation of Ti(C, N)-based cermets containing various types of secondary carbides

In this paper, the effects of type and amount of various secondary carbides on the microstructure and cutting performance of Ti(C_0.7N_0.3)–12Co system have been investigated. Nine alloys with different amounts of WC, Mo₂C and Ta_0.7Nb_0.3C additives were studied, using scanning electron microscopy (SEM), Vickers hardness (HV), transverse rupture strength (TRS) and continuous turning tests. Alloys including Mo₂C and WC presented finer carbonitride grain structure, as well as higher wear resistance resulting from their higher hardness and highly solution hardened binder phase.     

Effect of deposition parameters on adhesion, hardness and wear resistance of Sn-Ni electrolytic coatings

The present investigation has been conducted in order to determine the influence of both the chemical composition of the bath and current density employed, on the adhesion, hardness and wear resistance of electrolytic Sn-Ni coatings deposited on a steel substrate. The micro-scratch test method was employed to evaluate the coating adhesion. Three scratches were performed at progressive loads. The subsequent observation of the surface damage by means of optical microscopy allowed the determination of the critical load, defined as the smallest load at which coating delamination will occur. The composite hardness of the system was determined by means of Vickers indentation and represented as a function of the relative indentation depth (R.I.D.). The absolute hardness of the coatings was computed by using a model published previously in the literature by one of the authors. The evaluation of the wear resistance was carried out through an accelerated wear test, without lubricant, under a ball-on-disc configuration, using a ball of AISI 52100 steel as a static counterpart. The wear scar morphology was studied by Scanning Electronic Microscopy (SEM) techniques coupled with the energy dispersive X-ray analysis (EDS). The results indicate that the Sn-Ni coatings obtained by means of the chloride-fluoride bath (CF) have apparently a higher adhesion to the steel substrate and wear resistance, in comparison with the coatings which were obtained by using the pyrophosphate bath (PF), irrespective to the current density value employed during deposition. However, the hardness results indicate that the coatings obtained from the pyrophosphate bath have a better endurance against indentation loads. Such a behavior has been partially explained in terms of the different microstructural features that characterized both coatings. The CF deposits were observed to present an elongated columnar grain structure free of cracks, whereas the PF coatings were observed to have an equiaxial structure with a high crack density. The present study has allowed the conclusion that the CF coatings have an overall better performance than the PF coatings.     

Solvent-free synthesis of benzoic esters and benzyl esters in novel Brønsted acidic ionic liquids under microwave irradiation

Fischer esterifications of benzoic acid with a variety of alcohols and a variety of acids with benzyl alcohol could be promoted by four novel Brønsted acidic ionic liquids a–d that bear a benzyl on the imidazolium or pyridinium cation. The reactions were carried out smoothly without the need of added catalyst with good to excellent isolated yields (77–98.5%) under solvent-free microwave irradiation conditions in the presence of 50 mol% ionic liquids. These ionic liquids could be recovered easily and recycled three times without any significant loss in their catalytic activity.     

Selective Oxidation of Hydrocarbons on Composite Oxides

A catalyst for the selective oxidation of hydrocarbons to unsaturated aldehydes, acids, acid anhydrides, divinyls, or styrenes has to perform several functions. First, it must supply a limited amount of oxygen to the reactant, sufficient to allow the formation of the desired product but not enough to allow complete oxidation. Further, it must provide appropriate sites for the adsorption of the hydrocarbons in deformed, reactive states. Last, the catalyst should be capable of transferring electrons from and to the reactants. These three demanding characteristics of an active catalyst impose severe limitations on the systems that can effectively perform selective oxidation reactions. Therefore catalyst selectivity, normally measured by the rate of formation of the specific product relative to that of undesired products, is sensitive to reaction conditions (temperature, feed rate, feed composition, and reactor design) and is very dependent on the details of the structure of the catalyst itself, its carriers, and promoters.     

基于2,3-吡啶二羧酸阳离子的系列Br(o)nsted酸性离子液体的合成与表征

以2,3-吡啶二羧酸、1-溴丁烷、苄基氯、相应的有机或无机酸为原料,经两步反应,在2,3-吡啶二羧酸阳离子基础上合成了8种结构新颖的室温功能化离子液体,这些功能化离子液体在室温下呈液相,同时表现出较强的Brnsted酸性.     

Effects of Simulated Herbivory on Defensive Compounds in Forage Plants of Norwegian Alpine Rangelands

A field study on the effects of current grazing practices on plants in central Norway found no increase in either phenolic compounds or proteinase inhibitors in plants subjected to grazing by sheep. This could either reflect insufficient damage to the plants due to low grazing intensity or a lack of a long-term response of the plants to grazing. In this study, we tested the hypothesis that damage to forage plants used by sheep and rodents in Norwegian alpine rangelands can stimulate a long-term (at least 2-week) increase in levels of defensive compounds. We used clipping experiments to manipulate the severity and timing of damage to eight species of common plants used by herbivores in Norway. Under greenhouse conditions (i.e., climate-controlled), we subjected mature plants to one of four clipping treatments: control (0% leaf tissue removed), low (10–15% leaf tissue removed), high (70–75% leaf tissue removed), or sustained (15% of leaf tissue removed every other day up to a total removal of 75%, i.e., five clippings over 9 days). Samples were collected 2 weeks after final clipping and analyzed for concentrations of total phenolics, proteinase inhibitors, ratio of total phenolics to soluble proteins, and ratio of proteinase inhibitors to soluble plant proteins. As expected, the different species of plants responded differently to simulated herbivory, but most plants either showed no response to mechanical wounding and tissue loss or had reduced defensive compounds. Thus, our results do not support the hypothesis that herbivory induces a long-term increase in defensive compounds in alpine rangelands of Norway, a result consistent with those from field studies.     

Vector phase correlation

Phase correlation has been applied for over 25 years to applications such as registration of images, but there has never been a simple generalisation to vector images. Here, for the first time, a vector approach to phase correlation, based on hypercomplex Fourier transforms, is proposed and demonstrated     

Instant Ciphertext-Only Cryptanalysis of GSM Encrypted Communication

In this paper we present a very practical ciphertext-only cryptanalysis of GSM (Global System for Mobile communications) encrypted communication, and various active attacks on the GSM protocols. These attacks can even break into GSM networks that use “unbreakable” ciphers. We first describe a ciphertext-only attack on A5/2 that requires a few dozen milliseconds of encrypted off-the-air cellular conversation and finds the correct key in less than a second on a personal computer. We extend this attack to a (more complex) ciphertext-only attack on A5/1. We then describe new (active) attacks on the protocols of networks that use A5/1, A5/3, or even GPRS (General Packet Radio Service). These attacks exploit flaws in the GSM protocols, and they work whenever the mobile phone supports a weak cipher such as A5/2. We emphasize that these attacks are on the protocols, and are thus applicable whenever the cellular phone supports a weak cipher, for example, they are also applicable for attacking A5/3 networks using the cryptanalysis of A5/1. Unlike previous attacks on GSM that require unrealistic information, like long known-plaintext periods, our attacks are very practical and do not require any knowledge of the content of the conversation. Furthermore, we describe how to fortify the attacks to withstand reception errors. As a result, our attacks allow attackers to tap conversations and decrypt them either in real-time, or at any later time. We present several attack scenarios such as call hijacking, altering of data messages and call theft. An earlier version of this paper appears in Barkan et al. (Advances in Cryptology, Proceedings of Crypto 2003, Lecture Notes in Computer Science, vol. 2729, pp. 600–616, 2003).