Analysis of the life of cemented carbide drills with modified surfaces

The performance of cemented carbide cutting tools during machining is influenced not only by the mechanical properties of the coating and substrate but also by the topographies of their surfaces. A tool with good coating and substrate properties but unsuitable topographies may exhibit accelerated wear and, consequently, impaired performance. In this work, drills coated using physical vapor deposition (PVD) were produced with different substrate textures, which in turn generated different coating textures. The surface roughness values of the coated drills were measured together with the residual stress at the interface between substrate and coating. Drilling tests were performed and tool wear was measured during the machining process. Two different tool coatings were studied: TiAlN and TiAlCrSiN. The goal was to study how the characteristics of the substrate and coating (material, surface topography, and residual stress) influence tool life. Tool life experiments were carried out using drilling tests in AISI 1548 steel, which is often used in crankshafts. The primary tool wear mechanism was attrition in all the drills. The main conclusion of this work is that the tool with the lowest roughness and a TiAlCrSiN coating had the best performance in the conditions tested here.     

Investigation of the thermal,mechanical and morphological properties of poly(vinyl chloride)/polyhedral oligomeric silsesquioxane nanocomposites

Research into organic–inorganic nanocomposites has recently become popular, particularly the development of new polymer nanocomposites. Compared to pristine polymers or conventional composites, these nanocomposites exhibit improved properties. The storage modulus of a poly(vinyl chloride) (PVC)/polyhedral oligomeric silsesquioxane (POSS) nanocomposite slightly decreased with POSS content, but had a higher modulus from 50 to 100 °C. Some of the material appeared to be aggregated with 1 wt% POSS in the polymeric matrix. Conversely, with a POSS content of 5 wt%, a better dispersion of the nanoparticles was observed. The presence of POSS in the plasticised PVC compound had little influence on the final properties of the nanocomposites, showing weaker interactions between the POSS and the plasticised PVC compound. Copyright © 2010 Society of Chemical Industry     

Proportional differentiated admission control

This letter presents a new admission control policy inspired in the framework of proportional differentiated services (PDS). While most of previous PDS has focused on average queueing delays and packet drops to differentiate the performance of adaptive applications, the proportional differentiation admission control (PDAC) differentiates inelastic traffic in terms of blocking probabilities. The PDAC is built up using asymptotic approximation theory, employs a class based approach, and conforms with the PDS requirements of predictability and controllability . Numerical experiments confirm a good performance of the approach.     

Inhibition of angiotensin I converting enzyme by anacardic acids isolated from Cashew nut (Anacardium occidentale Linn.) shell liquid

Hypertension represents one of the most common maladies of western civilizations caused by bad dietary practices and lack of exercise. Angiotensin-I-converting enzyme inhibitors (ACEi) have been shown to be very efficient in the prevention of hypertension. ACEi are also implicated (by their ability to reduce the product of ACE activity namely angiotensin-II levels, which has oncogenic and increased cell proliferation effects) to be efficient anticancer agents. Therefore, we evaluated the potential antihypertension capacities of anacardic acids purified from Cashew (Anacardium occidentale Linn.) nut shell liquid by inhibition of ACE using analytical reverse-phase high performance liquid chromatography. The ability to inhibit ACE showed the following relation: anacardic-3 (IC₅₀ = 12 µM) > anacardic acid-4 (IC₅₀ = 20 µM) > anacardic acid-2 (IC₅₀ = 33 µM) > anacardic acid-1 (IC₅₀ = 39 µM) as compared to the positive control captopril (IC₅₀ = 6.85 nM). Salicylic acid lacking a phytyl side chain was negative. The capacity of purified anacardic acids to inhibit ACE thereby represents the most potent naturally available plant chemicals described so far, as a potential means of reducing hypertension. The inhibition of angiotensin II production indicated that anacardic acids could also have utility in cancer prevention and recurrence, and reduction of cardiotoxicity during chemotherapy.     

An AS-level overlay network for IP traceback

Distributed denial of service attacks currently represent a serious threat to the appropriate operation of Internet services. To deal with this threat, we propose an overlay network that provides an IP-traceback scheme at the level of autonomous systems. Our proposed autonomous system-level IP-traceback system contrasts with previous works because it does not require a priori knowledge of the network topology and allows single-packet traceback and incremental deployment. Our first contribution is a new extension to the Border Gateway Protocol update-message community attribute that enables information to be passed across autonomous systems that are not necessarily involved in the overlay network. The second contribution is a new sequence-marking process to remove ambiguities in the traceback path. Two different strategies for incremental system deployment are investigated and evaluated. We show that strategic placement of the system on highly connected autonomous systems produces relevant results for IP traceback even if the system operates on only a few autonomous systems. The main conclusion is that the proposed system is suitable for large-scale networks such as the Internet because it provides efficient traceback and allows incremental deployment.     

Cross-modal interactions between taste and smell: Odour-induced saltiness enhancement depends on salt level

In recent years, health concerns related to salt have led to extensive research on low-salt foods. One major remaining issue is to reduce sodium content while still providing the salty fix, to maintain food appreciation, acceptance and choice. Using well-selected odours has been proposed to compensate for sodium chloride reduction in food, due to the cross-modal interactions between odour and taste. However, interactions between taste and odour, with regards to saltiness, remain poorly investigated. Moreover, although a few studies have assessed the influences of odour and sweet supra-threshold intensity on cross-modal interactions, none focused directly on how they influence saltiness. Therefore, the aim of the present study is to determine if the level of saltiness, i.e., the concentration of sodium chloride in aqueous solutions, influences odour-induced saltiness enhancement (OISE). A panel of 64 untrained panellists evaluated the saltiness of water solutions including salt and a tasteless odorant. Following a full factorial design, three concentrations of salt were used in conjunction with three aroma conditions. The results confirmed that OISE depends on odour-taste congruency but also clearly indicated that OISE depends on salt concentration (salty intensity): the saltiness of a low- or medium-salt-content solution increased significantly when subjects perceived simultaneously the congruent sardine aroma, but OISE was no more significant with high-saltiness solutions. This effect has to be taken into account when using OISE as a compensation strategy in low-salt food.     

Interaction between Nanoparticles,Membranes and Proteins: A Surface Plasmon Resonance Study

Regardless of the promising use of nanoparticles (NPs) in biomedical applications, several toxic effects have increased the concerns about the safety of these nanomaterials. Although the pathways for NPs toxicity are diverse and dependent upon many parameters such as the nature of the nanoparticle and the biochemical environment, numerous studies have provided evidence that direct contact between NPs and biomolecules or cell membranes leads to cell inactivation or damage and may be a primary mechanism for cytotoxicity. In such a context, this work focused on developing a fast and accurate method to characterize the interaction between NPs, proteins and lipidic membranes by surface plasmon resonance imaging (SPRi) technique. The interaction of gold NPs with mimetic membranes was evaluated by monitoring the variation of reflectivity after several consecutive gold NPs injections on the lipidic membranes prepared on the SPRi biochip. The interaction on the membranes with varied lipidic composition was compared regarding the total surface concentration density of gold NPs adsorbed on them. Then, the interaction of gold and silver NPs with blood proteins was analyzed regarding their kinetic profile of the association/dissociation and dissociation constants (k_off). The surface concentration density on the membrane composed of 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine and cholesterol (POPC/cholesterol) was 2.5 times higher than the value found after the injections of gold NPs on POPC only or with dimethyldioctadecylammonium (POPC/DDAB). Regarding the proteins, gold NPs showed preferential binding to fibrinogen resulting in a value of the variation of reflectivity that was 8 times higher than the value found for the other proteins. Differently, silver NPs showed similar interaction on all the tested proteins but with a variation of reflectivity on immunoglobulin G (IgG) 2 times higher than the value found for the other tested proteins.     

Influence of the addition of multi-walled carbon nanotubes on the thermal and mechanical properties of polyamide-11 before and after aging tests

In this work, the preparation and characterization of nanocomposites of commercial polyamide-11 reinforced with multi-walled carbon nanotubes (MWCNT), untreated, oxidized or with the modified surface through silanization with 3-aminopropyl trimethoxy silane (APTMS), in concentrations of 0.1%, 0.5%, and 1.0 wt% in the polymer matrix was investigated. The processing of the nanocomposites was carried out via mixing in the molten state in a twin-screw mini-extruder at 200°C under 60 rpm screw rotation speed, with a residence time of 7 min. The addition of the MWCNT increased the thermal stability of PA11, predominantly with 0.5% of silanized nanotubes, as observed by the thermogravimetric analysis. X-ray diffraction and differential scanning calorimetry analyses indicated that the degree of crystallinity of the formulations increased with the nanofiller content. On the other hand, the use of the highest concentration generated agglomerates, suggesting less dispersion in the matrix and, consequently, a reduction in crystallinity. Dynamic mechanical thermal analysis showed that the silanization process promoted an increase in both loss and storage moduli. All produced nanocomposites obtained values of corrected inherent viscosity above 1.20 dl/g, before and after the aging test. The use of lower load levels promoted better processability due to the lubricating effect of the nanotubes and an increase in the hydrophobic character of the samples, as observed by the increase of the contact angle.     

Heuristic and exact algorithms for a min–max selective vehicle routing problem

In this work, we investigate a vehicle routing problem where not all clients need to be visited and the goal is to minimize the longest vehicle route. We propose two exact solution approaches for solving the problem: a Branch-and-cut (BC) algorithm and a Local Branching (LB) method that uses BC as its inner solver. Our computational experience indicates that, in practice, the problem is difficult to solve, mainly when the number of vehicles grows. In addition to the exact methods, we present a heuristic that relies on GRASP and on the resolution of a restricted integer program based on a set covering reformulation for the problem. The heuristic was capable of significantly improving the best solutions provided by BC and LB, in one tenth of the times taken by them to achieve their best upper bounds.