Viscoelastic State for the Solutions of Spherically Symmetric Viscoelasticity Problems

The solutions of the spherically symmetric, linear, isothermal, and transient viscoelasticity problems via reciprocity theorem have been investigated for a specific material. The integral form of stress–strain relations has been used. The Laplace transform of a viscoelastic state, which is necessary for the integral equation arising as a result of reciprocity theorem, has been derived. This integral equation has been solved by Laplace transform. A sample problem has been solved to test the presented formulation. A numerical application of the analytic solution of this problem has been given.     

Semantic weaving of configuration fragments into a consistent system configuration

Configuration fragments developed separately and focusing on different aspects, such as availability, security or performance of a system need to be integrated into a consistent system configuration to avoid system malfunctions. The main challenges of such integration are due to the overlapping entities and the integration relations between the entities of the different configuration fragments. In this paper we propose a model based approach for a consistent integration of configuration fragments into a system configuration. We use and extend the model weaving technique to capture the semantics of the relations between the entities of the configuration fragments. Moreover, we generate automatically the constraints corresponding to these semantic relations to complete the target system configuration profile. These constraints can be used to guard the configuration consistency during runtime modifications.     

Grammar constraints

With the introduction of the Regular Membership Constraint, a new line of research has opened where constraints are based on formal languages. This paper is taking the next step, namely to investigate constraints based on grammars higher up in the Chomsky hierarchy. We devise a time- and space-efficient incremental arc-consistency algorithm for context-free grammars, investigate when logic combinations of grammar constraints are tractable, show how to exploit non-constant size grammars and reorderings of languages, and study where the boundaries run between regular, context-free, and context-sensitive grammar filtering.     

An Analytical Approach to the Concept of Counter-UA Operations (CUAOPS)

Unmanned Aircraft (UA) have become an integral part of the present-day joint air operations. UA have potential to be employed across the full spectrum of Air Force functions. On the other hand, UA technology could be a subject of an asymmetric use by state actors in high or low density conflict, and/or by non-state actors in many ways including terrorism, drug smuggling, and limited attack with unconventional payloads i.e. biological or chemical agents. Therefore countering the threat associated with the hostile UA use could be necessary in the future. First part of the research revealed that UA can be a threat in the future. In the second part of the research, the SWOT (Strengths-Weaknesses-Opportunities-Threats) analysis supplemented with the Tree analysis (SWOT+Tree) provided a broader look for investigating the factors related to hostile UA use analytically. In literature, there is little information about the concepts for CUAOPS. The final goal of the paper is to find possible solutions and means for a better understanding of the nature of CUAOPS.     

A comparative study of SiAlON ceramics

Two different varieties of Si₃N₄ powders were used to prepare SiAlON ceramics. 100% β-Si₃N₄ was used from refractory grade powders (B1) and another purer 98% α-Si₃N₄ (50A) powder was used to prepare the SiAlON samples. Since SiC + SiAlON composites reportedly perform better, batches were prepared with 15% SiC addition to the refractory powders (B1) and 17.5% SiC was added to the other SiAlON composition (50A). The samples were gas pressure sintered at 1840 °C and at 22 bar with 1 h dwelling time. Thereby, we could achieve 97–98% theoretical density. The hardness was recorded 14–17 GPa while fracture toughness varied from 4.3 to 5 MPa m^1/2. Fretting experiments showed initial running-in period of 300 cycles for all the tribo-couples. After which, the steady state coefficient of frictions (COF) were achieved. Steel ball of 10 mm diameter, fretting against 50A composition, showed 0.6 average steady state COF while the same composition while fretting against alumina ball of the same diameter, showed 0.57 average steady state COF. Results have been compared with SiAlON composition derived from refractory powder (B1) and found that the 50A composition performs better under identical test conditions. Moreover, cytocompatibility study also suggests that the investigated 50A composition can be used as substrate to support cell adhesion and proliferation of L929 mouse fibroblast cell lines whereas B1 composition derived from refractory powders are toxic in nature.     

Chemical reactivity of mineral aggregates in aqueous solution: relationship with bitumen emulsion breaking

This paper reports a study on chemical reactivity of gneiss, diorite and limestone aggregates in aqueous solution. The originality of this study is that it extended to very short times (less than 1440 min). Rise in pH tests was implemented and dissolution kinetics was analysed. The results showed that calcium was the major element released by the aggregates. It has also been found that dissolution had an influence on the final morphology of aggregates. Polyamine emulsifier adsorption onto aggregates has been assessed using electrophoresis. Finally, the rise in pH and electrophoretic tests were compared to the breaking test traditionally performed to characterise bitumen emulsions. It was found that breaking values were controlled by both the surface area and the surface charge of the particles. Results may be correlated to polyamine adsorption on aggregates. Adsorption seemed to be efficient for gneiss and diorite: at pH 2, their charge turned from slightly negative to highly positive. At this pH value, limestone particles were dissolved and polyamine adsorption must be less efficient than with gneiss and diorite, for which the emulsion breaking was facilitated by the high attraction of particles for the emulsifier, due to their negative surface charge.     

Optimum design of cam-roller follower mechanism using a new evolutionary algorithm

Selection of tooling to perform specific operations like drilling and milling on ceramic materials using rotary ultrasonic machining process is an important aspect to meet stringent dimensions on workpiece as well as intended performance of tool. This phenomenon is more critical for micro rotary ultrasonic machining. In the present study, an effort was made to do micro drilling operation of Ø0.3 mm tool with varying geometry, having different wall thicknesses and abrasive grain sizes using design of experiments. The effect of tool-based parameters like grain size and wall thickness has been studied on axial cutting force, radial cutting force, tool wear, edge chipping area and taper. After examining axial and radial cutting forces, it has been concluded that lower wall thickness (80 μm) tool is good for drilling operation; and higher wall thickness (100 μm) tool is good for milling operation under same material removal rate conditions. It has been also investigated that lower wall thickness (80 μm) tool has less edge chipping area and less taper and can impart high drilling depth as compared to higher wall thickness (100 and 150 μm) tool. It is also concluded that lesser grain size (15 μm) tools are advantageous in terms of edge chipping area and cutting force for drilling and milling operations as compared to higher grain size (30, 35 and 45 μm) tool at constant material removal rate. Higher grain size tools have been broken at 1.13 mm³/h material removal rate conditions due to bad profile accuracy. But higher grain size tools have worked fairly well at less material removal rate condition. Higher grain size tools produced less wear. Tool wear was found minimum in higher wall thickness (100 μm) tool having higher abrasive grain size (30 μm). Using inferred results, Ø0.3 mm drilling experiments have been carried out on six aerospace ceramic materials. Also, groove of 0.5 mm size using Ø0.3 mm optimised tool has been successfully carried out in sintered SiC.     

Hybrid dual-curable cyanate ester/boron phosphate composites via sequential thiol-ene photopolymerization and thermal polymerization

The aim of this study was to improve hybrid dual-curable cyanate ester/boron phosphate composites via sequential thiol-ene photopolymerization and thermal polymerization for high performance applications such as aerospace and electronic devices. A novel 2,2′-diallylbisphenol A dicyanate ester (DA-BADCy) which is the allyl group containing cyanate ester was synthesized and characterized. DA-BADCy, silicon containing monofunctional thiol compound, trifunctional thiol compound and boron phosphate were cured using both ultraviolet (UV) and thermal methods. Using thiol-ene system, cyanate ester formulations, which are normally prepared at high temperatures, were prepared at room temperature. This study maintains ease of application for cyanate esters. Thermal stability, flammability and thermal conductivity of the samples were evaluated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), limiting oxygen index (LOI) and laser flash method, respectively. The samples were characterized with the following analysis; gel content, water absorption capacity and stress–strain test. Hydrophobicity of the samples was determined by the contact angle measurements. Moreover, the surface morphology of the samples was investigated by a scanning electron microscopy (SEM–EDS). The obtained results prove that the composites have good thermal and mechanical properties and with the help of easier preparation techniques, they can be used in many applications such as aerospace, electronic devices, materials engineering.     

Kinome-Wide Profiling Identifies Human WNK3 as a Target of Cajanin Stilbene Acid from Cajanus cajan (L.) Millsp.

Pigeon Pea (Cajanus cajan (L.) Millsp.) is a common food crop used in many parts of the world for nutritional purposes. One of its chemical constituents is cajanin stilbene acid (CSA), which exerts anticancer activity in vitro and in vivo. In an effort to identify molecular targets of CSA, we performed a kinome-wide approach based on the measurement of the enzymatic activities of 252 human kinases. The serine-threonine kinase WNK3 (also known as protein kinase lysine-deficient 3) was identified as the most promising target of CSA with the strongest enzymatic activity inhibition in vitro and the highest binding affinity in molecular docking in silico. The lowest binding affinity and the predicted binding constant pKi of CSA (−9.65 kcal/mol and 0.084 µM) were comparable or even better than those of the known WNK3 inhibitor PP-121 (−9.42 kcal/mol and 0.123 µM). The statistically significant association between WNK3 mRNA expression and cellular responsiveness to several clinically established anticancer drugs in a panel of 60 tumor cell lines and the prognostic value of WNK3 mRNA expression in sarcoma biopsies for the survival time of 230 patients can be taken as clues that CSA-based inhibition of WNK3 may improve treatment outcomes of cancer patients and that CSA may serve as a valuable supplement to the currently used combination therapy protocols in oncology.     

The food preservative potential of essential oils: is lemongrass the answer?

Several essential oils of medicinal plants possess proven antimicrobial activity and are suitable for applications on the food industry. The oil from Cymbopogon citratus (lemongrass) has been reported to have a wide range of biological activities. However, there are few controlled studies confirming its antimicrobial activity. The aim of our study was to assess the antimicrobial potential of lemongrass oil against a wide spectrum of food spoilage and pathogenic bacteria and yeast in liquid and vapour phase. The chemical composition of the oil was analyzed by gas chromatography; 14 components were identified and geranial (28.93 %), neral (24.30 %) and myrcene (23.92 %) were the most abundant constituents. Lemongrass oil showed potent antimicrobial activity against Gram positive bacteria and exhibited the strongest antifungal effect against Candida albicans and C. parapsilosis. Minimum inhibitory concentration varied from 0.019 to 1.25 mg mL^?1 for Gram positive bacteria and yeasts, indicating Staphylococcus aureus, S. epidermidis and C. albicans as the most susceptible strains. Moreover, the diameter of inhibition zone (DIZ) increased with increasing essential oil (EO) volume. Considerably superior antimicrobial activity was observed in the vapour phase. The DIZ resulting from the exposure to EO vapour was significantly larger than that from the same volume in the liquid phase. The DIZ varied from 22 to 90 mm for Candida strains. There is growing evidence that EO in vapour phase are effective antimicrobial systems and that they do have advantages over the use of oil in liquid phase. Our results imply that lemongrass oil could be useful for the development of novel types of natural preservatives for food control.