Electric field assisted solid-state interfacial joining of TaC-HfC ceramics without filler

The application of ultra-high-temperature ceramics (UHTCs) demands effective ways of joining in overcoming the problems associated with the fabrication of complex-shaped components. In this study, we choose to investigate a new method of rapidly joining pre-sintered TaC and HfC ceramics without any filler material using the spark plasma sintering (SPS) technique. A well-bonded TaC–HfC interface was observed with no apparent cracking and porosity at the joint. The joining mechanisms were predominantly driven by solid-state diffusion and localized plastic deformation. The nanomechanical properties of the TaC-HfC joint are better than the HfC while comparable to that of the TaC. High-load indentation (up to 200 N) results suggest that the TaC–HfC interface is stronger than the parent UHTCs with no crack propagating at the interface. Upon comparison with the parent UHTCs, the damaged area and the average crack length at the interface, reduced up to ~94% and ~56%, respectively. This study shows that the SPS technique can also apply to joining other UHTCs without any filler, resulting in the new field of developing complex components for the thermal protection system (TPS).     

A Service Level Agreement Aware Online Algorithm for Virtual Machine Migration

The demand for cloud computing has increased manifold in the recent past. More specifically, on-demand computing has seen a rapid rise as organizations rely mostly on cloud service providers for their day-to-day computing needs. The cloud service provider fulfills different user requirements using virtualization - where a single physical machine can host multiple Virtual Machines. Each virtual machine potentially represents a different user environment such as operating system, programming environment, and applications. However, these cloud services use a large amount of electrical energy and produce greenhouse gases. To reduce the electricity cost and greenhouse gases, energy efficient algorithms must be designed. One specific area where energy efficient algorithms are required is virtual machine consolidation. With virtual machine consolidation, the objective is to utilize the minimum possible number of hosts to accommodate the required virtual machines, keeping in mind the service level agreement requirements. This research work formulates the virtual machine migration as an online problem and develops optimal offline and online algorithms for the single host virtual machine migration problem under a service level agreement constraint for an over-utilized host. The online algorithm is analyzed using a competitive analysis approach. In addition, an experimental analysis of the proposed algorithm on real-world data is conducted to showcase the improved performance of the proposed algorithm against the benchmark algorithms. Our proposed online algorithm consumed 25% less energy and performed 43% fewer migrations than the benchmark algorithms.     

Development of the knowledge‐based learning system for distance education

This article addresses difficulties in developing a knowledge base for application to educational environments. To solve this problem, fundamental principles used for building similar systems are proposed. A mathematical model is chosen to propose a mathematical design of educational materials based on linguistic variables. A membership function of knowledge evaluation and an architecture of fuzzy knowledge were created, on the basis of a set of two types of fuzzy rules that cover all possible situations in the educational environment, with a demonstration of its application based on the original method of selection questions for procedure evaluation of student knowledge. In the end, the studies analyzing the utility of the experiment clearly showed an increase in the efficiency of the educational process, with the advantage of applied models and technologies in the long term. © 2012 Wiley Periodicals, Inc.     

Densification Kinetics of CeO<Subscript>2</Subscript> Reinforced 8 Mol.% Y<Subscript>2</Subscript>O<Subscript>3</Subscript> Stabilized ZrO<Subscript>2</Subscript> Ceramics

The grain growth kinetics of 8YSZ ceramics processed using spark plasma sintering (SPS) has been investigated in the temperature ranging from 1100°C to 1500°C. The activation energy during SPS densification was obtained as 332 kJ/mol with grain boundary diffusion as a dominant mechanism. Further, the effect of CeO₂ on the densification kinetics of 8YSZ ceramic processed via SPS and conventional sintering (CS) has been delineated. The lower grain boundary mobility of CS-processed composites (an order of magnitude lower than SPS) is attributed to the solute drag and lattice distortion mechanism. However, no significant change in the grain boundary mobility was observed with CeO₂ addition (~?14.7–43.9?×?10^?18 m³/N/s for CS and 107.2–116.7?×?10^?18 m³/N/s for SPS) revealing that the defect concentration is nearly constant in 8YSZ. The study highlights the effect of sintering techniques (SPS and CS) and reinforcement (CeO₂) on engineering the desired microstructure of 8YSZ ceramic.     

Comparison of constituents, antioxidant potency, and acetylcholinesterase inhibition in Lentinus edodes, Sparassis crispa, and Mycoleptodonoides aitchisonii

This study evaluates three edible mushrooms: Lentinus edodes, Sparassis crispa, and Mycoleptodonoides aitchisonii, in terms of acetylcholinesterase (AChE) inhibition, antioxidant potency and constituents free amino acids and mineral. The concentration of essential amino acids was found to be 34.10 mg/g in M. aitchisonii, 26.25 mg/g in S. crispa, 25.99 mg/g in L. edodes. S. crispa displayed the highest DPPH scavenging activity and phenolic contents. The best results for AChE inhibition were obtained from M. aitchisonii. These results suggest that M. aitchisonii has high potential for cognitive improvement by AChE inhibition and antioxidant potency.     

Physical and chemical modification of distillery sludge for Pb(II) biosorption

The waste distillery sludge from sugar-cane industry was pretreated physically (boiled, heated and autoclaved) as well as chemically (HCl, H(2)SO(4), H(3)PO(4), NaOH, Ca(OH)(2), Al(OH)(3), C(6)H(6), HCHO, CH(3)OH and C1(2)H(25)OSO(3)Na (sodium dodecyl sulphate (SDS)) for assessing the comparative sorption capacity of untreated and modified distillery sludge for Pb(II) biosorption from aqueous solutions. Experiments were conducted in shake flasks on a batch basis to access the effect of different experimental parameters such as pH, biosorbent dosage, biosorbent size, initial Pb(II) concentration and contact time. The uptake capacity 'q' (mg/g) of untreated and pretreated distillery sludge was in following order: NaOH (51.29+/-1.21)>HCl (49.82+/-1.22)>HCHO (49.56+/-1.14)>H(2)SO(4) (47.71+/-1.20)>HgCl(2) (45.32+/-1.06)>Ca(OH)(2) (44.01+/-1.18)>MeOH (43.73+/-1.23)>C(6)H(6) (42.72+/-1.19)>H(3)PO(4) (42.01+/-1.17)>SDS (40.87+/-1.27)>autoclaved (40.23+/-1.24)>Boiled (39.95+/-1.19)>heated (38.87+/-1.32)>Al (OH)(3) (38.30+/-1.14)>untreated (37.76+/-1.21). In further parameter studies, the optimized biosorbent size was 0.250 mm at pH 5 and best dose was 0.05 g of biosorbent. The applicability of the Langmuir and Freundlich models for sorption process was tested and best fitted model was Langmuir with the coefficient of determination (R(2)) value, 0.97, the process followed second order kinetic mechanism.     

Nanosilica Supported Dual Acidic Ionic Liquid as a Recyclable Catalyst for the Rapid and Green Synthesis of Polycyclic Phenolic Compounds

Generally ionic liquids have gained increasing attention in organic synthesis as catalyst and solvent. However, there are some drawbacks, including the difficulties in the product purification, ionic liquid recycling, and use of excess amounts of the expensive ionic liquid when the ionic liquid is used in the organic reactions. In addition, the high viscosity of ionic liquids can lead to mass transfer limitations in fast chemical reactions. These problems can be overcome by the use of supported ionic liquid phases. In this article, a simple, efficient and green method has been developed for the synthesis of bisphenolic antioxidants by the reaction of 2-tert-butyl-4-methylphenol and aldehydes in the presence of nanosilica supported dual acidic ionic liquid (NSSDAIL) as robust and reusable catalyst under solvent-free conditions. Three different NSSDAILs were synthesized and characterized using SEM, BET, IR, and XRD techniques. High yields of the products, short reaction times, use of a non corrosive, non toxic and reusable catalyst, and use of solvent-free condition are the worthwhile advantages of the current method.