Carbon deposition and the role of reducing agents in hot-corrosion processes

Sodium sulfate deposits generated by impurities in the fuels can be reduced to more corrosive sulfide in the presence of partially uncombusted hydrocarbons, the reduction temperature depending upon the carbon particle size. Thermogravimetric studies indicate that nickel oxide and oxidized nickel metal are rapidly reduced by methane between 500° and 1000°C with deposition of pyrolytic carbon. The analogy is pointed out between the attack on a Ni-13Al-10Cr alloy by Na₂SO₄ both in the presence of carbon deposits and in a reducing atmosphere of hydrogen. It appears that carbon deposition by promoting local reducing conditions can play an important role in the occurrence of hot-corrosion in gas turbines.     

Optimizing NFV placement for distributing micro-data centers in cellular networks

With the popularity of mobile devices, the next generation of mobile networks has faced several challenges. Different applications have been emerged, with different requirements. Offering an infrastructure that meets different types of applications with specific requirements is one of these issues. In addition, due to user mobility, the traffic generated by the mobile devices in a specific location is not constant, making it difficult to reach the optimal resource allocation. In this context, network function virtualization (NFV) can be used to deploy the telecommunication stacks as virtual functions running on commodity hardware to meet users’ requirements such as performance and availability. However, the deployment of virtual functions can be a complex task. To select the best placement strategy that reduces the resource usage, at the same time keeps the performance and availability of network functions is a complex task, already proven to be an NP-hard problem. Therefore, in this paper, we formulate the NFV placement as a multi-objective problem, where the risk associated with the placement and energy consumption are taken into consideration. We propose the usage of two optimization algorithms, NSGA-II and GDE3, to solve this problem. These algorithms were taken into consideration because both work with multi-objective problems and present good performance. We consider a triathlon circuit scenario based on real data from the Ironman route as an use case to evaluate and compare the algorithms. The results show that GDE3 is able to attend both objectives (minimize failure and minimize energy consumption), while the NSGA-II prioritizes energy consumption.

     

Availability analysis of design configurations to compose virtual performance-optimized data center systems in next-generation cloud data centers

Next-generation cloud data centers are based on software-defined data center infrastructures that promote flexibility, automation, optimization, and scalability. The Redfish standard and the Intel Rack Scale Design technology enable software-defined infrastructure and disaggregate bare-metal compute, storage, and networking resources into virtual pools to dynamically compose resources and create virtual performance-optimized data centers (vPODs) tailored to workload-specific demands. This article proposes four chassis design configurations based on Distributed Management Task Force's Redfish industry standard applied to compose vPOD systems, namely, a fully shared design, partially shared homogeneous design, partially shared heterogeneous design, and not shared design; their main difference is based on the used hardware disaggregation level. Furthermore, we propose models that combine reliability block diagram and stochastic Petri net modeling approaches to represent the complexity of the relationship between the pool of disaggregated hardware resources and their power and cooling sources in a vPOD. These four proposed design configurations were analyzed and compared in terms of availability and component's sensitivity indexes by scaling their configurations considering different data center infrastructure. From the obtained results, we can state that, in general, when one increases the hardware disaggregation, availability is improved. However, after a given point, the availability level of the fully shared, partially shared homogeneous, and partially shared heterogeneous configurations remain almost equal, while the not shared configuration is still able to improve its availability.     

DCAV: A software system to evaluate next-generation cloud data center availability through a friendly graphical interface

To assess the availability of different data center configurations, understand the main root causes of data center failures and represent its low-level details, such as subsystem's behavior and their interconnections, we have proposed, in previous works, a set of stochastic models to represent different data center architectures (considering three subsystems: power, cooling, and IT) based on the TIA-942 standard. In this paper, we propose the Data Center Availability (DCAV), a web-based software system to allow data center operators to evaluate the availability of their data center infrastructure through a friendly interface, without need of understanding the technical details of the stochastic models. DCAV offers an easy step-by-step interface to create and configure a data center model. The main goal of the DCAV system is to abstract low-level details and modeling complexities, becoming the data center availability analysis a simple and less time-consuming task.     

Broadband light emission induced by laser absorption and optimized by thermal injection in Nd3+:Y2SiO5 ceramic powder

Laser-induced broadband (white) light emission has been studied in different particle systems for use in light-emitting devices. The photoinduced phenomenon occurs above a certain excitation power threshold and it is generally studied under vacuum conditions. In this work, the phenomenon is studied in neodymium-doped yttrium silicate ceramic powder synthesized by combustion method. White light is observed when the sample is excited in ambient air with a continuous-wave near-infrared (λ = 808 nm) laser powered above 1.3 W. When the temperature of the sample is externally raised above 200°C, white light is observed above 1.0 W and a large enhancement of the broadband emission intensity is observed.     

3‐Aminoazetidin‐2‐one Derivatives as N‐Acylethanolamine Acid Amidase (NAAA) Inhibitors Suitable for Systemic Administration

N‐Acylethanolamine acid amidase (NAAA) is a cysteine hydrolase that catalyzes the hydrolysis of endogenous lipid mediators such as palmitoylethanolamide (PEA). PEA has been shown to exert anti‐inflammatory and antinociceptive effects in animals by engaging peroxisome proliferator‐activated receptor α (PPAR‐α). Thus, preventing PEA degradation by inhibiting NAAA may provide a novel approach for the treatment of pain and inflammatory states. Recently, 3‐aminooxetan‐2‐one compounds were identified as a class of highly potent NAAA inhibitors. The utility of these compounds is limited, however, by their low chemical and plasma stabilities. In the present study, we synthesized and tested a series of N‐(2‐oxoazetidin‐3‐yl)amides as a novel class of NAAA inhibitors with good potency and improved physicochemical properties, suitable for systemic administration. Moreover, we elucidated the main structural features of 3‐aminoazetidin‐2‐one derivatives that are critical for NAAA inhibition.     

Nonlinear optical materials by electrospinning technique

The possibility of using electrospinning to deposit, and simultaneously electrically pole, polymeric mats containing nonlinear optical (NLO) molecules is studied. Disperse Red 1 (DR1) chromophore dispersed into polymethyl methacrylate (PMMA) fibers is chosen as test system. Aligned fibers of DR1/PMMA are deposited by means of the rotating collector electrospinning technique. The processing parameters are optimized to obtain an oriented texture of fibers and the NLO activity is characterized by means of second harmonic generation measurements. Comparison with spin coating and corona poling samples of the same material is discussed. The results point toward a low efficiency of chromophore orientation for the electrospun samples in comparison to the poled ones. An improvement in the electrospinning apparatus is proposed to enhance the chromophore orientation in the polymeric fibers. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40913.     

Flexible Wearable Pre-fractal Antennas for Personal High-Temperature Monitoring

Wireless Personal Communications - This paper proposed a new flexible and wearable antennas design based on teragon pre-fractal geometry until the third level, for monitoring high-temperature in...