Latest developments on application of heterogenous basic catalysts for an efficient and eco friendly synthesis of biodiesel: A review

Heterogeneous catalysts are now being tried extensively for biodiesel synthesis. These catalysts are poised to play an important role and are perspective catalysts in future for biodiesel production at industrial level. The review deals with a comprehensive list of these heterogeneous catalysts which has been reported recently. The mechanisms of these catalysts in the transesterification reaction have been discussed. The conditions for the reaction and optimized parameters along with preparation of the catalyst, and their leaching aspects are discussed. The heterogeneous basic catalyst discussed in the review includes oxides of magnesium and calcium; hydrotalcite/layered double hydroxide; alumina; and zeolites. Yield and conversion of biodiesel obtained from the triglycerides with various heterogeneous catalysts have been studied.     

Heterogeneous Labour Markets in a Microsimulation–AGE Model: Application to Welfare Reform in Germany

Labour market reforms that are designed to stimulate labour supply at the lower end of the wage distribution can never be precisely restricted to the target group. Spillovers to and feedback from other segments of the labour market are unavoidable and may counteract the direct effects of the reform. An adequate representation of heterogeneous labour markets becomes therefore an important issue for the assessment of reforms. We analyse the possible interactions between labour market segments in a combined, consistent microsimulation–AGE model with a flexible representation of substitution possibilities and different mechanisms of wage determination. We look at a stylised reform and find labour-demand cross-price elasticities between the low and medium skilled to be the main drivers of the results. Interaction with the high-skilled segment is less pronounced.      

Coupled size and boundary-condition effects in viscoelastic heterogeneous and composite bodies

Previous results of the author on the influence of size and boundary-conditions on the apparent properties of elastic heterogeneous materials are recalled and extended to the viscoelastic case. Materials with random microstructures, possibly with anisotropy, defects or damage, are considered. In place of the classical concept of effective properties, which holds for the representative volume only, the concept of apparent properties is recalled. It makes use of special kinds of boundary-conditions and appropriate stochastic averages for which the required Hill condition is still valid while the ergodic assumption – legitimating the use of the concept of equivalent homogeneous medium – is relaxed. Statistical apparent properties are defined on various partitions of a given initial specimen D₀ into a set of coarse specimens on the one hand, and of smaller specimens on the other hand. The boundary-condition and size-effects hierarchies derived in Huet (1990. Journal of Mechanical Physics and Solids 38, 813; 1997. Engineering Fracture Mechanics, (special issue) 58 (5–6) 459) are recalled. Examples of numerical verification by micromechanical simulations are shown using 3D finite element models of elastic granular composites. Some salient features of the viscoelastic behavior of non-metallic construction materials used in civil engineering are recalled. 3D simulations on viscoelastic micromechanical models are also shown, with results exhibiting trends similar to the elastic case and for which theoretical justification and generalisation is seeked in the paper. Use is made of a Statistical Continuum Thermodynamics approach through which the concept of equivalent homogeneous medium and effective properties is first discussed for materials with constituents having dissipative constitutive equations of any kind and from which natural definitions of dissipative potential and complementary energies are derived. Dissipative extensions of the so-called Hill condition are obtained. Then, new minimum theorems for viscoelasticity are derived from a slight modification of the pseudo-convolutive procedure used in Huet (1992. European Journal of Mechanics, A/Solids 5 (11) 653; In: Bazant, Z.P., Carol, I. (Eds.), Creep and Shrinkage of Concrete. Spon, London, pp. 189–200). From this, theoretical bounds and size-effect hierarchies on the statistical viscoelastic stiffness and compliance function tensors and their rates are obtained in the time domain. It is found that viscoelastic heterogeneous bodies smaller than the representative volume exhibit, for the two classes of uniform boundary-conditions, the same kind of size-effects as the elastic ones. Possible extensions to other kinds of time-dependent physical properties are quoted.     

A high-level energy consumption model for heterogeneous data centers

Data centers consume anywhere between 1.7% and 2.2% of the United States’ power. A handful of studies focused on ways of predicting power consumption of computing platforms based on performance events counters. Most of existing power-consumption models retrieve performance counters from hardware, which offer accurate measurement of energy dissipation. Although these models were verified on several machines with specific CPU chips, it is difficult to deploy these models into data centers equipped by heterogeneous computing platforms. While models based on resource utilization via OS monitoring tools can be used in heterogeneous data centers, most of these models were linear model. In this paper, we analyze the accuracy of linear models with the SPECpower benchmark results, which is a widely adopted benchmark to evaluate the power and performance characteristics of servers. There are 392 published results until October 2012; these servers represent most servers in heterogeneous data centers. We use R-squared, RMSE (Root Mean Square Error) and average error to validate the accuracy of the linear model. The results show that not all servers fit the linear model very well. 6.5% of R-squared values are less than 0.95, which means linear regression does not fit the data very well. 12.5% of RMSE values are greater than 20, which means there is still big difference between modeled and real power consumption. We extend the linear model to high degree polynomial models. We found the cubic polynomial model can get better results than the linear model. We also apply the linear model and the cubic model to estimate real-time energy consumption on two different servers. The results show that linear model can get accurate prediction value when server energy consumption swing in a small range. The cubic model can get better results for servers with small and wide range.     

Using a modified CINDER90 routine in MCNPX 2.6.0 for the prediction of helium production in minor actinide targets

Fast reactors containing heterogeneous minor actinide (MA) target rods are now being modeled. When studying transmutation in these rods, helium production from α-decay must be considered since it is produced in substantial quantities. This research utilized an innovative method to calculate gas production by modifying the CINDER90 depletion code used by MCNPX 2.6.0 to include helium production from α-decay. The modified CINDER90 code was verified using the ORIGEN-ARP module of SCALE6. It was tested using the Sodium-Cooled Heterogeneous Innovative Burner Reactor model created at the University of South Carolina. It is recommended that the modified version of the cinder.dat file be distributed in subsequent MCNPX 2.6.0 releases for use in fast reactor calculations using heterogeneous MA target rods since it includes helium production otherwise not available from the current version.     

Advances on the development of novel heterogeneous catalysts for transesterification of triglycerides in biodiesel

This paper describes experimental work done towards the search for more profitable and sustainable alternatives regarding biodiesel production, using heterogeneous catalysts instead of the conventional homogenous alkaline catalysts, such as NaOH, KOH or sodium methoxide, for the methanolysis reaction. This experimental work is a first stage on the development and optimization of new solid catalysts, able to produce biodiesel from vegetable oils. The heterogeneous catalytic process has many differences from the currently used in industry homogeneous process. The main advantage is that, it requires lower investment costs, since no need for separation steps of methanol/catalyst, biodiesel/catalyst and glycerine/catalyst. This work resulted in the selection of CaO and CaO modified with Li catalysts, which showed very good catalytic performances with high activity and stability. In fact FAME yields higher than 92% were observed in two consecutive reaction batches without expensive intermediate reactivation procedures. Therefore, those catalysts appear to be suitable for biodiesel production.     

A model of domain-polymorph component for heterogeneous system design

Heterogeneous systems mix different technical domains such as signal processing, analog and digital electronics, software, telecommunication protocols, etc. Heterogeneous systems are composed of subsystems that are designed using different models of computation (MoC). These MoCs are the laws that govern the interactions of the components of a subsystem. The design of heterogeneous systems includes the design of each part of the system according to its specific MoC, and the connection of the parts in order to build the model representing the system. Indeed, this model allows the MoCs that govern different parts of system to coexist and interact.To be able to use a component which is specified according to a given MoC, under other, different MoCs, we can use either a hierarchical or a non-hierarchical approach, or we can build domain-specific components (DSC). However, these solutions present several disadvantages. This paper presents a new model of component, called domain-polymorph component (DPC). Such a component is atomic and is able to execute its core behavior, specified under a given MoC, under different host MoCs. This approach is not a competitor to the approaches above but is complementary.     

Preparation and characterization of P4MVPMnO4/SBA-15 as an efficient heterogeneous oxidant: An organic–inorganic hybrid polymer

This work is concerned about the preparation and characterization of MnO₄⁻ supported poly (4-methyl vinylpyridinium)/SBA-15 which was effectively employed as a heterogeneous oxidant for oxidation of aromatic alcohols. P4MVPMnO₄/SBA-15 exhibited excellent activity and selectivity under mild and solvent-less conditions.     

Navigating a robotic swarm in an uncharted 2D landscape

Navigation is a major issue in robotics due to the necessity for the robots’ course of movement. Navigation consists of two essential components known as localization and planning. Localization in robotics refers to one’s location with reference to a well known position inside the map. Planning is considered as the computation of a path through a map which represents the environment. This given path would be chosen based on the potential of the problem so that the expected destination would be achieved. As such, a reliable map is essential for navigation without which robots would not be able to accomplish the goals. In navigational approaches, reliability of the map would be challenged due to the dynamic and unpredictable nature of real-world applications. It is, consequently, crucial to implement solutions for searching such environments—those affected by dynamic and noisy constraints. In the present study, two enhanced versions of particle swarm optimization (PSO) called area extension PSO (AEPSO) and cooperative AEPSO (CAEPSO) are employed. During the study, AEPSO and CAEPSO are employed as decision-makers and movement controllers of simulated robots (hereafter referred to as agents). The agents’ task is to seek for survivors in realistic simulations based on real-world hostile situations. This study examines the feasibility of AEPSO and CAEPSO on uncertain and time-dependent simulated environments. The simulations follow two phases of training and testing model. Agents use past knowledge gathered during the training phase in their testing phase. The study addresses the impacts of past knowledge, homogeneity and heterogeneity in robotic swarm search. The results demonstrate the feasibility of CAEPSO as robot controller and decision-maker.     

Organofunctionalized catalyst surfaces highly active and selective for carbon–carbon bond-forming reactions

This article illustrates two types of organofunctionalized heterogeneous catalysts for variety of organic carbon–carbon bond-forming reactions, summarizing our previous reports and also presenting new data. Organic amines with an alkoxysilane moiety were immobilized on inorganic silica-alumina surfaces (SA-NR₂) by simple silane-coupling reactions between the silica-alumina surface (SA) and the alkoxysilane. This SA-NR₂ acted as acid–base bifunctional heterogeneous catalysts for carbon–carbon bond-forming reactions, such as cyano-ethoxycarbonylation, Michael reaction of nitriles, and nitro-aldol reaction. These reactions did not occur with either SA or homogeneous amine compounds. In addition, the mixture of SA and homogeneous amine showed low catalytic activity due to undesirable acid–base neutralization reaction. Achiral organic silane-coupling reagents with a variety of functional groups were also immobilized on a SiO₂ surface that had been immobilized with chiral bis(oxazoline) (BOX), to which Cu ions were coordinated to make chiral Cu–BOX complexes on the SiO₂ surface. The SiO₂-supported Cu–BOX complex catalyst functionalized with achiral 3-methacryloxypropyltrimethoxysilane dramatically increased enantioselectivity in the asymmetric Diels–Alder reaction of cyclopentadiene and 3-acryloyl-2-oxazolidinone. The organofunctionalized catalysts showed much better performances for the C–C bond-forming reactions compared to the corresponding homogeneous systems. The heterogeneous catalysts thus obtained were characterized by solid-state ¹³C and ²⁹Si MAS NMR, FT-IR, UV/vis, XAFS, ESR, XRF, and elemental analysis.