Synthesis of gold nanospheres and nanotriangles by the Turkevich approach

Gold nanoparticles of triangular morphology possess interesting optical properties with potential application in medicine and infrared absorbing coatings, however, little is known about conditions that favor their growth. In this paper, we have reinvestigated a time-tested recipe for the formation of gold nanospheres by citrate reduction of aqueous gold ions under boiling conditions (Turkevich recipe). Our principle findings are that gold nanotriangle formation is kinetically controlled and is highly favored at low temperatures. Furthermore, the presence of chloride ions from the precursor chloroaurate ions plays a major role in promoting the growth of <111> oriented triangular/truncated triangular particles. The presence of bromide and iodide ions that possess the ability to replace surface-bound chloride ions inhibits triangle formation to varying degrees.     

Equal-valued grounded-capacitor active RC realisation of all-pole transfer functions

An active RC structure with equal-valued grounded-capacitors and employing, at the most, two amplifiers is proposed for realising an all-pole transfer function of any order. Such a structure is attractive for integrated-circuit fabrication.     

A two-pass solar air heater

An air heater, in which the air first flows between metallic and cover plates and is then made to flow between two metallic plates in opposite direction, is discussed theoretically. The governing equations of the model are solved explicitly under suitable conditions. The measured values of the solar insolation and ambient temperature are represented by Fourier series. The effects of collector length and flow rate have been studied. The air heater in this mode of operation is more efficient than one in which air flows between two metallic plates in the same direction, provided the plate length is less than 5 m.     

Torsion problem for elastic cylinder with holes

An integral equation method is given to solve the classical torsion problem in elasticity theory for a multiply connected region. As is well known, the solution depends upon finding the solution of the two-dimensional Laplace's equation which takes the value $\text{1}\text{2}$(x²+y²)+c_i on the boundary, where x,y are the usual Cartesian coordinates, and c_i are unknown constants. The usual approaches are extremely cumbersome. In this paper a new approach is suggested to solve such problems. This method is simple and straightforward and requires the solution of simultaneous linear equations. An example is given which substantiates the theory. The method is very general and can take into account the discontinuity in the displacement component w. The result can therefore be applied to dislocation theory.     

Theoretical analysis of some configurations of double exposure solar air heaters

We present a theoretical analysis of three different configurations of double exposure solar air heaters. The heat-balance equations are written in each case and are solved explicitly. The periodic responses have been studied for different combinations of parameters. Measured values of solar radiation in the plane of the collector and the ambient temperature are used in the analysis. The effects of collector length, reflectance and flow rate have been studied.The outlet air temperature increases with an increase in plate length but the instantaneous and average efficiency decrease. The outlet air temperature is approximately the same, for a given model and combinations of parameters, when the ratio of the length of the air heater to the mass flow rate is constant. A double exposure solar air heater performs better than a single exposure air heater if the reflectance for solar radiation is greater than 10%.     

Efficient Broadcasting in Mobile Ad Hoc Networks

This paper presents two efficient flooding algorithms based on 1-hop neighbor information. In the first part of the paper, we consider sender-based flooding algorithms, specifically the algorithm proposed by Liu et al. In their paper, Liu et al. propose a sender-based flooding algorithm that can achieve local optimality by selecting the minimum number of forwarding nodes in the lowest computational time complexity O(n logn), where n is the number of neighbors. We show that this optimality only holds for a subclass of sender-based algorithms. We propose an efficient sender-based flooding algorithm based on 1-hop neighbor information that reduces the time complexity of computing forwarding nodes to O(n). In Liu's algorithm, n nodes are selected to forward the message in the worst case, whereas in our proposed algorithm, the number of forwarding nodes in the worst case is 11. In the second part of the paper we propose a simple and highly efficient receiver-based flooding algorithm. When nodes are uniformly distributed, we prove that the probability of two neighbor nodes broadcasting the same messageneighbor nodes broadcasting the same message exponentially decreases when the distance between them decreases or when the node density increases. The analytical results are confirmed using simulation.     

Aerobic Alcohol Oxidation by Ruthenium Species Stabilized on Nanocrystalline Magnesium Oxide by Basic Ionic Liquids

The selective oxidation of various alcohols into their corresponding aldehydes and ketones was achieved by ruthenium species stabilized on the nanocrystalline magnesium oxide (NAP‐MgO) by the incorporation of choline hydroxide, a basic ionic liquid, in excellent yields. The procedure is simple, efficient and environmentally benign. The catalyst can be used for four cycles with almost consistent activity.     

Graphene oxide nanoflakes from various agrowastes

Nowadays, the synthesis of graphene/ graphene oxide from graphite precursor using oxidizing agents is the most common procedure, but the direct synthesis of graphene or graphene oxide from a non-graphitic carbonaceous material without using inert atmosphere is really a great challenge. Besides, the chemistry behind the development of graphitic structure from a non-graphitic material during the thermal heating is still not clearly understood. In this research work, three agrowaste materials viz. rice husk, sugarcane bagasse and newspaper were selected and subjected to pyrolysis in presence of trace amount of air. The continued heating at the optimum temperature has resulted in aromatization and condensation along with the oxidation within the cellulosic structure of the agrowaste, which finally resulted in the formation of graphene oxide nanoflakes directly. The mechanism of formation of graphene oxide from these agrowaste materials was studied, which suggested that any carbonaceous waste materials can be converted to graphene oxide by optimizing the thermal heating conditions.     

Application of ameliorated Harris Hawks optimizer for designing of low-power signed floating-point MAC architecture

Neural Computing and Applications - Recently established Harris Hawks optimization (HHO) has natural behaviour for finding an optimum solution in global search space without getting trapped in...