Preparation of gold nanoparticles (GNP) aqueous suspensions by a new method involving Tiron

A new method is proposed to produce gold nanoparticles (GNP) by in situ reduction of a gold salt dissolved in water. The reducing agent used is Tiron instead of the citrate anion most often mentioned in literature. The influence of various parameters has been investigated, such as the content of Tiron with respect to that of the precursor of gold HAuCl₄, or the initial pH of the solution after mixing of reactants. It is shown that Tiron also exerts a positive influence as a dispersant, which impedes agglomeration of gold nanoparticles. The typical average size of GNP synthesized in the present work is close to 7 nm.     

Workplane illuminance prediction method for daylighting control systems

A new prediction method with an interior light sensor for the workplane illuminance in daylighting control systems is introduced. Based on radiosity theory, the spatial distributions of daylight and electric light in the space are discussed and the prediction method is developed. An experimental verification of the technique is performed in an outdoor test-room for a double-glazed window system with a motorized venetian blind integrated between the two glazings. Electric light and daylight predictions were performed in accordance with the proposed method. The results showed that the electric light workplane illuminance can be predicted with high accuracy (±5 lux error with a linear correlation) and that the daylight workplane illuminance can be predicted within ±20 lux (with a linear correlation) for any sky conditions (overcast, clear sky, or variable) with the window system controlled to prevent direct daylight transmission. This method is useful for integrated control of motorized daylighting devices and dimmable electric lights.     

A note on the satisfaction of the boundary conditions for Chebyshev collocation methods in rectangular domains

The way boundary conditions are imposed when applying Chebyshev collocation methods to Poisson and biharmonic-type problems in rectangular domains is investigated. It is shown that careful selection of the number of collocation points leads to a linear system ofn linearly independent equations inn unknowns.     

Stimulation of negative magnetoresistance by an electric field and light in silicon doped with boron and manganese

It is experimentally ascertained that light stimulates the negative magnetoresistance observed in a high electric field in silicon doped with boron and manganese. The optimum conditions (the electric field, temperature, illumination, and resistivity of the material) for observation of the largest magnitude of negative magnetoresistance in (Si:B):Mn are determined. The dependence of the negative magnetoresistance on the concentration of compensating impurity is established.     

The stress intensity factors for a short crack partially penetrating an inclusion of arbitrary shape

Some approximate solutions for predicting the stress intensity factor of a short crack penetrating an inclusion of arbitrary shape have been developed under mode I and mode II loading conditions. The derivation of the fundamental formula is based on the transformation toughening theory. The transformation strains in the inclusion are induced by the crack-tip field and remotely applied stresses, and approximately evaluated by the Eshelby equivalent inclusion theory. As validated by detailed finite element (FE) analyses, the developed solutions have good accuracy for different inclusion shape and for a wide range of modulus ratio between inclusion and matrix material.     

An overview of nondestructive evaluation methods

ondestructive evaluation is described as nondestructive testing (NDT), nondestructive inspection (NDI), and nondestructive examination (NDE). The activities associated with the evaluation include testing, inspection, and examination and primarily involve looking at (or through) and/or measuring some characteristic of an object. Frequently there is a desire to determine some characteristic of the object or to determine whether the object contains irregularities, discontinuities, or flaws. These examinations, inspections, or tests are used to determine the physical soundness of a material without impairing its usefulness. Nondestructive evaluation is a powerful tool that can help assure safety, quality, and reliability; increase productivity; decrease liability; protect the environment; and save money. In this article, nondestructive evaluation is represented by the acronym NDE.     

Influence of the preparation conditions on the size and morphology of nanocrystalline lanthanum orthoferrite

Nanocrystalline LaFeO₃ is prepared by the dehydration of coprecipitated lanthanum and iron(III) hydroxides. It is shown that the behavior of the samples during heating and the size distribution of LaFeO₃ nanocrystals can be considerably different depending on the scheme used for coprecipitation of lanthanum and iron hydroxides; independently of the method employed for coprecipitation of the initial compounds, sintering of the samples at 950°C leads to the formation of lanthanum orthoferrite crystals up to 100 nm in size.