Tribological properties of thin coatings based on epilams modified by nanosized silica

The results of studying the effect of the Tarkosil SiO₂ nanopowder on the tribological behavior of the steel-antifriction coating model systems are presented. The dependences of the coefficient of friction, the wear resistance, and the microhardness of the test specimens on the concentration of the silica nanopowder in the thin coatings are obtained. It is shown that the modification of the coatings by 1% of silica favors an increase in their microhardness and a decrease in their coefficient of friction. At the limiting concentrations of the nanosized filler and under heavy specific loads, the brittle fracture of the coatings occurs.     

Methods of determination of liquid transfer coefficient in building materials

At present there is no unified, widely recognized method of estimation of the dependency between the liquid transfer coefficient and the moisture content in material. It is possible to determine such relation by several methods requiring long-term and laborious experimental research, expensive apparatus and complex calculating procedures. The original method of determination of the liquid transfer coefficient in building materials is presented in this work. This method is limited to obtaining experimental data of the kinetics of one-way capillary water uptake by specimens and calculations based on the suggested model. Accuracy of the given method was confirmed using experimental results of capillary absorption process of lightweight concrete and ceramic material. Since the suggested method is theoretically grounded and its accuracy is comparable with other known methods and at the same time it is less laborious and cost-consuming, it can be recommended for practical application.     

Photoalignment dynamics of azo dyes series with different coordination metals

There are many photoaligned azo dyes that can be used for orientation of liquid crystals in various display devices. However, the structure of these compounds needs to be optimized to increase the rate of the process of molecule photoalignment, as well as to spread the application of these compounds. The main coordination metal that presents in the molecules of azo dyes is sodium derivatives. The use of other alkali metals remains an open question. We used quantum‐chemical computation methods and reversible intermolecular bonding model to determine the effect of metal coordination on the velocity of photoalignment. The theoretical predictions were experimentally verified using sodium, potassium, lithium, and cesium salts of the model azo dye synthesized by us. We conclude that potassium azo derivatives are the fastest, ceteris paribus.     

Contribution of ADHD symptoms to substance problems and delinquency in conduct-disordered adolescents

We examined adolescents with conduct disorder (CD) and substance problems to determine if those with attention deficit hyperactivity disorder (ADHD) symptomatology had more severe delinquency and substance involvement. ADHD symptomatology was assessed in two ways: (1) by self-reports using the Diagnostic Interview Schedule for Children (DISC) and (2) by use of DISC plus reports of others (parents, program staff, and program teacher). We divided boys into three ADHD groups based on DISC: those who met criteria, those who reported at least eight current symptoms, and those who reported fewer than eight symptoms. We also divided the same boys into two groups: those with reports of ADHD by two or more sources and those without this multisource ADHD. Examining these definitions of ADHD revealed that boys with either self- or multisource ADHD had more CD symptoms, earlier age of CD onset, more substance dependence diagnoses, and more comorbid depression and anxiety.     

Influence of texture on the short fatigue crack growth in austenitic stainless steel

We study the influence of texture on the propagation of short cracks on the basis of the evolution of a family of microcracks in 316L austenitic stainless steel under the conditions of symmetric tension-compression. It is shown that the process of crack initiation is concentrated on grain boundaries and strongly depends on the mesostructure. In the process of fatigue fracture, the transcrystalline propagation of the largest crack (affected mainly by the global texture) is predominant. We discuss two approaches to the prediction of the influence of texture on the fatigue life. According to the concept of equivalent crack, this influence can be estimated depending on the size of the largest crack. On the contrary, the Zhurkov criterion deals with the state of the defect characterized by the presence of a family of microcracks. Published in Fizyko-Khimichna Mekhanika Materialiv, Vol. 42, No. 4, pp. 84–94, July–August, 2006.     

Photodiodes for Detecting the Emission of Quantum-Sized Disc Lasers Operating in the Whispering Gallery Modes (2.2–2.3 μm)

Semiconductors - Photodiodes based on solid solutions in the GaSb–InAs system are for the first time applied to study the spectral characteristics of single and coupled...     

Experience of OAO Mosenergo on increasing the effectiveness of managing combined energy production at cogeneration plants

Operation of cogeneration plants according to two demand curves and with the use of two types of management, i.e., technical and economical, is considered. It is shown that efficient management of the combined production of energy is connected with simultaneously accounting for a great number of interacting factors and that such an account can be realized only with the use of mathematical models of plant operation.     

Language games in investigation of social networks: Finding communities and influential agents

The paper presents an investigation method of social networks based on language games. This method is used for finding implicit communities and influential agents in social networks. The authors introduce a naming game and explain how it is applied in investigation of social networks. Simulation results are demonstrated for specially designed graphs and a real-data graph. The authors also survey alternative methods of community detection and compare them with the above-mentioned method.     

Waterproof material for liquid crystals photoalignment based on azo dyes

We have designed and synthesized azo dyes with reversible intermolecular bonds, which can be used as materials for liquid crystal photoalignment. The generation of anisotropic structures in azo dye thin film is possible due to the presence of intermolecular hydrogen or coordination (metal–oxygen) bonds. All thin film materials are resistant to air moisture, while photoalignment material with reversible hydrogen bonds is inert to direct water contact. In this paper, we study photoalignment dynamics of obtained materials and discuss possible formation of intramolecular and intermolecular hydrogen bonds within the photoalignment dye layer.