Search results

The purpose of the study is regarding the development of eco-oriented technologies for obtaining the building gypsum materials with the involvement of industrial by-products or waste.

The scanning electron microscopy, X-ray microanalysis and IR spectral analysis were used to study the structure of gypsum matrix. The method of comparison of modified and unmodified gypsum matrix was used. Physical modeling of gypsum matrix crystallization is used to study changes in the morphology of hydration products.

The experimental results show that the addition of technical soot into a gypsum binder leads to a change in the morphology of crystalline hydrates of calcium sulfate dihydrate. Results of the scanning electron microscopy, X-ray microanalysis and IR spectral analysis confirm the change of physical and mechanical characteristics of the gypsum binder due to the structural modification of the gypsum matrix with ultrafine carbon soot. The achieved degree of the structural modification of the gypsum matrix is compatible with the results obtained when the gypsum binder was modified with dispersions of carbon nanotubes.

The morphology of the crystalline hydrates of the gypsum matrix with the addition of 0.04%, 0.06% and 1% of the carbon soot is characterized by the transition of the classical needle-like structure of gypsum dihydrate to the lamellar structure of increased density. One can observe the formation of intergrowths around ultrafine carbon soot particles. The studied carbon additive can improve strength characteristics of the gypsum matrix.

This paper aims to introduce and illustrate a computational technique capable of determining the geometry and complex permittivity of a supplementary dielectric insert making distributions of microwave-induced dissipated power within the processed material as uniform as possible.

The proposed technique is based on a 3D electromagnetic model of the cavity containing both the processed material and the insert. Optimization problem is formulated for design variables (geometrical and material parameters of the insert) identified from computational tests and an objective function (the relative standard deviation [RSD]) introduced as a metric of the field uniformity. Numerical inversion is performed with the method of sequential quadratic programming.

Functionality of the procedure is illustrated by synthesis of a dielectric insert in an applicator for microwave fixation. Optimization is completed for four design variables (two geometrical parameters, dielectric constant and the loss factor of the insert) with 1,000 points in the database. The best three optimal solutions provide RSD approximately 20 per cent, whereas for the patterns corresponding to all 1,000 non-optimized (randomly chosen) sets of design variables this metric is in the interval from 27 to 136 per cent with the average of 78 per cent.

As microwave thermal processing is intrinsically inhomogeneous and the heating time is not a part of the underlying model, the procedure is able to lead only to a certain degree of closeness to uniformity and is intended for applications with high heating rates. The initial phase of computational identification of design variables and their bounds is therefore very important and may pre-condition the “quality” of the optimal solution. The technique may work more efficiently in combination with advanced optimization techniques dealing with “smart” (rather than random) generation of the data; for the use with more general microwave heating processes characterized by lower heating rates, the technique has to use the metric of non-uniformity involving temperature and heating time.

While the procedure can be used for computer-aided design (CAD) of microwave applicators, a related practical limitation may emerge from the fact that the material with particular complex permittivity (determined in the course of optimization) may not exist. In such cases, the procedure can be rerun for the constant values of material parameters of the available medium mostly close to the optimal ones to tune geometrical parameters of the insert. Special manufacturing techniques capable of producing a material with required complex permittivity also may be a practical option here.

Non-uniformity of microwave heating remains a key challenge in the design of many practical applicators. This paper suggests a concept of a practical CAD and outlines corresponding computational procedure that could be used for designing a range of applied systems with high heating rates.

In this paper, we regard public procurement as an instrument used by the government for indirect support of enterprises. In this context, we have investigated the place that public procurement occupy in statebusiness interrelations. Using data from a large survey of Russian manufacturing enterprises conducted in 2009 we show that in Russia public procurement cannot be regarded as a component in the system of exchanges, and the extent of combination between direct and indirect support depends on the level of government. At the federal level direct and indirect instruments of government support complement each other. At the regional and local levels the effect of mutual complementation can be observed only in relations with firms, which conceal information about their ownership structure and are supposedly affiliated with regional and local bureaucrats. In relations with other firms at regional and local levels direct and indirect support substitutes each other.

This paper aims to measure the cost of procurement because public procurement procedures prescribed by legislation not only enhance transparency and competition but also entail certain transaction costs for both customers and suppliers.

These costs are important to the efficiency of the procurement system. However, very few previous studies have focused on estimating procurement costs. This paper proposes a methodology for public procurement cost evaluation.

This paper shows how procurement costs can be calculated using a formalized survey of public customers. This methodology was tested with a representative group of public customers operating in one region of the Russian Federation.

The authors formulate the policy implications of this paper, as they relate to the improvement of public procurement regulations and argue that this methodological approach can be applied in other developing and transitioning economies.

FOR some years the writer of this article has carefully studied the scanty and conflicting information available on the aircraft of the U.S.S.R. and the organization of both military and civil aeronautics. It has been our policy to publish, whenever possible, articles giving accurate—if of necessity limited—details of Russian developments. In this respect we would point out to readers that the contents of this present article may appear somewhat conservative, because only undoubted facts have been presented and, as such, it offers a commentary upon the mixture of fanciful propaganda and restricted information available—a fact which we have had to mention on each previous occasion that we have published a similar article.— EDITOR

In this study, we empirically investigate the effect of military expenditure on economic growth in the five South Asian countries of Bangladesh, India, Pakistan, Nepal, and Sri Lanka over the period of 1990–2006. By applying a Solow Growth Model, empirical evidences derived from panel estimation methods indicate that defense has a negative effect on economic growth in the region.

How do informal lending institutions affect entrepreneurship? This paper aims to investigates the role of formal and informal credit market institutions in the decision to become an entrepreneur over the life cycle.

The author developed a dynamic Roy model in which a decision to become an entrepreneur depends on the access to formal and informal credit markets, nonpecuniary benefits of entrepreneurship, career-specific entry costs, prior work experience, education, unobserved abilities and other labor market opportunities (salaried employment and nonemployment). Using detailed Russian panel microdata (the Russia longitudinal monitoring survey) and estimating a structural model of labor market decisions and borrowing options, the author assesses the impact of the development of informal and formal credit institutions.

The expansion of traditional (formal) credit market institutions positively impacts all workers’ categories, reduces the share of entrepreneurs who borrow from informal sources and incentivizes low-type entrepreneurs to switch to salaried employment. The development of the informal credit market reduces the percentage of high-type entrepreneurs who borrow from formal sources. In the case of default, a higher value of the social network or higher costs of losing social ties demotivate low-type entrepreneurs to borrow from informal sources. The author highlights the practical implications of estimates by evaluating policies designed to promote entrepreneurship, such as subsidies and accessibility regulations in credit market institutions.

This study contributes to the literature in several ways. Unlike other studies that focus on individual characteristics in the selection for self-employment [Humphries (2017), Hincapíe (2020), Gendron-Carrier (2021), Dillon and Stanton (2017)], the paper models labor and borrowing decisions jointly. Previous studies discuss transitions between salaried employment and self-employment, taking into account entrepreneurial earnings, wealth, education and age, but do not consider the availability of financial institutions as a driving factor for the selection into self-employment. To the best of the author’s knowledge, this paper shows for the first time that the transition from salaried employment to self-employment is standard and consistent with changes in access to financial institutions. Another feature of this study is incorporating both types of credit markets – formal and informal. The survey by the European Central Bank on the Access to Finance of Enterprises (2018) shows 18% of small and medium enterprise in EU pointed funds from family or friends. Therefore, the exclusion from consideration of informal credit markets may distort the understanding of the role of the accessibility of credit markets.

The paper introduces and illustrates the use of numerical models for the simulation of electromagnetic and thermal processes in an absorbing ceramic layer (susceptor) of a new millimeter-wave (MMW) heat exchanger. The purpose of this study is to better understand interaction between the MMW field and the susceptor, choose the composition of the ceramic material and help design the physical prototype of the device.

A simplified version of the heat exchanger comprises a rectangular block of an aluminum nitride (AlN) doped with molybdenum (Mo) that is backed by a thin metal plate and irradiated by a plane MMW. The coupled electromagnetic-thermal problem is solved by the finite-difference time-domain (FDTD) technique implemented in QuickWave. The FDTD model is verified by solving the related electromagnetic problem by the finite element simulator COMSOL Multiphysics. The computation of dissipated power and temperature is based on experimental data on temperature-dependent dielectric constant, loss factor, specific heat and thermal conductivity of the AlN:Mo composite. The non-uniformity of patterns of dissipated power and temperature is quantified via standard-deviation-based metrics.

It is shown that with the power density of the plane wave on the block’s front face of 1.0 W/mm², at 95 GHz, 10 × 10 × 10-mm blocks with Mo = 0.25 – 4% can be heated up to 1,000 °C for 60-100 s depending on Mo content. The uniformity of the temperature field is exceptionally high – in the course of the heating, temperature is evenly distributed through the entire volume and, in particular, on the back surface of the block. The composite producing the highest level of total dissipated power is found to have Mo concentration of approximately 3%.

In the electromagnetic model, the heating of the AlN:Mo samples is characterized by the volumetric patterns of density of dissipated power for the dielectric constant and the loss factor corresponding to different temperatures of the process. The coupled model is run as an iterative procedure in which electromagnetic and thermal material parameters are upgraded in every cell after each heating time step; the process is then represented by a series of thermal patterns showing time evolution of the temperature field.

Determination of practical dimensions of the MMW heat exchanger and identification of material composition of the susceptor that make operations of the device energy efficient in the required temperature regime require and expensive experimentation. Measurement of heat distribution on the ceramic-metal interface is a practically challenging task. The reported model is meant to be a tool assisting in development of the concept and supporting system design of the new MMW heat exchanger.

While exploitation of a finite element model (e.g. in COMSOL Multiphysics environment) of the scenario in question would require excessive computational resources, the reported FDTD model shows operational capabilities of solving the coupled problem in the temperature range from 20°C to 1,000°C within a few hours on a Windows 10 workstation. The model is open for further development to serve in the ongoing support of the system design aiming to ease the related experimental studies.

The purpose of the research is to determine the stages of the development of information economy in modern Russia and to create a conceptual model of establishment and development of information economy in modern Russia.

The methodology of the research includes a systemic approach and the method of comparative analysis.

The authors conclude that despite large potential, Russia is still at the initial stage of information economy’s formation due to the influence of the determined institutional, structural, and investment barriers. At present, Russia is in the process of transition from the initial stage of information economy’s formation, which is related to the formation of technosphere (spheres of the ICT), to the middle stage, in which sociosphere (information society) is established. However, despite this, there is a large potential in the sphere of informatization of socio-economic system of Russia, which belongs to the final stage of the formation of information economy.

The created conceptual model of establishment and development of information economy in modern Russia showed structural disproportions in information economy of modern Russia. Insufficient technological support, which has resulted in ineffective state management during the formation of information economy at the initial stage, cannot be combined with independently formed social core, the process of creation of which, initiated by the state directive on transition to the middle stage of the formation of information economy, should have started this year. The authors offer practice-oriented recommendations for correction of the current strategy of information economy’s formation in modern Russia.

The purpose of this paper is to investigate the links between investment activity and personal contacts for small- and medium-sized firms with public officials at the subnational level in Russia.

A list-experiment design, using a survey of 21,000 Russian firms in 2017, was used to evaluate the importance of personal connections with officials for conducting business.

A total of 27% of firms without investment and 37% with investment considered personal connections with officials an important factor for doing business. The importance of such contacts was lower in regions with a better investment climate. However, a higher proportion of firms were likely to invest in the regions where higher importance was placed on political connections. Therefore, in Russia in the mid-2010s, investment from politically connected firms did not crowd out investment from other firms.

Although the available data did not allow causality to be defined, the research shows that political connections are important for investors in emerging markets and that the importance of political connections diminishes with improvement in the business climate.

This paper provides a quantitative estimate of the relationship between political connections and firm investment in Russia, an example of large emerging economy. This relationship is moderated by institutional quality at the subnational level. The results provide empirical support for the theory of limited access orders elaborated by North et al. (2009), and stress the importance of rents and their productive utilization for the development of emerging economies.