Pure Space-Charge-Limited Electron Current in Silicon

Phosphorus diffusion on π‐type silicon is used to fabricate n^+πn^+ structures of base widths between 3 μ and 60 μ with π‐type resistivities of 300 Ω⋅cm and 8 kΩ⋅cm. The V‐I characteristics of the structures are measured at room temperature and at liquid‐nitrogen temperature. The change in current for constant applied voltage is also observed in that temperature range. The results are interpreted in terms of simple models based on the assumption that pure space‐charge‐limited current of electrons is present. The models describe well the characteristics measured on 300‐Ω⋅cm samples, except for the range of small biases on the thinnest samples. It is concluded that the drift velocity of electrons at 78°K tends towards saturation at 1.0×10^7 cm∕sec ± 10%. The current observed at this temperature actually reaches this value. The critical electric field at 78°K is 10^3 V∕cm±30% but the meaning of this concept for electrons in silicon is vague. The temperature dependence of the current at fixed bias voltages is in general agreement with the variation of the low field mobility. Results obtained on 8‐kΩ⋅cm samples need clarification. Effects of breakdown and trapping are not observed

Cultural indicators of sustainable regional development (the case of Serbian National Park)

This study discusses tourism as a means of regional development by focusing on specific cultural indicators. In this paper, we are dealing with the case of the Djerdap National Park – the largest national park in Serbia and one of the most popular of the country's destinations. This area has an extraordinary diversity of geomorphological forms, it is rich in cultural and historical monuments. At the same time this area is sparsely populated and is demonstrating an insufficient economic growth. For our analysis, we apply comparative indicators to measure sustainable regional tourism development that were proposed by the European Union’s experts. This set of indicators consists of five groups and includes the ratio of accommodation capacities to the number of local inhabitants and the intensity of tourism. Our calculations are based on the statistical data on accommodation capacities and the tourist traffic provided in several municipalities. These data are provided by the Statistical Office of Serbia (2015). We also use the 2011 census data on the number of local inhabitants. We have found that the ratio of accommodation capacities to the number of local inhabitants in Djerdap is in the so-called ‘green’ zone, which shows the sustainability of tourism in this region and an insignificant impact that tourism has on the cultural identity of the local community. The intensity of tourism in Djerdap is in the ‘red’ zone, however, which demonstrates an alarming trend and requires further analysis, especially regarding the carrying capacity of the area. Thus, the conclusion is made that the development of tourism in Djerdap should be balanced with the protection of natural resources

Utilization of geothermal springs as a renewable energy source: Vranjska Banja case study

Despite the significant natural potential, geothermal energy in Serbia has traditionally been used in balneology and recreation, while its share in the country’s total energy balance is almost negligible (0.05%). The present paper deals with the City Municipality of Vranjska Banja as a pioneer in the territory of Serbia in using geothermal energy for heating. The concept and methodology of the present research are directly related to the utilization of geothermal resources for district heating in the Vranjska Banja area. The presented analysis includes: determining the available amount of energy, identifying the energy needs of selected public facilities, and the estimation of investment necessary for energy utilization. A survey, combined with field research, is focused on four public facilities connected to the heating system relying on geothermal sources, as well as on two facilities that should be connected to the system in the next phases. The results show economic, ecological, and technological advantages of using geothermal heating systems, as well as the acceptable price of equipment maintenance. An economic assessment of the transition of one facility from the existing heating system to a system relying on geothermal energy has also been made. The analysis confirms the cost-effectiveness of using geothermal energy and reveals numerous ecological advantages (safe heating, absence of CO2 emission) over other energy sources

The Analysis of Local Marketplace Business on the Selected Urban Case - Problems and Perspectives

Local marketplaces and street vendors represent an important segment of trade in a community and one of the initiators of the rural and peri-urban development. Agricultural and other products available at marketplaces and street vendors very often originate from a wider urban surrounding or nearby villages, so both are also an important factor of the daily migrations, exchange of goods, services, and money on the relation suburb-downtown and village-town/city. This study aims to analyze the social segments of the organization and operation of marketplaces, to provide an insight into the contemporary market processes and decision-making, and also to illustrate the future tendencies of the market outcomes of this aspect of the business. Using qualitative data processing, the results of one of the first empirical research on this topic in Serbia and this part of Europe will be analyzed. The results will show the economic, social, and cultural impact that marketplaces have on people’s everyday life and the economy of Serbia, along with defining future development guidelines. Besides, the findings of this research may be used by local authorities, the economy, and communities for future strategic development planning of this market segment. The outcomes may have an impact on future research of other aspects of marketplaces depending on the difference of regions, on one side, and also alternative opportunities for local development in less-advantaged communities, on the other side. Moreover, this contributes to the identification of the differences in the marketplace business management and sheds light on future initiatives for the encouragement of this local/global process

What Are the Current Directions in the Local Marketplaces Fiscalization? The Online Media Content Analysis

Local markets have been a special setting throughout human history. Apart from their important social role, they had immeasurable economic importance as primary forms of exchange of goods (trade). Nonetheless, they experienced numerous transformational changes that affected their functioning. Like other countries, Serbia has a long tradition of market activity. However, several novelties have been introduced in recent years. Among many, the process of e-fiscalization is the main issue. Therefore, the focus of our research is based on a qualitative analysis of online media content (news and comments) related to the fiscalization of market activity. The attitudes of different categories of participants (state authorities, vendors, and customers) were analyzed. LIGRE open-access software was used for this purpose. The results of the analysis showed conflicting parties. Legislators emphasize the exclusive positive effects, while vendors point to the negative side of fiscalization. As a third party, customers (service users) have an undefined attitude in relation to fiscalization (pros/cons/neutral). There is an agreement to introduce market activity into legal flows. However, the key prerequisite is the prior resolution of a number of problems (working conditions, business costs, market monopoly, etc.)

Intravenous calcitriol therapy in an early stage prevents parathyroid gland growth

Background. Both the phenotypic alterations of parathyroid (PT) cells, e.g. down-regulation of the calcium-sensing receptor, and the increase of the PT cell number in nodular hyperplasia are the main causes of refractory secondary hyperparathyroidism. It is of great importance to prevent PT growth in an early stage